• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.161-169
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• 2004

In this study, we investigated fatigue crack growth behavior of laser welded sheet metal due to a single overload. Fatigue specimens were made using butt joint of cold rolled sheet metal that was welded by $CO_2$ laser. The fatigue crack propagation tests were performed in such a way that fatigue loading was parallel to the weld line while crack propagation was perpendicular to the weld line. Single overload was applied when fatigue crack tip was arrived near the weld line. The distances between the crack tip and the weld line at which a single overload was applied were 6, 4 and 2mm. The effect of specimen thickness and overload ratio on the fatigue behavior was determined. The plastic zone size of crack tip due to the single overload was determined from the finite element analysis. For investigating fatigue crack growth behavior, we used different thickness specimen 0.9mm and 2.0mm, and variable overload ratio applied fatigue crack propagation test. Also we used finite element analysis for investigating the plastic zone size of crack tip when single overload applied

• The Mathematical Education
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• v.50 no.1
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• pp.103-118
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• 2011

The study examined whether the relation between mathematics self-efficacy and mathematics achievement was partially mediated by the learning strategies, using latent growth model analyses. It was also examined the auto-regressive, cross-lagged (ARCL) panel model for testing the stability and change in the relation of mathematics self-efficacy and learning strategy over time. The study analyzed the first-year to the third-year data of the Korean Educational Longitudinal Survey (KELS). The result of ARCL panel model analysis showed that earlier mathematics self-efficacy could predict later learning strategy use. There were linear trends in mathematics self-efficacy, learning strategy, and mathematics achievement. Specifically, mathematics achievement was increased over the three time points, whereas mathematics self-efficacy and learning strategies were significantly decreased. In the analyses of latent growth models, the mediating effects of learning strategies were overall supported. That is, both of initial status and change rate of rehearsal strategy partially mediated the relation of mathematics self-efficacy and mathematics achievement. However, in elaboration and meta-cognitive strategies, only the initial status of each variable showed the indirect relationship.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.945-950
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• 2002

Shape optimization of a flow system is done to obtain the required effects, in the engineering fields. Most of these designs are accomplished by empirical or numerical analysis. In empirical analysis, it is difficult to obtain an optimal shape in the feasible design region. And, in numerical method, it usually needs much calculation expenses for shape optimization, because of design sensitivity analysis. In this study, we used the growth-strain method having only one distributed parameter such as a design variable. It optimizes a shape by making a distributed parameter such as dissipation energy uniform in a flow system, and then applied to two-flow systems. In order to overcome the stability occurred in numerical analysis performed by Azegami, the equation of volumic strain has been modified. Also, the shapes were compared with the known optimal shapes for the flow systems. Consequently, we confirm that the modified growth-strain method is very efficient and practical in shape optimization of the flow systems.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.6
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• pp.920-928
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• 2015

This study aims to reveal the relationship between growth of young sea bass and environmental variables in two adjacent eelgrass beds. Fishes were collected from Gamak Bay (GB) and Yeoja Bay (YB) on the southern coast of Korea from February 2006 to February 2007 using a dragnet (15 m in length and 3 m in width). During the study period, a total of 367 individuals of young sea bass Lateolabrax japonicus were collected from GB (171 inds.) and YB (196 inds.). Significant differences were observed in the occurrence periods and growth patterns of young sea bass, as well as in environmental variables between GB and YB. Young sea bass were collected from April to December in GB, but from April to July in YB. These differences may be associated with differences in eelgrass density, leaf width, and zooplankton density between GB and YB.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.4
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• pp.309-316
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• 2020

This research aims to revisit the hypothesis that bribery hurts firm performance in the context of a perceptibly corrupt country. Specifically, we use micro-data from Vietnamese small and medium firm surveys in 2013 and 2015 to examine whether bribery impedes firm revenue growth and labor productivity growth. An issue arising in this type of research is the potential endogeneity between firm bribing behaviors and firm performance. To go around the issue, we follow the literature to instrument bribery variable with the average probability of bribery in other provinces. We further employ the Analysis of Variance technique (ANOVA) to unveil if the effect of bribery is dependent on bribing purposes. The regression results show that firm performance is significantly influenced by firm size, firm age and firm bribing behavior. Larger firms are more likely to grow faster while firm performance tends to be negatively related to firm age. Particularly, we find that bribery significantly impedes firm revenue growth and labor productivity growth. The analysis of variance shows that the effect of bribery on firm performance may vary across bribing purposes. Our findings, therefore, support the sand-the-wheels hypothesis that bribery hurts firm performance even in a highly corrupt business environment.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2819-2822
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• 2010

