Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 85-93).

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2006. / Includes bibliographical references (leaves 96-105).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 60-63). Also available on the World Wide Web.

A theoretical formalism to reconstruct structural and dynamical properties of polymer liquids from their coarse-grained description is developed. This formalism relies on established earlier analytical coarse-graining of polymers derived from the first principles of liquid theory. The polymer chain is represented at a mesoscale level as a soft particle. Coarse-grained computer simulations provide input data to the reconstruction formalism and allow one to achieve the most gain in computational efficiency. The structure of polymer systems is reconstructed by combining global information from mesoscale simulations and local information from small united-atom simulations. The obtained monomer total correlation function is tested for a number of systems including polyethylene melts of different degrees of polymerization as well as melts with different local chemical structure. The agreement with full united-atom simulations is quantitative, and the procedure remains advantageous in computational time. The dynamics in mesoscale simulations is artificially accelerated due to the coarse-graining procedure and needs to be rescaled. The proposed formalism addresses two rescalings of the dynamics. First, the internal degrees of freedom averaged out during coarse-graining procedure are reintroduced in "a posteriori" manner, rescaling the simulation time. The second rescaling takes into account the change in friction when switching from a monomer level description to mesoscopic. Both friction coefficients for monomer and soft particle are calculated analytically and their ratio provides the rescaling factor for the diffusion coefficient. The formalism is extensively tested against the united-atom molecular dynamic simulations and experimental data. The reconstructed diffusive dynamics of the center-of-mass for polyethylene and polybutadiene melts of increasing degrees of polymerization show a quantitative agreement, supporting the foundation of the approach. Finally, from the center-of-mass diffusion the monomer friction coefficient is obtained and used as an input into Cooperative Dynamics theory. The dynamics of polymer chains at any length scale of interest is described through a Langevin equation. In summary, the proposed formalism reconstructs the structure and dynamics of polymer melts enhancing computational efficiency of molecular dynamic simulations. This dissertation includes previously published and unpublished co-authored material.

abstract: Improved knowledge connecting the chemistry, structure, and properties of polymers is necessary to develop advanced materials in a materials-by-design approach. Molecular dynamics (MD) simulations can provide tremendous insight into how the fine details of chemistry, molecular architecture, and microstructure affect many physical properties; however, they face well-known restrictions in their applicable temporal and spatial scales. These limitations have motivated the development of computationally-efficient, coarse-grained methods to investigate how microstructural details affect thermophysical properties. In this dissertation, I summarize my research work in structure-based coarse-graining methods to establish the link between molecular-scale structure and macroscopic properties of two different polymers. Systematically coarse-grained models were developed to study the viscoelastic stress response of polyurea, a copolymer that segregates into rigid and viscous phases, at time scales characteristic of blast and impact loading. With the application of appropriate scaling parameters, the coarse-grained models can predict viscoelastic properties with a speed up of 5-6 orders of magnitude relative to the atomistic MD models. Coarse-grained models of polyethylene were also created to investigate the thermomechanical material response under shock loading. As structure-based coarse-grained methods are generally not transferable to states different from which they were calibrated at, their applicability for modeling non-equilibrium processes such as shock and impact is highly limited. To address this problem, a new model is developed that incorporates many-body interactions and is calibrated across a range of different thermodynamic states using a least square minimization scheme. The new model is validated by comparing shock Hugoniot properties with atomistic and experimental data for polyethylene. Lastly, a high fidelity coarse-grained model of polyethylene was constructed that reproduces the joint-probability distributions of structural variables such as the distributions of bond lengths and bond angles between sequential coarse-grained sites along polymer chains. This new model accurately represents the structure of both the amorphous and crystal phases of polyethylene and enabling investigation of how polymer processing such as cold-drawing and bulk crystallization affect material structure at significantly larger time and length scales than traditional molecular simulations. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2016

