Adhesive contact of model randomly rough rubber surfaces

We study experimentally and theoretically the equilibrium adhesive contact between a smooth glass lens and a rough rubber surface textured with spherical microasperities with controlled height and spatial distributions. Measurements of the real contact area $A$ versus load $P$ are performed under compression by imaging the light transmitted at the microcontacts. $A(P)$ is found to be non-linear and to strongly depend on the standard deviation of the asperity height distribution. Experimental results are discussed in the light of a discrete version of Fuller and Tabor's (FT) original model (\textit{Proceedings of the Royal Society A} \textbf{345} (1975) 327), which allows to take into account the elastic coupling arising from both microasperities interactions and curvature of the glass lens. Our experimental data on microcontact size distributions are well captured by our discrete extended model. We show that the elastic coupling arising from the lens curvature has a significant contribution to the $A(P)$ relationship. Our discrete model also clearly shows that the adhesion-induced effect on $A$ remains significant even for vanishingly small pull-off forces. Last, at the local asperity length scale, our measurements show that the pressure dependence of the microcontacts density can be simply described by the original FT model

University Clean Room Management Program

Implementation of a computerized clean room monitoring system at the RIT facility and the benefits of the RIT Management Program are discussed in this paper. Clean room parameters of interest with respect to environment, contamination, and process control were identified and the management of a commercial and university clean room will be contrasted

Statistical analysis of hyper-spectral data: a non-Gaussian approach

We investigate the statistical modeling of hyper-spectral data. The accurate modeling of experimental data is critical in target detection and classification applications. In fact, having a statistical model that is capable of properly describing data variability leads to the derivation of the best decision strategies together with a reliable assessment of algorithm performance. Most existing classification and target detection algorithms are based on the multivariate Gaussian model which, in many cases, deviates from the true statistical behavior of hyper-spectral data. This motivated us to investigate the capability of non-Gaussian models to represent data variability in each background class. In particular, we refer to models based on elliptically contoured (EC) distributions. We consider multivariate EC-t distribution and two distinct mixture models based on EC distributions. We describe the methodology adopted for the statistical analysis and we propose a technique to automatically estimate the unknown parameters of statistical models. Finally, we discuss the results obtained by analyzing data gathered by the multispectral infrared and visible imaging spectrometer (MIVIS) sensor

CARTOGRAPY IN THE EXPLOITATION OF NATURAL AND CULTURAL HERITAGE: 3D LASER SCANNER APPLICATIONS

La presente proposta è relativa all’utilizzo dei rilievi Laser Scanner 3D per la valorizzazione dei beni culturali e naturali. Alla base di ogni intervento volto alla valorizzazione dei beni culturali e naturali è fondamentale che ci sia un percorso di conoscenza che non sia solo storico-artistico come accade spesso, ma anche attraverso la conoscenza accurata delle sue caratteristiche (posizione, forma, geometria, materia e colore), dettagli fondamentali per tutelare e valorizzare il patrimonio. La tecnologia del laser scanner 3D consente di ottenere risultati di eccellente qualità in tempi relativamente brevi e di intervenire in ambienti complessi laddove altre tecniche mostrano numerosi limiti. L’innovativa metodologia di rilievo rivela la sua efficacia non solo nell’acquisizione e restituzione dei dati, ma soprattutto nella rappresentazione cartografica. Rispetto alle altre tecniche, il rilievo non è parziale ma completo e oggettivo: tutto ciò che è presente nel range di azione del laser scanner 3D viene rilevato senza alcuna distinzione. Il suo impiego risulta, pertanto, essenziale per rilevare e acquisire informazioni su beni particolarmente articolati ed irregolari, su parti inaccessibili o comunque non facilmente raggiungibili (notevoli altezze, presenza di asperità, ecc.), su elementi delicati, evitandone il contatto diretto. In questa nota sono riportati alcuni esempi applicativi della metodologia laser scanner 3D ed il beneficio delle relative informazioni cartografiche attraverso il rilievo di alcuni importanti beni culturali di grande valenza architettonica, storica e naturale quali il, gli ipogei di piazza della città di Matera e di un tratto del torrente Gravina di Matera che intaglia formazioni coerenti determinando suggestivi paesaggi.The present paper deals with the use of the 3D Laser Scanner ion the development of natural and cultural resources. Any intervention pointed to the development of natural and cultural resources needs to learn, besides the fundamental historical and artistic knowledge, some of their characteristics such as location, form, geometrical aspects, material properties and colour, all features that must be considered basic for both the safeguard and the development of the resource itself. The 3D Laser Scanner technology enables to obtain in a short time excellent results and to be active in particular environments where other techniques result to be rather limited. This technique is particularly effective not only in the acquisition and rendering processes, but also in cartographic representation of data. Compared to other technique, the 3D Laser Scanning is complete and objective: everything that is in the activity range of the used instrument is completely registered without any distinction. Ultimately, its use results to be absolutely necessary to survey and collect information in case of quite irregular and articulated structures, of very difficult or completely inaccessible parts and of fragile elements, avoiding the direct contact. Some examples of the use of the 3D Laser Scanner technique are here quoted emphasizing the advantages of the cartographic information as result from the survey of some important cultural resources relevant from architectural, historical and natural points of view, in particular: the Santuario della Palomba, the Vittorio Veneto Square in Matera hypogees, and a part of the Gravina di Matera, a torrent deeply incised in limestones rocks that creates striking sceneries

