• Transactions of Materials Processing
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• v.8 no.3
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• pp.233-233
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• 1999

To investigate the effect of tungsten addition on mechanical properties, we prepared refractory (62χ)Nb-18Si-l00Mo-l0Ti-χW (χ=0, 5, 10 and 15 mol.%) in-situ composites by the conventional arc-casting technique, and then explored the microstructure, hardness and elastic modulus at ambient temperature and tensile properties at 1670 K. The microstructure consists of relatively fine (Nb, Mo, W, Ti)/sub 5/Si₃, silicide and a Nb solid solution matrix, and the fine eutectic microstructure becomes predominant at a Si content of around 18 mol.%. The hardness of (Nb, Mo, W, Ti(/sub 5/Si₃, silicide in a W-free sample is 1680 GPa, and goes up to 1980 GPa in a W 15 mol.% sample. The hardness, however, of Nb solid solution does not exhibit a remarkable difference when the nominal W content is increased. The elastic modulus shows a similar tendency to the hardness. The optimum tensile properties of the composites investigated are achieved at W 5 mol.% sample, which exhibits a relatively good ultimate strength of 230 MPa and an excellent balance of yield strength of 215 MPa, and an elongation of 3.7%. The SEM fractography generally indicates a ductile fracture in the W-free sample, and a cleavage rupture in W-impregnated ones.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.331-337
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• 2014

Ge is becoming an increasingly popular semiconductor material with high Si compatibility for on-chip optical interconnect technology. For a better manifestation of the meritorious material properties of Ge, its surface treatment should be performed satisfactorily before the electronic and photonic components are fabricated. Ex-situ rapid thermal annealing (RTA) processes with different gases were carried out to examine the effects of the annealing gases on the thin-film quality of Ge grown epitaxially on Si substrates. The Ge-on-Si samples were prepared in different structures using the same equipment, reduced-pressure chemical vapor deposition (RPCVD), and the samples annealed in $N_2$, forming gas (FG), and $O_2$ were compared with the unannealed (deposited and only cleaned) samples to confirm the improvements in Ge quality. To evaluate the thin-film quality, room-temperature photoluminescence (PL) measurements were performed. Among the compared samples, the $O_2$-annealed samples showed the strongest PL signals, regardless of the sample structures, which shows that ex-situ RTA in the $O_2$ environment would be an effective technique for the surface treatment of Ge in fabricating Ge devices for optical computing systems.

• Proceedings of the KSRS Conference
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• v.1
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• pp.82-85
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• 2006

The Geostationary Ocean Color Imager (GOCI) will be loaded in Communication, Ocean and Meteorological Satellite (COMS). To efficiently apply the GOCI data in the variety of fields, it is essential to develop the standard algorithm for estimating the concentration of ocean environmental components (, , and ). For developing the empirical algorithm, about 300 water samples and in situ measurements were collected from sea water around the Korean peninsula from 1998 to 2006. Two kinds of chlorophyll algorithms are developed by using statistical regression and fluorescence technique considering the bio-optical properties in Case-II waters. The single band algorithm for is derived by relationship between Rrs (555) and in situ concentration. The CDOM is estimated by absorption coefficient and ratio of Rrs(412)/Rrs(555). These standard algorithms will be programmed as a module of GOCI Data Processing System (GDPS) until 2008.

• Journal of Korea Foundry Society
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• v.30 no.1
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• pp.5-13
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• 2010

This article aims to introduce the synchrotron radiation for its utilization in the casting and solidification fields as an unique tool for observation of real time phenomena of molten metal during solidification. General features of the synchrotron radiation were briefly introduced for readers in the casting and solidification fields, with no background regarding to synchrotron radiation. And basic principles of imaging technologies using synchrotron light for in-situ observation of molten metal were explained together with exemplary research works, which were reported on the casting and solidification fields in recent years. As a practical guide, real time observation of Al-Si casting alloy was introduced with experimental facilities, image acquisition, and processing together with representative results.

• Korean Journal of Agricultural Science
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• v.39 no.3
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• pp.407-412
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• 2012

Soil texture has an important influence on agriculture such as crop selection, movement of nutrient and water, soil electrical conductivity, and crop growth. Conventionally, soil texture has been determined in the laboratory using pipette and hydrometer methods requiring significant amount of time, labor, and cost. Recently, in-situ soil texture classification systems using optical diffuse reflectometry or mechanical resistance have been reported, especially for precision agriculture that needs more data than conventional agriculture. This paper is a part of overall research to develop an in-situ soil texture classification system using image processing. Issues investigated in this study were effects of sensor travel speed and light source and intensity on image quality. When travel speed of image sensor increased from 0 to 10 mm/s, travel distance and number of pixel were increased to 3.30 mm and 9.4, respectively. This travel distances were not negligible even at a speed of 2 mm/s (i.e., 0.66 mm and 1.4), and image degradation was significant. Tests for effects of illumination intensity showed that 7 to 11 Lux seemed a good condition minimizing shade and reflection. When soil water content increased, illumination intensity should be greater to compensate decrease in brightness. Results of the paper would be useful for construction, test, and application of the sensor.

