• Title/Summary/Keyword: Formation mechanism

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Formation Mechanism of Y-type Barium Ferrite Prepared by the Glass-ceramic Method

  • Hori, Chinatsu;Miki, Hiroki;Nagae, Masahiro;Yoshio, Tetsuo
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1181-1182
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    • 2006
  • Y-type barium ferrite $(Ba_2Zn_2Fe_{12}O_{22})$ was prepared by the glass-ceramic method. Glasses with composition of $0.1ZnO{\cdot}0.9(0.3Fe_2O_3{\cdot}0.5BaO{\cdot}0.2B_2O_3)$ were prepared, and the precipitation behavior of Y-type ferrite from the glass matrix was investigated by heating glass specimens at various temperature. $\alpha-BaFe_2O_4$ which is a precursor of M-type ferrite $(BaFe_{12}O_{19})$ was precipitated at about 813 K and an unknown compound, phase X, was precipitated at about 850 K. M-type ferrite and Y-type ferrite started to form at about 923 K and 1103 K, respectively. The formation of Y-type ferrite was int erpreted as the result of the reaction of M-type ferrite with a melt of phase X.

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Role of Nitric Oxide in the Lovastatin-Induced Stimulation of Melanin Synthesis in B16 Melanoma Cells (B16 흑색종세포에서 로바스타틴에 의한 멜라닌 합성 촉진효과에 미치는 산화질소의 역할)

  • Lee, Yong Soo
    • YAKHAK HOEJI
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    • v.57 no.6
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    • pp.388-393
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    • 2013
  • Previously, we have reported that lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, increased melanin synthesis through intracellular $Ca^{2+}$ release in B16 cells. In this study we investigated the possible involvement of nitric oxide (NO) in the mechanism of lovastatin-induced melanogenesis. Lovastatin elevated NO formation in a dose-dependent manner. Treatment with mevalonate, farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), precursors of cholesterol, did not significantly alter the lovastatin-induced NO production, suggesting that inhibition of cholesterol metabolism may not be involved in the mechanism of this action of lovastatin. Both NO formation and melanogenesis induced by lovastatin was significantly suppressed by treatment with $N^G$-nitro-L-arginine methyl ester (L-NAME) and 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide (cPTIO), an inhibitor of NO synthase and a NO scavenger, respectively. The lovastatin-induced NO production was significantly affected not by EGTA, an extracellular $Ca^{2+}$ chelator, but by an intracellular $Ca^{2+}$ chelator (BAPTA/AM) and intracellular $Ca^{2+}$ release blockers (dantrolene and TMB-8). Taken together, these results suggest that lovastatin may induce melanogenesis through NO formation mediated by intracellular $Ca^{2+}$ release in B16 cells. These results further suggest that lovastatin may be a good candidate for the therapeutic application of various hypopigmentation disorders.

Constraining the ICL formation mechanism using fossil clusters at z~0.47

  • Yoo, Jaewon;Ko, Jongwan;Kim, Jae-Woo
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.33.3-34
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    • 2018
  • Galaxy clusters contain a diffuse component of stars outside galaxies, that is observed as intracluster light (ICL). Since the ICL abundance increases during various dynamical exchanges of galaxies, the amount of ICL can act as a measurement tool for the dynamical stage of galaxy clusters. There are two prominent ICL formation scenarios; one is related to the brightest cluster galaxy (BCG) major mergers, and the other to the tidal stripping of galaxies. However, it is still under debate as to which is the main ICL formation mechanism. In this study we improve on earlier observational constraints of the ICL origin, by investigating it in a massive fossil cluster at z~0.47. Fossil clusters are believed to be dynamically matured galaxy clusters which have dominant BCGs. Recent simulation studies imply that, BCGs have assembled 85~90% of their mass by z~0.4 (e.g., Contini et al. 2014). Thus our target is an optimal test bed to examine the BCG-related scenario. Our deep images and Multi-Object Spectroscopic observations of the target fossil cluster (Gemini North 2018A) allow us to extract the ICL distribution, ICL color map and ICL fraction to cluster light. We will present a possible constraint of the ICL origin and discuss its connection to the BCG and the host galaxy cluster.

