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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.
531

Säker fillagring i hemmiljö : Hur säkrar man upp fillagring i en hemmiljö?

Clarenfjord, Johan, Göransson, Christian January 2015 (has links)
I det här arbetet har författarna valt att fokusera på lagringssäkerhet ur synvinkelnhemmiljö. För att kunna ge målgruppen någon form av riktlinje definieras olika kravpå säkerhet och lagring från författarnas sida att utgå från vid diskussion och arbetetsupplägg. Arbetet inriktar sig på vad det finns för möjligheter för att kunna säkra uppde olika formerna av lagringsmöjligheter. Är det möjligt att göra? Vilka källor kanman förvänta sig att målgruppen använder för att lösa de här problemen? Genom attstudera tidigare forskning och göra omfattande dokumentstudier kommer författarnafram till vad som kan vara lämpligt att använda i en hemmiljö för säker fillagring.Arbetet mynnar ut i ett resultat med vad de olika lagringslösningarna och lagringstjänsternaklarar av för krav samt vad de klarar av för olika funktioner. Det finns ävenen form av rekommendation för användaren vad som kan vara en lämplig väg att gå,dock inte ett direkt svar på hur denna skall se ut. / The authors of this essay have chosen to focus on secure data storage from a homeenvironment standpoint. In order to give this target group something that resembles aguideline, several demands regarding security and storage will be defined. This willalso be used as a basis both for how the essay is approached and the discussion of it.The essay focuses on the possibilities when it comes to securing the varyingforms of storage solutions. Can it be done securely? In order to solve these problems,what sources are the target group most likely to use?Through study of earlier research, and extensive document studies, the authorsfind solutions regarding secure data storage that are feasible to use in a home environment.In the end, the essay will point out which of the defined demands thevarious storage solutions and services can handle, and which functions they can handle.There is also a recommendation for the reader regarding what is feasible andsuitable for use, though not a clear-cut answer saying which solution is the better;that’s still up to the reader herself to determine.
532

High density ammonia storage materials

Royse, David M. January 2011 (has links)
This Thesis considers the use of solid-state metal ammines as ammonia storage materials and endeavours to understand these materials on a fundamental chemical level. The ammines of LiBH₄, MgCl₂, MgBr₂, MgI₂ and Mg(BH₄)₂, are investigated. The structures of lithium borohydride ammines, Li(NH₃)<sub>n</sub>BH₄ with n = 1, 2, 3 and 4 are solved using X-ray and neutron diffraction, vibrational spectroscopy, nuclear magnetic resonance, and first-principles calculations. The reversibility, bonding and ammonia storage properties of this system are discussed, and investigated using gravimetric analysis and vibrational spectroscopy. The ammines of magnesium halides are investigated using X-ray and neutron powder diffraction, gravimetric techniques, nuclear magnetic resonance, first-principles calculations and vibrational spectroscopy. Their disordered structures, bonding, and decomposition are discussed, and the trends in their properties are used to interpret the properties of other ammines. The ammines of magnesium borohydride are investigated using X-ray and neutron powder diffraction, gravimetric techniques, first-principles calculations and vibrational spectroscopy. The structure, decomposition and reversibility of Mg(NH₃)₆(BH₄)₂ as an ammonia store are presented. Throughout the Thesis and at the end of each Chapter the possibility of using these ammines as solid-state ammonia stores is discussed.
533

Enabling Utility-Scale Electrical Energy Storage through Underground Hydrogen-Natural Gas Co-Storage

