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International audience; This paper presents a nonlinear control scheme to stabilize the problem of torsional vibration suppression with boundary impulsive conditions. A new nonlinear dynamical system is developed. Based on semi-group theory, we prove the well-posednes of the proposed system. In the model development, nonlinearities that arise due to dry friction and loss of contact is considered. Therefore, the impulsive system stability analysis is carried out by using Lyapunov theory and a comparison method. Numerical simulations show the relevance of our result for impulsive system.

International audience; To address security issues in oilwell drillstring system, the drilling operation handling which is in generally not autonomous but ensured by an operator may be drill bit destructive or fatal for the machine. To control of stick-slip phenomenon, the drillstring control at the right speed taking only the drillstring vibration is not sufficient as the mud dynamics and the pressure change around the drill pipes cannot be neglected. A coupled torsional vibration and pressure model is presented, and the well-posedness problem is addressed. As a Partial Differential Equation-Ordinary Differential Equation (PDE-ODE) coupled system, and in order to maintain a non destructive downhole pressure, we investigate the control stability with and without the damping term in the wave PDE. In terms of, the torsional variable, the downhole pressure, and the annulus pressure, the coupled system equilibrium is shown to be exponentially stable.

The process of securing water supply is one of the biggest problems in the world. Along with the ever-increasing demand for water for different users, water resource management agencies face many challenges, some of which may be an obstacle to achieving sustainability and guaranteeing water for the various sectors of water supply. To face this dilemma, integrated water resources management is the best approach. The region of Tipaza is facing this problem. Through this work the WEAP model is applied to assess and analyze the current and projected balance of water resource management taking into account the different policies and operational factors that can affect the demand up to the year 2050. The results of the simulation showed that a deficit of 18.936Mm3 will be registered in the year 2042. For the years 2043 and 2044, the demand will be of the same order as the supply. For the period 2045 to 2050 a deficit of (3.44Mm3 to 85.48 Mm3) will be recorded in the case of scenario RCP4.5. On the other hand, in the case of the pessimistic scenario RCP8.5, the deficit will start from the year 2025 and will continue until the horizon of the year 2050 with 130.95 Mm3.

The objective of this study was to follow-up on the evolution of the hydro-pluviometric schemes and particular elements of Wadi Mina (6048 km(2)) to the Sidi M'Hamed Ben Aouda Dam to evaluate the silting origin and status of this dam situated in the northwest of Algeria. The pluviometric study targeted a series of rains during 77 years (1930-2007), the liquid discharge data cover a period of 41 years (1969-2010) and the solids and suspended sediment concentrations data cover very variable periods, starting from 22 to 40 years for the entire catchment area. The statistical tests for ruptures detection on the chronological series of rains and discharges indicate a net reduction of rains of more than 20% on the entire basin since 1970. The evolution of solids inputs was quantified: the maximum values are registered on autumn start and at the end of spring. The Wadi Mina basin brings annually 38 x 106 m(3) of water with a specific degradation of 860 t.km(-2) year(-1). By comparing the results found, we thus observe that the basin upstream of SMBA (1B) Dam is the greatest sediment producer towards the dam because it shows a specific degradation equal to 13.36 t.ha(-1) year(-1).

International audience; It is well known that torsional vibrations in oil well system affect the drilling directions and may be inherent for drilling systems. The drill pipe model is described by second order hyperbolic Partial Differential Equation (PDE) with mixed boundary conditions in which a sliding velocity is considered at the top end. In this paper, we consider the problem of boundary observer design for one-dimensional PDE with the usually neglected damping term. The main purpose is the construction of a control law which stabilizes the damped wave PDE, using only boundary measurements. From the Lyapunov theory, we show an exponentially vibration stability of the partially equipped oil well drilling system. The observer-based control law is found using the backstepping approach for second-order hyperbolic PDE. The numerical simulations confirm the effectiveness of the proposed PDE observer based controller.

