• 설비공학논문집
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• 제18권1호
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• pp.55-65
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• 2006

The air and water flow distribution are experimentally studied for a round header - flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is thirty. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.

• 설비공학논문집
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• 제28권11호
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• pp.444-449
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• 2016

The main objective of this work is to experimentally investigate the effect of angle variation and intrusion depth of channels on the distribution of two-phase flow at header-channel junctions. The dimensions of the header and the channels in cross-section were fixed at $16mm{\times}16mm$ and $12mm{\times}1.8mm$, respectively. Air and water were used as the test fluids. Two different header-channel positions were tested : a vertical header with horizontal channels (case VM-HC) and a horizontal header with horizontal channels (case HM-HC). In all cases, the intrusion depths of the channels are 0 mm, 2 mm, and 4 mm. For the case of the intrusion depth of VM-HC, the flow distribution became more uniform. However, the intrusion depth negatively affected the flow distribution for the case of HM-HC because liquid separation delay occurred.

• 자원환경지질
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• 제32권5호
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• pp.503-517
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• 1999

The purpose of this study is to verfify a more effecive techique for calculating geothermal gradient. this study examines 370 data of temperature-logging having been collected since 1985. The daya are divided into three different grades grades according to the type of temperature-depth plots: 204 data show typical linear gradient (Grade A); 126 data do not explicitily show the gradient becase of various external effects such as water flow (Grade B); and the rest 40 data do not show the gradient at all (Grade D). The new technique for calculating geothermal gradient is to be required to use Greade-B data more effctiviely. This new technique includes (1) calculating the independer depth of atmospheric temperature in the earth; (2) drawing a distribution map of subsurface tempurature by using the distribution map of subsurface temperature by using Grade-A data at the independent depth; and (3) recalculating geothermal gradient of Grade-B data by using the distrbution map of subsurface temperature, borehole depth, and bottom temperature of Grade-B data by using the distribution map of subsurface temperature, borehole depth, and bottom temperature of Grade-B data. As a result, 330 data-both Grade-A and Grade-B data--can be used to draw a distribution map of hot spradient. The map clearly distinguishes anomaly areas, and helps interpret their relations to the distribution of hot springs, geology, geological structures, and geophysical anomaly areas. These new results reveal that the average of geothermal in south Korea is 25.6$^{\circ}C$/km, when calculated to the Kriging method.

• 설비공학논문집
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• 제27권9호
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• pp.491-496
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• 2015

Generally, the phase of the refrigerants that circulate in air-conditioning systems is repeatedly changed from liquid to gas and from gas to liquid. In vapor-compression refrigeration, the refrigerant at the inlet of the evaporator is in a gas-liquid two-phase state; therefore, to enhance the heat-transfer performance of the evaporator, the even distribution of the refrigerant across multiple passages of the evaporator is essential. Unlike the distribution of a single-phase refrigerant, multi-phase distribution requires further considerations. It is known that the multi-phase distribution at the outlet of the distributor is affected by factors such as the operating condition, the distributor's shape, and the insertion depth of the outlet pipes; here, the insertion depth of the outlet pipes is especially significant. In this study, for a cylindrical distributor with a 90-degree bend entrance and three outlet pipes, the flow uniformity at the outlet pipes was numerically tested in relation to variations of the insertion depth of the outlet pipes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.2068-2070
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• 2000

Ground potential rise is a vital part of personal safety, this paper presents the ground potential rise distribution induced by a ground rod. The experiments were conducted with the AC square wave currents according to the buried depth of ground rod. The ground potential is significantly varied in the vicinity of ground rod and the ground potential distribution is flat and few with increasing the buried depth of ground rod.

• Journal of Advanced Marine Engineering and Technology
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• 제28권8호
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• pp.1195-1202
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• 2004

In this paper an experimental study was investigated for two-phase flow distribution in compact heat exchanger header. A test section was consisted of the horizontal bottom dividing header($\phi$: 5 mm, L: 80 mm) and 10 upward circular mini channels ($\phi$: 1.5 mm, L: 850 mm) using an acrylic tube. Three different types of tube intrusion depth were tested for the mass flux and inlet mass quality ranges of 50 - 200 kg/$m^2$s and 0.1 - 0.3, respectively. Air and water were used as the test fluids. The distribution of vapor and liquid is obtained by measurement of the total mass flow rate and the calculation of the quality. Two-phase flow pattern was observed, and pressure drop of each channel was measured. By adjusting the intrusion depth of each channel an uniform liquid flow distribution through the each channel was able to solve the mal-distribution problem.

