EM procedures using mean field-like approximations for Markov model-based image segmentation

Image segmentation using Markov random fields involves parameter estimation in hidden Markov models for which the EM algorithm is widely used. In practice, difficulties arise due to the dependence structure in the models and approximations are required. Using ideas from the mean field approximation principle, we propose a class of EM-like algorithms in which the computation reduces to dealing with systems of independent variables. Within this class, the simulated field algorithm is a new stochastic algorithm which appears to be the most promising for its good performance and speed, on synthetic and real image experiments.     

An analysis of shielding against DC magnetic fields generated by electric railways. Evaluation of effective permeability of fine structure

This paper describes an effective analysis of magnetic shielding based on homogenization. The analyses become time‐consuming if the problems include the magnetic substances having fine structure. The homogenization of the structure makes it possible to analyze effectively the magnetic fields. The authors introduce a method to estimate the effective permeability of the homogenized substance. This method can be applied to any periodic structure made of magnetic substance. The magnetic shielding effects by the structures against direct‐current (DC) fields generated by electric railways are analyzed by using the present method. As a result, it is found that the overhead way and the protective fence near the railway work as a magnetic shield, whose effects can be improved by appropriate arrangement of those constructions. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 7–15, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20310     

油管电热清防蜡技术在强水敏油田的应用

江苏油田的庄 2、韦 2油田属强水敏油田 ,采用热 (水 )洗油井和化学清防蜡效果较差 ,两油田每年因洗井造成地层污染影响的产量损失在 5 0 0 0t以上 ,约占油田产量的 4 5 %。根据集肤效应 ,采用油管电热清蜡技术 ,在含水小于 6 0 %、井斜小于 4 0°的油井上可正常使用 ,一般通电加热 4 0～ 80min后 ,油井井口温度能达到 5 0℃左右 ,最高可达到 6 5℃以上 ,连续加热 5～ 6h即可达到清蜡目的 ,电热清蜡为周期 6 0～ 90d。影响电热清蜡主要指标因素是油井的产液量 ,产液量越小 ,所需要的加热电流和加热电压也越小 ,井口温度达到最高值越低 ,清蜡效果越差。试验的 7口井平均年度投入产出比达到 1∶5 ,经济效益和社会效益十分明显。     

基于压水试验数据的渗透系数应力敏感性研究

岩体渗透率与应力关系是进行岩体渗流应力耦合分析的基础。基于龙滩水电站边坡岩体渗流压水试验结果和边坡岩体岩性及物理力学性质，对岩体渗透系数和地应力进行了分析计算，给出了边坡岩体渗透率随应力变化的关系式，为进行边坡岩体渗流一应力耦合分析提供了可靠数据。     

Simulating Experiment for Temperature Field of Frozen Subgrade Using Regulation Tubes

The main factors that influence the temperature field of frozen subgrade were analyzed.The experimental equipment for simulating frozen subgrade was built up,and the declining regulating tubes were placed at the foot of the embankment. By means of this equipment two simulating experiments of controlling temperature filed of frozen subgrade were carried out in the laboratory. One method is to collect natural cold energy, and the other one is to collect natural cold energy ccompanied by artificial refrigeration simultaneously. The result indicates that the latter is an effective method for maintaining the stability of the frozen subgrade.     

Characterization of EBPVD micro-layer composites and simulation of its internal stress state

Based on the basic operating principal and the technology characteristic of electron beam physical vapor deposition(EBPVD) technique, EBPVD was used to prepare the micro-layer composites. The effect on the substrate preheating temperature was taken into accounts and the finite element analysis package ANSYS was used to simulate the internal stress field and the potential displacement changing tendency. The results show that one of the most important quality factors on the judgment of micro-layer composites is the adhesion between the substrate and the deposition layers as well as among the different deposition layers. Besides the existance of temperature gradient through the thickness of layers, the main reason for the internal stress in micro-layer composites is the mismatch of various properties of the layer and the substrate of different thermal expansions and crystal lattice types. With the increase of substrate preheating temperature, the inter-laminar shear stress also takes on a tendency of increase but the axial residual stress decrease.     

旋风分离器减阻杆对流场的影响

在研究发现旋风分离器减阻杆的基础上，研究了减阻杆对流场的影响，发现了减阻杆使切向速度分布趋于平缓、轴向速度上升峰值内移、径向上压力梯度减小、轴向上中心区从逆压梯度变为顺压梯度等重要规律，从而为分析旋风分离器减阻杆的减阻机理提供了依据。同时本文还首次发现旋风分离器入口附近有近２４％的短路流量，提出设法减小这部分短路流量是提高分离效率的一个研究方向。     

Analysis of brushless three-phase synchronous generator without exciter

Recently, a demand for small-capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines. It is desired that the structure of small-capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled. This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results.     

核测井仪器中的磁屏蔽研究

核测井仪器受套管剩磁的影响比较严重，常常用在探测器的周围缠绕多层坡莫合金带的方法进行磁屏蔽，由于缠绕的坡莫合金圆筒不能闭合，加上缠绕过程中坡莫合金带的形变造成材料本身磁导率的下降，传统的磁屏蔽方法的效果不好。本文介绍一种简单易行、磁屏蔽效果较好的方法，实验的结果说明用电工纯铁做探测器的外壳可以达到令人满意的效果。     

H9000系统在西北电网水调自动化系统工程中的应用

西北电网水调自动化系统主要用于自动采集管理西北电网分布在三大水系的8个水电厂、相关流域内100个水文站、200个雨量站的实时信息，以便实现水库群跨流域补偿，统一协调发电与防洪、排沙、防凌、灌溉等一系列矛盾，解决水库群综合利用问题．系统主要具有上。下特点：（1）开放的系统环境；（2）高可乘性；（3）多样化的数据规约；（4）开放的人机联系手段；（5）务性能的数据库；（6）丰富的水调应用软件．其中水调应用软件包括：（1）汉江上游石泉、安康梯级联合洪水预报；（2）黄河上游龙羊峡、李家峡、刘家峡两库三站短期（日）调度；（3）水务综合统计分析软件．西北水调自动化系统将使H9000系统在大规模网络关系数据库管理技术、高级图形处理技术、复杂网络组网技术、容措技术、水调高级应用软件技术等方面提高到一个更高的水平．