Дисертації з теми "BOX-BEHNKEN DESIGNS"

Box-Behnken designs are used to estimate parameters in a second-order response surface model (Box and Behnken, 1960). These designs are formed by combining ideas from incomplete block designs (BIBD or PBIBD) and factorial experiments, specifically 2^k full or 2^k-1 fractional factorials. In this dissertation, a more general mathematical formulation of the Box-Behnken method is provided, a general expression for the coefficient matrix in the least squares analysis for estimating the parameters in the second order model is derived, and the properties of Box-Behnken designs with respect to the estimability of all parameters in a second-order model are investigated when 2^kfull factorials are used. The results show that for all pure quadratic coefficients to be estimable, the PBIB(m) design has to be chosen such that its incidence matrix is of full rank, and for all mixed quadratic coefficients to be estimable the PBIB(m) design has to be chosen such that the parameters λ₁, λ₂, ...,λ_m are all greater than zero. In order to reduce the number of experimental points the use of 2^k-1 fractional factorials instead of 2^k full factorials is being considered. Of particular interest and importance are separate considerations of fractions of resolutions III, IV, and V. The construction of Box-Behnken designs using such fractions is described and the properties of the designs concerning estimability of regression coefficients are investigated. Using designs obtained from resolution V factorials have the same properties as those using full factorials. Resolutions III and IV designs may lead to non-estimability of certain coefficients and to correlated estimators. The final topic is concerned with Box-Behnken designs in which treatments are applied to experimental units sequentially in time or space and in which there may exist a linear trend effect. For this situation, one wants to find appropriate run orders for obtaining a linear trend-free Box-Behnken design to remove a linear trend effect so that a simple technique, analysis of variance, instead of a more complicated technique, analysis of covariance, to remove a linear trend effect can be used. Construction methods for linear trend-free Box-Behnken designs are introduced for different values of block size (for the underlying PBIB design) k. For k= 2 or 3, it may not always be possible to find linear trend-free Box-Behnken designs. However, for k ≥ 4 linear trend-free Box-Behnken designs can always be constructed.
Ph. D.

Industrial development is one of the pioneer enablers of the economic and social prosperity of any nation. High efficiency, low cost and reliable system are the most critical factors that are focussed by industries. New developments in this direction are observed in the past few decades. Researchers thrive for new inventions and technologies by which high-quality output can be attained with effective and robust systems. Materials play an essential role in achieving high efficiency by providing an outcome-based response to any process. With the advent of composite materials, industries have started focusing on using lighter weight materials with the same mechanical properties. Metal matrix composites have the edge over the parent metals for rotor applications as it has a higher specific modulus and specific modulus is the critical material factor for vibration responses. Aluminium /alumina MMCs have shown prominent growth in the composite material market because of their compatibility with the rotor systems. Several types of research are available for the development of aluminium based metal matrix composites for industrial applications. The main focus of this research is to propose a method of development of metal matrix composite for specific rotary applications. This work focuses on the development, characterization and dynamic analysis of the metal matrix rotor. The rotors are developed through a cost-effective, flexible, and readily available method called the stir casting process. The physical properties of the composites depend primarily on the homogeneity and the fraction of reinforcement in the matrix. The uniformity and the concentration have been enhanced by optimizing process parameters in various researches. However, these vii researches are based on the qualitative analysis (visual observation) of the microstructure of composites. These qualitative methods do not assist in providing numerical and objective-oriented results. Therefore, these methods lack a objective judgment that is crucial for comparing the dispersion of reinforcements consistently. Therefore, quantitative measurement of dispersion is essential for optimizing the process parameters in order to attain better results. There are several techniques for the quantitative measurement of particle dispersion in the matrix. The mean free path has been calculated by dividing micrograph images into multiple grid lines and was utilized for quantifying particle dispersions. The quantitative distribution index and area fraction may be beneficial in optimizing the process parameters and providing more authentic and reliable results than the qualitative analysis. There are various methods used for parametric optimization having multivariant parameters. Box- Behnken designs (BBD) are rotatable or nearly rotatable second-order designs based on three-level incomplete factorial designs. BBD is one of the main types of response surface design, the other being central composite design. The BBD design requires a smaller number of runs as compared to the central composite design. The Box-Behnken design operates within the range of parameters and does not generate experimentation points beyond the range of parameters like the central composite design. BBD is suitable for designs where the range of operations are constrained by manufacturing conditions. In this work, a novel technique has been adopted where newly developed quantitatively assessed responses are used for process optimization instead of conventional qualitative analysis and thus, it provides a profound methodology for optimization of process parameters. viii A novel characterization approach has been adopted in this work, which determines the effect of reinforcements on the dynamic properties and residual stress of the Al 6061/Al2O3 shafts. Long and slender shafts were fabricated through a stir casting process. Grain structure has been obtained through optical microscopy, and morphological evaluation of the composites was performed through Scanning Electron Microscopy (SEM). In addition to that, an X-ray diffraction pattern (XRD) were analyzed, and residual stress was calculated by X-ray residual stress measurement system μ-X360 Ver. 2. 3. 0. 1. Tensile strength and microhardness were also determined in this analysis for various compositions of the composite material. For composite materials, the system response changes abruptly with a change in the properties of the material. Therefore, attaining significant knowledge about the effect of material composition on material properties is crucial. The researchers are looking for new computational methods which can predict these alterations so that the effort in experimental testing can be reduced. In this direction, this paper presents a robust and novel methodology of validating the estimation of the composite's effective properties through a multi-scale approach by a set of standardized experimentation. These effective properties are estimated through the mean-field homogenization technique, whose parameters are driven from the image analysis of Scanning Electron Microscopy (SEM) images. The predicted results are validated with the results obtained by the experimentation as per ASTM E1876 standard. This research work has adopted a novel approach of providing a dedicated methodology for determining the calibrated internal damping factor for bond graph dynamic analysis, which has been used in various literature for transient and stable ix responses. The investigation has been performed on long and slender shafts of the metal matrix composites. An insight into the change in dynamic response with the difference in the composition of composite shafts is provided in this work. Many valuable insights and findings were obtained in this work related to the development and response of different compositions of metal matrix composite shafts. The optimization of the stir casting parameters using a quantitative distribution index and area fraction resulted in uniformly distributed composite shafts. The mechanical properties such as tensile strength, microhardness, specific modulus increased with the addition of reinforcement in the composite up to a particular limit. Above that limit, the agglomeration and porosity become prominent factors and further depletes the properties of a composite. The natural frequency of the composite shaft increased, and the amplitude of vibration was reduced for the composites with a high volume fraction of reinforcements. The values of Young's modulus of different compositions determined through computation were congruent with the experimental results. The dynamic response was simulated using bond graph analysis, and it was observed that the amplitude of orbits was also reduced for the composites with a high volume fraction of reinforcements.

