Shape Bifurcation of a Spherical Dielectric Elastomer Balloon under the Actions of Internal Pressure and Electric Voltage

Under the actions of internal pressure and electric voltage, a spherical dielectric elastomer balloon usually keeps a sphere during its deformation, which has also been assumed in many previous studies. In this article, using linear perturbation analysis, we demonstrate that a spherical dielectric elastomer balloon may bifurcate to a non-spherical shape under certain electromechanical loading conditions. We also show that with a non-spherical shape, the dielectric elastomer balloon may have highly inhomogeneous electric field and stress/stretch distributions, which can lead to the failure of the system. In addition, we conduct stability analysis of the dielectric elastomer balloon in different equilibrium configurations by evaluating its second variation of free energy under arbitrary perturbations. Our analyses indicate that under pressure-control and voltage-control mode, non-spherical deformation of the dielectric elastomer balloon is energetically unstable. However, under charge-control or ideal gas mass-control mode, non-spherical deformation of the balloon is energetically stable

Adsorption of Pure and Multicomponent Gases on Wet Coal

The purpose of this research was to investigate the competitive adsorption behavior of methane, carbon dioxide and nitrogen on the surface of coal. Measurements were focused on the adsorption of the pure gases methane, nitrogen, carbon dioxide and their mixtures. Experiments were conducted on wet Fruitland and Illinois-6 coals at 115 (deg) F. Mathematical models have been applied to describe the observed behavior. Five models: Langmuir, Loading-Ratio-Correlation (LRC), Zhou-Gasem-Robinson (ZGR) equation of state, Park-Gasem-Robinson (PGR) equation of state and Sirnplified-LocalDensity (SLD) approach were used to correlate the experimental data of pure methane, carbon dioxide and nitrogen adsorption on wet Fruitland and Illinois-6 coals at 115 (deg) F . The LRC model and the ZGR equation of state were used to correlate the adsorption measurements of binary mixtures involving methane, carbon dioxide and nitrogen on wet Fruitland coal at 115 (deg) F . Precise pure gas adsorption on wet Fruitland and Illinois-6 coals and binary mixture adsorption data on wet Fruitland coal have been obtained. The uncertainty for pure gas adsorption is less than 5% for pressures from 100 to 1800 psia, and the uncertainty for the total adsorption in binary gas mixtures is within 7%. The mathematical models can correlate the experimental data precisely. Results show that all five models can represent the pure gas experimental data less than 3% average absolute error

Generation of OAM Radio Waves with Three Polarizations Using Circular Horn Antenna Array

This paper provides an effective solution of generating OAM-carrying radio beams with all three polarizations: the linear, the left-hand circular, and the right-hand circular polarizations. Through reasonable configuration of phased antenna array using elements with three polarizations, the OAM radio waves with three polarizations for different states can be generated. The vectors of electric fields with different OAM states for all three polarizations are presented and analyzed in detail. The superposition of two coaxial OAM states is also carried out, and the general conclusion is provided

Lattice strain effects on the optical properties of MoS2 nanosheets.

"Strain engineering" in functional materials has been widely explored to tailor the physical properties of electronic materials and improve their electrical and/or optical properties. Here, we exploit both in plane and out of plane uniaxial tensile strains in MoS2 to modulate its band gap and engineer its optical properties. We utilize X-ray diffraction and cross-sectional transmission electron microscopy to quantify the strains in the as-synthesized MoS2 nanosheets and apply measured shifts of Raman-active modes to confirm lattice strain modification of both the out-of-plane and in-plane phonon vibrations of the MoS2 nanosheets. The induced band gap evolution due to in-plane and out-of-plane tensile stresses is validated by photoluminescence (PL) measurements, promising a potential route for unprecedented manipulation of the physical, electrical and optical properties of MoS2

Wrinkles Riding Waves in Soft Layered Materials

The formation of periodic wrinkles in soft layered materials due to mechanical instabilities is prevalent in nature and has been proposed for use in multiple applications. However, such phenomena have been explored predominantly in quasi-static settings. In this work, we measure the dynamics of soft elastomeric blocks with stiff surface films subjected to high-speed impact, and observe wrinkles forming along with, and riding upon, waves propagating through the system. We analyze our measurements with large-deformation, nonlinear visco-hyperelastic Finite Element simulations coupled to an analytical wrinkling model. The comparison between the measured and simulated dynamics shows good agreement, and suggests that inertia and viscoelasticity play an important role. This work encourages future studies of the dynamics of surface instabilities in soft materials, including large-deformation, highly nonlinear morphologies, and may have applications to areas including impact mitigation, soft electronics, and the dynamics of soft sandwich composites