The purpose of this study was to characterize the craze growth behavior of polycarbonate (PC) as a function of stress level, model the residual mechanical properties of PC at various craze levels and strain rates, and determine if the total surface area of crazing is the sole factor in residual properties or if the crazing stress plays a role. To obtain these goals, a new in-situ reflective imaging technique was developed to quantify the craze severity in transparent polymers. To accomplish the goal of craze growth rate characterization, polycarbonate samples were placed under a creep load in a constant temperature, constant humidity environment. Using the new technique, the relative craze density was measured as a function of time under load at stresses of 40, 45, and 50 MPa. The craze growth rates were found to increase exponentially with stress level, and the times to 1% relative craze density were found to decrease exponentially with stress level. One exception to this behavior was found at a crazing stress of 50 MPa at which over half of the samples tested experienced delayed necking, indicating competitive mechanisms of crazing and shear yielding. The draw stress was found to be a lower bound below which delayed necking will not occur in a reasonable time frame. The yield stress, elastic modulus, failure stress, and ductility were correlated to crazing stress, relative craze density, and strain rate using a Design of Experiments (DOE) approach. The yield stress was found to correlate only to the strain rate, appearing to be unaffected by the presence of crazes. No correlation was found between the elastic modulus and the experimental factors. The failure stress was found to decrease with an increase in relative craze density from 0 to 1%, increase with an increase in crazing stress from 40 to 45 MPa, and correlate to the interaction between the crazing stress and the strain rate. The ductility of polycarbonate was found to decrease significantly with an increase in relative craze density, a decrease in crazing stress, and an increase in strain rate. The craze microstructure was correlated to the magnitude of stress during craze formation. The area of a typical craze formed at 40 MPa was measured to be more than 2.5 times larger than the area of a typical craze formed at 45 MPa. The fewer, but larger, crazes formed at the lower stress level were found to decrease the failure strength and ductility of polycarbonate more severely than the large number of smaller crazes formed at the higher stress level. / Ph. D.

The use of turbocharged Diesel engines is nowadays a widespread practice in the automotive sector: heavy-duty vehicles like trucks or buses, in particular, are often equipped with turbocharged engines. An accurate study of the flow field developing inside both the main components of a turbocharger, i.e. compressor and turbine, is therefore necessary: the synergistic use of CFD simulations and experimental tests allows to fulfill this requirement. The aim of this thesis is to investigate the performance and the flow field that develops inside a centrifugal compressor for automotive turbochargers. The study is carried out by means of numerical simulations, both steady-state and transient, based on RANS models (Reynolds Averaged Navier-Stokes equations). The code utilized for the numerical simulations is Ansys CFX.   The first part of the work is an engineering attempt to develop a CFD method for predicting the performance of a centrifugal compressor which is based solely on steady-state RANS models. The results obtained are then compared with experimental observations. The study continues with an analysis of the sensitivity of the developed CFD method to different parameters: influence of both position and model used for the rotor-stator interfaces and the axial tip-clearance on the global performances is studied and quantified.   In the second part, a design optimization study based on the Design of Experiments (DoE) approach is performed. In detail, transient RANS simulations are used to identify which geometry of the recirculation cavity hollowed inside the compressor shroud (ported shroud design) allows to mitigate the backflow that appears at low mass-flow rates. Backflow can be observed when the operational point of the compressor is suddenly moved from design to surge conditions. On actual heavy-duty vehicles, these conditions may arise when a rapid gear shift is performed. / Användningen av turboladdade dieselmotorer ärr numera utbredd inom bilindustrin: i synnerhet tunga fordon som lastbilar eller bussar ärr ofta utrustade med turbo-laddade motorer. En utförlig förståelse av flödesfältet som utvecklas innuti båda huvudkomponenterna hos en turboladdare, dvs kompressor och turbin, är därför nödvändig: den synergistiska användningen av CFD-simuleringar och experimentel-la tester möjliggör att detta krav uppfylls. Syftet med denna avhandling är att undersöka prestanda och det flödesfält som utvecklas i en centrifugalkompressor för turboladdare. Studien utförs genom nu-meriska simuleringar, både steady state och transient, baserat på RANS-modeller (Reynolds Averaged Navier-Stokes-ekvationer). Koden som används för de numeriska simuleringarna är Ansys CFX.   Den första delen av arbetet ¨ar ett försöka att utveckla en CFD-metod för att förutsäga prestanda för en centrifugalkompressor med hjälp av steady-state RANS-modeller. De erhållna resultaten jämförs sedan med experimentella observationer. Studien fortsätter med en analys av känsligheten hos den utvecklade CFD-metoden till olika parametrar: Inflytande av både position och modell som används för rotor-statorgränssnitt samt axiellt spel mellan rotor och hus på de globala prestationerna studeras och kvantifieras.   I andra delen utförs en designoptimeringsstudie baserad på Design of Experiments (DoE). I detalj används tidsupplösta RANS-simuleringar för att identifiera vilken utformning av ported shroud som minskar backflöde i kompressorn under en snabb minskning av massflöde och varvtal och därmed ger bättre prestanda i transient surge. På tunga fordon kan dessa förhållanden uppstå under växling.

