• Journal of Powder Materials
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• v.27 no.3
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• pp.233-240
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• 2020

Nano-sized ZnSe particles are successfully synthesized in an aqueous solution at room temperature using sodium borohydride (NaBH₄) and thioglycolic acid (TGA) as the reducing agent and stabilizer, respectively. The effects of the mass ratio of the reducing agent to Se, stabilizer concentration, and stirring time on the synthesis of the ZnSe nanoparticles are evaluated. The light absorption/emission properties of the synthesized nanoparticles are characterized using ultraviolet-visible (UV-vis) spectroscopy, photoluminescence (PL) spectroscopy, and particle size analyzer (PSA) techniques. At least one mass ratio (NaBH4/Se) of the reducing agent should be added to produce ZnSe nanoparticles finer than 10 nm and to absorb UV-vis light shorter than the ZnSe bulk absorption wavelength of 460 nm. As the ratio of the reducing agent increases, the absorption wavelengths in the UV-vis curves are blue-shifted. Stirring in the atmosphere acts as a deterrent to the reduction reaction and formation of nanoparticles, but if not stirred in the atmosphere, the result is on par with synthesis in a nitrogen atmosphere. The stabilizer, TGA, has an impact on the Zn precursor synthesis. The fabricated nanoparticles exhibit excellent photo-absorption/discharge characteristics, suggesting that ZnSe nanoparticles can be alloyed without the need for organic solutions or high-temperature environments.

• YAKHAK HOEJI
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• v.37 no.2
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• pp.129-135
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• 1993

Serratia sp. Y-4 was isolated from soil. Many characteristics of the strain and optimum cultivation condition for protease production were investigated.,The protease from Serratia sp. Y-4 was purified and studied for the properties of the enzyme. The isolated strain was identified to the genus Serratia. The strain was cultivated in 1%-casein, 0.5%-Na$_{3}$PO$_{4}$.7H$_{2}$O, 0.1%-NaCl, 0.05%-KCI, 0.02%-MgSO$_{4}$.7H$_{2}$O, 0.02%-CaCl$_{2}$.2H$_{2}$O, 0.02%-ZnSO$_{4}$.7H$_{2}$O, 0.02%-MnCl$_{2}$.4H$_{2}$O and 0.5%-soy bean oil at pH 7.0 for 35 hrs. The enzyme was purified about 5.89 fold from the culture broth with 31.1% recovery and 19,613 u/mg through ultrafiltration, ammonium sulfate, DEAE-sephacel and Superose-12 chromatography. The purified enzyme was identified as one band by isoelectric focusing, SDS- and native-PAGE. It has maxium activity at $37^{\circ}C$ and pH 9.0. Molecular weight of it is approx. 50 kD and pl is about 6.70. Its Km value for casein was 20 mg/ml. 5 mM-EDTA, 5mM-SDS, Ag$^{+1}$, Cu$^{+2}$, Hg$^{+2}$ and Pb$^{+2}$ inhibited the enzyme.

• Journal of Digital Convergence
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• v.16 no.10
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• pp.115-123
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• 2018

This study explores unified service experience to boost O2O services. Previous studies on service management and marketing only focused on customer experience in offline stores, while prior works on information systems looked only at the experience of services in mobile applications. In this vein, this study took into accounts the characteristics of offline stores and the benefits of their mobile applications. Moreover, the final dependent variable was share of wallet to measure customer's expenditure within the category. The theoretical model was tested based on 219 consumers who frequently visit Starbucks and use its mobile application. PLS method was applied to analysis the research model and hypotheses. The analysis results showed that customer satisfaction about offline store is not significantly related to share of wallet, while satisfaction about mobile application plays a significant role in enhancing share of wallet. Hedonic and social benefits were found to have significant effects on satisfaction about mobile application. The analysis results help establish service marketing and strategies to enhance the unified customer experience of O2O service.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.6
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• pp.386-391
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• 2018

