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Optimized Parameters (optimized + parameter)
Selected AbstractsInfluence of Hydrogen Plasma on the Defect Passivation of Polycrystalline Si Thin Film Solar CellsPLASMA PROCESSES AND POLYMERS, Issue S1 2009Benjamin Gorka Abstract Hydrogen passivation (HP) of polycrystalline silicon (poly-Si) thin film solar cells was performed in a parallel plate radio-frequency (rf) plasma setup. The influence of hydrogen pressure p and electrode gap d on breakdown voltage Vbrk is presented showing that the minimum in Vbrk shifts with higher pressures towards higher p,·,d values. Cell test structures provided by CSG Solar AG were used to examine the influence of p and d on the open circuit voltage VOC. The highest VOC's were achieved for p,·,d values that correspond to a minimum in Vbrk. HP strongly improved the VOC. After the hydrogen plasma treatment the VOC improved significantly by a factor of 2 and amounted to 450 mV. Optimized parameters were then applied to different poly-Si solar cells prepared by electron beam evaporation. [source] Determining soil saturated hydraulic conductivity and sorptivity from single ring infiltration testsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007J. Touma Summary The difference between the cumulative infiltration occurring during three-dimensional axisymmetric and one-dimensional vertical flow is a linear function of time. The slope of this line is a function of the source radius, initial and final volumetric soil water contents and the soil sorptivity. This allows the determination of the sorptivity and saturated conductivity of the soil from data of axisymmetric flow in a single ring of small diameter under negligible head of water. The method is based on the optimization of the sorptivity and saturated conductivity on the one-dimensional vertical cumulative infiltration inferred from axisymmetric flow data. To examine the reliability of the method to determine these parameters, numerical three- and one-dimensional data are generated on soils with known hydrologic properties from the literature. The linearity versus time of the difference of the two types of flow is verified. Several physically based expressions for the vertical cumulative infiltration as a function of time are considered. The optimized values of the sorptivity and saturated conductivity are compared to the their real known values. Despite the large errors on the optimized parameters, namely the saturated conductivity, the error on the vertical predicted cumulative infiltration is limited to 10%. This makes possible the application of this method on a large scale for hydrological modelling purposes. [source] Parameter optimization for a PEMFC model with a hybrid genetic algorithmINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2006Zhi-Jun Mo Abstract Many steady-state models of polymer electrolyte membrane fuel cells (PEMFC) have been developed and published in recent years. However, models which are easy to be solved and feasible for engineering applications are few. Moreover, rarely the methods for parameter optimization of PEMFC stack models were discussed. In this paper, an electrochemical-based fuel cell model suitable for engineering optimization is presented. Parameters of this PEMFC model are determined and optimized by means of a niche hybrid genetic algorithm (HGA) by using stack output-voltage, stack demand current, anode pressure and cathode pressure as input,output data. This genetic algorithm is a modified method for global optimization. It provides a new architecture of hybrid algorithms, which organically merges the niche techniques and Nelder,Mead's simplex method into genetic algorithms (GAs). Calculation results of this PEMFC model with optimized parameters agreed with experimental data well and show that this model can be used for the study on the PEMFC steady-state performance, is broader in applicability than the earlier steady-state models. HGA is an effective and reliable technique for optimizing the model parameters of PEMFC stack. Copyright © 2005 John Wiley & Sons, Ltd. [source] Sequential parametric optimization of lipase production by a mutant strain Rhizopus sp.JOURNAL OF BASIC MICROBIOLOGY, Issue 4 2005BTNT- Lipase production by the mutant strain Rhizopus sp. BTNT-2 was optimized in submerged fermentation. Different chemical and physical parameters such as carbon sources, nitrogen sources, oils, inoculum level, pH, incubation time, incubation temperature and aeration have been extensively studied to increase lipase productivity. Potato starch (1.25% w/v) as a carbon source, corn steep liquor (1.5% w/v) as a nitrogen source and olive oil (0.5% v/v) as lipid source were found to be optimal for lipase production. The optimal levels of other parameters are 4 ml of inoculum (2.6 × 108 spores/ml), initial pH of 5.5, incubation time of 48 hours, incubation temperature of 28 °C and aeration rate of 120 rpm. With the optimized parameters, the highest production of lipase was 59.2 U/ml while an yield of only 28.7 U/ml was obtained before optimization resulting in 206% increase in the productivity. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Small microstrip patch antennas with short-pin using a dual-band operationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2008Cheol Yoon Abstract This article presents the design and fabrication of a short-pin dual-band E-shaped microstrip patch antenna for application in a 2.630,2.655 GHz band satellite-DMB with a 5.725,5.825 GHz band wireless LAN. The prototype consist of a short-pin and E-shaped patch. To obtain sufficient bandwidth in VSWR < 2, an air layer is inserted between the ground plane and the substrate. A small short-pin patch that has a dual-band characteristic is used. Important design parameters are the slot's existence, length, the air-gap's height, the feed point's position, and the short-pin's existence and point position. From these optimized parameters, an E-shaped antenna is fabricated and measured. The measured results of the fabricated antenna are obtained individually at 200 and 700 MHz bandwidths in VSWR < 2 referenced to the center frequency, and the individual gain at 8.79 and 10.26 dBi. The experimental 3 dB beam width is shown to be broad across the pass band in the E-plane, and in the H-plane is individually 73°, 65°, 74°, and 42°, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 367,371, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23099 [source] Calculation of optimized parameters of rectangular microstrip patch antenna using particle swarm optimizationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2007A. Egemen Yilmaz Abstract In this letter, the particle swarm optimization has been applied to calculate the optimized length and width of rectangular microstrip antennas. The inputs to the problem are the dielectric constant and thickness of the substrate; together with the desired resonant frequency; the outputs are the optimized length and width; where the antennas are considered to be electrically thin. The results are in good agreement with the results (experimental and calculated by other heuristics) in the literature. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2905,2907, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22918 [source] | ||||||||||