• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.61-67
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• 2018

Welding preheating means that the surface of the base material to which the metal is welded before the main welding is heated to a constant temperature. It prevents the cracks of the adjacent influences such as reduction of material hardening degree by controlling the cooling rate, suppression of segregation of impurities, prevention of thermal deformation, and moisture removal. For this reason, it is a necessary operation for high quality welding. Induction heating is an efficient heating method that converts electric energy into heat energy by applying electromagnetic induction phenomenon. Compared with combustion heat generated by gas and liquid, it is clean, stable, and economical as well as rapid heating. It can be heated regardless of the shape, depth and material of the heating body by modifying the shape of the frequency and the coil with a simple structure. In this paper, we implemented a low frequency welding preheating system using induction heating technique and observed the temperature changes of coil resistance, inductance and automotive transmission parts according to the height of each transmission in winding coil for three kinds of automotive transmission parts. We confirmed that the change of current is a very important factor in the low frequency heating.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.5
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• pp.361-372
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• 1990

Processing conditions of whole sardine into modified fish sauce were investigated. Thawed and chopped sardine was homogenized and hydrolyzed using commercial proteolytic enzymes such as complex enzyme-2000($2.18{\cdot}10^4U/g solid$) and alcalase($1.94{\cdot}10^4\;U/g solid$) in a cylindrical vessel with 4 baffles and 6-bladed impeller. Optimal pH, enzyme concentration and temperature for the hydrolysis with complex enzyme-2000 were 7.0, $7\%$ (W/W) and $52^{\circ}C$, and-those with alcalase were 8.0, $6\%$ (W/W) and $60^{\circ}C$. In both cases, the reasonable amount of water for homogenization, agitation speed and hydrolyzing time were $100\%$ (W/W), 100 rpm and 210 minutes. Thermal treatment of the filtered hydrolysate at $90^{\circ}C$ for 2 hours with $6\%$ of invert sugar was adequated to inactivation of the enzymes and pasteurization of the hydrolysate. Flavor, taste and color of the hydrolysate were improved during the heating process in which the browning products might participate. The content of free amino nitrogen in the fish sauce seasoned with $15\%$ of table salt was ca. $1,640 mg\%$. Yield of the fish sauce based on the contents of proteinous and free amino nitrogen in the raw whole sardine was ca. $86\%$, and ca. $96\%$ of these compounds of the fish sauce was in the form of free amino nitrogen. The pH, salinity and histamine content of the fish sauce were $6.1\~6.3,\;14.2\~14.3\%$ and less than $10\;mg\%$.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.97-97
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• 2013

Recently, Cu2ZnSn(S,Se)4 (CZTSS), which is one of the In- and Ga- free absorber materials, has been attracted considerable attention as a new candidate for use as an absorber material in thin film solar cells. The CZTSS-based absorber material has outstanding characteristics such as band gap energy of 1.0 eV to 1.5 eV, high absorption coefficient on the order of 104 cm-1, and high theoretical conversion efficiency of 32.2% in thin film solar cells. Despite these promising characteristics, research into CZTSS based thin film solar cells is still incomprehensive and related reports are quite few compared to those for CIGS thin film solar cells, which show high efficiency of over 20%. I will briefly overview the recent technological development of CZTSS thin film solar cells and then introduce our research results mainly related to sputter based process. CZTSS thin film solar cells are prepared by sulfurization of stacked both metallic and sulfide precursors. Sulfurization process was performed in both furnace annealing system and rapid thermal processing system using S powder as well as 5% diluted H2S gas source at various annealing temperatures ranging from $520^{\circ}C$ to $580^{\circ}C$. Structural, optical, microstructural, and electrical properties of absorber layers were characterized using XRD, SEM, TEM, UV-Vis spectroscopy, Hall-measurement, TRPL, etc. The effects of processing parameters, such as composition ratio, sulfurization pressure, and sulfurization temperature on the properties of CZTSS absorber layers will be discussed in detail. CZTSS thin film solar cell fabricated using metallic precursors shows maximum cell efficiency of 6.9% with Jsc of 25.2 mA/cm2, Voc of 469 mV, and fill factor of 59.1% and CZTS thin film solar cell using sulfide precursors shows that of 4.5% with Jsc of 19.8 mA/cm2, Voc of 492 mV, and fill factor of 46.2%. In addition, other research activities in our lab related to the formation of CZTS absorber layers using solution based processes such as electro-deposition, chemical solution deposition, nano-particle formation will be introduced briefly.

