抗高温降滤失剂PAX的合成及性能

采用氧化还原体系以2-丙烯酰胺基-2-甲基丙磺酸(AMPS),丙烯酰胺(AM),等乙烯基单体为基本原料合成出了新型抗高温二元共聚物PAX系列处理剂.该降滤失剂在220℃的高温下及饱和盐水中具有良好的降滤失作用.     

球内凝固过程的近似解分析

对球内凝固相变过程作了较为系统和全面的理论分析 ,建立了能够揭示在第三类边界条件下球体内相变传热过程物理机制的数学模型 ,用Lighthill奇异摄动法给出了球体内对称凝固问题的近似分析解 ,并以Ba(OH) 2 ·8H2 O为相变材料 ,得到了相变界面、相变介质温度随时间和热流密度随相变位置的变化规律 ,以及球囊半径和对流换热系数对凝固过程的影响。得到结论 :对一般工程背景 ,球囊半径为 1 .5～ 2 .0cm ,h <1 0 0 0W /(m2 ·K)较为合适 ,从而为以球为相变贮能单元的贮能装置的优化设计提供了一定的理论参考。     

ZnO导电陶瓷的制备及电性能研究

采用注浆成型法制得ZnO导电陶瓷 ,通过添加Al2 O3、Cr2 O3、Fe2 O3、La2 O3,探讨了各添加剂对ZnO陶瓷电性能的影响。结果表明 ,聚丙烯酸胺 (PMMA)是ZnO粉体良好的分散剂 ,其质量分数在 0 3%时可得到低粘度、高固含量的ZnO悬浮体。各种氧化物添加剂的添加量对ZnO陶瓷的室温电阻率及电阻温度特性具有较大的影响。随着Al2 O3添加量的增加 ,ZnO陶瓷体的电阻率先略微减小然后增大 ;添加Cr2 O3与添加Al2 O3的效果相反 ;随着Fe2 O3、La2 O3添加量的增加 ,ZnO陶瓷体的电阻率增大。添加Al2 O3、Cr2 O3、Fe2 O3、La2O3的ZnO陶瓷呈现负电阻温度特性。     

一种基于小波的奇异信号检测方法

介绍了小波二进制变换的基本原理，简述了小波变换奇异性和信号突变的关系。基于小波变换，给出一种结合3δ准则、软硬阚值折衷法的奇异信号小波检测方法。仿真结果表明此法既能有效地消除噪声，又能较好保留奇异信号,从而改善信号中奇异性信息的提取效果；在对信号奇异程度和奇异点位置的确定上，较以往的处理方法有明显的改善。     

由一般鞅驱动的正倒向随机微分方程的比较定理

本文首次研究由连续局部鞅驱动的完全藕合的正倒向随机微分方程的比较定理 .首先考虑对正倒向随机微分方程中的倒向随机微分方程的终端的比较 ,得到定理 3.1,说明倒向随机微分方程的终端值越大 ,其初始值越大 .然后研究对正倒向随机微分方程中的正向随机微分方程的初始端的比较 ,得到定理 3.3,说明正向随机微分方程的初始值越大 ,倒向随机微分方程的初始值也越大 .     

Exact algorithms for the job sequencing and tool switching problem

The job Sequencing and tool Switching Problem (SSP) involves optimally sequencing jobs and assigning tools to a capacitated magazine in order to minimize the number of tool switches. This article analyzes two integer linear programming formulations for the SSP. A branch-and-cut algorithm and a branch-and-bound algorithm are proposed and compared. Computational results indicate that instances involving up to 25 jobs can be solved optimally using the branch-and-bound approach.     

Probabilistic Approach to Predict Cracking in Lightly Reinforced Microconcrete Panels

The ultimate strength of structures made of brittle materials—such as microconcrete—strongly depends on microstructural defects, the structure size, and the loading pattern. Probabilistic approaches allow one to take account of such dependencies. By using a Weibull model, cracking of ferrocement panels is analyzed. Provided the behavior of the reinforcement remains elastic, it is shown that the Weibull parameters identified on unreinforced microconcrete samples tested in flexure may be used to predict multiple cracking in ferrocement panels tested in tension. A key aspect of the analysis is related to the understanding and modeling of the stress heterogeneity effect on the local failure probability of unreinforced as well as reinforced microconcrete by the use of a so-called Weibull stress.     

A Diffusion Model Analysis of the Effects of Aging in the Lexical-Decision Task.

The effects of aging on response time (RT) are examined in 2 lexical-decision experiments with young and older subjects (age 60-75). The results show that the older subjects were slower than the young subjects, but more accurate. R. Ratcliff s (1978) diffusion model provided a good account of RTs, their distributions, and response accuracy. The fits show an 80-100-ms slowing of the nondecision components of RT for older subjects relative to young subjects and more conservative decision criterion settings for older subjects than for young subjects. The rates of accumulation of evidence were not significantly different for older compared with young subjects (less than 2% and 5% higher for older subjects relative to young subjects in the 2 experiments). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Normalizing Behavior of Unsaturated Granular Pavement Materials

One of the important components of a flexible pavement structure is granular material layers. Unsaturated granular pavement materials (UGPMs) in these layers influence stresses and strains throughout the pavement structure, and have a large effect on asphalt concrete fatigue and pavement rutting (two of the primary failure mechanisms for flexible pavements). The behavior of UGPMs is dependent on water content, but this effect has been traditionally difficult to quantify using either empirical or mechanistic methods. This paper presents a practical mechanistic framework for determining the behavior of UGPMs within the range of water contents, densities, and stress states likely to be encountered under field conditions. Both soil suction and generated pore pressures are determined and compared to confinement under typical field loading conditions. The framework utilizes a simple soil suction model that has three density-independent parameters, and can be determined using conventional triaxial equipment that is available in many pavement engineering laboratories.     

基于参数辨识的一种动态补偿数字滤波器

提出了一种能明显改善系统动态性能的动态补偿数字滤波器。分析了动态补偿数字滤波器的基本原理。为了使动态补偿滤波器始终工作在最佳参数状态下,且更具有通用性,结合参数辨识,利用基于Householder变换的自适应最小二乘法对传感器的动态性能进行在线补偿,其特点是数值稳定性好、估计精度高。试验表明:对动态品质较差的双孔悬臂梁式压力传感器进行在线补偿,可以使其动态性能得以较好的改善。