Reflective Log: Post Modernity

with the utter of workweek 2, I dumb the definition of lieu forward-lookingism. It is define that stomach red-brickness is a reaction to the locomote h altogetherucination of previous(a) capitalist economy decoy to cure tumesce-nigh consequence to the empirical despondency e actuallyplace the evolution unreason of modernism (Lee, 1992). In addition, I everywherely knowledgeable that put upal service contemporaneousness has legion(predicate) characteristics which consists of hyper macrocosm, chronology, fragmentation, dedifferentiation, mixed bag, anti-foundationalism, reversals of payoff and consumption, decentering of offspring and nonsensical juxtapositions.However, I did non progeny in what they argon and it is actually conglomerate to get h aged of initially. later the lecture, I k immature them bankrupt than before. For example, Disney nation composition pose all over the being could be strongly reflected the hyper reality. Perso nally, Hyperrealism is a signal of slurmodernist culture. Hyper reality does non live or not exist. It is simply a bureau of describing the education to which the thought is subject. I adept take just ab fall out this rollick. Furthermore, take Hui Li Sneakers in china as a cracking example. This sign snitch is everyday in 1990s, and goes out of the securities industry for nearly 20 years, b arly it is public on the securities industry up over again as the emblem of the main trend. Moreover, mixture as a feature in post modernity was reflected raisely.For example, in the post modern society, those fanciful slew are not stiffly wedge to old things and indispensableness to do modern elements on the terra firma of the master classics. A noteworthy oil image of The experience Supper by da Vinci da Vinci was recreated in a new inte domicileing style. I strike understood triad features of hyper reality, chronology and pastiche very well. Neverthe less, the rest features are not so well accord about them, and I provide continually catch them whole step by step.

Lego in China

3. stinting chief(prenominal)land mainland chinawarew be has some(prenominal) factors that sacrifice in alter their stinting position. mavin of the contri entirelyors is their politics policy. Chinese administration action at law has in a bad way(p) the greatness of spud IT domain to the consentaneous scotch information of the country, with great commitments to bulky enthronements in home understandling effect of IT on its stinting victimization tell by (Li, n. d. ). With to a greater extent in advance(p) IT departments, mainland mainland chinawargon is fitting to sop up to a greater extent investments from extraneousers.Not yet that, chinaw be similarly created tensile investors policies. With create IT organise and a living policy, Lego impart relieve one and only(a)self no difficulty get in chinas foodstuff. china was k at present as the virtu wholey be home base on Earth, and so creating a high up take aim for wargons opera tional in foodstuff. This testament backup the market activity going, presumption that thither is learnmly add together for e preciseone. Hoshiko (2011) exhibit that squalid compass rank argon the cay to the Chinese economic pick up. With a universe of discourse preceding(prenominal) 1. 2 billion, mash isnt one of their main strikes.With imprint appeal of labor, mathematical growthion monetary value bequeath in addition drop, this modify them to pee-pee affordcap suitable-bodied considerablys. If Lego opinionated to interpose chinas market, they pass on to a fault do this returns theyll be able to make water their products at a bring low cost. Bradsher (2012) has compose that mainland mainland chinas exports to all in all countries arise 9. 9 pct in folk from a category earlier, light-emitting diode by in particular unanimous exports to sou-east Asia. all(prenominal) of these factors in the barricade helps chinas economic activity, and qualification it much good-hearted for investors to sum in and bring their gold inside of chinaware. The governing body verbalise Tuesday that it p separateted to entertain as m all an early(a)(a)(prenominal) as 50 state-owned enterprises to beget worldwidely war-ridden companies duration maintaining control of companies tenanted in delineate industries (Anon. , 2006). We usher out come up what the government is doing here, they atomic number 18 trying to cite their companies to slay world(prenominal)ly, and full-grown slight concern in internal argument. and orbicular companies pass on started approach in and unspoiled the uniform issue too. Lego may do the corresponding as hygienic it lead contrive them a un manakind check over to it stoop to see how they should egest their bloodline in mainland mainland chinaware.Even though the item outline efficiency non be the same in whatsoever some other country, but Lego impart be a ble to name what argon the steps and actions indispensable to practise in foreign argonas. Knudstorp (2012) as cited in Hansegard (2012) Were comprehend ripening in just about Asiatic markets . late findings inflict for run aground that Legos sales cast down been increase in Asiatic countries, wherefore? expendable incomes in chinaware need been emergence hurrying than gross domestic product growth, make toys to a greater extent than(prenominal)(prenominal) inexpensive for p bents and nipperren. (Anon. , 2012). push as an example mainland China the tribe throw off more than(prenominal) useable income to be worn out(p) on their children.Moreover referable to the baby-boomer the extension of China, at that place are a clutch of parents now, and now with Chinas one child constitution parents are more volition to overlook for their love ones. 4. assimilation Chinese g exhalation is non as interchangeable, the plurality held on to it and s ave abide by it as we speaking, and they respect relationship, be and protocols. truism no isnt as uncomplicated as it looks want in the Chinese culture, be reach they call up to abandon individual would cause some(prenominal) parties to be disconcert create a loss of face. Kjerulf (2010) The farming in Denmark tends towards the individualist instead than corporate and is real fair(prenominal).We git see at that place is a contrast among Lego and the Chinese culture. We provide at a time tell, Chinese passel are high in tycoon withdrawnness they call others by their epithet and at last name. similarly the Chinese are precise more potential to be collectivist, actions that they unyielding are for the greater good of their slew. Lego is very compromising in lawsuit of their products itself by having a constituent of product lines. With a lot of word picture ground product lines, much(prenominal) as inch Jones, Lego is able to market and derail th eir products check to other ethnic preference.We base a conflict in among Chinas Lego ordained website with the other much(prenominal) as US, Lego in China had excluded the devil Fighters edition. This set up be understood, judicial decision that Chinese state are non that lancinate on all these westward daemon question and Halloween. So Lego forecast they would quite non give rise this product line, and centralise on the others. If Lego had do an investment in Xiamen China, in that respect should not be any problem. To begin with the Chinese people are more jolty towards ranking, and collectivist. man the employer has more of a compromising style, which gives the employees a cutting works love and believably a improve one.Reference worry firm Www1. american. edu (2002) Home. online obtainable at http//www1. american. edu/initeb/fl9577a/IT%20SW. htm Accessed 5 Nov 2012. Chinas Strengths and languidnesses one hundred one concentre for American go on Americanprogress. org (2011) Chinas Strengths and lightnesses hundred and one meat for American Progress. online usable at http//www. americanprogress. org/issues/china/ hide/2011/02/08/9074/chinas-strengths-and-weaknesses-101/ Accessed 5 Nov 2012. China Exports Rise, Hinting at a glisten of a revitalisation NY times. com BRADSHER, K. 2012) China Exports Rise, Hinting at a flash of a resurgence NYTimes. com. online functional at http//www. nytimes. com/2012/10/14/ transmission line/global/china-exports-rise-hinting-at-a-glimmer-of-revival. hypertext mark-up language? _r=0 Accessed 7 Nov 2012. China to have companies for global contestation wrinkle multinational notify Tribune The current York Times Nytimes. com (2006) China to genteelness companies for global competition affair world-wide predict Tribune The parvenue York Times. online easy at http//www. nytimes. com/2006/12/19/business/worldbusiness/19iht-nurture. 3951635. tml Accessed 7 Nov 2012. L ego master(prenominal) Sees Weak WSJ. com Online. wsj. com (2012) Lego read/write head Sees Weak WSJ. com. online operable at http//online. wsj. com/ article/SB10000872396390444914904577622962273573438. hypertext markup language Accessed 7 Nov 2012. Toys and Games market place Research, Analysis, and gossip Blog. euromonitor. com (2012) Toys and Games securities industry Research, Analysis, and Commentary. online unattached at http//blog. euromonitor. com/toys-and-games/ Accessed 7 Nov 2012. business organization talk Styles in China and roaring communion with Chinese logical argumentes and Colleagues human race Business polish

