A study of the quantum oscillations in the thermopower of molybdenum

1982 ◽  
Vol 60 (2) ◽  
pp. 122-130 ◽  
Author(s):  
R. Fletcher
Keyword(s):  
Liquid Helium ◽  
Field Dependence ◽  
Large Amplitude ◽  
Experimental Results ◽  
Quantum Oscillations ◽  
Magnetic Breakdown ◽  
Good Agreement

This paper is concerned with quantum oscillations in the thermoelectric coefficients of metals which do not undergo magnetic breakdown, and in particular focuses on the compensated metal Mo. An expression for the amplitude of the oscillations in the thermopower has been developed and is tested using a detailed set of experimental results on Mo taken with [Formula: see text] over the range 1.5–8 T at liquid helium temperatures. Good agreement is obtained for the temperature and field dependence, and absolute amplitudes are predicted to within a factor near unity. Oscillations of appreciable amplitude arc neither expected nor observed in the Nernst–Ettingshausen (N.E.) coefficient of Mo. Available thermopower data on In have also been analysed; it is concluded that, contrary to a previous speculation. In does not undergo magnetic breakdown at fields of the order of 2 T. It is suggested that, contrary to the thermopower. the N.E. coefficient will provide an unambiguous test for the occurrence of breakdown in metals since it is expected to exhibit large amplitude quantum oscillations only under breakdown conditions.

Theoretical study of the rovibrational spectrum of He2–OCS

2010 ◽  
Vol 88 (8) ◽  
pp. 779-786 ◽  
Author(s):  
Xiao-Gang Wang ◽  
Tucker Carrington,
Keyword(s):  
Dipole Moment ◽  
Large Amplitude ◽  
Theoretical Study ◽  
Van Der Waals ◽  
Potential Functions ◽  
Experimental Results ◽  
Basis Sets ◽  
Van Der Waals Complex ◽  
Good Agreement

We report calculated microwave and infrared rovibrational transitions of the van der Waals complex He2–OCS. The calculations were done using a product basis, a Lanczos eigensolver, and potentials built from He–OCS, and He–He potential functions taken from the literature. All five of the large amplitude coordinates are treated exactly and calculations are done for J values up to five. All rovibrational levels are converged to 0.001 cm–1 by using basis sets with as many as 87 million funcions. Good agreement is found with previously reported experimental results. Although we assume that the dipole moment is along the OCS axis, we find transitions with appreciable intensity between different torsion states.

Anomalous effect of magnetic breakdown on the oscillatory magnetization

1985 ◽  
Vol 400 (1818) ◽  
pp. 145-161 ◽  
Keyword(s):  
Orbit Interaction ◽  
Energy Band Structure ◽  
Field Amplitude ◽  
Conventional Theory ◽  
Anomalous Effect ◽  
Quantum Oscillations ◽  
Magnetic Breakdown ◽  
Field Modulation ◽  
The Magnetic Field ◽  
Good Agreement

It is shown that the effect of magnetic breakdown on the oscillatory magnetization in metals can vary dramatically from that predicted by conventional theory. We report a detailed study of the amplitude of the de Haas–van Alphen (d. H. v. A.) magnetization of the magnetic breakdown β orbit in aluminium, which exhibits unexpected behaviour as a function of the magnitude and orientation of the magnetic field. Amplitude measurements have been made by using a sensitive field-modulation technique in which the interference, in particular, from quantum oscillations in the conductivity, could be reliably separated out. A generalized model for the effect of magnetic breakdown on the amplitude has been developed to explain these results. Calculations of the amplitude based on this model, with the use of breakdown fields deduced from an energy band structure including the spin–orbit interaction, are found to be in good agreement with experiment. The new model indicates that when breakdown is important, the d. H. v. A. frequency is not determined in general by an extremal cross section of the Fermi surface, as is conventionally assumed.

STRUCTURE OF THE Cu-NQR SPECTRUM IN Hg-1223 BETWEEN 4.2 K AND 145 K

2000 ◽  
Vol 14 (29n31) ◽  
pp. 3362-3367 ◽  
Author(s):  
H. BREITZKE ◽  
K. LÜDERS ◽  
A. A. GIPPIUS ◽  
E. V. ANTIPOV
Keyword(s):  
Structural Change ◽  
Crystal Lattice ◽  
Liquid Helium ◽  
Spectral Width ◽  
Low Noise ◽  
Experimental Results ◽  
The Other ◽  
Strong Variation ◽  
Temperature Range ◽  
Good Agreement

