• Journal of Korean Society of Environmental Engineers
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• v.39 no.12
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• pp.741-749
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• 2017

This study aims to provide the technical considerations and implications for the development of soil vulnerability assesment tool based on the review of existing tools and case studies applied both domestically and internationally. For this study, we specifically investigated the basic theories and major features implemented in the screening models abroad. In contrast, one case study of prioritizing the vulnerable districts was presented to identify the research trends in Korea. Our literature review suggested that the characteristic of target areas and contaminants needed to be properly incorporated into soil vulnerability assessment because the current tools in Korea neglected these properties which prevented this tool from being used as a correct measure of soil management and prevention. We also reached the conclusion that in terms of technical aspect, the soil vulnerability assessment tool should be developed based on the physical theory and environmental data that were varied over space and time so that the end-users were able to readily and effectively screen soil vulnerability over large areas. In parallel with technical improvement, great effort needed to be devoted to develop an integrated environmental information system that increased the availability of data and shared various types of environmental data through enhanced multi-agency collaboration.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.2
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• pp.89-97
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• 2013

The purpose of this study is to investigate fluoride release in the oral cavity from polymer adhesive tape which is NaF coated PVA. 45 healthy adults were divided into 3 groups by the type of topical fluoride applied: 60seconds taste$^{(R)}$ APF gel (group 1), FluoroDose$^{(R)}$ varnish (group 2) and NaF-PVA (group 3). Topical fluoride was applied to the facial surface of maxillary 12 teeth and unstimulated whole saliva was collected to measure fluoride release after 1, 3, 6, 12, 24, and 48 hours. Fluoride-sensitive electrode was used for measuring the fluoride concentration in the saliva samples. All three groups showed significantly higher value for fluoride concentration than the baseline after 1 and 3 hours (p < 0.05). After 6 hours, group 3 showed significantly higher fluoride concentration than the baseline (p < 0.05) and also showed significantly higher value for fluoride concentration than group 1 and group 2. Between group 1 and group 2, however, there was no significant difference statistically with respect to fluoride concentration value (p > 0.05).

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.2
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• pp.79-91
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• 2020

Accurate assessment of greenhouse gas emissions is a cornerstone of every climate change response study, and reliable assessment of greenhouse gas emission data is being used as a practical basis for the entire climate change prediction and modeling studies. Essential, fundamental technologies for estimating greenhouse gas emissions include an on-site monitoring technology, an evaluation methodology of uncertainty in emission factors, and a verification technology for reductions. The closed chamber method is being commonly used to measure gas fluxes between soil-vegetation and atmosphere. This method has the advantages of being simple, easily available and economical. This study presented the technical bases of the closed chamber method for measuring methane fluxes from a rice paddy. The methane fluxes from rice paddies occupy the largest portion of a single source of greenhouse gas in the agricultural field. We reviewed the international and the domestic studies on automated chamber monitoring systems that have been developed from manually operated chambers. Based on this review, we discussed scientific concerns on chamber methods with a particular focus on quality control for improving measurement reliability of field data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.721-728
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• 2017

High-grade gray cast iron (HCI350) was prepared by adding Cr, Mo and Cu to the gray cast iron (GC300). Their microstructure, mechanical properties and fatigue strength were studied. Cast iron was made from round bar and plate-type castings, and was cut and polished to measure the percentage of each microstructure. The size of flake graphite decreased due to additives, while the structure of high density pearlite increased in volume percentage improving the tensile strength and fatigue strength. Based on the fatigue life data obtained from the fatigue test results, the probability - stress - life (P-S-N) curve was calculated using the 2-parameter Weibull distribution to which the maximum likelihood method was applied. The P-S-N curve showed that the fatigue strength of HCI350 was significantly improved and the dispersion of life data was lower than that of GC300. However, the fatigue life according to fatigue stress alleviation increased further. Data for reliability life design was presented by quantitatively showing the allowable stress value for the required life cycle number using the calculated P-S-N curve.

• Journal of the Korea Convergence Society
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• v.10 no.3
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• pp.49-57
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• 2019

The core technology development of the Fourth Industrial Revolution is linked to the development of other core technologies, which will change the industrial structure in the future and create a new smart business model. In this paper, tried to analyze the technology maturity level and analyze the technology maturity. To do this, used technology trend information to investigate and integrate the market, policy, etc. Of core technology of the 4th Industrial Revolution to achieve a comprehensive maturity level. Because technology maturity measures are scored by technology developers, prejudices may be acted upon according to a person's tendency, which may be a subjective evaluation. It is also a measure of the maturity of individual technologies, and thus is not suitable for evaluating the overall system integration perspective. However, it is possible to evaluate the maturity before integrating the core element technologies constituting the whole system and to use it as a means to compare the effect of the whole system and its feasibility and play an important role in the planning of technology development.

