• Journal of Advanced Marine Engineering and Technology
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• v.7 no.2
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• pp.29-35
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• 1983

In general, for measuring residual stresses in plane stress state, two principal stresses {\sigma}_1 , {\sigma}_2$ and their directions .theta., should be determined. Naturally, for deciding three unknowns ${\sigma}_1, {\sigma}_2, ${\theta}$-three informations are necessary and therefore three strain gages are required for determining residual stresses at one point. In this paper, we tried to measure the residual stresses of one point with only two strain gages by drilling twice the hole of different diameters at the point and by detecting relaxation strains for each hole-drilling. We present also the formulas for determining the residual stresses from relaxation strains detected by strain gages in each hole-drilling. We carried out experiment, determining principal stresses and their directions of specimens applied specified uniform stress, and compared experimental results with the values calculated by formulas presented in this paper. The values calculated by formulas presented in this paper are always a little greater than the experimental results.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.79-79
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• 2010

To investigate whether the present-day active galaxies follow the same black hole mass vs. stellar velocity dispersion (MBH-$\sigma*$) relation as quiescent galaxies, we measured the velocity dispersions of a sample of local Seyfert 1 galaxies, for which black hole masses were measured via reverberation mapping. We measured stellar velocity dispersions from high S/N optical spectra centered on the Ca II triplet region (${\sim}8500^{\circ}A$), obtained at the Keck, Palomar, and Lick Observatories. For two objects, in which the Ca II triplet region was contaminated by nuclear emission, we used high-quality H-band spectra obtained with the OH-Suppressing Infrared Imaging Spectrograph and laser-guide star adaptive optics at the Keck-II Telescope. Combining our new measurements with data from the literature, we assemble a sample of 24 active galaxies with stellar velocity dispersions and reverberation MBH in the range of black hole mass 106< MBH /$M{\odot}$ < 109,toobtainthefirstreverberationmappingconstraintsontheslopeandintrinsicscatteroftheMBH- $\sigma*$ relation of active galaxies. Assuming a constant virial coefficient f for the reverberation MBH, we find a slope ${\beta}=3.55{\pm}0.60$ and the intrinsic scatter ${\sigma}int=0.43{\pm}0.08$ dex in the relation log (MBH/M${\odot}$)=$\alpha+\beta$ log(${\sigma}*$/200 km s-1), which are consistent with those found for quiescent galaxies. We derive an updated value of the virial coefficient f by finding the value which places the reverberation masses in best agreement with the MBH - $\sigma*$ relation of quiescent galaxies; using the quiescent MBH - $\sigma*$ relation determined by Gultekin et al. we find log f=0.72+0.09 (or $0.71{\pm}0.10$) with an intrinsic scatter of $0.44{\pm}0.07$ (or 0.46+0.07) dex. No correlations between f and parameters connected to the physics of accretion (such as the Eddington ratio or line-shape measurements) are found. The uncertainty of the virial coefficient remains one of the main sources of the uncertainty in black hole mass determination using reverberation mapping, and therefore also in single-epoch spectroscopic estimates of black hole masses in active galaxies.

• Journal of Integrative Natural Science
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• v.5 no.3
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• pp.195-197
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• 2012

Halogen atoms in a molecule are traditionally considered as electron donors, since they have unshared electrons. Normally when they are bonded, there are three lone pair electrons. These lone pairs can function as Lewis bases. However, when they are bound to electron withdrawing groups, they can act as Lewis acids. Since the situation is similar hydrogen bonding (HB), this type of interaction is named as halogen bonding (XB). This mainly comes from the uneven distribution of electron density around the halogen atoms. Since the electron density around halogen atom opposite to ${\sigma}$-bond is depleted, its electropositive region is called ${\sigma}$-hole. This ${\sigma}$-hole can attract halogen bond acceptors, requiring more stringent directionality compared to HB. Since this interaction mainly comes from electrostatic origin, the geometry tends to be linear. Since the XB energy is comparable to corresponding HB. Still in its infancy, XB shows a broad range of applicability, with potentially more useful properties, compared to corresponding HB.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.46.2-46.2
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• 2012

The black hole mass-stellar velocity dispersion ($M_{BH}-{\sigma}_*$) relation observed in the present-day universe has motivated numerous studies on the black hole-galaxy co-evolution. It is crucial to define the$M_{BH}-{\sigma}_*$ local active galaxies since cosmic evolution of the correlations is calibrated based on the local relation. However, stellar velocity dispersion is difficult to measure in active galaxies due to much higher AGN continuum than stellar pseudo-continuum, resulting in a small sample with reliable velocity dispersion measurements for studying the AGN $M_{BH}-{\sigma}_*$ relation. To increase the sample size and improve the measurements, we obtained high S/N near-IR spectra for 3 local AGNs, i.e., NGC 3227, Akn 120, 3C 390.3, for which reverberation black hole masses are measured, using the TripleSpec at the Palomar 5-m Telescope. By investigating aperture effect and correcting for rotation component, we determine the luminosity-weighted ${\sigma}_*$, based on the spatially resolved kinematics and compare them with optical measurements from literature. Combining our new measurements with literature data, we present an improved $M_{BH}-{\sigma}_*$ relation for the enlarged sample of reverberation-mapped AGNs.

