MULTI-SCALE MODELING OF POLYMERIC MATERIALS: AN ATOMISTIC AND COARSE-GRAINED MOLECULAR DYNAMICS STUDY

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

The Experience of Rising Inequality in Russia and China during the Transition

This paper examines the changes in regional and sectoral inequality that accompanied economic transformation in Russia and China throughout the 1990s. The experiences of the two countries are widely viewed as having been polar opposites. While the Soviet collapse had adverse consequences for many parts of the post-Soviet population, the Chinese experience produced a continuing rise of average living standards. Nevertheless, both countries experienced a drastic increase in economic inequality. In both cases, regional inequalities rose more sharply than inequalities across sectors but within regions. In particular, major urban centers gained dramatically relative to the hinterlands. Also, in Russia as in China, those sectors exercising the largest degrees of monopoly power gained the most (or lost the least) in relative terms. In both countries, the respective position of finance improved greatly, while that of agriculture declined. The decline of agriculture in China, however, was not as precipitous as in Russia, and certain sectors, such as education and science, maintained their position in China in a way that was not possible for them in Russia.Inequality; Russia; China; Provinces; Sectors

Evaluation of Pose Tracking Accuracy in the First and Second Generations of Microsoft Kinect

Microsoft Kinect camera and its skeletal tracking capabilities have been embraced by many researchers and commercial developers in various applications of real-time human movement analysis. In this paper, we evaluate the accuracy of the human kinematic motion data in the first and second generation of the Kinect system, and compare the results with an optical motion capture system. We collected motion data in 12 exercises for 10 different subjects and from three different viewpoints. We report on the accuracy of the joint localization and bone length estimation of Kinect skeletons in comparison to the motion capture. We also analyze the distribution of the joint localization offsets by fitting a mixture of Gaussian and uniform distribution models to determine the outliers in the Kinect motion data. Our analysis shows that overall Kinect 2 has more robust and more accurate tracking of human pose as compared to Kinect 1.Comment: 10 pages, IEEE International Conference on Healthcare Informatics 2015 (ICHI 2015

Optimal remanufacturing strategies in name-your-own-price auctions with limited capacity

We study optimal pricing and production strategies faced by a manufacturer in a remanufacturing/manufacturing system. In the reverse channel, returns are collected under a name-your-own-price (NYOP) bidding mechanism. The manufacturer has a limited capacity to produce new and remanufactured products. We characterize the optimal decisions of the consumers and the manufacturer. We find that under the NYOP mechanism, the manufacturer׳s optimal strategies mainly depend on the bidding cost, the cost saving of remanufacturing, the production capacity, and the market scale. In addition, when remanufacturing needs more capacity than manufacturing , the manufacturer may adopt pure manufacturing strategy without remanufacturing. We also compare this mechanism with the traditional list-price mechanism and find that the manufacturer prefers the NYOP mechanism under the conditions of a low reverse market share, a high manufacturing cost, a sufficient capacity, or a low capacity requirement of remanufacturing. Numerical studies investigate the effect of key parameters on the manufacturer׳s profit and some managerial insights are obtained

Preparation of desulfurizing activated carbon from corn stalk and characterization of desulfurizing structure

This study investigated the optimal conditions for preparing desulfurizing stalk carbon, using corn stalk as a raw material and zinc chloride as an activator. The structure of stalk carbon was characterized using thermogravimetry (TG), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer – Emmelt – Teller (BET). Results found no significant difference in stalk carbon desulfurization properties when using stalk skin, core, or a skin-core mixture as raw material. The desulfurization performance of stalk carbon prepared using a skin-core mixture, was the most effective when the material : liquid ratio was 1:2; activation temperature was 350 °C; and activation time was 70 min. The corresponding H2S adsorption time was 74 min. The large specific surface area of 562.28 m2/g and abundant pore-volume of 0.3851 ml/g was found in the desulfurization stalk carbon prepared using these conditions. The increase in micropores and the abundant oxygen-containing functional surface groups were conducive to H2S adsorption. The desulfurization products were found to be mainly elemental S and sulfite