• ETRI Journal
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• 제45권3호
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• pp.394-403
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• 2023

Direct tracking problem of moving noncircular sources for multiple arrays is investigated in this study. Here, we propose an improved unscented particle filter (I-UPF) direct tracking method, which combines system proportional symmetry unscented particle filter and Markov Chain Monte Carlo (MCMC) algorithm. Noncircular sources can extend the dimension of sources matrix, and the direct tracking accuracy is improved. This method uses multiple arrays to receive sources. Firstly, set up a direct tracking model through consecutive time and Doppler information. Subsequently, based on the improved unscented particle filter algorithm, the proposed tracking model is to improve the direct tracking accuracy and reduce computational complexity. Simulation results show that the proposed improved unscented particle filter algorithm for noncircular sources has enhanced tracking accuracy than Markov Chain Monte Carlo unscented particle filter algorithm, Markov Chain Monte Carlo extended Kalman particle filter, and two-step tracking method.

• 한국레이저가공학회지
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• 제4권1호
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• pp.21-28
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• 2001

Simulation on the electron beam welding of Al 2219 alloy was carried out by using commercial FEM code MARC, which encounters moving heat sources. Due to axisymmetry of geometry, a half of the cylinder was simulated. A coupled thermo-mechanical analysis was carried out and subroutine for heat flux was substituted in the program. The material properties such as specific heat, heat transfer coefficient and thermal expansion coefficient were given as a function of temperature and the latent heat associated with a given temperature range is considered. As a result, the proper beam power is 60㎸${\times}$60㎃ and welding speed is 1∼1.5 m/min. The residual stress in the heat-affected zone as well as the fusion zone does not increase. It is necessary to use jigs for preventing distortion of cylinder and improving weld quality.

• 한국음향학회지
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• 제23권3호
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• pp.206-213
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• 2004

본 논문에서는 수중에서 빠른 속도로 기동하는 표적 환경에 적합한 조향각 오차 보정기법을 제안한다. 기존의 협대역 조향각 오차 보정기법에서는 다수의 시간 데이터 단편을 이용한 반면, 제안한 기법은 하나의 시간 데이터 단편에서 다수의 주파수 성분들로부터 모드 공분산행렬을 구성하고, 이를 이용하여 얻어진 광대역 MVDR (Minimum Variance Distortionless Response) 빔출력을 최대화시키는 조향각 오차를 추정함으로써 짧은 관측시간 내에 정확한 표적의 방위각을 추정할 수 있다. 모의신호와 실제 해상 실험 데이터를 이용하여 제안한 기법의 성능을 기존의 기법과 비교, 분석하였다.

• 대한전자공학회논문지
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• 제23권2호
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• pp.149-169
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• 1986

Fundamentals of electrodynamics of moving sources with constant velocity in an anisotripic plasma when the do magnetic field and the relative motion are oriented in arbitrary directions are presented. The well-known Minkowski's relations are generalized to accomodate anisotropic and dispersive media, and relativistic transformation formulae of constitutive parameters are derived and expanded into polynomials of the speed ratio \ulcornerto increase the utility of the formulae. The helmholtz wave equation of electromagnetic fields is generalized to the media charactrized by tensor parameters, and is solved in operator form. Also the solution of wave equation is expressed as a porcuct of the inverse of the wave operator matrix and the source function vector, and the inverse of the wave operator matrix is presented in an explicit form. The equations and formulae derived in this paper are all general, and can be reduced to known and proven results upon imposing the restriction called for by specific situations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.200-204
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• 2005

The use of beamforming method and de-Dopplerization technique was applied in studying the rotating sound sources. Acoustic analysis of a moving sound source required that the measured sound signals be do-Dopplerized and restored as of the original emission signals. Two main issues of the signal reconstruction in time domain are addressed herein: First, to remove Doppler effect from the measured data and to restore the original emission data of the moving source. The difference of the time domain beamforming from the frequency domain beamforming was mentioned. Also, the time domain beamforming method is deployed in the test and the comparisons were made to the frequency domain results. The time domain signal reconstruction was numerically simulated prior to the application. To validate the de-Dopplerization Performance, the rotating Point sources were examined and localized by the use of a phased array of microphone. The application of prop-rotor was conducted in a hovering condition. The results of reconstructing time signals of rotating sources and its locations were shown in the power distribution maps. In the prop-rotor measurements, the acoustic source locations were successfully verified in varying positions for different frequencies of interest.

