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Thesis (Ph. D. - Microbiology)--University of Arizona, 1982. / Includes bibliographical references (leaves 95-101).

Co-rotating twin-screw extruders are unique and versatile machines that are used widely in the plastics and food processing industries. Due to the large number of operating variables and design parameters available for manipulation and the complex interactions between them, it cannot be claimed that these extruders are currently being optimally utilised. The most significant improvement to the field of twin-screw extrusion would be through the provision of a generally applicable dynamic process model that is both computationally inexpensive and accurate. This would enable product design, process optimisation and process controller design to be performed cheaply and more thoroughly on a computer than can currently be achieved through experimental trials. This thesis is divided into three parts: dynamic modelling, measurement and control. The first part outlines the development of a dynamic model of the extrusion process which satisfies the above mentioned criteria. The dynamic model predicts quasi-3D spatial profiles of the degree of fill, pressure, temperature, specific mechanical energy input and concentrations of inert and reacting species in the extruder. The individual material transport models which constitute the dynamic model are examined closely for their accuracy and computational efficiency by comparing candidate models amongst themselves and against full 3D finite volume flow models. Several new modelling approaches are proposed in the course of this investigation. The dynamic model achieves a high degree of simplicity and flexibility by assuming a slight compressibility in the process material, allowing the pressure to be calculated directly from the degree of over-fill in each model element using an equation of state. Comparison of the model predictions with dynamic temperature, pressure and residence time distribution data from an extrusion cooking process indicates a good predictive capability. The model can perform dynamic step-change calculations for typical screw configurations in approximately 30 seconds on a 600 MHz Pentium 3 personal computer. The second part of this thesis relates to the measurement of product quality attributes of extruded materials. A digital image processing technique for measuring the bubble size distribution in extruded foams from cross sectional images is presented. It is recognised that this is an important product quality attribute, though difficult to measure accurately with existing techniques. The present technique is demonstrated on several different products. A simulation study of the formation mechanism of polymer foams is also performed. The measurement of product quality attributes such as bulk density and hardness in a manner suitable for automatic control is also addressed. This is achieved through the development of an acoustic sensor for inferring product attributes using the sounds emanating from the product as it leaves the extruder. This method is found to have good prediction ability on unseen data. The third and final part of this thesis relates to the automatic control of product quality attributes using multivariable model predictive controllers based on both direct and indirect control strategies. In the given case study, indirect control strategies, which seek to regulate the product quality attributes through the control of secondary process indicators such as temperature and pressure, are found to cause greater deviations in product quality than taking no corrective control action at all. Conversely, direct control strategies are shown to give tight control over the product quality attributes, provided that appropriate product quality sensors or inferential estimation techniques are available.

Co-rotating twin-screw extruders are unique and versatile machines that are used widely in the plastics and food processing industries. Due to the large number of operating variables and design parameters available for manipulation and the complex interactions between them, it cannot be claimed that these extruders are currently being optimally utilised. The most significant improvement to the field of twin-screw extrusion would be through the provision of a generally applicable dynamic process model that is both computationally inexpensive and accurate. This would enable product design, process optimisation and process controller design to be performed cheaply and more thoroughly on a computer than can currently be achieved through experimental trials. This thesis is divided into three parts: dynamic modelling, measurement and control. The first part outlines the development of a dynamic model of the extrusion process which satisfies the above mentioned criteria. The dynamic model predicts quasi-3D spatial profiles of the degree of fill, pressure, temperature, specific mechanical energy input and concentrations of inert and reacting species in the extruder. The individual material transport models which constitute the dynamic model are examined closely for their accuracy and computational efficiency by comparing candidate models amongst themselves and against full 3D finite volume flow models. Several new modelling approaches are proposed in the course of this investigation. The dynamic model achieves a high degree of simplicity and flexibility by assuming a slight compressibility in the process material, allowing the pressure to be calculated directly from the degree of over-fill in each model element using an equation of state. Comparison of the model predictions with dynamic temperature, pressure and residence time distribution data from an extrusion cooking process indicates a good predictive capability. The model can perform dynamic step-change calculations for typical screw configurations in approximately 30 seconds on a 600 MHz Pentium 3 personal computer. The second part of this thesis relates to the measurement of product quality attributes of extruded materials. A digital image processing technique for measuring the bubble size distribution in extruded foams from cross sectional images is presented. It is recognised that this is an important product quality attribute, though difficult to measure accurately with existing techniques. The present technique is demonstrated on several different products. A simulation study of the formation mechanism of polymer foams is also performed. The measurement of product quality attributes such as bulk density and hardness in a manner suitable for automatic control is also addressed. This is achieved through the development of an acoustic sensor for inferring product attributes using the sounds emanating from the product as it leaves the extruder. This method is found to have good prediction ability on unseen data. The third and final part of this thesis relates to the automatic control of product quality attributes using multivariable model predictive controllers based on both direct and indirect control strategies. In the given case study, indirect control strategies, which seek to regulate the product quality attributes through the control of secondary process indicators such as temperature and pressure, are found to cause greater deviations in product quality than taking no corrective control action at all. Conversely, direct control strategies are shown to give tight control over the product quality attributes, provided that appropriate product quality sensors or inferential estimation techniques are available.

