• Journal of Preventive Medicine and Public Health
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• v.29 no.4 s.55
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• pp.863-875
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• 1996

In order to prepare the fundamental data for the health promotion by assessing the exposure level of styrene, the author determined the concentration of mandelic acid and phenylglyoxylic acid in urine of 42 workers who were exposed to styrene by high performance liquid chromatography and surveyed 16 symptoms, by questionnaire and also tested neurobehavioral test(digit symbol, benton visual retention) in 2 FRP plants of Kyung Nam area from July to September, 1995. Control was sampled by age sex matching method. The concentration of styrene in air was determined by gas chromatography. The results were as follows; 1. Geometric mean concentration of styrene in air was 17.4ppm, geometric mean concentration of mandelic acid(MA) in urine were 404.3mg/g creatinine for exposure group, 46.4mg/g creatinine for control group, geometric mean concentration of phenylglyoxylic acid(PGA) in urine were 57.5mg/g creatinine for exposure group, 9.5mg/g creatinine for control group. Mean concentration of MA and PGA showed statistically significant difference between exposure group and control group(p<0.01). 2. Number of symptom were 2.9 for exposure group, 3.3 for control group, number of digit symbol were 24.1 for exposure group, 32.5 for control group, number of Benton visual retention test were 6.1 for exposure group, 6.0 for control group, respectively. As result of adjusting the education year, number of Benton visual retention test showed statistically significant difference between exposure group and control group(p<0.05). 3. Excellent correlation were observed between environmental styrene exposure and urinary MA(r=0.80), PGA(r=0.73), and MA+PGA(r=0.81).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.2
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• pp.12-28
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• 2019

Road geometry is one of the many factors that cause crashes, but the effect on traffic accident depends on weather conditions even under the same road geometry. This study identifies the variables affecting the crash severity by matching the highway accident data and weather data for 14 years from 2001 to 2014. A hierarchical ordered Logit model is used to reflect the effects of road geometry and weather condition interactions on crash severity, as well as the correlation between individual crashes in a region. Among the hierarchical models, we apply a random intercept model including interaction variables between road geometry and weather condition and a random coefficient model including regional weather characteristics as upper-level variables. As a result, it is confirmed that the effects of toll, ramp, downhill slope of 3% or more, and concrete barrier on the crash severity vary depending on weather conditions. It also shows that the combined effects of road geometry and weather conditions may not be linear depending on rainfall or snowfall levels. Finally, we suggest safety improvement measures based on the results of this study, which are expected to reduce the severity of traffic accidents in the future.

• Journal of Korea Water Resources Association
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• v.51 no.12
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• pp.1181-1194
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• 2018

This study suggests a novel approach of estimating stream flow discharge using the Synthetic Aperture Radar (SAR) images taken from 2015 to 2017 by European Space Agency Sentinel-1 satellite. Fifteen small to medium sized rivers in the Han River basin were selected as study area, and the SAR satellite images and flow data from water level and flow observation system operated by the Korea Institute of Hydrological Survey were used for model construction. First, we apply the histogram matching technique to 12 SAR images that have undergone various preprocessing processes for error correction to make the brightness distribution of the images the same. Then, the flow estimation model was constructed by deriving the relationship between the area of the stream water body extracted using the threshold classification method and the in-situ flow data. As a result, we could construct a power function type flow estimation model at the fourteen study areas except for one station. The minimum, the mean, and the maximum coefficient of determination ($R^2$) of the models of at fourteen study areas were 0.30, 0.80, and 0.99, respectively.

