• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.789-796
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• 2000

This paper deals with magnetic field and characteristic analysis for ring type slotless synchronous motors by using analytical method. Since magnetic air-gap in the slotless motors is much larger than mechanical air-gap, it is necessary to analyze the magnetic flux distribution at the whole magnetic airgap region. therefore, this paper analyzes the duplicated magnetic field derived by both Permanent Magnet(PM) and armature current and estimates the back electromotive force and torque characteristic by subdividing the conductor region. The analysis results are verified by comparing with Finite Element Analysis(FEA) results.

• Tribology and Lubricants
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• v.18 no.1
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• pp.34-41
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• 2002

This paper presents the contact thermal behaviors of mechanical seals depending on the contacting face geometry. Using the finite element analysis, the temperature distribution, thermal distortion and leakage have been analyzed as functions of sealing gap and rotating speed of the seal ring shaft. The FE results indicate that the inclined contacting face may be more effective and stable based on the results of thermal characteristic analysis if the seal ring has been designed with a same thermal capacity between conventional rectangular sealing faces and inclined seating surface of seal rings.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.52-54
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• 2005

In this paper, a new approach monitoring rotor vibrations in a squirrel-cage induction motor is proposed. The air-gap flux variation analysis was done using search coils inserted in stator slots when rotor vibration conditions occur. An accurate modelling and analysis of air-gap flux variation in the induction motor are developed using finite-element(FE) software packages, and measuring the flux are made using search coils. In the FE analysis, the three-phase squirrel-gage induction motor with 380 (V), 5 (HP), 4 Poles, 1,742 [rpm] ratings is used. The results of FE analysis can be useful for on-line vibration monitoring of the induction motors.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.49-53
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• 1996

Corona discharges in air insulated electric power systems cause power loss, produce interfering electromagnetic radiation, and can indicate incipient failure. An understanding of corona discharges in air gap is clearly Important. The Wavelet transformation is an extended method of fourier transformation. The fourier method is a powerful tool for signal analysis, but it can't include information for time. However the wavelet transformation analysis can include on the information of time and frequencies at the same time. In this paper we apply the wavelet transformation to the corona signals in needle-plane air gap for the purpose of analysis of developing aspects of corona discharges. We analyzed the developing aspects of corona discharges, namely, corona discharge current, repetition rates, width of Pulse distribution region, pulseless region and frequencies distribution of corona discharge pulses.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.92-98
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• 1999

Dynamic behavior of missile which is fired in canister is analyzed by flexible multibody dynamics. The bending elasticity of missile is very important in case that missile is fired in the inclined launcher. In this paper, the force element model for the missile launching stage and the finite element model of missile are developed. The FEA model of missile is condensed into five lumped mass element model and the consistence between FE model and lumped mass model of missile is verified by modal analysis. As a result of analysis, sabot reaction force and pitch rate of missile for the variation of gap size and force element are obtained.

• Journal of Food Hygiene and Safety
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• v.33 no.1
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• pp.1-11
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• 2018

It is ten years since the Good Agricultural Practices (GAP) certification system was implemented in Korea, and the government aims to acquire GAP certification up to 25% of the total agricultural areas by 2022. As of the end of 2017, 6.3% of the total cultivated area and 8.1% of the total farm households were certified, which is slower than expected. The purpose of this study was to investigate the causes of the GAP accreditation through the surveys and on site inspections of the GAP certified farmers and to propose the development plans according to the problems analysis of the current system in order to expand the GAP certification. Certified farmers recognized the need for agricultural safety and hygiene, but there were a lot of nonconformities regarding practical practices. This is due to the ambiguity of the certification standards and the wrong ways in the training method for the producers. GAP certification is slow to expand to farmers and low consumer awareness is considered a structural problem of GAP certification system, and improvement measures are needed accordingly. It is necessary to convert the state-led GAP certification system into a state-led private certification system. It is necessary for the government to focus on policy, research and follow-up management. In addition, it is necessary to establish a separate organization in the form of a contribution organization for the certification, education, and public relations. In addition, long-term plan must be established and systematically carried out. It is necessary to integrate too many certification agencies compared to the farming scale of Korea, and it is necessary to realize the application fee for realizing the financial independence of the certification body and correct certification work. In addition, inspector qualification standards should be strengthened and training system should be improved to nurture high quality inspectors. Simplified certification standards based on statutes need to be subdivided into practical action plans. In order to improve the GAP certification system, it is necessary to have a discussion through a committee composed of specialists from industry and academia, and it will be possible to contribute to the safety of the food of the people through the production of safe by drawing concrete development plans.

