排序方式: 共有41条查询结果,搜索用时 31 毫秒
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To resolve problems of complicated clutter, fast-varying scenes, and low signal-clutterratio (SCR) in application of target detection on sea for space-based radar (SBR), a target detection approach based on adaptive waveform design is proposed in this paper. Firstly, complicated sea clutter is modeled as compound Gaussian process, and a target is modeled as some scatterers with Gaussian reflectivity. Secondly, every dwell duration of radar is divided into several sub-dwells. Regular linear frequency modulated pulses are transmitted at Sub-dwell 1, and the received signal at this sub-dwell is used to estimate clutter covariance matrices and pre-detection. Estimated matrices are updated at every following sub-dwell by multiple particle filtering to cope with fast-varying clutter scenes of SBR. Furthermore, waveform of every following sub-dwell is designed adaptively according to mean square optimization technique. Finally, principal component analysis and generalized likelihood ratio test is used for mitigation of colored interference and property of constant false alarm rate, respectively. Simulation results show that, considering configuration of SBR and condition of complicated clutter, 9 dB is reduced for SCR which reliable detection requires by this target detection approach. Therefore, the work in this paper can markedly improve radar detection performance for weak targets. 相似文献
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Jyh-Woei Lin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
This paper examines China’s Wenchuan Earthquake of 12 May 2008 (UTC) (Mw = 7.9) using principal component analysis and image processing of the global ionospheric map (GIM) for the region. Transforms are conducted for 4, 8, and 9 May 2008. The GIMs are subdivided into 100 (36° in Long. and 18° in Lat.) smaller maps. The smaller maps (71 × 71 pixels) form the transform matrices of corresponding dimensions (2 × 1) through image processing. The transform allows for principle eigenvalues to be assigned to TEC anomalies for May 8 and 9. These may represent the seismo-ionospheric signature described by Zhao et al. (2008). The May 4 result shows no evidence of TEC anomalies. These results are in keeping with the findings of Liu et al. (2009). It is evident in this research that PCA could have the capacity to detect both the seismo-ionospheric signature and determine the approximate location of an earthquake’s epicenter prior to nucleation. 相似文献
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张俊岭 《郑州航空工业管理学院学报(管理科学版)》2006,24(1):97-99
在多指标体系评价方法的研究中,不同研究者根据自身数据资料、时间等有限条件,选择或主观赋权评价或客观评价,但仅仅采用一种方法进行评价,结果很难令人满意。为了解决这一问题,提出了结合国内外学术界盛行的以主观赋权来进行评价的层次分析法(AHP)和以客观赋权来进行评价的主成分分析法(PCA)两种方法,通过位次进行最终评价的加权评价模型,命名为“位次加权复合评价模型”。该模型是两种基本方法的组合,能达到优势互补的目的,全面、准确地做出评价。 相似文献
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线性模型最小二乘方估计的改进大致有两条途径:利用验前信息,如贝叶斯估计,改变估计形式,如特征根估计,主成分估计,本文提出BL(贝叶斯加特征根)估计和BP(贝叶斯加主成分)估计,实现两类途径的综合,有实用和理论价值。 相似文献
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Lin Jyh-Woei 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
This paper uses principal component analysis (PCA) to determine the spatial pattern of total electron content (TEC) anomalies in the ionosphere post the China’s Wenchuan Earthquake of 12 May, 2008 (UTC) (Mw = 7.9). PCA and image processing are applied to the global ionospheric map (GIM) with transforms conducted for the time period 08:00–10:00 UT on 12 May 2008. Results show that at a height of approximately 200 km the anomaly is widespread and less intense; however, it becomes more localized with height reaching maximum intensity and localization at an altitude of 300 km. The spatial distribution is remarkably similar to that reported for a TEC anomaly previously identified as a precursor anomaly on May 9, 2008 for the same time period. Potential causes of the results are discussed with emphasis given to vertical acoustic gravity waves based on the spatial pattern identified. 相似文献
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本文研究自旋航天器的旋转轴的试验测定方法,给出自旋轴方向的表示方法及其与转动惯量,惯性积的关系,建立了利用动平衡试验的不平衡量确定自旋轴相对平衡旋转轴偏差的计算机公式,从而可以利用动平衡试验的测试结果确定自自旋轴的方向,文末的例中讨论了动平衡机的最小可达剩余不平衡量对试验结果的影响。 相似文献