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(1 - 13 of 13)
- Title
- A Framework for Lean Transformation in Developing Countries: The Case of Saudi Arabian Industry.
- Creator
-
Andejany, Murad, Elshennawy, Ahmad, Rabelo, Luis, Lee, Gene, Darwish, Mohammed, University of Central Florida
- Abstract / Description
-
Lean is a dynamic, knowledge-driven, and customer focused philosophy that continuously eradicates waste and generates value, with a goal to improve a company's productivity, efficiency, and quality. Successful implementation of lean does not only offer cost reduction and improved quality and productivity, but also provides efficient guidance for organizations to attain significant and continued growth. Although its adoption by companies has proven successful in developed countries, there is...
Show moreLean is a dynamic, knowledge-driven, and customer focused philosophy that continuously eradicates waste and generates value, with a goal to improve a company's productivity, efficiency, and quality. Successful implementation of lean does not only offer cost reduction and improved quality and productivity, but also provides efficient guidance for organizations to attain significant and continued growth. Although its adoption by companies has proven successful in developed countries, there is no sufficient evidence of its successful implementation in developing countries such as Saudi Arabia. A review of the literature indicates that there is a need to study lean transformation in developing countries as part of a comprehensive approach to their survival in the global economy. The purpose of this research is to develop a framework for a successful lean transformation in developing countries. The framework was developed by conducting a thorough literature review analysis and interviewing key personnel in ten local and eight multinational Saudi Arabian companies. The framework reacted to general data about lean transformation in developing countries, assessed a lean transformation level, and constructed the Interpretive Structure Molding (ISM) for barriers to achieve a successful lean transformation. Expert opinions were used for validation of the main components of this study, which are assessment, barriers, ISM and framework. Similar to the literature findings which indicated that the level of successful lean transformation in developing countries is low, the assessment revealed that the lean transformation level in local companies in Saudi Arabia is between 30% and 40%, and in multinational companies the level is between 50% and 60%. Both local and multinational companies in the case of Saudi Arabian industry considered lack of suppliers' involvement, lack of cooperation from suppliers, lack of good quality suppliers, and slow response to market due to demand fluctuations as the root barriers that need to be addressed at the primary stages of lean transformation. The resulting framework provides clear phases with an estimated timeline for each phase, from the foundation phase to the excellence level phase. In addition, it involves executive leaders and a cross-functional team to mentor and assess the transformation after each phase. The framework comprises several methods and tools that can be considered critical success factors for lean transformation, which will enable companies in developing countries to move toward achieving a successful lean transformation and sustainability, as well as reaching higher and persistent levels of growth.
Show less - Date Issued
- 2017
- Identifier
- CFE0006713, ucf:51892
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006713
- Title
- A Framework for Quantifying Sustainability of Lean Implementation in Healthcare Organizations.
- Creator
-
Bahaitham, Haitham, Elshennawy, Ahmad, Mollaghasemi, Mansooreh, Lee, Gene, Uddin, Nizam, Furterer, Sandra, University of Central Florida
- Abstract / Description
-
Due to the remarkable positive effect of lean adoption in various firms in the manufacturing sector, it has been adopted by several organizations within the healthcare industry. Although the rate of adopting lean by hospitals in the developed countries is slower than it should be, it proved to be effective in helping healthcare organizations maintain or even improve their quality of care while containing their related costs. However, such adoption did not take place until the beginning of the...
