采动区建筑物附加地基反力变化规律研究

为了研究采动区建筑物附加地基反力的变化规律,采用采动区建筑物地基、基础和结构协同作用力学模型,研究了建筑物位于采动区不同位置时附加地基反力的分布变化规律,指出地表曲率变形值是控制附加地基反力大小及分布形态的主导因素;并研究了建筑物长度、弹性模量、地基系数、开采厚度、建筑物高度等各种因素对建筑物附加地基反力的影响规律,同时建立了附加地基反力最大值与各影响因素之间的关系式.     

聚合物驱剖面返转类型及变化规律

聚合物驱过程中的注入剖面变化在注聚初期,其吸水剖面与水驱基本相同,聚合物溶液还是主要进入高渗透层,随着高渗透层渗流阻力的增加,聚合物溶液开始进入低渗透层,注入剖面得到改善.随着低渗透层聚合物溶液的不断进入,其渗流阻力增加,导致其吸水比例逐渐下降,吸水剖面出现返转.其吸水变化类型主要有一次返转型、二次或多次返转型和不返转型.通过对现场实际资料的研究表明:①在注聚过程中,各沉积单元相对吸水量往复变化;②注聚过程中,低渗透层剖面返转时机先于中渗透层;③低渗透层注聚剖面第二次返转时相对吸水量峰值低于第一次返转时的峰值;④高渗透层的厚度比例越大,聚合物调整低渗透层吸水剖面能力越差;⑤聚驱全过程中,高渗透层的累积吸水量仍大于中、低渗透层;⑥绝大多数单元的吸水剖面在吸水指数、含水下降期发生初次返转.另外,相对于一类油层聚合物驱,二类油层具有返转出现时间早于一类油层、返转幅度大于一类油层等特点.     

Investigations on the effects of friction modeling in finite element simulation of machining

Accurately predicting the physical cutting process variables, e.g. temperature, velocity, strain and stress fields, plays a pivotal role for predictive process engineering for machining processes. These predicted field variables, however, are highly influenced by workpiece constitutive material model (i.e. flow stress), thermo-mechanical properties and contact friction law at the tool-chip-workpiece interfaces. This paper aims to investigate effects of friction modeling at the tool-chip-workpiece interfaces on chip formation process in predicting forces, temperatures and other field variables such as normal stress and shear stress on the tool by using advanced finite element (FE) simulation techniques.For this purpose, two distinct FE models with Arbitrary Lagrangian Eulerian (ALE) fully coupled thermal-stress analyses are employed to study not only the effects of FE modeling with different ALE techniques but also to investigate the influence of limiting shear stress at the tool-chip contact on frictional conditions, which was never done before. A detailed friction modeling at the tool-chip and tool-work interfaces is also carried by coupling sticking and sliding frictions. Experiments and simulations have been performed for machining of AISI 4340 steel using tungsten carbide tooling and the simulation results under increasing limit shear stress have been compared to experiments. The influence of limiting shear stress on the tool-chip contact friction was explored and validity of friction modeling approaches was examined. The results presented in this work not only provide a clear understanding of friction in FEM modeling of machining but also advance the process knowledge in machining.     

含色散项Zabolotskaya-Khokhlov方程的对称、约化、精确解和守恒律

利用修正的Clarkson-Kruskal (CK)直接方法得到了含色散项的Zabolotskaya-Khokhlov(简写为DZK)方程的对称、约化和一些精确解,包括双曲函数解,有理函数解,三角函数解等,同时得到了该方程的守恒律.     

Prevailing wage legislation and public school construction efficiency: a stochastic frontier approach1

Stochastic frontier regression is used to examine the effect of introducing prevailing wage legislation on public school construction efficiency in British Columbia. Prior to the legislation, public school projects were from 16% to 19% smaller, in terms of square feet, than comparable private structures. However, likelihood ratio tests consistently indicate that the coefficients measuring the effect of the policy on the size differential between covered and uncovered projects are not statistically different from zero. These results suggest that construction wage requirements did not alter input utilisation in a way that significantly affected construction output. Average inefficiency for school construction in British Columbia over the period of the study is 12.1%.     

切削变形规律观测装置的设计与实验分析

根据实验教学的经验,研究了金属切削过程中采集试样标本的“快速落刀”装置和制备试样样本的镶嵌机,并进行了切削变形规律观察和测量,取得了一定的实验效果,设计的两种装置,被用于本科生的实验教学和研究生的课题实验中,由于它制造容易,成本价低,结构简单,使用方便,采集和制备试样稳靠,作为本科生课堂的实验装置和研究生的课题试验装置是可行的.     

工程塑料膨胀阻燃存在的问题和解决方法

针对我国环保法令对膨胀阻燃工程塑料的要求,以及我国的商品化膨胀阻燃剂(IFR)阻燃工程塑料一直未能真正开发和应用的问题,总结了制约IFR阻燃工程塑料发展的原因,如IFR存在热稳定性不能适应工程塑料较高的加工温度,阻燃配方优化设计复杂,吸湿性大、耐迁出性差,和工程塑料的相容性差等问题.提出了微胶囊包覆、偶联剂表面处理、无机金属化合物和分子筛协同、IFR的"三位一体"化、计算机辅助模拟优化IFR阻燃配方等解决方法.     

肥城国家庄井田地质构造发育特征研究

该文主要研究肥城煤田国家庄井田构造展布特征,包括断裂和褶皱的发育规律,得出该区构造演化为五期构造应力场的叠加,致井田内断裂发育四组,分别为NE向、NNE向、NW向和NEE向,区内褶皱总体为一宽缓向斜构造,轴向N50°E左右。     

老井复查评价技术在浅层油藏中的研究与应用

本文以靖安地区浅层老井为例,利用钻井、录井、测井、取心等资料,结合现代测井解释评价技术,对受当时技术条件限制被误判的储层进行再分析研究.制定可行的复查评价标准与流程,确定出油下限,优选补孔潜力井,并结合精细地质研究成果筛选建产目标区,达到挖潜增效和滚动增储的双重目的.对老区日后寻找新储量进行勘探开发具有十分重要的意义.     

保护层卸压瓦斯抽采及涌出规律研究

随着我国煤矿开采深度的增加,煤与瓦斯突出矿井和变出煤层的数量不断增加,利用保护层开采过程中的被保护层的卸压作用对卸压瓦斯进行强化抽采,使被保护层由高瓦斯突出危险煤层变为低瓦斯无突出危险煤层,从而实现煤与瓦斯资源的安全高效共采．系统介绍了基于分源原理的回采工作面瓦斯涌出预测方法,保护层开采及卸压瓦斯强化抽采技术的发展和工程应用．结合淮南潘一矿下保护层和谢一矿上保护层开采及卸压瓦斯强化抽采实例,将保护层工作面瓦斯涌出量预测结果与保护层工作面瓦斯涌出量实测结果进行了对比分析．研究结果表明,由于保护层开采的卸压作用,使被保护层卸压瓦斯抽采率远大于被保护层卸压瓦斯的自然排放率,导致保护层工作面瓦斯涌出量预测结果小于实际瓦斯涌出量．