A Bayesian Hierarchical Approach to Ensemble Weather Forecasting

In meteorology, the traditional approach to forecasting employs deterministic models mimicking atmospheric dynamics. Forecast uncertainty due to the partial knowledge of initial conditions is tackled by Ensemble Predictions Systems (EPS). Probabilistic forecasting is a relatively new approach which may properly account for all sources of uncertainty. In this work we propose a hierarchical Bayesian model which develops this idea and makes it possible to deal with an EPS with non-identifiable members using a suitable definition of the second level of the model. An application to Italian small-scale temperature data is shown.Ensemble Prediction System, hierarchical Bayesian model, predictive distribution, probabilistic forecast, verification rank histogram.

Mesoscopic Numerical Methods for Reactive Flows: Lattice Boltzmann Method and Beyond

Reactive flows are ubiquitous in several energy systems: internal combustion engines, industrial burners, gas turbine combustors. Numerical modeling of reactive flows is a key tool for the development of such systems. However, computational combustion is a challenging task per se. It generally includes different coupled physical and chemical processes. A single model can come to deal with simultaneous processes: turbulent mixing, multi-phase fluid-dynamics, radiative heat transfer, and chemical kinetics. It is required not only of mathematically representing these processes and coupling them to each other, but also of being numerical efficient. In some applications, the numerical model needs to be able to deal with different length scales. For instance, a continuum approach to reactive flows in porous media burners is not adequate: processes occurring at the pore-scale are not taken into account properly. It is therefore fundamental to have numerical methods able to capture phenomena at the microscopic scales and incorporate the effects in the macroscopic scale. The lattice Boltzmann method (LBM), a relatively new numerical method in computational fluid-dynamics (CFD), summarizes the requirements of numerical efficiency and potential to relate micro-and macro-scale. However, despite these features and the recent developments, application of LBM to combustion problems is limited and hence further improvements are required. In this thesis, we explore the suitability of LBM for combustion problems and extend its capabilities. The first key-issue in modeling reactive flows is represented by the fact that the model has to be able to handle the significant density and temperature changes that are tipically encountered in combustion. A recently proposed LBM model for compressible thermal flows is extended to simulate reactive flows at the low Mach number regime. This thermal model is coupled with the mass conservation equations of the chemical species. Also in this case a model able to deal with compressibility effects is derived. To this purpose, we propose a new scheme for solving the reaction-diffusion equations of chemical species where compressibility is accounted for by simply modifying the equilibrium distribution function and the relaxation frequency of models already available in the literature. This extension enables one to apply LBM to a wide range of combustion phenomena, which were not properly adressed so far. The effectiveness of this approach is proved by simulating combustion of hydrogen/air mixtures in a mesoscale channel. Validation against reference numerical solution in the continuum limit are also presented. An adequate treatment of thermal radiation is important to develop a mathematical model of combustion systems. In fact, combustion incorporates also radiation process, which tends to plays a significant role if high temperatures (and solid opaque particles) are involved. In the thesis a LBM model for radiation is presented. The scheme is derived from the radiative transfer equation for a participating medium, assuming isotropic scattering and radiative equilibrium condition. The azimuthal angle is discretized according to the lattice velocities on the computational plane, whereas an additional component of the discrete velocity normal to the plane is introduced to discretize the polar angle. The radiative LBM is used to solve a two-dimensional square enclosure bechmark problem. Validation of the model is carried out by investigating the effects of the spatial and angular discretizations and extinction coefficient on the solution. To this purpose, LBM results are compared against reference solutions obtained by means of standard Finite Volume Method (FVM). Extensive error analysis and the order of convergence of the scheme are also reported in the thesis. In order to extend the capabilities of LBM and make it more efficient in the simulation of reactive flows, in this thesis a new formulation is presented, referred to as Link-wise Artificial Compressibility Method (LW-ACM). The Artificial Compressibility Method (ACM) is (link-wise) formulated by a finite set of discrete directions (links) on a regular Cartesian grid, in analogy with LBM. The main advantage is the possibility of exploiting well established technologies originally developed for LBM and classical computational fluid dynamics, with special emphasis on finite differences, at the cost of minor changes. For instance, wall boundaries not aligned with the background Cartesian mesh can be taken into account by tracing the intersections of each link with the wall (analogously to LBM technology). LW-ACM requires no high-order moments beyond hydrodynamics (often referred to as ghost moments) and no kinetic expansion. Like finite difference schemes, only standard Taylor expansion is needed for analyzing consistency. Preliminary efforts towards optimal implementations have shown that LW-ACM is capable of similar computational speed as optimized (BGK-) LBM. In addition, the memory demand is significantly smaller than (BGK-) LBM. Two- and three-dimensional benchmarks are investigated, and an extensive comparative study between solutions obtained through FVM. Numerical evidences suggest that LW-ACM represents an excellent alternative in terms of simplicity, stability and accurac

