• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.52-60
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• 2015

Nuclear power plant contain many dissimilar metal welds that connect carbon steel components with stainless steel pipes using alloy600 welding materials. Primary water stress corrosion cracks at dissimilar metal welds have been continuously reported around the world. In periodic integrity evaluations, dissimilar metal welds are examined using a generic ultrasonic testing procedure, KPD-UT-10. In this procedure, the gap between the probe and examination surface is limited to 1/32 inch (0.8mm). It is not easy to test some dissimilar metal welds in Korean plants applying ordinary technology because of their tapered shapes and irregular surface conditions. This paper introduces a method for applying a flexible phased array technology to improve the reliability of ultrasonic testing results for various shapes and surface conditions. The artificial flaws in specimens with irregular surfaces were completely detected using the flexible phased array ultrasonic technology. Therefore, it can be said that the technology is applicable to field examination.

• Mycobiology
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• v.48 no.3
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• pp.184-194
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• 2020

Macrofungi play important roles in forest ecology as wood decayers, symbionts, and pathogens of living trees. For the effective forest management, it is imperative to have a comprehensive overview of macrofungi diversity in specific areas. As a part of the National Institute of Biological Resources projects for discovering indigenous fungi in Korea, we collected macrofungi in Gayasan National Park from 2017 to 2018. These specimens were identified based on morphological characteristics and sequence analysis of internal transcribed spacer (ITS) or the nuclear large subunit rRNA (LSU) region. We discovered 17 macrofungi new to Korea: Butyrea japonica, Ceriporia nanlingensis, Coltricia weii, Coltriciella subglobosa, Crepidotus crocophyllus, Cylindrobasidium laeve, Fulvoderma scaurum, Laetiporus cremeiporus, Lentinellus castoreus, Leucogyrophana mollusca, Marasmius insolitus, Nidularia deformis, Phaeophlebiopsis peniophoroides, Phanerochaete angustocystidiata, Phlebiopsis pilatii, Postia coeruleivirens, and Tengioboletus fujianensis. We described their detailed morphological characteristics.

• Korean Journal of Environmental Biology
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• v.17 no.4
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• pp.467-479
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• 1999

The factors of local disappearance and a plan of restoration fer Parnassius bremeri from Okchon-gun, Chungchongbukdo, Korea, were investigated. The population of this butterfly from Okchon-gun was much more abundant than the other areas of Korea in the past. But only two adults were observed in 1997 at this site and no more observation was made in 1998. So we considered that Parnassius bremeri is disappeared from this area. To know the factors of local disappearance of this species, we analyzed data of the monitoring from seven localities of Okchon-gun from 1990 to 1998 and also checked 252 specimens from this area by several collections. As a result of it, the habitat changes by recent road constructions and the frequent collecting activity around this area are shown as the factors for the local disappearance of this species. We are intending to establish the programs for restoration of Parnassius bremeri in Okchon-gun. Firstly, the breeding plan of this species was designed by investigation on life cycle. Secondly, the environmental conditions among seven localities were compared and the suitable places of the restoration were selected. The most suitable localities for restoration by this study were of two localities, Dongrakjeong and Jangwahri, which are considerd as highly successful breeding places in the view of growth condition of host plant.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.130-140
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• 2018

An AU-composite beam based on U-shaped steel beams and steel plate anchors of type A was developed. The composite beam reduced the height of the building floor and construction cost. In addition, it decreased the length of construction work, and improved the flexural strength and stiffness as a form of tubes. In this study, AU-composite beams were tested directly and their performance was evaluated through bending experiments. The strength of the specimens was increased initially by linear loads and reached a maximum strength due to destruction of the concrete slab. All of the experiments showed more than 85% of the maximum stress and performed gentle movement. In addition, there was good composite behavior with the steel plate anchor that had excellent composite effects and reached full strength until the maximum strength was reached. When the thickness of the steel plate was increase, the flexural stiffness and strength of the specimen were improved. Therefore, the flexural strength of AU-composite beams can be estimated using the flexural strength formula according to the KBC 2016.

• Korean Journal of Materials Research
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• v.13 no.7
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• pp.429-435
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• 2003

In this study the new creep test using miniaturized specimen(10${\times}$10${\times}$0.5 ㎣) was performed to evaluate the creep characteristics for degraded materials of 2.25Cr-1Mo steel. For this creep test, the artificially aged materials for 330 hrs and 1820hrs at $630^{\circ}C$ were used. The test temperatures applied for the creep deformation of miniaturized specimens was X$630^{\circ}C$ and the applied loads were between 45 kg∼80 kg. After creep test, macro- and microscopic observation were conducted by the scanning electron microscope(SEM). The creep curves depended definitely on applied load and microstructure and showed the three stages of creep behavior like uniaxial tensile creep curves. The load exponents of virgin, 330 hrs and 1820 hrs materials based on creep rate showed 14.8, 9.5 and 8.3 at $550^{\circ}C$ respectively, The 1820 hrs material showed the lowest load exponent and this behavior was also observed in the case of load exponent based on creep rupture time. In contrast to virgin material which exhibited fined dimple fractography, a lot of carbides like net structure and voids were observed on the fractography of degraded materials.

