• The KIPS Transactions:PartC
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• v.18C no.3
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• pp.143-150
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• 2011

The adoption of VoIP is continuously increasing in public institutions, private enterprises and households due to cheaper cost and various supplementary services. Also, it is expected to spread widely the use of VoIP in mobile environment through the increasing use of smartphone. With the growing concern over the incidents of VoIP service while the VoIP service has become increasingly. Especially eavesdropping, it is possible to invade user privacy and drain the secret of company. So, it is important to adopt the protocols for VoIP secure communication. VoIP security protocols are already adopted in public institutions, but it is not adopted in private enterprises and households. In addition, it is necessary to verify whether the VoIP security protocol could be adopted or not in mobile VoIP due to its limited computing power. This paper compared the VoIP security protocol under fixed network and mobile network through performance evaluation. Finally, we found that it is possible to adopt the VoIP security protocols in mobile network.

• Clean Technology
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• v.27 no.2
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• pp.146-151
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• 2021

Pure and Sm ion doped BiVO₄ catalysts were synthesized using a conventional hydrothermal method and characterized by XRD, DRS, SEM, and PL. We also examined the activity of these materials on the photocatalytic decomposition of rhodamine B under visible light irradiation. The doping of Sm ion into BiVO₄ catalyst changed the ms-BiVO₄ crystal structure into the tz-BiVO₄ crystal structure in the low synthesis temperature. Light absorption analysis using DRS showed that all the catalysts displayed strong absorption in the visible range of the electromagnetic spectrum regardless of Sm ion doping. In addition, an amorphous morphology was shown in the pure BiVO₄ catalyst, but the morphology of the BiVO₄ catalyst doped with Sm ion was changed into an ellipse shape and also the particle size decreased. In the photocatalytic decomposition of rhodamine B, Sm ion doped BiVO₄ catalyst showed higher photocatalytic activity than the pure BiVO₄ catalyst. In addition, the Sm3-BVO catalyst doped with 3% Sm ion showed the highest photocatalytic activity, as well as the highest formation rate of OH radicals (•OH) and the highest PL peak. This result suggests that the formation rate of OH radicals produced in the interface between the photocatalyst and water is well correlated with the photocatalytic activity.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.153-156
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• 2003

In this paper, we propose QoS guarantee system fur multi-functional VoIP end Terminal. This system guarantees low delay of voice data for Internet telephony in VoIP end terminal that has various kinds of Internet dependant application. QoS system we propose support low delay transmission in VoIP terminal interface.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.99-107
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• 2008

In this paper, we analyse the vulnerability of spam attacks and develop the Spamtester to confirm these spam attacks in SIP-based VoIP networks. Although there are several spam attacks on VoIP networks, the detail information for the SPIT is not enough to confirm the procedure and the result of spam attacks on VoIP networks. Specially, the spam attacks through abnormal process are difficult to trace the sender of spam. Also, it is not easy to impose the legal restriction to the spammer because of lack of information for the spam attack. Therefore, on VoIP networks, the possible scenario and detail procedure for VoIP spam is needed to be confirmed. This paper designes and implementes the spamtester, which is helpful to protect VoIP networks from the spam attacks.

• Journal of Life Science
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• v.17 no.9 s.89
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• pp.1255-1259
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• 2007

The purpose of this study was to elucidate incidence of $VO_2$ plateau by comparing data derived from different time averaging intervals during incremental cycling exercise to $VO_2max$. Seventeen subjects (age: $23.5{\pm}3.3$ years and $VO_2max$: $3.65{\pm}0.73$ L/min, respectively) completed $VO_2max$ tests on cycle ergometer which breath by breath gas ex-change data were obtained. These data were time-averaged into 11-breath, 15, 30 and 60 s sampling intervals. The incidence of plateau were 100, 35, 24 and 6% for the 11 breath, 15 s, 30 s and 60 s averaging, respectively. No correlation was between ${\Delta}$ $VO-2$ at $VO_2max$ and $VO_2max$ (r=0.008). 53% (maximal HR within 10 b/min) and 100% $(RER{\geq}1.15)$ of subjects met the criteria for attainment of $VO_2max$. This data indicate that shorter sampling intervals (11 breath) is the most suitable for de-tection of the $VO_2$ plateau and RER can be used for the criteria for attainment of $VO_2max$ but not maximal HR. Also, the incidence of a plateau is not related to training status or physical fitness of subjects.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.414-418
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• 2003

