• Journal of Environmental Impact Assessment
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• v.15 no.4
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• pp.271-277
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• 2006

In this study, we investigated the applicable plan of GIS on the environmental impact assessment of 60 Hz Powerline. So we assessed distance data based on calculations by use of 2D and 3D Geographical information systems(GIS) and distance data based on measurements on 1: 5000 maps accord with on site distance measurements to use input data for calculating magnetic field. One hundred eight of the on site measured addresses were selected from residences. The data were achieved by measuring the distance between residence and power line on maps with scales of 1: 5000. The digital map was obtained from National Geographic Information Institute with scales of 1: 5000, and we made 2D and 3D map. Correlation analyses were performed for statistical analyses. For the 3D GIS versus on site comparison of different exposure categories, 70 of 108 measurements were assigned to the correct category. Similarly for 2D GIS versus on site comparison, 71 of 108 were correctly categorized. When comparing map measurement with on site measurement, 62 of 108 were correctly categorized. When the correlation analysis was performed, best correlation was found between 3D GIS and on site measurements with r = 0.84947 (p<0.0001). The correlation between map and on site measurement yielded an r of 0.76517 (p<0.0001). Since the GIS measurements and map measurement were made from the center point in the building and the on site measurements had to be made from the closest wall on the building, this might introduce and additional error in urban areas. The difference between 2D and 3D calculations were resulted from the height of buildings.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.1-8
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• 2005

Microwave tomographic imaging technology using a bi-focusing operator has been developed in order to detect the internal voids/objects inside concrete structures. The imaging system consists of several cylindrical or planar array antennas for transmitting and receiving signals, and a numerical focusing operator is applied to the external signals both in transmitting and in receiving fields. In this study, the authors developed 3-dimensional (3D) electromagnetic (EM) imaging technology to detect such damage and to identify exact location of steel rebars or dowel. The authors have developed sub-surface two-dimensional (2D) imaging technique using tomographic antenna array in previous works. In this study, extending the earlier analytical and experimental works on 2D image reconstruction, a 3D microwave imaging system using tomographic antenna way was developed, and multi-frequency technique was applied to improve quality of the reconstructed image and to reduce background noises. Numerical simulation demonstrated that a sub-surface image can be successfully reconstructed by using the proposed tomographic imaging technology. For the experimental verification, a prototype antenna array was fabricated and tested on a concrete specimen.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.133-137
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• 2016

Millimeter wave wireless communication systems, especially those targeting indoor high rate data transfer, have a strong requirement for high quality wireless link. Unfortunately, in this frequency band, the electromagnetic wave has to sustain the high propagation loss caused by the smaller wavelengths. In this scenario, beamforming technique, which enhances the link quality by focusing the radiation power on a direction, becomes one of the most important techniques in millimeter wave band wireless communication. In recent year, there been conducted many research on beamforming to improve the performance of wireless system. In this paper, we evaluate the performance of a simplified codebook-based beamforming scheme which is based on multiple-procedure and three-state beam selection. The simplified scheme significantly reduces beamforming setup time, comparing to the exhaustive searching, two-level searching adopted in IEEE 802.15.3c standard, and also conventional multi-level scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3357-3362
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• 2014

The purpose of this research was to develop a resonance electric power generator to harvest vibration energy while the vehicle is driving on a road surface. The electric power generator in the paper was designed using the resonance phenomenon to effectively respond to vibrations from the road surface, which is a comparatively small energy source. Vibration displacement analysis using MATLAB and transient analysis using Ansys MAXWELL, which is a commercial electromagnetic analysis program, was performed to predict the input velocity for the generator and verify the electric power generation. If this electric power generator is applicable to hybrid or electric vehicles, it can be valuable around an automotive electric system and help maintain the performance of the vehicle battery.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.313-315
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• 2005

In a power system, an out-of-step condition causes a variety of risk such as serious damage to system elements, tripping of loads and generators, mal-operation of relays, etc. Therefore, it is very important to detect the out-of-step condition and take a proper measure. Several out-of-step detection methods have been employed in relays until now Mo,;t common method used for an out-of-step detection is based on the transition time through the blocking impedance area in R-X diagram. Also, the R-R dot out-of- step relay, the out-of-step prediction method and the adaptive out-of-step relay using the equal area criterion (EAC) and Global Positioning Satellite (GPS) technology have been developed. This paper presents the out-of-step detection algorithm using the time variation of the complex power. The complex power is calculated and the mechanical power of the generator is estimated by using the electrical power, and then the out-of-step detection algorithm, which is based on the complex Power and the estimated mechanical power, is presented. This algorithm, may detect the instant when the generator angle passes the Unstable Equilibrium Point (UEP). The proposed out-of-step algorithm is verified and tested by using Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP) MODELS.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.958-967
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• 2014