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Biodiesel is a fuel derived from biomass sources, among them vegetable oils from agroindustrial activities. As a promising fruit for use as bioenergy matrix in the biodiesel synthesis highlights the soursop (Annona muricata L.) due to its potential productivity in semi-arid region of Northeast Brazil, which is favored by its edaphoclimatic conditions. Thus, the aim of this work was to optimize the reaction conditions for transesterification via ethanolysis for biodiesel production from soursop seed oil. It was first performed an exploratory study using Plackett-Burman design with the following variables: reaction time, oil/alcohol molar ratio, catalyst concentration, and temperature. It was identified as statistically significant variables catalyst concentration, temperature and oil/alcohol molar ratio, which were employed in a Rotatable Central Composite Design. However, the model used to describe this process exhibited lack of fit. This drawback was overcome with the implementation of a BoxBehnken Design, whose greatest mass yield of 94.99% was obtained using 1.25% of catalyst concentration, temperature of 50 °C and oil/alcohol molar ratio of 1:10. The built model was used to establish an optimal experiment, at a 95% confidence level, with a 95.51% determination coefficient for the following experimental conditions: catalyst concentration of 1.18%, temperature of 52.20 °C, and oil/alcohol molar ratio of 1:8.39. Finally, the physical and chemical analysis showed the conditions for obtaining biodiesel from soursop seed oil as a promising alternative to its mixture with petroleum diesel.
O biodiesel é um combustível derivado de fontes de biomassa, dentre elas óleos vegetais provenientes de atividades agroindustriais. Dentre as promissoras fruteiras a serem utilizadas como matriz bioenergética na síntese do biodiesel destaca-se a graviola (Annona muricata L.), devido ao seu potencial produtivo no semiárido nordestino favorecido pelas características edafoclimáticas da região. Assim, objetivou-se com este trabalho otimizar as condições reacionais por transesterificação via rota etílica para produção de biodiesel do óleo de sementes de graviola. Inicialmente foi realizado um estudo exploratório utilizando planejamento Plackett-Burman com as variáveis: tempo reacional; razão molar óleo/álcool; porcentagem do catalisador; e temperatura. Foram identificadas como variáveis estatisticamente significativas porcentagem de catalisador, temperatura e razão molar óleo/álcool, as quais foram empregadas em um Planejamento Composto Central Rotacional. Todavia, o modelo utilizado para descrever o processo apresentou falta de ajuste. Este inconveniente foi superado com a execução do planejamento Box Behnken, cujo maior rendimento mássico de 94,99% foi obtido usando porcentagem de catalisador de 1,25%, temperatura de 50 ºC e razão molar óleo/álcool de 1:10. Com o modelo construído foi possível estabelecer como ótimo experimental, a um nível de confiança de 95%, com coeficiente de determinação de 95,51% para as seguintes condições experimentais: porcentagem de catalisador de 1,18%, temperatura de 52,20 ºC e razão molar óleo/álcool de 1:8,39. Por fim, as análises físicas e químicas apontaram para condições de obtenção do biodiesel de graviola como uma alternativa promissora para mistura em diesel de petróleo.

Ilex guayusa, a tree native from the Amazon Rainforest, represents an important part of the culinary traditions and folk medicine of the indigenous tribes. In fact, infusions of different parts of the tree have been used as natural remedies. Particularly, the infusion obtained by the dry leaves of guayusa is a source of phenolic compounds, which are considered as antioxidant substances and have been associated with numerous benefits for human health. Currently, the growing interest of consumers towards healthy food and drinks has led to the rapid spread of this drink. However, the scientific literature about the content of polar compounds in infusion of guayusa leaves is scarce. Therefore, the aims of the present work were to enhance the extraction conditions of phenolic compounds from guayusa leaves by infusion and to characterize them via HPLC-ESI-TOF-MS. To reach these objectives, a Box-Behnken design (BBD) was applied to test the effect of different extraction conditions (time 2, 8 and 14 min), temperature (25, 62.5 and 100 °C) and solid ratio (0.25, 0.375 and 0.50 g) on the sum of phenolic content. On the one hand, the optimal conditions were 1 min infusion, 100 °C and 0.370 g of dry leaves. On the other hand, the 99% of the nine phenolic compounds identified were phenolic acids derivatives from hydroxycinnamic acid and the 1% belonged to the flavonoid family. The major compound was dicaffeoylquinic acid (68%). The difference between the results obtained and those of other researches is probably due to the stochastic nature of the vegetable matrix samples, since their chemical composition is susceptible to multiple factors. To sum up, the use of experimental design provided greater quantity of phenolic compounds than other extraction techniques such as blanching, or only to the oxidation process. Besides, the high resolution of the TOF spectrometer allowed the characterization of new isomers of the compounds previously described.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Environmental sustainability has become one of the topics of greatest interest in industry, mainly due to effluent generation. Phenols are found in many industries effluents, these industries might be refineries, coal processing, pharmaceutical, plastics, paints and paper and pulp industries. Because phenolic compounds are toxic to humans and aquatic organisms, Federal Resolution CONAMA No. 430 of 13.05.2011 limits the maximum content of phenols, in 0.5 mg.L-1, for release in freshwater bodies. In the effluents treatment, the liquid-liquid extraction process is the most economical for the phenol recovery, because consumes little energy, but in most cases implements an organic solvent, and the use of it can cause some environmental problems due to the high toxicity of this compound. Because of this, exists a need for new methodologies, which aims to replace these solvents for biodegradable ones. Some literature studies demonstrate the feasibility of phenolic compounds removing from aqueous effluents, by biodegradable solvents. In this extraction kind called "Cloud Point Extraction" is used a nonionic surfactant as extracting agent of phenolic compounds. In order to optimize the phenol extraction process, this paper studies the mathematical modeling and optimization of extraction parameters and investigates the effect of the independent variables in the process. A 32 full factorial design has been done with operating temperature and surfactant concentration as independent variables and, parameters extraction: Volumetric fraction of coacervate phase, surfactant and residual concentration of phenol in dilute phase after separation phase and phenol extraction efficiency, as dependent variables. To achieve the objectives presented before, the work was carried out in five steps: (i) selection of some literature data, (ii) use of Box-Behnken model to find out mathematical models that describes the process of phenol extraction, (iii) Data analysis were performed using STATISTICA 7.0 and the analysis of variance was used to assess the model significance and prediction (iv) models optimization using the response surface method (v) Mathematical models validation using additional measures, from samples different from the ones used to construct the model. The results showed that the mathematical models found are able to calculate the effect of the surfactant concentration and the operating temperature in each extraction parameter studied, respecting the boundaries used. The models optimization allowed the achievement of consistent and applicable results in a simple and quick way leading to high efficiency in process operation.
A sustentabilidade ambiental tem se tornado um dos temas de maior interesse nas ind?strias, principalmente devido ? gera??o de efluentes. Os fen?is s?o encontrados em efluentes de v?rias ind?strias, como em refinarias, processamento de carv?o, ind?strias farmac?uticas, de pl?sticos, de tintas e de papel e celulose. Devido os compostos fen?licos serem compostos t?xicos ao ser humano e tamb?m a organismos aqu?ticos, a Resolu??o Federal CONAMA n? 430, de 13/5/2011 limita o teor m?ximo de fen?is, para lan?amento em corpos de ?gua doce, em 0,5 mg.L-1. No processo de tratamento desses efluentes, o processo de extra??o l?quido-l?quido ? o processo mais econ?mico para a recupera??o do fenol, pois consome pouca energia, mas, na maioria das vezes, implementa um solvente org?nico, sendo que o uso deste pode acarretar certos problemas ambientais, decorrentes da alta toxicidade que ele apresenta. Devido a isto, existe a necessidade de desenvolver novas metodologias, as quais visem a substitui??o destes solventes por compostos biodegrad?veis. Alguns trabalhos da literatura comprovam a viabilidade da remo??o de compostos fen?licos de efluentes aquosos, atrav?s de solvente biodegrad?vel. Nesse tipo de extra??o denominada Extra??o Ponto Nuvem ? utilizado um tensoativo n?o i?nico como agente extrator dos compostos fen?licos. Visando otimizar o processo de extra??o de fenol, o presente trabalho aborda a modelagem matem?tica e otimiza??o dos par?metros da extra??o e investiga o efeito das vari?veis independentes no processo. Foi empregando um delineamento fatorial 32 completo que teve como vari?veis independentes a temperatura de opera??o e a concentra??o de tensoativo e, como vari?veis dependentes, os par?metros de extra??o: Fra??o volum?trica da fase coacervato, concentra??o residual de tensoativo e de fenol na fase dilu?da ap?s a separa??o de fases e efici?ncia de extra??o do fenol. Para se alcan?ar os objetivos, o trabalho foi realizado em cinco etapas: (i) sele??o de alguns dados da literatura; (ii)aplica??o do modelo Box-Behnken para encontrar modelos matem?ticos que descrevem o processo de extra??o de fenol; (iii) C?lculo da ANOVA com aux?lio do programa STATISTICA 7.0 para avaliar a signific?ncia e predi??o dos modelos; (iv) Otimiza??o dos modelos atrav?s de superf?cies de respostas; (v) Valida??o dos modelos matem?ticos a partir da tomada de medidas adicionais, com amostras diferentes das utilizadas na obten??o dos modelos. Os resultados obtidos mostraram que os modelos matem?ticos encontrados s?o capazes de calcular o efeito da concentra??o do tensoativo e da temperatura de opera??o em cada par?metro de extra??o estudado, respeitando as faixas trabalhadas. A otimiza??o dos modelos obtidos permitiu de forma simples e r?pida resultados coerentes e aplic?veis na opera??o para se alcan?ar resultados elevados de efici?ncia

