http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Numerical Investigation on a Rotor Tip-Vortex Instability in Very Low Advance Ratio Flight
Kihoon Chung,Changjeon Hwang,Duckjoo Lee,Jongbong Yim 한국항공우주학회 2005 International Journal of Aeronautical and Space Sc Vol.6 No.2
Helical tip vortex is known as stable vortex structure, however the specific frequency component of far wake perturbation induces the vortex pairing in hover and axial flight. It is expected that the tip vortex pairing phenomena may happen in transition flight and very low advance ratio flight so that inflow may be most nonuniform in the low advance ratio flight. The objectives of this paper are that a tip-vortex instability during the transition from hover into very low advance ratio forward flight is numerically predicted to understand a physics by using a time-marching free-wake method. To achieve the objectives, numerical method is firstly validated in typical axial and forward flights cases. Present scheme with trim routine can predict airloads and inflow distribution of forward flight with good accuracy. Then, the transition flight condition is calculated. The rotor used in this wake calculation is a small-scale AH-1G model. By using a tip-vortex trajectory tracking method, the tip-vortex pairing process are clearly observed in transient flight(μ=0.03) and disappears at a slightly higher advance ratio(μ=0.05). According to the steady flight simulation at μ=0.03, it is confirmed the tip-vortex pairing process is continued in the rear part of rotor disk and not occurs in the front part. Time averaged inflow in this case is predicted as smooth distribution.
Kihoon Chung,Kwanjung Yee,Changjeon Hwang,Duckjoo Lee 한국항공우주학회 2004 International Journal of Aeronautical and Space Sc Vol.5 No.2
CFD method has been coupled with a time-marching free-wake model by using field velocity approach suggested by J. D. Baeder (Ref. 1). The coupled method has been applied to rectangular and BERP-like blades and the calculated performance data are compared with the experimental results. For hovering analysis, the present method could yield sufficiently good results with reasonable computation time and is particularly suitable for the flow field analysis with the complex shaped blade.
정기훈(Kihoon Chung),강희정(Hee Jung Kang),김도형(Do-Hyung Kim),윤철용(Chul Yong Yun),김승호(Seungho Kim),박구환(Kuhwan Park),이상기(Sang-Gi Lee) 한국항공우주학회 2013 韓國航空宇宙學會誌 Vol.41 No.9
헬리콥터 로터 블레이드는 헬리콥터의 성능을 좌우하는 동시에 비행 시 주된 소음을 발생함에 따라 고성능, 저소음 특성이 요구되는 구상품이다. 국내 소형무장헬기 개발과 병행하여 개발될 민수헬기는 해외체계업체 보유 민수헬기를 기반으로한 국제공동 업그레이드 개발이 추진됨에 따라 해외체계업체 제시 대상기종의 로터 블레이드 성능파악이 매우 중요하다. 본 연구는 해외체계업체 제시 대상기종 블레이드의 성능분석을 통하여 최신 해외블레이드 대비 성능파악 및 국내고유형상 블레이드 개발 가능성을 타진하는 것을 목적으로 수행되었다. 본 연구의 결과는 일차적으로 향후 민수헬기개발사업의 해외협상 및 국내 고유형상 블레이드 개발 시 목표 성능지표 등으로 활용될 수 있다. The rotor blade of helicopter is the core component determining helicopter performance and requiring low noise and low vibration because the blade becomes the major source of noise during flight. The performance analysis of candidates rotor blades is very critical because LCH(Light Civil Helicopter) will be developed parallel with LAH(Light Armed Helicopter) as an international upgrade program based on the existing platform of foreign civil helicopter. This research was aimed to recognize the performance of the candidates rotor blades compared with the newly developed foreign rotor blades and to investigate the feasibility about developing korea unique shape rotor blades by analysis the rotor performance and noise. The result of this research can be used for the target performance index during negotiation with foreign helicopter company and developing korea unique shape rotor blades.
