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排序方式: 共有482条查询结果,搜索用时 234 毫秒
451.
提出了复杂表面之间平行光辐射传递系数的一种新型计算方法,克服了蒙特卡洛法在计算平行光辐射系数时存在运算量较大、计算精度难以保证等缺点,并且从计算精度及耗时性两方面对新方法进行了比较分析,计算结果表明新方法在计算精度及耗时性上都要优于蒙特卡洛法。 相似文献
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455.
Bipasha Paul Shukla V. Sathiyamoorthy P.K. Pal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009,43(12):1931-1939
In this paper, the shortwave and longwave anisotropy for clear sky Indian desert scene has been estimated using long-term surface data, radiative transfer calculations and Helmholtz reciprocity for missing values. This study is important in the perspective of the low inclination satellites like Megha–Tropiques (MT) mission, carrying Scanner for Radiation Budget (ScaRaB) payload, which will provide broadband radiative fluxes at the top of the atmosphere (TOA). Due to low inclination angle, the angular models for clear sky land scenes for the MT-ScaRaB orbits will be dominated by desert points.The Angular Distribution Models (ADMs) determined in this study were compared with existing desert models. It is observed that for longwave radiation, the largest disagreement is observed for higher values of viewing zenith angle, especially for the summer season, where the difference in flux can reach up to 13 W/m2. For the shortwave radiation, higher values of both solar zenith angle and viewing zenith angle cause largest incongruity in the computed albedo from the different models, suggesting the need of caution in interpretation of the flux computations from these bins. In fact at the higher solar zenith angle bin, the disparity in albedo can go up to 6.4%. 相似文献
456.
利用激光多普勒测速仪(LDV)对直径D 300mm×3420mm圆管内的旋转流场进行了实验测量,重点测量切向速度与轴向速度的分布以及湍流强度分布.测量结果表明圆管内的旋转流是Rankine涡结构形态,旋转流强度沿轴向存在着明显的衰减特性,且最大切向速度的径向位置沿轴向逐渐向内移动,即由上游的刚性涡逐渐向下游的准自由涡和刚性涡组合过渡;轴向速度的分布存在着很大的不均匀性,在r=0.5R区域存在一个轴向速度的低速区,甚至出现上行,但在轴向位置z>10R后轴向速度全部向下,并向均匀分布发展;圆管内的切向湍流强度比轴向湍流强度大一倍,两者的湍流强度在准自由涡区径向分布比较平均,中心刚性涡区域的湍流强度比较高,而且随轴向位置的变化衰减不明显. 相似文献
457.
沙云东 《沈阳航空工业学院学报》2000,17(2):23-28
有普通内燃机试验间内用声强法对发动机噪声进行测量,重点依据ISO9614-I国际标准对测试数据的有效性和精度进行较深入的分析和校核,结果表明其方法可行,数据有效。通过测量分析,估算了发动机辐射的声功率及声能分布,进行了内燃机声源识别,获得了该型发动机噪声的有关特征和规律。此项研究为在普遍试验间进行内燃机噪声测量分析提供了经验。 相似文献
458.
将强度关联量子成像理论引入到雷达成像技术中,提出了一种全新的微波关联成像方法。向目标发射多个幅度、相位可控的单元信号,同时记录各个信号的状态并结合距离信息制作"成像底版",通过对回波信号和"成像底版"的关联结果进行数理统计后可实现雷达高分辨成像。 相似文献
459.
Xingming Bao Wenbin Xie 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
On 2010 February 8, the Extreme ultraviolet (EUV) flux variation in 195 Å and flare brightening has been examined in different sizes of active regions by using SOHO/EIT, MDI and Hα observational data. These three active regions represent a large active region with a sunspot group, a moderate active region without a sunspot and a small region with weak plage in Hα band respectively. Our study shows that the main full disk EUV flux comes from active regions, especially from large active regions. The sudden increases of EUV flux are corresponding to the EUV flare brightenings. For the large active region, the local EUV 195 Å flux peaks are well correlated to that of the GOES X-ray flux. The EUV 195 Å flux peaking time of M-class flares delay GOES X-ray flux a few minutes. For the moderate active region, the local EUV 195 Å flux is not well correlated to GOES X-ray flux. The EUV 195 Å flare brightenings in the moderate active region appeared in the duration of sudden increase of its own local EUV flux. For the small active region, the local EUV 195 Å flux varied almost independently of the GOES X-ray flux. Our study suggests that for an active region its local EUV 195 Å flux is more closely correlated to the EUV flare brightening than the full disk GOES X-ray flux. 相似文献
460.
Devajyoti Dutta Sanjay Sharma Jyotirmay Das R.M. Gairola 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
The present study emphasize the development of a region specific rain retrieval algorithm by taking into accounts the cloud features. Brightness temperatures (Tbs) from various TRMM Microwave Imager (TMI) channels are calibrated with near surface rain intensity as observed from the TRMM – Precipitation Radar. It shows that Tb–R relations during exclusive-Mesoscale Convective System (MCS) events have greater dynamical range compared to combined events of non-MCS and MCS. Increased dynamical range of Tb–R relations for exclusive-MCS events have led to the development of an Artificial Neural Network (ANN) based regional algorithm for rain intensity estimation. By using the exclusive MCSs algorithm, reasonably good improvement in the accuracy of rain intensity estimation is observed. A case study of a comparison of rain intensity estimation by the exclusive-MCS regional algorithm and the global TRMM 2A12 rain product with a Doppler Weather Radar shows significant improvement in rain intensity estimation by the developed regional algorithm. 相似文献