Wear of composite ceramics in mixed-material combinations in total hip replacement under adverse edge loading conditions

Further development of ceramic materials for total hip replacement aim to increase fracture toughness and further reduce the incidence of bearing fracture. Edge loading due to translational mal positioning (microseparation) has replicated stripe wear, wear rates, and bimodal wear debris observed on retrievals. This method has replicated the fracture of early zirconia ceramic-on-ceramic bearings. This has shown the necessity of introducing microseparation conditions to the gait cycle when assessing the tribological performance of new hip replacement bearings. Two novel ceramic matrix composite materials, zirconia-toughened alumina (ZTA) and alumina-toughened zirconia (ATZ), were developed by Mathys Orthop€adie GmbH. In this study, ATZon- ATZ and ZTA-on-ZTA bearing combinations were tested and compared with alumina-on-alumina (Al2O3-on-Al2O3) bearings under adverse microseparation and edge loading conditions using the Leeds II physiological anatomical hip joint simulator. The wear rate (695% confidence limit) of ZTA-on-ZTA was 0.1460.10 mm3/million cycles and that of ATZ-on-ATZ was 0.0660.004 mm3/million cycles compared with a wear rate of 0.7461.73 mm3/million cycles for Al2O3- on-Al2O3 bearings. Stripe wear was evident on all bearing combinations; however, the stripe formed on the ATZ and ZTA femoral heads was thinner and shallower that that formed on the Al2O3 heads. Posttest phase composition measurements for both ATZ and ZTA materials showed no significant change in the monoclinic zirconia content. ATZon- ATZ and ZTA-on-ZTA showed superior wear resistance properties when compared with Al2O3-on-Al2O3 under adverse edge loading conditions. VC 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000–000, 2013

Caractérisation basse fréquence et simulation physique de transistors bipolaires hétérojonction en vue de l'analyse du bruit GR assisté par pièges

This work presents the development of a thermal test bench for I(V) characteristics, for low frequency impedance and for low frequency noise of semiconductor components. This thermal bench for low frequency noise measurement is composed of a low-noise voltage amplifier, a low-noise transimpedance amplifier, an FFT vector signal analyzer and a thermal chuck. This measurement bench has allowed to extract the current noise sources equivalent to the access transistor at different current densities and at different temperatures. In order to calculate the activation energy and the capture cross section of traps thanks to the localization of the cutoff frequency of GR noise in HBT InGaP / GaAs technology. Secondly, we studied the low frequency noise in the transistor InGaP / GaAs and the differents junctions: emitter base, collector base and the base represented by the TLM resistance using physical simulations and measurements of low-frequency noise power spectrum density. Using this measurements, we extract the controlled and not controlled local internal noise sources. The extraction has allowed us to calculate the activation energy, the capture cross sections and validate the physical simulation.Ce travail présente le développement d’un banc de mesure thermique, pour la mesure : de réseaux I (V), d’impédance basse fréquence et de bruit basse fréquence des composants semi-conducteurs. Le banc de mesure de bruit BF est composé d’un amplificateur de tension faible bruit, d’un amplificateur transimpédance, d’un analyseur FFT et d’un support thermique. Ce banc a permis d’extraire les sources de bruit en courants équivalentes aux accès du transistor pour différentes densités de courant et à différentes températures. Dans le but de calculer l’énergie d’activation et la section de capture des pièges grâce à la localisation des fréquences de coupures de bruit GR dans la technologie du TBH InGaP/GaAs. Dans un deuxième temps, nous avons étudié le bruit basse fréquence dans le transistor InGaP/GaAs et les jonctions base émetteur, base collecteur et la résistance TLM par le moyen de simulation physique et de mesure de densité spectrale de puissance de bruit basse fréquence. Grâce à ces mesures, nous avons pu extraire les sources de bruit internes locales commandées et non commandées. Cette extraction nous a permis de calculer les énergies d’activations, les sections de capture et de valider la simulation physique

Une approche pour la comparaison, du point de vue fonctionnement hydraulique, de propositions d'extension d'un réseau d'assainissement

