土星磁层顶的Kelvin-Helmholtz不稳定性和磁流体表面波

本文采用可压缩磁流体力学近似并选取Voyager-1的观测数据,讨论了土星磁层顶的Kelvin-Helmholtz不稳定性和磁流体表面波.计算表明,土星磁层随星体自转同磁鞘流之间的速度差,可以在地方时午前、中午和距中午不远的午后磁层顶激发不稳定性;午前和午后区有很强的非对称性.计算所得的波的特性与观测一致.      

M stars as targets for terrestrial exoplanet searches and biosignature detection

The changing view of planets orbiting low mass stars, M stars, as potentially hospitable worlds for life and its remote detection was motivated by several factors, including the demonstration of viable atmospheres and oceans on tidally locked planets, normal incidence of dust disks, including debris disks, detection of planets with masses in the 5-20 M() range, and predictions of unusually strong spectral biosignatures. We present a critical discussion of M star properties that are relevant for the long- and short-term thermal, dynamical, geological, and environmental stability of conventional liquid water habitable zone (HZ) M star planets, and the advantages and disadvantages of M stars as targets in searches for terrestrial HZ planets using various detection techniques. Biological viability seems supported by unmatched very long-term stability conferred by tidal locking, small HZ size, an apparent short-fall of gas giant planet perturbers, immunity to large astrosphere compressions, and several other factors, assuming incidence and evolutionary rate of life benefit from lack of variability. Tectonic regulation of climate and dynamo generation of a protective magnetic field, especially for a planet in synchronous rotation, are important unresolved questions that must await improved geodynamic models, though they both probably impose constraints on the planet mass. M star HZ terrestrial planets must survive a number of early trials in order to enjoy their many Gyr of stability. Their formation may be jeopardized by an insufficient initial disk supply of solids, resulting in the formation of objects too small and/or dry for habitability. The small empirical gas giant fraction for M stars reduces the risk of formation suppression or orbit disruption from either migrating or nonmigrating giant planets, but effects of perturbations from lower mass planets in these systems are uncertain. During the first approximately 1 Gyr, atmospheric retention is at peril because of intense and frequent stellar flares and sporadic energetic particle events, and impact erosion, both enhanced, the former dramatically, for M star HZ semimajor axes. Loss of atmosphere by interactions with energetic particles is likely unless the planetary magnetic moment is sufficiently large. For the smallest stellar masses a period of high planetary surface temperature, while the parent star approaches the main sequence, must be endured. The formation and retention of a thick atmosphere and a strong magnetic field as buffers for a sufficiently massive planet emerge as prerequisites for an M star planet to enter a long period of stability with its habitability intact. However, the star will then be subjected to short-term fluctuations with consequences including frequent unpredictable variation in atmospheric chemistry and surficial radiation field. After a review of evidence concerning disks and planets associated with M stars, we evaluate M stars as targets for future HZ planet search programs. Strong advantages of M stars for most approaches to HZ detection are offset by their faintness, leading to severe constraints due to accessible sample size, stellar crowding (transits), or angular size of the HZ (direct imaging). Gravitational lensing is unlikely to detect HZ M star planets because the HZ size decreases with mass faster than the Einstein ring size to which the method is sensitive. M star Earth-twin planets are predicted to exhibit surprisingly strong bands of nitrous oxide, methyl chloride, and methane, and work on signatures for other climate categories is summarized. The rest of the paper is devoted to an examination of evidence and implications of the unusual radiation and particle environments for atmospheric chemistry and surface radiation doses, and is summarized in the Synopsis. We conclude that attempts at remote sensing of biosignatures and nonbiological markers from M star planets are important, not as tests of any quantitative theories or rational arguments, but instead because they offer an inspection of the residues from a Gyr-long biochemistry experiment in the presence of extreme environmental fluctuations. A detection or repeated nondetections could provide a unique opportunity to partially answer a fundamental and recurrent question about the relation between stability and complexity, one that is not addressed by remote detection from a planet orbiting a solar-like star, and can only be studied on Earth using restricted microbial systems in serial evolution experiments or in artificial life simulations. This proposal requires a planet that has retained its atmosphere and a water supply. The discussion given here suggests that observations of M star exoplanets can decide this latter question with only slight modifications to plans already in place for direct imaging terrestrial exoplanet missions.     

