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991.
Je-Eun Choi Masahiro Takei Hyo-Jae Jo Javier Ortiz-Villafuerte 《Nuclear Engineering and Design》2008,238(8):2055-2063
Currently, wavelet transforms are widely used for the analyses of particle image velocimetry (PIV) velocity vector fields. This is because the wavelet provides not only spatial information of the velocity vectors, but also of the time and frequency domains. In this study, a discrete wavelet transform is applied to real PIV images of bubbly flows. The vector fields obtained by a self-made cross-correlation PIV algorithm were used for the discrete wavelet transform. The performances of the discrete wavelet transforms were investigated by changing the level of power of discretization. The images decomposed by wavelet multi-resolution showed conspicuous characteristics of the bubbly flows for the different levels. A high spatial bubble concentrated area could be evaluated by the constructed discrete wavelet transform algorithm, in which high-leveled wavelets play dominant roles in revealing the flow characteristics. 相似文献
992.
Although many products are made through several tiers of supply chains, a systematic way of handling reliability issues in a various product planning stage has drawn attention, only recently, in the context of supply chain management (SCM). The main objective of this paper is to develop a fuzzy quality function deployment (QFD) model in order to convey fuzzy relationship between customers needs and design specification for reliability in the context of SCM. A fuzzy multi criteria decision-making procedure is proposed and is applied to find a set of optimal solution with respect to the performance of the reliability test needed in CRT design. It is expected that the proposed approach can make significant contributions on the following areas: effectively communicating with technical personnel and users; developing relatively error-free reliability review system; and creating consistent and complete documentation for design for reliability. 相似文献
993.
Wen-Jie Shen Ki-Won Jun Ho-Suk Choi Kyu-Wan Lee 《Korean Journal of Chemical Engineering》2000,17(2):210-216
The thermodynamics involved in the catalytic hydrogenation of CO2 have been examined extensively. By assuming that methanol and dimethyl ether (DME) are the main products, two reaction systems
each consisting of two pararell reactions were analyzed and compared in terms of the equilibrium yield and selectivity of
the useful products, methanol and DME. The calculation results demonstrated that the production of DME allows much higher
oxygenate yield and selectivity than that of methanol. 相似文献
994.
Jong-Hwan Kim Keh-Kun Choi 《Automatic Control, IEEE Transactions on》1987,32(5):438-442
This note presents a direct adaptive control scheme for nonminimum phase systems where controller parameters are estimated from the recursive least-squares algorithm. Some additional auxiliary parameters are obtained from the proposed polynomial identity,, and a local convergence is guaranteed without any extra conditions. Integral action is incorporated into the adaptive controller to eliminate the steady-state error, and to satisfy a condition of the unique solution for the polynomial identity as well. 相似文献
995.
996.
The addition of the chelating polymer polyacrylic acid (PAA) to assist in the removal of manganese from groundwater by membranes was investigated using membranes with different pore sizes under various operating conditions. Negligible manganese removal was achieved with the UF and NF membranes at acidic pH values, but removals exceeding 90% could be achieved at elevated pH (pH 9), presumably due to the formation of manganese hydroxides. Mn removal increased substantially when PAA was added to the feed solution, due to chelation of Mn by the PAA and rejection of the chelates by the membranes. The chelate could be broken at acidic pH, releasing free PAA that could then be separated from the Mn ions and reused. Smaller PAA molecules were lost in the first regeneration cycle, but negligible PAA was lost in subsequent cycles. In the systems with PAA, nitrate ions were rejected more efficiently than in the PAA-free systems, presumably because of electrical repulsion between nitrate ions and PAA sorbed on the membrane surface. With increasing PAA dose, the volumetric flux first decreased and then increased; the latter result was accompanied by a change in the physical-chemical form of the polymers, as indicated by an increase in turbidity. 相似文献
997.
Ali Malik Dongdong Chen Younhee Choi Moon Ho Lee Seok-Bum Ko 《Electrical and Computer Engineering, Canadian Journal of》2008,33(3):169-175
With gate counts of ten million, field-programmable gate arrays (FPGAs) are becoming suitable for floating-point computations. Addition is the most complex operation in a floating-point unit and can cause major delay while requiring a significant area. Over the years, the VLSI community has developed many floating-point adder algorithms aimed primarily at reducing the overall latency. An efficient design of the floating-point adder offers major area and performance improvements for FPGAs. Given recent advances in FPGA architecture and area density, latency has become the main focus in attempts to improve performance. This paper studies the implementation of standard; leading-one predictor (LOP); and far and close datapath (2-path) floating-point addition algorithms in FPGAs. Each algorithm has complex sub-operations which contribute significantly to the overall latency of the design. Each of the sub-operations is researched for different implementations and is then synthesized onto a Xilinx Virtex-II Pro FPGA device. Standard and LOP algorithms are also pipelined into five stages and compared with the Xilinx IP. According to the results, the standard algorithm is the best implementation with respect to area, but has a large overall latency of 27.059 ns while occupying 541 slices. The LOP algorithm reduces latency by 6.5% at the cost of a 38% increase in area compared to the standard algorithm. The 2-path implementation shows a 19% reduction in latency with an added expense of 88% in area compared to the standard algorithm. The five-stage standard pipeline implementation shows a 6.4% improvement in clock speed compared to the Xilinx IP with a 23% smaller area requirement. The five-stage pipelined LOP implementation shows a 22% improvement in clock speed compared to the Xilinx IP at a cost of 15% more area. 相似文献
998.
999.
LEO satellite CDMA systems, characterized by round-trip delay and high variation in slow fading, call for different considerations on power control algorithms. Based on the criteria of fast response, small over-compensation, oscillation-avoiding and minimum power control error, the transient behavior of the fixed step, adaptive step, and multistep power control algorithms are investigated and compared. A new generic multistep power control algorithm with excellent dynamic performance is proposed for LEO satellite systems 相似文献
1000.
Kee-Sun- Sohn Yoon Young Choi Kyoung Hwa Kim Se Young Choi Hee Dong Park 《Journal of Materials Science: Materials in Electronics》2001,12(3):179-186
The photoluminescence of Terbium-activated yttrium aluminate with the general formula Y3-xTbXAl5O12was investigated as a function of Tb3+concentration. The main attention is focused on the 5D3/5D4fluorescence and its energy transfer behavior. The emission and excitation spectra were measured in terms of Tb3+concentration and analyzed in view of the application for plasma display panel (PDP). Also, the diffuse reflectance spectra were measured and analyzed in the range from VUV to UV. As a result, the yttrium aluminate was found to have a broad excitation band extending from VUV to UV range and to show the typical concentration quenching behaviors both for 5D3and 5D4fluorescence. The energy transfer was investigated by analyzing the decay curve of 5D3and 5D4emission based on the multipolar interaction or the exchange interaction. The decay curves of 5D3emission, for which well known cross relaxation has been accepted as a main factor, were analyzed by Inokuti and Hirayama's formula based on the direct quenching scheme. The decay curves of 5D4emission were analyzed by Yokota and Tanimoto's formula based on the diffusion limited quenching scheme. 相似文献