• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2819-2832
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• 1996

The estimation of the remaining life for the aged components in power plant as well as chemical and petroleum plants has been recently concerned. The raw materials used in this study are the 1Cr-1Mo-0.25V steel which intensified P and S compositions along with the nominal compositions of ASTM A 470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging heat treatment at 630.deg.C. The mechanical properties and rotated bending fatigue strength of virgin and aged 1Cr-1Mo-0.25V steel have been investigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at 538.deg.C and room temperature, respectively. 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 yield and tensile strength due to degradation was distinguished until 50, 000hrs simulated service time. And it 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 rotated bendingd fatigue strength at 538.deg.C of virgin, 25, 000, 50, 000, 75, 000 and 100, 000 hrs aged material was decreased 44.6 %, 49.6 %, 51.5 %, 52.4% and 53.8% than that of virgin material at 10$_{7}$cycles of room temperature, respectively. The major cracks of virgin and aged materials mainly initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.n.

• Resources Recycling
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• v.27 no.3
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• pp.39-47
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• 2018

According to Vietnam government establishes additional coal-fired power plants to secure generation capacity, emission of ashes is accelerating and processing them is urgent issue. This study targeted utilize fly ashes that occurred in circulating fluidized bed combusion (CFBC) power plant to use ground solidification materials. CFBC fly ashes are used to make solidification with ground granulated blast furnace slag (GGBFS), gypsum and cement. Then produced specimens by mixing with soft ground soil to confirm mixing effect of fly ash in solidification. As a result it was possible to find mixture design that is satisfied 3 MPa compressive strength in age 28 days and reduce weight loss rate over 50% in acid immersion test than plain specimens that using only ordinary portland cement.

• 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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.278-285
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• 2006

Coating mixtures of the resin B-H for the application to the desulfurization system of power plant were coated on carbon steels and cured at the temperature of $65^{\circ}C{\sim}80^{\circ}C$. After being contacted with 70wt% $H_2SO_4$ solution of $100^{\circ}C\;and\;120^{\circ}C$ for several hours, their composition, Vicker's hardness and microstructures by SEM were examined. Corrosion resistance of the coating mixtures to $H_2SO_4$ solution was related to the content of $SO_3$ in the coated specimens after corrosion test. The lower curing temperature and the shorter curing time the coated specimens went through, the higher corrosion resistance to acid they showed, but the more cracks were developed at higher temperature. It was realized that the corrosion resistance to sulfaric acid solution was increased on the condition of curing temperature above $65^{\circ}C$ and curing time above 12 hours at least.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1569-1573
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• 2008

This paper describes a development of Ultrasonic NDE software to analyze steam generator of nuclear power plant. The developed software includes classical analysis method such as A, B, C and D-scan images. And it can analyze the detected internal cracks using 3D image processing method. To do such, we obtain raw data from specimens of real pipeline of power plants, and get the envelope signal using Empirical Mode Decomposition from obtained ultrasonic 1-dimensional data. The reconstructed 3D crack images offer useful information about the location, shape and size of cracks, even if there is no special 2D image analysis technique. The developed analysis software is applied to specimens containing various cracks with known dimensions. The results of application showed that the developed software provided accurate and enhanced 2D images and reconstructed 3D image of cracks.

• Mycobiology
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• v.45 no.4
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• pp.255-262
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• 2017

A total of 121 species of lichens belonging to the genus Arthothelium have been described to date, most of which have been found in tropical regions. Here, we describe the discovery of a novel Arthothelium species for the first time in South Korea. Until now, Arthothelium ruanum was the only Arthothelium species reported in South Korea. Among the 113 specimens collected in this study, we identified A. ruanum and a putative new species, Arthothelium punctatum (J. S. Park & J.-S. Hur, sp. nov.). The diagnostic characters of A. punctatum are as follows: apothecia punctate, shortly elongate to branched, small, 0.1-0.2 mm wide, hypothecium hyaline to pale brown and obovate to broadly ellipsoid, muriform ascospores, $29.5-44.6{\times}12.2-18.2{\mu}m$. The new species was found in Mt. Seokbyeong at an altitude of 790 m on smooth bark. Upon phylogenic analysis, the putative new species, A. punctatum, was separated from other Arthothelium species although the specimens analyzed were clustered with Arthoniaceae in phylogenetic trees based on both the mitochondrial small subunit (mtSSU) sequence and combined mtSSU and nuclear ribosomal large subunit sequences. Our data clearly indicate that this species is a new species belonging to the family Arthoniaceae. To elucidate the taxonomic characteristics of the new species, we provide morphological descriptions and a distribution map.

