• Maritime Security
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• v.1 no.1
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• pp.149-173
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• 2020

While the United States and other Western states are in trouble with COVID-19 crisis, China is continuing its aggressive ocean expansion with its Gray-zone strategy. The Gray-zone strategy, which China uses around the South China Sea, refers to a strategy that promotes a change in international politics by creating an unclear state, neither war or peace. China, which is trying to expand its influence across East Asia, will also try to project a Gray zone strategy on the Korean Peninsula. The possible scenarios are as follows: 1) South Korea is accidentally involved in a dispute in the South China Sea, 2) Military conflicts between South Korea and China is caused by illegal fishing of Chinese boats in Yellow Sea, 3) China tries to interfere with Socotra Rock, 4) Unlikely, but possible in the future that China induce the military conflicts between Korea and Japan on the Dokdo issue. In order to cope with these scenarios, Korea should prepare the following measures from a long-term perspective: the creation of an Asian maritime safety fleet, the integ rated operation of the navy and the coast guard in the framework of the national fleet, and strengthening the conflict control system for China's provocations.

• Convergence Security Journal
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• v.20 no.5
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• pp.65-74
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• 2020

Recently, with the rapid development of eXtended Reality(XR) technology, the development and use of education and training systems using XR technology is increasing significantly. In particular, in areas that involve great risks and high costs such as military training and counter-terrorism training, the use of XR based simulators is preferred because they can improve training performance, reduce training costs, and minimize the risk of safety issues that may occur in actual training, by creating a training environment similar to actual training. In this paper, we propose a plan to build and evaluate an XR based hyper-realistic counter-terrorism education, training, and evaluation system to improve the ROK police's ability to respond to terrorist situations using the 5G and AR based Integrated Command and Control Platform previously developed by the Korea Military Academy. The proposed system is designed to improve counter-terrorism capabilities with virtual training for individual and team units based on hyper-realistic content and training scenarios. Futhermore, it can also be used as a on-site command and control post in connection with a simulation training site and an actual operation site.

• Atmosphere
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• v.31 no.5
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• pp.489-510
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• 2021

In this paper, we propose an algorithm for detecting convective initiation (CI) using GEO-KOMPSAT-2A/advanced meteorological imager data. The algorithm identifies clouds that are likely to grow into convective clouds with radar reflectivity greater than 35 dBZ within the next two hours. This algorithm is developed using statistical and qualitative analysis of cloud characteristics, such as atmospheric instability, cloud top height, and phase, for convective clouds that occurred on the Korean Peninsula from June to September 2019. The CI algorithm consists of four steps: 1) convective cloud mask, 2) cloud object clustering and tracking, 3) interest field tests, and 4) post-processing tests to remove non-convective objects. Validation, performed using 14 CI events that occurred in the summer of 2020 in Korean Peninsula, shows a total probability of detection of 0.89, false-alarm ratio of 0.46, and mean lead-time of 39 minutes. This algorithm can be useful warnings of rapidly developing convective clouds in future by providing information about CI that is otherwise difficult to predict from radar or a numerical prediction model. This CI information will be provided in short-term forecasts to help predict severe weather events such as localized torrential rainfall and hail.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.183-191
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• 2022

A design method for a propeller type rim-driven axial-flow turbine for a micro-hydropower system is presented. The turbine consists of pre-stator, impeller and post-stator, where the pre-stator plays a role as a guide vane to provide circumferential velocity to the on-coming flow, and the impeller as a rotational power generator by absorbing angular momentum of the flow. BEM(Blade Element Method), which is based on the turbine Euler equation, is employed to design the pre-stator and impeller blades. NACA 66 thickness form and a=0.8 mean camber line, which is widely accepted as a marine propeller blade section, is used for the pre-stator and turbine blade section. A CFD method, derived from the discretization of the RANS equations, is applied for the analysis of the designed turbine system. The design conditions of the turbine is confirmed by the CFD calculation. Turbine characteristic curve is calculated by the CFD method, in order to provide the performance characteristics at off-design operation conditions. The proposed procedures for the design of a propeller type rim-driven axial-flow turbine are established and confirmed by the CFD analysis.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.83-89
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• 2022

Internet of Things technology is rapidly developing due to the recent development of information and communication technology. IoT technology utilizes various sensors to generate unique data from each sensor, enabling diagnosis of system status. However, the equipment management system currently in effect is a post-preservation concept in which administrators must deal with the problem after the problem occurs, which could mean system reliability and availability problems due to system errors, and could result in economic losses due to negative productivity disruptions. Therefore, this study confirmed that edge controller control decision algorithms for more efficient operation of rectifiers in the factory by applying intelligent IoT (AIoT) technology and domain knowledge-based modeling for each sensor data collected based on this, outputting appropriate status messages for each scenario.

