Global exponential stabilisation of a class of nonlinear time-delay systems

This paper deals with the state and output feedback stabilisation problems for a family of nonlinear time-delay systems satisfying some relaxed triangular-type condition. The delay is supposed to be constant. Parameter-dependent control laws are used to compensate for the nonlinearities. Based on the Lyapunov–Krasovskii functionals, global exponential stability of the closed-loop systems is achieved. Finally, an extension to nonlinear time-varying delay systems is given.     

Selective access to novel aryl alkyl disulfonates via photosulfochlorination process: An eco-benign approach to a highly active class of surfactants

In this work we report the synthesis of a new family of surfactants based on aryl alkyl disulfonates; the latter compounds were derived from a mixture of linear alkylbenzene with the resulting disulfonate groups residing on the linear alkyl side-chain rather than the usual aromatic ring structure. The Reed sulfochlorination reaction was successfully utilized to selectively promote the formation of disulfonates on the alkyl group. A number of analytical methods in the form of liquid chromatography–mass spectrometry (LC–MS), gas chromatography–mass spectrometry (GC–MS), Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) were used to characterize the resulting compounds and intermediates. The critical micelle concentration, the surface tension at the critical micelle concentration, the surface excess concentration at surface tension, and the area per molecule were measured at different concentrations and temperatures. Thermodynamic parameters and Krafft temperature were also determined. The obtained results were compared to those of commercial n-dodecylbenzene sulfonates and linear alkylbenzene sulfonates surfactants, showing that these new synthesized surfactants present good surface properties.     

Heat Recovery of a Diammonium Phosphates Drying Unit

Solid product drying is a widely used unit operation in the chemical industry. It is highly energy intensive, requiring hot, dry air streams at high temperatures to dry a wide range of products. Exhaust air from a dryer is usually vented to the atmosphere with little or no heat recovery. In the present work, a study was performed to analyze the performance of an absorption heat transformer (AHT) applied to the evaluation of thermal rejections of drying unit of diammonium phosphates (DAP). First, a basic AHT system is described and the operating sequence is explained. Next, an application of the AHT system to an industrial company is analyzed. A numerical simulation of the system using Aspen Plus software was performed to determine the effect of different parameters on the AHT system performance and the results are presented in graphical form.     

Deterioration of a Tunisian coastal aquifer due to agricultural activities and possible approaches for better water management

The purpose of this study is to provide a better understanding of the impact of agricultural activities on groundwater quality in a semi‐arid coastal environment (Korba, Tunisia). Impacts have been assessed through groundwater samples that were analysed for a range of chemical and biological parameters. Results indicate that groundwater overexploitation for irrigation and fertiliser use have affected the quality of the groundwater not only by direct contamination but also seawater intrusion. The implementation of appropriate regulatory and economic instruments to foster sustainable practices in the agricultural sector have been analysed within the framework of the EC (European Community) FP6 (funding program 6) INECO (Institutional and Economic Instruments for Sustainable Water Management in the Mediterranean Region) Project. Through stakeholder involvement processes, the project analysed issues relating to the regulation and control of groundwater abstractions, the promotion of wastewater reuse, efficiency improvements in irrigation water use, as well as instruments to strengthen the socioeconomic and institutional environment towards better managing and conserving available groundwater resources.     

The pressure-induced mechanical and optoelectronic behavior of cubic perovskite PbSnO3 via ab-initio investigations

The density functional theory based full-potential linear-augmented-plane-wave plus local-orbital method has been used to study the physical properties of PbSnO₃ in hypothetical cubic perovskite. An external pressure up to 40?GPa has been applied on PbSnO₃ to realize the variation in its electronic band structure and the subsequent optical properties. The stability of the PbSnO₃ has been investigated by the mechanical properties, the enthalpy of formation and Goldschmidt tolerance factor. Moreover, the Born criteria have been adopted to justify the mechanical stability of the PbSnO₃ perovskite. We show that the electronic bandgap of PbSnO₃ can be tailored from indirect to direct band gap at high symmetry (X-X) direction at an external pressure of magnitude ~ 26?GPa. The effect of pressure on the optical properties has been studied in terms of dielectric function, absorption, refraction, reflection, and optical loss factor. The application of hydrostatic pressure has shifted the maximum absorption toward the visible range, revealing that PbSnO₃ can be used for high- pressure optoelectronic applications.     

