• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.8
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• pp.1465-1471
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• 2007

The electro-magnetic wave propagates through the air in the terrestrial communications, but the acoustic wave propagates through the seawater in the underwater acoustic communication(UAC). It makes the differences between the UAC link and the well hon air communication links. In this paper, we have studied path loss, absorption and ambient noise of the ocean as a medium for UAC. We have analyzed the absorption coefficient and ambient noise level of the coastal area of South Korea and suggested a strategy for the selection of the frequency band by considering the absorption coefficient and ambient noise level. Also, we present an illustrative example of a link budget for the QPSK UAC system which has carrier frequency 25kHz, bit rate 10kbps, range 1km and BER $10^{-3}$ in the shallow water environment with an ideal AWGN assumption.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.1
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• pp.87-94
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• 2016

Although studies and investments on electro-magnetic fields in terrestrial areas are being conducted, they are not applied to a ship. Especially ship is consist of Top Side, Bridge, and Engine Room. Top Side is mounted Antenna and radar. Bridge is mounted navigation and navigation equipment that have a safe voyage. Finally, Engine Room is mounted switchboard and this is used to ship propulsion system. Therefore the purpose of this paper is for suggesting optimized standard to apply to marine environment through analyzing electromagnetic wave environment in ship. For this, we were measured EMF in Hanbada ship in Korea Maritime and Ocean University and we compared and analyzed to measured values in Korea standards and international standards. Consequently, Engine Room of ship for the identified that there are limits to apply. The proposed results of this research will be expected to utilize for establishing standard a plan for EMF in ship.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.10b
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• pp.18-28
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• 1996

The outer-most electrons of metal atoms and the remaining valence electrons of any molecular atoms make three-dimensional crystallizing $\pi$-bondings. The rotating electrons on the three-dimensional crystallizing $\pi$-bonding orbitals of atoms make $\pi$-far infrared rays. Longitudinal wave is a propagation of a bundle of $\pi$-far infrared rays, which are produced by a dynamic impact on a solid bar. The $\pi$-far infrared rays make three-dimensional crystallizing $\pi$-bondings in the material, which reproduce the same $\pi$-far infrared rays. If a current signal is input into water molecules under a given electric potential field with $\pi$-far infrared rays (input information), the signal can be amplified because the $\pi$-far infrared rays make the $\pi$-bondings, which reduce electric resistance. The three-dimensional crystallizing $\pi$-bondings can induce normal electrons to move from one orbital to next one with a aid of potential electric field. Quantum Resonance Spectrometer is composed of tesla coil absorbing $\pi$-far infrared rays, tesla coil emitting varying electromagnetic waves signal generator, signal storage, human body amplifier, signal analyzer and data indicator. The absorbing tesla coil making varying magnetic field and downward and upward electric field, which resonates the $\pi$-far infrared rays coming out from specimen and absorbs them. The modulated current signal from the input square signal can generate and emit varying electromagnetic waves from the tesla coil. The varying electro-magnetic waves make the three-dimensional crystallizing $\pi$-bondings and the $\pi$-far infrared rays in the water molecules.

• Journal of Environmental Science International
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• v.24 no.4
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• pp.371-381
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• 2015

In the mountain streams in Jeju Island, strong turbulence and roughness usually made it nearly impossible to utilize most of intrusive instrumentation for streamflow discharge measurements. Instead, a non-intrusive fixed electro-magnetic wave surface velocimetry (fixed EWSV: Kalesto) became alternatively popular in many representative streams to measure stream discharge seamlessly. Currently, Kalesto has shown noteworthy performance with little loss in flood discharge measurements and also has successfully provided discharge for every minute. However, Kalesto has been operated to regard its measured one-point velocity as the representative mean velocity for the given cross-section. Therefore, it could be highly possible to potentially encompass discharge measurements errors. In this study, we analyzed the difference between such Kalesto discharge measurements and other alternative concurrent discharge measurements such as Acoustic Doppler Current Profiler (ADCP) and mobile EWSV which were able to measure velocity in multi-points in the cross-section. Consequently, Kalesto discharge deviated from ADCP discharge in amount of 48% for relatively low flow, and more than 20% difference for high flow compared with mobile EWSV discharge measurements. These results indicated that the one-point velocity measured by Kalesto should be used as a cross-sectional mean velocity, rather it should be accounted for as an index-velocity in conjunction with directly measured cross-sectional mean velocity by using more reliable instrumentations. After inducing Kalesto Discharge Correction Coefficient (KDCC) that actually means relationship between index velocity and cross-sectional mean velocity, the corrected discharge from Kalesto was significantly improved. Therefore, we found that index velocity method should be applied to obtain better accuracy of discharge measurement in case of Kalesto operation.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.157-163
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• 1999