• Journal of The Korean Society of Integrative Medicine
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• v.10 no.2
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• pp.145-153
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• 2022

Purpose : This study aimed to investigate the effects of blended learning on learning satisfaction in nursing students. Methods : This study was conducted with 160 current nursing students in the department of nursing at K university located in city B. All students included in the study understood the purpose of the study and provided informed consent to participate. Data were collected between May 3 and July 9, 2021 and analyzed using SPSS/WIN 22.0. The frequency, percentage, mean, and standard deviation were created, and t-test, ANOVA, and Scheffé test for post hoc analysis were performed. Correlations were analyzed using Pearson's correlation coefficient. The factors influencing learning satisfaction were analyzed using multiple regression. Results : Significant differences were observed for academic stress according to the online classes environmental satisfaction (F=4.10, p=.001), online classes experience (t=4.11, p=.001) and self-directed learning ability according to the grade (F=4.10, p=.001), online classes environmental satisfaction (t=4.11, p=.001). The academic stress of nursing students who experienced blended learning was significantly negatively correlated with self-directed learning ability (r=-.480, p<.001), and learning satisfaction (r=-.236, p<.001). self-directed learning ability showed a significant positive correlation with learning satisfaction (r=.524, p<.001). The regression model for the factors affecting the learning satisfaction of the subjects was statistically significant (F= 3.027, p<.001). The major influential factors of learning satisfaction were grade (𝛽=.154, p=.013), satisfaction with school life (𝛽=.168, p=.032), and satisfaction with non-contact learning environment (𝛽=-.141, p=.028). The explanatory power was 28 %. Conclusion : These results indicate that it is necessary to reduce academic stress and increase self-directed learning ability to enhance learning satisfaction in nursing students through blended learning. In addition, the development and operation of a tailored intervention program is required to help improve learning satisfaction.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.715-727
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• 2021

This research is to investigate the concept of Local Housing Association, and stepwise implementation procedure, through the theoretical consideration, and then to find out overall problems happening in the process of pushing ahead with Local Housing Association, including problems in the corresponding business stage, based on the cases of Local Housing Association that have been appearing in Changwon areas, Gyeongnam, and to present legal and policy directions for solutions to it, based on it. First, regarding improvement measures at the stage of promotion committee, it is necessary to introduce the system to report the establishment of promotion committee to cities, provinces, and districts under the jurisdiction of the location of overall business, for the establishment of association. In order to secure the professionalism of promotion committee, it is necessary to enforce those members to receive education and training for a certain period, and improve the system to post on Website or through public notices. Second, regarding improvement measures at the stage of the approval of establishment, Local Housing Association have difficulties in replacing members and joining new memberships, after getting the approval of the establishment, which can put the brake on business operation. Finally, in order to prevent crime actions, such as embezzlement or breach of duty, in advance, it is necessary to establish the institutional system that allows every member to check details of business fund. It is expected that this research would minimize side effects incurred by Local Housing Association System and help Local Housing Association take full institutional responsibility and play an axis of housing supply policy.

• Journal of Chest Surgery
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• v.55 no.3
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• pp.189-196
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• 2022

