432 research outputs found
Possible Means of Electrostatic Propulsion According to the Mbelek–Lachièze-Rey Scalar-Tensor Theory of Gravitation
As was shown recently, the scalar-tensor theory of gravitation proposed by Mbelek and Lachièze-Rey allows for a possible explanation of the forces reported in asymmetric microwave cavities. We show here that the theory in its revised version predicts a much simpler way of producing thrust by electrostatic means. We here briefly present the equations and derivations indicating that a constant force is predicted for a spherical capacitor with an asymmetric mass distribution, kept at constant voltage. Apart form other practical implications, this particular prediction, and a complementary proposal in which the spherical capacitor takes the place of the large mass in a Cavendish-like experiment, provides an additional possibility of experimentally testing this particular scalar-tensor gravitational theory.Fil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin
Electromagnetic Signatures of Possible Charge Anomalies in Tunneling
We reconsider some well-known tunneling processes from the point of view of Aharonov-Bohm electrodynamics, a unique extension of Maxwell’s theory which admits charge-current sources that are not locally conserved. In particular we are interested into tunneling phenomena having relatively long range (otherwise the non-Maxwellian effects become irrelevant, especially at high frequency) and involving macroscopic wavefunctions and coherent matter, for which it makes sense to evaluate the classical e.m. field generated by the tunneling particles. For some condensed-matter systems, admitting discontinuities in the probability current is a possible way of formulating phenomenological models. In such cases, the Aharonov-Bohm theory offers a logically consistent approach and allows to derive observable consequences. Typical e.m. signatures of the failure of local conservation are at high frequency the generation of a longitudinal electric radiation field, and at low frequency a small effect of “missing” magnetic field. Possible causes of this failure are instant tunneling and phase slips in superconductors. For macroscopic quantum systems in which the phase-number uncertainty relation (Formula presented.) applies, the expectation value of the anomalous source (Formula presented.) has quantum fluctuations, thus becoming a random source of weak non-Maxwellian fields.Fil: Minotti, Fernando Oscar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Modanese, Giovanni. Free University of Bozen-Bolzan; Itali
Quantum Uncertainty and Energy Flux in Extended Electrodynamics
In quantum theory, for a system with macroscopic wavefunction, the charge density and current density are represented by non-commuting operators. It follows that the anomaly I = ∂t ρ + ∇ · j, being essentially a linear combination of these two operators in the frequency-momentum domain, does not admit eigenstates and has a minimum uncertainty fixed by the Heisenberg relation ∆N∆φ ≃ 1, which involves the occupation number and the phase of the wavefunction. We give an estimate of the minimum uncertainty in the case of a tunnel Josephson junction made of Nb. Due to this violation of the local conservation of charge, for the evaluation of the e.m. field generated by the system it is necessary to use the extended Aharonov–Bohm electrodynamics. After recalling its field equations, we compute in general form the energy–momentum tensor and the radiation power flux generated by a localized oscillating source. The physical requirements that the total flux be positive, negative or zero yield some conditions on the dipole moment of the anomaly I.Fil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Modanese, Giovanni. University of Bozen-Bolzano; Itali
Aharonov–Bohm Electrodynamics in Material Media: A Scalar e.m. Field Cannot Cause Dissipation in a Medium
In the extension of Maxwell equations based on the Aharonov–Bohm Lagrangian, the e.m. field has an additional degree of freedom, namely, a scalar field generated by charge and currents that are not locally conserved. We analyze the propagation of this scalar field through two different media (a pure dielectric and an ohmic conductor) and study its property over a frequency range where the properties of the media are frequency-independent. We find that an electromagnetic (e.m.) scalar wave cannot propagate in a material medium. If a scalar wave in vacuum impinges on a material medium it is reflected, at most exciting in the medium a pure “potential” wave (which we also call a “gauge” wave) propagating at c, the speed of light in vacuum, with a vector potential whose Fourier amplitude is related to that of the scalar potential by (Formula presented.), where (Formula presented.).Fil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Modanese, Giovanni. Free University of Bozen-Bolzano; Itali
Large-scale model of the axisymmetric kinematic dynamo
A formulation of a kinematic dynamo is presented, based on a previously derived self-consistent procedure for obtaining large-scale models for complex system of equations. The model has only a small number of parametrized variables: the small-scale magnetic diffusivity, the scale of the large-scale fields, and a factor in the explicit expression of the αφφ component of the α tensor. Explicit expressions of what corresponds to the other components of the α tensor and of the diffusivity tensor are derived in terms of the large-scale meridional flow and of the differential rotation law, without introducing additional parameters. A very simple simulation of a solar-like dynamo, employing the model without meridional flow shows reasonable magnetic field evolution, with a cycle duration of about 2/3 that of the Sun, shift of the magnetic field from mid-latitudes towards the equator, poleward migration of the radial field at high latitudes, and correct phase relation between radial and azimuthal components.Fil: Sraibman, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin
Numerical investigation of the double-arcing phenomenon in a cutting arc torch
