Robust self-tuning control based on discrete-time sliding mode for auto-regressive mathematical model in the presence of unmodelled dynamics

In this paper, we propose a new robust self-tuning control, called the generalized minimum variance αl-equivalent selftuning control (GMVSTC-αl) for the linear timevarying (LTV) systems, which can be described by the discrete-time auto-regressive exogenous (ARX) mathematical model in the presence of unmodelled dynamics. The estimation of the parameters contained in this mathematical model is made on the basis of the proposed modified recursive least squares (m-RLS) parametric estimation algorithm with dead zone and forgetting factor. The stability analysis of the proposed parametric estimation algorithm m-RLS is treated on the basis of a Lyapunov function. A numerical simulation example is used to prove the performances and the effectiveness of the explicit scheme of the proposed robust self-tuning control GMVSTC-αl.     

Disperse-within-disperse patterning on ternary/binary mixed-brush single crystals using polyaniline,polystyrene and poly(methyl methacrylate) grafts

Novel binary rod-coil and ternary rod-coil-coil mixed-brushes were designed using poly(ethylene glycol) (PEG)-b-poly(styrene) (PS), PEG-b-poly(methyl methacrylate) (PMMA), and PEG-b-polyaniline (PANI) block copolymers. In the current rod-coil mixed-brushes, the brush osmotic pressure did not absolutely affect the surface morphology, instead, the rigidity or flexibility of brushes was a dominant factor. The flexibility of coily PS brushes caused them to be easily entered into the system compared to the rod brushes with higher osmotic pressure, thereby they composed the matrix phase. In a similar growth condition but with packed pancake PMMA brushes, a more faise osmotic pressure was detected for PANI nanorods in the vicinity of PMMA brushes compared to PS ones. A higher faise osmotic pressure for PANI nanorods reflected the lower diameter dispersity and population of PANI nanorods in PEG-b-PMMA/PEG-b-PANI compared to PEG-b-PS/PEG-b-PANI. Via enhancing the amorphous brushes molecular weight, in a constant PANI nanorods molecular weight, the diameter dispersity and population of PANI nanorods increased. The PANI nanorods diameter in binary PS/PANI and PMMA/PANI mixed-brushes ranged in 6–10 nm. With elevating the crystallization temperature, no changes were detected in the morphology of rod-coil mixed-brush single crystals. In the novel ternary mixed-brushes with the amorphous PS and PMMA brushes and the PANI nanorods, the PANI nanorods were dispersed within both matrix (PS) and disperse (PMMA) phases. In these systems, the PANI diameters were 6 and 7 nm in PMMA disperses and 6–9 nm in PS matrix phase. The overall PANI nanorods population was in the range of 594–1392 for binary mixed-brushes. Furthermore, in ternary structures, the PANI overall populations were about 222 and 316 in PMMA and PS phases, respectively. Generally, in all binary and ternary mixed-brush systems, the amorphous brushes (PS and PMMA), due to their flexibility could be arranged in the vicinity of each other in a more facile manner compared to the PANI nanorods, they thus developed matrix phase.

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Graphical abstract The mixed-brush single crystals were carefully patterned with double rod-coil and triple rod-coil-coil grafted polymer chains

     

Assessment of thermal,morphological, and mechanical properties of poly(methyl methacrylate)/glass flake composites

In this work, poly(methyl methacrylate)/(glass flake) (GF) composites were prepared with different compositions via melt mixing. The effect of the filler ingredient on thermal behavior, morphology, and mechanical and optical properties was investigated by using various techniques, namely differential scanning calorimetry, ultraviolet‐visible spectra, mechanical testing, and scanning electron microscopy. For evaluating the level of dispersion of particles, energy dispersive X‐ray analysis was performed. Differential scanning calorimetry analysis showed that the glass transition temperature of the samples slightly increased by increasing GF content. Scanning electron microscopy images showed that sized flakes were uniformly dispersed within poly(methyl methacrylate). Energy dispersive X‐ray analysis images of samples with different inclusions of GFs showed that the appearance of white dense spots represents the GF particles. It was found that the presence of 0.5 wt% of GF in composites gave more transparency than the other compositions. Furthermore, this composition indicated maximum tensile strength and elongation‐at‐break values in comparison with the other compositions. J. VINYL ADDIT. TECHNOL., 23:62–69, 2017. © 2015 Society of Plastics Engineers     

