• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1000-1002
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• 2017

Here, the unsteady Navier-Stokes solver has been developed using implicit dual time stepping method. The implicit dual time stepping method introduced the pseudo time step for solving the new residual including the steady state residual and real time derivative. For the validation of code, Stokes 2nd problem, the laminar flow on the oscillating flat plate was selected and compare the calculating results with analytic solutions. The calculating velocity profile and skin friction has a good agreement with analytic solutions.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1082-1083
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• 2007

Electric motors are widely used from precision industry to home appliance. For the precision control of the motors, if it is possible, we need the information of the correct motor parameters. In the motor torque equation, the motor inertia moment and the viscosity friction coefficient are regarded as constant. However the viscosity friction coefficient is not constant in the real system. In this paper, we show that the viscosity friction coefficient has the nonlinear property through the real test and we present the nonlinear function for the viscosity friction coefficient.

• Journal of the KSME
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• v.35 no.1
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• pp.26-35
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• 1995

직물은 경사와 위사가 직각으로 교차하여 만들어진 것으로 여기에 사용하는 경사와 위사를 준 비하는 것을 제직 준비라 한다. 사이징(sizing)은 원사에 풀을 먹이는 제직 준비 공정의 한 가 지로서 제직시에 발생하는 마찰, 긴자으로부터 사(사)를 보호하여 제직 효율을 향상시키는 데 목적이 있다. 이러한 작업에서 호재가 균일하게 접착되고 양호한 품질로 대량생산을하여 경제 적인 합리화를 이루기 위하여 기계 사이징을 한다. 그림 1은 일반적인 합성 섬유용 사이징기의 구조이다. 호재는 용액상태로 준비되며, 원사는 호재용액을 가로질러 이동하여 연결되는 다음 공정에서 용이하게 취급되도록 건조되어 권추된다. 표면에 점성이 높은 호재가 부착된 원사를 단시간에 효과적으로 건조시키는 것이 사이징기 건조부의 역할이며, 가공되는 원사의 종류가 다양해짐에 따라 각 원사의 특성에 적합한 건조방법이 발전되어 왔다. 이 글에서는 건조시스템의 이론적인 고찰과 신합섬용 사이징기 SUPER-500에 대한 건조 시스템의 구조 및 동작 원리를 소개하고 향후 발전 방향을 제시코자 한다.

• Journal of KSNVE
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• v.9 no.2
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• pp.387-392
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• 1999

This paper presents design guidelines for the automatic ball balancer in CD/DVD systems with varying eccentricity. In these systems, the size of balancing balls should be limited by the restricted race space so that determination of the number and mass of balls should consider the radii of the race and the balls. In addition, the effects of viscosity and friction also should be taken into account for sufficient balancing. Based on the static equilibrium conditions, the number and mass of balls corresponding to the range of varying eccentricity have been determined. Dynamic simulation with viscosity and friction shows sufficient viscosity must exist to ensure stability and friction between balls and race must be minimized to guarantee accurate balancing.

• Journal of Fisheries and Marine Sciences Education
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• v.10 no.1
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• pp.63-68
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• 1998

The microbubble splits injection system are improved for the enhancement efficiency of viscous frictional drag reduction. It was confirmed that the experimental results is effective more than Mercle's[7] using the present system in the comparisons. And the new experimental equation is derived to get viscous frictional drag reduction useful for the present experimental data. The new experimental equation approaches Mercle's[7] experimental data wel.

• Composites Research
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• v.21 no.2
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• pp.15-24
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• 2008

In this study, shear thickening fluid (STF) filled with rigid nano silica particles was impregnated in plain woven Kevlar fabrics to improve the impact resistance performance. The nano silica particles with an average diameter of 100nm, 300nm, and 500nm were used to make shear thickening fluid to estimate the effect of particle size on the impact behavior of STF impregnated Kevlar fabrics. The yam pull-out and frictional tests were conducted to estimate the effect of impregnated STF on the frictional characteristics. The test results showed that the friction forces were dramatically increased at the STF onset shear strain rates that were measured in preliminary rheology tests. The low speed impact tests were performed using the drop test machine. The results showed that the impregnated STF improved the impact resistance performance of the Kevlar fabrics in terms of the impact energy absorption and the deformation. It has been shown through tests that the impregnated STF affects the interfacial friction which contributes to improve the energy absorption in the Kevlar fabrics. Especially, the impregnation of the STF with the smaller particle size into the Kevlar fabrics showed the better performance in impact energy absorption.

• Geotechnical Engineering
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• v.11 no.3
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• pp.123-138
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• 1995

To study the grout flow in jointed rock, various nurser characteristics of grout in a single joint plane and two-dperorbed. The joint plane is described as a channel nets properties of grout are considered. To deal with various prob generator and i oint network generator are used. A loss of head due to friction in laminal flow is adopted to between the grout and joint wall. The grout flow is stopped, setting time. To consider this phenomenon, the idea of maxim From the results of numerical simulation on the single jai etration of grout is confirmed. The basic principles for the ation and the selection of the grout are presented. Correlation ant and grouting pressure is defined by analyzing the effects grout flow. Finally, the grout flow around a tunnel is simulate ins grouting operation for jointed rock mass.

• Journal of the Korean Geotechnical Society
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• v.32 no.5
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• pp.27-36
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• 2016

This paper presents the investigation of the major influence factors on the degree of soil plugging for open-ended piles based on the Coupled Eulerian-Lagrangian (CEL) numerical technique. The main objective of this study was to investigate the effect of soil plugging on the response of piles in various conditions. Through comparison of the results of field load tests, the CEL methodology was found to be in good agreement with the general trend observed by in situ measurement. Additionally, the parametric studies were performed by controlling the soil conditions, soil elastic moduli, end-bearing conditions and multi layers. It was found that the degree of soil plugging for sand layers was greater than that of clay layers. Also, the degree of soil plugging increased with an increase in both the soil stiffness and length of pile embedded in the bearing layer.

• Korean Journal of Food Science and Technology
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• v.29 no.1
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• pp.72-76
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• 1997

The effect of the energy supplied in extrusion on the starch gelatinization was analyzed. The energy needed for extrusion is generated by motor and heater. The motor energy is transformed into a thermal energy by heat dissipation and a mechanical energy, and the heater energy is of a thermal energy. At the low barrel temperature $({\leq}80^{\circ}C)$, it was found out there are two kinds of thermal energy by heat dissipation: one by a powder friction of corn grit with low moisture contents and the other by a viscous dissipation of corn grit with high moisture contents. The dissipated thermal energy by the powder friction was more effective on the starch gelatinization than that by the viscous dissipation. The effect of the mechanical energy was also analyzed in terms of a relative mechanical energy. The gelatinization of corn grit with high moisture contents $({\geq}33%)$ largely depended on the change in the relative mechanical energy, whereas that with low moisture contents $({\leq}30%)$ hardly depended on it.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.6-11
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• 2009

Flow field in a roller conveyor system, induced from the movement of a cassette in which glasses for flat panel display are loaded, is numerically studied in this paper. Contamination on the glass surface by dust particles produced from mechanical friction between roller and cassette is predicted from the analysis results of flow fields. Results show that a large swirl flow is formed under the moving cassette with constant speed. This swirl flow is confined only under the cassette because two main streams from the backward and the fan filter unit on the top ceiling are sufficiently strong. Therefore, it can be said that possibility of the contamination by the particles originated from the friction is relatively low. It is also revealed that flow direction between glass plates is changed according to the speed of the cassette movement due to the shear force of glass plates.