Dissertations / Theses on the topic 'Total degradation'

The experimentally observed trends in the total-dose gain-degradation response of modern, BiCMOS compatible bipolar transistors are presented. A model for the post-irradiation excess base current is described. The model is applied to separately calculate the two radiation-induced damage densities: the net oxide charge density and the midgap-level interface-trap density. Hardness assurance testing recommendations are made based on the observed experimental trends.

Long term (>2 years) failure of UHMWPE components in-vivo is predominantly caused by wear of the UHMWPE component. The surface properties of UHMWPE greatly influence the adhesive and abrasive mechanisms of wear that occur in the hip. However, there is not a clear understanding of how in-vivo wear mechanisms influence surface mechanical properties of UHMWPE. In addition, previous researchers have reported wear rates for Charnley UHMWPE acetabular components that vary considerably between patients. It is conceivable that these variations in wear are a result of variations in the surface mechanical properties of UHMWPE. This study used a combination of instrumented indentation testing and Ff-IR imaging to assess the depth dependent micromechanical and chemical properties of 32 retrieved UHMWPE acetabular components. Significant variations in the mechanical and chemical properties of samples taken from worn and unworn regions of retrieved UHMWPE acetabular components were found. In unworn regions, these variations were principally caused by post-irradiation ageing. However, in worn regions, the variation in properties was primarily caused by the wear process.

The gas-phase reactions of ozone with alkenes can be significant sources of free radicals (OH, HO2 and RO2) in the Earth’s atmosphere. While there are a number of quantitative indirect OH and HO2 yield measurements from ozonolysis in the literature, obtained, for example, through the use of radical tracer / scavenger species, few direct observations have been reported. This thesis presents the first direct measurements of OH and HO2 by Laser Induced Fluorescence for a homologous series of alkenes. The radical and stable products from ethene, propene, 1-butene, 2 methylpropene, cis-2-butene, trans-2-butene and 2,3-dimethyl-2-butene ozonolysis have been observed. The experiments were carried out in the EUPHORE atmospheric simulation chamber, utilising various instrumentation including Fourier Transform Infrared Spectroscopy and Peroxy Radical Chemical Amplification. The alkene-ozone reaction systems were investigated with and without an OH radical scavenger and as a function of humidity. The results were interpreted through detailed chemical chamber box modelling, incorporating the Master Chemical Mechanism degradation scheme for each specific alkene, supplemented with a more explicit representation of the alkene-ozone reaction mechanism. The observed yields are interpreted in terms of branching ratios for each channel within the postulated alkene ozonolysis mechanism, and their implications for atmospheric radical production were considered.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work aimed to evaluate digestibility and degradability of nutrients, and kinetics of passage in horses fed with forages using mobile bag and in situ cecal digestion. Two digestion trials were carried out and seven forages were used, lucerne (Medicago sativa), peanut (Arachis pintoi), Desmodium ovalifolium, Stylosanthes guianensis, Cajanus cajan, Macroptyloma axilares and coastcross (Cynodon dactylon cv. coastcross). Basal diet were composed by 80% hay and 20% concentrate. In first assay with mobile bags, five crossbreed horses were used with age varying from 17 to 27 years and average weight of 350 kg. A nylon cloth were used with 45? pore size, and bags with dimensions of 7,5 x 2 cm, containing 510mg DM of sample/bag. These assay had 12 days of duration, and three for adaptation, five days for naso-gastric insertion of bags and four days for bags collection in feces. Randomized block design were used with seven treatments and five repetitions. Naso-gastric insertion of bags were made twice a day, at morning and afternoon, inserting 29 bags, and four bags of each feed and one blank. Transit time and excretion of bags were evaluated until 96h from insertion. Nutrients digestibility of forages were calculated through residues inside the bags. In situ assay was conducted with caecum fistulated horse, weight 210Kg. Bags with 20x 6,5cm were used with 5,2g of sample incubated inside caecum along times 0, 2, 4, 6, 8, 12, 24, and 48 hours. A randomized design was used with seven treatments and three repetitions during 30 days. Orskov & McDonald degradation model was used to fit the nutrients degradation curves. Nutrients digestibility of peanut, Desmodium and Macroptiloma were high than others roughages (P<0.05). Any difference were observed (P>0.05) among transit time, mediun retention time and passage rate, average values were 23.34, 48.63 and 2.07, respectively. Degradation rate were high to peanut, Desmodium and Macroptyloma. Peanut fiber and protein degradability is superior to others tropical legumes, and peanut presented high protein contents. Tropically forages peanut, Stylosanthes guianensis and Macroptyloma axilares presented potential to be use in horse diets.
