• The Korean Journal of Mycology
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• v.27 no.3 s.90
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• pp.181-186
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• 1999

Osmotolerant yeast isolated from soy paste could grow on media with 2 M NaCl. This strain was identified as Zygosaccharomyces rouxii by biological characteristics, RFLP of ribosomal DNA and mating with compatible haploid strain. Growing rate of the Z. rouxii YDJ was slower than Saccharomyces cerevisiae. Z. rouxii YDJ accumulated trehalose, which is known as one of the osmolytic protectants, in cells cultured on media with salt. Enzyme activity of trehalose phosphate synthase related to trehalose biosynthesis of the YDJ was lower than those of S. cerevisiae. Trehalase activity related trehalose degradation was also lower in Z. rouxii YDJ than S. cerevisiae. However, as Z. rouxii accumulated trehalose by salt treatment, salt tolerancy of Z. rouxii was assumed to be related to trehalose in additon to glycerol.

• Journal of Microbiology and Biotechnology
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• v.20 no.11
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• pp.1529-1533
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• 2010

The inulinase gene (INU1) from Kluyveromyces marxianus NCYC2887 was overexpressed by using the GAL10 promotor in a ${\Delta}ga180$ strain of Saccharomyces cerevisiae. The inulinase gene lacking the original signal sequence was fused in-frame to a mating factor ${\alpha}$ signal sequence for secretory expression. Use of the ${\Delta}ga180$ strain allowed for the galactose-free induction of inulinase expression using a glucose-only medium. Shake-flask cultivation in YPD medium produced 34.6 U/ml of the recombinant inulinase, which was approximately 13-fold higher than that produced by K. marxianus NCYC2887. It was found that the use of the ${\Delta}ga180$ strain improved the expression of inulinase in the recombinant S. cerevisiae in both aerobic and anaerobic conditions by about 2.9- and 1.7-fold, respectively. A 5-l fed-batch fermentation using YPD medium was performed under aerobic condition with glucose feeding, which resulted in the inulinase production of 31.7 U/ml at the $OD_{600}$ of 67. Ethanol fermentation of dried powder of Jerusalem artichoke, an inulin-rich biomass, was also performed using the recombinant S. cerevisiae expressing INU1 and K. marxianus NCYC2887. Fermentation in a 5-l scale fermentor was carried out at an aeration rate of 0.2 vvm, an agitation rate of 300 rpm, and with the pH controlled at 5.0. The temperature was maintained at $30^{\circ}C$ and $37^{\circ}C$, respectively, for the recombinant S. cerevisiae and K. marxianus. The maximum productivities of ethanol were 59.0 and 53.5 g/l, respectively.

• Development and Reproduction
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• v.18 no.1
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• pp.25-31
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• 2014

This study was investigated spawning behavior, structure of egg masses and egg development in Aplysia kurodai inhabiting the coastal waters of Jeju Island, Korea. The mating and courtship behavior of A. kurodai occurred in the form of unilateral copulating with chain formation. In chain copulation, only the first animal acted as a female; the second and succeeding animals acted as males (sperm donors) to the animals in front and as females to the animals behind. The fertilized eggs were packaged in capsules that are embedded in jelly to form a cylindrical string called an egg masses. The number of capsule per cm of the egg masses was 55 to 60 capsules and each capsule within the egg masses held 15 to 25 eggs. After spawning, the egg masses were bright yellow or orange in color. This egg masses color not changed until embryos developed into trochophore stage. Thereafter, as embryo developed from trochophore stage to veliger stage the egg masses color became brownish. The fertilized eggs were spherical, with a diameter of approximately $80{\pm}1{\mu}m$ at spawning. At 5 to 6 days after spawning, the embryo developed into trochophore stage and began to rotate within the egg capsule. In the trochophore stage, the precursor of the velum, called the prototroch or prevelum, developed. At 10 days after spawning, the prevelum is transformed into the velum, and the trochophore developed into veliger stage. Between 10 to 15 days after spawning, the veligers broke out of the egg capsule, and hatched as free-swimming larvae.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.33-41
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• 2014

