Novel Coupled Electric Field Method for Defect Characterization in Eddy Current Non-destructive Testing Systems

This article presents a defect modeling in eddy current non-destructive testing systems by using a new developed method called coupled electric field. It permits to improve qualitatively several models developed so far by many authors using coupled circuit methods that consider the defect only as loss of material. However, a defect can occur with a finite conductivity such as impurity, small burns and micro-solder. For this reason, this investigation consists of extending the coupled circuit method to the modeling of this kind of defects. The proposed approach consists of firstly considering the defect as an electric conductive volume and secondly changing the state variable presenting the electric current by the electric field one. This procedure permits expressing explicitly the impedance variation caused by the presence of an axi-symmetrical defect according to its characteristics. The comparison between the impedance variations calculated using finite elements method and the proposed one demonstrates a very good concordance. After this validation, the study covers also the influence of the defect shape and position on encircling probe impedance. This method is interesting since it permits a fully characterization of this kind of defects and facilitates the inversion process. Moreover, using a 3D finite element observation, this fast tool of simulation can be adapted for a fast phenomenological modeling of asymmetrical configurations.     

IRH-OF: A New Objective Function for RPL Routing Protocol in IoT Applications

Wireless Personal Communications - Faced to challenges of low power and lossy networks (LLN’s) as well as the nature of these networks without infrastructure, it remains the subject of...     

Correlation Between the Superfluid Density ns(T) ∝ 1/λ2ab(T) at Low Temperatures and Nanostructures in the a–b Planes of YBCO

A correlation between the superfluid density n _s(T) 1/² _ab(T) at low temperatures and the nanoscopic disorder in the a–b planes of YBCO thin films has been revealed. It has been found that a degree of this disorder can be determined from the two-component dependence of the critical current density on temperature. These findings are consistent with a discovery of a nanodomain structure in the a–b planes of an optimally doped YBCO [J. Etheridge, Phil. Mag. A73, 643 (1996)].     

The effect of grain boundary on the visible light absorption of BaTi1-x[Ni1/2Nb1/2]xO3-δ ferroelectric ceramics

(Ni²⁺, Nb⁵⁺) co-doped BaTiO₃ ceramics BaTi_1-x(Ni_1/2Nb_1/2)_xO_3-δ (BTNN-100x) are prepared by a solid-state reaction method, and their electrical and light absorption properties are investigated. The results show that BTNN-100x can generate oxygen vacancies which pin the domain walls. BTNN-100x bulk ceramics show strong visible light absorption. However, the phenomenon of visible light absorption disappear for BTNN-100x ceramic powders, and the band gap of doped ceramic powders are nearly unchanged. The experiments demonstrate that stress and density have little effect on the band gap. And the grain boundary shows stronger cathodoluminescence (CL) emission. Actually, oxygen vacancies can be enriched at grain boundaries, and defect [V_o-Ni_Ti-V_o] complex structures can be form and give rise to the visible light absorption as demonstrated by First-principles calculations. Thus, the engineering design of ferroelectric grain boundaries may pave the way for the application of coupled ferroelectric-photovoltaic processes.     

Influence of Conductive Pollution on Eddy Current Sensor Signals

This paper presents a study of a surface crack detection in which the volume is filled by conductive substances due to the polluting environment. Hence, this investigation demonstrates by numerical simulation that electric conductivity is a crucial property that has to be added to the other defect geometrical characteristics in order to complete the developed models. Consequently, introducing the tolerance in percent in the measured impedance is necessary in some conditions. So, the obtained results demonstrate that the signal amplitude passes from 0 to 78% of the maximal amplitude when the defect conductivity rises from 0 to 0.5 Ms/m. On the other hand, the relative difference of the resistance partincreases according to defect volume. For example, for a defect of 0.3 MS/m, the relative difference of the resistance varies from 52 to 62% of the maximal amplitude when the defect depth varies from 0.5 to 2.25 mm. These results can be exploited to show the effect of the conductive substances occupying the crack volume. In fact, the controller using EC-NDT technique must take into consideration the presence of conductive polluting elements in the crack volume. So, this condition becomes primordial and necessary according to the degree and nature of pollution.     

Timing–driven variation–aware synthesis of hybrid mesh/tree clock distribution networks

Clock skew variations adversely affect timing margins, limiting performance, reducing yield, and may also lead to functional faults. Non-tree clock distribution networks, such as meshes and crosslinks, are employed to reduce skew and also to mitigate skew variations. These networks, however, increase the dissipated power while consuming significant metal resources. Several methods have been proposed to trade off power and wires to reduce skew. In this paper, an efficient algorithm is presented to reduce clock skew variations while minimizing power dissipation and metal area overhead. With a combination of nonuniform meshes and unbuffered trees (UBT), a variation-tolerant hybrid clock distribution network is produced. Clock skew variations are selectively reduced based on circuit timing information generated by static timing analysis (STA). The skew variation reduction procedure is prioritized for critical timing paths, since these paths are more sensitive to skew variations. A framework for skew variation management is proposed. The algorithm has been implemented in a standard 65 nm cell library using standard EDA tools, and tested on several benchmark circuits. As compared to other nonuniform mesh construction methods that do not support managed skew tolerance, experimental results exhibit a 41% average reduction in metal area and a 43% average reduction in power dissipation. As compared to other methods that employ skew tolerance management techniques but do not use a hybrid clock topology, an 8% average reduction in metal area and a 9% average reduction in power dissipation are achieved.     

System identification of a class of Wiener systems with hysteretic nonlinearities

Existing works on Wiener system identification have essentially been focused on the case where the output nonlinearity is memoryless. When memory nonlinearities have been considered, the focus has been restricted to backlash like nonlinearities. In this paper, we are considering Wiener systems where the output nonlinearity is a general hysteresis operator captured by the well‐known Bouc–Wen model. The Wiener system identification problem is addressed by making use of a steady‐state property, obtained in periodic regime, referred to as ‘hysteretic loop assumption’. The complexity of this problem comes from the system nonlinearity as well as its unknown parameters that enter in a non‐affine way in the model. It is shown that the linear part of the system is accurately identified using a frequency method. Then, the nonlinear hysteretic subsystem is identified, on the basis of a parameterized representation, using a prediction‐error approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Fast Analytical Modeling of Eddy Current Non-Destructive Testing of Magnetic Material

This article presents the modeling of non-destructive testing systems containing magnetic materials using a fast numerical method. Its main aim consists of correcting the half analytical expression of the impedance variation, formulated by some authors, caused by the presence of a conducting plate below of an absolute ferrite core probe. The obtained results of this correction are found to be consistent and satisfactory comparatively to those of finite element method. It also deals with the study the method rapidity by comparing its simulation time to that of the finite element method. As result, the proposed method is found to be very fast and a very short simulation time is required to calculate the sensor impedance. Indeed, for the studied system the coupled circuit simulation time is lower than 1.09 s. This study is appreciable, since it permits to solve quickly the inverse problem by expressing the physical and geometrical features of the material or defect according to the measured parameters. More importantly, this method is applicable to any axi-symmetric systems and can be adapted for the simulation of three-dimensional configurations.     

Numerical Simulation and Optimization of n-Al-ZnO/n-CdS/p-CIGS/p-Si/p-MoOx/Mo Tandem Solar Cell

Silicon - CdS/CIGS mono junction is a potential approach to produce an ultra-high efficiency and low-cost all-thin-film solar cell. In this article, a conventional mono junction with a maximum...