• 한국해양공학회지
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• 제32권2호
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• pp.116-122
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• 2018

Dean's equilibrium beach profile formula was used to investigate the correlation between the static shoreline position and the incident wave energy. The effect of the longshore sediment transport was neglected, and the results showed the reasonable agreement compared with the field observations of Yates et al.(2009), which were conducted for almost 5 years on southern California beaches, USA. The shoreline response varies with the scale factor of Dean's equilibrium beach profile. This implies that the shoreline response could be simply estimated using the sampled grain size without laborious long-term field work. Therefore, the present study results are expected to be practically used for the layout design of submerged or exposed detached breakwaters although the further work is required for performance verification. In addition, after laborous mathematical reviews, the linear relation between incident energy and shoreline response, which was obtained from Yates's field study, yielded a clear mathematical equation showing how the beach slope is related to the grain size.

• 한국수학교육학회지시리즈A:수학교육
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• 제44권4호
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• pp.603-625
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• 2005

Identity is the concept which approaches individuals' affective problems with the social and cultural view. The previous studies on the problems, studied the attitudes, beliefs, or emotions while they restricted the problems to teachers or students' private problems. Otherwise, identities focus on individuals which participate to any community and share its social practices(Mclead, 1994). This study purposed to get an understanding on the teaching and learning mathematics in elementary mathematics classroom with an ethnographic view, while we consider mathematics as a kind of social practices, and mathematics classrooms as communities of practice. We analysed teacher's identities on mathematics and teaching mathematics depending on her responses of the questions as following: How does she think about mathematics, what are the instructional goals in her mathematics classroom, how do students learn mathematics in her mathematics classroom. In addition, we analysed students' identities on mathematics and learning mathematics depending on their responses of the questions as following: What do students think of mathematics, do they like mathematics, why do they study mathematics, how do they feel their mathematics classroom(describe your classroom) and themselves in it(describe yourselves in your classroom), what are their duties and what do they do actually in their mathematics classroom.

• 대한수학교육학회지:수학교육학연구
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• 제23권2호
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• pp.117-133
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• 2013

수학적 오개념은 학습 부진 학생들이 올바른 수학 학습을 하는 데 큰 방해 요소 중 하나이다. 오개념의 발생을 줄이고 올바른 개념 형성을 돕고자 중학교 수학 학습에서 흔히 발생하는 수학적 오개념을 정리하여 '중학교 수학과 학습 부진 학생 지도를 위한 맞춤형 교수 학습 방법 자료'를 개발하였다. 이는 수학과 학습 부진 학생 지도를 담당한 교사들에게 교수 학습에 필요한 주요 교육 내용과 창의적이고 흥미 있는 수업 아이디어를 제공하기 위한 자료이다. 뿐만 아니라 오개념을 가진 학생들이나 학습부진아 학생들의 수업자료로 사용하거나, 교사들의 연수 자료로도 사용할 수 있을 것이다.

• 대한수학회보
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• 제21권2호
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• pp.99-106
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• 1984

J. Yeh has recently introduced the concept of conditional Wiener integrals which are meant specifically the conditional expectation E$^{w}$ (Z vertical bar X) of a real or complex valued Wiener integrable functional Z conditioned by the Wiener measurable functional X on the Wiener measure space (A precise definition of the conditional Wiener integral and a brief discussion of the Wiener measure space are given in Section 2). In [3] and [4] he derived some inversion formulae for conditional Wiener integrals and evaluated some conditional Wiener integrals E$^{w}$ (Z vertical bar X) conditioned by X(x)=x(t) for a fixed t>0 and x in Wiener space. Thus E$^{w}$ (Z vertical bar X) is a real or complex valued function on R$^{1}$. In this paper we shall be concerned with the random vector X given by X(x) = (x(s$_{1}$),..,x(s$_{n}$ )) for every x in Wiener space where 0=s$_{0}$ $_{1}$<..$_{n}$ =t. In Section 3 we will evaluate some conditional Wiener integrals E$^{w}$ (Z vertical bar X) which are real or complex valued functions on the n-dimensional Euclidean space R$^{n}$ . Thus we extend Yeh's results [4] for the random variable X given by X(x)=x(t) to the random vector X given by X(x)=(x(s$_{1}$).., x(s$_{n}$ )).

• 한국학교수학회논문집
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• 제13권2호
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• pp.225-241
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• 2010

기하는 수학의 기초를 이루는 중요한 영역이다. 그러나 수학영재를 위한 기하 학습프로그램과 영재를 지도하기 위한 교수전략 연구가 부족한 실정이다. 이에 본 연구는 해석기하학과 사영기하학을 중심으로 영재들의 특성을 고려한 학생중심의 학습 프로그램 설계에 대한 모델을 제시하고 새로운 교수전략으로 기초전략단계(문제제시, 문제해결), 지지전략단계(수학적 개념추출, 수학화, 확장), 전이전략단계 등을 소개한다. 이를 통해 수학영재들에게 필요한 기하교육의 방향성을 제시하고자 한다.

