Search results for "POLARIZATION"
showing 10 items of 1884 documents
Scattering of electromagnetic waves from a graphene-coated thin cylinder of left-handed metamaterial
2017
Abstract In this paper, we explored the scattering behavior of thin cylinders made of a left-handed material (LHM) and coated by a monoatomic graphene layer. A spectral tunability of the resonance peaks is evidenced by altering the chemical potential of the graphene coating, a fact that occurs at any state of polarization of the incident plane wave in opposition to the case of scatterers of dielectric core. On the contrary, no invisibility condition can be satisfied for dielectric environments. A singular performance is also found for cylinders with permittivity and permeability near zero. Practical implementations of our results can be carried out in sensing and wave manipulation driven by…
Influence of Uniaxial Pressure on Dielectric Properties and Aging Effect of BiFeO3Ceramic
2015
The external stress (0–1500 bar) dependence of dielectric properties and an aging effect of BiFeO3 ceramic has been investigated. The electric permittivity and dielectric losses first increased (up to about 700 bar) and next decreased with uniaxial pressure applied parallel to the ac field direction, while increased with the stress perpendicularly applied. It was suggested that combination of the de-aging, clamping of the domain walls, and the polarization reorientation mechanisms can be responsible for these changes. The aging effect is followed logarithmic law and is related to the relaxation of the domain structure towards an equilibrium configuration.
Comparison of the Influences of a Perpendicular and Parallel Uniaxial Stress on the Dielectric and Ferroelectric Properties of Fe Doped BaTiO3Ceramics
2014
The dielectric and ferroelectric properties of Fe-doped BaTiO3 ceramic under uniaxial stress applied perpendicular and parallel to the electric field are presented and analyzed. For the dielectric properties, the results showed that the uniaxial stress reduced an electric permittivity and dielectric losses for the both directions of applied stress. It was also found that an applied uniaxial pressure also enhanced a diffuse phase transformation behaviour. In the case of the ferroelectric properties the applied stress weakens a polarization when it is applied parallel (p∥ac) to the electric field. These results were interpreted through the stress induced domain switching process.
Effect of a filler on the dielectric properties of an epoxy resin
1983
The effect of aluminum hydroxide upon the dielectric properties of an epoxy resin has been studied in a wide frequency and temperature range. An interfacial polarization effect, known as the Maxwell–Wagner–Sillars polarization is evidenced for the filled resin, which shows a higher permittivity, a higher dielectric loss, and a β transition with a larger relaxation time. The glass transition temperature is, on the contrary, mostly unaffected by the presence of the filler.
Evolution of dielectric properties in transparent PLZT 8.3/70/30 ceramics at the diffused phase transition
1999
Abstract The time evolution of dielectric properties after a temporary change of temperature and electric field is investigated. It is found, that below the temperature of ˛' maximum Tm the change of temperature and electric field creates an increase of dielectric permittivity followed by logarithmic decay when the change of these parameters is finished. At every temperature the dielectric properties are characterized by a unique ˛'(t) independent on previous thermal history. If the applied electric field is E< Ec, the state of polarization is not affected. The dependence on dielectric constant of storage time under field as well as field intensity is determined.
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…
Relation of Dielectric Permittivity and Electric Field Dependence of Polarization in Some Relaxors with Perovskite Structure
2011
The dielectric nonlinearity is studied in ferroelectric relaxors 0.92PbMg1/3 Nb2/3O3-0.08PbTiO3, 0.4Na1/2Bi1/2TiO3-0.5SrTiO3-0.1PbTiO3 and Pb0.9075La0.0925 (Zr0.65Ti0.35)0.9775O3. It is shown that above the temperature of dielectric permittivity maximum nonlinearity of dielectric permittivity corresponds to electric field dependence of polarization. The influence of electric field on distribution of relaxation times is studied below the maximum of dielectric permittivity. The role of internal bias field in Pb0.9075La0.0925(Zr0.65Ti0.35)0.9775O3 ceramics is discussed.
Local hydrogen-clearance and 257-01257-01257-01- measurements in micro-areas of the rat brain
1970
La pression partielle de l'oxygene et la «clearance» de l'hydrogene ont ete mesurees dans des regions circonscrites. Les deux valeurs sont enregistrees par la meme microelectrode de platine (diametre de la pointe 10μ). Cette methode nouvelle est appliquee dans des experiences faites sur le cerveau de Rats narcotises et on est capable d'evaluer les inhomogenites locales de l'apport d'oxygene dependant du flux du sang.
Über den Einfluss von Acetylcholin auf das Membranpotential denervierter Rattenzwerchfelle
1957
The membran potential of isolated rat-diaphragms has been measured by means of intracellular micro-electrodes, in order to study changes of the resting potential and of the depolarizing action of acetylcholine after section of the phrenic nerve. Within 80 days after denervation, the membrane potential was found to fall exponentially from 87 mV to 66 mV. The action of acetylcholine, on the other hand, was found to be independent of the duration of denervation: between the 4th and the 80th day of denervation: 10−5g/ml acetylcholine always caused the membrane potential to fall by an average of the 9 mV.
Ca-abh�ngige Membranpotential�nderungen am Herzen und ihre Bedeutung f�r die elektro-mechanische Kopplung. Versuche mit Tetrodotoxin in Na-haltigen L…
1969
1. Tetrodotoxin (TTX), at a concentration of less than 10−6 g/ml, had no effect on membrane potential and contraction of isolated, thin ventricular trabeculae of sheep and calf hearts. 10−6 to 2 × 10−5 g/ml TTX decreased the rate of rise, over-shoot, and duration (phase of 90% repolarisation) of the action potential and the amplitude of contraction, without change in the resting potential and the plateau (20% repolarisation phase) of the action potential. Excitation block regularly occurred only with 10−5 to 2×10−5 g/ml TTX. 2. In a solution containing Na and TTX (5×10−6-2×10−5 g/ml) graded depolarisation was possible if the preparations were stimulated by square wave pulses of 500 msec dur…