• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.969-978
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• 1997

The properties of microstructure, hydrophobicity/hydrophilicity, mechanical strength, and thermal conduction of pure/opacified silica aerogels synthesized by the sol-gel supercritical drying technique were investigated. The hydrophobic surface of opacified silica aerogels doped with carbon (0.13 g/cm3 density, 94% porosity, 580 m2/g specific surface area) transformed to hydrophilic surface after heat-treated above 30$0^{\circ}C$. The values of compressive modulus (1.85 MPa) and strength (0.5 MPa) of opacfied silica aerogels were about 20 times higher than those of pure silica aerogels. The mechanical properties of pure silica aerogels heat-treated at $700^{\circ}C$ were also considerably improved without changing their porosity and density. Particularly, compressive modulus and compressive strength of pure silica aerogels GPSed under 100$0^{\circ}C$ and 80 bar were improved 140 and 37 times, respectively. Thermal conductivities of pure/opacified silica aerogels measured at room temperature and 227$^{\circ}C$ were about 0.013 and 0.019 W/m.K, respectively, and were to be found very low value of 0.004 W/m.K below 10 torr pressure at room temperature.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.953-959
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• 2001

Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution of ammonium $metatungstate(NH_4)_6(H_2W_{12}O_{40}){\cdot}4H_2O,\; AMT)$ and cobalt nitrate $hexahydrate(Co(NO_3)_2{\cdot}6H_2O)$. The thermal decomposition process of spray dried W-Co salt powders was studied by TG, XRD, SEM, TEM and FT-IR. Spray dried W-Co salt powders were calcined for 1 hour in the temperature from$ 350^{\circ}C$ to $800^{\circ}C$ in atmosphere of air. At the temperatures over $600^{\circ}C$, spherical $CoWO_4/WO_3$ composite oxide powders were obtained. The primary particle size of W/Co composite oxide powders increased with increasing thermal decomposition temperature due to the particle growth. The observed crystallite size by TEM was in the range of 60nm and that of $CoWO_4$ calculated by Scherrer's formula at $800^{\circ}C$ was smaller than 55nm. The crystallite site was identified by XRD and TEM.

• Journal of Biosystems Engineering
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• v.23 no.4
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• pp.351-358
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• 1998

It was intended to investigate that how hardness of chestnut shell affects the flame peeling characteristics of Korean Chestnut. Effects of the hardness on the flame peeling characteristics need to be found to establish the optimum drying conditions for chestnut of various cultivars, sizes and harvested years. The equation based on the hardness of the chestnut shells was developed. It was found that the flame peeling characteristics of the corresponding to the various drying conditions did not differ significantly to the groups with the same hardness. The flame peeling characteristics of the chestnut with the same hardness were not influenced by cultivars, size, and harvested year, The peeling ratio and the heating depth were increased by decrease of the hardness of the chestnut shells. On the other hand, the peeling ratio and the heating depth were increased as the flame temperature was increased with the same hardness. When the heating depth was limited to 2.1 mm regarding the process characteristics and the damage ratio, the proper hardness and peeling ratio of chestnut shells were 1,369.8 g/$\textrm{mm}^2$ and 83.9%, respectively, at the flame temperature of $700^{\circ}C$. And also 1,517.7 g/$\textrm{mm}^2$ and 80.7% at 75$0^{\circ}C$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.9-15
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• 2013

Roll-to-roll printing technology has lately become a subject of special interests in the field of printed electronics. Since this technology has the advantage that continuous and mass production is possible. And for high precision register control is required in multi-layer printing to produce the electronic devices, this is one of the most important technologies in roll-to-roll printing technology. Register error could be generated by various reasons like eccentricity of roll and thermal deformation due to temperature variation in drying section. In this study, the effect of tension variation on the register was analyzed. The results of these analyses show that it is essential to consider the tension disturbance which is generated by the change of temperature in drying section, and conventional register model has limitation to estimate the register error. In order to overcome the limitation of the register model, advanced register model based on the SI process was developed. Also, the performance of the developed model was verified experimentally.

• Journal of the Korean Wood Science and Technology
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• v.23 no.4
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• pp.33-38
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• 1995

The rates of fixation of CCA-Type B and CCFZ in blocks of radiata pine sapwood were compared at various temperatures and conditioning methods (drying and nondrying conditioning). Also the time required to proper fixation of preservative components in the treated wood was estimated. Fixation was monitored by the rates of depletion of free hexavalent chromium in the cell lumens in the teated blocks. The rate of preservative fixation in wood was highly temperature dependent. The fixation rate was considerably accelerated by means of heating and complete fixation of hexavalent chromium was achieved within about 12 hours by heating at $60^{\circ}C$. The moisture content of treated wood during fixation apparently played an important role in the fixation process. The fixation rate of treated wood conditioned in nondrying conditions was much more faster than that of treated wood conditioned in drying conditions. particularly when the moisture content of treated wood was below fiber saturation point. Time required to full fixation could be predicted successfully using the fixation temperatures applied since the correlation between the fixation temperature and the fixation time was excellent. regardless of conditioning methods.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.419-425
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• 2005

