• 한국의류학회지
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• 제25권2호
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• pp.287-292
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• 2001

This study was conducted to investigate preferred clothing selected by females for thermal comfort in follicular phase (FP) and luteal phase (LP) of the menstrual cycle. Eight healthy college students volunteered as subjects. They stayed for 60 minutes at $25^{\circ}C$, 55%RH (stage 1) for baseline followed by a 60 minute stay at 2$0^{\circ}C$, 55%RH (stage 2) in a climatic chamber. Obtained results were analyzed using paired t-test and repeated measures of ANOVA. Arm and hand skin temperatures were maintained higher in FP than in LP, while mean skin temperature did not show any significant difference between FP and LP. The subjects selected additional clothing faster in FP than in LP. Six of the subjects wore heavier clothing in FP than in LP, while two of them wore heavier in LP than in FP.

• Journal of Welding and Joining
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• 제21권4호
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• pp.25-30
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• 2003

There have been many researches for small scale packages such as CSP, BGA, and Flipchip. Underfill encapsulant technology is one of the latest assembly technologies. The underfill encapsulant could enhance the reliability of the packages by flowing into the gap between die and substrate. In this paper, the effects of underfill packages by both aspects of thermal and mechanical reliabilities are studied. Especially, it is focused to value board-level reliability whether by the underfill is applied or not. First of all, The predicted thermal fatigue lifes of underfilled and no underfilled $\mu$ BGA solder joints are performed by Coffin-Manson's equation and FEA program, ANSYS(version 5.62). Also, the thermal fatigue lifes of $\mu$ BGA solder joints are experimented by thermal cycle test during the temperature, 218K to 423k. Consequently, both experimental and numerical study show that $\mu$ BGA with underfill has over ten times better fatigue lift than $\mu$ BGA without underfill.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1541-1550
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• 1997

Since the ceramic/metal joint material is made at a high temperature, the residual stress develops when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of Si$_3$N$_4$STS304 joints quantitatively and to compare the strength of joints. The difference of residual stress is measured when repeated thermal cycl is loaded, under the conditions of the practical use of the ceramic/metal joint. The residual stress increases at 1 cycle of thermal load but decreases in 3 cycles to 10 cycles of thermal load. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a result, it is known that the stress of joint decreases as the number of thermal cycle increases.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1141-1148
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• 2008

One of the methods to increase the efficiency of an engine is to expand pressures obtained from combustions equal to the pressure of atmosphere as much as possible and then convert thermal energy into mechanical energy also as much as possible. In this research, the Diesel cycle was thermodynamically interpreted to evaluate the possibility of high efficiency by converting Diesel engines to the Atkinson cycle, and general cycle features were analyzed after comparing these two cycles. In the case of fuel air the Diesel-Atkinson cycle considering intake and exhaust similar to real cycles, the value of thermal efficiency and average effective pressure increased, though their values were smaller than those of standard air amount cycle, when expansion compression ratio increased. When normal Diesel engines of which compression stroke and expansion stroke are all the same, was converted to the Atkinson cycle by changing the time of intake value close, combustion pressure reduced due to reduced expansion compression ratio and intake air amount due to decreased effective cycle volume.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1349-1352
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• 2005

This paper is to investigate a defect for thermal barrier coating layers by acoustic emission method in 4-point bending test. The two-layer thermal barrier coating is composed of $150\mu{m}\;CoNiCrAlY\;bond\;coating\;by\;vacuum\;plasma\;spray(VPS)\;process\;and\;250\mu{m}\;ZrO_2-8wt%Y_2O_3$ ceramic coating layer by air plasma spray(APS) process on Inconel-718. The specimen prepared by cyclic thermal test(500, 1000, 2000cycle) at $1050^{\circ}C$ The AE monitoring system is composed of PICO type sensor, a wide band pre-amplifier(40dB), PC and AE DSP(16/32 PAC) board. The AE event, amplitude, Cumulative energy and count of coating specimens is evaluated according to cyclic thermal test.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.606-610
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• 2003

