Mechanical characterization and modelling of Ultra High Performance Fiber Reinforced Concrete

In the last two decades the use of Ultra High Performance Fiber Reinforced Concrete (UHPFRC) for the construction of structural and non-structural elements has increased, but there is still a strong need to establish a complete method for its mechanical characterization, especially of its tensile behavior. In this paper, a mechanical investigation carried out on four UHPFRC specimens with a fiber volume fraction of 3.3% is presented. The fiber content resulted to be sufficient to cause strain hardening behavior, characterized by a multicracking phase. The tensile constitutive law provided by Model Code 2010 for the inverse analysis from bending tests is hereby discussed. In particular, the size of the mul-ticrack diffusion zone is investigated with vision-based measurement tools and used as a characteristic length

La fisica tra la scuola secondaria e l’università. Riflessioni e orientamenti

L’università ha da sempre una porta aperta verso il mondo della scuola secondaria, il che ne fa un interlocutore privilegiato in continua e mutua interazione, sia per la formazione degli insegnanti (dal punto di vista contenutistico e metodologico), sia per la platea di studenti che quella porta la attraverseranno per continuare il loro cammino di apprendimento. Spesso non sono solo i soggetti (insegnanti e studenti) ad essere parte dell’interazione, ma anche gli oggetti (tematiche e metodologie), in particolare per le materie STEM (Science, Technology, Engineering, Mathematics); in tal caso nel passaggio dalla scuola all’università lo studente ritrova la materia che ha affrontato sino a qualche mese prima, talvolta proseguendola con uno sviluppo tematico successivo e talvolta affrontando la stessa tematica con diversa profondità. Questo è particolarmente vero nel caso della fisica, in cui le macro-tematiche classiche principali (la meccanica, la termodinamica, l’elettromagnetismo, l’ottica, cenni alla fisica moderna) trovano spazio comune nelle due realtà formative

Energy dispersive x-ray spectroscopy for nanostructured thin film density evaluation

In this paper, we report on two fast and non-destructive methods for nanostructured film density evaluation based on a combination of energy dispersive x-ray spectroscopy for areal density measurement and scanning electron microscopy (SEM) for thickness evaluation. These techniques have been applied to films with density ranging from the density of a solid down to a few mg cm(-3), with different compositions and morphologies. The high resolution of an electron microprobe has been exploited to characterize non-uniform films both at the macroscopic scale and at the microscopic scale

Sheep head frame validation for CT and MRI studies

Abstract IntroductionsAim of EDEN 2020 project’s Milestone 5 is the development of a steerable catheter for CED system in glioblastoma therapy. The VET group is involved in realization and validation of the proper animal model.Materials and methodsIn this part of the study two fresh sheep’s head from the local slaughter were used.The heads were located into an ad hoc Frame system based on anatomical measures and CT images, producted by Renishaw plc partner in this project. The frame was adapted and every components were checked for the ex vivo validation tests.CT imaging was taken in Lodi at Università degli studi di Milano, Facoltà di Medicina Veterinaria, with CT scanner and MRI imaging was taken in La Cittadina, CremonaResultsSystem validation was approved by the ex vivo trial.The frame system doesn’t compromise the imaging acquisition in MRI and CT systems.Every system components are functional to their aims.DiscussionThe Frame system is adapted to the sheep head. It is composed by elements able to lock the head during the imaging acquisition. Frame system is characterized by a support base helpings the animals to keep the head straight forward during imaging time, under general anesthesia. The design of these device support the airways anatomy, avoiding damaging or obstruction of airflows during anesthesia period.The role of elements like mouth bar and ovine head pins is to lock the head in a stable position during imaging acquisition; fixing is guaranteed by V shape head pins, that are arranged against the zygomatic arches. Lateral compression forces to the cranium, and the V shape pins avoid the vertical shifting of the head and any kind of rotations. (fig. 1

An extensive questionnaire about Metacognition during Emergency Remote Teaching involving more than 3000 engineering students

By 11 March 2020, the phrase “COVID-19” had officially entered everyday life across most of the word. Each level of education suddenly faced new changes and new challenges. Emergency remote teaching became widespread, and new methodologies to deliver classes and courses were adopted by educational institutions. In this paper, we focus on the impact of the remote learning experience of engineering students enrolled at the Politecnico di Milano. The subjects were recruited from all engineering courses from the first to the fifth year and were asked to complete a multidimensional survey. The survey featured 66 items regarding the participants’ perceptions of the challenges of emergency remote teaching compared with pre-COVID-19 in-person teaching. The questionnaire addressed six dimensions: the organization of emergency remote teaching, subjective well-being, metacognition, self-efficacy, identity, and socio-demographic information. In this paper, we describe the entire survey and discuss a preliminary analysis. Using Cronbach’s alpha test, a confirmatory factor analysis, and the t-test, we performed a more in-depth analysis concerning the outcomes of metacognition and self-efficacy. The data analysis suggested a small, unexpected change in the metacognition strategies. The students, in some regards, improved their learning strategies. Some other answers underlined their appreciation of the courses’ organization and the lack of relationships with their peers and teachers

