• Journal of Electrochemical Science and Technology
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• v.8 no.4
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• pp.314-322
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• 2017

The electrolyte plays one of the most significant roles in the performance of electrochemical supercapacitors. Most liquid organic electrolytes used commercially have temperature and potential range constraints, which limit the possible energy and power output of the supercapacitor. The effect of elevated temperature on a lithium bis(oxalate)borate(LiBOB) salt-based electrolyte was evaluated in a symmetric supercapacitor assembled with activated carbon electrodes and different electrolyte blends of acetonitrile(ACN) and propylene carbonate(PC). The electrochemical properties were investigated using linear sweep voltammetry, cyclic voltammetry, galvanostatic charge-discharge cycles, and electrochemical impedance spectroscopy. In particular, it was shown that LiBOB is stable at an operational temperature of $80^{\circ}C$, and that, blending the solvents helps to improve the overall performance of the supercapacitor. The cells retained about 81% of the initial specific capacitance after 1000 galvanic cycles in the potential range of 0-2.5 V. Thus, LiBOB/ACN:PC electrolytes exhibit a promising role in supercapacitor applications under elevated temperature conditions.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.43 no.5
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• pp.60-67
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• 2011

Hemicelluloses pre-extracted from Korean mixed wood chip were investigated as a wet-end additive. Hemicelluloses dissolved in hot water and alkali solution were isolated by ethyl alcohol precipitation from pre-extractives. They showed molecular weight of 9,000 ~ 27,000 g/mol as revealed by size exclusion chromatography. The reduction of molecular weight through hot water extraction was caused by autohydrolysis. Chemical composition of the hemicelluloses were analyzed with high-performance liquid chromatography and UV-Vis spectroscopy. As the surface charge of isolated hemicelluloses were negative, the adsorption of hemicelluloses onto softwood unbleached kraft pulp fiber was promoted by poly-DADMAC. The physical properties of handsheets increased as the molecular weight of hemicellulose increased. On the other hands, the optical property decreased with hemicellulose adsorption.

• Korean Journal of Materials Research
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• v.9 no.1
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• pp.57-64
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• 1999

The electrical conductivity of TiO$_2$ doped with 0.05~1.5mol% WO$_3$ was measured in the oxygen partial pressure range of 10\ulcorner~10\ulcorner atm and temperature range of 1100~130$0^{\circ}C$ to investigate the defect types and the electrical properties. The grain size and density were increased as the liquid phase was formed by the doped WO$_3$. The secondary phase and WO$_3$peaks at the sample doped up to 4.0 mol% were not detected from the XRD results. The data(log$\sigma$/logPo$_2$) over 110$0^{\circ}C$ were divided into the four regions. From these experimental results, we proposed the following defect regions. 1) Magneli phase(extended defect), 2) Reduced rutile region which is similar to the behavior of undoped rutile, 3) Nearly stoichiometric Ti\ulcornerW\ulcornerO$_2$region in which extra charge of W\ulcorner cation is expected to be compensated by an electron, 4) Overstoichiometric Ti\ulcornerW\ulcornerO\ulcorner region which is a metal deficiency not to be observed in pure TiO$_2$. The electrical conductivity of w-doped TiO$_2$ was influenced by the measuring temperature, oxygen partial pressure, and the dopig content.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.193-197
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• 2006

The sodium/sulfur(Na/S) battery has many advantages such as high theoretical specific energy(760Wh/kg), and low material cost based on the abundance of electrode material in the earth. It has been reported that the electrochemical properties of sodium/sulfur cell above $300^{\circ}C$, utilized a solid ceramic electrolyte and liquid sodium and sulfur electrodes. A lot of researches have been performed in this field. Recently, Na/S battery system was applied for electricity storage system for load-leveling. One of severe problems of sodium/sulfur battery was high operating temperature above $300^{\circ}C$, which could induce the explosion and corrosion by molten sodium, sulfur and polysulfides. In order to develop sodium battery operated at low temperature, sodium ion battery has been studied using carbon anode, and sodium oxides cathodes. However, the energy densities of the sodium ion batteries were much lower than high temperature sodium/sulfur cell. In this study, the sodium/sulfur battery with 1M $NaCF_3SO_3$ is tested at room temperature. The charge-discharge mechanism was discussed based on XRD, DSC, SEM and EDS results.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.200-200
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• 2003

Polycrystalline Si(polysilicon) TFTs have opened a way for the next generation of display devices, due to their higher mobility of charge carriers relative to a-Si TFTs. The polysilicon W applications extend from the current Liquid Crystal Displays to the next generation Organic Light Emitting Diodes (OLED) displays. In particular, the OLED devices require a stricter control of properties of gate oxide layer, polysilicon layer, and their interface. The polysilicon layer is generally obtained by annealing thin film a-Si layer using techniques such as solid phase crystallization and excimer laser annealing. Typically laser-crystallized Si films have grain sizes of less than 1 micron, and their electrical/dielectric properties are strongly affected by the presence of grain boundaries. Impedance spectroscopy allows the frequency-dependent measurement of impedance and can be applied to inteface-controlled materials, resolving the respective contributions of grain boundaries, interfaces, and/or surface. Impedance spectroscopy was applied to laser-annealed Si thin films, using the electrodes which are designed specially for thin films. In order to understand the effect of grain size on physical properties, the amorphous Si was exposed to different laser energy densities, thereby varying the grain size of the resulting films. The microstructural characterization was carried out to accompany the electrical/dielectric properties obtained using the impedance spectroscopy, The correlation will be made between Si grain size and the corresponding electrical/dielectric properties. The ramifications will be discussed in conjunction with active-matrix thin film transistors for Active Matrix OLED.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.23 no.2
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• pp.71-96
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• 1997