Fretting is a kind of surface degradation mechanism observed in mechanical components and structures. When two pieces of materials, pressed together by an external static load, are subjected to a transverse cyclic loading or various vibrations, so that one contacting face is relatively displaced cyclically parallel to the other face, wear of the mating surfaces occurs. These fretting damages may be observed in electrical connectors for automotive components, where there are special environments and various vibration conditions. This study aims to evaluate the usefulness of fretting test equipment that was developed for reliability test of electrical connector. Fretting tests were carried out using tin coated connectors and friction force, contact resistance, contact area and roughness of contact region were investigated. The following results that will be helpful to understand the fretting wear mechanism, increase process the contact resistance and contact area were obtained. (1) In the same frequency and slip amplitude, the friction force, roughness and contact area increased rapidly until about $10^3$ cycles, after which it was slightly changed. (2) In the various frequency and slip amplitude, the contact area increased with slip amplitude and cyclic numbers, but it did not depend on cyclic frequency. (3) The surface roughness of contact region did not depend on the cyclic frequency. From these results, the applicability of the fretting wear test equipment and reliability of connector were discussed.

• Korean Journal of Animal Reproduction
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• v.7 no.1
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• pp.19-23
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• 1983

Present studies were conducted to investigate the developmental stage and the location of embryos in the reproductive tract at various times after ovulation, the morphologically normal after thawing of embryos preserved in liquid nitrogen, and the survival after transferring frozen-thawed embryos. The results obtained were as follows: 1. Embryo stage and location in the reproductive tract after hCG administration. For the investigation of embryo stage and location in the reproductive tract after ovulation, rabbits were laparotomized at 24, 40, 48, 72 and 120 hrs post hCG injection, simultaneously with mating. the oviducts and uteri were flushed out with PBS medium containing 50% rabbit serum, respectively. 1) Most of embryos was remained in the oviduct within 48 hrs, with the lapse of time, embryos were started to move to uterus and shifted in uterus at 72 hrs after hCG injection. 2) The representatives of embryos stage collected at 24, 40, 48, 72 and 120 hrs were 1-cell(60.4%), 8-cell to early morula (52.3, 39.3%), late blastocyst (95.5%) stages, respectively. 2. Morphological normality and survival of the frozen-thawed embryos. For the evalution of the quality and viability on the frozen-thawed embryos, immediately after thawing, embryos were assessed by morphologically normal under a dissecting microscope, and a further test of frozen-thawed embryos was made by transferring the morphologically normal embryos to the uteri of recipient rabbit induced pseudopregnancy by the injection of hCG at the time of hCG injection in donor rabbits. 1) The propotions of embryos which a, pp.ared morphologically normal was higher when 8-cell (85.7%) and morula(90.5%) were used for freezing than when 4-cell (66.7%) and blastocyst (75.8%) were used. 2) Preganacies were observed at Day 15 after transfer of frozen-thawed 8-cell (7/13), morula (19/42) and blastocyst (3/19) but not after transfer of embryos at 4-cell stage.

• Tribology and Lubricants
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• v.32 no.5
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• pp.154-159
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• 2016

This paper presents an experimental study of the leakage performance and endurance performance of a mechanical face seal in the 7-ton-class turbopump of the Korea Space Launch Vehicle 2 third-stage engine. We install a mechanical face seal between the fuel pump and turbine to prevent the mixing of the fuel and turbine gas. We design and manufacture a prototype mechanical face seal, which has two parts, namely, a bellows seal assembly and mating ring. We set up a test facility to measure the leakage and endurance of the mechanical face seal. For the similarity tests, we use water under real operating conditions such as high rotational speed, high temperature, and high pressure. Through investigation of the leakage and carbon wear rate, it is possible to evaluate the performance of the mechanical face seal. The results of the leakage and endurance performance test demonstrate the absence of any leakage from the prototype mechanical face seal after a trial run and clarify that the acceptable wear rate fully satisfies the turbopump requirements. Finally, we install a qualified mechanical face seal in a 7-ton-class turbopump and perform a validation test in the turbopump real-propellant test facility in the Korea Aerospace Research Institute. The test results confirm that the mechanical face seal works well under real operating conditions.

