• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.237-242
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• 2006

Nowadays, LEDs has been applied to the luminescent devices of various fields because of the invention of high efficient blue chip. Recently, especially, the white LEDs composed of InGaN blue chips and a yellow phosphor (YAG:Ce3+) have been investigated extensively. With the exception of YAG:Ce3+ phosphor, however, there are no reports on yellow phosphor that has significant emission in the 450~470 nm excitation range and this LED system is the rather low color rendering index due to their using two wavelength. Hence, we have attempted to synthesize thiogallate phosphors that efficiently under the long wavelength excitation range in the present case. Among those phosphors, we have synthesized Sr2Ga2S5:Eu2+ phosphor by change the host material of SrGa2S4:Eu2+ which is well known phosphor and we investigated the luminescent properties. In order to obtain the harmlessness and simplification of the synthesis process, sulfide materials and mixture gas of 5 % H2/95 % N2 were used instead of the CS2 or H2S gas. The prepared phosphor shows the yellow color peaking at the 550 nm wavelength and it possible to emit efficiently under the broad excitation band in the range of 300~500 nm. And this phosphor shows high luminescent intensity more than 110 % in comparison with commercial YAG:Ce3+ phosphor and it can be applied for UV LED due to excitation property in UV region.

• Journal of the Korean Magnetics Society
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• v.12 no.2
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• pp.41-45
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• 2002

The low-field tunnel-type magnetoresistance (MR) properties of sol-gel derived $La_{0.7}Pb_{0.3}MnO_3(LPMO)$ thin film deposited on different substrate have been investigated. Polycrystalline thin films were fabricated by spin-coating on $SiO_2/Si(100)$ substrate and that with yttria-stabilized zirconia (YSZ) buffer layer, while c-axis-oriented thim film was grown on $LaAlO_3(001)$ (LAO) single crystal substrate. The full width half maximum (FWHM) of the rocking curve scan of LPMO/LAO film is $0.32^{\circ}$. Tunnel-type MR ratio is 0.52 % in $LPMO/SiO_2/Si$(100) film and that of $LPMO/YSZ/SiO_2/Si$(100) film is as high as 0.68 %, whereas that of LPMO/LAO(001) film is less than 0.4 % under the applied field of 500 Oe at 300 K. Well-pronounced MR hysteresis was registered with an MR peak in the vicinity of the coercive field. The low-field tunnel-type MR characteristics of thin films deposited on different substrates originates from the behavior of grain boundary properties.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.698-706
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• 2019

Over the last few decades, there have been a lot of efforts to develop soft actuators, which can be external stimuli-responsive and applied to the human body. In order to fabricate medical soft actuators with a dynamic precision control, the 3D crosslinked poly(acrylic acid) (PAAc)/poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogels were synthesized in this study by using a radiation technique without noxious chemical additives or initiators. After irradiation, all hydrogels showed high gel fraction over 75% and the ATR-FTIR spectra indicated that PAAc/PVA/PEG hydrogels were successfully synthesized. In addition, the gel fraction, equilibrium water content, and compressive strength were measured to determine the change in physical properties of PAAc/PVA/PEG hydrogels according to the irradiation dose and content ratio of constituents. As the irradiation dose and amount of poly(ethylene glycol) diacrylate (PEGDA) increased, the PAAc/PVA/PEG hydrogels showed a high crosslinking density and mechanical strength. It was also confirmed that PAAc/PVA/PEG hydrogels responded to electrical stimulation even at a low voltage of 3 V. The bending behavior of hydrogels under an electric field can be controlled by changing the crosslinking density, ionic group content, applied voltage, and ionic strength of swelling solution.

