Glasses of the following composition 45Na2O•(55 - x)P2O5•xNb2O5 and 50Na2O•(50 - x)P2O5•xNb2O5 are studied. It is found that under the influence of γ-radiation the glass color changes. Optical absorption spectra, photoluminescence spectra, Rayleigh and Mandel'shtam - Brillouin scattering (RMBS) spectra are investigated in dependence of glass composition, europium concentration, thermal treatment duration and radiation dose. Effect of secondary thermal
treatment is studied on the base of 45Na2O•25P2O5•30Nb2O5 doped with 1 mol.% Eu2O3. It is found that intensity of
photoluminescence gives rise and decay time as well under thermal treatment at the temperature exceeding transition
temperature by 50 degrees. RMBS spectra of glasses after thermal treatment demonstrate decrease of scattering intensity
while Eu2O3 being doped. Effects obtained are accounted for europium ion local symmetry changes.
One of the main problems that should be solved to design prospective materials as fluorophosphates glasses for optical
fiber amplifiers is spatial distribution of rare-earth ions in glass matrix. Doped fluorophosphate glasses 5 Ba(P03)2 95
MgCaSrBaA12F14 compositions are studied by means of γ-induced ESR and optical absorption spectra. Analysis of
radiation center behavior in these glasses makes it possible to elucidate local environment composition of small concentration
of RE-ions.
The structural microinhomogeneity of EuF3 doped fluorophosphate glasses is studied to elucidate the influence of the Eu3+ ion environment on Rayleigh scattering. The measurements of Rayleigh and Mandelstam-Brillouin scattering, small-angle x-ray scattering, y-ray induced optical absorption, and fluorescence are used. It is shown that the introduction of Eu3+ ions into fluorophosphate glass with a small amount of phosphate decreases the Landau-Placzek ratio. Based on the analysis of the optical absorption and x-ray scattering spectra, the grouping of the Eu3+ ions with the phosphate groups is demonstrated. Applying the capture volume model, the maximum concentration of the Eu3+ ions in the phosphate environment is estimated to be 1.05x1018cm-3. It is found that the capture volumes of the Eu3+ located in the phosphate and mixed environment differ by two orders of magnitude, which approves the discussion in terms of the doped ion segregation.
The main goal of this study is to derive information on parameters characterizing airflows over the sea surface, particularly downwind natural obstacles from the analysis of SAR imagery. A series of ERS-2 SAR images of the sea surface recorded over north-eastern part of the Black Sea near the Caucasus coast is considered. This set of radar data has been collected in various seasons during 4 years. Related meteorological data, weather and cloudiness maps are available. A distinctive feature of the region is the mountain ridge stretched along shore and having a complicated structure with multiple canyons opening to the sea. Depending on the airflow characteristics radar images of sea surface can bear imprints associated with convection, internal waves in atmosphere, air jets, mushroom-like flows, lee waves, vortices, etc. Radar image patterns are investigated in relation to airflow speed and direction, boundary layer
stratification and local topography.
Results of microwave sounding of ocean surface are discussed. The study is based upon the data from airborne two-polarisation side-looking Ku-band radar, satellite based ERS SAR and the 'ALMAZ' SAR. The paper is dedicated to the theory and practice of analysis of radar images of sea surface, obtained under unstable atmosphere, when ocean is warmer than near-surface air. In this case, the sea surface reveals wind field variations in the MABL caused by atmospheric convective processes, accompanied by air motions with mainly vertical direction. Changes in radar manifestations of convection signatures are connected with the degree of thermodynamic instability of the atmosphere. It is shown that radar images of ocean under unstable atmosphere provide the imprints of convective processes in forms prescribed by theory, but in natural conditions air circulation in cylinder- or cell-formed structures differs from the model ones. It is suggested that the detection and investigation of active ocean-atmosphere energy exchange should be based on the polarization differences of radar cross section, especially under low grazing angles. The 2D-correlation functions of VV and HH-polarized radar images are considered with the aim to establish a quantitative criterion for the identification and discrimination between stable, unstable and neutral ocean-atmosphere stratifications.
The analysis of ERS-1,2 SAR data of the Bering Strait, obtained in summer 1995, 1998 and 2000 has allowed to observe many important oceanic processes. They include meandering fronts and vortex activity (well pronounced in the eastern part of the Strait), strong jet current at the Prince Wales Cape, intrusions of the cold Chukchi Sea water (extensions of the Siberian Coastal Current) in the western part of the Strait. These images demonstrate some interesting diversions from the northward current typical for the Bering Strait. The flow direction in the central part of the Bering Strait can be revealed from prominent wake features. Also, generation of internal waves on fronts can be detected in some images. Especially impressive is the large variety of surface manifestations of vortex streets north of the Fairway Rock due to high variability of the incident flow. The asymmetry of the Rock causes a special form of the Karman vortex street consisting of a row of single vortices. Specific arc-like features resembling internal wave manifestations can be observed in ERS-SAR images, obtained in the Bering Strait and surrounding waters. Two possible reasons of such features - meander of low salinity water or/and interaction of tidal currents with the bottom relief are discussed.
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