• Journal of Sericultural and Entomological Science
• /
• v.41 no.1
• /
• pp.54-60
• /
• 1999

Antheraea pernyi silk powder was prepared by treatment with HCl and NaOH. The degree of hydrolysis of Antheraea pernyi silk fiber was examined. The morphology and structural characteristics of Antheraea pernyi silk powder were investigated by using SEM, FTIR and X-ray diffractometer. As the concentration of HCl and NaOH and tratment temperature increased, in general, the degree of hydrolysis of Antheraea pernyi silk fiber increased. On the other hand, the degree of hydrolysis of Antheraea pernyi treated with 3 N NaOH at 120$^{\circ}C$ for 24 hr was 70 wt%, which was lower than that of 90$^{\circ}C$(83 wt%). The morphology of acid/alkali resistance fraction of Antheraea pernyi silk fibroin was transformed from fiber form to powered one with an increase of hydrolysis. The conformation of Antheraea pernyi silk powder characterized by FT-IR spectrometer and X-ray diffractometer ${\beta}$-sheet and ${\alpha}$-helix structure.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.4
• /
• pp.595-604
• /
• 2006

The growth characteristics of Commercially Developed Nitrifying Bacteria (CDNB) were studied in laboratoryscale. CDNB, a pure, artificially isolated bacterium, was cultivated to produce Cultivated Nitrifying Bacterium Group (CNBG). The average ammonia removal rate of CDNB was 0.0234g $NH_4^+-N/g$ MLSS/hr. CNBG was produced in the batch reactor and Specific Nitrification Rate (SNR) was determined at 0.0107g $NH_4^+-N/g$ MLSS/hr. The SNR of CNBG was lower than the SNR of CDNB because the diverse and multi-cultured microbial growth took place during cultivation. The effect of the temperatures and the mixing ratios of sewage and culture solution on the SNR of CNBG was studied. The SNR of CNBG, 0.0107g $NH_4^+-N/g$ MLSS/hr at $27^{\circ}C$, decreased to 0.0048g $NH_4^+-N/g$ MLSS/hr at $15^{\circ}C$, and temperature coefficient (${\Theta}$) was calculated to be 1.07. With the varied sewage mixing ratios, the SNR of CNBG remained unchanged. Activated sludge reactors maintaining an MLSS of 2,000mg/L at HRT of 4 h were operated under conditions in which dosage of Concentrated CNBG Solution (CCNBGS, 10,000mg MLSS/L) and application method of CNBG were varied. The reactor with 20mL of CCNBGS took shorter time to oxidize $NH_4^+-N$ reaching 1mg/L than the reactor with 5mL of CCNBGS showing that higher dosages were associated with greater mass removal of $NH_4^+-N$. However, the total removal was not great. In terms of different methods of CNBG application, reactor seeded with 20mL of CCNBGS took 3days to reach 1mg/L of effluent ammonia concentration while reactor dosed with 20% (v/v) CNBG implanted media took 2days. Both the control reactor and the reactor dosed with 20% (v/v) media only did not reach 1mg $NH_4^+-N/L$ after operating 18days. The reactor with CNBG implanted media had the highest $NH_4^+-N$ removal rate because of maintaining high concentration of Nitrifying Oxidizing Bacteria (NOM), and is regarded as an appropriate method for the activated sludge process.

• Journal of the Korean Vacuum Society
• /
• v.7 no.4
• /
• pp.293-299
• /
• 1998

We have investigated the atomic and electronic structures of Cu-adsorbed Si(100)-2$\times$1 surface, by using LEED and UPS. In the UPS spectra, the weak structures (peaks) related to Cu silicide appeared for low coverages less than 1.3 ML at room temperature, and the intensity of Cu 3d band rapidly increased with respect to Cu coverages. The Cu silicide peaks become clear after Cu deposition at room temperature followed by high temperature annealing ($\geq 300^{\circ}C$) or for Cu deposited surface at the substrate temperature of $400^{\circ}C$. On the other hand, these structures disappeared by annealing at $750^{\circ}C$. At very low coverage, a surface state near Fermi level $(E_F)$ was observed at $400^{\circ}C$. According to the rigid band model, it seems to be originated from the surface empty state occupied partially with Cu 4s electron. In the LEED patterns, no Cu-induced superstructure observed for RT-depositions and post annealing, while there were several surface structures which depend on substrate temperatures and coverages. we observed the clean surface 2$\times$1+2$\times$2 phase for 1.5 ML at $400^{\circ}C$, the clean surface 2$\times$1+5$\times$1 phase for 0.5 ML at $450^{\circ}C$ and the clean surface 2$\times$1+2$\times$2+5$\times$2+5$\times$5+10$\times$2 mixed phases for 3 ML at $450^{\circ}C$.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.15
• /
• pp.6131-6136
• /
• 2014

