Engineering Commons^™

Dissolution Rate And Mechanism Of Metals In Molten Aluminum Alloy A380, Hengyu Zhu

Open Access Theses

Shot sleeve is a very easily worn out part in a high-pressure die-casting machine due to serious dissolution of the area underneath the pouring hole. It is because during a normal pouring process, the high temperature molten aluminum will impact and dissolve that area of the shot sleeve by complex chemical and physical process. Rotation experiment was carried out to H13 and four kinds of refractory metal samples. SEM and EDS pictures were taken in order to investigate the microstructure and the dissolution mechanism of these materials. This suggests a high strength niobium is an ideal material for that area …

Evaluating Intensity As A Controller Function For Nextgen Scenarios With Increased Capacity, Caitlin Anne Surakitbanharn

Open Access Theses

Automated separation assurance is the most mature concept to handle increasing airspace traffic and capacity needs, yet the system lacks a way to pre-emptively identify aircraft separation problems. The intensity control measure looks to find situations where if an aircraft pair makes an unplanned change in heading or altitude at the wrong moment, an unrecoverable situation arises. This research analyzes static, open loop air traffic data in an en-route sector to determine how many high intensity aircraft pairs (HIP) exist per minute, and if the intensity measure is a safely manageable function for air traffic controllers. It is found that …

The Multi-Depot Minimum Latency Problem With Inter-Depot Routes, Timothy W. Duket

Open Access Theses

The Minimum Latency Problem (MLP) is a class of routing problems that seeks to minimize the wait times (latencies) of a set of customers in a system. Similar to its counterparts in the Traveling Salesman Problem (TSP) and Vehicle Routing Problem (VRP), the MLP is NP-hard. Unlike these other problem classes, however, the MLP is customer-oriented and thus has impactful potential for better serving customers in settings where they are the highest priority. While the VRP is very widely researched and applied to many industry settings to reduce travel times and costs for service-providers, the MLP is a more recent …

Detailed Inventory Record Inaccuracy Analysis, Hayrettin Kaan Okyay

Graduate Theses and Dissertations

This dissertation performs a methodical analysis to understand the behavior of inventory record inaccuracy (IRI) when it is influenced by demand, supply and lead time uncertainty in both online and offline retail environment separately. Additionally, this study identifies the susceptibility of the inventory systems towards IRI due to conventional perfect data visibility assumptions. Two different alternatives for such methods are presented and analyzed; the IRI resistance and the error control methods. The discussed methods effectively countered various aspects of IRI; the IRI resistance method performs better on stock-out and lost sales, whereas error control method keeps lower inventory. Furthermore, this …

Poisson Distributed Individuals Control Charts With Optimal Limits, Negin Enayaty Ahangar

Graduate Theses and Dissertations

The conventional method used in attribute control charts is the Shewhart three sigma limits. The implicit assumption of the Normal distribution in this approach is not appropriate for skewed distributions such as Poisson, Geometric and Negative Binomial. Normal approximations perform poorly in the tail area of the these distributions. In this research, a type of attribute control chart is introduced to monitor the processes that provide count data. The economic objective of this chart is to minimize the cost of its errors which is determined by the designer. This objective is a linear function of type I and II errors. …

Exploratory Study In Container Loading Embraer 190 Aircraft, Ryan H. Auyeung

Open Access Theses

Since the dawn of aviation, cargo loading on aircraft has remained virtually constant. A person and a baggage cart together have been the primary method of loading baggage on to aircraft, and this practice has virtually remained unchanged, especially for narrow body aircraft. This study explores the question of whether a loading device, designed for Embraer 190 aircraft, can increase economic efficiency by reducing aircraft turnaround times, increasing aircraft utilization and reducing work hours. In the course of designing a theoretical loading device for an Embraer 190, various literature ranging from elaborate articulating conveyor belts, to the use of LD3-45W …

Detecting Air Traffic Controller Interventions In Recorded Air Transportation System Data, Yul Kwon

