Search results for "waves"
showing 10 items of 1766 documents
Conditions for achieving invisibility of hyperbolic multilayered nanotubes
2016
Invisibility of nanotubes has recently been demonstrated in highly anisotropic metamaterials in the transition regime from hyperbolic to elliptic dispersion [Sci. Rep. 5 (2015) 16027]. In such study, the characterization of a realistic multilayered metamaterial was carried out by means of an effective medium approach providing average components of the permittivity tensor and wave fields. Here, the edge effects of the metal-dielectric stratified nanotube for different combinations were thoroughly analyzed. We show how the boundary layers, which in principle remain fully irrelevant in the estimation of the effective permittivity of the nanotube, however play a critical role in the scattering…
GPR multi-component data analysis
2007
In order to test the capabilities of ground-penetrating radar (GPR) detection, models were reproduced in a laboratory using both plastic and metal cylinders as well as sheets to represent anomalies buried in a plastic tank containing sand. These models, which represent pipes and dipping layers in a homogeneous medium (i.e., sand), were used to detect the object’s position and study its polarization properties based on the different dielectric contrasts between the object and the surrounding medium. We paid particular attention to the choice of medium through which the wavefield propagated, to be sure of its isotropy and homogeneity, in order for the velocity to be the same for every path tr…
Noninvasive monitoring of polymer curing reactions by dielectrometry
2011
A microwave sensor system for the noninvasive monitoring of the curing process of a thermoset material placed inside a metallic mold is described. The microwave sensor is designed as an open-ended coaxial resonator with a curved surface adapted to the mold inner shape. The analysis of the microwave resonator comprises a recently developed method for deembedding the effect of coupling network in overcoupled resonators, so the range of permitted measurements encompass both low and high dielectric losses of polymeric materials. Results show that noninvasive, continuous monitoring of the microwave dielectric properties of the thermoset material can be performed in real time, allowing one to che…
Uniaxial Pressure Effect on Electric Properties of PSN and 0.95PSN-0.05PLuN Ceramics
2006
The dielectric, pyroelectric and hysteresis loops measurements of PSN and 0.95PSN-0.05PLuN ceramics stress-free and under the stress (0–1.5 kbar) have been carried out. It was shown that axial pressure seems to change the partially ordered state to a disordered one, shifts the phase transformation and decreases the thermal hysteresis of the dielectric permittivity and the field-polarization hysteresis. These effects can be connected with change in domain structure, inter-ionic distances and defect density under the action of uniaxial pressure. The thermodynamic parameters of the phase transition were also determined.
A multicommutated flow system for determination of bismuth in milk shakes by hydride generation atomic fluorescence spectrometry incorporating on-lin…
2004
Abstract A highly sensitive method was developed for determination of bismuth in milk shakes by multicommutation hydride generation atomic fluorescence spectrometry (HG-AFS) based on off-line sonication for 10 min with aqua regia 8% (v/v) and on-line waste treatment. The instrumentation and chemistry variables were studied in order to provide the best performance. The limit of detection in the original samples, established for a probability level of 99.6% (k = 3), was 1.67 ng/g Bi. The method provides a fast alternative in control analysis with a sampling throughput of 72 h as compared with 31 h obtained by the classical continuous measurement. Additionally, multicommutation reduces waste g…
High-repetition-rate source delivering optical pulse trains with a controllable level of amplitude and temporal jitters
2020
International audience; We theoretically propose and numerically validate an all-optical scheme to generate optical pulse trains with varying peak-powers and durations. A shaping of the spectral phase thanks to discrete /2 phase shifts enables an efficient phase-to-intensity conversion of a temporal phase modulation based on a two-tone sinusoidal beating. Experiments carried out at telecommunication wavelengths and at a repetition rate of 10 GHz confirm the ability of our approach to efficiently generate a train made of pulses with properties that vary from pulse-to-pulse. The levels of jitters can be accurately controlled.
Long-term pulse profile study of the Be/X-ray pulsar SAX J2103.5+4545
2007
Aims. We present the first long-term pulse profile study of the X-ray pulsar SAX J2103.5+4545. Our main goal is to study the pulse shape correlation either with luminosity, time or energy. Methods. This Be/X-ray binary system was observed from 1999 to 2004 by RXTE PCA, and by INTEGRAL from 2002 to 2005, during the Performance and Verification (PV) phase and the Galactic Plane Scan survey (GPS). X-ray pulse profiles were obtained in different energy ranges. The long-term spectral variability of this source is studied. The long-term flux, frequency and spin-up rate histories are computed. A new set of orbital parameters are also determined. Results. The pulse shape is complex and highly varia…
Active locking and entanglement in type II optical parametric oscillators
2018
Type II optical parametric oscillators are amongst the highest-quality sources of quantum-correlated light. In particular, when pumped above threshold, such devices generate a pair of bright orthogonally-polarized beams with strong continuous-variable entanglement. However, these sources are of limited practical use, because the entangled beams emerge with different frequencies and a diffusing phase-difference. It has been proven that the use of an internal wave-plate coupling the modes with orthogonal polarization is capable of locking the frequencies of the emerging beams to half the pump frequency, as well as reducing the phase-difference diffusion, at the expense of reducing the entangl…
Detecting gravitational waves from cosmological phase transitions with LISA: an update
2020
MC was funded by the Royal Society under the Newton International Fellowship program. GD would like to thank CNPq (Brazil) for financial support. MH was supported by the Science and Technology Facilities Council (grant number ST/P000819/1), and the Academy of Finland (grant number 286769). SJH was supported by the Science and Technology Facilities Council (grant number ST/P000819/1). The work of JK was supported by Department of Energy (DOE) grant DE-SC0019195 and NSF grant PHY-1719642. TK and GS are funded by the Deutsche Forschungsgemeinschaft under Germany's Excellence Strategy - EXC 2121 \Quantum Universe" - 390833306. JMN is supported by Ramon y Cajal Fellowship contract RYC-2017-22986…
Mechanisms for the Dynamics of Phase Transformations
1984
An introductory review of the dynamics of (first- order) phase transitions is given. Concepts describing the initial stages of the transition, such as nucleation, spinodal decomposition (in the case of unmixing) are introduced, and their validity is critically discussed. The theoretical results are compared to recent computer simulations and pertinent experiments. Then the scaling concepts describing the late stages of domain growth are discussed, and open problems are outlined.