• 대한수학회지
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• 제45권6호
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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).

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 2008년도 International Meeting of the Microbiological Society of Korea
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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.

• 한국주조공학회지
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• 제26권6호
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• pp.272-276
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• 2006

[ $CaCO_3$ ]를 발포제로 사용하여 균일한 기공구조를 가지는 AZ91과 AM60 마그네슘 합금의 발포 금속을 주조법을 통하석 제조하였다. 발포 금속의 제조가 가능한 이유와 발포 마그네슘 합금의 기공구조가 연구를 통하여 논의되었다. 마그네슘 합금의 용탕은 $CaCO_3$의 분해 거동에 영향을 미친다. 제조된 AZ91 마그네슘 합금의 발포 금속은 높은 기공률과 큰 기공의 크기를 가졌으며, 발포 금속들 중에서 상대적으로 쉽게 발포되는 것으로 판단된다.

• 센서학회지
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• 제23권6호
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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.

• 대한본초학회지
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• 제33권3호
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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.

• 한국버섯학회지
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• 제22권1호
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• pp.17-21
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• 2024

균사 매트를 글리세롤로 가소화 하여 기호성 코팅을 적용한 개 껌은 기존의 균사 매트의 맛과 향이 모두 개선되어 강아지가 무리 없이 시식하는 결과를 보였다. 향후 개선방향으로 질김 수준을 저하시키기 위해 연육 공정이 포함될 수 있으며, 조섬유 함량을 낮추는 공정도 고려할 수 있다. 환경에 유해하지 않은 친환경 소재 및 공정으로 제조된 균사 매트 기반 개 껌은 물성이 조절되어 출시할 경우 친환경 반려동물용 간식으로써 시장 진입이 가능할 것으로 보인다.

• 대한기계학회논문집
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• 제18권11호
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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.

• 식물조직배양학회지
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• 제25권6호
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• pp.477-485
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• 1998

감자 plastid 형질전찬을 위한 새로운 DNA 절편을 확보하고자, 감자의 trnK-matK 유전자를 PCR 방법으로 클로닝하고 특성을 조사하였다. 염기서열 분석을 통하여 trnK-matK 유전자에는 두 종류의 polymerase 인지부위[Prokaryotic site(plastid encoded polymerase)와 eukaryotic site (nuclear-encoded polymerase)]가 족재함을 알 수 있었다. 이 사실은 trnK-matK 유전자의 발현이 광합성조직과 비광합성조직에서 서로 다른 polymerase에 의하여 조절됨을 시사하였다. 한편 MatK의 아미노산서열을 분석한 결과 식물에 따라 아미노산 identity가 39-75%로 다양하였으나, 감자와 담배는 98%의 아주 높은 identity를 보였다. Northern분석을 통하여 포장과 기내에서 생육된 감자 식물체 모두에서, trnK-matK 의 전사 수준이 잎에서 높고 괴경에서는 낮음을 알 수 있었다. 한편 잎에서의 16s rDNA의 전사수준은 괴경에 비해 약 50배 높았다. 이것으로 미루어보아 괴경에서 수준이 낮을 것은, 괴경에서는 plastid genome copy 수가 적거나 plastid 수가 적기 때문으로 추정된다. 이상의 결과로서 엽록체와 amyloplst 모두에서 trunK-matK 유전자가 활발하게 발현되고 있음을 알 수 있었다. Plastid genomic DNA의 Southern 분석을 통하여 trnK는 1 copy로 존재하고, matK는 trnK intron을 포함하고 있음을 확인하였다. 따라서 감자 plastid형질전환의 새로운homologous recombination 부위로 trnK-matK유전자를 이용할 수 있을 것이다.

• 대한수학회보
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• 제47권4호
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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.

• East Asian mathematical journal
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• 제14권2호
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• pp.259-268
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• 1998

In this paper, for a commutative ring R with an identity, considering the endomorphism ring $End_R$(M) of left R-module $_RM$ which is (quasi-)injective or (quasi-)projective, some discriminations of prime endomorphism were found as follows: each epimorphism with the irreducible(or simple) kernel on a (quasi-)injective module and each monomorphism with maximal image on a (quasi-)projective module are prime. It was shown that for a field F, any given square matrix in $Mat_{n{\times}n}$(F) with maximal image and irreducible kernel is a prime matrix, furthermore, any given matrix in $Mat_{n{\times}n}$(F) for any field F can be factored into a product of prime matrices.