• 소음진동
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• 제8권6호
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• pp.1015-1022
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• 1998

This paper addresses the results of an experimental and analytical research of a helical coil spring subjected to dynamic behavior using space curve vector after considering elongation rate. Vibrations in helical coil spring can be divided into 3 modes such as vibrations of coil spring center axis' vertical direction. axis' horizontal direction, direction about center axis. However. these 3 modes are dependent one another and are characterized as coupled. The dependency was proved through both theoretically and experimentally analyzing the results of dynamic characteristics of coil spring center axis' vertical direction vibration by transfer matrix method using the governing equation of static equilibrium. Also this paper shows that pitch angle and active coils in coil spring affect the dynamic spring characteristics of the above 3 modes and are especially sensitive to the mode for vibration of axis' horizontal direction which most affects especially on dynamo stability of helical coil spring.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.919-924
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• 2006

This paper presents active vibration control using a hybrid mount which consists of rubber element and the piezostack actuator. After identifying stiffness and damping properties of the rubber element and piezoelectric elements, a mechanical model of the hybrid mount is established. The mount model is then incorporated with the vibration system, and the governing equation of motion is obtained in a state space. A sliding mode controller and LQG controller are designed in order to actively attenuate the vibration of the system subjected to high frequency and small magnitude excitations. Control responses such as acceleration and force transmission through the hybrid mount are evaluated by computer simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.915-918
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• 2006

This paper presents an active vibration control of a 1-DOF system using a hybrid mount which consists of elastic rubber and electromagnetic actuator. After identifying stiffness, damping properties of the elastic rubber and electromagnetic element, a mechanical model of the hybrid mount is established. The mount model is then incorporated into the 1-DOF system and the governing equation of motion is obtained in a state space. A sliding mode controller is designed in order to actively attenuate the vibration of the system control responses such as acceleration and transmitted force of the 1 -DOF system are presented in time domain.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.428-433
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• 2006

This paper presents a new type of jetting dispenser for the integrated circuit(IC) fabrication and surface mount technology. The proposed system is featured by the piezoelectric actuator and hydraulic magnification device. After describing structural component of the dispensing mechanism and its operation principle, both the fluid modeling and the hydraulic magnification modeling are undertaken with a lumped-parameter method based on the analogy of the fluid system and mechanical system. A mathematical governing equation is then derived by integrating the fluid model with the mechanical model of the driving piston and piezoelectric actuator. Subsequently, in order to achieve a desired dispensing amount, control algorithm adjusting duty cycle of the driving voltage is synthesized and control responses are presented in time domain.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.805-808
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• 2006

This paper deals with the dynamic stability analyses of columns with constant volume and both clamped ends. Numerical methods are developed for solving natural frequencies of such column, subjected to an axial compressive load. Differential equation governing free vibration of such column is derived. The numerical methods developed herein for computing natural frequencies are found to be efficient and robust. From the numerical results, the dynamic stability regions of such columns are obtained.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.801-804
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• 2006

The purpose of this paper is to investigate the stability of stepped cantilever columns with a tip mass of rotatory inertia and a translational spring at one end. The column model is based on the Bernoulli-Euler theory which neglects the effects of rotatory inertia and shear deformation. The governing differential equation for the free vibration of columns with stepwise variable cross-section and subjected to a subtangential follower force is solved numerically using the corresponding boundary conditions. And the bisection method is used to calculate the critical divergence/flutter load. The frequency and critical divergence/flutter load for the stepped column with a single step are presented as functions of various non-dimensional system parameters: the segmental length parameter, the section ratio, the subtangential parameter, the mass, the moment of inertia of the mass, and the spring parameter.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 유체기계 연구개발 발표회 논문집
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• pp.223-232
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• 1998

To investigate the flow inside the centrifugal impeller, computer program which can solve Three-dimensional compressible turbulent flow has been developed. The Navier-Stokes equations were chosen as the governing equation for viscous flow while Euler equations for inviscid case. Time marching method was incorporated with the Flux Difference Splitting method suggested by Roe to capture the steep gradients such as a shock. For high order of accuracy, MUSCL approach was adopted while differentiable limiter to ensure TVD property. For turbulence closure, Baldwin- Lomax model was applied due to its simplicity. To demonstrate the capabilities of present program, several validation problems have been solved and compared with experiments and other available data. From the above calculations generally good agreements were obtained. Finally, the developed code was applied to Eckardt's impeller and the performance prediction was carried out. Some important aspects on boundary condition for successful simulation were discussed and the remedy was also introduced.

• International Journal of Safety
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• 제1권1호
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• pp.13-17
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• 2002

A new system of equations governing the nonlinear thin laminated plates with large deflections using von Karman equations is derived. The effects of transverse shear in the thin interlayer are included as part of the analysis. The finite difference method is used to perform the geometrically nonlinear behavior of the plate. The resultant equations permit the analysis of the effect of transverse shear stress deformation on the overall behavior of the interlayer using the load incremental method. For the purpose of feasibility and validity of this present method, the numerical results are compared with other available solutions for accuracy as well as efficiency. The solution techniques have been implemented and the numerical results of example problem are discussed and evaluated.

• 한국안전학회지
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• 제6권3호
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• pp.40-49
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• 1991

To better understand the phenomena inside an absorber, where heat and mass transfer coexist, this study selected the most baslc absorption model from in whifh water vapor is absorbed on the surface of a stationary lithium bromide absurbent solution. The purpose of this study is to obtain basic knowledge of heat and mass transfer processes as affected by Marangoni convection induced by addition of surfactant. We apply a non-flowing bulk absorption model and assume that dropwise surfactant is fixed on the absorbent surface. Four governing equation-continuity, laminar monentum, energy and diffusion are solved numerically to obtain temperature and concentraion distributions during steam absorption with Marangonl convection.. In conclusion, Sh and Nu genrally increase at the initial absorption stage.

• 한국안전학회지
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• 제14권4호
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• pp.3-12
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• 1999

This research concentrates on the influence of non-linearities associated with impact for the nonlinear rocking behavior of rigid block subjected to one dimensional sinusoidal excitation of horizontal direction. The transition of two governing rocking equations, the abrupt reduction in the kinetic energy associated with impact, and sliding motion of block. In this study, two type of rocking vibration system are considered. One is the undamped rocking vibration system, disregarding energy dissipation at impact and the other is the damped rocking system, including energy dissipation and sliding motion. The response analysis using non-dimensional rocking equation is carried out for the change of excitation parameters and friction coefficient. The chaos responses were discovered in the wide response region, particularly, for the case of high excitation amplitude and their chaos characteristics were examined by the time history, Poincare map, power spectra and Lyapunov Exponent of rocking responses. The complex behavior of chaos response, in the phase space, were illustrated by Poincare map. The bifurcation diagram and Poincare map were shown to be effective in order to understand chaos of rocking system.