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia
The consumption of vegetables is widely recognized to be beneficial to human health and this is mainly attributed to their high content in functional constituents. The aim of this work was to develop a green extractin process of watercress for the recovery of bioactive compounds with application in the nutraceutical industry. Initially the matrix was characterized with respect to its content of polyphenols, terpenes and carotenoids. A Design of Experiments (DOE) was used to plan the extractions using two solutions water: co-solvent GRAS (water:ethanol and water:propylene glycol,) varying the extraction temperature, the ratio matrix:solvente and ratio water:cosolvent, in order to improve their content of polyphenols, carotenoids, and terpenes (spectrophotometric and chromatographic methods), their antioxidant activity and their cosmeceutical potential. The most promising extract, considering the content of polyphenols and the antioxidant activity, was PG 13. Regarding the cosmeceutical potential, TT / EtOH5 have proved to be more auspicious for antipigmentation activity and H2O7 proved to be more favorable on anti-wrinkle assay. Watercress reveled to be a promising natural source of numerous phytochemicals, namely polyphenols, terpenes, isothiocyanates and fatty acids, rich in antioxidant activity, advantageous for the development of functional products and with potential to be included in cosmeceuticals

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Atualmente, um dos mais graves problemas relacionado com a poluição ambiental é a contaminação da água, principalmente, devido ao descarte inadequado de resíduos industriais e agrícolas. Deste modo, o presente trabalho tem como objetivo avaliar a remoção de Al3+ em meio aquoso por adsorção em casca de arroz in natura e cascas de arroz modificadas quimicamente. Para tal foram realizados experimentos em escala laboratorial e em batelada verificando-se a remoção da concentração de alumínio quando em contato com o biossorvente até atingir-se o tempo de equilíbrio. Foram utilizados três tipos de biosorventes: casca de arroz in natura (CN) e cascas modificadas quimicamente com solução ácida (CTA) e solução básica (CTB), a fim de avaliar qual delas proporciona a melhor adsorção do alumínio solúvel. Foram realizados três planejamentos estatísticos de experimento fatoriais 33 Box-Behnken para a otimização das condições de modo a encontrar a melhor resposta para a adsorção do alumínio em sistema de batelada. As condições ótimas encontradas através do planejamento para CTB, que teve melhor resposta de adsorção do metal, com uma recuperação de 97,60 % foram: (X1) massa 0,1500 g; (X2) volume 7,5 mL e (X3) tempo de contato solução de alumínio e o biossorvente de 5 horas. Durante a execução do planejamento de experimento fatorial 33 Box-Behken foi mantido em comum o pH 5,0 e a concentração do Al3+ em 30,0 mg L-1. A técnica analítica utilizada para quantificação do metal na solução após a adsorção foi à espectrometria de absorção atômica com chama (F AAS). Encontradas as condições ótimas prosseguiu-se com os demais estudos, a exemplo do estudo de efeito de pH considerando a faixa de 4,0 a 6,0 e estudos de isotermas de adsorção adotando os modelos de Langmuir e Freundlich. O melhor pH para adsorção do Al3+ foi 5,0 sendo que acima deste valor ocorrem perdas por precipitação em forma de hidróxido. Essas perdas devem ser levadas em consideração durante os cálculos após a sua adsorção. O modelo de Langmuir, foi o que teve valores de coeficientes de determinação (R2) altos e relativamente próximo de 1, apresentando desse modo o devido ajuste das isotermas linearizadas, comparativamente ao modelo de Freundlich que apresentou coeficientes de determinação inferiores. Desse modo o biossorvente usado neste trabalho mostrou-se eficiente na remoção do alumínio, tanto na forma modificada CTB assim como na forma CN, em detrimento da forma modificada CTA que apresentou sempre baixas capacidades adsortivas de Al3+, nas condições estabelecidas e consideradas ótimas neste trabalho.
Nowadays, one of the most serious problems related to environmental pollution is the contamination of water, mainly, through improper discard of industrial and agricultural waste. Thus, the main objective of the present study is to evaluate the removal of Al3+ in aqueous environment by adsorption on raw rice husk and chemically modified rice husks. For this purpose experiments were performed on a laboratory scale batch and was seen that actually occur a removing of aluminum concentration when it is in contact with the biosorbent until to be achieved an balance adsorption time. Three types of biosorbents were used: raw rice husk (R-RH), and chemically modified rice husk with an acid (CM-RHA) and basic solution (CM-RHB) in order to evaluate which one has the best adsorption of soluble aluminum. Three statistical 33 Box-Behnken experiment designs were performed to optimize the conditions in order to find the best answer for aluminum adsorption in batch system. The optimum conditions found for CM-RHB, which had better metal adsorption response, with a recovery about 97.60% were: (X1) mass 0.1500 g; (X2) volume 7.5 mL and (X3) contact time between the aluminum solution and biosorbent which is about 5 hours. During the execution of factorial experiment design 33 Box-Behnken was kept in common, the value of pH (pH ~ 5) and the concentration of Al3+ 30,0 mg L-1. The flame atomic absorption spectrometric (F AAS), was used to quantify the metal in solution after its adsorption. Found the optimal conditions, were carried on other studies, such as the study of effect pH where was considered the range of 4,0 to 6,0 as well the study of adsorption isotherms adopting the models of Langmuir and Freundlich. The best pH for adsorption of Al3+ was 5,0 and above this value there are losses by precipitation in form of hydroxide. These losses should be taken into account during the calculations after its adsorption. The Langmuir model was the one which showed high determination coefficient values (R2) and relatively close to 1, thereby presenting the best fit of the linearized isotherms compared to Freundlich model which showed lower determination coefficient values. Thus the biosorbent used in this work was efficient in aluminum removal, either in CM-RHB form and R-RH form rather than CM-RHA form that always showed low adsorption capacity of Al3+ under the conditions established and considered optimum in this work.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
RESUMO O presente trabalho propÃs investigar a tecnologia de eletrocoagulaÃÃo (EC) para o tratamento de efluente tÃxtil utilizando corrente contÃnua pulsada (CCP) e eletrodos de aÃo inoxidÃvel 304. O efluente utilizado foi coletado em uma indÃstria tÃxtil fabricante de redes localizada no municÃpio de Jaguaruana-CE. A Metodologia de SuperfÃcie de Resposta Box-Behnken foi utilizada para analisar e otimizar as condiÃÃes operacionais, visando a mÃxima remoÃÃo de cor, turbidez e demanda quÃmica de oxigÃnio (DQO) do efluente tÃxtil. Os experimentos foram realizados com um volume reacional de 2,6 L, em modo batelada. A cinÃtica de degradaÃÃo de DQO foi estudada atravÃs do ajuste de regressÃo nÃo linear, obedecendo ao modelo de cinÃtica de segunda ordem. Diante dos resultados obtidos a configuraÃÃo Ãtima considerada foi: velocidade de agitaÃÃo=200 rpm, frequÃncia dos pulsos elÃtricos=1000 Hz e espaÃamento entre os eletrodos=1 mm, em 50 minutos de EC. Nestas condiÃÃes foram obtidas remoÃÃes de cor, turbidez e DQO, respectivamente de 98,94%, 85,87% e 81,23%, adequando o valor de DQO ao padrÃo de lanÃamento exigido pela Portaria n 154/2002 da SuperintendÃncia Estadual do Meio Ambiente (SEMACE). Em adiÃÃo, verificou-se que o processo de EC tambÃm foi eficaz para a reduÃÃo de sÃlidos suspensos totais, nitrogÃnio total, sulfato e sulfeto, como tambÃm para a reduÃÃo da toxicidade aguda frente à Lactuca sativa, elevando os valores do Ãndice de Crescimento Relativo (ICR) e Ãndice de GerminaÃÃo (IG) inicialmente registrados para o efluente bruto. A concentraÃÃo de Ãons cloreto nÃo decresceu durante a EC, apresentando-se como um aspecto favorÃvel para a reutilizaÃÃo do efluente tratado no prÃprio processo produtivo tÃxtil, o qual demanda uma elevada concentraÃÃo de cloreto de sÃdio (NaCl).
The present work proposed to investigate the electrocoagulation technology (EC) for the treatment of textile effluent using pulsed direct current (CCP) and stainless steel electrodes 304. The effluent used was collected in a textile manufacturer networks in the municipality of Jaguaruana -CE. The Response Surface Methodology Box-Behnken was used to analyze and optimize the operating conditions, aimed at maximum removal of color, turbidity and chemical oxygen demand (COD) of the textile effluent. The experiments were performed with a reaction volume of 2.6 L in batch mode. The COD degradation kinetics was studied using non-linear regression fit, according to the second order kinetics model. Based on these results the optimal configuration was considered: agitation speed = 200 rpm, frequency of electrical pulses = 1000 Hz and spacing between electrodes = 1 mm, in 50 minutes of EC. Under these conditions color removals were obtained, turbidity and COD, respectively 98.94%, 85.87% and 81.23%, adjusting the COD value to discharge standard required by Ordinance No. 154/2002 of the State Superintendent of Half Environment (SEMACE). In addition, it was found that the CS process is also effective for reduction of total suspended solids, total nitrogen, sulfide and sulfate, as well as for the reduction of acute toxicity Lactuca sativa forward, raising the value of the Growth Index Relative (ICR) and germination index (GI) initially recorded for the raw wastewater. The concentration of chloride ions has not decreased during the EC, presenting itself as a favorable aspect for the reuse of treated effluent in own textile production process, which demands a high concentration of sodium chloride (NaCl).

