2021, Articolo in rivista, ENG
Giacomo Mele, Gilda Buscemi, Laura Gargiulo*, Fabio Terribile
Although scientific literature focuses mainly on earthworms, all soil macroinvertebrates play an important role in modifying the architecture of the soil pore space and, in turn, in soil functions. Notwithstanding the fact that non-invasive technology, such as X-ray tomography, has long been used to differentiate non-biopores from biopores, it is still difficult to distinguish the specific contribution different macroinvertebrates make to the soil biopore system. Unlike the object-based image analysis approach, when applied to a soil pore system, mathematical morphology permits the user to obtain a very accurate pore size distribution consistent with the physical principle of water retention. The aim of this work was to evaluate the potential of the parameters of this kind of biopore size distribution to differentiate between the burrows of five different macroinvertebrate groups, namely Earthworms, Millipedes juliform, Centipedes, Campodeiform larvae and Elateriform larvae, inoculated into repacked soil mesocosms and incubated (14 days) in the field from where the soil animals were originally collected. A two-fold approach was proposed in this work so as to obtain parameters by both pore size population distributions and Weibull modelling of the cumulative distributions. Then a predictive discriminant analysis was performed on selected parameters by using macroinvertebrate groups as grouping variables and a very good prediction was obtained in both cases. The most useful parameters were the skewness and FFT indices in the first case and the shape parameter ? of the Weibull model along with its RMSE in the second one. In addition, topological characterization was performed on gallery-shaped biopores. Vertical deviation was the only parameter that was independent of the individual body size and showed the statistically significant lowest value for the earthworms. The experiment and analyses performed in this work to explore the connection between macroinvertebrate groups and the corresponding biopore size distributions may represent a suitable methodological approach to performing a general investigation into the relationships between soil management and its impact on the system of soil macropores.
2019, Contributo in atti di convegno, ENG
Radogna A.V.; D'Amico S.; Capone S.; Francioso L.
This paper presents a simulation study of an optimized and computationally low-cost method for estimating the Electrical Impedance Spectra (EIS) of semiconductor gas sensors and in particular for Metal-Oxide (MOX) chemiresistive sensors. The approach is applied directly to the sensor without using a voltage divider and is based on a well-known signal processing principle: a Linear Time-Invariant (LTI) system's Impulse Response (IR) is estimated by stimulating the system with a Maximum Length Sequence (MLS) and thus performing the circular cross-correlation between input and output signals. Finally, the system's frequency response, i.e. the impedance spectrum, is obtained through the Fast Fourier Transform (FFT) of the estimated impulse response. The technique is demonstrated in simulation environment using a time-invariant passive network that simulates a MOX sensor. Simulation results and performance analysis are discussed showing design trade-offs.
2019, Articolo in rivista, ENG
Lei, Lei; Ferrarini, Giovanni; Bortolin, Alessandro; Cadelano, Gianluca; Bison, Paolo; Maldague, Xavier
This paper explores cooling instead of heating for external stimulation in infrared thermography for NDT & E. Liquid nitrogen is poured on the surface of a steel sample with flat-bottom holes and a thermal camera captures the whole process. Pulsed thermography and lock-in thermography are also employed to obtain a good comparison. In image processing procedure, the principal component thermography method is performed on all thermal images. Moreover, the corresponding receiver operating characteristic curves are established and discussed. A comparison of the results indicates that the liquid nitrogen technique could be considered as a valid option for NDT & E.
2019, Contributo in atti di convegno, ENG
Lorenzo Verdoscia (1), Amin Saheb (i2,3), and Roberto Giorgi(2)
The native implementation of the N-point digital Fourier Transform involves calculating the scalar product of the sample buffer (treated as an N-dimensional vector) with N separate basis vectors. Since each scalar product involves N multiplications and N additions, the total time is proportional to N2, in other words, its an O(N2) algorithm. However, it turns out that by cleverly re-arranging these operations, one can optimize the algorithm down to O(Nlog2(N)), which for large N makes a huge difference. The optimized version of the algorithm is called the Fast Fourier Transform, or the FFT. In this paper, we discuss about an efficient way to obtain Fast Fourier Transform algorithm (FFT). According to our study, we can eliminate some operations in calculating the FFT algorithm thanks to property of complex numbers and we can achieve the FFT in a better execution time due to a significant reduction of N/8 of the needed twiddle factors and to additional factorizations.
2017, Tesi, ITA
Manuela Rosaria Bonavina(Candidata), Francesco dell'Accio (Relatore), Claudia Roberta Calidonna (Relatore),
La tesi tratta dell'aplicazione della FFT e metodi statistici a serie temporali della direzione del vento per il riconoscimento automatico di casi di brezza.
1997, Rapporto tecnico, ENG
Carracciuolo, L.; de Bono, I.; De Cesare, M.L.; di Serafino, D.; Perla, F.
In this paper we describe a parallel FFT routine for MIMD distributed- memory machines, which performs two-dimensional mixed-radix complex-to-complex FFTs. It has been developed for the software library of PINEAPL, an ESPRIT project funded by the European Commission and aimed mainly at producing a general-purpose library of parallel numerical software suitable for a wide range of computationally intensive industrial applications. The parallel FFT algorithm used in the routine is based on a row-block distribution of the matrix to be transformed and has two main computational kernels, one executing multiple one-dimensional FFTs and the other computing the transpose of a matrix distributed in row-block form. The routine has been implemented in Fortran 77, using the BLACS communication library. The accuracy of the routine has been analyzed, comparing experimental results on a IBM RISC System/6000 with known theoretical error bounds. The parallel performance has been evaluated on an Intel iPSC/860, measuring execution time, efficiency and scaled e#ciency. Satisfactory results have been obtained.
1993, Articolo in rivista
R. Lanari, H. Hirosawa
A fully focused Synthetic Aperture Radar (SAR) image can be obtained only if the raw data processing procedure takes into account the space-variance of the SAR system transfer function. This paper presents a nonconventional Fast Fourier Transform (FFT) algorithm which allows an efficient compensation of the space-variant effect. It is specially designed for the SAR data of the Japanese Earth Resources Satellite (JERS-1) but can be extended to different cases.
1982, Altro prodotto, ENG
Alia G.; Barsi F.; Martinelli E.
Many FFT processor designs have been proposed, most of which have been limited by hardware costs when a large number of is to be processed. In recent years, VLSI technology modified design methodology and determined a general reduction of costs. The scope of this work is to present a fast near optimum VLSI architecture for solving an N-point 22 FFT which exhibits T= (loglogN) and = (N log N 10glogN). Main features are: very high parallelism. proper communication lelism, residue arithmetic, table lock-up techniques and pipeline of data. Moreover, it will be shown that design performance does not depend on the and output data representation (residue or weighted notation) .