• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.535-540
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• 2011

Organic-inorganic hybrid coating solutions were prepared starting from colloidal silica, lanthanum nitrate and ${\gamma}$-glycidoxypropyl trimethoxysilane by the sol-gel method. Also, spiropyran-doped hard coating solutions were prepared by mixing the spiropyran solution, obtained after dissolving spiropyran dye into tetrahydrofuran solvent, with the organic-inorgnic hybrid coating solutions. The spiropyran-doped hard coating solutions were applied as a thin layer to polycarbonate sheets, and their photochromic properties were investigated. The effect of amount of colloidal silica added into the coating solutions was investigated on the photochromic properties of coating films. Both decoloration rate and pencil hardness of the coating films were increased with increasing the amounts of colloidal silica.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.86-93
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• 2009

In this paper, we propose a method that generates a sketch likely to be drawn by a human from a real image(a computer generated image or a photo image). The method can create human friendly images with pen strokes by using image processing techniques such as spatial filters. In order to create the human friendly image, first, we made the tiny unnecessary contours. Second, we made the second image by inverting the first image and performed a processing similar to the first processing. Last, we subtracted the second image from the first image and added a hatch to it. The sequence of processing enables us to generate a human friendly image with line shading, likely to be sketched by water pen compared to the past method(pencil hatching and sketch effects). Also the proposed method can represent the sketch effects more effectively with applying different hatch to the shading area of a input image.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.465-475
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• 2004

This paper is the first part of the study on the development of a smart active layer (SAL) sensor, which consists of two parts. In this first part, the theory and concept of the SAL sensor is investigated, which is designed for the detection of elastic waves caused by internal cracks and damages in structures. For the development SAL sensor, (i) the basic theory of elastic waves was studied, (ii) the feasible study of the SAL as an elastic waves detection sensor using the finite element analysis (FEA) with respect to a piezoceramic disc was performed. (iii) the comparison of performances between some piezoceramic sensors and a commercial acoustic emission (AE) sensor was accomplished to ensure the applicability by the experimental means, such as a pencil lead break test. Also, the conceptional study for the SAL sensor, which can be utilized for the effective detection and locating of defects by the arrangement of regularly distributed sensors, was discussed.

• Journal of The Korean Association For Science Education
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• v.17 no.1
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• pp.65-73
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• 1997

The purpose of this study is to develop a valid and reliable instrument, applicable to high school Earth Science class experiment. In advance of developing items, I was selected 14 inquiry process skills and specified evaluative objectives for each of them to develop scales and criteria for them. I developed 28 evaluation items for 5 experiment subjects among those of high school Earth Science class. The first field trial was performed a sample of 5 high school students, and the second one using a sample of 25 high school students. The results are as follows. (1) The content validity and reliability(Cronbach $\alpha$) of the developed items were 82.7% and .86, respectively, the developed instrument in this study is considered valid and reliable. (2) The average difficulty index was .69 and the discrimination index was .30. (3) Answer sheets based on the reported results were rated 5 teachers and Inter-rater Reliabilitiy and Inter-rater Consistency were analyzed, its indices were .80 and .76, respectively. (4) The developed items show a low coefficient of .45 with TESIS, a set of paper-and-pencil test items developed by Lee, Hang-Ro(1991). That the experiment assessment is solely subject to the rater's viewpoint has been one of the major problems raised concerning the matter. This research, however, shows that a set of more specified scales and criteria for the evaluation will make it more valid, reliable and efficient.

• Progress in Medical Physics
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• v.14 no.1
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• pp.1-7
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• 2003

In this work we developed a EGS4 control code to calculate the dose distributions for high energy electron beams in water phantom applied longitudinal magnetic field. We reviewed the electron's motion in magnetic field and delivered equations for direction changs of the electron by the external magnetic field. The mathematical results are inserted into the EGS4 code system to account for the presence of external magnetic fields in phantom. The electron pencil beam paths of 6 MeV in water phantom are calculated for magnetic fields of 1-3 T and the dose distributions for a field of 1.0 cm in diameter are calculated for magnetic fields of 0.6-1 T using the code. From the results of path calculations we found that the lateral ranges of the electrons are reduced in the magnetic field of 3 T. For a field of 1 cm diameter and a magnetic field of 1 T, the small dose enhancement near the range of the electrons on the depth dose and the penumbra reduction of 0.15 cm on the beam profile are observed. We discussed and evaluated the results from the theoretical concepts.

