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Um estudo sobre os relacionamentos entre formas de distribuição da capacidade produtiva e sistemas de programação e controle da produção / A study on the relationship between types of productive capacity distribution and production planning and control systemsSouza, Fernando Bernardi de 20 December 2001 (has links)
A maioria das pesquisas na área de alocação de capacidades entre recursos de uma linha de manufatura propõe as formas balanceadas e em bowl como as mais eficientes para o desempenho de linha como um todo. A maior parte destes estudos é baseada em sistemas simplificados de empurrar a produção, desconsiderando sistemas mais atuais de planejamento e controle da produção (PCP). Por outro lado, estudos referentes à eficiência de sistemas de planejamento e controle da produção não consideram o efeito que critérios distintos de alocação de capacidades podem ter seus desempenhos. Este trabalho tem como objetivo estudar o relacionamento entre as políticas de alocação de capacidades e os sistemas de PCP. O principal critério de desempenho adotado foi o throughput, obtido segundo níveis médios e máximos de estoque em processo em uma linha de produção com cinco recursos. Foram estudados oito tipos de critérios de alocação de capacidades e quatro tipos de sistemas PCP, segundo três níveis de desbalanceamento de cargas, três níveis de coeficiente de variabilidade dos tempos de processamento dos recursos e cinco níveis máximos de estoque em processo. Foi utilizada uma ferramenta de simulação para criar modelos e simular 1386 cenários distintos. Como resultado, percebeu-se uma estreita interdependência entre políticas de alocação e sistemas de PCP. A pesquisa identificou; ainda, que não há um critério de alocação de capacidades nem um sistema de PCP que se mostre melhorem todas as condições testadas, contrariando diversos estudos sobre o tema. / Most of the researches on production capacity allocation among resources, proposes the use of balanced and bowI allocation as the most efficient methods in terms of performance. Such studies were generally based on simplified push production systems, not considering other production pIanning and controI systems (PPC). On the other hand, studies about efficiency of PPC systems don\'t consider the effect of different criteria of capacity allocation on the performance of the PPC systems. The purpose of this research is to investigate how different capacity allocation criteria and different PPC systems interreIate among each other. The major performance criteria used to rank each combination was the resulting throughput, considering several average and maximum levels of work in process (WIP) in a production line with five resources. Eight different types of capacity allocation criteria and four types of PPC systems were studied, with three levels of unbalanced loads, three levels of variability coefficient for processing times and tive maximum WIP levels. A simulation tool was used in order to generate the models and run 1386 different scenarios. As a result, it could be noticed a strong interrelationship between the allocation criteria and the PPC systems. The research also showed, on the contrary of many studies on this subject, that for all the combination tested, none of capacity allocation criteria nor PPC systems stood out on the best option.
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Um estudo sobre os relacionamentos entre formas de distribuição da capacidade produtiva e sistemas de programação e controle da produção / A study on the relationship between types of productive capacity distribution and production planning and control systemsFernando Bernardi de Souza 20 December 2001 (has links)
A maioria das pesquisas na área de alocação de capacidades entre recursos de uma linha de manufatura propõe as formas balanceadas e em bowl como as mais eficientes para o desempenho de linha como um todo. A maior parte destes estudos é baseada em sistemas simplificados de empurrar a produção, desconsiderando sistemas mais atuais de planejamento e controle da produção (PCP). Por outro lado, estudos referentes à eficiência de sistemas de planejamento e controle da produção não consideram o efeito que critérios distintos de alocação de capacidades podem ter seus desempenhos. Este trabalho tem como objetivo estudar o relacionamento entre as políticas de alocação de capacidades e os sistemas de PCP. O principal critério de desempenho adotado foi o throughput, obtido segundo níveis médios e máximos de estoque em processo em uma linha de produção com cinco recursos. Foram estudados oito tipos de critérios de alocação de capacidades e quatro tipos de sistemas PCP, segundo três níveis de desbalanceamento de cargas, três níveis de coeficiente de variabilidade dos tempos de processamento dos recursos e cinco níveis máximos de estoque em processo. Foi utilizada uma ferramenta de simulação para criar modelos e simular 1386 cenários distintos. Como resultado, percebeu-se uma estreita interdependência entre políticas de alocação e sistemas de PCP. A pesquisa identificou; ainda, que não há um critério de alocação de capacidades nem um sistema de PCP que se mostre melhorem todas as condições testadas, contrariando diversos estudos sobre o tema. / Most of the researches on production capacity allocation among resources, proposes the use of balanced and bowI allocation as the most efficient methods in terms of performance. Such studies were generally based on simplified push production systems, not considering other production pIanning and controI systems (PPC). On the other hand, studies about efficiency of PPC systems don\'t consider the effect of different criteria of capacity allocation on the performance of the PPC systems. The purpose of this research is to investigate how different capacity allocation criteria and different PPC systems interreIate among each other. The major performance criteria used to rank each combination was the resulting throughput, considering several average and maximum levels of work in process (WIP) in a production line with five resources. Eight different types of capacity allocation criteria and four types of PPC systems were studied, with three levels of unbalanced loads, three levels of variability coefficient for processing times and tive maximum WIP levels. A simulation tool was used in order to generate the models and run 1386 different scenarios. As a result, it could be noticed a strong interrelationship between the allocation criteria and the PPC systems. The research also showed, on the contrary of many studies on this subject, that for all the combination tested, none of capacity allocation criteria nor PPC systems stood out on the best option.
