• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.313-324
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• 2004

A rich phenomenon in the dynamics of azimuthal vortices in a circular cylinder caused by the inertial oscillation is investigated numerically at high Reynolds numbers and moderate Rossby numbers. In the actual spin-up flow where both the Ekman circulation and the bottom friction effects are included, the first appearance of a seed vortex is generated by the Ekman boundary-layer on the bottom wall and the subsequent roll-up near the corner bounded by the side wall. The existence of the small vortex then rapidly propagates toward the inviscid region and induces a complicated pattern in the distribution of azimuthal vorticity, i.e. inertial oscillation. The inertial oscillation however does not deteriorate the classical Ekman-pumping model in the time scale larger than that of the oscillatory motion. Motions of single vortex and a pair of vortices are further investigated under a slip boundary-condition on the solid walls. For the case of single vortex, repeated change of the vorticity sign is observed together with typical propagation of inertial waves. For the case of a pair of vortices with a two-step profile in the initial azimuthal velocity, the vortices' movement toward the outer region is resisted by the crescent-shape vortices surrounding the pair. After touching the border between the core and outer regions, the pair vortices weaken very fast.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.242-245
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• 2009

AlN crystals were grown by a sublimation process without seed crystals and the growth morphology of them was characterized. The grown AlN crystals were a polycrystalline phase, which had a diameter of $60\sim200\;{\mu}m$ and were grown with a growth rate of $0.2\sim0.5\;{\mu}n/hr$. It was observed that the as-grown crystals had a hexagonal crystal structure and revealed that these crystals were grown with a morphology of columnar morphology in the initial stage of the growth before they were enlarged in a way of a lateral growth behavior in the final stage. On the surface, a lot of pinholes were observed on the surface of crystals grown. The evolution of a growth morphology was characterized by optical and scanning electron microscopic observation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.155-163
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• 2008

This paper presents a novel framework for analysis of power system wide-area blackout based on so called fault cascading scenarios. For a given power system operating state, "triggering" faults or a "seed faults" are chosen based on the probabilities estimated from the hazard rates. The fault probabilities reflect both the load and the weather conditions. Effects of hidden failures in protection systems are also reflected in establishing the fault propagation scenarios since they are one of the major causes for the wide-area blackouts. A tree type data structure called a PS-BEST(Power System Blackout Event Scenario Tree) is proposed for construction of the fault cascading scenarios, in which nodes represent various power system operating states and the arcs are the events causing transitions between the states. Arcs can be either probabilistic or deterministic. For a given initial fault, the total probability of leading to wide-area blackout is estimated by aggregating the individual probability of each fault sequence route leading to wide-area blackout. A case study is performed on the IEEE RTS-79(24 bus) system based on the fault data presented by the North American Electrical Reliability Council(NERC). Test results demonstrate the potentials and the effectiveness of the proposed technique for the future wide-area blackout analysis.

• Asian-Australasian Journal of Animal Sciences
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• v.3 no.3
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• pp.177-182
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• 1990

A reproductive potential trial using randomized complete block design with $3{\times}3{\times}2$ factorial, was conducted on 84 Baluchi yearling ewes. Ewes grazed on rangeland dominated by Artemisia maritime and Holoxylon grifthii with or without flushing and supplementation of barley grain (BG) and cotton-seed-cake (CSC) during premating, late pregnancy and lactation of 90 days. Analysis of variance revealed that conception rate which ranged 64.28 to 85.71, was significantly greater (p<.05) in ewes flushed with CSC followed by ewes under BG or control feeding regimes. During the gestation period, liveweight of ewes changed from 31.24 to 21.2 kg. A loss of 32% of initial body weight was observed at lambing. Losses in live weight of ewes, regardless the supplementation, were uniform and non-significantly different. Live weight of ewes at lambing and weaning were also similar. Birth weight of lambs was significantly different at p<.05. Lambs born to larger ewes seemed to be heavier than lighter ones. Lambs suckling to ewes with losses in body weight during lactation gained more weight which was significantly different at p<.05. In the paper, factors affecting the conception rate, changes in liveweight of ewes during gestation and lactation and subsequently growth of lambs are discussed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.3 no.3
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• pp.203-209
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• 2002

The Korean venture industry showed a rapid growth due to various government incentive measures, development in information technology, and explosive growth of the KOSDAQ market. Recently, however, the Korean venture industry has revealed numerous side effects, which seemed to be coming from excessively aggressive government involvement in the industry, and fallen into a deep depression. This phenomenon may imply that the Korean venture industry has been established by the government policy rather than based on the venture capital market, whereas the venture industry in advanced nations has grown up autogenously based on it. This paper analyzes the Korean venture capital market and suggests policy recommendations to revitalize the domestic venture capital market. They include facilitating the supply of funds through limited partnerships and overseas venture capital, extending the direct equity investment, and actively promoting the KOSDAQ market.

