Elastic and Ultrasonic Studies on RM (R = Tb, Dy, Ho, Er, Tm; M = Zn, Cu) Compounds

2019 ◽  
Vol 74 (12) ◽  
pp. 1123-1130
Author(s):  
Chandreshvar Prasad Yadav ◽  
Dharmendra Kumar Pandey ◽  
Devraj Singh
Keyword(s):  
Thermal Conductivity ◽  
Wave Propagation ◽  
Relaxation Time ◽  
Elastic Moduli ◽  
Potential Model ◽  
Thermal Relaxation ◽  
Ultrasonic Velocities ◽  
Nearest Neighbours ◽  
Thermo Physical Properties ◽  
Model Approach

AbstractThe present article comprises computation of elastic, ultrasonic, and thermo-physical properties of RM (R = Tb, Dy, Ho, Er, Tm; M = Zn, Cu) compounds at 300 K. The second-order elastic constants (SOECs) and elastic moduli are evaluated initially, using potential model approach considering interaction up to second nearest neighbours. The ultrasonic velocities are obtained for wave propagation along <100>, <110>, and <111> crystallographic directions using evaluated SOECs. The Debye temperature, specific heat at constant volume, thermal energy density, thermal conductivity, and thermal relaxation time are also calculated. The obtained results are compared and analysed for justification and application of materials.

scholarly journals Применение неохлаждаемых микроболометров для регистрации импульсного терагерцового и инфракрасного излучения

2022 ◽  
Vol 92 (3) ◽  
pp. 443
Author(s):  
М.А. Демьяненко ◽  
В.В. Старцев
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Terahertz Radiation ◽  
Continuous Wave ◽  
Thermal Relaxation ◽  
Temperature Response ◽  
Thermal Relaxation Time ◽  
Frame Rate ◽  
Wave Radiation ◽  
Analytical Relations

Analytical relations for temperature response of the bolometer to periodic radiation pulses are obtained. It is theoretically shown and experimentally confirmed by the example of infrared bolometers that when detecting short radiation pulses, in contrast to the case of constant radiation, increasing the thermal conductivity of the bolometer and, accordingly, decreasing its thermal relaxation time, it is possible to significantly increase the response rate of the receiver, practically without reducing its sensitivity. The possibility of effective registration of pulsed terahertz radiation by microbolometers with a resistively coupled, thermally non-isolated antenna is considered. It is shown that such bolometers, which have increased thermal conductivity and, accordingly, reduced sensitivity to continuous-wave radiation, can be highly effective when detecting pulsed radiation with a duration shorter than the thermal relaxation time of the bolometer. On their basis, uncooled matrix detectors of pulsed terahertz radiation, characterized by a minimum detectable energy of less than 110-12 J and a frame rate of up to 1000 Hz, can be developed.

Mechanical Characterization of Apricena Marble by Ultrasonic Immersion Tests

2014 ◽  
Vol 628 ◽  
pp. 109-116 ◽  
Author(s):  
Anna Castellano ◽  
Pilade Foti ◽  
Aguinaldo Fraddosio ◽  
Salvatore Marzano ◽  
Mario Daniele Piccioni
Keyword(s):  
Wave Propagation ◽  
Elastic Moduli ◽  
Mechanical Characterization ◽  
Experimental Results ◽  
Elastic Response ◽  
Ultrasonic Velocities ◽  
Elastic Materials

We characterize the elastic response of Apricena marble by using advanced ultrasonic nondestructive techniques. An innovative experimental device for ultrasonic immersion tests is employed for the determination of ultrasonic velocities of waves travelling into the sample for any angle of propagation. The interpretation of the experimental results within the theoretical framework of wave propagation in elastic materials allows for both the classification of the anisotropy and the determination of the elastic moduli.

