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Automatic Detection of Type II Solar Radio Burst by Using 1-D Convolution Neutral Network
조경석,김준영,김록순,박은수,Yûki Kubo,Kazumasa Iwai 한국천문학회 2023 Journal of The Korean Astronomical Society Vol.56 No.2
Type II solar radio bursts show frequency drifts from high to low over time. They have been known as a signature of coronal shock associated with Coronal Mass Ejections (CMEs) and/or flares, which cause an abrupt change in the space environment near the Earth (space weather). Therefore, early detection of type II bursts is important for forecasting of space weather. In this study, we develop a deep-learning (DL) model for the automatic detection of type II bursts. For this purpose, we adopted a 1-D Convolution Neutral Network (CNN) as it is well-suited for processing spatiotemporal information within the applied data set. We utilized a total of 286 radio burst spectrum images obtained by Hiraiso Radio Spectrograph (HiRAS) from 1991 and 2012, along with 231 spectrum images without the bursts from 2009 to 2015, to recognizes type II bursts. The burst types were labeled manually according to their spectra features in an answer table. Subsequently, we applied the 1-D CNN technique to the spectrum images using two filter windows with different size along time axis. To develop the DL model, we randomly selected 412 spectrum images (80%) for training and validation. The train history shows that both train and validation losses drop rapidly, while train and validation accuracies increased within approximately 100 epoches. For evaluation of the model's performance, we used 105 test images (20%) and employed a contingence table. It is found that false alarm ratio (FAR) and critical success index (CSI) were 0.14 and 0.83, respectively. Furthermore, we confirmed above result by adopting five-fold cross-validation method, in which we re-sampled five groups randomly. The estimated mean FAR and CSI of the five groups were 0.05 and 0.87, respectively. For experimental purposes, we applied our proposed model to 85 HiRAS type II radio bursts listed in the NGDC catalogue from 2009 to 2016 and 184 quiet (no bursts) spectrum images before and after the type I bursts. As a result, our model successfully detected 79 events (93%) of type II events. This results demonstrates, for the first time, that the 1-D CNN algorithm is useful for detecting type II bursts.
Evaluation of the Wear Resistance of PVD Coatings on Drills by Using a Slurry Jet Impact Test
Y. IWAI,Y. UENO,T. SUEHIRO,T. HONDA,S. HOGMARK 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
In this paper, we propose a slurry jet (water containing 1 ㎛ alumina particles) impact test in order to quickly evaluate the wear properties of physical vapor deposited (PVD) coatings on commercial cutting tools. Linear wear was obtained for both coating and substrate material, and the penetration through the coating into the substrate was signified by a sharp increase in slope of the wear versus time curve. The PVD coatings deposited on the tools showed the same wear rates as those on reference plate specimens produced by the same coating methods. We conclude that our proposed evaluation technique for coatings is considerably useful as a screening test when evaluating coated tools like twist drills, taps, end mills, gear hobs, etc.
Design of the Advanced Metadata Service System with AMGA for the Belle II Experiment
S. Ahn,K. Cho,S. Hwang,J. Kim,H. Jang,B. K. Kim,H. Yoon,J. Yu,Z. Drasal,T. Hara,Y. Iida,R. Itoh,G. Iwai,N. Katayama,Y. Kawai,S. Nishida,T. Sasaki,Y. Watase,R. Fruhwirth,W. Mitaroff,R. Grzymkowski,M. S 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.4
The Belle II experiment is expected to produce 50 times more data than the existing Belle experiment. Such huge data production requires not only scalability with respect to the storage service but also scalability regarding the metadata service. There has already been a metadata service at the Belle experiment, but it is not proper for the Belle II experiment because it has scalability problems and it is not intended to be used in a distributed grid environment. To deal with these issues, we designed an advanced metadata service system based on AMGA, which provides efficient and scalable metadata searching. We have built testbed sites to test the correctness, performance and scalability of the advanced metadata service system, and it has been proved to be able to provide efficient metadata searching for the Belle II experiment.
