• Interaction and multiscale mechanics
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• v.1 no.2
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• pp.279-301
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• 2008

This paper develops a 3D homogenization based continuum damage mechanics (HCDM) model for fiber reinforced composites undergoing micromechanical damage under monotonic and cyclic loading. Micromechanical damage in a representative volume element (RVE) of the material occurs by fiber-matrix interfacial debonding, which is incorporated in the model through a hysteretic bilinear cohesive zone model. The proposed model expresses a damage evolution surface in the strain space in the principal damage coordinate system or PDCS. PDCS enables the model to account for the effect of non-proportional load history. The loading/unloading criterion during cyclic loading is based on the scalar product of the strain increment and the normal to the damage surface in strain space. The material constitutive law involves a fourth order orthotropic tensor with stiffness characterized as a macroscopic internal variable. Three dimensional damage in composites is accounted for through functional forms of the fourth order damage tensor in terms of components of macroscopic strain and elastic stiffness tensors. The HCDM model parameters are calibrated from homogenization of micromechanical solutions of the RVE for a few representative strain histories. The proposed model is validated by comparing results of the HCDM model with pure micromechanical analysis results followed by homogenization. Finally, the potential of HCDM model as a design tool is demonstrated through macro-micro analysis of monotonic and cyclic damage progression in composite structures.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1997.04a
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• pp.53-70
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• 1997

The purpose of this study is to propose what developments for Korean Maritime high school are. In order to find out some proposals, the concerned literature survey and sata are used accordingly. This paper is consisted of 4 chapters. The contents of first chapter are focused on the study purpose and problems facing on the maritime high schools. The second are on the present situation of these schools. The third are on the improving proposals, the fourth are on the conclustions of this paper. The following proposals are abstracted through this study. The first, competent authority should be transferred to ministry of education from ministry of marine. The second, education system should be upgraded to junior college or 5 years education course. The third, maritime university permission should be opened for maritime high schol graduates. The fourth, training ship should be build for effective training course required from STCW 95. The fifth , if the graduates from maritime high school engage on board , all of them should be exempted from military service responsibility. The sixth , the education course should be diversified according to the need and demand from the industry society and students. The seventh, the on board-training system for teachers and instructors should be programmed in order to help them keep and utilize the on board experience in actural eudcation situation.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.2 no.3
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• pp.174-178
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• 2002

This paper discusses a blind equalization technique for FIR channel system, that might be minimum phase or not, in digital communication. The proposed techniques consist of two parts. One is to estimate the original channel coefficients based on fourth-order cumulants of the channel output, the other is to employ RBF neural network to model an inverse system fur the original channel. Here, the estimated channel is used as a reference system to train the RBF. The proposed RBF equalizer provides fast and easy teaming, due to the structural efficiency and excellent recognition-capability of R3F neural network. Throughout the simulation studies, it was found that the proposed blind RBF equalizer performed favorably better than the blind MLP equalizer, while requiring the relatively smaller computation steps in tranining.

• Journal of applied mathematics & informatics
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• v.13 no.1_2
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• pp.11-27
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• 2003

A fourth order in time and second order in space scheme using a finite-difference method is developed for the non-linear Boussinesq equation. For the solution of the resulting non-linear system a predictor-corrector pair is proposed. The method is analyzed for local truncation error and stability. The results of a number of numerical experiments for both the single and the double-soliton waves are given.

• Journal of the Korean Geographical Society
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• v.46 no.2
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• pp.115-133
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• 2011

Yamada's mountain ordering is to be said as an upward system, because the area and volume of the mountains become the larger as more than two lower order mountains constitute the higher order mountain. However, his mountain ordering shows some limitations to totally understand the mountain systems and to systematically manage the various kinds of mountainous informations. Because the independent third, fourth and so on, as well as the second lower order mountains are included in the higher order mountain. In order to solve the problem above, the downward system is suggested as the alternative of his upward system. The downward system means that the higher order mountain is classified into the second lower order mountains, and the second lower order mountain is classified into the third lower order mountains and finally the 2nd order mountain classified into the 1st order mountains. The method to classify a certain mountain systematically into all mountainous elements and the new nomenclature to be used for the classified elements are developed, using the downward system above. And the structure of database could be also suggested for the integrated and systematic management of mountain informations.

