Results 1 - 10 of 14661
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[en] In this paper is presented a method to find the conditions of existence for anisotropic different plasmas which present the same reflection coefficient. The analytical dependence of the complex reflection coefficient on the plasma parameters wao examinated. Then the numerical calculations were made with the use of a computer. The results of these calculations have been plotted on a special diagram thus allowing the direct determination of the plasma parameters ωsub(p)/ω, ωsub(b)/ω, ν/ω with the reflection coefficient being known from measurements and on of the above mentioned parameters, or to establish what are the distinct sets of values for the plasma parameters ωsub(p), ωsub(b), ν for which the same reflection coefficient is obtained. The method also could be applied in two both cases of plasma explored by means of TEM mode and by guided waves respectively. (authors)
[en] In ion conducting solids, we show that the frequency-independent dc conductivity and the frequency-dependent polarization conductivity are two distinct physical processes and the same time they are related to each other. The dc conductivity is a barrier hopping short-time relaxation mechanism, whereas, the polarization conductivity is a modified barrier hopping with a long-time relaxation mechanism in the polarization process. Both these processes are shown to be related through an exponent in the relaxation process and it signifies trapping of hopping charge carriers due to the disorder in the solids. The polarization conductivity data are analyzed and results are reported. (author)
[en] The transformation optics technique is applied to design three novel devices-a wave collimator, far-zone and near-zone focusing flat optical lenses and a right-angle bend for propagating beam fields. The structures presented in this paper are all two-dimensional (2D), however, the transformation optics design methodologies can be easily extended to develop 3D versions of these optical devices. The required values of the permittivity and the permeability tensors are derived for each of the three devices considered here. Furthermore, the functional performance of each device is verified using full-wave electromagnetic simulations. A wave collimator consists of a 2D rectangular cylinder where the fields (cylindrical waves) radiated by an embedded line source emerge normal to the top and bottom planar interfaces thereby producing highly directive collimated fields. Next, a far-zone focusing lens for a 2D line source is created by transforming the equi-amplitude equi-phase contour to a planar surface. It is also demonstrated that by aligning two far-zone focusing flat lenses in a back-to-back configuration, a near-zone focusing lens is obtained. Finally, a 2D square cylindrical volume is transformed into a cylinder with a fan-shaped cross section to design a right-angle bend device for propagating beam fields.
[en] We propose a scheme for preparing optical Schroedinger-cat states in a traveling wave setting. Two states are similarly prepared via the self-Kerr effect, and after mixing them, one mode is measured by homodyne detection. In the other mode, a superposition of coherent states is conditionally prepared. The advantage of the scheme is that assuming a small Kerr effect, one can prepare with a high probability one of a set of Schroedinger-cat states. The measured value of the quadrature provides information about which one of the set of states is actually prepared.
[en] Here, we report quantitative measurements of nanoscale permittivity and conductivity using tuning-fork (TF) based microwave impedance microscopy (MIM). The system is operated under the driving amplitude modulation mode, which ensures satisfactory feedback stability on samples with rough surfaces. The demodulated MIM signals on a series of bulk dielectrics are in good agreement with results simulated by finite-element analysis. Using the TF-MIM, we have visualized the evolution of nanoscale conductance on back-gated MoS2 field effect transistors, and the results are consistent with the transport data. Our work suggests that quantitative analysis of mesoscopic electrical properties can be achieved by near-field microwave imaging with small distance modulation.
[en] The influence of temperature on surface magnetic structure has been studied in Co- and Fe-rich magnetic glass covered microwires. The investigations have been performed using magneto-optical Kerr effect technique with a thermo-controlled system. It was found different types of domain structures depending on the temperature and the microwire composition. These types are characterised by the different domain period and the angle of the inclination of domain walls. It was established the direct correlation between surface domain structures and hysteresis loops. The coexistence of domain walls with different value of mobility has been found. It was observed original mechanism of the domain structure transformation: sharp change in the domain structure without movement of the domain walls. - Highlights: • Different types of domain structures depending on the temperature are observed. • Coexistence of domain walls with different value of mobility has been found. • Sharp change of domain structure without movement of the domain walls takes place.
[en] Using B probes Meyer et al. [J. Appl. Phys. 79, 1298 (1996)] have described a method for calculating the azimuthal current, electric field, plasma permittivity, and electron density in a planar inductively coupled plasma source. They assume the phases associated with the time rate of change of the radial and axial field components to be the same. Furthermore, they restrict their analysis to the situation where the phase is independent of radius. We demonstrate that the phases for the two field directions are different. The subsequent modified forms for the plasma properties considered by Meyer et al. are presented. We also show that their procedure can be extended to cover phases which are an arbitrary function of position, and for completeness, give forms for the generalized plasma properties. copyright 1997 American Institute of Physics
[en] We present a theoretical study of an ensemble of X-like four-level atoms placed in an optical cavity driven by a linearly polarized field. We show that the self-rotation (SR) process leads to polarization switching (PS). Below the PS threshold, both the mean field mode and the orthogonal vacuum mode are squeezed. We provide a simple analysis of the phenomena responsible for the squeezing and trace the origin of vacuum squeezing not to SR, but to a crossed Kerr effect induced by the mean field. Last, we show that this vacuum squeezing can be interpreted as polarization squeezing