• Journal for History of Mathematics
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• v.22 no.1
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• pp.89-110
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• 2009

This paper observed the effect of CAS calculator usage while studying algebra on the achievement of low-achievement students. Participants were composed of 70 low-achievement tenth grade students from a high school located in a metropolitan city. That had never used a mathematics educational calculator before. Target participants were divided into two groups: an experiment group that studied activity papers with the aid of a CAS calculator, and a control group that studied the same activity papers using only paper-and-pencil. The content of the activity papers for the two groups was the same, but the structure differed. Content consisted of numbers and operations, equations and inequalities(character and expressions), and functions. Students in the experiment group exhibited matacognition learning using a CAS calculator. The two groups completed mathematics achievement tests both before and after the activity papers. Therefore, ANCOVA analysis results showed that compared to the pretest, results of the experiment group improved considerably more than the control group.

• Journal of Educational Research in Mathematics
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• v.23 no.2
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• pp.153-171
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• 2013

The purpose of this study is to investigate characteristics of students' problem solving processes based on their mathematical thinking styles and thus to provide implications for teachers regarding how to employ multiple representations. In order to analyze these characteristics, 202 university freshmen were recruited for a paper-and-pencil survey. The participants were divided into four groups on a mathematical-thinking-style basis. There were two students in each group with a total of eight students being interviewed. Results show that mathematical thinking styles are related to defining a mathematical concept, problem solving in relation to representation, and translating between mathematical representations. These results imply methods of utilizing multiple representations in learning and teaching mathematics by embodying Dienes' perceptual variability principle.

• Journal of Educational Research in Mathematics
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• v.27 no.3
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• pp.391-410
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• 2017

This study aims to analyze mathematically gifted students' characteristics of generalization and justification for a given mathematical task and induce didactical implications for individual teaching methods by students' learning styles. To do this, we identified the learning styles of three mathematically gifted 6th graders and observed their processes in solving a given problem. Paper-pencil environment as well as dynamic geometrical environment using Geogebra were provided for three students respectively. We collected and analyzed qualitatively the research data such as the students' activity sheets, the students' records in Geogebra, our observation reports about the processes of generalization and justification, and the records of interview. The results of analysis show that the types of the students' generalization are various while the level of their justifications is identical. Futhermore, their preference of learning environment is also distinguished. Based on the results of analysis, we induced some implications for individual teaching for mathematically gifted students by learning styles.

• School Mathematics
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• v.6 no.4
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• pp.411-433
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• 2004

Many researchers have reported that 7th graders have severe difficulties in using letters and algebraic expressions. This study investigated the way Microsoft Excel contributes to student's understanding of letters and algebraic expressions. For six hours through two weeks, four 7th grade students experienced various activities with Excel after school and both before and after the experimentation, the interviews to check their understanding was conducted. The results were as follows; First, after the experimentation, students used various letters to express formulas and recognized that letters represent not only some objects but also changing objects. Also they accepted that same objects could be represented by different letters and different objects could be represented by the same letters. Second, Excel improved students' abilities to discriminate variables and invariables in the problem and to find mathematical relationships among variables. And with Excel students could divide the whole calculation procedure into several steps in order to handle it more easily. Also, Excel made immediate numerical feedback possible and it made students express the calculation in a more formalized way than a paper and pencil environment did.

• The Journal of the Acoustical Society of Korea
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• v.13 no.6
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• pp.50-59
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• 1994

Spectral analysis of transient elastic waves were carried out in order to identify the propagation modes in glass and unidirectional carbon fibre reinforced plastic (CFRP) plates. Pencil leads were broken on the surface of plates to generate elastic waves, and two broad band transducers of 6.35 mm in diameter and 10 MHz center frequency were placed at the linear location from the source. The frequency spectra of detected signals showed that the wave propagation in the plates obeyed the Lamb wave dispersion relation. The transient signals were the fast propagating modes around maximum group velocity of the lowest and first order symmetric $modes(S_{0} and S_{1}),$ and first order antisymmetric $mode(A_{1})$. The transient signals were not severely distorted due to relatively small dispersion of those modes around the maximum group velocity. The fastest propagating mode in the plates was shown to be $S_{0}$ mode less the than cut-off frequency of $A_{1}$ mode.