Open Access Theses

In this study, I propose a systematic method of detecting aircraft deviation due to air traffic controller (ATC) intervention. The aircraft deviations associated with ATC interventions are detected using a heuristic algorithm developed from analyzing the actual positions of an aircraft to its filed flight plan when the aircraft trajectories were identified as having an encounter in a loss-of-separation incident. An actual (closed-loop) flight trajectory of the Cleveland Air Route Traffic Control Center (ZOB ARTCC) was collected from the FlightAware database. This was compared with the corresponding planned (open-loop) trajectory dataset generated by the Microsoft© Flight Simulator X (FSX). I …

Modeling And Optimization Of Care Transitions, Yuming Mo

Open Access Theses

More than 145 million people live with at least one chronic condition, and almost half of them have multiple conditions. As a result, many managed care and integrated delivery systems have taken a great interest in alleviating the many deficiencies in managing the current care system that spans across various care delivery settings. In addition, many Americans have to rely on some social health insurance plan to cover her care expenses. As a result, these patients often may not been sufficiently cured but have to be transitioned to less expensive but less medically intensive facilities, due to the increasing pressure …

A Comparative Analysis Of An Original And A Post-Hoc Application Of Lean Six Sigma Methodology, Jin Qiu

Open Access Theses

Current society develops faster and faster every day with customers' demands increasing rapidly. Decreasing time for product development and enhancing customer satisfaction are becoming more significant. In the business world, there is no industry that could exist without an efficient supply chain. In the fierce competitive environment of today, the supply chain must address potential problems and risks that may exist and assure continuous improvement.

One common supply chain management practice in many industries is to apply lean methodology to the supply chain model in order to maximize the customers' value and eliminate waste. By eliminating waste, the process can …

A Lean Logistics Assessment Tool For Smes In The Manufacturing Sector, Diana Lorena Sanchez Ramirez

Open Access Theses

This study developed an assessment tool to rate the maturity of the current and desired states of lean logistics operations in small and medium enterprises. The tool consists of 48 best practices classified into 8 critical factors: Inventory, Transportation, Administration, Information Systems, Warehouse, Forecasting, Packaging and Supplier Network. Each of the best practices and critical factors were identified throughout a thorough literature review and comparative analysis between authors to define commonalities among them. Using gap analysis; this tool results in a SWOT matrix providing a roadmap for lean implementation. The resulting model was evaluated by subject matter experts in different …

The Effect Of Job Performance Aids On Quality Assurance, Erik David Fosshage

Open Access Theses

Job performance aids (JPAs) have been studied for many decades in a variety of disciplines and for many different types of tasks, yet this is the first known research experiment using JPAs in a quality assurance (QA) context. The objective of this thesis was to assess whether a JPA has an effect on the performance of a QA observer performing the concurrent dual verification technique for a basic assembly task. The JPA used in this study was a simple checklist, and the design borrows heavily from prior research on task analysis and other human factors principles. The assembly task and …

Nanohub Database Analysis: Using Anomaly Detection Method And Principal Component Analysis, Mengyang Qi

Open Access Theses

This thesis analyzes usage data from nanoHUB.org, which is a web-based infrastructure for e-collaboration among nanotechnology simulation community. Previous analysis of nanoHUB database showed he nanoHUB usage data follows an unknown, heavy-tailed distributions. This thesis extends the analysis and develops an automatic anomaly detection method based on piece-wise linear approximation. The anomaly here refers to collective user behaviors different from others. The result shows that the method can accurately detect the anomalies in the unknown, heavily detailed distribution. This thesis also applies anomaly detection method and principal component analysis to other databases in nanoHUB and successfully reveals differences between different …

Modeling Preventive Maintenance In Complex Systems, Jessica Rivas

Open Access Theses

This thesis presents an explicit consideration of the impacts of modeling decisions on the resulting maintenance planning. Incomplete data is common in maintenance planning, but is rarely considered explicitly. Robust optimization aims to minimize the impact of uncertainty--here, in contrast, I show how its impact can be explicitly quantified. Doing so allows decision makers to determine whether it is worthwhile to invest in reducing uncertainty about the system or the effect of maintenance. The thesis consists of two parts. Part I uses a case study to show how incomplete data arises and how the data can be used to derive …

Human Cognitive Performance In Healthcare Information System Environment And Its Application On Nursing Tasks, Byung Cheol Lee

