• Design & Manufacturing
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• 제13권3호
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• pp.41-47
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• 2019

In conventional machining, the use of cutting fluid is essential to reduce cutting heat and to improve machining quality. However, to increase the performance of cutting fluids, various chemical components have been added. However, these chemical components during machining have a negative impact on the health of workers and cutting environment. In current machining, environment-friendly machining is conducted using MQL (minimum quantity lubrication) or cryogenic air spraying to minimize the harmful effects. In this study, the injection nozzle that can combined injecting minimum quantity lubrication(MQL) and cryogenic gas was designed and the shape optimization was performed by using computational fluid dynamics(CFD) and design of experiment(DOE). Performance verification was performed for the designed nozzle. The diameter of the sprayed fluid at a distance of 30 mm from the nozzle was analyzed to be 21 mm. It was also analyzed to lower the aerosol temperature to about 260~270K.

• 한국산림과학회지
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• 제62권1호
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• pp.1-18
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• 1983

수종별(樹種別) 생육온도(生育温度) 범위(範圍)를 조사분석(調査分析) 하므로써 조림예정지(造林豫定地)에 대한 올바른 수종(樹種) 선택방법(選擇方法)을 제시(提示)하고자, 30년간(年間)의 일(日) 평균기상자료(平均氣象資料)를 이용(利用)하여, 생육기(生育期)(3~10월(月))의 일(日) 평균기온합계(平均氣温合計), 일(日) 평균상대습도합계(平均相對濕度合計), 일(日) 평균일조시간합계(平均日照時間合計)와 휴면기(休眠期)(11~2월(月))의 일(日) 평균기온합계(平均氣温合計), 일(日) 평균상대습도합계(平均相對濕度合計), 일(日) 평균(平均) 최저기온합계(最低氣温合計)를 조사(調査)하여 우리나라 지도(地圖)에 등지선(等指線)으로 표시(表示)하였다. 조림예정지(造林豫定地)에 대한 생육기(生育期) 일(日) 평균기온합계(平均氣温合計)와 휴면기(休眠期) 일(日) 평균최저기온합계(平均最低氣温合計)를 추정(推定)하기 위하여 우리나라를 6개(個) 지역(地域)으로 나누어, 각각(各各) 이에 상응(相應)하는 추정식(推定式)을 다중회귀직선식(多重回歸直線式)으로 유도(誘導)하였다. 정대현(鄭臺鉉)과 이우철(李愚喆)의 우리 나라 수목(樹木)의 수직(垂直) 및 수평분포표(水平分布表)를 기준(基準)으로 수종별(樹種別) 생육범위(生育範圍)를 일(日) 평균기온합계(平均氣温合計)와 일(日) 평균최저기온합계치(平均最低氣温合計値)에 의하여 나타냈다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.667-672
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• 2002

Concrete cooled to very low temperature cyclically is deteriorated by ice formation in micro-pores. Although the factors to the deterioration are various, storage at very low temperature is mentioned as one of the factors. In practice, storage of cryogenic structure is kept at very low temperatures, and as such, it is important to take into consideration the influence of storage at such low temperature on the deterioration of concrete. Thus, in this study, the influence of storage on the deterioration of concrete at minimum temperatures taking into consideration the different W/C and air content.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.335-338
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• 2010

A recent study for tracing the profiles of supersonic axisymmetric Minimum Length Nozzle with uniform and parallel flow at the exit section, the stagnation temperature is taken into account. The aim of this work is to add optimization algorithm to the supersonic nozzle design in order to get the optimum nozzle shape. The comparisons of the nozzle contours based on the method of characteristics are presented. The specific heats and their ratio vary with the stagnation temperature when this temperature of a perfect gas increases. An application is made for air in a supersonic nozzle.

• Journal of Magnetics
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• 제4권4호
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• pp.111-114
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• 1999

Numerical calculation for temperature dependence of galvanomagnetic properties of thin bismuth films is pursued. The quasi-two dimensional system is treated in the perturbation formalism of previous study, where realistic screened potential due to impurity is assumed to be the only scattering channel. The potential is separated into pure two dimensional part and the remaining presumed perturbation part. Relaxation time and mobilities for both electron and hole are evaluated, then temperature dependence of the Hall coefficient and magnetoresistance is obtained. The broad minimum of magnetoresistnace is manifested, and the interpretation under the kinetic theory is made. Thickness dependence of the quantities are also shown, which are in good agreement with the expected quantum size effect.

• 한국토양비료학회지
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• 제46권5호
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• pp.359-364
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• 2013

This study was conducted to develop a model to estimate crop leaf surface temperature. The results were as following; A definition for the daily time based on elapsed time from the midnight (00:00) as "E&E time" with the unit of Kmin. was suggested. The model to estimate the scaled temperature ($T^*e$) of crop leaf surface temperature by scale factor ($T^*$) according to the "E&E time : Kmin."(X) was developed as eq. (1) $T^*e=0.5{\cdot}sin(X+780)+0.5$ (2) $T^*=(Tx-Tn)/(Tm-Tn)$, Tx : Daily leaf temperature, Tm : Daily maximum leaf temperature, Tn : Daily minimum leaf temperature. Relative sensitivity of the measured temperature compared to the estimated temperature of red pepper, soybean and persimmon was 1.078, 1.033 and 0.973, respectively.

