• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.639-642
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• 2015

As attack to routing function on MANET(Mobile Ad-Hoc Network), hole attack make cause some critical effects. MANET is easily influenced with hole attack and can be critically effected on transmission performance, because it is configured with terminal device as temporary network and dose not have effective means for malicious attack. In this paper, effects of grayhole attack to network performance on MANTE is analyzed with computer simulation. Voice traffic is used in simulation, effects of grayhole attack is compaerd with blackhole attack. The method and result of this paper can be used for data to study grayhoke attack.

• ETRI Journal
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• v.31 no.4
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• pp.408-418
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• 2009

Adopting an encryption function in voice over Wi-Fi service incurs problems such as additional power consumption and degradation of communication quality. To overcome these problems, a partial encryption (PE) algorithm for compressed speech was recently introduced. However, from the security point of view, the partial encryption sets (PESs) of the conventional PE algorithm still have much room for improvement. This paper proposes a new selection method for finding a smaller PES while maintaining the security level of encrypted speech. The proposed PES selection method employs the perceptual evaluation of the speech quality (PESQ) algorithm to objectively measure the distortion of speech. The proposed method is applied to the ITU-T G.729 speech codec, and content protection capability is verified by a range of tests and a reconstruction attack. The experimental results show that encrypting only 20% of the compressed bitstream is sufficient to effectively hide the entire content of speech.

• Speech Sciences
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• v.15 no.2
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• pp.55-65
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• 2008

Recently, the multi-model based speech recognizer has been used quite successfully for noisy speech recognition. For the selection of the reference HMM (hidden Markov model) which best matches the noise type and SNR (signal to noise ratio) of the input testing speech, the estimation of the SNR value using the VAD (voice activity detection) algorithm and the classification of the noise type based on the GMM (Gaussian mixture model) have been done separately in the multi-model framework. As the SNR estimation process is vulnerable to errors, we propose an efficient method which can classify simultaneously the SNR values and noise types. The KL (Kullback-Leibler) distance between the single Gaussian distributions for the noise signal during the training and testing is utilized for the classification. The recognition experiments have been done on the Aurora 2 database showing the usefulness of the model compensation method in the multi-model based speech recognizer. We could also see that further performance improvement was achievable by combining the probability density function of the MCT (multi-condition training) with that of the reference HMM compensated by the D-JA (data-driven Jacobian adaptation) in the multi-model based speech recognizer.

• Asian Journal for Public Opinion Research
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• v.1 no.2
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• pp.73-89
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• 2014

Everyone has a voice and can broadcast it to the world. We hear about the old maxim of media do not tell people what to think but what to think about. Under this theory or approach, a key function of political communication is to make the public think about an issue in a way that is favorable to the sender of the message. In a democracy, political communication is seen as crucial for the building of a society where the state and its people feel they are connected. Thus, this is a study on how social media (e.g., Facebook, blogs, and YouTube) were used in the domain of Malaysian politics during the 13th general election campaigning period in order to set the agenda to form public opinion. The study found that Facebook was the most popular social media tool that political parties actively engaged with during the 13th general election campaign period. Apart from that, issues pertaining to the election were significantly highlighted by the political parties in social media, especially Facebook. However, other issues that were also important to the people such as the economy, crime, and education were not sufficiently highlighted during the election campaign period. This indicates that the political parties influence the public on what to think about using social media.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.642-645
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• 2012

MANET has disadvantage for information intrusion caused from non-infra structure. That is based on mixed problems caused from terminal devices has no capability of various resources using abilities to run intrusion prevention function, and also from difficulty of no easy using infra structural server like as firewall. In this paper, transmission performances, be effected from information intrusion and IDS(Intrusion Detection System), are analyzed for large scale MANET, and weakness from information intrusion of MANET are studied. This study is for large scale MANET which has some large communication area and lots of nodes, voice traffic, based on VoIP protocols, is considered as application services be transmitted over MANETs. Computer simulation using NS-2 is used to measure and show MOS and call connection ratios.

