• 대한수학교육학회지:수학교육학연구
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• 제27권3호
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• pp.351-373
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• 2017

나눗셈의 의미는 수의 범위가 확장되어도 연결된다. 즉, 자연수 범위에 적용되는 나눗셈의 의미는 분수 및 소수를 다루는 유리수 범위로 확장되어도 적용가능하다. 이러한 측면에서 자연수의 나눗셈과 분수의 나눗셈, 소수의 나눗셈을 서로 연결하여 가르치는 것은 수학의 내적 연결성을 통하여 나눗셈을 의미 있게 학습하는데 도움이 될 것이다. 본 연구에서는 5학년 2학기에 제시되는 분수의 나눗셈과 소수의 나눗셈 단원을 나눗셈의 의미와 절차가 연결되도록 재구성한 뒤 수업을 실행하고 분석하였다. 연구 결과, 학생들은 수의 범위가 확장되더라도 나눗셈의 의미를 이해하여 문제를 해결하거나 만들 수 있었다. 또한 문제 해결 과정에서 자연수의 나눗셈, 분수의 나눗셈, 소수의 나눗셈의 원리를 이용할 수 있었다. 단, 일부 학생들의 경우 나눗셈 의미를 이해하지 못하여 잘못된 나눗셈식을 세우거나 문제를 만들었으며, 특정한 해결 절차만을 선호하는 모습도 발견할 수 있었다. 본 연구를 통하여 초등학교 전 과정에 제시되는 나눗셈을 연결성을 강조하여 의미 있게 지도 학습할 수 있는 방향을 모색하는데 도움이 되기를 기대한다.

• Journal of Biosystems Engineering
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• 제5권2호
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• pp.26-39
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• 1980

A study was investigated to find out the mechanical optimum conditions of power tiller-plow system on both paddy field and upland. Mathematical model was developed for the theoretical analysis of this system and the experimentation on the field was carried out with two different sizes of 5PS and 8PS power tiller equipped with rubber tire. 1) The relationship between the plowing depth and draft resistance of the power tiller-plow system was a quadratic function. 2) The minimum point of the specific draft resistance of the 5 PS plow was found at the smaller plowing depth than that of 8 PS plow, therefore we can find that the curved surface of 5PS plow bottom should be improved for the effective plowing operation. 3) As the improvement of the mechanical balance by the desirable change of the curved surface of plow bottom, the relative position of hitch point and dimension of plow beam would be realized, the 5 PS power tiller could be used to plow deeply (about 16-17cm). 4) The virtual acting point of the total draft resistance on the plow bottom approached to the land side as the plowing depth increased. 5) The resultant of vertical reaction force $R_2$ on the landside was increased with the plowing depth, while the vertical reaction force $R_1$ on the wheel was decreased as the slope angle of the body of power tiller increased. 6) For the effective plowing operations ; a) The slope angle of the body should be as small as possible. b) The diameter of the wheel should be as small possible. c) The horizontal and vertical distances $l_2, h_1$ between the wheel axis and plow bottom should be as large as possible. 7) To use the 5PS power tiller as the major unit of agricultural machinery, the curved surface of the 5 PS plower bottom and the mechanism of attachment between the power tiller and the plow should be changed as the indications of this study, and in addition to these, the new operation method of the field work should be developed.

• 정보보호학회논문지
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• 제26권1호
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• pp.17-30
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• 2016

본 논문에서는 효율적인 공개키 기반 공모자 추적 및 제외 스킴을 제안하고자 한다. 공모자 추적 및 제외 스킴은 암호 전송 스킴(Broadcast encryption scheme)에 공모자 추적과 제외 기능을 추가한 것으로 악의적인 사용자들이 유출한 개인키 또는 공모한 해적판 키를 시스템에서 제외함으로서 스킴의 안전성을 유지하는 것이다. 또한 제외 기능은 일부 사용자만을 위한 암호문을 만들 수 있어 다양한 응용 환경에 적용할 수 있는 스킴이다. 본 논문에서는 합성수 위수의 겹선형 군을 기반으로 설계된 스킴[Augmented broadcast encryption scheme]을 소수 위수의 겹선형 군을 기반으로 하는 스킴으로 변화시켰고, 효율성의 척도인 공개키, 개인키, 암호문의 크기를 크게 개선했다. 또한 제외 기능에 대한 분석을 통해 기존 논문의 제한적인 제외 기능을 충분한 제외 기능으로 확장하는 결과를 얻을 수 있었다. 본 논문에서 제안하는 스킴의 구조는 계층적 구조 또는 피라미드 구조를 갖는 우리나라 정부, 군 조직 등에 쉽게 적용 가능하다.