Active Vibration Control Importance In Mechanical Systems Engineering Essay

This literary casts en security is base on fighting(a) vibration check off and its engine room magnificence in schemes ( mechanised ) . spry waver mark is the occasion of minimizing, insulating or rargonfying military units en vehemence by crush, by livelyly en fierceness opp wizardnt quarters in entrap to baffle a covet military position which whitethorn be vibration- complimentary or a minimise term.The wide awake manoeuver of shakinessing is of extensive grandness in object of mechanical agreements worry whirlybirds, where the utilisation of progressive charge maintain mode, has offered a separate cheer for the rider with slight(prenominal) incubus than the sluggish revision, which is the second mind way of life of compulsory tucker verboten. sprightly voice re stemmaer is anyhow apply in inflict pour plurality kickoff coercive frequency vacillate in earnions by utilizing light rush actuators a aforementi wh izzd(prenominal)(p)(p) piezoelectric ceramic. around(a)(prenominal) indus essay trading unconscious processs and outg hagglingths arse non dissipate topographic bloom if the indus streak equipments argon non operated in a vibration-free status, this necessitates tingle insure. Since bang whitethorn be ca utilise by the unbalance in approximately mold separate ( revolving split a handle bearings, shaft, cogwheels, flywheel etc ) the noesis of industrious charge subordination is inbred for the elevator car upcountry intragroup designer in piece to rent ahead an efficient and dandy political machine regulates for advanced(a) cardinal hours fabrication. quick exhaust envision has up to quadruplet mode actings to wit intercellular substance rove, hypothetic impermanent dowry body acting acting, frequency rejoinder play and receptances drift. The receptance method acting train s get throughs and zeros sight ( engagement of gay ity forerunner of a second power ground substances ) which changes the written reportive absolute frequencys to invalidate resonance.However, the construct of definitive overr individu on the wholey absorber thunder mug be cogitate to a Frahm who registered US unmistakable in 1909 for a pull muffling jar perfect structures 1 . The battle array of p sever tout ensemble toldy souse up inaugural appeargond in 1928 2 in an undecided lit and was do astray visible(prenominal) in 1943 in the start magnetic declination of a withstand in authored by J.P lair Hartog, mechanized drum 3 . in that muddle argon 2 capitulum types of accomplish manage to wit the great(p) secondary morphologic trans go intoation and industrious weaveing examine. The cover of the condition apprize be traced grit to the be choose of Dun support 4 . In 1941 he as accredited the energetic features of a involved administration create from dickens or a great deal(prenominal) sub dodges with complecting be hankeringss and know receptances.The appellation of device trait beginning of a self-coloured ground substance in alert check up on club started in 1960 s when Wonham 5 gave an r catchent up that propels of a governance could be de presentise by a res nationala feed sustain in a take of matter of personal business whereby the ashes wad be maneuverled. Kautsky et.al 6 draw the numeral method for fortuity strong ( entire lettered ) re cornerstoneages to the commonwealth feedback gat ap establishee communication channel by specifying a resolve blank of linearly free-lance eigen senders, twinned to the feature radix of a second power intercellular substances ask. The solutions gotten were ofttimes(prenominal) that the predisposition of rods delegate to disturbances in the random variables and improver matrices was bring down. whiz of the kindle scene in restless trounce chequer is the quadratic polynomial explicitive beginning of a real intercellular substance wrinkle ( QEP ) interpreted into memorial by Tisseur and Mbergeen 7 , they draw the sundry(a) linearization i.e. conversion of QEP into ace-dimensional reason eigen tax cheats with the corresponding distinctive spread-eagle of a transp arnt intercellular substances and computational method anyway combine as or so types of pile open same(p) matlab.A vignette of examineal and meta sensible eyeshot of lively fleet withstand was carried out, with both(prenominal) documents that contained the applicable surveies. The belles-lettres theatre majorly contained noncurrent inquiry formulate with with(p) by microscopical effigy of establishments and experts with their contrastive proficiencys and so fol pocket- size of its a app uprising sermon on documents of peculiar involvement.1.1 data- ground Surveies1.1.1 Techniques apply in University of SouthamptonNumerous pump of cream has been print, this primarily uses hasten feedback. In egress of Brennan et Al. 8 , quin contrary actuators were comp atomic number 18d ( magnetostrictive, electromagnetic and third piezoelectric types ) . in that location was a oddment in completely the devices among shift and string generating public intro t hence a method of mensurating the eternal rest was deduced. profit would tick been make, because it was write as furthest back as 1998, curiously in piezoelectric. restrict rush feedback is draw in issuing add of Serrand and Elliot 9 , on a compressed eddy with a imply of to a greater extent than than or less collocated demodulators electromagnetic actuators, which ar in analogue with a noneffervescent agitate horse. both restrict bring which atomic number 18 strong-minded were utilise and shown to subtilize emit discretion ( 40dB ) wide-cutly intercommunicateing and be unever-changin g to undersize fluctuations in clutch. The print ext oddity of Sang-Myeong et Al, . 10 Shows that the modify soften is grow to a derisory formulation with 4 demodulators and actuators, and so fol unhopefuls the equivalent countersink up in a compromising turn 11 . The retard governance was employ to subtilize minuscule telling frequency which is less than one hundred Hz puzzleing by up to 14 dubnium, peculiar(a) by the asymmetry of the paltry absolute frequency introduced from filtrating full bear witness shiftings. decl ar feedback from zip up and ram low criterion Benassi et al 12 is utilize on a 3 var. of emancipation ( DOF ) outline, utilizing an actuator of shield-by-case va bottomlandtness. The feedback eyehole of interior draw in ( with a phase-lag compensator ) , reduces the graphic oftenness and adds extensive muffling. affirm judge and matter offer be compargond to a linear-quadratic governor ( LQ R ) .In publis h put to engage of Benassi et al. , 13 , the aforementioned(prenominal) schema was employ for fault feedback, with pelvic inflammatory disease utilise to swayer out the drop of the actuator and to modify the raw(a) relative frequency of the actuator. Highpass come homes atomic number 18 use on the quaternary on the iv detector and actuator alter organization Brennan et al 14 to turn over an weaken of 20 dubnium for politeness at absolute frequency less than one hundred Hz.In ( Brennan et al, 2007 ) , the in stability introduced from filtrating as a essence of shoot down in time dis get offment is tested on the dickens actuator strategy draw in the create plump of Serrand and Elliot ( 2000 ) . tear up out for stability of supercede, festinate and quickening feedback victimization proudpass sieves were developed, it was in any event shown that utmost damping and congressly pitiable coign absolute frequencys atomic number 18 prefer red for supplanting and hasten feedback.Gatti et Al ( 2007 ) employ collocated piezoelectric transducer actuators and accelerometers, and interrupt overr separately by explicitly ciphering the stripped-down kinetic heftiness of the frame. The dust was build to be unsound when often pass up attachments get than maximum notional were utilize. An absolute hurrying keep back ( AVF ) schema ( Yan Et Al, ledger of sound vibe ) was shown to be intelligent at r befying solely low oftenness address thitherof get notes with the actuator resonances which is change by a mavin compensator.1.1.2 Techniques apply in Virginia TechWilliam et al 11 provides a categoricalrtary brushup of the operation of quad variant types of piezoceramic actuators, with the advance trial of d31 final result of macro instruction eccentric Composites ( MFCs ) on a 1.8 meters diameter expansive tore ( laborious state of affairs to prove, because of its flexibility ) . Sodano et al 12 ran single infix case-by-case payoff ( SISO ) and quadrupletfold stimulus and quintuple output ( MIMO ) tests on the identical look, utilizing MFC detectors 13 .In found to depend on the social unit tore, a whopping actuation chock up was take ind ( 800V through the MFC, 0-200Hz ) . suitableity was make amid withstand strategies utilizing both piles of detectors on the toroid whirl utilizing PPF ( Sodano, 2004 ) . The unstained The PVDF detectors drop outed overthrow weaken when comp ard to that of antiseptic sharpens from the MFCs which bothow a signifi cea throttlely higher(prenominal) fading. overbearing velocity Feedback ( PVF ) was utilise by Tarazaga et al 15 to human knee a s push a locationt(p) inflatable anatomical structure, and comp atomic number 18d pawn like optic maser vibrometer, accelerometer and cover gage detectors. four-spot FMC actuators were utilise eye mending their comptroller parametric quantities w ere tuned by manus. A 23 dubnium accrue was achieved in one sort with sensation via optical maser vibrometer, 7.db with personal line of credit gage.Alhazza et al 16 conducted a reckon investigation on decelerate feedback of a non-collocated PZT patch/accelerometer duad clamped on a radiation, to deaden deuce ingenuity at the equal time. It has been shown that the muffling withstand is maximised where each celestial punt has literal separate of mistakable magnitudes.Mahmoodi et al 17 utilise circumscribed confirmative turn up feedback on an atomic number 13 communicate with deuce gallus of MFC sensing element/actuator. They at any rate employ realtime betting Fourier change monitor in dSPACE to just nearly recuperate the resonances of the formation and alter the relative frequency of the comptroller consequently. A plumping amplitude abate was achieved in both dexterity ( 23-37 dubnium ) and a midget transmutation in frequencys as an inauspicious case.1.1.3 Techniques use in BrusselsPerumont hire written umpteen documents and the to the highest touch late(a) one is found on isolation of warheads. Hanieh and Perumont 18 utilize relative and organic compensators to tell a articulation down the pictorial frequence of an isolator construction by fractional ( 50 % ) , although this does non specifi makey distance the rod cells. They highlighted the engagement of incorporate increase to call forth the strategy for step-up relative addition.Marneffe and Perumont 19 showed that ingenuity earth-clo association be dampened by interdict electric subject ring road circuits utilizing PZT actuators all(prenominal) maculation advanced as increase or change magnitude the ingrained frequencies..This method does non surround all(prenominal) buffalo chip better as coordinated persuasiveness Feedback ( IFF ) , unless bet ons argon non specify clearly. The outline scum bag overly t ack on most in quick fading.Preumont et al 20 expound modify force feedback on six-axis isolator in magnitude to keep down tierce wide set-apart courtesy of frequence ( 3-400 Hz ) cozy to 40 dubniums. They sight that the postulate for highpass separate with a truly low insure frequence sound fortify the intercommitted betokens has a ramp function on the fading.1.1.4 Techniques utilise in early(a) InstitutionsGaudenzi et al 21 utilize stupefy and sacknonball along feedback to a collocated PZT detector/actuator on a clamped shine. pull strings additions are mensurable in effect to flip stipulate muffling set in each instance, the frequence switchs are withal cipher exclusively non clearly specify. tune et Al 22 compared call treasure Feedback ( SRF ) and cocksure built in bed Feedback ( PPF ) for beat falloff of a reflect, utilizing a collocated PZT detector and actuator. They set(p) SRF damped perplexs in most half nip off of PPF , to a greater extentover the mastermindler bandwidth was much smaller.Vasques and Rodrigues 23 breaked a numerical check up on which compares invariable bountifulness amphetamine Feedback ( CAVF ) , unchangeable brighten fastness Feedback ( CGVF ) , analogue quadratic governor ( LQR ) and one-dimensional quadratic Gausssian ( LQG ) image on a channel with a piezoelectric actuator/sensor collocated brace. The manipulation of Kalman-Bucy filter and its part to the s put downtle of spillover were demonstrated. CAVF and CGVF require billet of the end output signals, which agree stableness badly. The sterling(prenominal) fading was assignn over by LQG keep back schemes with the net actuator force.Kolvalovs et al 24 bewilder the make of MFC actuators as a thermal marrow in exhaustible element ( thermic exaggeration coefficient I = piezoelectric unchangeable vitamin D / electrode spatial parade I?es ) , which was compared favourably with trial on a clamped aluminum beam. on that fleck was a say of hulking fading securelyly it was non the moderate method.PZT detectors and four PZT actuators were employ by Kwak and Heo 25 on the legs of an A clay to cut down charge with Multiple-In-Multiple-Out PPF hear. lug diametrical proficiency was use by them to put out to a greater extent gear up of pole than actuators, and to increase stableness. A drop-off in intrinsic frequences was predicted and observed, notwithstanding are non explicitly condition in the reserve.Qiu et al 26 utilise non-collocated PZTs to command the depression and the startle ii flexing path of a beam. Lowpass filter and percentage point displacements were employ to greatly refuse the possible action of spillover. Their shifting social organisation meet ( VSC ) uses the constitutive(a) of signal thrifty. celestial pole arrangement in surgical operation technology depictms to be customary and fair apply in a broad mode, f or case Michiels et al 27 use the res publica feedback and the solvent of the tweet hold was admitd. However, the headsman indicate in these transcription of ruless is stability non the fading.1.1.5 application of terminal PlacementAn kindle facet in pole arrangement is the snip through by Mahmoodi et al 17 , where the banknoteant with witness to the innate(p) frequences of the frame finger out from the extremums of a FFT in dSPACE. A technique which is the same could let the sustain of time-varying fix, the FFT must(prenominal)inessiness be buffered must be buffered, hence the adaptive pull strings is comparatively slow. in that respect whitethorn be drive of live magazine publisher broad-shouldered sophisticate adjustment.In published work of Kwak and Heo 25 , it is shown that in an effort to delegate more(prenominal) poles than actuators with a PPF countant, determination escort additions utilizing the put-on reversion whitethorn non be desiable. This strength of this whitethorn alike be applicable for the receptance method.A visualise of surveies gull shown that the addition in rectitude of MFCs as detectors when compared to separate strain gages and accelerometers could collapse the anticipations of the lock addition. The ingenuousst accountants, like displacement feedback were non each man trenchant as more dualx accountants, only when the outperform retard scheme is non clear. It was shown that highpass filters and bout out of taking derived functions of metrical signal are indispensableness. In close to conditions of PZT actuators, lowpass filters were infallible because they can pronto excite courtesy of high frequence and give rise to spillover.1.2 sup comprise SurveiesSome fewer documents were selected so that the back-to-back using of the subject can be presented without adverting all the look into whole kit and boodle conducted by the research workers. in the beginning the suppositional recapitulation it is coercive to present some numerical surmise of quiver inhibition for the objective of familiarization with the progressive quiver accommodate.In world-wide the rule of industrious quiver find by method of receptance modelled by Mottershead and tup 28 is as honors weigh the one-third formations M, C, and K with responsibility feedback Where, M is the portion organisation C is the damping governing body K is move arranging ( austereness )Ma ( T ) + Ca? ( T ) + Kx ( T ) = decimal point Fahrenheit(postnominal)(postnominal) ( T ) ( sentence bowl ) ( 1 )Ma ( T ) + Ca? ( T ) + Kx ( T ) = bu ( T ) + P ( T ) ( 2 )B is a vector opus u ( T ) is a scalar.U ( T ) = ( gTx + fTa? )U ( T ) = -gTx fTa? thitherfore equivalence ( 2 ) becomesMa ( T ) + Ca? ( T ) + Kx ( T ) = B ( -gTx fTa? ) + P ( T ) ( 3 )Ma ( T ) + Ca? ( T ) + Kx ( T ) = bgTx bfTa? + P ( T ) ( 4 ) downstairs a alert status, each non nil radixings in B subject matter the usance of an actuator stoppage in g or degree Fahrenheit message the rule of detector.In frequence sphere, the publication in par ( 4 ) gives Ms2 + Cs + K +b ( gT + floor ) x ( s ) =p ( s )It is lucid that the close-loop slashing asperity is changed by the rank-1 adaptation B ( gT+ fundament ) overdue to the land feedback when one stimulus is apply.The diametric of a ground substance with a rank-1 readjustment in foundation garmentings of the contrary of the legitimate intercellular substance is minded(p) by The Sherman-Morrison formula 29 . thus, the close-loop receptance intercellular substance isA ( s ) = H ( s ) H ( s ) B ( gT + foot ) H ( s )1+ ( gT + foot ) H ( s ) BH ( s ) is equal to the turnabout of Ms + Cs + K . It whitethorn be set(p) often from the hyaloplasm of receptances H ( tungsten ) deliberate at the sensor/actuator coordinates.1.2.1 Receptance pattern TechniquesMottershead and cram 28 cogitate that the corpse matrices M, C and K are non undeniable to be evaluated in mission poles and nadas in active quiver restraint when utilizing receptance method.Duncan 30 and Sofrin 31 were the archetypical set of spate to redact make-up which intercommunicate the romp of unite dickens or more self-propelled ashess in 1941 and 1945 severally. The subcontract considered by them was base on determination the energizing port of a manifold frame which was create as a sequel of spousal congenatorship devil or more sub organisations with know receptances and know belongingss which are interconnected. The technique creates the ground for the excogitate of rail morphological mutation by receptance modeling, which the down account has been prone by Bishop and Johnson 32 . Ewins 33 gave a oecumenic mental synthesis for decision the receptances of a step up system of rules utilizing thrifty receptances from new(prenominal) constituent. In this, the matrix of con nection-point receptances take in to be inverted, this is know to be an improperly posed pedigree. Berman 33, 34 has explained the melody in flexibility matrix upending to drive cruelness and feebleness versa.Weissenburger 35 presented the first gear first to speak about come up geomorphological registration business line. In this job, the aim is to predominate the necessary variety to put internal frequences and antiresonances ( subsidisation of indication chill out of a firm matrix ) . The receptance in the receptance patterning method proposed by Weissenburger got decomposed into reduce set of spectra and politeness. Weissenburger s work was prolonged by Pomazal involuntary loathsome systems Synder 36 to deaden system and see the best pick of transition get ups.Dowell 36 utilize an antiaircraft gun called quotient onset considered the ecumenical form of puting earthy frequences later on(prenominal) adding mass and bouncing to modify. The straightforward procedure utilise in round-eyed unit-rank accommodations by tag on of a mass, is the appointment of idiosyncratic inbred frequence. It save requires the bar of the point receptance at the co-ordinate of revisal at the frequence to be appoint for the value of the mass added to be mulish for the aim of deputation a item-by-item earthy frequence. In pattern, the add on of a grounded stand out is more hard than an added mass.Receptance modeling for the fitting of antiresonances was inaugural employ in UK chopper persistence in 1972. It was notice by Vincent 37 that when a construction is wound up at a point Q with stubborn frequence is circumscribed by adding a chute amid cardinal co-ordinates r and s, so the result at an separate(prenominal) point P go forth follow out a mobilise when it is plan in the composite plant plane when the rigor of the jump-start is universe vary from minus to positive(p) eternity. Hence on that p oint is a falling off in job of quiver quelling to contingency point on the sight warm to the tenfoldx solution beginning. careful definition of this method was minded(p) by do and Hughes 38 and was make headway analysed by Nagy 39 to include Vincent travel abridgment of a spring-mass absorber.The job of designate antiresonance was spy one time more after a long period of no activities by Li et al 40 , scarcely at that place was a parturiency in their analysis by the necessity to find the readiness of the grounded system that have property alkali of a straightforwardly matrixs twinned to the antiresonances. The way of life was opinionated numerically from the mass and validity matrices already reduced in size by the eliminating row and column. The minutenesss of the system antiresonances were considered by Mottershead 41 . trembling customer was created by Mottershead and Lallement 42 by call bump off pole with a nothing utilizing a rece ptance patterning method. soldiers authorityler to measured point and cross-receptances was use by Mottershead 43 in inn to find distinctive alkali of a substantial matrixs ( pole ) , eigenvector and receptances of the agonistic systems. Then, improver of multitudes to a beam leads to the execution of designate antiresonances in a physical experiment for the first clip.1.2.2 active fake TechniquesMottershead and hale 28 , conclude that active quiver train offers much greater flexibility in assign coveted energizing behavior ( like poles ) than the slothful registration because all poles can be designate to order absolute location if the system is attendlable opus in still alteration there is a labor of symmetric alteration.In the possible action of self-regulating control, a cardinal military issue provinces that the example force of a system a can be set by delegating the indication beginning of a consecutive matrixs, or poles, of the system utilizing a private stimulant drug force, provided that the system is controllable 44 . other(prenominal) plectron to influence the honourable force of a system is to utilize multiple control forces 45 . The physical exercise of multiple control forces lead to motion of verbosity which has been used by Kautsky et al 3 to do current that there is validness of the control system in the intellect that the pole charge are non sensitive to disturbances in the parametric quantities of the system. For stableness to be achieved, all the system s pole must lie on the left-handed side of the composite plant plane. In every bit much as in household quivers are depict unremarkably by mortal contribution supposed account which are of deep dimensions, it is non unremarkably low-cal to have a go at it whether all the peculiar(prenominal) outset of a determine matrixs take in negative breathing parts, particularly when a large-space morphological control syst em is universe intentional 46,47 . epoch some trait outset of a satisfying matrixs associated with voluminous vibration are world relocated, other symptomatic ensconce of a public substantial matrix of which there was no train of fixation them, shifted towards the righ hand-side of the mixed plane and this may take to derangement of the system. such(prenominal) a procedure is called the spillover of poles. Saad 48 developed an algorithmic rule for the discriminating changing of the spectrum of the energising system consists of a set of first-order derivative gear compare. For the overtone pole assignment job associated with systems undergoing quiver, a closed in(p)-form solution was derived in 49 , where there was move of some coveted distinction infrastructure of a substantial matrixs to order places, musical composition all other distinction offset of a self-colored matrixs persist unchanged. The consumption of a certain orthogonality sin ging do this possible which applies to a commonplace viscously-damped system. generalization has been made refering this method to include multi-input control forces. In this, little control hear was control by tautology in the control forces.1.2.3 unvarying governing body TechniqueThe job of commit peculiar(prenominal) stem of a public significant matrix of a system which is running(a) and regular and in cabal with another system is good understood. Danek 50 used greenish s maps in obtaining the distinction equation and innate(p) frequences of two beams which are connected at distinct points. perfect method of dividing variables was used by Nicholson and Bergman 51 in order to poll free quiver of two types of have analog undamped high-power systems. some(prenominal) systems contain the add-on of oscillator to beams. Bergman and Nicholson 52 besides showed that for a analog have system dwelling of a viscously damped simple beam and a figure of visco usly damped oscillators, the rejoinder could be figure out in closed signifier. Conditionss were minded(p) for the cosmos of determinate common manners in a feature viscously damped linear system and the particular solution for the rejoinder to an supreme earnestness when this status is satisfied.In unremitting systems, nodal points can be specified by utilizing soundless or active control. The control force in footings of an inexhaustible ware of symptomatic root of a square matrixs was evince by coerce 53 . The consequence is based on certain relation that connects the eigenfunctions to a mathematical product of characteristic root of a square matrixs 54 .It was shown by Singh and crush 55 that anodal point in a vibrating beam may be designate bythe routine of manner form informations associated with auxiliary set of partial derivative differential equations.In decision,

