The first simultaneous X-raygamma-ray observations of Cyg X-1 by Ginga and OSSE

合集下载

英文版原子物理课件

Shanxi University Atomic Physics
1.1 Introduction
The origins of atomic physics :quantum mechanics Bohr model of the H This introductory chapter surveys some of the early ideas: Spectrum of atomic H and Bohr Theory Einstein's treatment of interaction of atom with light the Zeeman effect Rutherford scattering And so on
Shanxi University Atomic Physics
1.2 Spectrum of atomic hydrogen_3
Wavenumbers may seem rather old-fashioned but they are very useful in atomic physics
the characteristic spectrum for atoms is composed of discrete lines that are the ‘fingerprint' of the element.
In 1888, the Swedish professor J. Rydberg found that the spectral lines in hydrogen obey the following mathematical formula:
Shanxi University Atomic Physics
Lyman series: n’ = 2; 3; 4; … n = 1. Balmer (n = 2), Paschen series: (n = 3), Brackett (n = 4) and Pfund (n = 5)

关于人造太阳英语单词

关于人造太阳英语单词全超导托卡马克核聚变实验装置东方超环（EAST）近日实现了稳定的101.2秒稳态长脉冲高约束等离子体运行，创造了新的世界纪录。

由于核聚变的反应原理与太阳类似，因此，东方超环也被称做“人造太阳”。

Chinese scientists announced they have set a new world record by achieving 101.2 seconds of steady-state H-mode operation of the tokamak, an experimental device designed to harness the energy of fusion.我国科学家宣布，他们成功实现了托卡马克101.2秒稳态高约束运行，创造了新的世界纪录。

托卡马克是一种旨在利用核聚变能量的实验装置。

The milestone meant China's Experimental Advanced Superconducting Tokamak (EAST), dubbed "artificial sun," became the world's first tokamak device to achieve the 100-second-level, Hefei Institute of Physical Science under the Chinese Academy of Sciences said Wednesday.中科院合肥物质科学研究院5日称，这一里程碑式事件标志着，我国的"全超导托卡马克实验装置(东方超环)"成为世界首个运行时间达到百秒量级的托卡马克装置。

东方超环也被称作"人造太阳"。

东方超环（Experimental Advanced Superconducting Tokamak，EAST）是世界上第一个实现稳态高约束模式运行持续时间达到百秒量级的托卡马克核聚变实验装置，对国际热核聚变试验堆（International Thermonuclear Experimental Reactor，ITER）计划具有重大科学意义。

