• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.202-210
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• 2006

In the nuclear power plant, emergency core coolant system (ECCS) is furnished at reactor coolant system (RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can be occurred due to coolant leaking in the check valve. The thermal stratification produces excessive thormal stresses at the pipe wall so as to yield thermal fatigue crack (TFC) accident. In the present study, when the turbulence penetration occurs in the branch pipe, the maximum temperature differences of fluid at the pipe cross-sections of the T-branch with thermal stratification are examine.

• Physical Therapy Korea
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• v.1 no.1
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• pp.83-87
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• 1994

The purpose of this paper is to provide an overview of the clinical physical therapy program used at the University of Yonsei Rehabilitation Hospital, for the practicing university trained physical therapists who may be unfamiliar with patients who have suffered a myocardial infarction. The four primary phases of the cardiac physical therapy graded exercise program are: 1) coronary care unit program (phase I), 2) general ward program (phase II), 3) convalescence program (phase III), 4) maintenance program (phase IV). The exercise prescription defines the exercise intensity, duration, frequency, and mode of exercise a after pre- discharge low level graded exercise test(LL-GXT) or symptom limited maximum graded exercise test. A typical exercise routine consists of preparation warm-up exercise, therapeutic exercise, cool-down exercise. Physical therapy is involved in the acute care and rehabilitation of the patient after a myocardial infarction. Therefore, the physical therapist must throughly comprehened the cardiac anatomy, cycle, performance, conduction system, pathogenesis, risk factors, and exercise benefits.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.379-386
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• 2018

A heat-sink has been widely used to cool down the heat generated from an electronic device, but it can bring unwanted electromagnetic radiation which may cause EMI problems. We propose a systematic method to reduce the electromagnetic radiation by using the multiple grounding technique based on the grounding criteria and the theory of characteristic mode analysis. Our proposed method provides the insight to find the specific grounding positions which can be effectively reduced the radiation from the heat-sink. Numerical experiments are accomplished to validate this approach.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1101-1106
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• 2004

Magnetic refrigeration is based on the magnetocaloric effect (MCE)-the ability of some materials to heat up when magnetized and cool down when demagnetized. A rotary magnetic refrigeration device using gadolinium (Gd) ribbon and permanent magnets was constructed for experimental study. Gd ribbon attached around a rotating wheel is cyclically magnetized and demagnetized by permanent magnets and exchanges heat with liquid in the surrounding container. Temperature of the liquid in each divided section of the container was measured and the experimental results obtained in this study were discussed.

• 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.

• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.36-40
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• 2010

In this paper, a noble method for rapid cooldown of pulse tube refrigerator (PTR) was proposed and experimentally investigated. An orifice pulse tube refrigerator generates refrigeration effect by expansion PV work at the cold-end, and its amount is affected by the orifice valve opening. There exists the optimum valve opening for maximum cooling capacity and it varies as cold-end temperature. It is verified from simulation results using isothermal model that the optimum valve opening increases as the cold-end temperature increases. In the experiments, a single stage orifice pulse tube refrigerator is fabricated and tested. The fabricated PTR shows 97.5 K of no-load temperature and 10 W at 110 K of cooling capacity with the fixed orifice valve opening. From experiments, the initial cooldown curve with four cases of valve opening control scenario are obtained. And it is experimentally verified that the initial cooldown time can be reduced through the control of orifice valve opening.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.66-70
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• 2010

The operational temperature range of thermosiphon is generally limited from the critical point to the triple point of the working fluid to maintain two-phase state. Thermosiphon with mixed working fluid has a potential to widen the operational temperature range. In this study, the physical behavior of mixed working fluid during the transient operation of thermosiphon was analyzed with temperature-mole fraction diagram. The condenser and the evaporator temperature variations were explained by the dew line and the bubble line of the mixture. It is encouraging that the thermosiphon operation commences early with larger fraction of high boiling point component, but the temperature gap between the condenser and the evaporator due to the separation of two components has a negative effect on the officient cool down process.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.156-156
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• 2011

VPH (Volume Phase Hologram) grating is one of the transmission gratings and is known as its remarkable efficiency (>90%). It has two different densities of gelatins causing interference patterns. The VPH grating is favored in many astronomical instruments these days and also IGRINS, which is up coming near infrared high-resolution spectroscope expected to see the first light next year, uses the VPH grating as its cross-disperser. The infrared astronomical instruments operate at cryogenic temperature (~100K) in order to cut down thermal noise and the optical components of IGIRNS will be operated at 130K. The VPH grating is sandwiched in between fused silica or glass and glued together using optical adhesive. IGRINS is expected to go through 50 times of thermal cycling in 10 years including the performance test and this research is to check whether the physical characteristic such as the adhesion or dichromatic gelatin does not break and change from the several cryogenic thermal cycling. The two identical test gratings provided from Kaiser Optical System, Inc. are used in this test. One VPH grating is cooled down to 100K for 2 hours with maximum dT/dt = 5 and warmed up to the room temperature and another grating is kept stored in the room temperature and used as a control sample. In order to check the change, we inspected the grating with eyes and checked its efficiency and transmission at the room temperature every 10 cycling. From the 40 times of cryogenic temperature cool down cycling, the VPH grating showed no signs of change within the error compared to the control sample. We concluded the VPH grating is durable through several cryogenic thermal cycling.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1462-1468
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• 2014

Xe gas is moved to target from GPM. It is used to feasible nuclear reaction from proton of 30MeV cyclotron being investigated by the Xe-124 gas target system. This system is divided into four parts. The hardware system was constructed by solidworks 3-D CAD and Helium supply is to cool the Havor foil. The Cooling water has the job of cooling down the temperature when Xe gas is being investigated in the target. Temperature and pressure gauges are attached to be checked easily. GPM has the part that prepares to transport Xe gas. There are storage vessel that stores Xe gas, the cold trap that filters humidity and impurity and lastly storage vessel that temporarily stores Xe gas. HCS using the helium is to clean and cool for each part. These parts are configured with SIEMENS PLC and PcVue monitoring program for more comfortable and easy maintenance.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.51-59
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• 2013

It is usual to evaluate the performance of the cool roof by measuring in-site rooftop temperature using thermal infra-red camera. The principal advantage of rooftop thermal infrared image acquired in oblique vantage point of super high-rise building as a remote sensor is to provide, in a cost-effective manner, area-wide information required for a scattered rooftop target with different colors, utilizing wide view angle and multi-temporal data coverage. This research idea was formulated by incorporating the concept of traditional remote sensing into rooftop temperature monitoring. Correlations between infrared image of super high-rise building and in-situ data were investigated to compare rooftop surface temperature for a total of four different rooftop locations. The results of the correlations analyses indicate that the rooftop surface temperature by the infrared images of super high-rise building alone could be explained yielding $R^2$ values of 0.951. The visible permanent record of the oblique thermal infra-red image was quite useful in better understanding the nature and extent of rooftop color that occurs in sampling points. This thermal infrared image acquired in oblique vantage point of super high-rise made it possible to identify area wide patterns of rooftop temperature change subject to many different colors, which cannot be acquired by traditional in-site field sampling. The infrared image of super high-rise building breaks down the usual concept of field sampling established as a conventional cool roof performance evaluation technique.