• Computational Structural Engineering
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• v.10 no.1
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• pp.149-158
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• 1997

This paper presents the illustration of application under attached point mass to the special orthotropic plates with a pair of opposite edges simply supported and the other pair of opposite edges free. Design engineers need to calculate the natural frequencies of such elements but obtaining exact solution to such problems is very much difficult. Pretlove reported a method of analysis of beams with attached masses using the concept of effective mass. This method, however, is useful only for certain simple types of beam. Therefore, considering the method has been developed by D. H. Kim(1974) is simple, accurate, and very effective for the plates with arbitrary boundary conditions and irregular sections, this paper calculates the natural frequencies of composite laminated plate under attached point mass/masses.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.285-286
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• 2013

이번 연구에서는 제일원리 계산을 통해 실리콘의 전자구조를 분석하였다. 특히 strain이 걸렸을 때에 실리콘의 전자이동도는 전자구조의 변화와 밀접하게 관련이 있음을 밝혔다. Strain이 걸린 경우와 그렇지 않은 경우에 대한 conduction band의 effective한 유효질량 계산을 하였고 이를 통해 tensile strain이 걸린 경우 전자의 이동도가 증가하는 것을 보였다.

• The Journal of the Acoustical Society of Korea
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• v.10 no.2
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• pp.13-22
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• 1991

The presence of an unbalanced mass is originated the common source of vibration in machines with rotating rotor. In this study, the unbalanced rigid rotor mounted on an overhang shaft is balanced using the static balancing procedure, and the compensation mass is estimated by the phase angle method and four run method. Also, the reduction of vibration level before and after balancing is examined. In the experimental results, it is shown that the vibration due to the unbalanced mass is decreased by eliminating the effect of the unbalance. Above all, the four run method is proved more effective on the ability of vibration reduction, in small unbalanced mass, the phase angle method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1013-1019
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• 2014

Solid-liquid Phase Change Material(PCM) as a thermal control hardware for the electro-optical payload of low earth orbit satellite is numerically studied which can be substituted with Thermal Buffer Mass(TBM). The electro-optical module in LEO satellite is periodically work and high heat is dissipated during the imaging period, however, the design temperature range is very tight and sensitive. In order to handle this problem TBM is added and as a result the time constant of the module temperature increases. TBM is made of Al6010 and its mass directly affects the system design. To save the mass PCM is suggested in this study. The latent heat of melting or solidification is very high and small amount of PCM can play a role instead of TBM. The result shows that only 12% of TBM mass is enough to control the module temperature using PCM.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.8
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• pp.783-790
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• 2010

In this paper, we propose a turbine mass flow rate model for a variable geometry turbocharger (VGT) using an artificial neural network (ANN). The model predicts the turbine mass flow rate using the VGT vane position, engine rotational speed, exhaust manifold pressure, exhaust manifold temperature, and turbine outlet pressure. The ANN is used for the estimation of the effective flow area. In order to validate the results estimated by the proposed model, we have compared estimation results with engine experimental results. The results, in addition, represent improved estimation accuracy when compared with the performance using the turbine map.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.5
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• pp.450-456
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• 2009

Semi-active vibration control is one of the attractive control methods for space application due to its robustness as passive damping system and much higher damping performance than passive system. In this paper, performance investigation of semi-active damper considering a mass modeling of functional fluid inside of the damper has been performed. Numerical investigation results confirmed that the damper model considering the fluid mass is effective for vibration suppression performance at a relatively low viscosity range of functional fluid. Based on the analysis results, design method to enhance the performance of semi-active damper has been proposed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.203-209
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• 2016

According to the wear detection history for the steam generator tubes in the nuclear power plant, the outer tubes inside the steam generator have more problems on the flow-induced vibration than inner tubes. Many researchers and engineers have used a specified added mass coefficient for a given tube array during the design stage of the steam generator even though the coefficient is not constant for entire tube in cylindrical shell. The aim of this study is to find out the distribution of added mass coefficients for each tube along the radial location. When numbers of tubes inside a cylindrical shell are increased, values of added mass coefficients are also increased. Added mass coefficients at outer tubes are less than those of inner tubes and they are decreased with increasing the gap between the outermost tube and the cylindrical shell. It also turns out when the gap between the outermost tube and the cylindrical shell approaches infinite value, the added mass coefficient converges to an asymptotic value of given tube array in a free fluid field.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.145-151
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• 2019

The fragility analyses for the partially filled horizontal cylindrical tank having a flexible wall were conducted to evaluate seismic performance. An equivalent simplified model with two lumped masses representing to impulsive and convective masses was used to represent the liquid storage system. This simplified model was validated by comparing its time history analysis results with the 3D FSI model results. The horizontal tank was analyzed under bi-directional excitations. Seismic fragility curves for the stability were developed in transverse and longitudinal directions. Fragility curves show that seismic damage for the horizontal storage system is more susceptible in the transverse direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1763-1773
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• 1991

본 연구에서는 포화수증기와 공기의 혼합기내에서 분무수적으로의 열 및 질량 전달률을 계산하기 위하여 수적의 부분혼합모형과 비혼합모형에 대하여 수적내 과도온 도분포의 해석해를 적용성이 보장되면서도 계산상의 어려움이 수반되지 않는 형태로 구하기 위하여 수적내부의 열전도해석에 있어서 적분법을 적용하였다. 적분법으로 얻어지는 과도온도분포의 해는 유한차의 다항식으로 표시되어 비혼합모형인 경우 각시 간 구간의 경계에서의 온도분포가 연속성을 유지하면서 물성치들의 온도에 대한 종속 성이 쉽게 고려되고 계산도 용이한 형태이다. 본 보에서 제시하는 해석결과의 적용 성을 조사하기 위하여 완전혼합모형을 포함하는 세가지 수적모형들에 대한 계산결과들 로부터 얻어진 시간변화에 따른 수적의 무차원 체적평균온도변동을 유효한 실험결과들 과 비교, 검토하였으며, 부분혼합모형에 대하여 혼합기의 압력, 수적의 초기온도, 혼 합기 속에 포함되어 있는 수증기의 체적분율, 수적의 초기크기, 수적의 초기속도 및 분사각도가 주위혼합기로부터 수적으로 전달되는 열 및 질량전달에 미치는 영향을 조] 사하고 도출된 대표적인 검토 결과를 제시하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.416-423
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• 2004

In this paper, an experimental verification of system identification technique for constructing finite element model is conducted for a three-story test structure equipped with an active mass driver (AMD). Twenty Gaussian white noises were used as the input for AMD, and the corresponding accelerations of each floor are measured. Then, the complex frequency response function (FRF) for the input, the force induced by the AMD, was obtained and subsequently, the Markov parameters and system matrices were estimated. The magnitudes as well as phase of experimentally obtained FRFs match well with those of analytically obtained FRFs.