An epitaxial GaN layer was grown on a cone-shape-patterned sapphire substrate (PSS) (Sample A) and an AlN-buffered PSS (Sample B) with two growth steps under the same process conditions by employing the hydride vapor phase epitaxy (HVPE) method. We have investigated the characteristics of the GaN layer grown on two kinds of substrates at each growth step. The cross-sectional SEM image of the GaN layer grown on the two types of substrates showed growth states of GaN layers formed during the 1st and 2nd growth steps with different growth durations. Dislocation density was obtained by calculation using the FWHM value of the rocking curve for (002) and (102). Sample A showed 2.62+08E and 6.66+08E and sample B exhibited 5.74+07E and 1.65+08E for two different planes. The red shift was observed is photoluminescence (PL) analysis and Raman spectroscopy results. GaN layers grown on AlN-buffered PSS exhibited better optical and crystallographic properties than GaN layers grown on PSS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1219-1226
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• 2013

The purpose of this study was aimed to analyze factors affecting on continuous intention to use of Smartphone based on the innovation diffusion theory. Also, by using the demographic characteristics were compared whether the difference in the loyalty on between user group of iOS and Android platform. Predictor factors were selected innovation, convenience, economic cost, social influence, communication channel, compatibility and complexity suggested on the innovation diffusion theory. Participants of this study were 278 Smartphone users in Busan city and Gyeongnam province in accordance with convenience sampling. IBM SPSS Statistics 19 were employed for descriptive statistics, Smart PLS(partial least squares) was employed for confirmatory factor analysis and path analysis of casual relationship among variables and effect. Analytical results show that all paths except path from complexity to the continuous intention to use and loyalty are significant. The comparison loyalty on between user group of iOS and android platform are significant. This study suggests practical and theoretical implications based on the results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.344-344
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• 2007

본 연구에서는 X선 영상 검출기로의 적용을 위하여 $Gd_2O_3$:Eu 형광체 필름을 제작하여 X선에 대한 발광 특성을 분석하였다. $Gd_2O_3$:Eu는 저온 액상법을 이용하여 분말 형태로 제조한 후 Particle-in-binder (PIB)으로 필름 형태로 제작한 후, 도핑된 Europium(Eu)의 농도와 소결 온도에 따른 X선에 대한 발광 특성을 분석하였다. Photolumimescence (PL) spectrum에서 611nm에서 가장 높은 발광 효율을 나타내었으며, 입자의 크기가 줄어듦에 따라 610nm에서 새로운 peak가 형성 되었다. 또한 Eu의 농도에 따라서 발광 강도의 차이가 관찰되었는데, 5wt%의 도핑 농도에서 가장 높은 발광 효율을 나타냈으며, 도핑 농도에 매우 의존적인 결과를 나타냈다. 소결 온도에 따른 발광 특성 분석에서, $500^{\circ}C$에서 소결하였을 때는 623nm에서 강한 peak를 나타내는 단사정계상의 발광 peak는 거의 관찰되지 않았으나 소결 온도가 $700^{\circ}C$와 $900^{\circ}C$에서는 peak가 확인되었다. 이를 통해 $Gd_2O_3$ 모체가 대부분 입방 대칭 구조를 가지는 $Gd_2O_3$:Eu가 합성되었음을 확인할 수 있었다. 또한 소결 온도에 따른 발광 강도를 분석한 결과 $900^{\circ}C$에서 소결하였을 때 가장 높은 발광 강도를 나타냈다. Luminescent decay time 측정 결과에서 도핑된 Eu의 농도가 커질수록 Luminescent decay time이 짧아짐을 확인할 수 있었다.

