• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.115-119
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• 2005

In this paper, we propose a method that search the sweet spot of array antenna beam, and keep it for fast speed transmission in millimeter wave on single array antenna link. We use TDD(Time Division Duplex) as transfer method, and it transfers the control data of antenna. The proposed method is the modified genetic algorithm which selects a superior initial group through slave-processing in order to resolve the local solution of genetic algorithm. The efficiency of the proposed method is verified by means of simulations with white Gaussian noise and not on single array antenna link.

• Journal of Aerospace System Engineering
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• v.12 no.6
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• pp.41-49
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• 2018

In this study, the theoretical dynamic characteristics of a thin-walled composite beam with a single-cell of chordwise asymmetric cross-section was studied. Mathematical modeling was done by considering the transverse shear effects, the warping restraint effects, the constant taper ratio in the longitudinal direction of the beam, and the geometrical cross-section ratio. The mass coefficients, stiffness coefficients, and Eigen frequencies of the selected section were investigated. In particular, the effects of the taper ratio and cross-section ratio of the model on the Eigen frequencies were analyzed and compared when the asymmetry of the section was considered and the warping function was not corrected.

• The Journal of the Acoustical Society of Korea
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• v.25 no.7
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• pp.333-338
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• 2006

This paper proposes an improved do-noising method using multi-thresholding function based on translation-invariant (W) wavelet proposed by Donoho et al. for underwater radiated noise measurement. The traditional wavelet thresholding de-noising method causes Pseudo-Gibbs phenomena near singularities due to discrete wavelet transform. In order to suppress Pseudo-Gibbs Phenomena, a do-noising method combining multi-thresholding function with the translation-invariant wavelet transform is proposed in this paper. The multi-thresholding function is a modified soft-thresholding to each node according to the discriminated threshold so as to reject かon external noise and white gaussian noise. It is verified by numerical simulation. And the experimental results are confirmed through sea-trial using multi-single sensors.

• The Transactions of the Korea Information Processing Society
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• v.6 no.6
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• pp.1542-1555
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• 1999

This paper proposes an algorithm for class hierarchies which can optimize member data and member function. This algorithm considers single/multiple inheritance, static/dynamic binding, overloading/overriding, pure virtual/virtual function, and constructor on the hierarchy of C++ class. We need to eliminate unused function that possesses many component element, because the program uses a limited of function in class hierarchies. Previous works on slicing mainly focused on selecting output data and including the related program statement. It was consists of structured programming language and also centralized on error detection, maintenance, and flexible testing. In this paper, we extend to the object-oriented language, makes a linked-table for objects to raise the efficiency of information management, and proposes necessary algorithm for optimizing system Through this process, we can obtain the simplification of program code and the progress of system performance by eliminating unused member data and member function.

• School Mathematics
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• v.11 no.1
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• pp.111-129
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• 2009

This paper is about didactical transposition, which is to transpose academic knowledge into practical knowledge intended to teach. The research questions are addressed as follows. 1. Are the 13 mathematics textbooks of the 10-Na level indisputable regarding with the didactical transposition, in terms that the order of arrangement and the way of explaining the knowledge of trigonometric functions being analyzed and that its logical construction and students' understandings are considered? 2. Can some transpositions for easier use of didactical manipulative, for more practical and for more principle based be proposed? To answer these questions, this research examined previous studies of mathematics education, specifically the organization of the textbook and the trigonometric functions, and also compared orders of arranging and ways of explaining trigonometric functions from the perspective of didactical transposition of 13 versions of the 10-Na level reorganized under the 7th curriculum. The paper investigated what lacks in the present textbook and sought a teaching guideline of trigonometric functions(especially about sector and graph, period, characters of trigonometric function, and sine rule).

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.259-259
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• 2019

