Measurement of the Structure Constant of Refractivity at Optical Wavelengths Using a Scintillometer

The structure constant of the atmospheric refractive index is used for characterizing the turbulence strength and for predicting the scintillation of electromagnetic waves in atmosphere. It is measured continuously in Prague using an optical scintillometer. First monthly and seasonal statistics obtained from the data gathered in the summer 2011 are provided. Lognormal distribution parameters are fitted to the empirical cumulative distribution. The hourly statistics of the structure constant show the typical evolution of turbulence strength during a day

Prussian Blue-coated interdigitated array electrodes for possible analytical application

Thin films of iron(III) hexacyanoferrate(II) (Prussian Blue) were electrochemically deposited on interdigitated array (IDA) electrodes, yielding systems which can be considered as chemiresistors in sensing alkali metal ion concentrations in an adjacent electrolyte. This is due to the fact that the conductivity of the film being measured by a steady-state current on application of a voltage to the two-fingered electrodes of the IDA depends on both the redox stare of the film and the cation concentration in the electrolyte. From the dependence of the steady-state current on the electrode (bias) potential at variable cation concentrations for different alkali metal ions and for mixtures of alkali metal ions, the possibilities of analytical application were elucidated. In addition, by using the methods of staircase coulometry and scanning conductivity, the electron diffusion coefficient De was determined as a function of the redox state of Prussian Blue. It is concluded that Prussian Blue-coated IDA electrodes are, in principle, suitable as chemiresistors for the determination of alkali metal ion concentrations with increasing selectivity in the series Li < Na < K < Rb < Cs

Propagation Characteristics and Availability Performance Assessment for Simulated Terrestrial Hybrid 850 nm/58 GHz System

Results of a propagation study on a free space optical link at 850 nm on a path 853 meters long and on a parallel 58 GHz radio link obtained over a 3-year period of observation are presented. The cumulative distributions of attenuation due to all of the hydrometeors combined as well as due to individual hydrometeors were obtained for both paths. The availability performances of the FSO link, the RF link and the simulated hybrid FSO/RF system were assessed. Significantly higher availability performance was achieved for the simulated hybrid FSO/RF system than for the FSO link alone. The diversity improvement factor reached significant values for attenuation greater than 5 dB and a significant diversity gain was obtained for the percentages of time smaller than 2%

Generator of Time Series of Rain Attenuation: Results of Parameter Extraction

Rain attenuation has a significant impact on the availability of millimeter wave communication systems. In order to dynamically simulate such radio systems, several generators of artificial time series of rain attenuation have been developed. This paper briefly describes the DLR channel model and presents the results of model parameter extraction from time series measured on terrestrial microwave paths in the Czech Republic

BER and Availability Measured on FSO Link

The BER and the availability belong among the basic qualitative parameters of free space optical (FSO) links. The BER parameter is usually mentioned by FSO manufacturers, but it is not defined what conditions a certain value of BER stands for. This article deals with problems of measuring the BER of free space optical link and with questions how to determine the probability of unavailability of a certain link. The implementation of bit error rate tester with the E1 interface system is presented. In the article the statistics of the meteorological optical range for the year 2006 are shown. Using these data one can determine the probability of a certain value of atmospheric attenuation that influences the link unavailability

Semi-regular continued fractions and an exact formula for the moments of the Minkowski question mark function

This paper continues investigations on the integral transforms of the Minkowski question mark function. In this work we finally establish the long-sought formula for the moments, which does not explicitly involve regular continued fractions, though it has a hidden nice interpretation in terms of semi-regular continued fractions. The proof is self-contained and does not rely on previous results by the author.Comment: 8 page

s

A space X is called s-point finite refinable (ds-point finite refinable) provided every open cover of X has an open refinement such that, for some (closed discrete) C⫅X