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Cho Y.-J.,The Attached Institute of ETRI
International Journal of Control and Automation | Year: 2013

Because nonlinear systems have more complex behaviors than linear systems, it is hard to apply classical linear system theories and techniques to analyze and control nonlinear systems. So, to apply these theories and techniques, the feedback linearization method is used when the nonlinear system satisfies certain conditions. In the linearizing procedure, there exist infinite pairs of coordinates transformations and feedback controllers. The freedom in the exact linearization technique is used to improve the feedback system in some sense. So, by the switching control with the proper switching rule, we can obtain the better transient behavior than that of using one diffeomorphism. For many real processes, nonlinear systems have uncertainties. Because the linearizing method requires the accurate mathematical models of the system for the exact linearization, the uncertainties have an effect on stability of the nonlinear system. But, if we know the bounds of uncertainties, we can compensate the uncertainties based on the Lyapunov redesign technique. In this paper, we propose a switching rule for taking the transient behavior improvements in the case of uncertain time-varying nonlinear system. Source


Lee C.,Dong - A University | Jung D.,The Attached Institute of ETRI | Lee K.-W.,Chungwoon University
International Journal of Control and Automation | Year: 2013

Conventional electric-power grids generally have unidirectional power flows from the power plant to the consumers. At small factories, however, the problem is that they inefficiently consume electricity because they consume the electrical power depending on the time of day (e.g., on-peak usually during the day and off-peak usually at night time). In this paper, we try to improve the existing energy management system and propose an energy management system that mainly focuses on the efficiency of electricity consumption. In the proposed management system, PMU (Power Management Unit) installed in switchboard is allowed to collect electric power data in a real time. We also use data mining method, which is applied to analyze the collected data for improving energy efficiency. Also, our proposed energy management system is designed to efficiently control electricity between PMU and management system in case of a shortage of electricity or surplus electricity. Through the experiment, we demonstrate that our proposed system improves the efficiency of electric power of small scale power plant. Source


Jung D.,The Attached Institute of ETRI | Lee C.,Soongsil University
International Journal of Multimedia and Ubiquitous Engineering | Year: 2014

Recently, due to the interest for personal safety, intelligent image recognition technology using the CCTV has received a lot of attention in many areas. Real-time video or image tracking technology is the technology to continuously track the movement of the target object and maintain the specified information of the object. However, the problem is that unnecessary noise or environmental changes of the input video from CCTV make it difficult to accurately detect and track the target object. In this paper, we propose a fast object tracking algorithm, which is divided into two parts: i) object detection process and ii) object tracking process. In the background image replacement technique, we compute the difference between the initial input image and input video image. Then, it replaces N×M blocks based on the changed pixels, finally leading to replacing the background images. If it changes over the pre-defined threshold value, we set the block size and generate the variable search window for object tracking. Since the variable search window only generates the minimum search area for object tracking, our proposed method is quickly able to compute the variable region for object tracking. Through various experiments, our proposed scheme outperforms the other object detection and tracking methods in terms of object tracking counts and tracking error counts. © 2014 SERSC. Source


Kim K.S.,The Attached Institute of ETRI | Jeong I.R.,Korea University
Security and Communication Networks | Year: 2015

In 2012, D. Schr öder and H. Schr öder introduced verifiable data streaming (VDS) that enables a client to append, search, verify, and update the streamed data efficiently. After storing the data with a server, a client issues a query to receive a proof that the data of the client are still correctly stored. Anyone can check the validity of the proof publicly in VDS. However, the length of a secret of a client, the length of a proof, and the complexity of appending an element in the previous VDS schemes are O(logn), where n is the upper bound on the number of elements to be stored. In this paper, we suggest a more efficient VDS scheme. In our scheme, the length of a secret of a client is only O(1), and the length of a proof and the complexity of appending an element are O(logi), where i(≤n) is the index of an element. We also show that our scheme is secure under any collision-resistant hash functions and unforgeable signature schemes without random oracles. © 2015 John Wiley & Sons, Ltd. Source


Jung D.,The Attached Institute of ETRI | Lee C.,Dong - A University
International Journal of Control and Automation | Year: 2013

Multi-packet reception (MPR) technology makes it possible for wireless nodes to successfully receive multiple packets from simultaneous transmitters in wireless networks. As it can provide more transmission opportunities, the network throughput performance can be dramatically improved. In this paper, we propose a transmission chance adaptation strategy, which decides an appropriate level of channel access probability for each node in wireless networks. With the appropriate setting of channel access probability, the number of concurrent trans-missions would be close to MPR capability such that the throughput performance can be improved. Through extensive simulations, we show that the proposed transmission protocol outperforms the conventional IEEE 802.11 DCF mode in terms of the aggregate throughput. Source

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