• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.100-109
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• 2006

This study evaluated the effects of water velocity, substrates, and phosphorus concentrations on the growth of filamentous periphytic algae (FPA) in the two types of artificial channel systems using treated wastewater. Controlled parameters included 5 ${\sim}$ 15 cm $s^{-1}$ for the water velocity; 10 and 20 mm wire meshes, natural fiber net, gravel and tile for the substrates: and 0.05 ${\sim}$ 1.0 mgP $L^{-1}$ for the P concentration. Algal growth rate of FPA was compared using both chi. a and dry weight change with time. Under the controlled water velocity range, the growth of FPA increased with the velocity, but the maximum growth rate was shown in the velocity of 10 cm $s^{-1}$. The substrate that showed the maximum growth of FPA differed between the artificial channel and indoor channel, due to the influence of suspended matters which caused the clogging of the meshed substrates. Under the controled range of P concentration, the growth rates of all three FPA species (Spirogyra turfosa, Oedogonium fovelatum, Rhizoclonium riparium) increased with the P increase, but they showed the differential growth rates among different P concentrations. The results of this study suggest that under the circumstance having an large amount of nutrients FPA develop the biomass rapidly and that even a little increase over the threshold velocity causes the detachment of filamentous periphytic algae. Thus, FPA dynamics in eutrophic streams, such as those receiving treated wastewater, seem to be sensitive to the water velocity. On the other hand, detached algal filaments could deteriorate water quality and ecosystem function in receiving streams or down-stream, and thus they need to be recognized as an important factor in water quality management in eutrophic streams.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.1
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• pp.12-19
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• 2001

Study of turbulent mixing layers has been a popular subject from the point of view of both practical application and phenomenological importance in engineering field. Turbulent mixing layers can be applied in many fields where rapid transition to turbulence is desirable in order to prevent boundary layer separation or to enhance mixing. The ability to control mixing, structure and growth of the shear flow would obviously have a considerable impact on many engineering applications. In addition to practical applications, free shear flows are one of the simplest flows to understand the fundamental mechanism in the transition process to turbulence. After the discovery of large-scale vortical structure in free shear flows many researchers have investigated the physical mechanism of generation and dissipation processes of the vortical structure. This study investigated the role of the large-scale vortical structures in the turbulent mixing layer using LES(Large-Eddy Simulation). The result shows that the pairing interaction of the vortical structure plays an important role in the growth rate of a mixing layer. It is found that the turbulence quantities depend strongly on the velocity ratio. It is also found that the vorticity in the high-velocity-side can extract energy from the mean flow, while the vorticity in the low-velocity-side lose energy by the viscous dissipation. Finally the results suggest the guideline to obtain the desired flow by control of the velocity ratio.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.122-124
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• 2008

The partial phase diagram of $NaNO_3$-NaCl system was investigated and the eutectic temperature was determined as $294.5^{\circ}C$. A typical rod eutectics of $NaNO_3$-4.56 wt%NaCl was directionally solidified. The results of interrod spacing, ${\lambda}_E$ as a function of growth velocity, V, were. obtained as ${\lambda}_E\;V^{0.39}\;=\;5.26$ (temperature gradient, $G_l\;=\;21.4^{\circ}C/mm$) and ${\lambda}_E\;V^{0.32}\;=\;5.45$ ($G_l\;=\;3.9^{\circ}C/mm$) and the exponent numbers of growth velocity were smaller than the theoretical value, 1/2. The sample rotation applied during directional solidification made the interrod spacing decrease slightly.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.379-384
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• 1997

Al-15Cu-lMg alloys have been directionally solidified in 3mm diameter alumina tubes under the conditions of $760^{\circ}C$ of furnace temperature and 12 cm/hr of furnace moving velocity(V). By analyzing the evolution of the temperature profiles along the alloy length, the position of the solid/liquid interface, temperature gradient(G) and local growth velocity (R) were determined. These growth characteristics were compared for 6, 10, 14 cm length alloys. Steady state growth region was obtained in 15 cm length alloy, not in 6, 10 cm.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3322-3333
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• 1996

