• Title/Summary/Keyword: 동적격자

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Supersonic and Hypersonic Flutter Characteristics for Various Typical Section Shapes of Missile Fin (유도무기 날개 단면형상에 따른 초음속 및 극초음속 플러터 특성)

  • Kim, Dong-Hyun;Kim, Yu-Sung;Kim, Yo-Han;Oh, Il-Kwon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.5
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    • pp.496-502
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    • 2008
  • In this study, supersonic and hypersonic flutter characteristics have been analyzed for the various typical section shapes of missile fin configurations. Nonlinear flutter analyses are conducted considering the effect of moving shock waves. Computational fluid dynamic method is applied to accurately predict unsteady aerodynamic loads due to structural motions for the solution of aeroelastic governing equations. Commonly used typical section shapes of supersonic and hypersonic launch vehicles are considered in the present numerical study. Detailed flutter responses for four different typical section models are presented and the flutter characteristics are physically investigated.

Self-starting phase conjugate laser in population inverted Nd:YAG (밀도 반전된 Nd:YAG에서의 자체 발진 위상공액 레이저)

  • ;M.J.Damzen
    • Korean Journal of Optics and Photonics
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    • v.8 no.5
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    • pp.357-361
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    • 1997
  • We report the operation of a self-starting phase conjugate laser(PCL) oscillator which compensates intracavity phase distortion. The self-starting PCL in the population inverted Nd:YAG gain media produced an output energy of 200 mJ in a 20 ns single-longitudinal-mode pulse at 10Hz. And it showed well-defined Gaussian spatial profile.

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A Dynamic Structure Design of PC type Sub-structure for next Semi-conduct, TFT-LCD Fab based on Dynamic Test and Simulation (차세대 반도체, TFT-LCD Fab 구조설계를 위한 PC형 격자보에 대한 동적 특성 평가 및 개선방안)

  • 손성완;김강부;전종균
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.237-242
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    • 2004
  • In design stage of high precision manufacture/inspection FAB building, it is necessary to investigate the vibration allowable limits of high precision equipment and to study a structure dynamic characteristics of C/R and Sub-structure in order to provide a structure vibration environment to satisfy thess allowable limits. The aim of this study is to investigate the dynamic characteristics of PC-Type mock-up structures designed for next TFT LCD FAB through vibration measurement and analysis procedure, therefore, to provide a proper dynamic structure design for high precision manufacture/inspection work process, which satisfy thess allowable limits.

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Numerical Study on Transient Aerodynamics of Moving Flap Using Conservative Chimera Grid Method (보존적 중첩격자기법을 이용한 동적 플랩의 천이적 공력거동에 관한 수치적 연구)

  • Choi S. W.;Chang K. S.
    • 한국전산유체공학회:학술대회논문집
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    • 1999.11a
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    • pp.85-94
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    • 1999
  • Transient aerodynamic response of an airfoil to a moving plane-flap is numerically investigated using two-dimensional Euler equations with conservative Chimera grid method. A body moving relative to a stationary grid is treated by an overset grid bounded by a 'dynamic domain-dividing line' the concept of which is developed in this study. A conservative Chimera grid method with a dynamic domain-dividing line technique is applied and validated by solving the flowfield around circular cylinder moving supersonic speed. The unsteady and transient characteristics of the flow solver is also examined by computations of a oscillating airfoil and a ramp pitching airfoil respectively. The transient aerodynamic behavior of an airfoil with a moving plane-flap is analyzed for various flow conditions such as deflecting rate of flap and free stream Mach number.

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Extended Q-larning under Multiple Tasks (복수의 부분 작업을 위한 확장된 Q-Learning)

  • 오도훈;윤소정;오경환
    • Proceedings of the Korean Information Science Society Conference
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    • 2000.04b
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    • pp.229-231
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    • 2000
  • 많은 학습 방법 중에서 비교적 최근에 제시된 강화학습은 동적인 환경에서 뛰어난 학습 능력을 보여주었다. 이런 장점을 바탕으로 강화학습은 학습을 기초로 하는 에이전트 연구에 많이 사용되고 있다. 하지만, 현재까지 연구 결과는 강화학습으로 구축된 에이전트로 해결 할 수 있는 작업의 난이도에 한계가 있음을 보이고 있다. 특히, 복수의 부분 작업으로 구성되어 있는 복합 작업을 처리할 경우에 기존의 강화학습 방법은 문제 해결에 한계를 보여주고 있다. 본 논문에서는 복수의 부분 작업으로 구성된 복합 작업이 왜 처리하기 힘든가를 분석하고, 이런 문제를 처리할 수 있는 방안을 제안한다. 본 논문에서 제안하고 있는 EQ-Learning은 강화학습 방법의 대표적인 Q-Learning을 개량하고 기존의 문제를 해결한다. 이 방법은 각각의 부분 작업 해결 방안을 학습시키고 그 학습 결과들의 적절한 적용 순서를 찾아내 복합 작업을 해결한다. EQ-Learning의 타당성을 검증하기 위해 격자 공간에서 복수의 부분작업으로 구성된 미로 문제를 통하여 실험하였다.

