A hybrid method for synthesizing antenna's three dimensional (3D) pattern is proposed to obtain the low sidelobe feature of truncated cone conformal phased arrays. In this method, the elements of truncated cone con...A hybrid method for synthesizing antenna's three dimensional (3D) pattern is proposed to obtain the low sidelobe feature of truncated cone conformal phased arrays. In this method, the elements of truncated cone conformal phased arrays are projected to the tangent plane in one generatrix of the truncated cone. Then two dimensional (2D) Chebyshev amplitude distribution optimization is respectively used in two mutual vertical directions of the tangent plane. According to the location of the elements, the excitation current amplitude distribution of each element on the conformal structure is derived reversely, then the excitation current amplitude is further optimized by using the genetic algorithm (GA). A truncated cone problem with 8x8 elements on it, and a 3D pattern desired side lobe level (SLL) up to 35 dB, is studied. By using the hybrid method, the optimal goal is accomplished with acceptable CPU time, which indicates that this hybrid method for the low sidelobe synthesis is feasible.展开更多
陆表切割密度(Land Dissection Density,LDD)的空间格局与陆地表面土壤侵蚀息息相关,国内相关研究主要基于流域或局地尺度分析黄土高原和东北地区的陆表切割情况,全国尺度上陆表切割情况仍未知。该文基于ALOS World 3D-30 m DEM数据和...陆表切割密度(Land Dissection Density,LDD)的空间格局与陆地表面土壤侵蚀息息相关,国内相关研究主要基于流域或局地尺度分析黄土高原和东北地区的陆表切割情况,全国尺度上陆表切割情况仍未知。该文基于ALOS World 3D-30 m DEM数据和全国二级流域数据,利用Geomorphons地形元素分类方法制成全国陆表切割密度分布图,并结合地貌区划分析各地貌区内不同等级切割密度的分布情况。结果显示:全国二级流域的陆表切割密度介于0~7 km/km^(2)之间,强烈切割(3~<5 km/km^(2))流域面积约占国土面积的0.54%;切割密度与流域地形因素密切相关,缓斜坡(2°<~5°)、高丘陵和小起伏山地(100~400 m)以及低海拔(<1000 m)地区是切割易发区;一级地貌大区间的切割密度空间格局差异显著,中度及以上切割(LDD≥2 km/km^(2))流域空间分布呈现出不同模式,体现了地貌区内外营力的共同作用;陆表切割易发生在受剥蚀外营力作用影响的二级地貌区,且不同等级切割密度在不同地貌类型上具有一定聚集性。研究结果可拓展现有陆表切割研究的空间尺度,为宏观层面的陆表切割现状和全国各地土壤侵蚀评估提供科学依据。展开更多
基金supported by the Fundamental Research Funds for the Central Universities(YWF-13D2-XX-13)the National High-tech Research and Development Program(863 Program)(2008AA121802)
文摘A hybrid method for synthesizing antenna's three dimensional (3D) pattern is proposed to obtain the low sidelobe feature of truncated cone conformal phased arrays. In this method, the elements of truncated cone conformal phased arrays are projected to the tangent plane in one generatrix of the truncated cone. Then two dimensional (2D) Chebyshev amplitude distribution optimization is respectively used in two mutual vertical directions of the tangent plane. According to the location of the elements, the excitation current amplitude distribution of each element on the conformal structure is derived reversely, then the excitation current amplitude is further optimized by using the genetic algorithm (GA). A truncated cone problem with 8x8 elements on it, and a 3D pattern desired side lobe level (SLL) up to 35 dB, is studied. By using the hybrid method, the optimal goal is accomplished with acceptable CPU time, which indicates that this hybrid method for the low sidelobe synthesis is feasible.