Biswajit Nayak

Influence of the cavity dimension on encapsulation of halides within the capsular assembly and side-cleft recognition of a sulfate–water cluster assisted by polyammonium tripodal receptors

The p-nitrophenyl and p-bromophenyl functionalized tris-polyamine receptors, L1 and L2, have formed capsular assembly with halide ions in an encapsulated fashion through efficient hydrogen-bonding. On the other hand, the positional isomer of L1, the m-nitrophenyl functionalized tripodal amine receptor L3, displays a rather flat-open conformation and is unable to bind halide anions in an encapsulated form. The presence of a smaller cavity in these receptors hinders the binding of larger oxyanions like sulfate. As a result, the protonated tripodal scaffold encapsulates small solvent molecules and helps in side-cleft binding of the larger sulfate anion. Herein, we report the design, synthesis and characterization of tren-based polyammonium receptors L1, L2 and L3 and their complexation as well as binding discrepancy with several anions in the presence of acid. The solid state crystal structure of the anion complexes with L1, L2 and L3 reveal that the anions are recognized via stable N–H⋯A, C–H⋯A, anion–π interactions with the protonated receptor molecule in a unimolecular fashion either inside or outside the cavity. The sulfate–water complexes of receptors L1, L2 and L3 are stabilized by (NH)+⋯O type H-bonding and electrostatic interactions among sulfate, water and ammonium groups. The polyammonium based tripodal scaffold with positional variation of the functional group shows significant difference in anion binding fashion through either capsular or non-capsular complex formation.

Vibration analysis of a three-layer magnetorheological elastomer embedded sandwich beam with conductive skins using finite element method:

In this article, the free and forced vibration analyses of a three-layered magnetorheological elastomer embedded viscoelastic cored sandwich beam with conductive and non-conductive skins have been carried out using finite element method. The finite element method formulation is validated by conducting experiments for a viscoelastic cored sandwich cantilever beam. For an adaptive magnetorheological elastomer embedded viscoelastic cored sandwich beam, results have been compared with those obtained from analytical method. The natural frequencies and loss factors of the magnetorheological elastomer embedded viscoelastic cored sandwich beam have been determined for various system parameters. The forced vibration responses of the magnetorheological elastomer embedded sandwich beam are also evaluated under harmonic force excitations. The results suggest that the natural frequencies and transverse displacement response of the magnetorheological elastomer embedded sandwich beams are strongly influenced by the strength of the applied magnetic field, the location, the length of the magnetorheological elastomer patch and the magnetoelastic loads due to the conductive skins.

Free Vibration Control of MRE Embedded Viscoelastic Cored Sandwich Beam With Time Varying Magnetic Field

The present work deals with the free vibration control of a simply supported and cantilevered sandwich beam with magnetorheological elastomer (MRE) embedded viscoelastic core and conductive skins subjected to time varying magnetic field. The skins of the sandwich beam are conductive such that magnetic loads are applied to the skins. Considering the core to be stiff in transverse direction, classical sandwich beam theory has been used along with extended Hamilton’s principle and Galarkin’s method to derive the governing equation of motion. The resulting equation reduces to that of a parametrically excited system. Method of multiple scales has been used to study the response and stability of the system. Critical parameters of amplitude and frequency of magnetic field have been determined to actively control the free vibration response of the system. Effects of percentage of iron particles and carbon black in attenuation of vibration of the sandwich beam have been studied. Here the experimentally obtained properties of recently developed magnetorheological elastomers based on natural rubber containing iron particles and carbon blacks have been considered in the numerical simulation.Copyright