Kihoon Jeon,Sanghwa Chung,Donghwa Yoo 한국정보과학회 2020 Journal of Computing Science and Engineering Vol.14 No.2
Owing to the development of the Internet of Things (IoT) paradigm, the energy consumption of devices and the reliability of communication have become important issues. Enhanced TSCH technology introduces a technique to select high-quality channels by using energy detection in the TSCH protocol to improve the reliability of communication in a dynamic environment where interference changes. However, it is difficult to apply ETSCH technology to a multi-hop network because the node that performs energy detection consumes more energy than the node that does not. In this article, we propose an adaptive channel-quality estimation (ACE), which flexibly adjusts the duty cycle of energy detection according to whether interference dynamically changes or not. ACEs are generally applicable regardless of the degree of change of interference, which improves energy efficiency. Also, we present ACE-blacklisting based TSCH (ACEBTSCH) that uses ACE and local channel blacklisting to blacklist the wireless channel based on energy detection in a multi-hop network. Experimental results show that ACEB-TSCH has a performance improvement of 15.94% over TSCH and 8.59% over PDR-blacklisting based TSCH.
Regulated RalBP1 Binding to RalA and PSD-95 Controls AMPA Receptor Endocytosis and LTD
Han, Kihoon,Kim, Myoung-Hwan,Seeburg, Daniel,Seo, Jinsoo,Verpelli, Chiara,Han, Seungnam,Chung, Hye Sun,Ko, Jaewon,Lee, Hyun Woo,Kim, Karam,Heo, Won Do,Meyer, Tobias,Kim, Hyun,Sala, Carlo,Choi, Se-Youn Public Library of Science 2009 PLoS biology Vol.7 No.9
<▼1><P>A two step mechanism was identified that regulates receptor endocytosis during the development of long-term depression (LTD), a long-lasting decrease in synaptic transmission.</P></▼1><▼2><P>Long-term depression (LTD) is a long-lasting activity-dependent decrease in synaptic strength. NMDA receptor (NMDAR)–dependent LTD, an extensively studied form of LTD, involves the endocytosis of AMPA receptors (AMPARs) via protein dephosphorylation, but the underlying mechanism has remained unclear. We show here that a regulated interaction of the endocytic adaptor RalBP1 with two synaptic proteins, the small GTPase RalA and the postsynaptic scaffolding protein PSD-95, controls NMDAR-dependent AMPAR endocytosis during LTD. NMDAR activation stimulates RalA, which binds and translocates widespread RalBP1 to synapses. In addition, NMDAR activation dephosphorylates RalBP1, promoting the interaction of RalBP1 with PSD-95. These two regulated interactions are required for NMDAR-dependent AMPAR endocytosis and LTD and are sufficient to induce AMPAR endocytosis in the absence of NMDAR activation. RalA in the basal state, however, maintains surface AMPARs. We propose that NMDAR activation brings RalBP1 close to PSD-95 to promote the interaction of RalBP1-associated endocytic proteins with PSD-95-associated AMPARs. This suggests that scaffolding proteins at specialized cellular junctions can switch their function from maintenance to endocytosis of interacting membrane proteins in a regulated manner.</P></▼2><▼3><P><B>Author Summary</B></P><P>Neurons adapt over time in order to dampen their response to prolonged or particularly strong stimuli. This process, termed long-term depression (LTD), results in a long-lasting decrease in the efficiency of synaptic transmission. One extensively studied form of LTD requires the activation of a specific class of receptors known as NMDA glutamate receptors (NMDARs). A key molecular event initiated by NMDA receptor activation is the stimulation of protein phosphatases. Another key event is internalization via endocytosis of synaptic AMPA glutamate receptors (AMPARs). However, the mechanism by which protein dephosphorylation is coupled to AMPAR endocytosis has remained unclear. Here, we help to define this mechanism. We show that endocytic proteins, including RalBP1, are widely distributed in neurons under normal conditions. Upon NMDAR activation, the small GTPase RalA becomes activated and binds to RalBP1, resulting in the translocation of RalBP1 and RalBP1-associated endocytic proteins to synapses. At the same time, RalBP1 becomes dephosphorylated, which promotes its binding to the postsynaptic scaffold protein PSD-95, a protein that itself associates with AMPARs. This concerted recruitment of endocytic proteins to the vicinity of AMPARs results in AMPAR endocytosis. On the basis of our data, we propose a model in which dual binding of RalBP1 to both RalA and PSD-95 following RalBP1 dephosphorylation is essential for NMDAR-dependent AMPAR endocytosis during LTD.</P></▼3>