Trapping of oil in an epoxy-based polymer matrix with activated carbon and its effect on tribological behavior

The incorporation of lubricating oil at high levels in the epoxy composite materials makes it possible to obtain materials with low friction and wear. This article evaluates the wear behaviour of an epoxy-based composite obtained by the addition of lubricating oil and activated carbon. An oil content of up to 31wt% is trapped and maintained in the matrix by the presence of activated carbon. The wear experiments are carried out on a pin-on-disk type tribometer. The tests are carried out on pins of different compositions sliding on steel discs (XC48) under dry friction conditions. The effect of various parameters such as speed and loading has been investigated. The wear surfaces are analyzed by using a scanning electron microscope to observe the different wear mechanisms. The results show that the addition of activated carbon made it possible to trap large quantities of oil in the matrix. This decreased greatly the coefficient of friction and increased the capacity of the sample to withstand higher values of sliding velocities and pressures

Reforms and Growth in MENA Countries:New Empirical Evidence

In this paper we empirically analyze the linkages among economic reforms, human capital, physical infrastructure, and growth for a panel of 44 developing countries over 1970-80 to 1999. For this purpose, we generate aggregated reform indicators using principal component analysis. We show that the growth performance of the MENA region has been disappointing because these economies have lagged behind in terms of economic reforms. However, our analysis also reveals that the growth dividend of some reforms has been small. This is the case when structural reforms are implemented in an unstable macroeconomic environment (which corresponds to the situation of the MENA countries in the 1980s), and when macroeconomic reforms are accompanied by a low level of structural reforms (as observed during the 1990s). Our result illustrates the complementarities between reforms as modeled by Mussa (1987) and Williamson (1994). Actually, after human capital and physical infrastructure, our analysis finds that macroeconomic and external stability are key variables for the reform process and for the growth prospects of the developing world.

PV System Linked to an Electrical Network with an Active Power Filter Using DPC Modified Method Under Distorted Grid Voltage Conditions

This article presents an energy system that enhances the quality of electrical energy by injecting photovoltaic (PV) renewable energy into the electrical network in the presence of a polluting load. This system is based on a new control approach known as Zero Direct Power Command (ZDPC). The innovative aspect of the proposed work is the addition of clean energy while simultaneously removing the unsettling harmonics produced by the nonlinear loads provided by distorted voltages. This approach combines a traditional Proportional Integrator (PI) controller for regulating the DC bus voltage with a clever technique (fuzzy logic) for tracking the Maximum Power Point Tracking (MPPT). The current has a harmonic distortion rate of about 1% with unity power factor due to the suppression of undesirable harmonics from the source currents. A PV panel connected in series with a chopper and managed by fuzzy logic via a two-state inverter ensures the injection of PV energy into the electrical network. Software called MATLAB/Simulink is used to model this system. The outcomes demonstrate the reliability and viability of the ZDPC control, which concurrently ensures harmonic current compensation, power factor correction, and the introduction of solar power into the electrical network despite distorted source voltages

Exchange Rate Management within the Middle East and North Africa Region:The Cost to Manufacturing Competitiveness

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Governance and private investment in the Middle East and North Africa

This paper addresses the issue of the low level of private investment in the Middle East and North Africa (MENA) region, with special emphasis on the role of governance. Based on the existing literature, the authors categorize what types of governance institutions are more detrimental to entrepreneurial investments. They then estimate a simultaneous model of private investment and governance quality where economic policies concurrently explain both variables. The empirical results show that governance plays a significant role in private investment decisions. This result is particularly true in the case of"administrative quality"in the form of control of corruption, bureaucratic quality, investment-friendly profile of administration, and law and order, as well as for"political stability."Evidence in favor of"public accountability"seems, however, less robust. The estimations also stress that structural reforms-such as financial development and trade openness-and human development affect private investment decisions directly, and/or through their positive impact on governance. These findings bring new empirical evidence on the subject of private investment in the developing world and in MENA countries in particular.Governance Indicators,Investment and Investment Climate,Economic Theory&Research,National Governance,Trade and Regional Integration

" Quand rédiger c'est décrire " : Mise en forme matérielle des textes et construction d'ontologies à partir de textes

National audienceLa construction d'ontologie à partir de textes met classiquement en oeuvre des outils issus du Traitement Automatique de la Langue et/ou des outils d'apprentissage supervisé ou non. Dans cet article nous revenons sur la possibilité d'exploiter des objets textuels à la fois facilement identifiables, souvent fertiles en connaissances ontologiques, et dont la sémantique peut clairement être explicitée par les théories du discours : les structures énumératives. Ici, nous ajoutons une nouvelle classe de relations sémantiques portée par les structures énumératives très présentes dans nos corpus : les relations lexicales telles que l'homonymie ou la synonymie. Ces relations semblent propices pour alimenter la facette terminologique d'une Ressource Termino-Ontologique. Nous montrons que ces relations peuvent être formellement caractérisées. Une évaluation de notre approche à partir d'un corpus annoté manuellement nous permet de valider notre position, ce qui constitue une première étape vers un outil d'apprentissage supervisé pour la construction d'ontologie à partir de texte

Study of Structural Stability of a Concrete Gravity Dam Using a Reliability Approach

The safety of dams is a priority at the international level, based on a large amount of data from a dam-reservoir allows analysts to make optimization on its structural stability, the latter is based on the estimation of the probability of failure from the effects of stress and resistance acting on the dam-reservoir system. This investigation is to establish a methodology in order to optimize the safety of a concrete gravity dam in operation by carrying out a risk analysis which includes the identification of the sources of danger in terms of scenarios that can occur due to a failure on the dam-reservoir system on an implication of natural hazards (floods, earthquakes) and technical accidents such as malfunction of a spillway gate, drain valve, drainage system or important silting. Reliability methods provide a basis for the probabilistic assessment of the structural safety of a dam. They make it possible to take into account in a probabilistic context, the uncertainties in the data associated with the calculation parameters used in the justifications of structural stability and make it possible to assess as closely as possible the intrinsic safety of a concrete gravity dam

Trapping of oil in an epoxy-based polymer matrix with activated carbon and its effect on tribological behavior

The incorporation of lubricating oil at high levels in the epoxy composite materials makes it possible to obtain materials with low friction and wear. This article evaluates the wear behaviour of an epoxy-based composite obtained by the addition of lubricating oil and activated carbon. An oil content of up to 31wt% is trapped and maintained in the matrix by the presence of activated carbon. The wear experiments are carried out on a pin-on-disk type tribometer. The tests are carried out on pins of different compositions sliding on steel discs (XC48) under dry friction conditions. The effect of various parameters such as speed and loading has been investigated. The wear surfaces are analyzed by using a scanning electron microscope to observe the different wear mechanisms. The results show that the addition of activated carbon made it possible to trap large quantities of oil in the matrix. This decreased greatly the coefficient of friction and increased the capacity of the sample to withstand higher values of sliding velocities and pressures