un approccio teorico-sperimentale per la ricostruzione del profilo trasversale di rotaie usurate

La sovrastruttura ferroviaria durante la sua vita utile è sottoposta oltre ai carichi dinamici generati dai rotabili (azioni verticali, laterali, ecc.), anche ai carichi termici e ad azioni ambientali di varia natura. Tali sollecitazioni, interagendo sinergicamente tra loro, determinano il deterioramento della sovrastruttura ferroviaria inteso come discostamento dalla configurazione geometrica di progetto e l’usura dei singoli componenti del binario e della massicciata. Per valutare lo stato di efficienza della sovrastruttura è consuetudine far riferimento ad alcuni parametri geometrici del binario che, peraltro, permettono di formulare un giudizio oggettivo circa il livello di sicurezza offerto dalla linea ferroviaria in una data tratta. A tal riguardo, in genere, vengono esaminati distintamente in seguenti parametri geometrici [1] e [2]: i) scartamento; ii) allineamento “A”; iii) livello longitudinale “L”; iv) livello trasversale XL; v) scarto di livello trasversale SCARTXL; vi) difetto di sopraelevazione H; vii) sghembo; viii) ulteriori parametri geometrici (scartamento depurato ed in media mobile, allineamento su base 20 m, ecc.). Invece, per quanto riguarda il deterioramento dei materiali, generalmente vengono presi in esame: i) usura verticale della rotaia; ii) usura a 45° della rotaia; iii) usura orizzontale della rotaia; iv) presenza nelle campate delle rotaie di fori, fenditure, e stato delle saldature alluminotermiche ed a scintillio nelle lunghe rotaie saldate; v) tenuta degli attacchi; vi) stato delle traverse in c.a.p. ed in legno. Con riferimento allo stato di usura delle rotaie, oltre ai tradizionali metodi di auscultazione, in futuro, in ambito ferroviario, potrebbero trovare ampio impiego anche le tecniche basate sull’image processing, in grado di ricostruire con alto livello di dettaglio il profilo trasversale di una rotaia in esercizio, e dunque, di poter effettuare il confronto con il profilo originario (rotaia nuova) al fine di determinare lo stato di usura del profilato. Tale approccio metodologico, dettagliatamente descritto nei seguenti paragrafi, si basa sulle “informazioni” contenute in immagini fotografiche ad alta risoluzione delle rotaie e su specifici algoritmi che permettono di ottenere l’esatto profilo geometrico delle rotaie stesse.A new procedure for reconstructing the transverse profile of worn-out tracks by means of the image-processing technique is studied. In order to analyze the image of a track plane section, the first step of the procedure is the edge detection of the transverse profile through Canny's algorithm. This algorithm examines the behavior of the gradient operator applied to a noisy contour. Moreover, the algorithm is able to distinguish some clearer pixels near the track edge which do not belong to its micro-wrinkles, obtained from an enlargement of the upper profile of the railhead. For every chromatic plane of the analyzed image, a median filter is applied. The centroid position of the worn-out track and its contour coordinates were determined, gathered from Freeman's algorithm developed on the result formalized by relations after carrying out the proper morphological closing operations. The distances between the two profiles have been determined by the intercepts of the straight lines from the centroid of the profile I

Image analysis for detecting the transverse profile of worn-out rails

Over its useful life a railway track is subject tomany mechanical and environmental stresses which graduallylead to its deterioration. Monitoring the wear condition of therailway superstructure is one of the key points to guarantee anadequate safety level of the railway transport system; in thisfield, the use of high-efficiency laser techniques has becomeconsolidated and implemented in diagnostic trains (e.g. the“Archimede train” and the “Talete train” ) which allow to detectthe track geometric parameters (gauge, alignment, longitudinallevel, cross level, superelevation defect, etc.) and the state of railwear (vertical, horizontal, 45-degree etc.) with very highaccuracy. The objective of this paper is to describe a new nonconventionalprocedure for detecting the transverse profile ofworn-out rails by means of image-processing technique. Thismethodological approach is based on the analysis of theinformation contained in high-resolution photographic images ofrails and on specific algorithms which allow to obtain the exactgeometric profile and the measurement of the relevant deviationscompared to new rails of the same typology.The analyses and the first results, obtained from laboratoryresearches, concern rails cross sections taken from railway linesunder upgrading. The procedure has shown high precision in thewear evaluation as well as great rapidity in being performed

