Dislocation emission from nanovoid with the effect of neighboring nanovoids and surface stresses

In the light of the vital mechanism for nanovoid evolution depending strongly on the effect of neighboring nanovoids, a generalized self-consistent model is suggested to describe nanovoid growth by the dislocation emission from nanovoid surface accounting for the effect of neighboring nanovoids and surface stresses in ductile porous materials. The explicit solution of the critical stress for dislocation emission is derived by means of the complex variable method. Analysis shows the advanced model can be implemented as the effective means to address the strong dependence of the nanovoid growth by the dislocation emission upon the size and volume fraction of nanovoid, growth/shrinkage of the neighboring nanovoid, remote applied stress as well as the surface effect.     

Coral: QSAR models for acute toxicity in fathead minnow (Pimephales promelas)

CORrelation And Logic (CORAL) is a software that generates quantitative structure activity relationships (QSAR) for different endpoints. This study is dedicated to the QSAR analysis of acute toxicity in Fathead minnow (Pimephales promelas). Statistical quality for the external test set is a complex function of the split (into training and test subsets), the number of epochs of the Monte Carlo optimization, and the threshold that is a criterion for dividing the correlation weights into two classes rare (blocked) and not rare (active). Computational experiments with three random splits (data on 568 compounds) indicated that this approach can satisfactorily predict the desired endpoint (the negative decimal logarithm of the 50% lethal concentration, in mmol/L, pLC₅₀). The average correlation coefficients (r²) are 0.675 ± 0.0053, 0.824 ± 0.0242, 0.787 ± 0.0101 for subtraining, calibration, and test set, respectively. The average standard errors of estimation (s) are 0.837 ± 0.021, 0.555 ± 0.047, 0.606 ± 0.049 for subtraining, calibration, and test set, respectively. The CORAL software together with three random splits into subtraining, calibration, and test sets can be downloaded on the Internet ( http://www.insilico.eu/coral/ ). © 2012 Wiley Periodicals, Inc.     

Effect of change point and imperfect debugging in software reliability and its optimal release policy

This article presents a software reliability growth model based on non-homogeneous Poisson process. The main focus of this article is to deliver a method for software reliability modelling incorporating the concept of time-dependent fault introduction and fault removal rate with change point. Also in this article, a cost model with change point has been developed. Based on the cost model optimal release policy with change point has been discussed. Maximum likelihood technique has been applied to estimate the parameters of the model. The proposed model has been validated using some real software failure data. Comparison has been made with models incorporating change point and without change point. The application of the proposed cost model has been shown using some numerical examples.     

关于高等代数课程教学改革和教学实践的几点体会

高等代数是大学本科数学专业一门重要的基础课程,但由于该课程的内容、思想的抽象性,传统的教学模式很难使大一的学生入门,也很难培养学生对高等代数的兴趣.若将其与解析几何、数学软件、数学建模等结合起来,并将其内容的先后顺序做适当的调整,能使其内容具体化、生动化.更易适应大一新生的学习方式.切实培养大学生的数学素质,提高教学质量.     

软件测试力系统要素及属性的模型研究

在深入研究测试过程及工程实践的基础上,提出了软件测试力概念,构建了基于多要素及属性的测试力系统结构模型.以此为依据,通过对测试力系统构成要素进行定量化解析,分析各要素对系统贡献度的大小,计算出系统要素间的关联度指标,确立了影响测试效力的核心因素,为进一步研究软件测试力系统高效的运行机理和测试领域科学的发展机制提供了依据.     

微波谐振器系统的调谐实验研究

圆台谐振腔和微波产生及传输装置可以形成一套和外界独立的微波谐振器系统.由于壁面上电磁压强差的作用,圆台谐振腔可能产生净电磁力,这需要从实验上给予证明.为此首先应对独立的微波谐振器系统进行调谐实验研究,使系统时刻处于谐振状态,这是实验证明净电磁力存在的重要保证.为此,本文对圆台谐振腔进行低信号调谐实验,同时配合调谐元件,准确地调试2.45 GHz频率下的谐振状态,分析温度对谐振状态的影响.实验结果表明该微波谐振器谐振频率2.44895 GHz、品质因数117495.0823,而且当腔体壁温升高时谐振频率减小、品质因数出现周期性振荡.     

一种多次反射怀特池的研究与设计

在传统怀特池的基本原理上,采用高斯光学分析方法推导出了多次反射怀特池的总光程和光斑分布的数学公式。分析表明:连续奇数号光斑间距与连续偶数号光斑间距相等,为两次镜曲率中心间距的2倍,且交替排布;当主镜上有N个光斑时,怀特池总光程OP≈2(N+1)L,其中L为怀特池的基长。根据分析所得结论,对传统怀特池进行了改进,使其能够在减小主镜口径的同时充分利用其有效口径和中间光程。结合设计实例,将结构数据在CODE V上进行模拟和优化计算,通过实际装调验证了所推得的数学公式和结论对指导设计多次反射池的正确性。     

基于扩展光源的LED小角度自由曲面透镜设计

提出了一种基于扩展光源的自由曲面透镜设计算法,运用该算法实现了小角度的均匀照明。在扩展光源与接收面之间建立一种能量对应关系,利用非成像边缘光线法求出自由曲面轮廓曲线的离散数据点,拟合离散点并生成透镜实体。对不同光源尺寸的透镜进行非序列光线追迹模拟,讨论了光源的尺寸对于在均光前提下的发光角度的影响,模拟结果表明,该算法对扩展光源实现均匀照明有较好的适应性,光束的发散角控制在其最小角度。     

Characterization of charge distribution on the high voltage glass insulator string

Irregularity in charge distribution of an insulator may lead to accelerated aging and electrical breakdown. However, knowledge of charge distribution on the insulation surface is still insufficient albeit has gained worldwide attention. The insufficiency is particularly on the charge profile along the string insulator under AC excitation. Therefore, charges distributions on the surfaces of glass insulators without installed grading ring are investigated in this paper. Simulation and experimental results were found in good agreement when studying the charge distribution pattern along glass insulator string where the polarity of charge swinging occurs at the center of suspension string insulator of I-type.     

O rig in8．0软件在实验数据处理中的应用*--以“测定电源的电动势和内阻”作研究

结合实测数据,采用 O rigin8．0软件对实验数据进行线性拟合及绘图,通过图像斜率和截距法,计算电源的电动势和内阻．实验计算结果表明,利用 Origin8．0软件处理“测定电源的电动势和内阻”实验数据非常准确和高效,避免了人为因素所造成的误差．上述方法可以很好地应用于物理实验中线性关系变量的实验数据分析与处理．