• The Journal of the Petrological Society of Korea
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• v.23 no.4
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• pp.351-366
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• 2014

We assumed the situation where an eruption column had been formed by the explosive Plinian eruption from Mt. Baekdu and that the collapse of eruption column had caused pyroclastic density currents to occur. Based on this assumption, we simulated by using a Titan2D model. To find out about the range of the impacts of pyroclastic density currents by volcanic eruption scenarios, we studied the distance for the range of the impacts by VEIs. To compare the results by each volcanic eruption scenario, we set the location of the vent on the 8-direction flank of the outer rim and on the center of the caldera, the internal friction angle of the pyroclastic density currents as $35^{\circ}$, the bed friction angle as $16^{\circ}$. We set the pile height of column collapse and the vent diameter with various VEIs. We properly assumed the height of the column collapse, the diameter of the vent, the initial rates of the column collapse and the simulation period, based on the VEIs, gravity and the volume of the collapsed volcanic ash. According to the comparative analysis of the simulation results based on the increase of the eruption, the higher VEI by the increase of eruption products, the farther the pyroclastic density currents disperse. To the northwest from the vent on the northeast slope of the outer rim of the caldera, the impact range was 3.3 km, 4.6 km, 13.2 km, 24.0 km, 50.2 km, 83.4 km or more from VEI=2 to VEI=7, respectively. Once the database has been fully constructed, it can be used as a very important material in terms of disaster prevention and emergency management, which aim to minimize human and material damages in the vicinity of Mt. Baekdu when its eruption causes the pyroclastic density currents to occur.

• Journal of the Korean Geotechnical Society
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• v.27 no.6
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• pp.81-95
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• 2011

This study investigates relative density test of standard sand and bottom ash which were devided into No.40, No.60, No.100, No.200 and resonant column tests were conducted for samples with the relative density of 40%, 55%, and 70% on the basis of the test results. Resonant column tests were also conducted for each residual bottom ash which contains the passing sample of No.200 with the relative density of 55%. By compressing each residual sample with the compaction energy of A-compact mold test, the passing percentage of No.200 sieve increased up to 30%, which led to the adjustment of relative density to 10%, 20%, and 30%. Test results show that maximum shear modulus and damping ratio of bottom ash are smaller than those of standard sand because crushing strength and unit weight of the former are smaller than those of the latter.

• Journal of Navigation and Port Research
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• v.29 no.3 s.99
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• pp.263-268
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• 2005

Laboratory evaluation of the effect of fines, confine stress and dry density on the permeability characteristics in sand columns is presented. The triaxial permeability tests were conducted on different contents of fines(5, 15, 25, $35{\%}$), confine stress ($\sigma_3^'=0.5,\;1.0,\;2.0,\;3.0{\cal}kg/{\cal}cm^2$), and dry density($\gamma_d=1.50,\;1.55,\;1.60,\;1.65{\cal}g{\cal}cm^3$). The results of triaxial permeability tests showed that as the contents of fines, confine stress and dry density became increase permeability became decrease. For the contents of fines, when the fines that smaller than $0.01{\cal}mm$ increases the permeability decreases significantly. For the confine stress and the dry density, the permeability is decreased significantly at changes of the confine stress($\sigma_3^'=0.5{\~}1.0{\cal}kg/{\cal}cm^2$) and the dry density($\gamma_d=1.50{\~}1.55{\cal}g/{\cal}cm^3$) at lower levels.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.35.3-35.3
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• 2018

Incorporating the fully quantum mechanical computation of scattering cross-section and statistical moment analysis of absorption profiles, we investigate the Lyman line asymmetry of extremely high column density systems. Recent high redshift observations detected strong damped Lyman alpha systems (DLAs) whose column density is larger than N_HI ~ [10]^21.3 cm^(-2). Absorption profiles of these DLAs are characterized by the broad and asymmetric damping wing. For accurate description of radiation damping, the second-order time-dependent perturbation theory is adopted. To quantitatively address line asymmetry, we define a distribution function for each Lyman line, and compute statistical moments (mean, standard deviation, skewness and kurtosis) regarding column densities N_HI > [10]^18 cm^(-2). In this work, we present statistical properties of the intrinsic line profiles, and compare them with the Lorentzian cases.

• 전기의세계
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• v.31 no.3
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• pp.197-203
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• 1982

The effects on the characteristics of 20-W fluorescent lamp were studied when applying magnetic field to its positive column. First, when the direction of the magnetic field is axial, i.e., along the lamp, if the magnitude of the field is stronger than the critical field, lamp voltage is increased, lamp current decreased, luminous flux increased, starting voltage decreased, as increasing the applied magnetic field. At the magnetic flux density is 130 gauss, luminous flux is increased to about 6 percents and starting voltage is increased to about 45 percents. Second, when the direction of the magnetic field is transverse to the lamp axis, as increasing the applied magnetic field, lamp voltage is increased, lamp current decreased, luminous flux increased and starting voltage is nearly constant, but the rates of increase or decrease of this case is different from those of the first. At the magnetic flux density is 300 gauss, luminous flux is increased about 45 percents. In both cases, electric power dissipated by lamps is the same as that of the lamp which magnetic field is not applied to.