Riemannian geometry of Hartogs domains

Let D_F = \{(z_0, z) \in {\C}^{n} | |z_0|^2 < b, \|z\|^2 < F(|z_0|^2) \} be a strongly pseudoconvex Hartogs domain endowed with the \K metric $g_F$ associated to the \K form $\omega_F = -\frac{i}{2} \partial \bar{\partial} \log (F(|z_0|^2) - \|z\|^2)$. This paper contains several results on the Riemannian geometry of these domains. In the first one we prove that if $D_F$ admits a non special geodesic (see definition below) through the origin whose trace is a straight line then $D_F$ is holomorphically isometric to an open subset of the complex hyperbolic space. In the second theorem we prove that all the geodesics through the origin of $D_F$ do not self-intersect, we find necessary and sufficient conditions on $F$ for $D_F$ to be geodesically complete and we prove that $D_F$ is locally irreducible as a Riemannian manifold. Finally, we compare the Bergman metric $g_B$ and the metric $g_F$ in a bounded Hartogs domain and we prove that if $g_B$ is a multiple of $g_F$, namely $g_B=\lambda g_F$, for some $\lambda\in \R^+$, then $D_F$ is holomorphically isometric to an open subset of the complex hyperbolic space.Comment: to appear in International Journal of Mathematic

Improved angular discretization and error analysis of the lattice boltzmann method for solving radiative heat transfer in a participating medium

In this paper, some improvements to the lattice Boltzmann method (LBM) for solving radiative heat transfer in a participating medium are presented and validated. Validation of the model is performed by investigating the effects of spatial and angular discretizations and extinction coefficient on the solution. The error analysis and the order of convergence of the scheme are also reporte

Filling the gap. Human cranial remains from Gombore II (Melka Kunture, Ethiopia; ca. 850 ka) and the origin of Homo heidelbergensis

African archaic humans dated to around 1,0 Ma share morphological affinities with Homo ergaster and appear distinct in cranio-dental morphology from those of the Middle Pleistocene that are referred to Homo heidelbergensis. This observation suggests a taxonomic and phylogenetic discontinuity in Africa that ranges across the Matuyama/Brunhes reversal (780 ka). Yet, the fossil record between roughly 900 and 600 ka is notoriously poor. In this context, the Early Stone Age site of Gombore II, in the Melka Kunture formation (Upper Awash, Ethiopia), provides a privileged case-study. In the Acheulean layer of Gombore II, somewhat more recent than 875±10 ka, two large cranial fragments were discovered in 1973 and 1975 respectively: a partial left parietal (Melka Kunture 1) and a right portion of the frontal bone (Melka Kunture 2), which probably belonged to the same cranium. We present here the first detailed description and computer-assisted reconstruction of the morphology of the cranial vault pertaining to these fossil fragments. Our analysis suggest that the human fossil specimen from Gombore II fills a phenetic gap between Homo ergaster and Homo heidelbergensis. This appears in agreement with the chronology of such a partial cranial vault, which therefore represents at present one of the best available candidates (if any) for the origin of Homo heidelbergensis in Africa

SAFE: Self-Attentive Function Embeddings for Binary Similarity

The binary similarity problem consists in determining if two functions are similar by only considering their compiled form. Advanced techniques for binary similarity recently gained momentum as they can be applied in several fields, such as copyright disputes, malware analysis, vulnerability detection, etc., and thus have an immediate practical impact. Current solutions compare functions by first transforming their binary code in multi-dimensional vector representations (embeddings), and then comparing vectors through simple and efficient geometric operations. However, embeddings are usually derived from binary code using manual feature extraction, that may fail in considering important function characteristics, or may consider features that are not important for the binary similarity problem. In this paper we propose SAFE, a novel architecture for the embedding of functions based on a self-attentive neural network. SAFE works directly on disassembled binary functions, does not require manual feature extraction, is computationally more efficient than existing solutions (i.e., it does not incur in the computational overhead of building or manipulating control flow graphs), and is more general as it works on stripped binaries and on multiple architectures. We report the results from a quantitative and qualitative analysis that show how SAFE provides a noticeable performance improvement with respect to previous solutions. Furthermore, we show how clusters of our embedding vectors are closely related to the semantic of the implemented algorithms, paving the way for further interesting applications (e.g. semantic-based binary function search).Comment: Published in International Conference on Detection of Intrusions and Malware, and Vulnerability Assessment (DIMVA) 201