Gamma Ray Bursts as Probes of the First Stars

a r X i v :a s t r o -p h /0111030v 1 1 N o v 2001Gamma Ray Bursts as Probes of the First StarsJames E.RhoadsSTScI,3700San Martin Dr.,Baltimore,MD 21210,USAAbstract.The redshift where the ﬁrst stars formed is an important and unknown milestone in cos-mological structure formation.The evidence linking gamma ray bursts (GRBs)with star formation activity implies that the ﬁrst GRBs occurred shortly after the ﬁrst stars formed.Gamma ray bursts and their afterglows may thus offer a unique probe of this epoch,because they are bright from gamma ray to radio wavelengths and should be observable to very high redshift.Indeed,our on-going near-IR followup programs already have the potential to detect bursts at redshift z ∼10.In these proceedings,we discuss two distinct ways of using GRBs to probe the earliest star formation.First,direct GRB counts may be used as a proxy for star formation rate measurements.Second,high energy cutoffs in the GeV spectra of gamma ray bursts due to pair production with high redshift op-tical and ultraviolet background photons contain information on early star formation history.The second method is observationally more demanding,but also more rewarding,because each observed pair creation cutoff in a high redshift GRB spectrum will tell us about the integrated star formation history prior to the GRB redshift.INTRODUCTION The high redshift frontier of observational cosmology currently stands at redshifts z ≈6.The current redshift record is a quasar at z =5.8,and a few galaxies are known at marginally lower redshift.Beyond z =6,we have yet to identify any individual objects.We do know that hydrogen was predominantly neutral at redshifts z ∼>30based on the observed anisotropy of the cosmic microwave background,which would be smoothed out by Thomson scattering if the free electron density at z ∼>30were too great.The redshift range 6∼<z ∼<30remains unknown territory.It is a very interesting territory,too,for it should include the formation of the ﬁrst stars,galaxies,and quasars,and certainlyincludes the epoch at which hydrogen was reionized.Searches for starlight (and other rest-frame near ultraviolet tracers)can make incre-mental progress into the low-redshift end of this period.However,these methods face a practical limit where the Lyman break redshifts out of the optical window to the near-infrared,at z ≈7.At higher redshift,essentially no ﬂux is expected in the optical window (observed wavelengths 0.36µm ∼<λobs ∼<1µm ).Atmospheric conditions and present de-tector technologies conspire to make searches at λobs ∼>1µm much less efﬁcient.Future instrumentation like the Next Generation Space Telescope (NGST)promise extensions of “conventional”optical methods to the observed near-IR and thus to redshifts z ≫6,but this may be a decade or more away.In the meantime,we expect the upcoming ex-tension of our Large Area Lyman Alpha (LALA)survey (Rhoads et al 2000;Malhotra et al 2001)to z =6.6to be at or near the practical limit for some years.We would like to ﬁnd tracers of z >6objects that are accessible now.Fortunately,this is possible so long as we are willing to use something besides starlight.In practice,this means higher energy photons(γand x-rays),since lower energies still face either confusion or sensitivity issues.Gamma ray bursts(GRBs)are an excellent candidate for detection at high redshift because the bursts and their afterglows are extremely bright at all wavelengths.Two conditions must be met for such a candidate to work well.First,there should be a reasonable expectation that the object exists at high redshift;and second,it should be detectable there.The best argument that gamma ray bursts should occur at high redshift comes from the growing body of evidence linking GRBs to star formation activity(and hence presumably to the deaths of massive,short-lived stars):GRB host galaxy colors are characteristically blue(Fruchter et al1999);the spatial distribution of GRBs on their hosts matches expectations for hypernova models(Bloom,Kulkarni,&Djorgovski 2000);and the emission lines of GRB host galaxies are unusually strong(Fruchter et al 2001).Structure formation models yield estimated redshifts z∼15±5for theﬁrst stars to form in the universe(cf.Barkana&Loeb2001).This is supported by studies of heavy element abundances:It has proven extremely difﬁcult toﬁnd objects with primordial (i.e.,big bang nucleosynthesis)abundances at any redshift currently accessible.The immediate inference is that a substantial generation of stars must have existed at earlier redshifts to produced the ubiquitous metals.The association of GRBs with star formation then implies that theﬁrst GRBs also occurred in the redshift range z∼15±5.The detectibility of GRBs at z≫6has been considered in detail by Lamb&Reichart (2000),whoﬁnd that the bright end of the luminosity distribution would be detectable at very high redshifts(though quantitative predictions depend substantially on unknown details of the GRB luminosity function).This applies also to the X-ray and optical after-glows,for which time dilation of the most distant afterglows helps offset the increase in luminosity distance with redshift(Lamb&Reichart2000;Ciardi&Loeb2000).The Lyman break will render afterglows at z>7invisible to optical detectors,just as it does for galaxies.But the problem here is not so serious.Searches for z>7galaxies suffer because galaxies at such high redshifts are faint,and the required combination of large solid angles and high sensitivity toﬁnd them is not yet practical at near-IR wavelengths.Because GRB afterglows outshine their host galaxies at early times,and because X-ray detectors can determine GRB locations with accuracy comparable to the current near-IRﬁeld of a4m class telescope,an afterglow at this redshift is easier toﬁnd than are the galaxies around it.Indeed,published near-infrared afterglow observations (Rhoads&Fruchter2001)already achieve a sensitivity sufﬁcient to detect afterglows at z∼10for several hours following a GRB(cf.ﬁgures2,3of Lamb&Reichart2000). The followup program described in Rhoads&Fruchter2001is continuing at the NASA Infrared Telescope Facility,and we have a similar program at the National Optical Astronomy Observatory.The observed signature of a z>7GRB would be a near-infrared afterglow exhibiting a Lyman break atλobs=0.1215(1+z)µm>1µm.Such breaks have been used to measure z=2.05for GRB000301C(Smette et al2001)and to estimate z≈5for GRB980329(Fruchter1999;see also Reichart et al1999).Their extension to longer wavelengths is straightforward.Thus,it is reasonable to expect that z>7GRBs will be detected with current technology.The prospect of detecting gamma ray bursts at z>7opens two possible methods of studying star formation activity at these epochs:GRB rate evolution,which should tracestar formation activity;and pair production cutoffs in the GeV spectra of bursts,which probe the total optical-ultraviolet background light produced by high redshift stars.BURST RATE EVOLUTIONThe most basic inference from the observed burst rate is that the highest redshift where a burst has been detected z max,grb implies the onset of star formation at some redshift z max,∗>z max,grb.It is likely that in fact z max,∗≈z max,grb:The association of GRBs with star formation tracers requires short progenitor lifetimes(≪108years),so the redshift difference between theﬁrst stars formed and the earliest possible hypernovae is small. It will be possible to go further by measuring the GRB rate as a function of red-shift,R grb(z),and taking it as a surrogate for the star formation rate.Such studies would require a large sample(several tens)of high redshift GRBs,together with an under-standing of the selection effects that went into the sample.This method is likely to be limited by at least two systematic factors.First,uncertainties in the GRB luminosity function will introduce uncertain corrections to the inferred total GRB rate and the in-ferred star formation