Band 76, Heft 4

Zero tunneling time and thereby a faster than light traversal velocity was calculated nearly a hundred years ago and has been observed recently. We report about experimental results and estimations, which confirm the zero time tunneling for elastic as well as for electromagnetic and Schrödinger waves. Zero time tunneling was first observed with microwaves 1992 (H. Aichmann and G. Nimtz, Found. Phys. , vol. 44, p. 678, 2014; A. Enders and G. Nimtz, J. Phys. I , vol. 2, p. 169, 1992). In 2008, zero time was also observed for tunneling electrons (P. Eckle, A. N. Pfeiffer, C. Cirelli, et al., Science , vol. 322, p. 1525, 2008). Presumably, this effect took place with atoms quite recently (R. Ramos, D. Spierings, I. Racicot, and A. M. Steinberg, Nature , vol. 583, p. 529, 2020). The Einstein relation E 2  = ( ħk ) 2 c 2 is not satisfied in the tunneling process, since the wave number k is imaginary (E is the total energy, ħ the Planck constant, and c the vacuum velocity of light), Zero time tunneling is described by virtual photons (A. Stahlhofen and G. Nimtz, Europhys. Lett. , vol. 76, p. 189, 2006). The tunneling process itself violates the Special Theory of Relativity. Remarkably, Brillouin conjectured that wave mechanics is valid for all waves independent of their field (L. Brillouin, Wave Propagation in Periodic Structures, Chap. VIII , New York, Dover Publications, 1953).

The electron paramagnetic resonance (EPR) parameters ( g factor g i , and hyperfine structure constants A i , with i  =  x , y , z ) and local structures for Cu 2+ centers in M 2 Zn(SO 4 ) 2 ·6H 2 O (M = NH 4 and Rb) are theoretically investigated using the high order perturbation formulas of these EPR parameters for a 3 d 9 ion under orthorhombically elongated octahedra. In the calculations, contribution to these EPR parameters due to the admixture of d -orbitals in the ground state wave function of the Cu 2+ ion are taken into account based on the cluster approach, and the required crystal-field parameters are estimated from the superposition model which enables correlation of the crystal-field parameters and hence the studied EPR parameters with the local structures of the Cu 2+ centers. Based on the calculations, the Cu–H 2 O bonds are found to suffer the axial elongation ratio δ of about 3 and 2.9% along the z -axis, meanwhile, the planar bond lengths may experience variation ratio τ (≈3.8 and 1%) along x - and y -axis for Cu 2+ center in (NH 4 ) 2 Zn(SO 4 ) 2 ·6H 2 O and Rb 2 Zn(SO 4 ) 2 ·6H 2 O, respectively. The theoretical results show good agreement with the observed values.

The present work presents the behavior of a liquid drop placed onto a surface of the perforated plate experimentally. Micro holes were created on the brass plate by a laser marking method. The actuator made of brass and piezoelectric discs driven by a sine input voltage, and it bonded rigidly to the perforated plate. This study aimed to reveal the behavior of the drop placed on the perforated plate and the effects of the initial acceleration value on the rate of change in the drop projected area onto the surface. For this purpose, a frequency-response function of the dry micro-perforated plate was measured by a laser vibrometer, and the acceleration distribution was determined on the perforated plate. Further, the drop was excited with five different initial acceleration values, and the drop projected area onto the surface was recorded by a camera during the atomization process. It was observed that droplets were atomized at the air–liquid interface on two sides of the perforated plate. The time-varying function of the drop projected area onto the surface for each initial acceleration value was presented graphically. The polynomial function was fitted to the experimental data points for each acceleration value, and thus the effects of the initial acceleration on the varying drop size were analyzed. The authors emphasized that the drop projected area onto the surface first increased and then decreased during the atomization process. The rate of change in the drop projected area onto the surface increased as the initial acceleration increased. The drop was atomized both by ejecting from the surface and sucking through the holes.

