• 말소리와 음성과학
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• 제4권3호
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• pp.25-30
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• 2012

This study investigated whether native Korean listeners could use visual cues for the identification of the English consonants /b/ and /v/. Both auditory and audiovisual tokens of word minimal pairs in which the target phonemes were located in word-initial or word-medial position were used. Participants were instructed to decide which consonant they heard in $2{\times}2$ conditions: cue (audio-only, audiovisual) and location (word-initial, word-medial). Mean identification scores were significantly higher for audiovisual than audio-only condition and for word-initial than word-medial condition. Also, according to signal detection theory, sensitivity, d', and response bias, c were calculated based on both hit rates and false alarm rates. The measures showed that the higher identification rate in the audiovisual condition was related with an increase in sensitivity. There were no significant differences in response bias measures across conditions. This result suggests that native Korean speakers can use visual cues while identifying confusing non-native phonemic contrasts. Visual cues can enhance non-native speech perception.

• 한국지능시스템학회논문지
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• 제13권4호
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• pp.461-468
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• 2003

In a sequence of images obtained by surveillance cameras, facial regions appear very small and their colors change abruptly by lighting condition. This paper proposes a new face detection scheme, robust on complex background, small size, and lighting conditions. The proposed method is consisted of three processes. In the first step, the candidates for the face regions are selected using face color distribution and motion information. In the second stage, the non-face regions are removed using face color ratio, boundary ratio, and average of column-wise intensity variation in the candidates. The face regions containing eyes and mouth are segmented and classified, and then they are scored using their topological relations in the last step. To speed up and improve a performance the above process, a block based image segmentation technique is used. The experiments have shown that the proposed algorithm detects faced regions with more than 91% of accuracy and less than 4.3% of false alarm rate.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2561-2576
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• 2013

The ship ad-hoc network (SANET) extends the coverage of the high data-rate terrestrial communications to the ships with the reduced cost in maritime communications. Cognitive radio (CR) has the ability of sensing the radio environment and dynamically reconfiguring the operating parameters, which can make SANET utilize the spectrum efficiently. However, due to the dynamic topology nature and no central entity for data fusion in SANET, the interference brought into the primary network caused by the hidden primary user requires to be carefully managed by a sort of decentralized cooperative spectrum sensing schemes. In this paper, we propose a self-weighted decentralized cooperative spectrum sensing (SWDCSS) scheme to solve such a problem. The analytical and simulation results show that the proposed SWDCSS scheme is reliable to detect the primary user in SANET. As a result, secondary network can efficiently utilize the spectrum band of primary network with little interference to primary network. Referring the complementary receiver operating characteristic (ROC) curves, we observe that with a given false alarm probability, our proposed algorithm reduces the missing probability by 27% than the traditional embedded spectrally agile radio protocol for evacuation (ESCAPE) algorithm in the best condition.

• 한국멀티미디어학회논문지
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• 제10권12호
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• pp.1559-1565
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• 2007

The many target-detection methods that use forward-looking infrared (FUR) images can deal with large targets measuring $70{\times}40$ pixels, utilizing their shape features. However, detection small targets is difficult because they are more obscure and there are many target-like objects. Therefore, few studies have examined how to detect small targets consisting of fewer than $30{\times}10$ pixels. This paper presents a small target detection method using clutter rejection with stochastic hypothesis testing for FLIR imagery. The proposed algorithm consists of two stages; detection and clutter rejection. In the detection stage, the mean of the input FLIR image is first removed and then the image is segmented using Otsu's method. A closing operation is also applied during the detection stage in order to merge any single targets detected separately. Then, the residual of the clutters is eliminated using statistical hypothesis testing based on the t-test. Several FLIR images are used to prove the performance of the proposed algorithm. The experimental results show that the proposed algorithm accurately detects small targets (Jess than $30{\times}10$ pixels) with a low false alarm rate compared to the center-surround difference method using the receiver operating characteristics (ROC) curve.

• 한국통신학회논문지
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• 제29권7C호
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• pp.931-936
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• 2004

GPDF(Gaussian Probability Density Function)을 효율적으로 군집화할 수 있는 GBFCM(DM)(Gradient Based Fuzzy c_means with Divergence Measure) 알고리즘이 본 논문에서 제안되었다. 제안된 GBFCM(DM)은 데이터 사이의 거리 척도로 발산거리(Divergence measure)를 적용한 새로운 형태의 FCM으로, 기존의 GBFCM에 기반을 두는 알고리즘이다. 본 논문에서는 MPEG VBR 비디오 데이터를 GPDF형태의 다차원 데이터로 변형시켜 모델링 하고, 모델링 한 MPEG VBR 비디오 데이터를 영화 또는 스포츠 형태로 분류하는데 응용되었다. 본 논문의 실험에서 기존의 FCM, GBFCM과 새롭게 제안된 GBFCM(DM)을 사용하여 모델링 및 분류결과를 상호 비교하였다. 비교결과 GBFCM(DM)이 오분류율의 기준에서 기존의 다른 알고리즘들에 비해 약 5∼l5%의 향상된 성능을 보였다.

