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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
441

Adaptive tool selection strategies for drilling in flexible manufacturing systems

Chander, Karthik Balachandran 30 September 2004 (has links)
The thesis presents an approach to adaptive decision making strategies to reduce bottlenecks in a drilling operation and to extend tool life. It is an attempt to portray the real drilling system in a typical Flexible Manufacturing System (FMS) layout. The system designed serves as back end intelligence to drilling machines (INTELLIDRILL) in a Flexible Manufacturing System for making dynamic and real time decisions. INTELLIDRILL uses mathematical and adaptive tool reliability models to simulate the machining conditions and tool availability for an operation based on history of tool failures. The results are used to compute the machining parameters and the tools required for an operation. INTELLIDRILL can devise strategies for different tool materials to operate on batches of different materials. INTELLIDRILL decisions could lead to significant savings in tooling costs and reduction in flow line bottlenecks.
442

Developing high performance manufacturing systems

Karlsson, Anders January 2002 (has links)
<p>The work detailed in this dissertation relates to thedevelopment of high performance manufacturing systems. Theperformance factor aimed for is especially flexibility, butthere is an intention of making the results adaptable to focuson performance factors of the readers or users choice. Thefocus of the presented research is not only to provide meansfor accomplishing manufacturing that can handle changes butalso to accomplish flexibility in another area. The resultsshould be applicable in many different situations. The researchhas been divided into three parts: the further development of amanufacturing strategy, the development of a base for amanufacturing system design method and the development of amanufacturing control system.</p><p>The developed strategy is called Assembly-InitiatedProduction (AIP). An implementation of the strategy shouldprovide high manufacturing system flexibility but at the sametime contribute to the lowering of inventory levels andlead-times. Different solutions coupled to technicalrequirements found are also discussed.</p><p>The design method research focuses on basic manufacturingsystem properties and the possibility of expressing theseproperties by using simple combinable abstract units calledconcepts. The principle is the same as in physics where realworld phenomena may be expressed by using standard concepts asfor example time and mass. The intended use of the results isin an early manufacturing system design phase. The method isnot directly linked to the AIP strategy, but could be used forimplementing it.</p><p>Production Planning and Control (PPC) is an important partof a manufacturing system. After having reviewed current PPCpractices, a need for a factory floor PPC system workingregardless of factory floor layout, was identified. Based ontheoretical and industrial studies, the suggested solution is acomputerised, decentralised control system, physicallyseparated from the PPC/ERP system. In order to be able to makequick changes in the schedule, to obtain flexibility and toprovide the organisation with a tool for manufacturing controland decision-making, the system works in real time to provideaccurate and valid data.</p>
443

Study on a second-order bandpass Σ∆-modulator for flexible AD-conversion

Svensson, Hanna January 2008 (has links)
<p>An important component in many communication system is the digital to analog converter. The component is needed in order to convert real world analog quantities to digital quantities which are easier to process. As the market for hand held devices with wireless communication with the outer world has increased new approaches for sharing the frequency spectrum are needed. Therefore it would be interesting to look at the possibility to design an analog to digital converter that, in runtime, can change the frequency band converted, and hence the used standard. This thesis study one of the possibilities to design such an ADC, as a Σ∆ modulator, and more precise the structure called Cascade of resonators with distributed feedback and input (CRFB). The order of the modulator in this study is two.</p>
444

Combined integral and robust control of the segmented mirror telescope

Looysen, Michael W. January 2009 (has links) (PDF)
Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Agrawal, Brij; Kim, Jae Jun. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: MIMO control, Robust control, adaptive optics, segmented mirrors, flexible structures, space telescopes, Shack-Hartmann sensors, hybrid controller. Includes bibliographical references (p. 77). Also available in print.
445

An empirical investigation of manufacturing flexibility and organizational performance as moderated by strategic integration and organizational infrastructure

Rogers, Pamela Rose Patterson. White, Richard E., January 2008 (has links)
Thesis (Ph. D.)--University of North Texas, Aug., 2008. / Title from title page display. Includes bibliographical references.
446

