• 한국전산유체공학회:학술대회논문집
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• 2002.10a
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• pp.47-52
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• 2002

We present an improved Lagrangian vortex method in 2-D incompressible unsteady viscous flows, which is based on a mesh-free integral approach of the velocity-vorticity formulation. Vorticity fields are represented by discrete vortex blobs that are updated by the Lagrangian vorticity transport with the particle strength exchange scheme. Velocity fields are expressed in a form of the Helmholtz decomposition, which are calculated by a fast algorithm of the Biot-Savart integration with a smoothed kernel and by a well-established panel method. No-slip condition is enforced through viscous diffusion of vorticity from a solid body into field. The vorticity flux is determined in such a way that spurious slip velocity vanishes. Through the comparison with the existing finite volume scheme for the transient vortical flows around an impulsively started cylinder at Reynolds number Re=550, we would obtain a more accurate scheme for vortex methods in complicated flows.

• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.836-844
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• 2000

In this research any abnormal motion of a vehicle is detected by utilizing the difference between the reference and actual yaw velocities as sell as the information on vehicle slip angle and slip angular velocity. This information is then used as a criterion for execution of the yaw moment control. A yaw moment control algorithm based on the brake control is proposed for improving the directional stability of the vehicle. The controller executes brake controls to provide each wheel with adequate brake pressures, which generate the needed yaw moment. It is shown that the proposed yaw moment control logic can provide excellent cornering capabilities even on low friction roads. This active control scheme can prevent a vehicle from behaving abnormally, and can assist normal drivers in coping with dangerous situations as well as experienced drivers.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.179-186
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• 2002

The absolute longitudinal speed of a vehicle is estimated by using vehicle acceleration data from an accelerometer and wheel speed data from standard 50-tooth antiknock braking system wheel speed sensors. An intuitive solution to this problem is, "When wheel slip is low, calculate absolute velocities from the wheel speeds; when wheel slip is high, calculate absolute velocity by integrating the accelerometer." Fuzzy logic is introduced to implement the above idea and a new algorithm of "modified velocities with step integration" is proposed. This algorithm is verified experimentally to estimate speed of a vehicle, and is also shown to estimate absolute longitudinal vehicle speed with a 6% worst-case error during a hard braking maneuver lasting three seconds.

• Membrane and Water Treatment
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• v.5 no.1
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• pp.57-71
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• 2014

In this study, a theoretical model for the transport phenomena in an Air Gap Membrane Distillation used for desalination was developed. The model is based on the conservation equations for the mass, momentum, energy and species within the feed water solution as well as on the mass and energy balances on the membrane sides. The rarefaction impacts are taken into consideration showing their effects on process parameters particularly permeate flow and thermal efficiency. The theoretical model was validated with available data and was found in good agreement especially when the slip condition is introduced. The rarefaction impact was found considerable inducing an increase in the permeate flux and the thermal efficiency.

• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.185-189
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• 2012

While there is no standards on slip risk for contaminants on surface, glycerol is described in standard contaminant for measuring coefficient of friction(COF) and slip resistance such as ISO 13287. But that is just used to measure the slip resistance of surface materials and shoes not to evaluate the contaminant materials. Therefore the objective of this study was to find out the relationship between standard contaminant and the contaminants used usually at the workplaces. For this, some measurement criteria were acquired from the analysis based on biomechanics and kinetics of human gait during slips. The slip resistance according to viscosity of the contaminants was measured applying the criteria and slip probability was determined by the gait analysis. Some factors which should be considered when measuring the slip resistance were identified. The velocity, acceleration, contact time and contact pressure should be 1 m/sec, 10 $m/sec^2$, 350 kPa and less than 0.5sec respectively. The variation of viscosity according to temperature for working oils was different from that of standard contaminant. The static coefficient of friction (SCOF) of working oils was almost 0.5 times as large as the SCOF of standard contaminant. So it was assumed to be difficult to compare the contaminants at the workplaces with the glycerol as a standard contaminant for estimating the slip risk.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.4
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• pp.587-593
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• 2002

The present research proposes a pressure based approach along with Langmuir slip condition for predicting microscale fluid flows. Using this method, gaseous slip flows in 2 -dimensional microchannels are numerically investigated. Compared to the DSMC simulation, statistical errors could be avoided and computing time is much less than that of the aforementioned molecular approach. Maxwell slip boundary condition is also studied in this research. These two slip conditions give similar results except for the pressure nonlinearity at high Knudsen number regime. However, Langmuir slip condition seems to be more promising because this does not need to calculate the streamwise velocity gradient accurately and to calibrate the empirical accommodation coefficient. The simulation results show that the proposed method using Langmuir slip condition is an effective tool for predicting compressibility and rarefaction in microscale slip flows.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.479-484
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• 2003

In this paper, film thickness and temperature distribution are measured in EHL point contact at high slip ratios. Infrared temperature mapping with two band pass fillers. proposed by Ausherman (1976). is used to measure temperature distribution. And the optical interferornetric method with two filters (red and green filters) is used to measure film thickness. Result of experiment showed that temperature rising at film and ball surface occurred very dramatically in Dimple zone. As slip velocity, slip ratio and load increased, size of Dimple and temperature rising became more large In addition, Position and shape of Dimple we changed by slip ratios, and increasing of Dimple size decreased traction coefficient. In short, it is appointed that the Dimple phenomenon be developed by the effect of viscosity wedge.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2197-2202
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• 2006

The steady hydromagnetic flow due to a rotating disk is studied with heat transfer considering the ion slip. The governing equations are solved numerically using finite differences. The results show that the inclusion of the ion slip has important effects on the velocity distribution as well as the heat transfer.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.135-138
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• 1991

In this study, a variety of characteristics is considered when LIM for transit is driven with acceleration and deceleration. From the characteristics of constant voltage, with V/f ratio fixed, slip frequency is derived. With slip frequency of 12[Hz] and objective velocity of 40[km/h], the robust control characteristics which are generated constant thrust and normal force, except for open-loop control interval, are obtained.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.133-138
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• 1993

This paper presents neural network based position estimation method in slippery environment as an approach to solve one of problems which are engaged in dead reckoning method. Position estimator is composed of slip detector and linear velocity estimator. Both of them are based on the fact that dynamic characteristic of mobile robot in slippery environment is different from the case without slip. To find out the dynamic relation among driving torque, angular acceleration of driving wheel and linear acceleration of mobile robot, accelerometer is used for measuring acceleration of mobile robot and neural network is used for dynamic system identifier in slippery environment.