• 한국수학교육학회지시리즈A:수학교육
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• 제55권1호
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• pp.1-19
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• 2016

Given the importance of understanding the equal sign in developing early algebraic thinking, this paper investigated how a total of 695 students in grades 2~6 understood the equal sign. The students completed a questionnaire with three types of items (equation structure, equal sign definition, and open equation solving) based on the construct map by four different levels of understanding the equal sign. The questionnaire was analyzed by Rasch model. The results showed that about 80% of the students were at least Level 3 which means a basic relational understanding of the equal sign. However, the success rates varied across grades and it was noticeable that about 70% of the second graders remained at Level 1 or 2 which maintains an operational understanding of the equal sign. The results of item types demonstrated that item difficulty for the advanced relational thinking was the highest and this is the same even for the Level 4 students. This paper is expected to investigate elementary school students' understanding of the equal sign and provide implications of how to deal with the equal sign in the elementary school.

• 한국소음진동공학회논문집
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• 제23권11호
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• pp.943-950
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• 2013

This paper discusses a harmonic response estimation method on the L$\acute{e}$vy plate with two opposite edges simply supported and the other two edges having free boundary conditions. Since the equation of motion of the plate is not self-adjoint, the modes are not orthogonal to each other on the domain. Noting that the L$\acute{e}$vy plate can be expressed using one term sinusoidal function that is orthogonal to other sinusoidal functions, this paper suggested the calculation method that is equivalent to finding a least square error minimization solution of the finite number of algebraic equations. Example problems subjected to a distributed area loading and a distributed line loading are defined and their solutions are provided. The solutions are compared to those of the commercial code, ANSYS. According to the verification results, it is expected that the suggested method will be useful to predict the forced response on the L$\acute{e}$vy plate with the distributed area or line loading conditions.

• Coupled systems mechanics
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• 제8권2호
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• pp.129-146
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• 2019

The main goal of this work is to develop a numerical simulator to study an isothermal single-phase two-component flow in a naturally fractured oil reservoir, taking into account advection and diffusion effects. We use the Peng-Robinson equation of state with a volume translation to evaluate the properties of the components, and the discretization of the governing partial differential equations is carried out using the Finite Difference Method, along with implicit and first-order upwind schemes. This process leads to a coupled non-linear algebraic system for the unknowns pressure and molar fractions. After a linearization and the use of an operator splitting, the Conjugate Gradient and Bi-conjugated Gradient Stabilized methods are then used to solve two algebraic subsystems, one for the pressure and another for the molar fraction. We studied the effects of fractures in both the flow field and mass transport, as well as in computing time, and the results show that the fractures affect, as expected, the flow creating a thin preferential path for the mass transport.

• Communications for Statistical Applications and Methods
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• 제28권5호
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• pp.477-491
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• 2021

The Markov modulated Brownian motion is a substantial generalization of the classical Brownian Motion. On the other hand, the Markovian arrival process (MAP) is a point process whose family is dense for any stochastic point process and is used to approximate complex stochastic counting processes. In this paper, we consider a superposition of the Markov modulated Brownian motion (MMBM) and the Markovian arrival process of jumps which are distributed as the bilateral ph-type distribution, the class of which is also dense in the space of distribution functions defined on the whole real line. In the model, we assume that the inter-arrival times of the MAP depend on the underlying Markov process of the MMBM. One of the subjects of this paper is introducing how to obtain the first passage probabilities of the superposed process using a stochastic doubling algorithm designed for getting the minimal solution of a nonsymmetric algebraic Riccatti equation. The other is to provide eigenvalue and eigenvector results on the superposed process to make it possible to apply the GTH-like algorithm, which improves the accuracy of the doubling algorithm.

