Unrest at the Laguna del Maule volcanic field 2005–2020: renewed acceleration of deformation

The Laguna del Maule volcanic field in Chile has been exhibiting unrest since 2005. New GPS and InSAR data reveal a second episode of accelerated deformation beginning in late 2016 and continuing through May 2020, with an uplift rate > 290 mm/year between 2019 and 2020. To explain the spatial and temporal pattern of deformation, we apply a dynamic model of viscous magma flowing through a conduit into a fluid-filled reservoir surrounded by a heterogeneous, viscoelastic crust. A Monte Carlo procedure optimizes the ellipsoid reservoir geometry and the inlet pressure history. The two episodes of accelerating uplift are each modeled with a pressure increase rate of $\sim $ ∼ 9 MPa/year. Since 2016, 0.10 km3 of magma was injected into the system for a total of 0.37 km3 since 2005.

Lightning Performance Evaluation of Italian 150 kV Sub-Transmission Lines

A significant majority of overhead transmission lines’ (OHLs) outages is due to backflashovers caused by direct lightning strikes: the realistic assessment of the lightning performance is thus an important task. The paper presents the analysis of the lightning performance of an existing 150 kV Italian OHL, namely, its backflashover rate (BFOR), carried out by means of an ATP-EMTP-based Monte Carlo procedure. Among other features, the procedure makes use of a simplified pi-circuit for line towers’ grounding system, allowing a very accurate reproduction of transient behaviours at a very low computational cost. Tower grounding design modifications, aimed at improving the OHL lightning performance, are also proposed and discussed.

Sensitivity of boundary crossing probabilities of the Brownian motion

The paper analyzes the sensitivity of boundary crossing probabilities of the Brownian motion to perturbations of the boundary. The first- and second-order sensitivities, i.e. the directional derivatives of the probability, are derived. Except in cases where boundary crossing probabilities for the Brownian bridge are given in closed form, the sensitivities have to be computed numerically. We propose an efficient Monte Carlo procedure.

The solid angle subtended by a collimated detector and a nuclear fuel assembly

A Monte Carlo procedure is presented to calculate the solid angle subtended between a HPGe collimated detector and a PWR 17 x 17 fuel assembly. Self-shielding within the assembly is assessed in the case of gamma rays encountered in gamma spectroscopy of spent nuclear fuel. Self-shielding renders a non-uniform 3-D distribution of the radioactivity within the assembly whose extend depends on gamma ray energies of interest. Hence, the solid angle is reduced to an effective one for each of the different energies of interest.