The focus of this dissertation is on improving decision-maker trade-offs and the development of a new constrained methodology for multiple response surface optimization. There are three key components of the research: development of the necessary conditions and assumptions associated with constrained multiple response surface optimization methodologies; development of a new constrained multiple response surface methodology; and demonstration of the new method. The necessary conditions for and assumptions associated with constrained multiple response surface optimization methods were identified and found to be less restrictive than requirements previously described in the literature. The conditions and assumptions required for a constrained method to find the most preferred non-dominated solution are to generate non-dominated solutions and to generate solutions consistent with decision-maker preferences among the response objectives. Additionally, if a Lagrangian constrained method is used, the preservation of convexity is required in order to be able to generate all non-dominated solutions. The conditions required for constrained methods are significantly fewer than those required for combined methods. Most of the existing constrained methodologies do not incorporate any provision for a decision-maker to explicitly determine the relative importance of the multiple objectives. Research into the larger area of multi-criteria decision-making identified the interactive surrogate worth trade-off algorithm as a potential methodology that would provide that capability in multiple response surface optimization problems. The ISWT algorithm uses an ε-constraint formulation to guarantee a non-dominated solution, and then interacts with the decision-maker after each iteration to determine the preference of the decision-maker in trading-off the value of the primary response for an increase in value of a secondary response. The current research modified the ISWT algorithm to develop a new constrained multiple response surface methodology that explicitly accounts for decision-maker preferences. The new Modified ISWT (MISWT) method maintains the essence of the original method while taking advantage of the specific properties of multiple response surface problems to simplify the application of the method. The MISWT is an accessible computer-based implementation of the ISWT. Five test problems from the multiple response surface optimization literature were used to demonstrate the new methodology. It was shown that this methodology can handle a variety of types and numbers of responses and independent variables. Furthermore, it was demonstrated that the methodology can be successful using a priori information from the decision-maker about bounds or targets or can use the extreme values obtained from the region of operability. In all cases, the methodology explicitly considered decision-maker preferences and provided non-dominated solutions. The contribution of this method is the removal of implicit assumptions and includes the decision-maker in explicit trade-offs among multiple objectives or responses.

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Hochtemperatur-Konversionsprozesse sind ein wesentlicher Bestandteil von industriellen Produktionsprozessen, die maßgeblich den Prozesswirkungsgrad und die Produktionskosten beeinflussen. Die modellgestützte Optimierung ermöglicht eine gezielte Verbesserung verschiedener Parameter unter Berücksichtigung von prozesstechnischen, ökonomischen und ökologischen Aspekten. Bisher existiert in der Literatur kein Vergleich der Einsatzmöglichkeiten verschiedener Modellierungsmethoden zur modellgestützten, multikriteriellen Optimierung von Hochtemperatur-Konversionsprozessen. Daher werden in dieser Arbeit drei exemplarische Konversionsprozesse mit unterschiedlichen Modellierungsmethoden optimiert und anhand der Ergebnisse die Potenziale und Einsatzgrenzen für die modellgestützte Optimierung bewertet. Die Modellierung eines Wirbelschichtvergasers zeigt, dass detaillierte CFD-Modelle für komplexe mehrphasige Prozesse zu rechenaufwändig sind. Hingegen ist für einfache einphasige Prozesse wie ein Quench-Reaktor die Optimierung mit reduzierten CFD-Modellen realisierbar. Die Integration von Ersatzmodellen beschleunigt das Optimierungskonzept bei gleicher Ergebnisqualität, was die Optimierung von komplexen Prozessen für einfache Optimierungsprobleme ermöglicht. Die Optimierung der Partialoxidation von flüssigen Einsatzstoffen zur Methanolproduktion zeigt, dass sich Fließbildmodelle gut zur Optimierung von vollständigen Produktionsprozessen und komplexen Optimierungsproblemen eignen. Die Ergebnisse dieser Arbeit können als Basis für die Erstellung von Modellierungs- und Optimierungskonzepten für weitere Hochtemperatur-Konversionsprozesse genutzt werden.