On equations for regular languages, finite automata, and sequential networks

We consider systems of equations of the form where A is the underlying alphabet, the Xi are variables, the Pi,a are boolean functions in the variables Xi, and each δi is either the empty word or the empty set. The symbols υ and denote concatenation and union of languages over A. We show that any such system has a unique solution which, moreover, is regular. These equations correspond to a type of automation, called boolean automation, which is a generalization of a nondeterministic automation. The equations are then used to determine the language accepted by a sequential network; they are obtainable directly from the network.

Efficient Simulation of Freak Waves in Random Oceanic Sea States

Numerical simulations of freak wave generation are studied in random oceanic sea states described by JONSWAP spectrum. The evolution of initial random wave trains is numerically carried out within the framework of the modified four-order nonlinear Schroedinger equation (mNLSE), and some involved influence factors are also discussed. Results show that if the sideband instability is satisfied, a random wave train may evolve into a freak wave train, and simultaneously the setting of the Phillips parameter and enhancement coefficient of JONSWAP spectrum and initial random phases is very important for the formation of freak waves. The way to increase the generation efficiency of freak waves though changing the involved parameters is also presented.

Synthesis and random laser application of ZnO nano-walls: a review

This review paper summarises briefly some important achievements of our recent research on the synthesis and novel applications of nanostructure ZnO such as honeycomb shaped 3-D (dimension) nano random-walls. A chemical reaction/vapour transportation deposition technique was employed to fabricate this structure on ZnO/SiO2/Si substrate without any catalyst and additive in a simple tube furnace to aim the low-cost and high qualified samples. Random laser action with strong coherent feedback at the wavelength between 375 nm and 395 nm has been firstly observed under 355 nm optical excitation with threshold pumping intensity of 0.38 MW/cm(2).

NEW FORMATION MECHANISM OF ELECTRIC-FIELD DOMAIN DUE TO GAMMA-X SEQUENTIAL TUNNELING IN GAAS/ALAS SUPERLATTICES

We have studied the sequential tunneling of doped weakly coupled GaAs/ALAs superlattices (SLs), whose ground state of the X valley in AlAS layers is designed to be located between the ground state (E(GAMMA1)) and the first excited state (E(GAMMA2)) of the GAMMA valley in GaAs wells. The experimental results demonstrate that the high electric field domain in these SLs is attributed to the GAMMA-X sequential tunneling instead of the usual sequential resonant tunneling between subbands in adjacent wells. Within this kind of high field domain, electrons from the ground state in the GaAs well tunnel to the ground state of the X valley in the nearest AlAs layer, then through very rapid real-space transfer relax from the X valley in the AlAs layer to the ground state of the GAMMA valley of the next GaAs well.

THE ADSORPTION OF O2 ON FESI SURFACES

The initial adsorption stages and the interaction of oxygen on FeSi surfaces have been studied as a function of exposure and annealing temperature using a variety of techniques including HREELS, AES, LEED, XPS and UPS. O2 was found to adsorb dissociatively on the FeSi surfaces at room temperature. The whole adsorption process can be divided into four stages. Heating promotes the oxidation of Si, and a thin SiO2 overlayer is formed on the surface when annealed at 450-degrees-C, while all FeOx species are reduced. Models for adsorbed atomic O on the FeSi(100) surface exposed to different oxygen exposures have been put forward to account for the observed experimental results.