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Master of Science / Department of Industrial & Manufacturing Systems Engineering / John R. English / Inventory accuracy is critical for almost all industrial environments such as distribution, warehousing, and retail. It is quite common for companies with exceptional inventory accuracy to use a technique called cycle counting. For many organizations, the time and resources to complete cycle counting are limited or not available. In this work, we promote statistical process control (SPC) to monitor inventory accuracy. Specifically, we model the complex underlying environments with mixture distributions to demonstrate sampling from a mixed but stationary process. For our particular application, we concern ourselves with data that result from inventory adjustments at the stock keeping unit (SKU) level when a given SKU is found to be inaccurate. We provide estimates of both the Type I and Type II errors when a classic c chart is used. In these estimations, we use both analytical as well as simulation results, and the findings demonstrate the environments that might be conducive for SPC approaches.

<p>A bidding process is one of the main activities of construction project management. For general contractors, the chance of awarding projects in a bidding process directly relies on the success of selecting the best subcontractor. Therefore, an effective and accurate method of choosing subcontractors affect directly on the profit earned by the general contractors. Traditionally, a general contractor makes selection decision based on its managers&rsquo; subjective opinion regarding subcontractors&rsquo; price quotations. This approach in selecting subcontractors may result in low efficiency and quality of work. This thesis presents an Analytic Hierarchy Process (AHP) method considering the weight of each factor when a subcontractor is valued. The Genetic Algorithm method is on the basis of AHP for dealing with the subcontractor selection to establish a subcontractor value rating system. A real project example is explained and evaluated to demonstrate the feasibility of the method. This thesis is of value to general contractor with a regard to providing a tool for bidding process in the early stage of construction projects. </p>

This dissertation addresses a class of fundamental logistical problems where two or more potential users (or players) compete for a common set of resources. Each user has a criterion (cost or performance requirement) that he/she wishes to optimize. The users' criteria are often in conflict, that is, choosing a decision that optimizes one user's criterion may not also optimize the criteria of others. How should the resources be utilized to satisfy the user demands? In this dissertation, optimization and game theoretical models are employed to examine the equilibrium points and efficiently find the frontier of non-dominated solutions to three logistics problems with competing users: (1) single machine scheduling, (2) network resource allocation and (3) assignment to multiple servers (queues). New cooperative game theoretic methods are developed to negotiate on the Pareto frontier. In addition, a Stackelberg leader-follower game framework is introduced in a queueing system which includes both competitive users and competitive servers. The existence of a unique equilibrium is shown. The models and methodologies developed in the dissertation can be applied in many areas, such as Internet pricing, scheduling resources among competitors, network routing of users' requirements, analysis of competitive market, etc.

A new fracture grouting technology has been developed to meet the requirements of high-level nuclear waste isolation. Bentonite fracture grouting tests are performed on a fracture model, made of circular acrylic plates with outer diameter of 30 cm and a central injection hole of 2.5 cm diameter. Suspensions with bentonite concentration of 9% to 31% have been injected into fractures with apertures of 9 to 39 microns under injection pressures less than 0.5 MPa. After grouting, the hydraulic conductivities of the fractures are reduced from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studied.

First, this thesis presents four types of dynamic models for one-link flexible manipulators: Euler-Bernoulli model, Euler-Bernoulli model with rotatory inertia, Timoshenko model, and Euler-Bernoulli model with tip mass through Hamilton Principle, and exact modal frequencies and vibration modes are derived through Laplace transformation and eigenanalysis. The numerical analysis is conducted to verify the established models and investigate the influences of rotatory inertia, shear deformation and tip mass. Second, this thesis presents the exact dynamic solutions of Euler-Bernoulli model for the step torque input and design of a dynamics simulator for one-link flexible manipulators based on the exact dynamic solutions. Several types of sensor models have been specified in the designed simulator to provide various sensory data sets required for feedback controls. A simulation study is performed to verify the designed simulator and to demonstrate the usage of the dynamics simulator for controller design and evaluations.

