• Korean Journal of Materials Research
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• v.12 no.4
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• pp.240-247
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• 2002

Tin oxide thin films doped with silicon as anodes for lithium secondary battery were fabricated by R.F. magnetron sputtering technique. The electrochemical results showed that the irreversible capacity was reduced during the first discharge/charge cycle, because the audition of silicon decreased the oxidic state of Tin. Capacity was increased with the increase of substrate temperature, however decreased with the increase of RTA temperatures. The reversible capacity of thin films fabricated under the substrate temperature of $300^{\circ}C$ and the Ar:$O_2$ratio of 7:3 was 700mA/g.

• Journal of the Korean Mathematical Society
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• v.45 no.6
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• pp.1647-1659
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• 2008

Let R be a ring with identity, X the set of all nonzero, nonunits of R and G the group of all units of R. First, we investigate some connected conditions of the zero-divisor graph $\Gamma(R)$ of a noncommutative ring R as follows: (1) if $\Gamma(R)$ has no sources and no sinks, then $\Gamma(R)$ is connected and diameter of $\Gamma(R)$, denoted by diam($\Gamma(R)$) (resp. girth of $\Gamma(R)$, denoted by g($\Gamma(R)$)) is equal to or less than 3; (2) if X is a union of finite number of orbits under the left (resp. right) regular action on X by G, then $\Gamma(R)$ is connected and diam($\Gamma(R)$) (resp. g($\Gamma(R)$)) is equal to or less than 3, in addition, if R is local, then there is a vertex of $\Gamma(R)$ which is adjacent to every other vertices in $\Gamma(R)$; (3) if R is unit-regular, then $\Gamma(R)$ is connected and diam($\Gamma(R)$) (resp. g($\Gamma(R)$)) is equal to or less than 3. Next, we investigate the graph automorphisms group of $\Gamma(Mat_2(\mathbb{Z}_p))$ where $Mat_2(\mathbb{Z}_p)$ is the ring of 2 by 2 matrices over the galois field $\mathbb{Z}_p$ (p is any prime).

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.118-118
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• 2008

The phylogenetic diversity of microbial communities in calcareous mats from Spearfish Creek, a freshwater stream located in the Black Hills of South Dakota, was examined using PCR-based 16S rDNA sequence analysis. In this study, two types of calcareous mats were compared: mature mats formed on the natural substrate of rock surfaces and developing mats on an artificial substrate of glass slides. Among 63 unique isolates from a clone library of 16S rRNA genes from mature mat samples, there were 8 phyla of Bacteria represented. The predominant phylum was Proteobacteria (48%), with the $\beta$ subclass being the largest group. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes from slide samples collected at intervals for four months showed considerable diversity of the microbial community from the earliest stages of community development. Amplicons isolated from DGGE gels and sequenced indicated that community succession has occurred without increasing microbial diversity. However, light microscopic analysis revealed a significant increase in microbial cell density throughout the community development. Scanning electron microscopy of mat samples provides evidence that diatoms are also important members of calcareous mat communities.

• Journal of Korea Foundry Society
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• v.26 no.6
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• pp.272-276
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• 2006

For the first time AZ91 (MgAl9Zn1) and AM60 (MgAl6) Mg alloy foams with homogeneous pore structures were prepared successfully via melting foaming method by using $CaCO_3$ powder as blowing agent. The possible foaming mechanisms and pore structures of these Mg alloy foams were discussed and investigated. The results show that Mg alloy melt can affect $CaCO_3$ decomposition behavior and AZ91 Mg alloy is relative easy to be foamed into metal foam with high porosity and big pore size.

• Journal of Sensor Science and Technology
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• v.23 no.6
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• pp.383-387
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• 2014

Electrically conductive polypyrrole-polyvinylpyrrolidone (PPy-PVP) nanofiber mats with a core-shell structure have been successfully fabricated by a two-step process: the formation of FeCl3-containing PVP nanofiber mat by electrospinning, and the vapor-phase polymerization (VPP) of pyrrole monomer on the mat in a sealed chamber at room temperature. Surface morphology and chemical composition of the PPy-PVP mat were characterized by SEM, EDX and FTIR analyses. The as-prepared nonwoven mat was composed of PPy-PVP nanofibers with an average diameter of 300 nm. The sheet conductivity of the nanofiber mat was measured to be approximately 0.01 S/cm by a four-point probe. We have also investigated gas-sensing properties of PPy-PVP nanofiber mat upon exposure to methanol vapor. The PPy-PVP nanofiber sensors were observed to have excellent methanol-sensing performance. The nanofiber-based core-shell nanostructure could give an opportunity to fabricate a highly sensitive and fast response sensor due to its high surfaceto-volume ratio.

