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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

Cellulose fiber dissolution in sodium hydroxide solution at low temperature: dissolution kinetics and solubility improvement

Wang, Ying 31 July 2008 (has links)
Sodium hydroxide can cause cellulose to swell and can even dissolve cellulose in a narrow range of the phase diagram. It was found that for cellulose with low to moderate degree of polymerization, the maximal solubility occurs with 8~10% soda solution. In recent years, researchers found that sodium hydroxide with urea at cold temperature can dissolve cellulose better than sodium hydroxide alone. However, the lack of sufficient understanding of the NaOH and NaOH/urea dissolution process significantly constrains its applications. In order to fully understand the cellulose dissolution in alkali system, there are several aspects of problems that need to be addressed. Our focus in this study is in the interaction of cellulose with alkali solution at low temperatures, the improvement of its solubility, and the effect of hemicellulose and lignin.
22

Novel sustainable solvents for bioprocessing applications

Kassner, Michelle Kimberly 17 November 2008 (has links)
Bioprocessing applications are gaining importance in the traditional chemical industries. With environmental, political, and economical concerns growing, research efforts have recently focused on the substitution of petroleum-derived transportation fuels and materials. As possible products and feedstocks are being investigated, it is important to ensure the new processes are also sustainable. There are several aspects to developing sustainable processes: minimize waste, use environmentally-benign chemicals, find renewable feedstocks, and limit the number of processing steps. This thesis examines ways to enhance the sustainability of bioprocesses. Novel, alternative solvent systems are studied and applied to a variety of bioprocesses. Downstream processing steps and waste can be minimized by designing systems that combine reactions and separations into one process unit. This is accomplished by designing new reactor systems and by replacing currently used solvents. Additional studies, involving analytical techniques that reduce the use of organic solvents, are tested and applied to industrial problems. Finally, new solvent systems are examined for potential processes using renewable carbohydrate feedstock.
23

Including severe uncertainty into environmentally benign life cycle design using information gap-decision theory

Duncan, Scott Joseph. January 2008 (has links)
Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Bras, Bert; Committee Member: Allen, Janet; Committee Member: Chameau, Jean-Lou; Committee Member: McGinnis, Leon; Committee Member: Paredis, Chris.
24

Laccase in organic synthesis and its applications

Witayakran, Suteera. January 2008 (has links)
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009. / Committee Chair: Ragauskas, Arthur; Committee Member: Bunz, Uwe; Committee Member: Cairney, John; Committee Member: Collard, David; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.
25

Thermodynamic input-output analysis of economic and ecological systems for sustainable engineering

Ukidwe, Nandan Uday, January 2005 (has links)
Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xxiii, 306 p.; also includes graphics (some col.) Includes bibliographical references (p. 297-306). Available online via OhioLINK's ETD Center
26

Managing energy efficiency in base stations for green cellular networks

Mwashita, Weston January 2016 (has links)
With the astronomical increase in cellular traffic, there is need to cut down on the power consumption so as to reduce CO2 emissions and in the process lowering network operational expenditure (OPEX). In this thesis, one method that can be used to lower a Base Station energy consumption is proposed. Traditional cellular networks are designed to offer maximum coverage and connectivity for peak traffic. This is not energy efficient since a lot of energy will go to waste during the time cellular traffic is very low. The scheme that was developed, identifies Base Stations that have very low traffic loads and User Equipment that can all be transferred to neighbouring Base Stations and put the Base Stations to sleep for as long as necessary to save energy and to maintain Quality of Services (QoS) at an acceptable level. The Next Generation Networks (specifically 5G) will be heterogeneous networks as heterogeneous are a promising solution in increasing network performance especially in providing indoor and cell-edges coverage. The solution that was developed in this thesis was specifically designed to work with heterogeneous networks and its performance was also tested on heterogeneous networks. OMNeT++ V4.6 together with INET 2.3.0 and SimuLTE 9.1 were used for the validation of the proposed scheme. After extensive simulations were carried out, it was concluded that some Base Stations in a cellular network, can be put to sleep during the time that cellular traffic is low without compromising the Quality of Service. End-to-end delay, sum throughputs, queue length and Channel Quality Indicator were some of the performance metrics that were used to check whether the developed scheme did not reduce the QoS of a network. / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)
27

