Shape recovery studies for coupled deformations in an epoxy based amorphous shape memory polymers

In this work, the effect of sequence of shape setting on the shape recovery response for an epoxy based amorphous SMP was studied. The shape setting for coupled axial-twist deformations was done at two different temperatures within the glass transition band. A simple set-up with cameras was used to study the shape recovery behavior under free recovery experiments. Results show that the recovery behavior is independent of sequence of shape setting process but a shift in the shape recovery curve is noticed. The shape memory cycle for coupled deformations was also simulated in ABAQUS-VUMAT using the model proposed earlier by the authors based on multiple natural configurations. The simulated results show the capability of the model to analyze the memory effects of an amorphous polymer subjected to coupled deformations.     

Correct Modeling of Cisplatin: a Paradigmatic Case

Quantum chemistry is a useful tool in modern approaches to drug and material design, but only when the adopted model reflects a correct physical picture. Paradigmatic is the case of cis ‐diaminodichloroplatinum(II), cis ‐[Pt(NH₃)₂Cl₂], for which the correct simulation of the structural and vibrational properties measured experimentally still remains an open question. By using this molecule as a proof of concept, it is shown that state‐of‐the‐art quantum chemical calculations and a simple model, capturing the basic physical flavors, a cis ‐[Pt(NH₃)₂Cl₂] dimer, can provide the accuracy required for interpretative purposes. The present outcomes have fundamental implications for benchmark studies aiming at assessing the accuracy of a given computational protocol.     

Geometric and transformational properties of Lipschitz domains,Semmes-Kenig-Toro domains,and other classes of finite perimeter domains

In the first part of this article we give intrinsic characterizations of the classes of Lipschitz and C¹ domains. Under some mild, necessary, background hypotheses (of topological and geometric measure theoretic nature), we show that a domain is Lipschitz if and only if it has a continuous transversal vector field. We also show that if the geometric measure theoretic unit normal of the domain is continuous, then the domain in question is of class C¹. In the second part of the article, we study the invariance of various classes of domains of locally finite perimeter under bi-Lipschitz and C¹ diffeomorphisms of the Euclidean space. In particular, we prove that the class of bounded regular SKT domains (previously called chord-arc domains with vanishing constant, in the literature) is stable under C¹ diffeomorphisms. A number of other applications are also presented. Acknowledgements and Notes. The work of the authors was supported in part by NSF grants DMS-0245401, DMS-0653180, DMS-FRG0456306, and DMS-0456861.     

Two nonlinear models of a transversely vibrating string

Modeling transverse vibration of nonlinear strings is investigated via numerical solutions of partial-differential equations and an integro-partial-differential equation. By averaging the tension along the deflected string, the classic nonlinear model of a transversely vibrating string, Kirchhoff’s equation, is derived from another nonlinear model, a partial-differential equation. The partial-differential equation is obtained via neglecting longitudinal terms in a governing equation for coupled planar vibration. The finite difference schemes are developed to solve numerically those equations. An index is proposed to compare the transverse responses calculated from the two models with the transverse component calculated from the coupled equation. A steel string and a rubber string are treated as examples to demonstrate the differences between the two models of transverse vibration and their deviation from the full model of coupled vibration. The numerical results indicate that the differences increase with the amplitude of vibration. Both models yield satisfactory results of almost the same precision for vibration of small amplitudes. For large amplitudes, the Kirchhoff equation gives better results.     

仿真技术在半导体老化板计算中的应用

老化测试是半导体封测阶段中非常重要的一个环节,但由于老化测试本身所具有时间不确定性,以及半导体生产中的诸多随机性因素,导致老化测试板的需求计算非常困难。如何比较准确地计划老化测试板的需求,既能保证生产的正常进行,又可以避免不必要的成本支出,已经成为半导体生产厂商们日益关注的问题。本文结合实例,通过仿真软件对某一内存厂商的老化测试工序进行初步研究,来说明计算机仿真手段在半导体老化测试板需求计算中的作用。     

循环子空间回归为喹喏酮N1位构效关系建模

拟从线性泛函的角度分析循环子空间回归(CSR).CSR方法将从自变量参数矩阵和因变量向量中提取成分,循环地构造并扩张Krylov子空间,且以此作为源空间,运用最小二乘准则解得映射到因变量实空间的线性泛函.整个求解过程包容了最小二乘回归(LSR)、主成分回归(PCR)、偏最小二乘回归(PLS)以及其它中间的回归方法.然后由预报能力的强弱,从中确定最佳回归模型.本文应用CSR方法为喹喏酮N₁位抗菌构效关系建模,效果良好.     

Characterization and theoretical analysis of protein fouling of cellulose acetate membrane during constant flux dead-end microfiltration

A rapid characterization method was used to study protein fouling of cellulose acetate membrane during dead-end, in-line, constant flux microfiltration. Based on pressure-permeate volume profiles, two fouling phases could be identified and compared at different permeate fluxes. Using protein staining dyes, the model foulant (bovine serum albumin) was found to deposit on the upstream side of the membrane as a loose cake at its isoelectric point. The effects of solution pH on both the nature and extent of membrane fouling, and membrane cleaning were examined. To further understand and quantitatively analyze the fouling behavior, a combined mathematical model which took into account pore blocking, cake formation and pore constriction was developed based on existing fouling models. The data obtained by modeling was in good agreement with experimental fouling data. Theoretical analysis of data clearly indicated that cake formation was the main fouling mechanism. Using methods such as dynamic light scattering, the significant role of large protein aggregates in membrane fouling was confirmed. The dimer composition of protein did not change significantly during the fouling experiments, clearly indicating that smaller aggregates played less important role in membrane fouling.     

基于UML韵物流运输管理系统分析建模

本文以物流运输管理系统的开发为背景,探讨了UML（统一建模语言）在系统分析、设计中的应用问题。运用UML可视化建模方法,对物流运输管理系统进行分析建模。     

空间目标可见光散射特性建模方法研究

针对空间目标的可见光散射特性提出一种建模方法.在分析空间目标所处的背景辐射环境基础上建立了空间目标背景辐射物理模型.对目标表面进行面元划分后,基于辐射理论引入双向反射分布函数模型来描述目标表面面元的光散射特性,将目标各个表面所有面元散射分量叠加建立了目标可见光散射特性的数学模型.建立目标本体坐标系,通过坐标变换确定目标、背景辐射源与探测器的相对位置关系,利用矢量坐标法确定目标对观测系统的“可视表面”.根据给定的目标几何结构尺寸和物性参量仿真获得了目标在轨光学特性.计算结果验证了建模的有效性.