• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.104-106
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• 1998

For the development of the 0.7 MJ small-sized superconducting magnetic energy storage (${\mu}$SMES) device, quench currents of a kA class superconducting cable were tested for various winding tensions because a dry superconducting coil is usually quenched by an abrupt heat pulse due to strand motions. The test coil similar to parameters of the optimally designed 0.7 MJ ${\mu}$SMES except a stored energy and a size was fabricated based on the test results of the kA class superconducting cable and tested. These experimental results show that the highly prestressed test coil has an excellent DC performance in spite of a dry type coil but its quench current is much degraded even at the low field ramping rate of about 0.4 T/s.

• 생명과학회지
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• 제15권1호
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• pp.66-70
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• 2005

본 연구에서는 천연 항균제 CFSE를 이용하여 적절한 온도 하에서 당근과 시금치의 저장성 향상에 대한 효과를 보았다. 먼저, $70^{\circ}C$ 및 $90^{\circ}C$에서의 당근과 시금치의 열처리에 대한 영향과 아울러 GFSE 첨가시의 효과에 대한 예비 실험을 실시한 결과, 당근과 시금치의 경우 CFSE첨가에 관계없이 $70^{\circ}C$에서 2 분간 열처리하였을 때 비교적 정상적인 색상과 texture유지 및 미생물의 생육억제 가능성을 나타내었다. 이들 예비실험으로부터 이후 열처리는 $70^{\circ}C$에서 고정하고 GFSE의 농도별 영향을 실시한 결과, GFSE를 10 ppm 이상 첨가한 경우 당근이나 시금치 모두 $4^{\circ}C$에서 저장 17일까지 호기성세균 및 yeast의 성장을 억제하는 효과를 보였으며 특히 50 ppm 이상에서는 뚜렷한 억제 효과를 보였다. 당근과 시금치의 다양한 농도의 GFSE 첨가와 아울러 $70^{\circ}C$ 2 분간 처리는 이미 1차 실험에서와 같이 색상 및 조직의 연화에는 영향이 없었다. 그러므로 잔류독성 문제가 대두되고 있는 화학 항균제가 아닌 천연 항균제 GFSE를 활용한 과일과 채소류의 저장성을 높인 상품을 개발함으로서 소비자들에게 호응을 얻을 수 있는 식품으로써의 개발이 가능할 것이다.

• Journal of Microbiology and Biotechnology
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• 제30권2호
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• pp.259-270
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• 2020

Listeria monocytogenes is a gram-positive, facultative anaerobe food pathogen responsible for the listeriosis that mostly occurs during the low-temperature storage of a cold cut or dairy products. To understand the systemic response to a wide range of growth temperatures, L. monocytogenes were cultivated at a different temperature from 10℃ to 42℃, then whole cell proteomic analysis has been performed both exponential and stationary cells. The specific growth rate increased proportionally with the increase in growth temperature. The maximum growth rate was observed at 37℃ and was maintained at 42℃. Global protein expression profiles mainly depended on the growth temperatures showing similar clusters between exponential and stationary phases. Expressed proteins were categorized by their belonging metabolic systems and then, evaluated the change of expression level in regard to the growth temperature and stages. DnaK, GroEL, GroES, GrpE, and CspB, which were the heat&cold shock response proteins, increased their expression with increasing the growth temperatures. In particular, GroES and CspB were expressed more than 100-fold than at low temperatures during the exponential phase. Meanwhile, CspL, another cold shock protein, overexpressed at a low temperature then exponentially decreased its expression to 65-folds. Chemotaxis protein CheV and flagella proteins were highly expressed at low temperatures and stationary phases. Housekeeping proteins maintained their expression levels constant regardless of growth temperature or growth phases. Most of the growth related proteins, which include central carbon catabolic enzymes, were highly expressed at 30℃ then decreased sharply at high growth temperatures.