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-04-10T19:08:52Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Laís Benvenutti.pdf: 1732667 bytes, checksum: 0cbf85a73624f6269213298d5973c50f (MD5) / Made available in DSpace on 2018-04-10T19:08:52Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Laís Benvenutti.pdf: 1732667 bytes, checksum: 0cbf85a73624f6269213298d5973c50f (MD5) Previous issue date: 2018-02-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A maçã apresenta alta concentração de compostos fenólicos, distribuídos em diferentes classes as quais apresentam capacidade antioxidante. Além disso, conferem efeito positivo na formação do sabor, cor e aroma em bebidas derivadas da fruta. No entanto, durante o processamento, parte da composição fenólica fica retida no bagaço, principal subproduto da agroindústria da maçã. Desta forma, este trabalho teve como objetivo a otimização da extração de compostos fenólicos presentes no bagaço da maçã utilizando solvente de grau alimentício, visando sua aplicação em sidras a fim de melhorar as características tecnológicas, nutricionais e sensoriais do produto final. Nos ensaios de extração foram avaliados os efeitos da concentração de solvente (etanol), temperatura e razão sólido/líquido sobre o rendimento e atividade antioxidante dos extratos, utilizando o método de superfície de resposta (MSR). Além disso, foi estudada a cinética da extração, bem como a estabilidade do extrato. A análise de regressão linear múltipla acoplada ao MSR sugeriu que a extração seja efetuada utilizando etanol 60%, a 50 °C, na razão sólido/líquido de 1:20 (m/v). Por meio de um modelo cinético de primeira ordem foram avaliados os efeitos do tempo e da temperatura sobre a concentração de equilíbrio da extração, a qual foi atingida aproximadamente aos 50 minutos, independente da temperatura, com teores de 1852,77; 1728,35 e 1265,29 mg CAT/kg para as temperaturas de 50, 35 e 20 °C, respectivamente. A partir desses resultados, a energia de ativação necessária para que ocorra a transferência do soluto foi 9,01 kJ/mol. Em geral, os flavonoides apresentaram boa estabilidade durante período de 90 dias, sendo sugerido armazenamento ou aplicação sob temperatura de 10 °C em pH de aproximadamente 3,5. O extrato obtido nas melhores condições foi adicionado ao mosto antes do inóculo de levedura e a fermentação foi monitorada por meio do estudo cinético. Os mostos e pontos da fermentação (1, 4, 7, 11 e 15 dias) foram avaliados quanto aos fenóis individuais, açúcares e etanol em cromatografia líquida de alta eficiência (CLAE). Além disso, foi avaliada a composição fenólica total, flavonoides totais, flavanóis, flavonóis e atividade antioxidante, bem como, o teor de acidez total titulável, pH e cor. Os produtos finais foram analisados sensorialmente quanto à intensidade de cor, acidez, adstringência e amargor por meio de uma escala estruturada, e quanto à qualidade do odor em escala hedônica de aceitação. A adição do extrato aumentou cerca 40% a concentração de flavonoides totais, apresentando glicosídeos de quercetina, compostos presentes apenas no epicarpo da maçã, os quais foram um dos compostos relacionados com o aumento da atividade antioxidante na sidra com adição de extrato. A adição do extrato também resultou em maior intensidade de cor e percepção do amargor e adstringência. Apesar das alterações na composição fenólica, a adição do extrato não prejudicou a qualidade do odor do produto final. Portanto, o extrato fenólico obtido com etanol em condições otimizadas foi capaz de reincorporar parte dos compostos bioativos retidos no bagaço, aumentando a capacidade antioxidante e alterando características sensoriais responsáveis pela aceitabilidade da bebida. / Apple has high amounts of phenolic compounds, distributed in different classes which show antioxidant capacity. In addition, the phenolic compounds contribute to flavor, color and aroma in apple beverages. However, most of the phenolic compounds, especially the flavonoids, are retained in the apple pomace, during processing. In this way, this work aimed to optimize the flavonoids extraction from apple pomace using food grade solvent, and to apply the extracts in ciders in order to improve the technological, nutritional and sensorial characteristics of the final product. In the extraction experiments, the effects of solvent concentration (ethanol), temperature and solid/liquid ratio on process yield and antioxidant activity of the extracts were evaluated using response surface methodology (RSM). In addition, the extraction kinetics as well as the stability of the extract were studied. The multiple linear regression analysis coupled to RSM suggested that the extraction be performed using ethanol 60% at 50 °C and with solute-solvent ratio of 1:20 (w/v). The effects of time and temperature on the equilibrium concentration of the extraction were evaluated, which was reached at approximately 50 minutes with contents of 1852.77; 1728.35 and 1265.29 mg CAT/kg for the temperatures of 50, 35 and 20 ° C, respectively. The activation energy required for solute transfer to occur was determined, 9.01 kJ mol-1. In general, the flavonoids showed good stability during the period of 90 days, being suggested its storage or application