Search

International audience; The present study aims to assess the temporal variations of some biotic and abiotic biodegradation parameters of 2 polymers (LDPE and PP) by the bacteria P. aeruginosa and S. aureus at acidic, neutral, and alkaline pH under mesophilic conditions. LDPE and PP fragments were immersed in the mineral solutions free of carbon sources containing P. aeruginosa or S. aureus cells. The initial pH values (pHi) of solutions were 5, 7 and 9. Incubation was carried out at 28°C for 10, 20, 30, 40, 50 and 60 days. Results showed that during incubations, the pH of the solutions varies over time. In most cases, the electrical conductivity and cell abundances increased. The weights of the polymers decreased. The cell abundance apparent increasing rates (CAAIR), the electrical conductivity apparent increasing rates (ECAIR), and the polymer weight apparent decreasing rates (PWADR) were estimated. The highest PWADR in the presence of LDPE was 0.4 mg/10days with P. aeruginosaat pHi 5 and 7, and 0.6 mg/10days with S. aureus under pHi 7. For PP, it was constant (0.7 mg/10days) under all pHi with S. aureus, but decreased in the presence of P. aeruginosa with increasing in pHi solutions. The ECAIR with LDPE decreased with increasing pHi with both bacterial species.The highest ECAIR of PP was recorded under pHi 5 with S. aureus and under pHi 7 with P. aeruginosa.The highest CAAIR with LDPE was 185.18 CFU/10days for P. aeruginosa at pHi 5 and 116.79 CFU/10days for S. aureus at pHi 7. With PP, it was 297.61 CFU/10days for P. aeruginosa at pHi 5 and 67.64 CFU/10days for S. aureusat pHi 7. The biodegradation parameters values recorded with of P. aeruginosa differed significantly (P

Mobile Access to the Web of Data is currently a real challenge in developing countries, mainly characterized by limited Internet connectivity and high penetration of mobile devices with the limited resources (such as cache and memory). In this paper, we survey and compare proposed solutions (such as models and architectures) that could contribute to solving this problem of mobile access to the Web of Data with intermittent Internet access. These solutions are discussed in relation to the underlying network architectures and data models considered. We present a conceptual study of peer-to-peer solutions based on gossip protocols dedicated to design the connected overlay networks. In addition, we provide a detailed analysis of client-server and data replication systems generally designed to ensure the local availability of data on the system. We conclude with some recommendations to achieve a connected architecture that provides mobile contributors with local access to the Web of data.

International audience; Floods are considered as the natural hazards that affect the world's major metropolises the most. Thus, the present study aimed at evaluating the sensitivity to flood risks of the Mfoundi watershed (96.5 km2) located in the heart of the Cameroonian political capital in a tropical humid forest zone, more precisely in the South Cameroon plateau. The methodological approach adopted was to identify the factors that most favor the risk of flooding in the area from intense literature review and field investigations; the analysis of these factors and the calculation of the Flood Harzard Index (FHI) using the Analytical Hierarchy Process (AHP) approach coupled with the Geographical Information System (GIS) environment. The results reveal that among the ten parameters of the natural environment (elevation, drainage density, rainfall, slope, distance from the river, topographic humidity, hydraulic conductivity, groundwater level, geology and land cover) selected, the land cover, elevation and the geology are the factors that most influences the flooding phenomenon in the area. The value of Flood Hazard Index (FHI) varied from 4.16 to 9.16, the higher the value, the more sensitive the area is to the risk of flooding. Five main classes of flood susceptibility are highlighted: very low, low, moderate, high and very high, representing 9.50, 26, 23, 22 and 19.5%, respectively of the study area. To validate the efficiency of the obtained flood susceptibility map, the adopted Area Under the Curve (AUC) method shows a very good accuracy (0.84 or 84%). The results of this study constitute a basic tool for decision-making for environmental management by public authorities and decentralised territorial authorities with territorial jurisdiction.

International audience; Alkylglycerols (AKGs) with a straight-chain alkane or alkene are ether lipids abundant in the liver oil of some elasmobranch fish species such as ratfishes and some sharks. Natural shark liver oil (SLO) mixture displays several known biological activities and most of its identified alkylglycerols were also obtained individually in pure form by total synthesis. However, the synthesis of alkylglycerols containing at least one alkyne moiety in the alkyl chain has yet not been reported. In this work, we describe the first total synthesis of 1-O-alkylglycerols based alkyne (2S)-3-((4-methoxytridec-6-yn-1-yl)oxy)propane-1,2-diol (10) and (S)-3-(((R)-12-methoxyoctadec-9-yn-1-yl)oxy)propane-1,2-diol (11), analogues of bioactive ether lipids found in the SLO mixture. Oxiranes opening by alkynyl boranes and solketal etherification are the key steps with a global yield up to 72 % in eight steps sequence.

L’objet de la présente étude est d’évaluer l’impact des revenus issus de l’exploitation du gaz naturel sur la croissance économique au Cameroun. Pour tester notre hypothèse selon laquelle les revenus issus de l’exploitation du gaz naturel au Cameroun affectent positivement la croissance, nous avons effectué une analyse de régression par la Méthode des Moindres Carrés Ordinaires pour notre modélisation sur la période 2005-2020. Les résultats des estimations économétriques obtenus montrent que les revenus issus du gaz naturel affectent positivement la croissance économique au Cameroun. Le gouvernement gagnerait à améliorer le climat des affaires au Cameroun afin d’attirer des capitaux étrangers dans le sous secteur gazier. La mise en place d’une politique de formation des jeunes camerounais aux métiers d’extraction et valorisation du gaz serait un atout et permettra au Cameroun de disposer des ressources humaines compétentes capables d’intervenir dans chaque maillon de la chaîne

