• 해양환경안전학회:학술대회논문집
• /
• 해양환경안전학회 2007년도 추계학술발표회
• /
• pp.9-14
• /
• 2007

한국 남해안 거제도 앞바다에 구축된 인공용승구조물로 인하여 발생하는 유동 변화를 파악하기 위해 ADCP(Acoustic Doppler Current Profiler)를 이용한 정선관측을 2003년 하계 및 추계에 실시하였다. 관측 결과 하계에는 수심 약 $30{\sim}40$ m를 기준으로 상층과 하층의 유동분포가 상이한 경계수심이 존재하였으며, 추계에는 이러한 현상이 3층 구조로 나타났다. 또한 연직유동성분은 수심과 지역에 따라 상승류와 하강류가 번갈아 분포하였으며 이러한 현상은 관측범위를 확장하였을 때도 유사한 유동분포를 보이고 있다. 한편 ADCP의 수평유동성분을 이용하여 계산된 연직전단(vertical shear) 및 상대와도(relative vorticity)는 상승류가 발생하는 지역에서 연직전단은 큰 값을 나타내었고, 상대와도는 +값으로 상승류의 방향을 나타내었다. 이러한 결과는 유동성분의 상승류 분포역과 유사하게 나타났다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권1호
• /
• pp.30-34
• /
• 2005

This study shows the lasing characteristics of InGaAs/InGaAsP multiple-quantum-well waveguide-type depleted optical thyristor (DOT) using the vertical window. The measured switching voltage and current are 3.36 V and 10 ㎂, respectively. The lasing threshold current is 131 mA at 25 ℃. The output peak wavelength is 1570 nm at a bias current of 1.22 Ith and there is not input signal anymore in the output port. The vertical injection depleted optical thyristor - laser diode (VIDOT-LD) using the vertical-injection structure shows very good isolation between input and output signal.

• Ocean and Polar Research
• /
• 제33권spc3호
• /
• pp.397-407
• /
• 2011

To understand the vertical structure of ocean currents from raw data observed by lowered-ADCP (LADCP), these data require post-processing. Data were processed using Krahman's version 10.8 processing software based on Matlab. It is estimated the influence of auxiliary data affecting the processed current structure. The bottom-tracked velocities and the GPS information significantly contribute the offset on reference velocities in the bottom layer and barotropic ones in the middle layer, respectively. Good quality data can be obtained when LADCP is least tilted in pitch and roll during observation. In situ application of LADCP to the (northward) volume transports of Kuroshio in the East China Sea proved to be 24.8. Sv (= $1{\times}10^6m^3s^{-1}$) in October 2007, and 28.2 Sv in June 2008, respectively. The volume transport is relatively large over the continental slope when compared to the shelf or the deep sea.

• 전력전자학회논문지
• /
• 제25권3호
• /
• pp.195-203
• /
• 2020

This paper presents a parasitic inductance reduction design method for the stable driving of GaN HEMT. To reduce the parasitic inductance, we propose a vertical lattice loop structure with multiple loops that is not affected by the GaN HEMT package. The proposed vertical lattice loop structure selects the reference loop and designs the same loop as the reference loop by layering. The design reverses the current direction of adjacent current paths, increasing magnetic flux cancellation to reduce parasitic inductance. In this study, we validate the effectiveness of the parasitic inductance reduction method of the proposed vertical lattice loop structure.

• 한국산업정보학회논문지
• /
• 제21권1호
• /
• pp.1-6
• /
• 2016

본 논문에서는 기생 트랜지스터를 억제하여 대기 전류를 낮춰 기동전류를 개선한 수직 PNP 트랜지스터의 특성을 소개한다. 기생 효과를 억제하기 위해, 회로 변경 없이 "DN+ 링크"를 사용하여 기생 PNP 트랜지스터를 억제 시킨 수직 PNP 트랜지스터를 설계하였으며, 표준 IC 프로세서를 이용한 LDO 레귤레이터를 제작했다. 제작된 기생 PNP 트랜지스터의 hFE 가 기존의 18에서 0.9로 감소하였다. 개선된 "DN+ 링크" 구조 수직 PNP 트랜지스터로 제작된 LDO 레귤레이터의 기동 전류는 기존의 기동 전류 90mA에서 32mA 로 감소되었다. 이로 인해 대기상태에서 저 소비전력을 구현한 LDO 레귤레이터를 개발하였다.

