h-multigrid agglomeration based solution strategies for discontinuous Galerkin discretizations of incompressible flow problems

In this work we exploit agglomeration based $h$-multigrid preconditioners to speed-up the iterative solution of discontinuous Galerkin discretizations of the Stokes and Navier-Stokes equations. As a distinctive feature $h$-coarsened mesh sequences are generated by recursive agglomeration of a fine grid, admitting arbitrarily unstructured grids of complex domains, and agglomeration based discontinuous Galerkin discretizations are employed to deal with agglomerated elements of coarse levels. Both the expense of building coarse grid operators and the performance of the resulting multigrid iteration are investigated. For the sake of efficiency coarse grid operators are inherited through element-by-element $L^2$ projections, avoiding the cost of numerical integration over agglomerated elements. Specific care is devoted to the projection of viscous terms discretized by means of the BR2 dG method. We demonstrate that enforcing the correct amount of stabilization on coarse grids levels is mandatory for achieving uniform convergence with respect to the number of levels. The numerical solution of steady and unsteady, linear and non-linear problems is considered tackling challenging 2D test cases and 3D real life computations on parallel architectures. Significant execution time gains are documented.Comment: 78 pages, 7 figure

Essential connectedness and the rigidity problem for Gaussian symmetrization

We provide a geometric characterization of rigidity of equality cases in Ehrhard's symmetrization inequality for Gaussian perimeter. This condition is formulated in terms of a new measure-theoretic notion of connectedness for Borel sets, inspired by Federer's definition of indecomposable current.Comment: 38 page

BeRTo: An Efficient Spark-Based Tool for Linking Business Registries in Big Data Environments

Linking entities from different datasets is a crucial task for the success of modern businesses. However, aligning entities becomes challenging as common identifiers might be missing. Therefore, the process should rely on string-based attributes, such as names or addresses, thus harming precision in the matching. At the same time, powerful general-purpose record linkage tools require users to clean and pre-process the initial data, introducing a bottleneck in the success of the data integration activity and a burden on actual users. Furthermore, scalability has become a relevant issue in modern big data environments, where a lot of data flows daily from external sources. This work presents a novel record linkage tool, BeRTo, that addresses the problem of linking a specific type of data source, i.e., business registries, containing information about companies and corporations. While being domain-specific harms its usability in other contexts, it manages to reach a new frontier in terms of precision but also scalability, as it has been built on Spark. Integrating the pre-processing and cleaning steps in the same tool creates a user-friendly end-to-end pipeline that requires users only to input the raw data and set their preferred configuration, allowing to focus on recall or precision

Sleep Deprivation in Mood Disorders

Growing clinical evidence in support of the efficacy and safety of sleep deprivation (SD), and its biological mechanisms of action suggest that this technique can now be included among the first-line antidepressant treatment strategies for mood disorders. SD targets the broadly defined depressive syndrome, and can be administered according to several different treatment schedules: total versus partial, single versus repeated, alone or combined with antidepressant drugs, mood stabilizers, or other chronotherapeutic techniques, such as light therapy and sleep phase advance. The present review focuses on clinical evidence about the place of SD in therapy, its indications, dosage and timing of the therapeutic wake, interactions with other treatments, precautions and contraindications, adverse reactions, mechanism of action, and comparative efficacy, with the aim of providing the clinical psychiatrist with an updated, concise guide to its application

Guidelines for reporting and analysing laboratory test results for biomass cooking stoves

One of the key challenges in the evaluation of Improved Cooking Stoves (ICSs) performance is the correct interpretation of test results. Indeed, a large amount of the reports or studies in the literature provide results that do not allow drawing any statistically significant conclusion, thus leading to possible misinterpretations. These Guidelines are conceived as a support to all the actors involved in sector of biomass stoves performance evaluation, from the technicians and researchers engaged in laboratory testing, to those who need to better understand and interpret test results in order to select a promising stove model for field trials. The concepts and the methodology here proposed draw upon the most recent studies in the scientific literature on this topi

Thermal boundary resistance from transient nanocalorimetry: a multiscale modeling approach

The Thermal Boundary Resistance at the interface between a nanosized Al film and an Al_{2}O_{3} substrate is investigated at an atomistic level. A room temperature value of 1.4 m^{2}K/GW is found. The thermal dynamics occurring in time-resolved thermo-reflectance experiments is then modelled via macro-physics equations upon insertion of the materials parameters obtained from atomistic simulations. Electrons and phonons non-equilibrium and spatio-temporal temperatures inhomo- geneities are found to persist up to the nanosecond time scale. These results question the validity of the commonly adopted lumped thermal capacitance model in interpreting transient nanocalorimetry experiments. The strategy adopted in the literature to extract the Thermal Boundary Resistance from transient reflectivity traces is revised at the light of the present findings. The results are of relevance beyond the specific system, the physical picture being general and readily extendable to other heterojunctions.Comment: 12 pages, 8 figure

An Ab Initio Investigation of Ultra‐Low Thermal Conductivity in Organically Functionalized TaS2TaS2{\rm TaS}_2

An ab initio characterization of the impact of tert-Butyl isocyanate (C5H9NO) functionalization on TaS2 lattice thermal conductivity is presented. Such a system has been previously synthetized and experimentally charachterized, showing that the incorporation of covalently bonded C5H9NO on bulk TaS2 leads to a dramatic in-plane lattice thermal conductivity decrease by more than two orders of magnitudes. To elucidate these experimental findings, detailed calculations of the phonon dispersion relations and scattering rates in TaS2 are performed. The analysis is addressed to discern the impact of inter-layer covalently bonded C5H9NO molecules on these phonon properties, providing insights into the underlying mechanisms of the observed thermal conductivity decrease. Present calculations provide evidence that the observed lattice thermal conductivity reduction is attributed to two effects: ) the increase of inter-layer separation and ) the presence of low-frequency molecular optical modes. The first inhibits specific Van der Waals quasi-acoustic inter-layer vibrational modes contributing as much as approximate to 55% in bulk TaS2. The second effect dramatically decreases the phonon group velocities as a consequence of phonon-crossing phenomena among low-frequency molecular modes and TaS2 acoustic modes, eventually leading to a strong reduction of all phonon lifetimes