We have used a novel liquid surface forces apparatus to determine the variation of disjoining pressure with film thickness for dodecane-water-dodecane emulsion films. The LSFA allows measurement of film thicknesses in the range 5-100 nm and disjoining pressure from 0-1500 Pa. Disjoining pressure isotherms are given for films stabilised by the nonionic surfactnat n-dodecyl pentaoxyethylene glycol ether$(C_{12}E_5)$ and n-decyl-$\beta$-D-glucopyranoside($C_{10}- $\beta$-Glu)$ and the anionic surfactant sodium bis(2-ethylhexyl) sulphosuccinate(AOT) in the presense of added electrolyte. For $C_{12}E_5$ and AOT, the emulsion films are indefinitely stable even for the highest concentration of NaCl tested (136.7 Nm) whereas the $C_{10}-{eta}-Glu$ film shows coalescence at this salt concentration. For film thicknesses greater than approximately 20 nm with all three surfactants, the disjoining pressure isotherms are reasonably well described in terms of electrostatic and van der Waals, forces. For the nonionic surfactant emulsion films, the charge properties of the monolayers are qualitatively similar to those seen for foam films. For AOT emulsion films, the monolayer surface potentials estimated by fitting the isotherms are similar to the values of the zeta potential measured for AOT stabilised emulsion droplets. For thin emulsion films certain systems showed isotherms which suggested the presence of an additional repulsive force with a range of approximately 20 nm.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.2
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• pp.54-60
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• 2000

Most droplet generators are based on the Rayleigh's theory of droplet breakup, and various kind of droplet generation devices have been designed in accordance with vibrating method of capillary liquid column. At present, VOAG(Vibrating Orifice Monodisperse Aerosol Generator) is used to generate primary aerosol standards. For the combustion experiments with isolated single droplet, it is found that dripping method or separating method of suspended drop at an end of filament are more effective. Single drops can be separated from continuous streams of droplets by controlling electric charge.

• Journal of ILASS-Korea
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• v.16 no.4
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• pp.167-175
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• 2011

The HCCI engines have been known with high efficiency and low pollution and can be actualized as the new internal combustion engines. However, As for(??) the ignition and combustion depend strongly on the oxidation reaction of the fuel, so it is difficult to control auto-ignition timing and combustion duration. Purpose of this paper is creating the database for development of multi-dimensional simulation and investigating the influence of different molecular structure. In this research, the effect of n-heptane mole ratio in fuel (XnH) on the ignition delay from homogeneous charge compression ignition(HCCI) has been investigated experimentally. By varying the XnH, it was possible to ascertain whether or not XnH is the main resource of ignition delay. Additionally, the information on equivalence ratio for varying XnH was obtained. The tests were performed on a RCM (Rapid Compression Machine) fueled with n-heptane and iso-octane. The results showed that decreasing XnH (100, 30, 20, 10,0), the ignition delays of low temperature reaction (tL) and high temperature reaction (tH) is longer. And the temperature of reaction increases by about 30K. n-heptane partial equivalence ratio (fnH) affect on tL.and TL. When ${\phi}$nH was increased as a certain value, tL was decreased and TL was increased.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4C
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• pp.389-395
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• 2007

The Film X-ray and the CCD method of current medical image system have the disadvantages such as required large place and diagnosis time. In this paper, we implement an effective medical image system using TXT-DXD method's digital X-ray detector(DR1000C). The implemented medical image system has advantages of placing efficiency and short diagnosis time. In order to make the image out of the system more effective, we develop an LCD(Liquid Crystal Display) control driver, having the resolution of 1900*1200. And we propose an enhancement unsharp masking method to update image enhancement of DR1000C medical image system, and compare it with the current methods.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.353-356
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• 1999

Highly proten-conductive elastic composites have been successfully prepared from $H_3PO_4$-doped silica gel and styrene-ethylene-butylene-styrene block elastic copolymer. In addition solid state electric double-layer capacitors have been fabricated using the composite as an electrolyte and activated carbon powders(ACP) hybridized with the composite as a polrizable electrode. The cyclic voltammogram of the electric double-layer capacitor fabricated demonstrated that electric charge was stored in the elecric double-layer at the interface between the polarizable electrode and the electrolyte. The value of capacitance of the capacitor was 10 F/(gram of total ACP), which was comparable to that of the capacitors using conventional liquid electrolytes.