Modelization of the whispering gallery mode in microgear resonators using the Floquet-Bloch formalism

In this paper, a two-dimensional (2-D) method describing the whispering gallery mode in a microgear resonator is presented. The microgear is a microdisk surrounded by a circular grating. The method, which is based on the Floquet-Bloch formalism, analytically describes the field within the disk and outside the grating. On the other hand, the field within the grating is calculated using a finite-difference scheme in polar coordinates. Matching the boundary conditions, it is possible to work in a forced oscillation regime or in a free oscillation regime (laser mode). The resonant wavelength and quality factor can then be deduced. Compared to the coupled mode theory and to 2-D finite-difference time-domain computations, the method is faster and more accurate. Moreover, a polarization effect of the microgear is demonstrated. The TE polarization experiences a Q-factor improvement contrary to TM polarization. Finally, microgear structures prove to be more efficient than micro flowers.     

Markov analysis of qualitative dynamics1

Common sense sometimes predicts events to be likely or unlikely rather than merely possible. We extend methods of qualitative reasoning to predict the relative likelihoods of possible qualitative behaviors by viewing the dynamics of a system as a Markov chain over its transition graph. This involves adding qualitative or quantitative estimates of transition probabilities to each of the transitions and applying the standard theory of Markov chains to distinguish persistent states from transient states and to calculate recurrence times, settling times, and probabilities for ending up in each state. Much of the analysis depends solely on qualitative estimates of transition probabilities, which follow directly from theoretical considerations and which lead to qualitative predictions about entire classes of systems. Quantitative estimates for specific systems are derived empirically and lead to qualitative and quantitative conclusions, most of which are insensitive to small perturbations in the estimated transition probabilities. The algorithms are straightforward and efficient.     

10?30 GHz monolithic GaAs travelling-wave divider/combiner

A four-way monolithic GaAs travelling-wave power divider/combiner has been designed, fabricated and evaluated. With a design centre frequency of 20 GHz, a bandwidth of from 10 GHz to 30 GHz has been measured. The insertion loss per dividing or combining action is less than 0.5 dB, with isolation between ports no worse than 20 dB. The input/output VSWRs are better than 2:1 across the same band. This divider/combiner can readily be used with monolithic GaAs power FET amplifiers to produce a several-fold increase in output powers over the 10 to 30 GHz frequency range.     

Convective transfer processes in chemically stable and reacting liquids with an internal structure

Dynamic processes are studied in media with softly and hardly internal destroyable configurations. A method is examined for the measurement of properties of media with spatial separation of the chemical transformation stages and thermal hydrodynamic measurements.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 5, pp. 781–789, November, 1987.     

Time-series model for wireless fading channels in isotropic and nonisotropic scattering environments

An autoregressive (AR) model is presented for isotropic and nonisotropic scattering environments characterized by Rice factor 0/spl les/K相似文献   

PECVD of diamond-like carbon (a-C:H) from the decomposition of methane in a high-density inductively coupled discharge

The paper describes an experimental investigation of the diamond-like carbon deposition process from methane precursor with an innovative high-density inductively coupled plasma source. It appears that a high plasma density allows a fast growth of diamond-like carbon coatings exhibiting a high hardness. In contrast to what is usually found in the literature, it seems that the ion species participate significantly to the growth of the carbon film when exposed to a high ion flux.     

To Be or Not to Be Electronic Money, That's the Question

The European Electronic Money Directive contains a definition of electronic money. However, determining which systems involving the use of electronic value fall under its scope can be more complicated than one might think. This issue is explored in this article through consideration of the question of whether prepaid mobile phone credits qualify as electronic money—a question that is currently being debated by telecommunications operators and regulators.     

The X-HPD—conceptual study of a large spherical hybrid photodetector

We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to readout the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal.

Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10–30 keV energy range. The scintillation light was readout with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT.