• Cement
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• s.125
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• pp.12-17
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• 1991

• Cement
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• s.104
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• pp.4-10
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• 1986

• Journal of the Korean Wood Science and Technology
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• v.48 no.2
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• pp.121-135
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• 2020

This study aims to evaluate applicability for the continuous drying process using saturated and superheated steam for large-square timber. During drying of the boxed heart square timber, changes in moisture content were examined through the slices of the surface, inner and core layers. The results showed that there was a large moisture content difference between the surface and inner layers during saturated steam drying and between the inner and core layers during superheated steam drying. However, despite the moisture content difference between the layers, no surface check occurred, and an internal check occurred only near the pith or juvenile parts of the wood. The maximum value of the drying stress of the dried larch boxed heart square timber, calculated from the elastic strain of the slice and the tangential elastic modulus of the larch, was 1.30 MPa. The tangential tensile strength of the larch was estimated at 5.21 MPa under temperature and moisture content conditions when drying stress was at a maximum. That is, in the continuous drying process, the saturated and superheated steam did not generate a check in the surface because the drying stress of the wood did not exceed the tangential tensile strength. In further studies, the superheated steam drying conditions will need to be relaxed to suppress the occurrence of internal checks. Such studies would make the continuous drying process using saturated and superheated steam available for the drying of large-square timber.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.3
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• pp.195-202
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• 2007

The normalized difference in incident solar energy between a target surface and a level surface (overheating index, OHI) is useful in eliminating estimation error of site-specific maximum temperature in complex terrain. Due to the complexity in its calculation, however, an empirical proxy variable called northern exposure index (NEI) which combines slope and aspect has been used to estimate OHI based on empirical relationships between the two. An experiment with real-world landscape and temperature data was carried out to evaluate performance of the NEI - derived OHI (N-OHI) in reduction of spatial interpolation error for daily maximum temperature compared with that by the original OHI. We collected daily maximum temperature data from 7 sites in a mountainous watershed with a $149 km^2$ area and a 795m elevation range ($651{\sim}1,445m$) in Pyongchang, Kangwon province. Northern exposure index was calculated for the entire 166,050 grid cells constituting the watershed based on a 30-m digital elevation model. Daily OHI was calculated for the same watershed ana regressed to the variation of NEI. The regression equations were used to estimate N-OHI for 15th of each month. Deviations in daily maximum temperature at 7 sites from those measured at the nearby synoptic station were calculated from June 2006 to February 2007 and regressed to the N-OHI. The same procedure was repeated with the original OHI values. The ratio sum of square errors contributable by the N-OHI were 0.46 (winter), 0.24 (fall), and 0.01 (summer), while those by the original OHI were 0.52, 0.37 and 0.15, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.563-569
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• 2012

The superheater and reheater tubes of a heavy-load fossil power plant boiler can be damaged by overheating, and therefore, the degree of overheating is assessed by measuring the oxide scale thickness inside the tube during outages. The tube temperature prediction from the oxide scale thickness measurement is necessarily accompanied by destructive tube sampling, and the result of tube temperature prediction cannot be expected to be accurate unless the selection of the overheated point is precise and the initial-operation tube temperature has been obtained. In contrast, if the tube temperature is to be predicted analytically, considerable effort (to carry out the analysis of combustion, radiation, convection heat transfer, and turbulence fluid dynamics of the gas outside the tube) is required. In addition, in the case of analytical tube temperature prediction, load changes, variations in the fuel composition, and operation mode changes are hardly considered, thus impeding the continuous monitoring of the tube temperature. This paper proposes a method for the short-term prediction of tube temperature; the method involves the use of boiler operation information and flow-network-analysis-based tube heat flux. This method can help in high-temperaturedamage monitoring when it is integrated with a practical tube-damage-assessment method such as the Larson-Miller Parameter.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.12
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• pp.1881-1888
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• 2014

Pre-thermal treatment is important to minimize quality changes during main cooking or storage. In this study, to optimize pre-thermal treatment of carrots, three types of pre-thermal treatments were applied to carrots and quality changes such as physicochemical, nutritional, or sensory properties were observed. Washed and sliced carrots were thermally treated by hot-water immersion ($100^{\circ}C$, 1~10 min), steaming ($100^{\circ}C$, 1~10 min), and stir-frying with oil (10~80 sec). Carrot tissue was maintained until 2 min hot-water immersion or steaming, and they were damaged by just 30 sec of stir-frying. Color and hardness were significantly affected by treatment time and temperature. Color was completely changed after 5 min and 7 min by hot-water and steam treatments, respectively. Hardness decreased to 44% compared with fresh carrot (4,500 g) after 1 min, 3 min, and 20 sec of hot-water, steam, and stir-frying, respectively. For nutritional changes, ascorbic acid, organic acid, and peroxide activity were reduced by all treatments compared with fresh carrot. Especially, succinic acid was dramatically reduced by hot-water treatment. Otherwise, free sugar contents were increased with greater treatment time in all samples. In this study, pre-thermal treatment of carrot was optimal at 2 min steaming treatment.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.186-187
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• 2013

본 논문에서는 과부하, 과열에 의한 환풍기 동작 특성을 분석하기 위해 노후, 외부 이물질에 의한 날개의 강제 구속을 상정한 환풍기 내부 3개소의 온도 및 발화 특성을 실험적인 방법으로 분석하였다. 환풍기 신품 조건에서 날개 구속에 의한 실험 결과 온도퓨즈 용단으로 과열에 의한 변형이나 발화 위험의 징조는 발견하지 못하였으며 향후 노후 및 오염, 절연불량 등 추가적인 요인을 고려한 발화 위험의 실험이 필요하다고 사료된다.

• Electric Engineers Magazine
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• v.216 no.8
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• pp.28-33
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• 2000

최근 power electronics 응용 기기의 사용증가로 비선형 특성부하에 의한 고조파가 상당히 발생하고 있으며 고조파에 의한 영향이 심각한 수준에 이르고 있다. 빌딩의 인텔리전트화에 의한 OA기기 및 자동화에 따른 다량의 고조파가 변압기 과열, 중성선과열, 소음, 진동, Noise 등의 현상으로 나타나고 있으며 공장의 전력변환장치 사용증가에 따라 지금까지 고려되지 않았던 여러 가지 현상이 나타나고 있다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1999.06a
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• pp.207-214
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• 1999

카세트식 이동식부탄연소기의 사고는 과열에 의한 화재뿐만 아니라 접합용기의 파열에 따른 피해가 더 큰 위험성을 내포하고 있다. 접합용기의 파열원인은 화재에 의한 파열과 접합용기 장착 불량에 의한 가스누출로 화염에 의한 파열, 그리고 과대 조리기구를 사용하여 조리기구 및 화염에서 발생되는 열이 접합용기에 전달되어 온도상승에 따른 파열로 구분된다. 현재 카세트식 이동식부탄연소기의 조리기구 크기에 따라 과열에 따른 정확한 검증이 부족하며, 사용자에게 사용장소와 조리기구외 크기만 권고하고 있어 이에 대한 자료가 필요하다. (중략)

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.11a
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• pp.143-148
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• 2002

산업현장 뿐만 아니라 일반가정에서 냉난방기기와 다양한 전기제품의 사용으로 전기용량은 해마다 증가하고 있으며 이로 인해 전선의 과열에 따른 화재위험성이 점점 높아지고 있다. 전기화재의 발생원인을 살펴보면, 합선, 과부하, 누전, 접촉부과열, 스파크등 주로 전선에서 화재의 위험성이 높다. 전선은 종류와 굵기에 따라 최고허용전류와 온도가 정해져 있다.(중략)