• Journal of information and communication convergence engineering
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• v.12 no.1
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• pp.39-45
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• 2014

A numerical method for solving Hamiltonian equations is said to be symplectic if it preserves the symplectic structure associated with the equations. Various symplectic methods are widely used in many fields of science and technology. A symplectic method preserves an approximate Hamiltonian perturbed from the original Hamiltonian. It theoretically supports the effectiveness of symplectic methods for long-term integration. Although it is also related to long-term integration, numerical stability of symplectic methods have received little attention. In this paper, we consider explicit symplectic methods defined for Hamiltonian equations with Hamiltonians of the special form, and study their numerical stability using the harmonic oscillator as a test equation. We propose a new stability criterion and clarify the stability of some existing methods that are visually based on the criterion. We also derive a new method that is better than the existing methods with respect to a Courant-Friedrichs-Lewy condition for hyperbolic equations; this new method is tested through a numerical experiment with a nonlinear wave equation.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.219-224
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• 2019

Textbooks with a lot of numerical information, such as the year, need to apply the mnemonic system. The mnemonic-system in numbers are used in many ways, such as dots, lines, and bars, and information images serve as symbols to help memory. The memory structure of the brain is more efficient in providing more information than just numbers. Previous studies have suggested graphical or arrayed image algorithms for mobile environments. In this study, we would like to link additional information related to figures with original data by selecting a subject with a lot of numerical information. We propose unique processes in mobile environments and evaluate the numerical algorithms to link meaning.

• Journal of Computing Science and Engineering
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• v.3 no.2
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• pp.73-87
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• 2009

A hybrid system is a dynamical system in which states can be changed continuously and discretely. Simulation based on numerical methods is the widely used technique for analyzing complicated hybrid systems. Numerical simulation of hybrid systems, however, is subject to two types of numerical errors: truncation error and round-off error. The effect of such errors can make an impossible transition step to become possible during simulation, and thus, to generate a simulation behavior that is not allowed by the model. The possibility of an incorrect simulation behavior reduces con.dence in simulation-based analysis since it is impossible to know whether a particular simulation trace is allowed by the model or not. To address this problem, we define the notion of Instrumented Hybrid Automata (IHA), which considers the effect of accumulated numerical errors on discrete transition steps. We then show how to convert Hybrid Automata (HA) to IRA and prove that every simulation behavior of IHA preserves the discrete transition steps of some behavior in HA; that is, simulation of IHA is sound with respect to HA.

• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.1123-1132
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• 2008

In this paper, by introducing a parameter, we establish a new Ostrowski's integral inequality which generalizes the result of [5]. Finally, we apply the new Ostrowski's inequality to numerical integration and special means.

• Journal of The Korean Association For Science Education
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• v.41 no.1
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• pp.59-70
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• 2021

Ability to make informed decisions by critically evaluating media information on socioscientific issues (SSI) is one of the crucial elements of scientific literacy that citizens should obtain. This study aims to investigate how middle school students evaluated media information about socioscientific issues (SSI) when they faced two different types of information (i.e., numerical and empathic information). To achieve the aim, 96 middle school students responded to the questionnaires asking them to evaluate reliability and persuasiveness of SSI media information. The questionnaires consisted of two sets of newspaper articles on each SSI (pro-numerical/empathic, against-numerical/empathic). After reading the articles, the students evaluated reliability and persuasiveness of each article and wrote the reasons for their evaluation. The results were as follows: First, the students believed that news articles with numerical information were more reliable than the ones with empathic information in all SSI contexts. They tended to trust scientific evidence and data from numerical information, and real cases, societal problems, expressions, and values from empathic information. In addition, they evaluated their reliability based on the logic of information, accuracy of information, breadth and depth of data, and quantity and quality of sources both numerical and empathic information. Second, in case of evaluating persuasiveness of the articles, they focused more on the values that information contained, richness and logicality of the information, rather than the types of information, regardless of the type of information.

• The Journal of the Korea Contents Association
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• v.16 no.4
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• pp.624-633
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• 2016

Although a number of information is emerging in the big data era and studies on the infographic studies for delivering it effectively are becoming an issue, the visualization study on the numerical information delivered through the credit card statement is very poor compared to its importance. The effective visualization method following each information characteristics was by analyzing the numerical information types focusing on the credit card statement. The type of the figure information classified into the comparative analysis, progress of time change, proportion, relationship, scope, and distribution, and it was made into the graph form proper to the nature of each information to study the most effective and ideal visual form. Therefore, this study is significant because it suggests a control point of the visualization by pointing out an effective visual form for delivering the numerical information that appears on the credit card statement with the figure characteristics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.202-211
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• 2017

In this study, numerical simulations were performed using the ${\gamma}-Re_{\theta}$ transition model of KFLOW for the transitional flow over the KARI-11-180 airfoil. Numerical results of KFLOW were compared with experimental data and two other numerical results of XFoil and MSES. Fully turbulence model was predicted high skin friction drag than transition model because fully turbulence model could not solve the transitional flow. Numerical predictions using the ${\gamma}-Re_{\theta}$ model of KFLOW show a good agreement with experimental data and other numerical results. Present numerical results were confirmed the state of drag bucket due to dramatic changing of the transition location on the airfoil surface.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.5-10
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• 2015

Femtosecond laser machining has been applied for creating a sensor function in silica glass optical fibers. Femtosecond laser pulses make it possible to fabricate micro structures in processed regions of a very thin glass fiber line because femtosecond laser pulses can extremely minimize thermal effects. With the laser machining to optical fiber using a single shot of 210-fs laser at a wavelength of 800 nm, it was observed that a processed region surrounded a thin layer which seemed to be a hollow cavity monitored by scanning electron microscopy (SEM). This study aims at a theoretical investigation for the processed region by using a numerical analysis in order to embed sensing function to optical fibers. Numerical methods based finite element method (FEM) has been used for an optical waveguide modeling. This report suggests two types modeling and describes a comparative study on optical losses obtained by the experiment and the numerical analysis.

• Journal of the Korean Mathematical Society
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• v.33 no.2
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• pp.235-247
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• 1996

Many numerical computations in science and engineering can only be solved approximately since the available infomation is partial. For instance, for problems defined ona space of functions, information about f is typically provided by few function values, $N(f) = [f(x_1), f(x_2), \ldots, f(x_n)]$. Knwing N(f), the solution is approximated by a numerical method. The error between the true and the approximate solutions can be reduced by acquiring more information. However, this increases the cost. Hence there is a trade-off between the error and the cost.

• Journal of Computing Science and Engineering
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• v.4 no.2
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• pp.110-127
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• 2010

In this study, we propose a method for encoding documents into string vectors, instead of numerical vectors. A traditional approach to text categorization usually requires encoding documents into numerical vectors. The usual method of encoding documents therefore causes two main problems: huge dimensionality and sparse distribution. In this study, we modify or create machine learning-based approaches to text categorization, where string vectors are received as input vectors, instead of numerical vectors. As a result, we can improve text categorization performance by avoiding these two problems.