940 resultados para semi conducting polymers, electroluminescence, photovoltaics


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Transparent and conductive Zn-In-Sn-O (ZITO) amorphous thin films have been deposited at room temperature by the rf magnetron co-sputtering of ITO and ZnO targets. Co-sputtering gives the possibility to deposit multicomponent oxide thin films with different compositions by varying the power to one of the targets. In order to make ZITO films with different Zn content, a constant rf power of 50 W was used for the ITO target, where as the rf power to ZnO target was varied from 25 W to 150 W. The as deposited films showed an increase in Zn content ratio from 17 to 67 % as the power to ZnO target was increased from 25 to 150 W. The structural, electrical and optical properties of the as deposited films are reported. The films showed an average transmittance over 80% in the visible wavelength range. The electrical resistivity and optical band gap of the ZITO films were found to depend on the Zn content in the film. The ZITO films deposited at room temperature with lower Zn content ratios showed better optical transmission and electrical properties compared to ITO film.

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Indium tin oxide (ITO) is one of the widely used transparent conductive oxides (TCO) for application as transparent electrode in thin film silicon solar cells or thin film transistors owing to its low resistivity and high transparency. Nevertheless, indium is a scarce and expensive element and ITO films require high deposition temperature to achieve good electrical and optical properties. On the other hand, although not competing as ITO, doped Zinc Oxide (ZnO) is a promising and cheaper alternative. Therefore, our strategy has been to deposit ITO and ZnO multicomponent thin films at room temperature by radiofrequency (RF) magnetron co-sputtering in order to achieve TCOs with reduced indium content. Thin films of the quaternary system Zn-In-Sn-O (ZITO) with improved electrical and optical properties have been achieved. The samples were deposited by applying different RF powers to ZnO target while keeping a constant RF power to ITO target. This led to ZITO films with zinc content ratio varying between 0 and 67%. The optical, electrical and morphological properties have been thoroughly studied. The film composition was analysed by X-ray Photoelectron Spectroscopy. The films with 17% zinc content ratio showed the lowest resistivity (6.6 × 10 - 4 Ω cm) and the highest transmittance (above 80% in the visible range). Though X-ray Diffraction studies showed amorphous nature for the films, using High Resolution Transmission Electron Microscopy we found that the microstructure of the films consisted of nanometric crystals embedded in a compact amorphous matrix. The effect of post deposition annealing on the films in both reducing and oxidizing atmospheres were studied. The changes were found to strongly depend on the zinc content ratio in the films.

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Distortions in a family of conjugated polymers are studied using two complementary approaches: within a many-body valence bond approach using a transfer-matrix technique to treat the Heisenberg model of the systems, and also in terms of the tight-binding band-theoretic model with interactions limited to nearest neighbors. The computations indicate that both methods predict the presence or absence of the same distortions in most of the polymers studied.

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Distortions of polyacene polymers are studied within a many-body valence-bond framework using a powerful transfer-matrix technique for the valence-bond (or Heisenberg) model of the system. The computations suggest that the ground-state geometry is either totally symmetric or possibly exhibits a slight (A2 or B2 symmetry) bond-alternation distortion. The lowest-energy (nonsymmetric, in-plane) distortions are the A2 and B2 modes, which, within our approximations, are degenerate.

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Application of semi-distributed hydrological models to large, heterogeneous watersheds deals with several problems. On one hand, the spatial and temporal variability in catchment features should be adequately represented in the model parameterization, while maintaining the model complexity in an acceptable level to take advantage of state-of-the-art calibration techniques. On the other hand, model complexity enhances uncertainty in adjusted model parameter values, therefore increasing uncertainty in the water routing across the watershed. This is critical for water quality applications, where not only streamflow, but also a reliable estimation of the surface versus subsurface contributions to the runoff is needed. In this study, we show how a regularized inversion procedure combined with a multiobjective function calibration strategy successfully solves the parameterization of a complex application of a water quality-oriented hydrological model. The final value of several optimized parameters showed significant and consistentdifferences across geological and landscape features. Although the number of optimized parameters was significantly increased by the spatial and temporal discretization of adjustable parameters, the uncertainty in water routing results remained at reasonable values. In addition, a stepwise numerical analysis showed that the effects on calibration performance due to inclusion of different data types in the objective function could be inextricably linked. Thus caution should be taken when adding or removing data from an aggregated objective function.

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Conjunctival nevi are lesions observed commonly occasionnally and can be found later in a life. Such a lesion was observed on the conjunctival semilunar fold in a 76-year-old female patient. It was oval in shape, pigmented, and was mainly visible when the affected eye was in abduction. As no accurate anterior clinical history was available, surgical resection was performed. Hitopathological study disclosed a subepithelial nevus, which was completely resected. Regular follow-up was recommended, as is usual after surgical resection of a conjunctival pigmented tumor.