International audience; In this study, we integrate anisotropy of magnetic susceptibility (AMS) and microstructural data including quartz crystallographic preferred orientation (CPO) from SEM-EBSD from the Manchi Pan-African granitic pluton with the objective of deciphering the time relationship between fabric development, emplacement and regional tectonics. The Manchi pluton, located in the western Cameroon domain of the Pan-African Fold Belt of Central Africa in Cameroon, is made of hornblende-biotite granite (HBtG), biotite granite (BtG) and protomylonites of HBtG. The pluton intruded the high grade country rocks made of banded gneiss and amphibolites. AMS of the pluton is controlled dominantly by paramagnetic phases such as, Fe-bearing silicates (biotite and hornblende). This is inferred from the low Km values (-6 SI units) as well as from hysteresis data. The AMS ellipsoid shape is mostly oblate, implying that flattening component of the strain was important during granite emplacement. Microstructural observations reveal presence of magmatic to sub-magmatic and solid-state deformation textures developed at moderate- to low-temperatures. This is consistent with the presence of rhomb and basal slip systems established from quartz c-axis data through EBSD analysis. The pluton recorded top-toward SW to top-toward south sense of shear as established by the kinematic markers. This indicates a component of simple shear during tectonic evolution of the pluton. We infer that the magnetic fabrics recorded in the Manchi granitic pluton is a manifestation of the D2 regional deformation. The dominance of flattening strain and the concentric pattern of magnetic data are indicative of ballooning being an important mechanism under transpressive regime.

International audience; In the present work, UVA light-driven g-C3N4/TiO2 photocatalyst was synthesized for the photodegradation of Carbamazepine (CBZ) in aqueous medium. The morphological, the optical properties and the structure of the TiO2, g-C3N4 and the prepared composites were analyzed using X-ray diffraction (XRD), Nitrogen adsorption-desorption isotherm based on BET, Raman Spectroscopy, Scanning Electron Microscopy (SEM) with EDX, UV-vis Diffuse Reflectance Spectroscopy (UVvis DRS). Optical absorption studies revealed a 2.97 and 2.78 eV of band gap for the developed composites for 10%g-C3N4/TiO2 (A10) and 30%g-C3N4/TiO2 (A30), respectively. The N2 adsorption-desorption isotherm showed an 80.64 and 59.67 m 2 /g of specific surface area for A10 and A30, respectively. Photodegradation studies show that A10 a composite photo-catalyst can eliminate 71.41% of CBZ with 30.38 % of mineralization yield within 360 min of UVA irradiation at optimum conditions (10 ppm of initial CBZ concentration and 0.1 g of 10%g-C3N4/TiO2 loading). The kinetic results showed that the removal of this pollutant nearly followed a First-order kinetic model with a regression coefficient (R 2) values more than 0.98 and a Hight reaction rate constant recorded of 0.0034 min-1 for A10.

In this paper, we use the Mellin transform to obtain the analytical formulas of European option (call or put) values, when the evolution of the underlying asset return is governed by a mixed modified fractional stochastic process. As an extension of the Dupire model Dupire (1994)[12], we also introduce the so-called “Mixed-Modified-Fractional-Dupire model”, by giving the expression of it’s local volatility and it’s sensitivity in relation to the Hurst coefficient H . Finally, in the same vein, we highlight an analytical relationship between local volatility and implied volatility.

International audience; We price options so as to take into account the existence of memory (short or long) characterizing the stochastic processes that generate prices, volatility and interest rates. In particular, we propose a model for Bull Spread options in a Mixed Modified Fractional Hull-White-Vasicek stochastic volatility and stochastic interest rate model. We propose a specific Bull Spread Vulnerable option pricing based on MMFHWV model.

The gonotrophic cycle of mosquitoes conditions the frequency of mosquito-human contacts. The knowledge of this important phenomenon in the mosquito life cycle is a fundamental element in the epidemiological analysis of a communicable disease such as mosquito-borne diseases. In this work, we analyse a deterministic model of complete life cycle of mosquitoes which takes into account the principal phases of female mosquitoes gonotrophic cycle, and the Sterile Insect technique combined with the use of insecticide as control measures to fight the proliferation of mosquitoes. We compute the corresponding mosquito reproductive number N * and prove the global asymptotic stability of trivial equilibrium. We prove that the model admits two non trivial equilibria whenever N * is greater than other threshold, Nc, which depends of the total number of sterile mosquitoes. Numerical simulations, using mosquito parameters of the it Aedes species, are carried out to illustrate our analytical results and permit to show that the strategy which consists in combining the sterile insect technique with adulticides, when it is well done, effectively combats the proliferation of mosquitoes., Le cycle gonotrophique des moustiques conditionne la fréquence des contacts homme-moustique. La connaissance de cet important phénomène du cycle de vie du moustique est un élément fondamental dans l'analyse épidémiologique des maladies transmises par les moustiques. Dans ce travail, nous faisons l'analyse d'un modèle déterministe traduisant le cycle de vie du mous-tique et qui prend en compte les principales phases du cycle gonotrophique et la lutte antivectorielle basée sur la technique de l'insecte stérile et l'utilisation des insecticides. Nous Calculons le nombre de reproduction de moustique N * et montrons la globale stabilité de l'équilibre trivial. Nous mon-trons que quand N * est strictement supérieur à 1 et plus grand qu'un certain seuil Nc dépendant du nombe total de moustiques stériles, alors le modèle admet deux équilibres non triviaux. Des simulations numériques, utilisant les paramètres des moustiques de l'espèce Aedes, sont réalisées pour illustrer nos résultats analytiques et permettent de montrer que la stratégie qui consiste à combiner la technique des insectes stériles aux adulticides, quand elle est bien menée, combat efficacement la prolifération des moustiques.