Este trabalho foi realizado com o objetivo de estimar a digestibilidade e a degrada??o dos nutrientes e a cin?tica de passagem de alimentos volumosos em eq?inos utilizando as t?cnicas de sacos de n?ilon m?veis e da digest?o in situ. Foram realizados dois ensaios de digest?o e os alimentos volumosos utilizados nos dois estudos foram, alfafa (Medicago sativa), amendoim forrageiro (Arachis pintoi), Desmodium ovalifolium, Stylosanthes guianensis, guandu (Cajanus cajan), Macroptyloma axilares e capim coastcross (Cynodon dactylon cv. coastcross). A alimenta??o foi uma dieta basal composta por 80% de feno e 20% de concentrado. No primeiro ensaio, com sacos m?veis, foram utilizados cinco eq?inos mesti?os com idades variando de 17 a 27 anos, com peso vivo m?dio de 350kg. Para a confec??o dos sacos, utilizou-se tecido de n?ilon com porosidade de 45? com dimens?es de 7,5x 2cm, inserindo 510mg de MS de amostra/saco. O ensaio teve dura??o de 12 dias, sendo tr?s para a adapta??o, cinco para inser??o g?strica dos sacos e quatro de coleta dos sacos. O delineamento foi em blocos inteiramente casualizados com sete tratamentos e cinco repeti??es. A sonda nasog?strica foi inserida duas vezes ao dia, de manh? e ? tarde com 29 sacos, sendo quatro para cada alimento e um em branco, anotou-se o tempo de tr?nsito e a excre??o dos sacos foi considerada at? 96 horas ap?s a inser??o. A estimativa da digestibilidade dos nutrientes dos alimentos volumosos foi calculada atrav?s do res?duo obtido no saco. No ensaio in situ utilizou-se um animal fistulado no ceco, com peso vivo de 210 Kg e sacos de 20 x 6,5 cm, com 5,2 g de amostra, incubadas no ceco nos tempos de 0, 2, 4, 6, 8, 12, 24 e 48 horas. Utilizou-se o delineamento inteiramente casualizado com sete tratamentos e tr?s repeti??es, com dura??o de 30 dias e o modelo de degrada??o citado por Orskov & McDonald para descrever as curvas de degrada??o dos nutrientes. A digestibilidade dos nutrientes dos alimentos volumosos Amendoim, Desmodium e Macroptyloma foram maiores (P<0,05). N?o houve diferen?a (P>0,05) entre os alimentos em rela??o ao tempo de tr?nsito, tempo m?dio de reten??o e taxa de passagem dos sacos, observando-se os valores m?dios de 23,3 h, 48,6 h e 2,0 h, respectivamente. Os valores da taxa de degrada??o foram superiores no Amendoim, Desmodium e Macroptiloma. A degrada??o da fibra do amendoim forrageiro ? superior ?s demais leguminosas tropicais, assim como seu conte?do prot?ico. Os alimentos volumosos tropicais amendoim, Stylosanthes guianensis e Macroptyloma axilares apresentaram potencial para o uso em dietas para eq?inos.

Bisphenol A (BPA) is widely used in the production of plastics, epoxy resins and polycarbonates. It is a toxic, endocrine disruptor compound. Different studies have shown the presence of BPA in several environmental systems, classifying it as a worldwide persistent pollutant which may act synergistically with other pollutants. In this context, advanced oxidation processes (AOP) have received great attention due to their ability to degrade pollutants with such characteristics, through their transformation into less hazardous compounds or even their mineralization. Although there are investigations on the use of AOPs for BPA degradation, systematic studies on the effects of process variables, coupled with the statistical interpretation of the results are virtually non-existent. Furthermore, to the best of our knowledge, a rigorous kinetic model has not yet been proposed for the degradation of this pollutant by the H2O2/UV process. The objective of this work was to evaluate BPA degradation by the H2O2/UV process, investigating the effects of the initial H2O2 concentration and the specific rate of photons emission (EP,0) by means of a Doehlert experimental design, combined with the response surface methodology. The experiments were performed in a photochemical tubular reactor equipped with a 254-nm UV lamp, for [H2O2]0 and EP,0 in the ranges 1.6-9.6 mmol L-1 and 0.87 × 1018-3.6 × 1018 photons L-1 s-1, respectively. Total BPA degradation was achieved after 60 min of irradiation in all experiments. The best conditions were [H2O2]0 = 7.6 mmol L-1 and EP,0 = 3.6 × 1018 photons L-1 s-1, for which the best performance was obtained regarding the BPA degradation rate, BPA degradation after 15 min, and the second highest TOC removal after 180 min. However, in most experiments less than 75% TOC removal was observed, with 95% mineralization obtained only for the superior [H2O2]0 and EP,0. A mathematical model was developed, considering the reactor characteristics and the radiation field, based on the line source with parallel emission (LSPP) approach, in combination with the radiative transfer equation (RTE), mass balances, and a detailed kinetic model of the H2O2/UV process. The steady-state approximation was applied for all radical species. In the estimation of unknown kinetic constants, the non-linear least squares method was employed. The model was able to satisfactorily fit experimental BPA and H2O2 concentrations as a function of time. This work shows that the H2O2/UV process is a good alternative for BPA removal from aqueous streams, with total degradation of the target compound and adequate percent mineralization under optimal operating conditions. Such conditions may serve as first guidelines for pilot-plant and industrial processes operation. In addition, simulations using the proposed kinetic model may provide useful information for the design and scale-up of pre- or post-treatment of effluents containing this pollutant.