• Journal of Welding and Joining
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• v.31 no.2
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• pp.43-48
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• 2013

This paper Investigated the characteristics of residual stress in weld is composed of typical specimens, are investigated by using three dimensional thermal elasto-plastic FEM analysis. Numerically calculated residual stresses in the gas welds were then compared with experimental results obtained by the hole-drilling method. Using the stress amplitude (${\sigma}a$)R at the hot spot point of gas weld, the relations obtained as the fatigue test results for typical specimens having various dimensions and shapes were systematically rearranged to obtain the (${\sigma}a$)R-Nf relationship. It was found that more systematic and accurate evaluation of the fatigue strength of plug- and ring-type gas-welded joints can be achieved by using (${\sigma}a$)R.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.46.1-46.1
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• 2013

WIth high accretion rate and low black hole mass, narrow line seyfert 1 galaxies (NLS1s) are an interesting sub-class of AGNs. To investigate whether NLS1s follow the same M-${\sigma}*$ relation as other AGNs, we selected a sample of 110 NLS1s at relatively low redshift z < 0.1 from SDSS DR7 by constraining the FWHM of Ha broad component, and determined their black hole masses. We measured stellar velocity dispersion of 65 objects which showed strong enough stellar lines in the SDSS spectra, while we adopted the ${\sigma}*$ measurements of 45 objects from Xiao et al. 2011. We find that NLS1s follow the M-${\sigma}*$ relation of active and inactive galaxies while there is a dependency due to the galaxy inclination, which probably cause rotational broadening of stellar absorption lines.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.4 no.4
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• pp.33-41
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• 1995

This study includes thermal plasticity analyses for a turbine rotor with the simple geometry and the boundary conditions. When centrifugal or thermal stress are applied at the high temperature material of engine blade, stress distributions I material ($\sigma$${\gamma}$${\gamma}$, $\sigma$$\theta$$\theta$, $\tau$${\gamma}$$\theta$, Mises stress) are analyzed by computer simulation(ABQUS) as followings; 1. The maximum stress at the radial direction() is applied at the upper middle part of spline hole. 2. The maximum stress at the tangential direction() is applied at the upper right boundary of spline hole. 3. The maximum shear stress () in () direction is applied at the upper middle part of spline hole. 4. The maximum Mises stress is applied at the upper right boundary of spline hole. This stress is due to the critical stress by which rotor can be fractured according to elapsed time.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.335-339
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• 2015

Using black hole masses which span $10^5-10^{10}M_{\odot}$, the distribution of galaxies in the (host spheroid stellar mass)-(black hole mass) diagram is shown to be strongly bent. While the core-$S{\acute{e}}rsic$ galaxies follow a near-linear relation, having a mean $M_{bh}/M_{sph}$ mass ratio of ~0.5%, the $S{\acute{e}}rsic$ galaxies follow a near-quadratic relation. This is not due to offset pseudobulges, but is instead an expected result arising from the long-known bend in the $M_{sph}{-{\sigma}}$ relation and a log-linear $M_{bh}{-{\sigma}}$ relation.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.62.2-62.2
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• 2011

The correlation between black hole mass and stellar velocity dispersion provides an important clue on the black hole growth and galaxy evolution. In the case of AGN, however, it is extremely difficult to measure stellar velocity dispersions in the optical since AGN continuum dilutes stellar absorption features. In contrast, stellar velocity dispersions of active galaxies can be measured in the near-IR, where AGN-to-star flux ratio is much smaller. Expecting that more stellar velocity dispersion measurements will be available using future near-IR facilities, it is crucial to test whether the stellar velocity dispersions measured from the near-IR spectra are consistent with those measured from the optical spectra. For a sample of 35 nearby galaxies, for which optical stellar velocity dispersion measurements and dynamical black hole masses are available, we obtained high quality H-band spectra, using the TripleSpec at the Palomar 5-m Telescope, in order to calibrate the stellar velocity dispersions and define the $M_{BH}-sigma_*$ relation in the near-IR. Based on the spatially resolved kinematics, we correct for the rotation component and determine the luminosity-weighted stellar velocity dispersion of the spheroid component in each galaxy. In this presentation, we will show the comparison between optical and near-IR stellar velocity dispersion measurements and define the $M_{BH}-sigma_*$ relation based on uniformly measured stellar velocity dispersion in the near-IR.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.47.1-47.1
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• 2012

Given high accretion rates close to the Eddington limit, narrow-line Seyfert 1 galaxies (NLS1) are arguably the most important AGN subclass in investigating the origin of the black hole mass-galaxy stellar velocity dispersion ($M_{BH}-{\sigma}$) relation. Currently, it is highly debated whether NLS1s are offset from the local $M_{BH}-{\sigma}$ relation. The controversy mainly comes from the fact that the [OIII] line width has been used as a proxy for stellar velocity dispersion due to the difficulty of measuring stellar velocity dispersion in NLS1s. Using the SDSS spectra of a sample of 105 NLS1, we performed multi-component fitting analysis to separate stellar absorption lines from strong AGN [FeII] complex in order to directly measure stellar velocity dispersion. We will present the result of decomposition analysis and discuss whether NLS1s follow the same $M_{BH}-{\sigma}$ relation based on the direct measurements of stellar velocity dispersion.