A Study on Dynamic Vibration Absorber Using Zener`s Model

A dynamic vibration absorber using the Zener's model has been taken into account with respect to frequency response characteristics. The concept of the tuned mass damper with a single degree of freedom has been well applied for many industrial fields, because many researchers have extensively studied various basic characteristics, performance and optimization methods for long time. The Zener's model has an additional spring, which is connected between a damper and a mass, while the tuned mass damper with a single degree of freedom consists of a mass, a spring and a damper connected in parallel. In previous works, the basic performance and characteristics of the Zoner's model as a dynamic vibration absorber have not been investigated. In this study, the frequency response characteristics according to the parameter change of the Zener's model have been described. In order to find the optimum value of several parameters, we use iterative scheme with three dimensional frequency response diagram by MATLAB programming. Present results shows the Zener's model can give more good damping performance than the simple tuned mass damper, and the numerical of optimization method should be developed for the efficient vibration absorbtion

Thermopiezoelastic Nonlinear Dynamic Characteristics of Piezolaminated Plates

Nonlinear dynamics of active piezolaminated plates are investigated with respect to the thermopiezoelastic behaviors. For largely deformed structures with small strain, the incremental total Lagrangian formulation is presented based on the virtual work principles. A multi field layer wise finite shell element is proposed for assuring high accuracy and non-linearity of displacement, electric and thermal fields. For dynamic consideration of thermopiezoelastic snap through phenomena, the implicit Newmark's scheme with the Newton-Raphson iteration is implemented for the transient response of various piezolaminated models with symmetric or eccentric active layers. The bifurcate thermal buckling of symmetric structural models is first investigated and the characteristics of piezoelectric active responses are studied for finding snap through piezoelectric potentials and the load path tracking map. The thermoelastic stable and unstable postbuckling, thermopiezoelastic snap through phenomena with several attractors are proved using the nonlinear time responses for various initial conditions and damping loss factors. Present results show that thermopiezoelastic snap through phenomena can result in the difficulty of buckling and postbuckling control of intelligent structures

Vibration Analysis of Cylindrical Hybrid Panel With Viscoelastic Layer Based on Layerwise Finite Elements

Based on a full layerwise displacement shell theory, the nitration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modelling. The present finite element model Is formulated by using Hamilton's virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factors and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping

ACTIVE FREQUENCY SELECTIVE SURFACE, MANUFACTURING METHOD AND OPERATING THEREOF

능동적 주파수 선택 표면 및 그 제조 방법이 제공된다. 여기서, 능동적 주파수 선택 표면은 특정 주파수를 가진 전자파를 투과하거나 또는 반사시키는 주파수 선택 표면으로서, 유전 탄성체, 상기 유전 탄성체의 상부면에 도전성 패턴이 패터닝된 제1 유연 전극, 그리고 상기 유전 탄성체의 하부면에 상기 도전성 패턴이 패터닝된 제2 유연 전극을 포함하고, 상기 제1 유연 전극과 상기 제2 유연 전극에 전압이 인가되면, 상기 제1 유연 전극과 상기 제2 유연 전극 간의 전기적 인력에 따라 상기 유전 탄성체에 가해진 압축력으로 인해 상기 도전성 패턴의 기하학 구조가 변형되어 주파수 특성이 가변된다

Nonlinear Transient Responses of Isotropic Plates Under Thermo-Acoustic Load

For high-speed aircraft and high-speed civil transport planes, certain structural skin components are subjected to very large acoustic loads in an elevated thermal environment. In this study, we used the single-mode Fokker-Panck distribution to predict displacements of isotropic plates subject to thermo-acoustic combined load. The single mode was formulated to predict the nonlinear dynamic responses of postbuckled plates under acoustic random excitation. Acoustic random excitation was used with Gauss distribution. Some important effects of the snap-through motion on the dynamic responses of the postbuckled plates are described

CATALYTIC ELECTRODE FOR OXYGEN EVOLUTION AND METHOD FOR PREPARING THE SAME

본 발명에서는 탄소섬유 직물을 포함하는 전극집전체, 상기 탄소섬유의 표면에서부터 방사형으로 성장된, 금속산화물계 다공성 나노와이어를 포함하는 나노와이어층, 및 상기 나노와이어의 표면을 둘러싸며 위치하는, 다공성의 탄소 코팅층을 포함함으로써, 비표면적이 극대화되고, 전자의 이동 속도가 증가되어 산소 발생 반응(oxygen evolution reaction; OER)에 대해 우수한 촉매활성을 나타낼 수 있는 산소 발생용 촉매 전극 및 그 제조방법이 제공된다