Determining stress intensity factors of composites using crack opening displacement

The main purpose of this paper is to find the mixed-mode stress intensity factors of composite materials using the crack opening displacement (COD). First, a series solution of the composite material with a crack was used to evaluate COD values. Then, the least-squares method was used to calculate mixed-mode stress intensity factors. This algorithm can be applied to any method that generates or measures COD values. The major advantage of this method is that COD values very near the crack tip are not necessary. Both finite element simulations and laboratory experiments were applied to validate this least-squares method with acceptable accuracy if the even terms of the series solution are removed.     

Symmetric BEM formulations for 2-D steady-state and transit potential problems

This paper presents a new concept for symmetric boundary element method (SBEM) applicable to 2-D steady-state and transit potential problems. Two kinds of SBEM formulations are derived. Symmetry is obtained simply through matrix manipulation, and no hypersingularity appears. Therefore, SBEM is much easier than the traditional symmetric Galerkin BEM. Compared with the traditional asymmetric BEM, the present SBEM can reduce the computational cost for time domain problems only. However, when applied to BEM/FEM coupling procedure, SBEM can reduce the computational cost for both steady-state and time domain problems. Three numerical examples are included to illustrate the effectiveness and accuracy of the present formulations.     

High-yield synthesis of single-crystalline 3C-SiC nanowires by a facile autoclave route

Single-crystalline 3C-SiC nanowires have been synthesized in large scale through a one-step autoclave route by the reaction of SiCl₄, (C₅H₅)₂Fe and metallic Na at 500 °C. Electron microscopy investigations show that the nanowires have typical diameters of 15-50 nm, lengths up to several tens of micrometers and grow along the [111] direction. The possible growth mechanism of the nanowires is discussed.     

N-Type Field-Effect Transistors Using Multiple Mg-Doped ZnO Nanorods

Nanorod field-effect transistors (FETs) that use multiple Mg-doped ZnO nanorods and a SiO₂ gate insulator were fabricated and characterized. The use of multiple nanorods provides higher on-currents without significant degradation in threshold voltage shift and subthreshold slopes. It has been observed that the on-currents of the multiple ZnO nanorod FETs increase approximately linearly with the number of nanorods, with on-currents of ~1 muA per nanorod and little change in off-current (~4times10^-12). The subthreshold slopes and on-off ratios typically improve as the number of nanorods within the device channel is increased, reflecting good uniformity of properties from nanorod to nanorod. It is expected that Mg dopants contribute to high n-type semiconductor characteristics during ZnO nanorod growth. For comparison, nonintentionally doped ZnO nanorod FETs are fabricated, and show low conductivity to compare with Mg-doped ZnO nanorods. In addition, temperature-dependent current-voltage characteristics of single ZnO nanorod FETs indicate that the activation energy of the drain current is very low (0.05-0.16 eV) at gate voltages both above and below threshold     

碳酸化分解工艺的改进与实践

本文针对烧结法生产氧化铝过程中,铝酸钠溶液的碳酸化分解工艺,由间断分解到连续分解的改进进行了论述,指出连续分解是碳酸化分解的发展方向。     

MDT的特征建模及其在冶金设备设计中的应用

介绍MDT软件三维实体建模的特点及方法。从草图设计开始 ,通过施加尺寸约束和几何约束生成草图特征 ,再应用尺寸驱动技术自动生成零件或设备的三维实体模型。在冶金设备及零部件设计应用中 ,根据设备或零件构成特征 ,对规则形体采取拉伸、旋转、扫掠处理 ,对不规则形体则根据特征进行切割处理 ,经过编辑就能得到符合实际的三维实体模型 ,进一步进行有限元分析、运动学和动力学仿真     

广钢3#高炉大修炉渣处理工艺探讨与分析

本文对处理高炉炉渣的图拉法工艺设计进行了总结，并对广钢3#高炉使用中出现的问题做了分析，生产实践表明，该工艺安全可靠，水渣质量好，而且有利于环境保护。     

自由口通信模式下计算机读写PLC存储区的程序设计

本文介绍了在自由口通信模式下，用计算机读写S7—200PLC存储区内相邻的多个字节数据的通信程序设计方法，程序设计中采用了多种可靠性措施。     

EXPERIMENTAL INVESTIGATIONS ON LONGITUDINAL DISPERSION CHARACTERISTICS OF TIDAL RIVERS

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基于嵌入式以太网的异步电机矢量控制系统体系结构设计

为了实现异步电机现场控制与上层管理的无缝集成，提出在通用变频器一异步电动机调速系统的基础上，采用基于ARM7TDMI核的微控制器和以太网控制芯片，实现异步电机的网络化控制。详细介绍了该系统的体系结构设计方案。