• 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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.663-670
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• 2020

In the present study, we assessed the accuracy of aerial triangulation using a UAV (Unmanned Aerial Vehicle) capable of network RTK (Real-Time Kinematic) survey in a disaster situation that may occur in a semi-urban area mixed with buildings. For a reliable survey of check points, they were installed on the roofs of buildings, and static GNSS (Global Navigation Satellite System) survey was conducted for more than four hours. For objective accuracy assessment, coded aerial targets were installed on the check points to be automatically recognized by software. At the instance of image acquisition, the 3D coordinates of the UAV camera were measured using VRS (Virtual Reference Station) method, as a kind of network RTK survey, and the 3-axial angles were achieved using IMU (Inertial Measurement Unit) and gimbal rotation measurement. As a result of estimation and update of the interior and exterior orientation parameters using Agisoft Metashape, the 3D RMSE (Root Mean Square Error) of aerial triangulation ranged from 0.153 m to 0.102 m according to the combination of the image overlap and the angle of the image acquisition. To get higher aerial triangulation accuracy, it was proved to be effective to incorporate oblique images, though it is common to increase the overlap of vertical images. Therefore, to conduct a UAV mapping in an urgent disaster site, it is necessary to acquire oblique images together rather than improving image overlap.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.6A
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• pp.139-149
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• 2008

The amount of personal information collected by organizations and government agencies is continuously increasing. When a data collector publishes personal information for research and other purposes, individuals' sensitive information should not be revealed. On the other hand, published data is also required to provide accurate statistical information for analysis. k-Anonymity and ${\iota}$-diversity models are popular approaches for privacy preserving data publication. However, they are limited to static data release. After a dataset is updated with insertions and deletions, a data collector cannot safely release up-to-date information. Recently, the m-invariance model has been proposed to support re-publication of dynamic datasets. However, the m-invariant generalization can cause high information loss. In addition, if the adversary already obtained sensitive values of some individuals before accessing released information, the m-invariance leads to severe privacy disclosure. In this paper, we propose a novel technique for safely releasing dynamic datasets. The proposed technique offers a simple and effective method for handling inserted and deleted records without generalization. It also gives equivalent degree of privacy preservation to the m-invariance model.

• Composites Research
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• v.33 no.6
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• pp.365-370
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• 2020

The icing formation at aircraft occur problems such as increasing weight of the body, fuel efficiency reduction, drag reduction, the error of sensor, and etc. The viscosity of polyurethane (PU) topcoat was measured at 60℃ in real time to set the pre-curing time. SiO2 nanoparticles were dispersed in ethanol using ultra-sonication method. The SiO2/ethanol solution was sprayed on PU topcoat that was not cured fully with different pre-curing conditions. Surface roughness of SiO2/PU nanocomposites were measured using surface roughness tester and the surface roughness data was visualized using 3D mapping. The adhesion property between SiO2 and PU topcoat was evaluated using adhesion pull-off test. The static contact angle was measured using distilled water to evaluate the hydrophobicity. Finally, the pre-curing time of PU topcoat was optimized to exhibit the hydrophobicity of SiO2/PU topcoat.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.160-168
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• 2021

This study attempts to identify how incivility and clinical learning environment affects clinical practice stress among nursing students. This study enrolled 204 nursing students in the third- and fourth-grades, having practical clinical experience. Data were collected from April 1 to April 30, 2019, by the self-reported method. Data analysis was achieved by applying descriptive statistics, t-test, ANOVA, Pearson correlation coefficient, and multiple regression analysis, using the SPSS 22.0 program. Our results showed that the average values for incivility experienced by nursing students was 2.58, clinical learning environment was 2.79, and clinical practice stress was 3.33. Incivility experienced and clinical practice stress appeared to be a static correlation, whereas the clinical learning environment and clinical practice stress, and incivility experienced and clinical learning environment, were identified as amulet correlations. Incivility experienced and clinical learning environment exerted significant influences on clinical practice stress, where the explanatory power was confirmed at 22.5%. Based on the results of this study, we propose the necessity to develop and apply various programs to effectively manage the clinical practice stress of nursing students.

