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임병준(Byeung Jun Lim),이동호(Dong ho Rhee),김춘택(Choon Tak Kim) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
수소 연료의 사용은 주어진 연료 중량에 대하여 항공기에 탑재 가능한 에너지의 양을 증가시킬 수 있다. 또한, 고고도 장기체공 무인기의 수소왕복엔진은 정찰/감시와 통신 중계에 필요한 임무장비 탑재가 가능한 정도의 비출력을 제공할 수 있다. 이러한 이유들 때문에 최근 수소왕복엔진을 사용하는 고고도 장기체공 무인기들이 개발되고 있다. 수소왕복엔진 추진 시스템은 수소왕복엔진, 다단 터보차저, 열교환기, 수소저장 및 공급시스템으로 구성된다. 본 논문에서는 수소왕복엔진 고고도 장기체공 무인기 개발 동향에 대하여 기술하였다. The use of hydrogen increases the amount of energy that can be stored on-board an aircraft for a given fuel mass. Additionally, hydrogen reciprocating engine of a high altitude long endurance(HALE) UAV can supply sufficient specific power to carry a payload for surveillance and communications relay mission. For these reasons, HALE UAVs using a hydrogen reciprocating engine system have been developed. The hydrogen reciprocating engine propulsion system consists of a hydrogen reciprocating engine, multistage turbocharger, heat exchangers, a hydrogen storage and supply system. This paper is a review of research and development trends of HALE UAV using hydrogen reciprocating engine.
The Influence of Spondylolisthesis Reduction on the Adjacent Lumbar Segment
Park Tae-Hwan,Choi Yunhee,Kim Tae-Shin,Kim Jun-Hoe,Lee Chang-Hyun,Kim Sum,Kim Young Rak,Ko Yong San,Yuh Woon Tak,Rhee John M.,Kim Kyoung-Tae,Chung Chun Kee,Kim Chi-Heon 대한말초신경학회 2023 The Nerve Vol.9 No.2
Objective: Mild to moderate stenosis at the adjacent level sometimes co-occurs with lumbar spondylolisthesis, but whether to include the adjacent level during surgery for the index level is a matter of debate. Spondylolisthesis causes anterior slipping of the vertebra and reduces the segmental angle at the index level, and the adjacent level may compensate for this change through hyperextension to maintain spinal balance. This study investigated the radiological changes and clinical outcomes of adjacent segment stenosis in patients with lumbar spondylolisthesis. Methods: Forty consecutive patients (12 men and 28 women, age 66.6±10.4 years) underwent single-level oblique lumbar interbody fusion for L4-5 or L5-S1 spondylolisthesis. Lumbar central stenosis at the cranial adjacent segment was present in 16 patients (stenosis group) and absent in 24 patients (no-stenosis group). Clinical and radiological parameters were longitudinally compared between the stenosis and no-stenosis groups. Results: Both groups showed similar and significant clinical improvement. The segmental angle at the index level significantly improved in both groups (p<0.05), but the segmental angle at the cranial adjacent segment significantly decreased only in the stenosis group (p<0.05). The spinal canal area at the adjacent level significantly improved only in the stenosis group (p<0.05). Conclusion: Realigned spondylolisthesis may reduce hyperextension of the adjacent segment. If mild lumbar spinal stenosis is present at an adjacent level to spondylolisthesis, it may not be essential to include it in surgery.
Aging Study with High-Level Radiation Sources for the CMS Forward RPCs
김현철,이경세,Byun Il Kim,홍병식,Chong Kim,D. H. Moon,Duk Gil Koo,E. Won,J. K. Lim,Ji Hyun Kim,Jun Tak Rhee,K. B. Lee,Kwang-Souk Sim,M. S. Ryu,Rong Jiang Hu,S. K. Nam,Sang Yeol Bahk,이석재,Seong Jong Hong,Sung Hw 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.3
An aging study with intensive radiation sources was performed for the forward resistive plate chambers (RPCs) of the Compact Muon Solenoid (CMS) detector in the Large Hadron Collider experiment (LHC). The expected rate of the radiation background to be induced in the forward RPCs ranges from a few tens of Hz/㎠ to as much as ~1 kHz/㎠. Therefore, the radiation hardness for the forward RPCs should be sufficient to ensure the safe operation of the CMS and successful achievement of the LHC physics. Two oil-coated and one plain double-gap RPCs were manufactured and tested with the neutron beam provided by the MC50 cyclotron of the Korea Institute of Radiological and Medical Science (KIRAMS) and with gamma rays from a 200-mCi137Cs source. The estimated radiation dose induced by the fast neutrons was approximately 50 Gy. No significant aging effect was found to be a consequence of the neutron irradiation, However, a degradation of the RPC performance was observed after intense gamma irradiation for a total of 32.5 days. The mean gamma-signal rate drawn in each RPC was 4.0 kHz/㎠, which was approximately two times the maximum rate expected in the highest η-region covering the particle trigger. Increases in the noise rates and the currents accounted for the degradation in the efficiencies for the RPCs. As a result, safe operation of the forward RPCs in the avalanche mode was ensured for signal rates up to 2 kHz/㎠.