Development of data-based model-free representation of non-conservative dissipative systems

A general procedure is presented for developing data-based, non-parametric models of non-linear multi-degree-of-freedom, non-conservative, dissipative systems. Two broad classes of methods are discussed: one relying on the representation of the system restoring forces in a polynomial-basis format, and the other using artificial neural networks to map the complex transformations relating the system state variables to the needed system outputs. A non-linear two-degree-of-freedom system is used to formulate the approach under discussion and to generate synthetic data for calibrating the efficiency of the two methods in capturing complex non-linear phenomena (such as dry friction, hysteresis, dead-space non-linearities, and polynomial-type non-linearities) that are widely encountered in the applied mechanics field. Subsequently, a reconfigurable test apparatus was used to generate experimental measurements from a physical non-linear “joint” involving two-dimensional motion (translation and rotation) and complicated interaction forces between the different motion axes, among its internal elements. Both the polynomial-basis approach and the neural network method were used to develop high-fidelity, non-parametric models of the physical test article. The ability of the identified models to accurately “generalize” the essential features of the non-linear system was verified by comparing the predictions of the models with experimental measurements from data sets corresponding to different excitations than those used for identification purposes. It is shown that the identification techniques under discussion can be useful tools for developing accurate simulation models of complex multi-dimensional non-linear systems under broadband excitation.     

Immobilized triazine bis[mercapto amine] complexes of Pd(0) anchored nickel ferrite as a nanocatalyst for C–C coupling reaction

Immobilized triazine bis[mercapto amine] complexes of Pd(0) (NiFe₂O₄@TABMA-Pd(0)) was easily synthesized and applied as highly efficient and versatile nanocatalyst for the synthesis of various trans stilbenes with high performance for the Heck coupling reaction of several types of aryl halides under thermal conditions. In short reaction time, excellent yields of trans stilbene derivatives have been achieved using NiFe₂O₄@TABMA-Pd(0) catalyst.     

Synthesis and application of polythiophene-coated Fe3O4 nanoparticles for preconcentration of ultra-trace levels of cadmium in different real samples followed by electrothermal atomic absorption spectrometry

In this research, magnetic Fe₃O₄ nanoparticles were synthesised by co-precipitation method and modified with polythiophene (PT) to produce Fe₃O₄-PT nanoparticles for preconcentration and determination of cadmium (??) ion followed by electrothermal atomic absorption spectrometry. The results of FT-IR spectroscopy, EDX analysis and SEM images show that Fe₃O₄-PT nanoparticles were synthesised successfully. Different parameters such as sample pH, amounts of adsorbent, sample volume, extraction time, type and concentration of eluent and desorption time were completely investigated and optimum conditions were selected.

Under the optimum conditions, the calibration curve was linear in the range of 0.01–0.25 µg L^?1 of cadmium (??). The relative standard deviation was 4.7% (n = 7, 0.10 µg L^?1 Cd²⁺) and limit of detection was 3.30 ng L^?1. The accuracy of the proposed method was verified by the analysis of a certified reference material and spike method. Finally, the proposed method was applied for the determination of ultra-trace levels of cadmium (??) in different water and food samples.     

Fischer–Tropsch synthesis: evaluation of Gd and Ru promoters effect on Co/<Emphasis Type="Italic">γ</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst at different conditions

In this study, the effect of Ru and Gd promoters on 15Co/\(\gamma\)-Al₂O₃ catalyst in the Fischer–Tropsch synthesis is investigated. The catalysts were synthesized by dry impregnation method and characterized by XRD, adsorption/desorption of nitrogen, TPR, TEM, ICP and XPS analyses. Activity and selectivity of the catalysts were examined in a fixed bed reactor at 210–230 °C with a H₂/CO ratio of 2 and atmospheric pressure. The results showed that the Ru-promoted catalyst has the highest activity and methane selectivity which reduce the chain growth probability. The Gd-promoted catalyst was shown smaller particle size and higher dispersion of cobalt particles in compared with unpromoted catalyst. The smaller particles have more interaction and thus show the lower catalyst reducibility. The presence of Gd in the catalyst cause higher chain growth probability compared to the unpromoted one. The Ru–Gd-promoted catalysts were shown a synergic effect in the catalyst reducibility. Based on the screening of the catalysts in the atmospheric pressure; the unpromoted, 0.1Ru/15Co/Al₂O₃, and 0.1Ru1Gd/15Co/Al₂O₃ catalysts were selected to test at high pressure conditions, which the 0.1Ru1Gd/15Co catalyst showed the highest C₅ ⁺ selectivity (75%) compared with the 0.1Ru/15Co/Al₂O₃ and the unpromoted one.     

