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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Fabrication and Characterization of Polycarbonate Polyurethane (PCPU) Nanofibers Impregnated with Nanofillers

Katakam, Hruday chand 12 March 2015 (has links)
Polycarbonate polyurethane (PCPU) has been studied as a novel polymer impregnated with nanoparticles for improved mechanical, thermal and adhesion properties [4]. This study investigates the synthesis of polycarbonate polyurethane (PCPU) polymeric nanofiber membranes by the process of electrospinning. This study further examines all the parameters associated with electrospinning a novel PCPU polymeric solution impregnated with nanofillers, such as nanoparticles, to produce fiber membranes. Tetrahydrofuran (THF) and N, N dimethylformamide (DMF) are used as solvents to dissolve PCPU polymer. One percent (1%) of nanofillers like silver and silica nanoparticles are added to PCPU polymer solution to investigate the impact on polymer solution properties, which in turn affects the fiber formation. Process parameters are studied by evaluating the impact each parameter has on the fiber formation. PCPU polymer concentrations of three polymer solutions (PCPU, PCPU + 1% silver and PCPU + 1% silica) with the appropriate solvent mixture ratio are achieved to produce polymeric fiber membranes with minimal bead formation. Polymeric nanofiber membranes of PCPU, PCPU + 1% silver and PCPU + 1% silica are produced using THF/DMF: 70/30 (V/V) solvent mixture. The polymeric nanofiber membranes obtained are characterized by using a scanning electron microscopy, rotational viscometer, tensiometer, contact angle measurement device, fourier transform infrared spectroscopy (FTIR). A comparative life cycle assessment (LCA) is performed to evaluate environmental impacts associated with solvents in the process of producing PCPU polymeric nanofiber membranes. The LCA is completed to gauge the potential impacts PCPU nanofiber membranes may have when utilized for various applications. This study discusses the successful production and characterization of good quality (no beading) polymeric nanofiber membranes of PCPU and novel composites of PCPU + 1% silver and PCPU + 1% silica. This two dimensional production of impregnated PCPU in nanofiber form will give researchers the opportunity to capitalize on the large surface areas of PCPU nanofibers versus PCPU thin films.
22

Fabrication and Comparison of Electrospun Cobalt Oxide-Antimony Doped Tin Oxide (CoO-ATO) Nanofibers made with PS: D-limonene and PS: Toluene

Devisetty Subramanyam, Manopriya 04 November 2014 (has links)
This work investigates the fabrication, process optimization, and characterization of cobalt oxide-antimony doped tin oxide (CoO-ATO) nanofibersusing polystyrene (PS) solutions with toluene orD-limonene as solvents. These nanofibers are produced by anelectrospinning process. Nanofibers are fabricated using polymeric solutions of CoO doped ATO and mixtures of PS: D-limonene and PS:toluene. PSis a base aromatic organic polymer, a non-toxic material, and a versatile catalyst for fiber formation. PSsolutions are made by mixing polystyrene beads and D-limonene or toluene at specific weight percentages. These polymeric solutions of PS: D-limonene and PS:toluene are then mixed with CoO-ATO at various weight percentages. The two solutions are electrospun and the best process parameters optimized to obtain nanofibers with limited beading. Process optimization is completed by analyzing how changes in the electrospinningexperimental set up impact nanofiber formation and production efficiency (speed of formation). CoO-ATO nanofibers are characterizedby scanning electron microscopy, hydrophobicity via contact angle measurements, and viscosity measurements. Additional analysis is conducted to evaluate the environmental impact of using two different solvents to fabricate the CoO-ATO nanofibers. In this project, I was able to successfully produce novel nanofiber membranes of CoO-ATOusing two different solvents. These investigations were conducted and nanofiberprocess optimized to provide a technological contribution to future industrial scaleproductions of thermally reflective materials.
23

Poverty, human capital, life-cycle and the tax and transfer bases : the role of education for development and international competition

