Boundary stabilisation of the wave equation in the presence of singularities

We study the boundary stabilisation of the wave equation by a nonlinear feedback active on a part of the boundary in geometric situations for which the solutions have singularities. These singularities appear at the interfaces at which the mixed Neumann–Dirichlet boundary conditions meet. Under a simple geometrical condition concerning the orientation of the boundary, we obtain sharp energy decay rates under a general growth assumption on the feedback. We show that the singularities do not affect the energy decay rates and give examples.     

Les formations plio-quaternaires de la région de Casablanca (Maroc): aspects sédimentologique et géotechnique

The Plio-Quaternary formations of the Casablanca area consist of a sequence of cross-bedded strata. They frequently begin with a lumachelle conglomerate occasionally associated with gravels and marine calcarenite. The marine deposits are overlain by yellow and grey dune sandstones, locally oxidized at depositional horizons. These dunal calcarenites have been extensively exploited and hence their sedimentological and geotechnical parameters have been determined from numerous samples taken from the quarries in the region. The sedimentological study results show that these generally homogeneous materials consist mainly of well-graded fine to coarse carbonate sands (98%) containing both bioclasts and calcareous cements. It is clear that at the time of deposition there was little detrital material, with the marine deposits formed mainly of shell debris. Study shows that the marine deposits underwent early lithification in a shallow marine environment which then continued in a continental environment by the movement of meteoric water. The marine deposits are well cemented. They have a low degree of dissolution but quite a high degree of recrystallization, notably towards the bottom of the individual horizons. The dunal deposits which underwent lithification in a continental environment are characterized by a very low cementation, mainly at point contact, a high dissolution and a weak recrystallization. The difference in diagenesis affects both the physical and mechanical features of these Plio-Quaternary calcarenites. From a geotechnical point of view, the consolidated marine and dunal deposits have a weak to medium compressive strength (502), a very weak resistance to shocks (453. 8.?Density and percentage CaCO₃. 9.?Compression resistance and percentage CaCO₃. In view of the graph relationships, it is possible to estimate the other parameters from the determination of a single physical or mechanical feature of the calcarenite. However, the sedimentological and petrographical analyses show that the following factors can be subject to quantitative variations: (1) the carbonate content; (2) the nature of the bioclastic elements; (3) the grain size of the detrital elements; (4) the cement percentage and its grain size; and (5) the importance of dissolution and the vacuum percentage. These factors control the physical and mechanical features of the Plio-Quaternary formations of the Casablanca area. As a consequence, it is suggested that when considering the sedimentological features and physical and mechanical characteristics of the Plio-Quaternary formations of the Casablanca area, the particular deposits must first be categorized into one of the four following facies: lumachelle; marine calcarenite; yellowish dunal calcarenite; or grey dunal calcarenite.     

First Principle Calculations and Monte Carlo Simulations Investigation of Structural,Electronic, Magnetic,Elastic and Thermoelectric Properties of Antiperovskites $$Mn_3ZnX (\mathrm{X}= \mathrm{C, \ N})$$ M n 3 Z n X ( X = C,N )

Journal of Superconductivity and Novel Magnetism - The structural, electronic, magnetic elastic and thermoelectric properties of $$Mn_3ZnX$$ (X = N,C) have been investigated in the framework of...     

Soft Computing Based Pattern Classifiers for the Obstacle Avoidance Behavior of Intelligent Autonomous Vehicles (IAV)

To ensure more autonomy and intelligence with real-time processing capabilities for the obstacle avoidance behavior of Intelligent Autonomous Vehicles (IAV), the use of soft computing is necessary to bring this behavior near to that of humans in the recognition, learning, adaptation, generalization, reasoning and decision-making, and action. In this paper, pattern classifiers of spatial obstacle avoidance situations using Neural Networks (NN), Fuzzy Logic (FL), Genetic Algorithms (GA) and Adaptive Resonance Theory (ART) individually or in combination are suggested. These classifiers are based on supervised learning and adaptation paradigms as Gradient Back-Propagation (GBP), FL, GA and Simplified Fuzzy ArtMap (SFAM) resulting in NN/GBP and FL as Intelligent Systems (IS) and in NN/GA, NN/GA-GBP, NN-FL/GBP and NN-FL-ART/SFAM as Hybrid Intelligent Systems (HIS). Afterwards, a synthesis of the suggested pattern classifiers is presented where their results and performances are discussed as well as the Field Programmable Gate Array (FPGA) architectures, characterized by their high flexibility and compactness, for their implementation.     

