• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1397-1400
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• 2013

The influence of electron beam irradiation on photocatalytic activity of $TiO_2$ thin films was investigated. $TiO_2$ thin films were prepared by anodization of Ti foil, and they were then subjected to an 1 MeV electron beam. Changes in physical properties and photocatalytic activity of $TiO_2$ before and after e-beam irradiation were investigated. The crystallinity of the synthesized materials was investigated by X-ray diffraction, and the oxidation states of both titanium and oxygen were determined by X-ray photoelectron spectroscopy (XPS). The density of donor ($N_d$) and flat band potential ($E_{fb}$) were investigated by Mott-Schottky analysis, and photocurrent was measured under a 1kW Xenon lamp illumination. After e-beam irradiation, significant change of Ti oxidation state was observed. $Ti^{3+}/Ti^{4+}$ ratio increased mainly due to the surface reduction by electron, and photocurrent was observed to increase with e-beam irradiation.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.34 no.1
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• pp.1-7
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• 2024

Objectives: The study was performed to investigate characteristics of hazardous factors regarding chemical(liquid lime) tank dredging workers by case survey. Methods: Field data such as working condition, MSDS and respirators applied to chemical tank dredging work were analyzed and the work environmental factors of noise and indoor air quality were measured to compare existing data with actual work situations. Results: No health hazards to workers due to working conditions were confirmed during dredging work inside the chemical storage tank. All air quality measurement data during dredging work satisfied the management standards, and there were no by-products. During dredging work, there was a significant change in noise depending on the type of work, but considering the noise reduction rate(NRR) of the earplugs worn by workers, there was no actual health hazard due to noise exposure. Conclusions: A fit test for respirator and the expiration date of the safety helmet should be observed to ensure an appropriate level of safety and health for dredging workers in the chemical storage tank.

• Journal of Conservation Science
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• v.26 no.1
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• pp.61-67
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• 2010

After selecting five types of adhesive epoxy resin for metallic cultural assets such as $Araldite^{(R)}$ rapid type, $Devcon^{(R)}$, $Araldite^{(R)}$ SV427+HV427, $CDK^{(R)}$520, $Araldite^{(R)}$ AW106+HV953 which had already been studied, this paper approached more closely the problem of yellowing and the signal of aging with time passing by connecting the problems with the safety of metallic cultural assets. The change of physical properties according to the change of state of epoxy adhesives was investigated through the change of flexural strength and the change of surface hardness by artificially providing the possible environmental change factors such as ultra-violet ray, and acid base, and how the epoxy chemically changes in its ingredients by the environment was analyzed through FT-IR. As a result of the experiment, for the most part of adhesives brought about the physical change of flexural strength, the change of surface hardness, and the chemical change of chemical ingredients as the product of alcohol, which were respectively different according to the time of ultraviolet irradiation, and acid base change. Under most of the conditions, SV427+HV427 and $CDK^{(R)}$520 were fairly stabilized under each condition of weatherability, but it seems that they should be refrained from being applied in case that the area to restore is thin and wide because the degree of flexural strength of themselves is low. Also, it is found that the preservation environment is very important not only for artifacts but also for the preservation of resins sused for preservation treatment.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.391-397
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• 2012

The depletion of conventional oil reserves and the increasing energy need in developing countries such as China and India result in exceeding oil demand over supply. As a solution of the problem, the efficient utilization of heavy oil has been receiving more and more interest. In order to utilize heavy oil, upgrading processes are required. Among the upgrading processes, thermal decomposition is thought to be relatively simple and economical. In this study, to understand basic characteristics of thermal decomposition of heavy oil, we conducted pyrolysis experiments of deasphalted oil (DAO) produced by a solvent deasphalting process. DAO is a mixture of many components and consists mainly of materials of carbon number 20~40. For the comparison with results of DAO pyrolysis, additional pyrolysis experiments with single materials of carbon number 30 ($C_{30}H_{62}$, $C_{30}H_{58}O_4S$, $C_{30}H_{63}O_3P$) were conducted. Pyrolysis experiments were carried out non-isothermally with variation of heating rate (10, 50, $100^{\circ}C$/min) in a thermogravimetric analyzer. Average pyrolysis activation energy determined by using Arrhenius method, Ingraham and Marrier method, and Coats and Redfern method was 72~99 kJ/mol. In the activation energy calculated by Ozawa-Flynn-Wall method, DAO had wider variation than other single materials.