三维平壁进气道的特性研究

介绍三维进气道和超声速燃烧冲压式喷气发动机 (SCRAMJET)模型一项实验研究的结果。Scramjet模型由进气道和燃烧室组成 ,此模型组件的设计是为了研究流动结构以获得进气道的特性 ,以及研究燃烧室和进气道、燃料 (氢及碳氢燃料 )点火和燃烧的相互影响。这些试验是在下吹式风洞(M =2 ～ 6,Reunit=( 8～ 54) × 1 0 6)和热射式风洞 (M =6及 7 2 ,Reunit =( 1 0 ～ 32 )× 1 0 6,Tt =1 50 0 ～ 2 50 0K)中进行的。     

A regenerable carbon dioxide removal and oxygen recovery system for the Japanese Experiment Module

The Japanese Space Station Program is now under Phase B study by the National Space Development Agency of Japan in participation with the U.S. Space Station Program. A Japanese Space Station participation will be a dedicated pressurized module to be attached to the U.S. Space Station, and is called Japanese Experiment Module (JEM). Astronaut scientists will conduct various experimental operations there. Thus an environment control and life support system is required. Regenerable carbon dioxide removal and collection technique as well as oxygen recovery technique has been studied and investigated for several years. A regenerable carbon dioxide removal subsystem using steam desorbed solid amine and an oxygen recovery subsystem using Sabatier methane cracking have a good possibility for the application to the Japanese Experiment Module. Basic performance characteristics of the carbon dioxide removal and oxygen recovery subsystem are presented according to the results of a fundamental performance test program. The trace contaminant removal process is also investigated and discussed. The solvent recovery plant for the regeneration of various industrial solvents, such as hydrocarbons, alcohols and so on, utilizes the multi-bed solvent adsorption and steam desorption process, which is very similar to the carbon dioxide removal subsystem. Therefore, to develop essential components including adsorption tank (bed), condenser. process controller and energy saving system, the technology obtained from the experience to construct solvent recovery plant can be easily and effectively applicable to the carbon dioxide removal subsystem. The energy saving efficiency is evaluated for blower power reduction, steam reduction and waste heat utilization technique. According to the above background, the entire environment control and life support system for the Japanese Experiment Module including the carbon dioxide removal and oxygen recovery subsystem is evaluated and proposed.     

低检测概率雷达中随机PRF信号的性能估算

为了产生低检测概率(LPD)的雷达信号，提出了随机PRF(脉冲重复频率)方法。本文对这种方法进行了研究，并简要讨论了该方法对雷达接收机性能的影响。此外还用理论检测法获得了未经许可的接收机及其性能的最佳检测器。然后用这些结果对采用随机PRF的LPD信号特性进行大量的改进。因此，首先要从LPD的观点来估算这些信号的性能，而且表明这种随机PRF信号是非常有用的，可看做是一个可靠的LPD信号。     

海上舰船目标的机载高分辨率ISAR成像

本文提出了机载高分辨率二维逆合成孔径雷达(ISAR)对舰船目标的侧视成像问题。通过采用舰船运动的简单模型，避免了采用高级的联合-时间频率(JTF)变换。研究了包括运动估计与校正、最佳处理时间与持续时间估计以及目标形状提取的鲁棒处理方案。强调了这样一个事实，即该处理的鲁棒性造就了单个ISAR成像分析而不必由一组雷达图像进行数据融合。     

用鲁棒算法使宽带雷达信号与目标实现最佳匹配的目标识别新方法

介绍了一种采用耦合振荡器阵列进行宽带雷达信号传输的新方法。这种方法表明振荡器阵列的总体输出是一种能够与特定方位目标匹配的灵活信号。此外，还介绍了一种新的基于相关矩阵本征向量的鲁棒算法，用此算法可以使耦合振荡器阵列产生的信号与目标在有限方位范围内实现匹配。因为雷达不能够精确估计真实目标的方位，所以具有这种性能是很重要的。在这种用于雷达目标识别的新方法中，在估计了未知目标的近似方位后，依次合成并向目标发射了大量与不同潜在目标相匹配的各种波形。这样，后向散射信号的最大峰值功率就会标明出目标的身份。计算机模拟表明这项技术对附加噪声和方位角不定性尤其有效。     

Adsorption water-related potential chemical and biological processes in the upper martian surface

Mars Odyssey has given strong evidence for the existence of water in the upper martian surface at equatorial latitudes. The water content, which corresponds to the hydrogen in the soil, can regionally reach values up to about 15%. This water is mainly in the form of structurally and partially irreversibly bound "crystal" water, and of reversibly bound and partially unfrozen adsorption water. This adsorption water, which has "liquid-like" properties as a two dimensional fluid or film, can trigger-in the presence of ultraviolet light and in concentrations similar to what has been measured on Mars-photocatalytic processes that are important for martian surface chemistry. The consequences of the diurnally variable presence of adsorption water on the chemistry and hypothetical biological processes at and in the upper martian surface at equatorial and mid-latitudes are discussed in terms of water-related environmental aspects for chemical and hypothetical life processes on Mars.     

钛合金扩散连接界面完整性超声定量评估

利用高分辨率超声扫描显微成像检测技术对钛合金扩散连接界面的微缺陷分布进行研究 ,从而得到有关扩散界面微观完整性的定量信息 ,给出了钛合金扩散连接界面的超声扫描成像检测的典型试验结果