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

The cost of trauma operating theatre inefficiency.

The National Health Service (NHS) is currently facing a financial crisis with a projected deficit of £2billion by the end of financial year 2015/16. As operating rooms (OR) are one of the costliest components in secondary care, improving theatre efficiency should be at the forefront of efforts to improve health service efficiency. The objectives of this study were to characterize the causes of trauma OR delays and to estimate the cost of this inefficiency. A 1-month prospective single-centre study in St. Marys Hospital. Turnaround time (TT) was used as the surrogate parameter to measure theatre efficiency. Factors including patient age, ASA score and presence of surgical and anaesthetic consultant were evaluated to identify positive or negative associations with theatre delays. Inefficiency cost was calculated by multiplying the time wasted with staff capacity costs and opportunity costs, found to be £24.77/minute. The commonest causes for increased TT were delays in sending for patients (50%) and problems with patient transport to the OR (31%). 461 min of delay was observed in 12 days, equivalent to loss of £951.58/theatre/day. Non-statistically significant trends were seen between length of delays and advancing patient age, ASA score and absence of either a senior clinician or an anaesthetic consultant. Interestingly, the trend was not as strong for absence of an anaesthetic consultant. This study found delays in operating TT to represent a sizable cost, with potential efficiency savings based on TT of £347,327/theatre/year. Further study of a larger sample is warranted to better evaluate the identified trends

An update of the JPL program to develop Li-SOCl2 cells

The goal of producing spiral wound D cell was met. The cell design and electrodes, particularly the carbon cathodes were produced in-house. Also all parts were assembled, the welding performed, the electrolyte aided and the cells sealed in-house. The lithium capacity (theoretical) was 19.3 Ah and that of the SOCl2 in the 1.8 m LiAlCl4 electrolyte, 16.4 Ah (a greater excess of SOCl2 is necessary for safe high rate operation). The electrode surface area was 452 sq cm. The carbon electrode comprised Shawinigen Black/Teflon -30 (90/10 by weight) mixture 0.020 inches thick on an expanded metal screen prepared in the JPL laboratory. There were two tab connections to the cathode. The 0.0078 inch thick lithium foil was rolled into an expanded nickel screen. The separator was Mead 934-5 fiberglass material

Efficient Portfolios Versus Efficient Market

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108275/1/jfir00282.pd

Sputter Deposition and Thallination of Ti-Ba-Ca-Cu-O Superconducting Thin Films

Thallination techniques used for the fabrication of sputter-deposited TI2Ba2CaCu 2Ox and TI2Ba2Ca2Cu3Ox superconducting thin films were investigated. Differences in elemental composition of precursor Ba-Ca-Cu-O sputtering targets were found to yield different superconducting phases. Thallination conditions which yielded transition temperatures as high as 122 K for samples annealed in air are described. Finally, reactive ion etching of films using a mixture of chlorine and argon gases is discussed

\u27Kids in design\u27: designing creative schools with children

There is a consensus that children should be involved in the planning and design process of their schools, and attempts have been made throughout the world. This paper introduces a \u27Kids in Design\u27 project, through which primary school children worked with university architecture students to design a school playground. The aim of the project was to encourage the full potential of children\u27s creativity and generate creative school design outcomes. From October to December 2011, the \u27Kids in Design\u27 project was conducted in Roslyn Road Primary School (Geelong, Australia). Through eight weeks of workshops, children in Year 5 & 6 worked with architecture students from Deakin University (Geelong, Australia) to design a school playground. Assessing the design outcomes of this project, assertions are made that creative design outcomes have been achieved. Deakin University is currently working with another primary school to replicate the \u27Kids in Design\u27 project in 2012

A Preliminary Study on Induced Spawning of the Catfish Clarias batrachus (Linnaeus) in Malaysia

Ten gravid Clarias batrachus females were administered with a single dose of common carp pituitary homogenate (CPR). Bifore injection, the eggs were light yellow and the diameter rangedfrom 0.94 mm to 1.08 mm. Ovulation occurred approximately 12 hours after the adminstration of CPR. The colour of the eggs turned brown and the diameter rangedfrom o. 99 mm to 1.27 mm. The fertilization rates rangedfrom 10-81%. The eggs hatched after about 30-36 hours of incubation at 26°C to 28°C. The hatching rates ranged from 13-67070

Structural Reliability of the Tampico Bridge under Wind Loading

A highway bridge located in Tampico, on the east coast of Mexico, is analyzed to determine its structural reliability against wind loading. The inherent variabilities of the random wind force and of the mechanical properties of steel constitute the aleatory uncertainty; this contributes to the probability of failure of the steel girder. The idealization of the loading and of the bridge structure, and the analysis of the structural response to wind loading, contribute to additional uncertainty of the epistemic type, which leads to a range of possible (or distribution of) failure probabilities. The design with the minimum expected life-cycle cost is the optimal design. However, for this optimal design, the 90% value (or the mean plus one standard deviation value) of the corresponding failure probability or safety index may be selected for a risk-aversive design. The proposed criteria constitute a new approach to make conservative decisions and involve the epistemic uncertainty on the bridge design and assessment proces

Liquefaction Fragilities for Buried Lifelines

For buried structures, such as conduits and underground pipes, liquefaction induced forces will depend on the volume of soil surrounding the structure that will liquefy. Here, a methodology to calculate the probability of the onset of liquefaction at a given depth in a soil deposit is extended to assess the probability that a specified volume of soil will liquefy when liquefaction occurs at a given depth in the deposit. To account for the variability of soil properties with depth, the soil deposit is divided into horizontal layers and the volume of liquefied soil in each layer is calculated as the product of the layer thickness by the lateral extent of liquefaction. Within each layer, the horizontal variability of the soil properties is described by a homogeneous and axisymmetric random field. It is assumed that the ground motions in the horizontal direction are perfectly correlated. The results are presented in terms of the probability of liquefaction spreading over a given area (a circle of radius R) as a function of the intensity of the ground motion