一种红外成像引信中的飞机姿态识别方法

红外成像引信可以获得飞机的由完整到局部的一系列动态红外图像，飞机姿态识别对基于导引头信息利用的成像引信确定瞄准点具有非常重要的意义。文中分析了高速交会情况下飞机目标的运动特性，提出了一种飞机姿态识别方法，通过利用遗传算法确定像平面上飞机图像的旋转情况和机头位置，利用测距装置提供的距离信息、飞机图像的长度及红外探测器的系统参数确定飞机的俯仰情况，并利用弹目交会过程中机轴方位角和高低角的不变性重建局部成像跟踪情况下的空间机轴，最后实现了成像引信局部成像跟踪过程中飞机飞行姿态的识别。     

Ultrastructural and geochemical characterization of Archean-Paleoproterozoic graphite particles: implications for recognizing traces of life in highly metamorphosed rocks

Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai graphite particles were extracted for further investigation. Laser Raman spectroscopic analysis of a population of extracted graphite discs indicated that they experienced a maximum metamorphic temperature of 513 +/- 50 degrees C, which is consistent with the metamorphic grade of the host rock and supports their indigenicity. Scanning and transmission electron microscopy revealed that the particles bear morphological features (such as hexagonal sheets of graphite crystals) related to metamorphism and crystal growth, but a small fraction of them (graphite discs) are characterized by a circular morphology, distinct marginal concentric folds, surficial wrinkles, and complex nanostructures. Ion microprobe analysis of individual graphite discs showed that their carbon isotope compositions range from -7.4 per thousand to -35.9 per thousand V-PDB (Vienna Pee Dee Belemnite), with an average of -20.3 per thousand, which is comparable to bulk analysis of extracted carbonaceous material. The range of their size, ultrastructures, and isotopic signatures suggests that the morphology and geochemistry of the Wutai graphite discs were overprinted by metamorphism and their ultimate carbon source probably had diverse origins that included abiotic processes. We considered both biotic and abiotic origins of the carbon source and graphite disc morphologies and cannot falsify the possibility that some circular graphite discs characterized by marginal folds and surficial wrinkles represent deflated, compressed, and subsequently graphitized organic-walled vesicles. Together with reports by other authors of acanthomorphic acritarchs from greenschist-amphibolite-grade metamorphic rocks, this study suggests that it is worthwhile to examine carbonaceous materials preserved in highly metamorphosed rocks for possible evidence of ancient life.     

关于设备保障质量指标计算方法的探索

引言浙江空管分局技术保障部作为空管基层设备运行保障单位,多年来,在设备保障质量指标计算方法上持续探索,力求统计指标能够科学合理地反映设备保障情况和维护维修状况,为基层管理者的科学决     

Results of impact simulation for the GIOTTO mission

The European Space Agency (ESA) has decided to carry out a fly-by mission to the comet Halley. The spacecraft will be launched by an ARIANE II and intercept the retrograde Halley orbit on 13 March, 1986. One group of experiments is designed to obtain data on size, mass and composition of the dust in the cometary tail. Because of the very high relative velocity during fly-by (69 km/s) laboratory experiments are necessary to develop and calibrate the experiments. These experiments are presently under way in the laboratory of the Lehrstuhl für Raumfahrttechnik of the Technische Universität München. First results have been obtained for both the Dust Impact Detection System (DIDSY) and the P?articulate Impact Analyzer (PIA). These results are compared with the theoretical models for hypervelocity impact craters. The agreement is good at impact velocities around 15 km/s.     

