Samuel Bignardi

Samuel Bignardi
Georgia Institute of Technology | GT · School of Electrical & Computer Engineering

Ph.D. Computational Geophysics

About

74
Publications
20,873
Reads
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409
Citations
Additional affiliations
May 2017 - present
Georgia Institute of Technology
Position
  • Research Engineer II
Description
  • Modeling and inversion of radar data (SAR, GPR) through the study of the full waveform and the use of active surfaces
September 2014 - April 2017
University of Ferrara
Position
  • Research Associate
Description
  • Development of 2-D and 3-D Modelling and Inversion of seismic surface waves
March 2014 - September 2014
Georgia Institute of Technology
Position
  • PostDoc Position
Description
  • Development of Hibrid BEM and level set method computational algorithms
Education
January 2008 - December 2010
University of Ferrara
Field of study
  • Geophysics
January 1998 - July 2006
University of Ferrara
Field of study
  • Physics

Publications

Publications (74)
Article
We investigate a multiview shape reconstruction problem based on an active surface model whose geometric evolution is driven by radar measurements acquired at sparse locations. Building on our previous work in the context of variational methods for the reconstruction of a scene conceptualized as the graph of a function, we generalize this inversion...
Chapter
Full-text available
Negli ultimi anni, le tecniche di indagine non invasiva del sottosuolo sono diventate di estrema utilità in diversi campi di studi, compreso quello archeologico. La possibilità di comprendere l'estensione, lo spessore o l'articolazione del deposito archeologico permette di indirizzare in modo mirato le operazioni di scavo. Le indagini non invasive...
Chapter
The particular geological and logistical context of the site (prevailing fine-grained lithologies and the presence of metal frames of the greenhouses) prevented the authors to use the most common geophysical prospection methods, in first place the geomagnetic technique. The Chapter presents and discusses the use of microtremors: passive seismic met...
Conference Paper
We propose Directionally Paired Principal Component Analysis (DP-PCA), a novel linear dimension-reduction model for estimating coupled yet partially observable variable sets. Unlike partial least squares methods (e.g., partial least squares regression and canonical correlation analysis) that maximize correlation/covariance between the two datasets,...
Conference Paper
Principal Component Analysis (PCA) is a widely used technique for dimensionality reduction in various problem domains, including data compression, image processing, visualization, exploratory data analysis, pattern recognition, time-series prediction, and machine learning. Often, data is presented in a correlated paired manner such that there exist...
Article
In recent decades, numerous observations of the connection between sedimentary basins structure and severity and variability of damages during earthquake events have sparked a series of studies for characterization of such subsurface structures. However, these investigations were always accompanied with cost concerns and executive restrictions. Amo...
Technical Report
Full-text available
This article tackles the use of active seismic methods base on the spectral analysis of surface waves in the characterization of the subsurface of urban areas. On one hand, this work describes the use of the land-streamer for rapid and continuous data acquisition along linear profiles. On the other hand, presents the DIPL (Direct Interpretation of...
Article
Full-text available
Background: Our study assesses the diagnostic value of different features extracted from high resolution computed tomography (HRCT) images of patients with idiopathic pulmonary fibrosis. These features are investigated over a range of HRCT lung volume measurements (in Hounsfield Units) for which no prior study has yet been published. In particular...
Article
Delineation of tumours in Positron Emission Tomography (PET) plays a crucial role in accurate diagnosis and radiotherapy treatment planning. In this context, it is of outmost importance to devise efficient and operator-independent segmentation algorithms capable of reconstructing the tumour three-dimensional (3D) shape. In previous work, we propose...
Chapter
In this paper, we demonstrate how a semi-automatic algorithm we proposed in previous work may be integrated into a protocol which becomes fully automatic for the detection of brain metastases. Such a protocol combines 11C-labeled Methionine PET acquisition with our previous segmentation approach. We show that our algorithm responds especially well...