An Emerging Technology Assessment of Factory-Grown Food

January 2014 (has links)
abstract: In vitro, or cultured, meat refers to edible skeletal muscle and fat tissue grown from animal stem cells in a laboratory or factory. It is essentially meat that does not require an animal to be killed. Although it is still in the research phase of development, claims of its potential benefits range from reducing the environmental impacts of food production to improving human health. However, technologies powerful enough to address such significant challenges often come with unintended consequences and a host of costs and benefits that seldom accrue to the same actors. In extreme cases, they can even be destabilizing to social, institutional, economic, and cultural systems. This investigation explores the sustainability implications of cultured meat before commercial facilities are established, unintended consequences are realized, and undesirable effects become reified and locked in. The study utilizes expert focus groups to explore the social implications, life cycle analysis to project the environmental implications, and economic input-output assessment to explore tradeoffs between conventionally-produced meat and factory-grown food products. The results suggest that, should cultured meat be widely adopted by consumers, food is likely to be increasingly a product of human design, perhaps becoming integrated into existing human institutions such as health care delivery and education. Environmentally, cultured meat could require smaller quantities of agricultural inputs and land than livestock. However, those avoided costs could come at the expense of more intensive energy use as biological processes are replaced with industrial systems. Finally, the research found that, since livestock production is a driver of significant economic activity, shifting away from traditional meat production in favor of cultured meat production could result in a net economic contraction. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2014
28

The green township infrastructure design toolkit : creating eco efficient engineering solutions

Saroop, Shian Hemraj January 2017 (has links)
Submitted in fulfillment of the academic requirements for the degree of Doctor of Engineering, Department of Civil Engineering and Surveying, Durban University of Technology, Durban, South Africa, 2017. / There is a growing need for co-ordination of design, sustainability, economic and environmental aspects of infrastructure projects. The provision of civil infrastructure has a major impact on the natural environment and on the quality of life. A literature review conducted highlighted that infrastructure development was focused mainly on the financial and engineering aspects of projects. There is an urgent need to apply technologies and methods that deliver better and more sustainable performance of civil infrastructure as well as a need to establish a standard of measurement for greener infrastructure. The literature review revealed that the existing tools do not adequately rate and monitor civil engineering infrastructure design decisions from concept stage, through to detailed design and implementation. The objectives of the research were to identify green design technologies that can be used in township infrastructure and to encourage sustainable design on infrastructure township services, at various stages of the project. This would require the development of a green reporting system that incorporates environmentally friendly infrastructure design solutions. This study identified alternative eco-efficient civil infrastructure design solutions and developed sustainability criteria to analyse the eco-efficiency of infrastructure projects. The study proposed a Green Township Infrastructure Design Toolkit aimed at ensuring high-performance, eco-efficient, economical and environmentally friendly design decisions on stormwater, roads, water and sanitation related to township infrastructure projects. Various case studies were undertaken on a range of infrastructure projects to ensure consistency and reliability of the toolkit. Through a series of green reports, developed for each stage of a project, the toolkit measured the environmental efficiency of the design solutions. Recommendations suggest that engineering practitioners should endeavour to integrate greener engineering solutions into the traditional method of designing of infrastructure projects. The Green Township Infrastructure Design Toolkit with the use of its green reporting tools ensures the design of sustainable township infrastructure services, by progressively ensuring efficient, affordable, economical and sustainable provision of infrastructure services. / D
29

Technical and Financial Viability of Utilizing Waste Heat for Chilled Water Production and Biomass for Heating Applications in Hospitality Industry

Godawitharana, Sampath, Rajaratne, Rohitha January 2012 (has links)
The purpose of the thesis is to determine the potential of lessening the high energy cost in the hospitality industry so that the industry could stay alive after a three decades of civil war in Sri Lanka. The hospitality industry is a significant contributor to the country’s economic growth. Tourism industry has much hope of recovering in the year 2010. Improved tourism would also benefit larger part of Sri Lankan population as they are directly and indirectly employed to serve the tourism industry. Sri Lanka has a high electricity production cost as it depends heavily on the imported fossil fuel. Survival of hospitality industry would depend on the manner in which the energy cost - the second highest overhead in hotels is managed. If the industry survives, Sri Lanka would receive more foreign exchange and thereby improve country’s foreign currency reserve which could contribute to high growth rate. As electricity production is mainly depending on thermal, the volatility of world crude oil prices is directly affecting the country’s electricity prices. However, low dependence on the grid would help the hospitality industry to mitigate the energy cost. As the electricity and diesel costs -the highest and the next - are considerable portions in energy cost in hospitality industry, the study aims to discuss the possible ways of mitigating such costs. Measurements done by the presenters found that the usage of electricity for air conditioning system does constitute most of the electricity consumption for a hotel whilst most of the diesel consumption is for thermal applications. If Air Conditioning (AC) can be operated without electricity and thermal applications could be operated using abundantly available alternative energy sources then the overall energy costs of hospitality industry could be reduced thereby making higher profits. This would ensure industry survives and country gets more foreign exchange.  Study and calculations done by the presenters proved that operating of generators only for electricity production is not viable, due to high fossil fuel cost, however if its high exhaust temperature which is wasted otherwise, could be utilized for operation of absorption chillier then the dependence of grid electricity for air conditioning could be minimized. Further studies also revealed that if water cooled generator is used for such purpose instead of air cooled, and then the hot water requirement of hotel also could be fulfilled, thus mitigating the dependence of fossil fuel which is used otherwise for hot water production. Study also revealed that if thermal energy could be fed with biomass- Sri Lanka being a tropical country is blessed with abundantly available biomass - then the dependency on the fossil fuel for thermal applications could be avoided. This would not only mitigate the second highest energy cost for hotels but also create less carbon foot print, more environmental friendly and produce less noxious exhaust gases thereby creating an advertisement to attract tourists who longing to support green hotels
30

