• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.449-455
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• 2019

This paper proposes a flyback diode of bridgeless PFC converter as SiC SBD (Schottky Barrier Diode) to achieve high efficiency. In addition, through the explanation of the operation principle of the bridgeless PFC converter, the conduction section of the freewheel diode is shown in the bridgeless PFC converter to verify the contribution of system loss due to the loss of the freewheel diode. The advantages of the SiC SBD device's physical properties and the reverse recovery characteristics are explained, and the efficiency is measured by measuring the turn-on and turn-off losses. The loss was calculated. The simulation results were calculated in consideration of device characteristics and verified through the waveform analysis and comparison of the actual system. In order to consider the device characteristics, the simulation was conducted using the thermal module of PSIM. As a result of the prototype test, the turn-on loss was 0.608W and the turn-off loss was 21.62W, resulting in the total switching loss of 22.228W. The comparison of the two results proved the validity of the experimental method. In addition, a high efficiency of 94.58% is achieved.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.657-673
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• 2019

A monitoring method based on acoustic emission (AE) sensor has been widely used to evaluate the damage of structures in underground rock. The acoustic emission signal generated from cracking in material is analyzed as various acoustic emission parameters in time and frequency domain. To investigate from initial crack generation to final failure of rock material, it is important to understand the characteristics of acoustic emission parameters according to the stress ratio and rock strength. In this study, uniaxial compression tests were performed using very strong and weak rock specimen in order to investigate the acoustic emission parameters when the failure of specimen occurred. In the results of experimental tests, the event, root-mean-square (RMS) voltage, amplitude, and absolute energy of very strong rock specimen were larger than those of the weak rock specimen with an increase of stress ratio. In addition, the acoustic emission parameters related in frequency were more affected by specification (e.g., operation and resonant frequency) of sensors than the stress ratio or rock strength. It is expected that this study may be meaningful for evaluating the damage of underground rock when the health monitoring based on the acoustic emission technique will be performed.

• Journal of the Korea Convergence Society
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• v.10 no.10
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• pp.67-74
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• 2019

The purpose of this study was to determine whether changes of position might effect the convergence pulmonary function of the 20s men of mild intellectual disabilities with obesity. Ten subjects of mild intellectual disabilities with obesity(fat group) and ten contrary subjects without obesity(control group) were participated in the experiment. Subjects were assessed for their pulmonary function by using Fit mate according to the position changes(supine position, 45 lean sitting position, 90 sitting position). One-way repeated ANOVA analyzed each region data of pulmonary function of both the fat group and the control group according to their position changes. The result of the experiment showed that the 20s men of mild intellectual disabilities with obesity have lower pulmonary function than the contrary subjects in the each given posture. In comparison with three experimental positions, supine position was the lowest in the pulmonary function. This study showed the 20s men of mild intellectual disabilities with obesity have lower function of pulmonary volume than the control group, and thus, it suggests that the pulmonary functional data of 20s men of mild intellectual disabilities with obesity in this experiment can be used as a basic respiratory one for the various exercise programs in the area of the physical activities.

• Journal of the Korean Society of Earth Science Education
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• v.12 no.2
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• pp.165-173
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• 2019

This study purposes to figure out the effects of applying discussion-based science class on concept of science achievement and science teaching efficacy. This study established an twelve-week period of experimental treatment from April to June 2019, and the students who participated in this study formed a research group consisting of 27 students in the first semester of the second year of the B University of Education. and taking courses in 'elementary Science Textbook Research 1' For the classes applying discussion-based science class, the analysis was made on 2015 revised curriculum, and 12th process-centered performance assessment based on discussion. The developed data had designed to develop concept of science achievement and science teaching efficacy. The study group applied process-centered performance assessment based on discussion science class, so unaffectedly study group could improve their concept of science achievement and science teaching efficacy. B University of education is singleness class that doesn't have compare group, so this study is constituted only study group. Applying based-discussion science class to study group, before and after concept of science concept test, science teaching efficacy test is performed. The results of the study were as follows. First, the study group applied discussion-based science class had statistically significant differences in concept of science achievement (p<.05). Second, the study group applied discussion-based science class had statistically significant differences in science teaching efficacy(p<.05). Third, after discussion-based science class of pre-service teachers have a very good feeling. Through such study results, the study could figure out that the class applying discussion-based science class has positive effect on concept of science achievement and science teaching efficacy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.5
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• pp.418-426
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• 2019

