• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.31.3-32
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• 2021

We quantify the relative role of galaxy environment and bar presence on AGN triggering in face-on spiral galaxies using a volume-limited sample with 0.02 < z < 0.055, Mr < 19.5, and σ > 70 km s-1 selected from Sloan Digital Sky Survey (SDSS) Data Release 7. To separate their possible entangled effects, we divide the sample into bar and non-bar samples, and each sample is further divided into three environment cases of isolated galaxies, interacting galaxies with a pair, and cluster galaxies. The isolated case is used as a control sample. For these six cases, we measure AGN fractions at a fixed central star formation rate and central velocity dispersion, σ. We demonstrate that the internal process of the bar-induced gas inflow is more efficient in AGN triggering than the external mechanism of the galaxy interactions in groups and cluster outskirts. The significant effects of bar instability and galaxy environments are found in galaxies with a relatively less massive bulge. We conclude that from the perspective of AGN-galaxy coevolution, a massive black hole is one of the key drivers of spiral galaxy evolution. If it is not met, a bar instability helps the evolution, and in the absence of bars, galaxy interactions/mergers become important. In other words, in the presence of a massive central engine, the role of the two gas inflow mechanisms is reduced or almost disappears. We also find that bars in massive galaxies are very decisive in increasing AGN fractions when the host galaxies are inside clusters.

• Culinary science and hospitality research
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• v.9 no.4
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• pp.54-68
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• 2003

This study aims at efficiency of kitchen management by adoption of a systematic central kitchen and conversion of conventional kitchen to convenience kitchen at ' H ' restaurant. First, integrated menu control of banquet buffet functions became more competitive with quality menu and eventually brought about guests satisfaction. Second, systematic central kitchen made possible standardization and mass production through simplified production line. Efficiency through quick service and shortened preparation time was realized, and food materials were recycled effectively at the same time. Integrated ordering lowered purchasing price and built an efficient cost control system. Third, conversion of conventional kitchen to convenience kitchen and strengthened central kitchen system facilitated agreeable work conditions and optimal work flow with butcher's and even sauce making utensils. Fourth, integrated supply system of buffet menu and sauce from western restaurants saved about 520 million won of labor costs. Last, one integrated kitchen out of two was easier in sanitation control with pleasant restaurant space. Sharing kitchen facilities and equipments also saved about 30% of maintenance fee. Power, water, and gas were also saved and eventually curtailed overall expenses.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.719-722
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• 2002

Cylindrical cam mechanisms are used commonly in many automatic machinery. But the cylindrical cam is very difficult to design and manufacture the shape. The motion analysis of the cylindrical cam can check the accuracy between designed data and manufactured data of the cam shape and can reproduce without the cam design data. The motion analysis of the cylindrical cam consists of displacement analysis, velocity analysis and acceleration analysis. This paper performs the motion analysis of a cylindrical cam with translating follower by using a relative velocity method and a central difference method. The displacement is calculated by using the central difference method and the velocity is calculated by the relative velocity method. The relative velocity method is defined by the relative motion between follower and cam at a center of a follower roller. The central difference method is derived in the 3 dimensional space.

• Journal of International Area Studies (JIAS)
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• v.13 no.4
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• pp.129-154
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• 2010

In Post-soviet Space, particularly the Central Asian is a great turbulence region called the 'Eurasian Balkan', where diverse factors of conflict and dispute are existed. In Central Asia, a current regional security system is characterized by various multilateral cooperation relations among Central Asian nations and the world powers, such as NATO(PfP), OSCE, CIS, CSTO, CACO, SCO, CICA and so on. But nothing could obtain superiority as pan-regional security system. Unless internal problems and conflicts of the Central Asian nations be solved, security won't be assured in this region. Narrow-minded and blind realism will spread insecure region, make a lasting trouble spot in Eurasian continent. The purpose of this article is to explore significance for international relations of security system in the Central Asia. I examine general features of regional security environment formed after the Soviet Union's collapse, characteristics of multilateral cooperation related with Central Asian nations. Through consideration current situations I suggest prospects of security system in Central Asia.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.78.1-78.1
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• 2012

We have studied the physical properties of X-ray point sources in galaxy clusters using ~600 Chandra archival observations. The goal of this study is to investigate the density environmental effects on the physical properties of X-ray point sources by comparing the properties of X-ray point sources in galaxy clusters to those in typical blank fields. In this presentation, we show the nature of X-ray point sources which are expected to be related with galaxy clusters with different core properties. Using ~60 galaxy clusters observed with Chandra, we investigate the physical properties of X-ray point sources in cool-core and non-cool-core clusters. The cool-core clusters are known to have short central cooling time, and are characterized by low central entropy, systematic central temperature drops, and a brightest cluster galaxy at the X-ray peak. While the non-cool-core clusters have longer central cooling time, and are characterized by large central entropies and flat or centrally rising temperature profile. We show that how central core properties of galaxy clusters affect on the physical properties of X-ray point sources.