Attitude control of flexible structures

Ward, Christina C. January 1990 (has links) (PDF)
Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Agrawal, Brij N. Second Reader: Titus, Harold. "September 1990." Description based on title screen as viewed on December 17, 2009. DTIC Identifier(s): Attitude Control Systems, Flexible Structures, Spacecraft, Structural Response, Resonant Frequency, Experimental Design, Model Tests, Active Control, Gifts Computer Program, Dynamic Response, Computerized Simulation, Control Theory, Modal Analysis, Laboratory Tests, Theses. Author(s) subject terms: Attitude Control, Flexible Structures. Includes bibliographical references (p. 52). Also available in print.
447

An agent based infrastructure for manufacturing cell control /

Fan, Chi-kit. January 2001 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references.
448

Characterization of cement-kiln-dust stabilized base/subbase aggregate /

Zhu, Jianhua, January 1998 (has links)
Thesis (Ph. D.)--University of Oklahoma, 1998. / Includes bibliographical references (leaves 215-221).
449

High-performance single-unit and stacked inverted top-emitting electrophosphorescent organic light-emitting diodes

Knauer, Keith Anthony 08 June 2015 (has links)
This thesis reports on the design, fabrication, and testing of state-of-the-art, high-performance inverted top-emitting organic light-emitting diodes (OLEDs). The vast majority of research reports focuses on a device architecture referred to as a conventional OLED which has its anode on the bottom of the device and its cathode on the top. Moreover, most conventional OLEDs are bottom-emitting such that light exits the structure through both a semitransparent bottom electrode of indium-tin oxide and a glass substrate. The particular device architecture developed in this thesis is one in which the devices are inverted (i.e. their cathode is on the bottom as opposed to on top) and top-emitting. Despite the advantages that inverted top-emitting OLEDs possess over conventional bottom-emitting OLEDs, their development has been relatively slow. This is because inverted OLEDs have traditionally been hampered by the difficulty of injecting electrons effectively into the device. In this work, a novel method of injecting electrons from bottom cathodes into inverted OLEDs is discovered. In several previous reports, bottom Al/LiF cathodes had been used with the electron-transport material Alq3 to produce inverted OLEDs, but the resulting inverted OLEDs exhibited inferior performance to conventional OLEDs with top cathodes of Al/LiF. A new route for the development of highly efficient inverted OLEDs is shown through the use of electron-transport materials with high electron mobility values and large electron affinities. After systematic device optimization, inverted top-emitting OLEDs are demonstrated that currently define the state-of-the-art in terms of device efficiency. Optimized green and blue inverted top-emitting OLEDs are demonstrated that have a current efficacies of 92.5 cd/A and 32.0 cd/A, respectively, at luminance values exceeding 1,000 cd/m2. Finally, this discovery has enabled the development of the first stacked inverted top-emitting OLEDs ever made, combining all of the advantages offered by an inverted architecture, a top-emissive design, and a stacked structure. These OLEDs have a current efficacy of 200 cd/A at a luminance of 1011 cd/m2, attaining a maximum current efficacy of 205 cd/A at luminance of 103 cd/m2.
450

Framework for compressed workweek implementation for TxDOT maintenance forces and flexible work arrangements for employees

Loskorn, Jeffrey Aaron 16 February 2012 (has links)
With the increasing need for highway maintenance and the decreasingly available funds, the Texas Department of Transportation (TxDOT) Austin District has sought to better utilize maintenance section employee resources by implementing a compressed workweek. The primary goal of this thesis is to establish a framework and methodology to study the effects of a compressed workweek on maintenance crews in both rural and urban environments. Secondly, this thesis will provide a background of best practices of popular flexible work arrangements, including compressed workweeks, telework, and flextime. The compressed workweek is a type of flexible work arrangement that allows employees to work longer days during a part of the week in exchange for a partial or full day off later in the week. Compressed workweeks can offer numerous benefits to maintenance crews, including increased production, less set up and shut down time per week, decreased operating costs, reduced overhead, and increased employee morale. TxDOT will implement a six-month pilot project in two rural maintenance sections and one urban section. Compressed workweeks have proven to be successful in other districts with rural maintenance sections, but application of a compressed workweek in an urban maintenance section has yet to be studied. Therefore, maintenance crew activity data from previous years will be compared to data collected during the trial period to understand changes in productivity and to estimate vehicle operating costs. Lastly, surveys of maintenance employees will be conducted throughout the study to solve any personal issues that arise as well as determine employee satisfaction with the new schedule. / text

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