published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

No description available.

The thesis systematically investigates the laser interference nanomanufacturing technology taking into account its advantages and abilities to realise various potential applications. The latest progresses have addressed the major issues hampering the cross-scale developments of structural applications, such as cost-ineffective fabrication, limited area, low efficiency and challenging integration. The studies carried out on high-resolution and large-area laser interference nanomanufacturing technology will complement the exploration of modern optical devices and extraordinary functional applications. With respect to classical interference theory and relevant references, there is still a lack of studies providing insight into the effects of polarisation on the multi-beam interference while it is found that the polarisation vector plays a key role in the formation, period and contrast of interfering patterns. Herein, the theory of multi-beam interference is developed through the integration of the polarisation vector and electric field vector. It is worth pointing out that based on the detailed analysis of the four-beam interference with the special polarisation modes, it is demonstrated that the modulation phenomenon in four-beam laser interference is the result of the misalignment of incident angles or unequal incident angles only in the case of the TE-TE-TM-TM mode. In the experiments, a straightforward method of generating various well-defined structures on material surfaces is proposed using the nanosecond laser interference system. The experimental results of two-, three- and four-beam interference show a good correspondence to the theoretical analyses and simulations. Artificial bio-structures are fabricated using the four-beam interference method with the TE-TE-TE-TE polarisation mode and the fabricated microcone structures exhibit excellent properties with both a high contact angle (CA=156.3°) and low omnidirectional reflectance (5.9-15.4%). In order to fabricate high-resolution structures, the 266nm nanosecond laser interference system is employed to treat the organic and metal-film materials. Nanograting structures with feature sizes of sub-100nm width and 2nm height are fabricated on the organic material surface. An attempt is successfully conduced to produce the nanoelectrode arrays by using laser interference lithography and chemical deposition. Finally, the advantages of the developed laser interference technology and contributions of the research are summarised, and recommendations of future work are given.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Engineering. / The requirement of the project was to design an automatic storage and retrieval system (AS/RS) to be incorporated into a flexible manufacturing cell (FMC) at the University of the Witwatersrand. This flexible manufacturing cell currently being developed in the Industrial engineering department consists of a CNC milling machine and a CNC turning centre supported by an automated materials handling system, and an integrated computer control system. The automated materials handling system consists of a loop conveyor, parts transfer device, tool changing robot and the AS/RS. All the devices of the materials handling system have been constructed from low cost items readily available or alternatively have been manufactured at the University. The research philosophy adopted was to produce a low cost FMC, using local technology and expertise, to produce a system that is both economically feasible and relatively simple to implement. The AS/IRS is computer controlled consisting of three axis, driven by direct current motors. The AS/RS has a storage matrix of sixteen pallets (four by four) and is able to operate autonomously. The controlling software was written in turbo Pascal and designed to allow interface with the other material handling devices. The software allows for future incorporation of scheduling rules such as first in first out, shortest operating time or a schedule desired by the user. The AS/RS also allows the system to generate managerial reports on the status of the system as well as feedback to the FMC supervisory computer. The design was carried out with the same philosophy used In the FMC i.e, to use low cost items to provide an economically feasible design that is both flexible yet simple to incorporate within a FMC. In conclusion the AS/RS performs the required pick and place function with sufficient accuracy to ensure that parts are correctly positioned. The controlling program of the AS/RS functions correctly in terms of controlling the AS/RS. The AS/RS is fully autonomous in all operations. The AS/RS has the following specifications : Value Units Accuracy 3.67 mm Repeatability 7.2 mm Resolution 0.00977 mm Average pick & place time 41.6 s X Axis travel 1000 mm Y Axis travel 640 mm Z Axis travel 420 mm Lifting capacity 20 N Gripping force 10 N Degrees of freedom 3 The design can be further improved by using stepper motors instead of direct current motors to provide a finer control in terms of velocity and position accuracy. A!though the stepper motors need to have the same price for performance characteristics. / AC 2018

A research report submitted in fulfilment of the requirements for the degree of Master’s in Engineering to the Faculty of Engineering and the Built Environment, School of Mechanical, Industrial and Aeronautical Engineering, University of the Witwatersrand, Johannesburg, 2018 / The automotive industry is experiencing a major transition with regards to powertrain where the traditional internal combustion engine is being replaced by hybrid or all-electric solutions. As a result of this transition, many powertrain engineering firms, such as Integral Powertrain, are required to adapt or develop tools to improve the quality and time to respond to the rapid increase in new electric motor enquiries. This paper details the development of the foundations of a software tool (AIEED) used to improve the time and quality of response to new motor enquiries. The foundations of the AIEED tool are built into a Microsoft Excel document which contains the necessary logic required to convert customer requirements data into geometrical design data. A series of macros are included in the tool which allow for the automated generation of a first-level computer-aided design (CAD) model of the motor, including the following components; stator, windings, rotor, magnets, housing and cover. The CAD models, which serve to improve the quality of response to new motor enquiries and provide a basis for further detailed development, are generated on the CATIA V5 design platform. In addition, the tool makes use of the CAD model to determine the estimate cost of the unit based on average material costs per unit mass defined in the materials database stored in the tool. It is estimated that the AIEED tool reduces the response time to new motor enquires by 75%. Certain assumptions and limitations have been applied such that the foundations of the tool only include support for the following motor specifications: Surface Permanent Magnet Alternating Current cylindrical radial flux motors (external stator and internal rotor). • The units are designed for 3-phase supply. • The winding configuration is limited to concentrated double layer option. • Parallel tooth, arc-bottom, semi-closed stator slot profiles. • Arc-shaped radially magnetised surface magnet rotor configuration option. A simple data verification filter is applied to minimise the potential for invalid inputs. However, a full validation and verification process is recommended for future work. In addition, it is recommended that the tool be expanded to support additional motor types and specifications as well as package the foundations into a single, easy-to-use utility. / XL2019

by Wai Ki Ching. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (p. 82-87). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

The goal of the research described here is to develop tools to assist the rapid analysis and design of manufacturing systems. The methods we describe are based on mathematical models of production systems. We combine earlier work on the decomposition method for factory performance prediction and design with the hedging point method for scheduling. We propose an approach that treats design and operation in a unified manner. The models we study take many of the most important features and phenomena in factories into account, including random failures and repairs of machines, finite buffers, random demand, production lines, assembly and disassembly, imperfect yield, and token-based control policies. / Singapore-MIT Alliance (SMA)