• 한국수산과학회지
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• 제6권1_2호
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• pp.27-36
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• 1973

The effect of water activity on degradation of pigments in dried lavers, Porphyra tenera Kjellm. was examined when stored at room temperature for fifty days. Chlorophyll pigment was extracted with methanol-petroleum ether mixture solvent(2:1 v/v), partitioned in ether, and analysed spectrophotometrically at 662 nm as chlorophyll a. The degradation products of chlorophyll were isolated on sugar-starch column(85:15 w/w) with n-propanol-petroleum ether solution(1:200 v/v) as a developing solvent. The isolated green colored zones were analysed individually at the wavelengths of 650, 662, and 667 nm as allomerized product, chlorophyll a retained, and pheophytin formed respectively. Carotenoida were also extracted with the methanol mixture solvent, partitioned in ether, and finally redissolved in acetone after the evaporation of ether in a rotary vacuum evaporator. The total carotenoid content was measured as lutein at 450 nm. From the results, it is noted that the rate of chlorophyll degradation reached a minimum at 0.11 to 0.33 water activity while progressively increased at higher moisture levels resulting in rapid conversion of chlorophyll to pheophytin. At lower activity, autocatalysed oxidizing reaction like allomerization seemed prevailing the acid catalysed conversion reaction. The loss of carotenoid pigment was also greatly reduced at the range of 0.22 to 0.34 water activity with much faster oxidative degradation at both higher and extremely lower moisture levels. These two moisture levels indicated above at which the both pigments exhibited maximum stability are considerably higher than the BET monolayer moisture which appeared 7.91 percent on dry basis at Aw=0.10 calculated from the adsorption isothermal data of the sample at $20^{\circ}C$. The rate of pigment loss in heat treated samples at 60 and $100^{\circ}C$ for 2 hours prior to storage somewhat decreased, particularly at higher moisture levels although the final pigment retention was not much stabilized.

• Journal of Biosystems Engineering
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• 제4권2호
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• pp.65-83
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• 1979

Low-temperature drying systems have been extensively used for drying cereal grain such as shelled corn and wheat. Since the 1973 energy crisis, many researches have been conducted to apply solar energy as supplemental heat to natural air drying systems. However, little research on rough rice drying has been done in this area, especially very little in Korea. In designing a solar drying system, quality loss, airflow requirements, temperature rise of drying air, fan power and energy requirements should be throughly studied. The factors affecting solar drying systems are airflow rate, initial moisture content, the amount of heat added to drying air, fan operation method and the weather conditions. The major objectives of this study were to analyze the effects of the performance factors and determine design parameters such as airflow requirements, optimum bed depth, optimum temperature rise of drying air, fan operation method and collector size. Three hourly observations based on the 4-year weather data in Chuncheon area were used to simulate rough rice drying. The results can be summarized as follows: 1. The results of the statistical analysis indicated that the experimental and predicted values of the temperature rise of the air passing through the collector agreed well. 2. Equilibrium moisture content was affected a little by airflow rate, but affected mainly by the amount of heat added, to drying air. Equilibrium moisture content ranged from 12.2 to 13.2 percent wet basis for the continuous fan operation, from 10.4 to 11.7 percent wet basis for the intermittent fan operation respectively, in range of 1. 6 to 5. 9 degrees Centigrade average temperature rise of drying air. 3. Average moisture content when top layer was dried to 15 percent wet basis ranged from 13.1 to 13.9 percent wet basis for the continuous fan operation, from 11.9 to 13.4 percent wet basis for the intermittent fan operation respectively, in the range of 1.6 to 5.9 degrees Centigrade average temperature rise of drying air and 18 to 24 percent wet basis initial moisture content. The results indicated that grain was overdried with the intermittent fan operation in any range of temperature rise of drying air. Therefore, the continuous fan operation is usually more effective than the intermittent fan operation considering the overdrying. 4. For the continuous fan operation, the average temperature rise of drying air may be limited to 2.2 to 3. 3 degrees Centigrade considering safe storage moisture level of 13.5 to 14 perceut wet basis. 5. Required drying time decrease ranged from 40 to 50 percent each time the airflow rate was doubled and from 3.9 to 4.3 percent approximately for each one degrees Centigrade in average temperature rise of drying air regardless of the fan operation methods. Therefore, the average temperature rise of drying air had a little effect on required drying time. 6. Required drying time increase ranged from 18 to 30 percent approximately for each 2 percent increase in initial moisture content regardless of the fan operation methods, in the range of 18 to 24 percent moisture. 7. The intermittent fan operation showed about 36 to 42 percent decrease in required drying time as compared with the continuous fan operation. 8. Drymatter loss decrease ranged from 34 to 46 percent each time the airflow rate was doubled and from 2 to 3 percent approximately for each one degrees Centigrade in average temperature rise of drying air, regardless of the fan operation methods. Therefore, the average temperature rise of drying air had a little effect on drymatter loss. 9. Drymatter loss increase ranged from 50 to 78 percent approximately for each 2 percent increase in initial moisture content, in the range of 18 to 24 percent moisture. 10. The intermittent fan operation: showed about 40 to 50 percent increase in drymatter loss as compared with the continuous fan operation and the increasing rate was higher at high level of initial moisture and average temperature rise. 11. Year-to-year weather conditions had a little effect on required drying time and drymatter loss. 12. The equations for estimating time required to dry top layer to 16 and 1536 wet basis and drymatter loss were derived as functions of the performance factors. by the least square method. 13. Minimum airflow rates based on 0.5 percent drymatter loss were estimated. Minimum airflow rates for the intermittent fan operation were approximately 1.5 to 1.8 times as much as compared with the continuous fan operation, but a few differences among year-to-year. 14. Required fan horsepower and energy for the intermittent fan operation were 3. 7 and 1. 5 times respectively as much as compared with the continuous fan operation. 15. The continuous fan operation may be more effective than the intermittent fan operation considering overdrying, fan horsepower requirements, and energy use. 16. A method for estimating the required collection area of flat-plate solar collector using average temperature rise and airflow rate was presented.