rate,since the high redshift sample will contain only bright bursts. Second,evolution in the burst progenitor population may inﬂuence the burst rate.One plausible example is that the GRB rate could depend on progenitor metallicity,which is likely to be lower in the early universe.Another is that the stellar initial mass function (IMF)may vary,thereby affecting the relation between GRB rate and star formation rate, and perhaps also the shape of the GRB luminosity function.Possible evidence for IMF variations has recently been found in at some high redshift Lymanαemitting galaxies (Malhotra et al2001).Overall,these complications suggest that calibration of the GRB rate as an indicator of global star formation might be possible to within a factor of a few.While higher accura-cies would be desirable,the present uncertainties with more conventional star formation estimators are not much better.For example,rest ultraviolet continuum measurements are corrected by a factor of∼7for dust absorption,and the uncertainty in this correction could easily be a factor of two given the range of possible dust properties.PAIR PRODUCTION CUTOFFS IN GRB SPECTRAThe observed spectra of gamma ray bursts sometimes extend to very high photon energies:The EGRET experiment on the Compton Gamma Ray Observatory detected four bursts with unbroken power law tails extending to Eγ>1GeV,and the Milagrito air shower experiment has tentatively detected one burst at Eγ∼>1TeV.Photons withsuch high energies have mean free paths shorter than a Hubble distance due toγ+γ→e++e−interactions with low energy background photons.The threshold for such pair production reactions is Eγεγ>m2e c4=(511keV)2,corresponding to the requirement that each photon have the rest mass energy of an electron in their center of momentum frame. (Here Eγandεγare the two photon energies measured in an arbitrary frame,and Eγ≥εγby convention.)The cross section(for a head-on collision)peaks at Eγεγ=2m2e c4andfalls asymptotically as1/(Eγεγ)for Eγεγ≫2m2e c4.Pair production cutoffs in the TeV gamma ray spectra of blazars due to interactions with the cosmic infrared background have been predicted(Stecker,De Jager,&Salamon 1992;MacMinn&Primack1996;Madau&Phinney1996;Malkan&Stecker1998)and observed(e.g.,De Jager,Stecker,&Salamon1994;Konopelko et al1999)for several years now.The extension of the same physics to higher redshifts and lower gamma ray energies has been explored recently by several groups(Salamon&Stecker1998; Primack et al2000;Oh2000).The observer frame gamma ray energy determines simultaneously the redshift and rest frame energies of the background photons that dominate the pair production optical depth.At low redshifts(z≪1),the effective absorption coefﬁcientα(Eγ)increases with Eγand changes relatively little with redshift,so that the relevant physics is simply α(E cut)d=1,with d the distance to the source.However,at z∼>1,redshift effects become important:The threshold energyεγ(z)∝1/(1+z),and the background radiation ﬁeld will also evolve with redshift.The optical depth for photons near E cut is therefore dominated by absorption at high redshift,unless the source redshift is so high as to precede the creation of any substantial optical-IR background.By the time the photon reaches lower redshifts,the threshold for pair creation grows so large that the density of relevant photons is extremely low.Oh(2000)has shown that the highest energy background photons capable of producing optical depthτ≈1over a Hubble distance have energies below the ionization threshold for hydrogen(i.e.,εγ<13.6eV),since hydrogen absorption in stellar atmospheres,galaxies,and the intergalactic medium ensures a strong decrement in background photon number density at13.6eV.The most robust observable consequence of the pair creation cutoff is the observer frame gamma ray energy E cut(z)for which the optical depthτ=1.Lower pair creation optical depths(τ≪1)cannot be measured reliably because of our imperfect knowledge of the intrinsic(i.e.,unabsorbed)source spectrum,while at higher optical depths(τ≫1) the absorption reduces theﬂux below detection thresholds of present or near-future instruments.We might measureτ(Eγ)with reasonable accuracy over the range1/2∼<τ∼<2.Detailed predictions of E cut(z)differ from model to model,depending on the the-oretical treatment adopted for the earliest star formation(see Primack et al2000;Oh 2000).For example,the observer frame energy whereτ=1for redshift z=6is 4GeV∼<E cut(6)∼<6GeV for different models in Primack et al(2000),and10GeV∼< E cut(6)∼<26GeV for models in Oh(2000).Therein lies the power of this method for learning about theﬁrst generations of stars,for these strong differences in predictions allow the models to be distinguished with comparative ease from even a modest data set. Moreover,if we can observe the GeV cutoffs in spectra of a few GRBs spread over the redshift range6∼<z<z max,∗,we can infer the evolution of the optical-UV background radiation over the same period with little dependence on models.This follows because the difference in pair creation optical depth between two bursts at redshifts z1and z2 (z1<z2)is determined only by the background radiation in the range z1<z<z2.DISCUSSIONThe two methods of using gamma ray bursts to probe high redshift star formation com-plement each other in many ways.GRB rate measurements at high redshift are techni-cally easier.They require a GRB monitor plus rapid multiband near-infrared followup. Existing instrumentation and indeed existing observational programs are already ade-quate for this work.Pair creation cutoffs require one additional observation,namely,a GeV energy spectrum obtained during the GRB.This GeV spectrum will have to come from GLAST or a similar space mission.The physical assumption behind the GRB rate evolution method is that the bursts are associated with star formation activity.Under this assumption,there will be some systematic uncertainties in converting the GRB rate to the star formation rate(see above).In contrast,the pair creation cutoff method requires only that some high redshift GRBs have GeV spectra that are sufﬁciently bright and sufﬁciently smooth for the cutoff to be observed.Beyond this,there is no requirement on the nature of the bursters,which are needed only as beacons to probe the intervening background radiation.The physics of pair creation is then well understood and probes the total background radiation produced by high redshift stars.Thus,combining the two methods of studying high redshift star formation with GRBs may overcome the physical uncertainties of either method alone.Additional constraints from other techniques using other classes of objects(galaxies observed at infrared wavelengths,or quasars at X-ray wavelengths)will become available over the next few years,and will again have complementary strengths and weaknesses.By adding these to the GRB results,we can reasonably expect to understand star formation at z∼10as well as we understand it at z∼3today.REFERENCES1.Barkana,R.,&Loeb,A.2001,Physics Reports,in press2.Bloom,J.S.,Kulkarni,S.R.,&Djorgovski,S.G.2000,submitted to AJ,astro-ph/00101763.Ciardi,B.,&Loeb,A.2000,ApJ540,6874.De Jager,O.C.,Stecker,F.W.,&Salamon,M.H.1994,Nature369,2945.Fruchter,A.S.,et al1999,ApJ519,L136.Fruchter,A.S.1999,ApJ512,L17.Fruchter,A.S.,et al20018.Konopelko,A.K.,Kirk,J.G.,Stecker,F.W.,&Mastichiadis,A.1999,ApJ518,L13mb,D.Q.,&Reichart,D.E.2000,ApJ536,110.MacMinn,D.,&Primack,J.R.1996,Space Science Reviews75,41311.Madau,P.,&Phinney,E.S.1996,ApJ456,12412.Malhotra,S.,et al2001,in preparation13.Malkan,M.A.,&Stecker,F.W.1998,ApJ496,1314.Oh,S.P.2001,to appear in ApJ,astro-ph/000526315.Primack,J.R.,Somerville,R.S.,Bullock,J.S.,&Devriendt,J.E.G.2000,astro-ph/001147516.Reichart,D.E.,et al1999,ApJ517,69217.Rhoads,J.E.,Malhotra,S.,Dey,A.,Stern,D.,Spinrad,H.,&Jannuzi,B.T.2000,ApJ545,L8518.Rhoads,J.E.,&Fruchter,A.S.2001,ApJ546,11719.Salamon,M.H.,&Stecker,F.W.1998,ApJ493,54720.Stecker,F.W.,De Jager,O.C.,&Salamon,M.H.1992,ApJ390,L49。

