• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.5
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• pp.59-65
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• 2009

Adsorption of an oil-proof agent (OPA）onto cellulose fibers during the papermaking process was investigated using UV-Vis spectrophotometry by measuring the OPA concentration decrease in the solution. From the calibration curve, the spectrum were converted to chemical concentrations in solution, from which the amount adsorbed onto the fiber surface could be determined. Thus, it was possible to determine the total amount adsorbed onto the fibers and in solution. Using this approach, we studied the adsorption behavior of the OPA onto the fiber surface and derived its, ${\Gamma}^s_t={\Gamma}^s_{\infty}(1-e^{-k_{\alpha}t})$. The values of the parameters kaand ${\Gamma}^s_{\infty}$ were determined using a mathematic model based on a mass transfer equation. Ultimately, a complete was derived: $Q={\alpha}{\cdot}\sum\limits_{i-1}^m{\pi}d_il_i{\cdot}M_A{\cdot}(1-e^{-k_{\alpha}t})/A_N$.

• Macromolecular Research
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• v.11 no.6
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• pp.399-409
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• 2003

The first esterification reactor in the continuous polymerization of poly(ethylene terephthalate) has been analyzed by solving the material balances for the two-phase system with respect to the solubility of terephthalic acid. The Newton-Raphson method was used to solve the material balance equations instead of the Simplex method that is frequently used for finding a minimum point of a residual rather than a solution of an equation. A solution for the material balance equations, with the constraint of non-zero liquid phase fraction, could not be obtained with the solubility data of Yamada et al., but could be obtained with solubilities over a minimum value that is larger than their data. Thus, the solubility data of Yamada et al. are considered to be too small. On the other hand, the solubility data of Baranova and Kremer are so large that they gave a solution with the liquid phase only. Based on our results, several typical solubility curves satisfying the constraint of a non-zero liquid phase fraction are suggested in this study; we studied the reaction characteristics of the system using these curves. A higher temperature and a lower pressure are preferred for reducing the content of diethylene glycol.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3293-3303
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• 1996

Numerical analyses have been performed to estimate the absorption heat and mass transfer coefficients in absorption process of the LiBr aqueous solution and the total heat and mass transfer rates in a vertical tube absorber which is coolING ed by air. Axisymmetric cylindrical coordinate system was adopted to model the circular tube and the transport equations were solved by the finite volume method. Absorption behaviors of heat and mass transfer were analyzed through falling film of the LiBr aqueous solution contacted by water vapor in tube. Effects of film Reynolds number on heat and mass transfer coefficients have been also investigated. Especially, effects of tube diameter have been considered to observe the total heat and mass transfer rates through falling film along the tube. Based on the analysis it has been found that the total mass transfer rate increases rapidly in a region with low film Reynolds number(10 ~ 40) as the film Reynolds number increases, while decreases beyond that region. The total heat and mass transfer rates increase with increasing the tube diameter.

• Structural Engineering and Mechanics
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• v.65 no.1
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• pp.111-120
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• 2018

This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.

• Journal of the Korean Applied Science and Technology
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• v.28 no.3
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• pp.306-312
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• 2011

In this study, we are crystallized to the low density polyethylene (LDPE) micro-particles in $n$-dodecanol solution by thermally induced phase separation(TIPS) method. The Low density polyethylene micro-particles is used in a wide variety of polymer coatings and industrial application. The utility of that for a particular application depends on a number of factors such as the particle size and distribution, and chemical composition of the materials. However, there are still needs for new methods of preparation which will provide the structure with unique sizes. The widely used processes for micro-size particles are crystallization method and thermally induced phase separation. TIPS process based on the phase separation mechanism was performed for the LDPE system which undergoes liquid-solid phase separation. Effects of various operating parameters were examined on the structure variation of the particles. Professionality, take-up speed and crystallization rate depended on temperature and concentration of polymer in solution.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.192-206
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• 2005

