Estimates for functions of the Laplace operator on homogeneous trees

In this paper, we study the heat equation on a homogeneous graph, relative to the natural (nearest–neighbour) Laplacian. We find pointwise estimates for the heat and resolvent kernels, and the L p − L q L^{p}-L^{q} mapping properties of the corresponding operators

Tensile behaviour of FRC under high strain-rate

This paper presents experimental results on two types of concrete reinforced with steel and polyvinyl-alcohol (PVA) fibres subjected to dynamic tensile loading. The tests were carried out by using a Modified Hopkinson Bar apparatus on fibre reinforced concrete notched-specimens under three different strain-rates (50, 100, and 200s−1). From the experiments it was found that there is a significant enhancement in tensile strength with increasing strain-rates. The dynamic tests on steel FRC with the smaller loading rate (50s−1) showed a strength similar to the one measured from static tests; however, for increasing loading rates, a remarkable decrease of post-peak strength and ductility occurs. In specimens with PVA fibres, an enhancement of the tensile strength was also observed and a significant reduction of fracture energy and ultimate deformation occurred. Some experimental aspects are also discussed as the specimen shape, its dimension, the loading rate as well as the different post-peak behaviour from static and dynamic test

optimization of gfrp reinforcement in precast segments for metro tunnel lining

The possibility of replacing the traditional steel reinforcement with glass fiber reinforced polymer (GFRP) cages in precast concrete tunnel segmental lining has been shown by the authors in previous papers. The use of GFRP rebars as structural reinforcement in precast tunnel segments, allows several advantages in terms of structural durability or in cases of temporary lining that will have to be demolished later. Furthermore, this reinforcement type can be a suitable solution to create dielectric joints, ensuring the interruption of possible stray currents, which often lead to corrosion problems. Nevertheless, this peculiar application requires curvilinear shape of the reinforcement, and then different production process and rebar geometries. In the present work, a suggestion for the optimization of the GFRP reinforcement for tunnel segment is given. Four different GFRP cage typologies are analysed and applied as a reinforcement in full-scale tunnel segments. Both bending and point load tests are developed and the structural performances of the specimens are compared and discussed. Finally, the best solution, in terms of cost-benefit analysis is proposed

Quantifying backflash radiation to prevent zero-error attacks in quantum key distribution

Single-photon avalanche diodes (SPADs) are the most widespread commercial solution for single-photon counting in quantum key distribution applications. However, the secondary photon emission that arises from the avalanche of charge carriers that occurs during the detection of a photon may be exploited by an eavesdropper to gain information without inducing errors in the transmission key. In this paper, we characterize such backflash light in gated InGaAs/InP SPADs and discuss its spectral and temporal characterization for different detector models and different operating parameters. We qualitatively bound the maximum information leakage due to backflash light and propose solutions for preventing such leakage

Quantifying backflash radiation to prevent zero-error attacks in quantum key distribution

Single-photon avalanche diodes (SPADs) are the most widespread commercial solution for single-photon counting in quantum key distribution applications. However, the secondary photon emission that arises from the avalanche of charge carriers that occurs during the detection of a photon may be exploited by an eavesdropper to gain information without inducing errors in the transmission key. In this paper, we characterize such backflash light in gated InGaAs/InP SPADs and discuss its spectral and temporal characterization for different detector models and different operating parameters. We qualitatively bound the maximum information leakage due to backflash light and propose solutions for preventing such leakage

Fire behaviour of non-load bearing double stud cold-formed steel frame walls

This work investigates the behaviour of Double stud Light Steel Frame (LSF) walls under ISO834 standard fire through a series of experimental tests. The walls were covered on both sides with one or two fire-resistant gypsum plasterboards (Type F), and the cavity of the steel frame was either empty, partially or fully insulated with ceramic fibre. The fire resistance of the assemblies is improved due to the existence of a wider cavity, the employment of additional gypsum plasterboard layers and the use of ceramic fibre cavity insulation. In partially insulated assemblies, significantly higher fire resistance is achieved when the ceramic fibre is placed towards the fire-exposed gypsum plasterboard. Moreover, the number of studs in contact with the unexposed gypsum plasterboard affects the fire resistance of the specimens. The experimental data acquired is useful to conduct further numerical analyses and experimental studies, as well as to understand the unique thermal behaviour of different configurations of double stud LSF walls at elevated temperatures.info:eu-repo/semantics/publishedVersio

Sobre la relación de intensidades características del espectro K de rayos X

La variación de la energía de transición de un elemento en función de su número de coordinación, es un parámetro que proporciona información sobre la estructura electrónica de un elemento en diferentes compuestos, por lo que ha sido estudiado con especial interés. En este trabajo se demuestra que la relación de intensidades entre las líneas características de un elemento en diferentes tipos de enlace, es un parámetro sensible con respecto a la estructura electrónica. Esto se prueba en los casos del Si y Al.The variation of the transiction energy of an element in function of bis coordination number, is a parameter that gives information about the electronic structure of an element in different compounds. This aspect has been studied with special interest. In this work it has been outlined that the relation of intensities between the characteristic lines of an element in different chemical bounds is a sensitive parameter comported with the electronic structure. It has been proved in the cases of silicium and aluminium

A methodology for the evaluation of morphology-based constitutive laws of corroded steel rebars

The assessment of degraded reinforced concrete (RC) existing structures is nowadays a topical problem since several ones have an age close to or higher than their design life. The degradation state of the structure needs to be properly assessed and included in the adopted numerical or analytical models. In this framework, rebars corrosion phenomena can modify the structural behavior of RC members, especially when the corrosive attack is localized in specific areas. As an example, in presence of localized concentrations of chlorides, pitting corrosion of the steel bars occurs, with a localized reduction of the bar section through pits. In this work, the results of a preliminary experimental survey performed on artificially corroded steel rebars are shown, to define an integrated methodology for the definition of material constitutive laws, accounting for morphological aspects of the corrosion phenomenon. A set of steel rebars, embedded in concrete prisms, have been artificially corroded with an accelerated process through electrolytic cells, to obtain local marked pits. The steel rebars have been extracted, cleaned, weighed and subjected to 3D scanning using two different techniques (one based on laser scanning and the other based on structured-light scanning) to evaluate the effective corrosion amount and morphology. Finally, tensile tests were carried out to evaluate the stress-strain curves and the values of yielding, ultimate strengths and elongation to fracture. The presented data and methodology can represent a useful reference for the definition of phenomenological constitutive laws for steel rebars affected by pitting corrosion