• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.211-217
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• 1998

Many practical control problems for the complex, uncertain or large-scale plants, need to simultaneously achieve a number of objectives, which may conflict or compete with each other. If the conventional optimization methods are applied to solve these control problems, the solution process may be time-consuming and the resulting solution would ofter lose its original meaning of optimality. Nevertheless, the human operators usually performs satisfactory results based on their qualitative and heuristic knowledge. In this paper, we investigate the control strategies of the human operators, and propose a fuzzy model-based multi-objective satisfactory controller. We also apply it to the automatic train operation(ATO) system for the magnetically levitated vehicles(MAGLEV). One of the human operator's strategies is to predict the control result in order to find the meaningful solution. In this paper, Takagi-Sugeno fuzzy model is used to simulated the prediction procedure. Another str tegy is to evaluate the multiple objectives with respect to their own standards. To realize this strategy, we propose the concept of a satisfactory solution and a satisfactory control scheme. The MAGLEV train is a typical example of the uncertain, complex and large-scale plants. Moreover, the ATO system has to satisfy multiple objectives, such as seed pattern tracking, stop gap accuracy, safety and riding comfort. In this paper, the speed pattern tracking controller and the automatic stop controller of the ATO system is designed based on the proposed control scheme. The effectiveness of the ATO system based on the proposed scheme is shown by the experiments with a rotary test bed and a real MAGLEV train.

• Journal of KIISE:Information Networking
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• v.30 no.6
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• pp.705-713
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• 2003

For group security to protect group data or to charge, group keys should be updated via key update messages when the membership of group changes. If we lose these messages, it is not possible to decrypt the group data and so this is why the recovery of lost keys is very significant. Any message lost during a certain member is logged off can not be recovered in real-time. Saving all messages and resending them by KDC (Key Distribution Center) not only requests large saving spaces, but also causes to transmit and decrypt unnecessary keys. This paper analyzes the problem of the loss of key update messages along with other problems that may arise during member login procedure, and also gives an efficient method for recovering group keys and auxiliary keys. This method provides that group keys and auxiliary keys can be recovered and sent effectively using information stored in key-tree. The group key generation method presented in this paper is simple and enable us to recover any group key without storing. It also eliminates the transmissions and decryptions of useless auxiliary keys.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1326-1333
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• 2016

It is important to clear the fault and prevent resulting in damage to power system. Although the frequency of generator internal fault is relatively low, it can lead to incalculable damage to power system as well as generator. Especially, loss of field on generator can cause the generator to lose synchronism for a short time if it is not removed promptly. Therefore, it is needed to conduct research on loss of field relay for detecting or clearing the loss of field. However, the setting of the relay may vary in generator operator or engineer, and the relay is not coordinated well with other elements associated with loss of field. In this paper, we address specifically the coordination of positive offset mho loss of field relay which is one of the protection schemes for loss of field. Computer simulations are performed by using ElectroMagnetic Transients Program-Restructured Version (EMTP-RV) based on actual data.

• The Journal of the Korea Contents Association
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• v.17 no.5
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• pp.90-99
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• 2017

Sports climbing requires repeated movements within a limited space, which may cause climbers to lose their constant interest in it. Furthermore, it is important that coaches should give lessons focusing on demonstrations to make sure that learners can understand the movements on their own, However, in traditional sports climbing lessons, they give instructions on almost every movement of learners' hands and feet. Hence, there have been constant calls for replacing these existing sports climbing lessons and presenting new methods to ensure that learners can observe their coaches' demonstrations in real time and emulate them. An introduction of the image training using spatial augmented reality techniques to solve these problems may have a positive effect on the improvement of learners' motor skills and attitudes toward lessons. This study aims to verify the effectiveness of the Climbing Character Animation (CCA) as a learning tool for sports climbing. To achieve this research objective, it applied it to actual sports climbing to verify its utility. As a result, it was shown that the lessons using spatial augmented reality-based CCA had a higher effectiveness than traditional sports climbing lessons in the degree of interest inducement, emersion and learning effects.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.4
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• pp.299-308
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• 2001

The company invests its time and money for temporary maintenance to satisfy the fast change of the computer use environment and the user's demands. Therefore, various problems occur including low performance because of duplication of codes and unstable structures from the restructuring and redevelopment. Furthermore, if a developer, who did not participate in initial process of development, wrote additional program codes to upgrade or restructure, it would cause many problems such as lack or lose of development documentation, understanding of documentation and reuse of existing program language. This study, Object-oriented Refactoring Process, suggests that the developers can reuse object unit to overcome the limit of the reusing code. In addition, this paper shows case study to verify our process by adjusting the project called "D2D", which is a case tool for developing windows system from Company D. Our works get positive results such as improvement of system pelfonnance, decreased cost of development and maintenance and optimizing structure and class.

• International Journal of Advanced Culture Technology
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• v.9 no.3
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• pp.253-258
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• 2021

This study aims to expose the potential dangers of K-pop through the past and present of K-pop choreography copyrights and to suggest the need to secure digital choreography copyrights for the sustainability of K-pop considering national responsibility. As the content industry quickly sought countermeasures to digital transformation, such as the launch of K-pop platforms and the evolution of OMO (Online Merges with Offline) media commerce in response to changes in the industrial environment due to COVID-19, the annual export of the domestic content industry increased by 6.3% compared to the previous year. Accordingly, our copyright does not require that works be fixed in tangibles, as in Japan and Germany, on the basis of entrusting each country's legislation to determine whether to require fixation on choreographed works. On the other hand, the United States, France and the United Kingdom are demanding that it be fixed. Although choreography is at the center of K-pop and the value and influence of K-pop videos including cover dance through new media are discussed from various perspectives, copyright on choreography that needs to be resolved in business platforms for K-pop scalability The fact that there is such a big difference in problem perception is an area where we must not lose our vigilance. As the development of today's technology, the method of fixing a choreography looks very easy as an image, but at the same time can be stolen very quickly. Therefore, compared to overseas cases, it is urgent to improve the difference in perception of copyright registration for K-pop choreography and to supplement the system include the NFT.