• Microbiology and Biotechnology Letters
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• v.20 no.2
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• pp.203-206
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• 1992

Conditions of fermentation for the production of demethyltetracycline were examined using the mutant, which was obtained through the cell fusion of demeclocycline producing strains, The optimum temperature and the initial pH of broth for demethyltetracycline fermentation were $25^{\circ}C$ and 6.7, respectively. Unlike any other cases, the control of pH with alkali solution during the fermentation process affected the productivity. As a general rule, the larger the inoculum size the higher the early consumption of sugar and the viscosity of broth, which means that fermentation proceeds more rapidly as the inoculum size is increased. The highest productivity was shown when the inoculum size was 5% (v/v), and the phase of seed also influenced the fermentation. Among the parameters of pre-culture thus examined, pH was the most important factor.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.3
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• pp.252-258
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• 2013

The quality and quantity of food organisms in fish seed production are important. The marine microalgae Nannochloropsis oculata are used as initial food organisms in the field. We investigated the effects of salinity (0, 10, 20, 30, 40 and 50 psu) on the lipid and fatty acid composition of N. oculata. Cultivation of N. oculata at varying salinities showed the highest growth rate at 20 psu. Total lipid content ranged from 17.26 to 18.63% at salinities from 0 to 50 psu). The nonpolar lipid content increased markedly at 30 psu and was highest at 15.55%. The polar lipid content was lowest at 30 psu, by 84.45%. It was also found that the omega-3 and EPA contents were inversely proportional to salt concentration. For the polar and nonpolar lipid compositions, there was no significant effect of salinity. Omega-3 polyunsaturated fatty acid content especially the content of EPA in the seawater larvae is the essential fatty acid in this food organism. It is thus advantageous to culture N. oculata at 20 psu.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.8
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• pp.451-454
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• 2000

We have grown vertically aligned carbon nanotubes in a large area of Co-Ni codeposited Si substrates by the thermal CVD usign $C_2H_2$ gas. Since the discovery of carbon nanotubes, growth of carbon nanotubes has been achieved by several methods such as laser vaporization, arc discharge, and pyrolysis. In particular, growth of vertically aligned nanotubes is important to flat panel display applications. Recently, vertically aligned carbon nanotubes have been grown on glass by PECVD. Aligned carbon nanotubes can be also grown on mesoporous silica and Fe patterned porous silicon using CVD. In this paper, we demonstrate that carbon nanotubes can be vertically aligned on catalyzed Si substrate when the domain density of catalytic particles reaches a certain value. We suggest that steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically and each nonotubes are grown in bundle.

• Korean Journal of Plant Taxonomy
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• v.48 no.3
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• pp.218-229
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• 2018

Myanmar's plant diversity is expected to be very high given the wide variety of climates and the diverse vegetation and geographical features of the country. Since the publication of Kress et al.'s plant checklist in 2003, new and unrecorded species have been constantly reported by various botanists, but much of Myanmar's flora requires more intensive examinations. We conducted joint floristic surveys of several Ywangan areas, including the Panlaung-Pyadalin Cave Wildlife Sanctuary in southern Shan State of Myanmar. The initial identification of seed plant specimens collected from three short floristic expeditions revealed that 23 species were newly recorded species in Myanmar. More than half of these were found to be geographically notable species, which are known to be endemic to neighboring countries such as China (4 spp.), Thailand (6 spp.), and India (2 spp.). A considerable number of these unrecorded species are distributed in the limestone areas of neighboring countries, reflecting the geological characteristics of the survey area. The results of this study reemphasize the need for intensive and continuous research on the flora of Myanmar for a more comprehensive understanding of the distribution patterns of flowering plants in Southeast Asia.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.625-630
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• 2014

The amount of information is increasing rapidly with the development of the internet and the computer. Since these enormous information is managed by the document forms, it is necessary to search and process them efficiently. The document clustering technique which clusters the related documents through the similarity between the documents help to classify, search, and process the large amount of documents automatically. This paper proposes a method to find the initial seed points through principal component analysis when the documents represented by vectors in the feature vector space are clustered by K-means algorithm in order to increase clustering performance. The experiment shows that our method has a better performance than the traditional K-means algorithm.