• The Korean Journal of Food And Nutrition
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• v.25 no.1
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• pp.142-148
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• 2012

This study compared the quality and antioxidant characteristics of commercial and traditional Doenjangs from various regions of Korea. The pH, salinity, and brix degree of the samples tested ranged from 4.61~6.36, 0.90~1.00% and 0.97~1.10 $^{\circ}Bx$, respectively. The pH was highest for Doenjang made in the Jeonnam region. No significant differences in the salinity or brix degree of Doenjang from different regions of Korea were found(p>0.05). The L, a, and b-values for color of the Doenjang samples ranged from 52.92~55.00, 0.03~0.62 and -0.74~2.70, respectively. The total polyphenol content(TPC) ranged from 18.71~25.78 mg GAE/$m{\ell}$, and the 1,1-diphenyl-2-picrylhydrazyl(DPPH) and 2,2-azinobis(3-ethyl benzothiazoline)-6-sulfonic acid(ABTS) radical scavenging activities ranged from 6.43~14.38 and 2.46~7.08 mg AE/$m{\ell}$, respectively. The TPC was highest for Doenjang from Gyeongnam, while that from Gyeongbuk had the lowest content. The DPPH radical scavenging activity was highest for Doenjang from Jeonnam and lowest for Doenjang from Gangwon. The ABTS radical scavenging activities for Doenjang from Gyeonggi and Gyeongbuk were lower in comparison to samples from other regions. Consequently these results should provide better information for standardizing and improving the quality and functional activity of commercial Doenjang in Korea.

• The Korean Journal of Food And Nutrition
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• v.25 no.3
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• pp.664-670
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• 2012

In this study, we investigated the quality characteristics and the sensory evaluation for madeleine added with peach (Prunus persica L. Batsch) juice. The pH and specific volume of madeleine were decreased with increase of peach juice, whereas the moisture and loss rate were increased. In the color of madeleine crust, L and b value were decreased with increase of peach juice, and these results showed significant differences compared to control(p<0.05). The other hand, the colors of madeleine crumb showed less significant changes compared to the control. On texture of madeleine with increase of peach juice, the hardness, chewiness, gumminess and cohesiveness were increased, whereas the adhesiveness was decreased. In the sensory evaluation with taste, color, flavor and overall preference, the madeleine with 20%(w/w) peach juice showed the highest value. Consequently, these results should provide the possibile use of peach processing in bakery industry because the addition of peach juice enhanced the quality and sensory characteristics of madeleine.

• Journal of the Korean Ceramic Society
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• v.31 no.5
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• pp.513-519
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• 1994

Alumina composite was fabricated by introducing tetragonal ZrO2 in alumina composite of $\alpha$-alumina reinforced with in-situ formed La-$\beta$-aluminate (LaAl11O18). The powder mixture of composition (100-x)[88 Al2O3+(La2O3+11 Al2O3)]+x vol% ZrO2 was prepared with x from 0 to 40. Dense composites fabricated by hot-pressing exhibited bending strength up to 1200 MPa. The gain growth inhibiting effect of ZrO2 grains and La-$\beta$-aluminate platelets, and possibly the stress-induced phase transformation of ZrO2 have resulted in the high bending strength. The fracture toughness of the composite also increased up to 8.5 MPa.m1/2. The enhancement in toughness can be explained by transformation and microcrack toughening of ZrO2 and by crack deflection and bridging of La-$\beta$-aluminate platelets and ZrO2.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1202-1207
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• 2003

Using a recently developed Hybric Plasma-Particle Accelerating Impact Deposition (HP-PAID) process, synthesis of nanostructured silicon coatings has been investigated by injecting vapor-phase TEOS (tetraethosysilane, (C$_2$H$\_$5/O)$_4$Si) into an Ar hybrid plasma. The plasma jet with reactants was expanded through nozzle into a deposition chamber, with the pressure dropping from 700 to 10 torr. Ultrafine particles accelerated in the free jet downstream of the nozzle, deposited by an inertial impaction onto a temperature controlled substrate. By using this process, nanostructured amorphous silicon coatings with grain size smaller than 10 nm could be synthesized. These samples were annealed in an Ar and crystallized at 900$^{\circ}C$ for 30 min. TEM analysis showed that the annealed coatings were also composed of nanoparticles smaller than 10 nm, which showed a good consistency that the average grain size of 7 nm was also estimated from a peak shift of 2.39 cm$\^$-1/ and Full Width at Half Maximum (FWHM) 5.92 cm$\^$-1/ of Raman analysis. The noteworthy is that a strong PL peak at 398 nm was also obtained for this sample, which indicates that the deposited coatings also contained 3∼4 nm nanostructured grains.

