• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.411-416
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• 2016

Existing moving robots has several kinds of moving method; using wheel, jointed leg structure and so on. Wheel type can be operated by DC motor so it is simple and efficient. However, it is not appropriate to pass irregular terrain and obstacle. Leg structure type has an advantage in those cases. Generally, Leg structure is operated by several servo motors attached to each joint. It makes a robot heavier and more complicate due to increase of the degree of freedom. However, by using Theo Jansen Mechanism, one (or more) leg have only single-degree of freedom and can be operated by only one DC motor. So leg structure using Theo Jansen Mechanism will be good choice if robots have to be mass-produced. This paper describes the following a walking robot designed and produced based on Theo Jansen Mechanism, simulating process of Theo Jansen leg structure using Edison m.Sketch and how to solve several of discovered problem of the robot.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.170-177
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• 2004

A single degree of freedom system and transmissibility are key concepts in many problems of vibration isolation. In order to apply this approach, however, several assumptions must be satisfied, which are often not realistic. In this paper, an approach using vibration power flow is introduced to deal with vibration isolations in a more practical way. Procedures of this approach and some results of research are presented. Difficulties in this method are also discussed.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.94-95
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• 2002

Recently, we have seen a rapid advance in the evolving field of spin electronics (or spintronics). In spintronics, some feasibilities of new electronic applications utilizing spin degree of freedom have been explored. Diluted magnetic semiconductors (DMSs) are premising materials for spintronics because they have both charge and spin degree of freedom in a single substance. DMSs are refereed to semiconductor alloys in which some atoms are randomly substituted for by magnetic atoms. (omitted)

• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.115-124
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• 2017

In this paper, a different technique to predict the effects of soil-structure interaction (SSI) on seismic response of building systems is investigated. The technique use a machine learning algorithm called Support Vector Regression (SVR) with technical and analytical results as input features. Normally, the effects of SSI on seismic response of existing building systems can be identified by different types of large data sets. Therefore, predicting and estimating the seismic response of building is a difficult task. It is possible to approximate a real valued function of the seismic response and make accurate investing choices regarding the design of building system and reduce the risk involved, by giving the right experimental and/or numerical data to a machine learning regression, such as SVR. The seismic response of both single-degree-of-freedom system and six-storey RC frame which can be represent of a broad range of existing structures, is estimated using proposed SVR model, while allowing flexibility of the soil-foundation system and SSI effects. The seismic response of both single-degree-of-freedom system and six-storey RC frame which can be represent of a broad range of existing structures, is estimated using proposed SVR model, while allowing flexibility of the soil-foundation system and SSI effects. The results show that the performance of the technique can be predicted by reducing the number of real data input features. Further, performance enhancement was achieved by optimizing the RBF kernel and SVR parameters through grid search.

• Structural Engineering and Mechanics
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• v.30 no.4
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• pp.445-466
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• 2008

This paper presents a novel structural damage detection method with a new damage index based on the statistical moments of dynamic responses of a structure under a random excitation. After a brief introduction to statistical moment theory, the principle of the new method is put forward in terms of a single-degree-of-freedom (SDOF) system. The sensitivity of statistical moment to structural damage is discussed for various types of structural responses and different orders of statistical moment. The formulae for statistical moment-based damage detection are derived. The effect of measurement noise on damage detection is ascertained. The new damage index and the proposed statistical moment-based damage detection method are then extended to multi-degree-of-freedom (MDOF) systems with resort to the leastsquares method. As numerical studies, the proposed method is applied to both single and multi-story shear buildings. Numerical results show that the fourth-order statistical moment of story drifts is a more sensitive indicator to structural stiffness reduction than the natural frequencies, the second order moment of story drift, and the fourth-order moments of velocity and acceleration responses of the shear building. The fourth-order statistical moment of story drifts can be used to accurately identify both location and severity of structural stiffness reduction of the shear building. Furthermore, a significant advantage of the proposed damage detection method lies in that it is insensitive to measurement noise.

