• The Journal of the Acoustical Society of Korea
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• v.34 no.4
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• pp.328-334
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• 2015

This paper describes an acoustic analysis of a Jing, Korean percussion instrument, according to different drive point and blow strength, and this analysis is focused on the softening and beat phenomena. Three kinds of blow strength (very strong, strong, and weak) and three locations of drive point (center, up, and right) are applied, and the spectrogram function built in Matlab is utilized to analyzing the softening and beat of target sounds. The stronger blow you drive to the center of the Jing, the more clearly softening is observed. Frequency shifting is increased proportionally to the blow strength and frequency and it is stand out on the harmonics in contrast with that of other partials. Beat of the Jing can be classified into the early beat and late beat. The beats by the outside driven Jing are distributed in wider frequency band than the beats by the center driven Jing. In addition, it is observed that the early beat is affected by few specific partials developed around harmonics for the center driven Jing.

• Journal of the Korea Society for Simulation
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• v.23 no.3
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• pp.33-40
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• 2014

Drifter is equipment which is hard to localize. Performance of prototype hasn't performed well compared to product of leading companies even though advanced foreign firm's product were dead copied. This study shows cases of approaching the factor which produces performance gap through drifter hydraulic analysis model which is core component of rock drill. Progression of procedure is following. 1) Securing reliability of the analysis model by comparing impact test result with analysis result. 2) Drawing a graph which indicates performance gap between prototype and drifter of advanced foreign firm by using analysis model. 3) Approaching the factor which produces performance gap with analysing variable of the analysis model. Software used for this analysis is SimulationX.

• Journal of Drive and Control
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• v.11 no.3
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• pp.14-21
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• 2014

The goal of this study drifter is to understand the operating mechanism of a drifter and to suggest a reliable analysis model which can be used for evaluating the drifter's performance from the viewpoint of impact frequency and energy. For this, the working principle of drifter and functions of its main components were analyzed, and a simulation model was developed based on the analysis. The model was validated using experimental tests on a test-bench. A comparative study of simulation and experimental results indicated that the suggested model accurately represents the real drifter system in terms of impact frequency and impact energy per blow.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.526-527
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• 2014

• The Journal of the Acoustical Society of Korea
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• v.14 no.4
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• pp.12-20
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• 1995

This paper describes principles and experimental results in conjunction with examining the possibility of the detection of effects from a cylindrical objects. Cylindrical objects have its own resonance frequency. The frequency varies according to the diameter, length etc. And acoustic sound, whose frequency and the harmonic components corresponding to resonance frequency, is radiated from the object. When an object have defect in itself, the radiated acoustic sound is different from normal one. So we can detect its defect by analysing frequency components of acoustic sound. We proved that detection of defective objects by acoustic signal analysis is possible automatically. Also the result can be applied to other kinds of objects.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.439-440
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• 2018

본 논문에서는 제작한 가상현실 게임의 소개와 적용기술에 대해여 논한다. HTC VIVE를 이용하여 강력한 주요 게임 개발엔진 중 하나인 Unreal engine4를 이용하여 쉽게 접근 할 수 있는 VR 리듬게임 구현을 목적으로 한다. 플랫폼의 한계의 벗어나 HUD로 좀 더 현실감과 몰입을 요구하는 게임개발을 목표로 리듬감 증진 혹은 운동효과도 기대할 수 있다. 사운드 플러그를 이용하여 주파수별 스펙트럼을 시각화하여 재생되는 음원중 스펙트럼 값이 조건을 만족하면, 노트가 자동으로 생성되고 일정 시간이 경과한 후 사라지거나, 플레이어가 타격하여 점수를 획득 하는 방식으로 진행되며, 플레이어가 노트를 맞을 경우 체력값이 단계별로 낮아져 게임이 종료된다. 더 많은 곡과 맵을 추가하여 흥미소요를 늘릴 수 있으며, 단순타격이 아닌 조건이나 임무를 부여 다양성과 복잡함을 추가해 낮은 접근성과 높은 정복성을 가질 수 있다.