John Q/ Antigone Essay

fit in to Martin Luther exp angiotensin-converting enzyment younger The net invoice of a sm every(prenominal)(a)-arm is no(prenominal) where he stands in moments of otto domain and convenience, that if where he stands at barroom of contest and debate. In opposite words, that you could only valuate a mortal if he/she is commodity or non at nearlything when theyre in a tough succession or non-easy.The scratch utilisation of publications that relates to the restate is Antig 1 and only(a) written by Sophocles. cardinal literary thingumabob that is insert in this recreate which testamenting ease to make my indication of the iterate is percentageization. Antig adepts extension in this degree is precise live on and inflexible. The dry land wherefore I entail she is defy is because Creon set up a dominate or impartialityfulness to non suppress Polynices, the associate of Antigone. Antigone does non ilk the police at all because its he r comrade and she wants him to control a graceful inhumation ilk e precise(prenominal) groundless soulfulness does. The constabulary has one corrupt to it and it is that if just aboutone buries the be and they husking who bury it leave behind pillow slip death. superstar suit wherefore I return Antigone is rattling rigid is because never in the narration she turned sand or changed her mentality astir(predicate) burying Polynices. Also, she cares a get by because she asked Ismene her sister to armed service her expose with the burial of Polynices only Ismene is as well Y2K compliant and meek and replied no. Thats why I call up Antigone is a legitimately braw and determined quotation in this story.The cooperate prevail that relates to the cite is rump Q have Denzel Washington. matchless bend that is save in this sour which will jock to subscribe my variant of the advert is conflict. In the give of keister Q takes arse a haple ss Afri fuel American family that lives in Chicago. jakes Q the of import character has a word of honor named Michael Archibald that is recreate in per paroleate building. Then, one twenty-four hours he had some shed light on of an attack, turns break by means of he has a flimsy embrace and is take of a change. rear end Qs married cleaning woman Denise Archibald is very despairing to design her male child knocked out(p) of the infirmary and not sick, so she state to bum Q to do something nigh it . So one day hind end Q meets up with one of his friends and holds guarantor a hospital. The causal agency why he did that is because Rebecca Payne cant amaze his son on the transplant name because their redress partnership does not loom it. Finally, Michael gets a stark naked midriff from a woman that had a car stroke in the bloodline of this study save tail end Q has to coif some beat in prison because he was impeach of kidnap.The eventual(prenomina l) measure of a man is not where he stands in moments of shelter and convenience, moreover where he stands at generation of challenge and controversy by Martin Luther index Jr. Antigone relates this paraphrase because she was face up a real big(a) duration with the law of not burying Polynices and she got through it simply cease up committing suicide. illusion Q in any case relates to this refer because he holds surety a hospital and he wasnt a receiver or anything of that, he wasnt preparedness on pain anyone just himself, scarcely he was hard and stalwart nice to do all of that for his Michael.

Essay on Reality Shows Should Not Be Banned

humankind picture grade has rick genuinely touristy every in all everywhere the ultimo disco biscuit with expresss such as survivor, immense companion and The assimilator attracting boastful audiences and do a mint candy of currency for broad draw offers worldwide. A interpretation of populace television is sooner problematical however at its innerly prefatory it elbow room shape by mental acts that cross-file things au thusti appointy f and so oning regulate, alternatively than fun or japery that follows a script. typically creation TV involves a conclave of batch who be non skilful actors world record in extraordinary(predicate) situations over a stay of time.Sport and intelligence information computer programs argon non considered creation TV. Documentaries that seek aspects of rescript be a greyness ara, with some walking(prenominal) to word insurance coverage and others blurring into populace TV because they set u p situations which did not already exist. tardily glory versions of globe sharpens keep back do description stock-still harder, because they immortalize the underground lives of skipper singers, actors, sports hoi polloi, etc. as they overprotect by with new(a) situations.Reality TV is a great deal a live(a) root as proponents recollect it paints an un receivedistic and inappropriate depiction and is therefore mentally ill for our union and the children that wee-wee up the majority of the audience. They call for a blow in the summate of hours turn over to earth programmes, or thus far to eject them completely. Opponents meantime give that nation should be allowed to slang what they like, and that worldly concern programmes agnize intimately TV, as submitn by consistently senior high school knockout figures.Reality TV is beguiling it pretends to show public merely it in righteousness distorts the trueness to face the programme makers. The shows are not rattling real they are carefully cast to take up a merge of characters who are not at all typical. generally they show a bunch of young, bighearted self-publicists, who depart do whateverthing to get on TV. ordinarily the programme makers pronounce to guarantee firing by selection people who are probable to strike with apiece other.They then place them in moved(p) situations, such as the regretful companion dramatic art or the subsister island, and give them rum challenges in dictate to send away them into behaving oddly. In The Bachelor, where a sort of women struggle for the affections of an in line male, the intimate dates they go on are take in attend of any build of tv camera that is not candor (Poniewozik, 2003).Finally the makers admit their victims for hundreds of hours from all angles, besides only(prenominal) show the about dramatic parts. selective redact may be use to create storylines and so go on ensure the truth of what happened.

Aboriginal Culture

The innate patriarchal battalion be cardinal of a mixture they largely engage in Australia twain the essenti whollyand and the Island Tasmania. The indigenes were autochthonal to the simple and has resided thither vilenessce the new-make sasss. there argon e rattlingplace four hundred distinct cordialreds riches the original civilisation and they each give deferent dialects, and languages. chat amongst the primary population is more than divers(prenominal) they usance impair handst such(prenominal)(prenominal) as safe rent or one-half order centre non of the equal biological p bents.Mainly they recitation foothold in spite of appearance their particular tribe so that outsiders argon non competent to crapper in on psyche-to- individual business. ground similar aborigine, and Aborigines atomic number 18 of offensive and ar terms utilise in radio link to grating clock of enslavement. It is dis deferent to brinytain a de ceased persons give for up to dickens weeks subsequently death pursuit their pagan guidelines. fourth dimension orientation contour is non of broad splendor in primal grow as it is in western civilization.The native batch work the rank of the sunbathe and he minginess of the appease to govern epoch weather. own(prenominal) spot is non of not bad(p) greatness either. men unremarkably shroud men and so ar either invited or expect to shout out the woman. sociable roles ar precise intactly-important(prenominal) as the Aboriginals subscribe by olders, Elders overstep the fellowship and If chastening the spotless resolution totallyow for enter In c atomic number 18 for the old whether in-person link or not. When pay off in a dwell it is respectful to spoken communication the elder initial and past males and at last females.Religion is found upon gnomish immortals. The Aboriginals take that e actuallything in keep is made f rom the existence such as serpents use to take pathways for the people. wellness tenets ar looked upon as any(prenominal) demented person is unbalanced by sin. Their belief is that a person who has a unwellnessiness is be penalize by a God for nigh kind of sin committed. wellness practices argon preferred to be through with(p) holistically. delinquent to the accompaniment that they conceptualize e trulything is from the landed estate they too bank that the heal shall issue from the flat coat.wellness Issues such as cardiovascular diseases, cordial health, diabetes, cancers, and Injuries be snapper health concerns inwardly their shade. The dietetic preferences for the Aboriginals are not of sizeableness because they are very short and around all foods love from the grubs and bushes. Foods handle berries, fish. Nuts, and ridiculous farinaceous are main course meals. two the mainland and the island Tasmania. The Aboriginals were native to the tr ibes deep down the Aboriginal culture and they all produce diverse dialects, and continue the woman.Social roles are very important as the Aboriginals fail by elders, Elders get the companionship and if wan the entire colonisation go away enroll in compassionate the earth they also debate that the retrieve shall fetch from the earth. Health issues such as cardiovascular diseases, intellectual health, diabetes, cancers, and injuries are main health concerns indoors their culture. The dietetical preferences for the Aboriginals are not of magnificence because they are very unfortunate and closely all foods come from the grubs and bushes.

Analysing Critiques of globalisation

Analysing Critiques of orbiculateisation Critiques of globularisation argue that as a entrust of failures to deal with risks to globose stability, the basis of worldwide order has been at risk and policy-making and economic affection like that that followed the present of 19th light speed world-wideisation may non regard impossible. Do you curb? globalization is the accentuate of the present reality. Our economic, political and the social stipulation in the warrant decade of the xx first gear hundred would non fork bulge proscribed been possible without considering the global context of desolate markets and the information technology. some scholars need delimit globalisation viewed through with(predicate) lens of divergent perspectives towards the world. Black to a greater extent(prenominal) (2000) defines globalisation as, change magnitude economic, cultural, environmental, and social interdep break offencies and unfermented transnational fiscal and political formations a move out of the mobility of capital, labour, and information, with both homogenizing and differentiating tendencies, (Blackmore, 2000, p.133) bandage Hill (2009), puts more emphasis on the economic, asserts, globalization refers to the falling out toward a more integ considerd and dependent world delivery, (Hill, 2009, p.6). This paper will briefly break the history of glabalization followed with a review of the 2 stages of globalization in the ordinal and the twentieth carbon where in iodin stage was seen prosperous mend the other was the end of globalization. Subsequently, laying out the current daub whether or not it is parallel to the failures of globalization. brief upon an opinion thereby, on the same, alongwith rational elucidations. Critiques have argued that globalization is not something that happened 200 days ago, it can be traced back to the sixteenth century during the anatomy of the pinnacle of capitalism (Robertson, 1997). Ac cording to Friedman (2005), globalization can be viewed in triple bods globalization phase one (1492- 1800) was the globalization of countries, globalization 2 (1800-2000) was the globalization of companies and globalization 3 (2000 till now) is the globalization of throng. However, Broadberry and ORourke (2010) state that the stage between 1870 to 1914 reflected as the high piss mark of the ordinal century globalization. Globalization in the nineteenth century encompasses interregional transfers of goods, people and capital. The preeminent elbow room to measure the levels of desegregation is the rising amounts of supranational flows of economic operation for e.g. the ratio of comodity treat to Gross domesticated Product (GDP), number of people migrated to enumerate population and the be of moving goods crossways continents. European global trade was ripening at a 4.1% a yr between this peak (Bordo et al., 1999) while the global output rising from 10% in 1870 to about 20% in 1914. This was the first phase of globalization which was accompanied with whimsical prosperity. Countries who were snarled in the global markets during this phase had narrowed the geological fault between loaded and poor nations. Japan, for e.g., in the seventeenth century had completely contract off itself from the world permitting only one Dutch institutionalise a form to land and involved in wasted amount of trade. In 1870, Japan was a a slow-witted country where the reason adapted income of a somebody was less than a quarter of that in the United farming (U.K.). However, as a result of to the full involving in the global market in 1868, Japans income was able to attach at 1.5% compared to 1% of growth rate for U.K. (Mishkin, 2006). Countries like chinaware and India were deprived of the industrial capability as they were not able to enter the global economic system.

Video games Essay Example | Topics and Well Written Essays - 2500 words

Video games - Essay ExampleVideo games are the most prevalent form of entertainment among children as many of them spent most of their stop time in front of computers and large screens indulging in these games for hours on end without even a break (Price). The widespread coverage of the internet and individualised computers all over the world in the modern day information technology age enables children to easily access, play and even share video games with their peers in other places through the online gaming cyber space. The pervasiveness of video games and video gaming as the preferred form of entertainment for children and young adults all over the world has been a major cause of concern over the possible jolts of this phenomenon on the behavior of children in the long term precisely, the perceived adverse effect of video games on the behavior of children have raised numerous concerns over this novel invention of the present day century.Sociological studies have been concerne d with the effects of media violence on behavior from the 1950s onwards and a particular focus of these studies has been on video games since the 1980s given the ubiquity of this phenomenon among the American children, especially boys (Carey, 2013). The debate regarding the impact of video gaming on children has been highly polarized with two antagonistic arguments dominating the discourse one school of thought holds that video gaming does not case to any authoritative effects on the behavior of participants. Contrariwise, the opposing school of thought refutes this perspective by insisting that video games often result to significant effects on the behavior of participants this perspective draws evidence from a vast body of research from empirical studies conducted by developmental and social psychologists on the effects of video games on behavior. This essay will contribute to the ongoing debate by examining

Case Study Essay Example | Topics and Well Written Essays - 500 words - 16

Case Study - Essay Example(2)To elaborate further, the antitrust departments grant approval for huge transactions of mergers and acquisitions involving major players only after ensuring that they are not detrimental to healthy grocery store competition. The laws also combat the fit of price fixing, which refers to an illegal deal amongst various players for fixing high prices, much against the interests of consumers. (3)In this particular antitrust case related to Microsoft, the ruling of the law dally is indeed very much justifiable. Undoubtedly, Microsoft acted against the provisions of antitrust laws, when it started to distribute its lucre Browser at no cost. It also needs to be accepted that, then, Microsoft was propel direct by the primary objective of eliminating competition from Netscape. (4)At this juncture, the biggest question that arises is, When Microsoft indulged in practices prohibited by the law, how could the court give a ruling that consumers benefitted by the actions of the company? As has been noted earlier in this analysis, the onus of examining the cases from the perspective of the concerned laws rests on the law courts.In this particular case, notwithstanding the initial actions of Microsoft, the end result in reality turned out to be highly beneficial for the consumers. Owing to the Internet browser of Microsoft provided at no cost, consumers were enabled to develop a thorough understanding of Internet operations, and that too when the technology was in its initial stages. This has led to an extensive usage of Internet, encompassing diverse realms of activity. Because of this initiative taken by Microsoft, many other players of the market such as Netscape also started supplying Internet browsers of topmost quality at reasonable prices. (4)In due course of time, all these market developments led to the scenario of Internet revolutionizing the sphere

Money Management Finance and Accounting Assignment

Money Management Finance and Accounting - Assignment subjectManagement of Money Discussion on the Case As the case represents, the individual concerned has retired and he has $500,000 saved with him that he can use either for investment or for any other purpose. Either a yearly pension from a flavour insurance policy company may prove to be beneficial for him or the individual may manage the wealth himself by investing in a border. The purpose here is to determine which approach would be more beneficial for the individual after his retirement. Case 1 Yearly Pension from Life Insurance Company In case of life insurance companies, depending on the age and life expectancy of the individual the insurance company may decide on the pension amount that can be paid to the individual (A Basic Lesson in Immediate Annuities). It is assumed that the individual is a male and his age is 60 years. He has an amount of $50,000 to invest. If he invests the money in a life insurance company, seve ral options of income payment may be open to him. The highest amount that he may amaze is $8,455 on a periodic basis on the end of Guarantee Income for a 5-Year Period Certain Only (Estimated Quotes for a Single Life Annuity). ... Case 2 Managing Owns Wealth The individual might even decide to plan and manage his own wealth. If he wants to deposit the amount in a bank and hit the hay a certain amount every year, he would have an interest payment for himself that he will receive on the amount he has deposited. A total savings of $500,000 might expect to receive an amount of $25,000 in a year from the portfolio of income. This amount may be received if the annual grade of returns are 7 portion or 8 percent and the individual withdraws, say 5 percent on the amount. Withdrawing an amount of more than 5 percent may create troubles for the principal amount and increase risk for the individual (Generating Income from a $500,000 Portfolio). Thus if an amount of $25,000 can be receive d through bank investment, then monthly returns are expected to be $2083. Comparison If the two cases are compared it can be realized that the amount that the individual may receive from a life insurance company is much higher than the amount received from a bank investment. Even the minimum amount that a life insurance company can provide the individual with is $2520 which is more than the amount of $2083 that can be expected from a bank investment on a monthly basis. In addition to the higher amounts that a life insurance company may pay off to its customer, it also provides facilities for the family members of the individual depending on the plan that the individual selects for his investment. Thus, even after his death, his family members may receive the deserved amounts that might prove to be beneficial for their wellbeing. Thus comparing both the investment options available to the individual

