The objective of the present study was to understand how the visual and mental processes work in tandem to affect the overall information processing capability of the individual, especially the older population, in a dynamic visual task such as driving. More specifically, our aim was to understand how the different parameters related to display of visual information in an in-vehicle display system and the age of the subject affect the information processing performance. The effects of stimulus distance, target size, display time, bits of information and the age group of the subject (young versus old) on the reading performance (information processing ability) under photopic and scotopic viewing conditions were thoroughly investigated in this study. Fifty-six individuals (28 young, 28 elderly) from the Montgomery County region were tested in the study in a mixed factorial repeated measures design with age as between subjects and the other independent variables as within subjects. The dependent variable was the reading score, i.e., the number of letters correctly identified. Results obtained from this study revealed that all of the independent variables had significant effects on the reading performance of the participants, except ambient illumination. Specifically, age has an important influence on the specific values of the design parameters. Also, these parameters interact among themselves so that one can be used to compensate for the other. These results can be used for developing the most relevant and optimal in-vehicle visual displays for the older population. / Master of Science

Determinations of design parameters and investigation on operation performance of a tar removal system for gas cleaning of biomass producer gas have been undertaken. The presence of the tars in the producer gas has been the major hindrance for the commercialisation of the biomass gasification technology for power generation, hydrogen production, Fischer Tropsch (FT) synthesis, chemical synthesis and synthetic natural gas (SNG) synthesis. The characteristic of the tars to condense at reduced temperatures cause problems in the downstream processing as the tars can block and foul the downstream process equipment such as gas engines reactor channels, fuel cells, etc. Considerable efforts have been directed at the removal of tars from the producer gas where the tars can be either chemically converted into lighter molecular weight molecules or physically transferred from gas phase to liquid or solid phase. In the former, the tars have been removed in a scrubber by transferring them from the producer gas to a scrubbing liquid and then removed from the liquid to air in a stripper and finally recycled them into air to a gasifier to recover their energy. A tar removal test system involving a scrubber and stripper has been designed based on the predicted tar solubility in canola methyl ester (CME) as the scrubbing liquid and its measured properties (CME is a type of methyl ester biodiesel). The tar solubility has been predicted to decrease with increasing temperatures and thus its value increases at lower temperatures. In designing the test system, the design parameters are needed including equilibrium coefficients of the gas-liquid system, molar transfer coefficient and the optimum liquid to gas flow rate ratio. The equilibrium coefficients have been predicted based on thermodynamic theories where the required data are determined from CME composition and known properties of each component of the CME as well as the properties of the model tar (naphthalene). The molar transfer coefficients are then experimentally determined and the correlations as a function of liquid and gas flow rates are proposed which are consistent with literature. The optimum liquid to gas flow rate ratios have been found to be 21.4±0.1 for the scrubber and 5.7±0.1 for the stripper. Using these optimum ratios, the tar removal efficiencies in the scrubber and the stripper are 77 and 74%, respectively. The analysis of the system performance has been achieved after an innovative method of determining tar concentrations in both the liquid and gas phase had been developed based on the concept of the density of liquid mixtures. However, these tar removal efficiencies are low due to the fact that the targeted tar concentration in the scrubber’s off-gas was large. As a result the system has been redesigned based on the determined design parameters and its operation performance retested. In the redesigned system, the tar removal efficiency in the scrubber and stripper is 99%. The redesigned system would be integrated with the UC gasifier for downstream gas cleaning. Since 1% of tars are not removed, a makeup tar free CME of 0.0375 litres per hour for the 100kW UC gasifier has been introduced in the recycle stream between the scrubber and stripper to avoid tar accumulation in the system.

When developing an aircraft, one of several important aspects is to predict and properly design the dynamic behaviour of the aircraft. This holds for manned aircraft as well as for UAVs. The optimal dynamic behaviour for an aircraft depends on the mission or purpose: for a certain use an aircraft should be agile, other may require a more stable one. In aeronautics, the properties that describe the aircraft ecacy with respect to some task are known as ying qualities, and our goal is to study their dependence on some design parameters. As a test model we use an existing UAV. After deriving its 6-DOF dynamic model and assessing its baseline characteristics, we perform parametric studies. The strategy followed is divided in two steps: the rst consists on analyzing ying qualities sensitivity to changes in model parameters. The second step studies how specific design changes affect model parameters. Because the rst step only depends on the dynamic model form, we verify, by testing two other dierent aircrafts, that conclusions drawn from this step are valid to other congurations. Finally we show how results from parametric studies can be used to improve the UAV ying qualities regarding a certain mission, through the introduction of slight modications on baseline design.

