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클라우드 환경에서의 적응적 예약형 가상 자원 관리 기법
강동기 ( Dong-ki Kang ),김성환 ( Seong-hwan Kim ),하윤기 ( Youn-gi Ha ),윤찬현 ( Chan-hyun Youn ) 한국정보처리학회 2013 한국정보처리학회 학술대회논문집 Vol.20 No.2
다양한 이종의 클라우드 서비스 제공자들은 자원 할당 기간에 기반하여 온디맨드(On-demand) 및 예약형(Reserved) 인스턴스 2 가지로 구분하여 할당하는 가상 머신 인스턴스의 가격을 결정한다. 즉 자원할당 기간이 상대적으로 짧은 온디맨드 인스턴스의 경우에는 가격이 비싸지만 할당 기간이 상대전으로 긴 예약형 인스턴스는 가격이 저렴하게 책정된다. 본 논문에서는 이와 같은 가격 정책을 기반으로 적응적 예약형 기반 가상 자원 관리 기법을 소개하여 동일한 클라우드 서비스를 달성하면서도 비용을 효과적으로 절감할 수 있도록 한다.
지리적 특성을 고려한 클라우드 컴퓨팅 서비스 관리 기법 연구
강동기 ( Dong-ki Kang ),김성환 ( Seong-hwan Kim ),김우중 ( Woo-joong Kim ),하윤기 ( Youn-gi Ha ),윤찬현 ( Chan-hyun Youn ) 한국정보처리학회 2013 한국정보처리학회 학술대회논문집 Vol.20 No.2
멀티 클라우드 서비스 제공자가 연동된 환경에서 각 데이터 센터에 위치하고 있는 물리 노드들의 위치에 따라서 클라우드 서비스 사용자와 연결된 네트워크 속도에 차이가 발생하고 이에 의해서 각 물리 노드에서 생성되는 가상 자원 인스턴스의 작업 처리 성능에도 영향을 미치게 된다. 특히 웹 어플리케이션과 같은 네트워크 성능에 의존도가 높은 응용의 경우 이에 대한 성능 영향의 정도가 매우 크게 증가한다. 본 논문에서는 이러한 문제를 해결하기 위하여 클라우드 서비스 사용자와 가상 자원 인스턴스간의 물리적인 거리 및 동적인 네트워크 상황을 고려한 적응적 가상 자원 할당 기법을 소개한다.
이혁기,조재훈,이성락,강동기,김상철,김용선,Lee, Hyuk Gi,Cho, Jae Hoon,Lee, Sung Lak,Kang, Dong Gee,Kim, Sang Chul,Kim, Yong Sun 대한신경외과학회 2000 Journal of Korean neurosurgical society Vol.29 No.2
Posterior transarticular screw fixation for atlantoaxial instability due to trauma or rheumatoid arthritis provides immediate rigid fixation of the C1-2 vertebral segment while preserving motion between the occiput and C1. This technique provides more resistance to translational and rotational forces than wiring technique. However, the technique of transarticular screw fixation is inherently demanding because of the complex anatomy of the occipitocervical region and vertebral artery(VA) at risk for arterial damage. VA injury may lead to serious subsequent neurological deficits and possibly death from bilateral VA injury. We report a case of a vertebral artery-to-epidural venous plexus fistula after posterior transarticular screw fixation which was treated with balloon occlusion.
전산유체역학을 이용한 유도무기 선두부 절단 비율에 대한 공력해석
정기연(Kiyeon Jeong),강동기(Dong-Gi Kang),이대연(Daeyeon Lee),노경호(Gyeongho Noh) 한국항공우주학회 2019 韓國航空宇宙學會誌 Vol.47 No.4
본 논문에서는 유도무기의 선두부 형상 절단 비율에 따라서 달라지는 공력특성에 대해 전산유체역학을 이용하여 분석하였다. 해석을 수행하는 형상은 유도무기 동체만 있으며 직경대 길이비는 10.7이다. 선두부 형상은 세 가지를 선택했으며 구형, 25% 절단, 50% 절단형을 비교하였다. 유도무기 동체의 정확한 해석을 위해서 NASA의 풍동시험 데이터를 이용하여 격자 구성법과 해석 기법을 선택하고 검증하였다. 선두부 세 가지 형상에 대해서 비행마하수에 대해 항력을 분석한 결과 절단과 구형이 6~20% 정도 차이 났으며, 동체의 선두부와 기저부의 압력분포를 통해 특성을 분석하였다. This paper describes on aerodynamic analysis based on the truncation rate of guided-weapon nose using computational fluid dynamics. The shape to perform the analysis is only the body of the guided weapon and the diameter to length ratio is 10.7. Three nose shapes were selected and hemisphere, 25% and 50% truncation were compared. For the accurate CFD analysis of the body, the grid method and the analytical method were selected and verified using NASA wind tunnel test data. For the three nose shapes, the drag analysis for the flight Mach number is 6~20% different. This difference was analyzed by the pressure distribution from nose to base.
