• Journal of Energy Engineering
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• v.7 no.2
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• pp.180-186
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• 1998

In this study, the effect of shear rate on the viscosity variation is examined to understand the flow characteristics of the mixture of bentonite and water. The variation of film thickness according to mixing ratio and viscosity is measured to characterize the film formation. And, the separation of dried film is studied according to film thickness. Specific surface area affecting on adsorption capability is measured using BET method. The viscosity decreases and the film thickness increases as the mixing ratio increases. The separation characteristic of dried film is suitable within a range of 40 to 150 ${\mu}{\textrm}{m}$ in film thickness and 5 to 10% in mixing ratio.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.68-74
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• 2008

This paper describes the causes and effects that have influence on thermoelectric generation. If heat transfer is unequal to thermoelectric modules, we could not get the maximum thermoelectric power. So, by experiment, we analysed the differences of power generation according to the state of the contact between thermoelectric module and heat source. And with the variation of heat transfer area, the generated power was analysed also. Using the experimental results we proposed a thermoelectric generation system.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.4
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• pp.371-374
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• 2012

DC/DC switching power converters produce DC output voltages from different stable DC input sources regulated by a bi-polar transistor. The converters can be used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The voltage mode DC/DC converter is composed of a PWM (Pulse Width Modulation) controller, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), an inductor, and capacitors, etc. PWM is applied to control and regulate the total output voltage. It is shown that the output of DC/DC converter depends on the variation of threshold voltage at MOSFET and the variation of pulse width. In the PWM operation, the missing pulses, the changes in pulse width, and a change in the period of the output waveform are studied by SPICE (Simulation Program with Integrated Circuit Emphasis) and experiments.

• Journal of Hydrogen and New Energy
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• v.20 no.5
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• pp.390-396
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• 2009

The flooding, especially in channel, is one of the critical issue to put proton exchange membrane fuel cell (PEMFC) to practical use. In this paper, channel flooding was investigated the pressure difference at cathode channel outlet. A ratio of pressure difference changes to 25, 50% as its variation rate. The pressure variable rate is reflected in dimensionless number FN. As a result, modified dimensionless number $FN^*$ correctly predicted the channel flooding. This study analyzes that a variety of pressure difference is how to affect flooding at the cathode of the PEMFC.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.87-92
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• 2016

Van der Pol's oscillators is non-conservative oscillator that having nonlinear damping phenomena. The energy of its system is dissipative at a high amplitude whereas its system creates the energy at low amplitude. In order to identify another behaviors in the Van der Pol oscillator, the periodic external force applied in the Van der Pol oscillator. This paper confirms the pattern of variation for the limit cycle according to parameter variation in order to identify another behaviors in the Van der Pol oscillator.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.553-563
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• 1984

Heat transfer modeling was performed in order to study a natural solar heating system. Simulation of the system was obtained by writing instantaneous energy balance equations for the various components. A thermal-network provided the means for systematically accounting for each of the energy balances. The resulting balances were solved using time varying inputs, such as solar gain and ambient temperature, and the initial temperatures of the components. Parametric heat transfer calculations were performed. Results are discussed which illustrate several effects, including variation of thermal capacity of the storage wall, installation of night insulation, installation of a thermally controlled fan between the sunspace and room, and variation of the width of the sunspace.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2828-2835
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• 2000

This paper presents the fatigue behavior of composite materials with impact-induced damage. The impact damage parameter is proposed to evaluate the effect of impact damage on fatigue life. Subsequently, a new model is developed to predict the fatigue life of impacted composite materials. Also, a stochastic model is proposed to describe the variation of fatigue life due to the material nonhomogeneity. For these models, the fatigue tests were performed on the unimpacted and impacted composite materials, The effect of impact damage on fatigue life can be characterized by the impact damage parameter. Additionally, the results by the present fatigue life prediction model agree will with experimental results regardless of applied impact energy. Also, the variation of fatigue life can be described by the present stochastic model and is reduced with applied impact energy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.7
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• pp.649-658
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• 2000

Thermodynamic modeling of low-pressure scroll compressor was developed by combining continuity and energy conservation equation. Suction gas heating was considered using energy balance inside the low pressure shell. Pressure, temperature and mass of refrigerant-22 as a function of orbiting angle were calculated by solving the governing equations using fourth order Rung-Kutta scheme. Motor efficiency was taken by experiments with a variation of frequency. The developed model was applied to the analysis of an inverter driven scroll compressor with a variation of frequency, pressure ratio and operating conditions. The model was verified with the experimental results at the same operating conditions. The developed model was adequate to predict performance of the inverter driven scroll compressor as a function of operating conditions. Calculated parameters from the model were discharge temperature, mass flow rate, power input, COP, and thermodynamic properties with respect to orbiting angle. To enhance the performance of a scroll compressor, it is essential to diminish leakage at low frequency level and improve the mechanical efficiency at high frequency level.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.453-456
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• 2006

To examine the effect of shape and crest width variation of a permeable submerged breakwater on the wave energy dissipation, Two-Dimensional numerical model with Large Eddy Simulation, which is able to simulate directly WAve Structure Seabed interaction (hereafter, LES-WASS-2D) has been newly developed. A good agreement has been obtained by the comparison between the existing experimental results and LES-WASS-2D model's results for the permeable submerged breakwater. Moreover, based on the LES-WASS-2D model, the wave energy dissipation due to a permeable submerged breakwater are discussed for regular and irregular waves with relation to its crest width and shape.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.25-27
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• 1997

The precise measurement of consumed power for a given time is very important in the energy management aspect. Up to days, most power meter has been used and designed for use on circuits in which the voltage and current are essentially sinusoidal. Recently the increase of switching element in power system causes the current and voltage with harmonics. Therefore, power energy involving harmonics is supplied to the system and the error of power measurement of watthour meter is existed. In this paper, we present a characteristic analysis by input frequency variation and analytical basis of induction watthour meter considering harmonics.