Background: This study investigated the predictive value of the frailty index calculated using laboratory data and vital signs (FI-L) in patients who underwent coronary artery bypass grafting (CABG). Methods: This study included 508 patients (age 67.3±9.7 years, male 78.0%) who underwent CABG between 2018 and 2021. The FI-L, which estimates patients' frailty based on laboratory data and vital signs, was calculated as the ratio of variables outside the normal range for 32 preoperative parameters. The primary endpoints were operative and medium-term all-cause mortality. The secondary endpoints were early postoperative complications and major adverse cardiac and cerebrovascular events (MACCEs). Results: The mean FI-L was 20.9%±10.9%. The early mortality rate was 1.6% (n=8). Postoperative complications were atrial fibrillation (n=148, 29.1%), respiratory complications (n=38, 7.5%), and acute kidney injury (n=15, 3.0%). The 1- and 3-year survival rates were 96.0% and 88.7%, and the 1- and 3-year cumulative incidence rates of MACCEs were 4.87% and 8.98%. In multivariable analyses, the FI-L showed statistically significant associations with medium-term all-cause mortality (hazard ratio [HR], 1.042; 95% confidence interval [CI], 1.010-1.076), MACCEs (subdistribution HR, 1.054; 95% CI, 1.030-1.078), atrial fibrillation (odds ratio [OR], 1.02; 95% CI, 1.002-1.039), acute kidney injury (OR, 1.06; 95% CI, 1.014-1.108), and re-operation for bleeding (OR, 1.09; 95% CI, 1.032-1.152). The minimal p-value approach showed that 32% was the best cutoff for the FI-L as a predictor of all-cause mortality post-CABG. Conclusion: The FI-L was a significant prognostic factor related to all-cause mortality and postoperative complications in patients who underwent CABG.

• Journal of Chest Surgery
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• v.55 no.2
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• pp.151-157
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• 2022

Background: We investigated surgical outcomes after the surgical repair of cor triatriatum sinister (CTS). Methods: Thirty-two consecutive patients who underwent surgical repair of CTS from 1993 through 2020 were included in this study. The morphological characteristics, clinical features, and surgical outcomes were described and analyzed. Results: The median age and body weight at operation were 9 months (interquartile range [IQR], 3-238 months) and 7.5 kg (IQR, 5.8-49.6 kg), respectively. There were 16 males (50%). According to the modified Lucas classification, type IA (classical CTS) was most common (n=20, 62.5%). Atrial septal defect was associated in 22 patients (68.8%) and anomalous pulmonary venous return in 8 patients (25%). Pulmonary hypertension was preoperatively suspected with a high probability in 18 patients (56.3%). There was 1 early death (3.1%) after emergent membrane excision and hybrid palliation in a high-risk hypoplastic left heart syndrome patient. There were no late deaths. The overall survival rate was 96.9% at 15 years post-repair. No early survivors required reoperation during follow-up. Most survivors (31 of 32 patients, 96.9%) were in New York Heart Association functional class I at a median follow-up of 74 months (IQR, 39-195 months). At the latest echocardiography performed at a median of 42 months (IQR, 6-112 months) after repair, no residual lesion was observed except in 1 patient who had moderate pulmonary hypertension (mean pulmonary arterial pressure of 36 mm Hg). Conclusion: Surgical repair of cor triatriatum could be performed safely and effectively with an extremely low risk of recurrence.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.83-89
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• 2023

The Korea Augmentation Satellite System (KASS) system is a Satellite Based Augmentation System (SBAS) under development to provide APV-I SBAS service in the Republic of Korea. The KASS ground segment generates correction and integrity information for GPS measurements of KASS users using the accurate positions of KASS Reference Station (KRS) antenna phase centers. For this reason, the accuracy of KRS reference points through geodetic survey campaigns is one of the important factors for providing the KASS service in compliance with the required navigation performance. In order to obtain accurate positions, two geodetic survey campaigns were performed at several reference points, such as Mark, Center of Mast at Ground Level (CMGL), and Center of Hole in Top Plate (CHTP), of each KRS site using three different survey methods, the Virtual Reference Station (VRS), Flächen Korrektur Parameter (FKP), and raw data post-processing methods. By comparing and analyzing the results, the computed coordinates of the reference points were verified and Antenna Phase Center (APC) positions were calculated using KRS Antenna Reference Point (ARP) data, and the first KASS Site Acceptance Test (SAT#1) was performed successfully using the verified APC coordinates. After the first site survey activities, the KASS operators should maintain the coordinates with the required performance such that the overall KASS navigation performance commitment is guaranteed during the lifetime of 15 years. Therefore, the maintenance plan for the KRS antenna coordinates should be developed before the commissioning of KASS operation planned after 2023. Therefore, this paper presents a geodetic survey method selected for the maintenance activities and provides the rationale for using this method.