压缩式封隔器胶筒变形阶段力学分析

封隔器是常用试采井下工具,胶筒是封隔器中最重要的部件。将压缩式胶筒的变形分为自由变形和约束变形2个阶段,分析了其绝对体积变化规律,得到了使胶筒刚好与井壁接触的轴向力,据此可以确定最小坐封载荷;得到了井壁和中心管对胶筒的约束压力,在此基础上得到了压缩式胶筒的各个应力分量和第四相当应力,据此可以给出坐封力下胶筒的强度,确定合理的坐封力。实例计算解释了现场封隔器胶筒在坐封载荷作用下损坏的原因。     

中国进口沥青市场分析

分析国内中长期沥青需求，分析我国近十年的沥青进出口状况及主要进口国的产销情况，分析影响沥青进口的因素尤其是进口关税对进口量的影响和进口的发展趋势。     

Efficient solution of population balance equations with discontinuities by finite elements

Two refinements of Galerkin's method on finite elements were evaluated for the solution of population balance equations for precipitation systems. The traditional drawbacks of this approach have been the time required for computation of the two-dimensional integrals arising from the aggregation integrals and the difficulty in handling discontinuities that often arise in simulations of seeded reactors. The careful arrangement of invariant integrals for separable aggregation models allows for a thousandfold reduction in the computational costs. Discontinuities that may be present due to the hyperbolic nature of the system may be specifically tracked by the method of characteristics. These discontinuities will arise only from the initial distribution or nucleation and are readily identified. A combination of these techniques can be used that is intermediate in computational cost while still allowing discontinuous number densities. In a case study of calcium carbonate precipitation, it is found that the accuracy improvement gained by tracking the slope discontinuity may not be significant and that the computation speed may be sufficient for dynamic online optimization.     

大庆油田深层岩石力学特性参数的试验研究

通过对岩石可钻性、硬度、抗压强度等参数的测量 ,对大庆油田深井不同深度、不同层位、不同岩性的具有广泛代表性的岩心进行试验。并通过线性回归分析 ,建立了适用性较广的钻井岩石力学特性参数预测模型 ,为深井钻头选型提供了依据。     

随机过程的一个小波表示定理

得到一类随机过程 xt( E|xt|2 <+∞ )的一个小波表示定理     

机械结构与系统精度通用计算法及其应用——机器人机构误差分析与计算

本文详细论述了机械结构与系统精度的通用计算法,并以 PUMA 型机器人机构和圆柱型空间缩放机构为例,进行了误差分析,建立了相应的误差数模,证明了用精度通用计算法分析机器人机构误差是简单而适用的。     

丰城电厂1～4号循环水泵电机线圈温度异常分析及处理

分析了循环水泵电机线圈温度高的原因，提出处理温度高的措施并实施。     

不能移动封隔器管柱变形受力分析——封隔器管柱受力分析系统讨论之五

不能移动封隔器管柱是油气井封隔器完井的一种常见类型 ,在井内压力、温度、流体 (井内压力、温度、流体简称井内条件 ,下同 )发生变化时 ,不能移动封隔器管柱受力分析是保证井下安全和完井作业成功的关键 ,同时该管柱受力分析与自由移动封隔器管柱受力分析有很大的差别。文中对不能移动封隔器管柱变形受力的有关问题进行了分析、推导和讨论 ,并给出了算例。     

Φ90mm圆盘延伸机前卡钢分析

探讨了造成Φ90mm圆盘延伸机前卡钢的原因,分析了轧件轧制过程中的第一、第二次咬入的受力情况,提出了预防前卡钢的措施。该措施实施后,基本消除了前卡钢现象。     

An algorithm for the three-dimensional packing problem with asymptotic performance analysis

The three-dimensional packing problem can be stated as follows. Given a list of boxes, each with a given length, width, and height, the problem is to pack these boxes into a rectangular box of fixed-size bottom and unbounded height, so that the height of this packing is minimized. The boxes have to be packed orthogonally and oriented in all three dimensions. We present an approximation algorithm for this problem and show that its asymptotic performance bound is between 2.5 and 2.67. This result answers a question raised by Li and Cheng [5] about the existence of an algorithm for this problem with an asymptotic performance bound less than 2.89. This research was partially supported by FAPESP (proc. 93/0603-1) and by CNPq/ProTeM-CC, project ProComb (proc. 680065/94-6).