固体火箭发动机冷气冲击瞬态内流场分析

运用高压氮气冲击固体火箭发动机来模拟在发动机点火时产生的高压峰值对药柱及发动机壁面的冲击,测量出发动机头部、中部、尾部的压力分布,对固体火箭发动机冷气冲击试验过程进行模拟。应用(fluent)流体计算软件,对瞬时内流场进行了二维轴对称非定常数值分析。研究结果表明,所模拟的3个测量点压力-时间曲线与试验曲线吻合较好,药柱头部位置及内端面受冲击力较大,易造成结构完整性破坏,进一步证明试验能够较好的模拟真实点火峰压对发动机及药柱造成的影响,为发动机点火设计及试验提供有力的参考。     

High velocity impact characterization of Al alloys for oblique impacts

This paper describes the experimental and computational analyses of a high velocity aluminum projectile impact on an Al6061-T6 spacecraft inner wall at different oblique angles. Al2017-T4 spherical projectiles of 5.56 mm in diameter and 0.25 g in weight were chosen within the velocity range of 1000±200 m/s due to the limitation of the light gas gun. The energy absorbed was calculated by measuring the velocities before and after impact on the inner wall. The energy absorbed by the wall and the remaining energy carried by the projectile helped to estimate the severity of further damage to inner components. Afterwards, validation was done by using the commercially available software LS-DYNA with a dedicated SPH. On average, a 10% energy absorption difference between experimentation and simulation was found. By using C-SCAN, the damage area proportion of the total inner wall to impact penetration hole area was found to be on average 6%, 26% and 53% greater than the projectile cross sectional area for the oblique angle impacts of 30°, 45°, and 60°, respectively. These findings helped to understand the relationship between the oblique impact event and the damage area on a spacecraft inner wall along with space debris cloud propagation and comparison with experimental results using LS-DYNA.     

掠海飞行器主动触水撞水力分析

随着掠海飞行器飞行高度的不断降低,海浪和海况条件已成为制约其飞行高度的重要因素,严重时可引起飞行器姿态的倾覆。基于小升角楔形体入水模型和解析法,研究了掠海飞行器主动击水时所产生的撞水力变化特点,得到了击水滑板的外形参数和入水姿态角的选取准则,即入水弹道倾角-2°～0°,滑板等效斜升角β1≥10°,俯仰角变化范围0°～5°、滚动角变化范围-30°～30°,保证掠海飞行器在主动击水条件下产生的撞水力小于最大限定值20 gn的要求,实现了飞行器在恶劣海况下的掠海飞行。采用有限元法进行的三维仿真结果表明,此解析法所计算结果具有较高的可信度。     

上面级发动机小功率冲击式涡轮性能试验研究

设计了一种适用于小功率冲击式涡轮性能试验方案,该方案由燃气路和水路组成,通过酒精发生器获取高温高压空气驱动涡轮转动,泵为水介质增压作为负载进行涡轮性能试验,保证了试验涡轮状态与真实产品状态的一致性.以涡轮相似换算准则为基础在试验系统能力允许的范围内设计试验工况.本涡轮性能试验方案利用泵水力性能核算涡轮输出功,根据实测的涡轮压力、温度等参数,最终获得涡轮效率随涡轮速比变化的性能曲线.通过设计考台试验件及考验方法,确保试验系统参数测量的稳定可靠.经某上面级发动机涡轮泵作为试验对象验证,采用该试验方案可以获取涡轮效率.同时3件试验涡轮转子的性能试验结果对比表明该上面级发动机涡轮转子性能一致.     

导弹落点散布的Bayes试验鉴定优化设计

针对工程实际中所普遍存在的小子样问题，研究了落点样本量、验前信息可信度以及Bayes决策风险三者之间的关系，得到了有意义的结论，即：在综合Bayes决策风险上限的条件下，试验次数越少，则对“验前信息可信度”的要求就越高。在此基础上，通过算例说明了“最优样本量”概念在实际工程应用中的不适应性，为尽量减少试验次数，提出了“次优样本量”的概念，并由此得到了一种确定落点样本量的新方法。     

无人机机载导弹落角和时间控制导引律研究

改进了一种能同时控制命中角和命中时间的修正比例导引律,将其用到无人机机载空对地导弹中,将其中的剩余时间估计加入了命中角约束的影响,旨在保证无人机机载导弹垂直命中目标的同时,使命中时间更为准确.通过对此导引律和一种仅考虑垂直命中角约束的修正比例导引律以及和改进前导引律的比较,仿真表明,此导引律使无人机机载导弹能在保证垂直...     

