• Title/Summary/Keyword: CR-structure

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CR GEOMETRY/ANALYSIS AND DEFORMATION OF ISOLATED SINGULARITIES

  • Miyajima, Kimio
    • Journal of the Korean Mathematical Society
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    • v.37 no.2
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    • pp.193-223
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    • 2000
  • In the late 1970's, M. Kuranishi proposed to control the moduli of the germ of a normal Stein space by deformations of the CR structure on the boundary. I this paper, we will see that it is naturally accomplished by considering stably embeddable deformations of CR structures.

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The Cr*-Tree Supporting a Circular Property of Objects (객체의 순환 속성을 지원하는 Cr*-트리)

  • Seon, Hwi-Jun;Kim, Hong-Ki
    • The KIPS Transactions:PartD
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    • v.10D no.7
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    • pp.1077-1088
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    • 2003
  • To increase the retrieval performance in spatial database systems, it is required to develop spatial indexing methods considered the spatial locality. The spatial locality is related to the location property of objects. The previous spatial indexing methods are not considered the circular location property that objects will be taken. In this paper, we propose a dynamic spatial index structure called $Cr^*$-tree, and evaluate the performance of the proposed index structure. This is a new spatial index structure considered the circular location property of objects in which a search space is constructed with the circular and linear domains. By the simulation results, the $Cr^*$-tree shows that the number of disk across is low and the bucket utilization is high regardless of object distribution and bucket capacity.

Corrosion Behavior and Crystal Structure of Zn-Cr Coatings by EB-PVD and Electroplating (EB-PVD법과 전기화학방법으로 형성된 Zn-Cr film의 구조와 부식특성)

  • 최한철
    • Journal of the Korean institute of surface engineering
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    • v.36 no.6
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    • pp.423-429
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    • 2003
  • It has been investigated corrosion resistance and crystal structure of Zn-Cr coatings fabricated by electroplating method and electron-beam physical vapor deposition method(EB-P VD). The electroplated Zn-Cr alloy consists mainly of η'-Zn phase for the lower Cr content than 7.9 wt% Cr and ${\gamma}$'-ZnCr phase for the higher Cr content. In the Zn-Cr alloy fabricated by EB-PVD the ${\gamma}$'-ZnCr phase appeared clearly at 3 wt% Cr and it became the sole phase at 50 wt%Cr. The amount of η'-Zn phase decreased obviously with increasing Cr content when it exceeded 15 wt% Cr. The electrochemical measurement of the electroplated Zn-Cr film has shown corrosion potential of about -1000 mV. The current density of active region and the amount of dissolved Zn and Cr decreased significantly with increasing Cr content. The electrochemical characteristics of Zn-Cr alloy fabricated by EB-PVD have shown that the alloy of 50 wt% Cr had the highest corrosion potential(-500 mV) and the lowest critical passive current density than that of the electroplated.

Corrosion Behavior of Dental Alloys Cast by Various Casting Methods (치과용 주조합금의 주조방법에 따른 부식거동)

  • Choe Han-Cheol;Ko Yeong-Mu
    • Journal of the Korean institute of surface engineering
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    • v.37 no.5
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    • pp.296-300
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    • 2004
  • The defects of partial denture frameworks are mainly shrinkage porosity, inclusions, micro-crack, particles from investment, and dendritic structure. In order to investigate a good casting condition of partial denture frameworks, the three casting alloys and casting methods were used and detected casting defects were analyzed by using electrochemical methods. Three casting alloys (63Co-27Cr-5.5Mo, 63Ni-16Cr, 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting (Kerr, USA), high frequency induction casting (Jelenko Eagle, USA), vacuum pressure casting (Bego, Germany). The casting temperature was $1,380^{\circ}C$ (63Co-27Cr-5.5Mo and 63Ni-16Cr) and $1,420^{\circ}C$ (63Co-30Cr-5Mo). The casting morphologies were analyzed using FE-SEM and EDX. The corrosion test of the dendritic structure was performed through potentiodynamic method in 0.9% NaCl solutions at $36.5^{\circ}C$ and corrosion surface was observed using SEM. The defects of partial denture frameworks improved in the order of centrifugal casting, high frequency induction casting, and vacuum pressure casting method, especially, pore defects were found at part of clasp in the case of centrifugal casting method. The structure of casting showed dendritic structure for three casting alloys. In the 63Co-27Cr-5.5Mo and 63Co-30Cr-5Mo, $\alpha$-Co and $\varepsilon$-Co phases were identified at matrix and $${\gamma}$-Ni_2$Cr second phase were shown in 63Ni-16Cr. Also, the corrosion resistance of cast structure increased in the order of vacuum pressure casting, high frequency induction casting, and centrifugal casting method.