• Korean Journal Plant Pathology
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• v.10 no.4
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• pp.261-269
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• 1994

One hundred and ninety two isolates of Armillaria were obtained from mycelial fans on infected hosts, rhizomorphs, and single basidiospores or trauma tissue of fruiting bodies. Mating tests showed that two of these isolates were A. mellea, eight were A. tabescens, 20 were A. ostoyae, and 162 were A. gallica. Armillaria ostoyae was mainly isolated from Pinus koraiensis and Qurecus spp., A. tabescens from fruiting bodies on Pinus densiflora and Qurecus spp., and A. gallica from many tree species but not Pinus koraiensis. Armillaria mellea, A. gallica, A. ostoyae and A. tabescens showed distinct protein banding patterns. Mycelial growth and rhizomorph formation was good on basal medium with ethanol added. A. gallica and A. mellea formed many rhizomorphs, but A. ostoyae did not. A. gallica showed the best rhizomorph formation on media with tannic acid and ethanol, but a. mellea formed the most rhizomorphs on gallic acid. Rhizomorphs showed monopodial branching for A. gallica and dichotomous branching for A. ostoyae. Fruiting bodies. formed in the laboratory on sawdust media most abundantly by A. tabescens. In nature, fruit body formation by A. tabescens was from early to mid August. A. ostoyae and A. gallica fruit bodies were formed from early August to late October. While there are common names in Korea for A. mellea and A. tabescens, such as mulberry mushroom relative, no common names are available for A. gallica and A. ostoyae. Therefore, we refer to a. gallica as the Gastrodia mushroom because it has been used to produce Gastrodia and A. ostoyae as the Korean pine mushroom because it is frequently found as mushrooms on Korean pine.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.303-310
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• 2004

To establish a prediction table of parturition day real-time B-mode ultrasonographic examinations were performed in 12 pregnant Shih-tzu bitches. Measurement of inner chorionic cavity diameter and fetal head diameter was performed from 15 days of gestation to parturition. These were converted retrospectively based on the day of parturition (Day 0). The data of inner chorionic cavity diameter obtained from Day -44 to Day -25 and fetal head diameter obtained from Day -25 to Day -1 were used to compile a prediction table of parturition day. The 22 pregnant Shih-tzu with unknown mating time were examined to assess an accuracy of the table established in this study. And these results were applied to the prediction of parturition day and compared to actual parturition day. Parturition day prediction based on the inner chorionic cavity diameter and fetal head diameter was 100% accurate within ${\pm}2$ days. In addition, the accuracy for parturition day within 0, ${\pm}1$, and ${\pm}2$ days interval using the prediction table of parturition day were 68, 82, and 100%, respectively. Therefore, the prediction table of parturition day seems to be a useful tool for the prediction of parturition day in practice.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1404-1411
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• 1993

This study was undertaken to investigate the corrosive wear charateristics upon various transformation condition of austempered low-alloy ductile cast iron in corrosive environments against mating specimen made of the hardened SM45C. The corrosive wear test was carried out by rubbing the annular surface of two test pieces in distilled water and aqueous solution at constant sliding speed of 0.5m/s. In severe wear region, the corrosive wear rate Wc increased hastily with NaCl concentration owing to intermetallic adhesion but Wc went down slowly in mild wear region due to lubricating effect of the corrosion product. The critical sliding distance decreased with increasing NaCl concentration due to increased generation rate of the corrosion product and the specific corrosive wear rate has maximum in 1% NaCl aqueous solution at mild wear region. With the variation of matrix, the corrosive wear resistance of the fine acicular bainite was higher than that of coarse upper bainite because of reducing the local cell reaction by carbides. A growth in volume fraction of retained austenite in matrix increased the Wc due to soften surface, but has a declining tendency of Wc in mild wear region.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.207-216
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• 2005

Spawning behaviors of Squalidus gracilis majimae (Cyprinidae) were observed in the laboratory whose environmental factors such as light (D/L = 16 : 8), temperature ($20\;{\sim}\;24\;＾{\circ}C$), and dissolved oxygen (>8 mg $L^{-1}$) were quite regularly controlled. The behavioral patterns were categorized into three stages ofpre-spawning, spawning, and Post-spawning behaviors. In Particular, the pre-spawning stage was specified by 11 specific behavioral patterns of aggressive mating behaviors. During the spawning stage, the male and female performed four distinct spawning behaviors including sexual temptation, stimulation, egg spawning, and the separation, and randomly laid about 200 ${\sim}$ 300 eggs on the bottom substrates through the night. After finishing spawning, two adults separated toward their refuges and showed 3 types of post-spawning behaviors such as the resting, occasional eggs protecting, and the egg eating. The fish was identified as a partial-parental care species after the spawning.