In general, a minimum aberration criterion is used to evaluate fractional factorial designs. This dissertation begins with a comprehensive review and comparison of minimum aberration criteria definitions regarding their applications, relationships, advantages, limitations and drawbacks. A new criterion called the general balance metric, is proposed to evaluate and compare mixed-level fractional factorial designs. The general balance metric measures the degree of balance for both main effects and interaction effects. This criterion is related to, and dominates orthogonality criteria as well as traditional minimum aberration criteria. Besides, the proposed criterion provides immediate feedback and comprehensively assesses designs and has practical interpretations. The metric can also be used for the purpose of design augmentation to improve model fit. Based upon the proposed criterion, a method is proposed to identify the optimal foldover strategies for efficient mixed-level designs. The analysis of mixed-level designs involving qualitative factors can be achieved through indicator variables or contrast coefficients. A regression model is developed to include qualitative factor interactions which have been previously ignored. / A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2006. / April 7, 2006. / Mixed-Level Designs, Augmentation, Qualitative Factor, General Balance Metric, Design Of Experiments, Foldover, Minimum Aberration Criterion / Includes bibliographical references. / James R. Simpson, Professor Directing Dissertation; Xufeng Niu, Outside Committee Member; Samuel A. Awoniyi, Committee Member; Joseph J. Pignatiello, Jr., Committee Member.

To prepare dielectric materials for High Temperature Superconductor (HTS) cables, nanocomposites consisting of Polymethylmethacrylate (PMMA) and Barium Titanate (BTA) nanoparticles have been manufactured and evaluated. The main objective of this research is to enhance the dielectric breakdown strength and reduce the dielectric losses of the nanocomposites. Polymethylmethacrylate (PMMA) with the addition of BTA (5wt.% and 10wt.% ) nanocomposites were fabricated by using two different methods. The breakdown voltage measurements have been conducted under AC, DC and lightning impulse high voltage. The measurements were conducted at both room temperature (293 K) and liquid nitrogen temperature (77 K). The results of the electrical breakdown field measurements of the nanocomposites are compared with those of the base polymer. Fracture surface analysis was carried out with SEM analysis. The difference in the breakdown area due to different modes of voltages applied and effect of the nanoparticles was studied. Mechanical characterization of the resultant nanocomposites was also carried out at both the room temperature (293K) and at cryogenic temperature (77K). The effects of nanoparticles on the electrical and mechanical properties were observed. A marginal increase in the dielectric strength of the nanocomposites was observed for AC conditions at both the temperatures. There was a decrease in the values of nanocomposites for impulse conditions. At cryogenic temperature nanocomposites showed higher dielectric strength when DC voltage was applied. For both the temperatures, dielectric losses increased as the voltage was increased for all the materials studied, except for PMMA/10wt.%BTA nanocomposites at cryogenic temperature, which showed decrease of losses by ~ 70%. An increase of ~12% in Young's modulus and ~ 65% increase in tensile strength of the nanocomposites were observed at cryogenic temperature. It also shows that more material damage was observed under AC breakdown voltage compared to the impulse and DC voltage breakdown cases. Also the material damage was more pronounced at 77 K than that at 293 K. / A Thesis submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Summer Semester, 2010. / July 6, 2010. / Tan Delta Losses, Impulse Breakdown, DC Breakdown, AC Breakdown, Barium Titanate, Polymethylmethacrylate (PMMA), Cryogenic Insulation, High Temperature Superconductors (HTS), Nanodielectrics, Mechanical Breakdown, Surface Fracture Analysis, Weibull Plots / Includes bibliographical references. / Zhiyong Richard Liang, Professor Directing Thesis; Horatio Rodrigo, Committee Member; Okenwa Okoli, Committee Member; Mei Zhang, Committee Member.

