• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.47-53
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• 2011

The signal transmission properties of the connector such as insertion loss and return loss are investigated using analysis procedure of S-parameter simulation, equivalent model extraction, and characteristic impedance calculation. S-parameter simulation is performed by connector's modeling and solving based on 3-dimensional finite element method. The connector's equivalent model of ${\pi}$ type is are proposed and extracted with an optimization process of circuit analysis simulator. The characteristic impedance of the connector is calculated with results of circuit analysis simulation and S-parameter data. According to the connector's characteristic impedance, it's revised design is carried out. In this work, the connector's effective contact area is increased and its body is applied as a high dielectric material in order to increase its capacitance and then obtain impedance matching. Therefore, return loss of the connector is improved by approximately 10 dB due to its design revision.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.285-298
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• 2015

Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to study the structure of and physical conditions in relativistic outflows. For such studies, multi-frequency polarimetric very long baseline interferometric (VLBI) observations are important as they directly probe particle densities, magnetic field geometries, and several other parameters. We present results from first-epoch data obtained by the Korean VLBI Network (KVN) within the frame of the Plasma Physics of Active Galactic Nuclei (PAGaN) project. We observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129 GHz in dual polarization mode. Our observations constrain apparent brightness temperatures of jet components and radio cores in our sample to > 10^8.01 K and > 10^9.86 K, respectively. Degrees of linear polarization m_L are relatively low overall: less than 10%. This indicates suppression of polarization by strong turbulence in the jets. We found an exceptionally high degree of polarization in a jet component of BL Lac at 43 GHz, with m_L ~ 40%. Assuming a transverse shock front propagating downstream along the jet, the shock front being almost parallel to the line of sight can explain the high degree of polarization.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.27.2-27.2
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• 2010

We have studied the formation of coronal holes (CHs) associated with halo CMEs. For this study, we used multi-wavelength data from Yohkoh Soft X-ray Telescope (SXT), GOES Soft X-ray Imager (SXI), SOHO EIT 195 ${\AA}$, SOHO MDI magnetogram, MLSO He I 10830 ${\AA}$, and BBSO H-alpha. The CHs are characterized by open magentic field regions with low emission, density, and temperature and their open fields drive high speed solar winds which cause geomagnetic storms. So far, the formation and the evolution of CHs are not well understood. The formation of the dark region associated with the eruption of a CME is well known as "coronal dimming" which may be caused by the mass depletion near the CME footpoint. It is different from a typical CH since it persists for only one or two days. In this study, we present three cases that show the formation of coronal holes which are associated with three halo CMEs: 1) 2000 Jul 14, 2) 2003 Oct 28, 3) 2005 May 13. In the first case, hot plasma was ejected during a weak eruption and then filled out the pre-existing CH. After the halo CME occurred, the hot plasma region becomes a CH again. In the second and the third cases, we found newly formed CHs just after their associated CMEs. All three coronal holes are associated with strong flares and persist over 3 days until they disappeared by the solar rotation. Examining the MDI magnetograms, we found that the magnetic polarity of each CH region has one polarity. Based on these results, we suggest that the coronal holes can be formed by the CMEs and they should be distinguished from the coronal dimming.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2005.04a
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• pp.35-38
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• 2005

In our country, the skin image and MR Microscopy research has been processed but there were not their outstanding results. So this study start to improve the techniques can get high resolution skin images and to make RF surface coils. Volume coils are sometimes unavailable, or do not provide adequate RF power or SNR for some applications. In high resolution skin and tissue structure images current coils have a technical limitation. It is well known that standard single-loop surface coils, although offering high SNR characteristics, have poor B1 homogeneity. As the RF surface coil need change its geometry we get improved images. So, The magnetic field simulation that is first step to make and design RF surface coil will support reference data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.517-520
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• 2005

Wireless sensor network combines sensing and computing technology which can sense light, temperature, vibration, magnetic field and wind etc, as each purpose of using those. Wireless nodes operate signal processing skill which has proceeded sensed information from the sensor, transmission which makes information reached to observer and limited energy managing skill which is needed on account of using battery to operate wireless. To make responsible measuring and sensing out of them, efficient energy management is so important to maintain life time of network. In this paper, after explaining CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance) traditional wireless MAC protocol, and ER-MAC(Energy Rate Medium Access Control) which are not managing resource of hardware but MAN(Medium Access Control), data-link layer out of OSI 7 layer. We would like to analyze those efficiency of power saving comparing with each protocol.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2137-2142
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• 2016

The electrical current generated by heart creates not only electric potential but also a magnetic field. In this study, the signals obtained magnetocardiogram(MCG) using 61 channel superconducting quantum interference device(SQUID) system, and the clinical significance of various feature parameters has been developed MCG. Neural network algorithm was used to perform the classification of ischemic heart disease. The MCG signal was obtained to facilitate the extraction of parameters through a process of pre-processing. The data used to research the normal group 10 and ischemic heart disease group 10 with visible signs of stable angina patients. The available clinical indicators were extracted by characteristic point, characteristic interval parameter, and amplitude ratio parameter. The extracted parameters are determined to analysis the significance and clinical parameters were defined. It is possible to classify ischemic heart disease using the MCG feature parameters as a neural network input.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3133-3139
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• 2023

Neutron imaging technology as a means of non-destructive detection of materials is complementary to X-ray imaging. Silicon photomultiplier (SiPM), a new type of optical readout device, has overcome some shortcomings of traditional photomultiplier tube (PMT), such as high-power consumption, large volume, high price, uneven gain response, and inability to work in strong magnetic fields. Its application in the field of neutron detection will be an irresistible general trend. In this paper, a thermal neutron imaging detector based on ⁶LiF/ZnS scintillation screen and SiPM array readout was developed. The design of the detector geometry was optimized by geant4 Monte Carlo simulation software. The optimized detector was evaluated with a step wedge sample. The results show that the detector prototype with a 48 mm × 48 mm sensitive area can achieve about 38% detection efficiency and 0.26 mm position resolution when using a 300 ㎛ thick ⁶LiF/ZnS scintillation screen and a 2 mm thick Bk7 optical guide coupled with SiPM array, and has good neutron imaging capability. It provides effective data support for developing high-performance imaging detectors applied to the China Spallation Neutron Source (CSNS).

