• Journal of the Korean School Mathematics Society
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• v.15 no.2
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• pp.299-316
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• 2012

In this paper, we examine high school in order to know their ability for understanding about fundamental functions, such as polynomial, trigonometric, logarithm and exponential functions which have learned from high school. The result of this study shows as follows. More than half students are not able to draw shape of given functions, except polynomial. More students do not fully understand about function properties such as domain, codomain, range, maximum and minimum value.

• Journal of Korean Ophthalmic Optics Society
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• v.2 no.1
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• pp.17-24
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• 1997

The Voight function which results from the convolution of the Gauss and Lorentz function is applied the MAS-NMR simulation of mixed alkali glasses and the glasses doped transition metal oxides. It is well known that the convolution of the Gauss and Lorentz function cannot be integrated in closed form for arbitrary values. So we make the new computer simulation program from which the Voight lineshape is obtained. The results are accorded well with the MAS-NMR spectra and we can find out the very small change of MAS-NMR lineshape.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.519-526
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• 2005

Hydrolysis of soda-lime waste glass was investigated to test the feasibility for use of waste glass as feed material in the production of foamed glass. The soda-lime glass, such as plate glass and various bottle glasses, was effectively hydrolyzed by steam and water under high pressure. The proper condition for the hydrolysis was found to be reaction temperature of $250^{\circ}C$ and reaction time of 2 h. Under this condition, the water content of hydrated glass through hydrolysis was 7.85~10.04%, allowing successful foaming process for production of foamed glass. Using Na as the modifying agent of glass was effective in the hydrolysis by water. The highest water content of hydrated glass was obtained when weight ratio of NaOH to the glass was 0.04.

• The Journal of the Korea Contents Association
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• v.9 no.2
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• pp.97-105
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• 2009

This paper presents a combination of the generalized Cascade Correlation and generalized Recurrent Cascade Correlation learning algorithms. The new network will be able to grow with vertical or horizontal direction and with recurrent or without recurrent units for the quick solution of the pattern classification problem. The proposed algorithm was tested learning capability with the sigmoidal activation function and hyperbolic tangent activation function on the contact lens and balance scale standard benchmark problems. And results are compared with those obtained with Cascade Correlation and Recurrent Cascade Correlation algorithms. By the learning the new network was composed with the minimal number of the created hidden units and shows quick learning speed. Consequently it will be able to improve a learning capability.

• Communications of Mathematical Education
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• v.21 no.2 s.30
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• pp.283-302
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• 2007

It is said that the university mathematics education in Korea faces critical situations due to the decreases of both qualities and quantities of students. In this paper we examine college students in order to know their basic ability for understanding about fundamental functions, such as polynomial, trigonometric, logarithm and exponential functions which have learned from highschool mathematics courses. The subject are 354 freshmen of 4 universities located in Daejeon and Chongchung area. The result of this study shows as follows. i ) More than half students are not able to draw graphs of given functions, except polynomial. ii ) More students do not fully understand about function properties such as domain, codomain, range, max and min value, cycle and parallel translation.

• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.1-11
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• 2017

In this study, novel approximate form of the square-root operator of three dimensional acoustic Parabolic Equation (3D PE) is proposed using a rational approximant for two variables. This form has two advantages in comparison with existing approximation studies of the square-root operator. One is the wide-angle capability. The proposed form has wider angle accuracy to the inclination angle of ${\pm}62^{\circ}$ from the range axis of 3D PE at the bearing angle of $45^{\circ}$, which is approximately three times the angle limit of the existing 3D PE algorithm. Another is that the denominator of our approximate form can be expressed into the product of one-dimensional operators for depth and cross-range. Such a splitting form is very preferable in the numerical analysis in that the 3D PE can be easily transformed into the tridiagonal matrix equation. To confirm the capability of the proposed approximate form, comparative study of other approximation methods is conducted based on the phase error analysis, and the proposed method shows best performance.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.107-113
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• 2004

In order to model a connection part between a control fin and actuator, the related characteristics of a dynamic stiffness were extracted from experiments. These characteristics include the static stiffness of a control fin and the dynamic stiffness of an actuator, so they are called the mixed dynamic stiffness here. This mixed dynamic stiffness is used as the boundary condition of a control fin connected to an actuator when the flutter characteristics are analyzed. The simulated stiffness of an actuator is corrected from the experiment results and the mixed dynamic is finally formulated in the domain of frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.573-578
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• 2009

Starting from the rotating beam finite element in which the interpolating shape functions satisfies the governing static homogeneous differential equation of Euler-Bernoulli rotating beams, we derived new shape functions that satisfies the governing differential equation which contains the terms of hub radius and setting angle. The shape functions are rational functions which depend on hub radius, setting angle, rotational speed and element position. Numerical results for uniform and tapered cantilever beams with and without hub radius and setting angle are compared with the available results. It is shown that the present element offers an accurate method for solving the free vibration problems of rotating beam.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.6
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• pp.591-598
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• 2009

Starting from the rotating beam finite element in which the interpolating shape functions satisfy the governing static homogeneous differential equation of Euler-Bernoulli rotating beams, we derived new shape functions that satisfy the governing differential equation which contains the terms of hub radius and setting angle. The shape functions are rational functions which depend on hub radius, setting angle, rotational speed and element position. Numerical results for uniform and tapered cantilever beams with and without hub radius and setting angle are compared with the available results. It is shown that the present element offers an accurate method for solving the free vibration problems of rotating beams.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.642-645
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• 2016

본 논문은 풍력 발전기와 ESS(Energy Storage System)를 효율적으로 연결하는 퍼지 스위치를 제안한다. 최근들어 친환경 전력 시스템의 중요성이 날로 커지고 있다. 친환경 에너지의 대표적인 태양광과 풍력의 경우 지속적인 발전이 불가능하므로 ESS의 사용이 필수적이다. 즉, 발전 가능할 때에 ESS에 충전하고 발전이 어려울 때는 ESS를 방전하는 방식이다. 이러한 스위치는 애매 모호한 구간이 존재하는데 이를 효율적으로 제어하기 위하여 퍼지를 적용하였다. 충전레벨이 낮을 경우 충전하고 충전레벨이 높을 경우 방전하는 것은 기본적인 로직이지만 충전레벨이 중간인 경우 충전이 유리한지 방전이 유리한지 모호해진다. 3단계 충전레벨과 2단계 전력레벨을 입력으로 받아 효율적인 퍼지 스위치를 구성하였다. 또한 효과적인 구현을 위하여 서피스플롯울 참조테이블로 변환하여 사용하였다. 특히, 3단계 충전레벨은 가우시한 함수를 사용하고 2단계 전력레벨은 삼각함수를 사용하여 출력 멤버쉽함수가 보다 잘 반영될 수 있도록 감안하였다.