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1.
Planar laser-induced fluorescence visualisation is used to investigate nonuniformities in the flow of a hypersonic conical nozzle. Possible causes for the nonuniformity are outlined and investigated, and the problem is shown to be due to a small step at the nozzle throat. Entrainment of cold boundary layer gas is postulated as the cause of the signal nonuniformity.
PACS 47.80.Jk, 47.40.Ki, 47.60.+i 相似文献
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For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of u′zi's. In this paper, we also consider another test statistic Srange=Smax−Smin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given. 相似文献
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实现均匀照度光伏聚光镜设计 总被引:2,自引:0,他引:2
为满足聚光光伏系统的聚光需求,解决传统点聚焦式聚光光伏系统中聚焦光斑不均匀、径长比过大和聚光比较小的缺点,在不增加二次匀光器件的前提下,设计了径长比小、聚焦光斑相对均匀、聚光比高的聚光光伏系统。根据几何光学柯勒照明原理、等光程原理和反射定律,通过数值求解等光程方程组获得聚光镜各个面型的轮廓曲线。利用TracePro软件对所设计的聚光系统进行光线追迹模拟,结果表明:在聚光比为725的情况下,聚焦光斑最大照度仅为太阳照度的2300倍,是点聚焦情况下的1/10左右,系统的径长比为0.3,接收角为0.72°。系统设计实现了结构紧凑,聚光性能高的设计目标,为高倍聚光光伏系统的小型化,简单化提供了一种有效的解决途径。 相似文献
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In this paper, we propose a compensated pixelwise calibration that integrates the effects of the camera housing temperature. The results of this calibration are compared on black body images to classic two points Non Uniformity Correction based calibrations, compensated or not. It is shown that the proposed approach leads to a significant improvement in the thermal resolution with a reduction in the mean error as well as the standard deviation. The approach is finally challenged on a real case measurement focusing on thermoelasticity. The gain in terms of accuracy measurement is highlighted by comparing the proposed calibration to classic calibrations and the scope of interest of this new calibration is discussed. 相似文献
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Min Cheng Daoyuan Kang Xiaoli Zhang Huawei Yin Yuhong Wang 《Crystal Research and Technology》2015,50(4):331-337
Comparing with the traditional concentric rotation method (rotation radius is 0 cm), the effects of different rotation radii on the growth rate of KDP crystals were studied by experimental methods. It was found that with the increase of rotation radius from 0 cm, the growth rate of each direction of crystals first increased and then decreased in a size‐unchanged vessel. The smaller the distance between the crystal and vessel wall, the less the growth rate. This phenomenon was named the “wall collision effect”. Also, the value of growth rate reached a maximum when the rotation radius was about half of its allowable largest value in the size‐unchanged vessel. In addition, an increase of the rotation radius could improve the crystal growth rate under the same linear velocity of crystal movement. Finally, the uniformity of crystal growth has also been analyzed compared with the concentric rotation radius. It was found that the uniformity of crystal growth was best when the rotation radius was half of its allowable maximum value, and it was more conducive to the actual application of KDP crystals. 相似文献
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对电极在染料敏化太阳能电池(DSCs)中主要起催化氧化还原反应及收集电荷的作用,铂对电极常用的制备方法为磁控溅射法,但其成本较高,制备条件苛刻. 本文通过引入低成本的表面活性剂Span-85,所制得的铂对电极的附着力、透光率和均匀性显著改善,实现了面积可控,与两步浸泡法和旋涂热解法制备的对电极在DSCs中的光电转换效率分别为7.30%,6.96%和7.03%. 紫外-可见吸收光谱、扫描电镜和附着力测试等结果表明,(1)添加表面活性剂有利于增加附着力及改善透光率和均匀性;(2)使用该法制备的Pt/FTO对电极的透光率与两步浸泡法制作的相同,且铂粒子分布更加均匀. 电化学阻抗图谱、塔菲尔极化曲线和循环伏安曲线结果表明,丝网印刷方法制备的Pt/FTO对电极具有更加优异的催化性能,且该法更有利于降低其生产成本和大规模生产. 相似文献
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尚雷蔡啸 王曼王志刚 方建刘春秀 刘万金孙丽君李光毅 严亮张宏杰 张振华单利民周莉 俞伯祥袁诚赵正印 秦纲夏小米 赖元芬董明义 谢文杰胡涛 吕军光 《中国物理 C》2007,31(2):177-182
利用宇宙射线进行探测器模型的性能测试是高能物理普遍采用的方法,其中最重要的步骤之一就是确定宇宙线入射的准确位置和径迹.多数采用丝室探测器来进行宇宙线的精确定位,需要很高的造价和复杂的电子学系统.本文介绍一种简单的定位方法,采用塑料闪烁体条加波移剂光纤编码读出的方式,可以实现精度为1cm的定位.据此建立了一套实验装置,对BESⅢ电磁量能器CsⅠ(Tl)晶体探测器单元的光输出强度和不均匀性进行了测量. 相似文献