A framework for generating operational characteristic curves for semiconductor manufacturing systems using flexible and reusable discrete event simulations

This thesis proposes a framework for generating operating curves for semiconductor manufacturing facilities using a modular flexible discrete event simulation (DES) model embedded in an application that automates the design of experiments for the simulations. Typically, operating curves are generated using analytical queueing models that are difficult to implement and hence, can only be used for benchmarking purposes. Alternatively, DES models are more capable of capturing the complexities of a semiconductor manufacturing facility such as re-entrancy, rework and non-identical toolsets. However, traditional craft-based simulations require much time and resources. The proposed methodology aims to reduce this time by automatically calculating the parameters for experimentation and generating the simulation model. It proposes a novel method to more appropriately allocate simulation effort by selecting design points more relevant to the operating curve. The methodology was initially applied to a single toolset model and tested as a pilot case study using actual factory data. Overall, the resulting operating curves matched that of the actual data. Subsequently, the methodology was applied to a full semiconductor manufacturing facility, using datasets from the Semiconductor Wafer Manufacturing Data Format Specification. The automated framework was shown to generate the curves rapidly and comparisons against a number of queueing model equivalents showed that the DES curves were more accurate. The implications of this work mean that on deployment of the application, semiconductor manufacturers can quickly obtain an accurate operating curve of their factory that could be used to aid in capacity planning and enable better decision-making regarding allocation of resources

Development and Evaluation of Thermal Protection Material for Solid Rocket Motors

Process Engineerin

Development and analysis of micro polygeneration systems and adsorption chillers

About a fifth of all primary energy in the US is consumed by residential buildings, mostly for cooling, heating and to provide electricity. Furthermore, retrofits are essential to reducing this consumption, since the buildings that exist today will comprise over half of those in use in 2050. Residential combined heat and power (or micro CHP, defined by <5 kW electrical generation capacity) has been identified as a retrofit technology which can reduce energy consumption in existing homes during the heating season by 5-30%. This thesis investigates the addition of a thermally-driven chiller/heat pump to a CHP system (to form a trigeneration system) to additionally provide savings during the cooling season, and enhance heating season savings. Scenarios are identified in which adding thermally-driven equipment to a micro CHP system reduces primary energy consumption, through analytical and experimental investigations. The experimental focus is on adsorption heat pump systems, which are capable of being used with the CHP engines (prime movers) that are already widely deployed. The analytical analysis identifies energy saving potential off-grid for today's prime movers, with potential on-grid for various fuel cell technologies. A novel dynamic test facility was developed to measure real-world residential trigeneration system performance using a prototype adsorption chiller. The chiller was designed and constructed for this thesis and was driven by waste heat from a commercially available natural gas-fueled 4 kW (electric) CHP engine. A control strategy for the chiller was developed, enabling a 5-day experiment to be run using a thermal load profile based on moderate Maryland summer air conditioning loads and typical single-family domestic hot water demand, with experimental results in agreement with models. In this summer mode, depending on electrical loads, the trigeneration system used up to 36% less fuel than off-grid separate generation and up to 29% less fuel than off-grid CHP without thermally driven cooling. However, compared to on-grid separate generation, the experimental facility used 16% more primary energy. Despite high chiller performance relative to its thermodynamic limit, this result is primarily due to the electrical efficiency of the prime mover being lower than the grid. A residential trigeneration system utilizing a high temperature fuel cell is predicted to save up to 42% primary energy relative to the grid