• Journal of the Korean School Mathematics Society
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• v.24 no.3
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• pp.283-308
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• 2021

This study aims to analyze statistical tasks in Korean and Singaporean textbooks with the mathematical modeling perspective and compare the learning contents and experiences of students from both countries. I analyzed mathematical modeling tasks in the textbooks based on five aspects: (1) the mathematical modeling process, (2) the data type, (3) the expression type, (4) the context, and (5) the mathematical activity. The results of this study show that Korean and Singaporean textbooks provide the highest percentage of the "working-with-mathematics" task, the highest percentage of the "matching task," and the highest percentage of the "picture" task. The real-world context and mathematical activities used in Korean and Singaporean textbooks differed in percentage. This study provides implications for the development of textbook tasks to support future mathematical modeling activities. This includes providing a balanced experience in mathematical modeling processes and presenting tasks in various forms of expression to raise students' cognitive level and expand the opportunity to experience meaningful mathematizing. In addition, it is necessary to present a contextually realistic task for students' interest in mathematical modeling activities or motivation for learning.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.685-693
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• 2021

This study examined the fire risk of the region in Goyang City using the spatial information data of buildings. The economic damage by industry was assessed according to the probability of fire risk. The study area was confined to Goyang-si, Gyeonggi-do, and the same fire risk reduction rate was applied to each region for the convenience of analysis. The possibility of fire was derived based on the buildings' density and usage in the area by National GIS building-integrated information standard data. The calculation of economic damage by industry in Goyang City due to the fire risk was calculated by combining the Goyang-si industry-related model produced by matching with 30 industrial categories in Input-Output Statistics of Korea Bank and 20 industrial categories in the Goyang-si business survey and the possibility of fire. The basic scenario of production impossibility during six months and business loss due to fire was established and analyzed based on the supply model. The analysis showed that Ilsan-dong-gu, Ilsan-seo-gu, and Deokyang-gu suffered the most economic damage. The "electricity, gas, steam, and water business" showed the greatest loss by industry.

• Journal of Christian Education in Korea
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• v.74
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• pp.273-294
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• 2023

The purpose of this study is to use K-MOOC, which has limitations in utilization because it is centered on theory delivery, to derive tasks to activate the teaching methods of instructors, and to implement the derived tasks using the metaverse platform. to develop a prototype. According to the purpose of the study, the study was conducted as follows. First, from October 4 to November 15, 2022, a Delphi survey was conducted on 21 experts with experience of consulting, research, class development, and operation related to the K-MOOC project. Second, in order to realize the tasks in the teaching method field derived from the Delphi survey, matching with the teaching method class model elements to result of Delphi survey was applied was carried out. Finally, based on the results of expert Delphi and the elements of the class model applicable to the metaverse platform, a teaching method was developed. Through the process of the study, a total of 16 detailed items were derived for the teaching method-related tasks for the activation of K-MOOC: support strategic tasks, teaching method competency, aspect of class design, evaluation and sharing of learning outcomes. By applying the metaverse, the teaching model elements for K-MOOC revitalization were derived from four categories: self-directed repetition, individualized problem solving, practice opportunity expansion, and immediate feedback, and matched with the first 16 detailed items. A four-step teaching model was completed: course attendance (step 1), mission analysis by individual level (step 2), sharing of mission solutions (step 3), and mission evaluation and feedback (step 4). Through the results of this study, the possibility of using the metaverse as a teaching practice platform was confirmed even in terms of the introduction and development of specialized techniques.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.17 no.4
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• pp.101-114
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• 2022

Recently, various studies on the entrepreneurial ecosystem have been conducted. The entrepreneurial ecosystem is composed of various elements such as entrepreneurs, governments, and infrastructure, and these factors interact to contribute to economic development. The purpose of this study was to analyze differences in importance and performance of the entrepreneurial ecosystem for startups using the importance-performance analysis (IPA) method. Based on this, the importance and current level of the components of the entrepreneurial ecosystem were identified and policy implications were presented. The results of the study are as follows. The importance ranking was in the order of startup support program(4.43), startup funding (4.39), market accessibility(4.30). The ranking of performance was startup support program(3.81), ease of starting a business(3.76), support for startup support institutions(3.66), and startup funding(3.66). All elements of the entrepreneurial ecosystem showed higher importance than performance. This means that the components of the entrepreneurial ecosystem in Korea are recognized as important, but do not play a significant role in terms of performance for startups. In addition, the factors with the highest improvement in the importance-performance matrix were 「safety nets for startup failure」, 「culture of acceptance of failure」, 「ease of market entry」, 「ease of startup survival」, and 「ease of exit」. This study suggested improvement measures such as establishing a social safety net, improving awareness of startup failure culture, matching successful startups, strengthening scale-up support by growth stage, easing regulations in new business fields, and diversifying investment recovery strategies.

