• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.5
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• pp.499-506
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• 2019

This paper is concerned with the operating stability of 7kW inverter using SIC hybrid module and verifies the validity of the simulation results by comparing the result of the loss equation and the simulation result, Simulation results using Si module and SiC hybrid module are compared to compare switch loss and diode loss. Through the loss equation calculation, the conduction loss of SiC Hybrid module is 168W, switching loss is 9.3W, diode loss is 10.5nW, When compared with the simulation results, similar values were shown. As a result of comparing the simulation results of the Si module and the SiC Hybrid module, The total device loss of the Si module was 246.2W, and the total device loss of the SiC Hybrid module was 189.9W. The loss difference was 56.3W, which was about 0.8W. thereby verifying the reverse recovery characteristics of the SiC SBD. In addition, temperature saturation test was conducted to confirm the stability of SiC Hybrid module and Si module under high temperature saturation, In the case of the Si module, the output power was stopped at 4kW, and the SiC Hybrid module was confirmed to operate at 7kW. Based on this, an efficiency graph and a temperature graph are presented, and the Si module is graphed up to 4kW and the SiC Hybrid module is graphed up to 7kW.

• Atmosphere
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• v.29 no.1
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• pp.87-103
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• 2019

This study introduces the overall characteristics of LOVECLIM version 1.3, the earth system model of intermediate complexity (EMIC), including the installation and operation processes by conducting two kinds of past climate simulation. First climate simulation is the equilibrium experiment during the mid-Holocene (6,000 BP), when orbital parameters were different compared to those at present. The overall accuracy of simulated global atmospheric fields by LOVECLIM is relatively lower than that in Coupled Model Intercomparison Project phase 5 (CMIP5) and Paleoclimate modelling Intercomparison Project phase 3 (PMIP3) simulations. However, surface temperature over the globe, the 800 hPa meridional wind over the mid-latitude coastal region, and the 200 hPa zonal wind from LOVECLIM show similar spatial distribution to those multi-model mean of CMIP5/PMIP3 climate models. Second one is the transient climate experiment from mid-Holocene to present. LOVECLIM well captures the major differences in surface temperature between preindustrial and mid-Holocene simulations by CMIP5/PMIP3 multi-model mean, even though it was performed with short integration time (i.e., about four days in a single CPU environment). In this way, although the earth system model of intermediate complexity has a limit due to its relatively low accuracy, it can be a very useful tool in the specific research area such as paleoclimate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.435-447
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• 2019

In order to prevent unnecessary re-admission, it is necessary to intensively manage the groups with high probability of re-admission. For this, it is necessary to develop a re-admission prediction model. Two - year discharge summary data of one university hospital were collected from 2016 to 2017 to develop a predictive model of re-admission. In this case, the re-admitted patients were defined as those who were discharged more than once during the study period. We conducted descriptive statistics and crosstab analysis to identify the characteristics of rehospitalized patients. The re-admission prediction model was developed using logistic regression, neural network, and decision tree. AUC (Area Under Curve) was used for model evaluation. The logistic regression model was selected as the final re-admission predictive model because the AUC was the best at 0.81. The main variables affecting the selected rehospitalization in the logistic regression model were Residental regions, Age, CCS, Charlson Index Score, Discharge Dept., Via ER, LOS, Operation, Sex, Total payment, and Insurance. The model developed in this study was limited to generalization because it was two years data of one hospital. It is necessary to develop a model that can collect and generalize long-term data from various hospitals in the future. Furthermore, it is necessary to develop a model that can predict the re-admission that was not planned.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.669-676
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• 2018

Schedule management in construction work is an important step for determining the construction period. On the other hand, there is a difference between the planned schedule and execution schedule because the estimation and calculation of Non-Working days, in which possible at the design stage is not performed properly. This paper proposes a method for estimating the working days by analyzing characteristics of the major work type and estimating the Non-Working days reflecting the Chuseok and New Year Holidays, which is the closest method to the actual work in the schedule planning. By applying the correction factor of the existing method and the improved method for the same construction in the same site, improved method was reduced by 22 days (9.1%) based on the actual working days. The importance of schedule management was confirmed as an example by comparing the data before and after the application of the standard (plan). These results show that the schedule delays, which are caused by the inconsistency between actual working days calculation that had been practiced conventionally and the working days on the schedule table, can be prevented. In addition, it will help to establish a schedule plan that is closer to reality.

