As the foundation for a new computational implementation, we survey the calculation of the complex electrical conductivity tensor based on the Kubo-Greenwood (KG) formalism (Kubo, 1957; Greenwood, 1958), with emphasis on derivations and technical aspects pertinent to use of projector augmented wave datasets with plane wave basis sets (BIlichl, 1994). New analytical results and a full implementation of the KG approach in an open-source Fortran 90 post-processing code for use with Quantum Espresso (Giannozzi et al., 2009) are presented. Named KGEC ([K]ubo [G]reenwood [E]lectronic [C]onductivity), the code calculates the full complex conductivity tensor (not just the average trace). It supports use of either the original KG formula or the popular one approximated in terms of a Dirac delta function. It provides both Gaussian and Lorentzian representations of the Dirac delta function (though the Lorentzian is preferable on basic grounds). KGEC provides decomposition of the conductivity into intra- and inter band contributions as well as degenerate state contributions. It calculates the dc conductivity tensor directly. It is MPI parallelized over k-points, bands, and plane waves, with an option to recover the plane wave processes for their use in band parallelization as well. It is designed to provide rapid convergence with respect to k-point density. Examples of its use are given.

The research reported here is a study of detector systems to determine those most suited for simultaneous organic acid, inorganic anion determination. Comparisons are made on the basis of detection limits and sensitivities for conductivity, UV/Vis, photoconductivity, and derivative conductivity detection systems. The investigation was made using a constant chromatographic system with the only variable component being the detector system. Eluant optimization conditions for each detector are reported along with tables reporting detection limits and sensitivities for each detector system. Various chromatograms are also shown to provide a visual comparison between detector results.

The accurate measurement of multiphase flows of oil/water/gas is a critical element of oil exploration and production. Thus, over the last three decades; the development and deployment of in-line multiphase flow metering systems has been a major focus worldwide. Accurate measurement of multiphase flow in the oil and gas industry is difficult because there is a wide range of flow regimes and multiphase meters do not generally perform well under the intermittent slug flow conditions which commonly occur in oil production. This thesis investigates the use of Doppler and cross-correlation ultrasonic measurements made in different high gas void fraction flow, partially separated liquid and gas flows, and homogeneous flow and raw slug flow, to assess the accuracy of measurement in these regimes. This approach has been tested on water/air flows in a 50mm diameter pipe facility. The system employs a partial gas/liquid separation and homogenisation using a T-Y junction configuration. A combination of ultrasonic measurement techniques was used to measure flow velocities and conductivity rings to measure the gas fraction. In the partially separated regime, ultrasonic cross-correlation and conductivity rings are used to measure the liquid flow-rate. In the homogeneous flow, a clamp-on ultrasonic Doppler meter is used to measure the homogeneous velocity and combined with conductivity ring measurements to provide measurement of the liquid and gas flow-rates. The slug flow regime measurements employ the raw Doppler shift data from the ultrasonic Doppler flowmeter, together with the slug flow closure equation and combined with gas fraction obtained by conductivity rings, to determine the liquid and gas flow-rates. Measurements were made with liquid velocities from 1.0m/s to 2.0m/s with gas void fractions up to 60%. Using these techniques the accuracies of the liquid flow-rate measurement in the partially separated, homogeneous and slug regimes were 10%, 10% and 15% respectively. The accuracy of the gas flow-rate in both the homogeneous and raw slug regimes was 10%. The method offers the possibility of further improvement in the accuracy by combining measurement from different regimes.

