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순환천이변조 주파수도약대역확산/시분할다중접속 시스템의 성능 개선에 관한 연구
김은철,김승춘,이형근,Kim, Eun-Cheol,Kim, Seung-Chun,Lee, Hyung-Keun 한국전기전자학회 2012 전기전자학회논문지 Vol.16 No.1
In this paper, we propose to employ a ternary sequence as a cyclic code shift keying (CCSK) modulation sequence. And we simulate the performance in a frequency hopping spread spectrum/time division multiple access (FHSS/TDMA) system with CCSK. Wireless channel is modeled as Rayleigh fading channel. From the simulation results, it is demonstrated that the system adopting the ternary sequence as a CCSK sequence has higher performance than that with a random sequence. 본 논문에서는 순환천이변조 (CCSK: cyclic code shift keying) 시퀀스로 삼진 시퀀스를 적용하는 것을 제안하였다. 그리고 순환천이변조를 적용한 주파수도약대역확산/시분할다중접속 (FHSS/TDMA: frequency hopping spread spectrum/time division multiple access) 시스템에서 성능을 모의실험 하였다. 실험에서 무선 채널은 레일레이(Rayleigh) 페이딩 채널로 모델링하였다. 모의 실험 결과로부터 순환천이변조 시퀀스로 무작위 시퀀스를 사용한 시스템보다 삼진 시퀀스를 적용한 시스템이 더 높은 성능을 보이는 것이 증명되었다.
가토 사체 보관 온도 및 안구 적출 시간에 따른 각막내피세포의 변화
김은철,이경택,김만수,Eun Chul Kim,M,D,Kyung Taek Lee,M,D,Man Soo Kim,M,D 대한안과학회 2008 대한안과학회지 Vol.49 No.2
`Purpose: To evaluate corneal endothelial cell changes in Optisol-GS? according to enucleation time at different storage temperatures after death. Methods: Eight rabbit cadavers (16 eyes) were stored at -3℃ and room temperature, and enucleation was performed 10 and 24 hours postmortem. The samples were divided into four groups (Group 1 was -3℃, 10 hours, Group 2 was room temperature, 10 hours, Group 3 was -3℃, 24 hours, and Group 4 was room temperature, 24 hours). The corneas were stored in Optisol-GS? at 4℃, and we measured corneal endothelial cell density and thickness by specular microscopy on days 1, 3, 5, 7, 10, and 14 of preservation. Results: The densities and thicknesses of corneal endothelial cells of each of the four groups after enucleation showed no significant difference. Corneal endothelial cell density acceptable for penetrating keratoplasty (CD>2500 cells/mm2) was found in groups 1 and 3 until 14 days, in group 2 until 10 days, and in group 4 until 7 days. In particular, eyes stored at -3℃ had less corneal endothelial cell loss than at room temperature after 7 days and 14 days (P<0.05). Conclusions: This study demonstrated that when rabbit cadavers were stored at -3℃, corneas could be preserved in Optisol-GS? for 14 days, even if the eyeballs from which they were prepared were extracted within 24 hours postmortem. Within 24 hours postmortem, the storing temperature of the cadavers was found to be more important than the enucleation time for the survival of corneal endothelial cells.`
EPON에서 하향 데이터 전송을 고려한 동적 대역폭 할당 방안
김은철,이강원,최영수,조유제,Kim Eun-Chul,Lee Kang-Won,Choi Young-Soo,Cho You-Ze 대한전자공학회 2005 電子工學會論文誌-TC (Telecommunications) Vol.42 No.12
EPON 환경에서 효율적인 상향 채널의 사용을 위해 다양한 동적 대역폭 할당 방안이 제안되고 있다. 일반적으로 가변 폴링 주기 방안은 고정 폴링 주기 방안에 비해 optical network unit(ONU)의 대역폭 요청량을 보다 유연하게 반영하여 폴링 주기를 결정하기 때문에 상향 채널에서 향상된 전송 성능을 나타낸다. 그러나, 가변 폴링 주기 방안은 ONU의 상향 트래픽 부하가 낮은 환경에서는 폴링 오버헤드에 의한 하향 채널의 대역폭 낭비가 심한 문제점이 있다. 본 논문에서는 Ethernet passive optical network(EPON)에서 가변 폴링 주기와 고정 폴링 주기 방안의 장점만을 취한 새로운 동적 대역폭 할당 방안을 제안한다. 제안한 방안은 대표적인 가변 폴링 주기 방안인 interleaved polling with adaptive cycle time(IPACT) 방안에 기반을 두고, 하향전송을 위한 optical line terminal(OLT) 큐의 상태에 따라 가변 폴링 주기 혹은 고정 폴링 주기로 동작한다. 시뮬레이션을 통해 제안 방안은 상향 전송에서 IPACT 방안과 유사한 지연 성능을 유지하면서도 하향 전송에서는 고정 폴링 주기 방안에 근접하는 수율을 나타냄을 보였다. This paper proposes a hybrid scheme for dynamic bandwidth allocation(DBA) in Ethernet passive optical network(EPON), which combines advantages of adaptive cycle and constant cycle-based schemes. The proposed scheme is based on IPACT scheme, but it operates as adaptive cycle or constant cycle mode according to the queue status of optical line terminal(OLT) for downstream transmission. Simulation results showed that the proposed scheme could achieve a similar throughput in downstream transmission to a constant cycle-based DBA scheme, while producing a similar delay performance to the IPACT scheme in upstream transmission.