Practical restrictions on randomization are commonplace in industrial experiments due to the presence of hard-to-change or costly-to-change factors. Employing a split-plot design structure minimizes the number of required experimental settings for the hard-to-change factors. In this research, we propose classes of equivalent estimation second-order response surface split-plot designs for which the ordinary least squares estimates of the model are equivalent to the generalized least squares estimates. Designs that possess the equivalence property enjoy the advantages of best linear unbiased estimates and design selection that is robust to model misspecification and independent of the variance components. We present a generalized proof of the equivalence conditions that enables the development of several systematic design construction strategies and provides the ability to verify numerically that a design provides equivalent estimates, resulting in a broad catalog of designs. We explore the construction of balanced and unbalanced split-plot versions of the central composite and Box-Behnken designs. In addition, we illustrate the utility of numerical verification in generating D-optimal and minimal point designs, including split-plot versions of the Notz, Hoke, Box and Draper, and hybrid designs. Finally, we consider the practical implications of analyzing a near-equivalent design when a suitable equivalent design is not available. By simulation, we compare methods of estimation to provide a practitioner with guidance on analysis alternatives when a best linear unbiased estimator is not available. Our goal throughout this research is to develop practical experimentation strategies for restricted randomization that are consistent with the philosophy of traditional response surface methodology.
Ph. D.

Distorções geométricas em partes metálicas unidas através de soldagem a arco elétrico são consequências inerentes ao processo devido ao elevado fluxo de calor necessário para fusão dos metais de base e adição (quando houver). Embora inevitáveis, estas distorções podem ser reduzidas ou eliminadas através do prévio conhecimento do comportamento da junta de acordo com energia aplicada, características geométricas, propriedades do material, entre outros fatores, possibilitando assim a redução de custos com possíveis retrabalhos por meio de alterações de projeto ou ações que as previnam durante a soldagem. Este trabalho utilizou a metodologia de Projeto de Experimentos para avaliar o efeito da energia de soldagem, espessura da aba e espessura da alma na distorção angular em juntas de filete soldadas pelo processo MIG/MAG com modo de transferência curto-circuito. Foi aplicada a Análise de Variância para as distorções angulares das amostras e identificou como significativo o efeito linear da energia de soldagem, o efeito quadrático da espessura da aba e a interação dos fatores energia de soldagem e espessura da aba na distorção angular de juntas de filete. Observou-se mínimas distorções para a combinação de maior energia de soldagem e menor espessura de aba, sendo mínimas também as distorções angulares para a combinação de menor energia de soldagem e maior espessura de aba, independente da espessura da alma para as condições estudadas. Através das macrografias das amostras, identificou-se que razão entre a área total do metal de solda e espessura da aba que gera maior distorção angular é aproximamente 5, com menores distorções angulares para valores inferiores e superiores a esse. Através de um modelo numérico, demonstrou-se que o gradiente de temperatura na aba da junta não determina a máxima distorção angular, e sim a máxima temperatura atingida na superfície inferior da aba, com máxima distorção angular obtida para a amostra que atingiu aproximadamente 425 ºC em ponto na superfície inferior da aba e paralelo à margem do cordão. Por fim, para distorções angulares em função da razão entre a energia de soldagem conduzida pela aba e espessura de aba ao quadrado, observou-se que a distorção angular é crescente até atingir 15,00 J/mm³, e menores distorções angulares para relações superiores a esse valor.
Welding deformation on metallic parts joined by electric arc welding are inherent consequences of the process due to the high heat flux required for melting the base and filler metals (when used). Although unavoidable, these deformations can be reduced or eliminated through prior knowledge of joint behavior in accordance with applied heat input (welding energy), geometric characteristics, material properties, among other factors, thus reducing costs with possible rework through design changes or actions that prevent them during welding. This work uses a methodology proposed by Experimental Design theories to evaluate the effect of heat input, flange thickness and web thickness on angular distortion in fillet joints welded by the GMAW process with short-circuit transfer mode. Was applied Analysis of Variance for the angular distortions of the test specimens and there are significant the linear effect of heat input, the quadratic effect of flange thickness and the interaction of heat input and flange thickness on the angular distortion of fillet joints, observing minimum distortion for the combination of higher heat input and lower flange thickness, and also angular distortions for the combination of lower heat input and higher flange thickness, regardless of the thickness of the web are minimal. Through the macrographs of the samples, it was identified that the ratio of a region of the weld metal to the flange thickness that generates the greatest angular distortion is approximately 5, with smaller angular distortions for lower values and higher than that. Through a numerical model, it has been shown that the temperature gradient in the flange does not determine the maximum angular distortion, but the maximum temperature reached in the lower surface of the flange, with maximum angular distortion obtained for the sample that reached approximately 425ºC in point on the surface bottom of the flange and parallel to the edge of the weld bead. Finally, for angular distortions as a function of the ratio between the heat input conducted by the flange and the squared flange thickness, it was observed that the angular distortion is increasing until reaching 15,00 J/mm³, and smaller angular distortions for higher relations to this value.

This thesis deals with the possibility of applying the method of Design of Experiments (DoE) on specific data. In the first chapter of theoretical part, this method is described in detail. The basic principles and guidelines for the design of the experiment are written there. In the next two chapters, factorial design of the experiment and response surface design are described. The latter one includes a central composite design and Box-Behnken design. The following chapter contains practical part, which focuses on modelling firing range of ball from a catapult using the above three types of experimental design. In this work, the models are analysed together with their different characteristics. Their comparison is made by using prediction and confidence intervals and by response optimizing. The last part of the thesis comprises overall evaluation.

