• Journal of the Korean School Mathematics Society
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• v.22 no.1
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• pp.63-80
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• 2019

This study aims to investigate noticing of pre-service secondary mathematics teachers. For the purpose of this study, we analyzed journals of four pre-service mathematics teachers. Our analysis was based on a framework including three categories such as Aware, Interpret, and Response. As results, we found a tendency that pre-service secondary mathematics teachers have more general awareness of students and relatively fewer interpretations of students' mathematical thinking than other categories. In addition, in the category of Response, the pre-service secondary mathematics teachers were more likely to explain to students than to promote students' thinking through questions. Based on these results, we would like to discuss implications for pre-service secondary mathematics teacher education.

• Korean Journal of Optics and Photonics
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• v.30 no.3
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• pp.94-100
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• 2019

The near-field subwavelength squint-less focusing system of a phased array antenna is designed and demonstrated by numerical simulation. The Huygens-Fresnel principle is applied to numerical simulation for calculation of the phased array antenna at microwave frequency. It was shown that beam squinting can be eliminated, utilizing true-time optical delay lines based on a chirped fiber grating in the proposed system. Furthermore, subwavelength focusing with high numerical aperture can be achieved by considering the fact that the array elements of the phased-array antenna can be treated as diffractive elements in an optical lens system. Also, side lobes can be suppressed by decreasing the distance between element antennas to less than half of the wavelength.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.381-388
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• 2016

Biopolishing using cellulases was introduced in the production of cotton fabric in order to improve the quality of fabric environmental friendly and is commonly used in the textile industry. In this study, the application of a crude cellulase from Acanthophysium sp. KMF001, which was excellent for the saccharification of cellulose, on biopolishing was evaluated. The optimum treatment biopolishing condition was at $50^{\circ}C$ and pH 4.5 for 60 minutes with 10% crude cellulase of fabric weight. After the optimized biopolishing, the crude cellulase of Acanthophysium sp. KMF001 reduced the tensile strength of the tested cotton fabric less than a commercial cellulase. The appearance of the cotton fabric after the treatment of the crude cellulase of Acanthophysium sp. KMF001 was similar to the fabric after a commercial cellulase treatment. All these results support that the crude cellulase of Acanthophysium sp. KMF001 was a good biopolishing cellulase.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.667-674
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• 2013

Improving the earthquake resistance of buildings through seismic retrofitting using steel braces can result in brittle failure at the connection between the brace and the building, as well as buckling failure of the braces. This paper proposes a new seismic retrofit methodology combined with glass fiber sheet (GFS) and non-compression X-brace system using carbon fiber (CFXB) for reinforced concrete buildings damaged in earthquakes. The GFS is used to improve the ductility of columns damaged in earthquake. The CFXB consists of carbon fiber bracing and anchors, to replace the conventional steel bracing and bolt connection. This paper reports the seismic resistance of a reinforced concrete frame strengthened using the GFS-CFXB system. Cyclic loading tests were carried out, and the hysteresis of the lateral load-drift relations as well as ductility capacities were investigated. Carbon fiber is less rigid than the conventional materials used for seismic retrofitting, resulting in some significant advantages: the strength of the structure increased markedly with the use of CF X-bracing, and no buckling failure of the bracing was observed.

• Journal of the Korean Geosynthetics Society
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• v.19 no.3
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• pp.23-33
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• 2020

The lateral bearing characteristics are important factors in the case of large diameter drilled shafts and the measures to increase this are to improve the adjacent ground of the pile to increase the rigidity and to increase the rigidity of the pile itself. There are many suggestions for increasing rigidity by reinforcing casing on the pile, but few studies have been done related to this. Therefore, in this study, the lateral bearing characteristics according to casing reinforcement length were studied for each ground condition using non-linear analysis to evaluate the appropriate casing reinforcement length of the large diameter drilled shafts depending on the ground conditions. As a result, the lateral bearing characteristics of the large diameter drilled shafts are most effective if the casing reinforcement length ratio is 1.2, and depending on the ground conditions, the more loose the ground, the greater the reinforcement effect.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3722-3730
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• 2015

