• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권5호
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• pp.249-256
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• 1999

This paper describes static characteristics analysis of linear pulse motor(LPM) with two permanent magnets. Linear pulse motors are finding a wide range of application for the Factory-Automation or the Office-Automation. Typically, LPM provides for a reliable and precise control of position, velocity, or acceleration without using a closed-loop system. Some of the advantages of LPMs are ease of control, step multiplication, static and dynamic positioning, and locking force. The flux density and thrust of LPM is computed by the FEM and magnetic equivalent circuits which considered the magnetic nonlinear phenomena. The result of characteristics analysis are shown as the flux, the air gap reluctance and the thrust. The velocity and position characteristics as a function of unit step input is measured. To estimate the unit step response charecteristic of LPM, the simulation results by Matlab and the experimental results is compared.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.46-48
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• 1998

This paper introduces the design method of a variable reluctace liner pulse motor to be analysed by a 3-dimensional problem in the 2-dimension. And it shows the thrust force density with respect to the ratio of the slot width to the teeth width, the height of mover and the height of tooth.

• Bulletin of the Korean Chemical Society
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• 제28권1호
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• pp.85-88
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• 2007

Ab initio periodic Hartree-Fock calculations with the full potential and minimum basis set are applied to interpretation of scanning tunneling microscope (STM) and atomic force microscope (AFM) images on 1TVTe2. Our results show that the simulated STM image shows asymmetry while the simulated AFM image shows the circular electron densities at the bright spots without asymmetry of electron density to agree with the experimental AFM image. The bright spots of both the STM and AFM images of VTe2 are associated with the surface Te atoms, while the patterns of bright spots of STM and AFM images are different.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2010년도 정기 학술대회
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• pp.578-583
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• 2010

본 연구는 전통적인 형상탐색 기법중의 하나인 내력밀도법을 건축구조물의 통합설계최적화 과정에 도입하고 이와 관련된 이론적 배경과 수치해석 결과를 기술하였다. 통합설계최적화 기법은 크기최적화, 형상최적화 그리고 위상최적화와 같이 다양한 개별최적화 기법을 이용하게 되는데 본 연구에서는 구조물의 형상을 결정하는 단계에서 내력밀도법을 이용하였다. 특히 본 연구에서는 내력밀도법과 다른 개별최적화기법과의 연계성에 대하여 기술하고 아치형 트러스 구조물의 통합설계최적화를 수행하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1063-1065
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• 1993

LDM, easy to minute position control, is using as X-Y plotter or other recording instruments. Brushless LDM has better properties than the conventional Brush type LDM in many aspects. This paper presents magnetic flux density distribution by FEM and a way to reduce thrust force ripple particurary in low speed drive. And we apply this method to a real mode of LDM. This LDM is operated by IBM-PC host computer and uses rotary encoder to make position signal.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.310-313
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• 2005

In recent years, as the robot technology is developed, the researches on the artificial muscle actuator that enable robot to move dexterously like biological organ become active. The widely used materials for artificial muscle are the shape memory alloy and the electro-active polymer. These actuators have the higher energy density than the electro-mechanical actuator such as motor. However, there are some drawbacks for actuator. SMA has the hysterical dynamic characteristics. In this paper, the simulation of anthropomophic robotic hand is performed using ADAMS and the segmented binary control for reducing the hysteresis of SMA is proposed. SMA is controlled by thermo-electric module. The relations between the force and the hysteresis are developed to verify the validity of the suggested method.

• Wind and Structures
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• 제32권4호
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• pp.341-354
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• 2021

Articulated towers are one of the class of compliant offshore structures that freely oscillates with wind and waves, as they are designed to have low natural frequency than ocean waves. The present study deals with the dynamic response of a double-pendulum articulated tower under hydrodynamic and aerodynamic loads. The wind field is simulated by two approaches, namely, single-point and multiple-point. Nonlinearities such as instantaneous tower orientation, variable added mass, fluctuating buoyancy, and geometrical nonlinearities are duly considered in the analysis. Hamilton's principle is used to derive the nonlinear equations of motion (EOM). The EOM is solved in the time domain by using the Wilson-θ method. The maximum, minimum, mean, and standard deviation and salient power spectral density functions (PSDF) of deck displacement, bending moment, and central hinge shear are drawn for high and moderate sea states. The outcome of the analyses shows that tower response under multiple-point wind-field simulation results in lower responses when compared to that of single-point simulation.

