• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.2001-2006
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• 2017

This paper explains the effects of the weak signal of a rotating-type electric field mill sensor fabricated for measuring the intensity of the electric field generated by high-voltage direct current (HVDC) power transmission lines. The fabricated field mill consists of two isolated electrode vanes, a motor driver, and a ground part. The sensor plate is exposed to and shielded from the electric field by means of a rotary shutter consisting of a motor-driven mechanically complementary rotor/stator pair. When the uncharged sensor plate is exposed to an electric field, it becomes charged. The rotating electrode consists of several conductive vanes and is connected to the ground part, so that it is shielded. Determining the appropriate design variables such as the speed of the vane, its shape, and the distance between the two electrodes, is essential for ensuring optimal performance. By varying the speed, the weak signal characteristics which is used to signal processing and calibration experiment are quite different. Each weak signal pattern was analyzed along with the output voltage characteristics, in order to be able to determine the intensity of the electric field generated by HVDC power transmission lines with accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4891-4895
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• 2010

RF coil is an important component of the Magnetic Resonance Imaging (MRI) system and the performance of RF coil is one of major factors for high SNR images. Sensitivity and RF field uniformity are parameters for evaluating RF coil performance. Since the B1 field is induced by RF coil, MR signal is strongly affected by RF coil structure and arrangement. In receiving MR signal, the RF coil sensitivity to MR Signal is also determined by the induced B1 field of RF coil. Therefore, the spatial distribution of B1 field must be verified. In this work, we performed computer simulation of the basic RF coil structures using Matlab and verified their sensitivity and uniformity through their B1 field distribution. This work will be useful for the advanced multi-channel RF coil design.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.4
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• pp.111-119
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• 2012

Time Stretched Pulse (TSP) is used for transmitting and analyzing the impulse signal over the designated spatial place. However, if transfer functions of transmitter and receiver are unknown, performance investigation of free field in temporal domain is barely possible due to the overlap between the direct and indirect signal from the space. Generally, the free field or hemi-free field is evaluated by the Annex A of ISO 3745 in which utilizing the inverse square law with one-third octave band signals. In this paper, the author performs analysis of free field via applying TSP with inverse square law and the results are compared with the one-third octave band signals. According to the analysis of deviation between the corresponding signal and inverse square law model, the proposed TSP method provides the comparable performance index to the one-third octave band signal with reduced measuring time. Provided that the pre-whitening can be implementable by employing the speaker and microphone transfer function, further analyses from TSP compression are able to be performed such as multipath separation from time domain data. The anechoic chamber used in this experiment is verified conformance with ISO 3745 for free field and hemi-free field condition for limited frequency of the signal.

• Journal of Power Electronics
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• v.16 no.2
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• pp.805-814
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• 2016

Electric-field coupled power transfer (ECPT) systems have been proposed as an alternative wireless power transfer (WPT) technology in recent years. With the use of capacitive plates as a coupling structure, ECPT systems have many advantages such as design flexibility, reduced volume of the coupling structure and metal penetration ability. In addition, wireless communications are effective solutions to improve the safety and controllability of ECPT systems. This paper proposes a power and signal shared channel for electric-field coupled power transfer systems. The shared channel includes two similar electrical circuits with a band pass filter and a signal detection resistor in each. This is designed based on the traditional current-fed push-pull topology. An analysis of the mutual interference between the power and signal transmission, the channel power and signal attenuations, and the dynamic characteristic of the signal channel are conducted to determine the values for the electrical components of the proposed shared channel. Experimental results show that the designed channel can transfer over 100W of output power and data with a data rate from 300bps to 120 kbps.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.12
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• pp.620-625
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• 2004

In this paper, we studied the emissive electric field due to the communication signal and the noise in medium voltage power-line. There are many types of conductive noise in power-line channel, which gives rise to radiation. And if the DMT carrier signal was excited, the current by this term was added to the current by noise and, generate radiation. We calculated input impedance by means of signal input network model of medium voltage power-line channel for calculating these currents. We calculated currents by input impedance and, calculated the emissive electric field by this calculated currents. From the measurement results, we knew that the measured results are very similar to the calculated results and if the input signal power level was higher than -40 dBm, the emissive electric field exceeds FCC radiation limit level 69.5 dB$\mu$V/m.

