• Korean Journal of Fisheries and Aquatic Sciences
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• 제36권1호
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• pp.24-29
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• 2003

In the previous reports, the authors isolated two strains of marine bacteria, Shewanella sp. SR-14, which has Chaetonros sp. growth inhibition activity, and Vibrio alginolyticus, that did not affect growth of the alga. In the present study, fatty acid compositions of diatoms, Chaetoceros calcitrans and Skeletonema costatum, and marine bacteria, Shewanella sp. SR-14 and V. alginolyticus, were analyzed. Changes of fatty acid composition in the diatoms grown with the marine bacteria were also determined. Major fatty acids of Sbewanella sp. SR-14 were 16:1n-7 $(29.4\%)$ and 16:0 $(19.2\%)$ during incubation in peptone broth at $20^{\circ}C$ for 3 days. The compositions of V. alginolyticus detected were 16:0 $(23.7\%),$ 16:1n-7 $(27.7\%)$ and 18:1n-7 $(21.0\%).$ C. calcitrans consisted of 16:1n-7 $(33.3\%),$ 16:0 $(27.1\%)$ and 14:0 $(12.1\%).$ S. costatum mainly contained 16:1n-7 $(28.9\%),$ 16:0 $(21.6\%)$ and 20:5 $(19.8\%).$ When halves of cell numbers of C. calcitrans were moribund cells by Shewanella sp. SR-14, the C. calcitrans and S. costatum simultaneously cultured with the bacteria were harvested by filtration with GE/D glass microfibre filter. In the fatty acid composition of both diatoms, saturated fatty acid contents in both diatoms grown with Shewanella sp. SR-14 were decreased, but unsaturated fatty acid contents were increased. The differences were greater in C. calcitrans than those in S. costatum. During the growth of diatoms with V. alginolyticus, C. calcitrans showed increase of saturated fatty acid contents and decrease of unsaturated fatty acid contents; however, S. costatum did not show sharp difference in fatty acid content. In this study, Shewanella sp. SR-14, which showed growth inhibition activity against C. calcitrans, influenced on the changes of fatty acid contents in the diatom. It was suggested that increased unsaturated fatty acid was synergistically activated algal growth inhibition activity of Shewanella sp. SR-14.

• Korean Journal of Heritage: History & Science
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• 제55권3호
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• pp.120-129
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• 2022

The purpose of this study is to analyze the chemical composition of smalt pigments used in 10 large Buddhist paintings in the Joseon Dynasty using energy dispersive X-ray spectroscopy, and to clarify the material and characteristics by observing morphological characteristics using polarized light microscopy and a scanning electron microscope. Through chemical composition analysis, the smalt of all 10 large Buddhist paintings is judged to be potash glass using SiO₂ as a former and K₂O as a flux. In addition to the components related to cobalt ore used as a colorant, the paintings were found to contain high levels of As₂O₃, BaO, and PbO. The smalt particles did not have specific forms, and were blue in color, with various chromaticity. In some particles, conchoidal fracture, spherical bubbles, and impurities were observed. Through backscattered electron images, it was found that the smalt from paintings produced in the early 18th century AD had a high level of As, but the smalt from paintings produced from the mid-18th century AD onwards exhibited various contrast differences from particle to particle, and there was smalt with high levels of As, Ba, and Pb. Through the above results, the large Buddhist paintings in the Joseon Dynasty are divided into three smalt types. Type A is a type with high As₂O₃, type B is a type with high BaO, and type C is a type with high PbO. Looking at the three types of smalt pigments by the period of production, although some in-between periods were not detected, type A was confirmed to have been used from 1705 to 1808, while type B and type C were shown to have appeared in 1750 and used until 1808. This reveals that only one type of smalt was used until the early 18th century AD, and from the middle of the 18th century AD, several types of smalt were mixed and used in one large Buddhist painting. Studies such as this research are expected to provide insights into the characteristics of the smalt pigments used to produce large Buddhist paintings at the time.