Peng, Dan 11 September 2013 (has links)
Energy storage technology is needed for the storage of surplus baseload generation and the storage of intermittent wind power, because it can increase the flexibility of power grid operations. Underground storage of hydrogen with natural gas (UHNG) is proposed as a new energy storage technology, to be considered for utility-scale energy storage applications. UHNG is a composite technology: using electrolyzers to convert electrical energy to chemical energy in the form of hydrogen. The latter is then injected along with natural gas into existing gas distribution and storage facilities. The energy stored as hydrogen is recovered as needed; as hydrogen for industrial and transportation applications, as electricity to serve power demand, or as hydrogen-enriched natural gas to serve gas demand. The storage of electrical energy in gaseous form is also termed “Power to Gas”. Such large scale electrical energy storage is desirable to baseload generators operators, renewable energy-based generator operators, independent system operators, and natural gas distribution utilities. Due to the low density of hydrogen, the hydrogen-natural gas mixture thus formed has lower volumetric energy content than conventional natural gas. But, compared to the combustion of conventional natural gas, to provide the same amount of energy, the hydrogen-enriched mixture emits less carbon dioxide. This thesis investigates the dynamic behaviour, financial and environmental performance of UHNG through scenario-based simulation. A proposed energy hub embodying the UHNG principle, located in Southwestern Ontario, is modeled in the MATLAB/Simulink environment. Then, the performance of UHNG for four different scenarios are assessed: injection of hydrogen for long term energy storage, surplus baseload generation load shifting, wind power integration and supplying large hydrogen demand. For each scenario, the configuration of the energy hub, its scale of operation and operating strategy are selected to match the application involved. All four scenarios are compared to the base case scenario, which simulates the operations of a conventional underground gas storage facility. For all scenarios in which hydrogen production and storage is not prioritized, the concentration of hydrogen in the storage reservoir is shown to remain lower than 7% for the first three years of operation. The simulation results also suggest that, of the five scenarios, hydrogen injection followed by recovery of hydrogen-enriched natural gas is the most likely energy recovery pathway in the near future. For this particular scenario, it was also found that it is not profitable to sell the hydrogen-enriched natural gas at the same price as regular natural gas. For the range of scenarios evaluated, a list of benchmark parameters has been established for the UHNG technology. With a roundtrip efficiency of 39%, rated capacity ranging from 25,000 MWh to 582,000 MWh and rated power from 1 to 100 MW, UHNG is an energy storage technology suitable for large storage capacity, low to medium power rating storage applications.
534

Enhancing storage performance in virtualized environments: a pro-active approach

Sivathanu, Sankaran 17 May 2011 (has links)
Efficient storage and retrieval of data is critical in today's computing environments and storage systems need to keep up with the pace of evolution of other system components like CPU, memory etc., for building an overall efficient system. With virtualization becoming pervasive in enterprise and cloud-based infrastructures, it becomes vital to build I/O systems that better account for the changes in scenario in virtualized systems. However, the evolution of storage systems have been limited significantly due to adherence to legacy interface standards between the operating system and storage subsystem. Even though storage systems have become more powerful in the recent times hosting large processors and memory, thin interface to file system leads to wastage of vital information contained in the storage system from being used by higher layers. Virtualization compounds this problem with addition of new indirection layers that makes underlying storage systems even more opaque to the operating system. This dissertation addresses the problem of inefficient use of disk information by identifying storage-level opportunities and developing pro-active techniques to storage management. We present a new class of storage systems called pro-active storage systems (PaSS), which in addition to being compatible with existing I/O interface, exerts a limit degree of control over the file system policies by leveraging it's internal information. In this dissertation, we present our PaSS framework that includes two new I/O interfaces called push and pull, both in the context of traditional systems and virtualized systems. We demonstrate the usefulness of our PaSS framework by a series of case studies that exploit the information available in underlying storage system layer, for overall improvement in IO performance. We also built a framework to evaluate performance and energy of modern storage systems by implementing a novel I/O trace replay tool and an analytical model for measuring performance and energy of complex storage systems. We believe that our PaSS framework and the suite of evaluation tools helps in better understanding of modern storage system behavior and thereby implement efficient policies in the higher layers for better performance, data reliability and energy efficiency by making use of the new interfaces in our framework.
535

Enabling Utility-Scale Electrical Energy Storage through Underground Hydrogen-Natural Gas Co-Storage

Peng, Dan 11 September 2013 (has links)
Energy storage technology is needed for the storage of surplus baseload generation and the storage of intermittent wind power, because it can increase the flexibility of power grid operations. Underground storage of hydrogen with natural gas (UHNG) is proposed as a new energy storage technology, to be considered for utility-scale energy storage applications. UHNG is a composite technology: using electrolyzers to convert electrical energy to chemical energy in the form of hydrogen. The latter is then injected along with natural gas into existing gas distribution and storage facilities. The energy stored as hydrogen is recovered as needed; as hydrogen for industrial and transportation applications, as electricity to serve power demand, or as hydrogen-enriched natural gas to serve gas demand. The storage of electrical energy in gaseous form is also termed “Power to Gas”. Such large scale electrical energy storage is desirable to baseload generators operators, renewable energy-based generator operators, independent system operators, and natural gas distribution utilities. Due to the low density of hydrogen, the hydrogen-natural gas mixture thus formed has lower volumetric energy content than conventional natural gas. But, compared to the combustion of conventional natural gas, to provide the same amount of energy, the hydrogen-enriched mixture emits less carbon dioxide. This thesis investigates the dynamic behaviour, financial and environmental performance of UHNG through scenario-based simulation. A proposed energy hub embodying the UHNG principle, located in Southwestern Ontario, is modeled in the MATLAB/Simulink environment. Then, the performance of UHNG for four different scenarios are assessed: injection of hydrogen for long term energy storage, surplus baseload generation load shifting, wind power integration and supplying large hydrogen demand. For each scenario, the configuration of the energy hub, its scale of operation and operating strategy are selected to match the application involved. All four scenarios are compared to the base case scenario, which simulates the operations of a conventional underground gas storage facility. For all scenarios in which hydrogen production and storage is not prioritized, the concentration of hydrogen in the storage reservoir is shown to remain lower than 7% for the first three years of operation. The simulation results also suggest that, of the five scenarios, hydrogen injection followed by recovery of hydrogen-enriched natural gas is the most likely energy recovery pathway in the near future. For this particular scenario, it was also found that it is not profitable to sell the hydrogen-enriched natural gas at the same price as regular natural gas. For the range of scenarios evaluated, a list of benchmark parameters has been established for the UHNG technology. With a roundtrip efficiency of 39%, rated capacity ranging from 25,000 MWh to 582,000 MWh and rated power from 1 to 100 MW, UHNG is an energy storage technology suitable for large storage capacity, low to medium power rating storage applications.
536

