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Because of the media digitization, a large amount of infor- mation such as speech, audio and video data is produced everyday. In order to retrieve data for these databases quickly and precisely, multimedia tech- nologies for struc...
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Because of the media digitization, a large amount of infor- mation such as speech, audio and video data is produced everyday. In order to retrieve data for these databases quickly and precisely, multimedia tech- nologies for structuring and retrieving of speech, audio and video data are strongly required. In this paper, we overview the multimedia technologies such as structuring and retrieval of speech, audio an video data, speaker indexing, audio summarization and cross media retrieval existing today for RV news detabase.
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Spatially periodic and localized structures in the transverse plane of a medium displaying electromagnetically induced transparency in an optical cavity and under the action of two pumps are investigated. The system supports a mul...
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Spatially periodic and localized structures in the transverse plane of a medium displaying electromagnetically induced transparency in an optical cavity and under the action of two pumps are investigated. The system supports a multitude of different complex spatial structures depending on the chosen initial condition.We explore regimes of multistable patterns, filaments, stable defects, scrolling structures, nested patterns, fronts, and the spontaneous occurrence of multiple cavity solitons. To simulate realistic conditions of operation, we replace periodic boundary conditions with pumps of finite size. Many of the multistable features are recovered apart from the scrolling of patterns with defects.
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Numerical modelling of deformation in hydromechanical systems can be time-consuming using fully coupled classical numerical methods for large representative porous media samples. In this paper, we present a new two-way coupled par...
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Numerical modelling of deformation in hydromechanical systems can be time-consuming using fully coupled classical numerical methods for large representative porous media samples. In this paper, we present a new two-way coupled partitioned fluid-solid system. The coupled system is applied for simulating geomechanical processes at the pore-scale. We track the deformation of the solid resulting from the drainage of resident fluids in the pores, as well as the evolution of fluid properties from dynamic loading. The finite element method is responsible for capturing the structural deformation in the coupled system while the dynamic pore network is used for modelling multiphase flow in the fluid subsystem. A fictitious fluid-solid interface is created at each pore network-finite element node junction via convex hulling, followed by data exchange using linear interpolation. The results show good agreement with a pre-existing coupled finite volume model and the computations are completed in much less time.
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The field distribution of a symmetric surface wave (SW) propagating on a weakly ionized unmagnetized plasma placed in a cylindrical ideal waveguide, in which a quartz tube is surrounded by vacuum, is presented in the diffusion-con...
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The field distribution of a symmetric surface wave (SW) propagating on a weakly ionized unmagnetized plasma placed in a cylindrical ideal waveguide, in which a quartz tube is surrounded by vacuum, is presented in the diffusion-controlled regime. This is done to better understand the effect of some physical parameters such as electron temperature, SW frequency, etc on the plasma column. The graphs of electric and magnetic fields versus the plasma column radius under the radial electron density profile dependency are obtained in the commercial radio frequency region where spatial dispersion might be important.
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The effect of dipolar and exchange interactions on the magnetic behaviour of sputtered CoFe-Ag(Cu) granular alloys is examined through the study of remanence curves and Delta M plots as a function of the ferromagnetic volume conte...
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The effect of dipolar and exchange interactions on the magnetic behaviour of sputtered CoFe-Ag(Cu) granular alloys is examined through the study of remanence curves and Delta M plots as a function of the ferromagnetic volume content, x(nu), and annealing temperature. As-deposited samples, with either a random distribution of weakly interacting fine magnetic particles (3 nm in size) at low x(nu) or with strong dipolar and exchange interactions (leading to a long range out-of-plane stripe-like domain structure) at x(nu) greater than or equal to 0.25, display negative Delta M values. In the former, this is attributed to dipolar interactions being dominant in a random distribution of well separated particles. In the latter, Delta M < 0 is attributed to the flux closure between antiparallel neighbouring domains, which is strongly demagnetizing. Annealing causes phase segregation and particle growth, while particle clusterization occurs. These facts lead to an increase of the direct exchange through the surface of neighbouring grains in the same particle clusters, at the expense of dipolar interactions, which decrease as the clusters become more separated. Consequently, at high x(nu), annealed samples display positive Delta M values. [References: 25]
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ChemSpider provides access to over 26 million structures with data and information imported from many scientific, industrial and research based data sources. This free chemical structure database is owned and maintained by the Roy...
