Notizie da 5 fonti
Using nonequilibrium molecular dynamics simulations, a comprehensive study of the asymmetric heat conduction in the composite system consisting of the Frenkel—Kontorova (FK) model and Fermi—Pasta—Ulam (FPU) model is conducted. The calculated results show that in a larger system, the rectifying direction can be reversed only by adjusting the thermal bias. Moreover, the rectification reversal depends critically on the system size and the properties of the interface. The mechanisms of the two types of asymmetric heat conduction induced by nonlinearity are discussed. Considering the novel asymmetric heat conduction in the system, it may possess possible applications to manage the thermal rectification in situ directionally without re-building the structure.
We present a numerical study of a model of quantum walk in a periodic potential on a line. We take the simple view that different potentials have different affects on the way in which the coin state of the walker is changed. For simplicity and definiteness, we assume that the walker's coin state is unaffected at sites without the potential, and rotated in an unbiased way according to the Hadamard matrix at sites with the potential. This is the simplest and most natural model of a quantum walk in a periodic potential with two coins. Six generic cases of such quantum walks are studied numerically. It is found that, of the six cases, four cases display significant localization effect where the walker is confined in the neighborhood of the origin for a sufficiently long time. Associated with such a localization effect is the recurrence of the probability of the walker returning to the neighborhood of the origin.
A high quality-factor ( Q ) cavity based on a one-dimensional (1D) photonic crystal with gradated elliptical holes was designed using FDTD simulation. Different gradient profiles of the mirror holes were found to correspond to different Q -values of the cavities. A simple strategy is proposed to construct high- Q cavities by using an S-shaped gradient profile for the elliptical holes' minor axes, such as a cosine function or Gaussian function. Using such a strategy, a Q value exceeding two million is obtained with only ten mirror holes in a cavity.
Bi 0.9 Ba 0.1 FeO 3 (BBFO)/La 2/3 Sr 1/3 MnO 3 (LSMO) heterostructures are fabricated on LaAlO 3 (100) substrates by pulsed laser deposition. Giant remnant polarization value (~ 85 μC/cm 2 ) and large saturated magnetization value (~ 12.4 emu/cm 3 ) for BBFO/LSMO heterostructures are demonstrated at room temperature. Mixed ferroelectric domain structures and low leakage current are observed and in favor of enhanced ferroelectric properties in the BBFO/LSMO heterostructures. The magnetic field-dependent magnetization measurements reveal the enhancement in the magnetic moment and improved magnetic hysteresis loop originating from the BBFO/LSMO interface. The heterostructure is proved to be effective in enhancing the ferroelectric and ferromagnetic performances in multiferroic BFO films at room temperature.