• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.5
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• pp.207-217
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• 2015

In order to increase seismic performance of nuclear power plant (NPP) in strong seismic zone, lead-rubber bearing (LRB) can be applied to seismic isolation system of NPP structures. Simple equivalent linear model as structural analysis model of LRB is more widely used in initial design process of LRB than a bilinear model. Seismic responses for seismically isolated NPP containment structures subjected to earthquakes categorized into 5 different soil-site classes are calculated by both of the equivalent linear- and bilinear- LRB models and compared each others. It can be observed that the maximum displacements of LRB and shear forces of containment in the case of the equivalent linear LRB model are larger than those in the case of bilinear LRB model. From the seismic fragility curves of NPP containment structures isolated by LRB, it can be observed that seismic fragility in the case of equivalent linear LRB model are about 5~30 % larger than those in the case of bilinear LRB model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.4
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• pp.397-404
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• 2010

The use of equivalent circuit models of piezoelectric energy harvesters is inevitable when power circuitry including rectifying and smoothing circuit elements is connected to them for evaluating DC electrical outputs. This is because it is difficult to incorporate the electro-mechanical coupling resulting from the additional circuitry into the conventional finite element analysis. Motivated by this observation, we propose a method to accurately extract the equivalent circuit parameters by using commercially available FEM software such as ANSYS which provides three-dimensional AC piezoelectric analysis. Then the equivalent circuit can be analyzed by circuit simulators such as $SimPowerSystems^{TM}$ of MATLAB. While the previous works have estimated the circuit parameters by experimental measurements or by analytical solutions developed only for limited geometries and boundary conditions, the proposed method has no such limitation because piezoelectric energy harvesters of any shapes and boundary conditions can be treated in FEM software. For the verification of the proposed method, multi-modal AC electrical power output by using a corresponding equivalent circuit is compared with that by ANSYS. The proposed method is then shown to be very useful in the subsequent evaluation of DC electrical output which is obtained by attaching a bridge diode and a storage capacitor to a piezoelectric energy harvester.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1626-1631
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• 2007

This paper presents a new modeling method using lamp output power and the modeling coefficients of the lamp. The proposed method utilizes the lamp modeling coefficients such as equivalent impedance Z(p), coupling coefficient of the transformer k(p), turns ratio of the transformer n(p), and plasma resistance Rp(p) as a function of lamp output power. The equivalent impedance Z(p) was developed from the equivalent resistance Req(p) and equivalent inductance Leq(p) of the lamp. Simulation and experimental results of the proposed model are presented in order to validate the proposed method. The modeling method can use to design an impedance matching circuit for a Class-D inverter.

• Journal of Power Electronics
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• v.17 no.2
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• pp.422-431
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• 2017

The equivalent circuit of a three-leg, four-wire voltage source converter (VSC) is derived using switching functions. Simulations and experiments are conducted (i) to investigate the effects of the zero sequence on VSCs when a three-phase imbalance exists and (ii) to use the consistency of simulations and laboratory experiments to validate the equivalent circuit. The impact of a three-phase imbalance on the VSC has yet to be fully investigated because of the lack of an equivalent circuit to show rigorously how the zero sequence currents flow through the VSC.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1057-1059
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• 1999

A procedure to develop dynamic equivalent systems of the KEPCO power system in the year 2010 was proposed, and 3 different equivalent systems in which the number of generators are 39, 30, and 19 were developed in this paper. The static and dynamic property of the reduced systems was verified by the comparison of time-domain simulation for the original system and the reduced systems.

• Journal of Power System Engineering
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• v.17 no.4
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• pp.131-138
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• 2013

The purpose of this study is to suggest the evaluation standard of cost-effectiveness analysis for renew of architectural equipment in public building. Evaluation items of cost-effectiveness analysis for renew of architectural equipment in public building were used life cycle cost, energy consumption(ton of oil equivalent), green house gas emissions(ton of carbon dioxide) and maximum power demand. Life cycle cost is the process of making an economic assessment of an item, area, system, or facility by considering all significant costs of ownership over an economic life, expressed in terms of equivalent costs. The essence of life cycle costing is the analysis of equivalent costs of various alternative proposals. The social concern with green house gas and maximum power demand of architectural equipment field has been growing for the last several years.

