• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.766-773
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• 2013

A transparent film was fabricated based on bacterial cellulose (BC), BC has excellent physical strength and stability at high temperature and it is an environmental friendly flexible material. In order to improve the conductivity, silver nanowire (AgNW) and/or graphene were introduced to the BC membrane. The aspect ratio of the AgNW synthesized in this study was 214, with a length of $15{\mu}m$ and width of 70 nm. The higher aspect ratio improved the conductivity by reducing the contact resistance. The thermal and electrical properties of 7 types of films prepared were investigated. Each film was fabricated with rectangular shape ($2mm{\times}2mm{\times}50{\mu}m$). The films were scored with a net shape by a knife, and filled with AgNW and graphene to bestow conductivity. The film filled with AgNW showed favorable electrical characteristics with a thickness of $350{\mu}m$, electron concentration of $1.53{\times}10^{19}$, electron mobility of $6.63{\times}10^5$, and resistivity of 0.28. The film filled with graphene had a thickness of $360{\mu}m$, electron concentration of $7.74{\times}10^{17}$, electron mobility of 0.17, and resistivity of 4.78. The transmittances at 550 nm were 98.1% and 80.9%, respectively. All the films were able to light LEDs bulbs although their brightness differed. A thermal stability test of the BC and PET films at $150{\pm}5^{\circ}C$ showed that the BC film was more stable, whereas the PET film was quickly banded. From these results, it was confirmed that there it is possible to fabricate new transparent conductivity films based on BC.

• The Journal of Korea Robotics Society
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• v.8 no.3
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• pp.150-155
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• 2013

Vibrotactile actuators for small consumer electronic products, such as mobile devices, have been widely used for conveying haptic sensation to users. One of the most important things in vibrotactile actuators is to be developed in the form of thin actuator which can be easily embedded into mobile devices and to provide vibrotactile signals with wide frequency band to users. Thus, this paper proposes a thin film type haptic actuator with an aim to convey vibrotactile information with high frequency bandwidth to users in mobile devices. To this end, a vibrotactile actuator which creates haptic sensation is designed and constructed based on cellulose acetate material. A cellulose acetate material charged with an electric potential can generate vibration under the AC voltage input. It is found that the motion of the actuator can have concave or convex shape by controlling a polarity of both charged membranes and the actuator performance can be modulated by increasing level of biased electric potential. The experiment clearly shows that the proposed actuator creates enough output force to stimulate human skin with a large frequency bandwidth and to simulate various vibrotactile sensations to users.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.273-284
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• 2002

The purpose of this study is to characterize damage propagation in granite which exists in South Korea. Coarse, medium and fine-grained granite specimens were sampled respectively In order to perform this study, elastic wave velocity test and permeability test were carried out to estimate the physical specificities of specimens before and after damage. Cellulose acetate film duplication method was used to select only cracks from cross section and to make these visible. Using dark-field illumination, approach photographing technique was used to get more distinct photographs of cracks from acetate peel. Computer programs named Photoshop were used to describe cracks. After damage, coarse and medium-grained granite had lower elastic wane velocity, higher permeability, more cracks and more distinct shear fractures than fine-grained granite.

• Polymer(Korea)
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• v.32 no.1
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• pp.63-69
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• 2008

The mechanical properties and morphologies of cellulose blends with two different additives were compared. Poly (vinyl alcohol) (PVA) of ethylene glycol (EG) were used as additives in the formation of cellulose blends through the solution blending. The properties of blends were varied with the additive content in the polymer matrix. The ultimate tensile strength and initial modulus of the cellulose blends were highest for a blend PVA content of 30 wt% and for a blend EG content of 10 wt%, respectively. Ternary blended systems of composition of cellulose/PVA (70/30=w/w)/EG were also prepared by the solution blending method with different EG contents. The mechanical properties of these systems were found to be optimal for EG contents of up to 40 wt%. The mechanical properties of the cellulose ternary blend films were superior to those of the cellulose binary blend films. The oxygen permeability transmission rate ($O_2TR$) monotonically decreased with increasing EG content in the ternary blend films. Overall, the mechanical properties of the cellulose blend films were found to be better than those of pure cellulose films.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.1
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• pp.55-63
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• 2016

New materials and shapes for a humidifying element were developed which outperformed the widely used crisscross glass wool Glasdek media design. The new material consists of 50% cellulose and 50% PET. The parallel channel configuration was devised to reduce excessive pressure loss caused by the reduced height (from 7.0 mm to 5.0 mm) of the crisscross configuration. For the same crisscross configuration, the humidification efficiency of the cellulose/PET element was 26% higher than that of the glass wool element. For the same cellulose/PET material, humidification efficiency of the parallel channel configuration was 14% higher than that of the crisscross configuration. As for the pressure drops, the cellulose/PET element was 2-52% higher than those of the glass wool element. For the same cellulose/PET material, the pressure drop of the parallel channel configuration was 14% higher than that of the crisscross configuration. Data were compared against the predictions from existing correlations and those by the proposed model.

