• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.170-191
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• 2024

The transmission of confidential data using cover media is called steganography. The three requirements of any effective steganography system are high embedding capacity, security, and imperceptibility. The text file's structure, which makes syntax and grammar more visually obvious than in other media, contributes to its poor imperceptibility. Text steganography is regarded as the most challenging carrier to hide secret data because of its insufficient redundant data compared to other digital objects. Unicode characters, especially non-printing or invisible, are employed for hiding data by mapping a specific amount of secret data bits in each character and inserting the character into cover text spaces. These characters are known with limited spaces to embed secret data. Current studies that used Unicode characters in text steganography focused on increasing the data hiding capacity with insufficient redundant data in a text file. A sequential embedding pattern is often selected and included in all available positions in the cover text. This embedding pattern negatively affects the text steganography system's imperceptibility and security. Thus, this study attempts to solve these limitations using the Part-of-speech (POS) tagging technique combined with the randomization concept in data hiding. Combining these two techniques allows inserting the Unicode characters in randomized patterns with specific positions in the cover text to increase data hiding capacity with minimum effects on imperceptibility and security. Format-preserving encryption (FPE) is also used to encrypt a secret message without changing its size before the embedding processes. By comparing the proposed technique to already existing ones, the results demonstrate that it fulfils the cover file's capacity, imperceptibility, and security requirements.

• 말소리와 음성과학
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• 제1권2호
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• pp.119-128
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• 2009

Many researchers have argued about the relationship between information structure and intonation. Their results can be summarized in three main points: the intonation of topic and focus in English information structures is implemented as i) a pitch accent, ii) a tune (a pitch accent + (an) edge tone(s)), or iii) a boundary tone. The purpose of this paper is to study various intonational patterns of topic and focus in English information structures, using natural conversations. In this paper, the types of topics and foci are divided, based on contrastiveness. The topics are classified as five non-contrastive and four contrastive topics. The foci are classified as neutral focus, informational focus, and contrastive focus. The results show that the intonation of the topic in English information structures is mainly implemented as a pitch accent, except for the type of the pronoun topic (Lp) which is not implemented as a pitch accent or a tune. However, the intonation of the focus is implemented as a tune in the neutral focus (Fn) and as a pitch accent or a tune in the informational focus (Fi) and the contrastive focus (Fe). In our discussion and conclusion, we suggest that it is not always true that for the meaning of contrast, the topic or the focus is represented as a $L+H^{\ast}$ pitch accent, which has been the main contrastive intonation from earlier studies.

• 음성과학
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• 제11권3호
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• pp.7-21
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• 2004

The present study aims to investigate domain-initial strengthening phenomenon, which refers to strengthening of articulatory gestures at the initial positions of prosodic domains. More specifically, this paper presents the result of an experimental study of initial syllables with onset consonants (initial-syllable vowels henceforth) of various prosodic domains in English and Hamkyeong Korean, a pitch accent dialect spoken in the northern part of North Korea. The durations of initial-syllable vowels are compared to those of second vowels in real-word tokens for both languages, controlling both stress and segmental environment. Hamkyeong Korean, like English, tuned out to strengthen the domain-initial consonants. With regard to vowel durations, no significant prosodic effect was found in English. On the other hand, Hamkyeong Korean showed significant differences between the durations of initial and non-initial vowels in the higher prosodic domains. The theoretical implications of the findings are as follows: The potentially universal phenomenon of initial strengthening is shown to be subject to language specific variations in its implementation. More importantly, the distinct phonetics- phonology model (Pierrehumbert & Beckman, 1998; Keating, 1990; Cohn, 1993) is better equipped to account for the facts in the present study.

• 음성과학
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• 제12권3호
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• pp.139-151
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• 2005

Previous studies have shown that Korean students have difficulty identifying some English consonants which are not in the Korean sound inventory. The aim of this study was to examine the accuracy rate of English consonants correctly identified by 130 college students in order to find out which English consonants were difficult for the students to perceive. The subject's task was to identify one of the minimal pairs played in a quiet laboratory classroom. 100 minimal pairs consisted of syllables with various onsets or codas: stops, fricatives, affricates, liquids and nasals. Results were as follows: First, the average score of the English major group was significantly higher than that of the non-English major group. Second, there was a similar distribution in the rank order of minimal pairs sorted by the accuracy rate between the two groups. Third, the accuracy rate systematically decreased as each score range decreased. Fourth, the students showed higher accuracy in the perception of liquids than that of the stop-fricative contrast. Fifth, the accuracy score in onset position was higher than in coda position. Finally, the students still had problem telling voiced consonants from voiceless ones, especially in coda position. It would be desirable to extend the present research to middle or high school students to fundamentally resolve those listening problems.

• 전기학회논문지
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• 제60권6호
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• pp.1196-1203
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• 2011

The reduced frequency selectivity is a typical phenomenon of sensorineural hearing loss. In this paper, we compared two modeling methods for reduced frequency selectivity of hearing impaired people. The two models of reduced frequency selectivity were made using LPC(linear prediction coding) algorithm and bandwidth control algorithm based on ERB(equivalent rectangular bandwidth) of auditory filter, respectively. To compare the effectiveness of two models, we compared the result of PESQ (perceptual evaluation of speech quality) and LLR(log likelihood ratio) using 36 Korean words of two syllables. To verify the effect on noise condition, we mixed white and babble noise with 0dB and -3dB SNR to speech words. As the result, it is confirmed that the PESQ score of bandwidth control algorithm is higher than the score of LPC algorithm, on the other hands, and the LLR score of LPC algorithm is lower than the score of bandwidth control algorithm. It means that both non-linearity and widen auditory filter characteristics caused by reduced frequency selectivity could be more reflected in bandwidth control algorithm than in LPC algorithm.

