Relationship Between the Parameters of Acoustic Structural Noise and the Mechanical Properties of Structural Steels

Materials Science - We perform the comparative analysis of the parameters of acoustic structural noise in specimens of 40G structural steel with the use of ultrasonic flaw detectors with phased...     

A Model for the Forward Problem in Magnetic Induction Tomography Using Boundary Integral Equations

We propose a new formulation for the forward problem in magnetic induction tomography (MIT). We formulate the problem in terms of interior and exterior boundary integral equations (BIEs), subject to appropriate boundary conditions. We then transform a standard exterior BIE involving the magnetic vector potential to a BIE involving the electric fields. This transformation eliminates two boundary conditions involving the magnetic vector potential and its normal derivative. This greatly reduces the computational complexity of the model. Here, we compare numerical solutions of the model to analytical solutions.      

振动系统参数识别的ARMA模型与Ibrahim-Randec模型的关系

本文研究了用多变量ARMA模型描述振动系统的受迫响应进行参数识别的数学理论,给出随机减量函数的某些性质,指出了对受白噪声激励下的ARMA模型同Ibrahim-Randec之间的关系.     

Relationship Between Closure Stress of Small Fatigue Crack and Ultrasonic Response

This paper describes a new methodology for analyzing the closure stress of small fatigue cracks using ultrasonics. Surface connected back-wall cracks in steel specimens are considered. The crack-corner echo of ultrasonic shear wave beam of 50° incidence in the material is used. In order to account for the exact effect of closure stress on ultrasonic response, the echo amplitude is analyzed based on artificially applying additional closure stress. The initial closure stress at no load condition is determined by the standard compliance technique. A relationship between the closure stress and the crack-echo response is established which provides the facility of getting a true model of crack closure stress. The relationship is found to be independent of crack depth. The present approach can be used to overcome the difficulties encountered by crack closure in recent nondestructive ultrasonic techniques and may lead the way in quantitative evaluation of crack depth as well as exact closure stress.     

利用MATLAB建立不确定度评定测量模型分析变量的相关系数

在测量不确定度中,运用MATLAB模拟生成相关随机变量,评定随机变量先关系数,可以提升评定结果的准确性,符合实际需求。以下本篇基于具体变量分析问题,浅析如何通过MATLAB建立不确定度评定测量模型,分析变量的相关系数。     

PZT和PT陶瓷的热释电效应与晶格参数的关系

测量了锆钛酸铅（PZT和钛酸铅（PT）陶瓷材料的热释电效应，利用X射线衍射测量了陶瓷材料在不同温度下晶格结构变化，研究了PZT和PT陶瓷材料的热释电效应与晶格参数之间的相互关系，实验表明，陶瓷材料的热释电系数的大小与晶格参数随温度变化的情形有关，c轴与c／a比随温度变化大的材料，其热释电系数较高．     

Relationship Between Stress, Interaction and the Mechanical Properties of Some Pigmented Tablet Coating Films

The mechanical properties of pigmented free films of hydroxypropyl methylcellulose in combination with either polyvinyl alcohol or polyethylene glycol 1000 and cast from aqueous systems, were measured using a stress-strain method. The pigments incorporated were two types of talc (differing in average particle size) and two types of titanium dioxide (one of which was surface-treated). Specific surface area data for the pigments and the pH of the aqueous solution or suspension of the film components were determined in order to understand the factors affecting the mechanical properties of pigmented films.     

Relationship Between Stress,Interaction and the Mechanical Properties of Some Pigmented Tablet Coating Films

Abstract

The mechanical properties of pigmented free films of hydroxypropyl methylcellulose in combination with either polyvinyl alcohol or polyethylene glycol 1000 and cast from aqueous systems, were measured using a stress-strain method. The pigments incorporated were two types of talc (differing in average particle size) and two types of titanium dioxide (one of which was surface-treated). Specific surface area data for the pigments and the pH of the aqueous solution or suspension of the film components were determined in order to understand the factors affecting the mechanical properties of pigmented films.     

An Efficient Procedure for Identifying the Prediction Model Between Residual Stress and Barkhausen Noise

Residual stress of case-hardened steel samples is predicted in this paper with the linear multivariable regression model. The development of the prediction model is based on the huge set of features calculated from the Barkhausen noise measurement signal among which the most suitable ones are chosen. The selection uses a genetic algorithm with leave-multiple-out cross-validation in the objective function. The original feature set contains collinear features that make the selection task even more complex. Thus a feature elimination procedure based on the successive projections algorithm is studied in this paper. Also the standard genetic algorithm is slightly modified to better serve the feature selection task. The obtained results are good showing that the proposed procedures suit well for residual stress predictions. Also the applied feature elimination procedure is applicable and can be safely used to reduce the dimensionality of the selection problem.     

