• The Journal of Korean Association of Computer Education
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• v.11 no.2
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• pp.107-117
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• 2008

The agent system that can adjust the workload dynamically through thc periodical monitoring of the VoD system comprises the agency part interfacing the VoD system and the intelligence part reasoning or learning the facts required for the adjustment of workload. This paper proposes a learning method that can apply to the intelligence part of the agent system. The proposed method can adjust the workload more efficiently by the rule's reasoning process and case-based learning process. An experiment of implementing a simulator was conducted to see whether or not application of the proposed method to VoD systems is efficient. As a result of the experiment, it was found that the throughput and the average waiting time of the VoD server were relatively improved when the proposed method was applied compared to existing means.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.11a
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• pp.211-214
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• 2006

이동통신의 발달과 함께 모바일을 통한 VoD서비스 요구 또한 증가하고 있는 추세이다. 모바일 VoD서비스는 언제, 어디서든 비디오 정보를 쉽게 액세스할 수 있는 편리함과 교육, 연예, 비즈니스와 같은 많은 어플리케이션 영역에서 유용하게 사용되고 있다. 그러나 모바일 시스템의 특성상 클라이언트의 빈번한 이동과 끊어짐으로 원활한 VoD서비스를 제공하기에는 많은 어려움이 존재하고 있다. 보다 안정된 모바일 VoD서비스를 위한 방법으로 브로드캐스트 기법의 중요성이 강조되고 있으며 본 논문에서는 모바일 VoD환경에서 효율적인 브로드캐스트를 위한 채널 할당 기법을 제안하고자 한다.

• Journal of the Korean Magnetic Resonance Society
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• v.9 no.2
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• pp.138-154
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• 2005

Vanadium-incorporated aluminophosphate molecular sieve $VO^{2+}-SAPO-5$ was studied by electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies to determine the vanadium structure and interaction with various adsorbate molecules. It was found that the main species at low concentration of vanadium is a monomeric vanadium units in square pyramidal or distorted octahedral coordination, both in oxidation state (IV) for the calcined hydrated material and in oxidation state (V) for the calcined material. After calcinations in $O_2$ and exposure to moisture, only species A is observed with reduced intensities. It is suggested as a $VO(H_2O)_3^{2+}$ complex coordinated to two framework oxygen bonded aluminum. When calcined, hydrated $VO^{2+}-}SAPO-5$ is dehydrated at elevated temperature, a species loses its water ligands and transforms to $VO^{2+}$ ions coordinated to two framework oxygens (species B). Species B reduces its intensity, significantly after treatment with $O_2\;at\;600^{\circ}C$ for 5 h, thus suggesting oxidation of $V^{4+}\;to\;V^{5+}$. When dehydrated $VO^{2+}-SAPO-5$ contacts with $D_2O$ at room temperature, the EPR signal of species A is observed. Thus species assumed as a $VO^{2+}(O_f)_2(D_2O)_3$, by considering two framework oxygens. Adsorption of deuterated ethanol, propanol on dehydrated $VO^{2+}_{-}SAPO-5$ result in another new vanadium species E and F, respectively, which are identified as a $VO^{2+}-(CH_3CH_2OD)_3,\;VO^{2+}-(CH_3CH_2CH_2OD)_2$ complex. When deuterated benzene is adsorbed on dehydrated $VO^{2+}-SAPO-5$, another new vanadium species G, identified as a $VO^{2+}-(C_6D_6)$ is observed. Possible coordination geometries of these various complexes are discussed.

• The KIPS Transactions:PartD
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• v.14D no.5
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• pp.565-572
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• 2007

In this paper, we developed a VoWLAN(Voice over WLAN) system based on an open source software. The system aims to provide VoIP service over wireless LAN with an IP-PBX server. The features of system presented in this paper are as follows. First, the initial cost for the development is reduced since the system is developed based on open source software. Second, the system provides various additional services such as Voice Mail, Conference Call, and Interactive Voice Response with a software IP-PBX server. Third, the VoWLAN terminal provides high-level user applications with minimal system resources using lightweight open software solutions. Finally, it is highly scalable since it is based on the open source software.

