• 천문학논총
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• 제30권2호
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• pp.417-421
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• 2015

We analyzed 0.5-45 keV data of NGC 3227 observed by Suzaku six times between 2008 October 28 and December 2. The count-count plot between the 0.5-3 keV and 3-10 keV bands exhibits a clear break, separating the data into bright and faint phases. Applying the difference spectrum method and time-averaged spectral fits to the phase data, we found the presence of two kinds of variable primary X-rays, (1) a hard primary component with ${\Gamma}{\sim}1.7$ dominating in the faint phase and (2) a soft primary continuum with ${\Gamma}{\sim}2.4$ appearing in the bright phase, both affected by partial absorption. Considering their timing and spectral characteristics, component (1) is presumably identical to a Compton continuum in the low/hard state, while component (2) may correspond to the hard tail emission in the high/soft state, or compact-jet emission. In that case, an accretion ow onto the central super massive black hole in NGC 3227 can be interpreted to include the two different states.

• 한국전자통신학회논문지
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• 제9권11호
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• pp.1297-1304
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• 2014

사람의 감정 중의 하나인 사랑은 사회학과 심리학에서 주된 관심사로 연구되어 왔다. 본 논문에서는 로미오와 줄리엣의 사랑 방정식[ ]에서 이들의 거동을 시계열과 위상 공간으로 나타내고, 이들 사이에 외부적인 자극인 3자가 개입했을 때의 관계를 시계열과 위상 공간으로 나타내어 이들 사이의 거동 관계를 분석한다.

• 한국세라믹학회지
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• 제37권1호
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• pp.63-69
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• 2000

Electrically-induced strain(S) and polarization(P) for Pb(Sc1/2Nb1/2)O3-PbTiO3(1-x)PSN-xPT) crystalline solutions were studied. From the compositional dependence of S and P we could observe two maximum values at x=0.10 and x=0.425. It is considered that PSNT10(x=0.10) composition is the structural phase boundary to indicate the variable order-disorder[VOD] region. PSNT(x=0.425) composition is the morphotropic phase boundary[MPB] to indicate the rhombohedral to tetragonal phase transition. Higher S (0.437%) and P (0.3974$\mu$C/$\textrm{cm}^2$) values were attained by the La substitution (5 wt%) at Pb site in the MPB composition of 57.5PSN-42.5PT.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.301-302
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• 2014

This paper describes four switch three-phase Z-source rectifier with improved switching characteristics. This configuration has some advantages switching loss and optimal drive circuit. The rectifier has buck-boost function by shoot-through state. Also, the rectifier has the advantage of decreasing inrush current in start-up and transient states. In order to reduce harmonics PWM modulation technique with a variable index has been suggested. Four switch three-phase Z-source rectifier with improved switching characteristics can output stable DC voltage at the same time decreasing the system's harmonic current. And also the paper presents an application of DCC method in Z-source rectifier. Principles and dynamics of the system are discussed in detail. After having viewed the results we can confirm that the proposed method is eligible and efficient.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.303-304
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• 2014

This paper describes Four Switch Three-Phase Z-Source rectifier with reduced value capacitors. This configuration has some advantages in term of small size of the circuit. The rectifier has buck-boost function by shoot-through state. Also, the rectifier has the advantage of decreasing inrush current in start-up and transient states. In order to reduce harmonics PWM modulation technique with a variable index has been suggested. Four Switch Three-Phase Z-Source rectifier with reduced value capacitors can output stable DC. Principles and dynamics of the system are discussed in detail.

• 전기학회논문지
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• 제58권11호
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• pp.2162-2167
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• 2009

A Low cost and variable speed brushless motor drive system with single switch per phase is presented. The motor drive is realized with a novel two-phase flux-reversal-free switched reluctance motor and a split AC two switch converter. The strategy of the controller and the converter for its realization are described. Comparisons between a split AC converter, asymmetric converter, split DC converter, single controllable switch converter, and N+1 converter are performed for its device rating, cost, switching losses and conduction losses, and converter efficiency. The split AC converter is analyzed and simulated to verify the characteristics of the converter circuitry and control feasibility and the simulation results are presented. The efficiency with various loads is numerically estimated and experimentally compared from viewpoint of subsystem and system in details. The focus of this paper is to compare the presented motor drive system to the asymmetric converter system throughout experiments and demonstrate single switch per phase converter having comparable efficiency as the asymmetric converter system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.377-380
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• 2004

The phase transition between amorphous and crystalline states in chalcogenide semiconductor films can controlled by electric pulses or pulsed laser beam; hence some chalcogenide semiconductor films can be applied to electrically write/erase nonvolatile memory devices, where the low conductive amorphous state and the high conductive crystalline state are assigned to binary states. GeSbTe(GST), AsSbTe(AST), SeSbTe(SST) used to phase change materials by appling electrical pulses. Thickness of ternary chalcogenide thin films have about 100nm. Upper and lower electrode were made of Al. It is compared with I-V characteristics after impress the variable pulses.

