• 한국전문물리치료학회지
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• 제1권1호
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• pp.67-74
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• 1994

Our purpose of this study was to determine the most effective cool-down exercise. The recovery times of dynamic strength after isometric and isotonic cool-down exercise were measured immediately post cool-down exercise, 30 seconds later and 60 seconds later in 30 normal, healthy men from 19 to 29 years, using dumbells(Model, Iron). The recovery time of dynamic strength had a significant positive correlation with isotonic and isometric cool-down exercise using the Chi-square method (p<0.01). Sources of significant differences were determined by the Wilcoxon signed-ranks test (p<0.01). The isometric cool-down exercise significantly shortened the recovery time of dynamic strength. We suggest that the isometric cool-down exercise may be more effective than isotonic cool-down exercise in shortening the recovery time of dynamic strength.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2160-2164
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• 2008

Miniature Joule-Thomson cryocoolers 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 cool-down time, the temperature at the cold end, the running time and the gas consumption are the important indicators of the performance of the J-T cryocooler. In this study, the initial cool-down stages of the J-T cryocooler were investigated by numerical simulations. The results show the effects of the initial charging pressures of gas on the cool-down time and the temperature at the cold end and the gas consumptions.

• International Journal of Contents
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• 제8권2호
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• pp.97-102
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• 2012

The purpose of this study was to investigate the effects of various cool-down exercises on muscular strength and endurance. After receiving a treadmill training for main exercise, the subjects conducted isotonic and isometric cool-down exercises four times for three weeks. Isotonic exercise with leg press of 10kg was repeated by 20 times and isometric exercise was conducted at flexion of hip joint and knee joint with leg press of 10kg by maintaining it for 6 sec and resting for 2 sec by 20 times. Muscular strength after exercise was measured with 1 RM by times and muscular endurance with maximum repetition frequency using time to keep for loading the weight of 10 RM and 65% of maximum muscular strength. As a result of comparing and analyzing measured values, exercise recovery shape of isotonic and isometric cool-down group were more effective than rest recovery shape of the control group. The isometric cool-down group was more effective than isotonic cool-down group. In conclusion, isometric exercise was more effective than isotonic exercise or simple rest on muscular strength and endurance.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.681-688
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• 2014

Hydride reorientation behaviors of PWR cladding tubes under typical interim dry storage conditions were investigated with the use of as-received 250 and 485ppm hydrogen-charged Zr-Nb alloy cladding tubes. In order to evaluate the effect of typical cool-down processes on the radial hydride precipitation, two terminal heat-up temperatures of 300 and $400^{\circ}C$, as well as two terminal cool-down temperatures of 200 and $300^{\circ}C$, were considered. In addition, two cooling rates of 2.5 and $8.0^{\circ}C/min$ during the cool-down processes were taken into account along with zero stress or a tensile hoop stress of 150MPa. It was found that the 250ppm hydrogen-charged specimen experiencing the higher terminal heat-up temperature and the lower terminal cool-down temperature generated the highest number of radial hydrides during the cool-down process under 150MPa hoop tensile stress, which may be explained by terminal solid hydrogen solubilities for precipitation, and dissolution and remaining circumferential hydrides at the terminal heat-up temperatures. In addition, the slower cool-down rate generates the larger number of radial hydrides due to a cooling rate-dependent, longer residence time at a relatively high temperature that can accelerate the radial hydride nucleation and growth.

• Nuclear Engineering and Technology
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• 제48권2호
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• pp.545-553
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• 2016

The failure probabilities of the reactor pressure vessel (RPV) for low temperature over-pressurization (LTOP) and cool-down transients are calculated in this study. For the cool-down transient, a pressure-temperature limit curve is generated in accordance with Section XI, Appendix G of the American Society of Mechanical Engineers (ASME) code, from which safety margin factors are deliberately removed for the probabilistic fracture mechanics analysis. Then, sensitivity analyses are conducted to understand the effects of some input parameters. For the LTOP transient, the failure of the RPV mostly occurs during the period of the abrupt pressure rise. For the cool-down transient, the decrease of the fracture toughness with temperature and time plays a main role in RPV failure at the end of the cool-down process. As expected, the failure probability increases with increasing fluence, Cu and Ni contents, and initial reference temperature-nil ductility transition ($RT_{NDT}$). The effect of warm prestressing on the vessel failure probability for LTOP is not significant because most of the failures happen before the stress intensity factor reaches the peak value while its effect reduces the failure probability by more than one order of magnitude for the cool-down transient.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.566-572
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• 2005

The most crucial factor in membrane LNG ships to ensure sage operations, is how to effectively control tank pressure at the time of excessive generation of boil off gas (BOG). When the ships carry out tank cool down with her retaining heel prior to arrival at loading port, the vessel encounters the critical situation of excessive BOG and high tank pressure that can lead to high degree of risk. This is to provide one of the best ways to secure safe and effective LNG ship operations focusing on the detailed methods of tank cool down to achieve ATR(Arrival Temperature requirement) without building up high tank pressure and excessive BOG and calculating the appropriate heel quantity to be unutilized for tank cool down and fuel during ballast voyage.

