JUSTIFICATION OF PARAMETERS OF THE 2D CDP FIELD SYSTEM

2020 ◽  
pp. 59-65
Author(s):  
A. P. Sysoev ◽  
Keyword(s):  
Digital Processing ◽  
Sampling Theorem ◽  
Observation System ◽  
Discrete Function ◽  
High Frequencies ◽  
Spatial Aliasing ◽  
Shot Point ◽  
Static Corrections ◽  
Function Of Two Variables ◽  
Continuous Field

When performing seismic observations, 2D seismograms of a common shot point are represented as a discrete function of two variables, i.e. time and receiver – source offset. When recording a wave field using single seismic receivers placed small distance apart (UniQ technology), two goals are pursued : maintaining high frequencies of reflected signals by eliminating the effect of microstatics and fulfilling the Kotelnikov sampling theorem when discretizing a continuous field with respect to a spatial variable, thereby eliminating the effect of spatial aliasing of regular interference waves. At the stage of digital processing, this allows to solve the problem of extracting useful signals and suppressing noise more effectively. Taking the idea of a close array of receivers as a whole, it is proposed to optimize the profile observation system by source – receiver spacing combining analog and digital grouping of seismic receivers. In this case, the spatial sampling of the field is determined by the distance between the centers of receiver groups, and the parameters of the analog – digital grouping are calculated from the condition of suppressing spatial aliasing frequencies. Based on the analysis of static corrections obtained during processing of previous seismic studies, a method is proposed for assessing the effect of lateral microstatics variations on the results of analog grouping.

High‐resolution velocity notch filter without Gibbs effect

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 274-287 ◽  
Author(s):  
Eugene Lichman ◽  
E. John Northwood
Keyword(s):  
Dynamic Range ◽  
Inverse Fourier Transform ◽  
Notch Filter ◽  
Seismic Profile ◽  
Energy Separation ◽  
Profile Data ◽  
Discrete Function ◽  
Spatial Aliasing ◽  
Time Space ◽  
A New Technique

A new technique has been developed to reject or pass constant velocity coherent energy. Compared to the widely used frequency‐wavenumber (ο‐k) filtering method, this technique does not show either spatial aliasing or Gibbs effect. The filter operator is designed analytically as an infinite continuous function in the ο‐k domain. This function has the property that, when transformed by the integral inverse Fourier transform into the time‐space (t‐x) domain, it becomes a short discrete function with the same properties as the continuous infinite function in the ο‐k domain. No sampling or truncation of the filter operator is needed, hence no Gibbs oscillations are introduced into the operator impulse response or into the filtered data. Because of the extremely high‐velocity resolution and dynamic range of the designed coherent energy filter, it is particularly useful for the up‐ and downgoing energy separation on the vertical seismic profile data and for the peg‐leg multiples attenuation.

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

A method to measure pores and fissures in geologic materials under S.E.M. by digital image processing

1978 ◽  
Vol 36 (1) ◽  
pp. 212-213
Author(s):  
L. Montoto ◽  
M. Montoto ◽  
A. Bel-Lan
Keyword(s):  
Image Processing ◽  
Optical Microscopy ◽  
Digital Image Processing ◽  
Digital Image ◽  
Digital Processing ◽  
Free Surfaces ◽  
Geologic Materials ◽  
Automatic Information ◽  
Detector Output ◽  
Rock Specimens

INTRODUCTION.- The physical properties of rock masses are greatly influenced by their internal discontinuities, like pores and fissures. So, these need to be measured as a basis for interpretation. To avoid the basic difficulties of measurement under optical microscopy and analogic image systems, the authors use S.E.M. and multiband digital image processing. In S.E.M., analog signal processing has been used to further image enhancement (1), but automatic information extraction can be achieved by simple digital processing of S.E.M. images (2). The use of multiband image would overcome difficulties such as artifacts introduced by the relative positions of sample and detector or the typicals encountered in optical microscopy.DIGITAL IMAGE PROCESSING.- The studied rock specimens were in the form of flat deformation-free surfaces observed under a Phillips SEM model 500. The SEM detector output signal was recorded in picture form in b&w negatives and digitized using a Perkin Elmer 1010 MP flat microdensitometer.

