• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.20-29
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• 2018

The dynamic characteristics of power systems become more and more complex because of the integration of large-scale wind power, which needs appropriate control strategy to guarantee stable operation. With wide area measurement system(WAMS) creating conditions for realizing realt-ime transient stability analysis, a new coordinated control strategy for power system transient stability control based on phase-plane trajectory was proposed. When the outputs of the wind farms change, the proposed control method is capable of selecting optimal generators to balance the deviation of wind power and prevent transient instability. With small disturbance on the base operating point, the coordinated sensitivity of each synchronous generator is obtained. Then the priority matrix can be formed by sorting the coordinated sensitivity in ascending order. Based on the real-time output change of wind farm, coordinated generators can be selected to accomplish the coordinated control with wind farms. The results in New England 10-genrator 39-bus system validate the effectiveness and superiority of the proposed coordinated control strategy.

• Journal of Information Processing Systems
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• v.16 no.1
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• pp.201-209
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• 2020

The graph data structure is popular because it can intuitively represent real-world knowledge. Graph databases have attracted attention in academia and industry because they can be used to maintain graph data and allow users to mine knowledge. Mining reachability relationships between two nodes in a graph, termed reachability query processing, is an important functionality of graph databases. Online traversals, such as the breadth-first and depth-first search, are inefficient in processing reachability queries when dealing with large-scale graphs. Labeling schemes have been proposed to overcome these disadvantages. The state-of-the-art is the 2-hop labeling scheme: each node has in and out labels containing reachable node IDs as integers. Unfortunately, existing 2-hop labeling schemes generate huge 2-hop label sizes because they only consider local features, such as degrees. In this paper, we propose a more efficient 2-hop label size reduction approach. We consider the topological sort index, which is a global feature. A linear combination is suggested for utilizing both local and global features. We conduct experiments over real-world and synthetic directed acyclic graph datasets and show that the proposed approach generates smaller labels than existing approaches.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.196-198
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• 2007

In the substations for traction systems and the large-scale discharging system of secondary batteries, the voltage of DC bus line goes up by the regenerated energy and the energy is usually wasted in resistor for system stability. This paper proposes the DC power regenerating system using a three phase PWM inverter. The proposed system can regenerate the excessive DC power from DC bus line to AC supply and control the power factor of AC supply to unity. To implement unity power factor, the magnitude of the inverter output voltage should be higher than that of AC supply and therefore SVPWM technique is adopted. Computer simulations are carried out to verify the validity of the proposed system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.971-977
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• 2010

A flood of biological data has caused many challenges in computing. Bioinformatics, the application of computational techniques to analyze the information associated with biomolecules on a large-scale, has now firmly established itself as an interdisciplinary subject in molecular biology, and encompasses a wide range of subject areas from structural biology, genomics, proteomics, systems biology, biostatistics to computer science. In this review, I provide an introduction and overview of the current state of bioinformatics. Looking at the types of biological information and databases that are commonly used, I also deals with some of bioinformatics application domains which are closely related to areas of computer science.

• Nuclear Engineering and Technology
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• v.52 no.1
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• pp.27-36
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• 2020

Natural convection and thermal stratification phenomena are found in large water pools that are being used as heat sinks for decay heat removal from the reactor core using passive heat removal systems. In this study, the two-phase (water and air) natural convection and thermal stratification phenomena with conjugate heat transfer in the rectangular enclosure were investigated numerically using ANSYS Fluent 17.2 code. The transient numerical simulations of these phenomena in the full-scale computational domain of the experimental facility were performed. Generation of water vapour bubbles around the heater rod and evaporation phenomena were included in this numerical investigation. The results of numerical simulations are in good agreement with experimental measurements. This shows that the natural convection is formed in region above the heater rod and the water is thermally stratified in the region below the heater rod. The heat from higher region and from the heater rod is transferred to the lower region via conduction. The thermal stratification disappears and the water becomes well mixed, only after the water temperature reaches the saturation temperature and boiling starts. The developed modelling approach and obtained results provide guidelines for numerical investigations of thermal-hydraulic processes in the water pools for passive residual heat removal systems or spent nuclear fuel pools considering the concreate walls of the pool and main room above the pool.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.6
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• pp.710-715
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• 2006

