• Journal of the Korean Ceramic Society
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• v.42 no.10 s.281
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• pp.672-677
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• 2005

In this study we prepared the Sr-ferrite powders and magnet by a molten salt method using the (NaCl+KCl) salt mixture. Starting materials of $Fe_{2}$$O_{3}$ and Sr$Co_{3}$ were mixed as the molar ratio of 5.70:1, and 0.08 mol$ \% $ $Al_{2}$$O_{3}$, 0.10 mo1$ \% $ Si$O_{2}$ and 0.12 mo1$ \% $ CaO were added as additives. Sr-ferrite powders synthesized at the reaction temperatures of 800$\∼$1200$ ^{\circ}C $ showed the typical M-type hexagonal ferrite phase, and hexagonal plate-like morphology with uniform distribution of 1$\∼$3 $\mu$m particle size. The bulk density of the sintered Sr-ferrite magnet prepared with powders by the molten salt method showed the maximum density of 4.82 g/$cm^{3}$ at the sintering temperature of 1200$^{\circ}C $. The maxima of remanent flux density (Br, 45 emu/g) and coercive force (iHc, 3.75 kOe) occurred at the sintering temperatures of 1150$ ^{\circ}C$ and 1200$^{\circ}C $.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.5
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• pp.241-246
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• 2012

$Yb^{3+}$, $Er^{3+}$ co-doped $SrMoO_4$ ($SrMoO_4$ : $Yb^{3+}/Er^{3+}$) specimens have been successfully synthesized via the complex citrate-gel method and their structural and optical properties were investigated in detail. Under 980 nm excitation, $SrMoO_4$ : $Yb^{3+}/Er^{3+}$ UC phosphors have been emitted strong green luminescence at 530 and 550 nm with weak red emission around 670 nm corresponding to the intra 4f transitions of $Er^{3+}$ ($^4F_{9/2}$, $^2H_{11/2}$, $^4S_{3/2}$) ${\rightarrow}$ $Er^{3+}$ ($^4I_{15/2}$). The optimal doping concentrations of $Er^{3+}$ and $Yb^{3+}$ ions were verified to 2/16 mol% and a possible upconversion mechanism depending on pump power dependence is studied in detail.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.78.2-78.2
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• 2007

• Progress in Superconductivity
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• v.9 no.1
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• pp.18-22
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• 2007

For interlayer tunneling spectroscopy using a small stack of $Bi_2Sr_2CaCu_2O_{8+x}$ (Bi-2212) intrinsic junctions in a high-bias range, large self-heating takes place due to the poor thermal conductivity of Bi-2212. In this study, we numerically estimate the self-heating around a Bi-2212 sample stack for I-V or dI/dV-V measurements. Our results show that the temperature discrepancy between the Bi-2212 sample stack and top Au electrodes due to bias-induced self-heating is small enough along the c-axis direction of Bi-2212. On the other hand, the lateral temperature discrepancy between the sample stack and the Bi-2212 on-chip thermometer stack can be as large as ${\sim}20\;K$ for the highest bias required to observe the pseudogap hump structure. We thus suggest a new in-situ ac thermometry, employing the Au current-bias electrode itself deposited on top of the sample stack as the resistive thermometer layer, which is supposed to allow safe temperature measurements for the interlayer tunneling spectroscopy.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.620-626
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• 2015

$Ho^{3+}$ doped $SrAl_2O_4$ upconversion phosphor powders were synthesized by spray pyrolysis, and the crystallographic properties and luminescence characteristics were examined by varying activator concentrations and heattreatment temperatures. The effect of organic additives on the crystal structure and luminescent properties was also investigated. $SrAl_2O_4:Ho^{3+}$ powders showed intensive green emission due to the $^5F_4/^5S_2{\rightarrow}^5I_8$ transition of $Ho^{3+}$. The optimal $Ho^{3+}$ concentration in order to achieve the highest luminescence was 0.1%. Over this concentration, emission intensities were largely diminished via a concentration quenching due to dipole-dipole interaction between activator ions. According to the dependence of emission intensity on the pumping power of a laser diode, it was clear that the upconversion of $SrAl_2O_4:Ho^{3+}$ occurred via the ground state absorption-excited state absorption processes involving two near-IR photons. Synthesized powders were monoclinic as a major phase, having some hexagonal phase. The increase of heat-treatment temperatures from $1000^{\circ}C$ to $1350^{\circ}C$ led to crystallinity enhancement of monoclinic phase, reducing hexagonal phase. The hexagonal phase, however, did not disappear even at $1350^{\circ}C$. When both citric acid (CA) and ethylene glycol (EG) were added to the spray solution, the resulting powders had pure monoclinic phase without forming hexagonal phase, and led to largely enhancement of crystallinity. Also, N,N-Dimethylformamide (DMF) addition to the spray solution containing both CA and EG made it possible to effectively reduce the surface area of $SrAl_2O_4:Ho^{3+}$ powders. Consequently, the $SrAl_2O_4:Ho^{3+}$ powders prepared by using the spray solution containing CA/EG/DMF mixture as the organic additives showed about 168% improved luminescence compared to the phosphor prepared without organic additives. It was concluded that both the increased crystallinity of high-purity monoclinic phase and the decrease of surface area were attributed to the large enhancement of upconversion luminescence.