• Fire Science and Engineering
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• v.32 no.6
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• pp.134-140
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• 2018

This study examined the adequacy of a school classroom's occupant load density standard to cope with the issues associated with the decreasing number of students and regional variations. Therefore, this study analyzed the occupant load density standards of kindergarten, elementary school, middle school, high school, and universities using the data open to the public by the Ministry of Education. The results revealed a high variance in the occupant load density according to the school type. The median values were 1.49, 3.45, 2.64, 2.45, and $3.41m^2/person$ for kindergarten, elementary school, middle school, high school, and universities, respectively. Although the occupant load density was higher than the current standard ($1.9m^2/person$), except for kindergarten, the present standard did not need to be improved immediately, considering the purpose of calculating the maximum occupancy. On the other hand, if improvements are made in line with other enhancements of a national education policy, it will be possible to mitigate the measure to $2.5m^2/person$ based on the survey results.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.71-77
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• 2011

Recently, non-destructive stress measurement method using magnetic anisotropy sensor has been applied to the construction site such as steel bridges and steel pipes. In addition, steel rib used in the tunnel construction site was found to be possible to measure the stress by non-destructive method. In this study, steel loading experiments using magnetic anisotropy sensor developed in Japan and strain gauges were conducted to derive stress sensitivity curve for domestic steel SS400. Also, additional steel loading experiments and numerical analysis were performed for evaluation of applicability for non-destructive stress measurement method using magnetic anisotropy sensor. As a result of this study, stress sensitivity curves for domestic steel SS400 were derived using output voltage measured by magnetic anisotropy sensor and average of stress measured by strain gauges depending on the measurement location. And as a result of comparing additional steel loading experiments with the numerical analysis, error level of magnetic anisotropy sensor is around 20MPa. When considering the level of the yield stress(245MPa) of steel, in case of using magnetic anisotropy sensor in order to determine the stress status of steel, it has sufficient accuracy in engineering. Especially, magnetic anisotropy sensor can easily identify the current state of stress which considers residual stress at steel structure that stress measurement sensor is not installed, so we found that magnetic anisotropy sensor can be applied at maintenance of steel structure conveniently.

• Journal of The Korean Association of Information Education
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• v.26 no.3
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• pp.197-207
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• 2022

In this paper, we develop a machine learning based block code generation and recommendation model for the purpose of reducing cognitive load of learners during coding education that learns the learner's block that has been made in the block programming environment using natural processing model and fine-tuning and then generates and recommends the selectable blocks for the next step. To develop the model, the training dataset was produced by pre-processing 50 block codes that were on the popular block programming language web site 'Entry'. Also, after dividing the pre-processed blocks into training dataset, verification dataset and test dataset, we developed a model that generates block codes based on LSTM, Seq2Seq, and GPT-2 model. In the results of the performance evaluation of the developed model, GPT-2 showed a higher performance than the LSTM and Seq2Seq model in the BLEU and ROUGE scores which measure sentence similarity. The data results generated through the GPT-2 model, show that the performance was relatively similar in the BLEU and ROUGE scores except for the case where the number of blocks was 1 or 17.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.135-139
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• 2014

The hydride vapor phase epitaxy (HVPE) grown GaN samples to precisely measure the surface characteristics was applied to a molten KOH/NaOH wet chemical etching. The etching rate by molten KOH/NaOH wet chemical etching method was slower than that by conventional etching methods, such as phosphoric and sulfuric acid etching, which may be due to the formation of insoluble coating layer. Therefore, the molten KOH/NaOH wet chemical etching is a better efficient method for the evaluation of etch pits density. The grown GaN single crystals were characterized by using X-ray diffraction (XRD) and X-ray rocking curve (XRC). The etching characteristics and surface morphologies were studied by scanning electron microscopy (SEM). From etching results, the optimum etching condition that the etch pits were well independently separated in space and clearly showed their shape, was $410^{\circ}C$ and 25 min. The etch pits density obtained by molten KOH/NaOH wet chemical etching under optimum etching condition was around $2.45{\times}10^6cm^{-2}$, which is commercially an available materials.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.333-346
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• 2002

The continuous indentation techniques are one of the most effective methods to nondestructively estimate mechanical properties. There are many applications in various dimensions of materials from macro-scale, through micro-scale, even to nano-scale range. The macro-range technology of kgf-load level is now focused on the evaluation of tensile properties and residual stress of bulk materials, for example, used in conventional load-bearing structures and in-use pipelines. The technology and the apparatus were successfully developed by a domestic research group. The micro-range technology of gf-load level can be applied to investigate some property-gradient materials such as weldment. Because it has better spatial resolution than the macro-range technology. The nano-range technology (called nanoindentation technique) of mgf-load level is basically used to evaluate hardness and modulus of micro- and nano-materials. Moreover, many researches are going on to measure tensile properties and residual stress. The nanoindentation technology is easy to be applied to the various fields, such as semiconductor devices, multiphase materials, and biomaterials, though other methods are too difficult to be applied due to dimensional or environmental limitations. On the basis of these accomplishments, the international and the domestic standards are being established.