With recent advances in device fabrication technology, economical deployment of large scale sensor networks, a design of pervasive monitoring and control system has been made possible. In this paper, we present a new algorithm for one of the most likely applications for sensor networks; tracking moving targets. The proposed algorithm uses a cooperations between the sensor nodes which detect moving objects. Therefore, the proposed scheme is robust against prediction failures which may result in temporary loss of the target. Using simulations we show that tile proposed moving object tracking algorithm is capable of accurately tracking targets with random movement patterns.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.600-606
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• 2019

Studies on the application of the lead rubber bearing (LRB) isolation system to nuclear power plants are being carried out as one of the measures to improve seismic performance. Nuclear power plants with isolation systems require seismic probabilistic safety assessments, for which the seismic fragility of the structures, systems, and components needs be calculated, including for beyond design basis earthquakes. To this end, seismic response analyses are required, where it can be seen that the behaviors of the isolation system components govern the overall seismic response of an isolated plant. The numerical model of the LRB used in these seismic response analyses plays an important role, but in most cases, the extreme performance of the LRB has not been well studied. The current work therefore develops an extreme nonlinear numerical model that can express the seismic response of the LRB for beyond design basis earthquakes. A full-scale LRB was fabricated and dynamically tested with various input conditions, and test results confirmed that the developed numerical model better represents the behavior of the LRB over previous models. Subsequent seismic response analyses of isolated nuclear power plants using the model developed here are expected to provide more accurate results for seismic probabilistic safety assessments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1689-1701
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• 2019

In recent years, personal videos have been shared online due to the popular uses of portable devices, such as smartphones and action cameras. A recent report predicted that 80% of the Internet traffic will be video content by the year 2021. Several studies have been conducted on the detection of main video events to manage a large scale of videos. These studies show fairly good performance in certain genres. However, the methods used in previous studies have difficulty in detecting events of personal video. This is because the characteristics and genres of personal videos vary widely. In a research, we found that adding a dataset with the right perspective in the study improved performance. It has also been shown that performance improves depending on how you extract keyframes from the video. we selected frame segments that can represent video considering the characteristics of this personal video. In each frame segment, object, location, food and audio features were extracted, and representative vectors were generated through a CNN-based recurrent model and a fusion module. The proposed method showed mAP 78.4% performance through experiments using LSVC data.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.4
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• pp.76-84
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• 2021

Military aircraft R&D projects require large-scale investment in cost and time, and involve a complex coordination process in decision-making. The R&D project manager should determine the development management priorities as accurately as possible and focus on R&D capabilities, thereby reducing the risks of the aircraft R&D project. To this end, this study aims to reduce R&D risk by prioritizing cost, schedule, and performance, which are basic management factors used in R&D project management in defense project management regulations. Analytic Hierarchy Process (AHP) is applied using a questionnaire for managers in charge of aviation R&D under the Defense Acquisition Program Administration. As a primary result, the importance of the factors that the aircraft R&D project manager should consider was derived in the order of performance, cost, and schedule, and the priorities of performance and cost in the lower layer were also identified. In addition, in order to provide practical risk management measures to aircraft R&D project managers, the results of analyzing 28 cases of US National Transportation Safety Board accidents were compared and analyzed with the AHP analysis results, and management measures suitable for the situation were specified.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.1
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• pp.109-122
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• 2022

The purpose of information security activities is to reduce large-scale material and human accidents that are concerned about hacking damage to important systems, such as control systems, through periodic preventive activities in addition to finding the cause and taking follow-up measures after damage caused by hacking. For this reason, although each institution is using a security work audit model in accordance with the relevant regulations, it is not easy to conduct company-wide inspection activities due to the constraints of manpower and time. Therefore, in this paper, we will analyze the major vulnerabilities of public institutions over the past 10 years and present a security audit model that can perform efficient security activities compared to the models for domestic and foreign security audits.