O bisfenol A (BPA) é amplamente utilizado na fabricação de plásticos, resinas epóxi e policarbonatos. Trata-se de um composto tóxico e um desregulador endócrino. Diferentes estudos evidenciam a presença do BPA em diversos compartimentos ambientais em todo planeta, identificando-o como um poluente persistente e resistente à degradação biológica, que apresenta efeitos sinergéticos com outros poluentes. Nesse contexto, os processos oxidativos avançados (POA) têm recebido atenção devido a sua capacidade em degradar poluentes com tais características, transformando-os em compostos menos perigosos ou até mesmo mineralizando-os totalmente. Apesar de haver trabalhos na literatura acerca da utilização de POA para degradação de BPA, estudos sistemáticos dos efeitos de variáveis de processo junto com a interpretação estatística dos resultados são virtualmente inexistentes. Além disso, até onde se sabe um modelo cinético rigoroso ainda não foi proposto para a degradação desse poluente por meio do processo H2O2/UV. Este trabalho teve por objetivo avaliar a degradação do BPA pelo processo H2O2/UV, investigando os efeitos da concentração inicial de H2O2 e da taxa específica de emissão de fótons (EP,0) por meio de um projeto experimental Doehlert, combinado com a análise de superfície de resposta. Os experimentos foram realizados em um reator tubular fotoquímico equipado com uma lâmpada UV de 254 nm, para [H2O2]0 e EP,0 entre 1,6-9,6 mmol L-1 e 0,87 × 1018 - 3,6 × 1018 fótons L-1 s-1, respectivamente. Todos os experimentos sob H2O2/UV resultaram em total degradação do BPA após 60 min de irradiação. Nesse caso, as melhores condições foram [H2O2]0 = 7,6 mmol L-1 e EP,0 = 3,6 × 1018 fótons L-1 s-1, para as quais se obteve o melhor desempenho quanto à taxa de degradação de BPA e à remoção após 15 min, e a segunda maior remoção de COT após 180 min. Entretanto, na maioria dos experimentos menos de 75% de remoção de COT foram observados, com 95% de mineralização obtida apenas para os maiores [H2O2]0 e EP,0. Elaborou-se um modelo matemático que considera as características do reator utilizado e o campo de radiação, baseado no modelo de fonte linear de emissão em planos paralelos (LSPP), combinado à equação de transferência radiativa (RTE), aos balanços materiais e a um modelo cinético detalhado do processo H2O2/UV. Foi empregada a aproximação de estado estacionário para todas as espécies radicalares. Na estimativa das constantes cinéticas desconhecidas, utilizou-se o método de mínimos quadrados não linear. Esse modelo foi capaz de ajustar satisfatoriamente as concentrações experimentais de BPA e de H2O2 em função do tempo. Este trabalho mostra que o processo H2O2/UV constitui uma alternativa conveniente para a degradação de BPA em matrizes aquosas, com total degradação do composto alvo e porcentagem de mineralização adequada nas condições ótimas de operação. Tais condições podem servir como diretrizes iniciais de processamento em escalas piloto e industrial. Por sua vez, simulações empregando o modelo matemático proposto permitem gerar informações úteis para projeto e aumento de escala de processos de pré- ou pós-tratamento de efluentes contendo esse poluente.

O uso da suplementação com levedura viva em equinos tem sido estudado, pelo potencial de redução da produção de lactato no intestino grosso sendo relatado por alguns autores, melhora da digestibilidade aparente da proteína bruta. Porém, o uso de levedura viva protegida ainda não foi relatado para a espécie. O objetivo do trabalho foi avaliar a digestibilidade aparente dos nutrientes e parâmetros de fermentação intestinal e gástrica com a suplementação de levedura viva e levedura viva protegida em equinos em manutenção. O delineamento experimental foi o quadrado latino duplo balanceado com oito animais, quatro dietas avaliados por quatro períodos de 22 dias cada, sendo 15 dias de adaptação à dieta, 5 dias de coleta de fezes (CTF), 1 dia para coleta de conteúdo gástrico e 2 semanas de intervalo entre os períodos. As médias dos tratamentos foram comparadas através de contrastes ortogonais (C1: controle [CTR] versus levedura [LEV], levedura protegida [PROT] e levedura viva + levedura protegida [L + P]; C2: L + P versus LEV e PROT; C3: LEV versus PROT). O nível de significância do teste utilizado foi a 10%. Não foram observados efeitos para pH nas fezes, concentração sérica de fator tumoral alfa, concentrações de ácido lático e ácidos de cadeia curta nas diferentes dietas. Não foi observado significância para a digestibilidade aparente dos nutrientes da dieta quando se usou levedura viva ou protegida (P=0,0683). Houve aumento das concentrações de ácido acético com o uso de levedura no conteúdo gástrico (P=0,0082). Avaliando a técnica de coleta sugerida, a adaptação realizada para este procedimento de coleta de digesta gástrica apresentou fácil aplicabilidade, com alta tolerância pelos equinos, além de proporcionar perfeita precisão do local de coleta a ser avaliado. A levedura viva e levedura protegida não apresentam efeito quanto a degradabilidade in vitro da matéria seca e da fibra em detergente neutro (P > 0,05). A fermentação com inóculo de fezes possui maiores taxas de produção de gás quando se utiliza feno como substrato e suplementação com levedura viva (P=0,0190). Quando se utiliza de conteúdo gástrico como inóculo, a levedura protegida apresenta menor produção de gases (P=0,0484).