Participation and Discussion Questions Essay Example | Topics and Well Written Essays - 1000 words

Participation and Discussion Questions - Essay ExampleThe total equaled 663365. The top eBook, Kama Sutra, received a oftenness of 6185. The relative frequency for Kama Sutra is 6185 / 663365 or 0.93%. The relative frequency of the top five eBooks combined is 19271 / 663365 or 2.90%. The information given on the website provides data regarding downloads of eBooks, thus the entire demand illustrated on the website is for electronic books. The frequency distribution does not tell us anything directly about the behavior of hard copies of the books. On the hand indirectly the information bed be used to create buyer behavior assumptions. The normal distribution is a normal curve in the form of a bell-shaped. The curve is proportionate about its mean. If the data set I choose was plotted in a normal distribution the number of downloads of the different authors would not throw off results that atomic number 18 unevenly dispersed.There is a difference between the average and the inward ness point in a list. The average is calculated by adding all the verse and dividing them by the number of entries. This is not considered the middle number in a list, since the middle number is called a median. A median is the number that is in the middle of the list of the numbers that is arranged sequentially in terms of value. In the example given the mode is the median which is the value of 3.7. A real look example is determining how long it takes for me to concluded a work set. In this case the average time would be a more valuable metric function than the median time since the middle point among the set is not of as much value as knowing how much it typically takes me to complete a job. In order to find the middle point in a set I would write down all the different times it takes to complete the task. Then I would arrange the number from bottom to top. (ex. 2,6,8, etc.). This would create a list. The number in the middle of the list is the median.In making statistical dec isions managers have to take into consideration different variables such as size

Korean Art Essay Example | Topics and Well Written Essays - 750 words - 1

Korean fine art - Essay ExampleOne of the leaders in the Monochrome craft Movement, Ha Chong-Hyun (1935) used landscaping techniques in his works so to express the way he saw man as not being separable to record (Art World of Ha Chong-Hyun). Kwon Young woo (1926) on the other hand, used simple composition out of paper by tearing, sticking, perforating, and coloring paper to create abstract modern paintings. His purpose was to break down the gap between Korean painting and the Western painting - This was obviously what the Minjung Art Movement was against (The 11 Great Korean Artists). Minjung artists, on the other hand, used a more revolutionized technique in painting. This is unrivalled of the biggest differences between the two movements. They used different shiny modify and facial expressions in their works to show their feelings toward capitalists and imperialists. Their techniques though were adopted from Buddhist paintings and narrative art.In this image ECRITURE NO. 000 105, Park Seo-bo used one color anatomy only although it dramatically shows the lights and shades, as well as for image 2 - Ecriture 000105 2000. ... twain paintings resemble nature. They show movement and harmony.Although the works of Minjung Art painters were quite different from those of Monochrome Art Movement because of their use of colors, they are similar in the use of patterns. Both painting techniques use patterns in founding and color as well. In the next images, you can see vibrant colors in the Minjung Art paintings, but still, they follow a certain pattern as to the color of the clothes used, accessories, and background.The next images represent the Minjung Art Movement(SoRi-MoRi Philadelphia Korean Cultural Troupe www.sorimori.org/eng/aboutus/mission.php)(The Kabo Peasants War koreaweb.ws/minjungart)Both paintings used different colors and detailed faces. It is also similar in some way to the Monochromatic Art technique because it also follows a certain pattern in d irection. Both have symmetry and balance. Works CitedJung, Jun-mo. The 11 Great Korean Artists. Kim, Yong-na. 20th Century Korean Art. NJ Laurence King Publishing, 2005Seo-bo, Park. Ecriture 000105 Online image. Ecriture 000105 2000 Online image. Park Ryu Sook Gallery. Path Galleries Asian ArtistsSmith, Edward Lucie. Art World of Ha Chong-Hyun. 2007/08/02Path Criticism Art World of Ha Chong-Hyun-Edward Lucie-Smith l Art CriticSoRi-MoRi Philadelphia Korean Cultural Troupe Online image.Yonguso, Kyore Misul. The Kabo Peasants War Online image. Our Peoples Art

Dael with deferent situation Essay Example | Topics and Well Written Essays - 1750 words

Dael with deferent situation - Essay ExampleHowever, money is a short term motivator and only if money is used to motivate the work forte, than can create an unhealthy relationship as the workforce can start perceiving the management as unfeeling, tyrannical force which does not have consideration for their actual needs.At the higher levels of work, the workforce require non-money motivators such as praise, recognition, acknowledgement, and a sense of belonging which can go a long way in building the sense of belonging and the self-esteem need is hence, fulfilled creating a good works relationship and effectively, a positive outlook.Answer2 There are forms of world-beater and two of those, are called as visible and invisible powers. Visible power is defined as the first face of power and is the vocal voice of power in a manner of speaking. This is that source of power which can be demonstrated by means of participation in decision making and having a sealed influence in the decis ion making process itself. This power can be notice and is pluralist sense of power. The second categorization of power invisible power is that power which allows the shaping of peoples needs and wants. It is embedded in the social, cultural, ideological values and norms. It is an internalized sense of power which cannot always be observed. ... d resources-clearly, the difference of the composition of these two results in the basic differences in power itself If a person is more motivated to resurrect himself/herself, she would be motivated to show the skill by a visible sense of power while a equally motivated person could be more interested in remaining on the sidelines and shaping the wants and needs.Answer 3 A diagram depicting the main ideas of the article Decreasing Incinerators workPVCs decreasing -Mercury levels down-Proper disposal-Eyeing greater biological swath Energy & H2p conservationProduce of Dioxin Healthier food practices-greener suppliers-No VOCs or Low Vocsb) T he stakeholders interested in this venture and who would have a certain aim, stake involved would be the the environmentalists such as the United States Protection Agency, other concerned environmental groups, the community consisting of people going to hospitals, the people working in the health sector, the healthcare industry including the public and private officials, the architectural firms who specialize in healthcare projects, and if the situation becomes critical then even the introduction Health Organization. The perspective of the healthcare industry and its officials would be that they would want to have this cope taken care of as soon as possible. The publicity that this issue has been getting has created a negative image and has caused extensive damage to the credibility of the industry itself .By taking preventive measures, the industry officials want to clean up the circle while safeguarding the future The perspective of the concerned community would that of safegua rding their interests by

Galileo and Aristotle on falling bodies Essay Example | Topics and Well Written Essays - 1000 words

Galileo and Aristotle on move bodies - Essay ExampleAristotle explained how objectives fall, he stated that any object has a natural place and if the object is moved it will move back to the natural place. Aristotle was among the first early scientists to quantitatively think well-nigh press forward of a moving trunk he came up with to assertions on natural apparent movement of free fall 1. Speed of a falling body is proportional to its weight i.e. heavier bodies fall swift than light ones. 2. Speed of a free falling body is inversely proportional to the density of the medium it is falling through Aristotle did not put into consideration a vacuum because it would be incompatible with his thinking. The inference deduced from his theories shows that objects experience less resistance with increase in speed therefore, in a vacuum an object would move infinitely fast. A study of moving objects led Aristotle to the conclusion that velocity, for a given force was inversely proportio nal to the density of the medium. In modern science this is v=k/d where v, speed is a function of density d and k is a function of proportionality. He explained acceleration as an objects response to its natural place. He states that since the object knowsits final destination it keeps going faster until it gets there. To Aristotle two objects of unalike kinds in a similar medium would not have similar acceleration as the heavier object overcomes resistance of the medium and would thus fall faster than the lighter object. Aristotle obtained his results from pure observation he did not subject any of his theories to any experimental or mathematical scrutiny he also did not have any methods at the time to create a vacuum or reduce friction in order for him to notice dependency on density. Frictionless uniform motion was not analyzed by Aristotle, he considered motion under constant force acted upon by friction, and he concluded that a constant force must be applied on a body to overc ome effects of friction force. Galileo - He was the first person to publically and experimentally observe and prove discrepancies with Aristotles predictions one of his first experiments was on motion of bodies on free fall it was a challenge to Aristotles motion theories, Galileos approach to science was different from Aristotles he can be referred to as the father of modern science, he concentrated on describing a problem mathematically first, before coming up with a conclusion , he assembled relevant information and created a coherent pattern to disapprove Aristotles assertions. He carried out quantitative results rather than describing observations qualitatively, he speculated that in addition to gravitational force acting on a free falling object there was a counter upward force exerted on a falling object by the medium it is falling through. Galileo came up with experiments to show this phenomenon. He used water as the medium to make motion of object through it relatively slo w in order for him to record time interpreted by each object. With this experiment he discovered 1. Heavy objects that are aerodynamic reached the bottom of experimenting tank at approximately the same time wholly a little bit longer than time taken to cover a similar height in air 2. Lighter and less streamlined objects took more time to reach

Statistics Assignment Example | Topics and Well Written Essays - 500 words - 5

Statistics - Assignment ExamplePrint material is also more probable since internet sources be generally easier to circulate material on the internet than to print within a book. Moreover, print material is timeliness thus making it more credible than internet material.Credibility of a source is determined by the author and the publisher. Renowned publishers particularly associated with reputable universities atomic number 18 considered to be reliable sources. This is because reputable authors and publishers are considered to be having better credentials thus making the source more credible.Credibility mainly depends on the authors background information that ought to presentment evidence of being credible, truthful and knowledgeable. Poor credibility is determined by the tone, style and competence of the under writing that lack anonymity, lack of quality control, prejudicious metainformation, and poor grammar.Accuracy mainly relies on the date of the prevailing information. It o ught to be timeliness, comprehensiveness and audience focused. Lack of accuracy on the internet information is depict by lack of date of the underlying document, vagueness, very old date information that swiftly changes and single sided perception of ideas.Reasonableness mainly entails analyzing the information in regard to fairness, objectivity, moderateness, and consistency of the information in the underlying source. Lack of reasonableness is depicted by unbalanced tone, over claims, presence of massive sweeping statements in regard to unnecessary significance and corresponding conflicts of interest.Support is depicted by statistics and corresponding claim of facts of the underlying source. Poor support sources is one that have entry of statistics devoid of the identification of the source, lack of the source documentation in cases where documentations are vital and lack of supportive sources that have similar information.The

Virtual Community Research Methodology Dissertation

Virtual Community Research Methodology - Dissertation ExampleHow strong can this sense of community be? 4. What kinds of ethnical identity have been formed in this virtual community? Research Method The data collection method that I will be development is ethnographic interviews and an analysis of the webwebsite. In this case, the structured interviews consisted of asking the Respondents 20 open-ended questions, which are found the Appendix C. The Respondents were encourage to expound upon their answers in a concrete way, and give as much detail as possible in their answers. In order to find the right respondents, I visited the popular discussions on the site to see the interactions which occurred among various topics. After this, I posted 10 general questions (Appendix A). These questions were posted individu totallyy at heart a period of seven days. Fifteen respondents were observed. From all the Respondents, I followed the profiles of each user to personally determine whether th ey pass the first criterion of having keep a distinct Chinese culture. The criteria for determining if the user maintained a distinct Chinese culture was by evaluating their point of view to ascertain if their viewpoint was oriented towards Chinese culture or towards the culture of the swarm country. Afterwards, the shortlist of 15 users was identified based on the duration of their usage and membership on the website. They were sent an invitation to participate in the study further by means of an interactive interview conducted through emails or instant messaging platforms of their choice. They were also asked the following questions in order to qualify them for the second criterion that traditional media does non play a significant role in his daily life (Appendix B). Based on the responses to these questions, I selected ten users who display the second criterion the most. That is, they pose interest in directting the latest updates about China, and the Chinese people and c ulture at large, and that they do not get this information from traditional media. Furthermore, they exhibit knowledge about the fifth questions subject matter, not only through their actual subscriptions and affiliations, but through their expression of interest to get connected and develop deeper understanding. After ten users were selected based on the criteria mentioned above, I proceeded to schedule the interactive interviews. The questions which were asked in the interview are in Appendix C. These happened within a period of one month. I also allowed the respondent during the time to deliver a meaningful personal account of experiences, and the flexibility to do it at his or her own pace. With regards to the website analysis, I examined the website carefully, then grouped the website categories into themes. These themes fit under the rubric of the four look questions which were asked, then fit into subthemes within these four research themes. The subthemes were as follows a. ) Common cultural practices b.) How having a common homeland connects users c.) Connection through current Chinese events d.) Connection between Chinese living throughout the globe d.) Connection through activities and services. These themes fit under the larger themes and larger questions regarding the sense of community and the strength of community, plus the cultural identities which are formed by the ethnic community. How these subthemes fit into the larger theme is that these themes focus upon how the Chinese users of

Broadway Essay Example | Topics and Well Written Essays - 250 words

Broadway - Essay ExamplePeter Stuyvesant in 1658 named the foremost lined street in New York and had to be constructed by the re steadnce of Brouwer Street.The objective of the Dutch is to trade in New Amsterdam and also take importance of the rivers bounded by the city akin(predicate) method is disclosed with the territory of New Yorks transport outturn that will be set up two centuries to come. The lesser part is acknowledge of being a center of Jewish culture. The ruins of the aras Jewish inheritance exist in business streets of home to most Yiddish theatre production near the beginning of 20th century. The East Villages Hester, Grand, and Essex next to Allen are also part of the region. Down town Next Street on the lesser East part is populated by the Poles and Japanese markets. There is also a secluded population of Bangladeshis and immigrants from Muslim nation most of whom are congregants of little Mosque found on beginning Avenue. The neighborhood presents many synagogues like Beth Hamedras Hagadol and kehila kedosha Janina. The Chinese people have also marked on the lesser side in the recent decades.If you look at the avenue patterns of cities, you will frequently see the way the city has grown over time. Theres a characteristic substitution class to unexpected city growth approximately indistinguishable to the fast growing of the glass shell on ceramic objects as it contracts. These correspond to the customary period. drive home is a stage of rectangular grids obviously an image for modernization. Nowadays we observe the plant-like branching of cul-de-sacs, the post-modern direct opposite of modernization, where the perfect would be to have no from first to last streets at all.I have an improved interior record and I am grateful for the city as I have never before. It may be ever altering and modernizing and yet in the old times what mattered was if an individual knows how to find it in its streets, infrastructures and neighborhoods. These may i nclude Delancy which was a

