The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Nabil Kahale - One of the best experts on this subject based on the ideXlab platform.
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on the second eigenvalue and Linear Expansion of regular graphs
Foundations of Computer Science, 1992Co-Authors: Nabil KahaleAbstract:The authors investigate the relation between the second eigen-value and the Linear Expansion of regular graphs. The spectral method is the best currently known technique to prove lower bounds on the Expansion. He improves this technique by showing that the Expansion coefficient of Linear-sized subsets of a k-regular graph G is at least k/2(1- square root max(0,1-/sub lambda 1(G)2//sup 4k-4/))/sup -/ , where lambda /sub 1/(G) is the second largest eigenvalue of the graph. In particular, the Linear Expansion of Ramanujan graphs, which have the property that the second largest eigenvalue is at most 2 square root k-1, is at least (k/2)/sup -/. This improves upon the best previously known lower bound of 3(k-2)/8. For any integer k such that k-1 is prime, he explicitly constructs an infinite family of k-regular graphs G/sub n/ on n vertices whose Linear Expansion is k/2 and such that lambda /sub 1/(G/sub n/) >
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Expanding Graphs - On the second eigenvalue and Linear Expansion of regular graphs
Proceedings. 33rd Annual Symposium on Foundations of Computer Science, 1992Co-Authors: Nabil KahaleAbstract:The authors investigate the relation between the second eigen-value and the Linear Expansion of regular graphs. The spectral method is the best currently known technique to prove lower bounds on the Expansion. He improves this technique by showing that the Expansion coefficient of Linear-sized subsets of a k-regular graph G is at least k/2(1- square root max(0,1-/sub lambda 1(G)2//sup 4k-4/))/sup -/ , where lambda /sub 1/(G) is the second largest eigenvalue of the graph. In particular, the Linear Expansion of Ramanujan graphs, which have the property that the second largest eigenvalue is at most 2 square root k-1, is at least (k/2)/sup -/. This improves upon the best previously known lower bound of 3(k-2)/8. For any integer k such that k-1 is prime, he explicitly constructs an infinite family of k-regular graphs G/sub n/ on n vertices whose Linear Expansion is k/2 and such that lambda /sub 1/(G/sub n/) >
Sergey Lavruk - One of the best experts on this subject based on the ideXlab platform.
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exit of a heterogeneous detonation wave into a channel with Linear Expansion ii critical propagation condition
Combustion Explosion and Shock Waves, 2018Co-Authors: A. V. Fedorov, T A Khmel, Sergey LavrukAbstract:Propagation of a detonation wave in monodisperse suspensions of reacting particles (based on the model of the suspension of aluminum particles in oxygen) in channels with Linear Expansion is studied within the framework of mechanics of heterogeneous reacting media. Reduced kinetics is described with allowance for the transitional (from diffusion to kinetic) regime of combustion of micron-sized and submicron-sized spherical aluminum particles. The effects of the channel width, particle diameter, and Expansion angle on propagation conditions and detonation regimes are determined. The critical channel width is found to be a nonmonotonic function of the Expansion angle, which is associated with qualitatively different wave patterns behind an oblique step. Flow charts are constructed, and the results are compared with solutions of problems of heterogeneous detonation wave propagation in channels with a backward-facing step and with sudden Expansion.
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exit of a heterogeneous detonation wave into a channel with Linear Expansion i propagation regimes
Combustion Explosion and Shock Waves, 2017Co-Authors: A. V. Fedorov, T A Khmel, Sergey LavrukAbstract:Propagation of a plane detonation wave in a stoichiometric mixture of a gas and aluminum particles in a plane channel with a Linear Expansion section is studied by methods of numerical simulation. The slope of the wall is varied from 15 to 60°. The basic regimes of detonation propagation are analyzed: supercritical (without detonation failure), critical (with partial failure and re-initiation), and subcritical (with complete separation of the shock front and combustion front and with detonation failure). The detonation configuration formed in the expanding section can be a cellular structure with large differences in cell sizes at large angles of Expansion or a close-to-uniform structure at the wall angle of 15°.
