油田开发过程中单井经济界限研究

应用技术经济学原理和油藏工程方法,即利用盈亏平衡原理和产量递减规律,以固定成本和可变成本的划分为前提,以成本,产量和利税之间的关系（原油产量和销售收入＝固定成本＋可变成本＋利润＋税金）为基础的一种综合分析模式,根据油田开发的实际特点,以 一技术经济条件下某一影响经济效益的因素达到一定数值,使得生产达到规定标准时的界限,分别给出了不同类型油井的产量界限、投资界限、价格界限,成本界限模型及各项经济极限指标,系列模型比较高度准地描述了油田开发过程中单井经济运行规律,为油田的经济有效开发提供了一种评价手段。     

基于模糊聚类和时域跟踪的视频分割

本文提出了一种基于模糊聚类和时域跟踪的视频分割方法。它把视频序列的连续7帧图像作为一组,对每组中间那一帧图像进行初始分割,对组内其他帧图像采用时域跟踪方法进行分割。初始分割采用了改进的多特征模糊聚类方法：时域跟踪是利用上一帧的分割结果通过运动估计向下一帧投影,作为下一帧的初始分割来完成的。     

单模光纤有效面积及其测试方法

有效面积（Aeff)是一个与光纤非线性密切相关的极其重要的参数,随着通信距离的延长和WDM通道的增加,人们对光纤Aeff的值越来越关心,如何准确方便地测量出Aeff值成了关注的问题,文章介绍了Aeff的概念,定义及其测试方法,并对几种测试方法特点进行了比较和分析。     

Indexing Techniques for Power Management in Multi-Attribute Data Broadcast

In this paper, we discuss the power conservative indexing techniques for managing multi-attribute data broadcast on wireless channels. These indexing techniques, namely, index tree, signature and hybrid, aim at improving the battery power consumption of mobile clients. By taking into account the broadcast management factors such as clustering and scheduling, these three indexing schemes may significantly reduce tune-in time while maintaining a reasonable access time. Cost models for single and multi-attribute query processing are developed. Our performance evaluation shows that the signature and hybrid methods are superior to the index tree method.     

Novel cooling channel shapes in pressure die casting

The pressure die casting involves die designs incorporating cooling channels positioned to facilitate the controlled extraction of energy from a solidifying casting. It is now known that subcooled nucleate boiling can occur in cooling channels and this paper is concerned with novel cooling channel shapes that are optimized to promote and enhance this boiling and thus reduce casting times. Shape sensitivity analysis is applied to a boundary element model using the material derivative adjoint variable technique. Mesh node positions on the cooling channels are used as the design parameters. The sensitivities are used in a conjugate gradient non‐linear optimization routine. It is shown that with this approach cooling channels can be designed to maximize boiling heat transfer whilst at the same time allow some degree of control of spatial temperature variation over the die cavity surface. Simulation and experimental results are presented for a traditional die and an optimized die. A 60 per cent reduction in cycle time is achieved with the optimized die. Copyright © 2001 John Wiley & Sons, Ltd.     

双模铁氧体器件的发展及应用

主要介绍了旋转场变极化器、旋转场双工移相器、变极化移相器等铁氧体双模元器件以及它们在现代雷达通信领域上的新应用.     

利用SAW技术实现极低功耗无线数字通信

压电基片上的叉指换能器在外接不同阻抗负载时对声表面波会有不同的反射强度。利用此特性,通过控制外电路负载的变化就可实现数字信号 的无线传输,发射端无需用于发射信号的能量,所以系统只需要用于控制的能量,耗能可以极小,文中分析了系统的结构与原理、特性参数的估算及其优点。     

Stress and Failure Analysis of Composite Laminates with an Inclusion under Multiaxial Compression-Tension Loading

The present paper investigates the failure of orthotropic laminates with a filled hole subjected to biaxial compression-tension loading. This is an idealised case that simulates a situation where the impact damaged laminate has been repaired by drilling a hole and then plugging the hole with a perfect-fit core made of a dissimilar material. The exact stress distribution in the laminate has been determined using the complex variable mapping method. These stresses are then employed in a fracture mechanics failure model to predict the failure load of a laminate with a filled hole under in-plane compression-dominated multi-axial loading. Failure strength predictions are compared to open hole results and experimental data.     

交流电机变速恒频风力发电技术

变速恒频风力发电系统是20世纪70年代中后期逐渐发展起来的一种新型发电系统,其结构和运行原理与传统的恒速恒频风力发电机有较大的不同.在该系统中,风力机可在很宽的风速范围内保持近乎恒定的最佳的叶尖速比,从而提高了风力机的运行效率和系统的稳定性.此外,还可以实现无电流冲击的软并网.变速恒频风力发电技术因其高效性和实用性正受到越来越多的重视.以交流电机为基础,详细地介绍了目前国内外采用交流电机的变速恒频风力发电系统的研究现状,并对各系统的性能进行了对比、分析总结.     

离散变结构控制系统的广义变速趋近律

为了研究离散变速趋近律的稳定参数区域,依据离散变速趋近律滑模的特点,得出了离散变速趋近律渐近稳定的充分条件,依照此条件获得了变速趋近律各个参数的具体范围,进而提出了广义离散变速趋近律的概念,同时也给出了其保证系统稳定的参数范围,设计了两个离散系统的广义变速趋近律的控制方案。仿真结果表明,得出的参数范围能保证系统渐近稳定。