chapter_1

•Lecturer:–盛蕴–Tel: 54345185–Email: ysheng@–Addr.: 华东师范大学闵行校区信息楼612室•Aims–To understand Digital Image Processing (DIP) and its relevant algorithms, which serve as basis of many other applications.–To be able to implement these DIP algorithms with MATLAB. •Assignments: N•Assessment–Assignment + Final Design(?)–60% + 40% or 100%1.《数字图像处理数字图像处理（（第3版）（）（英文版英文版英文版）》，）》，）》，Rafael C. Gonzalez & Richard E. Woods Rafael C. Gonzalez & Richard E. Woods著，电子工业出版社电子工业出版社201020102010年影印年影印年影印。

2.《数字图像处理数字图像处理（（MATLAB MATLAB版版）（）（英文版英文版英文版）》，）》，）》，Rafael C. Gonzalez & Richard E. Woods Rafael C. Gonzalez & Richard E. Woods著，电子工业出版社电子工业出版社200920092009年影印年影印年影印。

English = Kit ?•Digital image fundamentals (4 hrs)•Image enhancement in spatial domain (6 hrs)•Image enhancement in frequency domain (6hrs)•Image restoration (4hrs)•Colour image processing (4hrs)•Wavelet and multiresolution processing (6 hrs)•Image compression (6 hrs)•Digital Image Fundamentals–History and applications of digital image processing –Fundamental steps in digital image processing–Elements of visual perception–Light and the electromagnetic spectrum–Image sensing and acquisition–Image sampling and quantization–Some basic relationships between pixels•One picture is worth more than ten thousand words•无图无真相xyf (x, y )•Picture element/image element/Pixel /Pels •Intensity /Gray Level•The field of Digital Image Processing(DIP) refers to processing digital images by means of a digital computer.•Distinction among–DIP–Image Analysis–Computer Vision•Three types of computerised processes–Low-level process–Mid-level process–High-level process•DIP defined by our textbook•First application of DIPwas the picture sent by the Bartlane cable picture transmission system through submarine cable between London & NY in the early 1920s.out meaningful DIP wasduring the spaceprogramme in the early1960s.•By a US spacecraft Ranger7 in 1964.•Gamma-rays (Positron Emission Tomography)•X-rays (Computerised Tomography)•Ultraviolet band•Visible and infrared bands•Microwaves (Radar)•Radio waves (MRI)•Others (Ultrasound)λ= c/v E = hvwhere λand v are wavelength and frequency, respectively. c is the speed of light, hindicates Planck’s constant.•Most of the images in which we are interested are generated by the combination of an “illumination”source and the reflection or absorption of energy from that source by the elements of the “scene”being imaged.Image Sampling & Quantisation•Digitising the coordinate values is called sampling. •Digitising the amplitude value is called quantisation.Image Sampling & QuantisationNM•The number of intensity level L = 2k •The number of bits required to store a digitised image b=M×N×kImage Sampling & Quantisation• Spatial resolution– Line pairs per unit distance – Dots (pixels) per unit distance e.g. 4800 dpi – Measures of spatial resolution must be stated with respect to spatial units.• Intensity resolution L = 2kImage Sampling & QuantisationImage Sampling & QuantisationImage Sampling & QuantisationImage Interpolation• Interpolation– A process of using known data to estimate values at unknown locations. – Used in scaling, zooming, shrinking, transforming and geometric correction etc. – Nearest neighbour interpolation, bilinear interpolation, bicubic interpolation etc.Image InterpolationBicubic InterpolationBilinear InterpolationImage InterpolationNeighbours of a pixel• 4-neighbours of p: N4(p)p• Diagonal neighbours: ND(p)p•8-neighbors = 4-neighbours+diagonal neighbours : N8(p)。

开启片剂完整性的窗户(中英文对照)

