Search results for "DECOMPOSITION"
showing 10 items of 766 documents
Photocatalytic behavior of mixed WO3/WS2 powders
2000
Polycrystalline mixed WO3/WS2 powders have been prepared by different methods. The samples have been characterized by bulk and surface techniques and tested as catalysts for the photodegradation of phenol. The results have indicated that the coupling of WO3 and WS2 leads to an enhanced rate of disappearance of the organic substrate. The effect is explained as the result of the simultaneous electron transfer from WS2 to WO3 and hole transfer from WO3 to WS2. The efficiency of the mixed WO3/WS2 systems strongly depends on the relative amounts of WO3 and WS2 in the various samples. A maximum of photoactivity is obtained when the surface WS2 and WO3 molar fraction is about 0.5.
Spectral decomposition of cerebrovascular and cardiovascular interactions in patients prone to postural syncope and healthy controls.
2022
We present a framework for the linear parametric analysis of pairwise interactions in bivariate time series in the time and frequency domains, which allows the evaluation of total, causal and instantaneous interactions and connects time- and frequency-domain measures. The framework is applied to physiological time series to investigate the cerebrovascular regulation from the variability of mean cerebral blood flow velocity (CBFV) and mean arterial pressure (MAP), and the cardiovascular regulation from the variability of heart period (HP) and systolic arterial pressure (SAP). We analyze time series acquired at rest and during the early and late phase of head-up tilt in subjects developing or…
Conceptual Understanding of Newtonian Mechanics Through Cluster Analysis of FCI Student Answers
2018
The Force Concept Inventory is a multiple-choice test and is one of the most popular and most analyzed concept inventories. It is used to investigate student understanding of Newtonian mechanics. A structured approach to data analysis can transform it in a “diagnostic” instrument that can validate inferences about student thinking. In this paper, we show how cluster analysis methods can be used to investigate patterns of student conceptual understanding and supply useful details about the relationships among student concepts and misconceptions. The answers given to the FCI questionnaire by a sample of freshman engineering have been analyzed. The analysis takes into account the decomposition…
Empirical mode decomposition and neural network for the classification of electroretinographic data
2013
The processing of biosignals is increasingly being utilized in ambulatory situations in order to extract significant signals' features that can help in clinical diagnosis. However, this task is hampered by the fact that biomedical signals exhibit a complex behaviour characterized by strong non-linear and non-stationary properties that cannot always be perceived by simple visual examination. New processing methods need be considered. In this context, we propose to apply a signal processing method, based on empirical mode decomposition and artificial neural networks, to analyse electroretinograms, i.e. the retinal response to a light flash, with the aim to detect and classify retinal diseases…
Variance-based sensitivity analysis for wastewater treatment plant modelling.
2014
Global sensitivity analysis (GSA) is a valuable tool to support the use of mathematical models that characterise technical or natural systems. In the field of wastewater modelling, most of the recent applications of GSA use either regression-based methods, which require close to linear relationships between the model outputs and model factors, or screening methods, which only yield qualitative results. However, due to the characteristics of membrane bioreactors (MBR) (non-linear kinetics, complexity, etc.) there is an interest to adequately quantify the effects of non-linearity and interactions. This can be achieved with variance-based sensitivity analysis methods. In this paper, the Extend…
Global sensitivity analysis in wastewater applications: A comprehensive comparison of different methods
2013
Three global sensitivity analysis (GSA) methods are applied and compared to assess the most relevant processes occurring in wastewater treatment systems. In particular, the Standardised Regression Coefficients, Morris Screening and Extended-FAST methods are applied to a complex integrated membrane bioreactor (MBR) model considering 21 model outputs and 79 model factors. The three methods are applied with numerical settings as suggested in literature. The main objective considered is to classify important factors (factors prioritisation) as well as non-influential factors (factors fixing). The performance is assessed by comparing the most reliable method (Extended-FAST), by means of proposed…
A methodology to assess the energetic valorization of bio-based polymers from the packaging industry: pyrolysis of reprocessed polylactide
2012
The energetic valorization process of bio-based polymers is addressed in this study, taking polylactide (PLA) as model. The pyrolysis of virgin and multiple-injected PLA was simulated by means of multi-rate linear-non-isothermal thermogravimetric experiments. A complete methodology, involving control of gases, thermal stability and thermal decomposition kinetics was proposed. The release of gases was monitored by Evolved Gas Analysis of the fumes of pyrolysis, by in-line FT-IR, with the aid of 2D-correlation IR characterization. A novel model to establish the thermal stability of PLAs under any linear heating profile was proposed. A kinetic strategy was methodically applied to assess the th…
A real time electromyostimulator linked with EMG analysis device
2013
International audience; In this study, a new system composed of two modules (electromyostimulation + electromyography recording) is presented. It can analyze in real time EMG signals during electromyostimulation. In addition, we propose a new method based on wavelet decomposition to analyze changes in M-wave characteristics. It leads to introduce a new index related to muscular fatigue.
Assessment of data and parameter uncertainties in integrated water-quality model
2011
In integrated urban drainage water quality models, due to the fact that integrated approaches are basically a cascade of sub-models (simulating sewer system, wastewater treatment plant and receiving water body), uncertainty produced in one sub-model propagates to the following ones depending on the model structure, the estimation of parameters and the availability and uncertainty of measurements in the different parts of the system. Uncertainty basically propagates throughout a chain of models in which simulation output from upstream models is transferred to the downstream ones as input. The overall uncertainty can differ from the simple sum of uncertainties generated in each sub-model, dep…
Efficient software tool for the analysis of planar-based metamaterial structures
2007
We present a software tool specialized in the analysis of metamaterial structures based on planar circuits. The tool implements a formulation for open transversal multilayered structures, which reduces the number of unknowns employed in the problem. Besides, the formulation has been efficiently accelerated by means of a Kummer-like decomposition, extracting the singular behaviour of the Green's functions from the frequency analysis. By means of this formulation, several different kinds of metamaterial structures built in coplanar and microstrip technologies are successfully analyzed, obtaining bandpass and stopband filter responses in a fast and accurate way. (7 pages)