A hybrid backtracking search algorithm with wavelet mutation-based nonlinear system identification of Hammerstein models

In this paper a novel and accurate approach is presented to identify varieties of nonlinear Hammerstein models (closed loop and open loop) with the help of an optimization algorithm that combines a recently proposed backtracking search algorithm with wavelet theory-based mutation scheme (BSA-WM). The optimum output MSE associated with each plant along with its statistical information justifies the better precision and accuracy of BSA-WM-based identification approach as compared to the other methods reported in earlier literature.     

Rician noise removal in magnitude MRI images using efficient anisotropic diffusion filtering

In this article, a new methodology for denoising of Rician noise in Magnetic Resonance Images (MRI) is presented. MRI imaging creates a distinctive view into the interior of a human body and has become an essential tool of clinical diagnosis. However, Rician noise is a type of artifact inherent to the acquisition process of the magnitude MRI image, making diagnosis difficult. We proposed a moment‐based Rician noise reduction technique in anisotropic diffusion filtering. We extend the work of the classical anisotropic diffusion filter and have customized it to remove Rician noise in the magnitude MRI image in 3D domain space. Our proposed scheme shows better results against various quality measures in terms of noise removal and edge preservation while retaining fine textures.     

Application of rice husk ash in brick aggregate concrete to improve the permeability and resistance against acid and sulfate attack

Brick-aggregate-concrete with a greater permeability is susceptible to decay at a faster rate under the action of acid and sulfate. This study tries to improve the durability of brick aggregate concrete by the addition of rice husk ash, which has been termed brick-ash concrete in this paper. The permeability and sorptivity of stone-aggregate-concrete, brick-aggregate concrete, and brick-ash concrete samples with different percentages of rice husk ash and different water-to-binder ratios were investigated. The concrete samples were also exposed to 1.5 % hydrochloric acid and 5 % sodium sulfate along with periodic drying and wetting cycle and periodic observations in terms of compressive strength, weight loss, and ultrasonic pulse velocity test for 360 days. 5 % to 10 % rice husk ash can significantly improve the permeability and resistance to the harsh environment of brick aggregate concrete. Additionally, this study also presents the equations to predict the actual strength from ultrasonic pulse velocity values for the brick ash concrete specimen exposed to acid and sulfate environments.     

Friction stir processing of Al6061-SiC-graphite hybrid surface composites

Friction stir processing (FSP) of Al6061-SiC-Graphite hybrid composites is studied in detail via force analysis, spectroscopic, microstructural and indentation studies. Effect of various tool rotational speeds was assessed, and the axial force variation was monitored. The presence of graphite as a reinforcement influences the axial force fluctuations due to its flaky nature and high thermal conductivity. Variation in microstructure at different tool rotational speed is studied using scanning electron microscope. The tool rotational speed has a significant influence on the area of FSP zone, fragmentation and depth of penetration of particles, dispersion of agglomerates and grain refinement of the matrix material. Spectroscopic characterization of the processed samples was done using Raman analysis and X-Ray diffraction studies. A noticeable change in intensity and shift in the respective Raman peak positions were observed, indicating residual stresses and various disorders in the crystal structure of the reinforced particles. Influence of tool rotational speed and existence of SiC and Graphite particles on the mechanical properties were further evaluated using nano indentation testing. The hybrid composite shows the combination of best and uniform mechanical properties at an optimum set of processing parameters.     

Experimental Simulation of a Diamond Betavoltaic Battery

Diamond single-crystal Schottky barrier mip-structures (metal–intrinsic diamond–p-doped diamond) with dimensions of 3 × 3 and 4.1 × 4.28 mm are fabricated on the basis of HTHP p-diamond and CVD i-diamond. The betavoltaic characteristics of the diamond structures are studied using a wide-aperture electron beam with an initial energy of 110 keV, partially scattered on the way to a converter by a 14-μm-thick aluminum layer and a 17-mm-thick air layer. The maximum generated power reached 2.18 mW (41 mW/cm²) with a conversion efficiency of 2–3%.     