开启片剂完整性的窗户日本东芝公司，剑桥大学摘要：由日本东芝公司和剑桥大学合作成立的公司向《医药技术》解释了FDA支持的技术如何在不损坏片剂的情况下测定其完整性。

太赫脉冲成像的一个应用是检查肠溶制剂的完整性，以确保它们在到达肠溶之前不会溶解。

关键词：片剂完整性，太赫脉冲成像。

能够检测片剂的结构完整性和化学成分而无需将它们打碎的一种技术，已经通过了概念验证阶段，正在进行法规申请。

由英国私募Teraview公司研发并且以太赫光（介于无线电波和光波之间）为基础。

该成像技术为配方研发和质量控制中的湿溶出试验提供了一个更好的选择。

该技术还可以缩短新产品的研发时间，并且根据厂商的情况，随时间推移甚至可能发展成为一个用于制药生产线的实时片剂检测系统。

TPI技术通过发射太赫射线绘制出片剂和涂层厚度的三维差异图谱，在有结构或化学变化时太赫射线被反射回。

反射脉冲的时间延迟累加成该片剂的三维图像。

该系统使用太赫发射极，采用一个机器臂捡起片剂并且使其通过太赫光束，用一个扫描仪收集反射光并且建成三维图像(见图)。

技术研发太赫技术发源于二十世纪九十年代中期13本东芝公司位于英国的东芝欧洲研究中心，该中心与剑桥大学的物理学系有着密切的联系。

日本东芝公司当时正在研究新一代的半导体，研究的副产品是发现了这些半导体实际上是太赫光非常好的发射源和检测器。

二十世纪九十年代后期，日本东芝公司授权研究小组寻求该技术可能的应用，包括成像和化学传感光谱学，并与葛兰素史克和辉瑞以及其它公司建立了关系，以探讨其在制药业的应用。

虽然早期的结果表明该技术有前景，但日本东芝公司却不愿深入研究下去，原因是此应用与日本东芝公司在消费电子行业的任何业务兴趣都没有交叉。

这一决定的结果是研究中心的首席执行官DonArnone和剑桥桥大学物理学系的教授Michael Pepper先生于2001年成立了Teraview公司一作为研究中心的子公司。

TPI imaga 2000是第一个商品化太赫成像系统，该系统经优化用于成品片剂及其核心完整性和性能的无破坏检测。

X射线的种类及应用

X射线的种类及应用摘要：Like many imperishable discoveries,X-rays’s invention or discovery was accidental. 1895 at Wurzburg, Wilhelm Rontgen discovered X-rays (Rontgen rays). After all these years, the technology of the X-rays has not only got extensivedevelopment in industry, also play a more and more important role in medical science. It is mainly used for the human body perspective and check injury. While scientists explore the essence of，they found the phenomenon of diffraction of X-rays and opened the gate of the crystal structure. With the widely use of x-ray both in micro fields and macro fields, it have brought great gospel to human.引言：自1895年X射线被发现，X射线已被广泛应用到医疗卫生、军事、科学及工农业各方面，为人类社会的发展做出了巨大贡献。

在X射线自从发现以来，医学就成为其主要应用，经过近百年的发展，X射线技术已广泛的应用于医学影像诊断，成为医学临床和科研不可或缺的因素。

本文就X射线的分类以及X射线的主要运用展开论述。

具体内容如下：内容X射线是一种波长很短的电磁辐射，其波长约为（20～0.06）×10-8厘米之间，又称伦琴射线。

科技英语阅读理解35篇

科技英语阅读理解目录Contents1.Mae Jemison (2)2.Can a Computer Think?……………………………………………………………………(4)3. BlackHoles (6)cation May Protect against Effects of Shrinking Brain (9)5.Radioactivity ……………………………………………………………………………(11)6. Uses of Ultrasound (14)7.Challenges for a Webbed Society (16)8.The World of Robots (19)9.The Scientific Exploration of Space…………………………………………………(21) 10. Improving IndustrialEfficiency through Robotics (24)11. Heat Loss from the Human Body ...............................................................(26) 12. Energy and Public Safety (28)13.Earth Resources Technology Satellites (32)14.Can Stress Make You Sick? (35)15.Can It Really Happen? (37)16.An Ultrasonic Torch ……………………………………………………………………(40) 17. Miracle of theBrain (42)18.All Over in a Flash (45)19.Control Earthquakes……………………………………………………………………(48) 20. Smoking and Cancer (51)21.How Well Do You See? (54)22. A Killer Is Born (56)23.It May Be Easy To Live Longer--Just Stop Eating (59)24.Study: T. Rex No Speedster (62)25.Modern Examination (64)26.Ecology (68)27.Appearances Can Be Important (70)28.Animal Senses (74)29.Telecommunications Satellite Spins Out of Control (76)30.Building Better Ultralight Computers (78)31.NASA Oks Second Space Tourist (81)32.Drink to - and for - Your Health (84)33.Three Things That Will Change Your Life (86)34.Bye-bye Credit Cards & Hello Digital Money (88)35.Gender Detector (90)1. Mae JemisonImagine you are lying on your back, strapped into a chair, with your knees bent in front of you. You feel your heart beating with excitement as you hear a voice on the earphone inside your helmet counting down slowly,” Three, two, one,” Then, beneath you, a deep rumble start as rocket fuel ignites in the huge engines. You① feel a lurch as the docking mechanisms let go, and your rocket begins to rise. This is the moment Mae Jemison has been waiting and working for since 1987. The firstAfrican-American female astronaut-in-training at the National Aeronautics and Space②Administration (NASA) , Jemison is scheduled to “fly” in September 1992. She is to serve as a specialist on Spacelab—J, a joint Japanese—American research project.Mae Jemison was thirty-three when she was selected for NASA’s astronaut training program. Astronaut candidates must have science degree. They must be fit and healthy with normal blood pressure and good eyesight. They must stand between five feet and six feet four inches tall. They must complete a one-year training program that includes water-survival lessons and weightless walks in a huge antigravity tank. On the 1991 mission, astronaut Jemison says that her “responsibility are to be familiar with the shuttle and how it operates, to do the experiments once you get③ into orbit, to help launch the payloads or satellites, and also to do extra-vehicular activities, or space walks.”How did Mae Jemison grow up to become such a special person? Science —especially astronomy—fascinated her from childhood.She also had a strong desire to help other people. Born in Alabama, but raised in Chicago, she studied chemical engineering and African—American culture and history at Stanford University. To help others, she decided to become a doctor. While still a medical student, she went to Cuba and Kenya on study trips, then worked in④a refugee camp in Thailand. She spent three years in West Africa as a doctor with the Peace Corps. When Dr. Jemison finally returned to the United States, she settled in California to practice medicine. And it was then that she decided to reach for the stars.Mae Jemison’s first application to NASA was not successful. Then, in 1986, the⑤Challenger space shuttle exploded, killing all aboard . NASA did not take in any new astronauts for about a year. When it finally reopened its application process, Mae Jemison was ready, and so was NASA. After being selected as a minority astronaut, Mae Jemison received a good deal of attention from newspaper and television. She explained to reporters that the space program and other fields in high technology offer promising careers for African-Americans and other minorities who study hard⑥and make the most of their opportunities .1.The first paragraph is about ______.A.how excited Mae Jemison was when she became an astronautB. how Mae Jemisonbecame an astronautC.how the people usually feel when the rocket they take begins to riseD.what Mae Jemison did after she was able to fly a rocket2.Which of the following statements is true?A.Mae Jemison had a strong desire to become famous.B.Mae Jemison was brought up in Alabama.C.Mae Jemison studied astronomy at Stanford University.D.Mae Jemison studied medicine.3.When did the Challenger space shuttle explode? A. Before Mae Jemison became a doctor.B.Shortly after Mae Jemison graduated from Stanford University.C.About a year before Mae Jemison was selected as an astronaut.D.About a year after Mae Jemison became famous all over the world.4.Mae Jemison believed that _______.A.men and women were not equalB.women were better paid than men wereC.American blacks were unable to find satisfactory jobs no matter how hard they studiedD.American blacks were able to find satisfactory jobs if they studied hard and made gooduse of their chance5.What is the attitude of the writer towards Mae Jemison’s achievements?A.JealousB.UpsetC. NegativeD. PositiveNotes:①lurch v. : To roll or pitch suddenly or erratically. 突然倾斜,突然地或者无规则地倾斜或坠落。

