• 한국과학교육학회지
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• 제22권3호
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• pp.571-585
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• 2002

형식적인 사고를 가능하게 하는 논리적 사고력의 형성 가능성에 대한 기초적인 연구 활동의 하나로, '생각하는 과학' 프로그램에 있는 변인통제 활동의 학습효과를 조사하였다. 초등학교 5학년 306명의 학생들이 연구에 참가하였으며, 같은 분량의 사간에 실험반에서는 교육과정에 따른 과학 교과 수업과 변인통제 활동을 병행하였고, 통제반에서는 과학교과 수업만을 수행하였다. 연구 초기에 논리적 사고력 검사와 변인통제 검사를 이용하여 사전 상태를 비교하고, 한 학기 동안 변인통제 활동 6개를 12차시에 걸쳐 진행하면서, 처치별, 성별, 인지수준별 학습효과를 알아보았다. 처치활동은 초등학교 5학년 학생들의 변인통제능력 신장에 매우 효과적인 것으로 나타났다. 변인통제능력의 하위요소별로 분석한 결과, 특별히 실험조건 통제, 변인측정과 결과변인 학습에 매우 효과적인 것으로 나타났고, 원인변인 학습효과도 다소 있는 것으로 나타났다. 남 여학생들의 사전 변인통제능력을 비교한 결과 여학생들이 월등히 높은 점수를 보였다. 변인통제 학습 후 남 여학생들 모두에게 거의 같은 정도로 우수한 학습효과가 나타났으며, 통제반에서 차이가 더 벌어진 반면, 실험반에서는 그 격차가 좁혀졌다. 학생들의 인지수준에 따란 변인통제 학습효과를 분석한 결과, 모든 인지수준에서 실험반 학생들의 변인 통제능력이 상당히 향상되었다. 특히 전기 구체적 조작기, 중기 구체적 조작기와 후기 구체적 조작기에 있는 학생들의 변인통제능력은 크게 향상되었다. 변인판별 능력은 전기 구체적 조작기, 중기 구체적 조작기와 후기 구체적 조작기에 있는 학생들이 거의 같은 정도의 우수한 발전을 보여주었으며, 실험설계 능력은 모든 수준에서 상당히 향상되었다. '생각하는 과학'의 변인통제 활동과 같은 형태의 학습내용을 현행 학교 과학교육에 적극적으로 도입해볼 필요가 있다.

• 응용통계연구
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• 제17권2호
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• pp.347-357
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• 2004

의사결정나무에서 분리 변수를 선택하는 것은 매우 중요한 일이다. C4.5는 변수 선택에 있어 연속형 변수로의 변수 선택 편의가 심각하고, QUEST는 연속형 변수와 관련해서 정규성 가정이 위반될 경우 변수 선택력이 떨어진다. 본 논문에서는 통계적 로버스트 검정 알고리즘을 제안하고, 모의 실험을 통하여 C4.5, QUEST그러고 제안된 알고리즘의 효율성을 비교하였다. 실험 결과 제안된 알고리즘이 변수 선택 편의와 변수 선택력 측면에서 로버스트함을 알 수 있었다.

• International journal of advanced smart convergence
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• 제9권1호
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• pp.10-18
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• 2020

In the case of a belt-pulley type CVT that transmits a driving force by using a variable pulley and a metal belt, slippage occurs due to transmission of power by using a belt, which results in a decrease in efficiency. Therefore, in this study, the rails were machined on the plate surface of the pulley to reduce the friction and slip between the belt and the pulley while applying the characteristics of the CVT. As the plate is rotated by the shape of the rail, a centrifugal belt pulley type continuously variable transmission system which shifts while varying the radius of rotation of the belt that transmits power is studied. Accordingly, the structure of the pulley was designed and the centrifugal belt pulley type continuously variable transmission was Manufactured. In addition, to verify the suitability of the manufactured transmission, the power transmission efficiency was monitored by establishing an interface with the controller. The structural analysis of the plate proved the suitability of the centrifugal belt pulley type continuously variable transmission.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.662-674
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• 2017

This paper describes the multidisciplinary design optimization (MDO) process of a tailless unmanned combat aerial vehicle (UCAV) using global variable fidelity aerodynamic analysis. The developed tailless UAV design framework combines multiple disciplines that are based on low-fidelity and empirical analysis methods. An automated high-fidelity aerodynamic analysis is efficiently integrated into the MDO framework. Global variable fidelity modeling algorithm manages the use of the high-fidelity analysis to enhance the overall accuracy of the MDO by providing the initial sampling of the design space with iterative refinement of the approximation model in the neighborhood of the optimum solution. A design formulation was established considering a specific aerodynamic, stability and control design features of a tailless aircraft configuration with a UCAV specific mission profile. Design optimization problems with low-fidelity and variable fidelity analyses were successfully solved. The objective function improvement is 14.5% and 15.9% with low and variable fidelity optimization respectively. Results also indicate that low-fidelity analysis overestimates the value of lift-to-drag ratio by 3-5%, while the variable fidelity results are equal to the high-fidelity analysis results by algorithm definition.