Subsurface filamentous fabrics: an evaluation of origins based on morphological and geochemical criteria, with implications for exopaleontology

The fossil record of the subsurface biosphere is sparse. Results obtained on subsurface filamentous fabrics (SFF) from >225 paleosubsurface sites in volcanics, oxidized ores, and paleokarst of subrecent to Proterozoic age are presented. SFF are mineral encrustations on filamentous or fibrous substrates that formed in subsurface environments. SFF occur in association with low-temperature aqueous mineral assemblages and consist of tubular, micron-thick (median 1.6 micron) filaments in high spatial density, which occur as irregular masses, matted fabrics, and vertically draped features that resemble stalactites. Micron-sized filamentous centers rule out a stalactitic origin. Morphometric analysis of SFF filamentous forms demonstrates that their shape more closely resembles microbial filaments than fibrous minerals. Abiogenic filament-like forms are considered unlikely precursors of most SFF, because abiogenic forms differ in the distribution of widths and have a lower degree of curvature and a lower number of direction changes. Elemental analyses of SFF show depletion in immobile elements (e.g., Al, Th) and a systematic enrichment in As and Sb, which demonstrates a relation to environments with high flows of water. Sulfur isotopic analyses are consistent with a biological origin of a SFF sample from a Mississippi Valley-Type deposit, which is consistent with data in the literature. Fe isotopes in SFF and active analogue systems, however, allow no discrimination between biogenic and abiogenic origins. The origin of most SFF is explained as permineralized remains of microbial filaments that possibly record rapid growth during phases of high water flow that released chemical energy. It is possible that some SFF formed due to encrustation of mineral fibers. SFF share similarities with Microcodium from soil environments. SFF are a logical target in the search for past life on Mars. The macroscopic nature of many SFF allows for their relatively easy in situ recognition and targeting for more detailed microstructural and geochemical analysis.     

网电空间战对未来防空体系的影响研究

网电一体战的作战目标是破坏和控制敌方的信息基础和战略命脉,摧毁和致瘫敌方的作战指挥控制系统.分析了网电空间战的一般特点和军事特点,并结合网电攻击的案例分析了其对未来防空战争的影响,其影响主要表现在：作战空间由“地表维”和“垂直维”延伸至“网电维”,利用和控制网电空间将成为未来防空作战的主题,网电空间对抗成为提升未来防空作战能力的核心.     

Location and sampling of aqueous and hydrothermal deposits in martian impact craters

Do large craters on Mars represent sites that contain aqueous and hydrothermal deposits that provide clues to astrobiological processes? Are these materials available for sampling in large craters? Several lines of evidence strongly support the exploration of large impact craters to study deposits important for astrobiology. The great depth of impact craters, up to several kilometers relative to the surrounding terrain, can allow the breaching of local aquifers, providing a source of water for lakes and hydrothermal systems. Craters can also be filled with water from outflow channels and valley networks to form large lakes with accompanying sedimentation. Impact melt and uplifted basement heat sources in craters > 50 km in diameter should be sufficient to drive substantial hydrothermal activity and keep crater lakes from freezing for thousands of years, even under cold climatic conditions. Fluid flow in hydrothermal systems is focused at the edges of large planar impact melt sheets, suggesting that the edge of the melt sheets will have experienced substantial hydrothermal alteration and mineral deposition. Hydrothermal deposits, fine-grained lacustrine sediments, and playa evaporite deposits may preserve evidence for biogeochemical processes that occurred in the aquifers and craters. Therefore, large craters may represent giant Petri dishes for culturing preexisting life on Mars and promoting biogeochemical processes. Landing sites must be identified in craters where access to the buried lacustrine sediments and impact melt deposits is provided by processes such as erosion from outflow channels, faulting, aeolian erosion, or excavation by later superimposed cratering events. Very recent gully formation and small impacts within craters may allow surface sampling of organic materials exposed only recently to the harsh oxidizing surface environment.     