• Korean Journal of Soil Science and Fertilizer
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• 제6권3호
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• pp.141-152
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• 1973

The mineralogical studies of the eleven sub-soil samples derived from granite, granodiorite, diorite and arkose sandstone, taken from apple orchards in the province of Kyungsangbukdo, Korea are made to investigate the relationships between the mineral weathering, soil forming processes and mineralogical composition. The fine sand fraction (less than 0.2mm) and the clay fraction (less than 2 micron) are dispersed with the shaker after hydrogen peroxide treatment for the removal of organic matter, and separated from each suspension by gravity sedimentation. The fine sand are observed by mineral microscope and the clay are observed by X-ray diffraction patterns, differential thermal analysis curves and infrared spectrum. The outline of the results are as follows. 1. The primary minerals ; Quartz, changed-feldspar, plagioclase, alkali-feldspar are dominant in almost all samples, and some samples contain an appreciable amount of hornblende, biotite, muscovite and plant opal. There are also those samples which contain very small quantity of pyroxene group, tourmaline, epidote, cyanite, magnetite, volcanic glass and zircon. They are mainly derived from weathering products of granite, granodiorite, diorite, arkose or its mixtures. 2. All samples contain expanding or nonexpanding $14{\AA}$ minerals, illite and kaolin minerals, and some samples contain chlorite, cristobalite, gibbsite, and those primary minerals as quartz and feldspar, but the quantities vary according to the parent matrials. 3. Non-expanding $14{\AA}$ minerals may be dioctahadral vermiculite which sandwiches gibbsite layer or chlorite in between layer lattices. 4. As for clay minerals, montmorillonite was principal component in the samples derived from weathering products of arkose sandstone and tertiary. Minerals which are derived from weathering products of arkose have kaolin minerals and vermiculite as their principal component, and minerals derived from weathering products of acidic rock group are generally classified into two groups, the kaolin mineral group, and the kaolin minerals and vermiculite group.

• Korean Journal of Materials Research
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• 제9권3호
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• pp.274-281
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• 1999

Usually sputtering and electroless plating methods were used for manufacturing metal-alloy thin film magnetic memory devices. Since electroless plating method has many merits in mass production and product variety com­pared to sputtering method, many researches about electroless plating have been performed in the United State of America and Japan. However, electroless plating method has not been studied frequently in Korea. In these respects the purpose of this research is manufacturing Co-Mn-P alloy thin film on the corning glass 2948 by electroless plating method using sodium hypophosphite as a reductant, and analyzing deposition rate, alloy composition, microstructure, and magnetic characteristics at various pH's and temperatures. For Co-P alloy thin film, the reductive deposition reaction 0$\alpha$urred only in basic condition, not in acidic condition. The deposition rate increased as the pH and temperature increased, and the optimum condition was found at the pH of 10 and the temperature of $80^{\circ}C$. Also magnetic charac­teristics was found to be most excellent at the pH of 9 and the temperature of $70^{\circ}C$, resulting in the coercive force of 8700e and the squareness of 0.78. At this condition, the contents of P was 2.54% and the thickness of the film was $0.216\mu\textrm{m}$. For crystal orientation, we could not observe fcc for $\beta$-Co. On the other hand,(1010), (0002), (1011) orientation of hcp for a-Co was observed. We could confirm the formation of longitudinal magnetization from dominant (1010) and (1011) orientation of Co-P alloy. For Co-Mn-P alloy deposition, coercive force was about 1000e more than that of Co P alloy, but squareness had no difference. For crystal orientation, (l01O) and (lOll) orientation of $\alpha$-Co was dominant as same as that of Co- P alloy. Likewise we could confirm the formation of longitudinal magnetization.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제18권4호
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• pp.1-7
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• 2017

