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1、THEINTERNET,mappedontheoppositepage,isascale-freenetworkinthatsomesiteS(starburstsanddetailabove)haveaseeminglyunlimitednumberofconnectionstoothersites.Thismap,madeonFebruary6,2003,tracestheshortestroutesfromatestWebsinHoabout100,000others,usinglikecolorsforsimilarWebaddresses.a-Sc
2、ientistshaverecentlydiscoveredthatvariouscomplexsystemshaveantlnderlyihg~..'~tJ;i~e~tu"eg~Ye'l"rne(;lb9.$haredorganilingprincipies.Thisinsighthasimportantimpli~ationsforahostofapplications,fromdrugdevelopmenttoInternetsecurityBYALBERT-USZLOBARABASIANDERICBONABEAU50SCIENTIFICAMERIC
3、ANMAY2003i<;z"~"a..'""~~"'","""u"3:~~"G~;c~~~~~Thebrainisanetworkofnervecellscon-numberoflinksandnonodeistypicalofnetworktheoryisthat,despitetheran-nectedbyaxons,andcellsthemselvesaretheothers.Thesenetworksalsobehaveindomplacementoflinks,theresultingsys-networksofmoleculesconnected
4、bybio-certainpredictableways;forexample,temwillbedeeplydemocratic:mostchemicalreactions.Societies,too,arenet-theyareremarkablyresistanttoacciden-nodeswillhaveapproximatelythesameworksofpeoplelinkedbyfriendships,talfailuresbutextremelyvulnerabletonumberoflinks.Indeed,inarandomnet-fa
5、milialrelationshipsandprofessionalcoordinatedattacks.workthenodesfollowaPoissondistrib-ties.Onalargerscale,foodwebsandeco-Suchdiscoverieshavedramaticallyutionwithabellshape,anditisextreme-systemscanberepresentedasnetworkschangedwhatwethoughtweknewaboutlyraretofindnodesthathavesigni
6、ficant-ofspecies.Andnetworkspervadetech-thecomplexinterconnectedworldaroundlymoreorfewerlinksthantheaverage.nology:theInternet,powergridsandus.Unexplainedbypreviousnetworkthe~Randomnetworksarealsocalledexpo-transportationsystemsarebutafewex"ories,hubsofferconvincingproofthatnential
7、,becausetheprobabilitythataamples.Eventhelanguageweareusingvariouscomplexsystemshaveastrictar-nodeisconnectedtokothersitesde-toconveythesethoughtstoyouisanet-chitecture,ruledbyfundamentallaws-creasesexponentiallyforlargek.work,madeupofwordsconnectedbylawsthatappeartoapplyequallytoc
8、ells,Soin1998,whenwe,toget