International audience; District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Natural materials are widely used in the field of environmental remediation and are appreciated for their surface physical and chemical properties. Clay constitutes a typical example. In this work, we report the evaluation of sorbent and photocatalytic potentials of local clay of two irrigated rice field waters in the degradation of crystal violet. The structural, textural and compositional properties of the local clay were investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analysis. The analysis results showed that these materials were composed mainly of quartz and kaolinite. The efficiency of these adsorbents (Y. Clay and L. Clay) to eliminate crystal violet dye from aqueous medium was examined at different initial concentrations, pH, contact time, adsorbent dose and the possible interference of inorganic salts from fertilizers. Kinetic studies showed that the adsorption process was well described by the pseudo-second order model and the equilibrium modelling results fitted adequately to the Freundlich model. The maximum amount of uptake capacity achieved at pH 2.0 was 18.40 (mg·g−1) and 20.40 (mg·g−1), respectively, for Y. Clay and L. Clay. The evaluation of the photocatalytic potential showed that the raw clay samples do not show photocatalytic activities during the 30 min of exposure to UV light. On the other hand, their photocatalytic potential is manifested when loaded with titanium dioxide (TiO2). Clays coupled with TiO2 under UV light showed an improvement in the degradation of the crystal violet dye by 15%. The synergistic effects between the high photocatalytic activity of TiO2 and the strong adsorption capacity of clays can be one promising technique for in situ remediation of contaminated soaked rice field.

The desert locust, Schistocerca gregaria (Forskål) (Orthoptera: Acrididae), a major Old World pest, is associated with agricultural losses and undesirable societal effects. There are three broad approaches to its control: reaction, proaction, and outbreak prevention. Reaction protects crops from swarms but it is costly and disruptive. Proaction involves early intervention during outbreaks to avert further development to plague status, it is in current use because it is effective, relatively inexpensive, and it is the best available option for now. Outbreak prevention, largely unavailable since the 1970s, at least on a regional scale, will require highly sensitive surveillance to detect the onset of gregarization. Sufficiently early intervention can, hypothetically, extend desert locust recession indefinitely. While research on desert locust biology and behavior is, almost, no longer an urgent requirement to improve the efficacy of control, new priorities have arisen for developing outbreak prevention capability (and for enhancing proaction). Salient needs presently include long residual tactics for prophylactic (preventive) control in breeding areas, intervention thresholds, and improved, sustainable coordination among stakeholders at national, regional, and international levels. The most recent desert locust episode of 2020 provides an illustrative example of how prevention might have averted the entire upsurge, and how proaction in some countries contained the spread of swarms. The initial outbreak in Saudi Arabia escaped control due to unpreparedness, and impacts of armed conflict in Somalia and Yemen, which weakened surveillance and control, further contributed to the invasion of ≥22 countries, and the spraying of ≈4.9 million ha, by the end of 2020.

International audience; The Piptadeniastrum Africanum bark tannin extract was characterized using MALDI TOF, ATR-FT MIR. It was used in the development of a resin with Vachellia nilotica extract as a biohardener. This tannin is consisting of Catechin, Quercetin, Chalcone, Gallocatechin, Epigallocatechin gallate, Epicatechin gallate. The gel time of the resin at natural pH (pH = 5.4) is 660 s and its MOE obtained by thermomechanical analysis is 3909 MPa. The tenacity of Urena lobata fibers were tested, woven into unidirectional mats (UD), and used as reinforcement in the development of biocomposite. The fibers tenacity at 20, 30 and 50 mm lengths are respectively 65.41, 41.04 and 33.86 cN·Tex−1 . The UD biocomposite obtained had very interesting mechanical properties. Its density, tensile MOE, ultimate strength, bending MOE and MOR are respectively 926 kg·m−3 , 6 GPa, 55 MPa, 9.3 GPa and 68.3 MPa. This biocomposite can be used in a building exterior structure.

In the present work, the potential of wind electric pumping systems (WEPS) utilization has been investigated for eight localities of the North Region of Cameroon, using long-term satellite-derived data and measured data at 10 m height above ground level (agl). Statistical indexes of accuracy performed the comparison between measured and satellite-derived data. The results suggested that satellite-derived data can accurately represent measured data. Furthermore, satellite-derived data can be suitable to assess the wind resource when measured ground level data are missing. The two-parameter Weibull Probability distribution function (PDF) and parabolic law were utilized, respectively to model wind speeds characteristics and wind turbines power curve. Four wind turbines (WT), represented by WT1, WT2, WT3 and WT4, with a rated capacity of 20 kW and a 30 m tower, were considered to simulate the power output and energy produced. The results showed that annual power densities at 10 m agl, for Bashéo, Beka, Figuil, Garoua, Pitoa, Poli, Rey-Bouba and Touboro were, respectively, 29.74, 17.45, 33.64, 17.94, 22.28, 11.99, 16.46 and 15.98 W/m2, while corresponding energy densities were 0.71, 0.42, 0.81, 0.43, 0.53, 0.29, 0.40 and 0.38 kWh/m2/day, in that order. Annual average frequencies for wind speeds greater or equal to WT’s cut-in wind speeds for each of the eight sites were determined. The greatest probability of observing higher wind speeds is for the site of Figuil, .This site showed the best combination of capacity factors (CF), costs of energy (COE), costs of water (COW) and flow rate capacity, At the opposite, the greatest probability of observing lower speeds is for the site of Poli that displayed the worst values of CF, COE, COW and flow rate capacity independently of the WT used. As a result, choosing WT for low wind speeds sites, would require to combine location wind resource and WT characteristics such as cut-in and rated wind speeds in order to take full advantage of costs of energy and water produced.

In this paper, The generalized Mixed-Modified-Fractional-Merton like partial differential equation with multi-assets under mixed modified fractional geometric Brownian motion was derived. The multidimensional Mellin transform was applied to derive the integral equation for the price of theEuropean put option on a bear spread basket of multi-assets.