• Korean Journal of Microbiology
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• v.36 no.3
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• pp.221-227
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• 2000

This study was performed to investigate the biological characteristics of twenty isolates of extended spectnlm $\beta$-lactamase (ESBL) producing Klebsiellapnezm~onia collected kom the various clinical specimens of three hospitals in Pusan. Isoelectric focusing (IEF) and PCR were used to determine the types of $\beta$-lactamase gene in this study. Twenty isolates of ESBL producing Klebsiellnp~ieun~or~iae could be divided by PCR, such as TEM type (I1 strains), SHV type (8 strains); non TEM non SHV type (1 strain). In the isoelechic focusing test, the PI of TEM type was 5.2-6.0 and that of SHV type was 6.9-7.4. According to the pI value and PCR bands, twenty strains of ESBL Klebsiellapneumoniae were divided into 5 types: TEM type @I 5.2-6.0; 1080 bp on PCR band), TEM + SHV type (pI 5.2-6.0; andpI 7.0-7.4; 1080 bp and 599 bp on PCR band), SHV type (pl7.0-7.4; 599 bp on PCR band), non TEM non SHV type, and otber type (PCR result was SHV type but pI was not detected).

• Journal of the Korean Applied Science and Technology
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• v.19 no.2
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• pp.103-107
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• 2002

Diphosphine dinuclear gold(I) complexes were synthesized from the reaction of bridged diphosphines and gold ions. As a bridged diphosphine, 1,2-bis(diphenylphosphino)metbane (dppm) or 1,1'-Bis(diphenylphosphino) ferrocene (dppf) was introduced. As anionic ligands, CI was first coordinated to Au, resulting in (diphosphine)$(AuCl)_{2}$. Then, the ligand, SPh, was substituted for Cl in the chloride complex to give (diphosphine)$(AuSPh)_{2}$. As a result, three digold complexes, (dppm)$(AuCl)_{2}$. (I), (dppf)$(AuCl)_{2}$. (II), and (dppf)$(AuSPh_{2}$. (III) were prepared in this study. The thermal properties were investigated at first hand to confirm that the gold complexes were in fact formed. The digold complexes were decomposed above $200^{\circ}C$ while the ligand, dppm or dppf, melts under $180^{\circ}C$ The photoluminescence (PL) spectra of the spin-coated thin films showed the maximum peak at 590, 595, and 540nm for the complex, I, II, and III, respectively. These complexes were found to give the orange color phosphorescence. Therefore, these digold complexes can be candidates for orange-red phosphorescent materials in organic electroluminescent devices (OELD). Further studies on application of the complexes as a dopant in an emitting layer are in progress in our laboratory.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.23-28
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• 2019

The Titanium oxide ($TiO_2$) is an attractive ceramic material which shows non-toxic, high refractive index, catalytic activity and biocompatibility, and can be fabricated at a low cost due to its high chemical stability and large anisotropy. $TiO_2$ nanoparticles have been prepared by sol-gel method. The pH of solution can affect the $TiO_2$ crystallinity during the formation of nanoparticles. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy in order to investigate their structural and photoluminescence properties. Through these analysis, the size of $TiO_2$ nanoparticles were found to be smaller than 5 nm. As the crystallinity of the nanoparticles increased, the emission of PL in the 550 nm region increased. Therefore, luminescence characteristics can be improved by controlling the crystallinity of the $TiO_2$ nanoparticles.

• Korean Journal of Materials Research
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• v.31 no.1
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• pp.16-22
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• 2021

In this study, quantum dot-sensitized solar cells (QDSSC) using CdSe/ZnS quantum dots (QD) of various sizes with green, yellow, and red colors are developed. Quantum dots, depending their different sizes, have advantages of absorbing light of various wavelengths. This absorption of light of various wavelengths increases the photocurrent production of solar cells. The absorption and emission peaks and excellent photochemical properties of the synthesized quantum dots are confirmed through UV-visible and photoluminescence (PL) analysis. In TEM analysis, the average sizes of individual green, yellow, and red quantum dots are shown to be 5 nm, 6 nm, and 8 nm. The J-V curves of QDSSC for one type of QD show a current density of 1.7 mA/㎠ and an open-circuit voltage of 0.49 V, while QDSSC using three type of QDs shows improved electrical characteristics of 5.52 mA/㎠ and 0.52 V. As a result, the photoelectric conversion efficiency of QDSSC using one type of QD is as low as 0.53 %, but QDSSC using three type of QDs has a measured efficiency of 1.4 %.