Soon-Do Yoon

A study of the application of upper bound method to the CONFORM process

Abstract This paper is concerned with the calculation of the powers required in the steady-state CONFORM process. For this goal, similarity is applied to the CONFORM process for an equivalent side extrusion process, to which the upper bound method is used to derive the equation for calculating the powers. Even though the global flow characteristics between the real and the simplified processes are not similar, the calculated results for both processes show good agreement. Furthermore, FEM simulation is carried out using the DEFORM commercial program in order to verify the theoretical results.

204% enhanced efficiency of ZrO2 nanofibers doped dye-sensitized solar cells

Zirconia (ZrO2) nanofibers added mesoporous titania (TiO2) photoelectrode has been synthesized for dye-sensitized solar cells to enhance the efficiency of cell. The ZrO2 nanofibers had reduced the resistance of the photoelectrode as well as enhancement of the absorption spectra in the ultraviolet (UV), visible, and near infrared (IR) region. The internal resistance of the photoelectrode is one of the important factor to affects the power conversion efficiency directly. The ZrO2 nanofibers provide the more photon harvest and optimal electron pathway. Finally, about 200% increases in conversion efficiency has been achieved.

Bubble-point measurement for the CO2+diethylene glycol diacrylate and CO2+diethylene glycol dimethacrylate systems at high pressure

Pressure-composition isotherms are measured by using a static apparatus for the phase behavior data for the CO2+diethylene glycol diacrylate (DEGDA) and CO2+diethylene glycol dimethacrylate (DEGDMA) systems. The experiments are performed at five temperatures of (313.2 to 393.2) K and pressures up to 28.3 MPa. The solubility of CO2 for the two systems decreases as the temperature increases at a fixed pressure. The CO2+DEGDA and CO2+ DEGDMA systems exhibit type-I phase behavior. The experimental results for the CO2+DEGDA and CO2+DEGDMA systems are correlated with Peng-Robinson equation of state using a mixing rule.

Experimental measurement and correlation of phase behavior for the CO2+heptafluorobutyl acrylate and CO2+heptafluorobutyl methacrylate systems at high pressure

Experimental data of high pressure phase behavior from 313.2 to 393.2 K and pressures up to about 14.3 MPa were reported for binary mixture of 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA) and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (HFBMA) in supercritical carbon dioxide. The high pressure experiment was performed by static method using variable-volume view cell apparatus. The CO2+HFBA and CO2+HFBMA systems are correlated with the Peng-Robinson equation of state using a van der Waals one-fluid mixing rule. The CO2+HFBA and CO2+HFBMA systems exhibit type-I phase behavior with continuous critical mixture curves.

High pressure phase behavior for the binary mixture of pentafluoropropyl methacrylate and poly(pentafluoropropyl methacrylate) in supercritical carbon dioxide and dimethyl ether

Pressure-composition isotherm is obtained for the carbon dioxide+2,2,3,3,3-pentafluoropropyl methacrylate (PFPMA) using static apparatus with a variable volume view cell at temperature range from 40 °C to 120 °C and pressure up to 130 bar. This system exhibits type-I phase behavior with a continuous mixture-critical curve. The experimental result for carbon dioxide+PFPMA mixture was modeled using the Peng-Robinson (P-R) and multi-fluid nonrandom lattice fluid (MF-NLF) equation of state. Experimental cloud-point data of pressure up 470 bar and temperature to 182 °C were reported for the binary mixture of poly(2,2,3,3,3-pentafluoropropyl methacrylate) [Poly(PFPMA)] in supercritical carbon dioxide and dimethyl ether (DME). The Poly(PFPMA)+carbon dioxide and Poly(PFPMA)+DME systems showed LCST behavior.

Isolation and characterization of a bacterial cellulose- producing bacterium derived from the persimmon vinegar

T(99.929%), hence, it was specifically named as Gluconacetobacter sp. RKY5. Although the traditional bacterial cellulose (BC) production medium (Hestrin and Schramm medium) was used, the amount of BC produced under a static culture condition reached 5.0 g L -1 . The X-ray diffraction pattern and scanning electron micrograph of the BC produced revealed that it was composed of ribbon-shaped fibrils with the network structure and pure cellulose without any other impurities.

