• 한국분말재료학회지
• /
• 제9권5호
• /
• pp.307-314
• /
• 2002

The high temperature deformation behavior of the activated sintered W powder compacts was investigated. The W compact showed the relative density of 94% with the average W grain size of $23\mutextrm{m}$ by activated sintering at $1400^{\circ}C$ for 1 hour. Compression tests were carried out in the temperature range of $900-1100^{\circ}C$ at the strain rate range of $10^{0}$/sec - $10^{-3}$/sec. True stress-strain curve and microstructure exhibited the grain boundary brittleness which was dependent on the compression test temperature. The activated sintered W compact showed that the maximum stress as well as the strain at the maximum stress was abruptly decreased as the test temperature increase from $900^{\circ}C$ to 1000 and $1100^{\circ}C$ regardless of the strain rate. The discrepancy of the microstructure in the specimen center was obviously observed with the increase of the test temperature. After compression test at $900^{\circ}C$ the W grain was severely deformed normally against the compression axis. However, after compression test at $1000^{\circ}C$ and $1100^{\circ}C$ the W grain was not deformed, but the microcrack was formed in the W grain boundary. The Ni-rich second phase segregated along the W grain boundary could be partly unstable over $900^{\circ}C$ and affect the poor mechanical property of the activated sintered W compact.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2011년도 춘계학술발표대회
• /
• pp.243.2-243.2
• /
• 2011

ZnO materials with a wide band gap of approximately 3.3 eV has been used in transparent conducting oxides (TCO) due to exhibitinga high optical transmission, but its low conductivity acts as role of a limitation for conducting applications. Recently, Ga or Al-doped ZnO (GZO, AZO) becomes transparent conducting materials because of high optical transmission and excellent conductivity. However, the fundamental mechanism underlying the improvement of electrical conductivity of the GZO is still the subject of debate. In this study, we have fully investigated the reasons of high conductivity through the characterization of plane defects, crystal orientation, doping contents, crystal structure in Zn1-xGaxO (x=0, 3, 5.1, 5.6, 6.6 wt%). We manufactured Zn1-xGaxO by sintering ZnO and Ga2O3 powers, having a theoretical density of 99.9% and homogeneous Ga-dopant distribution in ZnO grains. The GZO containing 5.6 wt% Ga represents the highest electrical conductivity of $7.5{\times}10^{-4}{\Omega}{\cdot}m$. In particular, many twins and superlattices were induced by doping Ga in ZnO, revealed by X-ray diffraction measurements and TEM (transmission electron microscopy) observations. Twins developed in conventional ZnO crystal are generally formed at (110) and (112) planes, but we have observed the twins at (113) plane only, which is the first report in ZnO material. Interestingly, the superlattice structure was not observed at the grains in which twins are developed and the opposite case was true. This structural change in the GZO resulted in the difference of electrical conductivity. Enhancement of the conductivity was closely related to the extent of Ga ordering in the GZO lattice. Maximum conductivity was obtained at the GZO with a superlattice structure formed ideal ordering of Ga atoms.

• 한국어병학회지
• /
• 제7권2호
• /
• pp.95-103
• /
• 1994

미꾸라지의 성장호르몬 유전자를 분리하기 위하여 미꾸라지의 cDNA library를 준비하였다. total RNA는 미꾸라지의 뇌하수체로부터 얻었으며 oligo (dT)-coupled magnetic bead를 이용하여 total RNA로부터 mRNA를 순수분리하였다. 정제된 mRNA는 cDNA를 합성하기 위한 기질로 사용하였으며, 합성된 cDNA는 EcoRV/Smal으로 절단된 pBlueKS+ plasmid vector에 삽입하였다. 모든 ligation 반응용액을 E. coli, JM109 균주에 형질전환을 유도하였으며 형질전환 효율을 최대화시키기 위하여 전기천공법을 이용하였다. 얻어진 모든 형질전환주들을 DIG로 표지된 Tilapia의 성장호르몬 유전자를 이용하여 고밀도 colony hybridization 에 의하여 검색하였다. 양성반응을 나타내는 10개의 형질전환주를 분리하여 2차 colony hybridization 및 southern hybridization에 의하여 성장호르몬 유전자가 cloning 되었음을 확인하였다. 10 개의 형질전환주 중 하나인 pCGH1을 probe로 사용한 Tilapia 성장 호르몬 유전자의 염기서열과 비교분석하였으며 53.2%의 유사성을 나타냄을 확인하였다.

