• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.62-66
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• 2008

The characteristic of the superconducting magnetic energy storage(SMES) system is faster response, longer life time, more economical, and environment friendly than other uninterruptible power supply(UPS) using battery. So, the SMES system can be used to develop methods for improving power quality where a short interruption of power could lead to a long and costly shutdown. Recently, cryogen free SMES has developed using BSCCO(Bismuth Strontium Calcium Copper Oxide) wire. We fabricated and tested the conduction cooling system for the 600 kJ class HTS SMES. The experiment was accomplished for the simulation coils. The simulation coils were made of aluminium, it is equivalent to thermal mass of 600 kJ HTS SMES coil. The coil is cooled with two GM coolers through the copper conduction bar. In this paper, we report that the test results of cool-down and heat loads characteristics of the simulation coils. The developed conduction cooling system adapted to 600 kJ HTS SMES system and cope with the unexpected sudden heat impact, too.

• Journal of Environmental Science International
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• v.15 no.1
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• pp.95-100
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• 2006

Heat transfer and flow characteristics in a pipe in which the rotating cutting tool for boring a underground pipe without digging were considered in this study. The amount of heat generation due to the friction between the rotating cutter and pipe wall, mixing (low of air and water injected to cool down are the two important factors to design the boring machine Computational fluid dynamics analysis using the Eulerian mixture model and the standard $\kappa-\varepsilon$ turbulence model was used to analyze the complex phenomena in a pipe during the process. Results show that pipe wall temperature decreased with increasing the cooling water inlet velocity. it is also shown that pipe wail temperature was lowered when the cutter rotation speed was increased until 600 rpm. There was no further cooling effect over 600 rpm.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.46-50
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• 2004

The Experimental results of the in-line type inertance tube pulse tube cryocooler for cooling superconductor RF filter are presented in this paper. The pulse tube refrigerator, which has no moving parts at its cold section, is attractive in obtaining higher reliability, simpler construction, and lower vibration than any other small refrigerators. The purpose of this study is to analyze the characteristics of in-line type inertance tube pulse tube refrigerator (IPTR), and to get main factor to improve the performance of the in-line type IPTR. Firstly, design parameters of the in-line IPTR are discussed by ARCOPTR program, and then to find optimal conditions of in-line type IPTR, cool down characteristics according to the variations of the charging pressure, inertance tube volume, regenerator volume and pulse tube volume are measured by the experiment. The lowest temperature of the cold end was about 50 K. Cooling capacity was the highest in the charging pressure of 32 atm. and 5W at 72K. On the other hand, COP of the in-line type IPTR was the highest in the charging pressure of 21 atm. and 0.018 at 77K.

• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.46-51
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• 2004

This paper presents the results of a series of performance and reliability tests for the Stirling cryocooler. Infrared sensor systems incorporating cryocoolers are required to be qualified to the appropriate specification for the performance and reliability. FPFD Stirling cryocooler is currently under development for cooling infrared detector. Manufactured Stirling cryocooler delivers approximately 0.9W cooling at 80K for 30W∼40W of input power. It takes approximately 2 minutes to cool down to 80K at the ambient temperature of 23$^{\circ}C$. Performance characteristics for the vibration, acoustic noise, EMI and leak rate of the Stirling cryocooler are evaluated. We performed low and high temperature keeping test from -32$^{\circ}C$ to +52$^{\circ}C$ and operating test at high and low temperature cyclic range with acceptance tests performed at scheduled intervals. Cooling capacity is determined as a function of the temperatures at the compressor, hot end and cold tip at the expander. Finally, we describe the experimental facility for the MTTF evaluation and some typical results of the Stirling cryocooler.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.55-59
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• 2009

Miniature Joule-Thomson refrigerators have been widely used for rapid cooling of infrared detectors, probes of cryosurgery, thermal cameras, missile homing head and guidance system, due to their special features of simple configuration, compact structure and rapid cool-down characteristics. The thermodynamic performance of J-T refrigerator highly depends on the hydraulic and heat transfer characteristics of the recuperative heat exchanger. The typical recuperative heat exchanger of the J-T refrigerator has the double helical tube and fin configuration. In this study, effectiveness-NTU approach was adopted to predict the thermodynamic behaviors of the heat exchanger for the J-T refrigerator. The thermodynamic properties from the REFPROP were used to account the real gas effects of the gas. The results show the effect of the operating conditions on the performance of the heat exchanger and refrigerator for the given heat exchanger. The influences of mass flow rate and the supply pressure on the effectiveness of heat exchanger and the ideal cooling capacity are discussed in details.

