• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.15-23
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• 2021

In this paper, service life for RC(Reinforced Concrete) substructure subjective to carbonation was evaluated through deterministic and probabilistic method considering field investigation data and Design Code(KDS 14 20 40). Furthermore changes in service life with increasing COV(Coefficient of Variation) and equivalent safety index meeting the same service life were studied. From the investigation, the mean and its COV of cover depth were evaluated to 70.0 ~ 90.0 mm and 0.2, respectively. With intended failure probability of 10.0 % and 70 mm of cover depth, service life decreased to 137 years, 123 years, and 91 years with increasing COV of 0.05, 0.1, and 0.2, respectively. In the case of 80 mm of cover depth, it changes to 179 years, 161 years, and 120 years with increasing COV. The equivalent safety index meeting the same service life from deterministic method showed 1.66 ~ 3.43 for 70 mm of cover depth and 1.61 ~ 3.24 for 80 mm of cover depth, respectively. The various design parameters covering local environment and quality condition in deterministic method yields a considerable difference of service life, so that determination of design parameters are required for exposure conditions and parameter variation.

• Journal of the Korean Geotechnical Society
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• v.35 no.6
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• pp.17-26
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• 2019

In this study, the statistical characteristics of the resistance bias factors were analyzed using a high-quality field load test database, and the total resistance bias factors were estimated considering the soil uncertainty and construction errors for the application of the limit state design of aggregate pier foundation. The MLR model by Bong and Kim (2017), which has a higher prediction performance than the previous models was used for estimating the resistance bias factors, and its suitability was evaluated. The chi-square goodness of fit test was performed to estimate the probability distribution of the resistance bias factors, and the normal distribution was found to be most suitable. The total variability in the nominal resistance was estimated including the uncertainty of undrained shear strength and construction errors that can occur during the aggregate pier construction. Finally, the probability distribution of the total resistance bias factors is shown to follow a log-normal distribution. The parameters of the probability distribution according to the coefficient of variation of total resistance bias factors were estimated by Monte Carlo simulation, and their regression equations were proposed for simple application.

• Journal of the Korean earth science society
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• v.40 no.3
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• pp.259-271
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• 2019

A statistical downscaling method was adopted in order to establish the high-resolution wave prediction system in the East Sea coastal area. This system used forecast data from the Global Wave Watch (GWW) model, and the East Sea and Busan Coastal Wave Watch (CWW) model operated by the Korea Meteorological Administration (KMA). We used the CWW forecast data until three days and the GWW forecast data from three to seven days to implement the statistical downscaling method (inverse distance weight interpolation and conditional merge). The two-dimensional and station wave heights as well as sea surface wind speed from the high-resolution coastal prediction system were verified with statistical analysis, using an initial analysis field and oceanic observation with buoys carried out by the KMA and the Korea Hydrographic and Oceanographic Agency (KHOA). Similar to the predictive performance of the GWW and the CWW data, the system has a high predictive performance at the initial stages that decreased gradually with forecast time. As a result, during the entire prediction period, the correlation coefficient and root mean square error of the predicted wave heights improved from 0.46 and 0.34 m to 0.6 and 0.28 m before and after applying the statistical downscaling method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.154-159
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• 2019

The glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system was fabricated by using yttrium oxide and iron oxide that it can reduce the melting temperature and affect the homogenization. Zirconium sulfate was used as a nucleation agent. Calcium phosphate was used to improve the flow the glass so as reduce the viscosity of the glass. The glass-ceramics met a thermal shock test of more than $750^{\circ}C$ and the temperature at which the coefficient of thermal expansion rapidly increased at over $800^{\circ}C$ was shifted by about the above $30^{\circ}C$. Therefore, it is concluded that the glass-ceramic of $Li_2O-Al_2O_3-SiO_2$ system with yttrium oxide and iron oxide was founded to have good melting conditions and excellent thermal expansion resistance at high temperature such as special field for kitchen utensils.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.93-101
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• 2019

The purpose of this study is to identify the control effect of empowerment from the effect to the task satisfaction of the nursing staff of the manager of followership, to study the relationship between the followership of nursing manager, task-satisfaction and empowerment that the nurse recognized. The data collection was conducted for nurses working at four general hospitals with 500 beds or more in Jeollanam-do from March 2 to March 17, 2019. The data were analyzed with the general characteristics of the subjects, and the degree of measurement variables were determined by frequency analysis and technical statistical analysis. The differences in the relevant factors according to the general characteristics were analyzed by t-test and ANOVA, and the correlation and multicollinearity among the measurement variables were analyzed as Pearson's correlation coefficiency, and Moderator regression analysis was performed to verify the adjustment effect of the empowerment. The results of the study showed significant results nursing managers' followership, empowerment and job satisfaction by the educational level. In addition, difference from work experience has shown statistically significant differences in job satisfaction. It has been shown that there is a static correlation between the followership of nursing manager that the subject recognized, empowerment and task satisfaction, the influence between followership and job satisfaction has been found to act as adjustment variables on empowerment. The conclusion of this study is meaningful in that it has verified its influence by applying recently emerging followership to nursing field. From now on, extensive research is important for the members to develop the leadership of members and followership.