• Journal of Veterinary Clinics
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• v.16 no.1
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• pp.75-79
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• 1999

Magnetic resonance imaging (MRI) is an imaging technique used to produce high quality images of the inside of the animal body. MRI is based on the principles of nuclear magnetic resonance (NMR) and started out as a tomographic imaging technique, that is it produced an image of the NMR signal in a thin slice through the animal body. The animal body is primarily fat and water, Fat and water have many hydrogen atoms. Hydrogen nuclei have an NMR signal. For these reasons magnetic resonance imaging primarily images the NMR signal from the hydrogen nuclei. Hydrogen protons, within the body align with the magnetic field. By applying short radio frequency (RF) pulses to a specific anatomical slice, the protons in the slice absorb energy at this resonant frequency causing them to spin perpendicular to the magnetic field. As the protons relax back into alignment with the magnetic field, a signal is received by an RF coil that acts as an antennae. This signal is processed by a computer to produce diagnostic images of the anatomical area of interest.

• Journal of Magnetics
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• v.21 no.3
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• pp.330-339
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• 2016

A magnetic field sensing system with a single primary sensor and multiple reference sensors deployed locally and orthogonally, was proposed for downlink signal reception and interference cancelling for Through-the-Earth Communication (TEC). This paper mathematically analyzes a design optimization process for a search coil magnetometer (SCM), and applies that process to minimize the bandwidth of the primary SCM for TEC signal reception and the volume of reference SCMs for multiple distributions. The primary SCM achieves a 3-dB bandwidth of 7 Hz, a sensitivity threshold of 120 fT/${\surd}$Hz, and a volume of $2.32{\times}10^{-4}m^3$. The entire sensing system volume is as small as $10^{-2}m^3$. Experiments with interference from industrial frequency harmonics demonstrated an average of 36 dB and 18 dB improvements in signal-to-interference ratio and signal-to-interference plus noise ratio, respectively, using multichannel recursive-least-squares algorithm. Thus, the proposed sensing system can reduce the interference effectively and allows reliable downlink signal reception.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.05
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• pp.213-217
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• 1992

An inductively coupled magnetical signal (pulse wave, 0.7 to 60Hz, eighteen volts peak to Peak) that was applied non-invasively on the skin surface overlying the approximate site(measure position). In the group with unipolar pulse signal currents produced smaller than in the group with bipolar pulse signal. The signal was transmitted to the active coil, including a time-varying magnetic field: this in turn induced a the-varying electrical field in the field in the bone. It is very important to determine system parameters due to treatment time(healing) and the simplicity. This paper investigation was designed to compare the relative effects of pulsed unipolar currents with the effects of an identical pulsed bipolar currents. Since Inductive coupling is non-invasive and involves portable equipment, it is easy to apply and requires precise localization, it has distinct advantages and field characteristics along the bone for each different signal.

• The Journal of Korea Robotics Society
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• v.4 no.4
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• pp.320-326
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• 2009

This paper proposed a new magnetic field detection algorithm to detect metal pieces in food producing processes. This algorithm can detect mixed metal pieces by sensing magnetic field. Some metal pieces are passed through an over-current circuit to magnetize them. The magnetic field sensor can detect the change in the magnetic field on theconveyor belt caused by the flow of the metal pieces in the food product. However, such a method detects the output of signals that change their amplitude and phase according to the movement of the conveyor belt with the food product, in which the equilibrium of the positive signal that is created in the receiver coil loses its balance due to the magnetized material. This includes not only the signal elements resulting from the effect of the alternating magnetic fields of the mixed metals, but also the signal elements resulting from the effect of the alternating magnetic fields of the examined object itself.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.4
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• pp.361-366
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• 2003

Most sensor array signal processing methods for multiple source localization require knowledge of the correct shape of array(the correct positions of sensors that consist array), because sensor position uncertainty can severely degrade the performance of array signal processing. In particular, it is assumed that the correct positions of the sensors are known, but the known positions may not represent the true sensor positions. Various algorithms have been proposed for 2-D sensor array shape calibration in far field environment. However, they are not available in near field. In this paper, 3-D sensor array shape calibration algorithm is proposed, which is available in near field.