用计算流体力学解读急剧机翼失速

文章描述了在为期4年的急剧机翼失速（AWS）国家研究计划中用计算流体动力学所做的工作及获得的经验；详细论述了在跨音速机动状态现代美国战斗机和强击机遭遇到的跨音速流的复杂特性，内容包括针对这种高度复杂、有激波诱导的大分离粘性流动的网格处理、计算存储器和处理器要求、湍流模型、定常和非定常计算以及高度复杂的雷诺平均NS方程解与脱体涡模拟方法的比较。对F／A-18C飞机、AV-8B飞机、预生产F／A-18E飞机和F-16C飞机的跨音速机动状态进行了CFD模拟。模拟了各种襟翼位置，并将计算结果与大规模的风洞数据进行了比较；将结构与非结构网格获得的结果进行了对比；通过对模型在风洞中获得的表面油流和压敏涂层（psp）试验结果的定性比较以及有试验结果的详细定量压力系数数据来评估不同CFD方程式的适用性和计算精度。对比了这些计算软件和在这次研究中涉及的每种飞机的试验数据之间的静升力系数。     

Analysis of a crossed Bragg cell acousto-optical spectrometer for SETI

The search for radio signals from extraterrestrial intelligent beings (SETI) requires the use of large instantaneous bandwidth (500 MHz) and high resolution (20 Hz) spectrometers. Digital systems with a high degree of modularity can be used to provide this capability, and this method has been widely discussed. Another technique for meeting the SETI requirement is to use a crossed Bragg cell spectrometer as described by Psaltis and Casasent. This technique makes use of the Folded Spectrum concept, introduced by Thomas. The Folded Spectrum is a 2-D Fourier Transform of a raster scanned 1-D signal. It is directly related to the long 1-D spectrum of the original signal and is ideally suited for optical signal processing. The folded spectrum technique has received little attention to date, primarily because early systems made use of photographic film which are unsuitable for the real time data analysis and voluminous data requirements of SETI. An analysis of the crossed Bragg cell spectrometer is presented as a method to achieve the spectral processing requirements for SETI. Systematic noise contributions unique to the Bragg cell system will be discussed.     

机载雷达的多个分辨率信号处理技术

合成孔径雷达（SAR）利用通过时间积累和自身的运动所获得的很高空间分辨率，可以降低某一给定分辨单元中的背景杂波功率，从而探测出非运动目标。而地面动目标显示（GMTI）雷达为了探测则采用低得多的分辨处理，利用的是实际孔径与动目标和杂波之间的空．时响应的相对差别。因此，SAR和GMTI代表了两种不同的时间处理分辨尺度，它们对探测固定（在SAR情况下）或者外围杂波中的（在GMTI情况下）目标来说是最佳的，并已经单独验证过，能够很好地工作。基于机载雷达数据处理的这种多个分辨率说明，就有可能研究出一种探测技术，该技术将着手优化信号处理分辨尺度（比如时间积累的长度）来与所关注目标的动态情况相匹配。本文研究怎样利用长相参处理时间间隔（CPI）的信号处理技术来改善GMTI雷达的探测性能。     

The SERENDIP piggyback SETI project

The SERENDIP project is an ongoing program of monitoring and processing broadband radio signals acquired by existing radio astronomy observatories. SERENDIP operates in a piggyback mode: it makes use of whatever observing plan (sequence of frequencies, sky coordinates, and polarizations) is under way at its host observatory. Moreover, the SERENDIP data acquisition system, once installed, operates autonomously. This approach makes it possible to obtain large amounts of high quality observing time in a manner that is economical and that does not adversely affect ongoing radio astronomy survey work. The SERENDIP II system has been installed at the NRAO 300-foot telescope at Green Bank, West Virginia, and has operated there for several thousand hours. In this report, we summarize our findings from these observations and describe the present status of the project. Two key elements of SERENDIP are the automated data acquisition system that uses adaptive thresholds and logs only statistically significant peaks in the real-time power spectra, and the subsequent off-line analysis programs that identify and reject a variety of interference signals. Several specific correlations have been identified that offer promise. At present, the development and testing of these interference rejection algorithms is the main thrust of our work.     

含硝酸酯增塑剂的固体推进剂的脆化研究

本文介绍硝酸酯增塑的聚醚聚氨酯推进剂在低温贮存中,解决失去应变能力(脆化)问题的研究结果。这种高度增塑的推进剂在低温下短期贮存,几乎完全失去了应变能力。研究这种脆化的原因表明,交联密度以及粘合剂配方是起作用的因素。湿度曾被考虑是因素之一,但实验证明并非如此。实验表明增塑剂结晶是脆变的主要原因但不一定与增塑剂的凝固点有关。重新测定某些增塑剂的凝固点是研究工作的一部份。放入增塑剂晶体增加了推进剂脆变速度。单独采用丁三醇三硝酸酯(BTTN)或是混合增塑剂可以解决这个问题。采用混合增塑剂可以得到最好的低温性能。     