• 대한기계학회논문집A
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• 제24권8호
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• pp.2074-2082
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• 2000

In this study, to investigate and to predict the crack growth behavior under variable amplitude loading, crack growth tests are conducted on 7075-T6 aluminum alloy. The loading wave forms are generated by normal random number generator. All wave forms have same average and RMS(root mean square) value, but different standard deviation, which is to vary the maximum load in each wave. The modified Forman's equation is used as crack growth equation. Using the retardation coefficient D defined in previous study, the load interaction effect is considered. The variability in crack growth process is described by the random variable Z which was obtained from crack growth tests under constant amplitude loading in previous work. From these, a statistical model is developed. The curves predicted by the proposed model well describe the crack growth behavior under variable amplitude loading and agree with experimental data. In addition, this model well predicts the variability in crack growth process under variable amplitude loading.

• Smart Structures and Systems
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• 제6권8호
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• pp.953-974
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• 2010

The performance of variable dampers for seismic protection of the benchmark highway bridge (phase I) under six real earthquake ground motions is presented. A simplified lumped mass finite-element model of the 91/5 highway bridge in Southern California is used for the investigation. A variable damper, developed from magnetorheological (MR) damper is used as a semi-active control device and its effectiveness with friction force schemes is investigated. A velocity-dependent damping model of variable damper is used. The effects of friction damping of the variable damper on the seismic response of the bridge are examined by taking different values of friction force, step-coefficient and transitional velocity of the damper. The seismic responses with variable dampers are compared with the corresponding uncontrolled case, and controlled by alternate sample control strategies. The results of investigation clearly indicate that the base shear, base moment and mid-span displacement are substantially reduced. In particular, the reduction in the bearing displacement is quite significant. The friction and the two-step friction force schemes of variable damper are found to be quite effective in reducing the peak response quantities of the bridge to a level similar to or better than that of the sample passive, semi-active and active controllers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.321-325
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• 1986

A new control scheme for the state space model of the robot system using the theory of optimal multi-variable structure is presented in this paper. It is proposed to optimize multi-dimensional variable structure systems for obtaining the required stabilizing signal by minimizing a performance index with respect to the state vector in the sliding mode. It is concluded the proposed variable structure controller yields better system dynamic performance than that obtained by using the only linear optimal controller inthat responses for a step disturbance have a shorter setting time, no matter what overshoot values and rising time.

• 대한음성학회:학술대회논문집
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• 대한음성학회 1996년도 10월 학술대회지
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• pp.404-408
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• 1996

In this paper, temporal variables of French oral discourse are analyzed and interpreted. They are distinguished in two Troops, the temporal external variable and the temporal internal variable The external variable is determined by the breathing function as the physical condition of the verbal message and the internal variable is directly associated with multiple effects by the accentuation on final syllable of rhythmic group in actual French. Temporal variables, external and internal, are taken as devices of verbal support that serve to create immediate effects of oral production.

• Journal of applied mathematics & informatics
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• 제36권5_6호
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• pp.475-489
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• 2018

In this paper, by using the polylogarithm function, we introduce a generalized poly-Bernoulli numbers and polynomials with variable a. We find several combinatorial identities and properties of the polynomials. We give some properties that is connected with the Stirling numbers of second kind. Symmetric properties can be proved by new configured special functions. We display the zeros of the generalized poly-Bernoulli polynomials with variable a and investigate their structure.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.183-185
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• 2002

Heavy ion and proton therapy necessitate range weeks, which are time consuming. Three types of variable compensator, membrane type liquid variable compensator, are proposed by some of the authors to overcome the difficulties, by those arbitrarily thickness distribution of compensator obtained from treatment planning is created at the site of treatment. None of the ideas, however, is yet realized. In this research, we are trying to construct prototype membrane-type liquid variable compensator. This variable compensator partitions air and liquid with elasticity membrane and changes the surface of the elasticity membrane with the thread. The air and oil move through holes to and from the out of beam side of two boxes in which they are contained. The boxes are made of Plexiglas(PMMA), the thread which is made of nylon, the elasticity film which is made from latex for the moment.