A MATHEMATICAL MODEL FOR THE DYNAMIC PARTICIPATE FILTRATION IN DIESEL FOAM FILTERS

Diesel Particulate Filters (DPFs) are probably the most effective means for trapping the exhaust-emitted participate from diesel engines. Foam type filters become a promising alternative to the common wall flow filters, since they are effective in filtering small size particles and provide a larger specific surface area for catalytic coatings. A mathematical model taking into account the significant phenomena during the dynamic filtration of foam filters is developed. The model predicts the filtration efficiency and the induced backpressure as function of the geometric filter properties and operating conditions. Due to the particular structure properties of the foam filters it is necessary to employ a tunable parameter, which accounts for the influence of non-Stokes flow in foam filters. This parameter is easily derived by simple measurements. The model is employed to identify and understand the critical parameters of the filtration in foam filters. Indicative parametric runs are presented, which illustrate the applicability of the model in system optimization procedures.     

THE DEVELOPMENT OF A MATHEMATICAL MODEL FOR PREDICTING THE DEPTH OF PLASTIC DEFORMATION IN A MACHINED SURFACE

The development and verification of a mathematical model for the prediction of plastic deformation in a machined surface are presented. The main assumption for developing this model is that there is a linear relation between plastic strain and the depth to which it extends. The model relates the work required to shear the workpiece material to the work needed to compress the workpiece material ahead of the cutting tool. The resulting depth of plastic deformation in the machined surface is a function of the true stress-strain characteristics of the workpiece material, the shear stress and shear strain on the shear plane, and the distribution of plastic strain. Results of the model agree well with data found in the literature. An improvement of the model is suggested through application of actual distribution data of plastic strain and calculation of frictional behavior on the rake face of the tool.     

COMPARISONS OF MECHANICAL MELT-BLOWN FILTERS AND ELECTROSTATICALLY ENHANCED SPLIT-FIBER FILTERS FOR CABIN AIR FILTRATION APPLICATIONS

In this paper, compared are filtration characteristics of two different filters made from uncharged melt-blown media and electrostatically charged split-fiber media. The split-fiber filters have stronger electrostatic charges in the media than the melt-blown filter, which in turn enhances the initial fractional efficiency. The compared parameters are fractional efficiencies, dust holding capacities, incremental fractional efficiencies, and pressure drop. The advantages and disadvantages of these filters for cabin air filtration applications are discussed based on the experimental results obtained using SAE-fine dust and sodium chloride test aerosol. The optimization process of the filter selection is also discussed.     

腐蚀磨损数学模型

测试了化学镀Ｎｉ－Ｐ合金静腐蚀、动腐蚀和腐蚀磨损试验结果。通过对试验结果的处理，建立了动腐蚀速率和腐蚀磨损速率与冲击速度Ｖ、介质浓度Ｃ的数学模型：Ｖ＝Ｋ１Ｖ＾ｎ１＋Ｋ２Ｖ＾ｎ２Ｃ＾ａ（ａ＝Ｋ３Ｖ＾ｎ３）。建立了腐蚀磨损速率Ｖｗｃ与纯磨损速率Ｖｗｏ、纯腐蚀速率Ｖｐｃ及动腐蚀速率Ｖｏｃ之间数学模型：Ｖｗｃ＝Ｖｗｏ＋Ｖｐｃ＋ＫｗｃＶｗｏ，Ｖｐｃ＝Ｖｗｏ＋（１＋Ｋｗ）Ｖｏｃ＋Ｋｗｃ（１＋Ｋｗ）ＶｗｃＶｏｃ     

高速柴油机曲轴动态特性研究

本文利用ＳＵＰＥＲ ＳＡＰ９１微机版工程分析软件，对某高速柴油机曲轴进行了有限元计算模态分析，获得了其前五阶模态参数；利用随机信号与振动分析系统ＣＲＡＳ４．１版对该曲轴进行了试验模态分析，其固有频率与计算结果的相对误差在５．７％之内，验证了计算结果的正确性，为结构的动态特性分析提供了可靠的数据。     

圆环斜二测投影数学模型的建立

本文建立了圆环斜二测投影的数学模型，并对投影中轮廓线的可视性进行了分析，导出了可见轮廓线端点坐标的计算公式，为计算机辅助绘较提供了依据。     

残余应力平板表面裂纹的线弹簧模型

建立了残余应力平板表面裂纹的线弹簧模型,利用边裂纹权函数得到了裂纹表面上沿厚度非线性分布残余应力向线性分布转化的公式;基于Reissner板理论和连续分布位错思想,通过积分变换方法,推导了问题的控制方程和应力强度因子表达式;利用Gauss-Chebyshev方法给出了数值计算结果,并与现有的有限元解进行了比较,结果表明:该模型简单有效,而且精度较高。     

A CONTINUUM MODEL FOR DYNAMIC DAMAGE EVOLUTION OF ANISOTROPIC BRITTLE MATERIALS

This paper is concerned with the development of a computational model for the damage evolution of brittle materials under dynamic loading. Two models for dynamic damage evolution of brittle materials with or without microflaws in general anisotropic damage state are presented; the first one is based on power function of principal tensile stress and the second one is based on damage strain energy release rate. A second-order tensor based elastic–brittle damage model is formulated which is efficient computationally and consistent in its treatment of damage evolution. Measured Weibull strength distribution may be employed to account for flaw size distribution effects on the damage accumulation rate. Methods of computing the accumulated damage of a structural component and their implementation in a finite element program together with some numerical results are presented. Finally, a comparison has been made between the two damage models.     