under a temperature of 10 °C and pH about 3.5. The extract obtained under the best conditions was added to the must prior to addition of the yeast inoculum and the fermentation was monitored by kinetic study. The musts and ciders (1, 4, 7, 11 and 15 days) were evaluated as to the individual phenols and sugar and ethanol contents were quantified in high performance liquid chromatography (HPLC). In addition, the total phenolic composition, total flavonoids, flavanols, flavonols and antioxidant activity, as well as total titratable acidity, pH and color were evaluated. The final products were sensorially analyzed for color intensity, acidity, astringency and bitterness by means of a structured scale. The odor quality was evaluated in a hedonic scale of acceptance. The addition of the extract increased about 40% in the total flavonoid content. Quercetin glycosides, compounds present only in the apple epicarp, were found, being one of the compounds associated for the increase in antioxidant activity. The cider with the extract addition showed higher intensity of color and perception of the bitterness and astringency. Despite the changes in phenolic composition, the addition of the extract did not affect the odor quality of the final product. Therefore, the phenolic extract obtained with ethanol under optimized conditions was able to reincorporate bioactive compounds retained in the pomace, increasing the antioxidant capacity and changing sensorial characteristics responsible for the acceptability of the beverage.

This thesis deals with the near-field of confluent jets, which can be of interest in many engineering applications such as design of a ventilation supply device. The physical effect of interaction between multiple closely spaced jets is studied using experimental and numerical methods. The primary aim of this study is to explore a better understanding of flow and turbulence behavior of multiple interacting jets. The main goal is to gain an insight into the confluence of jets occurring in the near-field of multiple interacting jets. The array of multiple interacting jets is studied when they are placed on a flat and a curved surface. To obtain the boundary conditions at the nozzle exits of the confluent jets on a curved surface, the results of numerical prediction of a cylindrical air supply device using two turbulence models (realizable 𝑘 − 𝜖 and Reynolds stress model) are validated with hot-wire anemometry (HWA) near different nozzles discharge in the array. A single round jet is then studied to find the appropriate turbulence models for the prediction of the three-dimensional flow field and to gain an understanding of the effect of the boundary conditions predicted at the nozzle inlet. In comparison with HWA measurements, the turbulence models with low Reynolds correction (𝑘 − 𝜖 and shear stress transport [SST] 𝑘 − 𝜔) give reasonable flow predictions for the single round jet with the prescribed inlet boundary conditions, while the transition models (𝑘 − 𝑘l − 𝜔𝜔 and transition SST 𝑘 − 𝜔) are unable to predict the flow in the turbulent region. The results of numerical prediction (low Reynolds SST 𝑘 − 𝜔 model) using the prescribed inlet boundary conditions agree well with the HWA measurement in the nearfield of confluent jets on a curved surface, except in the merging region. Instantaneous velocity measurements are performed by laser Doppler anemometry (LDA) and particle image velocimetry (PIV) in two different configurations, a single row of parallel coplanar jets and an inline array of jets on a flat surface. The results of LDA and PIV are compared, which exhibit good agreement except near the nozzle exits. The streamwise velocity profile of the jets in the initial region shows a saddle back shape with attenuated turbulence in the core region and two off-centered narrow peaks. When confluent jets issue from an array of closely spaced nozzles, they may converge, merge, and combine after a certain distance downstream of the nozzle edge. The deflection plays a salient role for the multiple interacting jets (except in the single row configuration), where all the jets are converged towards the center of the array. The jet position, such as central, side and corner jets, significantly influences the development features of the jets, such as velocity decay and lateral displacement. The flow field of confluent jets exhibits asymmetrical distributions of Reynolds stresses around the axis of the jets and highly anisotropic turbulence. The velocity decays slower in the combined regio  of confluent jets than a single jet. Using the response surface methodology, the correlations between characteristic points (merging and combined points) and the statistically significant terms of the three design factors (inlet velocity, spacing between the nozzles and diameter of the nozzles) are determined for the single row of coplanar parallel jets. The computational parametric study of the single row configuration shows that spacing has the greatest impact on the near-field characteristics.

