Search results for "signal processing"
showing 10 items of 2451 documents
Can back-projection fully resolve polarity indeterminacy of independent component analysis in study of event-related potential?
2011
a b s t r a c t In the study of event-related potentials (ERPs) using independent component analysis (ICA), it is a traditional way to project the extracted ERP component back to electrodes for correcting its scaling (magnitude and polarity) indeterminacy. However, ICA tends to be locally optimized in practice, and then, the back-projection of a component estimated by the ICA can possibly not fully correct its polarity at every electrode. We demonstrate this phenomenon from the view of the theoretical analysis and numerical simulations and suggest checking and modifying the abnormal polarity of the projected component in the electrode field before further analysis. Moreover, when several co…
Determining the number of sources in high-density EEG recordings of event-related potentials by model order selection
2011
To high-density electroencephalography (EEG) recordings, determining the number of sources to separate the signal and the noise subspace is very important. A mostly used criterion is that percentage of variance of raw data explained by the selected principal components composing the signal space should be over 90%. Recently, a model order selection method named as GAP has been proposed. We investigated the two methods by performing independent component analysis (ICA) on the estimated signal subspace, assuming the number of selected principal components composing the signal subspace is equal to the number of sources of brain activities. Through examining wavelet-filtered EEG recordings (128…
Bilevel heat exchanger network synthesis with an interactive multi-objective optimization method
2012
Abstract Heat exchanger network synthesis (HENS) has been an active research area for more than 40 years because well-designed heat exchanger networks enable heat recovery in process industries in an energy- and cost-efficient manner. Due to ever increasing global competition and need to decrease the harmful effects done on the environment, there still is a continuous need to improve the heat exchanger networks and their synthesizing methods. In this work we present a HENS method that combines an interactive multi-objective optimization method with a simultaneous bilevel HENS method, where the bilevel part of the method is based on grouping of process streams and building aggregate streams …
Design of a Cleaning Program for a PV Plant Based on Analysis of Energy Losses
2015
Solar photovoltaic (PV) energy has grown significantly over the past few years. However, despite the increase in installed capacity, this energy source still raises important concerns related to the variability of power production. The short-term effects such as cloud shadowing and supply interruptions, as well as long-term effects such as dust accumulation, seasonal variation, and ageing of PV modules, can cause variability of power production. Therefore, the analysis of all the variability sources in order to provide statistically consistent power production data is an important challenge. This study presents a methodology to analyze data from a PV plant in order to have an independent ev…
Thermal anomalies detection in a photovoltaic plant using artificial intelligence: Italy case studies
2021
This paper proposes the application of artificial intelligence techniques for the identification of thermal anomalies that occur in a photovoltaic system due to malfunctions or faults, with the aim to limit the energy production losses by detecting faults at an early stage. The proposed approach is based on a Thermographic Non-Destructive Test conducted with Unmanned Aerial Vehicles equipped with a thermal imaging camera, which allows the detection of abnormal operating conditions without interrupting the normal operation of the PV system rapidly and cost-effectively. The thermographic images and videos are automatically inspected using a Convolutional Neural Network, developed by an open-s…
Laser fluence, repetition rate and pulse duration effects on paint ablation
2006
Abstract The efficiency (mm3/(J pulse)) of laser ablation of paint was investigated with nanosecond pulsed Nd:YAG lasers (λ = 532 nm) as a function of the following laser beam parameters: pulse repetition rate (1–10,000 Hz), laser fluence (0.1–5 J/cm2) and pulse duration (5 ns and 100 ns). In our study, the best ablation efficiency (η ≅ 0.3 mm3/J) was obtained with the highest repetition rate (10 kHz) at the fluence F = 1.5 J/cm2. This ablation efficiency can be associated with heat accumulation at high repetition rate, which leads to the ablation threshold decrease. Despite the low thermal diffusivity and the low optical absorption of the paint (thermal confinement regime), the ablation th…
Search for photons with energies above 1018 eV using the hybrid detector of the Pierre Auger Observatory
2017
A search for ultra-high energy photons with energies above 1 EeV is performed using nine years of data collected by the Pierre Auger Observatory in hybrid operation mode. An unprecedented separation power between photon and hadron primaries is achieved by combining measurements of the longitudinal air-shower development with the particle content at ground measured by the fluorescence and surface detectors, respectively. Only three photon candidates at energies 1-2 EeV are found, which is compatible with the expected hadron-induced background. Upper limits on the integral flux of ultra-high energy photons of 0.027, 0.009, 0.008, 0.008 and 0.007 km-2 sr-1 yr-1 are derived at 95% C.L. for ener…
Water and Energy Saving in Urban Water Systems: The ALADIN Project
2016
The ALADIN project was aimed at contributing to environmental and energy sustainability of the urban water system by means of a decision support tool able to allow an evaluation of the energy impact related to each different macro-sectors of urban water cycle highlighting the main energy flows and to assess the system energy balance and identify the possible energy-efficient solutions. Moreover the tool suggests the most efficient actions in reducing water losses. In the present paper the main features of the developed tool are presented. (C) 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.
Sing and Measure: Sound as Voice as Quanta
2022
The universal concept of a “music of the spheres” traverses the history of philosophy, science and art, from Pythagoras to Kepler and beyond. In modern times, a sphere in three dimensions—the Bloch sphere—is used to illustrate the state of a qubit, the basic unit of quantum information. On the same spherical surface, the fundamental components of voice production can be located, so that any utterance can be seen as the evolution of a unit two-dimensional vector having complex coefficients. Indeed, any sound can be analyzed and decomposed into overlapping sinusoidal components, broadband noises, and impulsive transients, which in turn can be associated to fundamental means of vocal sound pro…
Relationship between volume and energy of vector fields
2001
Abstract A unified study of energy and volume functionals is presented here by determining the critical points of a functional that extends simultaneously energy and volume and that is defined on the product of the manifold of smooth maps C∞(M,N) times the manifold M of riemannian metrics on M. The restriction of this functional to different submanifolds of the space of vector fields X (M)× M is also considered, and used to study several functionals generalizing volume and energy or total bending of vector fields