• Journal of The Korean Astronomical Society
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• v.27 no.1
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• pp.1-11
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• 1994

We have observed the emission of $HC_3N$ J=4-3, 5-4,10-9 and 12-11 transitions toward the Sgr B2 central region in an area of $150'\times150'$ with resolutions of 16'-48'. The intensities and central velocities of line profiles show significant variations with positions. In contrast to the intensities of the low J-level transitions which gradually increase from the central source toward the outside region, the $HC_3N$ emission of the high J-level transition become stronger toward 'the central radio continuum source MD5. Systematic change in the radial velocity of each line profile occurs along north-south direction. There are a few peaks in most line profiles, and these indicate that there are multiple velocity components along the line of sight. Distributions of excitation temperature and column density which were estimated from the excitation calculations show the existence of a small $(1\times2pc),\;hot\;(T_{ex}>50K)$ core which contains two temperature peaks at-15' east and north of MD5. The column density of $HC_3N\;is\;(1-3)\times10^{14}cm^{-2}$ Column density at distant position from MD5 is larger than that in the central region. We have deduced that this 'hot-core' has a mass of 105M 0, which is about an order of magnitude larger than those obtained by previous studies.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.797-798
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• 2006

To investigate a arc behavior when the flux density linking arc current is different, two kinds of models having the different flux density with each other are proposed. Calculations of the flux density and the electromagnetic force acting on arc column using finite element method is described in this paper. And, arc behavior photographs by the high speed camera are illustrated at breaking DC 100V, 100A on the resistance load. So, the arc driving forces are compared with according to the arc types.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.3
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• pp.332-337
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• 2018

The Pacific cod Gadus macrocepahlus, lays demersal eggs and the hatching larvae rise toward the surface layer of the ocean to feed. The change in the specific gravity of eggs and larvae was investigated to examine their vertical distribution and movement in the water column. The specific gravities of fertilized eggs and various size classes of larvae were measured using a density gradient apparatus. In total, the instantaneous specific gravity of 146 eggs and 225 larvae were measured. To prevent any disturbance in the gradient water column due to larval movement, 0.004% MS222 was used for anesthesia. Due to their high specific gravity, eggs spawned were deposited over the sea-bed of the spawning ground. The specific gravity of hatching larvae decreased abruptly. However, Pacific cod larvae still had a comparatively high specific gravity at hatching ($1.03655{\pm}0.00146g/cm3$, n=4, mean SL=3.62 mm) and their specific gravities tended to decrease as they grew. The specific gravity stabilized 6 days after hatching ($1.02590{\pm}0.00212g/cm3$, n=15, mean SL=4.67 mm) and the cod larvae were eventually able to float in the water column.

• Structural Engineering and Mechanics
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• v.36 no.5
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• pp.561-573
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• 2010

The potential of the liquid column vibration absorber (LCVA) as a seismic vibration control device for structures has been explored in this paper. In this work, the structure has been modeled as a linear, viscously damped single-degree-of-freedom (SDOF) system. The governing differential equations of motion for the damper liquid and for the coupled structure-LCVA system have been derived from dynamic equilibrium. The nonlinear orifice damping in the LCVA has been linearized by a stochastic equivalent linearization technique. A transfer function formulation for the structure-LCVA system has been presented. The design parameters of the LCVA have been identified and by applying the transfer function formulation the optimum combination of these parameters has been determined to obtain the most efficient control performance of the LCVA in terms of the reduction in the root-mean-square (r.m.s.) displacement response of the structure. The study has been carried out for an example structure subjected to base input characterized by a white noise power spectral density function (PSDF). The sensitivity of the performance of the LCVA to the coefficient of head loss and to the tuning ratio have also been examined and compared with that of the liquid column damper (LCD). Finally, a simulation study has been carried out with a recorded accelerogram, to demonstrate the effectiveness of the LCVA.

• Journal of Life Science
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• v.9 no.1
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• pp.99-105
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• 1999

The aims of this studies were carried out to investigate the antioxidant activity on low density lipoprotein(LDL) using substances extracted from Bacillus sp. RH-5. The antioxidative substances produced extracellular in the culture broth by Bacillius sp. RH-S was obtained by elution of chloroform : methanol from silicagel column (80cm x100cm) chromatography. Band 4 eluted from fraction 3 by TLC was appeared at highest level of antioxidative activity using thiocyanate methed. Band 4 at a concentration of 100 or 200$\mu$g/$m\ell$ inhibited oxidation of LDL induced by the mouse transformed macrophage. According to IR. NMR or GC/MASS, the antioxidant substance was identified as 5-hydroxyindole.