• International journal of advanced smart convergence
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• v.13 no.2
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• pp.1-6
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• 2024

Reconfiguration and miniaturization of antennas have become key attributes in modern wireless communication systems. Reconfiguration of radiation pattern can alleviate the problems encountered in modern wireless communication systems such as multi-path problems. Physical limitation of miniaturization also can be overcome by using a zeroth-order resonance (ZOR) antenna based on metamaterial. In order to achieve reconfiguration and miniaturization of antennas at the same time, we propose a new pattern reconfigurable zeroth-order resonance (ZOR) antenna that reconfigures the radiation patterns by varying the position and the number of unit cells comprising the antenna. The antenna is fabricated in an equilateral triangular shaped symmetrical structure to increase pattern variety. This structure can easily provide eight different radiation patterns (two omnidirectional and six monopole like patterns).

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.11
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• pp.596-603
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• 2004

This paper proposes an expert system based on the pattern recognition method which can enhance the accuracy and effectiveness of real-time bus reconfiguration strategy for the transfer of faulted load when a main transformer fault occurs in the automated substation. The minimum distance classification method is adopted as the pattern recognition method of expert system. The training pattern set is designed MTr by MTr to minimize the searching time for target load pattern which is similar to the real-time load pattern. But the control pattern set, which is required to determine the corresponding bus reconfiguration strategy to these trained load pattern set is designed as one table by considering the efficiency of knowledge base design because its size is small. The training load pattern generator based on load level and the training load pattern generator based on load profile are designed, which are can reduce the size of each training pattern set from max L/sup (m+f)/ to the size of effective level. Here, L is the number of load level, m and f are the number of main transformers and the number of feeders. The one reduces the number of trained load pattern by setting the sawmiller patterns to a same pattern, the other reduces by considering only load pattern while the given period. And control pattern generator based on exhaustive search method with breadth-limit is designed, which generates the corresponding bus reconfiguration strategy to these trained load pattern set. The inference engine of the expert system and the substation database and knowledge base is implemented in MFC function of Visual C++ Finally, the performance and effectiveness of the proposed expert system is verified by comparing the best-first search solution and pattern recognition solution based on diversity event simulations for typical distribution substation.

• ETRI Journal
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• v.31 no.3
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• pp.318-320
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• 2009

A switchable Yagi-Uda antenna prototype with radiation pattern reconfiguration is presented in this letter. The proposed reconfigurable antenna is based on the concept of switching between the reflector and director of a Yagi-Uda antenna using a radio frequency PIN diode. As a result, the minimum/maximum radiation can be steered towards desired signals or away from interfering signals in opposite directions. The measured 10 dB impedance bandwidth and gain are 210 MHz (7%) and 8.02 dBi at 3 GHz, respectively. Details of the antenna design and its performance are described and empirically analyzed.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.10
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• pp.410-417
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• 2006

Generally, the training set of maximum $m{\times}L(m+f)$ patterns in the pattern recognition method is required for the real-time bus reconfiguration strategy when a main transformer fault occurs in the distribution substation. Accordingly, to make the application of pattern recognition method possible, the size of the training set must be reduced as efficient level. This Paper proposes a methodology which obtains the minimized training set by applying the pattern clustering method to load patterns of the main transformers and feeders during selected period and to obtain bus reconfiguration strategy based on it. The MaxMin distance clustering algorithm is adopted as the pattern clustering method. The proposed method reduces greatly the number of load patterns to be trained and obtain the satisfactory pattern matching success rate because that it generates the typical pattern clusters by appling the pattern clustering method to load patterns of the main transformers and feeders during selected period. The proposed strategy is designed and implemented in Visual C++ MFC. Finally, availability and accuracy of the proposed methodology and the design is verified from diversity simulation reviews for typical distribution substation.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.330-332
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• 2001

Distribution systems is consist of network in physical and radial in electrical aspect. Therefore radial operation is realized by changing the status of sectionalizing switches, and is usually done for loss reduction in the system. In this paper, we propose a optimal method for distribution systems reconfiguration. Specifically we use genetic algorithm method to solve distribution systems reconfiguration for loss minimization problem. A genetic algorithm(GA) is set up, in which some improvements are made on string coding, fitness function and mutation pattern. As a result, premature convergence is avoided.

