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Comparison between Commercial and Recycled Carbon-Based Fillers and Fibers for the Development of Smart and Sustainable Multifunctional Mortars
Full text linkLa società moderna è in gran parte fondata sulle infrastrutture che garantiscono la fornitura di beni, trasporti e mezzi di comunicazione. La loro salvaguardia e il risparmio delle risorse necessarie per il loro funzionamento è di crescente importanza per l’Ingegneria civile. Per questo motivo, la ricerca sui materiali da costruzione si sta concentrando sul riutilizzo di sottoprodotti industriali riciclati, per un’industria edilizia più sostenibile. L’Ingegneria dei materiali, grazie al recente sviluppo di nanomateriali ad alte prestazioni, propone molteplici spunti per la realizzazione di materiali strutturali multifunzionali.
La presente ricerca mira a sviluppare compositi multifunzionali a base di leganti idraulici, con l'aggiunta di filler e fibre a base di carbonio di origine riciclata, ottenuti da sottoprodotti industriali. Sono stati studiati i miglioramenti in termini di resistenze meccaniche e di durabilità, nonché le loro proprietà disinquinanti e fotocatalitiche. Le proprietà elettriche delle miscele sono state studiate, per la valutazione delle capacità di schermatura delle interferenze elettromagnetiche delle aggiunte, e come base di studio per lo sviluppo di materiali auto-sensibili per il monitoraggio strutturale.
Sono state realizzate paste e malte contenenti grafene o altri filler a base di carbonio di origine riciclata (da 0.25 a 4% sul peso del legante) e fibre di carbonio (da 0.05 a 1.6% sul volume della miscela).
Sui composti sono stati eseguiti test di resistenza meccanica e durabilità, nonché test di adsorbimento degli inquinanti, di fotocatalitisi e di resistività elettrica. La sensibilità elettrica alla deformazione è stata valutata misurando la variazione percentuale della resistività su provini soggetti a carichi di compressione semi-statici.
I risultati mostrano che l’aggiunta di filler a base di carbonio riciclati porta a un raffinamento della microstruttura della matrice e a un incremento delle resistenze meccaniche, nonché a un decremento della permeabilità all’acqua. L’aggiunta di micro-fibre di carbonio riciclate porta a un incremento delle resistenze meccaniche a flessione, e a un notevole aumento della conducibilità elettrica (di svariati ordini di grandezza, rispetto ai tradizionali materiali cementizi).Today's society is largely based on infrastructures that guarantee goods, transport and communication networks. Their safeguarding and saving of resources for their operation is becoming increasingly important in the field of building engineering. For this reason, research on building materials is increasingly focused on the re-use of recycled industrial by-products, for a more sustainable construction industry. Materials engineering, thanks to the development of high performance nanomaterials, offers several ideas for the construction of multifunctional building materials.
The present research aims to develop multifunctional hydraulic binder-based composite with the addition of recycled carbon-based fillers and fibers obtained from industrial by-products. The enhancement of mechanical strength and durability of the composites have been studied, together with their de-polluting and photocatalytic properties. The electrical properties of the mixtures have been studied to analyze the Electromagnetic interference shielding capability of carbon-based admixtures, and to provide a basis for the development of strain-sensing materials for structural health monitoring.
Pastes and mortars containing graphene or other commercial and recycled carbon-based fillers (from 0.25 to 4.0% on binder weight) and fibers (from 0.05 to 1.6% by mixture volume) were realized. Tests of mechanical resistance and durability were performed on the mixtures, together with test of pollutants adsorption, photocatalysis and electrical resistivity. Strain-sensitivity has been evaluated by measuring the fractional change in resistivity of the specimens subjected to quasi-static compressive loads.
Results show that the addition of recycled carbon-based fillers leads to a refinement of the matrix microstructure, increasing the mechanical strength and decreasing the water permeability. The addition of recycled carbon micro-fibers leads to an increase in flexural strengths and to a noticeable increase in electrical conductivity (up to several orders of magnitude compared to the traditional cementitious materials)
Studio e sviluppo di dispositivi wireless indossabili per applicazioni Ambient Assisted Living ed e-health
No full textL’attività di ricerca può essere suddivisa in due ambiti: dispositivi indossabili wireless per Ambient Assisted Living e Wireless Sensor Networks per applicazioni e-health.
