A Study on Frequency Response Functions in Pavement Engineering

Mechanical impedance (MI) defines the ability of a system to vibrate as a consequence of force application. In the recent years, the correlation of this parameter with tire-road noise and other characteristics has gained certain attention. Nevertheless, the information about this topic is still insufficient. Usually, the force is set through an impulse hammer as a master and the acceleration is measured through an accelerometer as a response in order to measure the corresponding Frequency Response Function (FRF). The objectives of the study presented in this paper are i) to analyse the differences between the axial mechanical impedance (complex ratio of force and velocity referred to the same point, named driving-point impedance) and the non-axial mechanical impedance (complex ratio of the force at the point i and velocity at the point j, named transfer impedance); ii) to analyse the effect of adding crumb rubber (2% by mixture weight) and of the percentage of bitumen on the mechanical impedance for the bituminous samples. Therefore, laboratory tests on asphalt concrete specimens have been performed, using an instrumentation system composed of i) an impact hammer reporting the impact force value; ii) an impedance head measuring the direct impact force and the direct acceleration at the hitting point location; iii) a piezoelectric accelerometer measuring the transfer acceleration at a certain distance from the hitting point location. Results demonstrate that the ratio between the repeatability and the average is quite constant, while for heights higher than 10 cm, also MI tends to be independent on the height. A number of recommendations have been made based on the results of the present research

Misura sperimentale della rigidità dinamica di pavimentazioni stradali

Le diverse sorgenti di rumore che caratterizzano un autoveicolo sono note da tempo e comprendono il rumore del motore e delle altre parti meccaniche, il rumore aerodinamico e il rumore di rotolamento. In particolare, quest’ultimo interessa l’interazione tra lo pneumatico e la pavimentazione stradale. Uno dei parametri che influenza il rumore di rotolamento è la rigidità della pavimentazione. La sua misura sperimentale, ed in particolare il suo spettro in frequenza, non sono ovvi da determinare e solo nell’ultimo decennio sono emersi studi sul tema. In questi vengono impiegate due diverse catene strumentali: il martello strumentato e l’eccitatore dinamico (shaker), che si è nel tempo affermato come riferimento. L’obiettivo di questo lavoro è mettere a punto un sistema di misura della rigidità dinamica delle pavimentazioni stradali mediante il martello strumentato che abbia prestazioni analoghe a quelle dello shaker minimizzando i costi. Durante il lavoro è stato progettato e realizzato un dispositivo di automatizzazione della prova (test automation device TAD) che incrementa la riproducibilità delle misure. Sono state poi ottimizzate l’esecuzione e l’analisi dei risultati e la modalità con cui questi vengono rappresentati, consentendo di ottenere risultati aderenti al modello di rigidità proposto in letteratura. Il metodo così ottimizzato è stato, quindi, utilizzato per la misura in situ e in laboratorio della rigidità di pavimentazioni con aggiunta di polverino di gomma appartenenti ai progetti europei LIFE NEREiDE (Noise Efficiently Reduced by Recycled Pavements) e LIFE E-VIA (Electric vehicle noise control by assesment and optimization of tyre/road interaction). I risultati ottenuti in situ, per la prima volta su questo tipo di pavimentazioni, hanno evidenziato una diminuzione della rigidità dovuta all’aggiunta di polverino di gomma all’interno della pavimentazione. I risultati in laboratorio hanno inoltre evidenziato differenze di rigidità tra pavimentazioni entrambe con polverino, ma realizzate con due diversi processi produttivi: dry e wet. Nel corso dell’elaborato di tesi, dapprima approfondiremo la tematica del rumore stradale e in particolare il rumore di rotolamento, ponendo l’accento sui parametri della pavimentazione che lo influenzano, tra cui la rigidità. In seguito descriveremo la misura della rigidità, riporteremo le diverse metodiche utilizzate in letterature e ne discuteremo i risultati. Quindi descriveremo il TAD, il lavoro di ottimizzazione della misura con il martello strumentato, l’analisi dei dati effettuata e la modalità di rappresentazione dei risultati proposta. Infine, presenteremo i risultati ottenuti e le possibili prospettive future

Regulating Hartshorne's connectedness theorem

A classical theorem by Hartshorne states that the dual graph of any arithmetically Cohen--Macaulay projective scheme is connected. We give a quantitative version of Hartshorne's result, in terms of Castelnuovo--Mumford regularity. If $X \subset \mathbb{P}^n$ is an arithmetically Gorenstein projective scheme of regularity $r+1$, and if every irreducible component of $X$ has regularity $\le r'$, we show that the dual graph of $X$ is $\lfloor{\frac{r+r'-1}{r'}}\rfloor$-connected. The bound is sharp. We also provide a strong converse to Hartshorne's result: Every connected graph is the dual graph of a suitable arithmetically Cohen-Macaulay projective curve of regularity $\le 3$, whose components are all rational normal curves. The regularity bound is smallest possible in general. Further consequences of our work are: (1) Any graph is the Hochster-Huneke graph of a complete equidimensional local ring. (This answers a question by Sather-Wagstaff and Spiroff.) (2) The regularity of a curve is not larger than the sum of the regularities of its primary components.Comment: Added Remark 1.1 and Example 4.3; improved expositio

