Bacterial growth at the high concentrations of magnesium sulfate found in martian soils

The martian surface environment exhibits extremes of salinity, temperature, desiccation, and radiation that would make it difficult for terrestrial microbes to survive. Recent evidence suggests that martian soils contain high concentrations of MgSO? minerals. Through warming of the soils, meltwater derived from subterranean ice-rich regolith may exist for an extended period of time and thus allow the propagation of terrestrial microbes and create significant bioburden at the near surface of Mars. The current report demonstrates that halotolerant bacteria from the Great Salt Plains (GSP) of Oklahoma are capable of growing at high concentrations of MgSO? in the form of 2 M solutions of epsomite. The epsotolerance of isolates in the GSP bacterial collection was determined, with 35% growing at 2 M MgSO?. There was a complex physiological response to mixtures of MgSO? and NaCl coupled with other environmental stressors. Growth also was measured at 1 M concentrations of other magnesium and sulfate salts. The complex responses may be partially explained by the pattern of chaotropicity observed for high-salt solutions as measured by agar gelation temperature. Select isolates could grow at the high salt concentrations and low temperatures found on Mars. Survival during repetitive freeze-thaw or drying-rewetting cycles was used as other measures of potential success on the martian surface. Our results indicate that terrestrial microbes might survive under the high-salt, low-temperature, anaerobic conditions on Mars and present significant potential for forward contamination. Stringent planetary protection requirements are needed for future life-detection missions to Mars.     

蜂窝夹层结构板的改制技术

基于同一公用平台卫星舱体蜂窝夹层结构板的外形和机械接口大致相同的特点,介绍了一种卫星舱体壁板的改制技术,采用切割、填充、加强、制孔、后埋等工艺方法,将结构星产品改制为电性星产品,能够大大降低成本,缩短周期。     

Study on Conceptual Selection for Provision of Trainers in Primary and Intermediate Training Stage

为了在初/中级教练机装备方案决策中体现出训练需求,选用质量功能展开的方法对其进行了分析.先利用比较矩阵确定训练需求重要度,建立训练需求与能力属性之间的QFD关系矩阵,得到不同能力属性的重要度,最后计算出个方案的能力属性值,通过线性加权计算将属性值反映到不同方案对于训练需求的满足程度上来,得出了量化分析的结果,为教练机装备决策方法研究提供了一个新思路.     

商用喷气式飞机DMC分析模型应用研究

首先对影响民机维修成本的要素进行了讨论,并给出一些飞机维修成本数据。然后归纳总结了欧美多种飞机维修成本计算方法。最后,通过算例进行比较分析,确定出一种符合国内市场情况的DMC计算方法用于型号初步设计,工程实践表明该方法符合中国市场情况,并给出未来的研究方向。     

民用客机增升装置气动噪声研究进展

随着民用飞机数量的快速增加,航空噪声问题日益引起世界范围的关注。增升装置作为重要的机体噪声源之一以其流动复杂性和声源多样性成为民用航空气动声学的难点之一,欧美各国为此开展了大量的研究。总结了增升装置气动噪声的产生机理以及控制措施的研究现状,在此基础上还特别关注了目前工业部门气动与声学的设计思想及需求。     

翼身组合体的变可信度优化设计

基于信赖域思想,发展了一种变可信度优化设计方法组织和管理不同可信度模型,有效利用低可信度模型建立近似模型,进行优化设计,高可信度模型仅修正优化近似模型,使最终优化结果收敛到高可信度模型上.采用全位势边界层有粘无粘迭代方法作为低可信度模型,多重网格Navier-Stokes方程方法作为高可信度模型,对翼身组合体进行优化设计,优化结果表明:发展的变可信度优化方法优化效率高,且能保证优化精度,具有实际的工程应用价值.     

不同迎角的翼型气弹特性风洞实验研究

基于可在不同迎角下作沉浮、俯仰两自由度运动的翼段振动装置,在低速风洞中分别针对普通薄翼型NA-CA0012和风力机翼型NREL S809进行气动弹性测试,得到不同实验状态的气动弹性振动时域响应。分别观察到经典颤振和失速颤振现象,并证明了迎角改变对两种翼型颤振特性的影响。     

一种多路通用基带处理硬件平台设计

介绍一种应用于各种信号体制的多路通用基带处理硬件平台的设计方案,并详细说明硬件平台的组成及性能。平台采用LVDS串行技术,大大提高了硬件集成度;同时采用低抖动时钟方案和LVPECL差分时钟,使得硬件平台的整体性能大幅度提升。最终,在较小面积的印制板上实现了16路数字接收通道,并包含了当前主流中央处理器DSP、两片大容量FPGA以及大容量外部存储器FLASH。方案可适用于处理较多输入信号的情况。     

基于第二代小波包解调技术的船载天线轴承故障诊断方法研究

针对船载天线传动机构中滚动轴承易损坏问题,研究基于第二代小波包解调技术的轴承故障诊断方法。首先将原始振动信号进行第二代小波包分解和分频带重构,求得各频带重构信号的希尔伯特包络谱分贝值;然后分别提取各频带包络谱中轴承故障特征频率处的分贝值,从而得到最大分贝值;最后依据冲击脉冲法故障等级经验计算公式识别轴承的状态。实际应用结果表明,第二代小波包解调技术可实现轴承故障的定位定量诊断。     

Ionospheric disturbances on 8 September, 2010: Was it connected with the incoming moderate Chongqing earthquake?

Earthquake prediction stimulates the searches for a correlation between seismic activity and ionospheric anomalies. Contrary to common focuses on strong earthquakes, we report the ionospheric disturbances, 2 days before a moderate Ms = 4.7 Chongqing earthquake (29.4°N, 105.5°E, depth = 7.0 km, occurred at 21:21 LT, 10 September, 2010) with the data of ground-based ionosondes and IGS receivers. The data covering the period under the quiet geomagnetic conditions and a geomagnetic storm was analyzed with upper and lower bounds. It is found that there were significant enhancements of foF2 and total electron content (TEC) on the afternoon of 8 September, 2010, with a limited area close to the epicentre, which was different from the feature of ionospheric perturbations triggered by the geomagnetic storm on 15 September. Taking into account the heliogeomagnetical condition, we conclude that the observed ionospheric enhancements were very likely associated with the forthcoming moderate Chongqing earthquake, which implies that the relationship between the amplitudes of ionospheric disturbances and earthquakes is very complicated.