• Journal of Mechanical Science and Technology
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• v.14 no.6
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• pp.633-644
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• 2000

Recently, in proportion to the increase of earthquake occurrence-frequency and its strength in the countries within the circum-pan Pacific earthquake belt, a concept of earthquake-proof design for huge structures containing liquid has been growing up. This study deals with the refinement of classical numerical approaches for the free vibration analysis of separated structure and liquid motions. According to the liquid-structure interaction, LNG-storage tanks exhibit two distinguished eigenmodes, the sloshing mode and the bulging mode. For the sloshing -mode analysis, we refine the classical rigid-tank model by reflecting the container flexibility. While, for the bulging-mode analysis, we refine the classical uncoupled structural vibration system by taking the liquid free-surface fluctuation into consideration. We first construct the refined dynamic models for both problems, and present the refined numerical procedures. Furthermore, in order for the efficient treatment of large-scale matrices, we employ the Lanczos iteration scheme and the frontal-solver for our test FEM program. With the developed program we carry out numerical experiments illustrating the theoretical results.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.299-303
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• 2005

The crystal structure and ferroelectricity of the $(1-x)BiFeO_3\;(BF)-xPbTiO_3$ (PT) ceramic system with the addition of $DyFeO_3$ (DF) have been investigated for attaining a high temperature piezoelectric material. This study is focused on the relation between crystal structure and ferroelectric property with the addition of DF over the phase boundary in the (1-x)BF-xPT system. Hysteresis curves of polarization-electric field at room temperature have been measured. The X-ray and neutron diffraction data were analyzed by the rietveld refinement method. The addition of 0.1 mole DF into BF-PT system greatly increases the ferroelectric remanant polarization Pr values, e.g. 17 ${\mu}C/cm^2$ in 0.6BF-yDF-(0.4-y)PT and 31${\mu}C/cm^2$ in 0.5BF-yDF-(0.5.y)PT, respectively. The improved Pr value has been discussed in relation with crystal structure and electrical property.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1048-1049
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• 2006

Rapidly solidified ribbon-consolidation processing was applied for preparation of high strength bulk Mg-Zn-Gd alloys. Mg alloys have been used in automotive and aerospace industries. Rapid solidification (RS) process is suitable for the development of high strength Mg alloys, because the process realizes grain-refinement, increase in homogeneity, and so on. Recently, several nanocrystalline Mg-Zn-Y alloys with high specific tensile strength and large elongation have been developed by rapidly solidified powder metallurgy (RS P/M) process. Mg-Zn-Y RS P/M alloys are characterized by long period ordered (LPO) structure and sub-micron fine grains. The both additions of rare earth elements and zinc remarkably improved the mechanical properties of RS Mg alloys. Mg-Zn-Gd alloy also forms LPO structure in -Mg matrix coherently, therefore, it is expected that the RS Mg-Zn-Gd alloys have excellent mechanical properties. In this study, we have developed high strength RS Mg-Zn-Gd alloys with LPO structure and nanometer-scale precipitates by RS ribbon-consolidation processing. $Mg_{97}Zn_1Gd_2$ and $Mg_{95.5}Zn_{1.5}Gd_3$ and $Mg_{94}Zn_2Gd_4$ bulk alloys exhibited high tensile yield strength (470 MPa and 525 MPa and 566 MPa) and large elongation (5.5% and 2.8% and 2.4%).

• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.1-5
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• 2003

[ $LiNi_{1-x}Co_xO_2\;(x=0.0\~1.0)$ ] powders were synthesized by citrate method, and their crystal structures and electrochemical performance as the cathode material in Li secondary batteries were analyzed. X-ray diffraction analysis revealed that all the samples carry a single phase regardless of the Co substitution. The results of Rietveld refinement suggested that the crystal structure of solid solutions varies according to the Co substitution. When the Co substitution is low $(x=0.3\~0.5)$, the solid solutions carry a cubic-like structure with a relatively small value in the ratio of lattice parameters (c/a). The solid solutions made with a higher Co substitution (x=0.7), however, exhibit a layered structure with a higher c/a ratio. This difference was also observed in the electrochemical voltage spectroscopy (EVS) profiles, whereby the Co component in scarcely substituted materials shows a charging reaction at $3.7V\;(vs.\;Li/Li^+)$, but in the heavily substituted ones at 3.92V.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.1
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• pp.11-18
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• 2013

Rapid advances of computational power and method have made it practical to apply the time-consuming calculations with all-atom force fields and sophisticated potential energies into refining NMR structure. Added to the all-atom force field, generalized-Born implicit solvent model (GBIS) contributes substantially to improving the qualities of the resulting NMR structures. GBIS approximates the effects that explicit solvents bring about even with fairly reduced computational times. Although GBIS is employed in the final stage of NMR structure calculation with experimental restraints, the effects by GBIS on structures have been reported notable. However, the detailed effect is little studied in a quantitative way. In this study, we report GBIS refinements of ubiquitin and GB1 structures by six GBIS models of AMBER package with experimental distance and backbone torsion angle restraints. Of GBIS models tested, the calculations with igb=7 option generated the closest structures to those determined by X-ray both in ubiquitin and GB1 from the viewpoints of root-mean-square deviations. Those with igb=5 yielded the second best results. Our data suggest that the degrees of improvements vary under different GBIS models and the proper selection of GBIS model can lead to better results.

