• Journal of the Korean Society for information Management
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• v.36 no.2
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• pp.57-77
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• 2019

Random Forest (RF), a representative ensemble technique, was applied to automatic classification of journal articles in the field of library and information science. Especially, I performed various experiments on the main factors such as tree number, feature selection, and learning set size in terms of classification performance that automatically assigns class labels to domestic journals. Through this, I explored ways to optimize the performance of random forests (RF) for imbalanced datasets in real environments. Consequently, for the automatic classification of domestic journal articles, Random Forest (RF) can be expected to have the best classification performance when using tree number interval 100~1000(C), small feature set (10%) based on chi-square statistic (CHI), and most learning sets (9-10 years).

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.59.1-59.1
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• 2018

SNe light curves have been used to understand the expansion history of the universe, and a lot of efforts have gone into understanding the overall shape of the radioactively powered light curve. However, we still have little direct observational evidence for the theorized SN progenitor systems. Recent studies suggest that the light curve of a supernova shortly after its explosion (< 1 day) contains valuable information about its progenitor system and can be used to set a limit on the progenitor size, R*. In order to catch the early light curve of SNe explosion and understand SNe progenitors, we are performing a ~8hr interval monitoring survey of nearby galaxies (d < 50 Mpc) with 1-m class telescopes around the world. Through this survey, we expect to catch the very early precursor emission as faint as R=21 mag (~0.1 Rsun for the progenitor). In this poster, we outline this project, and provide updates on IMSNG projects during 2017/2018 seasons.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.24 no.1
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• pp.100-108
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• 2021

Purpose: Percutaneous endoscopic gastrostomy (PEG) tube placements are commonly performed pediatric endoscopic procedures. Because of underlying disease, these patients are at increased risk for airway-related complications. This study compares patient characteristics and complications following initial PEG insertion with general endotracheal anesthesia (GETA) vs. anesthesia-directed deep sedation with a natural airway (ADDS). Methods: All patients 6 months to 18 years undergoing initial PEG insertion within the endoscopy suite were considered for inclusion in this retrospective cohort study. Selection of GETA vs. ADDS was made by the anesthesia attending after discussion with the gastroenterologist. Results: This study included 168 patients (GETA n=38, ADDS n=130). Cohorts had similar characteristics with respect to sex, race, and weight. Compared to ADDS, GETA patients were younger (1.5 years vs. 2.9 years, p=0.04), had higher rates of severe American Society of Anesthesiologists (ASA) disease severity scores (ASA 4-5) (21% vs. 3%, p<0.001), and higher rates of cardiac comorbidities (39.5% vs. 18.5%, p=0.02). Significant associations were not observed between GETA/ADDS status and airway support, 30-day readmission, fever, or pain medication in unadjusted or adjusted models. GETA patients had significantly increased length of stay (eβ=1.55, 95% confidence interval [CI]=1.11-2.18) after adjusting for ASA class, room time, anesthesia time, fever, and cardiac diagnosis. GETA patients also had increased room time (eβ=1.20, 95% CI=1.08-1.33) and anesthesia time (eβ=1.50, 95% CI=1.30-1.74) in adjusted models. Conclusion: Study results indicate that younger and higher risk patients are more likely to undergo GETA. Children selected for GETA experienced longer room times, anesthesia times, and hospital length of stay.

• The Journal of Korean Physical Therapy
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• v.33 no.6
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• pp.265-271
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• 2021

Purpose: We aimed to analyze the reliability of the test for choice stepping reaction time (CSRT) under an unstable surface and determine whether there were differences in CSRT between support surface conditions (stable vs. unstable conditions) and between age groups (young adults vs. community-dwelling older adults). Methods: Twenty healthy community-dwelling older adults and twenty young adults performed the stepping task under an unstable condition over two visits. The mean of the two trials measured for each visit was used for the analysis. The test-retest reliability was analyzed using intra-class correlation coefficient (ICC) with a 95% confidence interval, standard error of measurement (SEM), and minimal detectable change (MDC). Differences in CSRT between support surface conditions and age groups were analyzed using the independent t-test with Bonferroni correction. Results: Excellent consistency was observed for ICC >0.90 in both groups. Moreover, the SEM and MDC values of the CSRT in older and young adults were 0.03 and 0.09 and 0.01 and 0.04, respectively. There was a significant difference in the CSRT between the age groups under stable (p<0.001) and unstable conditions (p<0.001). Conclusion: The findings demonstrated that the test for CSRT under an unstable condition had reliable results in both groups. Although older adults demonstrated longer reaction times than younger adults in all surface conditions, increasing the balance control demand by implementing a choice stepping task concomitant with a balance task had no influence on the reaction time in both age groups.