골격성 III급 부정교합자의 체질량지수에 따른 술후 연조직 변화
김은철,이상철,Kim, Eun-Cheol,Lee, Sang-Chull 대한악안면성형재건외과학회 1999 Maxillofacial Plastic Reconstructive Surgery Vol.21 No.3
This study has been carried out in order to measure the thickness of soft-tissue on lateral cephalographs based on body mass index(BMI) and the change in soft-tissue thickness after surgical correction of mandibular protrusion. The control material in cephalometric study comprised students at The Dental College, 38 persons, aged 21~24 years and the patient material comprised 20 women and 12men, aged 19~28 years with mandibular protrusion.The thickness of the soft-tissue based on BMI in control and study groups, the comparison between them, immediate postoperative change in the thickness, 6 months after surgery, ratio of soft-tissue response and correlation was established through various statistical methods. The result were as follows : 1. The groups based on BMI showed significant differences each other as regards the linear measurements. The thickest soft-tissue was measured 13.6mm, 15.47mm, 16.76mm at Ss, the thinnest at G' 6.0mm, 6.7mm, 7.26mm respectively. 2. The differences between control and experimental groups based on BMI showed to be significant. There were no differences at G'. The soft-tissue in prognathic patients was thicker at Ss, Ls and thinner at Li, Ls, Pg', Gn', Me'. Differential gap was greater in overweight groups. 3. The immediate soft-tissue change after surgery showed the increase at Li, Ls, Pg', Gn', Me' except G', Ls in all groups. 4. The postoperative soft-tissue change 6 months after surgery was similar with immediate change. The soft-tissue shows the increase in the thickness at Li, Pg', Gn', Me' and the greatest difference occurred at Li, 1.1mm, 0.98mm, 1.2mm respectively. 5. The patients with lower BMI index showed higher soft-tissue response to bony movement at Pg'. The immediate response ratio was 91%, 87%, 81% in A,B,C groups respectively, the response 6 months after surgery showed 96%, 91%, 84%.
김은철,Kim, Eun-Cheol 사단법인 한국당뇨협회 2008 당뇨 Vol.221 No.-
당뇨병은 인슐린 분비 부족이나 내성에 의해 체내의 고혈당이 생기는 질환으로 주로 미세혈관계에 이상이 발생하여 우리 몸의 모든 곳에 합병증이 생기는 질환이다. 당뇨로 인한 합병증이 주로 나타나는 곳은 신경, 콩팥, 그리고 눈이며 특히 최근에 선진국에서 실명의 가장 큰 원인은 당뇨병성 망막증이다. 당뇨로 인하여 생기는 눈의 변화는 각막진무름, 백내장, 녹내장, 망막증, 외안근마비, 시신경염 등 다양하게 나타날 수 있으며 조기에 치료하지 않으면 결국 실명에 까지 갈 수 있는 무서운 결과를 초래한다.
여대생의 체육수업 재미요인이 체육활동만족과 체육소비행동에 미치는 영향
김은철(Kim, Eun-Chul) 한국체육과학회 2012 한국체육과학회지 Vol.21 No.5
This study of female physical education and physical education meets fun physical activity factors impact on consumer behavior to identify the purpose and the results the following conclusions were drawn. First, differences in grade group, third grade girls satisfaction is higher than 4,2,1 compared to physical activity, physical consumption behavior. Second, the physical education classes than girls to participate in the live sports and physical education majors to participate in society, such as physical education students physical activity and physical education meet the high consumer behavior. Depending on the number of Physical education classed and athletic activities and sports meets are not significantly different consumption behavior. Physical education class time, usually longer and the number of participants, the more satisfied with physical activity and physical education was higher consumer behavior. Third, improve the athletic skills of the fun factor and the freedom and feelings of health and physical activity positively affects satisfaction. Fourth, the fun factor in athletic health and athletic demonstrated a positive impact on consumer behavior.