Dissertations / Theses on the topic 'Cooling treatment'

The controlled lowering of core body temperature to 32°C to 34°C is defined as therapeutic hypothermia (TH). Therapeutic hypothermia has been shown to improve neurological outcome and survival in unconscious patients successfully resuscitated after cardiac arrest. Brain temperature is important for cerebral protection therefore methods for primarily cooling the brain have also been explored. This thesis focuses on the likelihood that intranasal cooling can induce, maintain and control cerebral hypothermia. The method uses bilaterally introduced intranasal balloons circulated with cold saline. Selective brain cooling induced with this method was effectively accomplished in pigs with normal circulation while no major disturbances in systemic circulation or physiological variables were recorded. The temperature gradients between brain and body could be maintained for at least six hours. Intranasal balloon catheters were used for therapeutic hypothermia initiation and maintenance during and after successful resuscitation in pigs. Temperature reduction was also obtained by combined intranasal cooling and intravenous ice-cold fluids with possible additional benefits in terms of physiologic stability after cardiac arrest. Rewarming was possible via the intranasal balloons. In these studies brain temperature was recorded invasively by temperature probes inserted in the brain. The fast changes in pig’s brain temperature could also be tracked by a non-invasive method. High-spatial resolution magnetic resonance spectroscopic imaging (MRSI) without internal reference showed a good association with direct invasive temperature monitoring. In addition the mapping of temperature changes during brain cooling was also possible. In awake and unsedated volunteers subjected to intranasal cooling brain temperature changes were followed by two MR techniques. Brain cooling was shown by the previously calibrated high-spatial resolution MRSI and by the phase-mapping method. Intranasal cooling reduced body temperature slightly. The volunteers remained alert during cooling, the physiological parameters stable, and no shivering was reported.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PERÓXIDOS DO BRASIL
O tratamento de águas de resfriamento normalmente é feito com a adição de cloro, porém este produto apresenta algumas desvantagens em sua aplicação. Como alternativa ao cloro, algumas indústrias no Brasil e no exterior estão começando a utilizar outros biocidas, dentre estes o peróxido de hidrogênio, um poderoso oxidante que apresenta forte ação biocida. O objetivo deste trabalho foi comparar a eficiência do cloro e do peróxido de hidrogênio como biocidas em diferentes condições, através de testes em água da torre de resfriamento de uma indústria siderúrgica localizada no Rio de Janeiro. A contaminação microbiológica desta água foi medida sem a adição dos biocidas e com a adição de cloro e peróxido de hidrogênio, permitindo assim comparar o desempenho destas substâncias no combate aos grupos bacterianos presentes na amostra. Foi realizado também um estudo sobre o efeito corrosivo destas substâncias através de testes de corrosão em aço carbono 1020, que permitiram avaliar a taxa de corrosão por perda de massa provocada pela aplicação destes produtos na água. Os resultados mostraram que o peróxido de hidrogênio possui uma ação biocida satisfatória para aplicações em águas de resfriamento. Foi constatado que o efeito biocida do peróxido de hidrogênio é mais limitado do que o cloro e que sua eficiência depende do tempo de contato e pode ser afetada pela presença de impurezas dissolvidas na água. Os ensaios de corrosão revelaram que o peróxido de hidrogênio provoca um efeito corrosivo comparável ao do cloro no material testado.
Cooling water treatment generally is made with the addition of chlorine, although it´s application has some disadvantages. There is an active development in Brazil and other countries to use alternative chemical disinfectants in place of chlorine, such as hydrogen peroxide, a powerful oxidant which is known for its high biocidal efficiency. The aim of this research is to study the effectiveness of hydrogen peroxide as a disinfectant compared to chlorine in different operational conditions. The experiments were carried out using an water sample from a cooling water system of a steelmaking plant in the city of Rio de Janeiro. The microbial contamination of this water sample was measured without adding any kind of disinfectant. After that, water sample was treated by adding hydrogen peroxide and chlorine, in order to compare and evaluate the efficiency of the two biocides to control bacterial growth in water. Besides microbiological tests, experiments were conducted to compare the degree of corrosion caused by the addition of hydrogen peroxide and chlorine in water. The experimental methodology employed 1020 carbon steel specimens and corrosion rates were measured by weight loss determination after the period of exposure. The results showed that the application of hydrogen peroxide leads to satisfactory bacterial control. However, compared to chlorine, hydrogen peroxide is a rather poor disinfectant. The efficiency of hydrogen peroxide depends on reaction time and it is affected by dissolved polluants in water. Evaluation of corrosion rates showed that hydrogen peroxide causes basically the same corrosion rates than chlorine.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O objetivo deste estudo foi avaliar o efeito biocida do ácido peracético (APA) em águas de sistemas de resfriamento, de forma a buscar alternativas ao uso do cloro, que é corrosivo e reage com a matéria orgânica natural ou sintética presentes na água, formando subprodutos tóxicos. Para atingir este objetivo, experimentos utilizando amostras de água retiradas da bacia de uma torre de resfriamento de uma indústria química foram realizados. Ensaios foram executados utilizando-se uma solução comercial de APA, mantendo-se concentrações do biocida em 1,0 mgL-1 e 2,0 mgL-1 em pH 8,0 e 8,8. Cada condição de estudo foi monitorada ao longo de 5 dias, e contagens de bactérias heterotróficas mesófilas totais foram realizadas tanto antes da aplicação do biocida como em diferentes tempos de contato do biocida com a microbiota natural da água. Os tempos de contato monitorados foram de 5 min, além de 1, 2 e 4 h por dia considerando a aplicação do biocida em períodos totais de 4 h por dia. Com esta metodologia foi possível concluir que as duas dosagens aplicadas foram eficientes no combate aos microrganismos presentes naturalmente nas amostras de água, nos dois valores de pH estudados. A partir de uma carga microbiana natural da água de 106 a 107 UFC/mL, após o tratamento houve uma redução para contagens de no máximo de 104 UFC/mL em todos os experimentos, limite máximo esse adotado pelas indústrias para carga microbiana em águas de sistemas de resfriamento, entretanto, houve maior eficiência, cerca de 10 vezes maior, quando 2,0 mgL-1 de APA foi aplicado. Além disso, em pH 8,0 a ação do biocida também foi superior em 10 vezes em detrimento ao pH 8,8 para a mesma concentração de APA.
The purpose of this study was to evaluate the biocidal effect of peracetic acid (PAA) in cooling water, in order to find alternatives to the use of chlorine, which is corrosive and reacts with natural and synthetic organic matter present in water, forming toxic byproducts. To achieve this goal, experiments using water samples taken from a basin of a chemical industry cooling tower were conducted. Experiments were performed using a commercial PAA solution, with concentrations of 1,0 mgL-1 and 2,0 mgL-1 and pH 8,0 and 8,8. Each study condition was monitored for 5 days and total mesophilic heterotrophic bacteria counts were made without biocide and after different contact times of the biocide and microorganisms present in water. The contact times were 5 min, and 1, 2 and 4 h per day, considering the application of the biocide in total periods of 4 h per day. This methodology has allowed concluding that two dosages applied were efficient in controlling microorganisms at the two pH values. From a water natural microbial count of 106 to 107 UFC/mL, after treatment there was a reduction to maximum counts to 104 UFC/mL in all experiments, that being the upper limit adopted by industries for microorganisms in cooling water systems. However, the results were 10 times more efficient when 2,0 mgL-1 of PAA were applied. In addition, at pH 8,0 the biocidal action was 10 times higher in comparison to pH 8,8 for the same PAA concentration.

With the pollution of freshwater sources and the continual increase in freshwater demand due to rapid industrialization and population explosion, the globe is facing an eminent danger of scarcity of freshwater. One way to increase the water supply beyond the hydrological cycle is to reuse and recycle the waste water by developing an onsite recycling/reclamation technology. Such a bench-scale treatment technology was developed to treat the cooling tower blowdown water (CTBW) from the cooling towers of California State University, Long Beach (CSULB). The CTBW was treated by using electrodialysis.

The main objective of this project was to bring down the level of total dissolved solids (TDS) of the CTBW to lower than 230 mg/L which is equivalent to the TDS level of tap water provided by the Long Beach Water Department. The secondary objective was to regenerate the hydrochloric acid using the waste ions. Two differently configured electrodialysis cells (onechambered and two-chambered cell) were used and their treatment efficiencies were compared. The one-chambered cell successfully reduced the TDS level by upto 48% for three samples tested in the setup. The two-chambered cell achieved the TDS reduction up to 93.4% for the four samples tested in the setup. The study was successful in regenerating 1.42 mol/L concentration of hydrochloric acid. An economic and water savings analysis was also performed. Calculations showed that by implementing this technology, it is possible to save 10,362,564.76 L/year which translates to $10,813.13 in economic savings. The total annual savings were estimated to be $12,984.01. The payback period for the investment in this study was 50 months, thus a profit of $15,949.48 is expected by the end of the equipment life of the setup.

Orientador: Valdemar Silva Leal
Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-04T02:09:31Z (GMT). No. of bitstreams: 1 Carvalho_AntonioRogerioTorres_M.pdf: 2108495 bytes, checksum: 57b748cffef6835e43201549b90022af (MD5) Previous issue date: 2004
Resumo: Estuda-se a influência da variação da agitação e da severidade de têmpera do meio de resfriamento sobre as curvas e taxas de resfriamento durante o processo de têmpera do aço. Os ensaios foram realizados com amostras dos aços 1045, 8620 e 8640, temperadas em água e salmoura, promovendo-se a variação do estado de agitação do refrigerante. Os dados apontam para variação da taxa de resfriamento máxima de 27,65% a 110,09% e uma diminuição nos tempos de resfriamento de 7,83% a 63,25%, para os três materiais estudados, com o aumento da agitação do meio. Verificam-se ainda, ganhos nas taxas e tempos de resfriamento com a variação da severidade de têmpera pela troca do meio, água por salmoura, da ordem de 73,27%, sem agitação do meio, e diminuição do tempo de resfriamento em aproximadamente 20%. Os dados ainda demonstram ganhos no tempo e nas taxas de resfriamento devido ao aumento do percentual de carbono no aço, quando se compara os dados obtidos para as amostras dos aços 8620 e 8640
Abstract: Study about the influence of the agitation range and quench severity of the quenchant on cooling times and rates during the quench. The assays were accomplished with samples of steel 1045, 8620 and 8640, water and brine quenched, by increasing the agitation of the quenchant. The data show a rise in the maximum cooling rates of the 27.65% - 110%, and a reduction in the times of cooling of the 7.83% - 63.25%, on the three materials studied, with the increase of the agitation of the quenchant. They were verified too, a gain in the cooling rates and times with the variation of the quenchant severity, water to brine, of 73.27%, without agitation, and reduction of cooling time in approximately 20%. The data still show a gain in the cooling time and rates caused by the percentage of carbon increase on the steel, when be compared with the data scored in the samples of steel 8620 and 8640
Mestrado
Instrumentação e Controle Industrial
Mestre Profissional em Engenharia Mecanica

The press hardening belongs to state-of-the-art technology at sheet metal forming to gain high strength and crash resistant parts in automotive industry. This process could establish due to its cost- and esourceefficiency. According to ongoing developments on direct press hardening processes it is necessary to describe and understand the thermo-mechanical treatment of 22MnB5. Therefore the flow behavior and phase transformation during cooling with simultaneous forming is investigated. The experimental process considers industrial parameters in order to get industry-oriented results. In deep drawing processes the sheet metal is roped into the draw die and bended around the die edge. Thereby sheets perform different stages of compressive and tensile strain at the die oriented side and the punch oriented side of the sheet. There are different stages and values of stress and strain according to several layers of the sheet over its cross-section. The values of stress, strain and forming rate were FEcalculated for industry-relevant bending radii and sheet thicknesses of manganese-boron steel 22MnB5. According to the calculations different cooling and forming strategies were performed by dilatometric tests. The forming behavior is described by the microstructural development with regard to the cooling rate and temperature. Beside the influence of austenite forming on the phase transformation and mechanical properties is considered. A prospective view is given to illustrate ongoing examinations under compressive and combined tensional and compressive forces.

Victims of exertional heat stroke (EHS) in whom treatment is delayed have higher rates of multi-organ failure and a greater number of fatalities. Death related to EHS is preventable, through immediate treatment via cold-water immersion (CWI). To date little is known about the influence of treatment delays on core cooling following EHS. Thus we sought to examine the effects of treatment delays on cardiovascular and thermal responses prior to, during, and following CWI treatment in individuals with exercise-induced hyperthermia. Our findings demonstrate that treatment delays resulted in a sustained level of hyperthermia and cardiovascular strain that significantly increased the time an individual is at risk to the potential lethal effects of EHS. Moreover, we report that cold water immersion treatment is powerful enough to overcome the adverse effects of treatment delays and rapidly reduce core temperatures while facilitating the re-establishment of blood pressure towards normal resting levels.

