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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.
551

Optimal Control and Its Application to the Life-Cycle Savings Problem

Taylor, Tracy A 01 January 2016 (has links)
Throughout the course of this thesis, we give an introduction to optimal control theory and its necessary conditions, prove Pontryagin's Maximum Principle, and present the life-cycle saving under uncertain lifetime optimal control problem. We present a very involved sensitivity analysis that determines how a change in the initial wealth, discount factor, or relative risk aversion coefficient may affect the model the terminal depletion of wealth time, optimal consumption path, and optimal accumulation of wealth path. Through simulation of the life-cycle saving under uncertain lifetime model, we are not only able to present the model dynamics through time, but also to demonstrate the feasibility of the model.
552

Optimisation of membrane technology for water reuse

Raffin, Marie January 2011 (has links)
Increasing freshwater scarcity is making reclamation of wastewater effluent more economically attractive as a means of preserving freshwater resources. The use of an integrated membrane system (IMS), the combination of micro/ultra-filtration (MF/UF) followed by reverse osmosis (RO) membranes, represents a key process for municipal wastewater reuse. A major drawback of such systems is the fouling of both the MF/UF and RO membranes. The water to be treated by the IMS system varies from one wastewater treatment plant (WWTP) to another, and its fouling propensity changes correspondingly. It is thus preferable to conduct pilot trials before implementing a full-scale plant. This thesis aims to look at the sustainability of IMS technology dedicated to indirect potable reuse (IPR) in terms of fouling minimisation and cost via a 600 m3 .d- 1 pilot plant. Wastewater reuse plants, using IMS, as well as statistical methods for membrane optimisation were reviewed. Box-Behnken design was used to define optimum operating envelopes of the pilot plant for both the microfiltration and the reverse osmosis in terms of fouling minimisation. Same statistical method was used to enhance the efficiency of the MF cleaning-in place through bench-scale test. Data from the pilot plant MF process allow to determine relationship between reversible and irreversible fouling, and operating parameters and feed water quality. Life cycle cost analysis (LCCA) of the both trains (MF/RO/AOP and MF/AOP) of the pilot plant was performed and compared with the LCCA of two full-scale plant.
553

Techno-economic environmental risk analysis of advanced biofuels for civil aviation

Lokesh, Kadambari January 2015 (has links)
Commercial aviation has demonstrated its ability to be a key driver of global socio-economic growth to this date. This growth, resulting from an ever increasing need for air-travel, has been observed to be environmentally unsustainable. Any technological enhancements to the upcoming fleet of aircraft or operational improvements have been overshadowed by this very demand for air-travel. Any further investigation into innovative concepts and optimisation approaches bring in trade-off difficulties due to limitations in current technology. This creates a constraint on design space exploration. The need to mitigate civil aviation’s environmental impact has necessitated this sector to expand its frontier and seek radical technologies. Among a range of other technologies, advanced biofuels for civil jet engines have been claimed to be one of the most promising solutions. “Techno-economic Environmental Risk Analysis (TERA) of Advanced Biofuels for Civil Aviation” is a study that contributes to knowledge through conception plus application of quantitative/ qualitative approaches to assess the technical viability, financial feasibility and environmental competence of 2nd and 3rd generation biojet fuels, through their application into the existing scenario of civil aviation, against that of the fossil-derived conventional jet fuel (Conv.Jet fuel). TERA of advanced biofuels aims to accomplish the aforementioned through a holistic, multi-disciplinary study entailing life cycle studies, carbon-foot printing, sustainability analysis, fuel chemistry, virtual studies comprising combustion thermodynamic, engine/aircraft performance and emission prediction, economic studies entailing biofuel price prediction and business case analysis as opposed to earlier studies. TERA of Advanced biofuels study entails development of elaborate life cycle models, ALCEmB (Assessment of Life Cycle Emissions of Biofuels) and ALCCoB (Assessment of Life Cycle Cost of Biofuels) to predict life cycle emissions and costs, respectively, of the advanced biofuels from the point of raw material generation to the point of finished product consumption (a “cradle-grave” approach). A virtual experiment, to assess the impact of the “performance” properties of the advanced biofuels on a representative twin-shaft turbofan/airframe combination, relative to that of Conv.Jet fuel, was also undertaken through numerical modelling and simulation.Evaluation through ALCEmB revealed that Camelina-SPK, Microalgae-SPK and Jatropha-SPK delivered 70%, 58% and 64% savings in life cycle emission, relative to Conv.Jet fuel. The Net Energy Ratio (NER) analysis indicates that current technology for the biofuel processing is energy efficient and technically feasible. An elaborate post-combustion gas property evaluation infers that the Bio-SPKs exhibit improved thermodynamic behaviour. This thermodynamic effect has a positive impact on mission-level fuel consumption which reflected as fuel savings in the range of 3 - 3.8% and, therefore, emission savings of 5.8-6.3% in CO2 and 7.1-8.3% in LTO NOx, relative to that of Jet-A1. An economic feasibility analysis which entails prediction of hypothetical biofuel price prediction and its impact on direct operating cost (DOC) of an aircraft which infers that Bio-SPKs, over a user-defined medium-range mission profile, costs an additional 95-100% in terms of aircraft DOC, relative to that operated with conventional Jet-fuel, within short (2020) and medium (2020). However, the advanced biofuels are able to exhibit financial competence from 2020 onwards, relative to that of Conv.Jet fuel. However, the Bio-SPKs exhibit this economic feasibility only against a backdrop of persistent Conv.Jet fuel price volatility and severe environmental taxation between the analysis periods (2020-2075).
554

