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Synthesis and Dielectric Properties of New Niobate Ba_5BiTi_3Nb_7O_(30)

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Journal of Wuhan University of Technology(Materials Science) 2003年第1期18卷 29-30页

作者：张辉 WuhanUniversityofTechnology

A new niobate Ba 5BiTi 3Nb 7O 30 was synthesized by the solid state *** was characterized by X ray diffraction and dielectric constant *** results show that Ba 5BiTi 3Nb 7O 30 is paraelectric at room temperature and belongs to tetragonal 4/mmm symmetry with unit cell parameters a=1.25020 nm,c=0.39704 *** 5BiTi 3Nb 7O 30 has only one phase transition,paraelectric to ferroelectric,below 0℃.

关键词： niobate structural analyses dielectric properties

Geological,structural and Mineralogical Approach to Investigate the Evolution of Low-and very Low-Grade Metamorphic Units from the Intra-Pontide Suture Zone,Central Pontides,Turkey

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Journal of Earth Science 2021年第6期32卷 1512-1527页

作者： Alessandro Ellero Chiara Frassi Mehmet Cemal Göncüoğlu Marco Lezzerini Michele Marroni Giuseppe Ottria Luca Pandolfi Kaan Sayit Marco Tamponi Istituto di Geoscienze e Georisorse-CNR Via G.Moruzzi 156124PisaItaly Dipartimento di Scienze della Terra Universitàdi PisaVia S.Maria 5356126PisaItaly Department of Geological Engineering Middle East Technical University06800AnkaraTurkey

A multidisciplinary approach combining multiscale geological-structural analyses(from field to microscale) and clay mineral transformations(clay mineralogy, illite and chlorite "crystallinity" and b cell dimension(b_(0)) of K-white mica) was adopted to unravel the tectono-metamorphic evolution of low-and very low-grade tectono-metamorphic units from the Intra-Pontide suture zone in northern Turkey. The mineralogical study allowed to better evaluate the structural stacking outlined during the geological mapping, leading to distinguish three tectono-metamorphic units, two in epizone(Daday and Emirkoy units) and one in anchizone(Cifter Unit) metamorphic conditions. The mesostructural and microstructural analyses suggest a polyphase tectonic-metamorphic evolution. The different macroscopic features observed between the two units characterized by the same epizone metamorphism, can be justified by the evidence that these metamorphic conditions were acquired during the last stages of exhumation in the Daday Unit, while they constrained the metamorphic-peak conditions in the Emirkoy Unit. Contemporary analyses and comparison between structural and mineralogical data have thus proven to be a powerful tool to investigate the low-grade and very low-grade metamorphic environments, allowing at the same time to solve the apparent contradictions deriving from the mineralogical study and to significantly improve the detail of the geological mapping in the field.

关键词： clay minerals structural analyses low-temperature metamorphism epizone anchizone diagenesis Intra-Pontide suture zone Turkey

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Design of the Cryostat for HT-7U Superconducting Tokamak

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Plasma Science and Technology 2002年第3期4卷 1297-1304页

作者：郁杰武松涛宋云涛翁佩德 Institute of Plasma Physics Chinese Academy of Sciences Hefei 230031 China

The cryostat of HT-7U tokamak is a large vacuum vessel surrounding the entirebasic machine with a cylindrical shell, a dished top and a flat bottom. The main function ofHT-7U cryostat is to provide a thermal barrier between an ambient temperature test hall and aliquid helium-cooled superconducting magnet. The loads applied to the cryostat are from sourcesof vacuum pressure, dead weight, seismic events and electromagnetic forces originated by eddycurrents. It also provides feed-through penetrations for all the connecting elements inside andoutside the cryostat. The main material selected for the cryostat is stainless steel 304L. Thestructural analyses including buckling for the cryostat vessel under the plasma operation conditionhave been carried out by using a finite element code. Stress analysis results show that the maximumstress intensity was below the allowable value. In this paper, the structural analyses and designof HT-7U cryostat are emphasized.

关键词： structural analyses superconducting magnet finite element code cylindrical shell temperature test stress intensity stainless steel vacuum vessel eddy currents