• Journal of the Korean Wood Science and Technology
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• v.24 no.3
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• pp.37-44
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• 1996

포수상태(包水狀態)의 루부라참나무(Quercus rubra) 시험편을 3가지 등온조건(等溫條件)에서 건조한 결과를 비정상상태(非正常狀態)의 확산(擴散)모델로 추정한 결과와 비교하였다. 표면이 충분히 젖은 상태인 건조초기에는 불안정(不安定)한 확산현상(擴散現象)이 관찰되었으나, 함수율(含水率)별 건조속도의 변이를 Fick's의 확산법칙과 비교할 때 유사한 형태를 보였다. 실험에서 얻은 건조조건별 건조곡선은 확산모델의 수치해석(數値解析) 결과와 거의 일치하였으며, 같은 평위함수율(平衛含水率) 조건에서 건조온도의 증가는 목재표면 보다 내부의 함수율 변화에 더 크게 영향하여 결과적으로 낮은 온도에서의 건조조건이 목재 내의 수분경사(水分傾斜)를 급하게 하는 것으로 밝혀졌다. 본 연구를 통해 목재 건조 중의 내부에 발생하는 수분경사를 추정하는데 비정상상태의 확산모델이 모든 함수율 범위에 걸쳐 유용하게 사용될 수 있음이 밝혀졌다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.545-551
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• 2018

For domestic application of the temperature gradient model proposed by foreign design standards, a specimen of steel box girder bridge was fabricated with the following dimensions: 2.0 m width, 2.0 m height and 3.0 m length. Temperature was measured using 24 temperature gauges during the summer of 2016. The reliability of the measured data was verified by comparing the measured air temperature with the ambient air temperature of the Korea Meteorological Administration. Of the measured gauges, four temperature gauges that can be compared with the temperature difference of the Euro code were selected and used to analyze the distribution of the measured temperatures at each point. The reference atmospheric temperature for the selection of the maximum temperature difference was determined by considering the standard error. Maximum and minimum temperatures were calculated from the four selected points and the resulting temperature difference was calculated. The model for the temperature difference in the steel box girder bridge was shown by graphing the temperature difference. Compared to the temperature distribution of the Euro code, the presented temperature difference model showed a temperature difference of $0.9^{\circ}C$ at the top and of $0.3^{\circ}$ to $0.4^{\circ}C$ at the intermediate part. These results suggested that the presented model could be considered relatively similar to the Euro code The calculated standard error coefficient was 2.71 to 2.84 times the standard error and represents a range of values. The proposed temperature difference model may be used to generate basic data for calculating the temperature difference in temperature load design.

• Journal of Bio-Environment Control
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• v.14 no.2
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• pp.76-82
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• 2005

Evaporative cooling pad system is one of the main cooling methods in greenhouses and its efficiency is very high. However, it has some disadvantages such as greenhouse temperature distributions are not uniform and installation cost is expensive. In this study, a CFD simulation model f3r predicting the air temperature distribution in the fan and fad cooling greenhouse was developed. The model was calibrated and validated against experimental data and a good fit was obtained. The influence of different outside wind, fan and pad height, ventilation rate, shading, and greenhouse length, were then examined. In order to reduce the internal temperature gradients, it is desired that the prevail wind direction and the fan and pad heights are considered. The simulation indicates that high ventilation rates and shading contribute to reduce the temperature gradients in the fan and pad cooling greenhouse. In order to maintain the desired greenhouse temperature, the pad-to-fan distance should be restricted according to the design climate conditions, shading and ventilation rates. The developed CFD model can be a useful tool to evaluate and design the fan and pad systems in the greenhouses with various configurations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.4
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• pp.99-106
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• 2014

In order to study the reasonable design thermal loads, the steel box girder bridge specimen which have no concrete slab was manufactured with the real size dimension. The temperature data were measured for 5 month at the 18 thermo gauges which were attached according to height. The temperature differences between the top and bottom flange in steel box girder specimen were calculated and the temperature gradient models were proposed by the probabilistic method. This proposed model showed a correlation of approximately 97% when compared with the similar model of Euro Code. Thus, the temperature gradient models which were suggested in this study may be used as the basis data in calculating the design load temperature.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.67-72
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• 2002

Water content of soils within pavement varies seasonally depending on climatic factors such as rainfall, temperature and so on, since a hydraulic gradient due to rainfall causes moisture flow, and a thermal gradient due to temperature change induces not only heat flow but also moisture flow directly and indirectly. Soils within pavement are usually in an unsaturated state, and heat flow and moisture flow have been recognized as coupled processes with complex interactions between them. This paper presents a one-dimensional analysis model by the finite element method for the coupled heat flow and moisture flow in unsaturated soils. The model can be used to predict not only the change of temperature and water content, but also frist heave with time. It will be a meaningful work for the design and maintenance of pavement to predict the change of the temperature and water content and frist heave. The model is tested through comparisons with the results by other models.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06c
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• pp.5-10
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• 2010

