• 한국기계기술학회지
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• 제13권3호
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• pp.107-111
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• 2011

This carbon nano heating system was consisted of power supply equipment, a carbon fiber and a stainless flexible hose. carbon nano heating system was manufactured by carbon fiber of a power capacity 30kw/h and light-oil hot air heater in control plot was the heating capacity 30,000kcal/h, As the result, Temperature difference due to carbon nano heating system and hot air heater in greenhouse showed that air temperature at experimental greenhouse, comparison greenhouse were $14.8^{\circ}C$, $13.4^{\circ}C$ respectively. It was found that carbon nano heating system and light-oil hot air heater heating cost were 1,095,740won, 2,683,628won. therefore as heating cost saving 60%. Yield of tomatoes cultured in greenhouse using carbon nano heating pipe was 4% inclease. Economic analysis comparison between the carbon nano heating pipe and the hot air heater in greenhouse were 41% respectively.

• 한국염색가공학회지
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• 제32권4호
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• pp.239-244
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• 2020

Polyethylene (PE) micro-fiber have been prepared at different hot air temperature (60, 80 and 100 ℃) and different pressure (20, 40, 60 and 80 kPa) by melt centrifugal spinning technique. The parameters of melting centrifugal spinning including polymer contents, rotational velocity, temperature of hot air and pressure were optimized for the fabrication process. The study showed that 8000 rpm rotational velocity, 80 ℃ heated hot air and 40 kPa air pressure are the best condition to obtain uniform and strong PE fiber. The prepared PE fibers were analyzed by field emission scanning electron microscope and universal testing machine and found that fibers with reduced diameter and improved tensile strength are obtained at hot air condition.

• 한국자동차공학회논문집
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• 제5권6호
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• pp.1-12
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• 1997

In an SI engine, the characteristics of the air flow is important not only for the design of the intake system geometry but also for the accurate measurement of the induction air mass. In this study, an air flow rate measurement using the ultrasonic flow meter and hot wire flow meter was conducted at the upstream of the intake port and the throttle. At the upstream of the intake port, the pulsating flow into the cylinder affected by the pressure wave was detected directly with the flow meters instead of pressure sensors. At the upstream of the throttle, the reverse flow phenomena were showed by comparing the flow pattern measured by the hot wire air flow meter and the ultrasonic air flow meter. The results of this study can be used for the analysis of the tuning effect in the intake manifold and estimation of the error in real time measurement for the air flow rate.

• Preventive Nutrition and Food Science
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• 제13권3호
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• pp.225-230
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• 2008

Onion slices were dehydrated in a single layer at drying air temperatures ranging from $50{\sim}70^{\circ}C$ in a laboratory scale convective hot-air dryer at an air velocity of 0.66 m/s. The effect of drying air temperature on the drying kinetic characteristics were determined. It was found that onion slices would dry within $210{\sim}460\;min$ under these drying conditions. Moisture transfer during dehydration was described by applying the Fick's diffusion model and the effective diffusivity changed between $1.345{\times}10^{-8}$ and $2.658{\times}10^{-8}\;m^2/s$. A non-linear regression procedure was used to fit 9 thin layer drying models available in the literature to the experimental drying curves. The Logarithmic model provided a better fit to the experimental drying data as compared to other models. Temperature dependency of the effective diffusivity during the hot-air drying process obeyed the Arrhenius relationship with estimated activation energy being 31.36 kJ/mol. The effect of the drying air temperature on the drying model constants and coefficients were also determined.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1021-1026
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• 2014

본 논문에서는 hot-gas를 이용한 다양한 바이패스 제어 방식 중에서 증발기 흡입부 방식에 대해 각각의 성능에 영향을 미치는 외기온도, 출수온도, 과열 및 과냉도 등에 대해서 알아보았다. 그 주요 결과를 요약하면 다음과 같다. 우선, 증발기 흡입부로 hot-gas를 바이패스 하였을 경우에 냉동장치의 성능은 외기온도, 출수온도, 과열 및 과냉도 등에 영향을 받는 것을 알 수 있었다. 따라서 이러한 변수에 대한 최적화를 통해 본 냉동장치의 기초 설계 자료를 제공할 수 있다. 그리고 증발기 흡입부 hot-gas 바이패스 방식의 운전특성을 고찰하여 본 논문에서 제안하는 냉동장치에 대한 적용 가능성을 확인할 수 있었다.