A probe into the status quo of interfacial adhesion in the compatibilized ternary blends with core/shell droplets: Selective versus dictated compatibilization

A simple approach was applied to probe into the situation of interfacial adhesion in the compatibilized ternary polymer blends with core/shell morphology. The performance of compatibilization was discussed in terms of thermal, rheological, and mechanical properties analyses for blends prepared through different mixing strategies for which maleic anhydride‐grafted high‐density polyethylene (HDPE‐g‐MAH) could be localized at the interface of HDPE/poly(ethylene‐co‐vinyl alcohol) copolymer (EVOH) or HDPE/polyamide 6 (PA‐6) in their ternary blends. Two mixing strategies, one simultaneously (one‐step or selective) and two sequentially (two‐step or dictated), were performed, compared, and discussed. It was found that mixing policy (dictated or selective) significantly changes the interfacial adhesion, as signaled by variations in rheological and thermal properties. In the case of mechanical properties, facilitation of stress transfer across the matrix/shell/core interfaces was detected by calculation of semi‐experimental models' coefficients. It was found that one‐step mixing or selective localization of HDPE‐g‐MAH helps in accumulation of more compatibilizer molecules at the interface HDPE/EVOH or EVOH/PA‐6. By contrast, addition of compatibilizer to minor phase (masterbatch of EVOH and PA‐6) or to HDPE matrix alone in case of two‐step blending causes imperfect stress transfer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45503.     

Pervaporation properties of polypyrrolidinone‐based membranes for EtOH/ETBE mixtures separation

The separation of ethanol/ethyl‐tertiobutylether mixtures by pervaporation was studied with new membranes prepared from N‐vinyl‐pyrrolidinone (NVP) and N‐[3‐(trimethylamoniopropyl)]methacrylamidemethylsulfate) (TMA). The pervaporation results showed that highly EtOH selective membranes could be obtained from PVP blends and from pyrrolidinone‐based crosslinked copolymers. The influences of the polymer blend composition and the role of the polymer microstructures on the membrane properties were investigated. Whatever the exact NVP/TMA composition used, the membranes strongly favored the pervaporation of ethanol. The ethanol selectivity was higher for the lower PVP/TMA ratio. On the one hand, these results were ascribed to the high pyrrolidinone residues content, which is responsible of the enhanced EtOH sorption affinity. The observed permeation selectivity was in agreement with the swelling data also recorded with the different polymers, showing higher affinity for ethanol with PVP‐enriched materials compared with TMA ones. This is a direct consequence of the Lewis base feature of pyrrolidinone sites towards EtOH molecules. On the other hand, the TMA residues improved the overall stability and selectivity of the membranes thanks to crosslinking reactions, which were induced by thermal treatment. A close comparison made between polymer blend and copolymer pervaporation results helped to clarify the TMA role of the membrane transport properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3622–3630, 2006     

Anchoring of Copper(II) Schiff Base Complex into Aminopropyl-Functionalised MCM-41: A Novel,Efficient and Reusable Catalyst for Selective Oxidation of Alcohols

A copper(II) complex containing tetradentate N₂O₂ Schiff base ligand immobilized into aminopropyl-functionalised MCM-41 (mobile crystalline material number 41), was prepared and characterized by Fourier-transform infrared, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, N₂ adsorption–desorption and inductively coupled plasma analysis techniques. The novel heterogeneous catalyst, MCM-41-pr-NH₂-CuL, can be successfully applied for efficient and selective oxidation of different primary and secondary alcohols to the corresponding carbonyl compounds using hydrogen peroxide as an oxidant in acetonitrile at 60 °C. The effect of reaction parameters such as solvent, amount of catalyst, temperature and kind of oxidant on the oxidation of benzyl alcohol was also studied. The prepared catalyst could be recovered and reused four times without important loss of its catalytic performance. The heterogeneous MCM-41-pr-NH₂-CuL catalyst was found to be catalytically more active in the oxidation of alcohols compared to the similar type of copper(II) Schiff base complex in homogeneous media under the same reaction conditions.     