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A Mechanism Study on Formation and Reduction of Residual Li of High Nickel Cathode for Lithium-ion Batteries (층상계 하이니켈 양극재의 잔류 리튬 생성 및 저감 메커니즘 연구)

  • MinWook, Pin;Beom Tak, Na;Tae Eun, Hong;Youngjin, Kim
    • Journal of Industrial Technology
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    • v.42 no.1
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    • pp.7-12
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    • 2022
  • High nickel layered oxide cathodes are gaining increasing attention for lithium-ion batteries due to their higher energy density and lower cost compared to LiCoO2. However, they suffer from the formation of residual lithium on the surface in the form of LiOH and Li2CO3 on exposure to ambient air. The residual lithium causes notorious issues, such as slurry gelation during electrode preparation and gas evolution during cell cycling. In this review, we investigate the residual lithium issues through its impact on cathode slurry instability based on deformed polyvinylidene fluoride (PVdF) as well as its formation and reduction mechanism in terms of inherently off-stoichiometric synthesis of high nickel cathodes. Additionally, new analysis method with anhydrous methanol was introduced to exclude Li+/H+ exchange effect during sample preparation with distilled water. We hope that this review would contribute to encouraging the academic efforts to consider practical aspects and mitigation in global high-energy-density lithium-ion battery manufacturers.

Effect of Cutting Fluid on the Metal-Cutting Mechanism (절삭유제가 금속절삭기구에 미치는 영향에 관한 연구)

  • Seo, Nam-Seob
    • Journal of the Korean Society for Precision Engineering
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    • v.2 no.2
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    • pp.69-75
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    • 1985
  • The object of this study is to discuss the effect of cutting fluid on the mechanism of chip formation in orthogonal cutting. Rehbinder effect has been known as a phenomenon, the reduction of mechanical strength, when the metal is exposed in a polar organic environment or the surface of metal is coated with some polar organic substances. About the cause of Rehbinder effect there have been many different ideas by Rehbinder, Merchant, Shaw, Sakakida and etc. In this report, the effects of surface active medium (magic ink) upon the mechanism of chip formation on the orthogonal cutting of copper and the mechanical properties of the work material are experimentally discussed with constant rake angle. Under the condition of polar organic environment the experimental results are as follows; 1) The chip thickness becomes thinner and slip line pitch on the free surface of chip becomes smaller than that of dried cutting area. 2) The order of alternation of cutting ratio was changed. 3) The friction angle on the tool face is not affected by the depth of cut. 4) The cutting force and shear strain on the shear plane decrease remarkably, therefore the work material must be embrittled under polar organic environment.

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The Weldability of Laminated Stator Core for Motor by Pulsed Nd:YAG Laser [II] - Investigation of Mechanism on Formation of Weld Defect - (펄스 Nd:YAG 레이저를 이용한 모터용 스테이터 적층코어의 용접특성 [II] - 용접결함의 형성 메커니즘 규명 -)

  • Kim Jong-Do;Kil Byung-Lea;Lee Chang-Je
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.5
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    • pp.636-644
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    • 2006
  • Recently, there were some successful examples that the laser welding was introduced into production line. However, the spread of laser welding is not sufficient in many industries. There are several reasons why it is difficult to penetrate the laser welding into production lines. Because it is different from reflection, absorption and permeation of laser beam according to material and surface condition. Moreover, there are significant problems in processing such as absorption and scattering of beam by the induced plasma or plume. Therefore, understanding of mechanism on formation of weld defect in laser welding of the laminated core for motor is very important. In this paper, it was analyzed in terms of materials which was source of defect in laser welding and conventional arc welding. As a results of analysis, insulation coating film of the laminated core was judged to main factor of weld defect. it could be well aware as tracing carbon volume, and it was deduced that weld defect by insulation coating film was caused by difference of mechanism between the two heat sources.

Acid Dairy Drink Induced by Pectin -on Stabilization Mechanism and Effective Use of Pectin- on Stabilization Mechanism and Effective Use of Pectin-

  • Kim, iaki-Abe
    • Proceedings of the Korean Society for Food Science of Animal Resources Conference
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    • 2002.05a
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    • pp.82-89
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    • 2002
  • Acid dairy drinks(ADD) are a worldwide product existing in many variations: fruit milk drinks, yogurt drinks, soy milk, butter milk, whey drinks and kefir etc. These drinks are marketed with different shelf lives depending on processing: -Short shelf life(maximum 3 weeks, cold storage) - Long shelf life(2 to 9 months, pasteurized, sterilized or retorted) Acidic protein drinks tend to a separation or destabilization process in the absence of stabilizing system during the shelf life of the ADD. A phase separation results in sedimentation of large particles at the bottom of the package and/or the formation of a serum layer at the top(whey off). These beverages are usually composed of an acid dairy phase (fermented base)or a natural base(milk, soymilk etc.)with an acidic medium (fruit phase: pulp, fruit concentrate etc.) which can be flavored. Sugar and stabilizers are added. It has been proved since the late 1950's that adding high methoxy pectin (HM pectin)to acid milk drinks is the best way to prevent the formation of a sediment and/or the whey off. In this presentation, we explain about stabilization mechanism of ADD induced by pectin. Applications and market trend of ADD in Asia and Europe are explained.

