• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1992.04a
• /
• pp.58-64
• /
• 1992

It is usual that underground structures are constructed within multi-layered medium. In this paper, an efficient numerical model ling of multi-layered structural systems is studied using coupled analysis of finite elements and boundary elements. The finite elements are applied to the area in which the material nonlinearity is dominated, and the boundary elements are applied to the far field area where the nonlinearity is relatively weak. In the boundary element model 1 ins of the multi-layered medium, fundamental solutions are restricted. Thus, methods which can utilize existing Kelvin and Melan solution are sought for the interior multi-layered domain problem and semi infinite domain problem. Interior domain problem which has piecewise homogeneous layers is analyzed using boundary elements with Kelvin solution; by discretizing each homogeneous subregion and applying compatibility and equilibrium conditions between interfaces. Semi-infinite domain problem is analyzed using boundary elements with Melan solution, by superposing unit stiffness matrices which are obtained for each layer by enemy method. Each methodology is verified by comparing its results which the results from the finite element analysis and it is concluded that coupled analysis using boundary elements and finite elements can be reasonable and efficient if the superposition technique is applied for the multi-layered semi-infinite domain problems.

• Bulletin of the Korean Mathematical Society
• /
• v.50 no.1
• /
• pp.175-184
• /
• 2013

In this paper, the reverse Bonnesen style inequalities for convex domain in the Euclidean plane $\mathbb{R}^2$ are investigated. The Minkowski mixed convex set of two convex sets K and L is studied and some new geometric inequalities are obtained. From these inequalities obtained, some isoperimetric deficit upper limits, that is, the reverse Bonnesen style inequalities for convex domain K are obtained. These isoperimetric deficit upper limits obtained are more fundamental than the known results of Bottema ([5]) and Pleijel ([22]).

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.10a
• /
• pp.137-142
• /
• 2003

A fundamental study for developing a system of fault diagnosis of a pump is performed by using neural network. The acoustic signals were obtained and converted to frequency domain for normal products and artificially deformed products. The signals were obtained in various driving frequencies in order to obtain many types of data from a limited number of pumps. The acoustic data in frequency domain were managed to multiples of real driving frequency with the aim of easy comparison. The neural network model used in this study was 3-layer type composed of input, hidden, and output layer. The normalized amplitudes at the multiples of real driving frequency were chosen as units of input layer, Various sets of teach signals made from original data by eliminating some random cases were used in the training. The average errors were approximately proportional to the number of untaught data. The results showed neural network trained by acoustic signals can be used as a simple method far a detection of machine malfunction or fault diagnosis.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.13 no.5
• /
• pp.81-86
• /
• 2004

A fundamental study for developing a system of fault diagnosis of a pump is performed by using neural network. The acoustic signals were obtained and converted to frequency domain for normal products and artificially deformed products. The signals were obtained in various driving frequencies in order to obtain many types of data from a limited number of pumps. The acoustic data in frequency domain were managed to multiples of real driving frequency with the aim of easy comparison. The neural network model used in this study was 3-layer type composed of input, hidden, and output layer. The normalized amplitudes at the multiples of real driving frequency were chosen as units of input layer. Various sets of teach signals made from original data by eliminating some random cases were used in the training. The average errors were approximately proportional to the number of untaught data. The results showed neural network trained by acoustic signals can be used as a simple method for a detection of machine malfuction or fault diagnosis.

• Journal of the Korean School Mathematics Society
• /
• v.15 no.4
• /
• pp.719-745
• /
• 2012

This research is a study on student's understanding fundamental conception of mathematical curriculum, especially in geometry domain. The goal of researching is to analyze student's wrong conception about that domain and get the mathematical teaching method. We developed various questions of descriptive assessment. Then we set up the term, procedure of research for the understanding student's knowledge of geometry. And we figured out the student's understanding extent through analysing questions of descriptive assessment in geometry. In this research, we concluded that most of students are having difficulty with defining the fundamental conception of mathematics, especially in geometry. Almost all the students defined the fundamental conceptions of mathematics obscurely and sometimes even missed indispensable properties. Prior to this study, we couldn't identify this problem. Here are some suggestions. First, take time to reflect on your previous mathematics method. And then compile some well-selected questions of descriptive assessment that tell us more about student's understanding in geometry.

