美国导弹预警卫星系统分析及其启示

预警卫星是实现导弹预警,监视、发现和跟踪敌方弹道导弹发射,并发出警报的侦察卫星。美国现役的预警卫星系统为“国防支援计划”(DSP)卫星系统。由于DSP存在着问题和未来对空间预警的需求发生变化,美国正在发展“天基红外系统”(SBIRS)。     

低碳钢Q235A搅拌摩擦焊接的接头金相组织分析

用钼合金搅拌头对3mm厚低碳钢Q235A钢板进行搅拌摩擦焊接,焊接过程中采用加辅助热源和无辅助热源两种情况,获得质量良好的焊接接头,焊接温度最高可达1000℃以上。切取焊缝区域制成试样,用光学显微镜观察其显微组织进行分析,发现焊缝接头分为母材区、热影响区及搅拌区三个明显区域,而热机械影响区不甚明显。热影响区主要为等轴晶粒铁素体和球化珠光体,搅拌区金属在焊接过程中因塑性变形发生动态再结晶,抑制了晶粒长大,冷却后获得细小的先共析铁素体、铁素体和珠光体组织。     

巡航导弹景象匹配算法适应性研究

针对景象匹配制导的需求，研究了去均值归一化、基于直方图拉伸和基于局部平滑相关匹配算法，分析了算法的适应性、计算量和实时性等，比较了每种算法的优缺点。结合巡航导弹的使用，讨论了影响匹配结果的一些基本的、可能的因素，主要是环境因素。用三种分辨率的图像作了大量的实验．针对这些算法的匹配概率及地物适应性等方面进行了编程验证和综合分析，给出了有关结论。     

H∞控制理论在飞航导弹姿态控制中的应用

用H∞／混合灵敏度方法，设计了该型导弹的纵向控制回路，并给出了加权函数的选取方法。最后进行了实验和仿真计算，其仿真结果与经典的PD控制的结果相比，H∞／混合灵敏度方法设计的控制器有更强的鲁棒性，说明了该H∞／混合灵敏度方法能有效地解决导弹控制系统设计中气动参数不确定性问题。     

Aqueous corrosion of phosphide minerals from iron meteorites: a highly reactive source of prebiotic phosphorus on the surface of the early Earth

We present the results of an experimental study of aqueous corrosion of Fe-phosphide under conditions relevant to the early Earth. The results strongly suggest that iron meteorites were an important source of reactive phosphorus (P), a requirement for the formation of P-based life. We further demonstrate that iron meteorites were an abundant source of phosphide minerals early in Earth history. Phosphide corrosion was studied in five different solutions: deionized water, deionized water buffered with sodium bicarbonate, deionized water with dissolved magnesium and calcium chlorides, deionized water containing ethanol and acetic acid, and deionized water containing the chlorides, ethanol, and acetic acid. Experiments were performed in the presence of both air and pure Ar gas to evaluate the effect of atmospheric chemistry. Phosphide corrosion in deionized water results in a metastable mixture of mixed-valence, P-bearing ions including pyrophosphate and triphosphate, key components for metabolism in modern life. In a pH-buffered solution of NaHCO(3), the condensed and reduced species diphosphonate is an abundant corrosion product. Corrosion in ethanol- and acetic acid-containing solutions yields additional P-bearing organic molecules, including acetyl phosphonate and a cyclic triphosphorus molecule. Phosphonate is a major corrosion product of all experiments and is the only P-bearing molecule that persists in solutions with high concentrations of magnesium and calcium chlorides, which suggests that phosphonate may have been a primitive oceanic source of P. The stability and reactivity of phosphonate and hypophosphite in solution were investigated to elucidate reaction mechanisms and the role of mineral catalysts on P-solution chemistry. Phosphonate oxidation is rapid in the presence of Fe metal but negligible in the presence of magnetite and in the control sample. The rate of hypophosphite oxidation is independent of reaction substrate.     

Surface characteristics of spacecraft components affect the aggregation of microorganisms and may lead to different survival rates of bacteria on Mars landers

Layers of dormant endospores of Bacillus subtilis HA101 were applied to eight different spacecraft materials and exposed to martian conditions of low pressure (8.5 mbar), low temperature (-10 degrees C), and high CO(2) gas composition and irradiated with a Mars-normal ultraviolet (UV-visible- near-infrared spectrum. Bacterial layers were exposed to either 1 min or 1 h of Mars-normal UV irradiation, which simulated clear-sky conditions on equatorial Mars (0.1 tau). When exposed to 1 min of Mars UV irradiation, the numbers of viable endospores of B. subtilis were reduced three to four orders of magnitude for two brands of aluminum (Al), stainless steel, chemfilm-treated Al, clear-anodized Al, and black-anodized Al coupons. In contrast, bacterial survival was reduced only one to two orders of magnitude for endospores on the non-metal materials astroquartz and graphite composite when bacterial endospores were exposed to 1 min of Mars UV irradiation. When bacterial monolayers were exposed to 1 h of Mars UV irradiation, no viable bacteria were recovered from the six metal coupons listed above. In contrast, bacterial survival was reduced only two to three orders of magnitude for spore layers on astroquartz and graphite composite exposed to 1 h of Mars UV irradiation. Scanning electron microscopy images of the bacterial monolayers on all eight spacecraft materials revealed that endospores of B. subtilis formed large aggregates of multilayered spores on astroquartz and graphite composite, but not on the other six spacecraft materials. It is likely that the formation of multilayered aggregates of endospores on astroquartz and graphite composite is responsible for the enhanced survival of bacterial cells on these materials.     

一种有效的锯齿波调频信号识别方法

分析了锯齿波调频信号相位差分序列的特征,在此基础上给出了锯齿波调频信号的识别和参数估计方法,并采用多重相位差分改善了算法对低信噪比环境的适应能力.仿真给出了不同信噪比下对锯齿波调频的识别率.     

固体推进剂燃烧中凝相粒子的激光全息测试

概述了测试凝相粒子尺寸的基本方法，较详细地阐述了研究燃烧场凝相粒子尺寸分布的激光全息测量方法和测试结果。     

C/C喉衬稳态烧蚀的工程计算

根据固体火箭发动机燃烧中氧化性组分扩散控制喷管喉衬烧蚀和Ａｌ２Ｏ３沉积对喉衬的保护，提出Ｃ／Ｃ喉衬稳态烧蚀的工程方法。３个分动机的烧蚀预示结果与实测结果吻合，该计算方法具有较高的精度。     

摆动扫描地球敏感器数学模型及飞行试验结果

描述了东方红三号卫星(DFH-3)控制系统设计和数学仿真中采用的摆动扫描地球敏感器IRES-01的数学模型，东方红三号卫星近三年飞行试验结果与数学仿真结果基本一致，证明数学模型是正确的。