Department: Industrial and Systems Engineering ![[clear]](close-x.png "Remove this limiter")
168 matches in the database.
These are records: 1 - 30.
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1.
Afful-Dadzi, Anthony.
Robust Optimal Maintenance Policies and Charts for Cyber Vulnerability Management.
Degree: PhD, Industrial and Systems Engineering, 2012, Ohio State University
► Cyber-attacks are considered the greatest domestic security threat in the United States…
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▼ Cyber-attacks are considered the greatest domestic security threat in the United States and among the greatest international security threats. Hypothetically, every personal computer connected to the internet and many other types of devices could be attacked. Many organizations scan all their computers monthly and system administrators attempt to reduce or eliminate vulnerabilities, while juggling other demands on their time. In the first part of this dissertation, we present data from three organizations about both vulnerabilities and remedial actions. We also synthesize sixty-seven articles relating to industrial engineering and operations research (IEOR) and cyber vulnerabilities. We conclude that persistent and critical vulnerabilities result in a large fraction of successful attacks. We then describe the activities and decisions faced by the system administrators and staff members who may be relied on for manual activities that address persistent and critical vulnerabilities. The resulting findings establish an important decision-support role for IEOR contributions to mitigating cyber threat. Also, by analyzing the 67 articles in the Science Citation Index on IEOR topics and cyber vulnerabilities, we are able to identify potential gaps in the existing literature. The second part of the dissertation discusses robust maintenance and monitoring techniques for managing cyber vulnerability. One challenge hindering the effective application of existing models is the scarcity of available data partly because of security concerns. We propose a method based on Markov Decision Processes (MDP) for the generation and graphical evaluation of relevant maintenance policies for cases with limited data availability. The proposed method also provides an estimate of the cost benefit of collecting additional data. Both Bayesian and non-Bayesian formulations of the transition probabilities and cost models of the MDP are considered. We apply the proposed method to a real world cyber vulnerability dataset and generate specific guidance and cost predictions. We also illustrate the relevance of the proposed method to general Markov Decision Process modeling using a numerical example involving three levels of data scarcity. Currently, the number of known cyber vulnerabilities continues to increase exponentially. This complicates the application of control charting which might otherwise be used for monitoring and evaluating the quality level of cyber systems. We describe the challenge and propose residual demerit charts for monitoring quality levels of organizational computer networks. A tangential issue is the comparison of Bayesian and non-Bayesian control charts. Bayesian control charts permit the user to include expert knowledge about a system. However, the fair evaluation of such systems is complicated by the potential mismatch between built-in assumptions (fitting prior), including about the direction of the shift, and method evaluation assumptions (the sampling prior). We end the second part of the dissertation by providing a comparison between the two types of charting methods and conclude that non-directional non-Bayesian methods generally remain competitive. The final part of the dissertation summarizes all results for the layperson and information technology (IT) system administrator. The general results uncovered are described and cases are used to illustrate the practical relevance of the technical methods.
Advisors/Committee Members: Allen, Theodore.
Subjects: Industrial Engineering
Keywords: Cyber Attack, Value function, Markov Decision Processes, Control Charts
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2.
Agarwal, Kuldeep.
Physics Based Hierarchical Decomposition of Processes for Design of Complex Engineered Systems.
Degree: PhD, Industrial and Systems Engineering, 2011, Ohio State University
► Manufacturing processes like aeroengine manufacturing, sheet manufacturing or rod manufacturing are examples…
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▼ Manufacturing processes like aeroengine manufacturing, sheet manufacturing or rod manufacturing are examples of complex engineered systems because they have many interconnected components and there is little knowledge about the interactions between these different components. These processes consist of a raw material in the form of powder or a preform (pre-manufactured shape) which is an input from another manufacturing process and through a series of steps, converts it into a product. These manufacturing processes are designed and operated to achieve a specific goal: the final quality of the product being output from that process. The current design cycle for these different manufacturing processes treats the different system components (sub-processes) in isolation. Each engineer and personnel looks at the problem in his own perspective and optimizes the solution pertaining to the requirements or specifications of his particular department or sub-process only.This approach leads to a non-optimal design and lot of variation in the quality attributes. To overcome these limitations, a new approach and methodology for the design of these systems is presented in this dissertation. This methodology decomposes the quality attribute into the various factors which affect it and determine its value. These factors are further decomposed into the physical phenomena which cause these factors to affect the quality attribute. The physical phenomena are finally decomposed into the manufacturing processes and material uncertainties which cause them to influence the quality attributes.Interdependencies are determined between the different sub-processes and only those sub-processes are concentrated on which affect the quality attributes. Novel approach of combining process models with the data obtained by testing sensors is developed through the use of Bayesian Hierarchical modeling. Case studies involving sheet, rod and aeroengine manufacturing are demonstrated. The developed Bayesian models are used in designing these processes for improved quality.
Advisors/Committee Members: Shivpuri, Rajiv.
Subjects: Industrial Engineering
Keywords: Complex Engineered Systems; Metal Forming; Bayesian Hierarchical Modeling; Steel Bar Manufacturing; Aeroengine Disk Manufacturing
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4.
Alder, Emma K.
Temporomandibular Joint Disorder: An Investigation of Masseter Muscle Activity in Response to Stressful Computer Data Entry.
Degree: MS, Industrial and Systems Engineering, 2012, Ohio State University
► Temporomandibular joint disorder (TMD) is a set of conditions affecting the joint…
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▼ Temporomandibular joint disorder (TMD) is a set of conditions affecting the joint connecting the mandible to the temporal bone and the surrounding structures responsible for controlling jaw movement. Symptoms of TMD are characterized by facial pain and/or muscle tenderness, popping or clicking joint sounds, and a limited range of mandible motion. Previous research suggests that 60-70% of the population may have at least one symptom of TMD while only 5% will seek treatment. There is evidence that psychological stress can factor into the disorder. A number of studies have used electromyography (EMG) to attempt to correlate experiment-induced stress with increased masseter activity; the results from these studies are generally mixed and inconsistent. Similar studies also failed to present a stressful stimulus with suitable external validity. The current study improves upon this research by using EMG to investigate masseter muscle response to stressful computer data entry among symptomatic and control participants. There were 8 symptomatic and 8 control participants recruited. The independent variables in the study were computer condition (neutral vs. stressful) and group (symptomatic vs. controls). The dependent variable was the EMG activity associated with the clenches. The study employed a repeated measures design; all participants completed 20 minutes of non-stressful (neutral) data entry followed by 20 minutes of stress-inducing data entry. The stressful computer program had a variable lag built in and would at times inform the participant that data they entered was incorrect, even though it was not. The EMG activity for participant clenches was analyzed. The clenches were normalized to each participant’s own maximum voluntary clench (MVC) and characterized by count, average duration, average peak, average power, total duration, maximum peak, and total power (defined as the area under the normalized EMG curve). Skin conductivity readings and self-report results confirmed that the participants were significantly more stressed during the stressful data entry. It was found that there was a significant main effect for group for the dependent variables of clench count, total duration, and total power; these mean values were significantly greater for the symptomatic group than for the control group. A significant main effect for computer condition was found for total clench duration; the total duration of the clenches in the stressful data entry was longer than those in the neutral data entry task. Significant interaction effects were found for average power, average peak, and maximum peak; the means of these variables increased for the control participants during the stressful data entry but decreased for the symptomatic group. Possible muscle fatigue and stress adaptation among the symptomatic group was suggested to explain the interaction. Further research in this area needs to be conducted to understand risk factors, such as stress, for TMD.