• 한국정보통신학회논문지
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• 제8권3호
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• pp.679-685
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• 2004

전기영동전착법은 제작장치와 공정이 간단하고 두께제어 및 다양한 형태의 초전도 막과 선재 제작이 가능한 경제적 효율성과 기술적 장점을 가지고 있다. 본 논문에서는 전착공정 개발을 통한 분말의 치밀성 및 배향성 향상을 위한 최적화 방안과, 건조 및 열처리 과정에서의 크랙 및 기공현상과 같은 문제점을 극복할 수 있는 균일한 표면의 확보에 관한 연구를 수행하였으며 전기영동전착 초전도 후 막 테이프 제조를 위한 공정의 최적화 방안에 대하여 연구하였다. YBCO 초전도 후막의 균일한 표면과 초전도특성 향상을 위한 공정개선방법으로는 수직방향 교류전계 인가 방식을 적용한 시스템을 최초로 개발하여 전기영동전착 공정에 적용하였다. 본 연구에서 제안한 수직방향 교류전계 인가 방식은 경제적 효율성을 위하여 60 Hz의 25∼120 V/cm의 상용전원을 사용하였으며, 제작된 후막은 기공과 크랙현상이 제거된 균일한 후막으로 여기서 얻어진 대표적인 특성 값들은 임계온도(Tc,zero) 90 K, 임계전류밀도 3419 A/$\textrm{cm}^2$의 값을 얻었다. 직류 전착전계만을 사용하여 제작된 후막의 임계전류밀값인 2354 A/$\textrm{cm}^2$에 비하여 45% 이상 향상된 특성을 확보하였다.

• 한국해안·해양공학회논문집
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• 제33권3호
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• pp.93-100
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• 2021

고정된 격자시스템에서 임의형상의 불투과 경계를 갖는 물체와 유체와 연성해석이 가능한 IB(Immersed Boundary)법이 개발 된 이후로 다양한 CFD 모델에서 IB법의 활용이 증가하고 있다. 기존의 IB법의 대부분은 구조물의 경계면에서 산정되는 유체력으로부터 수치적으로 경계조건을 만족시키는 directing-forcing법이나 구조물 내부에 가상셀을 위치시켜 보간을 통해 경계조건을 만족시키는 ghost-cell법들로 알고리즘이 복잡하다. 본 연구에서는 고정된 격자시스템에서 가동물체형 구조물 해석이 가능함과 더불어 3차원으로의 확장도 용이한 SIB(Simplified Immersed Boundary)법을 제안하였다. 본 연구에서 제안한 SIB법은 각 상(phase)의 밀도함수가 국소질량의 중심과 함께 이동하는 것으로 가정한 단일유체모델(one-field model for immiscible two-phase fluid)을 기초로 하였다. 또한 이동하는 고체상태의 구조물을 취급하기 위해 고체의 밀도함수를 이용한 체적가중평균법을 적용하고, 수치확산을 방지하기 위해 이류계산에는 CIP법을 적용하였다. 제안된 SIB법의 해석성능을 검토하기 위해 자유수면으로 낙하하는 물체에 대한 수치모의를 수행하였다. 수치해석결과는 자유수면으로 낙하하는 물체를 양호하게 재현하였다.

• Structural Engineering and Mechanics
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• 제54권2호
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• pp.257-289
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• 2015

Shear connectors are generally used to link the slab and girders together in slab-on-girder bridge structures. Damage of shear connectors in such structures will result in shear slippage between the slab and girders, which significantly reduces the load-carrying capacity of the bridge. Because shear connectors are buried inside the structure, routine visual inspection is not able to detect conditions of shear connectors. A few methods have been proposed in the literature to detect the condition of shear connectors based on vibration measurements. This paper proposes a different dynamic condition assessment approach to identify the damage of shear connectors in slab-on-girder bridge structures based on power spectral density transmissibility (PSDT). PSDT formulates the relationship between the auto-spectral densities of two responses in the frequency domain. It can be used to identify shear connector conditions with or without reference data of the undamaged structure (or the baseline). Measured impact force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at sensor locations by experimental modal analysis. PSDT from the slab response to the girder response is derived with the obtained frequency response functions. PSDT vectors in the undamaged and damaged states can be compared to identify the damage of shear connectors. When the baseline is not available, as in most practical cases, PSDT vectors from the measured response at a reference sensor to those of the slab and girder in the damaged state can be used to detect the damage of shear connectors. Numerical and experimental studies on a concrete slab supported by two steel girders are conducted to investigate the accuracy and efficiency of the proposed approach. Identification results demonstrate that damages of shear connectors are identified accurately and efficiently with and without the baseline. The proposed method is also used to evaluate the conditions of shear connectors in a real composite bridge with in-field testing data.