Recently, many studies on vital sign detection using a radar sensor related to Internet of Things(IoT) smart home systems have been conducted. Because vital signs such as respiration and cardiac rates generally cause micro-motions in the chest or back, the phase of the received echo signal from a target fluctuates according to the micro-motion. Therefore, vital signs are usually detected via spectral analysis of the phase. However, the probability of false alarms in cardiac rate detection increases as a result of various problems in the measurement environment, such as very weak phase fluctuations caused by the cardiac rate. Therefore, this study analyzes the difficulties of vital sign detection and proposes an efficient vital sign detection algorithm consisting of four main stages: 1) phase decomposition, 2) phase differentiation and filtering, 3) vital sign detection, and 4) reduction of the probability of false alarm. Experimental results using impulse-radio ultra-wideband radar show that the proposed algorithm is very efficient in terms of computation and accuracy.

• Explosives and Blasting
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• v.36 no.4
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• pp.35-47
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• 2018

In this study, several concrete-block blast tests and AUTODYN numerical analyses were conducted to analyze the effects of different stemming and coupling materials on explosion results. Air, sand, and polymer gel were used as both the stemming and coupling materials. The stemming and coupling effects of these materials were compared with those of the full-charge condition. Soil-covered or buried concrete blocks were used for field crater tests. It was found from the concrete block tests and numerical analyses that both the crater size and the peak pressure around the blast hole were higher when the polymer gel was used than when the sand and the decoupling condition were used. The numerical analyses revealed the same trend as those of the field tests. Pressure peaks in concrete block models were calculated to be 37, 30, and 16 MPa, respectively, for the cases of the polymer gel, sand, and no stemming and decoupling condition. The pressure peak was 52 MPa in the case of full-charge condition, which was the highest pressure. But the damage area for the case was smaller than that obtained from the use of polymer gel. Full-charge was also used as a reference test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.592-599
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• 2018

The kinetics and thermodynamics of the adsorption of acid blue 40 from an aqueous solution by activated carbon were examined as a function of the activated carbon dose, pH, temperature, contact time, and initial concentration. The adsorption efficiency in a bathtub was increased at pH 3 and pH 11 due to the presence of sufonate ions ($SO_3{^-}$) and amine ions ($NH_2{^+}$). The equilibrium adsorption data were fitted to the Langmuir, Freundlich and Temkin isotherms. The results indicated that the Langmuir model provides the best correlation of the experimental data. The separation factor of the Langmuir and Freundlich model showed that the adsorption treatment of acid blue 40 by activated carbon could be an effective adsorption process. The adsorption energy determined by the Temkin equation showed that the adsorption step is a physical adsorption process. Kinetics analysis of the adsorption process of acid blue 40 on activated carbon showed that a pseudo second order kinetic model is more consistent than a pseudo second order kinetic model. The estimated activation energy was 42.308 kJ/mol. The enthalpy change (80.088 J/mol) indicated an endothermic process. The free energy change (-0.0553 ~ -5.5855 kJ/mol) showed that the spontaneity of the process increased with increasing adsorption temperature.

