• Journal of the Korean Magnetics Society
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• v.14 no.4
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• pp.131-137
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• 2004

For the aim of thin electromagnetic wave absorbers used in mobile telecommunication frequency band (0.8-2.0㎓), we investigate high-frequency magnetic, dielectric and microwave absorbing properties of iron particles dispersed in rubber matrix in this study. The major experimental variables are particle shape (sphere and flake) and initial particle size (in the range 5-70 $\mu\textrm{m}$) of iron powders. High value of magnetic permeability and dielectric permittivity can be obtained in the composites containing thin plate-shape (flake) iron particles (of which thickness is less than skin depth in ㎓frequency), which can be produced by mechanical forging of spherical iron powders using an attrition mill. This result is attributed to the reduction of eddy current loss (increase of permeability) and the increase of space charge polarization (increase of permeability). The optimum initial particle size is found to be about 10 $\mu\textrm{m}$ for the attainment of the material parameters (particularly, real part of complex permeability) satisfying the wave impedance matching. With the iron powders controlled in size and shape as absorbent fillers in rubber matrix, the thickness can be reduced to about 0.7mm with respect to -5㏈ reflection loss (70% power absorption) in mobile telecommunication frequency band.

• Korean Journal of Materials Research
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• v.1 no.4
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• pp.229-235
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• 1991

A new electrode material for $Ta_2O_5$ capacitor was developed to obtain both high dielectric constant and improved electrical properties for use in DRAM. High leakage current and low breakdown field of as-deposited $Ta_2O_5$ film on Si is due to the reduction of $Ta_2O_5$ by silicon at $Ta_2O_5$/electrode interface. $Dry-O_2$ anneal improves the electrical properties of $Ta_2O_5$ capacitor with Si electrode, but it thickens the interfacial oxide and lowers the dielectric constant, subsequently. $Ta_2O_5$ capacitor with TiN exectrode shows better electrical properties and higher dielectric constant than post heat treated $Ta_2O_5$ film on Si. No interfacial oxide layer at $Ta_2O_5$/TiN interface suggests that there\`s no Interaction between $Ta_2O_5$ and electrode. TiN is a adequate electrode material for $Ta_2O_5$ capacitor.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.256-262
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• 2000

The dielectric properties of complex perovskite ($Pb_{1-x}Ca_{x}$)($Fe_{0.5}Ta_{0.5}$)$O_{3}$ with >($0.5{\le}x{\ge}0.65$ were investigated at microwave frequencies. Dilectric constant decreased with increasing Ca content, and was directly proportional to the cube of average ionic ra야 of A-site. For the specimen of x=0.6 sintered at $1250^{\circ}C$ for 3 h in air, dielectric constant (k) of 63, QF of 11000 GHz, and the temperature coefficient of resonant frequency(TCF) of -14ppm/$^{\circ}C$ were obtained. As Ca content increased, TCF of the specimen negatively increased due to the reduction of the tolerance factor(t). Changes in intrinsic loss with varying Ca content was investigated by the infrared reflectivity spectra ranging 50 to 4000 $cm^{-1}$, which were calculated by the Kramers-Kronig analysis and classical oscillator model. The relative tendency of microwave dielectric properties of the ($Pb_{1-x}Ca_{x}$)($Fe_{0.5}Ta_{0.5}$)$O_{3}$ specimens calculated from the reflectivity data were in good agreement with the results by the post resonant method.

• Korean Journal of Plant Taxonomy
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• v.43 no.2
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• pp.139-145
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• 2013

This study was carried out to determine the karyotype and chromosomal localizations of 45S and 5S rDNAs using FISH in Astragalus koraiensis. The somatic metaphase chromosome number of this species was 2n = 16 with basic chromosome number of x = 8. The karyotype of A. koraiensis was consisted of six pairs of median region chromosomes(chromosome 1, 3, 4, 5, 6, 8) and two pairs of submedian chromosomes(chromosome 2, 7). Based on the FISH, one pair of 45S rDNA site was detected on the centromeric region of chromosome 5. Whereas, two pair of 5S sites were detected on the short arm of chromosome 4 and centromeric region of chromosome 7, respectively. These are quite different patterns from A. membranaceus, A. membranaceus var. alpinus, and A. mongholicus. Although A. koraiensis is considered as Korean endemic species, therefore, it should be conducted out comparative FISH study with A. sikokianus and A. bhotanensis which are very similar to A. koraiensis morphologically.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.334-340
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• 1997

Electric and dielectric properties of the $SrTiO_3$films have been studied. The influence of impurities on $SrTiO_3$ films was evaluated to reduce the leakage current density. Acceptor doping, with a small concentration of Fe or Cr, has led to a substantial improvement to $10^{-9}$ order in the leakage current density. The experimental results can be explained by a model in which oxygen vacancies are the key defects responsible for the leakage current. The $SrTiO_3$ film 200 nm in thickness with 5 mol% excess SrO fabricated in $Ar/O_2$ at $550^{\circ}C$ obtained the lowest leakage current density $1.0 {\times} 1.0 A/\textrm{cm}^2$. The improved results can be introduced into the capacitor dielectric of giga bit DRAM memories.

