Individual Listening Zone with Frequency-Dependent Trim of Measured Impulse Responses

Acoustic Contrast Control (ACC) has been widely used to achieve individual audio delivery in shared environments. The effectiveness of this method is reduced when the control is performed in reverberant environments. Even if control filters are computed using measured transfer functions, the robustness of the system is affected by the presence of reverberation in the plant matrix. In this paper a new optimization method is presented to improve the ACC algorithm by applying a frequency-dependent windowing of the measured impulse response used for the filter computation, thus removing late reflections. The effects of this impulse response optimization are presented by means of sound zoning results obtained from experimental measurements performed in a car cabin

Exploitation of large archives of ERS and ENVISAT C-band SAR data to characterize ground deformations

In the last few years, several advances have been made in the use of radar images to detect, map and monitor ground deformations. DInSAR (Differential Synthetic Aperture Radar Interferometry) and A-DInSAR/PSI (Advanced DInSAR/Persistent Scatterers Interferometry) technologies have been successfully applied in the study of deformation phenomena induced by, for example, active tectonics, volcanic activity, ground water exploitation, mining, and landslides, both at local and regional scales. In this paper, the existing European Space Agency (ESA) archives (acquired as part of the FP7-DORIS project), which were collected by the ERS-1/2 and ENVISAT satellites operating in the microwave C-band, were analyzed and exploited to understand the dynamics of landslide and subsidence phenomena. In particular, this paper presents the results obtained as part of the FP7-DORIS project to demonstrate that the full exploitation of very long deformation time series (more than 15 years) can play a key role in understanding the dynamics of natural and human-induced hazards. © 2013 by the authors

Workers in the crowd : the labour market impact of the online platform economy

We compare individuals engaged in online crowdwork against workers in traditional occupations from the US and EU, investigating the determinants of access into crowd employment and the nature of the deterioration of salary conditions and job quality characterising these markets. We do so by matching responses from comparable working conditions surveys, and controlling for most individual and socio-economic characteristics affecting pay. We find that most differences in earnings are largely unexplained by the ability of individuals, and that labour in crowdwork is vastly under-utilised.Peer reviewe

Piecework and Job Search in the Platform Economy

The massive growth of jobs in the platform economy has reignited a long-standing debate on the wage elasticity of labour supply for the self-employed. Overwhelming empirical evidence seems to suggest that workers in the platform economy will work more hours than they wish to, for a lower wage, suggesting a backward-bending labour supply curve. Is this puzzling outcome explained by target earning behaviour or rather by the uncertainty arising from task search? In this paper, we test these hypotheses making use of new data on on-location and online platform workers earning on a piece-rate basis in the EU, exploiting search shocks in a difference-in-differences strategy to reassess the wage elasticity of labour supply. We find that uncertainty in search plays a central role in inflating hours of work, revealing a positive and inelastic wage elasticity for all platform workers. On average, a percentage increase in job search leads to a net loss in income, suggesting that piecework might be an endemic source of demand surplus for monopsonistic markets

Workers in the Crowd: The Labour Market Impact of the Online Platform Economy

In this paper, we compare wages and labor market conditions of individuals engaged in online platform work and in traditional occupations by exploiting individual-level survey data on crowdworkers belonging to the largest micro-task marketplaces, focusing on evidence from the United States and Europe. To match similar individuals, survey responses of crowdworkers from the US and EU have been harmonised with the American Working Conditions Survey (AWCS) and the European Working Conditions Survey (EWCS). Our findings indicate that traditional workers retain a significant premium in their earnings with respect to online platform workers, and that those differences are not affected by the observed and unobserved ability of individuals. This holds true also taking into account similar levels of routine intensity and abstractness in their jobs, as well as the time spent working. Moreover, labour force in crowdworking arrangements appears to suffer from high levels of under-utilisation, with crowdworkers being more likely to be left wanting for more work than comparable individuals

Individual listening zone with frequency-dependent trim of measured impulse responses

Acoustic Contrast Control (ACC) has been widely used to achieve individual audio delivery in shared environments. The effectiveness of this method is reduced when the control is performed in reverberant environments. Even if control filters are computed using measured transfer functions, the robustness of the system is affected by the presence of reverberation in the plant matrix. In this paper a new optimization method is presented to improve the ACC algorithm by applying a frequency-dependent windowing of the measured impulse response used for the filter computation, thus removing late reflections. The effects of this impulse response optimization are presented by means of sound zoning results obtained from experimental measurements performed in a car cabin

