1,721,273 research outputs found
Statistical analysis of Sound Reduction Index measurements on typical Italian lightweight concrete block walls
No full textItalian buildings are typically realized in heavy masonry walls both for internal partitions and for façades. The most common construction technology for internal partitions is the brick masonry realized both with single layer and with double layer walls. The sound reduction index of these partitions, made in the past century, was hardly greater than 50 decibels. As a consequence of these poor acoustic performances and after the publication of the first Italian law on the acoustic performances of buildings, in the first decade of the new century there was a great evolution in sound insulation of internal walls. In particular, in recent years lightweight concrete block walls have had an increased diffusion as a consequence of their good acoustic performances and their simple building procedures. The research carried out by the Universities of Ferrara and Firenze, supported by the Italian national association of expanded clay, concerns the sound reduction index measurements of about one hundred different lightweight concrete block walls, realized in a great number of building yards. The statistical analysis of measurement results shows the stability of the acoustic performance of this technology and points out the more common realization errors and their typical influence on the acoustic performance of internal walls
Multiple solutions for Schrödinger equations on Riemannian manifolds via -theorems
No full textWe study multiple solutions for Schrödinger equations on Riemannian
manifolds via ∇-theorems
Acoustic Measurements on a 1:1 Scale Model of a Shading System for Building Façade in a Semi-Anechoic Chamber
No full textIn many buildings shading systems are installed over the façades to enhance both the thermal and the visual comfort of the inhabitants, especially when large windows or curtain walls are used. Although the use of the brise-soleil systems is quite widespread, their acoustic effects on the sound pressure level (SPL) on the building façades and in the urban environment are generally not considered.
This work presents the results of an investigation on a shading system model, in scale 1:1, carried out in a semi-anechoic chamber. The intention of this study was to analyse the changes in SPL given by the presence of the louvres, both on the façade plane (simulated by the floor of the chamber) and at 2 m from it.
Measurements were performed using three different sound source positions and three tilt angles of the louvres. The acoustic behaviour of the system was evaluated with various configurations using louvres without and with sound absorptive material attached to their lower sides.
The measurements highlighted an increase in SPL over the “façade” when the standard louvres are installed, while the sound absorptive louvres give an evident SPL reduction on the façade plane and at 2 m from it.In many buildings shading systems are installed over the façades to enhance both the thermal and the visual comfort of the inhabitants, especially when large windows or curtain walls are used. Although the use of the brise-soleil systems is quite widespread, their acoustic effects on the sound pressure level (SPL) on the building façades and in the urban environment are generally not considered. This work presents the results of an investigation on a shading system model, in scale 1:1, carried out in a semi-anechoic chamber. The intention of this study was to analyse the changes in SPL given by the presence of the louvres, both on the façade plane (simulated by the floor of the chamber) and at 2 m from it. Measurements were performed using three different sound source positions and three tilt angles of the louvres. The acoustic behaviour of the system was evaluated with various configurations using louvres without and with sound absorptive material attached to their lower sides. The me..
Facade sound insulation: Experimental analysis of different solutions
No full textThe sound insulation of building façade is one of the most important parameters of acoustic performance required for building elements. The choice of particular technical solutions depends on the specific limits set by national rules and regulations, and it is strictly correlated to other environmental parameters, like indoor lighting and ventilation. From this point of view particular cases are analysed, such as schools, hospital, or buildings near public infrastructures (railways, airports). In this paper a critical analysis of different façade sound insulation solutions is presented correlated to national regulations and to experimental data, with particular regard to measurement techniques. Comparison with theoretical predictions according to the method proposed by EN 12354 are also reported
On critical Kirchhoff problems driven by the fractional Laplacian
Full text linkWe study a nonlocal parametric problem driven by the fractional Laplacian operator combined with a Kirchhoff-type coefficient and involving a critical nonlinearity term in the Sobolev embedding sense. Our approach is of variational and topological nature. The obtained results can be viewed as a nontrivial extension to the nonlocal setting of some recent contributions already present in the literature
Intertwining solutions for magnetic relativistic Hartree type equations
No full textWe consider the magnetic pseudo-relativistic Schrödinger equation √(-i∇ - A(x))2 + m2u + V(x)u = (Iα ∗ |u|p)|u|p-2u, in RN where N ≥ 3, m > 0, V: RN → R is an external continuous scalar potential, A: RN →N is a continuous vector potential and Iα(x) = cN, α/|x|N-α (x ≠ 0) is a convolution kernel, cN,α > 0 is a constant, 2 ≤ p < 2N/(N-1), (N - 1) p - N < α < N. We assume that A and V are symmetric with respect to a closed subgroup G of the group O(N) of orthogonal linear transformations of RN. If for any x ∈ RN \ {0}, the cardinality of the G-orbit of x is infinite, then we prove the existence of infinitely many intertwining solutions assuming that A(x) is either linear in x or uniformly bounded. The results are proved by means of a new local realization of the square root of the magnetic laplacian to a local elliptic operator with Neumann boundary condition on a half-space. Moreover we derive an existence result of a ground state intertwining solution for bounded vector potentials, if G admits a finite orbit
Schr\"odinger equation on Cartan-Hadamard manifolds with oscillating nonlinearities
Full text linkWe study the equation on a
-dimensional homogeneous Cartan-Hadamard Manifold with . Without using the theory of topological indices, we prove the existence of
infinitely many solutions for a class of nonlinearities which have an
oscillating behavior either at zero or at infinity
Analisi sperimentale dell’efficacia di sistemi frangisole per ridurre la pressione sonora in facciata
No full textL’utilizzo di sistemi frangisole è largamente diffuso nei nuovi edifici, ma le verifiche sul loro effetto sul campo sonoro in facciata sono ancora piuttosto limitate. Questo lavoro illustra i risultati di uno studio condotto in una camera semi-anecoica su un modello in scala reale di una porzione di facciata dotata di sistemi frangisole. Lo scopo era quello di verificare l’influenza sul livello sonoro in facciata di sistemi frangisole in differenti configurazioni (lamelle diversamente inclinate, con o senza rivestimento fonoassorbente). Le misure evidenziano che i frangisole con lamelle fonoassorbenti possono ridurre significativamente il livello sonoro sul piano della facciata.
------
The use of shading systems is quite widespread in new buildings, but their acoustic effect on the sound pressure level on building façades has generally not been considered. This work presents the results of an investigation on a 1:1 scale model of a louvers system, carried out in a semi-anechoic chamber. The aim was to analyze the changes in SPL on the façade given by the presence of the louvers in different configurations (three tilt angles of the louvers, with or without sound absorptive material). The measurements highlighted a slight increase in SPL on the façade when the standard louvers were installed, while the sound absorptive material gave an evident SPL reduction on the façade
- …
