• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.651-653
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• 2000

In this study, a distance-measurement system was proposed by using principle of the Michelson Interferometer and a fundamental research was carried out. In case of the rnichelson interferometer, relativity distance was measured by relativity-difference of two course of light. But wavelength of light source were changed in this system in order to use interference phenomenon of michelson interferometer in measuring absolutely distance. Wavelength of input signal were changed periodically and were interfered electrically. So absolute distance can be calculated by using $\Delta\lambda$ and measuring $\eta\Delta$ in electric interference. Nose by a external factor was small in this system because a absolutely distance was measured by phase difference. And a dispersion of noise was small in pulse-echo response because a error was occurred in range of phase difference of signal. Also very wide range can be measured by only single system because informations of distance were acquisited in wavelength level.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.4
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• pp.337-343
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• 2000

Physical properties of matt georgette knitted fabrics, which has been developed recently, were investigated to provide fundamental information for the textile industry. Dimensional characteristics were examined with three different loop lengths, where the plain knitted fabrics were knitted with cotton yam and polyester yarn. The matt georgette plain knitted stitch was fully relaxed after wet relaxation treatment at $130^{\circ}C$ for 30minutes and subsequent tumble dry treatment at $70^{\circ}C$ for 90minutes. As the treatment temperature of wet relaxation became higher and the loop length did shorter, all of stitch density, course density and wale density were increased with 31 of $K_1$ 8.3 of $K_2$ and 3.8 of $K_3$. Also, The higher value of $K_4$ could be obtain with shorter loop length. When the loop length became longer, the $K_4$ value was varied in a wide range with the treatment of wet relaxation and subsequent tumble dry.

• Journal of Korean Neurosurgical Society
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• v.61 no.6
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• pp.661-668
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• 2018

Among the spinal disorders, the treatment approach for spinal deformities has been discussed least among department of neurosurgery. But nowadays, more and more neurosurgeons are interested in spinal deformities as well as complex spinal disorders and are doing not a few surgeries for these kinds of disease. Nevertheless, it is mandatory to understand the course of spinal deformity, principles of treatment, and surgical outcomes and complications. Understanding of the biology, biomechanics and metallurgy of the spine and instrumentation are also required for successful spinal deformity surgery. We need senior mentors and good surgical and neurophysiologic monitoring team. Knowledge of spinal deformity may be augmented with spine fellowships and surgical experience. Step by step training such as basic knowledge, orthopedic as well as neurosurgical disciplines and surgical skills would be mandatory. Neurosurgeons can have several advantages for spinal deformity surgeries. By high-level technical ability of the spinal cord handling to preserve neurological function and familiarity with microscopic surgery, better synergistic effect could be expected. A fundamental understanding of pediatric spinal deformity and growing spine should be needed for spinal deformity surgery.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.106-116
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• 2021

Purpose: This is to provide fundamental resources for the improvement in the department of dental technology curriculum which will ensure effective preparation for the license examination for dental technicians as well as improvement in the students practical skills. Methods: Research analysis was conducted regarding the 2020 academic curriculum table of the department of dental technology established in 19 universities nationwide, from 5th of October 2020 to 30th of November 2020. Results: Research of the ratio of the establishment credit of the 3-year-course major in department of dental technology to the establishment credits of the license examination subjects showed, second semester of the first year (p<0.05), by academic discipline the whole first year (p<0.05) and second semester of first year, to be statistically significant. Conclusion: Hence, it can be concluded that there is a need for the management of a curriculum with distribution of adequate subjects according to academic year and semester, in order to satisfy not only the preparation for the license examination for dental technicians, but also students' academic desires.

• STI Policy Review
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• v.9 no.1
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• pp.55-76
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• 2018

This study analyzed the effect of the government R&D subsidy program on long-term firm survival. In order to estimate the average treatment effect for the treated group, we used the survival analysis and matching method by constituting a comprehensive dataset of more than 90,000 observations. The analysis results show that the government R&D subsidy has a negative impact on long-term firm survival. In particular, not only the subsidy does not have a statistically significant effect on firm survival in the relatively short-term, the survival probability of the subsidized firms is statistically significantly lower than the non-subsidized firms after six years. These results can be seen as weakening the justification of government R&D support. There may be problems in the subsidy policy itself and the process of selection of subsidy awardees; however, the more fundamental problem is that the subsidy policy is concluded as the one-time event. Admittedly, it would be difficult for the government to precisely manage the subsidized projects over a long term period. However, in the case of a project in which short-term performance is detected, it would be necessary to provide a step-by-step support to strengthen the firm's competitiveness through further support and continuous development of performance. Of course, mid- and long-term evaluations of subsidy support policy should be performed in parallel with such phased support.