• Speech Sciences
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• v.9 no.4
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• pp.237-252
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• 2002

MIT has been applied for nonfluent aphasic patients on the basis of lateralization of brain hemisphere. However, its applications for different languages have some inquiry for aphasic patients because of prosodic and rhythmic differences. The purpose of this study is to develop the Korean Melodic Intonation Therapy program using personal computer and its clinical effects for nonfluent aphasic patients. The algorithm was composed to voice analog signal, PCM, AMDF, Short-time autocorrelation function and center clipping. The main menu contains pitch, waveform, sound intensity and speech files on window. Aphasic patients' intonation patterns overlay on selected kMIT patterns. Three aphasic patients with or without kMIT training participated in this study. Four affirmative sentences and two interrogative sentences were uttered on CSL by stimulus of ST. VOT, VD, Hold and TD were measured on Spectrogram. In addition, articulation disorders and intonation patterns were evaluated objectively on spectrogram. The results indicated that nonfluent aphasic patients with kMIT training group showed some clinical effects of speech intelligibility based on VOT, TD values, articulation evaluation and prosodic pattern changes.

• Speech Sciences
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• v.15 no.4
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• pp.171-188
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• 2008

This study was purposed to introduce Korean Oro-motor Mechanism Screening Examination (KOMSE) and to provide the standardized scores taken from 120 normal adults aged $18{\sim}59$. KOMSE was composed of 13 items of structure, 17 items of function, 3 items of voice, and 14 items of regularity and accuracy of articulation during diadochokinesis. Additionally, maximum phonation time and diadochokinetic rates were measured. Total score of KOMSE is ranged from 0 to 200. It was significantly higher in the $50{\sim}59$ age group than in the $20{\sim}29$ age group, but was not significantly different in sex. MPT had a significant difference in sex, but no significant difference among different age groups. The rate of DDK was also had no significant difference among different age groups. However, some reducing trend in the rate of DDK was observed as age increased. KOMSE would be very helpful for SLPs to screen the abnormality of oro-motor mechanism.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.436-440
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• 2008

Among those various facilities attached to the school building, the Auditorium is being utilized for not only the Exercise Activity but also for many purposes such as Culture, Public Performance, Education, Assembly and so on. In order to utilize in maximum such function of the multipurpose auditorium, an adequate acoustic design with regard to the Clarity of Voice and Music in accordance with its use-purpose should be accompanied. However, as the most part of multipurpose auditoriums is designed with high ceiling-height by its peculiar character, and due to use of the material of strong reflexibility, it is appearing the defect that excessively exposes the reverberation of sound. In order to make out an optimal acoustic condition within the broad space such as an auditorium, the acoustic characteristics must be considered from the planning stage, however in the most case, those acoustic problems are being settled through the repair works after construction. On such viewpoint, this Study intends to analyze the room acoustic characteristics from the planning stage using a computer simulation based on the blueprint of multipurpose auditorium in S High School located in Gwangju. It is considered that the material analyzed in such way could be practically applied as a fundamental material enables to improve the acoustic capability when a similar broad space is planned hereafter.

• Phonetics and Speech Sciences
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• v.12 no.1
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• pp.43-50
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• 2020

This study investigated whether listeners' perceptual patterns varied according to base token selected for stimuli manipulation. Voice onset time (VOT) and fundamental frequency (F0) values were orthogonally manipulated, each in seven steps, using naturally produced words that contained a lenis (/kan/) and an aspirated (/k^han/) stop in Seoul Korean. Both native and non-native groups showed significantly higher numbers of aspirated responses for the stimuli constructed with /k^han/, evidencing the use of minor cues left in the stimuli after manipulation. For the native group the use of the VOT and F0 cues in the stop categorization did not differ depending on whether the base token included the lenis or aspirated stop, indicating that the results of previous studies remain tenable that investigated the relative importance of the acoustic cues in the native listener perception of the Korean stop contrasts by using one base token for manipulating perceptual stimuli. For the non-native group, the use patterns of the F0 cue differed as a function of base token selected. Some findings indicated that listeners used alternative cues to identify the stop contrast when major cues sound ambiguous. The use of the manipulated VOT and F0 cues by the non-native group was not native-like, suggesting that non-native listeners may have perceived the minor cues as stable in the context of the manipulated cue combinations.

• Journal of Service Research and Studies
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• v.1 no.1
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• pp.113-122
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• 2011

In this research, we developed an practical service module as a application which operating on the smart phones based on the Android operating system. The service module supports on the voice processing function and inquiry windows also. After some documents and screens related on system analysis, service module are designed and implemented. The details about these modules are explained. We can expect to enhance the learning effects of english words memorizing competence for smart-phone users.