1,721,821 research outputs found
Applied Machine Learning for Health Informatics: Human Motion Analysis and Affective Computing Application
No full textIl monitoraggio della qualità della vita e del benessere della persona rappresenta una sfida
aperta nello scenario sanitario. La necessità di risolvere questo task nella nuova era
dell'Intelligenza Artificiale porta all’applicazione di metodi dal campo del machine learning.
Gli obiettivi e i contributi di questa tesi riflettono le attività di ricerca svolte (i) nell’ambito
dell’analisi del movimento: valutazione e monitoraggio automatico del movimento umano
durante la riabilitazione fisica, e (ii) nell’ambito dell’affective computing: stima dello stato
affettivo del soggetto.
Nel primo tema il candidato presenta un algoritmo in grado di estrarre le caratteristiche di
movimento clinicamente rilevanti dalle traiettorie dello skeleton acquisite da un sensore RGBD,
e fornire un punteggio sulla prestazione del soggetto. L'approccio proposto si basa su
regole derivate da indicazioni cliniche e su un algoritmo di machine learning (i.e., Hidden
Semi-Markov Model). L'affidabilità dell'approccio proposto è studiata su un dataset
collezionato dal candidato rispetto ad un algoritmo gold standard e alla valutazione clinica. I
risultati sostengono l'uso della metodologia proposta per la valutazione quantitativa delle
prestazioni motorie durante la riabilitazione fisica.
Nel secondo topic il candidato propone l’applicazione del framework di Multiple Instance
Learning per l'apprendimento della risposta emotiva in presenza di label continui ed ambigui.
Questa varaibilità è spesso presente nella risposta affettiva ad uno stimolo esterno (e.g.,
interazione multimediale). L'affidabilità dell'approccio di Multiple Instance Learning è
indagata su un database di benchmark e un dataset più vicino alle problematiche del mondo
reale acquisito dal candidato. I risultati ottenuti evidenziano come la metodologia proposta è
consistente per la stima dello stato affettivo.The monitoring of the quality of life and the subject's well-being represent an open challenge
in the healthcare scenario. The emergence of solving this task in the new era of Artificial
Intelligence leads to the application of methods in the machine learning field.
The objectives and the contributions of this thesis reflect the research activities performed on
the topics of (i) human motion analysis: the automatic monitoring and assessment of human
movement during physical rehabilitation and (ii) affective computing: the inferring of the
affective state of the subject.
In the first topic, the author presents an algorithm able to extract clinically relevant motion
features from the RGB-D visual skeleton joints input and provide a related score about
subject’s performance. The proposed approach is respectively based on rules derived by
clinician suggestions and machine learning algorithm (i.e., Hidden Semi Markov Model). The
reliability of the proposed approach is tested over a dataset collected by the author and with
respect to a gold standard algorithm and with respect to the clinical assessment. The results
support the use of the proposed methodology for quantitatively assessing motor performance
during a physical rehabilitation.
In the second topic, the author proposes the application of a Multiple Instance Learning (MIL)
framework for learning emotional response in presence of continuous and ambiguous labels.
This is often the case with affective response to external stimuli (e.g., multimedia interaction).