Cobalt silicide was used as a counter electrode in order to confirm its reliability in dye-sensitized solar cell (DSSC) devices. 100 nm-Co/300 nm-Si/quartz was formed by an evaporator and cobalt silicide was formed by vacuum heat treatment at $700^{\circ}C$ for 60 min to form approximately 350 nm-CoSi. This process was followed by etching in $80^{\circ}C$-30% $H_2SO_4$ to remove the cobalt residue on the cobalt silicide surface. Also, for the comparison against Pt, we prepared a 100 nm-Pt/glass counter electrode. Cobalt silicide was used for the counter electrode in order to confirm its reliability in DSSC devices and maintained for 0, 168, 336, 504, 672, and 840 hours at $80^{\circ}C$. The photovoltaic properties of the DSSCs employing cobalt silicide were confirmed by using a simulator and potentiostat. Cyclic-voltammetry, field emission scanning electron microscopy, focused ion beam scanning electron microscopy, and energy dispersive spectrometry analyses were used to confirm the catalytic activity, microstructure, and composition, respectively. The energy conversion efficiency (ECE) as a function of time and ECE of the DSSC with Pt and CoSi counter electrodes were maintained for 504 hours. However, after 672 hours, the ECEs decreased to a half of their initial values. The results of the catalytic activity analysis showed that the catalytic activities of the Pt and CoSi counter electrodes decreased to 64% and 57% of their initial values, respectively(after 840 hours). The microstructure analysis showed that the CoSi layer improved the durability in the electrolyte, but because the stress concentrates on the contact surface between the lower quartz substrate and the CoSi layer, cracks are formed locally and flaking occurs. Thus, deterioration occurs due to the residual stress built up during the silicidation of the CoSi counter electrode, so it is necessary to take measures against these residual stresses, in order to ensure the reliability of the electrode.

• Korean Journal of Heritage: History & Science
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• 제54권4호
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• pp.22-35
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• 2021

Recently, as the climate changes rapidly and the prevalence of airborne fine particulate matter increases, the pattern of pollutants in the atmospheric environment is also changing. Therefore, the importance of studying the stability of pigments used in colored cultural properties is emerging. Hoecheong is an inorganic blue glass pigment called smalt; it is made by using cobalt as a coloring element in potash glass, and was widely used in colored cultural assets, such as murals and paintings. In this study, we collected three other hoecheong pigments to analyze their properties. The percentage of Co and K contained are different according to the manufacturer, and the smalt-3 sample has a lower cobalt content (15.1 wt.%) and higher potassium content (29.6 wt.%). After this analysis, colored specimens were prepared. Prepared specimens were exposed to ultra-violet rays, CO₂/NO₂, and NaCl, which are known to have the greatest influence on the stability of pigments. We found that factors affecting the color stability were NO₂ gas, ultra-violet rays, and water-soluble salts (NaCl). Among them, NO₂ has the most severe impact on color change of the pigments. Results of the component analysis showed that the color change depends on the potassium and cobalt content of the hoecheong pigment. Among the specimens, smalt-3 showed the most vulnerability after exposure to NO₂ gas and water-soluble salts. Pigment film stability is affected by watersoluble salts, giving rise not only to color change, but also weakening the physical properties of the film. However, there was no significant change in composition and color after exposure to CO₂ gas. In conclusion, we found that hoecheong pigments underwent color change and increased instability of the coating film when exposed to any of the atmospheric environmental factors used in this study, except for CO₂.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제15권7호
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• pp.4081-4086
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• 2014

Cellulose acetate butyrate (CAB) is a biodegradable resin with excellent optical properties, but it is difficult to apply film process. In this study, an attempt was made to improve the processability of CAB using polyactic acid and the mechanical properties using an impact modifier. Polylacitc acid (PLA)/Cellulose acetate butyrate (CAB) blends with an impact modifier were prepared using a twin screw extruder. The temperature range was $140^{\circ}C$ to $200^{\circ}C$, and the screw speed was fixed to 200 rpm. To evaluate the miscibility of impact modified CAB/PLA, the glass transition behavior and morphology were observed by DSC and FE-SEM. The mechanical properties were investigated by dynamic mechanical analysis (DMA) and a Universal Testing Machine (UTM). In addition, the effect of an impact modifier in the polymer matrix was determined using a notched Izod impact strength tester. Finally, the PLA/CAB/impact modifier 75/25/10 ratio was found to be a compatible system. In the 10wt.% impact modifier, the sample had a 4 times higher izod impact strength than the non-toughening composition.