Physical properties and photocatalytic activity of chitosan-based nanocomposites added titanium oxide nanoparticles

In this study, nanocomposite films were prepared by using chitosan (CHS), poly(vinyl alcohol) (PVA), titanium oxide (TiO2) nanoparticles, sulfosuccinic acid (SSA) as a crosslinking agent, and sorbitol (SO) and citric acid (CA) as plasticizers. The CHS/PVA nanocomposite films were characterized by X-ray diffraction (XRD), Fourier transform IR spectrophotometry (FTIR), and scanning electronic microscopy (SEM). The results of the XRD and FTIR analysis verified that TiO2 characteristic peaks existed in the prepared nanocomposite films. In addition, the intensity of TiO2 characteristic peaks increased with the increase of TiO2 contents. The physical properties such as tensile strength (TS), elongation at break (%E), swelling behavior (SB), and solubility (S) were investigated. The results indicated that compared with films without added TiO2, the mechanical properties and water resistance were enhanced up to 1.42-1.50 times with the addition of TiO2. The photocatalytic degradability of the prepared films containing TiO2 was evaluated using bisphenol A (BPA) and methyl orange (MO) as photodegradation targets. In addition, the photocatalytic degradation kinetics were evaluated using the pseudo-first-order Lagergren equation.

Preparation and antibacterial activities of chitosan-gallic acid/polyvinyl alcohol blend film by LED-UV irradiation

Active blend films from chitosan-gallic acid (CGA) and polyvinyl alcohol (PVA) were prepared via a simple mixing and casting method through the addition of citric acid as a plasticizer. The CGA/PVA blend films were characterized using Fourier transform infrared spectroscopy (FT-IR). The mechanical properties including tensile strength (TS) and elongation at break (%E), degree of solubility (S) and swelling behavior (DS), water vapor adsorption, and antimicrobial activities of the CGA/PVA blend films with and without LED (light emitting diode)-UV irradiation were also investigated. The CGA/PVA blend films exposed to UV irradiation exerted a higher TS (43.5MPa) and lower %E (50.40), S (0.38) and DS (2.73) compared to the CGA/PVA blend films (TS=41.7MPa, %E=55.40, S=0.42, and DS=3.16) not exposed LED-UV irradiation, indicating that the cross-linkage between CGA and PVA had been strengthened by LED-UV irradiation. However, the water vapor adsorption in the CGA/PVA blend films increased due to the changes of surface roughness and pore volume after LED-UV irradiation, and all values increased by increasing the CGA concentrations in the CGA/PVA blend films. The antimicrobial activities of the CGA/PVA blend films showed that the efficient concentration of CGA in the CGA/PVA blend films was over 1.0%. Taken together, the CGA/PVA blend films have potential for use as food packing materials.

Preparation of functional chitosan-based nanocomposite films containing ZnS nanoparticles

In this study, nanocomposite films were synthesized by chitosan (CH), PVA, ZnS, sulfosuccinic acid, and plasticizers. The nanocomposite films were cross-linked by the heat curing process. ZnS was synthesized by the reaction of Zn(CH3COO)2 and Na2S2O3·5H2O in aqueous solution via a template-free hydrothermal process. The prepared ZnS and CH/PVA nanocomposite films were characterized by X-ray diffraction, Fourier transform IR spectroscopy, and scanning electronic microscopy. The results of this study confirmed the presence of specific peaks of ZnS in the prepared nanocomposite films, and the intensity of these peaks increased with increasing ZnS contents. Tensile strength, elongation at break, water barrier properties, and thermal properties of the prepared nanocomposite films were also investigated, indicating that the addition of ZnS nanoparticles improved the physical and thermal properties. In addition, the photocatalytic degradability of the prepared films containing ZnS nanoparticles was evaluated using 2,4-dichlorophenoxyacetic acid and methyl orange.

Preparation of chitosan/polyvinyl alcohol blended films containing sulfosuccinic acid as the crosslinking agent using UV curing process

This paper reports on a method of preparing chitosan-based films to which sulfosuccinic acid (SSA) is added for crosslinking agent with/without UV curing treatment and applications of a coating materials for foods. The physical, thermal, and optical properties of the UV cured chitosan-based films are investigated including their tensile strength (TS), elongation at break (%E), degree of swelling (DS), solubility (S), and water vapor absorption as well as their biodegradability in soil and applicability of the coating on a fruit. We also evaluated the physical properties of the prepared films to which glycerol (GL), xylitol (XL), and sorbitol (SO) are added to be used as plasticizers. The surface and topography of the prepared films are investigated by scanning electronic microscopy (SEM) and atomic force microscopy analysis (AFM). The results indicate that the films UV cured for 20min possess optimal physical and thermal properties compared to that of non-cured films. The mechanical, thermal, and water barrier properties of SO-added film are also found to be superior to other films with added GL and XL. The degree of biodegradability revealed that the films are degraded by about 40-65% after 220days.