• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.4
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• pp.151-159
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• 2015

Paper records were generally degraded by some factors from atmospheric environments, like temperature, relative humidity or air pollutants. In this study, the degradation behavior of paper records by single or mixed gases of $NO_2$, $SO_2$, HCHO and TVOC was evaluated. The mechanical, optical and chemical properties of 4 kinds of paper (acid and neutral-based printing paper, traditional Hanji, and filter paper) were directly and indirectly affected by gaseous harmful materials. The brightness and $L^*$ value in all papers were slightly increased by accelerated aging under gaseous HCHO and TVOCs, but highly decreased by conditions under gases $NO_2$ and $SO_2$. The optical properties of paper records were most vulnerable in acid-based paper and high stable in filter paper and traditional Hanji by air pollutant degradation. The aging treatments under mixed gas pollutants including $NO_2$ resulted in decrease of physical, mechanical and optical properties of paper, so it was supposed that the concentration of $NO_2$ gas would be strictly controlled for optimum indoor air quality management in domestic storage centers for paper records.

• Composites Research
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• v.37 no.2
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• pp.68-75
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• 2024

Polypropylene (PP), a thermoplastic resin with excellent mechanical, thermal, chemical, and water resistance properties, has been attracting attention due to its economic efficiency and recyclability. However, repeated processing of thermoplastic resins can lead to property degradation, and the point at which quality degradation occurs varies depending on the processing conditions. In this study, we evaluated the performance changes of composite materials with repeated processing by blending PP resin with various additives and conducting extrusion and injection processes repeatedly. In addition, we evaluated the mechanical properties of composite materials to evaluate the effect of MFI value change during repeated processing on fiber impregnation in composite material processing.

• Journal of Adhesion and Interface
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• v.13 no.1
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• pp.45-50
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• 2012

Recently developed polyketone fiber has various applications in the mechanical rubber goods as reinforcement because of its good mechanical properties. However, its surface is not suitable for good adhesion with the rubber matrix. Thus, a surface modification is essential to obtain the good interfacial adhesion. Plasma treatment, in this study, has been conducted to modify the surface of the polyketone fiber. The morphological changes of the fibers by oxygen plasma treatment were observed by using SEM and AFM. The chemical composition changes of PK fiber surface treated with oxygen plasma were investigated using an XPS (X-ray photoelectron spectroscopy). Finally, the effect of these changes on the interfacial adhesion between fiber and rubber was analyzed by using a microdroplet debonding test. By the plasma treatment, oxygen moieties on the fiber surface increased with processing time and power. The surface RMS roughness increases until the proper processing condition, but a long plasma processing time resulted in a rather reduced roughness because of surface degradation. When the treatment time and power were 60 s and 80 W, respectively, the highest interfacial shear strength (IFSS) was obtained between the PK fiber and natural rubber. However, as the treatment time and power were higher than 60 s and 80 W, respectively, the IFSS decreased because of degradation of the PK fiber surface by severe plasma treatment.

• Journal of Ocean Engineering and Technology
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• v.10 no.2
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• pp.77-87
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• 1996

The estimation of the remaining life for the aged components in power plant as well as chemical and peroleum plants has been recently coberned. The raw materials used in this syudy are the 1Cr-1Mo-0.25V rotor steel which intensified P and S compositions along with the nominal compositions of ASTM A470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging teat treatment at $630^{\circ}C$ The mechanical properties and fatigue strength of virgin and aged 1Cr-1Mo-0.25V rotor steel have been inbestigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at room temperature. Thus, the data of aged specimens were compared with those of virgin specimen to evaluate the aging effects. The main results obtained in this study are as follows; The decrease of the hardness due to degradation was distinguished until 50, 000hrs simulated service time. And is was confirmed that the considerable amount of P, Mn, Cr and S was precipitated at the grain boundary of aged material through the SEM and EDS analysis. The fatigue strength of 25, 000, 50, 000, 75, 000 and 100, 000hrs aged material was decreased 29.5%, 24.4%, 28.6%, 35.7% than that of virgin material at $10^7$ cycles of room temperature. The major cracks of virgin and aged materials initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.5
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• pp.457-464
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• 2010