Show moreDue to the remarkable positive effect of lean adoption in various firms in the manufacturing sector, it has been adopted by several organizations within the healthcare industry. Although the rate of adopting lean by hospitals in the developed countries is slower than it should be, it proved to be effective in helping healthcare organizations maintain or even improve their quality of care while containing their related costs. However, such adoption did not take place until the beginning of the new millennium. And with such adoption, it has been accompanied with major challenges related to proper lean implementation, sustainability of achieved levels of performance, and staff engagement in infinite cycles of continuous improvement towards perfection. Thus, the purpose of this study is to develop a framework that helps healthcare organizations quantify their experience with lean. Such quantification is obtained by measuring the agreement level of hospital staff members about the degree of adopting two sets of critical factors of successful lean implementation within their hospital. These two sets of factors are classified as process factors and organizational factors. The proposed framework has been validated by determining the sustainability level of lean implementation within one of U.S. hospitals in the State of Florida. The developed framework provides a balanced assessment of both process and organizational factors essential for achieving sustainable levels of lean implementation. In order to accommodate for the observed variation in lean adoption in hospitals, individual hospital departments are considered the (")analysis units(") of the developed framework. In order to quantify the implementation status of lean within a hospital department, a survey-based lean sustainability assessment tool has been developed based on the defined sets of factors. The sustainability level of lean implementation of a hospital can be obtained by combining various responses of its surveyed departments. The developed framework is the first that addresses both process and organizational factors of sustainable lean implementation in a balanced manner while fulfilling the assessment needs of all healthcare organizations regardless of their current level of lean adoption. In addition, utilizing the framework within a hospital enhances employee involvement and respect for employee which are essential for sustainable lean implementation. Finally, the developed framework provides healthcare supervising authorities (i.e. ministries of health or corporate offices of hospitals' groups) a macro-level benchmarking view regarding the progress of their hospitals towards implementing sustainable levels of lean.
Show less - Date Issued
- 2011
- Identifier
- CFE0004086, ucf:49140
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004086
- Title
- The Challenges and Barriers Facing Successful Lean Implementation in the Qatari Manufacturing Organizations.
- Creator
-
Alyousef, Abdulwahab, Elshennawy, Ahmad, Rabelo, Luis, Lee, Gene, University of Central Florida
- Abstract / Description
-
The success of Toyota, the inventor of Lean Systems has drawn the attention of academics, researchers, and executives in the last decades. However, existing lean research is largely focused on developed economies in Europe, the Americas, and in Southeast Asia with little focus on the Arab world in general and Qatar specifically. There has been an emergence of manufacturing organizations and Small and Medium- sized Enterprises (SME) in Qatar recently which was the focus of this research....
Show moreThe success of Toyota, the inventor of Lean Systems has drawn the attention of academics, researchers, and executives in the last decades. However, existing lean research is largely focused on developed economies in Europe, the Americas, and in Southeast Asia with little focus on the Arab world in general and Qatar specifically. There has been an emergence of manufacturing organizations and Small and Medium- sized Enterprises (SME) in Qatar recently which was the focus of this research. Despite the many attempts to implement lean in organizations, there have been a large number of failed attempts. This research aims to study the Qatari Manufacturing Organizations attempts in implementing lean. The main goal of the thesis is to shed a light on the current state of awareness of lean in Qatari Manufacturing Industry and SME and the potential barriers and challenges that prevent the successful adoption of lean. In order to do so, an online survey was designed through the SurveyMonkey tool and organizations were asked to participate.Numerical and statistical results from the survey are discussed along with Pareto charts and two hypothesis tests. The finding indicates that there is no difference between ISO certified and Non-ISO certified organizations in lean implementation. Further, it is understood that most of the manufacturing organizations in Qatar have some level of awareness of lean concepts/tools and practices. The results also show that organizations are not implementing lean concepts and are not using quality management practices effectively. The main obstacle that manufacturing organizations in Qatar face when implementing lean is (")Lack of Employee Engagement(") and (")Unsupportive Organization Culture("). However, it is noted that the research has some limitations such as having most participating organizations in the survey from specific sectors.
Show less - Date Issued
- 2019
- Identifier
- CFE0007778, ucf:52368
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007778
- Title
- MASS CUSTOMIZATION STRATEGIES AND THEIR RELATIONSHIP TO LEAN PRODUCTION IN THE HOMEBUILDING INDUSTRY.
