• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.105-110
• /
• 2008

The behaviour of an unsaturated soil was analyzed by performing $K_0$ consolidated triaxial tests. Unsaturated triaxial tests were performed with matric suctions for weathered soils and could catch stress paths under consolidation and stress-strain relationships under shear. As a result, both isotropic and $K_0$ conditions had similar shear strength envelopes in the same matric suction. Especially, strength parameters could obtain by stress variables based on critical state theory reasonably which was better than those by Mohr circles at failure.

• The Bulletin of The Korean Astronomical Society
• /
• v.39 no.2
• /
• pp.112.2-112.2
• /
• 2014

We propose simultaneous monitoring observations of 22 GHz $H_2O$ and 43/86/129 GHz SiO masers toward ~15 evolved stars in order to investigate spatial structure and dynamical effect from SiO to $H_2O$ maser regions including mass-loss process and development of asymmetry in circumstellar envelopes. We also aim at investigating mutual association and difference between SiO and $H_2O$ masers for establishing SiO and $H_2O$ maser models coupled to hydrodynamical model of circumstellar envelope. In addition, the correlation and difference of SiO maser properties among J=1-0, J=2-1, and J=3-2 transition masers are traced according to different type of stars for constraining SiO pumping models. These scientific goals and target sources were determined based on KVN single dish and VLBI feasibility test observations at 4 bands. As a total observing time of every 2 month monitoring, about 90 and 360 hours (in average per year) are required for single dish and VLBI observations, respectively. From the 2014B observing season, these monitoring observations will be derived as one of KVN key science programs.

• International Journal of Concrete Structures and Materials
• /
• v.10 no.3
• /
• pp.355-371
• /
• 2016

In this study seismic performance of reinforced concrete staggered wall system structures were investigated and their behavior factors such as overstrength factors, ductility factors, and the response modification factors were evaluated from the overstrength and ductility factors. To this end, 5, 9, 15, and 25-story staggered wall system (SWS) structures were designed and were analyzed by nonlinear static and dynamic analyses to obtain their nonlinear force-displacement relationships. The response modification factors were computed based on the overstrength and the ductility capacities obtained from capacity envelopes. The analysis results showed that the 5- and 9-story SWS structures failed due to yielding of columns and walls located in the lower stories, whereas in the 15- and 25-story structures plastic hinges were more widely distributed throughout the stories. The computed response modification factors increased as the number of stories decreased, and the mean value turned out to be larger than the value specified in the design code.

• Journal of The Korean Astronomical Society
• /
• v.29 no.spc1
• /
• pp.257-258
• /
• 1996

1607 OH/IR stars associated with IRAS sources are assembled and the IRAS LRS spectra of 980 OH/IR stars are examined in this paper. The nature of the circumstellar dust for these sources is classified. The distributions of these subgroups of OH/IR stars in the IRAS color-color diagram and the period-color diagram are interpreted with their evolutionary status. The Galactic and the velocity distributions of these subgroups of OH/IR stars are also presented. The correlations among the expanding velocities of the envelopes, colors, periods and the pumping efficiencies for subgroups of OH/IR stars are investigated to outline the evolutionary status of OH/IR stars.

• Journal of The Korean Astronomical Society
• /
• v.29 no.spc1
• /
• pp.259-259
• /
• 1996

Circumstellar peculiarities of the young Herbig Ae/Be stars are analyzed using high-resolution CCD spectroscopic data, obtained in 1991-1996 at the ESO and the Crimean Astrophysical Observatory (about 450 spectrograms). The results of investigation of the rapid line variability in H$\alpha$, H$\beta$, HeI 5876 and DNaI lines are presented for AB Am, HD 163296, HD 36112, HD 100546, and HD 50138. We conclude that the behaviour of these lines can be explained in the framework of the model containing an equatorially concentrated and azimuthally inhomogeneous stellar wind, and an external cool shell that occasionally looses matter in form of infall onto the star.

• 한국전산유체공학회:학술대회논문집
• /
• 2007.10a
• /
• pp.157-161
• /
• 2007

The prediction of the safe separation of the external stores carried on military aircraft is an important task in the aerodynamic design area having the objective to define the operational, release envelopes. The major concern of this study is only safe jettison problem with ejections. This work consists of concept and some results for external store configurations. A Computational Fluid Dynamics technique is applied to calculate the aerodynamic forces. The FLUENT with an implicit Euler solver is used for the present simulations. The computational results are validated against the experimental data.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03a
• /
• pp.374-377
• /
• 2008

The prediction of the separation trajectories of the external stores released from a military aircraft is an important task in the aircraft design area having the objective to define the operational and release envelopes. This paper presents the results obtained for store separation by employing commercial sorftwares, FLUENT and CFD-FASTRAN. FLUENT treats the rigid body motion by employing the remeshing scheme. CFD-FASTRAN uses the chimera(overset) grid and interpolations. It was found that, for the prediction of the trajectories and behavior of the stores separated from the wing, both codes shows the good agreement with the experimental results.

• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.178-188
• /
• 2003

The wear of steam generator tubes is due to the vibration occurred between tubes and tube supporters. To predict the future wear depth, the wear constants of the impact and the sliding model is used. The wear constants, 3C/2 and K/3H, are found inversely from known wear depth and time. Using these constants, the future wear depths are found from two bodies that deform the elliptical shape. The results are compared with the measured wear depth of steam generator tubes in a nuclear power plant. The results show that the predicted wear depth envelopes the measured wear depth.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.10a
• /
• pp.374-377
• /
• 2008

The prediction of the separation trajectories of the external stores released from a military aircraft is an important task in the aircraft design area having the objective to define the operational and release envelopes. This paper presents the results obtained for store separation by employing commercial sorftwares, FLUENT and CFD-FASTRAN. FLUENT treats the rigid body motion by employing the remeshing scheme. CFD-FASTRAN uses the chimera(overset) grid and interpolations. It was found that, for the prediction of the trajectories and behavior of the stores separated from the wing, both codes shows the good agreement with the experimental results.

• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.763-766
• /
• 2002

A BEM is highly efficient method in the sense of economic computation. However, boundary integration is not easy for the complex and moving surface e.g. in a rotating blade. Thus, Kirchhoff surface is designed in an effort to overcome the difficulty resulting from complex boundary conditions. A Kirchhoff surface is a fictitious surface which envelopes acoustic sources of main concern. Acoustic sources may be distributed on each Kirchhoff surface element depending on its acoustic characteristics. In this study, an axial fan is assumed to have loading noise as a dominant source. Dipole sources can be computed based on the FW-H equation. Acoustic field is then computed by changing Kirchhoff surface on which near-field is implemented, to analyze the effect of Kirchhoff surface on it.