Suppression of bruchids infesting stored grain legumes with the predatory bug Xylocoris flavipes (Reuter) (hemiptera: anthocoridae)

Sing, Sharlene E. January 1997 (has links)
Biological control of pest Bruchidae may provide an important management strategy against infestation of stored grain legumes, a key source of dietary protein in developing countries. Previous related research has focused on the potential of parasitoids to control bruchids; the role of generalist predators in this application has not yet been extensively explored. / The anthocorid true bug Xylocoris flavipes (Reuter) exhibited a Type II density dependent functional response to five species of adult bruchids. The rate of kill of these large prey was quite low but fairly consistent and female predators were generally more effective. Of the species examined, only the eggs and neonate larvae of A. obtectus were accessible and predation on these stages was high. / Population interaction studies evaluating the effects of predator density and of time elapsed between infestation of commodity and predator addition indicated that adding the predator simultaneously with the pests significantly reduced the number of F$ sb1$, bruchid progeny for all species. Predator density contributed less to bruchid suppression than time of predator addition and bruchid progeny suppression was much greater than anticipated given the rate of kill observed in the functional response experiments. Reproduction by A. obtectus was almost entirely inhibited by the predator. / The high levels of suppression achieved with the predator indicated a significant biological control potential; however, the more fecund bruchid species with inaccessible immature stages continued to produce a large number of progeny. The predator was then combined with larval parasitoids capable of utilizing the internally-developing stages of the bruchids; bruchid suppression was considerably enhanced over the predator alone, and for the most fecund pests, suppression was greater than for the parasitoids alone.
537

Determinants of the supply-side fragmentation of maize storage in the North Western Free State production area / Mathys Johannes Nicolaas van der Merwe.

Van der Merwe, Mathys Johannes Nicolaas January 2012 (has links)
For decades commercial silos in South Africa was the only option in which maize could be delivered and sold. After deregulation in the late 1990s commercial silo owners came to face the challenge of alternative storage solutions and loss of market share. The reasons are determined for a shift from commercial storage to on-farm storage. The extent to which on-farm storage will change the current maize storage industry is discussed. The study commences by describing the birth and rapid growth of maize production in South Africa. Soon after maize became a major role-player in the export industry, it was characterised by regulation. The rationale why the market was regulated and how it influenced grain storage is explained. The deregulation process and the objectives of the new Marketing of Agricultural Products Act, No. 47 of 1996, are paraphrased. In the deregulated market, current and future, maize prices are determined by supply and demand. Incentives for storage emerged and cheaper substitutes with various other advantages began to propose alternative storage solutions to farmers. These concurrences of circumstances then lead to fragmentation of grain storage in South Africa. As a relatively young free market, the maize value chain is described to illustrate the position of each role-player in relation to the silo owner. The new price determination factors, price movement rationale and the use of market instruments are subsequently explained. Naturally, a critical assessment of the main different storage solutions available for farmers, are investigated next. Fragmentation is defined and discussed in terms of market equilibrium. A comparison is drawn between the South African and the Australian as well as the US maize storage industry. The empirical research was conducted on two sample groups of farmers in the Free State. The first group is farmers that already make use of an on-farm storage facility. The second group is farmers that annually produce more than 5000 tons of maize and currently do not make use of an on-farm storage facility. Seven important reasons for an on-farm storage facility are determined in the literature study as well as a qualitative study that preceded the quantitative study. Respondents are asked to rank the reasons in order of, in their opinion, importance. A generalized profile of a respondent in each sample group was compiled. Hereafter the outcome of the reasons ranked by both sample groups is discussed. It appeared that Flexible Marketing Option was the most important reason for farmers that already make use of on-farm storage. Farmers did not indicate that Handling and Storage costs are the most important reason why they would invest in an on-farm storage facility. Correlations are drawn between groups and the significance of differences is determined. It is concluded that on-farm storage is sustainable and there will be an increase of the phenomenon over the next three years. Recommendations are given for commercial silo owners to regain market share. Costs analyses and effective cost management along with the promotion that marketing options are just as flexible within commercial silos, as it is outside, are some of the recommendations made. / Thesis (MBA)--North-West University, Potchefstroom Campus, 2013.
538

