• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 1995년도 춘계학술발표회 초록집
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• pp.223-229
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• 1995

Heat transfer phenomena during freezing process of the water in a vertical cylinder were experimentally studied. Purified water was inserted into the vertical cylinder Experiment was performed with two conditions ; the inlet temperature of the working fluid was maintained to be -1$0^{\circ}C$ and the direction of the working fluid was to be upward or downward. Both the mean temperature of the liquid and temperature difference of cylinder tube wall in the upward were lower than those in the downward. In addition, shape of ice layer in the upward was more uniform than that in the downward. Finally, time-varying total heat energy stored in the water in the upward was higher than that in the downward.

• 태양에너지
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• 제6권1호
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• pp.60-69
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• 1986

Two-dimensional finite difference numerical analysis is used to study conjugate natural convection heat transfer from a horizontal conducting tube with one vertical axial fin. By increasing dimensionless fin length ($L_F$), the mean total Nusselt number of the upward fin is slightly less than that of the downward fin at $L_F\;{\le}\;0.18$ and is higher than that of the downward fin at $L_F\;>\;0.18$. However comparing the upward fin and the downward fin with the no fin, the mean total Nusselt numbers of downward fin and upward fin at $L_F=0.30$ are increased approximately 4.01% and 5.51%, respectively. As Rayleigh number, Prandtl number and Biot number increase, the mean total and the mean tube Nusselt numbers are increased, but as wall thickness increases, the mean total and the mean tube Nusselt numbers are decreased. As the fin conduction parameter increases, the mean total Nusselt number is slightly increased because of increasing the mean fin Nusselt number.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.546-553
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• 2022

Narrow rectangular channels are employed in nuclear research reactors that use plate-type nuclear fuels, high heat-flux compact heat exchangers, and high-performance micro-electronics cooling systems. Two-phase flow in narrow rectangular channels is important, and it needs to be better understood because it is considerably different than that in round tubes. In this study, mechanistic models were developed for the flow regime transition criteria for various flow regimes in co-current air-water two-phase flow for vertical downward flow inside a narrow rectangular channel. The newly developed criteria were compared to a flow regime map of downward air-water two-phase flow inside a narrow rectangular channel with a 2.35-mm gap width under ambient temperature and pressure conditions. Overall, the proposed model showed good agreement with the experimental data.

• 대한정형도수물리치료학회지
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• 제22권1호
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• pp.51-58
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• 2016

Background: Evidence for effective management of scapular downward rotation syndrome is limited. The present study was performed to compare the scapular muscle activation through 4weeks wall slide exercise and sling slide exercise in subjects with scapular downward rotation syndrome. Methods: Twenty-two subjects with scapular downward rotation syndrome participated in the study. Surface electromyography data were collected from the upper and lower trapezius, serratus anterior and pectoralis major during shoulder flexion of $60^{\circ}$, $90^{\circ}$ and $120^{\circ}$ in the sagittal plane. The alignment of the scapula was measured using radiographic analysis. Subjects were assessed pre and post a 4 weeks exercise (wall slide, sling slide). The significance of the difference in pre- and post-exercise within each groups was assessed using a paired t-test. The significant difference between wall- and sling-exercise was used a independent t-test. Results: In the wall slide group, the muscle activity of upper trapezius decreased significantly during shoulder flexion at $60^{\circ}$, $90^{\circ}$ and $120^{\circ}$ after 4 weeks, and the muscle activity of serratus anterior increased significantly at all angles. Also, the muscle activity of pectoralis major decreased significantly at $90^{\circ}$ and $120^{\circ}$. Conclusions: Based on such results, it can be said that wall slide exercise is effective than sling slide exercise for the subjects with scapular downward rotation syndrome.

• 한국전문물리치료학회지
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• 제21권3호
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• pp.73-79
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• 2014

The purposes of the current study were to (1) estimate the inter-rater agreement for visual assessment of scapular downward rotation (SDR), (2) develop the scapular downward rotation index (SDRI) as a method to measure SDR objectively and quantitatively, and (3) analyze the intra- and inter-rater reliability of the SDRI. Twenty subjects with scapular downward rotation syndrome (SDRS) were recruited for this study. The visual assessment and the measurement for the SDRI were conducted by two examiners in two sessions each. The SDRI [$(a-b){\div}a{\times}100$] is calculated with the measurement of two linear distances: One is a perpendicular distance from the root of the scapular spine to the thoracic mid-line (a), and the other is a perpendicular distance from the inferior angle of the scapula to the thoracic mid-line (b). Cohen's kappa coefficient was calculated to estimate the inter-rater agreement for visual assessment. Intra-class correlation coefficients (ICCs) with a 95% confidence interval (CI), the standard error of measurement, and minimal detectable differences were calculated to assess intra- and inter-rater reliability of SDR measurement using the SDRI. The results indicated that the kappa coefficient of inter-rater agreement for visual assessment was fair (${\kappa}=.21$). The intra-rater reliability of SDR measurement using the SDRI was excellent for examiner 1 (ICC=.92, 95% CI=.78~.97) and good for examiner 2 (ICC=.82, 95% CI=.55~.93). The inter-rater reliability was moderate (ICC=.73, 95% CI=.32~.89). These findings showed that SDR measurement using the SDRI for subjects with SDRS may be considered reliable and better than the visual assessment.