• 제어로봇시스템학회논문지
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• 제19권7호
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• pp.577-582
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• 2013

In this paper Legendre wavelets are used to approximate the solutions of linear time-invariant system. The Legendre wavelet and its integral operational matrix are presented and an efficient algorithm to solve the Sylvester matrix equation is proposed. The algorithm is based on the decomposition of the Sylvester matrix equation and the preorder traversal algorithm. Using the special structure of the Legendre wavelet's integral operational matrix, the full order Sylvester matrix equation can be solved in terms of the solutions of pure algebraic matrix equations, which reduce the computation time remarkably. Finally a numerical example is illustrated to demonstrate the validity of the proposed algorithm.

• 대한기계학회논문집B
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• 제29권2호
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• pp.232-238
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• 2005

The 'Mixing Index($D_I$)' is used as a conventional guidance measuring the degree of mixing for multiphase flows. For the case when insoluble solutions flow in a passive micromixer, a new method to calculate $D_I$ is proposed. The 'Vortex Index(${\Omega}_I$)' is suggested and formulated. We infer that ${\Omega}_I$ relates to the degree of chaotic advection. Various arbitrary shaped microchannels were tested to calculate the $D_I\;and\;{\Omega}_I$, and then a simple algebraic equation, $D_I=Aexp(B{\Omega}_I)$, is obtained. This equation may be used instead of the conventional partial differential equation, concentration equation, to estimate the degree of mixing.

• 전자공학회논문지A
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• 제32A권12호
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• pp.25-35
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• 1995

An analysis method of electromagnetic coupling through an arbitrarily shaped aperture on the upper wall of parallel-plate waveguide, when excited by an electromagnetic plane wave from outside, is considered. The mixed-potential integral equation, in which Green's functions are expressed in a computationally efficient closed form by using the Prony's method and the Sommerfeld identity, is formulated. Expanding the unknown equivalent magnetic surface current in terms of two-dimensional rooftop-type basis functions and choosing razor testing, the integral equation is reduced to a linear algebraic equation, which is solved. The results are compared with the previous results. Fairly good agreements between them are observed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1800-1805
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• 2008

A "finite volume method" is proposed to predict heat transport in a spherical enclosure at micro/nanoscale with the Boltzmann transport equation (BTE). The gray version of the BTE with the relaxation time approximation has been applied. Pointing out similarity between radiative transfer equation (RTE) and BTE, the mapping process in RTE is adopted to treat the angular derivative term and linear algebraic discretization equation is derived by using the established method which is used in 2-D BTE in cartesian coordinates. The simulation results are compared to exact solution to RTE for various acoustic thicknesses and ratio of radii. The comparison shows that this method is logical and accurate, and it is possible to easily adopt various models in spherical BTE.

• 한국수학사학회지
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• 제30권3호
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• pp.137-162
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• 2017

The Chinese algebraic method, the tian yuan shu, was developed during Song period (960-1279), of which Li Ye's works contain the earliest testimony. Two 18th century editors commentated on his works: the editor of the Siku quanshu and Li Rui, the latter responding to the former. Korean scholar Nam Byeong-gil added another response in 1855. Differences can be found in the way these commentators considered mathematical objects and procedures. The conflicting nature of these commentaries shows that the same object, the quadratic equation, can beget different interpretations, either a procedure or an assertion of equality. Textual elements in this paper help modern readers reconstruct different authors' understandings and reconsider the evolution of the definition of the object we now call 'equation'.

• Journal of information and communication convergence engineering
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• 제2권3호
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• pp.187-192
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• 2004

A method using two dimension Haar functions approximation for solving the problem of a partial differential equation and estimating the parameters of a non-linear distributed parameter system (DPS) is presented. The applications of orthogonal functions, including Haar functions, and their transforms have been given much attention in system control and communication engineering field since 1970's. The Haar functions set forms a complete set of orthogonal rectangular functions similar in several respects to the Walsh functions. The algorithm adopted in this paper is that of estimating the parameters of non-linear DPS by converting and transforming a partial differential equation into a simple algebraic equation. Two dimension Haar functions approximation method is introduced newly to represent and solve a partial differential equation. The proposed method is supported by numerical examples for demonstration the fast, convenient capabilities of the method.