This research addresses the novel application of design of experiment, artificial neural net-works and logistic regression to study the effect of demographic characteristics on the risk of acquiring HIV infection among the antenatal clinic attendees in South Africa. The annual antenatal HIV survey is the only major national indicator for HIV prevalence in South Africa. This is a vital technique to understand the changes in the HIV epidemic over time. The annual antenatal clinic data contains the following demographic characteristics for each pregnant woman; age (herein called mother's age), partner's age (herein father's age), population group (race), level of education, gravidity (number of pregnancies), parity (number of children born), HIV and syphilis status. This project applied a screening design of experiment technique to rank the effects of individual demographic characteristics on the risk of acquiring an HIV infection. There are a various screening design techniques such as fractional or full factorial and Plackett-Burman designs. In this work, a two-level fractional factorial design was selected for the purposes of screening. In addition to screening designs, this project employed response surface methodologies (RSM) to estimate interaction and quadratic effects of demographic characteristics using a central composite face-centered and a Box-Behnken design. Furthermore, this research presents the novel application of multi-layer perceptron’s (MLP) neural networks to model the demographic characteristics of antenatal clinic attendees. A review report was produced to study the application of neural networks to modelling HIV/AIDS around the world. The latter report is important to enhance our understanding of the extent to which neural networks have been applied to study the HIV/AIDS pandemic. Finally, a binary logistic regression technique was employed to benchmark the results obtained by the design of experiments and neural networks methodologies. The two-level fractional factorial design demonstrated that HIV prevalence was highly sensitive to changes in the mother's age (15-55 years) and level of her education (Grades 0-13). The central composite face centered and Box-Behnken designs employed to study the individual and interaction effects of demographic characteristics on the spread of HIV in South Africa, demonstrated that HIV status of an antenatal clinic attendee was highly sensitive to changes in pregnant mother's age and her educational level. In addition, the interaction of the mother's age with other demographic characteristics was also found to be an important determinant of the risk of acquiring an HIV infection. Furthermore, the central composite face centered and Box-Behnken designs illustrated that, individual-ally the pregnant mother's parity and her partner's age had no marked effect on her HIV status. However, the pregnant woman’s parity and her male partner’s age did show marked effects on her HIV status in “two way interactions with other demographic characteristics”. The multilayer perceptron (MLP) sensitivity test also showed that the age of the pregnant woman had the greatest effect on the risk of acquiring an HIV infection, while her gravidity and syphilis status had the lowest effects. The outcome of the MLP modelling produced the same results obtained by the screening and response surface methodologies. The binary logistic regression technique was compared with a Box-Behnken design to further elucidate the differential effects of demographic characteristics on the risk of acquiring HIV amongst pregnant women. The two methodologies indicated that the age of the pregnant woman and her level of education had the most profound effects on her risk of acquiring an HIV infection. To facilitate the comparison of the performance of the classifiers used in this study, a receiver operating characteristics (ROC) curve was applied. Theoretically, an ROC analysis provides tools to select optimal models and to discard suboptimal ones independent from the cost context or the classification distribution. SAS Enterprise MinerTM was employed to develop the required receiver-of-characteristics (ROC) curves. To validate the results obtained by the above classification methodologies, a credit scoring add-on in SAS Enterprise MinerTM was used to build binary target scorecards comprised of HIV positive and negative datasets for probability determination. The process involved grouping variables using weights-of-evidence (WOE), prior to performing a logistic regression to produce predicted probabilities. The process of creating bins for the scorecard enables the study of the inherent relationship between demographic characteristics and an in-dividual’s HIV status. This technique increases the understanding of the risk ranking ability of the scorecard method, while offering an added advantage of being predictive.

Increasing freshwater scarcity is making reclamation of wastewater effluent more economically attractive as a means of preserving freshwater resources. The use of an integrated membrane system (IMS), the combination of micro/ultra-filtration (MF/UF) followed by reverse osmosis (RO) membranes, represents a key process for municipal wastewater reuse. A major drawback of such systems is the fouling of both the MF/UF and RO membranes. The water to be treated by the IMS system varies from one wastewater treatment plant (WWTP) to another, and its fouling propensity changes correspondingly. It is thus preferable to conduct pilot trials before implementing a full-scale plant. This thesis aims to look at the sustainability of IMS technology dedicated to indirect potable reuse (IPR) in terms of fouling minimisation and cost via a 600 m3 .d- 1 pilot plant. Wastewater reuse plants, using IMS, as well as statistical methods for membrane optimisation were reviewed. Box-Behnken design was used to define optimum operating envelopes of the pilot plant for both the microfiltration and the reverse osmosis in terms of fouling minimisation. Same statistical method was used to enhance the efficiency of the MF cleaning-in place through bench-scale test. Data from the pilot plant MF process allow to determine relationship between reversible and irreversible fouling, and operating parameters and feed water quality. Life cycle cost analysis (LCCA) of the both trains (MF/RO/AOP and MF/AOP) of the pilot plant was performed and compared with the LCCA of two full-scale plant.

Devido à demanda de aumento de produtividade na indústria, a utilização de materiais mais leves, busca por processos de reparos com melhor custo, em conjunto com o avanço das tecnologias, evolução dos processos de soldagem, e esses fatores aliados aos benefícios de uma maior taxa de fusão, melhor controle da penetração, faz com que o processo MIG/MAG com polaridade variável apresente consideráveis avanços tecnológicos nos dias de hoje. Porém, a seleção dos parâmetros da curva típica de corrente do processo (composta por corrente de pico, corrente de base positiva e corrente negativa), é ainda um desafio. Buscando um melhor entendimento da influência da polaridade negativa no processo de soldagem, em especial para aplicações de revestimento, este trabalho tem como objetivo analisar os parâmetros da polaridade negativa individualmente em relação a geometria do cordão de solda, utilizando aço ao carbono como metal base e aço inoxidável como metal de adição. O planejamento e execução do experimento foi realizado com base na metodologia de projeto de experimentos Box-Behnken, variando três fatores: tempo de corrente negativa, intensidade de corrente negativa e tempo de corrente de base positiva, em três níveis cada um. Primeiramente alcançou-se a minimização da diluição, onde o tempo de corrente negativa apresentou efeito significativo no resultado final, sendo seu nível máximo (15 ms) o responsável pelos menores valores de diluição, aproximadamente 12%, recomendado em soldagem para revestimento. Posteriormente, foi avaliado o efeito dos parâmetros em relação à penetração, altura e largura do cordão de solda, sendo o tempo de corrente negativa em 15 ms e corrente negativa em -150 A os níveis que apresentaram melhores resultados. Após, os parâmetros da polaridade negativa utilizados foram comparados com os termos proporcionais sugeridos pela literatura (%EN). E, por fim, avaliou-se uma forma de curva de corrente sem a corrente de base positiva, onde foi concluído que não há significância das diferentes formas de curva de corrente sobre os resultados na penetração do cordão de solda, assim como a necessidade da corrente de base na estabilidade do arco elétrico do processo.
Due to the demand to increase productivity in the industry, use lighter materials, search for repair processes with better cost, in combination with advancement of technologies, evolution of welding processes, connected with the benefits of a higher melting rate and better control of the process penetration, it was possible to verify advances in the MIG / MAG Variable Polarity welding technique. However, the selection of the parameters of the typical process current curve (composed by peak current, positive current and negative current), is still a challenge today. The aim of this work is to analyze the negative polarity parameters individually in relation to the weld bead geometry, using carbon steel as base metal and stainless steel as addition metal. The planning and execution of the experiment was performed based on the Box-Behnken design methodology, varying three factors: negative current time, negative current intensity and positive base current time, at three levels each one. Firstly, dilution minimization was achieved, which showed that the negative current time had a strong influence on the final result, and the maximum level (15 ms) was responsible for the lowest dilution values, nearby 12%, ideal for welding cladding. Then, the parameters were evaluated in relation to penetration, height and width of the weld bead, which for welding cladding, the negative current time 15 ms and negative current -150 A presented better results. Next, the negative polarity parameters were compared with the proportional terms suggested by the literature (%EN). Finally, a form of current curve without positive base current was evaluated, where it can be concluded that the current curve form does not have significance on the penetration results, as well as the necessity of the base current in the arc electric stability.

Furthering our understanding of the physics of flapping flight has the potential to benefit the field of micro air vehicles. Advancements in micro air vehicles can benefit applications such as surveillance, reconnaissance, and search and rescue. In this research, flapping kinematics of a ladybug was explored using a direct linear transformation. A flapping mechanism design is presented that was capable of executing ladybug or other species-specific kinematics. The mechanism was based on a differential gear design, had two wings, and could flap in harsh environments. This mechanism served as a test bed for force analysis and optimization studies. The first study was based on a Box-Behnken screening design to explore wing kinematic parameter design space and manually search in the direction of flapping kinematics that optimized the objective of maximum combined lift and thrust. The second study used a Box-Behnken screening design to build a response surface. Using gradient-based techniques, this surface was optimized for maximum combined lift and thrust. Box-Behnken design coupled with response surface methodology was an efficient method for exploring the mechanism force response. Both methods for optimization were capable of successfully improving lift and thrust force outputs. The incorporation of the results of these studies will aid in the design of more efficient micro air vehicles and with the ultimate goal of leading to a better understanding of flapping wing aerodynamics and the development of aerodynamic models.

