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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.
11

Simulation of the irradiation behaviour of the PBMR fuel in the SAFARI-1 reactor / B.M. Makgopa

Makgopa, Bessie Mmakgoto January 2009 (has links)
Irradiation experiments for the pebble bed modular reactor PBMR fuel (coated fuel particles and pebble fuel) are planned at the South African First Atomic Reactor Installation (SAFARI-1). The experiments are conducted to investigate the behavior of the fuel under normal operating and accelerated/accident simulating conditions because the safe operation of the reactor relies on the integrity of the fuel for retention of radioactivity. For fuel irradiation experiments, the accurate knowledge and analysis of the neutron spectrum of the irradiation facility is required. In addition to knowledge of the neutron spectrum in the irradiation facility, power distributions and knowledge of nuclear heating values has to be acquired. The SAFARI-1 reactor boosts operating fluid temperatures of about 300 K. On the contrary, the PBMR can reach temperatures in up to about 1370 K under normal operating conditions. This calls for design of high temperature irradiation rigs for irradiation of the PBMR fuel in the SAFARI-1 reactor. The design of this instrument (rig) should be such that to create an isolated high temperature environment in the SAFARI-1 reactor, to achieve the requirements of the PBMR fuel irradiation program. The design of the irradiation rig is planned such that the rig should fit in the existing irradiation channels of the SAFARI-1 reactor, a time and cost saving from the licensing perspective. This study aims to establish the know-how of coated particle and pebble modeling in using the Monte Carlo N-Particle code (MCNP5). The study also aims to establish the know-how of rig design. In this study, the Necsa in-house code Overall System for the Calculation of Reactors (OSCAR-3), a software known as OScar 3-Mcnp INTerface (OSMINT) linking OSCAR-3 and MCNP5, also developed at Necsa, as well as MCNP5 code developed and maintained by the Los Alamos team, are used to calculate neutronic and power distribution parameters that are important for fuel irradiations and for rig design. This study presents results and data that can be used to make improvements in the design of the rig or to confirm if the required operational conditions can be met with the current preliminary rig design. Result of the neutronic analysis are presented for the SAFARI-1 core, core irradiation channel B6 (where the PBMR fuel irradiation rig is loaded for the purpose of this study), the rig structure and the pebble fuel are presented. Furthermore results of the power distribution and nuclear heating values in the reactor core, the irradiation channel B6, the rig structures and the pebble fuel is also presented. The loading of the PBMR fuel irradiation rig in core position B6 reduces the core reactivity due to the fact that the loading of the rig displaces the water moderator in channel B6 introducing vast amounts of helium. This impacts on the keff value because there will be less neutron thermalization and reproduction due to the decreased population of thermal neutrons. The rig is found to introduce a negative reactivity insertion of 46 pcm. The loading of this rig in the core leads to no significant perturbations on the core power distribution. The core hottest channel is still localized in core channel C6 both with RIG IN and RIG OUT cases. A power tilt is observed, with the south side of the core experiencing reduced assembly averaged fission power, with correspondingly small compensations from the assemblies on the north side of the core. The perturbations on the core assembly averaged fluxes are more pronounced in the eight assemblies surrounding B6. Core position B6 suffers an 18% neutron flux depression with the loading of the rig. The fluxes in core positions A5, A6, A7, B5, B7 and C7 are increased when the rig is loading. The largest increases are noted as 12% in A7, 9% in A6 and 6% in A5 and B7. All the eight core positions surrounding B6 experience reduced photon fluxes with the loading of the rig. Core position B6 shows a flux depression of up to 20%, with 10% reduction in core position A6. The remainder seven positions surrounding B6 shows flux depressions of no more than 5%. Further on, due to decreased moderation effects, the axial neutron flux in core position B6 is reduced by 20% when the rig is loaded. The energy dependent neutron flux in B6 decreases by 50% in the thermal energy range with corresponding increases of up to 50% in the resonance and fast energy regions. The axial and the energy dependent photon flux in core position B6 decreases by up to 20% when the rig is loaded. The magnitude of the neutron and photon fluxes is found to have a direct proportion on the neutron and photon heating values. While the amount of neutron heating in core position B6 increases by one order of magnitude, when the rig is loaded, the photon heating values increases by up to 60% in the region spanning ±10cm about the core centerline. The amount of photon heating in the rig structural materials dominates neutron heating, except in the helium regions of the rig, where neutron heating dominates photon heating. In the fuel region of the pebble, fission heating (3803W) largely dominates photon heating (119W). / Thesis (M.Sc. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2009
12