The use of live yeast supplementation in equines has been studied for the potential reduction of lactate production in the large intestine and is reported by some authors to improve the apparent digestibility of crude protein. However, the use of protected live yeast has not yet been reported for the species. The aim of this study was to evaluate the apparent digestibility of nutrients and parameters of intestinal and gastric fermentation with the supplementation of live yeast and protected live yeast in horses. The experimental design was the double balanced latin square with eight animals, four diets evaluated for four periods of 22 days each, being 15 days of adaptation to the diet, 5 days of collection of feces (CTF), 1 day for collection of gastric content and 2 weeks interval between periods. The treatments were compared by means of orthogonal contrasts (C1: control [CTR] versus yeast [LEV], protected yeast [PROT] and live yeast + protected yeast [L + P]; C3: LEV versus PROT). The level of significance of the test used was 10%. No effects were observed for faecal pH, serum concentration of alpha tumor factor, lactic acid concentrations and short chain acids in the different diets. It was no possible to observe a difference significance on apparent digestibility in nutrients of diets when living or protected yeast (P = 0.0683). There was an increase in acetic acid concentrations with the use of yeast in gastric contents (P = 0.0082). Evaluating the suggested collection technique, the adaptation performed for this procedure of gastric digestion was easy to apply, with high tolerance by the horses, besides providing perfect accuracy of the collection site to be evaluated. Live yeast and protected yeast have no effect on the in vitro degradability of dry matter and neutral detergent fiber (P> 0.05). Fermentation with fecal inoculum has higher rates of gas production when hay is used as a substrate and supplementation with live yeast (P = 0.0190). When gastric contents are used as the inoculum, the protected yeast presents lower gas production (P = 0.0484).

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
Diets formulated with protein sources presenting different resistance to ruminal degradation were compared by evaluating intake, total and partial digestibility, nitrogen balance, fluxes of nutrients to omasum, production and microbial efficiency and ruminal parameters in goats. Eight rumen cannulated non-lactating, non- pregnant goats were distributed in a 4 x 4 Latin square design with two repeats. Treatments consisted of four diets where different source of plant protein account for the major protein source named soybean meal (SM), roasted soybean (RS), corn gluten meal (CGM), and cottonseed cake (CC). No difference was found as both intake and apparent digestibility of dry matter and nutrients were compared among diets. Reduction of ruminal digestibility for dry matter, crude protein and non fiber carbohydrates by using ration with RS, CGM and CC. Biological values and true digestibility for diets were similar. Amount of rumen protein were similar among rations, however fluxes of dry matter, protein and non fiber carbohydrate to omasum were higher for rations using roasted soybean, corn gluten meal and cottonseed cake. Ammonia nitrogen concentration was higher for ration with soybean meal as major protein source. Values of pH higher values were obtained for rations with RS and CC. Regarding kinetic of transit similar values were found among rations. Rations containing RS, CGM and CC as major protein source presented degradability smaller than diet using soybean meal as the major source of protein, but no difference among rations were found as availability and use by animals were compared. Diets with protein sources presenting reduced ruminal degradation do not compromised the bacterial growth, increasing flux of nutrients to omasum. Although pH and rumen ammonia are altered no compromise is observed in both production and microbial efficiency as those sources are used for dairy goats, which grant their use with similar efficiency to rations using source of more degradable protein.