- Creator
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Nahmens, Isabelina, Mullens, Michael, University of Central Florida
- Abstract / Description
-
Current housing trends point to an increasing interest from homebuyers to demand houses that reflect their personal and unique styles, and which are individually configured according to these needs (NAHB, 2004). These homebuyers in turn are unwilling to settle for standard models that sacrifice what they really want in a home. At the same time this creates pressure on builders who are reluctant to sacrifice production efficiencies by deviating from standard models. Such customization desired...
Show moreCurrent housing trends point to an increasing interest from homebuyers to demand houses that reflect their personal and unique styles, and which are individually configured according to these needs (NAHB, 2004). These homebuyers in turn are unwilling to settle for standard models that sacrifice what they really want in a home. At the same time this creates pressure on builders who are reluctant to sacrifice production efficiencies by deviating from standard models. Such customization desired by demanding customers can disrupt the entire estimating, production, delivery and management process, making it even more difficult to manage homebuilding efficiently and effectively. The question faced by homebuilders in this conditions is, how to manage this trade-off and deliver exactly what homebuyers want, at reasonable prices and lead times with minimal disruptions in efficiencies. Mass Customization (MC) is an emerging production paradigm that seeks to manage the trade-offs between product variety and mass efficiency, while fulfilling individual customer requirements. The general purpose of this research is to improve the effectiveness and efficiency of housing production through the implementation of mass customization strategies. More specifically, this research focuses on the study of the production system through the application of lean production principles, as an approach to enable mass customization. This study first characterizes how much product choice is currently being offered by U.S. homebuilders and what is the impact of customization on production efficiency; and then focuses on the evaluation of the relationships between mass customization and lean production principles. Results revealed that homebuilders offering increased product choice are likely to suffer poorer labor productivity, greater inventory, higher production costs, more quality issues, less satisfied homebuyers, and lower space efficiency. In general, operational performance deteriorated with an increase in product choice. Therefore, industrialized housing manufacturers have not reached the ideal of mass customization and are paying a price for offering more choices to their customers. Homebuilders could mitigate these challenges by using lean concepts. In general, case studies showed that product choice does not necessarily make the implementation of lean concepts more difficult. Some lean concepts, like workload balancing and standardizing tasks, clearly facilitated the handling of product choice. Other lean concepts, like creating a continuous process flow, can be made to work well, even with increased choice. Case study results suggested that good concepts for lean (e.g., efficient continuous flow, effective pull system, workload leveling, defect-free processes, standard tasks, good visual controls, and reliable technology) were also good concepts for (or easily accommodated) handling a range of product choice.
Show less - Date Issued
- 2007
- Identifier
- CFE0001778, ucf:47277
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001778
- Title
- A Framework for Measuring and Analyzing Customer Satisfaction at Computer Service Company using Lean Six Sigma.
- Creator
-
Abboodi, Mohammed, Elshennawy, Ahmad, Rabelo, Luis, Xanthopoulos, Petros, University of Central Florida
- Abstract / Description
-
The computer service industry has been expanding dramatically due to the increase in the number of computing machineries in the last two decades. The entrance of large size companies in the market and the release of online tools that have the ability for diagnosing and troubleshooting hardware and software issues have boosted the competition. In the meantime, many of the small and medium size companies find themselves unable to keep their customers satisfied since their competitors provide...