No Brasil, tanto o agronegócio quanto a fabricação de celulose trazem resultados relevantes para a economia. Sob uma perspectiva de sustentabilidade, as indústrias beneficiadoras de materiais vegetais geram grande volume de resíduos, os quais podem servir de fonte de celulose, configurando-se numa alternativa atraente para gerar lucros e diminuir impactos ambientais negativos. O objetivo geral desta dissertação é realizar um estudo exploratório de extração de celulose a partir de resíduo do processo produtivo de empresa beneficiadora de material vegetal, sob perspectiva das dimensões ambiental e econômica da sustentabilidade. O estudo foi desdobrado em cinco etapas: i) identificação na literatura das diretrizes para os processos produtivos sustentáveis, por meio das abordagens que tratam da sustentabilidade; ii) identificação dos processos industriais de extração de celulose e suas características operacionais; iii) definição da empresa para realização do estudo, a sazonalidade e o volume disponível dos resíduos vegetais provenientes do processo de beneficiamento de vegetais; iv) adaptação do processo industrial de extração de celulose para uso com resíduos vegetais e atendimento às restrições da fábrica definida para o estudo e v) realização de testes de extração com o uso de projeto de experimentos para posterior caracterização da polpa de celulose obtida do resíduo. Neste último, foi empregado um Projeto Fatorial Composto de Segunda Ordem (PSCO) com Metodologia de Superfície Resposta (MSR) para analisar a influência dos fatores controláveis sobre as variáveis de resposta. Os fatores controláveis foram definidos de acordo com dados da literatura específica e foram analisadas as variáveis de resposta que caracterizam polpa de celulose, aplicáveis a fins sanitários, como Número Kappa, capacidade de absorção, velocidade de absorção e densidade. Resultados indicaram que limitações quanto ao uso de altas temperaturas no processo de extração é um fator relevante, para atingir maiores teores de deslignificação. Os estudos mostraram a influência do uso de aditivo de processo, antraquinona, carga alcalina e tempo de polpeamento, bem como, tratamento de hidrólise ácida no resíduo na qualidade da polpa. / Agribusiness and pulp production bring both relevant results to the Brazilian economy. In a sustainable perspective, the wastes of Industries that benefit vegetable materials may serve as pulp’s source, configuring itself as an attractive alternative for profit generation and reduction of negative environmental impacts. The aim in this dissertation is to carry out an exploratory study of pulp extraction from the waste of productive process of a firm which processes vegetal material, under the perspective of environmental and economic dimensions of sustainability. The study was unfolded in five steps: i) identification, in literature, the guidelines for sustainable productive processes, through approaches that embrace sustainability; ii) identification of industrial processes of pulp extraction and respective operational features; iii) definition of an industrial unit to perform the study, as well as the seasonality and the availability of vegetal wastes coming from the vegetable process; iv) adaptation of the industrial process of pulp extraction for using with vegetable wastes, and attendance to constraints of the current process in the industrial unit chosen for the study; and v) the performance of extraction tests using a project of experiments for further characterization of the cellulose pulp resulting from the waste. It was employed a Factorial composite second-order design in a Surface Response Methodology (SRM) in order to analyze the influence of the controlled variables over the response variables. Variables of the extraction process were defined according with the specific literature’s data, and response variables, adequate to the cellulose pulp characterization as Kappa Number, capability, absortion speed and apparent density were analyzed. Results indicate that constraints related to the high temperature used in the equipment available for extraction is a relevant factor in the process for obtaining higher contents of delignification. Studies show the influence of using additive process, anthraquinone, load time and alkaline pulping, as well as treatment of hydrolysis in the waste of pulp quality. The remarkable difference in the quality of vegetable waste after hydrolysis treatment indicates that a pretreatment stage of such waste is interesting, since the fiber is resistant and requires high alkali and addictive charges.