• Bulletin of the Korean Mathematical Society
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• v.25 no.2
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• pp.195-201
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• 1988

In general relativity, analyzing causality is central to the study of black holes, to cosmology, and to each of the major recent mathematical theorems. By causality we refer to the general question of which points in a space-time can be joined by causal curves; relativistically which events can influence (be influenced by) a given event. Various causality conditions have been developed for space-times of the problems associated with examples of causality violations (2, 4). Causally continuous space-times were defined by Hawking and Sachs (5). Budic and Sachs (3) established causal completion. A metrizable topology on the causal completion of a causally continuous space-time was studied by Beem(1). Recently the region of space-time where causal continuity is violated was studied by Ishikawa (6) and Vyas and Akolia (8). In this paper we show characterization for reflectingness in terms of continuity of set valued functions. We investigate some properties of the region related to a causally continuous space-time where distinguishingness is violated, and characterize the chronology condition in terms of distinguishing-violated region.

• Journal of The Korean Astronomical Society
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• v.47 no.4
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• pp.123-135
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• 2014

A silicate carbon star is a carbon star which shows circumstellar silicate dust features. We collect a sample of 44 silicate carbon stars from the literature and investigate the validity of the classification. For some objects, it is uncertain whether the central star is a carbon star. We confirm that 29 objects are verified silicate carbon stars. We classify the confirmed objects into three subclasses based on the evolution phase of the central star. To investigate the effect of the chemical transition phase from O to C, we use the radiative transfer models for the detached silicate dust shells. The spectral energy distributions and the infrared two-color diagrams of the silicate carbon stars are compared with the theoretical model results. For the chemical transition model without considering the effect of a disk, we find that the life time of the silicate feature is about 50 to 400 years depending on the initial dust optical depth.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.1-7
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• 2016

The influence of boundary condition of the bodies with gas flows is one of the most important problems in high-altitude aerodynamics. In this paper presents the results of the calculation of aerodynamic characteristics of aerospace vehicle using Monte-Carlo method based on three different gas-surface interaction models - Maxwell model, Cercignani-Lampis-Lord (CLL) model and Lennard-Jones (LJ) potential. These models are very sensitive for force and moment coefficients of aerospace vehicle in the hypersonic free molecular flow. The models, method and results can be used for new generation aerospace vehicle design.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.43-46
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• 2005

[1] There are systematical errors associated with ionospheric influence in retrieving key atmospheric parameters from radio occultation (RO) soundings. In order to obtain better-quality retrievals, we develop a new method, hereafter called National Central University Radio Occultation (NCURO) scheme, to reduce the ionospheric influence. The excess phase is divided into two parts, namely geometric excess length and path excess length (excess length along ray path due to refractivity effect). An excess phase equation is presented and implemented in the NCURO scheme Whose performance is evaluated through comparisons with model simulation and experimental data. The model simulation is based on the use of the ionospheric model 002001 and atmospheric model NRLMSISE-OO. Results show that the NCURO scheme significantly reduces the ionospheric influence at altitudes above 70 km as does the scheme presented in the literature, and provides better corrections for the atmospheric profile. INDEX TERMS: 2400 Ionosphere: Ionosphere; 6964 Radio Science: Radio wave propagation; 6969 Radio Science: Remote sensing.

• Korean Institute of Interior Design Journal
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• v.14 no.1
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• pp.20-27
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• 2005

This study is focused on the concept and spatial organization of bifurcation. After discussing the concept of bifurcation used in Borges' literature and Deleuze's Fold philosophy, case examples in contemporary architecture are analysed to comparatively investigate the relationship between the concept and space. In Deleuze's philosophy, bifurcation as well as pleats, inflection are used to form the world of fold that goes to infinity while, in Borges' literature, the structure of bifurcation is the key method to create the labyrinth of time. There are various projects in contemporary architecture based on the Deleuzian concept of bifurcation. Rem Koolhaas's Two Libraries for Jussieu University and UN Studio's Arnhem Central are selected and researched for further comparison study. In Jussieu project, the bifurcating spatial organization is 'intentionally' used to construct the indeterminant space whereas in Arnhem Central, bifurcation can be found in both the ever-bifurcating design process as well as the final spatial organization'unintentionally'generated from the process. This study is concluded with the comparative analysis between the representation and actualization of a concept that are crucially different.