稠油热采井改性纤维复合防砂实验研究

单一的防砂技术在稠油热采井中的应用受到一定限制，为解决热采井防细粉砂，从改善纤维复合防砂技术体系中的基体（树脂涂敷砂）性能入手，以期使纤维复合防砂技术能够用于热采井防砂。通过考察水溶性酚醛树脂、ER树脂粉末、偶联剂、增强剂加量对砂体抗压强度和渗透率的影响，分析了体系中各组分的作用机理。通过室内实验优化了纤维防砂体的配方，研究表明，偶联剂、改性剂、增强剂、ER树脂粉末、水溶性酚醛树脂SR1、石英砂之间的质量比为（0.15~0.20）∶3.1∶1.5∶（2~4）∶10∶100时体系具有较高的防砂强度，并且在350℃下仍能保持在3MPa左右，较不加入纤维时高30%，渗透率可增加10%左右。     

恒电流下聚乙烯醇纤维水泥基复合材料钢筋锈蚀率的研究

湿通电法是加速聚乙烯醇纤维水泥基复合材料中钢筋锈蚀的一种有效方法。在本试验中将电流设定为一恒定值,测试在不同聚乙烯醇（ polyvinyl alcohol 简称PVA）纤维掺量下的闭合回路电阻;以及在NaCl溶液侵蚀下PVA纤维水泥基复合材料的钢筋锈蚀率。试验结果表明,恒电流条件下,PVA纤维掺量的增加能提高水泥基复合材料的抗渗性,但对钢筋锈蚀率影响不大。     

Conditional Choice Probability Estimation of Dynamic Discrete Choice Models With Unobserved Heterogeneity

We adapt the expectation–maximization algorithm to incorporate unobserved heterogeneity into conditional choice probability (CCP) estimators of dynamic discrete choice problems. The unobserved heterogeneity can be time‐invariant or follow a Markov chain. By developing a class of problems where the difference in future value terms depends on a few conditional choice probabilities, we extend the class of dynamic optimization problems where CCP estimators provide a computationally cheap alternative to full solution methods. Monte Carlo results confirm that our algorithms perform quite well, both in terms of computational time and in the precision of the parameter estimates.     

Dynamic Female Labor Supply

The increase in female employment and participation rates is one of the most dramatic changes to have taken place in the economy during the last century. However, while the employment rate of married women more than doubled during the last 50 years, that of unmarried women remained almost constant. To empirically analyze these trends, we estimate a female dynamic labor supply model using an extended version of Eckstein and Wolpin (1989) to compare the various explanations in the literature for the observed trends. This dynamic model provides a much better fit to the life‐cycle employment pattern than a static version of the model and a standard static reduced form model (Heckman (1979)). The main finding using the dynamic model is that the rise in education levels accounts for about 33 percent of the increase in female employment, and the rise in wages and narrowing of the gender wage gap account for another 20 percent, while about 40 percent remains unexplained by observed household characteristics. We show that this unexplained portion can be empirically attributed to cohort‐specific changes in preferences or the costs of child‐rearing and household maintenance. Finally, the decline in fertility and the increase in divorce rates account for only a small share of the increase in female employment rates.     

Constrained Optimization Approaches to Estimation of Structural Models

Estimating structural models is often viewed as computationally difficult, an impression partly due to a focus on the nested fixed‐point (NFXP) approach. We propose a new constrained optimization approach for structural estimation. We show that our approach and the NFXP algorithm solve the same estimation problem, and yield the same estimates. Computationally, our approach can have speed advantages because we do not repeatedly solve the structural equation at each guess of structural parameters. Monte Carlo experiments on the canonical Zurcher bus‐repair model demonstrate that the constrained optimization approach can be significantly faster.     

差分对振荡电路分析

通过对差分电路在大信号模型下的集电极电流的频谱分析 ,讨论了差分振荡电路的非线性失真、起振条件、输出电压等特性 ,并简要说明了差分振荡电路的调整方法     

光纤Bragg光栅全光调谐滤波器

针对非线性特性对光纤布拉格光栅禁带的影响进行了研究;对光栅在非线性作用下所呈现的Bragg波长偏移特性作了理论分析。仿真结果表明,随着输入信号功率的增大,光栅的布拉格波长向长波方向移动,反射峰值下降,反射带宽变窄。基于此原理提出了一种新的全光可调谐滤波方案,并对不同光栅参数下的输出波形和反射谱特性进行了比较。该方案通过控制光实现了对光纤布拉格光栅固有波长的调节,从而实现了全光可调谐滤波,仿真结果表明脉冲形状保持良好。     

导电纤维在抗静电面料中应用的研究

本文综述了导电纤维的发展状况，并对日本工作服面料进行了测试分析，重点讨论了导电纤维在消除静电方面的应用，提出了产品开发的方向.     

2n阶J-自伴向量微分算子的预解算子及其谱

采用分析的方法,给出2n阶J-对称向量微分算式所生成的J-自伴向量微分算子在正则情形时的预解算子,得到其预解算子是积分算子及预解算子的核(Green函数)的一些基本性质;然后,从预解算子的全连续性证得:在正则情形下,其谱是离散的.