The average size of hot-work tools has gradually increased over the past years.This affects the effective temperature cycle tools experience during hardening,as large dimensions prevent uniform and rapid cooling, and thereby the resulting microstructures and properties. In order to avoid the formation of coarse structures or cracking during heat treatment it has become common practise to lower the austenitising temperature below that recommended by the steel manufacturer.In this work, therefore, the effects of austenitising at temperatures lower thancommonly recommended are investigated. Three 5% Cr hot-work tool steelsalloyed with Mo and V were heat treated, resulting microstructures andtempering carbides were studied and transformation characteristics determined for different austenitising temperatures and different cooling rates. The temperatures and cooling rates have been chosen to be representative for heat treatments of different sizes of tools. Bainite rather than martensite formed during slow cooling regardless of austenitising temperature. A lowered austenitising temperature produced largeramounts of both bainite and retained austenite while a higher caused graingrowth. Carbon partitioning during the bainitic transformation resulted in anincrease of the carbon content in the retained austenite of at least 0.3 wt.%. The austenitising temperature influences also the type and amount of tempering carbides that precipitate, which affects the properties of the steel. Higher austenitising temperatures favour the precipitation of MC carbides during tempering. The Mo rich M2C type carbides were proven to be more prone to coarsening during service at 560°C-600°C, while V rich MC carbides preserve their fine distribution. A best practice heat treatment needs to balance the increase of grain size with increasing austenitising temperatures, with the possibility to form more tempering carbides. Higher austenitising temperatures also give less retained austenite, which can affect dimensional stability and toughness negatively after tempering

A otimização de processos e a redução de custos são os dois principais fatores que sustentam a competitividade das indústrias atualmente. Diante deste cenário, buscou-se otimizar o processo de fabricação de barras trefiladas de aço mola SAE 9254, através da eliminação do recozimento anterior ao processo de trefilação, por intermédio de um resfriamento controlado no cooling conveyor, na laminação.. Para isso, a taxa de resfriamento do fio-máquina após a laminação foi variada a fim de garantir a homogeneização da dureza ao longo das espiras, característica essa essencial para o processamento na trefila. Além da redução de custos com o recozimento, se o objetivo fosse alcançado, poder-se-ia otimizar o processo de reaquecimento deste aço na laminação. Como resultado, seria possível melhorar a qualidade superficial do fio-máquina e, por conseqüência, aumentar o rendimento metálico do produto, sem que a descarbonetação máxima e média fossem prejudicadas. Os experimentos foram desenvolvidos com base no resfriamento do fio-máquina no cooling conveyor. Durante o processamento na laminação, foi realizada uma amostragem especial a fim de mapear a variação das propriedades ao longo das espiras. Os resultados apontaram que é possível a otimização do processo de fabricação do aço mola SAE 9254, principalmente para a condição de resfriamento na laminação quando utilizado um escalonamento na velocidade de transporte do fio-máquina no cooling conveyor. Este incremento nas velocidades de deslocamento do material, feita através do escalonamento da velocidade, propicia uma alteração nos “pontos quentes” das espiras, gerando uma uniformidade maior em seu resfriamento, garantindo assim, uma homogeneidade nas propriedades mecânicas.
The process optimization and cost reduction are the two main factors that gives sustainability for today industries competitiveness. For this reason, it was attempted to optimize the manufacturing process of cold draw bars of SAE 9254 spring steel by eliminating pre-annealing of wire drawing, through a controlled cooling on the cooling conveyor, in the rolling mill process. For this, the cooling rate of wire rod after rolling process was varied to ensure the homogeneity of hardness along the coil, the essential feature for wire drawing process. In addition to reducing costs annealing, if the purpose was reached, the reheating process would be optimized in the rolling mill. As a result, it would be possible to improve the surface quality of wire rod and, consequently, increase the metallic yield of the product, without the decarburization maximum and average were damaged. The experiments were developed based on wire rod cooling thermograph in the cooling conveyor. During rolling mill processing, special sampling was performed to map the variation of properties along the coils. The results showed that it is possible to optimize the manufacturing process of the SAE 9254 spring steel, mainly for the cooling condition in the rolling process when scaling speeds in wire rod transportation was used on the cooling conveyor. This speed increase of the material transportation, through the scaling speed, provides a change in "hot spots" of the coils, generating a greater uniformity in their cooling, thus ensuring uniformity in mechanical properties.

O segmento industrial é um grande usuário de água e, na maior parte das situações, está localizado junto a aglomerações urbanas, caracterizando situação de dificuldade na obtenção deste recurso para as suas operações. As fontes de água estão cada vez mais saturadas e os processos de tratamento mais sofisticados. O objetivo deste estudo foi avaliar a viabilidade técnico-econômica da implantação do tratamento eletromagnético para água de resfriamento em indústrias químicas, substituindo ou complementando o tratamento químico convencional. O texto descreve inicialmente os fundamentos do tratamento de água baseado na aplicação de campo eletromagnético e, em seguida, os efeitos do uso dessa tecnologia sobre custos anuais de resfriamento em um caso típico da indústria química. Neste estudo foi dada ênfase ao efeito sobre os custos anuais da menor adição de produtos químicos, redução na vazão de purga e de reposição de água, além da redução na frequência de limpeza dos equipamentos e redução da carga poluente nos efluentes líquidos. O estudo foi aplicado a uma torre de resfriamento industrial, para a qual foi elaborado um modelo matemático considerando as taxas de consumo e especificações de água de resfriamento, além de parâmetros do processo de tratamento de água convencional e eletromagnético. São apresentados resultados de um estudo de sensibilidade para diferentes cenários, em que são identificados os fatores com maior efeito sobre os custos. Além disso, na aplicação ao sistema proposto, são estimadas condições ótimas de operação, considerando os ciclos de concentração para os quais pode haver maior redução de custos. Utilizando-se o tratamento eletromagnético para a água de resfriamento, há uma economia significativa, pois o número de paradas para a manutenção dos equipamentos pode ser reduzido. Dessa forma, o produto final do trabalho constitui-se em uma estrutura de cálculo voltada à estimação de custo do tratamento físico de água de resfriamento, o qual pode ser aplicado a diferentes cenários e condições de operação industrial.
The industrial sector is a major water user and in most situations is located next to urban areas, in a situation of increasing difficulty in collecting and treating water resources for its operations. The water sources are becoming more saturated and thus demanding more sophisticated treatment processes. The aim of this study was to evaluate the technical and economic feasibility of the implementation of electromagnetic treatment of cooling water in chemical industries, thus replacing or complementing the conventional chemical treatment. The text initially describes the principles of the physical process for water treatment based on the application of an electromagnetic field, and then focuses on the effects of the use of this technology on the annual costs of cooling in a typical case of the chemical industry. The study is focused on the effects of the electromagnetic treatment on the annual cost of cooling in view of the reduced consumption of chemicals, as well as reduction in purge flow and water replacement, reduced frequency of equipment cleaning, and reduction of pollution load caused by wastewater. The study results were applied to an industrial cooling tower for which a mathematical model was developed by considering consumption rates and cooling water specifications, as well as parameters of the electromagnetic and conventional water treatment processes. A sensitivity study was carried out for different scenarios, in which the most important factors affecting the annual cost are identified, and optimal process conditions are estimated for maximum concentration cycles. The study shows that the use of electromagnetic treatment for cooling water results in significant savings due to the reduced number of maintenance periods. The final product of this study is a calculation structure for cost estimation related to the physical treatment of cooling water, which can be applied to different scenarios and industrial operation conditions.

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The aerospace- and automotive industries have an urgency to save space and reduce weight, as well as a need to increase fuel efficiency and reduce emissions. This has led to the use of lightweight structural materials, such as Ti6A14V alloy, which is the most widely used titanium alloy in the aerospace industry. This alloy has an exceptional strength-to-density ratio. The work also covers studies on tool steel 40CrMnMo7 that is used in applications in the tooling-, aerospace and automotive industry. In the quest for improved performance new alternative methods of efficiently machining these materials are investigated. One of the important criteria during machining of these materials is their machinability. This study discusses current research in high performance machining strategies and techniques for advanced materials such as Ti6Al4V and 40CrMnMo7. The properties that make these materials advantageous for the use in the aerospace- and automotive industry also make them difficult to cut. The widespread application of Ti6Al4V in the aerospace industry has encouraged investigations into cooling strategies or -techniques to maintain and improve tool life. Ti6Al4V has a low thermal conductivity causing the heat generated during machining to accumulate on the cutting edge of the tool. During various experiments the application of external compressed air blow cooling (dry cutting), flood cooling, high pressure through spindle cooling (HPTSC) and modifications thereof were investigated. The research project also evaluated the performance of a coating (TiAlN) and various coating treatments. The objectives of the HPTSC modifications were to improve the coolant stream impingement on the tool surface, effectively compressing the thermal barrier, and to reduce the chip-tool contact area. This would lead to a decrease in tool heating and wear. The modified techniques failed to increase tool life but showed signs of increased heat removal capability under the given conditions. It was observed that air blow cooling (dry cutting) delivered the best results when considering cutting materials, coating, coating treatment and cooling strategies or –techniques throughout the experiments conducted.
AFRIKAANSE OPSOMMING: Die Ruimte-en motor-industrie het 'n dringendheid om ruimte te bespaar en gewig te verminder, sowel as 'n behoefte om brandstofdoeltreffendheid te verbeter en emissies te verminder. Dit het gelei tot die gebruik van liggewig strukturele materiale, soos Ti6A14V Allooi , wat die mees gebruikte titanium allooi in die Ruimte is. Hierdie allooi het 'n uitsonderlike krag-tot-digtheid-verhouding. Die studie dek ook gereedskapstaal 40CrMnMo7 wat in die gereedskap, Ruimte-en motor-industrie aangewend word. In die soeke na verbeterde prestasie word nuwe alternatiewe metodes om effektief bewerking van hierdie materiaal ondersoek. Een van die belangrikste kriteria tydens bewerking van hierdie materiaal is die bewerkbaar daarvan. Hierdie studie bespreek die huidige navorsing in hoë prestasie bewerking strategieë en tegnieke vir gevorderde materiale, soos Ti6Al4V en 40CrMnMo7. Die eienskappe wat hierdie materiaal voordelig maak vir die gebruik in die lug-en Ruimte-en motor-industrie, maak dit terselfdetyd moeilik om te sny. Die wydverspreide toepassing van Ti6Al4V in die lug-en Ruimte industrie moedig ondersoeke aan na koelstrategieë of -tegnieke om die instrumentlewe te handhaaf en te verbeter. Ti6Al4V het lae termiese geleidingsvermoë wat veroorsaak dat die hitte, wat gegenereer word tydens bewerking, versamel op die voorpunt van die instrument. Tydens verskillende eksperimente was die toepassing van eksterne saamgeperste lugblaas-verkoeling (droë sny), vloed verkoeling, hoë-druk-deur-die-spil-afkoeling (HPTSC) en aanpassings daarvan geondersoek. Die navorsingsprojek het ook die prestasie van 'n bedekkingslaag (TiAlN) en verskeie bedekkingslaagbehandelings geëvalueer. Die doelwit van die HPTSC aanpassing was om die koelmiddelstroom beklemming op die instrument oppervlak te verbeter, en effektiewelik die termiese versperring saam te pers, asook die skerf-teenoorinstrument kontak te verminder. Dit sou lei tot 'n afname in die instrumentverwarming en -slytasie. Die gewysigde tegnieke het daarin misluk om die instrumentlewe te verhoog, maar het tekens getoon van 'n toename in hitte verwydering vermoë onder die gegewe omstandighede. Dit is dus waargeneem dat lugblaasverkoeling (droë sny) die beste resultate gelewer het in die oorweging van sny materiale, bedekkingslaag, bedekkingslaagbehandelings en verkoeling strategieë of -tegnieke wat regdeur die eksperimente uitgevoer was.

