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In this paper, the structural vibration control of short-period systems by a sliding model of a tuned liquid column damper (herein referred to as STLCD) is investigated from both theoretical and experimental points of view. The proposed STLCD is essentially composed of a U-tube container with liquid inside, which can slide on a linear guide rail and is connected to the structure by a spring-dashpot system. Unlike traditional fixed TLCDs, this type of arrangement allows the proposed STLCD to be tuned to short-period structural systems since the spring can be used for tuning while the dashpot provides additional damping. Details on the selection of the optimal design parameters of the STLCD are provided, and the validity of the introduced mathematical model is verified both in time and frequency domains through experimental tests conducted at the Laboratory of Experimental Dynamics at the University of Palermo, Italy. For the experimental tests, a scale model of an STLCD-controlled structure is considered, focusing on the reduction of the roof accelerations. Finally, for comparison purposes, the control performance of the proposed control strategy for the vibration suppression of stiff structures is evaluated by analyzing its structural responses in contrast with the corresponding uncontrolled structure under harmonic excitations. [ABSTRACT FROM AUTHOR]

Poly-diallyldimethylammonium (PDADMAC) chloride is a flocculant agent extensively used in water clarification treatments. Commercial polyelectrolyte formulations often contain residual monomer (DADMAC), reaction by-products and other reactants as contaminants that could potentially affect human health. In the present study, we optimized an analytical method based on reversed-phase ion-pair chromatography coupled with mass spectrometry for quantifying ultra-trace levels of DADMAC, without preliminary treatments, in drinking water distributed by the Palermo aqueduct. The method was validated in terms of accuracy (recovery between 80 to 120%), precision (RSD < 10%), linearity range (from 0.5 to 15 µg/L), limit of quantification and limit of detection (LOQ 0.42 µg/L and LOD 0.12 µg/L). DADMAC was detected in all analysed water samples and the concentration ranged from 1.2 to 3.8 µg/L whit a mean value of 1.7 µg/L. To the best of our knowledge, this paper represents the first study concerning DADMAC concentration in water samples collected in Italy and, in this context, this paper can be considered very interesting when comparing future data on DADMAC monitoring in water. Moreover, this is one of a few cases where DADMAC was found in drinking water. [ABSTRACT FROM AUTHOR]

Services from the Continuously Operating Reference Stations (CORS) of the Global Navigation Satellite System (GNSS) provide data and insights to a range of research areas such as physical sciences, engineering, earth and planetary sciences, computer science, and environmental science. Even though these fields are varied, they are all linked through the GNSS operational application. GNSS CORS have historically been deployed for three-dimensional positioning but also for the establishment of local and global reference systems and the measurement of ionospheric and tropospheric errors. In addition to these studies, CORS is uncovering new, emerging scientific applications. These include real-time monitoring of land subsidence via network real-time kinematics (NRTK) or precise point positioning (PPP), structural health monitoring (SHM), earthquake and volcanology monitoring, GNSS reflectometry (GNSS-R) for mapping soil moisture content, precision farming with affordable receivers, and zenith total delay to aid hydrology and meteorology. The flexibility of CORS infrastructure and services has paved the way for new research areas. The aim of this study is to present a curated selection of scientific papers on prevalent topics such as network monitoring, reference frames, and structure monitoring (like dams), along with an evaluation of CORS performance. Concurrently, it reports on the scientific endeavours undertaken by the Geomatics Research Group at the University of Palermo in the realm of GNSS CORS over the past 15 years. [ABSTRACT FROM AUTHOR]

This paper presents the path of knowledge developed for assessing the structural safety of the Norman-age Pisan Tower, which is mostly incorporated into the Royal Palace in Palermo, Italy. Historical, geomatic, and mechanical investigations were conducted and the most relevant results are herein collected and presented. The research path was addressed to specific tasks: identification of the building, geometric surveys, recognition of the sequence of phases of building transformation, detection of the components of the load-bearing structure, structural diagnostic surveys, and investigation of the subsoil and foundations. The explicit vulnerabilities found were mostly confined to the Piazzi library floor, while implicit vulnerabilities were identified in the presence of false walls and in high loads and fillings on the vaults of the last levels. The results of the analyses allowed the individuation of the confidence factors to use in structural analysis models aimed at the assessment of the seismic safety of the building. [ABSTRACT FROM AUTHOR]

The widespread availability of Continuosly Operating Reference Station (CORS) all over the world, allows to improve more scientific and technical studies on the use of satellite positioning techniques. The aim of this paper is to understand the effects of a GNSS CORS network geometry and differential corrections on the solutions. The analysis is carried out using ten different network configurations, with different inter-distances between the stations within GNSMART Geo++ software. The coordinates of one control point placed on the top of the Department of Engineering (University of Palermo, Italy) have been used to perform several static positioning mode test within fourthy hours. Different surveys have been performed, including four separate session tests, with acquisitions of one hour each. The analysis has been carried out using the traditional network solutions, such as the Virtual Reference Station (VRS), the Flächen Korrektur Parameter (FKP) and other two more recent techniques, which use the satellite corrections from the nearest (Near) and the farest (Far) stations. Results confirmed the great reliability of the GNSS network, with centimetre precision in terms of coordinates (North, East and Ellipsoidal Height), whether changing the geometric configuration of the network or the corrections. [ABSTRACT FROM AUTHOR]

Heavy and localized summer events are very hard to predict and, at the same time, potentially dangerous for people and properties. This paper focuses on an event occurred on 15 July 2020 in Palermo, the largest city of Sicily, causing about 120 mm of rainfall in 3 h. The aim is to investigate the event predictability and a potential way to improve the precipitation forecast. To reach this aim, lightning (LDA) and radar reflectivity data assimilation (RDA) was applied. LDA was able to trigger deep convection over Palermo, with high precision, whereas the RDA had a key role in the prediction of the amount of rainfall. The simultaneous assimilation of both data sources gave the best results. An alert for a moderate–intense forecast could have been issued one hour and a half before the storm developed over the city, even if predicting only half of the total rainfall. A satisfactory prediction of the amount of rainfall could have been issued at 14:30 UTC, when precipitation was already affecting the city. Although the study is centered on a single event, it highlights the need for rapidly updated forecast cycles with data assimilation at the local scale, for a better prediction of similar events. [ABSTRACT FROM AUTHOR]