Microstructural Features of Multicomponent FeCoCrNiSix Alloys

  • Kong, Kyeong Ho;Kim, Kang Cheol;Kim, Won Tae;Kim, Do Hyang
    • Applied Microscopy
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    • v.45 no.1
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    • pp.32-36
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    • 2015
  • The microstructural features of FeCoCrNi, FeCoCrNiAl and FeCoCrNiSix (x=0, 5, 10, 15, 20) alloys have been investigated in the present study. The microstructure of FeCoCrNi alloy changes dramatically with equiatomic addition of Al. The fcc irregular shaped grain structure in the as-cast FeCoCrNi alloy changes into the bcc interconnected structure with phase separation of Al-Ni rich and Cr-Fe rich phases in the as-cast FeCoCrNiAl alloy. The microstructure of FeCoCrNi alloy changes with the addition of Si. With increasing the amount of Si, the fcc structure of the grains is maintained, but new phase containing higher amount of Si forms at the grain boundary. As the amount of Si increases, the fraction the Si-rich grain boundary phase increases.

Phonetic Realization of Aspiration of Stops in English /Cr/ and /sCr/ Clusters and their Syllable Structure at the Phonetic Level: a Comparison between Two Speaker Groups (영어의 /Cr/과 /sCr/ 자음군 내 폐쇄음의 기식성 실현과 음성 단위의 음절구조: 두 화자집단 간 비교)

  • Sohn, Hyang-Sook
    • Phonetics and Speech Sciences
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    • v.6 no.3
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    • pp.121-130
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    • 2014
  • This study investigates the acoustic property of aspiration realized in English voiceless stops of /Cr/ and /sCr/ clusters. VOT is measured from stops in these clusters produced by two groups; one from native speakers of English and the other from Korean native speakers. Aspiration of stops in different types of clusters is compared to various phonological factors such as location of stress, syllable type, and position in word. Pursuing the idea that phonetic realization is correlated with phonological representation, attempts are made to account for the gradient nature of aspiration of stops on the basis of syllable structure at the phonetic level, which may vary in the wake of resyllabification. Voiceless stops in /Cr/ and /sCr/ clusters are further compared to results obtained in the previous study on /sC/ cluster. Variations in aspiration are also characterized in terms of segmental precedence relation of stops in the clusters, namely, post-[s], pre-[r], or both.

ON CONTACT THREE CR SUBMANIFOLDS OF A (4m + 3)-DIMENSIONAL UNIT SPHERE

  • Kwon, Jung-Hwan;Pak, Jin--Suk
    • Communications of the Korean Mathematical Society
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    • v.13 no.3
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    • pp.561-577
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    • 1998
  • We study (n+3)-dimensional contact three CR submanifolds of a Riemannian manifold with Sasakian three structure and investigate some characterizations of $S^{4r+3}$(a) $\times$ $S^{4s+3}$(b) ($a^2$$b^2$=1, 4(r + s) = n - 3) as a contact three CR sub manifold of a (4m+3)-dimensional unit sphere.

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Crystal Structure and Magnetic Properties of $(LaS)_xCrS_2(x{\approx}1.20)$ ($(LaS)_xCrS_2(x{\approx}1.20)$의 결정구조와 자기적 특성)

  • Jo, Nam-Ung;Yu, Gwang-Su;Jeong, Hyeong-Jin
    • Korean Journal of Materials Research
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    • v.4 no.6
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    • pp.704-709
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    • 1994
  • The $(LaS)_xCrS_2(x \approx 1.20$) of the incommensurate misfit layer was systhesized from reactant mixture of$La_S_3$,Cr and S at 1273K. Powder X-ray diffration of $(LaS)_xCrS_2(x \approx 1.20$) was indexed as a complex structure consisted with a monoclinic LaS-sublattice, a triclinic $CrS_{2}$-sublattice and their superlattice. The temperature dependence of sublattice dimension was investigated by the X-ray diffraction analysis at low temperature. The magnetic susceptibility of $(LaS)_xCrS_2(x \approx 1.20$) was measured between 77K and room temperature using a Faraday balance method. $(LaS)_xCrS_2(x \approx 1.20$) was paramagnetic on a $\sigma$-H plot at room temperature. The observed effective magnetic moment( p dr) was in fair agreement with the value calculated by spin-only contribution for $Cr^{3+}$ and spin and orbital contribution for $La^{3+}$.

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First-principles Study on the Magnetism and Electronic Structure of (CrAs)3(MnAs)3(110) Superlattice ((CrAs)3(MnAs)3(110) 초격자의 전자구조와 자성에 대한 제일원리 연구)

  • Lee, J.I.;Hong, S.C.
    • Journal of the Korean Magnetics Society
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    • v.16 no.2
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    • pp.111-114
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    • 2006
  • We investigated the magnetism and electronic structures for the layered structures consisting of (110) layers of zinc-blende CrAs and MnAs. We calculated the electronic structures for $(CrAs)_3(MnAs)_3(110)$ superlattice consisted of alternating three layers of CrAs(110) and MnAs(110) by the full-potential linearized augmented plane wave (FLAPW) method. The calculated magnetic moment of Cr in interface layer ($3.07\;\mu_B$) was slightly larger than that of Cr atom in center layer ($3.06\;\mu_B$), while that of interface Mn atom ($3.74\;\mu_B$) was slightly smaller than the value of Mn atom in center layer ($3.76\;\mu_B$). The electronic structure and half-metallicity in this superlattice were discussed using the calculated density of states.