The carrot is a crop rich in carotenoids, pro-vitamin A, minerals and carbohydrates, and is a food with high nutritional value. Brazil is among the five largest producers and consumers of carrot (Daucus carot L .) in the world, concentrating its production in the Southeast. In search of products more attractive, practical, nutritious and healt hy, the consumer's sous vide technology is an alternative technology for the industry in providing food ready for consumption. The sous vide consists in cooking food packaged in plastic vacuum -sealed, subjected to temperatures lower than 100ÂC for extended periods of time, chilled quickly and stored under refrigeration. The aim of this study was to evaluate the quality and shelf life of carrots ( Daucus carot L.) diced submitted to sous vide technology, produced on an industrial scale. The samples were subje cted to physical and chemical analysis and chemical, microbiological and with three replications, with five repetitions of the products, and soon after processing by 2, 4, 6 and 8 weeks of storage (3ÂC). Sensory analysis was carried out on days 0 and 4 weeks, with a repeat. The results indicated a significant difference of 5% (p ≤0.05) in carbohydrate, protein, ash, titratable acidity and chromaticity between the carrot fresh carrot and processed by sous vide technology at time 0. In times of 2, 4, 6 and 8 weeks of storage at 3ÂC difference was significant (p ≤ 0.05) only for protein and total acidity. In sensory analysis, no significant difference (p ≤ 0.05) in any of the attributes studied. It was also observed that the technology sous vide was effective in eliminating vegetative cells of micro-organisms pathogenic and spoilage, yet not been able to eliminate spores. The carrot processed by sous vide technology retains its nutritional characteristics, sensory, chemical and microbiologically stable for up to eight weeks of storage at 3ÂC.
A cenoura à uma olerÃcola rica em carotenÃides, prÃ-vitamina A, minerais e carboidratos, constituindo um alimento com alto valor nutritivo. O Brasil està entre os cinco maiores produtores e consumidores de cenoura (Daucus carot L.) do mundo, concentrando sua produÃÃo na regiÃo sudeste. Na busca de produtos mais atrativos, prÃticos, nutritivos e saudÃveis pelo consumidor, a tecnologia sous vide surge como uma alternativa tecnolÃgica para a indÃstria no fornecimento de pratos prontos para consumo. O sous vide consiste em cozinhar alimentos acondicionados em embalagens plÃsticas seladas à vÃcuo, submetidos a temperaturas inferiores à 100ÂC por longos perÃodos de tempo, resfriados rapidamente e armazenados sob refrigeraÃÃo. O objetivo desse trabalho foi avaliar a qualidade e a vida de prateleira de cenouras (Daucus carot L.) cortadas em cubos submetida a tecnologia sous vide, produzida em escala industrial. As amostras foram submetidas as anÃlises fÃsico-quÃmicas e quÃmicas, com trÃs repetiÃÃes e microbiolÃgicas, com cinco repetiÃÃes, dos produtos, logo apÃs o tecnologia e por 2, 4, 6 e 8 semanas de armazenamento refrigerado (3ÂC). A anÃlise sensorial foi realizada nos tempos de 0 e 4 semanas, com uma repetiÃÃo. Os resultados indicaram que houve diferenÃa significativa de 5% (p≤0,05) nos carboidratos, proteÃnas, cinzas, acidez total titulÃvel e na cromaticidade entre a cenoura in natura e a cenoura processada por tecnologia sous vide no tempo 0. Nos tempos de 2, 4, 6 e 8 semanas de armazenamento a 3ÂC houve diferenÃa significativa (p≤0,05) apenas nas proteÃnas e acidez total titulÃvel. Na anÃlise sensorial, nÃo houve diferenÃa significativa (p≤0,05) em nenhum dos atributos estudado. Observou-se tambÃm que a tecnologia sous vide foi eficiente na eliminaÃÃo de cÃlulas vegetativas de micro-organismos deteriorantes e patogÃnicos, porÃm nÃo foi capaz de eliminar esporos. A cenoura processada por tecnologia sous vide conservou suas caracterÃsticas nutricionais, sensoriais, quÃmicas e manteve-se estÃvel microbiologicamente atà oito semanas de armazenamento à 3ÂC.

Disponibilidade dos recursos energéticos junto com o despertar da consciência ambiental criaram um interesse por uma condição climática sensível compatível com os recursos disponíveis. Dentro desse cenário o trabalho se volta à necessidade de se criarem e manterem ambientes industriais termicamente adequados aos processos de produção para minimizar as interferências que as condições ambientais exercem sobre os custos dos processos de produtivos e sobre o consumo energético. Os sistemas de resfriamento evaporativo, por sua vez, têm sido a ferramenta de maior potencial de aplicação na criação de ambientes termicamente adequados aos processos. Este modelo revisto de conforto térmico nos coloca um passo à frente para o aumento eficiência energética na construção de projeto de climatização vinculados a temperaturas interiores que atendam conjuntamente tanto aos ocupantes como às atividades que desenvolvem no interior da área climatizada. Apesar de esse sistema apresentar vantagens operacionais, quando comparado a outros sistemas convencionais, existem certas limitações no seu desempenho. Uma das maiores dificuldades das instalações destes sistemas reside na existência de incertezas em qualquer resultado. Possibilitar um controle dos parâmetros, minimizando os erros de aplicação, evitando criar no ambiente um desconforto de tal grau que inviabilize sua aplicação, é o fundamento deste trabalho. A busca passa a ser pela garantia da aceitabilidade dos resultados do sistema projetado e seus limites de aplicabilidade. O estudo das variáveis que interferem no processo do resfriamento por micro aspersão permitiu desenvolver um processo que alterara esses parâmetros durante o funcionamento do sistema, interferindo, conforme a necessidade no seu desempenho, garantindo a completa evaporação da água micro aspergida.
Energy resources along with an environmental conscience awakening has created an interest in sensitive climate together with a more understanding regarding the use of available resources. Inside this scenario our work focus on the needs of creating and maintaining industrial environments thermally suited to these production processes that seeking to minimize interference that environmental conditions have on the costs of production processes and energy consumption. Evaporative cooling systems, in turn, has been a interesting tool to be used in the creation of thermally suitable environments to these processes. This new revised thermal comfort model puts us a step forward to increase energy efficiency in elaborating air treatment projects linked to indoor temperatures that meet both the occupants and the activities that develop inside the controlled area. Although this system has operational advantages when compared to other conventional systems, there are some limitations in their performance. A major difficulty of the installation envolving these systems is about the existence of uncertainty in any results. To allow the control of these parameters in order to minimize the errors in this kind of application and to avoid creating environmental discomfort to such a degree that prevent the implementation, it is the foundation of this work. The search is to ensure the acceptability of the results of the system designed and their limits of applicability. The study of the variables that affect the cooling process by misting allowed us to develop a process that altered these parameters during operation of the system, interfering, as required in its performance, ensuring complete evaporation of water applied by misting in the area.

High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The wear resistance and mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The Hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the hypereutectic alloy and these will have a negative influence on the wear resistance. In this thesis, the Ti-added hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is quantitatively studied based on the type, size distribution, composition and morphology of hard carbides and martensite units. A 11.2μm border size is suggested to classify the primary M7C3 carbides and eutectic M7C3 carbides. Thereafter, the change of the solidification structure and especially the refinement of carbides (M7C3 and TiC) size by changing the cooling rates and Ti addition is determined and discussed. Furthermore, the mechanical properties of hypereutectic HCCI related to the solidification structure are discussed. Mechanical properties of HCCI can normally be improved by a heat treatment process. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). Especially for the matrix structure, EBSD is a useful tool to classify the fcc (γ) and bcc (α) phases. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI.

QC 20121130

O crescente consumo de energia produzida a partir do petróleo e do gás natural conduz a melhoria das propriedades mecânicas dos aços microligados empregados na construção dos oleodutos e gasodutos para incrementar o transporte dos recursos a menores custos e elevar a confiabilidade. O aumento do controle das diferentes fases, agregados eutetóides, microconstituintes e precipitados neste tipo de aço, garante a melhoria na resistência mecânica, tenacidade e soldabilidade. Dentro deste contexto foi realizado um trabalho de caracterização microestrutural do aço um microligado para tubos API 5L X80 em amostras de aço como recebido e em diferentes condições de resfriamento. Para o estudo da cinética das transformações de fase, o aço microligado foi submetido a ensaios de dilatometria onde foram identificadas as temperaturas e tempos de início e fim de transformação de fases, para varias velocidades de resfriamento. A partir das diferentes temperaturas e tempos obtidos, em função das taxas de resfriamento, foi possível extrair a curva de Transformação por Resfriamento Continuo (TRC). Os dados da curva TRC foram comparados com as microestruturas de cada corpo de prova por meio de microscopia óptica (MO), microscopia eletrônica de varredura (MEV), microscopia eletrônica de varredura com Field Emission Gun (FEG) e microdureza, caracterizando a evolução morfológica da matriz ferrítica, agregados eutetóides e microconstituinte austenita/martensita (MA). Para a caracterização microestrutural das amostras também foram utilizadas técnicas de análise microestrutural como, nanodureza, análise por difração de raios X em amostras obtidas por extração de precipitados, saturação magnética e microscopia de força atômica (AFM). A técnica de saturação magnética foi desenvolvida por médio de curvas de histerese medidas em um histeresígrafo com peças polares e anel de Rowland para diversas amplitudes de intensidade de campo magnético. Esta técnica permitiu a detecção da saturação magnética do aço sem tratamento térmico e a saturação máxima nos aços com tratamento térmico, o que indicou a total transformação da austenita retida. A relação das duas saturações permitiu determinar a fração de austenita retida no MA. Para as medidas de nanodureza foi utilizado um nanodurômetro acoplado ao microscópio de força atômica (AFM). As nanodurezas obtidas em diferentes grãos foram comparadas com os valores constantes na literatura para identificar as fases, agregados eutetóides e possíveis precipitados da microestrutura.
The continuous increase of energy generated from petroleum and natural gas created the need to improve the mechanical properties of microalloyed steels used in gas and oil pipelines, in order to increase their flow with smaller costs and higher reliability. The control of the different phases, morphology of microconstituents like ferrite plus carbide aggregates and precipitates in this kind of steels is essential to the improvement of mechanical strength, toughness and weldability. In this context, a work of microestrutural characterization of a microalloyed steel for API X80 pipelines was carried out both on an as-received steel sample as in samples submitted to different cooling conditions. The kinetics of austenite transformations was investigated using dilatometric experiments, identifying start and end of the phase transformations as well as the time spent temperatures for the phase transformations at each cooling rate. The temperature and time curves obtained as a function of the cooling rates allowed the determination of a Continuous Cooling Transformation curve (CCT). The data from the CCT curve was compared with the microstructures of each sample through optical microscopy (OM), scanning electron microscopy (SEM), scanning electron microscopy with Field Emission Gun (FEG) and microhardness, characterizing the morphologic evolution of the ferritic matrix, ferrite plus carbide eutectoid aggregates (perlite and bainite) and the microconstituent martensite/austenite (MA). The microestrutural characterization of the samples was performed also using different techniques of microestrutural analysis: precipitate extraction followed by Xrays diffraction analysis, magnetic saturation and atomic force microscopy (AFM) measurements. The magnetic saturation technique was developed through hysteresis curves measured with a hysteresigraph with polar pieces and Rowland ring for several ranges of magnetic field intensity. This technique allowed to detect the magnetic saturation of the steel without thermal treatment and the maximum saturation in the heat treated steels were the retained austenite has transformed. The relationship between those saturations curves allowed a determination of the retained austenite fraction in the MA microconstituent. The nanohardness was measured using a specific device coupled to a atomic force microscope (AFM). The nanohardness of different grains were compared with the hardness values from the literature in order to help identify phases and microconstituents, as well as possible precipitates.

No presente trabalho são relatados os resultados obtidos por meio de ensaios de caracterização para os diferentes tipos de óleos vegetais (algodão, canola, girassol, milho e soja), no estado novo e puro, tais como viscosidade, número de acidez, índice de iodo, índice de saponificação, cromatografia gasosa, curvas de resfriamento e coeficiente de transferência de calor. Esses mesmos ensaios foram realizados também com as amostras de óleo de soja com diferentes concentrações de aditivos antioxidantes. As diferentes formulações feitas com óleo de soja foram submetidas a um processo de envelhecimento acelerado (durante 72 horas), suas propriedades foram comparadas com as de dois óleos minerais utilizados para têmpera. O mesmo foi feito para os óleos vegetais, estes porém foram envelhecidos durante 48 horas. Pode-se então, comparar qual amostra sofreu menor oxidação durante um mesmo tempo de envelhecimento e, desta maneira, avaliar qual aditivo antioxidante obteve melhor desempenho, retardando o processo de oxidação no óleo de soja. Esses estudos também permitiram verificar qual, dentre os óleos vegetais, possui as melhores propriedades para ser utilizado no tratamento térmico de têmpera. Amostras do aço AISI 4140 foram temperadas nos diferentes óleos estudados, obteve-se a curva de dureza e as micrografias óticas para cada amostra temperada.
In this work, the results obtained from the characterization of different vegetable oils (cotton, canola, sunflower, corn and soybean) are reported. The oils were evaluated at \"new condition\" and \"pure\" by viscosity, acid and iodine number, saponification, gas chromatography, cooling curves and heat transfer coefficient. These same analyses were also performed on samples of soybean oil containing various concentrations of antioxidant. The various formulations prepared with soybean oil were accelerated aged for 72 hours and their properties were compared with two mineral oils used for quenching. Likewise, the vegetable oils were aged for 48 hours long. Therefore, it was possible to identify which sample exhibited the lower oxidation process at the same aging time and, thus, evaluate the antioxidant additive that promoted the improved oxidation performance for soybean oil. Also, these studies allowed verifying which of the vegetable oils had the best properties to be used as quenchants. Samples of AISI 4140 steel were quenched in different oils and the hardness curve and optical microscopy for each sample were obtained.

