154 research outputs found
Communities in C.elegans connectome through the prism of non-backtracking walks
The fundamental relationship between the mesoscopic structure of neuronal
circuits and organismic functions they subserve is one of the major challenges
in contemporary neuroscience. Formation of structurally connected modules of
neurons enacts the conversion from single-cell firing to large-scale behaviour
of an organism, highlighting the importance of their accurate profiling in the
data. While connectomes are typically characterized by significant sparsity of
neuronal connections, recent advances in network theory and machine learning
have revealed fundamental limitations of traditionally used community detection
approaches in cases where the network is sparse. Here we studied the optimal
community structure in the structural connectome of C.elegans, for which we
exploited a non-conventional approach that is based on non-backtracking random
walks, virtually eliminating the sparsity issue. In full agreement with the
previous asymptotic results, we demonstrated that non-backtracking walks
resolve the ground truth annotation into clusters on stochastic block models
(SBM) with the size and density of the connectome better than the spectral
methods related to simple random walks. Based on the cluster detectability
threshold, we determined that the optimal number of modules in a recently
mapped connectome of C.elegans is 10, which precisely corresponds to the number
of isolated eigenvalues in the spectrum of the non-backtracking flow matrix.
Broadly, our work provides a robust network-based framework to reveal
mesoscopic structures in sparse connectomic datasets, paving way to further
investigation of connectome mechanisms for different functions.Comment: This work previously appeared as arXiv:2207.00767 under an accidental
replacemen
Light Clusters and Pasta Phases in Warm and Dense Nuclear Matter
The pasta phases are calculated for warm stellar matter in a framework of
relativistic mean-field models, including the possibility of light cluster
formation. Results from three different semiclassical approaches are compared
with a quantum statistical calculation. Light clusters are considered as
point-like particles, and their abundances are determined from the minimization
of the free energy. The couplings of the light-clusters to mesons are
determined from experimental chemical equilibrium constants and many-body
quantum statistical calculations. The effect of these light clusters on the
chemical potentials is also discussed. It is shown that including heavy
clusters, light clusters are present until larger nucleonic densities, although
with smaller mass fractions.Comment: 15 pages, 13 figures, accepted for publication in Physical review
NetCluster: A clustering-based framework to analyze internet passive measurements data
Internet measured data collected via passive measurement are analyzed to obtain localization information on nodes by clustering (i.e., grouping together) nodes that exhibit similar network path properties. Since traditional clustering algorithms fail to correctly identify clusters of homogeneous nodes, we propose the NetCluster novel framework, suited to analyze Internet measurement datasets. We show that the proposed framework correctly analyzes synthetically generated traces. Finally, we apply it to real traces collected at the access link of Politecnico di Torino campus LAN and discuss the network characteristics as seen at the vantage point
Non-intrusive load monitoring techniques for activity of daily living recognition
Esta tesis nace con la motivación de afrontar dos grandes problemas de nuestra era: la falta de recursos energéticos y el envejecimiento de la población.
Respecto al primer problema, nace en la primera década de este siglo el concepto de Smart Grids con el objetivo de alcanzar la eficiencia energética. Numerosos países comienzan a realizar despliegues masivos de contadores inteligentes ("Smart Meters"), lo que despierta el interés de investigadores que comienzan a desarrollar nuevas técnicas para predecir la demanda. Así, los sistemas NILM (Non-Intrusive Load Monitoring) tratan de predecir el consumo individual de los dispositivos conectados a partir de un único sensor: el contador inteligente.
Por otra parte, los grandes avances en la medicina moderna han permitido que nuestra esperanza de vida aumente considerablemente. No obstante, esta longevidad, junto con la baja fertilidad en los países desarrollados, tiene un efecto secundario: el envejecimiento de la población. Unos de los grandes avances es la incorporación de la tecnología en la vida cotidiana, lo que ayuda a los más mayores a llevar una vida independiente. El despliegue de una red de sensores dentro de la vivienda permite su monitorización y asistencia en las tareas cotidianas. Sin embargo, son intrusivos, no escalables y, en algunas ocasiones, de alto coste, por lo que no están preparados para hacer frente al incremento de la demanda de esta comunidad.
Esta tesis doctoral nace de la motivación de afrontar estos problemas y tiene dos objetivos principales: lograr un modelo de monitorización sostenible para personas mayores y, a su vez, dar un valor añadido a los sistemas NILM que despierte el interés del usuario final. Con este objetivo, se presentan nuevas técnicas de monitorización basadas en NILM, aunando lo mejor de ambos campos. Esto supone un ahorro considerable de recursos en la monitorización, ya que únicamente se necesita un sensor: el contador inteligente; lo cual da escalabilidad a estos sistemas.
