• Journal of Energy Engineering
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• v.21 no.1
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• pp.18-25
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• 2012

This work investigated the influence of the chimney dimensions(exit and entrance length, and diameter) on the heat transfer of a vertical cylinder in a duct. The measured mass transfer rates for the natural convection of vertical cylinder in a duct were presented for Prandlt number 2,094, Rayleigh number in the range of $4.55{\times}10^9$, $5.79{\times}10^{10}$, and $1.69{\times}10^{11}$. Experiments were performed using a copper sulfate electroplating system to simulate heat transfer based upon the analogy concept. The diameter of the duct was varied from 0.06 m to 0.14 m, and the heights from 0.30 m to 1.10 m. Nusselt numbers measured at open channel condition agreed well with the existing laminar heat transfer correlations for vertical plate developed by Le Fevre. The increase of the exit length enhanced the heat transfer up to a certain duct height but further increase does not affects the heat transfer. The heat transfer decreased with increasing the entrance length up to a certain duct height and was constant at further increase. The Nusselt number decreased with increasing the diameter of duct, until Nusselt number becomes similar to that at open channel beyond a certain diameter.

• Journal of the Korean Society of Radiology
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• v.11 no.4
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• pp.247-252
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• 2017

Radiologists who experience extravasation of the contrast medium even once suffer mentally during testing due to the fear of its reoccurrence. Establishing a plan for preventing it beforehand is necessary above all because patients experience severe physical and mental pain and become distrusting of medical staff and treatment. Therefore, the present study attempts to prevent extravasation, which is the result of damage from pressure applied to the patient's blood vessels, by lowering PSI, and conducted a comparative analysis of PSI changes during contrast medium injection depending on the diameter of the Y-shape connecting tube which connects the automatic injector and the intravenous injection of the patient. In the case of product A in which the diameter of the Y-shape connecting tube is about 2mm, the average PSI for all ages was 98.5 and standard deviation was 9.72. In the case of product B in which the diameter of the Y-shape connecting tube is about 3mm, the average PSI for all ages was 62.0 and standard deviation was 8.59. Product B with its wider diameter decreased in average pressure by 37.05% when compared to product A, and when product B is used with the p-value at 0.00, pressure decreased even more, achieving statistically significant results.

• Journal of Korean Society of Forest Science
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• v.111 no.3
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• pp.394-404
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• 2022

This study was conducted to optimize the amount of drip irrigation for Prunus×yedoensis Matsum., one of the major medium-sized landscaping trees used mainly for streetscapes and as ornamentals. The experiment was conducted in a container nursery, where we assessed the growth and physiological characteristics of 4- and 8-year-old seedlings watered at different rates (x) by a drip irrigation system. The relative growth rates (based on height and root collar diameter (RCD) measurements) were highest at 288 and 416 L/year/tree for the 4- and 8-year-old containerized seedlings, respectively. These age and treatment combinations also produced significantly different dry weight and seedling quality index values, indicating good growth. The two age groups had significantly different total root lengths, root diameters, and root volumes under these respective irrigation treatments. In addition, the 4-year-old containerized seedlings irrigated at 288 L/year/tree and the 8-year-old containerized seedlings irrigated at 416 L/year/tree had the highest activations in their chlorophyll contents. Overall, the results (differences in irrigation amounts affect the seedlings morphological relative growth, biomass growth, seedling quality, and physiological reaction) indicate that the optimal irrigation amounts for container-grown Prunus×yedoensis are 288 L/year/tree for 4-year-old (RCD class, 3cm) and 416 L/year/tree for 8-year-old (RCD class, 7 cm) containerized seedlings.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.793-800
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• 2004

In this paper, we propose a new automatic pipe grading algorithm for an efficient management of transmission pipe under the ground. Since the conventional transmission pipe evaluation was conducted by subjective decision made by an individual operator, it was difficult to grade them by means of numerical methods and also hard to realistically construct numerical database system. To solve these problems, we Int obtain some information on the current condition of pipes' sections by shooting laser beam at a regular rate and then apply grading algorithm after complete calculation of minimum diameter of pipe. We use some of preprocessing techniques to reduce noise and also use various color models to consider special conditions of each inner pipe. The measurement of pipes' minimum diameter and decision of grade are performed through a detailed processing stages. By some experimental results performed in the field, we show that over 90 percent of correct grade decisions are made by the proposed algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2195-2201
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• 2009

This paper considers the influence of suction-line heat exchangers on the efficiency of a refrigeration cycle using hydrocarbon refrigerants such as R290, R600a and R1270. These suction-line heat exchangers can, in some cases, yield improved system performance while in other cases they degrade system performance. A steady state mathematical model is used to analyze the performance characteristics of refrigeration cycle with suction-line heat exchanger. The influence of operating conditions, such as the mass flowrate of hydrocarbon refrigerants, inner diameter tube and length of suction-line heat exchanger, to the performance of the cycle is also analyzed in the paper. Results showed that the mass flowrate of hydrocarbon refrigerants, inner diameter tube and length of suction-line heat exchanger, and effectiveness have an effect on the cooling capacity, compressor work and RCI(Relative Capacity Index) of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle of hydrocarbon refrigerants using suction-line heat exchanger.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.136-143
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• 1997

