• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.271-279
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• 2012

9-12% Cr steels have been used in thermal power plants which repeat start and stop operations. Major factors of fatigue life are temperature, frequency, stress ratio, holding time, microstructure, and environment. Normally, fatigue life decreases at high temperature, low frequency, high stress ratio, and long holding time conditions. A Mod.9Cr-1Mo steel, called G91, was developed at ORNL (Oak Ridge National Laboratory, USA) and was adopted as a high-temperature structural material in the ASME Code in 2004. However, its low-cycle fatigue and fatigue crack growth characteristics have been rarely studied. In this work, we have investigated the low-cycle fatigue crack growth behaviors of G91 steel under various test conditions in terms of temperature and stress ratio. As temperature and stress ratio increase, the crack growth rate becomes faster and striation distance also increases. On the other hand, the number of branch cracks decreases.

• Journal of Veterinary Clinics
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• v.9 no.1
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• pp.273-276
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• 1992

Present study was undertaken in order to evaluate the lead contents of various feedstuffs produced in Chonbuk area. Fifty-five samples were collected from 5 regions. All of the samples were dry-ashed and analyzed for lead content using atomic absorption spectrophotometer. The results obtained were summarized as followed : 1. The lead content in $\mu\textrm{g}$/g of agriculture by-products were measured with the following mean values and ranges : soybean pod 7.01${\pm}$2.49(4.71∼10.66), rice bran 4.56${\pm}$0.90(3.17∼5.65), rice straw 3.89${\pm}$2.01(1.29∼6.33), rice hull 1.92${\pm}$1.77(0∼3.63). 2. The lead content in $\mu\textrm{g}$/g of pasture plants were measured with the following mean values and ranges : kudzu 20.29${\pm}$4.75(14.84∼25.34), clover 13.92${\pm}$2.68(10.17∼16.44), lespedeza 10.91${\pm}$9.00 (3.35∼23.54), sagebrush 10.75${\pm}$3.28(5.14∼13.18), Korean lawn grass 5.05${\pm}$2.29(2.57∼7.79), cornstalk 3.91${\pm}$2.55(0.50∼7.22), reed 2.92${\pm}$1.88(0.50∼5.73). 3. Seventeen samples (30.9%) out of 55 samples showed lead content of more than 10$\mu\textrm{g}$/g which are said to be the upper limit value for all animals. 4. The regional mean v짓ues for 리1 kinds of samples were Wanju-gun 10.02${\pm}$8.55$\mu\textrm{g}$/g, Mooju-gun 8.16${\pm}$4.91$\mu\textrm{g}$/g, Namwon-gun 7.09${\pm}$4.59$\mu\textrm{g}$/g, Okgu-gun 7.06${\pm}$7.11$\mu\textrm{g}$/g, Jeongup-gun 6.35${\pm}$6.50$\mu\textrm{g}$/g.

• Journal of Conservation Science
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• v.37 no.6
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• pp.689-700
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• 2021

This study aims to optimize the measurement conditions of handmade Hanji paper to reduce the time required for measurement while meeting folding endurance standards, for various basis weights. Thirteen types were selected, including 12 types of Hanji with grammages of 17 g/m², 30 g/m², and 45 g/m², and one type of 75 g/m² copy paper, and 24 sheets were prepared in the laid and chain directions. Subsequently, folding endurance experiments at different load (14.72 N, 9.81 N, 4.91 N) and specimen width conditions (15 mm, 10 mm, 5 mm) were performed, using a 4-MIT folding endurance tester. The results showed that, for specimen widths of 15 mm and 10 mm under a load of 4.91 N, the folding endurance falls within the reference range (10~10000 times). In particular, reduced folding endurance range and measurement time were observed at a width of 10 mm under a load of 4.91 N. Moreover, the endurance trend lines based on the average values of load and specimen width ranges enabled the prediction of the folding endurance within those ranges, according to the decreasing slope. Furthermore, for a specimen width of 15 mm under a load of 4.91 N, the folding endurance in the comparison group (35 to 17723 times) significantly exceeds the upper limit of the reference range (10~10000 times). Therefore, the measurement conditions of 4.91 N with a specimen width of 10 mm are proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.891-892
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• 2011

• Microbiology and Biotechnology Letters
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• v.43 no.2
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• pp.164-168
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• 2015