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Migration during the Dust Bowl /Kerr, Devin. January 2007 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 106-109).
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Katastrofhantering i kapitalets förlovade land : Den amerikanska statens hantering av Dust Bowl och orkanen Katrina / Disaster Management in the Beloved Land of Capital : The United States' Governmental Response to the Dust Bowl and Hurricane KatrinaPhilipsson Svensson, Erik January 2015 (has links)
In this thesis, I enquire into how the USA – our world’s wealthiest and most powerful nation – and its federal government has dealt with two of its most severe natural disasters: the drought and dust storms that plagued the Great Plains during the 1930’s, i.e. the Dust Bowl, and Hurricane Katrina, which made landfall in late August 2005. I attempt to identify differences and similarities and analyze if and, in that case, how the hegemonic politico-economic paradigm affected the federal management of these crises. This comparison is made relevant by the fact that two differing paradigms were at play during these events. In the thirties, President Franklin D. Roosevelt launched his “New Deal”, a series of counter cyclical measures in line with the Keynesian school of economics, as a response to the overwhelming economic depression as well as the raging drought. In sharp contrast, Hurricane Katrina swept over a country ridden by decades of neoliberal governance. I show that political economy plays an important role in the success and/or failure of, in this case, the United States’ management of natural disasters. Finally, I argue for the return (or, rather, the creation) of an expanded and more socially and environmentally conscious public sector, which, in times of crisis, is able to represent all of its citizens – regardless of class or race.
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Analysis of the combustion process and soot formation in a single cylinder optical engine fueled with e-fuels and using different piston geometriesVargas Lewiski, Felipe de 10 January 2022 (has links)
[ES] La reducción de emisiones en motores de combustión interna (MCI) es uno de los mayores desafíos técnicos de la sociedad. Aunque están surgiendo nuevas tecnologías para la movilidad, el ICE seguirá teniendo un papel clave en el transporte durante las próximas décadas. Los motores diesel son un desafío en términos de emisiones contaminantes, en particular óxidos de nitrógeno (NOX) y hollín. De hecho, el último representa el 50 % de las emisiones totales de este tipo de motores. En este contexto, las nuevas tecnologías de hardware y los nuevos combustibles renovables han mostrado un gran potencial para reducir las emisiones de hollín sin afectar la eficiencia del motor (emisiones de CO2). Por esta razón, los impactos del uso de e-fuels (OMEX y FT diesel) y diferentes geometrías del bowl del pistón (reentrante, labio escalonado y labio escalonado con ondas) en la formación de hollín y el desarrollo de la combustión han sido analizados en un motor óptico mono cilíndrico diesel. Primero, se realizó una caracterización del flujo en el cilindro utilizando un pistón de geometría real (Reentrante) y aplicando la técnica de velocímetro de imágenes por partículas (PIV). Posteriormente, se analizó el movimiento de la llama, el proceso de combustión y la formación de hollín para diferentes geometrías de pistón mediante diversas técnicas ópticas como la velocímetro de imagen por combustión (CIV), luminosidad natural, quimioluminiscencia OH * y pirometría de 2 colores. Finalmente, se estudió el proceso de combustión y la formación de hollín al utilizar diferentes e-fuels aplicando las mismas técnicas ópticas utilizadas anteriormente. Además, para esta parte del estudio, se incluyó una técnica óptica específica denominada espectroscopia de alta velocidad para el análisis de hollín. Con respecto a la evaluación de las distintas geometrías del bowl, el labio escalonado y el labio escalonado con ondas presentaron una oxidación tardía del hollín que ha sido más rápida en comparación con la geometría reentrante. En condiciones extremas de hollín, también se observaron diferencias entre el labio escalonado y el labio escalonado con ondas. Se observó una oxidación más rápida del hollín para el segundo. Los e-fuels mostraron una notable reducción en la formación de hollín (especialmente OMEX) en comparación con el diesel fósil. A partir del análisis de espectroscopia, es posible afirmar la ausencia de hollín durante la combustión de OMEX puro. En general, tanto la aplicación de nuevos hardware (geometrías de bowls) como nuevos tipos de combustibles (e-fuels) en motores diesel han presentado un gran potencial para disminuir las emisiones de hollín / [CA] La reducció d'emissions en motors de combustió interna (MCI) es un dels majors reptes tècnics de la societat. Encara que estan sorgint