Numerical modeling of underwater parametric propagation to detect buried objects

In underwater acoustics, detection of buried objects in sediments (cables, mines,…) is a complex problem. One reason is that acoustic attenuation in these sediments increases with frequency. To ensure sufficient penetration depth in marine sediments, low frequencies have to be used, implying a low resolution. A solution proposed to solve this problem is the parametric emission based on the nonlinear properties of the propagation medium. This method can generate a low frequency wave from two directional high frequencies beams. The parametric propagation is simulated in seawater and marine sediments. The model developed is based on the fractional-step numerical method introduced by Christopher and Parker [1]. In this method, the normal particle velocity is calculated plane by plane from the surface of the transducer to a specified distance. The effects of nonlinearity, attenuation and diffraction are calculated independently for each spatial step. Moreover, to reduce the number of spatial steps, a second order operator splitting scheme is used. The diffraction computation is based on a method of angular spectrum in the frequency domain where the field across a source plane is described by a spatial frequency distribution. To improve code stability, the effects of nonlinearity and attenuation are calculated and associated in shorter propagation substeps. At the interface between water and marine sediments, the transmission conditions are applied. Several tests have been carried out in different configurations (changing the primary frequencies, the parametric frequency, the source geometry, the inclination of the source with the interface, the focal distance,…). The 3D velocity field is calculated in each case, thereby allowing to know the directivity of the source, the velocity amplitude in sediments and the performance

An indicator-based assessment framework to identify country-specific challenges towards greener grow

The paper sets the basis for an indicator-based analytical framework to assess Member States' policies to promote "green growth".An illustrative application of this new analytical framework reveals that it can be used to provide a nuanced economic assessment of Member States' environmental performance. This framework can serve to highlight country-specific strengths in addressing environmental challenges in a way that best fosters growth and jobs. To prepare for future economic policy monitoring at the EU level, a test was also run to analyse performance in various dimensions of environmental policy in combination with information about macroeconomic performance.Overall, this framework can contribute to identify country-specific challenges to create new sources of green growth; it may therefore serve to encourage relevant structural reforms bringing about a competitive greener economy.europa european commission institutions news calendar organisation commissioners president recruitment contact services european union eu

The parametric propagation in underwater acoustics : experimental results

In underwater acoustics, detection of buried objects in sediments (cables, mines, . . . ) is a complex problem. Indeed, in order to ensure sufficient penetration depth in marine sediments, low frequencies have to be used, implying a low resolution. A solution proposed to solve this problem is the parametric emission based on the nonlinear properties of seawater. This method can generate a low frequency wave from two directional high frequencies beams. The aim of this work is to present experimental results of a parametric propagation. Experiments have been carried out in a water tank in various configurations. These experimental measurements are then compared with simulation results obtained with a numerical model based on a fractional-step method presented at the Underwater Acoustic Measurements conference in 2011

Reply to comment of Legates et al.

In the previous comment, Legates et al. express concern about the statistical reliability of the positive runoff–temperature relationship presented by Labat et al. We are grateful for this opportunity to respond to these concerns. As Legates et al. correctly points out, the effect of temperature on runoff is a complex relationship, which involves precipitation, evaporation, anthropomorphic affects, among others. As such, the effect of increased temperature on runoff is strongly dependent on the identity of the watershed of interest. For example, a watershed located in a glaciated region, such as Iceland, exhibits a strong positive correlation between runoff and temperature, whereas a watershed located in a arid climate, such as the Sahara desert, exhibits a negative correlation; often there is no run off at all during the summer months in such watersheds

Evidence for global runoff increase related to climate warming

Ongoing global climatic change initiated by the anthropogenic release of carbon dioxide is a matter of intense debate. We focus both on the impact of these climatic changes on the global hydrological cycle and on the amplitude of the increase of global and continental runoff over the last century, in relation to measured temperature increases. In this contribution, we propose an original statistical wavelet-based method for the reconstruction of the monthly discharges of worldwide largest rivers. This method provides a data-based approximation of the evolution of the annual continental and global runoffs over the last century. A consistent correlation is highlighted between global annual temperature and runoff, suggesting a 4% global runoff increase by 1 C global temperature rise. However, this global trend should be qualified at the regional scale where both increasing and decreasing trends are identified. North America runoffs appear to be the most sensitive to the recent climatic changes. Finally, this contribution provides the first experimental data-based evidence demonstrating the link between the global warming and the intensification of the global hydrological cycle. This corresponds to more intense evaporation over oceans coupled to continental precipitation increase or continental evaporation decrease. This process finally leads to an increase of the global continental runoff

What is the growth potential of green innovation? An assessment of EU climate policy options

This paper provides a model-based analysis of the cost-efficiency of different EU climate policy options that could direct innovation in the private sector towards an environmentally sustainable growth path. Our objective is to assess different policy options in order to identify an appropriate policy-mix of environmental and innovation market instruments in terms of their cost-effectiveness. For this purpose, we develop a fully-dynamic, multisectoral DSGE model with endogenous technological change where we specifically identify its environmental content and we calibrate the model for the EU and the rest of the world. Our results suggest that an appropriate policy mix should intensively stimulate R&D in the green sectors in the short-run and phase-it out by spreading the R&D support to all sectors of the economy in the medium-term. Although intuitive, the orders of magnitude presented in this paper should be interpreted with caution by taking into account the underlying assumptions of the model and identification of green innovation data.Carbon revenue recycling, climate change, directed technical change, double dividend, dynamic general equilibrium model, endogenous growth, R&D

The Dreaded Performance Appraisal: Can the Process Ever be Comfortable?

Previous research has indicated that individuals dislike and resist the performance appraisal process. Fewer studies have examined reasoning for unintentional rating distortion that may result from a lack of training and clear understanding of how to effectively evaluate behaviors. Researchers have shown that the appraisal process is uncomfortable for raters, but empirical studies have yet to explore how to reduce this discomfort. Rater training research has revealed that trained raters have improved observational skills, a more precise vocabulary to describe behaviors, and improved rating accuracy. This research explored the relationship between performance appraisal discomfort and trait motivational factors (i.e., personality and self-efficacy) and rater behavior (i.e., leniency and accuracy), along with the impact of the experience of training. Additionally, these studies investigated whether performance appraisal discomfort could be reduced after experiencing rater training (specifically, Frame-of-Reference training). Results revealed that individual difference variables (personality and self-efficacy) were not consistently related to ratings of discomfort; however, rater training was found to be an effective mechanism for reducing discomfort with making performance ratings. Future research ideas and practical implications are discussed