Lake Hayq is a closed, freshwater basin on the eastern margin of the north-central highlands, Ethiopia. Using a sediment core extracted from the northern basin, this thesis aims to provide a high-resolution, detailed palaeolimnological reconstruction of changes to the environment and climate in the region since the late Pleistocene. A multi-proxy approach was applied, utilising diatoms, photosynthetic pigments and X-ray fluorescence (XRF) spectrometry. Lithological and chronological analyses were also performed, as well as the development of a transfer function to model diatom-inferred conductivity, and other quantitative analyses. Between ~ 15.6 15.1 cal kyr BP, Lake Hayq experienced a lowstand, synchronous with the timing of Heinrich Event 1 and an intense drought across East Africa. At ~ 15.1 cal kyr BP a lake began to develop at the core site in response to wetter, more humid conditions, most likely caused by the reactivation of the African-Indian monsoonal circulation. This was abruptly ended however at ~ 14.7 cal kyr BP, as the climate shifted back towards aridity and Lake Hayq shallowed, in contrast to the majority of other East African lakes, which continued to refill. This most likely reflects changes to the Indian Ocean monsoon system caused by variability in the Atlantic Meridional Overturning Circulation at this time, in conjunction with site-specific mechanisms affecting the delivery of precipitation to Lake Hayq. At ~ 12.3 cal kyr BP the African Humid Period resumed over Lake Hayq and the lake refilled, reaching maximum water depth between ~ 12.0 10.0 cal kyr BP. The lake was dominated by planktonic diatom taxa and photosynthetic pigments indicate it was meromictic. Lake level gradually declined throughout the Holocene, culminating in the termination of the African Humid Period. A high-resolution study of the period tentatively suggests that climate flickering , in the form of oscillations between dominant diatom taxa, occurred in the build up to the major climatic shift. The termination spanned ~ 600 cal years between ~ 5.2 4.6 cal kyr BP. A lowstand occurred between ~ 3.9 2.2 cal kyr BP, during which the lake became occasionally subsaline. In the late Holocene, ~ 2.2 1.3 cal kyr BP, Lake Hayq became deep and fresh again, although there is evidence of lake level variability. The palaeo-record from Lake Hayq indicates that it broadly experienced the same high-latitude, glacial-interglacial dynamics and sub-millennial shifts in climate found in other palaeolimnological records from across East Africa. The precise timing and expression of these climatic events is not always synchronous between Lake Hayq and other East African waterbodies however, most likely caused by local, site-specific positive feedback mechanisms and variability in lake morphometry. This highlights the heterogeneous pattern of climate across the region and the significance of regional drivers. This palaeo-record, spanning the late Quaternary, will help bridge gaps in current knowledge and understanding of the underrepresented, climatically sensitive and vulnerable north Ethiopian highlands. This is vital for future climate change modelling and regional downscaling, and may also inform ethnographic-archaeological research in a region considered to be the cradle of humankind.

Le travail présenté dans cette thèse porte sur la synthèse et les caractérisations thermiques et rhéologiques d’un nouveau type de nanofluide : le système Cu2O/Glycérol. La caractérisation est faite en fonction de la taille des particules mises en suspension, de la température et de la fraction volumique solide. Ce travail a nécessité la synthèse des nanoparticules et des nanofluides par la méthode de décomposition thermique des précuseurs organométalliques, qui présente un bon rendement en quantité de nanoparticules (17%). Et le montage d’un dispositif de caractérisation thermique utilisant la méthode 3ω. Finalement, nous avons passé à la caractérisation rhéologique et thermique de ces échantillons. Les résultats obtenus avec ce nouveau système sont intéressants, car l’augmentation de la conductivité thermique atteint des valeurs importantes : 120% et 35% respectivement pour des fractions volumiques aussi faibles que 0,625% et 0,078% de nanoparticules de 7 nm de diamètre, sans influence notable sur la viscosité du fluide hôte, permettant une bonne amélioration du bilan énergétique total. Nous avons observé que la concentration et la taille (surface) des nanoparticules sont des paramètres clefs du comportement de la conductivité thermique effective du nanofluide Cu2O/Glycérol. Nos mesures nous ont permis de déduire la prédominance des modifications de la surface des nanoparticules (par fonctionnalisation ou par réaction chimique secondaire) sur le mouvement brownien dans les transferts thermiques nanoparticules/ fluide hôte. / The work presented in this thesis involves the synthesis and thermal and rheological characterization of a new type of nanofluid : the Cu2O/glycerol system. The characterization was carried out as a function of the size of the particles in suspension, the temperature and the volume fraction of nanoparticles. The nanoparticles and nanofluids were synthesised by the thermal decomposition method, providing a good yield of nanoparticles (17%). Apparatus for thermal measurements using the 3ω method was constructed, and rheological and thermal characterization was carried out. Significant increases in thermal conductivity were observed : 120% and 35% for volume fractions as low as 0.625% and 0.078%, respectively, of 7-nm-diameter nanoparticles, without noticeable effect on the viscosity of the host fluid, leading to a considerable improvement in the energy content.We found that the concentration and surface area of the nanoparticles are key parameters influencing the behaviour of the effective thermal conductivity of the nanofluid. Surface modification of the nanoparticles by functionalization or secondary chemical reactions has a profound effect on the Brownian motion in the heat transfer between nanoparticles and fluid host.

