• Journal of the Korean Wood Science and Technology
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• 제2권2호
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• pp.5-7
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• 1974

1. This study indicates that above the fiber saturation point the drying rate can be increased with increasing the velocity of the air circutation, i.e., the drying rate of sample boards is proportional to the air velocity, but below the fiber saturation point, the effect of the velocity of air circulation is very low as shown in Figs. 1 and 2. 2. Under the controlled temperature and humidity in the kiln, the more the sample boards have moisture, the higher drying rate of it can be obtained. In other words, this means that even though in the case of drying various moisture content of wood, at the final drying stage, approximately the same percentage of moisture content of wood can be secured by employing the higher velocity of air circulation. 3. This study shows that the rate of drying in kiln changes distinctly at the fiber saturation point, i, e., above the fiber saturation point, the drying curve shows concave aginst the X axsis, but below the fiber saturation point, in the range from 30 percent of moisture content to 20 percent of moisture content, the curve shows convex as shown in Fig. 3. As the drying progresses, however, the drying curve shows concave again below 20 percent of moisture content. This means that inflection point of drying curve may be located clearly at the fiber saturation point, i.e., 30 percent of moisture content. As mentioned above, the 30 percent of moisture content of wood at which the inflectional point appears can be recognized as a critical point, i. e., the fiber saturation point at which all free water was removed from wood. The existence of inflectional point indicates that the evaporation of hygroscopic water in a cell wall is more difficult than the evaporation of free water in a cell cavity and the minor space of cell wall. The convex curve in the range of moisture content from 30 percent to 20 percent means that the evaporation of capillary condensed water has a tendency of the same rates of drying approximately, but as approaching to the 20 percent of moisture, the transfusion of moisture from wood becomes difficult because of having less moisture in cell wall. Below 20 percent of moisture content, the drying curve shows concave again, which means that it is difficult to remove the moisture located nearer to the surface of cellulose molecules and the surface bound water. These relations were revealed in Fig. 4. In comparison AC curve which does not have the two inflection points with BD curve which has two inflection points, i.e., Band D, they are mentioned already, by existence of the inflection points, the curve BD shows that the change of drying rate in the interval from 20 percent of moisture content to 30 percent of moisture content is not greater than in the case of the curve AC in the same interval. At the inflection point of 30 percent of moisture content, it can be noticed that the changing of the drying rate is very conspicuous. This phenomenon also can be recognized, as it is noticed by the Fig. 3, the drying rate from green to 30 percent of moisture content is very great. But the inclination of the curve is very slow from 30 percent of moisture content to 20 percent of moisture content, i.e., the inclination of the curve becomes almost horizontal lines. Acknowledgments Gratitude is expressed to Fred E. Dickinson, Professor of 'Wood Technology, School of Natural Resources, University of Michigan, USA for his suggestion to carry out this study.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.189-189
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• 2012

Lead sulfide (PbS) nanocrystal quantum dots (NQDs) are promising materials for various optoelectronic devices, especially solar cells, because of their tunability of the optical band-gap controlled by adjusting the diameter of NQDs. PbS is a IV-VI semiconductor enabling infrared-absorption and it can be synthesized using solution process methods. A wide choice of the diameter of PbS NQDs is also a benefit to achieve the quantum confinement regime due to its large Bohr exciton radius (20 nm). To exploit these desirable properties, many research groups have intensively studied to apply for the photovoltaic devices. There are several essential requirements to fabricate the efficient NQDs-based solar cell. First of all, highly confined PbS QDs should be synthesized resulting in a narrow peak with a small full width-half maximum value at the first exciton transition observed in UV-Vis absorbance and photoluminescence spectra. In other words, the size-uniformity of NQDs ought to secure under 5%. Second, PbS NQDs should be assembled carefully in order to enhance the electronic coupling between adjacent NQDs by controlling the inter-QDs distance. Finally, appropriate structure for the photovoltaic device is the key issue to extract the photo-generated carriers from light-absorbing layer in solar cell. In this step, workfunction and Fermi energy difference could be precisely considered for Schottky and hetero junction device, respectively. In this presentation, we introduce the strategy to obtain high performance solar cell fabricated using PbS NQDs below the size of the Bohr radius. The PbS NQDs with various diameters were synthesized using methods established by Hines with a few modifications. PbS NQDs solids were assembled using layer-by-layer spin-coating method. Subsequent ligand-exchange was carried out using 1,2-ethanedithiol (EDT) to reduce inter-NQDs distance. Finally, Schottky junction solar cells were fabricated on ITO-coated glass and 150 nm-thick Al was deposited on the top of PbS NQDs solids as a top electrode using thermal evaporation technique. To evaluate the solar cell performance, current-voltage (I-V) measurement were performed under AM 1.5G solar spectrum at 1 sun intensity. As a result, we could achieve the power conversion efficiency of 3.33% at Schottky junction solar cell. This result indicates that high performance solar cell is successfully fabricated by optimizing the all steps as mentioned above in this work.