<p> The purpose of this qualitative phenomenological study was to examine the phenomenon of enhanced, risk-based Federal Aviation Administration (FAA) oversight of Part 145 repair stations that performed aircraft maintenance for Part 121 air carriers between 2007 and 2014 in Oklahoma. Specifically, this research was utilized to explore what operational changes have occurred in the domestic Part 145 repair station industry such as variations in management or hiring practices, training, recordkeeping and technical data, inventory and aircraft parts supply-chain logistics, equipment, and facilities. After interviewing 12 managers from Part 145 repair stations in Oklahoma, six major theme codes emerged from the data: <i>quality of oversight before 2007, quality of oversight after 2007, advantages of oversight, disadvantages of oversight, status quo of oversight,</i> and <i>process improvement </i>. Of those six major theme codes, 17 subthemes appeared from the data that were used to explain the phenomenon of enhanced oversight in the Part 145 repair station industry. Forty-two percent of the participants indicated a weak FAA oversight system that has hindered the continuous process improvement program in their repair stations. Some of them were financially burdened after hiring additional full-time quality assurance inspectors to specifically manage enhanced FAA oversight. Notwithstanding, the participants of the study indicated that the FAA must apply its surveillance on a more standardized and consistent basis. They want to see this standardization in how FAA inspectors interpret regulations and practice the same quality of oversight for all repair stations, particularly those that are repeat violators and fail to comply with federal aviation regulations. They believed that when the FAA enforces standardization on a consistent basis, repair stations can become more efficient and safer in the performance of their scope of work for the U.S. commercial air transportation industry.</p>

The literature is replete with articles extolling the benefits or the drawbacks associated with the implementation of quality management programs. The divergent levels of performance associated with these programs may be associated with the breadth and depth to which the characteristics of quality management become ingrained within organizational structures and systems. / This study employed large sample questionnaire administration to gather measures of the key characteristics of quality management programs in ISO-9000 registered organizations. Use of data reduction techniques on the questionnaire data suggest that there are eleven key, statistically significant and statistically reliable, characteristics associated with quality management programs in ISO-9000 registered organizations. Prediction of profitability and liquidity measures with these eleven factors, across three levels of performance, suggested differential usage of these factors within above-average, average, and below-average performing firms that responded to the questionnaire. / Source: Dissertation Abstracts International, Volume: 57-03, Section: A, page: 1217. / Major Professors: Thomas D. Clark, Jr.; Ralph M. Stair, Jr. / Thesis (Ph.D.)--The Florida State University, 1996.

<p> The subject of extensive research has been the establishing of lower temperature soldering of electronic assemblies that are similar to the once common yet still preferred eutectic Tin-Lead (SnPb) soldering manufacturing processes that are below 217 &deg;C. This research opportunity will contribute data on mixed solder alloy assemblies that can be formed at lower process temperatures. There are many environmental and economic benefits of avoiding the current reliability concerns of assembling electronics at the standard high temperatures which peak at 230 &deg;C 260 &deg;C. To reduce this temperature the use of Bismuth containing solder pastes are mixing with the standard high temperature SAC solders for electronic assemblies. The materials evaluated are the (in weight percentages) 96.5Tin/3Silver/.5Copper (Sn/Ag/Cu) solder ball mixed with each solder paste, the eutectic 58Bismuth/42Tin (58Bi/42Sn), 57Bi/42Sn /1Ag and a propriety alloy that has a lower Bismuth content along with various micro alloys, 40-58Bi/Sn/X (X representing proprietary micro alloys or doping). In the assembly portion of this research the solder alloys were exposed to three different peak temperatures 180 &deg;C, 195 &deg;C, 205 &deg;C. Another reflow profile attribute of focus was times above 138 &deg;C the melting point of the eutectic Sn58Bi alloy. The ball and paste assembly portion of this research used the times above melting of 120sec and 240sec to represent process extremes and verify their significance on improving mixing level results. These times above melting did not consistently improve the mixing levels and therefore are not recommended or required during mixed low temperature solder assemblies. The results in this study suggest the recommended and optimum reflow profile to have a time above the melting point to be less than or equal to 90 seconds for mixed solder alloy assemblies in &ldquo;low&rdquo; (&lt; 200 &deg;C) peak temperature reflow oven profiles. This attribute ensures a reflow window similar to that of the eutectic SnPb processing. The second leg of this research was with a component assembly of a large ball grid array at the same various peak temperatures with a single time above 138 &deg;C, 90sec. This &ldquo;large&rdquo; (> 20mm a side) component is a SAC405 solder balled BGA with the dimensions of 42 &times; 28 &times; 0.8mm. With any large component the temperature gradient across the component is a risk factor and the results show that there are significantly differences of mixing from the center of the component to the edge due to an average 2.3 &deg;C temperature difference during convection reflow. The average mixing % levels recorded for T_peak= 180 &deg;C for the solder pastes with a 58Bi = 47%, 57Bi = 47% and 40-58Bi = 44%. The average mixing % levels recorded for T_peak= 195 &deg;C for the solder pastes with a 58Bi = 69%, 57Bi = 77% and 40-58Bi = 57%. The conclusions found also match previous work identifying the reflow peak temperatures remain a significant factor on the mixing %. This work&rsquo;s goal was to add to the knowledge of the electronics industry to better understanding the microstructure and mixing mechanisms of Bi/Sn/X-SAC solder joints for low temperature reflow assembly processes. </p><p>

acase@tulane.edu