• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.51.1-51.1
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• 2011

Red dusty Active Galactic Nuclei (AGNs) are suspected to mid-stage between ULIRG and AGN phase. As well as, red AGNs are suspected that they have more than 50% of whole AGN population. In order to understand the character of red AGNs, Black Hole (BH) mass of red AGN is a key property and can not measured by existing method such as reverberation mapping and single epoch method. Thus we still don't know their character and properties in clearly. To estimate properties of red AGNs without the effect of dust-obscuration, we have obtained Near InfraRed (NIR) spectra of 31 reverberation mapped AGNs and 49 Palomar-Green(PG) Quasi-Stellar Object (QSO) by using the infrared camera (IRC) for AKARI with unique wavelength range $2.5-5.0{\mu}m$. From this spectra, we measured the FWHM and luminosity of brackett ${\alpha}$ and ${\beta}$ at 4.0, 2.6 micron meter for deriving new BH mass estimators based on the properties of Brackett line emission.

• Communications of the Korean Mathematical Society
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• v.20 no.2
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• pp.231-238
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• 2005

In this paper, we study the arithmetic properties of orders in a quaternion algebra over a dyadic local field and we find the mass formula of orders.

• Tunnel and Underground Space
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• v.12 no.3
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• pp.220-228
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• 2002

Thermal flow through jointed rock mass was analyzed by numerical methods. The effect of a single set of joints on the heat conduction was analyzed by one-dimensional model and compared with the analytical solution. When a joint is completely dry, the joint behaves as a thermal break inducing jumps in temperature distribution even at steady state. Therefore when joints are completely dry, individual joint has to be taken into consideration to get a good result. When joints are partially or fully saturated, the thermal conductivity of the joints increases drastically and the jumps in temperature distribution become less severe. Therefore the effect of joint in heat conduction can be well absorbed by continuum anisotropic model whose thermal properties represent overall thermal properties of the intact part and the discontinuities. Since the effect of joints becomes less important as the degree of the saturation increases, the overall thermal response of the rock mass also becomes close to isotropic. Therefore it can be concluded that a great effort has to be made to obtain a precise in-situ thermal properties in order to get a good prediction of the thermal response of a jointed rock mass.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.22-29
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• 1995

An experimental method to identify the rigid properties (mass, moment of inertia, center of mass) of mounted structures is presented. A direct system identification method is developed and applied to identify the mass, damping and stiffness martix directly from the translational response of vibration testing. Conventional method is sensitive to noise since it needs artificial rotational response of temporary center of mass which is made by the linear transformation of translational response. A presented method needs only the translational response, and it is robuster to noise than conventional method. Several experimental and numerical implementations show the presented method is effective.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.205-209
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• 2009

Wetting properties between silver-copper-titanium braze alloys with different titanium contents up to 2.8 mass% and hexagonal boron nitride ceramics were investigated using sessile drop method at 1123K in Argon. The final contact angle is less than $30^{\circ}$ when the Ti content was over 0.41 mass%. Meanwhile, the contact angle curves show different behavior. In case of using braze alloy containing 2.8 mass% of titanium, the initial contact angle is acute angle just after the melting of braze. In case of brazes containing titanium less than 2.26 mass%, the contact angle is larger than $90^{\circ}$ at the beginning and slowly decreases to acute angle. The reaction layer of titanium nitride is observed at the interface. In addition, the reaction of Ti in the braze and N in the bulk h-BN seemed to show diffusion limited spreading.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.36.2-36.2
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• 2014

We present results of the analysis of FLS 1718+59, a galaxy-galaxy gravitational lens system in the Spitzer First Look Survey (FLS) Field. A background galaxy (z = 0.245) is severely distorted by an elliptical galaxy (z = 0.08), by gravitational lensing. We analyze this system by several methods, including Ellipse and Galfit fitting, gravitational lens modeling (gravlens), and SED fitting. Properties of the lens galaxy can be obtained: from Galfit we measure the effective radius and the average surface brightness inside it, and from gravlens we estimate the total mass inside the Einstein radius (lensing mass). We use these parameters to check that the lens galaxy is located on the Fundamental Plane. Also, we conduct SED fitting for the lens galaxy and estimate the stellar mass, and compare this with the lensing mass of the lens galaxy to check the M-L relation.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.80.1-80.1
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• 2012

The $2.5-5.0{\mu}m$ spectrum of AGN was poorly understood due to the atmosphere effect beyond $2{\mu}m$. Nevertheless, the $2.5-5.0{\mu}m$ range includes several important lines, such as $Br{\beta}$ ($2.63{\mu}m$), $Br{\alpha}$ ($4.05{\mu}m$), PAH (3.3${\mu}m$) and many molecular or atomic lines. We compile $2.5-5.0{\mu}m$ spectra of 79 AGNs and QSOs from infrared camera (IRC) on AKARI infrared astronomy satellite. Our $2.5-5.0{\mu}m$ spectra will provide an access to full wavelength spectra of AGNs for the first time. Moreover, we present the Brackett line properties, FWHMs and luminosities, of AGNs. Using these Brackett line properties, we derive new black hole (BH) mass estimators. The new BH mass estimators using NIR hydrogen lines will be very useful to estimate BH mass of dusty red AGNs in the future.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.407-414
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• 2004

Interfacial properties between rock mass and shotcrete play a significant role in the transmission of loads from the ground to shotcrete. These properties have a major effect on the behaviours of rock mass and shotcrete. They, however, have merely been assumed in most of numerical analyses, and little care has been taken in identifying them. This paper aimed to identify interfacial properties including cohesion, tension, friction angle, shear stiffness, and normal stiffness, through direct shear tests as well as interface normal compression tests for shotcrete/rock cores obtained from a tunnel sidewall. Mechanical properties such as compression strength and elastic modulus were also measured to compare them with the time-dependent variation of interfacial properties. Based on experiments, interfacial properties between rock and shotcrete showed a significant time-dependent variation similar to those of its mechanical properties. In addition, the time-dependent behaviours of interfacial properties can be well regressed through exponential and logarithmic functions of time.

• Explosives and Blasting
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• v.25 no.1
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• pp.67-77
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• 2007

The drill monitoring data are useful for the detection of abrupt and unexpected changes in ground renditions. This paper introduces a new approach to how drill performance parameters can be used for the prediction of quantitative rock mass properties ahead of tunnel face and the blasting design. The drill monitoring parameters available for the predictions include the instantaneous advance speed, thrust force, torque, tool pressure and penetration rate. The assessment of the drill monitoring parameters will be able to build a database provided that in-situ drill monitoring informations are accumulated and enable us to make a reasonable blast design based on quantitative assessment of rock mass.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.489-492
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• 2008

Adiabatic temperature rise and autogenous shrinkage experiments were performed for three silica-fume included mass concrete mixtures and a reference mixture without silica-fume, in order to investigate the influence of silica-fume on the hydration heat and autogenous shrinkage properties of mass concrete, and to examine applicability of silica-fume to mass concrete. It was revealed from the experiment that, for mass concrete, the rate of hydration was hardly increased while the maximum adiabatic temperature rise decreased about 5$^{\circ}$C by the addition of silica-fume, and the amount of autogenous shrinkage was almost the same regardless of silica-fume replacement. These facts imply that silica-fume can enhance the resistance of mass concrete to temperature cracking as well as the durability.