An important note on symmetry line boundary conditions in fibre-reinforced laminated anisotropic composites

Symmetry line boundary conditions of symmetrical and unsymmetrical laminated fibrereinforced anisotropic composite structures are discussed. A simple C⁰ isoparametric finite element formulation based on the Reissner-Mindlin first-order shear deformation theory is used. The effects of boundary conditions on the laminated scheme and the orientation of fibres are studied. Numerical results for deflections presented herein should be of interest to composite-structure designers, experimentalists, and numerical analysts in verifying their results.     

Frequency analysis of the acoustic emission signals from PZT ceramics during the application of AC fields

Frequency analysis of Acoustic Emission signals in the range of 100-1200 kHz obtained from PZT ceramics during the application of limited and continuous cycles of ac field was undertaken to understand the fatigue behaviour of these ceramics. In the limited cycles experimentation, lower fields yielded higher range of frequency components (200-900 kHz) and higher fields yielded lower range of frequency components (200-500 kHz) at differnt temperatures of 60° C and 160° C. During continuous application of ac field, the initial stages of application yielded higher frequency components (100-850 kHz) and with increasing time of application, the frequency components of acoustic emission signal shifted towards lower frequency (less than 400 kHz). Electrical discharge induced cracking, resulted in the emission of frequency components in the range of 100-275 kHz.     

Electrically modulated transport of diclofenac salts through hydrogels of sodium alginate,carbopol, and their blend polymers

The electrically modulated transdermal migration of diclofenac sodium (DS), diclofenac potassium (DP), and diclofenac diethylammonium (DD) drugs from the hydrogels of sodium alginate (NaAlg), carbopol (CP), and blends of NaAlg with CP prepared in 2:1, 2:1.5, and 2:2 ratios was investigated. The release of DS, DP, and DD was investigated through excised rat skin to study the effects of viscosity, pH, and the ionic strength of the receptor medium under the influence of an electrical current in a switch‐on and switch‐off mode. A pulsatile pattern of transport was observed that depended on the presence or absence of an electrical current. Drug transport was dependent on the electrical current, the ionic nature of drugs, and the ionic strength of the diffusion medium. Drug transport followed the sequence DS > DP > DD. A decrease in viscosity and an increase in the pH of the hydrogel were observed when an electrical current was applied. CP was more responsive to an electrical stimulus, but the rate of transport was higher for NaAlg. Increasing the amount of CP in the blends increased the electrical responsiveness. The blend hydrogel with a high CP content showed the highest enhancement in drug transport, whereas the NaAlg hydrogel showed the least. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 301–311, 2005     

Molecular transport of n‐alkanes through diol chain‐extended polyurethane membranes

Molecular transport of n‐alkanes was investigated by calculating sorption, diffusion, and permeation of liquids through the diol chain‐extended polyurethane (PU) membranes in the temperature interval 25–60°C. Sorption experiments were performed gravimetrically. Diffusion coefficients were calculated from Fick's equation. These results showed a dependency on the nature and size of interacting n‐alkane molecules as well as morphology of the chain‐extended PUs. Transport kinetics followed an anomalous trend. Using the temperature‐dependent transport parameters, activation energies were calculated for diffusion and permeation processes using an Arrhenius equation. The van't Hoff relationship was used to obtain enthalpy and entropy of sorption. Concentration profiles of liquids through PU membranes were computed using Fick's equation, solved under appropriate initial and boundary conditions. A correlation was attempted between transport properties of liquids and physicomechanical properties of PU membranes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 874–882, 2005     

Novel high dielectric constant nanocomposites of polyaniline dispersed with γ‐Fe2O3 nanoparticles

Novel nanocomposites of polyaniline dispersed with γ‐Fe₂O₃ nanoparticles were prepared by the in situ polymerization of aniline in the presence of ammonium peroxysulfate as an oxidizing agent. Dielectric constants of the derived composites varied with the composition of γ‐Fe₂O₃ present in the matrix. A maximum dielectric constant of ～5500 was achieved when 10 mass % γ‐Fe₂O₃ nanoparticles were present. Nanocomposites were characterized by X‐ray diffraction, Fourier transform infrared, scanning electron microscopy, and thermal analytical techniques. Conductivity increased marginally by increasing the amount of γ‐Fe₂O₃ in the matrix. Dielectric constants increased 100–150 times compared to plain polyaniline matrix and were 20–40 times higher than that of γ‐Fe₂O₃ nanoparticles. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1868–1874, 2005     

Navigation of non-holonomic mobile robot using neuro-fuzzy logic with integrated safe boundary algorithm

