• Fibers and Polymers
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• v.1 no.2
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• pp.103-110
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• 2000

Flow analysis of profile extrusion is essential for design and production of a profile extrusion die. Velocity, pressure, and temperature distribution in an extrusion die are predicted and compared with the experimental results. A two dimensional numerical method is proposed for three dimensional analysis of the flow field within the profile extrusion die by applying a modified cross-sectional numerical method. Since the cross-sectional shape of the die is varied gradually, it is assumed that the pressure is constant within a cross-sectional plane that is perpendicular to the flow direction. With this assumption, the velocity component in the cross-sectional direction is neglected. The exact cross-sectional shape at any position is calculated based on the geometry of standard cross-sections. The momentum and energy equations are solved with proper boundary conditions at a cross-section and then the same calculation is carried out for the next cross-section using the current calculated values. An L-shaped profile extrusion die is produced and employed for experimental investigation using a commercially available polypropylene. Numerical prediction for the varying cross-sectional shape provides better results than the previous studies and is in good agreement with the experimental results.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.20-28
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• 2010

The computational flow analysis using LES technique was carried out to investigate the flow characteristics of a RAC chassis consisting of a rear-guider, a stabilizer and a cross-flow fan. The commercial SC/Tetra software was used in this analysis. In view of the results so far achieved, the distribution trends of static pressure and velocity vector of central region except the edges of a CFFan are similar regardless of the number of revolution, and an eccentric vortex exists around the bottom blade of a CFFan. Also, a reverse flow is found in the region between stabilizer and CFFan. Moreover, near the edges of a CFFan, an eccentric vortex is separated to two vortexes. Also these vortexes increase the velocity near a rear-guider, and guide the flow near a rear-guider into stabilizer inlet. Therefore, the reverse flow region is formed in the bottom of a CFFan.

• Geomechanics and Engineering
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• v.14 no.5
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• pp.407-419
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• 2018

In order to investigate flow characteristics after water inrush from the working face in process of karst tunnel construction, numerical calculation for two class case studies of water inrush is carried out by using the FLUENT software on the background of Qiyueshan tunnel. For each class water inrush from the tunnel face, five cases under different water-inrush velocity are simulated and researched. Three probing lines are selected respectively in the left tunnel, cross passage, right tunnel and in the height direction of the tunnel centerline. The variation characteristics of velocity and pressure on each probing line under the five water-inrush velocities are analyzed. As for the selected four groups probing lines in the tunnels, the change rules of velocity and pressure on each group probing lines under the same water-inrush velocity are discussed. Finally, the water flow characteristics after inrush from the tunnel face are summarized by comparing the case studies. The results indicate that: (1) The velocity and pressure change greatly at the intersection area of the cross passage and the tunnels. (2) The velocity nearby the tunnel side wall is the minimum, while it is the maximum in the middle position. (3) The pressure value of every cross section in the tunnels is basically fixed. (4) As water-inrush velocity increases, the flow velocity and pressure in the tunnels also increase. The former is approximately proportional to their respective water-inrush velocity, while the latter is not. The research results provide a theoretical basis for making scientific and rational escape routes.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2833-2838
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• 2007

Recently, small hydropower attracts attention because of its clean, renewable and abundant energy resources to develop. However, suitable turbine type is not determined yet in the range of small hydropower and it is necessary to study for the effective turbine type. Moreover, relatively high manufacturing cost by the complex structure of the turbine is the highest barrier for developing the small hydropower turbine. Therefore, a cross-flow turbine is adopted because of its simple structure and high possibility of applying to small hydropower. The purpose of this study is to examine the optimum configuration of nozzle shape to further optimize the cross-flow hydraulic turbine structure and to improve the performance. The results show that pressure on the runner blade in Stage 1 and velocity at nozzle outlet have close relation to the turbine performance.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2000.05a
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• pp.140-145
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• 2000

