• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.907-913
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• 2011

Swirling flows are related to the spiral motion in the tangential direction in addition to the axial and radial direction using several swirl generators. These type of flows are used in combustion chambers to improve flame stability, heat exchanger to enhance heat transfer coefficients, agricultural spraying machines and some vertical pipes to move slurries or transport of materials. However, only a few studies three dimensional velocity profiles in a vertical pipe have been reported. In this present paper, 3 dimension particle image velocimetry(PIV) technique was employed to measure the velocity profiles in water along a vertical circular pipe with Reynolds number from 6000 to 13,000. A tangential inlet condition was used as the swirl generator to produce the required flow. The velocities were measured with swirling flow in the water along the test section using the PIV technique.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.605-610
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• 2002

The purpose of this study is to develop an analytic model which can describe the behavior or concrete compressive member strengthened by CFS(Carbon Fiber Sheet) with various cross-sectional shapes such as circular. square, and octagonal and various laminate angles. The failure criterion of laminated CFS is based on Tsai-Wu failure criterion. The stress strain model of confined concrete compressive member is based on an equation proposed by Mander. The effective lateral confining pressure is considered and modified according to various cross-sectional shapes. Octagonal cross-section shows the best results in the aspect of ductility, while circular does in compressive strengthening effects. In addition, [0/0/0/0] laminate in which the direction of fiber is parallel to the direction of principal stress shows the superior strength and ductility than other laminates. The analytic results show that strength and ductility of the analytic model depend on the cross-sectional shapes as well as the laminate angles.

• 한국지구과학회지
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• 제33권5호
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• pp.395-400
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• 2012

One of the main problems concerning the shallow seismic survey is how to generate high frequency signals with large amplitudes using small seismic sources. If one could focus the seismic energy in the direction of the survey line, it will be much helpful in identifying the first break. In this research, we have used hammer as an impulsive source and compared the signal powers generated by different shapes of the hammer plates: circular, square, and rectangular. The experiment was conducted by calculating the power spectral density function to compare the frequency spectrum and signal power. In the direction perpendicular to the long side of the rectangular plate, the largest seismic energy with the highest frequency was achieved even with the same weights of hammer plates. Our conclusion is that it is more efficient to use a rectangular plate than a circular (or square) one when conducting a 2-D shallow seismic survey.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.334-339
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• 2000

In order to predict the noise of the spur gear system, a simplified model of spur system including the housing is studied. The spur gear is modeled as a single degree of freedom system. The shaft-housing system is modeled as a clamped circular plate connected with a beam. The moment components of the beam excited by the spur gear mesh force are considered in the calculation of plate vibration and radiated noise. The out-of-displacements of the clamped circular plate due to the r-direction moment and ${\theta}$-direction moment are calculated. Radiated noise from the plate in the air is also calculated using Rayleigh integral. Using the numerical example, the numerical validation of the analytical procedure on the noise prediction are given.

• 한국정보전자통신기술학회논문지
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• 제1권2호
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• pp.57-63
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• 2008

In this paper, we develop the Hipass antenna that is used in electronic tall-gate charging (ETC) system in Korea expressway. This antenna has circular polarized characteristics, and especially has 45 degree tilted beam properties. These properties are very effective in ETC communication between the vehicle antenna and the tall-gate antenna. To achieve these properties on a small microstrip type antenna structure, we propose a annular ring microstrip antenna with stubs. When the length and angle of stubs are changed, the direction of the circular polarized beam is generally tilted by $45^{\circ}$ in elevation angle. Especially, by using the stubs in inner area or outer area of ring antenna, it is found that the beam direction of in azimuth angle can be rotated.

• 한국CDE학회논문집
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• 제8권4호
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• pp.243-253
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• 2003

This paper presents a new geometric morphing algorithm for polygons based on a simple geometric structure called direction map, which is mainly composed of a circular list of direction vectors defined by two neighboring vertices of a polygon. To generate a sequence of intermediate morphing shapes, first we merge direction maps of given control shapes based on a certain ordering rule of direction vectors, and scale the length of each direction vectors using Bezier or blossom controls. We show that the proposed algorithm is an improvement of the previous methods based on Minkowski sum (or convolution) in th aspects of computational efficiency and geometric properties.

• 한국융합학회논문지
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• 제6권5호
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• pp.249-255
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• 2015

본 논문에서는 상관형 위상비교(correlative interferometer) 방향탐지의 방위각 오차에 대해서 기술하였다. 상관형 위상비교 방식은 잡음이 없는 이상적인 환경에서 계산한 위상과 잡음이 있는 실제 환경에서 측정한 위상을 상호 비교하여 상관계수가 가장 큰 방위각을 전파 발신기의 방향으로 추정하는 방식이다. 5개의 안테나를 원형으로 배치하는 원형 배열안테나(circular array antenna)를 이용하여 각 안테나 사이의 상관함수를 유도하여 잡음에 의한 방향탐지 오차를 유도하였다. 이 방법은 잡음에 대한 방탐오차가 매우 작고, 특히 전파 발사체와 방향탐지 장치의 고도 차이가 큰 경우에도 방향탐지 오차가 작은 것으로 나타났다.

