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您的检索式：作者名="Brahim Mehdi"
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| 1 | Mechanical and Metallurgical Characterization of HSLA X70Welded Pipeline Steel Subjected to Successive Repairs显示文摘The aim of this work is to study the influence of successive weld repairs on the microstructure and the mechanical behavior of the heat-affected zone(HAZ) of an HSLA X70 steel. Detailed microstructural examination combined to grain size measurement showed that beyond the second weld repair, the microstructure of the HAZ undergoes significant change in the grain morphology and grain growth. The results of the X-ray diffraction analyzed using MAUD software indicated an increase in the crystallite size and a decrease in the dislocation density according to the number of weld repair operations. Consequently, a loss of mechanical properties, namely the yield strength and the toughness with the number of weld repairs, was recorded. Beyond the second weld repair operation, the properties of the welded joint do not fulfill the standards applied in piping industry. | Bouzid Maamache Mabrouk Bouabdallah Abdelhalim Brahimi Youcef Yahmi Billel Cheniti Brahim Mehdi | 2016 | Acta Metallurgica Sinica(English Letters)2016，29，6： | 2 |
| 2 | Adaptive state estimation of groundwater contaminant boundary input flux in a 2-dimensional aquifer显示文摘In many circumstances involving heat and mass transfer issues,it is considered impractical to measure the input flux and the resulting state distribution in the domain.Therefore,the need to develop techniques to provide solutions for such problems and estimate the inverse mass flux becomes imperative.Adaptive state estimator(ASE)is increasingly becoming a popular inverse estimation technique which resolves inverse problems by incorporating the semi-Markovian concept into a Bayesian estimation technique,thereby developing an inverse input and state estimator consisting of a bank of parallel adaptively weighted Kalman filters.The ASE is particularly designed for a system that encompasses independent unknowns and/or random switching of input and measurement biases.The present study describes the scheme to estimate the groundwater input contaminant flux and its transient distribution in a conjectural two-dimensional aquifer by means of ASE,which in particular is because of its unique ability to efficiently handle the process noise giving an estimation of keeping the relative error range within 10%in 2-dimensional problems.Numerical simulation results show that the proposed estimator presents decent estimation performance for both smoothly and abruptly varying input flux scenarios.Results also show that ASE enjoys a better estimation performance than its competitor,Recursive Least Square Estimator(RLSE)due to its larger error tolerance in greater process noise regimes.ASE's inherent deficiency of being slower than the RLSE,resulting from the complexity of algorithm,was also noticed.The chosen input scenarios are tested to calculate the effect of input area and both estimators show improved results with an increase in input flux area especially as sensors are moved closer to the assumed input location. | Muhammad Malik Nauman Murtuza Mehdi Asif Iqbal Muhammad Saifullah Abu Bakar Brahim Aissa Dk Nur Afiqah Jalwati Puteri Amer Farhan Rafique | 2019 | Journal of Groundwater Science and Engineering2019，7，4： | 0 |
| 3 | Sensor Faults Observer Design with H_∞ Performance for Non-linear T-S systems显示文摘This paper deals with the problem of the state estimation and the sensor faults detection for nonlinear perturbed systems described by Takagi-Sugeno(T-S)fuzzy models with unmeasurable premise variables.Indeed,a T-S observer is synthesized,in descriptor form,to estimate both the system states and the sensor faults simultaneously.The idea of the proposed approach is to introduce the sensor fault as an auxiliary variable in the state vector.Besides,the T-S model with unmeasurable premise variables is reduced to a perturbed model with measurable variables.Convergence conditions are established with Lyapunov theory and the H∞performance in order to guarantee the best robustness to disturbances.These conditions are expressed in terms of linear matrix inequalities(LMIs).The parameters of the observer are computed using the solution of the LMI conditions.Finally,a numerical example is given to illustrate the design procedures.Simulation results show the satisfactory performances. | Imen Haj Brahim Maha Bouattour Driss Mehdi Mohamed Chaabane Ghani Hashim | 2013 | International Journal of Automation and computing2013，10，6： | 0 |
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