• 대한수학교육학회지:수학교육학연구
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• 제25권3호
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• pp.431-448
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• 2015

이 연구는 비(比) 관련 수학용어를 둘러싼 혼란이 한국과 미국에서 각각 어떻게 전개되고 있는지를 살펴보고, 이를 통해 혼란의 실체를 이해하고 문제를 해결하기 위한 방안을 모색하고자 시도되었다. 이를 위해 미국의 수학교과서, 교사교육용 교재, 사전, 수학전문 인터넷 사이트, 한국의 역대 초등 수학과 교육과정 등 다양한 출처의 자료들을 수집하여, 비(比) 관련 수학용어들을 다양한 관점으로 분석하였다. 분석결과 본 연구에서는 다음 두 가지 결론을 도출하였다. 첫째, 비(比) 관련 수학용어를 사용함에 있어 미국과 한국이 상이한 관점을 가지고 있다. 둘째, 한국 초등교육과정에 포함된 수학용어 '비'와 '비율' 만으로는 비(比)에 내재된 본질적 속성을 다루기에 부족한 면이 있다.

• 한국농공학회지
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• 제32권E호
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• pp.33-46
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• 1990

Abstract Over 700/0 of the rural land area in Korea is mountainous and small watersheds provide most of the water resources for agricutural use. To provide an appropriate tool for the agricultural water resource development project, SNUA2, a mathematical model for simulating the physical processes governing the precipitation-runoff relationships and predicting the storm and long-term runoff quantities from the small mountainous watersheds was developed. The hydrological characteristics of small mountainous watersheds were reviewed to select appropriate theories for the simulation of the runoff processes, and a deterministic and distributed model was developed. In this, subsurface flows are routed by solving Richard's two dimensional equation, the dynamics of soil moisture contents are simulated by the consideration of phenological factors of canopy plants and surface flows are routed by solving the kinematic wave theory by numerical analysis. As a result of an application test of the model to the Sanglim watershed, peak flow rates of storm runoff were over-estimated by up to 184.2%. The occurence time of peak flow and total runoff volume of storm runoffs simulated were consistent with observed values and the annual runoff volumes were simulated in the error range of less than 5.8%.

• International Journal of Automotive Technology
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• 제7권5호
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• pp.535-545
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• 2006

A nonlinear analysis of torsional self-excited vibration in the driveline system for wheeled towing tractors was presented, with a 2-DOF mathematical model. The vibration system was described as a second-order ordinary differential equation. An analytical approach was proposed to the solution of the second-order ODE. The mathematical neighborhood concept was used to construct the interior boundary and the exterior boundary. The ODE was proved to have a limit cycle by using $Poincar\'{e}-Bendixson$ Annulus Theorem when two inequalities were satisfied. Because the two inequalities are easily satisfied, the self-excited vibration is inevitable and even the initial slip rate is little. However, the amplitude will be almost zero when the third inequality is satisfied. Only in a few working modes of the towing tractor the third inequality is not satisfied. It is shown by experiments that the torsional self-excited vibration in the driveline of the vehicle is obvious.

• 대한수학회보
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• 제35권4호
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• pp.641-652
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• 1998

Chung and et al. ([2].1991) introduced a new concept of a manifold, denoted by $^{\ast}g-SEX_n$, in Einstein's n-dimensional $^{\ast}g$-unified field theory. The manifold $^{\ast}g-SEX_n$ is a generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by the unified field tensor $^{\ast}g^{\lambda \nu}$ through the SE-connection which is both Einstein and semi-symmetric. In this paper, they proved a necessary and sufficient condition for the unique existence of SE-connection and sufficient condition for the unique existence of SE-connection and presented a beautiful and surveyable tensorial representation of the SE-connection in terms of the tensor $^{\ast}g^{\lambda \nu}$. Recently, Chung and et al.([3],1998) obtained a concise tensorial representation of SE-curvature tensor defined by the SE-connection of $^{\ast}g-SEX_n$ and proved deveral identities involving it. This paper is a direct continuations of [3]. In this paper we derive surveyable tensorial representations of constracted curvature tensors of $^{\ast}g-SEX_n$ and prove several generalized identities involving them. In particular, the first variation of the generalized Bianchi's identity in $^{\ast}g-SEX_n$, proved in theorem (2.10a), has a great deal of useful physical applications.

• 대한수학회보
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• 제53권4호
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• pp.1051-1069
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• 2016

Combining the concept of self-certified public key and message recovery, Li-Zhang-Zhu (LZZ) gives the proxy signature scheme with message recovery using self-certified public key. The security of the proposed scheme is based on the discrete logarithm problem (DLP) and one-way hash function (OWHF). Their scheme accomplishes the tasks of public key verification, proxy signature verification, and message recovery in a logically single step. In addition, their scheme satisfies all properties of strong proxy signature and does not use secure channel in the communication between the original signer and the proxy signer. In this paper, it is shown that in their signature scheme a malicious signer can cheat the system authority (SA), by obtaining a proxy signature key without the permission of the original signer. At the same time malicious original signer can also cheat the SA, he can also obtain a proxy signature key without the permission of the proxy signer. An improved signature scheme is being proposed, which involves the remedial measures to get rid of security flaws of the LZZ et al.'s. The security and performance analysis shows that the proposed signature scheme is maintaining higher level of security, with little bit of computational complexity.