• Wind and Structures
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• v.36 no.4
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• pp.277-292
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• 2023

Low-rise structures are generally immersed within the roughness layer of the atmospheric boundary layer flows and represent the largest class of the structures for which wind loads for design are being obtained from the wind standards codes of distinct nations. For low-rise buildings, wind loads are one of the decisive loads when designing a roof. For the case of cylindrical roof structures, the information related to wind pressure coefficient is limited to a single span only. In contrast, for multi-span roofs, the information is not available. In this research, the numerical simulation has been done using ANSYS CFX to determine wind pressure distribution on the roof of low-rise cylindrical structures arranged in rectangular plan with variable spacing in accordance with building width (B=0.2 m) i.e., zero, 0.5B, B, 1.5B and 2B subjected to different wind incidence angles varying from 0° to 90° having the interval of 15°. The wind pressure (P) and pressure coefficients (C_pe) are varying with respect to wind incidence angle and variable spacing. The results of present numerical investigation or wind induced pressure are presented in the form of pressure contours generated by Ansys CFD Post for isolated as well as variable spacing model of cylindrical roofs. It was noted that the effect of wind shielding was reducing on the roofs by increasing spacing between the buildings. The variation pf Coefficient of wind pressure (C_pe) for all the roofs have been presented individually in the form of graphs with respect to angle of attacks of wind (AoA) and variable spacing. The critical outcomes of the present study will be so much beneficial to structural design engineers during the analysis and designing of low-rise buildings with cylindrical roofs in an isolated as well as group formation.

• Archives of Plastic Surgery
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• v.50 no.3
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• pp.254-263
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• 2023

Background The three-dimensional (3D) evaluation of skeletal stability after orthognathic surgery is a time-consuming and complex procedure. The complexity increases further when evaluating the surgery-first orthognathic approach (SFOA). Herein, we propose and validate a simple time-saving method of 3D analysis using a single software, demonstrating high accuracy and repeatability. Methods This retrospective cohort study included 12 patients with skeletal class 3 malocclusion who underwent bimaxillary surgery without any presurgical orthodontics. Computed tomography (CT)/cone-beam CT images of each patient were obtained at three different time points (preoperation [T0], immediately postoperation [T1], and 1 year after surgery [T2]) and reconstructed into 3D images. After automatic surface-based alignment of the three models based on the anterior cranial base, five easily located anatomical landmarks were defined to each model. A set of angular and linear measurements were automatically calculated and used to define the amount of movement (T1-T0) and the amount of relapse (T2-T1). To evaluate the reproducibility, two independent observers processed all the cases, One of them repeated the steps after 2 weeks to assess intraobserver variability. Intraclass correlation coefficients (ICCs) were calculated at a 95% confidence interval. Time required for evaluating each case was recorded. Results Both the intra- and interobserver variability showed high ICC values (more than 0.95) with low measurement variations (mean linear variations: 0.18 mm; mean angular variations: 0.25 degree). Time needed for the evaluation process ranged from 3 to 5 minutes. Conclusion This approach is time-saving, semiautomatic, and easy to learn and can be used to effectively evaluate stability after SFOA.

• International Journal of Advanced Culture Technology
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• v.11 no.1
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• pp.1-11
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• 2023

Backgrounds: As the COVID-19 pandemic continues, the university students population is one of the high risk and vulnerable groups. This study analyzed the status of student's mental health, including anxiety and depression caused by COVID-19, and its related factors among a university students in Korea. Methods : Our study subjects included university students in Korea. The survey items included general characteristics, teaching methods, physical activity, eating habits (SDBQ-L), weight-related questions, general anxiety disorder-7(GAD-7), and depression symptoms checklist. Frequency analysis, chi-square test, and logistic regression analysis were performed and data was analyzed using R version 4.1.2 program. Results : The prevalence of anxiety complaints was 5.5%, while the prevalence of depression complaints was 30.8%. In the multivariable logistic regression analysis of factors influencing anxiety, anxiety occurred 19.081 times (95% confidence interval (CI): 2.352-154.807) in the group with unhealthy diet (p<0.01). While in the multivariable analysis to identify factors affecting depression, women were 2.607 times significantly higher (95% CI: 1.255-5.415) than men, 0.407 times (95% CI:0.197-0.840) for residents of the metropolitan area, 3.418 times higher (95% CI:1.633-7.198) for unhealthy dietary people, and 2.225 times higher (95% CI: 1.080-4.582) for weight gainers (p<0.05). The type of class had no effect. Conclusions: COVID-19 and its associated interventions had negative effects on the mental health status including anxiety and depression in university students in Korea. Based on our results we recommend developing mental health interventions and prevention strategies for students in all universities in Korea.

