• Macromolecular Research
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• 제15권1호
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• pp.59-64
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• 2007

Star-shaped, nonlinear optical (NLO) material was synthesized and its optical, thermal, and electro-optic properties were investigated. Three NLO-active dipolar chromophores containing a phenylene ring substituted with a bulky alkyl chain as a conjugation bridge were chemically bonded to the core of 1,1,1-tris(4-hydroxyphenyl)ethane to form a dendritic architecture. The chemical structure and purity of the chromophore were verified by NMR spectroscopy. The chromophore exhibited a broad absorption band centered at around 608 nm tailing up to 760 nm in toluene solution and also showed a discernible solvatochromic shift in more polar solvent. The chloroform solution of the dendrimer produced an absorption band with a red-shifted maximum as large as 28 nm when compared to that of the toluene solution. It was thermally stable up to $275^{\circ}C$ in a nitrogen atmosphere and had a glass transition temperature of $76^{\circ}C$. In a preliminary result, the polymer film containing the dendritic compound exhibited a shift of 19 pm/V taken at $1.55{\mu}$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집
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• pp.1-6
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• 2004

In this paper author describe the undoped and $Co^{2+}$ (0.5mole%)doped $Cd_4GeS_6$ single crystals were grown by the chemical transporting reaction(CTR) method using high purity(6N) Cd, $GeS_2$, S elements. It was found from the analysis of X-ray diffraction that the undoped and $Co^{2+}$(0.5mole%) doped $Cd_{4}GeS_{6}$ compounds have a monoclinic structure in space grop Cc. The optical energy band gap was direct band gap and temperature dependence of optical energy gap was fitted well to Varshni equation. Impurity optical absorption peaks due to the doped cobalt in the $Cd_4GeS_6:Co^{2+}$ single crystal were observed at 3593cm-1, 5048cm-1, 5901cm-1, 7322cm-1, 12834cm-1, 13250cm-1, 14250cm-1，and 14975cm-1 at 11.3K.

• Journal of Microbiology and Biotechnology
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• 제7권5호
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• pp.329-332
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• 1997

Cell-free extracts of Streptomyces neyagawaensis SL-387 grown on a chemically defined medium supplemented with DL-3-amino-3-phenylpropionic acid (APP) produced N-acetyl-APP (Ac-APP) in the presence of APP and acetyl coenzyme A. The APP obtained by acid hydrolysis of the Ac-APP was D-configuration: $[\alpha]_D+6.5^{\circ}(H_2O)\;at\;20^{\circ}C$, optical purity 92% enantiomeric excesses (ee). These results suggest that an N-acetyltransferase exists in the cell-free extract as a novel enzyme with specificity for D-APP.

• Journal of Microbiology and Biotechnology
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• 제7권5호
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• pp.318-322
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• 1997

In order to isolate a microorganism having preferential degradation of D-carnitine from DL-carnitine, a bacterium assimilating D-carnitine as a sole carbon and energy source was isolated from soil by enrichment culture and partially identified as Enterobacter sp. Also, a mutant having lessened L-carnitine decomposition rates was selected with nitrosoguanidine mutagenesis, which led to decrease the specific activities of carnitine dehydrogenase (7.6-fold) and ${\beta}$-hydroxybutyrate dehydrogenase (9.5-fold) as compared to the wild strain. Meanwhile, optimal culture conditions for optical resolution of DL-carnitine were investigated. Under optimal conditions, 3.53 g/l L-carnitine was obtained from 20 g/l DL-carnitine, which corresponded to 35.3% L-carnitine yield and 97.9% optical purity.

• 분석과학
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• 제15권1호
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• pp.87-90
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• 2002

The content of $SiHCl_3$ as a trace impurity in $SiCl_4$ was analyzed by Near IR spectrophotometer with optical fiber. The strong absorption bands of $5345{\sim}5116cm^{-1}$ and $4848{\sim}4349cm^{-1}$ were used for analysis of $SiHCl_3$, and the detection limit of impurity $SiCl_3$ was appeared to be 0.005 ％ in the spectrum. The quantitative analysis by Near IR spectrophotometry showed the analytical possibility of trace impurity in $SiCl_4$ without sample pre-treatment not only in the laboratory but also in the field.

• 대한전자공학회논문지
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• 제26권11호
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• pp.1814-1818
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• 1989

The crystals of ZnGa2S4 and ZnGa2S4:Co(2mole%) were synthesized from high-purity (99.999%) elements of Zinc, Gallium, and sulfur. The crystal structure of these crystals belong to a tetragonal system with layer type and the lattice constants are a =5.35\ulcorner c=10.43\ulcornerfor ZnGa2S4: Co(2 mole%) crystal at 298\ulcorner. The optical absorption spectra of these compounds were obtained through reflectance measurements using a 60 mm diameter intergrating sphere. The optical energy gaps are 3.18eV for ZnGa2S4 and 2.60eVfor ZnGa2S4:L Co(2mole%)at 298\ulcorner, respectively.

• 한국세라믹학회지
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• 제55권2호
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• pp.174-177
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• 2018

ZnO/Ag/ZnO multilayers were fabricated and their optical properties were investigated in terms of the micro-cavity effect in electroluminescent devices based on colloidal quantum dots. The top and bottom ZnO layers were formed by a sol-gel method while the middle Ag layer was deposited by thermal evaporation. After the fabrication of the ZnO/Ag/ZnO structure, the transmittance increased to 74%. When the oxide/metal/oxide multilayers were applied to quantum dot light-emitting diodes, the color purity was enhanced due to the narrower full width at half maximum.

