• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.3
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• pp.48-56
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• 1995

This paper presents a method of implementing efficient optical flow estimation for dynamic scene analysis using the hierarchical Hopfield neural networks. Given the two consequent inages, Zhou and Chellappa suggested the Hopfield neural network for computing the optical flow. The major problem of this algorithm is that Zhou and Chellappa's network accompanies self-feedback term, which forces them to check the energy change every iteration and only to accept the case where the lower the energy level is guaranteed. This is not only undesirable but also inefficient in implementing the Hopfield network. The another problem is that this model cannot allow the exact computation of optical flow in the case that the disparities of the moving objects are large. This paper improves the Zhou and Chellapa's problems by modifying the structure of the network to satisfy the convergence condition of the Hopfield model and suggesting the hierarchical algorithm, which enables the computation of the optical flow using the hierarchical structure even in the presence of large disparities.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.175-178
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• 2007

Valves has been used widely in various industries. There are many purposes for valve usage in a piping system. One of them is to control the flow rate. For a design of ball valves, it is important to know the characteristics of flows inside a ball valve. In this study, the computation fluid dynamics were conducted to observe flow velocity, flow coefficient and pressure distribution using CFX 10 according to the valve angles and uniform incoming velocity.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.2 s.146
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• pp.186-196
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• 2006

The turbulent wake flow of an axisymmetric body at incidence of $10.1^{\circ}$ is investigated by commericial CFD code, Fluent 6.2. Reynolds stress turbulence model with wall function is applied for the turbulent flow computation. For the grid generation, the Gridgen V15 is used. Numerical predictions are compared with experimental data for the validation. The computed results show goof agreements with the experimental measurements, implying that the CFD analysis is a useful and efficient tool for predicting turbulent flow characteristics of wake field of an axisymmetric body at incidence.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.6
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• pp.305-311
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• 2000

This paper presents a hybrid algorithm for solving optimal power flow(OPF) in order to enhance a systems capability to cope with outages, which is based on combined application of evolutionary computation and local search method. The efficient algorithm combining main advantages of two methods is as follows : Firstly, evolutionary computation is used to perform global exploitation among a population. This gives a good initial point of conventional method. Then, local methods are used to perform local exploitation. The hybrid approach often outperforms either method operating alone and reduces the total computation time. The objective function of the security constrained OPF is the minimization of generation fuel costs and real power losses. The resulting optimal operating point has to be feasible after outages such as any single line outage(respect of voltage magnitude, reactive power generation and power flow limits). In OPF considering security, the outages are selected by contingency ranking method(contingency screening model). The OPF considering security, the outages are selected by contingency ranking method(contingency screening model). The method proposed is applied to IEEE 30 buses system to show its effectiveness.

• Korea-Australia Rheology Journal
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• v.14 no.4
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• pp.143-159
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• 2002

Although much progress has been made in the computation of Eulerian steady flows with high viscoelasticity, less work has been done for the case of transient flows. Because of their importance in injection moulding, blow moulding and other forming processes, as well as their Intrinsic interest, we believe more attention should be focussed in this area. Hence in this paper we review progress in unsteady flow computations with high elasticity, and show some new results in this area.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.412-412
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• 2006

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.17-25
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• 2019

An intake of Aircraft becomes S-shaped geometry due to spatial limitation or procuring survivability. But curvature of the S-shaped geometry makes secondary flow or flow separation which is the cause of non-uniform pressure distribution. In this study, boundary layer suction is applied to RAE M 2129 S-Duct by attaching sub duct. Design variable is suction location and angle. A mass flow rate drawn out by suction at the sub duct outlet is constant over every model. A grid dependency test was conducted to verify validity of computation. The comparison among the CFD (Computation Fluid Dynamics), ARA experimental result, and ARA computation result of non-dimensional pressure distribution on the Port side and Starboard Side confirmed the validity of CFD. In this study, Distortion Coefficient was used for evaluating aerodynamic performance of S-Duct. The analysis, which was about flow separation, vortex, mass flow rate distribution, and pressure distribution were also investigated. Maximum 26.14% reduction in Distortion Coefficient was verified.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.627-641
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• 2003

The structural intensity fields of rectangular plates with single cutout and multiple cutouts are studied. The main objective is to examine the effect of the presence of cutouts on the flow pattern of vibrational energy from the source to the sink on a rectangular plate. The computation of the structural intensity is carried out using the finite element method. The magnitude of energy flow is significantly larger at the edges on the plate near the cutout boundary parallel to the energy flow. The effects of cutouts with different shape and size at different positions on structural intensity of a rectangular plate are presented and discussed. A case study on a plate with two cutouts is also presented.

• Journal of Industrial Technology
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• v.17
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• pp.183-189
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• 1997

The computation of the flow around a supercritical airfoil with a divergent trailing edge(DTE) modification(DLBA 243) is compared to that of original supercritical airfoil(DLBA 186). For this computation, Reynolds-Averaged Navier-Stokes equations are solved with a linearized block implicit ADI method and a mixing length turbulence model. Results show the effects of the shock and separated flow regions on drag reduction due to DTE modification. Results also show that DTE modification accelerates the boundary layer flow near the trailing edges which has an effect similar to a chordwise extension that increases circulation and is consistent with the calculated increase in the recirculation region in the wake. Airfoil with DTE modification achieves the same lift coefficient at a lower incidence and thus at a lower drag coefficient, so that lift-to-drag ratio is increased in transonic cruise conditions compared to the original airfoil. The reduction in drag due to DTE modification is associated with weakening of shock strength and delay of shock which is greater than the increase in base drag.

• Water for future
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• v.15 no.4
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• pp.39-44
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• 1982

A numerical computation of unsteady flow in the open channel was studied with the linearized four-point method of characteristics. A seiche test for this model was fulfilled and its result was very close to the exact solution. The effect of linearization to the accuracy of the result was small enough for the analysis of nearly horizontal flow, and this model would be applicable for the real unsteady flow problem because of its convenience.