• Journal of Power Electronics
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• 제16권3호
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• pp.1163-1175
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• 2016

In recent years, microgrids have been the focus of considerable attention in distributed energy distribution. Microgrids contain a large number of power electronic devices that can potentially cause negative impedance instability. Harmonic impedance is an important tool to analyze stability and power quality of microgrids. Harmonic impedance can also be used in harmonic source localization. Precise measurement of microgrid impedance and analysis of system stability with impedances are essential to increase stability. In this study, we introduce a new square wave current injection method for impedance measurement and stability analysis. First, three stability criteria based on impedance parameters are presented. Then, we present a new impedance measurement method for microgrids based on square wave current injection. By injecting an unbalanced line-to-line current between two lines of the AC system, the method determines all impedance information in the traditional synchronous reference frame d-q model. Finally, the microgrid impedances of each part and the overall microgrid are calculated to verify the measurement results. In the experiments, a simulation model of a three-phase AC microgrid is developed using PSCAD, and the AC system harmonic impedance measuring device is developed.

• 한국의학물리학회지:의학물리
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• 제7권2호
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• pp.3-17
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• 1996

방사선 치료분야에서 선량 보상체가 널리 이용되고 있으나, 그 보상효과에 대한 확실한 검증 방법은 알려진 바가 거의 없다. 본 연구에서는 Missing Tissue 뿐 아니라, Internal Tissue Inhomogeneity 까지 고려한 3차원 보상체를 제작하고, Exit Beam Dose Profile의 측정값과 본 연구에서 고안한 방법으로 기대값을 구해 비교함으로써 보상체의 성능을 평가하고자 하였다. 환자정보는 CT Simulator를 사용하여 얻었고, 보상체 정보는 Render Plan 3-D Planning System을 통해 얻었다. Computer Controlled Milling Machine으로 알루미늄 보상체를 제작해서 보상체가 있는 경우와 없는 경우의 선량 프로파일을 측정하여 비교하였다. 측정은 폴리스티렌 팬톰 사이에 필름을 삽입하여 팬톰 내에서의 실제 선량 분포를 구하고, 필름 카셋트를 이용해서 Exit Beam Dose Profile 을 동시에 얻었다. Oblique Beam, Parallel Opposing Beam, Inhomogeneus Human Phantom에 대해 제작된 보상체가 각각 선량보상 효과가 잘 나타남을 볼 수 있었고, 이 연구에서의 성능확인 방법을 통해 보상체의 성능을 확인할 수 있었다.

• 정보처리학회논문지D
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• 제10D권1호
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• pp.101-108
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• 2003

동북아 중심 항만의 기반을 다지기 위해 자동화항만의 건설이 시급히 요청되고 있다. 따라서 우리나라에 적합한 자동화항만의 운영시스템 레이아웃 설계방안을 제시하고자 한다. 본 논문에서는 자동화항만의 운영시스템이 추구해야말 목표를 충족시키며, 각 자동화 장비를 통한 화물의 수출입 이동경포에 따라 운영시스템의 모델을 4가지로 구분하고 여러 입력 요소들을 변경시켜 가며 시행착오를 거쳐 동적으로 분석해 나감으로서 최적의 운영시스템 모델을 선정하고, 그에 대한 수출입화물별 야드 운영시스템 레이아웃을 설계하였다. 특히 미래의 자동화항만에서는 어떠한 자동화 장비를 사용하느냐에 따라 그 생산성이 달라진다. 그러나 현실적으로 비용측면과 현재의 작업 흐름을 도외시 할 수 없기 때문에 현재의 작업을 최적화하고 현재의 사용 장비와 자동화 장비의 대체로 작업의 혼선이 발생하지 않은 방법을 선택하여 레이아웃을 설계하였다. 본 논문의 야드 운영시스템에서 기술한 장비들은 Q/C(Quay Crane)을 제외한 모든 야드 장비가 완전자동화를 전제로 한 것이다.

• Journal of Power Electronics
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• 제5권1호
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• pp.36-44
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• 2005

This paper presents an implementation of high performance control of a reluctance synchronous motor (RSM) using a neural network with a direct torque control. The equivalent circuit in a RSM, which considers iron losses, is theoretically analyzed. Also, the optimal current ratio between torque current and exiting current is analytically derived. In the case of a RSM, unlike an induction motor, torque dynamics can only be maintained by controlling the flux level because torque is directly proportional to the stator current. The neural network is used to efficiently drive the RSM. The TMS320C3l is employed as a control driver to implement complex control algorithms. The experimental results are presented to validate the applicability of the proposed method. The developed control system shows high efficiency and good dynamic response features for a 1.0 [kW] RSM having a 2.57 ratio of d/q.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.586-588
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• 2002

This study investigaties magnetic circuit design of the Line-Start Permanent Magnet Synchronous Motor (LSPM) for advanced reluctance torque in steady state. Back-emf and d-/q-axial inductance is analyzed by using 2 dimensional Finite Element Method (FEM). These results are reflected characteristic analysis of LSPM.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.119-123
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• 2009

In this paper, effects of major design parameters of cold forging dies on die mechanics are quantitatively investigated with emphasis on shrink fit using a thermoelastic finite element method. A ball-stud cold forging process found in a cold forging company is selected as a test process and the effects of die insert material, shrink fit, dimension of ring, partition of die inert and clamping force on effective stress and circumferential stress are analyzed.

• 충청수학회지
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• 제15권2호
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• pp.1-12
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• 2003

L. H. Encinas, A. J. Menezes, and J. M. Masque in [2] proposed a classification of isomorphism classes of hyperelliptic curve of genus 2 over finite fields with characteristic different from 2 and 5. Y. Choie and D. Yun in [1] obtained for the number of isomorphic classes of hyperelliptic curves of genus 2 over $F_q$ using direct counting method. In this paper we will classify the isomorphism classes of hyperelliptic curves of genus 2 over $F_{2^n}$ for odd n, represented by an equation of the form $y^2+a_5y=x^5+a_8x+a_{10}(a_5{\neq}0)$.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.177-178
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• 2013

To implement servo system using LIM, thrust and normal force control must be made in a moment. Thus, vector control is required to control magnetic flux and toque. In this paper, we applied to constant slip frequency vector control method by controlling d-q axis current and presented various simulation results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.336-338
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• 1996

In this paper, a simple control strategy to interconnect the utility line system for three-phase inverter. Conventionally, such interconnection is based on the 3-phase time-domain waveform analysis, though the control based on the plane defined by the two-axis theory is common in the area of the motor control. The new instantaneous power control strategy is introduced, which is based on the d-q axis theory. Simulation results show that proposed control method has good controllability with simple strategy.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.52-55
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• 2001

This paper is to see the availability of electrical signatures as a means for evaluating the performance and monitoring mechanical anomalies of (MOVs). To estimate motor torque, two methods such as d-q frame conversion and air-gap method are suggested and estimated results are compared with measured values. The error between measured and estimated torques is within acceptable error bound with below $1\%$ under varied load. Frequency domain analysis of calculated torque has been done as well. It is shown that monitoring of peak frequency could give useful clues to detect anomalies of MOV. As results, electrical signatures at MOV motor is expected to be an available tool for estimation of motor capacity and monitoring of electrical and mechanical abnormalities.