A numerical investigation of the double-arcing phenomenon in a cutting arc torch is reported. The dynamics of the double-arcing were simulated by using a two-dimensional model of the gas breakdown development in the space-charge layer contiguous to the nozzle of a cutting arc torch operated with oxygen. The kinetic scheme includes ionization of heavy particles by electron impact, electron attachment, electron detachment, electron-ion recombination, and ion-ion recombination. Complementary measurements during double-arcing phenomena were also conducted. A marked rise of the nozzle voltage was found. The numerical results showed that the dynamics of a cathode spot at the exit of the nozzle inner surface play a key role in the raising of the nozzle voltage, which in turn allows more electrons to return to the wall at the nozzle inlet. The return flow of electrons thus closes the current loop of the double-arcing. The increase in the (floating) nozzle voltage is due to the fact that the increased electron emission at the spot is mainly compensated by the displacement current (the ions do not play a relevant role due to its low-mobility) until that the stationary state is achieved and the electron return flow fully-compensates the electron emission at the spot. A fairly good agreement was found between the model and the experiment for a spot emission current growth rate of the order of 7×104A/s. © 2014 AIP Publishing LLC.Fil: Mancinelli, Beatriz Rosa. Universidad Tecnológica Nacional. Facultad Regional Venado Tuerto; ArgentinaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Prevosto, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Kelly, Hector Juan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin
Tunable fluidic lenses with high dioptric power
We report a complete theoretical model and supporting experimental results on the fabrication and characterization of macroscopic adaptive fluidic lenses with high dioptric power,tunablefocaldistance,andapertureshape. Thelensis17mmwideandismadeofan elastic polydimethylsiloxane (PDMS) polymer, which can adaptively restore accommodation distance within several cm according to the fluidic volume mechanically pumpedin. Moreover, the lens can provide for magnification in the range of +25 diopter to +100 diopter with optical aberrations within a fraction of a wavelength, and overall lens weight of less than 2 g. The agreement between the non-linear theoretical model describing the elastic membrane deformation and the experimental results is apparent. We stress that these features make the proposed lenses appropriate for the low vision segment,as well as for applications in videomagnifiers,camera zooms,telescope and microscopes objectives,andother machine vision applications where large magnification is required.Fil: Osamu Takayama. Technical University of Denmark; DinamarcaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Puentes, Graciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin
Relation between circuit current and plasma current density in plasma discharges with dielectric media
The theoretical derivation of the relation between moving charges in the plasma and external circuit current was first established on a firm basis by Sato1 for the case of a discharge with constant applied voltage between bare electrodes. The generalization to time varying applied voltages was established by Morrow and Sato2 , still considering bare electrodes. In the present work we extend the latter derivation to include general devices with arbitrarily arranged linear dielectric media, and multiple electrodes with time dependent voltages, of interest, for instance, for a Dielectric Barrier Discharge (DBD). In particular, the present derivation determines a general, practical expression for the reactive term present in Morrow and Sato formula. Using the expression derived we show how in simple DBD geometries usual circuit approximations of the plasma discharge can be obtained and its validity justified. Also, we consider the determination of the internal plasma current from the measurement of the external circuit current for a cylindrical DBD operated with helium at atmospheric pressure. Finally, we apply the theory to a three-electrode device in order to relate electric measurements to volume integrals on the plasma that were shown to be useful in order to quantify species production by electron impact.Fil: Giuliani, Leandro Estanislao. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Grondona, Diana Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin
About Superrotation in Venus
In this work we study in a general view slow rotating planets as Venus or Titan which present superrotating winds in their atmospheres. We are interested in understanding what mechanisms are candidates to be sources of net angular momentum to generate this kind of dynamics. In particular, in the case of Venus, in its atmosphere around an altitude of 100 km relative to the surface, there exists winds that perform a full rotation around the planet in four terrestrial days, whereas the venusian day is equivalent to 243 terrestrial ones. This phenomenon called superrotation is known since many decades. However, its origin and behaviour is not completely understood. In this article we analise and ponderate the importance of different effects to generate this dynamics.Fil: Cirilo, Diego Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Mayochi, Mariano Gustavo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Vigh, Carlos Donato. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Characterization of Titanium Films Deposited with a Cathodic Arc Using a Straight Magnetic Duct
Nanostructured Ti films were obtained employing a cathodic arc with a straightmagnetic filter. The films were characterized using X-ray diffraction, scanning electron andatomic force microscopy. The films were found to be dense and with columnar grains,whose size increased with the exposure time. The number of macroparticles, the filmroughness and the deposition rate were also analyzed, and the latter compared with theresults of a fluid plasma model. Number of macroparticles and film roughness in sampleslocated ahead of the magnetic duct inlet were higher than those determined fromsamples placed inside the magnetic duct. The deposition rate depended on the axial andradial position inside the duct. The thickness along the radial position was more uniformfor samples located at axial positions near the filter extremes, but the mean depositionrate was lower at these positions. Measured and modeled deposition rates agreed reasonablywell.Fil: Bermeo, Diego Fernando. Universidad Santiago de Cali; ColombiaFil: Della Torre, H.. Universidad del Valle de Mexico; MéxicoFil: Kleiman, Ariel Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Minotti, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Marquez, Adriana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin
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