• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.56-62
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• 2004

We present a diffraction grating interferometer of large equivalent wavelength specially designed for flatness testing of rough surfaces. Two transmission diffraction gratings are illuminated on the object under test by use of two measurement beams with different angles of incidence, which yields a large equivalent wavelength. This interferometer design minimizes unnecessary diffraction rays and the systematic error caused by the diffraction gratings, and provides a large working distance and easy alignment. To improve the measurement accuracy, phase shifting technique is applied and the equivalent wavelength error caused by defocus is calibrated. Test results obtained from mirror surfaces and machined rough surfaces are discussed.

• Journal of the Korea Computer Graphics Society
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• v.24 no.1
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• pp.1-8
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• 2018

We propose a modified real-time marching cubes technique that extracts isosurfaces in the form of connected meshes instead of triangle soup. In this way, a various mesh-based isosurface rendering techniques can be implemented and additional information of the isosurfaces such as its topology can be extracted in real-time. In addition, we propose a real-time technique to extract adjacency-triangle structure for geometry shaders that can be used for various shading effects such as silhouette rendering. Compared with the previous technique that welds the output triangles of classical marching cubes, our technique shows up to 300% performance improvement.

• Computational Structural Engineering
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• v.3 no.1
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• pp.109-116
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• 1990

Live load data in domestic office buildings have been collected in a systematic manner. Based on surveyed data, equivalent uniformly distributed load intensities, which produce the same load effect as the actual spatially varying, live load, have been obtained for various structural members (such as slab, beam, column, etc. ). Influence surface method has been employed to compute load effects under real live load, including beam moment, slab moment as well as axial force in column. The results have been examined to find probabilistic characteristics and relationship between influence area and load intensity (or coefficient of variation). The results were also compared with other survey results and found to be reasonable. Based on the probabilistic load models obtained, the lifetime extreme values have been analyzed and compared with current design loads. Tentative equations applicable to decide more rational design loads are also suggested as functions of influence area.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.525-532
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• 2015

In this paper, we propose an equivalent model of array antennas that use open-ended waveguides for effective EM simulation. We first investigate an individual element that consists of an open-ended waveguide and square ground plane. The waveguide length, aperture size, and ground size of the individual element are adjusted to give a similar radiation pattern to that of the individual element of the original antenna. We then apply the designed equivalent model to two different types of array antennas, such as a microstrip patch array and a waveguide array antenna. Comparison of the simulation results using the equivalent model with the results obtained with the original antenna reveals a difference in gain of less than 0.2 dB and a difference in half power beam width(HPBW) of less than $1^{\circ}$. The designed equivalent model is then mounted on a simple aircraft, and the simulation results are again compared to results from the original antenna. We find a 60 % reduction in simulation resources and time when compared with the original antenna model.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.372-377
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• 2007

This paper proposes a novel fault diagnosis method of a electrolytic capacitor used for DC-link voltage smoothing in adjustable speed drives. The equivalent series resistance (ESR) of the electrolytic capacitor is directly estimated from DC-link voltage and load currents and the status of the electrolytic capacitor is determined from the estimated ESR. To compensate the variation of the ESR owing to temperature variation, diodes are located on the same PCB near the capacitor and the temperature of the capacitor is sensed indirectly from the voltage drop of diodes. Simulation and experimental studies show the effectiveness of the proposed method.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.108-113
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• 1998

By using an equivalent network based on Floquet's theorem and bisection principle, the optical properties of planar DFB guiding structure are evaluated. The optical parameters, such as Bragg condition and the reflectivity as a function of grating period, are numerically calculated. The numerical results reveal that this method offers a simple and convenient algorithm to analyze the optical characteristics of DFB configurations.

• Computational Structural Engineering
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• v.11 no.4
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• pp.177-186
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• 1998

PSC 연속 평판슬래브의 설계는 부정정 평판슬래브에 대한 정확한 해석의 어려움 등으로 등가보이론과 등가골조이론에 의한 근사식을 수정없이 사용하거나 컴퓨터를 이용한 해석에 의존하고 있으나 해석결과를 간단하게 정확히 평가할 수 있는 기법은 없는 실정이다. 또한 PSC 연속 평판슬래브의 부재력은 긴장재의 곡선형태에 따라 변하므로 실제 설계시 PS 긴장재의 정확한 곡선식을 찾는 것은 매우 중요하다. 본 연구에서는 비부착 PSC 연속 평판슬래브를 설계할 때 기둥과 기둥을 연결하는 PS 긴장재의 기하학적 곡선형태를 결정하는 방법과, PS 긴장력으로 인해 발생하는 평판슬래브의 기둥부 휨모멘트에 대하여 판이론을 기초로 간편하게 계산하는 방법을 제안하였다. 본 연구에서 제안된 이론으로 계산된 PSC 연속 평판슬래브에 대한 해석값과 유한요소 해석에 의한 지점 부모멘트를 비교 검토하여, 본 논문에서 제시한 기법의 타당성을 입증하였다. 따라서 본 연구는 설계자에게 컴퓨터의 해석결과를 간단하고 정확하게 검증할 수 있도록 하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.57-64
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• 2000

본 연구에서는 항만 및 어항시설의 내진설？준서에서 채택하고 있는 수정 Seed와 Idriss 방법을 이용하여 액상화 평가를 수행하고 액상화 가능지수(liquefaction potential index, LPI)와 등가 액상화 안전율(FE)을 이용하여 액상화 가능성에 대한 구역도를 작성하였다. 이 두결과가 유사한 것으로 나타나 등가 액상화 안전율의 적합성을 확인하였다 국내 연안의 두지역에 대하여 Hachinohe 지진기록과 Ofunato 지진기록을 이용한 액상화 가능성 구역도를 FE를 이용하여 작성한 후 비교한 결과 Hachinohe 지진기록에 의한 액상화 가능성 구역도가 더 과소평가되는 경향을 보이는 것으로 나타났다 또한 FE는 안전율의 형태로 표현되었기 때문에 구역도 작성과 해석에 편의 성을 제공하였다.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1012-1016
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• 2004

In the present paper, equivalent beam and equivalent bimorph beam models for IPMC(ionic Polymer-Metal Composite) actuators are described. Physical properties of an IPMC, such as Young's modulus and electro-mechanical coupling coefficient. are determined from the rule of mixture, bimorph beam equations, and measured force-displacement data of a cantilevered IPMC actuator. By using a beam equation with estimated physical properties, actuation displacements of a cantilevered IPMC actuator was calculated and a good agreement between the computed tip displacements and the measured data was observed. Finite element analysis(FEA) combined with the estimated physical properties was used to reproduce the force-displacement relationship of an IPMC actuator. Results from the FEA agreed well with the measure data. The proposed models might be used for modeling of IPMC actuators with complicated shapes and boundary conditions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.115-124
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• 2003

In this paper, the effects of vehicle loads on flat slab system are investigated on the basis of the previous studies for beam-gilder parking structural system. The influence surfaces of flat slab for a typical design section are constructed lot the purpose of obtaining maximum member forces under vehicle loads. In addition, the equivalent vehicle load factors for flat slab parking structures are suggested using artificial neural network. The network responses we compared with the results obtained by numerical analyses to verify the validation of Levenberg-Marquardt algorithm adopted as training method in this Paper. Many parameter studies for the flat slab structural system show dominant vehicle load effects at the center positive moments in both column and middle strips, like the beam-girder parking structural system.