• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.256-256
• /
• 2012

Oxide semiconductors such as zinc tin oxide (ZTO) or indium gallium zinc oxide (IGZO) have attracted a lot of research interest owing to their high potential for application as thin film transistors (TFTs) [1,2]. However, the instability of oxide TFTs remains as an obstacle to overcome for practical applications to electronic devices. Several studies have reported that the electrical characteristics of ZnO-based transistors are very sensitive to oxygen, hydrogen, and water [3,4,5]. To improve the reliability issue for the amorphous InGaZnO (a-IGZO) thin-film transistor, back channel passivation layer is essential for the long term bias stability. In this study, we investigated the instability of amorphous indium-gallium-zinc-oxide (IGZO) thin film transistors (TFTs) by the back channel contaminations. The effect of back channel contaminations (humidity or oxygen) on oxide transistor is of importance because it might affect the transistor performance. To remove this environmental condition, we performed vacuum seasoning before the deposition of hybrid passivation layer and acquired improved stability. It was found that vacuum seasoning can remove the back channel contamination if a-IGZO film. Therefore, to achieve highly stable oxide TFTs we suggest that adsorbed chemical gas molecules have to be eliminated from the back-channel prior to forming the passivation layers.

• Korea-Australia Rheology Journal
• /
• v.11 no.4
• /
• pp.279-285
• /
• 1999

Draw resonance is both an important and interesting instability encountered in various extensional-deformation-dominated polymer processing operations. It is important because of its paramount relevance to the productivity and quality issue in the related industry: and it is interesting because of as yet unanswered questions as to what its cause and origin are in terms of physics involved. Specifically, a short chronological account of the draw resonance research is presented in this paper bringing several previous results together and focusing on the derivation of a new criterion for draw resonance based on the interaction of the traveling times of some kinematic waves propagating along the spinline from the die exit to the take-up position. The new explanation of draw resonance put forward here based on the physics of the system is seen to have wide implications on both theoretical and practical aspects of draw resonance instability. The importance of the role played by spinline tension in determining draw resonance is an example of the former whereas interpretation of the mechanism of the draw resonance eliminator is an example of the latter. Finally, an approximate yet a very fast and convenient method for determining draw resonance is also derived based on the above findings and found to agree well with the exact stability results.

• Mass Spectrometry Letters
• /
• v.9 no.2
• /
• pp.61-65
• /
• 2018

KPLA-012, a benzopyranyl 1,2,3-triazole compound, is considered a potent $HIF-1{\alpha}$ inhibitor based on the chemical library screening, and is known to exhibit anti-angiogenetic and anti-tumor progressive effects. The aim of this study was to investigate the pharmacokinetic properties of KPLA-012 in ICR mice and to investigate in vitro characteristics including the intestinal absorption, distribution, metabolism, and excretion of KPLA-012. The oral bioavailability of KPLA-012 was 33.3% in mice. The pharmacokinetics of KPLA-012 changed in a metabolism-dependent manner, which was evident by the low recovery of parent KPLA-012 from urine and feces and metabolic instability in the liver microsomes. However, KPLA-012 exhibited moderate permeability in Caco-2 cells ($3.1{\times}10^{-6}cm/s$) and the metabolic stability increased in humans compared to that in mice (% remaining after 1 h; 47.4% in humans vs 14.8% in mice). Overall, the results suggest that KPLA-012 might have more effective pharmacokinetic properties in humans than in mice although further studies on its metabolism are necessary.

• Geomechanics and Engineering
• /
• v.20 no.6
• /
• pp.547-556
• /
• 2020

An understanding of the influence of MR (Magmatic Rock) thickness on the surrounding rock behaviors is essential for the prevention and management of dynamic disasters in coal mining. In this study, we used FLC3D to study the breaking and instability laws of surrounding rock with different MR thicknesses in terms of strata movement, stress and energy. The mechanism of dynamic disasters was revealed. The results show that the thicker the MR is, (1) the smaller the subsidence of the overlying strata is, but the subsidence span of the overlying strata become wider, and the corresponding displacement deformation value of the basin edge become smaller. (2) the slower the growth rate of abutment pressure in front of the working face is, but the peak value is smaller, and the influence range is larger. The peak value decreases rapidly after the breaking, and the stress concentration coefficient is maintained at about 1.31. (3) the slower the peak energy in front of coal wall, but the range of energy concentration increases (isoline "O" type energy circle). Finally, a case study was conducted to verify the disaster-causing mechanism. We anticipate that the research findings presented herein can assist in the control of dynamic hazards.

