• Microbiology and Biotechnology Letters
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• v.49 no.3
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• pp.403-412
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• 2021

This study aimed to identify plant growth-promoting activity, phytopathogenic fungi growth inhibitory activity, mineral solubilization ability, and extracellular enzyme activity of the genus Bacillus in soil and the rhizosphere. With regards to antifungal activity against phytopathogenic fungi, DDP257 showed antifungal activity against all 10 pathogenic fungi tested. ANG20 showed the highest ability to produce indole-3-acetic acid, a plant growth-promoting factor (70.97 ㎍/ml). In addition, 10 species were identified to have 1-aminocyclopropane-1-carboxylate deaminase production ability, and most isolates showed nitrogen fixation and siderophore production abilities. Thereafter, the isolated strains' ability to solubilize minerals such as phosphate, calcite, and zinc was identified. With extracellular enzyme activity, the activity appeared in most enzymes. In particular, all the strains showed similar abilities for alkaline phosphatase, esterase (C4), acid phosphatase, and naphtol-AS-BI-phosphohydrolase production. This result was observed because the genus Bacillus secreted various organic substances, antibiotics, and extracellular enzymes. Therefore, through the results of this study, we suggest the possibility of using strains contributing to the improvement of the soil environment as microbial agents.

• Journal of Life Science
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• v.31 no.7
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• pp.641-653
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• 2021

The purpose of this study was to confirm the antifungal activity, plant growth-promoting activity, and mineral solubilizing activity of 18 types of bacteria isolated purely from rhizosphere soil. The potential of isolates of the genus Bacillus and Pseudomonas as biocontrol agents was confirmed through the antifungal activity of these isolates. This activity has been determined to be due to various hydrolytic enzymes on the cell wall of plant pathogenic fungi and the production of siderophores in isolates. In addition, most of the isolates have been found to have aminocyclopropane-1-carboxylate deaminase production activity, indole-3-acetic acid production activity, and nitrogen fixation activity. These characteristics are believed to have a positive effect on root development, growth, and the productivity of crops via a reduction in the concentration of ethylene under conditions of environmental stress, to which plants are commonly exposed. In addition, on testing for the solubilizing activity of the isolates for phosphoric acid, silicon, calcium carbonate, and zinc, some isolates were found to have mineral solubilizing activities. Inoculation of these isolates during plant growth is expected to assist plant growth by converting nutrients necessary for growth into usable forms that can be absorbed by plants. The 18 isolated strains can be used as biocontrol agents due to their antifungal activity, plant growthpromoting activity, and mineral solubilizing activity.

• Microbiology and Biotechnology Letters
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• v.47 no.3
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• pp.390-400
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• 2019

In this study, strains isolated from soil samples collected from Busan, Changwon, and Jeju Island were examined to verify their abilities of phosphate solubilization and nitrogen fixation, production of indole-3-acetic acid (IAA), siderophore, and 1-aminocylopropane-1-carboxylyic acid (ACC) deaminase in order to select strains that promote plant growth and play a role in biocontrol of pests or pathogens. According to the results of this study, most of the isolated strains were found to have ability of phosphate solubilization, nitrogen fixation, IAA production, siderophore production, and production of ACC deaminase. These isolated strains might help plant growth by directly improving absorption of nutrients essential for phosphate solubilization and nitrogen fixation. In addition, they can promote plant growth and control resistance to plant diseases through extracellular enzyme activity and antifungal activity. In addition, most of the selected strains were found to survive in various environmental conditions such as temperature, salinity, and pH. Therefore, Pseudomonas plecoglossicida ANG14, Pseudarthrobacter equi ANG28, Beijerinckia fluminensis ANG34, and Acinetobacter calcoaceticus ANG35 were finally selected through a comparative advantage analysis to suggest their potential as novel biological agents. Further studies are necessary in order to prove their efficacy as novel biological agents through formulation and optimization of effective microorganisms, their preservation period, and crop cultivation tests.

• Korean Journal of Food Science and Technology
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• v.51 no.4
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• pp.369-378
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• 2019

This study aimed to compare the quality characteristics of carrot juice based on different extraction methods such as centrifugation, single gear, and twin gear methods. Juice quality was evaluated based on extraction yield, nutritional components, and cloud stability. Twin gear extraction resulted in the highest extraction yield, and the highest mineral content. In addtion, ${\beta}$-carotene level higher than the recommended daily intake was obtained only in the carrot juice prepared using twin gear extraction of 100 g carrots. The minimum particle size was observed in twin gear extraction, followed by single gear extraction and centrifugation method. Therefore, twin gear extraction was selected as the optimal method, and changes in the antioxidant and metabolic activity of carrot juice were investigated using this method. Consequently, the carrot juice showed a higher lipid peroxidation inhibition rate than ${\alpha}$-tocopherol (1 mg/mL), and angiotensin I-converting enzyme (ACE) inhibitory activity was increased upon digestion.

