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Cortical representations of auditory and tactile perceptual decisions
No full textPerceptual decision making is the process that makes a rich environment manageable by compartmentalizing stimuli into various categories. Parietal cortex is involved in many tasks that require perceptual decisions. While much work in both the human and monkey domains has investigated processes related to visual decision making in the frontal and parietal lobes in a predominantly unimodal fashion, relatively little research has explored auditory and tactile perceptual decisions. As such, we wanted to know whether these regions also play a role in auditory and tactile decision making and to what extent information therein may be represented supramodally. Using functional magnetic resonance imaging and a paradigm requiring human participants to categorize auditory and tactile frequency-modulated sweeps, we sought to disentangle motor confounds and minimize linguistic processing from the perceptual decisions that participants made. We ran a series of experiments that utilized whole-brain multivariate pattern analysis implemented via linear discriminant analysis classification in order to detect cortical representations of such potentially supramodal information. Ultimately, we showed that learned categories were best decoded within the right parietal lobe and the medial frontal gyrus, supramodal representations of “up- vs. down-sweeps” were localized to the left parietal-temporal-occipital junction, and, most consequentially, cross-modality decoding of category membership was strongest in the left posterior insula and precuneus. Given our choice of paradigm, such results appear to demonstrate that the information representations in the posterior insula and precuneus are independent of motor and language processing and instead reflect supramodal or modality-free mechanisms that underlie the categorization process
Mathematical models for vector-borne disease: effects of periodic environmental variations.
No full textFirstly, I proposed a very simple SIS/SIR model for a general vector-borne disease transmission considering constant population sizes over the season, where contact between the host and the vector responsible of the transmission is assumed to occur only during the summer of each year. I discussed two different types of threshold for pathogen persistence that I explicitly computed: a "short-term threshold" and a "long-term threshold". Later, I took into account the seasonality of the populations involved in the transmission. For a single season, the model consists of system of non linear differential equations considering the various stages of the infection transmission between the vector and the host population. Assuming the overwintering in the mosquito populations, I simulated the model for several years. Finally, I studied the spatial spread of a vector-borne disease throught an impusive reaction-diffusion model and I showed some simulations
Mining and Learning in Sequential Data Streams: Interesting Correlations and Classification in Noisy Settings
No full textSequential data streams describe a variety of real life processes: from sensor readings of natural phenomena to robotics, moving trajectories and network monitoring scenarios. An item in a sequential data stream often depends on its previous values, subsequent items being strongly correlated. In this thesis we address the problem of extracting the most significant sequential patterns from a data stream, with applications to real-time data summarization and classification and estimating generative models of the data. The first contribution of this thesis is the notion of Conditional Heavy Hitters, which describes the
items that are frequent conditionally – that is, within the context of their parent item. Conditional Heavy Hitters are useful in a variety of applications in sensor monitoring, analysis, Markov chain modeling, and more. We develop algorithms for efficient detection of Conditional Heavy Hitters depending on the characteristics of the data, and provide analytical quality guarantees for their performance.
We also study the behavior of the proposed algorithms for different types of data and demonstrate the efficacy of our methods by experimental evaluation on several synthetic and real-world datasets. The second contribution of the thesis is the extension of Conditional Heavy Hitters to patterns of variable order, which we formalize in the notion of Variable Order Conditional Heavy Hitters. The significance of the variable order patterns is measured in terms of high conditional and joint probability and their difference from the independent case in terms of statistical significance.
The approximate online solution in the variable order case exploits lossless compression approaches. Facing the tradeoff between memory usage and accuracy of the pattern extraction, we introduce several online space pruning strategies and study their quality guarantees. The strategies can be chosen depending on the estimation objectives, such as maximizing the precision or recall of extracted significant patterns. The efficiency of our approach is experimentally evaluated on three real datasets.