• Mycobiology
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• v.42 no.2
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• pp.140-146
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• 2014

In Seoul, a majority of plant communities have undergone significant changes over the last few decades; however, how wood decay fungi have responded and adapted to the changes in vegetation remains unknown. Through an ongoing investigation of Korean indigenous fungi, ca. 300 specimens with poroid basidiocarp were collected in Seoul during 2008~2012. Morphological examination and molecular analysis using the internal transcribed spacer and nuclear large subunit ribosomal DNA region sequences helped identify 38 species belonging to 28 genera, 10 families, and 5 orders in this area. Among them, three polypores, Abundisporus pubertatis, Coriolopsis strumosa, and Perenniporia maackiae were found to be new to South Korea.

• The Korean Journal of Mycology
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• v.46 no.3
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• pp.353-358
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• 2018

Solidago virgaurea subsp. gigantea is native to Ulleung-do, island in East Sea, and cultivated as a vegetable in Korea. Rust fungus on this plant was first reported as Coleosporium asterum in 2014. Recent studies on Solidago-Coleosporium association mainly based on North American materials suggested that the Korean isolates of C. asterum on S. virgaurea subsp. gigantea reported in Korea might be placed in the C. solidaginis clade. Accordingly, to confirm this suggestion, three additional Korean samples were morphologically and molecularly studied and identified as C. solidaginis in current species concept. Three specimens on S. altissima (syn. S. canadensis) from China and Japan were previously determined to be phylogenetically differentiated from C. solidaginis, hinting at a cryptic species. Therefore, this is the first confirmed report on the presence of C. solidaginis on Solidago spp. in Asia.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.291-298
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• 2017

The objective of the present study is to evaluate the cyclic flexural behavior of a hybrid H-steel-reinforced concrete (HSRC) beam at the connection with a H-steel column. The test parameter investigated was the configuration of dowel bars at the joint region of the HSRC beam. The HSRC beam was designed to have plastic hinge at the end of the H-steel beam rather than the RC beam section near the joint. All specimens showed a considerable ductile behavior without a sudden drop of th applied load, resulting in the displacement ductility ratio exceeding 4.6, although an unexpected premature welding failure occurred at the flanges of H-steel beams connecting to H-steel column. The crack propagation in the RC beam region, flexural strength, and ductility of HSRC beam system were insignificantly affected by the configuration of dowel bars. The flexural strength of HSRC beam system governed by the yielding of H-steel beam could be conservatively evaluated from the assumption of a perfect plasticity state along the section.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.427-434
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• 2016

The purpose of this study is to propose a mixture proportioning approach based on the replacement level of natural sand for reducing $CO_2$ emissions from artificial lightweight aggregate concrete(LWAC) production. To assess the effect of natural sand on the reduction of $CO_2$ emissions and compressive strength of LWAC, a total of 379 specimens compiled from different sources were analyzed. Based on the non-linear regression analysis using the database and the previous mixture proportioning method proposed by Yang et al., simple equations were derived to determine the concrete mixture proportioning and the replacement level of natural sand for achieving the targeted performances(compressive strength, initial slump, air content, and $CO_2$ reduction ratio) of concrete. Furthermore, the proposed equations are practically applicable to straightforward determination of the $CO_2$ emissions from the provided mixture proportions of LWAC.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.419-426
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• 2016

This study examined the effect of transverse reinforcement and compressive stress on the shear friction performance at the shear interface intersecting two structural elements with various concrete types. From the prepared 12 push-off test specimens, various characteristics at the interface were measured as follows: crack propagation, shear load-relative slip relationship, initial shear cracking strength, ultimate shear friction strength, and shear transfer capacity of transverse reinforcement. The configuration of transverse reinforcement and compressive strength of concrete insignificantly influenced the amount of relative slippage at the shear friction plane. With the increase of applied compressive stress, the shear friction capacity of concrete tended to increase proportionally, whereas the shear transfer capacity of transverse reinforcement decreased, which was insignificantly affected by the configuration type of transverse reinforcement. The empirical equations of AASHTO-LRFD and Mattock underestimate the shear friction strength of concrete, whereas Hwang and Yang model provides better reliability, indicating that the mean and standard deviation of the ratios between measured shear strengths and predictions are 1.02 and 0.23, respectively.