Made available in DSpace on 2014-06-11T19:32:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-10-04Bitstream added on 2014-06-13T18:43:51Z : No. of bitstreams: 1 rocha_rc_dr_botfca.pdf: 684550 bytes, checksum: f3505330644443bdf256bec93d86c071 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conduziu-se o experimento em cinco ambientes protegidos, tela termo refletora, tela de sombreamento branca, tela de sombreamento preta, tela difusora e céu aberto, sendo cada ambiente de 10mx24m, com pé direito de 3,0 m, estrutura tipo “Sombreiro”, no município de Juazeiro, BA, em área experimental do Departamento de Tecnologia e Ciências Sociais (DTCS) da UNEB (Campus III), entre julho a dezembro de 2006. O delineamento experimental foi de blocos ao acaso, em cinco ambientes com quatro repetições e dois tratamentos por bloco, representados por dois híbridos de tomateiro de crescimento determinado, fruto tipo Caqui e Santa Cruz, D-4768 e C-5240, respectivamente, e análise realizada em grupos de experimentos, com parcelas de 2,0m x 3,6m (7,2m2). A utilização das telas de sombreamento reduziu a intensidade da energia radiante, proporcionando melhor qualidade e distribuição da radiação solar dentro dos ambientes protegidos, resultando melhor performance da cultura, quando comparada com o cultivo a céu aberto. O melhor desempenho dos genótipos foi registrado nos ambientes: tela difusora e tela de sombreamento preta, respectivamente, que apresentaram a menor transmitância da radiação global, evitando-se o excesso de radiação incidente na cultura, melhorando fisiologicamente todos os processos da distribuição de fotoassimilados nas plantas, com conseqüente aumento da produção. / The experiment was carried out under four shading houses covered with different shade nets (heat reflector net, white shade net, black shade net and net diffuser) and open field. Each environment measured 10mx24 m, 3.0 m tall, in shade net structure, in the county of Juazeiro- BA, in the Experimental Field of UNEB – DTCS (Departamento Tecnologia e Ciências Sociais), in the period between July and December of 2006. The experiment was carried out in a randomized block design, in five environments with four replications and two treatments (two tomato hybrids) in each block. The two hybrids of tomato presented plants with a determined growth (hybrids D-4768 and Santa Cruz C-5240). The plot size was 2.0m x 3.60 m (7.2m2). The use of screens reduced the intensity of the radiant energy, what brought about a better distribution of the solar radiation within the protected environments. This resulted in a better crop performance when compared with open sky crops. The best genotype performance was registered for the environments diffuser screen and black screen, respectively. They showed the smallest transmittance of the global radiation, avoiding excess of incident radiation on the crop, improving physiologically the distribution of assimilate in the plants, which consequently increased the production.

This diploma thesis is concerned with the analysis of economic growth in the Czech Republic since its origin in 1993 till 2009, aimed at the determination of strengths and weaknesses of the economic growth. According to the findings, the diploma thesis will afford several recommendations for the economic policy. The diploma thesis is divided into the theoretical and analytical part. The theory brings some economist's view of the economic growth questions. It mentions the transformation period of the Czechoslovakia centrally planned economy into the market economy. The analysis sets up the data in order to determine the Czech economic growth strengths and weaknesses with the help of demand, supply and resource analysis, the prognosis made by significant institutions and the international comparison for which the Slovak and European Union economics are used. At the end of the diploma thesis there are these findings used to conceive the economic policies arrangements.

Considering 91 countries with seaports, this study conducted an empirical inquiry into the broader economic contribution of seaborne trade, from a port infrastructure quality and logistics performance perspective. Investment in quality improvement of port infrastructure and its contribution to economy are often questioned by politicians, investors and general public. A structural equation model (SEM) is used to provide empirical evidence of significant economic impacts of port infrastructure quality and logistics performance. Furthermore, analysis of a multi-group SEM is performed by dividing countries into developed and developing economy groups. The results reveal that it is vital for developing countries to continuously improve the quality of port infrastructure as it contributes to better logistics performance, leading to higher seaborne trade, yielding higher economic growth. However, this association weakens as the developing countries become richer.

