• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.18 no.2
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• pp.121-129
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• 1989

헬륨을 이용한 극저온 냉동기는 압축기(compressor)을 통하여 압력을 10-20 기압 정도로 높혀준후 여러 단계의 열교환기(heat exchanger)를 통하여 상전위온도(maximum inversion temperature) 이하로 떨어뜨린후 Joule-Thomson 밸브를 통하면 4K까지 온도가 떨어진다. 이때 압력은 1기압 정도이며 헬륨가스는 액체로 변한다. 본 연구의 목적은 Gifford-McMahon 냉동기와 Joule-Thomson 냉동기의 혼합형인 극저온 냉동기를 설계, 제작하여 죠셉슨(Josephson) 소자를 이용한 SQUID(초전도양자 간섭장치), 여러 종류의 탐지기, 컴퓨터 소자 개발 등을 위한 냉동기로 사용하는데 그 목적이 있다. 개발되는 법동기의 용량은 1 W이며, 최저온도는 4K 정도가 된다.

• Korean Journal of Weed Science
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• v.13 no.2
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• pp.132-137
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• 1993

Some biological characteristics with respect to tuber formation of Eleocharis kuroguwai Ohwi were investigated. Tuber formation was initiated at the descending time of daily maximum and minimum temperatures, accelerated under the minimum temperature lower than $20^{\circ}C$, and terminated at about $10^{\circ}C$. Tubers produced at the early season were located at deeper soil layers. Large tubers were found at deeper soil depths and required the longer period for sprouting as compared with small tubers. Percent emergence decreased as the emergence depth increased, while percent old-tuber produced during previous years was greater at the deeper depths.

• Fire Science and Engineering
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• v.20 no.1 s.61
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• pp.1-5
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• 2006

The spontaneous ignition of a flammable matter is a crucial factor for the prevention of a fire. The minimum ignition temperatures of Gasoline and Cenox in $1000{\mu}l$ of a sample were determined to be $340.5^{\circ}C\;and\;368.5^{\circ}C$ respectively. In addition when the time taken for ignition was 1.0 sec, the instantaneous ignition temperatures were $416^{\circ}C\;and\;427^{\circ}C$ respectively. Moreover, the changes in the minimum ignition temperature were small when less than 60 v/v% of Cenox was added, but the changes were great when 80 v/v% or more was added. Therefore, it is hypothesized that, when used as a fuel in the Gasoline engine, the ratio of the mixture of Cenox and Gasoline will be a very important factor.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.77-77
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• 2013

