• 한국음향학회지
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• 제21권7호
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• pp.592-599
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• 2002

본 연구에서는 상용 유한요소 해석 프로그램인 PZflex를 이용하여 초음파 탐촉자를 설계하고 이에 따라 제작하였다. 제작된 탐촉자는 복부 진단용에 적합한 크기와 형태로 중심 주파수 5 ㎒에 128개의 압전 소자가 곡면상에 1차원 배열된 컨벡스 (convex)형이며 두 층의 음향정합층, 하나의 후면층 그리고 각 압전소자 간의 커프로 구성된다. 제작된 탐촉자의 성능을 평가하여 설계치의 타당성을 검증하였으며, 등가회로 해석법에 의한 결과와 비교하여 유한 요소 해석법에 의한 설계법의 우수성을 확인하였다

• Journal of Magnetics
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• 제19권2호
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• pp.130-139
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• 2014

This paper focuses on the modeling and analysis a novel two-axis rotary normal-stress electromagnetic actuator with compact structure for fast steering mirror (FSM). The actuator has high force density similar to a solenoid, but its torque output is nearly a linear function of both its driving current and rotation angle, showing that the actuator is ideal for FSM. In addition, the actuator is designed with a new cross topology armature and no additional axial force is generated when the actuator works. With flux leakage being involved in the actuator modeling properly, an accurate analytical model of the actuator, which shows the actuator's linear characteristics, is obtained via the commonly used equivalent magnetic circuit method. Finally, numerical simulation is presented to validate the analytical actuator model. It is shown that the analytical results are in a good agreement with the simulation results.

• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1523-1530
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• 2007

The first reduction peak of the cyclic voltammogram (CV) for sulfur reduction in dimethyl sulfoxide has been studied using time resolved Fourier transform electrochemical impedance spectroscopic (FTEIS) analysis of small potential step chronoamperometric currents. The FTEIS analysis results reveal that the impedance signals obtained during short potential steps can be resolved into electron transfer reactions of two different time constants in a high frequency region. The FTEIS method provides snap shots of impedance profiles during an earlier phase of the reaction, leading to time resolved EIS measurements. Our results obtained by the FTEIS analysis are consistent with a series of electron transfer and chemical equilibrium steps of a complex reaction, making up an ECE (electrochemical-chemical-electrochemical) mechanism postulated from the results of computer simulation.

• Journal of Magnetics
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• 제16권2호
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• pp.157-160
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• 2011

The magnetostrictive material is magnetized in magnetic field and produces a nonuniform demagnetizing field inside and outside it. The demagnetization is decided by the permeability of magnetostrictive material and its size. The magnetoelectric performances are determined by the synthesis of the applied and demagnetizing fields. An analytical model is proposed to predict the magnetoelectric voltage coefficient (MEVC) of magnetostrictive/piezoelectric laminate composite using equivalent circuit method, in which the nonuniform demagnetizing field is taken into account. The theoretical and experimental results indicate that the MEVC is positively connected with the permeability and the piezomagnetic coefficient of magnetostrictive material. To obtain the maximum MEVC, both the permeability and the piezomagnetic coefficient of magnetostrictive material should be taken into account in selecting the suitable magnetostrictive material.

• 한국응용과학기술학회지
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• 제25권1호
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• pp.52-57
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• 2008

In the present study, impedance characteristics for AgO-Zn cell at various State-of-Charge (SoC) has been studied. The impedance measurements of AgO-Zn cell at various SoC were made over the frequency range from 100kHz to 10mHz with an amplitude 5mV. The impedance parameters have been evaluated by the analysis of the data using an equivalent circuit and a Non-linear least squares (NLLS) fitting method. The total resistances reflects the SoC of the cell. This indicates that the total resistance is important parameter for predicting SoC of AgO-Zn cell.

• 한국전자파학회논문지
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• 제23권9호
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• pp.1073-1078
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• 2012

본 논문에서는 손실을 고려한 등가 회로 분석을 통하여 자계 결합 무선 전력 전송 시스템에서의 결합 계수 추출식을 유도하였다. 부하 저항을 고려한 유도된 추출식을 이용하여 결합 모드 이론을 이용한 기존의 추출식을 일반화시켰다. 따라서 우수/기수 모드 해석이 불필요하기 때문에 측정 과정에서 쉽게 결합 계수를 구할 수 있다. 또한, EM 시뮬레이션에서 두 루프를 통과하는 자속의 비를 이용하여 구한 결합 계수와 유도된 추출식을 이용하여 구한 결합 계수가 일치함을 확인할 수 있다. 자계 결합 무선 전력 전송에서의 정확한 결합 계수를 추출한다면, 시스템을 분석하고 최적화시키는 데 유용하게 활용할 수 있다.

