scholarly journals Phase-Stretch Adaptive Gradient-Field Extractor (PAGE)

Coding Theory ◽  
2020 ◽  
Author(s):  
Madhuri Suthar ◽  
Bahram Jalali
Keyword(s):  
Gradient Field

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

scholarly journals A gradient field defeats the inherent repulsion between magnetic nanorods

2014 ◽  
Vol 1 (2) ◽  
pp. 140271 ◽  
Author(s):  
Yu Gu ◽  
Ruslan Burtovyy ◽  
John Custer ◽  
Igor Luzinov ◽  
Konstantin G. Kornev
Keyword(s):  
Phase Portrait ◽  
High Speed ◽  
Uniform Magnetic Field ◽  
Gradient Field ◽  
Physical Parameters ◽  
Uniform Field ◽  
Experimental Conditions ◽  
Magnetic Nanorods ◽  
Field Gradients ◽  
And Control

When controlling the assembly of magnetic nanorods and chains of magnetic nanoparticles, it is extremely challenging to bring them together side by side while keeping a desired spacing between their axes. We show that this challenge can be successfully resolved by using a non-uniform magnetic field that defeats an inherent repulsion between nanorods. Nickel nanorods were suspended in a viscous film and a non-uniform field was used to control their placement. The in-plane movement of nanorods was tracked with a high-speed camera and a detailed image analysis was conducted to quantitatively characterize the behaviour of the nanorods. The analysis focused on the behaviour of a pair of neighbour nanorods, and a corresponding dynamic model was formulated and investigated. The complex two-dimensional dynamics of a nanorod pair was analysed analytically and numerically, and a phase portrait was constructed. Using this phase portrait, we classified the nanorod behaviour and revealed the experimental conditions in which nanorods could be placed side by side. Dependence of the distance between a pair of neighbour nanorods on physical parameters was analysed. With the aid of the proposed theory, one can build different lattices and control their spacing by applying different field gradients.

scholarly journals Influence of eddy current, Maxwell and gradient field corrections on 3D flow visualization of 3D CINE PC-MRI data

2013 ◽  
Vol 72 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Ramona Lorenz ◽  
Jelena Bock ◽  
Jeff Snyder ◽  
Jan G. Korvink ◽  
Bernd A. Jung ◽  
...  
Keyword(s):  
Flow Visualization ◽  
Eddy Current ◽  
Gradient Field ◽  
3D Flow

Evaluation of Relaxation Time Measurements by Magnetic Resonance Imaging

1987 ◽  
Vol 28 (3) ◽  
pp. 345-351 ◽  
Author(s):  
L. Kjær ◽  
C. Thomsen ◽  
O. Henriksen ◽  
P. Ring ◽  
M. Stubgaard ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Diffusion Processes ◽  
Relaxation Times ◽  
Gradient Field ◽  
Maximum Deviation ◽  
Resonance Imaging ◽  
T2 Relaxation ◽  
T1 And T2

Several circumstances may explain the great variation in reported proton T1 and T2 relaxation times usually seen. This study was designed to evaluate the accuracy of relaxation time measurements by magnetic resonance imaging (MRI) operating at 1.5 tesla. Using a phantom of nine boxes with different concentrations of CuSO4 and correlating the calculated T1 and T2 values with reference values obtained by two spectrometers (corrected to MRI-proton frequency=64 MHz) we found a maximum deviation of about 10 per cent. Measurements performed on a large water phantom in order to evaluate the homogeneity in the imaging plane showed a variation of less than 10 per cent within 10 cm from the centre of the magnet in all three imaging planes. Changing the gradient field strength apparently had no influence on the T2 values recorded. Consequently diffusion processes seem without significance. It is concluded that proton T1 and T2 relaxation times covering the majority of the biologic range can be measured by MRI with an overall accuracy of 5 to 10 per cent. Quality control studies along the lines indicated in this study are recommended.

Sign in / Sign up

Export Citation Format

Share Document