• 대한의생명과학회지
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• 제23권4호
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• pp.362-371
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• 2017

The purpose of this study is to investigate difficulties in using prosodic information to identify the meaning of ambiguous sentences in children with high functioning autism (HFA). Fifteen high functioning autistic children and fifteen children who matched their chronological age (CA) participated in this study. We compared the performance of the two groups by conducting syntactically and affectively ambiguous sentence comprehension (SASC and AASC) tasks. The results of this study show that in both tasks, the difference between the two groups was statistically significant at each condition and the performance of high functioning autistic children was significantly lower. In a correlation analysis of major variables, children who matched CA showed a correlation between prosody-only (PO) and AASC, while children with HFA showed a correlation between PO and MO (morpheme-only). Children with HFA used grammatical morpheme information to understand general sentences. We found that the ability to use prosodic information in children with HFA is significantly lower than that of normally developed children. Considering the relevance of prosody to linguistic, non-linguistic and emotional aspects of communication, improving prosodic perception is thought to be a way to mediate deficits in the comprehension of ambiguous sentences in children with HFA.

• 한국멀티미디어학회논문지
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• 제13권9호
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• pp.1322-1328
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• 2010

최근 핵심어 검출 시스템은 유비쿼터스 홈네트워크의 UI(User Interface) 기술로써 각광받고 있다. 핵심어 검출 시스템은 TV, 라디오, 떠드는 소리 등과 같은 동적 생활 잡음에 매우 취약하다. 특히, 실제 임베디드 DSP(Digital Signal Processor) 환경에서는 상대적으로 CPU(Central Processing Unit) 연산능력이 떨어지므로, 실시간으로 입력되는 음성을 인식하기가 어려워 인식율은 급격히 하락하게 된다. 본 논문은 임베디드 DSP 환경에서 원활한 연속음성인식을 수행하기 위하여 '나래야', '홈매니저'등과 같은 호출명령어를 선정하고 잡음을 포함한 묵음구간과 호출명령어로 구성된 최소의 인식네트워크를 토큰으로 구성하여 입력된 음성에 대해 실시간 음성인식을 계속적으로 수행한다.

• 말소리와 음성과학
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• 제5권2호
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• pp.25-31
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• 2013

This study examined cross-generational changes in the vowel system of Seoul Korean. Acoustic analyses of the vowel formants of /o/ and /u/, and their Euclidean distances in the vowel space were undertaken to explore an on-going merger of these two vowels as proposed in previous acoustic studies and a phonological analysis by Chae (1999). A robust cross-generational change of /o/ and /u/ was found, more evident for female speakers than for male speakers. For female speakers, with each successive generation, /o/ became increasingly approximated with /u/, regardless of the syllable positions that the target vowels were posited, whereas the cross-generational differences in the Euclidean distances were only shown in the second syllable position for the male speakers. These results demonstrate that 1) women are more advanced than men in the on-going approximation of /o/ and /u/; 2) the approximation of /o/ and /u/ is common in the non-initial position. Taken together, the merger of /o/ and /u/ appears to be in progress in Seoul Korean.

• 한국음향학회지
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• 제32권6호
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• pp.556-562
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• 2013

본 논문은 컴포트 노이즈(comfort noise)를 이용하는 주파수 밴드선택 음성/오디오 코덱에서 컴포트 노이즈 대신 SBR(Spectral Band Replication) 기술을 이용하여 여기 신호를 대체 함으로서 밴드 선택 광대역 음성/오디오 부호화기의 성능 향상을 목표로 한다. 비 전송 밴드에 SBR 기술로 합성된 신호를 삽입하기 위하여 부밴드 별로 전송된 신호를 활용하며, 각각의 부밴드 별로 에너지 가중치를 설정한다. 백색잡음 성분의 컴포트 노이즈 대신 전송신호에 의존하는 신호를 합성 함으로서 보다 높은 음질의 밴드 선택 부호화기를 제안하였다.

• 말소리와 음성과학
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• 제7권2호
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• pp.29-38
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• 2015

This study explores reading fluency among elementary school students considering language level and family income(low SES). Forty eight students from 1st to 3rd grades participated in two paragraph reading tasks. Half of the children were from low income family and half of the children had low lexical knowledge. Reading fluency as in the number of correctly read syllables per minute, the total error frequency and error types were used to compare group differences. There were significant differences in the number of correctly read syllables per minute between two income groups and two language groups. There was a significant difference between low income group and non-low income group in total number of errors only when children's lexical knowledge were low. There were no group differences in error types of repetition and omission. Substitution and insertion error seemed to reflect the total error pattern. These results imply the importance of early screening and early involvement for children with low lexical knowledge from low income family. Monitoring and early intervention will support these children's reading development.