Les outils informatiques développés dans le cadre de la conception des réseaux d'assainissement permettent de concevoir plusieurs solutions de réseaux pour un même problème. Il revient ensuite au décideur de choisir quelle solution retenir. Le problème qui se pose alors est la comparaison des propositions selon des critères économiques, écologiques, de fonctionnement, de maintenance, .... La difficulté vient du fait que certains de ces critères sont difficiles à évaluer. Nous présentons dans cet article une méthode permettant d'évaluer l'un de ces critères : le fonctionnement global d'un réseau d'assainissement suite à l'extension de ce dernier. Cette méthode est basée sur des simulations hydrauliques. Or ces simulations donnent des informations en chaque noeud du réseau (histogrammes de vitesses, débits ou hauteurs de charge) et non une indication sur la qualité de fonctionnement du réseau dans son ensemble. Il nous a donc fallu élaborer une technique d'agrégation permettant de passer de l'élément isolé (le tronçon) à l'ensemble organisé (le réseau). Cette technique d'agrégation utilise les notions de "période d'insuffisance" d'un tronçon qui est la période de retour d'une pluie pour laquelle ce tronçon dépasse un certain seuil de dysfonctionnement (dans notre cas, le débordement) et de sensibilité du tissu urbain à un dysfonctionnement hydraulique du réseau. Cette dernière notion est nécessaire car certains tronçons peuvent très bien déborder sans induire de désordres apparents s'ils ont, par exemple, une capacité d'écoulement faible et/ou s'ils se trouvent dans une zone non bâtie. Les informations nécessaires à l'utilisation de cette méthode étant souvent de qualité inégale en termes de précision, nous avons pris le parti de raisonner non sur des valeurs déterminées ais sur des classes d'appartenance modélisées sous forme de sous-ensembles flous.Software packages developed for the design of urban storm drainage networks allow several solutions to be proposed for the same problem. It then falls to the designer to choose which solution to use, the main problem being the evaluation of the efficiency (quality) of each solution. A multi-criteria approach represents one theoretical solution to the problem. This necessitates the determination of which criteria to use and how to evaluate them. In this paper, we present a method of evaluation of the criteria related directly to the functioning of an urban storm drainage network after its extension. This method is developed on the basis of hydraulic simulations of the network. These simulations produce results (histograms of discharge, water levels, rates of filling, hydraulic head, ...) for each pipe. Given these results, the designer must be able to assess whether the proposed solution is satisfactory, and then compare it with other solutions. The problem is therefore to be able to evaluate a complete network, whereas the results of conventional simulations present a fragmented and partial view of its functioning (pipe by pipe). A solution to this problem is proposed in the form of a tool, able to calculate a single combined value from the simulation results. The following calculation steps are proposed:1. First we model the effectiveness of each pipe. To do that, we determine the "return period of failure" of a pipe which is the return period of a rainfall for which the pipe passes a certain level of failure (in this paper, we take the level of failure as the state of overflow). The rainfall model used is the same one used for the design of the network. Then we attribute a numerical value (S) for the operation of a pipe according to its return period of failure by way of a satisfaction function. 2. Secondly we model the weighting given to each pipe. This weighting is constructed from the discharge capacity of the pipe and the sensitivity of the urban fabric (in proximity to the pipe) to system failure. The discharge capacity is calculated using Manning's formula on the basis of diameter, slope and internal roughness. The value of the coefficient (R), which indicates the sensitivity, necessitates a good knowledge of the urban fabric. Among the important variables related to this factor, we can identify the population density, the traffic density and the density of land use -DLU- (this variable is identified by the density of residential land use, the density of commercial land use, ...). We can then write R=f(density of population, density of traffic, DLU,...). Considering the difficulty of the identification of (f), we preferred to explore an expert approach. The rules have been identified from a bibliographical analysis and limited expertise. An example of theses rules is presented here : IF density of population is high and density of commercial land use is average THEN the degree of sensibility is average. The examination of the identified rules shows the use of words like low, average and high. To model this linguistic qualifying information, we have chosen fuzzy sets. Also the inferences of fuzzy information are treated by using operations of fuzzy logic. 3. Finally, we aggregate the results with the following equation:     nC=∑QaixRix∆Si  i=1where DSi=Si - Si' represents a measure of the effect of network modification upon the operation of the pipe i (Si and Si' are the effectiveness of the pipe respectively before and after the proposed modification), Qai is the discharge capacity of the pipe i, Ri is the coefficient of sensitivity of the area to failure associated with pipe i and C is a factor which quantifies the effect on the general operation of the network. With the coefficient C, the designer is now able to classify the different solutions of extension of an existing urban drainage network according to their impacts on its functioning and to introduce this classification order in a multi-criteria method

THE IMPACT OF CORPORATE GOVERNANCE ON EARNINGS MANAGEMENT IN ISLAMIC AND CONVENTIONAL BANKS

Purpose – This paper aims to examine the association between internal corporate governance and earnings management and to compare earnings management practices in Islamic banks versus conventional banks in the MENA region. Design/methodology/approach – This paper uses an unbalanced panel data of 20 Islamic banks and 100 conventional banks, from eleven countries in the MENA region over the period 2012-2017. Discretionary accruals are used to measure earnings management by estimating loan loss provision. Regression analysis is used to test the hypotheses. Findings – The results indicate that Islamic banks provide fewer earnings management practices compared to conventional banks. Besides, the results show that among the six corporate governance mechanisms studied in this paper only board meetings, board size, and board independence can help in mitigating earnings management for conventional banks. Whereas, for the case of Islamic banks, corporate governance mechanisms have no impact on reducing earnings management. Practical implications – This paper could offer some recommendations for policymakers, regulators, and users of financial statements. The results of this study could assist in improving the monitoring role of the board of directors and understanding the relationship between corporate governance mechanisms and earnings management. Originality/value – This paper contributes by investigating the effect of new mechanisms on earnings management, and by examining earnings management practices in Islamic banks compared to conventional banks in unexamined countries and periods. Keywords Earnings management, Earnings quality, Islamic banks, Conventional banks, Corporate governance mechanisms, Annual reports, MENA region. Paper type Research pape

