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Various monolayer a-Se-based photoreceptor devices were fabricated by vacuum evaporation and their electrical properties were investigated. Three experimental techniques, namely xerographic time of flight (XTOF), electroded time of flight (TOF) and xerographic discharge were used to determine the drift mobility, carrier lifetime, dark decay and residual voltage. Where possible, these measurements were carried out as a function of applied field and composition, namely As-0.3 wt%, Te up to 17 wt% and Cl up to 60 ppm. The addition of As or Te alone reduced both hole and electron drift mobilities and increased the carrier lifetime. Both XTOF and TOF experiments showed a trap-limited response for electron transport in Se +Cl and Se:Te + Cl systems. The addition of As was found to restore the electron response in these photoreceptors. The drift mobility in all Se-based systems was found to be field dependent, satisfying the algebraic relation p a Y " where n is a constant varying from 0.03 (for electronic mobility in a-Se) to 0.47 (for electron response in a-Se + 17 wt% Tel. Xerographic discharge measurements showed that alloying a-Se with Te increases the dark decay, due to a bulk thermal generation process. Analysing of dark-decay curves indicates that the volume density and energy spread of the mid-gap localised states in a-Se increases with the Te content. The repetition of the xerographic cycle over a number of times leads to the saturation of the residual voltage which was used to calculate the concentration Nt of deep hole traps. The results showed that the addition of Te increases N , from about 1.9 x l O " C ~-~ for a-Se to 7 x l 013 cm-3 for a-Se + 8 wt% Te. From the charge transport data and saturated residual voltage measurements, the hole capture coefficient in a-Se was estimated to be about 1 .O x 1 O-' c& S" .

Uncertainty is an inherent part of control systems used in real world applications. Various instruments used in such systems produce uncertainty in their measurements and thus influence the integrity of the data collection. Type-1 fuzzy sets used in conventional fuzzy systems cannot fully handle the uncertainties present but type-2 fuzzy sets that are used in type-2 fuzzy systems can handle such uncertainties in a better way because they provide more parameters and more design degrees of freedom. There are membership functions that can be parameterized by a few variables and when optimized, the membership optimization problem can be reduced to a parameter optimization problem. This paper deals with the parameter optimization of the type-2 fuzzy membership functions using a new proposed reinforcement learning algorithm in automatic voltage regulator. The results of the proposed method referred to as the Extended Discrete Action Reinforcement Learning Automata algorithm are compared with the results obtained by the Discrete Action Reinforcement Learning Automata algorithm and well known genetic algorithm. The performance of the proposed method on initial error reduction and error convergence issues are investigated by computer simulations.

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This paper describes the aims, health and safety issues, learning aspects and assessment of work placement for professional experience as an optional module offered to our undergraduate students. Some examples of activities carried out by students during their placement are also presented. It is argued that this module develops the capabilities and skills of our students as well as enabling them to become aware of the culture and structure of a working environment.