An automatic procedure to forecast tephra fallout

Tephra fallout constitutes a serious threat to communities around active volcanoes. Reliable short-term forecasts represent a valuable aid for scientists and civil authorities to mitigate the effects of fallout on the surrounding areas during an episode of crisis. We present a platform-independent automatic procedure with the aim to daily forecast transport and deposition of volcanic particles. The procedure builds on a series of programs and interfaces that automate the data flow and the execution and subsequent postprocess of fallout models. Firstly, the procedure downloads regional meteorological forecasts for the area and time interval of interest, filters and converts data from its native format, and runs the CALMET diagnostic model to obtain the wind field and other micro-meteorological variables on a finer local-scale 3-D grid defined by the user. Secondly, it assesses the distribution of mass along the eruptive column, commonly by means of the radial averaged buoyant plume equations depending on the prognostic wind field and on the conditions at the vent (granulometry, mass flow rate, etc). All these data serve as input for the fallout models. The initial version of the procedure includes only two Eulerian models, HAZMAP and FALL3D, the latter available as serial and parallel implementations. However, the procedure is designed to incorporate easily other models in a near future with minor modifications on the model source code. The last step is to postprocess the outcomes of models to obtain maps written in standard file formats. These maps contain plots of relevant quantities such as predicted ground load, expected deposit thickness and, for the case of or 3-D models, concentration on air or flight safety concentration thresholds

Human (in)security and psychological well-being in Palestinian children living amidst military violence: A qualitative participatory research using interactive maps

Background Research has widely evidenced the effects of war and political violence on the functioning of children, with a great accord in diagnosing children\u27s psychological burdens related to their exposure to violence. Yet, within this literature, the influence of the chronic sense of insecurity on their psychological functioning during and after hostilities remains unexplored. Methods The present study aimed at exploring interrelated relationships between the perceived insecurity and the children\u27s psychological well-being and their adjustment to trauma. Based on drawings and walk-along interviews with 75 Palestinian children, residents of both the West Bank and Gaza Strip, we offer an analysis of human security-related risks and protective factors that contribute to either promoting or undermining the child\u27s psychological functioning in a context characterized by chronic instability and political violence. Results A complex network of sources of security and insecurity emerged from the narratives depicting an ecological portrait encompassing the determinants of children\u27s mental health and psychological functioning. The TCA led to the identification of eight main themes: school and associativism; social relations and house as a source of security/insecurity; military occupation as a source of insecurity; national and political identity as a source of safety; mosque and spirituality as a source of safety/unsafety; environment as a source of security/insecurity; and mental health. Discussion An approach encompassing human security as an explicative model can help in exhaustively portraying the complexity of the Palestinian children\u27s suffering and their competence in adjusting to their traumatic reality. The study draws attention to social, political, environmental and economic determinants of children psychological well-being

investigation of particle dynamics and classification mechanism in a spiral jet mill through computational fluid dynamics and discrete element methods

Abstract Predicting the outcome of jet-milling based on the knowledge of process parameters and starting material properties is a task still far from being accomplished. Given the technical difficulties in measuring thermodynamics, flow properties and particle statistics directly in the mills, modelling and simulations constitute alternative tools to gain insight in the process physics and many papers have been recently published on the subject. An ideal predictive simulation tool should combine the correct description of non-isothermal, compressible, high Mach number fluid flow, the correct particle-fluid and particle-particle interactions and the correct fracture mechanics of particle upon collisions but it is not currently available. In this paper we present our coupled CFD-DEM simulation results; while comparing them with the recent modelling and experimental works we will review the current understating of the jet-mill physics and particle classification. Subsequently we analyze the missing elements and the bottlenecks currently limiting the simulation technique as well as the possible ways to circumvent them towards a quantitative, predictive simulation of jet-milling