OLIVEIRA, Ticiane Coelho Abreu de. Estudo da qualdiade microbiológica, química, físico-química e sensorial de cenoura (Daucus carot, L.) submetida à tecnologia Sous vide produzida em escala industrial. 2012. 98 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Centro de Ciências Agrárias, Departamento de Tecnologia de Alimentos, Fortaleza-CE, 2012
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The carrot is a crop rich in carotenoids, pro-vitamin A, minerals and carbohydrates, and is a food with high nutritional value. Brazil is among the five largest producers and consumers of carrot (Daucus carot L .) in the world, concentrating its production in the Southeast. In search of products more attractive, practical, nutritious and healt hy, the consumer's sous vide technology is an alternative technology for the industry in providing food ready for consumption. The sous vide consists in cooking food packaged in plastic vacuum -sealed, subjected to temperatures lower than 100°C for extended periods of time, chilled quickly and stored under refrigeration. The aim of this study was to evaluate the quality and shelf life of carrots ( Daucus carot L.) diced submitted to sous vide technology, produced on an industrial scale. The samples were subje cted to physical and chemical analysis and chemical, microbiological and with three replications, with five repetitions of the products, and soon after processing by 2, 4, 6 and 8 weeks of storage (3°C). Sensory analysis was carried out on days 0 and 4 weeks, with a repeat. The results indicated a significant difference of 5% (p ≤0.05) in carbohydrate, protein, ash, titratable acidity and chromaticity between the carrot fresh carrot and processed by sous vide technology at time 0. In times of 2, 4, 6 and 8 weeks of storage at 3°C difference was significant (p ≤ 0.05) only for protein and total acidity. In sensory analysis, no significant difference (p ≤ 0.05) in any of the attributes studied. It was also observed that the technology sous vide was effective in eliminating vegetative cells of micro-organisms pathogenic and spoilage, yet not been able to eliminate spores. The carrot processed by sous vide technology retains its nutritional characteristics, sensory, chemical and microbiologically stable for up to eight weeks of storage at 3ºC.
A cenoura é uma olerícola rica em carotenóides, pró-vitamina A, minerais e carboidratos, constituindo um alimento com alto valor nutritivo. O Brasil está entre os cinco maiores produtores e consumidores de cenoura (Daucus carot L.) do mundo, concentrando sua produção na região sudeste. Na busca de produtos mais atrativos, práticos, nutritivos e saudáveis pelo consumidor, a tecnologia sous vide surge como uma alternativa tecnológica para a indústria no fornecimento de pratos prontos para consumo. O sous vide consiste em cozinhar alimentos acondicionados em embalagens plásticas seladas à vácuo, submetidos a temperaturas inferiores à 100°C por longos períodos de tempo, resfriados rapidamente e armazenados sob refrigeração. O objetivo desse trabalho foi avaliar a qualidade e a vida de prateleira de cenouras (Daucus carot L.) cortadas em cubos submetida a tecnologia sous vide, produzida em escala industrial. As amostras foram submetidas as análises físico-químicas e químicas, com três repetições e microbiológicas, com cinco repetições, dos produtos, logo após o tecnologia e por 2, 4, 6 e 8 semanas de armazenamento refrigerado (3ºC). A análise sensorial foi realizada nos tempos de 0 e 4 semanas, com uma repetição. Os resultados indicaram que houve diferença significativa de 5% (p≤0,05) nos carboidratos, proteínas, cinzas, acidez total titulável e na cromaticidade entre a cenoura in natura e a cenoura processada por tecnologia sous vide no tempo 0. Nos tempos de 2, 4, 6 e 8 semanas de armazenamento a 3ºC houve diferença significativa (p≤0,05) apenas nas proteínas e acidez total titulável. Na análise sensorial, não houve diferença significativa (p≤0,05) em nenhum dos atributos estudado. Observou-se também que a tecnologia sous vide foi eficiente na eliminação de células vegetativas de micro-organismos deteriorantes e patogênicos, porém não foi capaz de eliminar esporos. A cenoura processada por tecnologia sous vide conservou suas características nutricionais, sensoriais, químicas e manteve-se estável microbiologicamente até oito semanas de armazenamento à 3ºC.

Estudou-se a cinética das transformações de fase em resfriamento contínuo e em tratamentos isotérmicos de cinco ligas de aços TRIP microligados com Nb, contendo teores variáveis de Mn e Si, através de ensaios dilatométricos, de caracterização morfológica dos produtos de transformação e de cálculos termodinâmicos e simulações numéricas usando os programas Thermocalc ® e Dictra®. Foram determinados os diagramas RC para a transformação da austenita, e foi estudada a influência da precipitação de ferrita pró-eutetóide e de bainita na fração volumétrica de austenita retida. Através dos diagramas de resfriamento contínuo foi possível delimitar a extensão do campo intercrítico dos cinco aços analisados, com determinação da janela de resfriamento e seus intervalos de temperaturas. Isso permitiu projetar os ciclos de resfriamento controlado a serem aplicados durante o processamento termomecânico dos Aços TRIP-D, TRIP-E e TRIP-H. Os cálculos pelo modelo numérico de redistribuição de carbono e de elementos substitucionais na interface ferrita/austenita, bem como as medidas de microanálise química por WDS e EDS permitiram verificar que a taxa de crescimento da ferrita pró-eutetóide é controlada pela difusão do carbono na austenita. Para tempos curtos de tratamento, o modelo de crescimento que melhor se ajusta é o do equilíbrio local com partição negligível de soluto. Verificou-se através de tratamentos isotérmicos no campo bainítico, que o silício atrasa a precipitação de carbonetos durante a reação bainítica, o que justifica o aumento da estabilidade da austenita retida no aço de maior Si (TRIP-H), quando comparado com o aço de menor Si (TRIP-E). Baseado nos resultados dos estudos das transformações de fase por resfriamento contínuo foram selecionadas as ligas TRIP-D, TRIP-E e TRIP-H, para simular dois esquemas de laminação controlada por meio de ensaios de torção a quente. Nesses ensaios foram variados o grau de deformação e a temperatura de acabamento, de modo a estudar os efeitos dos parâmetros de deformação mecânica na fração transformada dos diferentes constituintes microestruturais, e em particular na fração volumétrica de austenita retida. O primeiro ensaio refere-se à laminação controlada por recristalização estática (LCRE) e o segundo à laminação convencional (LCC), com temperatura de acabamento de 1030°C e 850°C, respectivamente. O resfriamento consistiu em dois tratamentos isotérmicos consecutivos: o primeiro no campo intercrítico (austenita + ferrita), e o segundo no campo bainítico. O aumento do grau de deformação na simulação por torção a quente da laminação controlada por recristalização estática, levou a um aumento da porcentagem de austenita retida obtida durante o resfriamento controlado (de 9 a 14,0 %). O acúmulo de energia de deformação abaixo da TNR na simulação do processo de laminação controlada convencional provocou uma diminuição da fração volumétrica de austenita retida bem como da concentração de carbono contido nela. Os perfis de Mn e C obtidos a partir de análises químicas com EDS e WDS em amostras do aço TRIP-E, deformadas com deformação total de 2,1 e deformação total de 2,8, mostram a contribuição do refinamento de grão para a difusão destes elementos na frente da interface ferrita/austenita, durante a precipitação de ferrita pró-eutetóide.
The phase transformation kinetics of five Nb microalloyed Si-Mn TRIP steels was studied under continuous cooling and isothermal treatments, using dilatometric techniques, morphologic characterization, Thermocalc computational thermodynamics and Dictra numerical simulation. WDS and EDS X-ray microanalysis and Dictra numerical modeling of C, Mn and Si distribution during transformation showed that the reaction is carbon diffusion controlled and growth occurs under local equilibrium with negligible partition. CCT diagrams for austenite transformation were determined and the effect of the amount of proeutectoid ferrite and bainite precipitation on the volume fraction of retained austenite was also estimated. The CCT diagrams allowed determining the boundaries of the critical zone and the processing window to obtain bainite plus austenite microstructures. Based on this information cooling cycles were selected to perform thermomechanical treatments. Three TRIP steels were selected to simulate, in a hot torsion testing machine, two different controlled rolling sequences: Recrystallization Controlled Rolling and Conventional Controlled Rolling. The influence of the degree of deformation and the finishing temperature on the amount of retained austenite was studied. After rolling the cooling cycle comprised two isothermal treatments, one in the austenite + ferrite field and the other in the bainitic field. Increasing the strain during simulation of Recrystallization Controlled Rolling led to an increase in the volume fraction of retained austenite to the range 9 to 14 %. The energy stored during simulation bellow TNR of the Conventional Controlled Rolling led to a decrease in the volume fraction and in the carbon content of retained austenite. The Mn and C contents measured by EDS and WDS analysis of TRIP-E steel, showed that grain refinement due to recrystallization contributes to diffusion of these elements in front of the ferrite/austenite interface during precipitation.

High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the hypereutectic alloy and these will have a negative influence on the wear resistance. In this thesis, the Ti-alloyed hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is studied based on the experimental results and calculation results. The type, size distribution, composition and morphology of hard carbides and martensite units are discussed quantitatively. For a as-cast condition, a 11.2μm border size is suggested to classify the primary M7C3 carbides and eutectic M7C3 carbides. Thereafter, the change of the solidification structure and especially the refinement of carbides (M7C3 and TiC) size by changing the cooling rates and Ti addition is determined and discussed. Furthermore, the mechanical properties of hypereutectic HCCI related to the solidification structure are discussed. Mechanical properties of HCCI can normally be improved by a heat treatment process. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM), in-situ observation by using Confocal Laser Scanning Microscope (CLSM), Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). Especially for the matrix structure and secondary M7C3 carbides, EBSD and CLSM are useful tools to classify the fcc (γ) and bcc (α) phases and to study the dynamic behavior of secondary M7C3 carbides. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI. Finally, the maximum carbides size is estimated by using statistics of extreme values (SEV) method in order to complete the size distribution results. Meanwhile, the characteristic of different carbides types will be summarized and classified based on the shape factor.

QC 20130913

The presented diploma thesis deals with various types of quenching and their respective effects on mechanical and structural properties of AlSi7Mg0.6 alloy castings. Cast with precision casting technology into a self-supporting ceramic shell made by plaster investment technology, flat test bars cast by Alucast were used as experimental samples. Sample castings were used in both cast state and after T6 heat treatment. Air-flow and air-water combination with varying water passage (spraying) were used as the quenching media in the quenching process of the castings. In order to evaluate the effect of five different quenching processes on the structure and mechanical properties of the castings, the method of light microscopy, Brinell hardness test and static traction test were used. Evaluation and porosity and SDAS quantifications were carried out by means of image analysis. Experiments did not prove right the hypothesis holding that low SDAS values inevitably mean higher mechanical properties of the castings. On the other hand, distinct is the negative influence of heterogeneous structure and porosity. Despite the fact that the heat treatment was successful in reducing the influence of structural inhomogeneities, it cannot be concluded that spray quenching has an utterly positive bearing on the mechanical and structural properties of the castings.

In-line heat treatment is a part of technological process uses a phase and structure changes to obtain required mechanical properties. Heat treatment of rolled products offers a reduction of steel making costs and a creation of new steel products. For example the TRIP steel is a part of modern steels which is used in the automobile industry for higher safety of passengers. The heat treatment is often described in the literature. But the authors are often focused on the method how to get the required structure and mechanical properties for different metallic materials. Nevertheless just few articles are focused on the technical observing of temperature regimes and which parameter is necessary to consider during designing the cooling section. Eight parameters were tested by the experimental way to examine their influence on the cooling intensity. They were: gravity (orientation of the cooled surface), coolant pressure, amount of coolant spraying on the surface (the flow rate), rolling velocity, nozzle configuration, kind of nozzles (full cone or flat fan nozzle), coolant temperature and the surface quality (surface roughness and scales). All these parameters have an influence the heat transfer coefficient. Based on knowledge gained in this work was created the cooling section, which comply with the required cooling temperature regimes.