About 8 tons of dry undigested solid waste is generated by the MixAlco process for every 40 tons of food residue waste fed into the process. This MixAlco process produces liquid fuels and the sludge generated can be further converted into synthesis gas using the process of pyrolysis. The hydrogen component of the product synthesis gas may be separated by pressure swing adsorption and used in the hydrogenation of ketones into fuels and chemicals. The synthesis gas may also be catalytically converted into liquid fuels via the Fischer-Tropsch synthesis process. The auger-type pyrolyzer was operated at a temperature between 630-770 degrees C and at feed rates in the range of 280-374 g/minute. The response surface statistical method was used to obtain the highest syngas composition of 43.9 +/- 3.36 v % H2/33.3 +/- 3.29 v % CO at 740 degrees C. The CH4 concentration was 20.3 +/- 2.99 v %. For every ton of sludge pyrolyzed, 5,990 g H2 (719.3 MJ), 65,000 g CO (660 MJ) and 21,170 g CH4 (1055.4 MJ) were projected to be produced at optimum condition. At all temperatures, the sum of the energies of the products was greater than the electrical energy needed to sustain the process, making it energy neutral. To generate internal H2 for the MixAlco process, a method was developed to efficiently separate H2 using pressure swing adsorption (PSA) from the synthesis gas, with activated carbon and molecular sieve 5A as adsorbents. The H2 can be used to hydrogenate ketones generated from the MixAlco process to more liquid fuels. Breakthrough curves, cycle mass balances and cycle bed productivities (CBP) were used to determine the maximum hydrogen CBP using different adsorbent amounts at a synthesis gas feed rate of 10 standard lpm and pressure of 118 atm. A 99.9 % H2 purity was obtained. After a maximum CBP of 66 % was obtained further increases in % recovery led to a decrease in CBP. The synthesis gas can also be catalytically converted into liquid fuels by the Fischer-Tropsch synthesis (FTS) process. A Co-SiO2/Mo-Pd-Pt-ZSM-5 catalyst with a metal-metal-acid functionality was synthesized with the aim of increasing the selectivity of JP-8 (C10-C17) fuel range. The specific surface areas of the two catalysts were characterized using the BET technique. The electron probe microanalyzer (with WDS and EDS capabilities) was then used to confirm the presence of the applied metals Co, Mo, Pd and Pt on the respective supports. In addition to the gasoline (C4-C12) also produced, the synthesis gas H2:CO ratio was also adjusted to 1.90 for optimum cobalt performance in an enhanced FTS process. At 10 atm (150 psig) and 250 degrees C, the conventional FTS catalyst Co-SiO2 produced fuels rich in hydrocarbons within the gasoline carbon number range. At the same conditions the Co-SiO2-Mo-Pd-Pt/HZSM-5 catalyst increased the selectivity of JP-8. When Co-SiO2/Mo-Pd-Pt-HZSM-5 was used at 13.6 atm (200 psig) and 250 degrees C, a further increase in the selectivity of JP-8 and to some extent diesel was observed. The relative amounts of olefins and n-paraffins decreased with the products distribution shifting more towards the production of isomers.