• 한국미생물·생명공학회지
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• 제30권4호
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• pp.373-379
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• 2002

Nitrile 비대칭 가수분해효소를 지닌 미생물을 이용하여 DL-lactonitrile로부터 D-lactic acid를 생산하기 위하여, DL-acetonitrile을 효소유도제로 이용할 수 있는 균주를 분리하였다. 분리한 균주들 중 WJ-003균주가 D-lactic acid의 생산능력이 가장 우수하였고, Pseudomonas sp.로 부분동정하였다. DL-lactonitrile로부터 D-lactic acid를 생산하기 위한 최적 반응조건을 검토하였으며 결과들을 요약하면 다음과 같다. 반응혼합액은 10mM의 DL-lactonitrile과 20g(wet weight)의 균체를 포함한 11의 20mM 인산완충액(pH7.0)이었으며, 이때 반응온도는 $30^{\circ}C$이었다. 또한, 18시간 반응이 진행되는 동안 0.843 g/l D-lactic acid가 생산되었고, 이때의 전환율은 93.7%,광학순도는 99.8%이었다 한편, 10mM의 DL-lactonitrile을 14시간 후에 다시 첨가했을 때 28시간에 1.64g/l의 D-lactic acid가 생산되었으며 이때의 전환율은 91.1%, 광학순도는 99.8%이었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.56-56
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• 2010

Single-walled carbon nanotubes (SWCNTs) have attracted much attention as a promising material for transparent conducting films (TCFs), due to their superior electrical conductivity, high mechanical strength, and complete flexibility as well as their one-dimensional morphological features of extremely high length-to-diameter ratios. This study investigated three kinds of SWCNTs with different purities: as-produced SWCNTs (AP-SWCNTs), thermally purified SWCNTs (TH-SWCNTs), thermally and acid purified SWCNTs (TA-SWCNTs). The purity of each SWCNT sample was assessed by considering absorption peaks in the semiconducting ($S_{22}$) and metallic ($M_{11}$) tubes with UV-Vis NIR spectroscopy and a metal content with thermogravimetric analysis (TGA). The purity increased as proceeding the purification stages from the AP-SWCNTs through the thermal purification to the acid purification. The samples containing different contents of SWCNTs were dispersed in water using sodium dodecyl benzensulfate (SDBS). Aqueous suspensions of different purities of SWCNTs were prepared to have similar absorbances in UV-Vis absorption measurements so that one can make the TCFs possess similar optical transmittances irrespective of the SWCNT purity. Transparent conductive SWCNT networks were formed by spraying an SWCNT suspension onto a poly(ethyleneterephthalate) (PET) substrate. As expected, the TCFs fabricated with AP-SWCNTs showed very high sheet resistances. Interestingly, the TH-SWCNTs gave lower sheet resistances to the TFCs than the TA-SWCNTs although the latter was of higher purity in the SWCNT content than the former. The TA-SWCNTs would be shortened in length and be more bundled by the acid purification, relative to the TH-SWCNTs. For both purified (TH, TA) samples, the subsequent nitric acid ($HNO_3$) treatment greatly lowered the sheet resistances of the TCFs, but almost eliminated the difference of sheet resistances between them. This seems to be because the electrical conductivity increased not only due to further removal of surfactants but also due to p-type doping upon the acid treatment. The doping effect was likely to overwhelm the effect of surfactant removal. Although the nitric acid treatment resulted in the similar. electrical properties to the two samples, the TCFs of TH-SWCNTs showed much lower sheet resistances than those of the TA-SWCNTs prior to the acid treatment.

• 한국세라믹학회지
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• 제36권8호
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• pp.813-819
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• 1999

Ion implantation, photo-lithography, Ar ion milling과 hot press 법을 이용한 micro-fabrication techrique을 사용하여 고순도 알루미나 단결정인 사파이어의 내부에, 조절된 Ca의 첨가량을 갖고 있는, crack과 비슷한 형태의 기공들을 형성시켰다. 이 bi-cryslal을 각각의 온도에서 열처리하여 Ca 이온이 고온에서 알루미나의 morphology와 hcaling에 미치는 영향을 관찰하였다. 열처리 온도가 올라감에 따라서 crack-like pore의 내부에 hcxagonal bridging ligaments가 생성되었는데, 열처리 온도와 Ca의 첨가량이 증가할수록 크기가 커지는 것을 관찰할 수 있었고, 생성된 hexagonal bndgmg ligaments는 열처리가 진행됨에 따라 서서히 커지면서 모서리가 둥글어지는 현상을 관찰할 수 있었다. Bicrystal 내부에 형성된 crack-like pore는 열처리가 진행되면서 edge regression. ligamcnt growth 및 flow의 3가지의 특징적인 형태로 진행되었다. 이때 edge regression은 상대적으로 저온에서부터 전체 crack-like pore에서 서서히 일어나기 시작하였으며, ligament growth는 일부 crack-like pore에서 진행되있으며, 대단히 빠른 속도로 crack healing이 진행됨을 추정할 수 있었다. Flow는 $1800^{\circ}C$ 이상의 고온에서 모든 crack-like pore에 걸쳐서 느리게 일어남을 알 수 있었다.