精铸涡轮叶片非线性收缩率计算方法的研究

在航空发动机涡轮叶片精铸模具设计过程中,铸件收缩率计算是比较重要的环节.文章以实测数据为基础,讨论了3种不同的收缩率计算方法.通过对3种计算方法得出的收缩率进行比较,得出了较为精确、有效的收缩率计算方法即基于叶片截面内切圆圆心的计算方法,并得出了叶身收缩率呈非线性非均匀分布的结论.     

基于动态聚类的网上学员细分实证研究

自主式学习在远程教育中占有重要的地位,如何更高效、快捷的建立学员所需要的知识资源库是当前我们研究的一个热门领域。本文以自贡电大2009级近百名本科学员基本资料及学习记录为采样数据,利用动态聚类的方法进行了有效的学员细分及数据分析,并在此基础上提出了相应的建立适合远程教育的资源库的策略。     

版面分析中表格与图形的鉴别

在版面分析过程中,有时会将表格误判为图形或将图形误判为表格。为避免对误判的表格或图形进行识别而产生的错误结果,文章提出了一种根据表格框线信息和表格单元信息来区分表格与图形的方法。该方法结合表格的结构特征,提出了作为一个表格的重要组成要素的表格框线和表格单元所必须满足的若干约束条件,通过验证每个条件是否得到满足来区分表格与图形。实验表明,该方法能有效地区分绝大多数表格与图形,极大地降低了对表格与图形的误判率。     

Realizing fragment spawning and fragment growth in the parallelized Discrete Element Method (DEM) during modelling of comminution

The particle based Discrete Element Method (DEM) can be applied to examine comminution processes. In this study, a DEM framework has been extended to model particle breakage without mass loss. After a breakage event occurs, spherical particles, as often considered in the DEM, are replaced by size reduced spherical fragments. During the following time steps, the fragments grow to their desired sizes, so that the mass loss can be counterbalanced. Previously defined overlaps with adjacent unbroken and broken particles (fragments) as well as walls are allowed. The breakage model has been realized in a parallelized DEM framework because comminution processes are often attributed to large numbers of particles and by parallelization the computational time can be reduced efficiently. An oedometer (one-dimensional compression in axial direction of a confined particle bed) has been modelled to investigate the parallelization efficiency and the influence of the permitted overlaps during the growth process on the growth duration. A simplified roller mill has been considered to examine the applicability of the breakage procedure considering parallelization. The results show that parallelization reduces computational time considerably. The breakage procedure is suitable to model comminution processes involving even densely packed particle systems and is superior to existing approaches.     

Experimental and computational study on the separation performance of an electrostatic precipitator with curved transvers collecting plates

Aiming at the problems of low collection efficiency of fine particulate matter and large area occupied by existing electrostatic precipitators (ESP), a new type of horizontal electrode ESP is proposed. It has the advantages of accelerating turbulent coalescence, increasing the effective dust collecting area and increasing the particle driving speed. The performance of the new type of ESP is systematic studied through simulation and experiment at the same time, and the results matches well. By comparing the dust removal effect of the horizontal electrode ESP and the conventional ESP, it can be concluded that the horizontal electrode ESP has a better dust removal efficiency, and can still maintain a better dust removal effect under high air velocity. The dust removal efficiency of new ESP can reach above 98% under the experimental conditions.     

基于Gabor小波变换的ICA火灾图像纹理识别算法

针对火灾图像纹理识别问题,提出了基于Gabor小波变换的ICA火灾图像纹理识别算法,并根据火灾图像纹理识别特点进行了优化;首先用不同尺度和方向的Gabor滤波器对待识别图像滤波,得到其特征图像,然后将特征图像转化成特征向量作为ICA的输入,得到基矢量子空间,再将测试图像经过Gabor滤波器的特征向量投影到ICA子空间中得到系数向量作为目标识别特征,最后用支持向量机进行识别;通过与Gabor滤波器法和ICA方法的对比实验,表明该算法可以在火灾纹理图像的识别率上比传统方法提高5％以上,为火灾图像识别提供了一种新思路.     

基于AT89S52智能安居报警电话的设计

本文设计了一款智能安居报警系统.采用单片机AT89S52为控制核心,通过模拟电子开关,实现本地与远程自动报警功能,较好地解决了传统报警器地域的局限性,同时根据需要还可扩展到其它不同种类的报警信息.经过软件仿真及测试,结果表明:在不改变电话内部结构的基础上,所设计的报警系统能正常完成各种报警功能,而且工作稳定.     

基于融合分析的感应电机轴承故障检测方法

根据感应电机轴承发生故障时的振动信号特性以及定子电流特性,求出三相电流的Park矢量模信号,并将其与电机滚动轴承振动信号经解调处理后的包络信号进行融合分析。可以从振动信号与电流信号的融合谱图中有效地提取轴承故障特征信息,并将其作为故障识别的依据。实验结果表明,本文检测方法具有较高的信噪比,提高了诊断的可靠性。     

Experimental study on the controlled air oxidation of sawdust in a packed-bed reactor

The controlled air oxidation technology is a promising way of disposing medical waste, which has been a huge challenge in China. It converts waste through partial oxidation into a gaseous mixture, small quantities of char and condensable compounds. But operational performance of the primary chamber of the controlled air incinerator is poorly understood, leading to difficulty in control. In this paper, a packed-bed reactor was established to study the effect of O₂ concentration on sawdust oxidation. The feed gas flow rate was kept constant at 0.6 m³/h at room temperature (26 °C) with O₂ concentrations varied from 6% to 12%. Temperature profiles of the beds, product yields and gas compositions in the out-of-bed fuel gas were measured in detail. The results showed that the sawdust beds achieved low temperatures for the given O₂ concentrations and leveled off in the oxidation processes. The bed temperatures increased and the solid yields decreased with the increase of O₂ concentrations. When the O₂ concentration was 10%, the gas yield reached a minimum and the liquid reached a maximum correspondingly. When the O₂ concentration increased from 6% to 10%, the peak concentrations of CO and CH₄ in the gas yield increased. However, when the O₂ concentration exceeded 10%, CO and CH₄ concentrations decreased. As O₂ concentration varied from 6% to 12%, CO₂ concentration increased continuously. This study provides a fundamental insight that the reaction processes could be well regulated by means of adjusting the feed air in practical units.     

Design of the HL-2M power supply control system

The power supply control system is one of the most important local control systems of HL-2M tokamak. The power supply system of HL-2M is composed of four flywheel generator sets with total capacity of 600 MVA, all the magnetic field coil power supplies and high voltage power supplies of auxiliary heating system. The control system of power supply should make sure the large amount of on-site equipment and facilities to operate steadily and reliably.This paper presents the architecture of HL-2M control system and four kinds of established control networks. It describes how the power supply control system is built by using the established hardware structures and software agreements. Specially, it is focused on introducing an application of real-time technology based on the reflective shared memory and the fully digital compact solution for controlling the high power converters. Otherwise, a scheme which adopts PROFINET and Sequence of Events technology to carry out the intellect interlock control system is given.