The Swift X-Ray Telescope

he Swift Gamma-Ray Explorer is designed to make prompt multiwavelength observations of gamma-ray bursts (GRBs) and GRB afterglows. The X-ray telescope (XRT) enables Swift to determine GRB positions with a few arcseconds accuracy within 100 s of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/EPIC MOS CCD detector to provide a sensitive broad-band (0.2–10 keV) X-ray imager with effective area of > 120 cm² at 1.5 keV, field of view of 23.6 × 23.6 arcminutes, and angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2×10⁻¹⁴ erg cm⁻² s⁻¹ in 10⁴ s. The instrument is designed to provide automated source detection and position reporting within 5 s of target acquisition. It can also measure the redshifts of GRBs with Fe line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return for each frame as the source intensity fades. The XRT will measure spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and will follow each burst for days or weeks. Dedicated to David J. Watson, in memory of his valuable contributions to this instrument.     

The Swift Ultra-Violet/Optical Telescope

The Ultra-Violet/Optical Telescope (UVOT) is one of three instruments flying aboard the Swift Gamma-ray Observatory. It is designed to capture the early (∼1 min) UV and optical photons from the afterglow of gamma-ray bursts in the 170–600 nm band as well as long term observations of these afterglows. This is accomplished through the use of UV and optical broadband filters and grisms. The UVOT has a modified Ritchey–Chrétien design with micro-channel plate intensified charged-coupled device detectors that record the arrival time of individual photons and provide sub-arcsecond positioning of sources. We discuss some of the science to be pursued by the UVOT and the overall design of the instrument.     

达芬奇:十年华丽,繁华伊始

贵族,并非遥不可及,宫廷皇室级的豪宅,也并非真的只停留在欧洲怀旧的电影之中。雕刻细腻华美的沙发,镶嵌着蔷薇花图案的餐桌椅,缀着金色绳饰的窗帘,烛光摇曳里的背景总是令人迷眩……这些欧洲古典小说中上流社会的景象,在独一无二的达芬奇家居的华丽殿堂,已为您一一呈现。     

识别大学生心理咨询言语隐藏性的快捷方法--从表情"测谎"

通过表情反映情绪变化的论述，说明了表情可以“测谎”。表情“测谎”又分为面部表情“测谎”，体态表情“测谎”和言语表情“测谎”，它已成为识别大学生心理咨询言语隐藏性的快捷方法。     

会计信息系统的产生、发展及其对未来会计的影响

信息理论与信息技术的发展使得会计演变成数字化会计信息系统，并实现其管理型与网络化，成为企业管理系统的核心。这对现行的会计理论和实务带来了巨大的甚至革命性的影响。一些会计的基本理论，基本方法和基本操作技能方面的问题。需要迅速地作出相应的研究与解释。文章回顾了我国会计电算化发展的历程和会计软件发展的五个阶段，指出未来会计的新变化将表现在会计的反映与控制空间的拓展，社会责任会计的产生，会计信息的实时性和多计量属性的实现等方面。     

推力室中压力剧烈振荡区域的燃烧特性分析

在不施加任何扰动的情况下,对液氧/煤油双组元液体火箭发动机模型燃烧室进行三维非稳态数值模拟,获得了其中的压力自激振荡现象。基于定义的能够辨识定容和定压燃烧特征的第三邓克尔数分析了压力剧烈振荡区域的燃烧特性。结果表明,在压力剧烈振荡区域内,第三邓克尔数取值很大,即发生了准定容燃烧或介于定容和定压之间的燃烧过程。可见尽管液体火箭发动机燃烧室整体表现为定压燃烧特性,但在头部附近区域出现了局部具有非定压特性的燃烧过程,其产生的压力膨胀波来不及迅速传播而使当地的压力迅速升高,形成了定容弹效应,从而导致了燃烧不稳定性的发生。该压力峰的传播及其与室壁相互作用在燃烧室中产生声学不稳定性,与研究燃烧不稳定性的定容弹试验机理相同。     

大气层外拦截弹末制导段的目标搜索算法

以搜索时间最短为设计指标,根据目标相对于拦截弹方向的概率分布,设计了一种搜索算法.分析了采用该搜索算法时,搜索范围、搜索时间以及拦截弹视场角与算法中调节系数的关系.给出了典型情况下的仿真算例,并利用统计方法分析了目标相对于拦截弹方向的概率分布的标准差对搜索时间期望值的影响.仿真表明了该搜索算法的有效性.     