The objective of experimental study is to apply simultaneous measurement by PIV(Particle Image Velocimetry) to high_speed flow characteristics within ginseng cleaner model. Three different kinds of flow rate(15.20 27ℓ/min) are selected as experimental condition. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. The instantaneous velocity distribution time0mean velocity distribution and velocity profile are represented quantitatively for the deeper understanding of the flow characteristics in a ginseng cleaner model.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.370-377
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• 2002

Generally, the system of calculation for the multi-path ultrasonic flow meters can be divided into two methods by how to get the mean velocity, namely, weighting and direct method. Weighting-method derive the mean velocity through modeling in theoretical velocity profile. Direct-method derive the mean velocity though actual flow distribution. The system of calculation varies with maker's transducer configuration and integration method. Each system has merits and demerits. This paper describes the system of integration that calculates line velocity over cross-section of the circular pipe. Flow rate mr discussed in this paper is a difference between theoretical flow rate and integrated flow rate according to values of Reynolds number in symmetric flow field or theoretical flow rate and integrated flow rate according to rotated model in asymmetric flow field.

• 연구논문집
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• s.30
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• pp.59-65
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• 2000

The objective of experimental study is to apply simultaneous measurement by PIV(Particle Image Velocimetry)to high_speed flow characteristics within Ginseng washing machine. Three different kinds of flow rate(15,20,27 $\ell$/min)are selected as experimental conditions. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. Instantaneous velocity distribution, time-mean velocity distribution and velocity profiles are represented quantitatively at the full-scale region for the deeper understanding of the flow characteristics in Ginseng washing machine.

• Journal of The Geomorphological Association of Korea
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• v.23 no.1
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• pp.103-115
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• 2016

At present, an acoustic Doppler current profiler (ADCP) is one of the most suitable tools for measurement of three dimensional flow characteristics in the river. The data resulting from this approach can be used for flow visualization and velocity mapping together with post-processing software tools. Among them, 'adcptools' is the latest one and provides more realistic velocity distribution in the cross-section since it uses velocity along the beam direction. In this study, a flow analysis was made using the 'adcptools' for the Amazon River and the Han River dataset. Discharge was recalculated and accuracy of discharge and velocity was evaluated. Streamwise velocity distribution and secondary flow pattern in cross-sections were visualized. Geo-referenced velocity distribution was also mapped. A summary with future prospect of 'adcptools' for studies on fluvial geomorphology is briefly given.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.467-472
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• 2000

Most of the past experimental or analytical studies were performed for the curved bend with a square cross-section. Velocity profiles and Reynolds stresses of the turbulence flow in the 270 degree bend with circular cross-section were measured by a hot-wire anemometer. The mean velocity of primary flowing direction effected by the downstream of bend in the entry region of the bend. The flow in the inner part of the bend slowed the distribution velocity relatively large and unsymmetric phenomenon. In the strong secondary flow occurred when the flow passed in the region of 45 degree to 90 degree. The secondary flow appeared very large value in the neighbor region of inner wall.

• Journal of International Academy of Physical Therapy Research
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• v.11 no.1
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• pp.1954-1959
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• 2020

Background: Due to aging, blood flow rate decreases, also posture and chewing habit may be changed. Objective: To identify that changes in blood velocity in the common carotid arteries (CCAs) in old persons with unilateral chewing habit (UCH) and forward head posture (FHP) in the elderly. Design: An observational cross-sectional study. Methods: Chewing habits, FHP, and CCAs velocities were assessed in 85 elderly subjects. Chewing habits were measured by visual observation. CCAs measured the peak systolic velocity (PSV), end-diastolic velocity (EDV), minimum diastolic velocity, and resistivity index. The subjects were divided into UCH and bilateral chewing habit groups depending on chewing habit. The subjects were also divided into >49 degrees and <49 degrees for comparison of blood flow between the left and right CCAs. Results: In the UCH, the chewing side had significantly higher EDV (P=.003), PSV (P=.023) than the non-chewing side. There was no significant difference in velocity between the CCAs in the FHP. Conclusion: This study shows that the blood flow velocity of the chewing side of UCH was higher, and unilateral chewing affects the CCAs velocity and thus highlight the importance of chewing habit in the elderly than head posture.