Ce travail de thèse explore la capacité des ligands anilates d’être employés pour la préparation de nouveaux matériaux moléculaires fonctionnels avec des propriétés magnétiques et de conduction électrique. Les anilates, qui sont les dérivés du 2,5-dihydroxy-1,4- benzoquinone substitués sur les positions 3 et 6, ont été sélectionnés comme ligands puisque leurs caractéristiques électroniques et structurales, leurs modalités de coordination et leur capacité de médiation des interactions de super-échange magnétique en font d’excellents ligands pour la préparation de ces matériaux. Plusieurs ligands anilates ont été utilisés pour le design et la préparation d'une nouvelle classe de complexes paramagnétiques octaédriques tris-chélates de formule générale [MIII(X2An)3]3- (MIII = Cr, Fe; X = Cl, Br, I, H, Cl/CN, An = C6O4 2- = anilate). Ces complexes métalliques paramagnétiques ont été complètement caractérisés et utilisés comme briques moléculaires pour la préparation de i) une nouvelle classe de ferriaimants moléculaires, dans laquelle la modification des substituants sur le ligand permet de modifier les interactions entre les centres métalliques, et, par conséquent, les propriétés magnétiques, ii) des conducteurs paramagnétiques moléculaires obtenus par combinaison avec le donneur organique BEDT-TTF, iii) une série de conducteurs moléculaires chiraux obtenus par combinaison du donneur organique TM-BEDT-TTF avec des couches hétéro-bimétalliques anioniques obtenues par association in situ de complexes tris(chloranilate)ferrate(III) et des ions potassium. En outre, ont été synthétisés de nouveaux dérivés anilates avec des propriétés electroactives et de luminescence, afin de démontrer la capacité du motif anilate d’être fonctionnalisé avec différents substituants comme porteurs de propriétés physiques spécifiques. / This work explores the potential of anilate-based ligands in the synthesis of new rational designed functional molecular materials exhibiting improved magnetic and conducting properties. Anilates, namely 3,6-disubstitued 2,5-dihyroxy-1,4- benzoquinones in their dianionic form, have been selected as ligands since their electronic/structural features, coordination modes and ability to mediate magnetic exchange interactions between coordinated metal centers make them potential candidates for the preparation of theabove-mentioned materials. Various anilate derivatives have been used for the preparation of a family of rationally designed tris-chelated octahedral paramagnetic metal complexes of general formula [MIII(X2An)3]3- (MIII = Cr, Fe; X = Cl, Br, I, H, Cl/CN, An = C6O4 2- = anilate). These paramagnetic metal complexes have been thoroughly characterized and used, in turn, as molecular building blocks for the preparation of i) a family of molecule-based magnets, where subtle changes in the nature of the substituents on the anilate moiety were employed as “adjusting screws” in tuning the magnitude of the magnetic interaction between the metals, and thus, the magnetic properties, ii) hybrid paramagnetic molecular conductors in combination with the BEDT-TTF organic donor, iii) a complete series of isostructural chiral molecular conductors obtained by combining the TMBEDT- TTF chiral donor with 2D heterobimetallic anionic layers obtained in situ by the self-assembling of tris (chloranilato)ferrate(III) metal complexes and potassium cations.Moreover, novel anilate derivatives showing electroactive and luminescent properties have been further synthesized, highlighting the versatility of the anilate moiety to be functionalized with suitable substituents carrying selected physical properties.

In recent times, high power density trends and temperature constraints in integrated circuits have led to conventional cooling techniques not being sufficient to meet the thermal requirements. The ever-increasing desire to overcome this problem has led to worldwide interest in micro heat sink design of electronic components. It has been found that geometric configurations of micro heat sinks play a vital role in heat transfer performance. Therefore, an effective means of optimally designing these heat sinks is required. Experimentation has extensively been used in the past to understand the behaviour of these heat extraction devices. Computational fluid dynamics (CFD) has more recently provided a more cost-effective and less time-consuming means of achieving the same objective. However, in order to achieve optimal designs of micro heat sinks using CFD, the designer has to be well experienced and carry out a number of trial-and-error simulations. Unfortunately, this will still not always guarantee an accurate optimal design. In this dissertation, a design methodology which combines CFD with a mathematical optimisation algorithm (a leapfrog optimisation program and DYNAMIC-Q algorithm) is proposed. This automated process is applied to three design cases. In the first design case, the peak wall temperature of a microchannel embedded in a highly conductive solid is minimised. The second case involves the optimisation of a double row micropin-fin heat sink. In this case, the objective is to maximise the total rate of heat transfer with the effect of the thermal conductivity also being investigated. The third case extends the micropin-fin optimisation to a heat sink with three rows. In all three cases, fixed volume constraint and manufacturing restraints are enforced to ensure industrial applicability. Lastly, the trends of the three cases are compared. It is concluded that optimal design can be achieved with a combination of CFD and mathematical optimisation. / Dissertation (MEng)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / Unrestricted

