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排序方式: 共有179条查询结果,搜索用时 15 毫秒
1.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
2.
3.
4.
The crystal structure of La3ReO8, prepared at 1425°C, is reported to be different from a previous result on a preparation at 900°C (BAUD et al., 1979). The high temperature modification crystallizes in the monoclinic space group P21/m with a = 7.757(1), b = 7.777(1), c = 5.928(1) Å, γ = 111.1°, Z = 2. The structure was solved by Patterson and Fourier methods from single crystal diffractometer data and refined to final R(F) = 0,073. The structure consists of isolated, distorted ReO6 octahedra and double chains of edge-shared La4O tetrahedra. 相似文献
5.
The crystal structures of the high-temperature modifications of sodium and silver orthophosphates have been determined using powder neutron diffraction (PND) data. II-Na3PO4 adopts the space group Fm3m with
at 400°C. The PO3−4 group is centered around the origin, but it shows high orientational disorder. The sodium ions occupy the
and
sites. II-Ag3PO4, at 650°C, is similar with
. The structure of I-Ag3PO4 at room temperature
has been re-examined by single-crystal X-ray diffraction. The derived model, with R=0.019 for 116 independent reflections, is in agreement with the latest work reported in the literature. The structure of I-Ag3PO4 at 375°C, as determined by PND, has
, and displays no gross modifications from that observed at 25°C, although the anisotropic nature of the silver sites is markedly more pronounced at this higher temperature. The cation mobility is discussed in relation to the high-temperatures structures. 相似文献
Full-size image (<1K)
6.
Kim DS Forster PM de Delgado GD Park SE Cheetham AK 《Dalton transactions (Cambridge, England : 2003)》2004,(20):3365-3369
We have obtained three layered hybrid materials from the hydrothermal reaction of 4-cyclohexene-1,2-dicarboxylic acid with Co and Mn salts: Co(C(8)H(8)O(4))[1], Mn(H(2)O)(C(8)H(8)O(4))[2], and Mn(4)(H(2)O)(C(8)H(8)O(4))(4).0.3(H(2)O)[3]. The structures for all materials were solved by single-crystal XRD ([1]P1, a=4.805(2) A, b=6.650(3) A, c=12.960(6) A, alpha=98.285(7) degrees, beta=98.986(7) degrees, gamma=95.689(7) degrees, V= 401.6(3) A(3), R(1)= 0.0438; [2] P2(1)/c, a=11.151(2) A, b=11.330(2) A, c=7.6560(15) A, beta=108.813(3) degrees , V=915.6(3) A(3), R(1)=0.0412; [3] P1, a= 11.412(3) A, b=12.136(4) A, c=13.809(4) A, alpha=104.703(6) degrees, beta=103.207(6) degrees, gamma=92.468(5) degrees, V=1790.6(9) A(3), R(1)=0.1056). While all three structures are two-dimensional overall, the metal-oxygen-metal dimensionality within the layers varies from isolated metal atoms in the case of [1] to 1D ribbons of vertex sharing MnO(6) octahedra [2] and 2D arrays of edge- and vertex-sharing polyhedra in [3]. 相似文献
7.
Nilgün KABAY Yasemin BAYGU Metin AK zzet KARA EsraNur KAYA Mahmut DURMU Yaar G
K 《Turkish Journal of Chemistry》2021,45(1):143
The current study describes the synthesis, electrochemical, computational, and photochemical properties of octa (3-hydroxypropylthio) substituted cobalt (II) ( 4 ), copper (II) ( 5 ), nickel (II) ( 6 ) and zinc(II) ( 7 ) phthalocyanine derivatives. These novel compounds were characterized by elemental analysis,1H,13C NMR, FT-IR, UV-Vis, and MS. The redox behaviors of these metallo-phthalocyanines were investigated by the cyclic voltammetric method. The optimized molecular structure and gauge-including atomic orbital (GIAO)1H and13C NMR chemical shift values of these phthalocyanines in the ground state had been calculated by using B3LYP/6–31G(d,p) basis set. The outcomes of the optimized molecular structure were given and compared with the experimental NMR values. The photochemical properties including photodegradation and singlet oxygen generation of zinc(II) phthalocyanine were studied in DMSO solution for the determination of its photosensitizer behaviors. 相似文献
8.
9.
H.S.S. Ramakrishna Matte A.K. Cheetham C.N.R. Rao 《Solid State Communications》2009,149(23-24):908-910
Hybrid organic–inorganic framework compounds constitute an important class of materials whose properties, especially paired ones, have not been adequately investigated hitherto. In this communication, we report the non-linear optical properties of hybrid compounds exhibiting interesting magnetic properties. 相似文献
10.
Zibo Zhang Rayner J.P. Cheetham A.D. Lund T. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(1):104-112
This paper reports work on the development of an automatic control system for a Helicon plasma processing source. The lack of a definitive physical model for the plasma physics of the source and the power coupling mechanism to the plasma precludes the use of traditional control algorithms. This paper develops a fuzzy model that simulates the behavior of the plasma source using the process of genetic algorithms to identify and optimize the parameters of the fuzzy model. This type of model will eventually be used to test a fuzzy control system for the plasma source. In this work, an extensive set of experimental data was acquired where the magnetic field and input power to the plasma source were varied over a wide range while the electron number density was measured. From this learning dataset, the genetic algorithm derived the values of the parameters for the difference equation that describes the system. The fuzzy model so constructed was used to predict the behavior of the source from known input parameters. Comparing the predictions with experimental observations showed that the fuzzy model was generally able to predict the behavior of the plasma as its input parameters were varied with a precision of better than 10% 相似文献