• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.573-577
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• 2004

We have synthesized a Eu$^{2＋}$-activated Sr$_3$MgSi$_2$ $O_{8}$ blue phosphor and investigated an attempt to develop blue LEDs by combining it with a InGaN blue LED chip (Len=405 nm). The InGaN-based Sr$_3$MgSi$_2$ $O_{8}$：Eu LED Lamp shows two bands at 405 nm and 460 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the Sr$_3$MgSi$_2$ $O_{8}$：Eu phosphor. The 460 m emission band is ascribed to a radiative recombination of Eu$^{2＋}$ impurity ions in the Sr$_3$MgSi$_2$ $O_{8}$ host matrix. As a consequence of a preparation of W blue LED Lamp using the Sr$_3$MgSi$_2$ $O_{8}$：Eu blue phosphor, the highest luminescence efficiency was obtained at the ration of epoxy/blue phosphor(1/0,202). At this time, the CIE chromaticity was x=0.1417 and y=0.0683.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.3
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• pp.453-467
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• 1998

This study helps to clarify conflicting reports by comparing the physical properties and accuracy of complete denture processed by the pack and press technique, continuous- pressure injection technique(SR-Ivocap system) and Mark press technique. The 6 different specimens have been evaluated using the SEM, Impact test, DSC (Differential Scanning Calorimetry) and DMTA (Dynamic Mechanical Thermal Analysis). Each sample was made of SR-Ivocap resin and QC-20 resin by different processing methods. The results were as follows ; 1. As the result of the observation on the fracture surface of resin by use of SEM, sample SR-Ivocap resin cured by continuous pressure injection method showed the most homogeneous structure. This is why molecules in SR-Ivocap resin have no orientation. 2. As the result of the Impact test in order to measure the deformity, fracture energy and impact resistance of resin, the samples with QC-20 acrylic resin and SR-Ivocap resin cured by continuous pressure injection method were exellent. 3. In consequence of measuring ${\alpha}$-glass transition temperature by use of DSC on the basis of temperature change, the glass transition temperatures of sample QC-20 resin cured by pack and press method and sample SR-Ivocap resin cured by continuous pressure injection method were very similar. Thus volumetric stability could not be evaluated only by glass transition temperature. 4. In comparing volumetric stability data by DMTA, the glass transition temperature(Tg) showed $137.88^{\circ}C$ at sample QC-20 resin cured by pack and press method and $139.78^{\circ}C$ at sample SR-Ivocap resin cured by continuous pressure injection method. Therefore sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in the dimensional stability at high temperature. 5. In comparing storage modulus data by DMTA, the storage modulus of sample SR-Ivocap resin cured by continuous pressure injection method was higher than that of sample QC-20 resin cured by pack and press method. So. sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in impact strength.

• Resources Recycling
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• v.11 no.5
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• pp.16-20
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• 2002

This experiment was carried out to examine the effects of La-Co substitution on Sr-ferrite. The magnetic properties of calcined and sintered materials varied with the substitutional amount of La and Co elements in Sr-ferrite. Anisotropy field and coercivity for Sr ferrite were increased with raising La-Co substitution amounts. The microstructure observation for Sr ferrite substituted by La-Co revealed that La-Co inhabited grain growth during calcination and promoted lateral grain growth during sintering. The relationship between $B_{r}$ and $_{i}$ /$H_{c}$ for La-Co substituted Sr-ferrite was found to be $B_{r}$$≒0.097_{i}$ /$H_{c}$/+4500. In case of $SrFe_{12}$ $O_{19}$, $B_{r} was 4090 G and $_{ i}$$H_{c}$ was 3560 Oe, but $B_{r}$ was 4080 G and and $_{i}$ $H_{c}$ was 4800 Oe for $Sr_{0.7}$ $La_{0.3}$ $Fe_{11.7}$ /$Co_{0.3}$ $O_{19}$.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.196-199
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• 2007