International audience; In our study, the effectiveness of photocatalytic degradation of methyl orange (MO) in the presence of several catalysts under simulated solar light was studied. A comparative study was conducted between four different catalysts (TiO2, Cu2O, WO3, and Bi2O3) to assess their photocatalytic activities by varying the illumination time. The photodegradation was examined through quantification of the photogenerated reactive oxygen species (ROS). In situ photogenerated hydroxyl radicals ((OH)-O-center dot) were detected with terephthalic acid (TA) dosimetry based on fluorescence spectroscopy. Therefore, the concentration of (OH)-O-center dot was expressed according to the relative fluorescence intensity. Moreover, proof of a nonlinear relationship connecting the kinetics of the photocatalytic degradation of MO and the generation of (OH)-O-center dot radicals was demonstrated using coefficients of determination (R-2). This brought new insights regarding the mechanism of the photocatalytic activity. Our findings indicate that the generated (OH)-O-center dot radicals from heterogeneous photocatalytic systems are not the unique factor involved in organic pollutant elimination; the double metal structure of metal oxides should also be taken into consideration.

International audience; We propose and evaluate MoRAI (Mobile Read Access in Intermittent internet connectivity), a distributed peer-to-peer architecture organized in three levels dedicated to RDF data exchanges by mobile contributors. We present the conceptual and technical aspects of this architecture as well as a theoretical analysis of the different characteristics. We then evaluated it experimentally and results show the relevance of considering geographical positions during data exchanges and of integrating RDF graph replication to ensure data availability in terms of requests completion rate and resistance to crash scenarios.

L'analyse prédictive permet d'estimer les tendances des évènements futurs. De nos jours, les algorithmes Deep Learning permettent de faire de bonnes prédictions. Cependant, pour chaque type de problème donné, il est nécessaire de choisir l'architecture optimale. Dans cet article, les modèles Stack-LSTM, CNN-LSTM et ConvLSTM sont appliqués à une série temporelle d'images radar sentinel-1, le but étant de prédire la prochaine occurrence dans une séquence. Les résultats expérimentaux évalués à l'aide des indicateurs de performance tels que le RMSE et le MAE, le temps de traitement et l'index de similarité SSIM, montrent que chacune des trois architectures peut produire de bons résultats en fonction des paramètres utilisés., Predictive analytics allow to estimate future trends of events. Nowadays, Deep Learning algorithms allow making good predictions. However, it is necessary to choose the architecture that produces the most efficient results for each kind of problem. In this paper, the Stack-LSTM, the CNN-LSTM and the ConvLSTM models are applied to a time series of sentinel-1 radar images. The goal is to predict the next occurrence in a sequence of images. Experimental results are evaluated with performance metrics such as the RMSE and MAE loss, the processing time and the SSIM index. The values show that each of the three architectures can produce good results depending on used parameters.

International audience; In recent years, technological advances and the ever-increasing power of embedded systems have seen the emergence of so-called smart cities. In these cities, application needs are increasingly calling for Large-Scale Wireless Sensor Networks (LS-WSN). However, the design and implementation of such networks pose several important and interesting challenges. These low-cost, low-power devices are characterized by limited computing, memory storage, communication, and battery power capabilities. Moreover, sensors are often required to cooperate in order to route the collected data to a single central node (or sink). The many-to-one communication model that governs dense and widely deployed Wireless Sensor Networks (WSNs) most often leads to problems of network overload and congestion. Indeed, it is easy to show that the closer a node is geographical to the sink, the more data sources it has to relay. This leads to several problems including overloading of nodes close to the sink, high loss rate in the area close to the sink, and poor distribution of power consumption that directly affects the lives of these networks. In this context, we propose a contribution to the problem of LS-WSN energy consumption. We designed a hierarchical 3-tier architecture of LS-WSNs coupled with a modeling of the activities of the different sensors in the network. This architecture that is based on clustering also includes a redeployment function to maintain the topology in case of coverage gaps. The results of the performed simulations show that our architecture maximizes the lifetime than compared solutions.

International audience; A charge-controlled memristor model, with the memristive expression M(q) defined as the ratio between the voltage through the memristor and the current flowing into it, is used in the quantitative study of the charge transfer between two cells initially charged with known voltages. Calling q0 the total charge having flown into the memristor since its first use illustrating the memory feature of this component-, we show that the derivative of M(q) versus q must be a continuous function of q, leading us to improve the expression for M(q). Then, the dynamics of this charge transfer, as well as the time evolution of the voltages of both cells, is analyzed analytically and confirmed by numerical experiments.Fig. 3: TiO 2 memristor description.Fig. 5: Comparing the continuity of memristance functions [6].

