The Rayleigh–Brillouin spectrum of compressed H2; a test of translational hydrodynamics

1977 ◽  
Vol 55 (1) ◽  
pp. 23-26 ◽  
Author(s):  
M. Hubert ◽  
A. D. May
Keyword(s):  
Reasonable Agreement ◽  
Hydrodynamic Theory ◽  
Rotational States ◽  
Energy And Momentum ◽  
Brillouin Spectrum

This paper reports on a comparison between the observed Rayleigh–Brillouin spectra of compressed hydrogen and those computed according to the translational hydrodynamic theory of Desai and Kapral. Reasonable agreement is found in the range of densities from 19 to 61 amagat units. It is suggested that small residual discrepancies may be due to the neglect of part of the coupling between the energy and momentum fluctuations arising from relaxation of the rotational states, i.e. due to the neglect of the 1ν1 terms.

The Rayleigh–Brillouin spectrum of hydrogen at high densities

1978 ◽  
Vol 56 (9) ◽  
pp. 1168-1174 ◽  
Author(s):  
A. D. May ◽  
M. Hubert ◽  
V. Ghaem-Maghami
Keyword(s):  
Relaxation Time ◽  
Theoretical Calculations ◽  
Hydrodynamic Theory ◽  
Normal Hydrogen ◽  
Brillouin Spectrum

The Rayleigh–Brillouin spectrum of light scattered from hydrogen at high densities is reported. The observations are compared with translational hydrodynamic theory and ultrasonic experiments. The range of densities includes the relaxation region and we find evidence for multiple relaxation. A mean relaxation time for normal hydrogen at 24 °C of (1.41 ± 0.06) × 10−8 s is found, in agreement with theoretical calculations.

Rayleigh–Brillouin Scattering in Compressed H2, D2, and HD. II

1972 ◽  
Vol 50 (12) ◽  
pp. 1227-1229 ◽  
Author(s):  
E. H. Hara ◽  
A. D. May
Keyword(s):  
Thermal Conduction ◽  
Brillouin Scattering ◽  
Hydrodynamic Theory ◽  
Brillouin Spectrum

The observations presented by Hara et al. for the Brillouin spectrum of H2, D2, and HD are compared with the thermo-hydrodynamic theory of Bhatia and Tong. It is noted that although this theory is qualitatively correct it fails to describe accurately the spectrum at low to medium densities. It is suggested that the introduction of a relaxing thermal conduction might account for the discrepancy observed.

Traction Measurements in Mixed Elastohydrodynamic Lubrication with a Controlled Circumferential Roughness

1991 ◽  
Vol 205 (4) ◽  
pp. 265-273 ◽  
Author(s):  
M P F Sutcliffe
Keyword(s):  
Film Thickness ◽  
Transition Region ◽  
Reasonable Agreement ◽  
Hydrodynamic Lubrication ◽  
Elastohydrodynamic Lubrication ◽  
Hydrodynamic Theory ◽  
Good Picture ◽  
Sliding Speed ◽  
Simple Variation ◽  
Oil Films

The transition between smooth elastohydrodynamics (EHL) and micro-EHL is investigated. Traction measurements in a disc machine with a controlled circumferential roughness are used to infer film thicknesses under the asperity tops. These are then compared with hydrodynamic theory. At the two extremes where there is little pressure rippling between the asperity tops and the adjoining valleys or where there is little pressure in the valleys the theoretical and experimentally inferred films are in reasonable agreement. In the transition region the experimentally deduced films are not reliable. Traction behaviour is estimated in the transition region by making some simple assumptions. The film thickness under the asperities is taken as that given by theory for no pressure in the valleys, and the valley pressure in the transition region is estimated by assuming a simple variation with speed. Theoretical traction curves are calculated by apportioning the load between the valleys and the asperity tops and agree well with measured curves, suggesting that this is a good picture of the contact. The traction behaviour was found to depend on sliding speed in a way typical of hydrodynamic lubrication even for estimated oil films as small as 8 nm.