• 전자공학회논문지SC
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• 제47권6호
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• pp.27-32
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• 2010

오늘날 FMCW 레이더 시스템은 차량의 능동 안전 시스템에 널리 활용되어지고 있다. 레이더 시스템에서 탐지확률을 높이고 오경보율을 줄이기 위해서는 정지타겟을 포함한 클러터 성분을 제거하고 관심 있는 이동타겟을 효과적으로 탐지하기 위한 알고리즘이 필요하다. 본 논문에서는 이동타겟 탐지 및 클러터 제거 알고리즘을 제안한다. 먼저 제안된 이동타겟 비트주파수 검출 필터를 이용하여 클러터를 제거한다. 검출된 이동타겟 비트주파수들을 이용하여 데이터-결합 한 후, 제로-도플러 제거 알고리즘을 이용하여 남아있는 클러터를 제거한다. 이 알고리즘을 검증하기 위해 실제 FMCW 레이더를 이용하여 도로 상에서 실험하였다.

• Journal of Communications and Networks
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• 제12권6호
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• pp.582-591
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• 2010

Probabilistic modeling and analysis of correlation metrics have been receiving considerable interest for a long period of time because they can be used to evaluate the performance of communication receivers, including satellite broadcasting receivers. Although differential correlators have a simple structure and practical importance over channels with severe frequency offsets, closedform expressions for the output distribution of differential correlators do not exist. In this paper, we present detection error probability expressions for frame synchronization using differential correlation, and demonstrate their accuracy over channel parameters of practical interest. The derived formulas are presented in terms of the Marcum Q-function, and do not involve numerical integration, unlike the formulas derived in some previous studies. We first determine the distributions and error probabilities for single-span differential correlation metric, and then extend the result to multispan differential correlation metric with certain approximations. The results can be used for the performance analysis of various detection strategies that utilize the differential correlation structure.

• 전자공학회논문지
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• 제51권6호
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• pp.3-8
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• 2014

TV 대역에 나타날 수 있는 무선 마이크 신호를 검출하는 방안으로 전력 스펙트럼의 최대값을 시험 통계량으로 사용하는 방안이 최근 발표되었다. 이 방식은 시험 통계량을 임계값과 비교하여 우선 사용자의 유무를 판정하는데, 이때 임계값은 목표로 하는 오경보 확률뿐만 아니라 배경 잡음 전력 수준에 따라 달라진다. 따라서 잡음 전력에 대한 불확실성이 존재하는 경우 그로 인한 성능 저하가 발생할 수 있다. 이에 대한 해결책으로 본 논문은 전력 스펙트럼의 최대값과 최소값의 비율을 시험 통계량으로 사용하는 방식을 제안하고, 그 분석 결과를 제시하고자 한다.

• 한국음향학회지
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• 제20권3호
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• pp.3-7
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• 2001

CW (Continuous Wave) 신호를 사용하는 능동형 소나에서 잔향을 포함한 잡음의 특성이 백색 (white)이 아닌 경우 일정 오경보 확률 처리 (CFAR: Constant False Alarm Rate)를 수행할 때 잔향 부근에서 높은 문턱치를 추정하게 된다. 이로 인해 표적을 검출하지 못하며. 근접한 다중 표적을 구분하지 못하는 단점이 있다. 본 논문에서는 이러한 문제점을 해결하기 위한 적응 잔향 제거 필터를 제안하였다. 제안된 필터는 적응 필터와 이 필터로부터 일정한 시간 차를 두고 계수 값을 복제해 쓰는 필터로 구성된다. 능동형 소나가 움직이는 수중 환경에서 수집된 실측 데이터를 이용하여 제안된 적응 잔향 제거 필터의 성능을 고찰하였다. 그 결과 제안된 방법은 기존의 방법에 비해 표적 신호 구간이 긴 경우 향상된 성능을 나타내었다.

• Communications for Statistical Applications and Methods
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• 제19권5호
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• pp.685-696
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• 2012

These days the interest of quality leads to the necessity of control charts for monitoring the process in various fields of practical applications. The $\overline{X}$ chart is one of the most widely used tools for quality control that also performs well under the normality of quality characteristics. However, quality characteristics tend to have nonnormal properties in real applications. Numerous recent studies have tried to find and explore the performance of $\overline{X}$ chart due to non-normality; however previous studies numerically examined the effects of non-normality and did not provide any theoretical justification. Moreover, numerical studies are restricted to specific type of distributions such as Burr or gamma distribution that are known to be flexible but can hardly replace other general distributions. In this paper, we approximate the false alarm rate(FAR) of the $\overline{X}$ chart using the Edgeworth expansion up to 1/n-order with the fourth cumulant. This allows us to examine the theoretical effects of nonnormality, as measured by the skewness and kurtosis, on $\overline{X}$ chart. In addition, we investigate the effect of skewness and kurtosis on $\overline{X}$ chart in numerical studies. We use a skewed-normal distribution with a skew parameter to comprehensively investigate the effect of skewness.