Social demands of recycle is becoming strong. In modern production systems, largenumber of one model of product is manufactured at a time and the way ofproduction operations are well specified. In recycling systems, on the contrary, it isusual that operation of disassemble for each works differs. Because of this,achieving high efficiency in recycling systems have been difficult. Quality FunctionDeployment (QFD) was implemented in the project to obtain clear understandingof the problem being dealt with. Being a case study in the recycling of end-of-liferefrigerators means there are several stakeholders which must be satisfied includinggovernment regulations, workforce, and the business organisation. At the same timeproductivity is maximised while cost and time is diminished. Designing withfunction, brainstorming and patent searches were used to generate new ideas.Building morphology was also used to generate ideas as well as document them.The results of the project are different concepts that can be applied individually anda comprehensive concept that will entail exhaustive change in the entire system.The recycling of compressors for material recovery is discussed.
http://www.diva-portal.se/smash/get/diva2:1326957/FULLTEXT02.pdf

It is an established fact that segregation during casting affects the physical properties of carbon-based ferro alloys; this motivates the study of the segregation behaviour of carbon and carbide-forming solute elements. In this context, this thesis investigates two different situations: the effects of cooling rate and turbulence on the precipitation behaviour of the graphite nodules in nodular cast iron; the nature of carbide precipitation in a bearing steel grade and the effects of subsequent soaking on these carbides. The structures of boiling water reactor inserts cast by the uphill and downhill casting of nodular cast iron were examined. The samples were taken from representative locations in the top, middle and bottom cross sections of the castings. It was observed that in uphill-cast inserts the nodules were larger but fewer in number the bottom section, whereas in downhill-cast inserts the nodules in the bottom section were smaller, but greater in number. Variation in volume fraction of the graphite nodules across the inserts was also observed. The probable cause of this variation was the difference in cooling rate in different sections of the insert. Between the steel tubes located at the central part of the casting, the fraction of graphite was lower, which could be the result of carburization of the steel tubes. To study the effects of melt stirring during the solidification of nodular cast iron, several experiments were conducted at variable cooling rates and for different stirring times. Examination of the microstructure was conducted using Light Optical Microscope (LOM) and Scanning Electron Microscope (SEM). It was observed that during stirring the melt oxidized and oxide nuclei were formed. The number of nucleation sites for the precipitation of graphite nodules increased, which raised the nodule count and the fraction of the graphite precipitated. The matrix transformed from pearlite to ferrite, which could be due to the fact that more carbon had diffused out of the matrix. The segregation behaviour in hypereutectoid bearing steel produced by ingot casting was also studied. The effects of soaking on micro and macro segregation was investigated in samples taken from as cast and soaked ingots; emphasis was laid on the bulk matrix and A-segregation channels. Samples were also taken from ingots which were soaked and then hot worked. The micro and macro examination of the microstructure was conducted using LOM and SEM. Quantitative and qualitative composition analysis was performed using Energy-dispersive X-ray spectroscopy (EDX) and an electron micro probe analyzer (EMPA). It was observed that M3C, M2C and M6C had precipitated. The carbide morphology in the bulk matrix was different to that in the A-segregation channels. All the primary carbides in the bulk matrix were found to have dissolved after 4 hours of soaking at 1200oC.
Det är ett faktum att segringar som uppstår under gjutning påverkar materialegenskaperna hos kolbaserade järnlegeringar; detta utgör motivationen till studien av segringsuppträdandet hos kol och karbidbildande ämnen. Denna avhandling behandlar två olika aspekter inom ramen för detta ämne: påverkan av kylningshastighet och turbulens på kärnbildningen av grafitnoduler i nodulärt gjutjärn samt karbidbildning i kullagerstål och dess påverkan på den efterföljande värmebehandlingen av dessa karbider. Strukturen hos rör till vattenkokare som tillverkats av nodulärt gjutjärn som gjutits med fyllning från botten eller från toppen undersöktes. Prover togs från representativa tvärsnittspositioner från toppen, mitten och botten av de gjutna ämnena. Resultaten visade att användandet av bottenfyllda kokiller gav upphov till större men färre karbider i nedre delen av ämnet, medans användandet av toppfyllda kokiller gav upphov till mindre men fler karbider i nedre delen av ämnet. Variationer av volymfraktionen av grafitnoduler längs tvärsnitten observerades också. Den mest sannolika orsaken till denna variation var skillnaden i kylhastighet i de olika områdena av tvärsnitten. Hos rör tillverkade av det centrala delen av ämnet så var fraktionen grafit lägre, vilket kan bero på en uppkolning av rören. Ett flertal experiment utfördes med varierande kylningshastigheter och olika omrörningstider för att studera inverkan av omrörning av smältan på stelningen av nodulärt gjutjärn. Studier av mikrostrukturen genomfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Resultaten visade att smältan oxiderades under omrörningen, vilket resulterade i bildandet av oxider. Detta ledde till en ökning av kärnbildningsområden för grafitnoduler, vilket ledde till en ökning av antalet noduler samt fraktionen av grafit som fälldes ut. Strukturen omvandlades från perlit till ferrit, vilket troligen orsakades av att kol hade diffunderat ut från strukturen. Segringsbeteendet hos hypereutektoida kullagerstål tillverkade genom götgjutning undersöktes också. Effekten av värmebehandling på mikro- och makrosegringar undersöktes i prover tagna från gjutna och värmebehandlade ämnen. Fokus var på att studera strukturen i ämnena samt A-segringar. Dessutom togs prover från ämnen som först värmebehandlats och därefter varmbearbetats. Både mikro- och makroundersökningar av mikrostrukturen utfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Dessutom så genomfördes kvantitativa sammansättningsbestämningar med energidispersiv röntgenspektroskopi och elektronmikroprobsanalys. Resultaten visade att M3C, M2C och M6C karbider hade fällts ut. Karbidmorfologin i huvuddelen av strukturen skiljde sig från den som återfanns i A-segringar. Samtliga primära karbider i huvuddelen av strukturen hade lösts upp efter 4 timmars värmebehandling vid 1200oC.

QC 20180523

Die Temperaturverhältnisse beim Ziehen und Wärmebehandeln von Draht werden mit mathematisch-analytischen Methoden auf der Grundlage der FOURIERschen Wärmeleitungsgleichung eingehend untersucht. Insbesondere wird unter den spezifischen Wärmeübergangsbedingungen zwischen Draht und Ziehdüse sowie zwischen Draht und Ziehtrommel deren thermische Wechselwirkung analysiert. Ein Näherungsverfahren zur Berechnung der Drahttemperaturen in Zugfolgen unter Berücksichtigung des Ziehdüseneinflusses wird angegeben und mit einem Beispiel zum Nassziehen stark verzinkten Stahldrahts illustriert. Aus geschwindigkeitsabhängig gemessenen Änderungen des Drahtdurchmessers werden unter thermoelastischer Ziehringdurchmesserkorrektur Schmierfilmdicken bestimmt. Diffusionsgleichungen werden analysiert und ein Zusammenhang zur Reaktionskinetik wird hergestellt. Ein neues reaktionskinetisches Werkstoffmodell, das insbesondere auch im Falle stärker anisothermer Verhältnisse, also bei Kurzzeitwärmebehandlung anwendbar ist, wird vorgestellt.

Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia do Ambiente, Gestão de Sistemas Ambientais
The main goal of this study is to assess the impact of the discharges of the semi-closed water cooling circuits of CERN (European Center for Nuclear Research) on the overall quality of CERN’s effluents, taking as guidelines the international legislation supported on the knowledge of the water systems of CERN. In order to reach this goal, a thorough analysis of the functioning of the semi-closed water cooling systems of CERN’s particle accelerators was done, as well as, an analysis of the treatment that is done to prevent the proliferation of bacteria such as Legionella. The products used in these water treatments, as well as their impact, were also researched. In addition, a study of the applicable regulation to CERN’s effluent was done. This study considered not only the regulation of France and Switzerland (CERN’s host states) but also the international regulation from the European community, Portugal Germany, Spain, U.S. and Canada, having in view a better understanding of the limit values of the parameters of the CERN’s host states, as well as, the possibility of setting a CERN’s internal regulation concerning water discharges. Considering the applicable regulation, the products used and the discharge conditions of the water systems, a research on the types of parameters to analyse was undertaken, bearing in mind the controversy on parameters such as AOX. This research was the foundation for conducting four water sampling campaigns: two of which during preventive shock treatment and the remaining two during regular treatment. The objective of the first two campaigns was broader and intended to check the conformity of CERN’s effluents with the regulations of the host states; On the other hand, the sampling campaigns conducted during regular treatment were oriented to deepen the knowledge on problematical parameters such as AOX, COD, DOC, Chlorine and Zinc. The preparation for these campaigns included also the choice of other aspects such as: the three sampling points (RAMSES, SF1 and building 863), the definition of the schedule for sampling and the selection of an external laboratory to conduct the analyses. The results of the analyses of CERN’s effluents, at the discharge point (RAMSES), were fully compliant with the regulation. However, at the source of this effluents (circuits SF1 and building 863) non-conformities have surged. The parameters AOX, DOC, COD, Chlorine, Brome, Suspended matter, Zinc and Aluminium demonstrated to be the most problematic. To conclude this work, a search for alternative methods to conventional water quality parameters was done that included a study on the applicability of ecotoxicological tests. As a result of this study, a final sampling campaign was performed using the tests Microtox (Vibrio fischeri), Green Algae (Pseudokirchneriella subcapitata), Micro- crustaceans (Daphnia magna), Macrophytes (Lemma minor) having obtained results that were conducive with the previous results. This way, RAMSES didn’t not show any toxicity on the four tests whilst SF1 evidenced toxicity, being most sensitive to the Micro-crustaceans test where it presented a UT50 value of 7,1 and EC50 value of 14,2 %.

Des pommes (pyrus malus l. Cv. "golden delicious" ont ete entreposees apres la recolte, a 0,12 et 35**(o)c. Apres 4 semaines, des lots de fruits ont ete transferes de 0 a 12**(o)c ou inversement de 12 a 0**(o)c. Les basses temperatures (0**(o)c) favorisent la levee de dormance, tandis que les temperatures elevees (12 et 35**(o)c) sont favorables a une meilleure resistance au gel et ces 2 phenomenes sont independants. L'analyse thermique differentielle a montre que l'embryon de pommier ne peut survivre au gel qu'en evitant la congelation intracellulairegrace a une surfusion prolongee. Plus la temperature de conservation des fruits est elevee, plus la temperature de surfusion est basse

碩士
國立中央大學
環境工程學系
85
In recent years, the use of ozone in cooling water treatment has received a great deal of attention because of its effect replacing the other chemical inhibitors and little or none toxicant discharge. The study was interested in understanding the maximum operating cycles of concentration of tap water and groundwater with ozone treatment. The study was also investigate the feasibility of recovery and reuse of municipal effluent as the make-up with ozone treatment. In addition, three kinds of couples (carbon steel, brass, and stainless steel) could be understood the effect of ozone on corrosion and scaling control under different kinds of make-up and the concentration of ozone. Finally, The study also used the XRD and SEM-EDS to identify and analysis the corrosion and scaling on the surface of couples. In order to simulate the increasing cycles of concentration in cooling water system, the study added some chemicals into the batch reactor. Results showed that the presence of ozone in the range of 0.05 ~ 0.1 mg/l, 0.8 ~ 1.2 mg/l, and 0.1~ 0.2 mg/l in tap water, groundwater, and municipal effluent respectively which can produce passivation layer on carbon steel and reduce corrosion. Positive effect of corrosion and scaling control on the brass and stainless steel dictated by the characteristics of metal, regardless of the presence of ozone. In the tap water and municipal effluent, the presence of ozone in the range of 0.05 ~ 0.1 mg/l could raise the solubility of calcium carbonate to 1.5 ~ 2.0 times. When the presence of ozone was in the range of 0.05 ~ 0.2 mg/l in municipal effluent, the ratio of calcium and DOC was about 25 ~ 30 mg/mg, which would raise the concentration of suspensible calcium ion to 1.5 times and improve the effect of scaling control. Furthermore, utilizing the XRD and SEM-EDS to identify the surface of carbon steel couple without ozone treatment, revealed that not only the deposit concern with corrosion was formed, but also the calcium carbonate scaling. However, none corrosion and scaling was observed on the surface of carbon steel with passivation layer.On the other hand, utilizing the Practical ozone scale index(POSI) to predict the maximum safe operating cycles of concentration of tap water and groundwater as make-up , and cooling water quality in no scale tendency, revealed that the maximum cycles of concentration were 6.5 and over 10 respectively. The municipal effluent contained 18.5 mg/l of calcium ion, 77.4 mg/l as CaCO3 of alkalinity, and 25 mg/l of chloride ion, and its maximum cycles of concentration was about 10. Apparently, the municipal effluent could be reused as make-up when using ozone in the cooling water treatment.