广义逆特征值方法在动力模型修正中的应用

本文针对土木工程中理论计算的要求和特点,基于逆特征值理论给出了一种适合有限元动力模型修正的广义逆特征值方法,该方法在给出修正解的表达式基础上,要求修正解满足动力模型的力学特征,且仅需要少量试验数据,是一种简单、实用的有限元模型修正方法。     

动载荷识别的时间有限元模型理论及其应用

本文利用广义正交多项式作为时间有限元的形函数,推导了基于时间有限元的动载荷识别模型.成功地将时域下动载荷识别的复杂逆卷积关系转变为广义正交域的线性算子逆运算,这种模型识别精度高,抗干扰能力强,具有良好的计算稳定性,尤其适用于具有短时间样本的冲击类型动载荷识别,使该类问题在工程应用时的复杂程度大大降低,具有较高的工程应用价值.该方法为结构动力学逆问题的研究提供了一种新的技术途径.     

基于物理力学机制的黄土震陷数学估算模型

通过分析黄土震陷物理力学机制,将影响震陷的主导因素归纳为粘聚力与内摩擦角(土体强度特征)、孔隙比(土体沉降特征)和外部动荷载特性(能量输入特征)等3方面。在此基础上,推导了应用孔隙比描述震陷系数的定量关系;利用摩尔-库伦破坏准则,提出了考虑动应力和固结应力的应力比概念,用以刻画动载输入对土体结构强度的影响;结合室内动三轴试验数据,给出了孔隙比压缩量与应力比之间的定量统计关系。耦合以上分析结果,建立了基于物理力学机制的求算地震动作用下黄土残余应变(震陷系数)的数学估算模型。     

雷达目标识别的滤波器法

本文讨论了基于高分辨率距离像提取不敏感于方位角变化的特征矢量的方法和利用特征矢量间的相关性进行目标识别的问题，并对一些目标进行了识别实验，识别结果验证了本文所提出的利用相关滤波器法进行目标识别的有效性和可行性。     

A HEURISTIC FOR THE DYNAMIC FACILITY LAYOUT PROBLEM

This paper presents a heuristic for the dynamic facility layout problem. All existing methods for solving this problem require the use of a dynamic programming model, the optimal solution of the quadratic assignment problem, or both. The proposed heuristic is based on the steepest-descent pairwise-interchange procedure to develop layouts utilizing material handling cost data from varying lengths of forecast windows as well as the explicit consideration of the corresponding rearrangement costs. Numeric results indicate that it typically performs as well as any existing methodology and only slightly worse than optimal.     

线型高分子无规交联和裂解的一个动力学模型

建立了线型高分子无规交联和裂解的一个动力学模型。通过模型,推导了一级反应的数均分子量的计算公式,探讨了交联和裂解速率对最终产物数均分子量的影响,以及在纯交联过程中,起始分子量分布对凝胶化时间的影响。文中指出,无规裂解的Simha模型仅仅是本模型中的一个特例。     

肘型流道弯曲段数模分析,工程应用与程序实现

建立肘型流道弯曲段的数学模型，从程序实现和工程实际应用方面加以分析，选择其应用数学模型，并给出其程序实现结果。     

一种基于单片机控制的导弹伺服舵系统的建模与仿真

提出了一种以8098单片机作控制器、直流力矩电机作执行机构的导弹伺服舵系统控制方案,建立了系统的数学模型,开发了8098单片机控制器及其控制算法,最后进行了仿真实验,结果表明采用这种单片机控制器的舵系统具有良好的快速性和控制精度。     

HP-Nb转化管寿命计算及其数学模型的建立

对HP－Nb转化管进行了蠕变损伤分析,计算了不同温度下HP－Nb转化管的寿命,探讨了每年开停车次数对其寿命的影响。对计算结果应用优化、回归的方法进行了整体拟合,导出了单元损伤与时间和温度的关系,建立了数学模型,为计算机预测HP－Nb转化管剩余寿命提供了算法。     

圆环面正轴测投影的数学模型

本文运用图解法，在对圆环面正轴测投影外形线的曲线性质进行投影分析的基础上，导出了圆环面正轴测投影外形线的参数方程；给出了产生尖点的几何条件和判别式；解决了尖点和虚实分界点的定位问题，为圆环面正轴测投影的计算机绘图提供了可靠的教学依据。