A numerical analysis has been conducted to investigate a modified floating-zone crystal growth process in which most of the melt surface is covered with a heated ring. The crystal rod is not only pulled downward but rotated around its axisymmetric line during crystal growth process in order to produce the flat interface of crystal growth and the single crystal growth of NaNO3 is considered in 6mm diameter. The present study is made from a full-equation-based analysis considering a pulling velocity in all of solid and liquid domains and both of solid-liquid interfaces are tracked simultaneously with a governing equation in each domain. Numerical results are mainly presented for the comparison of the surface shape of rotational crystal rod with that of no-rotational crystal rod and the effects of revolution speeds of the crystal rod. Results show that the rotation of crystal rod produces more its flat surface. In addition, the shape of crystal growth near the centerline is more concaved with the increase in the revolution speed of crystal rod. The flow pattern and temperature distribution is analyzed and presented in each case. As the pulling velocity of crystal rod is increasing, the free surface of the melt below the heated ring is enlarged due to the crystal interface migrating downward.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.8
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• pp.1519-1529
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• 1992

A stepped specimen which is subjected to step loading is modeled to study the initiation and growth of adiabatic shear band using explicit time integration finite element code. The material model for specimen includes effects of thermal softening, strain hardening and strain rate hardening. Various mesh sizes are tested to check whether they are small enough to model highly localized discontinuous phenomena reasonably well. It is shown that the number of adiabatic shear band depends on impact velocity and it is also shown that the initiation and growth of adiabatic shear band inversely depends on prescribed velocity at the top of specimen.

• Korean Journal of Health Education and Promotion
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• v.6 no.1
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• pp.75-90
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• 1989

This study tries to show the physical growth patterns and various adolescent characteristics by using longitudinal data for the height, weight, chest girth and sitting height of 1, 132 high school students in Seoul. And this study also tries to show what influencing factors on the physical growth of this aged population. The followings are the results. 1. The boys have their peak velocity of height when they are 12~13 years old. And the girls have when they are 10~11 years old. Peak velocity of weight for boys is at the age of 13~14. And for girls is at the age ofr11~12. Peak velocity of chest girth for boys is at the age of 12~13. And for girls is at the age of 11~12. Peak velocity of sitting height for boys is at the age of 13~14. And for girls is at the age of 11~13. So girls of this period grow more rapidly by around two years than boys. 2. The menarche of girls begins at the age of 12.4. So it begins 1.4 year before peak height velocity period. 3. Of life behavior boys contingency coefficient between essential time and height and weight is .5150 and .479 5, that between studying time and height and weight is .3344 and and .2912(In case of girls is .4735, .4321, .3247, .3134).

• Journal of Ocean Engineering and Technology
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• v.12 no.2 s.28
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• pp.111-120
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• 1998

Laboratory settling experiments (column, recirculating flume) were conducted for further understanding of the physical processes of cohesive sediment transport. \In still water experiments, the growth rate of flocculation is dependent upon the initial suspended concentration. Consequently, the settling velocity increases with concentration of flees. In flocculation settling regime, the exponent n in the settling velocity, $w_s=kC^n$, for Nakdong estuary mud was obtained empirically. The exponents were found to be 1.33, and 1.06 for the initial suspended concentrations of 1 g/i and 3 g/t, respectively. In flowing water, experiments for the median settling velocity with Nakdong mud in a recirculating flume were conducted. Settling velocity was found to depend much more strongly on the current velocity than initial concentrations. The temporal variation of suspended concentration increases as current velocity decreases.

• Korean Journal of Crystallography
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• v.5 no.2
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• pp.93-99
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• 1994

Growth form and surface morphology of NYAB single crystal grown by TSSG technique using a K2O/3MoOS/0.5B203 flux was investigated. In the crystal grown from <100> or <120> seed, prismatic and (101) faces were well developed with different size each other. (001) face was also developed in the crystal grown from <001> seed. While growth hillocks were observed on the prismatic face of the crystal grown from <100> seed, surface striations parallel to neighbor (101) faces were formed on that face of the crystal grown from <001> seed. The (101) faces were grown by two dimensional nucleation growth. (001) face which was developed at slow growth velocity of [001] direction was grown by screw dislocation Anisotropy of growth velocity as to seed orientation affected on crystal morphology and surface morphology.