An extremely low noise RF preamplifier cooled with liquid helium has been developed and is used to perform Cu-NQR measurements for Hg-1223 (T c =134 K ) at temperatures from 4.2 K to 145 K. At temperatures from 4.2 K to 20 K the spectra are centered at 15 MHz with a spectral width of approximately 2 MHz, similar to the Cu-NQR spectra of the other members of the HgBa 2 Ca n -1 Cu n O 2 n +2+δ series. The Cu-NQR spectra in this temperature range exhibit some features indicating an unresolved splitting but they can still be fitted quite well by a set of two pairs of 63/65 Cu lines, as expected for the 1223 structure. The spectra at 40 K and above clearly show a structure that can not be fitted suitable by a set of two pairs of 63/65 Cu lines. However, a fit with a set of four pairs of 63/65 Cu lines is in good agreement with the experimental results. Furthermore, the spectra at 80 K, 85 K and 90 K show a strong variation with respect to each other which might indicate a structural change like the formation of a superstructure, as discussed for other high-T c compounds, instead of a simple disorder in the crystal lattice.

Inducing Frictional Force to Enhance the Transient Response in Beams

2019 ◽  
Vol 22 (2) ◽  
pp. 88-93
Author(s):  
Hamed Khanger Mina ◽  
Waleed K. Al-Ashtrai
Keyword(s):  
Numerical Analysis ◽  
Transient Response ◽  
Frictional Force ◽  
Damping Ratio ◽  
Experimental Results ◽  
Damping Capacity ◽  
Tightening Force ◽  
Contact Areas ◽  
Good Agreement ◽  
Ansys Workbench

This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.

PHOTOINDUCED NONLINEAR OCTUPOLAR POLARIZATION: TRANSIENT AND PERMANENT REGIMES

1996 ◽  
Vol 05 (04) ◽  
pp. 653-670 ◽  
Author(s):  
CÉLINE FIORINI ◽  
JEAN-MICHEL NUNZI ◽  
FABRICE CHARRA ◽  
IFOR D.W. SAMUEL ◽  
JOSEPH ZYSS
Keyword(s):  
Theoretical Analysis ◽  
Second Harmonic ◽  
Experimental Results ◽  
Polar Field ◽  
Rotational Spectrum ◽  
Dual Frequency ◽  
One Dimensional ◽  
Ethyl Violet ◽  
Disperse Red 1 ◽  
Good Agreement

An original poling method using purely optical means and based on a dual-frequency interference process is presented. We show that the coherent superposition of two beams at fundamental and second-harmonic frequencies results in a polar field with an irreducible rotational spectrum containing both a vector and an octupolar component. This enables the method to be applied even to molecules without a permanent dipole such as octupolar molecules. After a theoretical analysis of the process, we describe different experiments aiming at light-induced noncentrosymmetry performed respectively on one-dimensional Disperse Red 1 and octupolar Ethyl Violet molecules. Macroscopic octupolar patterning of the induced order is demonstrated in both transient and permanent regimes. Experimental results show good agreement with theory.

scholarly journals Comparison of Experimental and Numerical Transient Drop Deformation during Transition through Orifices in High-Pressure Homogenizers

2021 ◽  
Vol 5 (3) ◽  
pp. 32
Author(s):  
Benedikt Mutsch ◽  
Peter Walzel ◽  
Christian J. Kähler
Keyword(s):  
High Pressure ◽  
Visual Analysis ◽  
Imaging Technique ◽  
Extensional Flow ◽  
Droplet Breakup ◽  
Experimental Results ◽  
Drop Deformation ◽  
Droplet Deformation ◽  
Shadow Imaging ◽  
Good Agreement

The droplet deformation in dispersing units of high-pressure homogenizers (HPH) is examined experimentally and numerically. Due to the small size of common homogenizer nozzles, the visual analysis of the transient droplet generation is usually not possible. Therefore, a scaled setup was used. The droplet deformation was determined quantitatively by using a shadow imaging technique. It is shown that the influence of transient stresses on the droplets caused by laminar extensional flow upstream the orifice is highly relevant for the droplet breakup behind the nozzle. Classical approaches based on an equilibrium assumption on the other side are not adequate to explain the observed droplet distributions. Based on the experimental results, a relationship from the literature with numerical simulations adopting different models are used to determine the transient droplet deformation during transition through orifices. It is shown that numerical and experimental results are in fairly good agreement at limited settings. It can be concluded that a scaled apparatus is well suited to estimate the transient droplet formation up to the outlet of the orifice.

