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排序方式: 共有832条查询结果,搜索用时 421 毫秒
421.
针对卫星在轨太阳辐射热流计算过程中计算参数多,计算过程复杂的问题,提出了一种简化的计算方法。该方法在分析卫星、地球和太阳三者之间空间几何关系的基础上,建立了新的计算坐标系,在计算坐标系中对卫星、地球和太阳的位置进行了重新规定,并在此坐标系中推导了卫星太阳辐射热流的计算公式。运用此方法对卫星太阳辐射热流进行分析求解时,轨道参数之间的空间角度关系更为简单,仅需对7个主要参数进行计算,与传统方法相比较计算量减少了约2/3。 相似文献
422.
A three-dimensional infrared radiation code for exhaust system was developed by the finite volume method coupled with narrow band k-distribution in non-gray absorbing-emitting media. The final infrared signature had considered the atmosphere effect, and the simulation values were favorably consistent with testing ones. The results indicate that the relative errors considering the effect of atmosphere compared with that of the contrary condition reduce by 31%, it shows that when simulating the infrared radiation of the target which is received by the infrared detectors, even the calculation band is in atmospheric windows 3~5 μm, the effect of atmospheric transmission on infrared signature of the target should not be neglected. 相似文献
423.
基于ProE的航天器三维屏蔽与辐射剂量评估方法研究 总被引:3,自引:0,他引:3
为准确评估结构异常复杂的航天器内部遭遇的辐射剂量,本文将直线近似原理和ProE工程软件相结合,自主开发了一种新型的航天器三维屏蔽与辐射剂量评估方法。利用本方法对立方体、球、平板等简单几何体内部的屏蔽厚度和辐射剂量进行了分析计算,计算结果表明基于ProE的三维屏蔽与辐射剂量计算方法是可靠的。结构复杂程度相当于中等规模航天器的模型计算结果表明,本方法能够较高效的分析评估复杂航天器内部遭遇的屏蔽厚度和辐射剂量。
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424.
Removing Solar Radiation Based on the Empirical Mode Decomposition Method for Seismo-Ionospheric Anomaly Before the M9.0 Tohoku Earthquake
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The ionospheric effect from solar activity can be seen as the background in the process of detecting the ionospheric precursor prior to strong earthquakes. The ionospheric variation induced by the forthcoming earthquake can be covered by the strong solar background during the period of high solar activity. The issue of how to remove the ionospheric effect from solar radiation is of outstanding significance. In this paper, a method of Empirical Mode Decomposition (EMD) is used to eliminate the solar background. As a case study, the global ionospheric map TEC before the M9.0 Tohoku earthquake on 11 March 2011 is analyzed. After the effect of solar radiation is removed using the EMD method, the precursor of the imminent earthquake is more obvious. The ionospheric anomaly had a local character and only appeared close to the earthquake epicenter while the useful signals were covered by the solar radiation background with traditional method, which implies that the EMD method is effective in eliminating solar radiation background. 相似文献
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高能脉冲X射线辐照材料时,能量沉积会使材料表层发生气化,并在材料内部形成高压热击波。目前一般采用差分方法对高压热击波过程进行数值模拟。文章尝试采用光滑粒子流体动力学(SPH)方法对X射线辐照材料进行数值模拟,由于材料表层的气化膨胀所致,膨胀后的粒子体积是原来的几十倍甚至上百倍,产生粒子大变形的粒子穿透现象;分析了产生粒子穿透现象的主要原因是气化边界处密度计算公式不合适所致,为此对密度计算公式进行了改进,并开展了基于改进密度计算公式的两种方法的数值模拟,两种方法的计算结果比较一致。 相似文献
428.
用于电子设备或系统辐射发射趋势预测的数据大多呈现非线性、样本量小的特点,这大大增加了预测建模的难度,而经验模态分解(EMD)可以将非线性、非平稳的数据分解成若干个呈现一定周期性的本征模态函数(IMF),并且EMD具有完备性和正交性,可通过分别对分解得到的IMF分量建模,从而完成对原始数据的建模。但EMD被端点效应问题所困扰,为了提高EMD的分解精度,针对分解过程中的端点效应问题,以及辐射发射趋势预测的时间序列数据样本量小的特点,利用建立灰色均值GM(1,1)预测模型所需数据量小的优点,提出了一种基于灰色均值GM(1,1)预测模型的边界延拓方法,在原始数据两端各拓展一个极大值和一个极小值,对原始数据进行边界延拓,从而抑制EMD的端点效应。仿真对比结果表明:该方法在分解层数和平均相对误差方面均优于未经延拓处理的EMD,且对数据样本量要求不高。 相似文献
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Experimental investigation of transient thermal behavior of an airship under different solar radiation and airflow conditions 总被引:1,自引:0,他引:1
De-Fu Li Xin-Lin Xia Chuang Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Knowledge of the thermal behavior of airships is crucial to the development of airship technology. An experiment apparatus is constructed to investigate the thermal response characteristics of airships, and the transient temperature distributions of both hull and inner gas are obtained under the irradiation of a solar simulator and various airflow conditions. In the course of the research, the transient temperature change of the experimental airship is measured for four airflow speeds of 0 m/s (natural convection), 3.26 m/s, 5.5 m/s and 7.0 m/s, and two incident solar radiation values of 842.4 W/m2 and 972.0 W/m2. The results show that solar irradiation has significant influence on the airship hull and inner gas temperatures even if the airship stays in a ground airflow environment where the heat transfer is dominated by radiation and convection. The airflow around the airship is conducive to reduce the hull temperature and temperature nonuniformity. Transient thermal response of airships rapidly varies with time under solar radiation conditions and the hull temperature remains approximately constant in ∼5–10 min. Finally, a transient thermal model of airship is developed and the model is validated through comparison with the experimental data. 相似文献