• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.149-153
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• 2008

Since magnesium alloy sheets have been employed in industrial field which requires the light weight and thin engineering components, most of researches have been focused on the formability of magnesium ahoy sheet. In warm press forming of magnesium alloy sheet, it is important to control the sheet temperature by heating the sheet in closed die. When forming a commercial AZ31 magnesium alloy sheets which are 0.5mm and 1.0mm thick, respectively, time arriving at target temperature and temperature variation in magnesium alloy sheet have been investigated. Sheet metals were mostly formed in simple shapes such as circular or rectangular. Few studies about forming of complex shapes were reported. Thus, the formability of magnesium alloy sheet for complex shapes is investigated. The process variable for a double sink shape deep drawing with circular and rectangular shape was investigated by varying temperature, velocities, and clearances. Accordingly, temperature, velocities, and clearances suitable for forming were suggested through investigating the thickness variation of the product.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권4호
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• pp.149-153
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• 2005

We have investigated thermal properties showed by changing the content of carbon black which is the component parts of semiconductive shield in underground power transmission cable. Specimens were made of sheet with the nine of those for measurement. Heat capacity (${\Delta}$H), glass transition temperature (Tg) and melting temperature (Tm) were measured by DSC (Differential Scanning Calorimetry). The ranges of measurement temperature were from -100($^{\circ}C$) to 100($^{\circ}C$), and heating rate was 4($^{\circ}C$/min). And then thermal diffusivity was measured by LFA 447. The dimension of measurement temperature was 25[$^{\circ}C$]. Glass transition temperature of specimens was showed near -25[$^{\circ}C$] and the heat capacity and the melting temperature from the DSC results were simultaneously decreased according to increasing the content of carbon black, while thermal diffusivity was increased according to increasing the content of carbon black. Because ionic impurities of carbon black having Fe, Co, Mn, Al and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• 설비공학논문집
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• 제18권11호
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• pp.896-905
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• 2006

An optimal control of an air-conditioning system with slab thermal storage is investigated by making use of the Maximum Principle. An optimal heat input to a plenum chamber and an air-conditioned room is determined by minimizing a criterion function which is given as integral sum of two terms. The first term is the square of the deviation in the room air temperature from the set-point value, and the second is the absolute value of the heat input. The result indicates that it tries to keep a room air temperature in set-point value by heating as much as possible at the time of a setup of a room air temperature or just before that, in order to avoid a heat loss arising at the time of the non-air conditioning. The result is compared with that of the case when the square of the heat input is used as a criterion.

• Steel and Composite Structures
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• 제33권1호
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• pp.111-122
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• 2019

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

• 에너지공학
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• 제22권4호
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• pp.355-361
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• 2013

본 연구에서는 하수슬러지를 이용하여 높은 에너지 밀도와 균일한 품질의 고형연료 생산을 위해 반탄화 기술을 적용하여 반탄화 생성물의 특성과 에너지원으로서의 가치를 확인하였다. 운전인자로 반응온 도($150-230^{\circ}C$)와 반응시간(10-60분)을 달리한 결과, 반응온도가 높고, 반응시간이 길어질수록 반탄화 생성물의 수분함량은 감소하고, 발열량은 증가하였다. 또한 반응온도 조건의 상승과 함께 탄소의 함량 이 초기 시료(하수슬러지 탈수케이크) 대비 최대 60%까지 증가하였고, 산소와 수소의 함량은 감소하는 경향을 나타내었다. 특히 반응온도 $210^{\circ}C$ 이상에서는 반응시간에 관계없이 평균 발열량 약 4,818 kcal/kg를 나타내었으며, 연료비, 석탄밴드 분석 결과 H/C와 O/C의 원자수비가 낮아져 반탄화를 통해 저등급 석탄에 가까운 연료등급으로 개선되었음을 확인 할 수 있었다.

• 한국응용과학기술학회지
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• 제40권5호
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• pp.1163-1175
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• 2023

Cholesterol is prone to oxidation, which results in the formation of cholesterol oxidation products (COPs). This occurs because it is a monounsaturated lipid with a double bond on C-5 position. Cholesterol in foods is mostly non-enzymatically oxidized by reactive oxygen species (ROS)-mediated auto-oxidative reaction. The COPs are found in many common foods of animal-origin and are formed during their manufacture process. The formation of COPs is mainly related to the temperature and the heating time the food is processed, storage condition, light exposure and level of activator present such as free radical. The level of COPs in processed foods could reach up to 1-10 % of the total cholesterol depending on the foods. The most predominant COPs in foods including meat, eggs, dairy products as well as other foods of animal origin were 7-ketocholesterol, 7 α-hydroxycholesterol (7α-OH), 7β-hydroxycholesterol (7β-OH), 5,6α-epoxycholesterol (5,6α-EP), 5,6β-epoxycholesterol (5,6β-EP), 25-hydoxycholesterol (25-OH), 20-hydroxycholesterol (20-OH) and cholestanetriol (triol). They are mainly formed non-enzymatically by cholesterol autoxidation. The COPs are known to be potentially more hazardous to human health than pure cholesterol. The procedure to block cholesterol oxidation in foods should be similar to that of lipid oxidation inhibition since both cholesterol and lipid oxidation go through the same free radical mechanism. The formation of COPs in foods can be stopped by decreasing heating time and temperature, controlling storage condition as well as adding antioxidants into food products. This review aims to present, discuss and respond to articles and studies published on the topics of the formation and inhibition of COPs in foods and key factors that might affect cholesterol oxidation. This review may be used as a basic guide to control the formation of COPs in the food industry.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1993년도 추계학술대회
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• pp.128-131
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• 1993