• Tribology and Lubricants
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• v.37 no.5
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• pp.189-194
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• 2021

A straightforward, yet effective surface modification method of stainless steel mesh and its interesting anti-wetting characteristics are reported in this study. The stainless steel mesh is electrochemically etched, and the specimen has both micro and nano-scale structures on its surface. This process transforms the two types of mesh specimens known as the regular and dense specimens into hydrophobic specimens without applying any hydrophobic chemical coating process. The fundamental wettability of the modified mesh is analyzed through a dedicatedly designed experiment to investigate the waterproof characteristics, for instance, the penetration threshold. The waterproof characteristics are evaluated in a manner that the modified mesh resists as high as approximately 2.7 times the pressure compared with the bare mesh, i.e., the non-modified mesh. The results show that the penetration threshold depends primarily on the advancing contact angles, and the penetration stop behaviors are affected by the contact angle hysteresis on the surfaces. The findings further confirm that the inexpensive waterproof meshes created using the proposed straightforward electrochemical etching process are effective and can be adapted along with appropriate designs for various practical applications, such as underwater devices, passive valves, and transducers. In general, , additional chemical coatings are applied using hydrophobic materials on the surfaces for the applications that require water-repelling capabilities. Although these chemical coatings can often cause aging, the process proposed in this study is not only cost-effective, but also durable implying that it does not lose its waterproof properties over time.

• Journal of Practical Engineering Education
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• v.12 no.2
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• pp.309-319
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• 2020

Billiards is a fun and popular sport, but both route planning and cueing prevent beginners from becoming skillful. A beginner in billiards requires constant concentration and training to reach the right level, but without the right motivating factor, it is easy to lose interests. This study aims to induce interest in billiards and accelerate learning by utilizing billiard path prediction and visualization on a highly immersive augmented reality platform that combines a stereo camera and a VR headset. For implementation, the placement of billiard balls is recognized through the OpenCV image processing program, and physics simulation, path search, and visualization are performed in Unity Engine. As a result, accurate path prediction can be achieved. This made it possible for beginners to reduce the psychological burden of planning the path, focus only on accurate cueing, and gradually increase their billiard proficiency by getting used to the path suggested by the algorithm for a long time. We confirm that the proposed AR billiards is remarkably effective as a learning assistant tool.

• The Journal of Information Systems
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• v.30 no.4
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• pp.21-42
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• 2021

Purpose In order for companies to continue to grow, they should properly manage human resources, which are the core of corporate competitiveness. Employee turnover means the loss of talent in the workforce. When an employee voluntarily leaves his or her company, it will lose hiring and training cost and lead to the withdrawal of key personnel and new costs to train a new employee. From an employee's viewpoint, moving to another company is also risky because it can be time consuming and costly. Therefore, in order to reduce the social and economic costs caused by employee turnover, it is necessary to accurately predict employee turnover intention, identify the factors affecting employee turnover, and manage them appropriately in the company. Design/methodology/approach Prior studies have mainly used logistic regression and decision trees, which have explanatory power but poor predictive accuracy. In order to develop a more accurate prediction model, XGBoost is proposed as the classification technique. Then, to compensate for the lack of explainability, SHAP, one of the XAI techniques, is applied. As a result, the prediction accuracy of the proposed model is improved compared to the conventional methods such as LOGIT and Decision Trees. By applying SHAP to the proposed model, the factors affecting the overall employee turnover intention as well as a specific sample's turnover intention are identified. Findings Experimental results show that the prediction accuracy of XGBoost is superior to that of logistic regression and decision trees. Using SHAP, we find that jobseeking, annuity, eng_test, comm_temp, seti_dev, seti_money, equl_ablt, and sati_safe significantly affect overall employee turnover intention. In addition, it is confirmed that the factors affecting an individual's turnover intention are more diverse. Our research findings imply that companies should adopt a personalized approach for each employee in order to effectively prevent his or her turnover.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.3
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• pp.138-151
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• 2023

Korea's port infrastructure is rapidly aging, with old port facilities with more than 30 years of public life expected to surge from about 23% in 2019 to 47% in 2029. Traditional, aging ports lose competitiveness in logistics processing, reducing development around the port and increasing human casualties due to the human resource-based maintenance of the facilities. Therefore, it is necessary to solve this problem by establishing systematic management technology based on a digital twin. This research aimed to present the specific implementation steps of a digital twin reflecting smart port technology through cases of port infrastructure disasters, aging status, and smart ports. The study analyzed the port infrastructure linkage system and created and mapped scenarios essential for digital twin implementation. Three-dimensional (3D) modeling and simulation data for disaster and aging management among existing port infrastructure systems were collected. A digital twin port was implemented with 3D modeling. It implements a port digital twin simulation that links data such as sensing data and image data acquired from the port infrastructure in real time. Implementing a digital twin port for port infrastructure disasters and aging management can secure predictive port infrastructure management and disaster safety