• Journal of the Korean GEO-environmental Society
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• v.10 no.7
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• pp.117-123
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• 2009

This study is to investigate the characteristics of scour around pipeline in current and hydraulic model tests were performed. All the model test are 45 cases, which were conducted with velocities of 0.2 m/s to 0.5 m/s and pipe diameters of 45, 60, 90 mm. The developments of scour around pipeline were observed and equilibrium scour depths were recorded due to variation of pipe diameter and current velocity. According to the results, the equilibrium scour depth was proportional to current velocity and pipe diameter. The effect of diameter of pipeline on the equilibrium scour depth was bigger than current velocity. The correlations of relative scour depth and dimensionless number such as a Reynolds number, Shields number, and Froude number were analyzed. The Froude number and the relative scour depth had a high correlation of 0.900.

• Journal of computational fluids engineering
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• v.18 no.4
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• pp.1-8
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• 2013

The performance of small-size impellers with ruled surfaces was investigated for flank milling over a wide speed range, using computational fluid dynamics analyses and gas bench tests. An impeller with a ruled surface was designed, manufactured, and tested to evaluate the effects of blade loading, the backsweep angle, and the relative velocity distribution on the compressor performance. The simulations and tests were completed using the same compressor cover with identical inlet and outlet channels to accurately compare the performance of the abovementioned impeller with a commercial impeller containing sculptured blades. Both impellers have the same number of blades, number of splitters, and shroud meridional profiles. The backsweep angles of the blades on the ruled impeller were selected to work with the same pinched diffuser as for a sculptured impeller. The inlet-to-exit relative velocity diffusion ratio and the blade loading were provided to maximize the flow rate and to minimize the surge flow rate. The design flow rate, rpm, were selected same for both impellers. Test results showed that for the compressor stage with a ruled impeller, the efficiency was increased by 0.32% with an extended surge margin without a reduction in the pressure ratio as compared to the impeller with the sculptured design. It was concluded that an increased relative velocity diffusion coupled with a large backsweep angle was an effective way to improve the compressor stage efficiency. Additionally, an appropriate blade loading distribution was important for achieving a wide operating range and higher efficiency.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1065-1070
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• 2004

Optimal collision avoidance algorithm for unmanned aerial vehicles based on proportional navigation guidance law is investigated this paper. Although proportional navigation guidance law is widely used in missile guidance problems, it can be used in collision avoidance problem by guiding the relative velocity vector to collision avoidance vector. The optimal navigation coefficient can be obtained if an obstacle if an obstacle moves at constant velocity vector. The stability of the proposed algorithm is also investigated. The stability can be obtained by choosing a proper navigation coefficient.

• Water Engineering Research
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• v.1 no.4
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• pp.293-298
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• 2000

Optimal values of $\alpha$ characterizing the linear dispersion property in the modified Boussinesq equations are determined by minimizing the combined relative errors of the phase and group velocities. The value of $\alpha$ is fixed in previous studies, whereas it is varying in the present study. The phase and group velocities are calculated by using variable $\alpha$ and compared to those of the linear Stokes wave theory and previous studies. It is found that the present study produces the best match to the linear Stokes theory.

• Journal of Astronomy and Space Sciences
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• v.7 no.1
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• pp.47-55
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• 1990

From the study of a spectroscopic plate of $\varepsilon$ Auriage, we can measure the radial velocity and the relative abundance for this eclipsing binary. Calculated radial velocity is -37Km/s and the abundance of [Fe] is estimated as -1.5.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.144-146
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• 1992

Surface acoustic wave(SAW) oscillator offers many attractive features for application to vapor sensors. The perturbation of SAW velocity by the hexafluoropropence plasma polymer thin film has been studied for relative humidity sensing. adsorption of moisture produces rapid aid changes in the properties of the film, resulting in a change in the velocity of surface acoustic waves and, hence, in the frequency of one SAW oscillator. The device used in our experiments have 55 MHZ SAW oscillator fabricated on a LiNbO substrate.

• Journal of the Korean Chemical Society
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• v.56 no.5
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• pp.548-555
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• 2012

Ultrasonic velocity and density measurements have been undertaken for a number of binary liquid mixtures involving different commercial solvent extractants, LIX reagents. The binary mixtures under investigation have been classified under two categories such as polar-polar, and polar-non-polar types. Different theories and relations such as Schaaff's Collision Factor Theory (CFT), Nomoto's relation (NOM), and Van Dael & Vangeel ideal mixing relation (IMR) have been used to evaluate the velocity theoretically for all these binary systems. The relative merits of afore-mentioned theories and relations compared to experimental values of velocity have been discussed in terms of percentage variations. However, the CFT and Nomoto's relation show better agreement with the experimental findings than the ideal mixing relation for all the systems under investigation.

• 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 A
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• v.20 no.12
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• pp.3741-3747
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• 1996

This paper presents a method for the inverse dynamic anlaysis of mechanical systems. Actuating forces(or torques) depending on the driving constraints are analyzed in the relative coordinate space using the velocity transformation technique. A systematic method to compose the inverse velocity transformation matrix, which is used to determine the joint reaction forces, is proposed. Two examples are taken to verify the method developed here.

• Journal of the Korean Society of Safety
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• v.7 no.4
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• pp.85-94
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• 1992

This paper, discribes analysis of theree - dimensional extrusion with the use of dual stream functions, By this method admissible velocity fields for the extrusion of three- dimensional flow was newly derived kinematically. For square section the extrusion pressure was calculated by numerical solution program which was based on the upper bound analysis. The relationship between relative extrusion pressure and reduction of area, relative die length and constant friction factors were successfully calculated which was newly developed in this study. The results could be applied to design extrusion die.