Petersen, Hans-Georg January 2011 (has links)
The paper is based on an individual life-cycle model, which describes the purely economic components of human capital. The present value of human capital is determined by all future income flows, which at the same time constitute the individual as well as the total tax base of a nation. Therefore, the income of the productive population determines the total tax revenue, which is spent for public goods (including education) and transfers (for poverty reduction). The efficient design of the education system (by private and public education investments) determines the quality of the human capital stock as well as the future gross income flows. The costs of public goods and the transfer expenditures have to be financed from the total tax revenue, which also affects the individual tax burden via the specific tax bases and tax rates. Especially the redistribution of income is connected with serious disincentives, influencing the preferences for work and leisure as well as for consumption and saving. An efficient tax and transfer system being accompanied by an education system financed in public private partnership, which treats equally labor and capital income, sets positive incentives for the formation of human, financial, and real capital. An important prerequisite for a sustainable growth process is the efficient design of the social security system, being based on the family as well as a collective risk equalization scheme. If that system is diminishing absolute poverty in an appropriate time period by transfers and vocational education measures for the grown-up as well as high quality primary, secondary and tertiary education programs for the children, the transfer expenditure would decrease and the tax bases (income and consumption) increase, lowering the burden on the productive population. For the first time, this micro model presented in this paper pools all the relevant variables for development within a simple life-cycle model, which can also be used for a powerful analysis of the current failures in existing tax and transfer schemes and fruitful empirical investigations. Hence, an efficient tax and transfer scheme strongly contributes to an improved national position in the global competition.
24

Building energy simulation of a Run-Around Membrane Energy Exchanger (RAMEE)

Rasouli, Mohammad 22 February 2011
<p>The main objective of this thesis is to investigate the energetic, economic and environmental impact of utilizing a novel Run-Around Membrane Energy Exchanger (RAMEE) in building HVAC systems. The RAMEE is an energy recovery ventilator that transfers heat and moisture between the exhaust air and the fresh outdoor ventilation air to reduce the energy required to condition the ventilation air. The RAMEE consists of two exchangers made of water vapor permeable membranes coupled with an aqueous salt solution.</p> <p>In order to examine the energy savings with the RAMEE, two different buildings (an office building and a health-care facility) were simulated using TRNSYS computer program in four different climatic conditions, i.e., cold-dry, cool-humid, hot-humid and hot-dry represented by Saskatoon, Chicago, Miami and Phoenix, respectively. It was found that the RAMEE significantly reduces the heating energy consumption in cold climates (Saskatoon and Chicago), especially in the hospital where the required ventilation rate is much higher than in the office building. On the other hand, the results showed that the RAMEE must be carefully controlled in summer to minimize the cooling energy consumption.</p> <p>The application of the RAMEE in an office building reduces the annual heating energy by 30% to 40% in cold climates (Saskatoon and Chicago) and the annual cooling energy by 8% to 15% in hot climates (Miami and Phoenix). It also reduces the size of heating equipment by 25% in cold climates, and the size of cooling equipment by 5% to 10% in hot climates. The payback period of the RAMEE depends on the air pressure drop across the exchangers. For a practical pressure drop of 2 cm of water across each exchanger, the payback of the RAMEE is 2 years in cold climates and 4 to 5 years in hot climates. The total annual energy saved with the RAMEE (including heating, cooling and fan energy) is found to be 30%, 28%, 5% and 10% in Saskatoon, Chicago, Miami and Phoenix, respectively.</p> <p>In the hospital, the RAMEE reduces the annual heating energy by 58% to 66% in cold climates, and the annual cooling energy by 10% to 18% in hot climates. When a RAMEE is used, the heating system can be downsized by 45% in cold climates and the cooling system can be downsized by 25% in hot climates. For a practical range of air pressure drop across the exchangers, the payback of the RAMEE is immediate in cold climates and 1 to 3 years in hot climates. The payback period in the hospital is, on average, 2 years faster than in the office building). The total annual energy saved with RAMEE is found to be 48%, 45%, 8% and 17% in Saskatoon, Chicago, Miami and Phoenix, respectively. The emission of greenhouse gases (in terms of CO<sub>2</sub>-equivalent) can be reduced by 25% in cold climates and 11% in hot climates due to the lower energy use when employing a RAMEE.</p>
25

Life Cycle Exergy Analysis of Wind Energy Systems : Assessing and improving life cycle analysis methodology

Davidsson, Simon January 2011 (has links)
Wind power capacity is currently growing fast around the world. At the same time different forms of life cycle analysis are becoming common for measuring the environmental impact of wind energy systems. This thesis identifies several problems with current methods for assessing the environmental impact of wind energy and suggests improvements that will make these assessments more robust. The use of the exergy concept combined with life cycle analysis has been proposed by several researchers over the years. One method that has been described theoretically is life cycle exergy analysis (LCEA). In this thesis, the method of LCEA is evaluated and further developed from earlier theoretical definitions. Both benefits and drawbacks with using exergy based life cycle analysis are found. For some applications the use of exergy can solve many of the issues with current life cycle analysis methods, while other problems still remain. The method of life cycle exergy analysis is used to evaluate the sustainability of an existing wind turbine. The wind turbine assessed appears to be sustainable in the way that it gives back many times more exergy than it uses during the life cycle.
26