Simulation of the irradiation behaviour of the PBMR fuel in the SAFARI-1 reactor / B.M. Makgopa

Makgopa, Bessie Mmakgoto January 2009 (has links)
Irradiation experiments for the pebble bed modular reactor PBMR fuel (coated fuel particles and pebble fuel) are planned at the South African First Atomic Reactor Installation (SAFARI-1). The experiments are conducted to investigate the behavior of the fuel under normal operating and accelerated/accident simulating conditions because the safe operation of the reactor relies on the integrity of the fuel for retention of radioactivity. For fuel irradiation experiments, the accurate knowledge and analysis of the neutron spectrum of the irradiation facility is required. In addition to knowledge of the neutron spectrum in the irradiation facility, power distributions and knowledge of nuclear heating values has to be acquired. The SAFARI-1 reactor boosts operating fluid temperatures of about 300 K. On the contrary, the PBMR can reach temperatures in up to about 1370 K under normal operating conditions. This calls for design of high temperature irradiation rigs for irradiation of the PBMR fuel in the SAFARI-1 reactor. The design of this instrument (rig) should be such that to create an isolated high temperature environment in the SAFARI-1 reactor, to achieve the requirements of the PBMR fuel irradiation program. The design of the irradiation rig is planned such that the rig should fit in the existing irradiation channels of the SAFARI-1 reactor, a time and cost saving from the licensing perspective. This study aims to establish the know-how of coated particle and pebble modeling in using the Monte Carlo N-Particle code (MCNP5). The study also aims to establish the know-how of rig design. In this study, the Necsa in-house code Overall System for the Calculation of Reactors (OSCAR-3), a software known as OScar 3-Mcnp INTerface (OSMINT) linking OSCAR-3 and MCNP5, also developed at Necsa, as well as MCNP5 code developed and maintained by the Los Alamos team, are used to calculate neutronic and power distribution parameters that are important for fuel irradiations and for rig design. This study presents results and data that can be used to make improvements in the design of the rig or to confirm if the required operational conditions can be met with the current preliminary rig design. Result of the neutronic analysis are presented for the SAFARI-1 core, core irradiation channel B6 (where the PBMR fuel irradiation rig is loaded for the purpose of this study), the rig structure and the pebble fuel are presented. Furthermore results of the power distribution and nuclear heating values in the reactor core, the irradiation channel B6, the rig structures and the pebble fuel is also presented. The loading of the PBMR fuel irradiation rig in core position B6 reduces the core reactivity due to the fact that the loading of the rig displaces the water moderator in channel B6 introducing vast amounts of helium. This impacts on the keff value because there will be less neutron thermalization and reproduction due to the decreased population of thermal neutrons. The rig is found to introduce a negative reactivity insertion of 46 pcm. The loading of this rig in the core leads to no significant perturbations on the core power distribution. The core hottest channel is still localized in core channel C6 both with RIG IN and RIG OUT cases. A power tilt is observed, with the south side of the core experiencing reduced assembly averaged fission power, with correspondingly small compensations from the assemblies on the north side of the core. The perturbations on the core assembly averaged fluxes are more pronounced in the eight assemblies surrounding B6. Core position B6 suffers an 18% neutron flux depression with the loading of the rig. The fluxes in core positions A5, A6, A7, B5, B7 and C7 are increased when the rig is loading. The largest increases are noted as 12% in A7, 9% in A6 and 6% in A5 and B7. All the eight core positions surrounding B6 experience reduced photon fluxes with the loading of the rig. Core position B6 shows a flux depression of up to 20%, with 10% reduction in core position A6. The remainder seven positions surrounding B6 shows flux depressions of no more than 5%. Further on, due to decreased moderation effects, the axial neutron flux in core position B6 is reduced by 20% when the rig is loaded. The energy dependent neutron flux in B6 decreases by 50% in the thermal energy range with corresponding increases of up to 50% in the resonance and fast energy regions. The axial and the energy dependent photon flux in core position B6 decreases by up to 20% when the rig is loaded. The magnitude of the neutron and photon fluxes is found to have a direct proportion on the neutron and photon heating values. While the amount of neutron heating in core position B6 increases by one order of magnitude, when the rig is loaded, the photon heating values increases by up to 60% in the region spanning ±10cm about the core centerline. The amount of photon heating in the rig structural materials dominates neutron heating, except in the helium regions of the rig, where neutron heating dominates photon heating. In the fuel region of the pebble, fission heating (3803W) largely dominates photon heating (119W). / Thesis (M.Sc. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2009
13

