• 조명전기설비학회논문지
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• 제28권3호
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• pp.63-71
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• 2014

A single-inverted-pendulum model is presented to simulate and predict the passive response of human balance control. This simplified biomechanical model was comprised of a torsional spring and damper, and a lump mass. An estimation of frequency response function was conducted to parameterize the complexity. The frequency domain identification method is used to identify the parameters of the model. The equivalent viscoelastic parameters of standing body were obtained and there was good conformity between the simulation and experimental result.

• 대한기계학회논문집A
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• 제25권4호
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• pp.555-563
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• 2001

Support dynamics are often important in rotordynamic analyses. It may well happen in real situation of machines such as centrifugal pumps or turbines operating on flexible structure. This paper presents the applications of the impedance coupling method and the improved rotor model for including the support effects on the interaction with the rotor. The impedance coupling techniques are based on the FRFs of each substructure. Its dynamic stiffness matrix can be assembled to generate the system matrix, which satisfy the constraint conditions in the connection coordinates. And, the improved rotor uses the simplified spring-mass models as support properties. The equivalent support models are directly incorporated into the finite element rotor model. To verify the suggested analytical procedures, the results are compared to those of the pump system.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 추계학술대회 논문집
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• pp.217-222
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• 2001

The best method to evaluate crashworthiness of a trainset as a whole is to analyse one dimensional dynamic model composed of nonlinear dampers, springs and bars, and masses. In this study, crashworthiness of KHST was evaluated by analysing a nonlinear spring/bar-damper-mass model. The numerical results show that the KHST can easily absorb kinetic energy at lower impact force and acceleration in a heavy collision, when compared with KTX. Also, the KHST can be protected from any damage in its carbody and components except the prepared energy absorbing tube in a light collision, like a traint-to-train accident at speed under 8 kph. However, the KTX can be much damaged in the a light collision because there is no energy absorbing tube.

• 소음진동
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• 제8권4호
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• pp.616-622
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• 1998

An analytical method has been developed to estimate the dynamic contact force between wheel and rail when trains are running on rail with vertical irregularities. In this method, the effect of Hertzian deformation at the contact point is considered as a linearized spring and the wheel is considered as an sprung mass. The rail is modelled as a discretely-supported Timoshenko beam, and the periodic structure theory was adopted to obtain the driving-point receptance. As an example, the dynamic contact force for a typical wheel/rail system was analysed by the method developed in this research and the dynamic characteristics of the system was also discussed. It is revealed that discretely-supported Timoshenko beam model should be used instead of the previously used continuously-supported model or discretelysupported Euler beam model, for the frequency range above several hundred hertz.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.249-260
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• 2015

Damage detection based on a reference set of measured data usually has the problem of different environmental temperature in the two sets of measurements, and the effect of temperature difference is usually ignored in the subsequent model updating. This paper attempts to identify the structural damage including the temperature difference with artificial measurement noise. Both local damages and the temperature difference are identified in a gradient-based model updating method based on dynamic response sensitivity. The sensitivities of dynamic response with respect to the system parameters and temperature difference are calculated by direct integration method. The measured dynamic responses of the structure from two different states are used directly to identify the structural local damages and the temperature difference. A single degree-of-freedom mass-spring system and a planar truss structure are studied to illustrate the effectiveness of the proposed method.

• 한국산업융합학회 논문집
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• 제20권5호
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• pp.431-439
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• 2017

Since the power transmission line(PTL) passes through the high mountain and heavy snowfall region, it is necessary to keep the stability of the PTL. In this study, PTL is modeled as a mass-spring-damper system by using RecurDyn. The lumped mass model is verified by calculated from the simulation comparing the deflection analysis according to the sag and tension. In order to analyze the dynamic behavior of PTL, a damping coefficient for a multi-body model is derived by using the free vibration test and Rayleigh damping theory. Sleet jump simulation according to the region is performed. The maximum jump height, icing sag and amount of jump are confirmed. Also, the amount of jump and the reaction force at the supporting point according to the tension and load of ice are analyzed, respectively. As a result, it is noted that the amount of jump and reaction force are influenced more by the load of ice than by the tension of PTL.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.477-485
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• 2020

Finite element (FE) model based structural damage detection (SDD) methods play vital roles in effectively locating and quantifying structural damages. Among these methods, structural model updating should be conducted before SDD to obtain benchmark models of real structures. However, the characteristics of updating parameters are not reasonably considered in existing studies. Inspired by the l_∞ norm regularization, a novel anti-sparse representation method is proposed for structural model updating in this study. Based on sensitivity analysis, both frequencies and mode shapes are used to define an objective function at first. Then, by adding l_∞ norm penalty, an optimization problem is established for structural model updating. As a result, the optimization problem can be solved by the fast iterative shrinkage thresholding algorithm (FISTA). Moreover, comparative studies with classical regularization strategy, i.e. the l₂ norm regularization method, are conducted as well. To intuitively illustrate the effectiveness of the proposed method, a 2-DOF spring-mass model is taken as an example in numerical simulations. The updating results show that the proposed method has a good robustness to measurement noises. Finally, to further verify the applicability of the proposed method, a six-storey aluminum alloy frame is designed and fabricated in laboratory. The added mass on each storey is taken as updating parameter. The updating results provide a good agreement with the true values, which indicates that the proposed method can effectively update the model parameters with a high accuracy.

• 대한의용생체공학회:의공학회지
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• 제34권4호
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• pp.218-225
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• 2013

In this paper hair bundle feature model and integration method for hair cell models were proposed. The proposed hair bundle feature model was based on spring-damper-mass model. Input of integrated vestibular hair cell model was frequency and output was interspike interval of hair cell that was reflected the feature of hair bundles. Irregular afferents that had a great gain variation showed reduction of negative stiffness section. Regular afferents that had a small gain variation, however, showed same feature with base negative stiffness feature. As a result, integrated vestibular hair cell model showed almost the same modeling data with experimental data in the modeled eleven frequency bands. It is verified that the proposed model is a good model for hair bundle feature modeling.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.419-426
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• 2008

As pulse detonation engine(PDE) does not need compression mechanisms such as compressors because self-sustained detonation waves are able to compress propellant gases by their incident shock waves, the PDE can have a simple straight-tube structure. In this study, we propose an autonomous driving valve system of the PDE, which fill premixed gases into the PDE tubes at high frequency with high mass flow rate. The proposed valve is composed of only three parts: a piston, a cylinder, and a spring. This valve system can produce intermittent flow at high mass flow rate, and also can keep stable reciprocal motion by using the propellant-gas enthalpy. When the cylinder content product is assumed to be constant, experimental results of the mass flow rate were approximately equal to the calculation model. We confirmed the autonomous driving valve performance by experiments, and concluded that this extremely simple valve with no electrical power and controller can be used as the PDE propellant supply system.

• Smart Structures and Systems
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• 제12권3_4호
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• pp.441-463
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• 2013

In this paper, a simplified planar model is developed for damage estimation of interlocked caisson systems. Firstly, a conceptual dynamic model of the interlocked caisson system is designed on the basis of the characteristics of existing harbor caisson structures. A mass-spring-dashpot model allowing only the sway motion is formulated. To represent the condition of interlocking mechanisms, each caisson unit is connected to adjacent ones via springs and dashpots. Secondly, the accuracy of the planar model's vibration analysis is numerically evaluated on a 3-D FE model of the interlocked caisson system. Finally, the simplified planar model is employed for damage estimation in the interlocked caisson system. For localizing damaged caissons, a damage detection method based on modal strain energy is formulated for the caisson system.