Digital Processing of STEM Images

1981 ◽  
Vol 39 ◽  
pp. 236-237
Author(s):  
A. V. Crewe ◽  
M. Ohtsuki
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Assembly Language ◽  
Processing System ◽  
Principal Component ◽  
Digital Processing ◽  
Image Analysis System ◽  
Black And White ◽  
Analysis System ◽  
Dose Imaging

We have assembled an image processing system for use with our high resolution STEM for the particular purpose of working with low dose images of biological specimens. The system is quite flexible, however, and can be used for a wide variety of images.The original images are stored on magnetic tape at the microscope using the digitized signals from the detectors. For low dose imaging, these are “first scan” exposures using an automatic montage system. One Nova minicomputer and one tape drive are dedicated to this task.The principal component of the image analysis system is a Lexidata 3400 frame store memory. This memory is arranged in a 640 x 512 x 16 bit configuration. Images are displayed simultaneously on two high resolution monitors, one color and one black and white. Interaction with the memory is obtained using a Nova 4 (32K) computer and a trackball and switch unit provided by Lexidata.The language used is BASIC and uses a variety of assembly language Calls, some provided by Lexidata, but the majority written by students (D. Kopf and N. Townes).

Routine Digital Processing of Microscope Images

1990 ◽  
Vol 48 (1) ◽  
pp. 550-551
Author(s):  
E. Wisse ◽  
A. Geerts ◽  
R.B. De Zanger
Keyword(s):  
Operating System ◽  
Digital Processing ◽  
Hard Disks ◽  
The Sun ◽  
Tape Drive ◽  
High Definition ◽  
Fluorescent Microscope ◽  
Microscope Images ◽  
Helical Scan ◽  
Ethernet Connection

The slowscan and TV signal of the Philips SEM 505 and the signal of a TV camera attached to a Leitz fluorescent microscope, were digitized by the data acquisition processor of a Masscomp 5520S computer, which is based on a 16.7 MHz 68020 CPU with 10 Mb RAM memory, a graphics processor with two frame buffers for images with 8 bit / 256 grey values, a high definition (HD) monitor (910 × 1150), two hard disks (70 and 663 Mb) and a 60 Mb tape drive. The system is equipped with Imaging Technology video digitizing boards: analog I/O, an ALU, and two memory mapped frame buffers for TV images of the IP 512 series. The Masscomp computer has an ethernet connection to other computers, such as a Vax PDP 11/785, and a Sun 368i with a 327 Mb hard disk and a SCSI interface to an Exabyte 2.3 Gb helical scan tape drive. The operating system for these computers is based on different versions of Unix, such as RTU 4.1 (including NFS) on the acquisition computer, bsd 4.3 for the Vax, and Sun OS 4.0.1 for the Sun (with NFS).

Recent Progress and Plans in Computer-Controlled High Resolution Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 154-155
Author(s):  
W.J. de Ruijter ◽  
Peter Rez ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Digital Processing ◽  
High Resolution Electron Microscopy ◽  
Objective Lens ◽  
Linear Filter ◽  
Contrast Transfer Function ◽  
Image Displacement ◽  
Spatially Resolved ◽  
Wide Range ◽  
On Line

Digital computers are becoming widely recognized as standard accessories for electron microscopy. Due to instrumental innovations the emphasis in digital processing is shifting from off-line manipulation of electron micrographs to on-line image acquisition, analysis and microscope control. An on-line computer leads to better utilization of the instrument and, moreover, the flexibility of software control creates the possibility of a wide range of novel experiments, for example, based on temporal and spatially resolved acquisition of images or microdiffraction patterns. The instrumental resolution in electron microscopy is often restricted by a combination of specimen movement, radiation damage and improper microscope adjustment (where the settings of focus, objective lens stigmatism and especially beam alignment are most critical). We are investigating the possibility of proper microscope alignment based on computer induced tilt of the electron beam. Image details corresponding to specimen spacings larger than ∼20Å are produced mainly through amplitude contrast; an analysis based on geometric optics indicates that beam tilt causes a simple image displacement. Higher resolution detail is characterized by wave propagation through the optical system of the microscope and we find that beam tilt results in a dispersive image displacement, i.e. the displacement varies with spacing. This approach is valid for weak phase objects (such as amorphous thin films), where transfer is simply described by a linear filter (phase contrast transfer function) and for crystalline materials, where imaging is described in terms of dynamical scattering and non-linear imaging theory. In both cases beam tilt introduces image artefacts.

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