Sharif Digital Repository

In this paper, we employ tunneling Hamiltonian formulation to obtain analytical expression for the Josephson current in (n, m) Carbon nanotubes (CNT) sandwiched between s-wave superconductors. For metallic tubes, we find that the dominant contribution to the Josephson current arises from modes crossing the Dirac points. Contribution from such conducting channels is independent of tube diameter of carbon nanotubes. Josephson current for each CNT is determined in terms of the spacing d between the superconductors, and the angle between the tube axis and the vector normal to the interface. Averaging over orientation angles gives the Josephson current through an assembly of randomly oriented... 

We investigate short-term non-linearity of solar irradiance fluctuations using the multifractal detrended fluctuation analysis (MFDFA). The MFDFA shows that time series of solar irradiance have a long range correlation function with a multifractal behavior. We apply this method to solar irradiance time series from several regions around the world with resolutions of seconds and minutes. The obtained generalized Hurst and Renyi exponents h(q) and τ(q) suggest the non-linear and non-stationary essence of measured irradiance time series. Also, we analyze shuffled, random phase, and rank-wised surrogated data to reveal the nature of the multifractality and conclude that linear and non-linear... 

A body insonified by a constant (time-varying) intensity sound field is known to experience a steady (oscillatory) force that is called the steady-state (dynamic) acoustic radiation force. Using the classical resonance scattering theorem (RST) which suggests the scattered field as a superposition of a resonance field and a background (non-resonance) component, we show that the radiation force acting on a cylindrical shell may be synthesized as a composition of three components: background part, resonance part and their interaction. The background component reveals the pure geometrical reflection effects and illustrates a regular behavior with respect to frequency, while the others...