• The Journal of the Korea Contents Association
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• v.19 no.5
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• pp.389-403
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• 2019

This study has a purpose, that investigating influence of learning characteristic, lifelong learning participation motive, and wisdom that adult has at learning outcome and whether it has mediating effect of wisdom at influence that learning characteristic and lifelong learning participation motive have. For this, the subjects of the study was 425 adult learners from 20 to 69 years old who participated or are participating at Seoul, Incheon, and Gyeonggi-do. The results of this study are as in the following. At first, as a result of investigating relationship between learning characteristic, lifelong learning participation motive, wisdom, and learning outcome, the correlation coefficient of all variables appeared meaningfully. Second, as a result of investigating influence that learning characteristic, lifelong learning participation motive, and wisdom have in learning outcome, the most influential variable was learning value, the rest were cognitive capability, activity direction motive, learning direction motive and positive life attitude in this order. The third, as a result of investigating mediation effect of wisdom at influence that learning characteristic and lifelong learning participation motive have in learning outcome, Wisdom at the influence that learning characteristic have on learning outcome had completely mediated effect, and the wisdom at the influence that lifelong participation motive have on learning outcome had partially mediated effect. Thus, it was shown up that adult's learning characteristic and lifelong learning participation motive are able to increase effectively learning outcome by mediating wisdom. Therefore it is implying that it is essential to consider learning characteristic and lifelong learning participation motive in lifelong education field, and learning circumstance related with wisdom is important, as wisdom is important variable for increasing learning outcome.

• The Journal of the Korea Contents Association
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• v.21 no.10
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• pp.240-263
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• 2021

A study on the public design rules of the government and each local government showed that the historical and cultural street landscape was included in the public design field, but it did not provide a clear evaluation index for the historical and cultural street public design. Against this background, this study intends to provide basic data for the improvement and improvement of the public design of the historical and cultural street in the future by producing an evaluation index for the public design of the historical and cultural street landscape. First, in this study, 6 evaluation indicators and 19 detailed items were derived by conducting expert Delphi survey twice on the basis of previous studies. Second, exploratory factor analysis and AHP analysis were conducted through a survey to verify the validity of the evaluation index and the priority of the index items, and as a result of the analysis, the Cronbach'α coefficient and the consistency ratio were verified. Among the evaluation indicators objectively derived through the above method, the priority was 'historical and culture-related> public-related> safety-related> accessibility-related> lasting-related> related to aesthetic harmony. The results of this study are meaningful in that they can provide basic data for the improvement and improvement of public design of historical and cultural streets in the future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.5
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• pp.320-333
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• 2019

In this study, a physics-based 3D morphology model for the estimation of an erosion rate of nourished beach is newly proposed. As a hydrodynamic module, IHFOAM toolbox having its roots on the OpenFoam is used. On the other hand, the morphology model comprised a transport equation for suspended sediment, and Exner type equation derived from the viewpoint of sediment budget with the bed load being taken to accounted. In doing so, the incipient motion of sediment is determined based on the Shields Diagram, while the bottom suspended sediment concentration, the bed load transport rate is figured out using the bottom shearing stress directly calculated from the numerically simulated flow field rather than the conventional quadratic law and frictional coefficient. In order to verify the proposed morphology model, we numerically simulate the nonlinear shoaling, breaking over the uniform beach of 1/m slope, and its ensuing morphology change. Numerical results show that the partially skewed, and asymmetric bottom shearing stresses can be successfully simulated. It was shown that sediments suspended and eroded at the foreshore by wave breaking are gradually drifted toward a shore and accumulated in the process of up-rush, which eventually leads to the formation of swash bar. It is also worth mentioning that the breaker bar formed by the sediments dragged by the back-wash flow which commences at the pinnacle of up-rush as the back-wash flow gets weakened due to the increased depth was successfully duplicated in the numerical simulation.

• Tunnel and Underground Space
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• v.30 no.6
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• pp.540-550
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• 2020

Machine learning has been actively used in the field of automation due to the development and establishment of AI technology. The important thing in utilizing machine learning is that appropriate algorithms exist depending on data characteristics, and it is needed to analysis the datasets for applying machine learning techniques. In this study, advance rate is predicted using geotechnical and machine data of TBM tunnel section passing through the soil ground below the stream. Although there were no problems of application of statistical technology in the linear regression model, the coefficient of determination was 0.76. While, the ensemble model and support vector machine showed the predicted performance of 0.88 or higher. it is indicating that the model suitable for predicting advance rate of the EPB Shield TBM was the support vector machine in the analyzed dataset. As a result, it is judged that the suitability of the prediction model using data including mechanical data and ground information is high. In addition, research is needed to increase the diversity of ground conditions and the amount of data.

• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.503-514
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• 2021

Rice production with adequate level of area is important for decision making of rice supply and demand policy. It is essential to grasp rice cultivation areas in advance for estimating rice production of the year. This study was carried out to classify paddy rice cultivation in Gimje-si using sentinel-1 SAR (synthetic aperture radar) and UAV imagery in early July. Time-series Sentinel-1A and 1B images acquired from early May to early July were processed to convert into sigma naught (dB) images using SNAP (SeNtinel application platform, Version 8.0) toolbox provided by European Space Agency. Farm map and parcel map, which are spatial data of vector polygon, were used to stratify paddy field population for classifying rice paddy cultivation. To distinguish paddy rice from other crops grown in the paddy fields, we used the decision tree method using threshold levels and random forest model. Random forest model, trained by mainly rice cultivation area and rice and soybean cultivation area in UAV image area, showed the best performance as overall accuracy 89.9%, Kappa coefficient 0.774. Through this, we were able to confirm the possibility of early estimation of rice cultivation area in Gimje-si using UAV image.