• Applied Chemistry for Engineering
• /
• v.19 no.4
• /
• pp.413-420
• /
• 2008

Over the past decade, there have been significant advancement in the field of electrospinning area. This study has focused on preparing yarn using polycarbonate (PC) nanofibers including modified multi-walled carbon nanotube (mMWNT) by solution electrospinning process using the mixture of solvents consisting of tretrahydronfuran (THF) and N,N-dimethylformamide (DMF). In order to enhance the dispersion, MWNT was chemically modified. TEM analysis for the prepared PC/mMWNT nanofibers reveals that mMWNT was well-dispersed into the PC nanofiber matrix. Also with increasing contents of mMWNT, thermal stability of PC/mMWNT nanofibers was improved than that of PC nanofibers. Moreover when 3 to 5 wt% of mMWNT was added, the nanofibers showed good electrical properties expecting antistatic effect, ranging 109.1~109.5 ${\Omega}$. It was confirmed that the multi-filament fibers using PC/mMWNT had $60{\sim}100{\mu}m$ in diameter and 4~5 cm in length.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.142.2-142.2
• /
• 2018

One-dimensional metal oxide nanostructures have attracted considerable research activities owing to their strong application potential as components for nanosize electronic or optoelectronic devices utilizing superior optical and electrical properties. In which, semiconducting $SnO_2$ material with wide-bandgap Eg = 3.6 eV at room temperature, is one of the attractive candidates for optoelectronic devices operating at room temperature [1, 2], gas sensor [3, 4], and transparent conducting electrodes [5]. The synthesis and gas sensing properties of semiconducting $SnO_2$ nanomaterials have become one of important research issues since the first synthesis of SnO2 nanowires. In this study, $SnO_2$ nanowire networks were synthesized on a basis of a two-step process. In step 1, Sn spheres (30-800 nm in diameter) embedded in $SiO_2$ on a Si substrate was synthesized by a chemical vapor deposition method at $700^{\circ}C$. In step 2, using the source of these Sn spheres, $SnO_2$ nanowire (20-40 nm in diameter; $1-10{\mu}m$ in length) networks on a spherical Sn surface were synthesized by a thermal oxidation method at $800^{\circ}C$. The Au layers were pre-deposited on the surface of Sn spherical and subsequently oxidized Sn surface of Sn spherical formed SnO2 nanowires networks. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that $SnO_2$ nanowires are single crystalline. In addition, the $SnO_2$ nanowire is also a tetragonal rutile, with the preferred growth directions along [100] and a lattice spacing of 0.237 nm. Subsequently, the $NO_2$ sensing properties of the $SnO_2$ network nanowires sensor at an operating temperature of $50-250^{\circ}C$ were examined, and showed a reversible response to $NO_2$ at various $NO_2$ concentrations. Finally, details of the growth mechanism and formation of Sn spheres and $SnO_2$ nanowire networks are also discussed.

• Journal of Sensor Science and Technology
• /
• v.11 no.2
• /
• pp.102-110
• /
• 2002

The chemical and mechanical characteristics of a new surface modifier, dichlorodimethysilane (DDMS, $(CH_3)_3SiCl_2$), for stiction-free polysilicon surfaces are reported. The main strategy is to replace the conventional monoalkyltrichlorosilane(MTS, $RSiCl_3$) such as octadecyltrichlorosilane (ODTS) or 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) with dialkyldichlorosilane (DDS, $R_2SiCl_2$) with twit short chains, especially DDMS. DDMS, with shorter chains in aprotic media, rapidly deposits on the chemically oxidized polysilicon surface at room temperature and successfully prevents long cantilevers of 3 mm in length from in-use as well as release stiction. DDMS-modified polysilicon surfaces exhibit satisfactory hydrophobicity, long term stability and thermal stability, which are comparable to those of FDTS. DDMS as an alternative to FDTS and ODTS provides a few valuable advantages; ease in handling and long-term storage in solution, low temperature-dependence and low cost. In addition to the new modifier molecule, the simplified process of direct release right after washing the modified surface with isooctane was proposed to cut the processing time.