• Journal of Microbiology and Biotechnology
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• v.22 no.2
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• pp.176-183
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• 2012

Eukaryotic translation termination is governed by eRF1 and eRF3. eRF1 recognizes the stop codons and then hydrolyzes peptidyl-tRNA. eRF3, which facilitates the termination process, belongs to the GTPase superfamily. In this study, the effect of the MC domain of eRF1a (eRF1aMC) on the GTPase activity of eRF3 was analyzed using fluorescence spectra and high-performance liquid chromatography. The results indicated eRF1aMC promotes the GTPase activity of eRF3, which is similar to the role of eRF1a. Furthermore, the increased affinity of eRF3 for GTP induced by eRF1aMC was dependent on the concentration of $Mg^{2+}$. Changes in the secondary structure of eRF3C after binding GTP/GDP were detected by CD spectroscopy. The results revealed changes of conformation during formation of the eRF3C GTP complex that were detected in the presence of eRF1a or eRF1aMC. The conformations of the eRF3C eRF1a GTP and eRF3C eRF1aMC GTP complexes were further altered upon the addition of $Mg^{2+}$. By contrast, there was no change in the conformation of GTP bound to free eRF3C or the eRF3C eRF1aN complex. These results suggest that alterations in the conformation of GTP bound to eRF3 is dependent on eRF1a and $Mg^{2+}$, whereas the MC domain of eRF1a is responsible for the change in the conformation of GTP bound to eRF3 in Euplotes octocarinatus.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.81-86
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• 1996

The physical properties of epoxy molding compound (EMC) according to the change of softening point of epoxy resin have been investigated in order to study the relationship between the properties of o-cresol novolac epoxy resin, which is main component of EMC for semiconductor encapsulation, and EMC. The softening points of used epoxy resin are 65.1 $^{\circ}C$, 72.2 $^{\circ}C$, and 83.0 $^{\circ}C$, respectively. The flexural strength and flexural modulus as mechanical properties were measured, and thermal expansion coefficient, thermal conductivity and glass transition temperature (Tg) as thermal properties, and spiral flow as moldability have been investigated to see the change of physical properties of EMC. The flexural modulus, thermal expansion coefficients in the glass state (${\alpha}_1$), and thermal conductivity of EMC were found to be keep constant value irrespective of the change of softening point, but Tg increased with softening point of epoxy resin, and the spiral flow decreased with that. It can be considered that these phenomena are due to the increase of crosslinking density of EMC according to the increase of softening point. The transition points were found out in the thermal expansion coefficient data in the rubbery state (${\alpha}_2$) and the flexural strength data. These can show the decrease of filler dispersion according to increase of epoxy resin viscosity.

• Journal of the Korean Chemical Society
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• v.54 no.6
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• pp.749-754
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• 2010

In this study, rubber vulcanization property, change in physical property, morphology and chemical characteristics of blended rubber depending on various IR/CR ratio were investigated for the purpose of the improvement of material property and durability. The effect of surface treatment by chlorine on the friction coefficient was also studied with various conditions of surface treatment. In terms of vulcanization property, as the amount of CR content increased, the speed of cure was decreased, while the density of crosslinking stayed constant. It means hardness and modulus were increased as the CR content increased. It is related to change in cure property and mechanical strength was improved by the effect of crystallization reaction. In the aging property, as the CR content increases, the changed amount of basic properties were decreased, which acts as a reducing factor in change of aged property by complementing weak point in mechanical property. It was found that the degree of property change for surface treated samples were reduced. According to the microscopic result, the degree of surface dispersion on rubber blends was increased by increasing CR content. Rubber surface showed uniform direction in pattern with increased smoothness and luster by treatment with chlorine. The degree of rubber reforming was measured by the remaining amount of chlorine and the friction coefficient was dependent on the amount of chlorine combined with rubber. In the initial stage of surface treatment, from 10 to 40 phr, the friction coefficient of specimen was rapidly reduced. However, as the concentration of chlorine solution increased, the change in friction coefficient was decreased.