Open Access Dissertations

The US healthcare system has serious issues in care quality and patient safety. Patients often do not receive the care they need or the given care service cause harm. In addition, the significant amounts of medical and medication errors occur, and recurring adverse drug events due to damaging side effects from medications threaten patient safety. To solve these issues, healthcare information systems (HIS) have been recommended in various care processes. Though several studies have confirmed the benefits and usefulness of the systems (Cordero, Kuehn, Kumar, & Mekhjian, 2004; Kohn, Corrigan, & Donaldson, 2000; Sittig, Krall, Kaalaas-Sittig, & Ash, 2005; Weiner …

Design, Development, And Testing Of A Conformal Power Control Interface For Thrust Vectoring Aircraft, David Rozovski

Open Access Dissertations

Over the last five years, a new power control inceptor for tiltrotor aircraft, known as the Rotational Throttle Interface (RTI) was designed and built. Prior to the RTI, no tiltrotor inceptor had been able to simultaneously indicate both the direction and magnitude of thrust conformally. The purpose of the RTI is to provide an interface that maps to the intended vehicle response throughout ALL ranges of operation. Doing so is expected to reduce confusion that may have contributed to several tiltrotor accidents

Two tests were conducted with the RTI, one at the NASA Vertical Motion Simulator, and one at Canada's …

Parameterizing Analytical Models To Support An Empirically Based Warehouse Design Methodology, Lisa Thomas

Graduate Theses and Dissertations

Research in the area of warehouse design is characterized by a myriad of analytical models that address one, typically small and isolated, area of the warehouse. These models, although important in gaining insight into one question of warehouse design, are of limited value when one considers the larger question of overall warehouse design. Thus, research in the area of overall warehouse design typically consists of procedure-driven processes based on qualitative factors and not the quantifiable results of analytical models.

In contrast, practitioners have significant empirical data related to how a design alternative performs in an industry, a company, or a …

High Speed Turning Of Compacted Graphite Iron (Cgi) Using Controlled Modulation, Tyler Paul Stalbaum

Open Access Theses

Compacted graphite iron (CGI) is a material which emerged as a candidate material to replace cast iron (CI) in the automotive industry for engine block castings. Its thermal and mechanical properties allow the CGI-based engines to operate at higher cylinder pressures and temperatures than CI-based engines, allowing for lower fuel emissions and increased fuel economy. However, these same properties together with the thermomechanical wear mode in the CGI-CBN system result in poor machinability and inhibit CGI from seeing wide spread use in the automotive industry.

In industry, machining of CGI is done only at low speeds, less than V = …

Scheduling In Mohs Micrographic Surgery Clinics, Stephen Vincent Steidle

Open Access Theses

Mohs Micrographic Surgery (MMS) is a surgical method used for the excision of aggressive skin cancers in areas of high cosmetic importance, such as the face and hands. The practice has been gaining popularity worldwide for its low recurrence rates and cosmetic results. Current clinics though are plagued by extreme wait times and an overall poor patient experience. In this paper we look to explore this problem by applying systems engineering principles including optimization and scheduling with the goal of improving the patient experience. Currently, little literature exists exploring the difficulties associated with scheduling for MMS clinic which primarily revolve …

Locating And Protecting Facilities Subject To Random Disruptions And Attacks, Hugh Medal

Graduate Theses and Dissertations

Recent events such as the 2011 Tohoku earthquake and tsunami in Japan have revealed the vulnerability of networks such as supply chains to disruptive events. In particular, it has become apparent that the failure of a few elements of an infrastructure system can cause a system-wide disruption. Thus, it is important to learn more about which elements of infrastructure systems are most critical and how to protect an infrastructure system from the effects of a disruption. This dissertation seeks to enhance the understanding of how to design and protect networked infrastructure systems from disruptions by developing new mathematical models and …

Patient And Nurse Considerations In Home Health Routing With Remote Monitoring Devices, Jessica Spicer

Graduate Theses and Dissertations

We build on the current consistent vehicle routing problem literature by formulating a novel multi- objective mathematical model of the home health scheduling and routing problem that includes the option of assigning some patient visits to remote monitoring devices, with the objectives of mini- mizing total cost, achieving nurse consistency and creating balanced nurse workloads. A heuristic solution approach that approximates the efficient frontier of this multiobjective problem is pre- sented and validated, and the results of using this methodology to solve several realistic instances are included. We also analyze the assignment of patients to devices and present some managerial …