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ChemSpider provides access to over 26 million structures with data and information imported from many scientific, industrial and research based data sources. This free chemical structure database is owned and maintained by the Royal Society of Chemistry. However, the fact that it is free is not what makes it unique. It is the fact that it is a dynamic chemical database created by chemists for chemists. The user does not have to register to use the database.
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The potential of piezoelectric, continuously twisted, structurally chiral materials (PCTSCMs) for sensing shear waves is explored. The shear waves to be sensed are supposed to be incident normally on the open face of a PCTSCM slab...
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The potential of piezoelectric, continuously twisted, structurally chiral materials (PCTSCMs) for sensing shear waves is explored. The shear waves to be sensed are supposed to be incident normally on the open face of a PCTSCM slab with hexagonal 6mm reference crystal symmetry. The back face is assumed to be perfectly rigid. After using the quasi-electrostatic approximation, an expression for the potential difference generated across the PCTSCM slab is obtained. Numerical results confirm that the potential difference displays zonal characteristics that depend on the pitch of the PCTSCM and the operating frequency. [References: 14]
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Simple design formulae are derived for the co-, contra- and cross-handed reflection and transmission coefficients for light incident axially to a structurally chiral medium surrounded by dissimilar isotropic dielectrics. The resul...
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Simple design formulae are derived for the co-, contra- and cross-handed reflection and transmission coefficients for light incident axially to a structurally chiral medium surrounded by dissimilar isotropic dielectrics. The results obtained agree well with exact calculations over the full range of achieved experimental parameters of practically manufactured structurally chiral media. The formulae are used to illustrate a number of design strategies.
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In this paper we consider the near-tip region of a fluid-driven fracture propagating in permeable rock. We attempt to accurately resolve the coupling between the physical processes - rock breakage, fluid pressure drop in the visco...
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In this paper we consider the near-tip region of a fluid-driven fracture propagating in permeable rock. We attempt to accurately resolve the coupling between the physical processes - rock breakage, fluid pressure drop in the viscous fluid flow in the fracture and fluid exchange between the fracture and the rock - that exert influence on the hydraulic fracture propagation, yet occur over length scales often too small to be efficiently captured in existing coarse grid numerical models. We consider three fluid balance mechanisms: storage in the fracture, pore fluid leak-in from the rock into the fracture as the result of dynamic suction at the dilating crack tip, and fluid leak-off from the fracture into the rock as the fluid pressure in the fracture recovers with distance away from the tip. This process leads to the formation of a pore fluid circulation cell adjacent to the propagating fracture tip. We obtain the general numerical solution for the fracture opening and fluid pressure in the semi-infinite steadily propagating fracture model, while assuming that the hydraulic fracturing and pore fluids have the same properties. We fully characterise the solution within the problem parametric space and identify different regimes of the fracture propagation. We assess the impact of the pore fluid leak-in and the associated near-tip circulation cavity on the solution and explore limitations of the widely used, pressure-independent Carter's leak-off model. The obtained solution could be potentially used as a tip element in the finite crack models (penny-shaped, Planar3D), provided that a fast numerical implementation is further elaborated.
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Similarities and differences between the phenomena of kink banding in compressed layered structures and shear banding in compressed granular media are explored. Simple models are introduced for both, and the focus is directed onto...
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Similarities and differences between the phenomena of kink banding in compressed layered structures and shear banding in compressed granular media are explored. Simple models are introduced for both, and the focus is directed onto how they can nucleate from the perfectly flat state. A convincing scenario is found for each in which a mode develops from an initial bifurcation into a periodic state, followed by rapid localization under falling load, while retaining decaying but wavy tails. At a certain lower critical load, the tails lose their waviness, and the expected form of the kink or shear band appears. In each case, good numerical evidence is provided for the existence of this form of behaviour. A second potential instability for the layered case is also explored, linked to the appearance of a critical force dipole that overcomes bending stiffness locally at some point along the length. This mode, which should appear with non-wavy decaying tails at the lower of the two critical loads mentioned earlier, proves somewhat elusive. Evidence is found for its existence in the linearized approximation to the layered model, but the search for numerical solutions to the underlying nonlinear equation is hindered by a shortage of suitable boundary conditions.
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