The Embedment of a Metadata System at Grid Farms at the Belle II Experiment
S. Ahn,J. H. Kim,T. Huh,S. Hwang,조기현,H. Jang,B. K. Kim,H. Yoon,J. Yu,Z. Drasal,T. Hara,Y. Iida,R. Itoh,G. Iwai,N. Katayama,Y. Kawai,S. Nishida,T. Sasaki,Y. Watase,T. Uglov,R. Fruhwirth 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.4
In order to search for new physics beyond the standard model, the next generation of B-factory experiment, Belle II will collect a huge data sample that is a challenge for computing systems. The Belle II experiment, which should commence data collection in 2015, expects data rates 50 times greater than that of Belle. In order to handle this amount of data, we need a new data handling system based on a new computing model, which is a distributed computing model including grid farms as opposed to the central computing model using clusters at the Belle experiment. We have constructed a metadata system and embedded the system in the grid farms of the Belle II experiment. We have tested the system using grid farms. Results show good performance in handling such a huge amount of data.
The Rolling-Sliding Friction of Rubber and the Behavior of Contact Area
Y. UCHIYAMA,N. MONDEN,T. MIYAO,T. IWAI 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
Rolling-sliding friction was investigated for three SBR (styrene-butadiene rubber) specimens including silica-tilled. HAF carbon black-tilled, and SAF carbon black-tilled SBR. When a rubber wheel was rolled against a glass disk, the coefficient of friction varied with the slip ratios. The coefficient of friction for the silica-tilled SBR showed the highest value of the rubber specimens examined under various slip ratios. The contact areas of silica-filled SBR were larger than those of the carbon black-filled SBRs, as indicated the modulus of the silica-tilled SBR showing the lowest value. The contact area during rolling-sliding friction was always smaller than those during the static contact. The friction force at the unit contact area for the silica-filled SBR under braking and driving was higher than those of carbon black-filled SBRs.
WEAR BEHAVIOR OF SiC-PARTICLE REINFORCED ALUMINUM MATRIX COMPOSITES IN VARIOUS ENVIRONMENTS
T. MIYAJIMA,T. YAMAMOTO,Y. IWAI 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
Wear behavior of SiC-particle reinforced aluminum matrix composites (MMC) were investigated by pin-on-disk tests in vacuum with various pressures, argon, and air with various levels of humidity. The wear rate of 2024Al and MMC increased in the following order: in a vacuum at 5.0×10?⁴ ㎩, at 1.0㎩, in argon at 0% RH, in argon at 60% RH, in argon at 90% RH, in air at 0% RH, in air at 60% RH and in air at 90% RH. In other words, the influence of environment on wear becomes stronger in the following order: moisture, oxygen, and a combination of moisture and oxygen. In various environments, the difference of the wear rate of 2024Al and MMC was compared. In argon and air at 0% RH, the wear rates of MMC were higher than that of 2024Al. In contrast, in argon and air at 60, 90% RH, the wear rates of MMC were lower than that of 2024Al.
SEARCH FOR STRANGE TRIBARYON STATES IN THE 4He(STOPPED K-, p) REACTION
SATO, M.,BHANG, H.,CHIBA, J.,CHOI, SEONHO,FUKUDA, Y.,HANAKI, T.,HAYANO, R. S.,IIO, M.,ISHIKAWA, T.,ISHIMOTO, S.,ISHIWATARI, T.,ITAHASHI, K.,IWAI, M.,IWASAKI, M.,KIENLE, P.,KIM, J. H.,MATSUDA, Y.,OHNIS World Scientific 2009 International Journal of Modern Physics A Vol.24 No.2
<P> We have measured a proton energy from the stopped K<SUP>-</SUP> reaction on <SUP>4</SUP> He to search for strange tribaryon states at KEK 12 GeV PS. No statistically significant signal was observed in the missing mass spectrum obtained by the inclusive <SUP>4</SUP> He ( stopped K<SUP>-</SUP>, p) measurement. Upper limits of the formation branching ratio at the 95 % C.L. were derived for neutral tribaryon states with strangeness -1 to be (0.4 ~ 6) × 10<SUP>-4</SUP>, (0.2 ~ 6) × 10<SUP>-3</SUP> and (0.06 ~ 5) × 10<SUP>-2</SUP>/(stopped K<SUP>-</SUP>) for assumed natural widths of 0, 20 and 40 MeV /c<SUP>2</SUP>, respectively. </P>