View angle effects on the discrimination of selected Amazonian land cover types from a principal‐component analysis of MISR spectra

Multi‐angle Imaging Spectroradiometer (MISR) data, collected in four bands and at nine view angles in the Brazilian Amazon region, were used to describe view‐angle effects on the spectral response and discrimination of three forest types; close and open lowland forests, open submontane forest and green/emerging pastures. A principal‐component analysis (PCA) was applied over 450 bidirectional reflectance factor (BRF) MISR spectra (10 pixels, five land covers and nine view angles) to characterize the spectral‐angular variability in the dataset and to identify the best view direction to enhance land cover discrimination. The analysis was extended into the images of the different cameras, which were classified for the presence of the forest covers using the minimum distance of the pixels to the average PC1 and PC2 scores of each forest class calculated from spectra analysis. Results showed an increase in the mean reflectance over the spectral bands (brightness) of the land covers from nadir to extreme viewing, as indicated by the first principal component, especially in the backward direction due to the predominance of sunlit view vegetation components. The transition from the backward (sunlit view surface components) to the forward (shaded view surface components) scattering directions was also characterized by changes in the shape of the BRF spectra, as indicated by decreasing PC2 score or near‐infrared/blue ratio values. The variations in the MISR BRF followed the regularities expected from theory. PCA results also indicated that the best viewing to discriminate the forest types was the backward scattering direction (?26.1° view angle), whereas the less favourable viewing was the forward scattering direction under the view shading condition (e.g. +45.6° view angle). The overall classification accuracy for the three forest types increased from 52.4% at +45.6° view angle to 78.7% at nadir, and to 95.0% at a ?26.1° view angle. From nadir to extreme view angles, directional effects produced a NDVI decrease for the forest types and an NDVI increase for the green and especially emerging pastures. Results demonstrated that data acquisition in off‐nadir viewing may improve the discrimination and mapping of the Amazonian land cover types.     

Virtualized Web server cluster self-configuration to optimize resource and power use

This work proposes a reusable architecture that enables the self-configuration of a supporting infrastructure for Web server clusters using virtual machines. The goal of the architecture is to ensure service quality, evaluating how broadly it complies with the application's operating restrictions and proportionally acting on the configuration of physical servers (hosts) or virtual machines. In addition, through the rational use of resources, the proposal aims at saving energy. A prototype of the architecture was developed and a performance evaluation carried out with two different resource management approaches. This evaluation shows how fully functional and advantageous the proposal is in terms of using resources, avoiding waste, yet maintaining the application's quality of service within acceptable levels. The architecture also shows to be flexible enough to accept, with a reasonable amount of effort, different resource self-configuration policies.     

On the necessity of looped-functionals arising in the analysis of pseudo-periodic,sampled-data and hybrid systems

Looped-functionals have been shown to be relevant for the analysis of a wide variety of systems. However, the conditions obtained in previous papers on the analysis of sampled-data, impulsive and switched systems have only been shown to be sufficient for the characterisation of their associated discrete-time stability conditions. We prove here that these conditions are also necessary. This result is derived for a wider class of linear systems, referred to as impulsive pseudo-periodic systems, that encompass periodic, impulsive, sampled-data and switched systems as special cases.     

An Automated Investing Method for Stock Market Based on Multiobjective Genetic Programming

Stock market automated investing is an area of strong interest for the academia, casual, and professional investors. In addition to conventional market methods, various sophisticated techniques have been employed to deal with such a problem, such as ARCH/GARCH predictors, artificial neural networks, fuzzy logic, etc. A computational system that combines a conventional market method (technical analysis), genetic programming, and multiobjective optimization is proposed in this work. This system was tested in six historical time series of representative assets from Brazil stock exchange market (BOVESPA). The proposed method led to profits considerably higher than the variation of the assets in the period. The financial return was positive even in situations in which the share lost market value.     

Ultra-high doping levels of GaAs with beryllium by molecular beam epitaxy

P-type doping levels up to 2×1020 at cm?3 in GaAs are presented using molecular beam epitaxy and beryllium as acceptor impurity. The epilayers present a perfect surface morphology and Be is not found to diffuse into the substrate, which permits the incorporation of such films into multilayer structures for device applications.     

Microstructure formation in chalcogenide thin films assisted by thermal dewetting

The spontaneous formation of self-assembled and/or self-organized patterns is a fundamental and technologically significant topic. This process is achieved via a phenomenon called dewetting, should it be thermally induced, or caused by laser exposure. Although dewetting seems to be a well-known phenomenon for metallic and polymeric thin films, no proper investigation regarding glassy thin films seems to have been done. Thus, in the present study we try to elaborate on the process of thermal dewetting applied to glassy thin films of the system Ag_x(As₂₀S₈₀)_100?x.     

Some comments about “Comment on hardness definitions”, by J. Malzbender [J. Eur. Ceram. Soc. 23 (2003) 1355–1359]

Malzbender has suggested a model to determine hardness and elastic modulus as a function of the mechanical energies involved during tip penetration in instrumented indentations tests. However, the values obtained with these expressions are not consistent with the ones determined by the well-accepted Oliver and Pharr method. After revision, based on Malzbender's study itself, equations were rewritten and then, the obtained indentation hardness (H) for soda-lime glass was in agreement with the literature data. However, the reduced elastic modulus (E_r) was still about 20% higher than the values in the literature. Developing Malzbender's proposal by the inclusions of additional mechanical energy assumptions, a new expression for E_r is now suggested. Using the new expression, the hardness and reduced elastic modulus agreed very well with the Oliver and Pharr method.     

Fractal initialization for high-quality mapping with self-organizing maps

Initialization of self-organizing maps is typically based on random vectors within the given input space. The implicit problem with random initialization is the overlap (entanglement) of connections between neurons. In this paper, we present a new method of initialization based on a set of self-similar curves known as Hilbert curves. Hilbert curves can be scaled in network size for the number of neurons based on a simple recursive (fractal) technique, implicit in the properties of Hilbert curves. We have shown that when using Hilbert curve vector (HCV) initialization in both classical SOM algorithm and in a parallel-growing algorithm (ParaSOM), the neural network reaches better coverage and faster organization.     

Estimation of the parameters of oxide film growth on nickel-based alloys in high-temperature water electrolytes

The Mixed-Conduction Model (MCM) has been adapted to obtain the main kinetic and transport parameters for passive film growth on nickel-based alloys in high-temperature electrolytes. For the purpose, a procedure for the calculation of these parameters from electrochemical impedance spectroscopic data measured on Ni-15% and Ni-20%Cr alloys in 0.1 M Na₂B₄O₇ at 300 °C in a wide potential range has been devised. The obtained sets of parameters have been used to successfully predict the steady-state current density versus potential dependence for the two Ni-Cr alloys, as well as the thickness versus time dependence for films grown on Alloy 600 at times ranging between a few minutes and a few thousand hours. The calculations are supported by results of previous XPS measurements of film growth on Alloy 600 showing that the barrier layer growing in the early stage consists of Cr₂O₃.