利用κ—ε湍流能量闭合方法对城市街渠内气流结构的模拟

利用非静力、能量闭合的大气边界层模式分别绎二维情况下不同高宽比的街渠内部的气流结构和三维情况下城市街渠在来流方向不同的条件下的内部气流结构进行了数值模拟。并且对三维情况下街渠的上风向建筑物顶部的风向与街渠中心近地面的风向之间的关系和街渠内部上层的风向与街渠中心近地面的风向之间的关系进行了模拟研究，将这些结果与G T Johnson等人的现场观测和模式模拟结果进行了比较，表明两者有较好的一致性。     

一种自适应控制增稳方案的实时仿真研究

 本文介绍一种侧向自适应控制增稳方案的实时数模混合仿真研究工作。内容包括软件设计编制和系统试验分析。研究结果表明:系统软件设计合理,运算精度高,稳定可靠;自适应控制增稳方案具有良好的自适应功能;带有该系统的飞机飞行品质满足MIL-F-8785C和MIL-F-9490C的要求。文章在最后指出了今后研究工作的方向和应解决的问题。     

转动惯量测量研究的进展及展望

对转动惯量测量的研究情况作了综述,对三线摆法、扭摆法、落体法等转动惯量测量方法的测量原理及其优缺点进行了总结,介绍了针对以上缺点的一种新的测量方法,预测该方法将代表转动惯量测量的发展方向。     

Application of the Mars Organic Analyzer to nucleobase and amine biomarker detection

The Mars Organic Analyzer (MOA), a portable microfabricated capillary electrophoresis instrument being developed for planetary exploration, is used to analyze a wide variety of fluorescamine-labeled amine-containing biomarker compounds, including amino acids, mono and diaminoalkanes, amino sugars, nucleobases, and nucleobase degradation products. The nucleobases cytosine and adenine, which contain an exocyclic primary amine, were effectively labeled, separated, and detected at concentrations <500 nM. To test the general applicability of the MOA for biomarker detection, amino acids and mono- and diamines were extracted from bacterial cells using both hydrolysis and sublimation followed by analysis. The extrapolated limit of detection provided by the valine biomarker was approximately 4 x 10(3) cells per sample. Products of an NH(4)CN polymerization that simulate a prebiotic synthesis were also successfully isolated via sublimation and analyzed. Adenine and alanine/serine were detected with no additional sample cleanup at 120 +/- 13 microM and 4.1 +/- 1 microM, respectively, corresponding to a reaction yield of 0.04% and 0.0003%, respectively. This study demonstrates that the MOA provides sensitive detection and analysis of low levels of a wide variety of amine-containing organic compounds from both biological and abiotic sources.     

基于时频域转换及雨流法的电子设备随机振动概率疲劳损伤预测

针对电子设备随机振动疲劳损伤存在高度的不确定性问题,提出了一种基于频时域转换及雨流法的概率疲劳损伤预测方法,用于预测某航空电子设备在特定随机振动载荷条件下的疲劳损伤分布。通过采用“等效单元谱”近似计算,本文提出的方法能够在短时间内给出电子设备的损伤概率分布,且计算得到的疲劳寿命均值与试验结果吻合较好。因此在开展复杂功率谱密度（Power spectral density, PSD）载荷谱作用下的随机振动疲劳损伤计算时,具有计算效率高、工程适应性强等优势。     

交互多模型PHD滤波跟踪多目标方法

在机动多目标跟踪问题中,目标数未知或随时间而变化,概率假设密度（PHD）滤波可以在每一时间步估计多目标状态和目标数,但单模型方法不能给出精确的估计。提出了一种交互多模型PHD滤波方法,建立多模型描述多目标运动方式,利用PHD滤波结合多模型跟踪目标运动轨迹。同时,给出了多传感器交互多模型PHD滤波方法,以提高目标跟踪精度。     

Modeled microgravity increases filamentation, biofilm formation, phenotypic switching, and antimicrobial resistance in Candida albicans

Candida albicans is an opportunistic fungal pathogen responsible for a variety of cutaneous and systemic human infections. Virulence of C. albicans increases upon exposure to some environmental stresses; therefore, we explored phenotypic responses of C. albicans following exposure to the environmental stress of low-shear modeled microgravity. Upon long-term (12-day) exposure to low-shear modeled microgravity, C. albicans transitioned from yeast to filamentous forms at a higher rate than observed under control conditions. Consistently, genes associated with cellular morphology were differentially expressed in a time-dependent manner. Biofilm communities, credited with enhanced resistance to environmental stress, formed in the modeled microgravity bioreactor and had a more complex structure than those formed in control conditions. In addition, cells exposed to low-shear modeled microgravity displayed phenotypic switching, observed as a near complete transition from smooth to "hyper" irregular wrinkle colony morphology. Consistent with the presence of biofilm communities and increased rates of phenotypic switching, cells exposed to modeled microgravity were significantly more resistant to the antifungal agent Amphotericin B. Together, these data indicate that C. albicans adapts to the environmental stress of low-shear modeled microgravity by demonstrating virulence-associated phenotypes.     

防风网对煤堆遮风效果的风洞实验研究

为了考察防风网对堆场煤堆的遮风效果,进行了防风网与煤堆之间区域的流场可视化实验。使用风洞模拟大气边界层条件,并将开孔率为38．5％的防风网模型布置在煤堆模型前方。实验中采用粒子成像测速（PIV）系统测量了防风网和堆场区域的平均风速分布,并且获得了煤堆表面的摩擦风速分布,进一步估算煤堆起尘量的变化情况。实验发现,防风网可有效降低煤堆表面迎风区域的摩擦风速,而对背风面的流场分布影响较小。研究结果可为防风网的遮护作用提供一定的实验支持。     

低铝低燃速HTPB推进剂工艺性能影响研究

为研究固体填料粒度级配及工艺助剂对低铝低燃速HTPB推进剂工艺性能的影响,本文依据固体颗粒堆积最密集排列理论,建立了固体颗粒级配模型,结合固体填料实际粒径,计算得到两种理想刚性球的堆积结果,并在此基础上考察了不同级配配方药浆流动性及触变性。同时,通过筛选工艺助剂种类及优化最适助剂用量,对比了加入不同工艺助剂配方药浆的触变性。结果表明：当采用双二级配模型,计算出的固体颗粒级配比例最优;通过进一步优化固体颗粒级配,结合药浆触变环大小快速判定了推进剂固体级配的合理性,提高了低铝低燃速HTPB推进剂配方工艺性能的可设计性;当工艺助剂选用SU-2,且用量为0.03%时,推进剂工艺性能明显改善,适用期可达596min。     

俄罗斯打算建立镜—KS区域通信卫星系统

俄罗斯中央科学研究所（Ｋｏｍｅｔａ）提出了一种称为镜－ＫＳ（Ｚｅｒｋａｌｏ－ＫＳ）的区域通信卫星系统，它可为２００万个用户提供卫星电话业务，其通话费不会超过２０美分／分钟。目前，研究所正在寻找系统的投资者。该研究所的首席研究员、Ｚｅｒｋａｌｏ－ＫＳ系...