Show moreThe computer service industry has been expanding dramatically due to the increase in the number of computing machineries in the last two decades. The entrance of large size companies in the market and the release of online tools that have the ability for diagnosing and troubleshooting hardware and software issues have boosted the competition. In the meantime, many of the small and medium size companies find themselves unable to keep their customers satisfied since their competitors provide high quality service with lower cost. The lack of a good measurement system to assess and analyze the satisfaction level with the provided service is the fundamental cause of customer decline. The aim of this study is to construct a robust framework to measure customer satisfaction and highlight the root causes of dissatisfaction in the computer service sector. This framework brings together the key aspects of Six Sigma and SERVQUAL instruments into a structured approach to measure and analyze customer satisfaction with computer services. It deploys the DMAIC problem solving methodology along with the SERVQUAL model, which contributes service dimensions and the Gap Analyze technique. Literature review indicates there have not been enough studies conducted to integrate Lean Six Sigma with SERVQUAL. To explore the effectiveness of the current framework, a computer service company has been selected. The satisfaction levels are calculated and the root causes of dissatisfaction have been identified. With a low overall customer satisfaction level, the company did not fulfill their customer requirements due to five major causes. Eliminating those causes will boost customer satisfaction, reduce the cost of acquiring new customers and improve the company performance in general.
Show less - Date Issued
- 2014
- Identifier
- CFE0005117, ucf:50751
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005117
- Title
- A FRAMEWORK ROADMAP FOR IMPLEMENTING LEAN SIX SIGMA IN LOCAL GOVERNMENTAL ENTITIES.
- Creator
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Furterer, Sandra L., Elshennawy, Ahmad K., University of Central Florida
- Abstract / Description
-
Lean Six Sigma is an approach focused on improving quality, reducing variation and eliminating waste in an organization. The concept of combining the principles and tools of Lean Enterprise and Six Sigma has occurred in the literature over the last several years. The majority of Lean Six Sigma applications have been in private industry, focusing mostly on manufacturing applications. The literature has not provided a framework for implementing Lean Six Sigma programs applied to local...
Show moreLean Six Sigma is an approach focused on improving quality, reducing variation and eliminating waste in an organization. The concept of combining the principles and tools of Lean Enterprise and Six Sigma has occurred in the literature over the last several years. The majority of Lean Six Sigma applications have been in private industry, focusing mostly on manufacturing applications. The literature has not provided a framework for implementing Lean Six Sigma programs applied to local government. This research provides a framework roadmap for implementing Lean Six Sigma in local government. The Service Improvement for Transaction-based Entities Lean Six Sigma Framework Roadmap (SITE MAP) identifies the activities, principles, tools, and important component factors to implement Lean Six Sigma. The framework provides a synergistic approach to integrating the concepts and tools of Lean Enterprise and Six Sigma using the DMAIC (Define-Measure-Analyze-Improve-Control) problem solving approach. A case study was used to validate the framework. Lean Six Sigma was successfully applied in a 7,000-citizen municipality to reduce the cycle time of the financial administrative processes in the Finance Department of the city government.
Show less - Date Issued
- 2004
- Identifier
- CFE0000021, ucf:46067
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000021
- Title
- A Framework for the Development of a Model for Successful, Sustained Lean Implementation and Improvement.
- Creator
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Sisson, Julie, Elshennawy, Ahmad, Rabelo, Luis, Xanthopoulos, Petros, Porter, Robert, University of Central Florida
- Abstract / Description
-
Lean is a business philosophy focused on shortening lead times by removing waste and concentrating on value-added processes. When implemented successfully, it not only allows for cost reduction while improving quality, but it can also position a company to achieve tremendous growth. The problem is that though many companies are attempting to implement lean, it is estimated that only 2-3% are achieving the desired level of success. The purpose of this research is to identify the key...
Show moreLean is a business philosophy focused on shortening lead times by removing waste and concentrating on value-added processes. When implemented successfully, it not only allows for cost reduction while improving quality, but it can also position a company to achieve tremendous growth. The problem is that though many companies are attempting to implement lean, it is estimated that only 2-3% are achieving the desired level of success. The purpose of this research is to identify the key interrelated components of successful lean transformation. To this end, a thorough literature review was conducted and the findings indicate six key constructs that can act as enablers or inhibitors to implementing and sustaining lean. A theoretical framework was developed that integrates these constructs and develops research propositions for each. A multiple-case study analysis then was used to test the framework on four companies that have achieved successful, sustained results from their lean implementation in order to validate the model. The resulting model provides companies who are planning to implement lean with tangible actions that can be taken to make their lean transformations more successful.
