振动惯性加速度计（VIA）——一种高精度低成本的微型传感器

对于有标度因数精度要求的应用来说,振梁加速度计是一种很有吸引力的仪表。其工作原理基于：一个振动的梁在受到由加速度引起的压缩式拉伸的应力时其谐振频率将会改变。     

Quantitative electrocardiography during extended space flight

To assess the effects of prolonged space flight on the electrophysiological properties of the heart, vectorcardiograms (VCG) were obtained on the Skylab crews at regular intervals during flight and the pre- and postflight periods. The VCG signals were telemetered from Skylab and analyzed by digital computer. Conventional 12-lead electrocardiograms were derived from the VCG signals by a lead transformation program. Standardized exercise loads were incorporated into the experiment protocol to increase the sensitivity of the VCG for effects of deconditioning and to detect susceptibility for arrhythmias. In Skylab II, 24 preflight, 21 inflight, and 19 postflight experiments were analyzed. Statistically significant inflight changes observed in two or more crew members included: decreased resting heart rate, increased QRS duration, anterior shift QRS vector, increased QRS vector magnitude, anterior shift T vector, and increased T vector magnitude. One astronaut had occasional premature ventricular contractions (PVC) during the pre- and postflight phases. He had a single episode of multiple PVC's during heavy-load exercise testing in flight. A second astronaut had no arrhythmia during pre- or inflight testing. On postflight day 21 he had multiple PVC's and salvos of ectopic ventricular beats. He has had no recurrence of the arrhythmia. With the exception of the cardiac arrhythmias, no deleterious electrophysiological changes were observed during Skylab II.     

Caenorhabditis elegans survives atmospheric breakup of STS-107, space shuttle Columbia

The nematode Caenorhabditis elegans, a popular organism for biological studies, is being developed as a model system for space biology. The chemically defined liquid medium, C. elegans Maintenance Medium (CeMM), allows axenic cultivation and automation of experiments that are critical for spaceflight research. To validate CeMM for use during spaceflight, we grew animals using CeMM and standard laboratory conditions onboard STS-107, space shuttle Columbia. Tragically, the Columbia was destroyed while reentering the Earth's atmosphere. During the massive recovery effort, hardware that contained our experiment was found. Live animals were observed in four of the five recovered canisters, which had survived on both types of media. These data demonstrate that CeMM is capable of supporting C. elegans during spaceflight. They also demonstrate that animals can survive a relatively unprotected reentry into the Earth's atmosphere, which has implications with regard to the packaging of living material during space flight, planetary protection, and the interplanetary transfer of life.     

自适应有限元的应用和发展

自适应有限元（ＡｄａｐｔｉｖｅＦＥＭ）是一种通用后验误差估计,不断进行网络优化提高计算机精度的数值方法,它是有限元法（ＦＥＭ）的新发展,具有高效率,高可靠性的特点,在现代工程得到了广泛应用,本文分析了自适应有限元的关键技术,总结了其在在国内外的应用情况,并展望了其发展前景。     

美国国防部签订24个有关JAST的合同

美国国防部最近已同美国18家公司签订了总价值为1.278亿美元的24个合同,用于JAST(联合先进攻击技术)计划的方案定义和有关的设计研究。美国三大军用飞机制造商都已接收到一个15个月的合同,为JAST提出一个总体武器系统的方案定义和设计,其中麦道得到的合同价值为282万美元,诺斯罗普公司为241万美元,洛克希德公司为199万美元。在此以前波音已经获得了一个价值为276万美元的合同,也将提出一个武器系统的方案。     

~(201)Hg~+离子贮存式频率标准

本文讨论利用在潘宁离子收集器中贮存~201Hg~+离子实现微波频率(和时间)标准以及光频标性能的潜力与存在的问题。有许多讨论一般都适用于离子贮存式频标。激光致冷、光抽运、以及微波或光时钟跃迁的光检测,可利用在194.2nm6P~2P_(1/2)←6~2S_(1/2)跃迁的窄带幅射,而有选择地将基态超精细能级与适当的微波幅射加以混频来完成。特别适用于采用潘宁(冷阴极)离子收集器的一阶独立场微波时钟跃迁是在1.534T 磁场的25.9GHz(F,M_F)=(2,1)←→(1,1)超精细跃迁。在563nm(毫微米)的双量子无多普勒5d~96S~(22)D_(5/2)←→5d~(10)6S~2S_(1/2)迁可能是光频标所要选用的。两种频标的绝对准确度具有达到好于1×10~(-15)而频率稳定度低于10~(-16)的潜力。     