• 한국음향학회지
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• 제24권1호
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• pp.1-10
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• 2005

본 논문에서는 이동하는 광대역 음원의 위치추정에 적합한 높은 분해능을 가지는 광대역LPA (local polynomial approximation) 빔형성기법을 제안한다. 제안한 기법은 여러 개의 데이터 단편으로부터 구하는 공분산행렬 대신, 하나의 데이터 단편의 여러 개 주파수 성분으로부터 얻은 조향 공분산행렬을 이용하는 STMV(steered minimum variance) 기법을 LPA 빔형성기법에 적용하였다. STMV 기법의 센서가중벡터를 이용하여 LPA 가격함수를 구성하였으며 이를 최대화 시키는 방위각과 각속도를 2차원 탐색을 통하여 추정함으로써 높은 방위각 분해능을 가지도록 하였다. 모의신호와 실제 해상 실험 데이터를 이용하여 제안한 기법의 성능을 기존의 기법과 비교, 분석 하였다

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.96.6-96
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• 2002

In this study an image processing system is designed and developed, which can detect and assort some defects on the surface of an object moving with high speed. For real time surface detection of high speed moving object, the fast processing should be managed and the image information including some surface features should be captured. It is difficult to acquire the noise free image due to various light sources and high speed moving materials under the environment of the general industrial site. In general, because pre-processing methods are employed for getting a noise free feature, the image processing speed has some limitation and the expensive image processing devices are required. This...

• Journal of information and communication convergence engineering
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• 제5권1호
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• pp.12-16
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• 2007

In this paper, a new method is proposed for tracking the direction-of-arrival (DOA) of the wideband moving source incident on uniform linear array sensors. DOA is estimated by focusing transformation matrices. To update focusing matrices along with new data snap shots, we use the FAST (Fast Approximate Subspace Tracking) method. Present focusing matrices are constructed by previous signal and its orthogonal basis vectors as well as present signal and its orthogonal basis vectors, which are the left and right singular vectors of the inner product of two approximated matrices. Simulation results are shown to illustrate the performance of the proposed method.

• 한국항공우주학회지
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• 제36권3호
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• pp.238-243
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• 2008

최근에 들어 이동하는 운송체의 외부에서 발생하는 소음의 위치를 판별하는 몇가지 방법들이 개발되었고, 운송체의 저소음화 설계과정에 적용되어 지고 있다. 빔형성법은 여러개의 마이크로폰으로부터 측정된 신호의 위상차를 이용하여 소음원의 위치를 판정하는 기법으로서 비교적 복잡한 환경하에서도 좋은 결과를 얻을 수 있는 기법으로 확인되고 있다. 본 연구에서는 빔형성법을 적용하여 승용차가 주행할 때 발생하는 소음원의 위치를 판별하는 연구를 수행하였다. 정지된 소음원의 경우와는 달리 이동하는 소음원의 경우는 도플러 효과에 의하여 측정된 신호가 변형되는데, 운송체의 움직이는 속도와 마이크로폰들과의 상대적 거리차를 이용하여 보정해주는 방법을 적용하였다. 움직이는 운송체에서 발생되는 소음원은 여러 가지로 분류될 수 있는데, 본 실험에서 수행된 조건하에서는 이중 타이어 소음과 엔진에서 발생하는 소음이 가장 큰 것으로 측정되었다.

• International Journal of Control, Automation, and Systems
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• 제5권6호
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• pp.701-706
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• 2007

The measurement accuracy for heart rate or $SpO_2$ using photoplethysmography (PPG) is influenced by how well the noise from motion artifacts and other sources can be removed. Eliminating the motion artifacts is particularly difficult since its frequency band overlaps that of the basic PPG signal. Therefore, we propose the Periodic Moving Average Filter (PMAF) to remove motion artifacts. The PMAF is based on the quasi-periodicity of the PPG signals. After segmenting the PPG signal on periodic boundaries, we average the $m^{th}$ samples of each period. As a result, we remove the motion artifacts well without the deterioration of the characteristic point.