Modelling of an axial flow compact separator using neural network

A novel design axial flow cyclonic separator called I-SEP was tested with an extensive set of experiments using air-water two phase flow mixture at atmospheric pressure. These experiments provided valuable data on the separation efficiency and pressure drop under different inlet conditions. The performance parameters i.e. Gas Carry Under (GCU) and Liquid Carry Over (LCO) were found to be non-linearly related to the inlet operating conditions. However it was found that resistance on the tangential outlet of the I-SEP affects the GCU and that manipulating the pressure difference between the two outlets and the inlet of the I-SEP through manual control valves, the GCU could be controlled. The separator was also extensively tested and compared with a gravity separator, when they were placed at the exit of a riser, in severe slugging condition frequently encountered in the production pipe work from some oil fields. The tests revealed that the I-SEP has better tendency to suppress severe slugging as compared to the gravity separator. A framework for neural network based on multiple types of input was also developed to model the separation performance of the I-SEP. Mutual Information (one of the key elements of the information theory) was applied to select the appropriate candidate input variables to the neural network framework. This framework was then used to develop a neural network model based on dimensionless input parameters such as pressure coefficient. This neural network model produced satisfactory prediction on unseen experimental data. The inverse function of a trained neural network was combined with a PID controller in a closed loop to control the GCU and LCO at a given set point by predicting the manipulating variable i.e. pressure at the I-SEP outlets. This control scheme was simulated using the test data. Such controller could be used to assist the operator in maintaining and controlling the GCU or LCO at the I-SEP outlets.The work performed during this study also includes the development of a data repository system to store and query the experimental result. An internet based framework is also developed that allows remote access of the experimental data using internet or wireless mobile devices

Corporate decision analysis : an engineering approach

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2006.Includes bibliographical references (p. 313-330).We explore corporate decisions and their solutions under uncertainty using engineering methods. Corporate decisions tend to be complex; they are interdisciplinary and defy programmable solutions. To address these challenges, we take an engineering approach. Our proposition is that as in an engineering system, corporate problems and their potential solutions deal with the behavior of systems. Since systems can be studied with experiments, we use Design of Experiments (DOE) to understand the behavior of systems within which decisions are made and to estimate the consequences of candidate decisions as scenarios. The experiments are a systematically constructed class of gedanken experiments comparable to "what if' studies, but organized to span the entire space of controllable and uncontrollable options. In any experiment, the quality of data is important. Grounded on the work of scholars, we develop a debiasing process for eliciting data. And consistent with our engineering approach, we consider the composite consisting of the organization, their knowledge, data bases, formal and informal procedures as a measurement system. We then use Gage theory from Measurement Systems Analysis (MSA) to analyze the quality of the measuring composite.(cont.) To test this engineering approach to decision analysis, we perform four experiments. The first two are a set of simulations using a company surrogate. Using a progression of experiments, we simulate two major corporate decisions. Simulation data show that there is support for the validity of our decision analysis method. We then perform two in situ experiments: with a manufacturing company and with a technology services company. Findings from these company experiments also support the validity and efficacy of our decision analysis method. The company executives were very satisfied with our findings. Finally, we evaluate our method using method-evaluation criteria. The evaluation suggests that our DOE-based decision analysis method is valid. Unexpectedly every experiment resulted in near-decomposable systems at the scale we formulated our problems. Scaling of corporate decision problems at the appropriate level of abstraction and the resultant properties of their dynamic behavior are identified as areas of future work. This research breaks new ground in corporate decision-analysis as engineering and it furthers DOE and MSA research to a new domain and a new class of problems.by Victor Tang.Ph.D

