• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.47.1-47.1
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• 2017

We study the alignment of kinematic position angles (PAkin) of early-type galaxies in the Virgo cluster using Atlas3D data. The PAkin represent the direction of the angular momentum of the galaxies better than the photometric position angles. Therefore, the alignment of their PA$_{kin}$ is a useful tool to trace the momentum direction. The early-type galaxies in the Virgo cluster have been known to be distributed as filamentary structures inside the cluster. We found that their PAkin are aligned to two directions of 20degree and -80degree. This fact is confirmed using the bootstrap test, and that is, the two alignment angles are statistically significant. Besides, these two angles are surprisingly aligned parallel to the filamentary structures inside the cluster. These results suggest that early-type galaxies were formed by major merging in the filament structures and then fall into the Virgo cluster while maintaining their position angles.

• Coupled systems mechanics
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• v.8 no.6
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• pp.523-535
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• 2019

Artificial Intelligence (AI) is anticipated to be the future of technology. Hence, AI has been applied in various fields over the years and its applications are expected to grow in number with the passage of time. There has been a growing need for accurate, direct, and quick prediction of geotechnical and foundation engineering models especially since the success of each project relies on numerous amounts of data. In this study, two applications of AI in the field of geotechnical and foundation engineering are presented - spatial interpolation of standard penetration test (SPT) data and prediction of consolidation of clay. SPT and soil profile data may be predicted and estimated at any location and depth at a site that has no available borehole test data using artificial intelligence techniques such as artificial neural networks (ANN) based on available geospatial information from nearby boreholes. ANN can also be used to accelerate the calculation of various theoretical methods such as the one-dimensional consolidation theory of clay with high efficiency by using lesser computation resources. The results of the study showed that ANN can be a valuable, powerful, and practical tool in providing various information that is needed in geotechnical and foundation design.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.31.2-31.2
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• 2010

We have performed a spectroscopic study of globular cluster (GC) system associated with the Virgo cD galaxy M87 using the Subaru/FOCAS MOS mode. We derive ages, metallicities and abundance ratios from the GC spectra using Simple Stellar Population (SSP) models. The metallicity distribution function (MDF) obtained empirically based on Milky Way GCs is consistent with the MDF derived from SSP models. A comparison with a meta-analysis using literature data sample of 15 other GC systems shows good agreement with our results. The properties of GCs acquired from the spectra will be used to test the recent theoretical prediction of a significant inflection along the colour-metallicity relations (Yoon et al. 2006). If confirmed, the non-linearity of the relations would shed new light on the interpretation of the GC colour bimodality. The robustness of our results is being tested against the choice of a SSP model, measurement errors and sample selection towards the goal of better understanding the formation history of GCs and host galaxy.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.41.2-41.2
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• 2010

We present ultraviolet (UV) properties of dwarf galaxies in the Ursa Major cluster comparing with those in the Virgo cluster. We have constructed SDSS DR7/GALEX GR5 matched optical/UV catalog for dwarf galaxies with various morphologies in these two clusters. Membership of galaxies belonging to the Ursa Major cluster was made by hierarchical grouping method using SDSS spectroscopic data. We classified morphologies of dwarf galaxies using the combination of visual inspection of the images and spectral features returned from SDSS data. In contrast to the case of the Virgo cluster, majority of dwarf galaxies in the Ursa Major cluster lies in the blue cloud of the UV color-magnitude relations (CMRs) implying strong recent or on-going star formation. We discuss the cluster environment on the star formation history and evolution of dwarf galaxies.

• Korean Journal of Biological Psychiatry
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• v.18 no.1
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• pp.36-45
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• 2011

Objectives : Though a proportion of Alzheimer's disease(AD) patients treated with donepezil have shown positive response on cognition, but the responders' characteristics are still uncertain. This study attempts to identify whether a single oral dose of donepezil(5mg) can change cognition and the relationship between single dose responder items and long-term responder are examined. Methods : Twenty-three AD patients for single donepezil challenge study group and eleven AD patients for controls were participated in the study. Seven days after baseline study for neuropsychological test and EEG, same studies were rechecked after donepezil medication in study group. In donepezil study groups, 12 weeks after donepezil medication, neuropsychological test and EEG were rechecked. Results : After single donepezil challenge, forward digit span, Rey-Osterrieth Complex Figure Test copy, SVLT delayed recall were significantly improved, and beta spectra power in anterior, theta spectra power in posterior field were significantly decreased. According to linear regression analysis, forward digit span after single donepezil challenge was significantly positive correlated with long-term responders. Conclusions : This study suggests that single donepezil medication can significantly change cognitive functions and EEG in AD patients. Among these responsive items, forward digit span was significantly correlated with long-term responder.