• Journal of the Korea Society for Simulation
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• v.12 no.3
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• pp.83-94
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• 2003

For 24 hours-7 days service on distributed systems, a great deal of efforts are investigated on high availability for seamless operation. In this paper, we propose a dynamic reconfiguration framework of distributed systems, called "hot-swapping" framework. This framework allows us to upgrade and exchange a number of modules of a distributed system without stopping running service as well as the system itself. In order to hide the state of service operation, the framework employes the "proxy" design pattern. Our framework provides two types of proxies: a static proxy and a dynamic proxy, Static proxies can achieve fast execution time, but they need to be changed whenever any minor change exists in the related swappable module. Meanwhile, dynamic proxies takes longer execution time, but do not need to be changed under minor changes of swappable modules. We compare performances of static and dynamic proxies and also apply the framework to a real situation with security management modules. management modules.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.12
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• pp.637-644
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• 2004

This paper proposes an expert system with the knowledge learning capability which can enhance the safety and effectiveness of substation operation in the automated substation as well as existing substation by inferring multiple events such as main transformer fault, busbar fault and main transformer work schedule under multiple inference mode and multiple objective mode and by considering totally the switch status and the main transformer operating constraints. Especially inference mode includes the local minimum tree search method and pattern recognition method to enhance the performance of real-time bus reconfiguration strategy. The inference engine of the expert system consists of intuitive inferencing part and logical inferencing part. The intuitive inferencing part offers the control strategy corresponding to the event which is most similar to the real event by searching based on a minimum distance classification method of pattern recognition methods. On the other hand, logical inferencing part makes real-time control strategy using real-time mode(best-first search method) when the intuitive inferencing is failed. Also, it builds up a knowledge base or appends a new knowledge to the knowledge base using pattern learning function. The expert system has main transformer fault, main transformer maintenance work and bus fault processing function. It is implemented as computer language, Visual C++ which has a dynamic programming function for implementing of inference engine and a MFC function for implementing of MMI. Finally, it's accuracy and effectiveness is proved by several event simulation works for a typical substation.

• Journal of Internet Computing and Services
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• v.9 no.4
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• pp.29-41
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• 2008

Currently, IETF MANEMO(Mobile Adhoc for NEMO) working group is working on standardization supporting internal routing in nested NEMO networks. Nested NEMO has a independent topology feature that Mobile IP and basic NEMO protocol did not caused. This is the reason that causes exceptional mobility pattern. Such mobility patterns also trigger each other reconfiguration requirements. This paper classified and analyzed probable new mobility patterns in nested NEMO network. In concludion, we derived configuration problem from the new mobility patterns and suggested differential reconfiguration requirements through analytical approach.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.2
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• pp.1-5
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• 2007

Wavelength-division multiplexed (WDM) networks are emerging to be the right choice for the future transport networks. In WDM networks, the optical layer provides circuit-switched lightpath services to the client layer such as IP, SONET and ATM. The set of lightpaths in the optical layer defines the virtual topology. Since the optical switches are reconfigurable, the virtual topology can be reconfigured in accordance with the changing traffic demand pattern at theclient layer in order to optimize the network performance. We present a new approach to the virtual topology reconfiguration and loadbalancing problem for wavelength-routed, optical wide-area networks under dynamic traffic demand. By utilizing the measured Internet backbone traffic characteristics, our approach follows the changes in traffic without assuming that the future traffic pattern is known. For the simulation traffic modeling, we collected the data from real backbone traffic. Experiments show that the standard deviation compared to previous technique is reduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.2
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• pp.201-206
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• 2007

In this paper, we propose the efficient low power test methodology of NoC(Network-on chip) for the test of core-based systems that use this platform. To reduce the power consumption of transferring data through router channel, the scan vectors are partitioned into flits by channel width. The don't cares in unspecified scan vectors are mapped to binary values to minimize the switching rate between flits. Experimental results for full-scanned versions of ISCAS 89 benchmark circuits show that the proposed method leads to about 35% reduction in test power.