Produção de biodiesel a partir de microalgas heterotróficas

Orientadores: Telma Teixeira Franco, Lucas Antonius Maria van der WielenTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química e Delft University of Technology.Resumo: Esta tese descreve os resultados da pesquisa de doutorado executada na Universidade de Campinas e na Universidade Técnica de Delft, como parte do program de Doutorado de Dupla Titulação entre as duas universidades. O projeto de pesquisa foi desenvolvido em parceria com a Petrobras S. A., que proveu a maior parte do suporte financeiro assim como suporte técnico, com o objetivo de avaliar o potencial de microalgas heterotróficas para a produção de biocombustíveis. Microalgas têm gerado muito interesse devido a seu inquestionável potencial para produção de biomassa e lipídeos através de fotossíntese. Nas últimas duas décadas, a busca por novas fontes de bio-energia causou um salto na pesquisa científica sobre cultivo de microalgas, o que impulsionou rapidamente o estado da arte. Apesar disso, a produção em larga escala ainda enfrenta obstáculos significativos, que encarecem os custos de produção and impedem que as microalgas se tornem uma fonte viável de bioenergia. A maior limitação das microalgas autotróficas é a necessidade da luz para o crescimento e o inevitável efeito de auto-sombreamento que ocorre com o aumento populacional. Quando a cultura se torna mais densamente povoada, a luz não consegue atingir camadas mais profundas, consequentemente desacelerando o crescimento. Isto limita a biomassa a baixas concentraçoes e, consequentemente, aumenta os volumes de cultivo e a demanda de grande quantidade de energy para separação da água. Apesar de extensa bibliografia sobre microalgas ter sido produzida nas últimas duas décadas, apenas uma pequena fração dos estudos se focaram no potencial heterotrófico desses versáteis microorganismos. Microalgas heterotróficas utilizam carbono orgânico como fonte energética e estrutural, ao invés de absorver carbono da atmosfera. Nesta condição, as microalgas podem crescer sem limitações pela luz e alcançar altas concentrações de biomassa e lipídeos. Porém, o cultivo heterotrófico e autotrófico não são comparáveis, já que o primeiro necessita de uma fonte de carbono orgânica e o segundo absorve carbono atmosférico. A tecnologia e os custos associados a cada um dos processos diferem fortemente. O desenvolvimento do cultivo heterotrófico inicia com a seleção de cepas adequadas para a produção de biocombustíveis e outros produtos de interesse. Este ainda é um campo de pesquisa pouco explorado, já que o cultivo heterotrófico representa apenas uma pequena fração de toda a literatura sobre algas. No capítulo 2, cepas de microalgas foram avaliadas em relação a sua capacidade de crescimento heterotrófico e produção de lipídeos. Após a análise do crescimento e composição celular, potenciais aplicações comerciais foram sugeridas para cada espécie estudada, já que diferentes composições de biomassa e lipídeos podem ser adequadas a diferentes produtos, como combustíveis, alimentos e produtos químicos. Chlorella vulgaris CPCC 90 foi identificada como uma opção adequada para a produção de biodiesel devido ao seu alto conteúdo lipídico e alta produtividade. Uma cepa produtora de ácidos graxas omega-3 poliinsaturados foi identificada e um breve estudo de otimização foi conduzido para aumentar a produção do ácido graxo de alto valor agregado. Após a seleção da cepa mais adequada para a produção de bio-combustíveis, o próximo passo foi o desenvolvimento de um cultivo altamente produtivo. A maior vantagem do cultivo heterotrófico é a possibilidade de alcançar altas concentrações de biomassa e conteúdo lipídico e, consequentemente, maiores produtividades volumétricas. Porém, o acúmulo de lipídeos ocorre quando células de microalgas são expostas a certas condições limitantes, que afetam negativamente o crescimento da biomassa. Desta forma, as condições de cultivo devem ser equilibradas de modo a promover o crescimento da biomassa e aumentar o conteúdo lipídico. Inicialmente, cultivos em batelada alimentada foram avaliados quanto ao acréscimo na concentração de biomassa e teor de lipídeos. A separação do crescimento e acúmulo de lipídeos em dois diferentes estágios permitiu a obtenção de uma cultura altamente concentrada e com elevado teor lipídico. Os lipídeos resultantes foram extraídos da biomassa e convertidos a biodiesel. Os rendimentos totais dos processos de cultivo, extração e reação foram calculados e discutidos (Capítulo 3). Apesar do cultivo em batelada alimentada ter-se mostrado altamente produtivo, o cultivo contínuo tem o potencial de reduzir o tempo ocioso da planta e aumentar a produtividade global e, consequentemente, reduzir custos