• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.280-288
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• 2016

This study proposes improved welding tools for magnesium alloys. Two types of tools were used for friction stir welding (FSW). The effect of the welding tools on the FSW joints was investigated with a fixed welding speed of 200mm/min and various rotation speeds of 400 to 800 rpm. After FSW, the joints were cross-sectioned perpendicular to the welding direction to investigate the defects. A tensile test and Vickers hardness test were conducted to identity the mechanical properties of the joints. Defects were observed when the rotation speed was 400 rpm, regardless of the welding tool, and the amount of defects tended to decrease with increases in rotational speed. Defect-free welds were obtained when the rotation speed was 800 rpm. The best weld quality was acquired using the C type welding tool. The rotation speed of 800 rpm and welding speed of 200 mm/min produced the best joining properties. The ultimate tensile strength, yield strength, and elongation of the welded region were 90.0%, 69.1%, and 83.2% those of the base metal, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.521-526
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• 2017

In the GTA welding process of Al 7075 alloy using different types of filler metals, the tensile test and micro-hardness test were conducted to evaluate the mechanical characteristics. Also, the radiographic test result showed that the weld met the criterion of level 1 in accordance with KS D 0242 for verifying the welding integrity and there were no welding defects. The tensile test result obtained using Al 7075 as a filler metal showed that the material was fractured in the weld zone. The tensile strengths of the materials using Al 7075 and ER 4043 as the filler metal were about 240MPa and 253MPa, their yield strengths were about 132MPa and 120MPa and their elongation percentages were 6.6% and 13%, respectively. The micro-hardness value of the deposited metal zone when using Al 7075 as the filler metal was Hv 132. However, the micro-hardness of the material using ER4043 as the filler metal was about 24% lower than that using Al 7075. When the chemical composition of the filler metal is the same as that of the material itself, fracture can occur in the deposited metal zone. Therefore, it is not desirable to use the same material as the filler metal for the welding of Al 7075 alloy. Moreover, the use of Al-Si based ER 4043 as a filler metal is more desirable than using the same material as a filler metal for welding Al 7075.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.500-508
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• 2014

For this research, synthesis acrylic resin by ethyl acrylate monomer(EAM) and prepared samples which set by difference amount of monoammonium phosphate solution in waterborne acrylic resin. Use these resins, analyzed mechanical properties and thermal stability by films and leather surface coated. The test of DSC experiment sample WAC-APS3 was $410^{\circ}C$ Tm values which means the highest content of monoammonium phosphate had highest thermal stability in acrylic resin. According to measure data for solvent resistance, all samples showed good property. As known in the results, increase of ammonium phosphate constant did not influence to big change of resin properties. In abrasion test WAC-APS3 was good abrasion properties(68.729 mg.loss). Test of tensile strength, as increase as monoammonium phosphate resin analyzed low properties $1.505kgf/mm^2$ to $1.275kgf/mm^2$. In elongation case, same as strength test result 425 % to 384 % by increase to monoammonium phosphate amount in acrylic resin.

• Journal of Korean Society of Forest Science
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• v.78 no.4
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• pp.401-411
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• 1989

The embryos of Pinus taeda, P. rigida, and P. taeda ${\times}$ rigida were cultured for adventitious shoot regeneration in vitro. Culture media were modified from Gresshoff and Doy (MGD), Murashige and Skoog (MMS), Lloyd and McCown (MLM), and Schenk and Hildebrandt (MSH). NAA was added to initiation media at a concentration of 0.1 or 0.01 mg/l. BAP was used at the concentrations of 0.1. 0.5, 1, 2, or 5mg/l. Each explant was induced for 3-4 weeks on solid medium. All explants were cultured up to 16 weeks. Illumination was about $1506{\pm}540lux$ at the level of the tissues in the growth room with a temperature of $25{\pm}2^{\circ}C$. A 16-hour photoperiod per 24 hours was used. Half-strength medium was used for all the subcultures. For shoot production by loblolly pine, MMS, MLM, or MSH is preferred with 5 mg/l BAP with either 0.1 or 0.01 mg/l NAA. For shoot production by pitch pine, MMS, MLM, or MSH is recommended with 2 or 5 mg/l BAP with 0.1 mg/l NAA. For shoot production by the hybrid pine, MMS or MLM is more effective with 1, 2 or 5 mg/l BAP with 0.1 mg/l NAA. There were no differences recognized among the species tried in the patterns of bud formation and shoot development. Different composition of media, in major and minor salts or possibly in vitamins, should be tested for the two developmental stages of adventitious shoots ; the induction of shoot buds and the elongation of them into shoots.

