• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.999-1008
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• 2009

A series of sedimentary rocks which are formed in the Tertiary are distributed around Samcheok(Samcheok-Pukpyoung basin), Younghae(Younghae basin), Pohang(Pohang basin), Gyeongju(Yangnam basin), Ulsan(Ulsan basin), Jeju(Seogyuipo formation) in the southern region of the Korean Peninsula. This study concerned with geological, geophysical, geotechnical properties of the unconsolidated rocks in the Pohang area. A consolidated rocks are classified as hard rock - soft rock - weathered rock - residual soil follows in degree of weathering. But unconsolidated rocks has soil properties as well as rock's at the same time. The results of field excursion, boring, borehole-logging, rock testing, geophysical survey, laboratory test are soft rock range, but the durability of the rock until the residual soil from the weathered rock. We accomplished the rock mass classification of the unconsolidated rocks.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.04a
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• pp.165-172
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• 1996

Recently, the response of a high-rise building to external dynamic force created by wind and earthquake has received much attention. This response is dependent on wind intensity, surrounding environment, building size, shape, mass, stiffness and amount of energy dissipation available in the system. The study has been done on these parameters. Attempts have been made to increase the damping in building system and thereby reduce structural response. These attempts have centered on adding an energy-dissipative system(passive tuned mass damper; passive TMD) to the building system and increasing the overall effective damping. In this paper the optimum condition of passive TMD will be derived with respect to random excitation and the properties of the optimum condition will have been studied.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1546-1551
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• 2004

This paper presents a mathematical model to predict the frost properties and heal and mass transfer within the frost layer formed on a cold plate. The laminar flow equations for the air-side are analyzed. and the empirical correlations of local frost properties are employed in order to predict the frost layer growth. The correlations of local frost density and effective thermal conductivity of frost layer, obtained from various experimental conditions, are derived as functions of various frosting parameters (Reynolds number, frost surface temperature, absolute humidity and temperature of moist air, cooling plate temperature, and frost density). The numerical results are compared with experimental data and the results of various models to validate the present model, and agree well with experimental data within a maximum error of 10%. The heat and mass transfer coefficients obtained from the numerical analyses are presented, as the results, it is found that the model for frost growth using the correlation of heat transfer coefficient without solving air flow have a limitation in its application.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.1
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• pp.10-15
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• 2011

Recently, renewable energy sources such as wind turbine, solar cell are interested in preventing global warming which is caused by the consumption of fossil fuel. SCM440(H) and SNCM439 have been used in the major components of the wind turbine gear because of excellent mechanical properties. In the present study, the heat treated mechanical properties of SCM440(H) and SNCM439 with 150 mm diameter were compared with those with 25 mm diameter which is generally accepted material for structural application. Heat treated SCM440(H) showed better mechanical properties such as tensile strength, hardness and impact absorbed energy compared with those in SNCM439. Hardenss value between as-quenched and as-quenched followed by tempering showed big difference in SNCM439, however the difference in SCM440(H) was relatively small. Heat treated mechanical properties of the alloys with 25 mm diameter were more uniform value than those with 150 mm diameter.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.42.1-42.1
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• 2017

We investigate the evolutionary properties of red supergiant stars (RSGs), using stellar evolution model of Modules for Experiments in Stellar Astrophysics (MESA). In this study, we calculate models with mass range of 9-39M_sun and several different convection parameters (e.g. mixing length, overshooting, and semiconvection) at SMC, LMC, Milky Way, and M31 metallicities. We compare the calculated evolutionary tracks with observed RSGs in SMC, LMC, Milky Way and M31, and discuss appropriate input physical parameters in model calculation. We find that a larger mixing length parameter is necessary for M31 metallicity to fit the positions of RSGs in H-R diagram, compared to lower metallicity environments. Theoretically predicted numbers of yellow supergiant stars (YSGs) are also compared with the observed population. We find that Ledoux models with semiconvection can better explain the number of YSGs. Finally, we investigate the final radius, final star mass, and final hydrogen envelope mass of RSGs and discussed the their properties as type II-P supernova progenitors.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.675-681
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• 2014

The purpose of this study is to analyze fundamental combustion characteristics of woods used for indoor applications. The combustion characteristics such as heat release rate, total heat release, gas yield, and mass loss were analyzed by the method of cone calorimeter or thermogravimetry. These analysis results show that material properties of wood are closely related to flammability. It was shown that the relationship between the mass loss and gas emission. The results of combustion properties of woods would be useful for fundamentals of guiding the safe use of wood indoor application.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.29.2-29.2
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• 2011