Behavior Study of the Nanostructured Zn1-xCdxO (0 ≤ x ≤ 0.1) Semiconductor Thin Films Deposited onto Silicon Substrate by Dip-Coating Method

Silicon - The specimens of nanostructured semiconductor of Zn1-xCdxO (0 ≤ x ≤ 0.1) thin films were grown on silicon substrate using a dip-coating method. The...     

Numerical study of the wake induced by a porous disk under deflected inflow

This study examines the wake of a porous disk that generates a velocity deficit equivalent to that of a wind turbine. Three-dimensional unsteady numerical simulations based on the finite volume method are performed. The URANS-SST (k–ω) model is applied for the turbulence closure. Two investigations are carried out in this study: (i) the influence of the disk porosity on the wake, for porosities values (p) ranging from 0 to 0.55 in the case of a perpendicular flow; and (ii) the influence of the yaw angle on the wake deviation, for yaw angles ranging from 5° to 30°. Good agreements with the available experimental data are obtained for the mean x-velocity component. The results confirm that wake length increases as porosity decreases. For nonporous disks, most part of the fluid is deflected toward the mast and above the disk. The y-velocity contours highlight two contra-rotating vortices in the vicinity of the disk. In both cases (nonporous and porous disks), a high turbulent kinetic energy is obtained near the disk area, with a higher maximum value for the nonporous disk.     

Structural,Electrical and Optical Properties of PVC/ZnTe Nanocomposite Thin Films

Journal of Inorganic and Organometallic Polymers and Materials - ZnTe nanoparticles (NPs) were synthesized using hydrothermal method and then were dispersed in poly(vinyl-chloride) (PVC) to prepare...     

Solubility Prediction of Active Pharmaceutical Compounds with the UNIFAC Model

The crystallization from solution of an active pharmaceutical ingredient requires the knowledge of the solubility in the entire temperature range investigated during the process. However, during the development of a new active ingredient, these data are missing. Its experimental determination is possible, but tedious. UNIFAC Group contribution method Fredenslund et al. (Vapor–liquid equilibria using UNIFAC: a group contribution method, 1977; AIChE J 21:1086, 1975) can be used to predict this physical property. Several modifications on this model have been proposed since its development in 1977, modified UNIFAC of Dortmund Weidlich et al. (Ind Eng Chem Res 26:1372, 1987), Gmehling et al. (Ind Eng Chem Res 32:178, 1993), Pharma-modified UNIFAC Diedrichs et al. (Evaluation und Erweiterung thermodynamischer Modelle zur Vorhersage von Wirkstofflöslichkeiten, PhD Thesis, 2010), KT-UNIFAC Kang et al. (Ind Eng Chem Res 41:3260, 2002), \(\ldots \) In this study, we used UNIFAC model by considering the linear temperature dependence of interaction parameters as in Pharma-modified UNIFAC and structural groups as defined by KT-UNIFAC first-order model. More than 100 binary datasets were involved in the estimation of interaction parameters. These new parameters were then used to calculate activity coefficient and solubility of some molecules in various solvents at different temperatures. The model gives better results than those from the original UNIFAC and shows good agreement between the experimental solubility and the calculated one.     

Modelling of damage and failure of glass/epoxy composite plates subject to impact fatigue

An investigation has been carried out to study the impact fatigue damage of glass/epoxy laminated composites. Accumulation of damage, such as matrix cracking, delamination and fibre breakage, with repeated impact of the composite material may reduce the overall stiffness. These damage modes have been combined in a very complicated way to describe damage growth and fracture. A model is proposed for characterising the damage as a function of the normalised impact number. The scalar variable D, which characterises the material damage, is written as a function of the life duration β, using a modified form of the Mankowsky empirical law [Int J Solids Struct 32(11) (1995) 1607]. The macroscopic failure mode and the internal damage in laminated specimens of glass/epoxy as a consequence of impact fatigue are analysed at different levels of incident impact energy. The impact fatigue tests have been conducted on an apparatus built in our laboratory.