de produção. Porém, manter cultivos contínuos com altas concentrações celulares não é trivial. O equilíbrio entre a vazão específica e a concentração de biomassa é crucial para a manutenção de alta produtividade. Cultivos em batelada alimentada e contínuos foram comparados quanto às produtividades totais, e o efeito da vazão específica sobre a concentração e produtividade de biomassa foi estudado (Capítulo 4). Cultivos contínuos também permitem um melhor controle da qualidade do produto final. A vazão específica e outros parâmetros, tais como a razão de alimentação de Carbono e Nitrogênio, afetam significativamente a composição de biomassa e o perfil de ácidos graxos dos lipídeos intracelulares. Através da variação destes parâmetros sob regime estacionário, tanto o conteúdo lipídico como a composição de ácidos graxos foi afetadas. Através da modelagem destes efeitos, é possível otimizar o processo, de acordo com o produto lipídico desejado (Capítulo 5). A integração de processos com outros setores da indústria pode, potencialmente, aumentar a viabilidade da produção de biocombustíveis de microalgas. Como o cultivo heterotrófico exige grande disponibilidade de fontes de carbono baratas, a integração com a indústria de cana-de-açúcar é uma opção atraente. Existem também potenciais ganhos para a industria da cana-de-açúcar, já que um terço de suas emissões de carbono resulta da queima de grandes quantidades de diesel de origem fóssil em operações agrícolas e de transporte. A produção de biodiesel de microalgas heterotróficas a partir de substratos da cana-de-açúcar representa uma oportunidade de de substituir a utilização de combustível de origem fóssil e aumentar a renovabilidade das refinarias de cana-de-açúcar. No Capítulo 6, é proposto um modelo de integração em que o melaço da cana-de-açúcar, vapor e eletricidade gerados na biorefinaria de cana-de-açúcar são utilizados para a produção de biodiesel de microalgas. Os resultados das simulações mostraram que a viabilidade do modelo proposto depende ainda da maturação da tecnologia, assim como de fatores externos, tais como o preço do petróleo e políticas e incentivos favoráveis a tecnologias sustentáveis. Esta tese representa uma contribuição ao estado da arte do desenvolvimento de biocombustíveis e outros produtos a partir de microalgas heterotróficas, especificamente focado no uso de culturas com alta densidade celular. Oferece ainda uma visão geral de alguns dos desafios que devem ser superados e das mais importantes variáveis na obtenção de um processo altamente produtivo e economicamente viávelAbstract: This thesis summarizes the results of a doctoral research executed in the State University of Campinas and in the Technical University of Delft as part of the PhD Dual Degree Program between the two universities. The research project was designed in partnership with Petrobras S. A. (Brazilian Petroleum Corporation), which provided most of the financial support as well as technical cooperation, with the goal of evaluating the potential of heterotrophic microalgae for biofuels production. Microalgae have generated a lot of interest due to their undoubted potential for the production of biomass and lipids through photosynthesis. In the last two decades, the search for new bio-energy feedstocks created a boom in scientific research on microalgae cultivation, which has improved the state of art of the technology at a rapid pace. However, large scale production still faces significant bottlenecks, which increase manufacturing costs and prevent microalgae from becoming a feasible bioenergy source. The main limitation related to autotrophic microalgae is the need of light for growth and the inevitable self-shading effect with the increase in cell population. As the culture becomes more densely populated, the light cannot reach deeper layers, thus slowing down the growth. This limits biomass to low concentrations and, consequently, increases cultivation volumes and demands high amounts of energy for water separation. Although extensive research about microalgae has been produced in the last two decades, only a small fraction of the studies aimed at the heterotrophic potential of these versatile microorganisms. Heterotrophic microalgae utilize organic carbon as energy source and building blocks rather than absorbing carbon from the atmosphere. In such circumstances, they can grow without light limitations and achieve high biomass and lipid concentrations. Nevertheless, heterotrophic and autotrophic cultivations are hardly comparable, since the former requires an organic carbon feedstock and the latter absorbs carbon from the atmosphere. The costs associated with each process are remarkably different, as well as the technology involved. The development