多相流测量技术及模型化方法

多相流测量技术及模型化方法Multiphase flow measurement technology and modeling methods are critical in various industrial processes, such as oil and gas production, chemical processing, and environmental monitoring. 多相流测量技术是为了有效监控和管理多相混合物在管道和储罐中的流动状况而发展起来的。

In these processes, accurate measurement and prediction of multiphase flow characteristics are essential for ensuring safe and efficient operations. 它们不仅可以帮助工程师了解流体的性质和行为，也可以为生产过程的优化提供重要的数据支持. Therefore, the development of reliable measurement technologies and robust modeling methods is of great significance for the industry.这就需要不断创新和发展多相流测量技术和模型化方法。

One of the key challenges in multiphase flow measurement is the complex nature of the flow, which involves the simultaneous movement of multiple phases, such as gas, liquid, and solid particles. 多相流的复杂性使得传统的单相流测量技术难以适用，因此需要针对多相流的特点开发新的测量方法。

介绍我的偶像谷爱凌英文作文

介绍我的偶像谷爱凌英文作文The vast expanse of the universe has captivated the human imagination for millennia. From the ancient astronomers who gazed up at the stars to the modern-day scientists who peer into the depths of space, the cosmos has been a source of wonder, mystery, and endless fascination. As we continue to explore and unravel the secrets of the universe, we are confronted with the profound realization that we are but a tiny speck in the grand scheme of things.One of the most awe-inspiring aspects of the universe is its sheer scale. The distances between celestial bodies are so vast that it is almost impossible for the human mind to comprehend. Even the nearest star to our solar system, Proxima Centauri, is over 4 light-years away. To put that into perspective, if you were to travel at the speed of light, it would take you more than 4 years to reach that star. And that is just the beginning – the Milky Way galaxy, our home, is estimated to contain over 200 billion stars, each with the potential to host its own planetary systems.Beyond our galaxy, the universe is teeming with countless other galaxies, each with its own unique characteristics and fascinating histories. The Andromeda galaxy, our closest galactic neighbor, is amere 2.5 million light-years away, yet it is so vast that it could swallow our own Milky Way whole. The scale of the universe is truly mind-boggling, and it is a testament to the incredible power and complexity of the cosmos.As we peer deeper into the universe, we are confronted with the profound mysteries that lie at the heart of its existence. What is the nature of dark matter and dark energy, the enigmatic forces that appear to make up the majority of the universe? How did the first stars and galaxies form, and what role did they play in the evolution of the cosmos? These are just a few of the questions that continue to drive scientists and researchers in their quest to unravel the secrets of the universe.One of the most intriguing and perplexing aspects of the universe is the phenomenon of black holes. These incredibly dense and massive objects, with gravitational fields so strong that not even light can escape them, have captured the imagination of scientists and the public alike. The discovery of black holes has revolutionized our understanding of the universe, and has led to the development of new theories and models that seek to explain the nature of these enigmatic entities.As we continue to explore the universe, we are also confronted with the sobering realization that our own planet, Earth, is but a tinyspeck in the vastness of the cosmos. Yet, despite its relative insignificance, Earth is the only known home of life in the universe. The emergence and evolution of life on our planet is a remarkable and complex process, one that has been shaped by the unique conditions and circumstances of our world.The search for extraterrestrial life is one of the most exciting and compelling areas of scientific exploration. As we continue to discover exoplanets – planets orbiting other stars – the possibility of finding evidence of life beyond Earth becomes increasingly tantalizing. The discovery of life elsewhere in the universe would have profound implications for our understanding of the universe and our place within it.Yet, even as we gaze outward into the vast expanse of the cosmos, we must also turn our attention inward and consider the deeper philosophical and existential questions that the universe raises. What is the meaning of our existence in the grand scheme of the universe? How do we reconcile the vastness and complexity of the cosmos with our own individual lives and experiences? These are the kinds of questions that have captivated thinkers and philosophers throughout human history, and they continue to be the subject of intense debate and exploration.Ultimately, the universe is a place of profound mystery and wonder.As we continue to explore and unravel its secrets, we are confronted with the humbling realization that we are but a tiny part of a vast and complex cosmos. Yet, this knowledge does not diminish our sense of wonder and curiosity – rather, it serves to inspire us to continue our quest for understanding, and to strive to unlock the secrets of the universe that have eluded us for so long.Whether we are gazing up at the stars, peering through the lenses of powerful telescopes, or pondering the deeper philosophical questions raised by the cosmos, the universe remains a source of endless fascination and inspiration. It is a testament to the incredible power and complexity of the natural world, and a reminder of the limitless potential of the human mind to explore and understand the world around us.。

