基于网上开放虚拟实验室的研究与设计

首先对网上开放虚拟实验室的基本概念、体系结构和管理模式进行介绍,分析了设计网上开放虚拟实验室的关键技术。最后设计和实现了网上开放虚拟实验室。     

金属材料断裂韧度JIC试验方案研究

鉴于多数断裂韧度JIC试验无法按GB／T2038—1991测出结果，对JIC试验方案进行了分析，探讨了在JIC测试中存在的问题并应用GB／T2038—1991和GB／T2038—1980进行了相应的试验。结果表明，按照GB／T2038—1991标准试验的可行性与材料的有效屈服强度有关；采用GB／T2038—1991标准测出的JIC值一般比旧标准偏大；GB／T2038—1991已经不能适应材料发展的需要，迫切需要修订和完善。     

官能化噻咯合成研究进展Ⅱ.交联法、取代法、硼化法与硅烷化法

官能化噻咯(silole音译)是一种重要的噻咯衍生物,不仅在有机金属合成领域占重要地位,也是建构新型π共轭体系的重要组成部分。本文介绍了官能化噻咯的几种重要合成方法,并对各种方法的特点及适用范围作了分析和总结。     

人工智能技术课程实践教学改革

根据人工智能技术课程的教学情况,从教学内容、教学方法、教学案例、考核方式、培养实践能力五个方面探讨教学改革.提出在不断更新教学内容和"课堂讲授-课下辅导"模式的基础上,加强网络资源的利用,增加贯穿整个教学过程的分组报告,设计出提高创新能力的教学案例,开展具有多元考核方式以及循序渐进的动态实验设置模式的实践教学改革,以有...     

Numerical Simulation of Brittle Damage in Concrete Specimens

A framework for damage mechanics of concrete is applied to simulate the nonlinear elastic deformation behavior of concrete using finite element method (FEM). A rather simple isotropic damage model containing essentially no adjustable parameters is shown to produce results in remarkably good agreement with sample experimental data: the damage law requires only the fracture energy to be defined completely. The model is achieved by introducing a damage surface that is similar to the yield function in the conventional theory of plasticity. A special form of damage surfaces is constructed to illustrate the application of the model. A new damage criterion, defined as an equivalent strain norm, is proposed, in order to take into consideration the asymmetric behavior of concrete. For verifying the FEM program including the model, deformations predicted by this model are compared with both the experimental ones for the concrete structural model and the ones calculated without application of the continuum damage mechanics.__________Translated from Problemy Prochnosti, No. 3, pp. 57 – 74, May – June, 2005.     

A numerical study of a semi‐algebraic multilevel preconditioner for the local discontinuous Galerkin method

In this work, we consider the local discontinuous Galerkin (LDG) method applied to second‐order elliptic problems arising in the modeling of single‐phase flows in porous media. It has been recently proven that the spectral condition number of the stiffness matrix exhibits an asymptotic behavior of ??(h^?2) on structured and unstructured meshes, where h is the mesh size. Thus, efficient preconditioners are mandatory. We present a semi‐algebraic multilevel preconditioner for the LDG method using local Lagrange‐type interpolatory basis functions. We show, numerically, that its performance does not degrade, or at least the number of iterations increases very slowly, as the number of unknowns augments. The preconditioner is tested on problems with high jumps in the coefficients, which is the typical scenario of problems arising in porous media. Copyright © 2007 John Wiley & Sons, Ltd.     

Calculation of derivative of complex modes using classical normal modes

In this paper, a method to calculate derivatives of eigenvectors of damped discrete linear dynamic system with respect to the system parameter is presented. Due to the non-proportional nature of the damping, the eigenvectors become complex, and as a consequence, the derivatives also become complex. The derivatives are calculated using small damping assumption, and the method avoids using the state-space approach. The results are obtained in terms of complex modes and frequencies of the second-order system, which in turn are related to the eigensolutions of the undamped system using perturbation method. Based on the derivatives, an expression for total change of the complex eigenvectors is obtained for a more general case when all the elements of mass, stiffness and damping matrices are varying. Application and accuracy of the derived expressions are demonstrated by considering numerical examples.     

ICT: performance evaluation of community development worker’s in South Africa on e-skills*

ABSTRACT

Community development service practitioners have been increasingly burdened with a broader range of responsibilities and ICT could enhance their productivity. Therefore, it is prudent to incorporate information communication technology (ICT) skills into the skills matrix required by the practitioners in order to deliver the service effectively. Furthermore, ICT use is prevalent in almost every organization, therefore, ICT can also serve as a major factor in flexibility of delivery of community development service to the communities, but only if the practitioners possess adequate skills in using ICT tools (software applications) in retrieving, presenting and disseminating valuable and adequate information within the workplace to the parties involved. The study determines the current work conditions, level of performance and expertise in the use of ICT among community development workers (CDWs) in KwaZulu-Natal, South Africa, by evaluating their abilities and experiences, with a view to identify the areas to enhance their effectiveness. Determining the competency of their use of ICT applications is not an easy task; thus a survey methodology was adopted, with a sample of 189 CDWs (63% female and 37% male). Respondents were given the opportunity to rate of their own current ability to use common computer software applications.     

移动阅读终端介绍及测试方法研究

基于对信息需求的硬性需求,随着通信技术、显示技术、数据版权和计算机技术的飞速发展,移动阅读悄然进入我们的生活,改变着我们传统的阅读方式,由此也产生了信息量无限大而又具备纸质阅读感受的移动阅读终端。本文首先对移动阅读终端的软、硬件和功能进行介绍,进而简要介绍移动阅读终端的测试方法,最后对移动阅读终端发展进行了展望。     

Comparative Antimicrobial Activity of Silver Nanoparticles Obtained by Wet Chemical Reduction and Solvothermal Methods

The synthesis of nanoparticles from noble metals has received high attention from researchers due to their unique properties and their wide range of applications. Silver nanoparticles (AgNPs), in particular, show a remarkable inhibitory effect against microorganisms and viruses. Various methods have been developed to obtain AgNPs, however the stability of such nanostructures over time is still challenging. Researchers attempt to obtain particular shapes and sizes in order to tailor AgNPs properties for specific areas, such as biochemistry, biology, agriculture, electronics, medicine, and industry. The aim of this study was to design AgNPs with improved antimicrobial characteristics and stability. Two different wet chemical routes were considered: synthesis being performed (i) reduction method at room temperatures and (ii) solvothermal method at high temperature. Here, we show that the antimicrobial properties of the obtained AgNPs, are influenced by their synthesis route, which impact on the size and shape of the structures. This work analyses and compares the antimicrobial properties of the obtained AgNPs, based on their structure, sizes and morphologies which are influenced, in turn, not only by the type or quantities of precursors used but also by the temperature of the reaction. Generally, AgNPs obtained by solvothermal, at raised temperature, registered better antimicrobial activity as compared to NPs obtained by reduction method at room temperature.