• 드라이브 ㆍ 컨트롤
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• 제15권2호
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• pp.46-51
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• 2018

Many research studies have been carried out related to saving energy and environmental pollution in the field of construction machinery. The best solution for reducing the related environmental pollution is to reduce fuel consumption by upgrading the energy efficiency of machinery used in this field. An efficiency upgrade in the field of construction machinery would mean minimizing the pressure loss in hydraulic pipe lines or achieving optimal operating conditions while responding to a load. One way to achieve this is to make an equivalent circuit, like an electrohydrostatic actuator, or to improve the spool type valve using the 4/3 way method. This study deals with an electrohydraulic proportional flow control valve. SimulationX software is used as a simulation tool for analyzing the dynamic characteristics. The analysis results, including the performance and characteristics of design parameters, are discussed and the validity of the theoretical analysis is also evaluated.

• 전력전자학회논문지
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• 제3권1호
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• pp.77-84
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• 1998

본 논문에서는 비선형상태피드백을 적용한 무효전력보상기의 제어시스템을 설계하여 시뮬레이션과 축소모형 실험에 의한 성능해석에 관해 기술하였다. 무효전력 보상기의 수리모형을 3상 등가회로와 대표적인 동작점에 대한 상태방정식을 이용하여 도출하였으며, 비선형 상태피드백을 고려한 무효전력 보상기의 동특성을 표현하는 전달함수를 유도하였다. 또한 근궤적을 이용한 시스템 안정도 해석을 실시하여 제어시스템 설계를 실시하였다. 고안된 제어시스템의 성능해석은 EMTP를 이용한 시뮬레이션과 축소모형 실험을 통해 검증하였는데, 검증결과 고안된 제어시스템은 송전계통의 무효전력보상에 우수한 성능을 갖음이 확인되었다.

• 대한전자공학회논문지TC
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• 제44권12호
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• pp.8-15
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• 2007

본 논문에서는 기존의 Right/left-handed 전송선(RLH-TL)에 집중 직렬 캐패시터와 병렬 인덕터 구현으로 발생하는 방사 효과를 포함하여 단위 셀을 모델링한다. 방사 효과가 고려된 RLH-TL 단위셀의 등가 회로를 제공하고 갭 커패시터와 션트 인터터에서의 방사율에 따른 Bloch 임피던스와 복소 전파상수를 해석한다. 두 개의 방사율이 같을 때 RLH-TL의 Block 임피던스는 RH-TL의 특성임피던스와 같아짐을 보인다. 게다가, 주어진 주파수에서 특정한 위상 변화를 위한 단위 셀의 설계 공식을 유도하여 제공한다. 마지막으로, 안테나 응용을 위해 RLH-TL에서 다양한 방법으로 방사효과를 control할 수 있는 설계 공식을 제공한다.

• Journal of Magnetics
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• 제22권1호
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• pp.133-140
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• 2017

Split magnetic fluid sealing is a combination of magnetic fluid rotary and plane sealing. Using the theory of equivalent magnetic circuit design as basis, the author theorized the pressure resistance performance of magnetic fluid plane sealing. To determine the pressure resistance of magnetic fluid plane sealing, the author adopted the method of finite element analysis to calculate the magnetic field intensity in the gap between plane sealing structures. The author also analyzed the effect of different sealing gaps, as well as different ratios between the sealing gap and tooth and solt width, on the sealing performance of split magnetic fluid. Results showed that the wider the sealing gap, the lower the sealing performance. Tooth width strongly affects sealing performance; the sealing performance is best when the ratio between tooth width and sealing gap is 2, whereas the sealing performance is poor when the ratio is over 8. The sealing performance is best when the ratio between the solt width and sealing gap is 4, indicating a slight effect on sealing performance when the ratio between the solt width and sealing gap is higher. Theoretical analysis and simulation results provide reference for the performance evaluation of different sealing equipment and estimation of critical pressure at interface failure.