Low-Cost Sensors for Urban Noise Monitoring Networks—A Literature Review

Noise pollution reduction in the environment is a major challenge from a societal and health point of view. To implement strategies to improve sound environments, experts need information on existing noise. The first source of information is based on the elaboration of noise maps using software, but with limitations on the realism of the maps obtained, due to numerous calculation assumptions. The second is based on the use of measured data, in particular through professional measurement observatories, but in limited numbers for practical and financial reasons. More recently, numerous technical developments, such as the miniaturization of electronic components, the accessibility of low-cost computing processors and the improved performance of electric batteries, have opened up new prospects for the deployment of low-cost sensor networks for the assessment of sound environments. Over the past fifteen years, the literature has presented numerous experiments in this field, ranging from proof of concept to operational implementation. The purpose of this article is firstly to review the literature, and secondly, to identify the expected technical characteristics of the sensors to address the problem of noise pollution assessment. Lastly, the article will also put forward the challenges that are needed to respond to a massive deployment of low-cost noise sensors.

Experimental and Numerical Determination of the Required Initial Sheet Width in Die Bending

So far, determining the necessary precut dimensions of metal sheets prior to bending has been an unsolved question. During the last decades numerous calculation methods have been suggested. However, comparing these different methods indicates that different calculation methods suggest diverging precut dimensions. Especially in roll-forming, where multiple bend operations occur within the same bend part, these differences between several calculation methods can add up to some millimetres. The accuracy of presently available methods can hardly be compared. Thus an optimized method is needed. One possibility to determine the initial sheet width is identifying the position of the unlengthened layer in the bend zone. This study compares the position of the unlengthened layer determined in experiments and numerical simulations for different bend geometries and materials. The results indicate that even state of the art measuring technique is not accurate enough to determine the position of the unlengthened layer properly. Due to high measurement uncertainties, numerical simulations are required to assess the influence of geometry or material parameters on the position of the unlengthened layer. However, combining numerical and experimental results shows that the geometry of the bend part influences the position of the unlengthened layer and thus the required precut dimension. In contrast, a significant influence of material strength on the position of the unlegthened layer was not found.

Dynamic Response of Three-Layered Annular Plate with Imperfections

This paper presents the imperfection sensitivity of annular plate with three-layered structure. The plate composed of thin elastic facings and a thicker elastic core is loaded in facing plane. The classical issue of a three-layered plate was solved for dynamic deflection problem using the approximation methods: orthogonalization and finite difference. The solution includes the axisymmetric and asymmetric plate modes of the dynamic stability loss. The evaluation of the rate of plate sensitivity to imperfection of plate preliminary geometry has been enriched by the analysis of plate models built of finite elements. The ABAQUS program has been used. The numerous calculation results in the form of deflection characteristics, buckling modes, values of critical parameters create the view of response of dynamic plate structure with different rate of imperfection and linear in time loading growth, too.

Bestimmung der Zuschnittslänge beim Walzprofilieren von Kaltprofilen*/Calculation of initial sheet width in roll forming

Ein wesentlicher Schritt in der Produktionsplanung von walzprofilierten Kaltprofilen besteht in dem Ermitteln der Breite des benötigten Coils. Im Stand der Technik lassen sich hierzu zahlreiche Methoden finden, die sich in ihren Prognosen jedoch widersprechen und somit keine zuverlässige Bestimmung der abgewickelten Länge erlauben. Diese Arbeit zeigt einen Weg auf, wie durch experimentelle Versuche eine verbesserte Methode zum Bestimmen der abgewickelten Länge abgeleitet werden kann.   Determining the dimension of the initial blank sheet is a crucial step in planning roll forming processes. The state of the art provides numerous calculation methods for this, leading to different results and thus preventing the reliable determination of the unfolded length. This paper presents an approach for developing an improved calculation model for determining the initial sheet width by experimental analysis.

Comparison and Analysis of the Calculation Formulas for the Bearing Capacity of Concrete Filled Steel Tubular Columns

At present, many analysis methods and calculation formulas of the bearing capacity of concrete filled steel tubular columns have been researched. But these numerous calculation formulas of the bearing capacity have varied forms, and the application scope and the calculation precision of them are also quite different, which makes it difficult and confused for engineering designer to choose a suitable formula. Primary calculation formulas of the bearing capacity of concrete filled steel tubular columns are summarized. The calculation results of these formulas are compared with some test results of the concrete filled steel tubular columns with a large diameter. The applicability and the accuracy of these formulas are analyzed. Based on these comparisons and analyses, reasonable suggestion is given to select the suitable formula. Finally, one formula is provided to calculate the ultimate bearing capacity of concrete filled steel tubular columns reinforced with steel bars.

VEROAD: A Viscoelastic Multilayer Computer Program

The mathematical principles and derivation of a linear viscoelastic multilayer computer program are described. The principles of the derivation apply equally to conventional linear elastic programs. The practical consequences of the viscous material properties for the mathematical derivation have been solved by Fourier transformation; another mathematical consequence is that complex calculus was inevitable. The program is called VEROAD, (viscoelastic road analysis Delft). The program's primary extension is that the analyzed material can be vis-coelastic. Consequences of this extension are numerous: calculation from physical material properties of quantities such as time-dependent displacements, stresses and strains, permanent deformations, and dissipated energies is made possible. All these quantities depend on velocity of traffic, which is explicitly included in the calculations. The material model assumes the bulk modulus to be elastic and the shear modulus to be viscoelastic. The latter follows Burger's model. For illustrative purposes some mechanical analyses of asphaltic road structures are carried out, with emphasis on the distribution of stresses, strains, (permanent) deformations, and dissipated energies.