743 research outputs found

    Modeling the effects of proton irradiation [on] CIGS solar cells

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    The space environment is very harsh on photovoltaic devices. Solar protons (hydrogen ions) cause large numbers of vacancies, which act as recombination centers at deep levels and can create compensating defects that reduce the acceptor concentration at shallow levels in semiconductors. This in turn, can reduce the output power generated by photovoltaic devices. Damage can also occur from atomic oxygen, plasma discharges and electron irradiation. Solar arrays have to be manufactured to produce more power than necessary so that the solar array will still produce the needed amount of power after degradation occurring from charged particle irradiation. A major challenge is to be able to model these devices so that the effects of charged particle irradiation can be taken into account in calculations for the End of Life (EOL) open-circuit voltage, short-circuit-current, fillfactor,and efficiency. Models presently being used do not provide distinct values without more calculations. Also, models presently being used tend to have proton irradiation incident normal to the surface, which does not reflect actual conditions, and require a significant amount of input data. In an effort to correct these problems, a new model was created that finds the remaining factor of the normalized basic cell parameters for CuInGaSe2 (CIGS) solar cells. This model uses significantly fewer inputs than other computer models, provides a more realistic model with respect to entry angles of incident protons, and provides actual and normalized values without extra calculations

    Implementation of horizontal well CBM/ECBM technology and the assessment of effective CO2 storage capacity in a Scottish coalfield

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    Acknowledgements The authors wish to thank Composite Energy Ltd., the BG Group, Scottish Power and the Royal Bank of Scotland for their funding and contributions towards the research reported in this paper.Non peer reviewedPublisher PD

    Aquaculture production and its environmental sustainability in Thailand : challenges and potential solutions

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    Though aquaculture plays an important role in providing foods and healthy diets, there are concerns regarding the environmental sustainability of prevailing practices. This study examines the trends and changes in fisheries originating from aquaculture production in Thailand and provides insights into such production’s environmental impacts and sustainability. Together with an extensive literature review, we investigated a time series of Thai aquaculture production data from 1995 to 2015. Overall, Thai aquaculture production has significantly increased during the last few decades and significantly contributed to socio-economic development. Estimates of total aquaculture production in Thailand have gradually grown from around 0.6 to 0.9 million tons over the last twenty years. Farmed shrimp is the main animal aquatic product, accounting for an estimated 40% of total yields of aquaculture production, closely followed by fish (38%) and mollusk (22%). Estimates over the past decades indicate that around 199470 ha of land is used for aquaculture farming. Out of the total area, 61% is used for freshwater farms, and 39% is used for coastal farms. However, this industry has contributed to environmental degradation, such as habitat destruction, water pollution, and ecological effects. Effective management strategies are urgently needed to minimize the environmental impacts of aquaculture and to ensure it maximally contributes to planetary health. Innovative and practical solutions that rely on diverse technology inputs and smart market-based management approaches that are designed for environmentally friendly aquaculture farming can be the basis for viable long-term solutions for the future

    Modeling of soil weathering on hillslopes : coping with nonlinearity and coupled processes using a data-driven approach

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    Orientadores: Carlos Roberto de Souza Filho, Michael James FriedelTese (doutorado) - Universidade Estadual de Campinas, Instituto de GeociênciasResumo: Esta tese de doutorado tem como objetivo aprofundar o conhecimento sobre as relações das propriedades físico-quimicas do solo com a morfometria do relevo, buscando quantificar essas relações para a construção de modelos conceituais e preditivos. Mapas auto-organizáveis e modelos de sistemas de informação geográfica foram utilizados para investigar as relações não lineares associadas ao intemperismo químico e físico, fatores associados a fenômenos hidrológicos e à evolução dos solos. Três estudos de caso são apresentados: o intemperismo químico de solo no estado do Paraná (22 variáveis e 304 amostras), o transporte físico de sedimentos em Poços de Caldas (9 variáveis e 29 amostras), e hidroquímica de aqüíferos na Formação Serra Geral no Estado do Paraná (27 variáveis e 976 amostras). O método combinando simulação estocástica e mineração de dados permitiu explorar as relações entre relevo, granulometria e geoquímica dos solos. Regiões mais elevadas e com morfometria convexa apresentaram alta denudação de elementos móveis (e.g., Ca) e baixa de elementos pouco móveis (e.g., Al). O mesmo padrão foi observado para granulometria de solos, ou seja, alta proporção de areia em áreas altas e convexas da bacia e altos teores de argila, com baixa condutividade hidráulica, em regiões convexas próximas aos canais de drenagem. O comportamento espacial da hidroquímica das águas do aqüífero Serra Geral apontou áreas de potencial conectividade entre aqüíferos, áreas de recarga recente e de alto tempo de residência. Foram construídos modelos preditivos não tendenciosos das propriedades do solo em subsuperfície partindo da premissa de que o intemperismo e a morfometria se relacionam através de um processo duplamente dependente, onde a denudação física e química atua no delineamento do relevo e a morfometria do terreno é um fator que caracteriza as condições físico-químicas do soloAbstract: This Doctoral thesis aims to explore the relationship between soil physical-chemical properties and relief morphometry, and quantifying these relationships to build conceptual and predictive models. Self-organizing maps and Geographic Information Systems modeling are here used to investigate nonlinear correlations associated with chemical and physical denudation; which are factors connected with hydrological phenomena and soil evolution. Three study cases are presented: soil chemical weathering within the limits of the Parana State, southern Brazil (22 variables and 304 samples), physical transport of sediments in the alkaline intrusive complex of Poços de Caldas, southeastern Brazil (9 variables and 29 samples), and hydrochemistry of Serra Geral aquifers also in the Parana State (27 variables and 976 samples). The method combining stochastic simulation and data mining allows exploring the relationships between topography, soil texture and soil geochemistry. In the Parana State, higher regions and areas with convex morphometry shows, respectively, higher and lower denudation rates of mobile (e.g., Ca) and less mobile (e.g., Al) elements. The same pattern is observed for soil particle size. In this case, high proportion of sand is found in highlands and convex areas inside the basin, and high clay content, with low hydraulic conductivity, occurs in convex regions, near drainage channels. The spatial behavior of the Serra Geral aquifer?s hydrochemistry pointed out to areas with potential connectivity with the Guarani aquifer system, recent recharge areas, and long-standing waters. Predictive, unbiased models are built for soil properties on the premise that weathering and morphology are related through a two-way dependent process, where the physical and chemical denudation delineates the elevations of the land surface, and terrain morphometry is a factor that characterizes the physical-chemical conditions of the soilDoutoradoGeologia e Recursos NaturaisDoutor em Ciência