• 전력전자학회논문지
• /
• 제20권2호
• /
• pp.130-136
• /
• 2015

This study describes the structure and operation modes of vertical stabilization (VS) converter for international thermonuclear experimental reactor (ITER) and proposes a protection method. ITER VS converter supplies voltage (${\pm}1000V$)/current (${\pm}22.5kA$) to superconducting magnets for plasma current vertical stabilization. A four-quadrant operation must be achieved without zero-current discontinuous section. The operation mode of the VS converter is separated in 12-pulse mode, 6-pulse mode and circulation current mode according to the magnitude of the load current. Protection measures, such as bypass and discharge, are proposed for abnormal conditions, such as over current, over voltage, short circuit, and voltage sag. VS converter output voltage is controlled to satisfy voltage response time within 20 msec. Bypass operation is completed within 60 msec and discharge operation is performed successfully. The feasibility of the proposed control algorithm and protection measure is verified by assembling a real controller and implementing a power system including the VS converter in RTDS for a hardware-in-loop (HIL) facility.

• Earthquakes and Structures
• /
• 제12권6호
• /
• pp.673-687
• /
• 2017

A three-dimensional; structural health monitoring; vertical; planar; cross-sample entropy; multiscaleA three-dimensional structural health monitoring (SHM) system based on multiscale entropy (MSE) and multiscale cross-sample entropy (MSCE) is proposed in this paper. The damage condition of a structure is rapidly screened through MSE analysis by measuring the ambient vibration signal on the roof of the structure. Subsequently, the vertical damage location is evaluated by analyzing individual signals on different floors through vertical MSCE analysis. The results are quantified using the vertical damage index (DI). Planar MSCE analysis is applied to detect the damage orientation of damaged floors by analyzing the biaxial signals in four directions on each damaged floor. The results are physically quantified using the planar DI. With progressive vertical and planar analysis methods, the damaged floors and damage locations can be accurately and efficiently diagnosed. To demonstrate the performance of the proposed system, performance evaluation was conducted on a three-dimensional seven-story steel structure. According to the results, the damage condition and elevation were reliably detected. Moreover, the damage location was efficiently quantified by the DI. Average accuracy rates of 93% (vertical) and 91% (planar) were achieved through the proposed DI method. A reference measurement of the current stage can initially launch the SHM system; therefore, structural damage can be reliably detected after major earthquakes.

• 한국초전도ㆍ저온공학회논문지
• /
• 제4권1호
• /
• pp.78-83
• /
• 2002

Since the KSTAR superconducting magnet structure should be maintained at a cryogenic temperature of about 4 K, even a small amount of heat might be a major cause of the temperature rise of the structure. The Joule heating by eddy currents induced in the magnet structure during the KSTAR operation was found to be a critical parameter for designing the cooling scheme of the magnet structure as well as defining the requirements of the refrigerator for the cryogenic system. Based on the Joule heating calculation, it was revealed that the bulk temperature rise of the magnet coil structure was less than 1 K. The local maximum temperature especially at the inboard leg of the TF coil structure increased as high as about 21 K for the plasma vertical disruption scenario. For the CS coil structure, the maximum temperature was obtained from the PF fast discharging scenario. This means that the vertical disruption and PF fast discharging scenarios are the major scenarios for the design of TF and CS coil structures, respectively. For the reference scenario, the location of maximum temperature spot changes according to the transient current variation of each PF coil.

• Structural Engineering and Mechanics
• /
• 제61권5호
• /
• pp.663-674
• /
• 2017

The determination of the fundamental period of vibration of a structure is essential to earthquake design. Current codes provide formulas for the approximate estimation of the fundamental period of earthquake-resistant building systems. These formulas are dependent only on the height of the structure or number of storeys without taking into account the presence of infill walls into the structure, despite the fact that infill walls increase the stiffness and mass of the structure leading to significant changes in the fundamental period. Furthermore, such a formulation is overly conservative and unable to account for structures with geometric irregularities. In this study, which comprises the companion paper of previous published research by the authors, the effect of the vertical geometric irregularities on the fundamental periods of masonry infilled structures has been investigated, through a large set of infilled frame structure cases. Based on these results, an attempt to quantify the reduction of the fundamental period due to the vertical geometric irregularities has been made through a proposal of properly reduction factor.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2012년도 춘계학술대회 논문집
• /
• pp.336-341
• /
• 2012

The vertical-axis tidal current turbine (VAT) consisting of blades, struts to support blades, shaft, generator and so forth requires anti-resonance design against fluid fluctuation forces generated on blades to ensure its stable operation. In this study, a free vibration analysis program based on the finite element method is developed for efficient anti-resonance design of VAT in the preliminary design stage. In the finite element modeling, the VAT structure components are regarded as beam elements. Added masses due to the fluid and structure interaction of VAT evaluated by empirical formulas are considered as lumped mass elements. In addition, input parameters required for the analysis can be automatically prepared from the principal dimensions of VAT to make anti-resonance design more convenient. The validity of applied methods is verified by the comparison of the numerical results obtained from MSC/Nastran and the developed program for two VAT models.