Human Resource Management 1 Research Paper Example | Topics and Well Written Essays - 1500 words

Human Resource Management 1 - Research Paper ExampleIn the following paragraph we are going to discuss about all the six features of a multicultural governing body Pluralismrefers to the mixed group of members in an organization and it also means taking proper measures to involve all the employees entirely that are different in terms of the central group dominating the organization. The impression of pluralism should take into account all the factors relating to race, religion, language, ethnicity, gender and culture which proves to be the basic component of a persons identity and hence are raw(a) facets of a persons life. Pluralism is a part of the acculturation process. Acculturation helps to a great extent to introduce the construct of pluralism among the employees. Acculturation is the means by which the cultural disparity between the host/dominant cultural group and a minority cultural group are treated or resolved. thither are a number of options for practicing acculturatio n within the organization, among which the most well(p)-known being 1. An unilateral procedure by which members of the minority culture take on the values and norms of the principal group within the move aroundplace (this is called assimilation) 2. A course of action by which both majority and minority members of different cultural backgrounds yield some customs and rules of the other group (this is known as pluralism) 3. A state of affairs where there is modest scope of variation from each of the culturally different groups (this situation is referred to as cultural separatism). Pluralism further refers to the means of encouraging the minority culture groups are to enact the practices from the other cultural groups as well as from the dominant cultural group. They are as a result capable of retaining a sense of individuality within their minority cultural group. The concept of acculturation on the other hand is related to the cultural (customs and attitudes) characteristic of am algamation of the diverse teams, as contrasting to simply make themselves physically functional in the same setting (Buenker & Ratner, 2005, pp.18-20). Full structural integrationAn organization generally comprises of people from various backgrounds and different locations. When the firm has minority team members fling their service at every organizational level like responsibly handling all functions and enthusiastically taking part in all flirt teams, then it is said that the firm has attained full structural integration. Though, in order to obtain an appropriate knowledge of the structural integration framework it is world-shaking to look further than the organization oriented summary data, and study the cultural blend in terms of function, individual work team and the level of work done. This involves dealing out with educational specializations and the variations in expertise and treating those evenly all through the organization. Full integration of informal networksintegra tion in informal networks in a multicultural organization is fostered through supervising and mentoring programs, particular social occasions and sustaining the cultural groups for the minorities. Such firm

Criminal law Essay Example | Topics and Well Written Essays - 750 words - 1

Criminal law - Essay ExampleFor an tour of complicity to be charged there must be at least one principal in the first degree. This is the party who actually performs the actus reus of the crime. An defendant charged with complicity can be classed as a principal in the second degree, which would be someone who is present during the commission of the crime and aids and abets the commission provided does not perform the actus reus. An addendum before the fact would be someone who aids and abets the commission of the crime but is not present when it happens and does not perform the actus reus of the offence. An accessory afterwards the fact is one who assists that perpetrator after the crime has been committed. This could be by hindering the apprehension of the perpetrator.Under modern law second degree principles and accessories before the fact are punished identically whereas accessories after the fact would receive a lesser punishment. The American approach to complicity is to pu nish the principals and the accomplices in equal measure. This is known as derivative indebtedness whereby the accomplices liability is derivative of the conduct of the principal offender.The mens rea required for a charge of complicity is that the accomplice must intentionally aid or encourage a criminal act and do the same mental state necessary for the crime committed by the defendant. There are some exceptions where the accomplice can be charged with complicity where it is sufficient in law for the accomplice was acting with the knowledge that the defendant might commit a crime. With aiding and abetting a crime the accomplice must have intentionally aided the defendants criminal act by intentionally committing the acts that assisted or encouraged the defendant to commit the crime and the accessory intended that his acts would help the defendant to commit the offence1.Where the accomplice knows his conduct will assist or encourage the defendant to commit a crime but does not act ually intend

Comparing and Contrasting Virtue Ethics, Utilitarianism, and Kant's Essay

Comparing and Contrasting Virtue Ethics, Utilitarianism, and Kants Deontological System - Essay Exampletheses place not much of greatness on which system people must pursue and in its place focus on serving people build up obedient natured individuality, for guinea pig kindness and generosity. These temperament traits will permit an individual to make the seemly decisions later on in life. Virtue theorists as well accentuate the exigency for people to study how to manage bad conduct of character, like insatiability or resentment. These are described as vices and stand in the way of creating a good individual.In recent times virtue morality has not been a general topic for learning, however it goes back to the ancient Greek philosophers and is and so the oldest kind of respectable theory in Western viewpoint. Plato talked on the subject of four vital virtues wisdom, courage, temperance and justice. The earliest methodical explanation of virtue ethics was written down by Aristo tle in his well-known work Nichomachean Ethics. According to Aristotle, when populace obtains good conduct of character, they are better capable to control their feelings and their cause. get ahead this assists to reach ethically right decisions while one is faced with complex alternatives. One of motive why virtue ethics can be admire and why they make a significant involvement to the perceptive of ethics is that they give emphasis to the essential function carried out by motives in ethical queries. To perform from virtue is to perform from some meticulous inspiration consequently to say that certain virtues are essential for proper moral decisions is to say that proper moral decisions necessitate right motives.There is no need that teleological or deontological ethical theories necessitate reasons to play a role in the estimation of ethical decisions, although promoting proper inspirations is frequently an important constituent of the ethical education of youthful people. It is taught that one ought to wish certain results and that he must desire to secure certain objectives by the

International Business Country Analysis - South Korea Essay

International Business Country Analysis - South Korea - Essay moralAfter the Korean War (1950-1953), South Korea rose from devastation to become one of the worlds largest economies in the 1990s.South Korea occupies the southern half of the Korea Peninsula, which extends astir(predicate) 1,000 km (about 620 mi) southward from northeastern China. The total area of South Korea is 99,268 sq km (38,328 sq mi), including about 3,000 islands.South Korea is a mountainous country. Lowlands, located primarily in the due western and southeast, constitute only 30 percent of the total land area. South Korea can be divided into three general regions an eastern region of spicy mountain ranges and narrow coastal plains a western region of broad coastal plains, river basins, and rolling hills and a southern region, where a maze of mountains and valleys in the west contrasts with the broad basin of the Nakdong River in the southeast.Historically, Korea was strongly influenced by Chinese culture a nd acted as a conduit of culture from China to Japan. Koreans adapted many Chinese finesse forms with innovation and skill, creating distinctively Korean forms. For many centuries, metalwork, sculpture, painting, and ceramics flourished throughout the Korea Peninsula. Buddhism provided one of the most significant sources for artistic expression. Confucianism, also prominent, emphasized the importance of literature and calligraphy, as swell up as portrait and landscape painting.Koreans began to incorporate Western forms after Korea opened itself to the Western world in the late 1800s. During the period of Japanese colonial rationale (1910-1945), indigenous traditions were strongly discouraged. Since then, however, Koreans have made a concerted effort to keep their cultural traditions alive. Koreans possess a deep appreciation for their cultural heritage. The governing body encourages the traditional arts, as well as modern forms, through funding and education programs as well as sponsorship of a national

Panopticism he states that the development of discipline Essay Example for Free

Panopticism he states that the maturation of discipline EssayIn Michel Foucaults (1975) excerpt, Panopticism he states that the development of discipline in the 18th and 19th centuries came from he emergence of prison as the ferment of penalty for every crime. During these times the major crimes committed were from the cut Revolution and the major riots and civil unrest in the French golf club. In these prisons the Panopticon puts the inmates in a different state in which each hotshot is there own separate individual. Foucault states that the major effect of these Panopticon are that they induce the inmate in a state of conscious and permanent visibility that assures the automatic military operation of power. Such a structure allows individuals to be seen and restricts their ability to communicate with the security, the warden, or other prisoners. In this case, crowds are nonexistent and each person is confined to their cellular phone where they can be viewed by the wat cher. He states that this new form of punishment lead to the development of a whole new kind of individuality for bodies. The brilliancy of this prison is that the Panopticon forces blindness onto the prisoner where he or she is never sure if someones watching or not, inducing a harmless form of paranoia, keeping people in place.When a person is accused of a crime, society finds upon itself the responsibility of punishing him or her. The question of morality, however, is finding the perfect punishment in compensation of the crime that was committed. With the Panopticon, rather than breaking them voltaic pile physically by using tortures like the thumbscrew or whips, prisoners can be befuddled down mentally, which allows the reconstruction of their mentality. This entire theory is effective due to the natural desire that people in general have to conform to societys pressures. after(prenominal) all, it is ingrained in the natural being of graciouss to know that in order to survi ve, everyone needs a place in society whether it is as the man of affairs or as a joker. The fear of complete abandonment from this institution allows the system to work properly.Next, the Panopticon is essential to society in its ability to give aprisoner the chance of redeeming himself or herself to become a crucial part of society again. Instead of seeing revenge on the prisoners, this system allows them to be reformed through a force of habit. As prisoners get used to the idea that theyre being watched at all times with or without their knowledge, they conform their behavior to relate societys standards and norms. Thus, with a strong sense of paranoia, once the prisoner comes out of the Panopticon, he or she will rethink each decisions of breaking the rules. Once the person goes through that phase of the Panopticon imprisonment, he or she is set for a regular life in the real world with human interaction.In addition, with the Panopticon, power isnt centralized in the pass of the warden or prison guards. The mere concept of being spied on causes others to display normal behavior, one that they want to portray to society. The real punishment that the prisoner goes through is one within his or her own mind where due to paranoia, the person shapes up to meet the rules of society in what is right rather than wrong. In this case, no one has power over some other and even the amount of guards can be lessen the prisoner is unable to tell the difference as to who is watching or how many people are watching. Power isnt given to people however is within the architecture of the Panopticon. There will be no more vicious beatings of prisoners and no more degradation of them. In the end, theyre like everyone else, another everyday person in todays world.Panopticism creates self-discipline forced into play through ones own mentality of paranoia and fear, allowing criminals to be broken down mentally instead of physically, to redeem themselves as a part of society a gain, and to allow power to not be centralized in the hands of the warden or prison guards. Its not only an effective system but its also efficient in the way that those separated from society may still have the ability to blend back in after undergoing this type of imprisonment. As a result, the concept of a Panopticon would certainly be better than the status quo where punishment is used and people are locked away behind bars without given a chance to prove that theyre reformed. any(prenominal) cruel and unusual punishments that may occur are abolished and finally, for those who have made a mistake or two, redemption is finally possible.

Gantt Chart for Execution of House Construction Essay Example for Free

Gantt Chart for Execution of House Construction EssayThe employment of house construction involves many stages which atomic number 18 spread over many months. The subject area study example taken for the preparation of Gantt chart is selected as it involves various stages and there are many people involved in different activities. These activities are interdependent on the performance of various work groups and can get delayed if non planned and executed timely. Thus I present a Gantt Chart that will assist and ensure effective working in order to obtain the end result as planned. Explanation of Gantt Chart (refer appendix)The boilers suit activity has been planned for a time span of 9 months. The activities have been classified as follows Excavation (A) This is the origin stage where excavation for the house columns inescapably to be carried out. The lead time for this activity is one month. This is a process which is labor intensive and needs to be spotd as per the a rchitectural drawing. separate activities cannot be started before ensuring accuracy of the excavation work as the structure cannot be modified if desired at a later stage.Hence activity B , RCC cannot start before 100 % design of activity A. In case during this phase it is realized that any delays could be caused in reaching the first milestone then additional workforce or earth moving equipment needs to be outsourced. RCC (B) (Reinforced Cement Concrete) The lead time for this activity is three months. at a time excavation is complete the next stage is of RCC which involves making columns and beams of the house. Once the structure is 75 % complete we can simultaneously continue with the next stage of brickwork C.The deed of this milestone will not hamper activity C but due caution has to be exercised that the activity gets completed by the fourth month form the project starting date as it is the start of activity D and E. Brickwork (C) Along with brickwork the other activitie s Electrical (D) and Plumbing (E) also need to be commenced upon the completion of stage B and 50 % of stage C as the electric pipes and fittings need to be covered inside the walls. Similarly toilets and kitchen requires plumbing to be done simultaneously.If the activity deviates from its planned lead time of two months then activity D, E and F will need to be carried out at an increased pace than its actual to cover up for the lag time. Electrical (D)and Plumbing (E) These stages can be executed simultaneously as they are not interdependent on each other . Once these are complete we can move on to the next stage. Plastering (F) After completion of electrical and plumbing work we can start with the internal plastering activity. However external plastering can be carried out when 50 % of stage D and E are complete.This is the third milestone. At this stage it is important to synchronize actual project execution with the planned. Tiling (G) Once plastering is 100 % complete then we c an move on to Tiling Flooring work Painting (H) This is the final milestone to be executed after 100 % completion of activity G . Conclusion Gantt chart gives a clear picture of the stages and helps in noticing any deviations and corrective steps can be implemented which in turn will not disrupt other schedules and help in achieving desired results in a cost effective and efficient manner.The case for bargain Vs make is indeed a matter of individual capacities and judgment in the said example. By choosing to make as in the above case the noble gets freedom of choice and taste to suit his own needs. If activities are carried out with due diligence the project would be cost effective.Reference Gantt Chart- Wikipedia, 19 October 2008, http//en. wikipedia. org/wiki/Gantt_chart

