GEOPHYSICS BRIGHT SPOTS

2012 ◽  
Vol 31 (4) ◽  
pp. 383-384
Author(s):  
Yonghe Sun
Keyword(s):  
Bright Spots

Analysis of Dark-Field Images of Disordered Materials

1972 ◽  
Vol 30 ◽  
pp. 560-561
Author(s):  
J. M. Cowley
Keyword(s):  
Amorphous Materials ◽  
Careful Analysis ◽  
Dark Field ◽  
Minimum Diameter ◽  
Statistical Fluctuations ◽  
Bright Spots ◽  
Sufficient Detail ◽  
Random Arrangement ◽  
Diffraction Patterns ◽  
Imaging Conditions

Recently a number of authors have reported detail in dark-field images obtained from diffuse-scattering regions of electron diffraction patterns. Bright spots in images from short-range order diffuse peaks of disordered binary alloys have been interpreted as evidence for the existence of microdomains of ordered lattice or of segragated clusters of one component. Spotty contrast in dark field images of near-amorphous materials has been interpreted as evidence for the existense of microcrystals. Without a careful analysis of the imaging conditions such conclusions may be invalid. Usually the conditions of the experiment have not been specified in sufficient detail to allow evaluation of the conclusions.Elementary considerations show that even for a completely random arrangement of atoms the statistical fluctuations of density will give a spotty contrast with spots of minimum diameter determined by the dark field aperture size and other factors influencing the minimum resolvable distance under darkfield imaging conditions, including fluctuations and drift over long exposure times (resolution usually 10Å or more).

THE GEOLOGIC AND STRATIGRAPHIC CONTEXT OF THE BRIGHT SPOTS IN OCCATOR CRATER ON CERES

2016 ◽  
Author(s):  
Jennifer E.C. Scully ◽  
◽  
Debra L. Buczkowski ◽  
Paul M. Schenk ◽  
Adrian Neesemann ◽  
...  
Keyword(s):  
Bright Spots

scholarly journals Optical Spin Hall Effect in Closed Elliptical Plasmonic Nanoslit with Noncircular Symmetry

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 851
Author(s):  
Xiaorong Ren ◽  
Xiangyu Zeng ◽  
Chunxiang Liu ◽  
Chuanfu Cheng ◽  
Ruirui Zhang ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Hall Effect ◽  
Light Field ◽  
Analytical Calculation ◽  
Spin Hall Effect ◽  
Spin Component ◽  
Phase Gradient ◽  
Bright Spots ◽  
Principal Axes ◽  
Output Field

We investigated the optical spin Hall effect (OSHE) of the light field from a closed elliptical metallic curvilinear nanoslit instead of the usual truncated curvilinear nanoslit. By making use of the characteristic bright spots in the light field formed by the noncircular symmetry of the elliptical slit and by introducing a method to separate the incident spin component (ISC) and converted spin component (CSC) of the output field, the OSHE manifested in the spot shifts in the CSC was more clearly observable and easily measurable. The slope of the elliptical slit, which was inverse along the principal axes, provided a geometric phase gradient to yield the opposite shifts of the characteristic spots in centrosymmetry, with a double shift achieved between the spots. Regarding the mechanism of this phenomenon, the flip of the spin angular momentum (SAM) of CSC gave rise to an extrinsic orbital angular momentum corresponding to the shifts of the wavelet profiles of slit elements in the same rotational direction to satisfy the conservation law. The analytical calculation and simulation of finite-difference time domain were performed for both the slit element and the whole slit ellipse, and the evolutions of the spot shifts as well as the underlying OSHE with the parameters of the ellipse were achieved. Experimental demonstrations were conducted and had consistent results. This study could be of great significance for subjects related to the applications of the OSHE.

scholarly journals The formation and evolution of bright spots on Ceres

Icarus ◽  
2019 ◽  
Vol 320 ◽  
pp. 188-201 ◽  
Author(s):  
N.T. Stein ◽  
B.L. Ehlmann ◽  
E. Palomba ◽  
M.C. De Sanctis ◽  
A. Nathues ◽  
...  
Keyword(s):  
Bright Spots ◽  
Formation And Evolution

