No description available.

Desenvolvemos urna teoria cinética para urna mistura de gases ionizados em presença de campos elétricos e magnéticos. As leis de Ohm, Fourier e Navier-Stokes são obtidas por dois métodos distintos que se baseiam na equação de Boltzmann. Verificamos que o emprego de teoremas de representação torna o método de Chapman-Enskog mais direto. Entretanto o método combinado mostrou-se extremamente simples, onde os coeficientes de transporte são determinados através da inversão de tensores de segunda e quarta ordens. Calculamos também a integral de colisão para as possíveis interações em gases ionizados tais como, entre partículas carregadas, partícula carregada e partícula neutra e entre partículas neutras. Como uma aplicação do método combinado, determinamos os coeficientes de condutividade elétrica, condutividade térmica, coeficiente termo-elétrico e o coeficiente de viscosidade cisalhante para um gás totalmente ionizado. Obtemos seus respectivos gráficos, considerando então um gás ionizado formado a partir do gás de hélio. / We develop a kinetic theory for ionized gases mixtures under the presence of electric and magnetic fields. The laws of Ohm, Fourier and Navier-Stokes are obtained by two different methods based on the Boltzmann equation. We verify that the use of representation theorems makes the Chapman-Enskog method more direct. However the combined method shows up as extremely simple where the transport coefficients are determined through inversion of second-order and fourth order tensors. We calculate also the collision integrals for possible interactions in ionized gases like: between charged particles, between charged particles and neutral particles and between neutral particles. As an application of the combined method, we determine the electrical and thermal conductivity coefficients, thermo-electric and shear viscosity coefficients for a completely ionized gas. We obtain their respective graphics considering an ionized gas of helium.

by Tsui Chi Wa. / Chinese title: / Bibliography: leaf 51 / Thesis (M.Phil.) -- Chinese University of Hong Kong, 1983

by Chan Pui-King. / Bibliography: leaf 45 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

