• Food Science and Preservation
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• v.20 no.5
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• pp.650-658
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• 2013

Apple juices were sterilized by continuous pulsed electric field (PEF) treatments of pulse width of 25 ${\mu}s$ at electric field intensity of 20.0 kV/cm, and with the varied pulse frequencies of 35 Hz (40 kJ/L), 55 Hz (70 kJ/L), 72 Hz (100 kJ/L) and 85 Hz (130 kJ/L). The PEF treatments of apple juice reduced the microbial counts from 5.3 log CFU/mL of initial state to 3.0 log CFU/mL after PEF treatment at energy density of 130 kJ/L. Also yeast and fungi after PEF treatments were reduced from 5.3 log CFU/mL to 3.0 log CFU/mL and Escherichia coli were from 5.3 log CFU/mL of initial state to 4.7 log CFU/mL to < $10^1$ CFU/mL. The soluble solids and free sugars did not significantly differ (p<0.05) depending on conditions of PEF treatment. The total phenolic contents and antioxidant activity such as the DPPH and ferric reducing antioxidant power (FRAP) by PEF treatments were significantly partly reduced, but the PEF-reduced value came in smaller quantities than the heat treatment at $65^{\circ}C$. The iterative PEF treatments with pulse width of 25 ${\mu}s$ and pulse frequency of 85 Hz at electric field intensity of 20.0 kV/cm showed limited in microbial reduction. Also, total phenolic contents and antioxidant activity such as DPPH and FRAP, significantly decreased depending on treatment numbers of PEF (p<0.05).

• Clean Technology
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• v.26 no.2
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• pp.122-130
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• 2020

The isotherm, kinetic, and thermodynamic parameters of reactive blue 4 adsorbed by activated carbon were investigated for activated carbon dose, pH, initial concentration, contact time, and temperature data. The adsorption of the RB 4 dye by activated carbon showed a concave shape in which the percentage of adsorption increased in both directions starting from pH 7. The isothermal adsorption data were applied to Langmuir, Freundlich, and Temkin isotherms. Both Freundlich and Langmuir isothermal adsorption models fit well. From determined Freundlich separation factor (1/n = 0.125 ~ 0.232) and Langmuir separation factor (R_L = 1.53 ~ 1.59), adsorption of RB 4 by activated carbon could be employed as an effective treatment method. The constant related to the adsorption heat (B_T = 2.147 ~ 2.562 J mol^-1) of Temkin showed that this process was physical adsorption. From kinetic experiments, the adsorption process followed the pseudo second order model with good agreement. The results of the intraparticle diffusion model showed that the inclination of the first straight line representing the surface diffusion was smaller than that of the second straight line representing the intraparticle pore diffusion. Therefore, it was confirmed that intraparticle pore diffusion is the rate-controlling step. The negative Gibbs free energy change (ΔG = -3.262 ~ -7.581 kJ mol^-1) and the positive enthalpy change (ΔH = 61.08 kJ mol^-1) indicated the spontaneous and endothermic nature of the adsorption process, proving this process to be spontaneous and endothermic.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.65-65
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• 2012

Copper zinc tin sulfide ($Cu_2ZnSnS_4$, CZTS) is a very promising material as a low cost absorber alternative to other chalcopyrite-type semiconductors based on Ga or In because of the abundant and economical elements. In addition, CZTS has a band-gap energy of 1.4~1.5eV and large absorption coefficient over ${\sim}10^4cm^{-1}$, which is similar to those of $Cu(In,Ga)Se_2$(CIGS) regarded as one of the most successful absorber materials for high efficient solar cell. Most previous works on the fabrication of CZTS thin films were based on the vacuum deposition such as thermal evaporation and RF magnetron sputtering. Although the vacuum deposition has been widely adopted, it is quite expensive and complicated. In this regard, the solution processes such as sol-gel method, nanocrystal dispersion and hybrid slurry method have been developed for easy and cost-effective fabrication of CZTS film. Among these methods, the hybrid slurry method is favorable to make high crystalline and dense absorber layer. However, this method has the demerit using the toxic and explosive hydrazine solvent, which has severe limitation for common use. With these considerations, it is highly desirable to develop a robust, easily scalable and relatively safe solution-based process for the fabrication of a high quality CZTS absorber layer. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 1.5~2.0 ${\mu}m$ and micrometer-scaled grains using two different non-vacuum approaches. The first solution-processing approach includes air-stable non-toxic solvent-based inks in which the commercially available precursor nanoparticles are dispersed in ethanol. Our readily achievable air-stable precursor ink, without the involvement of complex particle synthesis, high toxic solvents, or organic additives, facilitates a convenient method to fabricate a high quality CZTS absorber layer with uniform surface composition and across the film depth when annealed at $530^{\circ}C$. The conversion efficiency and fill factor for the non-toxic ink based solar cells are 5.14% and 52.8%, respectively. The other method is based on the nanocrystal dispersions that are a key ingredient in the deposition of thermally annealed absorber layers. We report a facile synthetic method to produce phase-pure CZTS nanocrystals capped with less toxic and more easily removable ligands. The resulting CZTS nanoparticle dispersion enables us to fabricate uniform, crack-free absorber layer onto Mo-coated soda-lime glass at $500^{\circ}C$, which exhibits a robust and reproducible photovoltaic response. Our simple and less-toxic approach for the fabrication of CZTS layer, reported here, will be the first step in realizing the low-cost solution-processed CZTS solar cell with high efficiency.

