• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1274-1279
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• 2003

In this paper, a new meshfree technique which improves the numerical integration accuracy is introduced. This new method called the Petrov-Galerkin natural element(PG-NE) is based on the Voronoi diagram and the Delaunay triangulation which is based on the same concept used for conventional natural element method called the Bubnov-Galerkin natural element(BG-NE). But, unlike BG-NE method, the test shape function is differently chosen from the trial shape function. The proposed technique ensures that the numerical integration error is remarkably reduced.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.358-365
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• 2005

In induction machine drive without a speed sensor, the estimation of the motor flux and speed often becomes deteriorated at low speeds with low back EMF. Our analysis shows that, in addition to the state resistance variation, the estimated value of field orientation angle is often corrupted by accumulative errors from the integration of voltage variables at motor terminals that have low signal/noise ratio at low frequencies. A repetitive loop path of integration in the feedback can amplify this type of error, thus speeding up the degradation process. The control system runs into information starvation due to the loss of correct field orientation. The machine's spiral vectors are controlled only in a reduced dimension in this situation. A novel control scheme is developed to improve the control performance of motor's current, torque and speed at low frequencies. The scheme gains a full-dimensional vector control and is less sensitive to the combined effect of the error sources at the low frequencies. Experimental tests demonstrate promising performances are achievable even below 0.5 Hz.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.591-594
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• 2002

Generating NC-code from 3D part model needs a lot of effort to make many decisions, including machining area, tool change data, tool data, cutting condition, etc., by using either manual or computer aided method. This effort can be reduced by integration of automated process planning and NC-code generation. In case of generating NC code with a help of the process planning system, many data mentioned from the process planning can be used. It means that we can create NC-code about a full part. In this study, integration of FAPPS(Feature based Automatic Process Planning) with a NC-code generating module is described and additional data to adapt NC-code for machine shop is discussed.

• Korean System Dynamics Review
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• v.12 no.3
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• pp.67-86
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• 2011

This study shows the reduction effect of freight volume by the supply chain redesign for the alliance of distributors with system dynamics simulation. The as-is model is composed of 3 independent companies which one has 3 distribution centers (DCS) and 24 agents, another has 1 dc and 9 agents, the other has 3 DCS and 15 agents each. The to-be model is an integrated logistics model and composed of 1 company having 5 areal DCS and 38 agents. Each agent in the same area is integrated with each other. Two models have same demands but very different result. As a result, the freight volume between DCS and agents is reduced by 33.55%. This case study will be useful to analyze the similar cases about the logistics integration by supply chain redesign.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.2
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• pp.67-75
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• 2013

In order to improve osseo-integration of a dental implant with bone crystal we studied an implant with holes inside its body to deliver bioactive materials based on a proposed patent. After bioactive material is absorbed, bone crystal can grow into holes to increase implant bonding in addition to surface integration. The larger cross section area of outlet holes showed the less values of the maximum stress, and the stress concentrations near the uppermost outlet holes were also reduced with an increasing number of outlet holes. The conclusion, that the uppermost outlet design improvement was most effective to reduce the stress concentration and improve the growth rate of bone crystal, could be drawn. After the design optimizations, Type 6-C had provided the best results in this study. The overall shape optimization studies on the shape, location, number, and so on, of the outlet holes, should be carried out further.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.191-194
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• 2000

A level of integration will increase, if the number of elements of the circuit can be reduced. We aim to design the circuit of the new system for any further integration by using Neuron MOS Transistor. In this paper, we consider to introduce Soft-Hardware Logic and multiple-valued logic to the design methods for reducing the number of elements and inner wiring. We have designed 4-valued add-subtracter circuit using above logic. We discuss the design methods, features, and characteristics of this circuit by SPICE simulation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.11-17
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• 2000

,An residual stress and out-of plane deformation produced by butt welding was analyzed by four kinds of 3D-FEM programs(Thermal El-P1 Analysis) developed by authors. The magnitude of deformation of perpendicular to the welding line generated by butt welding was large when the reduced integration method was used. This was because of removal of the locking phenomenon, which it was generally known that the stiffness of the shear component of out-of-plane was largely evaluated. And the magnitude of residual stress was analyzed by using the FEM program based on a large and small deformation theory was similar to that was analyzed by the redeced integration method.

• Coupled systems mechanics
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• v.1 no.3
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• pp.235-245
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• 2012

The nonlinear resonant response of an axially moving beam is investigated in this paper via two different numerical techniques: the pseudo-arclength continuation technique and direct time integration. In particular, the response is examined for the system in the neighborhood of a three-to-one internal resonance between the first two modes as well as for the case where it is not. The equation of motion is reduced into a set of nonlinear ordinary differential equation via the Galerkin technique. This set is solved using the pseudo-arclength continuation technique and the results are confirmed through use of direct time integration. Vibration characteristics of the system are presented in the form of frequency-response curves, time histories, phase-plane diagrams, and fast Fourier transforms (FFTs).

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.399-405
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• 2014

For stable integration of large-scale wind farms, integration standards (Grid codes) have been proposed by the system operator. In particular, voltage control of large-scale wind farms is gradually becoming important because of the increasing size of individual wind farms. Among the various voltage control methods, Secondary Voltage Control (SVC) is a method that can control the reactive power reserve of a control area uniformly. This paper proposes hybrid SVC when a large-scale wind farm is integrated into the power grid. Using SVC, the burden of a wind turbine converter for generating reactive power can be reduced. To prove the effectiveness of the proposed strategy, a simulation study is carried out for the Jeju system. The proposed strategy can improve the voltage conditions and reactive power reserve with this hybrid SVC.

• Structural Engineering and Mechanics
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• v.17 no.6
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• pp.735-749
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• 2004

This work presents a direct integration scheme, based on a fourth order finite difference approach, for elastodynamics. The proposed scheme was chosen as an alternative for attenuating the errors due to the use of the central difference method, mainly when the time-step length approaches the critical time-step. In addition to eliminating the spurious numerical oscillations, the fourth order finite difference scheme keeps the advantages of the central difference method: reduced computer storage and no requirement of factorisation of the effective stiffness matrix in the step-by-step solution. A study concerning the stability of the fourth order finite difference scheme is presented. The Finite Element Method and the Boundary Element Method are employed to solve elastodynamic problems. In order to verify the accuracy of the proposed scheme, two examples are presented and discussed at the end of this work.