Definition of Key Performance Indicators for Noise Monitoring Networks

The European Noise Directive fixed a well-defined schedule on a five-year basis for the noise exposure evaluation of citizens. Noise monitoring is needed to validate noise maps of the main transportation infrastructures and it can also represent an improvement. By comparing with average noise maps, a properly set sensor network can report noise information in a more case-specific way, including time variations. To the best of the authors’ knowledge, key performance indicators (KPIs) evaluating the technical performance and financial sustainability of acoustic networks have never been presented in the scientific literature. Therefore, in the present work, a set of KPIs are proposed on the basis of KPIs defined for monitoring networks of other pollutants. It is then tuned according to noise monitoring, in line with the current legislations. As a case study, the performance of three monitoring networks installed in ports are evaluated and discussed. The resulting investment and maintenance costs can be helpful for decision makers to calculate the cost–benefits in the installation of new monitoring stations and also to evaluate the performance of the already-existing ones

Experimental validation of a dynamic modelling of a Reversible Solid Oxide Cells (rSOCs)

The integration of Hydrogen technologies in different end-uses such as transport, electric microgrids, residential and industrial applications, will increase exponentially soon. Hydrogen as energy carrier allows more favourable energy conversion than other conventional systems and is crucial in worldwide decarbonize end uses. The production of green hydrogen, using RES, is a key area for the evolution of this technology. In this context, SWITCH is a Horizon 2020 European Project that aims to design, build and test an in-situ fully integrated and continuous multisource hydrogen production system, based on solid oxide cell technology. Reversible Solid Oxide Cell (rSOCs) technologies allow to convert renewable energy as hydrogen in the power-to-gas application (P2G) and in reversible mode is able to produce electricity from hydrogen stored, power-to-power application (P2P). rSOCs are really interesting to stabilize the random nature of RES because a combined electrolysis and fuel cell system should be able to switch between the two modes as quickly as possible in order to optimize the integration and the use of RES. However, rSOCs need a complex BoP from the thermal point of view, able to guarantee high efficiency even at partial load mode as well as easy start-up and shutdown procedures. In this work, a Stack Box Module dynamic model was developed in Modelica environment as a dynamic tool for the definition and optimization of BoP requirements. Stack model was validated in SOFC (Solid Oxide Fuel Cell) and SOE (Solid Oxide Electrolyser). The results of the simulation provide verification of the technical/thermodynamic behaviour and flexibility of a stack box of 70 cells. Dynamic modelling allows to evaluate the effect of the reagent inlet temperatures on the operation and hydrogen production/consumption in terms of yield as well as the transients between the different operative modes. Model has been validated by experimental measurements performed in the laboratory. In particular, the kinetics of the reactions governing steam methane reforming (SMR) was considered from data found in the literature, while the ASR (Area Specific Resistance) value was calibrated according to experimental data. The results of the dynamic model show as model can be a useful design and optimization tool for the SOCs technology

Source characterization guidelines for noise mapping of port areas

Maritime transport for both passengers and freight is continuously increasing and, consequently, the global attention toward its sustainability is growing. Ships offer advantages in terms of environmental impact compared to other transportation systems but the increasing traffic volume is expected to increase pollutants. Noise produced in port areas has been neglected for too long, until the INTERREG Maritime programme Italy-France 2014-2020 has brought to light how citizen complaints are emerging for some of the main ports in the Mediterranean. However, port noise prevention and management is difficult as knowledge on specific sources is very limited in the literature. Furthermore, on field measurements are difficult to be performed given the complexity of the port area, where multiple types of sound emitters mix and confuse each other. Noise maps represent the first important step in order to align ports to the requirements set by the Environmental Noise Directive to the transportation infrastructures. Once computed, they are an excellent tool supporting port management towards the reduction of citizens' noise exposure while ensuring traffic growth. The present paper reports a guideline for the characterization of noise sources needed as inputs for the noise maps, as developed in the framework of the INTERREG Maritime programme Italy-France 2014-2020. On the basis of the current state of the art, a procedure has been elaborated for different categories of noise sources acting in port, ranging from stationary to moving ships, from mooring operations to loading/unloading operations, from industrial activities to road and railway traffic

Outcome and Morphofunctional Changes on Cardiac Magnetic Resonance in Patients With Acute Myocarditis Following mRNA COVID-19 Vaccination

Messenger RNA (mRNA) COVID-19 vaccination has been associated with a higher-than expected occurrence of acute myocarditis, although the benefits of the vaccine greatly outweigh the risk of myocarditis. Even if the short-term prognosis of mRNA vaccine–related myocarditis has been reported to be favorable, scarce information is available on midterm prognosis. The current series included 7 to 9 patients with baseline and follow-up cardiac magnetic resonance imaging (CMRI). Questions on acute myocarditis following mRNA COVID-19 vaccination addressed by this study are the risk of adverse events after discharge and the extent of residual myocardial dysfunction and scar formation