시계열 자료들을 분석하고자 하는 경우 자료가 정상성(stationarity)을 만족하는 경우는 드물다. 특히 계절성을 제거한 자료들에서는 정량화하기 어려운 주기성이 많이 관찰된다. 즉, 어떤 특정지역에서 나타나는 현상이 다른 기상 현상에 영향을 미칠 것은 자명한 일이나 그 관련성이 선형(linearity)일 가능성은 극히 드물다. 따라서 그들 사이의 관련성이 선형성에 근거한 지표들로 정량화되어야 한다. 이러한 문제점을 해결하기 위해서 다양한 방법이 사용되며 그중에서 웨이블릿 분석을 통해 본 연구를 진행하였다. 웨이블릿 변환(wavelet transforms)은 특수한 함수의 집합으로 구성되어 기존 웨이블릿 신호의 분석을 위해 사용되는 방법이다. 이 변환은 푸리에 변환에서 변형된 방법으로 특정한 기저 함수(base function)를 이용하여 기존의 시계열 자료를 주파수로 바꾸는 변환이다. 웨이블릿 변환에서 기저 함수를 모 웨이블릿이라고 하며 이를 천이, 확대 및 축소 과정을 통해 주파수를 구성한다. 웨이블릿 분석은 모 웨이블릿을 분해하고 재결합하여 시계열 분석을 할 수 있다. 모 웨이블릿 함수에는 Haar, Daubechies, Coiflets, Symlets, Morlet, Mexican Hat, Meyer 등의 여러 가지 종류의 모 웨이블릿 함수가 있으며 모 웨이블릿이 달라지면 결과가 다르게 나타난다. 기존에는 Morlet 웨이블릿을 주로 이용하여 주파수분석에 사용하여 결과를 도출하였다. 그리고 시계열 자료는 크게 백색잡음(White Noise), 장기기억(Long Term Memory), 단기기억(Short Term Memory)으로 나뉜다. 각 시계열 자료의 종류에 따라 임의의 시계열 자료를 산정하여 그에 따른 웨이블릿 분석을 통해 모 웨이블릿의 특성을 도출하였다. 본 연구에서는 웨이블릿 분석을 통해 시계열 자료의 최적 모 웨이블릿을 결정하고자 남방진동지수(SOI), 북극진동지수(AOI)의 자료를 이용하여 웨이블릿 분석을 시도하였다. 웨이블릿 분석은 모 웨이블릿에 따라 달라지는 결과를 토대로 분석하였으며 이를 정상성과 지속성에 따라 분류된 시계열에 적용하여 최적 모 웨이블릿을 결정하고자 하였다. 본 연구에서는 임의의 시계열 자료에서 설정한 최적의 모 웨이블릿을 AOI와 SOI와 같은 실제 시계열 자료에 대입하여 분석을 진행하였다. 본 연구에서는 시계열 자료의 종류를 구분하고 자료의 특성에 따라 가장 적합한 모 웨이블릿을 구하고자 하였다.

• The Korean Journal of Applied Statistics
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• v.36 no.4
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• pp.309-322
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• 2023

The Hawkes process is a point process with self-exciting characteristics. It has been mainly used to describe seismic phenomena in which aftershocks occur due to the main earthquake. Recently, it has been used to explain various phenomena with self-exciting properties, such as the spread of infectious diseases and the spread of news on SNS. The Hawkes process can be flexibly modified according to the characteristics of events by using various types of excitation functions. Since it is difficult to implement a maximum likelihood estimator numerically, estimation methods have been improved until recently. In this paper, the conditional intensity function and excitation function are explained to describe the Hawkes process. Then, existing examples of Hawkes processes used in seismic, epidemiological, criminal, and financial fields are described and estimation methods are introduced. I analyze earthquakes that occurred in gyeongsang-do, Korea from November 2017 to December 2022, using R package ETAS.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.795-798
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• 1998

In this paper, a new class of bandpass filter using a modified Chebyshev lowpass filter function is described. The prosposed bandpass filter which exhibits diminishing ripples in the passband has maximum value at the center frequency. Due to the lower pole-Q, the performance in the frequency and time domains is improved as compared with the classical Chebyshev bandpass filter.

• Transactions of the Korean Society of Mechanical Engineers
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• v.6 no.2
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• pp.169-175
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• 1982

원주체의 전단스피닝 가공에서 가공물의 반경과 두께 방향의 상대 위치가 변화하지 않는다는 조건 아래서 흐름 함수에 의하여 속도장을 구하고, 접촉계수에 대하여 변형에너지의 국소치를 구함으로써 상당히 낮은 상계치를 얻었으며, 이를 A1-1100-1, A1-1100-H14, A1-6061-0 등 여러 가지 재료에 대한 실험치와 비교한 결과, 정량적으로 일치하였다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.11a
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• pp.303-308
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• 1998

암반을 대상으로 하는 건설공사는 많은 시간과 비용, 설계, 시공, 안전상에 많은 문제점을 일으키고 있다. 이러한 암반들은 흡수, 풍화 등에 기인하여 안정성이 약화되어 낙석, 산사태, 붕괴 등의 위험을 안고 있으며 이러한 현상은 우기, 해빙기에 두드러지게 나타나고 있다 비균질, 비등방성의 역학적 성질을 지닌 암석은 변형 거동을 완벽하게 예측하지는 못하고 있는 실정으로 이러한 거동은 암석의 종류와 구성 광물, 내부 불연속면의 상태, 응력 조건과 온도, 습도의 함수비등과 같은 다양한 요소에 의해 영향을 받으며, 이러한 경향은 퇴적암의 경우 두드러지게 나타나고 있다. (중략)