In the present work, autonomous mobile robot (AMR) system is intended with basic behaviour, one is obstacle avoidance and the other is target seeking in various environments. The AMR is navigated using fuzzy logic, neural network and adaptive neuro-fuzzy inference system (ANFIS) controller with safe boundary algorithm. In this method of target seeking behaviour, the obstacle avoidance at every instant improves the performance of robot in navigation approach. The inputs to the controller are the signals from various sensors fixed at front face, left and right face of the AMR. The output signal from controller regulates the angular velocity of both front power wheels of the AMR. The shortest path is identified using fuzzy, neural network and ANFIS techniques with integrated safe boundary algorithm and the predicted results are validated with experimentation. The experimental result has proven that ANFIS with safe boundary algorithm yields better performance in navigation, in particular with curved/irregular obstacles.     

A Multi-band Multi-slot MIMO Antenna with Enhanced Isolation

Communication fields are growing rapidly in the recent era, so transmitting the multimedia contents through an open channel becomes a challenging task. The multimedia contents that are transmitted through this channel are highly prone to vulnerabilities and attacks. Therefore, secure and efficient data communication is considered as a major concern in the multimedia communication systems. So, major efforts are taken by researchers to safeguard the originality of each image. In a conventional system, the secure image communication process was achieved by compressing the content first, and then encryption is performed over the compressed data. Even though it met the required security and compression ratio, but some applications may require the reverse system. In this method, the encryption process is conducted prior to compression to improve the privacy of user data. Moreover, the initial concentration is given for improving content privacy rather than concentrating on size reduction. This paper proposes a reversed system that uses block based perceptual encryption algorithm for encryption and vector quantization (VQ) with hybrid Lloyd–Buzo–Gray (LBG)-Adaptive Deer Hunting Optimization (ADHO) algorithm (VQ-LBG-ADHO) for compression. So, the content secrecy gets improved. The involvement of this adaptive optimization method enhances the performance of VQ in the compression process. This method highly concentrates on secure communication, so the reverse process is followed in this method. It not only improves the image secrecy, however, it further enhances the image quality. The performance of this secure communication process is compared with state-of-the-art algorithms, and the results reveal that the proposed method outperforms the other existing methods.

     

MHD radiative ohmic heating nanofluid flow of a stretching penetrable wedge: A numerical analysis

The present numerical investigation has focused on the magnetohydrodynamics flow of a viscous nanofluid over a stretching wedge with the boundary convective conditions, thermal radiation, and ohmic heating. Buongiorno's two-component nonhomogeneous nanoscale model was used and a dilute nanofluid with spherical type particles is considered. Similarity transformations are used to render the system of governing partial differential equations into a system of coupled similarity equations. The transformed equations are solved numerically with the BVP4C method. Validation of solutions with previous studies based on special cases of the general model is included. The salient features of fluid velocity profile, temperature as well as concentration profiles are discussed in a graphical manner for various values of selected governing factors. The skin friction coefficient, mass, and heat transfer rates are calculated and summarized. It is worthwhile noticing that the validation results exhibit an excellent agreement with already existing reports. The modeling of the present problem is useful in the thermal processing of sheet-like substances that is a necessary operation in paper procurement, wire drawing, drawing of plastic films, polymeric sheets, and metal spinning.     

Preparation and characterization of pH sensitive poly(vinyl alcohol)/sodium carboxymethyl cellulose IPN microspheres for in vitro release studies of an anti-cancer drug

Interpenetrating polymeric network microspheres (IPNMs) consisting of poly(vinyl alcohol) and sodium carboxymethylcellulose were prepared by water-in-oil emulsion method and were cross-linked with glutaraldehyde. 5-Fluorouracil (5-FU), an anti-cancer drug, was loaded into IPNMs via in situ method. These IPNMs have been characterized by Fourier transform infrared spectroscopy, which confirms the cross-linking of IPNMs through glutaraldehyde. Differential scanning calorimetry and X-ray diffraction analysis of the drug-loaded IPNMs have confirmed uniform molecular dispersion of 5-FU in the IPNMs. Particle size measured using optical microscopy gave an average size of 80–250 μm. Scanning electron microscopy also confirmed the formation of microspheres with smooth surface and spherical shape. Encapsulation efficiency of 5-FU in these IPNMs was achieved up to 62%. Drug release profiles of the IPNMs at different pH conditions (pH 1.2 and 7.4) confirmed that microspheres formed are pH sensitive, resulting controlled release of drug during in vitro dissolution experiments. It has been analyzed with an empirical equation to understand the diffusion nature of drug through the IPNMs. Both encapsulation efficiency and release patterns are found to depend on the nature of the cross-linking agent as well as amount of drug loading. In vitro release studies indicated the release of 5-FU for more than 10 h.