• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.151-151
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• 2019

Because drought is a complex and stochastic phenomenon in nature, statistical approaches for drought assessment receive great attention for water resource planning and management. Generally drought characteristics such as severity, duration and intensity are modelled separately. This study aims to develop a relationship between drought characteristics using a bivariate copula model. To achieve the objective, we calculated the Standardized Precipitation Index (SPI) using rainfall data at 6 rain gauge stations for the period of 1961-1999 in Jehlum River Basin, Pakistan, and investigated the drought characteristics. Since there is a significant correlation between drought severity and duration, they are usually modeled using different marginal distributions and joint distribution function. Using exponential distribution for drought severity and log-logistic distribution for drought duration, the Galambos copula was recognized as best copula to model joint distribution of drought severity and duration based on the KS-statistic. Various return periods of drought were calculated to identify time interval of repeated drought events. The result of this study can provide useful information for effective water resource management and shows superiority against univariate drought analysis.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.3
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• pp.100-106
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• 1990

Microcracking of type 304 stainless steel at $593^{\circ}C(1,100^{\circ}F)$ has been studied, in particular, initiation, growth, and coalescence of fatigue and creep microcracks on smooth specimens and small notch specimens via surface replicas and photomicrographs. Quantitative information, such as, initiation period, growth, and coalescence behavior, statistical distributions of crack length, density of cracks, distribution patterns and crack growth properties, were obtained. From this study, the fracture process, fatigue life, and creep life prediction characterized by the growth of surface microcracks have been analysed by a new approach unifying the conventional approaches based on the final fracture of materials with the fracture mechanics approach. Knowledge of these parameters is critical for the application of fracture mechanics to fatigue and creep life assessment, and the damage evaluation of structures at elevated temperature.

• Journal of Magnetics
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• v.21 no.4
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• pp.603-615
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• 2016

In this study, in order to determine the validity and accuracy of MR imaging of 3D gradient dual echo 2-point DIXON technique for measuring abdominal adipose tissue volume and distribution, the measurements obtained by CT were set as a reference for comparison and their correlations were evaluated. CT and MRI scans were performed on each subject (17 healthy male volunteers who were fully informed about this study) to measure abdominal adipose tissue volume. Two skilled investigators individually observed the images acquired by CT and MRI in an independent environment, and directly separated the total volume using region-based thresholding segmentation method, and based on this, the total adipose tissue volume, subcutaneous adipose tissue volume and visceral adipose tissue volume were respectively measured. The correlation of the adipose tissue volume measurements with respect to the observer was examined using the Spearman test and the inter-observer agreement was evaluated using the intra-class correlation test. The correlation of the adipose tissue volume measurements by CT and MRI imaging methods was examined by simple regression analysis. In addition, using the Bland-Altman plot, the degree of agreement between the two imaging methods was evaluated. All of the statistical analysis results showed highly statistically significant correlation (p<0.05) respectively from the results of each adipose tissue volume measurements. In conclusion, MR abdominal adipose volumetry using the technique of 3D gradient dual echo 2-point DIXON showed a very high level of concordance even when compared with the adipose tissue measuring method using CT as reference.

• Herbal Formula Science
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• v.29 no.4
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• pp.253-266
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• 2021

Objective : This is to analyze the factors affecting the satisfaction of curriculum at korean medicine college and suggest the direction of the curriculum reformation of korean medicine colleges. Method : The collected data were conducted multiple linear regression analysis using the SPSS ver.26 statistical program, using 'curriculum satisfaction' as a dependent variable after analyzing the frequency of each variable. Result : The average score for curriculum satisfaction at Korean Medicine college was 2.87 points, which was relatively low. The factors affecting the satisfaction of the curriculum were 'A favorable impression of Korean Medicine College of W University' β=0.351(p<.001), 'connectivity between major subjects' β=0.312(p<.001), 'duplex between major subjects' β=-0.163(p<.05), 'recognition of the importance of Chinese characters' β=0.114(p<.0.5). Conclusion : The curriculum of Korean Medicine College should first, be organized to allow students to be proud of themselves, second, the goal of education should set goals optimized for job competency, third, the content of learning should be consisted of student led problem based learning, fourth, the link between major subjects should be intensified, fifth, the clinical practice time should be expanded significantly and lastly the assessment evaluates the performance process.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.39 no.5
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• pp.329-341
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• 2021

This study derives the risk-Influence factors for subway structures, the basis for the transition from the current subway disaster recovery-oriented maintenance system to a preemptive disaster management system, to reduce risk factors for existing subway structures. To apply reasonable risk assessment techniques, risk influence factors for subway underground structures using statistical information(spatial information) and risk influence factors according to frequency of accidents were selected to derive the risk factors. The significant risk factors were verified through ground subsidence (SI: Subsidence Impact)-based correlation analysis. This process confirmed that the subsidence of the ground was a risk influence factor for the subway structure. The main result of this study is that derive the risk factors to improve the risk factors of subway structures due to the rapid increase in disaster risk factors. The derived risk factors that were expected to affect the depression around subway stations and track structures did not show a noticeable correlation, but the cause of this may be that there is no physical connection between them, but on the other hand, the accumulated data may not accurately record the surrounding depression. Accordingly, in order to evaluate the risk of depression around the station and track, more intensive observation and data accumulation around the structure are required.