• Korean Journal of Microbiology
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• v.53 no.4
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• pp.292-296
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• 2017

In eukaryote, THO/TREX complex plays a critical role in transcriptional elongation, pre-mRNA processing, and nuclear mRNA export. This complex is evolutionally well- conserved, but there are some differences in composition and function according to organisms. Here we showed that spTex1, a component of THO/TREX complex, is not essential for growth and mRNA export in a fission yeast, Schizosaccharomyces pombe, which is more similar to higher eukaryote than budding yeast. Deletion and overexpression of the spTex1 gene do not lead to any detectable growth phenotype and accumulation of poly(A)+ RNA in the nucleus. And the spTex1-GFP protein is localized mainly in the nucleus. Yeast two-hybrid and Co-immunoprecipitation analysis showed that the spTex1 protein interacted with spHpr1 (THOC1) and spTho2 (THOC2), main subunits of THO complex. We conclude that the S. pombe Tex1 is a component of THO/TREX complex, but does not plays important roles in growth and bulk mRNA export from the nucleus.

• Korean Journal of Metals and Materials
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• v.56 no.11
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• pp.787-795
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• 2018

The effects of tempering condition on the microstructure and mechanical properties of 30MnB5 hot stamping steel were investigated in this study. Before the tempering, hot-stamped 30MnB5 steel was composed of only ${\alpha}^{\prime}$-martensite microstructure without precipitates. After the tempering at $180^{\circ}C$ for 120 min, nano-sized ${\varepsilon}$-carbides were precipitated in the ${\alpha}^{\prime}$-martensite laths. After tempering at $250^{\circ}C$ for 60 min, cementite was precipitated along the ${\alpha}^{\prime}$-martensite lath boundaries. The cementite was also observed in the specimens tempered at $350^{\circ}C$ for 30 min and $450^{\circ}C$ for 6 min, respectively. The globular ${\alpha}$-ferrite appeared at $350^{\circ}C-30min$ tempering, and the volume fraction of ${\alpha}$-ferrite increased when the tempering temperature was increased. The yield strength increased after tempering, and it reached a peak with the tempering condition of $180^{\circ}C-120min$, due to the nano-sized precipitates in the ${\alpha}^{\prime}$-martensite lath. After the tempering, the steel's ultimate tensile strength (UTS) was decreased due to the reduction in dislocation density and C segregation to lath boundaries. The highest elongation was observed at the $180^{\circ}C-120min$ tempering condition, due to the reduction of residual stress, and the lack of precipitates along the lath boundaries. The $180^{\circ}C-120min$ tempering condition was considered to have outstanding crash performance, according to toughness and anti-intrusion calculation results. In drop tower crash tests, the 30MnB5 door impact beam tempered at $180^{\circ}C$ for 120 min showed better crash performance compared to a 22MnB5 door impact beam.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.278-285
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• 2008

An efficient transformation method for soybean [Glycine max (L.) Merr.] using meristematic tissues of germinating seeds has been established. The embryonic axes were excised from germinating seeds of Korean soybean cultivar, Iksannamulkong and 0.5-2 cm long segment containing meristematic tissues were prepared by cutting hypocotyl region. The explants were inoculated with Agrobacterium tumefaciens strain LBA4404 harboring a binary vector with the bar gene as a selectable marker gene and a ${\beta}-glucuronidase$ (GUSINT) reporter gene, and then co-cultured for 7 days on co-cultivation medium (CCM). The meristematic tissues were cultured on shoot induction medium (SIMP6) supplemented with 0.4 mg/l $N_6-benzylaminopurine$ (BAP) and 0.1 mg/l indolebutyric acid (IBA) in the presence of 6 mg/l L-phosphinotricin (PPT) for 2 weeks and the surviving explants were transferred to shoot elongation medium (SEMP6). Transformation was confirmed by Southern blot analysis and the transformation efficiencies ranged from 1.48 to 2.07%. The new modified transformation method was successfully implemented for obtaining several transgenic lines with SMV-CP gene. It is expected that this method could efficiently be used for the transformation of recalcitrant soybean cultivars.