• 대한화학회지
• /
• 제54권6호
• /
• pp.671-679
• /
• 2010

벤젠이온-물 복합체[$C_6H_6^+-(H_2O)_n$(n=1-5)]의 여러 가능한 구조를 예측하고 다양한 양자역학적 이론 수준(ab initio, DFT 등)에서 분자구조를 최적화 하였으며, 조화 진동주파수를 계산하여 IR 스펙트럼을 예측하였다. $C_6H_6^+-(H_2O)$에 대하여 보다 정확한 결합에너지를 구하기 위하여 MP2 수준에서 분자구조를 최적화하여 결합에너지 계산을 하여 B3LYP 계산 결과와 비교하였으며, 영점 진동에너지(zero-point vibrational energy)를 보정하여 실험값과 비교하였다. $C_6H_6^+-(H_2O)$에 대한 결합에너지는 MP2/aug-cc-pVTZ 이론수준에서 8.6 kcal/mol로 계산되어 최근의 실험결과($8.5{\pm}1$ kcal/mol)와 매우 잘 일치하는 것으로 나타났다.

• 대한기계학회논문집B
• /
• 제25권11호
• /
• pp.1594-1605
• /
• 2001

In this study, a numerical simulation was developed which was capable of predicting the characteristics of NO formation in pilot scale combustor adopting the air-staged burner flame. The numerical calculation was constructed by means of establishing the mathematical models fur turbulence, turbulent combustion, radiation and turbulent nitric oxide chemistry. Turbulence was solved with standard k-$\xi$ model and the turbulent combustion model was incorporated using a two step reaction scheme together with an eddy dissipation model. The radiative transfer equation was calculated by means of the discrete ordinates method with the weighted sum of gray gases model for CO$_2$and H$_2$O. In the NO chemistry model, the chemical reaction rates for thermal and prompt NO were statistically averaged using the $\beta$ probability density function. The results were validated by comparison with measurements. For the experiment, a 0.2 MW pilot multi-air staged burner has been designed and fabricated. Only when the radiation was taken into account, the predicted gas temperature was in good agreement with the experimental one, which meant that the inclusion of radiation was indispensable for modeling multi-air staged gas flame. This was also true of the prediction of the NO formation, since it heavily depended on temperature. Subsequently, it was found that the multi-air staged combustion technique might be used as a practical tool in reducing the NO formation by controlling the peak flame temperature.

• Asian-Australasian Journal of Animal Sciences
• /
• 제21권6호
• /
• pp.818-823
• /
• 2008

The interaction of fibre degrading microbes and methanogens was studied using two forages, lucerne (Medicago sativa) hay and maize (Zea mays) hay, as substrate and 2-bromoethanesulphonic acid (BES) as an additive in an in vitro gas production test. Gas and methane production (ml/g dry matter) were significantly higher (p<0.05) on lucerne as compared to maize hay. Inclusion of BES in the incubation medium significantly suppressed methane emission irrespective of substrate. The population density of total bacteria, fungi, Ruminococcus flavefaciens and Fibrobacter succinogenes was higher, whereas that of methanogens was lower with maize hay as compared to lucerne as substrate. BES suppressed methanogen population by 7 fold on lucerene and by 8.5 fold on maize at 24 h incubation as estimated by real time-PCR. This suppression was accompanied by almost complete (>98% of control) inhibition of methanogenesis. The proportion of acetate decreased, whereas that of propionate increased significantly by inclusion of BES, resulting in narrowing of acetate to propionate ratio. In vitro true digestibility (IVTD) of lucerne was significantly higher as compared to maize but BES inclusion did not affect IVTD.

• 한국식품과학회지
• /
• 제40권6호
• /
• pp.621-625
• /
• 2008

오징어 간유 미세캡슐화 분말을 HPMC-FCC, zein-DP로 코팅하여 유동층 코팅 특성을 살펴본 결과, 유동층 코팅 효율은 HPMC-FCC, zein-DP 모두 90%의 효율을 나타내었다. 겉보기 밀도는 zein-DP 코팅분말이 0.6 g/mL로 높게 나타나 코팅 분말의 비중이 커져 흐름성이 개선되었음을 확인할 수 있었다. 인공위액과 인공장액에 대한 용해성을 살펴본 결과, HPMC-FCC는 각각 59.9%와 0%를 나타내었고 zein-DP는 각각 0%와 31.0%를 나타내어 코팅재료에 따라 용해성을 조절할 수 있었다. 저장 안정성은 zein-DP나 HPMC-FCC로 코팅한 분말이 미세캡슐화 분말보다 높은 PUFA/SFA 잔존율을 보여, 유동층 코팅 기술이 유지식품의 안정성을 확보할 수 있는 새로운 기술이 될 수 있음을 확인할 수 있었다.