Building energy simulation of a Run-Around Membrane Energy Exchanger (RAMEE)

Rasouli, Mohammad 22 February 2011 (has links)
<p>The main objective of this thesis is to investigate the energetic, economic and environmental impact of utilizing a novel Run-Around Membrane Energy Exchanger (RAMEE) in building HVAC systems. The RAMEE is an energy recovery ventilator that transfers heat and moisture between the exhaust air and the fresh outdoor ventilation air to reduce the energy required to condition the ventilation air. The RAMEE consists of two exchangers made of water vapor permeable membranes coupled with an aqueous salt solution.</p> <p>In order to examine the energy savings with the RAMEE, two different buildings (an office building and a health-care facility) were simulated using TRNSYS computer program in four different climatic conditions, i.e., cold-dry, cool-humid, hot-humid and hot-dry represented by Saskatoon, Chicago, Miami and Phoenix, respectively. It was found that the RAMEE significantly reduces the heating energy consumption in cold climates (Saskatoon and Chicago), especially in the hospital where the required ventilation rate is much higher than in the office building. On the other hand, the results showed that the RAMEE must be carefully controlled in summer to minimize the cooling energy consumption.</p> <p>The application of the RAMEE in an office building reduces the annual heating energy by 30% to 40% in cold climates (Saskatoon and Chicago) and the annual cooling energy by 8% to 15% in hot climates (Miami and Phoenix). It also reduces the size of heating equipment by 25% in cold climates, and the size of cooling equipment by 5% to 10% in hot climates. The payback period of the RAMEE depends on the air pressure drop across the exchangers. For a practical pressure drop of 2 cm of water across each exchanger, the payback of the RAMEE is 2 years in cold climates and 4 to 5 years in hot climates. The total annual energy saved with the RAMEE (including heating, cooling and fan energy) is found to be 30%, 28%, 5% and 10% in Saskatoon, Chicago, Miami and Phoenix, respectively.</p> <p>In the hospital, the RAMEE reduces the annual heating energy by 58% to 66% in cold climates, and the annual cooling energy by 10% to 18% in hot climates. When a RAMEE is used, the heating system can be downsized by 45% in cold climates and the cooling system can be downsized by 25% in hot climates. For a practical range of air pressure drop across the exchangers, the payback of the RAMEE is immediate in cold climates and 1 to 3 years in hot climates. The payback period in the hospital is, on average, 2 years faster than in the office building). The total annual energy saved with RAMEE is found to be 48%, 45%, 8% and 17% in Saskatoon, Chicago, Miami and Phoenix, respectively. The emission of greenhouse gases (in terms of CO<sub>2</sub>-equivalent) can be reduced by 25% in cold climates and 11% in hot climates due to the lower energy use when employing a RAMEE.</p>
27

Exploring the Environmental Impact of A Residential Life Cycle, Including Retrofits: Ecological Footprint Application to A Life Cycle Analysis Framework in Ontario

Bin, Guoshu January 2011 (has links)
The residential sector is recognized as a major energy consumer and thus a significant contributor to climate change. Rather than focus only on current energy consumption and the associated emissions, there is a need to broaden sustainability research to include full life cycle contributions and impacts. This thesis looks at houses from the perspective of the Ecological Footprint (EF), a well-known sustainability indicator. The research objective is to integrate EF and Life Cycle Analysis (LCA) measures to provide an enhanced tool to measure the sustainability implications of residential energy retrofit decisions. Exemplifying single-detached houses of the early 20th century, the century-old REEP House (downtown Kitchener, Canada), together with its high performance energy retrofits, is examined in detail. This research combines material, energy and carbon emission studies. Its scope covers the life cycle of the house, including the direct and indirect consumption of material and energy, and concomitant carbon emissions during its stages of material extraction, transportation, construction, operation, and demolition. The results show that the REEP House had a significant embodied impact on the environment when it was built and high operating energy and EF requirements because of the low levels of insulation. Even though the renovations to improve energy efficiency by 80% introduce additional embodied environmental impacts, they are environmentally sound activities because the environmental payback period is less than two years.
28

Environmental comparison of Michelin Tweel and pneumatic tire using life cycle analysis