O sinal de entrada na retina é decomposto em termos de frequência espacial (FE), variações periódicas de luminância ao longo do espaço. Existe vasta literatura sobre o processamento de FE no córtex visual primário. No entanto, não se sabe ao certo como esta informação sensorial básica é processada e integrada numa visão de alto nível. Esta tese aborda este tema ao investigar lateralidade cerebral, tempo de processamento e contexto cognitivo em três diferentes seções com objetivos específicos. Estas seções investigaram comportamentalmente visão de alto nível tendo a face humana como estímulo, dado sua relevância biológica e social. Na primeira seção (Theoretical Review), uma revisão apresenta estudos clínicos e neuropsicológicos que mostram áreas cerebrais envolvidas na percepção de faces e como os hemisférios esquerdo e direito realizam um processamento holístico e analítico baseado em informações de FEs. A especialização hemisférica de FE no reconhecimento de faces é então revisada e discutida. Concluiu-se que assimetrias sensoriais podem ser a base para assimetrias cognitivas de alta ordem. Ademais, foi destacado a influência do tempo de processamento. Na segunda seção (Study 1), foi investigado por método psicofísico a lateralidade de baixas e altas FEs no reconhecimento de faces em diferentes tempos de exposição. Faces com filtragem de FE foram apresentadas em campo visual dividido em alta e baixa restrição temporal em duas tarefas: reconhecimento facial (Experimento 1) e reconhecimento do sexo facial (Experimento 2). No Experimento 1, informações faciais de baixas e altas FEs foram mais eficientemente processadas no hemisfério direito e esquerdo, respectivamente, sem efeito do tempo de exposição das faces. Os resultados do Experimento 2 mostraram uma assimetria do hemisfério direito para baixas FEs em baixa restrição temporal. Conclui-se que o processamento de altas e baixas FEs é lateralizado nos hemisférios cerebrais no reconhecimento de faces. No entanto, a contribuição de altas e baixas FEs é dependente da tarefa e do tempo de exposição. Na terceira seção (Study 2) foi investigado qual estratégia temporal, coarse-to-fine (de baixas para altas FEs) ou fine-to-coarse, cada hemisfério cerebral utiliza para integrar informação de FE de faces humanas numa tarefa de categorização facial homem-mulher. Sequências dinâmicas breves coarse-to-fine e fine-to-coarse de faces foram apresentadas no campo visual esquerdo, direito e central. Os resultados do tempo de resposta e do score de eficiência invertida mostraram uma prevalência geral de um processamento coarse-to-fine, independente do campo visual de apresentação. Ainda, os dados da taxa de erro ressaltam o processamento coarse-to-fine realizado pelo hemisfério direito. No geral, esta tese fornece insights sobre assimetria cerebral funcional, integração de alto nível e curso temporal do processamento de FEs, principalmente para aqueles interessados na percepção de faces. Também foi mostrado que operações lateralizadas, tarefa-dependente e coarse-to-fine podem coexistir e interagir no cérebro para processar informação de FE. / Retinal input is decomposed in terms of spatial frequency (SF), i.e., periodic variations of luminance through space. There is extensive literature on the processing of SF in the primary visual cortex. However, it is still unclear how SF information is processed and integrated in high-level vision. This thesis addressed this issue in terms of laterality effects, processing time-course, and the cognitive context in three different sections with specific purposes. These sections behaviorally tackle high-level vision using human faces as stimuli due to their biological and social relevance. In the first section (Theoretical Review) a literature review presented clinical and neurophysiological studies that show brain areas that are involved in face perception and how the right and left hemispheres perform holistic and analytic processing, depending on SF information. The SF hemispheric specialization in face recognition is then reviewed and discussed. Our conclusion is that functional sensorial asymmetries may be the basis for high-level cognitive asymmetries. In addition, we highlighted the role of the processing time. In the second section (Study 1), we psychophysically investigated laterality of low and high SF in face recognition at different exposure times. The SF filtered faces were presented in a divided visual field at high and low temporal constraint in two tasks: face recognition (Experiment 1) and face gender recognition (Experiment 2). In Experiment 1, low and high SF facial information were more efficiently processed in the right and in the left hemisphere, respectively, with no effect of exposure time. In Experiment 2, results showed a right hemisphere asymmetry for low SF faces at low temporal constraint. We concluded that the processing of low and high SF is lateralized in the brain hemispheres for face recognition. However, low and high SF contribution is dependent on the task and the exposure time. In the third section (Study 2), we aimed to investigate which temporal strategy, i.e., coarse-to-fine (from low to high SF) or fine-to-course, each brain hemisphere performs to integrate SF information of human faces in a male-female categorization task. Coarse-to-fine and fine-to-course brief dynamic sequences of faces were presented in the left, right and central visual field. Results of the correct response time and the inverse efficiency score showed an overall advantage of coarse-to-fine processing, irrespective of the visual field of presentation. Data of the error rate also highlights the role of the right hemisphere in the coarse-to-fine processing. All in all, this thesis provided some insights on functional brain asymmetry, high-level integration, and processing time-course of SF information, mainly for those interested in face perception. It was also shown that lateralized, diagnostic-oriented, and coarse-to-fine operations may coexist and interact in the human brain to process SF information.

abstract: VCO as a ubiquitous circuit in many systems is highly demanding for the phase noises. Lowering the noise migrated from the power supply has been the trending topics for many years. Considering the Ring Oscillator(RO) based VCO is more sensitive to the supply noise, it is more significant to find out a useful technique to reduce the supply noise. Among the conventional supply noise reduction techniques such as filtering, channel length adjusting for the transistors, and the current noise mutual canceling, the new feature of the 28nm UTBB-FD-SOI process launched by the ST semiconductor offered a new method to reduce the noise, which is realized by allowing the circuit designer to dynamically control the threshold voltage. In this thesis, a new structure of the linear coarse-fine VCO with 1V supply voltage is designed for the ring typed VCO. The structure is also designed to be flexible to tune the frequency coverage by the fine and coarse tunable on-board resistors. The thesis has given the model of the phase noise reduction method. The model has also been proved to be meaningful with the newly designed VCO circuit. For instances, given 1μV/√Hz white noise coupled on the supply, the 3GHz VCO can have a more than 7dBc/Hz phase noise lowering at the 10MHz frequency offset. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