• Journal of Astronomy and Space Sciences
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• v.30 no.1
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• pp.59-67
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• 2013

We present a spectroscopic study of 343 blue compact galaxies (BCGs) at 0.20 < z < 0.35 from the Sloan Digital Sky Survey (SDSS) DR7 data. We derive gas phase oxygen abundance using the empirical and direct method. Stellar masses of galaxies are derived from the STARLIGHT code. We also derive star formation rates of galaxies based on $H{\alpha}$ emission line from the SDSS as well as far-ultraviolet (FUV) flux from the Galaxy Evolution Explorer GR6 data. Evolution of the luminosity-metallicity and mass-metallicity (M-Z) relations with redshift is observed. At a given luminosity and mass, galaxies at higher redshifts appear to be biased to low metallicities relative to the lower redshift counterparts. Furthermore, low mass galaxies show higher specific star formation rates (SSFRs) than more massive ones and galaxies at higher redshifts are biased to higher SSFRs compared to the lower redshift sample. By visual inspection of the SDSS images, we classify galaxy morphology into disturbed or undisturbed. In the M-Z relation, we find a hint that morphologically disturbed BCGs appear to exhibit low metallicities and high SSFRs compared to undisturbed counterparts. We suggest that our results support downsizing galaxy formation scenario and star formation histories of BCGs are closely related with their morphologies.

• Journal of Internet Computing and Services
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• v.11 no.4
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• pp.73-83
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• 2010

The scalability of a grid system should be efficiently designed to handle the increasing number of grid users. This paper presents a scalable resource sharing mechanism among virtual organizations (VO) in grid environment by the scalable virtual organizations (SVO). The proposed grid architecture is composed of standard services of a grid system to manage the SVO. We propose a group similarity function which is used to determine similarities among VOs to select the VOs to merge. We compared other similarity functions to the GSF and determined the throughput performance of the SVO using simulation for grid system.

• Sleep Medicine and Psychophysiology
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• v.5 no.2
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• pp.177-184
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• 1998

Objectives : Disturbance of sleep with or without sleep apnea may impair the memory function. Sleep deficiency, sleepiness, sleep apnea and emotional problem in sleep disorders can induce an impairment of memory function. Methods : In this study, the polysomnographies were administered to 58 sleep apnea patients and 38 sleep disorder patients without sleep apnea. Their clinical symptoms were quantitatively evaluated. Short term and long term memory were evaluated before and after polysom no graphy with Digit symbol test and Rey-Osterrieth complex figure test. And correlations among various sleep, repiratory and clinical variables were statistically studied in order to explore which variables may influence on memory function. Results and Conclusions : Results are as follows. Depth of sleep cis positively correlated with memory function. As sleep apnea increases and average saturation of blood oxygen decreases, memory function is more impaired. Emotional depression, high blood pressure, obesity or alcohol impaired memory function. However, daytime sleepiness was not significantly correlated with memory function. The possible mechanisms how above factors influence on the memory function were discussed.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.37.2-37.2
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• 2013

We present the galaxy luminosity function (LF) of the Abell 119 cluster. Deep images in u, g, r bands were taken using MOSAIC 2 CCD on a Blanco 4-m telescope at CTIO. Based on scaling relations at faint magnitudes and spectroscopy at bright magnitudes, accurate membership of galaxies is determined. The LF is fitted by a single Schechter function and a two components (Gauss + Schechter) function. Blue galaxies are well fitted by a single Schechter function with steep slope ${\alpha}$ ~ -1.55). Red galaxies in the inner, high density region are fitted by single Schechter function with shallow slope (${\alpha}$ ~ -1.30), while red galaxies in the outer, low density region are well fitted by a two components function. The different slope of LFs between the inner and outer seems to stem from the luminosity segregation of A119 indicating larger number ratio of luminous to faint ratio towards the cluster center. The different shape of LFs seems to be resulted from the different composition of luminous and faint galaxies among main-cluster, sub-cluster, and infall region.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.39.3-39.3
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• 2016

About one tenth of dwarf elliptical galaxies found in the Virgo cluster have a disk component, and some of them even possess substructures such as bars, lens, and spiral arms. We use N-body simulations to study the formation of these non-axisymmetric features in disky dwarf elliptical galaxies. By mimicking VCC 856, a bulgeless dwarf galaxy with embedded faint spiral arms, we construct 11 sets of initial conditions with slight dynamical variations based on observational data. Our standard model starts slowly to form a bar at ~3 Gyr and then undergoes buckling instability that temporarily weakens the bar although the bar strength continues to grow afterward. We find 9 of our models are unstable to bar formation and undergo buckling instability. This suggests that disky dwarf elliptical galaxies are intrinsically unstable to form bars, accounting for a population of barred dwarf galaxies in the outskirts of the Virgo cluster. To understand the origin of the faint grand-design spiral arms, we additionally construct 6 sets of models that undergo tidal interactions with their neighbors. We find that faint spiral arms consistent with observations develop when tidal forcing is relatively weak although strong encounter still results in bar formation. We discuss our results in light of the dynamical evolution of dwarf elliptical galaxies including mergers.