• Membrane Journal
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• 제15권2호
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• pp.147-156
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• 2005

It is well-known that polyethersulfone (PES) has high $CO_2$ selectivity over $N_2\;(or\;CH_4)$ and excellent pressure resistance of $CO_2$ plasticization among muy commercialized engineering plastics[1-4]. Asymmetric PES hollow fiber membranes for flue gas separation were developed by dry-wet spinning technique. The dope solution consists of PES, NMP and acetone. Water and water/NMP mixtures are used in outer and inner coagulants, respectively. Gas permeation rate (i.e., permeance) and $CO_2/N_2$ selectivity were measured with pure gas, respectively and the micro-structure of hollow fiber membranes was characterized by scanning electron microscopy. The effects of polymer concentration, ratio of NMP to acetone, length of air gap, evaporation condition and silicone coating were investigated on the $CO_2/N_2$ separation properties of the hollow fibers. Optimized PES hollow fiber membranes exhibited high permeance of $25\~50$ GPU and $CO_2/N_2$ selectivity of $30\~40$ at room temperature and have the apparent skin layer thickness of about $0.1\;{\mu}m$. The developed PES hollow fiber membranes, would be a good candidate suitable for the flue gas separation process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제25권10호
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• pp.805-810
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• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제17권9호
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• pp.206-211
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• 2016

Various applications require dry air at low temperature, such automation equipment, semiconductor manufacturing, chemical production lines, and coating processes for the shipbuilding industry. Four evaporators for low temperature (below $0^{\circ}C$) were installed for a dehumidification system. Moist air is cooled sequentially over three evaporators. The first evaporator has an evaporation temperature of $13^{\circ}C$, that of the second evaporator is $5^{\circ}C$, and that of the third evaporator is maintained at $-1.3^{\circ}C$. In the fourth evaporator implantation thereby the moisture contained in the moisture air. A pressure regulator (CPCE 12) is used at this point and is defrosted when the vapor pressure is below a set value. The non-implantation moisture of the air is a heating system that uses the waste heat of a condenser with high temperature. It develops the cooling type's dehumidifier, which is important equipment that prevents the destruction of protein and measures the temperature and humidity at each interval by changing the front air velocity from 1.0 m/s to 4.0 m/s. The cooling capacity was also calculated. The greatest cooling capacity was 1.77 kcal/h for a front air velocity of 2.0 m/s

• Journal of the Society of Cosmetic Scientists of Korea
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• 제44권3호
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• pp.211-218
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• 2018

Instant face lifting cosmetics contain various film forming agents for stretching the wrinkles on the skin surface. But, most of the film-forming polymers have sticky feels. And they are easily scrubbed out when skin is rubbed on. In this study, we focused on the influence of sodium silicate that has rapid film forming effect on skin surface and immediate wrinkle reducing effect. Sodium silicate, also known as water glass or soluble glass, is a compound containing sodium oxide and silica. Sodium silicate is a white powder that is readily soluble in water, producing an alkaline solution. Sodium silicate is stable in neutral and alkaline solutions. The sodium silicate solution hardens by drying in air and rapidly forms a thin film. When the solution is applied to the skin, the fine membrane coating is formed by water evaporation and ionic bond re-formation. It also makes the strong siloxane (Si-O) bonding on the skin surface. When these fixation properties are applied to cosmetics, they can give remarkable skin tightening effect. The sodium silicate solution can provide the lifting effect by forming a film on skin at a proper concentration. But, skin irritation may be caused with too high concentration of sodium silicate. We studied a desirable range of the sodium silicate concentration and combination with other fixatives for skin care formulation that has no sticky feels and no scrubbing out phenomenon. Immediate lifting gel was developed by using sodium silicate and various thickening systems. Among of the various thickeners, aluminum magnesium silicate showed the best compatibility with sodium silicate for rapid lifting effect. This instant physical lifting gel was confirmed as a low stimulating formula by skin clinical test.

• Journal of the Korean Vacuum Society
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• 제17권3호
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• pp.195-198
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• 2008

In this paper, it was demonstrated that organic thin-film transistors (OTFTs) were fabricated with the organic passivation layer by vapor deposition polymerization (VDP) processing. In order to form polymeric film as a passivation layer, VDP process was also introduced instead of spin-coating process, where polymeric film was co-deposited by high-vacuum thermal evaporation from 6FDA and ODA followed by curing. In order to investigate by compared with different passivation layer, the other OTFTs is fabricated to passivation by Polyvinylalcohol using spincoating. We can see that two different ways of passivation layer affect electric characteristic of OTFTs. The initial electric characteristic of OTFTs before passivation such as field effect mobility, threshold voltage, and on-off current ratio are $0.24cm^2/Vs$, -3V, and $10^6$, respectively. Then after polyimide passivation layer, field effect mobility change from $0.24cm^2/Vs$ to $0.26cm^2/Vs$, threshold voltage from -3V to 1V and on-off current ratio from $10^6$ to $10^6$, respectively. In the case of polyvinylalcohol passivation, the initial electric characteristic of OTFTs before passivation such as field effect mobility, threshold voltage, and on-off current ratio are $0.13cm^2/Vs$, 0V, and $10^6$, respectively. Then after polyvinylalcohol passivation layer, field effect mobility changes from $0.13cm^2/Vs$ to $0.13cm^2/Vs$, threshold voltage from 0V to 2V, and on-off current ratio from $10^6$ to $10^5$, respectively.