The last contribution of the thesis is related to the prediction quality of the classical and sequential classification algorithms under varying levels of label noise. We present the "Sigmoid Rule" Framework, which allows choosing the most appropriate learning algorithm depending on the properties of the data. The framework uses an existing model of the expected performance of learning algorithms as a sigmoid function of the signal-to-noise ratio in the training instances. Based on the sigmoid parameters we define a set of intuitive criteria that are useful for comparing the behavior of learning algorithms in the presence of noise. Furthermore, we show that there is a connection between these parameters and the characteristics of the underlying dataset, hinting at how the inherent properties of a dataset affect learning. The framework is applicable to concept drift scenarios, including modeling user behavior over time, and mining of noisy time series of evolving nature
Analysis of Complex Human Interactions in Unconstrained Videos
No full textThe literature in human activity recognition is very broad and many different approaches have been presented to interpret the content of a visual scene. In this thesis, we are interested in two-person interaction analysis in unconstrained videos. Specifically, we focus on two open issues:(1)discriminative patch segmentation,and (2) human interaction recognition. For the first problem, we introduce two models to extract discriminative patches of human interactions applied to different scenarios, namely, videos from surveillance cameras and videos in TV shows. For the other problem, we propose two different frameworks: (1) human interaction recognition using the self-similarity matrix, and (2) human interaction recognition using the multiple-instance-learning approach. Experimental results demonstrate the effectiveness of our methods
Common law con caratteri cinesi. Il diritto nella Regione Amministrativa Speciale di Hong Kong tra flussi linguistici inglesi e cinesi
No full textLa ricerca si propone di esaminare l’ordinamento giuridico della Regione Amministrativa Speciale di Hong Kong, costituita a seguito della fine del dominio coloniale britannico in terra cinese, analizzando come il ritorno sotto la sovranità della Repubblica Popolare Cinese ha inciso sul sistema di Hong Kong sia da un punto di vista della struttura giuridico-istituzionale sia da un punto di vista della lingua del diritto. L’analisi si svilupperà partendo da un preliminare inquadramento analitico con riferimento ai temi della circolazione dei modelli e dei flussi giuridici (con specifico riferimento ai processi storici della colonizzazione inglese), del fenomeno delle mixed jurisdictions e del bilinguismo giuridico e si dedicherà poi alla ricostruzione dell’evoluzione del sistema di common law di Hong Kong prima e dopo l’handover. In questa parte, dopo una ricostruzione da un punto di vista delle istituzioni e delle fonti del diritto della RAS, verranno messi in evidenza quali sono gli elementi di continuità e gli elementi di innovazione che si trovano all’interno dell’attuale sistema di Hong Kong. L’analisi si concerterà quindi sul tema del bilinguismo giuridico, prendendo in esame sia il suo sviluppo all’interno delle istituzioni giuridiche e della giurisprudenza delle corti della RAS, sia le strategie traduttive seguite nella costruzione del nuovo diritto bilingue. In questo contesto saranno altresì analizzate le questioni terminologiche legate alla trasposizione del diritto di common law in lingua cinese, esaminando alcuni termini impiegati nel lessico della statute law di Hong Kong. Infine si procederà a una riflessione conclusiva sulle criticità e sulle prospettive evolutive che segnano oggi il bilinguismo giuridico nell’ordinamento Hong Kong
Advanced methods for change detection in VHR multitemporal SAR images
No full textChange detection aims at identifying possible changes in the state of an object or phenomenon by jointly observing data acquired at different times over the same geographical
area. In this context, the repetitive coverage and high quality of remotely sensed images acquired by Earth-orbiting satellites make such kind of data an ideal information source for change detection. Among the different kinds of Earth-observation systems, here we focus on Synthetic Aperture Radar (SAR). Differently from optical sensors, SAR is able to regularly monitor the Earth surface independently from the presence of cloud cover or sunlight illumination, making SAR data very attractive from an operational point of view. A new generation of SAR systems such as TerraSAR-X, TANDEM-X and COSMO-SkyMed, which are able to acquired data with a Very High geometrical Resolution (VHR),
has opened new attractive opportunities to study dynamic phenomena that occur on the Earth surface. Nevertheless, the high amount of geometrical details has brought several
challenging issues related to the data analysis that should be addressed. Indeed, even though in the literature several techniques have been developed for the automatic analysis
of multitemporal low- and medium-resolution SAR data, they are poorly effective when dealing with VHR images. In detail, in this thesis we aim at developing advanced methods
for change detection that are able to properly exploit the characteristics of VHR SAR images. i) An approach to building change detection. The approach is based on a novel theoretical model of backscattering that describes the appearance of new or fully collapsed buildings. The use of a fuzzy rule set allows in real scenarios an efficient and effective detection of new/collapsed building among several other sources of changes. ii) A change detection approach for the identification of damages in urban areas after
catastrophic events such as earthquakes or tsunami. The approach is based on two steps: first the most damaged urban areas over a large territory are detected by analyzing high resolution stripmap SAR images. These areas drive the acquisition of new VHR spotlight images, which are used in the second step of the approach to accurately identify collapsed buildings. iii) An approach for surveillance applications. The proposed strategy detects the changes
of interest over important sites such as ports and airports by performing a hierarchical multiscale analysis of the multitemporal SAR images based on a Wavelet decomposi-
tion technique. iv) An approach to multitemporal primitive detection. The approach, based on the Bayesian rule for compound classification integrated in a fuzzy inference system, takes advantage of the multitemporal correlation of images pairs in order to both improve the detection of the primitives and identify the changes in their state.
