No Phase Change in a Constant Gradient Medium

1968 ◽  
Vol 44 (4) ◽  
pp. 1154-1155 ◽  
Author(s):  
D. H. Wood
Keyword(s):  
Phase Change ◽  
Constant Gradient ◽  
Gradient Medium

scholarly journals Analytical approximations of diving-wave imaging in constant-gradient medium

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. S131-S140 ◽  
Author(s):  
Alexey Stovas ◽  
Tariq Alkhalifah
Keyword(s):  
Initial Velocity ◽  
Waveform Inversion ◽  
Velocity Model ◽  
Image Point ◽  
Practical Applications ◽  
Analytical Approximations ◽  
Wave Imaging ◽  
Analytical Formulas ◽  
Constant Gradient ◽  
Gradient Medium

Full-waveform inversion (FWI) in practical applications is currently used to invert the direct arrivals (diving waves, no reflections) using relatively long offsets. This is driven mainly by the high nonlinearity introduced to the inversion problem when reflection data are included, which in some cases require extremely low frequency for convergence. However, analytical insights into diving waves have lagged behind this sudden interest. We use analytical formulas that describe the diving wave’s behavior and traveltime in a constant-gradient medium to develop insights into the traveltime moveout of diving waves and the image (model) point dispersal (residual) when the wrong velocity is used. The explicit formulations that describe these phenomena reveal the high dependence of diving-wave imaging on the gradient and the initial velocity. The analytical image point residual equation can be further used to scan for the best-fit linear velocity model, which is now becoming a common sight as an initial velocity model for FWI. We determined the accuracy and versatility of these analytical formulas through numerical tests.

scholarly journals An approximate elastic two-dimensional Green’s function for a constant-gradient medium

2001 ◽  
Vol 146 (1) ◽  
pp. 237-248 ◽  
Author(s):  
Francisco J. Sánchez-Sesma ◽  
Raul Madariaga ◽  
Kojiro Irikura
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Two Dimensional ◽  
Constant Gradient ◽  
Gradient Medium

Reflection of rays in a constant gradient medium: CRP geometry

Geophysics ◽  
1998 ◽  
Vol 63 (2) ◽  
pp. 707-712
Author(s):  
Franklyn K. Levin
Keyword(s):  
Velocity Gradient ◽  
Seismic Data ◽  
Constant Velocity ◽  
Finite Range ◽  
Velocity Increase ◽  
Rate Of Increase ◽  
Constant Gradient ◽  
Gradient Medium

In a medium having a velocity that increases linearly with depth (constant gradient), rays are arcs of circles (Slotnick, 1936). A constant gradient medium is not a good approximation to a real subsurface. Not only does velocity increase without limit with depth, but the rate of increase is constant. Nonetheless, over a finite range of depths, a constant gradient medium is closer to reality than a medium having constant velocity down to reflector of interest. For that reason, a number of investigators have considered the changes in processes applied to seismic data when a constant velocity gradient other than zero is assumed.

The effect of an aluminum heat-sink layer on the laser-induced amorphization of SiOx/TeGeSn/SiOx phase-change recording films

1989 ◽  
Vol 47 ◽  
pp. 574-575
Author(s):  
Matthew R. Libera ◽  
Martin Chen
Keyword(s):  
Thin Film ◽  
Phase Change ◽  
Heat Sink ◽  
Multilayer Film ◽  
Glassy Phase ◽  
Film Structure ◽  
Glass Forming ◽  
Active Storage ◽  
Dielectric Layers ◽  
Amorphous States

Phase-change erasable optical storage is based on the ability to switch a micron-sized region of a thin film between the crystalline and amorphous states using a diffraction-limited laser as a heat source. A bit of information can be represented as an amorphous spot on a crystalline background, and the two states can be optically identified by their different reflectivities. In a typical multilayer thin-film structure the active (storage) layer is sandwiched between one or more dielectric layers. The dielectric layers provide physical containment and act as a heat sink. A viable phase-change medium must be able to quench to the glassy phase after melting, and this requires proper tailoring of the thermal properties of the multilayer film. The present research studies one particular multilayer structure and shows the effect of an additional aluminum layer on the glass-forming ability.

Crystallization fractionation technology for paraffin-based phase change materials production

2020 ◽  
pp. 33-38
Author(s):  
S.S. Kruglov (Jr.) ◽  
◽  
G.L. Patashnikov ◽  
S.S. Kruglov (Sr.) ◽  
◽  
...  
Keyword(s):  
Phase Change ◽  
Phase Change Materials
Sign in / Sign up

Export Citation Format

Share Document