VoIP is a core technology used to transmit both voice and data in an integrated packet' form. Within this technology, SIP is the signaling protocol used for 'real time' call services; particularly those where H323 is used. Yet, when considering the needs of mobile users, it is essential we integrate VoIp within the mobile technology so the mobile host is able to receive the 'packet' transported and by, and connected to, any available internet-address. For all this to occur, we need to improve Network Delay by reducing transmission problems associated with mobile services. If we are to obtain an optimal service then we must reduce any network delays which may arise from joining Mobile IP and VoIp services. This paper, therefore, considers how, unlike previous research, these delays may be improved through the use of the signaling technology\ulcorner SIP. It also considers how this research may be introduced into current wired and wireless integrated services enabling them to use the IP 'packet'.

• KSCI Review
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• v.14 no.2
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• pp.215-224
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• 2006

Regarding a spam attack and the interception that a spinoff is largest among Vulnerability of VoIP at these papers study. Write scenario of a spam attack regarding VoIP Vulnerability, and execute Call spam. Instant Messaging spam, Presence spam attack. A spam attack is succeeded in laboratories, and prove. and confirm damage fact of a user in proposals of a spam interception way of VoIP service, 1) INVITE Request Flood Attack 2) Black/White list, 3) Traceback, 4) Black Hole-Sink Hole, 5) Content Filtering, 6) Consent based Communication, 7) Call act pattern investigation, 8) Reputation System Propose, and prove. Test each interception plan proposed in VoIP networks, and confirm security level of a spam interception. Information protection of VoIP service is enlarged at WiBro, BcN. and to realize Ubiquitous Security through result of research of this paper contribute, and may make.

• Journal of Digital Contents Society
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• v.13 no.4
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• pp.477-482
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• 2012

The mVoIP service is the technology which focuses on the wireless data service as the IP network having the transmission rate of 100 Mbps classes on the high-speed middle of movement through the WiFi, WiBro and 3G mobile radio communication network, and etc. and is developed. Since 2010, the mVoIP (mobile VoIP) service shows the rapid growth due to 4G-LTE service seriously disclosed from July with the Smart phone and 2,011 it begins to be rapidly popularized. In this research, additionally the mVoIP service industry activation plan is presented with the trends of technology development including the chip-set/module/terminal, etc. based upon local and foreign market trend searchlight through the market demand analysis. The mVoIP service downloads App to the mobile apparatus and or can provide the service as the software through the WiFi network. Therefore, the change which is large in the products development aspect is to be have no. Expected to is being provided as the added service in the case of 4G-LTE as a matter of course, the service deployment where it is based on the market principle and demand needs is needed.

• Journal of Korea Multimedia Society
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• v.10 no.3
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• pp.335-347
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• 2007

VoIP (Voice over IP) is a technology to transport video and voice traffic over IP networks such as Internet. Today, the VoIP technology is viewed as the right choice for providing voice, video, and data communication among various terminals over the next generation network. This paper discusses a multipoint VoIP implementation with end-point mixing model which can support multipoint conference without a conference bridge. The multipoint VoIP is implemented with SIP (Session Initiation Protocol), and supports STUN (Simple Traversal of UDP Through NATs) since it works in an asymmetric NAT (Network Address Translator) environment. The characteristics of this paper are as follows. It is possible that all terminals in the hierarchical conference don't receive the duplicated media information because we use the end-point mixing model with the new media processing module. And, the paper solves the problem that the hierarchical conference session should be separated into several sessions when a mixing terminal terminates the hierarchical conference session.

• Journal of the Korea Society of Computer and Information
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• v.11 no.5 s.43
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• pp.241-250
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• 2006

Regarding a spam attack and the interception that a spinoff is largest among weakness of VoIP service at these papers study. Write scenario of a spam attack regarding VoIP service, and execute Call spam, Instant Messaging spam, Presence spam attack. A spam attack is succeeded in laboratories, and prove, and confirm damage fact of a user in proposals of a spam interception way of VoIP service, 1) INVITE Request Flood Attack 2) Black/White list, 3) Traceback, 4) Black Hole-Sink Hole, 5) Content Filtering, 6) Consent based Communication, 7) Call act pattern investigation, 8) Reputation System Propose, and prove. Test each interception plan proposed in VoIP networks, and confirm security level of a spam interception. Information protection of VoIP service is enlarged at WiBro, BcN, and to realize Ubiquitous Security through result of research of this paper contribute, and may make.