• Korean Journal of Food Science and Technology
• /
• v.43 no.6
• /
• pp.696-701
• /
• 2011

To evaluate the processing adaptability of taro flours, the physicochemical properties of taro flour with different drying, roasting and steaming conditions were investigated. The moisture content and total dietary fiber were decreased as temperature increased with hot-air drying. Freeze-dried taro flours showed the highest vitamin C contents. Taro flours made by freeze-drying and hot-air drying showed significantly higher total dietary fiber content than those with roasting and steaming process. Steamed taro flours had the highest water absorption index, while hot-air dried and freeze dried taro flours had the highest water solubility index. No differences were displayed in the differential scanning calorimetry (DSC) thermal characteristics among hot-air dried and freeze dried taro flours. Roasted taro displayed decreased onset temperature and peak temperature as roasting temperature increased. Using a rapid visco-analyzer, the peak viscosity, through viscosity, and final viscosity of dried and steamed taro flours were higher than roasted taro flours, whereas the set back value, which is a prediction of retrogradation, decreased with steaming processing. From those results, it could be concluded that hotair dried taro flours, which have high gelatinization viscosity, are beneficial in imparting viscosity to dough products and hot-air drying after steaming taro flours, which retard retrogradation, is good for porridge and flake base products.

• Horticultural Science & Technology
• /
• v.29 no.2
• /
• pp.81-86
• /
• 2011

The effects of girdling on fruit quality and cold resistance of 'Kyoho' grapes were investigated. Girdling treatment was conducted on the trunk at 10 cm above ground with 1 cm width and grapes were harvested at 90 and 110 days after full bloom to compare the fruit quality. First harvesting rate in girdling treatment was higher than that in non-girdling treatment and coloration was also higher in girdled vines at the final harvest. In other words, coloring process of grape was promoted and enhanced by girdling, but this effect of coloring improvement was decreased after successive girdling treatment. Fruit quality showed no difference between the treated and non-treated berries, but fruit cracking rate was lower in girdled treated berries. Girdled trees were weakened and suffered from freezing damage. Especially, most grapevines withered up after being girdled for three consecutive years. Although girdling had effect on improving the berry coloring significantly, the effect wore off with continuous girdling. And it was possible that consecutive girdling leaded to wither and growth suppression especially in grapevines. These adverse effects may make the continuous girdling technique unsuitable in practice for 'Kyoho' grape.

• The Korean Journal of Food And Nutrition
• /
• v.11 no.2
• /
• pp.237-242
• /
• 1998

This study was carried out to process canned ark shell with highly quality by management of proper processing conditions for prevention of oxidation and discoloration by heating. Ark shell has hemoglobin as blood pigment in red blood shell which same as other cockles. Hemoglobin is easy to come oxidation and browning reaction, and it has large contents of carotenoid as meat pigment. Proximate compositions in ark shell were 76.9% of moisture, 18.1% of crude protein, 1.8% of crude lipid, 1.3% of carbohydrate and 1.6% of crude ash. And contents of carotenoid and hemoglobin were 0.67~1.02mg% and 0.98~1.64g/dl, respectively. When the living ark shell was soaked in 2% NaCl solutions, about 89% of mud was removed after 10 hours soaking, and over 91% was removed when the pH was adjusted to 7.5. Carotenoid pigment were prepared that extracted from ark shell by using acetone. And determined visible spectrum were two peak at 452nm and 687nm, and λmax were 452nm. During thermal treatment at 95$^{\circ}C$, 111$^{\circ}C$, 116$^{\circ}C$ and 121$^{\circ}C$ for 60 minutes, retention ratio of carotenoid were 71.8%, 66.8%, 64.4% and 36.5%, and after 120 minutes retention ratio were 56.6%, 30.6%, 30.3% and 17.2%, respectively. When heated at 95$^{\circ}C$, 111$^{\circ}C$, 116$^{\circ}C$ and 121$^{\circ}C$, formation of browning material were increased at high temperature and long time treatment.