Advisors/Committee Members: Sommerich, Carolyn M.
Subjects: Industrial Engineering
Keywords: tmj; tmd; stress; computer data entry
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5.
Al-Nasser, Amin Eyad.
Characterization of Sheet Materials for Stamping and Finite Element Simulation of Sheet Hydroforming.
Degree: MS, Industrial and Systems Engineering, 2009, Ohio State University
► The increase in using Advanced High Strength Steel (AHSS) and aluminum sheet…
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▼ The increase in using Advanced High Strength Steel (AHSS) and aluminum sheet materials is accompanied by many challenges in forming these alloys due to their unique mechanical properties and/or low formability. Therefore, developing a fundamental understanding of the mechanical properties of AHSS, as compared to conventional Draw Quality Steel (DQS), is critical to successful process/ tools design. Also, alternative forming operations, such as warm forming or sheet hydroforming, are potential solutions for the low formability problem of aluminum alloys. In this study, room temperature uniaxial tensile and biaxial Viscous Pressure Bulge (VPB) tests were conducted for five AHSS sheet materials; DP 600, DP 780, DP 780-CR, DP 780-HY, and TRIP 780, and the resulting flow stress curves were compared. Strain ratios (R-values) were also determined in the tensile test and used to correct the biaxial flow stress curves for anisotropy. The pressure vs. dome height raw data in the VPB test was extrapolated to the burst pressure to obtain the flow stress curve up to fracture. Results of this work show that flow stress data can be obtained to higher strain values under biaxial state of stress. Moreover, it was observed that some materials behave differently if subjected to different state of stress. These two conclusions, and the fact that the state of stress in actual stamping processes is almost always biaxial, suggest that the bulge test is a more suitable test for obtaining the flow stress of AHSS sheet materials to be used as an input to FE models. An alternative methodology for obtaining the flow stress from the bulge test data, based on FE-optimization, was also applied and shown to work well for the AHSS sheet materials tested. Elevated temperature bulge tests were made for three aluminum alloys; AA5754-O, AA5182-O, and AA3003-O, using a special machine where the tools and specimen are submerged in a fluid heated to the required temperature. Several challenges were faced in the experiments such as leakage of the bulging fluid and sample pre-bulging in the clamping stage prior to the test. Moreover, it was originally planned to measure the dome curvature by using three LVDTs; one at the dome apex, and the others at different off-center locations. However, the probes slightly penetrated the soft sheet. Consequently, the off-center probes deflected and gave incorrect data. As a result of these challenges, the pressure and dome height data was not considered reliable to be used in determining the flow stress curves. Only the experimental data is included in this report for documentation purposes, while the calculated flow stress curves are not included. A Sheet Hydroforming with a Punch (SHF-P) process was successfully simulated using the FE software Pamstamp 2G 2007. The objective was to develop a fundamental understanding of the process to reduce the expensive experimental trial and error. A systematic methodology to design the process was suggested and applied using FE simulation. A considerable improvement in the thinning distribution in the part was achieved by properly selecting the blankholding and pot pressure curves.
Advisors/Committee Members: Altan, Taylan.
Subjects: Automotive materials; Engineering; Industrial engineering; Materials science; Mechanical engineering
Keywords: AHSS; Uniaxial Tensile Test; Biaxial Bulge Test; Flow Stress; Formability; Dual Phase (DP); Transformation-Induced Plasticity (TRIP); Elevated Temperature Sheet Characterization; Alluminum; AA5754; AA5182; AA3003; Sheet Hydroforming with a Punch (SHF-P)
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6.
Anders, Shilo H.
Projecting trajectories of functional use for a new technology: The electronic ICU.
Degree: PhD, Industrial and Systems Engineering, 2008, Ohio State University
► There are an increasing number of new technological innovations emerging and being…
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▼ There are an increasing number of new technological innovations emerging and being fielded in the market, especially medical technologies. Studies of these new technologies should consider trajectories of change and adaptation as new systems and capabilities are introduced and mature. Within the literature is a variety of technology adoption, evolution and radical change models; one widely cited view of technology adoption is Rogers diffusion of innovation, which has been used to empirically examine attempts to inject new technologies into various domains. Rogers diffusion of innovation accounts for success stories of technology adoption; however, it is limited for technologies that are rejected by intended users, require significant tailoring, or are used for unexpected functions. The proposed dissertation research takes a cognitive systems engineering perspective to reinvigorate the study of the impact of new technology in complex, socio-technical settings, by focusing on the intersections of the domain, artifacts (e.g. tools and technologies), and practitioners. A case study of a specific new technology was conducted using a triangulation of ethnographic methods including: observations, interviews, and log analysis. The emerging telemedicine example studied in this research is the electronic intensive care unit (e-ICU). The e-ICU was implemented in a single hospital in 2000; it was not subsequently expanded to other hospital systems until years later and since then has seen increased usage around hospital systems. The study summarizes the current e-ICU functions into three groups: access to expertise, anomaly response, and sensemaking. Additionally, intervention logs where the e-ICU nurses write down every time a discourse occurs between the e-ICU and ICU were examined. The intervention log analysis lends support to the hypothesis that these functions and additional functions of the e-ICU are changing over time. Finally, the interviews provide a survey of additional functions that other e-ICUs across the country. Previous research utilizes these methods to identify patterns in how expert practitioners interact with computerized support to achieve domain-specific objectives, making no projections about potential trajectories of adaptation through use that may occur over the longer term. This research is novel in that the findings form the foundation of a proposed, expanded, theoretical framework of trajectories and indicators of technology change. This research is anticipated to have theoretical as well as applied contributions. First, an enhanced theoretical framework should better enable companies to predict the impacts of new technologies in emerging markets by providing possible trajectories and associated indicators. Thus, these projections may be further explored in future research as to how technology may be steered into more productive trajectories, and how to mitigate the negative side effects associated with particular trajectories. The research suggests that the ability to project possible trajectories in order to aid in selecting among alternatives and managing post-conditions of change can be done based on the pattern base built up through cognitive systems engineering and the proposed theoretical framework.
Advisors/Committee Members: Woods, David.
Subjects: Systems design; Technology
Keywords: cognitive systems engineering; cognitive task analysis; telemedicine
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7.
Aramphongphun, Chuckaphun.
In-mold coating of thermoplastic and composite parts: microfluidics and rheology.
