• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.1101-1116
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• 1996

It is desirable to use the renewable energy for the greenhouse heating in winter season, it makes possible not only to save fossil fuel and conserve green farm environment but also to promote the quality of agricultural products and reduce the agricultural production cost. In this study the heat pump system was developed to use the natural energy as thermal energy resource for the thermal environment control of the greenhouse.

• Journal of the Optical Society of Korea
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• 제17권6호
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• pp.500-505
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• 2013

In this paper, we propose a novel framework to evaluate the depth resolution of axially distributed stereo sensing (ADSS) under fixed resource constraints. The proposed framework can evaluate the performance of ADSS systems based on various sensing parameters such as the number of cameras, the number of total pixels, pixel size and so on. The Monte Carlo simulations for the proposed framework are performed and the evaluation results are presented.

• 대한임베디드공학회논문지
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• 제7권2호
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• pp.103-111
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• 2012

This paper introduces a novel concept of 'A Green LED Sensitivity Lighting System' which can automatically estimate QoS(quality of service) and emotional requirements of user using smart phone. And it can intelligently control ambient illumination lamp to conserve electric energy and to satisfy human sensitivity. The proposed system has 4 control modes; emotional lighting, smart lighting, green lighting and realistic lighting modes in order to comfort man's emotion, to maximize work efficiency, to save energy consumption and to make the entertainment more fun, respectively. When we choose green lighting mode for indoor office situations, an elaborate simulation shows that the proposed system with home network can reduce the energy by 50% compared to conventional light control system with a fixed time-based switching.

• Journal of Mechanical Science and Technology
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• 제15권8호
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• pp.1174-1180
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• 2001

Various experimental data, including mixing areas, cross correlation factors, surface flow patterns on nozzle walls, and far field noise spectra, was used to draw a noise control mechanism in a supersonic jet. In the underexpanded case, mixing of the jet air with ambient air was significantly enhanced as presented before, and mixing noise was also dramatically reduced. Screech tones, in the overexpanded case, were effectively suppressed by trailing edge modifications, although mixing enhancement was not noticeable. From mixing and noise performance of nozzles with modified trailing edges, enhancing mixing through streamwise vortices seems an effective way to reduce mixing noise in the underexpanded flow regime. However, screech tones in the overespanded flow regime is well controlled or suppressed by making shock cells and/or spanwise large scale structures irregular and/or less organized by a proper selection of trailing edges. The noise field in the overexpanded flow regime was greatly affected by the symmetricity of the nozzle exit geometry. In the underexpanded flow regime, the effects of the symmetricity of the nozzle exit on mixing were negligible.

• 대한기계학회논문집
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• 제19권7호
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• pp.1780-1786
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• 1995

The main goal of the present study is to establish the techniques and methodolgies of turbine performance test through evaluating the objective turbine test piece, and checking the reliability of the self-developed test facility by performing a series of turbine tests under ambient temperature condition. A high speed coupling, a lubrication system and a test bed of the test facility were modified through a series of preliminary test in order to reduce the vibration and oil leakage. The flowrate control of the test facility and data acquisition were accomplished by using a software called "Labview" The measurement of shaft horse power and control of rotational speed according to the conditions of turbine rotation were performed by a separate system. The preliminary evaluation of the measured data suggests that the developed test facility and the test technique can be used reliably for the performance test of turbines with the minor improvement.provement.