• 한국안전학회지
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• 제32권6호
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• pp.1-8
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• 2017

P-PIE is a program developed to estimate failure probability of pipes and pressure vessels considering fatigue and stress corrosion crack growth. Using the program, crack growth simulation was performed with an initially existing crack in order to examine the effects of initial crack depth distribution on the leak probability of pipes. In the simulation stress corrosion crack growth was considered and several crack depth distribution models were used. From the results it was found that the initial crack depth distribution gives great effect on the leak probability of pipes. The log-normal distribution proposed by Khaleel and Simonen gives lower leak probability compared other exponential distribution models. The effects of the number and the quality of pre-service and in-service inspections on the leak probability were also examined and it was recognized that the number and the quality of pre-service and in-service inspections are also give great effect on the leak probability. In order to reduce the leak probability of pipes in plants it is very important to improve the quality of inspections. When in-service inspection is performed every 10 years and the quality of inspection is above the very good level, the leak probability shows nearly constant value after the first inspection for an initially existing crack.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.214-215
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• 2002

Generally uniform dose distribution is assumed to be formed in a target region when a conventional dose formation method using a broad proton beam, a fixed modulation technique, a bolus and an aperture is employed. However, actual situations differ. We usually find non-uniformity in the target region. This is due to the insertion of a range-compensating bolus before the patient. Since the range-compensating bolus has an irregular shape, the scattering in the bolus depends on the lateral position. Dose distribution is overlapping results of dose distribution of pencil-proton beams traversing different lateral positions of the bolus. The lateral extent of dose distribution of each pencil beam traversing the different position differs each other at the same depth in the target object. This is a cause of the non-uniformity of the dose distribution. Therefore the same lateral extent of dose distribution should be attained for different pencil beams at the same depth to obtain a uniform dose distribution. For that purpose, we propose here a bi-material bolus. The bi-material bolus consists of a low-Z material determining mainly the range loss and a high-Z material defining mainly the scattering in the bolus. After passing through the bi-material bolus, protons traversing different lateral positions will have different residual range yet with the same lateral spread at a certain depth. Using the optimized bi-material bolus, we can obtain a more uniform dose distribution in the target region as expected.

• 한국농공학회지
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• 제42권1호
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• pp.66-72
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• 2000

A study was conducted to find distribution patterns of minisprinkler without a bridge for the desing of microirrigation systems. The experiments were executed in a plastic house to minimize the effect of the wind. Data were collected at four different operation pressures and at 3 different riser heights. Sprayed water were collected by aluminium cans with 65mm diameter and 100mm height placed at 0.3m grid spacing . A schematic distribution pattern with distance from a minisprinkler was suggested for the layout design of the minisprinkler. Distribution pattern of the minisprinkler was found irregular in space. Distributin performance characteristics of the minisprinkler such as effective radius. , effective area, mean application depth, absolute maximum application depth, effective maximum application depth and coefficient of variation were determined. It was indicated that there is a trend of decrease in variation coefficient adn better water distribution by the increase in operation pressures and riser heights.

• 아시안잔디학회지
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• 제11권2호
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• pp.89-95
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• 1997

Soil chemical properties were investigated to elucidate vertical movement of mineral nutrients in a fairway slope of 27 year-old golf course. Soil samples were taken at every 10cm depth to 4Ocm on 4 sites 20m apart each along two parallel lines 60m apart on the slope(15˚) in August. Accord-ing to the similarity of vertical distribution pattern they could be classified into 6 distinctive groups(magnesium, nitrate, phosphorus, ammonium, manganese and copper) and the slope tended to affect the vertical movement of minerals. The contents of Ca and Mg increased with depth while NO$_3$-N and Zn decreased and correlated positively. Soil pH showed significant positive correlation with depth, Ca and Mg. Phosphorus content was highest in 10~20cm depth and decreased resulting in relatively high content in 30~40cm depth of the bottom site of slope. Iron distribution pattern was similar to phosphorus. Potassium and $NH_4$showed various(irregular) patterns. Mn was highest in the deep layer at the lower sites of slope but it was reverse at the upper sites and negatively correlated with Fe. Cu content incresed with depth and heighest in 20~30cm depth. Electroconductivity showed significant positive correlation with $NO_3$-N. Magnesium, cal-cium and copper seem to be prone to defficiency due to fast leaching, and nitrate and phosphorus prone to excess problem. Preventive measures on acidification of surface soil should be taken.