• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.523-524
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• 2008

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.145-151
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• 2012

The pulsimeter is a representative device in the oriental medicine, which can analysis a risk factor in a cardiovascular diseases. However, most of the previous methods have the limit by the contacted sate of the brachial pulse and sensor in the measuring time, the inaccuracy of detected pulse, and the difficulty of pulse analysis. Accordingly, we propose the moving pulse image analysis based pulsimeter that can acquire a pulse of patient in real time by analyzing a moving image. then this video is shot the state change of the T.S. occurred by a pulse in capillary. In order to evaluate the performance of the our pulsimeter, we measured a respective detecting-rate about the essential 5 feature-points in the pulse analysis from the detected original pulse. As a result, the proposed method is very successful.

• Journal of Biomedical Engineering Research
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• v.41 no.1
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• pp.8-13
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• 2020

To develop cardiovascular simulator capable of implementing pulse waves similar to the human body, accurate information about reflection wave is required. However, the conclusion is still not clear and various discussions are underway. In this study, the pulse wave velocity of the tube used in the experiment was first determined by measuring the pressure waves at two points in a single tube system with the experimental device to implement the pulse wave transmission of blood vessels, and the superposition time and characteristics of the reflection wave were confirmed. After that, an air chamber was set at the reflection site, and the effect of the change of air volume on the reflection wave was investigated. Finally, the effect of the number of branches connected to a single tube on the reflection wave was investigated. The superposition time of the reflection wave can be controlled by the air volume of the air chamber, and the magnitude of the reflection wave is influenced by the number of reflection sites that generate the reflection wave. The results of this study may be of practical assistance to simulator researchers who want to implement pulse wave similar to clinical data. It is expected that the more results similar to clinical are provided, the greater the scope of the simulator's contribution to clinical cardiovascular research.

• The Journal of the Acoustical Society of Korea
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• v.34 no.3
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• pp.192-199
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• 2015

There is a gap between the inner wall of a pulse tube and an underwater acoustic material when the measurement for transmission loss by the pulse tube is carried out. In this paper, the effect, which is caused by the gap, for the measurement of transmission loss is analyzed. Transmission coefficient is derived from the ratio of the pressures between front and rear of the gap. Then, transmission loss for specimen with a gap is obtained by combining the transmission coefficients of the gap and specimen. The results of experiment and simulation for a specimen of stainless steel with 10 mm thickness are compared in order to evaluate the simulation model. Finally, simulations with respect to the gap size and transmission loss of a specimen are performed to analyze and evaluate the effect of the gap in measurement of transmission loss.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.5
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• pp.190-197
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• 2005

A reliable and compact pulse power supply using a thyratron and a magnetic pulse compression (MPC) circuit was developed for a metal vapor laser. The life time of the pulse power supply is expected to be much longer than that of a conventional thyratron-discharge type pulse power supply. A thyratron generated a long pulse of its conduction pulse width 500 ns and then it was compressed to less than 80 ns of its output voltage rise time by a three stage MPC circuit. This pulse power supply was applied to a laser plasma tube of 30 mm inner diameter and 1.5 m discharge length. It was operated several hundreds hours without any troubles.

• Journal of computational fluids engineering
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• v.19 no.3
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• pp.14-19
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• 2014

The flow characteristics of inertance pulse tube cryocooler(IPTC) was investigated with a computational thermal fluid dynamics for the reciprocating flow in IPTC including the piston movement of linear compressor. Two dimensional axisymmetric modeling was applied for the flow in an IPTC with a clearance between the piston and cylinder wall of linear compressor. The pressure, velocity, and temperature distribution were examined for the steady state. These were compared with previous results to confirm the validity in the modeling and computational results. The leakage between piston and cylinder wall affect the cooling capacity seriously. The dependence on mesh numbers were also examined to obtain a proper mesh numbers to improve the accuracy of calculation, which showed significant effect on the results. The user-defined function was used for the process of compression and expansion of piston.

• Journal of the Korean Vacuum Society
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• v.22 no.2
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• pp.45-54
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• 2013

The cryopump of the pulse tube type has been developed successfully, and manufacturing of a prototype pump is finished under leading of Woosung Vacuum. The target pumping speed of the prototype pump is above 3,600 L/s for nitrogen with the intake port of 14 inches I.D (16 inches O.D). For designing optimally the pump structure including the charcoal array, thermal shield, and baffle, the pumping speed was simulated for various configurations through Monte Carlo method. Pumping performances of the protype cryopump manufactured on the basis of optimal design were conformed experimentally with a standard test system and procedures. The measured $N_2$ pumping speed of the prototype cryopump was 4,600 L/s which agreed well with simulated one and exceeded the target value.

• Progress in Superconductivity and Cryogenics
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• v.20 no.3
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• pp.21-27
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• 2018

It is difficult to fabricate and maintain moving parts of expander at cryogenic temperature. This paper describes numerical analysis and experimental investigation on a cryogenic reciprocating expander without moving piston. An intake valve which takes high-pressure gas, and an exhaust valve which discharges low-pressure gas, are connected to a tube. The inside pressure of the tube is pulsated for work production. This geometric configuration is similar to that of pulse tube refrigerator but without regenerator. An orifice valve and a reservoir are installed to control the phase of the mass flow and the pressure. At the warm end, a heat exchanger rejects the heat which is converted from the produced work of the expanded gas. For the numerical analysis, mass conservation, energy conservation, and local mass function for valves are used as the governing equations. Before performing cryogenic experiments, we carried out the expander test at room temperature and compared the performance results with the numerical results. For cryogenic experiments, the gas is pre-cooled by liquid nitrogen, and then it enters the pulse tube expander. The experiments are controlled by the opening of the orifice valve. Numerical analysis also found the expander conditions that optimize the expander performance by changing the intake pressure and valve timing as well as the opening of the orifice valve. This paper discusses the experimental data and the numerical analysis results to understand the fundamental behavior of such a newly developed non-mechanical expander and elucidate its potential feature for cryogenic application.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.624-628
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• 2011

To develop a pulse detonation engine, it needs to understand the mechanism of a detonation initiation, and establish the methods for measuring and analyzing the detonation phenomenon. In this study, DDT tube, which use oxygen-acetylene propellant mixture, were designed and manufactured, and the effect of equivalent ratio and Schelkin spiral on the characteristics of the detonation initiation were discussed.

• Solar Energy
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• v.9 no.3
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• pp.64-72
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• 1989

In this study, the computer simulation for the heat transfer in pulse combustion water heater is performed. The attention is focused to the effects of the installation of corebuster in the flue tube on heat transfer. The energy equations are established for both wall and gas side in the combustion chamber, flue way, exhaust chamber and muffler, and the numerical calculation is executed. Zone method takes longer computer calculation time compared with semi-zone method. Semi-zone method is chosen for numerical calculation. As a result of this study, it is found that the installation of the core buster in flue tube increases total heat transfer. It is also found that the total heat transfer is increased with the increasing of the ratio of the cross section area of corebuster to that of the flue tube. However, the heat transfer effect is negligible for the area ratio above 0.5.