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A Study on Dynamic Response Analysis Algorithm of Plane Lattice Structure (평면격자형 구조물의 동적응답 해석알고리즘에 관한 연구)

  • Moon, D.H.;Kang, H.S.;Choi, M.S.;Kim, Y.B.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.11a
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    • pp.575-580
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    • 2000
  • Recently it is increased by degrees to construct complex and large lattice structure such as bridge, tower and crane structures. It is very important problem to know dynamic properties of such structures. Authors presented new dynamic response analysis algorithm for rectilinear structure already. This analysis algorithm is combined transfer stiffness coefficient method with Newmark method. Presented method improves the computational accuracy remarkably owing to advantage of the transfer stiffness coefficient method. This paper formulates dynamic response analysis algorithm for plane lattice structure expanding rectilinear structures.

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A Zone-Based Two-Level Routing with Power-Aware (ZTPA) for MANETs (MANET에서 Power-Aware를 고려한 2계층 Zone기반 라우팅 프로토콜(ZTPA))

  • Kim, So-Jung;Won, Soo-Seob;Park, Hae-Woong;Song, Joo-Seok
    • Proceedings of the Korea Information Processing Society Conference
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    • 2004.05a
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    • pp.1429-1432
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    • 2004
  • MANET(Mobile Ad Hoc Network)이란 어떠한 기반 구조나 중앙의 관리없이 동적으로 임시 네트워크를 형성하는 무선 mobile node의 집합이다. 이 논문에서는 MANET에서 근원지 node가 목적지 node로의 route를 발견하기 위해 전체 네트워크를 대상으로 route request 패킷을 flooding 할 경우 결과적으로 네트워크의 성능을 저하시킨다는 점과 mobile node가 제한된 양의 power를 가지고 있다는 점에 초점을 맞추어 연구가 진행되었다. 다시 말해 이 논문에서 제안된 ZTPA 라우팅 프로토콜은 기존의 ZRP를 기본으로 서로 겹치지 않는 격자 모양의 zone으로 네트워크가 구성된다. 또한 proactive 라우팅이 이루어지는 IARP에서 route 설정시 현재 node에 남아있는 power를 고려한 CMMBCR 라우팅 프로토콜이 사용되며 이와 더불어 두 개의 임계치(SVSZ, FVSZ)를 사용함으로써 설정된 route의 수명을 연장하고 신뢰성 있는 데이터 전송이 가능하여 전체적인 네트워크의 성능 향상을 야기할 수 있다.

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Modal Analysis of Wind Turbine Blade Using Optical-Fiber Bragg-Grating Sensors (광섬유 브레그격자 센서를 이용한 풍력발전기 날개의 모드 해석)

  • Kim, Chang-Hwan;Paek, In-Su;Yoo, Neung-Soo;Nam, Yoon-Su
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.5
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    • pp.513-516
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    • 2011
  • The dynamic behavior of a small wind-turbine blade was analyzed experimentally. Arrays of fiber Bragg-Grating (FBG) sensors attached along the blade were used to measure the strains of the blade surface. An impact test was performed to estimate the resonance frequencies of the fundamental and higher modes of the cantilever blade system developed for this study. The results were similar to the results for conventional strain gages. However, FBG sensors could sense modes that strain gauges could not sense. The strains obtained from the FBG sensor array were used to estimate displacement-mode shapes of the blade.

Nonlinear Simulation of Flutter Flight Test with the Forced Harmonic Motion of Control Surfaces (조종면 강제 조화운동을 고려한 비선형 플러터 비행시험 모사)

  • Yoo, Jae-Han;Kim, Dong-Hyun;Kwon, Hyuk-Jun;Lee, In;Kim, Young-Ik;Lee, Hee-Woo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.6
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    • pp.92-100
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    • 2002
  • In this study, transonic/supersonic nonlinear flutter analysis system of a complete aircraft including forced harmonic motion pf control surfaces has been effectively developed using the modified transonic small disturbance (TSD) equation. To consider the nonlinear effects, the coupled time marching method (CTM) combining computational structural dynamics (CFD) has been directly applied for aeroelastic computations. The grid system for a complex full aircraft configuration is effectively generated by the developed inhouse code. Intransonic and supersonic flight regimes, the characteristics of static and dynamic aeroelastic effect has been investigated for a complete aircraft model. Also, nonlinear flutter flight simulations for the forced harmonic motion of control surfaces are practically presented in detail.

A Study on the Fuel Assembly Stress Analysis for Seismic and Blowdown Events (지진 및 냉각재상실사고시의 핵연료집합체 응력해석에 관한 연구)

  • Kim, Il-Kon
    • Nuclear Engineering and Technology
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    • v.25 no.4
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    • pp.552-560
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    • 1993
  • In this study, the detailed fuel assembly stress analysis model to evaluate the structural integrity for seismic and blowdown accidents is developed. For this purpose, as the first step, the program MAIN which identifies the worst bending mode shaped fuel assembly(FA) in core model is made. And the finite element model for stress calculation of FA components is developed. In the model the fuel rods (FRs) and the guide thimbles are modelled by 3-dimensional beam elements, and the spacer grid spring is modelled by a linear and relational spring. The constraints come from the results of the program MAIN. The stress analysis of the 16$\times$16 type FA under arbitary seismic load is performed using the developed program and modelling technique as an example. The developed stress model is helpful for the stress calculation of FA components for seismic and blowdown loads to evaluate the structural integrity of FA.

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