No Brasil, tanto o agronegócio quanto a fabricação de celulose trazem resultados relevantes para a economia. Sob uma perspectiva de sustentabilidade, as indústrias beneficiadoras de materiais vegetais geram grande volume de resíduos, os quais podem servir de fonte de celulose, configurando-se numa alternativa atraente para gerar lucros e diminuir impactos ambientais negativos. O objetivo geral desta dissertação é realizar um estudo exploratório de extração de celulose a partir de resíduo do processo produtivo de empresa beneficiadora de material vegetal, sob perspectiva das dimensões ambiental e econômica da sustentabilidade. O estudo foi desdobrado em cinco etapas: i) identificação na literatura das diretrizes para os processos produtivos sustentáveis, por meio das abordagens que tratam da sustentabilidade; ii) identificação dos processos industriais de extração de celulose e suas características operacionais; iii) definição da empresa para realização do estudo, a sazonalidade e o volume disponível dos resíduos vegetais provenientes do processo de beneficiamento de vegetais; iv) adaptação do processo industrial de extração de celulose para uso com resíduos vegetais e atendimento às restrições da fábrica definida para o estudo e v) realização de testes de extração com o uso de projeto de experimentos para posterior caracterização da polpa de celulose obtida do resíduo. Neste último, foi empregado um Projeto Fatorial Composto de Segunda Ordem (PSCO) com Metodologia de Superfície Resposta (MSR) para analisar a influência dos fatores controláveis sobre as variáveis de resposta. Os fatores controláveis foram definidos de acordo com dados da literatura específica e foram analisadas as variáveis de resposta que caracterizam polpa de celulose, aplicáveis a fins sanitários, como Número Kappa, capacidade de absorção, velocidade de absorção e densidade. Resultados indicaram que limitações quanto ao uso de altas temperaturas no processo de extração é um fator relevante, para atingir maiores teores de deslignificação. Os estudos mostraram a influência do uso de aditivo de processo, antraquinona, carga alcalina e tempo de polpeamento, bem como, tratamento de hidrólise ácida no resíduo na qualidade da polpa. / Agribusiness and pulp production bring both relevant results to the Brazilian economy. In a sustainable perspective, the wastes of Industries that benefit vegetable materials may serve as pulp’s source, configuring itself as an attractive alternative for profit generation and reduction of negative environmental impacts. The aim in this dissertation is to carry out an exploratory study of pulp extraction from the waste of productive process of a firm which processes vegetal material, under the perspective of environmental and economic dimensions of sustainability. The study was unfolded in five steps: i) identification, in literature, the guidelines for sustainable productive processes, through approaches that embrace sustainability; ii) identification of industrial processes of pulp extraction and respective operational features; iii) definition of an industrial unit to perform the study, as well as the seasonality and the availability of vegetal wastes coming from the vegetable process; iv) adaptation of the industrial process of pulp extraction for using with vegetable wastes, and attendance to constraints of the current process in the industrial unit chosen for the study; and v) the performance of extraction tests using a project of experiments for further characterization of the cellulose pulp resulting from the waste. It was employed a Factorial composite second-order design in a Surface Response Methodology (SRM) in order to analyze the influence of the controlled variables over the response variables. Variables of the extraction process were defined according with the specific literature’s data, and response variables, adequate to the cellulose pulp characterization as Kappa Number, capability, absortion speed and apparent density were analyzed. Results indicate that constraints related to the high temperature used in the equipment available for extraction is a relevant factor in the process for obtaining higher contents of delignification. Studies show the influence of using additive process, anthraquinone, load time and alkaline pulping, as well as treatment of hydrolysis in the waste of pulp quality. The remarkable difference in the quality of vegetable waste after hydrolysis treatment indicates that a pretreatment stage of such waste is interesting, since the fiber is resistant and requires high alkali and addictive charges.

