装有重新设计燃料泵的YLR87-AJ-5火箭发动机涡轮泵瞬态试验及有关推进设备

试验目的已经达到了。两次试验是以抽吸侧脉动情况下作的,另一次试验是在排泄侧脉动情况下作的。重新设计燃料泵瞬态试验结果与产品燃料泵试验结果作了比较。从分析大力神Ⅱ纵向振动有关参数和减少纵向振动角度来看,比较起来,重新设计的泵显示出此产品泵有更显著的优越性。分析采用重新设计燃料泵对总系统的影响时,必须联系氧化剂系统。     

Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones

Atmospheric erosion of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 microm band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O ion pick up at orbital distances 相似文献   

Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry

The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5?GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.     

Sulfur-oxidizing chemolithotrophic proteobacteria dominate the microbiota in high arctic thermal springs on Svalbard

The thermal springs Trollosen and Fisosen, located on the High Arctic archipelago Svalbard, discharge saline groundwaters rich in hydrogen sulfide and ammonium through a thick layer of permafrost. Large amounts of biomass that consist of filamentous microorganisms containing sulfur granules, as analyzed with energy dispersive X-ray analysis, were found in the outflow. Prokaryotic 16S rRNA gene libraries and quantitative polymerase chain reaction (qPCR) analyses reported bacteria of the γ- and ?-proteobacterial classes as the dominant organisms in the filaments and the planktonic fractions, closely related to known chemolithoautotrophic sulfur oxidizers (Thiotrix and Sulfurovum). Archaea comprised ～1% of the microbial community, with the majority of sequences affiliated with the Thaumarchaeota. Archaeal and bacterial genes coding for a subunit of the enzyme ammonia monooxygenase (amoA) were detected, as well as 16S?rRNA genes of Nitrospira, all of which is indicative of potential complete nitrification in both springs. 16S rRNA sequences related to methanogens and methanotrophs were detected as well. This study provides evidence that the microbial communities in Trollosen and Fisosen are sustained by chemolithotrophy, mainly through the oxidation of reduced sulfur compounds, and that ammonium and methane might be minor, additional sources of energy and carbon.     

Earth as an extrasolar planet: Earth model validation using EPOXI earth observations

The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ～100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ～10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ～7% and brightness temperature errors of less than 1?K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth's time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology-Extrasolar terrestrial planets-Habitability-Planetary science-Radiative transfer. Astrobiology 11, 393-408.     

用运放制作的积分器的快速瞬态噪声响应

本文描述用运放制作的积分器在减少直流电源的高频噪声方面并不很有效,当受到高频噪声影响时,它似乎起着微分器的作用。这种现象是由于输入线和直流电源的快速瞬态噪声对运放作用的结果。