Made available in DSpace on 2014-06-11T19:28:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-28Bitstream added on 2014-06-13T18:34:43Z : No. of bitstreams: 1 mateus_cmd_me_jabo.pdf: 424839 bytes, checksum: b843560bbf22750f1a4ab33cb67bf70b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O amarílis figura entre as principais plantas ornamentais produzidas no Brasil, principalmente, visando produção de bulbos para exportação, porém estudos referentes ao manejo da cultura ainda são necessários. Desta forma, este trabalho teve como objetivo estudar o desenvolvimento e o acúmulo de nutrientes de amarílis, variedade Orange Souvereign, a pleno sol. No estudo relacionado ao crescimento, a área foliar determinada ao final do experimento foi, em média, de 3102,6 cm2, para uma média de 10 folhas por planta. O diâmetro do bulbo alcançado aos 420 DAP (dias após plantio) foi, em média, de 9,2 cm. A massa fresca total ao final do ciclo foi, em média, de 1051 g, dos quais 39% corresponderam à massa fresca obtida pelo bulbo + raízes. Em relação aos índices fisiológicos, a média foi de 7,10 g mês-1 para TCA (taxa de crescimento absoluto); 0,40 g g-1 mês-1 para TCR (taxa de crescimento relativo); 0,052 g cm-2 mês-1 para TAL (taxa de assimilação líquida) e 44,77 cm2 g-1 para RAF (razão de área foliar). No estudo relacionado à absorção de nutrientes, nas condições apresentadas de plantio, a quantidade de macronutrientes extraída, em mg planta-1, até os 420 DAP foi de: 1566 N; 185 P; 2583 K; 639 Ca; 198 Mg e 292 S. Para micronutrientes, a quantidade extraída, em μg planta-1, até os 420 DAP foi de: 2184 B; 1166 Cu; 22334 Fe; 2192 Mn e 4092 Zn. O acúmulo dos nutrientes nos últimos quatro meses representou, em relação ao total: 61% N; 60% P; 62% K; 56% Ca; 41% Mg; 67% S; 61% B; 65% Cu; 51% Fe; 73% Mn e 65% Zn. / The amaryllis is one of the major ornamental plants produced in Brazil, mainly targeting production of bulbs for export, but studies relating to the management of culture are still needed. Thus, this paper examines the development and accumulation of nutrients from amaryllis, variety Orange Souvereign, in full sun. In the growth study, the leaf area determined at the end of the experiment was, on average, to 3102.6 cm2 to an average of 10 leaves per plant. The diameter of the bulb throughout at 420 DAP (days after planting) was, on average, 9.2 cm. The total fresh weight at the end of the cycle was, on average, 1051 g, of which 39% were obtained by mass fresh bulb + roots. For physiological indices, the average was 7.10 g months-1 for TCA (absolute growth rate), 0.40 g g-1 months-1 for TCR (growth rate relative), 0.0516 g cm-2 months-1 to TAL (net assimilation rate) and 44.77 cm2 g-1 for RAF (ratio of leaf area). In the nutrients absorption study the conditions presented in planting was the amount of macronutrients extracted, in mg plant-1, until 420 DAP was: 1566 N; 185 P; 2583 K; 639 Ca; 198 Mg and 292 S. For micronutrients, the amount extracted, in μg planta-1, until 420 DAP was: 2184 B; 1166 Cu; 22334 Fe; 2192 Mn e 4092 Zn. The accumulation of nutrients in the last four months represented, in relation to the total: 61% N, 60% P, 62% K, 56% Ca, 41% Mg, 67% S, 61% B, 65% Cu, 51% Fe, 73% Mn and 65% Zn.

Orientador: Rumy Goto / Banca: João Domingos Rodrigues / Banca: Manuel Abílio de Queiróz / Banca: Max José de Araújo Junior / Banca: Dimas Menezes / Resumo: Conduziu-se o experimento em cinco ambientes protegidos, tela termo refletora, tela de sombreamento branca, tela de sombreamento preta, tela difusora e céu aberto, sendo cada ambiente de 10mx24m, com pé direito de 3,0 m, estrutura tipo "Sombreiro", no município de Juazeiro, BA, em área experimental do Departamento de Tecnologia e Ciências Sociais (DTCS) da UNEB (Campus III), entre julho a dezembro de 2006. O delineamento experimental foi de blocos ao acaso, em cinco ambientes com quatro repetições e dois tratamentos por bloco, representados por dois híbridos de tomateiro de crescimento determinado, fruto tipo Caqui e Santa Cruz, D-4768 e C-5240, respectivamente, e análise realizada em grupos de experimentos, com parcelas de 2,0m x 3,6m (7,2m2). A utilização das telas de sombreamento reduziu a intensidade da energia radiante, proporcionando melhor qualidade e distribuição da radiação solar dentro dos ambientes protegidos, resultando melhor performance da cultura, quando comparada com o cultivo a céu aberto. O melhor desempenho dos genótipos foi registrado nos ambientes: tela difusora e tela de sombreamento preta, respectivamente, que apresentaram a menor transmitância da radiação global, evitando-se o excesso de radiação incidente na cultura, melhorando fisiologicamente todos os processos da distribuição de fotoassimilados nas plantas, com conseqüente aumento da produção. / Abstract: The experiment was carried out under four shading houses covered with different shade nets (heat reflector net, white shade net, black shade net and net diffuser) and open field. Each environment measured 10mx24 m, 3.0 m tall, in shade net structure, in the county of Juazeiro- BA, in the Experimental Field of UNEB - DTCS (Departamento Tecnologia e Ciências Sociais), in the period between July and December of 2006. The experiment was carried out in a randomized block design, in five environments with four replications and two treatments (two tomato hybrids) in each block. The two hybrids of tomato presented plants with a determined growth (hybrids D-4768 and Santa Cruz C-5240). The plot size was 2.0m x 3.60 m (7.2m2). The use of screens reduced the intensity of the radiant energy, what brought about a better distribution of the solar radiation within the protected environments. This resulted in a better crop performance when compared with open sky crops. The best genotype performance was registered for the environments diffuser screen and black screen, respectively. They showed the smallest transmittance of the global radiation, avoiding excess of incident radiation on the crop, improving physiologically the distribution of assimilate in the plants, which consequently increased the production. / Doutor