"Střípky safari"- mozaikové obrazy, diptych / "Crocks of Safari"-mosaic images, a diptych

DOULÍKOVÁ, Radka January 2010 (has links)
My graduation thesis is called {\clq}qCrocks of Safari`` and it is divided into two main segments. The First part is theoretical which explains my inspiration, choice of theme and material, method of working - starting with design, ending with final artwork and its installation. It also considers the techniques of mosaic creation. It includes image documentation, which enriches and completes the text. The Second part is practical which includes its own graphic creation. That is two mosaic images made out of combined material {--} ceramics and glass (mirror) inserted into a metal frame. It features graphic structures and elements of an African fauna. It specifically interprets cut outs from herd of zebras and their typical stripes. My goal was to create abstract images where you can feel the character of used material and harmony of natural structures.
14

Browser Wars : Kampen om webbläsarmarknaden

Högström, Andreas, Pettersson, Emil January 2010 (has links)
The first browser war took place during the second half the 1990s, and Internet Explorer cameout as the winner over Netscape Navigator. Today a new browser war is being fought withmany competitors and the future is uncertain. The purpose of the thesis is to find out how theweb browser market has developed since the start of the previous conflict, and we ask ourselveshow it will continue to develop in the future. This is accomplished with, among otherthings, interviews, tests and already existing statistics. The thesis' conclusions shows that theweb browser market has developed in a positive way from several perspectives, both for theusers as well as for the web developers. The conclusions also show that the web browser market'sfuture looks stable and indicate a probability that the browser war will transition into anormal, healthy market situation with several competitors.The first browser war took place during the second half the 1990s, and Internet Explorer cameout as the winner over Netscape Navigator. Today a new browser war is being fought withmany competitors and the future is uncertain. The purpose of the thesis is to find out how theweb browser market has developed since the start of the previous conflict, and we ask ourselveshow it will continue to develop in the future. This is accomplished with, among otherthings, interviews, tests and already existing statistics. The thesis' conclusions shows that theweb browser market has developed in a positive way from several perspectives, both for theusers as well as for the web developers. The conclusions also show that the web browser market'sfuture looks stable and indicate a probability that the browser war will transition into anormal, healthy market situation with several competitors.
15

WhatsApp Forensics: Locating Artifacts in Web and Desktop Clients

Nicolas Villacis Vukadinovic (6623858) 14 May 2019 (has links)
WhatsApp is the most popular instant messaging application worldwide. Since 2016, users can send and receive messages through desktop clients, either through the WhatsApp desktop application or the web client accessible from supported web browsers. The author identified a gap in the literature in terms of WhatsApp forensics for desktop and web clients. The aim of the study was to locate forensic artifacts on WhatsApp clients. These clients included the desktop application on both Windows and Mac operating systems. Chrome and Firefox web clients were also analyzed for the Windows operating system, as well as Chrome and Safari web clients on the Mac operating system. A WhatsApp log file was identified as the main artifact providing information throughout all clients analyzed. Cached profile pictures were also found, as well as history information about visited websites and ran applications.
16