博士
國立中央大學
環境工程研究所
88
The cooling water is the major part of industrial wateruse in Taiwan, either from the view of demand priority or supply volume. In order to save water, the loading of supply system could be reduced whether the cooling water could be recovered and reused, or the effluent from wastewater treatment plant could be reclaimed as cooling water. For this reason, to explore the recent operation status of cooling water system has become essential in Taiwan. This study was initially focused on the current applications and reuse trends of cooling water in oil refineries, chemical industry, steel mills, food industry, electronics works, textile plants and power stations. According to the statistical analysis, the portable water and groundwater are the primary sources of makeup water for cooling systems. The multiple chemical dosing and makeup treatment are increasingly accepted for the reclamation of cooling water. However, most cooling water systems are only operated by operator’s experience according to field investigation. There was not any case plant found to be operated at appropriate cycles of concentration. In addition, sidestream treatment and blowdown reuse are not popular in Taiwan, the recovery rate of blowdown is only 26.8 %. The fact of higher cost is the major reason to depress the willingness of recovery. This study also demonstrates that the recovery and reuse of cooling water has great potential and is feasible for the available technologies in present Taiwan, but the industries are still unwilling to upgrade because of initial cost. Some approaches associated with technology, economics, environment and policy are proposed to be a reference for the industries and the government authorities. The results of pilot cooling tower (PCT) test demonstrated that ozone as a sole chemical was effective when using the portable water as make-up. It was found that brass and CS corrosion rates were kept at low level in the ozone-treated test due to the increasing of pH and alkalinity of reciculating water. But, it should note that overdosing ozone would enhance its oxidative ability and cause higher corrosion rate for brass and CS metal coupons as compare to that without ozonation. Furthermore, the results indicated that maintaining a suitable residual ozone concentration (0.1-0.2 mg/L) would produce an oxidative film on the metal surface and then reduce the corrosion rate. In addition, the metal corrosion rate would be decreased when COC of the cooling water system was increased because of the CaCO3 protective film was formed gradually. Ozone could inhibit CaCO3 scale in cooling water system might due to the presence of organic carbon or microorganisms. This study also revealed that ozone was an effective biocide for controlling bio-corrosion and bio-fouling. This study is also aimed at the feasibility of reusing the effluent as cooling water. The water qualities of each unit from Ming-Shen Community Wastewater Treatment Plant (MSP) and Da-Yang Industrial Park Wastewater Treatment Plant (DYP) had been investigated. The phosphate, ammonia and organic matter of MSP effluent were higher than the recommended cooling water quality criteria, that may induce the growth of microorganisms. The concentrations of chloride, sulfate, SS, and COD of DYP effluent were higher than the above suggested criteria. The operational problems of pilot cooling tower were also investigated when reusing the effluents as make-up water without any inhibitor. It was also suggested that reusing the effluent from secondary treatment of MSP as make-up water without any external treatment should be more feasible and economical, but that for DYP needs external treatment and would not pay. Ozone was used to treat the cooling water when the MSP effluent was reused as makeup. In the pilot cooling tower investigation, the biocidal efficiency of ozone was still excellent, but organic oxidation of ozone that decreased the pH and increased the brass and CS corrosion rate when the residual ozone concentration was maintained about 0.05-0.12 mg/L The other inhibitors would be needed when ozone be used to treat the municipal sewage effluent as make-up.

碩士
國立臺北科技大學
能源與冷凍空調工程系碩士班
97
The growth of algae and microorganisms in the air-conditioning system cooling tower causing the problem of strainer clogging and heat transfer efficiency decrease due to bio-fouling of heat exchanger. Traditional water treatment by addition of chemical oxidants causes environmental problems. Upon excitation by light of wavelength less than 380nm, the electron-hole pair generated on the TiO2 photocatalyst surface and produce hydroxyl radical which oxidize organic compounds. The study of photocatalytic inactivation of algae (Phormidum sp), a kind of fresh water algae usually found in the air- condition system cooling tower in Taiwan area was carried out. The results showed that after being irradiated with UV-A light in the presence of TiO2 dipped silica gel beads, the photosynthetic efficiency of the algae was reduced determined by Chlorophyll fluorescence method. In a separate experiment, by circulating the water containing algae through the fluidized bed photocatalytic reactor for 20 days, the weight of the algae collected from the water tank was 20% less than that of the water tank which was not subject to photocatalysis treatment. It suggested the algae growth have been inhibited.

碩士
國立中央大學
環境工程學系
86
The microbial-related problems frequently encountered in cooling water systems including bio-corrosion, bio-fouling, and causing Legionellosis. This study aimed to investigate and identify the microorganisms presented in real cooling water systems at various industrial sites as well as to evaluate the feasibility of reusing wastewater from treatment plants as cooling water make-up. Water samples and metal coupons of carbon steel and brass collected in field and laboratory tests were analyzed in order to realize the relationships between water qualities and operating problems of cooling water systems. Furthermore, the effects of ozonation on the control of microbial-related problems were also investigated.The evaluation of water qualities and water stabilization indexes indicated that the effluents from the units of secondary biological treatment process, tertiary filtration, and chlorination of Ming-Shen Community Wastewater Treatment Plant (MSCWTP) were suitable for reuse as cooling water. Similarly, the effluent from tertiary chemical coagulation process of Da-Yang Industrial Park Wastewater Treatment Plant (DYIPWTP) was also adaptable as cooling water make-up. However, considering the effects of scale, corrosion and fouling, the treated wastewater from MSCWTP was more suitable for reuse than that from DYIPWTP as cooling water. The investigation of microorganisms presented in real cooling water systems at various industrial sites showed that one case of Legionella contamination was detected out of 9 cooling water systems in this study. In addition, the groups of bacteria were identified at these cooling water systems including Serritia, Pseudomonas, Bacillus, Acinetobacter, Aeromonas, and Vibrio. The genera of algae such as Oscillatoria, Melosira, Colestrum, Cosmarium, Lyngbya, Trachelomonas, Celastrum, and Diatom were also found. Among these organisms, generally, Pseudomonas, Bacillus and Diatom were slime forming microorganisms. The water samples from the effluent of MSCWTP were detected the existence of Legionella and sulfate-reducing bacteria. Therefore, in order to protect public health from respiratory diseases and inhibit the bio-corrosion, appropriate biocide control as well as proper design and operation of cooling tower and heat exchanger are necessary when reusing the effluents of MSCWTP as cooling water. Ozonation of cooling water has been known for its excellent biocidal effect, and the results of this study were coincident with that. In pilot study, constant presence of 0~0.05 mg/l ozone in cooling water system could remove 97.8% total count of bacteria. The surface observation of metal coupons by scanning electron microscopy showed that ozonation could inhibit bio-fouling. In laboratory study, it found that intermittent addition of ozone could confine the growth of bacteria when using sewage effluent as cooling water make-up, however, the corrosion rate might be increased after ozonation.Keyword: cooling water, bio-fouling, ozonation, wastewater reuse.

碩士
國立中央大學
材料科學與工程研究所
100
According　to　this　research,　the　microstructure　of　solution　treatment　by　WQ　alloy　of　SP-700　is　constructed　by　αp(primary　α）+　α”(martensite)　+　βr(retained β). Stress　induced　martensite　transformation　happened　during tensile　process,　which　makes　strength　superior　due　to　βr　transformed　into　α”.　WQ　alloy　has　high　strength　and ductility　in　the　meanwhile.　In　addition,　α”　and　βr　is　going　to　precipitate　α+β　stable　phase　by　aging　treatment.　Aging　makes　WQ　alloy　became　much　stronger　but　poor　ductility.　The　microstructure　of　AC　and　FC alloys　are　both　formed　by　αp+α(precipitation)+β(stable), and　have　better　strength　than　WQ　alloy,　but　there　is　no　phase　transformation　during　aging　treatment.　From　the　above,　solution　treatment　and　aging　of　WQ　alloy　of SP-700,　which　has　the　best　strength.　Good　tensile　properties　prefer　WQ　alloy　without　aging.

碩士
國立勤益科技大學
冷凍空調系
98
In the semiconductor industry application, the process waste water was recycled mostly as the make-up cooling water of cooling tower for chiller units to save the dramatic water consumption. However, the recyeled water from process have the characteristic of being low pH values, calcium hardness and alkalinity, those will induce corrosion problem for chiller units and water piping systems. In this study, the field measurement of the recycled cooling water guality was conducted for two years in a full operation factory for wafer production. Some strategies for improvement of water treatment have been proposed to resolve the long term corrosion issues for cooling water piping systems. By conducting the improvement strategy and field survey of water treatment, the corrosion problem could be reduced effectively. The water treatment guality could be evaluated through sample field reports and water stabilization indices. The experiment results also revealed it is feasible to optimize the water treatment and operation strategy to combat piping corrosion by using the recycled process water. It is also expected to identify the best practice for investigation of water-saving, guality-controlled and energy-efficient cooling water system specific for semiconductor factory.

Dissertation submitted in partial compliance with the requirements for the Master's Degree in Technology: Chiropractic, Durban University of Technology, 2010.
Cryotherapy is commonly used to decrease pain, swelling and disability in acute injury. The most common form traditionally used is ice packs, with menthol based cooling gels being increasingly used by physicians in place of ice. More recently companies are experimenting with adding herbs containing anti-inflammatory properties to these menthol based gels to enhance their effectiveness. There is a paucity of literature comparing different forms of cryotherapy to one another, and more experiments are necessary to determine if cooling gels containing menthol and cooling gels with menthol and anti-inflammatory herbs are comparable to that of conventional ice pack cryotherapy. Objectives To determine the relative effectiveness of an ice pack, a menthol based gel, a menthol based gel with herbal extracts (combination gel) and placebo gel in the treatment of an acute grade 1 or 2 inversion ankle sprains, in terms of subjective and objective measurements. Any adverse reactions were also noted. Method A placebo controlled randomised, single blinded clinical trial (n=48) was conducted. Participants were randomly allocated into one of the four groups. Each group consisted of 12 people between the ages of 18 and 45. Each participant had a case history, physical and ankle examination prior to being accepted to ensure that they met the inclusion and exclusion criteria. On the initial consultation the respective treatments were administered and participants were instructed on how to apply the gel or ice pack, which they were required to utilise at home three times per day for 3 days. Those receiving the gels were blinded as to which gel they were receiving, all gels looked and smelt the same. On the 4th day the participants returned for data collection and were instructed to stop using the treatment and return 7 days later for further data collection. Statistical analysis consisted of repeated measures of ANOVA and Bonferroni post hoc tests, with a p-value of <0.05 considered statistically significant. Results Intra-group and inter-group analysis showed that all four groups had statistically significant improvements in terms of subjective and objective measurements. The results of the study demonstrated that the effects produced by the two cooling gels containing menthol, are comparable with those of conventional/traditional ice pack cryotherapy in the treatment of acute grade 1 or 2 inversion ankle sprains. No adverse reactions were reported. Conclusion This study found that all four treatment interventions were effective and safe in treating acute grade 1 and 2 inversion ankle sprains, however the ice pack and both cooling gel groups appear to statistically significantly improve treatment outcomes at a similarly higher rate when compared to the placebo gel group.

碩士
元智大學
機械工程學系
107
The cooling water system of the air-conditioning system transports the heat value carried by the refrigerant to the cooling tower through the cooling water, and finally absorbs the latent heat of vaporization through the cooling water evaporation to dissipate the heat value into the atmosphere. The cooling system is an open system . With the influence of air and water quality, there will be problems of scaling and algae on the heat exchange surface. The heat exchange efficiency of the cooling water system is greatly affected by scaling and algal growth. If the water quality of cooling water can be effectively managed, the problem of scaling and algae can be avoided. The air-conditioning system can save a lot of electricity and water resources. This study takes an electronics factory that introduce a (physical + O3) water treatment system to air conditioning cooling water system as an example. This study focus on the practical performance of the (physical+ O3) water treatment system applied to the cooling water system and the economic benefits it generates.