Degree: PhD, Industrial and Systems Engineering, 2006, Ohio State University
► The main technical issues in developing the in-mold coating (IMC) process of…
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▼ The main technical issues in developing the in-mold coating (IMC) process of polymer and composite parts include: (i) flow pattern, (ii) injection pressure, and (iii) mold deflection. The injection pressure is greatly influenced by the flow field and rheological properties of the coating material. Due to the very small length scale of the IMC flow, “apparent” wall slip occurs in the IMC flow. The high shear rates encountered in the microchannels make it necessary to include the higher shear rate plateau in the viscosity models. Including these two factors is critical in developing a predictive model of the IMC flow. Flow models based on the slip boundary conditions have been developed to determine the viscosity of microfluidics. A customized microslit rheometer – a slit rheometer with micrometer-sized channels of 100- and 25-micrometer gaps – was built to measure the viscosity. The reduced viscosity of the coating material was found in the 25-micrometer channel gap, which indicated the apparent wall slip in the flow system. The developed rheological models were used to analyze the experimental results and determine the slip parameter known as slip length. The value of the slip length was then used in modeling the slip flow to predict the pressure. The numerical solutions based on (i) the viscosity models: the power law and the Carreau models, and (ii) boundary conditions: no-slip, true slip, and apparent slip were compared with the experimental results. It was found that the Carreau viscosity model of the coating material improved the pressure prediction while the slip boundary condition was important to predict the pressure in the 25-micrometer channel gap. This work makes it now possible to predict the pressure for IMC of thermoplastics. The last issue, mold deflection, was studied in IMC of RTM. Simple mathematical models of IMC of RTM were derived to determine the pressure and hydraulic force. The effect of the mold deflection due to the pressure was integrated into the model in terms of the compressibility of the mold. The effect of the compressibility of both the substrate and mold on the pressure and hydraulic force is discussed in a case study.
Advisors/Committee Members: Castro, Jose.
Subjects: Engineering, Industrial
Keywords: In-mold coating; Process modeling; Microfluidics; Rheology; Slip flow
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8.
Aue-u-lan, Yingyot.
Hydroforming of tubular materials at various temperatures.
Degree: PhD, Industrial and Systems Engineering, 2007, Ohio State University
► This dissertation research covered two main areas in tube hydroforming process. The…
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▼ This dissertation research covered two main areas in tube hydroforming process. The first was to develop the methodology to determine the flow stress directly from the tube at room temperature. The hydraulic bulge test was selected for this purpose. The analytical model based on an incremental strain theory was used to predict the wall thickness at the apex of the dome. The thickness predictions were compared with the measured data. The agreement was good. The application of the hydraulic bulge test was extended for use as a tool for a quality control of incoming tubular materials. The experiments were performed to investigate the variations in formability of the tubes produced by roll forming process. The maximum bulge height at the bursting pressure was found to be the most sensitive variable. The second portion of this research was to develop a prototype tube hydroforming system that could be used to form lightweight alloy tubes (aluminum and magnesium alloys) at elevated temperatures. The existing knowledge on process development for forming these materials at the elevated temperature was not sufficient. Therefore, a new design approach, called “submerged concept”, was developed to reduce the heating and filling time and maintain uniform temperature in the tube during hydroforming. The system was used to investigate the effect of the tube extrusion processes (with mandrel –seamless and with porthole die –with seams) on the quality of tubes. Seamless extruded tubes were studied extensively regarding the effect of the process parameters (forming temperatures and forming rates) on the formability and loading behavior. The tubes with seams were found to have defects at the welding line that caused fracture during hydroforming. The results indicated that formability increases with increasing temperature. The forming pressure dropped before the tube touched the die surface, indicating of strain softening. Tensile test was used to obtain the flow stress of the tubes at different temperatures and strain rates. These flow stress data were used in Finite Element simulations to predict process variables, i.e. pressure and axial feed versus time. The comparison between the simulation and experimental results showed reasonable agreement.
Advisors/Committee Members: Altan, Taylan.
Keywords: Hydroforming, Tube Hydroforming, Warm Tube Hydroforming, Tubular Materials, Flow Stress
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9.
Babu, Sailesh.
A material based approach to creating wear resistant surfaces for hot forging.
Degree: PhD, Industrial and Systems Engineering, 2004, Ohio State University
► Tools and dies used in metal forming are characterized by extremely high…
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▼ Tools and dies used in metal forming are characterized by extremely high temperatures at the interface, high local pressures and large metal to metal sliding. These harsh conditions result in accelerated wear of tooling. This phenomenon becomes a serious issue when parts forged at complex and are expected to meet tight tolerances. The objective of this dissertation is to develop a computer-based methodology for analyzing the requirements hot forging tooling to resist wear and plastic deformation and to create wear resistant surfaces to overcome these failure mode, to increase hot forging tool life. The approach proposed and tested in the dissertation involves development of a FEM based approach to model material degradation caused by heat, load and sliding. This approach uses tempering parameters proposed by Holloman and Jaffe and published thermal softening behavior of tool steels to predict the drop in hardness of tool steels during service. Using a modified Archard’s model for wear that takes into account effect of temperature on hardness, this drop in hardness is then used to more accurately predict wear in hot forging tools, that are dominated by thermal softening. Dissertation outlines development of a new cyclic contact test design to recreate intermittent tempering seen in hot forging. This test has been used to validate the use of tempering parameters in modeling of in-service softening of tool steel surfaces. The dissertation also outlines an industrial case study, conducted at a forging company, to validate the wear model. This dissertation also outlines efforts at Ohio State University, to deposit Nickel Aluminide on AISI H13 substrate, using Laser Engineered Net Shaping (LENS). Dissertation reports results from an array of experiments conducted using LENS 750 machine, at various power levels, table speeds and hatch spacing. Results pertaining to bond quality, surface finish, compositional gradients and hardness are provided. Also, a thermal – based finite element numerical model that was used to simulate the LENS process is presented, along with some demonstrated results.
Advisors/Committee Members: Shivpuri, Rajiv.
Keywords: Hot forging; Die wear; Thermal softening; In-service tempering; Tempering parameters; Laser engineered net shaping (LENS); Nickel aluminide; AISI H13 tool steel; Cladding
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10.
Basinger, Karen Lynn.
Impact of inaccurate data on supply chain inventory performance.
Degree: PhD, Industrial and Systems Engineering, 2006, Ohio State University
► This research explores data inaccuracy and its impact on supply chain inventory…
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▼ This research explores data inaccuracy and its impact on supply chain inventory performance. Theft and data entry error cause differences between the physical inventory levels and inventory levels recorded in the computer system. Physical inventory counts are one method commonly used to align physical and recorded inventory levels. Expected benefits of new technology, such as radio frequency identification (RFID) include improvements in the accuracy of supply chain data, including possibilities of real-time alignment of the data. This research looks at the factors of theft, order error, lead time, synchronization frequency, demand variability, stock-out policy, two separate ordering policies and their impact on inventory performance in a three-level supply chain setting for a single item. The order policies considered are the reorder point (ROP) policy with a fixed order quantity and the order-up-to (OUT) policy with a variable order quantity. Simulation modeling is used to analyze factor impacts on the service level degradation, inventory level degradation, and inventory inaccuracy. Factors and performance measures are analyzed at the system level and the individual echelon level. There were several findings. Inaccuracy at one echelon in the supply chain has a negative impact on inventory performance at other echelons. Inventory error increases order size and variability under the OUT policy with variable order quantities compounding the bullwhip effect. The ROP policy with fixed order quantities responds by increasing order placement frequency and experiences less service level degradation than the OUT policy. Dominating factors were order policy, stock-out policy, theft, and inventory synchronization frequency. In general, theft reduction is more effective for improving service level than increasing the frequency of synchronization. Increasing synchronization frequency eliminates warehouse denials (failures to order) and under-ordering. These conditions are caused by inaccuracy where the recorded inventory level dictates a ‘no order’ decision and the physical inventory level dictates an ‘order’ decision. Increasing the synchronization frequency only partially removes the impact of theft, including order variability under the OUT policy. Reduced inventory levels caused by shorted deliveries continue to cause service level degradation even when inventory is synchronized prior to every order placement.
