Topic
Envelope (waves)
About: Envelope (waves) is a research topic. Over the lifetime, 9198 publications have been published within this topic receiving 107734 citations. The topic is also known as: wave envelope.
Papers published on a yearly basis
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Papers
TL;DR: In this paper, the problem of the gravitational collapse of isothermal spheres by applying the similarity method to the gas-dynamic flow is considered, and two types of similarity solutions are obtained: one is the prototype for starting states which correspond to unstable hydrostatic equilibrium; the other, for states where the mass of the cloud slightly exceeds the maximum limit allowable for hydrostatic equilibria.
Abstract: We consider the problem of the gravitational collapse of isothermal spheres by applying the similarity method to the gas-dynamic flow. We argue that a previous solution obtained by Larson and Penston to describe the stages prior to core formation is physically artificial; however, we find that the flow following core formation does exhibit self-similar properties.The latter similarity solution shows that the inflow in the dense central regions proceeds virtually at free-fall before the material is arrested by a strong radiating shock upon impact with the surface of the core. Two types of similarity solutions are obtained: one is the prototype for starting states which correspond to unstable hydrostatic equilibrium; the other, for states where the mass of the cloud slightly exceeds the maximum limit allowable for hydrostatic equilibrium. In both cases, an r/sup -2/ law holds for the density distribution in the static or nearly static outer envelope, and an r/sup -3///sup 2/ law holds for the freely falling inner envelope. Rapid infall is initiated at the head of the expansion wave associated with the dropping of the central regions from beneath the envelope. A numerical example is presented which is shown to be in good agreement with the envelopemore » dynamics obtained in previous studies of star formation using hydrodynamic codes.« less
2,003 citations
TL;DR: The generation of intense, few-cycle laser pulses with a stable carrier envelope phase that permit the triggering and steering of microscopic motion with an ultimate precision limited only by quantum mechanical uncertainty are reported.
Abstract: The amplitude and frequency of laser light can be routinely measured and controlled on a femtosecond (10(-15) s) timescale. However, in pulses comprising just a few wave cycles, the amplitude envelope and carrier frequency are not sufficient to characterize and control laser radiation, because evolution of the light field is also influenced by a shift of the carrier wave with respect to the pulse peak. This so-called carrier-envelope phase has been predicted and observed to affect strong-field phenomena, but random shot-to-shot shifts have prevented the reproducible guiding of atomic processes using the electric field of light. Here we report the generation of intense, few-cycle laser pulses with a stable carrier envelope phase that permit the triggering and steering of microscopic motion with an ultimate precision limited only by quantum mechanical uncertainty. Using these reproducible light waveforms, we create light-induced atomic currents in ionized matter; the motion of the electronic wave packets can be controlled on timescales shorter than 250 attoseconds (250 x 10(-18) s). This enables us to control the attosecond temporal structure of coherent soft X-ray emission produced by the atomic currents--these X-ray photons provide a sensitive and intuitive tool for determining the carrier-envelope phase.
1,778 citations
TL;DR: In this paper, the band structure of GaAs-GaAlAs and InAsGaSb superlattices is calculated by matching propagating or evanescent envelope functions at the boundary of consecutive layers.
Abstract: The band structure of GaAs-GaAlAs and InAs-GaSb superlattices is calculated by matching propagating or evanescent envelope functions at the boundary of consecutive layers. For GaAs-GaAlAs materials, the envelope functions are the solutions of an effective Hamiltonian in which both band edges and effective masses are position dependent. The effective-mass jumps modify the boundary conditions which are imposed to the eigenstates of the effective-mass Hamiltonian. In InAs-GaSb superlattices, the dispersion relations, although quite similar to those obtained in GaAs-GaAlAs materials, reflect the genuine symmetry mismatch of InAs (electrons) and GaSb (light-holes) levels. The evolution of the InAs-GaSb band structure with increasing periodicity is calculated and found to be in excellent agreement with previous LCAO results. The dispersion relations of heavy-hole bands are obtained.
1,348 citations
TL;DR: In this article, the authors derived the nonlinear wave equation for an envelope of an electromagnetic wave in a monomode dielectric waveguide and derived the coefficients of the Schrodinger equation with higher-order dispersion and dissipation (both linear and nonlinear) in terms of properties of the eigenfunction of the guided wave as well as of the material nonlinearity and dispersion.
Abstract: We derive the nonlinear wave equation for an envelope of an electromagnetic wave in a monomode dielectric waveguide. Concrete examples are given for a single-mode optical fiber where the coefficients of resultant nonlinear Schrodinger equation with higher-order dispersion and dissipation (both linear and nonlinear) are given in terms of properties of the eigenfunction of the guided wave as well as of the material nonlinearity and dispersion. Using a newly-developed perturbation method, we show that the higher-order dispersions (linear and nonlinear) perserve the profile of a single soliton but to split up a bound N soliton ( N \geq 2 ) into individual solitons with different heights which propagate at different velocities. We also show that the higher-order nonlinear dissipation due to the induced Raman effect downshifts the carrier frequency of a single soliton in proportion to the distance of propagation and to the fourth power of the soliton amplitude.
965 citations
Book•
19 Dec 1997
TL;DR: In this paper, a three-component Seismogram Envelope Synthesis based on the Radiative Transfer Theory (RTT) was proposed for earthquakes using Scattering Amplitudes from the Born Approximation.
Abstract: Introduction- Heterogeneity in the Lithosphere- Phenomenological Approaches to Seismogram Envelopes in short-periods- Born approximation for Wave Scattering in Random Media- Attenuation of High-Frequency Seismic Waves- Synthesis of Three-Component Seismogram Envelopes for Earthquakes Using Scattering Amplitudes from the Born Approximation- Envelope Synthesis Based on the Radiative Transfer Theory: Multiple Scattering Models- Parabolic approximation and Envelope Synthesis based on the Markov Approximation Summary and Epilogue
955 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2022 | 6 |
| 2021 | 234 |
| 2020 | 250 |
| 2019 | 272 |
| 2018 | 271 |
| 2017 | 235 |