An analysis of the transport properties and mechanical stability of rapidly solidified Al-Sb alloy

2015 ◽  
Vol 10 (2) ◽  
pp. 2663-2681
Author(s):  
Rizk El- Sayed ◽  
Mustafa Kamal ◽  
Abu-Bakr El-Bediwi ◽  
Qutaiba Rasheed Solaiman
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Melt Spinning ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Microstructural Analysis ◽  
Alloy System ◽  
Antimony Content ◽  
The Stability ◽  
Rapidly Solidified

The structure of a series of AlSb alloys prepared by melt spinning have been studied in the as melt–spun ribbons  as a function of antimony content .The stability  of these structures has  been  related to that of the transport and mechanical properties of the alloy ribbons. Microstructural analysis was performed and it was found that only Al and AlSb phases formed for different composition.  The electrical, thermal and the stability of the mechanical properties are related indirectly through the influence of the antimony content. The results are interpreted in terms of the phase change occurring to alloy system. Electrical resistivity, thermal conductivity, elastic moduli and the values of microhardness are found to be more sensitive than the internal friction to the phase changes. 

Correlating Blocking Temperatures in Single Molecule Magnets with Raman Relaxation

2018 ◽  
Author(s):  
Marcus J. Giansiracusa ◽  
Andreas Kostopoulos ◽  
George F. S. Whitehead ◽  
David Collison ◽  
Floriana Tuna ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Single Molecule ◽  
Energy Barrier ◽  
Thermal Relaxation ◽  
Relaxation Mechanism ◽  
Blocking Temperature ◽  
Single Molecule Magnets ◽  
Single Molecule Magnet ◽  
Key Parameter

We report a six coordinate DyIII single-molecule magnet<br>(SMM) with an energy barrier of 1110 K for thermal relaxation of<br>magnetization. The sample shows no retention of magnetization<br>even at 2 K and this led us to find a good correlation between the<br>blocking temperature and the Raman relaxation regime for SMMs.<br>The key parameter is the relaxation time (𝜏<sub>switch</sub>) at the point where<br>the Raman relaxation mechanism becomes more important than<br>Orbach.

scholarly journals The Stability of Mars’s Annular Polar Vortex

2017 ◽  
Vol 74 (5) ◽  
pp. 1533-1547 ◽  
Author(s):  
William J. M. Seviour ◽  
Darryn W. Waugh ◽  
Richard K. Scott
Keyword(s):  
Relaxation Time ◽  
Time Scales ◽  
Time Scale ◽  
Thermal Relaxation ◽  
Polar Vortex ◽  
Radiative Relaxation ◽  
Equilibrium Profile ◽  
Rotating Shallow Water ◽  
The Stability ◽  
Topographic Forcing

Abstract The Martian polar atmosphere is known to have a persistent local minimum in potential vorticity (PV) near the winter pole, with a region of high PV encircling it. This finding is surprising, since an isolated band of PV is barotropically unstable, a result going back to Rayleigh. Here the stability of a Mars-like annular vortex is investigated using numerical integrations of the rotating shallow-water equations. The mode of instability and its growth rate is shown to depend upon the latitude and width of the annulus. By introducing thermal relaxation toward an annular equilibrium profile with a time scale similar to that of the instability, a persistent annular vortex with similar characteristics as that observed in the Martian atmosphere can be simulated. This time scale, typically 0.5–2 sols, is similar to radiative relaxation time scales for Mars’s polar atmosphere. The persistence of an annular vortex is also shown to be robust to topographic forcing, as long as it is below a certain amplitude. It is therefore proposed that the persistence of this barotropically unstable annular vortex is permitted owing to the combination of short radiative relaxation time scales and relatively weak topographic forcing in the Martian polar atmosphere.

Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

1977 ◽  
Vol 32 (1) ◽  
pp. 57-60 ◽  
Author(s):  
H. E. Gunilla Knape ◽  
Lena M. Torell
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Viscosity Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Hypersonic Velocity ◽  
Frequency Shifts ◽  
Bulk Viscosity Coefficient ◽  
Good Agreement

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper­ sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap­ proaching the classical attenuation. The results are in good agreement with Mountain's theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

On measurement of the thermal relaxation time in transient thermal processes of solids

2015 ◽  
Vol 58 (3) ◽  
pp. 251-257 ◽  
Author(s):  
Yu. A. Kirsanov ◽  
A. Yu. Kirsanov ◽  
K. Kh. Gil’fanov ◽  
A. E. Yudakhin
Keyword(s):  
Relaxation Time ◽  
Thermal Relaxation ◽  
Thermal Relaxation Time ◽  
Thermal Processes ◽  
Transient Thermal
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