Advisors/Committee Members: Mount-Campbell, Clark.
Keywords: supply chain; inaccuracy; inventory; inventory performance; theft; radio frequency identification
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12.
Bernal, Fernando.
Lightweight Technology Functions for Small Ad Hoc Team Communication.
Degree: MS, Industrial and Systems Engineering, 2009, Ohio State University
► Escalation in adoption of communication and social networking technologies have triggered interest…
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▼ Escalation in adoption of communication and social networking technologies have triggered interest in understanding their functionality and potential in designing Computer-Supported Cooperative Work (CSCW) technologies. This thesis speaks of such emerging channels in terms of their “weight” and will show that “lighter weight” technologies tend to have better acceptance and more versatile applications. By using design research techniques a visual palette was created to describe teamwork after conducting a piloting team building experiment on ad hoc teams. An experiment was also conducted with ad hoc teams where they had to give a solution to a logistics problem under tight constraints. The task used in the experiment addressed four stages in macrocognition covering two main conditions: face to face interaction and distributed collaboration using a “lightweight” communication tool (Skype). The final part of the thesis provides design guidelines to enhance collaborative platforms by implementing lightweight approaches to improve the overall teamwork experience.
Advisors/Committee Members: Patterson, Emily.
Subjects: Communication
Keywords: Lightweight; communication; ad hoc
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13.
Bhagavatula, Narayan L.
Modeling and experimental verification of pressure prediction in the in-mold coating process for thermoplastic substrates.
Degree: PhD, Industrial and Systems Engineering, 2006, Ohio State University
► In-mold coating (IMC) process has emerged as a low cost and environmentally…
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▼ In-mold coating (IMC) process has emerged as a low cost and environmentally friendly alternative to painting and priming processes. Due to its successful application to exterior body panels made from compression molded Sheet Molding Compound (SMC), IMC is being developed as a technology that would ultimately replace painting of injection molded thermoplastic parts. In the short term,however, we believe IMC has the potential of being a substitute to primer.There are key issues that need to be addressed for a successful IMC operation.The location of IMC nozzle should be such that total coverage is achieved,the potential for air trapping is minimized and is accessible for ease of maintenance. This necessitates the use of fill patterns. To avoid leakage of the coating material, the generated hydraulic force must never exceed the clamping force. Therefore it is imperative that we predict the pressures generated during coating injection. Existing prediction tools based on the Hele-Shaw approximation, assuming the coating to be a power law fluid and using the traditional no-slip boundary condition adequately predict the fill patterns but do not predict pressures correctly. This deviation has been partly attributed to slip at the wall, as often found in flow through micro channels. Further, research has shown evidence of an upper Newtonian plateau for the coating viscosity at high shear rates. In this research work, a one-dimensional mathematical model including an advanced rheological model in the form of Sisko and Carreau models, in addition to the slip boundary condition has been developed and solved numerically using FDM. Coating thickness is predicted as a function of location and time. This model validates the approach of using slip and improved rheological equations in IMC flow modeling to predict pressures accurately.The model is further extended to a two-dimensional simulation tool based on the Hele-Shaw approximation, in order to simulate coating flows over more complex geometries. The compressibility of the substrate is described by the modified double domain Tait PVT model. CV/FEM is applied to solve the governing equations. The developed simulation tools are verified based on existing 2D experimental results obtained using the IMC pilot facility, as well as new results based on constant flow rate experiments.
Advisors/Committee Members: Castro, Jose M.
Keywords: In-Mold coating, flow simulation, control volume
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14.
Brady, James E.
Six sigma and the university:teaching, research, and meso-analysis.
Degree: PhD, Industrial and Systems Engineering, 2005, Ohio State University
► Six Sigma was introduced by industry practitioners and consultants as a means…
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▼ Six Sigma was introduced by industry practitioners and consultants as a means to improve any given company’s competitive position. Its acceptance by industry has been widespread over the past two decades, yet academic research on Six Sigma has been surprisingly limited. Further, most of the research has been focused on the tools and statistical techniques used in Six Sigma. Its relationship with university activities including teaching, research, and service is not clear. The purpose of this dissertation is to explore selected aspects of the relationship between Six Sigma and universities more fully. In doing so, there is an attempt to answer these fundamental questions: (i) What is Six Sigma? (ii) What roles can academics usefully play in relation to Six Sigma? and (iii) How can academia help companies to better use the new project related data sources created by Six Sigma. Results here divide into three chapters. First, the literature on Six Sigma is reviewed and synthesized. This includes detailed descriptions of research trends with an emphasis on establishing its relationship to quality management theory and topics for future research. Secondly, case base training is examined as a method to improve Six Sigma education and increase usage on the job among university student learners. Third, with Six Sigma’s emphasis on management by data and project based data collection, industry is starting to accumulate many large databases of “meta-data” concerning the successes or failures of individual quality improvement projects. We propose methods specifically for making use of the project data and illustrate their application using 39 case studies form a mid-western manufacturing firm.
Advisors/Committee Members: Allen, Theodore T.
Subjects: Engineering, Industrial
Keywords: Six Sigma, Meso-analysis
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15.
Branlat, Matthieu.
Challenges to Adversarial Interplay Under High Uncertainty: Staged-World Study of a Cyber Security Event.
Degree: PhD, Industrial and Systems Engineering, 2011, Ohio State University
► The vulnerability of critical and valued digital infrastructures and the difficulty of…
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▼ The vulnerability of critical and valued digital infrastructures and the difficulty of defending networks against attacks are a growing concern throughout domains. While numerous efforts exist to improve cyber defense through technological advances, human-centered research to uncover and address the difficulties experienced by network defenders is recent and still limited. Moreover, understanding cyber security, a fundamentally adversarial domain, requires investigations of the interrelated defense and attack processes, but such studies are rare. The dissertation presents results from a staged-world study of an adversarial cyber security exercise. This daylong exercise involved forty participants divided into an outside attacking team and a defending team operating in a simulated production environment. The first objective is to identify critical skills and forms of expertise of cyber security as a domain of practice. Designed by cyber security experts, the exercise allowed for the investigation of core dimensions of cyber events, which have seen limited empirical study in past work on cyber defense: (1) decision-making in cyber defense; (2) network security within larger production structures and processes; (3) decision-making in cyber attack; and (4) interplay of attack and defense. The second objective of the research is to discuss the approach designed and implemented in order to capture and analyze the cyber event observed. Challenges result especially from the scale of the processes to be tracked (attack and defense; number of participants; distribution of participants in teams, roles and space; duration of the exercise). The study we conducted aimed at exploring the domain of cyber security with an emphasis on the methodological dimensions of such investigation. Given the partially novel character of the research, a critical account of choices made, successes and pitfalls experienced aims at informing future advancements in the domain. The third objective is to connect this study of the particular domain of cyber security to other studies of work in real-world situations. Relevant theoretical frameworks include: decision-making under uncertainty, distributed anomaly response, joint activity, perception of intent, and more generally Resilience Engineering. Making this link allows for the discussion of potential directions to improve cyber defense, as well as to further develop these theoretical frameworks. Cyber security, because of its nature and the typical challenges associated, constitutes a rich environment for such purposes.