Právní regulace nakládání s obaly a odpady z obalů / Legal regulation of packaging and package waste management

Bílová, Petra January 2014 (has links)
This work aims to analyze legislation on the management of packaging and packaging waste. The object of the research is European legislation from the Czech -based treatment, which are discussed in detail. The focus of the work is the chapter dealing with the life cycle of the packaging. The rights and obligations of responsible persons related to different stages of the life cycle of the packaging are in Act No. 477/2001 Coll., On packaging and related regulations set out in detail so as to fulfill one of the basic principles of packaging issues "From the cradle to the grave." The work aims at the systematic distribution of these rights and obligations of the different stages. The last chapter focuses attention on beverage containers, specifically comparing the environmental impact of one-way and returnable beverage containers.
555

Posuzování životního cyklu ražby tunelové stavby metodou NRTM / LCA of NATM tunnel stamping method

Pokorná, Alice January 2016 (has links)
The aim of this thesis was to evaluate the environmental impacts of NATM tunnelling method using the assembly of LCA studies. Construction sector still has large potential for advancement, and therefore is a subject of interest for also for LCA studies. Underground constructions applies more with growing demands for space in infrastructure. If sustainable growth in construction is desired, it's important to have an idea about the environmental impacts of this sector. Sustainable growth requires methods and tools for measurement and comparison of impacts of human activities on the environment. These tools are provided by LCA studies, which also allow a proactive approach. The advantage of LCA is a preview of the entire life cycle of the product, so there is no shifting of problems between the individual stages of the product's life cycle. LCA study of cradle-to-gate type was selected to evaluate New Austrian tunnelling method. LCA study was done for one tunnel, length 850m with cross-section surface of 13,46m2 excavated by the NATM method, realized over the course of 18 months. GaBi 6 software tool was used for making of this study. Results show that the most important emission sources of NATM tunnelling method are production of cement, dumping of excavated material, production of reinforcing steel...
556

Fuel, Feedstock, or Neither? – Evaluating Tradeoffs in the use of Biomass for Greenhouse Gas Mitigation

