scholarly journals Anisotropic longitudinal electronic relaxation affects DNP at cryogenic temperatures

2017 ◽  
Vol 19 (24) ◽  
pp. 16087-16094 ◽  
Author(s):  
E. M. M. Weber ◽  
H. Vezin ◽  
J. G. Kempf ◽  
G. Bodenhausen ◽  
D. Abergél ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Spectral Diffusion ◽  
Electronic Relaxation ◽  
Cryogenic Temperatures ◽  
Nitroxide Radicals

Anisotropic longitudinal electronic relaxation in nitroxide radicals can impact DNP at low temperatures in cases of slow spectral diffusion.

Ferrites for Tunable RF and Microwave Devices

1999 ◽  
Vol 603 ◽  
Author(s):  
Gerald F. Dionne
Keyword(s):  
Low Temperatures ◽  
Magnetocrystalline Anisotropy ◽  
Phase Shifters ◽  
Full Potential ◽  
Cryogenic Temperatures ◽  
Variable Permeability ◽  
Ferrite Devices ◽  
Q Factors ◽  
Insertion Losses ◽  
Rf Signal

AbstractMicrowave systems for communications and radar require control of propagation of the rf signal. Devices that accomplish this function include phase shifters, isolators and circulators, and tunable filters. In many instances, these devices are magnetic and are based on the variable permeability of electrically insulating ferrimagnetic oxides (ferrites). Recent advances in microwave ferrite devices have featured superconductor circuitry that promises to virtually eliminate insertion losses due to rf surface resistance. Lower conduction losses allow the use of small lightweight microstrip configurations in place of traditional bulky waveguide structures. For operation at cryogenic temperatures ferrimagnetic spinels and garnets will require chemical alteration to realize the full potential of these devices. Challenges include the reduction of magnetocrystalline anisotropy to optimize switching energies and speeds, and the elimination of fast-relaxing impurities in the magnetic garnets that can increase magnetic losses and degrade resonator Q factors at low temperatures.

Spectral diffusion in glasses at low temperatures

1977 ◽  
Vol 24 (12) ◽  
pp. 813-816 ◽  
Author(s):  
P. Hu ◽  
L.R. Walker
Keyword(s):  
Low Temperatures ◽  
Spectral Diffusion

scholarly journals Characterization of the piezoresistance in highly doped p-type 3C-SiC at cryogenic temperatures

RSC Advances ◽  
2018 ◽  
Vol 8 (52) ◽  
pp. 29976-29979 ◽  
Author(s):  
Hoang-Phuong Phan ◽  
Karen M. Dowling ◽  
Tuan-Khoa Nguyen ◽  
Caitlin A. Chapin ◽  
Toan Dinh ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Gauge Factor ◽  
Cryogenic Temperatures ◽  
Sensing Applications ◽  
P Type

The piezoresistance in crystalline 3C-SiC epitaxially grown on Si was investigated at low temperatures down to 150 K. The large gauge factor in 3C-SiC indicates its feasibility for sensing applications in cryogenic environments.

scholarly journals Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 625 ◽  
Author(s):  
Le Thanh Hung Nguyen ◽  
Jae-Sik Hwang ◽  
Myung-Sung Kim ◽  
Jeong-Hyeon Kim ◽  
Seul-Kee Kim ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Low Temperatures ◽  
316L Stainless Steel ◽  
Charpy Impact ◽  
Cryogenic Temperatures ◽  
Absorbed Energy ◽  
Impact Properties ◽  
Charging Time ◽  
The Impact

316L stainless steel is a promising material candidate for a hydrogen containment system. However, when in contact with hydrogen, the material could be degraded by hydrogen embrittlement (HE). Moreover, the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study, 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology, respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel.

Effects of Sub-Freezing Temperatures on Graphite/Epoxy Composite Materials

1989 ◽  
Vol 111 (4) ◽  
pp. 438-439 ◽  
Author(s):  
T. K. Tsotsis
Keyword(s):  
Composite Materials ◽  
Residual Stresses ◽  
Low Temperatures ◽  
Epoxy Composite ◽  
Ice Crystals ◽  
Cryogenic Temperatures ◽  
The Past ◽  
The Subject ◽  
Freezing Temperatures

Moisture in composite materials has been the subject of considerable interest in the past decade. Many studies have shown that moisture directly causes damage in graphite/epoxy composite materials. With the increasing use of such composites in various environments, an assessment of the effects of sub-freezing and/or cryogenic temperatures on composites containing moisture is needed. This article presents a summary of these effects and demonstrates that reductions in strength at low temperatures are not due to the formation of ice crystals, but instead are due to changes in the residual stresses caused by absorbed moisture.

Hot Wire/Film Behavior in Low-Temperature Gases

1992 ◽  
Vol 114 (4) ◽  
pp. 859-865 ◽  
Author(s):  
E. Y. Kwack ◽  
P. Shakkottai ◽  
T. S. Luchik ◽  
K. M. Aaron ◽  
G. Fabris ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Thermal Loading ◽  
Large Range ◽  
Harsh Environment ◽  
Cryogenic Temperatures ◽  
Hot Wire ◽  
Aspect Ratios ◽  
Helium Gas ◽  
Hot Wires

Commercially available hot wires/films were used to measure the velocities of evaporated hydrogen or helium gas during cryogenic mixing experiments. Hot wires were found to be too delicate to use in this harsh environment. Hot films were rugged enough to use at cryogenic temperatures even though they failed after a number of thermal cycles. Since the hot films have small aspect ratios, 13.4 and 20, they are quite sensitive to the thermal loading, Tw/Tg, even with a correction for the conduction end loss. In general, although the increase of the Nusselt number with Reynolds number at low temperatures was similar to that at room temperature, there was also a pronounced variation with Tw/Tg over the large range of 1.2 to 12 investigated.

scholarly journals Testing and Applications of Non-Linear Wave Shaping Circuits Based on Zener Diodes at Cryogenic Temperatures

2017 ◽  
Vol 13 (4) ◽  
pp. 4910-4918
Author(s):  
A. M. Abd El-Maksood
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
The Other ◽  
Electronic Systems ◽  
Linear Wave ◽  
Cryogenic Temperatures ◽  
Temperature Variations ◽  
Wide Range ◽  
Non Linear ◽  
The Stability

            Applications of wave-shaping clipping circuits based on Zener diodes are of great interest in a wide range of modern electronic systems. As well, given the strong interest in space research and trips to distant planets, where the journey takes long periods. Therefore, the matter requires reliance on electronic systems with special specifications commensurate with the nature of the extremely low-temperature environments, down to cryogenic level (around 90 K). So, the present paper was concerned with studying the stability of the performance of different non-linear wave-shaping systems, based on silicon Zener diodes, whenever operates at very low temperatures down to cryogenic levels. From which, it is clear that for BZX79-C4V7 and BZX79-C5V6 Zeners, such electronic systems were shown to be insensitive to temperature variations. On the other hand, low breakdown voltage Zeners (BZV86-1V4 and BZX83-C3V6), the clipping edges were shown to be increased with lowering temperatures from 300 K down to 93 K. Finally, for Zener diodes with VZ greater than 6.0 V (BZX83-C6V8 and BZX55C9V1), the temperature coefficient is positive, so the clipping edges decrease with lowering temperatures, for the same range of temperatures.

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