Design and operation of modular optical head for a magneto-optic test system are described. Alternate solutions to design problems are discussed. A 30mW semiconductor laser with an integrated 250MHz oscillator is selected. The oscillator is used to modulate laser read current for a reduction in laser feedback noise. A collimating lens with an appropriate focal length is chosen so the beam's truncation at the objective yields the maximum write power density. Astigmatism associated with the laser diode is reduced to 0.125 waves by defocusing the collimating lens and circularizing with an anamorphic prism pair. Head components are aligned within several minutes of arc by using alignment apertures and an autocollimator. Aberrations due to tilt between the disk and beam are examined and coma is found to be the major contributor.

M. Tech. Industrial Engineering / The ability to respond to changes and uncertainty in production demands currently constitutes a crisis in small and medium scale mining industries in South Africa. The case study of various mining and mineral processing site visits which was carried out revealed that the existing conventional screening methods are not scalable or able to be integrated and have limited processing capacity, which constitutes a high production cost on a long-term basis. In view of this, the Reconfigurable Vibrating Screen machine was designed and manufactured with the intension of eliminating these challenges faced by small and medium scale mining industries. The newly developed vibrating screen utilizes the concept of re-configurability, making it simple to attain full capacity processing production on the same machine. The design of a reconfigurable vibrating screen is based on the idea of enhancing the processing capacity by adjustable width and length of the screen structure with regard to the desired processing output.

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published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy

No description available.

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This thesis presents a detailed comparison of the torque-speed characteristics of three permanent magnet synchronous machine designs based on how the magnets are mounted. The machines investigated are an interior permanent magnet machine, an interior-rotor surface-mounted machine and an exterior-rotor surface-mounted machine. They are designed for traction drives in hybrid electric vehicles. Two sets of comparisons based on the same machine volume and starting torque are performed. Important issues, such as machine mass and cost, cogging torque, and flux-weakening capability are addressed. Computer simulations were performed to estimate their performances and the results are presented. Design guidelines and tradeoffs of their performances are extracted from the simulation results. Relative strengths and limitations of different PM machine types are highlighted.

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The present study deals with the development of a single-stage implosion-driven hypervelocity launcher. A thin-walled tube filled with helium surrounded by explosives acts as a driver for the launcher. Implosion of the tube drives a strong shock that reflects back and forth between the projectile and the implosion pinch, generating very high temperatures and pressures. Simple analytic models were used to approximate the performance of the pump tube and its use as a driver for a launcher. Experiments to evaluate the implosion dynamics and performance of the pump tube were carried out, and implosion-driven launcher experiments demonstrated muzzle velocities above 4 km/s with 5-mm-diameter aluminum projectiles. Projectile integrity was verified by high-speed photography. Disagreement of experimental data with the analytical models of performance is mostly due to failure to seal the chamber of the launcher, resulting in loss of driver gas, and pump tube expansion, which weakens the precursor shock.