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Investigation of PEG(polyethyleneglycol) Removal Mechanism during UV/O2 Gas Phase Cleaning for Silicon Technology (UV/O2 가스상 세정을 이용한 실리콘 웨이퍼상의 PEG 반응기구의 관찰)

  • Kwon, Sung-Ku;Kim, Do-Hyun;Kim, Ki-Dong;Lee, Seung-Heun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.11
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    • pp.985-993
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    • 2006
  • An experiment to find out the removal mechanism of PEG(polyethyleneglycol) by using UV-enhanced $O_2$ GPC (gas phase cleaning) at low substrate temperature below $200^{\circ}C$ was executed under various process conditions, such as substrate temperature, UV exposure, and $O_2$ gas. The possibility of using $UV/O_2$ GPC as a low-temperature in-situ cleaning tool for organic removal was confirmed by the removal of a PEG film with a thickness of about 200 nm within 150 sec at a substrate temperature of $200^{\circ}C$. Synergistic effects by combining photo-dissociation and photo oxidation can only remove the entire PEG film without residues within experimental splits. In $UV/O_2$ GPC with substrate temperatures higher than the glass transition temperature, the substantial increase in the PEG removal rate can be explained by surface-wave formation. The photo-dissociation of PEG film by UV exposure results in the formation of end aldehyde by dissociation of back-bone chain and direct decomposition of light molecules. The role of oxygen is forming peroxide radicals and/or terminating the dis-proportionation reaction by forming peroxide.

Corrosion Mechanism and Bond-Strength Study on Galvanized Steel in Concrete Environment

  • Kouril, M.;Pokorny, P.;Stoulil, J.
    • Corrosion Science and Technology
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    • v.16 no.2
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    • pp.69-75
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    • 2017
  • Zinc coating on carbon steels give the higher corrosion resistance in chloride containing environments and in carbonated concrete. However, hydrogen evolution accompanies the corrosion of zinc in the initial activity in fresh concrete, which can lead to the formation of a porous structure at the reinforcement -concrete interface, which can potentially reduce the bond-strength of the reinforcement with concrete. The present study examines the mechanism of the corrosion of hot-dip galvanized steel in detail, as in the model pore solutions and real concrete. Calcium ion plays an important role in the corrosion mechanism, as it prevents the formation of passive layers on zinc at an elevated alkalinity. The corrosion rate of galvanized steel decreases in accordance with the exposure time; however, the reason for this is not the zinc transition into passivity, but the consumption of the less corrosion-resistant phases of hot-dip galvanizing in the concrete environment. The results on the electrochemical tests have been confirmed by the bond-strength test for the reinforcement of concrete and by evaluating the porosity of the cement adjacent to the reinforcement.

Formation Mechanism of SnO Plate (판상 SnO의 형성 메커니즘)

  • Kim, Byeung Ryeul;Park, Chae Min;Lee, Woo Jin;Kim, Insoo
    • Korean Journal of Metals and Materials
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    • v.48 no.12
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    • pp.1084-1089
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    • 2010
  • This study elucidates the formation mechanism of SnO plate observed during the precipitation reaction of a $SnCl_2$ aqueous solution. $Sn_{21}Cl_{16}(OH)_{14}O_6$ and $Sn_6O_4(OH)_4$ precipitates was formed at pH=3~5 and at pH=11, respectively. When the pH was in the range of 11.5~12.5, the $Sn_6O_4(OH)_4$ precipitates dissolved into $HSnO_2{^-}[Sn_6O_4(OH)_4+4OH^-={6HSnO_2{^-}+2H^+]$ and dissolved $HSnO_2{^-}$ ions reprecipitated to SnO plate $[HSnO_2{^-}+H^+=SnO+H_2O]$. The $Sn_6O_4(OH)_4$ precipitates completely transformed into SnO plate through a repeated process of dissolution-precipitation in the range of pH=11.5~12.5.