用于非均匀介质重建的选代算法收敛性的研究

研究轴对称二维非均匀介质重建迭代算法的收敛性问题。首先借助于玻恩近似将非线性积分方程线性化，然后，利用玻恩迭代法和变形玻恩迭代法，由散射场数据对轴对称二维非均匀介质进行重建。通过几个例子研究了影响迭代算法收敛性的几种因素，如送代算法本身、积分离散化后的网格划分、正则化方法中的正则化参数选取等。     

非均匀介质中的场与波：理论及其在电测井中的应用

本文综述了非均匀介质中场与波理论近年来的研究进展及其应用成果，着重介绍了非均匀介质中的电磁场正演分析和反演计算中的各种高效数值方法，以及它们在电法测井数值模拟和成象研究中的成功应用。     

数字聚焦微电阻率测井仪设计

提出了一种采用数字聚焦方法的微电阻率测井仪器设计方案，其主要特点利用DSP集成芯片的数字信号处理优势，实现仪器的控制与测量，并通过软件滤波和聚焦处理获得视电阻率。该设计用超大规模集成电路DSP及软件处理取代了老式微球形聚焦测井仪器复杂的硬件监控、反馈、检波和测量线路，提高了仪器的可靠性和测量精度。对仪器原理进行了较详细的说明，在DSP技术应用于测井井下仪器方面做了有益的探索。     

V型天线的行波加载公式

本文研究了ｖ型天线上电流分布与阻抗加载的关系，导出了支持天线上行波电流的阻抗加载公式。讨论了天线张角、振子半径以及振子长度与加载量的关系和规律，说明了加载Ｖ型天线的宽带特性。文中还计算了在高斯脉冲激励下，不同加载量的天线上瞬态电流的分布，由此可以表明所导加载公式的正确性与重要性。     

焊接箱型截面构件在不同焊缝熔深下承载力性能试验研究

为了有效改善大跨度桥梁中管翼缘焊接箱型截面构件的耐久性的问题,提出采用耐候钢代替普通钢的管翼缘箱型截面梁。同时,为了研究耐候钢管翼缘焊接箱型截面构件填充混凝土后在全熔透和部分熔透条件下的单轴承载力性能,开展了焊接矩形截面在三种不同焊缝熔深下的耐候钢管混凝土截面轴压短柱试验研究。分别测试每个试件在单轴压力作用下的静态应变、动态应变,以及竖向位移和侧向位移。对比构件承载力的试验结果及理论分析结果,得出不同熔深下焊接箱型截面管翼缘组合构件的承载力性能。研究结果表明:1）耐候钢管翼缘焊接箱型截面构件的全熔透焊缝承载力高于部分熔透焊缝承载力。2）全熔透试件开裂时的竖向位移较部分熔透试件的位移值大,而不同熔深下构件的横向位移测点L4随轴压荷载的增大而有增加,L3测点横向位移规律不明显。3）不同耐候钢管翼缘焊接箱型截面构件横向整体受拉,局部在顶部角部位置受压。构件的混凝土内部和钢板表面应变情况复杂,规律不明显。     

In Situ Chelating Synthesis of Hierarchical LiNi1/3Co1/3Mn1/3O2 Polyhedron Assemblies with Ultralong Cycle Life for Li‐Ion Batteries

Layered lithium transition‐metal oxides, with large capacity and high discharge platform, are promising cathode materials for Li‐ion batteries. However, their high‐rate cycling stability still remains a large challenge. Herein, hierarchical LiNi_1/3Co_1/3Mn_1/3O₂ polyhedron assemblies are obtained through in situ chelation of transition metal ions (Ni²⁺, Co²⁺, and Mn²⁺) with amide groups uniformly distributed along the backbone of modified polyacrylonitrile chains to achieve intimate mixing at the atomic level. The assemblies exhibit outstanding electrochemical performances: superior rate capability, high volumetric energy density, and especially ultralong high‐rate cyclability, due to the superiority of unique hierarchical structures. The polyhedrons with exposed active crystal facets provide more channels for Li⁺ diffusion, and meso/macropores serve as access shortcuts for fast migration of electrolytes, Li⁺ and electrons. The strategy proposed in this work can be extended to fabricate other mixed transition metal‐based materials for advanced batteries.     

Design of a novel monopulse antenna system using the time‐modulated antenna arrays

A novel monopulse antenna for a tracking radar system is proposed using the time modulated antenna array technique. The time modulation technique applied in the antenna arrays overcomes the usual need for compromise between sum and difference beams and avoids the need for implementation of two separate feed networks. The time modulated antenna array also relaxes the error tolerance of the tracking accuracy from the amplitude and phase errors, due to the new design freedom of “time” which can be controlled precisely and quickly. Moreover, the position of the target can be recovered by two reflected echoes from one previously transmitted pulse, thus the tracking errors resulting from the excitation errors and receiver noise in conventional antenna arrays can be greatly alleviated. Numerical results show that with the aid of time modulation technique, one sum beam and two difference beams can be simultaneously obtained either for the boresight or off‐boresight target tracking. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Efficient analysis of wireless communication antennas using an accurate [Z] matrix interpolation technique

An accurate impedance matrix interpolation technique based on the surface integral equation (SIE) is presented for the analysis of wireless communication antennas over wide frequency bands. The first‐order derivative of the impedance matrix at the internal frequency is considered in the cubic polynomial‐based interpolation scheme, thus the novel impedance matrix interpolation scheme will provide high accuracy and high efficiency over a frequency band. To demonstrate the efficiency and accuracy of the proposed method, numerical results for planar inverted F antennas (PIFA) and a wideband E‐shaped patch antenna are presented. Good agreement among the interpolation results, exact MoM solutions, finite element method (FEM) solutions, and measured data is observed over the bandwidth. Besides, dimensions of the feeding probe are also studied to investigate their effect on the input impedance and radiation patterns. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

二氢茉莉酮酸甲酯生产工艺的研究

二氢茉莉酮酸甲酯是一种深受人们喜爱的茉莉香型的重要香原料。本文以环戊酮和戊醛为原料在碱催化下 ,以缩合和异构化反应合成了 2 -戊基环戊烯酮。 2 -戊基环戊烯酮再与丙二酸二甲酯缩合 ,脱羧得二氢茉莉酮酸甲酯 ,并且进行了中试放大 ,确定了最佳工艺条件     

P2P网络技术的研究及应用

介绍了P2P技术的基本原理、发展、特点及应用,并探讨了它的不足和发展前景.