非结构混合网格下的三维舵面流动计算研究

运用非结构混合网格上N S方程的求解技术对三维舵面的粘性绕流进行了计算研究。在物面粘性作用区,运用改进的推进层方法生成三棱柱、金字塔和四面体型混合网格;在其它流动区域采用阵面推进方法生成四面体网格。采用基于重构中心格式的格心有限体积法和SPALART-A LLM ARAS一方程湍流模型对N S方程进行空间离散,运用通量线化假设和最大特征值方法进行雅可比矩阵分裂来实现隐式高斯-赛德尔时间迭代。以某带舵面偏转的机翼模型为数值算例,系统地计算和分析了迎角、舵偏角及马赫数对舵面气动特性和舵面流动分离的影响,并将计算得到的舵面铰链力矩与实验结果进行了对比验证。数值算例表明:该方法可以为三维舵面气动力和铰链力矩的计算与分析提供有效的数值工具。     

基于非结构嵌套网格的旋翼前飞流场计算

发展了一种基于线性弹簧理论的非结构动态嵌套网格方法,通过求解非定常Eu ler方程模拟了旋翼的前飞流场。根据距离参数快速生成便于计算的两个重叠网格子域,利用运动区子域网格的转动来模拟旋翼的旋转运动,并对其运用线性弹簧动态网格技术来处理旋翼的挥舞和变距运动。发展了一种快速查找插值贡献单元的方法,无需建立Inverse网格,提高了计算效率和精度。使用高效双时间方法分区求解非定常Eu ler方程,两个子域的流场参数在重叠区进行耦合。计算了旋翼的两种前飞状态,所得结果与实验和文献结果都很吻合。     

基于蚂蚁算法的电子元器件位置优化

首先介绍了基本蚂蚁算法原理和改进的蚂蚁算法，即最大-最小蚂蚁算法，根据传热学原理用微元体热平衡法建立了电子系统热分析求解温度场的数学模型，并采用高斯-赛德尔迭代法求解热平衡方程组，通过仿真实验证明用蚂蚁算法来优化电子元件的布局能够显著降低最大温度值，并提高了系统的可靠性。     

Modelling of water permeability in cementitious materials

This paper presents a network model to predict the permeability of cement paste from a numerical simulation of its microstructure. Based on a linked list pore network structure, the effective hydraulic conductivity is estimated and the fluid flow is calculated according to the Hagen–Poiseuille law. The pressure gradient at all nodes is calculated with the Gauss elimination method and the absolute permeability of the pore network is calculated directly from Darcy’s law. Finally, the permeability model is validated by comparison with direct water permeability measurements. According to this model, the predicted permeability of hydrating cement pastes is extremely sensitive to the particle size distribution of the cement and especially to the minimum size of the cement particles. Both in simulations and experiments, the permeability of cement pastes is mainly determined by the critical diameter and by the connectivity of the pore structure, regardless of w/c ratio and curing age. The permeability of cement pastes could be predicted reasonably well when a minimum particle size 1 μm was chosen for the cement.

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Résumé Cet article présente un modèle de réseau visant à prédire la perméabilité de la pate de ciment à l’aide d’une simulation numérique de sa microstructure. Sur la base d’une liste liée de la structure du réseau de pores, la conductivité hydraulique efficace est estimée et le flux de fluide est calculé selon la loi de Hagen–Poiseuille. Le gradient de pression est calculé à tous les nœuds par la méthode d’élimination de Gauss et la perméabilité absolue du réseau de pores est directement calculée à partir de la loi de Darcy. En conclusion, le modèle de perméabilité est validé par comparaison avec des mesures de perméabilité à l’eau. Selon ce modèle, la perméabilité prévue des pates d’hydratation de ciment est extrêmement sensible à la distribution des dimensions des particules du ciment et particulièrement à la taille minimale. Dans les simulations ainsi que dans les expériences, la perméabilité des pates de ciment est principalement déterminée par le diamètre critique et par la connectivité de la structure de pore, indépendante du rapport de l’eau au ciment et de la période de traitement. La perméabilité des pates de ciment pourrait être raisonnablement bien prédite lorsque l’on choisit 1 μm comme dimension de grain minimale du ciment.

