纳米结构电学性质的静电力显微镜研究方法

纳米尺度的材料具有许多不同于宏观体材料的奇特的物理和化学特性.了解纳米结构的物性随材料尺寸及形状的变化关系,对于设计和合成具有特定功能的纳米材料有重要的指导意义.静电力显微镜技术为研究微纳米尺度下材料的电学特性提供了强有力的工具.文章介绍了这种测量技术的基本原理,并列举了几种在静电力显微镜基础上发展起来的纳米材料电学性...     

STABILITY IN LAGRANGE SENSE FOR A CLASS OF STOCHASTIC STATIC NEURAL NETWORKS WITH MIXED TIME DELAYS

In this paper, the stability in Lagrange sense of a class of stochastic static neural networks with mixed time delays is studied. Based on the Lyapunov stability theory and with the help of stochastic analysis technique, the criteria for the stability in Lagrange sense of stochastic static neural networks with mixed time delays is obtained. One example is given to verify the advantage and applicability of the proposed results.     

二元体相分离模型的静态分歧

运用非线性分歧理论,研究二元体相分离模型的静态分歧,给出了一个与该模型线性问题第一特征值相关的临界值。当参数超过该临界值时,二元体相分离模型有静态分歧发生,此时相应的二元体有相分离现象发生。此外,提出影响二元体相分离现象发生的主要因素是晶格间距和二元体所在区域的形状。     

狭长体中静态裂纹与快速传播裂纹的精确分析解

本文用保角映射把狭长形裂纹静力学第一边值问题予以统一的彻底的解决,接着对更为困难的狭长体裂纹动力学进行了研究。基于作者已有的理论框架,采用z₁平面与z₂平面同时映射到ζ平面上单位圆内部一个保角变换,使这一复杂的边值问题也得以彻底解决。在以上两种情形都得到了封闭形式的精确分析解,并且当裂纹速度V→0时,动力学解还原为静力学解。这些解在科学(例如地球物理学、地震学)和工程(例如液压断裂采油工程、爆破工程)中有一定的应用价值。     

不识试题真“面目”只缘未破其“伪装”——一道中考题的思索

各类考试中的动态型探索性试题,常因其变化的干扰因素使许多同学觉得扑朔迷离,眼花缭乱,直接考验同学们的智慧和能力.分析题目时若能排除动态干扰因素的“伪装”,将动态型问题转化为静态问题,还原题目的静态“面目”,便能化解题目的难度,提高解题的成功率,收获解题的喜悦与快乐.下面结合一道中考试题谈谈笔者的一些思索.     

TWISTING STATICS AND DYNAMICS FOR CIRCULAR ELASTIC NANOSOLIDS BY NONLOCAL ELASTICITY THEORY

The torsional static and dynamic behaviors of circular nanosolids such as nanoshafts, nanorods and nanotubes are established based on a new nonlocal elastic stress field theory. Based on a new expression for strain energy with a nonlocal nanoscale parameter, new higher-order governing equations and the corresponding boundary conditions are first derived here via the variational principle because the classical equilibrium conditions and/or equations of motion can- not be directly applied to nonlocal nanostructures even if the stress and moment quantities are replaced by the corresponding nonlocal quantities. The static twist and torsional vibration of circular, nonlocal nanosolids are solved and discussed in detail. A comparison of the conventional and new nonlocal models is also presented for a fully fixed nanosolid, where a lower-order governing equation and reduced stiffness are found in the conventional model while the new model reports opposite solutions. Analytical solutions and numerical examples based on the new nonlocal stress theory demonstrate that nonlocal stress enhances stiffness of nanosolids, i.e. the angular displacement decreases with the increasing nonlocal nanoscale while the natural frequency increases with the increasing nonlocal nanoscale.     

煤与生物油的成浆性能研究

利用不同煤种的煤和生物油制备了不同浓度的生物油煤浆,考察了生物油煤浆的成浆浓度、表观黏度、流变特性和稳定性。结果表明,生物油煤浆是具有一定屈服应力的非牛顿流体,其流变特性可用宾汉姆方程来描述;生物油煤浆的屈服应力和表观黏度都随着固体浓度的增加而增大;随着剪切速率的增加,生物油煤浆的表观黏度减小;四种煤中,无烟煤的成浆浓度最高,可达42%,其含碳量高达49%,相当于同种煤制成的74%的水煤浆含量。烟煤次之,褐煤最低;生物油与煤粉之间能够形成絮凝性的大分子网络结构,使得生物油煤浆存在屈服应力并能够保持良好的静态稳定性,4.0~5.0 d天没有软沉淀产生,数月没有硬沉淀产生。     

浅谈GPS技术与高等级公路测量

全球定位系统为公路勘测设计工作者提供了一个可靠的提高外业测量精度及进度的工具,随着GPS越来越多地出现在人们的生产、生活中,这一先进的测量手段会被更广泛地应用到公路勘测工作中,从而可提高作业效率,缩短设计周期,推动交通事业的发展和公路的建设。     

超高介电常数非铁电单晶

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