The purpose of this study is to perform an investigation of the numerical methods that may contribute to the design and analysis of liquid containers. The study examines several of these methods individually, namely Computational Fluid Dynamics (CFD) analysis of sloshing and Finite Element Methods (FEM) analysis of impact, to evaluate their contribution to the design cycle. Techniques that enhance the use of the various methods are presented and examined to demonstrate effectiveness. In the case of sloshing analysis, experimental tests performed add to the understanding of the phenomena at hand and qualifies the validity of the numerical method used (CFD). As a final contribution, the study presents a method of utilising impact analysis tools, FEM, and CFD in a Multidisciplinary Design Optimisation (MDO) environment. This is an introductory attempt at demonstrating a single coupled multidisciplinary method of designing liquid containers. The results of the study demonstrate a number of valuable numerical techniques that may be used in the design of liquid containers. The presented Total Deviation Value (TDV) proves to be an effective single quantification of sloshing performance and the CFD tools used to determine the value demonstrate sufficient ability to reproduce the sloshing event itself. More advanced experimental facilities would provide a more in-depth understanding of the limitations of the CFD analysis. The use of numerical optimisation adds a valuable dimension to the use of numerical simulations. Significant design improvements are possible for several design variables without performing exhaustive studies and provide interesting information about design trends. Finally, the use of multiple disciplines, FEM and CFD, in conjunction with the available numerical optimisation routines offers a powerful multidisciplinary design tool that can be adapted to any base geometry and is capable of finding optimal trade offs between the two disciplines according to the designer’s needs. This study provides a platform for further investigations in the use and coupling of sloshing and impact analysis in the design of industrial liquid container applications. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

The main objective of this diploma thesis is to optimize the high lift device on the wing of the Phoenix Air U-15 ultralight aircraft, so that it complies with the UL-2 regulation regarding the stalling speed – 65 KPH. This is fulfilled by optimization of the slotted flap position. Methods used include the Response Surface Method and the Computational Fluid Dynamics approach – namely Ansys Fluent v6 software package. Furthermore, the paper deals with take-off flap optimization and construction of the flap deflection mechanism.

The main goal of doctoral thesis is optimization cooling of the synchronous machine. Problem is solved based on the finite element method with use of ANSYS software. Work is built up from theoretical part where is comparison of base equations for heat transfer and simulations for several models. Next part shows us two methods how simulate free and force convection. Depends on the better method from the previous two methods is used for next calculations with several algorithm which are used for find of best parameters for synchronous machine. Our control parameter is mass flow rate.

Der Small-Punch-Test (SPT) ist eine vielversprechende minimalinvasive mechanische Prüfmethode, wenn nur sehr wenig Material für Proben zur Verfügung steht. Die vorliegende Arbeit hat das Ziel, aus Small-Punch-Kleinstproben wahre Materialparameter der elastisch-plastischen Verformung und des spröden Versagens zu bestimmen. Die Kraft-Verschiebungs-Kurve des Versuchs stellt die nichtlineare Materialantwort der inhomogen beanspruchten Probe dar. Das inverse Problem der Identifikation konstitutiver Materialparameter wird numerisch mit Hilfe von Finite-Elemente-Simulationen in Verbindung mit einem Response-Surface-Modell und nichtlinearer Optimierungsverfahren gelöst, indem die Abweichung zwischen gemessener und simulierter Kurve minimiert wird. Mit Hilfe einer eigens entwickelten Kühlapparatur wurden Versuche mit ferritischen Stählen von Raumtemperatur bis hinunter zu -191°C durchgeführt und die temperaturabhängigen Fließkurven identifiziert. Bei tiefen Temperaturen wurden die Weibull-Parameter der zufällig streuenden Sprödbruchfestigkeit bestimmt und die Bruchzähigkeitsverteilung durch Simulation einer CT-Probe vorhergesagt. Für eine Aluminiumoxidkeramik wurden ebenfalls die Weibull-Parameter bestimmt sowie mit Indenterrissen versehene Proben zur Abschätzung der Bruchzähigkeit verwendet. / The small punch test (SPT) is a promising minimally invasive material testing method, especially in cases where only small amounts of material are available. This thesis is aimed at identifying true material parameters of elastic-plastic deformation and brittle fracture. The load-displacement curve of the test represents the non-linear material response of the nonuniformly stressed specimen. The identification of material parameters of constitutive laws is an inverse problem, which is solved numerically. Finite element simulations together with a response surface model and nonlinear optimization techniques are applied to minimize the error between measured and simulated curves. A specially developed cooling apparatus was used to perform tests with ferritic steels from room temperature down to -191°C. The temperature dependent yield stresses and hardening curves were identified. At low temperatures the Weibull parameters of randomly distributed cleavage fracture strength were estimated. The fracture toughness distribution was then predicted by the help of a finite element simulation of a CT specimen. Furthermore the Weibull parameters of an alumina ceramic were determined and its fracture toughness was predicted using specimens prepared with indentation cracks.