• 충청수학회지
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• 제28권3호
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• pp.391-396
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• 2015

$C^1$-generically, if a transitive diffeomorphism f is periodically expansive, then it is hyperbolic.

• 한국구조물진단유지관리공학회 논문집
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• 제15권1호
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• pp.120-128
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• 2011

변전소 구조물은 가스절연개폐기의 개폐로 유발되는 주기적인 충격하중을 받게 된다. 이러한 주기적인 충격하중은 구조물의 노후화 및 열화를 가속화하여 구조물의 일부 부재 혹은 전반적인 강성 감소를 초래할 수 있다. 본 연구에서는 이러한 주기적인 충격하중이 구조물에 미치는 영향을 정량적으로 평가하고, 손상 정도를 평가하는 방법을 선정하고자 한다. 따라서, 개략적인 손상 정도를 파악할 수 있는 효율적인 방법으로 인지되고 있는 시스템식별기법을 선정하였다. 선정된 기법에 대한 신뢰성을 검증하기 위해 3층 1경간 축소 모형을 대상으로 모의 손상실험 및 해석을 통해 모드형상 및 고유진동수를 산정하고 결과를 비교하였다.

• 대한전기학회논문지:전력기술부문A
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• 제48권9호
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• pp.1147-1153
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• 1999

The attitude control of a double inverted pendulum with a periodical disturbance at link top is dealt in this paper. The proposed system is consisted of the double inverted pendulum and a disturbing link; a triple inverted pendulum with two motors. The lower link is hinged on the plate to free for rotation in the vertical plane. The upper link is connected to the lower link through a DC motor. The DC motor is used to control the posture of the pendulum by adjusting the position of the upper link. The periodical disturbance can be generated by the additional like attached at the end of link 2 through another DC motor, which is the modeling of a posture for a biped supporting with one leg. The motor for the joint simulates the knee joint(or hip joint) and the disturbance for the legs moving in air. The algorithm for controlling the proposed inverted pendulum which is regarded as a virtual double inverted pendulum with a periodic disturbance, is consisted of a state feedback control and a fuzzy logic controller connected in parallel. The fuzzy controller keeps the center of gravity of the biped within the specified range through the nonlinear feedback compensator. The state feedback control takes over the role to maintain a desired posture regardless the disturbance at the link top. Simulations with a mathematical model and experiments are conducted to show the validity of the proposed controller.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2309-2311
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• 1998

The attitude control of a double inverted pendulum with a periodical disturbance at link top is dealt in this paper. The proposed system is consisted of the double inverted pendulum and a disturbance link. The lower link is hinged on the plate to free for rotation in the vertical plane. The upper link is connected to the lower link through a DC motor. The DC motor is used to control the posture of the pendulum by adjusting the position of the upper link. The periodical disturbance can be generated by the additional link attached at the end of link 2 through another DC motor, which is the modeling of a posture for a biped supporting with one leg. The motor for the joint simulates the knee joint(or hip joint) and the disturbance for the legs moving in air. The algorithm for controlling a proposed inverted pendulum is consisted of a state feedback control and a fuzzy logic controller. The fuzzy controller keeps the center of gravity of the biped within the specified range through the nonlinear feedback compensator. The state feedback control takes over the role to maintain a desired posture regardless the disturbance at the link top. In these case, the change of the angle and COG of an upper link is compensated with on-line. Simulations with a mathematical model are conducted to show the validity of the proposed controller.

• 한국수학사학회지
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• 제20권1호
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• pp.17-32
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• 2007

이 논문에서는 19세기 초에 영국 케임브리지 대학에서 나타났던 '해석학회'를 중심으로 18세기 후반에서 19세기 전반까지의 영국 수학계의 상황을 살펴볼 것이다. 이를 통해 흔히 매우 새롭고 혁신적인 사건으로 언급되는 해석학회의 등장이 19세기 이전 영국 수학계의 꾸준한 개혁 노력들이 축적된 결과 나타날 수 있었음을 보일 것이다. 그 결과 해석학회의 역할과 의의에 대해 새롭게 이해할 수 있게 될 것이다. 또한 이후 영국에서 해석적 방식이 받아들여졌던 과정과 그 경로를 통해 새로운 해석적 방식이 당시 영국의 독특한 지적, 사회적 상황 속에서 대륙과는 다른 방식으로 발전했던 과정을 이해할 수 있을 것이다.

• 대한전기학회논문지:전력기술부문A
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• 제51권4호
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• pp.202-208
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• 2002

In a dynamic game where the players move in a periodical sequence, each player observes the strategy of the others. So the players who move later in a game get to know the moves of others having made before them. Those who move earlier must take this into account in devising their optimal strategy. In the Poolco model, the bidding game is executed periodically. The player participating in the bidding game accumulates the information of its own and others'strategies, and payoffs through the repeated bidding process. Thereby, the players in this game would be able to map out how get the maximum profit, and get closer to the optimal strategy. This paper presents a mathematical modeling for a player to determine his or her optimal strategy at period T, based on the information acquired from the previous rounds for the periods, T-1, T-2, and so on. The proposed modeling is demonstrated with a dynamic fame theory.

