Plane wave propagation in 2D and 3D monodisperse periodic granular media

Plane wave propagation in periodic ordered granular media comprising of elastic spherical particles is investigated. The spheres are under zero precompression and are assumed to interact via the Hertzian contact potential. Various two- and three-dimensional granular structures such as hexagonal packing (2D and 3D), face-centered cubic and body-centered cubic packings are considered in the present study, with the plane impact either normal or oblique to the granular system. For the normal impact case, 1D chains equivalent to the 2D and 3D structures are obtained. A universal relation between the wavefront speed and the force amplitude is derived, valid for all the granular structures studied. In the angular impact case, the shear component of the amplitude of the particle velocity is found to initially decay exponentially and further in a series of linear regimes. By employing simpler models, semi-analytical predictions are obtained for the decay of shearing effect.     

Non-isothermal crystallization kinetics of TiO2 nanoparticle-filled poly(ethylene terephthalate) with structural and chemical properties

The present research work includes non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET)–titanium dioxide (TiO₂) nanocomposites as well as structural and chemical properties of these nanocomposites. The average grain size of chemically synthesized TiO₂ nanoparticles has been calculated 19.31 nm by TEM and XRD. The morphology and structural analysis of PET–TiO₂ nanocomposites, prepared via solution casting method, has been investigated using SEM and XRD, respectively. The nature of chemical bonds has been discussed on the basis of FTIR spectra. The effect of TiO₂ nanoparticles and cooling rates on non-isothermal crystallization kinetics of PET was examined by differential scanning calorimetry at various heating and cooling rates. It has been observed that TiO₂ nanoparticles accelerate the heterogeneous nucleation in PET matrix. The crystallization kinetics could be explained through Avrami–Ozawa combined theory. TiO₂ nanoparticles cause to make molecular chains of PET easier to crystallize and accelerate the crystallization rates during non-isothermal crystallization process; this conclusion has also been verified by Kissinger model for crystallization activation energy.     

Glass transformation studies in Ge-Se-Bi system

The thermal behavior of bulk glasses in the Ge₂₀Se_{80 − x} Bi _x (x = 2.5, 4.0, 6.0 at %) system is studied using modulated differential scanning calorimetry (MDSC). All samples have the same thermal history as a result of heating to a temperature above the glass transition point, equilibrating, and then cooling. The total heat flow, modulated heat flow, reversing heat flow, and nonreversing heat flow under heating and cooling schedules are measured. The glass transition temperature T _g , the relaxation enthalpy ΔH, the specific capacity C _p , and the specific heat capacity difference ΔC _p = C _pl − C _pg , which characterize the thermal events in the glass transition region, are also determined. These parameters reveal an increase with x, which can be attributed to the increase in the average coordination number with an increase in the bismuth content (at %) in the composite. The ratio of heat capacities C _pl /C _pg , the width of the glass transition temperature range ΔT _g , and the activation enthalpy for glass transition ΔH _Tg are also studied. The values of the ratio C _pl /C _pg vary in the range between 1.038 and 1.112. The activation energy of crystallization is evaluated using the Kissinger, modified JMA, and Matusita equations, which is found to be in the range of 100.92 kJ/mol. The text was submitted by the authors in English.     

Influence of hydrophobic block length and ionic liquid on the performance of multiblock poly (arylene ether) proton exchange membrane

The present article includes the synthesis of nanophase-separated poly (arylene ether) multiblock copolymers. A series of poly (arylene ether sulfone) hydrophobic oligomers consisting of bisphenol-A groups were reacted with a disulfonated poly (arylene ether ketone) hydrophilic oligomer containing 4, 4′- bis (4-hydroxyphenyl) valeric acid moieties to prepare multiblock copolymers. The synthesized oligomers and block copolymers were characterized by using FT-IR, ¹H NMR spectra and Gel Permeation Chromatography. The membranes obtained by solution casting method exhibited good dimensional and thermal stability. The increase in hydrophobic block length reduced the water uptake and methanol permeability of the membranes. The complexation of multiblock copolymer with ionic liquid (1-butyl-3-methyl-imidazolium tetrafluoroborate) resulted into novel hybrid membranes. These showed enhanced proton conductivity without affecting the mechanical stability. The Fenton's test revealed that the hybrid multiblock membranes were stable towards radical oxidation. The hydrophobic-hydrophilic phase separation was characterized by using tapping mode Atomic Force Microscopy (AFM). The hybrid membranes showed better fuel cell performance than that of pristine membrane.     

LiBH4 as solid electrolyte for Li-ion batteries with Bi2Te3 nanostructured anode

The present study highlights the first-ever application of fastest lithium (Li) ion conducting complex hydride containing cluster anions, namely lithium borohydride (LiBH₄) into an all-solid-state Li-ion battery having Bi₂Te₃ as anode material. Bi₂Te₃ nanostructures were prepared by the simple wet chemical method and characterized by their crystal structure, morphology and electronic structure using X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). SEM and TEM experiments revealed the dimensions as 20–60 nm for nanoparticles and 30–90 nm for nanosheets. The formation of Bi₂Te₃ nanostructures along with Bi₂O₃ as the residual phase is confirmed by XRD analysis. The crystallite size of nanoparticles and nanosheets are calculated as 19 nm and 39 nm respectively from XRD profile. The XPS study also confirms the formation of nanostructured Bi₂Te₃ along with Bi₂O₃. Finally, the electrochemical performance of these nanostructures is observed using the galvanostatic charge-discharge curve at 0.1C and 0.5C.     

