Computational study of the structural, thermodynamic and transport properties of polymeric materials at equilibrium requires multi-scale modeling techniques due to processes occurring across a broad spectrum of time and length scales. Classical molecular-level simulation, such as Molecular Dynamics (MD), has proved very useful in the study of polymeric oligomers or short chains. However, there is a strong, nonlinear dependence of relaxation time with respect to chain length that requires the use of less computationally demanding techniques to describe the behavior of longer chains. As one of the mesoscale modeling techniques, Coarse-grained (CG) procedure has been developed recently to extend the molecular simulation to larger time and length scales. With a CG model, structural and dynamics of long chain polymeric systems can be directly studied though CG level simulation. In the CG simulations, the generation of the CG potential is an area of current research activity. The work in this dissertation focused on both the development of techniques for generating CG potentials as well as the application of CG potentials in Coarse-grained Molecular Dynamics (CGMD) simulations to describe structural, thermodynamic and transport properties of various polymer systems. First, an improved procedure for generated CG potentials from structural data obtained from atomistic simulation of short chains was developed. The Ornstein-Zernike integral equation with the Percus Yevick approximation was invoked to solve this inverse problem (OZPY-1). Then the OZPY-1 method was applied to CG modeling of polyethylene terephthalate (PET) and polyethylene glycol (PEG). Finally, CG procedure was applied to a model of sulfonated and cross-linked Poly (1, 3-cyclohexadiene) (sxPCHD) polymer that is designed for future application as a proton exchange membrane material used in fuel cell. Through above efforts, we developed an understanding of the strengths and limitations of various procedures for generating CG potentials. We were able to simulate entangled polymer chains for PET and study the structure and dynamics as a function of chain length. The work here also provides the first glimpses of the nanoscale morphology of the hydrated sxPCHD membrane. An understanding of this structure is important in the prediction of proton conductivity in the membrane.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Manufacturers of digital circuits test their products to find defective parts so they are not sold to customers. Despite extensive testing, some of their products that are defective pass the testing process. To combat this problem, manufacturers have developed a metric called defective part level. This metric measures the percentage of parts that passed the testing that are actually defective. While this is useful for the manufacturer, the customer would like to know how long it will take for a manufacturing defect to affect circuit operation. In order for a defect to be detected during circuit operation, it must be excited and observed at the same time. This research shows the correlation between defect detection during automatic test pattern generation (ATPG) testing and normal operation for both combinational and sequential circuits. This information is then used to formulate a mathematical model to predict the expected latency to failure due to manufacturing defects.

The atomic arrangements and electronic structures of [0001] oriented GaN nanowires with different side surfaces have been studied by the first-principles molecular dynamics (MD) method and the conventional first-principles electronic structure calculation method. It is found that due to the dangling bond effects, the Ga-N bonds on the side surfaces of the nanowire tilt with Ga surface atoms moving inward. The radius of the nanowire is found to be reduced with respect to the wire truncated from a bulk GaN solid, which can be attributed to the surface tension effect. Due to the large ratio between the numbers of surface atoms and bulk atoms, the electronic structures of these nanowires are very different from those of bulk and films due to the large number of surface atoms or dangling-bond states, so that a bulk-like energy gap can not be clearly defined.

Thesis (M. Arch.)--Roger Williams University, 2008. / Title from title page screen (viewed on Feb. 8, 2010) Includes bibliographical references. Also available in print.

Thesis (M.A.)--University of Delaware, 2009. / Principal faculty advisor: Lawrence Nees, Dept. of Art History. Includes bibliographical references.

Manufacturers of digital circuits test their products to find defective parts so they are not sold to customers. Despite extensive testing, some of their products that are defective pass the testing process. To combat this problem, manufacturers have developed a metric called defective part level. This metric measures the percentage of parts that passed the testing that are actually defective. While this is useful for the manufacturer, the customer would like to know how long it will take for a manufacturing defect to affect circuit operation. In order for a defect to be detected during circuit operation, it must be excited and observed at the same time. This research shows the correlation between defect detection during automatic test pattern generation (ATPG) testing and normal operation for both combinational and sequential circuits. This information is then used to formulate a mathematical model to predict the expected latency to failure due to manufacturing defects.

No description available.

No description available.

As a candidate for dynamic electric contacts, Nano-twinned copper has intrinsic conductivity and enhanced fretting resistance. To better understand its general mechanical behavior, we conduct molecular dynamics simulation studies to investigate responses of nano-twinned copper to stress and to one-directional and two-directional sliding processes, in comparison with single crystal and nano-grained model systems. Obtained results suggest that the twin boundary blocks dislocation movement more effectively and the degree of emitting dislocations under stress is considerably lower than that of grain boundary. The inverse H-P relation only occurring in nano-grained materials does not necessarily result from grain boundary sliding. Under sliding conditions, dislocations are easier to be generated in the single crystal system. During the two-directional sliding process, Bauschinger effect is observed in the single crystal and nano-twinned systems, while the situation is opposite for the nano-grained system. The nano-twinned Cu shows the least dislocation accumulation during two-directional sliding. / Materials Engineering