• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
• /
• pp.560-564
• /
• 2003

This paper proposes a simple control strategy based on the discontinuous PWM(DPWM) to balance the DC-link voltage of three-level Neutral-Point-Clamped(WPC) inverters at low modulation index. New DPWM methods in multi-level inverter are also introduced. The proposed DPWM method changes the path and duration to flow the neutral point current out of or into neutral point of the DC-link and it makes the overall fluctuation of the DC-link voltage zero during a sampling time of reference voltage vector. Therefore, the voltage of the DC-link can be balanced fairly well and also the voltage ripple of the DC-link is reduced significantly. Moreover, comparing with conventional methods, the proposed strategy is very simple. The validity of the proposed DPWM method is verified by experiment

• 한국감성과학회:학술대회논문집
• /
• 한국감성과학회 2009년도 춘계학술대회
• /
• pp.163-166
• /
• 2009

본 연구는 동영상자극에 의한 정서유발시의 표정변화와 생리반응을 밝혀내는 것을 목적으로 실행되었다. 18명의 실험참가자에게 각각 2종류씩의positive, negative 그리고neutral의 총5가지의 동영상자극을 약5분간 제시하였다. 표정변화는 비디오카메라로 기록하였고, 생리반응으로 뇌파(64ch), 심전도, 임피던스카디오그램, 안면근전위등을 측정했다. 표정의 분석결과, positive조건은 neutral조건에 비해 눈구석간의 거리가 감소하였고, 입 꼬리간의 거리는 증가하였다. 반면, negative조건은 neutral조건에 비해 오른쪽 눈구석과 눈 꼬리간의 거리가 증가하였다. 뇌파의 alpha/beta ratio변화량에 있어 positive조건은 neutral조건에 비해 우전두엽을 중심으로 감소하였고, negative조건은 좌전두엽에서 감소하였다. 심박수 및 PEP/LVET는 negative조건에서만 감소하였다. 또한, 근전위의 변화는 positive조건이 neutral조건보다 좌우볼 및 입부위에서 증가한 반면, negative조건은 좌우눈썹부위에서 증가하였다. 이에 본 연구를 통해, 정서유발시의 표정변화와 생리반응의 특성을 알 수 있었다.

• 대한공간정보학회지
• /
• 제20권4호
• /
• pp.145-151
• /
• 2012

본 연구는 최근 건설 산업의 큰 흐름으로 시도되고 있는 건설 공간 정보 모델링을 위한 BIM 핵심 기술 중 하나인 라이브러리와 관련되어 IFC와는 또 다른 관점에서 파라메트릭 모델링 및 알고리즘을 묘사할 수 있는 중립 라이브러리 개발을 위한 기술 요소와 효과적인 개발 방향을 제안한다. 이를 위해 최근 관련 연구를 고찰하고 현재 활용되고 있는 라이브러리를 이용한 대표적인 BIM 모델러인 Revit, ArchiCAD의 라이브러리 기술을 분석하였다. 분석된 결과를 바탕으로 BIM 파라메트릭 모델 구조 및 알고리즘 정의를 위한 기술적 공통 요소들을 분석하고 개념적인 연구를 통해 이런 요소들을 포함한 BIM 묘사 스크립트 언어 기반 중립 라이브러리 개발 방향을 제시하였다.

• 구강회복응용과학지
• /
• 제17권2호
• /
• pp.113-123
• /
• 2001

The success of complete denture prosthesis is to satisfy three basic requirements for the edentulous patient : maximum comfort, efficiency, and esthetic appearance. This can be achieved only if the dentures are both stable and retentive. When the residual alveolar ridge has resorbed significantly, stability and retention are more dependent on the correct position of the teeth and external surfaces of the denture. The stability and retention of the denture can be improved by locating the denture in the neutral zone and reproducing exact mandibular border movement for balanced occlusion. The neutral zone philosophy is based upon the concept that there exists a specific area where the musculature function will not unseat the denture in the mouth. In here, forces generated by the tongue are neutralized by the forces generated by the lips and cheeks. One of the simplest methods for recording border movements in three dimensions is to make stereographic record of condylar movement. Stereographs are made in the mouth during mandibular movement with intraoral clutches and central bearing point, and used in dictating the condylar movement on the articulator later by generating the condylar paths in doughy acrylic resin. Its procedure is simpler and more convenient than that of Pantograph. In this clinical report, we introduce the concept of neutral zone and stereograph in complete denture fabrication.

