• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.243-248
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• 2012

In this paper we simulate the capacity of VOIP calls through WiFi network by computer simulations using OPNET modeler. The results show that sudden quality degradations occur on all VoIP calls when the number of call of an AP(Access Point) increases beyond a specific value. The reason of the quality degradation was turned out to be the queueing delay at the down link of AP. Under the IEEE 802.11b environments, the maximum number of VoIP calls of an AP maintaining the required voice quality (MOS > 2.5), was evaluated as 5, 12, and 27 when we use G.711, G.729a, and G.729a VAD codec, respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1077-1082
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• 2016

IDS can be used as a countermeasure for malicious attacks which cause degrade of network transmission performance by disturbing of MANET routing function. In this paper, effects of IDS for transmission performance on MANET under grayhole attacks which has intrusion objects for a part of transmissions packets, some suggestion for effective IDS will be considered. Computer simulation based on NS-2 is used for performance analysis, performance is measured with VoIP(: Voice over Internet Protocol) as an application service. MOS(: Mean Opinion Score), CCR(: Call Connection Rate) and end-to-end delay is used for performance parameter as standard transmission quality factor for voice transmission.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.22 no.2
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• pp.106-110
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• 2011

Western classical singing voices are different from those of pop song singer's singing voices as well as traditional Korean singing such as Pansori. We anlalysed the singing voices from three different categories with using free application programs available at the usual smart phones : sound level meter and Spectral View Analyzer and fiberoptic rhinolaryngoscopic evaluation. The intensity of voice produced by a classical western singer was 11 dB louder than that produced by a pop song singer. Source sound, glottic sound, as well as harmonic sound and singing resonant sound (Singer's formant) are much more prominent. When evaluated under video-rhinolaryngoscopy during singing, the resonance cavity especially oropharyngeal cavity and hypopharyngeal cavity are widely opened during singing of the western classical singer than those of the traditional Korean singer's singing. Difference of singing methods including producing the glottal sound, respiration and resonance are discussed. Possible explanation of development of 'Singer's Formant' is discussed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.279-287
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• 2001

In this paper, we discuss the scale of subjective speech quality measurement over VoIP(Voice over IP) network which is a component of broadband networks. Objective parameters of multimedia services like PSNR or jitter can easily measured and defined, but these factors are not easily meet the user's perceptual recognition. We suggest the speech quality measurement scale through the subjective measurement for end-to-end speech quality composed of sender-side quality, transmission quality, receiver-side quality, which provide the degree of correctness of representation of speaker, the degree of impairment caused by various factors, the degree of recognition of processed speech, respectively. Also, we examined the proposed method and verify it's availability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4C
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• pp.283-289
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• 2012

Web-based physiological signal monitoring system can provide appropriate healthcare services to transmit bio-signal processing, analysis of bulk in medical centers. Therefore, we constructed a design of system to analyze effect of cardiac associated auricular acupuncture reflexology based on physiological signals. System to analyze effect cardiac associated auricular acupuncture reflexology, which carried out analysis and measurement of bio-signal to apply cardiac-related biometrics input in biometric image and voice signal. In addition, we also confirmed through statistical analysis actual home healthcare system to performance evaluation of system on subjects 20.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12B
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• pp.1135-1144
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• 2003

In this paper, we proposed a semi-soft handoff mechanism to provide link mobility in IEEE 802.11 wireless LAN environment. Buffers and routing tables in APs and portals are provided in order to reroute frames, which have not been received during handoff time and have been buffered in an old AP, to a new AP after handoff is performed. For the re -routing operation, the MAC routing table should be updated by exchanging information of a mobile terminal between neighbor APs. With our proposed scheme. a wireless LAN node can perform semi soft handoff while changing its attached AP and provide mobile IP and/or real time service like voice over IP. Also, we have done simulation for evaluation of the performance of the proposed scheme. We show that our semi soft handoff mechanism can be applied for real-time service with no frame loss in mobile environment.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.22 no.2
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• pp.126-132
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• 2011

Background and Objectives : Vocal fold paresis is a clinical condition and considered as a continuum of neurologic dysfunction encompassing partial denervation and variable degrees and patterns of reinnervation. Its incidence, clinical presentation, significance are incompletely understood and still debated. This study describes the clinical, electromyographic findings in patients who presented with complaints of dysphonia and whose laryngoscopic finding revealed vocal fold paresis. Materials and Method : 47 patients (male : 25, female : 22) who referred to Ewha Womans University Medical Center Voice clinic for evaluation of vocal complaints were enrolled in this study. All patients had undergone a through history and physical examination including strobovideoscopic and laryngoscopic examination. Patients with in the history and/or laryngoscopic examination suggestive of vocal fold paresis were evaluated by laryngeal electromyography (LEMG). Results : Of these patients, 23 (48.9%) were found to have evidence of neuropathy on LEMG. There was no significant difference in voice symptoms and laryngoscopic findings between two groups of patients with evidence of neuropathy and who show normal findings on LEMG. Conclusion : LEMG can clinically help to guide the evaluation and management of vocal fold paresis. Due to some limitations of LEMG, laryngoscopic findings and clinical correlations should also be considered when diagnosing the vocal fold paresis.

• Journal of Science and Technology Studies
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• v.15 no.2
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• pp.33-64
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• 2015

World Wide Views (WWViews) on Climate and Energy was an experiment of public deliberation which was held in 77 countries with over 10,000 global citizens on June 6, 2015. The coordinator of this project (the Danish Board of Technology with Missions Publiques and the French National Commission for Public Debate) developed the overal procedure, and local partners implemented the actual events in each country on the same day. The coordinator gathered the results of the events from all local sites in order to submit them as global citizens' voice to the COP21 negotiations at the United Nations Framework Convention on Climate Change (UNFCCC) in Paris. This study examines the extent to which such new method of WWViews, standardized at global level to be implemented in different local contexts, achieves its quality of public deliberation (representativeness, transparency, impartial inclusion, deliberativeness, influence) by evaluating the Korean WWViews held in Seoul.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.3
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• pp.109-120
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• 2008

VoIP utilizes the Internet for the services, and therefore it is vulnerable to intrusions and attacks. Because provided services deal with information related to privacy of users, it requires high level security including authentication and the confidentiality/integrity of signaling messages and media streams. However, when such a protocol is implemented in a VoIP phone, the implementation can have limitations due to the limited resources. The present study purposed to implement VoIP security protocols and to evaluate their performance in terms of connection quality and voice quality by applying them to SIP proxy and UA (User Agent). In the result of performance evaluation, the application of the security protocols did not lower voice quality, but connection quality was high in the DTLS based security protocol. As the protocol was applicable to signaling and media paths based on DTLS, we found that it can be a solution for the limited resources of VoIP phone.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.123-126
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• 2005

We develop the evaluation method of functional requirements for excavator design. The functional requirement of the product can be deduced from voice of customer. QFD method is used in order to convert customer requirement to functional requirement. The measure of information index is used to evaluate quantitatively the product quality characteristics. The correlation score between customer requirements and functional requirements and benchmarking score of competitors are basic data for the measure of information.