168 research outputs found
A memory type boundary stabilization of a mildly damped wave equation
We consider the wave equation with a mild internal dissipation. It is proved that any small dissipation inside the domain is sufficient to uniformly stabilize the solution of this equation by means of a nonlinear feedback of memory type acting on a part of the boundary. This is established without any restriction on the space dimension and without geometrical conditions on the domain or its boundary
Soliton molecules in Fermi-Pasta-Ulam-Tsingou lattice: Gardner equation approach
We revisit the Fermi-Pasta-Ulam-Tsingou lattice (FPUT) with quadratic and
cubic nonlinear interactions in the continuous limit by deducing the Gardner
equation. Through the Hirota bilinear method, multi-soliton solutions are
obtained for the Gardner equation. Based on these solutions, we show the
excitation of an interesting class of table-top soliton molecules in the FPUT
lattice through the velocity resonance mechanism. Depending on the condition on
the free parameters, we classify them as dissociated and synthetic type
molecules. The main feature of the table-top soliton molecules is that they do
not exhibit oscillations in the coalescence region. This property ensures that
they are distinct from the soliton molecules, having retrieval force, of the
nonlinear Schr\"odinger family of systems. Further, to study the stability of
the soliton molecule we allow it to interact with a single (or multi)
soliton(s). The asymptotic analysis shows that their structures remain
constant, though the bond length varies, throughout the collision process. In
addition, we consider the FPUT lattice with quadratic nonlinear interaction and
FPUT lattice with cubic nonlinearity as sub-cases and point out the nature of
the soliton molecules for these cases also systematically. We achieve this
based on the interconnections between the solutions of the Gardner, modified
K-dV and K-dV equations. Finally, we simulate the FPUT chain corresponding to
the Gardner equation numerically and verify the existence of all the soliton
structures associated with it. We believe that the present study can be
extended to other integrable and non-integrable systems with applications in
fluid dynamics, Bose-Einstein condensates, nonlinear optics, and plasma
physics.Comment: Submitted For Publication (2023
Coupled Nonlinear Schr\"odinger System: Role of Four-Wave Mixing Effect on Nondegenerate Vector Solitons
In this paper, we investigate the role of four-wave mixing effect on the
structure of nondegenerate vector solitons and their collision dynamics. For
this purpose, we consider the generalized coupled nonlinear Schr\"odinger
(GCNLS) system which describes the evolution and nonlinear interaction of the
two optical modes. The fundamental as well as higher-order nondegenerate vector
soliton solutions are derived through the Hirota bilinear method and their
forms are rewritten in a compact way using Gram determinants. Very
interestingly, we find that the presence of four-wave mixing effect induces a
breathing vector soliton state in both the optical modes. Such breather
formation is not possible in the fundamental vector bright solitons of the
Manakov system. Then, for both strong and weak four-wave mixing effects, we
show that the nondegenerate solitons in the GCNLS system undergo, in general,
novel shape changing collisions, in addition to shape preserving collision
under suitable choice of wave numbers. Further, we analyze the degenerate
soliton collision induced novel shape changing property of nondegenerate vector
soliton by deriving the partially nondegenerate two-soliton solution. For
completeness, the various collision scenarios related to the pure degenerate
bright solitons are indicated. We believe that the results reported in this
paper will be useful in nonlinear optics for manipulating light by light
through collision.Comment: 23 pages, 15 figures, Submitted for publicatio
On Nonlinear Nonlocal Systems of Reaction Diffusion Equations
The reaction diffusion system with anomalous diffusion and a balance law ut+-Δα/2u=-fu,v,   vt+-∆β/2v=fu,v, 0<α, β<2, is con sidered. The existence of global solutions is proved in two situations: (i) a polynomial growth condition is imposed on the reaction term f when 0<α≤β≤2; (ii) no growth condition is imposed on the reaction term f when 0<β≤α≤2
Characterization of Streptomyces strain SLO-105 isolated from Lake Oubeira sediments in North-East of Algeria
A microbial strain, SLO-105, isolated from Lake Oubeira sediment was screened for its antimicrobial activity against pathogenic bacteria and fungi. The strain showed broad-spectrum antibacterial activity against Gram-positive bacteria Staphylococcus aureus MRSA, Bacillus subtilus, Micrococcus leutus,Streptococcus fecalis and fungi Aspergillus niger and Rodotorulla mucilaginosa. However, no activity of the strain was observed against Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa as well as on fungi Candida albicans. Analysis of 16S rDNA sequence and themorphological and physiological characteristics of the strain suggested that the isolate belonged to Streptomyces genus
Exponential stability of the wave equation with memory and time delay
We study the asymptotic behaviour of the wave equation with viscoelastic
damping in presence of a time-delayed damping. We prove exponential stability
if the amplitude of the time delay term is small enough
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