• 소음진동
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• 제7권2호
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• pp.319-329
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• 1997

Wigner-Ville distribution has been recognized as a useful tool and applied to various types of mechanical noise and vibration signals, but its limitation which mainly comes from the cross-talk has not been well addressed. The cross-talk takes place for a signal with multiple components, simply because the Wigner-Ville distribution is a bilinear transform. The cross-talk often causes a negative value in the distribution. This cannot be accepted for the Wigner- Ville distribution, because it is an expression of power. Smoothing the Wigner-Ville distribution by convoluting it wih a window, is most commonly used to reduce the cross-talk. There can be infinite number of distributions depending on the windows. In this paper, we attempted to develop a distribution which is the best or the optimal in reducing the cross-talk. This could be possible by employing the ambiguity function. For a general signal, however it is difficult to express the ambiguity function as a mathematically closed form. This requires an appropriate modeling to make such expression possible. We approximated the Wigner-Ville distribution as a sum of linear segments. In the ambiguity function domain, the legitimate components are reflected as linear lines passing through the origin. Every lines has its own length and slope. But, the cross-talk is widely distributed in the ambiguity function plane. Based on this realization, we proposed a two-dimensional window which is in fact 'rotating window', that can eliminate cross-talk component. The rotating window is examined numerically and is found to have a better performance in reducing the cross-talk than conventional windows, the Gaussian window.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.837-846
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• 2017

An accurate calculation of the stochastic wind field is the foundation for analyzing wind-induced structure response and reliability. In this research, the spatial correlation of structural wind field was considered based on the time domain method. A method for calculating the stochastic wind field based on cross stochastic Fourier spectrum was proposed. A flowchart of the proposed methodology is also presented in this study to represent the algorithm and workflow. Along with the analysis of regional wind speed distribution, the wind speed time history sample was calculated, and the efficiency can therefore be verified. Results show that the proposed method and programs could provide an efficient simulation for the wind-induced structure response analysis, and help determine the related parameters easily.

• Journal of Communications and Networks
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• 제12권4호
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• pp.382-394
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• 2010

Cross-domain event information sharing is a topic of great interest in the area of event based network management. In this work we use data sets which represent actual attacks in the operational Internet. We analyze the data sets to understand the dynamics of the attacks and then go onto show the effectiveness of sharing incident related information to contain these attacks. We describe universal data acquisition system for event based management (UniDAS), a novel system for secure and automated cross-domain event information sharing. The system uses a generic, structured data format based on a standardized incident object description and exchange format (IODEF). IODEF is an XML-based extensible data format for security incident information exchange. We propose a simple and effective security model for IODEF and apply it to the secure and automated generic event information sharing system UniDAS. We present the system we have developed and evaluate its effectiveness.

• 대한물리의학회지
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• 제10권3호
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• pp.47-55
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• 2015

PURPOSE: Stoke is one of most common disabling conditions and it is still lacking of measuring patient's functioning level. The aim of the study was to develop Korean language version of stroke impact scale 3.0. METHODS: Korean version of stroke impact scale 3.0 was developed in idiomatic modern Korean with a standard protocol of multiple forward and backward translations and an expert reviews to achieve equivalence with the original English version. Interviews with clinicians who were currently managing patients with stroke were also conducted for language evaluation. A reliability test was performed to make final adaptation using a pre-final version. To assess the reliability of the translated questionnaire, the intraclass correlation coefficient (ICC) was calculated for each domain of the scale. RESULTS: Thirty subjects (16 male, 14 female) aged from 20 to 75 years old participated to review the translated questionnaire. Reliability of each domain of the questionnaire was found to be good in strength (ICC=0.74), ADL (ICC=0.81), mobility (ICC=0.90), hand function (ICC=0.80) and social participation (ICC=0.79), communication (ICC=0.77) with total (ICC=0.76). However, domains of memory and thinking (ICC=0.66), and emotion (ICC=0.27) and showed poor reliability. CONCLUSION: This study indicates that the Korean version of SIS 3.0 was successfully developed. Future study needed for obtaining the validity of the Korean version of SIS 3.0.

• 한국음향학회지
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• 제28권3호
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• pp.285-289
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• 2009

본 논문에서는 음향학적 반향 제거(AES, acoustic echo suppression)를 위해 주파수영역에서 soft decision 기법에 근거한 새로운 동시통화 검출 (DTD, double-talk detection) 알고리즘을 제안한다. 제시된 방법은 효과적인 DTD를 위해 상관계수 (cross-correlation coefficient)에 기반하여 hard decision을 사용하는 기존의 알고리즘 대신 주파수 영역에서 입력 및 원단신호의 VAD (voice activity detection) 결과와 음성 통계모델에 기반한 soft decision 방법을 도입하여 전역 근단화자존 재확률 (GNSPP, global near-end speech presence probability)을 DTD에 적용한다. 제안된 알고리즘은 기존의 방법과 객관적인 실험을 통해 비교 평가한 결과 다양한 배경잡음 환경에서 우수한 성능을 보였다.

