Effect of Nb Doping on the Microstructure of Sol—Gel-Derived PZT Thin Films

Aliovalent Nb doping (<10 at.%) of sol—gel-derived lead zirconate titanate (PZT) thin films was investigated with the intention of improving the ferroelectric properties. Nb addition was found to significantly alter the perovskite crystallization by stabilizing the transient pyrochlore phase, resulting in the retention of pyrochlore second phases and an increase in the perovskite lateral grain size and columnarity. The occurrence and composition of Zr-rich (surface) pyrochlore phases were found to depend on Nb concentration, annealing temperature, and Pb content. The observed changes in ferroelectric and dielectric properties as a function of Nb dopant addition were found to be strongly influenced by microstructural effects and the occurrence of pyrochlore, and hence the intrinsic effects of Nb incorporation in the perovskite lattice could not be directly ascertained.     

Interactions of phospholipase D with 1,2 diacyl-sn-glycerol-3-phosphorylcholine,dodecylsulfate, and Ca2+

Some properties of the pure, soluble phospholipase D (phosphatidycholine phosphatido hydrolase, EC 3.1.4.4) interactions with phosphatidyl choline (1,2 diacyl-sn-glycerol-3-phosphoryl choline) in a system also containing dodecylsulfate and Ca²⁺ ions were studied. Concentrations of Ca²⁺ greater than 50 mM were necessary both for activity and adsorption of the enzyme to the “supersubstrate.” Ethylenediamine tetraacetic acid caused inhibition of activity, greater than one would expect from its chelating capacity. A nonlinear increase in activity with the increase of enzyme protein was observed, suggesting a subunit aggregation into a higher mol wt protein, catalytically more active. Upon centrifugation of the supersubstrate-enzyme complex at 4.5×10⁵ g·min at 30 C, most of the substrate molecules sedimented regardless of the pH. The reverse was true when centrifugation was done at 1 C. Phospholipase D hydrolyzed phosphatidylcholine molecules present in the supersubstrate at temperatures around 0 C at a rate 1/5 that of a maximal value measured at 30C. The Arrhenius plot was linear in the range from 0 to 30 C, and at that temperature the curve broke with a smaller slope. Activation energy of 9.1 Kcal/mol, below 30 C, was calculated. Adsorption of the enzyme to the sedimentable supersubstrate occurred at pH 8.0, regardless of temperature. At pH 5.6, a considerable portion of phosphatidylcholine was degraded at 30 C, thus minimizing the capacity of the supersubstrate to adsorb the enzyme. Although Mg²⁺ could replace Ca²⁺ in the formation of sedimentable supersubstrate, it neither assists in adsorption of the enzyme nor in activation of the phosphatidylcholine hydrolysis.     

Caffe CNN-based classification of hyperspectral images on GPU

Deep learning techniques based on Convolutional Neural Networks (CNNs) are extensively used for the classification of hyperspectral images. These techniques present high computational cost. In this paper, a GPU (Graphics Processing Unit) implementation of a spatial-spectral supervised classification scheme based on CNNs and applied to remote sensing datasets is presented. In particular, two deep learning libraries, Caffe and CuDNN, are used and compared. In order to achieve an efficient GPU projection, different techniques and optimizations have been applied. The implemented scheme comprises Principal Component Analysis (PCA) to extract the main features, a patch extraction around each pixel to take the spatial information into account, one convolutional layer for processing the spectral information, and fully connected layers to perform the classification. To improve the initial GPU implementation accuracy, a second convolutional layer has been added. High speedups are obtained together with competitive classification accuracies.

     

Optimization of gas injection conditions during deposition of AlN layers by novel reactive GIMS method

In 2011, we proposed a novel magnetron sputtering method. It involved the use of pulsed injection of working gas for the initiation and control of gas discharge during reactive sputtering of an AlN layer (Gas Injection Magnetron Sputtering — GIMS). Unfortunately, the presence of Al-Al bonds was found in XPS spectra of the AlN layers deposited by GIMS onto Si substrate. Our studies reported in this paper proved that the synchronization of time duration of the pulses of both gas injection and applied voltage, resulted in the elimination of Al-Al bonds in the AlN layer material, which was confirmed by the XPS studies. In our opinion the most probable reason of Al-Al bonds in the AlN layers deposited by the GIMS was the self-sputtering of the Al target in the final stage of the pulsed discharge.     