Continuous-time quantum walks in the presence of a quadratic perturbation

We address the properties of continuous-time quantum walks with Hamiltonians of the form H = L + \u3bbL2, with L the Laplacian matrix of the underlying graph and the perturbation \u3bbL2 motivated by its potential use to introduce next-nearest-neighbor hopping. We consider cycle, complete, and star graphs as paradigmatic models with low and high connectivity and/or symmetry. First, we investigate the dynamics of an initially localized walker. Then we devote attention to estimating the perturbation parameter \u3bb using only a snapshot of the walker dynamics. Our analysis shows that a walker on a cycle graph spreads ballistically independently of the perturbation, whereas on complete and star graphs one observes perturbation-dependent revivals and strong localization phenomena. Concerning the estimation of the perturbation, we determine the walker preparations and the simple graphs that maximize the quantum Fisher information. We also assess the performance of position measurement, which turns out to be optimal, or nearly optimal, in several situations of interest. Besides fundamental interest, our study may find applications in designing enhanced algorithms on graphs

Speed and power predictors of change of direction ability in elite snow athletes

Change of direction ability (COD speed) is an important physical component of snow sports. The aim of this study was to investigate the relationships between regular speed and vertical jumping ability, and COD speed in elite snow athletes. Moreover, the correlations between relative mean propulsive power (assessed in the jump squat exercise) and COD speed were quantified. Sixteen elite snow sport athletes executed squat jumps, countermovement jumps, jump squats, and 25 m sprint tests, in addition to a Zig-zag change of direction speed test. The outcomes revealed that vertical jumping height and mean propulsive power are strongly correlated (r ≈ 0.90) with COD speed. Furthermore, snow athletes capable of sprinting faster in a linear course of 25 m performed better in COD speed tests ( r = 0.91). Our results support the use of loaded and unloaded vertical jumping and regular speed tests to evaluate/monitor predictors of COD speed in elite snow athletes. Finally, these relationships suggest that plyometrics and regular speed training should be considered by coaches as effective strategies to enhance COD ability in this specific group of subjects

Preliminary Design and Numerical Analysis of a Scrap Tires Pyrolysis System

Abstract A plant prototype for whole scrap tires disposal and the consequent syngas production via pyrolysis has been developed. A numerical analysis on the innovative pyrolysis reactor, constituted by an autoclave closing device and an explosion-proof water system has been carried out. The aim of this analysis is to investigate the fluid-dynamics in the pyrolysis chamber and model the syngas production. The simulations, performed in the pre-realization system phase, have allowed to determine: i) the flow field of the fluid within the reactor, so as to optimize the geometry (e.g. size, vacuum system, water tank); ii) the temperature range, in order to determine the correct placement of thermocouples within reactor and prevent overheating that could compromise the safety of the system; iii) the pressure range, necessary to avoid the eventual flooding of the tires themselves. Thanks to these results, the test bench has been built at the CURTI S.p.A laboratory and experimental analysis has been performed. The experimental data are acquired and then elaborated, as shown in the paper

Design of a low band gap oxide ferroelectric: Bi6_6Ti4_4O17_{17}

A strategy for obtaining low band gap oxide ferroelectrics based on charge imbalance is described and illustrated by first principles studies of the hypothetical compound Bi$_6$Ti$_4$O$_{17}$, which is an alternate stacking of the ferroelectric Bi$_4$Ti$_3$O$_{12}$. We find that this compound is ferroelectric, similar to Bi$_4$Ti$_3$O$_{12}$ although with a reduced polarization. Importantly, calculations of the electronic structure with the recently developed functional of Tran and Blaha yield a much reduced band gap of 1.83 eV for this material compared to Bi$_4$Ti$_3$O$_{12}$. Therefore, Bi$_6$Ti$_4$O$_{17}$ is predicted to be a low band gap ferroelectric material

Interplay between proton ordering and ferroelectric polarization in H-bonded KDP-type crystals

The origin of ferroelectricity in KH_2PO_4 (KDP) is studied by first-principles electronic structure calculations. In the low-temperature phase, the collective off-center ordering of the protons is accompanied by an electronic charge delocalization from the "near" and localization at the "far" oxygen within the O-H...O bonds. Electrostatic forces, then, push the K+ ions towards off-center positions, and induce a macroscopic polarization. The analysis of the correlation between different geometrical and electronic quantities, in connection with experimental data, supports the idea that the role of tunnelling in isotopic effects is irrelevant. Instead, geometrical quantum effects appear to play a central role.Comment: 8 pages, 2 postscript figures, submitted to the X Conference on Computational Materials Science, Villasimius, Sardinia (Italy), 200