• 한국해양학회지
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• v.11 no.2
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• pp.64-70
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• 1976

Forty four dredged surface sediments from the bottom of the Hwajinpo Lake and its vicinity were investigated in terms of the sedimentary depositional environment. The characteristics of the sedimentary textures, chemistry and clay mineralogy of these sediments were analysed by X-ray diffraction, chemical (EDTA titration and atomic absorption), sieving and pipette techniques. The lake sediments were chiefly mud and the beach sediments were sand. However, the lake sediments from its seaward zone were sand or muddy sand. The textural parameters that is, mean size, sorting value and their pair diagram seems to be characteristic in the area studied. Based on these data it seems to be reasonable thatthe Hwajinpo Lake was developed by the accretion and growth of a barrier spit along the shore investigated. The chief clay minerals identified were kaolinite, muscovite and the presence of vermiculite was believed as minor composition. The major chemical compositions of these sediments, that is, SiO$\sub$2/, Al$\sub$2/O$\sub$3/, Fe$\sub$2/O$\sub$3/, CaO, Na$\sub$2/O and K$\sub$2/O were contained in unit sample. The ratio of alumina to sodium oxide as a chemical index seems to indicate that the inner lake sediments are more mature than the outer one.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.622-626
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• 2010

Cu doped $SnO_2$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and annealed at $500^{\circ}C$ in air, respectively. Structural properties of $SnO_2$ by X-ray diffraction showed (110), (101) and (211) dominant tetragonal phase. The effects of catalyst Cu in $SnO_2$-based gas sensors were investigated. Sensitivity of $SnO_2$:Cu sensors to 2,000 ppm $CO_2$ gas and 50 ppm $H_2S$ gas was investigated for various Cu concentration. The highest sensitivity to $CO_2$ gas and $H_2S$ gas of Cu doped $SnO_2$ gas sensors was observed at the 8 wt% and 12 wt% Cu concentration, respectively. The improved sensitivity in the Cu doped $SnO_2$ gas sensors was explained by decrease of electron depletion region in Cu and $SnO_2$ junction, and increase of reactive oxygen and surface area in the $SnO_2$.

• Journal of the Korean Society of Safety
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• v.28 no.2
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• pp.37-41
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• 2013

In this work, we report the effect on the volatole organic compounds(VOCs) sensing properties of Copper phthalocyanine(CoPc) and Dilithium phthalocyanine(DiLiPc) thin films onto alumina substrates. Use evaporation method and the spin-coated method for sensing device. The materials of metallophthalocyanine macrocyclic compound solutions blended with N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine and/or Poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] solutions. The influence of the blended in with metallophthalocyanine macrocyclic compounds on the resistance have been measured and analyzed in five different volatole organic compounds. The following results were obtained: The AFM 3D image of thin films deposited on metallophthalocyanine macrocyclic compound shows that the surfaces roughness were about CuPc 4.1~14.3 nm(7.5~8.1%), DiLiPc 10.3~22.2 nm(7.9~11.5%). The resistances decreases upon increasing the concentration of vapor organic compounds to CuPc and DiLiPc thin films. That thin films blended Copper phthalocyanine(CoPc) and Dilithium phthalocyanine(DiLiPc) with N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine and/or Poly[2-methoxy--5-(2'-ethylhexyloxy)-1,4-phenylenevinylene]. The resistances of blended thin films with N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine and/or Poly[2-methoxy--5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] decreases upon increasing the concentration of volatole organic compounds(VOCs) on DiLiPc than CuPc compound thin films.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.180-191
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• 2016