최근의 산업활동에서는 신규 원료 개발과 생산 효율성을 높이기 위하여 분체 공정이 증가하고 있는데, 미세 분진의 취급으로 분진운의 형성과 착화가 용이해지므로 분진폭발이나 화재 위험성이 증가하고 있다. 분진을 안전하게 사용하고 저장, 취급하기 위해서는 착화 전의 위험성 지표로서 최저발화온도(MIT ; Minimum Ignition Temperature)를 사전에 파악해 두는 것이 중요하다. 분진농도의 발화온도는 장치 내의 발화위험성이나 분진 취급 공정의 사고예방대책 관리를 위한 실용적 관점에서 중요하게 활용되는 폭발특성값이다. 또한 분진의 발화온도는 분진농도에 의존하며 농도변화에 따른 가장 낮은 온도를 MIT라고 한다. 본 연구에서는 화재폭발사고 빈도가 줄지 않고 있는 Mg 및 Mg-Al합금(60:40 wt%, 50:50 wt%, 40:60 wt%)을 대상으로 조성비율에 따른 최저발화온도를 실험적으로 조사하였다. Mg 및 Mg-Al(60:40 wt%), Mg-Al(50:50 wt%), Mg-Al(40:60 wt%) 시료의 평균입경은 142, 160, 151, $152{\mu}m$이다. MIT실험장치는 IEC 61241-2-1(Methods for Determining the Minimum Ignition Temperatures of Dust, 1994)에 준거하여 제작하여 사용하였다. 실험장치는 가열로, 분진운 시료홀더, 온도조절장치, 압축공기 제어장치 등으로 구성되어 있다. 구체적인 실험방법은 시험분진를 분진홀더에 장착하고 0.5 bar의 압축공기를 0.3 sec 동안 사용하여 일정 온도로 가열된 로의 내부로 분진운을 부유시킬 때에 분진운이 발화하여 가열로 하단부의 개방구에까지 화염이 전파하는지를 디지털비데오카메라로 기록, 평가하여 발화 유무를 판정하였다. Mg합금에 대한 MIT를 측정한 결과 $740^{\circ}C$가 얻어졌으며, Mg-Al(60:40 wt%)의 MIT는 $820^{\circ}C$로 조사되었다. 그러나 Mg-Al(50:50 wt%) 및 Mg-Al(40:60 wt%)에 대해서는 최대 가열로의 설정온도를 $890^{\circ}C$까지로 하여 농도를 변화시키면서 조사하였으나 발화가 일어나지 않았다. 문헌에 따르면 Mg입자 표면의 산화피막은 다공성으로 일정 온도에서 산화반응이 시간에 따라 직선적으로 증가하는데 반하여, Al의 산화피막은 보호 작용을 하여 일정 온도에서 산화반응속도가 표면과 내부의 농도 기울기에 의한 확산속도에 의존한다고 보고하고 있다. 본 연구결과를 토대로 Mg-Al합금의 발화특성을 고찰해 보면, Mg-Al합금에서 자기 전파성이 작은 Al성분의 증가는 착화지연이 증가하여 연소성이 감소하여 최저발화온도의 증가로 이어지는 것으로 추정되었다. 또한 발화온도는 주어진 조건의 온도장에서 분진이 존재하는 시간 길이에 따라 변화하므로, 발화온도를 실험적으로 측정하는 경우에는 측정장치나 방법에 따라 달라지므로 사업장의 현장에 발화온도를 적용하는 경우에는 장치 내의 분진의 존재시간을 고려할 필요가 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.62-68
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• 2016

The feeder cable assembly is an automotive part used for telecommunication. If it malfunctions, the control and safety of the automobile can be put at risk. ALT (Accelerated Life Testing) is a testing process for products in which they are subjected to conditions (stress, strain, temperatures, etc.) in excess of their normal service parameters in an attempt to uncover faults and potential modes of failure in a short amount of time. Failure is caused by defects in the design, process, quality, or application of the part, and these defects are the underlying causes of failure or which initiate a process leading to failure. Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. Thermal shock testing is performed to determine the ability of parts and components to withstand sudden changes in temperature. In this research, the main causes of failure of the feeder cable assembly were snapping, shorting and electro-pressure resistance failure. Using the Coffin-Manson model for ALT, the normal conditions were from Tmax = $80^{\circ}C$ to Tmin = $-40^{\circ}C$, the accelerated testing conditions were from Tmax = $120^{\circ}C$ to Tmin = $-60^{\circ}C$, the AF (Acceleration Factor) was 2.25 and the testing time was reduced from 1,000 cycles to 444 cycles. Using the Bxlife test, the number of samples was 5, the required life was B0.04%.10years, in the acceleration condition, 747 cycles were obtained. After the thermal shock test under different conditions, the feeder cable assembly was examined by a network analyzer and compared with the Weibull distribution modulus parameter. The results obtained showed good results in acceleration life test mode. For the same reliability rate, the testing time was decreased by a quarter using ALT.

• Fire Science and Engineering
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• v.18 no.2
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• pp.27-33
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• 2004

An accurate knowledge of the AIT(Autoignition temperatures) of chemicals is important in developing appropriate prevention and control measures in industrial fire protection. The AITs describe the minimum temperature to which a substance must be heated, without the application of a flame or spark, which will cause that substance to ignite. The measurement AITs are dependent upon many factors. namely initial temperature. pressure, volume, fuel/air stoichiometry. catalyst material, concentration of vapor, ignition delay time. This study measured the AITs of acids from ignition delay time by using ASTM E659-78 apparatus which was produced in the year 1994. The experiment AITs were a good agreement with the calculated AITs by the proposed equations with a few A.A.P.E.(average absolute percent error) and A.A.D.(average absolute deviation).