• Journal of Biosystems Engineering
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• 제4권2호
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• pp.64-64
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• 1979

Low-temperature drying systems have been extensively used for drying cereal grain such as shelled corn and wheat. Since the 1973 energy crisis, many researches have been conducted to apply solar energy as supplemental heat to natural air drying systems. However, little research on rough rice drying has been done in this area, especially very little in Korea. In designing a solar drying system, quality loss, airflow requirements, temperature rise of drying air, fan power and energy requirements should be throughly studied. The factors affecting solar drying systems are airflow rate, initial moisture content, the amount of heat added to drying air, fan operation method and the weather conditions. The major objectives of this study were to analyze the effects of the performance factors and determine design parameters such as airflow requirements, optimum bed depth, optimum temperature rise of drying air, fan operation method and collector size. Three hourly observations based on the 4-year weather data in Chuncheon area were used to simulate rough rice drying. The results can be summarized as follows: 1. The results of the statistical analysis indicated that the experimental and predicted values of the temperature rise of the air passing through the collector agreed well.2. Equilibrium moisture content was affected a little by airflow rate, but affected mainly by the amount of heat added, to drying air. Equilibrium moisture content ranged from 12.2 to 13.2 percent wet basis for the continuous fan operation, from 10.4 to 11.7 percent wet basis for the intermittent fan operation respectively, in range of 1. 6 to 5. 9 degrees Centigrade average temperature rise of drying air.3. Average moisture content when top layer was dried to 15 percent wet basis ranged from 13.1 to 13.9 percent wet basis for the continuous fan operation, from 11.9 to 13.4 percent wet basis for the intermittent fan operation respectively, in the range of 1.6 to 5.9 degrees Centigrade average temperature rise of drying air and 18 to 24 percent wet basis initial moisture content. The results indicated that grain was overdried with the intermittent fan operation in any range of temperature rise of drying air. Therefore, the continuous fan operation is usually more effective than the intermittent fan operation considering the overdrying.4. For the continuous fan operation, the average temperature rise of drying air may be limited to 2.2 to 3. 3 degrees Centigrade considering safe storage moisture level of 13.5 to 14 perceut wet basis.5. Required drying time decrease ranged from 40 to 50 percent each time the airflow rate was doubled and from 3.9 to 4.3 percent approximately for each one degrees Centigrade in average temperature rise of drying air regardless of the fan operation methods. Therefore, the average temperature rise of drying air had a little effect on required drying time.6. Required drying time increase ranged from 18 to 30 percent approximately for each 2 percent increase in initial moisture content regardless of the fan operation methods, in the range of 18 to 24 percent moisture.7. The intermittent fan operation showed about 36 to 42 percent decrease in required drying time as compared with the continuous fan operation.8. Drymatter loss decrease ranged from 34 to 46 percent each time the airflow rate was doubled and from 2 to 3 percent approximately for each one degrees Centigrade in average temperature rise of drying air, regardless of the fan operation methods. Therefore, the average temperature rise of drying air had a little effect on drymatter loss. 9. Drymatter loss increase ranged from 50 to 78 percent approximately for each 2 percent increase in initial moisture content, in the range of 18 to 24 percent moisture. 10. The intermittent fan operation: showed about 40 to 50 percent increase in drymatter loss as compared with the continuous fan operation and the increasing rate was higher at high level of initial moisture and average temperature rise.11. Year-to-year weather conditions had a little effect on required drying time and drymatter loss.12. The equations for estimating time required to dry top layer to 16 and 1536 wet basis and drymatter loss were derived as functions of the performance factors. by the least square method.13. Minimum airflow rates based on 0.5 percent drymatter loss were estimated.Minimum airflow rates for the intermittent fan operation were approximately 1.5 to 1.8 times as much as compared with the continuous fan operation, but a few differences among year-to-year.14. Required fan horsepower and energy for the intermittent fan operation were3. 7 and 1. 5 times respectively as much as compared with the continuous fan operation.15. The continuous fan operation may be more effective than the intermittent fan operation considering overdrying, fan horsepower requirements, and energy use.16. A method for estimating the required collection area of flat-plate solar collector using average temperature rise and airflow rate was presented.