A Bayesian Hierarchical Approach to Ensemble Weather Forecasting

In meteorology, the traditional approach to forecasting employs deterministic models mimicking atmospheric dynamics. Forecast uncertainty due to the partial knowledge of initial conditions is tackled by Ensemble Predictions Systems (EPS). Probabilistic forecasting is a relatively new approach which may properly account for all sources of uncertainty. In this work we propose a hierarchical Bayesian model which develops this idea and makes it possible to deal with an EPS with non-identifiable members using a suitable definition of the second level of the model. An application to Italian small-scale temperature data is shown

Aplicación móvil para la gestión y análisis de los datos espaciales de interés turístico en el territorio de Bilbao

El presente estudio ha desarrollado y puesto a punto los componentes software y datos de un sistema para la consulta in situ de cartografía en dispositivos móviles (smartphone y tablet) dotados de GPS y conexión a internet. Utilizando librerías de código abierto, ha sido implementada una aplicación para dispositivos Android que permite la consulta de servicios y análisis del territorio. La aplicación hace que el usuario obtenga información mediante combinaciones de consultas espaciales y de atributos. Mediante múltiples capas, la aplicación permite buscar el camino óptimo para alcanzar el punto o información deseada a través de implementación de algoritmos de routing sobre grafos de carretera. Los resultados de búsqueda se ven influidos por los ajustes personalizados por el usuario y se gestionan mediante un enfoque basado en la lógica difusa (fuzzy logic). Se obtuvieron múltiples objetivos: un mayor intercambio y utilización de datos espaciales, la mayor presencia de las entidades en el marco del geoturismo y el marco institucional y por último, la creación de un sistema de gestión y consulta de un territorio aumentado útil no sólo para los turistas y los ciudadanos, sino también para los profesionales y las empresas. Con particular importancia, se ha dado la posibilidad de seleccionar carriles bici con cálculos y algoritmos de routing adaptados a las exigencias de una movilidad sostenible

Effects of Chickpea in Substitution of Soybean Meal on Milk Production, Blood Profile and Reproductive Response of Primiparous Buffaloes in Early Lactation

This study aimed to evaluate the effects of the use of chickpea meal in substitution of soybean meal on plasma metabolites, reproductive response, milk yield and composition and milk coagulation traits of primiparous buffaloes in early lactation. Eighteen primiparous buffaloes were blocked by age, body weight and days in milk and equally allotted to two experimental groups from 10 to 100 days of lactation. The experimental diets consisted of the same forage integrated with two different isonitrogenous and isoenergetic concentrates containing either 210 g/kg of soybean meal or 371 g/kg chickpea. The use of chickpea meal had no negative effects on dry matter intake (p = 0.69), body condition score (p = 0.33) and milk yield (p = 0.15). Neither milk composition nor blood metabolites were influenced by dietary treatments (p > 0.05), but an increment of urea concentrations in milk (p 0.05) of the dietary treatment was highlighted on milk coagulation traits as well as buffalo reproductive responses. We concluded that soybean meal can be replaced by chickpea meal in the diet for primiparous dairy buffaloes in the early lactation period without impairing their productive and reproductive performance

Gymnema sylvestre R. Br., an Indian medicinal herb: traditional uses, chemical composition, and biological activity

Gymnema sylvestre R. Br. is one of the most important medicinal plants that grows in tropical forests in India and South East Asia. Its active ingredients and extracts of leaves and roots are used in traditional medicine to treat various ailments and they are present in the market for pharmaceutical and parapharmaceutical products. Commercial products based on substances of plant origin that are generally connoted as natural have to be subjected to monitoring and evaluation by health authorities for their potential impacts on public health. The monitoring and evaluation of these products are critical because the boundary between a therapeutic action and a functional or healthy activity has not yet been defined in a clear and unambiguous way. Therefore, these products are considered borderline products, and they require careful and rigorous studies, in order to use them as complement and/or even replacement of synthetic drugs that are characterized by side effects and high economic costs. This review explores the traditional uses, chemical composition and biological activity of G. sylvestre extracts, providing a general framework on the most interesting extracts and what are the necessary studies for a complete definition of the range of activities