The purpose of this study was to investigate the effect of electromagnetic field in orthodontic tooth movement, and the optimal application period of electromagnetic field to initiate tooth movement. Eighty male Hartley guinea pigs were utilized in this study. Laterally directed orthodontic force was applied to the maxillary central incisors. Half sine-wave pulsed electromagnetic field(HSPEMP) was applied to experimental group during 10 days. According to the period of application of HSPEMP(4 hours, 8 hours, 12 hours a day), they were divided into the three sub-groups The obtained results were as follows; 1. In case of application of HSPEMF during 4 hours a day, there was no significant difference in the final amount of orthodontic tooth movement between the experimental and the control group. 2. In case of application of HSPEMF during 8 and 12 hours a day, there was a significant increase in the final amount of orthodontic tooth movement since the eighth day, the sixth day respectively. 3. In comparison with the case of application of HSPEMF during 8 hours a day, there was a significant increase in the final amount of orthodontic tooth movement at the seventh day and the eighth day in case of application of HSPEMF during 12 hours a day.

• The Journal of Engineering Geology
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• v.14 no.4 s.41
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• pp.361-369
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• 2004

The authors designed a new technique to measure dielectric constant of a soil media by Frequency Domain Reflectometry (FDR) system and its measurement sensor probe with different length such as 7m, 10cm and 15cm for estimating the variations of dielectric constant. Measurement of dielectric constant of soil material is possible to measure an interference wave generated by between incidence wave and reflection wave which are detected to electro-magnetic wave through the directional coupler at the high frequency range,0.1 to 1.7GHz, by FDR system. The obtained experimental results verified that the technique is very promising for non-destructive and continuous soil volumetric water content measurement monitoring in a laboratory. The relationship between the soil volumetric water content and the dielectric constant of soil media (standard sand) was expressed by a single regression ewe independent of soil texture at a small experimental error. Also the derived regression curve coincided well with that obtained by Topp curve.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1116-1123
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• 2011

In this paper, we studied the propagation of the radio wave in the human body for WBAN system and proposed the path-loss models applicable in the MICS and ISM frequency band. Human Tissues are composed of complicate organ. So it is difficult to measure to insert the probe in human body. Accordingly, the equations were modelled by electromagnetic analysis using the numerical phantom based on the real human. The numerical analysis used XFDTD 6.5 of Remcom co. in commercial software based on the Finite-Difference Time-Domain method. Human body model used a standard adult Korean model developed by ETRI. The proposed channel models will be very helpful to design the WBAN system.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.363-369
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• 2016

Enhancing mechanical strength of concrete has been fascinated using carbon-based nanomaterials such as CNT and graphene. The key to improving strength is a dispersion of nanomaterials. A novel method is required to investigate the dispersion inner concrete nondestructively. In this study, the optical optical properties such as refractive index and absorption coefficient are measured in nano-cement mortar specimens containing MWCNT and GO using THz electro-magnetic waves. From the results, the properties of nano-cement mortar are confirmed to be 1.0% to 2.5% higher in refractive index, and -14% to 28% higher in absorption coefficient than those of cement mortar at the average values. Using these characteristics, visualizing the dispersion of nano-concrete structures seems possible in future.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.4
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• pp.287-293
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• 2005

Ultrasonic guided waves are gaining increasing attention for the inspection of platelike and rodlike structures. At the same time, inspection methods that do not require contact with the test piece are being developed for advanced applications. This paper capitalizes on recent advances in the areas of guided wave ultrasonics and noncontact ultrasonics to demonstrate a superior method for the nondestructive detection of defects thinning simulating hidden corrosion in thin aluminum plates. The proposed approach uses EMAT(electro-magnetic acoustic transducer) for the noncontact generation and detection of guided waves. Interesting features in the dispersive behavior of selected guided modes are used for the detection of plate thinning. It is shown that mode cutoff measurements provide a qualitative detection of defects thinning. Measurement of the mode group velocity can be also used to quantify depth thinning.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.22-29
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• 2002

Usually, much harmonics are included and cause harmonic loss of motor, torque pulsation, electro-magnetic noise and shock etc. by switching function of inverter when drive induction motor variableness inside. It applied partial resonant Buck converter and three phase voltage type SPWM inverter circuit to induction motor driving system in this paper that see to solve such problem. Changed operation condition variously to do input current of circuit that propose sine-wave by unit power factor almost and capacitor supplied bringing back to life voltage by power supply arranging properly assistance diode and electric power switching. Power factor and efficiency improved as that minimize variation of input at power supply voltage polarity reverse by that add voltage reversal function. Also, by using output filter, reduced harmonic of output line to line voltage components, and introduce state space analysis and forecast operation of rectifier. Such all items confirmed validity through simulation and an experiment.