Orientador: Alexandre Campane Vidal / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-24T10:58:04Z (GMT). No. of bitstreams: 1 Costanzo_CaetanoPontes_M.pdf: 3384236 bytes, checksum: 7b4516eef162c87ff3e03f0d56f08215 (MD5) Previous issue date: 2014 / Resumo: Em face da crescente demanda de execução de projetos de remediação de aquíferos contaminados, a técnica de bombeamento e tratamento está sendo utilizada de forma significativa. Esta ferramenta de recuperação ambiental consiste no bombeamento da água subterrânea em pontos estrategicamente posicionados de maneira a gerar uma barreira hidráulica que impeça o avanço da extensão de uma pluma de contaminação. Em áreas com alta heterogeneidade litológica, a organização espacial dos valores de condutividade hidráulica (K) em subsuperfície apresenta incertezas associadas à variabilidade na distribuição das fácies. No presente estudo foram analisadas estas incertezas por meio de métodos geoestatísticos (krigagem da indicatriz e simulações estocásticas) e também a partir de simulações numéricas de fluxo e transporte de contaminantes. Estas ferramentas permitiram a análise das possibilidades de deslocamentos espaciais das plumas de contaminação, bem como possíveis cenários de bombeamento e tratamento numa área contaminada, em função de distintos campos aleatórios de condutividade locais, devido à complexidade geológica. A partir da krigagem da indicatriz foi possível elaborar um modelo geoestatístico de fácies que foi utilizado como ferramenta para validar o uso da condutividade hidráulica em função de cada litologia, definindo assim os possíveis grupos de hidrofácies presentes na área. Por meio das simulações estocásticas foram gerados vinte campos distintos de condutividade hidráulica, os quais configuraram distintas distribuições espaciais das áreas das plumas de contaminação, como também cenários otimista, intermediário e pessimista para o deslocamento das mesmas. Foram simulados três cenários de bombeamento e tratamento resultando nove situações desta técnica de remediação. Dessa forma, os efeitos da heterogeneidade atrelada à condutividade hidráulica evidenciaram que, para a execução de um projeto de remediação por bombeamento e tratamento em áreas com certa heterogeneidade geológica, é necessária a análise de incertezas atreladas ao diagnostico hidrogeológico. Ao considerar modelos com homogeneidade na condutividade e mais simplistas, o projeto de remediação pode vir a ser ineficiente aumentando o tempo para a recuperação ambiental local e consequentemente aumentando os custos / Abstract: Due to the growing demand for project execution remediation of contaminated aquifers, the pump-and-treat is being used significantly. This remediation technique consists in groundwater pumping in strategically placed at points to generate a hydraulic barrier to prevent the advance of a contamination plume. In areas with high lithological heterogeneity, the spatial organization of the hydraulic conductivity (K) values in the subsurface introduces uncertainties associated with the variability in the distribution of facies. In this study these uncertainties were evaluated using geostatistical methods (indicator kriging and stochastic simulations) and also from numerical simulations of flow and contaminant transport. These tools enable the analysis of the contamination plumes areas, as well as scenarios for pump-and-treat, due to different random fields of local conductivity according to the geological complexity. By indicator kriging, was possible to provide a geostatistical facies model which was used as a tool to validate the hydraulic conductivity as a function of each lithology, thus defining the possible hydrofacies groups in the area. The stochastic simulations generated twenty distinct hydraulic conductivity fields, which represented different spatial distributions of contamination plumes, as well as scenarios optimistic, intermediate and pessimistic to offset these. Three scenarios for pump-and-treat were simulated resulting nine situations of this remediation technique. Therefore the effects of heterogeneity associated with hydraulic conductivity showed that, for the remediation design in areas with certain geological heterogeneity, the analysis of uncertainties linked to hydrogeological studies is needed. When considering models with homogeneous conductivity and most simplistic, the remediation project may prove to be inefficient increasing the time to the project and consequently increasing costs / Mestrado / Geologia e Recursos Naturais / Mestre em Geociências