Sulla sicurezza delle strutture in calcestruzzo armato esposte ad azione da esplosione

In questo lavoro viene discusso il problema della valutazione della sicurezza di strutture in calcestruzzo armato, esposte alle azioni eccezionali delle esplosioni. Negli ultimi anni, a seguito dei numerosi eventi terroristici, tale problema ha assunto un rilievo drammatico, mettendo in evidenza la necessità di valutare se le risorse di resistenza di una struttura esposta ad esplosione, risultino adeguate a far fronte a tali azioni eccezionali. Questa problematica tocca la sicurezza strutturale con riflessi significativi sui costi. e, quindi, non può essere disattesa nell’ottica della sostenibilità di opere e interventi volti al contenimento del rischio connesso alle esplosioni. Nello studio si evidenziano, a partire dal quadro tecnico-normativo nazionale e internazionale, gli aspetti di base connessi ad un progetto avanzato, in presenza di strutture esposte ad esplosioni. In particolare, con riferimento alla valutazione della sicurezza in relazione alla definizione delle azioni da esplosione, dei modelli di comportamento dei materiali e dei meccanismi resistenti in regime dinamico di strutture in calcestruzzo armato

On the characterization of materials and masonry walls of historical buildings: Use of optical system to obtain displacement maps in double-flat jack tests

Among the testing techniques aiming at the mechanical characterization of masonry, the double flat-jack testing method is widely adopted to identify the local value of significant parameters needed to perform structural analyses, such as elastic modulus, Poisson’s ratio and compressive strength. The experience gained from many applications has allowed not only to collect experimental data concerning different types of masonry, but also to highlight the difficulty in the interpretation of the results and the limitations of both single and double flat-jack tests. Although the accuracy of the flat-jack technique in detecting strength and deformability behavior of masonry is still debated in the technical literature and practical activities, changes in the testing procedure aiming at ascertaining the validity of the test results have not been formally defined yet. After a brief description of the standard test procedure and its uncertainties, the present paper proposes an upgrade of the test procedure for improving the level of reliability of the test results. In particular, an experimental case study related to a historical brick masonry building located in Italy is presented to point out the additional information necessary to validate the results of the testing process

Atmospheric Compensation of PRISMA Data by Means of a Learning Based Approach

Atmospheric compensation (AC) allows the retrieval of the reflectance from the measured at-sensor radiance and is a fundamental and critical task for the quantitative exploitation of hyperspectral data. Recently, a learning-based (LB) approach, named LBAC, has been proposed for the AC of airborne hyperspectral data in the visible and near-infrared (VNIR) spectral range. LBAC makes use of a parametric regression function whose parameters are learned by a strategy based on synthetic data that accounts for (1) a physics-based model for the radiative transfer, (2) the variability of the surface reflectance spectra, and (3) the effects of random noise and spectral miscalibration errors. In this work we extend LBAC with respect to two different aspects: (1) the platform for data acquisition and (2) the spectral range covered by the sensor. Particularly, we propose the extension of LBAC to spaceborne hyperspectral sensors operating in the VNIR and short-wave infrared (SWIR) portion of the electromagnetic spectrum. We specifically refer to the sensor of the PRISMA (PRecursore IperSpettrale della Missione Applicativa) mission, and the recent Earth Observation mission of the Italian Space Agency that offers a great opportunity to improve the knowledge on the scientific and commercial applications of spaceborne hyperspectral data. In addition, we introduce a curve fitting-based procedure for the estimation of column water vapor content of the atmosphere that directly exploits the reflectance data provided by LBAC. Results obtained on four different PRISMA hyperspectral images are presented and discussed

Superradiancia en agujeros negros cargados : Cohete superradiante de agujero negro