• Asian-Australasian Journal of Animal Sciences
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• 제10권5호
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• pp.478-483
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• 1997

Six adult female Murrah buffaloes of about 12 years were exposed to solar radiation during summer when minimum and maximum ambient temperatures were 27.1 and $44.1^{\circ}C$, respectively. The skin surface temperature at forehead, middle pinna, neck, rump, foreleg, hind legs were recorded using non-contact temperature measuring instrument and respiration rate and rectal temperature were measured throughout the 24 hours starting from 6:30 AM. The diurnal fluctuations and temperature gradients have been reported for buffaloes. During summer when ambient temperature and solar radiation was maximum, adult buffaloes were not able to maintain their thermal balance even after increasing the pulmonary frequency 5 - 6 times. The changes in skin temperature at various sites indicate that the temperature of skin surface not only varies in relation to exposure but also due to water diffusion and evaporation.

• 환경생물
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• 제30권1호
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• pp.1-8
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• 2012

To understand growth characteristics of eight dominant red tide species ($Prorocentrum$ $minimum$, $Heterocapsa$ $triquetra$, $Scrippsiella$ $trochoidea$, $Akashiwo$ $sanguinea$, $Chattonella$ $marina$, $Heterosigma$ $akashiwo$, $Amphidinium$ $carterae$ and $Rhodomonas$ $salina$) in the Korean coastal water, the growth rates were examined in relation with the impacts of water temperature and bio-volume. Of these, $P.$ $minimum$, $C.$ $marina$, $H.$ $akashiwo$, $A.$ $carterae$ and $R.$ $salina$ were eurythermal species with relatively high growth rates in a borad ranges (15 to $25^{\circ}C$) of water temperature. On the other hand, the growth rate of $H.$ $triquetra$, $S.$ $trochoidea$ and $A.$ $sanguinea$ were high in relatively mid temperature (optimum: $25^{\circ}C$) condition. In particular, $H.$ $triquetra$ was well adapted in low temperature of 5 to $15^{\circ}C$, implying that the species can survive and grows even at very low temperature. Based on results of our experiment, the growth characterestics of five eurythermal species and three mid temperature species may have dominated in Korean coastal water during summer season and fall season, respectively. Contrastively, the growth characteristics of $H.$ $triquetra$ make a consistently dominant during the cold winter season. In addition, the growth rates of large bio-volume species were lower than those of small bio-volume species, indicates that growth of single cells of several flagellates might be depended on the cells sizes.

• 한국양식학회지
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• 제15권1호
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• pp.39-42
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• 2002

이 연구에서는 북방대합의 과학적이고 효율적인 인공종묘생산을 위한 기초지식을 얻고자 난 발생에 미치는 수온의 영향에 관하여 조사하였다. 북방대합의 발생 가능 수온은 10∼25$^{\circ}C$ 인 것으로 나타났으며, 북방대합이 초기D상 유생에 도달한 시간은 10, 15, 20, 25$^{\circ}C$에서 각각 70, 47, 27, 20시간이 소요되었다. 수온 (WT : $^{\circ}C$)과 각 발생 단계별 소요시간 (h : hour)의 관계식은 다음과 같다. 2세포기 : 1/t = 0.0554WT-0.3769 8 세포기 : 1/t : 0.0210WT-0.1142 상실기 : 1/t : 0.0125WT-0.0712 담륜자기 : 1/t = 0.0039WT-0.0203 D상 유생 : 1/t = 0.0024WT-0.0108 이들 관계식을 기초로 하여 북방대합의 초기 발생에 있어서 난 발생이 정지하는 생물학적 영도 (Biological minimum temperature)는 평균 5.5$^{\circ}C$로 산정되었다.

• 한국화재소방학회논문지
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• 제33권1호
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• pp.7-14
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• 2019

우드펠릿은 화력발전소 및 화목 보일러의 연료로 많이 사용되고 있으나 발열량이 높은 우드펠릿을 장기간 보관 시 자연발화의 위험성이 있다. 본 연구에서는 시료 용기의 크기에 따라 유량의 변화에 따른 최소자연발화온도와 발화한계온도를 구하였으며, 발화한계온도를 이용하여 겉보기 활성화 에너지를 측정함으로써 우드펠릿의 발화 특성을 예측하였다. 겉보기 활성화 에너지는 190.224 kJ/mol을 구하였다. 용기에 저장된 시료량이 두꺼워질수록 시료 표면에서 중심까지의 열전달이 어려워 발화유도시간이 긴 것으로 나타났으며, 용기의 크기가 같을 경우 유량의 양이 많아 질수록 자연발화온도는 낮아졌다. 또한 시료용기가 커질수록 자연발화온도는 낮아지고 발화유도시간은 길어지는 것으로 나타났다.