| 11. |
- Anderson, D., et al.
(author)
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Modulational instabilities within the thermal wave model description of high energy charged particle beam dynamics
- 1999
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In: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 258:4-6, s. 244-248
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Journal article (peer-reviewed)abstract
- Within the thermal wave model (TWM) description, an investigation was made of the longitudinal instability properties of a coasting high energy charged particle beam, where the interaction between the beam and its surroundings is characterized in terms of a complex impedance. The analysis is shown to correctly reproduce the characteristic features of the coherent instability as obtained previously by conventional techniques based on the Vlasov equation for the beam distribution. The results further validate the TWM approach as a consistent alternative description for analyzing the dynamics of high energy charged particle beams.
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| 12. |
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| 13. |
- Cattani, F., et al.
(author)
-
Effect of self-phase modulation in chirped-pulse-amplification-like schemes
- 1999
-
In: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 16:11, s. 1874-1879
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Journal article (peer-reviewed)abstract
- A detailed analytical investigation is made of the effect of nonlinear self-phase modulation in chirped-pulse-amplification-like schemes. It is demonstrated that self-phase modulation in the amplifier between the stretcher and the compressor breaks the dispersive sign symmetry of the configuration. This implies that, although self-phase modulation is usually considered a deleterious effect, different situations are possible, depending on the parameter regimes considered. In particular, the influence of self-phase modulation on the low-intensity wings of the compressed pulse may be more or less deleterious, depending on the dispersive sign combination of the stretcher and the compressor; in certain parameter regimes, it may in fact even enhance the pulse compression.
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| 14. |
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| 15. |
- Dimitrevski, K., et al.
(author)
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Analysis of stable self-trapping of laser beams in cubic-quintic nonlinear media
- 1998
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In: Physics Letters A. - : Elsevier. - 0375-9601 .- 1873-2429. ; 248:5-6, s. 369-376
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Journal article (peer-reviewed)abstract
- A numerical and analytical analysis of two-dimensional laser beam propagation in cubic-quintic nonlinear optical media demonstrates the existence of stable stationary radially symmetric modes. By means of a variational method, involving super-Gaussian trial functions and Ritz optimization, approximate stationary solutions are obtained, showing very good agreement with numerical results, even in the strongly non-linear, almost saturated, regime. The stability of the stationary modes are verified by analytical analysis and by direct numerical simulations.
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| 16. |
- Harvey, P, et al.
(author)
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The electric field instrument on the Polar satellite
- 1995
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In: Space Science Reviews. - 0038-6308 .- 1572-9672. ; 71, s. 583-596
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Journal article (peer-reviewed)abstract
- The Polar satellite carries a system of four wire booms in the spacecraft spin plane and two rigid booms along the spin axis. Each of the booms has a spherical sensor at its tip along with nearby guard and stub surfaces whose potentials relative to that of their sphere are controlled by associated electronics. The potential differences between opposite sphere pairs are measured to yield the three components of the DC to >1 MHz electric field. Spheres can also be operated in a mode in which their collected current is measured to give information on the plasma density and its fluctuations. The scientific studies to be performed by this experiment as well as the mechanical and electrical properties of the detector system are described.
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| 17. |
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| 18. |
- Malomed, B. A., et al.
(author)
-
Decay of parametric solitons in a lossy medium with quadratic nonlinearity
- 1996
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In: Pure and Applied Optics (Print edition) (United Kingdom). - : IOP Publishing. - 0963-9659. ; 5:6, s. 941-946
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Journal article (peer-reviewed)abstract
- An investigation is made into the evolution of two-wave solitons in a second-haimonic-generation system under the action of weak dissipation. Using the balance equation for the soliton energy and a previously developed variational approximation for its shape, a general evolutional equation is derived for the soliton parameters. The equation is solved explicitly for the asymptotic stage of the evolution
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| 19. |
- Malomed, B. A., et al.
(author)
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Spatiotemporal solitons in multidimensional optical media with a quadratic nonlinearity
- 1997
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In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 56:4, s. 4725-4735
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Journal article (peer-reviewed)abstract
- We consider solutions to the second-harmonic generation equations in two- and three-dimensional dispersive media in the form of solitons localized in space and time. As is known, collapse does not take place in these models, which is why the solitons may be stable. The general solution is obtained in an approximate analytical form by means of a variational approach, which also allows the stability of the solutions to be predicted. Then, we directly simulate the two-dimensional case, taking the initial configuration as suggested by the variational approximation. We thus demonstrate that spatiotemporal solitons indeed exist and are stable. Furthermore, they are not, in the general case, equivalent to the previously known cylindrical spatial solitons. Direct simulations generate solitons with some internal oscillations. However, these oscillations neither grow nor do they exhibit any significant radiative damping. Numerical solutions of the stationary version of the equations produce the same solitons in their unperturbed form, i.e., without internal oscillations. Strictly stable solitons exist only if the system has anomalous dispersion at both the fundamental harmonic and second harmonic (SH), including the case of zero dispersion at SH. Quasistationary solitons, decaying extremely slowly into radiation, are found in the presence of weak normal dispersion at the second-harmonic frequency
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| 20. |
- Pettersson, Kerstin, 1944-
(author)
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Strong n-generators in some one-dimensional domains
- 1998
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Doctoral thesis (other academic/artistic)abstract
- Let R be a commutative Noetherian one-dimensional domain such that each ideal in R can be generated by n elements. A strong n-generator in R is an element r which can be chosen as one of n generators for each ideal in which it is contained. If moreover r is contained in some ideal requiring n generators, then r is said to be a proper strong n-generator. We prove that if R is two-generated, then r is a strong two-generator if and only if r doesn't belong to Mˆ2 for any non-invertible maximal ideal M of R. Let S be an index set such that for each i in S, M(i) is a maximal ideal such that the localization of R at M(i) possesses an ideal requiring n generators. We show that there is a unique biggest M(i)-primary ideal I(i) in R requiring n generators. We prove that r is a strong n-generator if and only if r doesn't belong to I(i)M(i) for any i in S. Let R' be the integral closure of R. Suppose moreover that the conductor C of R' in R is non-zero. We prove that if n > 2, then r is a proper strong n-generator if and only if r belongs to the complement of I(i)M(i) in I(i) for some i in S. And if n = 2, then r is a proper strong two-generator if and only if r belongs to the complement of Mˆ2 in M for some non-invertible maximal ideal M of R or r belongs to some non-principal invertible maximal ideal of R. We prove that if C requires n generators, then R is n-generated and the extension of C to the localization of R at M(i) for some i in S requires n generators.Suppose moreover that R is a Cohen-Macaulay ring, R possesses a superficial element and R' is a local domain. Then (R,M) is a local domain. Let B(M) be the blowing-up ring of R at M. We give an algorithm for determining the conductor J of B(M) in R. We determine the reduction exponent of M for a semigroup ring and give a sufficient condition for J not being a power of M.
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