• Journal of Magnetics
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• v.20 no.1
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• pp.57-61
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• 2015

In this paper wireless power transmission system based on magnetic resonance coupling circuit was carried out. With the research objectives based on the mutual coupling model, mathematical expressions of optimal coupling coefficients are examined. Equivalent circuit parameters are calculated by Maxwell software, and the equivalent circuit was solved by Matlab software. The power transfer efficiency of the system was derived by using the electrical parameters of the equivalent circuit. System efficiency was analyzed depending on the different air gap values for various characteristic impedances. Hence, magnetic resonance coupling involves creating a resonance and transferring the power without radiating electromagnetic waves. As the air gap between the coils increased the coupling between the coils were weakened. The impedance of circuit varied as the air gap changed, affecting the power transfer efficiency.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.125-129
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• 2000

To fine understand the visual acuity of female old age. This study was researched the visual acuity test by the object and subject methods. The major findings was as follows: 1. The eye types were 80.94% positive for hyperopia. 13.86% for myopia and 5.19% for emmetropia respectively. 2. The anbormal refraction eye was positive for mixed astigmatism for 78.27%, myoptic com pound astigmatism (10.99%), simple presbyopia(4.97%), myopic simple astigmatism(2.88%), presbyopia compound astigmatism (1.57%), simple myopia(0.78%) and presbyopia simple astigmatism(0.52%). 3. The axis of astigmatism was 60.23% for against regular astigmatism. 22.73% for oblique astigmatism and 17.05% for regular astigmatism respectively. 4. On the total myopic spheric power, the -0.50 spheric equivalent ${\leq}-2.00$ was 90.2%, the -2.00${\leq}-6.00$ was 9.8%. 5. On the total presbyopic spheric power, the -0.50${\leq}-2.00$ was 80.252%, the -2.00${\leq}-6.00$ was 16.99% and 2.56% for anything over the 6.00 diopter. 6. On the astigmatic power, the $0.50{\geq}$ cylinder power${\geq}1.00$ was 69.35%,the 1.00> cylinder power ${\geq}2.00$ was 27.38%, and anything over the 2.00 cylinder diopter was 3.27%.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.501-509
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• 2015

Purpose: To evaluate the reliability of refractive power by comparing the marked refractive power in an automatic phoropter and actually measured spherical/cylindrical refractive power. Methods: Actual refractive power of minus spherical lens and cylindrical lens in an automatic phoropter was measured by a manual lensmeter and compared with the accuracy of marked refractive power. Furthermore, combined refractive power and spherical equivalent refractive power of two overlapped lenses were compared and evaluated with the refractive power of trial lens. Results: An error of 0.125 D and more against the marked degree was observed in 70.6% of spherical refractive power of spherical lens which is built in phoropter, and the higher error was shown with increasing refractive power. Single cylindrical refractive power of cylindrical lens is almost equivalent to the marked degree. Combined spherical refractive power was equivalent to spherical refractive power of single lens when spherical lens and cylindrical lens were overlapped in a phoropter. Thus, there was no change in spherical refractive power by lens overlapping. However, there was a great difference, which suggest the effect induced by overlapping between cylindrical refractive power and the marked degree when spherical lens and cylindrical lens were overlapped. Spherical equivalent refractive power measured by using a phoropter was lower than that estimated by trial glasses frame and marked degree. The difference was bigger with higher refractive power. Conclusions: When assessment of visual acuity is made by using an automatic phoropter for high myopes or myopic astigmatism, some difference against the marked degree may be produced and they may be overcorrected which suggests that improvement is required.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.385-388
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• 1999

A new frequency-variant equivalent circuit model of power/ground plane is presented. The equivalent circuit is modeled with grid cells. The circuit parameters of each cell were extracted by using Fasthenry. To verify the developed circuit model, its s-parameters are compared with the measured s-parameters 〔2〕 and the full-wave simulation-based s-parameters. Consequently, it is shown that our frequency-variant equivalent circuit model can accurately predict imperfect ground effects under the high frequency operation of electronic package.