of the heterotrophic cultivation process starts with the selection of suitable strains for the production of biofuels and other products. This is still a poorly explored field of research, as heterotrophic cultivation represents only a small fraction of all literature about algae. In Chapter 2, strains of microalgae were evaluated on their capacity for heterotrophic growth and lipid production. After the analysis of growth characteristics and cell composition, potential commercial applications for each strain were suggested, as different biomass and lipid compositions may be suitable for different final products, from biofuels to food and chemicals. Chlorella vulgaris CPCC 90 was identified as a suitable option for biodiesel production due to its high lipid content and productivity. One polyunsaturated omega-3 fatty acid producing strain was identified and a short optimization study was performed in order to enhance the production of the high value added fatty acid. After selection of the most suitable strain for biofuels production, the next step was the development of a highly productive cultivation process. The greatest advantage of heterotrophic cultivation is the possibility of reaching high biomass concentrations and lipid contents and, consequently, high volumetric productivities. However, lipid accumulation occurs when microalgae cells are exposed to certain limiting conditions, which negatively affect biomass growth. Therefore, cultivation conditions must be balanced in order to promote biomass growth and increase lipid content. After identification of the most suitable strain for biofuels production, fed-batch strategies were evaluated as means of increasing biomass concentration and lipid content. Decoupling biomass growth and lipid accumulation in two different stages allowed the production of a highly concentrated culture with increased lipid content. The resulting lipids were extracted from the produced biomass and converted into biodiesel. The overall yields of cultivation, extraction and reaction processes were calculated and discussed (Chapter 3). Although fed-batch cultivation proved itself highly productive, continuous production can potentially reduce downtime operations and increase global productivity, consequently reducing production costs. Operating continuous cultivation at high cell concentrations such as in the fed-batch process, however, is not trivial. The balance between dilution rate and biomass concentration is crucial in order to maintain high productivities. Fed-batch and continuous cultures were compared in terms of overall productivities and the effect of dilution rates was evaluated over biomass concentration and productivity (Chapter 4). Continuous cultivation also allows a better control of the final product quality. Growth rates and other parameters, such as Carbon to Nitrogen feeding ratio, significantly affect biomass composition and the fatty acid profile of intracellular lipids. By varying these parameters in steady state cultivation, lipid content and fatty acid composition were affected. By modelling these effects, it is possible to optimize the process according to the desired lipid-based product (Chapter 5). Process integration with other industry sectors may potentially increase the feasibility of microalgae biofuels production. Since heterotrophic cultivation demands a large availability of cheap carbon feedstocks, integration with the sugarcane industry is an attractive option. There are potential gains for the sugarcane industry as well, since one third of their carbon emissions result from burning large quantities of fossil-based diesel in crops and transportation operations. The production of heterotrophic microalgae biodiesel from sugarcane feedstocks offers the possibility of replacing the fossil fuel utilization and increasing the overall renewability of the sugarcane biorefinery. In Chapter 6, an integration model is proposed in which molasses, steam and electricity of sugarcane biorefinery are used for the production of microalgae biodiesel. Simulation results showed that the feasibility of the proposed model depends on the further development of the technology, as well as on external factors, such as petroleum prices and sustainability-driven policies and incentives. This thesis represents a contribution to the state of the art on the development of biofuels and other products from heterotrophic microalgae, specifically focused on the use of high cell density cultures. It offers an overview of some of the challenges that need to be overcome and provide insights on the most important variables for achieving a highly productive and economically feasible processDoutoradoDesenvolvimento de Processos QuímicosDoutor em Engenharia Químic

