The pyroelectric properties of TGS for application in infrared detection

The pyroelectric property of triglycine sulfate and its application in the detection of infrared radiation are described. The detectivities of pyroelectric detectors and other types of infrared detectors are compared. The thermal response of a pyroelectric detector element and the resulting electrical response are derived in terms of the material parameters. The noise sources which limit the sensitivity of pyroelectric detectors are described, and the noise equivalent power for each noise source is given as a function of frequency and detector area

<i>In Situ</i> Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions

During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (~46.5% and ~61% of all particles; ~76.5 wt % and ~89 wt % of the relative particle load). Furthermore, ~69% and ~82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of ‘‘sand skirts.’’ Both sampled dust devils were relatively small (~15m and ~4–5m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ~58.5% to 73.5% of all lifted particles were small enough to go into suspension (<31 mm, depending on the used grain size classification). This relatively high amount represents only ~0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected

Fermionic functional renormalization group for first-order phase transitions: a mean-field model

First-order phase transitions in many-fermion systems are not detected in the susceptibility analysis of common renormalization-group (RG) approaches. Here we introduce a counterterm technique within the functional renormalization-group (fRG) formalism which allows access to all stable and metastable configurations. It becomes possible to study symmetry-broken states which occur through first-order transitions as well as hysteresis phenomena. For continuous transitions, the standard results are reproduced. As an example, we study discrete-symmetry breaking in a mean-field model for a commensurate charge-density wave. An additional benefit of the approach is that away from the critical temperature for the breaking of discrete symmetries large interactions can be avoided at all RG scales.Comment: 17 pages, 8 figures. v2 corrects typos, adds references and a discussion of the literatur

Scanning the critical fluctuations -- application to the phenomenology of the two-dimensional XY-model --

We show how applying field conjugated to the order parameter, may act as a very precise probe to explore the probability distribution function of the order parameter. Using this `magnetic-field scanning' on large-scale numerical simulations of the critical 2D XY-model, we are able to discard the conjectured double-exponential form of the large-magnetization asymptote.Comment: 4 pages, 4 figure

Physically derived sound synthesis model of a propeller

© 2017 Copyright held by the owner/author(s). A real-time sound synthesis model for propeller sounds is presented. Equations obtained from fluid dynamics and aerodynamics research are utilised to produce authentic propeller-powered aircraft sounds. The result is a physical model in which the geometries of the objects involved are used in sound synthesis calculations. The model operates in real-time making it ideal for integration within a game or virtual reality environment. Comparison with real propeller-powered aircraft sounds indicates that some aspects of real recordings are not replicated by our model. Listening tests suggest that our model performs as well as another synthesis method but is not as plausible as a real recording

Relativistic photoelectron spectra in the ionization of atoms by elliptically polarized light

Relativistic tunnel ionization of atoms by intense, elliptically polarized light is considered. The relativistic version of the Landau-Dykhne formula is employed. The general analytical expression is obtained for the relativistic photoelectron spectra. The most probable angle of electron emission, the angular distribution near this angle, the position of the maximum and the width of the energy spectrum are calculated. In the weak field limit we obtain the familiar non-relativistic results. For the case of circular polarization our analytical results are in agreement with recent derivations of Krainov [V.P. Krainov, J. Phys. B, {\bf 32}, 1607 (1999)].Comment: 8 pages, 2 figures, accepted for publication in Journal of Physics

Non-dipole recollision-gated double ionization and observable effects

Using a three-dimensional semiclassical model, we study double ionization for strongly-driven He fully accounting for magnetic field effects. For linearly and slightly elliptically polarized laser fields, we show that recollisions and the magnetic field combined act as a gate. This gate favors more transverse - with respect to the electric field - initial momenta of the tunneling electron that are opposite to the propagation direction of the laser field. In the absence of non-dipole effects, the transverse initial momentum is symmetric with respect to zero. We find that this asymmetry in the transverse initial momentum gives rise to an asymmetry in a double ionization observable. Finally, we show that this asymmetry in the transverse initial momentum of the tunneling electron accounts for a recently-reported unexpectedly large average sum of the electron momenta parallel to the propagation direction of the laser field.Comment: Amended the focus of the paper and discussion. 9 pages, 7 figure

Relativistic semiclassical approach in strong-field nonlinear photoionization

Nonlinear relativistic ionization phenomena induced by a strong laser radiation with elliptically polarization are considered. The starting point is the classical relativistic action for a free electron moving in the electromagnetic field created by a strong laser beam. The application of the relativistic action to the classical barrier-suppression ionization is briefly discussed. Further the relativistic version of the Landau-Dykhne formula is employed to consider the semiclassical sub-barrier ionization. Simple analytical expressions have been found for: (i) the rates of the strong-field nonlinear ionization including relativistic initial and final state effects; (ii) the most probable value of the components of the photoelectron final state momentum; (iii) the most probable direction of photoelectron emission and (iv) the distribution of the photoelectron momentum near its maximum value.Comment: 13 pages, 3 figures, to be published in Phys. Rev.