Objetivou-se com este estudo, avaliar o efeito do uso de fontes protéicas apresentando diferentes graus de resistência à degradação ruminal sobre o consumo, digestibilidade total e parcial, balanço de compostos nitrogenados, fluxo de nutrientes para o omaso, produção e eficiência microbiana e características ruminais. Foram utilizadas oito cabras fistuladas no rúmen, não-gestantes e não lactantes, distribuídas em um delineamento em quadrado latino 4 x 4, duplicado. Foram utilizadas quatro dietas com diferentes fontes de proteína: farelo de soja (FS), soja grão tostada (SGT), farelo de glúten de milho (FGM) e torta de algodão (TA). As rações contendo FS, SGT, FGM e TA como fontes principais de proteína não influenciaram o consumo, a digestibilidade aparente total da matéria seca e dos nutrientes. Houve redução da digestibilidade ruminal da matéria seca, da proteína bruta e dos carboidratos não-fibrosos com o uso das rações contendo SGT, FGM e TA. Os valores biológicos e a digestibilidade total das dietas contendo diferentes fontes de proteína foram semelhantes, independente do perfil da degradação ruminal. As rações com diferentes fontes protéicas não apresentaram diferença na quantidade de proteína presente no rúmen, porém as rações contendo SGT, FGM e TA promoveram um maior fluxo de matéria seca, de proteína e de carboidratos não-fibrosos para o omaso. Maiores valores para a concentração de nitrogênio amoniacal foram obtidos com a ração contendo farelo de soja como principal fonte principal de proteína. Na avaliação de pH foram obtidos maiores valores para as rações contendo SGT e TA. Não houve diferença entre as rações com diferentes fontes de protína quanto à cinética de trânsito. As rações contendo SGT, FGM e TA como principais fontes protéicas apresentam menor degradabilidade ruminal comparativamente ao FS, no entanto as mesmas não diferem entre si, quanto sua disponibilidade e aproveitamento pelos animais. O uso destas fontes de proteína de menor degradabilidade ruminal promovem aumento no fluxo de nutrientes para o omaso e alteram parâmetros digestivos (como nitrogênio amoniacal e pH), sem comprometer a produção e eficiência microbiana, podendo ser utilizadas na alimentação de cabras leiteiras, o que garante o seu uso com eficiência similar à rações utilizando fontes protéicas com maior degradabilidade.

Os tratamentos convencionais de efluentes em geral não são eficientes para a degradação de compostos persistentes como os fármacos. Neste trabalho, estuda-se o tratamento de soluções aquosas contendo o antibiótico ciprofloxacina (CIP) por meio de processo oxidativo avançado baseado em ozônio. Para tanto, foram realizados experimentos em semi-batelada com recirculação de líquido em um reator (coluna de bolhas) com escoamento gás-líquido em contracorrente. Amostras de líquido foram retiradas e analisadas para medida das concentrações de CIP e de carbono orgânico total (COT); a concentração de ozônio no gás foi medida por espectrofotometria UV-vis. Estudaram-se os efeitos das seguintes variáveis quanto à degradação de CIP, por meio de um planejamento Doehlert: concentração de ozônio à entrada do reator (8-25 mgO3 L-1), pH (3,5-10,5) e concentração inicial de CIP (5-26 mg L-1). Avaliaram-se as seguintes variáveis dependentes por meio da análise de superfícies de resposta: variação de concentração de CIP em 2 minutos; taxa inicial de degradação de CIP e variação de concentração de COT em 30 minutos. Os resultados indicaram total degradação de ciprofloxacina em menos de 15 minutos, tanto por via direta, com ataque por ozônio molecular em meio ácido, como por via indireta, com ataque por radicais hidroxila em meio básico. Os compostos resultantes da degradação da CIP mostraram-se recalcitrantes, obtendo-se maiores remoções de COT após 30 minutos apenas em meio básico ou neutro (máximo de 72,8% para pH=7, [O3]=24,9 mgO3 L-1 e [CIP]0=15,8 mg L-1). Apesar da persistência dos compostos orgânicos remanescentes, os ensaios respirométricos sugeriram que os produtos de degradação são menos tóxicos que o composto de partida, com menor inibição da atividade microbiana. No conjunto, os resultados do trabalho indicam que o processo de ozonização pode ser aplicado para pré-tratamento de efluentes aquosos contendo ciprofloxacina em baixas concentrações, podendo ser associado a processos de tratamento biológico em ETEs antes do descarte.
Conventional wastewater treatment processes are not generally efficient for the degradation of persistent substances like pharmaceutical compounds. In this work, the treatment of aqueous solutions containing the antibiotic ciprofloxacin (CIP) by means of the ozone-based advanced oxidation process is studied. With this aim, experiments were carried out in semi-batch mode with liquid circulation in a bubble column reactor with gas-liquid counter flow. Liquid samples were analyzed for CIP and total organic carbon (TOC) concentrations; ozone concentration in the gas was measured by UVvisible spectrophotometry. The effects of the following variables on CIP degradation were studied according to a Doehlert experimental design: inlet ozone concentration (8 to 25 mgO3 L-1), pH (3.5 to 10.5), initial CIP concentration (5 to 26 mg L-1). The following dependent variables were investigated by response surface analysis: variation in CIP concentration after 2 minutes; CIP initial degradation rate and variation in TOC concentration after 30 minutes. The results showed total degradation of ciprofloxacin in less than 15 minutes either by direct reaction with molecular ozone in acidic medium, or by indirect attack of hydroxyl radicals in alkaline medium. Compounds resulting from CIP degradation showed to be recalcitrant, yielding larger TOC removals after 30 minutes only in alkaline or neutral medium (maximum of 72.8% for pH=7, [O3]=24.9 mgO3 L-1, and [CIP]0=15.8 mg L-1). Despite the persistence of remaining organic compounds, respirometric assays suggested that degradation products are less toxic than the parent compound, exhibiting lower inhibition of microbial activity. Overall, the results indicate that the ozonation process can be used in the pre-treatment of aqueous effluents containing ciprofloxacin in low concentrations, and could be associated with biological treatment processes in wastewater treatment plants prior to final disposal.

