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天基光电望远镜极限星等探测能力研究 总被引:3,自引:1,他引:3
从辐射度学和光度学基本原理出发,通过对目标光度信号特征和背景以及CCD噪声光信号特征的分析,导出了天基光电望远镜对空间目标的极限星等探测能力的计算公式.根据该公式,分别研究了有光照和无光照条件下的极限星等探测能力.给出了一组典型参数,在无背景光照条件下得到极限探测星等为14.1个星等,并详细研究了极限探测星等随各参数变化的关系.在有背景光照条件下,研究了极限探测星等随太阳角的变化关系.结果证明,几乎只要有太阳光进入,极限探测星等就急剧下降,因此也证明了天基光电望远镜只能在背光条件下或在地影中工作. 相似文献
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天基光电望远镜对空间目标成像的模拟 总被引:10,自引:2,他引:8
提出了一种天基望远镜对空间目标成像的模拟方法。由卫星轨道参数计算得到卫星在地心赤道坐标系中的坐标,再通过平移、旋转和比例变换将其变换到望远镜坐标系中的坐标,模拟得到卫星的成像图。通过旋转和比例变换,将恒星坐标从地心赤道坐标系变换到望远镜坐标系,模拟得到星空成像图。两者合成得到总模拟图。将望远镜的位置矢量和光轴的方向矢量之间的夹角作为望远镜视场是否被地球遮挡的判断依据。以0星等和10星等为参考,用计算机模拟得到256级灰度图。仿真结果表明,该方法既能有效地模拟卫星的运动,又可以克服对相同星空背景的重复模拟。 相似文献
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大口径望远镜主镜支撑优化分析 总被引:4,自引:1,他引:3
大口径望远镜主镜的面形精度是影响望远镜成像质量的关键因素之一.光电系统中主镜轴向支撑点位置,对面形精度起着非常重要的作用,主镜支撑点位置合理与否,在一定程度上影响着光学系统的成像质量.本文对大口径望远镜主镜的轴向支撑和径向支撑技术进行了详细地研究,利用有限元软件ANSYS建立了主镜的参数化模型,对不同口径主镜的轴向支撑点数目和位置进行了优化,从而给出了最佳支撑点的位置.优化分析结果表明了,主镜的面形精度满足系统的精度要求,并且轴向支撑对镜面的面形影响较大. 相似文献
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本文修改了 JPEG2000 算法,通过改变编码顺序节约了大量的计算,提高了运行速度.用此算法对空间太阳望远镜的目标图像进行了实验,结果表明在相同压缩比的情况下,修改后的算法对图像质量没有明显的影响,在运行时间和压缩质量方面都能够满足空间太阳望远镜的压缩任务要求. 相似文献
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天文光电图像序列目标成像特征提取与分析 总被引:4,自引:3,他引:1
地基大视场天文光电观测系统获取的序列图像中,空间目标和数目众多的恒星目标成像特性相似,大部分都表现为弱、小目标特性,需根据二者特征之间的微小差异实现目标的正确可靠识别.首先分别从空域和时域的角度出发,将目标的成像特征分为静态特征和动态特征,并提出了相应的特征计算方法.然后结合实测数据,根据目标的特征提取结果深入分析了空间目标和恒星目标的成像特征,并详细比较了两者的成像特征差异.空间目标和恒星目标的成像特征提取和分析,为空间目标虚警的消除提供了大量的判决依据,有助于空间目标的低虚警率检测识别. 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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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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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
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Fco. Javier Franco Pérez Marc Gener Moret 《Materials and Manufacturing Processes》2017,32(7-8):876-884
ABSTRACTThe production of iron in Biscay (Basque Country, Spain) has been a hallmark of this territory of the North of the Iberian Peninsula throughout its history. The Archaeology team of the Basque Country Mining Museum has spent 13 years, so far, studying the origins of this activity through the evidences left at the old pre-hydraulic iron production workshops known as mountainside ironworks (ferrerías de monte) or haizeolak. It has catalogued 170 archaeometallurgical sites of this type in Biscay, and the archeological excavation of some of them has led to the knowledge of the different stages of the production process that took place in these workshops. The team has also experimentally reproduced the work carried out in a mountainside ironworks from the High Middle Ages, and it has currently started the characterization process of this type of activity through the study of the collected materials. 相似文献
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As demands about environment protection are growing up, dry cutting technology is getting more and more concerns from all over the world. Main works performed here are study on dry cutting performances and wear mechanisms of M2high-speed steel (HSS) twist drills with CrAlTiN multicomponent coatings, which was deposited using magnetron sputter ion plating system, in drilling 45 and 30CrMnSiA steel, and their comparisons to those in drilling the same steel but using monolayer CrN and commercial TiN coated drills. Drilling performances of drills are evaluated mainly through the measurements of width on outer corner flank land and the cutting forces. Results show that performances of CrAlTiN coated drills are better than those of monolayer CrN and TiN coated drills. In drilling 45 and 30CrMnSiA steel, the average tool life of the CrAlTiN coated drills are 17.2 and 11.8 times higher than those of the uncoated drills. Observing wear of the drill with scanning electronic microscope, results show that there is no crack or spallation of the CrAlTiN coatings in wear zones. Main mechanism of the wear here is adhesion. 相似文献
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Arc spraying coatings are widely used in various applications, but uncommon in cast iron substrate. Different surface pretreatment technology is tested on substrates of gray cast iron. Surface roughness and residual stress were measured by TR200 and X-ray diffraction analyzer. Influence of different surface pretreatment methods ( dry blasting and fusebond) on roughness and residual stress was analyzed. The arc-sprayed coatings of wire 3Cr13 (φ2mm) on gray cast iron substrate is studied. The microstructure and interface of bonding layer were observed by SEM. The bond strength was taken by tensile test. Results show that bond strength with grit blasting is higher than fuse-bond; it is feasible to make wire 3Cr13 coating with arc spraying on cast iron substrate roughened by grit blasting. 相似文献
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TiO2 ceramic coatings with thickness of 20 μm were formed on the surface of pure titanium by micro-plasma oxidation. Their micro-structures were investigated by by using X-ray diffraction and their surface images were detected by using scan electronic microscope. There were three kinds of TiO2 coatings, pure anatase type TiO2 phase, mixed phases consisted of rutile type TiO2 phase and anatase type TiO2 phase, pure rutile type TiO2 phase. The coating surface with the pure anatase type TiO2 phase is rough, while the coating surface with the pure rutile type TiO2phase is smooth. The upper coating surface with the mixed type TiO2 phases is anatase type TiO2 structure and the subsurface of the TiO2 coating is rutile type TiO2structure. 相似文献
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R. Owsiński S. Kamiński M. Szymaniec A. Niesłony T. Łagoda 《Materialwissenschaft und Werkstofftechnik》2015,46(10):1059-1067
The insightful discussion of the relationship between the construction of metallographic and fatigue life and proposition of mathematical relationships describing this relationship was conducted in the paper. This paper presents a method for estimating the fatigue life, based on the construction of the microstructural material taking into account the grain size and the participation of ferrite and pearlite phase. 相似文献