In This work, we characterized hyperelastic isotropic and incompressible materials using genetic algorithm. This method has allowed us to optimize the parameters of the hyperelastic models of energy to describe the behavior of rubbery materials in great deformation and great displacement.This method of optimization is implemented in theinteractive mode in the Matlab software. It is composed of four large operators: selection, crossing-over, mutation, and elitism.The setting-up of this algorithm in the optimization of the rheological parameters is the first original contribution of this work. To study the relevance of the algorithm, comparisons were carried out with the following methods: least squares method, Beda-Chevalier method, Leventberg-Marquardt method, Pattern Search algorithm method. The second originality of this work is the construction of a new hyperelastic energy density that isisotropic, incompressible and phenomenological. The study of the relevance of the model proposed is accompanied by the comparisons with the models existing (Ogden, Beda (2007), Boyce and Arruda, Nguessong et al, Gornet et al, and Pucci-Saccomandi) on their capacity to reproduce the experimental data available in the literature. At the exit of this comparison, it arises that the model suggested is best adapted to reproduce the experimental curve of Treloar in simple tension, biaxial tension and pure shear with the same set of parameters., Les travaux de cette thèse portent sur la caractérisation des matériaux hyperélastiques, isotropes et incompressibles par la méthode de l’algorithme génétique. Cette méthode permet d’optimiser les paramètres des modèles d’énergie hyperélastiques afin de décrire le comportement des matériaux caoutchouteux en grande déformation et en grand déplacement. Cette méthode d’optimisation est implémentée en mode interactif dans le logiciel de calcul Matlab. Elle est constituée de quatre grands opérateurs: la sélection, le croisement, la mutation et l’élitisme. La mise sur pied de cet algorithme dans l’optimisation des paramètres rhéologiques est la première contribution originale de ce travail de thèse. Afin d’étudier la pertinence de l’algorithme, des comparaisons sont réalisées avec les méthodes existantes: la méthode des moindres carrés, la méthode de Beda-Chevalier, la méthode de Leventberg-Marquardt, la méthode de pattern search algorithm. Ces comparaisons ont couronné l’algorithme génétique de succès. La deuxième originalité de ce travail est la construction d’une nouvelle densité d’énergie hyperélastique isotrope, incompressible etphénoménologique. L’étude de la pertinence du modèle proposé, s’est accompagnée des comparaisons avec les modèles existants (Ogden, Beda(2007), Boyce et Arruda, Nguessong et al, Gornet et al. et Pucci-Saccomandi.) sur la capacité à reproduire les données expérimentales disponibles dans la littérature (Treloar). Il ressort que le modèle proposé est le mieux adapté à reproduire la courbe expérimentale en traction simple, traction équibiaxiale et en cisaillement pur avec le même jeu de paramètre.

Due to the energy constraints of sensors owing to the limitation of their built-in batteries, the lifespan of Wireless Sensor Networks (WSNs) are significantly affected. These particular ad-hoc networks have a huge number of applications including surveillance and target tracking. Unfortunately, since sensor nodes are limited in terms of power resources, efficient utilization of these resources is an important goal to design power-aware WSNs. This led researchers to propose numerous methods, such as clustered WSNs, in order to effectively manage the power resources. In this work, we proposed a heuristic clustering based on the hypergraph theory, and called HyperGraph Clustering (HGC) that aims at optimizing the energy of sensor nodes. Theoretical evaluation highlighted that this clustering protocol consumed less energy during the cluster formation phase and the selection of the cluster head. In addition, we evaluated the performance of the proposed HGC and the results showed the effectiveness of our scheme to those we compared in terms of the number of nodes alive, residual energy and the total consumption of the network.

International audience; Telecommunication network infrastructures in Africa and the Middle East regions, are deployed and operated in challenging environments that are highly scattered particularly in rural areas. Moreover, considerable number of cell sites are located in areas difficult to access. Furthermore, low income in rural areas does not allow a fast return on investment since the cost of deployment and operation of a cell site is considerable. These issues lead to a difficult human resource management, particularly, in the assignment of technicians to cell site for maintenance purpose. In this paper, an optimized scheme for costs of maintenance operations on cell sites is proposed. We used the k-means clustering algorithm for allocating field technician to a pool of cell sites. Moreover, to alleviate the k-means sensitivity to initialization, we proposed an initialization method that is based on the geometry of a sphere. We conducted series of experiments with sample of thousands of cell towers from OpenCellID and the results demonstrate the effectiveness of the proposal.

International audience; Nowadays, floods have become the widest global environmental and economic hazard in many countries, causing huge loss of lives and materials damages. It is, therefore, necessary to build an efficient flood forecasting system. The physical-based flood forecasting methods have indeed proven to be limited and ineffective. In most cases, they are only applicable under certain conditions. Indeed, some methods do not take into account all the parameters involved in the flood modeling, and these parameters can vary along a channel, which results in obtaining forecasted discharges very different from observed discharges. While using machine learning tools, especially artificial neural networks schemes appears to be an alternative. However, the performance of forecasting models, as well as a minimum error of prediction, is very interesting and challenging issues. In this paper, we used the multilayer perceptron in order to design a flood forecasting model and used discharge as input–output variables. The designed model has been tested upon intensive experiments and the results showed the effectiveness of our proposal with a good forecasting capacity.

International audience; The application of memristor in non-linear diffusive network is introduced. A charged-controlled memristor model is used in the quantitative study of pixel-to-pixel communication via a memristor. To quantitatively understand the behaviour of the system, the authors emphasised on two cells: master and slave. Information is launched from the master cell to the slave cell through a memristor and the dynamics, as well as, the saturation of the system is observed.

The consumption rate of traditional foods is gradually being reduced with time due to the globalization of the food systems and non-availability of modernized ready-to-use traditional food products. In order to contribute to the sustainability and to promote the consumption of nah poh, the present study was undertaken to gather traditional culinary knowledge related to the consumption of some local spices in nah poh, as to contribute to the development of a ready-to-use spice formulation. It consisted in carrying out a qualitative and quantitative survey. The study revealed that there is a great variability with respect to the different Divisions of the Western Regions of Cameroon, regarding the spice composition of nah poh. All the local spices used for this study are utilized for the preparation of nah poh. Seven spices were found to be essential in most Divisions. Scorodophloeus zenkeri fruits and Xylopia africana were shown to be essential spices for consumers in Mezam Division. The quantities of essential spices for one litre of nah poh varied between 0.61 ± 0.24 g and 4.59 ± 2.06 g.