Although stellar flares have a long history of observations, there are few concrete understanding about underlying physical processes and meaningful correlations with other stellar properties. Most of previous observations dealt with only a small number of sample stars, and therefore not sufficient to support generalized statistical studies. Based on one-month long MMT time-series observations of the open cluster M37, we monitored light variations of nearly 2,500 M-dwarf stars and successfully identified 606 flare events from 422 stars. This is a rare attempt to estimate true flare rates and properties among many stars of the same age and mass group. For each flare, we considered both observational and physical parameters including flare shape, duration before and after the peak, baseline magnitude before and after the peak, peak magnitudes, total energy and peak energy, etc. We find significant correlations between some of key parameters over a wide range of energy ($Er=10^{32}{\sim}10^{36}ergs$). For instance, regardless of stellar luminosities, the energy power spectrum of flares can be approximated by a power law (${\beta}=0.83-0.97$). This suggests that flares follow similar physical mechanisms for atmospheric heating and cooling among these low-mass stars. From this MMT data set, we derived an average flaring rate of $0.019 hr^{-1}$ among flare stars and $0.003 hr^{-1}$ for all M-dwarf candidates. We will report the details of our analysis and discuss physical implications.

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.31-40
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• 1999

With a total 761 contact binary systems in Svechnikov & Kuznetsova(1990)'s catalogue, their physical properties by the mass ratio are investigated - for the early CE type with a common radiative envelope and the late CW type with a common convective envelope. It is found that the early CE type shows a higher temperature difference($\mid$$DeltaT$$\mid$) between the primary and secondary components, and also longer period, than the late CW type. The mass ratio of the CW type are distributed in period, than the late CW type. The mass ratio of the CW type are distributed in smaller ranges, from 0.3 to 0.7, than the CE type. Further, the relation between mass ratio and luminosity for the CW type shows a well-defined linear relation, such as ratio and luminosity for the CW type shows a well-defined linear relation, such as $L_2/L_1$ = 0.01 = 0.89q. In the mass ratio-radii relation, it is confirmed that the physical difference of the CE and CW types is a result of the secondary radius. A new mass ratio-radii relation for the CW type is suggested for both the total radius $({gamma}_1/{gamma}_2$ and the radius ratio $({gamma}_2/{gamma}_1$, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.32.2-32.2
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• 2013

We examine large-scale environmental effects on the formation and the mass growth of dark matter halos. To facilitate this, we constructed dark matter halo merger trees from a cosmological N-body simulation, which enabled us to trace the merger information and the assembly history of individual halos. In fact, since the massive halos are more likely to be distributed in denser regions than in less dense regions (Mo & White, 1996), the large-scale environment dependence of the properties of halos can be partly originated from the halo mass effect. In order to avoid such contamination, caused by the mass dependence of halo properties, we carefully measured the local overdensity as the indicator of large-scale environment, which was calculated to be as independent of halo mass as possible. Small halos (${\sim}10^{11-12}M_{\odot}$), which usually host isolated single galaxies, show a notable difference on the formation time of galaxies depending on their large-scale environments, which reconfirms halo assembly bias (Gao & White, 2007). Furthermore, we investigate how this environmental effect on small halos is correlated with the mass assembly history of galaxies by using our semi-analytic model. We found that assembly bias in small halos does not have significant effects on the formation time or on the star formation history of galaxies residing in those halos except for the individual stellar mass of galaxies at z = 0. On average, isolated galaxies in high-density regions tend to be slightly more massive than those in low-density regions. Although the observational data from the current galaxy surveys is not yet sufficient for testing this prediction, future galaxy surveys will be able to explore these small galaxies more thoroughly.

• Geomechanics and Engineering
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• v.6 no.6
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• pp.517-530
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• 2014

Seismic ground response analysis is one of the most important issues in geotechnical earthquake engineering. Conventional seismic site response and free field analysis of layered soils does not consider the effect of surcharge mass which may be present on the top layer. Surcharge mass may develop extra inertial force to the soil and, hence, significantly affect on the results of seismic ground response analysis. Methods of analysis of ground response may also be categorized into time domain and frequency domain concepts. Simplicity in developing analytical relations and accuracy in considering soil dynamic properties dependency to loading frequency are benefits of frequency domain analysis. In this part of the paper, seismic ground response is analyzed using transfer function method for soil layers considering surcharge mass on the top layer. Equation of motion, wave equation, is solved using amended boundary conditions which effectively take the impact of surcharge mass into account. A computer program is developed by MATLAB software based on the solution method developed for wave equation. Layered soils subjected to earthquake loading were numerically studied and solved especially by the computer program developed in this research. Results obtained were compared with those given by DEEP SOIL computer program. Such comparison showed the accuracy of the program developed in this study. Also in this part, the effects of geometrical and mechanical properties of soil layers and especially the impact of surcharge mass on transfer function are investigated using the current approach and the program developed. The efficiency and accuracy of the method developed here is shown through some worked examples and through comparison of the results obtained here with those given by other approaches. Discussions on the results obtained are presented throughout in this part.