• Structural Monitoring and Maintenance
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• v.4 no.4
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• pp.331-350
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• 2017

Based on the alternative stabilization diagram by varying the time lag parameter in the stochastic subspace identification analysis, this study aims to investigate the measurements from several cases of civil structures for extending the applicability of a recently noticed criterion to ensure stable identification results. Such a criterion demands the time lag parameter to be no less than a critical threshold determined by the ratio of the sampling rate to the fundamental system frequency and is firstly validated for its applications with single measurements from stay cables, bridge decks, and buildings. As for multiple measurements, it is found that the predicted threshold works well for the cases of stay cables and buildings, but makes an evident overestimation for the case of bridge decks. This discrepancy is further explained by the fact that the deck vibrations are induced by multiple excitations independently coming from the passing traffic. The cable vibration signals covering the sensor locations close to both the deck and pylon ends of a cable-stayed bridge provide convincing evidences to testify this important discovery.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.560-570
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• 2015

We present a simulation of a hybrid Reynolds-averaged Navier Stokes / Large Eddy Simulation (RANS/LES) based on detached eddy simulation (DES) for a Burrows and Kurkov supersonic planar mixing experiment. The preliminary simulation results are checked in order to validate the numerical computing capability of the current code. Mesh refinement studies are performed to identify the minimum grid size required to accurately capture the flow physics. A detailed investigation of the turbulence/chemistry interaction is carried out for a nine species 19-step hydrogen-air reaction mechanism. In contrast to the instantaneous value, the simulated time-averaged result inside the reactive shear layer underpredicts the maximum rise in $H_2O$ concentration and total temperature relative to the experimental data. The reason for the discrepancy is described in detail. Combustion parameters such as OH mass fraction, flame index, scalar dissipation rate, and mixture fraction are analyzed in order to study the flame structure.

• Nuclear Engineering and Technology
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• v.33 no.6
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• pp.619-625
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• 2001

An axial-flow-induced vibration model was proposed for a rod supported by two translational springs at both ends. For developing the model, a one-mode approximation was made based on the assumption that the first mode was dominant in vibration behavior of the single span rod. The first natural frequency and mode shape functions for the flow-induced vibration, called the FIV model were derived by using Lagrange＇s method. The vibration displacements at reactor conditions were calculated by the proposed model for the spring-supported rod and by the previous model for the simple-supported(55) rod. As a result, the vibration displacement for the spring-supported rod was larger than that of the 55 rod, and the discrepancy between both displacements became much larger as flow velocity increased. The vibration displacement for the spring-supported rod appeared to decrease with the increase of the spring constant. AS flow velocity increased, the increase rate of vibration displacement was calculated to go linearly up, and that of the rod having the short span length was larger than that of the rod having the long span length although the displacement value itself of the long span rod was larger than that of the short one.

• Journal of the Korean Data and Information Science Society
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• v.24 no.4
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• pp.669-677
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• 2013

Quasi-Monte Carlo method is known to have lower convergence rate than the standard Monte Carlo method. Quasi-Monte Carlo methods are using low discrepancy sequences as quasi-random numbers. They include Halton sequence, Faure sequence, and Sobol sequence. In this article, we compared standard Monte Carlo method, quasi-Monte Carlo methods and three scrambling methods of Owen, Faure-Tezuka, Owen-Faure-Tezuka in valuation of multi-asset European call option through simulations. Moro inversion method is used in generating random numbers from normal distribution. It has been shown that three scrambling methods are superior in estimating option prices regardless of the number of assets, volatility, and correlations between assets. However, there are no big differences between them.

• Journal of The Korean Astronomical Society
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• v.39 no.1
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• pp.19-24
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• 2006

We carried out CO survey toward IR-excess clouds using SRAO 6-m telescope in search of molecular $H_2$. These clouds, which show far-infrared excess over what is expected from HI column density, are considered to be candidates of molecular clouds. In order to find new high Galactic latitude clouds, we made mapping observations for 14 IR-excess clouds selected from Reach et al.(1998) in $^{12}CO$ J = 1 - 0 line, supplementing the similar survey in southern hemisphere (Onishi et al. 2001). $^{12}CO$ emission is detected from three IR-excess clouds among 14 objects. Three newly detected clouds exhibit somewhat clumpy morphology and column densities amount to ${\sim}10^{21}\;cm^{-2}$. One of three clouds, DIR120-28, show discrepancy between IR-excess center and CO emission center. It seems that IR-excess may not be an effective tracer of molecular gas. Instead, optical depth$(\tau)$ excess, i.e., IR-excess corrected for temperature dependence, may be more effective tracer of molecular clouds, since, by combining statistics from both hemispheres, we found that the detection rate is higher for IR-excess clouds with lower dust temperature.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.58-65
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• 1992