Societies are facing great challenges with obtaining a good quality and quantity of drinking water in the context of climate change. Increases in natural organic matter (NOM) and per- and polyfluoroalkyl substances (PFAS) have been observed in lakes and drinking water the past years, which is of great concern for water treatment plants in Sweden. It is therefore vital to increase the knowledge regarding the distribution of these substances in the environment. The main objective of this project was therefore to further develop a hydrodynamic model for lake Ekoln by including transportation and degradation of NOM. This was to be done by calibrating the model in terms of total organic carbon (TOC) and Water colour (Colour). A second objective was to investigate the requirements to successfully model PFAS in Ekoln for future studies. The study was done using the model MIKE 3 FM, developed by the Danish Hydraulic Institute (DHI) The two variables TOC and Colour, were calibrated separately for the period of February 2017 to September 2018. For TOC the within-lake processes were decay and sedimentation. These were described using a reference decay constant for 20 °C (k0), that was scaled using the Arrhenius temperature coefficient (θ), and sedimentation was represented by a settling velocity (vsm). For Colour the included process was photooxidation. This process was described using a maximum photooxidation rate (kphoto) that was scaled using the Monod relation including parameters for minimum photosynthetically active radiation (PAR) necessary for photooxidation to occur (Imin) and a PAR half saturation constant (I1/2). The calibration of TOC resulted in the following best fit parameters for k0  of 0.001 d-1, θ of 1.07 and vsm of 0.001 md-1. The calibration of Colour resulted in the following best fit parameters for kphoto of 0.0125 d-1, Imin of 0 µmol photons m-2s-1 and I1/2 of 4 µmol photons m-2s-1. Overall it can be concluded that the chosen processes managed to capture the seasonal variations of TOC and Colour, and the calibrated parameter values are in line with similar studies. The assumption of not including autochthonous input proved to be the biggest source of error in the calibration of TOC but proved to have a minor influence on the calibration of Colour. To achieve a more realistic representation of photooxidation in the vertical profile, for the simulation of Colour, more processes should be considered to be added in the model in future studies. The results presented in this study contributes with increased knowledge of carbon budgets in lakes and can be used to predict water quality hazards connected to climate change and extreme events. The limited access to PFAS data for Ekoln, constrained the study of PFAS and only two sources could therefore be studied: The sewage treatment plant Kungsängsverket and precipitation. The results showed that the simulated concentrations of PFAS in Ekoln only accounted for 40 % of the observed concentrations. It could further be concluded that the contribution from precipitation is negligible. For future studies it is judged to be vital to include Fyrisån as a PFAS source, and to look into processes that influence PFAS distribution, such as sedimentation and adsorption to organic matter.
Samhällen står idag inför stora utmaningar vad gäller att tillhandahålla god kvalitet och kvantitet av dricksvatten under rådande klimatförändringar. De senaste åren har det observerats ökande halter av naturligt organiskt material (NOM) och per- och polyfluorerade alkylsubstanser (PFAS) i sjöar och dricksvatten, vilket är bekymmersamt för Sveriges vattenreningsverk. Det är därför av största vikt att öka kunskapen om dessa ämnens distribution i miljön. Huvudsyftet med denna studie var därför att vidareutveckla en hydrodynamisk modell för sjön Ekoln så att den även inkluderar transporten och nedbrytningen av NOM. Detta utfördes genom att kalibrera modellen för totalt organisk kol (TOC) och Vattenfärg (Färg). Ett andra syfte var att undersöka vilka förutsättningar som krävs för att kunna modellera PFAS på ett korrekt sätt i Ekoln. Studien utfördes i modellverktyget MIKE 3 FM, utvecklat av DHI.  De två variablerna TOC och Färg kalibrerades separat för perioden februari 2017 – september 2018. Processerna som valdes att påverka TOC var nedbrytning och sedimentation. Dessa processer beskrevs med hjälp av en referens-nedbrytningskonstant för 20 °C (k0), vilken anpassades med hjälp av Arrhenius temperaturkoefficient (θ) och sedimentation beskrevs med hjälp av en sedimentationshastighet (vsm). Färg påverkades endast av processen fotooxidation vilken beskrevs med en maximal hastighet för fotooxidation  (kphoto) som anpassades med hjälp av Monods relation. Anpassningen skedde med hjälp av parametern för minimal fotosyntetiskt aktivt ljus (PAR) för att fotooxidation ska ske (Imin) samt en PAR halv mättnads konstant (I1/2) .  Kalibreringen resulterade i värden för k0 av 0.001 d-1, θ av 1.07 och vsm av 0.001 md-1. Kalibreringen för Färg resulterade i värden för kphoto av 0.0125 d-1, Imin av 0 µmol fotoner m-2s-1 och I1/2 av 4 µmol fotoner m-2s-1. Det kan konstateras att de valda processerna lyckas med att beskriva säsongsvariationerna av både TOC och Färg och att de kalibrerade parametervärdena stämmer överens med litteraturen. Antagandet om att inte inkludera autoktont tillförsel av organiskt material (NOM från ytvatten), visade sig vara den största felkällan i simulering av TOC, men visade sig ha en mycket liten påverkan på simuleringen av Färg. För en mer realistisk bild av fotooxidations spridning i djupled, för simuleringen av Färg, bör fler processer övervägas att inkluderas i modellen för framtida studier.  Studien av PFAS var begränsad av tillgången till data, vilket medförde att endast två källor av PFAS till Ekoln analyserades: reningsverket Kungsängsverket och nederbörd. Resultaten visade att den simulerade koncentrationen av PFAS endast motsvarade 40 % av den observerade. Vidare kunde det konstateras att tillförsel av PFAS från regn kan antas vara försumbar. För framtida studier av PFAS i Ekoln bedöms det vara avgörande att inkludera Fyrisån som en källa, samt att vidare undersöka processer som påverkar transporten av PFAS så som sedimentation och adsorption till organiskt material.