International audience; Sesame seeds collected in eight provinces of Yemen were used to prepare cold-pressed sesame oil over three consecutive years. After ascertaining the nutritional quality and compliance with official norm of each batch of oil, mineral composition was determined by ICP-OES. No major and significant variations were detected over three years indicating the high reproducibility of Yemeni sesame oil composition as a function of its geographic origin. Three physico-chemically distinct sub-groups were identified. A subgroup includes sesame oil from Al Bayda, Marib, Ibb, and Taiz; a second is constituted by sesame oil from Abyan, Shabwa, and Hadhramount while sesame oil from Hodeida presents its own specificity. Calcium content was between 3.02 and 9.66 mg/kg, this cation making up 50% of the total mineral content. The two other most abundant minerals were potassium (0.824–4.251 mg/kg) and magnesium (0.811–4.742 mg/kg). Potentially toxic metal (Cd, Pb, Cu, Sn and Zn) content was very low in all samples. Principal component analysis showed that Abyan oil presents a unique metal-content profile. The precise geographic origin of Yemeni sesame oil can be determined by element content analysis.

The Ficus sycomorus bark tannin was extracted and characterized using Attenuated Total Reflectance Fourier Transform Middle Infrared (ATR-FT MIR) spectra in the 1800 and 600 cm−1 range, Matrix Assisted Laser Desorption Ionisation Time of Flight Mass Spectrometry (MALDI-TOF MS) and Carbon-13 Nuclear Magnetic Resonance (13C NMR) spectroscopy methods. Ficus sycomorus species have a very high percentage (46%) yield of tannin. These three characterization methods have shown that the Ficus sycomorus bark tannin is condensed and particularly a procyanidin type. It is composed of quercetin, apigenin, fisetinidin, catechin, gallocatechin, chalcone, radicinin, catechin gallate units with the presence of carbohydrates, quinone and gallic acid residues. The analysis results revealed that quercetin are the major constituents of Ficus sycomorus bark tannin. This procyanidin type tannin can give good wood adhesives.

A totally bio hardener acting with an unusual and new hardening mechanism derived from the exudate extract of the African trees Vachellia nilotica and Senegalia senegal was used to harden a maritime pine tannin resin without any aldehyde obtaining a completely bio adhesive for interior particleboard. For a density and pH given, the internal bond (IB) values increased simultaneously with the rate of bio-hardener. The optimal dry IB values (0.63 MPa) were obtained with 15% of bio-hardener solids. The low IB value (0.38 MPa) was obtained with 6% of bio-hardener solids. The IB of panels manufactured with UF as hardener are slightly higher than those using the above bio-hardeners.

A totally “bio” hardener derived from the exudate extract of the African trees Vachellia nilotica and Senegalia senegal was investigated. It hardened a maritime pine tannin resin without any obvious presence of an aldehyde thus obtaining a completely “bio” adhesive for wood panels. MALDI-ToF and CP MAS 13C NMR analysis indicated that the hardeners cross-linking species was 2,5-dihydroxymethyl furan linked onto carbohydrate chains. The hydroxymethyl furan moieties reacted both after detachment from the carbohydrate chains but also with carbohydrate chains still attached. The carbohydrates too were then involved as part of the binder. The gel times were slower than what was obtainable with paraformaldehyde but sufficiently fast to possibly be of industrial significance.

International audience

The study of a foreign language like Spanish has as principal aim the development of the communicative competence. In a context characterizedby difficulties (the lack of infrastructures, of didactic material, etc.), developing that competence becomes difficult. The main objective of this article is to propose, from an empirical orientation, local methodological strategies that could permit to develop the communicative competence of spanish students of the secondary education of Cameroon. After presenting the socio-educational context related to the teaching of Spanish in Cameroon,we show that, in order to develop the language competence of students of rural zones, teachers could use illustrated dictionaries and materials with renewable energies in order to convoke in teaching-learning activities, audio-visuals inputs., El objetivo principal de estudiar una lengua extranjera como el español es el desarrollo de la competencia comunicativa. En un contexto educativo camerunés marcado por varias dificultades (falta de infraestructuras, materiales didácticos, etc.), desarrollar esta habilidad se vuelve difícil. El objetivo de este artículo es proponer, basándose en una orientación empírica, formas metodológicas locales para desarrollar la competencia comunicativa de los estudiantes de secundaria españoles en Camerún. Después de haber presentado el contexto socioeducativo relacionado con la enseñanza del español en Camerún, demostramos que para desarrollar la competencia lingüística de los estudiantes de zonas aisladas del país, los profesores pueden utilizar los diccionarios ilustrados y utilizar los materiales para Energía renovable para convocar insumos audiovisuales en actividades de enseñanza-aprendizaje.

This paper reports on a new development approach of off-grid systems based on PV and batteries, representing, among other things, a great interest for rural electrification in developing countries. A renewable energy production elementary block is proposed and analyzed. This block can work autonomously or as a basic element of a high power production cluster dedicated to rural areas. Replacement of AC bus by DC power bus is shown to be more advantageous thanks to better energy efficiency. The proposed approach also allows new architectures in the field of storage, and the systematic use of typical batteries associations, cause of their accelerated ageing, can thus be avoided. Each low voltage battery is found to be able to separately supply a high power standalone inverter or even a grid reinjection inverter following the retained boost ratio. The proposed architecture could be considered as a basis for solar DC micro-grids, gathering several individual producers on the same network, minimizing instabilities due to phase and frequency mismatches in case of AC grids. With even a high elevation ratio, the proposed block can be integrated in long-distances DC or HVDC power transport, thus, contributing to the improvement of wider spread of renewable energy.