• Journal of Preventive Medicine and Public Health
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• v.55 no.3
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• pp.234-242
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• 2022

Objectives: This study assessed the validity and reliability of the Health-related Quality of Life Instrument with 8 Items (HINT-8) in patients with diabetes. HINT-8 is a newly-developed, generic health-related quality of life (HRQoL) instrument. Methods: Three HRQoL instruments-HINT-8, EuroQoL 5-Dimension 5-Level (EQ-5D-5L), and Short Form Health Survey version 2.0 (SF-36v2)-were provided to 300 patients with diabetes visiting a tertiary hospital for follow-up visits in Korea. The HRQoL scores obtained using the HINT-8 were evaluated for subgroups with known differences based on demographics and diabetes-related characteristics (known-group validity). The mean scores of the instruments were compared between groups segmented by their responses to the HINT-8 (discriminatory ability). Correlation coefficients of the HINT-8 with other instruments were calculated (convergent and divergent validity). The Cohen kappa and intra-class correlation coefficient (ICC) were also evaluated (test-retest reliability). Results: The average HINT-8 indexes were lower among women, older, and less-educated subjects. Subjects who did not list any problems on the HINT-8 had significantly higher HRQoL scores than those who did. The correlation coefficients of the HINT-8 with the EQ-5D-5L index and EuroQoL visual analogue scale were 0.715 (p<0.001) and 0.517 (p<0.001), respectively. The correlation coefficients between the HINT-8 index and the scores of 8 domains of the SF-36v2 ranged from 0.478 (p<0.001) to 0.669 (p<0.001). The Cohen kappa values for the HINT-8 ranged from 0.268 to 0.601, and the ICC of the HINT-8 index was 0.800 (95% confidence interval [CI], 0.720 to 0.860). Conclusions: This study showed that the HINT-8 is a valid and reliable HRQoL instrument for patients with diabetes.

• Journal of Chest Surgery
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• v.24 no.7
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• pp.663-668
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• 1991

To evaluate risks, complications and mortality of reoperations on heart valve prosthesis, we reviewed clinical records of 53 patients who underwent reoperation because of prosthetic valve failure[PVF], from Jan 1959 through Jun. 1991. They had undergone 48 mitral, 10 aortic valve rereplacement Primary tissue failure was the main cause of reoperation : it occurred in 51 valves at a mean postoperative interval of 58 months. Calcification and collagen disruption of prosthesis were main causes of primary tissue failure in macro and micropathology, In 3 failing mechanical prostheses, paravalvular leak was in 2 cases, another one case had the thrombi at the hinge portion. If conditions such as emergency operation with or without endocarditis, thromboembolism and advanced NYHA functional class are prevented, we think that reoperative valve replacement has similar morbidity and mortality to initial valve replacement surgery. But our sturdy represents higher mortality [22.6%] because of late surgical intervention failing the prevention of conditions leading to myocardial damage. In conclusion if the tearing, calcification, and a new murmur were detected the early reoperation should be considered to increase late survival.

• Korean Circulation Journal
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• v.53 no.5
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• pp.331-343
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• 2023

Background and Objectives: The prognostic implication of right atrial (RA) and left atrial (LA) size for an immediate success of direct current cardioversion (DCCV) in atrial fibrillation (AF) remains unclear. This study aimed to compare RA and LA size for the prediction of DCCV success. Methods: Between 2012 and 2018, 734 consecutive outpatients were screened for our prospective registry. Each eligible patient received a medical history, blood analysis, and transthoracic echocardiography with a focus on indexed RA (iRA) area and LA volume (iLAV) prior to DCCV with up to three biphasic shocks (200-300-360 J) or additional administration of amiodarone or flecainide to restore sinus rhythm. Results: We enrolled 589 patients, and DCCV was in 89% (n=523) successful. Mean age was 68 ± 10 years, and 40% (n=234) had New York heart association class >II. A prevalence of the male sex (64%, n=376) and of persistent AF (86%, n=505) was observed. Although DCCV success was associated with female sex (odds ratio [OR], 1.88; 95% confidence interval [CI], 1.06-3.65), with absence of coronary heart disease and normal left ventricular function (OR, 2.24; 95% CI, 1.26-4.25), with short AF duration (OR, 1.93; 95% CI, 1.05-4.04) in univariable regression, only iRA area remained a stable and independent predictor of DCCV success (OR, 0.27; 95% CI, 0.12-0.69; area under the curve 0.71), but not iLAV size (OR, 1.16; 95% CI, 1.05-1.56) in multivariable analysis. Conclusions: iRA area is superior to iLAV for the prediction of immediate DCCV success in AF.