In this paper, we describe the luminescent properties of the phosphors synthesized via sol-gel technique. When the phosphor prepared by sol-gel technique, reaction factors, such as pH condition, $R_w$ and drying temperature affected the luminescent intensity, particle size and morphology of final product. Therefore, we attempt to control these reaction factors in order to improve the luminescent efficiency of phosphors. As a result of our study, when the acid catalyst (HCl) was used, emission intensity was higher than the case of base catalyst $(NH_4OH)$. The product prepared at $R_w=60$ indicated the maximum intensity. As the increase of the $R_w$ value, the particle was agglomerated and emission intensity was decreased. Finally, optimum drying temperature of gel was found to be$ 180^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.116-121
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• 2005

Immobilization technique by PVA encapsulation is an effective alternative for wastewater treatment. However little information is available about the effect of PVA characteristics on physical properties as an encapsulation media. This study aims at investigating the effect of the preparation methods of PVA and filler addition to media on the solubility of PVA. The solubility decreased as the freezing temperature decreased and the vacuum-drying was applied. Addition of the PAC (Powered Activated Carbon) and organoclay decreased the solubility of the PVA gels. Organoclay was more effective for lowering the solubility about 25% than the PAC. Nitrification with the PVA-coating media was less sufficient than with the polyurethane media due to the mass transfer restriction for oxygen and nutrients.

• Journal of the Korean Society of Tobacco Science
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• v.6 no.1
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• pp.39-49
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• 1984

In the tobacco industry, it is important to study the change of mechanical property occurring the expansion process. The purpose of this study is to attain basic data for development of a tobacco expansion method. 1 . Freon gas was adsorbed to tobacco under various conditions of temperature, relative humidity and pressure, and then the amount of freon gas adsorbed was analyzed by GC. Freon adsorption rate of Burley 21 was more than that of By104 at the same condition and about 17 $\pm$ 1% moisture content produced better adsorption rate. 2. Freon adsorbed sample were heated to about $150^{circ}C\;to\;230^{\circ}C$ in a drying oven and recycle duct form about 2 to 30 seconds, and then the change of mechanical property were measured. Heated leaf was damaged when the tissue was pressed by the force of above $0.5x10^8dyn/cm^2$. The optimum condition of no damage of the sample was below the temperature of 15$0^{\circ}C$ and heating time of 10 seconds. It was more economically advantages to treated sample in a recycle duct than to be in a drying oven. By this process, the specific volume of the heated sample was increased from 80 to 110 percent in comparison to that of untreated sample.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.109-112
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• 2008

A performance of micro thruster was measured with catalyst bed that was prepared by different catalyst loading condition for the optimization of catalyst bed size. Among the catalyst loading conditions, pH level of precursor solution was changed by several solutions like Nitric acid or Sodium hydroxide. For the each case, it was heated at different drying temperatures that can affect the phase of catalyst loaded on support. From these results, it was studied that the effect of catalyst loading condition on the performance. 90wt% hydrogen peroxide was used as a monopropellant, and platinum was chosen as a catalyst. Characteristic velocity efficiency and temperature efficiency were used for the performance evaluation.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.117-122
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• 2008

Quality control of the concrete pavement in the early stage of curing is very important because it has a conclusive effect on its life span. Therefore, examining and analyzing the initial behavior of concrete pavement must precede an alternative to control its initial behavior. There are largely two influential factors for the initial behavior of concrete pavement. One is the drying shrinkage, and the other is the heat generated by hydration and thermal change inside the pavement depending on the change in the atmospheric temperature. Thus, the coefficient of thermal expansion and drying shrinkage can be regarded as very important influential factors for the initial behavior of the concrete. It has been a general practice up until now to measure the coefficient of thermal expansion from completely cured concrete. This practice has an inherent limitation in that it does not give us the coefficient of thermal expansion at the initial stage of curing. Additionally, it has been difficult to obtain the measurement of drying shrinkage due to the time constraint. This research examined and analyzed the early drying shrinkage of the concrete and measurements of the thermal expansion coefficients to formulate a plan to control its initial behavior. Additionally, data values for the variables of influence were collected to develop a prediction model for the initial behavior of the concrete pavement and the verification of the proposed model. In this research, thermal expansion coefficients of the concrete in the initial stage of curing ranged between $8.9{\sim}10.8{\times}10^{-6}/^{\circ}C$ Furthermore, the effects of the size and depth of the concrete on the drying shrinkage were analyzed and confirmed.