• Korean Journal of Food Science and Technology
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• v.39 no.5
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• pp.534-540
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• 2007

In this study, waxy rice starch was chemically modified using phosphorous oxychloride ($POCl_3$, 0.002-0.008%). Then the physicochemical properties of resulting cross-linked waxy rice starches were investigated in order to reduce the steeping time of Yukwa (a Korean oil-puffed rice snack) processing. The swelling powers of the cross-linked waxy rice starch samples were higher than the native waxy rice starch at temperatures above $60^{\circ}C$, and their increases were proportional to the $POCl_3$, concentration. The solubility of the cross-linked waxy rice starch was lower (1.6-3.4%) than the native waxy rice starch (2.7-6.1%). However, the moisture sorption isotherm of the cross-linked waxy rice starch was not significantly different from the native waxy rice starch. The rapid visco analyze. (RVA) pasting temperatures $(65.4-67^{\circ}C)$ of the cross-linked waxy rice starch were lower than those of the native starch $(67^{\circ}C)$. The RVA peak viscosities (287-337 RVU) of the cross-linked waxy rice starch were higher than that of native starch (179 rapid visco units (RVU)), and increased with increasing $POCl_3$ concentration. For the differential scornning calorimeter thermal characteristics, although Tc shifted toward higher temperatures with cross-linking, the To, Tp, and amylopectiin melting enthalpy of the cross-linked waxy rice starch showed no differences compared to the native waxy rice starch. The X-ray diffraction patterns of both the native and cross-linked waxy rice starches showed typical A-type crystal patterns, suggesting that cross-linking mainly occurs in the amorphous regions of starch granules. Therefore, the cross-linking reaction did not change the crystalline region, but altered the amorphous region of the waxy rice starch molecules, resulting in changes of solubility and RVA pasting properties in the cross-linked waxy rice starch. In summary, since cross-linked waxy rice starch has a high puffing efficiency and no browning reaction, it may be applicable for Yukwa processing without a long steeping process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.508-512
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• 1998

The NTC thermistors were sintered by using microwave hybrid heating method at $1100^{\circ}C$~$1300^{\circ}C$ and those electrical properties were investigated. The obtained $B_{25^{\circ}C/85^{\circ}C}$ values from temperature dependence of electrical resisitivity were around 3100~3200 K which were almost the same values as conventionally sintered ones. Compared with conventional sintering process, this process could complete whole sintering process within 20 minutes. This the processing time and energy consumption could be reduced through this rapid heating by using microwave hybrid heating.t there were showed only two peaks, glycolide melting peak and lower molecular weight melting peak without lauryl alcohol. Conversion increased slowly with the reaction time up to 50 minutes, and then gave a sudden increase above that. The reaction time to disappear in glycolide melting peak during polymerization was shortened with the increase of lauryl alcohol content. Zero-shear viscosity of polyglycolic acid decreased with the increase of free acid content in glycolide.ssional energy and bending hysteresis increased. \circled3 Surface characteristics such as friction coefficient and thickness variation of highly shrinkage fabrics became relatively roughened state. \circled4 Since stiffened and roughened characteristics of highly shrinkage fabrics, drapabilities of them were significantly lowered. Additionally thermal insulation property of high shrinkage fabric was higher than that of low shrinkage fabric due to bulky and thickened feature. From the results, it is considered that the silk fabrics with high filling shrinkage have the good bulkiness and heat keeping properties and thus they have the suitable characteristics for high quality men's and women's formal garments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.16-22
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• 2002

This paper suggests the optimum processing conditions for obtaining good quality $P^{+}$-n shallow junctions formed by pre-amorphization and furnace annealing(FA) to reflow BPSG(bore phosphosilicate glass). $BF_2$ions, the p-type dopant, were implanted with the energy of 20keV and the dose of 2$\times$10$^{15}$ cm$^{-2}$ into the substrates pre-amorphized by As or Ge ions with 45keV, 3$\times$$10^{14}$ $cm^{-2}$. High temperature annealings were performed with a furnace and a rapid thermal annealer. The temperature range of RTA was 950~$1050^{\circ}C$, and the furnace annealing was employed for BPSG reflow with the temperature of $850^{\circ}C$ for 40 minutes. To characterize the formed junctions, junction depth, sheet resistance and diode leakage current were measured. Considering the preamorphization species, Ge ion exhibited better results than As ion. Samples preamorphized with Ge ion and annealed with $1000^{\circ}C$ RTA showed the most excellent characteristics. When FA was included, Ge preamorphization with $1050^{\circ}C$ RTA plus FA showed the lowest product of sheet resistance and junction depth and exhibited the lowest leakage currents.

• Korean Journal of Food Science and Technology
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• v.38 no.3
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• pp.385-391
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• 2006

Physicochemical properties of hydroxypropylated waxy rice starches were investigated to reduce steeping-time of yukwa (Korean oil-puffed rice snack) processing. Swelling power of hydroxypropylated waxy rice starch increased at relatively higher temperature $(60^{\circ}C)$ than native waxy rice starch $(70^{\circ}C)$. Solubility of hydroxypropylated waxy rice starches increased with increasing propylene oxide content. Pasting temperature $(66.3-66.9^{\circ}C)$ and peak viscosity (216-232 RVU) of hydroxypropylated waxy rice starch were higher than those of native starch (179 RVU) and increased with increasing propylene oxide content. DSC thermal transitions of hydroxypropylated waxy rice starches shifted toward higher temperature. Amylopectin melting enthalpy of hydroxypropylated waxy rice starch (8.4-9.2 J/g) was similar to native starch (9.0 J/g). X-ray diffraction patterns of native and hydroxypropylated waxy rice starches showed typical A-type pattern with no significant differences between them, suggesting hydroxypropylation only affected amorphous region. Results suggest hydroxypropylated waxy rice starch is not applicable for yukwa due to low puffing efficiency and dark color.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.490.2-490.2
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• 2014