• 생물환경조절학회지
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• 제9권3호
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• pp.166-170
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• 2000

자연열(태양열)을 효율적으로 이용하기위해 1999년부터 2000년 까지 2년간 상면적이 100$m^2$인 3동의 유리온실에 각기 다른 집열시스템을 설치하였다. 즉, 집열면적과 경사도가 각각 24$m^2$, 50$^{\circ}$로서 현재 시판되고 있는 태양열 집열기(평판형, Solar hart Inc.)를 이용하는 방법, 직경과 송풍량이 각각 1m, 2.5m$^{-3}$.m$^{-2}$ .min로서 라디에이터가 부착된 2개의 유동팬을 천장부에 설치하고 천창을 밀폐한 후 온실상부의 열을 집열하는 방법, 온실의 중도리 전부를 물이 순환되는 각관 (75x45x3t, 1m 간격x10줄x온실길이 12m=120m)으로 설치하여 집열하는 방법 등으로 하였다. 각 동마다 지하에 26톤의 저수 능력을 갖는 D2000xW1500xL8600의 축열조를 설치한 후 중간을 막아 저온수조와 고온수조로 구분하였고, 수조 중간 1.5m 높이에 통수로를 내어 일정량의 물(약 15톤)이 지속적으로 순화될 수 있도록 하였다. 최저기온 9$^{\circ}C$로 설정하여 1,000$m^2$를 공간 난방할 경우 난방연료 절감율은 태양열 집열기, 유동팬 및 각관에서 각각 7%, 19%, 28%로 나타났다. 태양열 집열기를 이용하는 대부분의 농가에서는 40~50$m^2$ 정도의 집열면적을 갖는 집열기를 이용하고 있는데 이 경우 년간 난방연료 절감율은 14% 정도로서 경제성이 없으며, 유동팬도 집열효율에 비해 제작, 설치 및 유지비가 과다하게 소요되므로 경제성이 없다. 각관의 경우 관 자체의 자재비나 설치비에 추가부담이 적으면서 집열효율이 비교적 높기 때문에 관의 부식, 골조 표면적 증가에 의한 시설내 차광 증가, 중도리의 각형 구조로 인한 강도저하 등의 문제가 해결되면 집열 방법으로 고려될 수 있을 것이다.

• 한국의류학회지
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• 제31권6호
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• pp.955-965
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• 2007

안전모는 다양한 산업현장에서 머리 보호를 위해 착용되는 보호구로 법적으로도 착용이 의무화되어있다. 그러나, 안전모 착용에 따른 불쾌감 및 생리적 부담은 작업자들이 착용을 꺼려하는 주된 원인이 된다. 본 연구에서는 이 문제를 해결하기 위한 하나의 방안으로 안전모에 냉매팩을 삽입하는 방법을 제안하였고, 동시에 냉매팩 삽입으로 인한 안전모의 무게 증가가 인체생리반응에 미치는 영향을 규명하고자 하였다. WBGT $33{\pm}1^{\circ}C$의 환경에서 인체착용평가 방법을 이용하여, 4가지 실험조건으로 안전모 착용시의 인체 생리반응을 조사하였고, 그 결과는 다음과 같다. 첫째, 안전모만 착용 시(OH)와 안전모 미착용시(NH)를 비교해 보면, 안전모 착용 시에 평균피부온, 직장온, 심박수, 발한량 등이 통계적으로 유의하게 높았고, 주관적인 감각에서도 더 덥고, 더 습하며, 불쾌하고 주관적으로도 힘들다고 느끼는 것으로 나타났다. 둘째, 냉매팩 삽입시의 경우(HA, HB), 냉매팩의 종류에 따라 여러 인체생리반응에 차이를 보였으나, 안전모만 착용한 경우(OH)와 비교 시 안전모내 기후, 발한량, 직장온 상승도, 열저장(heat storage) 등이 더 낮았다. 한서감과 쾌적감에서는 냉매팩 종류에 따라 다른 경향을 보였다. 본 결과를 통해 안전모 착용시의 생리적, 주관적 부담 정도를 객관적으로 파악할 수 있었으며, 안전모에 냉매팩을 삽입하는 방법을 서열 스트레스를 경감시키는 하나의 방법으로 제시할 수 있었다. 추후 연구에서는 냉매팩의 무게, 피복면적, 성분 등을 고려해야 할 것이며, 본 결과가 서열 환경에서 안전모를 착용하고 작업하는 여러 산업 근로자에게 도움이 되기를 기대한다.