Photocatalytic Ring Opening of α-Epoxyketones: 1,3-Dioxolane Formation

 Photocatalytic ring opening of α-epoxyketones by 2,4,6-triphenylpyrylium tetrafluoroborate in acetone resulted in the formation of 1,3-dioxolanes as major products through C–O bond cleavage and the formation of alcoholic by-products through C–C bond cleavage. The type and nature of the substituent affects the rate of ring opening.     

The presentation of an approach for estimating the intramolecular hydrogen bond strength in conformational study of β-Aminoacrolein

All the plausible conformations of β-aminoacrolein (AMAC) have been investigated by the Bekes-Lee-Yang-Parr (B3LYP) nonlocal density functional with extended 6-311++G** basis set for studying the stability order of conformers and the various possibilities of intramolecular hydrogen bonding formation. In general the ketoamine (KA) conformers of AMAC, by mean average, are more stable than the corresponding enolimine (EI) and ketoimine (KI) analogues and this stability is mainly due to the π-electron resonance in these conformers that established by NH2 functional group. The contribution of resonance to the stability of chelated KA conformers is about 75.6 kJ/mol, which is greater than that of the hydrogen bond energy (E_HB=35.0 kJ/mol). The relative decreasing order of the various hydrogen bond energies was found to be: O–HN_imine(strong)>N_amine-HO_keto (normal)>N_imine-HO_hydroxyl (weak) > N_imine-HO_keto (weak). Hydrogen bond energies for all systems were obtained from the method that we called related rotamers method (RRM). The topological properties of the electron density contributions for various type of intramolecular hydrogen bond have been analyzed in term of the Bader theory of atoms in molecules (AIM). The results of these calculations support the previous calculations, which obtained by the related rotamer methods.     

Vibration behavior of simply supported inclined single-walled carbon nanotubes conveying viscous fluids flow using nonlocal Rayleigh beam model

A mathematical model is proposed to investigate the dynamic response of an inclined single-walled carbon nanotube (SWCNT) subjected to a viscous fluid flow. The tangential interaction of the inside fluid flow with the equivalent continuum structure (ECS) of the SWCNT is taken into account via a slip boundary condition. The dimensionless equations of motion describing longitudinal and lateral vibrations of the fluid-conveying ECS are obtained in the context of nonlocal elasticity theory of Eringen. The unknown displacement fields are expressed in terms of admissible mode shapes associated with the ECS under simply supported conditions with immovable ends. Using Galerkin method, the discrete form of the equations of motion is derived. The time history plots of the normalized longitudinal and transverse displacements as well as the nonlocal axial force and bending moment of the midspan point of the SWCNT are provided for different levels of the fluid flow speed, small-scale parameter, and inclination angle of the SWCNT. The effects of small-scale parameter, inclination angle, speed and density of the fluid flow on the maximum dynamic amplitude factors of longitudinal and transverse displacements as well as those of nonlocal axial force and bending moment of the SWCNT are then studied in some detail.     

Copper,gold, and silver decorated magnetic core–polymeric shell nanostructures for destruction of pathogenic bacteria

Fe₃O₄ magnetic nanoparticles (MNPs) were prepared by co-precipitation method. The nanoparticles were silica coated using TEOS, and then modified by the polymeric layers of polypropylene glycol (PPG) and polyethylene glycol (PEG). Finally, the core-shell samples were decorated with Ag, Au, and Cu nanoparticles. The products were characterized by vibrating sample magnetometry (VSM), TGA, SEM, XRD, and FTIR methods. The antibacterial activity of the prepared samples was evaluated in inactivation of E. coli and S. aureus microorganisms, representing the Gram-negative and Gram-positive species, respectively. The effect of solid dosage, bacteria concentration and type of polymeric modifier on the antibacterial activity was investigated. TEM images of the bacteria were recorded after the treatment time and according to the observed changes in the cell wall, the mechanism of antibacterial action was discussed. The prepared nanostructures showed high antibacterial activity against both Gram-negative and Gram-positive bacteria. This was due to the leaching of metal ions which subsequently led to the lysis of bacteria. A theoretical investigation was also done by studying the interaction of loaded metals with the nucleotide components of the microorganism DNA, and the obtained results were used to explain the experimental data. Finally, based on the observed inactivation curves, we explain the antibacterial behavior of the prepared nanostructures mathematically.

     

Regio‐ and Stereoselective Reaction of α‐Epoxyketones with AlCl3: An Efficient Approach for the Synthesis of Functionalized β‐Chlorohydrines

A simple and efficient synthesis of functionalized β‐chlorohydrins is described from the regio‐ and stereoselective reaction of α‐epoxyketones with AlCl₃ in acetonitrile at room temperature.