The world’s energy use in buildings (residential and commercial) accounts for around 40% of the worldwide energy consumption, and space heating is the responsible for half of the energy need in the building sector. In Europe, only a small share (less than 10%) of existing buildings was built after 1990. Most of the building stock does not satisfy the recent energy technical standards; in addition there is a very low trend to construct new buildings in the last years. Renovation of the existing buildings is a feasible option to reduce the energy need in Europe, but finding the optimum solutions for a renovation is not a simple task. Each design parameter differently influences the final energy need of buildings and, furthermore, the different variables are differently correlated each other. Building refurbishment will benefit from a tool for the selection of the best measures in term of energy need. This work, through a global sensitivity analysis, aims at determining the contribution of the design parameters to the building energy demand and the correlation between the different variables. The considered parameters are related to the improvement of the thermal transmittance of both the opaque envelope and the windows, the solar transmittance of the glazing surfaces, the window size, the thermal inertia of the internal walls and the external sunshades for windows. Several dynamic simulations have been performed varying the design parameters from different starting conditions. Finally, due to the large number of cases elaborated, an inferential statistical analysis has been performed in order to identify the predominant factors and the correlation between the design parameters in a global context.

No description available.

Liquid mixture is everywhere in the chemical industry and widely studied by researchers. An accurate prediction of its physicochemical property is of vital importance in developing efficient process optimization. However, measurements from experiment are usually time consuming and inefficient. Furthermore, clear understanding of many of fundamental physicochemical phenomena hasn't been obtained, which restricts the development of novel products. Molecular simulation techniques have become an impressive tool to deal with these challenges during past decades. This thesis mainly applied molecular simulation to predict the physicochemical properties of industrially relevant mixtures and investigate the molecular mechanism behind observed phenomena. Among various properties, cohesive energy is the central focus, which reveals intermolecular interactions between molecules of different types. Mixture systems of two different areas of application were studied. The first is amorphous polymer-plasticizer mixtures, which, with varying composition, correspond to plastic products of different grades for application in different areas. The most important class of plasticizers are phthalate diesters, in which di (2-ethylhexyl) phthalate (DEHP) is the most frequently used compound. However, phthalates are prone to migration loss from the host poly(vinyl chloride) (PVC), which results in the contamination of surrounding environment, gradual deterioration of plastics performance, and potential harm to human health. It has thus prompted tightening governmental regulation on their usage. With this background, we aim to address three challenges: (I) model plasticized PVC to predict its physicochemical property, (II) obtain molecular insight into plasticization and plasticizer diffusion pattern inside PVC, (III) correlate plasticizer performance -- compatibility, efficacy, and mobility -- with its molecular structure. Cohesive energy plays a central role especially in understanding plasiticzer compatibility and migration tendency. Our modeling and simulation protocol is firstly tested on phthalates, where the simulated plasticization efficacy and thermodynamic compatibility with the host polymer agree well with all known experimental observations. Furthermore, through simulation of plasticizer diffusion pattern, we found relaxation of the alkyl side chains is a key factor in plasticizer migration. Next, we expand our simulation to a wider group of plasticizers including adipates, trimellitates, and citrates. The computed mixing enthalpy and Young's modulus again show an excellent agreement with available experimental data. Dependance of plasticizer performance on seven molecular design parameters are evaluated. The obtained relationship clearly tells us decreasing leg length or increasing branching on the leg will raise plasticizer compatibility with PVC, changing the torso group from benzene ring to alkane chain will highly improve plasticizer efficacy, and attaching three legs on the torso will decrease plasticizer mobility. As a side outcome, we also report a nontrivial chain-length dependence of the cohesive energy and solubility parameter of long-chain polymers, which is an important consideration in the calculation of these quantities using molecular simulation. The second area is azeotropes, the separation of which in chemical processes is usually very difficult due to the same composition in vapor and liquid phases at the azeotropic point. So far, a fundamental understanding of azeotrope formation is still missing. In this thesis, we aim to address two fundamental questions: (I) the mechanism for ethanol/benzene azeotrope formation, (II) classification of different polar-polar positive azeotropes. First, Gibbs ensemble Monte Carlo (GEMC) simulation is performed to predict the vapor-liquid equilibrium (VLE) phase diagram of ethanol/benzene, including an azeotrope point. The results match well with experiments. Free energy and cohesive energy profiles analyses are then performed. From a thorough liquid structure analysis, we conclude a three-stage mechanism for azeotrope formation: 1) formation of small ethanol clusters at low composition, 2) microscopic phase separation between ethanol and benzene, 3) isolation of benzene. This approach is then extended to four additional polar-polar mixtures (ethyl acetate/methanol, ethyl acetate/ethanol, ethanol/water, and 1-propanol/water) to obtain their VLE diagrams, which again match well with experiments. Free energy and cohesive energy analyses indicate that there are two types of mechanisms, a three-stage mechanism with weak cross-interactions (for the first two mixtures) and a three-stage mechanism with strong cross-interactions (for the last two mixtures). So far, our analyses on mixture liquid micro-structure can partially prove the existence and classification of those mechanisms. Overall, the successful prediction in physicochemical properties of two liquid mixtures with very different molecular scales proves the robustness of our study strategy, which could be used to study any liquid mixtures and understand their related physicochemical phenomena. / Thesis / Doctor of Philosophy (PhD)