noves tecnologies per a la mobilitat, el ICE seguirà tenint un paper clau en el transport durant les pròximes dècades. Els motors diesel son un dels reptes en termes d'emissió de contaminants, en particular òxids de nitrogen (NOX) i sutge. De fet, l'últim representa el 50% de les emissions totals d'aquest tipus de motor. Dins aquest context, les noves tecnologies de hardware y de nous combustibles renovables han mostrat un gran potencial per reduir les emissions de sutge sense afectar l'eficiència del motor (emissions de CO2). Per aquesta raó, els impactes sobre l'ús de e-fuels (OMEX i FT-diesel) i diferents geometries de bowl del pistó (re-entrant, llavi escalonat i llavi escalonat amb ones) en la formació de sutge i el desenvolupament de la combustió, han estat analitzats en un motor òptic mono-cilíndric diesel. Primer, es va realitzar una caracterització de flux en el cilindre utilitzant un pistó amb geometria real (re-entrant) i aplicant la tècnica de velocimetria de imatges per partícules (PIV). Posteriorment, es va analitzar el moviment de la flama, el procés de combustió i la formació de sutge per a diferents geometries de pistó mitjançant diverses tècniques òptiques com per exemple la de velocimetria de imatge per combustió (CIV), lluminositat natural, quimioluminescència de OH* i pirometria de 2 colors. Finalment, es va estudiar el procés de combustió i la formació de sutge utilitzant diferents e-fuels aplicant les mateixes tècniques òptiques utilitzades anteriorment. A més, per aquesta part de l'estudi, es va implementar una tècnica òptica específica denominada espectroscòpia d'alta velocitat per a l'anàlisi del sutge. Respecte a l'avaluació de les distintes geometries de bowl, els llavis escalonats i els escalonats amb ones presentaren una oxidació tardana del sutge que ha estat més ràpida en comparació amb la de geometria re-entrant. En condicions extremes de sutge, també es varen observar diferencies entre la geometria de llavi escalonat y la de llavi escalonat amb ones. Es va observar una oxidació més ràpida del sutge per al segon. Els e-fuels mostraren una reducció més ràpida del sutge (especialment l'OMEX) en comparació amb el diesel fòssil. A partir de l'anàlisi d'espectroscòpia, es possible afirmar l'absència de sutge durant la combustió de l'OMEX pur. En general, tant l'aplicació de nous hardwares (geometries de bowl) com nous tipus de combustibles (e-fuels) en motors diesel han presentat un gran potencial per a la reducció d'emissions de sutge. / [EN] The emissions reduction in internal combustion engines (ICE) is one of the greatest technical challenges of society. Although new technologies for mobility are emerging, the ICE will still have a key role in transport over the next decades. Diesel engines are challenging in terms of pollutant emissions, in particular nitrogen oxides (NOX) and particles. In fact, the last one represents 50 % of total emissions of this kind of engine. In this context, new hardware technologies as well as new renewable fuels have shown great potential to reduce soot emissions without affecting engine efficiency (CO2) emissions. For this reason, the impacts of using e-fuels (OMEX and FT-diesel) and different piston bowl geometries (re-entrant, stepped lip and stepped lip-wave bowl) on soot formation and combustion development were analyzed in a single cylinder optical diesel engine. First, an in-cylinder flow characterization when using a real bowl shape was performed by applying particle image velocimetry (PIV) technique. Subsequently, the flame movement, combustion process and soot formation were analyzed for different piston geometries through several optical techniques such as combustion image velocimetry (CIV), natural luminosity, OH* chemiluminescence and 2 color pyrometry. Finally, the combustion process and soot formation when using different e-fuels were studied by applying the same optical techniques used previously. In addition, for this part of the study, it was included a specific optical technique named high-speed spectroscopy for the soot analysis. Regarding the bowl geometries evaluation, the stepped lip and wave-stepped lip presented a faster late soot oxidation in comparison with the re-entrant geometry. Under extreme soot conditions, differences were also observed between the wave-stepped lip and the stepped lip. A faster soot oxidation was observed for the first one. The e-fuels showed a remarkable reduction in soot formation (especially OMEX) when compared with fossil diesel. From the spectroscopy analysis, it is possible to state the absence of soot during the combustion of pure OMEX. In general, the application of new hardware (bowl geometries) as well as new kind of fuels in diesel engines have presented a great potential in order to diminish the soot emissions. / This work was partially funded by Generalitat Valenciana through the Programa
