scholarly journals Signal-to-noise ratio and absorbed power as functions of main magnetic field strength, and definition of ?90�? RF pulse for the head in the birdcage coil

2001 ◽  
Vol 45 (4) ◽  
pp. 684-691 ◽  
Author(s):  
Christopher M. Collins ◽  
Michael B. Smith
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Signal To Noise Ratio ◽  
Main Magnetic Field ◽  
Birdcage Coil ◽  
Signal To Noise ◽  
Absorbed Power ◽  
Noise Ratio ◽  
Definition Of

scholarly journals Inference of the chromospheric magnetic field configuration of solar plage using the Ca II 8542 Å line

2020 ◽  
Vol 644 ◽  
pp. A43 ◽  
Author(s):  
A. G. M. Pietrow ◽  
D. Kiselman ◽  
J. de la Cruz Rodríguez ◽  
C. J. Díaz Baso ◽  
A. Pastor Yabar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Numerical Models ◽  
Signal To Noise Ratio ◽  
Field Configuration ◽  
Magnetic Field Configuration ◽  
Signal To Noise ◽  
Plage Region ◽  
Noise Ratio ◽  
The Magnetic Field

Context. It has so far proven impossible to reproduce all aspects of the solar plage chromosphere in quasi-realistic numerical models. The magnetic field configuration in the lower atmosphere is one of the few free parameters in such simulations. The literature only offers proxy-based estimates of the field strength, as it is difficult to obtain observational constraints in this region. Sufficiently sensitive spectro-polarimetric measurements require a high signal-to-noise ratio, spectral resolution, and cadence, which are at the limit of current capabilities. Aims. We use critically sampled spectro-polarimetric observations of the Ca II 8542 Å line obtained with the CRISP instrument of the Swedish 1-m Solar Telescope to study the strength and inclination of the chromospheric magnetic field of a plage region. This will provide direct physics-based estimates of these values, which could aid modelers to put constraints on plage models. Methods. We increased the signal-to-noise ratio of the data by applying several methods including deep learning and PCA. We estimated the noise level to be 1 × 10−3 Ic. We then used STiC, a non-local thermodynamic equilibrium inversion code to infer the atmospheric structure and magnetic field pixel by pixel. Results. We are able to infer the magnetic field strength and inclination for a plage region and for fibrils in the surrounding canopy. In the plage we report an absolute field strength of |B| = 440 ± 90 G, with an inclination of 10° ±16° with respect to the local vertical. This value for |B| is roughly double of what was reported previously, while the inclination matches previous studies done in the photosphere. In the fibrillar region we found |B| = 300 ± 50 G, with an inclination of 50° ±13°.

scholarly journals The Multi-resolution CLEAN

1991 ◽  
Vol 131 ◽  
pp. 268-271 ◽  
Author(s):  
B.P. Wakker ◽  
U.J. Schwarz
Keyword(s):  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Extended Sources ◽  
Noise Ratio ◽  
Definition Of

AbstractWe describe a modification to CLEAN which alleviates some problems for extended sources. This is accomplished by combining the results of a number of conventional CLEAN operations, each done at a different resolution. The algorithm is called “Multi-Resolution Clean” or “MRC”. Experiments on model sources have shown that it works well even when the source is so extended that the usual CLEAN becomes impractical. For extended sources, MRC enhances the signal-to-noise ratio, resulting in an easier definition of the area of signal. Moreover, MRC is in principle faster than a standard CLEAN because less δ-functions are needed. This work was published in Astr. Ap., 200, 312.

Aortic 4D flow: Quantification of signal-to-noise ratio as a function of field strength and contrast enhancement for 1.5T, 3T, and 7T

2014 ◽  
Vol 73 (5) ◽  
pp. 1864-1871 ◽  
Author(s):  
Aaron T. Hess ◽  
Malenka M. Bissell ◽  
Ntobeko A.B. Ntusi ◽  
Andrew J.M. Lewis ◽  
Elizabeth M. Tunnicliffe ◽  
...  
Keyword(s):  
Field Strength ◽  
Contrast Enhancement ◽  
Signal To Noise Ratio ◽  
Flow Quantification ◽  
Signal To Noise ◽  
4D Flow ◽  
Noise Ratio

scholarly journals Signal-to-noise ratio, T2 , and T2* for hyperpolarized helium-3 MRI of the human lung at three magnetic field strengths

2016 ◽  
Vol 78 (4) ◽  
pp. 1458-1463 ◽  
Author(s):  
Peter Komlosi ◽  
Talissa A. Altes ◽  
Kun Qing ◽  
Karen E. Mooney ◽  
G. Wilson Miller ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Human Lung ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Hyperpolarized Helium ◽  
Helium 3 ◽  
Noise Ratio ◽  
Field Strengths

scholarly journals Design and Research of Inductive Oil Pollutant Detection Sensor Based on High Gradient Magnetic Field Structure

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 638
Author(s):  
Wei Li ◽  
Chenzhao Bai ◽  
Chengjie Wang ◽  
Hongpeng Zhang ◽  
Lebile Ilerioluwa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Signal To Noise Ratio ◽  
Detection Accuracy ◽  
Iron Particles ◽  
Signal To Noise ◽  
Gradient Magnetic Field ◽  
High Gradient ◽  
Copper Particles ◽  
Pollutant Detection ◽  
Noise Ratio

An inductive oil pollutant detection sensor based on a high-gradient magnetic field structure is designed in this paper, which is mainly used for online detection and fault analysis of pollutants in hydraulic and lubricating oil systems. The innovation of the sensor is based on the inductance detection method. Permalloy is embedded in the sensing region of the sensor, so that the detection area generates a high gradient magnetic field to enhance the detection accuracy of the sensor. Compared with traditional inductive sensors, the sensor has a significant improvement in detection accuracy, and the addition of permalloy greatly improves the stability of the sensor’s detection unit structure. The article theoretically analyzes the working principle of the sensor, optimizes the design parameters and structure of the sensor through simulation, determines the best permalloy parameters, and establishes an experimental system for verification. Experimental results show that when a piece of permalloy is added to the sensing unit, the signal-to-noise ratio (SNR) of iron particles is increased by more than 20%, and the signal-to-noise ratio of copper particles is increased by more than 70%. When two pieces of permalloy are added, the signal-to-noise ratio for iron particles is increased by more than 70%, and the SNR for copper particles is increased several times. This method raises the lower limit of detection for ferromagnetic metal particles to 20 μm, and the lower limit for detection of non-ferromagnetic metal particles to 80 μm, which is the higher detection accuracy of the planar coil sensors. This paper provides a new and faster online method for pollutant detection in oil, which is of great significance for diagnosing and monitoring the health of oil in mechanical systems.

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