• Macromolecular Research
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• v.13 no.2
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• pp.102-106
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• 2005

Poly(methyl methacrylate) (PMMA)/sodium montmorillonite (Na-MMT) nanocomposites were prepared with a novel method utilizing a macroazoinitiator (MAI). To induce the intergallery polymerization of methyl methacrylate (MMA), the MAI containing a po1y(ethylene glycol) (PEG) segment was intercalated between the lamellae of Na-MMT and swelled with water to enhance the diffusion of MMA into the gallery. The structure of the nanocomposite was examined using X-ray diffraction and transmission electron microscopy, and the thermal properties were examined using differential scanning calorimetry and thermogravimetry. The PMMA/Na-MMT nanocomposite prepared by intergallery polymerization showed a distinct enhancement of its thermal properties; an approximately $30^{\circ}C$ increase in its glass transition temperature and an $80\sim100^{\circ}C$ increase in its thermal decomposition temperature for a $10\%$ weight loss.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.688-691
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• 1997

Good quality superconducting $YBa_2Cu_30_{7-{\delta}}$(YBCO) thin films were grown on Hastelloy (Ni-Cr-Mo alloys) with yttria-stabilized zirconia(YSZ) buffer layers by in situ pulsed laser deposition in a multi-target processing chamber. Generally, Hastelloy exhibits excellent resistance to corrosion, fatigue, thermal shock, impact, and erosion. However, it is difficult to make films on flexible metallic substrates due to interdiffusion problems between metallic substrates and superconducting overlayers. To overcome this difficulty, it is necessary to use YSZ buffer layer since it will not only limit the interdiffusion process but also minimize the surface microcrack formation due to smaller mismatch between the film and the substrate. In order to enhance the crystallinity of YBCO films on metallic substrates, YSZ buffer layers were grown at various temperatures different from the deposition temperature of YBCO films. On YSZ buffer layer grown at higher temperature than that for depositing YBCO film, the YBCO thin film was found to be textured with c-axis orientation by x-ray diffraction and had a zero-resistance critical temperature of about 85K.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.708-712
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• 2009

ITO films were achieved by sintering at $500{\sim}550{^{\circ}C}$. This was possible by inducing a seeding effect on an ITO sol by producing crystalline ITO nanoparticles in situ during heat treatment. Two kinds of ITO sols (named ITO-A and ITO-B) were prepared at 2.0 wt% from indium acetate and tin(IV) chloride in different mixed solvents. The ITO-A sol showed a high degree of crystallinity of ITO without any detectable Sn$O_2$ on XRD at $350{^{\circ}C}$/1 h, but the ITO-B sol showed a small amount of Sn$O_2$ even after annealing at $600{^{\circ}C}$/1 h. The 10 wt% ITO-A//ITO-B showed the sheet resistance of 3600$\Omega$/□, while the ITO-B sol alone showed 5200 $\Omega$/□ by sintering at $550{^{\circ}C}$ for 30 min. Processing parameters were studied by TG/DSC, XRD, SEM, sheet resistance, and visible transmittance.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.176-182
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• 2012

The main purpose of this study was to evaluate the endurance against Al alloy melts and wear resistance of an in-situ synthesized titanium matrix composite (TMC) sleeve for aluminum alloy die-casting. The conventional die-casting shot sleeve material was STD61 tool steel. TMCs have great thermal stability, wear and oxidation resistance. The in-situ reaction between Ti and $B_4C$ leads to two kinds of thermodynamically stable reinforcements, such as TiBw and TiCp. To evaluate the feasibility of the application to a TMCs diecasting shot sleeve, the interfacial reaction behavior was examined between Al alloys melts with TMCs and STD61 tool steel. The pin-on-disk type dry sliding wear test was also investigated for TMCs and STD61 tool steel.

• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.393-398
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• 2005

In-situ processing route was adopted to disperse carbon nanotubes (CNTs) into $Al_2O_3$ powders homogeneously. The $Al_2O_3$ composite powders with homogeneous dispersion of CNTs could be synthesized by a catalytic route for in-situ formation of CNTs on nano-sized Fe dispersed $Al_2O_3$ powders. CNTs/Fe/$Al_2O_3$ nanopowders were densified by spark plasma sintering (SPS). The hardness and bending strength as well as electrical conductivity increased with increasing sintering temperature. However, the electrical conductivity of the composites sintered at above $1500^{\circ}C$ showed decreased value with increasing sintering temperature due to the oxidation of CNTs.