Rayleigh–Brillouin Scattering in Compressed H2, D2, and HD

1971 ◽  
Vol 49 (4) ◽  
pp. 420-431 ◽  
Author(s):  
E. H. Hara ◽  
A. D. May ◽  
H. F. P. Knaap
Keyword(s):  
High Pressure ◽  
Thermal Conduction ◽  
Room Temperature ◽  
Brillouin Scattering ◽  
Photon Counting ◽  
High Pressure Cell ◽  
Rotational States ◽  
Pressure Cell ◽  
Fabry Perot ◽  
Brillouin Spectrum

The Rayleigh–Brillouin spectrum of light scattered from H2, D2, and HD has been measured at densities ranging from 1/2 to 104 amagat, all at room temperature. The apparatus consisted of a 20 mW He–Ne laser, a high pressure cell for 90° scattering, a pressure scanned Fabry–Perot interferometer, and photon counting electronics. A discrepancy is noted between the observed spectra and various theoretical spectra. It is suggested that the discrepancy arises from an omission in the theories of coupling between relaxation of the rotational states and thermal conduction.

Interstitial vs. Substitutional Metal Insertion in V2O5 as Post-Lithium Ion Battery Cathode: A Comparative GGA/GGA+U Study with Localized Bases

2020 ◽  
Author(s):  
Daniel Koch ◽  
Sergei Manzhos
Keyword(s):  
Electronic Structure ◽  
Plane Wave ◽  
Transition Metal Oxides ◽  
Reasonable Agreement ◽  
Correction Term ◽  
Lithium Ion ◽  
Generalized Gradient ◽  
Main Group Metals ◽  
Generalized Gradient Approximation ◽  
Metal Insertion

<p></p><p>The generalized gradient approximation (GGA) often fails to correctly describe the electronic structure and thermochemistry of transition metal oxides and is commonly improved using an inexpensive correction term with a scaling parameter <i>U</i>. We tune <i>U</i> to reproduce experimental vanadium oxide redox energetics with a localized basis and a GGA functional. We find the value for <i>U</i> to be significantly lower than what is generally reported with plane-wave bases, with the uncorrected GGA results being in reasonable agreement with experiments. We use this computational setup to calculate interstitial and substitutional <a>insertion energies of main group metals in vanadium pentoxide</a> and find <a>interstitial doping to be thermodynamically favored</a>.</p><p></p>

Membrane thickening of water works sludge

2001 ◽  
Vol 1 (5-6) ◽  
pp. 215-220
Author(s):  
A. Gillighan ◽  
S.J. Judd ◽  
R. Eyres
Keyword(s):  
Hydraulic Resistance ◽  
Reasonable Agreement ◽  
Chemical Cleaning ◽  
Solids Concentration ◽  
Significant Difference ◽  
Layer Resistance ◽  
Tubular Membranes ◽  
Resistance Data ◽  
Mechanical Cleaning ◽  
Dynamic Layer

The efficacy of ultrafiltration (UF) and microfiltration (MF) membranes was assessed for the concentration of actual waterworks sludges using crossflow tubular membranes operated at constant trans-membrane pressure. The MF membrane gave higher initial fluxes than the UF membrane but after 10 min of filtration the flux value and its decline tended to be very similar for both membranes operating under the same conditions. All membranes gave permeate product water of &lt;0.2 NTU and &lt;100ppb coagulant at all times. For both membranes mechanical cleaning, with sponge balls, was at least as effective as acid chemical cleaning, indicating that no significant permanent internal fouling occurred for these membrane materials. Hydraulic resistance data indicated a significant difference in the dynamic layer resistance between the two membranes. Whilst the UF membrane had a hydraulic resistance 3.7 times that of the MF membrane, the dynamic layer formed on the UF membrane during operation displayed a maximum hydraulic resistance almost nine times lower than that of the MF membrane operating under the same conditions. Correlation of cake resistance R versus feed solids concentration C for all the data generated for t&gt;0 demonstrated reasonable agreement with the expression R∝ca where a=0.37 in the current study. This trend has been recorded in previous reported studies, a varying between 0.33 and 0.62 depending on sludge dewaterability.

