New Rigidity Results for Critical Metrics of Some Quadratic Curvature Functionals

We prove a new rigidity result for metrics defined on closed smooth $n$-manifolds that are critical for the quadratic functional $\mathfrak{F}_{t}$, which depends on the Ricci curvature $Ric$ and the scalar curvature $R$, and that satisfy a pinching condition of the form $Sec > \epsilon R$, where $\epsilon$ is a function of $t$ and $n$, while $Sec$ denotes the sectional curvature. In particular, we show that Bach-flat metrics with constant scalar curvature satisfying $Sec > \frac{1}{48} R$ are Einstein and, by a known result, are isometric to $\mathbb{S}^{4}$, $\mathbb{RP}^{4}$ or $\mathbb{CP}^{2}$.Comment: 17 page

How to restart? An agent-based simulation model towards the definition of strategies for COVID-19 "second phase" in public buildings

Restarting public buildings activities in the "second phase" of COVID-19 emergency should be supported by operational measures to avoid a second virus spreading. Buildings hosting the continuous presence of the same users and significant overcrowd conditions over space/time (e.g. large offices, universities) are critical scenarios due to the prolonged contact with infectors. Beside individual's risk-mitigation strategies performed (facial masks), stakeholders should promote additional strategies, i.e. occupants' load limitation (towards "social distancing") and access control. Simulators could support the measures effectiveness evaluation. This work provides an Agent-Based Model to estimate the virus spreading in the closed built environment. The model adopts a probabilistic approach to jointly simulate occupants' movement and virus transmission according to proximity-based and exposure-time-based rules proposed by international health organizations. Scenarios can be defined in terms of building occupancy, mitigation strategies and virus-related aspects. The model is calibrated on experimental data ("Diamond Princess" cruise) and then applied to a relevant case-study (a part of a university campus). Results demonstrate the model capabilities. Concerning the case-study, adopting facial masks seems to be a paramount strategy to reduce virus spreading in each initial condition, by maintaining an acceptable infected people's number. The building capacity limitation could support such measure by potentially moving from FFPk masks to surgical masks use by occupants (thus improving users' comfort issues). A preliminary model to combine acceptable mask filters-occupants' density combination is proposed. The model could be modified to consider other recurring scenarios in other public buildings (e.g. tourist facilities, cultural buildings).Comment: 21 pages, 16 figures; submitted to Building and Environmen

Heterogeneous government spending multipliers in the era surrounding the Great Recession

We use novel quarterly data of U.S. states to examine the dynamics of relative spending multipliers in the decade surrounding the Great Recession. While multipliers were around 1 in expansions, they reached values above 4 when a state was in a recession. Also a high (low) degree of household indebtedness augmented (lowered) a state's multiplier by 0.5 in expansions and 2 in recessions. We further document modest positive spillover effects across states and show that a mere redistribution of spending across states also had a significant influence on the aggregate U.S. economy due to cross-state heterogeneity of the effects

A P. menziesii var. menziesii (=viridis) (Schwerin) Franco stand description dataset: a case study of Pavari's experimental Plot 412 ninety years after plantation

This paper describes a dataset containing the historical series of dendrometric data from a P. menziesii var. menziesii (=viridis) (Schwerin) Franco plantation. Implemented in 1932, the plantation is located in “Rio di Mercurella” place, in the Tyrrhenian coastal mountain range of Calabria region (Southern Italy). The experimental plot has been identified as Plot 412 and is characterized by trees with a relevant role for forest community biodiversity. The monitoring started in 1940.  The dataset reported five of all the inventories Until 2013, inventories have been carried out by Istituto Sperimentale di Selvicoltura and Unità di Ricerca per la Selvicoltura in Ambiente Mediterraneo, now CREA Forestry and Wood research centre which has taken over the last two. The following data have been collected: position, number, diameter at breast heigh (DBH) of all the trees and total height (Ht) of a trees sample. Collected data are an important historical source and testimony the first experimental test of P. menziesii introduction which will have to be monitored in the future and will constitute a fundamental contribution to enrich the knowledge on appropriate management in Calabria and evaluate the health state and stability of the forest stand in the future

Towards a user-centered framework to support proactive Building Operation and Maintenance: preliminary results of a communication platform between users and stakeholders

none3noUsers’ needs and behaviors can alter the building efficiency, thus leading to significant efforts to support Building Operation & Maintenance (O&M) tasks. This work develops the preliminary concepts of a framework for O&M including users’monitoring and engagement strategies. In the context of a complex university building, we developed and tested a users-stakeholders communication platform including a web-based application to report and check failures and damages to building’s components and devices.openBernardini, Gabriele; Di Giuseppe, Elisa; D’Orazio, MarcoBernardini, Gabriele; Di Giuseppe, Elisa; D’Orazio, Marc

COVID-19 impact on end-user's maintenance requests. A text mining approach

COVID-19 pandemic changed our way of working, limiting the usual physical attendance of working spaces. Despite the drastic reduction in the number of daily users due to the pandemic restrictions, working buildings were often kept open to provide services to internal and external users. Pandemic obliged to change operation and maintenance (O&M) plans, due to the increase of ventilation requirements and the reduction of other types of services, with a strong impact on cost and management. Now the pandemic is reducing its effects and is time to question the future asset of buildings’ O&M plans, based on the pandemic lesson. Data collected by Computerized Maintenance Management Systems (CMMS) during COVID-19 then become an important source of understanding the future management of working places. End-users’ maintenance requests are usually expressed by natural language, then a text mining approach can be a useful tool to discover hidden knowledge from unstructured data stored in CMMS. This study applies text mining methods, including sentiment analysis, to the field of building maintenance, with the scope to evaluate how COVID-19 changed some aspects of the facility management process, including users’ perception

flooding risk in existing urban environment from human behavioral patterns to a microscopic simulation model

Abstract Climate changes-related floods will seriously strike population in existing urban environment. Despite Current assessment methods seem to underestimate the human behaviors influence on individuals' safety, especially during outdoor evacuation. Representing pedestrians' evacuation would allow considering the "human" factor in risk analysis. This work proposes a flood-induced pedestrians' evacuation simulation model, based on a combined microscopic approach. Behavioral rules, obtained by real events videotapes analyses, are organized in an agent-based model. Motion criteria proposals are based on the Social Force Model. Experimental motion quantities values are offered. The model will be implemented in a risk assessment simulation tool

Helicopter Vibratory Loads Alleviation through Combined Action of Trailing-Edge Flap and Variable-Stiffness Devices

The aim of this paper is the assessment of the capability of controllers based on the combined actuation of flaps and variable-stiffness devices to alleviate helicopter main rotor vibratory hub loads. Trailing-edge flaps are positioned at the rotor blade tip region, whereas variable-stiffness devices are located at the pitch link and at the blade root. Control laws are derived by an optimal control procedure based on the best trade-off between control effectiveness and control effort, under the constraint of satisfaction of the equations governing rotor blade aeroelastic response. The numerical investigation concerns the analysis of performance and robustness of the control techniques developed, through application to a four-bladed helicopter rotor in level flight. The identification of the most efficient control configuration is also attempted