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무선이동통신망에서 스트리밍 서비스를 위한 프락시 기반Qos 보장 방안
김용술,홍정표,김화성,유지상,김동욱,Kim Yong-Sul,Hong Jung-Pyo,Kim Hwa-Sung,Yoo Ji-Sang,Kim Dong-Wook 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.7B
멀티미디어 스트리밍 서비스의 증가는 인터넷 콘텐츠의 새로운 국면으로 나타나고 있다. 특히, 무선이동통신망에서 증가하는 멀티미디어 응용에 대한 QoS 제공은 무엇보다 중요하다. 서비스 제공자는 클라이언트 가까이에 있는 프락시에서 자주 억세스되어지는 멀티미디어 스트림의 초기 세그먼트를 캐슁함으로써 성능을 향상 시킬 수 있다. 프락시는 서버로부터 스트림의 나머지 부분을 요구함과 동시에 클라이언트에 전송을 시작할 수 있다. 본 논문에서는 IETF의 RTSP 환경에서 프리픽스 캐슁 서비스를 무선망에 적용시키고, 무선 상황이나 핸드오프 시에 네트 워크 상황에 적응적으로 대응하고 단절현상을 줄일 수 있는 효과적인 RTSP 핸들링 기법을 제안 한다. 또한 캐슁 프락시의 성능을 향상시키기 위해 트래픽 기반 캐슁 기법(TSLRU)을 제안한다, TSLRU는 트래픽을 세 종류로 분류하여 캐슁하며, 교체 대상 결정시 여러 요소(traffic types, recency, frequency, object size)를 반영함으로써 캐슁 프락시의 성능을 향상 시킨다. 모의실험에서 캐슁 알고리즘은 byte hit Rate와 startup latency에서 높은 성능을 보였으며, 제안한 RTSP 핸들링 기법 역시 throughput에서 좋은 성능을 보였다. The increasing popularity of multimedia streaming services introduces new challenges in content distribution. Especially, it is important to provide the QoS guarantees as they are increasingly expected to support the multimedia applications. The service providers can improve the performance of multimedia streaming by caching the initial segment (prefix) of the popular streams at proxies near the requesting clients. The proxy can initiate transmission to the client while requesting the remainder of the stream from the server. In this paper, in order to apply the prefix caching service based on IETF's RTSP environment to the wireless networks, we propose the effective RTSP handling scheme that can adapt to the radio situation in wireless network and reduce the cutting phenomenon. Also, we propose the traffic based caching algorithm (TSLRU) to improve the performance of caching proxy. TSLRU classifies the traffic into three types, and improve the performance of caching proxy by reflecting the several elements such as traffic types, recency, frequency, object size when performing the replacement decision. In simulation, TSLRU and RTSP handling scheme performs better than the existing schemes in terms of byte hit rate, hit rate, startup latency, and throughput.
고품질 실시간 스트리밍 서비스 제공을 위한 네트워크 모니터링 기법
김용술,김화성,Kim, Yong-Sul,Kim, Hwa-Sung 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.11B
멀티미디어 서비스의 증가는 인터넷 콘텐츠의 새로운 국면으로 나타나고 있다. IP텔레폰, 화상채팅과 같은 멀티미디어 서비스는 대역폭, 지터, 패킷유실, 전송지연 듯의 네트워크 파라미터에 민감한 데이터이다. 멀티미디어 서비스의 QoS 보장을 위해서 RTP/RTCP를 이용하여 네트워크 상황을 판단하고 전송률을 조절하는 기법이 연구되고 있다. 본 논문에서는 최선형(Best-Effort) 서비스를 제공하는 현 인터넷 구조에서 RTP/RTCP 구조를 확장하여 단방향 전송 지연시간을 구하고 이를 이용하여 네트워크 상황을 판단하는 기법을 제안한다. 또한 단방향 전송지연을 이용하여 급변하는 네트워크 상황에 즉각적으로 대처하기 위한 동적인 RTCP 구조를 제안한다. 모의 실험결과 제안한 단방향 전송 지연 기법은 GPS를 이용한 단방향 전송 기법과 유사한 성능을 보였으며, 제안한 동적 RTCP 기법은 적은 RTCP RR패킷 전송으로 패킷 손실률이 감소하는 효과를 얻었다. Recently, there has been explosive growth in Internet service contents, and we have witnessed the emergence of many real-time applications on the Internet. These types of applications require special support from the underlying network such as reliability, timeless, and guaranteed delivery, as well as different levels of service quality. Estimation network status and transcoding data rate are researching for QoS of multimedia service by using the RTP/RTCP. We propose two schemes that the way to calculate the one-way delay by expanding the structure of RTP/RTCP in Internet that provides us 'best effort' service and to estimate the network condition by using this in this paper. And we propose the dynamic RTCP mechanism based on one-way delay to deal with rapidly changed network situation immediately. In simulation, proposed monitoring schemes using the one-way delay has similar in performance to monitoring schemes using the GPS, proposed dynamic RTCP scheme obtain the desired result of decreased packet loss rate by sending RTCP RR packet lower than other schemes.
김용술(Kim Yong-Sul),여명길(Yeo Myung-Kil),서윤규(Seo Youn-Kyu),김주영(Kim Ju-Young),홍원화(Hong Won-Hwa) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.4
We live in paradigm that is concentrated on the sustainable development, nowaday. This paradigm isn't perfectly solved but we deal with paradigm. According to the statistics about energy, South Korea imports 96% of energy materials and reliance ratio of energy is 17%. In domestic situation, the energy consumption ratio of the buildings is 23% of total energy consumption ratio. Especially, the stadium is the landmark in the cities where the stadium is situated. But the stadium consumes a lot of energy in the dark side. This study treats Deagu Stadium that is situated in Deagu. This stadium is the landmark of Deagu that connotes the historical meanings. This study are going to put the environment-friendly factor into exisiting landmark factor. To be environment-friendly building, the method is studied to install renewable energy system. If the method is defined, fossil fuel consumption decreases and the environment-friendly landmark increases.
γ-Al2O3 촉매상에서 열분해와 가수분해에 의한 NF3 촉매분해 특성
김용술 ( Yong Sul Kim ),박노국 ( No Kuk Park ),이태진 ( Tae Jin Lee ) 한국공업화학회 2015 공업화학 Vol.26 No.2
In this study, the catalytic activity of γ-Al2O3 was investigated for the decomposition of NF3. Reactions for NF3 decomposition were carried out in the range of reaction temperature of 330∼730 ℃ and GHSV of 3,000∼15,000 mL/g-cat?h in a fixed-bed catalytic reactor system. Thermal decomposition of NF3 was also performed in order to compare with the catalytic decomposition of NF3. The conversion of NF3 by the catalytic decomposition at 400 ℃ was four times higher than that of the thermal decomposition. It was confirmed that the reaction behavior of NF3 over γ-Al2O3 exhibited two reaction pathways in the presence of steam. Fluorine in NF3 over γ-Al2O3 was chemically absorbed to AlF3 by the gas-solid reaction in the absence of steam. The catalytic decomposition of NF3 occurred by hydrolysis with steam. It was also confirmed by FT-IR analysis that NF3 was completely decomposed to NOx and HF above 500 ℃.