Objective: Epidemiology studies have reported conflicting results between glutathione S-transferase Mu-1 (GSTM1), glutathione S-transferase theta-1 (GSTT1) and glutathione S-transferase pi-1 (GSTP1) and ovarian cancer (OC) susceptibility. In this study, an updated meta-analysis was applied to determine whether the deletion of GSTM1, GSTT1 and GSTP1 has an influence on OC susceptibility. Methods: A published literature search was performed through PubMed, Embase, Cochrane Library, and Science Citation Index Expanded database for articles published in English. Pooled odds ratios (ORs) and 95% confidence intervals (95%CIs) were calculated using random or fixed effects models. Heterogeneity between studies was assessed using the Cochrane Q test and $I^2$ statistics. Sub-group analysis was conducted to explore the sources of heterogeneity. Sensitivity analysis was employed to evaluate the respective influence of each study on the overall estimate. Results: In total, 10 published studies were included in the final analysis. The combined analysis revealed that there was no significant association between GSTM1 null genotype and OC risk (OR=1.01, 95%CI: 0.91-1.12). Additionally, there was no significant association between GSTT1 genetic polymorphisms and OC risk (OR=0.98, 95% CI: 0.85-1.13). Similalry, no significant associations were found concerning the GSTP1 rs1695 locus and OC risk. Meanwhile, subgroup analysis did not show a significant increase in eligible studies with low heterogeneity. However, sensitivity analysis, publication bias and cumulative analysis demonstrated the reliability and stability of the current meta-analysis. Conclusions: These findings suggest that GSTs genetic polymorphisms may not contribute to OC susceptibility. Large epidemiological studies with the combination of GSTM1 null, GSTT1 null and GSTP1 Ile105Val polymorphisms and more specific histological subtypes of OC are needed to prove our findings.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.115-115
• /
• 2010

고휘도 고효율 백색 LED (lighting emitting diode)가 차세대 조명광원으로 급부상하고 있다. 백색 LED를 생산하기 위한 공정에서 MOCVD (유기금속화학증착)장비를 이용한 에피웨이퍼공정은 에피층과 기판의 격자상수 차이와 열팽창계수차이로 인하여 생성되는 에피결함의 문제로 기판과 GaN 박막층 사이에 완충작용을 해줄 수 있는 버퍼층 (Buffer layer)을 만든다. 그 위에 InGaN/GaN MQW (Multi Quantum Well)공정을 하여 고휘도 고효율 백색 LED를 구현 할 수 있다. 이 공정에서 기판의 온도가 불균일해지면 wafer 파장 균일도가 나빠지므로 백색 LED의 yield가 떨어진다. 균일한 기판 온도를 갖기 위한 조건으로 기판과 induction heater의 간격, 가스의 흐름, 기판의 회전, 유도가열코일의 디자인 등이 장비의 설계 요소이다. 본 연구에서는 유도가열방식의 유도가열히터를 이용하여 기판과 히터의 간격에 차이에 따른 기판 균일도 측정했고, 회전에 의한 기판의 온도분포와 자기장분포의 실험적 결과를 상용화 유체역학 코드인 CFD-ACE+의 모델링 결과와 비교 했다. 또한 가스의 inlet위치에 따른 기판의 온도 균일도를 측정하였다. 본 연구에서 사용된 가열원은 유도가열히터 (Viewtong, VT-180C2)를 사용했고, 가열된 흑연판 표면의 온도를 2차원적으로 평가하기 위하여 적외선 열화상 카메라 (Fluke, Ti-10)를 이용하여 온도를 측정했다. 와전류에 의한 흑연판의 가열 현상을 누출 전계의 분포로 확인하기 위하여 Tektronix사의 A6302 probe와 TM502A amplifier를 사용했다. 흑연판 위에 1 cm2 간격으로 211곳에서 유도 전류를 측정했다. 유도전류는 벡터양이므로 $E{\theta}$를 측정했으며, 이때의 측정 방향은 흑연판의 원주방향이다. 또한 자기장에 의한 유도전류의 분포를 확인하기 위하여 KANETEC사의 TM-501을 이용하여 흑연판 중심으로부터 10 mm 간격으로 자기장을 측정 했다. 저항 가열 히터를 통하여 대류에 의한 온도 균일도를 평가한 결과 gap이 3 mm일때, 평균 온도 $166.5^{\circ}C$에서 불균일도 6.5%를 얻었으며, 회전에 의한 온도 균일도 측정 결과는 2.5 RPM일 때 평균온도 $163^{\circ}C$에서 5.5%의 불균일도를 확인했다. 또한 CFD-ACE+를 이용한 모델링 결과 자기장의 분포는 중심이 높은 분포를 나타냄을 확인했고, 기판의 온도분포는 중심으로부터 55 mm되는 곳에서 300 W/m3로 가장 높은 분포를 나타냈다. 가스 inlet 위치를 흑연판 중심으로 수직, 수평 방향으로 흘려주었을 때의 불균일도는 각각 10.5%, 8.0%로 수평 방향으로 가스를 흘려주었을 때 2.5% 온도 균일도 향상을 확인했다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.335-335
• /
• 2014