Determinants of the supply-side fragmentation of maize storage in the North Western Free State production area / Mathys Johannes Nicolaas van der Merwe.

Van der Merwe, Mathys Johannes Nicolaas January 2012 (has links)
For decades commercial silos in South Africa was the only option in which maize could be delivered and sold. After deregulation in the late 1990s commercial silo owners came to face the challenge of alternative storage solutions and loss of market share. The reasons are determined for a shift from commercial storage to on-farm storage. The extent to which on-farm storage will change the current maize storage industry is discussed. The study commences by describing the birth and rapid growth of maize production in South Africa. Soon after maize became a major role-player in the export industry, it was characterised by regulation. The rationale why the market was regulated and how it influenced grain storage is explained. The deregulation process and the objectives of the new Marketing of Agricultural Products Act, No. 47 of 1996, are paraphrased. In the deregulated market, current and future, maize prices are determined by supply and demand. Incentives for storage emerged and cheaper substitutes with various other advantages began to propose alternative storage solutions to farmers. These concurrences of circumstances then lead to fragmentation of grain storage in South Africa. As a relatively young free market, the maize value chain is described to illustrate the position of each role-player in relation to the silo owner. The new price determination factors, price movement rationale and the use of market instruments are subsequently explained. Naturally, a critical assessment of the main different storage solutions available for farmers, are investigated next. Fragmentation is defined and discussed in terms of market equilibrium. A comparison is drawn between the South African and the Australian as well as the US maize storage industry. The empirical research was conducted on two sample groups of farmers in the Free State. The first group is farmers that already make use of an on-farm storage facility. The second group is farmers that annually produce more than 5000 tons of maize and currently do not make use of an on-farm storage facility. Seven important reasons for an on-farm storage facility are determined in the literature study as well as a qualitative study that preceded the quantitative study. Respondents are asked to rank the reasons in order of, in their opinion, importance. A generalized profile of a respondent in each sample group was compiled. Hereafter the outcome of the reasons ranked by both sample groups is discussed. It appeared that Flexible Marketing Option was the most important reason for farmers that already make use of on-farm storage. Farmers did not indicate that Handling and Storage costs are the most important reason why they would invest in an on-farm storage facility. Correlations are drawn between groups and the significance of differences is determined. It is concluded that on-farm storage is sustainable and there will be an increase of the phenomenon over the next three years. Recommendations are given for commercial silo owners to regain market share. Costs analyses and effective cost management along with the promotion that marketing options are just as flexible within commercial silos, as it is outside, are some of the recommendations made. / Thesis (MBA)--North-West University, Potchefstroom Campus, 2013.
539

Microbial and physico-chemical assessment of on-site water supply systems /

Kolam, Joel. January 2003 (has links)
Thesis (M. Sc.) (Hons) -- University of Western Sydney, 2003. / "A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science (Hons.), University of Western Sydney, Australia, Water Research Laboratory, Centre for Water & Environmental Technology." Includes bibliography : leaves 168 - 183 and appendices.
540

Termisk energilagring

Fredriksson, Linda, Johansson, Julia January 2018 (has links)
Sweden is only utilizing half of the available excess heat. To utilize more of the excess heat a seasonal thermal energy storage could be implemented to store excessed heat from the summer when the demand is lower to the winter when the demand is higher. This can be achieved by an integration of a seasonal thermal energy storage to the district heating system. A seasonal thermal energy storage may also reduce the need of the system’s peak load, which often is economically costly and adversely affect the environment. The purpose of the paper is to investigate the possibility for Skövde Värmeverk to implement a seasonal thermal storage. The paper is performed by a literature collection and calculations are made by software programs. The result shows that it is technically possible to implement a pit thermal energy storage and a borhole thermal energy storage, but no outcome shows a profitability within 20 years. A pit thermal energy storage can replace the system’s peak load up to 79 percent and a borhole thermal energy storage up to 2,8 percent. The most suitable case for Skövde Värmeverk is to install a pit thermal energy storage with a storage capacity of 4 GWh.

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