• Journal of Microbiology and Biotechnology
• /
• v.16 no.4
• /
• pp.590-596
• /
• 2006

Clavulanic acid (CA) produced by Streptomyces clavuligerus is degraded during the bacterial cultivation. The degradation was examined in three different aspects, including physical, chemical, and enzymatic effects, in order to understand the degradation during the cultivation. The result showed that CA was unstable in the production medium containing ammonium salts and amino acids, owing to ammonium ions and amine groups. In addition, the degradation was not only due to instability of CA by metabolites and proteins, but also enzymes from S. clavuligerus such as $\beta-lactamase$ and penicillin-binding proteins. However, the degradation caused by these enzymes was not highly significant compared with the degradation during the cultivation, owing to irreversible reactions between CA and enzymes.

• Journal of Powder Materials
• /
• v.28 no.4
• /
• pp.287-292
• /
• 2021

In this study, the layered structures of immiscible Fe and Cu metals were employed to investigate the interface evolution through solid-state mixing. The pure Fe and Cu powders were cold-consolidated by high-pressure torsion (HPT) to fabricate a layered Cu-Fe-Cu structure. The microstructural evolutions and flow of immiscible Fe and Cu metals were investigated following different iterations of HPT processing. The results indicate that the HPT-processed sample following four iterations showed a sharp chemical boundary between the Fe and Cu layers. In addition, the Cu powders exhibited perfect consolidation through HPT processing. However, the Fe layer contained many microcracks. After 20 iterations of HPT, the shear strain generated by HPT produced interface instability, which caused the initial layered structure to disappear.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.4 no.1
• /
• pp.41-45
• /
• 1999

Microbial cellulose has many potential applications due to its excellent physical properties. The production of cellulose from Acetobacter xylinum in submerged culture is, however, beset with numerous problems. The most difficult one has been the appearance of negative mutants under shaking culture conditions, which is deficient of cellulose producing ability. Thus genetic instability of Acetobacter xylinum under shaking culture condition made developing a stable mutant major research interest in recent years. To find a proper type of bioreactor for the production of microbial cellulose, several production systems were developed. Using a reactor system with planar type impeller with bottoms sparging system, it was possible to produce 5 g/L microbial cellulose without generating cellulose minus mutants, which is comparable to that of static culture system.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.3
• /
• pp.363-367
• /
• 2006

The structure-property relations of ternary copper chalcogenides, $TlCu_{3-x}S_2$ and $\alpha-BaCu_{2-x}S_2$ are examined. The density of states, band dispersions, and Fermi surfaces of these compounds are investigated to verify the reason of the metal-insulator transitions by extended Huckel tight-binding band calculations. The origin of the metalinsulator transitions of non-stoichiometric $TlCu_{3-x}S_2$ and $\alpha-BaCu_{2-x}S_2$ is thought to be the electronic instability induced by their Fermi surface nesting.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.11
• /
• pp.3952-3958
• /
• 2011

The effect of sintering temperature on the electrochemical property of $LiMn_2O_4$ was investigated. Results showed that the particle size was increased at higher sintering temperatures while the initial capacity was decreased after high temperature sintering. Capacity fading, on the other hand, was suppressed at lower sintering temperatures since the sintering at higher temperatures (${\geq}800^{\circ}C$) increased the Mn ions with a lower oxidation state ($Mn^{+3}$), which induced structural instability during cycling due to dissolution of Mn ions into the electrolyte. In particular, $LiMn_2O_4$ sintered above $830^{\circ}C$ showed severe capacity fading (capacity loss was 38% of initial capacity) by lower coulombic efficiency due to the abnormally increased particle size.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1993.11a
• /
• pp.97-102
• /
• 1993

According as the high integrity of the semi conductor devices is definited required, the concern on the multi-layered wiring, and three-dimensional devices is growing these days. Therefore, plasma-enhanced chemical vapored deposition(PECVD) enables low-teperature process and is widely used, but it causes the instability of the devices due to a lot of impurities within the film. The PECVD oxynitride was formed by changing the gas ratio of (N$_2$O) to (N$_2$+NH$_3$). It's contained a small portion of hydrogen, had higher refrctive index and capacitance than oxide, and showed the capacitance increasement and the chemical stabi1ity. This is caused by nitrogen distribution increase of the interface lather than within the film.