• Korean Chemical Engineering Research
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• v.58 no.3
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• pp.480-485
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• 2020

The extended Maxwell-Wagner polarization model is employed to describe the ER behavior of the conducting particle ER suspensions, and solutions to the equation of motion are obtained by dynamic simulation. The simulation results show the nonlinear ER behavior (Δτ∝Eⁿ, n≈1.5) of the conducting particle ER suspensions. The response point, where shear stress reaches steady-state, is the point where stable break-up and rebuild of the chain-like structure of particles reaches. Also, it shows the minimum of shear stress, which corresponds the start-up of random particle configuration. The shear stress reaches plateau as particle volume fraction increases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.113-116
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• 2008

Pseudo-3D Spatial distribution of spray droplets is investigated by using Dual-mode Phase Doppler Anemometry (DPDA) in order to examine the disintegration and spreading behavior of spray exiting from liquid-thruster injector. Spray injected from nozzle orifice with length-to-diameter ratio $(L/d_o)$ of 1.67 and at the injection pressure of 27.6 bar is aligned to the vertical. Vertical and horizontal mean velocities of droplets, Arithmetic Mean Diameter (AMD), Sauter Mean Diameter (SMD), and volumetric flux decrease as droplets travel from center/upstream toward outer region/downstream of spray.

• Korean Chemical Engineering Research
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• v.58 no.4
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• pp.665-674
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• 2020

Low-frequency pressure fluctuations in an external-loop airlift reactor were investigated. Low-frequency pressure fluctuations could be measured by shooting videos about liquid levels in the four piezometric tubes which were installed at the lower and upper parts of the riser and downcomer using a cellular phone. The periodic characteristics of pressure fluctuations were proved by the calculation of their auto-correlation function and cross-correlation function. Even if the riser superficial gas velocity was constant, the riser and downcomer gas holdups as well as wall pressures were periodically changed due to the inertia of circulating liquid. In general, the intensity of pressure fluctuations increased with an increase in the gas velocity. When the unaerated liquid height was 0.04 m, the maximum period of pressure fluctuations was found at the specific gas velocity (0.14 ms^-1). It was because the maximum inertia of circulating liquid resulted from a reduction in the increasing rate of the liquid circulation velocity and a decrease in the volume of the effectively circulating liquid with an increase in the gas velocity.

• Journal of Mushroom
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• v.9 no.2
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• pp.80-83
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• 2011

Sparassis crispa(Cauliflower mushroom) was an edible mushroom that shows remarkably high contents of ${\beta}$-glucan compared to other edible mushroom. In this study, we aimed to select suitable conditions and materials for mycelial growth and fruit body production. The longer saccharification time of barely result in higher sugar content for eight hours. The optimal sugar content of media for mycelial growth was showed at level of 6 $^{\circ}Brix$. Optimum temperature and pH for mycelial growth in liquid spawn were $25^{\circ}C$ and pH 5.0~6.0, respectively. In case of sawdust was used Larix kaempferi as main material, the fruit body yield and cultivation period of supplemented with 10% wheat flour and 20% corn flour were highest and fastest, respectively.

• Korean Journal of Plant Resources
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• v.15 no.3
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• pp.221-226
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• 2002

This experiment was conducted to establish the mass propagation system of Calanthe discolor Lindley. When the Calanthe discolor seeds were sown in Murashige and Skoog medium, the percentage of germination was 65％. Seedlings grew more rapidly in the liquid medium than the solid medium. All regenerated plantlets were survived in acclimatized condition of 70% shade and more than 80％ humidity. Also, we found out that the 88% of survival ratio could be achieved in containing soil mixture of vermiculite and perlite as same as amount.

• Journal of the Korean Electrochemical Society
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• v.14 no.1
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• pp.1-8
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• 2011

Ionic liquids are room-temperature molten salts, composed of organic mostly of organic ions that may undergo almost unlimited structural variation. We approach the new aspects of ionic liquids in applications where the semiconductor nanoparticles used as sensitizers of solar cells. We studied the effects of ionic liquids as capping ligand and/or solvent, on the morphology and phase of the CdSe/ZnS nanoparticles. Colloidal CdSe/ZnS nanoparticles were synthesized using a series of imidazolium ionic liquids; 1-R-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([RMIM][TFSI]), where R = ethyl ([EMIM]), butyl ([BMIM]), hexyl ([HMIM]), octyl ([OMIM]). The average size of nanoparticles was 8~9 nm, and both zinc-blende and wurtzite phase was produced. We also synthesized the nanoparticles using a mixture of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide ([$P_{6,6,6,14}$][TFSI]) and octadecene (ODE). The CdSe/ZnS nanoparticles have a smaller size (5.5 nm) than that synthesized using imidazolium, and with a controlled phase from zinc-blende to wurtzite by increasing the volume ratio of [$P_{6,6,6,14}$][TFSI]. For the first time, the phase and size control of the CdSe/ZnS nanoparticles was successfully demonstrated using those ionic liquids.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.315-319
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• 1997

