• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.193-195
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• 2008

As arising the cost and decreasing of gasoline and fossil fuel, renewable energy sources such as photovoltaics, wind and fuel cell have been interested. Among of them, PEM fuel cells are good energy sources to provide reliable power at steady state regardless of weather, time of day and location as long as the fuel and air are supplied, but they cannot respond to electrical load transients as fast as desired. This is mainly due to their slow internal electrochemical and thermodynamic responses. Therefore, to use the fuel cells with high efficiency, this paper finds characteristic curve and understand operation of PEMFC based on three theoretical approaches such as activation, ohmic and concentration and make the model using MATLAB. That result was compared with real system to certify.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.975-976
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• 2007

Thermal and mechanical stresses, caused by repetitive start and stop and load fluctuation during long time operation, on winding stator bars are one of the main causes for electrical degradation of insulating materials. To understand the degradation process, we manufactured bar specimens with the same processes that make generator winding stator bars and the specimens were subjected to various degrees of thermal cycling. Measurements of the insulation properties, such as dissipation factor, tip-up and partial discharge, for un-aged specimens and for specimens aged by thermal cycling at 50, 100, 250, 500 and 1000 thermal cycles were performed. Finally all specimens were tested to obtain electrical breakdown voltages. In this paper we present the data and electrical degradation analysis results obtained during this program.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.127-134
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• 1998

This paper describes the design of a 6-component force/moment calibration machine with having the maximum capacities of 500 N in forces and 50 Nm in moments. To be used for the characteristic of a multi-component load cell. this machine consists of a body, a fixture, a force generating system, a moment generating system and weights. We have also evaluated the accuracy of the calibration machine. Test results show that the expanded relative uncertainty for force components $\pmFx,\;\pmFy\;and\;moment\;components\;\pmMx,\;\pmMy\;are\;less\; than\;8.6\times10^{-4}$, and force components +Fz, -Fz and moment components $\pmMz\;is\;less\;than\;1.6\times10^{-3},\;2.0\times10^{-5},\;1.7\times10^{-3}$ respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.1
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• pp.369-376
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• 1996

Variations of the drag and lift forces of a circular cylinder in a planar turbulent jet were experimentally investigated. The force was directly measured using the load cell and estimated by integrating the pressure distribution on the cylinder. As the cylinder moves outward from the center of the jet, the direction of lift force changes and the drag force decreases. Reynolds number, the ratio of cylinder's diameter to half width of jet had effect on maximum drag coefficient and the location where the direction of lift changes.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.252-253
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• 2010

본 논문에서는 Molten Carbonate Fuel Cell (MCFC)의 느린 동특성을 Load Leveler와 2차 전지로 구성된 back-up 시스템으로 보완하여 독립운전을 가능하게 한 대용량 연료전지 발전시스템을 제안한다. 제안한 독립운전 시스템의 발전 용량 및 battery 용량은 실제 전력사용 통계자료를 근거로 최적으로 산정되며, 컴퓨터 시뮬레이션을 통하여 타당성을 검증한다.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.32-33
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• 2010

This paper describes a droop control method for the autonomous operation of DC distribution system using distributed generations and energy storage. The method suppress the circulating current, and each unit could be controlled autonomously without communication system. Detailed model of wind power generation, photo-voltaic generation, fuel-cell generation and battery was implemented with the user-defined model of PSCAD/EMTDC software that is coded with C-language. The simulation and experimental results confirms that the proposed DC distribution system make it feasible to provide power to the load stably and verify effectiveness of the proposed method.

• Journal of the Korean Arthroscopy Society
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• v.13 no.3
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• pp.189-192
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• 2009

Although the articular cartilage is only a few milimiters thick, it has surprising stiffness to compression, exceptional ability to distribute load minimizing peak stress on subchondral bone and great durability. In many instances, it help to preserve normal joint function for more than 80 years. Varying in thickness, cell density, matrix composition, mechanical properties even within the same joint, it provides low-friction and pain free-motion. However, it lacks a blood or lymphatic supply and neurological elements are absent. It shows limited healing potential because of poor regenerative capacity.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.46.6-46
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• 2001

A servo gun welding system having a AC servo motor and a PC control system is presented for the improvement of quality control in the spot welding. The spot welding process is composed of the press stage, the weld stage, and the hold stage. The changes of gun press forces according to three stages in the spot welding process are controlled and measured through the load cell in order to know the influence on the welding quality. The relation between the measured force changes according to three stages and welding qualities is also implemented on the multilayer perceptrons, one of supervised learning method of neural network, which are powerful for realization of complex mapping characteristics. The estimated results and ...

• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.901-920
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• 2016

MeshFree methods have become popular owing to the ease with which high stress gradients can be identified and node density distribution can be reformulated to accomplish faster convergence. This paper presents a strategy for nodal density refinement with strain energy as basis in Element-Free Galerkin MeshFree technique. Two popular flat plate problems are considered for the demonstration of the proposed strategies. Issue of integration errors introduced during nodal density refinement have been addressed by suggesting integration cell refinement. High stress effects around two symmetrical semi-circular notches under in-plane axial load have been addressed in the first problem. The second considers crack propagation under mode I and mode II fracture loading by the way of introducing high stress intensity through line crack. The computational efficacy of the adaptive refinement strategies proposed has been highlighted.

• Food Science and Preservation
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• v.1 no.1
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• pp.37-43
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• 1994

A microcomputer system consisting of 16-bit microcomputer, PCL-711S interface board, censors, and converters have been set up in order to automatically measure temperature, humidity and weight loss which are major variables of storage of apple. This system was operated by PC-LabDAS software. It has been possible to measure continuously the weight loss of Fuji apple stored in CA with the weight converter made by a miniature load cell and a strain amplifier. The temperature was checked by a k-type thermocouple and Pt 100 $\Omega$ RTD, and humidity by PQ653JAl humidity sensor. It has been possible to set up a linear equation which showers high correlationship between the estimate of temperature, weight humidity and the output of the converter in that r2 is more than 0.99. Transpiration rate, a significant factor of quality deterioration for CA storage of apple, can be estimated with these values.