Synthesis of Lead Nickel Niobate–Lead Zirconate Titanate Solid Solutions by a B-site Precursor Method

A modified processing method for lead nickel niobate–lead zirconate titanate (Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr,Ti)O₃, PNN–PZT) solid solutions is presented. This method is based on the high-temperature synthesis of a precursor that contains all the B-site cations (Ti, Zr, Ni, and Nb). This synthesis yields a diphasic mixture that contains a ZrTiO₄-like phase and a rutile-like phase. Both phases exhibit a cationic valence of 4; thus, it is concluded that the mixing of Ni and Nb cations is adequate for the preparation of PNN–PZT solid solutions. Indeed, a pure perovskite phase has been obtained after calcination with lead oxide for compositions that contain 40 and 50 mol% PNN. Moreover, their electromechanical properties have been shown to be superior to values reported for standard columbite routes. This conclusion has been interpreted in terms of enhanced chemical homogeneity.     

Transformation in the photovoltaics industry in Australia,Germany and Japan: Comparison of actors,knowledge, institutions and markets

The paper analyses the evolution of the photovoltaics industry in Australia, Germany and Japan from a comparative policy perspective. It uses a sectoral innovation system framework to discuss the way the three countries have approached the development of knowledge and new technologies, the actors in the sector and the interactions between them, the role of institutions and availability of funding as well as the development of markets for photovoltaics. It outlines the different paths that the countries have adopted for the process of transition from niche to mass production. The findings show that various national players have specialised in different activities, with the institutions' building block being a key determinant for success or otherwise. In the case of Australia, it is also the least developed area which ultimately exposes the country to losing its innovation benefits.     

Towards interval techniques for model validation

Most physical models are approximate. It is therefore important to find out how accurate are the predictions of a given model. This can be done by validating the model, i.e., by comparing its predictions with the experimental data. In some practical situations, it is difficult to directly compare the predictions with the experimental data, since models usually contain (physically meaningful) parameters, and the exact values of these parameters are often not known. One way to overcome this difficulty is to get a statistical distribution of the corresponding parameters. Once we substitute these distributions into a model, we get statistical predictions—and we can compare the resulting probability distribution with the actual distribution of measurement results. In this approach, we combine all the measurement results, and thus, we are ignoring the information that some of these results correspond to the same values of the parameters—e.g., they come from measuring the same specimen under different conditions. In this paper, we propose an interval approach that takes into account this important information. This approach is illustrated on the example of a benchmark thermal problem presented at the Sandia Validation Challenge Workshop (Albuquerque, New Mexico, May 2006).     

Synthesis of product-driven coordination controllers for a class of discrete-event manufacturing systems

A synthesis approach is proposed for discrete-event coordination architectures applied to a class of automated manufacturing systems (AMS) in which a clear separation is established between equipment control activities and product manufacturing procedures. Manufacturing procedures are modeled by regular languages constructed with a class of control commands named imperative. Equipment controllers are synthesized as a standard discrete-event supervisors dealing only with operational and safety issues of equipment groupings. The control of equipment modules is carried out following the imperative control commands sequences. Conditions are established to guarantee that the manufacturing procedure of a given product can be achieved using the synthesized supervisors in a particular AMS. Therefore, equipment controllers are not needed to be modified to consider the manufacturing of different products, whilst the construction of achievable manufacturing procedures becomes an “ad hoc” simple process using a reduced set of procedural blocks. The approach is illustrated with an experimental AMS.     

Niobium Doping and Dielectric Anomalies in Bismuth Titanate

A study of the complex permittivity in bismuth titanate was conducted to reveal the nature of an anomaly in the real part of the permittivity, which occurs below the Curie temperature. This anomaly is frequency dependent and is caused by a combination of two relaxation phenomena that appear in the imaginary part of the permittivity. One of the relaxations showed classic characteristics of an ion-jump process. Niobium doping suppressed this relaxation and eliminated the nonferroelectric anomaly in permittivity. Niobium is proposed to affect the ion-jump relaxation through a decrease in the concentration and possibly the mobility of oxygen vacancies.