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자동점적관수에 의한 토성별 수분함량 및 장력 변화특성 비교 연구
김학진,안성욱,한경화,최진용,정선옥,노미영,허승오 (사) 한국생물환경조절학회 2013 생물환경조절학회지 Vol.22 No.4
Maintenance of adequate soil tension or content during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil tension and content for precision irrigation would allow optimal soil water condition to crops and minimize the adverse effects of water stress on crop growth and development. This research reports on a comparison of soil water tension and content variations in differently textured soils over time under drip irrigation using two different water management methods, i.e. pulse time and required water irrigation methods. The pulse time-based irrigation was performed by turning the solenoid valve on and off for preset times to allow the wetting front to disperse in root zone before additional water was applied. The required water estimation method was a new water control logic designed by Rural Development Administration that applies the amount of water required based on a conversion of the measured water tension into water content. The use of the pulse time irrigation method under drip irrigation at a high tension of −20 kPa and high temperatures over 30oC was not successful at maintaining moisture tensions within an appropriate range of 5 kPa because the preset irrigation times used for water control could not compensate for the change in evapotranspiration during day and night. The response time and pattern of water contents for all of the tested soils measured with capacitance-based sensor probes were faster and more direct than those of water tensions measured with porous and ceramic cup-based tensiometers when water was applied, indicating water content would be a better control variable for automatic irrigation. The required water estimation-based irrigation method provided relatively stable control of moisture tension,even though somewhat lower tension values were obtained as compared to the target tension of −20 kPa, indicating that growers could expect to be effective in controlling low tensions ranging from −10 to −20 kPa with the required water estimation system. 본 연구에서는 토성에 따른 물의 이용효율을 높이면서재배 작물의 생산성을 최대화하기 위한 효율적인 자동관개 로직을 개발하고자, 수분장력값을 관수 개시점으로하여 물 공급 유지와 멈춤을 간헐적으로 수행하는 펄스형 관개방식과 측정한 수분장력값을 이용하여 토양수분량을 예측해 재배작물에 적합한 물량을 추가 투입하는필요물량계산 관수방식을 적용하여 토성이 다른 실험베드에서 2년간 토마토 작물을 재배하면서 토양수분 함량과 장력의 변화를 측정비교하였다. 물공급 30초와 멈춤30분 및 15분 조건을 이용한 펄스형 관수방식과 필요물량계산 방식에서 얻어진 수분장력값은 목표한 −20kPa 조건에 비해 각각 −42~−8kPa, −20~−10kPa로 나타나 필요물량 계산방식이 균일한 수분장력을 유지하는 측면에서는 유리하였으나 토양수분상태는 상대적으로 습하였다. 공시 토성 모두에서 수분함량은 수분장력에 비해 시간반응이 빠르면서 물공급에 따라 비례적으로 증가하는 경향이 뚜렷하였다. 수분변화 값은 펄스형 관수와 필요물량계산 관수방식의 경우 사양토 기준으로 각각 17~24%, 19~31%로서 펄스형 관수방식이 수분변화 값이 작으면서 시간에 따라 안정적인 값을 유지한 것으로 나타났는데 이는 물공급에 따른 수분함량의 시간변화가 수분장력에 비해 뚜렷하게 빠름과 관계가 있는 것으로 판단하였다. 이러한 결과로부터 펄스형 관수방식은 수분함량값을 이용하여 수분을 조절하는 것이 유리함을 의미한다.
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Pulsed Nd:YAG 레이저를 이용한 Al 1050 재료의 미세 천공에 대한 기초 연구
안동규(Dong-Gyu Ahn),정광운(Kwang-Woon Jung),유영태(Young-Tae YOO),신호준(Ho-Jun Shin) 한국생산제조학회 2007 한국공작기계학회 춘계학술대회논문집 Vol.2007 No.-
Recently, industrial applications of laser micro-drilling have been continuously increased to produce micro-parts including electronic and photonic components, semiconductor and others. The objective of this paper is to investigate into the influence of process parameters, such as the laser power, a focal length and the gas pressure, on the quality of drilled parts for the case of micro-drilling of Al 1050 using the pulsed Nd:YAG laser. Several micro-drilling experiments have been carried out to obtain optimum drilling condition. In order to reduce a number of experiments, Taguchi's method with L?(3⁴) of orthogonal array has been utilized. From the results of the experiments, it has been shown that an optimum micro-drilling condition are the gas pressure of 0.02 ㎫, the focal length of 6 ㎜ and the laser power of 72.5 W.
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고체로켓 연소관 내 압력섭동에 대한 입자상 물질에 의한 음향 감쇠 및 연소응답 특성 측정
임지환(Jihwan Lim),이상협(Sanghyup Lee),윤웅섭(Woongsup Yoon) 한국추진공학회 2014 한국추진공학회지 Vol.18 No.2
T-Burner tests of an Al/HTPB propellant in conjunction with a Pulsed DB/AB Method were conducted to find an acoustic amplification factor. Aluminum-free and aluminum-heavy propellants were examined. Instant surface ignition was successfully made by the use of a supplementary propellant of fractionally higher reaction rate. With the presence of higher aluminum concentration in the propellants, the pressure perturbations were promptly damped down and the pressure fluctuations were no longer dispersive. Addition of aluminum particles into the propellant was advantageous for stabilizing pressure-coupled unstable waves.
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