• Journal of KSNVE
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• v.7 no.6
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• pp.937-943
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• 1997

Viscoelastic materials have the characteristics of elasticity and viscosity. Unlike the metals which show negligible damping characteristics, the damping characteristic of viscoelastic materials like rubber mounts is very important in the analysis of the dynamic system. So there has been a great interest in measuring the damping characteristics of the material can be measured. One is the resonant method which loss factor can be measured only in the resonant frequency. The other is the nonresonant method. In this paper, the test procedure and the physical meaning of the impedance method are introduced. The impedance test results, the loss factor by the impedance method, are compared to the results of the resonant method including some recommendations in the experimental setup.

• Environmental and Resource Economics Review
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• v.9 no.1
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• pp.49-69
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• 1999

본 연구는 1983년부터 1996년까지의 월별 자료를 이용하여, 전력 수요의 장기 탄력성을 추정하였다. 공적분모형인 Stock-Watson(1993)의 동태적 OLS(Dynamic OLS) 모형을 이용하여, 전력수요의 장기가격탄력성과 소득탄력성을 추정하였다. 장기균형식을 이용한 결과를 살펴보면, 실질국내총생산의 장기탄력성은 0.23으로 나타났으며, 실질전력요금의 장기탄력성은 -0.12로 추정되었다. 이와 같은 결과는 가격과 소득이 전력수요에 직접적 영향을 미치는 것을 의미한다. 단기오차수정모형에서 오차수정항의 계수는 -0.23으로 추정되었으며, 이는 단기적으로 장기수요곡선을 이탈하였을 경우 단기적 불안정이 새로운 균형을 찾아가는 기간이 약 4.4 개월 걸리는 것을 의미한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.324-330
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• 1990

In this study, in order to perform dynamic design of machine tools reasonably and effectively, a method was formulated to be applicable to the damped structures connected by joints having elasticity and damping by using substructure synthesis method. And a nonlinear solution method was proposed and it formulates the nonlinear parts by describing functions and uses the reducing transformation matrix by the substructure synthesis method. The results of frequency response analysis of a machine tool, where an NC lathe was partitioned by three parts of spindle, housing and bed-base part and the nonlinearity of bearing parts between spindle and housing was modelled, showed force dependency of the response.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.757-763
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• 2000

In vehicle exhaust systems the sound attenuation and the reduction of flow losses are often two competing demands. The present study considers a fully vehicle exhaust system and investigates experimentally both the sound attenuation and the flow performance of production configurations including the catalyst, the resonator, and the muffler. Dynamometer experiments have been This study is on the development of a new muffler composed of a valve system using an elasticity of spring. The valve system conducted with the daewoo 1500cc Lanos engine with speeds ranging from 1000 to 5000 rpm. Measurements include the flow rates, the temperatures and the absolute dynamic pressures of the hot exhaust gases at point locations. The present study describes the experimental aspects of an ongoing effort to validate and use the nonlinear fluid dynamic models in the time-domain for the prediction of the acoustic and power performance of firing internal combustion engines with full production exhaust systems.

• Advances in Computational Design
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• v.5 no.4
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• pp.349-362
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• 2020

Dynamic characteristics of a scale-dependent porous metal foam cylindrical shell under a traveling load have been explored within this article based on a numerical approach. Within the material texture of the metal foams, uniform and non-uniform porosities may be dispersed. Based upon differential quadrature method (DQM) and Laplace transforms, the equations of motion for a shear deformable scale-dependent shell may be solved numerically. Scale-dependent shell modeling has been provided based upon strain gradient elasticity. Solving the equations will give the shell deflection as a function of load speed. Also, it is reported that shell deflection relies on the porosity dispersion and strain gradient influences.

• Steel and Composite Structures
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• v.22 no.1
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• pp.13-24
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• 2016

In the present paper, glass fibers are substituted partially with monofilament fishnet and polyester matrix for making the composites. The composite specimens were prepared in accordance with ASTM for analyzing the flexural strength and dynamic mechanical properties. Furthermore, machinability revealed the interaction of glass fiber and partial substituted monofilament fishnet fiber with the matrix. Fiber pullouts on the fractured specimen during the physical testing of the composites are also investigated by COSLAB microscope. The results reveal that the fishnet based composites have appreciably higher flexural properties. Furthermore, the glass fiber, woven roving and fishnet composite has more storage modulus and significant mechanical damping. The composite specimens were fabricated by hand lay-up method. Hence, these composites are the possible applications to develop the value added products. The results of this study are presented.

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.1
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• pp.21-26
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• 2009

This study was performed to evaluate the physical and mechanical properties of concrete using waste activated carbon. Materials used were ordinary portlant cement, crushed coarse aggregate, natural fine aggregate, waste activated carbon, and superplasticizer. The substitution ratios of waste activated carbon were 0,1,2,3,4,5,6,7,8,9 and 10%. The unit weight was decreased and water absorption ratio was increased with increasing the waste activated carbon content, respectively. When the substitution ratio of waste activated carbon was 3%, compressive strength, flexural strength and dynamic modulus of elastisity were more higher than that of the ordinary portland cement (OPC), and it was decreased with increasing the waste activated carbon content, respectively. The most effective contents of waste activated carbon was 2% in performance and 4% in practical use Accordingly, waste activated carbon can be used for concrete material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.35-41
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• 1997

Viscoelastic materials shows the characteristics of elasticity and viscosity. Unlike metals which show negligible damping value, the damping characteristics of viscoelastic materials like rubber mounts is very important in the analysis of the dynamic system. So there has been a great interest in measuring the damping characteristics of viscoelastic materials. There are two kinds of methods which the damping characteristics can be measured. One is the resonant method where loss factor can be measured only in the resonant frequency. The other is the nonresonant method which is characterized by the impedance method are introduced. The impedance test results, the loss factor by the impedance method are compared to the results of the resonant method and recommendations in the experimental setup are suggested.

• Earthquakes and Structures
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• v.6 no.3
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• pp.251-266
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• 2014

Dynamic analyses for a suite of ground of motions were conducted on concrete gravity dam sections to examine the earthquake induced stresses and effective damping. For this purpose, frequency domain methods that rigorously incorporate dam-reservoir-foundation interaction and time domain methods with approximate hydrodynamic foundation interaction effects were employed. The maximum principal tensile stresses and their distribution at the dam base, which are important parameters for concrete dam design, were obtained using the frequency domain approach. Prediction equations were proposed for these stresses and their distribution at the dam base. Comparisons of the stress results obtained using frequency and time domain methods revealed that the dam height and ratio of modulus of elasticity of foundation rock to concrete are significant parameters that may influence earthquake induced stresses. A new effective damping prediction equation was proposed in order to estimate earthquake stresses accurately with the approximate time domain approach.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.3
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• pp.130-138
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• 1993

A mechanism for collision detection in general animation system is necessary to prevent the interpenetration among multiple objects. On the other hand, a dynamic simulation system which is a part of animation system simulates realistic motions using dynamics after the collision, which is called collision response. In this paper, a method for reducing the CPU time for collision detection by removing redundant calculations and object sorting is proposed. A dynamic simulation system including collision detection and response function was implemented to demonstrate the proposed methods, where the input data as elasticity, friction, gravity, object shape, external force and external torque are given by the user. The system simulates motions of multiple objects using dynamics, and generates the wireframe display.