Per quanto riguarda i dispositivi wireless indossabili per AAL è stato interamente sviluppato un Attitude and Heading Reference System wireless che, attraverso l’elaborazione dei dati rilevati da accelerometro, giroscopio e magnetometro, è in grado di fornire una stima dell’orientazione del segmento corporeo sul quale è posizionato mediante algoritmi di data fusion. Vista l’ottima precisione ottenuta dal dispositivo in protocolli sperimentali, l’AHRS è stato utilizzato per realizzare dei dispositivi custom in grado di monitorare l’equilibrio nei pazienti affetti da sclerosi multipla, analizzare il tremore nei Parkinsoniani, fornire uno strumento di ausilio alla valutazione del Flexion Relaxation Phenomenon e rilevare le cadute negli anziani. Dai risultati ottenuti nelle prove effettuate seguendo protocolli standard di validazione, il dispositivo per la rilevazione della caduta assicura prestazioni superiori rispetto a quelle di sistemi simili proposti in letteratura.
Nell’ambito delle WSN per applicazioni e-health è stato realizzato un sistema intelligente per il monitoraggio da remoto ed in tempo reale di anziani che vivono soli in casa. I principali elementi di tale sistema sono una coppia di lampade LED. La lampada LED posta a casa dell’anziano integra un dispenser automatico di medicinali per la somministrazione quotidiana di farmaci e un sistema di monitoraggio della mobilità domestica con generazione di allarmi derivanti da eventi critici quali la mancata somministrazione del farmaco o la prolungata permanenza dell’anziano in una stanza. Le informazioni relative alla mobilità dell’anziano, alla regolare assunzione di farmaci e alla gestione degli allarmi sono disponibili sulla seconda lampada LED posta a casa del caregiver e su un server web accessibile ad utenti autorizzati.The research activity was focused into two areas of interest: wireless wearable devices for Ambient Assisted Living and Wireless Sensor Networks for e-health applications.
With regard to the wireless wearable devices for AAL, an Attitude and Heading Reference System has been completely developed. This provides an estimate of the orientation of the body segment through data fusion algorithms using accelerometer, gyroscope and magnetometer measurements. Given the high accuracy achieved of the device in commonly adopted experimental protocols, the wireless AHRS is embedded into devices that can monitor balance in patients with multiple sclerosis, analyse the tremor in Parkinson's disease, provide an assessment tool for Flexion Relaxation Phenomenon and detect falls in elderly people. The results of the tests according to standard protocols indicate that the fall detection device achieves best performance respect to those proposed in literature.
In the context of WSN for e-health applications, a system for remote real-time assistance of elderly people living alone has been realized. The main elements of this system are a pair of LED lamps. The LED lamp located in the house of the elderly integrates an automatic dispenser of medicine for the daily dosage and a monitoring system of the elderly’s mobility with the generation of alarms resulting from critical events such as omission of taking medicines or prolonged permanence in a room. The information related to the mobility of the elderly, the regular intake of drugs and alarms management, are real time available on the second LED lamp located in the home of caregiver and on a web server accessible by authorized users
Metakaolin and fly ash alkali-activated mortars compared with cementitious mortars at the same strength class
No full textAlkali activated and cementitious mortars belonging to R1 ≥ 10 MPa, R2 ≥ 15 MPa and R3 ≥ 25 MPa strength classes are tested and compared in terms of workability, dynamic modulus of elasticity, porosimetry and water vapour permeability. Capillary water absorption, drying shrinkage, resistance to sulphate attack and corrosion behaviour of embedded bare and galvanized reinforcements have also been investigated.
