Thesis (M.S.)--Ohio University, June, 1995. / Title from PDF t.p.

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Much attention has been directed at off-line quality control techniques in recent literature. This study is a refinement of and an enhancement to one technique, the Taguchi Method, for determining the optimum setting of design parameters in a product or process. In place of the signal-to-noise ratio, the mean square error (MSE) for each quality characteristic of interest is used. Polynomial models describing mean response and variance are fit to the observed data using statistical methods. The settings for the design parameters are determined by minimizing a statistical model. The model uses a multicriterion objective consisting of the MSE for each quality characteristic of interest. Minimum bias central composite designs are used during the data collection step to determine the settings of the parameters where observations are to be taken. Included is the development of minimum bias designs for various cases. A detailed example is given.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Statistical experimental design techniques are powerful tools that are often approached with suspicion and apprehension by experimenters. The trend is to avoid any statistically structured and designed experimentation program, and to rather use the traditional method of following ones "gut feel". This approach, more often than not, will supply a satisfactory solution, but there is so much more information availablefor the same amount of effort. This thesis strives to outline the method and application of the Taguchi methodology of experimental design. The Taguchi method is a practical, statistical experimental design technique that does not rely on the designer's knowledge of the complex statistics typicallyneeded to design experimental programs, a fact that tends to exclude design of experiments from the averageengineers' toolbox. The essence of the statistical design of experiments is this: The traditional method of varying one variable at a time and investigating its effect on an output is no longer sufficient. Instead all the input variables are varied at the same time in a structured manner. The output trends resulting from each input variable are then statisticallyextracted from the data in the midst of the variation. Taguchi method achieves this by designing experiments where every level of every input variable occurs an equal number of times with every level of every other input variable. The experimental designs are represented in orthogonal arrays that are chosen and populated by the experimenter by following a simple procedure. Four case studies are worked through in this text and, where possible, compared to the "traditional" approach to the same problem. The case studies show the additional information and time savings availablewith the Taguchi method, as well as clearlyindicating the importance of using a stable system on which to do the experiments. The Taguchi method generated more information in fewer experiments than the traditional approaches as well as allowing analysis of problems too complex to analysewithout a statisticaldesign of the experimentation procedure. / AFRIKAANSE OPSOMMING: Statistiese eksperimentele ontwerptegnieke is besonder kragtige instrumente wat baie keer met agterdog deur ekspermenteerders beheen word. Die neiging is om enige statistiese gestruktureerde and ontwerpte eksperimentele program te vermy, en om liewer die tradisionele metode, wat op 'n mens se intuïsie staatmaak, te gebruik. Hierdie benadering sal baie keer 'n bevredigende oplossing gee, maar daar is veel meer inligting vir dieselfde hoeveelheid inspanning verkrygbaar, wanneer die Taguchimetode gebruik word. Hierdie tesis strewe om die metode en toepassing van die Taguchimetodologie van eksperimentele ontwerp voor te lê. Die Taguchimetode is 'n praktiese statistiese eksperimentele ontwerptegniek .wat nie op die ontwerper se kennis van komplekse statistiek om eksperimentele programme te ontwerp berus nie. Hierdie komplekse statistiek neig ook om eksperimentele ontwerp van die gemiddelde ingenieursvaardigehede uit te sluit. Die kern van statistiese eksperimentele ontwerp is die volgende: Die tradisionele metode van een veranderlike op 'n slag te varieer om die effek op die uitset te ondersoek, is onvoldoende. In plaas daarvan, word al die insetveranderlikes gelyktydig gevarieer in 'n gestruktureered manier. Die neigings van elke veranderlike is dan statisties ontleed van die data ten midde van die variasie van al die ander veranderlikes. Die Taguchimetode bereik die ontwerpte eksperimente deur elke vlak van elke insetveranderlik in 'n gelyke aantal keer met elke vlak van elke ander insetveranderlike te varieer. Hierdie is verteenwoordig deur ortogenale reekse wat gekies en gevul is deur 'n eenvoudige wisselpatroon te volg. Vier gevallestudies is deurgewerk en, waar moontlik, vergelyk met die tradisonele siening van dieselfde probleem. Die gevallestudies wys hoe toereikbaar die additionele inligting in die Taguchimethode toepassings is. Hulle beklemtoon ook die belangrikheid van 'n stabiele sisteem waarop die eksperimente berus. Die Taguchimetode het meer inligting verskaf met minder eksperimente as die tradisionele toenaderings, en ook toegelaat dat die analise van probleme, te kompleks om te analiseer sonder om 'n statistiese ontwerp van eksperimentele prosedure te volg, opgelos kon word.