휴대용 단말기를 활용하는 위치 기반 서비스는 기존의 단순한 위치 정보 제공 및 분석에서 보다 개인화되고 지능화되고 있다. 이러한 모바일 추천 서비스는 이동 객체의 위치 정보 뿐만 아니라 객체의 주변 환경 정보도 고려하여 보다 쾌적한 서비스를 제공한다. 이를 위해, 시간에 따라 변화하는 이동 객체의 위치추적은 물론, 온도, 습도, 미세먼지, 등의 다양한 센서 데이터도 상황에 맞게 해석하고 활용할 수 있어야 한다. 그리고 다양한 센서 종류와 함께 수많은 센서 데이터를 해석하여, 전체적인 상황을 판단하기 위해서는 센서 데이터를 적절히 표현하는 데이터 모델의 활용이 필요하다. 이 논문에서는 모바일 추천 서비스에서 환경 정보를 제공하기 위하여 활용한 경사 그리드 기반의 센서데이터 추상화 모델과 그 처리 방법을 기술한다. 추상화 모델은 경사 방향을 활용하여 간단하게 해당 지역의 데이터 경향을 나타낸다. 그리고 색인과 연산자를 활용한 처리방법을 통해 환경 정보를 제공하는 과정을 설명한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.134-142
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• 2012

This paper presents a study of system identification on the tilt response of the L-type retaining wall located at Tanhyun 11th ACE Apartment, Ilsan in order to understand mechanism how the structure behaves in operational conditions and to provide a reference tilt values for assessing structural abnormality. The retaining wall was extraordinarily tall (14m) in urban area so the long-term monitoring system had been installed with 3 tilts-meters and 9 temperature sensors operational from Oct 2004 upto Nov 2007. By using 5-months continuous data in which all the 12 channels were up and running, the two prediction models, 1) the linear model, and 2) the state-space equation (SSE) model, have been identified by finding the best fitness model among all possible 511 combinations of input temperatures out of the 9 temperatures. The linear model which was simple in the model structure achieved the validation fittness of 68% due to the fact that the static model wasn't able to represent thermal dynamics. The SSE model achieved the validation fitness of 90% which was quite accurate considering various unexpected noises happening in field measurements.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.193-203
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• 2014

Temperature-dependent stress analysis and heat transfer analysis of a rotating gas turbine blade made of functionally graded materials (FGMs) are presented considering turbine operating temperature and ceramic particle size. The material properties of functionally graded materials are assumed to vary continuously and smoothly across the thickness of the thin-walled blade. For obtaining system stiffness reflecting these characteristics, the one-dimensional heat transfer equation is applied along the thickness of the thin-walled blade for determining the temperature distribution. Using the results of the temperature analysis, the equations of motion of a rotating blade are derived with hybrid deformation variable modeling method along with the Rayleigh-Ritz assumed mode methods. The validity of the derived rotating blade model is evaluated by comparing its transient responses and temperature distribution with the results obtained using a commercial finite element code. The maximum tensile stress with operating speed and gradient index are obtained. Furthermore, the gradient index that minimizes blade temperature was investigated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7350-7356
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• 2014

To study the reasonable design thermal loads, a steel box girder bridge specimen, which has no concrete slab, was manufactured with real size dimensions. The temperature data was obtained at the web and diaphragm using thermo gauges that were attached according to height. In the hottest day, the temperature differences between the top and bottom of the bridge model were calculated. The temperatures in the actual bridge were measured and the temperature of the bridge specimen was compared. The temperature gradient models were proposed in both the web and the diaphragm. The proposed models showed a correlation of approximately 95.8% compared to the Euro code. This study can provide basis data for temperature-load design in the nation.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.219-224
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• 1993

본 연구는 철근콘크리트 격납구조물에서 가상의 냉각제 유출사고에 의한 온도하중과 압력에 따른 거동을 알아보기 위한 비선형 해석을 수행하였다. 시간에 따른 온도하중을 결정하기 위하여 과도온도해석을 통해 격납구조물 단면내의 온도분포를 구하였다. 구조물은 기하학적 비선형성과 재료비선형성을 고려한 판 및 쉘요소로 이상화되며, 쉘요소는 두께방향에 따라 변하는 응력을 고려하기 위해 몇 개의 층으로 이루어진 모델을 사용하였다. 열응력은 인접한 두시간 단계에서의 온도차를 하나의 하중증가로 고려하여 초기변형 문제로 변환하여 결정되었다. 본연구에서의 수치실험에 의하여 과도온도해석에 근거한 비선형온도경사를 고려할 때의 변위가 고려하지 않을 때의 변위에 비해 크게 나타남을 알 수 있다.