Enhanced and Long‐Lived Near‐Infrared Luminescence of Er3+ Ions in Lead Borate Glass‐Ceramics Containing PbWO4 Nanocrystals

Lead tungstate PbWO₄ nanocrystals in transparent lead borate glass‐ceramics containing Er³⁺ ions were fabricated. Luminescence spectra at about 1530 nm due to main ⁴I_13/2–⁴I_15/2 laser transition of Er³⁺ ions were examined for glass samples before and after heat treatment. Near‐infrared luminescence of Er³⁺ ions in glass‐ceramics is enhanced and long‐lived in comparison to precursor glasses. It suggests that the Er³⁺ ions are partially incorporated into PbWO₄ crystalline phase.     

Gabor filter and graph cut based texture analysis

This paper describes a method for texture based segmentation. Texture features are extracted by applying a bank of Gabor filters using two-sided convolution strategy. Probability texture model is represented by Gaussian mixture that is trained with the Expectation-maximization algorithm. Texture similarity, obtained this way, is used like the input of a Graph cut method. We show that the combination of texture analysis and the Graph cut method produce good results.     

A study of positional disorder in strontium barium niobate

The first systematic examination of trends in the site occupancies of strontium and barium ions in strontium barium niobate (SBN) at three compositions across the phase range is presented. X-ray powder diffraction and Rietveld structure refinement were used to obtain refined structures for SBN. Some problems were encountered in the structure refinement due to the domain structure in the material. Barium was found only at the A2 site for each composition. Ba/Sr occupancy for the A2 site varied from 91% for SBN (72-28) to 99% for SBN (50-50) in the unannealed state, while strontium occupancy of the A1 site varied from 70% to 54%. In annealed SBN (50-50), the A2 site occupancy decreased to 95%, while the A1 site occupancy increased to 62%. It is proposed that a twisting of the structure in the unannealed state decreases the sizes of the cages at the A1, A2 and C sites. After annealing, the structure becomes more regular, enlarging the A1, A2 and C sites and allowing more strontium atoms to occupy the A1 site. Cation distribution is controlled by the twisting of the octahedral framework. The overall properties of the material are modified by this distortion of the structure.     

Dosimetric properties of new cards with high-sensitivity MCP-N (LiF:Mg,Cu,P) detectors for Harshaw automatic reader

A new configuration for a thermoluminescent dosimetric card has been developed through collaboration between the Institute of Nuclear Physics in Kraków and several commercial dosimetric companies. The card is based on high-sensitivity LiF:Mg,Cu,P circular pellets (MCP-N) welded inside synthetic foils. The basic configuration consists of two pellets of 3.6 mm diameter and thicknesses from 0.25 up to 0.38 mm. The cards can be processed in a standard 6600 or 8800 Harshaw automatic TLD reader. The dosemeters demonstrate very high sensitivity, low background and good stability. This article presents results of the performance tests of the new dosimetric cards in the automatic TLD readers and a comparison of their properties.