Integration of mobile networks and Internet has started with 2.5 generation of mobile cellular networks. Internet traffic is today dominant traffic type worldwide. The hanger for higher data rates needed for data traffic and new IP based services is essential in the development of future wireless networks. In such situation, even 3G with up to 2 Mbit/s has not provided data rates that are used by Internet users with fixed broadband dial-up or through wired local area networks. The solution to provide higher bit rates in wireless access network has been found in wireless LAN although initially it has been developed to extend wired LAN into wireless domain. In this paper, we propose and describe a solution created for interoperability between mobile cellular network and WLAN. The integration between two networks, cellular and WLAN, is performed on the authentication, authorization, and accounting, i.e., AAA side. For that purpose we developed WLAN access controller and WLAN AAA gateway, which provide gateway-type access control as well as charging and billing functionalities for the WLAN service. In the development process of these elements, we have considered current development stadium of all needed network entities and protocols. The provided solution provides cost-effective and easy-to-deploy PLMN-WLAN Internetworking scenario.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.347-351
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• 2008

Acetyl-CoA carboxylase (ACC) is an excellent candidate for antibiotics drug target, which mediates malonyl-CoA synthesis from acetyl-CoA through acetylation process. It is also involved in the committed step of fatty acid synthesis which is essential for living organisms. We have determined the three dimensional structure of C terminal domain of HP0371, biotin-carboxyl carrier protein of H. pyroli, in solution state using heteronuclear multi-dimensional NMR spectroscopy. The structure of HP0371 shows a flatten b-sheet fold which is similar with that of E. coli. However, the sequence and structure of protruding thumb are different with that of E. coli and the thumb shows different basis of structural rigidity based on backbone dynamics data.

• Journal of Powder Materials
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• v.17 no.6
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• pp.449-455
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• 2010

The hybrid structured photo-electrode for dye-sensitized solar cells was fabricated based on the composites of $TiO_2$ nanoparticles and nanowires. Three samples with different hybrid structures were prepared with 17 vol%, 43 vol%, and 100 vol% nanowires. The energy conversion efficiency was enhanced from 5.54% for pure nanoparticle cells to 6.01% for the hybrid structure with 17 vol% nanowires. For the hybrid structured layers with high nanowires concentration (43 vol% and 100 vol%), the efficiency decreased with the nanowire concentration, because of the decrease of specific surface area, and of thus decreased current density. The random orientations of $TiO_2$ nanowires can be preserved by the doctor blade process, resulted in the enhanced efficiency. The hybrid structured $TiO_2$ layer can possess the advantages of the high surface area of nanoparticles and the rapid electron transport rate and the light scattering effect of nanowires.

• Journal of Radiation Industry
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• v.5 no.4
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• pp.305-311
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• 2011

We introduced a novel sustainable slow-releasing agrochemical formulation, a biopolymer bound to silica, for controlling plant diseases. The formulation was obtained through the following process. Curdlan, sodium silicate ($Na_2SiO_3$) and isopropyl alcohol were dissolved in DDW (Deionized-distilled water). The resultant solution was then irradiated using a $^{60}Co$ ${\gamma}$-irradiator (150 TBq of capacity; ACEL, Canada) at KAERI. The resultant solution was treated with phosphorous acid ($H_3PO_3$). Finally, we obtained a novel biopolymer-silica microsized formulation containing phosphorous acid ($H_3PO_3$) from the solution. The morphology of the complex was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and TEM images revealed that the curdlan-silica formulation has a particle size ranging from 1 to $3{\mu}m$ with high stability. We also detected that $H_3PO_3$ was distributed within the formulation through energy dispersive X-ray spectroscopy (EDX) analysis. $H_3PO_3$ was sustain-released from the formulation in water. Based on our results, it seems effectively that one or two applications of the formulation during a cropping season will assist in controlling various plant diseases.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1351-1355
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• 2018

The photocurrent characteristics of zinc-oxide (ZnO) thin-film transistors (TFTs) prepared using radio-frequency sputtering and spin-coating methods were investigated. Various characterization methods were used to compare the physical and the chemical properties of the sputtered and the spin-coated ZnO films. X-ray photoelectron spectroscopy was used to investigate the chemical composition and state of the ZnO films. The transmittance and the optical band gap were measured by using UV-vis spectrometry. The crystal structures of the prepared ZnO films were examined by using an X-ray diffractometer, and the surfaces of the films were investigated by using scanning electron microscopy. ZnO TFTs were prepared using both sputter and solution processes, both of which showed photocurrent characteristics when illuminated by light. The sputtered ZnO TFTs had a photoresponsivity of 3.08 mA/W under illumination with 405-nm light while the solution-processed ZnO TFTs had a photoresponsivity of 5.56 mA/W. This study provides useful information for the development of optoelectronics based on ZnO.