• 한국운동역학회지
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• 제24권2호
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• pp.151-160
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• 2014

The purpose of this study was to investigate the GRF(ground reaction force) parameters according to the shoes's heel heights and ground landing distances during downward stairs on bus. Participants selected as subject were consisted of young and healthy women(n=9, mean age: $21.30{\pm}0.48$ yrs, mean height: $164.00{\pm}3.05cm$, mean body mass: $55.04{\pm}4.41kg$, mean BMI: $20.47{\pm}1.76kg/m^2$, mean foot length: $238.00{\pm}5.37mm$). They were divided into 2-types of shoe's heel heights(0 cm/bare foot, 9 cm) and also were divides into downward stairs with 3 types of landing distance(20 cm, 35 cm, 50 cm). A one force-plate was used to collect the GRF(AMTI, USA) data from the sampling rate of 1000 Hz. The GRF parameters analyzed were consisted of the medial-lateral GRF, anterior-posterior GRF, vertical GRF, loading rate, Center of Pressure(${\Delta}COPx$, ${\Delta}COPy$, COP area) and Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) during downward stairs on bus. Medial-lateral GRF and vertical GRF didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 9 cm shoes heel showed higher vertical GRF than that of 0 cm bare foot in landing distance of 50 cm. Also anterior-posterior GRF didn't show significant difference statistically according to the shoe's heel heights, but landing distance of 20 cm showed higher than that of landing distances of 35 cm and 50 cm in anterior-posterior GRF. Loading rate didn't show significant difference statistically according to the landing distance, but 9 cm shoe's heel showed higher than that of 0 cm bare foot during downward stairs. The ${\Delta}COPy$ and COP area didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 0 cm bare foot showed higher than that of 9 cm shoe's heel in ${\Delta}COPx$. Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) didn't show significant differences statistically according to the landing distance, but 9 cm shoe's heel showed decreased value than that of 0 cm bare foot in dynamics balance. Considering the above, parameters of GRF showed different characteristics according to the shoe's heel heights and ground landing distances during downward stairs on bus.

• 자원환경지질
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• 제28권6호
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• pp.553-558
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• 1995

본 논문에서는 깊이에 따라 밀도값과 (종파)속도값이 변하는 지하 하부층들의 반사계수로부터 밀도와 속도 주상도를 구하는 알고리즘을 개발하고자 하였다 하향연속(下向連續) 혹은 박층(剝層 layer stripping) 방식 알고리즘은 적분방정식을 이용한 계산법보다 계산 과정을 상당히 줄일 수 있다. 본 논문에서는 여러 방향으로의 입사파에 의한 반사계수를 개선된 하향연속 알고리즘을 이용하여 처리하였으며, 각 깊이에서 최소자승 맞춤(fitting)을 실행하였다. 본 연구결과는 다른 하향연속 알고리즘에 비하여 상당한 성과를 보여주고 있다.

• 대한한의학회지
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• 제26권4호
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• pp.162-167
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• 2005

According to the principle of ascending water and descending fire, water has the property of wetting downward, which is the opposite of fire, which has the property of blazing upward. Thus, they work differently according to their innate properties. Nature and the human body maintain harmony through the interaction of ascending water and descending fire. When applied to the human body, the heart and kidney are the center of this principle. In other words, the heart above is the fire and the kidney downward is water. When the heart-fire harmonizes downward, the kidney becomes warm, enabling genuine vital functions to be active. When the kidney yin moves upward, the heart receives the nourishing yin to harmonize nutrients and blood. Thereby, physiological functions become normal throughout the blood meridians. However, in the ascending kidneywater and descending heart-yang of the heart and the kidney, the liver and lung are the major functional organs. In other words, the liver through the dispersing and raising yang functions moves water, which is the vital essence of the kidney, upward. And the lung, through the astriction?clearing of the lung and descending Qi?dispersing functions, moves the heart-fire downward. These functions are deeply related with changing seasons; thus, these functions can be explained with the ascending kidney-water and descending heart-yang of the five viscera.

• 설비공학논문집
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• 제3권4호
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• pp.222-230
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• 1991

Conjugate heat transfer by steady laminar natural convection from a conducting tube with two vertical axial fins has been studied by a finite difference numerical procedure under basic conditions; $Ra=10_6$, Pr = 5 and $L_F=0.15$. The maximum local tube Nusselt number appears at ${\theta}=140^{\circ}$ for $L_F=0.06$, at ${\theta}=130^{\circ}$ for $L_F=0.30$ and at ${\theta}=120^{\circ}$ for $L_F=0.30$, $L_F=0.06$, respectively. The maximum mean Nusselt number shows at $L_F=0.18$ for the downward fin and at $L_F=0.12$ for the upward fin. Therefore the optimized fin length is $L_F{\approx}0.15$ under these conditions. At $L_F=0.15$, the mean Nusselt number by increasing Rayleigh number is remarkably increased for downward fin and then is slowly increased except for downward fin, it by increasing Prandtl number is apparently increased at $Pr{\leq}2$, and slightly increased at Pr>2.

• Nuclear Engineering and Technology
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• 제35권4호
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• pp.274-285
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• 2003

Film boiling heat transfer coefficients for a downward-facing hemispherical surface are measured from the quenching tests in DELTA (Downward-boiling Experimental Loop for Transient Analysis). Two test sections are made of copper to maintain Bi below 0.1. The outer diameters of the hemispheres are 120 mm and 294 mm, respectively. The thickness of both the test sections is 30 mm. The effect of diameter on film boiling heat transfer is quantified utilizing results obtained from the two test sections. The measured heat transfer coefficients for the test section with diameter 120 mm lie within the bounding values from the laminar film boiling analysis, while those for diameter 294 mm are found to be greater than the numerical results on account of the Helmholtz instability. There is little difference observed between the film boiling heat transfer coefficients measured from the two test sections. In addition, the higher thermal conductivity of copper results in the higher minimum heat flux in the tests. For the test section of diameter 120 mm, the Leidenfrost point is lower than that for the test section of diameter 294 mm. Destabilization of film boiling propagates radially inward for the 294 mm test section versus radially outward for the 120 mm Test Section.