The NASA Performance Assessment Workstation: cognitive performance during head-down bed rest

The NASA Performance Assessment Workstation was used to assess cognitive performance changes in eight males subjected to seventeen days of 6 degrees head-down bed rest. PAWS uses six performance tasks to assess directed and divided attention, spatial, mathematical, and memory skills, and tracking ability. Subjective scales assess overall fatigue and mood state. Subjects completed training trials, practice trials, bed rest trials, and recovery trials. The last eight practice trials and all bed rest trials were performed with subjects lying face-down on a gurney. In general, there was no apparent cumulative effect of bed rest. Following a short period of performance stabilization, a slight but steady trend of performance improvement was observed across all trials. For most tasks, this trend of performance improvement was enhanced during recovery. No statistically significant differences in performance were observed when comparing bed rest with the control period. Additionally, fatigue scores showed little change across all periods.     

联锁式砼铺块机场道面

该文结合拉斯市沃思堡国际机场介绍了联锁式砼铺块机场道面的特点及其设计、施工的要求。     

超声自动检测系统的应用

介绍了基于无损探伤技术的C扫描自动检测系统的工作原理和软硬件设计思路,并提供了测试方法.     

Pyrite-induced hydrogen peroxide formation as a driving force in the evolution of photosynthetic organisms on an early earth

The remarkable discovery of pyrite-induced hydrogen peroxide (H2O2) provides a key step in the evolution of oxygenic photosynthesis. Here we show that H2O2 can be generated rapidly via a reaction between pyrite and H2O in the absence of dissolved oxygen. The reaction proceeds in the dark, and H2O2 levels increase upon illumination with visible light. Since pyrite was stable in most photic environments prior to the rise of O2 levels, this finding represents an important mechanism for the formation of H2O2 on early Earth.     

多输入多输出雷达的非均匀线性阵列配置(英文)

提出了利用非均匀线性阵列(Non-uniform linear array,NLA)对多输入多输出(Multiple-input multipleoutput,MIMO)雷达系统进行阵列配置优化的方法。在传统的相控阵雷达中,非均匀线性阵列配置被用来形成较窄的波束方向图,而在MIMO雷达中,利用非均匀线性阵列来获得更多的互不相同的虚拟阵元,以此来提高雷达的参数可辨识性能。文中所采用的一种非均匀线性阵列是最小冗余线性阵列,并给出了一种在物理阵元数量较大时最小冗余线性阵列的生成方法。实验结果表明:与均匀线性阵列(Uniform linear array,ULA)配置的MIMO雷达相比,非均匀线性阵列MIMO雷达能够利用较少的物理天线阵元获得相同的参数可辨识性能;而在两种配置的雷达系统的物理阵元个数相同的情况下,非均匀线性阵列MIMO雷达可以获得更大的阵列孔径长度和更低的克拉美.罗界。     

渗透法标准湿度发生器中渗透管的研制

详细介绍了适用于低湿测量领域、现场校准的内渗式渗透法标准湿度发生器中渗透管的设计、制作与使用寿命分析及使用注意事项。     

A model of habitability within the Milky Way galaxy

We present a model of the galactic habitable zone (GHZ), described in terms of the spatial and temporal dimensions of the Galaxy that may favor the development of complex life. The Milky Way galaxy was modeled using a computational approach by populating stars and their planetary systems on an individual basis by employing Monte Carlo methods. We began with well-established properties of the disk of the Milky Way, such as the stellar number density distribution, the initial mass function, the star formation history, and the metallicity gradient as a function of radial position and time. We varied some of these properties and created four models to test the sensitivity of our assumptions. To assess habitability on the galactic scale, we modeled supernova rates, planet formation, and the time required for complex life to evolve. Our study has improved on other literature on the GHZ by populating stars on an individual basis and modeling Type II supernova (SNII) and Type Ia supernova (SNIa) sterilizations by selecting their progenitors from within this preexisting stellar population. Furthermore, we considered habitability on tidally locked and non-tidally locked planets separately and studied habitability as a function of height above and below the galactic midplane. In the model that most accurately reproduces the properties of the Galaxy, the results indicate that an individual SNIa is ～5.6× more lethal than an individual SNII on average. In addition, we predict that ～1.2% of all stars host a planet that may have been capable of supporting complex life at some point in the history of the Galaxy. Of those stars with a habitable planet, ～75% of planets are predicted to be in a tidally locked configuration with their host star. The majority of these planets that may support complex life are found toward the inner Galaxy, distributed within, and significantly above and below, the galactic midplane.