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A measurement of weak lensing by large scale structure in RCS fields

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arXiv:astro-ph/0202285v1 14 Feb 2002DraftversionFebruary1,2008

PreprinttypesetusingLATEXstyleemulateapjv.14/09/00

AMEASUREMENTOFWEAKLENSINGBYLARGESCALESTRUCTUREINRCSFIELDS

HenkHoekstra1,2,3,HowardK.C.Yee2,3,4,MichaelD.Gladders2,3,4,L.FelipeBarrientos4,5,PatrickB.Hall2,3,4,5,6,andLeopoldoInfante4,5

DraftversionFebruary1,2008

ABSTRACT

Wehaveanalysed∼24squaredegreesofRC-bandimagingdatafromtheRed-SequenceCluster

Survey(RCS),andmeasuredtheexcesscorrelationsbetweengalaxyellipticitiesonscalesrangingfrom1

to30arcminutes.Wehaveuseddatafromtwodifferenttelescopes:∼16.4squaredegreesofCFHTdataand∼7.6squaredegreesofCTIO4-meterdata,distributedover13widelyseparatedpatches.Forthe

firsttime,adirectcomparisoncanbemadeofthelensingsignalmeasuredusingdifferentinstruments,whichprovidesanimportanttestoftheweaklensinganalysisitself.Themeasurementsobtainedfrom

thetwotelescopesagreewell.Forthelensinganalysisweusegalaxiesdowntoalimitingmagnitudeof

RC=24,forwhichtheredshiftdistributionisknownrelativelywell.Thisallowsustoconstrainsomecosmologicalparameters.ForthecurrentlyfavoredΛCDMmodel(Ωm=0.3,ΩΛ=0.7,Γ=0.21)

weobtainσ8=0.81+0.14−0.19(95%confidence),inagreementwiththeresultsfromVanWaerbekeetal.

(2001)whichusedfaintergalaxies(andconsequentlyhigherredshiftgalaxies).Thegoodagreement

betweenthesetwoverydifferentweaklensingstudiesdemonstratesthatweaklensingisausefultoolinobservationalcosmology.

Subjectheadings:cosmology:observations−darkmatter−gravitationallensing

1.introduction

Weakgravitationallensinghasproventobeapowerful

toolforstudiesofthemassdistributioninrichclustersof

galaxies(forareviewseeMellier1999).Sincethepioneer-ingworkbyTyson,Wenk,&Valdes(1990)muchprogress

hasbeenmade,andnowadaystheweaklensingsignalsin-

ducedbyclustersofgalaxiesatintermediateredshiftscanbemeasuredwithoutmuchdifficulty.

Thedevelopmentofadvancedtechniquestocorrect

forthevariousobservationaldistortions,suchastheanisotropyofthepointspreadfunction(PSF),thecircu-

larizationbythePSF,andthecamerainduceddistortion,

hasbeenacrucialstep,resultinginwellcalibratedsig-nals(e.g.,Kaiser,Squires,&Broadhurst1995;Luppino&

Kaiser1997;Hoekstraetal.1998;Kuijken1999;Refregier

2001).AnotherimportantdevelopmentinrecentyearsistheadventofmosaicCCDcameras,whichenableusto

quicklyimagelargeportionsofthesky.

Theseadvanceshavemadeitpossibletopursueoneofthemostdifficultmeasurementsinthefieldofweaklens-

ing:themeasurementofthecoherentdistortionsofthe

imagesoffaintgalaxiescausedbylensingbyinterveninglargescalestructure,theso-called‘cosmicshear’.The

analysisofthislensingsignalprovidesanimportantdirect

1CITA,UniversityofToronto,Toronto,OntarioM5S3H8,Canada2DepartmentofAstronomyandAstrophysics,UniversityofToronto,Toronto,OntarioM5S3H8,Canada3VisitingAstronomer,Canada-France-HawaiiTelescope,whichisoperatedbytheNationalResearchCouncilofCanada,LeCentreNationaldeRechercheScientifique,andtheUniversityofHawaii4GuestobserverattheCerroTololoInter-AmericanObservatory(CTIO),adivisionoftheNationalOpticalAstronomyObservato-ries,whichisoperatedbytheAssociationofUniversitiesforResearchinAstronomy,Inc.,undercooperativeagreementwiththeNationalScienceFoundation5UniversidadCat´olicadeChile,Depto.Astronom´ıayAstrof´ısica,Avda.Vicu˜naMackenna4860,Casilla306,Santiago22,Chile6PrincetonUniversityObservatory,Princeton,NJ98544-1001measurementofthestatisticalpropertiesofthelargescale

massdistribution(e.g.,Blandfordetal1991;Kaiser1992;

Bernardeau,vanWaerbeke,&Mellier1997;Schneideretal.1998).

