Open-ended coaxial probe measurements of complex dielectric permittivity in diesel-contaminated soil during bioremediation

In the bioremediation field, geophysical techniques are commonly applied, at lab scale and field scale, to perform the characterization and the monitoring of contaminated soils. We propose a method for detecting the dielectric properties of contaminated soil during a process of bioremediation. An open-ended coaxial probe measured the complex dielectric permittivity (between 0.2 and 20 GHz) on a series of six soil microcosms contaminated by diesel oil (13.5% Voil /Vtot ). The microcosms had different moisture content (13%, 19%, and 24% Vw/Vtot ) and different salinity due to the addition of nutrients (22 and 15 g/L). The real and the imaginary component of the complex dielectric permittivity were evaluated at the initial stage of contamination and after 130 days. In almost all microcosms, the real component showed a significant decrease (up to 2 units) at all frequencies. The results revealed that the changes in the real part of the dielectric permittivity are related to the amount of degradation and loss in moisture content. The imaginary component, mainly linked to the electrical conductivity of the soil, shows a significant drop to almost 0 at low frequencies. This could be explained by a salt depletion during bioremediation. Despite a moderate accuracy reduction compared to measurements performed on liquid media, this technology can be successfully applied to granular materials such as soil. The open-ended coaxial probe is a promising instrument to check the dielectric properties of soil to characterize or monitor a bioremediation process

Temporal diffeomorphic Free Form Deformation (TDFFD) applied to motion and deformation quantification of tagged MRI sequences

International audienceThis paper presents strain quantification results obtained from the Tagged Magnetic Resonance Imaging (TMRI) sequences acquired for the 1 st cardiac Motion Analysis Challenge (cMAC). We applied the Temporal Diffeomorphic Free Form Deformation (TDFFD) algorithm to the phantom and the 15 healthy volunteers of the cMAC database. The TDFFD was modified in two ways. First, we modified the similarity metric to incorporate frame to frame intensity differences. Second, on volunteer sequences, we performed the tracking backward in time since the first frames did not show the contrast between blood and myocardium, making these frames poor choices of reference. On the phantom, we propagated a grid adjusted to tag lines to all frames for visually assessing the influence of the different algorithmic parameters. The weight between the two metric terms appeared to be a critical parameter for making a compromise between good tag tracking while preventing drifts and avoiding tag jumps. For each volunteer, a volumet-ric mesh was defined in the Steady-State Free Precession (SSFP) image, at the closest cardiac time from the last frame of the tagging sequence. Uniform strain patterns were observed over all myocardial segments, as physiologically expected

Wearable Microwave Imaging System for Brain Stroke Imaging

This paper presents the experimental validation of the detection capabilities of a low complexity wearable system designed for the imaging-based detection of brain stroke. The system approaches the electromagnetic inverse problem via a 3-D imaging algorithm based on the Born approximation and the Truncated Singular Value Decomposition (TSVD). For testing, flexible antennas with custom-made coupling-medium are prototyped and assessed in mimicked hemorrhagic and ischemic stroke conditions. The experiment emulates the clinical scenario using a single-tissue anthropomorphic head phantom and strokes with both 20 cm 3 and 60 cm 3 ellipsoid targets. The imaging kernel is computed via full-wave simulation of a virtual twin model. The results demonstrate the capabilities for detecting and estimating the stroke-affected area

In-Line Microwave Nondestructive Evaluation of Packaged Food Products via the Support Vector Machine Algorithm

This paper presents a novel approach based on electromagnetic waves (EM) to classify food packages that hold water as one of the main ingredients from the inside into contaminated or uncontaminated products. A non-destructive technique that can handle a real-time food production line is proposed to achieve this goal. This technique combines the operation of a microwave sensing system (MW) with a machine learning (ML) classifier. An accuracy of 100% has been obtained from training the aforementioned ML tool on a dataset constructed from the retrieved scattering parameters of about 500 measuring samples

Estimation of banking technology under credit uncertainty

Credit risk is crucial to understanding banks' production technology and should be explicitly accounted for when modeling the latter. The banking literature has largely accounted for risk by using ex-post realizations of banks' uncertain outputs and the variables intended to capture risk. This is equivalent to estimating an ex-post realization of bank's production technology which, however, may not reflect optimality conditions that banks seek to satisfy under uncertainty. The ex-post estimates of technology are likely to be biased and inconsistent, and one thus may call into question the reliability of the results regarding banks' technological characteristics broadly reported in the literature. However, the extent to which these concerns are relevant for policy analysis is an empirical question. In this paper, we offer an alternative methodology to estimate banks' production technology based on the ex-ante cost function. We model credit uncertainty explicitly by recognizing that bank managers minimize costs subject to given expected outputs and credit risk. We estimate unobservable expected outputs and associated credit risk levels from banks' supply functions via nonparametric kernel methods. We apply this framework to estimate production technology of U.S. commercial banks during the period from 2001 to 2010 and contrast the new estimates with those based on the ex-post models widely employed in the literature

Are All U.S. Credit Unions Alike? A Generalized Model of Heterogeneous Technologies with Endogenous Switching and Correlated Effects

Credit unions differ in the types of financial services they offer to their members. This paper explicitly models this observed heterogeneity using a generalized model of endogenous ordered switching. Our approach captures the endogenous choice that credit unions make when adding new products to their financial services mix. Failure to do so is likely to yield biased and inconsistent estimates. The model that we develop also allows for the dependence between unobserved effects and regressors in both the selection and outcome equations and can accommodate the presence of predetermined covariates in the model. We use this model to estimate returns to scale for U.S. retail credit unions from 1996 to 2011. We document strong evidence of persistent technological heterogeneity among credit unions offering different financial service mixes, which, if ignored, can produce quite misleading results. Employing our generalized model, we find that credit unions of all types exhibit substantial economies of scale

Heterogeneous Credit Union Production Technologies with Endogenous Switching and Correlated Effects

Credit unions differ in the types of financial services they offer to their members. This paper explicitly models this observed heterogeneity using a generalized model of endogenous ordered switching. Our approach captures the endogenous choice that credit unions make when adding new products to their financial services mix. The model that we consider also allows for the dependence between unobserved effects and regressors in both the selection and outcome equations and can accommodate the presence of predetermined covariates in the model. We use this model to estimate returns to scale for U.S. retail credit unions from 1996 to 2011. We document strong evidence of persistent technological heterogeneity among credit unions offering different financial service mixes, which, if ignored, can produce quite misleading results. Employing our model, we find that credit unions of all types exhibit substantial economies of scale