Advisors/Committee Members: Woods, David D.
Keywords: cognitive systems engineering; resilience engineering; cyber security; adversarial event; staged-world study; decision-making; cyber defense; cyber attack; observational study
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16.
Cabrera Rios, Mauricio.
MULTIPLE CRITERIA OPTIMIZATION STUDIES IN REACTIVE IN-MOLD COATING.
Degree: PhD, Industrial and Systems Engineering, 2002, Ohio State University
► Reactive in-mold coating (IMC) products have been used successfully for many years…
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▼ Reactive in-mold coating (IMC) products have been used successfully for many years to improve the surface quality of Sheet Molding Compound (SMC) compression molded parts. IMC provides a smooth, sealed surface, used as a conductive or nonconductive primer for subsequent painting operations. The success of IMC for SMC parts has recently attracted the interest of thermoplastic injection molders. The potential environmental and economic benefits of using IMC as a primer and, in the ideal case, to replace painting completely are large. Acceptance of IMC as a competitor to the traditional painting processes will depend upon the improvement of its ability to deliver in-mold coated parts in short cycle times at the highest possible quality level. Most optimization studies in Reactive Polymer Processing involve compromising between different performance measures since, frequently, the controllable variables have conflicting effects on these measures. IMC is not the exception to the rule. The performance measures need to be balanced, each against the other, in order to obtain the best compromises. The goal of this research work is to develop an optimization strategy for the application of reactive in-mold coating to SMC and thermoplastic parts in presence of multiple and conflicting performance measures. To achieve this goal we explore the use of Artificial Neural Networks as metamodeling techniques and the use of Data Envelopment Analysis to solve multiple criteria optimization problems.
Advisors/Committee Members: Castro, Jose M.
Keywords: In-Mold Coating; Multiple Criteria Optimization; Artificial Neural Networks; Data Envelopment Analysis; Reactive Polymer Processing
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17.
Campbell-Kyureghyan, Naira Helen.
Computational analysis of the time-dependent biomechanical behavior of the lumbar spine.
Degree: PhD, Industrial and Systems Engineering, 2004, Ohio State University
► Significant effort has been invested in developing finite element models in the…
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▼ Significant effort has been invested in developing finite element models in the field of spinal biomechanics. However, nearly all previous studies have applied artificially set static or short duration dynamic loads (< 1 second) to a single motion segment, while most low back disorders found in industry today are due to tasks that are repetitive in nature. Accordingly, the purpose of this study was to develop a model of the complete lumbar spine capable of determining the response to realistic repetitive motion. A new finite element model of the lumbar spine was developed that considers nonlinear material and geometric behavior, including large displacements and rotations. The model was interfaced with an EMG-assisted free-dynamic model which provides subject specific motion data for use as partial input to the finite element model. The initial geometry of the lumbar spine is a crucial part of the input, and a new method for determining the neutral posture geometry using an external goniometer was developed and validated. Validation and sensitivity analyses were also performed on both the individual model components and the complete model. In addition, the model response, including stresses, deformations, and energy dissipation, for up to twenty minutes of continuous, measured repetitive sagittally-symmetric flexion was calculated. Furthermore, the dynamic creep and energy dissipation at all intervertebral discs levels was determined for 8 hours of cyclic loading. The model developed in this study is able to simulate large displacement, dynamic, cyclic behavior using realistic motions through linking to human subject experiments. Larger forces, creep, and energy dissipation were predicted at the lower lumbar spine levels, and the maximum stresses and energy dissipation were found to be highly dependent upon the bending motion, not only the axial compression. In addition, higher lifting frequencies and velocities lead to increased creep and energy dissipation, with velocity having a larger effect. Subject specificity, including the initial lumbar spine geometry and motion during flexion were found to have an important effect on the resulting spinal loads. The results suggest that the new model is a valid approach to assessing the effect of repetitive motion on the lumbar spine.
Advisors/Committee Members: Marras, William.
Keywords: biomechanics, spine, finite element modeling
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18.
Carbajal, Luis Rodrigo.
Microfluidics of In-Mold Coating Resins and Dilute DNA Suspensions.
Degree: MS, Industrial and Systems Engineering, 2010, Ohio State University
► In-mold coating (IMC) is carried out by injecting a low viscosity thermosetting…
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▼ In-mold coating (IMC) is carried out by injecting a low viscosity thermosetting liquid on to the surface of a substrate at the end of the molding process after it has solidified and while it is still in the mold. The coating then cures and adheres to the substrate. Due to its successful application to exterior body panels made from compression molded Sheet Molding Compound (SMC); IMC is being developed as an environmentally friendly technology that would ultimately replace painting of injection molded thermoplastics. Research has been done to simulate the coating flow during the IMC process assuming the coating to be a power law fluid and using the traditional no-slip boundary conditions. This model adequately predicted the fill pattern but did not predict pressures correctly. This deviation has been attributed to slip (or apparent slip) at the wall, as often found in flow through microchannels, due to microscopic length scale of the flow; and the existence of a high shear rate non-Newtonian plateau for the coating viscosity. Further research has been done on modeling the rheological behavior of IMC resin at high shear rates. This work points towards the behavior not being true slip but apparent slip due to the carbon black concentration in the resin increasing farther away from the wall. Since IMC resin behaves as a non-Newtonian fluid, we use a dilute salmon DNA solution as a model suspension to make further insights into the apparent slip phenomena encountered during the coating process. Researchers have been using DNA for flow visualization studies due to its ability to be tagged by a fluorescent dye. Using a confocal micro-particle tracking velocimetry we have measured the velocity profile of stained DNA flowing in micro channels as well as the concentration of DNA as a function of position in the channel. We have found that the DNA concentration increase as we move to the center of the channel. Using this information, we have developed a model that includes a viscosity that is a function of the concentration of DNA, to predict the pressure data without the need to calculate apparent slip.
Advisors/Committee Members: Castro, Jose.
Subjects: Industrial engineering
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20.
Chang, Keh-Chyou.
Analysis Of Minimum Safe Cycle Time In Injection Molding: Selection Of Frozen Layer Thickness.
Degree: MS, Industrial and Systems Engineering, 2008, Ohio State University
► The largest component of the injection molding cycle is the cooling time.…
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▼ The largest component of the injection molding cycle is the cooling time. Thus it is highly desirable, to be able to predict what its minimum acceptable value can be. This is becoming even more important with increased competition from regions where the labor cost is low. In an injection molding operation, the mold thermal state changes from its initial value until a quasi steady state is reached. The minimum required cooling time increases with continuous molding until a steady state value is achieved. Improving the mold thermal design will decrease the cooling time thus reducing total cycle time. The overall goal of this work is to develop a simple reliable method to predict a minimum safe cycle time for steady manufacturing. The first part of the thesis describes software capable of simulating the thermal state of the part and the mold for multiple injection molding cycles while balancing simulation time with results accuracy. Three case studies are presented, one done in our labs and two on-site at an automotive manufacturing facility. The three case studies are used to evaluate the ability of the software to predict part surface temperature for continuous molding. The second part of the thesis, evaluates, the minimum frozen layer thickness required before the part can be demolded and how the growth of this frozen layer is affected as the mold thermal state changes with continuous molding cycles. Experiments are conducted in our labs to relate the minimum frozen layer thickness to part dimensional stability. Based on these experiments, an ejection criterion is selected in order to obtain a minimum safe cooling time.