요추간 수핵탈출증에서 경피적 내시경 수핵절제술의 장기 임상 결과
김기현,이성락,조재훈,강동기,김상철,Kim, Gi Hyune,Lee, Sung Lak,Cho, Jae Hoon,Kang, Dong Gee,Kim, Sang Chul 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.2
Between January 1995 and May 1998, 177 patients with proven lumbar disc herniation were treated by microdiscectomy or by percutaneous endoscopic discectomy(PED). Among them, 43(24.2%) patients underwent PED and were followed for long term outcome. We included only those patients who were followed up more than 13 months. Three patients who did not improved immediately after PED and underwent microdiscectomy were excluded for this study. Of remaining 40 patients, there were 22 men and 18 women who ranged in age from 23 to 68 years (mean 38.1 years). The disc herniations were located at L1-2(1), L2-3(1), L3-4(1), L4-5(26) and L5-S1(11). Three patients were treated by biportal approach. The mean follow up period was 34.7 months(range 13-47 months). Overall, excellent and good results were achieved in 12(30%) and 19(47.5%) patients, and fair and poor results in 7(17.5%) and 2(5%) patients, respectively. Thirty-eight(95%) patients returned to their previous works and the mean duration was 5.7 months. Thirty-three(82.5%) patients answered that they would recommend this procedure to others. There was no complication except for one patient who suffered from discitis. The indication of PED is restricted to contained or small subligamentous lumbar disc herniation without stenosis, spondylolisthesis and sequestration. PED can be performed under local anesthesia and tissue trauma, risk of epidural scarring, hospitalization time and postoperative morbidity are minimal. The result of the present study justify the assumption that PED can be a surgical alternative for patients suitable for its indications.
Willis환 내 뇌동맥류 진단시 전산화단층촬영 뇌혈관 조영술의 유용성
이혁기,조재훈,이성락,강동기,김상철,Lee, Hyuk Gi,Cho, Jae Hoon,Lee, Sung Lak,Kang, Dong Gee,Kim, Sang Chul 대한신경외과학회 2000 Journal of Korean neurosurgical society Vol.29 No.3
Objective : The purpose of this study was to compare computed tomographic angiography(CTA) with conventional cerebral angiography(CCA) and to assess usefulness of CTA in detection and anatomic definition of intracranial aneurysms of the circle of Willis in subarachnoid hemorrhage. Patients and Methods : Fifty consecutive patients with known or suspected intracranial saccular aneurysms underwent CTA with preoperative CCA from 1997 to 1999. Using surface shaded display post-processing technique, CTA was interpreted for the presence, location of aneurysms and anatomic features. The image obtained with CTA was then compared with CCA image. Results : In 47 patients, CCA revealed 57 cerebral aneurysms and CTA revealed 54 aneurysms. Two of the 57 cerebral aneurysms were located outside of the imaging volume of CTA and one case was misdiagnosed. The sensitivity of CTA was 94.7% and the specificity was 100%. The results obtained with CTA were, compared with the results obtained with CCA, equal in determining dome shape, direction and lobularity. However, CTA provided a 3-dimensional representation of aneurysmal lesion very useful for surgical planning. Moreover, CTA was useful for rapid and relatively noninvasive detection of aneurysms in the circle of Willis. Conclusion : CTA can be a diagnostic tool for the patients with acute subarachnoid hemorrhage due to a ruptured aneurysm of the circle of Willis and provides adequate anatomic detail for surgical planning, especially to complex cerebral aneurysms. However, we think CCA is necessary because of CTA limitations including its difficulty in detecting unusually located aneurysms(including those in cavernous sinus or distal artery) and combined vascular lesion (including arteriovenous malformation) and acquiring dynamic flow information.