• 한국수소및신에너지학회논문집
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• 제7권2호
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• pp.121-128
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• 1996

수소액화를 위한 직접냉각장치를 개발하고, 이의 성능특성을 시험하였다. 직접냉각장치는 액화용기, 복사쉴드, 저온조와 GM냉동기 등으로 구성하였다. 개발된 액화장치의 cool-down 및 warm-up특성이 상세하게 규명되었다. 본 냉각장치에서 냉각이 시작된지 약 45분 후, 액화용기내의 수소가 액화되기 시작함을 확인하였다. 또한 동일한 실험을 기체헬륨에 대하여 수행하였으며, 기체헬륨은 주어진 작동조건에서 액화되지 않으므로 수소의 경우와는 다른 cool-down 및 warm-up 특성을 보였다. 충전된 기체의 자연대류현상의 영향을 고찰하기 위하여 액화용기내에 진공상태를 유지하면서 시험하였다. 이때 진공상태에서의 액화용기의 냉각시간은 현저히 증가함을 보였다.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.115-123
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• 2010

Cool-down performance after soaking is important because it affects passenger's thermal comfort. The cooling capacity of HVAC system determines initial cool down performance in most cases, the performance is also affected by location, and shape of panel vent, indoor seat arrangement. Therefore, optimal indoor designs are required in developing a new car. In this paper, initial cool down performance is predicted by CFD(computational fluid dynamics) analysis. Experimental time-averaging temperature data are used as inlet boundary condition. For more reliable analysis, real vehicle model and human FE model are used in grid generation procedure. Thermal and aerodynamic characteristics on re-circulation cool vent mode are investigated using CFX 12.0. Thermal comfort represented by PMV(predicted mean vote) is evaluated using acquired numerical data. Temperature and velocity fields show that flow in passenger's compartment after soaking is considerably unstable at the view point of thermodynamics. Volume-averaged temperature is decreased exponentially during overall cool down process. However, temperature monitored at different 16 spots in CFX-Solver shows local variation in head, chest, knee, foot. The cooling speed at the head and chest nearby panel vent are relatively faster than at the knee and foot. Horizontal temperature contour shows asymmetric distribution because of the location of exhaust vent. By evaluating the passenger's thermal comfort, slowest cooling region is found at the driver's seat.

• 설비공학논문집
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• 제9권3호
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• pp.284-291
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• 1997

A hydrogen liquefaction equipment by direct cooling has been designed and built at KIST. Cool-down characteristics and liquefaction performance of the equipment have been investigated. The hydrogen liquefaction equipment consists of a GM refrigerator, a liquefaction velssel, a radiation shield and a cryostat. It is found that the hydrogen starts to be liquefied in the liquefaction vessel after 40~50 minutes of cool-down from the gas state of 270K. The effect of natural convection phenomena of charged gas in liquefaction vessel on the cool-down characteristics is evaluated by comparing with those in vacuum of liquefaction vessel. It is seen that the cool-down time of a liquefaction vessel is substantially increased in vacuum environment of liquefaction vessel. The experiments have been performed for 1~5 atm of hydrogen pressure to investigate the influence of hydrogen pressure on the liquefaction rate and figure of merit(FOM). It is found that both liquefaction rate and FOM are increased as the charged hydrogen pressure is increased.

• 한국결정성장학회지
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• 제13권2호
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• pp.68-72
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• 2003

본 논문에서는 3차원 마이크로구조물을 위한 새로운 UV-LIGA 공정을 개발하였다. 일반적으로 photoresist는 얇은 두께로 코팅이 되지만, SU-8은 수십 $\mu\textrm{m}$ 이상의 두께를 가질 수 있으며, 높은 형상비를 갖는다. SU-8과 같은 Thick photoresist는 기존의 baking 공정과 같이 급격한 cool down을 할 경우 stress에 의한 crack이 발생한다. 이와 같은 경우 도금을 위한 마이크로구조물이 구현이 되지 않는다. SU-8의 코팅, bake에서의 시간 조절, 그리고 PEB의 시간 조절 및 cool down조절을 통하여 stress에 의한 crack이 발생하지 않도록 3차원 마이크로구조물을 제작 할 수 있도록 하였다.