• Journal of Surface Science and Engineering
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• v.46 no.5
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• pp.229-233
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• 2013

The small punch(SP) tests that can be applied to high strength sheet steel in automobile were carried out to evaluate the behavior of hydrogen embrittlement of DP sheet steels. In order to charge hydrogen at DP sheet steels, DP sheet steels were treated by the electrochemical hydrogen charging method under the charging conditions of current densities of 100, 150 and 200 $mA/cm^2$ for charging times of 5, 10, 25 and 50 hrs. Respectively, After hydrogen charging with experimental conditions, SP tests were performed. From the SP results, the correlations between the variation of bulb diameters and bulb heights with the hydrogen charging conditions were analysed. It was shown that the variation of bulb diameters were not significant with the hydrogen embrittlement due to the amounts of hydrogen charging. On the other hand, the bulb heights were observed to decrease with increasing hydrogen contents. It was thought that these results of the variation of bulb shapes after SP tests would be estimated as the index of evaluation of hydrogen embrittlement.

• Journal of the Korean Institute of Gas
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• v.18 no.1
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• pp.61-67
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• 2014

Small punch(SP) tests were performed on high strength Dual Phase(DP) steels in order to evaluate the behavior of hydrogen embrittlement. For this purpose, three different kinds of DP steel specimens were charged with hydrogen by electochemical hydrogen charging experiment. After charging with hydrogen, the amount of charged hydrogen was measured. The measurement results showed that amounts of charged hydrogen were largely dependent on the martensite volume fraction of DP steel. The hydrogen charging time of 25 hrs with current densities of 150 and $200mA/cm^2$ was investigated as saturation condition with hydrogen. The analysis results on the SP energy and height of SP bulbs after SP tests showed that those were decreased as the amount of charged hydrogen increased. Fractographs of SP bulbs were observed a brittle fracture mixed with quasi-cleavage fractures, layered structures and clear facets.

• The Korean Journal of Mycology
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• v.48 no.3
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• pp.251-271
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• 2020

Diversity and community composition of bulb-associated fungi of Fritillaria Cirrhosae Bulbus source plants, which are used in traditional chinese medicine, in the eastern Himalaya-Hengduan Mountains, southwestern China, were estimated based on the internal transcribed spacer rDNA sequence analysis, using host plant species, geographic area, and plant phenology as variables. A total of 1,486 fungal sequences assigned to 251 operational taxonomical units (OTUs) were obtained from the bulbs. Fungal OTUs comprised 96.41% Ascomycotina, 3.52% Basidiomycotina, and 0.07% Zygomycotina. Sordariomycetes, Hypocreales, and Nectriaceae were the most frequent fungal lineages at each taxonomic rank. Fusarium, Ilyonectria, Tetracladium, Leptodontidium, and Tomentella were the top OTU-rich genera. Fusarium sp. 03, Ilyonectria rufa, Fusarium sp. 08, Ilyonectria sp. 03, and Leptodontidium orchidicola 03 represented the most frequent OTUs. Fusarium spp. were the most frequent general taxa. The distribution of fungal community exhibited preferences for host plant species, geographic area, and plant phenology. These findings are the foundation of our research on culturing and active metabolites of bulb-associated fungi of Fritillaria Cirrhosae Bulbus source plants.

• Journal of the Korean Institute of Gas
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• v.18 no.5
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• pp.40-46
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• 2014

The hydrogen embrittlement degree of 5 type high strength DP steel charged with hydrogen by electrochemical method was evaluated by small punch test(SP test). After SP test, SP absorbed energy was remarkably decreased from 363 kgf-mm to 209 kgf-mm with increasing hydrogen charging time from 5hr to 50hr at DP5 specimen under the $200mA/cm^2$ current density condition. It was investigated that the decrease of hydrogen charging amount and SP absorbed energy according to the increase of current density and hydrogen charging time had a linear relationship. And it also investigated that the change of bulb height appeared by the SP test was decreased from 1.79mm to 1.59mm with the hydrogen charging conditions. It was supposed that it could be used as indicator of the evaluation of hydrogen embrittlement because of the similar trend of the formal results of SP absorbed energy. From the SEM observation of fracture area by crack in bulb, the morphology of fracture surface according to increasement of the hydrogen charging amount was varied with the cleavage mode.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.6
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• pp.39-48
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• 2010