The performance improvement of a small centrifugal compressor for waste water treatment has been conducted by the design change of vaneless diffuser and volute casing. Existing two compressors use a common impeller, but the width and length of the vaneless diffuser and the cross-sectional shape of the volute casing are different, respectively. Based on the experiment of the existing two compressors and their CFD results, the design of the vaneless diffuser and the volute casing has been changed. It was found that the strength of the interaction among the volute tongues, the vaneless diffusers and the impellers of two existing/one improved compressors, was affected by the cross-sectional area and inlet radial length of the volute casing including system losses' change. The efficiency of the impeller with one existing design was increased as the decrease of the width of the vaneless diffuser, but losses at the diffuser were accumulated. In conclusion, approximately 2.88%p efficiency increase at the design point of the new compressor with the improved design has been confirmed by CFD analysis results.

• Journal of Digital Convergence
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• v.17 no.8
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• pp.293-301
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• 2019

The purpose of this study was to explore the relationship andinfluence of Focusing manner to deal with somatization symptoms of adolescents with experience of cyberbullying. For this study, we conducted on teenagers aged 14 to 19. A total of 366 of these results -84 men (23%) and 282 women(77%)- were used for the analysis. Data was analyzed through frequency analysis, reliability analysis, correlation analysis, and multiple regression analysis. As a result, cyber-bullying experiences have a positive effect on somatizaion symptoms. Among the sub-factors of focusing manner, "knowledge" and "reviewing" have a negative effect on somatizaion symptoms, and "expression" has an negative effect on somatizaion symptoms. Based on the results of the study, the need for a therapeutic approach to focusing manner was presented when appealing for somatizaion symptoms of adolescents who experienced cyberbullying.

• The Mathematical Education
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• v.60 no.2
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• pp.229-247
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• 2021

Students' mathematical thinking is represented via various forms of outcomes, such as written response and verbal expression, and teachers could infer and respond to their mathematical thinking by using them. This study analyzed 39 elementary teachers' competency to notice students' problem-solving strategies containing mathematical errors in fraction addition and subtraction with uncommon denominators problems. Participants were provided three types of students' problem-solving strategies with regard to fraction addition and subtraction problems and asked to identify and interpret students' mathematical understanding and errors represented in their artifacts. Moreover, participants were asked to design additional questions and problems to correct students' mathematical errors. The findings revealed that first, teachers' noticing competency was the highest on identifying, followed by interpreting and responding. Second, responding could be categorized according to the teachers' intentions and the types of problem, and it tended to focus on certain types of responding. For example, in giving questions responding type, checking the hypothesized error took the largest proportion, followed by checking the student's prior knowledge. Moreover, in posing problems responding type, posing problems related to student's prior knowledge with simple computation took the largest proportion. Based on these findings, we suggested implications for the teacher noticing research on students' artifacts.

• The Mathematical Education
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• v.62 no.3
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• pp.341-362
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• 2023

This study analyzed student noticing in a lesson that emphasized relational understanding of equal signs for first graders from four aspects: centers of focus, focusing interactions, mathematical tasks, and nature of the mathematical activity. Specifically, the instructional factors that emphasize the relational understanding of equal signs derived from previous research were applied to a first-grade addition and subtraction unit, and then lessons emphasizing the relational understanding of equal signs were conducted. Students' noticing in this lesson was comprehensively analyzed using the focusing framework proposed in the previous study. The results showed that in real classroom contexts centers of focus is affected by the structure of the equation and the form of the task, teacher-student interactions, and normed practices. In particular, we found specific teacher-student interactions, such as emphasizing the meaning of the equals sign or using examples, that helped students recognize the equals sign relationally. We also found that students' noticing of the equation affects reasoning about equation, such as being able to reason about the equation relationally if they focuse on two quantities of the same size or the relationship between both sides. These findings have implications for teaching methods of equal sign.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.2
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• pp.246-251
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• 2012

Pulse electrochemical polishing process has been used to improve mechanical properties such as surface roughness and corrosion resistance on conductive metallic materials. In addition, pulse electrochemical polishing process with various frequency may produce a lustrous, smoother, deburred and cleaned surface on workpiece. The aim of this paper is to study surface characteristics of pulse electrochemical polishing for various frequency conditions using AFM to verify localized surface variation in nanometer scale.