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This study involves the characterization of thin films of copper indium diselenide (CuInSe2) deposited on soda-lime glass substrates using a two-step process. In this technique electron-beam-evaporated Cu-In precursor layers were reacted with an atmosphere containing H2Se gas. The morphological and structural aspects of the CuInSe2 layers were studied (by scanning electron microscopy and X-ray diffraction) as a function of the Cu-In film morphology and the selenization temperature profile and exposure time. It was found that the Cu-In precursor morphology has a significant influence on the structural properties of the final CuInSe2 film. Selenization of the Cu-In alloys (irrespective of the structure considered) directly at high temperature resulted in films with poor structural properties. However, a vast improvement in the adhesion properties and morphology of the CuInSe2 films were observed when the Cu-In films were exposed to a reactive selenium atmosphere while ramping the temperature between 150 C and 400 C. Selenization of triple-layer structures (Cu/In/Cu and In/Cu/In) resulted in films with good structural properties and excellent compositional uniformity. 相似文献
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Batch regeneration of barium carbonate (BaCO(3)) from barium sulphide (BaS) slurries by passing CO(2) gas into a pilot-scale bubbling column reactor under ambient conditions was used to assess the technical feasibility of BaCO(3) recovery in the Alkali Barium Calcium (ABC) desalination process and its use for sulphate removal from high sulphate Acid Mine Drainage (AMD). The effect of key process parameters, such as BaS slurry concentration and CO(2) flow rate on the carbonation, as well as the extent of sulphate removal from AMD using the recovered BaCO(3) were investigated. It was observed that the carbonation reaction rate for BaCO(3) regeneration in a bubbling column reactor significantly increased with increase in carbon dioxide (CO(2)) flow rate whereas the BaS slurry content within the range 5-10% slurry content did not significantly affect the carbonation rate. The CO(2) flow rate also had an impact on the BaCO(3) morphology. The BaCO(3) recovered from the pilot-scale bubbling column reactor demonstrated effective sulphate removal ability during AMD treatment compared with commercial BaCO(3). 相似文献
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Bernstein estimators attracted considerable attention as smooth nonparametric estimators for distribution functions, densities, copulas and copula densities. The present paper adds a parallel result for the first-order derivative of a copula function. This result then leads to Bernstein estimators for a conditional distribution function and its important functionals such as the regression and quantile functions. Results of independent interest have been derived such as an almost sure oscillation behavior of the empirical copula process and a Bahadur-type almost sure asymptotic representation for the Bernstein estimator of a regression quantile function. Simulations demonstrate the good performance of the proposed estimators. 相似文献
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We develop a general theorem to prove the uniform in bandwidth consistency of kernel-type function estimators. This method
unifies the approaches in some other recent papers. We show how to apply our results to kernel distribution function estimators
and the smoothed empirical process. The results are applicable to establish strong uniform consistency of data-driven bandwidth
kernel-type function estimators. 相似文献
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Multistep integration methods are being extensively used in the simulations of high dimensional systems due to their lower computational cost. The block methods were developed with the intent of obtaining numerical results on numerous points at a time and improving computational efficiency. Hybrid block methods for instance are specifically used in numerical integration of initial value problems. In this paper, an optimized hybrid block Adams block method is designed for the solutions of linear and nonlinear first-order initial value problems in ordinary differential equations (ODEs). In deriving the method, the Lagrange interpolation polynomial was employed based on some data points to replace the differential equation function and it was integrated over a specified interval. Furthermore, the convergence properties along with the region of stability of the method were examined. It was concluded that the newly derived method is convergent, consistent, and zero-stable. The method was also found to be A-stable implying that it covers the whole of the left/negative half plane. From the numerical computations of absolute errors carried out using the newly derived method, it was found that the method performed better than the ones with which we compared our results with. The method also showed its superiority over the existing methods in terms of stability and convergence. 相似文献
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Sanjib Kumar Karmee Wian Swanepoel Sanette Marx 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(3):294-300
Lipases namely Mucor miehei, Pseudomonas cepacia, Rhizopus delemar, Geotrichum candidum, Candida rugosa, Porcine pancreas-II, Pseudomonas fluorescence, and Candida antarctica lipase-B (Novozyme-435) were employed for biodiesel synthesis from spent coffee oil. Around 96% oil-to-biodiesel conversion was obtained using Novozyme-435 as a catalyst at 1:5 oil-to-methanol molar ratio and 40ºC. Total spent coffee grounds generated at the North-West University, Potchefstroom Campus (NWU PC) was estimated which could be used to produce 162 L of biodiesel. A waste valorization strategy was devised for converting organic wastes produced at the NWU PC to bioenergy. 相似文献
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A new type of engine concept is proposed, namely a rotating disk cylinder engine. Unique secondary rotors with grooves act as guide vanes for a working fluid to power a main rotor with multiple cylindrical pistons. Currently, no literature exists on the proposed device and the modelling thereof. The aim of this paper is to determine the dynamic and thermodynamic behaviour of the machine so that recommendations can be made for further research work. A transient as well as a steady‐state thermodynamic model is developed for an adiabatic expansion process using first and second law analysis with air as ideal gas. The model is compared with experimental results of a piston engine driven by compressed air. Results show that the secondary rotor's angle of rotation is not a linear function of the main rotor's angle of rotation, which suggests a limitation in terms of operating speed. Furthermore, for constant power, the efficiency increases as the inlet pressure and speed decrease, while for constant efficiency, the power increases as the inlet pressure and speed increase. Results show the advantage of using three secondary rotors as it drastically decreases the pressure requirement for a constant torque output. The speed and inlet pressure of the device is, however, limited by the mass and material properties of the rotors as well as the effects of leakage. These limitations have not been considered in this initial analysis of the device and are recommended for future work. 相似文献