Prediction of Long-term Immunity of a Phase-Locked Loop

Degradation mechanisms accelerated by harsh conditions (high temperature, electrical stress) can affect circuit performances. Submitted to electromagnetic interferences, aged components can become more susceptible, which stirs up questions about the safety level of the final application. Unfortunately, the impact of circuit aging on its susceptibility level remains under evaluated and is not taken into account at circuit design level. This paper presents a first attempt of a modeling methodology aiming at predicting the impact of circuit aging on the susceptibility to electromagnetic interferences. This methodology is applied to model and explain the measured variations of the susceptibility level of phase-locked loop after an accelerated-life test.     

A geostatistical approach for groundwater head monitoring network optimisation: case of the Sfax superficial aquifer (Tunisia)

In many developing countries, the groundwater monitoring network is randomly designed, and consequently needs to be revised and optimised to reduce operation time and cost, remove redundant piezometric data, and strengthen sparseness data zone with supplementary observation well. The geostatistical approach used in this work is based on the universal kriging variance combined with cross‐validation test. Hence, a rational interpolation of water table elevations was performed to evaluate the accuracy of data employed in the piezometric head modelling. In this study, the groundwater monitoring network of the Sfax superficial aquifer in the south east of Tunisia was optimised. The elimination of five observation wells induces the invariability in the variance of estimate due to their less contribution in interpretations of the groundwater level behaviour. However, 38 wells were added at areas of high variance of the kriging in order to ameliorate the spatial coverage of the monitoring network.     

Brown tumors in dialyzed patients with secondary hyperparathyroidism: Report of 16 cases

Brown tumors (BTs) are relatively uncommon but they are serious complications of renal osteodystrophy. The objective of this study was to analyze the clinical, biological, and radiological characteristics of 16 patients with BTs provoked by secondary hyperparathyroidism (sHPT) and its response to the decrease in parathyroid hormone levels after parathyroidectomy (PTX). The management of that uncommon condition was also reviewed. We conducted a retrospective study including 16 end‐stage renal disease patients who underwent subtotal PTX between 1997 and 2007 for severe sHPT with BTs. Our study included 10 men and 6 women, whose average age was 34 years. All patients were on dialysis. Ten of them were on dialysis for more than 5 years. The median duration on dialysis was 84 months. Patients included suffered from swellings associated with functional limitations. BTs had multiple locations in 7 patients. Jaw was the most frequent location (62%). Radiography and tomodensitometry demonstrated a mixed radio lucent and radio‐opaque lesions with an expansion of the cortical bone. Bone scan demonstrated an increased uptake of lesions. Chirurgical treatment was indicated in all cases because of severe refractory sHPT with functional limitations and/or disfiguring deformities. In all cases, BTs stopped its progression and even decreased in size. However, it was insufficient in four cases, which required a surgical resection. PTX remains an efficacious approach in resistant cases of sHPT with persistent BTs.     

Error estimation and model adaptation for a stochastic‐deterministic coupling method based on the Arlequin framework

The paper deals with the issue of accuracy for multiscale methods applied to solve stochastic problems. It more precisely focuses on the control of a coupling, performed using the Arlequin framework, between a deterministic continuum model and a stochastic continuum one. By using residual‐type estimates and adjoint‐based techniques, a strategy for goal‐oriented error estimation is presented for this coupling and contributions of various error sources (modeling, space discretization, and Monte Carlo approximation) are assessed. Furthermore, an adaptive strategy is proposed to enhance the quality of outputs of interest obtained by the coupled stochastic‐deterministic model. Performance of the proposed approach is illustrated on 1D and 2D numerical experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

A stochastic-deterministic coupling method for continuum mechanics

In this paper, we present a novel approach that allows to couple a deterministic continuum model with a stochastic continuum one. The coupling strategy is performed in the Arlequin framework, which is based on a volume coupling and a partition of the energy. A suitable functional space is chosen for the weak enforcement of the continuity between the two models. The choice of this space ensures that the mean of the stochastic solution equals the deterministic solution point-wise, and enforces appropriate boundary conditions on the stochastic dimension. The proof of the existence of the solution of the mixed problem is provided. The numerical strategy is also reviewed, in particular with a view at the Monte Carlo method. Finally, examples show the interest of the method, and possible strategies for use in adaptive modeling.     

Simulation and experimental investigation of a wide band PZ MEMS harvester at low frequencies

A commercial brass reinforced PZ bimorph cantilever of the type 5H4E was simulated using COMSOL FEM software and then a serious of experimental tests were carried out in a vibration laboratory using a labview of NI make as instrumentation and control system. By using a shaker the cantilever was vibrated and set into acceleration of 0.25?g?rms during all stages as this value was considered to be available and acceptable in balanced large rotating machines in industry. Field vibration spectrum analysis was carried out in a power station confirmed that. A band of frequencies ranging from 30 to 109?Hz was experimentally tested by using different perforated steel shims as a proof mass at the end of the cantilever. Values of 63?μW/cm³ at a frequency of 33?Hz for power density, 187?μW for max power, 14.8?V for max OCV, and 8.26?V for max, on load voltage, were obtained. Frequency resolution of 1?Hz was experienced. Trends of the results obtained experimentally and through simulation were comparable.     

Buckling of rolled thin sheets under residual stresses by ANM and Arlequin method

We present a numerical technique to model the buckling of a rolled thin sheet. It consists in coupling, within the Arlequin framework, a three dimensional model based on 8-nodes tri-linear hexahedron, used in the sheet part located upstream the roll bite, and a well-suited finite element shell model, in the roll bite downstream sheet part, in order to cope with buckling phenomena. The resulting nonlinear problem is solved by the Asymptotic Numerical Method (ANM) that is efficient to capture buckling instabilities. The originalities of the paper ly, first in an Arlequin procedure with moving meshes, second in an efficient application to a thin sheet rolling process. The suggested algorithm is applied to very thin sheet rolling scenarios involving “edges-waves” and “center-waves” defects. The obtained results show the effectiveness of our global approach.     

Organotin speciation in Bizerte lagoon (Tunisia)

For the first time, organotins have been assessed in samples collected from Bizerte lagoon, in Tunisia, during two seasons (summer and winter). The organotin distribution was studied in marine sediments and mussels tissues of this lagoon. Butyl-, phenyl- and octyltins were determined using a rapid speciation analytical method based on one-step ethylation/extraction with sodium tetraethylborate in aqueous phase. Simultaneously to the ethylation, the extraction was performed by either liquid/liquid extraction (LLE) or head-space solid phase microextraction (HS-SPME). Gas chromatography with pulsed flame photometric detection (GC-PFPD) was used to perform quantitative determination. The technique has been validated using biological and sediment reference materials. The different samples from Bizerte lagoon were found to be moderately contaminated, especially by butyltins. This pollution was attributed to industrial activities, which are very important in this area. Organotins appeared accumulated in both sediments and mussels, while significant degradations of triorganotins to monosubstituted ones was observed in water.     

On the use of XFEM within the Arlequin framework for the simulation of crack propagation

The Arlequin method is a generic numerical method that allows, by local superposition and coupling of models, to address multimodel and multiscale mechanical problems. In particular, this method has already been used to super-impose cracked patches on sound structures, reducing this way the global simulation resources a classical finite element approach would have required.In this paper, one of the key features of the extended-finite element method, namely the heaviside enrichment function, is used within the Arlequin framework to further reduce the costs of crack propagation simulations. The main goal of the paper is to describe the proposed methodology and to assess its performance through numerical experiments.