• Clean Technology
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• v.23 no.2
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• pp.188-195
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• 2017

This research studied the adsorption of basic dye, Basic Blue 3 (BB3) by using coal-based granular activated carbon (C-GAC) from aqueous solution. All experiments were performed in batch processes, and adsorption parameters such as C-GAC dosage, contact time, initial dye concentration and temperature were evaluated. The removal efficiency of BB3 was increased with increasing the C-GAC dosage and 100% of initial concentration, $50mg\;L^{-1}$ was removed above 0.2 g of C-GAC. Also, the time to reach equilibrium depended on the initial dye concentration. According to the Langmuir model, the maximum uptakes of C-GAC were calculated to be 66.45, 84.97 and $87.19mg\;g^{-1}$ at 25, 35 and $45^{\circ}C$, respectively. In addition, thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were investigated.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.631-635
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• 2012

Nickel oxide was doped with a wide range of concentrations (mol%) of Aluminum (Al) by solvothermal synthesis; single-phased nano powder of nickel oxide was generated after calcination at$900^{\circ}C$. When the concentration of Al dopant was increased, the reduced intensity was confirmed through XRD analysis. Lattice parameters of the synthesized NiO powder were decreased after treatment of the dopant; parameters were increased when the concentration of Al was over the doping limit (5 mol% Al). The binding energy of $Ni^{2+}$ was chemically shifted to $Ni^{3+}$ by doping $Al^{3+}$ ion, as confirmed by the XPS analysis. The tilted structure of the synthesized NiO with 5 mol% Al dopant and the polycrystalline structure of the $Ni_{0.75}Al_{0.25}O$ were observed by HR-TEM analysis. The electrical conductivity of the newly synthesized NiO was highly improved by Al doping in the conductivity test. The electrical conductivity values of the commercial NiO and the synthesized NiO with 5 mol% Al dopant ($Ni_{0.95}Al_{0.05}O$) were 1,400 s/cm and 2,230 s/cm at $750^{\circ}C$, respectively. However, the electrical conductivity of the synthesized NiO with 10 mol% Al dopant ($Ni_{0.9}Al_{0.1}O$) decreased due to the scattering of free-electrons caused by the large number of impurity atoms; the electrical conductivity of $Ni_{0.9}Al_{0.1}O$ was 545 s/cm at $750^{\circ}C$.

• Korean Journal of Materials Research
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• v.30 no.8
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• pp.383-392
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• 2020

In this paper, AgCl/Ag₃PO₄/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag₃PO₄/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag₃PO₄/diatomite composite under visible light are evaluated. In the AgCl/Ag₃PO₄/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag₃PO₄/diatomite remains at 95 % of the original level, much higher than that of pure Ag₃PO₄ (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag₃PO₄/diatomite composites can be attributed to the synergistic effect of Ag₃PO₄, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO₂ and H₂O. Even more remarkably, AgCl/Ag₃PO₄/diatomite can maintain above 95 % photo-degradation activity after five cycles.