• 정보처리학회 논문지
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• 제13권8호
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• pp.382-387
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• 2024

최근 성인 독서량은 지속적으로 감소하는데 비해 영상 콘텐츠 소비가 증가하고 있다. 이에 따라 새로운 사용자에 대한 선호도 및 행동 패턴에 대한 정보가 없고 새로운 도서에 대한 사용자 평가나 구매 정보가 부족해 콜드 스타트 문제와 데이터 희소성 문제가 발생하고 있다. 본 논문에서는 영상물 콘텐츠 기반 도서 하이브리드 추천 시스템을 제안하였다. 제안하는 추천 시스템은 영상물의 콘텐츠를 활용하여 콜드 스타트 문제와 데이터 희소성 문제를 해결할 수 있을 뿐만 아니라, 전통적인 도서 추천 시스템에 비해 성능이 향상됨을 보여주었다. 또한 장르, 줄거리, 평점 정보 등 사용자 취향 정보까지 모두 반영한 개인 맞춤형 추천 결과를 제시하였다.

• 산업기술연구
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• 제21권B호
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• pp.75-83
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• 2001

In the field of secure information systems including electronic commerces, public key infrastructure(PKI) is widely used for secure services. The more PKI domains are established, the more needs are required for cross-domain certifications. Furthermore, each country has many certificate authorities(CA) which require more complex cross certification: We may need a fast algorithm in order to find the possible certification paths. This will be more indispensible in the growing PKI systems. We designed and implemented the high-speed certification path discovery algorithm. Also, we investigated the feature of operation of the system.

• 자원환경지질
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• 제33권1호
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• pp.41-50
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• 2000

Geo-radar survey which has the advantage of high-resolution and relatively fast survey has been widely used for engineering and environmental problems. Three-dimensional effects have to be considered in the interpretation of geo-radar for high-resolution. However, there exists a trouble on the analysis of the three dimensional effects. To solve this problem an efficient three dimension numerical modeling algorithm is needed. Numerical radar modeling in three dimensional case requires large memory and long calculating time. In this paper, a finite difference method time domain solution to Maxwell's equations for simulating electromagnetic wave propagation in three dimensional media was developed to make economic algorithm which requires smaller memory and shorter calculating time. And in using boundary condition Liao absorption boundary. The numerical result of cross-hole radar survey for tunnel is compared with real data. The two results are well matched. To prove application to three dimensional analysis, the results with variation of tunnel's incident angle to survey cross-section and the result when the tunnel is parallel to the cross-section were examined. This algorithm is useful in various geo-radar survey and can give basic data to develop dat processing and inversion program.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.225-228
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• 2005

According to a popularization of the Internet and digital lifestyle, digital watermarks have been proposed for protection of copyrighted multimedia content. In blind watermark detection, which an original image is not provided, robustness against geometric distortion and compression remains challenging. In this paper, we propose a new perceptual blind discrete wavelet transform - discrete Fourier transform (DWT-DFT) composite watermarking scheme that is robust against both general linear transform and JPEG compression. This algorithm constructs an image-dependent watermark in the most significant DWT coefficients, which is determined by using a hierarchical tree structure. Strength of watermark is determined from a just-noticeable difference (JND) profile of a perceptual model. Furthermore, a desired template is inserted into DFT domain of the watermarked image. In new manner, a cross-ratio of four collinear points is used for detecting the template. Experimental results have showed that the proposed scheme is robust against general linear distortion, JPEG compression and various general kinds of attacks in the Stirmark 3.1 watermark evaluation tool.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2012년도 추계학술대회
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• pp.122-124
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• 2012

잡음이 존재하는 환경에서의 신호의 분산을 측정하는 것은 잡음 제거에 중요한 요소를 맡고 있다. 잡음을 제거하는 방법 중에 가장 보편적으로 사용하는 방법에는 위너 필터가 존재한다. 웨이블릿 기반의 위너 필터링은 저복잡성을 지닌 이미지 잡음 제거에 탁월한 효과를 보인다. 신호의 분산을 측정할 경우 어떤 모양의 필터를 적용하여 측정하느냐에 따라 분산이 달라지게 되므로 이미지의 잡음 제거에 영향을 미치게 된다. 이에 본 논문은 위너 필터에 적용되는 필터를 기존의 정사각형 모양(square-shaped)과 제안하는 십자가 모양(cross-shaped)을 각각 적용하여 이미지의 잡음을 제거하였다.