Inventory Models For Intermittent Highly Variable Demand And Policy Parameter Adjustments To Meet Desired Service Level Requirements, Yasin Unlu

Graduate Theses and Dissertations

This dissertation consists of three assays. The first assay examines the robustness of lead time demand models for the continuous review (r;Q) inventory policy. A number of classic distributions as well as distribution selection rules are examined under a wide variety of demand conditions. First, the models are compared to each other by assuming a known demand process and evaluating the errors associated with using a different model. Then, the models are examined using a large sample of simulated demand conditions. Approximation results of inventory performance measures - ready, rate excepted number of backorders and on-hand inventory levels are reported. …

Integrated Planning For Rural Rail Transportation, Jeffrey Cohan Gwaltney

Graduate Theses and Dissertations

Population growth in rural areas has led to new interest in rail transportation. Planning a passenger rail system involves numerous difficult decisions, most representing a trade-off between customer service and cost. In this work, we attempt to integrate many of these planning decisions. We consider strategic decisions such as station location and vehicle procurement, as well as tactical issues that include vehicle scheduling. Our integrated model exploits the linear network structure that best suits many rural American communities, including Northwest Arkansas. Due to the intractability of the integrated rail planning problem, we have developed a customized heuristic approach to solve …

Adaptive Intensity Modulated Radiation Therapy Planning Optimization With Changing Tumor Geometry And Biology Enforcing Both Cumulative And Fraction Size Dose Constraints, Behlul Saka

Graduate Theses and Dissertations

Intensity Modulated Radiation Therapy (IMRT) is a modern technique of delivering radiation treatments to cancer patients. In IMRT technology, intensities must be chosen for the many small unit grids into which the beams are divided to produce a desired distribution of dose at points throughout the body with the goal of maximizing dose delivered to the tumor while sparing healthy tissues from excessive radiation and keeping dose homogeneous across the tumor. Although IMRT plans are optimized as a single overall treatment plan, they are delivered over 30-50 treatment sessions (fractions) and both cumulative and per-fraction dose constraints apply. The extended …

An Empirical Investigation Of Supply Chain Excellence In Healthcare, Brian Keith Smith

Graduate Theses and Dissertations

This research is motivated by opportunities to improve the cost and quality of healthcare delivery through improved supply chain processes. This research assesses the quality of the healthcare supply chain and identifies factors that are driving supply chain excellence among organizations in the healthcare industry. The first objective of this research is to assess the state of quality measurement in the healthcare supply chain. The achievement of this first objective is presented in Chapter 3 of this dissertation in the form of a manuscript accepted for publication in The Quality Management Journal. The second research objective is to develop …

"Hedging Future Uncertainty: A Framework For Obsolescence Prediction, Proactive Mitigation And Management", Craig L Josias

Doctoral Dissertations 1896 - February 2014

Component obsolescence in the "high-tech" electronics industry has become a problem that cannot be ignored. Although recent attention has been given to component obsolescence, in general this issue is still dealt with reactively. This often results in sustainment of a long-life system such as ships, airplanes, power plant, and space based programs to be extremely costly. In addition, delayed schedules, extended downtimes, and technology lags are common occurrences in approaches that deal with obsolescence as it occurs. In wake of the rapid pace of technology innovation, turbulent markets and growing globalization, developing proactive approaches for dealing with obsolescence is a …

Investments In Energy Technological Change Under Uncertainty, Ekundayo Shittu

Doctoral Dissertations 1896 - February 2014

This dissertation addresses the crucial problem of how environmental policy uncertainty influences investments in energy technological change. The rising level of carbon emissions due to increasing global energy consumption calls for policy shift. In order to stem the negative consequences on the climate, policymakers are concerned with carving an optimal regulation that will encourage technology investments. However, decision makers are facing uncertainties surrounding future environmental policy. The first part considers the treatment of technological change in theoretical models.

This part has two purposes: (1) to show-through illustrative examples-that technological change can lead to quite different, and surprising, impacts on the …

An Analysis Of Sustained Collaborative Research Activities Between University Organized Research Units And Industry: A Case Study Of Three Institutions, Elizabeth Taraski Mcdonnell

Seton Hall University Dissertations and Theses (ETDs)

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