• Food Engineering Progress
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• v.21 no.3
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• pp.267-272
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• 2017

To improve dispersibility of cereal powder without additives, granulation of cereal powder was conducted using fluidized-bed granulator. Operation condition was sample 300 g, internal temperature $40^{\circ}C$, ventilation speed $30-90m^3/h$, inlet temperature $90^{\circ}C$ and spray pressure 2.5 bar. The amount of distilled water (20-45%) as binder, granulation time (10-15 min) and drying time (3-10 min) were controlled. Mean diameter over volume (Brouckere mean, $D_{4,3}$) was increased from $123{\mu}m$ to $263{\mu}m$ and dispersibility was improved from 73% to 92.25% at experiment conditions. Wettability (wetting time) was drastically decreased from 5,000 second to 7 second. Granulation of cereal powder did not affect sinkability and mean diameter over volume as wet analysis was about the same between raw and granulated cereals. Such phenomenon means that granulation with only water as binder enables cereal powder to disperse in water or milk without rapid sedimentation.

• Korean Journal of Heritage: History & Science
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• v.54 no.3
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• pp.204-227
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• 2021

This paper proposed the validity and necessity of establishing the Jungwon Historical and Cultural Area by reviewing the historical characteristics of the name Jungwon and its temporal and spatial range. We also explored ways to utilize the Jungwon historical and cultural Area under the Special Act on the Maintenance of Historical and Cultural Areas. Jungwon, which means the center of the country, has strategic value as a key area connecting the Korean Peninsula to the north and south through the Geripryeong and Jukryeong. It also includes Chungju, which connects the Namhan and Bukhan Rivers . From the Mahan period, the areas of Cheongju and Jincheon, the Miho Stream basin to the west, and Chungju to the east were closely connected to each other. Afterwards, Baekje, Koguryo, and Silla engaged in a fierce battle to occupy the Jungwon area. Jungwon culture was born through the negotiation and fusion of the cultures of the three kingdoms. In particular, Silla continued to value the Jungwon area, demonstrated by the installation of Seowongyeong in Cheongju and Bukwongyeong in Wonju, centering on the Jungwongyeong. Since we have a historical view with a focus on ancient kingdoms, we have overlooked the full value of the history and culture of Jungwon. We need to recognize the importance of Jungwon area and think about how to utilize it. Therefore, we suggested in this paper that there be more public information services on the cultural heritage of Jungwon, the historical heritage experience, and the education programs for local residents. The development and operation of Jungwon's history, culture, and tourism contents, as well as the various academic research papers should be used to reveal the identity of the Jungwon historical and cultural area.

• Journal of Internet Computing and Services
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• v.22 no.4
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• pp.123-134
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• 2021

This paper suggests that the Internet is not free through analysis of U.S. Internet history and lawsuits related to the Charter merger in 2016. Generally speaking, the players in internet connectivity market agree to Non-Disclosure Agreement, when connecting their facilities and networks each other. So, I adopted the case study & analysis as research methodologies due to limitation of collecting the transaction data between them. The former finds that Internet access has never been free in U.S Internet history. As we know, some including Content Providers(CPs) argue that the Internet is a free network and there are many cases to use the internet for free, so they came to conclusion that ISPs have no right to charge the users like CPs. This study refutes these arguments in two ways. One is that using the internet has never been free. From ARPANET, known as the beginning of the U.S. Internet, to the commercialization of backbone, no Internet has been considered or implemented for free since the early Internet network was devised. Also, the U.S government was paying subsidies or institutions were paying fees to secure network operations for the NSFNET backbone. the other is that "free peering" refers to barter transactions between ISPs, not to free access to counterpart internet networks. Second, this study analyze the FCC' executive order of conditioned merger approval and the court's related ruling and verify that using the internet is not free. According to the analysis, this study finds that it's real situation to make paid settlements between ISP-CPs (including OTTs) in the US Internet market at the moment. This study concludes that the Internet has never been free in terms of its technical characteristics, network structure, network operation, and system. Also it proposes how to improve the domestic settlement system between ISPs-CPs in terms of policy and regulation.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.485-492
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• 2021

