Improving peak local SAR prediction in parallel transmit using in situ S‐matrix measurements

2016 ◽  
Vol 77 (5) ◽  
pp. 2040-2047 ◽  
Author(s):  
Matthew Restivo ◽  
Alexander Raaijmakers ◽  
Cornelis van den Berg ◽  
Peter Luijten ◽  
Hans Hoogduin
Keyword(s):  
Parallel Transmit ◽  
S Matrix ◽  
Local Sar

scholarly journals Method for in situ characterization of radiofrequency heating in parallel transmit MRI

2012 ◽  
Vol 69 (5) ◽  
pp. 1457-1465 ◽  
Author(s):  
Leeor Alon ◽  
Cem Murat Deniz ◽  
Ryan Brown ◽  
Daniel K. Sodickson ◽  
Yudong Zhu
Keyword(s):  
In Situ Characterization ◽  
Parallel Transmit ◽  
Radiofrequency Heating

Studies of phase transformation of Fe1-xS by in Situ TEM

1989 ◽  
Vol 47 ◽  
pp. 648-649
Author(s):  
Thao A. Nguyen ◽  
Linn W. Hobbs
Keyword(s):  
Phase Transformation ◽  
Single Phase ◽  
Nucleation And Growth ◽  
In Situ Tem ◽  
Two Phase ◽  
S Matrix ◽  
In Situ Heating ◽  
Phase Mixture ◽  
Lamellar Type

The transformation from Fe1-xS (IC) phase to a mixture of FeS (2C) and iron poor Fe1-xS (IC) phases has been investigated by a series of in-situ heating experiments. The purpose of this study is to resolve the controversy over the mechanism of phase transformation (spinodal decomposition versus nucleation and growth) and to explain the different microstructures observed in the two phase mixture of FeS and Fe1-xS (Figure 1).In-situ heating experiments were carried out using a JEOL JEM EM-SHTH double tilt heating holder. Synthetic “single” Fe0.97S crystals were cut into 3 mm disks, mechanically and ion thinned to electron transparency. In all cooling experiments, the sample was first held at 390 K, a temperature above the transition temperature in order to generate an initial single phase material; then, the temperature was quickly reduced to the temperature of interest.Figure 2a shows the development of a lamellar type microstructure after the sample's temperature was reduced from 390 K to 363 K and then held at this temperature for ten minutes. At 363 K, the undercooling is 27 K. The troilite FeS (2C) phase heterogeneously nucleates and grows along the edge of the sample. Diffraction analysis shows that the FeS (2C) phase is embedded in the iron-poor Fe1-x,S matrix with a rod-like structure.

scholarly journals Comparison of simulated parallel transmit body arrays at 3 T using excitation uniformity, global SAR, local SAR, and power efficiency metrics

2014 ◽  
Vol 73 (3) ◽  
pp. 1137-1150 ◽  
Author(s):  
Bastien Guérin ◽  
Matthias Gebhardt ◽  
Peter Serano ◽  
Elfar Adalsteinsson ◽  
Michael Hamm ◽  
...  
Keyword(s):  
Power Efficiency ◽  
Parallel Transmit ◽  
Local Sar

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

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