A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Variations of the Tropospheric Refraction over the Sea. Simultaneous Measurements at Ground-to-Ground and Satellite-to-Ground Radio Paths
Measured results are presented concerning refractive properties of the near-water tropospheric layer. They were derived within two different methods, namely, from displacements of specific point in the records of satellite signals from the GPS navigation system obtained during its setting down over the sea, and by measuring levels of decimeter wavelength signals in the penumbra. It has been shown that the amount of correlation between the such parameters in some experiments may be as high as 0.6, increasing when the primary data one smoothened or shifted suitably.
The Impact of Errors in Channels with Constant Parameters on the Quality of Recovery of Compressed Messages Using Coding by Means of Barycentric Coordinates
Synthesis of Matching-Filtering Devices of Amplitude-Phase Manipulators with the Controlled Element Connected in Series with the Signal Source
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Peculiar Properties of Operating Modes of Klynotron-Type Oscillators
Peculiar properties of operating modes of klynotron-type oscillators and dispersion characteristics of the slow-wave structures using in klynotrons are considered. The conditions ensuring the optimal klynotron operating mode are determined on the basis of experimental research. The procedure of estimation of a slow-wave structure for the millimeter-band klynotron is described.
Kharkov National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkov, 61166, Ukraine
On Increasing of the Gain Ratio of Crossed Field Double-Row Amplifiers
The causes of the cathode-driven crossed field amplifiers (double-row amplitrons in particular) gain restriction are analyzed. It has been established that one of the reasons for this is a predominant electron stream control by the RF field amplifier designs are suggested having one or two axially shifted bunching spaces, which contain a cathode delay line only. Thus, a condition is ensured for an electron stream bunching under the influence of the input signal without disturbance from the anode line RF field.
Technological University of Mexico, Mexico
Optimal Detection System of Digital Watermarks in Spatial Domain
Many watermarking algorithms in spatial domain lack of a mathematical derivation of the detector of digital watermarks. On this subject, this paper proposes a statistical model which allows both blind digital watermark detection and blind threshold computing. This model with the assistance of other pre-processing tools such as pre-detection filtering and geometrical distortions compensation offers reliable fast and accurate watermark detection when strong attacks such as high power noise corruption, geometrical attacks and so on.
ESIME Culhuacan, National Polytechnic Institute of Mexico, Mexico
Analysis of Audio Watermarking Techniques
In this paper, three principal audio watermarking schemes are analyzed and summarized. Each audio watermarking scheme was evaluated from the point of view of fidelity and robustness. In the fidelity case the signal to noise ratio (SNR) was used, on the other hand, the watermarked signals were evaluated under several different attacks. Among them the Stirmark for audio, that is a program specifically designed to remove watermarks, in order to prove their robustness. The audio watermarking schemes were classified in three categories: Patchwork, based in the frequency domain, which can be applied to all frequency transforms such as DCT, DFT and DWT, the echo hiding that is based in the time domain and the cepstrum domain.
Institute of Transport Systems and Technologies “Transmag”
National Academy of Sciences of the Ukraine,
5, Pisargevskogo Str., Dnepropetrovsk, Ukraine
The Synthesis of a Fast-Acting Information-Control System on the Base of Hot-Electron Devices
Based on measuring microwave converters of the movement parameters a concept of development of the operated automatically control system for magnetically levitative vehicles is presented. The basic part of system is main communication waveguide transfer line arranged along active way structure, having coupling apertures with the microwave generator placed on a vehicle platform. A waveguide is excited by the modulated microwave signals carrying the information on spatial position of a vehicle. Moreover, the control system contains high-speed contactless autogenerating meters of distances between platform, active way structure and lateral guides, active oscillator meters of the magnetic field in the clierence, and devices for processing of the information and control by sections of propulsion-levitative systems.