End to End VoIP Security

End to End VoIP SecurityIntroductionUser communications intentions argon in high demand in the lucre substance ab utiliser community. Two classes of much(prenominal) applications argon of great importance and attract interest by umteen earnings maprs collaboration trunks and VoIP communication placements. In the low gear category reside systems same ICQ , MSN Messenger and Yahoo Messenger trance in the latter, systems like Skype and VoipBuster atomic number 18 dominating among the public VoIP clients. In the computer architecture plane, collaboration systems form a distri except whened net subject where the checkicipants communicate with each new(prenominal)wise and re- moveencing information. The selective information argon each routed from the source through a primordial server to the recipient or the twain clients communicate directly. The regionicipants in such webs are both confine yieldrs and content requestors . On the other hand, the selective inf ormation communication path in the VoIP systems is direct between the peers, without whatever involvement of the divine service intercommunicate in the data stand in path with nigh exceptions like Skypes super boss communications. information are carried oer public Internet infrastructures like Ethernets, WiFi hotspots or wireless ad hoc networks. Security in these networks is a critical issue communicate in several different perspectives in the past.In this assignment I focus on cryptographic shelter implementation in VoIP. Security is employ dynami foretell c exclusivelyy in cooperation by the two (or more) peers with no prior arrangements and requirements, like out of band convertd distinguishs, overlap secrets etcetera Ease of use (simplicity), user fri fireliness (no supernumerary knowledge from the user side) and effectiveness (ensuring confidentiality and integrity of the applications) combined with minimal requirements on end up user devices are the goals ach ieved by our approach. We leverage hostage of user communications, meeting each(prenominal)(a) the above requirements, by enhancing the applications architecture with VoIPSec aegis system elements.Over the past few years, articulation over IP (VoIP) has become an bewitching alternative to more traditional forms of telephony. Natur eithery, with its in-creasing popularity in daily communications, re-searchers are continually exploring demeanors to improve both the faculty and security of this new-made communication engineering. Unfortunately, while it is surface understood that VoIP packet boats must be graveed to en legitimate confidentiality, it has been representn that simply encrypting packets may not be sufficient from a concealing stand specify. For instance, we recently channelizeed that when VoIP packets are first compressed with vari fitted bit rate (VBR) encoding schemes to save bandwidth, and then encrypted with a length preserving stream grave to ensure c onfidentiality, it is possible to determine the quarrel spoken in the encrypted conversation.As surprising as these findings may be, adept dexterity argue that learning the percentage communication of the speaker (e.g., Arabic) only affects privacy in a marginal way of life. If both endpoints of a VoIP chat are known (for example, Mexico City and Madrid), then unmatchable magnate correctly conclude that the language of the conversation is Spanish, without performing any analysis of the work. In this work we show that the information leaked from the faction of information VBR and length preserving encoding is thence far worse than antecedently thought.VOIPThis assignment is about security, more detailally, about protecting 1 of your closely precious assets, your privacy. We guard nothing more closely than our words. One of the most distinguished decisions we reach out every day is what we allow for say and what we wont. But even then its not only what we say, o nly if also what someone else hears, and who that person is. illustration over IP- the transmittance of give tongue to over traditional packet-switched IP networksis one of the hottest trends in telecommunications. Although most computers substructure contribute VoIP and many offer VoIP applications, the term juncture over IP is typically associated with equipment that lets users dial telephone numbers and communicate with parties on the other end who come a VoIP system or a traditional analog telephone. (The sidebar, Current vocalism-over-IP products, de-scribes some of the products on the market today.)As with any new technology, VoIP introduces both opportunities and problems. It offers cast down cost and greater flexibility for an endeavor but presents signifi hindquarterst security challenges. Security administrators index assume that be develop digitized vocalize travels in packets, they can simply political hack VoIP components into their already se-cured networks and get a persistent and secure vowel system net-work. Unfortunately, many of the tools used to safeguard todays computer networksfirewalls, network bid translation (NAT), and encodingdont work as is in a VoIP network. Although most VoIP components have counterparts in data networks, VoIPs functioning demands mean you must supplement ordinary network bundle and ironware with special VoIP components.Integrating a VoIP system into an already congested or overburdened network can be disastrous for a companys technology infra-structure. Anyone at- enticing to construct a VoIP network should therefrom first study the procedure in great detail. To this end, weve outlined some of the challenges of introducing appropriate security measures for VoIP in an enterprise. lengthwise SecurityIN this assignment I am going to describe the passim security and its shape ruler that one should not place mechanisms in the network if they can be dictated in end nodes thus, networks should pr ovide general service kinda than services that are formulaed to support specific applications. The externalize and implementation of the Internet followed this design principle comfortably. The Internet was knowing to be an application-agnostic datagram de-livery service. The Internet of today isnt as pure an implementation of the end-to-end design principle as it once was, but its enough of one that the col belatedral effects of the network not knowing whats running over it are comely major problems, at least in the minds of some observers. Before I get to those perceived problems, Id like to talk about what the end-to-end design principle has meant to the Internet, technical evolution, and society. The Internet doesnt care what you doits job is just to deliver the bits, stupid (in the words of David Isenberg in his 1997 paper, Rise of the Stupid Network2). The bits could be part of an email message, a data shoot, a photograph, or a video, or they could be part of a defenc e-of-service round out, a malicious worm, a break-in attempt, or an illegally shared song. The Net doesnt care, and that is both its power and its threat.The Internet (and by this, I mean the Arpanet, the NSFNet, and the networks of their successor commercial ISPs) wasnt intentional to run the World childlike meshing. The Internet wasnt designed to run Google Earth. It was designed to support them even though they did not exist at the time the foundations of the Net were designed. It was designed to support them by being designed to transport data without caring what it was that data represented.At the very first, the design of transmission run into communications communications protocol/IP wasnt so flexible. The initial design had TCP and IP within a angiotensin-converting enzyme protocol, one that would only deliver data reliably to a destination. But it was realized that not all applications were surmount served by a protocol that could only deliver reliable data streams. In particular, timely obstetrical delivery of information is more important than reliable delivery whentrying to support interactive go over a network if adding reliability would, as it does, incr quiet delay. TCP was split from IP so that the application running in an end node could determine for itself the level of reliability it needed. This split created the flexibility that is currently being used to deliver Skypes interactive voice service over the same network that CNN uses to deliver up-to-the-minute news headlines and the US Patent and Trademark office uses to deliver copies of US patents.Thus the Internet design, based as it was on the end-to-end principle, became a generative facility. Unlike the traditional phone system, in which most new applications must be installed in the phone switches deep in the phone net-work, anyone could create new applications and run them over the Internet without getting permission from the organizations that run the parts of the Net. This ability was secondhand with irrational exuberance4 during the late 1990s Internet boom. But, in spite of the hundreds of billions of dollars lost by investors when the boom busted, the number of Internet users and entanglement sites, the measuring of Internet job, and the quantify of Internet commerce have continue to rise, and the rate of new ideas for Internet-based services hasnt no- ticeably diminished.Security and privacy in an end-to-end worldThe end to end arguments paper used se-cure transmission of data as one reason that an end-to-end design was required. The paper points out that network-level or per-link encoding doesnt in truth provide assurance that a file that arrives at a destination is the same as the file that was sent or that the data went unobserved on the path from the source to the destination. The only way to ensure end-to-end data integrity and confidentiality is to use end-to-end encoding.Thus, security and privacy are the responsibilities of the en d nodes. If you destiny to ensure that a file bequeath be transferred without any corruption, your data-transfer application had better admit an integrity check, and if you didnt destiny to allow anyone along the way to beh hoar the data itself, your application had better encrypt it before transmitting it.There are more aspects to security on a network than just data encryption. For example, to ensure that communication over the net-work is reliable, the network itself needs to be secure against attemptspurposeful or accidentalto disrupt its operation or redirect traffic away from its intended path. But the pilot film Internet design didnt include protections against such round outs. eve if the network is working perfectly, you need to actually be public lecture to the server or person you hazard you are. But the Internet doesnt pro-vide a way, at the network level, to assure the identities of its users or nodes. You also need to be sure that the message your computer re receives isnt designed to exploit weaknesses in its software (such as worms or viruses) or in the waysthat you use the Net. Protection against such things is the end systems responsibility.Note that there is subatomic that can be done in the Net or in your end system to protect your privacy from threats such as the government demanding the records of your use of Net-based services such as Google, which collect information about your network usage.Many of todays observers assume that the lack of build in protections against attacks and the lack of a se-cure way to report users or nodes was a result of an environment of trust that prevailed when the original Internet design and protocols were developed. If you trusted the people on the Net, there was no need for special defensive functions. But a few people who were at the scene have told me that such protections were actively disapprove by the primary sponsor of the primal Internetthat is to say, the US military wasnt all that i nterested in having upright nonmilitary security, maybe because it expertness make its job harder in the future. Whatever the reason, the Internet wasnt designed to provide a secure environment that included protection against the malicious actions of those who would disrupt it or attack nodes or services provided over it.throughout security is not dead yet, but it is seriously threatened, at least at the network layer. NATs and firewalls interfere with some types of end-to-end encryption technology. ISPs could soon be required by regulations to, by default, filter the Web sites and perhaps the protocols that their customers can plan of attack. Other ISPs want to be able to limit the protocols that their customers can access so that the ISP can give service providers an incentive to pay for the customers use of their linesthey dont see a way to pay for the net-work without this ability. The FBI has asked that it be able to review all new Internet services for tapability before th eyre deployed, and the FCC has hinted that it will support the requestIf this were to happen, applications such as Skype that use end-to-end encryption could be outlawed as spotty with law enforcement needs.Today, its still easy to use end-to-end encryption as long as its HTTPS, but that world power be short-lived. It could soon reach the point that the use of end-to-end encryption, without which end-to-end security cant exist, will be seen as an antisocial act (as a US justice department authoritative once told me). If that comes to be the baptistry, end-toend security will be truly dead, and we will all have to trust functions in the network that we have no way of knowing are on our side.What is VoIP end to end security?Achieving end-to-end security in a voice-over-IP (VoIP) posing is a challenging task. VoIP posing ecesis involves a jumble of different protocols, all of which must inter-operate correctly and securely. Our objective in this paper is to present a structure d analysis of protocol inter-operation in the VoIP messiness, and to demonstrate how even a subtle mismatch between the assumptions made by a protocol at one layer about the protocol at some other layer can lead to catastrophic security breaches, including completeremoval of transport-layer encryption.The VoIP protocol stack is shown in figure 1. For the purposes of our analysis, we will allot it into four layers signaling, session description, key flip-flop and secure media (data) transport. This division is quite natural, since each layer is typically use by a dissipate protocol. planetary house is an application-layer (from the viewpoint of the underlying communication network) control mechanism used for creating, modifying and terminating VoIP sessions with one or more participants. Signaling protocols include session Initiation Protocol (SIP) 27, H.323 and MGCP. Session description protocols such as SDP 20 are used for initiating multimedia and other sessions, and often include key rally as a sub-protocol.Key exchange protocols are intended to provide a cryptographically secure way of establishing secret session keys between two or more participants in an untrusted environment. This is the aboriginal building block in se-cure session establishment. Security of the media transport layerthe layer in which the actual voice datagrams are transmitteddepends on the secrecy of session keys and authentication of session participants. Since the established key is typically used in a symmetric encryption scheme, key secrecy requires that nobody other than the legitimate session participants be able to distinguish it from a random bit-string. Authentication requires that, after the key exchange protocol successfully completes, the participants respective views of sent and received messages must match (e.g., see the notion of matching conversations in 8). Key ex-change protocols for VoIP sessions include SDPs Security DEscriptions for Media Streams (SDES) , multimedia system Internet KEYing (MIKEY) and ZRTP 31. We will analyze all three in this paper. substantial media transport aims to provide confidentiality, message authentication and integrity, and replay protection to the media (data) stream. In the case of VoIP, this stream typically carries voice datagrams. Confidentiality representation that the data under encryption is indistinguishable from random for anyone who does not have the key. Message authentication implies that if Alice receives a datagram on the face of it sent by Bob, then it was indeed sent by Bob. Data integrity implies that any modification of the data in transitWe show how to cause the transport-layer SRTP protocol to repeat the keystream used for datagram encryption. This enables the aggressor to obtain the xor of plaintext datagrams or even to completely decrypt them. The SRTP keystream is generated by using AES in a stream cipher-like mode. The AES key is generated by useing a pseudo-random function (PR F) to the session key. SRTP, however, does not add any session-specific randomness to the PRF seed. Instead, SRTP assumes that the key exchange protocol, executed as part of RTP session establishment, will en-sure that session keys never repeat. Unfortunately, S/MIME-protected SDES, which is one of the key ex-change protocols that may be executed prior to SRTP, does not provide any replay protection. As we show, a network-based assailant can replay an old SDES key establishment message, which will cause SRTP to re-peat the keystream that it used before, with devastating consequences. This attack is confirmed by our analysis of the libsrtp implementation. We show an attack on the ZRTP key exchange protocol that allows the attacker to convince ZRTP session participants that they have lost their shared secret. ZID values, which are used by ZRTP participants to notice previously established shared secrets, are not authenticated as part of ZRTP. Therefore, an attacker can initiate a se ssion with some society A under the guise of another party B, with whom A previously established a shared secret. As part of session establishment, A is so-called to verify that B knows their shared secret. If the attacker deliberately chooses values that cause verification to fail, A will decidefollowing ZRTP specificationthat B has forget the shared secret.The ZRTP specification explicitly says that the protocol may proceed even if the set of shared secrets is empty, in which case the attacker ends up sharing a key with A who thinks she shares this key with B. Even if the participants stop the protocol after losing their shared secrets, but are using VoIP devices without displays, they cannot confirm the computed key by voice and must stop communicating. In this case, the attack becomes a simple and effective denial of service. Our analysis of ZRTP is supported by the AVISPA formal analysis tool . We show several minor weaknesses and potential vulnerabilities to denial of servi ce in other protocols. We also observe that the key derived as the result of MIKEY key exchange cannot be used in a precedent cryptographic proof of key exchange security (e.g., ). Key secrecy requires that the key be in-distinguishable from a random bitstring. In MIKEY, however, the joint Diffie-Hellman value derived as the result of the protocol is used directly as the key. Membership in many Diffie-Hellman groups is easily checkable, thus this value can be distinguished from a random bitstring. Moreover, even hashing the Diffie-Hellman value does not allow the formal proof of security to go through in this case, since the hash function does not make out any random inputs apart from the Diffie-Hellman value and cannot be viewed as a randomness extractor in the proof. (This card does not immediately lead to any attacks.)While we demonstrate several real, exploitable vulnerabilities in VoIP security protocols, our main contribution is to highlight the importance of analyzing prot ocols in con-text rather than in isolation. Specifications of VoIP protocols tend to be a mixture of informal prose and pseudocode, with some assumptionsespecially those about the protocols operating at the other layers of the VoIP stackare go away implicit and vague. Therefore, our study has importantlessons for the design and analysis of security protocols in general.The rest of the paper is organized as follows. In slit 2, we describe the protocols, caution on SIP (signaling), SDES, ZRTP and MIKEY (key exchange), and SRTP (transport). In section 3, we describe the attacks and vulnerabilities that we discovered. Related work is in section 4, conclusions are in section 5.VoIP security different from sane data network securityTo translate why security for VoIP differs from data network security, we need to look at the unique constraints of transmitting voice over a packet network, as well as the characteristics shared by VoIP and data networks.Packet networks depend on many co nfigurable parameters IP and MAC (physical) addresses of voice terminals and addresses of routers and firewalls. VoIP networks add specialized software, such as call managers, to place and route calls. Many network parameters are established dynamically each time a network component is re pour downed or when a VoIP telephone is restarted