The wind turbines with a rated capacity of 50kW or less are generally considered as small class. Small wind turbines are an attractive alternative for off-grid power system and electric home appliances, both as stand-alone application and in combination with other energy technologies such as energy storage system, photovoltaic, small hydro or diesel engines. The research objective is to develop the 50kW scale wind turbine blades in ways that resemble as closely as possible with the construction and methods of utility scale turbine blade manufacturing. The mold process based on wooden form is employed to create a hollow, multi-piece, lightweight design using carbon fiber and fiberglass with an epoxy based resin. A hand layup prototyping method is developed using high density foam molds that allows short cycle time between design iterations of aerodynamic platforms. A production process of five blades is manufactured and key components of the blade are tested by IEC 61400-23 to verify the appropriateness of the design. Also, wind system with developed blades is tested by IEC 61400-12 to verify the performance characteristics. The results of blade and turbine system test showed the available design conditions for commercial operation.

• The Journal of the Korea Contents Association
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• v.21 no.2
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• pp.499-506
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• 2021

Hackers' cyber attack techniques are becoming more sophisticated and diversified, with a form of attack that has never been seen before. In terms of information security vulnerability standard code (CVE), about 90,000 new codes were registered from 2015 to 2020. This indicates that security threats are increasing rapidly. When new security vulnerabilities occur, damage should be minimized by preparing countermeasures for them, but in many cases, companies are insufficient to cover the security management level and response system with a limited security IT budget. The reason is that it takes about a month for analysts to discover vulnerabilities through manual analysis, prepare countermeasures through security equipment, and patch security vulnerabilities. In the case of the public sector, the National Cyber Safety Center distributes and manages security operation policies in a batch. However, it is not easy to accept the security policy according to the characteristics of the manufacturer, and it takes about 3 weeks or more to verify the traffic for each section. In addition, when abnormal traffic inflow occurs, countermeasures such as detection and detection of infringement attacks through vulnerability analysis must be prepared, but there are limitations in response due to the absence of specialized security experts. In this paper, we proposed a method of using the security policy information sharing site "snort.org" to prepare effective countermeasures against new security vulnerability attacks.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.2
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• pp.162-172
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• 2021

This study was conducted to determine whether the layout of wheelhouse and work environment of coastal improved stow net fishing boats affect the physical abnormalities of wheelhouse workers through a survey and to use it as basic data to improve the wheelhouse work environment. The analysis results are as follows. The result of factor analysis on the wheelhouse work environment was classified into three factors: suitability of work environment, suitability of work space arrangement, and layout of navigational and fishing equipment. The result of factor analysis on physical abnormalities was divided into two factors: physical pain and fatigue. The results of regression model analysis showing factors affecting physical pain showed that the t-value in the regression model was 3.625 (p < 0.05), indicating that the work environment suitability had an effect on the physical pain. Work environment suitability had a significantly positive effect on the physical pain. As work environment suitability increased by 1, the physical pain increased by 0.371 (p < 0.05). The results of regression model analysis showing the influencing factors on fatigue were found to have a t-value of 3.009 (p < 0.05) in the regression model, indicating that the work environment suitability had a significantly positive effect on the feeling of fatigue. It was found that fatigue increased by 0.324 (p < 0.05) as the work environment suitability increased by 1. In addition, the manageability of task suitability was found to be t = -2.521 (p > 0.05). As the manageability of task suitability increased, the skipper's fatigue level decreased. From these results, it is inferred that the wheelhouse of the current coastal improved stow net fishing boats causes physical pain and fatigue for the skippers. In order to reduce such physical pain and fatigue, and to improve safe fishing operation and job satisfaction, it is necessary to provide a wheelhouse to fishermen on coastal improved stow net fishing boats in consideration of the characteristics of the wheelhouse work of fishing boats and in consideration of users.