For each of the above mentioned topic an analysis of the state of the art is carried out, the limitations of existing methods are pointed out and the proposed solutions to the considered problems are described in details. Experimental results conducted on simulated and real remote sensing data are provided in order to show and confirm the validity of
each of the proposed methods
Plagiarism as an axiom of legal similarity: a critical and interdisciplinary study of the Italian author's right and the UK copyright systems on the moral right of attribution
No full textPlagiarism may have accompanied acts of creation, either endorsing or contradicting them. Esteemed as a general rule of literature or censured as literary larceny, it embodies the disavowal of authorship in the intellectual works of others and thus breaches their right to be acknowledged as authors, while also feasibly deceiving the public and, in any case, contradicting the universal rule of creative imitation. Historically entangled with the concepts of counterfeiting and piracy, it only later reached an autonomous collocation as a violation of the moral right of attribution. Placed in the broadest context of copyright law, it yet struggles against its confinement to a strict legal characterisation, given its colourful appearance and inherent inconsistency according to the type of works or field of knowledge to which it relates, thus refuting any unyielding interpretation. In such a mutable context, the purpose of this research, which revolves around the systems of Italy and the United Kingdom, is to explore a view of plagiarism that appreciates the different instances in which a genuine borrowing or a deceitful practice appear, considering the dimension of copyright infringement, but also looking at other possible legal and non-legal means of construal. Given these premises, an accurate exploration of the phenomenon requires a preliminary consideration of the manifold literature on the subject, which increasingly progresses together with the development of technology and social practices. Furthermore, its literal absence in statutory law does not impede finding a collocation in the context of the judiciary, which is analysed with reference to the legal systems of both Italy and the United Kingdom. This does not infer that courts deliver a flawless and unfailing interpretation of plagiarism. On the contrary, a careful reading of the ruling confirms that the narrow realm of copyright law is shrinking. However, the unpredictability of the statutory and judicial approach towards plagiarism may also be welcomed as an attempt by the law to acknowledge the difficulty to appraise its complexity. Therefore, the present study openly adopts an interdisciplinary and comparative analysis that may help to describe its controversial legal breadth while also possibly unravelling any other principled range
Efficient Automated Security Analysis of Complex Authorization Policies
No full textAccess Control is becoming increasingly important for today's ubiquitous systems. Sophisticated security requirements need to be ensured by authorization policies for increasingly complex and large applications. As a consequence, designers need to understand such policies and ensure that they meet the desired security constraints while administrators must also maintain them so as to comply with the evolving needs of systems and applications. These tasks are greatly complicated by the expressiveness and the dimensions of the authorization policies. It is thus necessary to provide policy designers and administrators with automated analysis techniques that are capable to foresee if, and under what conditions, security properties may be violated. For example, some analysis techniques have already been proposed in the literature for Role-Based Access Control (RBAC) policies. RBAC is a security model for access control that has been widely adopted in real-world applications. Although RBAC simplifies the design and management of policies, modifications of RBAC policies in complex organizations are difficult and error prone activities due to the limited expressiveness of the basic RBAC model. For this reason, RBAC has been extended in several directions to accommodate various needs arising in the real world such as Administrative RBAC (ARBAC) and Temporal RBAC (TRBAC). This Dissertation presents our research efforts to find the best trade-off between scalability and expressiveness for the design and benchmarking of analysis techniques for authorization policies. We review the state-of-the-art of automated analysis for authorization policies, identify limitations of available techniques and then describe our approach that is based on recently developed symbolic model checking techniques based on Satisfiability Modulo Theories (SMT) solving (for expressiveness) and carefully tuned heuristics (for scalability). Particularly, we present the implementation of the techniques on the automated analysis of ARBAC and ATRBAC policies and discuss extensive experiments that show that the proposed approach is superior to other state-of-the-art analysis techniques. Finally, we discuss directions for extensions
Audiotactile interactions: psychophysical and neuroimaging approaches