Carbon nanotubes (CNTs) have excellent mechanical, electrical, and thermal properties making them outstanding reinforcements in polymer matrix composites. In this research, the effect of CNT-integration in polymer matrices (two-phase) and fiber-reinforced composites (three-phase) was studied theoretically and experimentally. This work sought to enhance the mechanical properties of composites by the improving dispersion of CNTs in polymers. This was achieved by optimizing the CNT/polymer composite manufacturing process. Generally, higher sonication intensity and longer sonication time improved the mechanical properties of CNT/polymer composites through improved CNT dispersion. Simulations for CNT/polymer composites (nanocomposites) and CNT/fiber/polymer composites (multiscale composites) were successfully carried out using a new method that combines nanocomposites micromechanics and woven fiber micromechanics. With this new method, the mechanical properties, including the Young's modulus, Poisson's ratio, and shear modulus, of nanocomposites and multiscale composites were predicted in terms of CNT loading in a polymer. The relationships between the mechanical properties of the composites and aspect ratios of the CNTs were studied and, as the third part of the simulation, the mechanical properties of multiscale composites that have no CNTs in the fiber strands were compared with those of multiscale composites that have CNTs in the fiber strands. In order to compare the predicted mechanical properties obtained by the simulations, nano and multiscale composites were manufactured and characterized. Good dispersion of the CNTs and strong bonding between the CNTs and polymer matrix and fibers and matrix are necessary to improve the mechanical properties of nanocomposites and multiscale composites. / A Dissertation submitted to the Department of Industrial and Manufacturing Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester, 2009. / April 3, 2009. / Carbon Nanotubes, Design of Experiments (DOE), Nanocomposites, Multiscale Composites, Mechanical Modeling / Includes bibliographical references. / Okenwa I. Okoli, Professor Directing Dissertation; Sachin Shanbhag, Outside Committee Member; Young-Bin Park, Committee Member; Zhiyong Liang, Committee Member; David Jack, Committee Member.

Carbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the nanotubes uniformly throughout the matrix. Carbon nanotubes are anisotropic in nature. Therefore to take advantage of the nanotubes in the axial direction, controlled tube orientation or degree of alignment of nanotubes in the polymer matrix is very important to realize their high mechanical and functional properties. The nanocomposites produced by current conventional methods using direct mixing, melt blending or solution casting have failed to yield significant improvements in composite modulus. Although tremendous progress has been made towards understanding the properties of individual carbon nanotubes, but attaining the true potential of the bulk polymeric nanocomposites have been hindered by the lack of uniform SWNT dispersion, poor interfacial bonding, inadequate tube loading and uncontrollable tube orientation or degree of alignment. This thesis work developed an innovative approach for producing nanocomposites that has uniform SWNT dispersion, high tube loading and most importantly controlled tube orientation. In this research, these properties in composites were achieved by using magnetically aligned buckypapers and resin infusion system. The aligned nanotube buckypaper and composite were characterized using AFM and SEM. The mechanical properties of these materials were experimentally determined using DMA and were theoretically verified. The electrical properties of these materials were also experimentally determined using 4-probe resistivity measurements. Significant tube alignment has been achieved in the resultant buckypaper and nanocomposites. It is shown that the developed method is an effective way for producing nanocomposites with uniform SWNT dispersion desired tube alignment and high tube loading. / A Thesis submitted to the Department of Industrial Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Fall Semester, 2003. / November 10, 2003. / Carbon, Nanotubes, SWNT Alignment, Composite, Polymer, Anisotropy, Resistivity, Nanocomposite / Includes bibliographical references. / Zhiyong Liang, Professor Directing Thesis; Ben Wang, Committee Member; Chuck Zhang, Committee Member.

The objective of this research was to develop a system to effectively monitor temperature in the selective laser melting of Inconel 625. This study established a monitoring system that collects temperature data and describes its relationship with process parameters, develops a control simulation based on the obtained results and determines how to change input parameters in situ. Such research was driven by the unreliability of additively manufactured components, which often contain internal voids and cracks as well as display poor surface finish. With the need for improved part quality, a temperature monitoring system, a promising method of solving several quality issues, proves necessary. This monitoring system was developed using a pyrometer and a thermal imager mounted on a powder bed metal printer to record the peak temperature of the melt pool. Experiments found that both laser power and scan speed affect the peak melt pool temperature of Inconel 625: as the peak melt pool increases as power increases and as scan speed decreases. A subset of experiments run with a thermal camera further revealed that there is no discernible temperature trend across the laser track, meaning that there was no significant difference in temperature at the start, middle or end of the track. The thermal camera also revealed that temperature across the melt pool resembled a second order response to laser input. Furthermore, according to preliminary offline measurements taken of the primary dendrite arm spacing (PDAS) of Inconel 625 coupons, PDAS increases with peak temperature. In addition to implementing and testing the monitoring system, this research created and simulated a first order model of the system using a discreet proportional integral derivative controller. Lastly, two separate methods were found to interface a controller with the Omnisint 160 in order to change the laser power based on the temperature feedback / Thesis / Master of Applied Science (MASc)