• Journal of Korea Society of Industrial Information Systems
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• v.13 no.1
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• pp.46-56
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• 2008

Double Patching is a multicasting technique for a VoD system which has been proposed to provide a true VoD service by making clients share a long patching stream as well as a regular stream For subsequent short patching streams, the technique always makes the long patching stream have extra data that will be played back during a double period of a patching window. In this paper, we propose a technique, using the start time of the latest short patching stream, optimizes Double Patching by deleting the useless data included in the long patching stream when the patching window of the long patching stream closes. The mean requirement for the server's bandwidth to provide the true VoD service is used as a performance metric, and the effect of the request inter-arrival time, the size of the client's local buffer and the video length on the mean bandwidth requirement is evaluated. Performance evaluation result shows that the proposed technique optimizes Double Patching in all cases.

• Journal of Internet Computing and Services
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• v.11 no.5
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• pp.9-17
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• 2010

During the last decade, Internet protocol television(IPTV), broadcasting of multimedia services using well understood Internet technologies, is a fast spreading technology for distributing multimedia content to consumers. As IPTV services advance, an increasing user demand and tremendous content volume of multimedia content cause some difficulties in network resource management. In this paper, we propose an improved load balancing algorithm for video-on-demand(VoD) service. Unlike existing algorithms, the proposed algorithm considers user's behaviors for VoD service, and determines the most efficient allocation of VoD requests by estimating expected server load and expected user waiting time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.784-791
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• 2005

To provide VoD Service on the Internet VoD server is required to have a large amount of system resource and network bandwidth. Therefore, overlay Multicast schemes are considered as suitable alternatives but they also have some drawbacks to support on-demand media services. In this paper, we propose an overlay multicast based on-demand media service scheme which could exploit server's system resource and its network bandwidth efficiently. Proposed scheme uses shared buffer of clients involving the relay of traffic and Patching while it gives no restrictions to this scheme compared with unicast. Our simulation results show that proposed scheme can support more user than unicast and improve the network performance at the same time.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.108-110
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• 1999

컴퓨터 하드웨어의 발달로 고속 네트워킹과 대용량 저장 장치가 가능해지면서 기존의 단순 계산 데이터가 아닌 멀티미디어 데이터를 조작하는 기술이 필요로 하게 되었다. 이 기술을 이용하는 대표적인 것이 VoD 서버 처리 기술이다. 기존 VoD 서버에서는 데이터의 분산 및 버퍼 구조 또는 병렬 I/O를 통하여 해결하려는 노력이 있어 왔다. 본 논문에서는 서버의 성능을 극대화시켰다. 디스크 저장 매체와 서버의 수를 증가시켜 시험하므로써 이 구조가 확장성 있음을 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.223-225
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• 2001

본 논문은 분산 환경에서 결함 허용성 있는 VoD서비스를 위한 결함 처리 방법을 제안하고 성능을 측정하였다. 디스크 결함, 서버 결함, 시스템 결함에 따른 결함 체크와 처리 방법을 제시하였다. 사용자에게 신뢰성과 실시간성을 보장하기 위한 서버 스위칭 방법을 제안하였다. 서버 스위칭 방법은 결함이 발생하지 않은 서버들의 여유 로드율에 따라 달라진다. 서버 스위칭이 일어나는 동안 클라이언트의 버퍼에 적정량의 데이터를 유지하기 위한 흐름제어 기법도 제시하였다. 본 논문에서 제안하는 방법을 통해 결함일 발생함에도 불구하고 클라이언트는 서비스의 중단 없이 VoD 서비스르 제공 받을 수 있다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.502-507
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• 2016

Vanadium dioxide, $VO_2$, is a thermochromic material that exhibits a reversible metal-insulator phase transition at $68^{\circ}C$, which accompanies rapid changes in the optical and electronic properties. To decrease the transition temperature around room temperature, a number of studies have been performed. The phase transition temperature of 1D nanowire $VO_2$ with a 100 nm diameter was reported to be approximately $29^{\circ}C$. In this study, 1D or 2D nanostructured $VO_2$ was grown using the vapor transport method. Vanadium dioxide has a different morphology with the same growth conditions for different substrates. The 1D nanowires $VO_2$ were grown on a Si substrate ($Si{\setminus}SiO_2$(300 nm), whereas the 2D & 3D nanostructured $VO_2$ were grown on an exfoliated graphene nanosheet. The crystallographic properties of the 1D or 2D & 3D nanostructured $VO_2$, which were grown by thermal CVD, and exfoliated-transferred graphene nanosheets on a Si wafer which was used as substrate for the vanadium oxide nanostructures, were analyzed by Raman spectroscopy. The as-grown vanadium oxide nanostructures have a $VO_2$ phase, which are confirmed by Raman spectroscopy.