Efficient buffer design algorithms for production line profit maximization

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 447-465).A production line is a manufacturing system where machines are connected in series and separated by buffers. The inclusion of buffers increases the average production rate of the line by limiting the propagation of disruptions, but at the cost of additional capital investment, floor space of the line, and inventory. Production lines are also a special case of assembly/disassembly systems as well as closed-loop systems. This thesis makes contributions to production system profit maximization. The profit of a production line is the revenue associated with the production rate minus the buffer space cost and average inventory holding cost. We assume that machines have already been chosen and therefore our only decision variables are the buffer sizes and the loop population. The difficulties of the research come from evaluation and optimization. We improve evaluation of loop systems. The optimization problem is hard since both the objective function and the constraints are nonlinear. Our optimization problem, where we consider the nonlinear production rate constraint and average inventory cost, is new. We present an accurate, fast, and reliable algorithm for maximizing profits through buffer space optimization for production lines, and extend the algorithm to closed-loop systems and production lines with an additional maximum part waiting time constraint. A nonlinear programming approach is adopted to solve the optimization problem. Two necessary modifications are proposed to improve the accuracy of the existing loop evaluation method before optimization of loops is studied. An analytical formulation of the part waiting time distribution is developed for two-machine one-buffer lines. It is used in the profit maximization for production lines with both the production rate constraint and the maximum part waiting time constraint. Numerical experiments are provided to show the accuracy and efficiency of the proposed algorithms. Finally, a segmentation method and an additive property of production line optimization are studied. They enable us to optimize very long lines rapidly and accurately.by Chuan Shi.Ph.D

Design Optimization and Combustion Simulation of Two Gaseous and Liquid-Fired Combustors

The growing effect of combustion pollutant emission on the environment and increasing petroleum prices are driving development of design methodologies for clean and efficient industrial combustion technologies. The design optimization methodology employs numerical algorithms to find the optimal solution of a design problem by converting it into a multivariate minimization problem. This is done by defining a vector of design parameters that specifies the design configuration, and an objective function that quantifies the performance of the design, usually so the optimal design outcome minimizes the objective function. A numerical algorithm is then employed to find the design parameters that minimize the objective function; these parameters thus specify the optimal design. However this technique is used in several other fields of research, its application to industrial combustion is fairly new. In the present study, a statistical optimization method called response surface methodology is connected to a CFD solver to find the highest combustion efficiency by changing the inlet air swirl number and burner quarl angle in a furnace. OpenFOAM is used to model the steady-state combustion of natural gas in the 300 KW BERL combustor. The main barrier to applying optimization in the design of industrial combustion equipment is the substantial computational effort needed to carry out the CFD simulation every time the objective function needs to be evaluated. This is intensified by the stiffness of the coupled governing partial differential equations, which can cause instability and divergent simulations. The present study addresses both of these issues by initializing the flow field for each objective function evaluation with the numerical results of the previously converged point. This modification dramatically reduced computation time. The combustion of diesel spray in the GenTex 50M process heater is investigated in the next part of this thesis. Experimental and numerical studies were carried out for both the cold spray and the diesel combustion where the numerical results satisfactorily predicted the observations. The simulation results show that, when carrying out a parametric design of a liquid fuel-fired combustor it is necessary to consider the effect of design parameters on the spray aerodynamic characteristics and size distribution, the air/spray interactions, and the size of the recirculation zones

Annual Report of the University, 1994-1995, Volumes 1-4

DEMONSTRATING THE STRENGTH OF DIVERSITY A walk around the UNM campus as students change classes demonstrates UNM\\u27s commitment to diversity. Students and professors from a variety of ethnic backgrounds crowd the sidewalks and fill classrooms. Over the past year UNM moved forward with existing and new programs to interest more minority students, faculty and staff in the University and to aid in their success while here. Hispanic Outlook in Higher Education recently recognized the University\\u27s endeavors, ranking UNM as one of the best colleges in the nation at graduating Hispanic students. Provost Mary Sue Coleman says diversity contributes to a stimulating environment where faculty and students have different points of view and experiences. The campus becomes a more intellectually alive place, she says. The efforts to build a diverse campus go hand in hand with the University\\u27s goals of achieving academic excellence and attracting the best and brightest. MINORITY ENROLLMENT In the fall of 1994 a total of 32 percent of the student body came from underrepresented groups. The UNM School of Law had the largest number of Native Americans enrolled in any law school in the country