The reliability of the MIL approach is investigated over a benchmark database and one dataset
closer to real-world problematic collected by the author. The obtained results point out how
the applied methodology is consistent for predicting the human affective response
Ventilazione naturale nella città storica. Metodologie e strumenti per la valutazione speditiva del fattore ventilativo per il miglioramento delle condizioni di comfort dello spazio aperto
No full textL’analisi del fattore ventilativo riveste un ruolo interessante per la comprensione delle condizioni di comfort dello spazio urbano. Partendo dalla porosità dell’organismo architettonico, si è voluto incentrare l’attenzione su potenzialità e limiti della ventilazione naturale, analizzandone con occhio critico possibili ricadute progettuali in relazione ad uno specifico campo di indagine: la città storica. Proprio in questi brani di città, che oggi risultano essere quelli maggiormente vulnerabili dal punto di vista climatico, si deve parlare di ventilazione e di sfruttamento delle potenzialità di raffrescamento, lavorando in equilibrio quasi statico tra l’invarianza di un tessuto da tutelare e le possibili libertà progettabili. Dalla rilettura critica di conoscenze già acquisite all’esperienza sul campo, il lavoro di ricerca propone una calibrazione ed integrazione di metodi e strumenti operativi per una sistematizzazione metodologica ed operativa sul tema della ventilazione in questo specifico ambito urbano in vista di una possibile azione progettuale. Non linee guida, ma uno strumento speditivo di supporto nelle prime fasi di analisi e valutazione dell’intervento, capace di fornire una immediata verifica pratica degli assunti teorici, che si dimostri iterabile (ripetibile con facilità su realtà differenti), implementabile nel tempo e soprattutto flessibile (adattabile all’eterogeneità del reale).The analysis of the wind factor plays an interesting role in under-standing the comfort conditions of urban space. Starting from the porosity of the architectural organism, it was decided to focus attention on the potential and limits of natural ventilation, analyzing with a critical eye possible design effects in relation to a specific field of investigation: the historical city. Precisely in these parts of cities, which today are the most vulnerable from a climatic point of view, we must talk about ventilation and exploitation of the cooling potential, working in an almost static balance between the invariance of a fabric to be protected and the possible designable freedoms. From the critical reinterpretation of already acquired knowledge to the field experience, the research work proposes a calibration and integration of methods and operational tools for a methodological and operative systematization on the theme of ventilation in this specific urban area aiming to a possible design action. Not guidelines, but a supporting instrument in the early stages of analysis and evaluation of the intervention, able to provide an immediate practical verification of theoretical assumptions, which proves to be iterable (easily repeatable on different realities), implementable over time and above all flexible (adaptable to the heterogeneity of reality)
Advisor: Prof. R.Marculescu System-Level Power/Performance Analysis for Embedded Systems Design
No full textIn todays world, the use of embedded systems is increasing extremely rapidly. The main concerns for people building these systems are shortening time-to-market and increasing complexity. Since many the embedded systems run on batteries, power is an important criteria throughout the design process. Very often, while making these decisions, the designer has to simply rely on simulation tools that can be extremely time consuming, or not sufficiently generic to be of much value. The objective of this thesis is to present a formal technique for system-level power/performance analy-sis that can help the designer to select the right platform starting from a set of target multimedia applica-tions. More precisely, we introduce the Stochastic Automata Networks (SANs) as an effective formalism for average-case analysis that can be used early in the design process to identify the best power/perfor-mance figure among several application-architecture combinations. Further, we describe algorithms that we have implemented, and discuss their limitations in some detail. As the experimental results show, our analysis can be orders of magnitude faster compared to explici
Design and neuroscience - for an evolution of the product design tools, from UCD to UX
No full textResearch starts with retracing the steps that have brought Ergonomics and Human Factors to evolve beyond usability. It addresses issues related to the emotional relationship that can be established between the user and the product, in the User-Centered Design paradigm. Therefore, the Research reviews the literature of the Design Research for Emotional Design, collecting the main tools and methods through which the user's emotional experience is measured in relation to a design product. The emotional response is today also measured with tools and methods of Cognitive Neurosciences, therefore the Research try to get the designer closer to some of the relevant aspect of this emerging field of research, looking at the touching points between Neurosciences and Design. Recent case-studies about Neuroaesthetics, Neuromarketing, and Neurodesign will be reviewed. With the Research Questions, it's stated that the purpose of this study is to explore if Cognitive Neurosciences can represent a shift in the approaches of Emotional Design; therefore, the Research investigates if the designers can interpret emotional responses analyzed by means of Cognitive Neurosciences’ tools. Finally, the study examines if it's possible to create a tool to support the design activity including data obtained from Cognitive Neurosciences. We participated in an interdisciplinary research group composed of neuroscientists, psychologists, communication experts, and bioengineers to explore the Research Questions. With the desk-research and the on-field validation, we found Cognitive Neurosciences to have potentials to represent a shift in the approaches of Emotional Design. To facilitate the dialogue between these two disciplines we defined the tool and method named AlPha Matrix and Cards, with which designers can integrate their specific knowledge and skills with new tools suggested by Cognitive Neurosciences, to understand even better the user's response