• Korean Journal of Plant Taxonomy
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• v.46 no.4
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• pp.371-377
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• 2016

The succulent herbaceous perennial Sedum sarmentosum commonly grows in the southern part of the Korean Peninsula. It is a species native to China, most likely introduced into Korea due to its edible and medicinal uses. If plants were introduced from a single source, we would expect no or low levels of genetic variation in Korean populations. Alternatively, if plants were introduced from multiple sources, we would expect, in contrast, high levels of genetic diversity. To test which is more likely, we surveyed the degree of allozyme variation in ten populations of this species from southern Korea. We found that S. sarmentosum was monomorphic at all fifteen allozyme loci. However, two congeners (S. polytrichoides and S. kamtschaticum) and two related species (Hylotelephium ussuriense and H. verticillatum) maintain moderate to high levels of genetic diversity ($H_e=0.144$, 0.203, 0.201, and 0.204, respectively). We suggest that southern Korean populations of S. sarmentosum likely descended from a single introduction of a few plants and then became naturalized exclusively via vegetative spreading (as plants in Korea, but also as occurs in other parts of its native and naturalized range, are sterile).

• Korean Journal of Microbiology
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• v.55 no.3
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• pp.242-247
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• 2019

Biological factors (e.g. microorganism activity) in wastewater treatment plant (WWTP) play essential roles for degradation and/or removal of organic matters. In this study, to understand the microbial functional roles in WWTP, we tried to isolate and characterize a bacterial strain from activated sludge sample. Strain S16 was isolated from the activated sludge of a municipal WWTP in Daejeon metropolitan city, the Republic of Korea. The cells were a Gram-stain-positive, non-motile, facultative anaerobe, and rod-shaped. Strain S16 grew at a temperature of $15{\sim}40^{\circ}C$ (optimum, $30^{\circ}C$), with 0~9.0% (w/v) NaCl (optimum, 1.0~2.0%), and at pH 5.5~9.0 (optimum, pH 7.0~7.5). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S16 was most closely related to the unique species Miniimonas arenae NBRC $106267^T$ (99.79%, 16S rRNA gene sequence similarity) of the genus Miniimonas. The cell wall contained alanine, glutamic acid, serine, and ornithine. Although the isolation source of the type strain NBRC $106267^T$ which considered as a marine microorganism is sea sand, that of strain S16 is terrestrial environment. It might raise an ecological question for habitat transition. Therefore, comparative genome analysis will be valuable investigation for shedding light on their potential metabolic traits and genomic streamlining.

• Journal of Life Science
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• v.32 no.9
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• pp.690-697
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• 2022

This study was conducted to analyze genome of red sea cucumber and to use it as basic data for the development of genetic markers for red sea cucumber. Microsatellite marker analysis of Ulleungdo_normal and Ulleungdo_native red sea cucumbers revealed that dinucleotide simple sequence repeats (SSRs) had the highest ratio, at 81.3~81.4%, and the number of the detected SSRs tended to decrease as the number of repeating sequence units in SSRs increased. In general, microsatellites with between 5 and 10 iterations were most common. As the size of the SSR repeating sequence units increased, the SSR iterations gradually decreased. The di-, tri-, and tetra-nucleotides in SSRs were detected in the highest numbers as (AT)₅, (AAT)₅, and (AAAT)₅, respectively. (CG) and (CCG) had very low frequencies compared to the numbers of other repeating SSR units. The numbers of di-and tri-nucleotide repeats were up to 35 and 32, respectively, and then increased discontinuously up to 44 and 43 repeats, respectively. Tetra-, penta-, and hexa-nucleotides in SSRs occurred in numbers up to 25, 21 and 14, respectively. This analysis of red sea cucumber indicated that it maintains its own repetition sequence and repetition number; therefore, we suggest that using it as basic data for molecular marker will be possible in future research.

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.45-48
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• 2006

The characteristics of plantlets redifferentiated from calli of F1 hybrid between Panax ginseng and Panax quinquefolius were investigated. Growth of plantlets redifferentiated from F1 hybrid was superior to the plants redifferentiated from Korean ginseng. Stem color of plantlets redifferentiated from F1 hybrid was more purple than that from Korean ginseng and leaf color of the former was also greener than that of the latter. Chunpoong, Yunpoong and Seonweon which are belonged to Korean ginseng showed same PCR band(A), while American ginseng showed different PCR band (B) in Internal Transcribed Spacer (ITS) region. F1 hybrid exhibited both A and B PCR band which belonged to Korean ginseng and American ginseng, respectively. F1 hybrid calli and plantlets redifferentiated from F1 hybrid calli showed same PCR band with that of F1 hybrid plant in ITS region. Therefore it was confirmed that piantlets redifferentiated from F1 hybrid exhibited genetic stability in ITS region.

• Journal of Aquaculture
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• v.22 no.1
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• pp.79-82
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• 2009

Reciprocal interspecific hybrids between two bitterling species Rhodeus uyekii (RU) and R. notatus (RN) were genetically identified based on the partial sequence analysis of recombination activating gene-1 (RAG-1) gene. Out of 863 bp positions analyzed, 13 nucleotide substitutions were detected between the two parental species (RU and RN genotypes). Both the induced hybrids (RU female$\times$RN male; UN genotype) and their reciprocal counterparts (RN female$\times$RU male; NU genotype) displayed the double peaks (or polymorphism) of sequence chromatograms at the 13 diagnostic positions, indicating that those hybrids were actual karyogamy derived from the two parental haploid genomes. However, it was not possible to distinguish between the reciprocal interspecific hybrids.