Article
Full-text available
Nell’ambito del progetto CLARA sono state sviluppate e sperimentate ed tecnologie sismiche ed elettromagnetiche per la diagnostica non invasiva nella zona di sottosuolo a media profondità (fino a -100 m), partendo dal presupposto che la conoscenza delle caratteristiche litostratigrafiche, idrogeologiche e geofisiche di questa zona del sottosuolo è...
Article
In this paper we used an integrated geomatics and geophysical investigation to gain insight about the Upper Pleistocene Cave deposit of Grotta di Fumane, located near to Verona city, Italy. Geophysical techniques are seldom considered for investigation of Paleolithic sites, mostly because as is typical in such a context, the physical properties of...
Article
Full-text available
In this article, a framework of building monitoring is developed and transient and permanent variations of the fundamental period of vibration caused by both damage and repair interventions are investigated. The buildings of the University of Ferrara (Emilia-Romagna Region, Northern Italy), struck by the 2012 Emilia seismic sequence, were monitored...
Article
Full-text available
During the seismic crisis of May-June 2012, that strongly affected the central sector of the Ferrara Arc, relevant coseismic effects were observed, such as ground deformations and amplification phenomena due to low quality mechanical characteristics of the shallow subsurface (i.e. few hundreds of meters). This portion of the subsurface is not inves...
Article
An algorithm for tumor delineation in positron emission tomography (PET) is presented. Segmentation is achieved by a local active contour algorithm, integrated and optimized with the k-nearest neighbor (KNN) classification method, which takes advantage of the stratified k-fold cross-validation strategy. The proposed approach is evaluated considerin...
Conference Paper
Full-text available
During the seismic crisis of May-June 2012, that strongly affected the central sector of the Ferrara Arc (Italy), relevant coseismic effects were observed, such as ground deformations and amplification phenomena due to the low quality of the mechanical characteristics in the shallow subsurface (i.e. few hundreds of meters). We exploited seismic noi...
Conference Paper
Full-text available
The Horizontal to Vertical Spectral Ratio, or "HVSR", has become popular in the last decades, especially because it leverages on inexpensive equipment and minimal workforce. One of the most attractive aspect is that elastic shear wave resonance frequency of a sedimentary basin can be retrieved and readily used to obtain an estimate of the depth of...
Article
In the context of cancer delineation using positron emission tomography datasets, we present an innovative approach which purpose is to tackle the real-time, three-dimensional segmentation task in a full, or at least nearly full automatized way. The approach comprises a preliminary initialization phase where the user highlights a region of interest...
Article
Positron Emission Tomography (PET) imaging has an enormous potential to improve radiation therapy treatment planning offering complementary functional information with respect to other anatomical imaging approaches. The aim of this study is to develop an operator independent, reliable, and clinically feasible system for biological tumour volume del...
Article
The investigation of seismic ambient noise (microtremor) in spectral ratio form, known as the Horizontal-to-Vertical Spectral Ratio technique, is extremely popular nowadays both to investigate large areas in a reduced amount of time, and to leverage a wider choice of low cost equipment. In general, measurements at multiple locations are collected t...
Conference Paper
Full-text available
The investigation of seismic ambient noise (microtremor) in spectral ratio form, known as HVSR, is extremely popular nowadays both to investigate large areas in a reduced amount of time, and to leverage a wider choice of low cost equipment. In general, measurements at multiple locations are collected to generate multiple HVSR curves which can indiv...
Conference Paper
Full-text available
The application of geophysical techniques is still seldom incorporated into the investigation of Paleolithic cave deposits, mostly because of their sedimentary nature and the almost complete absence of architectural remains that - in other contexts - are easily detected by geophysical methods (Piro et alii 2000; Quarto et alii 2007). These peculiar...
Conference Paper
Full-text available
Geophysical techniques are seldom used for the investigation of paleolithic archeological sites, mostly due to their sedimentary nature and the almost complete absence of architectural remains that can result in clear geophysical anomalies. The Fumane cave (Italy) is considered one of the most important sites in Europe. Recent investigations and st...
Article
The use of the ratio of microtremor spectra, as computed by the Nakamura's technique, was recently proved successful for the evaluating the thickness of sedimentary covers laying over both shallow and deep rocky bedrocks thus enabling bedrock mapping. The experimental success of such application and its experimental uncertainties are today reported...