Show less - Date Issued
- 2014
- Identifier
- CFE0005262, ucf:50608
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005262
- Title
- A TAXONOMY OF LEAN SIX SIGMA SUCCESS FACTORSFOR SERVICE ORGANIZATIONS.
- Creator
-
Hajikordestani, Reza, Geiger, Christopher, University of Central Florida
- Abstract / Description
-
ABSTRACT Six Sigma is a business improvement strategy that aims to improve process performance using a structured methodology that identifies and removes the causes of defects in manufacturing and business processes, while implementing the lean concepts attempts to remove wasteful activities from those processes. In practice, the Six Sigma strategy and the Lean philosophy are combined and often viewed as one integrated philosophy, where the philosophy of Lean Six Sigma simultaneously removes...
Show moreABSTRACT Six Sigma is a business improvement strategy that aims to improve process performance using a structured methodology that identifies and removes the causes of defects in manufacturing and business processes, while implementing the lean concepts attempts to remove wasteful activities from those processes. In practice, the Six Sigma strategy and the Lean philosophy are combined and often viewed as one integrated philosophy, where the philosophy of Lean Six Sigma simultaneously removes wasteful activities from a process and reduces the variability of that process. This thesis research reviews the concepts and implementation of Lean thinking, Six Sigma strategy, and the integrated concept of Lean Six Sigma, with emphasis in service organizations. Most importantly, this thesis summarizes the critical success factors for implementing Lean Six Sigma within a service business environment and categorizes them within a proposed multi-level taxonomy that can be used by service business units and service providers to improve the success of Lean Six Sigma implementation.
Show less - Date Issued
- 2010
- Identifier
- CFE0003526, ucf:48966
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003526
- Title
- Phosphatidic Acid Increases Lean Body Tissue and Strength In Resistance Trained Men.
- Creator
-
Williams, David, Hoffman, Jay, Fragala, Maren, Stout, Jeffrey, University of Central Florida
- Abstract / Description
-
ABSTRACTPhosphatidic Acid (PA) is a natural phospholipid compound derived from lecithin which is commonly found in egg yolk, grains, fish, soybeans, peanuts and yeast. It has been suggested that PA is involved in several intracellular processes associated with muscle hypertrophy. Specifically, PA has been reported to activate protein synthesis through the mammalian target of rapamycin (mTOR) signaling pathway and thereby may enhance the anabolic effects of resistance training. To our...
Show moreABSTRACTPhosphatidic Acid (PA) is a natural phospholipid compound derived from lecithin which is commonly found in egg yolk, grains, fish, soybeans, peanuts and yeast. It has been suggested that PA is involved in several intracellular processes associated with muscle hypertrophy. Specifically, PA has been reported to activate protein synthesis through the mammalian target of rapamycin (mTOR) signaling pathway and thereby may enhance the anabolic effects of resistance training. To our knowledge, no one has examined the effect of PA supplementation in humans while undergoing a progressive resistance training program. To examine the effect of PA supplementation on lean soft tissue mass (LM) and strength after 8 weeks of resistance training.Fourteen resistance-trained men (mean (&)#177; SD; age 22.7 (&)#177; 3.3 yrs; height: 1.78 (&)#177; 0.10m; weight: 89.3 (&)#177; 16.3 kg) volunteered to participate in this randomized, double-blind, placebo-controlled, repeated measures study. The participants were assigned to a PA group (750mg/day; Mediator(&)#174;, ChemiNutra, MN, n=7) or placebo group (PL; rice flower; n=7), delivered in capsule form that was identical in size, shape and color. Participants were tested for 1RM strength in the bench press (BP) and squat (SQ) exercise. LM was measured using dual-energy X-ray absorptiometry. After base line testing, the participants began supplementing PA or PLfor 8 weeks during a progressive resistance training program intended for muscular hypertrophy. Data was analyzed using magnitude-based inferences on mean changes for BP, SQ and LM. Furthermore, the magnitudes of the inter-relationships between changes in total training volume and LM were interpreted using Pearson correlation coefficients, which had uncertainty (90% confidence limits) of approximately +0.25.In the PA group, the relationship between changes in training volume and LM was large(r=0.69, +0.27; 90%CL), however, in the PL group the relationship was small (r=0.21, +0.44; 90%CL). PA supplementation was determined to be likely beneficial at improving SQ and LM over PL by 26% and 64%, respectively. The strong relationship between changes in total training volume and LM in the PA group suggest that greater training volume most likely lead to the greater changes in LM, however, no such relationship was found with PL group. For the BP data, the PA group resulted in a 42% greater increase in strength over PL, although the effect was considered unclear. While more research is needed to elucidate mechanism of action; the current findings suggest that in experienced resistance trained men supplementing 750mg PA per day for 8 weeks may likely benefit greater changes in muscle mass and strength compared with resistance training only. ?