Multi-source shared nearest neighbours for multi-modal image clustering

Shared Nearest Neighbours (SNN) techniques are well known to overcome several shortcomings of traditional clustering approaches, notably high dimensionality and metric limitations. However, previous methods were limited to a single information source whereas such methods appear to be very well suited for heterogeneous data, typically in multi-modal contexts. In this paper, we propose a new technique to accelerate the calculation of shared neighbours and we introduce a new multi-source shared neighbours scheme applied to multi-modal image clustering. We first extend existing SNN-based similarity measures to the case of multiple sources and we introduce an original automatic source selection step when building candidate clusters. The key point is that each resulting cluster is built with its own optimal subset of modalities which improves the robustness to noisy or outlier information sources. We experiment our method in the scope of multi-modal search result clustering, visual search mining and subspace clustering. Experimental results on both synthetic and real data involving different information sources and several datasets show the effectiveness of our method.     

On the output feedback stability for non-linear uncertain control systems

In this paper, we will study the stability problem by output feedback of a class of uncertain control systems, whose nominal part is linear and whose uncertain part is norm-bounded by a known function. We propose an output controller that forces the state to the origin, in the global exponential stability sense.     

Photo‐induced hydrogen on iron hexagonal mesoporous silica (Fe‐HMS) photo‐catalyst

The iron hexagonal mesoporous silica (Fe‐HMS)‐n photocatalyst, where n is the molar ratio Si/Fe in the precursor gel (=50), has been successfully synthesized at an ambient temperature using hexadecylamine as template agent. The material was characterized by X‐ray diffraction, N₂ adsorption measurement Brunauer, Emmet, Taller (BET) and Barrett–Joyner–Halenda theory, UV–Vis spectroscopy, high‐resolution transmission electron microscopy and electron spin resonance. The electrical conductivity follows an Arrhenius‐type law with activation energy of 0.04 eV. Fe₂O₃ is uniformly dispersed on the HMS surface; it works synergistically to make Fe‐HMS photoelectrochemically active. The flat band potential (?0.75 V_SCE) is higher than the potential of hydrogen generation (?0.50 V_SCE at pH~7), and the material shows high efficiency for hydrogen evolution upon visible light. The photoactivity in Na₂SO₄ and Na₂SO₃ (0.1 M) solution was found to be 136 and 175 µmol g^‐1 min^‐1, respectively under full light (29 mW cm^‐2). The tendency to saturation, observed only in SO₃^2‐ electrolyte, is ascribed to the competitive reduction of the end product, namely S₂O₆^2‐ with the water reduction. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigation of the corrosion protection of SiOx-like oxide films deposited by plasma-enhanced chemical vapor deposition onto carbon steel

The paper reports on the corrosion behavior of carbon steel coated with thin SiO_x-like oxide films. The SiO_x-like coatings were deposited by plasma-enhanced chemical vapor deposition (PECVD) and their thickness was varied between 20 and 200 nm. The coated carbon steel interfaces were investigated for their corrosion protection efficiency when immersed in an aqueous saline solution of 3% NaCl. FTIR measurements and electrochemical impedance spectroscopy (EIS) experiments revealed that thin SiO_x-like coating layers (20 nm thick) do not prevent the carbon steel from corrosion, while thicker silica layers (d ≥ 100 nm) protect efficiently carbon steel interfaces in highly saline media with a protection efficiency of about 96% for a 200 nm thick coating.