• Journal of Engineering Education Research
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• v.6 no.1
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• pp.22-31
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• 2003

The purpose of this study was to develop CD-ROM so that students can understand 8051 Microprocessor unit easily in electronics circuit practice subject of technical high school. The study gives students, who have difficulties in learning, a chance for self-directed and supplementary learning by suggesting interface process with 8051 Practice Kit. To achieve these purposes, literature survey, collecting textbooks and materials, development of CD-ROM were gradually carried out. Each steps were as follows: Firstly, in literature survey, concepts and characteristics of multimedia and application to class were reviewed. Secondly, text contents on 8051 Microprocessor unit were analyzed, main contents were extracted and graphic, sound, animation were made. It was consisted of eight basic learning subjects, and designed to flow systematically. In this study, we presented a kind of teaching-learning material by developing CD-ROM in 8051 microprocessor unit in electronics circuit practice subject as a central matter. This material will be able to help technical high school students in learning

• Journal of The Korean Association For Science Education
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• v.36 no.5
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• pp.791-800
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• 2016

This research aimed to identify core words used as associative words and definitions for expressing 'electricity' terminology and to find how core ones are activated to form a cognitive structure, using network analysis. The participants targeted 83 university freshmen students in the University of Education located in suburbs. Depending on their gender, whether or not they completed physics in high school, the associative words and definitions were analyzed using the network method, classifying two sections: before-lesson and after-lesson. The result is as follows: At before-lesson associative words for 'electricity' terminology, a slightly different network construction was revealed based on their two properties. However, after the class, they showed similar network structure irrespective of their distinctive characteristics. When it comes to other 'electricity' definitions, before taking the course, they had similar network connection across the gender but based on physics education status, there appeared subtle differences. Ultimately, after the class they demonstrated similar network structure regardless of their features. In conclusion, this paper suggests educational implications on network analysis, which covers 'electricity' terminology of university students.

• Clean Technology
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• v.18 no.1
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• pp.1-13
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• 2012

Starting with textile products in the middle of 1990, environmental requirements on prohibition of hazardous substances in products have been led by EU member countries and expanded to electrical and electronic equipment with implementaion of RoHS (Restriction of the use of certain hazardous substances in electrical and electronic equipment) in 2006. Under EU REACH (Registration, Evaluation and Authorization of CHemicals), the concept of SVHC (Substances of Very High Concern) and resulting regulatory duties regarding it have been introduced to the supply chain of almost all industry sectors. In this technical review, kinds of hazardous substances, reasons for restrictions and related directives and regulations are reviewed with its influence on the international market. Suggestions are made how to cope with environmental regulations as well as mid-to-long term market strategy to secure global market competitiveness.

• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.93-105
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• 2018

Precise investigation and interpretation of the ground subsidence risk factors needed to predict and evaluate the settlement problems of the surrounding ground due to the ground excavation. There are various geophysical exploration methods to investigate the ground subsidence risk factors. However, there are factors that influence the characteristics of the underground medium in these geophysical methods, and the actual soil contains complex factors affecting geophysical exploration. Therefore, it is necessary to analyze the effects on the geophysical methods based on the understanding of the geotechnical properties of soil. In this study, a test bed was constructed to consider various complicated factors in the complex ground and the ground behavior was analyzed by numerical analysis. In addition, we analyzed the limitations on investigating the ground subsidence risk factors through ground penetration radar (GPR) survey. As a result, ground subsidence of Open-cut Type Excavation is caused by various factors. Especially, in the case of soft ground condition, it was found that it was greatly influenced by the flow change of groundwater level. At the center frequency of GPR of 250 MHz, the attenuation of the electromagnetic wave is severely attenuated in the clay with high electrical conductivity, making it difficult to penetrate deeply into the ground (4 m below the surface). As the electromagnetic waves pass through the groundwater level below the groundwater, the attenuation of the electromagnetic waves becomes severe.

• Korean Chemical Engineering Research
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• v.60 no.4
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• pp.588-593
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• 2022