• International Journal of Control, Automation, and Systems
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• v.3 no.2
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• pp.202-210
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• 2005

This paper presents a new neural network control for nonlinear bridge systems with earthquake excitation. We design multi-layer neural network controllers with a single hidden layer. The selection of an optimal number of neurons in the hidden layer is an important design step for control performance. To select an optimal number of hidden neurons, we progressively add one hidden neuron and observe the change in a performance measure given by the weighted sum of the system error and the control force. The number of hidden neurons which minimizes the performance measure is selected for implementation. A neural network was trained for mitigating vibrations of bridge systems caused by El Centro earthquake. We applied the proposed control approach to a single-degree-of-freedom (SDOF) and a two-degree-of-freedom (TDOF) bridge system. We assessed the robustness of the control system using randomly generated earthquake excitations which were not used in training the neural network. Our results show that the neural network controller drastically mitigates the effect of the disturbance.

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.531-546
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• 2014

In this paper the extension of a recently established energy-based pushover procedure in order to include the higher mode contributions to the seismic response of structures is presented and preliminary evaluated. The steps of the proposed methodology in its new formulation are quite similar to those of the well-known Modal Pushover Analysis. However, the determination of the properties of the 'modal' equivalent single-degree-of-freedom systems is achieved by a rationally founded energy-based concept. Firstly, the theoretical background and the assumptions of the proposed methodology are presented and briefly discussed. Secondly, the sequence of steps to be followed for its implementation along with the necessary equations is systematically presented. The accuracy of the methodology is evaluated by an extensive parametric study which shows that, in general, it provides better results compared to those produced by other similar procedures. In addition, the main shortcoming of the initial version of the methodology now seems to be mitigated to a large extent.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.279-287
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• 2018

This study investigated applicability of the fast running model for damage assessment of underground structures by ground shock. For this reason, the fast running model that consists of two main models such as the ground shock generation and propagation model and the underground structural damage assessment model was developed. The ground shock generation and propagation model was programed using theoretical formula and empirical formula introduced in TM5-855-1(US army manual). The single degree of freedom model of structural components was utilized to predict structural dynamic displacements which are used as index to assess damage level of components. In order to confirm the feasibility of the developed fast running model, underground structural dynamic displacements estimated from the fast running model were compared to displacements obtained from the finite element analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.159-163
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• 2005

A dynamic vibration absorber using the Zener's model has been taken into account with respect to frequency response characteristics. The concept of the tuned mass damper with a single degree of freedom has been well applied for many industrial fields, because many researchers have extensively studied various basic characteristics, performance and optimization methods for long time. The Zener's model has an additional spring, which is connected between a damper and a mass, while the tuned mass damper with a single degree of freedom consists of a mass, a spring and a damper connected in parallel. In previous works, the basic performance and characteristics of the Zoner's model as a dynamic vibration absorber have not been investigated. In this study, the frequency response characteristics according to the parameter change of the Zener's model have been described. In order to find the optimum value of several parameters, we use iterative scheme with three dimensional frequency response diagram by MATLAB programming. Present results shows the Zener's model can give more good damping performance than the simple tuned mass damper, and the numerical of optimization method should be developed for the efficient vibration absorbtion.

• Interaction and multiscale mechanics
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• v.4 no.4
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• pp.273-289
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• 2011

The vibration response of the bridges under the moving vehicular load is of importance for engineers to estimate the serviceability of existing bridges and to design new bridges. This paper deals with the three dimensional vibration analysis of prestressed concrete bridges under moving vehicles. The prestressed bridges are modeled by four-node isoparametric flat shell elements with the transverse shearing deformation taken into account. The usual five degrees-of-freedom (DOFs) per node of the element are appended with a drilling DOF to accommodate the transformation of the local stiffness and mass matrices to the global coordinates. The vehicle is modeled as a single or two-DOF system. A single-span prestressed Tee beam and two-span prestressed box-girder bridge are studied as the two numerical examples. The effects of prestress forces on the natural frequencies and dynamic responses of the bridges are investigated.