Densities, microhardnesses and electron microscopic studies of As-Se glasses

Densities and microhardnesses of As-Se glasses have been measured over a wide range of composition. Anomalous variations of densities and microhardnesses have been noted. It has been found possible to explain the variation on the basis of chemical ordering in these glasses. Scanning electron microscopy has been used to investigate the nature of etching in various compositions. The chemical stabilities of these glasses towards etchants also seem to support chemical ordering in them

Structured GMM Based on Unsupervised Clustering for Recognizing Adult and Child Speech

International audienceSpeaker variability is a well-known problem of state-of-the art Automatic Speech Recognition (ASR) systems. In particular, handling children speech is challenging because of substantial differences in pronunciation of the speech units between adult and child speakers. To build accurate ASR systems for all types of speakers Hidden Markov Models with Gaussian Mixture Densities were intensively used in combinationwith model adaptation techniques.This paper compares different ways to improve the recognition of children speech and describes a novel approach relying on Class-StructuredGaussian Mixture Model (GMM). A common solution for reducing the speaker variability relies on gender and age adaptation. First, it is proposed to replace gender and age byunsupervised clustering. Speaker classes are first used for adaptation of the conventional HMM. Second, speaker classes are used for initializing structured GMM, where the components of Gaussian densities are structured with respect to the speaker classes. In a first approach mixture weights of the structured GMM are set dependent on the speaker class. In a second approach the mixture weights are replaced by explicit dependencies between Gaussian components of mixture densities (as in stranded GMMs, but here the GMMs are class-structured).The different approaches are evaluated and compared on the TIDIGITS task. The best improvement is achieved when structured GMM is combined with feature adaptation

Synthesis and structure of PrBa<SUB>2</SUB>Cu<SUB>2</SUB>Co<SUB>1</SUB>O<SUB>7+y</SUB>: a new nonsuperconducting orthorhombic 123 system

PrBa2Cu3-xCoxO7+y (0 &lt; x &lt; 1) crystallizes in tetragonal structure for small values of x (0.1 &lt; x &lt; 0.3) and in orthorhombic structure for 0.4 &lt; x &lt; 1, as revealed by X-ray and electron diffraction studies. The end member PrBa2Cu2CoO7.4 shows orthorhombic to tetragonal structural transition with decrease in oxygen content just as YBa2Cu3O7-y(123) and PrBa2Cu3O7-y (Pr123). From the structure and reactivity, the Co ion in PrBa2Cu2CoO7+y is suggested to occupy the Cu(2) (plane Cu) position and the oxygen excess over 7 to occupy the (0, 0, 1/2) position between the CuO2-CuO2 (CoO2) sheets. The structure supports two types of labile oxygen, one associated with the chain Cu(1) and the other in the interlayer associated with the Co ion, as revealed by anaerobic oxidation of ammonia

Thermal crystallization behaviour of Ge-Te-Se glasses

Ge10Te90-xSex (50 ⤠x ⤠70) and Ge20Te80-xSex (x = 30, 50) glasses have been prepared by melt-quenching. The thermal crystallization behaviour of these samples has been studied by Differential Scanning Calorimetry (DSC), in order to characterise these glasses for memory-threshold switching applications. It is found that Ge10Te90-xSex glasses have higher thermal stability and are more stable against devitrification. These samples may be suitable for threshold switching devices. Ge20Te80-xSex glasses, on the other hand, phase separate on heating and exhibit a double stage crystallization. Based on this, it can be expected that Ge20Te80-xSex samples will show memory behaviour. The activation energy for thermal crystallization of a representative Ge10Te40Se50 glass belonging to the Ge10Te90-xSex series has been found by the Kissinger's method to be 0.92 eV. The value of the activation energy obtained also indicates that Ge10Te90-xSex samples are less prone to devitrification and more suitable for threshold behaviour