• Educational Technology International
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• v.19 no.2
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• pp.175-197
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• 2018

Flipped classroom (FC) has gained attention as an active learning approach. Designing effective out-of-class activities to help prepare students for in-class activities is fundamental for successful implementation of FC. This study investigated the effectiveness of Goal-Based Scenarios (GBS) for out-of-class learning in FC. Four out of twelve units in a medical humanities course for Year 2 medical students was redesigned into a FC format, where e-learning modules were designed using a GBS approach for out-of-class activities and classroom debates were implemented for in-class activities. The other eight units were delivered in a conventional classroom debate format, which included reading text materials as pre-class assignments. A formative evaluation study was conducted using questionnaires and interview methods and students' academic achievements were evaluated by comparing their pre- and post-test scores between FC and conventional units. Students had positive perceptions of the e-learning modules in GBS approach and preferred the structure of learning in the FC format. Students' pre-test scores were slightly higher in the FC units, yet their post-test scores were comparable with conventional units. This study illustrates students' perceptions that the learning was bettered structured in FC and that the out-of-class learning using the GBS approach helped them better prepared for in-class activities.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.411-414
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• 2015

The purpose of this study is to conduct a comparative analysis between Korea and the United States of the supply process of unit modular housing at both the factory production phase and the transportation and lifting phase, as part of an attempt to invigorate the unit modular housing market in Korea. Unlike the practice in the United States, one of Korea's unique characteristics is that the floor is constructed with reinforced concrete and hot water heating system. To do this, the wet method in Korea is used that includes concrete placement, curing and constructing hot water floor heating system at the factory production phase, which results in a longer production time and also requires the lifting of heavier loads. In the United States, interior and exterior finishing works of modular housing are performed by different companies, and the distance between the unit module factory and the construction site is quite far. This kind of dualized production structure may cause confusion when it comes to schedule management, procurement management, and stock management. Moreover, problems caused by external environmental factors such as wind and rainfall were reported in the course of long-distance transportation. The results of this case comparison are expected to provide fundamental data that will reduce the amount of trial and error in the unit module production, transportation and lifting work in Korea, which has a comparatively small number of unit modular housing cases.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.688-706
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• 2024

Austenitic stainless steels (ASS) are extensively employed in various sectors such as nuclear, power, petrochemical, oil and gas because of their excellent structural strength and resistance to corrosion. SS304 and SS316 are the predominant choices for piping, pressure vessels, heat exchangers, nuclear reactor core components and support structures, but they are susceptible to stress corrosion cracking (SCC) in chloride-rich environments. Over the course of several decades, extensive research efforts have been directed towards evaluating SCC using diverse methodologies and models, albeit some uncertainties persist regarding the precise progression of cracks. This review paper focuses on the application of Acoustic Emission Technique (AET) for assessing SCC damage mechanism by monitoring the dynamic acoustic emissions or inelastic stress waves generated during the initiation and propagation of cracks. AET serves as a valuable non-destructive technique (NDT) for in-service evaluation of the structural integrity within operational conditions and early detection of critical flaws. By leveraging the time domain and time-frequency domain techniques, various Acoustic Emission (AE) parameters can be characterized and correlated with the multi-stage crack damage phenomena. Further theories of the SCC mechanisms are elucidated, with a focus on both the dissolution-based and cleavage-based damage models. Through the comprehensive insights provided here, this review stands to contribute to an enhanced understanding of SCC damage in stainless steels and the potential AET application in nuclear industry.

• IMMUNE NETWORK
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• v.22 no.3
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• pp.23.1-23.12
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• 2022

Natural infection with severe acute respiratory syndrome-coronavirus-2 or vaccination induces virus-specific immunity protecting hosts from infection and severe disease. While the infection-preventing immunity gradually declines, the severity-reducing immunity is relatively well preserved. Here, based on the different longevity of these distinct immunities, we develop a mathematical model to estimate courses of endemic transition of coronavirus disease 2019 (COVID-19). Our analysis demonstrates that high viral transmission unexpectedly reduces the rates of progression to severe COVID-19 during the course of endemic transition despite increased numbers of infection cases. Our study also shows that high viral transmission amongst populations with high vaccination coverages paradoxically accelerates the endemic transition of COVID-19 with reduced numbers of severe cases. These results provide critical insights for driving public health policies in the era of 'living with COVID-19.'

• Journal of Korean society of Dental Hygiene
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• v.8 no.1
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• pp.23-35
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• 2008

I got the following conclusion that analyzes the dental health recognition, attitude and the action of the students who major in health section executing questionnaire about dental health behaviors from March 3 through 26 with health-related university students in some area in order to arrange the fundamental data that manage their mouth health rationally by using the investigation and comparison by sex and department in dental health teaching. The results obtained were as follows : 1. A large number of students recognized dental health as an important problem, but they believed that the level of their knowledges on dental health was not so high and female students were more negative than male students with regards to their own dental health condition. 2. 49.8% of the students know about tap water fluoridation program control business and 60.7% agreed and boy's approval rate was higher than girl's. But 42.2% of the not-related buccal department's students have a reservation about tap water fluoridation program control business. 3. Average brushing number of the boy is 51.0% 2 times a day according to sex, A girl appeared highest by 48.3% 3 times a day and there was statistically significantly different according to (pE0.01). there wasn't statistically significantly different according to department. Also, the period of the brushing was the most right after a breakfast, in the order of before sleep and after dinner. 4. Whether they go to the dentist's or not, 90.8% of them say 'yes', the result showed statistically significant difference according to sex (pE0.01), but It didn't show statistically significant difference according to department. Also, the purpose for visiting the dentist's office lately was the most caries treatment. and there was statistically significantly different according to sex (pE0.01), but there was not statistically significantly different according to department. 5. Oral health education-related subject approval's rate when the education course open is 65.0% there was statistically significantly different according to department (pE0.01). Also when oral health education-related subject as the liberal arts open' the rate of taking a course application showed 50.2% high appear. there was statistically significantly different according to department(pE0.01).