• 천문학회보
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• 제41권2호
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• pp.42.1-42.1
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• 2016

The formation process and the dynamical properties of a large-scale quasi-circular flare ribbon were investigated using the SDO AIA and HMI data along with data from RHESSI and SOT. Within one hour time interval, two subsequent M-class flares were detected from the NOAA 12371 that had a ${\beta}{\gamma}{\delta}$ configuration with one bipolar sunspot group in the east and one unipolar spot in the west embedded in a decayed magnetic field. Earlier M2.0 flare was associated with a coronal loop eruption, and a two-ribbon structure formed within the bipolar sunspot group. On the other hand, the later M2.6 flare was associated with a halo CME, and a quasi-circular ribbon developed encircling the full active region. The observed quasi-circular ribbon was strikingly large in size spanning 650" in north-south and 500" in east-west direction. It showed the well-known sequential brightening in the clockwise direction during the decay phase of the M2.6 flare at the estimated speed of 160.7 km s-1. The quasi-circular ribbon also showed the radial expansion, especially in the southern part. Interestingly, at the time of the later M2.6 flare, the third flare ribbon parallel to the early two-ribbon structure also developed near the unipolar sunspot, then showed a typical separation in pair with the eastern most ribbon of the early two ribbons. The potential field reconstruction based on the PFSS model showed a fan shaped magnetic configuration including fan-like field lines stemming from the unipolar spot and fanning out toward the background decayed field. This large-scale fan-like field overarched full active region, and the footpoints of fan-like field lines were co-spatial with the observed quasi-circular ribbon. From the NLFF magnetic field reconstruction, we confirmed the existence of a twisted flux rope structure in the bipolar spot group before the first M2.0 flare. Hard X-ray emission signatures were detected at the site of twisted flux rope during the pre-flare phase of the M2.0 flare. Based on the analysis of both two-ribbon structure and quasi-circular ribbon, we suggest that a tether-cutting reconnection between sheared arcade overarching the twisted flux rope embedded in a fan-like magnetic field may have triggered the first M2.0 flare, then secondary M2.6 flare was introduced by the fan-spine reconnection because of the interaction between the expanding field and the nearby quasi-null and formed the observed large-scale quasi-circular flare ribbon.

• 한국지능시스템학회논문지
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• 제11권6호
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• pp.487-490
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• 2001

본 논문은 영상 해석 알고리즘의 하나인 원형 패턴벡터 알고리즘을 이용하여 손가락으로 커서를 제어하는 시스템을 구현하였다. 이 알고리즘을 적용하기위하여 영상에서 손 영역에만 해당하는 최대 원을 여러개 그린후 가장 큰 원의 중심점을 무게 중심점으로 사용하였으며, 무게 중심점에서 손의 외곽까지의거리를 구하여 가리키는 손가락을 찾도록 하였다. 화면상의 커서의 수평방향은 가리키는 손가락방향을 이용하여 평면 좌표로 해석하여 제어하였고, 수직방향은 모니터 중앙상단에 한대의 카메라를 사용하였기 때문에 손가락 길이를 이용하여 불연속적으로 상-중-하의 세 영역으로 제어하였다. 수직 방향의 커서이동이 불연속적이기때문에, 구축한 인터페이스 화면의 범위를 축소한 후 축소된 범위를 전체 화면으로 확대해 나감으로써 사용자가 원하는 목표지점으로 커서를 이동시킬수 있다.

• 한국해안해양공학회지
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• 제5권4호
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• pp.338-349
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• 1993

본 연구에서는 해저지형이 변화하는 원형의 섬 주변에서 발생하는 조석 잔차류에 대하여 3차원 수치실험을 수행했다. 본 연구에서 사용한 3차원 수치모델은 스펙트랄 모델로서 수평적으로는 유한 차분법을 적용하고 연직방향으로는 깊이에 따라 변하는 기저함수의 곱으로 확장하여 해류의 연직분포를 구하는 모델이다. 수치실험 결과 조석 잔차류 발생에 있어 수심변화의 효과와 비선형 효과가 중요한 역할을 했고 이것은 기존의 조석 잔차류 발생에 대한 2차원적 수치실험 연구결과와 일치했다. 또 조석 잔차류의 수평구조는 시계방향의 회전성 조류일 때 시계방향으로 순환하는 잔차류의 특성을 보였으며 3차원적 구조를 검토한 결과 잔차류의 수평속도 성분 즉 u, v의 연직구조는 대수함수적인 분포를 나타냈다.