Multi-Band Planar Antennas: a Comparative Study

The classical patch antenna is a basic building block of compared antennas. The multi-band behavior is achieved by etching perturbation slots to the patch, which influence resonant current distributions. The antennas are designed for GSM bands (900 MHz, 1 800 MHz), and for the Bluetooth band (2 400 MHz)

Coronal ion-cyclotron beam instabilities within the multi-fluid description

Spectroscopic observations and theoretical models suggest resonant wave-particle interactions, involving high-frequency ion-cyclotron waves, as the principal mechanism for heating and accelerating ions in the open coronal holes. However, the mechanism responsible for the generation of the ion-cyclotron waves remains unclear. One possible scenario is that ion beams originating from small-scale reconnection events can drive micro-instabilities that constitute a possible source for the excitation of ion-cyclotron waves. In order to study ion beam-driven electromagnetic instabilities, the multi-fluid model in the low-beta coronal plasma is used. While neglecting the electron inertia this model allows one to take into account ion-cyclotron wave effects that are absent from the one-fluid MHD model. Realistic models of density and temperature as well as a 2-D analytical magnetic field model are used to define the background plasma in the open-field funnel region of a polar coronal hole. Considering the WKB approximation, a Fourier plane-wave linear mode analysis is employed in order to derive the dispersion relation. Ray-tracing theory is used to compute the ray path of the unstable wave as well as the evolution of the growth rate of the wave while propagating in the coronal funnel. We demonstrate that, in typical coronal holes conditions and assuming realistic values of the beam velocity, the free energy provided by the ion beam propagating parallel the ambient field can drive micro-instabilities through resonant ion-cyclotron excitation.Comment: 8 pages, 6 figures, submitted to A&

Natural and projectively equivariant quantizations by means of Cartan Connections

The existence of a natural and projectively equivariant quantization in the sense of Lecomte [20] was proved recently by M. Bordemann [4], using the framework of Thomas-Whitehead connections. We give a new proof of existence using the notion of Cartan projective connections and we obtain an explicit formula in terms of these connections. Our method yields the existence of a projectively equivariant quantization if and only if an \sl(m+1,\R)-equivariant quantization exists in the flat situation in the sense of [18], thus solving one of the problems left open by M. Bordemann.Comment: 13 page

Nonuniform Self-Organized Dynamical States in Superconductors with Periodic Pinning

We consider magnetic flux moving in superconductors with periodic pinning arrays. We show that sample heating by moving vortices produces negative differential resistivity (NDR) of both N and S type (i.e., N- and S-shaped) in the voltage-current characteristic (VI curve). The uniform flux flow state is unstable in the NDR region of the VI curve. Domain structures appear during the NDR part of the VI curve of an N type, while a filamentary instability is observed for the NDR of an S type. The simultaneous existence of the NDR of both types gives rise to the appearance of striking self-organized (both stationary and non-stationary) two-dimensional dynamical structures.Comment: 4 pages, 2 figure

Speckle activity images based on the spatial variance of the phase

We propose the display of the local spatial variance of the temporal variations of the phase as an activity descriptor in dynamic speckle images. The spatial autocorrelation of the speckle intensity is calculated in sliding windows, and an estimation of the variance of the phase variations in each region of the sample is determined. The activity images obtained in this way depict some interesting features and in some cases they could be related to physical magnitudes in the samples. A simulation is presented, and examples corresponding to usual study cases are also shown, namely, fruit bruising and paint drying

Speckle activity images based on the spatial variance of the phase

We propose the display of the local spatial variance of the temporal variations of the phase as an activity descriptor in dynamic speckle images. The spatial autocorrelation of the speckle intensity is calculated in sliding windows, and an estimation of the variance of the phase variations in each region of the sample is determined. The activity images obtained in this way depict some interesting features and in some cases they could be related to physical magnitudes in the samples. A simulation is presented, and examples corresponding to usual study cases are also shown, namely, fruit bruising and paint drying.Facultad de Ingeniería (FI)Centro de Investigaciones Ópticas (CIOp

Speckle activity images based on the spatial variance of the phase

We propose the display of the local spatial variance of the temporal variations of the phase as an activity descriptor in dynamic speckle images. The spatial autocorrelation of the speckle intensity is calculated in sliding windows, and an estimation of the variance of the phase variations in each region of the sample is determined. The activity images obtained in this way depict some interesting features and in some cases they could be related to physical magnitudes in the samples. A simulation is presented, and examples corresponding to usual study cases are also shown, namely, fruit bruising and paint drying.Facultad de Ingeniería (FI)Centro de Investigaciones Ópticas (CIOp

Freeze-out configuration properties in the 197Au + 197Au reaction at 23 AMeV

Data from the experiment on the 197Au + 197Au reaction at 23 AMeV are analyzed with an aim to find signatures of exotic nuclear configurations such as toroid-shaped objects. The experimental data are compared with predictions of the ETNA code dedicated to look for such configurations and with the QMD model. A novel criterion of selecting events possibly resulting from the formation of exotic freeze-out configurations, "the efficiency factor", is tested. Comparison between experimental data and model predictions may indicate for the formation of flat/toroidal nuclear systems

Signals of dynamical and statistical process from IMF-IMF correlation function

In this paper we briefly discuss about a novel application of the IMFIMF correlation function to the physical case of binary massive projectile-like (PLF) splitting for dynamical and statistical breakup/fission in heavy ion collisions at Fermi energy. Theoretical simulations are also shown for comparisons with the data. These preliminary results have been obtained for the reverse kinematics reaction 124Sn+64Ni at 35 AMeV that was studied using the forward part of CHIMERA detector. In that reaction a strong competition between a dynamical and a statistical components and its evolution with the charge asymmetry of the binary break up was already shown. In this work we show that the IMF-IMF correlation function can be used to pin down the timescale of the fragments production in binary fission-like phenomena. We also made simulations with the CoMDII model in order to compare to the experimental IMF-IMF correlation function. In future we plan to extend these studies to different reaction mechanisms and nuclear systems and to compare with different theoretical transport simulations