Conference Paper
The microseismic network of Ferrara was established, in the beginning of 1990 and started its monitoring activity few months before the start of reservoir exploitation, for residential and industrial heating purposes, of the Casaglia geothermal site characterised by fluids of 100 °C: February 1990. The purpose was to monitor the natural seismicity...
Article
ABSTRACT Horizontal-to-Vertical Spectral Ratio (HVSR) is a widely used geophysical technique in seismic microzonation studies. It is based on a specific analysis of seismic ambient noise. The method allows to obtain the frequency and amplitude of the resonance peaks of a layered earth with increasing acoustic impedance contrasts. The peaks can be i...
Conference Paper
Full-text available
Conventionally employed geophysical methods in archaeological investigations , i.e. ground penetrating radar(GPR), magnetometry, geoelectric (electrical resistivity tomography: ERT) and geo-electromagnetic (FDEM) techniques, can be hampered by specific site conditions. In the case history here presented, i) magnetometry was ruled out due to the pre...
Article
OpenHVSR is a computer program developed in the Matlab environment, designed for the simultaneous modeling and inversion of large Horizontal-to-Vertical Spectral Ratio (HVSR or H/V) datasets in order to construct 2D/3D subsurface models (topography included). The program is designed to provide a high level of interactive experience to the user and...
Conference Paper
Full-text available
The architecture of the Po Plain foredeep filling, from Pleistocene onward, is characterized by a generally “regressive” trend, interrupted by lesser fluctuations, evidenced by the transition from offshore Pliocene deposits to marine-marginal and then to alluvial Quaternary sediments (Ricci Lucchi, 1986; Amorosi and Colalongo, 2005; Amorosi, 2008)....
Conference Paper
Full-text available
The soil stiffness is routinely evaluated by direct investigation, using geotechnical tests such as CPT-CPTu, SPT. While this approach allows retrieving detailed and reliable information, the procedure is invasive and the result is punctual hence of limited spatial extension. Moreover, the costs of a survey quickly grow with the number of probes. A...
Conference Paper
Full-text available
The evaluation of the soil stiffness is routinely performed by direct investigation, using geotechnical tests such as CPT-CPTu. A low cost complement to the direct investigation would be the use of seismic surface wave methods such as, for example, the “Spectral Analysis of Surface Waves” (SASW) or the more updated “Multi-channel Analysis of Surfac...
Conference Paper
Full-text available
Small scale prehistoric archaeological sites, such as the Fumane cave, located north of Verona city in north Italy, poses a lot of challenges both to archaeologists and geophysicists. The cave is considered as one of the most important Middle and upper Prehistoric sites of Europe, discovered in 1884. It contains a wellpreserved and impressive strat...
Conference Paper
Full-text available
Among the several types of induced polarization effects, electro-osmosis and membrane polarization by constrictivity of pores my result in non-linear behaviour, i.e. chargeability is not constant with supplied dc current. A new model, based on the second Fick’s equation succeeded in predicting, on laboratory samples, this behaviour. In fact, The no...
Conference Paper
Full-text available
The characterization of soil settlements below foundations of buildings using surface waves methods represent an extreme challenging problem because of the presence of localized shear waves variation and shallow heterogeneity. To tackle the near-foundation shear waves distribution reconstruction challenge a method for the elaboration of surface wav...
Book
Full-text available
Questo libro, nato dall’esperienza dell’insegnamento della Geofisica Applicata nel Corso di Laurea Magistrale di Scienze geologiche, georisorse e territorio dell’Università di Ferrara, raccoglie e analizza i metodi d’indagine raccolti sotto il nome di “Geofisica Applicata”: i metodi gravimetrico, magnetometrico, geoelettrico; i vari metodi sismici...
Conference Paper
In many laboratory measurements of resistivity and of chargeability on samples of porous, clay-free rocks, a nonlinear response was measured with intensity of supplied current and with time of supply. A physical-mathematical model of membrane polarization by constrictivity of pores was then built, by integrating the second Fick's law with suitable...
