• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.385-396
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• 1989

In this paper, using by the orthogonalities of modes for trainwheel (as Mindlin's annular plate and rail (as Timoshenko beam), the frequency equation of the coupled system are induced. It is convinced that the natural frequencies of coupled system are distributed to be about quadratic order function examined through the experimental and numerical analysis. The natural frequencies of the system coupled by both creep force and creep moment are composed of the natural frequencies of the system coupled by creep force and the natural frequencies of the system coupled by creep moment . And it is shown that the coupled natural frequencies up to 3rd do not make much difference from the values of the system coupled by individual creep force of creep moment. But the coupled natural frequencies higher than the 3rd are quite different from those of individual case.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1488-1489
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• 2006

Gas Discharge Tubes (GDTs) are widely used as surge protectors for communication applications due to their small internal capacitance. In these days, however, they are mostly used in combined configurations, because the activation voltage required to initiate the discharge process in the GDTs for sufficient amount of time can be large enough to damage surge-sensitive protected circuits. For GDTs with a considerably high initial over-voltage value, we should limit the peak voltage using a TVS or filter. As for ZnO varistors, even though their performance for voltage restriction is excellent their applications in high-frequency communication circuits have been limited because of higher internal capacitance when compared to the GDTs. In order to develop a surge protector for communication applications by taking advantages of these two devices, we built a combination circuit that connects a GDT and a ZnO varistor along with a choke coil in common and differential modes. We describe how the applied SPDs operate in protection process steps with the actual data obtained from the residual voltage measurements at each step. The experiment results show that the surge voltage restriction with the choke coil is more effective in differential mode than in common mode.

• Structural Engineering and Mechanics
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• v.73 no.1
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• pp.65-73
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• 2020

The present work describes a new time marching procedure for structural dynamics analyses. In this novel technique, time integration parameters are automatically evaluated according to the properties of the model. Such parameters are locally defined, allowing the user to input a numerical dissipation property for each element, which defines the amount of numerical dissipation to be introduced. Since the integration parameters are locally defined as a function of the structural element itself, the time marching technique adapts according to the model, providing enhanced accuracy. The new methodology is based on displacement-velocity relations and no computation of accelerations is required. Furthermore, the method is second order accurate, it has guaranteed stability, it is truly self-starting and it allows highly controllable algorithm dissipation in the higher modes. Numerical results are presented and compared to those provided by the Newmark and the Bathe methods, illustrating the good performance of the new time marching procedure.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.5-8
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• 2018

Emissions of diesel vehicles have been regulated by NEDC mode for a long time. However, the NEDC mode has been known the control of emission reduction is not reflected properly on actual road conditions. For these reasons, diesel vehicle emissions are regulated in both NEDC mode and WLTC mode from 2017 to 2020, from 2020 onwards, the emissions of diesel vehicles will measure in WLTC mode only and will not be able to exceed 1.5 times the regulated value. The purpose of this study is to analyze the development trend of diesel vehicle after-treatment system in order to comply with the future regulations on diesel vehicle. As a result, it is essential to reduce the NOx emissions of diesel vehicles for Euro 6, the NOx emissions of the test vehicle equipped with SCR were 30% to 50% loss than the test vehicle equipped with LNT despite the higher curb weight and engine displacement.

• The Journal of Advanced Prosthodontics
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• v.11 no.5
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• pp.297-304
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• 2019

PURPOSE. This in vitro study investigated the repair bond strength of the zirconia ceramic after different aging conditions. MATERIALS AND METHODS. In order to imitate the failure modes of veneered zirconia restorations, veneer ceramic, zirconia, and veneer ceramic-zirconia specimens were prepared and were divided into 4 subgroups as: control ($37^{\circ}C$ distilled water for 24 hours ) and 3000, 6000, 12000 thermal cycling groups (n=15). Then, specimens were bonded to composite resin using a porcelain repair kit according to the manufacturer recommendation. The repair bond strength (RBS) test was performed using a universal testing machine (0.5 mm/min). Failure types were analyzed under a stereomicroscope. Two-way ANOVA and Bonferroni test were used for statistical analysis. RESULTS. The RBS values of zirconia specimens were statistically significant and higher than veneer ceramic and veneer ceramic-zirconia specimens in control, 3000 and 6000 thermal cycling groups (P<.05). When 12000 thermal cycles were applied, the highest value was found in zirconia specimens but there was no statistically significant difference between veneer ceramic and veneer ceramic-zirconia specimens (P>.05). Veneer ceramic specimens exhibited cohesive failure types, zirconia specimens exhibited adhesive failure types, and veneer ceramic-zirconia specimens exhibited predominately mixed failure types. CONCLUSION. Thermal cycling can adversely affect RBS of composite resin binded to level of fractured zirconia ceramics.