Over the past several years, transparent conducting oxides have been extensively studied in order to replace indium tin oxide (ITO). Here we report on fluorine doped zinc tin oxide (FZTO) films deposited on glass substrates by radio-frequency (RF) magnetron sputtering using a 30 wt% ZnO with 70 wt% SnO2 ceramic targets. The F-doping was carried out by introducing a mixed gas of pure Ar, CF4, and O2 forming gas into the sputtering chamber while sputtering ZTO target. Annealing temperature affects the structural, electrical and optical properties of FZTO thin films. All the as-deposited FZTO films grown at room temperature are found to be amorphous because of the immiscibility of SnO2 and ZnO. Even after the as-deposited FZTO films were annealed from $300{\sim}500^{\circ}C$, there were no significant changes. However, when the sample is annealed temperature up to $600^{\circ}C$, two distinct diffraction peaks appear in XRD spectra at $2{\Theta}=34.0^{\circ}$ and $52.02^{\circ}$, respectively, which correspond to the (101) and (211) planes of rutile phase SnO2. FZTO thin film annealed at $600^{\circ}C$ resulted in decrease of resistivity $5.47{\times}10^{-3}{\Omega}cm$, carrier concentration ~1019 cm-3, mobility~20 cm2 V-1s-1 and increase of optical band gap from 3.41 to 3.60 eV with increasing the annealing temperatures and well explained by Burstein-Moss effect. Change of work function with the annealing temperature was obtained by ultraviolet photoemission spectroscopy. The increase of annealing temperature leads to increase of work function from ${\phi}=3.80eV$ (as-deposited FZTO) to ${\phi}=4.10eV$ ($600^{\circ}C$ annealed FZTO) which are quite smaller than 4.62 eV for Al-ZnO and 4.74 eV for SnO2. Through X-ray photoelectron spectroscopy, incorporation of F atoms was found at around the binding energy of 684.28 eV in the as-deposited and annealed FZTO up to 400oC, but can't be observed in the annealed FZTO at 500oC. This result indicates that F atoms in FZTO films are loosely bound or probably located in the interstitial sites instead of substitutional sites and thus easily diffused into the vacuum from the films by thermal annealing. The optical transmittance of FZTO films was higher than 80% in all specimens and 2-3% higher than ZTO films. FZTO is a possible potential transparent conducting oxide (TCO) alternative for application in optoelectronics.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1998.02a
• /
• pp.55.2-55
• /
• 1998

