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<p>The photovoltaics (PV) research community is currently pursuing many approaches to reduce the cost of PV and increase the energy conversion efficiency. Single-crystalline silicon (sc-Si) solar cells are able to achieve high efficiency but have a higher cost relative to other technologies. It may be possible to drastically reduce the cost of sc-Si PV by fabricating solar cells which are an order of magnitude thinner than conventional solar cells, i.e. thinner than 30 microns. Aside from new fabrication paradigms, ultra-thin sc-Si solar cells require advanced light-trapping techniques to enhance the absorption of long-wave radiation which is otherwise transmitted through the cell. In this thesis, a novel process flow for the fabrication of ultra-thin sc-Si solar cells in the laboratory was designed and implemented with the aim of testing light-trapping structures in the context of actual ultra-thin sc-Si devices. The process flow uses 10 micron thick sc-Si membranes, 0.95 cm in diameter, fabricated on silicon-on-insulator wafers using double-sided processing. The best fabricated device incorporated a back surface field, a white paint diffuse rear reflector and a silicon nitride antireflection coating. It achieved a fill factor, efficiency, short circuit current and open circuit voltage of 0.67, 9.9%, 27.9 mA cm^-2 and 0.53 V respectively. Simulations suggest the device efficiency can approach 15.4% without light-trapping and 16.5% with a diffuse rear reflector as a light trapping structure. This process flow is intended to be used as a platform on which to test further light-trapping structures with the continuation of this project.</p> / Master of Applied Science (MASc)

This report outlines developing a mechanism for a relatively low in price, portable, and mechanical ventilator prototype designed to bridge the gap in ventilator access brought about the COVID-19 pandemic. The key goal is to create a portable and easy to use device which will be capable of providing constant and effective respiratory support in areas having limited resources. The ventilator uses the Oscillating Cylinder Mechanism (OCM), which makes the ventilation smoothly and continuously. This eliminates the need for the user to put maximum effort and the patient benefits. Different ideas about designs were being put forward, concentrating on the portability, functionality, reliability, safety, and effectiveness. The OCM was selected because of its ventilation parameter adjustment ability to accommodate patient-specific needs, thereby functioning in a variety of clinical settings. Although upfront complexity and cost are developed, long-term perks such as lower user fatigue and maintenance expenses compensate for the financial investment. The end design will help in the emergency medical care especially in demand emergency situations, in ambulances, and in intensive care.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / Low Cost Automation (LCA) is of immense importance to industry, and even more so for small scale industries. In implementing LCA determining cost effective and efficient actuator alternatives present challenges for design engineers. Most often decisions are experiential or entirely based on manufacturer recommendations. Experience based decisions are most often biased with respect to the engineers’ knowledge. Similarly, manufacturer recommendations are restricted to their own products and are as such also biased. Either way, sub-optimum drive alternatives may sometimes be chosen. This demonstrates the need for making better informed decisions based on more than experience and what is available for use. This thesis reports the development of an electric actuator selection procedure and aid for use in the early layout design phase. It provides readily accessible information on technically viable actuator options. Experiential knowledge of experts in the field, commercial information, as well as data obtained from experimentation was used in its development. Being orientated towards LCA, the procedure has been targeted at the application of electric motors and their associated control technologies but can be extended to hydraulic, pneumatic and other actuators. In achieving a wider applicability of the selection aid, a generic set of actuator properties descriptive of most actuators was formulated. An AC drives control evaluation was conducted for developing the selection procedure and aid. It provided a means to validate some selection aid rules associated with actuator controllability. Quantitative data on speed and positioning accuracies of common AC three phase motors and their associated inverter technologies were the targeted results of the experimentation.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / GSFC in keeping with the tenets of NASA has been aggressively investigating new technologies for spacecraft and ground communications and processing. The application of these technologies, together with standardized telemetry formats, make it possible to build systems that provide high-performance at low cost in a short development cycle. The High Rate Telemetry Acquisition System (HRTAS) Prototype is one such effort that has validated Goddard's push towards faster, better and cheaper. The HRTAS system architecture is based on the Peripheral Component Interconnect (PCI) bus and VLSI Application-Specific Integrated Circuits (ASICs). These ASICs perform frame synchronization, bit-transition density decoding, cyclic redundancy code (CRC) error checking, Reed-Solomon error detection/correction, data unit sorting, packet extraction, annotation and other service processing. This processing in performed at rates of up to and greater than 150 Mbps sustained using a high-end performance workstation running standard UNIX O/S, (DEC 4100 with DEC UNIX or better). ASICs are also used for the digital reception of Intermediate Frequency (IF) telemetry as well as the spacecraft command interface for commands and data simulations. To improve the efficiency of the back-end processing, the level zero processing sorting element is being developed. This will provide a complete hardware solution to extracting and sorting source data units and making these available in separate files on a remote disk system. Research is on going to extend this development to higher levels of the science data processing pipeline. The fact that level 1 and higher processing is instrument dependent; an acceleration approach utilizing ASICs is not feasible. The advent of field programmable gate array (FPGA) based computing, referred to as adaptive or reconfigurable computing, provides a processing performance close to ASIC levels while maintaining much of the programmability of traditional microprocessor based systems. This adaptive computing paradigm has been successfully demonstrated and its cost performance validated, to make it a viable technology for the level one and higher processing element for the HRTAS. Higher levels of processing are defined as the extraction of useful information from source telemetry data. This information has to be made available to the science data user in a very short period of time. This paper will describe this low cost solution for high rate data processing at level one and higher processing levels. The paper will further discuss the cost-benefit of this technology in terms of cost, schedule, reliability and performance.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / Eglin Air Force Base (AFB) plans to demonstrate subminiature telemetry (SMT) spread spectrum technology, via an upgraded prototype SMT system, to validate its cost-effectiveness for both Department of Defense (DoD) and commercial use. The goal is to develop new and/or modify current SMT instrumentation using existing production methods to provide increased capabilities at lower costs and reduced size. The transmitter is to require less than 2 cubic inches of space and have a cost goal of $500/unit "in quantity." The cost goal of a ground-based, 24-channel capable ground receiver is $4000/unit "in quantity". The SMT project as well as its schedule, flight and ground demonstrations, validation criteria and goals, and various benefits are discussed.

Thesis (PhD (Sport Science))--Stellenbosch University, 2008. / The benefits of exercise training for patients with chronic obstructive pulmonary disease (COPD) are well-documented. In South Africa, exercise programmes for COPD patients are limited and often expensive and inaccessible to the broader community. The purpose of this study was to assess the responses of COPD patients to an exercise programme and to determine if the same results can be obtained through a less costly programme. In the primary programme of the study, 22 subjects were subjected to 12 weeks of exercise training. Each subject underwent comprehensive pre- and post-intervention assessments, which included the measurement of overall health status by a physician, level of dyspnoea, forced expiratory lung function, exercise capacity, body mass index and health-related quality of life. Exercise sessions included aerobic and strength training exercises and involved three, hour-long exercise sessions a week. In the modified programme, 18 subjects were randomly divided into an experimental and control group. Eleven subjects were included in the experimental group and seven subjects in the control group. Subjects had to complete 32, hour-long exercise sessions in a 10-week period. The experimental group’s exercise programme was adapted so that no specialised equipment was used, while the control group exercised in a well-equipped exercise- and rehabilitation centre.