• 한국진공학회지
• /
• 제19권2호
• /
• pp.121-127
• /
• 2010

소형위성의 추력시스템으로 사용되어지는 홀 추력기의 중성 기체 시뮬레이션을 수행하였다. 홀 추력기의 채널 내부에서의 난반사효과 및 초기 가스의 온도, 그리고 채널의 길이 등을 변수로 하여 계산되어진 밀도, 압력, 속도, 온도를 분석 하였다. 시뮬레이션에서 얻어진 결과를 통해 홀 추력기의 방전 시뮬레이션의 정확성을 높이는 동시에 실제 시스템의 이해에 기여할 것으로 예상되어 진다.

• 전기학회논문지
• /
• 제60권3호
• /
• pp.479-485
• /
• 2011

In 22.9kV underground distribution system, power cables are provided with multiple-point ground in which each neutral line of the distribution cable(A, B, C phases) and three-wire common grounded at every connecting section. But in such grounding methods, circulating current flows between the neutral wire and grounding wire. And power loss due to circulating current also occurs in all conductors. Therefore it is getting necessary reducing circulating current in underground distribution system. This paper presents improved grounding method to overcome such problems. The proposed grounding method eliminates circulating current in the neutral line effectively and is verified that there is no electrical problem or any ineffectiveness of operating protection systems. These analyses are carried out by EMTP/ATPDraw to compare each grounding methods in steady and transient state. This grounding method suggested in this paper can be applied on real distribution system after field tests considering elimination of circulating current was implemented.

• 조명전기설비학회논문지
• /
• 제22권10호
• /
• pp.76-83
• /
• 2008

중성선 전류는 부하 불평형 전류와 3배수 고조파 전류로 이루어져 있다. 중성선 전류의 주요한 원인이 되는 3배수 고조파 전류는 단상 비선형 부하가 사용하는 단상 정류회로에 기인하며, IEC 61000-3-2의 클래스 D에 속하는 TV, 컴퓨터, 모니터가 부하전류 대 3배수 고조파 전류를 가장 많이 발생시킨다. 배전계통에 미치는 고조파 영향의 예를 보이기 위해 고조파를 고려하지 않은 중성선 공용 문제에 대해 현행 배전설비 설계기준을 살펴보고 대책을 살펴본다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제50권6호
• /
• pp.281-287
• /
• 2001

In order to obtain guidelines for design and operation of a new plasma source by a magnetic neutral loop discharge(NLD), the electron behavior was studied experimentally and numerically. Experimentally, the magnetic field gradient was changed over a wide range, and it was found that there existed an optimum value for efficient plasma production. Analyses of the electron behavior were performed using a model that included effects of a three dimensional electromagnetic field configuration considering the spatial decay of the electric field, and the limitation to the motion of electron caused by the existence of walls and thus electron loss at wall surfaces. These three dimensional factors were found to explain the existence of the optimum magnetic field gradient. It was shown that the L dependence of the plasma production efficiency was firstly decided by the finite decay length of the electric field strength, which was further modified by electron elastic collisions with neutral atoms which drove the electron to walls. The latter effect tends to reduce the optimum value of L.

• Structural Engineering and Mechanics
• /
• 제57권1호
• /
• pp.127-140
• /
• 2016

In this paper, a new first shear deformation plate theory based on neutral surface position is developed for the static and the free vibration analysis of functionally graded plates (FGPs). Moreover, the number of unknowns of this theory is the least one comparing with the traditional first-order and the other higher order shear deformation theories. The neutral surface position for a functionally graded plate which its material properties vary in the thickness direction is determined. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Based on the present shear deformation plate theory and the neutral surface concept, the governing equations are derived from the principle of Hamilton. There is no stretching-bending coupling effect in the neutral surface based formulation. Numerical illustrations concern flexural and dynamic behavior of FG plates with Metal-Ceramic composition. Parametric studies are performed for varying ceramic volume fraction, length to thickness ratios. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.

• Journal of Power Electronics
• /
• 제19권1호
• /
• pp.119-133
• /
• 2019

Although the dual modulation wave method can solve the low-frequency neutral point potential (NPP) fluctuation problem for three-level neutral point clamped converters, it also increases the switching frequency and limits the zero-sequence voltage. That makes it harmful when dealing with the NPP drift problem if the converter suffers from a long dead time or asymmetric loads. By introducing two degrees of freedom (2-DOF), an NPP control based on a search optimization method can demonstrate its ability to cope with the above mentioned two types of NPP problems. However, the amount of calculations for obtaining an optimal 2-DOF is so large that the method cannot be applied to certain industrial applications with an inexpensive digital signal processor. In this paper, a novel optimal 2-DOF-based NPP control is proposed. The relationships between the NPP and the 2-DOF are analyzed and a method for directly determining the optimal 2-DOF is also discussed. Using a direct calculation method, the amount of calculations is significantly reduced. In addition, the proposed method is able to maintain the strongest control ability for the two types of NPP problems. Finally, some experimental results are given to confirm the validity and feasibility of the proposed method.