Conference Paper
Full-text available
Seismic surface wave methods allow to retrieve the shallow subsurface shear wave velocity. Among these, the "Multi-channel Analysis of Surface Waves" is to date one of the most widely adopted non-invasive active-source approaches in the professional world for the evaluation of the stiffness properties of the ground for geotechnical engineering purp...
Article
Full-text available
A massive surface fracturing and sand ejection took place following the main shock of May 20th, 2012 earthquake (ML=5.9 and hypocenter depth of 6.3 km), in the Emilia-Romagna Region, Northern Italy. These phenomena were induced by the liquefaction of a water-saturated, medium to coarse grained sand layer, laying at depths between 8 and 12 m below g...
Data
Full-text available
A pseudo-2D section showing the distribution of the shear-waves velocity has been reconstructed along a transect crossing the central sector of the Ferrara Folds (Figure 1). In order to achieve this goal, we acquired several 1D velocity profiles characterized by an investigation depth of ca. 150 m from the field surface.
Conference Paper
Full-text available
Following the earthquake sequence started on May 20th 2012, 7 earthquakes of local magnitude > 5.0, culminated by two main shocks with Ml: 5.9 and 5.8, struck the Emilia area, North Italy. The occurrence of these earthquakes and the associated damage, together with widespread liquefaction phenomena has urged the need to accelerate the measures to h...
Article
Surface waves methods exploit the dispersive properties of Rayleigh and Love waves to estimate the shear wave velocity profiles in vertically heterogeneous subsurfaces. Typically, they rely on a simplified one-dimensional (1-D) analytical forward model where the lateral variation of the layer thickness is neglected and so is the fraction of the inc...
Conference Paper
Full-text available
Following the main shock (ML 5.9) that hit North Italy on May 20, 2012 at 4:03:53 considerable coseismic site effects, represented by surface fractures, sand boils and lateral spreading, occurred. These were caused by the liquefaction of a saturated sand layer(s) located at shallow depths (< 15 m). The spatial distribution of these coseismic featur...
Conference Paper
Full-text available
Seismic surface wave methods gained popularity during the last decade to retrieve the shallow subsurface shear wave velocity (Vs) from the analysis of the recorded wave field. Besides early approaches, such as the Spectral Analysis of Surface Waves (Nazarian and Stokoe, 1984; Stokoe et al., 1994), based on a two-receiver setup and the passive metho...
Article
Full-text available
Massive surface fracturing and sand ejection took place during the main shock of the May 20, 2012, earthquake (Ml = 5.9) in the Emilia-Romagna region, northern Italy. These phenomena were induced by the liquefaction of water-saturated sand layers, and they damaged several buildings, as well as many roads and sidewalks. They were clustered between t...
Article
Surface-wave methods are widely used in earth sciences and engineering for the geometric characterization of geological bodies and tectonic structures of the subsurface. These techniques exploit the dispersive nature of Rayleigh waves to indirectly estimate shear wave velocity profiles from surface-wave measurements; however, they are limited to pa...
Conference Paper
Full-text available
Surface wave methods (SWM) are widely used for the geophysical characterization of geological bodies and tectonic structures in both Earth Sciences and Engineering. SWMs exploit the dispersive nature of Rayleigh waves to indirectly estimate shear wave velocity profiles from surface wave measurements, but they are limited to parallel-layered geometr...
Conference Paper
Full-text available
Il cimitero monumentale di Bologna ospita un gran numero manufatti di valore artistico e storico. Tale patrimonio pone problemi non trascurabili in termini di conservazione ed una mirata progettazione delle opere di restauro necessita della corretta caratterizzazione dello stato dei manufatti. In questa nota si presentano i risultati dell’applicazi...
Conference Paper
Full-text available
The use of Love-waves has been limited to seismological studies related to crustal and mantle characterisation being more sensitive to shear waves variations and independent on the Poisson’s ratio. However, their use in shallow subsurface characterisation is not widely employed, although in the last five years a number of papers has addressed this...