Citric acid is produced via submerged fermentation using yeasts. Among eight different strains of yeast, Candida zeylanoides was chosen as the strain for producing citric acid and optimized for various C/N ratios and effects of phosphate or Fe²⁺ ions in a clean carbon source medium (glucose: fructose, 1:1). The yield of citric acid was maximized at a C/N ratio of 40/1, a phosphate addition of 1.0 g/l, and an Fe²⁺ ion concentration of less than 50 mg/l, yielding up to 91 g/L in the broth with 18.5 g/l of isocitric acid in a six-day fermentation period using a pre-treated molasses medium. The yield of batch culture was 0.51 (Y_p/s, g/g) in a 5 L-Jar fermenter.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.837-845
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• 2009

We have performed DFT calculations to investigate the conformational characteristics and hydrogen bonds of the calix[6]arene (1) and p-tert-butylcalix[6]arene (2). The structures of various conformers of 1 were optimized by using the B3LYP/6-31G(d,p) and /6-31+G(d,p) methods followed by single point calculation of MPW1PW91/ 6-31G(d,p). The relative stability of the conformers of 1 is in the following order: cone (pinched: most stable) > partial-cone > cone (winged) $\sim$ 1,2-alternate $\sim$ 1,2,3-alternate > 1,4-alternate > 1,3-alternate > 1,3,5-alternate. The structures of different conformers of 2 were optimized by using the B3LYP/6-31G(d,p) method followed by single point calculation of MPW1PW91/6-31G(d,p). The relative stability of the conformers of 2 is in the following order: cone (pinched) > 1,2-alternate > cone (winged) > 1,4-alternate $\sim$ partial-cone > 1,2,3-alternate > 1,3,5alternate > 1,3-alternate. One of the important factors affecting the relative stabilities of the various conformers of the 1 and 2 is the number and strength of the intramolecular hydrogen bonds.

• Microbiology and Biotechnology Letters
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• v.17 no.5
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• pp.468-474
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• 1989

The cultural condition for polysaccharide production by Pseudomonus detafietdii was studied. The optimal medium contains the following composition per liter of distilled water: glucose (25g/$\ell$), peptone (2.06g/$\ell$), KH$_2$PO$_4$(2g/$\ell$), MgSO$_4$.7$H_2O$ (2g/$\ell$), yeast extract (0.5g/$\ell$), CaCO$_3$(2.5g/$\ell$). The temperature and pH optimum were 3$0^{\circ}C$ and 6.5. The agitation speed was 300 rpm. 5.91g of polysaccharide was produced at the condition in flask culture.

• Pediatric Infection and Vaccine
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• v.4 no.1
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• pp.133-139
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• 1997

Purpose : To determine the age-specific seropositivity and the level of measles specific IgG in vaccinated adolescents, the measles specific IgG titers were measured from the sera of junior & senior high school students in Seoul, Korea. Methods : From May to July in 1996, 216 sera were collected from junior & senior high school students(male : 110, female : 106) aged 12 to 17 years who were vaccinated and had no history of natural measles. Measles specific IgG titers were measured using ELISA method($SIA^{TM}$ Measles IgG Kit, Sigma Co. St. Louis, Mo). Results : The seropositivity of measles specific IgG in vaccinated adolescents aged 12 to 17 years was 91.2%. There were no significant correlations between age and seropositivity as well as between age and measles specific IgG level. Conclusions : We consider that our data suggest the necessity of revaccination of measles in adolescents. Further considerations should be required to establish an appropriate revaccination method and to evaluate the efficacy of revaccination of previously vaccinated adolescents.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.100-104
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• 2011

The structures of the conformers for 1,3-di-t-butyl-2,4-dinitro-tetramethoxysulfonylcalix[4]arene (1) and 1,2-di-t-butyl-3,4-dinitro-tetramethoxysulfonylcalix[4]arene (2) were optimized using DFT BLYP and mPW1PW91/6-31G(d,p) (hybrid HF-DF) calculation methods. We have analyzed the total electronic and Gibbs free energies and the differences between the various conformations (cone, partial-cone (PC), 1,2-alternate, and 1,3-alternate) of 1 and 2. For both compounds, the 1,3-alternate (1,3-A) conformers were calculated to be the most stable, which correlate very well with the experimental results. The orderings of the relative stability of 1 and 2 that resulted from the mPW1PW91/6-31G(d,p) calculations are the following: 1: 1,3-A (syn) > PC (syn) > PC (anti) > 1,2-A (anti) > CONE (syn); 2: 1,3-A (anti) > PC (anti) > PC (syn) > 1,2-A (anti) > 1,2-A (syn) > CONE (syn). The BLYP/6-31G(d) calculated IR spectra of the most stable 1,3-A conformers of 1 and 2 are compared.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.05a
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• pp.91.1-91.1
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• 2004