Optimizing energy usage for maximum efficiency is an essential goal for manufacturing plants in every industrial manufacturing sector. The generation and distribution of purifying compressed air is a large expense incurred in practically all manufacturing processes. Not only is the generation and treatment expensive equipment of compressed air, but frequent maintenance and effective operation is also required. As a plant's compressed air system is often an integral part of the production process, it needs to be reliable, efficient, and easy to be maintain. In this paper, we study to find operating method to save energy from the adsorption dryer in the process of purifying compressed air, which is required for a clean room production site in "A" company. The compressed air passes through a pressure vessel with two "towers" filled with a material such as activated alumina, silica gel, molecular sieve or other desiccant material. This desiccant material attracts the water from the compressed air via adsorption. As the water clings to the desiccant, the desiccant particle becomes saturated. Therefore, Adsorption dryer is an extremely significant facility which removes the moisture in the air $70^{\circ}C$ below the dew point temperature while using a lot of energy. Also, the energy consumption of the adsorption dryer can be varied by various operating conditions (time, pressure, temperature, etc). Therefore, based on existing operating experiments, we have searched operating condition to maximize energy saving by changing operating conditions of the facility. However, due to a short experiment period (from September to October), further research will be focused on considering seasonality.

• Advances in aircraft and spacecraft science
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• v.4 no.1
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• pp.37-52
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• 2017

Gas turbines operating in dusty or sandy environment polluted with micron-sized solid particles are highly prone to blade surface erosion damage in compressor stages and molten sand attack in the hot-sections of turbine stages. Commercial/Military fixed-wing aircraft engines and helicopter engines often have to operate over sandy terrains in the middle eastern countries or in volcanic zones; on the other hand gas turbines in marine applications are subjected to salt spray, while the coal-burning industrial power generation turbines are subjected to fly-ash. The presence of solid particles in the working fluid medium has an adverse effect on the durability of these engines as well as performance. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The focus of this research work is to simulate particle-surface kinetic interaction on typical turbomachinery material targets using non-linear dynamic impact analysis. The objective of this research is to understand the interfacial kinetic behaviors that can provide insights into the physics of particle interactions and to enable leap ahead technologies in material choices and to develop sand-phobic thermal barrier coatings for turbine blades. This paper outlines the research efforts at the U.S Army Research Laboratory to come up with novel turbine blade multifunctional protective coatings that are sand-phobic, sand impact wear resistant, as well as have very low thermal conductivity for improved performance of future gas turbine engines. The research scope includes development of protective coatings for both nickel-based super alloys and ceramic matrix composites.

• Journal of Sensor Science and Technology
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• v.11 no.5
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• pp.279-285
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• 2002

Two $SnO_2$ based sensing films(pure $SnO_2$ and $SnO_2$/Pt) and a Pt thin film for temperature sensor on an alumina substrate were designed and fabricated for classifying the indoor environmental gases. By controlling the heating power in the shape of trapezoid, unique four sensing response curves created from both $SnO_2$ film and $SnO_2$/Pt film. Then, various parameters were extracted from sensing response curves and carried out principal component analysis(PCA). The results confirm that a sensor array with the proposed operating mode was extremely effective in classifying indoor environmental gases such as $CO_2$, $C_3H_8$, $C_4H_{10}$.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.108-114
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• 2018

Degradations of durability and aesthetic performance in concrete happen during service life due to surface deterioration and dirt stains. Recently, many researches have been performed on self-cleaning and surface enhancement through surface impregnant using photocatalytic reaction with VOCs(Volatile Organic Compounds) removal. This paper is for preliminary study on surface impregnation with silicate and photocatalysis - $TiO_2$. For the work, two types of silicate based impregnants(CS - Coloidal Silica and SC - Sodium Alumina Silicate) are considered. Several tests for viscosity and surface tension are performed, and pull-off test on impregnated concrete is performed. For the surface impregnated concrete, $TiO_2$ is absorbed through submerging and spraying conditions. Through compressive strength test and SEM analysis, it is evaluated that spraying $TiO_2$ on surface impregnated concrete after 30min. of drying period is very effective both for strength enhancement and surface densification.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.2
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• pp.309-319
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• 1996