Comparedtomanyothermethodsthatareusedtocon-straincosmologicalparameters,weaklensinghasthead-

vantagethatnoassumptionsaboutthelightdistribution

arerequired.However,weaklensinginitselfcannotcon-strainalltheparameters,becauseofdegeneraciesbetween

them.Betterconstraintscanbeobtainedbycomparing

weaklensingstudiesthatprobedifferentredshifts(e.g.,Hu1999)orwhenthesedataarecombinedwithmeasure-

mentsofthefluctuationsofthecosmicmicrowaveback-

ground(e.g.,Hu&Tegmark1999).Bynow,severalgroupshavereportedthedetectionof

anexcesscorrelationbetweengalaxyellipticities,andhave

arguedthatthissignaliscausedbylensingbylargescalestructure(e.g.,Baconetal.2000;Kaiser,Wilson,&Lup-

pino2000;vanWaerbekeetal.2000;Wittmanetal.2000;

Maolietal.2001;vanWaerbekeetal.2001).Maolietal.(2001)combinedtheirownresultswithpublishedmea-

surementsinanattempttoobtainconstraintsonσ8,the

normalisationofthepowerspectrum,andΩm,thematterdensityoftheuniverse.Theyfoundgoodagreementwith

studiesofclusterabundances.However,thedatasetstud-

iedbyMaolietal.(2001)isveryinhomogeneous,whichlimitstheaccuracyofsuchadirectcomparison.

Aftertheseinitialdetections,whichdemonstratedthe

feasibilityofthemethod,theobviousnextstepistoob-tainlargeuniformdatasets.Thefirstresultsfromsuch

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求大神来帮忙翻译!糗友力量大

求大神来帮忙翻译!糗友力量大

This paper studied the interaction of low-frequency SH0 waves with

part-thickness cracks for the symmetric incidence problem. The

interaction was studied in terms of the influence on the specular reflection,

of the crack length, and the spatial and angular measurement positions at

different crack depths and operating frequencies. The FE modeling was

validated by comparison with experiments for the case of scattering by a

finite part-depth rectangular notch. The results from all the studies are

similar to those obtained for the corresponding through-thickness case

with the trend being identical and actual values differing only by a

frequency dependent scale factor. Theoretical analysis is used to reveal

the physical basis for such behavior and helps us obtain estimates for the

scale factor, exactly derived for the high frequency scattering regime and

Structural Biological Materials-Critical Mechanics-Materials Connections

Structural Biological Materials-Critical Mechanics-Materials Connections

DOI: 10.1126/science.1220854, 773 (2013);339 Science et al.Marc André MeyersConnectionsStructural Biological Materials: Critical Mechanics-Materials

This copy is for your personal, non-commercial use only.

clicking here.colleagues, clients, or customers by , you can order high-quality copies for yourIf you wish to distribute this article to others

here.following the guidelines can be obtained byPermission to republish or repurpose articles or portions of articles

): May 1, 2013 (this information is current as ofThe following resources related to this article are available online at

/content/339/6121/773.full.htmlversion of this article at: including high-resolution figures, can be found in the onlineUpdated information and services,

/content/339/6121/773.full.html#ref-list-1, 12 of which can be accessed free:cites 51 articlesThis article

目标rcs特性测量技术在雷达软件中的应用

目标rcs特性测量技术在雷达软件中的应用

信息通信

INFORMATION & COMMUNICATIONS2019

年第10

期

(总第202

期)2019

(Sum. No 202)

目标

RCS特性测量技术在雷达软件中的应用

王博儒

(中国西安卫星测控中心，陕西西安710000)

摘要：空间技术的快速发展，使人类战场扩展到了外层空间。空间中的航空航天器的生存问题将是空间攻防中研究的重

点。根据雷达目标截面积(RCS)

特性测量技术，设计了 RCS

测量软件系统，采用相对标定法对目标特性RCS

值进行了

模拟和检测。研究了该测量技术在雷达软件中的应用以期帮助常规雷达拓展使用范围，增强作战职能，在空间攻防中发

挥作用，更好的适应当代战场新形势。

关键词:RCS

；雷达;相对标定法

中图分类号:TN958

文献标识码:A

文章编号：1673-1131(2019)10-00013-02

0

引言

复杂目标的RCS (RadarCross Section),

因为电磁散射的

影响，现在还不能准确计算出来，因此，隐身技术在当今复杂

电磁环境下的战争中占有重要的地位。随着卫星在现代战争

中的作用日益增强,反卫星武器迅速发展，隐身技术就成了航

天器保证生存的一个可选项，为实际验证隐身航空航天器的

隐身性能，必须对隐身目标RCS

特性进行实际测量。

国外已有多部RCS

测量雷达，其测量技术已发展到相当

成熟的阶段，测量误差可小于ldB

。我国也已拥有了多部RCS

测量雷达，在各方面都取得了很多宝贵的经验,但数量仍不能

完全满足需要。

文中对常规雷达加装RCS

测量软件系统进行研究，是对 已投入使用的RCS

测量雷达的很好补充，同时对现有常规雷

达的作战职能进行了拓展。

1

雷达目标散射截面积(RCS)

雷达目标散射截面积(RCS)

就是假定一个目标垂直于天

线波束方向，并在全方向对雷达信号进行均匀的反射，用它来

类比实际目标的功率密度，这个假定目标的面积就可以等同

实际目标的散射面积&其表达式为：

& = 4

衣蜃 (1)

Lead paragraph

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