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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.
1

Stabilization of frictional soil through injection using CIPS (Calcite In-situ Precipitation System)

Palmén, Anders January 2012 (has links)
The precipitation system CIPS (Calcite In-situ Precipitation System) has been created as a permeation grouting system based on a two component fluid with the intention of slowly permeate and fill the pores. It causes cementation through a chemical reaction which bonds the soil particles together at the contact points. CIPS mimics one of the natural reactions in nature where sandstone is formed through calcite precipitation. This system is used in Australia with excellent results and there are many factors governing the outcome of the method, some of these factors are: flow rate, pressure, time, chemical recipe, temperature, composition of the soil matrix and number of performed injections at the same point of location. Some of these factors have been the focus of this report and where they have been examined from a Scandinavian point of view where our ground temperature conditions and soil compositions have governed the outcome of the accomplished results. The strength increase has been examined through laboratory tests where natural sand from a building site with known particle size and dry density has been treated once with the CIPS Fluid. This treatment was completed in a temperature controlled room of 12 degrees after which the treated soil was tested by unconfined compression tests. Even a rather low increase in bearing capacity of the soil would result in benefits during the construction of temporary constructions during the early building stages foundation work. Since the desired increase in bearing capacity of the soil is fairly low, 50-100 kPa, the investigations has concentrated on one single injection, in order to study if there is a clear trend in the increase in bearing capacity, and if it can be roughly predicted. In addition to the above mentioned laboratory work a small scale field test has been conducted, where the CIPS Fluid was injected into the ground with the aim of creating a column shaped object. This column was left for a certain time, a time long enough for the calcite crystal to bond the soil grains and generate an increase in strength. When the assumed cementation had occurred an ocular assessment was carried out in order to predict whether the strength had increased or not, and to what degree. Based on the laboratory results, some evidence of that strength increase occurs due to either the discharge of the spent fluid containing ammonium chloride or the process of drying. Either way, the strength increase takes place during the grounds natural process of adjusting towards the natural water content equilibrium for the specific site of interest. A strength increase at the laboratory experiments of between approximately 60-220 kPa has been achieved. The field tests where slightly less rewarding when difficulties of injecting the CIPS Fluid into the sandy soil arose due to challenging task of designing a pumping system where both a low pressure, less than the overburden pressure, and a low flow rate, less than 7 litres per minute, could be controlled. The flow rate could be controlled but with the effect of the pressure rising to too high levels. Due to the observations of CIPS Fluids exiting the ground at other points than near the injection spear, soil fractures are assumed to have occurred at one ore many locations. The volumes treated with CIPS Fluid displayed no increase in strength as long as they appeared somewhat wet with the spent fluid. When this fluid containing ammonium chloride vanished from the treated soil and the pH-value dropped, the build up in strength through calcite crystallisation at the contact points began. This crystallization which leads to a cementation was observed at the centre of the small spheres achieved through injection in the ground, which proves that the Calcite In-situ Precipitation System has caused a cementation of the soil grains treated.
2

Understanding Uncertainties for Polar Mesospheric Cloud Retrievals and Initial Gravity Wave Observations in the Stratopause from the Cloud Imaging and Particle Size Instrument

Carstens, Justin Neal 01 November 2012 (has links)
The Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere satellite images in the nadir at the UV wavelength of 265 nm. The camera array has an approximately 120° along track (2000 km) by 80° cross track (1000 km) field of view at a horizontal resolution of 1 by 2 km in the nadir. The satellite is in a sun synchronous orbit with an approximately noon local time equator crossing. The observed albedo is due to Rayleigh scattered sun light from an altitude of approximately 50 km and sunlight scattered from Polar Mesospheric Clouds (PMC) which occur in the summer mesosphere at 83 km. The goal of the CIPS instrument is to retrieve high horizontal resolution maps of PMC albedo and the mode radius of the particle size distribution. The first manuscript analyzes the uncertainties involved in the retrieval. The ability to infer mode radius from the PMC signal is made significantly harder by the presence of the Rayleigh signal. Much of the difference between PMC signals of different mode radii is also consistent with possible changes in the Rayleigh signal. The signal is decomposed into components which isolate the portion of the PMC signal's dependence on radius which is not consistent with changes in the Rayleigh signal. This isolated component is compared with the measurement noise to estimate and understand the uncertainties in the CIPS retrieval. The presence of the Rayleigh signal is a difficulty in the PMC retrieval, but it is also a valuable data product. The second manuscript highlights the initial findings of a new gravity wave data set developed by the author. The data set provides relative ozone variations at the stratopause with a horizontal resolution of 20 by 20 km. An abundance of gravity wave signatures can be seen in the data which appear to emanate from weather events like thunderstorms and hurricanes as well as orographic sources such as the Andes and the Antarctic Peninsula. The data set fills a gap that presently exists in our observational coverage of gravity waves, so the data set should help significantly in constraining Global Climate Models. / Ph. D.
3

Dinâmica espacial: persistência de um modelo mononuclear na Região Metropolitana do Recife