Incomplete AVO near salt structures

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 543-553 ◽  
Author(s):  
Christopher P. Ross
Keyword(s):  
Seismic Profiles ◽  
Spectral Modeling ◽  
Signal Degradation ◽  
Amplitude Versus Offset ◽  
Bright Spots ◽  
Close Proximity ◽  
Pseudo Spectral ◽  
Amplitude Versus ◽  
Structure Class ◽  
Made In

Amplitude versus offset (AVO) measurements for deep hydrocarbon‐bearing sands can be compromised when made in close proximity to a shallow salt piercement structure. Anomalous responses are observed, particularly on low acoustic impedance bright spots. CMP data from key seismic profiles traversing the bright spots do not show the expected Class 3 offset responses. On these CMPs, significant decrease of far trace energy is observed. CMP data from other seismic profiles off‐structure do exhibit the Class 3 offset responses, implying that structural complications may be interfering with the offset response. A synthetic AVO gather was generated using well log data, which supports the off‐structure Class 3 responses, further reinforcing the concept of structurally‐biased AVO responses. Acoustic, pseudo‐spectral modeling of the structure substantiates the misleading AVO response. Pseudo‐spectral modeling results suggest that signal degradation observed on the far offsets is caused by wavefield refraction—a shadow zone, where the known hydrocarbon‐bearing sands are not completely illuminated. Such shadow zones obscure the correct AVO response, which may have bearing on exploration and development.

A study of dayside auroral bright spots seen by the Viking Auroral Imager

1995 ◽  
Vol 100 (A3) ◽  
pp. 3649-3655 ◽  
Author(s):  
H. B. Vo ◽  
J. S. Murphree
Keyword(s):  
Bright Spots ◽  
Auroral Imager

scholarly journals Variations of the 630.0 nm airglow emission with meridional neutral wind and neutral temperature around midnight

2018 ◽  
Vol 36 (5) ◽  
pp. 1471-1481
Author(s):  
Chih-Yu Chiang ◽  
Sunny Wing-Yee Tam ◽  
Tzu-Fang Chang
Keyword(s):  
Emission Rate ◽  
Local Maximum ◽  
Neutral Wind ◽  
Emission Rates ◽  
Emission Layer ◽  
Neutral Winds ◽  
Neutral Temperature ◽  
Bright Spots ◽  
Different Temperatures ◽  
Volume Emission

Abstract. The ISUAL payload onboard the FORMOSAT-2 satellite has often observed airglow bright spots around midnight at equatorial latitudes. Such features had been suggested as the signature of the thermospheric midnight temperature maximum (MTM) effect, which was associated with temperature and meridional neutral winds. This study investigates the influence of neutral temperature and meridional neutral wind on the volume emission rates of the 630.0 nm nightglow. We utilize the SAMI2 model to simulate the charged and neutral species at the 630.0 nm nightglow emission layer under different temperatures with and without the effect of neutral wind. The results show that the neutral wind is more efficient than temperature variation in affecting the nightglow emission rates. For example, based on our estimation, it would require a temperature change of 145 K to produce a change in the integrated emission rate by 9.8 km-photons cm−3 s−1, while it only needs the neutral wind velocity to change by 1.85 m−1 s−1 to cause the same change in the integrated emission rate. However, the emission rate features a local maximum in its variation with the temperature. Two kinds of tendencies can be seen regarding the temperature that corresponds to the turning point, which is named the turning temperature (Tt) in this study: firstly, Tt decreases with the emission rate for the same altitude; secondly, for approximately the same emission rate, Tt increases with the altitude.

GEOPHYSICS BRIGHT SPOTS

2009 ◽  
Vol 28 (10) ◽  
pp. 1262-1265
Author(s):  
C. Liner
Keyword(s):  
Bright Spots
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