• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.645-650
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• 2004

There have been lots of efforts to analyze the dynamic characteristics of mechanical systems. However, it is difficult to know the dynamic characteristics of mechanical systems composed of many parts with joints. Specially, in case of a bolted joint structure, no effective modeling method has been defined to acquire dynamic characteristics of the structure, using the finite element (FE) analysis. In this research, a linear dynamic model is developed for bolted joints and large interfaces using con frusta method and linear spring elements, respectively. The developed modeling method for bolted joints is verified based on the experimental result.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.990-998
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• 2004

There have been lots of efforts to analyze the dynamic characteristics of mechanical systems. However, it is difficult the know the dynamic characteristics of mechanical systems composed of many parts with joints. Specially, in case of a bolted Joint structure, no effective modeling method has been defined to acquire dynamic characteristics of the structure using the finite element (FE) analysis. In this research, a linear dynamic model is developed for bolted feints and large interfaces using con frusta method and linear spring elements, respectively. The developed modeling method for bolted joints is verified based on the experimental result.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1551-1557
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• 2015

Magnetic coupling is used where required high reliability. because magnetic coupling's durability is stronger than mechanical coupling's durability. This paper shows the characteristics of radially magnetized tubular type magnetic coupling by using Analytical method such as space harmonic method. Analytical method was used, to find force characteristics. First, on the basis of the magnetic vector potential and two-dimensional(2-D) polar-coordinate system, the magnetic field solutions of the radially magnetized permanent magnet are obtained. And we obtain the analytical solutions for the flux density produced by permanent magnet. Finally, we can calculate the force by using the Maxwell stress tensor. And then, Finite element method(FEM) is used to validate force characteristics.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.762-763
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• 2015

Magnetic coupling is used where required high reliability. because magnetic coupling's durability is stronger than mechanical coupling's durability. This paper shows the force characteristics of halbach array magnetized tubular type magnetic coupling using Analytical method. Analytical method was used, to find force characteristics. Finite element method (FEM) is used to validate force characteristics.

• Journal of applied mathematics & informatics
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• v.15 no.1_2
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• pp.29-51
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• 2004

In this paper, we propose a new mixed finite element method, called the characteristics-mixed method, for approximating the solution to Burgers' equation. This method is based upon a space-time variational form of Burgers' equation. The hyperbolic part of the equation is approximated along the characteristics in time and the diffusion part is approximated by a mixed finite element method of lowest order. The scheme is locally conservative since fluid is transported along the approximate characteristics on the discrete level and the test function can be piecewise constant. Our analysis show the new method approximate the scalar unknown and the vector flux optimally and simultaneously. We also show this scheme has much smaller time-truncation errors than those of standard methods. Numerical example is presented to show that the new scheme is easily implemented, shocks and boundary layers are handled with almost no oscillations. One of the contributions of the paper is to show how the optimal error estimates in $L^2(\Omega)$ are obtained which are much more difficult than in the standard finite element methods. These results seem to be new in the literature of finite element methods.

• Journal of Korean Elementary Science Education
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• v.28 no.4
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• pp.440-449
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• 2009

The purpose of this study is to make a preference and result analysis on the free inquiry method of pre-service elementary school teachers. Also, this study investigates how free inquiry activities effect the science-related attitudes and the self-directed learning characteristics of pre-service elementary school teachers. For this study 76, second year, science education pre-service elementary school teachers from Busan National University of education were selected. The inquiry examined the effectiveness of each of the following teaching methods: the IIM method, the PBL method, the PROJECT method, and the small group inquiry method. The students were divided into groups in which they incorporated the respective methods into their practice. In conclusion, the IIM free inquiry activities proved to be much more effective than the PBL method, the PROJECT method, and the small group inquire method in terms of developing self-directed learning characteristics and science related attitudes at the significant difference of p=0.05.

• Journal of the Korean Society of Earth Science Education
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• v.3 no.3
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• pp.239-247
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• 2010

The purpose of this study is to examine the effects of an free inquiry method based on PBL(Problem-Based Learning: PBL) to improve students science process skills and self-directed learning characteristics. To verify this research, twenty-two third-grade students were selected from Chung-ryeol Elementary School located in Busan. They have received pre-test and post-test about their abilities in their science process skills and abilities for self-directed learning characteristics. Also, their self-reflection data was analyzed. The teaching and learning PBL process is to provide the information named 'I am the expert on Earth and Moon' which is recreated by analyzing the science curriculum and characteristics of students from Lesson 3 'Earth and Moon', and to make plans for solving the information with K/NK method. Then, to solve the information is gathered and investigated using the PBL workbook. Lastly, students present their finding using the free inquiry method in a group. The post-test showed following results : first, the free inquiry method based on PBL stimulates inquisitiveness in students about science learning and the research group shows improved science process skill. It shows us that using the free inquiry method based on PBL can be used effects to elevate science process skill. Second, the free inquiry method based on PBL has a positive effect on self-directed learning. The research tells us that using the free inquiry method based on PBL can improve a student self-directed learning characteristics.

• Journal of Korea Multimedia Society
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• v.22 no.5
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• pp.580-587
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• 2019

In this paper, a plane detection method using depth information is proposed. 3-D characteristics of a pixel are defined as a direction and length of a normal vector whose is calculated from a plane consisting of a local region centered on the pixel. Image coordinates of each pixel are transformed to 3-D coordinates in order to obtain the local planes. Regions of each plane are detected by calculating similarity of the 3-D characteristics. The similarity of the characteristics consists of direction and distance similarities of normal vectors. If the similarity of the characteristics between two adjacent pixels is enough high, the two pixels are regarded as consisting of same plane. Simulation results show that the proposed method using the depth picture is more accurate for detecting plane areas than the conventional method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.106-109
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• 2014

In order to obtain dynamic behaviors of complex structures, it demands large amounts computational cost and time to perform the numerical analysis. The model reduction method helps these problems by dividing the full model into primary and unnecessary parts. In this research, we perform the modal analysis using the dynamic substructuring method, which is one of the model reduction methods, in order to obtain the dynamic characteristics of the cylindrical structures efficiently. To select the master degrees of freedom (dofs), we consider the mode shapes of the cylindrical structures. And then, we identify the validity of the dynamic substructuring method by applying the method to the simple cylinder and core support barrel (CSB) which is one of the reactor internals with the cylindrical shape. The results demonstrate that the dynamic characteristics from the dynamic substructuring method are well matched with the original method.

• Journal of Integrative Natural Science
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• v.13 no.3
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• pp.92-96
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• 2020

Taguchi's robust parameter design is an approach to reduce the performance variation of quality characteristics in products and processes. In robust design, the signal-to-noise ratio (SN ratio) was used to find the optimum condition to minimize the variation of quality characteristics as much as possible and bring the average of quality characteristics closer to the target value. In this paper, we propose a simultaneous optimization method based on a linear model of the SN ratio as a method to find the optimal condition of the control factor in case of multi-characteristics. In addition, the proposed method and the existing method were compared and studied by taking actual cases.