Local sensitivity analysis for compositional data with application to soil texture in hydrologic modelling

Compositional data, such as soil texture, are hard to deal with in the geosciences as standard statistical methods are often inappropriate to analyse this type of data. Especially in sensitivity analysis, the closed character of the data is often ignored. To that end, we developed a method to assess the local sensitivity of a model output with resect to a compositional model input. We adapted the finite difference technique such that the different parts of the input are perturbed simultaneously while the closed character of the data is preserved. This method was applied to a hydrologic model and the sensitivity of the simulated soil moisture content to local changes in soil texture was assessed. Based on a high number of model runs, in which the soil texture was varied across the entire texture triangle, we identified zones of high sensitivity in the texture triangle. In such zones, the model output uncertainty induced by the discrepancy between the scale of measurement and the scale of model application, is advised to be reduced through additional data collection. Furthermore, the sensitivity analysis provided more insight into the hydrologic model behaviour as it revealed how the model sensitivity is related to the shape of the soil moisture retention curve

Using a biomechanical model for tongue tracking in ultrasound images

International audienceWe propose in this paper a new method for tongue tracking in ultrasound images which is based on a biomechanical model of the tongue. The deformation is guided both by points tracked at the surface of the tongue and by inner points of the tongue. Possible uncertainties on the tracked points are handled by the algorithm. Experiments prove that the method is efficient even in case of abrupt movements

Synergy Parks: collaborative strategies to valorise side streams between companies

This document is part of the deliverables for ARBOR, an Interreg IVB project for North-West Europe. ARBOR stands for Accelerating Renewable Energies through valorisation of Biogenic Organic Raw Material. Various of the projects consider multi-stakeholder collaborations, with or without a financial share of ARBOR in the project realisation. This project runs from 2011 till 2015. The framework for ARBOR are the EU 202020 targets in order to reduce climate change and the fact that biomass accounts for 50% of the renewables in Europe. Although a lot of expertise concerning biomass is available, it is noted that this information is not disseminated in a coordinated way, nor is it related to commercial exploitations. That is why the ARBOR-mission is to accelerate the sustainable development and use of biomass in North West Europe, to facilitate the achievement of the EU 202020 objectives. The increasing competition and environmental pressure and growing demand for food and resource efficiency requires cooperation and collaboration between agriculture and other business (Smeets, 2009) especially in the highly populated NWE. When companies systematically cooperate to achieve more sustainable biomass utilization through creating production synergies, we call this a synergy park. Ideally, synergy parks can be called a system innovation, that bring new technical, commercial, institutional, and social connections geared towards sustainable development. Ongoing collaboration and advice on stakeholder management should improve the synergy park composition, to the benefit of optimal biomass valorisation and energy efficiency. This report aims to describe outputs of ARBOR action 5 on Synergy parks, within individual ARBOR-regions. Following an initial meeting on the matter in Stoke-on-Trent, format with leading questions were circu-lated and filled out by the partners as far as possible for their single case

Articulatory copy synthesis from cine X-ray films

International audienceThis paper deals with articulatory copy synthesis from X-ray films. The underlying articulatory synthesizer uses an aerodynamic and an acoustic simulation using target area functions, F0 and transition patterns from one area function to the next as input data. The articulators, tongue in particular, have been delineated by hand or semi-automatically from the X-ray films. A specific attention has been paid on the determination of the centerline of the vocal tract from the image and on the coordination between glottal area and vocal tract constrictions since both aspects strongly impact on the acoustics. Experiments show that good quality speech can be resynthesized even if the interval between two images is 40\,ms. The same approach could be easily applied to cine MRI data

Prediction of water retention of soils from the humid tropics by the nonparametric k-nearest neighbor approach

