• 한국음향학회지
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• 제38권2호
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• pp.154-159
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• 2019

수중 이동 음원의 방사 소음을 측정하는 경우 음원과 수신기 사이의 거리 정보가 중요한 평가 요소이며, 수신기 위치, 음원의 수심 및 속도 등과 같이 측정 규격이 정해져 있다. 이동하는 수중 음원의 거리를 찾는 방법으로써 상호 상관도를 사용하는 방법이 있지만 이 방법은 송신기와 수신기 사이의 시간 동기화 과정을 필요로 한다. 본 논문에서는 이론적으로 계산된 다중 경로 신호 사이의 도달 주파수 차와 수신 신호에서 추정된 다중 경로 신호의 도달 주파수 차를 비교하여 거리를 추정하는 방법을 제안한다. 기존의 방법과는 다르게 제안한 방법은 시간 동기화 과정이 필요하지 않다. 성능 검증을 위해 모의실험을 수행하였으며, 거리 오차가 기존의 방법에 비해 약 95 % 감소하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.431-436
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• 2010

Recently, several open source codes for computational fluid dynamics (CFD) have been emerged and are spreading fast. Our group has chosen OpenFOAM as a platform to develop our own in-house code. In this paper, we would like to share the information on the codes and what we have experienced so far. We introduce several features of OpenFOAM, which include the performance compared with commercial packages, estimation for current user population and our own prospect for future improvement in performance and growth in user population. In addition, we briefly introduce our experience gained in embedding the level set method into the OpenFOAM.

• 한국전산유체공학회지
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• 제15권3호
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• pp.46-53
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• 2010

Recently, several open source codes for computational fluid dynamics (CFD) have been introduced and are spreading fast. Our group has chosen the OpenFOAM as a platform to develop our own in-house code. In this brief review, we would like to share the information on the codes and what we have experienced so far. We introduce several features of OpenFOAM, which include the performance compared with commercial packages, estimation for current user population, and our own prospect for future improvement in performance and growth in user population. In addition, we briefly introduce our experience gained in embedding the level set method into the OpenFOAM.

• 한국군사과학기술학회지
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• 제14권4호
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• pp.694-699
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• 2011

A closed-form technique is presented for estimating a single source location from a set of noisy time delay measurements between distributed sensors. The localization formula is derived from nonlinear least squares minimization over the unknowns of target range and bearing in polar coordinates. Computer simulation results are provided for the purpose of performance analysis. Constrained least squares minimization method with prior source location information is also discussed.

• 환경위생공학
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• 제14권3호
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• pp.1-9
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• 1999

In the estimation of pollution load in water basin, a data information has generally used from surveyed data. A Geographic Information System(GIS) was adopted to evaluate the amount of pollution load in Anyang stream basin which is one of the major tributaries in the Han river flows through urban area. The digital maps of administrative boundary, stream network, sub-basin, soil type, and land-use for spatial data as well as attribute data were generated. And the database of sub-basins and pollution source was structured to estimate pollution load in Anyang stream basin by an Arc/Info GIS.As the results of this investigation, the pollution load of Mokgam-chun sub-basin was the highest amount. And that of Hagi-chun sub-basin and the fourth main stream sub-basin were also high amount in Anyang stream basin. In general, it was found that the pollution load generated from the upstream area in Kyunggi province was higher than that from downstream area in Seoul. Because the point and non-point source pollution load played very significant role in the deterioration of the water quality of the Anyang stream, an integrated approach to water quality management should be required for the sub-basins of high pollution load amount.

• 한국정보과학회논문지:소프트웨어및응용
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• 제35권7호
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• pp.417-423
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• 2008

본 논문에서는 각 음원이 시간적 구조를 가졌을 경우 음원들을 분리해내는 확률적 음원분리 방법을 제안한다. 이를 위해 각 음원의 시간적 구조를 가우시안 프로세스(Gaussian process)로 모델링하고 기존의 음원분리 문제를 유사-가능도 최대화 문제(pseudo-likelihood maximization)로 공식화한다. 본 알고리즘을 통해 얻어진 데이타의 유사-가능도는 정규 분포이며 이는 가우시안 프로세스 회귀방법(Gaussian process regression)을 통해 쉽게 계산이 가능하다. 음원분리의 역혼합 행렬은 경도(gradient) 기반최적화 기법을 통해 데이타의 유사-가능도를 최대화하는 해를 찾음으로써 구해진다. 여러 실험을 통하여 제안 알고리듬이 몇 가지 특정 상황에서 기존의 분리 알고리듬들에 비해 우수한 성능을 보임을 확인 할 수 있다.

• 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.

• Asia pacific journal of information systems
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• 제30권3호
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• pp.457-496
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• 2020

This study aims to extensively analyze the performance of various Machine Learning (ML) techniques for predicting version to version change-proneness of source code Java files. 17 object-oriented metrics have been utilized in this work for predicting change-prone files using 31 ML techniques and the framework proposed has been implemented on various consecutive releases of two Java-based software projects available as plug-ins. 10-fold and inter-release validation methods have been employed to validate the models and statistical tests provide supplementary information regarding the reliability and significance of the results. The results of experiments conducted in this article indicate that the ML techniques perform differently under the different validation settings. The results also confirm the proficiency of the selected ML techniques in lieu of developing change-proneness prediction models which could aid the software engineers in the initial stages of software development for classifying change-prone Java files of a software, in turn aiding in the trend estimation of change-proneness over future versions.

• 한국군사과학기술학회지
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• 제5권2호
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• pp.169-184
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• 2002

In order to extract bearing information from the directional sensors of DIFAR(directional frequency analysis and recording) that is a kind of passive sonobuoy, the cardioid beamforming algorithm applicable to DIFAR system was studied in the frequency domain. the algorithm uses narrow-band signals propagated though the media from the acoustic sources such as ship machineries. The proposed algorithm is expected to give signal to noise ratio of 6dB when it uses the maximum response axis(MRA) among the Cardioid beams. The estimated bearings agree very well with those from GPS data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1~$6.7^{\circ}$ and 13.3~$43.6^{\circ}$, respectively. Estimation errors are caused by SMR degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

• 정보보호학회논문지
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• 제28권1호
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• pp.61-71
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• 2018

다양한 장비의 인터넷 연결을 지향하고 있는 사물인터넷시대에서 암호기술의 사용을 위해 암호학적으로 안전한 난수생성은 중요 요구사항이다. 특히, 생성된 난수의 안전성과 연관된 엔트로피 원은 예측하기 어려운 잡음원을 위해 부가적인 하드웨어 로직을 사용하기도 한다. 비록 성능 측면에서 좋은 결과를 나타낼 수 있으나, 부가적인 리소스의 사용에 기인한 추가적인 전력 소비 및 면적문제 때문에 기존 자원을 최대한 활용하는 엔트로피 수집방법이 요구된다. 본 논문에서 제시하는 엔트로피 원은 멀티쓰레드 프로그램을 지원하는 환경에서 부가적인 장치 없이 공통적으로 사용 가능하므로 암호기술 구현에 있어 경량화의 어려움을 완화시킬 수 있다. 또한, 제안하는 엔트로피 원이 NIST SP 800-90B에서 제시한 난수발생기를 위한 엔트로피 입력원 테스트에서 높은 보안강도를 갖는 것으로 평가 되었다.