The estimation of precipitation quantileshas always been an area of great importance to meteorologists, hydrologists, planners and managers of hydrotechnical infrastructures. In many cases, it is necessary to estimate the values relating to extreme events for the sites where there is little or no measurement, as well as their return periods. A statistical approach is the most used in such cases. It aims to find the probability distribution that best fitsthe maximum daily rainfall values. In our study, 231 rainfall stations were used to regionalize and find the best distribution for modeling the maximum daily rainfall in Northern Algeria. The L-moments method was used to perform a regionalization based on discordance criteria and homogeneity test. It gave rise to twelve homogeneous regions in terms of L-Coefficient of variation(L-CV), L-Skewness (L-CS)and L-Kurtosis (L-CK). This same technique allowed us to select the regional probability distribution for each group using the Z statistic. The generalized extreme values distribution (GEV) was selected to model the maximum daily rainfall of 10 groups located in the north of the steppe region and the generalized logistic distribution (GLO) for groups representing the steppes of Central and Western Algeria. The study of uncertainty by the bias and RMSE showed that the regional approach is acceptable. We have also developed maximum daily rainfall maps for 2, 5, 10, 20, 50 and 100 years return periods. We relied on a network of 255 rainfall stations. The spatial variability of quantiles was evaluated by semi-variograms. All rainfallfrequencymodelshave a spatial dependence with an exponential model adjusted to the experimental semi-variograms. The parameters of the fitted semi-variogram for different return periods are similar,throughout, while the nugget is more important for high return periods. Maximum daily rainfall increases from South to North and from West to East, andis more significant in the coastal areas of eastern Algeria where it exceeds 170 mm for a return period of 100 years. However,it does not exceed 50 mm in the highlands of the west.

International audience; The paper considers oilwell drilling operations and, in particular, the problem of minimizing drilling vibrations. We develop a stabilizing controller for a one dimension wave PDE with damping term that describes the drillstring torsional system. The drillstring system stability is studied via the Lyapunov theory and the control steps are deduced from a PDE backstepping approach. As a result, exponential vibration suppression is obtained in presence of stick-slip friction due to the drill-bit and the soil interactions. The torsional vibration rejection is shown through the developed simulation results.

International audience; Stick-slip oscillations also known as torsional vibrations appearing in oilwell drilling systems are a source of economic losses, borehole disruption, pipes disconnection, and prolonged drilling time. The torsional dynamics is modeled by a damped wave equation. An important stability issue is to find a control law that reject perturbations due to torsional vibrations. Hence, the primary aim of this paper is to prove the well-posedness of the damped wave equation. In the next step, using the Riemann invariants, the damped wave equation is transformed into 2 × 2 first-order transport equations. The backstepping techniques combined with kernel equations and the Lyapunov theory are used to prove the local exponential stability of the transformed system, consequently the torsional dynamic. Simulation results are presented to illustrate the effectiveness of the control law.

International audience; It is well known that vibrations in oilwell system affect the drilling directions and may be inherent for drilling systems. Further, the environment complexity requires a minimum number of sensor variables. In this paper, for an oilwell drilling system, we present an adaptive observer design for a second-order Partial Differential Equation (PDE) with the usually neglected damping term. The design relies on the top boundary measurements only. From the Lyapunov theory and the backstepping technique, we develop an observer based control law for the one dimension wave PDE. We show an exponentially vibration stability of the partially equipped oilwell drilling system. The simulation results confirm the effectiveness of the proposed PDE observer based controller.

ResumeDans cette etude, on a fait appel a la teledetection et aux systemes d’information geographiques (SIG) pour evaluer et cartographier l’erosion hydrique en utilisant l’equation universelle des pertes en sol USLE dans le bassin versant de l’Oued Mina en Algerie. Ce bassin est caracterise par une grande irregularite dans les precipitations, une forte pente, une lithologie essentiellement marneuse et une couverture vegetale tres faible ce qui le rend tres vulnerable a l’erosion. L’USLE est la combinaison de six facteurs specifiques qui decrivent les caracteristiques du bassin versant. Les donnees de teledetection multi-temporelles et les SIG sont utilises pour evaluer et cartographier chaque facteur individuellement. L’integration des cartes thematiques des facteurs du modele USLE dans le SIG permet de cerner l’impact de chaque facteur dans les pertes en sol, de classer par importance relative les zones d’erosion, et de quantifier les pertes en sol dans le bassin.Editeur Z.W. KundzewiczCitation Toumi, S...