No full textIn daily life, we are immersed in a continuous flow of stimuli targeting each of our different senses. Far from being independently processed, accumulating evidence has been widely documented by studies showing that stimuli from different modalities largely interact. However, despite the increasing interest, the interpretations of the results of experiments studying multisensory interaction are still controversial and the underlying mechanisms remain broadly unknown. The aim of this thesis is to investigate the interactions that occur between the senses of audition and touch. Audiotactile interactions have been far less studied than the ones existing between other modality pairings. Maybe because they go often unnoticed though being well present in many everyday life situations. This thesis focuses mainly on two aspects that concern interactions: understanding the impact of the relative saliency between the stimuli and investigating the mechanism behind perceptual integration. These questions are addressed respectively in two studies conducted by means of magnetoencephalography. The thesis is structured as following: in chapter 1, I provide the theoretical background to my scientific questions. A brief synthesis of the two main studies is presented in chapter 2. The two studies are entirely reported under the form of manuscripts in chapter 4. Finally, in appendix a behavioral study that investigates spatial aspects of AT interactions is reported. Although the results of this study are of pertinence of the project, given the preparatory character and the preliminary state of the study we decided to show them in the appendix rather than include them in the main body of the thesis
Micro- and Nanostructured Polymeric Materials for art protection and Restoration
No full textIn the restoration field the synthetic resins are commonly used and they are selected in order to replace natural products and possibly overcome their drawbacks. Nevertheless, these resins are not completely able to cover the specific mechanical properties required in each restoration work. The main aim of this research is the development of innovative micro/nanocomposite materials with enhanced features for artwork conservation operations. The introduction of appropriate amounts of micro- and nanofillers within commercially available art preserving polymers may allow the improvement of their mechanical deficiencies, without impairing their physical and chemical properties.
Cellulose microcrystals (CMC) and nanocrystals (CNC) were selected as natural reinforcing fillers for a commercial acrylic copolymer (Paraloid B72) widely applied as a consolidant of wooden objects and two molecular weights of a thermoplastic water soluble adhesive used in the restoration of oil paintings (Aquazol 200 and 500). In particular, melt-compounded Paraloid and Aquazol based microcomposites with various amounts (5÷30 wt%) of CMC and thin films of Aquazol 500 micro- and nanocomposites produced by the solution mixing method with a CMC and CNC content of 5-10-30 wt% were investigated. Several characterization techniques were used in order to assess the effect of micro- and nanocellulose on the physical and thermo-mechanical behavior of these three thermoplastic polymers.
In the first part of the work, the characterization of melt-compounded and compression molded microcomposites under dry and conditioned state (T= 23°C, RH= 55%) was performed. All dried and wet formulations showed a similar stabilizing effect of CMC flakes with an increase of elastic modulus and a decrease of thermal expansion coefficient and creep compliance, regardless of the moisture content. Interestingly, conditioned composites
exhibited the enhancement of the tensile properties at break, in contrast to
dried microcomposites that reported a drop in these properties. On the other hand, the highest amount of CMC led to a chromatic change of the three matrices towards yellow-brown tones.
In the second part of the work, the characterization of solution mixed micro and nanocomposites based on Aquazol 500 highlighted the systematic increment of the dimensional stability of the neat resin due to the presence of both CMC and CNC particles. Remarkably, CNC proved to be more effective than CMC in increasing of the stiffness and the elongation at break of Aquazol as the filler loading increased, without impairing the good optical properties of this material.
In the third part of the work, the application of melt-compounded Paraloid/CMC composites as consolidants for damaged wood was investigated. CMC introduction did not change the good viscosity of the neat matrix and especially its good water repellency. Wood samples treated with microfilled Paraloid exhibited an increment of the stiffness and the flexure strength under quasi-static and impact conditions and, additionally, a systematic enhancement of the radial and tangential surface hardness almost up to the intact wood values was observed.
In the last part of this thesis, the practical application of CMC and CNC Aquazol based adhesive films made by melt-compounding and solution mixing was investigated for the lining of oil paintings. Single-lap shear tests confirmed the stabilization action of both CMC and CNC particles on all experimental formulations with a progressive reduction of the compliance proportionally to the filler loading. Even in this case the increment of the Aquazol dimensional stability was mainly imparted by the presence of CNC. Only for solution mixed CMC composites a dramatic drop in the adhesive strength as the filler content increased was detected