Electrosynthesis of Poly(ortho-phenetidine) Coatings on Steel and Investigation of Their Corrosion Protection Properties

Poly(ortho-phenetidine) coatings on 304 stainless steel (304 SS) surface have been synthesized by using the galvanostatic technique. The electrosynthesized coatings were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), UV-visible absorption spectrometry and Scanning Electron Microscopy (SEM). The anticorrosion performances of poly(ortho-phenetidine) coatings were examined in 0.1 M HCl medium by the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization technique. The corrosion rate of poly(ortho-phenetidine)-coated 304 SS was found ~10 times lower than bare 304 SS and corrosion potential increased from –0.29 V for uncoated 304 SS to –0.19 V versus Ag/AgCl (3 M KCl) for poly(ortho-phenetidine)-coated 304 SS electrode. Electrochemical measurements indicate that poly(ortho-phenetidine) coating has good inhibiting properties with an efficiency of ~93% at 1.5 mA cm^–2 applied current density in acidic corrosive media. The results of this study obviously ascertain that the poly(ortho-phenetidine) has an outstanding potential to protect 304 SS against corrosion in an acidic environment.     

Carbon nanotube-modified glassy carbon electrode for anodic stripping voltammetric detection of Uranyle

A multi-wall carbon nanotube (MWNT) modified glassy carbon electrode (GCE) is described for the measurement of trace levels of uranium by anodic stripping voltammetry. In a pH 4.4 NaAc-Hac buffer containing 0.010 mol L⁻¹ Mg(NO₃)₂, UO₂ ²⁺ was adsorbed onto the surface of a MWNT film coated glassy carbon electrode and then reduced at −0.40 V vs. Ag/AgCl. During the positive potential sweep the reduced uranium was oxidized and a well-defined stripping peak appeared at +0.20 V vs. Ag/AgCl. Low concentrations of Mg²⁺ significantly enhanced the stripping peak currents since they induced UO₂ ²⁺ to adsorb at the electrode surface. The response was linear up to 1.2 × 10⁻⁷ mol L⁻¹ and the relative standard deviation at 2.0 × 10⁻⁸ mol L⁻¹ uranium was 5.2%. Potential interferences were examined. The attractive behavior of the new “mercury-free” uranium sensor holds promise for on-site environmental and industrial monitoring of uranium.     

Fibre embedding in aluminium alloy 3003 using ultrasonic consolidation process��thermo-mechanical analyses

This work presents a computational framework based on finite element methods to simulate the fibre-embedding process using ultrasonic consolidation process. The computational approach comprises of a material model which takes into account thermal and acoustic softening effects and a friction model which indicates the realistic friction behaviour at the interfaces. The derived material model and developed friction model have been incorporated in finite element model. Using the implemented material and friction model, thermo-mechanical analyses of embedding of fibre in aluminium alloy 3003 has been performed. Effect of different process parameters, such as velocity of sonotrode, displacement amplitude of ultrasonic vibration and applied loads, is studied and compared with the experimental results. The presented work has specially focused on the quality of the developed weld which could be evaluated by the friction work and the coverage of the fibre which is estimated by the plastic flow around the fibre. The computed friction work obtained from the thermomechanial analyses performed in this study show a similar trend as that of the experimentally found fracture energies.     

Nanometer-sized cerium oxide particles for solid phase extraction of trace amounts of mercury in real samples prior to cold vapor atomic adsorption spectrometry

Ceria (CeO₂) nanoparticles were synthesized using the microwave-assisted heating technique and employed as a sorbent for preconcentration of trace amounts of Hg(II) ions from aqueous solutions for the first time. The analysis of mercury was performed by cold vapor atomic absorption spectrometry (CV-AAS). The characteristics of nanoparticles were assessed using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Experimental parameters influencing the extraction procedure recovery were thoroughly investigated. Under the optimized experimental conditions, the calibration curve was linear in the range of 0.035–0.8 µg/L of mercury. The method was validated by analysis of a certified reference material.     

Post-FFT Beamforming in a Pilot-Assisted MIMO-OFDM System

It has been shown that by employing beamforming in the receiver of a Single-Input Multiple-Output-orthogonal frequency division multiplexing (SIMO-OFDM) system its performance has been greatly improved by suppressing co-channel interferences and mitigating fading effects of the channel. To get even greater performance applying a similar beamforming technique to the transmitter side of a Multiple-Input Multiple-Output (MIMO)-OFDM system was further employed. However, while in SIMO-OFDM systems both blind and reference-based methods have been investigated, in MIMO-OFDM systems only algorithms based on blind methods have been proposed so far. In this article we develop a reference-based joint transmit–receive beamforming technique, based on pilot symbols, in a MIMO-OFDM system. Post-FFT scheme is used in both sides as the beamforming method. Appropriate adaptive algorithms are developed to obtain the joint optimal beamforming weights in the receiver by minimizing the error signal between the estimated pilot symbols and their actual values. Receiver weights are used locally whereas transmitter weights are sent to the transmitter through a low-rate feedback channel similar to blind methods. The effect of various factors on the performance of the proposed beamforming structure is considered and it is shown that the joint transmit–receive beamforming is more effective than the sole receive beamforming although the improvement due to transmit beamforming is limited by the total transmit power constraint.     