Show less - Date Issued
- 2012
- Identifier
- CFE0004641, ucf:49897
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004641
- Title
- Experimental Investigation of Advanced Ignition Systems for High Efficiency Combustion.
- Creator
-
Almansour, Bader, Vasu Sumathi, Subith, Kapat, Jayanta, Kassab, Alain, Sarathy, S.Mani, University of Central Florida
- Abstract / Description
-
Consumption of fossil and bio-derived fuels is growing due to energy demands associated with increase in population and standard of living across the globe. Power generation and transportation sectors are the primary two sources of fuel consumption, which have raised the demand for crude oil and led to serious environmental pollution issues. This demand for energy forced various government agencies to strengthen the allowable exhaust pollutant concentration limits. Recently, CO, CO2,...
Show moreConsumption of fossil and bio-derived fuels is growing due to energy demands associated with increase in population and standard of living across the globe. Power generation and transportation sectors are the primary two sources of fuel consumption, which have raised the demand for crude oil and led to serious environmental pollution issues. This demand for energy forced various government agencies to strengthen the allowable exhaust pollutant concentration limits. Recently, CO, CO2, particulate matter, and nitrogen oxides (NOx) emission restrictions have become more stringent to the extent that engines must operate at higher energy densities and efficiencies. Towards this goal, this doctoral study focused on evaluating advanced ignition systems and testing new biofuels for automotive combustion applications. First, a natural gas lean combustion mode was assessed by using advance ignition systems to provide higher brake power while maintaining the exhaust limits. A rigorous combustion data analysis was performed to identify the main reasons leading to improved performance in the case of prechamber equipped laser ignition. An overall efficiency improvement of 2.1% points was observed, compared to spark ignition, which in turn leads to save 633 PJ per year. In the second part of this dissertation, a spherical chamber was designed and validated to measure the laminar burning velocity (LBV) of a promising biofuel: 2,4-Dimethyl-3-pentanone, (DIPK), for homogenous charge compression ignition engines. LBV measurements were carried out with various diluent species (N2, Ar, and He) in order to provide several data points for development and validation of DIPK chemical kinetic mechanisms. It has been found that DIPK does not only have higher temperature and pressure sensitivities (compared to iso-octane), but additionally enabled a faster laminar burning velocity which leads to higher rate of heat release in reciprocating engines.
Show less - Date Issued
- 2018
- Identifier
- CFE0007387, ucf:52062
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007387
- Title
- Catalytically Enhanced Heterogeneous Combustion of methane.
- Creator
-
Terracciano, Anthony, Orlovskaya, Nina, Vasu Sumathi, Subith, Chow, Louis, Kassab, Alain, University of Central Florida
- Abstract / Description
-
Heterogeneous combustion is an advanced internal combustion technique, which enables heat recuperation within the flame by utilizing a highly porous ceramic media as a regenerator. Heat released within the gas phase convectively transfers to the solid media. This heat within the solid media then travels towards the inlet, enabling reactant preheating. Such heat redistribution enables stable burning of both ultra-lean fuel/air mixtures, forming a more diffuse flame through the combustion...