The First Building Blocks of the Universe

The First Building Blocks of the Universe ALEXANDER STIRN【期刊名称】《中国科学院院刊（英文版）》【年(卷),期】2014(028)002【总页数】4页(P138-141)【作者】ALEXANDER STIRN【作者单位】【正文语种】英文The first galaxies evolved only a few hundred million years after the Big Bang. But why do they have such a great variety of shapes and structures? How did the universe evolve as a whole? Two German-Chinese Partner Groups at the Max Planck Institute for Astrophysics in Garching are using observations and simulations to investigate how the early universe evolved: LI Cheng and Guinevere Kauffmann, as well as GAO Liang and Simon White.TEXT ALEXANDER STIRN or blue, extremely massive or just bright, can be individuals or simply follow the crowd: the galaxies in the universe come in almost all conceivable shapes and sizes. But the cosmological standard model, which describes the evolution of the universe, doesn’t really provide forsuch a variety. The theory states only that minute density fluctuations shortly after the Big Bang must have been responsible fordistributing the mass and energy in the universe.“This results in a very useful, very simple picture of how the universe evolved,” says LI Cheng, professor at the Shanghai Astronomical Observatory of the Chinese Academy of Sciences. “But in reality, we come across, in this simple and beautiful universe, a surprisingly high number of different types of galaxies.”Within the framework of a Partner Group together with Guinevere Kauff-T hey can be large or small, red mann from the Max Planck Institute for Astrophysics, Li wants to resolve this apparent contradiction. The most important question here is: How did the different galaxies form and what were their fundamental building blocks?In the search for answers, so-called surveys play an important role - sky surveys where a telescope focuses its sights on a large region of the universe step by step. The Sloan Digital Sky Survey (SDSS), for example, has observed and mapped more than one million galaxies in the vicinity of the Milky Way. This involved dispersing the light captured from each object into its different wavelengths.In these spectra, lines show up - fingerprints that disclose, among other things, which elements are in the galaxy, how much metal the stars contain, how old they are and how quickly the y are forming. “A great deal of information on the properties of a galaxy can be gained from one of these spectra,” says LI Cheng.LI began to analyze this data together with Guinevere Kauffmann back in 2005, when he was still a postdoctoral student at the Max Planck Institutefor Astrophysics. They concentrated on searching for correlations with the environment in which the galactic systems are found. One of their findings was that galaxies with a large number of stars often turned up in a so-called galaxy cluster - a region with a particularly high density of galaxies. The SDSS spectra have one disadvantage, however: they have all been recorded in the range of visible light and thus show only stars. “Although galaxies are made up of these stars, the stars them-selves form from gas,” says Li. But it isn’t possible to make out this cold gas in the visible spectra. This is a problem for LI and his colleagues: “We still know very little about the gas, yet it is an important factor for the formation of galaxies.”When the cosmologist returned to China in 2010, this was an important motivation for establishing the Partner Group. “We didn’t just want to keep up the collaboration, we also wanted to move our focus from the visible range to wavelengths where the gas s hows up,”says Guinevere Kauffmann.The Partner Group eventually started work in January 2011 - the third such Group between the Max Planck Institute for Astrophysics and the Shanghai Astronomical Observatory. Max Planck researcher Gerhard Börner had already laid the foundation for the collaboration in 2000 when he formed the first Partner Group ever, which was established in Garching and Shanghai between the Max Planck Society and the Chinese Academy of Science.The new Group, with its concentration on wavelengths beyond the visible range, has already been able to clarify initial contradictions. At the centerof most galaxies is an extremely massive black hole that attracts, accelerates and swallows matter from its immediate vicinity - a process that is noticeable as a telltale signal in the light from the galaxies. Theoreticians are convinced, not least on the basis of simulations, that such an active galactic nucleus must emit significantly more radiation as soon as two galaxies collide. However, the images of the SDSS show no trace of this. “It didn’t matter whether a galaxy was close to another one or not, the activity always remained the same,” recalls LI.This changed only when the researchers also looked at data from the Wide-Field Infrared Survey Explorer (WISE), an American infrared telescope. “Significant differences were evident when the visible and the infrared images were compared,”says LI. It appears that galactic collisions create large numbers of new stars, whose dust hides the active galactic nuclei in the visible light - and this had initially led to incorrect conclusions being drawn.LI and Kauffmann have also turned their attention to even longer wavelengths: radio emission. With a diameter of 30 meters, the telescope of the Institute for Radio Astronomy in the Millimeter Range (IRAM) in southern Spain is able to analyze not only atoms, but also molecular gas in distant galaxies. Likewise, the Arecibo telescope in Puerto Rico has remained the largest radio telescope in the world for more than three decades, capable of surveying atomic gas with a temperature of 10,000 K. “Radio telescope technology lags far behind that of optical telescopes, so this gas is difficult to observe. But it is also more closely connected toaccretion from the external birth of new stars,” explains LI. He and his colleagues observed around 800 galaxies, and the results have been published in a series of joint papers.Around 1,000 kilometers further north, at the National Astronomical Observatories near the Beijing National Stadium, GAO Liang is working on a cosmic phenomenon that is even more difficult to make out: dark matter. GAO and Simon White, his colleague from Garching, head the sec-ond Chinese Partner Group of the Max Planck Institute; instead of observations, they rely on computer simulations.Dark matter is a good candidate for this: according to the current standard model of cosmology, it accounts for 24 percent of the universe; normal matter accounts for just below 5 percent, and the rest is what astronomers call dark energy. Dark matter is invisible; however, it betrays itself only indirectly - for example by slightly deflecting the light from distant stars. “This is how we know that dark matter interacts with other matter only via gravity,” says GAO. “This ma kes it relatively easy to simulate, even if we don’t yet know its true nature.”GAO uses his computations to investigate how matter could be distributed in galaxy clusters, among other things. Moreover, he wants to assist other astronomers in checking their theories on the strange substance - thus finally coming closer to the exact nature of dark matter. One of these theories predicts, for example, that the building blocks of the unknown matter destroy each other under certain conditions. Gamma radiation should be released in this process, and particularly large amounts in thecenter of galaxies such as the Milky Way. Observers have still been unable, however, to observe anything.Using a simulation that ran for four months on a supercomputer at the Chinese Academy of Sciences, GAO and his colleagues searched for regions in the universe where the reception of this signal should be better. Their finding: galaxy clusters in the close vicinity of the Milky Way could be a good place to find traces of dark matter - if the telltale gamma radiation exists at all.As the next step, GAO and White want to expand their computer simulations even further. The astronomers want to get a step closer to the mystery of dark energy on the Chinese supercomputer Tianhe-2, currently the fastest in the world. It will be, says GAO, the largest cosmological simulation the world has ever seen. First results are expected in summer 2014.The Partner Group also has big plans in Shanghai. FAST, the Five Hundred Meter Aperture Spherical Telescope, is currently being built in Guizhou Province in southern China. With a dish diameter of 500 meters, it will be the largest radio telescope in the world - perfect for an unobstructed view into distant galaxies. And in southern Africa and Australia, preparations are under way for the Square Kilometre Array (SKA), a link-up of radio telescopes that together will have a combined dish area of one square kilometer.The German and Chinese cosmologists are involved in both projects. “These telescopes,”says LI Cheng, “will finally make it possible for us toinvestigate the gas in near and more distant galaxies in more detail.”The Kauffmann-LI Group is based at the Shanghai Astronomical Observatory, CAS and went through its mid-term review in Garching last August. The White-GAO Group is based at the National Astronomical Observatories, CAS in Beijing and had its mid-term review in Beijing last October. Chinese scientists from both Groups are regular visitors to the Max Planck Institute for Astrophysics (MPA), and graduate students from both Groups are currently working on their Ph.D. research at MPA.。