• Journal of The Korean Society of Integrative Medicine
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• v.6 no.4
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• pp.63-73
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• 2018

Purpose : This study aims to verify the effects of flipped learning on self-directed learning and class satisfaction in a class of college physical therapy students. Methods : The subjects were 97 students in College A who had registered for musculoskeletal examination and assessment and practice at the second semester of 2017. All subjects were measured with the self-directed learning questionnaire for college student proposed by Lee et al., and the class satisfaction questionnaire proposed by Lee et al., before and after intervention. The collected data were processed using a computerized statistical program SPSS Win version 21.0. Mean, standard deviation, paired t-test and Cronbach's alpha coefficient were calculated. Results : The results showed significant differences in goal setting, identify resources for learning, effort attributed to results, self-reflection of self-directed learning and problem solving excellence, class methods and contents attention and understanding(p<.05), class interest of class satisfaction(p<.05). Conclusion : These results suggest that flipped learning improves learning motivation and attitudes. Therefore, follow-up study is necessary to investigate further the application of flipped learning in various students and teaching methods.

• Structural Engineering and Mechanics
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• v.69 no.4
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• pp.399-405
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• 2019

The present study assessed the reliability-based reinforcement ratio of FRP reinforced concrete structure applying recycled coarse aggregate (RCA) concrete. The statistical characteristics of FRP bars and RCA concrete were investigated from the previous literatures and the mean value and standard deviation were employed for the reliability analysis. The statistics can be regarded as the material uncertainty for configuring the probability distribution model. The target bridge structure is the railway bridge with double T-beam section. The replacement ratios of RCA were 0%, 30%, 50%, and 100%. From the probability distribution analysis, the reliability-based reinforcement ratios of FRP bars were assessed with four cases according to the replacement ratio of RCA. The reinforcement ratio of FRP bars at RCA 100% showed about 17.3% higher than the RCA 0%, where the compressive strength at RCA 100% decreased up to 27.5% than RCA 0%. It was found that the decreased effect of the compressive strength of RCA concrete could be compensated with increase of the reinforcement ratio of FRP bars. This relationship obtained by the reliability analysis can be utilized as a useful information in structural design for FRP bar reinforced concrete structures applying RCA concrete.

• Structural Engineering and Mechanics
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• v.69 no.1
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• pp.21-31
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• 2019

Optimizing composite structures to exploit their maximum potential is a realistic application with promising returns. In this research, simultaneous maximization of the fundamental frequency and frequency separation between the first two modes by optimizing the fiber angles is considered. A high-fidelity design optimization methodology is developed by combining the high-accuracy of finite element method with iterative improvement capability of metaheuristic algorithms. Three powerful nature-inspired optimization algorithms viz. a genetic algorithm (GA), a particle swarm optimization (PSO) variant and a cuckoo search (CS) variant are used. Advanced memetic features are incorporated in the PSO and CS to form their respective variants-RPSOLC (repulsive particle swarm optimization with local search and chaotic perturbation) and CHP (co-evolutionary host-parasite). A comprehensive set of benchmark solutions on several new problems are reported. Statistical tests and comprehensive assessment of the predicted results show CHP comprehensively outperforms RPSOLC and GA, while RPSOLC has a little superiority over GA. Extensive simulations show that the on repeated trials of the same experiment, CHP has very low variability. About 50% fewer variations are seen in RPSOLC as compared to GA on repeated trials.

• Journal of Korean society of Dental Hygiene
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• v.18 no.6
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• pp.903-910
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• 2018

Objectives: The study aimed to identify the oral health factors that affect the nutritional status of the elderly. Methods: The study was conducted over ten months from September 2013 to June 2014, and included senior citizens who were supported by the visiting health service. The rate of saliva release, the number of remaining teeth, and the ability of the elderly to identify nutritional conditions were evaluated. Statistical analyses were performed using the t-test, ANOVA, and multiple linear regression using SAS 9.4 (SAS Institute Inc., Cary, NC, USA.). Results: The study participants had an average irritation saliva secretion rate of $2.26{\pm}1.11mg$ per minute. The higher the rate of saliva secretion, the higher the mini nutritional assessment (MNA) score (p<0.001). The average number of remaining teeth was $8.21{\pm}9.76$. The MNA scores were highest in groups with 11 or more remaining teeth (p=0.001). The factors that affected the nutritional condition of the elderly were their ability to perform activities of daily living, saliva flow rate, and number of remaining teeth. The highest correlation among them was that of the standardized regression coefficient was - 0.386 by activity daily living, followed by a 0.170 saliva secretion rate and 0.118 remaining teeth in daily life performance. Conclusions: Activities of daily living and rate of saliva secretion showed the highest correlations to nutritional status of the elderly.

• Structural Engineering and Mechanics
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• v.70 no.5
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• pp.639-647
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• 2019

The performance of precast concrete structures is greatly influenced by the behaviour of beam-to-column connections. A single connection may be required to transfer several loads simultaneously so each one of those loads must be considered in the design. A good connection combines practicality and economy, which requires an understanding of several factors; including strength, serviceability, erection and economics. This research work focuses on the performance aspect of a specific type of beam-to-column connection using partly hidden corbel in precast concrete structures. In this study, the results of experimental assessment of the proposed beam-to-column connection in precast concrete frames was used. The purpose of this research is to develop and apply the Extreme Learning Machine (ELM) for moment-rotation prediction of precast beam-to-column connections. The ELM results are compared with genetic programming (GP) and artificial neural network (ANN). The reliability of the computational models was accessed based on simulation results and using several statistical indicators.