The chemical states of oxygen on the surfaces of $Pr_{1-x}Sr_{x}CoO_{3}$ (x=0.5 and 0.7) oxide systems were investigated by X-ray photoelectron spectroscopy. Merged oxygen peaks of $Pr_{1-x}Sr_{x}CoO_{3}$ (x=0.5 and 0.7) oxides could be divided as five sub-peaks. These five sub-peaks could be defined as lattice oxygen ($O_{L}$). chemisorbed oxygen peaks ($O_{C}$) and hydroxyl condition oxygen peak ($O_{H}$). In case of the $Pr_{0.5}Sr_{0.5}CoO_{3}$ and $Pr_{0.3}Sr_{0.7}CoO_{3}$, the binding energy (BE) of oxygen lattice were located at same BE. However, the BE of chemisorbed oxygen peaks including oxygen vacancy shows different BE. Especially, it was found that BE of chemisorbed oxygen peaks was increased when more Sr were substituted. Comparing atomic percentages of oxygens of $Pr_{0.5}Sr_{0.5}CoO_{3}$ and $Pr_{0.3}Sr_{0.7}CoO_{3}$, the ratio of $Pr_{0.3}Sr_{0.7}CoO_{3}$ was higher than that of $Pr_{0.5}Sr_{0.5}CoO_{3}$. It showed more chemically adsorbed site including oxygen vacancies were existed in $Pr_{0.3}Sr_{0.7}CoO_{3}$.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.360-363
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• 2006

We synthesized $(La,\;Sr)MnO_{3+{\delta}$ as a cathode for SOFC by glycine nitrate process(GNP) and knew the different properties of $(La_{1-x}Sr_x)MnO_3$ by using nitrate solution and oxide solution as starting material. In case of using nitrate solution as a starting material, main crystal phase peak of $LaMnO_3$ increased as Sr content added up and a peak of $Sr_2MnO_4\;and\;La_2O_3$ was showed as a secondary phase. We added Mn excess to control a crystal phase. In this case, the electrical conductivity had a high value 210.3S/cm at $700^{\circ}C$ On the other side, when we used oxide solution as a starting material, we found main crystal phase of $LnMnO_3$ to increase as Sr content added up and a peak of $La_2O_3$ as a secondary phase. Similary, we added Mn excess to control a crystal phase in this case. We knew $(La,\;Sr)MnO_3$ powder to sinter well and the electrical conductivity of the sintered body at $1200^{\circ}C$ for 4hrs was 152.7s/cm at $700^{\circ}C$. The sintered $(La,\;Sr)MnO_3$ powder at $1000^{\circ}C$ for 4hrs got the deoxidization peak, depending on the temperature md in case of using nitrate solution as a start ing material the deoxidization peak was showed at $450^{\circ}C$ which is lower than used a oxide solution as a starting material. As a result, when $(La,\;Sr)MnO_3$ powder was synthesized to add Mn excess and to use nitrate solution as a starting material, we found it to have the higher deoxidization property and considered it as a cathode for m properly. And we found it to have different electrical conduct ivity the synthesized $(La,\;Sr)MnO_3$ powder by using different start ing materials like nitrate solution and oxide solution which influence a sintering density and crystal phase.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.31-36
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• 1993

A pot experiment was carried out to investigate the influence of application of nitrogen, phosphorus and calcium on the yield and uptake of Sr-90 by soybean plant. The results obtained were summarized as follows : 1. The application of N tended to decrease the dry matter yield of soybean. There was, however, difference in the effect on the yield between $NH_4-N$ and $NO_3-N$ ; the yield was higher in the former in the latter. On the other hand, the application of P and Ca increased the yield. 2. The uptake of Sr was decreased by the application of N, but such effect was greater in $NH_4-N$ than in $NO_3-N$. 3. The effect of N application in reducing the uptake of Sr. was enhanced by the application of P with N. 4. The combined application of P and lime showed significant effect of reducing the uptake of Sr by soybean plant. The uptake of Sr was lowest in the pot that received P, lime and $NH_4-N$ together.

• Journal of the Korean Chemical Society
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• v.25 no.4
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• pp.236-245
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• 1981

The electrical conductivities of oxidized pure and Ni-doped $SrTiO_3$ single crystals were measured as a function of the oxygen partial pressure($Po_2$) at temperature from 700 to $1200^{\circ}C$ and $Po_2$ of $10^{-8}$ to $10^{-1}$ atm. Plots of log ${\sigma}$ vs. 1/T at constant $Po_2$ were found to be linear, and the activation energies obtained from the slopes of these plots have an average value of 1.34 eV for oxidized pure and 1.06 eV for oxidized Ni-doped $SrTiO_3$ single crystals at $Po_2$'s between $10^{-8}$ to $10^{-1}$ atm. The log ${\sigma}$ vs. log $Po_2$ curves at constant temperature were found to be linear with an average slope of ${\frac{-1}{5.6}}\;{\sim}\;{\frac{-1}{6.2}}$ in the $Po_2$ ranges. From the agreement between experimental and theoretically predicted values for the electrical conductivity dependences on $Po_2$, an oxygen vacancy defect model was found applicable to oxidized pure and Ni-doped $SrTiO_3$ single crystals over the temperature range, 700~$1200^{\circ}C$. Conduction mechanisms were proposed to explain the dependences of electrical conductivity on temperature and $Po_2$.

• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.52-57
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• 2007

We synthesized $(La_{1-x}Sr_x)MnO_3$ as a cathode for SOFC by glycine nitrate process (GNP) and knew the different properties of $(La_{1-x}Sr_x)MnO_3$ by using nitrate solution and oxide solution as a starting material. In case of using nitrate solution as a starting material, main crystal phase peak of $LaMnO_3$ increased as Sr content added up and a peak of $Sr_2MnO_4\;and\;La_2O_3$ was showed as a secondary phase. We added Mn excess to control a crystal phase. In this case, the electrical conductivity had a high value 210.3 S/cm at $700^{\circ}C$. On the other side, when we used oxide solution as a starting material, we found main crystal phase of $LaMnO_3$ to increase as Sr content added up and a peak of $La_2O_3$ as a secondary phase. Similary, we added Mn excess to control a crystal phase in this case. We knew $(La,Sr)MnO_3$ powder to sinter well and the electrical conductivity of the sintered body at $1200^{\circ}C$ for 4 h was 152.7 S/cm at $700^{\circ}C$. The sintered $(La,Sr)MnO_3$ powder at $1000^{\circ}C$ for 4 h got the deoxidization peak, depending on the temperature and in case of using nitrate solution as a starting material, the deoxidization peak was showed at $450^{\circ}C$ which is lower than used a oxide solution as a starting material. As a result, when $(La,Sr)MnO_3$ powder was synthesized to add Mn excess and to use nitrate solution as a starting material, we found it to have the higher deoxidization property and considered it as a cathode for SOFC properly. And we found it to have different electrical conductivity the synthesized $(La,Sr)MnO_3$ powder by using different starting materials like nitrate solution and oxide solution which influence a sintering density and crystal phase.

• The Journal of the Petrological Society of Korea
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• v.20 no.4
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• pp.207-217
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• 2011

Here we report major element composition, trace and rare earth element abundance, Sm-Nd and Rb-Sr isotopic composition from Deokgu leucogranite. Chondrite-normalized REE pattern and its Eu anomaly are divided into 3 types systematically, and have close relationship with $SiO_2$ contents. Such geochemical characteristic indicates that the leucogranite was derived by feldspar fractionation from a common source magma. Sm-Nd and Rb-Sr whole rock ages are $1,785{\pm}180Ma$ (initial $^{143}Nd/^{144}Nd\;ratio=0.51003{\pm}0.00016,\;2{\sigma}$; ${\varepsilon}_{Nd}(T)=-5.9$) and $1,735{\pm}260Ma$ (initial $^{87}Sr/^{86}Sr\;ratio=0.702{\pm}0.046,\;2{\sigma}$), respectively. Initial ${\varepsilon}_{Nd}$ value indicates that the magma should be derived from the crustal material. This initial ${\varepsilon}_{Nd}$ value also corresponds well with those from the Precambrian granitoids from North-China Craton rather than those of South-China Craton.

• The Korean Journal of Nuclear Medicine
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• v.27 no.1
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• pp.123-129
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• 1993

Chitosan is known to be one of the natural chelating agents. It is derived from chitin which is a cellulose-like biopolymer distributed widely in nature, especially in shellfish, insects, fungi, and yeast. There are two forms of chitosans, water soluble and insoluble, The purpose of the present study is to investigate whether water soluble chitosan can be applied to reduce the bioabailability of radios-trontium in foods. We compared the effect of water soluble and insoluble chitosans on the absorption of ingested radiostrontium ($^{85}Sr$). Three percent water soluble and insoluble chitosan solutions were given orally, and immediately after $^{85}SrCl_2$ ($0.2{\mu}Ci$) was administered to rats using a orogastric tube. In one group water soluble chitosan solution was given for additional 4 days. And in control group no chitosan was given. Each group consisted of 6 rats. The whole-body retention of $^{85}Sr$, determined by in vivo counting method, was lower in water soluble chitosan group than that of water insoluble chitosan group and that of control. Urinary excretion of $^{85}Sr$ in chitosan-treated rats was higher than that of control. And 5 day ingested group of water soluble chitosan showed least whole body retention of $^{85}Sr$. In conclusion water soluble chitosan was more effective in reducing bioavailability of ingested radiostrontium in the gastrointestinal tract than insoluble chitosan.