TOPIC 1 : A Distributed Approach for the Production Flow Control of Interconnected Flezible Manufacturing Systems A dynamic production control policy was developed for interconnected flexible manufacturing systems with stochastic capacity. The objective is to track a desired production rate target in a Just-In-Time manner by minimizing the average production surplus and backlog. The production rate target or demand was assumed to be piecewise constant with respect to time. A 'Manufacturing Flow Control' model was used to allocate dynamically available capacity to the production of various part types. The approach used was distributed, as the production rate at each work cell was scheduled on the basis of local information containing the current inventory level of the adjacent buffers and the present state of the work cell (number of up/down machines). TOPIC 2: Single Run Optimization in Discrete Event Simulations of Manufacturing Systems A new technique was devised to optimize the controllable parameters ( eg. buffer size, batch size, routing proportions, production rate etc.) of stochastic manufacturing systems in a single simulation run. Pertubation Analysis methods were used to estimate the derivatives in a single simulation run of the system model. In addition, a Sequential Hypothesis Testing approach was used to update the parameters on line, as the simulation was running. This algorithm is not only computationally inexpensive but also has the inherent property of escaping from poor local optima.

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Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 187-196).

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There is no doubt that technological innovation is an important element in today's business environment. The importance of new manufacturing technologies is increasing as the business environment is becoming more complex and competitively intense. The environments in which organisations are competing and operating are also increasingly cross-cultural due to the advent of globalisation. Achieving organisational objectives as a result of technological adoption is made more difficult when organisations set out to undertake innovations more suited to a different national environment. This might have posed a great challenge for organisations that are engaged in technology innovation, especially in developing countries like Nigeria. / It has been suggested that the innovation of new manufacturing technologies encourages the restructuring of human resource management strategies, especially employee empowerment and workforce composition, for example by the displacement of low skilled by highly skilled workers. The reason for this, it has been suggested, is based on the assumption that highly skilled and educated employees can be empowered more easily during the implementation of new innovations. However, it has been argued that the extent of employee restructuring will be different across-national boundaries due to differences in national cultural values. / Using an operational-level survey, this study investigates comparatively the implications of culture on human resource management strategies and practices during the implementation of advanced manufacturing technology innovation in Nigeria and New Zealand. Thus, the research questions are concerned with the extent to which differences in similar human resource management strategies practiced in the two distinct national environments: Nigeria and New Zealand, are attributable to differences in their national cultural values. / Data collected through questionnaire administration in over 150 manufacturing establishments and through interview enabled the examination of the relationship between culture and advanced manufacturing technology (including linked and integrated) and human resource management (employee empowerment and workforce composition) interactions in the two countries. / Three broad hypotheses of advanced manufacturing technology-human resource management interactions were developed on the premise of cultural value convergence and divergence. The results indicated that there is little or no convergence on Hofstede's cultural dimensions between the two counties (Nigeria and New Zealand). In other words, there are statistical significant differences in the two countries' values. The test of hypotheses showed that there are significant differences between the two countries in advanced manufacturing technology-human resource management interactions. / Specifically, the statistical analysis revealed that there is more employee empowerment and workforce re-composition in the New Zealand sample than the Nigerian one during the implementation of advanced manufacturing technology, including two categories - linked and integrated. For example, the overall workforce reduction and compositional shift in favour of skilled/educated workers is significantly greater in New Zealand when compared to Nigerian organisations. / Overall, compared to New Zealand, the results indicated that Nigeria has a lesser use of employee empowerment and workforce compositional strategies, which is consistent with their high power distance, high uncertainty avoidance, high collectivism, and short-term orientation position on the Hofstede dimensions. / Thesis (PhDBusinessandManagement)--University of South Australia, 2005