Study of Staebler-Wronsky degradation effect in a Si:H based P-I-N solar cells

The objective of this study is to improve the stability and efficiency of thin solar cells with emphasis on a-Si:H devices. The research project was broken down into three main phases. The first involves designing and building a UHV glow discharge system; the second involves making good quality films and eventually efficient cells; the final phase will be analytical

Hybrid Coding Technique for Pulse Detection in an Optical Time Domain Reflectometer

The paper introduces a novel hybrid coding technique for improved pulse detection in an optical time domain reflectometer. The hybrid schemes combines Simplex codes with signal averaging to articulate a very sophisticated coding technique that considerably reduces the processing time to extract specified coding gains in comparison to the existing techniques. The paper quantifies the coding gain of the hybrid scheme mathematically and provide simulative results in direct agreement with the theoretical performance. Furthermore, the hybrid scheme has been tested on our self-developed OTDR

Study of the Staebler-Wronski degradation effect in a-Si:H based p-i-n solar cell

Conversion of solar energy into electricity using environmentally safe and clean photovoltaic methods to supplement the ever increasing energy needs has been a cherished goal of many scientists and engineers around the world. Photovoltaic solar cells on the other hand, have been the power source for satellites ever since their introduction in the early sixties. For widespread terrestrial applications, however, the cost of photovoltaic systems must be reduced considerably. Much progress has been made in the recent past towards developing economically viable terrestrial systems, and the future looks highly promising. Thin film solar cells offer cost reductions mainly from their low processing cost, low material cost, and choice of low cost substrates. These are also very attractive for space applications because of their high power densities (power produced per kilogram of solar cell pay load) and high radiation resistance. Amorphous silicon based solar cells are amongst the top candidates for economically viable terrestrial and space based power generation. Despite very low federal funding during the eighties, amorphous silicon solar cell efficiencies have continually been improved - from a low 3 percent to over 13 percent now. Further improvements have been made by the use of multi-junction tandem solar cells. Efficiencies close to 15 percent have been achieved in several labs. In order to be competitive with fossil fuel generated electricity, it is believed that module efficiency of 15 percent or cell efficiency of 20 percent is required. Thus, further improvements in cell performance is imperative. One major problem that was discovered almost 15 years ago in amorphous silicon devices is the well known Staebler-Wronski Effect. Efficiency of amorphous silicon solar cells was found to degrade upon exposure to sunlight. Until now their is no consensus among the scientists on the mechanism for this degradation. Efficiency may degrade anywhere from 10 percent to almost 50 percent within the first few months of operation. In order to improve solar cell efficiencies, it is clear that the cause or causes of such degradation must be found and the processing conditions altered to minimize the loss in efficiency. This project was initiated in 1987 to investigate a possible link between metallic impurities, in particular, Ag, and this degradation. Such a link was established by one of the NASA scientists for the light induced degradation of n+/p crystalline silicon solar cells

Incentives for Fertilizer Use in Sub-Saharan Africa: A Review of Empirical Evidence on Fertilizer Response and Profitability

This research addresses two questions: Why is fertilizer not yet fulfilling its potential as a major stimulus to agricultural productivity in SSA? What can be done to improve the situation? Our answers are based on an extensive review of fertilizer response, profitability, and policy literature as well as some analysis of crop budgets and aggregate national statistics on fertilizer consumption. Much of the debate about fertilizer use in SSA focuses on two issues: whether the profit incentive is adequate and, if so, whether farmers have the capacity to access and use it.food security, food policy, fertilizer use, sub-Saharan Africa, Crop Production/Industries, Downloads May 2008-July 2009: 153, Q18,

Conceptualizing Core Practices for Professional Development of Novice Mentors

Purposeful and effective professional development of teacher mentors is often a proposed solution in many of the present debates about education, including teacher quality, teacher retention, and the student achievement gap. The literature about teacher mentoring suggests that if mentors in teacher education programs do not have significant professional development on mentoring, even a thoughtfully organized formal induction program can be ineffective in preparing good teachers, undermined by an unprepared mentor. The purpose of this conceptual paper is to propose a framework of professional development for veteran teachers who are to become mentors. Our framework will have a three-fold effect. The framework is designed to (a) develop or strengthen supportive and collaborative partnerships between schools and teacher education programs; (b) prompt veteran teachers to identify, share, and deconstruct their teaching practices with colleagues and teacher educators; and (c) scaffold teacher learning into research on and best practices in effective mentoring. Ultimately, the framework's aim is to structure the preparation of effective teacher mentors, who will go on to have positive impacts on interns and novice teachers' long-term successes. Notably, based on the research, our Professional Development (PD) framework is situated in schools, about subject area knowledge, and focused on mastery of mentoring skills.

Collector’s Relationship to Access-Based Consumption: A Sneakerhead’s Perspective

This research focuses on what persuades sneakerheads to partake in access-based consumption. This research is important because the relationship between collectors, particularly sneakerheads, and access-based consumption has not yet been explored. This topic was studied by conducting semi-structured interviews with sneakerheads, to find themes and correlations that depict motives for consumers to participate in access-based consumption. As well as motives, this topic was studied to discover deterrents that may drive sneakerheads away from renting their sneakers. These findings will contribute something new to the literature based upon access-based consumption, because currently there is no literature that depicts what motivates or discourages collectors/sneakerheads to become access-based consumers. To extract those findings, semi-structured interviews were conducted. The sample was a convenient sample from a Charlotte, N.C. mall. After conducting the interviews, it was found that saving money was a major motive for sneakerheads to rent their sneakers. Other than economic benefits, it was also found that for one-time use and status seeking purposes sneakerheads are motivated to rent their sneakers. Deterrents such as anxiety, hygiene, possessiveness, and sneaker condition were all discouragements that drove sneakerheads away from renting their sneakers. Within this study, there is also a proposed plan of how a sneaker-renting platform could benefit the consumer and the market simultaneously