Santiago Grisolía (GRISOLIAP/2018/142) program. / Vargas Lewiski, FD. (2021). Analysis of the combustion process and soot formation in a single cylinder optical engine fueled with e-fuels and using different piston geometries [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180351 / TESIS
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Dark Consciousness: Theory of Mind and Henry James’s The Golden BowlMaillet, Adam 04 August 2011 (has links)
Using the psychological concepts of Theory of Mind and embodied cognition, the author explores and questions the traditional readings of Henry James's novel, The Golden Bowl, and its protagonist, Maggie Verver. Although the majority of critics view her as a positive character, James takes great effort to subvert her thoughts and mislead the reader. Despite lacking a modern technical vocabulary, James remains acutely aware of how human cognitive structures both process a text and function within a social setting.
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Progress towards accessing a C3v [6,6] nanotube end-cap and development of a microwave assisted anionic cyclodehydrogenation reactionBelanger, Anthony January 2008 (has links)
Thesis advisor: Lawrence T. Scott / This dissertation describes the work that has been carried out towards accessing a C3v [6,6] nanotube end-cap through rational chemical synthesis. Continued advancement in carbon nanotube research has driven scientists to develop a successful route to usable quantities of nanotubes that are homogeneous in structure. Due to the current inability to separate nanotube mixtures efficiently, researchers in fields ranging from chemistry to computer science have been unable to exploit fully all that these unique molecules have to offer. Our envisioned approach to this obstacle involves elongation of a template endcap using iterative growth chemistry. The final stage of the proposed end-cap synthesis involves the execution of a six fold cyclodehydrogenation reaction. To carry out this desired transformation, a new microwave assisted variant of the anionic cyclodehydrogenation reaction has been developed. Through this chemistry we have been able to access a variety of both known and novel polycyclic aromatic hydrocarbons, often in impressively high yields. We hope that this chemistry will be useful to us in accessing the target nanotube end-caps, and to others in providing a new route to accessing a variety of polycyclic aromatic hydrocarbon cores. / Thesis (PhD) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
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Efeito tigela em linhas de produção: novas evidências computacionais / Bowl phenomenon in assembly lines: new computational evidenceCastellucci, Pedro Belin 17 December 2014 (has links)
Linhas de produção são sistemas fabris para produção em larga escala, com grande importância no sistema industrial atual. Como se trata de um sistema já consolidado, é natural que existam métricas de desempenho e estratégias para otimização de eficiência para as diversas configurações de linhas de produção existentes. Este trabalho se concentra em linhas seriais não-ritmadas e estocásticas. Em particular, o interesse é no efeito de se desbalancear adequadamente uma linha de produção para melhorar sua produtividade, o que é denominado na literatura de fenômeno Tigela (Bowl phenomenon). Uma revisão da literatura mostrou que esse fenômeno já foi estudado em diferentes cenários: linhas com e sem buffers, diversos perfis de carga ao longo da linha e diferentes distribuições probabilísticas regendo os tempos de execução das tarefas. Contudo, nenhum dos estudos considerou a indivisibilidade das tarefas, isto é, o fato de que cada tarefa deve ser executada em uma única estação. Essa é a principal lacuna explorada neste estudo. Para isso, são utilizadas instâncias recentemente propostas do Problema Simples de Balanceamento de Linhas de Produção (SALBP, na sigla em inglês) e instâncias do Problema de Designação de Trabalhadores e Balanceamento de Linhas de Produção (ALWABP), que são solucionadas a partir de modelos de programação inteira mista que induzem soluções de acordo com o efeito Tigela. Essas soluções são utilizadas em um modelo de simulação estocástico, também apresentado neste trabalho. Em linhas gerais, os resultados mostram que as soluções do SALBP e ALWABP obtidas podem se beneficiar do efeito Tigela. Além disso, a variedade das instâncias utilizadas nos experimentos argumentam em favor de uma maior capacidade de generalização dos resultados para casos práticos se comparados aos casos simplificados previamente discutidos na literatura. / Assembly lines are large-scale production systems with great value in modern industrial systems. Perfomance measures and strategies have been proposed in order to evaluate and improve the efficiency of numerous assembly line configurations. This dissertation focuses on serial unpaced (stochastic) assembly lines. In particular, the interest of this