• Title/Summary/Keyword: Complex Phenomena

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A Vibration Control of a Flexible Beam using a Nonlinear Compensator with Complex Dual-Input Describing Function (복소쌍입력 기술함수를 갖는 비선형 보상기를 이용한 유연한 빔의 진동제어)

  • 권세현
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.2
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    • pp.227-235
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    • 1999
  • In this paper a vibration control fo a one-link flexible beam is considered. At first a state-space model for a flexible beam is derived by using the assumed-modes approach. Based on this model the transfer function between the applied torque and the tip deflection fo the beam is presented because it is convenient to apply our method. In general there exist some control difference due to flexibility of the beam so we adop a forward-passive controller to reduce these phenomena. And a complex dual-input describing function compensator is used to control the tip deflection. The stabiltiy and the performance of the closed-loop system are analyzed. Finally the validity of the derived model and the effectiveness of proposed controller are confirmed throuth simula-tions and experiments.

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A Team-based Firefighter Training Simulator for Complex Buildings (대형 복합건물을 대상으로 하는 소방관 팀 훈련용 시뮬레이터 개발)

  • Lee, Jai-Kyung;Cha, Moo-Hyun;Choi, Byung-Il;Kim, Tae-Sung
    • Korean Journal of Computational Design and Engineering
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    • v.16 no.5
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    • pp.370-379
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    • 2011
  • The increasing complexity of complex buildings, such as high-rise buildings and underground subway stations, presents new challenges to firefighters. In a fire in complex buildings, the importance of the collaboration between firefighters is clear. The increased demand on firefighter training for such environment is now evident. Due to cost, time, and safety issues, it is impossible to experience a real fire in such environments for training. In addition, the use of real fire for training does not enable repeatable training and the evaluation of the training is difficult. We developed a team-based firefighter training simulator for complex buildings using the virtual reality technology. It provides the training and evaluation of firefighting and mission-based team training. To model real fire phenomena in virtual space, a numerical analysis method based on fire dynamics is used. To achieve an immersive virtual environment, an augmented reality technique for the compensation of real world image and a haptic technique for heat experience are adopted. The developed training simulator can help the firefighter to respond to large and complex firefighting scenarios, while maintaining the safety of the trainees.

Chaos Theory: An Alternative for a Paradigm Shift in the Social Science Studies (사회과학연구 패러다임 변화대안으로서의 카오스 이론)

  • Kim, Min Sun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.11
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    • pp.6621-6629
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    • 2014
  • Social phenomena require the fundamentals of novel scientific epistemology and methodology due to the continual change by complex variables. A systematic understanding of paradigm shifts is also necessary for analyzing the problems currently faced in society. This study presents chaos theory, which was developed from the natural sciences, to discuss the abnormality of modern society that underscores the importance of the chaos paradigm. Chaos theory is applicable to diverse social phenomena that stretches across politics, economics, and sociology. If social science research can appropriately and effectively develop and apply chaos theory, the theory can be utilized as a useful paradigm to reinforce the fundamentals of epistemology and methodology in exploring social phenomena.

Pressure Wave Propagation Phenomena in Water Containing Uniformly Distributed Gas Bubbles (소량의 기포를 함유한 이상유체 내에서의 압력파의 전파현상)

  • Kim, D.-H.
    • The Journal of the Acoustical Society of Korea
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    • v.8 no.1
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    • pp.23-30
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    • 1989
  • Propagation phenomena of nonlinear pressure waves in a bubbly mixture are studied. The governing equations for a bubbly mixture are derived heuristically and energy equation is incorporated with other governing equations to take thermal effects into consideration inside the bubble. This non-isothermal condition of the bubble inside is especially important when high amplitude pressure waves are treated. Keller's equation is adapted for the bubble dynamics as practical problem. Some numerical simulations are carried out for the shock tube problem using a computer program based on the above model. A comparison with experimental results of Noordzij and van Wijngaarden shows that the structure of the wave in the shock tube experiment seems to be much more significantly affected 요 the complex heat transfer phenomena inside the bubbles than by the relative translational motion between bubbles and surrounding liquid.

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Analysis of Partial Discharge Phenomena by means of CAPD (CAPD기법을 이용한 부분방전 현상 해석에 관한 연구)

  • Kim, Sung-Hong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07b
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    • pp.939-944
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    • 2002
  • PD phenomena can be regarded as a deterministic dynamical process where PD should be occurred if the local electric field be reached to be sufficiently high. And thus, its mathematical model can be described by either difference equations or differential equations using several state variables obtained from the time sequential measured data of PD signals. These variables can provide rich and complex behavior of detectable time series, for which Chaos theory can be employed. In this respect, a new PD pattern recognition method is proposed and named as 'Chaotic Analysis of Partial Discharges (CAPD)' for this work. For this purpose, six types of specimen are designed and made as the models of the possible defects that may cause sudden failures of the underground power transmission cables under service, and partial discharge signals, generated from those samples, are detected and then analyzed by means of CAPD. Throughout the work, qualitative and quantitative properties related to the PD signals from different defects are analyzed by use of attractor in phase space, information dimensions ($D_0$ and D2), Lyapunov exponents and K-S entropy as well. Based on these results, it could be pointed out that the nature of defect seems to be identified more distinctively when the CAPD is combined with traditional statistical method such as PRPDA. Furthermore, the relationship between PD magnitude and the occurrence timing is investigated with a view to simulating PD phenomena.