• The Journal of the Petrological Society of Korea
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• v.11 no.1
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• pp.1-16
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• 2002

The study area is mostly composed of Precambrian Gyeonggi gneiss complex, Jurassic Daebo granites, Cretaceous tonalite and dykes, and so on. On the basis of field survey and mineral assemblage, the granites can be divided into three types; biotite granite (Gb), garnet biotite granite (Ggb) and two mica granite (Gtm). They predominantly belong to monzo-granites from the modes. Field relationship and K-Ar mica age data in the surrounding area suggest that intrusive sequences are older in order of Gtm, Ggb and Gb. Gb and Ggb, major study targets, occur as medium-coarse grained rocks, and show light grey and light grey-light pink colors, respectively. Mineral constituents are almost similar except for opaque in Gb and garmet in Ggb. Gb and Ggb have felsic, peraluminous, subalkaline and calc alkaline natures. In Harker diagram, both rocks show moderately negative trends of $TiO_2$, MgO, CaO, $Al_2O_3$, $Fe_2O_3$(t), $K_2O$ and $P_2O_5$ as $SiO_2$ contents increase. Among them, $TiO_2$, MgO and CaO show two linear trends. From the trends and the linear patterns in AFM, Sr-Ba and Rb-Ba-Sr relations, it is likely that they were originated from the same granitic magma and Ggb was differentiated later than Gb. REE concentrations normalized to chondrite value have trends of parallel LREE enrichment and HREE depletion. One data of Ggb showing a gradually enriched HREE trend may be caused by garnet accompaniment. Ggb have more negative Eu anomalies than Gb, suggesting that plagioclase fractionation in Ggb have occurred much stronger than that in Gb. In modal (Qz+Af) vs. Op, Gb and Ggb belong to magnetite-series and ilmenite-series, respectively. From the EPMA results, opaques of Gb are magnetite and ilmenite, and those of Ggb are magnetite-free ilmenite or not observed. Bimodal distribution of magnetic susceptibility reveals two different granites of Gb (332.6 ${mu}SI$) and Ggb (2.3 ${mu}SI$). Based on the paleomagnetic analysis as well as modal analysis, the main susceptibilities of Gb and Ggb reside in magnetite and mafic minerals, respectively. They belong to S-type granite of non-magnetic granite by susceptibility value. In addition, $SiO_2$ contents, $K_2O/Na_2O$, A/CNK molar ratio and ACF diagram support that they all belong to S-type granites.

• Journal of the Korean earth science society
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• v.39 no.6
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• pp.519-532
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• 2018

We investigated the effect of galactic plane toward molecular motion and kinematics in the northern filament (NF) of Orion Molecular Clouds Complex (OMC) using $^{12}CO$ (J=1-0) line. Observed data were from three areas including NF1, NF2, and NF3 in far-out order from galactic plane, for a total 270 hours by Seoul National University Radio Astronomy Observatory (SRAO) 6m telescope, with 2arcmin spatial resolution. galactic plane and OMC NF were connected to each other along the magnetic field at a density of 3% for $^{12}CO$ (J=2-1) and 9% for the case of dust. $^{12}CO$ (J=1-0), $^{12}CO$ (J=2-1), and interstellar dusts were distributed uniformly in NF3, but only in certain regions with relatively high density in NF1 and NF2. NF showed a single structure, partial shrinking motion in NF1, and rotational motion at the bottom of NF2, and spiral rotation associated with magnetic field only in NF3. The position-velocity analysis showed that the materials including $^{12}CO$ (J=1-0) could flow toward galactic plane along NF2 and NF3. However, there was no clear cause for the material to flow toward galactic plane in this result. Further detailed observation for rotational motion at the top of NF1 and NF2 might help to confirm it.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.155-163
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• 2005

For an unbiased TF (Tansfer Function) estimations we investigate geomagnetic TF derived from ICHEON and YONGIN sites, employing RR (Remote Reference) and SNS (Signal Noise Separation) techniques. The Rh technique, which requires synchronized field variations recorded at a clean remote site, is a reliable method to minimize the bias of TF by uncorrelated noises in magnetic channels. Meanwhile, SNS technique based on the assumption of noise-free remote data can improve the signal-noise level by separating signal TF and noise TF, which is successfully applied to the environments with strong correlated noises. In this study, TF at YONGIN is analyzed using geomagnetic data from ICHEON site as a remote reference, which seem to have somewhat better data quality. The application of Rh technique reduces the bias of TF, which appears in single site robust estimation, and makes curves in the amplitude and phase of TF more smooth as frequency. Futhermore, in order to investigate noise source quantitatively, SNS technique is applied. The results of SNS suggest that dominant noise source seems to be located at western region of YONGIN. This noise source is considered to originate from railway system such as KTX and national subway. which passes through the west regions of YONGIN.