• 한국식품영양학회지
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• 제27권2호
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• pp.219-224
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• 2014

복숭아의 저장성 증진을 위하여 $46^{\circ}C$의 열풍건조기에서 0~9시간 동안 처리한 후, 저장 기간 중 화학성분들과 항산화 활성이 변화하는지를 측정하였다. 복숭아 중 ascorbic acid의 함량은 13.81 mg%였으며, 열풍처리군은 11.73~14.16 mg%로 대조군과 큰 차이를 보이지 않아, 열풍처리에 의한 변화는 없는 것으로 나타났으며 저장 중 함량 변화에서는 6시간 열풍처리군을 제외하고는 대체적으로 감소하는 경향이었으며, 대조군의 변화가 가장 빠른 것으로 나타났다. Polyphenol 화합물의 함량은 대조군은 22.64 mg%였으며, 열풍처리군은 19.03~23.19 mg%로 복숭아 저장성 증진을 위한 열풍처리의 변화는 없는 것으로 나타났으며, 저장 중의 변화에서는 대조군보다는 열풍처리군에서 약간 높은 함량을 유지하는 경향이었다. Flavonoid 함량에서는 대조군 및 열풍처리군 모두 저장하는 동안 특정한 경향을 보이지는 않는 것으로 나타났다. 유리당의 변화에서는 대조군 및 열풍처리군 모두 개체 차이일 뿐 큰 차이를 보이지 않았으며, 저장 중 변화에서도 차이를 보이지는 않는 것으로 나타났다. 항산화 활성의 변화도 대조군과 열풍처리군 모두 차이를 보이지 않았다.

• 설비공학논문집
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• 제30권3호
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• pp.149-157
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• 2018

In this research, the psychological and physiological reactions of the driver were measured during winter to evaluate thermal comfort. The experiment was conducted using 3 different cases which are hot air heating, warm-wire seat heating and hot air & warm-wire seat heater operating simultaneously. With regard to psychological reaction, the warm-wire heating mode was the most preferred. The reason is that it is dry in other cases. With regard to EEG response, thermal comfort increased by 37% in warm air mode heating. In addition, when the warm-wire heating mode and the hot air & warm-wire heating mode were simultaneously operated, the thermal comfort continuously increased by between 17% and 20% for 20 minutes after boarding. Under the change of the autonomic nervous system, the thermal stress level increased by 23% after 15 minutes on board in the hot air heating mode and decreased continuously by 13% during the warm-wire seat heating mode. We recommended the hot air heating mode is only used for a short time to raise the inside temperature during the early boarding period and that warm-wire seat heating mode be actively utilized.

• 한국태양에너지학회 논문집
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• 제35권3호
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• pp.73-79
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• 2015

In this study, a thermal storage performance and characteristics of daily operation were investigated when the air and the liquid were heated simultaneously by a hybrid solar air-water heater that can make hot water as well as heated air. The hybrid solar air-water heater is kind of a flat plate solar collector that can make hot water and heated air by installing air channel beneath absorber plate of traditional flat plate solar collector for hot water. As a result of daily operation, maximum water temperature reached in a thermal storage was shown $44^{\circ}C$ on 73kg/h of air mass flow rate and about $40^{\circ}C$ on 176kg/h of air mass flow rate. Thus, the necessity of heating water in thermal storage by operating only liquid side was confirmed when the temperature of liquid in thermal storage is lower than we need. In case of efficiency investigated on daily operation, the thermal efficiency of the liquid side was decreased with increment of the inlet liquid temperature and decrement of the solar radiation, but efficiency of the air side was increased with increment of inlet liquid temperature difference as the traditional solar air heater. Total thermal efficiency of the collector was shown from 65.85% to 78.23% and it was decreased with increment of the inlet liquid temperature and decrement of solar radiation same as the traditional system.

• Journal of Mechanical Science and Technology
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• 제18권2호
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• pp.286-293
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• 2004

The air fuel ratios of current gasoline engines are almost controlled by several air flow meters. When CVVT (Continuous Variable Valve Timing) is applied to a gasoline engine for higher engine performance, the MAP (Manifold Absolute Pressure) sensor is difficult to follow the instantaneous air fuel ratio due to the valve timing effect. Therefore, a HFM (Hot Film Flow Meter) is widely used for measuring intake air flow in this case. However, the HFMs are incapable of indicating to reverse flow, the oscillation of intake air flow has an negative effect on the precision of the HFM. Consequently, the various duct configurations in front of the air flow sensor affect the precision of HFM sensitivity. This paper mainly focused on the analysis of the reverse flow, flow fluctuation in throttle upstream and the geometry of intake system which influence the HFM measurement.

• Food Science and Biotechnology
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• 제14권5호
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• pp.661-666
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• 2005

The specific objectives of this study were to dry yam chips using microwave vacuum drying, freeze drying and hot air drying, then to coat the dried yam chips with ascorbic acid cocrystallized sucrose, and finally to compare the quality of yam chip snack foods with respect to drying and coating characteristics. The microwave vacuum dried sample showed the highest drying rates and much less surface damage than the hot air dried one did. The shape and color of the microwave vacuum dried/coated sample were allocated between those of the freeze dried/coated sample and the hot air dried/coated sample. The freeze dried/coated sample scored excessively low in organoleptic hardness and chewiness to be suitable as a snack. The hot air dried/coated sample was too deep in color, wrinkled, excessively high in organoleptic hardness and chewiness, and excessively low in mouthfeeling. Therefore, the microwave vacuum dried/coated sample presented the best overall attributes as a snack, with respect to organoleptic characteristics, shape, color, and drying rates.