• Fire Science and Engineering
• /
• v.24 no.2
• /
• pp.106-113
• /
• 2010

Fire characteristics can be analyzed more realistically by using more accurate material properties related to the fire dynamics and one way to acquire these fire properties is to use one of the inverse property analyses. In this study the genetic algorithm which is frequently applied for the inverse heat transfer problems is selected to demonstrate the procedure of obtaining fire properties of the solid charring material with relatively simple chemical structure. The thermal decomposition on the surface of the test plate is occurred by receiving the radiative energy from external heat sources, and in this process the heat transfer through the test plate can be simplified by an unsteady 1-D problem. The inverse property analysis based on the genetic algorithm is then applied for the estimation of the properties related to the reaction pyrolysis. The input parameters for the analysis are the surface temperature and mass loss rate of the char plate which are determined from the unsteady 1-D analysis with a givenset of 8 properties. The estimated properties using the inverse analysis based on the genetic algorithm show acceptable agreements with the input properties used to obtain the surface temperature and mass loss rate with errors between 1.8% for the specific heat of the virgin material and 151% for the specific heat of the charred material.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.23 no.5
• /
• pp.361-372
• /
• 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 Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.440-443
• /
• 2002

Present1y the X-Ray diagnosis system is a real condition that is changing by digital ways in it's existent analog ways. This digital radiation detector is divided by the direct method and the indirect method. The indirect method of applied voltage has special qualities that the resolution is low than direct method by diffusion effect that happens. The conversion process ( radiation${\rightarrow}$visible ray${\rightarrow}$electrical signal of two times, has shortcomings that the energy conversion efficiency of electrical signal is low. The direct method has shortcomings that need strong electric fie1d to detect electrical signal efficiently. This research achieved to develop digital detector of the Hybrid method that have form that mixes two ways to supplement shortcoming of direct. indirect method. A studied electrical characteristic by Iodine's Mixture ratio change is added to selenium in the detector which has a multi-layer structure (Oxybromide + a-Se). There are 8 kinds of Manufactured compositions to amorphous selenium Iodine each 30ppm, 100ppm, 200 ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm by a doped photoconductor through a vacuum thermal evaporation method. The phosphor layer is consisted of Oxybromide ($BrO_2$) which uses optical adhesives multi-layer structure. The manufactured compositions calculates and compares Net Charge and signal to noise ratio measuring Photocurrent about Darkcurrent and X-ray. When doped Iodine Mixture ratio is 500ppm to the multi-layer structure (Oxybromide + a-Se), applied voltage of $3V/{\mu}m$, leakage current of compositions $2.61nA/cm^2$ and net charge value by 764pC/$cm^2$/mR then the best result appeared.

• Journal of Energy Engineering
• /
• v.29 no.2
• /
• pp.1-9
• /
• 2020

In recent days, fuel cell has received attention from the world as an alternative power source to hydrocarbon used in automobile engines. With the industrial advances of fuel cell, There have been a lot of researches actively conducted to find a way of generating hydrogen. Among many hydrogen production methods, Solid Oxide Electrolysis Cell(SOEC) is not only a basic way but also environment-friendly method to produce hydrogen gas. Solid Oxide Electrolysis Cell has lower electrical energy demands and high thermal efficiency since it is possible to operate under high temperature and high pressure conditions. For these reasons, experimental researches as well as studies on numerical modeling for Solid Oxide Electrolysis Cell have been under way. However, studies on numerical modeling are relatively less enough than experimental accomplishments and have limited performance prediction, which mostly is considered as a result from inadequate effects of electrochemical properties by temperature and pressure. In this study, various experimental studies of commercial Membrane Electrode Assembly (MEA) composed of Ni-YSZ (40wt%, Ni-60 wt% YSZ)/8-YSZ (TOSOH, TZ8Y)/LSM (La_0.9Sr_0.1MnO₃) was utilized for improving effectiveness of SOEC model. After numerically analyzing effects of electrochemical properties according to operating temperature, causing the largest deviation between experiments and simulation are that Charge Transfer Coefficient (CTC), exchange current density, diffusion coefficient, electrical conductivity in SOEC. Analyzing temperature effect on parameter used in overpotential model is conducted for modeling of SOEC. cross-validation method is adopted for application of various MEA and evaluating feasibility of model. As a result, the study confirm that the numerical model of SOEC based on structured process of effectiveness evaluation makes performance prediction better.