In order to get the basic data for the study of the heat stimulation of burning moxa, the pattern of combustion temperature, which is one of the important factors of thermal characteristics, was measured by density of cone moxa along the time procedure. The following results have been obtained 1) The pattern of combustion temperature by moxa burning was classified into input period which means the infiltration of heat into the area and output period which means the radiation of heat from the area. The input period consists of preheating and heating periods, while the output period consists of heat retaining and cooling periods. 2) The pattern of combustion temperature showed the same type or curve, which was not influenced by the moxa weight. However, Its pattern gradient are varied by density. It is considered that the pattern of combution temperature is primarily influenced by the rate of combustion temperature, gradient temperature and duration of combustion.

• Journal of the Korean Wood Science and Technology
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• 제43권3호
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• pp.390-399
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• 2015

본 연구는 커피부산물(이하 CW)의 재자원화 방안으로 여러 조건에서 열처리한 CW를 폼알데하이드(이하 HCHO)와 함께 데시케이터에 방치한 후, CW에 흡착된 HCHO 양을 아세틸아세톤법과 dinitrophenylhydrazine (이하 DNPH)법으로 측정 및 비교하여 섬유판 제조에 있어 흡착제로서 CW의 적용 가능성을 탐색하기 위하여 수행하였다. 데시케이터 내의 증류수에 흡착된 HCHO 양을 아세틸아세톤법으로 측정한 결과 열처리하지 않은 CW에서 가장 낮았고 $100^{\circ}C$의 열처리 온도까지 계속 증가하였으나, $100^{\circ}C$ 이상의 온도에서는 차이가 없었다. CW에 직접 흡착된 HCHO양은 $100^{\circ}C$에서 열처리한 CW에서 가장 높았으며, $50^{\circ}C$, $150^{\circ}C$, $0^{\circ}C$, $250^{\circ}C$ 그리고 $200^{\circ}C$ 순으로 측정되었다. DNPH법으로 측정한 CW의 HCHO 흡착능 결과는 데시케이터 내에 HCHO와 함께 방치시킨 무열처리 CW의 증류수에 교반시킨 용액에서는 HCHO가 검출되지 않은 반면, 열처리 CW 교반액에서는 일정량의 HCHO가 검출되었다. 그 검출량은 $100^{\circ}C$에서 10분간 열처리시킨 CW에서 가장 높았다. 또한 HCHO가 흡착된 CW 자체의 HCHO 양은 열처리 시간과 상관없이 $100^{\circ}C$의 열처리 온도까지 계속 증가하였으나, 그 이상의 열처리 온도에서는 HCHO 검출량의 증가폭이 줄거나 검출량이 감소하는 것으로 나타났다. 결과를 종합하면, 최대 HCHO 흡착을 위한 CW의 열처리 조건으로 기술적 그리고 경제적 측면을 고려하여 $100{\sim}150^{\circ}C$의 온도 범위에서 10분으로 판단되며, 이 열처리 CW를 섬유판 제조에 있어 흡착제로 일정량 첨가한다면 기존 섬유판의 HCHO 방산량을 낮출 수 있는 하나의 방안이 될 것으로 생각한다.

• KEPCO Journal on Electric Power and Energy
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• 제5권2호
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• pp.83-92
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• 2019

Spontaneous combustion propensity of various coals of carbonization grade as a pulverized fuel of coal-fired power plant has been tested from an initial temperature of $25^{\circ}C$ to $600^{\circ}C$ by heating in an oven with air to analyze the self-oxidation starting temperature. These tests produce CPT (Cross Point Temperature), IT (Ignition temperature), and CPS (Cross Point Slope) calculated as the slope of time taken for a rapid exothermic oxidation reaction at CPT base. CPS shows a carbonization rank dependence whereby wood pellet has the highest propensity to spontaneous combustion of $20.995^{\circ}C/min$. A sub-bituminous KIDECO coal shows a CPS value of $15.370^{\circ}C/min$, whereas pet coke has the highest carbonization rank at $2.950^{\circ}C/min$. The nature of this trend is most likely attributable to a concentration of volatile matter and oxygen functional groups of coal surface that governs the available component for oxidation, as well as surface area of fuel char, and constant pressure molar heat.

• 자원리싸이클링
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• 제20권3호
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• pp.62-67
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• 2011

마이크로파와 고온발열체의 연속식 융합공정을 이용하여 수분변화와 전력변화 그리고 온도에 따라 유류오염토양의 분해 및 제거 특성을 연구하였다. 긴 탄소고리(C18-C50)를 가진 윤활유 계열의 오염물질은 온도변화에 따라 TPH 처리량이 6 kW, 700일 때 85.2%로 처리시간 40분에 1788 mg/kg로 제거되었다. 경유, 휘발유 오염토양의 경우 6 kW, 500일 때 처리사간 20분에 567 mg/kg로, 98.4%의 처리율을 보였다. 난분해성 유류오염물질의 경우 마이크로파 6 kW, 700, 30분안 처리를 한 경우 토양오염우려기준 3지역의 2000 mg/kg에 도달하는 것으로 나타났고, 이때 처리비용은 8,173원/ton으로 나타났다.