• 한국인터넷방송통신학회논문지
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• 제12권4호
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• pp.147-152
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• 2012

본 연구는 공간상에서 전파를 이용하여 원하는 목표물의 도래 방향을 추정 한다. 도래방향 추정은 수신 배열 안테나들로 입사하는 신호들 중에서 원하는 목표물의 위치를 찾는 것이다. 본 연구에서는 도래방향 추정의 고 분해능 MUSIC알고리즘과 비용함수를 사용하여 목표물에 대한 도래방향을 추정하였고, 최적의 가중치를 계산하였다. 모의실험을 통하여 목표물 도래 방향 추정에서 기존 ESPRIT 알고리즘과 제안 알고리즘의 성능을 비교 분석 하였다. 목표물 도래 방향 추정에서 제안한 알고리즘이 기존의 ESPRIT 알고리즘보다 도래 방향 추정 능력이 향상되었다.

• 대한전자공학회논문지TE
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• 제42권1호
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• pp.21-28
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• 2005

본 논문은 토모그라픽 영상시스템에 적합한 FBP 토모그라픽 영상복원 알고리즘의 분해능에 관하여 연구하였다. 고정좌표계를 이용하는 개선된 FBP 토모그라픽 영상복원 알고리즘으로부터 분해능을 분석할 수 있는 모호함수를 유도하였고, 이를 이용한 모의실험을 통하여 얻은 진폭분포로부터 측방향 및 축방향 분해능을 정량적으로 결정하였다. 개선된 FBP 토모그라픽 영상복원 알고리즘을 통해 기존의 SAM(Scanning Acoustic Microscope)시스템으로부터 얻을 수 있는 3dB와 6dB 축방향 분해능에 대해서도 각각 0.70 파장과 0.96 파장으로 SAM 영상의 3dB 축방향 분해능인 7 파장에 비하여 매우 개선된 분해능을 얻을 수 있음을 확인하였다. 평면 입사파의 회절 토모그라픽 영상복원을 위한 개선된 FBP 토모그라픽 영상복원 알고리즘은 미세하고 복잡한 다층 박막구조를 갖는 시료에 대하여 좋은 분해능을 갖는 토모그라픽 영상시스템을 개발하는데 유용하게 활용할 수 있도록 하였다.

• Smart Structures and Systems
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• 제26권2호
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• pp.227-239
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• 2020

Despite proven effectiveness and accuracy in laboratories, the existing damage assessment based on guided ultrasonic waves (GUWs) or acoustic emission (AE) confronts challenges when extended to real-world structural health monitoring (SHM) for railway tracks. Central to the concerns are the extremely complex signal appearance due to highly dispersive and multimodal wave features, restriction on transducer installations, and severe contaminations of ambient noise. It remains a critical yet unsolved problem along with recent attempts to implement SHM in bourgeoning high-speed railway (HSR). By leveraging authors' continued endeavours, an SHM framework, based on actively generated diffuse ultrasonic waves (DUWs) and a benchmark-free condition contrast algorithm, has been developed and deployed via an all-in-one SHM system. Miniaturized lead zirconate titanate (PZT) wafers are utilized to generate and acquire DUWs in long-range railway tracks. Fatigue cracks in the tracks show unique contact behaviours under different conditions of external loads and further disturb DUW propagation. By contrast DUW propagation traits, fatigue cracks in railway tracks can be characterised quantitatively and the holistic health status of the tracks can be evaluated in a real-time manner. Compared with GUW- or AE-based methods, the DUW-driven inspection philosophy exhibits immunity to ambient noise and measurement uncertainty, less dependence on baseline signals, use of significantly reduced number of transducers, and high robustness in atrocious engineering conditions. Conformance tests are performed on HSR tracks, in which the evolution of fatigue damage is monitored continuously and quantitatively, demonstrating effectiveness, adaptability, reliability and robustness of DUW-driven SHM towards HSR applications.

• 지구물리와물리탐사
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• 제3권2호
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• pp.70-75
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• 2000

탄성파 탐사자료의 구조보정에는 주로 Kirchhoff 및 역시간 구조보정이 이용되고 있다. 파동방정식을 이용한 역시간 구조보정에는 양방향 및 일방향 파동방정식이 이용된다. 일방향 파동방정식을 사용한 접근법은 하향 파동장 외삽연산자를 근사하게 계산하는 방식으로, 양방향 파동방정식을 이용한 방법에 비해, 계산량이 적고 작은 컴퓨터 주기억장치로 작업이 가능하다. 본 논문에서는 일방향 파동방정식을 이용하여 중합전 역시간 구조보정을 수행하였다. 주파수-공간영역에서 음원 파동장의 전파 및 관측 파동장의 역시간 전파에 단일주파수 일방향 파동방정식을 이용하였으며, 이 두 파동장의 영 지연 상호상관을 계산하여 구조보정하였다. 구조보정에는 초병렬 슈퍼검퓨터(MPP, Massively Parallel Processors) CRAYT3E가 사용되었으며, 이 작업을 통해 알고리즘이 쉽게 병렬화가 가능하여 효율적으로 구조보정에 이용될 수 있음을 확인하였다.