Cellulose nanocrystals (CNCs) are frequently prepared by sulfuric acid hydrolysis of a purified cellulose starting material. CNC yields, however, are generally low, often below 20%. This study employs response surface methodology to optimize the hydrolysis conditions for maximum CNC yield. Two experimental designs were tested and compared: the central composite design (CCD) and the Box–Behnken design (BBD). The three factors for the experimental design were acid concentration, hydrolysis temperature, and hydrolysis time. The responses quantified were CNC yield, sulfate group density, ζ-potential, z-average diameter, and Peak 1 value. The CCD proved suboptimal for this purpose because of the extreme reaction conditions at some of its corners, specifically (1,1,1) and (–1,–1, –1). Both models predicted maximum CNC yields in excess of 65% at similar sulfuric acid concentrations (~59 wt %) and hydrolysis temperatures (~65 °C). With the BBD, the hydrolysis temperature for maximum yield lay slightly outside the design space. All three factors were statistically significant for CNC yield with the CCD, whereas with the BBD, the hydrolysis time in the range 60–150 min was statistically insignificant. With both designs, the sulfate group density was a linear function of the acid concentration and hydrolysis temperature and maximal at the highest acid concentration and hydrolysis temperature of the design space. Both designs showed the hydrolysis time to be statistically insignificant for the ζ-potential of CNCs and yielded potentially data-overfitting regression models. With the BBD, the acid concentration significantly affected both the z-average diameter and Peak 1 value of CNCs. However, whereas the z-average diameter was more strongly affected by the hydrolysis temperature than the hydrolysis time, the Peak 1 value was more strongly affected by the hydrolysis time. The CCD did not yield a valid regression model for the Peak 1 data and a potentially data-overfitting model for the z-average diameter data. A future optimization study should use the BBD but slightly higher hydrolysis temperatures and shorter hydrolysis times than used with the BBD in this study (45–65 °C and 60–150 min, respectively).
Master of Science

Thesis (PhD (Chemical Engineering))--Cape Peninsula University of Technology, 2020
The use of bioproducts in different commercial sectors such as medicine, agriculture, cosmetics, food, and chemical industries motivates the need for easy production and recovery techniques of bioproducts at laboratory and pilot scale. This study aims at the production and recovery of some selected bioproducts using supercritical fluid extraction techniques. Three products are chosen as case studies: these are ethanol, acetoin, and vanillin, since the ease of separation is influenced by the concentration of the product in the broth, these compounds were selected based on their concentration in the fermentation broth, according to literature sources. A standard method was developed in a spectrophotometer for quantifying the targeted product in the broth, while the product recovery studies was carried out using a supercritical fluid extraction pilot plant. Saccharomyces and Bacillus species were chosen for the bioproduction of the selected bioproducts. Experimental design and statistical analysis of results were carried out using response surface methodology (RSM) and artificial neural network (ANN). Studies on each of the selected bioproducts are as justified in the paragraphs below. Bioethanol production has recently become an increasing trend in research, with a focus on increasing its economic viability. Hence, the need to develop a low-cost fermentation medium with minimum redundant nutritional supplements, thereby minimizing the costs associated with nutritional supplements whereby inoculum preparation becomes necessary for ethanol production. Corn steep liquor (CSL) in glucose fermentation by Saccharomyces Type 1 (ST1) strain and Anchor Instant Yeast (AIY), which are low-cost media, are used as replacements for yeast extract (YE). The fermentation process parameters were optimized using artificial neural networks (ANN) and the response surface methodology (RSM). The study shows that for CSL, a maximum average ethanol concentration of 41.92 and 45.16 g/L representing 82% and 88% of the theoretical yield were obtained after 36 h of fermentation in a shake flask for ST1 and AIY respectively. For YE, ethanol concentration equivalent to 86% and 88% of theoretical yield were obtained with ST1 and AIY respectively after 48 h. Although, ANN predicted the responses of ethanol yield better than RSM, optimum conditions for ethanol production were better predicted by RSM. The consumers’ preference for ‘naturally’ produced aromas drives the development of bioproduction of acetoin from glucose with a view to optimize its production. The results revealed that by using a cheap nitrogen source, corn steep liquor, the yield of acetoin was similar to those of yeast and beef extracts. Furthermore, it was shown that by using Box-Behnken design, the optimum parameters such as glucose concentration, corn steep liquor, and inoculum size to maximize the concentration of acetoin produced were 78.40 g/L, 15.00% w/v and 2.70% v/v respectively. The validated concentration of acetoin produced in a triplicate analysis, 10.7 g/L, was 0.06% less than the predicted value. Increasing awareness of consumers of healthy, eco-friendly flavors and fragrances motivates the bioproduction of vanillin. The interactive effects of three variables on vanillin yield were evaluated by response surface methodology (RSM) with Box-Behnken design (BBD) model. The results showed the optimum conditions for the biotransformation of ferulic acid into vanillin can be achieved with maximum overall desirability (D) of 1.0 and a significant (p<0.05) quadratic model with regression coefficient (R2) of 0.995. Corn steep liquor, initial ferulic acid concentration and pH significantly influence the concentration of vanillin in the broth. The results in triplicate experiments confirmed vanillin yield of 386 mg/L after validation, which was in agreement with the prediction of the model. The maximum vanillin yield of 384.40 mg/L was predicted when corn steep liquor, ferulic acid concentration and pH were 7.72 g/L, 2.33 g/L, and 9.34 respectively. Fermentation system in a bioreactor has been proven to be an efficient system for the study of controlled fermentation variables when compared to a shake flask study. The influence of agitation, aeration, time and pH were analysed by Taguchi orthogonal array design for the upscale of acetoin in a bioreactor. The optimized parameters in 1.3L of fermentation vessel were as follows: 300 rpm agitation, 1.5 slpm aeration; 2 days’ fermentation time and 6.5 pH value. Agitation with above 70% was the most contributing factor and other variables were less than 30% in the percentage analysis of variance of each fermentation variables in the batch study of acetoin. A fourfold gain in acetoin titre (42.30 g/L) was obtained with the same substrate concentration in a lab-scale bioreactor on scaling up when compared with the shake flask batch study. The validated acetoin concentration of 41.72 g/L was obtained after a triplicate experiment to confirm the possibility of reproducing acetoin using the optimized conditions. Many separation techniques have been proven to recover value-added products from fermentation broth with a preference for several methods above other and new techniques that are emerging. Supercritical fluids separation using CO2 is one such technique. The feasibility of acetoin concentration and recovery was studied in supercritical CO2 pilot plant with pressure ranges of 100 to 300 bar, CO2 feed rate of 5 to 15 kg/h, at a process temperature of 37 and 80 °C in simulated and fermentation broth, respectively. The validated conditions for the fractionation of acetoin by supercritical fluid extraction (SFE) were determined as follows: extraction pressure, 300 bar; CO2 feed rate, 15 kg/h; extraction temperature 37 °C; and fractionation time of 30 minutes. At these operating conditions, the percentage recovery of acetoin with respect to the feed solution at the raffinate for the simulated and actual ermentation broth was 77.8% (0.20 g/L) and 77% (0.15 g/L) respectively. A two-fold extract increase was obtained after 30 minutes of fractionation. The study provides the technical feasibility and the base case data which are critical to the development and design of processes for production and recovery of acetoin. The lesson gleaned from this study may be extended to develop processes for the production and recovery of other bioproducts (ethanol and vanillin).