Thermal crystallization behaviour of Ge-Te-Se glasses

823-827Ge10Te90-xSex (50 ≤ x ≤ 70) and Ge20Te80-xSex (x = 30, 50) glasses have been prepared by melt-quenching. The thermal crystallization behaviour of these samples has been studied by Differential Scanning Calorimetry (DSC), in order to characterise these glasses for memory-threshold switching applications. It is found that Ge10Te90-xSex glasses have higher thermal stability and are more stable against devitrification. These samples may be suitable for threshold switching devices. Ge20Te80-xSex glasses, on the other hand, phase separate on heating and exhibit a double stage crystallization. Based on this, it can be expected that Ge20Te80-xSex samples will show memory behaviour. The activation energy for thermal crystallization of a representative Ge10Te40Se50 glass belonging to the Ge10Te90-xSex series has been found by the Kissinger's method to be 0.92 eV. The value of the activation energy obtained also indicates that Ge10Te90-xSex samples are less prone to devitrification and more suitable for threshold behaviour

Thermal crystallization behaviour of Ge-Te-Se glasses

Ge10Te90-xSex (50 less than or equal to x less than or equal to 70) and Ge20Te80-xSex (x = 30, 50) glasses have been prepared by melt-quenching The thermal crystallization behaviour of these samples has been studied by Differential Scanning Calorimetry (DSC), in order to characterise these glasses for memory-threshold switching applications. It is found that Ge10Te90-xSex glasses have higher thermal stability and are more stable against devitrification. These samples may be suitable for threshold switching devices. Ge20Te80-xSex glasses, on the other hand, phase separate on heating and exhibit a double stage crystallization. Based on this, it can be expected that Ge20Te80-xSex samples will show memory behaviour. The activation energy for thermal crystallization of a representative Ge10Te40-xSe50 glass belonging to the Ge10Te90-xSex series has been found by the Kissinger's method to be 0.92 eV. The value of the activation energy obtained also indicates that Ge10Te90-xSex samples are less prone to devitrification and more suitable for threshold behaviour

Preparation and Characterization of Cu−Cu2OCu-Cu_2O Cermet Films

Metal-insulator composites (cermets) find use in a wide range of applications. In this paper the preparation of cermet films by dc reactive magnetron sputtering is presented. These cermets have been characterised by measuring their electrical resistance and the properties have been correlated to the microstructure and composition. Magnetron sputtering is found to be very effective in controlling the composition of the deposited films, enabling the preparation of films with tailored properties

Synthesis and Structure of PrBa2Cu2Co1O7+yPrBa_2Cu_2Co_1O_{7+y}: A New Nonsuperconducting Orthorhombic 123 System

$PrBa_2Cu_{3-x}Co_xO_{7+y}$(0 < x < 1) crystallizes in tetragonal structure for small values of .t (O.I < x < 0,3) and in orthorhombic structure for 0.4 < x < I, as revealed by X-ray and electron diffraction studies. The end member $PrBa_2Cu_2CoO_{7.4}$ shows orthorhombic to tetragonal structural transition with decrease in oxygen content just as $YBa_2Cu_3O_{7-y}$(l23) and $PrBa_2Cu_3O_{7-y}$(Prl23). From the structure and reactivity, the Co ion in $PrBa_2Cu_2CoO_{7+y}$ is suggested to occupy the Cu(2) (plane Cu) position and the oxygen excess over 7 to occupy the (0,0,1/2) position between the $CuO_2-CuO_2 (CoO_2)$ sheets. The structure supports two types of labile oxygen, one associated with the chain Cu(l)and the other in the interlayer associated with the Co ion, as revealed by anaerobic oxidation of ammonia

Microstructure and composition analysis of Cu−Cu20Cu-Cu_20 cermet films deposited by d.c. reactive magnetron sputtering

Microstructure and composition analyses of thin films are important in correlating the properties to the process parameters. In this paper, we discuss the details of such analyses of cermet films of copper and its oxide prepared by a d.c. reactive magnetron sputtering technique. The films were found to be homogeneous across the thickness. Electron microscopy coupled with an image analysis system was used in estimating the volume fraction of the metal in the deposited films. The metal content in the films varied from 0.88 to 0.15 depending on the deposition rate of the metal and the oxygen partial pressure. Magnetron sputtering was shown to be very effective in controlling the composition of the cermet films