• Journal of Korea Trade
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• v.26 no.5
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• pp.56-75
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• 2022

Purpose - This study examines the influencing factors of China's cross-border e-commerce exports in the context of the current situation and trends of China's cross-border e-commerce development. Through an improved trade gravity model, it provides more in-depth research and constructive opinions on the development of cross-border e-commerce in China. In this paper, factors such as consumption gap, volume of trade frictions, number of tourists, Internet usage and trade openness are added to the formula of the traditional trade gravity model in the improved trade gravity model to examine the influencing factors on China's cross-border e-commerce exports. Design/methodology - According to the empirical analysis, China's cross-border e-commerce exports to ten countries are used as dependent variables, and consumption gap, trade friction volume, trade distance, trade openness and number of Internet users are taken as independent variables. Regression analysis is conducted through a modified gravity model to test whether the hypotheses hold. Findings - The analysis shows that the hypothesis that China's cross-border e-commerce exports are influenced by trade openness, trade distance, consumption gap between trade parties, and the number of Internet users in the importing country is supported by these four hypotheses, but not all independent variables have an impact on them. Specifically, the number of travelers, trade frictions do not have an impact on China's cross-border e-commerce. That is to say, trade friction between China and the United States and political issues such as China-India and China-Japan territorial disputes that emerged before do not affect the development of cross-border e-commerce in China. Originality/value - The analysis shows that the factors influencing China's cross-border e-commerce exports are the trade openness of the importing country, the trade distance, the number of Internet users in the importing country, and the consumption gap between the two sides of the trade. The trade openness and the number of Internet users positively contribute to China's cross-border e-commerce, while the consumption gap and trade distance are negatively related to them. And the analysis found that the Sino-US trade war and the Sino-Indian territorial disputes and other trade frictions to China's cross-border e-commerce exports did not have a substantial impact.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.335-349
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• 2017

Submerged breakwaters installed under the water surface are a representative coastal structure to prevent coastal erosion, and various types of submerged breakwaters have been proposed and discussed so far. Generally, submerged breakwaters make the complex wave fields due to abrupt change in water depth at the crown of the breakwater. In this study, wave heights and mean water level formed around a breakwater are examined numerically for three-dimensional permeable submerged breakwaters. OLAFOAM, CFD open source code, is applied in the numerical analysis, and the comparisons are made with available experimental results on the permeable upright wall and the impermeable submerged breakwater to verify its applicability to the three-dimensional numerical analysis. Based on the applicability of OLAFOAM numerical code, the wave height and mean water level distribution formed around the permeable submerged breakwaters are investigated under the formation condition of salient. The numerical results show that as the gap width between breakwaters decreases, the wave height in the center of the gap increases, while it decreases behind the gap, and the installing position of the breakwater from the shoreline has little influence on the change of the wave height. Furthermore, it is found that the decrease of the mean water level near the gap between breakwaters increases with decreasing of the gap width.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.6
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• pp.90-100
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• 2017

The purpose of this study is to detect and label the vehicles using the drone images as a way to overcome the limitation of the existing point and section detection system and vehicle gap estimation on Arterial road. In order to select the appropriate time zone, position, and altitude for the acquisition of the drone image data, the final image data was acquired by shooting under various conditions. The vehicle was detected by applying mixed Gaussian, image binarization and morphology among various image analysis techniques, and the vehicle was labeled by applying Kalman filter. As a result of the labeling rate analysis, it was confirmed that the vehicle labeling rate is 65% by detecting 185 out of 285 vehicles. The gap was calculated by pixel unitization, and the results were verified through comparison and analysis with Daum maps. As a result, the gap error was less than 5m and the mean error was 1.67m with the preceding vehicle and 1.1m with the following vehicle. The gaps estimated in this study can be used as the density of the urban roads and the criteria for judging the service level.

• Journal of Digital Convergence
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• v.19 no.12
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• pp.531-539
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• 2021

Given the rapid development of information and communication technology (ICT) and the deepening of the information gap phenomenon in the context of the COVID-19 pandemic, researchers and practitioners need to understand the changing perceptions of new phenomena such as COVID-19 information gap on the existing information-vulnerable population. In this study, an empirical analysis was performed with the digital information gap survey data in 2020 to understand the potential impact of COVID-19 on the information gap according to the information-vulnerable class. This study is to verify the effect of information gap, marginalized groups, gender, and major factors of information services (contents, social relations, life services, information production, networking, social participation, non-face-to-face services) on the change in perception of digital information technology after Corona. Hierarchical regression analysis was performed. As a result of the analysis, it was found that the higher the content, social relationship, life service, networking, and digital non-face-to-face service, the higher the change in perception of digital information technology after Corona. Therefore, in light of the evolving phenomenon of COVID-19, it is considered that the government needs to provide education and training to strengthen the capabilities of the information-vulnerable class in order to resolve the digital information gap.