scholarly journals Processing the image gradient field using a topographic primal sketch approach

2015 ◽  
Vol 31 (3) ◽  
pp. e02706 ◽  
Author(s):  
A. M. Gambaruto
Keyword(s):  
Gradient Field ◽  
Image Gradient ◽  
Primal Sketch

HIERARCHICAL SHAPE DESCRIPTION AND SIMILARITY-INVARIANT RECOGNITION USING GRADIENT PROPAGATION

2001 ◽  
Vol 15 (08) ◽  
pp. 1251-1261 ◽  
Author(s):  
JEZEKIEL BEN-ARIE ◽  
ZHIQIAN WANG
Keyword(s):  
Experimental Results ◽  
Gradient Field ◽  
Shape Description ◽  
Indexing Scheme ◽  
Local Maxima ◽  
Image Gradient ◽  
Concave Shape ◽  
Similarity Invariant ◽  
Shape Component ◽  
Radial Propagation

This paper presents a novel hierarchical shape description scheme based on propagating the image gradient radially. This radial propagation is equivalent to a vectorial convolution with sector elements. The propagated gradient field collides at centers of convex/concave shape components, which can be detected as points of high directional disparity. A novel vectorial disparity measure called Cancellation Energy is used to measure this collision of the gradient field, and local maxima of this measure yield feature tokens. These feature tokens form a compact description of shapes and their components and indicate their central locations and sizes. In addition, a Gradient Signature is formed by the gradient field that collides at each center, which is itself a robust and size-independent description of the corresponding shape component. Experimental results demonstrate that the shape description is robust to distortion, noise and clutter. An important advantage of this scheme is that the feature tokens are obtained pre-attentively, without prior understanding of the image. The hierarchical description is also successfully used for similarity-invariant recognition of 2D shapes with a multi-dimensional indexing scheme based on the Gradient Signature.

A fast algorithm based on image gradient field reconstructing

2016 ◽  
Author(s):  
Chang Ding ◽  
Lili Dong ◽  
Wenhai Xu
Keyword(s):  
Fast Algorithm ◽  
Gradient Field ◽  
Image Gradient

Analysis of field uniformity and quantitative evaluation of subsurface pitting corrosion in conductors via GPEC

2020 ◽  
Vol 64 (1-4) ◽  
pp. 19-29
Author(s):  
Shuting Ren ◽  
Yong Li ◽  
Bei Yan ◽  
Jinhua Hu ◽  
Ilham Mukriz Zainal Abidin ◽  
...  
Keyword(s):  
Quantitative Evaluation ◽  
Eddy Current ◽  
Pitting Corrosion ◽  
Gradient Field ◽  
Uniform Field ◽  
Eddy Current Method ◽  
Optimal Position ◽  
Pulsed Eddy Current ◽  
Field Uniformity ◽  
Processing Algorithms

Structures of nonmagnetic materials are broadly used in engineering fields such as aerospace, energy, etc. Due to corrosive and hostile environments, they are vulnerable to the Subsurface Pitting Corrosion (SPC) leading to structural failure. Therefore, it is imperative to conduct periodical inspection and comprehensive evaluation of SPC using reliable nondestructive evaluation techniques. Extended from the conventional Pulsed eddy current method (PEC), Gradient-field Pulsed Eddy Current technique (GPEC) has been proposed and found to be advantageous over PEC in terms of enhanced inspection sensitivity and accuracy in evaluation and imaging of subsurface defects in nonmagnetic conductors. In this paper two GPEC probes for uniform field excitation are intensively analyzed and compared. Their capabilities in SPC evaluation and imaging are explored through simulations and experiments. The optimal position for deployment of the magnetic field sensor is determined by scrutinizing the field uniformity and inspection sensitivity to SPC based on finite element simulations. After the optimal probe structure is chosen, quantitative evaluation and imaging of SPC are investigated. Signal/image processing algorithms for SPC evaluation are proposed. Through simulations and experiments, it has been found that the T-shaped probe together with the proposed processing algorithms is advantageous and preferable for profile recognition and depth evaluation of SPC.

A new magnetic resonance head coil and head immobilization device for gamma knife radiosurgery: an analysis of geometric distortion and signal/noise characteristics

2002 ◽  
Vol 97 ◽  
pp. 563-568 ◽  
Author(s):  
Paul Jursinic ◽  
Robert Prost ◽  
Christopher Schultz
Keyword(s):  
Magnetic Resonance ◽  
Gamma Knife Radiosurgery ◽  
Geometric Distortion ◽  
Gradient Field ◽  
Main Magnetic Field ◽  
Content Type ◽  
Signal Noise ◽  
Noise Characteristics ◽  
Head Coil ◽  
Fine Print

Object. The authors report on a new head coil into which the Leksell aluminum localization frame can be easily and securely mounted. Mechanically, the head coil interferes little with the patient. Methods. The head coil, which is for magnetic resonance (MR) imaging, is a 12-element quadrature transmitand-receive high-pass birdcage coil with a nominal operation frequency (63.86 MHz). The coil was built into a plastic housing. This new head coil minimizes patient motion and provides a 20% increase in signal/noise ratios compared with standard head coils. An MR image test phantom was mounted in the coil and this allowed quantification of image distortion due to inhomogeneities in the main magnetic field, nonlinearity in the gradient field, and paramagnetism of the aluminum headframe. There were no significant differences in geometric distortion between the new head coil and the standard coil. Conclusions. The new head coil has advantages for reducing patient movement artifacts and has a better signal/noise ratio with no reduction in geometric accuracy.

A comparison of methods for gradient field estimation on simplicial meshes

2019 ◽  
Vol 80 ◽  
pp. 37-50 ◽  
Author(s):  
Claudio Mancinelli ◽  
Marco Livesu ◽  
Enrico Puppo
Keyword(s):  
Gradient Field ◽  
Comparison Of Methods ◽  
Field Estimation
Sign in / Sign up

Export Citation Format

Share Document