다견정 심리판-거l르마늄(JXlly-SiGe)은 TFT(thin-film transistor)와 갇븐 소자 응용에 있어서 중요한 불칠이다 .. LPCVD (low pressure chemical vapor deposition) 방법으로 비정칠 SiGc (a-SiGe) 박막올 증 착시키고 고상결정화(SPC: solid-phase crystallization)시켜 poly-SiGc옹 얻는 것은 잘 알려져 있다. 그러 나 그러나 PF'||'&'||'pound;VD-SPC 방법올 이용한 poly-SiGc의 제조에 대해서는 아직 두드러지게 연구된 바 없다. 우리단 PF'||'&'||'pound;VD 방법으로 a-SiGc 박막올 증착시키고 고상캘정화시켜 poly-SiGc올 얻었 R며, :~ 결정성, G Gc 농도, 결정핍의 평끌 크기 눔올 XRD (x-ray diffraction) 방법으호 조사하였다. 특히 pr'||'&'||'pound;VD 증착시 가판온도,Gc 함유량 등이 고상화에 미치는 영향에 대해서 조사하였다. P PECVD 장치는 터보펌프콸 사용하여 71저진공이 2xlOlongleftarrow5 Torr에 이르렀다. 가판윤 SiOOO) 웨이퍼륜 사용하고 기판 온도는 약 150- 35()"C 사이에서 변화되었다. 증착가스는 SiH4, GcH4, 112 등흘 썼다. 증착 압력과 r.f 전력용 각각 O.25ToIT와 3W로 일정하게 하였다 .. Gc 함유량(x)은 x x=O.O-O.5 사이에서 변화되었다 .. PECVD모 증착된 SiGc 박막들은 고상결정화를 위해 $\theta$X)"(:: Nz 분위기에서 24시간동안, 혹은 5OO'C에서 4열간 가열되었다. 고상결정화 후 poly-SiGc 박막은 SiGc(Ill), (220), (311) XRD 피크들올 보여주었으며, 각 피 크들은 poly-Si에 비하여 왼쪽으로 Bragg 각이 이동되었고, Vegard’slaw에 의해서 x의 값올 확 인할 수 있었다. 이것온 RBS 결과와 열치하였다. 약 150-350'C 사이에서 변화된 기판온도의 범위 에서 증착온도가 낮올수콕 견정립의 크기는 대체로 증가하는 것으로 나타났다 .. XHD로 추정된 형 균 결정립의 크기는 최대 약 3$\alpha$1m 정도였다. 또한 같끈 샘플뜰에 대해서 기판온도가 낮올수록 증착속도가 증가함옴 확인하였다 .. Gc 함유량이 x=O.1에서 x=O.5로 증가함에 따라서도 결정립의 크기와 SiGc 증착속도는 증가하는 것으로 나타났다 .. Hwang [1] , Kim[2] 둥의 연구자들은 Gc 함유 량이 증가함에 따라 결정 립 크기가 캄소하는 것올 보고하였으냐, Tsai [3] 둥은 반대의 결과플 보 고하고 Ge 힘유량의 증가시 결정립 크기의 증가에 대해 Gc의 Si보다 낮은 융점 (melting point) 올 강조한 바 있다. 결정립 크기의 증가는 대체로 SiGe 중착속도의 증가와도 관련이 있음올 볼 때, poly-SiGc의 경우에도 polv-Si의 고상화에서와 같이 증착속도가 빠를수록 최종적언 결정럽의 크기가 커지는 것으로 이해될 수도 있다 .. PECVD 증착시 증착속도의 증가는 증착된 박딱에서의 무켈서도를 증 가시킬 수 있음올 고려하면, 이라한 결파플온 p이y-SiGc의 고상결정화에서도 ploy-Si의 고상결정 화에서와 마찬가지로 초기 박막에서의 구조직 무절서도가 클수록, 고상결정화 후 결정 립의 크기 가 커칠 수 있음올 보여준다고 생각휠 수 있다,

• Korean Journal of Food Science and Technology
• /
• v.30 no.5
• /
• pp.1024-1028
• /
• 1998

Crystalline structure of the extrudate of high amylose corn starch was studied by X-ray diffractometer and $^{13}C\;NMR$. The X-ray diffraction crystal ratio of the extrudates (barrel temperature $100^{\circ}C$ )of high amylose corn starch slightly increased from 6.08% to 8.37% by increasing feed moisture content from 25% to 45%. But extrudates of high amylose corn starch showed similar crystal ratio on various extrusion conditions. Extrudates of high amylose corn starch (feed moisture content 20%, barrel temp $140^{\circ}C$) showed more enlarged crystal structure than that of non-extrudates. The perpendicular distance of crystal increased by extrusion. Crystal ratio was changed from $6.3{\sim}8.3%$ to $4.5{\sim}5.8%$ during storage at $4^{\circ}C$. Starch configuration was examined with $^{13}C\;NMR$. Double helical content was measured by $^{13}C\;NMR$ method. The highest double helical content (60%) was obtained from high amylose corn starch extrudate (barrel temp.: $100^{\circ}C$, feed moisture content 45%). Double helical contents and resistant starch (RS) yield (pancreatin) were positively correlated. However, double helical content of the extrudates was not changed by the storage at $4^{\circ}C$.