Rainwater harvesting på Storsudret : Potential för implementering på södra Gotland / Rainwater harvesting at Storsudret : Potential for implementation on southern Gotland

Ahlgren, Ellen, Nordborg, Mikael January 2019 (has links)
Vattenbrist är ett stort problem i många delar av världen. En lösning som tar vara på nederbörden och eventuellt kan säkerställa vattenförsörjningen lokalt är rainwater harvesting metoden. Det som denna rapporten analyserar är huruvida det finns potential att implementera rainwater harvesting system på Storsudret, på södra Gotland. Projektet inleddes med en litteraturstudie över befintliga metoder för rainwater harvesting. En sammanställning och utvärdering har gjorts för vad som lämpar sig för området. Detta tillsammans med data från lokala myndigheter, SMHI och Lantmäteriet har analyserats och sammanställts med hjälp av programmen Excel och ArcMap för att bedöma potentialen. Resultatet av rapporten visar att, utifrån de beräkningar och kartanalyser som gjorts, potential finns för rainwater harvesting metoder på Storsudret, Gotland. De bidragande faktorerna till hur stor potential metoden har är nederbördens fördelning över året, den totala mängden nederbörd samt boendesituationen som råder på Storsudret. Boendesituationen handlar främst om storleken på takytor i relation till antalet människor som är bosatta i de fem socknar som utgör området. Slutsatsen av i hur stor grad rainwater harvesting lösningar kan påverka det enskilda hushållets vattenförsörjning är individuellt, och beror på främst på hushållens förbrukning, takyta och lagringspotential. Lösningar som denna bidrar inte enbart med minskad belastning på grundvattendepåerna, utan hjälper även de hushåll där vattnet är otjänligt och/eller där det kommunala vattennätet inte är tillgängligt. Rainwater harvesting är därför en ingenjörsteknik som kan vara en del av det vattenbristproblem som råder, inte bara på Storsudret, utan även på andra platser i Sverige och världen med vattenbrist på grund av gällande hydrogeologiska förutsättningarna. / Many places around the world, including parts of Sweden, suffers from seasonal lack of water. This can be dealt with by storing precipitation in times when the availability is good. One example of such an area is Storsudret on the southernmost part of Gotland. The focus of this report was to analyze the potential of implementing rainwater harvesting methods in Storsudret. The project was initiated with a literature study of existing methods for rainwater harvesting and an evaluation was made whether or not they were suited for the area and data from SMHI and Lantmäteriet was analyzed and compiled in Excel and ArcMap to assess the potential for rainwater harvesting. What this report shows, according to the calculations and map analysis made, is that there is potential in applying rainwater harvesting methods to the area Storsudret, Gotland. The main factors include the meteorological conditions, more specifically, the general spread of precipitation over a year and to the total amount of precipitation in a year. This together with the other factors is needed to evaluate if rainwater harvesting is a viable option for water supply at Storsudret. The other factors are mainly the size of rooftops in relation to the amount of people living in this area. Depending on each households’ own conditions, mainly water usage, rooftop size and storage capacity, the extent of which rainwater harvesting can be applied, varies. These types of solutions can not only help with a less stress on the groundwater storage, but it can also help those households that doesn’t have acceptable groundwater quality or cannot be connected to the municipal water systems. What this comes to show is that rainwater harvesting is an engineering technique that could help solve problems concerning shortage of water, not only at Storsudret, but also in other places in Sweden or in the world.

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