• Journal of Sasang Constitutional Medicine
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• v.10 no.2
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• pp.1-14
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• 1998

1. Purpose : The correct constitutional diagnosis and the accurate prescription are very important in clinical application of Sasang Constitutional Medicine. Lee Je-ma emphasized that symptom is the best clue to diagnose constitution in "DongYi Suse Bowon". After research the characteristics of each constitution's symptoms and the backgrounds of constitutional prescriptions, this paper is to know the correct clinical application of Sasang Constitutional Medicine. 2. Method : Through the clinical applications of "DongYi Soose Bowon" and "Dongyi Sasang Sinpeun", the characteristics of constitutional symptoms and the application of prescription were researched 3. Results & Conclusions 1) The symptoms of Sasang Constitutional Medicine were came from the Hyung-Sang Medicine(形象醫學) which were important to mind-body equally and from the summarizing spirit of four Qi such as Warm-Hot-Cool-Cold(溫熱凉寒) 2) The symptoms of Soeumin and Soyangin are the Cold-Hot symptoms of ingestive food(水穀) and the treatment of symptoms is to control the ascent-descent of up and down. The symptoms of Taeumin and Taeyangin are the Warm-Cool symptoms of Qi-Yack(氣液) and the treatment of symptom is to control the unfasten-fasten of interior and exterior. 3) The symptoms of Taeyangin are 'Weak Lower part and Firm Upper part symptom'(下虛上實病證) and 'Blood and Yack Exhasted Symptom'(血液俱耗病證), the symptoms of Soeumin are 'Fall Down Symptom'(下陷病證) and Stomach Cold Symptom(胃寒病證), the symptoms of taeumin is 'Dryness Fever Symptom'(燥熱病證) and 'Interior Fever Symptom'(燥熱病證), the symptoms of Soyangin is 'Fire Fever Symptom'(火熱病證) and 'Interior Fever Symptom'(燥熱病證). 4) The characteristics of sasang constitutional symptoms are the exterior-interior symptoms classified with nature-emotion and cool-hot, the inclusive control of exterior-interior symptoms with healthy energy, and the classification of ingestive food symptoms and Qi-Yack symptoms. 5) The characteristics to treat symptoms are the classification of seriousness and obedience, the use herbs according to each constitutions, and inclusive symptoms control.

• Journal of IKEEE
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• v.22 no.2
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• pp.344-349
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• 2018

Low temperature variation of electrical characteristics for AlGaN/GaN/HEMT was studied. To investigate the effect of temperatures, transistor was cool down to $-178^{\circ}C$ and electrical characteristics were measured. The drain current density of an AlGaN/GaN HEMT with a gate length of $2{\mu}m$ was increased from 264 mA/mm to 388 mA/mm and the maximum transconductance was increased from 105 mS/mm to 134 mS/mm by decreasing the temperature to $-108^{\circ}C$. Also, the threshold voltage was shifted -0.39 V with the temperature. The reason for the variations was seemed to the reduced channel resistance corresponding to the temperature. However, most of the variation of the electrical characteristics takes places above $-108^{\circ}C$.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.118-122
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• 2003

Pulse tube refrigerator, which has no moving parts at its cold section, is attractive fer obtaining higher reliability, simpler construction and lower vibration than Stilting refrigerator or Gifford-McMahon refrigerator. Commonly used means to achieve optimum performance of Stilting type pulse tube refrigerator is an inertance tube. The use of inertance tube is a simple way to generate the phase shift needed to make pulse tube refrigerator operate as efficiently as Stilting refrigerator. In this study, the performance of the inertance pulse tube refrigerator (IPTR) was investigated experimentally. An in-line type IPTR consists of a linear compressor with two reciprocating pistons driven by linear motors, which makes pressure waves, a regenerator a pulse tube with the inertance tube, and a reservoir, The dynamic pressures (the compressor, pulse tube, reservior) and the temperature at the cold heat exchanger are measured to explore the dependence of the inertance tube on the performance of the IPTR. The experimental results show the dependency of cool-down characteristics, no-load temperature and amplitude of the pressures on the length and diameter of the inertance tube.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.177-181
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• 1999

Cold Neutron Source(CNS) facility comprises moderator circulation system, helium cooling system, neutron guide and auxiliary sistems. To increase the amount of cold neutron, the thermal neutron should pass cold moderator at cryogenic temperature. As cold moderator in Hanaro, the liquid hydrogen or liquid deuterium will be used and the temperature in operation will be used and the temperature in operation will be maintained to be $250^{\circ}C$ below zero. To maintain the moderator at this cryogenic temperature. He refrigerator is used to cool it down in thermosiphon having natural circulation. As a part of the conceptual design of Hanaro CNS, study on the characteristics of moderators, design of moderator chanmber and cooling method were done through the collaboration of Korea Atomic Energy Research Institute and Petersburg Nuclear Physics Institute. During the collaboration, a program for the design of moderator cooling system design concept through the parametric study using this program. In the parametric study, the effect of the moderator type on the design parameters was investigated. Also, the requirements on the performance test for the cooling system, which will be made before the basic design, were investigated.

• Transactions of Materials Processing
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• v.26 no.1
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• pp.35-40
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• 2017

Laser forming is an advanced process in sheet metal forming in which thermal stress originated from the laser heat source is used to shape the metal sheet. However, substantial waiting time is normally necessary for the workpiece to cool down between consecutive scans so that a steep temperature gradient can be reestablished in the next scan. In order to solve this drawback, laser bending characteristics are experimentally implemented in underwater condition. Laser forming effects under various conditions, including different laser power, scanning velocity, beam diameter, number of passes and material, are investigated. The results show that the underwater laser forming facilitates deliberate forming. The bending angle per respective laser scan is decreased with increasing the number of passes and scanning velocity.