共查询到20条相似文献,搜索用时 28 毫秒
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数字太阳敏是卫星姿态控制系统的敏感部件,对提高小卫星数字太阳敏系统的可靠性及精度具有重要意义.提出了基于FPGA的高可靠数字太阳敏算法,首先介绍了数字太阳敏系统原理,分析得出FLASH型FPGA的高可靠性能;然后利用Verilog HDL语言编写图像高斯滤波算法、太阳光斑质心提取算法,并设计了数字太阳敏系统的标定方法.实验结果显示:角度更新速率大于35 Hz,测量范围为-60°~+60°,测量精度优于0.03°,验证了数字太阳敏系统设计的合理性,表明其能够满足数字太阳敏设计要求,提高了小卫星姿态控制精度. 相似文献
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设计了一种大行程、高分辨率的一维纳米定位平台,并进行了性能测试.该平台采用差动杠杆原理和柔性铰链,运用两个压电陶瓷叠堆致动器驱动.对柔性铰链平台建模,通过材料力学及结构振动微分方程等相关知识,对柔性铰链微动平台的刚度、输入反作用力、放大倍数等参数进行了分析,得到平台结构参数对平台性能的影响,并结合有限元分析软件,确定了微动工作台参数;最后建立了实验系统,对微驱动定位系统的输出行程、分辨率性能进行了测试.实验结果表明,所设计的微驱动定位系统的行程达到240μm,分辨率达到10nm,外形尺寸80mm×60mm×20mm.可用于大行程高分辨率微动定位. 相似文献
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太阳敏感器是卫星等航天器上的重要姿态测量部件,其原理是测量太阳光线和敏感器本体主轴的夹角,近而确定卫星的指向.随着MEMS技术和高精度图像传感器技术的发展,将MEMS光线引入器阵列和APS(Active Pixel Sensor)图像传感器技术进行组合,在不增加系统的质量和功耗的情况下通过多个成像阵列来降低系统的随机误差,提高成像中心位置的准确性,从而将太阳敏感器的测量精度提高一个量级.同时采用图像预测提取相关算法(Future Extraction and Image Corre-lation-FEIC),提高了系统的鲁棒性,在部分小孔受到堵塞等干扰情况下,依然保证系统正常工作,精度上基本上不受影响.传统的太阳敏感器一般采用单孔式光线引入器和CCD等方案来实现的,精度比较低.这种新设计思路和实现方法为太阳敏感器系统的可靠性提供了重要保障. 相似文献
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空间太阳望远镜太阳导行镜原理样机的研制 总被引:2,自引:0,他引:2
太阳导行镜(SGT)是空间太阳望远镜(SST)姿态控制的关键技术之一。针对 SST 姿态控制系统高速高精度的导行要求成功研制了太阳导行镜样机,该样机采用折射望远镜成像,光学口径60mm,焦距 810mm,视场 1°×1°。SGT 样机首次将 APS 器件应用于空间太阳导行,利用有源像素传感器(APS)行像素可提取的特性,以 DSP 作为数据处理器,快速提取日像边缘并完成日心坐标计算。利用 SGT 样机对太阳的周日运动进行了观测,数据分析表明,SGT 样机测量精度达到了 1.5″(3σ),数据更新率优于 30Hz,满足 SST 姿控系统的要求。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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The end of over unit products of more than Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits beer wine yellow wine fruit syrup wine others cover over % of the national top-branded liquor products.…… 《中国标准化(英文版)》2008,25(1):30
The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.…… 相似文献
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Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster. 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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N.A. Odintsova N.V. Ageenko K.V. Kiselev N.M. Sanina E.Y. Kostetsky 《International Journal of Refrigeration》2006,29(3):387
We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes. 相似文献
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David R. Smith F. R. Fickett 《Journal of research of the National Institute of Standards and Technology》1995,100(2):119-171
Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability. 相似文献