• Earthquakes and Structures
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• v.17 no.4
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• pp.387-398
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• 2019

On the basis that ground motions may arrive at a structure from any horizontal direction and that different directions of seismic incidence would result in different structural dynamic responses, this paper focuses on orienting the crucial seismic incidence of transmission tower-line systems based on the wavelet energy method. A typical transmission tower-line system is chosen as the case study, and two finite element (FE) models are established in ABAQUS, with and without consideration of the interaction between the transmission towers and the transmission lines. The mode combination frequency is defined by considering the influence of the higher-order modes of the structure. Subsequently, wavelet transformation is performed to obtain the total effective energy input and the effective energy input rate corresponding to the mode combination frequency to further judge the critical angle of seismic incidence by comparing these two performance indexes under different seismic incidence angles. To validate this approach, finite element history analysis (FEHA) is imposed on both FE models to generate comparative data, and good agreement is found. The results demonstrate that the wavelet energy method can forecast the critical angle of seismic incidence of a transmission tower-line system with adequate accuracy, avoiding time-consuming and cumbersome computer analysis. The proposed approach can be used in future seismic design of transmission tower-line systems.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.107-116
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• 1993

In the design and operation of robitic arm with flexible links, the equation of motion are required to exactly model the interaction between rigid body motion and elastic motion and to be formulated efficientlyl. In this paper, the flexible link is represented by applying the D-H rigid link representation method to measure the elestic deformation. And the equations of motion of robotic arm, which are configured by the generalized coordinates of elastic and rigid degrees of freedom, are formulated from the principle of virtual power. Dynamic characteristics due to elastic deformation of each link are obtained by using F. E. M to model complex shaped link acurately and by eliminating elastic modes of higher order that do not largely affect motion to reduce the number of elastic degrees of freedom. Also presented is the result of simulation of flexible robotic arms whose joints are controlled by direct or PD control.

• Structural Engineering and Mechanics
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• v.87 no.3
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• pp.211-219
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• 2023

The structural health of a pipeline is usually assessed by visual inspection. In addition to the fact that this method is expensive and time consuming, inspection of the whole structure is not possible due to limited access to some points. Therefore, adopting a damage detection method without the mentioned limitations is important in order to increase the safety of the structure. In recent years, vibration-based methods have been used to detect damage. These methods detect structural defects based on the fact that the dynamic responses of the structure will change due to damage existence. Therefore, the location and extent of damage, before and after the damage, are determined. In this study, fuzzy genetic algorithm has been used to monitor the structural health of the pipeline to create a fuzzy automated system and all kinds of possible failure scenarios that can occur for the structure. For this purpose, the results of an experimental model have been used. Its numerical model is generated in ABAQUS software and the results of the analysis are used in the fuzzy genetic algorithm. Results show that the system is more accurate in detecting high-intensity damages, and the use of higher frequency modes helps to increase accuracy. Moreover, the system considers the damage in symmetric regions with the same degree of membership. To deal with the uncertainties, some error values are added, which are observed to be negligible up to 10% of the error.

• Steel and Composite Structures
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• v.44 no.4
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• pp.531-543
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• 2022

An exact dynamic analytical method for free vibrations of continuous partial-interaction composite beams is proposed based on the Timoshenko beam theory. The main advantage of this method is that the independent shear deformations and rotary inertia of sub-beams are considered, which is more in line with the reality. Therefore, the accuracy of eigenfrequencies obtained by this method is significantly improved, especially for higher order modes, compared to the existing methods where the rotary angles of both sub-beams are assumed to be equal irrespective of the differences in the shear stiffness of each sub-beam. Furthermore, the solutions obtained by the proposed method are exact owing to no introduction of approximated displacement and force fields in the derivation. In addition, an exact analytical solution for the case of simply supported is obtained. Based on this, an approximate expression for the fundamental frequency of continuous partial-interaction composite beams is also proposed, which is useful for practical engineering applications. Finally, the practicability and effectiveness of the proposed method and the approximate expression are explored using numerical and experimental examples; The influence factors including the interfacial interaction, shear modulus ratio, span-to-depth ratio, and side-to-main span length ratio on the eigenfrequencies are presented and discussed in detail.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.5
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• pp.495-503
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• 1997

In this paper, the E-polarized electromagnetic scattering problems by a resistive strip grating with tapered resistivity on 3 dielectric layers are analyzed to find out the effects for the tapered resistivity of resistive strip and the relative permittivity and thickness of 3 die- lectric layers by applying the Fourier-Galerkin moment methods. The induced surface current density is expanded in a series of Jacobi-polynomial ${P^{(\chi,\beta)}}_p$(.) of the order $\alpha$= 0 and $\beta$=1 as a kind of orthogonal polyomians, and the tapered resistivity assumes to vary linearly from 0 at one edge to finite resistivity at the other edge. The normalized reflected and transmitted powers are obtained by varying the tapered resistivity and the relative permittivity and thickness of dielectric layers. The sharp variation points are observed when the higher order modes are transferred between propagating and evanescent modes, and in general the local minimum positions occur at less grating period for the more relative permittivity of dielectric layers. It should be noted that the patterns of the normalized reflected and transmitted powers for the tapered resistivity are very much different from those of the uniform resistivity and perfectly conducting cases. The proposed method of this paper cna solve the scattering problems for the tapered resistive, uniform resistive, and PEC strip cases.