This study was performed to evaluate the fracture toughness of seven commercially available dental ceramics by indentation fracture method. All specimens were fabricated to the final dimensions of approximately 12mm in diameter 2mm in thickness. The characte-ristic indentation dimensions of Vickers or Knoop indentation were measured to calculate the fracture toughness values and Young’s moduli. The results obtained were summarized as follows; 1. Young’s modulus and Vickers hardness of Vita In-Ceram showed the maximum values of $154.4{\pm}49.2$ Gpa and $12.60{\pm}0.71$Gpa, respectively. Results of Scheff test exhibited the significant difference between Vita In-Ceram group and others(p<0.01). 2. Maximum fracture toughness of $2.562{\pm}0.37 MPam^{1/2}$ for Vita In-Ceram and the maxi-mum one of $0.908{\pm}0.132MPam^{1/2}$ for Vitadur-N were calculated. Results of Scheff test showed the significant difference between Vita In-Ceram group and Vita Hi-Ceram(p<0.05) : also between Vita In-Ceram or Vita Hi-Ceram and others(p<0.01). 3. The alumina-based core ceramics showed the aspect of Palmqvist crack for the indentation load of 49.0N, but others showed the median/lateral crack for the indentation load of 9.8N.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.1
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• pp.69-74
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• 2006

Thick film $H_2$ sensors were fabricated using $SnO_2$ loaded with $Ag_2O$ and $PtO_x$. The composition that gave the highest sensitivity for $H_2$ was in the weight% ratio of $SnO_2 : PtO_x : Ag_2O$ as 93 : 1 : 6. The nano-crystalline powders of $SnO_2$ synthesized by sol-gel method were screen printed with $Ag_2O$ and $PtO_x$ on alumina substrates. The fabricated sensors were tested against gases like $H_2$, $CH_4$, $C_3H_8$, $C_2H_5OH$ and $SO_2$. The composite material was found sensitive against $H_2$ at the working temperature $130^{\circ}C$, with minor interference of other gases. The $H_2$ gas as low as 100 ppm can be detected by the present fabricated sensors. It was found that the sensors based on $SnO_2-Ag_2O-PtO_x$ system exhibited the high performance, high selectivity and very short response time to $H_2$ at ppm level. These characteristics make the sensor to be a promising candidate for detecting low concentrations of $H_2$.

• Journal of Sensor Science and Technology
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• v.18 no.1
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• pp.54-62
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• 2009

${Co_3}{O_4}$ and ${Co_3}{O_4}$-based thick films with additives such as ${Co_3}{O_4}-{Fe_2}{O_3}$(5 wt.%), ${Co_3}{O_4}-{SnO_2}$ (5 wt.%), ${Co_3}{O_4}-{WO_3}$(5 wt.%) and ${Co_3}{O_4}$-ZnO(5 wt.%) were fabricated by screen printing method on alumina substrates. Their structural properties were examined by XRD and SEM. The sensitivities to iso-${C_4}H_{10}$, $CH_4$, CO, $NH_3$ and NO gases were investigated with the thick films heat treated at $400^{\circ}C$, $500^{\circ}C$ and $600^{\circ}C$. From the gas sensing properties of the films, the films showed p-type semiconductor behaviors. ${Co_3}{O_4}-{SnO_2}$(5 wt.%) thick film heat treated at $600^{\circ}C$ showed higher sensitivity to i-${C_4}H_{10}$ and CO gases than other thick-films. ${Co_3}{O_4}-{SnO_2}$(5 wt.%) thick film heat treated at $600^{\circ}C$ showed the sensitivity of 170 % to 3000 ppm iso-${C_4}H_{10}$ gas and 100 % to 100 ppm CO gas at the working temperature of $250^{\circ}C$. The response time to i-${C_4}H_{10}$ and CO gases showed rise time of about 10 seconds and fall time of about $3{\sim}4$ minutes. The selectivity to i-${C_4}H_{10}$ and CO gases was enhanced in the ${Co_3}{O_4}-{SnO_2}$(5 wt.%) thick film.