Impact of poaching on the marketability of safari lodges in the Eastern Cape

Loader, Rory James January 2015 (has links)
This research is presented in three sections. Section 1 presents the research report in an academic paper format. Section 2 provides a comprehensive literature review and Section 3 describes the research methodology and methods employed during the research. The tourism industry is the fastest growing sector within the South African Economy, with over 2.6 million foreign tourists visiting South Africa each year. Wildlife, landscapes and scenery are cited as the primary attractions for visiting the country, with over 45 percent of tourists visiting at least one wildlife or nature reserve during their stay in South Africa (Kerley et al., 2011:2). Sixty percent of those tourists travelled for leisure purposes, with 643,883 of the tourists utilising safari lodge accommodation during their visit (Ruggles-Brise, 2013). The Eastern Cape achieved 3.1 percent; of those tourist arrivals, with a bed-night contribution of 734,339, compared to the 16.8 percent (1.9million) and 10.5 percent (1.07million) for Mpumalanga and Limpopo provinces respectively (Ruggles-Brise, 2013). The Eastern Cape lodges represent less than half the bed-nights achieved by Mpumalanga and Limpopo lodges. Due to the number of possible bed-nights available to lodges in the Eastern Cape, it is increasingly important for individual lodges to provide a unique experience, in order to be competitive in attracting guests (Saayman, 2013:81). This was used form part of the foundation to this research in determining the marketability of three lodges in the Eastern Cape, which was derived from the attractiveness of the lodges, determined by guests visiting the lodges. This research follows on from four previous surveys commissioned by INDALO, the Eastern Cape Private Nature Reserve Association in 2004 Sims-Castley et al. 2004), 2006 (Langholz et al., 2006), 2008 (Snowball et al., 2008) and 2011 (Kerley et al., 2011). Part of the research was to identify the main attractions of the reserves. These previous surveys provided a foundation for this research to follow on investigating guest motivations for visiting the three sample lodges and to determine visitor perception of poaching and whether it would impact their motivations for visiting the reserve. In order to address the goals of the research qualitative data was gathered during survey interviews conducted at the three sampled reserves. Seventy five (75) guests were interviewed, equally over the three reserves. Quantitative data was also gathered during the interview surveys, utilising Likert scale questions, prompting guests to choose their top attractions, from which basic descriptive statistics were used to analyse the data being able to determine possible trends amongst respondents and lodges. Results verified guest motivations from the previous surveys, confirming that game viewing, especially the “Big 5” remained the most important attraction for visitors to the reserves while the availability of natural scenery and landscape, high end accommodation and service, the proximity to the garden route and being located in a malaria free area were also see as attractive attributes of the lodges as per the previous surveys. Where the gap in the research was indicated based on guests perception of poaching and whether it would impact their motivations for visit these lodges, impacting that lodges marketability (attractiveness). Results indicated that if they were unable to view the iconic ‘Big Five’ at the reserve due to the extent of poaching. Respondents indicated that the impact would likely and very likely impact their decision to choose the reserves over another reserve that could. Indicating the potential impact that poaching would have on lodges if they were to lose their iconic species which would spell the loss in attractiveness and therefore marketability.
17

Tourist Perceptions of their Environmental Impacts in Tanzania

Solberg, Anna Marie, Solberg 01 August 2017 (has links)
No description available.
18

NEXT GENERATION MOBILE TELEMETRY SYSTEM

Padilla, Frank Jr 10 1900 (has links)
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / White Sands Missile Range (WSMR) is developing a new transportable telemetry system that consolidates various telemetry data collection functions currently being performed by separate instrumentation. The new system will provide higher data rate handling capability, reduced labor requirements, and more efficient operations support which will result in a reduction of mission support costs. Seven new systems are planned for procurement through Requirements Contracts. They will replace current mobile systems which are over 25 years old on a one-on-one basis. Regulation allows for a sixty-five percent overage on the contract and WSMR plans to make this contract available for use by other Major Range Test Facility Bases (MRTFBs). Separate line items in the contracts make it possible to vary the design to meet a specific system configuration. This paper describes both current and replacement mobile telemetry system
19