• 교육시설
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• 제17권6호
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• pp.3-12
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• 2010

This study is a comparative study on the regional needs and features of new school establishment. It aims at developing a tool for evaluating the validity of school establishment, which would help more reasonable decision-making for new school construction and the class extension in the existing schools. In doing so, it employes a mathematical device - the School Establishment Index(SEI), which consists of class condition quotient, fluctuation quotient in the number of students and school location quotient. To explore the needs of new schools and classes in a district, this study estimates the number of students by a year from 2009 to 2020 and surveys the changing faces of student movement, school and class density, housing development in Incheon Metropolitan City, Gwangju Metropolitan City, Chungcheongbuk-do and Jeollanam-do. Finally, it shows the relative requirement of new schools in 4 districts, which the educational offices can use in the course of planning the student accomodations to schools and making decisions for new school construction and the class extension in the existing schools. This study would be expected to help the reasonable expenditure for school facilities and to restrict overbuilding of surplus classes.

• 한국항공우주학회지
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• 제46권7호
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• pp.527-534
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• 2018

본 논문은 최근에 각광 받고 있는 드론(멀티콥터)과 관련하여 비행체의 비행 성능, 특히 비행 가능 시간에 대한 예측과 실험 데이터를 통한 검증 등을 목표로 하여, 제자리 비행에 대한 연구 결과를 제시 하고 있다. 연구 방법을 드론 시스템을 구성하고 있는 여러 부품들을 기능별로 분류하여 부품 수준에서의 제원과 기능에 대한 정리 및 수학적 수식화를 통하여 단위 부품의 성능을 분석 및 실험 데이터를 확보하고, 이들 단위 부품 데이터의 조합을 통하여 드론 시스템의 제자리비행 성능을 예측하는 연구 결과를 보여 주고 있다. 또한 5kg급 쿼드콥터를 이용하여 제자리 비행에 대한 분석을 통하여 비행시간에 따른 전압 변화를 예측, 검증 하였으며 해당 방법을 통해 제자리 비행시간을 예측하였다.

• 한국학교수학회논문집
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• 제12권3호
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• pp.319-345
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• 2009

학교 현장에서 독서 교육이 강조되면서 수학효과에서도 독서 자료를 활용한 수업 연구가 많이 이루어져 왔다. 하지만, 대부분의 연구가 학생 개개인의 흥미, 적성, 관심 그리고 수준에 맞는 도서를 선정하기 보다는 일률적으로 단원과 관련된 읽을 거리를 제공하는데 그쳐왔다. 이에 본 연구에서는 수학에 흥미를 가질 수 있게 하는 보조 학습 자료로서 수학과 관련된 독서 자료를 활용하여 수준별 학생들이 어떤 차이점들을 가지고 있는지 분석하여, 독서 자료가 수준별 학생들의 수학 학습에 어떤 영향을 미치는지 알아보고자 한다. 독서 자료와 활동지를 학생들에게 적용시켜본 결과, 학생들의 수준에 맞는 수학 관련 독서 자료는 학생들의 수학에 대한 태도를 긍정적으로 변화시키고, 수학적 개념을 좀 더 깊이 있게 이해하고 활용할 수 있는 능력을 기를 수 있게 하여, 결과적으로 사회에서 필요로 하는 논리적이고 합리적인 사고력을 얻을 수 있을 것으로 기대되어진다.

• Journal of Biosystems Engineering
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• 제16권2호
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• pp.133-141
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• 1991

This study was undertaken to investigate the structural and configurational characteristics of the tailings return-unit in the commercially available head-feed combines and to study the aero-dynamical behavior of the tailings in the units. The mathematical model of the motion of tailings in the thrower casing was developed and the simulated trajectories for different type of units was analyzed to compare with the measured ones. The air-stream velocity profile in various locations along the tailings returning duct was measured to find the effect of configurational characteristics and blade tip speed. The results of the study are summerized as follows. 1. The ejecting angle, which is the angle between the direction of the particle velocity ejecting from the blade and the horizontal axis, was found to be about $66^{\circ}$ in both the simulation and experiment. The angle was much greater than the setting angle of actual duct of the combines studied, which were $48{\sim}56^{\circ}$. By comparison of these results, it was suggested to change duct setting angle so as to reduce the frictional force, between the duct wall and tailings, by reducing the difference between the ejecting and setting angles. 2. The velocity of the air stream in the duct was in general higher in the upper bound of the duct compared to the lower and decreased as the stream went toward the end of duct. The comparison of the tailings units among the combines studied showed a superior performance with the tapered duct having small diameter in the outlet and with greater number of thrower blade.