The ever-increasing complexity of software systems makes them hard to comprehend, predict and tune due to emergent properties and non-deterministic behaviour. Complexity arises from the size of software systems and the wide variety of possible operating environments: the increasing choice of platforms and communication policies leads to ever more complex performance characteristics. In addition, software systems exhibit different behaviour under different workloads. Many software systems are designed to be configurable so that policies (e.g. communication, concurrency and recovery strategies) can be chosen to meet the needs of various stakeholders. For complex software systems it can be difficult to accurately predict the effects of a change and to know which configuration is most appropriate. This thesis demonstrates that it is useful to run automated experiments that measure a selection of system configurations. Experiments can find configurations that meet the stakeholders' needs, find interesting behavioural characteristics, and help produce predictive models of the system's behaviour. The design and use of ACT (Automated Configuration Tool) for running such experiments is described, in combination a number of search strategies for deciding on the configurations to measure. Design Of Experiments (DOE) is discussed, with emphasis on Taguchi Methods. These statistical methods have been used extensively in manufacturing, but have not previously been used for configuring software systems. The novel contribution here is an industrial case study, applying the combination of ACT and Taguchi Methods to DC-Directory, a product from Data Connection Ltd (DCL). The case study investigated the applicability of Taguchi Methods for configuring complex software systems. Taguchi Methods were found to be useful for modelling and configuring DC-Directory, making them a valuable addition to the techniques available to system administrators and developers.

Semi-solid manufacturing is a near net shape forming process that takes advantage of an alloy's thixotropic behaviour. However, in order to obtain the desired thixotropic properties from an alloy in the semi -solid state, the microstructure of the as-cast feedstock metal needs to display a fine grained, equiaxed primary phase prior to reheating for the forming operation. Various methods are currently in use to obtain the required microstructure of which the MagnetoHydroDynamic (MHD) process is predominant. Two fundamental factors, namely shear rate and cooling rate, influence the formation of the fine grained, equiaxed primary phase during the MHD process. The aim of this research was to produce semi solid billets and in so doing, determine how the influence of the combination of the two fundamental factors contribute towards the final formation of the primary phase and to determine an optimal level ofthese factors' settings to deliver the desired microstructure. An MHD apparatus was constructed and the Taguchi method was used to design an experiment to investigate the influence ofthe fundamental factors involved in casting semi solid feedstock of aluminium A356.2. The issues ofthe formation of a fine eutectic phase and solidification shrinkage were also investigated. An experimental method was designed to investigate the significance ofthe fundamental factors' influence towards the appearance of the primary phase; the latter was evaluated using an image analysis system. The shear rate was controlled by varying the line frequency and the base frequency supplied to the electromagnetic stirrer and the cooling rate was controlled by initiation of a fixed, fast cooling rate at a certain melt temperature (TJ Results showed that a fine grained, equiaxed primary phase, with an average grain size of 55 /lm, was achieved after casting, prior to reheating for forming. The contribution of the base frequency and the line frequency were 8 % and 3.5 % respectively and the contribution ofTi was 86.5 % towards the outcome ofthe result. The cooling rate changed from approximately 0.3 QC/sec to 4.5 QC/sec at Ti. A fine textured eutectic phase was achieved with the fast cooling rate. The solidification shrinkage was accounted for by incorporating a riser on the mould. The feedstock produced in this research was compared, on a microstructural basis, to commercially available Semi Solid Metal (SSM) feedstock from Pechiney and SAG. The research feedstock had a larger, average primary grain size, however, it was more discrete and round grained than the commercial alloys which were finer and more rosette grained. Upon reheating to the semi solid state, ready for forming, the final, evolved grain sizes and shapes were almost identical between the research and commercial feedstock, despite the initial differences in grain sizes and shapes. However, the commercial alloys showed primary grains with trapped eutectic whereas in the research alloy, the primary grains were largely free of trapped eutectic. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.

No description available.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 2, 2009) Includes bibliographical references (p. 216-220).

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed October 24, 2007) Includes bibliographical references.