• Microbiology and Biotechnology Letters
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• v.49 no.4
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• pp.576-586
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• 2021

The purpose of this study was to evaluate the antifungal activity, plant-growth-promoting activity, and mineral solubilization ability of 10 species of phytopathogenic fungi to select a Bacillus sp. from rhizosphere soils and roots that can be used as a microbial agent. The antifungal activity for phytopathogenic fungi varied based on the Bacillus sp. Among the selected strains, DDP4, DDP16, DDP148, SN56, and SN95 exhibited antifungal activity for nine or more species of phytopathogenic fungi. Regarding nitrogen-fixation ability, all Bacillus sp. showed similar levels of activity, and siderophore production ability was relatively high in ANG42 and DDP427. The indole-3-acetic acid production abilities were in the range of 1.83-67.91 ㎍/ml, with variations in activity based on the Bacillus sp. One strain with a high activity was selected from each species, and their mineral solubilization abilities were examined. Most Bacillus sp. could solubilize phosphoric acid and calcium carbonate, and DDP148 and SN56 could solubilize silicon and zinc, respectively. These results suggested that Bacillus sp. can be considered potential multi-purpose microbial agents for plant growth promotion and disease prevention.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.6
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• pp.147-157
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• 2023

This paper investigates the financial factors affecting angel investors' investment decisions for 818 firms from 2009 to 2018 in the Korean venture investment market. We construct a quasi-experimental design using propensity scoring matching and compare the investment determinants between investment firms and matching firms. The main empirical findings are as follows. First, we find that angel investors are more likely to choose firms based on a firm's growth such as profit and assets rather than profitability or financial stability. In addition, we identify that they prefer the firm not only higher intangible assets but also higher R&D expenditures. Second, we find that angel investors consider both growth and activity ratios in the firms for over three years and have entered the mid-stage of startups. Overall, we confirm that the investment decision of angel investors mainly focuses on the venture startups' growth trend or future growth potential rather than the realized profitability or financial stability. We also infer that the possibility of performance creation is an important investment factor along with growth for the mid-stage startup.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.1
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• pp.171-181
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• 2001

Recently, the development of CNC machine tools seems to bring about progressional high speed, precision and automation in cutting processing, but is unlikely to avoid the generation of burr arising from plastic deformation, which may result in deterioration of improvement in the precision and productivty of products. In this study, Experiment has been carried out to prevent and decrease the grinding burr under various working conditions ; working speed, side cutting edge, back rake angle, disengage angel.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.122-125
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• 1993

The various geometry of tap been developed in order to tap special workmaterial at considerably higher cutting speed than that of the conventional HSS tap. In this paper a piezo type tool dynamomerer is constructed and used to measure the torque. The experimental tests are run with various cutting speed. It is clarified that the process of chip formation strongly depends on rake angle, relief angel, angel of twist.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.794-798
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• 1995

We performed analysis for crank shaft and connecting rod in driving device of Cold Heading Machine. The results of this study is following ; 1. The nominal pressure is happened at 8mm under bottom dead center. And then the theoretical angel of crank (.theta.) and connecting rod (.phi.) are .theta. = 25 .deg. 1' and .phi.= 6 .deg. 1' but the analysis angel are .theta. = 25 .deg. and .phi.= 7 .deg. 2. The load is loaded at theta. = 51 .deg. in crank angle. 3. The maximum stress of connecting rod is about290MPa. It is exited inner stress range in consideration of safety factor.

• Electronics and Telecommunications Trends
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• v.15 no.1 s.61
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• pp.71-80
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• 2000

최근의 코스닥 시장의 붐과 함께 개인투자가들의 벤처기업에 대한 투자가 본격적으로 이루어지고 있다. 특히 주요 엔젤클럽의 투자설명회를 통해 초기 단계의 벤처기업에게 많은 자금이 투자되고 있는데, 본 고에서 ’97년부터 ’99년 9월까지 투자설명회를 통해 엔젤들로부터 자금을 유입한 49개 벤처기업을 대상(벤처캐피탈 자본을 제외한 순수 엔젤자금)으로 벤처기업의 성향에 대해 분석해 보았다.