Characterization of in vivo wear debris from ceramic-ceramic total hip arthroplasties

In contrast to the much-studied mechanism of aseptic loosening of the metal-polyethylene joint couple, the mechanism responsible for failure of ceramic-ceramic (CC) total hip arthroplasties (THAs) has not been evaluated. The aim of this study was to conduct a systematic characterization of the in vivo wear debris from 15 cases of CC THAs revised for aseptic loosening. Two methods were used to evaluate the wear debris; a semiquantitative histological analysis of H&E-stained periprosthetic pseudomembranes; and an evaluation of isolated debris particles using SEM, energy-dispersive X-ray analysis, and image analysis. The three main types of particulate debris identified were titanium alloy (TiAlV) and alumina ceramic (Al2O3) of prosthetic origin, and zirconium dioxide (ZrO2) from the contrast agent used in the cement for prosthetic fixation. Alumina debris was present in the smallest proportion (12%) and was consistent with the low wear rate of the CC joint couple. Zirconium dioxide debris was present in the greatest proportion (76%) and was an unexpected finding. The ZrO2 debris represented microstructural grains of the original ZrO2 particles added as contrast agent to the cement. The presence of a histiocytic foreign body reaction to ZrO2 debris on histologic sections leads us to believe that these particles play an important role in aseptic loosening of the CC THAs evaluated in this study.     

Application of Millimeter Wave in Verification of Scale Model Measurement for Radar Cross Section

According to the physical optic approximation, a physical scale factor is suggested for scale model measurement of radar cross section (RCS). By this factor, the models of radar targets can be tested at the same frequency as prototype. This is significant for the lack of experimental equipment required or the problem of frequency dependency of radar absorbing materials on the objects. For the purpose of further verification and comparison, millimeter-wave is used to measure the model at the wavelength scaling down proportionally to the prototype. And the measurements of the models are also carried out at microwave band (same working wavelength with prototype). The computed results from models agree well with the data by prototype itself.     

Mechanical and Thermal Properties of Lead Borate Glasses Containing CaO and NaF

Glasses with the chemical composition 39PbO - 1NaF - (60-x){0.667B₂O_3-0.333Na₂O \(\}\)– x CaO (x \(=\) 0, 5, 10, 15, 20, and 25 mol %), were prepared by the usual melt quenching technique, and analyzed by using X-ray diffraction, density, differential thermal analysis (DTA), optical properties and mechanical properties. The structural variations due to the increase of the [BO₄] at the expense of [BO₃] structural units increase the ultrasonic velocity and the elastic moduli along with an increase of the density. The Makishima–Mackenzie model was applied successfully on the prepared glasses. The elastic moduli according to this model increase, which was due to the increase of CaO content. The increase of the glass transition temperature (T _g) according to DTA confirmed this behavior.     

An efficient authentication and key agreement scheme for secure smart grid communication services

The smart grid is a new and promising technology integrating new information and communication technologies to improve the distribution and consumption of electricity between energy suppliers and their end customers. However, this advanced solution is facing a serious security problem as regards the interception and falsification of power consumption data, hence generating falsified electricity consumption bills. This issue of security needs to be promptly and efficiently handled. Clearly, it is of paramount importance to have a security mechanism to avoid such losses. Our work focuses on this issue. It particularly concerns the development of a security mechanism to ensure a completely secure communication between energy suppliers and their consumers while preserving the privacy of end customers in terms of protection of their personal information including their identities. The experimental results underscore that our solution outperforms those of the literature in terms of computation cost and robustness against various types of attacks.     

Automatic detection of Moroccan coastal upwelling zones using sea surface temperature images

An efficient unsupervised method is developed for automatic segmentation of the area covered by upwelling waters in the coastal ocean of Morocco using the Sea Surface Temperature (SST) satellite images. The proposed approach first uses the two popular unsupervised clustering techniques, k-means and fuzzy c-means (FCM), to provide different possible classifications to each SST image. Then several cluster validity indices are combined in order to determine the optimal number of clusters, followed by a cluster fusion scheme, which merges consecutive clusters to produce a first segmentation of upwelling area. The region-growing algorithm is then used to filter noisy residuals and to extract the final upwelling region. The performance of our algorithm is compared to a popular algorithm used to detect upwelling regions and is validated by an oceanographer over a database of 92 SST images covering each week of the years 2006 and 2007. The results show that our proposed method outperforms the latter algorithm, in terms of segmentation accuracy and computational efficiency.     

Effect of wind stress forcing on ocean dynamics at air-sea interface

We evidence and study the differences in turbulence statistics in ocean dynamics carried by wind forcing at the air-sea interface. Surface currents at the air-sea interaction are of crucial importance because they transport heat from low to high latitudes. At first order, oceanic currents are generated by the balance of the Coriolis and pressure gradient forces (geostrophic current) and the balance of the Coriolis and the frictional forces dominated by wind stress (Ekman current) in the surface ocean layers. The study was conducted by computing statistical moments on the shapes of spectra computed within the framework of microcanonical multi-fractal formalism. Remotely sensed daily datasets derived from one year of altimetry and wind data were used in this study, allowing for the computation of two kinds of vector fields: geostrophy with and geostrophy without wind stress forcing. We explore the statistical properties of singularity spectra computed from velocity norms and vorticity data, notably in relation with kurtosis information to underline the differences in the turbulent regimes associated with both kinds of velocity fields.     

A state‐of‐art review on performance improvement of dielectric resonator antennas

This article outlines a compressive review on investigation carried out targeting to gain, circular polarization (CP), and mutual coupling reduction in dielectric resonator antenna (DRA). The DRA has already been created a separate position in antenna engineering domain because of its adept characteristics, such as wide bandwidth, high efficiency, low‐loss, and mainly 3D‐design flexibility which is rarely available in conventional antennas. In this context, the research on gain, circular polarization, and mutual coupling are quite interesting and being carried out from the last two decades. The ultimate aim of this article is to (i) give an overview of different techniques adopted in context to gain, CP, and mutual coupling reduction; (ii) give a compressive review of notable research carried out targeting to these three characteristics; and (iii) find out the research gap concentration for furtherance of the same.     

Slot antenna array synthesis using the infinitesimal dipole model technique: Theory and experiment

The present article proposes and validates a new general design methodology that can be used to automatically find proper positions and orientations of waveguide‐based radiating slots capable of realizing any given radiation beam profile. The new technique combines basic radiation theory and waveguide propagation theory in an analytical model that permits the prediction of the radiation characteristics of generic slots without the need to perform full‐wave numerical solution while completely avoiding using transmission‐line models or the slot impedance method. The analytical model is then used to implement a low‐cost objective function within a global optimization scheme and subsequently deployed to find optimum positions and orientations of clusters of radiating slots cut into the waveguide surface such that any desired beam pattern can be obtained, leading to very efficient and robust beamforming capability that can be applied to dynamic beamforming in real‐time scenarios like MIMO systems. The proposed design method is verified using both full‐wave numerical solution and experiment.