Pressure corrections for the potential flow analysis of Kelvin–Helmholtz instability with heat and mass transfer

Pressure corrections for the viscous potential flow analysis of Kelvin–Helmholtz instability at the interface of two viscous fluids have been carried out when there is heat and mass transfer across the interface. Both fluids are taken as incompressible and viscous with different kinematic viscosities. In viscous potential flow theory, viscosity enters through normal stress balance and effect of shearing stresses is completely neglected. We include the viscous pressure in the normal stress balance along with irrotational pressure and it is assumed that this viscous pressure will resolve the discontinuity of the tangential stresses at the interface for two fluids. It has been observed that heat and mass transfer has destabilizing effect on the stability of the system. A comparison between viscous potential flow (VPF) solution and viscous contribution to the pressure for potential flow (VCVPF) solution has been made and it is found that the effect of irrotational shearing stresses stabilizes the system.     

Synthesis of carbon nanotubes

Carbon nanotubes play a fundamental role in the rapidly developing field of nanoscience and nanotechnology because of their unique properties and high potential for applications. In this article, the different synthesis methods of carbon nanotubes (both multi-walled and single-walled) are reviewed. From the industrial point of view, the chemical vapor deposition method has shown advantages over laser vaporization and electric arc discharge methods. This article also presents recent work in the controlled synthesis of carbon nanotubes with ordered architectures. Special carbon nanotube configurations, such as nanocoils, nanohorns, bamboo-shaped and carbon cylinder made up from carbon nanotubes are also discussed.     

Formation of carbon nanotubes without iron inclusion and their alignment through ferrocene and ferrocene-ethylene pyrolysis

So far carbon nanotubes grown from the method most common method at present, that is, pyrolysis of ferrocene, invariably contains Fe inclusion. In addition, they are generally grown in random configurations. In the present investigations CNTs without Fe inclusion and in aligned configurations have been prepared by the pyrolysis of ferrocene (C10H10Fe) as well as pyrolysis of ferrocene in the presence of ethylene (C2H4). This has been achieved through optimization of growth parameters, for example, heating rate of ferrocene, pyrolysis temperature, and flow rates of carrier gas argon (Ar) and ethylene (C2H4). The as-synthesized samples have been characterized by transmission and scanning electron microscopic techniques. The optimum results relating to synthesis of carbon nanotubes without Fe inclusion and in aligned configurations have been obtained at 1000 degrees C pyrolysis temperature under flow rates of Ar of approximately 1000 sccm and of C2H4 of approximately 100 sccm. These carbon nanotubes have been found to have an outer diameter between approximately 20 and 60 nm and lengths between approximately 15 and 20 microns.     

Chained Dual-Generative Adversarial Network: A Generalized Defense Against Adversarial Attacks

Neural networks play a significant role in the field of image classification. When an input image is modified by adversarial attacks, the changes are imperceptible to the human eye, but it still leads to misclassification of the images. Researchers have demonstrated these attacks to make production self-driving cars misclassify Stop Road signs as 45 Miles Per Hour (MPH) road signs and a turtle being misclassified as AK47. Three primary types of defense approaches exist which can safeguard against such attacks i.e., Gradient Masking, Robust Optimization, and Adversarial Example Detection. Very few approaches use Generative Adversarial Networks (GAN) for Defense against Adversarial Attacks. In this paper, we create a new approach to defend against adversarial attacks, dubbed Chained Dual-Generative Adversarial Network (CD-GAN) that tackles the defense against adversarial attacks by minimizing the perturbations of the adversarial image using iterative oversampling and undersampling using GANs. CD-GAN is created using two GANs, i.e., CDGAN’s Sub-Resolution GAN and CDGAN’s Super-Resolution GAN. The first is CDGAN’s Sub-Resolution GAN which takes the original resolution input image and oversamples it to generate a lower resolution neutralized image. The second is CDGAN’s Super-Resolution GAN which takes the output of the CDGAN’s Sub-Resolution and undersamples, it to generate the higher resolution image which removes any remaining perturbations. Chained Dual GAN is formed by chaining these two GANs together. Both of these GANs are trained independently. CDGAN’s Sub-Resolution GAN is trained using higher resolution adversarial images as inputs and lower resolution neutralized images as output image examples. Hence, this GAN downscales the image while removing adversarial attack noise. CDGAN’s Super-Resolution GAN is trained using lower resolution adversarial images as inputs and higher resolution neutralized images as output images. Because of this, it acts as an Upscaling GAN while removing the adversarial attak noise. Furthermore, CD-GAN has a modular design such that it can be pre-fixed to any existing classifier without any retraining or extra effort, and can defend any classifier model against adversarial attack. In this way, it is a Generalized Defense against adversarial attacks, capable of defending any classifier model against any attacks. This enables the user to directly integrate CD-GAN with an existing production deployed classifier smoothly. CD-GAN iteratively removes the adversarial noise using a multi-step approach in a modular approach. It performs comparably to the state of the arts with mean accuracy of 33.67 while using minimal compute resources in training.     

Design of Compact Planar Triple Band-Notch Monopole Antenna for Ultra-wideband Applications

In this article a microstrip-fed mickey shaped monopole antenna with triple notched band characteristics for ultra-wideband applications is presented. By etching two slots in the ground plane, improved VSWR bandwidth is achieved. Mickey shape radiating patch provides 10 dB return-loss bandwidth from 3.10 to 10.60 GHz. By etching three simple C-shaped slots on the radiating patch, three existing wireless communication systems which interfere with UWB band is removed which includes WiMAX IEEE802.16 (3.30–3.80 GHz), WLAN IEEE802.11a/h/j/n (5.15–5.35, 5.25–5.35, 5.47–5.725, 5.725–5.825 GHz) and X-band downlink satellite system (7.1–7.9 GHz). Experimental results reveal that the proposed antenna exhibits desirable radiation patterns in the far field, resulting omnidirectional like pattern in the H-plane and nearly dipole like pattern in the E-plane.