No Brasil, tanto o agronegócio quanto a fabricação de celulose trazem resultados relevantes para a economia. Sob uma perspectiva de sustentabilidade, as indústrias beneficiadoras de materiais vegetais geram grande volume de resíduos, os quais podem servir de fonte de celulose, configurando-se numa alternativa atraente para gerar lucros e diminuir impactos ambientais negativos. O objetivo geral desta dissertação é realizar um estudo exploratório de extração de celulose a partir de resíduo do processo produtivo de empresa beneficiadora de material vegetal, sob perspectiva das dimensões ambiental e econômica da sustentabilidade. O estudo foi desdobrado em cinco etapas: i) identificação na literatura das diretrizes para os processos produtivos sustentáveis, por meio das abordagens que tratam da sustentabilidade; ii) identificação dos processos industriais de extração de celulose e suas características operacionais; iii) definição da empresa para realização do estudo, a sazonalidade e o volume disponível dos resíduos vegetais provenientes do processo de beneficiamento de vegetais; iv) adaptação do processo industrial de extração de celulose para uso com resíduos vegetais e atendimento às restrições da fábrica definida para o estudo e v) realização de testes de extração com o uso de projeto de experimentos para posterior caracterização da polpa de celulose obtida do resíduo. Neste último, foi empregado um Projeto Fatorial Composto de Segunda Ordem (PSCO) com Metodologia de Superfície Resposta (MSR) para analisar a influência dos fatores controláveis sobre as variáveis de resposta. Os fatores controláveis foram definidos de acordo com dados da literatura específica e foram analisadas as variáveis de resposta que caracterizam polpa de celulose, aplicáveis a fins sanitários, como Número Kappa, capacidade de absorção, velocidade de absorção e densidade. Resultados indicaram que limitações quanto ao uso de altas temperaturas no processo de extração é um fator relevante, para atingir maiores teores de deslignificação. Os estudos mostraram a influência do uso de aditivo de processo, antraquinona, carga alcalina e tempo de polpeamento, bem como, tratamento de hidrólise ácida no resíduo na qualidade da polpa. / Agribusiness and pulp production bring both relevant results to the Brazilian economy. In a sustainable perspective, the wastes of Industries that benefit vegetable materials may serve as pulp’s source, configuring itself as an attractive alternative for profit generation and reduction of negative environmental impacts. The aim in this dissertation is to carry out an exploratory study of pulp extraction from the waste of productive process of a firm which processes vegetal material, under the perspective of environmental and economic dimensions of sustainability. The study was unfolded in five steps: i) identification, in literature, the guidelines for sustainable productive processes, through approaches that embrace sustainability; ii) identification of industrial processes of pulp extraction and respective operational features; iii) definition of an industrial unit to perform the study, as well as the seasonality and the availability of vegetal wastes coming from the vegetable process; iv) adaptation of the industrial process of pulp extraction for using with vegetable wastes, and attendance to constraints of the current process in the industrial unit chosen for the study; and v) the performance of extraction tests using a project of experiments for further characterization of the cellulose pulp resulting from the waste. It was employed a Factorial composite second-order design in a Surface Response Methodology (SRM) in order to analyze the influence of the controlled variables over the response variables. Variables of the extraction process were defined according with the specific literature’s data, and response variables, adequate to the cellulose pulp characterization as Kappa Number, capability, absortion speed and apparent density were analyzed. Results indicate that constraints related to the high temperature used in the equipment available for extraction is a relevant factor in the process for obtaining higher contents of delignification. Studies show the influence of using additive process, anthraquinone, load time and alkaline pulping, as well as treatment of hydrolysis in the waste of pulp quality. The remarkable difference in the quality of vegetable waste after hydrolysis treatment indicates that a pretreatment stage of such waste is interesting, since the fiber is resistant and requires high alkali and addictive charges.