Submitted to the Faculty of Health at the Durban University of Technology in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Department of Chiropractic, Durban University of Technology, Durban, South Africa, 2015.
Background: Cryotherapy is often the first option in treating acute conditions and can be applied in various forms including ice packs and cooling gels. Cooling gels are easy to use and readily available making them popular with consumers. They can also contain additional ingredients which can assist with inflammation, making them ideal for musculoskeletal disorders. A cooling gel containing menthol and anti-inflammatory herbs is available in pharmacies nationwide in South Africa, but has not been clinically investigated. This gel is often used in the treatment of acute injuries such as low back pain but its effectiveness in treating this condition has not yet been verified. Objectives: To determine the effectiveness of a menthol cooling gel combined with anti-inflammatory herbs compared to a menthol gel and a placebo gel in the treatment of acute non-specific low back pain. Method: A double-blinded placebo controlled clinical trial (n = 60) was conducted. Each participant was randomly allocated into one of three treatment groups consisting of a minimum of 20 participants between the ages of 18 and 40 who met the study criteria. Informed consent was obtained from the participants prior to their participation in the study. At the initial consultation baseline measurements (pain rating, disability and pressure pain threshold) were taken and the respective treatments (menthol with anti-inflammatory herb, menthol or placebo gel) were administered. Participants were instructed on how to apply the gel at home and were requested to apply it three times a day for one week. Statistical analysis was performed using repeated measures ANOVA for inter- and intra-group analysis with one way ANOVA and chi square tests being used to compare baseline values. A p-value < 0.05 was considered to be statistically significant. The study received ethical clearance from the Durban University of Technology Institutional Research Ethics Committee (REC 81/13). Results: No significant differences were observed between the groups at baseline assessment, indicating that the groups were comparable. Participants were instructed on how to apply the gel at home and were requested to apply it three times a day for one week. Follow up appointments for data collection was scheduled at days three or four and six. No statistically significant differences were observed between the three groups over time for pain (p = 0.95), disability (p = 0.903) or pressure-pain threshold (p = 0.824), with all groups showing improvement. All three groups showed clinically significant changes in pain from moderate to mild over the duration of the study but no clinically significant changes were noted in terms of pressure-pain threshold and disability. Conclusion: The results indicate that irrespective of whether or not the gel contains active ingredients there was an improvement in acute low back pain. Further research needs to be conducted to determine if tissue depth and the concentration of the active ingredients such as menthol are factors affecting the efficacy of this gel.

Using seawater in cooling systems is a common practice in many parts of the world where there is a shortage of freshwater. However, biofouling is one of the major operational problems associated with the usage of seawater in cooling systems. Microfouling is caused by the activities of microorganisms, such as bacteria and algae, producing a very thin layer that sticks to the inside surface of the tubes in heat exchangers. This thin layer has a tremendously negative impact on heat transferred across the heat exchanger tubes in the system. In some instances, even a 250 micrometer thickness of fouling film can reduce the heat exchanger's heat transfer coefficient by 50 percent. On the other hand, macrofouling is the blockage caused by relatively large marine organisms, such as oysters, mussels, clams, and barnacles. A biocide is typically added to eliminate, or at least reduce, biofouling. Typically, microfouling can be controlled by intermittent dosages, and macrofouling can be controlled by continuous dosages of biocide. The aim of this research work is to develop a systematic approach to the optimal operating and design alternatives for integrated seawater cooling systems in industrial facilities. A process integration framework is used to provide a holistic approach to optimizing the design and operation of the seawater cooling system, along with the dosage and discharge systems. Optimization formulations are employed to systematize the decision-making and to reconcile the various economic, technical, and environmental aspects of the problem. Building blocks of the approach include the biocide water chemistry and kinetics, process cooling requirements, dosage scenarios and dynamic profiles, biofilm growth, seawater discharge, and environmental regulations. Seawater chemistry is studied with emphasis on the usage of biocide for seawater cooling. A multi-period optimization formulation is developed and solved to determine: * The optimal levels of dosing and dechlorination chemicals * The timing of maintenance to clean the heat-exchange * The dynamic dependence of the biofilm growth on the applied doses, the seawater-biocide chemistry, the process conditions, and seawater characteristics for each time period. The technical, economic, and environmental considerations of the system are accounted for and discussed through case studies.

The need for clean and renewable fuel such as hydrogen is driven by a growing worldwide population and increasing air pollution from fossil fuels. One of the major barriers for the use of hydrogen in automotive industry is the storage of hydrogen. Physisorption is the most promising storage technique due to its high storage density, reversibility and rapid sorption kinetics besides being safe and volume-efficient. A major challenge for physisorption is the need to manage the heat of adsorption at cryogenic temperatures. In this thesis, a 6061 aluminum microchannel cooling plate is designed to remove the equivalent heat flux required by the adsorption of hydrogen within an adsorption bed. Therefore, the objective of this thesis is to determine whether laser welding and heat treating strategies can be developed for a 6061 aluminum microchannel cooling plate as part of a larger hydrogen storage thermal management system. Key manufacturing process requirements include controlling the hermeticity, strength and dimensional stability of the heat-treated weld joint. A hermetic microchannel cooling plate was successfully laser welded and heat treated using free convection in air to quench the solution heat treatment. The weld strength and warpage obtained were within acceptable limits. Experimental testing of the fabricated microchannel cooling plate showed acceptable percent error with an experimental heat removal rate within 13.4% of computational fluid dynamics (CFD) analyses and an average pressure drop error of 25%. Calculations show that the cooling plate developed could support a hydrogen storage thermal management system taking up 5.0% and 10.3% of the system displacement volume and mass, respectively.
Graduation date: 2013

博士
義守大學
材料科學與工程學系
103
In this study, CM-247LC nickel-based superalloy was selected as a base material for alloy design, by revising heat treatment process and changing element content, to explore the effects of high temperature creep behavior and high temperature oxidation properties. The results showed that adding 1 wt.% Al element in CM-247LC nickel-based superalloy could promote gamma prime phase precipitation, improve volume fraction, enhance its high temperature creep properties, increase the Al activity, stimulate Al2O3 oxide layer at high temperatures, and advance oxidation resistance. When cooling rate after solution treatment is slower, gamma prime phase becomes thicker; consequently the high temperature creep properties are reduced. In the high temperature and ultra-high temperature creep testing, gamma prime phase was transformed into rafting structure to resist dislocation movement, but diffusion behavior is the main mechanism in the ultra-high temperature. Rafting structure was not produced in intermediate temperature; however the main deformation mechanism is dislocation movement.

碩士
國防大學理工學院
兵器系統工程碩士班
100
In this thesis, several commonly used industrial heat treatments such as annealing treatment or beta annealing were employed following electron beam welded (EBW) process of Ti-6Al-4V weldment. The correlation of the compositon of the produced oxide layer due to related annealing treatment and the corrosion resitance is investigated. It appears that the corrosion resistnace of both fusion zone and base metal zone is significantly influenced by the thickenss of oxide scale. Thicker oxide scale mainly dominated by higher temperature presents better corrosion resistacne along with the fact that the thickness of the oxide scale in fusion zone is being larger than that of the base metal zone in all heat treated conditions.

碩士
東海大學
畜產學系
91
This study used a 2 x 2 factorial experiment design to see the effects of improving energy density and the cooling treatment on the recovery of ovarian function and blood related metabolic materials in postpartum dairy cows under heat stress condition. The cooling treatment was performed from 8:00AM to 11:00AM and then from 2:00PM to 4:00PM. The Sprinkler and ventilation system were operated 5 minutes per cycle. The bypass fat was gradually increased from 100g to 400g at 4 weeks before parturition, then increased to 450g after parturition. During the experiment, the average temperature and relative humidity were 26.5℃ and 87.4 % from 8:00AM to 11:00AM, 29.℃ and 82% from 2:00PM to 5:00PM and 28.3℃ and 77% from 9:00PM to 11:00PM. Results show that the sprinkler and cooling system can effectively reduce the rectal temperature (p<0.05), increase feed and net energy intake (p<0.05), increase milk yield (P<0.001), and also achieve the earlier recovery of energy balance (P<0.001). There was no change (P>0.05) in body weight between fat and cooling treatments. The blood metabolite, such as insulin, was greater in both cooling and fat supplemented groups than the controlgroup (P<0.0001). Cooling has no effect on the serum cortisolconcentration (P>0.05). There is interaction of blood glucose concentration with fat and cooling treatment (P<0.0001). The fat treatment resulted in greater blood glucose level than the control groups (P<0.005). However, there is no change in the cooling treated cows. The blood glucose concentration was significantly (P<0.001) higher in the fat supplemented and cooling group (CF) than the other treated (UCNF、CNF and UCF) groups. Also, there is interaction of blood cholesterol concentration with fat and cooling treatment (P<0.0001). The blood cholesterol concentration was greater (P<0.05) in both fat treated and cooling group than the control groups. Besides, the cholesterol concentration was greater in CF cows than in the other groups (UCNF, CNF and UCF). In regards to reproductive performance, the interval from parturition to first ovulation was shorter (P<0.05) in the cooling treated cows than the control cows. However, there was no difference in the time of the second ovulation and in the interval between the first and second ovulations (P<0.05). On the other hand, the first ovulation time was delayed but the interval between the first and second ovulations were shortened in the fat added Cows (P<0.05). Cooling treated cows have more first class follicle than the untreated cows. But there was no difference between the two groups on rest classes of follicle development (P<0.05). Contrary to this, fat supplemented cows developed more second but less first class follicle than the control cows (P<0.05), There was no treatment effect observed on the third and fourth classes of follicle (P>0.01). From these results it was concluded that cooling and improving the energy concentration in ration has potential effects on alleviate heat stress from environmental temperature and further to improve the lactating and reproductive performance of dairy cattle. Keyword: dairy cattle、heat stress、fat、cooling、lactation performance、reproductive performance。

碩士
國立中興大學
畜產學系
88
The purpose of this study was to maintain the storage quality and extend the shelf life of hard-cooked eggs at room temperature using various coating materials. Paraffin wax, zein, ethyl cellulose and polyvinyl acetate were selected as coating materials in this experiment. The cooling methods of hard-cooked eggs directly affect both the production and storage quality. The degree of yolk discoloration of water cooling hard-cooked eggs was lighter than that of air cooling ones. As storage at 25℃, microbial penetration rate of water cooling hard-cooked eggs was more rapid than air cooling hard-cooked eggs, that made the former had the shorter shelf life of water cooling hard-cooked eggs. This experiment showed that reducing the microbial contamination during processes of hard-cooked and coating had marked effect on the storage quality of hard-cooked eggs. The shelf life of hard-cooked eggs stored at 25℃ was greatly extended by air cooling treatment after being cooked. Therefore, air cooling hard-cooked egg was used in coated hard-cooked storage test. The appearance of zein treated hard-cooked egg was much yellow and was significantly different from others. Scanning electron micrographs showed that both the number and the size of cracks on the eggshell surfaces increased after cooking. After coating, cracks on the eggshell surfaces were almost covered by coating materials. The bonding of coating materials was only on the eggshell surface, and there was no penetration of the coating materials below the surface. Both total plate counts and volatile basic nitrogen value of air cooling hard-cooked eggs stored at 25℃ for 12 days did not reached spoilage standard. During storage at 25℃, the pH values of albumen of all treatments tended to decline at early stage and then rise slowly. The pH values of yolk in all treated samples increased with storage time. The moisture loss of albumen of the uncoated and zein treated samples declined most seriously. The moisture content of yolk increased with storage time. The water activity in all treatments was between 0.967 and 0.975, which did not change markedly. The weight loss of all treatments increased with storage time, but of paraffin wax treatment significantly (p<0.05) lighter than other treatments. All the coating materials were only covered on eggshell surfaces and had no effect on the shell peelability of hard-cooked eggs. Coating treatment had effect on yolk color of hard-cooked eggs during storage. Paraffin wax treatment had effect on the scores of albumen and yolk color. Paraffin wax was the best coating material for holding hard-cooked egg flavor in this experiment. Results of sensory evaluation of appearance, color, flavor and texture showed that polyvinyl acetate was a good coating material for storage of the hard-cooked eggs.