• Journal of Internet Computing and Services
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• v.20 no.1
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• pp.87-96
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• 2019

In this paper, we propose a MapReduce-supported clustering technique for collecting and classifying distributed workflow enactment event logs as a preprocessing tool. Especially, we would call the distributed workflow enactment event logs as Workflow BIG-Logs, because they are satisfied with as well as well-fitted to the 5V properties of BIG-Data like Volume, Velocity, Variety, Veracity and Value. The clustering technique we develop in this paper is intentionally devised for the preprocessing phase of a specific workflow process mining and analysis algorithm based upon the workflow BIG-Logs. In other words, It uses the Map-Reduce framework as a Workflow BIG-Logs processing platform, it supports the IEEE XES standard data format, and it is eventually dedicated for the preprocessing phase of the ${\rho}$-Algorithm that is a typical workflow process mining algorithm based on the structured information control nets. More precisely, The Workflow BIG-Logs can be classified into two types: of activity-based clustering patterns and performer-based clustering patterns, and we try to implement an activity-based clustering pattern algorithm based upon the Map-Reduce framework. Finally, we try to verify the proposed clustering technique by carrying out an experimental study on the workflow enactment event log dataset released by the BPI Challenges.

• Journal of fish pathology
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• v.32 no.1
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• pp.9-20
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• 2019

The study investigated the dietary effects of medicinal herbs extract and multiple probiotics mixture on the growth performance, innate immune response and antibacterial activity of nile tilapia Oreochromis niloticus. Tilapia were divided in four groups. The first is a fish group fed a basal diet added with 40% medicinal herbs extract (MHE). The second is a fish group fed a basal diet supplied with $2{\times}10^8CFU/g$ of 2 Bacillus sp, 2 Lactobacillus sp and 2 Yeast sp, respectively (PB). The third group was fed with a mixture of probiotics (2 Bacillus sp, 2 Lactobacillus sp and 2 Yeast sp) with the medicinal herbs extract added in basal diet (MHE+PB). The fourth group was fed only a basal diet (C). In a non-specific immune parameters analysis, respiratory burst activity, lysozyme activity, phagocytic activity (PA), alternative complement pathway activity ($ACH_{50}$) and superoxide dismutase (SOD) activity were significantly (p<0.05) increased in the group MHE+PB compared to other groups. Both PB and MHE groups showed a significant (p<0.05) increase in respiratory burst activity, lysozyme activity compared to the control C group, whereas no significant differences were observed in PA, $ACH_{50}$ and SOD activity compared to the control group. In challenging test, fish were administered with Edwardsiella tarda (E. tarda) on 30 days after feeding with each experimental diet and viable E. tarda cell reduction was checked over 21 days post injection. MHE+PB group showed a significantly (p<0.05) reduced E. tarda cells compared to other groups. No significant antibacterial difference (p>0.05) was observed between PB and MHE only treated group. Compared to the control, a significant antibacterial difference (p<0.05) appeared in PB but not in MHE (p>0.05). The results suggest that the probiotics and MHE mixture could be utilized as an alternative to antibiotics in the control of fish diseases caused by E. tarda.

• Journal of Korea Water Resources Association
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• v.52 no.5
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• pp.313-323
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• 2019

Deep Tunnel system is a large-scale urban flood control facility installed underground in order to reinforce the lack of drainage systems in developed cities. In a structure like a deep tunnel system, the undular bore generated in the downstream causes a problem in the hydraulic stability of the tunnel. In this study, to investigate the influence of the undular bore on the hydraulic stability at the "Shinwol rainwater storage and drainage system", under construction for the first time in the country, a hydraulic model experiment was conducted on various flooding inflow scenarios. As a result of the hydraulic model experiment carried out in this study, the undular bore generated downstream is trapped in the pipe while moving to upstream, pushes the compressed air. It is judged that overflow occurred by choking the vertical drop shaft in the process when this compressed air is being exhaust through the upstream vertical drop shaft and blocking flood inflow. In addition, the analysis of velocity of undular bore shows that the undular bore transfers energy, and at this time, the pressure rose in the pipe and the velocity increment occurred of the undular bore. Further studies are needed to predict the size and velocity of undular bore, which plays an important role in the hydraulic stability of the tunnel in the deep tunnel system.