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이동 애드 혹 네트워크에서의 환경적응형 QoS AODV 라우팅 프로토콜에 관한 연구
裵振勝,宋東勳,吳世德,鄭燦赫,金玄郁,李光培,文泰洙,郭承郁,河載承 明知大學校 産業技術硏究所 2004 産業技術硏究所論文集 Vol.23 No.-
In this paper, we propose a bidirectional mobile Ad Hoc routing protocol based on AODV(ad-hoc on-demand distance vector routing) with QoS(quality of service) support. At presence, wireless mobile communication focuses on how to efficiently support mobility of users more than QoS guarantee. However, in order to satisfy requirement of various applications which have been or will be served, QoS guarantee between end points is a very important issue. The existing AODV routing protocol is implemented to use only BE (Best Effort) service. However, actual wireless mobile environment requires to reduce a waste of communication resources and meet with the real-time change of data paths by setting up routes with QoS support, considering available communication resources at each node in advance. Therefore, in this thesis, we propose an adaptive QoS support method using hello message in order to rapidly meet with the change of available communication resources and to smoothly perform route maintenance. For performance evaluation, we analyzed the average data reception rate. At that time, we used evaluation parameters such as node's mobility-stop time, hello message period, and packet priority, considering the node's mobility and the number of best effort/QoS data flows. As results, we found that with our proposed method the average data reception rate was increased 16.293%, 15.914%, 17.238% for 300 mobility-stop second case and 4.809%, 4.264%, 2.956% for 300 mobility-stop second case.
Kwak, Hyun-Duck,Kwon, Sejin,Choi, Chang-Ho Elsevier 2018 AEROSPACE SCIENCE AND TECHNOLOGY Vol.77 No.-
<P><B>Abstract</B></P> <P>An electrically driven pump-fed cycle for rocket engine is proposed and a viability of the proposed cycle is assessed compared to a gas generator cycle. The maximum possible thrust level is determined considering the technological maturity of the electric motor. Four types of battery cells were assessed in a screening test for the proposed cycle and the necessity of regenerative cooling for the battery pack is shown. The mass expressions of the proposed cycle and gas generator cycle are derived in terms of pump power and burning time. The basic features are demonstrated with respect to combustion chamber pressure, burning time, and thrust level. The results show that it is favorable to maintain a lower combustion chamber pressure, a longer burning time, and a higher thrust level to remedy the payload penalty incurred when the gas generator cycle is not used. In addition to focusing on the battery pack, the regenerative cooling effect on the battery pack mass is discussed. Further, the impact of optimal battery cell discharge time on the payload is explained. To estimate the payload for the proposed cycle quantitatively, hypothetical low earth orbit (LEO) and KSLV-II sun synchronous orbit (SSO) mission cases are used. In the analysis of the hypothetical LEO mission, it is found that the proposed cycle payloads are only 2.1% to 3.5% lower than those of the gas generator cycle when the combustion chamber pressure is 3.0 MPaA. For the KSLV-II SSO mission, the cargo payload is increased by 3.7% compared to that of gas generator cycle if the proposed cycle is employed for the third-stage engine.</P>
A Study on the Rotordynamic Stability of Turbo Pump Unit
Kwak, Hyun-Duck,Lee, Yong-Bok,Kim, Chang-Ho,Ha, Tae-Woong,Yoo, Woo-Chul Korean Tribology Society 2003 KSTLE International Journal Vol.4 No.1
A turbo pump unit provides high pressure oxygen and fuel in a space shuttle main engine (SSME). This paper focused on rotordynamics, investigating its characteristics based on a numerical simulation of turbo pump finite element model. Speeds up to 50,000 rpm are considered, as well as the special problems related to elastic-ring, seal hydrodynamic force, shroud force and clearance-excitation farce. The rotordynamic prediction shows that the elastic-ring which is inserted between the casing and the outer race of ball bearing allows far an acceptable separate margin of first critical speed. Additionally, the results show that the floating ring seal, which have a peculiar ring, adds substantial stiffness and damping to the system as well as exhibits superior performance in terms of rotordynamic stability of system compared to the plain seal.
Static Characteristics of Micro Gas-Lubricated Journal Bearings with a Slip Flow
곽현덕(Hyun-Duck Kwak),이용복(Yong-Bok Lee),김창호(Chang-Ho Kim),이남수(Nam-Soo Lee),최동훈(Dong-Hoon Choi) 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.35 No.-
The fluid mechanics and operating conditions of gas-lubricated journal bearings in micro rotating machinery such as micro polarization modulator and micro gas turbine are different from their larger size ones. Due to non-continuum effects, there is a slip of gas at the walls. Thus in this paper, the slip flow effect is considered to estimate the pressure distribution and load-carrying capacity of micro gas-lubricated journal bearings as the local Knudsen number at the minimum film thickness is greater than 0.01. Based on the compressible Reynolds equation with slip flow, the static characteristics of micro gas-lubricated journal bearings are obtained. Numerical predictions compare the pressure distribution and load capacity considering slip flow with the performance of micro journal bearings without slip flow for a range of bearing numbers and eccentricities. The results clearly show that the slip flow effect on the static characteristics is considerable and becomes more significant as temperature increases.
경북 문경 세계군인체육대회 유치 과정으로 살펴 본 세계무예마스터십의 향후 과제
남덕현 ( Duck Hyun Nam ),곽낙현 ( Nak Hyun Kwak ) 한국체육사학회 2015 체육사학회지 Vol.20 No.1
정부의 중대 기조는 창조경제와 문화융성이다. 본 연구는 정부 정책에 부응하고자 문화의 한 영역인 스포츠에서 창의적 경제발전의 일환으로 “세계군인체육대회” 유치 과정의 현대사를 통해 세계무예마스터십의 방향성을 조명해 보았다. 한국은 지금 문화콘텐츠를 활용한 다양한 경제 활성화 정책을 장려하고 있다. 그렇다면 문화와 창의적 경제발전의 기여를 위한 무예계의 과제는 무엇인가. 그것은 다양한 무예문화콘텐츠를 활용한 새로운 산업과 인재의 창출을 시도해야 하며 그 중요한 과제가 “세계무예마스터십”이다. 이 “세계무예마스터십”은 이전에 시행된 다양한 국제대회 유치의 시행착오를 확인하여 최적의 대회를 운영해야 한다. 이번 “2015년 세계 군인체육대회”유치 과정의 현대사를 면밀히 검토하여 “세계무예마스터십” 대회의 기초자료를 제공하고자 한다. 이 대회의 핵심 검토 내용은 운영비용에 대한 오류 최소화, 대회 개최에 대한 명분의 정당성, 정부의 후원이다. The key policy of administration is creative economy and cultural prosperity. to meet government policy, this research think World Martial Arts Masterships``s direction on inspecting bids. of 6th CISM World Game Korea. South Korea government encourages a variety activation policy of economic and cultural content. What is the most necessary thing Martial Arts needs for culture and creative economic development. It utilizes a variety of martial arts to create new industries and cultural content, talent. Among them, A cases is World Martial Arts Masterships. therefor, Martial Arts Masterships need to create the optimal tournament in considering trial-and-error in previous international games. this research seeks to provide Martial Arts Masterships basic data through closely review the modern history of the 6th CISM World Game Korea``s bids process. The core is game costs for error minimization, game justification, the auspices of the Government for the game.