超宽带TEM喇叭天线优化设计与实验

针对用于成像雷达系统的超宽带TEM喇叭天线进行了优化设计,兼顾辐射性能、馈入反射和小尺寸条件,采用平滑渐变结构和加载技术代替原设计,增加了低频电流的回流通道,从而改善了天线的低频特性,增强了其定向辐射能力。在理论分析的基础上对其进行了仿真,并按照仿真结果实际制作了一副天线,对天线进行了测试。仿真与实测结果表明:在电压驻波系数小于2时,该天线具有11∶1的阻抗带宽,较强的辐射能力和良好的定性辐射特性,能够满足雷达系统的需求。     

On classification of polarized varieties with non-integral nef values

Let be an -dimensional normal projective variety with only Gorenstein, terminal, -factorial singularities. Let be an ample line bundle on . Let denote the nef value of . The classification of via the nef value morphism is given for the situations when satisfies or .

     

An extended continuum mixed traffic model

With the development of vehicle technology, the number of vehicles equipped with the adaptive cruise control (ACC) system is increasing, and it is more and more common for ACC vehicles to drive with regular vehicles. In this work, we proposed a mixed traffic model with regular vehicles and ACC vehicles via the transformation of micro-model and macro-model. The linear stability analysis tells that the permeability of ACC vehicles has an important influence on the traffic system. Meanwhile, through the nonlinear analysis, the KdV–Burgers equation describing the density wave is obtained. Besides, the results of numerical simulations are consistent with the theory, which indicates that the increase in ACC vehicles is conducive to the stability of the transportation system.

     

PEO-LiC104-SiO2-SCA体系电化学性能研究

选用硅烷偶联剂(SCA)对聚环氧乙烯(PEO)基固态聚合物电解质体系进行改性.通过XRD,DSC,SEM,FTIR,EIS 和拉伸性能测试等方法对材料进行了表征,考察了SCA对电解质电化学性能和力学性能的影响;对SCA的作用进行了分析.结果显示,SCA的加入显著降低了体系的结晶度,材料的电化学性能和力学性能得到了明显的改善.PEOB-LiC1Oa-5%SiO2-SCA体系室温电导率达到9.0×10-4S/cm,屈服强度达到2.04MPa(25℃).同时,SCA使电解质膜表面变得更为光滑、致密,这有利于降低与电极片间的接触阻抗.     

天然冷源系统在水电企业应用研究

为研究天然冷源系统在水电企业应用的可行性,在SWOT分析方法的基础上,建立了天然冷源系统节能量与总投资关系的数学模型,得出模型的分析解,并提出了天然冷源节能投资系数(CEIC)的定义,分析了其在不同总节能量及冷源系统总投资条件下的变化规律,基于该模型对溪洛渡水力发电厂地下厂房天然冷源系统进行了特征参数计算及验证。研究表明,天然冷源节能投资系数受总节能量和系统总投资影响,当系数≥1时认为是应用可行的,系数≥2.5认为该系统具有良好的节能效益。     

Controlled synthesis of light rare-earth hydroxide nanorods via a simple solution route

Ln(OH)₃ (Ln=La, Pr, Nd, Sm, Eu, Gd) nanorods are synthesized without using any surfactants or templates at room temperature. The as-obtained nanorods are within 4–25 nm in diameter and up to 200 nm in length. The most important improvement is that the aspect ratio of the obtained nanorods can be effectively controlled by adjusting the reaction time and pH value of the reaction system. The as-synthesized nanorods are characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It is interesting to find that both the inherent crystal structure of light lanthanide hydroxide and the chemical potential affect the formation of nanorods. The photoluminescence (PL) instrument is used to investigate the optical properties of the Eu(OH)₃ nanorods and its abnormal luminescence behaviors are observed.     

关于高维簇的小收缩映射

设X是非奇异的n维射影簇,A是X上的一个Ample除子.本文研究了以K     

热声热机和斯特林热机振荡现象的网络描述

热力学循环的实质是一种非等熵的循环 ,热声热机和斯特林热机振荡现象在满足热力学循环一般规律的同时 ,而各有其特殊性 ,故其各自的振荡本质是有差异的 ,用于描述两者的网络模型也必然有差异。     

Smooth 4-folds which contain a P1-bundle¶as an ample divisor

We show that if a smooth projective 4-fold M contains an ample divisor A which is P ¹-bundle π :A→S over a smooth projective surface S, π is extended to a P ²-bundle π :S→S, unless $A$ is isomorphic to P ²×P ¹. Received: 28 September 1998 / Revised version: 16 August 1999