Grease is among the most widely used lubricants in rolling element bearings. Proper understanding of the effect of lubrication due to grease aging can provide a significant increase in the life of the engineering systems. However, at present, there is no sufficient understanding of the grease aging effect in rolling elements bearing. This restricts the optimal usage of the bearing and timely monitoring of the grease. The current research work tries to address this issue with an experimental investigation. This project studies the behavior of 4 types of greases in rolling elements bearings for various operating conditions by recording the temperature and acoustic emission data. The aged samples were prepared to keep in the oven at 150 °C for a series of time duration letting it go through the chemical changes and thermal degradation. Tests were carried out in a test rig with the different levels of oxidized greases for 5 hrs time. And the effects in bearing temperature, acoustic emission were recorded. This is an investigation to analyze the effects of grease composition and aging in rolling elements lubrication by means of acoustic emission and bearing temperature. The IR spectroscopy was carried from the samples collected from the oven in order to understand the change in lubricant composition. The results show that the grease with di-urea thickener and base oil of synthetic ether and polyolester gives the best bearing temperature and acoustic emission behavior compared to the other grease type. The possibility of using the acoustic emission and temperature data to monitor the grease aging is also presented. Along with this, the possibility of using the AE statistical methods, AE count method, and energy plot were also explored to relate with the degree of aging.

This thesis describes the synthesis and characterisation of titania photocatalysts for incorporation into a polyethylene film. Monodisperse, anatase-phase titania nanoparticles are prepared and the synthesis conditions necessary for attraction to a laponite clay support are determined. Methods of preventing agglomeration of the laponite system such as the use of a polyethylene oxide surfactant or chemical modification of the laponite plate edges with a dimethyloctyl methoxysilane are also explored. Finally, photocatalytic studies on the laponite-supported titania nanoparticles are performed, and the compatibility and photoactivity of these materials in the polyethylene film are examined.

碩士
朝陽科技大學
環境工程與管理系碩士班
98
A large volume of spent neutralization solution was generated from waste etching liquor by electronic industry. The pH of spent neutralization solution is high. The waste liquor could be further neutralized, but its high salt content is a big problem. If the waste liquor discharged into river, it could cause soil salinization and alkalization. It also contents high TOC (total organic carbon 200~4000 mg/L) carried from the photoresister developing process in the printed circuit board Manufacturer. In this research project TOC will be degraded by advanced oxidation processes (UV/H2O2、UV/O3、electrocatalysis). Consequently, the waste liquor acts as a raw material for the synthesis of sodium chlorate by an electrochemical process. This project focuses on the operation parameters of the above process. The results showed UV/H2O2 process can’t be adopted for treatment of spent neutralization solutions come from different batchs, and TOC remove ratios are not stable(some batches are 70~85%，other batches are 10~25%). UV/O3 process resulted in the solution bubbling and was unable to operate. Electrocatalysis process achieved stable remove ratios for spent solutions come from different batchs. Following electrocatalysis, electrosynthesis of sodium chlorate in the same tank is available. In the first 8 hours TOC remove ratios were about 85~90%, and in the following 8 hours the concentration of synthesized sodium chlorate achieved 44 g/L. This project develops a cleaner electrochemical production technology to treat high TOC and high salt content waste liquid and produce sodium chlorate.