SOHO: The Solar and Heliospheric Observatory

The Solar and Heliospheric Observatory (SOHO), together with the Cluster mission, constitutes ESA's Solar Terrestrial Science Programme (STSP), the first Cornerstone of the Agency's long-term programme Space Science — Horizon 2000. STSP, which is being developed in a strong collaborative effort with NASA, will allow comprehensive studies to be made of the both the Sun's interior and its outer atmosphere, the acceleration and propagation of the solar wind and its interaction with the Earth. This paper gives a brief overview of one part of STSP, the SOHO mission.     

The solar flare plasma: Observation and interpretation

In the past several years, X-ray observations of the Sun made from rockets and satellites have demonstrated the existence of high temperature (20 × 10⁶ – 100 × 10⁶ K), low density plasmas associated with solar flare phenomena. In the hard X-ray range ( < 1 ), spectra of the flaring plasma have been obtained using proportional and scintillation counter detectors. It is possible from these data to determine the evolution of the hard X-ray flare spectrum as the burst progresses; and by assuming either a non-thermal or thermal (Maxwellian) electron distribution function, characteristic plasma parameters such as emission measure and temperature (for a thermal interpretation) can be determined. Thermal interpretations of hard X-ray data require temperatures of 100 × 10⁶ K.In contrast, the soft X-ray flare spectrum (1 <<30 ) exhibits line emission from hydrogen-like and helium-like ions, e.g. Ne, Mg, Al, Si,... Fe, that indicates electron energies more characteristic of temperatures of 20 × 10⁶ K. Furthermore, line intensity ratios obtained during the course of an event show that the flare plasma can only be described satisfactorily by assuming a source composed of several different temperature regions; and that the emission measures and temperatures of these regions appear to change as the flare evolves. Temperatures are determined from line ratios of hydrogen-like to helium-like ions for a number of different elements, e.g., S, Si, and Mg, and from the slope of the X-ray continuum which is assumed to be due to free-free and free-bound emission. There is no obvious indication in soft X-ray flare spectra of non-thermal processes, although accurate continuum measurements are difficult with the data obtained to date because of higher order diffraction effects due to the use of crystal spectrometers.Soft X-ray flare spectra also show satellite lines of the hydrogen-like and helium-like ions, notably the 1s ²2s ² S-1s2s2p ² P transition of the lithium-like ion, and support the contention that in low density plasmas these lines are formed by dielectronic recombination to the helium-like ion. Also, series of allowed transitions of hydrogen-like and helium-like ions are strong, e.g., the Lyman series of S up to Lyman-, and ratios of the higher member lines to the Lyman- line can be compared with theoretical calculations of the relative line strengths obtained by assuming various processes of line formation.This review will discuss the X-ray spectrum of solar flares from 250 keV to 0.4 keV, but will be primarily concerned with the soft X-ray spectrum and the interpretation of emission lines and continuum features that lie in this spectral range.     

The Power-Inversion Adaptive Array: Concept and Performance

The use of a power-inversion adaptive array to improve the signal-to-interference ratio in a communication system is described. "Power inversion" refers to the ability of an adaptive array to invert the power ratio of two received signals. The power-inversion ion technique is useful because it does not require detailed ledgeknow about desired-signal structure or arrival angle. The perform ance attainable with a power-inversion array is described and typical al design curves are presented.     

Hybrid rocket engines: The benefits and prospects

The review of research avenues for working processes (ignition, combustion, etc.) in hybrid rocket engines (HRE), for thermal protection and power characteristics is stated. Based on conducted design and exploratory studies and design developments, the reasonable fields of application of HRE to launch systems for orbit insertion of payload are determined.     

The Magnetic Sun: Reversals and Long-Term Variations

A didactic introduction to current thinking on some aspects of the solar dynamo is given for geophysicists and planetary scientists.     

基础研究和创新能力是发展航空工业之本

当今世界,知识经济已露端倪,竞争也日趋激烈,人类正在经历一场全球性的科学技术革命。在科技发展日新月异的今天,以基础研究及其所孕育的高新技术的原始创新为主要标志的科技自主创新能力的竞争,已成为世界科技竞争的制高点,乃至国家间竞争成败的分水岭。航空工业在一个国家整体经济发展和科技进步中巨大的牵引作用,早已成为世界各国政府高层的共识,而航空航天技术所带来的丰厚社会和经济利益也是传统产业无法企及的。为此,如今无论是老牌的经济发达国家,还是新兴的有科     

欧美联手研究未来高效静音客机

欧美两家著名高等学府正在 NASA 的资助下从事一项高效、静音飞机研究计划。目前研究人员共研究了两种设计方案,一种为 SAX-40,另一种为降低风险方案 SAX-L/R1。欧美打算在2025年联合发起一种具有高效静音特性的采用翼身融合体设计布局的民用客机。它的启用对降低未来航空器的噪声污染,为人类营造更加宁静的生活环境具有重要意义。     

The mass and helium discrepancy in massive stars: The case Vela X-1

A NLTE-analysis is presented of high S/N spectra of the optical component of the standard massive X-ray binary Vela X-1. In combination with the orbital parameters we conclude that the optical star is highly helium enriched and is significantly overluminous compared to standard evolutionary tracks of massive accretion stars. We then propose a new accretion model able to explain these features.     