• Journal of the Korea Convergence Society
• /
• v.9 no.7
• /
• pp.301-308
• /
• 2018

The study conducted a meta analysis to identify the effects of physical activity programs for the elderly with disabilities. The 14 out of 177 studies, fulfilled the process and requirement, were selected for the Hedges'g, funnel plot, forest plot, Egger's regression test, trim-and-fill, fail-safe N. There were three conclusions based on the results. First, the physical activity was effective for the elderly with disabilities and showed good effects on the psychomotor, cognitive, and affective domains. Second, the physical activity programs of fundamental exercise skill, game and sport, and fitness exercise showed positive effects on the psychomotor, cognitive, and affective domains in the elderly with disabilities. Third, the fundamental exercise skill for the psychomotor domain, the game and sport for the cognitive domain, and the fitness exercise for the affective domain were the most effective for the elderly with disabilities.

• Journal of Ecology and Environment
• /
• v.36 no.3
• /
• pp.193-204
• /
• 2013

Altitudinal patterns of plant species richness and the effects of area, the mid-domain effect, climatic variables, net primary productivity and latitude on observed richness patterns along the ridge of the Baekdudaegan Mountains, South Korea were studied. Data were collected from 1,100 plots along a 200 to 1,900 m altitudinal gradient on the ridge. A total of 802 plant species from 97 families and 342 genera were recorded. Common and rare species accounted for 91% and 9%, respectively, of the total plant species. The altitudinal patterns of species richness for total, common and rare plants showed distinctly hump-shaped patterns, although the absolute altitudes of the richness peaks varied somewhat among plant groups. The mid-domain effect was the most powerful explanatory variable for total and common species richness, whereas climatic variables were better predictors for rare plant richness. No effect of latitude on species richness was observed. Our study suggests that the mid-domain effect is a better predictor for wide-ranging species such as common species, whereas climatic variables are more important factors for range-restricted species such as rare species. The mechanisms underlying these richness patterns may reflect fundamental differences in the biology and ecology of different plant groups.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.11
• /
• pp.1143-1148
• /
• 2003

The distortion of picosecond pulses caused by dispersion as it propagates along microstripline and CPW(Coplanar waveguide) is investigated and measured using time domain measurement. Especially, this study presents that the distortion of these lines is analyzed and compared considering the relation between the dispersion effect and cut-off frequency(f$\_$TE/) of fundamental TE mode for the substrate of line. To verify theoretical results, several samples of 50 $\Omega$ lines are fabricated on the two kind of substrates with the different values of f$\_$TE/. The propagation characteristics of picosecond Gaussian pulse on thess lines are simply measured using VNA(Vector Network Analyzer) with the time-domain analysis function.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.3
• /
• pp.1-7
• /
• 2019

In this paper, we propose an approach to design a practical filter and a mathematical modeling for images. In the areas of signal processing, including high-dimensional image processing, the filtering process has been fundamental and crucial in diverse practical applications such as image processing, computer vision, and pattern recognition. In general, the ideal filter is modeled as circular-shaped in the 2D frequency domain as the rectangular shape is ideal for the 1D frequency domain. This paper proposes an approach to modeling practical and efficient image filter in the 2D frequency domain. Instead of employing a circular-shaped filter, this study proposes a polygon-shaped filter inspired by the concept of a hexagon cellular system for frequency reuse in wireless communication systems. By employing the concept of frequency reuse, bandwidth efficiency is also achieved in the frequency domain. To substantiate the proposed approach, quantitative evaluation is performed using PSNR.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.1
• /
• pp.99-108
• /
• 2013

The high-voltage pulse generator is consist of transformers of fundamental wave and harmonic waves, and shunt capacitances. The pulse has the fundamental wave and the harmonic waves that have been increased as a series circuit by the transformers to make high voltage pulse. This paper shows that pulse generator circuit is analyzed using Miller's theorem and network theory(ABCD Matrix) and simulated in frequency and time domain using Matlab program. The output voltage of pulse were obtained to 2.5kHz, 1.8kV. Output pulse voltage increases as $L_m$ increases in low voltage circuit. In high voltage circuit, outer capacitors are related to frequency band pass characteristics.