Effect of an edge at cup rim on contact stress during micro-separation in ceramic-on-ceramic hip joints

Alumina ceramic total hip joint bearings have shown superior wear properties. The joint bearing may undergo adverse conditions such as micro-separation causing head contact on the cup rim. As a transition, an edge is formed between the cup bearing and the rim. The aim of this study was to predict the effect of the edge on contact stresses in order to better understand the mechanisms of wear. A finite element contact model was developed under the conditions of the head displacements 0.5 2 mm and vertical loads 0.5 3kN. The edge contact produced the most severe stresses capable of causing elevated wear and damage to ceramic bearings. The study shows that the bearing design should be considered in association with clinical conditions to eliminate severe stress

Estimation of Yield traits & Correlation in Zea Mays

Seven Zea mays genotypes were planted at two sites Aleppo and Edleb which are research centres belongs to the General Commission of Scientific Agricultural research GCSAR northern Syria. Yield traits (ear diameter, ear length, row number per ear-1, grain number per ear-1, thousand grain weight) were studied in order to estimate the variation between genotypes and to between sites and to select the best genotypes concerning studied yield  traits to be applied in maize breeding programs. Results showed that all Studied genotypes of maize had significant differences in yield traits in which both genotypes (Z 263, Z 67) were remarkable in all studied traits like thousand grain weight (391.7, 390.7) g for each of them respectively. Results also revealed that most studied traits were significantly superior in Aleppo comparing to Edleb. Results of correlation showed positively and significantly relations between all studied traits except between each of row number per ear-1 and grain number per ear-1 with thousand grain weight

Characterizing edge-wear in ceramic-on-ceramic acetabular cups

The use of fourth generation ceramic as an orthopaedic biomaterial has proved to be a very efficient and has gained popularity for primary hip surgery in the last 8-10 years. Cumulative percentage probability of revision after 7 years for uncemented CoC is 3.09% and for hybrid CoC is 2.00%, this compares favourably with traditional metal-on-UHMWPE uncemented at 3.05% and hybrid at 2.35% (12th Annual Report - NJR, 2015). Such ceramic-on-ceramic hip prostheses are being implanted in ever younger, more active patients, and yet very few long-term large cohort retrieval studies are yet to be carried out due to the survivorship of the implants. It has been seen in previous studies that levels of wear in ceramic-on-ceramic bearing surface can be of the order of 0.2 mm3/million cycles (Al-Hajjar, Fisher, Tipper, Williams, & Jennings, 2013). This is incredibly low when compared to studies that characterize wear in other bearing surface combinations. It has also been reported that an unusual stripe pattern of wear can occur in some in-vivo retrieved cups (Macdonald & Bankes, 2014) and it has further been postulated that this is caused by cup edge loading (Walter, Insley, Walter, & Tuke, 2004). The combined measurement challenge of stripe wear occurring at the edge of a low-wear ceramic-on-ceramic device is considerable, a solution to which is presented here. Current literature on wear measurement of such cases has been confined to in-vitro simulator studies and use of gravimetric measurement which by definition has limitations due to the lack of spacial characterisation. This paper details a novel method for measuring edge-wear in CoC acetabular liners. The method has been employed in an in-vitro study where it has been benchmarked against gravimetric measurements. These liners were measured on a CMM to determine the volume of material loss. The measurements were conducted as a blinded post-wear study akin to measurement of retrieved components. The most challenging part of this novel method was to create a reference geometry that replicates the free form edge surface of the ‘unworn’ cup using the residual post-wear surface. This was especially challenging due to the uncontrolled geometry at the cup edge and intersection of geometric features at this point. To achieve this, the geometry surrounding the wear patch was used to create a localized reference feature that minimised the effect of global form errors caused by hand polishing in the edge area. Furthermore, the reference geometry is compared with the measured surface to determine the linear penetration and volumetric wear loss. Result of this novel method can be seen in Fig 1 and Fig 2. The findings have been compared to gravimetric results and a bar graph comparing two results can be seen in Fig 3. Overall the accuracy of the method for this cohort was 0.03-0.2 mm3 when compared to gravimetric reference measurements. This compares very favourably with previously published wear measurement methods and gives confidence in the ability to measure such small measurement volumes over complex geometry