Nonparametric approaches such as the k-nearest neighbor (k-NN) approach are considered attractive for pedotransfer modeling in hydrology; however, they have not been applied to predict water retention of highly weathered soils in the humid tropics. Therefore, the objectives of this study were: to apply the k-NN approach to predict soil water retention in a humid tropical region; to test its ability to predict soil water content at eight different matric potentials; to test the benefit of using more input attributes than most previous studies and their combinations; to discuss the importance of particular input attributes in the prediction of soil water retention at low, intermediate, and high matric potentials; and to compare this approach with two published tropical pedotransfer functions (PTFs) based on multiple linear regression (MLR). The overall estimation error ranges generated by the k-NN approach were statistically different but comparable to the two examined MLR PTFs. When the best combination of input variables (sand + silt + clay + bulk density + cation exchange capacity) was used, the overall error was remarkably low: 0.0360 to 0.0390 m(3) m(-3) in the dry and very wet ranges and 0.0490 to 0.0510 m(3) m(-3) in the intermediate range (i.e., -3 to -50 kPa) of the soil water retention curve. This k-NN variant can be considered as a competitive alternative to more classical, equation-based PTFs due to the accuracy of the water retention estimation and, as an added benefit, its flexibility to incorporate new data without the need to redevelop new equations. This is highly beneficial in developing countries where soil databases for agricultural planning are at present sparse, though slowly developing

Global sensitivity analysis in hydrological modeling: Review of concepts, methods, theoretical framework, and applications

Sensitivity analysis (SA) aims to identify the key parameters that affect model performance and it plays important roles in model parameterization, calibration, optimization, and uncertainty quantification. However, the increasing complexity of hydrological models means that a large number of parameters need to be estimated. To better understand how these complex models work, efficient SA methods should be applied before the application of hydrological modeling. This study provides a comprehensive review of global SA methods in the field of hydrological modeling. The common definitions of SA and the typical categories of SA methods are described. A wide variety of global SA methods have been introduced to provide a more efficient evaluation framework for hydrological modeling. We review, analyze, and categorize research into global SA methods and their applications, with an emphasis on the research accomplished in the hydrological modeling field. The advantages and disadvantages are also discussed and summarized. An application framework and the typical practical steps involved in SA for hydrological modeling are outlined. Further discussions cover several important and often overlooked topics, including the relationship between parameter identification, uncertainty analysis, and optimization in hydrological modeling, how to deal with correlated parameters, and time-varying SA. Finally, some conclusions and guidance recommendations on SA in hydrological modeling are provided, as well as a list of important future research directions that may facilitate more robust analyses when assessing hydrological modeling performance

A Wavelet-Based Processing method for simultaneously determining ultrasonic velocity and material thickness

International audienceMethods of measuring ultrasonic wave velocity in an elastic sample require data on the thickness of the sample and/or the distances between the transducers and the sample. The uncertainty of the ultrasonic wave velocity measurements generally depends on that of the data available. Conversely, to determine the thickness of a material, it is necessary to have a priori information about the wave velocity. This problem is particularly hard to solve when measuring the parameters of biological specimens such as bones having a greater acoustical impedance contrast (typically 3-5 MRayl) than that of the surrounding soft tissues (typically 1.5 MRayl). Measurements of this kind cannot easily be performed. But obtaining the thickness of a bone structure and/or the ultrasonic wave velocity is a important problem, for example, in biomechanical field for the calculation of elastic modulus, or in acoustical imaging field to parameterize the images, and to reference the grey or color level set to a physical parameter. The aim of the present study was to develop a method of simultaneously and independently determining the velocity of an ultrasonic wave in an elastic sample and the wave path across the thickness of this sample, using only one acquisition in pure transmission mode. The new method, which we have called the ''Wavelet-Based Processing'' method, is based on the wavelet decomposition of the signals and on a suitable transmitted incident wave correlated with the experimental device, and the mathematical properties such as orthonormality, of which lend themselves well to the time-scale approach. By following an adapted algorithm, ultrasonic wave velocities in parallelepipedic plates of elastic manufactured material and the apparent thicknesses were both measured using a water tank, a mechanical device and a matched pair of 1 MHz ultrasonic focused transducers having a diameter of 3 mm, a focal length of 150 mmand beam width of 2 2 mmat the focus (mean temperature 22 ). The results were compared with those obtained with a conventional Pulse-mode method and with the control values, to check their validity. Measurements performed on bovine and human dry cortical bone samples are also presented to assess the limitations of the method when it is applied to elastic biological samples, including those of an equal-wavelength size ( 1.5 mm). The thicknesses and the ultrasonic wave velocities were then measured in this kind of (quasi-) parallelepipedic elastic materials with an mean estimated error ranged from 1% to 3.5% compared to the referenced values

'Exchange bias' in Co/CoO bilayers en de invloed van gereduceerde laterale afmetingen

status: publishe