L'utilisation d'alliages d'aluminium a augmenté énormément dans diverses applications au cours des vingt dernières années. Les demandes faites par l'industrie du transport pour des composants légers (afin de réduire la consommation de carburant) a mené à une plus grande utilisation des alliages d'aluminium dans la production d'une grande variété de bâtis, comprenant certains composants critiques tels que des blocs de moteur et des têtes de cylindre. Parmi ces derniers, les alliages Al-Si, qui sont les alliages commerciaux les plus utilisés pour ces applications, en raison de leur rapport élevé de force / poids, leurs propriétés élevées de tension et de fatigue, et leur excellente résistance à la corrosion. L'addition du silicium fournit une excellente coulabilité et une résistance élevée aux déchirures à chaud. La présence des éléments d'alliage tels que le magnésium et le cuivre offre aux alliages Al-Si des capacités de grande résistance à haute température. Avec ces bonnes propriétés, les alliages Al-Si sont particulièrement utilisés dans l'industrie automobile, l'armement et les industries aéronautique et spatiale. Les propriétés mécaniques d'un alliage coulé sont contrôlées par sa micro structure qui, elle même, est influencée par la composition chimique de l'alliage, c'est-à-dire par son contenu en silicium, en magnésium et en cuivre, ainsi que par la présence d'impuretés telles que le fer et de défauts du produit coulé (porosité, inclusions, etc.) comme les conditions de solidification (taux de refroidissement) et le traitement thermique appliqué. Dans le cas des alliages Al-Si, ce sont l'espace interdendritique d'o-Al (DAS), la morphologie et la taille des particules eutectiques de silicium, et la quantité d'intermétalliques et / ou d'autres constituants de deuxième phase présents dans la microstructure. Le taux de refroidissement, en général, commande la finesse de la microstructure : plus le taux de refroidissement est élevé, plus les dendrites d'à-Al et les particules d'autres phases sont fines, et plus l'espace interdendritique est petit. Dans les alliages Al-Si, il est connu que les caractéristiques eutectiques de particules de silicium (taille, morphologie et distribution) affectent sensiblement les propriétés mécaniques. Dans cet alliage sans traitement thermique le silicium eutectique est observé sous forme de plaquettes aciculaires fragiles qui sont nuisibles aux propriétés de tension et d'impact. Par l'utilisation d'un traitement de modification du métal liquide, la morphologie du silicium eutectique est changée ou modifiée de sa forme aciculaire à une forme fine et fibreuse qui améliore de manière significative la ductilité d'alliage et la résistance mécanique. La modification est effectuée par l'addition d'éléments tels que le Na, le Sr, le Câ ou encore par un mélange de métaux de terre rares (mischmetal). L'utilisation du Na et du Sr en tant qu'agents de modification pour les alliages Al-Si est bien établie. Récemment, cependant, l'intérêt a été concentré sur l'utilisation du mischmetal comme modificateur pour ces alliages. Le mischmetal est une combinaison de métaux de terre rares (Ce, La, Pr et Nd) et a été rapporté comme modificateur de particules de silicium pour les alliages Al-Si, avec une capacité de surmonter les problèmes d'absorption d'hydrogène, de porosité accrue et d'effacement (fading) liés à l'utilisation du strontium. Le mischmetal a également été rapporté comme ayant une réactivité chimique élevée avec l'Ai, le Si, le Cu et le Mg, provoquant la formation des composés intermétalliques durs de point de fusion élevé (AUCe, AULa, A^Ce, SiCe, etc.) dans les régions de joints de grains, renforçant ces derniers et améliorant de ce fait la résistance mécanique des alliages à température élevée. Le perfectionnement des caractéristiques eutectiques de particules de silicium peut également être obtenu par l'utilisation d'un procédé proportionné de traitement thermique (traitement thermique de mise en solution, trempe et vieillissement) où, pendant l'étape de traitement thermique de mise en solution, les particules eutectiques de silicium subissent des perturbations dans leur forme et commencent à se casser en plus petits segments (étape de fragmentation), et puis à se sphéroïdiser (étape de sphéroïdisation), acquérant ainsi une forme fibreuse. Des traitements thermiques sont également appliqués aux alliages Al-Si pour en améliorer la résistance mécanique par la précipitation des précipités fins tels que les Mg2Si ou AhCu, ce qui renforce la matrice de l'alliage. Les éléments d'alliage Mg et Cu entrent dans la solution pleine pendant l'étape de traitement thermique de mise en solution et précipitent pendant l'étape de vieillissement (précipitation durcissante). La présente recherche a été effectuée pour étudier l'effet du mischmetal comme modificateur ainsi que les effets du taux de refroidissement et du traitement thermique sur la microstructure et la dureté des alliages de fonderie A319.1, A356.2 et A413.1. Le but principal de cette étude était de déterminer le rôle du mischmetal comme agent de modification ainsi que l'effet combiné du Sr et de la modification par le mischmetal. La microstructure a été analysée au niveau de la taille et de la morphologie des particules eutectiques de silicium et des intermétalliques formés, en particulier des intermétalliques contenant du mischmetal, et corréler ces caractéristiques avec les valeurs de dureté correspondantes des alliages obtenues. Les coulées ont été préparées à partir des trois alliages cités plus haut, en utilisant une fois une modification en Sr (~ 250 ppm) et l'autre fois sans modification, avec les ajouts de mischmetal de 0, 2, 4 et 6 % en poids. Ayant une forme de L, le moule métallique utilisé pour la coulée a fourni des barres qui ont été employées pour des mesures de dureté. Deux arrangements différents de solidification de moule ont été employés pour fournir des taux bas et haut de refroidissement correspondant respectivement aux valeurs de 40 fixa, et 120 fim DAS. Les alliages coulés ont été soumis au traitement thermique T6 (comportant le traitement thermique de mise en solution à 495 °C / 8 heures pour les alliages A319.1 et A413.1, et à 540 °C / 8 heures pour l'alliage A356.2, la trempe à l'eau chaude (60 °C), suivie d'un vieillissement à 155 °C, à 180 °C, à 200 °C, à 220 °C et à 240 °C pour 5 h chacun). Des mesures de dureté ont été effectuées sur les échantillons tels que coulés et sur les alliages ayant subi un traitement thermique en utilisant un appareil de contrôle de dureté Brinell (500 Kgf appliqué pour 30 s, en utilisant une bille en acier de 10 mm de diamètre). Les caractéristiques des particules de silicium eutectiques (surface, longueur, rapport de la rondeur, rapport longueur / largeur et densité) ont été mesurées en utilisant un microscope optique relié à un analyseur d'image. Pour chaque échantillon d'alliage examiné, les caractéristiques de particules de silicium ont été mesurées sur un total de 50 champs et des caractéristiques moyennes de particules ont été déterminées. La fraction totale de tous les intermétalliques a été obtenue en utilisant la microsonde électronique (EMPA). La spectrométrie des rayons X par longueur d'ondes (WDS) a été employée pour l'identification de tous ces intermétalliques. Les mesures des particules de silicium eutectiques ont indiqué qu'une modification partielle a été obtenue avec les ajouts de mischmetal, contre la modification complète réalisée avec l'ajout de Sr dans la condition tel que coulé, et ce, aux deux taux de refroidissement. Une interaction entre le Sr et le mischmetal a été observée, celle-ci a affaibli l'efficacité du Sr comme modificateur. Cet effet était particulièrement évident au bas taux de refroidissement. Pendant le traitement thermique de mise en solution, les particules eutectiques de silicium dans les alliages non modifiés ont subi un grossissement rapide (Ostwald ripening), tandis que dans les alliages modifiés par le Sr, elles ont montré un taux élevé de sphéroïdisation. Le grossissement a été démontré par l'augmentation de l'épaisseur des particules de silicium (clairement observées en alliage A356.2 aux deux taux de refroidissement). Dans les alliages contenant du mischmetal, la présence de ce dernier a réduit la croissance des particules de silicium. L'analyse EPMA a indiqué que la fraction totale de tous les intermétalliques a augmenté avec l'ajout accru de mischmetal dans tous les alliages. Dans l'alliage A319.1, sans compter l'intermétallique AfeCu, un intermétallique de type AI40MM2TÍ4CUSÍ a été observé, sous forme de particules grises au taux de refroidissement élevé, avec un rapport élevé de Ce / La (4.1:1). Un autre intermétallique de type AI5MMO12SÍ a également été observé, sous forme des particules en plaquettes blanches, avec un bas rapport de Ce / La (1.8:1), et ce, aux deux taux de refroidissement. Cette phase intermétallique contenait 0.38 % en poids de Sr dans les alliages modifiés par le Sr, confirmant l'interaction entre le mischmetal et le Sr. Dans l'alliage A356.2, le mischmetal a formé différents types d'intermétalliques. Au taux de refroidissement élevé, une phase MM-Ti a été observée (AI4MMTi2Si à 0.26 % en poids de magnésium) sous forme de particules grises à un rapport élevé de Ce / La (3.4:1). Une autre phase de mischmetal contenant un intermétallique de type AI2MMSÍ2 a été observée, sous forme de particules arrondies blanches, aux deux taux de refroidissement, contenant 1.4-1.6 % en poids de Sr et 0.35-0.6 % en poids de magnésium, à un bas rapport de Ce / La (1.3:1). Au bas taux de refroidissement, un intermétallique sous forme d'écriture chinoise AI2MMSi2 avec 0.25 % de magnésium en poids a également été observé, à un bas rapport de Ce / La (1.5:1). À part les intermétalliques en mischmetal, la phase de Mg2Si dans ces échantillons d'alliage a été observée, sous forme d'écriture chinoise de couleur noire. Dans l'alliage A413.1, deux intermétalliques de fer ont été observés, à savoir, (i) la phase o-Fe Ali5(MnFe)3SÍ2 au bas taux de refroidissement et une autre phase o-Fe contenant un niveau élevé de Ni au taux de refroidissement élevé, avec une formule d'Alii(MnFeNiCu)4Si, sous forme de particules d'écriture chinoise grise, et (ii) la phase #- Fe AlsFeSi sous forme de particules en plaquettes gris foncé au taux de refroidissement élevé. La basse teneur en cuivre de l'alliage a eu comme conséquence la formation de la phase AI3NÍCU sous forme de blocs gris au taux de refroidissement élevé. Une phase intermétallique mischmetal blanche AI2MMSÍ2 au taux de refroidissement élevé a également été observé, à un bas rapport de Ce / La (1.18:1). Cette phase contenait 2.7 % en poids de Sr, indiquant l'interaction entre le mischmetal et le Sr et un affaiblissement conséquent de l'effet de modification du Sr. Cet intermétallique a encore combiné avec de l'Ai, le Si, le Cu et le Ni pour produire une phase intermétallique de type Al6MM(CuNi)Si en tiges de couleur gris clair, à un rapport modéré de Ce / La de 2:1. Dans les alliages A413.1 modifiés par le Sr et au bas taux de refroidissement, une phase intermétallique de mischmetal AI2MMSÍ2 sous forme d'écriture chinoise de couleur blanche a également été observée, à un rapport Ce / La de 1.48:1, contenant 0.48 % en poids de Sr, confirmant de nouveau l'interaction Sr - mischmetal. À un rapport légèrement plus élevé de Ce / La de 2.1:1, une autre phase intermétallique en mischmetal était produite, avec une formule d'Al5MM(CuNi)Si, observée dans la microstructure en tant que des particules en plaquettes de couleur gris clair. Les mesures de dureté ont indiqué que, en général, les valeurs de dureté des alliages tels que coulés étaient plus hautes au taux de refroidissement élevé qu'au bas taux de refroidissement. Les alliages non modifiés ont montré des niveaux légèrement plus élevés de dureté comparés aux alliages modifiés par le Sr, et la dureté a été diminuée par l'ajout de mischmetal, aux deux taux de refroidissement. Dans l'alliage A319.1 non modifié et après vieillissement aux différentes températures (155 °C - 240 °C / 5 h), deux valeurs maximales de dureté ont été observés (à 200 °C / 5 h et à 240 °C / 5 h) au taux de refroidissement élevé, alors que l'alliage A319.1 modifié par le Sr montrait seulement un maximum (à 200 °C / 5 h). Au bas taux de refroidissement, deux valeurs maximales de dureté ont été observés (à 155 °C / 5 h et à 180 °C / 5 h) dans les alliages non modifiés et dans ceux modifiés par le Sr. En général, les alliages contenant 0 et 2 % en poids de mischmetal ont montré les valeurs de dureté les plus élevées aux deux taux de refroidissement, et la dureté a diminué avec encore d'autres ajouts de mischmetal. Dans l'alliage A356.2, après vieillissement aux différentes températures (155 °C -240 °C / 5 h), la dureté maximale a été obtenue à 180 °C / 5 h dans les alliages non modifiés et les alliages modifiés par le Sr, aux deux taux de refroidissement. Les alliages sans mischmetal ont montré une dureté relativement plus élevée que ceux qui contiennent du mischmetal. La dureté a diminué avec l'augmentation de l'ajout de mischmetal. Au taux de refroidissement élevé, les alliages non modifiés ont montré des valeurs plus élevées de dureté que les alliages modifiés en Sr, alors que la tendance opposée était observée au bas taux de refroidissement. La diminution en valeurs de dureté peut être attribuée à l'interaction du mischmetal avec les éléments d'alliage Cu et Mg pour former les divers intermétalliques observés. La quantité de la précipitation des phases durcissantes formées dans les alliages A319.1 et A356.2 (AkCu et Mg2Si) est considérablement réduite, diminuant de ce fait la dureté. L'addition de mischmetal a changé l'ordre de précipitation de la phase Mg2Si dans l'alliage A356.2. Pour le cas de l'alliage A413.1, pour tous les états du vieillissement température / temps (155 °C - 240 °C / 5 h), la basse teneur en éléments d'alliage a eu comme conséquence une réponse faible de l'alliage au processus de durcissement, et ce, aux deux taux de refroidissement. Ainsi, aucune dureté maximale pour ces alliages n'a été observée.