7475铝合金在恒幅及所选变幅加载历程下的裂纹扩展研究

导致加载序列作用的加载历史极大地影响着变幅加载下的疲劳裂纹扩展行为。本研究完成了一个恒幅及简单变幅加载历程下的探索性试验研究计划,以进一步了解序列影响并提供一个评价和改进现有裂纹扩展预测方法的基础。本研究的第一部分是进行宽范围应力比下的恒幅裂纹扩展试验。试验结果以及试验期间断口型态的转变可以在有效应力强度因子范围△Keff 的基础上来表示。第二部分是进行系统变化高载、低载以及卸载的简单序列下的裂纹扩展试验,测量裂纹扩展行为。最后提出关于预测模型的进一步发展的一般性看法。     

激光熔覆制备金属间化合物抗冲蚀涂层

采用同轴送粉方法,激光熔覆制备了WC增强Ni3Al金属间化合物基复合涂层,通过试验,优化了工艺参数,对激光熔覆涂层的成分、组织和硬度进行了测试和分析.结果表明,激光熔覆涂层无裂纹和气孔,与基体形成良好的冶金结合,WC颗粒的添加显著提高了涂层硬度.     

精细精密件加工的独特利器——罗斯勒嵌入式、拖拉式研磨抛光技术及设备

对高品质工件逐一进行加工的整饰技术以及大批量工件的全自动加工技术几乎已在工业生产的所有领域中完全实现.光饰光整工艺技术的应用已经扩展到了对精细精密工件的整饰及去毛刺加工工艺中.当今,整个航空工业的繁荣主要源于新型航空器零部件及制造技术的不断发展以及对现有零部件及技术的改进.发动机是飞机的心脏,要采用许多精细的工艺,其中,有一些后续加工技术,例如盘类部件金属切削加工之后去除突出的、非常细微的毛刺以及榫头的倒角等都是不容易做好但又都是至关重要的.为了满足这方面的需求,罗斯勒公司开发了嵌入式及拖拉式研磨技术及设备.     

Iron-magnesium silicate bioweathering on Earth (and Mars?)

We examined the common, iron-magnesium silicate minerals olivine and pyroxene in basalt and in mantle rocks to determine if they exhibit textures similar to bioweathering textures found in glass. Our results show that weathering in olivine may occur as long, narrow tunnels (1-3 microm in diameter and up to 100 microm long) and as larger irregular galleries, both of which have distinctive characteristics consistent with biological activity. These weathering textures are associated with clay mineral by-products and nucleic acids. We also examined olivine and pyroxene in martian meteorites, some of which experienced preterrestrial aqueous alteration. Some olivines and pyroxenes in the martian meteorite Nakhla were found to contain tunnels that are similar in size and shape to tunnels in terrestrial iron-magnesium silicates that contain nucleic acids. Though the tunnels found in Nakhla are similar to the biosignatures found in terrestrial minerals, their presence cannot be used to prove that the martian alteration features had a biogenic origin. The abundance and wide distribution of olivine and pyroxene on Earth and in the Solar System make bioweathering features in these minerals potentially important new biosignatures that may play a significant role in evaluating whether life ever existed on Mars.     

跨声速机翼非定常气动力的全位势粘位迭代计算

采用Ｃ－Ｈ型网格,守恒型非定常全位势方程的时间精确近似因式分解差分地计算二维,三维的跨声速非定常位势流,用准定常,准二维方法计算边界层位移厚度,通过粘位迭代得到的跨声速翼型,机翼的非定常气动力,所得结果与实验数据吻合很好。     

Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E

In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110?nm) as well as the martian UV spectrum (λ≥200?nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.     

Olivine-respiring bacteria isolated from the rock-ice interface in a lava-tube cave, a Mars analog environment

The boundary between ice and basalt on Earth is an analogue for some near-surface environments of Mars. We investigated neutrophilic iron-oxidizing microorganisms from the basalt-ice interface in a lava tube from the Oregon Cascades with perennial ice. One of the isolates (Pseudomonas sp. HerB) can use ferrous iron Fe(II) from the igneous mineral olivine as an electron donor and O(2) as an electron acceptor. The optimum growth temperature is ～12-14°C, but growth also occurs at 5°C. Bicarbonate is a facultative source of carbon. Growth of Pseudomonas sp. HerB as a chemolithotrophic iron oxidizer with olivine as the source of energy is favored in low O(2) conditions (e.g., 1.6% O(2)). Most likely, microbial oxidation of olivine near pH 7 requires low O(2) to offset the abiotic oxidation of iron. The metabolic capabilities of this bacterium would allow it to live in near-surface, icy, volcanic environments of Mars in the present or recent geological past and make this type of physiology a prime candidate in the search for life on Mars.     

EXPOSE-E: an ESA astrobiology mission 1.5 years in space

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110?nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10?s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.     

国外天基信息网络概念和体系结构研究

介绍国外天基网络信息概念和体系结构研究领域的一些研究成果,主要从军用天基信息网络的体系结构、民用天基信息网络体系结构以及未来空间通信和导航体系结构三个方面介绍国外天基信息网络体系结构的研究现状和未来发展。分析国外天基信息网络系统关键技术,及其对我国未来发展天基信息网络系统的重要意义。