Las contribuciones de esta tesis se dividen en dos bloques principales. En el primero se proponen nuevas técnicas NILM optimizadas para la detección de la actividad humana. Así, se desarrolla una propuesta basada en detección de eventos (conexiones de dispositivos) en tiempo real y su clasificación a un dispositivo. Con el objetivo de que pueda integrarse en contadores inteligentes. Cabe destacar que el clasificador se basa en modelos generalizados de dispositivos y no necesita conocimiento específico de la vivienda.
El segundo bloque presenta tres nuevas técnicas de monitorización de personas mayores basadas en NILM. El objetivo es proporcionar una monitorización básica pero eficiente y altamente escalable, ahorrando en recursos. Los procesos Cox, log Gaussian Cox Processes (LGCP), monitorizan un único dispositivo si la rutina está estrechamente ligada a este. Así, se propone un sistema de alarmas si se detectan cambios en el comportamiento. LGCP tiene la ventaja de poder modelar periodicidades e incertidumbres propias del comportamiento humano. Cuando la rutina no depende de un único dispositivo, se proponen dos técnicas: una basada en gaussianas mixtas, Gaussian Mixture Models (GMM); y la otra basada en la Teoría de la Evidencia de Dempster-Shafer (DST). Ambas monitorizan y detectan deterioros en la actividad, causados por enfermedades como la demencia y el alzhéimer. Únicamente DST usa incertidumbres que simulan mejor el comportamiento humano y, por tanto, permite alarmas en caso de un repentino desvío.
Finalmente, todas las propuestas han sido validadas mediante la evaluación de métricas y la obtención de resultados experimentales. Para ello, se han usado medidas de escenarios reales que han sido recopiladas en bases de datos. Los resultados obtenidos han sido satisfactorios, demostrando que este tipo de monitorización es posible y muy beneficioso para nuestra sociedad. Además, se ha dado a lugar nuevas propuestas que serán desarrolladas en el futuro.
Códigos UNESCO: 120320 - sistemas de control medico, 332201 – distribución de la energía, 120701 – análisis de actividades, 120304 – inteligencia artificial, 120807 – plausibilidad, 221402 – patrones
Hadron Multiplicities
We review results on hadron multiplicities in high energy particle
collisions. Both theory and experiment are discussed. The general procedures
used to describe particle multiplicity in Quantum Chromodynamics (QCD) are
summarized. The QCD equations for the generating functions of the multiplicity
distributions are presented both for fixed and running coupling strengths. The
mean multiplicities of gluon and quark jets, their ratio, higher moments, and
the slopes of multiplicities as a function of energy scale, are among the main
global features of multiplicity for which QCD results exist. Recent data from
high energy e+e- experiments, including results for separated quark and gluon
jets, allow rather direct tests of these results. The theoretical predictions
are generally quite successful when confronted with data. Jet and subjet
multiplicities are described. Multiplicity in limited regions of phase space is
discussed in the context of intermittency and fractality. The problem of
singularities in the generating functions is formulated. Some special features
of average multiplicities in heavy quark jets are described.Comment: 140 pages, 33 figures, version for Physics Report
Economic and non-economic drivers of the low-carbon energy transition: evidence from households in the UK, rural India, and refugee settlements in Sub-Saharan Africa
In this thesis I investigate the drivers of household clean energy technology adoption, looking at the role of economic variables, such as prices and monetary incentives, but also at non-strictly economic dimensions, such as geography, peer influence, health concerns, and heterogeneity in experience, priorities and perceptions of the technology.
The topic develops into two main lines of inquiry. The first one explores the uptake of residential solar PV systems in the UK. In Chapter 1 I look at how the UK feed-in tariff (FIT) scheme contributed to shape the distribution of decentralised electricity generation around the country. I ask in particular how effective the policy was at triggering the siting of solar installations in locations with better generation potential. In Chapter 2 I show that peer effects contribute to the diffusion of this technology, and they act as complements to the monetary incentives. I discuss two possible channels through which peer effects may operate social utility derived from imitation, and social learning from information sharing among neighbours and find evidence consistent with a dominant role of the latter.
The second line of research focuses on valuation of non-traditional cookstoves in Sub-Saharan refugee settlements (Chapter 3) and rural villages in Odisha, India (Chapter 4). I use stated preferences to investigate how different features of the cooking technologies and household heterogeneity affect willingness to pay. In the context of refugee settlements in Sub-Saharan Africa (Chapter 3), I complement the analysis by looking at how the non-traditional cookstoves distributed among the residents affect fuel effciency, health and safety, time use and the gendered distribution of the cooking workload. In Chapter 4, I focus instead on how positive and negative experiences with biogas for cooking affect the stated willingness to pay for that technology in rural India, and how experience interacts with risk aversion, time preferences, and credit constraints
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