In this paper, wave resistance for a submerged body is calculated by a higher order panel method. The Neumann-Kelvin problem is solved by the source or normal dipole distribution method. The body surface is represented by a bicubic B-spline and the singularity strengths are approximated by a bilinear form. The results calculated by the higher order panel method are compared with those by the lowest order panel method developed by Hess & Smith. The convergence rate of the higher order panel method is much better than the lowest order panel method. But the wave resistance calculated by the higher order panel method still shows discrepancy with an analytic solution at low Froude number like that by the lowest order panel method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.1-6
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• 2016

The effect of reducing wave overtopping by use of the wave return wall was quantitatively analyzed based on physical experiments. The overtopping discharge for the arc seawall and the inclined seawall was measured and compared with the predictive formula that estimates reduction of overtopping by the wave return wall. When the overtopping discharge was relatively large ($q/{\sqrt{gH^3_s}}>10^{-3}$), the agreement in terms of overtopping reduction rate was fairly good between the prediction and the measurement. For the condition of smaller overtopping than the above criterion, however, the discrepancy was large between the predicted and measured result. In this context, it is required to develop a better formula for estimating reduction of wave overtopping by the wave return wall.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.191-202
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• 2013

A numerical analysis of thermal stratification in the upper plenum of the MONJU fast breeder reactor was performed. Calculations were performed for a 1/6 simplified model of the MONJU reactor using the commercial code, CFX-13. To better resolve the geometrically complex upper core structure of the MONJU reactor, the porous media approach was adopted for the simulation. First, a steady state solution was obtained and the transient solutions were then obtained for the turbine trip test conducted in December 1995. The time dependent inlet conditions for the mass flow rate and temperature were provided by JAEA. Good agreement with the experimental data was observed for steady state solution. The numerical solution of the transient analysis shows the formation of thermal stratification within the upper plenum of the reactor vessel during the turbine trip test. The temporal variations of temperature were predicted accurately by the present method in the initial rapid coastdown period (~300 seconds). However, transient numerical solutions show a faster thermal mixing than that observed in the experiment after the initial coastdown period. A nearly homogenization of the temperature field in the upper plenum is predicted after about 900 seconds, which is a much shorter-term thermal stratification than the experimental data indicates. This discrepancy may be due to the shortcoming of the turbulence models available in the CFX-13 code for a natural convection flow with thermal stratification.

• Biomolecules & Therapeutics
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• v.7 no.1
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• pp.1-6
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• 1999

Effects of Panax ginseng on the morphine toxicity were studied in relation to its effects on the opioid receptor-G protein interactions. Morphine treatments (3 days) reduced the body weight increment rate and the weight of the thymus and spleen. These changes were usually recovered by the concomitant administration of ginseng total saponin (GTS) but occasionally further deteriorated. This discrepancy was studied in relation to the opioid receptor coupling to G protein, that is, the effects of morphine and GTS on the opioid receptors were studied using the antagonist-agonist competitive binding studies. When GTS recovered the morphine toxicity, morphine shifted the striatal $\delta$ receptors to slightly higher affinity state, and this was partly recovered by the GTS treatment. However, morphine did not have any effect on the affinity state of $\delta$ receptor from NG108-15 cells, suggesting that additional factors were needed for the modulation of the affinity states of $\delta$ receptor. Effects of morphine and GTS on $\mu$ receptor were complicate and variable, and we could not reach a clear conclusion. The morphine toxicity might accompany complicate biological involvements, and the modulation of the affinity states of the opioid receptors might explain a part of the effects of GTS on the morphine toxicity.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.5
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• pp.349-357
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• 2003

Several microvascular anastomotic techniques have been described with methodical effectiveness, patency rates, healing state of microscopic findings. This experimental study presents the comparison of three types of arterial microvascular anastomotic techniques: end-to-end(ETE) anastomosis, end-in-end(EIE) anastomosis, and continuous technique. Sixty male Sprague-Dawley rats, 60 femoral arteries were used for this study. Twenty rats per each technique were used and sacrificed at post-operation 1 day, 3 days, a week, 2 weeks for scanning electromicroscopic findings. The patency was monitored by miniDoppler throughout total experimental periods. The anastomotic time on each method was measured to compare the technical effectiveness. The final results were as follows: 1. The anastomotic time for the end-in-end technique was significantly shorter than another techniques. The average time for each technique was measured as 15 minutes on EIE technique, 20 minutes on continuous technique and 25 minutes on ETE technique. 2. The patency rate for the end-in-end technique at 2 weeks also was superior to another techniques. The patency rate for each technique was demonstrated as 90 % on EIE technique, 85 % on ETE technique and 80 % on continuous technique. 3. The scanning electromicroscopic findings on healing condition of vessel endothelium during the observation period showed that the end results of EIE technique, ETE technique and continuous technique in sequence were good. The end-in-end technique proved to be the superior with regard to anastomotic time and patency rate when compared to end-to-end technuqe, so EIE techniqe might be well available for the case of large discrepancy of vessel size. The patency rate, microscopic healing findings in continuous technique were seen as the lowest level among the three anastomotic techniques, therefore the application of continuous technique was recommended only on the inevitable case.