• Nuclear Engineering and Technology
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• v.19 no.3
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• pp.169-179
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• 1987

The change of material J-R (J-T) curve with crack extension and J-calculation method was investigated to give experimental and analytical method for reliable J-R (J-T) curve, which was adapted recently as a tool for instability analysis of Nuclear Pressure Vessel. Experiments were carried out by Single Specimen Unloading Compliance Method using 1/2"T, Compact-Tension Type fracture mechanic specimens which were the same size and material as domestic nuclear pressure vessel material surveillance specimens. The results revealed that crack extension up to 25~30% of initial uncracked ligament and JD (Deformation theory J) calculation method, currently being used in NUREG-0744, could give rather reliable material J-R (J-T) curve than the small crack extension and JM (Modified J) calculation method. But as JM results more or less higher J at instability, the application of JM should be considered regarding to the problem of power plant availability.lity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.33-34
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• 2019

Malaysia, as a tropical rainforest country, enjoys an abundance of bamboo plant that proliferate throughout the country. The application of geopolymer technology has become a trend and preserve the environment from harm. Fly ash geopolymer concrete has low early strength and requires 24 hours for the concrete to harden. Thus, the presence of calcium and potassium content in bamboo ash could remedy this problem. Besides, there is no research regarding the use of bamboo ash as a binder in geopolymer concrete. Therefore, the presence of bamboo ash could improve the research field with the use of agriculture waste in a building construction. This research aim is to use bamboo ash in the production of fly ash geopolymer concrete. The specimens were casted in $100mm{\times}100mm{\times}100mm$ cubes and sodium based activator were used as the alkaline solutions. The binders are formulated with different binder ratio. All test specimens were cured at ambient temperature ($23^{\circ}C-25^{\circ}C$) and 100% fly ash was chosen as control specimen. To determine the mechanical properties of fly sh geopolymer concrete with the presence of bamboo ash, compressive strength test was conducted. The test results depicted that as the percentage of bamboo ash decreases, compressive strength increases. Also, the addition of 5% of bamboo ash into fly ash geopolymer concrete could improve the early strength in 7 days. The results were proven with the result explained by X-ray fluorescence (XRF) and X-ray diffraction (XRD). Therefore, it can be concluded that the addition of bamboo ash improved the properties of fly ash geopolymer concrete at early ages.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.1
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• pp.13-22
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• 2022

This study proposes a low-cycle fatigue life derived from measurement points on pipe elbows, which are components that are vulnerable to seismic load in the interface piping systems of nuclear power plants that use seismic isolation systems. In order to quantitatively define limit states regarding leakage, i.e., actual failure caused by low-cycle fatigue, in-plane cyclic loading tests were performed using a sine wave of constant amplitude. The test specimens consisted of SCH40 6-inch carbon steel pipe elbows and straight pipes, and an image processing method was used to measure the nonlinear behavior of the test specimens. The leakage lines caused by low-cycle fatigue and the low-cycle fatigue curves were compared and analyzed using the relationship between the relative deformation angles, which were measured based on each of the measurement points on the straight pipe, and the moment, which was measured at the center of the pipe elbow. Damage indices based on the combination of ductility and dissipation energy at each measurement point were used to quantitatively express the time at which leakage occurs due to through-wall cracking in the pipe elbow.

• Journal of Sensor Science and Technology
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• v.31 no.2
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• pp.85-89
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• 2022

We investigated a pH sensor using an Indium tin oxide (ITO) nanoparticle (NP) film printed on a flexible substrate. First, the printing precision and mechanical stability of the ITO-printed film were investigated. In particular, the factors that influence the crystallinity of ITO films were studied using X-ray diffraction pattern analysis. The response of the ITO pH sensor was calibrated using a series of standard pH solutions (pH 3-11). The pH values of various specimens were measured using an ITO pH sensor, and the results were compared with those of various pH measurement methods. As a result of the experiment, the maximum error was approximately ± 0.04 pH (0.4 %) at pH 9, which indicated that the ITO pH sensor is highly suitable for pH measurement. Finally, we used the ITO pH sensor to the measure of general specimens such as solvents and beverages and compared the results in comparison with those obtained from several conventional methods.