• Health Policy and Management
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• v.34 no.1
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• pp.87-93
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• 2024

Background: In recent years, studies have shown conflicting results regarding the benefits of dietary supplements in reducing healthcare expenditures. This study aimed to address this inconsistency by examining the association between supplement consumption and health expenditures using nationally representative data from the Korea Health Panel Survey (2019-2020). Methods: A 1:1 matched case-control dataset was established using propensity score matching technique based on supplement consumption. Then, total annual healthcare expenditures were compared between the two groups. In addition, a multivariate regression analysis (Proc Surveyreg) was performed to determine the association between the supplement consumption and medical costs. Results: The supplement user group spent about 1.72 million Korean won, while the non-user group spent about 1.43 million Korean won on medical services (p=0.0186). The results of multivariate regression showed that the costs were approximately 26.15% higher in the user group than in the non-user group (p=0.0004). Conclusion: Contrary to the previous studies that have shown the benefits of supplement use in reducing healthcare costs, this study showed that those who consistently consumed supplements spent more on medical services. This can be interpreted in the same context as previous studies suggesting that dietary supplement intake is a healthy behavior for managing one's health. However, we caution against drawing firm conclusions due to data limitations. Further analysis using patient-level epidemiologic data is needed.

• Journal of Dental Rehabilitation and Applied Science
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• v.40 no.3
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• pp.142-148
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• 2024

Purpose: The purpose of this study was to investigate the accuracy of digital mounting with occlusal scans in the interocclusal record for a full-mouth fixed prosthetic treatment condition. Materials and Methods: The entire maxillary teeth were prepared in a dentiform model and attached to an articulator in maximum intercuspation. Temporary crowns were fabricated and occlusion was adjusted. After scanning the arch with tooth preparation, digital mounting was performed using an occlusion scan of the anterior or posterior teeth areas. The accuracy of the positioned jaw relation was evaluated three-dimensionally through positional deviation and angular error of the occlusal plane. Afterwards, the same procedure was repeated on the partially edentulous model to evaluate the accuracy of digital interocclusal record. Kruskal-Wallis test and Mann-Whitney U test were used for statistical analysis, and the significance level was set at 0.05. Results: There was no significant difference in the positional error at the center of the arch in the digitally established jaw relation depending on the scan area used and remaining tooth conditions (P = 0.53). The angular error of the occlusal plane was larger when the anterior teeth were used as the overlapping area, and a smaller error value was observed when both posterior teeth were used as the overlapping area (P < 0.001). Conclusion: The use of bilateral posterior occlusal scans is recommended when digitally mounting the jaw relation established with temporary teeth during full-mouth fixed prosthetic treatment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.711-719
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• 2011

A study of miniaturization of an L-band orthomode transducer(OMT) for field experiments of radar backscatter is presented in this paper. The proposed OMT is not required the additional waveguide taper structures to connect with a standard adaptor by the newly designed junction structure which bases on a waveguide taper. Total length of the OMT for L-band is about 1.2 ${\lambda}_o$(310 mm) and it's a size of 60 % of the existing OMTs. And, to increase the matching and isolation performances of each polarization, two conducting posts are inserted. The bandwidth of 420 MHz and the isolation level of about 40 dB are measured in the operating frequency. The L-band scatterometer consisting of the manufactured OMT, a horn-antenna and network analyzer(Agilent 8753E) was used STCT and 2DTST to analysis the measurement accuracy of radar backscatter. The full-polarimetric RCSs of test-target, 55 cm trihedral corner reflector, measured by the calibrated scatterometer have errors of -0.2 dB and 0.25 dB for vv-/hh-polarization, respectively. The effective isolation level is about 35.8 dB in the operating frequency. Then, the horn-antenna used to measure has the length of 300 mm, the aperture size of $450{\times}450\;mm^2$, and HPBWs of $29.5^{\circ}$ and $36.5^{\circ}$ on the principle E-/H-planes.