无人机航迹规划技术研究及发展趋势

通过对无人机航迹规划的研究,构建了无人机航迹规划的结构框架;分析了无人机系统约束及威胁场约束,探讨了无人机航迹几何建模方法及规划算法的国内外研究概况;并着重分析了规划算法。最后,阐述了无人机航迹规划面临的关键问题及发展趋势。     

Siple VLF transmissions and their magnetospheric effects observed at Halley,Antarctica

Halley (75.5°S, 26.7°W, L = 4.3) is well placed for reception of subionospheric signals from the Siple transmitter. Occasionally a two-hop magnetospheric response to such signals can be observed. The data presented here are relevant to the problems of the radiation and propagation of VLF waves in the polar earth/ionosphere waveguide, duct stimulation and ducted wave amplification and the growth of triggered emissions. An upper sideband emission 20–40 Hz higher in frequency than the transmitted pulse was often received at a similar strength to, and simultaneously with the two-hop whistler mode echo.     

Power-line harmonic radiation and the electron slot

World maps of the occurrence of VLF emissions obtained by the satellites Ariel 3 and 4 reveal maxima above industrial regions of high power consumption in North America and Euro-Asia. A study of the generation and radiation of power line harmonics indicates that these may be a major source of the observed signals. The latter propagate in the whistler mode into the geomagnetically conjugate regions in the southern hemisphere. A particularly prominent zone of emission is obtained at VLF (3.2 kHz) over North America where frequent magnetospheric wave amplification/stimulated emission, up to 50 dB and typically 10 to 20 dB above a baseline level that we ascribe to power harmonic radiation (PLHR), is obtained at invariant latitudes 45 to 55° (2 < L < 3) centred on the electron slot. It appears that PLHR may be responsible for pitch angle diffusion of energetic electrons (E 100 keV) at large pitch angles by first-order resonance and thereby contribute to the formation of the electron slot. There is a strong seasonal variation in wave-amplification/stimulated emission which we suggest may be due to a variation in the ability of the waves to become entrapped in ducts where wave-amplification occurs through a phase-bunching process. There is a strong correlation between D _ST and signal intensity, the latter lagging by 1–5 hr in the morning and 10 hr in the evening; here again wave-amplification appears to depend on duct formation and wave trapping therein. One or two (or multi) hop emissions occur with about equal probability at 3.2 kHz; at 9.6 kHz one hop are predominant.Paper presented at the Fifth International Wrocaw Symposium on Electromagnetic Compatibility, Wroclaw (Poland), 17–19 September, 1980. Sci. Rpt. 1978 (1), Sheffield Univ. Space Physics Grp.     

对接综合试验台轨迹规划算法研究

为实现模拟空间两飞行器对接动力学过程的对接综合试验台的平稳对接，提出了一种基于加速度控制的轨迹规划算法。给出了不同初始条件下的规划方法，以及时转动自由度的特殊处理。物理试验结果表明，规划模型能精确控制平台从初始零位运动到主被动对接机构初次接触位置，且最后时刻平台姿态与对接试验的初始条件完全吻合。该算法可直接用于对接综合试验台的控制。     

Organic analysis of hydrogen cyanide polymers: prebiotic and extraterrestrial chemistry.

Hydrogen cyanide polymerizes readily to a black solid from which a yellow-brown powder can be extracted by water and further hydrolyzed to alpha-amino acids. These macromolecules could be major components of the dark matter observed on many bodies in the outer solar system, including comets and asteroids. Primitive Earth might therefore have been covered with HCN polymers through bolide bombardment or be terrestrial synthesis. Several instrumental methods were used for the separation and identification of these intriguing polymeric materials, including photoacoustic Fourier transform infrared spectroscopy, supercritical fluid extraction chromatography and pyrolysis mass spectrometry. Our integrated analytical approach revealed fragmentation patterns and chemical functionalities consistent with the presence of polymeric peptide precursors both in HCN polymers and in the Murchison meteorite.     

The occurrence of single hard X-raysources in solar flares

The ‘standard’ thick target flare model predicts the existence of strong hard X-ray emission at the footpointsof a flare loop. However, Yohkoh observations suggest that up to 20% of events with data available in three or more Hard X-ray Telescope (HXT) channels show only a single source. Combining datasets from Yohkoh, the Solar and Heliospheric Observatory (SOHO), and Nobeyama Radio Heliograph (NoRH), we compare the characteristics of these single source events to double source events. The objective of this study is to determine whether these represent unresolved double footpoints, asymmetric electron deposition due to magnetic mirroring effects, or a genuine departure from the ‘standard’ model.     

Multi-wavelength observations of the pre-cursor phase of solar flares

Observational studies of the pre-cursor phase of solar flares have shown that there are many and varied signatures that may or may not indicate the probable onset of a flare. Combining data from Yohkoh, SOHO and TRACE and more recent observations from RHESSI, SOHO and TRACE we, investigate the relationships between the different manifestations of pre-flare behaviour in two solar flares with a view to determining how they are related to the subsequent flare energy release. We find that in one case the preflare activity seems strongly related to the subsequent flare and probably represents a build-up of energy in the active region prior to flare onset. The second case we find to be less clear cut suggesting that significant further work remains to be done in order to determine which pre-flare signatures are most useful in indicating the build-up to flare onset.     

加工复杂零件的高端技术

瑞士加工中心制造商威力铭-马科黛尔公司着重于质量和生产效率,主要活跃于航空/航天、精密机械、钟表和医疗行业,并以其为用户提供的高性能交钥匙解决方案而著称.     

对接综合试验台控制系统软件快速原型开发技术

对基于快速原型设计睁对接综合试验台控制系统软件开发进行了研究。介绍了根据系统方案进行的中央控制台软件设计和模型计算机软件开发等。给出了快速原型设计,以及包括接口设计、配置管理、文档管理等软件工程化管理等关键技术。     

Hydrogen cyanide polymers from the impact of comet P/Shoemaker-Levy 9 on Jupiter.

Hydrogen cyanide polymers--heterogeneous solids ranging in color from yellow to orange to brown to black--may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orange-brown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to alpha-amino acids. Other polymers and multimers with ladder structures derived from HCN would also be present and might well be the source of the many nitrogen heterocycles, adenine included, detected by thermochemolytic analysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter could therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized from freshly formed HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.