Advisors/Committee Members: Castro, Jose M.
Subjects: Engineering; Industrial engineering; Plastics; Polymers
Keywords: Injection Molding; Cycle Time
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21.
Chantarat, Navara.
Modern design of experiments methods for screening and experimentations with mixture and qualitative variables.
Degree: PhD, Industrial and Systems Engineering, 2003, Ohio State University
► This dissertation re-examines some of the most basic design of experiment methods…
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▼ This dissertation re-examines some of the most basic design of experiment methods with respect to their ability to achieve intuitive objectives. For example, it provides probably the first comprehensive evaluation of the ability of standard screening approaches to correctly tell which factors have important effects on average outputs. Also, the dissertation examines the prediction errors that users of so-called mixture experimental design and qualitative response surface methods can achieve. In practical situations, the derived "decision support" information can tell the user in advance whether the number of runs used is adequate for the experimenter's needs and provide a basis for selecting one method over another when alternatives are presented. Also, the dissertation clarifies, perhaps for the first time, the potentially serious prediction error issues associated with the methods that have been proposed for response surface investigation when some factors are qualitative. In addition to developing comprehensive computational studies of existing methods, new methods are proposed with potentially important advantages. For example, the dissertation provides some of the first unbalanced screening experimental plans relevant to cases in which some combinations of settings have far higher costs than other combinations. For situations in which some factors are mixture components, e.g., %CO2, %Ar, %N, and other factors are process variables, the dissertation provides some of the first economically relevant experimental plans offering potentially substantial reductions in prediction errors. Also, the dissertation provides the first truly advisable experimental designs for many response surface cases in which some variables are qualitative. All new methods are derived from optimization formulations or "improvement systems design problems". In each case, the intent is to design the method using the objective or objectives that most directly describe the purpose of the improvement system. Also, the formulations build on the most realistic, concise assumption schemes in the applied statistics literature.
Advisors/Committee Members: Allen, Theodore Tetreault.
Keywords: Design of Experiments; DOE; Fractional Factorial Design; Mixture Design; Response Surface Method; Response Surface Design; Qualitative Factor; Categorical Factor; Qualitative Variable; Categorical Variable
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22.
Chan, Yong Jie.
Margin of Maneuver Approach to Define Resilient Control Systems.
Degree: MS, Industrial and Systems Engineering, 2012, Ohio State University
► The ability to be resilient, or the ability to remain in-control in…
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▼ The ability to be resilient, or the ability to remain in-control in the face of surprising challenge events, is relevant to various domains such as control theory, critical infrastructure, disaster response, ecosystems and business continuity. Evidence from studying specific fields of practice that are highly resilient has identified critical properties of human complex adaptive systems. Human systems are made up of multiple units or centers of adaptive behavior that exhibit control strategies to mitigate the potential for brittleness relative to the potential for surprise that carry high consequences. One key concept that has emerged from these studies is Margin of Maneuver (Woods and Branlat, 2010): a cushion of potential actions and additional resources that allows the system to continue functioning despite unexpected demands. When Margin of Maneuver is lost, so is the ability to control the system when unexpected shocks occur – in other words, if Margin of Maneuver is too low a system will not be able to remain in-control in the future should new challenge events occur. As a result, the concept Margin of Maneuver provides the basis to develop resilient control systems. This thesis takes the concept of Margin of Maneuver and develops a notation for the specific parameters and requirements that define how a resilient control system functions. The concept of Margin of Maneuver provides a means to assess the brittleness of systems a key goal of the Resilience Engineering research agenda (Woods, 2006). The concept of Margin of Maneuver also provides a focus for how organizations learn about and monitor their resilience/brittleness – about how the organization is able to bring extra adaptive capacity to bear before in-control strategies reach a point of breakdown. Finally, the concept of Margin of Maneuver provides a basis for identifying polycentric governance policies as one unit’s struggle to sustain its margin may undermine the ability of other units to hold sufficient margin to handle potential challenge events (Stephens et al., 2011). This thesis advances models of Margin of Maneuver by specifying a control process that can be implemented so that units or center of adaptive behavior will be able to maintain an appropriate Margin of Maneuver as situations change.
Advisors/Committee Members: Woods, David D.
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23.
Cheng, Xiaomin.
Experimental and numerical approaches for improving rolling contact fatigue of bearing steel through enhanced compressive residual stress.
Degree: PhD, Industrial and Systems Engineering, 2007, Ohio State University
► Hardened steels are attractive materials due to their desirable properties such as…
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▼ Hardened steels are attractive materials due to their desirable properties such as wear resistance and fatigue strength. They are widely used in transportation, energy generation and general mechanical engineering applications. The components in these applications are often loaded near their physical limits. Therefore, they have to be thermally treated to the desired mechanical properties and then finished in the hardened state in order to achieve surface integrity, dimensional accuracy, and shape. Hardened steel have traditionally been machined to finished geometries by abrasive processes such as grinding. Hard turning as a replacement for grinding becomes more and more attractive due to lower production cost, shorter cycle time, fewer process steps, and higher flexibility in machining the complex workpiece geometry. However, there are still several fundamental issues to be solved in order to replace grinding with hard turning. Rapid tool wear remains an impediment to the process being economically viable due to the high cost of CBN cutting tools and large down time due to frequent tool change. Another issue is related with surface integrity. A hard and brittle white layer, which is detrimental to part performance, will be generated at the machined surface under certain conditions. This white layer has to be avoided. In this research, a hybrid process was developed and carefully designed. It takes the advantages of both shot peening and hard turning processes that result in the extension of fatigue life, elimination of white layer and minimization of tool wear with acceptable surface finish. A hard turning model was developed to evaluate the influence of machining parameters and tool edge geometry on the temperature distribution, cutting force and residual stress profile. The model was validated by comparing the chip morphology and cutting forces with the experimental results. The predicted residual stress was also compared with the measured data. It was found that although honed edged gave the deeper and larger compressive residual stress, the cutting temperature and cutting forces increase dramatically which leads to quick tool wear. Shot peening process was also investigated for its efficacy in imparting compressive sub-surface residual stress in hardened surfaces. Single and multiple shot models were developed to study the effect of shot peening process parameters, workpiece material, surface conditions and the interaction between individual shots on the distribution of the compressive residual stress field. The models were both validated by experiments from literature and thos conducted by this author. It is shown that the presented results are in good agreement with the experiment data. Predictive models of the shot peening process were developed using Response Surface Methodology (RSM). FEM simulations using the multiple-shot model were conducted in order to develop response surfaces of the residual stress field. Stochastic simulations were carried out using these response surfaces. Statistics of the output variations were calculated using the stochastic Monte Carlo simulations. The results gave the quantitative numbers about the variations of the residual stress field. Interaction between the residual stress fields induced by shot peening and hard turning was investigated using numerical simulations and then validated by experiment. It was found that shot peening as a pre-process can enhance the residual stress and fatigue life of a hard turned component. However, improper hard machining of shot peened surface can lead to removal of shot-peened residual stress.