LAPROVITERA, Ana Cláudia Arruda 12 March 2015 (has links)
Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-07T13:19:03Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) UFPE TESE MDU pdf.pdf: 6598491 bytes, checksum: b2735ba43bc5f1fa72db66bef662ebaa (MD5) / Made available in DSpace on 2016-07-07T13:19:03Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) UFPE TESE MDU pdf.pdf: 6598491 bytes, checksum: b2735ba43bc5f1fa72db66bef662ebaa (MD5) Previous issue date: 2015-03-12 / O que se pretende nesta tese é analisar até onde os processos e fenômenos econômicos que estão acontecendo no entorno do Complexo Portuário Industrial de Suape – CIPS estão efetivamente determinando uma nova configuração espacial metropolitana. Parte-se da hipótese de que a estrutura espacial que vem sendo gestada no entorno do CIPS vem fortalecendo a articulação entre esse complexo e a Cidade do Recife, núcleo da RMR, e, portanto, vem reforçando o caráter monocêntrico dessa metrópole, em detrimento da emergência de uma nova centralidade no território do complexo. A metodologia adotada estabelece definições e teorias que contribuem para o tratamento objetivo da questão e ajuda a entender as estruturas econômicas e espaciais interurbanas, mais especificamente, os fluxos materiais que emanam do CIPS e de seu entorno, com implicações na estrutura espacial do território. Assume-se, também, como questão central, que a rede urbana – bem como os indicadores de performance econômica e social que se estabelecem a partir das estruturas físico-territoriais existentes –, consiste na condição fundamental para direcionar o processo de integração econômica e social e a consequente criação de novas centralidades. Assume-se, também, que o processo de desenvolvimento em curso no Estado de Pernambuco é um processo modernizante em bases conservadoras, no qual se assiste ao tradicional pacto político-social e tecnocrático do setor público com a tecnocracia e o grande capital imobiliário. Não há mudanças substanciais nos padrões das estruturas sociais, culturais e econômicas, e sim a manutenção e perpetuação do status quo pré-existente no que pese a transformações modernizadoras. Por fim, conclui-se que a Cidade do Recife, por possuir fortes características de polarização e atratividade em seu eixo central, além de vantagens competitivas históricas e naturais construídas ao longo do seu processo de desenvolvimento, possui fortes economias locais de aglomeração que fortalecem ainda mais a sua estrutura monocêntrica, em detrimento da criação de novas centralidades urbanas dinâmicas em seu entorno. / The aim of this thesis is to analyze how far the processes and economic phenomena that are going on around the Industrial Port Complex of Suape - CIPS are effectively determining a new metropolitan spatial configuration . It starts with the hypothesis that the spatial structure that it is growing in the vicinity of CIPS is strengthening the links between this complex and the City of Recife, core of RMR, and therefore has reinforced the monocentric character of this metropolis, to the detriment of emergence of a new centrality in the territory of the complex. The methodology establishes definitions and theories that contribute to the treatment purpose of the issue and help us to understand the economic and spatial structures long distance. More specifically, the structures include the material flows emanating from the CIPS and its surroundings, with implications for the spatial structure of the territory, and also the central issue, the urban network – and the indicators of economic and social performance that are established from the existing physical and territorial structures. This is the fundamental condition to direct the process of economic and social integration and the subsequent creation of new centers. It should also be assumed that the ongoing development process in the state of Pernambuco is a modernizing process on conservative bases, in which we witness the traditional political and social pact and technocratic public sector with the technocracy and the great real estate capital. There are no changes in the patterns of social, cultural and economic structures, but the maintenance and perpetuation of the pre-existing status quo despite the modernizing transformations. Finally, we have concluded that the city of Recife, because it has strong characteristics of polarization and attractiveness in its central axis, in addition to historical and natural competitive advantages built over its development process, has strong local agglomeration economies that greatly strengthen its monocentric structure, rather than creating new dynamic urban centralities in its surroundings.
4

The Simulation and Study of Conditions Leading to Axial Offset Anomaly in Pressurized Water Reactors

Hawkes, Joshua Mahlon 03 December 2004 (has links)
Axial offset anomaly (AOA) in pressurized water reactors (PWR) refers to deviation of the measured neutron flux in the top half of the core from the predicted values. Among other difficulties, AOA reduces the shutdown margin, and may force the plant to reduce power output. AOA is believed to be caused by three related phenomena occurring in the core while operating at full power: sub-cooled nucleate boiling concentrated mainly in the upper half of the core, corrosion product deposition on the cladding surface (crud), and the deposition of boron within the porous crud layer in regions of vigorous sub-cooled boiling. This study replicates the conditions within the PWR primary coolant; specifically, the temperature, pressure, peak surface heat flux, coolant velocity and water chemistry are simulated in order to produce prototypical crud on an electrically heated Zircaloy-4 test element. At the conclusion of each test run, the heated Zircaloy-4 test element is rapidly isolated from the coolant in order to trap any soluble boron species that may be present in the crud layer. The results of this investigation indicate that prototypical crud with significant boron deposition can be produced. The deposited boron compound has been determined to be lithium tetraborate (Li2B4O7). Comparative experiments have been run to determine the effect of coolant pH, concentration and type of additives, and duration of exposure on the thickness of the crud deposit. The data obtained in this investigation can be used to validate mechanistic models for crud deposition and AOA in pressurized water reactors.
5

Speciální aplikace VoIP / Special application of VoIP

Lembard, Tomáš January 2011 (has links)
The aim of this master's thesis is suggestion and following realization of voice transmission over the local network equipment and a description of used circuits and solutions in terms of hardware and software. This thesis deals with digitization of low-frequency signals, the structure of IP and UDP protocols, implementation of TCP/IP stack cIPS

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