• Herbal Formula Science
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• v.11 no.2
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• pp.159-171
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• 2003

This study was done to investigate effects of SR, CF and AR to angiogenesis of cerebral tissues, protecting damage of cerebral neurons and activating them in cerebral contusion-induced rats. I observed these conclusions as follows ; 1. Observation of VEGF-immunoreactive cells : Groups of administered AR were not meaningful in increasing VEGF-immunoreactive cells for 3 days and 7 days, groups of administered SR meaningfully increased them to control groups in all groups, and groups of administered CF meaningfully increased them to control groups in all groups, too, interestingly, increased double to control group for 7 days. 2. Observation on cerebral neurons by Cresyl violet stain : Dendrites and axons of groups of administered SR, AR for 3 days were clearly observed to control group. Cerebral neurons of groups of administered CF for 3days and 7 days were increased a little, but were not meaningful. In conclusion, AR will be careful of being used in cerebral contusion. CF and SR were effective to activating cerebral hemokinesis by inducing angiogenesis in trauma of tissue, but weakly to protecting trauma of cerebral neurons and activating them. I think more studies will be done in these facts.

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.05a
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• pp.15-15
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• 2002

• Journal of Navigation and Port Research
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• v.41 no.5
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• pp.353-358
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• 2017

This study aims to propose an assessment tool of port service quality (PSQ) in the context of container transport logistics (CTLs), by taking the perspectives from port users. The CTLs defined in this study are the relevant activities of serving the physical flows of a container box from a point of origin via a container port to a point of destination. To address the ports' role in collaboration between its channel members in CTLs, the PSQ measures for all port user groups (i.e. common PSQ measures) are selected based on the relevant CTLs activities involved by port, and its users within terminal/port area as well as throughout the CTLs chain. An importance-performance analysis (IPA) is applied as a diagnostic tool to analyse the status quo of Busan Port in CTLs contexts, by comparing the importance and performance (IP ) scores against each individual CTLs criterion. The findings from the IPA reveal that port managers and policy makers at the Busan Port should concentrate on six PSQ measures (i.e. SR1, SR4, ITS1, VAS1, VAS4, ICI3) to enhance PSQ in CTLs. However, four measures (i.e. ITS2, ITS3, ITS4, VAS2) are identified as a possible overkill, indicating an area of inefficiency where a remedial action of the cost-cutting decision is necessary. On the other hand, the Busan port shows an outstanding performance on four measures such as SR2, SR3, ICI1 and ICI2. The measures are not only important but also high performance. The study findings provide managerial guidance to port managers in Busan Port, in view of searching for managerial and operational strategies for sustainable port growth.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.447-454
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• 2003

Samples were prepared by the solid-state reaction method. The nominal composition of the samples was B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+{delta}$ prepared from powder of B $i_2$ $O_3$, PbO, SrC $O_3$, CaC $O_3$, and CuO. They were pulverized, mixed with AgO, A $u_2$ $O_3$and MgO of 50 wt%. Finally, they were sintered at 820 to 85$0^{\circ}C$ in air. The structural characteristics, the microstructure of surface and the critical temperature with respect to the each samples were analyzed by XRD, $T_{c}$, SEM and EDS respectively. It was found that the the critical temperature of the silver oxide additive samples (99.58 K) is higher than those of gold or magnesium oxides additive samples, but all those values are lower than that of pure Bi-2223 phase. The microstructure of surface showed the tendency which the AgO additive samples become more minuteness than A $u_2$ $O_3$ and MgO additive samples.s.samples.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04b
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• pp.88-91
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• 2000

The $(Sr_{0.85}Ca_{0.15})TiO_3$(SCT) thin films are deposited on Pt-coated electrode(Pt/TiN/$SiO_2$/Si) using RF sputtering method. The crystallinity of SCT thin films is increased with increase of substrate temperature in the temperature range of 200~500$[^{\circ}C]$. V-I characteristics of SCT thin films show the increasing leakage current with the increases of deposition temperature. The conduction mechanism of the SCT thin films observed in the temperature range of 25~100$[^{\circ}C]$ can be divided into four characteristic regions with different mechanism by the increasing current.