A Comparison of Shell Theories for Vibration Analysis of Single-Walled Carbon Nanotubes Based on an Anisotropic Elastic Shell Model

In the present paper, a comparison is conducted between three classical shell theories as applied to the linear vibrations of single-walled carbon nanotubes (SWCNTs); specifically, the evaluation of the natural frequencies is conducted via Donnell, Sanders, and Flügge shell theories. The actual discrete SWCNT is modelled by means of a continuous homogeneous cylindrical shell considering equivalent thickness and surface density. In order to take into account the intrinsic chirality of carbon nanotubes (CNTs), a molecular based anisotropic elastic shell model is considered. Simply supported boundary conditions are imposed and a complex method is applied to solve the equations of motion and to obtain the natural frequencies. Comparisons with the results of molecular dynamics simulations available in literature are performed to check the accuracy of the three different shell theories, where the Flügge shell theory is found to be the most accurate. Then, a parametric analysis evaluating the effect of diameter, aspect ratio, and number of waves along the longitudinal and circumferential directions on the natural frequencies of SWCNTs is performed in the framework of the three different shell theories. Assuming the results of the Flügge shell theory as reference, it is obtained that the Donnell shell theory is not accurate for relatively low longitudinal and circumferential wavenumbers, for relatively low diameters, and for relatively high aspect ratios. On the other hand, it is found that the Sanders shell theory is very accurate for all the considered geometries and wavenumbers, and therefore, it can be correctly adopted instead of the more complex Flügge shell theory for the vibration modelling of SWCNTs

Characterization of the ECN spray A in different facilities. Part 1: boundary conditions characterization

The Engine Combustion Network (ECN) community has greatly contributed to improve the fundamental understanding of spray atomization and combustion at conditions relevant to internal combustion engines. In this context, standardized spray experiments have been defined to facilitate the comparison of experimental and simulation studies performed in different facilities and with different models. This operating mode promotes collaborations among research groups and accelerates the advancement of research on spray. In efforts to improve the comparability of the ECN spray A experiments, it is of high importance to review the boundary conditions of different devices used in the community. This work is issued from the collaboration in the ECN France project, where two new experimental facilities from PPRIME (Poitiers) and PRISME (Orleans) institutes are validated to perform spray A experiments. The two facilities, based on Rapid Compression Machine (RCM) design, have been investigated to characterize their boundary conditions (e.g., flow velocity as well as fuel and gas temperatures). A set of standardized spray experiments were performed to compare their results with those obtained in other facilities, in particular the Constant Volume Pre-burn (CVP) vessel at IFPEN. It is noteworthy that it is the first time that RCM type facilities are used in such a way within the ECN. This paper (part 1) focuses on the facilities description and the fine characterization of their boundary conditions. A further paper (part 2) will present the results obtained with the same facilities performing ECN standard spray A characterizations. The reported review of thermocouple thermometry highlights that it is necessary to use thin-wires and bare-bead junction as small as possible. This would help to measure the temperature fluctuations with a minimal need for error corrections, which are highly dependent on the proper estimation of the velocity through the junction, and therefore it may introduce important uncertainties. Temperature heterogeneities are observed in all spray A devices. The standard deviation of the temperature distribution at the time of injection is approximately 5%. We report time-resolved temperature measurement from PPRIME RCM, performed in the near nozzle area during the injection. In inert condition, colder gases from the boundary layer are entrained toward the mixing area of the spray causing a further deviation from the target temperature. This emphasizes the importance of the temperature in the boundary (wall) layer. In reacting condition, the temperature of these entrained gases increases by the effect of the increased pressure, as the RCM has a relatively small volume. Generally, the velocity and turbulence levels are an order of magnitude higher in RCM and constant pressure flow compared to CVP vessels. The boundary characterization presented here will be the base for discussing spray behavior in the part 2 of this paper

Characterization of the ECN spray A in different facilities. Part 2: spray vaporization and combustion

One of the objective of Engine Combustion Network (ECN), (https://ecn.sandia.gov