• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.292-297
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• 2005

$LiMO_{2}(M=Co,Ni)$ samples were synthesized with $Li_{2}CO_{3},\;Co_{3}O_{4}$, and NiO by the solid-state reaction method. In the case of $LiCoO_{2}$, at low temperature$(T=400^{\circ}C)$ spinel structure was synthesized and the obtained spinel phase was transformed to layered phase at high temperature$(T\ge600^{\circ}C)$. The phase transition behaviors of $LiCoO_{2}$ were investigated with various heating temperature and time. The rate of transition was directly proportional to the concentrations of reactant, and activation energy of reaction was around 6.76 kcal/mol. When CoO(rock salt structure) was used as a starting material instead of $Co_{3}O_{4}$(spinel structure), layered structure of $LiCoO_{2}$ was obtained at low temperature. In the case of $LiNiO_{2}$ the transition from layered structure to rock salt structure occurred easily by disordering/ordering reaction, but did not occur in $LiCoO_{2}$. The difference in metal ion radii in $LiCoO_{2}$ and $LiNiO_{2}$ results in different behaviors of phase transitions.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.7-8
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• 2011

Basically, the lattice mismatch between film and substrate can make those BiFeO3(BFO) films distorted with strain structure. BFO phase can be stabilized on LaAlO3(LAO) represents the example of a multiferroic with giant axial ratio. Its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion and related to the rotation of the oxygen octahedra. In this study, we show that phases with a tetragonal-like epitaxial BFO films can indeed be ferroelectric and also can be stabilized via epitaxial growth onto LAO. Recent reports on epitaxial BFO films show that the crystal structure changes from nearly rhombohedral ("R-like") to nearly tetragonal("T-like") at strains exceeding approximately -4.5%, with the "T-like" structure being characterized by a highly enhanced c/a ratio. While both the "R-like" and the "T-like" phases are monoclinic, our detailed x-ray diffraction results reveal asymmetry change from MA and MC type, respectively. By applying additional strain or by modifying the unit cell volume of the film by substituting Ba for Bi, the monoclinic distortion in the "T-like" MC phase is reduced, i.e. the system approaches a true tetragonal symmetry. There are two different M-H loops for $Bi_{1-x}Ba_xFeO_{3-{\delta}}$(BBFO) and BFO films on SrTiO3(STO) & LAO substrates. Along with the ferroelectric characterization, these magnetic data indicate that the BFO phase stabilized on LAO represents the first example of a multiferroic with giant axial ratio. However, there is a significant difference between this phase and other predicted ferroelectrics with a giant axial ratio: its crystal structure is not strictly tetragonal, but tetragonal with a slight monoclinic distortion. Therefore, in going from bulk to highly-strained films, a phase sequence of rhombohedral(R)-to-monoclinic ["R-like" MA-to-monoclinic, "T-like" MC-to-tetragonal (T)] is observed. This sequence is otherwise seen only near morphotropic phase boundaries in lead-based solid-solution perovskites (i.e. near a compositionally induced phase instability), where it can be controlled by electric field, temperature, or composition. Our results show that this evolution can occur in a lead-free, stoichiometric material and can be induced by stress alone. Those major results are summarized as follows ; 1) Ba-doping increases the unit cell volume, 2) BBFO on LAO can be fully strained up to x=0.08 as a strain limit (Fig. 1), 3) P(E) & M(H) properties can be tuned by the variation of composition, strain, and film thickness.

• Journal of the Korean Electrochemical Society
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• v.12 no.4
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• pp.342-348
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• 2009

Zn/Air secondary batteries are high energy density type and environment-friendly. Also, they have safer properties than batteries of other type by low manufacturing cost and using the electrolyte solution. But, they have a weak concerning large output discharge. Oxygen evolution reaction(OER) and oxgen reduction reaction(ORR) in aqueous solution make a result of a decrease of cell efficiency and life span. Therefore, to minimize the voltage drop from between OCV and charge/discharge voltage is key point. The problem should be solved through developing catalysts of high efficiency. In this study, we synthesized $Pr_{1-x}(Sr,\;Ca)_x\;CoO_3$ powders by citric method and then measured physical characteristics of each powder by XRD, SEM, TGA etc. We examined its electrochemical properties by the cathodic polarization, anodic polarization and cyclic voltammogram. We achieved results that new catalysts showed better performances than existing $La_{1-x}Sr_xCoO_3$, $La_{1-x}Ca_xCoO_3$, ect. catalysts prepared in our lab.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.469-483
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• 1999

