Electro-optic (EO) beam deflectors are voltage-controlled devices widely used for scanning and switching applications. For example, high-speed, low-loss optical switches aimed at future optical networks can be built on EO deflectors. Novel EO deflectors distinguish themselves with a much-improved steering performance, high-speed response and simple fabrication requirements. Patterned ferroelectric crystals such as LiTaO3 are first poled to provide the required prism shaped domain structures. The application of an electrical field across the entire crystal can then be used to drive the trajectory of the beam as it travels through the poled wafer. The electric field induces an index change of opposite magnitude on the adjacent domain regions in the EO device, causing the optical beam to refract at the interfaces. / Although rectangular geometry is extensively employed in EO devices, nonrectangular scanners have demonstrated better deflection performance. Two new nonrectangular geometries capable of further enhancing the deflection performance of EO beam scanners, proposed in this dissertation, were constructed. Their parabola and half-horn geometries provide 2-3 degrees of steering, which is 2-3 times greater than the steering provided by rectangular deflectors. / EO deflectors based on the parabola and the half-horn geometries, which can provide larger deflection angles, were built. These devices demonstrated a deflection angle of 3.1°, less than 5 dB of insertion loss from fiber to fiber, and -40 dB of crosstalk. / Two packaged optical switches using rectangular EO deflectors were demonstrated. By combining these EO deflectors with fiber collimators and high voltage packaging, high speed optical switches were built and characterized. The switch design was based on a 500mum z-cut LiTaO3 single crystal wafer fabricated using the domain inversion method. The 1x2 switch had a maximum deflection angle of 1.22° with an applied voltage of 1.1 kV and the 1x4 switch had a maximum deviation angle of 2.14°, with an applied voltage of 1 kV. The average insertion loss and crosstalk figures were 2.36 dB and -36 dB, respectively. The worst case switching time was 86 ns.

No description available.

The development of a new angioplasty balloon is a time consuming process. This thesis aims at reducing the amount of time and materials spent on the experimental stage of the development of new angioplasty balloons. This can be achieved by building a nonlinear neural network model of the balloon forming process and implementing an off-line cycle-to-cycle controller. The controller can learn from the previous experiments and provide better input parameters for improving the quality of the next balloons formed in the process. It is shown in the experimental test results that the neural network model can provide accurate estimates of the process outputs. The neural network model combined with a cycle-to-cycle control strategy has the potential to replace the trial-and-error approach to balloon development that is commonly applied today.

A field tillage tool carrier was constructed using a tractor trailer, hydraulic cylinder and steel construction material. Tillage tool blades of varying lengths, widths and angles of attack were fabricated from steel and were used in the study of the effect of tool rake angle, tool width and depth of operation on soil strength properties, draft, draft efficiency, volume of soil manipulated, degree of soil loosening and penetration resistance. / The results showed that the draft increased with tool rake angle and width. Operating at a depth of 150 mm and 100 mm depth did not make any significant difference on the draft requirement. Low angles of attack were observed to have a greater potential to loosen the soil, and the loosening increased to a depth of 150 mm then decreased. The draft efficiency was affected by the angle of attack as well as the depth of operation. The cross sectional area of the furrow and hence the volume of soil manipulated was seen to depend on the width of the tool and the operating depth. / Slender tools and high rake angles were found to loosen the soil better than wide ones. No distinct trend existed between depth to width aspect ratio and draft requirement. No variation was observed between draft efficiency and d/w ratio. Penetration resistance increased with depth of operation as well as distance from the furrow centre after tillage. Some areas of residual high strength were sometimes left within the sphere of influence of the tools. Some tools dealt with these omissions better than others.

The motivation of the research presented in this thesis was to investigate the potential of using a commercial 2.3 kW heat pump dehumidifier (HPD) simultaneously as a dryer for high-moisture agricultural products and for other domestic dehumidification/heating applications. A drying system incorporating the HPD was designed and constructed, along with instrumentation to gather data on the properties of process air as well as real-time weight of the material being dried. The HPD was equipped with an external water-cooled condenser that rejected excess heat out of the system. The design of the system allowed for conducting drying with recirculation of air as well as use of electrical heaters. In an open mode, the drying could be carried out simultaneously with room dehumidification and water heating in the secondary condenser. / The drying experiments were conducted with apple, tomato and agar gels. The system was found to be more effective in drying of material with higher amount of free moisture such as tomato. Comparisons were made between HPD assisted drying (partial and complete) and hot air drying (at 45°C and 65°C) in the same system using apple as the test material. Colour changes (L*a*b* values) in the samples were compared between treatments. It was observed that the degree of undesirable colour change was least in case of the HPD assisted system. The HPD dried fruit exhibited better rehydration properties than the hot air dried samples. Water activity of the HPD dried samples was noticeably lower than that of the hot air dried samples at the same water content, indicating that the residual moisture was probably held under higher tension. Histological observation indicated that there was a lesser degree of damage to the cellular structure of apple when dried with the HPD than when dried with hot air alone. / In terms of energy consumption, the process of HPD assisted drying is more expensive. Much of the energy input is rejected at the secondary condenser as excess heat. Unless this heat is recovered for another purpose, or the system is modified to reuse it for drying, the drying process must carry this loss entirely. The specific moisture extraction rate (SMER) for apple was as low as 0.1 kg per kWh with the HPD assisted system. The SMER values for drying at 45°C was 0.5 kg per kWh and was almost 0.8 kg per kWh at 65°C. / The HPD assisted drying system demonstrated the ability of heat pumps to link different energy related activities viz., drying, space dehumidification and water heating. The energy expenditure is expected to be impressive when considered for all the related applications. The concept of utilizing heat pumps on farms to link up different energy streams for better utilization of the low-grade heat sources is discussed. A possible drying efficiency assessment in the form of energy-based evaluation is proposed.

No description available.

No description available.

No description available.

No description available.

No description available.