Gi-Hyun Hwang

Design of fuzzy power system stabilizer using adaptive evolutionary algorithm

This paper presents a design of fuzzy power system stabilizer (FPSS) using an adaptive evolutionary algorithm (AEA). AEA consists of genetic algorithm (GA) for a global search capability and evolution strategy (ES) for a local search in an adaptive manner when the present generation evolves into the next generation. AEA is used to optimize the membership functions and scaling factors of FPSS. The propose method is applied to single-machine infinite bus system (SIBS) and multi-machine power system (MPS). Results of numerical experiment show that the control performance of the FPSS is better than that of a conventional power system stabilizer (CPSS) for three-phase fault in heavy load. To show the robustness of FPSS, it is applied with disturbances such as change of mechanical torque and three-phase fault in nominal and heavy load, etc. FPSS shows better robustness than CPSS.

Design of fuzzy logic controller for firing angle of TCSC using real-type tabu search

This paper describes the application of fuzzy logic controller (FLC) to thyristor controlled series capacitor (TCSC) which can have significant impact on power system dynamics. The function of the FLC is to control the firing angle of the TCSC. We tune the scaling factors of the FLC using real-type tabu search (RTS). The proposed FLC is used for damping the low frequency oscillations caused by disturbances such as the sudden changes of small or large loads or the outages in the generators or transmission lines. To evaluate the usefulness of the proposed FLC, we perform the computer simulation for single-machine infinite system. The response of FLC is compared with that of PD controller optimized using real-type tabu search. The simulation results that the FLC shows the better control performance than PD controller.

Design of fuzzy logic controller for HVDC using an adaptive evolutionary algorithm

This paper presents an optimal design method for a fuzzy logic controller (FLC) of HVDC using an adaptive evolutionary algorithm (AEA). We propose an AEA, which uses a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner to take merits of the two different evolutionary algorithms. We use AEA to tune fuzzy membership functions and scaling constants. Simulation result shows that disturbances are well damped and the dynamic performances of FLC have better responses than those of PD controller when the AC system load changes suddenly.

The development of UHF RFID metal tag applying to license plat

This paper describes a design for RFID(Radio Frequency Identification) tag using license plate attached the vehicle bumper in UHF(Ultra High Frequency) MHz band. Its range of the fabricated tag antenna that the license plate and the vehicle bumper were fixed by volt and nut was observed 8.2 m. This measured readable range showed about 5 m above far distance more than the average readable range of commercial tag antenna. The RFID have ability of 0.5 seconds of recognition speed in the evaluation of performance.

Application of real-type tabu search in function optimization problems

An optimization solution performance of tabu search is influenced by initial solution, selection of neighbor solution, and size of tabu list etc. In this paper, we proposed a real-type tabu search (RTS) for function optimization, which uses belief space to create a neighbor solution. Belief space is made of upper 60% neighbors to effectively restrict searching limit, so it can improve searching time and local or global searching capability of RTS. Also short-term and long-term memory based tabu lists adequate to RTS are implemented to search a different region. All of theses procedures are independently applied to each determinant value for quick convergance and effective searching process. In order to show the usefulness of the proposed method, the RTS is applied to the minimization problems such as, De Jong functions, Ackley function, and Griewank functions etc., the results are compared with those of genetic algorithm (GA) or evolutionary programming (EP).

Design and Analysis of High-Performance Smart Card with HF/UHF Dual-Band RFID Tag and Memory Functions

In this paper, we introduce a novel design of high-performance smart card with HF/UHF dual-band RFID tag to overcome frequency interference problem. Firstly, we have designed and tested a UHF RFID tag using a simulation software system. In the smart card hardware design stage, we connect a HF antenna and a UHF antenna and place them in one inlay sheet. Using a spectrum analyzer, we systematically adjust the antenna pattern to detect the optimal patterns that fit the impedance of the RFID chip. We evaluate the performance of the resulting smart card with standard RFID testers. The experiments show that our proposed RFID tag outperforms other dual-band RFID tags and maintains itself in a reasonable size. Moreover, we increase IC chips memory capacity to resolve security-related problems when RFID tags are used in a financial transaction. We firstly exploit an IC contact protruded from the card to add an additional memory, and we integrate functions of the RFID tag to use the equipped memory through the induced current of the contact. The implemented prototype of our proposal can accommodate an extended memory ranging from one gigabyte up to four gigabytes.

Development of a New Personal Magnetic Field Exposure Estimation Method for Use in Epidemiological EMF Surveys among Children under 17 Years of Age

A number of scientific researches are currently being conducted on the potential health hazards of power frequency electric and magnetic field (EMF). There exists a non-objective and psychological belief that they are harmful, although no scientific and objective proof of such exists. This possible health risk from ELF magnetic field (MF) exposure, especially for children under 17 years of age, is currently one of Koreas most highly contested social issues. Therefore, to assess the magnetic field exposure levels of those children in their general living environments, the personal MF exposure levels of 436 subjects were measured for about 6 years using government funding. Using the measured database, estimation formulas were developed to predict personal MF exposure levels. These formulas can serve as valuable tools in estimating 24-hour personal MF exposure levels without directly measuring the exposure. Three types of estimation formulas were developed by applying evolutionary computation methods such as genetic algorithm (GA) and genetic programming (GP). After tuning the database, the final three formulas with the smallest estimation error were selected, where the target estimation error was approximately 0.03 μT. The seven parameters of each of these three formulas are gender (G), age (A), house type (H), house size (HS), distance between the subjects residence and a power line (RD), power line voltage class (KV), and the usage conditions of electric appliances (RULE).

Game Transformation from Non-Augmented Reality to Augmented Reality

The evolution of technology has lead gaming playable in augmented reality and more games are developed only for augmented reality. There are mainly no supportive reasons for game designed in nonaugmented reality and transforms to augmented reality. Genre of game played in augmented reality is always one of the defined game genres. In this paper, transformation process and effects of mobile games to augmented reality is discussed. Augmented reality game is recommended for mobile devices due to its portability. Modification for mobile games transformation including way of game rendering, game controlling, camera view controlling and game environment design are discussed. User experience is affected after the game transformed to augmented reality because of the differences in game controlling. The presence of game in real world is increased due to the usage of actual view in game playing.

Object tracking for mobile robot based on intelligent method

This paper proposed the real-time tracking algorithm in the active camera system, which is based on the intelligent method. To separate the object from background, the similarity of the color is analyzed through the fuzzy inference engine. And after segmentation, the local difference method between the continuous images is used to track the moving object. The experiment is performed using the developed embedded camera system with an ARM processor.

Efficient Conditional Proxy Re-encryption with Chosen-Ciphertext Security

In a proxy re-encryption (PRE) scheme a semi-trusted proxy can convert a cipher text under Alices public key into a cipher text for Bob. The proxy does not know the secret key of Alice or Bob, and also does not know the plaintext during the conversion. Conditional proxy re-encryption (C-PRE) can implement fine-grained delegation of decryption rights, and thus is more useful in many applications. In this paper, we propose an efficient C-PRE scheme, and prove its chosen-cipher text security under decisional bilinear Diffie-Hellman (DBDH) assumption in the random oracle model. Our scheme has significant advantages in both computational and communicational than previous schemes.