• Journal of applied mathematics & informatics
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• v.8 no.1
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• pp.165-180
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• 2001

This paper presents a new difference scheme for numerical solution of stiff system of ODE’s. The present study is mainly motivated to develop an absolutely stable numerical method with a high order of approximation. In this work a double implicit A-stable difference scheme with the sixth order of approximation is suggested. Another purpose of this study is to introduce automatic choice of the integration step size of the difference scheme which is derived from the proposed scheme and the one step scheme of the fourth order of approximation. The algorithm was tested by means of solving the Kreiss problem and a chemical kinetics problem. The behavior of the gas explosive mixture (H₂+ O₂) in a closed space with a mobile piston is considered in test problem 2. It is our conclusion that a hydrogen-operated engine will permit to decrease the emitted levels of hazardous atmospheric pollutants.

• International Journal of Control, Automation, and Systems
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• v.3 no.3
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• pp.387-396
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• 2005

The Rotational/Translational Actuator (RTAC) benchmark problem considers a fourth-order dynamical system involving the nonlinear interaction of a translational oscillator and an eccentric rotational proof mass. This problem has been posed to investigate the utility of a rotational actuator for stabilizing translational motion. In order to experimentally implement any of the model-based controllers proposed in the literature, the values of model parameters are required which are generally difficult to determine rigorously. In this paper, an approach to the least-squares estimation of the parameters of a system is formulated and practically applied to the RTAC system. On the other hand, this paper shows how to model a nonlinear system as a linear uncertain system via nonparametric system identification, in order to provide the information required for linear robust $H_\infty$ control design. This method is also applied to the RTAC system, which demonstrates severe nonlinearities, due to the coupling from the rotational motion to the translational motion. Experimental results confirm that this approach can effectively condense the whole nonlinearities, uncertainties, and disturbances within the system into a favorable perturbation block.

• Proceedings of the Technology Innovation Conference
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• 2000.06a
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• pp.65-83
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• 2000

In this study, we propose an expert system aided model necessary for extracting the rules, which can diagnose the success level of new product development project. For this purpose, first, we design a classification model to analyze the characteristics of $\ulcorner$parts development projects$\lrcorner$. Second, in order to select success factors, we explore literatures and interview with project managers working at large sized companies of electronic parts. And we conduct the enquete survey and statistical analysis to extract key success factors. Third, in order to decide the level of project success, we use the concept of 'Recearchitivity' as a framework of judgement criteria. Fourth, in order to extract diagnosis rules, we use expert system development tool.

• 한국전산유체공학회:학술대회논문집
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• 1996.05a
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• pp.46-51
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• 1996

The flow field around a three dimensional minivan-like body has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using second-order accurate schemes for the time derivatives, and third/second-order scheme for the spatial derivatives. The Marker-and-Cell concept is applied to efficiently solve continuity equation. The fourth -order artificial damping is added to the continuity equation for numerical stability. A H-H type multi-block grid system is generated around a three dimensional minivan-like body. Turbulent flows have been modeled by the Baldwin-Lomax turbulent model. The simulation shows three dimensional vortex-pair just behind body. And the flow separation is also observed the rear of the body. It has concluded that the results of present study properly agree with physical flow phenomena.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.551-556
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• 2018

With the rise of the fourth industrial revolution, the importance of establishing R&D strategies to develop ICT technologies such as Big Data, Artificial Intelligence, Robots, the Internet of Objects, and 3D Printing is increasing. In this study, we analyzed the effects of the fourth industrial revolution on society and the present state of the national defense technology planning system, and proposed improvement measures for the utilization of the fourth industrial revolution in the defense industry from the perspective of defense R&D. The current defense R&D strategy focuses on securing the core technologies of each weapon system required by the military through research and development. Under the current system, the role of fourth industrial revolution technology will be confined to some of the weapons systems required by the military. In order to overcome this limitation, we propose a technology roadmap for the future weapons systems.