• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1244-1249
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• 2008

This paper shows a perfonnance analysis for pneumatic servo cylinder. The pistons without seal have partly cylindrical and conical shapes. 2 dimensional Reynolds equation and FD(finite differential) numerical techniques are utilized for the perfonnance analysis. The relationship among self-centering forces and leakage flows are investigated. Also, optimal design values for a servo cylinder are presented. A prototype of servo cylinder which had rod bearing with four pockets, five pockets, and six pockets was manufactured respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.64-72
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• 1999

The fictitious power theory in time domain is very easy to understand, but power analyzing speed of active power is increased, because power is analyzed using signal tedmiques based on the corre1ation between voltage and current wavefonns. Also, conventional methods in time/frequency domain to evaluate the correlation performance of active power filters are not provided easy solutions. So, the authors have previously proposed 3-D current coordinates which is composed into active component, fundarrental reactive component and distorted component of nonlinear loads current. This trethod has excellent perfonnance, but can not evaluate the characteristics of nonlinear load current whether It is inductive or capacitive. Therefore, To overcorre problems trentioned previously, this paper deals with the simple average power theory and the modified 3-D current coordinates for evaluating the compensation perfonnance of active power filters. To confirm the validity, active power filter simulator is developed using C-language. From the simulation, results are discussed their utility.tility.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2686-2703
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• 1998

The widening pClformnnce gap between processor and memory causes an emergence of the promising architecture, processor-memory (PM) integration In this paper, various design issues for P-M integration are studied, First, an analytical model of the DRAM access time is constructed considering both the bank conflict ratio and the DRAM page hit ratio. Then the points of both the performance improvement and the perfonnance bottle neck are found by the proposed model as designing on-chip DRAM architectures. This paper proposes the new architecture, called the delayed precharge bank architecture, to improve the perfonnance of memory system as increasing the DRAM page hit ratio. This paper also adapts an efficient bank interleaving mechanism to the proposed architecture. This architecture is verified !II he better than the hierarchical multi-bank architecture as well as the conventional bank architecture by executiun driven simulation. Eight SPEC95 benchmarks are used for simulation as changing parameters for the cache architecture, the number of DRAM banks, and the delayed time quantum.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.795-802
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• 2005

Binary CDMA(B-CDMA) is a new modulation scheme that employs a constant envelope modulation scheme By quantizing the envelope of multi-codes CDMA signal into a small number of levels, the B-CDMA can reduce the peak-to-average power ratio, while preserving the advantages of CDMA signaling such as the soft capacity and robustness to interference. In this paper, we analyze the performance of B-CDMA systems in multi-path channel assuming that the spreading factor is not too small. Finally, the analytic results are verified by computer simulation.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.4
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• pp.404-413
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• 1997

Direct-drive robots are suitable to position and force control with high accuracy, but it is difficult to design a controller which gives satisfactory perfonnance because of the system's nonlinearity and link-interactions. This paper is concerned with the force control of direct-drive robots. The pro¬posed algorithm consists of feedback controllers and a neural network. Mter the completion of learning, the outputs of feedback controllers are nearly equal to zero, and the neural network con¬troller plays an important role in the control system. Therefore, the optimum adjustment of parameters of feedback controllers is unnecessary. In other words, the proposed algorithm does not need any knowledge of the controlled system in advance. The effectiveness of the proposed algo¬rithm is demonstrated by the experiment on the force control of a parallelogram link-type direct¬drive robot.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.2
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• pp.43-53
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• 2004

Collision avoidance for multiple aircraft can be stated as a problem ofmaintaining safe distance between aircraft in conflict. Optimal collision avoidanceproblem seeks to minimize the given cost function while simultaneously satisfyingconstraints. The cost function could be a function of time or control input. This paper addresses the trajectory time-optimization problem for collision avoidance of unmanned aerial vehicles(UAVs). The problem is difficult to handle in general due to the two-point boundary value problem subject to dynamic environments. Some simplifying aleorithms are used for potential applications in on-line operation.Although under possibility of more complicated problems, a dynamic problem is transformed into a static one by prediction of the conflict time and some appropriate assumptions.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.2
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• pp.62-70
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• 2004

CFD method has been coupled with a time-marching free-wake model by usingfield velocity approach suggested by J. D. Baeder (Ref. 1). The coupled method hasbeen applied to rectangular and BERP-like blades and the calculated perfonnance dataare compared with the experimental results.For hovering analysis, the present method could yield sufficiently good resultswith reasonable computation time and is particularly suitable for the flow fieldanalysis with the complex shaped blade.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.4
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• pp.341-347
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• 2004

An experimental study has been carried out on cooling perfonnance of a thennoelectric module. This problem is of particular interest in the design of the refrigeration systems using thermoelectric module, such as cosmetic refrigerator, wine cellar and air cooler. The effect of the input voltage and the hot side temperature on the cooling performance is studied in detail. The $\Delta$T, temperature difference between cold side and hot side surface of thermoelectric module, is described in terms of the input voltage and the hot side temperature. It is found that the cooling capacity can be improved by increasing the input voltage and by reducing the heat from the hot side of the thermoelectric module. However, COP is decreased with an increase in the input voltage, since power consumption is also increased. Thus, optimum input voltage can be selected based on cooling capacity and COP.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.15-20
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• 1999

A spectrophotorreter using two-beam type integrating sphere is developed, and the measurerrent accuracy is analyzed. The efficiency of the integrating sphere is analyzed, and the relation between the efficiency and the total measurerrent error is found. Especially, the integrating sphere is fabricated on the basis of its characteristics according to its shape such as the sample port. The perfonnance of the developed spectrophotorreter is tested using a black and a white standard reflectance plate, and the measurerrent error of $\pm0.5%$ is obtained.tained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.665-671
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• 2006

In this paper, we propose and observe a system that adopts Independent-MCS (Modulation and Coding Scheme) level for each layer in the combined AMC-V-BLAST (Adaptive Modulation and Coding-Vertical-Bell-lab Layered Space-Time) system. Also, comparing with the combined system using Common-MCS level, we observe throughput performance improvement. As a result of simulation, Independent-MCS level case adapts modulation and coding scheme for maximum throughput to each channel condition in separate layer, resulting in improved throughput compared to Common-MCS level case. Especially, the results show that the combined AMC-V-BLAST system with Independent-MCS level achieves a gain of 700kbps in $7dB{\sim}9dB$ SNR (Signal-to-Noise Ratio) range.