Cobert, Austin 03 September 2009 (has links)
Recently Michelin has been developing a new airless, integrated tire and wheel combination called the Tweel. The Tweel promises performance levels beyond those possible with conventional pneumatic technology because of its shear band design, added suspension, and decreased rolling resistance. However, many questions remain as to what kind of environmental impact this radical new design will have. The environmental impact of the Tweel will be compared to a current radial tire used on BMWs, but because of the complexity in manufacturing, using, and disposing these tires it is somewhat difficult to compare environmental problems. Currently there are environmental issues all throughout a tire's lifespan from rubber manufacturing emissions to tire disposal, and the rapidly growing method to evaluate all of these points is Life Cycle Analysis (LCA). LCA is the essential tool required by businesses in order to understand the total environmental impact of their products - cradle-to-grave. By considering the entire life cycle of a Tweel from manufacturing, through use and disposal, and comparing it to knowledge of current tires, an accurate assessment of the entire environmental impact of the Tweel will be made. Since the Tweel is currently still in the research phase and is not currently manufactured and used however, there are uncertainties with respect to end-of-life scenarios and rolling resistance estimates that will affect the LCA. Thus, it will be important to consider a range of options to determine which one will have the most environmental benefits while still keeping the strengths of the Tweel design intact.
29

Evaluation of scrap tire-derived porous rubber tubing as a green membrane for sustainable water filtration (ECOL-Mem process)

Garcia, Ana Maria 01 June 2007 (has links)
Increasing population and extensive urbanization have strained resources around the world, promoting water scarcity and solid waste accumulation. Addressing the issues of access to safe drinking water and basic sanitation in developing countries is challenging due to limited technological and financial resources. Therefore, it is imperative that durable, low-cost, and sustainable technologies are developed to help alleviate these problems. At the same time, the production of solid waste has increased and includes waste tires, which pose a health and environmental hazard. Although efforts have been made to develop new markets for recycled scrap tires, a vast majority are still being stockpiled or landfiled. This study aims to evaluate a water treatment system that addresses the problem of access to safe drinking water and sanitation, while providing a new market for recycled scrap tires. The system, termed ECOL-Mem, utilizes commercially available porous rubber tubing (PRT), which is marketed for drip irrigation purposes. To our knowledge, this is the first time this product has been used in a water treatment system. The PRT is manufactured through a hot extrusion process and contains 65% recycled crumb rubber and a binder (e.g. polyethylene). The proposed configuration simulates a hollow fiber membrane filtration system driven by a vacuum that operates inside-out. The system was first tested using clean water to obtain intrinsic characteristics. It was then tested using bentonite and sludge solutions that simulated impaired source water. For the case of a bentonite solution containing 700 mg/L, 20L of permeate could be obtained in one hour while the total solids removal remained around 20%. In order to improve the water quality, a flocculation-enhanced filtration phase was explored. The flocculant is chitin, a biopolymer that can be derived from waste shellfish. Upon addition of the chitin, between 60% and 70% of total solids removal could be obtained for different feed waters. Although optimization is needed, the PRT system has shown promising results, while providing a technology that targets the needs of developing countries in the areas of safe drinking water, basic sanitation, and solid waste recycling.
30

Environmental impact and performance of transparent building envelope materials and systems

Robinson-Gayle, Syreeta January 2003 (has links)
Building envelopes are elements with a long lifetime, which provide a barrier between internal and external space and contribute to the internal environmental conditions provision. Their complex role ensures a large impact on the environmental and energy performance of a building and the occupant perception of a space. This study looks at the use of novel materials and processes to help reduce the environmental impact of buildings by improving facade and transparent roof design. There are three main strands to the work. First, novel building components, ETFE foil cushions were examined. Physical testing has shown that ETFE foil cushions compare favourably to double glazing in terms of thermal and daylighting performance which was also noted as one of the most likeable feature by occupants. Environmental impact analysis has indicated that ETFE foils can reduce the environmental impact of a building through reduced environmental burden of both the construction and operation of the building. Secondly, a cradle-to-gate Life Cycle Analysis (LCA) was carried out for float glass, which considered the environmental impacts of glass manufacture. The embodied energy was calculated to be 13.4 ± 0.5 GJ per tonne while the total number of eco-points 243 ± 11 per tonne. It is shown that float glass is comparable to the use of steel, and highly preferable to the use of aluminium as a cladding panel. Finally, a concept design tool (FACADE) was developed by defining a large number of office facade models and employing dynamic thermal, daylighting and environmental impact modelling to create a database which can be accessed through a user friendly interface application. A parametric analysis has indicated that using natural ventilation where possible can reduce the environmental impact of offices by up to 16%. Improving the standard of the facade and reducing the internal heat loads from lighting and equipment can reduce environmental impact up to 22%. This study makes a significant contribution to understanding the environmental impact of building envelope individual and integrated components.

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