Show moreHeterogeneous combustion is an advanced internal combustion technique, which enables heat recuperation within the flame by utilizing a highly porous ceramic media as a regenerator. Heat released within the gas phase convectively transfers to the solid media. This heat within the solid media then travels towards the inlet, enabling reactant preheating. Such heat redistribution enables stable burning of both ultra-lean fuel/air mixtures, forming a more diffuse flame through the combustion chamber, and results in reduced pollutant formation. To further enhance heterogeneous combustion, the ceramic media can be coated with catalytically active materials, which facilitates surface based chemical reactions that could occur in parallel with gas phase reactions.Within this work, a flow stabilized heterogeneous combustor was designed and developed consisting of a reactant delivery nozzle, combustion chamber, and external instrumentation. The reactant delivery nozzle enables the combustor to operate on mixtures of air, liquid fuel, and gaseous fuel. Although this combustor has high fuel flexibility, only gaseous methane was used within the presented experiments. Within the reactant delivery nozzle, reactants flow through a tube mixer, and a homogeneous gaseous mixture is delivered to the combustion chamber. ?-alumina (?-Al2O3), magnesia stabilized zirconia (MgO-ZrO2), or silicon carbide (SiC) was used as the material for the porous media. Measurement techniques which were incorporated in the combustor include an array of axially mounted thermocouples, an external microphone, an external CCD camera, and a gas chromatograph with thermal conductivity detector which enable temperature measurements, acoustic spectroscopy, characterization of thermal radiative emissions, and composition analysis of exhaust gasses, respectively. Before evaluation of the various solid media in the combustion chamber the substrates and catalysts were characterized using X-ray diffraction, X-ray fluorescence, scanning electron microscopy and energy dispersive spectroscopy. MgO-ZrO2 porous media was found to outperform both ?-Al2O3 and SiC matrices, as it was established that higher temperatures for a given equivalence ratio were achieved when the flame was contained within a MgO-ZrO2 matrix. This was explained by the presence of oxygen vacancies within the MgO doped ZrO2 fluorite lattice which facilitated catalytic reactions. Several catalyst compositions were evaluated to promote combustion within a MgO-ZrO2 matrix even further.Catalysts such as: Pd enhanced WC, ZrB2, Ce0.80Gd0.20O1.90, LaCoO3, La0.80Ca0.20CoO3, La0.75Sr0.25Fe0.95Ru0.05O3, and La0.75Sr0.25Cr0.95Ru0.05O3; were evaluated under lean fuel/air mixtures. LaCoO3 outperformed all other catalysts, by enabling the highest temperatures within the combustion chamber, followed by Ce0.80Gd0.20O1.90. Both LaCoO3 and Ce0.80Gd0.20O1.90 enabled a flame to exist at ?=0.45(&)#177;0.02, however LaCoO3 caused the flame to be much more stable. Furthermore, it was discovered that the coating of MgO-ZrO2 with LaCoO3 significantly enhanced the total emissive power of the combustion chamber. In this work as acoustic spectroscopy was used to characterize heterogeneous combustion for the first time. It was found that there is a dependence of acoustic emission n the equivalence ratio and flame position regardless of media and catalyst combination. It was also found that when different catalysts were used, the acoustic tones produced during combustion at fixed reactant flow rates were distinct
Show less - Date Issued
- 2016
- Identifier
- CFE0006508, ucf:51364
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006508
- Title
- MEASURING THE EFFECT OF ERRATIC DEMANDON SIMULATED MULTI-CHANNEL MANUFACTURINGSYSTEM PERFORMANCE.
