简介:http://www.automation.com据美国机械制造技术协会AMT统计,3月份的美国制造技术订单总额达5.0791亿美元。据参与USMTO计划的公司报告,与2月份相比环比增长了30.4%,与2012年3月的4.9196亿美元相比,
简介:Anovelmethodfordesigningabeam-switchingantennawiththeplanedipoleispresented.Theantennaiscomposedofdoubledipolesplacedatthecenterofanactivesquarestructurethatisdividedinfourequalsectorsbymetallicsheets.Metallicpatchesattheoutsideofthestructureareusedtoenhancetheradiationperformanceoftheantenna.Ineachstep,thediodesinonesectorareon,whereasotherdiodesareoff.Thesectorwithoff-statediodesdefinesthedirectionoftheradiationpattern.AnantennamodelisdesignedonthesubstrateofFR4.Theproposedantennaoperatesfrom4.8GHzto5.5GHzwithgainof6.3dBiandF/B(fronttobackratio)of13.2dBiwhentheoperatingfrequencyis5.2GHz.Theantennaradiationpatterncanbesweptintheentireazimuthplaneinfourstepswitha3dBbeamwidthof90.Theresultsrevealthattheantennacouldbeusedinthebasestationofthewirelesscommunicationsystems.
简介:Inrecentyears,microstripantennashavebeenmorewidelyappliedinsatellitecommunications,mobilephones,unmannedaerialvehicle(UAV),andweapons.Amicro-electro-mechanicalsystems-based(MEMS-based)high-resistancesiliconC-bandmicrostripantennaarrayhasbeendesignedfortheintelligentammunition.Thecenterfrequencyis4.5GHz.Acavityhasbeendesignedinsubstratetoreducethedielectricconstantofsiliconandhigh-resistancesiliconhasbeenusedasthematerialofsubstratetoimprovethegainofantenna.ItisveryeasytobemanufacturedbyusingMEMStechnologybecauseoftheimprovedstructureoftheantenna.Theresultsshowthatthegainoftheantennais8dBandvoltagestandingwaveratio(VSWR)islessthan2bytheanalysisandsimulationinhighfrequencystructuresimulator(HFSS).
简介:Inthiswork,ahardwareintrusiondetectionsystem(IDS)modelanditsimplementationareintroducedtoperformonlinereal-timetrafficmonitoringandanalysis.TheintroducedsystemgatherssomeadvantagesofmanyIDSs:hardwarebasedfromimplementationpointofview,networkbasedfromsystemtypepointofview,andanomalydetectionfromdetectionapproachpointofview.Inaddition,itcandetectmostofnetworkattacks,suchasdenialofservices(DoS),leakage,etc.fromdetectionbehaviorpointofviewandcandetectbothinternalandexternalintrudersfromintrudertypepointofview.GatheringthesefeaturesinoneIDSsystemgiveslotsofstrengthsandadvantagesofthework.Thesystemisimplementedbyusingfieldprogrammablegatearray(FPGA),givingamoreadvantagestothesystem.AC5.0decisiontreeclassifierisusedasinferenceenginetothesystemandgivesahighdetectionratioof99.93%.
简介:Doubledataratesynchronousdynamicrandomaccessmemory(DDR3)hasbecomeoneofthemostmainstreamapplicationsincurrentserverandcomputersystems.Inordertoquicklysetupasystem-levelsignalintegrity(SI)simulationflowfortheDDR3interface,twosystem-levelSIsimulationmethodologies,whichareboard-levelS-parameterextractioninthefrequency-domainandsystem-levelsimulationassumptionsinthetimedomain,areintroducedinthispaper.BycomparingtheflowofSpeed2000andPowerSI/Hspice,PowerSIischosenfortheprintedcircuitboard(PCB)board-levelS-parameterextraction,whileTektronixoscilloscope(TDS7404)isusedfortheDDR3waveformmeasurement.Thelabmeasurementshowsgoodagreementbetweensimulationandmeasurement.ThestudyshowsthatthecombinationofPowerSIandHspiceisrecommendedforquicksystem-levelDDR3SIsimulation.