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871.
用定量分析的方法开发电子战战法是海军战役规划中必须解决的重要问题.借助仿真和博弈分析的混合方法,在博弈效用函数计算的基础上,构建基于识别真、假目标以及火力命中目标概率的二人非零和(TPNZS)非合作博弈模型来开发电子战战法,对一个典型的舰载导弹防空系统的初步研究表明:电子进攻与电子防御的战法分别为π*=(0,π*2,1-π*2)=(0.0000,0.5890,0.4110)和Δ*=(0.0000,0.0000,Δ*3)=(0.0000,0.0000,1.0000). 相似文献
872.
Hierarchical object oriented classification using very high resolution imagery and LIDAR data over urban areas 总被引:1,自引:0,他引:1
Yunhao Chen Wei Su Jing Li Zhongping Sun 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Urban land cover information extraction is a hot topic within urban studies. Heterogeneous spectra of high resolution imagery—caused by the inner complexity of urban areas—make it difficult. In this paper a hierarchical object oriented classification method over an urban area is presented. Combining QuickBird imagery and light detection and ranging (LIDAR) data, nine kinds of land cover objects were extracted. The Spectral Shape Index (SSI) method is used to distinguish water and shadow from black body mask, with 100% classification accuracy for water and 95.56% for shadow. Vegetation was extracted by using a Normalized Difference Vegetation Index (NDVI) image at first, and then a more accurate classification result of shrub and grassland is obtained by integrating the height information from LIDAR data. The classification accuracy of shrub was improved from 85.25% to 92.09% and from 82.86% to 97.06% for grassland. More granularity of this classification can be obtained by using this method. High buildings and low buildings can, for example, be distinguished from the original building class. Road class can also be further classified into roads and crossroads. The comparison of the classification accuracy between this method and the traditional pixel-based method indicates that the total accuracy is improved from 69.12% to 89.40%. 相似文献
873.
百家讲坛的传播学动因探析 总被引:1,自引:0,他引:1
<百家讲坛>作为中央电视台10套科教频道推出的一档电视文化栏目,在其学术传媒化过程中所引发了关于"学术明星"等众多争议.有人为<百家讲坛>的学术平民化喝彩,也有人置疑它的学术价值以及严谨性,但有一点是被受众所接受的,即<百家讲坛>的大众平民化取向.论文试图从传播学的角度,探究<百家讲坛>作为一次媒体介入学术传播的动因所在. 相似文献
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875.
Chen Yan Ding Lanying Fu Yucan Su Honghua Wu Jie Xu Jiuhua Xu Hongjun 《南京航空航天大学学报(英文版)》2014,(1):104-110
The purpose of this study is to investigate the effect of graphite lubricant on the dry grinding performance of Ti-6Al-4Valloy,using graphite-coated,brazed monolayer,cubic boron nitride(cBN)wheels.Brazed monolayer cBN wheels both with and without a coating of polymer-based graphite lubricant are fabricated and subsequently compared for grinding performance based on measurements of grinding temperature,surface microstructure and grinding.In terms of grinding temperature,considerable improvement in dry grinding performance of titanium alloy is achieved using coated brazed monolayer cBN wheels,with 42%—47%reduction in grinding temperature as opposed to uncoated wheels.The grinding force ratio with the coated wheels is observed to remain between 1.45to1.85despite material removal rates reaching up to 1 950mm3/mm.No tangible change in ground titanium surface microstructure is noted as a result of grinding with the graphite coated wheels as opposed to the uncoated ones. 相似文献
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879.
在航空航天领域,作用在结构上动载荷的确定对结构健康监测是非常必要和重要的。为此,本文以类似机翼结构的变截面悬臂梁结构为研究对象,提出了一种基于光纤光栅传感器与卡尔曼滤波器的动载荷识别方法。首先,根据变截面梁单元形式,推导出变截面梁的质量矩阵与刚度矩阵,建立动力学运动方程。然后,以光纤光栅传感器测得的应变信息作为观测信号,通过卡尔曼滤波器生成的增益矩阵、新息序列矩阵以及协方差矩阵,得到灵敏度矩阵和估计力的增益矩阵。在此基础上,利用广义回归模型及其最小二乘算法,估算出动载荷大小、判断出动载荷激励位置。借助数值仿真与实验手段,分别验证了该方法对于单点正弦激励、方波激励、锯齿波激励以及多点同时激励等工况下的动载荷识别效果。结果表明,本文所提算法具有较好的动载荷识别效果和噪声抑制能力,能够为未来风洞试验和真实飞行试验环境中诸如大展弦比机翼表面气动压力等载荷实时辨识、气动外形自适应控制以及结构健康监测提供技术支撑。 相似文献
880.
Jie Wang Xiuyun Meng Cuichun Li Wenjie Qiu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(12):4121-4141
The ability to achieve long-endurance station-keeping flights makes stratospheric airships desirable platforms for the provision of communication and surveillance services. To maintain long-endurance flights, it is necessary to consider the problem of energy consumption. In this paper, we discuss long-endurance flight scenarios of stratospheric airships in the presence of thermal effects. The balance between buoyancy and gravity is influenced by thermal effects during the diurnal cycle. We perform a theoretical analysis based on the helium’s mass, pressure differential, and altitude as the main factors. To verify the effectiveness of the control over the pressure differential and the altitude, three long-endurance flight scenarios are proposed and compared. Then, the corresponding optimization problems are constructed to determine the energy-minimum flight. Finally, further efforts are made to reduce energy consumption. The realization and limitations of two strategies for improvement are analyzed. A comparison with other scenarios shows the effectiveness of energy conservation. The study in this paper thus provides a reference for station-keeping applications of stratospheric airships. 相似文献