Two different types of deep groundwaters occur together in the Jungwon area: $CO_2$-rich water and alkali water. Each water shows distrinct hydrogeochemical and environmental isotopic characteristics. The $CO_2$-rich waters are characterized by lower pH(6.0~6.4), higher Eh (25~85mV) and higher TDS content (up to 3,300 mg/l), whereas the alkali type waters have higher pH (9.1~9.5), lower Eh (-136~-128mV) and lower TDS content (168~254 mg/l). The CO2-rich waters ($Pco_2$=up to 1atm) were probably evolved by the local supply of deep $CO_2$ during the deep circulation, resulting in enhanced dissolution of surrounding rocks to yield high concentrations of $Ca^{2+}, Na^+, Mg^{2+}, K^+\; and \;HCO_3\;^-$ under low pH conditions. On the other hand, the alkali type waters ($Pco_2$=about 10-4.6 atm) were evolved through lesser degrees of simple wate/rock (granite) interaction under the limited suppy of $CO_2$. The alkali waters are relatively enriched in F- (up to 14mg/l), whereas the F- concentration of$CO_2$-rich water is lower (2.2~4.8 mg/l) due to the buffering by precipitation of fluorite. The oxygen-hydrogen isotopes and tritium data indicate that compared to shaltion ($\delta$18O=-9.5~-7.8$\textperthousand$),two different types fo deep groudwaters (<1.0TU)were both derived from pre-thermonuclear (more than 40 years old) meteoric waters with lighter O-H isotopic composition ($\delta$18O=-9.5~-7.8$\textperthousand$) and have evolved through prolonged water/rock interaction. The $CO_2$-rich waters also show some degrees of isotopic re-equilibration with $CO_2$ gas. The $\delta^{34}S$ values of dissolved sulfates (+24.2~+27.6$\textperthousand$) in the $CO_2$-rich waters suggest the reduction of sulfate by organic activity at depths. The carbon isotope data show that dissolved carbon in the $CO_2$-rich waters were possibly derived either from dissolution of calcite or from deep $CO_2$ gas. However, strontium isotope data indicate Ca in the $CO_2$-rich waters were derived mainly from plagioclase in granite, not from hydrothermal calcites.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.230-237
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• 2017

In this study, electrochemical methods were used to determine the optimum protection potential of S355ML steel for the cathodic protection of offshore wind-turbine-tower substructures. The results of potentiodynamic polarization experiments indicated that the anodic polarization curve did not represent a passivation behavior, while under the cathodic polarization concentration, polarization was observed due to the reduction of dissolved oxygen, followed by activation polarization by hydrogen evolution as the potential shifted towards the active direction. The concentration polarization region was found to be located between approximately -0.72 V and -1.0 V, and this potential range is considered to be the potential range for cathodic protection using the impressed current cathodic protection method. The results of the potentiostatic experiments at various potentials revealed that varying current density tended to become stable with time. Surface characterization after the potentiostatic experiment for 1200 s, by using a scanning electron microscope and a 3D analysis microscope confirmed that corrosion damage occurred as a result of anodic dissolution under an anodic polarization potential range of 0 to -0.50 V, which corresponds to anodic polarization. Under potentials corresponding to cathodic polarization, however, a relatively intact surface was observed with the formation of calcareous deposits. As a result, the potential range between -0.8 V and -1.0 V, which corresponds to the concentration polarization region, was determined to be the optimum potential region for impressed current cathodic protection of S355ML steel.

• Journal of Life Science
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• v.24 no.12
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• pp.1291-1300
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• 2014

Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant enzymes that participate in a variety of biological processes, including $H_2O_2$-mediated signal transduction, molecular chaperoning, and mitochondrial function. In this study, we isolated and characterized a Prx 2 cDNA from abalone (Haliotis discus hannai). The abalone Prx 2 cDNA encoded a 199-amino acid polypeptide that belongs to a class of typical 2-Cys Prxs that contain peroxidatic and resolving cysteines. The deduced abalone Prx 2 protein showed strong homology (64-99%) with Prx 2 proteins from other species, including mollusk, fish, amphibians, and mammals, and it was most closely related to disk abalone (H. discus discus) Prx 2. Abalone Prx 2 mRNA was ubiquitously detected in tested tissues, and its expression was comparatively high in the mantle, gills, liver, foot, and digestive duct. The expression level of abalone Prx 2 mRNA was 106.7-fold, 51.9-fold, and 437.8-fold higher, respectively, in the gills, digestive duct, and liver than in the muscles. The expression level of abalone Prx 2 mRNA in the liver peaked at 6 hr postinfection with Vibrio parahemolyticus and decreased at 12 hr postinfection. The expression level of abalone Prx 2 mRNA in hemocytes was drastically increased at 1 hr postinfection with V. parahemolyticus. These results suggest that abalone Prx 2 is conserved through evolution and that it may play a role similar to that of its mammalian counterpart.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.192-202
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• 1998

