An integrated fault estimation and fault tolerant control method using H∞-based adaptive observers

An integrated fault estimation/fault-tolerant control (FTC) scheme is developed in this article for nonlinear Lipschitz systems in the presence of external disturbances and actuator failures. To address this problem, coupled uncertainties between the observer error dynamics and the control system are considered, which is conveniently ignored in control approaches based on the separation principle. An H_∞ -based adaptive observer is proposed to simultaneously estimate the system states and actuator faults without the restrictive strictly positive realness or persistent excitation conditions. The FTC is constructed by sliding mode control using the estimated states generated by the developed observer. A novel sufficient condition is derived in terms of linear matrix inequality (LMI) including both the system control dynamics and the estimation errors; then, the control parameters and observer gains are simultaneously obtained via solving the mentioned LMI based on the H_∞ optimization. Finally, a flexible joint robot is considered to illustrate the effectiveness of the developed method.     

Silica chemically bonded N-propyl kriptofix 21 and 22 with immobilized palladium nanoparticles for solid phase extraction and preconcentration of some metal ions

Silica gel chemically bonded N-propyl kriptofix 21 (SBNPK 21) and N-propyl kriptofix 22 (SBNPK 22) and subsequently immobilized with palladium nanoparticles (PNP-SBNPK 21 and PNP-SBNPK 22) to produce two new complexing lipophilic materials. Then these novel sorbents were applied for the enrichment of some metal ions and their subsequent determination by flame atomic absorption spectroscopy (FAAS). The influences of the variables including pH, amount of solid phase, sample flow rate, eluent conditions and sample volume on the metal ion recoveries were investigated. The detection limit of proposed method was in the interval 2.1–2.3 and 1.7–2.8 ng mL^? 1 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively, while the preconcentration factor was 80 for two sorbents. The relative standard deviations of recoveries were between 1.23–1.31 and 1.28–1.49 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively. The method has high sorption-preconcentration efficiency even in the presence of various interfering ions. Due to the reasonable selectivity of proposed method, the relative standard deviation of recoveries of all understudied metal ions in some complicated matrices was less than 3.0%.     

Dissimilar Friction-Stir Lap Joining of 5083 Aluminum Alloy to CuZn34 Brass

In this research, lap joining of Al-Mg aluminum alloy and CuZn34 brass was produced by friction-stir welding during which the aluminum alloy sheet was placed on the CuZn34. Optical microscopy, scanning electron microscopy (SEM), X-ray diffraction analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis were used to probe the microstructures and chemical compositions. In addition, the mechanical properties of each sample are characterized using both shear and hardness tests. The optimum parameters resulted in no visible welding cracks and defects. A dark area in the Al/CuZn34 interface contained intermetallic compounds Al₂Cu, Al₄Cu₉, and CuZn. In addition, the results show that using high rotational speeds or low traverse speeds causes the growth of the interfacial intermetallic area.     

Novel Core–Shell of Polymethyl Methacrylate/butyl Acrylate/vinyl Silica Nanocomposite Particles through Seed Emulsion Polymerization

A new core–shell structure of polymethyl methacrylate/butyl acrylate copolymer/vinyl silica nanocomposite was successfully prepared in aqueous solution through seed emulsion polymerization. Vinyl-functionalized silica nanoparticles were synthesized using sol–gel technique of triethoxyvinylsilane in aqueous solution. New established covalent bond between the vinyl groups located on the surface of vinyl-functionalized silica nanoparticles and vinyl group of monomers and the encapsulation into methyl methacrylate/butyl acrylate copolymer through seed emulsion polymerization process. The prepared core–shell latex polymers were characterized by Fourier transform infrared, UV–vis, thermal analyses, tensile strength, elongation at break, field emission scanning electron microscope, transmission electron microscope, and zeta potential. The tensile strength improved by introducing vinyl silica into the matrix up to 5%, which proved the reinforcing role of vinyl silica in the matrix of polymer.     

A secure authentication scheme for VANETs with batch verification

Wireless Networks - Vehicular Ad-hoc Networks (VANETs) will start becoming deployed within the next decade. Among other benefits, it is expected that VANETs will support applications and services...     

Optical properties of cellulose derivatives blend film carrying a chalcogenide material

Polymeric films composed of mixture of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC) are prepared from casting combined solvent (methylene chloride and methanol in 1:1 ratio) containing 8% weight/volume of both polymers (EC to HPC in 1:3 weight ratio). The structural and optical studies of the films are carried out by X-ray diffraction and UV–vis spectrophotometer. The films are polycrystalline structure with an average grain size from 23.15 to 10.79 nm. The possible optical transition in these films is found to be allowed direct transition. The optical band gap energy (E_g) is estimated to be 5.02 eV for HPC–EC plain film and then decreases with increasing the filler content reaching to 4.24 eV for the film filled with maximum Se₈₀Te₁₄Sn₆ content of 1 w%. This suggests that Se₈₀Te₁₄Sn₆, as filler, is a good choice to control the optical properties of HPC–EC blend film.     

Rutting and moisture resistance evaluation of polyethylene wax–modified asphalt mixtures

One of the methods newly introduced in pavement technology to address environmental concerns and reduce total gas emission is warm mix asphalt (WMA) technology. In this study, polyethylene wax is used to produce WMA mixtures. Although this technology has several positive features, moisture and rutting resistance of WMA mixtures are always questionable. To evaluate moisture and rutting resistance of polyethylene-modified mixtures, indirect tensile strength and dynamic creep tests were used, respectively. Results indicated that polyethylene has positive effect at low compaction temperature on moisture resistance, and also has negative effect on rutting resistance.     

DC and AC Conductivity Study of Basalt Glasses Containing High Concentrations of Na+ Ions

Different glass samples prepared from Egyptian basalt with different Na₂O content according to the composition [(100-x) basalt + x Na₂O], where x = 10, 15, up to 35 mol%. The samples mixtures were melted at 1300 °C for 2 h. Each sample will be recognized from its sodium to basalt (S/B) ratio. The sample of 0.54 ratio exhibits a slight crystalline phase. As S/B ratio was increased, the density decreased gradually while the molar volume increased, and the pure amorphous nature was confirmed by comparing the experimental and the empirical density and molar volume values. The electrical conductivities, DC and AC, were found to increase as the (S/B) ratio was gradually increase up to 0.33, then the samples showed approximate stable value up to the sample of 0.54 ratio. While the activation energy showed gradual decrease up to 0.33 ratio, then it exhibits nearly a stable value. The activation energy values indicated that all the studied samples behave like semiconductors. It appeared also from the AC conductivity results that the relation of the s-factor with the sample temperature showed that the conduction mechanism of these samples obeys the correlated barrier hopping (CBH) model. The structure of the same samples was studied in our previous work by XRD, FTIR and Mössbauer spectrometer.