用导航星全球定位系统(GPS)第二阶段用户设备进行时间发布

导航星全球定位系统是用卫星建立的一种导航系统。它采用频谱扩展技术使用户能得到高精度的全球定位、速度和时间信息。这是用测量一组四颗卫星信号到达时间差的办法得到的。GPS 与其协调世界时(UTC)有确定关系,因此用户能够把 UTC 估算到亚微秒准确度。系统的关键性能是,GPS 用户设备(UE)对于 UE 参考钟和 GPS 时之间时差的估算能力。这种估算可通过精密控制硬件误差和计算误差来完成。因此,要求用户设备(UE)采用一种低相位噪声和可预报漂移特性的高质量石英晶振。在活动设施上实现精密守时是 GPS 用户设备装置的基本工作原理。该装置及其接收机利用导航星 GPS 空间部分供给的信息,向用户提供导航情报、GPS 时和对应的 UTC 数据。讨论了机械编排 GPS 用户设备装置守时功能程序的复杂性。讨论内容包括硬件和软件补偿技术。本文强调了该装置的晶体振荡器频标的应用和效果。     

设计一种性能评价系统的全面质量管理方法(英文)

本文在评价全面质量管理（Ｔｏｔａｌｑｕａｌｉｔｙｍａｎａｇｅ－ｍｅｎｔ,ＴＱＭ）的基础上,提出一种改进的性能评价系统（Ｐｅｒｆｏｒｍａｎｃｅａｐｐｒａｉｓａｌｓｙｓｔｅｍ,ＰＡＳ）。文中强调理解顾客（包括管理人员及雇员）对于ＰＡＳ的要求,从而突出简化该评价系统的基本要素及实施过程。经过改进的评价系统包括工作策划、审议及对个人、集体及管理人员所作的贡献进行评估。此外,将评估标准分为三类,这已成为方便大多数雇员有效的评价方法,同时给那些需要改进的个人以积极改进的余地。如果在全面质量管理中首先强调人的因素,那么人事体制也必须体现这一原则。     

Effects of a simulated martian UV flux on the cyanobacterium, Chroococcidiopsis sp. 029

Dried monolayers of Chroococcidiopsis sp. 029, a desiccation-tolerant, endolithic cyanobacterium, were exposed to a simulated martian-surface UV and visible light flux, which may also approximate to the worst-case scenario for the Archean Earth. After 5 min, there was a 99% loss of cell viability, and there were no survivors after 30 min. However, this survival was approximately 10 times higher than that previously reported for Bacillus subtilis. We show that under 1 mm of rock, Chroococcidiopsis sp. could survive (and potentially grow) under the high martian UV flux if water and nutrient requirements for growth were met. In isolated cells, phycobilisomes and esterases remained intact hours after viability was lost. Esterase activity was reduced by 99% after a 1-h exposure, while 99% loss of autofluorescence required a 4-h exposure. However, cell morphology was not changed, and DNA was still detectable by 4',6-diamidino-2-phenylindole staining after an 8-h exposure (equivalent to approximately 1 day on Mars at the equator). Under 1 mm of simulant martian soil or gneiss, the effect of UV radiation could not be detected on esterase activity or autofluorescence after 4 h. These results show that under the intense martian UV flux the morphological signatures of life can persist even after viability, enzymatic activity, and pigmentation have been destroyed. Finally, the global dispersal of viable, isolated cells of even this desiccation-tolerant, ionizing-radiation-resistant microorganism on Mars is unlikely as they are killed quickly by unattenuated UV radiation when in a desiccated state. These findings have implications for the survival of diverse microbial contaminants dispersed during the course of human exploratory class missions on the surface of Mars.     

Formation of replicating saponite from a gel in the presence of oxalate: implications for the formation of clay minerals in carbonaceous chondrites and the origin of life

The potential role of clay minerals in the abiotic origin of life has been the subject of ongoing debate for the past several decades. At issue are the clay minerals found in a class of meteorites known as carbonaceous chondrites. These clay minerals are the product of aqueous alteration of anhydrous mineral phases, such as olivine and orthopyroxene, that are often present in the chondrules. Moreover, there is a strong correlation in the occurrence of clay minerals and the presence of polar organic molecules. It has been shown in laboratory experiments at low temperature and ambient pressure that polar organic molecules, such as the oxalate found in meteorites, can catalyze the crystallization of clay minerals. In this study, we show that oxalate is a robust catalyst in the crystallization of saponite, an Al- and Mg-rich, trioctahedral 2:1 layer silicate, from a silicate gel at 60°C and ambient pressure. High-resolution transmission electron microscopy analysis of the saponite treated with octadecylammonium (n(C)=18) cations revealed the presence of 2:1 layer structures that have variable interlayer charge. The crystallization of these differently charged 2:1 layer silicates most likely occurred independently. The fact that 2:1 layer silicates with variable charge formed in the same gel has implications for our understanding of the origin of life, as these 2:1 clay minerals most likely replicate by a mechanism of template-catalyzed polymerization and transmit the charge distribution from layer to layer. If polar organic molecules like oxalate can catalyze the formation of clay-mineral crystals, which in turn promote clay microenvironments and provide abundant adsorption sites for other organic molecules present in solution, the interaction among these adsorbed molecules could lead to the polymerization of more complex organic molecules like RNA from nucleotides on early Earth.