Advisors/Committee Members: Shivpuri, Rajiv.
Subjects: Engineering, Industrial
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24.
Chen, Jian.
Experimental and Simulation Studies of Femtosecond Laser Stimulated Electrical Discharges in Small Gaps and Surface Modifications.
Degree: PhD, Industrial and Systems Engineering, 2009, Ohio State University
► Femtosecond (FS) laser-stimulated discharges in nanoscale and microscale gaps between etched nanoprobe…
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▼ Femtosecond (FS) laser-stimulated discharges in nanoscale and microscale gaps between etched nanoprobe tip cathodes and metal anodes with applied DC potential were experimentally studied to define parameter ranges for their controlled formation and resulting surface modifications. For appropriate values of gap length, applied potential and laser irradiance, breakdown discharges could be reliably stimulated by FS laser pulses and the mean breakdown field was approximately an order of magnitude smaller than for breakdown without laser stimulation. For 500nm gaps, controllable gold film surface melting by laser-stimulated discharge was detected. Minor cathode tip ablation could be observed for FS laser pulses that reliably stimulated discharges, suggesting that cathode material played an important role in stimulation of breakdown discharges in nanoscale gaps. Surface melting produced features as small as 70nm on gold film anodes when discharge current was limited by 1 MΩ series resistor. Numerical simulations of FS laser-stimulated electrical discharges without current-limiting in submicron gaps were performed by using a particle-in-cell—Monte Carlo collision model and the results were compared to experiments. The effect of laser-ablated cathode materials (partially-ionized platinum and electrons) at various densities on gap breakdown was simulated. Breakdown discharges were predicted to occur at a much lower applied potential with initial laser-ablated material than for gaps without mainly due to enhanced local electric field at the cathode tip. Simulated discharge current pulses had nearly equal peak magnitudes and shorter durations than experimental discharges at the same applied potential. The heat flux distributions on the anode surface at various applied potentials were predicted from the energy deposited by incident particles. The heat flux distributions were approximated by Gaussian distributions and their time axes were scaled for anode surface temperature calculations using analytical solutions of thermal diffusion in a semi-infinite solid. Anode melting predictions were compared to experiments. The predicted discharge potential for onset of anode melting and the diameters of anode melting for various applied potentials were comparable to the experimental results.
Advisors/Committee Members: Farson, Dave.
Subjects: Industrial engineering; Materials science
Keywords: electrical discharge; femtosecond laser; electrode modification; PIC-MCC
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25.
Chen, Lijian.
Stochastic programming in revenue management.
Degree: PhD, Industrial and Systems Engineering, 2006, Ohio State University
► Airline revenue management aims to assign the right seat to the right…
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▼ Airline revenue management aims to assign the right seat to the right customer with right prices at the right time. Due to the existence of large uncertainty in customer demand and the unavailability of perfect information, decisions must be made in advance. Also, such decisions are subject to constraints, such as seat availability, demand forecasts, and customer preferences. The objective of revenue management is to maximize the long term booking revenue. In this research, we studied two models in detail, the seat allocation model and the customer choice model based on preference orders. The seat allocation model is to decide the number of seats available for booking at class level by assuming the demands among booking classes are independent. The customer choice model is to assign seats at class level without forecasting demands individually. Both research topics in revenue management, the seat allocation optimization and customer choice optimization, are built by stochastic programming models. We present a multi-stage stochastic programming formulation to the seat allocation problem that extends the traditional probabilistic model proposed in the literature. Because of the lack of convexity properties, solving the multi-stage problem exactly may be difficult. In order to circumvent that obstacle, we use an approximation based on solving a sequence of two-stage stochastic programs with simple recourse. Our theoretical results show that the proposed approximation is robust, in the sense that solving more successive two-stage programs can only improve the expected revenue. We also discuss a heuristic method to choose the re-solving points. Numerical results are presented to illustrate the effectiveness of the proposed approach.
Advisors/Committee Members: Mount-Campbell, Clark.
Subjects: Engineering, Industrial
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26.
Chen, Shih-Kwang.
Searching for information on occupational accidents.
Degree: PhD, Industrial and Systems Engineering, 2008, Ohio State University
► Effective retrieval of the most relevant documents on the topic of interest…
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▼ Effective retrieval of the most relevant documents on the topic of interest from the Internet is difficult due to the large amount of information in all types of formats. Studies have been conducted on ways to improve information retrieval (IR). One approach to improve searches in large collections, such as the Web, is to take advantage of semantic representations in pre-existing relational databases that have been developed for explicit purposes besides supporting Internet searches in general. In an effort to enhance IR on the Internet, a prototype of a topic-oriented search agent, SAOA-1, was developed to use embedded semantics and domain-specific knowledge extracted from such a database. Activated when a set of retrieved keywords appears related to the topic of "occupational accidents", SAOA-1 constructs an alternative search query and pruned lists of suggested refinements by applying the search engine knowledge and the domain-specific knowledge and semantics extracted from a relational database. Information seekers could then use the alternative search query or refine it further with a modified search query developed by SAOA-1 based on its semantic representation of the topic of occupational accidents to complete context-sensitive pruning of the semantic neighborhood. An empirical study was conducted to evaluate the usefulness of SAOA-1 in assisting information seekers to retrieve relevant documents. Sixty participants were randomly assigned to one of two treatments: with or without the assistance of SAOA-1, to perform Internet searches. Prior to performing searches, each participant had to decide upon a topic based on two given articles addressing hand injuries in the workplace. The participants then performed searches and, when satisfied with the results, evaluated the relevance of the first forty documents of their final search to their research topics on a 1-to-5 scale Likert scale. It was hypothesized that the treatment type could have an overall effect on expected rating. Based on the data collected, the average expecting rating was statistically significant (p < 0.001) with a slight improvement of 10% due to the treatment. From a practical perspective, however, the size of the effect was modest. The findings suggest that a topic-oriented search agent might be useful in assisting information seekers to retrieve more relevant documents but suggest important directions for further evaluating methods and settings for taking advantage of such semantically-based search techniques.
Advisors/Committee Members: Smith, Philip J.
Subjects: Information Systems
Keywords: information retrieval; semantic representations
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27.
Chen, Xu.
MATHEMATICAL MODELING OF THE IN-MOLD COATING PROCESS FOR INJECTION MOLDED THERMOPLASTIC PARTS.