- Creator
-
Kohan, Nancy, Kulonda, Dennis, University of Central Florida
- Abstract / Description
-
ABSTRACT To handle uncertainties and variabilities in production demands, many manufacturing companies have adopted different strategies, such as varying quoted lead time, rejecting orders, increasing stock or inventory levels, and implementing volume flexibility. Make-to-stock (MTS) systems are designed to offer zero lead time by providing an inventory buffer for the organizations, but they are costly and involve risks such as obsolescence and wasted expenditures. The main concern of make-to...
Show moreABSTRACT To handle uncertainties and variabilities in production demands, many manufacturing companies have adopted different strategies, such as varying quoted lead time, rejecting orders, increasing stock or inventory levels, and implementing volume flexibility. Make-to-stock (MTS) systems are designed to offer zero lead time by providing an inventory buffer for the organizations, but they are costly and involve risks such as obsolescence and wasted expenditures. The main concern of make-to-order (MTO) systems is eliminating inventories and reducing the non-value-added processes and wastes; however, these systems are based on the assumption that the manufacturing environments and customers' demand are deterministic. Research shows that in MTO systems variability and uncertainty in the demand levels causes instability in the production flow, resulting in congestion in the production flow, long lead times, and low throughput. Neither strategy is wholly satisfactory. A new alternative approach, multi-channel manufacturing (MCM) systems are designed to manage uncertainties and variabilities in demands by first focusing on customers' response time. The products are divided into different product families, each with its own manufacturing stream or sub-factory. MCM also allocates the production capacity needed in each sub-factory to produce each product family. In this research, the performance of an MCM system is studied by implementing MCM in a real case scenario from textile industry modeled via discrete event simulation. MTS and MTO systems are implemented for the same case scenario and the results are studied and compared. The variables of interest for this research are the throughput of products, the level of on-time deliveries, and the inventory level. The results conducted from the simulation experiments favor the simulated MCM system for all mentioned criteria. Further research activities, such as applying MCM to different manufacturing contexts, is highly recommended.
Show less - Date Issued
- 2004
- Identifier
- CFE0000240, ucf:46275
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000240
- Title
- DESIGN AND DEVELOPMENT OF HETEROGENOUS COMBUSTION SYSTEMS FOR LEAN BURN APPLICATIONS.
- Creator
-
Terracciano, Anthony, Orlovskaya, Nina, Vasu Sumathi, Subith, Chow, Louis, Kassab, Alain, University of Central Florida
- Abstract / Description
-
Combustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering...
Show moreCombustion with a high surface area continuous solid immersed within the flame, referred to as combustion in porous media, is an innovative approach to combustion as the solid within the flame acts as an internal regenerator distributing heat from the combustion byproducts to the upstream reactants. By including the solid structure, radiative energy extraction becomes viable, while the solid enables a vast extension of flammability limits compared to conventional flames, while offering dramatically reduced emissions of NOx and CO, and dramatically increased burning velocities. Efforts documented within are used for the development of a streamlined set of design principles, and characterization of the flame's behavior when operating under such conditions, to aid in the development of future combustors for lean burn applications in open flow systems. Principles described herein were developed from a combination of experimental work and reactor network modeling using CHEMKIN-PRO. Experimental work consisted of a parametric analysis of operating conditions pertaining to reactant flow, combustion chamber geometric considerations and the viability of liquid fuel applications. Experimental behavior observed, when utilizing gaseous fuels, was then used to validate model outputs through comparing thermal outputs of both systems. Specific details pertaining to a streamlined chemical mechanism to be used in simulations, included within the appendix, and characterization of surface area of the porous solid are also discussed. Beyond modeling the experimental system, considerations are also undertaken to examine the applicability of exhaust gas recirculation and staged combustion as a means of controlling the thermal and environmental output of porous combustion systems. This work was supported by ACS PRF #51768-ND10 and NSF IIP 1343454.
Show less - Date Issued
- 2014
- Identifier
- CFE0005269, ucf:50549
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005269
