具有实时图像形成能力的高分辨率、四波段SAR试验台

描述了在Sandia国家实验室研制的双水獭SAR试验台。该试验台很灵活、适应性强，能工作于四种频：Ka、Ku和VHF／UHF频带。这种SAR的特点是在聚束模式和条带测绘模式下具有高分辨实时图像形成能力。高质量的图像是采用重叠子孔径（OSA）图像形成算法和相位梯度自聚然（PGA）算法实时形成的。     

Efficacy of Doppler ultrasound [correction of utrasound] for screening symptoms of decompression sickness during simulated extravehicular activities

Doppler ultrasound is frequently used for monitoring circulating microbubbles during decompression to assess the symptoms of Decompression Sickness (DCS). This analysis was carried out to evaluate its effectiveness for screening symptoms of DCS during simulated extravehicular activities (EVA). The information from various hypobaric chamber studies carried out at the NASA Johnson Space Center, Houston, TX was used in this analysis (n = 516). The circulating microbubbles were detected in the precordial area in 42% (218/516), and symptoms were reported in 16% (81/516) of these exposures. The accuracy of Doppler-detectable bubbles (Spencer grades) on all symptoms of DCS was examined by calculating measures of sensitivity and specificity. The efficacy of Doppler as a screening device was examined by calculating their positive predictive value (PPV) and negative predictive value (NPV). The results of these analyses indicated that the sensitivity of Doppler decreased, and the PPV increased with higher Spencer grades. However, the likelihood of detecting true negative cases (NPV) was consistently higher with all bubble grades. Due to the high false-positive rate and low prior probabilities of the risk of DCS, Doppler was found to be more useful to identify those who did not develop DCS, than to detect positive cases of DCS in the simulated EVA exposures.     

走进艺术殿堂

从菲利普二世到拿破仑三世,卢浮宫建筑前后历时600年。位于巴黎市中心赛纳河北岸的卢浮宫,是巴黎艺术的心脏,共收藏有40多万件来自世界各国的艺术珍品。它的整体建筑呈“埃”毡形,占地面积为24公顷,建筑物占地面积为4．8公顷,全长680米,是世界上最著名、最大的艺术宝库之一。98个展览大厅,最大的大厅达205米,如果你要参观卢浮宫,得先拟订一个周密的计划才能保证顺利参观完六大展馆。这种麻烦,对于艺术爱好者们而言,直到1988年由建筑大师贝聿铭设计的卢浮宫扩建工程完成,才算真正打开这座艺术殿堂的大门。     

Energy utilization rates during shuttle extravehicular activities

The work rates or energy utilization rates during EVA are major factors in sizing of life support systems. These rates also provide a measure of ease of EVA and its cost in crew fatigue. From the first Shuttle EVA on the STS-6 mission in 1983, we have conducted 59 man-EVA and 341 man-hours of EVA. Energy utilization rates have been measured on each of these EVA. Metabolic rate was measured during each EVA using oxygen utilization corrected for suit leakage. From 1981–1987, these data were available for average data over the EVA or over large segments of the EVA. Since 1987, EVA oxygen utilization data were available at 2-minute intervals. The average metabolic rate on Shuttle EVA (194 kcal/hr.) has been significantly lower than metabolic rates during Apollo and Skylab missions. Peak rates have been below design levels, infrequent, and of short duration. The data suggest that the energy cost of tasks may be inversely related to the degree of training for the task. The data provide insight on the safety margins provided by life support designs and on the energy cost of Station construction EVA.     

在杂波环境中目标跟踪的测量预处理方法

为了提高基于卡尔曼滤波器的传统跟踪算法的性能，本文提出了一种新的测量预处理技术。文中根据最大似然估值方法对接收测量值进行预处理。模拟结果表明该方法无论是在无杂波环境中还是在杂波环境中都具有最好的性能。     

用于障碍回避的毫米波雷达

本文讨论了目前在菲利浦研究实验室为雷达障碍回避系统所做的工作的原由，并给出一些实验结果。讨论了适于直升机和陆地车辆应用的系统的研究工作，强调了两者的类似之处。所阐述的方法以采用低成本９４ＧＨｚ前端为基础；采用了为灵巧武器发展的技术；依托先进的数字处理使之能够的取所需信息并以有效形式提供给用户。