• Nuclear Engineering and Technology
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• 제26권1호
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• pp.19-31
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• 1994

기사용 핵연료 저장조에 대한 열수력 해석과 관련된 인자들이 열수력 해석에 미치는 영향에 대한 분석을 수행하였다. 기사용 핵연료에서 발생하는 붕괴열(decay heat)을 제거하기 위해 일어나는 자연 순환(natural circulation)현상을 모사하기 위해 단순화된 유동망(simplified flow network)해석 모델을 사용하였다. 기사용 핵연료 저장조의 각 셀에 저장되는 연료 집합체에서 발생하는 붕괴열을 제거하기 위해 흐르는 유량의 압력 손실량이 자연순환을 일으키는 밀도차이에 의해 생성되는 구동력(driving force)과 평형을 이루는 관계를 이용하여 지배 방정식을 유도하였다. 그러나 유량, 저항 계수, 붕괴열, 밀도 등의 변수들이 서로 종속 관계를 갖기 때문에 반복 계산을 통해 해를 얻게 된다. 본 해석을 적용한 영광 3, 4호기의 경우, 12채널을 고려하였고 사용되는 입력 (저항 계수, 붕괴열)을 보수적으로 결정하였다. 본 연구를 통해 영광 3, 4호기 기사용 핵연료 저장조의 열수력 특성을 구하였다. 또한 유동로를 따라 형성되는 유동 저항중에 기하학적 요인에 의한 압력 손실은, 기사용 핵연료 저장조의 경우 압력 용기내의 유동과 달리 천이 영역(transition region)이 존재하게 되므로 Reynolds수에 민감한 것을 알 수 있다. 간극 유동은 조밀화된 연료 집합체 (consolidated fuel assembly)가 아닌 경우 무시할 수 있었다.

• 공업화학
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• 제33권1호
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• pp.58-63
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• 2022

흑연은 낮은 탈/리튬화 전압, 372 mAh/g의 높은 이론 용량, 낮은 가격 및 긴 수명 특성을 가져 지난 30년 동안 리튬이 온전지 음극 재료로 활용되었다. 최근 무기 고체 재료로 구성되어 높은 안정성을 가지는 전고체 리튬이온전지는 전기자동차 및 차세대 에너지 저장 장치로 엄청난 주목을 받고 있지만, 전고체 리튬이온전지 시스템에 잘 구동되는 흑연 연구는 부족한 실정이다. 그래서 우리는 탄소재료 표면에 존재하여 저항층으로 작용하는 비정질 탄소를 흑연으로부터 제거하여 흑연의 전기전도도 향상을 통해 황화물계 전고체 전지 음극 흑연 재료의 성능 향상을 유도했다. 400, 500 및 600 ℃ 공기 열처리된 흑연의 X-ray diffraction (XRD) 분석 결과, (002) 피크 반치폭(FWHM)이 bare 흑연보다 줄어들어 열처리 후 흑연의 결정성이 향상됨을 보였다. 또한 열처리 후 흑연의 결정성이 증가할수록 방전 용량, 초기 쿨롱효율(ICE) 및 수명 특성이 증가함을 확인했다. 500 ℃ 공기 열처리 한 흑연의 경우 331.1 mAh/g 및 ICE 86.2%와 10사이클 수명 측정 후 92.7%의 높은 용량 유지율을 나타내었다.