abstract: Space exploration is a large field that requires high performing circuitry due to the harsh environment. Within a space environment one of the biggest factors leading to circuit failure is radiation. Circuits must be robust enough to continue operation after being exposed to the high doses of radiation. Bandgap reference (BGR) circuits are designed to be voltage references that stay stable across a wide range of supply voltages and temperatures. A bandgap reference is a piece of a large circuit that supplies critical elements of the large circuit with a constant voltage. When used in a space environment with large amounts of radiation a BGR needs to maintain its output voltage to enable the rest of the circuit to operate under proper conditions. Since a BGR is not a standalone circuit it is difficult and expensive to test if a BGR is maintaining its reference voltage. This thesis describes a methodology of isolating and simulating bandgap references. Both NPN and PNP bandgap references are simulated over a variety of radiation doses and dose rates. This methodology will allow the degradation due to radiation of a BGR to be modeled easily and affordably. It can be observed that many circuits experience enhanced low dose rate sensitivity (ELDRS) which can lead to failure at low total ionizing doses (TID) of radiation. A compact model library demonstrating degradation of transistors at both high and low dose rates (HDR and LDR) will be used to show bandgap references reliability. Specifically, two bandgap references being utilized in commercial off the shelf low dropout regulators (LDO) will be evaluated. The LDOs are reverse engineered in a simulation program with integrated circuit emphasis (SPICE). Within the two LDOs the bandgaps will be the points of interest. Of the LDOs one has a positive regulated voltage and one has a negative regulated voltage. This requires an NPN and a PNP based BGR respectively. This simulation methodology will draw conclusions about the above bandgap references, and how they operate under radiation at different doses and dose rates.
Dissertation/Thesis
Masters Thesis Electrical Engineering 2019

Heterojunctions were generated between tungsten trioxide and tetraphenyl porphyrin with reduced graphene oxide or exfoliated graphite support for mineralisation of acid blue 25 dye under visible light radiation. Moreover, degradation of pharmaceuticals was conducted using p-n heterojunctions between WO3 and Co3O4 and a direct Z-scheme heterojunction between BiOI and Co3O4 prepared using in-situ method and solvothermal self-assembly method respectively. The synthesized materials were characterised using Raman, FTIR, SEM/EDS, TEM, XRD, TGA, BET, UV-Vis and PL techniques. UV-Vis, TOC and HPLC-QTOF-MS were used to study the degradation efficiency and pathway. Scavenger trapping experiments were conducted to propose the charge transfer mechanisms. The highest degradation efficiency (99 %) was achieved for the dye and the pharmaceuticals using visible light. The mineralisation ability of the fabricated nanomaterials was pH dependent with acidic conditions favouring the removal of the dye (pH 5) while alkaline conditions favoured the mineralisation of pharmaceuticals (pH 10 – 11).
Civil and Chemical Engineering

Multi-carrier systems based on orthogonal frequency division multiplexing (OFDM) are efficient technologies for the implementation of broadband wireless communication systems. OFDM is widely used and has been adopted for current mobile broadband wireless communication systems such as IEEE 802.a/g wireless LANs, WiMAX, 3GPP LTE, and DVB-T/H digital video broadcasting systems. Despite their many advantages, however, OFDM-based systems suffer from potentially high peak-to-average power ratio (PAR). Since communication systems typically include nonlinear devices such as RF power amplifiers (PA) and digital-to-analog converters (DAC), high PAR results in increased symbol error rates and spectral radiation. To mitigate these nonlinear effects and to avoid nonlinear saturation effects of the PA, the operating point of a signal with high peak power must be backed off into the linear region of the PA. This so-called output backoff (OBO) results in a reduced power conversion efficiency which limits the battery life for mobile applications, reduces the coverage range, and increases both the cost of the PA and power consumption in the cellular base station. With the increasing demand for high energy efficiency, low power consumption, and greenhouse gas emission reduction, PAR reduction is a key technique in the design of practical OFDM systems. Motivated by the PAR reduction problem associated with multi-carrier systems, such as OFDM, this research explores the state of the art of PAR reduction techniques and develops new signal processing techniques that can achieve a minimum PAR for given system parameters and that are compatible with the appropriate standards. The following are the three principal contributions of this dissertation research. First, we present and derive the semi-analytical results for the output of asymptotic iterative clipping and filtering. This work provides expressions and analytical techniques for estimating the attenuation factor, error vector magnitude, and bit-error-rate (BER), using a noise enhancement factor that is obtained by simulation. With these semi-analytical results, we obtain a relationship between the BER and the target clipping level for asymptotic iterative clipping and filtering. These results serve as a performance benchmark for designing PAR reduction techniques using iterative clipping and filtering in OFDM systems. Second, we analyze the impact of the selected mapping (SLM) technique on BER performance of OFDM systems in an additive white Gaussian noise channel in the presence of nonlinearity. We first derive a closed-form expression for the envelope power distribution in an OFDM system with SLM. Then, using this derived envelope power distribution, we investigate the BER performance and the total degradation (TD) of OFDM systems with SLM under the existence of nonlinearity. As a result, we obtain the TD-minimizing peak backoff (PBO) and clipping ratio as functions of the number of candidate signals in SLM. Third, we propose an adaptive clipping control algorithm and pilotaided algorithm to address a fundamental issue associated with two lowcomplexity PAR reduction techniques, namely, tone reservation (TR) and active constellation extension (ACE). Specifically, we discovered that the existing low-complexity algorithms have a low clipping ratio problem in that they can not achieve the minimum PAR when the target clipping level is set below the initially unknown optimum value. Using our proposed algorithms, we overcome this problem and demonstrate that additional PAR reduction is obtained for any low value of the initial target clipping ratio.
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