美国海军标准化精密时间与时间间隔(PTTI)平台式分配系统

美国海军的精密时间和时间间隔规划是一项世界范围的艰难尝试,它要给所有海军的水面、水下、空中和岸上的平台及其通讯、导航和武器系统提供溯源于美国海军天文台主钟系统的时间和频率基准。 PTTI系统包括三部分,即海军天文台主钟系统、PTTI发播系统和标准化PTTI平台式分配系统。     

磁层顶位置的卫星观测

本文用了自1963年到1979年卫星穿越磁层顶的1024个观测资料计算了向阳侧磁层顶椭球面的参数。企图从这些资料得出星际磁场和太阳风热压强对向阳侧磁层顶位置和形状的影响大小。但数值计算和理论分析都表明,目前所具有的观测资料的精度不足以获得星际磁场和太阳风热压强影响的数值。本文分析了各种因素所造成的在计算该椭球面参数时的不确定性。进而提出了对进一步工作的建议。该椭球面的平均大小、形状和方位的观测值与理论预计值是非常一致的。      

美国和欧洲支线航空公司的发展

TheGrowthofRegionalAirlinesintheU．S．A．andCanada编者按：当中国大力发展国内支线运输业之时,回顾世界其他地区支线航空运输业的改革是十分有益的。美国、欧洲及其他地区支线航空公司的发展,在很大程度上是航空业放松管制的结果。低成本、高航班密度的航空运输的需求创造了对小型涡桨支线飞机很高的初期市场需求。随着市场的扩大,支线机队发展为大型、现代化涡桨飞机和支线喷气式飞机并用,支线运营继而扩展到客运量低的长航线。枢纽机场诞生了,主要的大型航空公司通过对支线运输的控制,试图巩固其在枢纽机场的地位。这导致了…     

指控中心STS轨道器各系统飞行监视操作自动化

约翰逊航天中心任务操作部(MOD)的主要任务是为空间运输(STS)系统提供地面保障和训练宇航员。随着轨道器飞行频度增加,而且航天计划日益成为国家的科技实用资源,用现有方法和设施提供高质量的保障、产品以及宇航员训练面临着极其严峻的挑战。为此正在进行几项工作,通过应用自动化技术(特别是在遥测监视和分析领域)减轻目前压在训练有素的操作人员肩上的重担。利用由操作人员设计和开发的软件,分阶段引进多任务分布式工作站的工程也在顺利进行。确立了一种用户开发样机的新概念,样机与现有集中式监视系统同时工作,相互参照评价,然后分阶段投入实用。从概念提出到样机移交,用户和开发者的广泛参与可确保评价、改进,以及最重要的——验收高度成功。     

小长径比航天发动机的燃烧稳定性

根据线性稳定计算和发动机试验结果之间的差异(～100秒~(-1)),认为SSP(标准稳定预测)程序对不稳定的驱动的研究和阻尼的研究方法不适用于内孔长径比小、有周向槽和多头端的发动机。对SSP程序中的增益和损失机理的考察表明:(1)槽的流动拐弯损失处理得不合理,(2)气体档板的阻尼被忽略了,(3)在常规的R_(VC)=常数的范围内,T型燃烧器速度耦合的数据不能应用到小长径比的发动机里。因而从以上三方面对小长径比的航天发动机的计算进行了修正,从而改善了理论与试验的一致性。     

Mineral-enhanced hydrothermal oligopeptide formation at the second time scale

Accumulation of biopolymers should have been an essential step for the emergence of life on primitive Earth. However, experimental simulations for submarine hydrothermal vent systems in which high-temperature water spouts through minerals within a short time scale have not been attempted. Here, we show that enhancement of hydrothermal oligopeptide elongation by naturally occurring minerals was successfully verified for the first time by using a mineral-mediated hydrothermal flow reactor system (MMHF). MMHF consists of a narrow tubular reactor packed with mineral particles, and the enhancement or inhibitory activities of 10 types of naturally occurring minerals were successfully evaluated for an elongation reaction from (Ala)(4) to (Ala)(5) and higher oligopeptides in the absence of condensation reagents. It was unexpected that calcite and dolomite facilitated the elongation from (Ala)(4) to (Ala)(5) and higher oligopeptides with 28% yield at pH 7, while tourmaline, galena, apatite, mica, sphalerite, quartz, chalcopyrite, and pyrite did not show enhancement activities. These facts suggest the importance of carbonate minerals for the accumulation of peptide in primitive Earth environments.     

Survival of Deinococcus radiodurans against laboratory-simulated solar wind charged particles

In this experimental study, cells of the radiation-resistant bacterium Deinococcus radiodurans were exposed to several different sources of radiation chosen to replicate the charged particles found in the solar wind. Naked cells or cells mixed with dust grains (basalt or sandstone) differing in elemental composition were exposed to electrons, protons, and ions to determine the probability of cell survival after irradiation. Doses necessary to reduce the viability of cell population to 10% (LD(10)) were determined under different experimental conditions. The results of this study indicate that low-energy particle radiation (2-4?keV), typically present in the slow component of the solar wind, had no effect on dehydrated cells, even if exposed at fluences only reached in more than 1000 years at Sun-Earth distance (1 AU). Higher-energy ions (200?keV) found in solar flares would inactivate 90% of exposed cells after several events in less than 1 year at 1 AU. When mixed with dust grains, LD(10) increases about 10-fold. These results show that, compared to the highly deleterious effects of UV radiation, solar wind charged particles are relatively benign, and organisms protected under grains from UV radiation would also be protected from the charged particles considered in this study.