O presente trabalho objetiva estudar a eficiência térmica do arco elétrico e de fusão para o processo de soldagem MAG, do inglês Metal Active Gas, em diferentes geometrias de juntas soldadas. As soldas foram feitas inicialmente em um calorímetro de fluxo contínuo de água, seguidas de deposição de cordão sobre chapa e soldagem de juntas em ângulo “T”, sempre em aço carbono. A metodologia de projeto de experimentos Box-Behnken foi empregada para a avaliação da influência da variação dos parâmetros de soldagem (tensão, velocidade de alimentação do eletrodo e velocidade de soldagem) nas eficiências, dentro do modo de transferência metálica por curto circuito. Diferentes equações propostas na literatura para o cálculo da eficiência de fusão são comparadas. Para a adequada aquisição da eficiência térmica pelo calorímetro, preliminarmente é avaliada a influência da vazão de água e da geometria na entrada de um calorímetro de fluxo contínuo sobre a eficiência térmica do arco. O procedimento experimental consiste em testar diferentes vazões de água e três configurações geométricas na região de entrada de água no calorímetro: com rolha reta, com difusor cônico e com obstáculo. Os experimentos foram planejados e os resultados avaliados com base na análise de variância estatística de um único fator, no caso, a vazão de água na entrada do calorímetro. A maior eficiência térmica média de 80,5% foi obtida para a vazão de 4 l/min, com baixo erro estatístico, utilizando rolha de entrada com geometria de difusor cônico. O modelo em que o fluxo entra diretamente no tubo apresentou todos os valores de eficiência térmica do arco com pequeno decréscimo numérico se comparados com o difusor cônico, enquanto a rolha com obstáculo apresentou elevado erro estatístico. Com base nos resultados descritos, a eficiência térmica do arco elétrico foi avaliada com a vazão de 4 l/min para o projeto de experimentos Box-Behnken, os valores obtidos estão na faixa de 72 a 82% conforme a combinação dos parâmetros de soldagem. A velocidade de soldagem e a tensão do arco se mostraram como os parâmetros de maior influência na eficiência térmica do arco. Os resultados relativos à eficiência de fusão indicam maiores valores nas soldas realizadas no calorímetro e por simples deposição sobre chapa. A junta T apresentou os menores valores de eficiência de fusão e de diluição para todos os casos. O parâmetro de maior influência na eficiência de fusão foi a corrente de soldagem.
The main aim of the present work is to study arc thermal efficiency and fusion efficiency to Gas Metal Arc Welding – GMAW, using different joint geometries. At first, the welds were performed in a continuous water flow calorimeter, followed by bead on plate and T – joint deposits. The Box-Behken design of experiments methodology was used to analyze the effect of welding parameters (arc voltage, wire feed speed and welding speed) on the efficiencies, when using short circuit metal transfer. The results of the fusion efficiency calculation were compared using different equations found in the literature. To correctly evaluate the thermal efficiency, it was necessary to analyze the influence of water flow rate and calorimeter inlet geometry. The experimental procedure consists of varying water flow rate and testing three different calorimeter inlet seal geometries: straight seal, conical diffuser seal and seal with water flux obstacle. The experiments were designed and the results evaluated based in a one-factor statistical analysis of variance, in this case the inlet calorimeter water flow. The highest average thermal efficiency is 80.5% to water flow of 4 l/min, with a low statistical error, using the conical diffuser seal inlet geometry. The inlet with straight seal model shown all the arc thermal efficiency values with slightly lower numerical values compared with conical diffuser, while the seal with flux obstacle exhibited high statistical error. Based on these results, the arc thermal efficiency was evaluated using 4 l/min water flow to the Box-Behnken Design, resulting values in the 72 to 82% range, depending on the welding parameters. The welding speed and arc voltage were the parameters that significantly affect arc thermal efficiency. The fusion efficiency results of the welds performed on the calorimeter and bead on plate were. The welds performed in T joints exhibit lowest fusion efficiency and dilution to each welding parameters combination tested. The fusion efficiency is strongly affected by the welding current.

Though still in relative infancy, the field of flapping flight has potential to have a far-reaching impact on human life. Nature presents a myriad of examples of successful uses of this locomotion. Human efforts in flapping flight have seen substantial improvement in recent times. Wing kinematics are a key aspect of this study. This study summarizes previous wing trajectory generators and presents a new trajectory generation method built upon previous methods. This includes a novel means of commanding unequal half-stroke durations subject to robotic trajectory continuity requirements. Additionally, previous optimization methods are improved upon. Experimental optimization is performed using the new trajectory generation method and a more traditional means. Methods for quantifying and compensating for sensor time-dependence are also discussed. Results show that the Polar Fourier Series trajectory generator advanced rapidly through the optimization process, especially during the initial phase of experimentation. The Modified Berman and Wang trajectory generator moved through the design space more slowly due to the increased number of kinematic parameters. When optimizing lift only, the trajectory generators produced similar results and kinematic forms. The findings suggest that the objective statement should be modified to reward efficiency while maintaining a certain amount of lift. It is expected that the difference between the capabilities of the two trajectory generators will become more apparent under such conditions.

The methodology of the design of experimnet has become an integral part of the optimisation of manufacturing processes in recent decades. Problems regarding designs of experiments are still up to date, especially because of a variety of approaches to collecting and evaluating data. Scientists in different research and development areas often do not take into account possible shortcommings or even essential assumptions of selected design and/or its evaluation methods. This disertation thesis summarizes theoretical bases of selected designs of experiments. Describes several applications of central composite design on responses regarding wire electrical discharge machining process. And compares different designs of experiment for response surfaces of five parameters with regards to algoritmic selection of statistically signifficant parameters.

Over the years, concern about environmental contamination has been increasing. The generation of electronic waste (e-waste) is currently a serious environmental problem, due to inefficient management of this type of waste, with low recycling rates, which is partly due to technical difficulties. Since e-waste consists of several critical raw materials, such as rare earth elements (REE), its recovery would bring clear economic and environmental benefits. In the present dissertation, alternatives to the exploitation of these elements are presented, through the recycling of electronic waste using live macroalgae. The objective of this work is to optimize the process of extraction of REE from the electronic waste of the lighting industry (previously treated to originate a waste sludge) through an inorganic acid (nitric acid), and subsequently, the removal of REE elements using the living marine macroalgae Ulva lactuca, through a Box-Behnken experimental design and following the Response Surface Methodology. In view of a preferential extraction of REE, a sequential extraction method was developed which allowed to eliminate some undesirable elements in a 1st extraction step, and in a 2nd step to obtain an extract rich in Y and Eu (91 %). estimating high removals (%) under the optimized conditions by Box-Behnken experimental design (salinity 10, 9 g/L algae mass and initial Y concentrations of 20 mg/L). In order to obtain the maximum amount of Y in the algae tissues, the optimal conditions indicated the use of 3 g/L of algae mass and initial concentration of Y of 120 mg/L (21 mg of Y per mass of algae (g)). The analysis of the fit of kinetic models to the incorporation of Y by U.lactuca over time showed that the pseudo-first order model is the most suitable, pointing to physical sorption as the mechanism that governed the process. The concentrations of Y obtained in macroalgae at the end of the experiment are 20 times higher than those of the ore, which reinforces its use as an alternative source for the producers of electronic devices, being environmentally more sustainable.
Ao longo dos anos, a preocupação com a contaminação ambiental tem vindo a aumentar. A geração de lixo eletrónico é atualmente um grave problema ambiental, devido a uma gestão ineficaz deste tipo de resíduo, com baixas taxas de reciclagem, o que se deve em parte a dificuldades técnicas. Sendo o lixo eletrónico constituído por várias matérias-primas críticas, como os elementos terras raras (REE), a sua recuperação traria claros benefícios económicos e ambientais. Na presente dissertação são apresentadas alternativas à exploração destes elementos, através da reciclagem de resíduos eletrónicos utilizando macroalgas vivas. O objetivo deste trabalho é otimizar o processo de extração de REE proveniente de resíduos eletrónicos da indústria da iluminação (previamente tratados originando uma lama como resíduo) através de uma extração com um ácido inorgânico (ácido nítrico), e, posteriormente, a remoção dos REE com recurso a uma macroalga marinha viva, a Ulva lactuca, recorrendo à utilização de um desenho experimental de Box-Behnken e seguindo a Metodologia de Superfície de Resposta. Com vista à extração preferencial de REE, foi desenvolvido um método de extração sequencial que permitiu eliminar alguns elementos indesejáveis numa 1ª fase de extração, e numa 2ª fase obter um extrato rico em Y e Eu (91 %). As macroalgas demonstraram ser capazes de concentrar o Ítrio (Y) e Európio (Eu), estimando-se elevadas remoções (%) nas condições otimizadas pelo desenho experimental Box-Behnken (salinidade 10, 9 g/L de massa de alga e concentrações iniciais de Y de 20 mg/L). Para obter uma maior quantidade de Y nos tecidos da alga, as condições ideais indicaram o uso de 3 g/L de massa de algas e uma concentração inicial de Y de 120 mg/L (21 mg de Y por massa de alga (g). A análise do ajuste dos modelos cinéticos para a incorporação de Y pela U.lactuca ao longo do tempo mostrou que o modelo de pseudo-primeira ordem é o mais adequado, o que significa que a sorção física é o mecanismo que governa o processo. A concentração de Y obtida nas macroalgas no final do ensaio é 20 vezes superior às presentes no minério, o que reforça a sua utilização como fonte alternativa para os produtores de dispositivos eletrónicos, sendo ambientalmente mais sustentável.
Mestrado em Biotecnologia