• Journal of Korean Ophthalmic Optics Society
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• 제18권1호
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• pp.11-17
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• 2013

Purpose: To improve glasses temple's insert processibility of CA/PEG blend, triacetin with higher specific heat values in the processing temperature range is used as second plasticizer. Methods: The total amount of plasticizer is fixed at 30 wt% by CA. To determine optimal CA/PEG/triacetin blend for glasses frame, blends with different composition ratio were examined by various analysis: thermal properties, mechanical properties, glossiness. Results: Specific heat of the CA/PEG blend increased as the content of triacetin. In CA/PEG/triacetin blends, as triacetin concentration is increased, glass transition temperature is decreased and heat conservation rate of composites is increased. Furthermore, CA/PEG/triacetin blend exhibited higher mechanical properties and similar gloss characterization with CA/PEG blend. Conclusions: It is possible to improve the processibility inserting metal support to CA temple through varying the weight ratio of PEG/triacetin. The extruded sheets of CA/PEG/triacetin blend had better glossiness and mechanical properties than those of CA/PEG blend.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제21권2호
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• pp.60-64
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• 2011

High sensitivity IR image sensors require materials characteristics with temperature coefficient of resistance (TCR) and IR range absorption. In this study, the metal-dielectric thermo sensitive films (MDTF) based on $(SiO_2)_x-(Ti)_y$ composition were deposited on substrates of germanium and glass by thermal evaporator. The $SiO_2$ : Ti mixture was made from the ratio of 9 : 1, 8 : 2, 7 : 3, 6 : 4, respectively. $(SiO_2)_x-(Ti)_y$ mixture powder was loaded on tungsten boat in evaporator and was 15.5 cm from the substrate. Resistance of $(SiO_2)_x-(Ti)_y$ in the range of 273~333K were measured as a function of temperature. Temperature coefficient of resistance (TCR) was calculated by the resistance variation. Under the various mixture ratios condition, it is possible to obtain $SiO_2$-Ti layers with resistance from units kilo-ohm to hundreds kilo-ohm. Finally, our results showed that Temperature coefficient of resistance (TCR) of these films varies from -1.4 to $-2.6%K^{-1}$.

• Korean Journal of Materials Research
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• 제21권5호
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• pp.277-282
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• 2011

Negative temperature coefficient (NTC) materials have been widely studied for industrial applications, such as sensors and temperature compensation devices. NTC thermistor thick films of $Ni_{1+x}Mn_{2-x}O_{4+{\delta}}$ (x = 0.05, 0, -0.05) were fabricated on a glass substrate using the aerosol deposition method at room temperature. Resistance verse temperature (R-T) characteristics of the as-deposited films showed that the B constant ranged from 3900 to 4200 K between $25^{\circ}C$ and $85^{\circ}C$ without heat treatment. When the film was annealed at $600^{\circ}C$ 1h, the resistivity of the film gradually decreased due to crystallization and grain growth. The resistivity and the activation energy of films annealed at $600^{\circ}C$ for 1 h were 5.203, 5.95, and 4.772 $K{\Omega}{\cdot}cm$ and 351, 326, and 299 meV for $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$, $NiMn_2O_4$, and $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$, respectively. The annealing process induced insulating $Mn_2O_3$ in the Ni deficient $Ni_{0.95}Mn_{2.05}O_{4+{\delta}}$ composition resulting in large resistivity and activation energy. Meanwhile, excess Ni in $Ni_{1.05}Mn_{1.95}O_{4+{\delta}}$ suppressed the abnormal grain growth and changed $Mn^{3+}$ to $Mn^{4+}$, giving lower resistivity and activation energy.