Tuning the BODIPY core for its potential use in DSSC: a quantum chemical approach

Boron dipyrromethene (BODIPY) is a highly promising candidate for use in dye-sensitized solar cell (DSSC), because of its attractive absorption characteristics such as strong extinction coefficients in the visible and near-IR ranges (70000–80000 \(\hbox {M}^{-1}\) \(\hbox {cm}^{-1})\), large quantum yields, longer excited-state lifetime and also high solubility in many organic solvents. Moreover, the absorption peaks can be shifted towards longer wavelengths when functionalized at suitable positions of the BODIPY core. Herein, on the basis of density functional theory (DFT) and time-dependent DFT, we provide the opto-electronic properties of BODIPY core-functionalized dyes to see their applicability in organic DSSC. Our systematic analyses reveal that the 2,6 substituted dyes show better photovoltaic properties compared to the 3,5 substituted ones. On the basis of empirical relationship, we have also calculated the photo-induced electron injection times of some dye-\(\hbox {TiO}_{2}\) composites, which seem to be in the ultrafast time scale, thus rendering them a promising candidate for DSSC applications. Our theoretical studies provide that judiciously designed BODIPY core-derived dyes show certain unique spectroscopic and electronic features that make them highly advantageous in DSSC applications as compared to other organic dyes.     

Nonlinear tunneling of bright and dark rogue waves in combined nonlinear Schrödinger and Maxwell-Bloch systems

We derive the analytical rogue wave solutions for the generalized inhomogeneous nonlinear Schrödinger–Maxwell–Bloch (GINLS-MB) equation describing the pulse propagation in erbium-doped fibre system. Then by suitably choosing the inhomogeneous parameters, we delineate the tunneling properties of rogue waves through dispersion and nonlinearity barriers or wells. Finally, we demonstrate the propagating characteristics of optical solitons by considering their tunneling through periodic barriers by the proper choice of external potential.     

An Investigation on Vibration Welding of Amorphous and Semicrystalline Polymers

Vibration welding technique has been used to study the weld zone of thermoplastic polymers using ABS (amorphous), PC (amorphous), PMMA (amorphous), and PBT (semicrystalline). Polymers were welded using alike components and combinations of semicrystalline polymer with different amorphous polymers. Mechanical testing of welded polymers has proved that the tensile strength, elongation at break, and deformation was highest for PC–PC weld and least for ABS–ABS weld, when alike polymers were welded. However, welding of semicrystalline and amorphous polymer shows enormous reduction in its tensile strength as well as other tensile properties. Also, the tensile fracture of PBT with other amorphous polymers always occurred at weld zone which was not always in case of alike polymer welds. The weld strength of these polymers was observed to be dependent on the mechanical interlocking among the layers and not on interfacial bonding. This phenomenon may be due to the difference in glass transition temperatures of semicrystalline and amorphous polymers. XRD, FESEM, and AFM have been used in this study to observe the morphology of welded surfaces.     

Application of response surface methodology to evaluate the removal efficiency of Mn(II), Ni(II), and Cu(II) by surfactant-modified alumina

Surfactant-modified alumina (SMA) was prepared and used for the removal of Mn(II), Ni(II), and Cu(II) from aqueous environment. Batch studies were conducted to find out optimum pH of the medium, adsorbent dose of SMA, and contact time. They were further optimized using response surface methodology (RSM). In the present study, a three-factor, three-level Box–Behnken experimental design was used to derive a second-order polynomial equation and construct three-dimensional (3D) surface plots and two-dimensional (2D) contour plots to examine the response. The level of significance for each independent variable and their interaction effects were examined by means of analysis of variance (ANOVA), F test, and Student’s t test results. In addition, the percentage effects of the different factors and their interactions on the removal efficacy were also investigated by plotting a Pareto chart. The models were validated for accurate prediction of the percentage (%) removal by performing numerical optimization. The optimum values of three tested variables were determined at pH 6.2, 8.2, and 5.3; adsorbent dose = 20, 5, and 4 g/L; and contact time = 30, 60, and 75 min for the adsorption of Mn(II), Ni(II), and Cu(II) ions, and the corresponding removal efficiency was found to be 77.04, 93.83, and 97.23 %, respectively.     

A note on “Regular bipolar fuzzy graphs” Neural Computing and Applications 21(1) (2012) 197–205

In this note, we show by examples that Definitions 3.3, 3.5, Propositions 3.9, 3.10 and Theorem 3.17 in the paper by Akram and Dudek (Neural Comput Appl 21(1):197–205, 2012) contain some flaws, and then, we presented the updated results. Hence, we introduce generalized regular bipolar fuzzy graphs.