基于序列和局部信息熵的蛋白质折叠速率预测模型

<正>确预测蛋白质折叠速率对理解蛋白质的折叠机制非常重要。本文从AAindex数据库中的531种残基物理化学性质、序列长度信息和局部结构信息熵中筛选特征,从而提出了一个基于蛋白质序列信息的线性回归模型。针对三种折叠机制two-state,multi-state和mixed-state,用Jackknife验证模型,预测的折叠速率和实验验证的折叠速率相关系数分别为0.790,0.829和0.778。本文结果表明四阶局部结构信息熵和折叠速率有很高的负相关性;蛋白质的长度和蛋白质的折叠速率成反比关系;螺旋的含量会加快蛋白质的折叠过程。对two-state蛋白质β折叠的含量会减慢蛋白质的折叠过程;和其他模型相比,我们提出的线性回归模型具有输入参数少,计算简单,平均绝对误差小的优点。     

On the Effect of Triaxial State of Stress on Ductility Using Nonlinear CDM Model

Ductility takes into account the material capability to plastically deform. This parameter is not only modified by temperature but it is strongly affected by the stress triaxiality that, in the case of positive hydrostatic stress, reduces the material strain to failure. Due to the importance of this parameter in engineering design many attempts to predict the evolution of ductility with stress triaxiality have been done. Here, a nonlinear continuum damage model, as proposed by the author, is used to obtain the evolution of material ductility with stress triaxiality. The expression found relates the strain to failure in multi-axial state of stress regime only to the uniaxial strain to failure, to the damage strain threshold, to the material Poisson's ratio, and, of course, to stress triaxiality. The proposed model was successfully verified comparing the predicted evolution of material ductility with the experimental data relative to several metals. The procedure for the damage parameters identification is also discussed in details.     

试论精益生产方式与员工队伍素质的关系

通过对上海汽车工业（集团）总公司部分企业调查,探讨了汽车行业先进的精益生产方式与员工队伍素质之间的关系,用大量事实说明精益生产需要高素质的员工队伍,精益生产实践造就了一代新型员工,员工队伍素质的提高反过来促进精益生产向深层次发展,高素质的员工队伍是推进精益生产方式的重要保证。     

A Physical Model for the Prediction of Lateral Stress Exerted by Self-Compacting Concrete on Formwork

In this paper, a model is proposed to describe the evolutions of the lateral stress exerted by self compacting concrete (SCC) on a formwork during and after casting. The predictions of the model are compared to pressure drop measurements after the end of casting carried out on real formwork simultaneously with measurements of the evolution of the apparent yield stress of the cast concrete. Then, the predictions of the model during the casting phase are compared to results from the literature and show that the proposed model is able to explain and predict the experimental observations and the quantitative evolutions.     

动态断裂韧度与冲击功之间关系的探讨

将冲击功分为温度敏感分量和非温度敏感分量,通过对断裂过程中能量的分析,认为冷脆性金属材料在下平台的断裂阻力主要决定于非温度敏感分量,在塑-脆过渡区,随着温度升高,温度敏感分量的作用越来越大.得到动态断裂韧度(KId)与冲击功(CVN)之间的关系:K2Id=A+B(CVN),该式在上平台、塑-脆过渡区和下平台对KId的预测均与试验结果符合得比较满意.     

用支持向量机模型预测单体与苯乙烯竞聚率

为预测60种烯烃类单体(M1)与苯乙烯(M2)的自由基共聚合竞聚率lgr1S值,采用密度泛函理论(DFT)B3LYP方法在6-31G(d)基组水平上对烯烃类单体(C1H2=C2XY)进行了计算。用于构建支持向量机(SVM)模型的最佳参数子集包括:原子R3的Mulliken电荷qMR3,C1的Mulliken电荷QMC-1(H原子电荷全部合并到与之相连的重原子上),参数QMC-1与qMC-2之比RQq(=QMC-1/qMC-2),最低未占分子轨道(LUMO)能级(ELUMO)和最高占据分子轨道(HOMO)能级(EHOMO)之差ΔEg。最佳SVM模型为高斯径向基核函数(C=1000,ε=0.0001及γ=0.2)。该模型训练集、验证集及测试集的均方根(rms)误差分别为0.043,0.157及0.192,与现有竞聚率lgr模型相比,本文所得SVM模型具有更好的统计品质。     

A Variant of the Strain-Hardening Theory Allowing for the Stress and Temperature Dependence of Parameters in Constitutive Equations

A procedure is put forward for concrete definition of constitutive relationships of the strain-hardening theory allowing for the level of damage in a material. The parameters of the equation of creep and the damage evolution relationship are assumed to be functions of stress and temperature. Efficiency of this approach is illustrated by describing creep curves for 20Kh13 and EP44 steels over a fairly wide range of stress variation.__________Translated from Problemy Prochnosti, No. 2, pp. 19 – 27, March – April, 2005.