地热井中的光学测溫法

本文叙述以全光学装置为基础,利用双折射晶体的物理特性与温度之间关系的一种温度测量系统,要求系统测量地热井中最高达500℃的温度分布图,并具有优于0.1℃的分辨率,最大预期井深为3500米。本文也论述了光学纤维使用问题的技术解决办法,同时将叙述现场使用的试验样机及初步试验的结果。     

多向Sepcard碳—碳复合材料的力学分析进展

等温有限元模型业已取得良好进展,它首次用于4向(4D)碳—碳材料的热结构分析,并推广用于其它多向(nD)复合材料。从本质上讲,复合材料各向异性和非弹性性质的预估,要由各向同性的弹塑性材料(基体加界面)和弹性正交材料(均匀化杆组成的网络)叠加求得。加上模型的热塑性能使之能更好地描述热试车过程中 nD 整体喉衬入口段(ITE)的真实状态,尤其是,用经典弹性和轴对称热结构分析,可能大大低估了应力。另一方面表明,由4D 碳—碳复合材料试验研究得到的复合结构的基本性质可用于由同样成分制作的其它nD 织物结构。这样,无需用复合材料的具体特性,就可以预估出一个6D 碳—碳环的性质。     

用于军用计算机的浮点模块

本文介绍了扩充运算器通过其结构及其产生支持浮点计计算算法的方法达到提高性能的目的。     

Steering the station back on course

Rising costs of the International Space Station prompted NASA to convene a panel of experts to assess the quality of ISS cost estimates and review program assumptions and requirements. The panel concluded that NASA was unable to accurately predict ISS costs or to support requests for increased funding for the ISS through 2006 and should maintain a U.S. core complete program with three-person crews with 6-month stays on the ISS. International response to the panel report was negative with space agencies from Japan, Russia, Canada, and Europe taking issue with the expected impact on ISS construction and use.     

冲压发动机试验和模拟技术

模拟冲压发动机工作状态的流动条件需要独特的地面试验能力、暂冲式吹风试车台是一个经济设备,它能满足高流量和高压力比的要求。污染空气加热器提供了一种灵活而廉价的模拟弹道温度变化的有效方法。自由射流试验中,适当地模拟进口流动条件对发动机研制起着很重要的作用。本文讨论了冲压发动机地面试验要求,评论了直联式与自由射流的试验中模拟可用参数的方法,描述了满足气动模拟要求的技术与设备,并已证实是有效的。     

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.     

使用液态化学循环的高热效率动力研究(英文)

要使碳氢燃油在常规燃烧循环中高效燃烧,需要非常高的温度,化学循环燃烧可以为大型动力装置提供一个可行的方法。在化学循环燃烧中,使用含氧介质分子来传输两个氧化还原反应之间的氧气,含氧介质在一个反应中被氧化,在另一个与燃油的反应中被减少。从燃烧残余物中分离出含氧介质可以借助于不同的物态,如果介质用钠、钾或锌,这是液态化学循环燃烧的显著优点。液态化学循环燃烧的原理是能量和熵的循环,在考虑用于分离氮和二氧化碳零部件效率、结合水燃气交换、以及用空气作为氧气源的情况下,高的热效率(35Pa下约75%)在理论上可以达到。     

激光合成金属间化合物基复合材料研究进展

对激光合成颗粒增强金属间化合物基复合材料进行了研究,包括Ni3Al/WC、NiAl/TiC、Ti3Al/TiC和MoSi2/SiC,用扫描电镜、能谱仪和X射线衍射仪对材料成分和组织特征进行了分析,提出并讨论了影响激光合成金属间化合物基复合材料的关键问题.激光合成具有多种强韧化方法协同、提高金属间化合物强度和塑性的特点,有利于金属间化合物性能的综合改善.     

涡轮叶栅前缘上游端壁气膜冷却的传热实验研究

对前缘上游有单排和双排孔冷却的涡轮导向叶栅端壁进行了详细的传热实验,在吹风比1,2,3下获得了当地气膜冷却效率和换热系数,结合流场测量结果分析了端壁冷却和换热规律。结果表明端壁气膜冷却在很大程度上受二次流的影响,冷却效果主要由吹风比决定,低吹风比喷射时,压力面附近的一个三角形区域没有冷气的覆盖,中、高吹风比喷射可以大幅度提高平均冷却效率并使冷气很均匀的覆盖在端壁上,双排孔喷射比单排孔喷射平均效率提高1倍左右。结果还表明尽管冷气喷射使端壁换热系数随吹风比的增大而显著增大,气膜冷却还是能有效的降低端壁的热负荷,其中以中吹风比双排孔喷射的效果最为显著。      

用作热防护材料的PAN基碳纤维织物

粘胶基碳纤维织物已广泛用作烧蚀和绝热复合材料。由于行情和利润不断下降,用连续粘胶纤维制得的碳纤维制品最终可能不易买到或限制供应。因此,围绕获得相应的PAN基碳布、测定其性能并制作布带缠绕酚醛树脂复合材料开展了研究。市场上买得到的PAN基碳布具有强度高和质量均匀等特性,但绝热性和化学纯度较差。特殊的PAN基碳布是在较低的(低于1350℃)热处理温度下获得的,并且应用于20°布带缠绕酚醛复合材料中。对这种复合材料的烧蚀、热物理、机械和化学性能的测定表明,所研制的复合材料可以代替粘胶基碳布/酚醛,但纤维与基体之间的粘结和纤维的纯度尚需进一步改善。