Resumo: O amarílis figura entre as principais plantas ornamentais produzidas no Brasil, principalmente, visando produção de bulbos para exportação, porém estudos referentes ao manejo da cultura ainda são necessários. Desta forma, este trabalho teve como objetivo estudar o desenvolvimento e o acúmulo de nutrientes de amarílis, variedade Orange Souvereign, a pleno sol. No estudo relacionado ao crescimento, a área foliar determinada ao final do experimento foi, em média, de 3102,6 cm2, para uma média de 10 folhas por planta. O diâmetro do bulbo alcançado aos 420 DAP (dias após plantio) foi, em média, de 9,2 cm. A massa fresca total ao final do ciclo foi, em média, de 1051 g, dos quais 39% corresponderam à massa fresca obtida pelo bulbo + raízes. Em relação aos índices fisiológicos, a média foi de 7,10 g mês-1 para TCA (taxa de crescimento absoluto); 0,40 g g-1 mês-1 para TCR (taxa de crescimento relativo); 0,052 g cm-2 mês-1 para TAL (taxa de assimilação líquida) e 44,77 cm2 g-1 para RAF (razão de área foliar). No estudo relacionado à absorção de nutrientes, nas condições apresentadas de plantio, a quantidade de macronutrientes extraída, em mg planta-1, até os 420 DAP foi de: 1566 N; 185 P; 2583 K; 639 Ca; 198 Mg e 292 S. Para micronutrientes, a quantidade extraída, em μg planta-1, até os 420 DAP foi de: 2184 B; 1166 Cu; 22334 Fe; 2192 Mn e 4092 Zn. O acúmulo dos nutrientes nos últimos quatro meses representou, em relação ao total: 61% N; 60% P; 62% K; 56% Ca; 41% Mg; 67% S; 61% B; 65% Cu; 51% Fe; 73% Mn e 65% Zn. / Abstract: The amaryllis is one of the major ornamental plants produced in Brazil, mainly targeting production of bulbs for export, but studies relating to the management of culture are still needed. Thus, this paper examines the development and accumulation of nutrients from amaryllis, variety Orange Souvereign, in full sun. In the growth study, the leaf area determined at the end of the experiment was, on average, to 3102.6 cm2 to an average of 10 leaves per plant. The diameter of the bulb throughout at 420 DAP (days after planting) was, on average, 9.2 cm. The total fresh weight at the end of the cycle was, on average, 1051 g, of which 39% were obtained by mass fresh bulb + roots. For physiological indices, the average was 7.10 g months-1 for TCA (absolute growth rate), 0.40 g g-1 months-1 for TCR (growth rate relative), 0.0516 g cm-2 months-1 to TAL (net assimilation rate) and 44.77 cm2 g-1 for RAF (ratio of leaf area). In the nutrients absorption study the conditions presented in planting was the amount of macronutrients extracted, in mg plant-1, until 420 DAP was: 1566 N; 185 P; 2583 K; 639 Ca; 198 Mg and 292 S. For micronutrients, the amount extracted, in μg planta-1, until 420 DAP was: 2184 B; 1166 Cu; 22334 Fe; 2192 Mn e 4092 Zn. The accumulation of nutrients in the last four months represented, in relation to the total: 61% N, 60% P, 62% K, 56% Ca, 41% Mg, 67% S, 61% B, 65% Cu, 51% Fe, 73% Mn and 65% Zn. / Orientador: Kathia Fernandes Lopes Pivetta / Coorientador: Roberto Lyra Villas Boas / Banca: Regina Maria Monteiro de Castilho / Banca: Jairo Augusto Campos de Araújo / Mestre