Posen, I. Daniel 01 December 2016 (has links)
Biomass is the world’s largest renewable energy source, accounting for approximately 10% of global primary energy supply, and 5% of energy consumed in the United States. Prominent national programs like the U.S. Renewable Fuel Standard incentivize increased use of biomass, primarily as a transportation fuel. There has been comparatively little government support for using biomass as a renewable feedstock for the chemical sector. Such asymmetry in incentives can lead to sub-optimal outcomes in the allocation of biomass toward different uses. Greenhouse gas reduction is among the most cited benefits of bioenergy and bio-based products, however, there is increasing controversy about whether increased use of biomass can actually contribute to greenhouse gas emission targets. If biomass is to play a role in current and future greenhouse gas mitigation efforts its use should be guided by efficient use of natural and economic resources. This thesis addresses these questions through a series of case studies, designed to highlight important tradeoffs in the use of biomass for greenhouse gas mitigation. Should biomass be used as a fuel, a chemical feedstock, or neither? The first case study in this thesis focuses on the ‘fuel vs feedstock’ question, examining the greenhouse gas implications of expanding the scope of the U.S. Renewable Fuel Standard to include credits for bioethylene, an important organic chemical readily produced from bioethanol. Results suggest that an expanded policy that includes bioethylene as an approved use for ethanol would provide added flexibility without compromising greenhouse gas targets – a clear win scenario. Having established that bioethylene based plastics can achieve similar greenhouse gas reductions to bioethanol used as fuel, this thesis expands the analysis by considering how the greenhouse gas emissions from a wider range of bio-based plastics compare to each of the main commodity thermoplastics produced in the U.S. The analysis demonstrates that there are large uncertainties involved in the life cycle greenhouse gas emissions from bio-based plastics, and that only a subset of pathways are likely to be preferable to conventional plastics. The following chapter then builds on the existing model to compare the greenhouse gas mitigation potential of bio-based plastics to the potential for reducing emissions by adopting low carbon energy for plastics production. That chapter concludes that switching to renewable energy across the supply chain for conventional plastics energy cuts greenhouse gas emissions by 50-75%, achieving a greater reduction, with less uncertainty and lower cost, than switching to corn-based biopolymers – the most likely near-term biopolymer option. In the long run, producing bio-based plastics from advanced feedstocks (e.g. switchgrass) and/or with renewable energy likely offers greater emission reductions. Finally, this thesis returns to the dominant form of policy surrounding biomass use: biofuel mandates. That study takes a consequential approach to the ‘fuel or neither’ question. Specifically, this work examines how petroleum refineries are likely to adjust their production in response to biofuel policies, and what this implies for the success of these policies. The research demonstrates that biofuel policies induce a shift toward greater diesel production at the expense of both gasoline and non-combustion petroleum products. This has the potential to result in an increase in greenhouse gas emissions, even before accounting for the emissions from producing the biofuels themselves.
557

Invasion potential and colonization dynamics of Fusarium proliferatum

Reyes Gaige, Andres Jose January 1900 (has links)
Doctor of Philosophy / Department of Plant Pathology / James Stack / The trade of food, plant, and animal products has increased the worldwide movement and establishment of exotic pathogens with dramatic negative impacts on plant systems. Fusarium proliferatum is a broad host-range pathogen and among the most common maize pathogens globally. It is often seed-borne and symptomless in maize, making it a high risk for introduction in maize and other grains. Considering the global distribution of maize and the wide host range and production of mycotoxins by F. proliferatum, a better understanding of its life history is needed. To provide markers for tracking F. proliferatum in laboratory experiments, strains of F. proliferatum were transformed to express a green fluorescent protein (GFP). Active dispersal (at least 1.5cm at 25°C and -50mb soil matric potential) and colonization of organic matter in nonsterile field soil was demonstrated in soil microcosms. Fusarium verticillioides is commonly isolated from maize seed also colonized by F. proliferatum. A red fluorescent (mRFP) F. verticillioides transformant was developed to study competition with F. proliferatum. For quantification in host tissues, a TaqMan multiplex qPCR protocol was developed using primer and probe sets targeting fragments of the green and red fluorescence genes to detect F. proliferatum and F. verticillioides, respectively. Prior colonization of maize tissues by F. verticillioides (p=0.6749) and other seed-borne microorganisms (p=0.1910) did not affect subsequent colonization by F. proliferatum. Genotyping-by-sequencing (GBS) was used to identify genetic markers in F. proliferatum. Primer sets based GBS markers were designed to allow detection of specific isolates in field experiments. F. proliferatum populations were characterized from maize seed prior to planting and again after harvest. End-point PCR identified F. proliferatum isolates containing the GBS marker. AFLP-fingerprinting indicated that 23 of the 817 F. proliferatum isolates contained the molecular marker and were genetically related to the original isolate. Based on the subclade and percentage similarity in UPGMA phylogenetic trees, and the population grouping observed in STRUCTURE and Principal Coordinate Analysis, these isolates could have a single origin and be clonal. Understanding the life cycle of F. proliferatum is critical for learning more about the risk of introducing seed-borne exotic isolates into new environments.
558

Risk Management in Sustainable Projects in the Construction Industry : Cases of Swedish Companies