Erratum to: Textile Reinforced Concrete: experimental investigation on design parameters

Textile Reinforced Concrete (TRC) is an advanced cement-based material in which fabrics used as reinforcement can bring significant loads in tension, allowing architects and engineers to use thin cross-sections. Previous research projects, developed during the last 10 years mainly in Germany, Israel and the USA, have shown the capabilities of such a material. In this paper an extensive experimental investigation of TRC is presented: tensile tests were carried out to obtain a complete mechanical characterization of the composite material under standard conditions, considering the influence of different variables such as reinforcement ratio, fabric geometry, curing conditions, displacement rate and specimen size. ******* Due to an unfortunate turn of events this article was published with wrong citations in the text to the references at the end of the article. In order to provide the correct information this article is hereafter published in its entirety with the correct citations and should be regarded as the final version by the reader

An Italian large case study on Emergency Remote Teaching: factors and predictors which affect Higher Education students’ attitude

Research on concerns about Emergency Remote Teaching has focused on teaching and management strategies, with some studies considering learners’ satisfaction, reactions, learning and overall acceptance. The present large case study, based on a survey on 3,920 undergraduate and postgraduate learners, aimed at investigating Politecnico di Milano students’ self-reported experiences of the Emergency Remote Teaching after identifying the empirical factors characterising such experience and the predictors of the students’ responses. Participants’ evaluation was expressed based on a five-point Likert scale, whereby a score equal to 3 corresponded to neutrality. We validated the questionnaire empirically through factor analysis. This questionnaire consisted of 66 items across 6 sections and focused on different latent variables as well as socio-economic information about the students. Our findings highlighted both the students’ assessment of their overall online learning experience of Emergency Remote Teaching and the change in their metacognitive strategies and self-efficacy as a consequence of the new learning approach. These results did not appear to depend on the learners’ gender or their educational level of degree study, while the academic year of attendance seemed to influence their opinion on teaching. Moreover, the change in the learning approach that learners experienced in the passage from bachelor to master’s programmes was discovered to be a further predictor which might be more critical for females than males. Finally, implications for policy makers and higher education institutions for online learning in the post-pandemic scenario are discussed

Effect of Textile Characteristics on the AR-Glass Fabric Efficiency

Alkali-resistant (AR) glass textiles are used as the main reinforcement in several composite applications due to their good performance-to-cost ratio. A huge variety of textiles are already present in the market; they differ on various parameters, such as, for example, the filaments’ diameters, the geometry, the type of weaving, or the nature of the impregnation coating. To orient manufacturers towards the production of efficient textiles, the most important aspect is the balance between cost and performance. In this paper, a series of different fabrics designed for textile-reinforced cementitious composites were considered. Performance was assessed by means of uniaxial tensile tests and the results are presented in terms of load vs. displacement. Then, the selected AR-glass textiles were compared in terms of fabric efficiency, targeting the effect of each parameter on the textile capacity. The research here presented is part of a comprehensive campaign aimed at the optimization of glass-fabric-reinforced cementitious composites for structural retrofitting. To better discuss the different solutions tested, at the end, only considering a small number of the investigated textiles, an efficiency evaluation was carried out at the cementitious composite level

Peer learning for large size Physics lectures in higher education: yes, we can

The academic course on Mechanics and Electromagnetism “Fisica Sperimentale A+B” at Politecnico di Milano was selected to investigate peer learning effects in large size lectures. It was attended by both freshmen attending the first year of Chemical Engineering and those studying Materials and Nanotechnology Engineering during the first term of the academic year 2017-2018. After arranging the students in three different sections on the basis of an alphabetical order, the research team modified the design and pedagogical method of one of these sections. In addition to traditional lectures, the students of this section took periodical tests based on multiple choice quizzes whose provision was implemented by using the on-line portal Socrative and by allowing the students to use their own electronic devices. Immediately after each quiz and without getting any feedback on the accuracy, freshmen would discuss the quizzes in small groups for few minutes. At the end of this debate, they retook the same test. Thanks to the significant bulk of data collected, the findings are likely to show that the average score achieved by the students in the same test, normalised so that the highest value is equal to 10, increases considerably as a consequence of peer discussion: from 5.1 to 6.7 in Mechanics, corresponding to a growth by 32%, and from 3.6 to 5.6 in Electromagnetism, corresponding to an increase by 55%. Moreover, a sensible decrease in the incorrect answers rate emerges in relation to each quiz: on average, 43% and 30% in Mechanics and Electromagnetism respectively. Furthermore, significant and comparable reductions of this rate occur as regards quizzes characterised by both low and high percentage of incorrect answers in quizzes which precede peer learning and peer evaluation. Finally, the percent decrease in incorrect answers given by female students is higher than the male percent reduction in 90% of the Mechanics quizzes and lower in the remaining 10%; conversely, they are both equal to 50% with relation to Electromagnetism quizzes