Since the general solar cells accept sun light at the front side, excluding the electrode area, electrons move from the emitter to the front electrode and start to collect at the grid edge. Thus the edge of gridline can be important for electrical properties of screen-printed silicon solar cells. In this study, the improvement of electrical properties in screen-printed crystalline silicon solar cells by contact treatment of grid edge was investigated. The samples with $60{\Omega}/{\square}$ and $70{\Omega}/{\square}$ emitter were prepared. After front side of samples was deposited by SiNx commercial Ag paste and Al paste were printed at front side and rear side respectively. Each sample was co-fired between $670^{\circ}C$ and $780^{\circ}C$ in the rapid thermal processing (RTP). After the firing process, the cells were dipped in 2.5% hydrofluoric acid (HF) at room temperature for various times under 60 seconds and then rinsed in deionized water. (This is called "contact treatment") After dipping in HF for a certain period, the samples from each firing condition were compared by measurement. Cell performances were measured by Suns-Voc, solar simulator, the transfer length method and a field emission scanning electron microscope. According to HF treatment, once the thin glass layer at the grid edge was etched, the current transport was changed from tunneling via Ag colloids in the glass layer to direct transport via Ag colloids between the Ag bulk and the emitter. Thus, the transfer length as well as the specific contact resistance decreased. For more details a model of the current path was proposed to explain the effect of HF treatment at the edge of the Ag grid. It is expected that HF treatment may help to improve the contact of high sheet-resistance emitter as well as the contact of a high specific contact resistance.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.131-131
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• 2013

A single-layer graphene has been uniformly grown on a Cu surface at elevated temperatures by thermally processing a poly(methyl methacrylate) (PMMA) film in a rapid thermal annealing (RTA) system under vacuum. The detailed chemistry of the transition from solid-state carbon to graphene on the catalytic Cu surface was investigated by performing in-situ residual gas analysis while PMMA/Cu-foil samples being heated, in conjunction with interrupted growth studies to reconstruct ex-situ the heating process. The data clearly show that the formation of graphene occurs with hydrocarbon molecules vaporized from PMMA, such as methane and/or methyl radicals, as precursors rather than by the direct graphitization of solid-state carbon. We also found that the temperature for vaporizing hydrocarbon molecules from PMMA and the length of time the gaseous hydrocarbon atmosphere is maintained, which are dependent on both the heating temperature profile and the amount of a solid carbon feedstock are the dominant factors to determine the crystalline quality of the resulting graphene film. Under optimal growth conditions, the PMMA-derived graphene was found to have a carrier (hole) mobility as high as ~2,700 cm2V-1s-1 at room temperature, superior to common graphene converted from solid carbon.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.528-537
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• 2008

60 nm and 20 nm thick hydrogenated amorphous silicon(a-Si:H) layers were deposited on 200 nm $SiO_2$/single-Si substrates by inductively coupled plasma chemical vapor deposition(ICP-CVD). Subsequently, 30 nm-Ni layers were deposited by an e-beam evaporator. Finally, 30 nm-Ni/(60 nm and 20 nm) a-Si:H/200 nm-$SiO_2$/single-Si structures were prepared. The prepared samples were annealed by rapid thermal annealing(RTA) from $200^{\circ}C$ to $500^{\circ}C$ in $50^{\circ}C$ increments for 40 sec. A four-point tester, high resolution X-ray diffraction(HRXRD), field emission scanning electron microscopy(FE-SEM), transmission electron microscopy(TEM), and scanning probe microscopy(SPM) were used to examine the sheet resistance, phase transformation, in-plane microstructure, cross-sectional microstructure, and surface roughness, respectively. The nickel silicide from the 60 nm a-Si:H substrate showed low sheet resistance from $400^{\circ}C$ which is compatible for low temperature processing. The nickel silicide from 20 nm a-Si:H substrate showed low resistance from $300^{\circ}C$. Through HRXRD analysis, the phase transformation occurred with silicidation temperature without a-Si:H layer thickness dependence. With the result of FE-SEM and TEM, the nickel silicides from 60 nm a-Si:H substrate showed the microstructure of 60 nm-thick silicide layers with the residual silicon regime, while the ones from 20 nm a-Si:H formed 20 nm-thick uniform silicide layers. In case of SPM, the RMS value of nickel silicide layers increased as the silicidation temperature increased. Especially, the nickel silicide from 20 nm a-Si:H substrate showed the lowest RMS value of 0.75 at $300^{\circ}C$.