The purpose of this study was to analyze air temperature decreasing effects by shading and ventilation at micro-scale experiment plots, especially focused on the Wet Bulb Globe Temperature (WBGT) in outdoor spaces. To monitor the time-serial changes of Dry-bulb Temperature (DT), Globe Temperature (GT) and Relative Humidity (RH) in the wind blocking and shading conditions, Two hexahedral steel frames were established on the open grass field, the dimension of each frame was 1.5m(W)${\times}$1.5m(L)${\times}$1.5m(H). Four vertical side of one frame was covered by transparent polyethylene film to prevent wind passing through (Wind break plot; WP). The top side of the other frame was covered with shading curtain which intercept 95% of solar light and energy (Shading plot; SP). And, Another vertical steel frame without any treatment preventing ventilation and sunlight was set up, which represents natural conditions (Control plot; CP). The major findings were as follows; 1. The average globe temperature (GT) was highest at WP showing $50.94^{\circ}C$ and lowest at SP showing $34.58^{\circ}C$. The GT of natural condition (SP) was $42.31^{\circ}C$ locating the midst between WP and SP. The difference of GT of each plot was about $8-16^{\circ}C$, which means the ventilation and shading has significant effect on decreasing the temperature. 2. WP showed the highest average dry-bulb temperature (DT) of $38.41^{\circ}C$ which apparently differ from SP and CP showing $31.94^{\circ}C$ and $33.15^{\circ}C$ respectively. The DT of SP and CP were nearly the same. 3. The average relative humidity (RH) was lowest at WP showing 15.21%, but SP and CP had similar RH 28.79%, 28.02% respectively. 4. The average of calculated WBGT were the highest at the WP ($27.61^{\circ}C$) and the lowest at the SP ($23.64^{\circ}C$). The CP ($25.49^{\circ}C$) was in the middle of the others. As summery, compared with natural condition (CP), the wind blocking increased about $2.11^{\circ}C$ WBGT, but the shading decreased about $1.84^{\circ}C$ WBGT. So It can be apparently said that the open space with much shading trees, sheltering furnitures and well-delivered wind corridor can reduce useless and even harmful energy for human outdoor activity considerably in outdoor spaces.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.575-582
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• 2011

This experiment was conducted to study the qualitative changes of grafted cactus after harvest and to examine the decomposition characteristics of pathogenic fungi which occurs or grows during the simulated shipping period. Plant materials with four varieties of Gymnocalycium mihanovichii var. friedrichii including, 'Hukwang', 'Huhong', 'Hwangwol', 'Yeunhwa' and two varieties of Chamaecereus silvestrii f. variegate such as 'Goldcrown' and 'Yellowcrown' were used. During the simulated shipping period, the fresh-weight, bulb diameter, carbon dioxide emission rate, and decomposition rate were observed. The regeneration rate and decomposition rate were observed for the grafted cactuses that were placed in a greenhouse environment with a temperature of $28{\pm}12^{\circ}C$ and humidity of $36{\pm}15.3%$ after 40 days of simulated shipping. There were reductions in the fresh-weight and bulb diameter in every variety as time passed while the carbon dioxide emission rate showed no meaningful difference by each variety. Furthermore, the decomposition rate in the scion was higher than in the stock. According to the analysis of pathogenic fungi by decomposition characteristics, Alternaria sp., Cladosporium sp., Colletotrichum sp., Fusarium sp., Penicillium sp. in G. mihanovichii var. friedrichii were found and Alternaria sp., Bipolaris sp., Cladospoirum sp. in C. silvestrii f. variegate were identified. Therefore, to maintain and improve the quality of grafted cactus, it is necessary to analyze the factors of decomposition from the time of harvest until the point of export and develop a process technology to minimize the decomposition rate.

• Mycobiology
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• v.35 no.4
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• pp.235-237
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• 2007

Leaf blight and bulb rot symptoms were observed on narcissus plants grown in Yongin, Cheongwon and Namhae areas in Korea during disease survey from 1999 to 2002. A total of 15 isolates of Botrytis sp. were obtained from the infected plant parts of narcissus. All the isolates were identified as Botrytis narcissicola based on their morphological and cultural characteristics. Three isolates of B. narcissicola were tested for their pathogenicity to leaves and bulbs of narcissus by artificial inoculation. All the isolates induced leaf blight and bulb rot symptoms on the plants of narcissus by artificial inoculation. The symptoms induced by artificial inoculation were similar to those observed in the fields. This is the first report of narcissus smoulder caused by B. narcissicola in Korea.