Degree: PhD, Industrial and Systems Engineering, 2003, Ohio State University
► In-Mold Coating (IMC) has been successfully used for many years for exterior…
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▼ In-Mold Coating (IMC) has been successfully used for many years for exterior body panels made from compression molded Sheet Molding Compound (SMC). The coating material is a single component reactive fluid, designed to improve the surface quality of SMC moldings in terms of functional and cosmetic properties. When injected onto a cured SMC part, IMC cures and bonds to provide a pain-like surface. Because of its distinct advantages, IMC is being considered for application to injection molded thermoplastic parts. For a successful in mold coating operation, there are two key issues related to the flow of the coating. First, the injection nozzle should be located such that the thermoplastic substrate is totally covered and the potential for air trapping is minimized. The selected location should be cosmetically acceptable since it most likely will leave a mark on the coated surface. The nozzle location also needs to be accessible for easy of maintenance. Secondly, the hydraulic force generated by the coating injection pressure should not exceed the available clamping tonnage. If the clamping force is exceeded, coating leakage will occur. In this study, mathematical models for IMC flow on the compressible thermoplastic substrate have been developed. Finite Difference Method (FDM) is first used to solve the 1 dimensional (1D) IMC flow problem. In order to investigate the application of Control Volume based Finite Element Method (CV/FEM) to more complicated two dimensional IMC flow, that method is first evaluated by solving the 1D IMC flow problem. An analytical solution, which can be obtained when a linear relationship between the coating thickness and coating injection pressure is assumed, is used to verify the numerical results. The mathematical models for the 2 dimensional (2D) IMC flow are based on the generalized Hele-Shaw approximation. It has been found experimentally that the power law viscosity model adequately predicts the rheological behavior of the coating. The compressibility of the substrate is modeled by the 2-domain Tait PVT equation. CV/FEM is used to solve the discretized governing equations. A computer code has been developed to predict the fill pattern of the coating and the injection pressure. A number of experiments have been conducted to verify the numerical predictions of the computer code. It has been found both numerically and experimentally that the substrate thickness plays a significant role on the IMC fill pattern.
Advisors/Committee Members: Castro, Jose.
Keywords: IMC; COATING; THERMOPLASTIC; IN-MOLD; INJECTION; Control Volume; coating injection
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28.
Chen, Yang.
Thermal Forming Process for Precision Freeform Optical Mirrors and Micro Glass Optics.
Degree: PhD, Industrial and Systems Engineering, 2010, Ohio State University
► Glass thermal forming processes are an emerging industrial techniques that can be…
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▼ Glass thermal forming processes are an emerging industrial techniques that can be adopted for high volume manufacturing of common size spherical, aspherical, and freeform glass optics, as well as micro glass optical components. Thermal forming processes discussed in this dissertation include compression molding and thermal slumping. The thermal forming processes are net shape, environment friendly and high volume production manufacturing techniques. However, there are still quite a few technical challenges associated with these new processes which include proper curvature compensation, mold design and mold life issues, residual stresses in the molded lenses, and refractive index variation after molding. These difficulties must be overcome before glass thermal forming processes can be readily implemented in industry. This dissertation research seeks a fundamental understanding of the thermal forming process for both freeform glass mirrors and glass micro optical lenses by adopting a combined experimental, analytical and numerical Finite Element Method (FEM) approach. Preliminary investigation was conducted on the optical design for beam shaping reflector and freeform two-stage solar concentrator. The freeform primary mirrors were used as thermal slumping test samples. Thermal slumping experiments were performed to determine the effects of different molding parameters i.e. the slumping temperature, holding time and cooling rate on the final thermal formed glass mirrors’ quality. The surface roughness and contour error were evaluated based on the requirement of freeform solar concentrator. The manufacturing tolerance analysis of the freeform solar concentrator system was also performed. Numerical modeling was utilized to compensate the curvature deviation during a thermal forming process, and evaluated using experimental results with matching process conditions. Moreover, in compression molding of precision glass lens experiments were also performed to study the residual stresses under different cooling rate. An FEM simulation model was developed and predictions were compared with the actual experimental results. Based on the comparison, FEM simulation can be used to predict and optimize cooling rate in the thermal forming process. Finally, compression molding experiments were performed to fabricate glass microlens arrays and diffractive optical elements (DOEs). The molded glass micro optical lenses were measured with AFM/SEM, and the optical performance of the molded lens was also evaluated by using a home-built optical metrology setup. Experimental results have showed that the thermal forming processes are capable of producing precision freeform glass mirrors and glass micro optics with shape and surface quality within the tolerance requirement.
Advisors/Committee Members: Yi, Allen.
Subjects: Engineering
Keywords: glass molding, precision optics, freeform optics, micro optis, FEM simulation
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29.
Chia, Liang Wei.
Determination of an Optimal Green Solution of an Education Building Based On Net Present Value and Life Cycle Carbon Dioxide Emissions.
Degree: MS, Industrial and Systems Engineering, 2009, Ohio State University
► In a highly populated area such as university campus, there is limited…
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▼ In a highly populated area such as university campus, there is limited space available to implement green solution outside the buildings. Roof tops provide opportunities to implement solution that can reduce the net emission of the building operation. However, they might come with a high capital cost and higher life-cycle emissions. By comparing the installation of three different building energy-saving technologies on a roof top of a 6640 ft2 education building located in Midwest area, we found that green roof is the best option of the green solutions considered. Green roof has the least negative net present value that ranges from -$95,423 to -$93,381 and a reduction of 595.16 metric tons of life-cycle CO2 emissions, the highest among the three. For asphalt roof, the net present value ranges from -$103,020 to -$102,730 and reduction of 579.21 metric tons of life-cycle CO2 emissions. Photovoltaic (PV) system is the most costly option. If we assume the efficiency of the PV system increases by 10 percent every decade without adding any capital cost, the net present value will range from -$340,132.17 to -$317,366.04 and the life-cycle CO2 emissions will increase by 605.69 metric tons. On the other hand, if the efficiency does not improve, the net present value will range from -$342,365.46 to -$321,828.95 and the life-cycle CO2 emissions will be 718.14 metric tons.
Advisors/Committee Members: Sioshansi, Dr. Ramteen.
Subjects: Architecture; Chemical engineering; Civil engineering; Environmental engineering; Environmental science; Industrial engineering; Operations research
Keywords: asphalt roof, green roof, photovoltaics
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30.
Cho, Hyunjoong.
Development of advanced techniques for identification of flow stress and friction parameters for metal forming analysis.
Degree: PhD, Industrial and Systems Engineering, 2007, Ohio State University
► The accuracy of process simulation in metal forming by finite element method…
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▼ The accuracy of process simulation in metal forming by finite element method depends on the accuracy of flow stress data and friction value that are input to FEM programs. Therefore, it is essential that these input values are determined using reliable tests and evaluation methods. This study presents the development of inverse analysis methodology and its application to determine flow stress data of bulk and sheet materials at room and elevated temperatures. The inverse problem is defined as the minimization of the differences between the experimental measurements and the corresponding FEM predictions. Rigid-viscoplastic FEM is used to analyze the metal flow while a numerical optimization algorithm adjusts the material parameters used in the simulation until the calculated response matches the measured data within a specified tolerance. The use of the developed inverse analysis methodology has been demonstrated by applying it to the selected reference rheological tests; cylinder compression test, ring compression test, instrumented indentation test, modified limiting dome height test, and sheet hydraulic bulge test. Furthermore, using the determined material property data, full 3-D finite element simulation models, as examples of industrial applications for orbital forming and thermoforming processes have been developed for reliable process simulation. As results of this study, it was shown that the developed inverse analysis methodology could identify both the material parameters and friction factors from one set of tests, simultaneously. Therefore, this technique can offer a systematic and cost effective way for determining material property data for simulation of metal forming processes.
Advisors/Committee Members: Altan, Taylan.
Keywords: Flow Stress; Finite Element Method; Inverse Analysis; Material Characterization
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