Optimal Directivity Synthesis of an Arbitrary Array Subject to Sidelobe and Cross-Polarization Constraints

本文根据给定的期望极化方向,定义了扫描波束的期望主极化和交叉极化方向,并进一步给出了主极化方向性系数的定义,它可以更为准确的表征天线集中辐射主极; 化分量的程度.在没有副瓣约束和交叉极化约束的条件下,给出了任意阵列主极化方向性系数最优解的解析表达式.并且,在含副瓣约束、零陷约束以及交叉极化约; 束的条件下,我们发展了一种基于凸优化的高效数值综合方法,实现多约束条件下的主极化方向性系数的优化.数值阵列综合结果表明了本文所提出的最优主极化方; 向性系数解析解的正确性,以及这种可以综合考虑副瓣约束、零陷约束和交叉极化约束的数值方向性优化方法的有效性.Definitions of the desired co-polarization and cross-polarization; directions are given for a scanned beampattern according to a desired; polarization direction. Furthermore, the co-polarization directivity is; defined to more accurately represents the degree of the concentration of; co-polarization field over the total radiated power. With this; definition, the co-polarization directivity can be optimized. Its; analytical expression can be derived when no more pattern constraints; exist. In more general cases in which the constraints on the sidelobe; level,nulling points and cross-polarization level exist, an efficient; numerical algorithm based on convex optimization is proposed. Some; numerical synthesis experiments are conducted, and the results show the; effectiveness and robustness of the proposed synthesis techniques.国家自然科学基

Greening the fringes

The United Nations Environment Programme (UNEP) is spending US$50 million on a new phase of the Desert Margins Programme. The programme will marry indigenous knowledge with modern land management techniques to find new ways of protecting the environment in areas such as Matabeleland in Zimbabwe and the Sudano-Sahelian zone of Senegal. Seven other countries are covered in the programme: Botswana, Burkina Faso, Kenya, Mali, Namibia, Niger and South Africa. UNEP, November 2002The United Nations Environment Programme (UNEP) is spending US$ 50 million on a new phase of the Desert Margins Programme. The programme will marry indigenous knowledge with modern land management techniques to find new ways of protecting the..

Semantic Memory Impairment and Lateralization in Brain Injured Patients

目的运用本土化的语义记忆测验评估脑损伤患者的语义记忆水平,比较患者和对照组在语义记忆分数上的差异,同时研究语义记忆是否存在偏侧化特点。方法对25例脑损伤患者（左侧脑损伤16例,右侧脑损伤9例）和24例正常对照组进行图片版和词汇版相关匹配测验。结果左侧脑损伤患者组在图片版和词汇版相关匹配测验上的分数均低于正常对照组（P〈0.01）和右侧脑损伤患者组（P〈0.05）。患者图片版和词汇版相关测验的分数之间呈明显正相关（r=0.542,P〈0.01）。左侧脑损伤语义记忆障碍发生率明显高于右侧脑损伤（P〈0.01）。左侧基底节损伤语义记忆障碍发生率高于右侧基底节损伤（P〈0.05）。结论采用词汇版和图片版相关匹配测验可评估患者语义记忆水平。脑损伤患者中普遍存在语义记忆障碍,而且语义记忆存在左侧化优势