study is in the effect of deliberately unbalacing the line in a specific manner in order to enhance its performance, a strategy that exploits the so-called Bowl phenomenon. The literature has studied this phenomenon in different scenarios: buffered and unbuffered lines, different workload profiles along the line and different probabilistic task time distributions. However, none of the identified studies considers task indivisibility, an intrisic characteristic of real-world assembly line balancing problems, namely, each task has to be executed in a single station. This is the main gap explored in this study. Thereunto, we use recently proposed instances for the Simple Assembly Line Balancing Problem (SALBP) and some Assembly Line Worker Assignment and Balancing Problem (ALWABP) instances, which are solved using mixed integer programming models capable of inducing bowl workload profiles. These solutions are used as input in a stochastic simulation model, also presented in this study. Overall, the results show that SALBP and ALWABP solutions may benefit from the Bowl phenomenon. Furthermore, the variety of the instances considered in the experiments allows for a better generalization of the results to real-world scenarios if compared to the simplified cases previously shown in the literature.
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Composição nutricional e práticas higiênicossanitárias na produção de açaí na tigela: diagnóstico e intervenção / Nutritional composition and hygienic sanitary practices in the production of acai in the bowl: diagnosis and interventionMoura, Eveline Gomes Rosa de 28 February 2014 (has links)
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Previous issue date: 2014-02-28 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Why be manipulated during the entire production chain, the product derived
from acai may contain a high microbial load, which favors contamination of
food. This study aimed to analyze the chemical composition and microbiological
quality of acai in the bowl sold in the city of Goiânia and the impact of training
on Good Manufacturing Practices. Study conducted in three stages was
conducted in 23 stores. In the first and third step two samples with 300 mL of
acai in the bowl were collected, prepared with acai pulp, guarana syrup and
banana and another with acai pulp, guarana syrup and strawberry. Were also
collected swabs from surfaces of hands and nasal cavities of 34 handlers
involved in the preparation of acai and applied the checklist based on RDC
216/2004, to assess the physical and functional conditions of the
establishments. In the second stage, training in Good Manufacturing Practices
with applicable pre and post test was performed. The microbiological protocol
was based on the RDC 12/2001 and the American Public Health Association.
The chemical composition was determined by the method established by the
Association of Official Analytical Chemists. Of the 46 samples collected in the
first stage, 15.2 % had more than the maximum limit for coliform count at 45 ºC,
26% for coliforms at 35 ºC, 78.2 % for coagulase positive staphylococcus and
100% aerobic mesophilic. In the third stage, 21.7% had greater than allowed for
coliform count at 45 °C, 8.6% for coliforms at 35 ºC, 6.5% for coagulase positive
staphylococcus and 73.9% for mesophilic aerobic. As the handlers before
intervention contamination was detected by E. coli on the surfaces of the hands
of a handler and this result was the same after training. As to the nasal cavities,
the presence of this bacterium reduced from five to no handler contaminated.
For S.,aureus, a handler was with surfaces contaminated in the first stage
hands, and the number increased to three in the second. By analyzing the
nostrils five handlers harboring S. aureus prior to training seven after the
intervention. In the checklist, among the 12 items checked, only three showed
improvement with respect to the percentage of compliance from one stage to
another: raw materials, ingredients and packaging, documentation and
registration and accountability. Regarding training, the average accuracy in the
pretest was 86.8%, and 97% post-test. As to composition, there was no
difference in nutritional attributes in relation to the type of fruit added in the
preparation of acai in the bowl. It is concluded that most of the samples
collected showed inadequate sanitary higienic conditions, highlighting the need
to implement an effective system of quality control in the areas of food handling,
to ensure the safety of the final product. / Por ser manipulado durante toda a cadeia produtiva, o produto derivado do
açaí pode conter elevada carga microbiana, o que favorece a contaminação do
alimento. Este trabalho objetivou avaliar a composição centesimal e a
qualidade microbiológica de açaí na tigela comercializado na cidade de
Goiânia, bem como o impacto da capacitação em Boas Práticas de Fabricação.