Submitted by Gizele Lima (gizele.lima@inpa.gov.br) on 2017-02-13T20:44:28Z No. of bitstreams: 2 Tese_final.pdf: 4830454 bytes, checksum: 7daba652414fe412c8579fc6260edce0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-02-13T20:44:28Z (GMT). No. of bitstreams: 2 Tese_final.pdf: 4830454 bytes, checksum: 7daba652414fe412c8579fc6260edce0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-11-11 / Fundação de Amparo à Pesquisa do Estado do Amazonas - FAPEAM / Lakes and reservoirs are significant sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Hydroelectric reservoirs in the Amazon region emit more greenhouse gases (GHG) than reservoirs in other regions. However, few studies with direct in situ measurements of GHG have been performed in Amazonian tropical reservoirs. Therefore, in this study, direct in situ measurements were performed at the Balbina reservoir in Amazonas State, and at the Curuá-Una reservoir in the State of Pará. The CO2 flux measurements were performed using an eddy covariance system (Curuá- Una) and a floating chamber (Balbina). CO2 concentration measurements in air were made using a Li-7500A at Balbina and CO2 / CH4 measurements were made using an EC 150 and GGA-Los Gatos, respectively, and pCO2 was measured in the water with a CSense sensor at Curuá-Una. Gas measurements were related to meteorological variables (magnitude and direction of wind, precipitation, air temperature and atmospheric pressure) and environmental variables (water temperature, radiation, reservoir level). The study at Balbina, was performed between 15 and 20 July 2013, during the transition from wet to dry seasons, and had relatively low CO2 flux compared to another study from the same reservoir. This study showed that fluxes did not present a statistically significant relationship with the meteorological variables, however the current study identified the presence of a breeze contributing to the night concentration of CO2 over the reservoir. For Curuá-Una, an autonomous floating micrometeorological platform was used which conducted measurements during July 2015 to July 2016. Our results for Curuá-Una reveal that the turbulent fluxes of momentum, sensible and latent heat present daily and intraseasonal variability, the concentration downstream of CO2 and CH4, are influenced by variation in the level of the reservoir, CO2 flux was mainly negative throughout the day. pCO2 presented daily variability and high values with a significant difference between the measurements taken with the C-sense sensor and the headspace method. The basin of the Curuá-Una River, although small, is influenced by large-scale events such as El Nino and La Nina. The results presented here suggest that the dynamics of GHG emissions are affected by the size of the reservoir, allowing the influence of breezes and large scale events such as the El Niño of 2015-2016 which might increase emissions. The wide availability of radiation is responsible for much of the instability in the overlying layer of the water surface. The Curuá-Una reservoir, can act as a heat sink during the rainy season and as a heat source during the dry season, thus affecting the local heat balance of water and atmosphere and indirect GHG emissions. / Lagos e reservatórios são fontes significantes de dióxido de carbono (CO2) e metano (CH4) para a atmosfera. Na região amazônica, reservatórios hidrelétricos emitem mais gases de efeito estufa (GEE) do que reservatórios de outras regiões do mundo. No entanto, poucos estudos com medidas diretas e in situ de GEE foram realizadas em reservatórios tropicais amazônicos. Por isso, neste estudo, foram realizadas medições diretas e in situ nos reservatórios de Balbina no Amazonas e Curuá-Una no Pará. As medições de fluxo de CO2 foram realizadas usando método das covariâncias (Curuá-Una) e câmara flutuante (Balbina). Medidas da concentração no ar de CO2 usando Li-7500A (Balbina) e CO2/CH4 usando EC 150 e pCO2 na água com o sensor C-sense (Curuá-Una). As medidas gasosas foram relacionadas com variáveis meteorológicas (magnitude e direção do vento, precipitação, temperatura do ar e pressão atmosférica) e variáveis ambientais (temperatura da água, radiação, nível do reservatório). O estudo em Balbina, foi realizado entre os dias 15 e 20 de julho 2013, durante a estação de transição (chuvosa para seca) e revelaram fluxos de CO2 relativamente baixos, quando comparados com outro estudo para o mesmo reservatório. Mostraram ainda que os fluxos não apresentaram relação estatisticamente significante com as variáveis meteorológicas e identificou-se a presença de brisa contribuindo para a concentração noturna de CO2 sobre o reservatório. Para Curuá-Una, foi construída uma plataforma micrometeorológica flutuante autônoma, a qual realizou medições durante julho de 2015 à julho de 2016. Nossos resultados para Curuá-Una revelam que: os fluxos turbulentos de momentum, calor sensível e latente apresentam variabilidade diária e intrasazonal; a concentração à jusante de CO2 e CH4, sofrem influência da variação do nível do reservatório; o fluxo de CO2 foi predominantemente negativo ao longo do dia e o pCO2 apresentou variabilidade diária e valores muito elevados com diferença significante entre as medidas realizadas com o sensor C-sense e o método do headspace; a bacia do Rio Curuá-Una, apesar de pequena, sofre influência de eventos de grande escala como El-Ninõ e La-Ninã. Os resultados aqui apresentados sugerem que, a dinâmica das emissões de GEE são afetadas pelo tamanho do reservatório, o que permite a influência de brisa e eventos de grande escala. Eventos como o El-Niño 2015-2016 podem aumentar as emissões; a grande disponibilidade de radiação é responsável por boa parte da instabilidade na camada sobrejacente a superfície da água, o fluxo turbulento de CO2 foi, em média de – 0,8 µmol m-2 s-1 o reservatório de Curuá-Una, pode atuar como sumidouro de calor durante a estação chuvosa e como fonte de calor durante a estação seca, portanto afetando o balanço de calor local da água e atmosfera.