Compared to the known waves and transport PDEs, boundary conditions in drilling aren't trivial and depend on the system parameters. Further, nonlinearities are present due to bit-rock interaction. In this paper, torsional vibrations stabilization resulting from the bit stick-slip behavior are investigated. The second-order vibration dynamic is transformed into 2 × 2 first-order PDEs. The boundary stabilizing control law is constructed such that the transformed system tracks a designed stable target system. The backstepping techniques combined with kernel equations and the Lyapunov theory are used to prove the local exponential stability of the new system variables, consequently, the vibration suppression due to torsional dynamics. Simulations are presented to illustrate the effectiveness of the control laws.

Erosion, sediment transport, and deposition result in agricultural soil degradation, dam siltation, and significant and costly damage. In Algeria, despite a decrease in total rainfall, especially in the central and western parts of the country, dam siltation and erosion are on the rise according to recent studies by the National Agency of Dams and Transfers. Developing a map of the spatial variation of rainfall erosivity will provide a powerful tool for land and dam managers. Erosivity can be quantified using the R factor from the Universal Soil Loss Equation. The purpose of this work is to develop a model for estimating rain erosivity based on the modified Fournier index (MFI), longitude, altitude, and mean maximum daily rainfall, and then to produce a map of the spatial distribution of erosivity in Northern Algeria. The R factor reaches a maximum value of roughly 905 MJ mm ha−1 year−1 in the Jijel area of Mediterranean Eastern Algeria and a minimum value of 37 MJ mm ha−1 year−1 in the southern portion of the study area. The study of the temporal evolution of annual rainfall erosivity index (R) and I max over 30 min showed that R recorded a negative trend and I max recorded no trend.

Complete tubular colonic duplication (CTCD) is exceedingly rare. The association of CTCD with an anorectal malformation is unusual. This malformation may be found unexpectedly at laparotomy. We present 3 cases of surgically proven neonate CTCD discovered at laparotomy for anal atresia. We reviewed the mode of clinical presentation, the imaging, and laparotomy findings. Our series illustrates that this rare disease presents perinatally in association with anal atresia, with or without other associated anomalies.

End-of-life (EOL) decisions are not well studied in developing countries. We report EOL decision patterns in two Tunisian intensive care units [ICUs, medical (MICU) and surgical (SICU)] belonging to the same teaching hospital. Consecutive deaths that occurred in participating ICUs over 2 years were analysed. End-of-life decisions were prospectively recorded by the senior attending physicians, while subject’s characteristics were retrospectively collected. Deaths occurred in 326 of 1,733 ICU-admitted patients (median age: 64 years; median SAPS II at admission = 36). Overall, a decision for full support was taken in 69%, while decisions to withhold or withdraw life support were held in 22.1 and 8.9% of deaths, respectively. The rate of end-of-life decisions was similar in the MICU and the SICU. In no instance was there MV withdrawal during ICU stay. Discharging patients to die at home was observed only in the MICU (10 out of the 20 patients with a withdrawal decision). Two factors were independently associated with WH or WD decisions: a severe and ultimately fatal underlying disease was positively associated with such decisions (OR = 2.4, 95% CI: 1.3–4.36; p = 0.003), while having an independent functional status before the ICU was associated with a decreased rate of physician decisions of WH or WD (OR = 0.32, 95% CI: 0.15–0.67; p = 0.002). Withholding and withdrawing life support are common in medical and surgical ICUs of a Tunisian hospital. Withholding is more frequent than withdrawing life support. These decisions appear to be effected by functional status and underlying conditions.