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Iowa's county road system includes several thousands of miles of paved roads which consist of Portland cement concrete (PCC) surfaces, asphalt cement concrete (ACC) surfaces, and combinations of thin surface treatments such as seal coats and slurries. These pavements are relatively thin pavements when compared to the state road system and therefore are more susceptible to damage from heavy loads for which they were not designed. As the size of the average farm in Iowa has increased, so have the size and weights of implements of husbandry. These implements typically have fewer axles than a truck hauling the same weight would be required to have; in other words, some farm implements have significantly higher axle weights than would be legal for semi-trailers. Since stresses induced in pavements are related to a vehicle's axle weight, concerns have been raised among county and state engineers regarding the possible damage to roadway surfaces that could result from some of these large implements of husbandry. Implements of husbandry on Iowa's highway system have traditionally not been required to comply with posted weight embargo on bridges or with regulations regarding axle-weight limitations on roadways. In 1999, with House File 651, the Iowa General Assembly initiated a phased program of weight restrictions for implements of husbandry. To help county and state engineers and the Iowa legislature understand the effects of implements of husbandry on Iowa's county roads, the following study was conducted. The study investigated the effects of variously configured grain carts, tank wagons, and fence-line feeders on Iowa's roadways, as well as the possible mitigating effects of flotation tires and tracks on the transfer of axle weights to the roadway. The study was accomplished by conducting limited experimental and analytical research under static loading conditions

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We show how nonlinear embedding algorithms popular for use with shallow semi-supervised learning techniques such as kernel methods can be applied to deep multilayer architectures, either as a regularizer at the output layer, or on each layer of the architecture. This provides a simple alternative to existing approaches to deep learning whilst yielding competitive error rates compared to those methods, and existing shallow semi-supervised techniques.

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Asphalt binder is typically modified with poly type (styrene-butadiene-styrene or SBS) polymers to improve its rheological properties and performance grade. The elastic and principal component of SBS polymers is butadiene. For the last decade, butadiene prices have fluctuated and significantly increased, leading state highway agencies to search for economically viable alternatives to butadiene based materials. This project reports the recent advances in polymerization techniques that have enabled the synthesis of elastomeric, thermoplastic, block-copolymers (BCPs) comprised of styrene and soybean oil, where the “B” block in SBS polymers is replaced with polymerized triglycerides derived from soybean oil. These new breeds of biopolymers have elastomeric properties comparable to well-established butadiene-based styrenic BCPs. In this report, two types of biopolymer formulations are evaluated for their ability to modify asphalt binder. Laboratory blends of asphalt modified with the biopolymers are tested for their rheological properties and performance grade. Blends of asphalt modified with the biopolymers are compared to blends of asphalt modified with two commonly used commercial polymers. The viscoelastic properties of the blends show that biopolymers improve the performance grade of the asphalt to a similar and even greater extent as the commercial SBS polymers. Results shown in this report indicate there is an excellent potential for the future of these biopolymers as economically and environmentally favorable alternatives to their petrochemically-derived analogs.

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O estudo teve como objetivo avaliar um modelo físico do sistema de cria de bovinos para as áreas mais secas do Semi-Árido brasileiro, associando a pastagem natural com pastos cultivados tolerantes à seca. A caatinga foi pastejada no período verde, e o capim buffel no restante do ano. A suplementação com leucena ocorreu no período seco, sob pastejo direto e feno no cocho. Parâmetros de desempenho, monitorados de novembro de 1991 a outubro de 1995, mostraram uma taxa média de parição da ordem de 72,8% ao ano e taxas de mortalidade praticamente nulas. O peso vivo médio dos bezerros aos 205 dias de idade foi de 153,4 kg e a produ- ção de bezerros desmamados foi de 109,5 kg/matriz exposta/ano e de 25,5 kg/hectare/ano. Os resultados são considerados bastante expressivos, considerando-se que mais da metade da área era ocupada com pastagens nativas de caatinga e que a oferta de leucena foi limitada pela ocorrência de uma forte estiagem.

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In recent grammars and dictionaries also (`therefore, so, well¿) continues to be preferably presented as an adverb with a conclusive-consecutive connective function that essentially corresponds to its use in formal written German. Its function as a modal particle is documented, however, since the beginnings of what is known as Partikelforschung, though not all its uses have been systematically investigated contrasting oral and written German, either in mode or concept. In this article we analyse the uses of also in semi-informal oral interactions on the basis of empirical data (from a subsample of the VARCOM corpus). Specifically, we will analyse the presence and frequency of also at the beginning of a sentence or sequence, the functions it serves as a logical-semantic connector or discourse and interaction marker and the interrelations between these functions, in order to contrast these results with the description of also provided by current reference works.

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Foi realizado um experimento para avaliar a influência da suplementação alimentar na produção de leite de cabras da raça Anglo-nubiana, durante a época chuvosa, na região semi-árida do Nordeste brasileiro. Vinte e quatro cabras foram mantidas em pastagem nativa rebaixada, distribuídas ao acaso, por tipo de parto e produção de leite, em três níveis de suplementação: N0 - sem suplementação, N1 -150 g de concentrado/animal/dia e N2 - 300 g de concentrado/animal/dia. Não houve diferença significativa (p>0,05) entre os níveis de suplementação. A produção de leite foi descrita por uma regressão múltipla em função do período de lactação em semana. A interação semana x níveis de suplementação foi significativa (p<0,01). Os resultados revelam que a suplementação com concentrado, na dose de 300 g/animal/dia, foi a melhor opção para se produzir leite com cabras Anglo-nubianas, durante a época chuvosa.