未来机载雷达可靠性和寿命周期成本的研究

目前还没有对未来机载雷达系统的可靠性和维修性的要求充分量化，但已经认识到需要对现有可靠性和可用性的标准进行较大的改进。     

实现零电压开关的半桥DC—DC变换器的“改变占空比PWM控制”新方案

不对称控制方案是半桥隔离DC—DC变换器实现零电压开关（ZVS）的一种途径。但是由于电压不平稳和电流分量的压力，它不适宜于宽范围的输入电压。本文提出了一个半桥隔离dc—dc变换器的新“改变占空比PWM控制”方案，可以在没有不对称代价以及不增加额外元件的情况下实现ZVS工作。因为两个开关的占空比宽度保持相等。不对称电流和电压压力问题就消除了。说明了工作原理和主要特征。实验结果证实了用所提出的“改变占空比”控制方法可以获得较高的效率，尤其是在较高的开关频率。     

宽带相参机载雷达系统的动目标检测性能

详细分析了不存在模糊的瞬时宽带（10％）相参雷达系统在空-地应用和空-空应用中的主要优点和缺点，并通过实际杂波中的目标仿真进行了验证。     

波音757投入使用

英国航空公司和东方航空公司两家宣布合买大约四十架波音757的意图只不过是四年半之前的事。今天,这一新型窄体波音即将载运旅客,开始赢利了。回顾1978年,各家航空公司都在乐其所哉,无须费力便可以赚到钱。偏在这个时候,听说波音公司一半因为揽到一纸国外订货单,又有英国人提供发动机,就要投建一种新型客机,人们都无法置信。     

Artificial gravity: a possible countermeasure for post-flight orthostatic intolerance

Four payload crewmembers were exposed to sustained linear acceleration in a centrifuge during the Neurolab (STS-90) flight. In contrast to previous studies, otolith–ocular reflexes were preserved during and after flight. This raised the possibility that artificial gravity may have acted as a countermeasure to the deconditioning of otolith–ocular reflexes. None of the astronauts who were centrifuged had orthostatic intolerance when tested with head-up passive tilt after flight. Thus, centrifugation may also have helped maintain post-flight hemodynamic responses to orthostasis by preserving the gain of the otolith–sympathetic reflex. A comparison with two fellow Neurolab orbiter crewmembers not exposed to artificial gravity provided some support for this hypothesis. One of the two had hemodynamic changes in response to post-flight tilt similar to orthostatically intolerant subjects from previous missions. More data is necessary to evaluate this hypothesis, but if it were proven correct, in-flight short-radius centrifugation may help counteract orthostatic intolerance after space flight.     

COSAC onboard Rosetta: a bioastronomy experiment for the short-period comet 67P/Churyumov-Gerasimenko

The COSAC (Cometary Sampling and Composition Experiment) onboard the Rosetta mission is a combined gas chromatograph (GC)-mass spectrometer (MS). It is situated on Philae, the lander of the mission, which is intended to land on the nucleus of comet 67P/Churyumov- Gerasimenko. The purpose of the experiment is to analyze the volatile fraction of soil samples retrieved by a drill. For investigation, the samples will be pyrolysed, and the emanating gases fed into a GC, into an MS, or the combination of both. In the first part of this paper, the bioastronomical relevance of such measurements is outlined. In the second part the details of the hardware and its performance are described.     

考古,寻找进化的雕塑——对话罗伯特·巴克（下）

斯：你不仅是知名的古生物学家，而且是一位有造诣的艺术家。你是怎样学习绘画的？ 巴：任何人都能作画。绘画的能力不在你的指尖，而在你的眼睛里。如果你能看见结构，如果你能看见形式，你就能把它记录下来。我上解剖学课，就把学生带到动物园，对他们说：“画那头美洲豹。”“我不会画。”他们说。“你们能看见那头美洲豹吗？”“能看见。”“肘部是直的还是弯的？“‘噢，弯的”“踝关节是弯的吗？”“是的。”“它比狗的踝关节还要弯吧？”“不错。”“把它画下来。”要是你懂得怎样看结构，能在你的头脑中大概画下一系列东西，你就能把它画到纸上。