• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.61.1-61.1
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• 2013

In this study we apply Support Vector Machine (SVM) to the prediction of geo-effective halo coronal mass ejections (CMEs). The SVM, which is one of machine learning algorithms, is used for the purpose of classification and regression analysis. We use halo and partial halo CMEs from January 1996 to April 2010 in the SOHO/LASCO CME Catalog for training and prediction. And we also use their associated X-ray flare classes to identify front-side halo CMEs (stronger than B1 class), and the Dst index to determine geo-effective halo CMEs (stronger than -50 nT). The combinations of the speed and the angular width of CMEs, and their associated X-ray classes are used for input features of the SVM. We make an attempt to find the best model by using cross-validation which is processed by changing kernel functions of the SVM and their parameters. As a result we obtain statistical parameters for the best model by using the speed of CME and its associated X-ray flare class as input features of the SVM: Accuracy=0.66, PODy=0.76, PODn=0.49, FAR=0.72, Bias=1.06, CSI=0.59, TSS=0.25. The performance of the statistical parameters by applying the SVM is much better than those from the simple classifications based on constant classifiers.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.445-453
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• 2022

SiO_x was prepared from a mixture of Si and SiO₂ via high-energy ball milling as a negative electrode material for Li-ion batteries. The molar ratio of Si to SiO₂ as precursors and the milling time were varied to identify the synthetic condition that could exhibit desirable anode performances. With an appropriate milling time, the material showed a unique microstructure in which amorphous Si nanoparticles were intimately embedded within the SiO₂ matrix. The interface between the Si and SiO₂ was composed of silicon suboxides with Si oxidation states from 0 to +4 as proven by X-ray photoelectron spectroscopy and electrochemical analysis. With the addition of a conductive carbon (Super P carbon black) as a coating material, the SiO_x/C manifested superior specific capacity to a commercial SiO_x/C composite without compromising its cycle-life performance. The simple mechanochemical method described in this study will shed light on cost-effective synthesis of high-capacity silicon oxides as promising anode materials.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.92-95
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• 2014

In this work we have synthesized ZnS:Mn nanocrystals (NCs) using a simple one step thermochemical method. $Zn(NO_3)_2$ and $Na_2S_2O_3$ were used as the precursors and $Mn(NO_3)_2$ was the source of impurity. Thioglycolic acid (TGA) was used as the capping agent and the catalyst of the reaction. The structure and optical property of the NCs were characterized by means of X- ray diffraction (XRD), HRTEM, UV-visible optical spectroscopy and photoluminescence (PL). X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated cubic phase ZnS:Mn NCs with an average size around 3 nm. Synthesized NCs exhibited band gap of about 4 eV. Photoluminescence spectra showed a yellow-orange emission with a peak located at 585 nm, demonstrating the Mn incorporation inside the ZnS particles.

• Progress in Medical Physics
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• v.19 no.4
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• pp.209-218
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• 2008

According to improved radiation therapy technology such as IMRT and proton therapy, the accuracy of patient alignment system is more emphasized and IGRT is dominated research field in radiation oncology. We proposed to study the feasibility of cone-beam CT system using simple x-ray imaging systems for image guided proton therapy at National Cancer Center. 180 projection views ($2,304{\times}3,200$, 14 bit with 127 ${\mu}m$ pixel pitch) for the geometrical calibration phantom and humanoid phantoms (skull, abdomen) were acquired with $2^{\circ}$ step angle using x-ray imaging system of proton therapy gantry room ($360^{\circ}$ for 1 rotation). The geometrical calibration was performed for misalignments between the x-ray source and the flat-panel detector, such as distances and slanted angle using available algorithm. With the geometrically calibrated projection view, Feldkamp cone-beam algorithm using Ram-Lak filter was implemented for CBCT reconstruction images for skull and abdomen phantom. The distance from x-ray source to the gantry isocenter, the distance from the flat panel to the isocenter were calculated as 1,517.5 mm, 591.12 mm and the rotated angle of flat panel detector around x-ray beam axis was considered as $0.25^{\circ}$. It was observed that the blurring artifacts, originated from the rotation of the detector, in the reconstructed toomographs were significantly reduced after the geometrical calibration. The demonstrated CBCT images for the skull and abdomen phantoms are very promising. We performed the geometrical calibration of the large gantry rotation system with simple x-ray imaging devices for CBCT reconstruction. The CBCT system for proton therapy will be used as a main patient alignment system for image guided proton therapy.