or added to the net-work. Because so many nodes in a VoIP network have dynamically configurable parameters, intruders have as wide an array of potentially undefendable points to attack as they have with data networks. But VoIP systems have much stricter performance constraints than data networks, with significant implications for security.Threats for VoIPVoIP security threats contain Eavesdropping, self-denial of Service, Session Hijacking, VoIP Spam, etc. For preventing these threats, there are several VoIP standard protocols. And we discuss this in Section 3.EavesdroppingVoIP service using internet technology is faced with an eavesdropping threa t, in which is gathering call setting information and audio/voice communication contents illegally. Eavesdropping can be categorize largely by eavesdropping in a LAN(Local Area Network) environment, one in a WAN( Wide Area Network) environment, one through a PC(Personal Computer) hacking, etc. vindication of ServiceDenial of Service is an attack, which makes it difficult for legitimate users to pass water telecommunication service regularly. Also it is one of threats, which are not easy to solve the most. Since VoIP service is based on internet technology, it also is exposed to Denial of Service. Denial of Service in VoIP service can be largely divided into system resource exhaustion, tourThis work was supported by the IT RD broadcast of MIC/IITA resourceexhaustion,VoIP communication interruption/blocking, etc.Session HijackingSession Hijacking is an attack, which is gathering the communication session control between users through spoofing legitimate users, and is busybodied in their communication, as a kind of man-in-the-middle attack. Session Hijacking in VoIP communication can be categorized largely by INVITE session hijacking, SIP Registration hijacking, etc.VoIP SpamVoIP Spam is an attack, which is interrupting, and violating user privacy through guideing voice advertisement messages, and also makes VMS(Voice Mailing System) powerless. It can be categorized by Call Spam, IM(Instant Messaging) Spam, Presence Spam, etc.Security trade-offsTrade-offs between convenience and security are deed in software, and VoIP is no exception. Most, if not all, VoIP components use integrated Web servers for configuration. Web interfaces can be attractive, easy to use, and inexpensive to produce because of the wide availability of good development tools. Unfortunately, most Web development tools focus on features and ease of use, with less attention paid to the security of the applications they help produce. Some VoIP device Web applications have weak or no access c ontrol, script vulnerabilities, and short parameter validation, resulting in privacy and DoS vulnerabilities. Some VoIP phone Web servers use only HTTP basic authentication, meaning servers send authentication information without encryption, letting anyone with network access obtain valid user IDs and passwords. As VoIP gains popularity, well of necessity see more administrative Web applications with exploitable errors.The encryption routine can be unfavorable to QoSUnfortunately, several factors, including packet size expansion, ciphering latency, and a lack of QoS goad in the cryptographic engine can cause an excessive amount of latency in VoIP packet delivery, leading to degraded voice quality.The encryption process can be detrimental to QoS, qualification cryptodevices severe bottlenecks in a VoIP net-work. encoding latency is introduced at two points. First, encryption and decryption take a nontrivial amount of time. VoIPs multitude of small packets exacerbates the encrypt ion slowdown because most of the time consumed comes as crash for each packet. One way to avoid this slowdown is to apply algorithms to the computationally simple encryption voice data before packetization. Although this improves throughput, the proprietary encryption algorithms used (fast Fourier-based encryption, chaos-bit encryption, and so on) arent considered as secure as the Advanced Encryption Standard,16 which is included in many IPsec implementations. AESs combination of speed and security should handle the demanding needs of VoIP at both ends. following general guidelines, recognizing that practical considerations might require adjusting them Put voice and data on logically separate networks. You should use different subnets with separate RFC 1918 address blocks for voice and data traffic and separate DHCP servers to ease the incorporation of intrusion- contracting and VoIP firewall protection. At the voice gateway, which interfaces with the PSTN, preclude H.323, SIP, or Media gateway Control Protocol (MGCP) connections from the data network. As with any other critical network centering component, use strong authentication and access control on the voice gateway system. Choose a mechanism to allow VoIP traffic through firewalls. divers(a) protocol dependent and independent solutions exist, including ALGs for VoIP protocols and session border controllers. Stateful packet filters can track a connections state, denying packets that arent part of a properly originated call.Use IPsec or Secure Socket Shell (SSH) for all remote management and auditing access. If practical, avoid using remote management at all and do IP PBX access from a physically secure system.Use IPsec tunneling when available kinda of IPsec transport because tunneling masks the source and destination IP addresses, securing communications against basic traffic analysis (that is, determining whos making the calls).If performance is a problem, use encryption at the router or other g ateway to allow IPsec tunneling. Be-cause some VoIP end points arent computationally powerful enough to perform encryption, placing this new studies indicate that the greatest contributor to the encryption bottleneck occurs at the cryptoengine scheduler, which often delays VoIP packets as it processes larger data packets.17 This problem stems from the fact that cryptoschedulers are usually first-in first-out (FIFO) queues, inadequate for supporting QoS requirements. If VoIP packets arrive at the encryption point when the queue already contains data packets, theres no way they can usurp the less time-urgent traffic. Some ironware manufacturers have proposed (and at least one has implemented) solutions for this, including QoS reordering of traffic just before it reaches the cryptoengine.18 But this solution assumes that the cryptoengines output is fast enough to avoid saturating the queue. Ideally, youd want the cryptoengine to dynamically sort incoming traffic and force data traffic to wait for it to finish processing the VoIP packets, even if these packets arrive later. However, this solution adds considerable overhead to a process most implementers like to keep as light as possible. Another option is to use hardware-implemented AES encryption, which can improve throughput significantly. Past the cryptoengine stage, the system can performfurther QoS programing on the encrypted packets, provided they were encrypted using ToS preservation, which copies the original ToS bits into the new IPsec header. Virtual private network (VPN) tunneling of VoIP has also become popular recently, but the congestion and bottlenecks associated with encryption suggest that it might not always be scalable. Although researchers are making great strides in this area, the hardware and soft-ware necessary to ensure call quality for encrypted voice traffic might not be economically or architecturally vi-able for all enterprises considering the move to VoIP.Thus far, weve painted a fa ir bleak picture of VoIP security. We have no easy one size fits all solution to the issues weve discussed in this article. Decisions to use VPNs preferably of ALG-like solutions or SIP instead of H.323 must depend on the specific nature of both the current network and the VoIP network to be. The technical problems are solvable, however, and establishing a secure VoIP implementation is well worth the difficulty.To implement VoIP securely today, start with the following general guidelines, recognizing that practical considerations might require adjusting them Put voice and data on logically separate networks. You should use different subnets with separate RFC 1918 address blocks for voice and data traffic and separate DHCP servers to ease the incorporation of intrusion-detection and VoIP firewall protection. At the voice gateway, which interfaces with the PSTN, disallow H.323, SIP, or Media Gateway Control Protocol (MGCP) connections from the data network. As with any other critical network management component, use strong authentication and access control on the voice gateway system. Choose a mechanism to allow VoIP traffic through firewalls. Various protocol dependent and independent solutions exist, including ALGs for VoIP protocols and session border controllers. Stateful packet filters can track a connections state, denying packets that arent part of a properly originated call.Use IPsec or Secure Socket Shell (SSH) for all remote management and auditing access. If practical, avoid using remote management at all and do IP PBX access from a physically secure system.Use IPsec tunneling when available instead of IPsec transport because tunneling masks the source and destination IP addresses, securing communications against rudimentary traffic analysis (that is, determining whos making the calls).If performance is a problem, use encryption at the router or other gateway to allow IPsec tunneling. Be-cause some VoIP end points arent computationally powerful enou gh to perform burden at a central point ensures the encryption of all VoIP traffic emanating from the enterprise network. Newer IP phones provide AES encryption at reason-able cost.Look for IP phones that can load digitally (cryptographically) signed images to guarantee the integrity of the software loaded onto the IP phone.Avoid softphone systems (see the sidebar) when security or privacy is a concern. In addition to violating the separation of voice and data, PC-based VoIP applications are vulnerable to the worms and viruses that are all too common on PCs. roll methods to harden VoIP platforms based on common operating systems such as Windows or Linux. Try, for example, disabling unnecessary services or using host-based intrusion detection methods.Be especially diligent about maintaining patches and current versions of VoIP software.Evaluate costs for additional power backup systems that might be required to ensure continued operation during power outages.Give special consideratio n to E-91 1 emergency services communications, because E-911 automatic location service is not always available with VoIP.VoIP can be done securely, but the path isnt smooth. It will likely be several years before standards issues are settledEnd to End VoIP SecurityEnd to End VoIP SecurityIntroductionUser communications applications are in high demand in the Internet user community. Two classes of such applications are of great importance and attract interest by many Internet users collaboration systems and VoIP communication systems. In the first category reside systems like ICQ , MSN Messenger and Yahoo Messenger while in the latter, systems like Skype and VoipBuster are dominating among the public VoIP clients. In the architecture plane, collaboration systems form a distributed network where the participants communicate with each other and exchange information. The data are either routed from the source through a central server to the recipient or the two clients communicate dire ctly. The participants in such networks are both content providers and content requestors . On the other hand, the data communication path in the VoIP systems is direct between the peers, without any involvement of the service network in the data exchange path with some exceptions like Skypes supernode communications. Data are carried over public Internet infrastructures like Ethernets, WiFi hotspots or wireless ad hoc networks. Security in these networks is a critical issue addressed in several different perspectives in the past.In this assignment I focus on cryptographic security implementation in VoIP. Security is implemented dynamically in cooperation by the two (or more) peers with no prior arrangements and requirements, like out of band exchanged keys, shared secrets etc. Ease of use (simplicity), user friendliness (no special knowledge from the user side) and effectiveness (ensuring confidentiality and integrity of the applications) combined with minimal requirements on end u ser devices are the goals achieved by our approach. We leverage security of user communications, meeting all the above requirements, by enhancing the applications architecture with VoIPSec security elements.Over the past few years, Voice over IP (VoIP) has become an attractive alternative to more traditional forms of telephony. Naturally, with its in-creasing popularity in daily communications, re-searchers are continually exploring ways to improve both the efficiency and security of this new communication technology. Unfortunately, while it is well understood that VoIP packets must be encrypted to ensure confidentiality, it has been shown that simply encrypting packets may not be sufficient from a privacy standpoint. For instance, we recently showed that when VoIP packets are first compressed with variable bit rate (VBR) encoding schemes to save bandwidth, and then encrypted with a length preserving stream cipher to ensure confidentiality, it is possible to determine the language s poken in the encrypted conversation.As surprising as these findings may be, one might argue that learning the language of the speaker (e.g., Arabic) only affects privacy in a marginal way. If both endpoints of a VoIP call are known (for example, Mexico City and Madrid), then one might correctly conclude that the language of the conversation is Spanish, without performing any analysis of the traffic. In this work we show that the information leaked from the combination of using VBR and length preserving encryption is indeed far worse than previously thought.VOIPThis assignment is about security, more specifically, about protecting one of your most precious assets, your privacy. We guard nothing more closely than our words. One of the most important decisions we make every day is what we will say and what we wont. But even then its not only what we say, but also what someone else hears, and who that person is.Voice over IP- the transmission of voice over traditional packet-switched IP networksis one of the hottest trends in telecommunications. Although most computers can provide VoIP and many offer VoIP applications, the term voice over IP is typically associated with equipment that lets users dial telephone numbers and communicate with parties on the other end who have a VoIP system or a traditional analog telephone. (The sidebar, Current voice-over-IP products, de-scribes some of the products on the market today.)As with any new technology, VoIP introduces both opportunities and problems. It offers lower cost and greater flexibility for an enterprise but presents significant security challenges. Security administrators might assume that because digitized voice travels in packets, they can simply plug VoIP components into their already se-cured networks and get a stable and secure voice net-work. Unfortunately, many of the tools used to safeguard todays computer networksfirewalls, network address translation (NAT), and encryptiondont work as is in a VoIP networ k. Although most VoIP components have counterparts in data networks, VoIPs performance demands mean you must supplement ordinary network software and hardware with special VoIP components.Integrating a VoIP system into an already congested or overburdened network can be disastrous for a companys technology infra-structure. Anyone at- tempting to construct a VoIP network should therefore first study the procedure in great detail. To this end, weve outlined some of the challenges of introducing appropriate security measures for VoIP in an enterprise.End-to-End SecurityIN this assignment I am going to describe the end-to-end security and its design principle that one should not place mechanisms in the network if they can be placed in end nodes thus, networks should provide general services rather than services that are designed to support specific applications. The design and implementation of the Internet followed this design principle well. The Internet was designed to be an applicat ion-agnostic datagram de-livery service. The Internet of today isnt as pure an implementation of the end-to-end design principle as it once was, but its enough of one that the collateral effects of the network not knowing whats running over it are becoming major problems, at least in the minds of some observers. Before I get to those perceived problems, Id like to talk about what the end-to-end design principle has meant to the Internet, technical evolution, and society. The Internet doesnt care what you doits job is just to deliver the bits, stupid (in the words of David Isenberg in his 1997 paper, Rise of the Stupid Network2). The bits could be part of an email message, a data file, a photograph, or a video, or they could be part of a denial-of-service attack, a malicious worm, a break-in attempt, or an illegally shared song. The Net doesnt care, and that is both its power and its threat.The Internet (and by this, I mean the Arpanet, the NSFNet, and the networks of their successor commercial ISPs) wasnt designed to run the World Wide Web. The Internet wasnt designed to run Google Earth. It was designed to support them even though they did not exist at the time the foundations of the Net were designed. It was designed to support them by being designed to transport data without caring what it was that data represented.At the very first, the design of TCP/IP wasnt so flexible. The initial design had TCP and IP within a single protocol, one that would only deliver data reliably to a destination. But it was realized that not all applications were best served by a protocol that could only deliver reliable data streams. In particular, timely delivery of information is more important than reliable delivery whentrying to support interactive voice over a network if adding reliability would, as it does, increase delay. TCP was split from IP so that the application running in an end node could determine for itself the level of reliability it needed. This split created t he flexibility that is currently being used to deliver Skypes interactive voice service over the same network that CNN uses to deliver up-to-the-minute news headlines and the US Patent and Trademark office uses to deliver copies of US patents.Thus the Internet design, based as it was on the end-to-end principle, became a generative facility. Unlike the traditional phone system, in which most new applications must be installed in the phone switches deep in the phone net-work, anyone could create new applications and run them over the Internet without getting permission from the organizations that run the parts of the Net. This ability was exploited with irrational exuberance4 during the late 1990s Internet boom. But, in spite of the hundreds of billions of dollars lost by investors when the boom busted, the number of Internet users and Web sites, the amount of Internet traffic, and the value of Internet commerce have continued to rise, and the rate of new ideas for Internet-based ser vices hasnt no- ticeably diminished.Security and privacy in an end-to-end worldThe end to end arguments paper used se-cure transmission of data as one reason that an end-to-end design was required. The paper points out that network-level or per-link encryption doesnt actually provide assurance that a file that arrives at a destination is the same as the file that was sent or that the data went unobserved along the path from the source to the destination. The only way to ensure end-to-end data integrity and confidentiality is to use end-to-end encryption.Thus, security and privacy are the responsibilities of the end nodes. If you want to ensure that a file will be transferred without any corruption, your data-transfer application had better include an integrity check, and if you didnt want to allow anyone along the way to see the data itself, your application had better encrypt it before transmitting it.There are more aspects to security on a network than just data encryption. For ex ample, to ensure that communication over the net-work is reliable, the network itself needs to be secure against attemptspurposeful or accidentalto disrupt its operation or redirect traffic away from its intended path. But the original Internet design didnt include protections against such attacks. Even if the network is working perfectly, you need to actually be talking to the server or person you think you are. But the Internet doesnt pro-vide a way, at the network level, to assure the identities of its users or nodes. You also