• The Korea Journal of Herbology
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• v.33 no.3
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• pp.25-35
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• 2018

Objectives : Lepidii seu Descurainiae Semen has been frequently adulterated with the seeds of several inauthentic plant species. However, the accurate identification of these plant seeds is very difficult. To develop a reliable genetic authentication tool for Lepidii seu Descurainiae Semen, we analyzed matK sequence. Methods : To obtain the matK sequences of plant materials, genomic DNA was extracted from 24 samples and PCR amplification was carried out using matK-AF/matK-8R universal primer set and matK-LDSF/matK-LDSR primer set. For identifying species-specific nucleotides and phylogenetic analysis, matK regions were sequenced and comparatively analyzed by the ClustalW and Maximum Likelihood method. Results : We developed a new primer set to amplify matK region in Lepidii seu Descurainiae Semen and closely related plant samples. From the comparative analysis of matK sequences, we identified species-specific marker nucleotides for D. sophia, L. apetalum, L. latifolium, E. cheiranthoides, E. macilentum, and D. nemorosa, respectively. Furthermore, phylogenetic analysis revealed clear classification depending on the species. These results indicated that the matK sequence obtained a new primer set in this study was useful to identify Lepidii seu Descurainiae Semen in species level. Conclusions : We developed a primer set and identified species-specific marker nucleotides enough to distinguish authentic Lepidii seu Descurainiae Semen and adulterants at the species level based on the matK sequences. These genetic tool will be useful to prevent adulteration and to standardize the quality of Lepidii seu Descurainiae Semen.

• Journal of Mushroom
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• v.22 no.1
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• pp.17-21
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• 2024

Mushroom-based vegan meat has thus far been used as a food for humans instead of pets. However, based on its texture and nutritional content, it is considered suitable for processing into pet treats. In the present study, we developed a prototype dog chew with a sweetening coating added to a fungal mycelium mat obtained by culturing the Basidiomycetous fungus Trametes orientalis. The palatable coating applied to the mycelium mat by plasticizing the mat with glycerol improved the taste and aroma of the existing mat, and the dog consumed it without difficulty. Future improvements may include a softening process to reduce the chewiness level and a procedure to reduce the crude fiber content. Mycelium-mat-based dog chews, manufactured using eco-friendly materials and processes that are not harmful to the environment are expected to enter the market as eco-friendly alternatives to conventional pet treats. Controlling their physical properties require further study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.11
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• pp.2860-2870
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• 1994

When crack are detected in aged turbine rotors of power plants, information on fracture resistance of the aged material at operating temperature is needed for determination of critical loading condition and residual life of the turbine. In this study, fracture toughness (J$_lc$) and tearing modulus(T$_mat$) of virgin and thermally degraded 1Cr-1Mo-0.25V steel, which is one of the most widely used rotor steels, were measured at 538.deg. C according to ASTM E813 and ASTM E1152, respectively. Five kinds of specimen with different degradation levels were prepared by isothermal aging heat treatment at $630^{\circ}C.$ It was observed that J$_lc$ and T$_mat$ value decreased as the degradation level increased. Analysis of microstructures using a scanning electron microscope showed that the decrement of J$_lc$ is related to segregation of impurities at grain boundaries. It was also verified that the DC electric potential drop method is accurate and reliable for crack length monitoring at elevated temperature.

• Korean Journal of Plant Tissue Culture
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• v.25 no.6
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• pp.477-485
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• 1998

To underatand in vitro regulation of differentiation, the effects of growth regulators and nitrogen source on metabolism of cell wall polysaccharides in suspension culture of kidney bean (Phaseolus vulgaris L.) were investigated. The suspension cells (cell clusters) were directly induced from the epicotyl segments of the seedlings, which were cultivated in MS medium supplemented with 1.0mg/L of 2,4-D and 0.5 mg/L of kinetin. When compared with cell wall sugar contents of the epicotyl segments, the cellulose content of the suspension-cultured cells decreased; while the pectin and hemicellulose content increased; suggesting increases of rhamnogalacturonan I and arabinogalactan IIduring the dedifferentiation, respectively, The effects of growth regulators(2,4-D, 1.0mg/L and kinetin, 0.5mg/L) and nitrogen source (potasium nitrate, 19.0mg/L and ammonium nitrate, 16.5 g/L) in the medium on the proliferation and the turnover of the cell wall polysaccharides were investigated for 30 days. In the medium with growth regulators and without nitrogen source, the proliferation rate was extremely high (16 folds). Growth regulators and nitrogen source increased the pectin content. Analysis of neutral sugar composition of pectin fraction showed that nitrogen source enhanced rhamnose level remarkably, suggesting that rhamnogalacturonan I was the one most likely synthesized. In hemicellulose fraction, growth regulators reduced arabinose level, suggesting that arabinogalactan II was degraded. And nitrogen source reduced galactose level, suggesting that xyloglucan was also degraded.

• Bulletin of the Korean Mathematical Society
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• v.47 no.4
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• pp.715-726
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• 2010

We continue the study of fully idempotent rings initiated by Courter. It is shown that a (semi)prime ring, but not fully idempotent, can be always constructed from any (semi)prime ring. It is shown that the full idempotence is both Morita invariant and a hereditary radical property, obtaining $hs(Mat_n(R))\;=\;Mat_n(hs(R))$ for any ring R where hs(-) means the sum of all fully idempotent ideals. A non-semiprimitive fully idempotent ring with identity is constructed from the Smoktunowicz's simple nil ring. It is proved that the full idempotence is preserved by the classical quotient rings. More properties of fully idempotent rings are examined and necessary examples are found or constructed in the process.