THE STUDY OF THE MAGNETIC BREAKDOWN EFFECT AS A FUNCTION OF ANGLE IN THE ORGANIC CONDUCTOR K- (BEDT-TTF)2Cu(NCS)2 IN HIGH MAGNETIC FIELDS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3355-3359
Author(s):  
I. MIHUT ◽  
C. C. AGOSTA ◽  
C. H. MIELKE ◽  
M. TOKOMOTO
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Spin Splitting ◽  
High Magnetic Fields ◽  
Organic Conductor ◽  
Cross Sectional ◽  
Tank Circuit ◽  
Quantum Oscillations ◽  
Magnetic Breakdown ◽  
Splitting Factor

The magnetic breakdown effect can be seen by the growth of new frequencies in the quantum oscillations in clean metals as a function of magnetic field. We have studied the variation of the amplitudes in the quantum oscillations in the resistance (the Shubnikov-de Haas effect) as a function of angle in the quasi-two dimensional-organic conductor κ-(BEDT-TTF)2Cu(NCS)2. The measurements were made by means of a radio frequency (rf) tank circuit (~ 50 MHz) at very high magnetic fields(50T-60T) and low temperature(500 mK). The geometry of the rf excitation we used excited in-plane currents, and therefore we measured the in-plane resistivity. In contrast to conventional transport measurements that measure the inter-plane resistivity, the in-plane resistivity is dominated by the magnetic breakdown frequencies. As a result we measured much higher breakdown frequency amplitudes than conventional transport experiments. As is expected, the angular dependence of the Shubnikov-de Haas frequencies have a 1/cosθ behavior. This is due to the change of the cross sectional area of the tubular Fermi surface as the angle with respect to the magnetic field is changed. The amplitude of the oscillations changes due to the spin splitting factor which takes into account the ratio between the spin splitting and the energy spacing of the Landau levels which also has 1/cosθ behavior. We show that our data agree with the semi-classical theory (Lifshitz-Kosevich formula).

Simulation of Sphere’s Motion Induced by Shock Waves

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Dan Igra ◽  
Ozer Igra ◽  
Lazhar Houas ◽  
Georges Jourdan
Keyword(s):  
Shock Waves ◽  
Drag Coefficient ◽  
Drag Force ◽  
Stationary Flow ◽  
Experimental Results ◽  
Experimental Findings ◽  
Sphere Drag ◽  
Simulation Scheme ◽  
Good Agreement

Simulations of experimental results appearing in Jourdan et al. (2007, “Drag Coefficient of a Sphere in a Non-Stationary Flow: New Results,”Proc. R. Soc. London, Ser. A, 463, pp. 3323–3345) regarding acceleration of a sphere by the postshock flow were conducted in order to find the contribution of the various parameters affecting the sphere drag force. Based on the good agreement found between present simulations and experimental findings, it is concluded that the proposed simulation scheme could safely be used for evaluating the sphere’s motion in the postshock flow.

Viscoelastic Deformation of PC/ABS Alloy

2007 ◽  
Vol 353-358 ◽  
pp. 1229-1232
Author(s):  
Z.N. Yin ◽  
L.F. Fan ◽  
Tie Jun Wang
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Relaxation Modulus ◽  
Mechanical Analysis ◽  
Experimental Results ◽  
Viscoelastic Deformation ◽  
Dynamic Mechanical ◽  
Storage And Loss Moduli ◽  
Static Relaxation ◽  
Comparison Of The Results ◽  
Good Agreement

Dynamic Mechanical Analysis (DMA) and static relaxation tests are carried out to study the viscoelastic deformation of PC/ABS alloy with blending ratio of PC to ABS being 50/50. A modified approach is developed to calculate the relaxation modulus of PC/ABS alloy from the DMA experimental results of storage and loss moduli. Comparison of the results obtained from DMA and static relaxation tests is presented and good agreement is found.

Influence of the Morphology on the Optical Properties of Nanocermet Films: A Renormalization Approach

1990 ◽  
Vol 195 ◽  
Author(s):  
S. Berthier ◽  
K. Driss-Khodja
Keyword(s):  
Optical Properties ◽  
Critical Exponents ◽  
Inhomogeneous Media ◽  
Experimental Results ◽  
Percolation Transition ◽  
Position Space ◽  
Renormalization Approach ◽  
2D And 3D ◽  
Good Agreement ◽  
Effective Medium Models

ABSTRACTIn order to take into account the actual morphology of the inhomogeneous media, we have developed, effective medium models based on a 2D and 3D position space renormalization /1,2/. These models predict the dipolar resonance and the percolation transition with critical exponents in good agreement with theoretical values and fairly reproduce most of the experimental results, whatever the concentration is. Further more, this allows a valuable comparison of the predictions of our models when applied on different lattices like real digitized TEM of cermet films or randomly occupied lattices.

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