• Smart Structures and Systems
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• 제19권5호
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• pp.567-576
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• 2017

Design of piezoelectric energy harvester for a wide operating frequency range is a challenging problem and is currently being investigated by many researchers. Widening the operating frequency is required, as the energy is harvested from ambient source of vibration which consists of spectrum of frequency. This paper presents a new technique to increase the operating frequency range which is achieved by designing a harvester featured by a propped cantilever beam with variable over hang length. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory and the effectiveness of the harvester is demonstrated through experimentation. The results from analytical model and from experimentation reveal that the proposed energy harvester generates an open circuit output voltage ranging from 36.43 V to 11.94 V for the frequency range of 27.24 Hz to 48.47 Hz. The proposed harvester produces continuously varying output voltage and power in the broadened operating frequency range.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.303-306
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• 1994

This paper presents a new rotor resistance identification algorithm for induction motors. The algorithm is derived form the fact that the slip frequency given in the d-q rotating frame is equal to that measured in the x-y fixed frame. Rotor resistance varies greatly with the machine temperature. In certain cases, the rotor resistance can increase 100 % over its ambient or nominal value. This deteriorates the dynamic performance of vector control systems for induction motors. However, the control scheme proposed in this paper is robust with respect to variations in rotor resistance because an efficient identification algorithm for rotor resistance is employed. To illuminate the performance of the proposed controller further, the simulation results are presented.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.413-418
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• 1998

We often use induction motor in the hard environment including vibration and high ambient temperature, or in maintenance free operation, because induction motor has durable and simple structure. However, when we use it as servo actuator or accurate speed control motor, we have to equip sensor such as encoder and tachogenerator with the motor control system. And generally those sensor's abilities against bad environment are less than the induction motor itself, So if we can remove these sensors from the system, it'll have more environmental resistance, and the cost will also be reduced. Actually this removal has been achieved in limited field. However, that needs complex calculations and a certain elapse time for data processing. In our study, we intended to estimate the rotational speed from the motor current instead of speed sensor, easily and rapidly in comparison to former methods.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.681-684
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• 2006

Control of the temperature difference across a section is an effective way to minimize the hydration-heat-induced cracks for the structures where internal restraint is dominant. However, surface temperature may not be easily measured in situ due to the difficulty in maintaining the correct location during casting. A prediction equation for the temperature difference is proposed which can be applied without directly measuring the surface temperature if the curing condition and ambient temperature are known. Some strategies to control the temperature difference are revisited and a reasonable range of the temperature difference to minimize the crack is discussed.

• 한국농림기상학회지
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• 제18권4호
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• pp.179-187
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• 2016

본 연구는 미래 기후변화 시나리오에 근거하여 예측되는 온도 및 이산화탄소 농도 상승조건에서 노지채소인 '무한질주' 고추의 생육 및 과실품질에 미치는 영향을 구명하기 위해 SPAR (Soil Plant Atmosphere Research) 챔버에서 수행하였다. 대조구인 대기온도는 노지고추 주산지인 안동지역의 평년(1971~2000; 30년) 5~10월의 생육기 평균기온($20.8^{\circ}C$)을 기준으로 설정하였다. 처리구는 대조구(대기온도, 400ppm $CO_2$), 이산화탄소 상승구(대기온도, 800ppm $CO_2$), 온도 상승구(대기온도+$6^{\circ}C$, 400ppm $CO_2$), 이산화탄소+온도 상승구(대기온도+$6^{\circ}C$, 800ppm $CO_2$) 등 4수준으로 설정하였다. 대조구보다 고온 및 상승 이산화탄소 농도 조건에서 재배하였을 때 초장, 분지수, 엽수 등이 증가하였으나, 엽면적과 SPAD값은 급격히 감소하였다. 개화 및 꽃봉오리수도 온도 및 이산화탄소 농도가 증가할수록 급격히 감소되었다. 또한, 개체당 총 착과수와 총 착과중도 대조구에 비해 감소하였는데 과실무게도 약간 적었고 과실 길이와 과실 두께도 약간 줄었다. 이상의 결과로 보아 기후변화시나리오에 근거로 대기 중 $CO_2$ 농도는 2배, 기온은 $6^{\circ}C$ 높은 환경 조건에서는 고추의 착과가 저해되고 과실 수량도 크게 감소하였으나, 완숙 과실의 비율은 증가하여 수확시기가 다소 앞당겨질 것으로 보인다.