Terephthalaldehyde (TPA) is introduced as a cross liker to enhance electron transfer of hemin-based cathodic catalyst consisting of polyethyleneimine (PEI), carbon nanotube (CNT) for hydrogen peroxide reduction reaction (HPRR). In the cyclic voltammetry (CV) test with 10 mM H₂O₂ in phosphate buffer solution (pH 7.4), the current density for HPRR of the suggested catalyst (CNT/PEI/hemin/PEI/TPA) shows 0.2813 mA cm^-2 (at 0.2 V vs. Ag/AgCl), which is 2.43 and 1.87 times of non-cross-linked (CNT/PEI/hemin/PEI) and conventional cross liker (glutaraldehyde, GA) used catalyst (CNT/PEI/hemin/PEI/GA), respectively. In the case of onset potential for HPRR, that of CNT/PEI/hemin/PEI/TPA is observed at 0.544 V, while those of CNT/PEI/hemin/PEI and CNT/PEI/hemin/PEI/GA are 0.511 and 0.471 V, respectively. These results indicate that TPA plays a role in facilitating electron transfer between the electrodes and substrates due to the π-conjugated cross-linking bonds, whereas conventional GA cross-linker increases the overpotential by interrupting electron and mass transfer. Electrochemical impedance spectroscopy (EIS) results also display the same tendency. The charge transfer resistance (R_ct) of CNT/PEI/hemin/PEI/TPA decreases about 6.2% from that of CNT/PEI/hemin/PEI, while CNT/PEI/hemin/PEI/GA shows the highest R_ct. The polarization curve using each catalyst also supports the superiority of TPA cross liker. The maximum power density of CNT/PEI/hemin/PEI/TPA (36.34±1.41 μWcm^-2) is significantly higher than those of CNT/PEI/hemin/PEI (27.87±0.95 μWcm^-2) and CNT/PEI/hemin/PEI/GA (25.57±1.32 μWcm^-2), demonstrating again that the cathode using TPA has the best performance in HPRR.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.63-69
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• 2015

In this paper, infrared reflector design targeting infrared stealth effect is presented using structural optimization based on the phase field method. The analysis model was determined to accomplish the design that an incident infrared wave was reflected to a desired direction. The design process was to maximize the objective value at the measuring domain located in a target region and the design objective was set to the Poynting vector value which represents the energy flux. Optimization results were obtained according to the variation of some parameter values related to the phase field method. The model with a maximum objective value was selected as the final optimal model. The optimal model was modified to eliminate the gray scale using the cut-off method and it confirmed improved performance. In addition, to check the desired effect in the middle wave infrared range(MWIR), the analysis was performed by changing the input wavelength. The finite element analysis and optimization process were performed by using the commercial package COMSOL combined with the Matlab programming.

• Journal of the Korean Chemical Society
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• v.56 no.6
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• pp.731-738
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• 2012

The purpose of this study is to analyze the understandings of science high school students on the conception of chemical cell in relation to chemical equilibrium from the microscopic viewpoint at molecular level through questionnaires and follow-up interviews. The results show that they have high understandings on the chemical equilibrium states in the electrochemical cell and on the redox reaction taking place simultaneously when a metal electrode is immersed in the metal ion solution. However, they do not fully comprehend the development of electrical potential difference, electron movement, electrode potential measurement in the half-cells, and calculation of the net cell voltage between anode and cathode in the chemical cell because of difficulties in the microscopic understanding the interaction on the interface at the electrode and the electrolyte solution.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.1 s.4
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• pp.97-107
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• 2004

As one of the most serious urban problems, routine city traffic congestion causes not only unpleasantness but also damage with increases of road tolls. Recently, many TDM plans are being improved along with plans to more effectively utilize established facilities and maximize the effect. To achieve the purpose of Intelligent Transport Systems(ITS). Recently, the core of ITS is Advanced Traveler information Systems (ATIS.) that are activity researched. A development of various muti-media system is very important of road guideline. First of all a business processing for offering travel information and give a consideration to the United states of various muti-media systems.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.6
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• pp.574-579
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• 1999

A counter-flow type horizontal reactor of metal organic chemical vapor deposition was designed with the Reynolds and the Rayleigh numbers of Re = 4.5 and Ra = 215.8, respectively. The GaN thin films were grown and characterized by Hall measurement, double crystal X-ray diffraction analysis and photoluminescence measurement. The Si and Mg were also used for doping of GaN films. The dislocation density of $2.6{\times}10^8/\textrm {cm}^2$ was included in GaN films representing the geometrical lattice mismatch between sapphire substrates and GaN films. The Si doped n-GaN films provide the electron carrier density and mobility in the regions of $10^{17}~10^{18}/\textrm{cm}^3$ and 200~400 $\textrm{cm}^2$/V .sec, respectively. Mg doped p-GaN films were post-annealed and activated with the hole carrier density of $8{\times}10^{17}/{\textrm}{cm}^3$.

• Information Systems Review
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• v.11 no.3
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• pp.107-123
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• 2009

In this paper, we review digital certificate technologies and their applications in e-commerce. Current digital certificate technologies are evaluated and their importance is explained. The configuration of certificate flows from providers to users through software, hardware, and network technologies is described. These five domains and the configuration of digital certificate flows guide our review of the characteristics of digital certificates. We then develop a framework for the classification of digital certificates that integrate these five domains with VeriSign's types and levels of assurance. In order to demonstrate the adequacy of our digital certificate classification framework, we populated it with VeriSign's digital certificates. Within each domain, VeriSign's classes of digital certificates are classified in accordance with the VeriSign type and level of assurance. The results of our analysis suggest that the framework is a useful step in developing a taxonomy of digital certificate technologies. The strengths and weaknesses of the study are discussed, and opportunities for further research are identified and discussed.