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Predictive Location Management Strategy Using Two Directional Consecutive LAs a Cellular Network
장인갑(I.K. Chang),홍정식(J.S. Hong),김지표(J.P. Kim),이창훈(C. H. Lie) 한국경영과학회 2008 韓國經營科學會誌 Vol.33 No.3
In this paper, we have presented a dynamic, predictive location update scheme that takes into account each user's mobility patterns, A user's past movement history is used to create two-dimensional transition probability matrix which makes use of two directional consecutive location areas. A mobile terminal utilizes the transition probability to develop a predictive path which consists of several predictive nodes and then the location update is saved as long as a mobile user follows the predictive path. Using continuous-time Markov chain, cost functions of location update and paging are derived and it is shown that the number of predictive nodes can be determined optimally. To evaluate the proposed scheme, simulations are designed and the numerical analysis is carried out. The numerical analysis features user's mobility patterns and regularity, call arrival rates, and cost ratio of location update to paging, Results show that the proposed scheme gives lower total location management cost. compared to the other location update schemes.
확산과 전이 모형을 적용한 WiBro와 HSDPA 서비스 수요 예측
장인갑 ( In Kap Chang ),홍정완 ( Jung Wan Hong ),홍정식 ( Jung Sik Hong ),박광만 ( Gwang Man Park ),이광희 ( Gwang Hee Lee ),이창훈 ( Chang Hoon Lie ) LGCNS 엔트루정보기술연구소 2008 Entrue Journal of Information Technology Vol.7 No.1
WiBro와 HSDPA는 초고속의 무선 인터넷 서비스를 안정적으로 제공하는 것을 목표로 삼고 있으며, 이동통신 시장에서 매우 유사한 서비스를 제공하고 있음을 알 수 있다. 서비스 초기에는 HSDPA와 WiBro의 서비스 기술 한계로 인하여 보완 관계를 유지할 것으로 예상하지만, 관련 기술의 발전에 따라 잠재적으로 경쟁관계로 변화할 것이다. 따라서 기술 발전에 따라 WiBro와 HSDPA 서비스의 상호관계 변화를 고려한 수요 예측 모형의 개발이 필요하다. 이에 본 연구에서는 기술적 진보에 따른 이동통신 서비스들 간의 상호관계 변화를 고려하여 이동통신 시장에서 WiBro와 HSDPA의 보완 및 경쟁 관계, 그리고 시장 잠식 효과를 반영할 수 있는 새로운 수요 예측 모형을 제안한다. 수요 예측 모형은 확산 모형과 전이 모형을 혼합하여 제안하였으며, 일반인과 전문가 설문조사 방법을 이용하여 모형에 필요한 모수들을 추정하고 제안한 모형을 적용하여 WiBro와 HSDPA의 수요를 예측하였다. WiBro and HSDPA aim to provide wireless broadband internet service stably and it is well known that they provide similar services in telecommunication markets. WiBro and HSDPA are expected to be complementary due to the limit of technology in the early stage of service, but the relationship of them becomes competitive as the related technology develops. Therefore, the development of demand forecasting model considering the change of mutual relationship between WiBro and HSDPA is necessary. In this paper, we propose a novel demand forecasting model which reflects complementary and competitive relationship between WiBro and HSDPA in telecommunication markets according to the advance of the related technology. The proposed model consists of diffusion and transition model and the demand forecasting of WiBro and HSDPA is predicted by using the parameters estimated from the survey results.
1MW<sub>th</sub> 실험연소로를 이용한 석탄의 연소특성 연구
장길홍,장인갑,정석용,Jang, Gil Hong,Chang, In Gab,Jeong, Seok Yong 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.11
Design and operation of $1MW_{th}$ pulverized coal combustion testing facility are described. Also the influence of air staging on NOx emission and burnout of coal flames was investigated in this facility. The test facility consisted of coal feeding system, firing system and flue gas treatment system. A top-fired externally air staging burner was adopted in order to avoid influence of gravity on the coal particles and for easy maintenance. Distribution of temperature and chemical species concentration of coal flames could be measured in vertical pass of furnace. Main fuel was pulverized (83.4% less than $80{\mu}m$) Australian high bituminous coal. From variety of test conditions, overall excess air ratio was selected at 1.2(20% excess air). Tho study showed that increasing the staged air resulted in lower NOx omission, and it was suggested to be more than 40% of the total combustion air for the substantial NOx reduction. Sufficient burnout was not achievable when NOx emission was less than 500ppm. Also, the amount of core air did not influence tho NOx reduction.