• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.1
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• pp.40-47
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• 2013

By virtue of Rec. ITU-R P.1546 and geography information system, interference analysis for the fixed wireless system and radar has been presented based upon the frequency-distance rules with minimum coupling loss, and a comprehensive methodology for assessing interoperability between systems was examined in terms of received signal, protection ratio, frequency dependent rejection. Also to find the antenna gain from a discrimination angle, a useful S-I plane was introduced based on signal and interference vectors derived from the real map with geographic information. To show some computational results, geography information on the map was taken for the given area, and field strength and path profile were illustrated for the radar and fixed wireless system operating at 2.7 GHz, for convenience. In addition the interference effect of receiver was also checked as a function of radar beam direction including protection ratio and frequency dependent rejection. The developed interference analysis can be actually applied to evaluate interoperability for wireless systems in the VHF and UHF bands.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.1
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• pp.43-49
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• 2011

A distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, Zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome this problem clearly, this paper describes an improved backup protection coordination scheme using an IEC 61850-based distance relay for transformer backup protection. IEC 61850-based IED(Intelligent Electronic Device) and the network system based on the kernel 2.6 LINUX are realized to verify the proposed method. And laboratory tests to estimate the communication time show that the proposed coordination method is reliable enough for the improved backup protection scheme.

• IE interfaces
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• v.23 no.1
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• pp.24-34
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• 2010

In the telecommunication system which is based on the existing PSTN(public switched telephone network), feature interaction has been an important research issue in order to provide seamless services to users. Recently, rapid proliferation of IP-based network and the various types of IP media supply services, the feature interaction from the perspective of application services has become a significant aspect. This paper presents conflict detection and resolution algorithms for designing and operating a variety of services that are provided through IP-based network. The algorithms use explicit service interactions to detect conflicts between a new service and registered services. They then apply various rules to reduce search space in resolving conflicts. The algorithms are applied to a wide range of realistic service provision scenarios to validate that it can detect conflicts between services and resolve in accordance with different rule sets. By applying the algorithms to various scenarios, it is observed that the proposed algorithms can be effectively used in operating an IP-based services network.

• Water for future
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• v.29 no.1
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• pp.235-248
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• 1996

Apreliminary release scheme (PRS) is suggested for the operating rules during flood period to deal with conflicts between flood control and water conservation purposes. PRS can be used to decide the optimum releases, based on the forecast of an oncoming flood and flow rate at the control point downstream when comparing the variable restricted water level (VRWL) for flood control with the minimum required water level (MRWL) for conservation use. The model is applied to Chungju and Daechung reservoirs through simulations of the technique. This study illustrates the procedure to decide the time and size for preliminary releases. Also, effects of duration and magnitude of preliminary release are reviewed based on historicqal flood records. The simulation results indicate that the proposed PRS is effective for the managers to find optimal operating policies during flood period. The proposed scheme can be used with main release scheme using real-time operation on hour-to-hour basis to decide the release for a flood.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.94-99
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• 2021

UTM is an air traffic management ecosystem under development for autonomously controlled operations of UAS by the FAA, NASA, other federal partner agencies, and industry. They are collaboratively exploring concepts of operation, data exchange requirements, and a supporting framework to enable multiple UAS operations beyond visual line-of-sight at altitudes under AGL 500ft in airspace where air traffic services are not provided. Minimum Safe Altitude is a generic expression, used in various cases to denote an altitude below which it is unsafe to fly owing to presence of terrain or obstacles. The European drone regulation mentions that the UAS is maintained within 120 metres from the closest point of the surface of the earth during flight, except when overflying an obstacle. This study attempted to develop a minimum flight altitude database system. Based on domestic and international rules and regulations on setting the minimum flight altitude it is expected that it can be applied to the operation of aircraft and unmanned aerial system in UTM environments for specific area in Korea.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.851-859
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• 2021