Light-emitting diodes (LEDs) offer energy-efficient lighting and are widely adopted. However, LED drivers that regulate power can fail when subjected to voltage disturbances on the electrical grid. This research investigates how components within LED drivers durability when undergoing voltage impulses and swells using simulation-based methods. An LED driver circuit was modeled in LTspice circuit simulation software. Impulses from 35-65V and equivalent voltage swells were applied to the simulated driver. The electrical stresses on components were statistically analyzed using the design of experiments and general full factorial. This methodology identified the most vulnerable components and their common durability/failure mechanisms during impulse and swell events. The findings provide insights into design changes that harden drivers against grid disturbances. This study determines that higher capacitor voltage ratings improved voltage impulse and swell withstand. Additionally, adding a surge suppression diode across the LED minimized diode reverse breakdown during swells. This simulation-based approach enables the informed design of robust LED drivers that can withstand electrical grid perturbations through strategic hardening of the most vulnerable components. The methodology and findings provide a framework for the reliability optimization of LED drivers and other power electronic systems exposed to power quality disturbances.Keywords: LED driver, voltage disturbance, component failure, circuit simulation, design of experiments (DOE), general full factorial.

Orientador: Messias Borges Silva / Resumo: O cultivo de microalgas tem sido considerado como uma fonte promissora de lipídeos para a obtenção de ácidos graxos de alto valor agregado, como é o caso dos ômegas 3 (ω3) e ômegas 6 (ω6). O uso do planejamento de experimentos (DOE) permite estabelecer condições apropriadas de cultivo para as microalgas que favorece o acúmulo desses ácidos graxos. Desta forma, o presente trabalho teve como objetivo melhorar o desempenho dos cultivos das microalgas Nannochloropsis gaditana e Dunaliella salina, visando a produção de ω3 e ω6. Primeiramente, foram avaliadas, com o uso de uma matriz ortogonal Taguchi L4, as influências das concentrações de nitrato de sódio (de 25 a 75 mg L-1), de acetato de sódio e bicarbonato de sódio (ambas de 0 a 2 g L-1), sobre a produtividade de biomassa (Pb) e de lipídeos (Po). Como resultado, foi notado que tanto o acetato quanto o nitrato, influenciaram positivamente na Pb e na Po, para ambas as microalgas estudadas. O bicarbonato, por outro lado, não melhorou a Po, sendo excluído das etapas posteriores. Na etapa seguinte do trabalho foi realizado um planejamento fatorial completo 22 com ponto central, focando no estudo da concentração de nitrato (75 a 225 mg L-1) e acetato (2 a 6 gL-1) sobre a produtividade dos cultivos. As maiores Pb obtidas foram: 188,93 mg L-1 dia-1 para a microalga N. gaditana (225 mg L-1 de nitrato e 6 g L-1 de acetato) e 118,93 mg L-1 dia-1 para a D. salina (150 mg L-1 de nitrato e 4 g L-1 de acetato). Nestas condições de cultivo, a... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

This dissertation presents an empirical approach to identifying decisions for adapting cognitive radio parameters with no a priori knowledge of the environment. Cognitively inspired radios, attempt to combine observed metrics of system performance with artificial intelligence decision-making algorithms. Current architectures trend towards hybrid combinations of heuristics, such as genetic algorithms (GA) and experiential methods, such as case-based reasoning (CBR). A weakness in the GA is its reliance on limited mathematical models for estimating bit error rate, packet error rate, throughput, and signal-to-noise ratio. The CBR approach is similarly limited by its dependency on past experiences. Both methods have potential to suffer in environments not previously encountered. In contrast, the statistical methods identify performance estimation models based on exercising defined experimental designs. This represents an experiential decision-making process formed in the present rather than the past. There are three core contributions from this empirical framework: 1) it enables a new approach to decision making based on empirical estimation models of system performance, 