     

X-ray photoelectron spectroscopy characterization of the interface between Ag electrode and PVDF film treated by electric poling

Interface changes induced by electric poling treatment between an Ag electrode deposited by vacuum thermal evaporation and a polymer thin film have been investigated. The polymer film poly (vinylidene fluoride) (PVDF), a fluoropolymer of repeat unit (–CH₂–CF₂–) was treated under electric poling at high temperature of 90°C. The characterization was accomplished using X-ray photoelectron spectroscopy (XPS) as a primary tool. The results indicate that the piezoelectricity of PVDF thin films and adhesion force between polymer thin film and metallic electrode are improved by electric poling and chemical bond joint.     

Reproducibility and stability of N–Al codoped p-type ZnO thin films

Reproducible and stable p-type ZnO thin films have been prepared by the N–Al codoping method. Secondary ion mass spectroscopy measurements demonstrate that N and Al are incorporated into ZnO. The resistivity, carrier concentration, and Hall mobility are typically of 50–100 Ωcm, 1×10¹⁷–8×10¹⁷ cm⁻³, and 0.1–0.6 cm²/Vs, respectively, for the N–Al codoped p-type ZnO films. Hall measurement, X-ray diffraction, and optical transmission were carried out to investigate the changes of the properties with the storage period. Results show that the p-type characteristics of the N–Al codoped ZnO films are of acceptable reproducibility and stability. In addition, the N–Al codoped p-type ZnO films have good crystallinity and optical quality. The properties are time independent.     

Effects of Y concentration on luminescence properties of PbWO4 single crystals

The effects of Y³⁺ doping at different concentration on the luminescnece properties of PbWO₄ crystals have been investigated by means of Fourier transform infrared (FT-IR) spectrum, optical transmission, thermoluminescence (TL), X-ray excited luminescence (XEL), photoluminescence (PL) under excitation of UV light and light yield measurements. The series PbWO₄:Y crystal samples were grown by modified Bridgman method and the concentration of Y³⁺ in the melt was in the range of 0–1.0 mol%. The slight blue-shift and evident red-shift of the absorption edge in PbWO₄ crystal were observed at low and heavy doping concentration, respectively. TL peaks in the range of from room temperature to 250 °C disappeared after the doping with Y³⁺. With the increase of doping concentration, the luminescence intensity in the XEL and PL spectra was found to decrease accordingly, especially in the case of heavy doping. The measuring results demonstrate that Y³⁺ doping concentration below 100 ppm in the crystal seems to be the best for optimizing the optical and scintillation properties of the material. The mechanism of Y³⁺ doping concentration influence on luminescence was also discussed in this paper.     

基于小波分解的径流预报非线性模型

径流时间序列中包含了大量的信息,从频率域上来看,这些信息包括变化平稳的低频信息和变化相对剧烈的高频信息。本文利用小波分解,将径流时间序列分解为低频项和高频项,低频项采用逐步回归法预报,高频项采用基于自组织法求解的Volterra滤波器预报,两者结果综合,最终实现径流预报。实例计算表明,该模型具有足够高的计算精度。     

力控组态软件下的设备驱动程序开发

本文简要介绍了三维力控组态软件I／O驱动程序接口开发工具包（FIOS SDK），然后以力控组态软件与C8051单片机的RS-485异步串行通信为例，给出了如何运用FIOS SDK在Visual C＋＋ 6．0中开发设备驱动程序的步骤，包括界面的设计和代码的编写。     

安徽省发展核电的必要性和重要性

从安徽省作为煤炭大省和华东地区重要的能源基地出发,分析了核电作为安全能源、清洁能源、经济能源的优越性,讨论了安徽发展核电的必要性和重要性,提出应抓住安徽发展核电的优势,积极准备,早日立项,促进安徽省整个经济和社会加快发展。