The existing buildings in the UK are not designed to be functionally adaptive to fit a spectrum of purposes. Alternatively, scrapping these buildings and building anew does not appear to be an economically viable and environmentally sustainable solution either. Proactive solutions to respond to future potential changes of use are rare in previous and current building designs, which ultimately make these buildings functionally redundant. At present, curiosity about adaptable buildings is spreading among owners, developers and policy makers; however, no detailed investigation has been undertaken to identify the economic costs and benefits of adaptability in new buildings. Thus, the present endeavour was designed to bridge this gap. The research exploited both case studies and survey designs to explore the answers to the above problem. Two case studies were undertaken to establish that building changes occur over time, as well as to assess their economic implications in the current built environment at both macro and micro levels. Three web-based surveys (WBS) were designed and circulated among quantity surveyors and architects of the 100 leading consultancy practices in the UK to identify both the design and economic aspects of adaptability in buildings. The total numbers of respondents to WBS1, WBS2 and WBS3 were 13, 32 and 42, respectively. In addition, data was collected from semi-structured interviews with two policy makers, two structural engineers, a quantity surveyor and a facilities manager. Unstructured interviews with a senior planner, a project manager, two architects and a services engineer were used to clarify the issues of design and planning for adaptability in buildings. The findings were interwoven to develop a conceptual framework to identify the economic considerations for adaptability in new buildings. Two workshops were undertaken with the industry partners for the Adaptable Futures research project to verify the results obtained from the case studies and to test the usability of the developed conceptual framework. The group members had multi-disciplinary backgrounds of architecture, quantity surveying and structural engineering, allowing a robust grounding for verification. The results contribute to the body of knowledge in two ways. Firstly, the developed conceptual framework identifies the economic considerations (costs and benefits) for change of use in buildings within the wider context of adaptability over the lifecycle aspects. This will assist owners/clients and developers in their economic decisions for designing new buildings for potential adaptations. Secondly, the research findings strengthen the reliability of the existing body of knowledge whilst confirming the urgent need for designing new buildings towards potential adaptations. In addition, the findings strongly emphasise plan depth and floor to ceiling height as the most influential design parameters for building change of use, the details of which are not highlighted in the previous literature.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: All structures are designed for a particular set of load combinations. For roof structures the critical loading combinations are predominantly wind actions. The accumulative effect of wind actions, by wind entering through dominant openings to exert pressure on the inside of roof structures together with the suction of wind vortices on the outside of the roof, can contribute to extreme load combinations. Frequently recorded failures on roof structures suggest that either the loads are underestimated or the resisting capacity of the roof coverings is overestimated. The focus of this study is directed on the latter, determining the effective resistance of roof coverings in the form of sheeting against a Uniformly Distributed Load (UDL) such as wind actions. To determine the carrying capacity of a roofing structure, the standard approach used involves experimental tests on certain configurations with two or more spans. The structural test set-up is loaded with sandbags until failure is reached. For the design of roofing systems, design tables are used that list the maximum allowable purlin spacing. The purlin spacing is presented in the form of a fixed value in units of length and is shown independent of a UDL that the roof needs to be designed for. The need to a new approach to determining the resistance of roof covering systems was identified. The resistance of roof coverings for the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS) depends on a number of parameters such as the bending resistance, the stiffness of the sheeting in bending and the carrying capacity of the fastening system. To evaluate these structural parameters, experimental tests were performed. A full-scale experimental test setup, capable of simulating a UDL on roof sheeting, was developed. The experimental test set-up consists of four different configurations, each specifically schematized to evaluate a certain structural design parameter. The magnitude of the structural design parameters depends on the applied UDL and the span length, which is the distance between consecutive supports of the sheeting system. Therefore, by using the structural design parameters determined experimentally, a set of design tables could be generated. The design tables produce the maximum allowable span length of a roofing system that uses a desired UDL as a variable. By using the design tables, the purlin spacing for any roof structure can be calculated given its design loading combination. The calculated purlin spacings are now a function of the basic parameters that determine the resistance of the roof sheeting. / AFRIKAANSE OPSOMMING: Geen opsomming