In this paper, the inverse scattering approach is applied to the Kundu-Eckhaus equation with two cases of zero boundary condition (ZBC) and nonzero boundary conditions (NZBCs) at infinity. Firstly, we obtain the exact formulae of soliton solutions of three cases of N simple poles, one higher-order pole and multiple higher-order poles via the associated Riemann-Hilbert problem (RHP). Moreover, given the initial data that allow for the presence of discrete spectrum, the higher-order rogue waves of the equation are presented. For the case of NZBCs, we can construct the infinite order rogue waves through developing a suitable RHP. Finally, by choosing different parameters, we aim to show some prominent characteristics of this solution and express them graphically in detail. Our results should be helpful to further explore and enrich the related nonlinear wave phenomena.

In this paper we have studied the gradual evolution of stationary formations in electron acoustic waves at a finite temperature quantum plasma. We have made use of Quantum hydrodynamics model equations and obtained the KdV-Burgers equation. From here we showed how the amplitude modulated solitons evolve from double layer structures through shock fronts and ultimately converging into solitary structures. We have studied the various parametric influences on such stationary structure and also showed how the gradual variations of these parameter affect the transition from one form to another. The results thus obtained will help in the generation and structure of the structures in their respective domain. Much of the experiments on dense plasma will benefit from the parametric study. Further we have studied amplitude modulation followed by a detailed study on chaos.

The systematic studies are carried out on liquid crystalline N-(p-n-heptyloxybenzylidene)-p-n-pentyloxy aniline (7O.O5) pure compound and with dispersion of ZnO nanoparticles in 1 wt% respectively. The phase transition studies of the pure and LC nanocomposite are carried out using Polarizing Optical Microscope (POM) attached with hot stage along with digital camera and Differential Scanning Calorimetry (DSC) is used to measure enthalpy and transition temperature values. Further the presence of ZnO nano particles in 7O.O5 is determined by Scanning Electron Microscopy (SEM) analysis. It is identified that due to dispersion of nano particles SmG phase is Quenched and nematic thermal range is increased. To enhance the captured textural images, an algorithm that uses tuned intensification operators have been proposed in this article. Statistical parameters for enhanced output images are calculated and compared with existing algorithms such as Adaptive Gamma Correction (AGC) and Discrete Wavelet Transform – Singular Value Decomposition (DWT-SVD) to understand the effectiveness of proposed algorithm. Further, optical parameters have been computed to understand the thermo optical nature of liquid crystalline compounds.

Transition metal disulfides (TMDCs) have attracted extensive attention in recent years for their novel physical and chemical properties. Based on the first-principles calculations together with semi-classical Boltzmann transport theory, we explored the electronic structures and transport properties of van der Waals WSe 2 /WTe 2 heterostructure. WSe 2 /WTe 2 heterostructure has distinctive hexagon structure and isotropic thermal transport properties. To prove the accuracy of band structure, both Perdew–Burke–Eruzerhof (PBE) and Heyd–Scuseria–Ernzerhof (HSE06) have been used to calculate the band structures. We simulated the band structures under uniaxial and biaxial strains from −8% to +8% and found that all band gaps calculated by HSE06 are larger than results calculated by PBE. More importantly, it was found that when the biaxial strain reaches ±8%, it undergone semiconductor to metal and the dynamic stabilities of WSe 2 /WTe 2 heterostructure have been predicted at the same time. We calculated the mobilities of electrons and holes and found that the mobility of holes is larger than that of electrons. The obtained lattice thermal conductivity (LTC) of WSe 2 /WTe 2 heterostructure at room temperature (70.694 W/mK) is significantly higher than other transition metal tellurium and transition metal selenium, such as PdSe 2 (2.91 W/mK) and PdTe 2 (1.42 W/mK) monolayers. Our works further enrich studies on the strain dependence of electronic structures and predicted high LTC of WSe 2 /WTe 2 heterostructure, which provide the theoretical basis for experiments in the future.

We propose an extension, of a quantum graph model for a single sheet of graphene, to multilayer AA-stacked graphene and also to a model of the bulk graphite. Spectra and Dirac cones are explicitly characterized for bilayer and trilayer graphene, as well as for graphite. For weak layer interaction (as proposed in the text), simple perturbation arguments also cover any number of layers and it mathematically recovers basic cone existences from the theoretical and experimental physics literature; its main strength is its simplicity.