• Geomechanics and Engineering
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• v.11 no.5
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• pp.725-738
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• 2016

A theoretical study of the behavior of structured soils is presented herein. By introducing the effect of soil structure and loading history into the Cam Clay model, a new model was formulated. The concept of differing void ratios was modified to combine structural parameters and the over consolidation ratio, and an evolution law was proposed. Upon introducing the concept of the subloading yield surface, a new two-yield surface model was obtained. The predicted results were compared to the experimental data, demonstrating that the new model provided satisfactory qualitative modeling of many important features of structured soils.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.686-693
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• 2016

The analytical expressions for a partially coherent flat-topped vortex hollow beam propagating in uniaxial crystals orthogonal to the optical axis are derived, and the intensity and coherent vortex properties of partially coherent flat-topped vortex hollow beam propagation in uniaxial crystals orthogonal to the optical axis are analyzed by numerical examples. The influence of beam order parameter N, topological charge M, the coherence length and the ratio of refractive indices $n_e/n_o$ of uniaxial crystals on the normalized intensity distribution and coherent vortex of a partially coherent flat-topped vortex hollow beam propagating in uniaxial crystals are discussed in detail.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.247-249
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• 2015

We review recent results on superhump period variations in SU UMa-type dwarf novae. Our statistical studies have revealed that the evolution of the superhump period is basically composed of three stages: stage-A, during which the superhump period is long and constant, stage-B, during which the superhump period increases as the superoutburst proceeds, and stage-C, during which the superhump period is short and constant. We also introduce a new method of estimating a mass ratio using the stage-A superhump period. This method can extend to, for example, low mass X-ray binaries or AM CVn stars if the stage-A superhump period is well determined.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.121-146
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• 2000

A novel system of magneto-optical microscope magnetometer (MOMM), capable of simultaneous local problems of magnetic properties as well as real-time magnetic domain evolution imaging of ferromagnetic thin films with 400-nm spatial resolution, New findings in domain reveral dynamics of Co-based multilayers: The reversal ratio of V/R is a governing physical parameter. The activation volumes of wall-motion and nucleation processes are generally unequal. Submicron-scale local coercivity variation determines domain reversal dynamics. A thermally activated relaxation process during domain reversal is existed on the submicron-scale in realistic films. Local variation of magnetic properties should be considered for a realistic simulation. The fantastic capabilities of the MOMM can open many possibilities to broaden and deepen our understanding of domain reversal phenomena in ferromagnetic thin films.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.1
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• pp.62-66
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• 2015

In this paper, a fretting testing machine is developed using ball-on-flat test apparatus. Precise micro-slip motion is produced by a linear stage. A relative displacement between a ball and a flat specimen is measured with a laser displacement sensor. Dry friction tests are conducted with AISI 52100 steel balls and cold-rolled high strength steel plates at room temperature and ambient humidity. The evolution of the kinetic friction coefficient is determined. Comparison between measured friction coefficients and those found in the literature is then carried out. Fretting tests with an electro-deposited coating are employed at an amplitude of 0.05 mm. Slip regime is identified with slip ratio. It is demonstrated that a developed testing machine allows determining the friction coefficient under fretting condition.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.52.2-52.2
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• 2011

The correlation between black hole mass and galaxy stellar velocity dispersion gives 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 spectra 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, particularly with the laser-guide-star adaptive optics. However, it is crucial to test whether the stellar velocity dispersion measured from the near-IR spectra is consistent with that measured from the optical spectra. Using the TripleSpec at the Palomar 5-m Telescope, we obtained high quality spectra ranging from 1 to 2.4 micron for a sample of 35 nearby galaxies, for which dynamical black hole masses and optical stellar velocity dispersion measurements are available, in order to calibrate the stellar velocity dispersion in the near-IR. In this poster, we present the initial results based on 10 galaxies, with the stellar velocity dispersion measured in the H-band.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.464-467
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• 1996

The microstructural evolution during mechanical alloying of Nb and Sn powders, of average composition Nb3Sn, has been investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). Observations by SEM showed a progressive change of milling time. From the XRD studies, the structural development with milling time depends on the ball size for a given powder/ball ratio. Using a larger ball of 9.5mm diameter, the elemental powders initially alloy mechanically to form an A15 structure phase, and then amorphised with continued milling. However, in case of milling with a smaller ball of 3.968mm diameter, an amorphous phase is first formed. These results can be understood by considering the dependence of the milling energy on the ball size. The homogeneous stoichiometric $Nb_3Sn$ phase could be easily obtained by heat treatment of a supersaturated solid solution produced by MA. Heat treatment of an amorphous phase formed by MA resulted in the mixture of the $Nb_3Sn$ and $Nb_6Sn_5$ phases.

• Animal Systematics, Evolution and Diversity
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• v.34 no.4
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• pp.181-189
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• 2018

Cephalobus aff. quinilineatus (Shavrov, 1968) Anderson and Hooper, 1970 and Eucephalobus hooperi MarinariPalmisano, 1967 from the family Cephalobidae Filipjev, 1934 (Cephalobomorpha) are newly reported from South Korea. Cephalobus aff. quinilineatus is distinguished from other Cephalobus species by its high and rounded labial probolae and five lateral incisures, with three incisures extending to the tail terminus. Eucephalobus hooperi is distinguished from other Eucephalobus species by its three bifurcated labial probolae with pointed termini and by morphometric characters such as body and tail length and the corpus:isthmus ratio. In this study, the morphological characters and morphometrics of C. aff. quinilineatus and E. hooperi Korean population are described and illustrated based on optical and/or scanning electron microscopy.

• Animal Systematics, Evolution and Diversity
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• v.25 no.1
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• pp.41-47
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• 2009

Two ciliate species of Blepharisma were collected from the riverine wetland and mountain peak soil in Korea, Blepharisma undulans Stein, 1867 and B. steini Kahl, 1932, which are reported for the first time from Korea. The description was based on the observations of live and protargol impregnation specimens. Diagnostics of these species (Blepharisma undulans vs. B. steini) are as follows. Body length/width ratio in vivo about 6/1 vs. 2/1, shaped in spindle vs. pyriform to ellipsoid and colored in pinkish vs. reddish. Macronuclei 2 vs. 1, with 4-9 vs. 4-7 spherical micronuclei. Adoral zone of membranelles extends from anterior end to 1/3 vs. 1/2-2/3 of body length, with 47-56 vs. 33-45 adoral membranelles. The numbers of somatic kineties are 22-27 vs. 18-22.

• Advances in materials Research
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• v.8 no.1
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• pp.1-10
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• 2019

Roll bonding (RB) process of bi-metal laminates as a new noble method of bonding has been widely used in the production of bimetal laminates. In the present study, asymmetric roll bonding process as a new noble method has been presented to produce Al/Cu bimetallic laminates with the thickness reduction ratios 10%, 20% and 30% together with mismatch rolling diameter ($\frac{R_2}{R_1}$) ratio 1:1, 1:1.1 and 1:1.2. ABAQUS as a finite element simulation software was used to model the deformation of samples. The main attention in this study focuses on the bonding properties of Al/Cu samples. The effect of the $\frac{R_2}{R_1}$ ratios was investigated to improve the bond strength. During the simulation, for samples produced with $\frac{R_2}{R_1}=1:1.2$, the vertical plastic strain of samples was reach the maximum value with a high quality bond. Moreover, the peeling surface of samples after the peeling test was investigated by the scanning electron microscopy (SEM).