The 200 class insulation system which adopted to traction motor have excellent dielectric strength but weaken to thermal stress therefore deterioration phenomena analysis according to thermal stress is necessary. Accelerated thermal aging tests have been used to determine thermal reliability of stator coils used as traction motor in electric multiple unit. The conventional aging test is carried on according to IEC 60034-18-31 and IEEE Std. 275-1992. Variation in insulation resistance, P.I, capacitance, dielectric loss($tan{\delta}$) and partial discharge are measured during the aging cycle. Sample coils for traction motor were tested by accelerated aging test which composed of heat, vibration and moisture. Reliability and expected life were evaluated on the insulation system for traction motor.

• 한국전기전자재료학회논문지
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• 제29권3호
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• pp.152-158
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• 2016

The bonding characteristics of MLCCs (multi layer ceramic capacitor, C1608) lead-free solder (SAC305) joints were evaluated through thermal shock test ($-40^{\circ}C{\sim}125^{\circ}C$, total 1,800 cycle). After the test, IMCs( intermetallic compounds) growth and cracks were verified, also shear strengths were measured for degradation of solder joints. In addition, The thermal stress distributions at solder joints were analyzed to compare the solder joints changes before and after according to thermal shock test by FEA (finite elements analysis). We considered the effects of IMCs growth at solder joints. As results, the bonding characteristics degradation was occurred according to initial crack, crack propagations and thermal stress concentration at solder-IMCs interface, when the IMCs grown to solder inside.

• 한국압력기기공학회 논문집
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• 제11권2호
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• pp.40-44
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• 2015

The fatigue behavior of thermal butt fusion in safety class III high-density polyethylene (HDPE) buried piping for nuclear power plants was investigated using load-controlled bending fatigue on four-point bend test specimens. Based on the results, the presence of thermal butt fusion beads was confirmed to reduce the fatigue lifetime in the low- and medium-cycle fatigue regions while having a negligible effect in the high-cycle fatigue regions.

• 전력전자학회논문지
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• 제9권3호
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• pp.203-212
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• 2004

히트파이프를 이용하는 전력반도체 냉각용 히트파이프가 장기간 사용에도 안정된 작동을 이루도록 하기 위해서는 제조 과정에서 발생할 수 있는 산화막 존재 등 문제 요인의 제거와 함께 시험을 통한 확인이 필요하다. 본 연구에서는 전력반도체 냉각용 히트파이프가 요구하는 여러 기하학적, 열적조건에 의해 결정되는 열수송 한계 및 특성과 안정된 작동을 확인하기 위한 시험방법을 제시하고 시험을 통하여 확인된 결과를 정리하였다.

• 방사성폐기물학회지
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• 제13권2호
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• pp.99-112
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• 2015

본 연구에서는 고준위폐기물 처분시 완충재로 사용되는 벤토나이트의 열적 거동을 평가하기 위해 실내실험장치를 제작하였다. 그리고 실험 결과를 검증하기 위해 유한요소해석 프로그램인 ABAQUS를 이용한 열해석을 실시하였다. 그리고 실험기간 동안의 계절변화를 감안하여 외부대기 온도에 따른 벤토나이트의 열적거동을 평가하였다. 해석결과, 스테인리스스틸이 포함된 case3 해석모델의 결과가 실험결과와 1℃ 내외의 오차를 보이며 거의 일치함을 볼 수 있었다. 그리고 계절에 따른 벤토나이트 온도 해석을 수행한 결과, 시간에 따른 온도분포 경향이 일치함을 확인하였다. 이러한 열해석을 통해 완충재를 둘러싸고 있는 물질의 열전도도와 외부대기의 온도가 벤토나이트 완충재의 열적 거동에 큰 영향을 주는 요소임을 확인할 수 있었다. 향후 열원을 포함한 벤토나이트 완충재의 수분 포화 특성 실험이 실시 될 예정이므로, 실험에 대한 검증과 예측을 위해 보다 적합한 수치해석모델 개발에 대한 연구가 필요할 것이다.