• Journal of applied mathematics & informatics
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• v.25 no.1_2
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• pp.67-83
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• 2007

The characteristics of steady two-dimensional laminar boundary layer flow of a viscous and incompressible fluid past a moving wedge with suction or injection are theoretically investigated. The transformed boundary layer equations are solved numerically using an implicit finite-difference scheme known as the Keller-box method. The effects of Falkner-Skan power-law parameter (m), suction/injection parameter ($f_0$) and the ratio of free stream velocity to boundary velocity parameter (${\lambda}$) are discussed in detail. The numerical results for velocity distribution and skin friction coefficient are given for several values of these parameters. Comparisons with the existing results obtained by other researchers under certain conditions are made. The critical values of $f_0$, m and ${\lambda}$ are obtained numerically and their significance on the skin friction and velocity profiles is discussed. The numerical evidence would seem to indicate the onset of reverse flow as it has been found by Riley and Weidman in 1989 for the Falkner-Skan equation for flow past an impermeable stretching boundary.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.5
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• pp.700-712
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• 1997

The flowfield generated by a 2-D rotating cylinder on a plane moving at freestream velocity was experimentally investigated in a wind tunnel to simulate aerodynamic characteristics of rotating wheels of an automobile. In the flowfield around a rotating cylinder at 3*10$^{3}$ < Re$_{d}$<8*10$^{3}$, unique mean flow and turbulence characteristics were confirmed by hot-wire measurements as well as frequency analysis, which was supported by flow visualization. In the vicinity of a rotating cylinder, a unique turbulence structure on .root.over bar u'$^{2}$ profiles was formed in hump-like shape at 1 < y/d < 3. A peak frequency which characterized the effect of a rotating cylinder had the same value of the rotation rate of a cylinder. In case of cylinder rotation, the depths of mean velocity -defect and turbulent-shear regions were thickened by 20-40% at 0 < x/d < 10 compared with the case of cylinder stationary. Far downstream beyond x/d > 10, the flowfield generated by a rotating cylinder showed self-similarity in the profiles of mean velocity and turbulence quantities. The effect of a rotating cylinder was independent of its rotation rate and Reynolds number in the measurement range.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.15-25
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• 2006

Using kinematic wave equation, the influence of moving storms to runoff was analysised with a focus on watersheds. Watershed shapes used are the oblong, square and elongated shape, and the distribution types of moving storms used are uniform, advanced and intermediate type. The runoff hydrographs according to the rainfall distribution types were simulated and the characteristics were explored for the storms moving down, up and cross the watershed with various velocity. The shape, peak time and peak runoff of a runoff hydrograph are significantly influenced by spatial and temporal variability in rainfall and watershed shapes. A rain storm moving in the cross direction of channel flow produces a higher peak runoff than in the downstream direction and upstream direction. A peak runoff from a storm moving downstream exceeds that from a storm moving upstream. For storms moving downstream peak time was more delayed than for other storm direction in the case of elongated watershed. The runoff volume and time base of the hydrograph decreased with the increasing storm speed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.346-349
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• 2004

In the previous experimental study about extru-bending of angle product, the bending of extruded angle products with the '${\wedge}$' section and 'ㄱ' section can be abtained by the hot metal extru-bending machine with the two punches moving in the different velocity. The bending curvature can be controlled by the different velocity of billets through the two-hole container. This paper describes simulation of extru-bending process by the difference of punch velocities. The result of the forming simulation by $DEFORM^{TM}-3D$ shows that the bending phenomenon at the die exit during extrusion can be abtained by the two punches moving in the different velocity. And it is possible to design extrusion dies and to control the curvature of product through the simulation of extru-bending process by analysis

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2418-2425
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• 1993

A two-dimensional transient heat transfer model for reactive gas assisted laser cutting process with a moving Gaussian heat source is developed using a numerical finite difference technique. The kerf width, melting front shape and temperature distribution were calculated by using the boundary-fitted coordinate system to handle the ejection of workpiece material and heat input from reaction and evaporation. An analytical solution for cutting front movement was adopted and numerical simulation was performed to calculate the temperature distribution and melting front thickness. To calculate the moving velocity of cutting front, the normal distribution of the cutting gas velocity was used. The kerf width was revealed to be dependent on the cutting velocity, laser power and cutting gas velocity.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1377-1381
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• 2003