• Journal of Power Electronics
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• 제18권6호
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• pp.1720-1728
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• 2018

This paper proposes a novel soft starting algorithm by using PWM inverter technique to control an amplitude of the motor starting current at a single-phase induction motor (SPIM). Traditional SPIM starting methods such as a Split-Phase, Capacitor-Start, Permanent-Split Capacitor (PSC), Capacitor-Start Capacitor-Run (CSCR), basically cannot control the magnitude of starting current due to the fixed system structures. Therefore, in this paper, a soft starting algorithm based on a proportional resonant (PR) control with a variable and constant frequency is proposed to reduce the inrush current and starting up time. In addition, a transition algorithm for operation modes is devised to generate a constant voltage and constant frequency (CVCF). The validity and effectiveness of the proposed soft starting method and transition algorithm are verified through experimental results.

• 대한금속재료학회지
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• 제50권3호
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• pp.248-255
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• 2012

AlN thin films containing various amounts of Co, AlN-Co, and Al-Co alloy particles were prepared using a two-facing-target type dc reactive sputtering (TFTS) system. The as-deposited films exhibited the variable nature expected from an AlN-rich phase, and an amorphous-like phase, depending on the Co content in the films. Specific favorable microstructures were prepared by optimizing annealing conditions. Those microstructures and their magnetic properties and resistivity were investigated. As-deposited films showed very small saturation magnetization and an amorphous-like structure. However, when annealed, the as-deposited amorphous-like phase decomposes into phases of AlN, Co and Al-Co. These annealing induced changes in the microstructure improve the magnetization and resistivity of the films. Further improvement of soft magnetic properties could lead to the material being used for high density magnetic recording head material.

• 한국지진공학회논문집
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• 제8권5호통권39호
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• pp.35-43
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• 2004

대형 구조물의 지진응답을 실험적으로 연구할 경우, 실험장비의 용량과 실험모형의 크기 제약으로 인하여 축소모형이 일반적으로 적용되고 있다. 그러나 구조물의 지진응답은 비탄성 거동을 나타내기 때문에 거동예측이 복잡함에도 불구하고, 축소모형의 지진실험 결과로부터 원형구조물의 지진응답을 유추하기 위한 상사법칙의 연구는 미비한 실정이다. 철근콘크리트 구조물의 축소모형 제작 시 상사율이 커지면 상대적으로 부가질량이 증가하며, 또한 굵은 골재 크기의 영향으로 원형구조물과 축소모형의 제작에 동일한 재료를 사용하지 않는 것이 바람직하다. 따라서 동일한 재료를 사용하지 않을 경우, 상사법칙은 기하학적인 상사율과 재료적인 등가탄성계수비에 의존하게 된다. 본 연구에서는 원형구조물과 축소모형에 각각 적용되는 normal-concrete와 micro-concrete의 재료 비선형성을 파악하기 위해 압축강도시험을 수행하여, 재료의 거동구간을 극한 변형률을 기준으로 등가의 다단계로 나누어 등가탄성계수비를 적용시킴으로써 지진손상의 정도를 고려할 수 있는 equivalent multi-phase similitude law를 유도하였다. 유도된 상사법칙을 고려한 유사동적실험 알고리즘을 구성하였으며, 실험적인 검증을 위하여 철근콘크리트 column에 대하여 원형구조물과 1/5축소모형을 재료시험에서 정의한 등가탄성계수비를 고려하여 설계, 제작하였다. 검증실험에서는 constant modulus ratio와 variable modulus ratio를 적용하여 준정적실험과 유사동적실험을 수행한 결과, equivalent multi-phase similitude law를 고려한 유사동적실험 알고리즘에 의한 축소모형의 응답결과가 원형구조물의 거동을 비교적 정확히 재현함을 확인하였다.