• Journal of Korea Multimedia Society
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• v.14 no.11
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• pp.1507-1515
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• 2011

As the first step in research for sound synthesis of Pyungjong, timbre was analyzed by FFT analysis. There was no significant difference in the pitch of scale between modern Pyungjong and western twelve-tone equal temperament scale. The timbre of Pyunjong chagnes over time. When striking Pyunjong, the noises to be generated across all frequencies will disappear in a short period of time, and a unique partial only is left. Then it disappear from the partial of high frequency components in order, and two partials remain at release time. At this time, the beating is occurring by the frequency of the remaining partial. Pyungjong used in this study is relatively a recently manufactured Pyungjong, and for original sound synthesis of Pyungjong, a study of ancient Pyungjong's timbre should be additionally conducted later.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1414-1415
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• 2008

본 논문에서는 고출력 극초단파(High Power Microwave)가 쏘아지는 대상이 방어장비를 갖추고 있을 때 외부대상이 어떤 영향을 받는지를 규명하는데 목적이 있다. 입력펄스를 변조(modulation)시켜 저지대역(Stop Band) 주파수 대역에 맞추고, 펄스(Pulse)를 저대역 통과 필터의 저지대역에 통과시킨다. 이때 출력펄스의 응답(response)을 시간영역(Time-domain)에서 분석하여 정상상태(steady state)보다는 과도응답(Transient Response)을 확인하는 것을 제안한다. 이 방법은 저지대역의 파형이 필터를 통과해도 과도응답 때문에 필터가 제 역할을 하지 못한다는 이론을 규명한다. 이 이론은 고출력 극초단파가 외부대상에 미치는 영향에 있어서 전자파를 방어하려고 하여도 과도응답 상태 응답 때문에 타격을 받을 수 있다는 것을 규명한다.

• Information and Communications Magazine
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• v.28 no.4
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• pp.41-50
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• 2011

미래 전에서는 정보의 중요성이 더욱 부각되고 있으며 정보의 수집 및 전파, 정확한 지휘결심 및 전파, 기동타격체계의 통제 등으로 이어지는 지휘통제의 전 과정을 유기적으로 연결하여, 그 성능을 극대화시키는 것이 네트워크 중심전(NCW: Net-Centric Warfare)의 개념이다. NCW 실현을 위해 개발중인 여러 체계 중 주목 받고 있는 것이 무인기(UAV: Unmanned Aerial Vehicle) 이다. 무인기는 감시정찰, 고정밀 타격, 그리고 전투피해평가 기능 등을 수행하며, 전술적인 상황인식이 가능하게 한다. 무인기가 이러한 임무를 수행하기 위해서는 비행체의 상태정보, 비행체의 조종통제정보, 그리고 임무 탑재체가 획득한 정보의 간단없고 정확한 전달이 요구된다. 이러한 정보를 전송하기 위한 비행체와 지상체간의 제반 통신을 데이터 링크(Data Link)라 하며, NCW 구현에 있어서 가장 핵심이 되는 요소이다. 세계 각국은 영상정보 수집자산으로서 무인기와 데이터링크의 개발에 박차를 가하고 있는 실정이며, 우리 군도 전력화가 계획된 각 제대별 무인기의 통합운용을 위한 영상정보 공용데이터 링크 (MPI-CDL: Multi-Platform Image and Intelligence Commom Data Link)를 개발중에 있으며 지속적인 영상정보 수집자산의 소요증가에 따른 주파수 획득문제와 사업별 독자적인 데이터 링크의 개발을 지양하고 기존체계와의 상호운용 및 단절없는 통신을 보장을 위해 개발과 동시에 국가적 차원에서의 기술구조 표준화가 추진되어야 한다. 이러한 시점에서 본고에서는 먼저 선진국의 (CDL : Commom Data Link) 표준화 동향을 알아보고, 상호운용성과 연동을 위한 한국형 MPI-CDL 기술 표준화방향을 제시하고자 한다.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.51-60
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• 2021

River scour erodes the soil around the pier, reducing the lateral bearing capacity of the pier and lowering the stability of the structure. In this study, in order to examine the effect of scouring on the stability of the structure, an experiment was performed to measure the natural frequency of the pier according to the excavation of the surrounding ground. Impact vibration test was conducted on the pier with the caisson foundation of the Mangyeonggang Bridge, which is scheduled to be demolished. Accelerometers were attached to the top, center, and bottom of the pier and the acceleration responses were measured by hitting those three points. The experimental results showed that the top hit showed consistent and reasonable results of the acceleration responses according to the hitting position. The measured accelerations were converted to the frequency domain through Fast Fourier Transform (FFT), and then the natural frequency was determined. In addition, to analyze the scour effect on the natural frequency of the pier, the ground around the pier was excavated and the natural frequency change was analyzed. As a result, the natural frequency showed the decreasing tendency according to the excavation depth, but the decrease was small due to the large stiffness of the caisson foundation.