Damping characteristics of a spray-deposited shape memory alloy beam

The damping characteristics of an Ni–Ti shape memory alloy (SMA) beam are theoretically and experimentally studied with interest in identifying an appropriate damping model for the material. The SMA beam is manufactured by a spray deposition method followed by heat treatment and found to have nanocrystalline structure in which damping capacity is high. The beam is then tested to obtain an impulse response and the frequency response function (FRF). By using the Hilbert transform technique it is shown that damping of the beam is almost amplitude independent in the tested range of displacement. It is also shown from the FRF that the damping of the spray-deposited shape memory alloy beam is well represented by a model including both linear viscous and hysteretic dampings.     

Synthesis of ultrafine single crystals and nanostructured coatings of indium oxide from solution precursor

Indium oxide (In₂O₃) has been widely used in sensors, solar cells and microelectronics. There are several techniques available for making In₂O₃ such as vapor, electrochemical and atomic layer deposition, which are not only expensive but also time consuming processes. In this study, an inexpensive and straightforward synthesis approach is being presented to make micron/submicron size single crystals as well as nanostructured adherent coatings of In₂O₃ using Indium Chloride (InCl₃) powders and InCl₃ solution precursor. Both the powders and the solution precursor were calcined in a furnace to obtain the crystals; however, the liquid precursor was also treated by a DC plasma jet to obtain the nanostructured coatings. The phase transformations during thermal decomposition of InCl₃ powders and solution precursor were investigated via differential scanning calorimetry studies. The phase structure and crystallinity of the crystals and coatings were confirmed by X-ray diffraction. Microstructural characterization of the crystals and coatings was done by scanning electron microscopy, transmission electron microscopy and atomic force microscopy techniques. Size of the crystals was observed to be dependent on the heating schemes adapted during calcination. Solution precursor plasma sprayed In₂O₃ coatings showed porosity and ultrafine particulates with grain size ranging between 10 and 75 nm. Resistivity was determined to be ∼0.553 ± 0.337 kΩ cm. Optical transmittance of In₂O₃ coatings was ∼60-78% in the visible region and it was observed to decrease with increasing the number passes or the thickness of the coatings. Based on the optical transmission data, direct band gap of 3.57 eV was determined.     

Cucurbit[n]uril based supramolecular assemblies: tunable physico-chemical properties and their prospects

This Feature Article provides an account of the recent work by our research group (with some reference to relevant work of other groups) on the spectacular physico-chemical properties of cucurbituril-based supramolecular assemblies of chromophoric dyes having technological and biological importance. Simultaneous association of multiple hosts or guests either by cooperative binding or competitive displacement is an applied strategy to construct novel functional assemblies with predesignated characteristics. Here, effort has been made to briefly discuss the diverse photophysical characteristics of several host-guest complexes and the dynamic responses of such molecular assemblies towards external stimulants like metal ions. The detailed experimentation on these assemblies project their applications in the controlled uptake and release of drugs, photofunctional devices, aqueous-based dye lasers, and molecular architectures.     

Synthesis and Characterization of Poly(Aryl Ether-Bissulfone)s

A series of poly(aryl ether-bissulfone)s were synthesized from bis-phenols, 4,4′-bis(4-chlorophenylsulfonyl)biphenyl, and 4,4′-bis(4-fluorophenylsulfonyl)biphenyl. The bishalide monomers were synthesized by reaction of 4,4′-bis(chlorosulfonyl)biphenyl with a suitable aryl halide. Potassium carbonate mediated reaction in di-methylacetamide gave high molecular weight polymers in excellent yield. The polymers are soluble in dipolar aprotic solvents. Unlike the corresponding monosulfone analogues, the poly(aryl ether-bissulfone)s exhibited poor solubility in chlorinated hydrocarbons. The glass transition temperatures of the polymers are among the highest known for poly(aryl ether)s (241-271 °C). In addition, the polymers exhibit excellent thermal stability and they produce clear, colorless tough films by solution casting or compression molding.     

Plane Symmetric String Cosmological Model in Modified Theory of General Relativity

It is shown that homogeneous plane symmetric string cosmological model for Takabayasi string i.e. ρ=(1+ω)λ does not exist in Barber’s second self creation theory. Further it is found that the string cosmological model in this theory exist only when ω=0. Therefore model for ρ=λ (geometric string) is constructed. Some physical and geometrical properties of the model are discussed.     

PeV IceCube signals and Dark Matter relic abundance in modified cosmologies

The discovery by the IceCube experiment of a high-energy astrophysical neutrino flux with energies of the order of PeV, has opened new scenarios in astroparticles physics. A possibility to explain this phenomenon is to consider the minimal models of Dark Matter (DM) decay, the 4-dimensional operator \(\sim y_{\alpha \chi }\overline{{L_{L_{\alpha }}}}\, H\, \chi \), which is also able to generate the correct abundance of DM in the Universe. Assuming that the cosmological background evolves according to the standard cosmological model, it follows that the rate of DM decay \(\Gamma _\chi \sim |y_{\alpha \chi }|^2\) needed to get the correct DM relic abundance (\(\Gamma _\chi \sim 10^{-58}\)) differs by many orders of magnitude with respect that one needed to explain the IceCube data (\(\Gamma _\chi \sim 10^{-25}\)), making the four-dimensional operator unsuitable. In this paper we show that assuming that the early Universe evolution is governed by a modified cosmology, the discrepancy between the two the DM decay rates can be reconciled, and both the IceCube neutrino rate and relic density can be explained in a minimal model.     

Single‐cell fourth‐order difference approximations for $${\font\twelvesl=cmsl10\partial {\sl\bf u}\over\partial {\sl\bf x}},{\partial \sl\bf u\over\partial\sl\bf y}$$ , and $${\font\twelvesl=cmsl10\partial {\sl\bf u}\over\partial{\sl\bf z}}$$ of the three‐dimensional quasi‐linear elliptic equation

Finite difference methods of O(h⁴) are proposed for obtaining estimates of first‐order partial derivatives of the solution of three‐dimensional quasi‐linear elliptic equation with mixed derivative terms subject to Dirichlet boundary conditions on a uniform cubic grid. In all the cases, we use a single computational cell and the methods are applicable to the problems both in cartesian and polar coordinates. The utility of the new methods is shown by testing the methods on three‐dimensional poisson solvers in polar coordinates. Some numerical examples are provided to demonstrate the accuracy and efficiency of the methods discussed. © 2000 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 16: 417–425, 2000