• Journal of electromagnetic engineering and science
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• 제18권3호
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• pp.160-168
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• 2018

A wide spectrum of potential applications using substrate integrated waveguide (SIW) technologies in conjunction with air hole regions is introduced, and an efficient optimization methodology to cope with the multiple air hole effect in SIW applications is proposed. The methodology adopts a genetic algorithm to obtain optimum air hole dimensions for the specific propagation constant that can be accurately calculated using the recursive and closed form equations presented. The optimization results are evaluated by designing an SIW bandpass filter, and they show excellent performance. The optimization methodology using the proposed equations is effective in performance enhancement for the purposes of low loss and broadband SIW applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.369_370
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• 2009

This paper describes the fault location method for HVDC submarine cables. Most conventional fault location methods can be applied in off-line. However, in this paper, on-line fault location algorithm is proposed using multi-scale correlating of wavelet coefficient and travelling wave. The propagation velocity is measured by field test on Jeju-Heanam submarine cable section. Finally, the fault location algorithm is tested by same system modeling using EMTP/ATP.

• 한국소음진동공학회논문집
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• 제14권2호
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• pp.95-104
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• 2004

Leaks in underground pipelines can cause social, environmental and economical problems. One of relevant countermeasures against leaks is to find and repair of leak points of the pipes. Leak noise is a good source to identify the location of leak points of the pipelines. Although there have been several methods to detect the leak location with leak noise, such as listening rods, hydrophones or ground microphones, they have not been so efficient tools. In this paper, accelermeters aroused to detect leak locations which could provide an easier and more efficient method. Filtering, signal processing and algorithm of raw input data from sensors for the detection of leak location are described. A 120m-long and a 70m-long experimental pipeline systems are installed and the results with the systems show that the algorithm with the accelerometers offers accurate pinpointing for leaks location detection. Theoretical analysis of sound wave propagation speed of water in underground pipes, which is critically important in leak locating, is also described.

• 한국전산유체공학회지
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• 제14권1호
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• pp.53-61
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• 2009

The objective of this research is to design blade planform to reduce high speed impulsive(HSI) noise from a non-lifting helicopter rotor using CFD method and optimization techniques. As for the aero-acoustic analysis, CFD technique for aerodynamic analysis and Kirchhoff's method for the acoustic analysis were used. As for the optimization method, Kriging-based genetic algorithm(GA) model as a high-fidelity optimization method was chosen. Design variables and constraints are determined for arbitrary blade planform. The result shows that the optimized blade planform with high swept-back and taper ratio can reduce HSI noise by suppressing generation of the strong shock wave on blade surface and propagation of the noise to the farfield flow region.

• 소음진동
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• 제10권6호
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• pp.941-948
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• 2000

Active noise control is an approach to reduce the noise by utilizing a secondary noise source that destructively interferes with the unwanted noise. In general, active noise control systems rely on multiple sensors to measure the unwanted noise field and the effect of the cancellation. This paper develops an approach that utilizes a single sensor. The noise field is modeled as a stochastic process, and an adaptive algorithm is used to adaptively estimate the parameters of the process. Based on these parameter estimates, a canceling signal is generated. Oppenheim assumed that transfer function characteristics from the canceling source to the error sensor is only a propagation delay. This paper proposes a modified Oppenheim algorithm by considering transfer characteristics of speaker-path-sensor This transfer characteristics is adaptively cancelled by the proposed adaptive modeling technique. Feasibility of the proposed method is proved by computer simulations with artificially generated random noises and sine wave noise. The details of the proposed architecture. and theoretical simulation of the noise cancellation system for three dimension enclosure are presented in the Paper.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.189-199
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• 2020

Researchers have elaborated several accurate methods to calculate member-end rotations or moments, directly, for bridge-type structures. Recently, the concept of rotation and moment propagation (RMP) has been presented considering bending flexibility, only. Through which, in spite of moment distribution method, all joints are free resulting in rotation and moment emit throughout the structure similar to wave motion. This paper proposes a new set of closed-form equations to calculate member-end rotation or moment, directly, comprising both shear and bending flexibility. Furthermore, the authors program the algorithm of Timoshenko beam theory cooperated with the finite element. Several numerical examples, conducted on the procedures, show that the method is superior in not only the dominant algorithm but also the preciseness of results.