Made available in DSpace on 2016-01-26T18:56:25Z (GMT). No. of bitstreams: 1 FABIO_BENINCASA_Agronomia_02_07_2012.pdf: 854058 bytes, checksum: 5977b7bda5f28c21b5060e650a4e9387 (MD5) Previous issue date: 2012-05-21 / The monosaccharides (glucose and fructose) present in the sugarcane are reducing sugars because they have free carbonyl group, able to oxidize in the presence of oxidizing agents. The classical analytical methods (Lane-Eynon, Benedict, EDTA complexometric-, the Luff-Schoorl method, Musson-Walker, Somogyi-Nelson) based on the reduction of copper ions in alkaline solutions. Some industries use sucroalcooleiras methodology Lane-Eynon, other apparatus REDUTEC®, and others perform the calculation of RS (reducing sugar). The aim of this study was to understand the relationship between the variation of electric conductivity measurement in millivolts, mass wears and concentration of RS, with equipment similar to that proposed by Horii and Gonçalves, properly adapted, tested mathematical models with broth of sugar cane and held the automation of analyses. We used the apparatus REDUTEC ®, digital scales, peristaltic pump, digital camcorder, graphics and mathematical programs. It is concluded that there is a mathematical correlation between electrical conductivity (mv), RS. The mathematical model is statistically efficient solution of low concentration of RS (<0.3%). / Os monossacarídeos (glicose e frutose) presentes na cana-de-açúcar são açúcares redutores por possuírem grupo carbonílico livres, capazes de se oxidarem na presença de agentes oxidantes. Os métodos analíticos clássicos (Lane-Eynon, Benedict, complexométrica-EDTA, Luff-Schoorl, Musson-Walker, Somogyi-Nelson) baseiam-se na redução de íons cobre em soluções alcalinas. Algumas indústrias sucroalcooleiras utilizam a metodologia de Lane-Eynon, outras o aparelho REDUTEC® e outras realizam o calculo de AR (açúcares redutores). O objetivo do presente estudo foi compreender a relação entre a variação da condutividade elétrica medida em milivoltagem, massa gasta e concentração de AR, com aparelho semelhante ao proposto por Horii e Gonçalves, devidamente adaptado, testou-se modelos matemáticos com caldos de cana-de-açúcar e realizou-se a automação das análises. Utilizou-se o aparelho REDUTEC®, balança digital, bomba peristáltica, câmera de vídeo digital, programas matemáticos e gráficos. Conclui-se que existe uma correlação matemática entre condutividade elétrica (mv), massas gasta e AR, O modelo matemático gerado é eficiente estatisticamente, para solução de baixa concentração de AR (< 0,3%).

Made available in DSpace on 2016-07-18T17:51:09Z (GMT). No. of bitstreams: 1 FABIO_BENINCASA_Agronomia_02_07_2012.pdf: 854058 bytes, checksum: 5977b7bda5f28c21b5060e650a4e9387 (MD5) Previous issue date: 2012-05-21 / The monosaccharides (glucose and fructose) present in the sugarcane are reducing sugars because they have free carbonyl group, able to oxidize in the presence of oxidizing agents. The classical analytical methods (Lane-Eynon, Benedict, EDTA complexometric-, the Luff-Schoorl method, Musson-Walker, Somogyi-Nelson) based on the reduction of copper ions in alkaline solutions. Some industries use sucroalcooleiras methodology Lane-Eynon, other apparatus REDUTEC®, and others perform the calculation of RS (reducing sugar). The aim of this study was to understand the relationship between the variation of electric conductivity measurement in millivolts, mass wears and concentration of RS, with equipment similar to that proposed by Horii and Gonçalves, properly adapted, tested mathematical models with broth of sugar cane and held the automation of analyses. We used the apparatus REDUTEC ®, digital scales, peristaltic pump, digital camcorder, graphics and mathematical programs. It is concluded that there is a mathematical correlation between electrical conductivity (mv), RS. The mathematical model is statistically efficient solution of low concentration of RS (<0.3%). / Os monossacarídeos (glicose e frutose) presentes na cana-de-açúcar são açúcares redutores por possuírem grupo carbonílico livres, capazes de se oxidarem na presença de agentes oxidantes. Os métodos analíticos clássicos (Lane-Eynon, Benedict, complexométrica-EDTA, Luff-Schoorl, Musson-Walker, Somogyi-Nelson) baseiam-se na redução de íons cobre em soluções alcalinas. Algumas indústrias sucroalcooleiras utilizam a metodologia de Lane-Eynon, outras o aparelho REDUTEC® e outras realizam o calculo de AR (açúcares redutores). O objetivo do presente estudo foi compreender a relação entre a variação da condutividade elétrica medida em milivoltagem, massa gasta e concentração de AR, com aparelho semelhante ao proposto por Horii e Gonçalves, devidamente adaptado, testou-se modelos matemáticos com caldos de cana-de-açúcar e realizou-se a automação das análises. Utilizou-se o aparelho REDUTEC®, balança digital, bomba peristáltica, câmera de vídeo digital, programas matemáticos e gráficos. Conclui-se que existe uma correlação matemática entre condutividade elétrica (mv), massas gasta e AR, O modelo matemático gerado é eficiente estatisticamente, para solução de baixa concentração de AR (< 0,3%).