Small PWR can be used for power generation and heating. Considering that small PWR has the characteristics of flexible operating conditions and complex operating environment, the controller designed based on single power level is difficult to achieve the ideal control of small PWR in the whole range of core power range. To solve this problem, a flexible switching controller based on fuzzy controller and LQG/LTR controller is designed. Firstly, a core fuzzy multi-model suitable for full power range is established. Then, T-S fuzzy rules are designed to realize the flexible switching between fuzzy controller and LQG/LTR controller. Finally, based on the core power feedback principle, the core flexible switching control system of small PWR is established and simulated. The results show that the flexible switching controller can effectively control the core power of small PWR and the control effect has the advantages of both fuzzy controller and LQG/LTR controller.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.4
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• pp.17-26
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• 2017

In this study, EPANET model which is using on the pipe network analysis was applied to Haenam irrigation district has provided irrigation water by pipeline system about 1,125ha and then have built pipe network to study area and supply performance evaluation of existing structure was analyzed by SPA (Single Period Analysis) in EPANET. As model results of simulation average ratio of maximum supply quantity/irrigation water requirements(base demand) was analyzed by 2.63. It means also that was analyzed as being capable of ensuring the water supply capacity. It was provided the necessary information for the maintenance facility through analyzed hydraulic behaviors in the pipeline inside such as flow velocities, pressures and hydraulic grade lines. It was satisfied with the allowable design criteria that was compared analyzed results with presented allowable design standards at agricultural production infra improvement project planning and design (Pipeline design standard). In order to analyze efficiency promotions of irrigation water, using Extended Period Simulation it was compared supply quantity with irrigation water requirements while pumps set operating pattern in 24 hours, then efficiency promotions of irrigation water was determined through analyzed oversupply water quantity and occurrence time by branch lines. According to results for oversupply quantity in Haenam district by time and end of branch lines efficiency promotions of irrigation water was suggested from 0.33 % to 37.59 %. To draw reasonable operating rules for water use and through this research, it is expected to be helpful for efficient water use and operational management of agricultural pipeline system to the current agricultural irrigation.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.559-565
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• 2013

The purpose of this study is to prioritize improvement factors of the tug services in terms of the structural problem, operating system and the present condition of the tug at each port in Korea. It was identified that the tug operating system needs to be mostly improved among the improvement factors of the tug services in Korea. In addition, free contract and rotating system were found to be important factors which need to be improved comparing to other factors such as service quality, tug rules, operating practices of council for tug operation and customer factor. The service attitude of the tug companies was regarded as an important element. And the tug entry system appeared to be an important item. Finally, laws relating to tug business needs to be revised which allow new tug companies enter into the market. As the result of AHP analysis for tug systems and service improvement factors, some fundamental changes of tug operation systems are urgently needed.

• Journal of the Korea Safety Management & Science
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• v.10 no.2
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• pp.205-210
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• 2008

The research interprets the principles of sampling error design for quality statistics models such as hypothesis test, interval estimation, control charts and acceptance sampling. Introducing the proper discussions of the design of significance level according to the use of hypothesis test, then it presents two methods to interpret significance by Neyman-Pearson and Fisher. Second point of the study proposes the design of confidence level for interval estimation by Bayesian confidence set, frequentist confidential set and fiducial interval. Third, the content also indicates the design of type I error and type II error considering both productivity and customer claim for control chart. Finally, the study reflects the design of producer's risk with operating charistictics curve, screening and switch rules for the purpose of purchasing and subcontraction.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.2
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• pp.125-130
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• 2004

This paper describes an approach for synthesizing a Fuzzy Logic Controller(FLC) that combines the benefits of fuzzy logic control and fuzzy logic gain scheduling for the F/A-18 aircraft. Specially, fuzzy rules are utilized on-line to determine the denoralization factor(Κ) of a feedback fuzzy controller based on the dynamic pressure(Q) indicateing the region of the flight envelop the aircraft is operating in. Simulation results demonstrate that the proposed FLC provides excellent compensation for time-varying and/or nonlinear characteristics of the aircraft, and that it also exhibits satisfactory robustness with noisy air data sensors.