International audience

Increasingly, the technologies that are used in telecommunications contribute to improve intelligent transport systems. These technologies are systems that offer several concepts like vehicular ad hoc networks, which allow reduction of traffic accidents, traffic congestion and consequently increase road safety and the comfort of road users. Developing countries in general and those of sub-Sahara in particular do not have telecommunication infrastructures, even road infrastructures for the implementation of an intelligent transport system. Moreover, with the serious increase in vehicles in these countries, the problem of traffic regulation arise especially in the inter-urban context. One of the consequences of this problem is the high rate of road traffic accidents. Several models of traffic regulation as well as modeling systems of urban transport networks are presented in the literature. Unfortunately these models are intended for developed countries. The aim of this paper is to present, firstly the problems of the implementation of intelligent transport systems in developing countries like sub-Saharan Africa. Secondly, we present a survey of a road traffic model and an urban transport network models. Finally, we propose solutions, which provide methodologies for the modeling of a system and monitor traffic on inter-urban road transport networks in developing countries.

The recent fifth generation (5G) system enabled a highly promising evolution of Cloud Radio Access Network (C-RAN). Unlike the conventional Radio Access Network (RAN), the C-RAN decouples the baseband processing unit (BBU) from the remote radio head (RRH) by allowing BBUs from multiple Base Stations (BSs) to operate into a centralized BBU pool on a remote cloud-based infrastructure and a scalable deployment of light-weight RRHs. In this paper, we propose an efficient resource allocation scheme for 5G C-RAN called Bee-Ant-CRAN. The challenge addressed is to design a logical joint mapping between User Equipment (UE) and RRHs as well as between RRHs and BBUs. This is done adaptively to network load conditions, in a way to reduce the overall network costs while maintaining the user QoS and QoE. The network load has been formulated as a mixed integer nonlinear problem with a number of constraints. Then, the formulated optimization problem is decomposed into two stage resource allocation problem: UE-RRH association and RRH-BBU mapping. Therefore, a modified Artificial Bee Colony is developed as a swarm intelligence based approach to build the UE-RRH mapping (resource allocation). Moreover, an ameliorated Ant Colony Optimization algorithm is proposed to solve the RRH-BBU mapping (clustering) problem. Computational results demonstrate that our proposed Bee-Ant-CRAN scheme reduces the resource wastage and significantly improves the spectral efficiency as well as the throughput.

International audience; Les réalités dans les Petites et Moyennes Entreprises (PME) familiales s’expliqueraient par une monotonie observée, par l’apport d’information provenant le plus souvent du système de contrôle interne informel. Cependant, la littérature ne s’intéresse qu’assez peu à lier le népotisme au système de contrôle interne dans les entreprises familiales. Par ailleurs, dans un système oligarchique, le népotisme est assimilé à une forme de corruption jamais sanctionnée (Transparency International 2015). Alors, l’organisation ne peut-elle mieux s’assurer de l’efficacité du système de contrôle interne que grâce à un lien socio-familial ? L’objet de cet article est d’expliquer l’enjeu du népotisme dans l’efficacité du système de contrôle interne informel (SCII) dans les PME familiales. Pour cette étude approfondie, des entretiens semi-directifs sont menés auprès de sept PME camerounaises de trois secteurs d’activités (industrie, commerce, service). Les résultats de cette "étude de cas" montrent que, la dynamique de népotisme peut participer de manière multidimensionnelle au faisceau de causalités de contrôle et de la prise de décision, dont les conséquences sont plutôt positives à l’efficacité du SCII.

Introduction:In this article, we only focus on the probability distributions of the breakdown time whose causes are known, and we consider a partition of the observations into subgroups according to each of the causes as defined in Njamen and Ngatchou [1]. By adapting the stochastic processes developed by Aalen [2, 3], we derive a Kaplan-Meier [4] nonparametric estimator for the survival function in competiting risks.Result & Discussion:In a region where there is at least one observation, we prove on one hand that this new nonparametric estimator is unbiased in competiting risk and on the other hand, using the Lenglart inequality, we establish its uniform consistency in competiting risks.

International audience; We use the time-dependent variational method to examine the formation of localized patterns in dynamically unstable anharmonic lattices with cubic-quintic nonlineaarities and fourth-order dispersion. The governing equation is an extended nonlinear Schrodinger equation known for modified Frankel-Kontorova models of atomic lattices and here derived from an extended Bose-Hubbard model of bosonic lattices with local three-body interactions. In presence of modulated waves, we derive and investigate the ordinary differential equations for the time evolution of the amplitude and phase of dynamical perturbation. Through an effective potential, we find the modulationally unstable domains of the lattice and discuss the effect of the fourth-order dispersion in the dynamics. Direct numerical simulations are performed to support our analytical results, and a good agreement is found. Various types of localized patterns, including breathers and solitonic chirped-like pulses, form in the system as a result of interplay between the cubic-quintic nonlinearities and the second- and fourth-order dispersions.MODULATIONAL INSTABILITY; SCHRODINGER-EQUATION; COLLAPSE; REVIVAL; WAVES; MODEL

International audience

International audience

Considering the evolution of the semantic wiki engine on-based platforms, two main approaches could be distinguished: Ontologies for Wikis (OfW) and Wikis for Ontologies (WfO). OfW vision requires the existing ontologies to be imported. Most of them use the Resource Description Framework (RDF-based) systems in conjunction with the standard Structured Query Language (SQL) database to manage and query semantic data. But, relational database is not an ideal type of storage for semantic data. A more natural data model for Semantic MediaWiki (SMW) is RDF, a data format that organizes information in graphs rather than in fixed database tables. This paper presents an ontology on-based architecture, which aims to implement this idea. The Architecture mainly includes three-layered functional architecture: Web User Interface Layer, Semantic Layer, and Persistence Layer.