We investigated the geochemistry and environmental isotopes of granite-bedrock groundwater in the Yeongcheon diversion tunnel which is located about 300 m below the land surface. The hydrochemistry of groundwaters belongs to the Ca-HCO$_3$type, and is controlled by flow systems and water-rock interaction in the flow conduits (fractures). The deuterium and oxygen-18 data are clustered along the meteoric water line, indicating that the groundwater are commonly of meteoric water origin and are not affected by secondary isotope effects such as evaporation and isotope exchange. Tritium data show that the groundwaters were mostly recharged before pre-thermonuclear period and have been mixed with younger surface water flowing down rapidly into the tunnel along fractured zones. Based on the mass balance and reaction simulation approaches, using both the hydrochemistry of groundwater and the secondary mineralogy of fracture-filling materials, we have modeled the low-temperature hydrogeochemical evolution of groundwater in the area. The results of geochemical simulation show that the concentrations of Ca$\^$2＋/, Na$\^$＋/ and HCO$_3$and pH of waters increase progressively owing to the dissolution of reactive minerals in flow paths. The concentrations of Mg$\^$2＋/ and K$\^$＋/ frist increase with the dissolution, but later decrease when montmorillonite and illitic material are precipitated respectively. The continuous adding of reactive minerals, namely the progressively larger degrees of water/rock interaction, causes the formation of secondary minerals with the following sequence: first hematite, then gibbsite, then kaolinite, then montmorillonite, then illtic material, and finally microcline. During the simulation all the gibbsite is consumed, kaolinite precipitates and then the continuous reaction converts the kaolinite to montmorillonite and illitic material. The reaction simulation results agree well with the observed, water chemistry and secondary mineralogy, indicating the successful applicability of this simulation technique to delineate the complex hydrogeochemistry of bedrock groundwaters.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.9-15
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• 2005

In order to know the electrochemical decomposition characteristics of ammonia to nitrogen, this work has studied several experimental variables on the electrolytic ammonia decomposition. The effects of pH and chloride ion at $IrO_2$, $RuO_2$, and Pt anodes on the electrolytic decomposition of ammonia were compared, and the existence of membrane equipped in the cell and the changes of the current density, the initial ammonia concentration and so on were investigated on the decomposition. The performances of the electrode were totally in order of $RuO_2{\approx}IrO_2>Pt$ in the both of acid and alkali conditions, and the ammonia decomposition was the highest at a current density of $80mA/cm^2$, over which it decreased, because the adsorption of ammonia on the electrode surface was hindered due to the evolution of oxygen. The ammonia decomposition increased with the concentration of chloride ion in the solution. However, the increase became much dull over 10 g/l of chloride ion. The $RuO_2$ electrode among the tested electrodes generated the most OH radicals which could oxidized the ammonium ion at pH 7.

• Genes and Genomics
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• v.40 no.11
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• pp.1169-1180
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• 2018

Cave shrimps from the genera Typhlatya, Stygiocaris and Typhlopatsa (TST complex) comprises twenty cave-adapted taxa, which mainly occur in the anchialine environment. Anchialine habitats may undergo drastic environmental fluctuations, including spatial and temporal changes in salinity, temperature, and dissolved oxygen content. Previous studies of crustaceans from anchialine caves suggest that they have possessed morphological, behavioral, and physiological adaptations to cope with the extreme conditions, similar to other cave-dwelling crustaceans. However, the genetic basis has not been thoroughly explored in crustaceans from anchialine habitats, which can experience hypoxic regimes. To test whether the TST shrimp-complex hypoxia adaptations matched adaptive evolution of mitochondrial OXPHOS genes. The 13 OXPHOS genes from mitochondrial genomes of 98 shrimps and 1 outgroup were examined. For each of these genes was investigated and compared to orthologous sequences using both gene (i.e. branch-site and Datamonkey) and protein (i.e. TreeSAAP) level approaches. Positive selection was detected in 11 of the 13 candidate genes, and the radical amino acid changes sites scattered throughout the entire TST complex phylogeny. Additionally, a series of parallel/convergent amino acid substitutions were identified in mitochondrial OXPHOS genes of TST complex shrimps, which reflect functional convergence or similar genetic mechanisms of cave adaptation. The extensive occurrence of positive selection is suggestive of their essential role in adaptation to hypoxic anchialine environment, and further implying that TST complex shrimps might have acquired a finely capacity for energy metabolism. These results provided some new insights into the genetic basis of anchialine hypoxia adaptation.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.105-111
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• 2023

Electronic devices have been evolved to be mechanically flexible that can be endured repetitive deformation. This evolution emphasizes the importance of long-term reliability in metal wiring connecting electronic components, especially under bending fatigue in compressed environments. This study investigated methods to enhance adhesion between copper (Cu) and polyimide (PI) substrates, aiming to improve the reliability of copper wiring under such conditions. We applied oxygen plasma treatment and introduced a chromium (Cr) adhesion layer to the polyimide substrate. Our findings revealed that these adhesion enhancement methods significantly affect compression fatigue behavior. Notably, the chromium adhesion layer, while showing weaker fatigue characteristics at 1.5% strain, demonstrated superior performance at 2.0% strain with no delamination, outperforming other methods. These results offer valuable insights for improving the reliability of flexible electronic devices, including reducing crack occurrence and enhancing fatigue resistance in their typical usage environments.