In this study, the optimum analytical conditions for determination of distribution of propylene oxide in a nonionic surfactant and separation of fatty alcohols were investigated by Reversed Phase High Performance Liquid Chromatography. To analyse the distribution of propylene oxide (PO) and carbon chain length of a fatty alcohol, we derivatized samples for the purpose of using a UV detector. Also, we studied the influences of columns and mobile phase composition to obtain the optimum separation conditions. In our experiment, Waters Symmetry $C_8(3.9{\times}150mm)$ column was used. And the optimum condition were obtained by gradient elution with methanol and water as the mobile phase. In the plot of log k' vs composition of water in the binary phase, the linerality was very good. We ploted the calibration curve to conform the quality of fatty alcohol, a good linerality was obtained.

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.1035-1046
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• 1993

Some iron(III)porphyrin complexes were prepared, and identified by the spectroscopic methods. Elution behavior of iron(III)porphyrin complexes was investigated by reversed-phase HPLC. The optimum conditions for the separation of iron(III)porphyrin complexes were examined with respect to flow rate and mobile phase strength. These complexes were successfully separated on NOVA-PAK $C_{18}$ column using methanol / water(95/5) for $[T_pCF_3PP)Fe(R)]$ and methanol / water (98/2) for $[(P)Fe(C_6F_5)]$ as a mobile phase. It was found that these complexes were largely eluted in an acceptable range of capacity factor value ($0{\leq}logk'{\leq}1$). The dependence of the capacity factor (k') on the volume fraction of water in the binary mobile phase as well as the dependence of k' on the liquid-liquid extraction distribution ratio$(D_c)$ in methanol-water / n-pentadecane extraction system showed a good linearity. It means that the retention of iron(III)porphyrin complexes on NOVA-PAK $C_{18}$ column is largely due to the solvophobic effect. Also, there was a good linear dependence of the capacity factor(k') on the column temperature and enthalpy calculated by van't Hoff plot. From these results, it was confirmed that the retention mechanism of iron(III)porphyrin complexes in reversed-phase liquid chromatography was invariant under the condition of various temperature, and the solvophobic binding process exhibited isoequilibrium behavior.

• Journal of Energy Engineering
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• v.5 no.1
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• pp.19-27
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• 1996

Self-pressurization of cylindrical container of cryogen is numerically analyzed. The container is axi-symmetric and heated from side wall with constant heat flux. Natural convection by external heat flux is studied numerically using finite difference method. Oxygen, nytrogen and hydrogen are working fluids in this paper. Liquid is considered incompressible fluid and vapor is assumed to behave as gas meeting with virial equation of gas. The Second virial coefficients of gas are obtained from Lennard-jones model. The important variables which have effects on self-pressurization are external heat flux, heat capacity of wall and initial ullage in container. The most important variable of them is external heat flux. The pressure rise calculated from the virial gas model is slightly different from that calculated using Ideal gas model for oxygen.

• Journal of Korean Elementary Science Education
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• v.41 no.1
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• pp.150-161
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• 2022

Matter is a basic concept that students should understand during their science classes. However, many difficulties are associated with understanding the concepts of matter due to its abstraction. In this study, the elementary school students' understanding of the concept of matter and the examples of matter and non-matter are investigated and analyzed by grade. The subjects of this study were 418 students from third grade to sixth grade. The survey was conducted using a free-response questionnaire comprising three questions. The results are as follows. First, the elementary school students' conceptions of matter were "materials that make up objects," "what can be seen and touched," and "solid, liquid, and gas." As the grade increased, the explanations for a material decreased and the explanations for the state of matter increased. Furthermore, only few students explained matter in terms of mass and volume. Second, solids were the most common examples of matter presented by the students, and liquids and gases were included in the upper grades. However, there were many cases in the upper grades where students were unable to distinguish between objects and matter. Third, non-matter was properly presented by the 6th graders as compared to the other graders, and in many cases, objects, liquids, and gases were mentioned as non-matter. Fourth, it was found that the students' conceptions of matter influenced the examples of matter and non-matter that they presented.