Soil is the largest terrestrial carbon (C) store, containing an estimated ~1500 Gt C in the upper 1 m of soil. The long term storage of soil organic C (SOC) requires that it is somehow protected from microbial decomposition – or ‘stabilised’ – in the soil matrix. Three mechanisms are commonly identified as factors controlling the stability of SOM: chemical recalcitrance, physical protection in aggregates and adsorption to soil mineral surfaces. The stability of SOC in the soil matrix can be influenced by management practices and changes in soil structure can lead to loss of SOC and increases in greenhouse gas (GHG) emissions. It is, therefore, important to understand the impact that management practices have on SOC stability and to manage soils in such a way as to optimise the volume of SOC which is locked away for climatically significant periods of time. Two methods are generally used to estimate SOC stability: indirectly by measuring CO2 fluxes as a proxy for SOC microbial decomposition, or directly through physical fractionation of soil in to pools with different levels of physical and chemical protection. Both methods were employed in this thesis. Arable and grassland soils which represent the range of soil textures and climatic conditions of the main agricultural areas in the UK were incubated at two different moisture contents and with or without inorganic fertiliser application and GHG fluxes from them were monitored. Soil texture, mineral N concentration and soil C concentration were found to be the most important measured variables controlling GHG fluxes of the UK agricultural soils in this study. The results were generally in support of those found in the literature for a wide range of soils, conditions and locations; however, N2O emissions from the two Scottish soils appeared to be more sensitive to inorganic N fertilisation at the higher moisture content than the other soils, with the N2O emissions being exceptionally high in comparison. Although incubations of whole soils are useful in measuring the impacts of soil management practices on GHG emissions under controlled conditions they do not identify the mechanisms controlling the stability of SOC. Dividing SOM into functional pools may identify different C stabilising mechanisms and improves soil C models. A large number of operationally defined separation methods have been used to fractionate SOM into biologically meaningful pools of different stability. Direct comparisons of different fractionation methods using radiocarbon (14C) dating and spectroscopic analyses has not previously been undertaken. Average 14C ages and chemical composition of SOM fractions isolated from a grassland soil using three published and frequently applied fractionation methods were compared. (1) a density separation technique isolating three fractions (2) a combined physical and chemical separation isolating five fractions (3) a hot-water extraction method isolating two fractions. The fractions from Method 1 had the most distinct average 14C ages, the fractions from Method 2 fell into two age groups, and both Method 3 fractions were dominated by modern C. The average 14C ages of the labile fractions from Method 1 and 2 were higher than the mineral bound fractions, although they made up a relatively small proportion of the total SOC. This was a surprising result, and spectroscopic analysis confirmed that these fractions had greater relative contents of aliphatic and aromatic characteristics than the mineral bound fractions. The presence of black C in a whole soil sample and one of the labile fractions from Method 2 was confirmed by hydrogen pyrolysis. The availability of archived soils from an abandoned long term tillage treatment experiment and the ability to relocate the plots provided a unique opportunity to assess the resilience of SOC stocks to land management practices several years after the conversion from arable to grassland. SOC stability was assessed by soil fractionation of archived (1975) and freshly collected (2014) soil samples. The mass corrected SOC stocks from the four different treatments (deep plough, shallow plough, chisel plough and direct drill) were higher in 2014 than 1975 across the whole profile (0 – 36 cm). Reductions were observed at some depths for some treatments but the overall effect was an evening out of SOC stocks across all plots. The fractionations (using Method 2), revealed that there was a relative increase in the mass of the sand and aggregate fraction but a decrease in the relative proportion of SOC stored in this fraction (physically protected). There was also a significant increase in the C:N ratio of the silt and clay fraction (chemical adsorption). This suggests that reduced disturbance of agricultural soils leads to preferential physical stabilisation of fresh SOM but also increased adsorption of older material to mineral surfaces. The labile fractions were sensitive to land-use change in all tillage treatment plots, but were more sensitive in the low impact tillage plots (chisel plough and direct drill) than the inversion tillage plots (deep plough and shallow plough). It is well established that tillage disrupts aggregation. However, a direct measurement of the level of SOM physical protection in the soil matrix due to aggregation has not previously been undertaken. The soil was fractionated using Method 1 (fractions with distinctly different 14C ages) and isolated soil fractions were incubated separately, recombined and mixed in to whole soil at three different temperatures. The C respiration rate of the isolated intra-aggregate fraction was generally consistently as high as the whole soil. This supports the theory that there is a labile component of soil which is protected from decomposition by physical protection within aggregates. Therefore, the lack of any priming effect with the addition of labile fractions to the whole soil, and indeed the suppression of emissions relative to the whole soil, was unusual. Fractions and whole soils incubated at 25 and 35 °C had a wider range of Q10 (temperature sensitivity) values than those incubated at 15 and 25 °C, however, median values were surprisingly similar (range from 0.7 to 1.9). Overall, the results from this thesis highlight the importance of the soil structure in stabilising C. Disrupting aggregates leaves a proportion of otherwise stable C susceptible to loss through microbial decomposition, particularly when the entire soil matrix is disrupted. It also provided some unexpected results which warrant future investigation; in particular, further direct measurement of physical stabilisation of SOM in soils of different type, from different climates and different land uses would be useful.

No description available.