International audience; This article investigates combined effects of nonlinearities and substrate's deformability on modulational instability. For that, we consider a lattice model based on the nonlinear Klein-Gordon equation with an on-site potential of deformable shape. Such a consideration enables to broaden the description of energy-localization mechanisms in various physical systems. We consider the strong-coupling limit and employ semi-discrete approximation to show that nonlinear wave modulations can be described by an extended nonlinear Schrodinger equation containing a fourth-order dispersion component. The stability of modulation of carrier waves is scrutinized and the following findings are obtained analytically. The various domains of gains and instabilities are provided based upon various combinations of the parameters of the system. The instability gains strongly depend on nonlinear terms and on the kind of shape of the substrate. According to the system's parameters, our model can lead to different sets of known equations such as those in a negative index material embedded into a Kerr medium, glass fibers, resonant optical fiber and others. Consequently, some of the results obtained here are in agreement with those obtained in previous works. The suitable combination of nonlinear terms with the deformability of the substrate can be utilized to specifically control the amplitude of waves and consequently to stabilize their propagations. The results of analytical investigations are validated and complemented by numerical simulations. (C) 2017 Elsevier B.V. All rights reserved.

International audience; Using the theory of bifurcation, we provide and find gap soliton dynamics in a nonlinear Klein-Gordon model with anharmonic, cubic, and quartic interactions immersed in a parametrized on-site substrate potential. The case of a deformable substrate potential allows theoretical adaptation of the model to various physical situations. Nonconvex interactions in lattice systems lead to a number of interesting phenomena that cannot be produced with linear coupling alone. By investigating the dynamical behavior and bifurcations of solutions of the planar dynamical systems, we derive a variety of exotic solutions corresponding to the phase trajectories under different parameter conditions. Moreover, we demonstrate how and why traveling waves lose their smoothness and develop into solutions with compact support or breaking.

International audience

This paper aims to investigate the existence of a temporal connection between the flooding in the Far North region (21 events) and the observed trends in rainfall. The work is based on interannual and monthly rainfall recorded over a maximum period of 77 years (1935-2011) on nine stations. The selected stations and time periods obey the data quality criteria (no gaps) and the requirements of the World Meteorological Organization (30 observations). The months of July, August and September are high potential floods, and analyzes are performed especially there. So Mann-Kendall trend tests, Pettitt tests and Hubert segmentation procedure was applied in order to detect possible changes in rainfall recorded. Any more to examine the severity of meteorological drought, the standardized precipitation index method was used. The comparison of these results with flood events history collected and formatted for this study occurred in the region of the Far North Cameroon shows that there is no absolute link between trends rainfall and the flood events., Le présent papier a pour objectif de rechercher l’existence d’un lien temporelentre les inondations survenues dans la région de l’Extrême-Nord (21 événements) et les tendances de la pluviométrie observées. Les travaux s’appuient sur l’analyse des précipitations interannuelles et mensuelles enregistrées sur une durée maximum de 77 ans (1935-2011) de neuf stations. Les stations retenues et les périodes étudiées obéissent aux critères de qualité de données (absence de lacunes) et aux exigences de l’Organisation Mondiale de la Météorologie (30 ans d’observations). Les mois de juillet, août et septembre sont à fort potentiel d’inondations et des analyses complémentaires y sont particulièrement réalisées. Ainsi, à côté des tests de tendance de Mann-Kendall appliqués sur des séries pluviométriques interannuelles, des tests de Pettitt et la procédure de segmentation d’Hubert ont également été appliqués dans le but de déceler d’éventuels changements de pluviométrie. De plus, afin d’examiner la sévérité de la sécheresse météorologique, la méthode des indices pluviométriques standardisés a été utilisée.La confrontation de ces résultats avec l’historique des événements d’inondations, collectés et mis en forme pour cette étude, survenus dans la région de l’Extrême-Nord Cameroun montre qu’il n’existe pas de lien absolu entre les tendances de la pluviométrie et ces événements d’inondation.

In a renewable energy system, in order to ensure continuous production, batteries associated to a charge controller are always necessary whenever the source of charging is solar, wind, or hydraulics. For photovoltaic (PV) systems, an excessive energy produced by solar cells during intense sunlight peak conditions could damage the batteries. A charge controller is therefore used to maintain the suitable charging voltage to the batteries so that, as the input voltage from the PV module rises, the charge controller regulates the process, thus, preventing any overcharging. This paper presents a practical solution for off-grid PV systems using standard commercial elements. A detailed analysis is carried out based on experimental results of the battery charge control allowing a long-life and a high safety of the autonomous storage and production systems. The experimental work was performed with a solar battery (24 V-55 Ah) charged by a 175Wp PV module, through a Maximum-Power-Point-Tracking/Three-Stage-Charging-Cycle (MPPT/TSCC) charge controller. The benefits of the Three-Stage-Charging-Cycle (TSCC) control as well as the Maximum-Power-Point-Tracking (MPPT) have been thus proven for the efficiency of the recharge, both qualitatively and quantitatively.

International audience

Data collection is one of the main operations performed in Wireless Sensor Networks (WSNs). Even if several interesting approaches on data collection have been proposed during the last decade, it remains a research focus in full swing with a number of important challenges. Indeed, the continuous reduction in sensor size and cost, the variety of sensors available on the market, and the tremendous advances in wireless communication technology have potentially broadened the impact of WSNs. The range of application of WSNs now extends from health to the military field through home automation, environmental monitoring and tracking, as well as other areas of human activity. Moreover, the expansion of the Internet of Things (IoT) has resulted in an important amount of heterogeneous data that are produced at an exponential rate. Furthermore, these data are of interest to both industry and in research. This fact makes their collection and analysis imperative for many purposes. In view of the characteristics of these data, we believe that very large-scale and heterogeneous WSNs can be very useful for collecting and processing these Big Data. However, the scaling up of WSNs presents several challenges that are of interest in both network architecture to be proposed, and the design of data-routing protocols. This paper reviews the background and state of the art of Big Data collection in Large-Scale WSNs (LS-WSNs), compares and discusses on challenges of Big Data collection in LS-WSNs, and proposes possible directions for the future.