Performance Analysis of JavaScript

Smedberg, Fredrik January 2010 (has links)
<p>In the last decade, web browsers have seen a remarkable increase of performance, especially in the JavaScript engines. JavaScript has over the years gone from being a slow and rather limited language, to today have become feature-rich and fast. It’s speed can be around the same or half of comparable code written in C++, but this speed is directly dependent on the choice of the web browser, and the best performance is seen in browsers using JIT compilation techniques.</p><p>Even though the language has seen a dramatic increase in performance, there’s still major problems regarding memory usage. JavaScript applications typically consume 3-4 times more memory than similar applications written in C++. Many browser vendors, like Opera Software, acknowledge this and are currently trying to optimize their memory usage. This issue is hopefully non-existent within a near future.</p><p>Because the majority of scientific papers written about JavaScript only compare performance using the industry benchmarks SunSpider and V8, this thesis have chosen to widen the scope. The benchmarks really give no information about how JavaScript stands in comparison to C#, C++ and other popular languages. To be able to compare that, I’ve implemented a GIF decoder, an XML parser and various elementary tests in both JavaScript and C++ to compare how far apart the languages are in terms of speed, memory usage and responsiveness.</p>
20

Kampen fortsätter : En studie om kompatibilitetsproblem mellan moderna webbläsare / The fight continues : A study of compatibility problems of modern web browsers

Trenkler, Silja January 2006 (has links)
<p>Under 1990-talet utspelade sig en bitter kamp om marknadsandelar mellan de två ledande webbläsare Internet Explorer och Netscape Navigator, det så kallade webbläsar-kriget. Kriget hade till följd att webbläsarna blev nästan helt inkompatibla. Sedan dess pågår en ständig utveckling av gemensamma standarder för webben. Idag är förutsättningarna för kompatibilitet mycket bättre än för tio år sidan, men problemet är inte fullständigt avhjälpt. De moderna webbläsare Internet Explorer 6, Firefox 1.5, Opera 8.5 och Safari kan återge en och samma webbsida visas på olika sätt trots att det finns gemensamma standarder. Syftet med denna uppsats är att ta reda på de tekniska orsakerna bakom problemet samt att ta fram lösningsförslag för att skapa en webbsida som är helt kompatibel i de moderna webbläsarna. Uppsatsen innehåller ett omfattande teorikapitel som behandlar definitioner, historik och problem. Teorin kompletteras av tre fältintervjuer med professionella webbutvecklare. Undersökningarna visar att kompati-bilitetsproblem beror på flera faktorer och att det är omöjligt att skapa en heltäckande lösning som kommer åt alla problem. Men genom att kombinera olika tekniker kan man skapa en metod som täcker en stor del av såväl generella som specifika kompatibilitetsproblemen utan att kollidera med rekommenderade standarder.</p> / <p>During the 1990’s the two leading web browsers, Internet Explorer and Netscape Navigator, fought each other in a battle for market shares, the so-called browser war. This war caused almost complete incompatibility between the web browsers. Since then, there has been a continual development of common standards for the web. Today conditions for compatibility are a lot better compared to ten years ago, but the problem is not completely solved. The modern web browsers Internet Explorer 6, Firefox 1.5, Opera 8.5 and Safari can display the exact same web page differently despite common standards. The aim of this essay is to investigate the technical causes of the problem and to develop suggested solutions for creating a web page that is fully compatible in modern browsers. The essay contains an extensive literature study, considering definitions, history and problems. The theory was completed with three field interviews with professional web designers. The investigations show that compatibility problems depend on several factors and that it is impossible to create one exhaustive solution that encompasses all problems. However, by combining different techniques one can create a method that covers a large part of both general and specific compatibility problems without colliding with recommended standards.</p>

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