2) it provides a systematic method for initializing cognitive engine configuration parameters, and 3) it facilitates deeper understanding of system behavior by quantifying parameter significance, and interaction effects. Ultimately, this understanding enables simplification of system models by identifying insignificant parameters. This dissertation defines an abstract framework that enables application of statistical approaches to cognitive radio systems regardless of its platform or application space. Specifically, it assesses factorial design of experiments and response surface methodology (RSM) to an over-the-air wireless radio link. Results are compared to a benchmark GA cognitive engine. The framework is then used for identifying software-defined radio initialization settings. Taguchi designs, a related statistical method, are implemented to identify initialization settings of a GA. / Ph. D.

The Swedish truck industry is looking for new material solutions to achieve lighter engines with increased strength to meet customer demands and to fulfil the new regulations for more environmentally friendly trucks. This could be achieved by increasing the peak pressure in the cylinders. Consequently, a more efficient combustion is obtained and the exhaust lowered. This, however, exposes the engine to higher loads and material physical properties must therefore be enhanced. One material that could meet these demands is Compacted Graphite Iron (CGI). Its mechanical and physical properties make it ideal as cylinder block material, though there are drawbacks concerning its machinability as compared to other materials that are commonly used for the same purpose. Knowledge about machining of the material and its machinability is consequently inadequate. The main goal of this thesis is to identify and investigate the effect of the major factors and their individual contributions on CGI machining process behaviour. When the relationship between the fundamental features; machinability, material microstructure, and material physical properties, are revealed, the CGI material can be optimized, both regarding the manufacturing process and design requirements. The basic understanding of this is developed mainly through experimental analysis as, e.g., machining experiments and material characterization. The machining model presented in this thesis demonstrates the influence of material and process parameters on CGI machinability. It highlights machinability from both design and production planning perspectives. Another important objective of the thesis is an inverse thermo−mechanical FE model for intermittent machining of CGI. Here, experimental results obtained from a developed simulated milling method are used as input data, both to calibrate and validate the model. With these models, a deeper understanding is obtained regarding the way to achieve a stable process, which is the basis for future optimization procedures. The models can therefore be used as a foundation for the optimization of CGI component manufacturing. / <p>QC 20111121</p> / MERA - OPTIMA CGI / FFI - OPTIMA phase two

This thesis illustrates analysis of the influence of the non-machining processes on product quality by experimental design and statistical analysis. For the analysis objective / dishwasher production in Arcelik Dishwasher plant is examined. Sheet metal forming processes of dishwasher production constitutes the greatest portion of production cost and using the Pareto analysis technique / four pieces among twenty six pieces are determined to be investigated. These four pieces are the U Sheet, L Sheet, Inner Door and Side Panel of the dishwasher. By the help of the flow diagrams production process of the determined pieces are defined. Brainstorming technique and cause&amp / effect diagrams are used to determine which non-machining process parameters can cause pieces to be scrapped. These parameters are used as control factors in experimental design. Taguchi&amp / #8217 / s L16(215) orthogonal array, Taguchi&amp / #8217 / s L16(215) orthogonal array using S/N transformation and 28-4 fractional factorial design are used on purpose. With repetitions and confirmation experiments the effective parameters are determined and optimum level of these parameters are defined for the improvements on scrap quantity and quality of production.