某固体火箭发动机推力向量控制系统接头接触性能分析

以某固体火箭发动机推力向量控制系统摆动接头的单珠承载试验模型为计算模型,采用摩擦接触问题的Lagrange乘子法与弹塑性耦合的有限元理论,计算分析了摆动接头阳球试件在不同强化层厚度下的接触应力、变形及破坏机理;为降低系统摆动力矩,同时考虑大尺寸球面的表面强化和加工工艺,提出了满足接触性能的阳球表面强化层为1～1.4mm...     

电爆阀启动过程的响应特性与活塞撞击变形分析

对航天飞行器上的高压常闭式电爆阀启动过程的动态响应特性进行仿真,并通过试验验证两者基本吻合。在此基础上,对电爆阀启动过程活塞撞击变形情况进行分析。采用Abaqus软件对活塞与壳体碰撞行为进行显式非线性动态分析,研究了电爆管、材料性能以及电爆阀出口压力条件对活塞撞击变形量的影响。结果表明,电爆阀出口压力条件对活塞与壳体撞击变形量影响最大,出口压力增大对应变形量急剧减小,电爆阀工作的可靠性随之降低。     

Evaluation of craters formation in hypervelocity impact of debris particles on solid structures

The aim of this work is to develop simplified model of space debris particle collision on solid structures, which would provide closed form solution formulas for determining crater depth, radius and ejected mass being functions of impactor mass, speed and material of both impactor and target. The model will be verified with results of experiments.     

Some problems of identifying types of large-scale solar wind and their role in the physics of the magnetosphere

This paper discusses the errors in analyzing solar-terrestrial relationships, which result from either disregarding the types of interplanetary drivers in studying the magnetosphere response on their effect or from the incorrect identification of the type of these drivers. In particular, it has been shown that the absence of selection between the Sheath and ICME (the study of so-called CME-induced storms, i.e., magnetic storms generated by CME) leads to errors in the studies of interplanetary conditions of magnetic storm generation, because the statistical analysis has shown that, in the Sheath + ICME sequences, the largest number of storm onsets fell on the Sheath, and the largest number of storms maxima fell at the end of the Sheath and the beginning of the ICME. That is, the situation is observed most frequently when at least the larger part of the main phase of storm generation falls on the Sheath and, in reality, Sheath-induced storms are observed. In addition, we consider several cases in which magnetic storms were generated by corotating interaction regions, whereas the authors attribute them to CME.     

气动换向阀阀芯/阀座撞击特性研究

针对某型气动换向阀在研制过程中出现由于阀芯/阀座撞击变形导致阀芯卡死的现象,对阀芯/阀座的撞击特性进行了仿真研究,定量分析了撞击过程以及不同阀座高度对撞击特性的影响,根据仿真结果对换向阀进行了改进设计,试验结果表明改进后的换向阀满足使用要求.     

固体火箭发动机撞击变形及装药内部热点形成数值分析

以热粘弹理论和动力有限元法为基础,结合机械撞击载荷下固体推进剂裂纹摩擦热点细观模型,分析计算了发动机壳体和装药结构撞击变形及装药内部热点形成,确定了产生高温热点撞击临界速度。计算模型中考虑了推进剂初始弥散细观裂纹离散、裂纹扩展对推进剂宏观力学性能影响、基体粘性加热对热点形成影响等问题。通过与高能炸药Steven撞击试验结果进行对比分析,证明了理论模型及计算方法的有效性。计算了某小型发动机撞击试验临界速度。