• Journal of Industrial Convergence
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• v.18 no.6
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• pp.155-163
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• 2020

The purpose of this study was to verify the effect of job stress of caregivers on service quality for improve the quality of elderly long-term care services and the mediating effect of organizational commitment in the process. To this end, 30 long-term care facilities were randomly sampled out of 1,705 long-term care facilities in Gyeonggi-do, and as a result of a questionnaire survey of 500 caregiver for one month in May 2020, 443 samples were collected, and a total of 415 samples were finally analyzed. As for the analysis method, SPSS WIN 21.0 was used to verify the mediation model using frequency analysis, descriptive analysis, correlation analysis, and regression analysis. As a result of the study, first, job stress had a negative effect on service quality and organizational commitment. Second, organizational commitment has a static effect on service quality. Third, organizational commitment was verified as a perfect mediating in the relationship between job stress and service quality. This suggested the importance of the effect of organizational commitment in the process between job stress and service quality of caregivers and sought a policy ways to to improve the service quality of caregivers.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.1
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• pp.112-125
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• 2021

Marine spatial planning(MSP) designates the marine as nine kinds of use zones for the systematic and rational management of marine spaces. One of them is the fishery protection zone, which is necessary for the sustainable production of fishery products, including the protection and fosterage of fishing activities. This study intends to quantitatively identify the fishing activity space, one of the elements necessary for the designation of fisheries protection zones, by mapping of fishery activities using V-Pass data and deriving the fishery activity concentrated zone. To this end, pre-processing of V-Pass data was performed, such as constructing a dataset that combines static and dynamic information, calculating the speed of fishing vessels, extracting fishing activity points, and removing data in non-fishing activity zone. Finally, using the selected V-Pass point data, a fishery activity map was made by kernel density estimation, and the concentrated space of fishery activity was analyzed. In addition, it was confirmed that there is a difference in the spatial distribution of fishing activities according to the type of fishing vessel and the season. The pre-processing technique of large volume V-Pass data and the mapping method of fishing activities performed through this study are expected to contribute to the study of spatial characteristics evaluation of fishing activities in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.9-16
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• 2020

A CFRP sheet has been applied as a structural reinforcement in the field, and various studies are conducted to evaluate the effect of CFRP sheets on reinforced concrete. Although many experiments were performed from previous studies, there are still limitations to analyze structural behaviors with various parameters in experiments directly. This study shows the FEA on structural behaviors of RC beams reinforced with CFRP sheets using ABAQUS software. To simulate debonding failure of CFRP sheets which is a major failure mode of RC beam with CFRP sheets, a cohesive element was applied between the bottom surface of RC beam and CFRP sheets. Both quasi-static method and 2-D symmetric FE model technique were performed to solve nonlinear problems. Results obtained from the FE models show good agreements with experimental results. It was found that reinforcement level of CFRP sheets is closely related to structural behavior of reinforced concrete including maximum strength, initial stiffness and deflection at failure. Also, as over-reinforcement of CFRP sheets could give rise to the brittle failure of RCstructure using CFRP sheets, an appropriate measure should be required when installing CFRP sheets in the structure.

• Knowledge Management Research
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• v.22 no.4
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• pp.237-260
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• 2021

This study aims to make suggestions for more effective budget utilization and R&D project investment through verification of the efficiency of research results for the government's R&D projects. Efficiency was analyzed using Data Envelope Analysis(DEA) and 'Malmquist Index analysis' for the research results of convergence research projects organized by the National Science and Technology Research Association. The analysis targets were convergence research projects organized by the National Science and Technology Research Association and general entrusted research projects by government-funded research institutes, and dynamic analysis was conducted using DEA and Malmquist Index analysis. As a result of the analysis, the convergence research project showed high efficiency from the static perspective of DEA. On the other hand, from a dynamic perspective through the Malmquist Index analysis method, the efficiency of the general consignment project gradually declined, while the efficiency of the convergence research project improved every year. This suggests that convergence studies have higher results than general studies. Through the results of this study, we intend to present objective standards for performance evaluation of government R&D investment and provide objective implications for rational investment policies and research project planning of research personnel and research funds to improve efficiency for government-funded research institutes.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.646-659
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• 2022

Purpose: In this study, we developed a 4-way sway prevention brace that efficiently reduces the installation area and has excellent stability and seismic performance compared to the conventionl sway prevention brace used in existing firefighting facilities. The performance and reliability of the developed 4-way way prevention brace were analyzed by the tensile, compression tests and seismic tests. Method: As the static test, 4-way sway prevention braces were installed on the horizontal and vertical pipes to perform the tensile and compression tests based on the KFI certification standard and the maximum movement was measured at the rated load. As a dynamic test, 4-way sway prevention braces were installed in the pipes filled with water, and the test response spectrum to the input excitation wave were measured through the acceleration sensors. After the seismic tests, separation, failure, and local deformation of the pipes, and 4-way sway prevention braces were not observed. Result: The results of the tensile and compression tests indicated that the maximum movement of the pipe during tension and compression was 50% to 70% or less compared to the certification values, indicating that the performances of the 4-way sway prevention braces were very excellent. The results of the the seismic tests indicated that the test response spectrum of the 4-way sway prevention braces is within the required response spectrum. Conclusion: In this study, it was found that the 4-way sway prevention braces satisfied the KFI certification standard and were superior compared to the existing sway prevention brace in terms of the stability, cost, and installation area.