• Archives of Pharmacal Research
• /
• 제10권4호
• /
• pp.212-218
• /
• 1987

Intact brain cell aggregates were dissociated from adult rat brains without cerebellum using a sieving technique. This proparation was used to elucidate the binding characteristics of agonist to muscarinic acetylcholine receptors (mAchR) in brain. Incubation of cells with carbamylcholine (carbachol) was shown agonist-induced receptor down-regulation depending on the concentration of agonist, not depending on the incubation time. This effect of carbachol was due to a reduction in the maximal binding capacity ($B_{max}$) to the mAchR without decreasing the affinity of the remaining receptors in incubation at 37.deg.C but was not apparent inincubation at $15^{\circ}}C$In addition, it was abolished when the receptors were blocked by atropine. The decline in ($^3H$)N-methylscopolamine (($^3H$)NMS) binding induced by agonist was reflected as a significant reduction in the receptor density with no change in receptor affinity, suggesting that 'true' receptor down-regulation takes place. Moreover, when the receptors were labeled with the lipophilic antagonist ($^3H$) quinuclidinyl benzilate (($^3H$) QNB) insted of the hydrophilic ligand ($^3H$)NMS, the magnitude of the observed receptor down-regulation was significantly lower in case of the former than the latter. This suggested that exposure of intact brain cells to muscarinic agonists might induce a slight degree of accumulation of receptors in intracellular sites before the receptors are actually degraded.

• 전자공학회논문지CI
• /
• 제38권1호
• /
• pp.26-45
• /
• 2001

플래쉬 메모리는 데이터의 저장과 변경이 가능하고 전원이 차단되어도 저장된 데이터를 보존할 수 있는 RAM과 ROM의 장점을 모두 가지고 있는 메모리로서, 고성능의 전기 특성을 가지고 있어 이동 환경에서의 저장매체로 매우 접합하다. 향후 많은 정보단말기에 사용하게 될 플래쉬 메모리 및 스마트미디어 카드에 파일을 저장, 삭제, 재생하는 효과적인 알고리즘이 필요하다. 플래쉬 메모리를 일정한 크기의 세그먼트로 할당하고, 파일을 여러 개의 세그먼트로 분산시켜 관리한다. 본 논문에서는 특정 파일이 저장되어 있는 위치를 저장하는 테이블 및 보조 테이블을 이용하여 효과적인 파일 관리 알고리즘을 제시한다. 기존의 알고리즘은 비교적 작은 용량의 플래쉬 메모리를 관리하고 비교적 파일을 빈번한 횟수의 고속 저장, 삭제 등의 작동이 요구되는 응용에는 적합지 않는다. 본 논문에서 제안된 알고리즘은 몇 개의 플래쉬 메모리 칩 및 스마트미디어 카드로 구성된 비교적 큰 용량의 메모리 관리에 적합하다.

• 대한화학회지
• /
• 제55권6호
• /
• pp.905-911
• /
• 2011

[ $C_{60}(CH_2)_nOH$ ](n=0~2)와 $C_{60}(OH)_2$의 가능한 분자구조를 B3LYP/6-311G(d,f) 이론 수준에서 최적화 하였으며, 각 화합물의 가장 안정한 분자구조(global minimum)를 확인하고 결합에너지를 계산하여 구조적 특성에 따른 에너지와의 상호연관성을 고찰하였다. 보다 정확한 상대 에너지를 계산하기 위하여 진동주파수를 계산하여 영점 진동 에너지(zero-point vibrational energy, ZPVE)를 보정하였으며, IR 스펙트럼을 예측하였다. $C_{60}(CH_2)_nOH$ (n=0-2)에서 결합에너지의 경우, $-CH_2OH$기 보다 -OH기가 결합되었을 때 결합에너지가 약 10 kcal/mol 정도 더 안정한 것으로 나타났다.