Energy and Momentum

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
Time Dilation ◽  
Speed Of Light ◽  
Massless Particles ◽  
The Everyday ◽  
Low Speeds ◽  
Energy And Momentum ◽  
Deep Relationship ◽  
Insight Into ◽  
Momentum Relation

Tis chapter explains the famous equation E = mc2 as part of a wider relationship between energy, mass, and momentum. We start by defning energy and momentum in the everyday sense. We then build on the stretching‐triangle picture of spacetime vectors developed in Chapter 11 to see how energy, mass, and momentum have a deep relationship that is not obvious at everyday low speeds. When momentum is zero (a mass is at rest) this energy‐momentum relation simplifes to E = mc2, which implies that mass at rest quietly stores tremendous amounts of energy. Te energymomentum relation also implies that traveling near the speed of light (e.g., to take advantage of time dilation for interstellar journeys) will require tremendous amounts of energy. Finally, we look at the simplifed form of the energy‐momentum relation when the mass is zero. Tis gives us insight into the behavior of massless particles such as the photon.

scholarly journals Scattering in Terms of Bohmian Conditional Wave Functions for Scenarios with Non-Commuting Energy and Momentum Operators

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 408
Author(s):  
Matteo Villani ◽  
Guillermo Albareda ◽  
Carlos Destefani ◽  
Xavier Cartoixà ◽  
Xavier Oriols
Keyword(s):  
Single Particle ◽  
Degrees Of Freedom ◽  
Single Photon ◽  
Open Quantum Systems ◽  
Wave Functions ◽  
Practical Application ◽  
Light Matter Interaction ◽  
Pure States ◽  
Energy And Momentum ◽  
Full Quantum

Without access to the full quantum state, modeling quantum transport in mesoscopic systems requires dealing with a limited number of degrees of freedom. In this work, we analyze the possibility of modeling the perturbation induced by non-simulated degrees of freedom on the simulated ones as a transition between single-particle pure states. First, we show that Bohmian conditional wave functions (BCWFs) allow for a rigorous discussion of the dynamics of electrons inside open quantum systems in terms of single-particle time-dependent pure states, either under Markovian or non-Markovian conditions. Second, we discuss the practical application of the method for modeling light–matter interaction phenomena in a resonant tunneling device, where a single photon interacts with a single electron. Third, we emphasize the importance of interpreting such a scattering mechanism as a transition between initial and final single-particle BCWF with well-defined central energies (rather than with well-defined central momenta).

scholarly journals Four-dimensional vibrational spectroscopy for nanoscale mapping of phonon dispersion in BN nanotubes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ruishi Qi ◽  
Ning Li ◽  
Jinlong Du ◽  
Ruochen Shi ◽  
Yang Huang ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Energy Loss ◽  
Phonon Dispersion ◽  
Hexagonal Boron Nitride ◽  
Real Space ◽  
Boron Nitride Nanotubes ◽  
Detection Sensitivity ◽  
Optical Modes ◽  
Optical And Mechanical Properties ◽  
Energy And Momentum

AbstractDirectly mapping local phonon dispersion in individual nanostructures can advance our understanding of their thermal, optical, and mechanical properties. However, this requires high detection sensitivity and combined spatial, energy and momentum resolutions, thus has been elusive. Here, we demonstrate a four-dimensional electron energy loss spectroscopy technique, and present position-dependent phonon dispersion measurements in individual boron nitride nanotubes. By scanning the electron beam in real space while monitoring both the energy loss and the momentum transfer, we are able to reveal position- and momentum-dependent lattice vibrations at nanometer scale. Our measurements show that the phonon dispersion of multi-walled nanotubes is locally close to hexagonal-boron nitride crystals. Interestingly, acoustic phonons are sensitive to defect scattering, while optical modes are insensitive to small voids. This work not only provides insights into vibrational properties of boron nitride nanotubes, but also demonstrates potential of the developed technique in nanoscale phonon dispersion measurements.

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