• Journal of the Korean Magnetic Resonance Society
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• v.2 no.2
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• pp.85-105
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• 1998

Prions cause neurodegenerative diseases in animals and humans. The scrapie prion protein (PrPSc) is the major-possibly only-component of the infectious prion and is generated from the cellular isoform (PrPC) by a conformational change. Limited proteolysis of PrPSc produces an polypeptide comprised primarily of residues 90 to 231, which retains infectivity. The three-dimensional structure of rPrP(90-231), a recombinant protein resembling PrPC with the Syrian hamster (SHa) sequence, was solved using multidimensional NMR. Low-resolution structures of rPrP(90-231), synthetic peptides up to 56 residues, a longer (29-231, full-length) protein with SHa sequence, and a short here further structure refinement of rPrP(90-231) and dynamic features of the protein. Consideration of these features in the context of published data suggests regions of conformational heterogeneity, structural elements involved in the PrPC\longrightarrowPrPSc transformation, and possible structural features related to a species barrier to transmission of prion diseases.

• Archives of Pharmacal Research
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• v.25 no.3
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• pp.275-279
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• 2002

The crystal structure of byakangelicin, one of furanocoumarin aldose reductase inhibitors, was determined by X-ray diffraction method. The crystal is triclinic, with a=8.114(1), b=10.194(1), $c=11.428(1)\AA,{\;}{\alpha}=111.50(1),{\}{\beta}=95.57(1),{\}{\gamma}=112.52(1)^{circ},{\;}D_x=1.41,{\;}D_m=1.39{\;}g/cm^3$, space group P1 and Z=2. The intensity data were collected by ${\omega}-2{\theta}$ scan method with $CuK_{a}$ radiations. The structure was solved by direct method and refined by full matrix least-squares procedure to the final R-value of 0.056. There are two molecules with different conformations in an asymmetric unit. The molecules are kept by two intermolecular O-HO type hydrogen bonds and van der Waal's forces in the crystal. The absolute configuration of the molecules was estimated to S-form by the 'Eta refinement' procedure.

• Korean Journal of Materials Research
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• v.4 no.2
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• pp.177-186
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• 1994

The effect of solidification condition and vibration on structure refinement was investigatedfor unidirectionally solidified $AI-CuAI_{2}$ eutectic composites. Eutectic composites were unidirectionally solidifiedunder vibration with variation of growth rates (R) and thermal gradient((G), $32^{\circ}C$/cm, and 35$^{\circ}C$/cm. The lamellar structure was varied according to growth condition(G/R ratio). For the structure refinementthe effect of G/R was found out to be greater rather than that of vibration. The interlamellarspacing(l) in this materials was varied with the growth rates(R) by "$\lambda^{2}R$=Constant" relationshipquot; relationship

• Bulletin of the Korean Chemical Society
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• v.11 no.1
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• pp.15-19
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• 1990

The crystal structure of $(C_{12}H_{24}O_6{\cdot}K)_2K[Co(OH)_6Mo_6O_{18}]{\cdot}12H_2O$ has been determined by X-ray diffraction. Crystal data as follows ; monoclinic, space group $C_2/m,\;a\;=\;22.512(4)\;{\AA},\;b\;=\;18.304(4)\;{\AA},\;c\;=\;7.641(1)\;{\AA},\;{\beta}\;=\;90.52(2)\;{\AA}$, and Z = 2. A final conventional R value of 0.044 was obtained by least-squares refinement of 4173 independent observed $[{\mid}Fo{\mid}{\geq}3{\sigma}({\mid}Fo{\mid})]$ reflections. The $[Co(OH)_6Mo_6O_}{18}]^{-3}$ polyanion shows the well-known Anderson-structure and has approximate 3m symmetry. A $[Co(OH)_6Mo_6O_{18}]^{-3}$ polyanion is located between two crown ether complexed cations forming a sandwich structure. One potassium ion interacts with the crown ether via electrostatic interactions. The other potassium ion only interacts with the water molecules and terminal oxygen atoms of the polyanion.

• Bulletin of the Korean Chemical Society
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• v.19 no.4
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• pp.457-462
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• 1998

A chiral pentadentate bis-amide ligand, 1,9-bis(S)-pyrrolidinyl-2,5,8-triazanonane-1,9-dio ne$(S,S-prodienH_2)$ has been synthesized from the reaction of bis(2-aminoethyl)amine(dien) and S-proline, and the structure of $[Co(S,S-prodien)H_2O]ClO_4$ has be en determined by single crystal X-ray diffraction. The geometrical structure of the Co(III) complex has been an αβ -form, where the dien moiety of ligand chelates to a facial in metal center, and the aqua ligand coordinates a cis site to the secondary nitrogen of dien. The Co-N(1), Co-N(3) distances of two amide moiety in S,S-prodien are shorter than the other Co-N(2), Co-N(4), and Co-N(5) distances because of the increased basicity of nitrogen in amide. The complex crystallizes in the monoclinic space group $P2_1$(#4), with a=7.838(1), b=12.675(1), c=9.710(1) Å, β=100.39(1) and z=2. Refinement gives the final R and $R_w$ values of 0.045 and 0.057, respectively for 2130 observed reflections. Based upon the CD and X-ray data, it is identified that the absolute configuration of the αβ -$[Co(S,S-prodien)H_2O]ClO_4$ has a Λ-form.