• FLOWER RESEARCH JOURNAL
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• v.18 no.2
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• pp.87-92
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• 2010

This research was aimed to extend the vase life, improve the cut flower quality and promote flowering rate of bulbous cut Iris 'Blue Magic'. Three different concentrations of 1-MCP ranging from 250 to $750nL{\cdot}L^{-1}$ were treated on cut Iris flowers for the vase life elongation. Several effects of 1-MCP treatment has shown such as early flowering as one day but vase life showed no significant differences comparing to the untreated control. Flowering rate was 75% or more in the treated ones as compare to 64.2% in untreated control. Especially, in a treatment with $250nL{\cdot}L^{-1}$ 1-MCP for 12 hours it showed all flowering. In many post-harvest experiments of cut flowers, ethylene production from flower organ has considered as most critical factor on vase life. Ethylene production from flower organ was measured by gas chromatography (GC) and it showed that there is no direct relation between flower longevity and emission of the ethylene gas in cut Iris. In comparison with the untreated control, ethylene generation rather seems to be increased as 1-MCP treatment increased. There was a synergy effect when 1-MCP and BA applied simultaneously in which flowering and vase life were fastened and also extended, respectively. Therefore, treatment of 1-MCP for cut Iris at flower early harvest is able to improve the flower quality both by diminishing non-flowering rate and by extended flower longevity.

• FLOWER RESEARCH JOURNAL
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• v.18 no.1
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• pp.15-22
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• 2010

These investigations were conducted to standardize several chemical and physical environments affecting in vitro propagation of gametophytes of Climacium japonicum. Propagation of this moss species was established on basal medium containing Knop macro salts and Nitsch and Nitsch trace elements. Primary cultures were initiated from apical shoots of gametophytes. Gametophyte production was accessed using chopped gametophytes, apical shoots and basal shoots. Seven ty pes of culture media and four concentrations of total nitrogen and five strengths of sucrose were tested for in vitro gametophyte production. Light and temperature factors were also evaluated. Apical shoots were the greatest among three types explants used for gametophyte propagation. Medium containing Knop macro salts and Nitsch and Nitsch trace elements was more effective than other types of media. Higher sucrose concentrations showed a positive effect on the elongation and multiplication of gametophytes. Both nitrogen deficiency and excessiveness inhibited gametophyte growth. Light intensity variation showed highly significant changes in numbers, length and fresh weight of gametophytes. Optimum light intensity for gametophyte growth seemed to be around 3000-4000 lx. Both lower and higher temperature had a negative effect on gametophyte propagation and production. This study will provide large scale and high quality propagules, and effective moss propagation system.

• FLOWER RESEARCH JOURNAL
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• v.16 no.2
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• pp.134-142
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• 2008

This work aims to obtain basic information for seed propagation of Hydrangea serrata for. acuminata. The germination percentage of the seeds taken on 15 November, 30 December, and 23 January was $90.0{\pm}4.16%$, $84.4{\pm}5.52%$, and $88.9{\pm}2.40%$, respectively. This suggest that seeds of Hydrangea serrata for. acuminata are non-dormant seeds. The optimum temperature for germination was $25^{\circ}C$ and light was necessary. Most of the growth parameters (shoot and leaf length, stem diameter, root length, no. of roots, T/R ratio, and fresh and dry wts.) were significantly greater at $25/20^{\circ}C$ and $25^{\circ}C$ than at the other temperatures. Low T/R ratio at relatively cool temperatures (15 and $20^{\circ}C$) was caused by suppressed top growth. In light quality treatment, red light (RL) significantly enhanced stem elongation. The greatest photosynthetic pigments (total chl, chl a/b, and carotenoid) were observed in seedlings grown in blue light (BL), followed by seedlings grown in RL+BL. When blue light was added, higher pigment contents were found. Effect of plug cell size (50, 72, 128, 162 and 200 cells) on the growth of seedlings was investigated. The highest top growth was observed in seedlings grown in 50 cell trays, followed by seedlings grown in 72, 128, 162, and 200 cell trays. However, there was no significant differences between 162 and 200 cell trays. Especially, smaller size leaves were observed in seedlings grown in smaller cell trays (lower volume and high plant density).