A. V. Fedorov - One of the best experts on this subject based on the ideXlab platform.
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exit of a heterogeneous detonation wave into a channel with Linear Expansion ii critical propagation condition
Combustion Explosion and Shock Waves, 2018Co-Authors: A. V. Fedorov, T A Khmel, Sergey LavrukAbstract:Propagation of a detonation wave in monodisperse suspensions of reacting particles (based on the model of the suspension of aluminum particles in oxygen) in channels with Linear Expansion is studied within the framework of mechanics of heterogeneous reacting media. Reduced kinetics is described with allowance for the transitional (from diffusion to kinetic) regime of combustion of micron-sized and submicron-sized spherical aluminum particles. The effects of the channel width, particle diameter, and Expansion angle on propagation conditions and detonation regimes are determined. The critical channel width is found to be a nonmonotonic function of the Expansion angle, which is associated with qualitatively different wave patterns behind an oblique step. Flow charts are constructed, and the results are compared with solutions of problems of heterogeneous detonation wave propagation in channels with a backward-facing step and with sudden Expansion.
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exit of a heterogeneous detonation wave into a channel with Linear Expansion i propagation regimes
Combustion Explosion and Shock Waves, 2017Co-Authors: A. V. Fedorov, T A Khmel, Sergey LavrukAbstract:Propagation of a plane detonation wave in a stoichiometric mixture of a gas and aluminum particles in a plane channel with a Linear Expansion section is studied by methods of numerical simulation. The slope of the wall is varied from 15 to 60°. The basic regimes of detonation propagation are analyzed: supercritical (without detonation failure), critical (with partial failure and re-initiation), and subcritical (with complete separation of the shock front and combustion front and with detonation failure). The detonation configuration formed in the expanding section can be a cellular structure with large differences in cell sizes at large angles of Expansion or a close-to-uniform structure at the wall angle of 15°.
Robert Monjo - One of the best experts on this subject based on the ideXlab platform.
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Study of the observational compatibility of an inhomogeneous cosmology with Linear Expansion according to SNe Ia
Physical Review D, 2017Co-Authors: Robert MonjoAbstract:Most of current cosmological theories are built combining an isotropic and homogeneous manifold with a scale factor that depends on time. If one supposes a hyperconical universe with Linear Expansion, an inhomogeneous metric can be obtained by an appropriate transformation that preserves the proper time. This model locally tends to a flat Friedman-Robertson-Walker metric with Linear Expansion. The objective of this work is to analyze the observational compatibility of the inhomogeneous metric considered. For this purpose, the corresponding luminosity distance was obtained and was compared with the observations of 580 SNe Ia, taken from the Supernova Cosmology Project. The best fit of the hyperconical model obtains χ20=562, the same value as the standard ΛCDM model. Finally, a possible relationship is found between both theories.
T. G. Mammadov - One of the best experts on this subject based on the ideXlab platform.
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Effect of electric field on negative Linear Expansion of ferroelectric-semiconductor TlGaSe2
Journal of Applied Physics, 2009Co-Authors: Mirhasan Yu. Seyidov, Rauf A. Suleymanov, Emin Yakar, N. A. Abdullayev, T. G. MammadovAbstract:The effect of electric field on the thermal Expansion of the TlGaSe2 ferroelectric-semiconductor with a layer crystalline structure has been investigated. A strong transformation of negative Linear Expansion coefficient in the layer plane has been observed as a result of the applied electric field. It was concluded that internal electric fields created by local polarized states in the ferroelectric- semiconductor are responsible for a negative thermal Expansion and its behavior under the electric field. Predominantly, the electrostriction effect is the driving mechanism of the lattice deformation of TlGaSe2 crystals at low temperatures.
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Effect of illumination on negative Linear Expansion of TlGaSe2 layered crystals
Journal of Physics and Chemistry of Solids, 2008Co-Authors: Mirhasan Yu. Seyidov, Rauf A. Suleymanov, Emin Yakar, N. A. Abdullayev, T. G. MammadovAbstract:Abstract Effect of illumination on negative thermal Expansion of TlGaSe 2 crystals has been investigated. Strong trasformation of negative Linear Expansion coefficient has been observed after the illuminations. It is supposed that two main mechanisms are responsible for observed effect: formation of photoelectret states and reverse piezoelectric effect. The electronic nature of negative Linear Expansion of TlGaSe 2 crystals has been proved for the first time.