need to be sure that the message your computer re receives isnt designed to exploit weaknesses in its software (such as worms or viruses) or in the waysthat you use the Net. Protection against such things is the end systems responsibility.Note that there is little that can be done in the Net or in your end system to protect your privacy from threats such as the government demanding the records of your use of Net-based services such as Google, which collect information about your network usage.Many of todays observers assume that the lack of built-in protections against attacks and the lack of a se-cure way to identify users or nodes was a result of an environment of trust that prevailed when the original Internet design and protocols were developed. If you trusted the people on the Net, there was no need for special defensive functions. But a few people who were at the scene have told me that such protections were actively discouraged by the primary sponsor of the early Internetthat is to say, the US military wasnt all that interested in having good nonmilitary security, maybe because it might make its job harder in the future. Whatever the reason, the Internet wasnt designed to provide a secure environment that included protection against the malicious actions of those who would disrupt it or attack nodes or services provided over it.End-to-end security is not dead yet, but it is seriously threatened, at least at the network layer. N ATs and firewalls interfere with some types of end-to-end encryption technology. ISPs could soon be required by regulations to, by default, filter the Web sites and perhaps the protocols that their customers can access. Other ISPs want to be able to limit the protocols that their customers can access so that the ISP can give service providers an incentive to pay for the customers use of their linesthey dont see a way to pay for the net-work without this ability. The FBI has asked that it be able to review all new Internet services for tapability before theyre deployed, and the FCC has hinted that it will support the requestIf this were to happen, applications such as Skype that use end-to-end encryption could be outlawed as inconsistent with law enforcement needs.Today, its still easy to use end-to-end encryption as long as its HTTPS, but that might be short-lived. It could soon reach the point that the use of end-to-end encryption, without which end-to-end security cant exist, will be seen as an antisocial act (as a US justice department official once told me). If that comes to be the case, end-toend security will be truly dead, and we will all have to trust functions in the network that we have no way of knowing are on our side.What is VoIP end to end security?Achieving end-to-end security in a voice-over-IP (VoIP) session is a challenging task. VoIP session establishment involves a jumble of different protocols, all of which must inter-operate correctly and securely. Our objective in this paper is to present a structured analysis of protocol inter-operation in the VoIP stack, and to demonstrate how even a subtle mismatch between the assumptions made by a protocol at one layer about the protocol at another layer can lead to catastrophic security breaches, including completeremoval of transport-layer encryption.The VoIP protocol stack is shown in figure 1. For the purposes of our analysis, we will divide it into four layers signaling, session description, key exchange and secure media (data) transport. This division is quite natural, since each layer is typically implemented by a separate protocol. Signaling is an application-layer (from the viewpoint of the underlying communication network) control mechanism used for creating, modifying and terminating VoIP sessions with one or more participants. Signaling protocols include Session Initiation Protocol (SIP) 27, H.323 and MGCP. Session description protocols such as SDP 20 are used for initiating multimedia and other sessions, and often include key exchange as a sub-protocol.Key exchange protocols are intended to provide a cryptographically secure way of establishing secret session keys between two or more participants in an untrusted environment. This is the fundamental building block in se-cure session establishment. Security of the media transport layerthe layer in which the actual voice datagrams are transmitteddepends on the secrecy of session keys and authentication of session part icipants. Since the established key is typically used in a symmetric encryption scheme, key secrecy requires that nobody other than the legitimate session participants be able to distinguish it from a random bit-string. Authentication requires that, after the key exchange protocol successfully completes, the participants respective views of sent and received messages must match (e.g., see the notion of matching conversations in 8). Key ex-change protocols for VoIP sessions include SDPs Security DEscriptions for Media Streams (SDES) , Multimedia Internet KEYing (MIKEY) and ZRTP 31. We will analyze all three in this paper.Secure media transport aims to provide confidentiality, message authentication and integrity, and replay protection to the media (data) stream. In the case of VoIP, this stream typically carries voice datagrams. Confidentiality means that the data under encryption is indistinguishable from random for anyone who does not have the key. Message authentication implies th at if Alice receives a datagram apparently sent by Bob, then it was indeed sent by Bob. Data integrity implies that any modification of the data in transitWe show how to cause the transport-layer SRTP protocol to repeat the keystream used for datagram encryption. This enables the attacker to obtain the xor of plaintext datagrams or even to completely decrypt them. The SRTP keystream is generated by using AES in a stream cipher-like mode. The AES key is generated by applying a pseudo-random function (PRF) to the session key. SRTP, however, does not add any session-specific randomness to the PRF seed. Instead, SRTP assumes that the key exchange protocol, executed as part of RTP session establishment, will en-sure that session keys never repeat. Unfortunately, S/MIME-protected SDES, which is one of the key ex-change protocols that may be executed prior to SRTP, does not provide any replay protection. As we show, a network-based attacker can replay an old SDES key establishment message, which will cause SRTP to re-peat the keystream that it used before, with devastating consequences. This attack is confirmed by our analysis of the libsrtp implementation. We show an attack on the ZRTP key exchange protocol that allows the attacker to convince ZRTP session participants that they have lost their shared secret. ZID values, which are used by ZRTP participants to retrieve previously established shared secrets, are not authenticated as part of ZRTP. Therefore, an attacker can initiate a session with some party A under the guise of another party B, with whom A previously established a shared secret. As part of session establishment, A is supposed to verify that B knows their shared secret. If the attacker deliberately chooses values that cause verification to fail, A will decidefollowing ZRTP specificationthat B has forgotten the shared secret.The ZRTP specification explicitly says that the protocol may proceed even if the set of shared secrets is empty, in which case the attacker ends up sharing a key with A who thinks she shares this key with B. Even if the participants stop the protocol after losing their shared secrets, but are using VoIP devices without displays, they cannot confirm the computed key by voice and must stop communicating. In this case, the attack becomes a simple and effective denial of service. Our analysis of ZRTP is supported by the AVISPA formal analysis tool . We show several minor weaknesses and potential vulnerabilities to denial of service in other protocols. We also observe that the key derived as the result of MIKEY key exchange cannot be used in a standard cryptographic proof of key exchange security (e.g., ). Key secrecy requires that the key be in-distinguishable from a random bitstring. In MIKEY, however, the joint Diffie-Hellman value derived as the result of the protocol is used directly as the key. Membership in many Diffie-Hellman groups is easily checkable, thus this value can be distinguished from a random bit string. Moreover, even hashing the Diffie-Hellman value does not allow the formal proof of security to go through in this case, since the hash function does not take any random inputs apart from the Diffie-Hellman value and cannot be viewed as a randomness extractor in the proof. (This observation does not immediately lead to any attacks.)While we demonstrate several real, exploitable vulnerabilities in VoIP security protocols, our main contribution is to highlight the importance of analyzing protocols in con-text rather than in isolation. Specifications of VoIP protocols tend to be a mixture of informal prose and pseudocode, with some assumptionsespecially those about the protocols operating at the other layers of the VoIP stackare left implicit and vague. Therefore, our study has importantlessons for the design and analysis of security protocols in general.The rest of the paper is organized as follows. In section 2, we describe the protocols, focusing on SIP (signaling), SDES, ZRT P and MIKEY (key exchange), and SRTP (transport). In section 3, we describe the attacks and vulnerabilities that we discovered. Related work is in section 4, conclusions are in section 5.VoIP security different from normal data network securityTo understand why security for VoIP differs from data network security, we need to look at the unique constraints of transmitting voice over a packet network, as well as the characteristics shared by VoIP and data networks.Packet networks depend on many configurable parameters IP and MAC (physical) addresses of voice terminals and addresses of routers and firewalls. VoIP networks add specialized software, such as call managers, to place and route calls. Many network parameters are established dynamically each time a network component is restarted or when a VoIP telephone is restarted or added to the net-work. Because so many nodes in a VoIP network have dynamically configurable parameters, intruders have as wide an array of potentially vulnera ble points to attack as they have with data networks. But VoIP systems have much stricter performance constraints than data networks, with significant implications for security.Threats for VoIPVoIP security threats contain Eavesdropping, Denial of Service, Session Hijacking, VoIP Spam, etc. For preventing these threats, there are several VoIP standard protocols. And we discuss this in Section 3.EavesdroppingVoIP service using internet technology is faced with an eavesdropping threat, in which is gathering call setting information and audio/voice communication contents illegally. Eavesdropping can be categorized largely by eavesdropping in a LAN(Local Area Network) environment, one in a WAN( Wide Area Network) environment, one through a PC(Personal Computer) hacking, etc.Denial of ServiceDenial of Service is an attack, which makes it difficult for legitimate users to take telecommunication service regularly. Also it is one of threats, which are not easy to solve the most. Since VoIP service is based on internet technology, it also is exposed to Denial of Service. Denial of Service in VoIP service can be largely divided into system resource exhaustion, circuitThis work was supported by the IT RD program of MIC/IITA resourceexhaustion,VoIP communication interruption/blocking, etc.Session HijackingSession Hijacking is an attack, which is gathering the communication session control between users through spoofing legitimate users, and is interfering in their communication, as a kind of man-in-the-middle attack. Session Hijacking in VoIP communication can be categorized largely by INVITE session hijacking, SIP Registration hijacking, etc.VoIP SpamVoIP Spam is an attack, which is interrupting, and violating user privacy through sending voice advertisement messages, and also makes VMS(Voice Mailing System) powerless. It can be categorized by Call Spam, IM(Instant Messaging) Spam, Presence Spam, etc.Security trade-offsTrade-offs between convenience and security are rout ine in software, and VoIP is no exception. Most, if not all, VoIP components use integrated Web servers for configuration. Web interfaces can be attractive, easy to use, and inexpensive to produce because of the wide availability of good development tools. Unfortunately, most Web development tools focus on features and ease of use, with less attention paid to the security of the applications they help produce. Some VoIP device Web applications have weak or no access control, script vulnerabilities, and inadequate parameter validation, resulting in privacy and DoS vulnerabilities. Some VoIP phone Web servers use only HTTP basic authentication, meaning servers send authentication information without encryption, letting anyone with network access obtain valid user IDs and passwords. As VoIP gains popularity, well inevitably see more administrative Web applications with exploitable errors.The encryption process can be unfavorable to QoSUnfortunately, several factors, including packet si ze expansion, ciphering latency, and a lack of QoS urgency in the cryptographic engine can cause an excessive amount of latency in VoIP packet delivery, leading to degraded voice quality.The encryption process can be detrimental to QoS, making cryptodevices severe bottlenecks in a VoIP net-work. Encryption latency is introduced at two points. First, encryption and decryption take a nontrivial amount of time. VoIPs multitude of small packets exacerbates the encryption slowdown because most of the time consumed comes as overhead for each packet. One way to avoid this slowdown is to apply algorithms to the computationally simple encryption voice data before packetization. Although this improves throughput, the proprietary encryption algorithms used (fast Fourier-based encryption, chaos-bit encryption, and so on) arent considered as secure as the Advanced Encryption Standard,16 which is included in many IPsec implementations. AESs combination of speed and security should handle the dema nding needs of VoIP at both ends. following general guidelines, recognizing that practical considerations might require adjusting them Put voice and data on logically separate networks. You should use different subnets with separate RFC 1918 address blocks for voice and data traffic and separate DHCP servers to ease the incorporation of intrusion-detection and VoIP firewall protection. At the voice gateway, which interfaces with the PSTN, disallow H.323, SIP, or Media Gateway Control Protocol (MGCP) connections from the data network. As with any other critical network management component, use strong authentication and access control on the voice gateway system. Choose a mechanism to allow VoIP traffic through firewalls. Various protocol dependent and independent solutions exist, including ALGs for VoIP protocols and session border controllers. Stateful packet filters can track a connections state, denying packets that arent part of a properly originated call.Use IPsec or Secure Soc ket Shell (SSH) for all remote management and auditing access. If practical, avoid using remote management at all and do IP PBX access from a physically secure system.Use IPsec tunneling when available instead of IPsec transport because tunneling masks the source and destination IP addresses, securing communications against rudimentary traffic analysis (that is, determining whos making the calls).If performance is a problem, use encryption at the router or other gateway to allow IPsec tunneling. Be-cause some VoIP end points arent computationally powerful enough to perform encryption, placing thisRecent studies indicate that the greatest contributor to the encryption bottleneck occurs at the cryptoengine scheduler, which often delays VoIP packets as it processes larger data packets.17 This problem stems from the fact that cryptoschedulers are usually first-in first-out (FIFO) queues, inadequate for supporting QoS requirements. If VoIP packets arrive at the encryption point when the queue already contains data packets, theres no way they can usurp the less time-urgent traffic. Some hardware manufacturers have proposed (and at least one has implemented) solutions for this, including QoS reordering of traffic just before it reaches the cryptoengine.18 But this solution assumes that the cryptoengines output is fast enough to avoid saturating the queue. Ideally, youd want the cryptoengine to dynamically sort incoming traffic and force data traffic to wait for it to finish processing the VoIP packets, even if these packets arrive later. However, this solution adds considerable overhead to a process most implementers like to keep as light as possible. Another option is to use hardware-implemented AES encryption, which can improve throughput significantly. Past the cryptoengine stage, the system can performfurther QoS scheduling on the encrypted packets, provided they were encrypted using ToS preservation, which copies the original ToS bits into the new IPsec header. Virtual private network (VPN) tunneling of VoIP has also become popular recently, but the congestion and bottlenecks associated with encryption suggest that it might not always be scalable. Although researchers are making great strides in this area, the hardware and soft-ware necessary to ensure call quality for encrypted voice traffic might not be economically or architecturally vi-able for all enterprises considering the move to VoIP.Thus far, weve painted a fairly bleak picture of VoIP security. We have no easy one size fits all solution to the issues weve discussed in this article. Decisions to use VPNs instead of ALG-like solutions or SIP instead of H.323 must depend on the specific nature of both the current network and the VoIP network to be. The technical problems are solvable, however, and establishing a secure VoIP implementation is well worth the difficulty.To implement VoIP securely today, start with the following general guidelines, recognizing that practical considerat ions might require adjusting them Put voice and data on logically separate networks. You should use different subnets with separate RFC 1918 address blocks for voice and data traffic and separate DHCP servers to ease the incorporation of intrusion-detection and VoIP firewall protection. At the voice gateway, which interfaces with the PSTN, disallow H.323, SIP, or Media Gateway Control Protocol (MGCP) connections from the data network. As with any other critical network management component, use strong authentication and access control on the voice gateway system. Choose a mechanism to allow VoIP traffic through firewalls. Various protocol dependent and independent solutions exist, including ALGs for VoIP protocols and session border controllers. Stateful packet filters can track a connections state, denying packets that arent part of a properly originated call.Use IPsec or Secure Socket Shell (SSH) for all remote management and auditing access. If practical, avoid using remote manag ement at all and do IP PBX access from a physically secure system.Use IPsec tunneling when available instead of IPsec transport because tunneling masks the source and destination IP addresses, securing communications against rudimentary traffic analysis (that is, determining whos making the calls).If performance is a problem, use encryption at the router or other gateway to allow IPsec tunneling. Be-cause some VoIP end points arent computationally powerful enough to perform burden at a central point ensures the encryption of all VoIP traffic emanating from the enterprise network. Newer IP phones provide AES encryption at reason-able cost.Look for IP phones that can load digitally (cryptographically) signed images to guarantee the integrity of the software loaded onto the IP phone.Avoid softphone systems (see the sidebar) when security or privacy is a concern. In addition to violating the separation of voice and data, PC-based VoIP applications are vulnerable to the worms and viruses that are all too common on PCs.Consider methods to harden VoIP platforms based on common operating systems such as Windows or Linux. Try, for example, disabling unnecessary services or using host-based intrusion detection methods.Be especially diligent about maintaining patches and current versions of VoIP software.Evaluate costs for additional power backup systems that might be required to ensure continued operation during power outages.Give special consideration to E-91 1 emergency services communications, because E-911 automatic location service is not always available with VoIP.VoIP can be done securely, but the path isnt smooth. It will likely be several years before standards issues are settled