Water is a scarcer resource nowadays due to the stress applied to water systems, by the increase of the human population, which leads to a wastage of water manly due to agriculture and to anthropogenic activi-ties that contrite to the contamination of hydric resources. Examples of relevant water environmental contaminants are mercury (Hg) (a highly dangerous element that is very toxic to human health), gadolinium (Gd), and lanthanum (La) (rare-earth elements, present in most electric equipment and electronics). The presence of Gd and La in aquatic eco-systems is more and more frequent, without being well known their impacts on organisms. In this work, the biosorption and its optimization using the living macroalgae Ulva lactuca, was studied to evaluate if it is a promising alternative to deal with the problem of water contamina-tion. In the assays carried out (before optimization), the removal of the mentioned elements in a mono and multi-elementar scenario, achieved removals between 77 and 88 % for mercury, 37 and 53 % for lantha-num, and 38 and 65 % for gadolinium after 72 h. In the optimization test, algae mass (1.5 – 4.5 g/L), initial element concentration (5 – 50 μg/L for mercury and 100 μg/L – 1000 μg/L for lanthanum e gadolin-ium), and salinity (15 – 35) were the conditions chosen to evaluate the removal using Response Surface Methodology with the experimental design of Box-Behnken. The optimal conditions of the operation that lead to the maximum removal of the elements (until 100 % of removal for mercury and lanthanum, and 94 % for gadolinium) were deter-mined, and the results allow to conclude that the extension of time of the process further than 72 h is not justified. This work fills some gaps of the literature, namely the removal of potential toxic elements from waters in multi-elementar scenarios and in concentrations that are en-vironmentally realistic.
A água é um recurso cada vez mais escasso devido ao stress colocado sobre os recursos hídricos, que resulta do aumento da população hu-mana, de um elevado consumo de água, em grande parte associado à agricultura, e da sua contaminação por atividades antropogénicas. Entre os diversos contaminantes da água, destacam-se, por exemplo, o mer-cúrio (Hg) (elemento bastante tóxico e perigoso para a saúde humana), o gadolínio (Gd), e o lantânio (La) (dois elementos terras-raras, presen-tes na maioria dos equipamentos elétricos e eletrónicos). A presença Gd e La nos ecossistemas aquáticos é cada vez mais frequente, sem que ainda sejam bem conhecidos os seus impactos nos organismos. Neste trabalho, a biossorção e a sua otimização usando a macroalga viva Ulva lactuca, é proposta como alternativa promissora para combater o pro-blema da contaminação da água. Nos ensaios realizados (antes de oti-mização), a remoção dos três contaminantes pela macroalga, em cená-rios mono- e multi-elementar, apresentou percentagens entre 77 e 88 % para o mercúrio, entre 37 e 53 % para o lantânio, e entre 38 e 65 % para o gadolínio, após 72 h. No ensaio de otimização, a massa da alga (1.5 - 4.5 g/L), a concentração inicial dos elementos (5 – 50 μg/L para o mer-cúrio e 100 – 1000 μg/L para o lantânio e gadolínio) e a salinidade (15 – 35) foram escolhidas como as condições a estudar usando o Método de Superfície de Resposta com um desenho experimental de Box-Behnken. As condições ótimas de operação que levam à máxima remo-ção dos elementos (até 100 % de remoção para o mercúrio e para o lantânio, e 94 % para o gadolínio) foram determinadas, e os resultados permitiram concluir ainda que não se justifica estender o processo para além das 72 h. Este trabalho permite preencher algumas lacunas da atual literatura, tal como o estudo da remoção de elementos potencial-mente tóxicos de matrizes multi-elementares, em concentrações seme-lhantes às existentes atualmente no ambiente.
Mestrado em Biotecnologia

Human activity and survival as biodiversity depends on aquatic systems that, unfortunately, have been directly and indirectly threatened by anthropogenic actions, strongly contributing to the loss of water quality. Electronic waste (e-waste) is one of the most ascending waste streams, whose management has become a priority to avoid environmental impacts, such water contamination. At the same time, e-waste is a rich source of elements of high economic and technological interest such as gold, silver, copper, lithium, cobalt, platinum group elements, and rare earth metals, which can be recovered and re- introduced into the production cycle. The use of macroalgae as a biosorbent has gained focus as it can be considered a simple, economical and eco-friendly solution for contaminated water treatment. However, this process still faces some challenges, and most published articles are limited to evaluate the removal of one or a few elements from a single group, contrasting with the composition of real industrial effluents, and do not include process optimization. This means that there are still few commercially available biosorbents on the market. The main objective of the present work is to evaluate and optimize parameters that influence the efficiency of the biosorption/bioaccumulation process performed by a live marine macroalgae (Ulva lactuca), in a complex mixture of contaminants that simulates an effluent from a lamp industry, following the Response Surface Methodology (RSM) with a Box-Behnken Design. The results of the controls experiments pointed to the inexistence of losses or contaminations during the experiments, and the analysis of the central point of the Box-Behnken confirmed the reproducibility of the methodology. Based on the statistical treatment of the data, for a significance level of 0.05 (ANOVA), the factor with the greatest impact on the removal of elements revealed to be the initial macroalgae dosage, with higher values allowing for greater removals (up to 88 % in 24 h, for rare earth elements (REEs)). The conditions determined as optimal for the removal of REEs were: initial concentration of 10 μg/L, at salinity 10, and using 5.0 g/L of macroalgae. Through the cell partition of the sorbed elements, via selective extractions with EDTA, it was found that most of them were located on the external surface of U. lactuca. On the contrary, the Hg was accumulated internally and Co, Pt and Ce were distributed between the two fractions.
A atividade e sobrevivência humana, assim como a biodiversidade depende dos sistemas aquáticos que, infelizmente, têm sido ameaçados de forma direta e indireta por ações antropogénicas, contribuindo de forma relevante para a perda da qualidade da água. O lixo eletrónico (e-waste) é uma tipologia de resíduos cuja gestão se tem tornado uma prioridade para evitar impactos ambientais, como a contaminação da água. Ao mesmo tempo, o e-waste é uma importante fonte de elementos de elevado interesse económico e tecnológico, como ouro, prata, cobre, lítio, cobalto, elementos do grupo da platina e elementos de terras raras, que podem ser recuperados e reintroduzidos no ciclo de produção. O uso de macroalgas como biossorvente tem ganho destaque, pois pode ser considerada uma solução simples, económica e ecologicamente adequada para o tratamento de águas contaminadas. Contudo, este processo ainda enfrenta alguns desafios, sendo que a maioria dos artigos publicados avalia apenas a remoção de um ou alguns elementos de um único grupo, contrastando com a composição de efluentes industriais reais, e não incluem a otimização do processo. Isto faz com que continue a haver poucos biossorventes disponíveis comercialmente no mercado. O objetivo principal do presente trabalho é avaliar e otimizar parâmetros que influenciam a eficiência do processo de biossorção/bioacumulação realizado por uma macroalga marinha viva (Ulva lactuca), numa mistura complexa de contaminantes que simula um efluente de uma indústria de lâmpadas, seguindo a Metodologia de Superfície de Resposta (RSM) com um desenho experimental de Box-Behnken. Os resultados dos ensaios controlos indicam a inexistência de perdas ou contaminação dos elementos em estudo, e a análise do ponto central do modelo de Box-Behnken confirmou a reprodutibilidade da metodologia. Com base no tratamento estatístico dos dados, para um nível de significância de 0,05 (ANOVA), o fator com maior impacto na remoção dos elementos revelou ser a dosagem inicial de macroalga, com valores mais altos a permitirem obter remoções maiores (até 88 % em 24 h, para elementos de terras raras (REEs)). As condições determinadas como ótimas para a remoção dos REEs foram: concentração inicial de 10 μg/L, na salinidade 10, e usando 5,0 g/L de macroalgas. Através da partição celular dos elementos sorvidos, por meio de extrações seletivas com EDTA, verificou-se que a maioria deles estava localizada na superfície exterior da U. lactuca. Pelo contrário, o Hg estava acumulado internamente e o cobalto, Pt e Ce estavam distribuídos entre as duas frações.
Mestrado em Biotecnologia