Apine, Anete, Escobar Valdés, Francisco José January 2017 (has links)
Sustainable construction projects are expanding in the market and green codes andstandards are advancing giving the ground for development of technology and materialsapplied. With every new material and technology utilised in the field, also risks aregrowing. The importance of risk management in sustainable construction projects isthus increasing and more experience and expertise is needed. So, the purpose of thisthesis is to examine and gain deeper understanding of project related risks in sustainableconstruction projects in Swedish companies operating in built environment. It is crucialto gain knowledge of good practices within the industry to be able to propose furtherinvestigation of the subject that could improve the existing risk management andsustainable construction project goals.This thesis examines the existing theory of the risk management process and sustainableprojects by shedding light on the trends within the construction industry. The intentionof the thesis is to add value to the existing gap in the theory that suggests thatconstruction industry is exposed to more risks and uncertainty than perhaps otherindustries, and that introducing sustainability adds more uncertainties and risks. Thisphenomenon is claimed to be due to the lack of knowledge and experience in the areaand, thus, practitioners seek for new ways how to tackle the arising issues. This thesisattempts to display how Swedish companies who are working with green and highperformance buildings identify and deal with risks.Two Swedish companies operating in built environment were chosen in order toinvestigate different ways of dealing with risks and the trend of sustainability inconstruction. Those in charge of risk and sustainability within the companies wereinterviewed applying semi-structured interviews and additional information wasgathered through multiple sources, such as annual reports, web pages and otherdocuments. This thesis has exploratory and qualitative research design and appliesabductive approach for the purpose and the nature of phenomena.The findings showed the different tools how risk management is applied in thecompanies and how it is related to the risks faced in green building construction. Theresults showed the importance of tools applied tackling sustainable construction projectsthat companies have applied and added to their processes in order to manageuncertainties that could occur if these processes were not implemented. As regards thegeneralisability towards findings, there still could be added more companies and futureresearch could imply also maturity of the companies to make findings more precise.However, after consideration of the processes learnt from companies, the proposedmodel for achievement of successful sustainable construction projects can be followedand applied in other companies operating in this industry.
559

Constructing a Community Response Grid (CRG): The Dublin, Ohio Case Study

Freund, John 01 January 2012 (has links)
During an emergency, information availability is critical to preserving life and minimizing damages. During the emergency response, however, information may not be available to those who need it. A community response grid (CRG) can help ameliorate this lack of availability by allowing people to document and distribute emergency information to professional emergency responders (PERs). A CRG combines mobile communications services, Internet technologies, e-government applications, and social network concepts with traditional emergency response systems. The problem that this case study investigated was how to construct a CRG for the City of Dublin, Ohio, Division of Police that works in conjunction with an in-place emergency management system (EMS). The goal was to create a process that is replicable by similarly sized cities that wished to implement a CRG. In this investigation, the author examined CRG design and implementation issues such as message origin, training needs, policy design, security issues, and funding. The results of this investigation were organized in terms of Systems Development Lifecycle (SDLC) phases. Throughout these phases, the author identified information that can aid PERs in to better implement a CRG. Based on the results, the author developed a paradigm for constructing a CRG that meets the requirements of residents of the City of Dublin, Ohio, Division of Police and of similarly sized municipalities.
560

Phenotypic evolution and adaptive strategies in marine phytoplankton (Coccolithophores)

Šupraha, Luka January 2016 (has links)
Coccolithophores are biogeochemically important marine algae that interact with the carbon cycle through photosynthesis (CO2 sink), calcification (CO2 source) and burial of carbon into oceanic sediments. The group is considered susceptible to the ongoing climate perturbations, in particular to ocean acidification, temperature increase and nutrient limitation. The aim of this thesis was to investigate the adaptation of coccolithophores to environmental change, with the focus on temperature stress and nutrient limitation. The research was conducted in frame of three approaches: experiments testing the physiological response of coccolithophore species Helicosphaera carteri and Coccolithus pelagicus to phosphorus limitation, field studies on coccolithophore life-cycles with a method comparison and an investigation of the phenotypic evolution of the coccolithophore genus Helicosphaera over the past 15 Ma. Experimental results show that the physiology and morphology of large coccolithophores are sensitive to phosphorus limitation, and that the adaptation to low-nutrient conditions can lead to a decrease in calcification rates. Field studies have contributed to our understanding of coccolithophore life cycles, revealing complex ecological patterns within the Mediterranean community which are seemingly regulated by seasonal, temperature-driven environment changes. In addition, the high-throughput sequencing (HTS) molecular method was shown to provide overall good representation of coccolithophore community composition. Finally, the study on Helicosphaera evolution showed that adaptation to decreasing CO2 in higher latitudes involved cell and coccolith size decrease, whereas the adaptation in tropical ecosystems also included a physiological decrease in calcification rates in response to nutrient limitation. This thesis advanced our understanding of coccolithophore adaptive strategies and will improve our predictions on the fate of the group under ongoing climate change.

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