• Journal of Pharmaceutical Investigation
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• v.29 no.2
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• pp.127-136
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• 1999

In order to eliminate demerits of conventional dosage forms, dipotassium glycyrrhizate was formulated as a slim mucoadhesive film type dosage form. The mucoadhesive drug layer gel containing dipotassium glycyrrhizate was prepared using $Noveon^{\circledR}$ AA-1, hydroxypropylcellulose-M, ethylcellulose N 100 and citric acid, and the protective layer gel by using ethylcellulose N 100, $Eudragit^{\circledR}$ RS and castor oil. The viscosity of drug layer gel of mucoadhesive film was enhanced as the increased amount of $Noveon^{\circledR}$ AA-1 or hydroxypropyl cellulose-M. The drug content was unifonnly $1160{\pm}14.6\;{\mu}g$, and was varied within 3.5%. The optimum film dosage form showed a good fluidity and malleability of drug layer, with 179 g of thickness, pH 5.7, 411 min of in vitro adhesion time and 172 g in gravity adhesive strength. The release time of drug from the mucoadhesive film was significantly shorter but was delayed when polymers such as ethylcellulose was added. From these results, the new mucoadhesive film may be effective for the treatment of aphthous stomatitis.

• Journal of the Korean Society of Clothing and Textiles
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• v.8 no.1
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• pp.39-45
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• 1984

The effects of Temperature on the removal of triglyceride were studied with soaps having various chain lengths of alkyl group. Cellophane, polyester film and alkali-treated polyester film were soiled with tripalmitin, tagged with 0" and detergency was evaluated by analysing the tripalmitine on the fabric before and after washing by means of liquid scintillation counting. The results were as following: 1) Triglyceride was completely removed from cellophane in distilled water without surfactant at any temperature, because of the hydrophillic nature of cellulose. The detergency of triglyceride from polyester film fully depended on the state of tripalmitin. The detergency of alkali treated polyester film was better than that of untreated polyester film at lower temperature due to increased hydrophillcity, but worse at higher temperature due to the diffusion of molten tripalmitin into the grooves, formed by alkali treatment. 2) The detergency from polyester film was increased with elevating temperature and after reaching some optimum detergencies, the detergencies were rather decreased with increasing temperature. The temperatures of optimum detergency were shifted to higher with increasing chain length of alkyl group. 3) When the soiled film was baked at $60^{\circ}C$ and $70^{\circ}C$ for 20 min, the detergency vs. temperature was much the same as the case of without-baking. These results indicate that the detergency of triglyceride was largely correlated with the suspending power of surfactants at low temperature and with state of soil and hydrophilicity of substrates with elevating temperature.

• Mycobiology
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• v.47 no.2
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• pp.250-255
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• 2019

In the present study, we aimed to determine the cause of surface film formation in three rice vinegars fermented using the traditional static fermentation method. The pH and total acidity of vinegar were 3.0-3.3 and 3.0-8.7%, respectively, and acetic acid was the predominant organic acid present. Colonies showing a clear halo on GYC medium were isolated from the surface film of all vinegars. Via 16S rDNA sequencing, all of the isolates were identified as Acetobacter pasteurianus. Furthermore, field-emission scanning electron microscopy analysis showed that the bacterial cells had a rough surface, were rod-shaped, and were ${\sim}1{\times}2{\mu}m$ in size. Interestingly, cells of the isolate from one of the vinegars were surrounded with an extremely fine threadlike structure. Thus, our results suggest that formation of the surface film in rice vinegar was attributable not to external contamination, to the production of bacterial cellulose by A. pasteurianus to withstand the high concentrations of acetic acid generated during fermentation. However, because of the formation of a surface film in vinegar is undesirable from an industrial perspective, further studies should focus on devising a modified fermentation process to prevent surface film formation and consequent quality degradation.

• Korean Journal of Microbiology
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• v.36 no.2
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• pp.130-135
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• 2000

Decomposition rate of organic matiter in the mud flat of Sunchon Bay was estimated. Physicochemical parameters, cellulose degradation rate. distribution of heterotrophic bacteria, and extracellular enzymatic activities were measured from August 1997 to July 1998. Soil temperatures, water contents, concentration of $PO_4$-P and organic matter were -1-~$30^{\circ}C$, 42.1-53.1%, 0.0779-0.1961 mgig and 1.99-7.64%, respectively. Decomposition rate of cellulose film ranged from 7.7 to 100%imonth, high in summer and low in winter. The number of heterotrophic bacteria ranged from $0.87{\times}10^6 to 3.6{\times}10^7 $CUFsIg dq soil. Enzymatic activities of phosphatase, $\alpha$-D-gluEosidase, $\beta$-D-glucosidase and cellobiohydrolase, which were measured as decomposition rate of methylumbelliferyl(MLiF)-substrate, were 152.23-1779.80 nMIhr, 2.67-202.18 nM/hr, 5.03-258.26 M h r and 3.42-63.07 nM/hr, respectively Cellulose degradaaon rate and extracellular extracellular enzymatic activities were conelated with each other, and showed high correlation coefticiency with soil temperature.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.11
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• pp.1259-1264
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• 2011

This paper suggests a new film-type haptic actuator based on cellulose acetate electro-active paper. Conventional tiny haptic actuators in mobile devices can create vibrotactile sensation at only near resonant frequency. The strategy of operating near the resonant frequency, however, brought a new issue for creating vibrotactile sensation which can be strong enough to feel in arbitrary frequency. Another problem is that the size of the conventional actuator is not small enough to be embedded into slim mobile devices. In order to achieve these issues, we propose a thin and tiny actuator based on a cellulose acetate material charged with an electric potential. The motion of the actuator can be a concave or a convex by controlling a polarity of both charged membranes and the actuator performance can be modulated by increasing level of biased electric potential.