• 한국환경보건학회지
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• 제31권6호
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• pp.489-497
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• 2005

A numerical method for the mathematical water modeling in 2-dimensional flow has been developed. The model based on a split operator technique, in which, the advection term is calculated using the upwind scheme. The diffusion term is one- dimensionalized and calculated using Crank-Nicholson's implicit finite difference scheme to reduce the numerical errors from large time steps and variable spacings. It also provides a relatively simple and economic method for more accurate simulation of pollutant dispersion. Water depths and flow velocities in the Boreyong reservoir during the normal water periods were predicted by numerical experiments with a 2-dimensional flow model so as to provide current field data for the study of advection and diffusion of pollutants. Developed 2-dimensional water quality model is applied to Boreyong reservoir to simulate a spatial and periodical changes of water quality.

• Journal of Radiation Protection and Research
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• 제26권3호
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• pp.203-206
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• 2001

The mathematical processing (unfolding) of pulse height spectra from a scintillation detector helps to calculate the photon fluence rate energy distribution in a measured photon field. The data processing is based on the knowledge of detection system response function and directional dependence respectively. The experimental results of the photon fields measurements in the vicinity of the spent fuel temporary storage and inside the storage hall are presented. The containers Castor 440 are used for temporary storing of the burnt up fuel assemblies in the Czech nuclear power plant Dukovany. A set of periodical measurements was performed in order to get basic information on the time dependence of the photon fields spatial distributions and spectral characteristics in the temporary storage hall and its vicinity. The photon fields were measured by the scintillation system. The obtained photon fields spatial distributions and spectral characteristics present the information on the radiation hazard in the storage.

• 한국수학교육학회지시리즈A:수학교육
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• 제56권1호
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• pp.63-80
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• 2017

By analysing the examination papers from third grade high school students, we classified the errors occurred in the problem solving process of high school 'Geometry and Vectors' into several types. There are five main types - (A)Insufficient Content Knowledge, (B)Wrong Method, (C)Logical Invalidity, (D)Unskilled Expression and (E)Interference.. Type A and B lead to an incorrect answer, and type C and D cannot be distinguished by multiple-choice or closed answer questions. Some of these types are classified into subtypes - (B1)Incompletion, (B2)Omitted Condition, (B3)Incorrect Calculation, (C1)Non-reasoning, (C2)Insufficient Reasoning, (C3)Illogical Process, (D1)Arbitrary Symbol, (D2)Using a Character Without Explanation, (D3) Visual Dependence, (D4)Symbol Incorrectly Used, (D5)Ambiguous Expression. Based on the these types of errors, answers of each problem was analysed in detail, and proper ways to correct or prevent these errors were suggested case by case. When problems that were used in the periodical test were given again in descriptive forms, 67% of the students tried to answer, and 14% described flawlessly, despite that the percentage of correct answers were higher than 40% when given in multiple-choice form. 34% of the students who tried to answer have failed to have logical validity. 37% of the students who tried to answer didn't have enough skill to express. In lessons on curves of secondary degree, teachers should be aware of several issues. Students are easily confused between 'focus' and 'vertex', and between 'components of a vector' and 'coordinates of a point'. Students often use an undefined expression when mentioning a parallel translation. When using a character, students have to make sure to define it precisely, to prevent the students from making errors and to make them express in correct ways.

• 한국수학교육학회지시리즈A:수학교육
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• 제58권3호
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• pp.423-442
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• 2019

4차 산업혁명의 시대를 맞이하여 시대적 변화와 사회적 요구를 반영한 새로운 수학교육 계획 및 정책 수립을 위해서는 학교 현장의 수학교육 실태와 수학교사들의 인식조사가 필수적이다. 따라서 본 연구에서는 전국의 초 중 고등학교 교사를 대상으로 수학교육 전반에 대한 인식 및 현황 조사를 실시하고 그 결과를 분석하여 수학교육에 대한 정책적 제언을 제시하고자 한다. 분석 결과, 수학교사들의 수학교육에 대한 전반적인 인식과 학교 안 수학교육 현황에 대한 기본 정보와 함께, 교사의 수학수업 개선과 평가 전문성 신장을 위한 교육 및 환경 지원, ICT 및 공학도구 활용 관련 재교육 실시, 학교 관리자 대상 수학교육 인식 전환 교육 지원, 다양한 교수 학습 방법과 적극적인 교구 활용 방안 마련, 수학학습에 어려움을 겪는 학생 지원 방안 마련 등의 정책적 시사점을 도출할 수 있었다.