Includes bibliographical references (p. 107-121).

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 114-120). Also available in electronic version. Access restricted to campus users.

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Abstract Matrix solid-phase dispersion and gas chromatography-mass spectrometry were used for the rapid screening of 36 pesticides in agricultural products. Homogenized sample (0.5 g), C8-modified silica (0.5 g) and Na2SO4 (1 g) were mixed and transferred to a cartridge containing activated silica (0.5 g). Best recoveries (>60%) were found using dichloromethane-ethyl acetate (4:1) for elution. Analytical characteristics at spiking levels (10–100 lg/kg) were calculated for each pesticide. Matrix effects were studied by comparing the slopes of the matrix-matched calibration curves. Fruit and vegetable samples from South Africa complied with EU and South African current regulation, except for cypermethrin in green beans.

Fatigue testing of complete automotive wheels is carried out on rotary bendmachines. These commercial mac hin e s s imulnt e h ar d - c o rn e rin g c o n ditio n s an d mainly testthefatigue performance of the central section of an automotive wheel' . This paper develops a relationship for predicting the fatigue performance of the wheel,based onfatigue tests of hourglass specimens machinedfrom centre discs. This is more economical of material and, in principle, also allows the effect on fatigue performance of change inproduction parameters or starting alloy to be assess ed, by c o n sid e rin g a limit e d numb e r of w h e e I blanks take n from each stage of the production process. This is p ote ntially a v ery u s eful to ol in optimisin g mat e rial selection, wheel design and production parameters. The p arti c ular c e ntr e - dis c un d e r c o n s id e r atio n i s manufactured from a dual-phas e ste eI (DP S)2 . Good c o rr elatio n w as achie v e d b e tw e e n S - lr.' data fr o m th e automotiv e w he els qnd that from the ho urglas s (H G) specimens.

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This work examines a novel method of dynamic single frame interferometry. In this dynamic approach to phase shifting measurements, steps are taken to combat performance degradation due to environmental factors such as air turbulence and vibration. We explore the system functionality and performance, and examine some of the limiting factors using this technique such as effects due to imperfect system components, irradiance variations and sensitivity of the instrument accuracy based on calculation methodology. We present the errors associated with these various aspects of the system and show the majority cause phase calculation errors less than 0.005λ P-V to the calculated wavefront. This new approach involves the placement of a micropolarizer phase-shifting array directly onto a CCD camera which allows the construction of a dynamic single frame interferometric system. Hardware and manufacturing preparations such as inspection, positioning and alignment are discussed. Experimental results of system performance are combined with mathematical simulations to provide a performance baseline. We present experimental results showing the effects of averaging on measurement data, which results in a reduction of fringe print-through errors associated with a combination of many of the system error sources.