نتایج جستجو برای: ab semblance
تعداد نتایج: 43511 فیلتر نتایج به سال:
\Velocity Picking" is the problem of picking velocity-time pairs based on a coherence metric between multiple seismic signals. Coherence as a function of velocity and time can be expressed as a 2-D color image representing the \Semblance Velocity." Currently, humans pick velocities by looking at the Semblance Velocity image; picking velocities for a seismic survey can take days or even weeks. A...
In contrast to prestack migration methods based on data binning, common image gathers produced by shot-geophone migration exhibit the appropriate semblance property in either offset domain (focussing at zero offset) or angle domain (focussing at zero slope), when the migration velocity is kinematically correct and when events to be migrated arrive in the data along non-turning rays. The latter ...
Reflection-based waveform inversion introduces migration and demigration process to retrieve low-wavenumber component from reflection data, but both differenceand correlationbased methods suffer from the cycle-skipping problem when the time shifts change rapidly. In this abstract, we introduce model extension and differential semblance optimization into reflection-based waveform inversion. With...
Hypoxic ischemic encephalopathy (HIE) leads to significant morbidity and mortality. Impaired autoregulation after hypoxia-ischaemia has been suggested to contribute further to injury. Thalamic lactate/N-Acetylasperate (Lac/NAA) peak area ratio of > 0.3 on proton (1H) magnetic resonance spectroscopy (MRS) is associated with poor neurodevelopment outcome following HIE. Cytochrome-c-oxidase (CCO) ...
Are visual face processing mechanisms the same in the left and right cerebral hemispheres? The possibility of such 'duplicated processing' seems puzzling in terms of neural resource usage, and we currently lack a precise characterization of the lateral differences in face processing. To address this need, we have undertaken a three-pronged approach. Using functional magnetic resonance imaging, ...
Differential semblance velocity estimators have well–defined and smooth high frequency asymptotics. A version appropriate for analysis of CMP gathers and layered acoustic models has no secondary minima. Its structure suggests an approach to optimal parametrization of velocity models.
Unlike other organs that operate continuously, such as the heart and kidneys, many of the operations of the nervous system shut down during sleep. The evolutionarily conserved unconscious state of sleep that puts animals at risk from predators indicates that it is an indispensable integral part of systems operation. A reasonable expectation is that any hypothesis for the mechanism of the nervou...
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