The observation of light nuclei at ALICE and the X(3872) conundrum

The new data reported by ALICE on the production of light nuclei with pT < 10 GeV in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV are used to compute an order-of-magnitude estimate of the expected production cross sections of light nuclei in proton-proton collisions at high transverse momenta. We compare the hypertriton, helium-3 and deuteron production cross sections to that of X(3872), measured in prompt pp collisions by CMS. The results we find suggest a different production mechanism for the X(3872), making questionable any loosely bound molecule interpretation.Comment: 5 pages, 2 figures. Version accepted on PR

A LOGIC FUZZY MODEL FOR EVALUATION OF THE RAILWAY STATION'S PRACTICE CAPACITY IN SAFETY OPERATING CONDITIONS

Abstract The practice capacity of a railway junction depends, in addition to the effective operation's conditions, by the potential risk factors related to the design plan of the railway station. With the aim of an approach based on the "fuzzy sets" it is possible to determine the numeric value of the practice capacity by the logic - qualitative relations between the features of the railway junction and the potential risk factors. This methodology permits to try out the absolute value of a suitable vector β, (less then the unit) for the utilization of the theoretic capacity in conditions of maximum reliability of the system related to the aspect of safety (technique "fail safe")

Piezoelectric energy harvesting from raised crosswalk devices

This paper presents the main characteristics of an experimental energy harvesting device that can be used to recover energy from the vehicular and pedestrian traffic. The use of a piezoelectric bender devices leads to a innovative approach to Henergy Harvesting. The study focuses on the definition and specification of a mechanical configuration able to transfer the vibration from the main box to the piezoelectric transducer. The piezoelectric devices tested is the commonly used monolithic piezoceramic material lead-zirconate-titanate (PZT). The experimental results estimate the efficiency of this device tested and identify the feasibility of their use in real world applications. The results presented in this paper show the potential of piezoelectric materials for use in power harvesting applications

Comparing carbon isotope composition of bulk wood and holocellulose fromQuercus cerris,Fraxinus ornusandPinus radiatatree rings

Tree-ring \u3b413C is widely employed in ecophysiological studies, because it represents an integrated proxy of the ratio between photosynthesis (A) and stomatal conductance (g), which expresses the intrinsic water use efficiency (iWUE), strongly affected by the environmental conditions experienced by the plant during its life span. Tree-ring \u3b413C also reflects long term variations of atmospheric CO2 concentration and of its carbon isotope composition, partly due to increasing anthropogenic emissions. Carbon isotope abundances in tree rings can be assessed on bulk wood as well as on wood biochemical components, wich show different \u3b413C values because of secondary discrimination during biosynthesis. We present the results of a comparison between \u3b413C values of bulk wood and holocellulose samples obtained from the last three (1999, 2000 and 2001) annual growth rings of two hardwood (Quercus cerris L. and Fraxinus ornus L. and one conifer (Pinus radiata D. Don, species. We found that 13C values differed significantly among tree species, both in the case of holocellulose and bulk wood, but only in the case of P. radiata bulk wood samples tend to provide more negative \u3b413C values than holocellulose, as reported in the literature. We suggest that, at least for the two hardwood species studied, bulk wood is a suitable material to work with for \u3b413C assessment, whilst in P. radiata holocellulose could provide a more stable and reliable index, when studying plant ecophysiological responses to changing environmental conditions

Evidence of scavenging behaviour in crested porcupine

The vegetarian diet of many herbivorous mammals is supplemented with proteins of animal origin, especially in young individuals and in breeding females, to provide key proteins necessary for both growth and breeding. Among porcupine species, only the Cape porcupine (Hystrix africaeaustralis) has been observed to consume carrion flesh. From June to August 2019, a pigeon carcass was placed together with corn in 7 study settlements and near 2 monitored capture-traps, in order to assess the carrion flesh feeding habits of the crested porcupine (Hystrix cristata). Scavenging behaviour was recorded on four occasions. All the recorded individuals were adults and at least one was female. This demonstrates that the crested porcupine occasionally does eat flesh. Such evidence raises important questions concerning the relationship between feeding habits and the physiological needs of this herbivorous rodent

Four-Quark Hadrons: an Updated Review

The past decade witnessed a remarkable proliferation of exotic charmonium-like resonances discovered at accelerators. In particular, the recently observed charged states are clearly not interpretable as q-qbar mesons. Notwithstanding the considerable advances on the experimental side, conflicting theoretical descriptions do not seem to provide a definitive picture about the nature of the so-called XYZ particles. We present here a comprehensive review about this intriguing topic, discussing both those experimental and theoretical aspects which we consider relevant to make further progress in the field. At this state of progress, XYZ phenomenology speaks in favour of the existence of compact four-quark particles (tetraquarks) and we believe that realizing this instructs us in the quest for a firm theoretical framework.Comment: 120 pages, 53 figures. Several typos corrected and some refs. added in v