Radar Imaging Based on Iterative Algorithms

It has long been realized that the problem of radar imaging is a special case of image reconstruction in which the data are incomplete and noisy. In other fields, iterative reconstruction algorithms have been used successfully to improve the image quality. This paper studies the application of iterative algorithms in radar imaging. A discrete model is first derived, and the iterative algorithms are then adapted to radar imaging. Although such algorithms are usually time consuming, this paper shows that, if the algorithms are appropriately simplified, it is possible to realize them even in real time. The efficiency of iterative algorithms is shown through computer simulations.     

再辉效应对T9A钢显微组织和机械性能的影响

研究了T9A钢铅浴淬火时,再辉效应对其显微组织和机械性能的影响.在珠光体转变温度范围内等温时,随着等温温度的降低,引起塑性下降的原因是再辉效应促发颗粒状或短片状珠光体形成;在上贝氏体转变温度区,由于出现再辉效应产生的温度爬升现象,使试样温度升至屈氏体转变温度区从而形成上贝氏体和屈氏体的混合组织,使得强度增高曲线出现平台或稍有下降,且塑性发生下降,同时,还对等温淬火的定义提出了新的看法,绘出了反映实际情况的共析钢C-曲线上的组织形成图。     

大学生口算能力的实验研究

为考察大学生的口算能力,我们随机选取30名大学生为被试进行口算的实验研究,主要结论如下:(1)大学生的口算速率在加、减、乘、除法之间存在差异,从快到慢依次为:除法,借位减法,不借位减法,不进位加法,进位加法,乘法;(2)口算的广度从大到小依次为:不进位的加法广度,进位加法广度,不借位减法广度,借位减法广度,除法广度,乘法广度;(3)大学生口算的速度和广度既无显著的专业差异,也无显著的性别差异.     

浅谈直观教学在弱智学生语文教学中的功能

文章从直观教学的能趣化、活化、深化和强化几个方面对使用直观教学促进弱智学生语文教学的功能进行了探讨.     

CFG桩施工引起桩周土体开裂的原因探讨

由于郑东新区特殊的工程地质条件，长螺旋CFG（Cement Flyash Gravel）桩施工常常引起桩周土体开裂和周围建筑物开裂等施工事故。本文通过郑州某工地现场试验分析，否定了空桩效应引起桩周土体开裂的猜想，并分析了郑东新区由于CFG桩施工引起桩周土体开裂的原因。     

蒸汽机车水垢形成机理及解决方法

蒸汽机车锅炉水垢对机车的安全运行及工作效能有很大的影响,对蒸汽机车水垢的处理极其重要。蒸汽机车水垢是经过复杂的物理、化学变化而形成的。由于水垢的形成,造成锅炉的传热效率低,大量浪费燃料;降低锅炉出力危及锅炉安全运行;缩短使用寿命增大检修量,浪费工时、原料。为了缓解机车水垢的形成,可以采取尽量降低软化水硬度、确保洗修质量、合理安排排污时机和次数,提高排污效果等措施,并在实际运用中取得了一定的效果。     

对英语专业八级口语口译考试评分的探讨

本文通过对英语专业八级口语口译考试的评分标准的考察，指出八级口语口译考试评分中两个突出的特点，即突出口语考试和口译考试评分“信息单元化”，从而影响口译质量评估的有效性。适当改变评分比例和口译评分标准的改进将有助于改善测评效果。     

A theoretical model for mid-and low-latitude ionospheric electric fields in realistic geomagnetic fields

The geomagnetic fields, which play important roles in the ionospheric dynamo, can greatly affect the global distribution of ionospheric electric fields, currents and other ionospheric electrodynamics phenomena. In the study of ionospheric electrodynamics phenomena, such as the longitudinal variations of ionospheric electric fields, the non-dipolar component of the geomagnetic fields must be taken into account. In this paper, we deduce a theoretical electric field model for ionospheric dynamo at mid- and low-latitude which adopt a modified magnetic apex coordinates system. In the new electric field model, the geomagnetic fields can be calculated from either the IGRF model or the dipole field model, and the neutral winds and conductivities are calculated based on empirical models. Then the dynamo equation for the electric potential is finally solved in terms of the line-by-line iteration method, and the ionospheric electric fields and currents are derived from the calculated potential. Our model can reproduce the main features of the ionospheric electrodynamics processes, so it will be a useful tool for the investigation of the upper atmosphere and ionosphere.     

字符编辑器在CAI课件设计中的开发应用

该文介绍利用字符编辑器设计CAI课件屏幕图形和动画的方法以及TenCORE教学系统字符编辑器的基本原理和使用方法。