직경 비가 0.56인 이중동심관에 내외측모두 매끈한 벽면, 벽면 거칠기를 안측, 외측, 그리고 양측 모두의 4경우에 대한 난류 유동과 열전달특성을 실험과 이론으로 연구하였다. 시간평균속도분포, 마찰계수, 그리고 최대 속도 지점과 전단응력이 0인 지점들을 피토튜브와 X형 열선 풍속계로 측정하였다. 이중동심관내에서 4가지 경우에 따른 사각돌출형 거칠기효과가 난류 유동과 열전달에 미치는 영향을 수정난류모델을 기초로 하여 연구하였다. 직경비, 거칠기 위치, 레이놀즈수, 그리고 프란틀수 등의 여러 변수에 의해서 난류 유동과 열전달을 고찰하였다. 본 연구는 전체적 효율 측면에서 유리하게 열전달율을 향상시킬수 있는 거칠기 구조를 밝혔다.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.873-875
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• 2002

본 논문에서는 Magnetic Yoke를 이용, 자기저항을 최소화하여 관내의 자기장을 증가시키고, 또한 펌핑 압력을 증가시킨 Linear Pump를 설계하고 제작하였다. Magnetic Fluid Linear Pump는 직경 12mm인 관에 적용할 수 있도록 설계하였으며 Magnetic Yoke는 두께 0.5mm 규소강판을 적층하여 사용하였으며, Coil은 1000 Tum으로 하여 기자력을 발생시켰다. Pump의 동작 특성을 분석하기 위하여 제작된 Magnetic fluid Lineal Puup의 내부 자기장을 측정하였으며, 인가된 자기장에 의하여 형성되는 Magnetic Fiuld의 형상을 측정하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.865-871
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• 2014

This study was conducted with the aim of developing a venturi-type air supply system for a microbubble generator. In order to determine the influence of the varying geometry of the venturi tube on the flow characteristics, a computational fluid dynamics (CFD) simulation was performed using the commercial CFD software ANSYS CFX-15. Furthermore, in order to elucidate the effects of variation in major design dimensions such as the air supply hole size, position of holes, and number of holes on the air supply characteristics, two-phase multiflow CFD analysis was performed. The analysis results showed that the starting point of expansion on the venturi tube with 0.75 is the best hole position and that the air supply hole size and the number of holes are linearly proportional to the amount of air.

• Solar Energy
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• v.14 no.2
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• pp.39-50
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• 1994

Experiments have been conducted to measure the heat transfer coefficient and pressure drop in fluidized bed double pope heat exchangers with smooth tube and longitudinal finned tube. The effect of particle size(alumina beads; do=0.41, 0.54, 0.65, 0.77 mm) and static bed height on the heat transfer coefficient has been evaluated in terms of pumping power. The heat transfer coefficient for the smooth tube and finned tube heat exchangers has been compared with single phase double pipe heat exchanger. Results show that the heat transfer coefficients for the finned tube in $2.96{\sim}3.45$ times higher than the smooth tube. The heat transfer coefficients for the fluidized bed heat exchanger is higher than the single phase heat exchanger for the most of pumping power range tested. The maximum increase in the heat transfer coefficient for fluidized bed is 91.3% for the smooth tube and 127.1% for the finned tube.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.113-113
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• 2022

도라지(Platycodon grandiflorum)는 초롱꽃과 도라지속에 속하는 여러해살이풀로 7~8월에 보라색이나 흰색의 꽃을 피우고, 뿌리는 다육질로 원주형 또는 분지형이다. 잎은 거의 엽병이 없는 대생이며, 종자는 난형으로 3개의 모서리가 있다. 항염증 성분인 플라티코딘이 들어있어 편도염을 비롯한 후두염, 폐렴 등에 효과가 있어 우리나라 약용작물 재배면적의 상위를 차지하고 있는 주요 작물이다. 최근, 백수오, 감초 등 심근성 약용작물은 뿌리의 수확 비용 절감을 위해 용기재배가 도입되고 있다. 본 연구는 도라지 용기재배에 적합한 용기의 규격과 고온 경감을 위한 용기 재료 선발을 위해 수행하였다. 도라지 용기재배에 적합한 용기의 규격 선발은 기본 용기로 플라스틱 플륨관을 사용하였고, 높이는 40cm로 고정하여 직경을 10, 20, 30cm로 처리하였다. 2019년 4월 하순에 도라지 종자를 파종하여 용기 규격별로 각각 1주(10cm), 4주(20cm), 8주(30cm)를 남겨 두고 솎음 다음, 2020년 10월 하순에 수확하였다. 도라지의 생육 및 수량성을 조사한 결과, 용기의 직경이 증가함에 따라 근장, 근경, 근중 등 지하부 생육이 우수한 경향이었다. 또한, 10a당 수량은 노지재배 749kg에 비해 직경 10cm 778kg, 20cm 849kg, 30cm 1,156kg로 직경 30cm가 가장 우수하였다. 직경이 증가할수록 수량성이 증가하였으나 직경 30cm 이상의 용기는 수확 시 노동력이 증가하고, 배양토 비용이 증가하여 사용하지 않았다. 고온 경감을 위한 용기 재료 선발은 흰색과 검정색 플라스틱 플륨관을 높이 40cm × 직경 30cm 규격으로 절단하여 2020년 4월에 도라지 종자를 파종하였고, 2021년 10월 하순에 수확하였다. 이 중 검정색 용기는 무처리(대조), 유공, 반유공, 흰색부직포, 반사필름 처리를 하였다. 도라지의 수량성을 조사한 결과, 검정색 용기 중 유공처리가 무처리 대비 수량이 21%(1,080 → 1,304kg/10a) 증가하였다. 위의 결과로 도라지는 직경 30cm의 검정색 유공 용기가 용기재배에 적합한 것으로 판단되었다.