• Journal of Positioning, Navigation, and Timing
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• v.12 no.3
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• pp.245-255
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• 2023

Time comparison techniques are necessary for generating and keeping Coordinated Universal Time (UTC) and distributing standard time clocks. Global Navigation Satellite System (GNSS) Common View, GNSS All-in-View, Two-Way Satellite Time and Frequency Transfer (TWSTFT), Very Long Baseline Interferometry (VLBI), optical fiber, and Network Time Protocol (NTP) based methods have been used for time comparison. In these methods, GNSS based time comparison techniques are widely used for time synchronization in critical national infrastructures and in common areas of application such as finance, military, and wireless communication. However, GNSS-based time comparison techniques are vulnerable to jamming or interference environments and it is difficult to respond to GNSS signal disconnection according to the international situation. In response, in this paper, Code-Division Multiple Access (CDMA) based All-to-All TWSTFT operation method is proposed. A software-based simulation platform also was designed for performance analysis in multi-TWSTFT signal environments. Furthermore, code and carrier measurement jitters were calculated in multi-signal environments using the designed simulation platform. By using the technique proposed in this paper, it is anticipated that the TWSTFT-based time comparison method will be used in various fields and satisfy high-performance requirements such as those of a GNSS master station and power plant network reference station.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.8 no.12
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• pp.127-138
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• 1985

There are several methods which have been presented up to now in solving the simultaneous linear equations by computer. They are Gaussian Elimination Method, Gauss-Jordan Method, Inverse matrix Method and Gauss-Seidel iterative Method. This paper is not only discussed in their mechanisms compared with their algorithms, depicted flow charts, but also calculated the numbers of arithmetic operations and comparisons in order to criticize their availability. Inverse Matrix Method among em is founded out the smallest in the number of arithmetic operation, but is not the shortest operation time. This paper also indicates the many problems in using these methods and propose the new method which is able to applicate to even small or middle size computers.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.6
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• pp.767-775
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• 2018

To develop and check a Radar Processor Unit, checking the function and performance of the requirement is very important factor in developing Radar. General methods for verifying the Radar is simulation test, environment linkage test and field operation test, firstly, in case of requirement analysis phase, verify Radar algorithm and design by using mathematical method based simulation test method, and secondly, in case of unit test and integrated test phase, Test Equipment is set to simulate radar environment in the lab to verify radar function and performance. Lastly, field operation test phase is carried out to confirm the function and performance after it is mounted on the actual equipment. To successfully develop Radar Processor Unit, using the method of field operation test method after sufficient test cases are tested in radar environmental interlocking method in order to save cost and testing period and because of this reason, development of the Radar Processor Unit Test Equipment is becoming very important factor. In this paper, we introduce the concept of test equipment development and important factors in test equipment, which are target simulation, data processing and device interlocking.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.200-206
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• 2016

In the microgrid, inverters for energy storage system are generally constructed in a parallel structure because of capacity expandability, convenience of system maintenance, and reliability improvement. Parallel inverters are required to provide stable voltage to the critical load in PCC and to accurately share the current between each inverter. Furthermore, when islanding occurs, the inverters should change its operating mode from grid-connected mode to stand-alone mode. However, during clearing time and control mode change, the conventional control method has a negative impact on the critical load, that is, severe fluctuating voltage. In this study, a parallel operation control method is proposed. This method provides seamless mode transfer for the entire transition period, including clearing time and control mode change, and has accurate current sharing between each inverter. The proposed control method is validated through simulation and experiment.

• Journal of Korea Multimedia Society
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• v.18 no.10
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• pp.1189-1196
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• 2015

In this paper, we proposed automatic extraction of brain tumor using morphological operation and statistical tumors size in MR images. Neurosurgery have used gamma-knife therapy by MR images. However, the gamma-knife plan systems needs the brain tumor regions, because gamma-ray should intensively radiate to the brain tumor except for normal cells. Therefore, gamma-knife plan systems spend too much time on designating the tumor regions. In order to reduce the time of designation of tumors, we progress the automatical extraction of tumors using proposed method. The proposed method consist of two steps. First, the information of skull at MRI slices remove using statistical tumors size. Second, the ROI is extracted by tumor feature and average of tumors size. The detection of tumor is progressed using proposed and threshold method. Moreover, in order to compare the effeminacy of proposed method, we compared snap-shot and results of proposed method.

• Journal of Power Electronics
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• v.11 no.6
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• pp.801-810
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• 2011

An open circuit fault diagnostic method in IGBTs for the ac to dc converters used in microgrid applications is developed in this paper. An ac to dc converter is a key technology for microgrids in order to interface both distributed generation (DG) and renewable energy resources (RES). Also, highly reliable ac to dc converters are necessary to keep converters in continuous operation as long as possible during power switch fault conditions. Therefore, the proposed fault diagnostic method is developed to reduce the fault detection time and to avoid any other fault alarms because continuous operation is desired. The proposed diagnostic method is a combination of the absolute normalized dc current technique and the false alarm suppression algorithm to overcome the long fault detection time and fault alarm problems. The simulation and experimental results show that the developed fault diagnostic method can perform fault detection within about one cycle. The results illustrate that the reliability of an ac to dc converter interfaced with a microgrid can be improved by using the proposed fault diagnostic method.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.712-718
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• 2013

With the development of industry and the improvement of living standards, better quality in power electric service is required more than ever before. This paper deals with the optimal algorithms for voltage regulation in the case where Distributed Storage and Generation (DSG) systems are operated in distribution systems. It is very difficult to handle the interconnection issues for proper voltage managements, because the randomness of the load variations and the irregular operation of DSG should be considered. This paper proposes the optimal on-line real time voltage regulation methods in power distribution systems interconnected with the DSG systems. In order to deliver suitable voltage to as many customers as possible, the optimal sending voltage should be decided by the effective voltage regulation method by using artificial neural networks to consider the rapid load variation and random operation characteristics of DSG systems. The simulation results from a case study show that the proposed method can be a practical tool for the voltage regulation in distribution systems including many DSG systems.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.1
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• pp.21-26
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• 2007

In industry, multihead automatic combination weighers are used to provide accurate weights at high speed. To minimize giveaway, greater accuracy is desired, especially for valuable products. This paper describes a combination algorithm based on bit operation. The combination method is simple and saves time, since only the elements to be considered for combination are generated. The total number of combinations from which the desired output weight is chosen can be increased by extending the combination from memory hoppers to include some weighing hoppers. For an eight-channel weigher, three or four combination elements are best. In addition to targeting approximately equal amounts of products in each channel, this study investigated other schemes. Simulation results show that schemes targeting combination elements with an unequal distribution of the output weight are more accurate. The most accurate scheme involves supplying products to all memory and weighing hoppers before commencing the combination operation. However, this scheme takes more time.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.249-252
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• 2004

The automatic determination of vehicle operation status as well as continuous tracking of vehicle location with intelligent management is one of major elements to achieve the goals. Especially, vehicle operation status can only be analyzed in terms of expert experiences with real-time location data with scheduling information. However the scheduling information of individual vehicle is very difficult to be interpreted immediately because there are hundreds of thousand vehicles are run at the same time in the national wide range workplace. In this paper, we propose the location-based knowledge management system(LKMs) using the active trajectory analysis method with routing and scheduling information to cope with the problems. This system uses an inference technology with dispatching and geographic information to generate the logistics knowledge that can be furnished to the manager in the central vehicle monitoring and controlling center.