Representative methods for removing spilled oil include mechanical skimming, chemical treatment, burning at the surface of the spilled oil, and microbiological degradation. Among these methods, mechanical skimmer is the most efficient. Mechanical skimming can be classified into the following categories: belt-type, disk-type, weir-type, drum-type. We designed models with a submerged orifice for use in our experiments, for an objective and systematic evaluation of the recovery efficiency of mechanical skimming. Basically, oil is lighter than seawater and hence tends to float on the surface of the latter if there is sufficient time for floating. The present skimmer is kind of wear-type with the submerged orifice for seawater to be squeezed through, minimizing water content in the tank. From the experimental results, we identify the parameters that influence the oil recovery rate and recovery efficiency. The recovery efficiency can be enhanced by increasing the thickness of the oil layer in the first oil accumulative tank.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.291-291
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• 2006

Two different sources of clay, Na-Bentonite (Thai local clay) and Na-Montmorillonite were modified with Hexadodeccyltrimethyl ammonium bromide. The nanocomposites of polypropylene were successfully prepared via melt blending in a co-rotating twin screw extruder by using PP-g-MA as a compatibilizer at various contents of organoclays. The morphology of nanocomposites was investigated by using XRD and SEM. The results showed that the intercalated and exfoliated structures were obtained. The thermal behavior was also studied by using DSC and TGA. The degradation temperature of filled PP was greater than that of unfilled PP by 20%. And, the tensile strength and modulus were improved when a small amount of organoclays were added.

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.38-50
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• 1996

Recently carbon fiber reinforced plastic (CFRP) has been used structural materials in corrosive environment such as for water, chemical tank and pipes. However, mechanical properties of such materials may be change when CFRP and exposed to corrosive environment for long periods of time. The degradation behavior of carbon fiber/epoxy resin composite material in distilled water is investigated using acoustic emission (AE) technique, Fracture toughness tests are performed on the compact tension specimens that are pilled by two types of $[O_2/9O_2]_{3s}$ and $[O/9O]_6s$. During the testes, AE test was carried out to monitor the damage of CFRP by moisture absorption. The data was treated by 2-parameter Weibull distribution and the fracture surface was observed by scanning electron microscope.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1685-1687
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• 2002

High voltage(H.V.) induction motors have been applied to various industrial applications. But aging and failure of induction motors are initiated by electrical, mechanical, thermal and chemical processes during manufacturing or in-service. These detects reduce locally the dielectric strength of the insulation. At such defects partial discharges can occur, which cause further degradation of the insulation and reduce the life time of the H.V induction motors. Consequently in this paper, we studied the partial discharge pattern analysis of H.V. induction motor for on-site applications.

• Korea-Australia Rheology Journal
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• v.17 no.2
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• pp.71-77
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• 2005

We investigated thermal, rheological, morphological and mechanical properties of a binary blend of poly(lactic acid) (PLA) and poly(butylene succinate adipate) (PBSA). The blends were extruded and their molded properties were examined. DSC thermograms of blends indicated that the thermal properties of PLA did not change noticeably with the amount of PBSA, but thermogravimetric analysis showed that thermal stability of the blends was lower than that of pure PLA and PBSA. Immiscibility was checked with thermal data. The rheological properties of the blends changed remarkably with composition. The tensile strength and modulus of blends decreased with PBSA content. Interestingly, however, the impact strength of PLA/PBSA (80/20) blend was seriously increased higher than the rule of mixture. Morphology of the blends showed a typical sea and island structure of immiscible blend. The effect of the blend composition on the biodegradation was also investigated. In the early stage of the degradation test, the highest rate was observed for the blend containing $80wt\%$ PBSA.

• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.79-81
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• 2005

Chemical methods for moisture contents detection of insulation system in transformer must dismount equipment for sampling, and there is shortcoming such as acquiring partial data for measuring. Also the samples can't immediately analyze in field. The Recovery Voltage Method (RVM) will be able to measure a moisture contents at low voltage without dismounting equipment. Therefore, in advanced countries RVM would be used to measure the moisture contents which permeates to the insulation system without weighting additive degradation or mechanical damage. In this paper we have investigated for overcoming these shortcomings using the RVM, and we have measured the moisture contents of transformer insulation with temperature.