• Structural Engineering and Mechanics
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• 제53권2호
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• pp.249-260
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• 2015

Damage detection based on a reference set of measured data usually has the problem of different environmental temperature in the two sets of measurements, and the effect of temperature difference is usually ignored in the subsequent model updating. This paper attempts to identify the structural damage including the temperature difference with artificial measurement noise. Both local damages and the temperature difference are identified in a gradient-based model updating method based on dynamic response sensitivity. The sensitivities of dynamic response with respect to the system parameters and temperature difference are calculated by direct integration method. The measured dynamic responses of the structure from two different states are used directly to identify the structural local damages and the temperature difference. A single degree-of-freedom mass-spring system and a planar truss structure are studied to illustrate the effectiveness of the proposed method.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2254-2255
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• 2008

Thermoforming is one of the most versatile and economical process to produce polymer products. The drawback of thermoforming is difficult to control thickness of final products. Temperature distribution affects the thickness distribution of final products, but temperature difference between surface and center of sheet is difficult to decrease because of low thermal conductivity of ABS material. In order to decrease temperature difference between surface and center, heating profile must be expressed as exponential function form. In this study, Finite Difference Method was used to find out the coefficients of optimal heating profiles. Through investigation, the optimal results using Finite Difference Method show that temperature difference between surface and center of sheet can be remarkably minimized with satisfying Temperature of Forming Window.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.95-98
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• 2008

Temperature difference energy is a good energy source replacing the fossil fuels. In the study, we classified the temperature difference energy as 4 types by the source & using method. For the understanding economic property of temperature difference energy, we tried simle economic analysis. As the result, Pay back period of 4 case of the temperature difference energy are from 1.23 to 12.65 years. Major factors influenced economic effect are operation time and energy user distance from the temperature difference energy source. If we can select optimal capacity and look for more effient energy users, Temperature difference energy play a important role of replacing fossil energy. So, for dess emination of temperature difference energy, we suggest that temperature difference energy must be included in renewable energy. Applying the effective methods among various promotion program of renewable energy policy, utilization of temperature difference energy could be activated.

• 설비공학논문집
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• 제22권7호
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• pp.419-428
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• 2010

This paper presents the optimization process of liquid desiccant cooling system using LiCl aqueous solution as a working fluid. Operating conditions(mass flow rate, conditioner outlet concentration, difference concentration) and design factors for heat exchangers(difference temperature of the district heating water, leaving temperature difference of the conditioner, leaving temperature difference of the regenerator, air temperature difference of the conditioner, air temperature difference of the regenerator) were optimized by response surface method. As a result, we obtained the 7.297 kW of cooling capacity and 0.788 of COP at optimized condition. Effect of difference temperature of hot water on system performances was also examined. As difference temperature of the district heating water increases, the cooling capacity increases and COP decreases.

• 한국지열·수열에너지학회논문집
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• 제12권4호
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• pp.21-26
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• 2016

In this study, the control strategies of indoor air temperature in floor radiant heating system were researched by computer simulation. The temperature difference based time control method using the difference of indoor set temperature and indoor temperature is compared with the existing On-Off control one for heating control performances. As a result, the temperature difference based time control method shows better thermal environmental characteristics in case of selected operational conditions in comparison with existing control one.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.128-131
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• 2004

This paper is to investigate the mock up test results of mass concrete for transfer girder using setting time difference with super retarding agent(SRA) to reduce hydration heat. According to test results, the temperature history of plain concrete without placing lift had a steep rising curvature, and plain concrete had a big temperature difference between surface and middle section of mass concrete, which may result in occurrence of temperature crack. However, considering placing method B, because setting time of middle section concrete was retarded with an increase in SRA contents, higher hydration heat temperature was observed at surface section concrete compared with that at middle section concrete at early age, which can lower the possibility of hydration heat crack. In case of placing method C, although peak temperature of hydration heat was much lower, at early age, high crack occurrence possibility of the hydration heat attributable to the big temperature difference between middle section and bottom section of concrete was expected at bottom section concrete. Therefore, the structure above the ground like transfer girder is not applicable to consider the placing method C.