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.3
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• pp.119-123
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• 2012

The duration of low temperature in winter season is one of the important agrometeorological characteristics in crop growing fields. This study was conducted to develop a method to estimate the duration of low-temperature with monthly meteorological data. Using daily meteorological data from 61 observation sites from 1981 to 2010, we analyzed the relationships between the averages of monthly temperature minima and the durations of low-temperature ranging from -15 to $5^{\circ}C$, The monthly mean of the January minimum air temperature was appropriate for theestimation of the durations of lowtemperature below $0^{\circ}C$. We tested a simple second order equation to predict durations of low-temperature. To apply the equation to various temperature ranges, we suggested two different equations for the estimation of coefficients a and b, which are dependent on the base temperatures from -15 to $0^{\circ}C$. Thevalidation of the equations using other daily meteorological datasets from 1971 to 2000 showed that they were appropriate for the range from -10 to $0^{\circ}C$, but underestimated at $-15^{\circ}C$.

• Korean Journal of Poultry Science
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• v.11 no.2
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• pp.127-132
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• 1984

In order to investigate the effect of temperature variation in winter season on the egg production and energy utilization of poultry, 30week-old Warren layers were reared during 17 weeks of experimental period, from Nov. 1st, 1980 to Feb. 27th. 1981. The effect of temperature change on the body weight, feed intake and feed conversion was not found. But the outdoor average and the indoor minimum temperature had changed Positively 0.46 and 0.24% of henday egg production per 1$^{\circ}C$ fluctuation, respectively. Daily metabolizable energy utilized during 32 (Nov.15th), 34(Dec.1st) and 46(Feb. 27th) week-old reached to, respectively, 358, 385 and 419 kcal per bird, and 159, 173 and 176 kcal per kg body weight. Also the metabolizable energy utilization correlated negatively with the ambient temperature fluctuation, while the equation by NRC(1981) for metabolizable energy requirement estimation were well in accord with these results when the indoor minimum temperatures were based. And the metabolizable energy requirements per kg body weight were 1.7, 1.6 and 2.1 kcal, respectively, according as 1C fluctuation of outdoor, indoor maximum and indoor maximum and indoor minimum temperatures. Thus it is appeared that indoor temperatures fluctuated by outdoor temperatures will affect the egg Production and metabolizable energy utilization of hen in winter season of Korea.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.521-529
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• 2012

The aim of this study was to analyze radiological change of Kager's triangle area and retrocalcaneal surface temperature by shoes heel height. Area of Kager's triangle was measured by simple radiography study And PACS of INFINITI. Retrocalcaneal surface temperature were measured by DITI. Area of Kager's triangle and retrocalcaneal surface temperature were calculated for comparison and analysis, with flat shoes and high heel shoes. Area of Kager's triangle($0.88cm^2$) and retrocalcaneal surface temperature ($1.4^{\circ}C$)tends to decrease with high heel shoes. The highest and shortest of the Kager's triangle area and a surface temperature difference between flat shoes and high heel shoes, each $0.9cm^2$, $1.2cm^2$, $1.6^{\circ}C$, $0.5^{\circ}C$ and showed slight differences. The highest weight and the lowest weight of a surface area and the temperature difference between flat shoes and high heels, each $1.8cm^2$, $0.8cm^2$, $1.1^{\circ}C$, $0.2^{\circ}C$ and higher weight Kager's area and the surface temperature is decreased. The longest time and shortest time of a surface area and the temperature difference between high heels, each $0.8cm^2$, $1.4^{\circ}C$. In conclusion, Areas of Kager's triangle and retrocalcaneal surface temperature decrease with high heel shoes. If we wear high heel shoes for a long time, retrocalcaneal pain and blood flow disorder will occurs.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.4
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• pp.289-293
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• 1993

To comply with the increasing demand from the agricultural industry for more accurate short-range weather information, statistical method for forecasting soil temperature was presented. Regression equation was derived to predict daily mean 10cm soil temperature for any day the year. The equation was based upon 10-daily mean 10cm soil temperature(10DM 10ST) for 6 years(1982~1987) at grass in Suweon. The possibility of estimating daily mean 10cm soil temperature was examined.