Time-hopping ultra-wideband technology presents some very attractive features for future indoor wireless systems in terms of achievable transmission rate and multiple access capabilities. This paper develops an algorithm to design time-hopping system simulators specially suitable for ultra-wideband, which takes advantage of some of the specific characteristics of this kind of systems. The algor...

The Davydov D1 ansatz, which assigns individual bosonic trajectories to each spin state, is an efficient, yet extremely accurate trial state for time-dependent variation of the sub-Ohmic spin-boson model [N. Wu, L. Duan, X. Li, and Y. Zhao, J. Chem. Phys. 138, 084111 (2013)]. A surface hopping algorithm is developed employing the Davydov D1 ansatz to study the spin dynamics with a sub-Ohmic bos...

Conductivity and thermopower measurements of artificial three dimensional bismuth crystals are presented. Due to the size dependent band gap of bismuth, electron transport in the bismuth crystals is a combination of both metallic and hopping conduction. The conductivity and thermopower due to the hopping pathways alone can be extracted through a comparison of the properties of the artificial bi...

This paper considers the physical layer security of frequency hopping (FH) systems. Mainly due to the collision effect among different users, the spectral efficiency of the conventional FH is very low. To overcome this limitation, in this paper, we first propose a general collision-free frequency hopping (CFFH) scheme based on secure spectrum access control; Second, we incorporate the CFFH sche...

We present a uniÐed derivation of the mean-Ðeld (Ehrenfest) and surfacehopping approaches to mixed quantumÈclassical dynamics that elucidates the underlying approximations of the methods and their strengths and weaknesses. We then report a quantitative test of alternative mixed quantumÈclassical methods against accurate quantum mechanical calculations for a simple one-dimensional curve-crossing...

Transport properties of progressively reduced graphene oxide (GO) are described. Evolution of the electronic properties reveals that as-synthesized GO undergoes insulator-semiconductor-semimetal transitions with reduction. The apparent transport gap ranges from 10 to 50 meV and approaches zero with extensive reduction. Measurements at varying degrees of reduction reveal that transport in reduce...

The low-temperature surface diffusion of isolated Cr adatoms on Au(111) has been determined using nonperturbing x rays. Changes in the x-ray magnetic circular dichroism spectral line shape together with Monte Carlo calculations demonstrate that adatom nucleation proceeds via quantum tunneling diffusion rather than over-barrier hopping for temperatures <40K. The jump rates are shown to be as muc...

We propose a possible charge fluctuation effect expected in layered superconducting materials. In the multireference density functional theory, relevant fluctuation channels for the Josephson coupling between superconducting layers include the interlayer pair hopping derived from the Coulomb repulsion. When interlayer single-electron tunneling processes are irrelevant in the Kohn-Sham electroni...

Schrödinger’s equation with scalar and vector potentials is shown to describe “nothing but” hopping of a quantum particle on a lattice; any spatial variation of the hopping amplitudes acts like an external electric and/or magnetic field. The main point of the argument is the superposition principle for state vectors; Lagrangians, path integrals, or classical Hamiltonians are not (!) required. A...

In Ad hoc networks, malicious nodes can enter in radio transmission range on the routing path and disrupt network activity. Therefore, protecting from intrusion of malicious node and enhance data security is an important issue on Ad hoc networks. In this study, we provide a path hopping method based on reverse AODV (R-AODV). By reverse AODV, source node builds multipath to destination and adapt...