The Solar Dynamo: The Role of Penetration, Rotation and Shear on Convective Dynamos

In this paper I discuss the importance of turbulence, rotation, penetration and shear for solar dynamos (both local and global). An understanding of these processes is vital for progress towards a self-consistent theory for the generation of solar magnetic activity. I discuss the difficulties for large-scale field generation and suggest that large-scale solar magnetic activity may be driven by dynamos that arise owing to instabilities, with these dynamos modified by the presence of turbulence.     

Diffuse cosmic X- and gamma radiation: The isotropic component

SummaryA. Spectral features The ability of the various theories to explain the three main spectral features at 1/4 keV, 60 keV and 1 MeV is summarized in Tables II and III.Clearly, confirmation of the reality of these features, especially the soft X-ray and -ray excesses, is one of the key elements in enabling us to decide between the competing theoretical interpretations.B. Energy requirements None of the proposed interpretations are easily explained in terms of the available energy in cosmic rays (except perhaps the Seyfert galaxy proposal, and this runs into difficulties). It seems that one either has to regard normal galaxies at the present epoch as prolific sources of cosmic rays ( 10⁶⁰ erg/galaxy in protons), as is required by the Brecher-Morrison model, or to argue that at early stages in their evolution far more energy is available than at present. One ends up with much the same energy requirement in this approach.One could conceivably identify such an early phase with the radio galaxy or QSO phenomena: in any event, cosmological evolution plays a major role. Cosmology does ease the energy requirements, but only for the inefficient mechanisms, such as nonthermal bremsstrahlung or ° -production.It seems that one still needs the metagalactic cosmic ray flux to be 10^-2 of the galactic flux in the diffuse inverse Compton models, and 10^-2–10^-4 in the nonthermal bremsstrahlung models.Faced with problems of energetics, one is tempted to turn to the most energetic objects in the Universe, namely Seyfert nuclei and QSO's, to provide the basic energy source, whether directly or indirectly, for the diffuse X-ray background. A direct connection could be more readily investigated when X-ray observations are available of more extra-galactic sources.C. Angular variations Another approach, complementary to that of looking for remote discrete sources, is to seek angular fluctuations, or limits on such fluctuations in the diffuse X-ray background.The best results presently available are those from the X-ray experiment on board OSO 3. Schwartz (1970) reports a limit of I/Ifour percent on small-scale (10°) fluctuations over 10–100 keV over about one-quarter of the sky. If one assumes a astrophysics, namely the origin of cosmic rays, is intimately linked to the origin of the X-ray background.It may well be that no single mechanism suffices to account for the entire spectrum of isotropic X- and -radiation. Nature is sufficiently perverse for there to be a reasonable probability that several different processes are contributing, and considerable ingenuity will be required to ascertain which mechanism, if any, is assigned the dominant role in a given spectral region.This review is based on an invited paper presented at the joint meeting of the A. A. S. Division of High Energy Astrophysics, and the A. P. S. Division of Cosmic Physics, Washington, D. C., 28 April–1 May, 1970     

质量与人才是航空发动机研制永恒主题——访美国工程院院士、普惠公司技术与环境副总裁艾伦·艾伯斯坦

正艾伦·艾伯斯坦Alan H.Epstein美国工程院院士NAE Member麻省理工学院名誉教授Honorary Professor of MIT麻省理工学院名誉教授,美国航空航天学会和美国机械工程师协会成员。现主要负责为普惠公司制定技术发展方向并协调技术在产品性能及环境影响方面的应用,还负责为公司开发的所有新产品寻找和评估能够改善发动机性能与燃油效率的新方法。艾伯斯坦博士凭借其在热传导、涡轮机机械、仪表与控制、燃气涡轮机技术与微机电系统领域的研究屡获国际大奖,曾被美国机械工程师协会国际涡轮学院评为2003年年度学者,2015年6月,荣获美国机械工程师协会授予的航空发动机技术大奖。