• 대한의용생체공학회:의공학회지
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• 제38권5호
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• pp.232-236
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• 2017

In this study, We investigated the effect of foot cooling on the reduction of body temperature after hard exercise at the high temperature of $40^{\circ}C$. We performed a total of 30 subjects, and the subjects performed treadmill exercise for 30 minutes. We produced the cooling device to cool the foot using Peltier module. After the end of the exercise, We performed normal recovery method and cooling recovery method(one foot, both feet) for 1 hour on the same indoor environmental conditions and confirmed the change of body temperature of subjects. The results of deep body temperature measurement showed average $38.78{\pm}0.22^{\circ}C$ to $38.54{\pm}0.15^{\circ}C$ when the normal recovery method was performed. Cooling recovery method on one foot showed average $38.69{\pm}0.14^{\circ}C$ to average $38.06{\pm}0.17^{\circ}C$ and Cooling recovery method on both feet showed average $38.69{\pm}0.15^{\circ}C$ to average $37.84{\pm}0.21^{\circ}C$. There was a significant difference between the normal recovery method and the one foot cooling recovery method(p < .05), there was a significant difference between the normal recovery method and the both feet cooling recovery method(p < .05) and there was a significant difference between the one foot cooling recovery method and the both feet cooling recovery method(p < .05). Body temperature showed the lowest decrease rate when the normal recovery method was performed, and body temperature showed the highest decrease rate when the both feet cooling recovery method was performed. Therefore, recovery of cooling on the foot after hard exercise have decreased body temperature, delay fatigue in the body, and will be contributed to improvement of athlete performance.

• 청정기술
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• 제15권4호
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• pp.245-252
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• 2009

Poly(lactic acid) (PLA) 용융방사공정의 속도, 직경, 온도, 인장응력 분포를 구하기 위해 수치모사를 실시하였다. 유한차분법을 이용하여 반지름 방향으로의 온도분포곡선을 구하였다. 방사속도 1 km/min에서 5 km/min까지 방사속도에 따른 PLA 방사공정의 변화와 poly(ethylene terephthalate) (PET)와의 거동을 비교해 보았고, 방사공정변수가 섬유 중심부와 표면과의 온도차에 미치는 영향을 살펴보았다. PLA는 용융온도가 PET에 비해 낮음에도 불구하고 동일 방사조건에서 더딘 냉각속도를 보였고 방사거리에 따른 방사속도의 증가도 PET가 더 빠른 양상을 나타내었다. PLA의 섬유중심부와 섬유표면과의 온도차는 약 4.6 K에 이르렀는데, 이는 PET의 10.4 K에 비하여 낮은 값이다. PLA 섬유중심부와 표면과의 온도차는 냉각풍속도와 방사온도가 증가할수록 증가하였고, 냉각풍 온도가 감소할수록 증가하는 경향을 나타내었다.

• Current Optics and Photonics
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• 제6권3호
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• pp.297-303
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• 2022

Multiple fiber Bragg gratings (FBGs) have been proposed and demonstrated for gas-flow measurements in a flow channel, using the temperature-difference method. This sensor consists of two FBG temperature sensors and two coil heaters. Coil heaters are used to heat the FBGs. The flow rate of the gas can be obtained by monitoring the difference in the Bragg-wavelength shifts of the two FBGs, which has features that exclude the effect of temperature fluctuations. In this study, experiments are conducted to measure the wavelength shift based on the flow rate, and to evaluate the gas-flow rate in a gas tube. Experimental results show that the sensor has a linear characteristic over a flow-rate range from 0 to 25 ℓ/min. The measured sensitivity of the sensor is 3.2 pm/(ℓ/min) at a coil current of 120 mA.

• 대한토목학회논문집
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• 제33권2호
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• pp.729-737
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• 2013

콘크리트 포장의 환경하중은 온도하중과 수분하중으로 구분할 수 있으며, 이는 콘크리트 슬래브 내의 온도분포와 건조수축 및 크리프를 의미한다. 본 연구에서는 공항 콘크리트 포장의 역학적 설계에 필요한 환경하중을 산정할 수 있는 방법을 개발하였다. 먼저, 대상 지역과 설계 슬래브 두께를 결정한 후, 포장 온도 예측 프로그램을 사용하여 예측된 슬래브 깊이에 따른 콘크리트 온도분포를 등가선형 온도차이로 환산하였다. 기존 건조수축 예측 모형을 개선하여 지역별 상대습도를 고려하여 콘크리트의 건조수축을 예측한 후 부등건조수축 등가선형 온도차이로 환산하였다. 또한, 응력이완을 건조수축에 반영하였다. 결국, 온도에 의한 등가선형 온도차이와 수분에 의한 부등건조수축 등가선형 온도차이를 합하여 최종 환경하중인 총 등가선형 온도차이를 산정하였다. 적용 예를 보이기 위해 지역별 기상조건을 대표할만한 국내 민간공항 8곳 및 군공항 2곳의 환경하중을 본 연구에서 개발된 방법으로 계산하고 비교하였다.