• Journal of the Korean Chemical Society
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• v.18 no.5
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• pp.320-328
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• 1974

It is unable to derive the standard emf ($E^{\circ}$) of the cell at high pressure from the conventional method. However, when the concept of the complete equilibrium constant($K{\circ})$) is available to the conventional Nernst equation, it is possible to get the standard emf of the cell at high pressure(complete Nernst equation). Moreover, the other thermodynamic properties, such as the net change of solvation number(k), the compressibility of solvent(${\beta}$), ionization constant(K), the standard free energy change(${\Delta}G^{\circ}$), the standard enthalpy change(${\Delta}H^{\circ}$) and the standard entropy change (${\Delta}S^{\circ}$) of the cell reaction at equilibrium state have been also obtained. In this experiment, the emf of the cell; 12.5 % Cd(Hg)│$CdSO_4(3.105{\times}10^{-3}M),\;Hg_2SO_4│Hg$ have bee measured at temperature from 20 to $35^{\circ}C$ and at pressures from 1 to 2500 atms. The emf of the cell increased with increasing pressure at constant temperature, and did with increasing temperature at constant pressure. The net change of solvation number(k) of the cell reaction was 41.96 at $25^{\circ}C$, and kept constant value with pressure, while, K and ${\Delta}S^{\circ}$ increased with pressure, but whereas ${\Delta}G^{\circ}$ and ${\Delta}H^{\circ}$ decreased. Since the standard emf of the cell at high pressure can be calculated from the complete Nernst equation, the theory of chemical equilibrium could be developed with at high pressure as well as at the atmosphere.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.2
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• pp.22-29
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• 2014

Many government agencies have used domestic deacidification equipments to stabilize archives; however, no agency has verified archives' current preservative status. We studied the Nara National Archives' documents that had treated by mass deacidification process from 2001 to 2012, in order to examine the documents' preservative status and how efficient the mass deacidification has been. Approximately 1% of total 112,970 Nara National Archives' documents treated by mass deacidification were randomly selected and evaluated on their current measure of acidity and color change. Regardless of the kinds of document material, a wide range of pH level was found. Especially those documents that were treated by mass deacidification equipment after 2006 showed acidic conditions that were less than pH 6.8 level. Those documents were probably not treated properly by deacidifying chemical because of tightly packing style. The current measures of acidity and color records will be useful as a reference for future evaluations of further decay of the documents. It was the first study to evaluate acidity and color conditions of Nara National Archives' documents treated by mass deacidification equipment. We concluded that when using mass deacidification equipment, archives should not be loaded tightly in order for them to be fully in contact with deacidifying chemical.

• Journal of Adhesion and Interface
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• v.6 no.1
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• pp.11-18
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• 2005

The capsules were prepared from a phase change material (PCM) of octadecane as a core material and melamine formaldehyde resin as a shell material. The PCM capsule size was varied in the range of $3{\sim}25{\mu}m$. The core contents and sizes of the PCM capsule, were determined by DSC and SEM, respectively. An acrylic coating material which contains butyl acrylate (BA), methyl metacrylate (MMA) and acrylic acid (AA) were synthesized by emulsion polymerization. The films were prepared from the acrylic emulsion and PCM capsules which have various capsule sizes. From the results of SEM experiment, it was observed that the PCM capsules were well dispersed inside the film and the surface of the film became less rough when the PCM capsule size was small. The swelling ratio of the films were not significantly affected by the PCM capsule size. However, the tensile strength and elongation of the films were greatly decreased with increasing the PCM capsule size.