Estudo conduzido em três etapas foi realizado em 23 estabelecimentos. Na
primeira e terceira etapa foram coletadas duas amostras com 300 mL de açaí
na tigela, preparado com polpa de açaí, xarope de guaraná e banana e a outra
com polpa de açaí, xarope de guaraná e morango. Foram coletados, também,
swabs de superfícies de mãos e fossas nasais de 34 manipuladores envolvidos
no preparo do açaí e aplicou-se o checklist baseado na RDC nº 216/2004, para
avaliar as condições físico-funcionais dos estabelecimentos. Na segunda etapa
foi realizada a capacitação em Boas Práticas de Fabricação com aplicação de
pré e pós-teste. O protocolo microbiológico baseou-se na RDC nº 12/2001 e na
American Public Health Association. A composição centesimal foi determinada
segundo o método estabelecido pela Association of Official Analytical
Chemists. Das 46 amostras coletadas na primeira etapa, 15,2% apresentaram
contagem superior ao limite máximo para coliformes a 45 ºC; 26% para
coliformes a 35 ºC; 78,2% para estafilococos coagulase positiva e 100% para
aeróbios mesófilos. Na terceira etapa, 21,7% apresentaram contagem superior
ao permitido para coliformes a 45 ºC; 8,6% para coliformes a 35 ºC; 6,5% para
estafilococos coagulase positiva e 73,9% para aeróbios mesófilos. Quanto aos
manipuladores, antes da intervenção foi detectada a contaminação por E. coli
nas superfícies das mãos de um manipulador, sendo esse resultado o mesmo
após a capacitação. Quanto às fossas nasais, a presença desta bactéria
reduziu de cinco para nenhum manipulador contaminado. Para S. aureus, um
manipulador estava com as superfícies das mãos contaminadas na primeira
etapa, sendo este número aumentado para três na segunda. Ao analisar as
fossas nasais, cinco manipuladores albergavam S. aureus antes da
capacitação e sete após a intervenção. No checklist, dentre os 12 itens
verificados, somente três apresentaram melhorias com relação à porcentagem
de conformidade de uma etapa para a outra: matérias-primas, ingredientes e
embalagens, documentação e registro e responsabilidade. Em relação à
capacitação, a média de acerto no pré-teste foi de 86,8%, e no pós-teste 97%.
Quanto à composição centesimal, não houve diferença de atributos nutricionais
em relação ao tipo de fruta adicionada na preparação do açaí na tigela.
Conclui-se que a maioria das amostras coletadas apresentou condições
higiênicossanitárias inadequadas, evidenciando a necessidade de implantação
de um eficiente sistema de controle de qualidade nas áreas de manipulação de
alimentos, a fim de garantir a segurança higiênicossanitária do produto final.
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Mathematical modelling of wool scouringCaunce, James Frederick, Physical, Environmental & Mathematical Sciences, Australian Defence Force Academy, UNSW January 2007 (has links)
Wool scouring is the first stage of wool processing, where unwanted contaminants are removed from freshly shorn wool. In most scouring machines wool is fed as a continuous mat through a series of water-filled scour and rinse bowls which are periodically drained. The purpose of this project is to mathematically model the scour bowl with the aim of improving efficiency. In this thesis four novel models of contaminant concentration within a scour bowl are developed. These are used to investigate the relationships between the operating parameters of the machine and the concentration of contamination within the scour bowl. The models use the advection-diffusion equation to simulate the settling and mixing of contamination. In the first model considered here, the scour bowl is simulated numerically using finite difference methods. Previous models of the scouring process only considered the average steady-state concentration of contamination within the entire scour bowl. This is the first wool scouring model to look at the bowl in two dimensions and to give time dependent results, hence allowing the effect of different drainage patterns to be studied. The second model looks at the important region at the top of the bowl - where the wool and water mix. The governing equations are solved analytically by averaging the concentration vertically assuming the wool layer is thin. Asymptotic analysis on this model reveals some of the fundamental behaviour of the system. The third model considers the same region by solving the governing equations through separation of variables. A fourth, fully two-dimensional, time dependent model was developed and solved using a finite element method. A model of the swelling of grease on the wool fibres is also considered since some grease can only be removed from the fibre once swollen. The swelling is modelled as a Stefan problem, a nonlinear diffusion equation with two moving boundaries, in cylindrical coordinates. Both approximate, analytical and a numerical solutions are found.
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