Severe pre-eclampsia and acute tubular necrosis due to hemorrhagic shock are the major causes of postpartum acute renal failure. Cortical necrosis and haemolytic uraemic syndrome are less frequently. Post-infectious glomerulonephritis as a cause of postpartum acute glomerular disease and renal failure has been rarely reported. We report a patient with postpartum acute glomerulonephritis who presented nephritic syndrome, the diagnosis of which was confirmed by renal biopsy.

Algeria is periodically affected by severe and repeated flooding. Flood hazard studies require the estimation of extreme flood flows. To predict and estimate the characteristics of maximum flows, knowledge of their distribution law is essential. The L-moments method was used to determine homogeneous regions and the appropriate distribution for these regions. Three homogeneous regions were delineated. This technique produced a Pearson type III distribution for the coastal region and the Tell Atlas and a Pareto distribution for the steppe regions and high plateaus of Eastern and Western Algeria. To estimate maximum flow at ungauged sites for different return periods, the 'index-flood' method was used. An empirical formula was developed that uses the average annual maximum flow as a function of catchment area and the average slope of the main channel to estimate maximum flow at any point on the Oued. The coefficient of determination and the Nash criterion, for the three regions, are superiors to 88% and 83% respectively. The root mean squared error, for the three regions, is less than 12%. These values show the robustness of the developed models.

Severe pre-eclampsia and acute tubular necrosis due to hemorrhagic shock are the major causes of postpartum acute renal failure. Cortical necrosis and haemolytic uraemic syndrome are less frequently. Post-infectious glomerulonephritis as a cause of postpartum acute glomerular disease and renal failure has been rarely reported. We report a patient with postpartum acute glomerulonephritis who presented nephritic syndrome, the diagnosis of which was confirmed by renal biopsy.

Low flow hydrological regimes are crucial for an efficient development of water resources management tools, especially in those areas stressed by the combination of a dry climate and an excessive water demand, such as the Mediterranean basins. A lot of effort has been made by the worldwide scientific community toward the prediction of low flows features in ungauged catchments. The aims of the present study are: (1) the quantification of low flows characteristics, in particular with regard to the BFI and (2) the application of a simple regional approach to predict the BFI at ungauged sites. The investigated area is located in North West Algeria and has an extension of about 130,000 km 2 . The relevant extension and the poorly dense monitoring network, which consist in 24 hydrometric stations, require the identification of homogeneous regions, for further application of simple linear regional regression models. Regions delineation is accomplished through the Principal Component Analysis method (PCA) and the cluster analysis, based on physiographic and climatic data. Three significantly different homogeneous areas have been identified, and comparisons between global and local regional multiple linear regression models indicate a large percentage of BFI explained variance in each area.

The risk of erosion and desertification is a major problem in the Mediterranean region in general and Algeria in particular. Algeria has a known downward trend of very high rainfall since 1975, especially in the Central and Western regions. In this work, the spatial pattern and temporal trend of the modified Fournier index (MFI) are investigated. Also, it is aimed to answer the question of whether a change has occurred or not in the concentration of rainfall using the precipitation concentration index (PCI). A total of 117 rainfall stations are used to determine these two indices as well as the development of a formula for calculating MFI based on annual rainfall. For mapping the modified Fournier index, 273 stations are used. The results show no change in the seasonal distribution of rainfall. However, a downward trend of about 30% of MFI is present in the Central and Western regions. The eastern regions of the North Algeria have not experienced this decline. The spatial variability shows that the MFI value increases from the west to east and from the south to north.

Collected in the volume “L’Invincible espérance”, Christian de Chergé’s writings address the theme of mercy in the Christian Bible and in the Koran. De Chergé described also the practices of Christian life in a Muslim country. Hence my reflection followed in two stages: first, I propose to see the theological concepts of the author, anchored in the study of biblical and Koranic texts, in the spirit of religious pluralism, and then, to analyze the modes of living together of Christians among Muslims at the time of rupture. In this second part, I am inspired by the rule of Saint Benedict and the work of Michel de Certeau who perceives daily practices as an act of resistance.