El fenómeno de superradiancia en agujeros negros consiste en la absorción de información en forma de paquetes de onda, y al mismo tiempo la emisión de energía en forma de ondas planas monocromáticas por parte del agujero negro. Se investigó este fenómeno para campos escalares con carga cuando se coloca un espejo semiesférico concéntrico a un agujero negro estático y con carga. Se considera el sistema agujero negro-espejo inmerso en un baño térmico a una temperatura distinta a la del agujero negro. En primera instancia, se resolvió la ecuación de Klein-Gordon mínimamente acoplada para un campo escalar cargado en espacio curvo, dado por la métrica de Reissner-Nordström, obteniendo la condición de superradianza en el horizonte. Luego, se cuantizó el sistema teniendo en cuenta que el baño térmico sigue la estadística de Bose-Einstein y se calculó, mediante el tensor energía-momento del campo, el empuje total producido cuando los modos escalares emitidos por un agujero negro superradiante son reflejados por el espejo semiesférico. La forma que tiene el sistema junto al empuje obtenido nos permite describir este resultado como un "cohete superradiante de agujero negro'' (o simplemente cohete de agujero negro), el cual es resultado de un fenómeno clásico (superradianza) y no de un fenómeno cuántico (radiación Hawking) como se ha estudiado en la bibliografía. Por último, se analizaron numéricamente los resultados obtenidos tanto por la dispersión de un campo escalar como por el cohete de agujero negro en el baño térmico. En el caso de un campo escalar, obtenemos numéricamente las soluciones radiales que satisfacen las condiciones de contorno, luego proponiendo algunos valores para el campo incidente se observa una diferencia de comportamiento cerca del horizonte exterior del agujero negro (donde ocurre o no la superradianza). A partir de estos resultados, se determina la fuerza total del cohete de agujero negro en la cual se observa un pico para cierto valor del impulso k, donde existe una divergencia debido a la distribución de Bose-Einstein utilizada y que debe seguir siendo estudiada. Además, concluimos que la fuerza total obtenida es una primera aproximación y que para obtener un buen valor cuantitativo debe mejorarse en particular la aproximación numérica realizada sobre el índice azimutal cuántico m, ya que esta falla para ciertos valores.Facultad de Ciencias Exacta

Augustus Bridge in Narni (Italy): Seismic Vulnerability Assessment of the Still Standing Part, Possible Causes of Collapse, and Importance of the Roman Concrete Infill in the Seismic-Resistant Behavior

[EN] The final results of advanced FE analyses performed on a Roman arch bridge, namely the Augustus Bridge (Ponte di Augusto) in Narni, center Italy are presented. The bridge, one of the most impressive Roman artworks, has been injured by several traumatic events during the millennia, the result of which is its present ruined condition. The aims are manifold, starting from a better understanding of the causes at the base of the partial collapse occurred on the central pier, passing through a seismic assessment of the ruined still standing part and ending with a discussion on the role played by Roman concrete on the stability against horizontal actions. An advanced material model exhibiting damage, plastic deformation, and softening in both tension and compression is adopted for Roman concrete. Both the case of a foundation settlement of the central pier and the application of a seismic excitation are investigated, by means of nonlinear static and nonlinear dynamic analyses. Numerical simulations are carried out within the FE code ABAQUS by means of detailed 3D models, using historical documentation and previous results of the latest research carried out on materials, assuming realistic models on both the uniaxial stress-strain relationships under nonlinear load-unload conditions by using independent damage parameters in tension and compression, and the multiaxial behavior ruled by a regularized Drucker-Prager strength criterion. The methodological approach turns out to be potentially valid for all existing Roman bridges. Results highlight the vulnerability of the ruins, that the collapse of the central part was probably due to settlement of the central pier and that Roman concrete plays a crucial role in increasing the stability against earthquake actions.Bertolesi, E.; Milani, G.; Lopane, FD.; Acito, M. (2017). Augustus Bridge in Narni (Italy): Seismic Vulnerability Assessment of the Still Standing Part, Possible Causes of Collapse, and Importance of the Roman Concrete Infill in the Seismic-Resistant Behavior. International Journal of Architectural Heritage. 11(5):717-746. doi:10.1080/15583058.2017.1300712S71774611

Remineralization strategies in oral hygiene: a position paper of Italian Society of Oral Hygiene Sciences-S.I.S.I.O. working group

Background/Objective: The clinical conditions that lead to an alteration of the enamel structure are numerous. The diet high in sugars and acidifying substances, psychological stress that triggers parafunctional behaviors, the reduced intake of fiber-rich foods or alkalizing substances, together with other factors, contribute to demineralization of the tooth enamel. Dental mineralizing products on the current market are distinguished according to the dosage form, the active ingredient, the release technology, clinical indications and patient choice. Currently, it is necessary to propose to oral health professionals a guide to orient themselves in this chaotic choice, in order to prefer the most effective product for their own clinical target. Methods: Italian Society of Oral Hygiene Sciences-S.I.S.I.O. is one of the leading scientific Italian societies representing those dental hygienists working with high-quality standards and in agreement with scientific evidence: in the last year, the SISIO working group has carried out a study focused on remineralizing agents in dentistry, in order to give an authoritative point of view to indicate a guideline in the decision process of the choice of a remineralizing agent. We will report the results pointed out from the last consensus meeting in 2017. Results: We have reported the good the bad and the ugly have been discussed in a critical discussion of such topic. Conclusion: The SISIO experience has been reported in this position paper with the aim to serve as a useful aid in the daily choice of the clinical steps to perform, when dental professionals need to treat demineralized teeth. Keywords: Dental Hygiene, Oral health, Dental Remineralizing, Enamel, Toothpaste, Mouthwash