• Korean Journal of Materials Research
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• v.8 no.9
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• pp.860-864
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• 1998

We investigated the photoluminescence and the crystalline properties with Ga doping concentrations (0-12 mol%) in $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}\textrm{SiO}_{4}$ green phosphors prepared by the solid state reaction. The photoluminescence was improved by a doping of Ga element in $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}(\textrm{Si_{1-x}\textrm{Ga}_{x})\textrm{O}_{4}$ phosphors which showed the highest emission intensity and good color purity in the doping concentration of x=0.08. The emission intensity of $\textrm{Zn}_{1.98}\textrm{Mn}_{0.02}(\textrm{Si_{1-x}\textrm{Ga}_{x})\textrm{O}_{4}$(x= 0.08) phosphors was increased to 7 times with increasing the sintering temperatures from $1100^{\circ}C$ to $1400^{\circ}C$, showing the improved crystalline quality. The decay time was not affected by Ga doping concentrations with constant values around 24ms. It was found from SEM and PSA analyses that the phosphors were composed of a large number of small grains around 1-3$10\mu\textrm{m}$ with a small amounts of agglomerated particles above $10\mu\textrm{m}$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.4
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• pp.529-537
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• 2005

Ssamjang samples were prepared by central composite design for five independent variables, Gochujang mash aging period $(X_1)$, Doenjang aging period $(X_2)$, Doenjang content $(X_3)$, sterilization temperature $(X_4)$ and storage temperature $(X_5)$. Browning characteristics of Ssamjang were analyzed such as water activity, free amino acids, free sugars and color during storage. Water activities of Ssamjang were ranged from 0.605 to 0.666 at the beginning of storage, and were shown to be the highest at the 8th week of storage and then decreased gradually. Among free amino acids the content of glutamic acid was the highest. Proline, leucine, phenylalanine, lysine and serine were slightly higher than the others. Larger amounts of free amino acids and free sugars were observed from the sample sterilized at $60^{\circ}C$ when compared to that at $70^{\circ}C$. Glucose, fructose and maltose as free sugars were identified from Ssamjang and glucose content was the largest among. During the storage, lightness $(L^*)$, redness $(a^*)$ and yellowness $(b^*)$ of Ssamjang were decreased and total color difference $({\Delta}E)$ was increased. The color changes in the sample surface were more affected by temperature of which storage temperature was more influenced than sterilization temperature.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.3
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• pp.370-374
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• 2003

Cell cracking method using a non-collision was evaluated for the possibility of new red ginseng grinding technique. Based on particle size distribution analysis by 1size shaker, the ratios of 100 mesh penetrated particles were 94.9% for hammer mill (group A) and 95.6% for cell crack (group B). The ratio of 120 mesh penetrated particle of group A was higher than that in group B. The particle size distributions for 100 mesh non-penetrated Powder between 2 groups were not significantly different, and particle size distribution analysis by laser scattering analyzer showed that the particle size ranges were 0.77~128.07 ${\mu}{\textrm}{m}$ for group A and 4.24~180.07 ${\mu}{\textrm}{m}$ for group B. The Particle size distribution in group A was more broad than that in group B. The mean particle size in group B was larger than that in group A, while the standard deviation of particle size distribution in group B was less than that in group A. Structural surface characteristics, in group A, particle size distribution was broad and the distribution curve was amorphous. The structure of individual particles was similar to unequal stone which was roughly grinded and had soft cotton-like surface. In the contrary, in group B, particle size distribution was relatively narrow and also individual size particles were ubiquitously distributed. The structure of individual particles was unequal cut stone shape.