Ng Ching Man = 在不同氣體中一的維硒化鋅鈉米結構的發光研究 / 吳靜雯. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 67-69). / Text in English; abstracts in English and Chinese. / Ng Ching Man = Zai bu tong qi ti zhong yi de wei xi hua xin na mi jie gou de fa guang yan jiu / Wu Jingwen. / Contents / Acknowledgements --- p.ii / Abstract --- p.iii / Chapter Chapter 1- --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Motivation --- p.3 / Chapter 1.3 --- Our Work --- p.4 / Chapter Chapter 2 - --- Experiment --- p.5 / Chapter 2.1 --- MOCVD System --- p.5 / Chapter 2.2 --- Metalorganic Sources --- p.5 / Chapter 2.3 --- Substrates --- p.7 / Chapter 2.4 --- Growth of ZnSe Nanowires --- p.7 / Chapter 2.5 --- Sample Passivation --- p.8 / Chapter 2.6 --- PL measurements --- p.8 / Chapter 2.7 --- Ambient Gases --- p.9 / Chapter 2.8 --- Gases Handling Apparatus --- p.9 / Chapter 2.9 --- Ambient Gases and Laser Power Control in PL Measurements --- p.11 / Chapter Chapter 3 - --- Characterization --- p.13 / Chapter 3.1 --- Photoluminescence --- p.13 / Chapter 3.2 --- Secondary Electron Microscopy --- p.14 / Chapter 3.3 --- X-Ray diffraction --- p.15 / Chapter Chapter 4 - --- Results --- p.16 / Chapter 4.1 --- ZnSe Nanowires Grown on Si(100) --- p.16 / Chapter 4.1.1 --- Morphology and Structure of the As Synthesized Sample --- p.16 / Chapter 4.1.2 --- Morphology and Structure of the Sample after Passivation --- p.17 / Chapter 4.2 --- Effect of Ambient Condition on Photoluminescence --- p.19 / Chapter 4.2.1 --- PL in Vacuum Ambient --- p.20 / Chapter 4.2.2 --- PL Spectra in different Ambient Gases --- p.21 / Chapter 4.2.3 --- PL Reversibility --- p.23 / Chapter 4.3 --- "Effect of Pressure, Concentration and Power of Excitation on the Photoluminescence of Nanowires" --- p.26 / Chapter 4.3.1 --- Ambient Pressure --- p.27 / Chapter 4.3.1.1 --- H2S --- p.27 / Chapter 4.3.1.2 --- H2 --- p.30 / Chapter 4.3.1.3 --- CO --- p.32 / Chapter 4.3.2 --- Ambient Concentration --- p.33 / Chapter 4.3.2.1 --- H2S --- p.33 / Chapter 4.3.2.2 --- H2 --- p.36 / Chapter 4.3.3 --- Excitation Power --- p.38 / Chapter 4.3.3.1 --- H2S --- p.38 / Chapter 4.3.3.2 --- H2 --- p.40 / Chapter 4.3.3.3 --- CO --- p.41 / Chapter Chapter 5 - --- Discussions --- p.42 / Chapter 5.1 --- Quality of nanowires --- p.42 / Chapter 5.2 --- Surface Reaction --- p.43 / Chapter 5.2.1 --- Surface States --- p.43 / Chapter 5.2.2 --- Gas-surface interaction --- p.46 / Chapter 5.2.2.1 --- Physiosorption --- p.46 / Chapter 5.2.2.2 --- Chemisorption --- p.47 / Chapter 5.3 --- (NH4)2S passivation --- p.48 / Chapter 5.3.1 --- Etching --- p.48 / Chapter 5.3.2 --- (NH4)2S passivation --- p.48 / Chapter 5.4 --- PL increase in Vacuum --- p.50 / Chapter 5.5 --- Effects of different Gases --- p.50 / Chapter 5.5.1 --- H2S --- p.50 / Chapter 5.5.2 --- H2 --- p.53 / Chapter 5.5.3 --- CO --- p.54 / Chapter 5.5.4 --- Other explanations --- p.54 / Chapter 5.6 --- The amount of Intensity Change --- p.56 / Chapter 5.7 --- Rates of Adsorption and Desorption --- p.56 / Chapter Chapter 6 - --- Conclusions --- p.58 / Appendices --- p.60 / Chapter I - --- Fitted parameter of the adsorption and desorption of H2S and CO --- p.60 / Chapter II - --- Calculation of gas and photon fluxes --- p.65 / References --- p.67

Orientador: Helmut Karl Bockelmann / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-09-26T18:08:56Z (GMT). No. of bitstreams: 1 Machida_Munemasa_M.pdf: 1121342 bytes, checksum: 91ff8334d640576b32f3b83a9de60004 (MD5) Previous issue date: 1977 / Resumo: Realizamos neste trabalho a construção, diagnóstico por sondas magnéticas e análise de um sistema "Theta -Pinch" pequeno de 3KJ de energia total. Analisamos em detalhe teórico e experimental as várias fases da compressão e encontramos que a concordância é relativamente boa / Abstract: Not informed / Mestrado / Física / Mestre em Física

Typescript (photocopy) / 167 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Physics, University of Adelaide, 1978