机载雷达系统中的空—时自适应处理

本文概述了空—时自适应处理(STAP)在现代雷达系统中，尤其是在强干涉和人为干扰下的机载雷达系统中的应用情况。简要介绍处理方法后，叙述了STAP在导致非平稳信号环境的热杂波和非均匀雷达环境中STAP的应用结果。分析了在这种实际情况下采用STAP处理所存在的局限。结尾部分为使用圆形阵列所得到的一些STAP近期结果。     

Humans to Mars: a feasibility and cost-benefit analysis

Mars is a compelling astrobiological target, and a human mission would provide an opportunity to collect immense amounts of scientific data. Exploration alone, however, cannot justify the increased risk. Instead, three factors drive a human mission: economics, education, and exploration. A human mission has a unique potential to inspire the next generation of young people to enter critically needed science and engineering disciplines. A mission is economically feasible, and the research and development program put in place for a human mission would propel growth in related high-technology industries. The main hurdles are human physiological responses to 1–2 years of radiation and microgravity exposure. However, enabling technologies are sufficiently mature in these areas that they can be developed within a few decade timescale. Hence, the decision of whether or not to undertake a human mission to Mars is a political decision, and thus, educational and economic benefits are the crucial factors.     

Voluntary head stabilization in space during trunk movements in weightlessness

The ability to voluntarily stabilize the head in space during lateral rhythmic oscillations of the trunk has been investigated during parabolic flights. Five healthy young subjects, who gave informed consent, were examined. The movements were performed with eyes open or eyes closed, either during phases of microgravity or phases of normal gravity. The main result to emerge from this study is that the head may be stabilized in space about the roll axis under microgravity conditions with, as well as without vision, despite the reduction of the vestibular afferent and the muscle proprioceptive inputs. Moreover, the absence of head stabilization about the yaw axis confirms that the degrees of freedom of the neck can be independently controlled, as it was previously shown [1]. These results seem to indicate that voluntary head stabilization does not depend crucially upon static vestibular afferents. Head stabilization in space may be in fact organized on the basis of either dynamic vestibular afferents or a postural body scheme.     

Canada and the International Space Station program: overview and status

The twelve months since IAF 2000 have been perhaps the most exciting, challenging and rewarding months for Canada since the beginning of our participation in the International Space Station program in 1984. The highlight was the successful launch, on-orbit check out, and the first operational use of Canadarm2, the Space Station Remote Manipulator System, between April and July 2001. The anomalies encountered and the solutions found to achieve this success are described in the paper. The paper describes, also, the substantial progress that has been made, during the twelve months since IAF 2000, by Canada as it continues to complete work on all flight-elements of its contribution to the International Space Station and as we transition into real-time Space Station operations support and Canadian utilization. Canada's contribution to the International Space Station is the Mobile Servicing System (MSS), the external robotic system that is key to the successful assembly of the Space Station, the maintenance of its external systems, astronaut EVA support, and the servicing of external science payloads. The MSS ground segment that supports MSS operations, training, sustaining engineering, and logistics activities is reaching maturity. The MSS Engineering Support Center and the MSS Sustaining Engineering Facility are providing real-time support for on-orbit operations, and a Canadian Payloads Telescience Operations Center is now in place. Mission Controllers, astronauts and cosmonauts from all Space Station Partners continue to receive training at the Canadian Space Agency. The Remote Multi Purpose Room, one element of the MSS Operations Complex, will be ready to assume backroom support in 2002. Canada has completed work on identifying its Space Station utilization activities for the period 2000 through 2004. Also during the past twelve months the CSA drafted and is proceeding with the approval of a Canadian Space Station Commercialization Policy. Canadian astronauts have now participated in three ISS assembly missions--Julie Payette on STS-96, Marc Garneau on STS-97, and Chris Hadfield on STS-100 in April 2001 during which he performed Canada's first EVA and the successful installation of the Space Station Remote Manipulator System.     

Separation of bacterial cells by free flow electrophoresis under microgravity: a result of the SpaceLab-Japan project on Space Shuttle flight STS-47

We demonstrated free flow electrophoresis (FFE) of charged cells under microgravity, where gravitational effects are almost eliminated. Separation of a mixture of three bacterial strains (mutants of Salmonella typhimurium LT2) by FFE was conducted on NASA Space Shuttle flight STS-47 (September 1992). The experiment was designed to differentiate three strains having different lipopolysaccharide core structures in the cell membrane. The results were compared to those of ground experiments, in order to examine whether or not FFE in a weightless environment provides distinct advantages. Smooth strain SL1027 and rough strain SL3749 migrated to two separated fractions. The quality (viability) and the yields of the separated samples were sufficient to show the advantage of microgravity. Another rough strain, SL1102, exhibited unexpected electrophoretic behavior, which prevented the complete resolution of the three strains. All the strains were recovered as viable cells after 8 days of flight. The present study suggests that electrophoretic separation of bacterial cells is much more effective under microgravity conditions with relatively good resolution in comparison with the ground operation.