Charge noise and spin noise in a semiconductor quantum device
Full text linkSelf-assembled quantum dots are very attractive as the building blocks for quantum light sources and
spin qubits. For instance, a single quantum dot is a robust, fast, narrow-linewidth source of single
photons, features not shared by any other emitter. A spin qubit is implemented by a single electron
or hole confined to a quantum dot. Fundamental quantum mechanics have been explored in
experiments with single quantum dots and spectacular success has been achieved. Future
developments however demand an enhanced quantum coherence. For instance, indistinguishable
single photons and coherent spins are required to implement a quantum repeater. For quantum-dot-
based single photon sources, the linewidths are in the best case typically a factor of two larger than
the transform limit in which the linewidth is determined only by the radiative decay time. Photons
generated far apart in the time domain are therefore not indistinguishable. Spin coherence is
presently limited to microsecond timescales. Improving the quantum coherence involves dealing
with the noise inherent to the device. Charge noise results in a fluctuating electric field, spin noise in
a fluctuating magnetic field at the location of the qubit, and both can lead to dephasing and
decoherence of optical and spin states. Here, the noise and strategies to circumvent its deleterious
effects are explored in order to optimize the performance of solid-state quantum systems.
This thesis is divided into five parts. The first chapter describes in detail the main experimental tool
to explore noise in the solid-state: resonance fluorescence from single quantum dots. A polarization-
based dark-field microscope is realized allowing background-free resonance fluorescence detection
while operating in a set-and-forget mode.
Chapter 2 investigates charge fluctuations in a semiconductor. The origin of the main source of
charge noise in the commonly used optical field-effect devices is pinned down: charge fluctuations at
a GaAs/AlAs interface nearby the quantum dots. These defects are moved further away from the
quantum dots in an improved sample design resulting in close-to-transform limited optical
linewidths.
Even with the improved heterostructures, the transform limit is not reached. Noise spectra of both
charge noise and spin noise provide powerful insights into the noise inherent to the semiconductor,
discussed in chapter 3. A time trace of the resonance fluorescence from a single quantum dot is
translated into a noise spectrum. A crucial difference in their optical signatures allows the nature of
the noise, charge or spin, to be identified. The charge noise is centred at low frequencies, the spin
noise is centred at high frequencies. This technique is able to reveal the entire spectrum of the spin
noise. The combined noise falls rapidly with frequency becoming insignificant above 50 kHz for the
quantum dot optical transition as signalled by transform-limited linewidths.
The low frequency noise, charge noise, results in considerable noise in the emission frequency of the
single photons. This problem is solved in chapter 4 with a dynamic feedback technique that locks the
quantum emission frequency to a reference. The charge noise and its deleterious effects are highly
reduced. A frequency-stabilized source of single photons in the solid-state is realized.
The low frequency linewidths are in the best case typically a factor of two larger than the transform
limit. It is shown in chapter 5 that spin noise in the host material is the dominant exciton dephasing
mechanism. This applies to both the neutral and charged excitons. For the neutral exciton, the spin
noise increases with increasing excitation power. Conversely for the charged exciton, spin noise
decreases with increasing excitation power. This effect is exploited to demonstrate transform-
limited linewidths for the charged exciton even when the measurement is performed very slowly
On the geometry, topology and approximation of amoebas
No full textWe investigate multivariate Laurent polynomials f \in \C[\mathbf{z}^{\pm 1}] = \C[z_1^{\pm 1},\ldots,z_n^{\pm 1}] with varieties \mathcal{V}(f) restricted to the algebraic torus (\C^*)^n = (\C \setminus \{0\})^n. For such Laurent polynomials f one defines the amoeba \mathcal{A}(f) of f as the image of the variety \mathcal{V}(f) under the \Log-map \Log : (\C^*)^n \to \R^n, (z_1,\ldots,z_n) \mapsto (\log|z_1|, \ldots, \log|z_n|). I.e., the amoeba \mathcal{A}(f) is the projection of the variety \mathcal{V}(f) on its (componentwise logarithmized) absolute values. Amoebas were first defined in 1994 by Gelfand, Kapranov and Zelevinksy. Amoeba theory has been strongly developed since the beginning of the new century. It is related to various mathematical subjects, e.g., complex analysis or real algebraic curves. In particular, amoeba theory can be understood as a natural connection between algebraic and tropical geometry.