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Electromagnetic Scattering Resonances on a Periodic Strip Grating on a Grounded Dielectric Slab: Bragg Blazing Phenomena of TM Polarization Case (접지된 유전체 슬랩 위에 위치한 주기적인 스트립 격자구조에서의 전자기적 산란공진;TM편파 경우의 Bragg Blazing 현상)

  • 조웅희;홍재표;김종규;조영기
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.8
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    • pp.1363-1375
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    • 2000
  • The electromagnetic scattering characteristics by a periodic strip grating on a grounded dielectric slab for TM polarization case are examined from the viewpoints of both the reflection grating and the leaky wave antenna problems. Numerical results far two kinds of Bragg blazing (resonance type and non-resonance type) phenomena are given and some discussions on the properties(complex propagation constants, scattering characteristics, and distributions of strip current density) are presented. The comparison of the Bragg blazing phenomena between TM and TE polarization cases are also given in detail.

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A Study on Skin Tendency as New Design Phenomena in Contemporary Environments (새로운 조형현상으로서의 표피적 경향에 관한 연구)

  • 서정연
    • Korean Institute of Interior Design Journal
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    • no.40
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    • pp.26-33
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    • 2003
  • Contemporary architecture has two different movements that one is the utilization of digital technology and the other is the inclination to nature. After deconstructivism in architecture, the tendency of design shows the fusion between digitalism and organicism and as a consequence the phenomena of 'skin expression' has emerged which can be thought as 'organic digitalism' or 'digital organicism'. The definition of skin tendency in environmental design is the design of nature based on the technology. As a result, the surface becomes the design issue compared to structure and the momentum for new aesthetic value. There are post-structuralism, complex system theory and the organic architecture as theoretical background for the tendency of skin expression. Specially the ideas of post-structural philosophy has effected deeply to the formation of its movement and also offered the theoretical nutrition for digital architecture. The characteristics of the skin tendency can be analyzed as topological transformation, smooth continuum, deterritorialization, ecological response system, and tactility. These design characteristics has combined with conventional material and design vocabulary to transform and develope new spatial conception.

NUMERICAL SIMULATION OF BOILING PHENOMENA USING A LEVEL-SET METHOD (Level-Set 방법을 이용한 비등현상 해석)

  • Son, G.
    • 한국전산유체공학회:학술대회논문집
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    • 2009.11a
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    • pp.218-222
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    • 2009
  • A level-set (LS) method is presented for computation of boiling phenomena which involve liquid-vapor interfaces that evolve, merge and break up in time, the flow and temperature fields influenced by the interfacial motion, and the microlayer that forms between the solid and the vapor phase near the wall. The LS formulation for tracking the phase interfaces is modified to include the effects of phase change on the liquid-vapor interface and contact angle on the liquid-vapor-solid interline. The LS method can calculate an interface curvature accurately by using a smooth distance function. Also, it is straightforward to implement for two-phase flows in complex geometries. The numerical method is applied for analysis of nucleate boiling on a horizontal surface and film boiling on a horizontal cylinder.

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An experimental study on mechanism for the disintegration of liquid film surface waves by a parallel air flow (평행공기류에 의한 액막류 표면파의 분열기구에 관한 실험적 연구)

  • 이규영;양옥용
    • Journal of the korean Society of Automotive Engineers
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    • v.14 no.6
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    • pp.81-90
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    • 1992
  • This paper deals with an experimental study on the initial condition of liquid film surface waves disintegration and investigation on the behavior of liquid film surface waves formed by the high speed air flow on the solid plane surface. The authors conducted the qualitative and quantitative study to in vestigate the liquid film flow phenomena, the liquid film disintegration mechanism, and droplet formation process with breaking the liquid film surface wave. The newly devised transparent rectangular test section which has semi-two-dimensional flow at the center of the bottom was introduced to perform the experimental study, and it can generate the uniform thickness liquid film at the bottom. The strobo streak camera was used to obtain the instantaneously transformed photographs. The electronic measuring device was also used to measure the liquid film thickness variation in order to perform the easy and effective analysis of complex flow phenomena in the air-water cocurrent flow.

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Numerical Study on Characteristics of Low-Frequency Noise in a Cylindrical Combustor (원통형 연소기 내의 저주파 소음특성에 관한 수치적 연구)

  • 김재헌;이수갑
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1998.04a
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    • pp.492-497
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    • 1998
  • Thermoacoustic oscillation is a significant problem in cylindrical-type combustors such as common internal combustion engines, industrial furnaces, gas turbine, etc. This kind of low frequency oscillation can give rise to serious troubles such as the destruction of system or producing of a strong noise. Accurate numerical simulation of thermoacoustic phenomena is a complex and challenging problem. Especially, considering the reaction of mixture intensifies the difficulty of analysis. Like as other simulations of the aerodynamics and aeroacoustics, direct computation of thermoacoustic phenomena requires that the Navier-Stokes equations be solved using accurate numerical differentiation and time-marching schemes, with non-reflecting boundary conditions. In this study,, numerical approach aims at qualitative analysis and efficient prediction of problem, not at the development of an accurate scheme. Overally speaking, numerical prediction is reasonably matched with experimental result.

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