• 대한의용생체공학회:의공학회지
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• 제28권3호
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• pp.348-354
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• 2007

Polymer actuators, which are also called as smart materials, change their shapes when electrical, chemical, thermal, or magnetic energy is applied to them and are useful in wide variety of applications such as microelectromechanical systems (MEMS), machine components, and artificial muscles. For this study, Polyaniline/carbon-nanotube polymer actuator that is one of electroactive polymer actuators was prepared. Since the nonlinear phenomena of hysteresis and a step response are essential considerations for practical use of polymer actuators, we have investigated the movement of the Polyaniline/carbon-nanotube polymer actuator and have developed an integrated model that can be used for simulating and predicting the hysteresis and a step response during actuation. The Preisach hysteresis model, one of the most popular phenomenological models of hysteresis, were used for describing the hysteretic behavior of Polyaniline/carbon-nanotube polymer actuator while the ARX method, one of system identification techniques, were used for modeling a step response. In this paper, we first expain details in preparation of the Polyaniline/carbon-nanotube polymer then present the mathematical description of our model, the extraction of the parameters, simulation results from the model, and finally a comparison with measured data.

• Earthquakes and Structures
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• 제14권4호
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• pp.313-322
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• 2018

The present study is dedicated to investigate the SH body-as well as Love-waves propagation effects in porous media with uncertain porosity and permeability. A unified formulation of the governing equations for one-dimensional (1-D) wave propagation in anisotropic porous layered media is presented deterministically. The uncertainties around the above two cited parameters are taken into account by random fields with the help of Monte Carlo Simulations (MCS). Random samples of the porosity and the permeability are generated according to the normal and lognormal distribution functions, respectively, with a mean value and a coefficient of variation for each one of the two parameters. After performing several thousands of samples, the mathematical expectation (mean) of the solution of the wave propagation equations in terms of amplification functions for SH waves and in terms of dispersion equation for Love-waves are obtained. The limits of the Love wave velocity in a porous soil layer overlaying a homogeneous half-space are obtained where it is found that random variations of porosity change the zeros of the wave equation. Also, the increase of uncertainties in the porosity (high coefficient of variation) decreases the mean amplification function amplitudes and shifts the fundamental frequencies. However, no effects are observed on both Love wave dispersion and amplification function for random variations of permeability. Lastly, the present approach is applied to a case study in the Adapazari town basin so that to estimate ground motion accelerations lacked in the fast-growing during the main shock of the damaging 1999 Kocaeli earthquake.

• Wind and Structures
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• 제21권6호
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• pp.693-707
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• 2015

The efficiency of wind turbines (WT) is primarily reflected in their ability to generate electricity at any time. Downtimes of WTs due to "conventional" inspections are cost-intensive and undesirable for investors. For this reason, there is a need for structural health monitoring (SHM) systems, to enable service and maintenance on demand and to increase the inspection intervals. In general, monitoring increases the cost effectiveness of WTs. This publication concentrates on the application of two vibration-based SHM algorithms for stability and structural change monitoring of offshore WTs. Only data driven, output-only algorithms based on stochastic subspace identification (SSI) in time domain are considered. The centerpiece of this paper deals with the rough mathematical description of the dynamic behavior of offshore WTs and with the basic presentation of stochastic subspace-based algorithms and their application to these structures. Due to the early stage of the industrial application of SHM on offshore WT on the one side and the required confidentiality to the plant manufacturer and operator on the other side, up to now it is not possible to analyze different isolated structural damages resp. changes in a systematic manner, directly by means of in-situ measurement and to make these "acknowledgements" publicly available. For this reason, the sensitivity of the methods for monitoring purposes are demonstrated through their application on long time measurements from a 1:10 large scale test rig of an offshore WT under different conditions: undamaged, different levels of loosened bolt connections between tower parts, different levels of fouling, scouring and structure inclination. The limitation and further requirements for the approaches and their applicability on real foundations are discussed along the paper.