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排序方式: 共有321条查询结果,搜索用时 15 毫秒
101.
102.
No Heading We found a rich variety of vortex structures when a thin superconducting film (SC) is covered with a lattice of out-of-plane magnetized magnetic dots (MDs). The vortices are confined to the MD regions, and antivortices nucleate into regular lattices which relax through several second order transitions towards single-dot vortex-antivortex configurations with increasing period of the magnetic array. Creation of vortex-antivortex pairs with increasing MD-magnetization is controlled by a single quantity - the superfluid velocity. We demonstrate that due to the vortex-antivortex pairs and the supercurrents induced by the MDs, the critical current in the sample actually increases if exposed to a homogeneous external magnetic field, contrary to conventional SC behavior. We explain further experimental implications, such as the magnetic field-induced-superconductivity.PACS numbers: 74.78.–w, 74.25.Op, 74.25.Qt, 74.25.Dw. 相似文献
103.
G. R. Berdiyorov M. V. Milošević F. M. Peeters 《Journal of Low Temperature Physics》2005,139(1):229-238
No Heading We consider a mesoscopic square superconductor with 2 × 2 blind holes in the presence of a homogeneous magnetic field. Under suitable conditions a diagonal L = 2 state is realized and the system reduces to double degenerate states with different flux configurations, which can be considered as logic states. We show the possibility of manipulation of these states by circulating currents in a loop near the superconductor.PACS numbers: 74.20.De, 85.25.Hv, 74.78.Na, 74.25.Qt, 74.25.Ha. 相似文献
104.
105.
Numan Almonasy Miloš Nepraš Šárka Hyková Antonin Lyčka Jiři Čermák Miroslav Dvořák Martin Michl 《Dyes and Pigments》2009,82(3):416-421
An alternative procedure has been described for the syntheses of several bi- and trichromophoric compounds consisting of 1-aminopyrene and 3-aminobenzanthrone chromophoric subsystems connected by an s-triazinyl ring spacer. The synthetic method used, which utilises an autoclave under autogenous pressure, is suitable for the nucleophilic substitution of both chlorine atoms within the triazinyl ring by weakly basic aromatic amines. The structures of the synthesized compounds were confirmed using elemental analysis, 1H NMR, and mass spectra. UV/vis absorption and fluorescence spectra and fluorescence quantum yields were measured. The dependence of fluorescence intensity and fluorescence quantum yields on solvent polarity was investigated. 相似文献
106.
107.
Johann Boucl Sabina Chyla Milo S. P. Shaffer James R. Durrant Donal D. C. Bradley Jenny Nelson 《Advanced functional materials》2008,18(4):622-633
Hybrid bulk heterojunction solar cells based on nanocrystalline TiO2 (nc‐TiO2) nanorods capped with trioctylphosphine oxide (TOPO) and regioregular poly(3‐hexylthiophene) (P3HT) are processed from solution and characterized in order to relate the device function (optical absorption, charge separation, and transport and photovoltaic properties) to active‐layer properties and device parameters. Annealing the blend films is found to greatly improve the polymer–metal oxide interaction at the nc‐TiO2/P3HT interface, resulting in a six‐fold increase of the charge separation yield and improved photovoltaic device performance under simulated solar illumination. In addition, the influence of the organic ligand at the nc‐TiO2 particle surface is found to be crucial for charge separation. Ligand‐exchange procedures applied on the TOPO‐capped nc‐TiO2 nanorods with an amphiphilic ruthenium‐based dye are found to further improve the charge‐separation yield at the polymer–nanocrystal interface. However, the poor photocurrents generated in the hybrid blend devices, before and after ligand exchange, suggest that transport within or between nanoparticles limits performance. By comparison with other donor–acceptor bulk heterojunction systems, we conclude that charge transport in the nc‐TiO2:P3HT blend films is limited by the presence of an intrinsic trap distribution mainly associated with the nc‐TiO2 particles. 相似文献
108.
We have conducted research on the process for producing thermal insulation materials using calcium silicates with the addition
of glass fibres. These materials have excellent refractoriness, heat resistance, mechanical strength and dimensional stability
and are suitable for refractory coatings, as heat insulators, and as a lagging product.
Resume Nous avons mené une recherche sur le processus de fabrication de matériaux d’isolation avec des silicates de calcium renforcés de fibres de verre. Ces isolants présentent d’excelllentes résistances à la chaleur et au feu, aussi bien que de bonnes résistance mécanique et stabilité dimensionelle, et se prêtent donc à la confection de revêtements réfractaires, d’isolants thermiques et de calorifuges.相似文献
109.
XML documents are often viewed as trees (basically the parse tree
of the document), and queries over such documents typically test
for ancestor relationships among tree nodes. Search engines
process such queries using an index structure summarizing the
ancestor relations. In the index, each document item (tree node)
is identified using some logical id (node label), such that, given
two labels, the engine can determine the ancestor relationship
between the corresponding nodes. The length of the labels is a
main factor of the index size. Therefore, reducing this length,
even by a constant factor, is a critical issue. In this work we consider the
following problem. Given a rooted XML tree
T, label the nodes of T in the most compact way such that
given the labels of two nodes, one can determine in constant time, by
looking at the labels only, whether one node is an ancestor of the
other. Labelings currently being used are all variants of the
following interval scheme. Number the leaves say from left to right and label each
node with a pair consisting of the numbers of its smallest and largest
leaf descendants. An ancestor query then amounts to an interval
containment test on the labels. The maximum label length
using this scheme is 2 log n, where n is the number of nodes
in the tree. (All logarithms in this paper are to base 2.) The focus of this work is finding
a scheme that works best in practice on real XML data. We suggest an orthogonal prefix-based approach, where the labeling
is such that an ancestor query roughly amounts
to testing whether one label is a prefix of the other. We present
several new labeling schemes based on this approach and analyze
their performance both theoretically and empirically. 相似文献
110.
Within the non-linear Ginzburg-Landau (GL) theory, we investigate the vortex structure of a thin type II superconductor with a ferromagnetic dot on top of it. Spontaneous creation of vortex-antivortex pairs as well as specific arrangements of vortices are found. We show that the equilibrium vortex phase diagram depends on the size of the magnetic dot and its magnetization, and we discuss the shell structure of the multivortex states with magic numbers which are size and magnetization dependent. 相似文献