Forest of single-walled carbon nanotubes (SWNTs) was grown at $450^{\circ}C$ by water-plasma chemical vapor deposition using ultrathin iron on alumina supporting film. The growth rate of the SWNT forest is ${\sim}0.9\;{\mu}m/min$, and the diameters of nanotubes are mainly in a range of 3.0 ~ 3.5 nm. The low intensity ratio of D- to G-band ($I_D/I_G$ ~ 0.098) in Raman spectra indicates that our SWNT forest grown at $450^{\circ}C$ is fairly pure and crystalline. This low temperature growth of SWNT forest may enable variable applications requiring the vertically-aligned nanotubes to obtain large surface area.

• Culinary science and hospitality research
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• v.14 no.1
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• pp.21-38
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• 2008

This research aimed to analyze the differences in financial variables classifying chain restaurants. A total of 126 samples were drawn from financial statements for $2001{\sim}2006$. As a result of analysis, there was a significant difference in Pillai's Trace, Wilks' Lambda, Hotelling's Trace, and Roy's Largest Root values at the significant probability value(p<0.05) based on F value in terms of stability among chain restaurants. Difference was found only in current rate and liabilities in ANOVA. There was a great difference in current rate among institutional restaurants, fast food restaurants, and cafeterias. There was a significant difference in Pillai's Trace, Wilks' Lambda, Hotelling's Trace, and Roy's Largest Root values at the significant probability value(p<0.05) based on F value in terms of restaurants' profitability. In ANOVA, difference was found only in net profits to net sales. It was revealed that all factors showed no significant differences in multiple comparison. All multi-variant test statistics showed a significant difference in growth and turnover. ANOVA showed a significant difference in net sales growth rate, net profit growth rate, and total assets growth rate.

• Horticultural Science & Technology
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• v.33 no.1
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• pp.106-113
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• 2015

Effects of mineral salts (N, P, K, $Ca^{2+}$, $Mg^{2+}$, and $Fe^{3+}$) on the shoot growth and metabolite production of tea tree were studied using in vitro culture techniques. Among mineral s alts, ${H_2PO_4}^-$ was the most important for enhanced growth rate of tea tree, while $Mg^{2+}$ and $Ca^{2+}$ did not affect plant growth. Removal of ${NH_4}^+$ and $NO_3$ from the culture medium enhanced shoot multiplication compared to other treatments. Metabolite production was variable depending on mineral types and concentration. Removal of $Ca^{2+}$ decreased the production of caffeine; however, other treatments did not influence its production. $Ca^{2+}$, ${NH_4}^+$ and $Fe^{3+}$ were important factors for catechin production in tea tree. These results can be used as the basis for development of technical soil controls suitable for tea tree cultivation in the future.

• Journal of the Economic Geographical Society of Korea
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• v.20 no.1
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• pp.84-104
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• 2017

In this study, we divided Gyeonggi-do into Northern, Southern, Western, and Eastern Parts and found out fiscal variables which affected regional economic growth of each Part differentially. And we drew the strategy for economic growth of each Part. After we found out the variables which affected regional economic growth using fixed-effect model, we carried out causality test to determine whether a specific fiscal variable caused economic growth. In the Eastern Part, local tax revenues had a significant effect on the economic growth. Total expenditures, current expenditure in the Southern Part and social welfare expenditure, expenditure on industries, current expenditure in the Northern Part had noticeable effects on economic growth respectively. And we calculated multipliers of fiscal variables to compare the magnitudes of effects among these Parts.

• Microbiology and Biotechnology Letters
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• v.10 no.2
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• pp.101-108
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• 1982

The effects of ginseng extract and ginseng saponin on the growth of bacterial cells were variable depending upon the species of bacterium and concentrations of saponin. Serratia marcescens and Aerobocter aerosenes showed the maximum growth in the basal medium pius 0.1% of ginseng extract, but did the suppressed growth in the medium plus above 1 % of ainseng extract. Stophylococcus aureus and Escherichia coli showed the maximum growth in the basal medium plus 5% of ginseng extract. The slightly accelerated growth was shown with Micrococus flavus and Aerobacter aerogenes cultivated in the basal medium plus 0.002% of ginseng saponin, but the remarkably supressed growth was done in the medium plus above 0.02% of ginseng saponin. Ginseng saponin functioned a physiologically suppressing factor of growth to genus Serratia, but no antimicrobial activity was found against Erwinia aroideae and Sarcina marginata. The substance causing the antimicrobial activity from ginseng saponin was proven to be a ginsenoside Rg$_1$.