Calcium nitrite as a corrosion inhibitor is mainly used to protect steel reinforcement in concrete by reducing its corrosion rate. Hence the effectiveness of calcium nitrite depends on its availability as a free nitrite in the pore solution. The present research work aims to determine the concrete mixture component mostly responsible for nitrite binding in concrete. Firstly, the experimental program included testing of nitrite binding in cement paste. Secondly, the effect of adding the fine aggregate (mortar mix) on nitrite binding was assessed. Finally, the mix with coarse aggregate (concrete mix) was evaluated. In-situ leaching method was used to obtain the pore solution that was needed. Measurement of pore solution with the In-situ leaching method and after an average of 48 days showed that concrete specimens have the most nitrite binding capacity. Then, the binding of nitrite was less in mortar and paste specimens respectively. Therefore, concrete specimens bind more nitrite compared to the paste and mortar specimens. The binding ratio increased whenever the nitrite addition level increased. Nevertheless, the free nitrite were similar in the case of the lowest nitrite addition for all types of mix. The pH levels for the mixes with nitrite present, were lower than those of the control mixes.

The effect of replacing fine ore by coarse ore on sintering reactions was investigated using an infrared furnace on laboratory scale and sinter pots on pilot plant scale. Five sinter mixes were prepared by changing the percentage coarse ore from 0% to 100% in 25% increments. Coarse ore fraction, sintering temperature, holding time and oxygen partial pressure were selected as sintering parameters, and two-level factorial design was used for identification of parameters that significantly influence the formation of sinter phases. Experimental results showed that the coarse ore fraction has a higher effect on the sintering process compared to those of other parameters. The experiment design also enabled to set these parameters to their optimum values. The porosity of compacted pellets was measured using a helium pycnometer. The replacement of fine ore by coarse ore resulted in a decrease in porosity (increase in packing density) of compacted pellets. The particles are closer to each other in pellets consisting of more coarse particles than fine particles. Laboratory experiments were performed at 1300°C in air, using a high heating rate (15°C/s). The holding time was set to 2.5 minutes. X-ray diffraction (XRD), reflected light microscopy (RLM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize sintering reactions and sinter phases. XRD analysis revealed that sintered pellets consisted of hematite, SFCA, SFCA-I and calcium silicate. The proportions of SFCA slightly increased when the fraction of coarse ore varied from 0% to 25%, but decreased with a further increase in percentage coarse ore. At 25% coarse ore fraction, the porosity of the compacted pellets decreased, resulting in an increase in packing density and sintering rate. More hematite reacted, resulting in the formation of high amounts of SFCA. Above 25% coarse ore fraction, the amount of hematite increased, and the concentrations of columnar SFCA decreased despite a further decrease in porosity. This was attributed to the decrease in reaction surface area for coarse ore, and the short reaction time, which limited the extent of reaction of the coarse particles. The variation of SFCA-I and calcium silicate was not significant under laboratory conditions. Reflected light microscopy and SEM analysis easily identified two major sinter phases: hematite and SFCA. A clear distinction between the different types of SFCA could not be made using EDS analysis. Sinter pot tests were carried out in order to examine the effect of coarse ore fraction on physical and metallurgical properties of sinters. The tumbler and reduction disintegration indexes increased with increasing coarse ore fraction in the sinter bed. This was presumably due to the increase in amounts of hematite and decrease in surface area for reaction. Consequently, the reducibility of sinter decreased as the percentage coarse ore increased. This study has concluded that the presence of 25% coarse ore in the sinter mix led to enhance sintering reactions. The amounts of SFCA increased, and sinter quality was improved. It is recommended that in future work, sintering reactions should further be investigated by also measuring the permeability of the sinter bed and the reaction surface area of solid particles. Copyright / Dissertation (MSc)--University of Pretoria, 2012. / Materials Science and Metallurgical Engineering / unrestricted

The bricks are one of the primary materials required for construction of homes that no used completely when executes all the walls due, the excess purchase, the cutting to be settle, the breaking for their transfer and its fixed dimensions; this situation requires monitoring on work site the order, cleanliness and accidents. A common practice is these bricks and/or waste are included in the clearing construction before being deposited or eliminated in dumps or sanitary landfills, with their early clogging and shortening them to ther design lifespan. An important alternative to reduce this waste, is to recycle them and reuse them as a concrete component material, due to their high absorption percentage that allows them to keep the water inside of them and then use it in the cement hydration process as internal curing of the concrete. In the present investigation, the effect of crushed clay brick as a replacement for coarse aggregate in concrete processing is studied. The results indicate that with 21 % replacement brick, the plastic contraction decreases, and the compressive strength and flexural strength increase.