Fabrication of Ta nanoparticles induced by nanosecond laser ablation in ethanol: the study of laser fluence effects

Tantalum nanoparticles (Ta NPs) were synthesized in ethanol solution by ablation with a 1064 nm Nd:YAG laser. Prepared NPs were investigated by UV-visible absorption spectroscopy, Transmission electron microscopy, X-ray diffraction and Photoluminescence measurement. The average sizes of NPs were calculated to be in the range of 12–18 nm. From the UV-visible studies, the plasmon peak position of Ta NPs was observed in the spectral range of 206–208 nm. The XRD spectra clearly showed the crystalline structure of NPs and various peaks of Ta and Ta₂O₅. Moreover, the UV region in the PL spectrum included the free exciton and the bound exciton emission correlated with the defect concentration. In fact, the laser ablation in the organic and inorganic solvents is a strong technique to obtain some NPs with particular structures, which are impossible to produce by conventional methods.     

Pareto–Koopmans efficiency in two‐stage network data envelopment analysis in the presence of undesirable intermediate products and nondiscretionary factors

Many studies have recently been conducted on the evaluation of system performance with a two‐stage network structure in data envelopment analysis (DEA) literature. One of the topics of interest to researchers has been the mitigation of undesirable products or nondiscretionary factors into their corresponding possible production set (PPS) and their impact on overall efficiency calculations. Determination of decision‐making units (DMUs) with Pareto–Koopmans efficiency status is decisive in identifying benchmark units. The calculated overall efficiency status is compromised when both undesirable products and nondiscretionary factors are present. This work utilizes an axiomatic approach. A novel PPS for a two‐stage network in presence of undesirable intermediate products and nondiscretionary exogenous inputs is introduced. Based on this PPS and by focusing on the principle of mathematical dominance, new models for evaluating overall and divisional efficiencies are presented. In addition, by proposing a two‐step network DEA approach, a necessary and sufficient condition for detection of DMUs with Pareto–Koopmans efficiency status is provided. And by introducing a two‐step algorithm, a novel technique for determining overall efficiency conditions is produced. Finally, the proposed technology is applied to a practical example, and outcomes are discussed.     

Energy-Efficient Resource Optimization for Massive MIMO Networks Considering Network Load

This paper investigates the resource optimization problem for a multi-cell massive multiple-input multiple-output (MIMO) network in which each base station (BS) is equipped with a large number of antennas and each base station (BS) adapts the number of antennas to the daily load profile (DLP). This paper takes into consideration user location distribution (ULD) variation and evaluates its impact on the energy efficiency of load adaptive massive MIMO system. ULD variation is modeled by dividing the cell into two coverage areas with different user densities: boundary focused (BF) and center focused (CF) ULD. All cells are assumed identical in terms of BS configurations, cell loading, and ULD variation and each BS is modeled as an M/G/m/m state dependent queue that can serve a maximum number of users at the peak load. Together with energy efficiency (EE) we analyzed deployment and spectrum efficiency in our adaptive massive MIMO system by evaluating the impact of cell size, available bandwidth, output power level of the BS, and maximum output power of the power amplifier (PA) at different cell loading. We also analyzed average energy consumption on an hourly basis per BS for the model proposed for data traffic in Europe and also the model proposed for business, residential, street, and highway areas.     

Modelling end of life phase of the complex products: the case of end of life aircraft

There are different approaches to modelling the products at the End of Life (EOL), including closed loop approach, the ladder of lansink and material flow. The sustainability principles and the complexity of the products may affect the choice of modelling type. The life cycle costs, several subsystems and the interaction between design features, construction, technology, suppliers and legislation affect the degree of complexity of the products. Hence, developing appropriate strategies are required for modelling EOL phase of the complex products. This article presents strategies for modelling EOL phase of complex products considering sustainability tools, EOL phase models and the characteristics of these products. An ingenerated approach is proposed to address the four essential aspects of the complex product at the EOL: operational, tactical, strategic and sustainability. The case of aircraft at the EOL is presented to highlight the application of the proposed approach.