• Korean Journal of Materials Research
• /
• v.23 no.12
• /
• pp.714-721
• /
• 2013

A stoichiometric mixture of evaporating materials for $ZnAl_2Se_4$ single-crystal thin films was prepared in a horizontal electric furnace. These $ZnAl_2Se_4$ polycrystals had a defect chalcopyrite structure, and its lattice constants were $a_0=5.5563{\AA}$ and $c_0=10.8897{\AA}$.To obtain a single-crystal thin film, mixed $ZnAl_2Se_4$ crystal was deposited on the thoroughly etched semi-insulating GaAs(100) substrate by a hot wall epitaxy (HWE) system. The source and the substrate temperatures were $620^{\circ}C$ and $400^{\circ}C$, respectively. The crystalline structure of the single-crystal thin film was investigated by using a double crystal X-ray rocking curve and X-ray diffraction ${\omega}-2{\theta}$ scans. The carrier density and mobility of the $ZnAl_2Se_4$ single-crystal thin film were $8.23{\times}10^{16}cm^{-3}$ and $287m^2/vs$ at 293 K, respectively. To identify the band gap energy, the optical absorption spectra of the $ZnAl_2Se_4$ single-crystal thin film was investigated in the temperature region of 10-293 K. The temperature dependence of the direct optical energy gap is well presented by Varshni's relation: $E_g(T)=E_g(0)-({\alpha}T^2/T+{\beta})$. The constants of Varshni's equation had the values of $E_g(0)=3.5269eV$, ${\alpha}=2.03{\times}10^{-3}eV/K$ and ${\beta}=501.9K$ for the $ZnAl_2Se_4$ single-crystal thin film. The crystal field and the spin-orbit splitting energies for the valence band of the $ZnAl_2Se_4$ were estimated to be 109.5 meV and 124.6 meV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that splitting of the ${\Delta}so$ definitely exists in the ${\Gamma}_5$ states of the valence band of the $ZnAl_2Se_4/GaAs$ epilayer. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-exciton for n = 1 and $C_{21}$-exciton peaks for n = 21.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.108-108
• /
• 2000

급증하는 무선통신 정보수요는 특히, 고주파대역 (300NHz-300GHz)에서 사용되는 공진기, 필터, 발진기 등과 같은 소자의 품질향상을 요구하고 있다. 고주파용 유전체 중 ZrTiO4 는 $\alpha$-PbO2 계열의 사방정구조를 갖고 있는 유전체로서 높은 유전율 ($\varepsilon$=40)과 높은 품질계수 (Q=1/tan$\delta$=4700 at 7GHz)를 갖고 있고, Sn 첨가시 0ppm/$^{\circ}C$의 공진주파수 온도계수를 얻을 수 있다고 보고되어 있다. 본 연구에서는 약 110$0^{\circ}C$ 이상에서 안정한 상으로 존재하는 ZrTiO4를 저온에서 증착하여 준안정한 상태로 결정화되게 한후, 유전손실 (tan$\delta$)과 유전율($\varepsilon$)을 측정하였다. 또한 증착온도와 열처리과정에 따른 박막의 us형 (Strain) 정도의 변화를 X-선 회절결과로부터 분석하였으며 이를 측정된 유전특성 값과 비교하였다. ZrTiO4 박막은 DC magnetron reactive sputter로 Zr과 Ti 타겟으로부터 high phosphorous doped Si (100) 기판위에 증착하였다. 압력은 4mTorr로 유지하고 박막의 화학양론적 조성비를 맞추기 위해 각 타겟에 가해지는 power는 Zr/Ti=500W/650W로 고정하고, 반응가스의 비율을 Ar/O2=17sccm/3.5sccm으로 유지하여 박막내에 인입되는 산소량을 제어하였다. 증착 직후와 열처리 후의 박막특성을 비교하기 위해 증착온도를 상온에서부터 $600^{\circ}C$까지 변호시키고 증착후 각각의 시편을 80$0^{\circ}C$ 산소분위기에서 2시간동안 열처리하여 시편을 준비하였다. 박막의 상형성 여부와 결정성변화는 $ heta$-2$\theta$X-선 회절법을 사용하여 조사하였고, EPMA를 이용하여 박막의 조성을 확인하였다. 유전특성의 측정을 위해 백금 상부전극을 증착한 후, impedance analyzer를 이용하여 100kHz 영역에서의 유전손실을 측정하고, 측정된 정전용량과 박막의 두께로부터 유전율을 계산하였다. ZrTiO4 박막은 증착온도 20$0^{\circ}C$ 이상에서 결정성을 보이기 시작했으며, 열처리 이후에는 상온에서 비정질이었던 시편이 $650^{\circ}C$ 이상의 온도에서 결정화되기 시작하였다. 증착온도에 따라 유전손실은 0.038에서 0.017 정도로 감소하는 경향을 나타냈으며, 각각 열처리에 의해서 0.034, 0.005 정도로 다시 감소하였다. 박막의 유전율은 약 35 정도의 값을 나타내었으며 X-선 회절 data로부터 분석한 박막의 변형은 증온도에 따라 7.2%에서 0.04%로 감소하였고 이 이경향은 유전손실은 감소경향과 일치하였다.