• Research in Plant Disease
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• v.29 no.2
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• pp.184-187
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• 2023

In May 2020, we surveyed disease occurrence on vegetables grown in Seosan area, Korea. During the disease survey, white rot symptoms were observed in Korean wild chive (Allium monanthum) plants growing in fields. The symptoms occurred mainly in the seed bulb-producing fields of the crop. The above ground parts of the diseased plants displayed premature yellowing and dying of older leaves and stunting of the plants. The bulbs and roots of the diseased plants turned black and rotted. The disease occurred in a range of 1-60% in four of the eight fields surveyed. Three isolates of Sclerotium sp. were obtained from the bulb lesions of diseased plants. All isolates were identified as Stromatinia cepivora based on the morphological characteristics and phylogenetic analysis. Pathogenicity of the isolates on Korean wild chive was confirmed by artificial inoculation test. The lesions induced by the inoculation test were similar to those observed in the investigated fields. This is the first report of S. cepivora causing white rot in Korean wild chive.

• Journal of Species Research
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• v.10 no.1
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• pp.86-98
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• 2021

The genus Pholcus Walckenaer, 1805 is the largest genus among the cellar spider family Pholcidae C.L. Koch, 1850, including 339 species. To date, 33 species in the genus are known to be distributed in Korea, being placed into three species-groups(crypticolens-group, phalangioides-group, and phungiformes-group). About 91% of these species are endemic to Korea. In this study, four new species of the genus Pholcus were discovered in Korea, viz, Pholcus chuncheonensis Lee, Choi and Kim sp. nov., Pholcus pajuensis Lee, Choi and Kim sp. nov., Pholcus pocheonensis Lee, Choi and Kim sp. nov., and Pholcus unaksanensis Lee, Choi and Kim sp. nov. These new species are classified as members of the phungiformes-group, having morphological characteristics such as male chelicerae with a frontal apophysis, palpal tibia with a prolateroventral tubercle, and genital bulb without appendix or having pseudo-appendix, but can be distinguished from congeners by characteristics of the male palp and female genitalia. Detailed descriptions and a key to new species are provided with accompanying photographs.

• Horticultural Science & Technology
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• v.33 no.6
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• pp.883-890
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• 2015

The soilborne fungus Fusarium oxysporum f. sp. lilii (Fol) is a serious threat to all lily cultivars, especially infecting bulbs and flowers. It has become increasingly important to develop varieties resistant against the bulb rot disease. Genetic diversity of cultivars and reliable screening methods are required for this purpose. Here, an efficient in vitro screening system for evaluating resistance to Fol in 38 in vitro-grown lily plants was investigated. Various factors including culture conditions of Fol, inoculum density, appropriate plant materials, inoculation method and duration, and incubation period of plant materials after inoculation were combined to optimize the screening method. As a result, we suggest optimal conditions for an in vitro screening system for the selection of Fol-resistant lily cultivars as follows. Fol was grown on potato dextrose agar (PDA) medium for 6 days at $25^{\circ}C$ in darkness and used as working inoculation. Spore suspensions were prepared (inoculum density: $1.0{\times}10^4$ $spores{\cdot}mL^{-1}$), and then leaf segments $1.5{\times}2.0cm^2$ were inoculated by dipping for 22 hours at $25^{\circ}C$ in dark. Later, leaves were cultured on 0.6% agar plates at $25^{\circ}C$ and 50% humidity with a photoperiod of 16 hours light/8 hours dark (fluence rate of $40{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) to examine the progress of bulb rot. After 7 days, disease levels were classified into indices 1 (no symptom) to 6 (serious bulb rot). Soil inoculation of Fol carried out with resistant or susceptible lily cultivars that had been selected through in vitro screening confirmed the reproducibility of results. Therefore, the in vitro screening method established in this study is efficient and reliable for selection of lily cultivars resistant against bulb rot disease.