This paper describes real time object tracking of 3D objects in 2D image sequences. The moving objects are segmented from the image sequence using morphological operations. The moving objects are segmented by the method of differential image followed by the process of morphological dilation. The moving objects are recognized and tracked using statistical moments. The direction of moving objects are determined by the Hough transform. The straight lines in the moving objects are found with the help of Hough transform. The direction of the moving object is calculated from the orientation of the straight lines in the direction of the principal axes of the moving objects. The direction of the moving object and the displacement of the object in the image sequence is used to calculate the velocity of the moving objects. The simulation results of the proposed method are promising on the test images.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.3
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• pp.171-176
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• 2019

Drones are highly utilized because they can efficiently acquire long-distance videos. In drone operation, the speed, which is the magnitude of the velocity, can be set, but the moving direction cannot be set, so accurate information about the drone's movement should be estimated. In this paper, we estimate the velocity of the drone moving at a constant speed and direction. In order to estimate the drone's velocity, the displacement of the target frame to minimize the sum of absolute difference (SAD) of the reference frame and the target frame is obtained. The ground truth of the drone's velocity is calculated using the position of a certain matching point over all frames. In the experiments, a video was obtained from the drone moving at a constant speed at a height of 150 meters. The root mean squared error (RMSE) of the estimated velocities in x and y directions and the RMSE of the speed were obtained showing the reliability of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.6
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• pp.659-664
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• 2004

It is important to measure precisely the size and velocity of micro-bubbles used in various field. The synchrotron X-ray micro-imaging technique was employed to measure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Phase contrast images were obtained at interfaces of micro-bubbles between water and air due to their different refractive indices. The X-ray micro-imaging technique was found to measure an optical fiber with an accuracy of 0.2%. Micro-bubbles of 20∼60$\mu\textrm{m}$ diameter moving upward in an opaque tube (${\Phi}$＝2.7mm) were tested to measure bubble size and up-rising velocity. For DI water, the measured velocity of micro-bubbles is nearly proportional to the square of bubble size, agreed well with the theoretical result. In addition, the synchrotron X-ray micro-imaging technique can measure accurately the size and velocity of several overlapped micro-bubbles.

• Annals of Clinical Neurophysiology
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• v.1 no.2
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• pp.173-181
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• 1999

Eye movements serve vision by placing the image of an object on the fovea of each retina, and by preventing slippage of images on the retina. The brain employs two modes of ocular motor control, fast eye movements (saccades) and smooth eye movements. Saccades bring the fovea to a target, and smooth eye movements prevent retinal image slip. Smooth eye movements comprise smooth pursuit, the optokinetic reflex, the vestibulo-ocular reflex (VOR), vergence, and fixation. Saccades achieve rapid refixation of targets that fall on the extrafoveal retina by moving the eyes at peak velocities that can exceed $700^{\circ}/s$. Various brain lesions can affect saccadic latency, velocity, or accuracy. Smooth pursuit maintains fixation of a slowly moving target. The pursuit system responds to slippage of an image near the fovea in order to accelerate the eyes to a velocity that matches that of the target. When smooth eye movements velocity fails to match target velocity, catch-up saccades are used to compensate for limited smooth pursuit velocities. The VOR subserves vision by generating conjugate eye movements that are equal and opposite to head movements. If the VOR gain (the ratio of eye velocity to head velocity) is too high or too low, the target image is off the fovea, and head motion causes oscillopsia, an illusory to-and-fro movement of the environment.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1744-1748
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• 2004

It is important to measure precisely the size and velocity of micro-bubbles used in various field. The synchrotron X-ray micro-imaging technique was employed to measure the size and velocity of micro-bubbles moving in an opaque tube simultaneously. Phase contrast images were obtained at interfaces of micro-bubbles between water and air due to their different refractive indices. The X-ray micro-imaging technique was found to measure an optical fiber with an accuracy of 0.2%. Micro-bubbles of $10{\sim}60{\mu}m$ diameter moving upward in an opaque tube (${\phi}=2.7mm$) were tested to measure bubble size and up-rising velocity. For DI water, the measured velocity of micro-bubbles is nearly proportional to the square of bubble size, agreed well with the theoretical result. In addition, the synchrotron X-ray micro-imaging technique can measure accurately the size and velocity of several overlapped micro-bubbles.