Esta dissertação trata do apoio ergonomico durante atividades de conversa e leitura em bancos públicos quando o corpo assume variadas posturas. São estruturados parâmetros de projeto associados a dimensionamentos antropométricos relacionados a posturas observadas. Os parâmetros são incorporados à estratégia procedural para geração de formas utilizando modelo geométrico com regras de combinação. O procedimento é testado no software Rhinoceros (Grasshopper) gerando designs alternativos de bancos que, associados a parâmetros de desempenho ergonômico, são funcionalmente analisados. O sistema paramétrico formulado com as informações das posturas assumidas permitiu a estruturação de uma metodologia de projeto que otimiza as informações trazidas pelas observações de uso do objeto traduzindo-as simultaneamente, de forma automática, para o design do produto e para o processo de fabricação. / This dissertation is about ergonomic body support during activities of reading and conversation realized on public benches, when a variety of postures are assumed by users. Design parameters are structured associated to antropometric dimensions related to observed ergonomic postures. These parameters are incorpored to a procedural strategy for shape generation using a geometric model with combination rules. The procedure is tested in the software Rhinoceros (Grasshopper) allowing the generation of design options for benches that, associated to fitness ergonomic parameters, are functionally analyzed. The parametric system formulated with the information of postures adopted, enabled the construction of a design methodology that optimizes informations brought from observation of the object, relating it both, to the product design and fabrication process.

Esta dissertação trata do apoio ergonomico durante atividades de conversa e leitura em bancos públicos quando o corpo assume variadas posturas. São estruturados parâmetros de projeto associados a dimensionamentos antropométricos relacionados a posturas observadas. Os parâmetros são incorporados à estratégia procedural para geração de formas utilizando modelo geométrico com regras de combinação. O procedimento é testado no software Rhinoceros (Grasshopper) gerando designs alternativos de bancos que, associados a parâmetros de desempenho ergonômico, são funcionalmente analisados. O sistema paramétrico formulado com as informações das posturas assumidas permitiu a estruturação de uma metodologia de projeto que otimiza as informações trazidas pelas observações de uso do objeto traduzindo-as simultaneamente, de forma automática, para o design do produto e para o processo de fabricação. / This dissertation is about ergonomic body support during activities of reading and conversation realized on public benches, when a variety of postures are assumed by users. Design parameters are structured associated to antropometric dimensions related to observed ergonomic postures. These parameters are incorpored to a procedural strategy for shape generation using a geometric model with combination rules. The procedure is tested in the software Rhinoceros (Grasshopper) allowing the generation of design options for benches that, associated to fitness ergonomic parameters, are functionally analyzed. The parametric system formulated with the information of postures adopted, enabled the construction of a design methodology that optimizes informations brought from observation of the object, relating it both, to the product design and fabrication process.