In this thesis we investigate the geometry, topology and methods for the approximation of amoebas.
Let \C^A denote the space of all Laurent polynomials with a given, finite support set A \subset \Z^n and coefficients in \C^*. It is well known that, in general, the existence of specific complement components of the amoebas \mathcal{A}(f) for f \in \C^A depends on the choice of coefficients of f. One prominent key problem is to provide bounds on the coefficients in order to guarantee the existence of certain complement components. A second key problem is the question whether the set U_\alpha^A \subseteq \C^A of all polynomials whose amoeba has a complement component of order \alpha \in \conv(A) \cap \Z^n is always connected.
We prove such (upper and lower) bounds for multivariate Laurent polynomials supported on a circuit. If the support set A \subset \Z^n satisfies some additional barycentric condition, we can even give an exact description of the particular sets U_\alpha^A and, especially, prove that they are path-connected.
For the univariate case of polynomials supported on a circuit, i.e., trinomials f = z^{s+t} + p z^t + q (with p,q \in \C^*), we show that a couple of classical questions from the late 19th / early 20th century regarding the connection between the coefficients and the roots of trinomials can be traced back to questions in amoeba theory. This yields nice geometrical and topological counterparts for classical algebraic results. We show for example that a trinomial has a root of a certain, given modulus if and only if the coefficient p is located on a particular hypotrochoid curve. Furthermore, there exist two roots with the same modulus if and only if the coefficient p is located on a particular 1-fan. This local description of the configuration space \C^A yields in particular that all sets U_\alpha^A for \alpha \in \{0,1,\ldots,s+t\} \setminus \{t\} are connected but not simply connected.
We show that for a given lattice polytope P the set of all configuration spaces \C^A of amoebas with \conv(A) = P is a boolean lattice with respect to some order relation \sqsubseteq induced by the set theoretic order relation \subseteq. This boolean lattice turns out to have some nice structural properties and gives in particular an independent motivation for Passare's and Rullgard's conjecture about solidness of amoebas of maximally sparse polynomials. We prove this conjecture for special instances of support sets.
A further key problem in the theory of amoebas is the description of their boundaries. Obviously, every boundary point \mathbf{w} \in \partial \mathcal{A}(f) is the image of a critical point under the \Log-map (where \mathcal{V}(f) is supposed to be non-singular here). Mikhalkin showed that this is equivalent to the fact that there exists a point in the intersection of the variety \mathcal{V}(f) and the fiber \F_{\mathbf{w}} of \mathbf{w} (w.r.t. the \Log-map), which has a (projective) real image under the logarithmic Gauss map. We strengthen this result by showing that a point \mathbf{w} may only be contained in the boundary of \mathcal{A}(f), if every point in the intersection of \mathcal{V}(f) and \F_{\mathbf{w}} has a (projective) real image under the logarithmic Gauss map.
With respect to the approximation of amoebas one is in particular interested in deciding membership, i.e., whether a given point \mathbf{w} \in \R^n is contained in a given amoeba \mathcal{A}(f). We show that this problem can be traced back to a semidefinite optimization problem (SDP), basically via usage of the Real Nullstellensatz. This SDP can be implemented and solved with standard software (we use SOSTools and SeDuMi here). As main theoretic result we show that, from the complexity point of view, our approach is at least as good as Purbhoo's approximation process (which is state of the art)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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