A hybrid method based on high-frequency asymptotic optics was developed in order to predict the RCS of flying vehicles for RCS reduction studies. In cavity return, the rays are assumed to bounce from the inlet cavity based on the laws of geometrical optics and to exit the cavity via the aperture. In other parts of a flying vehicle, the physical optics method is applied to compute the back-scattered field from the solid surface. The hybrid method was validated by considering simple models of sphere and sphere with cavity. In addition, RCS analysis of a flying vehicle was conducted using the new hybrid electromagnetic scattering method based on physical optics and geometrical optics theories.

• Journal of the Korean Ceramic Society
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• v.42 no.8 s.279
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• pp.554-560
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• 2005

The engineering ceramic needs the properties of high strength, hardness, corrosion-resistance and heat-resistance in order to withstand thermal shock or applied nonuniform stresses without failure. The densely coated porous ceramics can be used for machine component, electromagnetic component, bio-system component and energy-system component by their high-performances from superior coating properties and light-weight characteristics due to the structure including pore by itself. In this study we controlled the porosity of silica and alumina, $8.2\~25.4\%$ and $23.4\~36.0\%$, respectively, by the control of sintering temperature and starting powder size. We made bilayer structures, consisting of a transparent glass coating layer bonded to a thick substrate of different porous ceramics by a thin layer of epoxy adhesive, facilitated observations of crack initiation and propagation. The elastic modulus mismatch could be controlled using different porous ceramics as the substrate layer. Then we applied 150 N force using WC sphere with a radius of 3.18 mm by Hertzian indentation. As a result, the crack initiation in the coating layer was delayed at lower porosity in the substrate layer, and the damage in the coating layer was relatively smaller at the bilayer structure coated on higher elastic substrate.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.89-95
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• 2018

In this paper, we analyze the antenna performance changes caused by the aircraft structure, diffraction and reflection, when the direction finding antenna used in the aircraft is mounted on the aircraft. Direction finding antenna is an antenna that receives radar threat signal in the direction finding device of aircraft electronic warfare system. Recently, because various antenna are mounted on an aircraft, various analyzes such as antenna performance and interference analysis are required. Therefore, the electromagnetic analysis was carried out by installing a broadband direction finding antenna with 50% bandwidth on simulated aircraft, and the direction finding performance was analyzed by comparing the single antenna performance with the performance mounted on the aircraft. The analyzed direction finding accuracy was $6.47^{\circ}$ RMS and predicted to be suitable as an antenna for aircraft direction finding antenna.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.689-692
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• 2015

That induced voltage by an electrified railway line is related with the position of telecommunication line between traction power feeding systems is practically varified by measurements in the real field. This experimented fact is conformed with the calculated simulation provided by the ITU-T Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway lines. Therefore it is needed to consider at what position a telecommunication line is parallelized with power feeding line of traction system when an induction phenomenon is evaluated or measurement is carried out besides the length of parallelization and the separate distance between power line and telecommunication line.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.471-473
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• 2002

Public concerns associated with the electromagnetic field (EMF) exposures from mobile phones on human body are increased. Although studies on the effects of the EMF exposures on human have been carried out for a long time, it is not proved yet whether the EMF effect is harmful or not. Based on the scientific results by experts, EMF exposure limits have been regulated as a precautionary approach on the assumption that the EMF effect may be harmful. It is well known that absorbed EMF can be transformed into heat within biological tissues and that thermal effects are related with the specific absorption rate (SAR) distribution. However, the relative magnitude and distribution of the energies are not well defined. Although there is comprehensive information of the thermal effects, most of them come from animal and in vitro studies. Considerable efforts have been made to analyze the EMF absorption model while the actual temperature in the human body has been rarely measured. Temperature changes on the face of a healthy male volunteer were studied. A digital mobile phone of 1.8GHz was used. A digital infrared imaging system (IRIS-5000, Medicore, Seoul, Korea) was applied to take infrared pictures of the face every minute while the volunteer talked over the mobile phone for 20 minutes. The specification of the imaging system was as follows: Temperature resolution = 0.1$^{\circ}C$; Range of temperature measurement = 17～40$^{\circ}C$; Pixel size = 0.9mm ${\times}$ 0.9mm; Frame time = 2.6s; Active temperature of detector = 77$^{\circ}$K. The result showed that temperature of the ear region was increased during the phone call and the region of the temperature increase on the face was expanded as the phone call time increased. Further study is necessary to investigate the temperature rise analytically and quantitatively.