• Geophysics and Geophysical Exploration
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• v.5 no.2
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• pp.108-117
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• 2002

We have introduced a new approach to obtain the conductivity information of subsurface using Cagniard impedance over two-dimensional (2-D) model in the presence of horizontal magnetic dipole source with the frequency range of $1\;kHz\~1\;MHz$. Firstly, we designed the method to calculate the apparent resistivity from the ratio between horizontal electric and magnetic fields, Cagniard impedance, considering the source effects when the plane wave assumption is failed in finite source EM problem, and applied it to several numerical models such as homogeneous half-space or layered-earth model. It successfully provided subsurface information even though it is still rough, while the one with plane wave assumption is hard to give useful information. Next, through analyzing Cagniard impedance and apparent resistivity considering source effect over 2-D models containing conductive- or resistive-block, we showed that the possibility of obtaining conductivities of background media and anomaly using this approach. In addition, the apparent resistivity considering source effect and phase pseudosections constructed from Cagniard impedance over the isolated conductive- and resistive block model well demonstrated outlines of anomalies and conductivity distribution even though there were some distortions came from sidelobes caused by 2-D body.

• Nuclear Engineering and Technology
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• v.41 no.5
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• pp.709-714
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• 2009

An ion implanter, which can serve as a metal-ion supply, has been constructed and performance tested. Copper ions are generated and extracted from a Bernas ion source with a heating crucible that provides feed gases to sustain the plasma. Sable arc plasmas can be sustained in the ion source for a crucible temperature in excess of $350^{\circ}C$. Stable extraction of the ions is possible for arc Currents less than 0.3 A. Arc currents increase with the induced power of a block cathode and the transverse field in the ion source. $Cu^+$ ions in the extracted beam are separated using a dipole magnet. A $20{\mu}A$ $Cu^+$ ion current can be extracted with a 0.2 A arc current. The ion current can support a dose of $10^{16}ions/cm^2$ over an area of $15\;cm^2$ within a few hours.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.313-320
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• 2003

Synthetic seismograms recorded with a logging-while-drilling (LWD) tool in the presence of slow formation are computed by the discrete wavenumber method. Monopole, dipole, and quadrupole logging tools are simulated with a source center frequency of 4 kHz. The modes in the responses are identified and characterized with time and frequency semblance plots. Numerical results show that, to obtain the formation shear velocity, we need to correct the peak velocities of the multipole modes in the semblance plots by using analytical dispersion curves.

• Korean Journal of Mathematics
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• v.23 no.1
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• pp.171-180
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• 2015

It is discovered in [7] that a dielectric material is coated by a plasmonic material of negative permittivity with dissipation, then cloaking by anomalous localized resonance may occur as the dissipation tends to zero. In this paper, we investigate numerically the pointwise behavior of the potential in the shell when cloaking by anomalous localized resonance (CALR) occurs. By changing locations a dipole source, we can observe some localizing properties of the potential in the shell.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.11
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• pp.680-688
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• 2005

The electrical current generated by heart creates not only electric potential but also a magnetic field. We have observed electrophysiological phenomena of the heart by measuring components of magnetocardiogram(MCG) using 61 channel superconducting quantum interference device(SQUD) system. We have analyzed the possibility and characteristics of MCG parameters for diagnosis of ischemic heart disease. A technique for automatic analysis of MCG signals in time domain was developed. The methods for detecting the position, the interval, the amplitude ratio, and the direction of single current dipole were examined in the MCG wave. The position and interval parameters were obtained by calculating the gradients of a envelope curve which could be formed by the difference between the maximum and minimum envelope of multi-channel MCG signals. We show some differences of the frequency contour map between the normal MCG and the abnormal (ischemic heart disease) MCG. The direction of single current dipole can be defined by rotating the magnetic field according to Biot-Savart's law at each point of MCG signals. In this study, we have examined the direction of single current dipole from searching for the centroids of positive and negative magnetic fields. The amplitude ratio parameters for measuring 57 deviation consisted of A$_{T}$/A$_{R}$ and other ratios. and We developed a new analysis method, which is based on the frequency contour map of electromagnetic field. Using theses parameters, we founded significant differences between normal subjects and ischemic patients in some parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.938-941
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• 2004

Sound generation and radiation from the duct-rotor system are calculated numerically. The wake geometries of a two-bladed rotor are calculated by using a time-marching fiee-wake method without a non-physical model of the far wake. Acoustic free field due to a rotating rotor is obtained by Lowson's equation. Using Kirchhoff source, rotating sources are modeled as stationary ones and can be inserted in the thin body boundary element method. The Kirchhoff source is validated through calculation of acoustic pressure due to a rotating point force. The thin body boundary element method (thin body BEM) is validated through calculation of acoustic radiation of ducted dipole. Using Kirchhoff source and thin body BEM, acoustic radiation of a ducted rotating source is calculated. Acoustic shielding is observed by inserting a duct and shows different phenomena at each major frequency. Acoustic radiation of a real duct-rotor system is also calculated using this method and the ducted acoustic field is significantly different from rotor only.

• The KSFM Journal of Fluid Machinery
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• v.3 no.3 s.8
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• pp.31-40
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• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.1
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• pp.29-42
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• 1992

A potential based panel method is used to predict the open water characteristics of spade-type rudders. The inflow velocity is assumed to be constant in lime and uniform in space. Source and dipole are distributed on the rudder surface. It is assumed that the wake surface is streaming from trailing edge and it is represented by dipole distribution. In this paper, wake geometry is assumed by imposing appropriate conditions at the trailing edge and far from the body. The effects of wake geometry are studied. The pressure Kutta condition is applied at the trailing edge, the effects of which are compared with those of two-dimensional Kutta condition. The results of calculations for a spade-type rudder are compared with published results. It is concluded that this approach shows fairly good agreement with experimental results and can be used in the initial design stage of a rudder.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.163-168
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• 1992

Results of magnetic measurement of a prototype Storage Ring dipole magnet for the Pohang Light Source (PLS) are summarized. Hall probe mapping and rotating coil methods are used to measure field profiles and integrated field properties. End chamfering experiments are performed on the as-built magnet, which has four removable pole-end pieces, to meet the specifications set from beam dy-namics requirement. The corrected magnet has efficiency of 99.7% at 2.0 GeV excitation ad higher order multipole error levels less than the specifications for all excitations, showing that the magnet has appropriate properties for the PLS Storage Ring.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.89-93
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• 2004

To numerically construct the sound fields by a plenum fan mostly found in Air-Handling Unit (AHU), the Kirchhoff-BEM approach was applied to the near-field data of a turbo fan. The scattering effects were found to be significant by the plenum box structure for high-frequency components of source. The directivity petterns and sound pressure levels were also dependent upon the helmholts number which must be considered of the design stage for sound reduction program.