    Rainfall Returns Periods in Iraq

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    بيانات الساقط المطري في اثنين وثلاثين محطة مناخية موزعة غلى العراق تم الاستعانة بها لايجاد العودة الزمنية للامطار والتي تساهم في تحسين خطط إدارة المياه في جميع أنحاء العراق خاصة خلال المواسم الجافة. بينت النتائج بان متوسط المجموع السنوي للامطار بان هناك نمطاً متناظر من تزايد الساقط المطري من المنطقة الجنوبية الغربية في العراق باتجاه مناطقه الشمالية الشرقية حيث اتسمت الاخيرة بكون الحدث المناخي بالاستناد للعودة الزمنية للامطار بكونه فوق طبيعي جدا الى فوق طبيعي بينما امتازت باقي مناطق العراق بحدث مناخي متمثل بتوزيع طبيعي للامطار بدلالة العودة الزمنية لها. اوضحت النتائج بان العراق يتميز بنوعين فقط من الظروف الجوية حسب فترات سقوط الأمطار متمثلة بحالة الطقس الرطب الموجودة في الجزء الشمالي الشرقي والظروف الجوية الجافة في الأجزاء الأخرى منه.Rainfall date obtained for thirty-two meteorological stations distributed in Iraq to find the rainfall returns period, which contributes in the improvement of water management plans all over Iraq, especially during dry seasons. Mean annual summation of rainfall has a symmetrical increasing pattern from southern west towards northern east, according to the increasing ratio of rainfall in the northern region of Iraq. The northern east region of Iraq has characterized by very abnormal and abnormal events regarding rainfall (P) in term of return periods, while the northern west, middle and southern regions characterize by a normal distribution of rainfall. , Iraq has only two types of weather conditions, according to rainfall returns periods: the humid weather condition located in the northern east part and dry weather condition in the other parts of it

    Study on the performance improvements of electrical domestic appliance factory

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    Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 43).This thesis has two objectives. First, it aims to help TECHSOL electronics domestic appliance measure and analyze its current performance. Secondly, it is aimed to ascertain where a small improvement can result in significant gain. A simulation model was used to model the factory in the abstract level. From the simulation model, areas of improvement for the factory are identified. It is also learned which stations constrain the factory production and which station performs badly. The thesis concluded with a suggestion of improvement in a particular station. The way and methodology to improve that particular station become the focus study for my project partner in the company.by Andy Darwin Kasan Hidayat.M.Eng

    RAVE as a Gaia precursor: what to expect from the Gaia RVS?

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    The Radial Velocity Experiment (RAVE) is a large wide-field spectroscopic stellar survey of the Milky Way. Over the period 2003-2013, 574,630 spectra for 483,330 stars have been amassed at a resolution of R=7500 in the Ca-triplet region of 8410-8795\AA. Wavelength coverage and resolution are thus comparable to that anticipated from the Gaia RVS. Derived data products of RAVE include radial velocities, stellar parameters, chemicals abundances for Mg, Al, Si, Ca, Ti, Fe, and Ni, and absorption measures based on the diffuse interstellar bands (DIB) at 8620\AA. Since more than 290000 RAVE targets are drawn from the Tycho-2 catalogue, RAVE will be an interesting prototype for the anticipated full Gaia data releases, in particular when combined with the early Gaia data releases, which contain astrometry but not yet stellar parameters and abundances.Comment: 7 pages, 3 color figures. Invited contribution to the GREAT-ITN conference "The Milky Way Unravelled by Gaia: GREAT Science from the Gaia Data Releases", 1-5 December 2014, University of Barcelona, Spain, EAS Publications Series, eds Nicholas Walton, Francesca Figueras, and Caroline Soubira

    Cogeneration Design Study for a Pilot Travel Center

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