• Journal of the Korean Society of Radiology
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• v.13 no.3
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• pp.425-431
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• 2019

The Study In order to obtain images of overlap of the two iron cores in the spinal cord simple x-ray scan after surgery of patients with ulcer lateral sclerosis and a fractured backbone, the researcher conducted a subjective evaluation on five radiographers of the university hospital's imaging department for more than 10 years. The results of the experiment showed that the lateral shot of lateral scoliosis of the spinal cord was taken with the middle face of the IR plane, and then the X-ray tube angle was taken vertically with the vertical spinal column fan-tom position, resulting in two overlapping images and high scores in the subjective evaluation. In addition, lateral shots of the lumbar dislocation fractured lumbar vertebrae were taken with the forehead aligned with the center of the IR plane and then with the X-ray angle perpendicular to the fourth waistline and the angle of the spinal cord perpendicular to the fourth waistline, the image of the two iron cores could be obtained from the radiographer.

• Journal of Biomedical Engineering Research
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• v.24 no.2
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• pp.83-89
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• 2003

The gas electron multiplier placed in the drift volume of conventional gas detectors, is a conceptually simple device for producing a large gas gain by concentrating the drift electric field over a very short distance to the point that electron avalanching occurs(〉 10$^4$ V/cm), greatly increasing the number of drifting electrons. This device consists of a thin insulating foil of several tens of urn in thickness. covered on each side with a thin metal layer(Cu), with tiny holes, usually 100 ${\mu}{\textrm}{m}$ or less in diameter. and with a spacing of 100-200 ${\mu}{\textrm}{m}$ through the entire foil. perforated by using chemical etching or high-powered laser beam technique In this study, we have investigated its operating properties with various experimental conditions, and demonstrated the possibility of using this device as a digital X-ray imaging sensor, by acquiring X-ray images based on the scintillation properties of the gas electron multiplier with standard CCD camera.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.1
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• pp.8-14
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• 2007

X-ray digital tomosynthesis is widely used in the nondestructive testing and evaluation, especially for the printed circuit boards (PCBs). In this study, we propose a simple method to reduce the blur artefact, frequently claimed in the conventional digital tomosynthesis based on SAA (shift-and-add) algorithm, and thus restore the image sharpness. The proposed method is basically based on the SAA, but has a correction procedure by finding blur artefacts from the forward-and back-projection for the firstly obtained, manipulated backprojection data. The manipulation is the replacement of the original data at the POI (plane-of-interest) by zeros. This method has been compared with the conventional SAA algorithm using the experimental measurements and Monte Carlo simulation for the designed PCB phantom. The comparison showed a much enhancement of sharpness in the images obtained from the proposed method.

• Journal of the Korean Chemical Society
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• v.28 no.5
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• pp.302-308
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• 1984

X-ray spectrometric determination of $Ta_2O_54, $Nb_2O_5$ and $ZrO_2$ in tin-slag samples using the double dilution technique was conducted. Tin-slag samples and one synthesized standard sample having similar composition to the samples were diluted with anhydrous $Li_2B_4O_7$ at the level of 1.00, 2.00 and 3.00% of the sample content, respectively. The diluted samples were fused at $1,150^{\circ}C$ for 30 minutes, and these glass beads were finely ground and pelletized. With the X-ray intensities measured, analytical results were calculated by the double dilution equation. The results agreed to the reference values obtained by the standard calibration method and the simple dilution technique within allowable error range and were reproducible.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2609-2612
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• 2012

A simple green method was developed for rapid synthesis of silver and gold nanoparticles (AgNPs and AuNPs) has been reported using Lonicera japonica flower extract as a reducing and a capping agent. AgNPs and AuNPs were carried out at $70^{\circ}C$. The successful formation of AgNPs and AuNPs have been confirmed by UV-Vis spectro photometer, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray Analysis (EDAX), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). To our knowledge, this is the first report where Lonicera japonica flower was found to be a suitable plant source for the green synthesis of AgNPs and AuNPs.

• Bulletin of the Korean Chemical Society
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• v.35 no.9
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• pp.2660-2664
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• 2014

A simple method of depositing titanium dioxide ($TiO_2$) nanoparticles onto graphene oxide (GO) as a catalytic support was devised for photocatalytic degradation of methylene blue (MB). Thiol groups were utilized as linkers to secure the $TiO_2$ nanoparticles. The resultant GO-supported $TiO_2$ (GO-$TiO_2$) sample was characterized by transmission electron microscopy (TEM), near-edge X-ray absorption fine structure (NEXAFS), and X-ray photoelectron spectroscopy (XPS) measurements, revealing that the anatase $TiO_2$ nanoparticles had effectively anchored to the GO surface. In the photodegradation of MB, GO-$TiO_2$ exhibited remarkably enhanced photocatalytic efficiency compared with thiolated GO and pure $TiO_2$ nanoparticles. Moreover, after five-cycle photodegradation experiment, no obvious deactivation was observed. The overall results showed that thiolated GO provides a good support substrate and, thereby, enhances the photodegradation effectiveness of the composite photocatalyst.