In alkali activated mortars, drying shrinkage is higher than that of cementitious mortars but restrained shrinkage is lower due to lower modulus of elasticity. Water vapour permeability is more pronounced in alkali activated mortars, and capillary water absorption is lower in those prepared with fly ash. The high alkalinity of alkali activated mortars was seen to delay the onset of the passive state in particular for galvanized reinforcements, but after one month of curing they were found to reach the same corrosion rates of those embedded in cementitious mortars
Comparison of Signal Pre-processing and Machine Learning Modelling for Water-leak Detection Using Vibration and Pressure Data
No full textLeak detection is important to enable automatic and early identification of leakages in water distribution systems, which may prevent water wastage, reduce the environmental impact of leakages, and also avoid structural damages to pipe networks. While there are different sensors, hardware and software-based methods for leak detection, this field still faces issues, especially regarding data scarcity and imbalance. In this paper, a comparison of different Machine Learning (ML) models for leak detection and leak type classification has been carried out, addressing data augmentation and balancing issues, and providing a comparison on the performance of pressure and accelerometric data for leak monitoring with ML. Compared to the state-of-the-art, mainly focusing on leak detection, the focus has also been on leak type identification, which may be useful for diagnosing pipe damage. Results indicate that accelerometer data is more consistent across tasks and performs better than pressure data for multi-class leak classification. The best-performing model is an Ensemble Bagged Trees classifier using accelerometer data and features extracted from 5 s long windows, and it achieved 91.7% accuracy in multi-class leak classification. While the proposed approach still faces issues in identifying longitudinal cracks, it provides a solid base for leak classification with ML and it identifies the accelerometer as a viable, non-invasive solution for leak monitoring
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Comportamento a corrosione di armature zincate in malte geopolimeriche e cementizie a parità di classe di resistenza - Corrosion behavior of galvanized steel reinforcements in geopolymeric and cementitious mortars at the same strength class
No full textThe corrosion behavior of galvanized steel rebars embedded in geopolymer mortar was compared to that of the same reinforcements embedded in a cementitious mortar with the same mechanical strength class. The corrosion potential and the corrosion rate of these bars were measured throughout the first month of curing for all manufactured specimens, and then one half was submitted to weekly wet-dry cycles in 3.5% NaCl solution and the other half to weekly wet-dry cycles in tap water after exposure to a chamber with 3% of CO2. In the first month, the high alkalinity of geopolymers delayed the achievement of the galvanized steel passive state, but after reinforcements reached the same corrosion rates of those embedded in the cementitious mortars. In chlorides exposure, the lowest porosity of geopolymers hindered the ingress of chloride ions offering the highest protection to reinforcements. Also in carbonated matrices, during exposure to wet-dry cycles in tap water, galvanized bars had the lowest corrosion rates when embedded in the geopolymeric matrices
Metakaolin and fly ash based geopolymers compared with cementitious mortars of the same strength class: performances and corrosion behaviour of black and galvanized steel bars
No full textMechanical, morphological and durability aspects of three types of geopolymer mortars were compared with those of traditional cementitious mortars of comparable compressive strength.
To this aim, mortars belonging to three mechanical strength classes (R1 ≥ 10 MPa, R2 ≥ 15 MPa and R3 ≥ 25 MPa according to EN 1504-3:2005) were tested and compared. Geopolymers were obtained with fly ash and metakaolin as precursors and a mixture of sodium silicate and NaOH or KOH as liquid activators. In order to obtain R1, R2 and R3 mortars cementitious mixtures were prepared by partial substitution of Portland cement with hydraulic lime, while geopolymers were prepared by varying the concentration of NaOH or KOH with a waterglass/hydroxide ratio always equal to 1.
The obtained samples were characterized both in the fresh and in the hardened state. The first was evaluated by workability and density of the fresh mortar, the latter by compressive strength, dynamic modulus of elasticity, adhesive strength on ceramic surface, free and restrained shrinkage and by microstructural analysis such as SEM and mercury porosimetry. Durability aspects were also investigated through water vapor permeability, capillary water absorption, resistance to salt crystallization and corrosion of possible embedded rebars. Corrosion tests were carried out by measuring corrosion potential and corrosion rates of black and galvanized steel bars during both the curing period and wet-dry cycles in a chloride solution.
At the same mechanical strength class, geopolymers shrink more than cementitious mortars if free while their low modulus of elasticity causes a lower shrinkage if mortars are restrained with bars. Pore dimensions affect the water vapor permeability, which resulted to be more pronounced in geopolymers than in cement mortars, and capillary water absorption with low values especially for fly ash geopolymers.
During the first month of curing, the higher alkalinity of geopolymers matrix prolongs the active state of both black and galvanized steel bars. However, when exposed to a chloride solution, fly ash based geopolymers offer a higher protection to reinforcements than cementitious mortars
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