• Nuclear Engineering and Technology
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• v.4 no.4
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• pp.306-321
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• 1972

Molecular reorientation in (NH$_4$)$_2$SO$_4$, has been studied by cold neutron scattering. For T=300$^{\circ}$K data, the isolated quasielastic spectra and form-factors at various scattering angles are compared with four reorientational models based on SKOLD theory. Front these, it is concluded that the NH$_4$ions are performing either 3-fold four axes or 2-fold three axes reorientation with $\tau$$_{c}$=2.0$\times$10$^{-11}$ sec. The temperature dependence of f. is studied over 100$^{\circ}$K-413$^{\circ}$K and for the high-temperature phase, the widths of composite spectra are compared with the results from NMR relaxation measurements. All the results have shown that the neutron scattering method is capable of giving detalis of the reorientational modes in solids and therefore some discussions are given on the application of this method. A study of the form-factor is applied for NH$_4$I (Phase I) by comparing the measurement with the calculation based on free rotation approximation and proposed a reorientation model of NH$_4$ ions in the octahedral potential cage with $\tau$$_{c}$$\leq$10$^{-12}$ sec. Also a brief theoretical prediction for the effect of reorientational motions on the inelastic spectrum is discussed.sed.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.211-216
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• 2001

Top synthetic spin valves wi th structure Ta/NiFe/CoFe/Cu/CoFe(Pl)/Ru/CoFe(P2)/FeMn/Ta on Si (100) substrate with SiO$_2$ of 1500 were prepared by dc magnetron sputtering system. We have changed only the thickness of the free layer and the thickness difference (Pl-P2) in the two ferromagnetic layers separated by Ru, and investigated the effect of magnetic film thickness on the GMR properties and the interlayer coupling field in a spin valve with a synthetic antiferromagnet. As thickness difference of pinned layer was decreased from +25 to -25 , MR ratio was decreased gradually. However, there was a dip zone indicating a big change of MR ratio around Pl = P2, which can be due to the large canting of pinned layers. The modified Neel model was suggested for the top synthetic spin valve to explain the interlayer coupling field according to the thickness change of ferromagnetic layers. The interlayer coupling field was decreased due to the magnetostatic coupling (orange peel coupling) as suggested by model. However, the interlayer coupling field was not explained at the dip zone by the modified Neel model. The deviation of modified Neel model at the dip zone could be due to the largely canting of the pinned layers as well, which depends on different thickness in synthetic antiferromagnetic structure.

• Korean Journal of Food Science and Technology
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• v.33 no.2
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• pp.184-189
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• 2001

Comparative effects of gamma irradiation and methyl bromide (MeBr) fumigation on water-soluble components of small red bean and mung bean were investigated. The levels of soluble solid and reducing sugar of soaked water at $20^{\circ}C$ for 16 h definitely increased as irradiation dose increased, which was more apparent in small red bean than in mung bean. But, their levels of MeBr-fumigated sample showed a similar result to those of the control, except for soluble solid of small red bean. The pH of soaked water was insignificantly different among treatments. The decrease in lightness (L value) and the increases of redness (a value) and yellowness (b value) were remarkable as irradiation dose increased, which was more significant in fumigated samples. The ${\Delta}E$ values of fumigated sample showed almost equaled to those of 10 kGy in red bean and 30 kGy in mung bean, respectively. Gamma irradiation caused the increase in free amino acids of soaked water, that mainly consisted of asparagine, glutamic acid, and valine, while fumigation reduced their contents. The extractables in soaked water, such as soluble solid and reducing sugar, showed a highly positive correlation with irradiation dose applied.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.3
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• pp.48-56
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• 2002

The flow characteristics around KRISO 3600TEU container ship model have been experimentally investigated in a circulating water channel. The instantaneous velocity vectors were measured using 2-frame PIV measurement system. The mean velocity fields and turbulent statistics including turbulent kinetic energy and vorticity were obtained by ensemble-averaging 400 instantaneous velocity fields. The free stream velocity was fixed at 0.6m/s and the corresponding Reynolds number was $9{\times}10^5$. The test sections were divided into two regions, three transverse sections of the wake region(Station -0.5767, -1, -3) and five longitudinal sections of the wake((Z/(B/2)=0, 0.1, 0.2, 0.4, 0.6). In the wake region, large-scale longitudinal vortices of nearly same strength are symmetric with respect to the wake centerline and a relatively weak secondary vortex is formed near the waterline. With going downstream, the strength of longitudinal vortex is decreased and the wake region expands.