40—50MeV能区的银河γ射线源

40—50MeV能区的银河γ射线源李惕碚;吴枚【期刊名称】《天文学报》【年(卷),期】1990(031)004【摘要】长期以来在E100 MeV能区,银河系已知天体中只有船帆座脉冲星和蟹状星云脉冲星被SAS-2和COS-B卫星证认为γ射线源。

我们分析COS-B数据得到了天鹅座X-3的γ射线像,使天鹅座X-3成为第三个被证认的银河高能γ点源,这是在这一能区中被证认的第一个γ射线双星。

COS-B卫星γ探测器可测能量下限为40 MeV,迄今所有已发表的分析COS-B数据的工作都只利用了50 MeV以上的事例。

对于50 MeV以下光子COS-B探测器的性能比几百MeV时差得多:探测效率只有1%左右。

【总页数】4页(P390-393)【作者】李惕碚;吴枚【作者单位】不详;不详【正文语种】中文【中图分类】P156【相关文献】1.50MeV／u12C离子实验靶区中子注量率的测量 [J], 李桂生;王经2.用阈探测器活化法测量50MeV/u重离子实验靶区的中子注量率、能谱和中子产额 [J], 李桂生;王经;赵彦森;李文健;张天梅;李宗强3.频率域线源近区(过渡区)测深理论初步研究 [J], 周磊;严良俊;何展翔;陈小斌4.50MeV／u 18O—ion靶区中子剂量当量率的活化测量 [J], 李桂生;张天梅5.寻找超高能宇宙线源——西藏广延空气簇射实验 [J], 贾焕玉;Amenomori M;戴本忠;丁林垲;冯振勇;HibinoK;HottaN;黄庆;霍安祥;KajinoF;KasaharaK;拉巴次仁;刘绍敏;梅东明;孟宪茹;MizutaniK;木均;NanjoH;NishizawaM;OguroA;OhnishiM;OhtaI;O因版权原因，仅展示原文概要，查看原文内容请购买。