Microscopic parabolic surfaces have been fabricated in thick positive photoresist by exposing it using a suitably designed mask on an X5 stepper projection reduction system. The resulting cylindrical parabolic surfaces were coated with reflective material to form parabolic micromirrors. Measurement results of focal length are in agreement with the expected theoretical values. The devices form the basis for the fabrication of compound parabolic microreflectors which are very suitable for thin solar cells.

Micromachined thin crystalline silicon solar cells have been fabricated with beam steering optical components on the surface. Microlens arrays focus light onto beam steering mirrors in V-grooves on the cell surface. One face of a V-groove is coated with aluminium to form the mirror so that the reflected light is coupled into the cell through the opposite face. The use of micromachining has allowed most of the cell surface to be covered by aluminium making it more effective in trapping light and giving good electrical contact.

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Hydrological factors such as volumetric water content (VWC) and pore-water content (PWC) have been cited widely as significant factors that trigger slope failures especially shallow landslides and debris flows. Over the years, researchers have studied these processes using a range of physically-based models which in many occasions are either too complex incorporating very many parameters or fail to mimic real field conditions. The principal objective of this study was to derive and incorporate a set of physically-based equations that describe the dependence of slope failures at laboratory scale on VWC into a factor of safety expression herein referred to as the hydro-dynamical landslide model. The model was validated by a series of physical tests on soil samples in the laboratory using the Chepflume. Results showed a close agreement between computational and experimental data, confirming the hypothesis that cohesion, internal friction angle and pore-water pressure are modulated by VWC especially for slopes with sandy-loam soils. More so, rapid change of soil water content was observed to accelerate build-up of negative pore-water pressures (PWP) which triggers slope failure. Apart from giving a simplified expression for the factor of safety, the proposed model circumvents the difficulties associated with tedious procedures employed in the measurement of cohesive stress by limiting the tests to only three sets of parameters i.e. VWC, PWP and displacement.

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