A robust adaptive observer for a class of singular nonlinear uncertain systems

This paper proposes a robust adaptive observer for a class of singular nonlinear non-autonomous uncertain systems with unstructured unknown system and derivative matrices, and unknown bounded nonlinearities. Unlike many existing observers, no strong assumption such as Lipschitz condition is imposed on the recommended system. An augmented system is constructed, and the unknown bounds are calculated online using adaptive bounding technique. Considering the continuous nonlinear gain removes the chattering which may appear in practical applications such as analysis of electrical circuits and estimation of interaction force in beating heart robotic-assisted surgery. Moreover, a simple yet precise structure is attained which is easy to implement in many systems with significant uncertainties. The existence conditions of the standard form observer are obtained in terms of linear matrix inequality and the constrained generalised Sylvester's equations, and global stability is ensured. Finally, simulation results are obtained to evaluate the performance of the proposed estimator and demonstrate the effectiveness of the developed scheme.     

The synthesis of poly(vinyl chloride) nanocomposite films containing ZrO2 nanoparticles modified with vitamin B1 with the aim of improving the mechanical,thermal and optical properties

In the present investigation, solution casting method was used for the preparation of nanocomposite (NC) films. At first, the surface of ZrO₂ nanoparticles (NPs) was modified with vitamin B₁ (VB₁) as a bioactive coupling agent to achieve a better dispersion and compatibility of NPs within the poly(vinyl chloride) (PVC) matrix. The grafting of modifier on the surface of ZrO₂ was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). Finally, the resulting modified ZrO₂ (ZrO₂–VB₁), was used as a nano-filler and incorporated into the PVC matrix to improve its mechanical and thermal properties. These processes were carried out under ultrasonic irradiation conditions, which is an economical and eco-friendly method. The effect of ZrO₂–VB₁ on the properties and morphology of the PVC matrix was characterized by various techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses showed a good dispersion of fillers into the PVC matrix with the average diameter of 37–40 nm. UV–Vis spectroscopy was used to study optical behavior of the obtained NC films. TGA analysis has con?rmed the presence of about 7 wt% VB₁ on the surface of ZrO₂. Also, the data indicated that the thermal and mechanical properties of the NC films were enhanced.     

Synthesis of Zinc Sulfide Nanostructures with Different Sulfur Sources via Mild Hydrothermal Route: Investigation of Crystal Phase and Morphology

In this paper, we report a facile hydrothermal route to prepare different morphologies of zinc sulfide nanostructures, using a new inorganic precursor, zinc phthalate [Zn(pht)(H₂O)]_n, and different sulfur sources. This study focuses on the effect of different sulfur sources on the crystal structure and morphology of the products. The structural and morphological studies of the products were performed by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The high temperature (over 1020 °C) hexagonal ZnS nanostructured spheres self-assembled from ZnS nanocrystals have been synthesized at a low temperature of 160 °C by using thioglycolic acid as sulfur source.     

Synthesis of a novel fluorescent coloured copolymer based on 4‐butylthio‐1,8‐naphthalimide

A novel fluorescent coloured copolymer based on naphthalimide was prepared. Acenaphthene was brominated and oxidised to prepare 4‐bromo‐1,8‐naphthalic anhydride and further reacted with butanethiol, 2‐aminoethanol and acryloyl chloride, in order to obtain a new polymerisable fluorescent dye. The synthesised dyes were characterised by differential scanning calorimetry, absorption spectroscopy (Fourier Transform–infrared, proton and carbon nuclear magnetic resonance, ultraviolet–visible spectroscopy) and fluorimetry. Molar extinction coefficients and wavelength maxima were obtained by examining the dye solution in ethanol. The solvatochromic effects of the prepared dyes have also been investigated. Finally, the dye was copolymerised with methyl methacrylate and an intrinsically coloured copolymer was obtained. The photophysical characteristics of the obtained copolymer have also been considered. It is assumed that 99% of the copolymerised dye is chemically bonded to polymer chains. The fluorescent characteristics of the copolymer in the solid state were determined by fluorometer and it was found that it has relatively high fluorescent intensity. The physical properties of the synthesised copolymer have been evaluated by differential scanning calorimetry and gel permeation chromatography.     

Automatic Detection of Words Associations in Texts Based on Joint Distribution of Words Occurrences

In this article, we propose a novel approach for measuring word association based on the joint occurrences distribution in a text. Our approach relies on computing a sum of distances between neighboring occurrences of a given word pair and comparing it with a vector of randomly generated occurrences. The idea behind this assumption is that if the distribution of co‐occurrences is close to random or if they tend to appear together less frequently than by chance, such words are not semantically related. We devise a distance function S that evaluates the words association rate. Using S, we build a concept tree, which provides a visual and comprehensive representation of keywords association in a text. In order to illustrate the effectiveness of our algorithm, we apply it to three different texts, showing the consistency and significance of the obtained results with respect to the semantics of documents. Finally, we compare the results obtained by applying our proposed algorithm with the ones achieved by both human experts and the co‐occurrence correlation method. We show that our method is consistent with the experts' evaluation and outperforms with respect to the co‐occurrence correlation method.