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The interaction between travelling wave impulses and spiral waves is studied and the results of their competition are related to the exciting period. From the results, it is known that the formation and development of spiral waves in cardiac tissue depend on the period by which the travelling wave impulses are excited. A method is proposed to eliminate spiral waves, which is easily operated.

Layered potassium cobaltate KxCoO2 with x = 0.36 has been successfully synthesized in KOH fluxes at 480 degrees C, and its hydrated form K0.36CoO2.yH2O (y≤0.8) has been obtained by intercalation with water. The diffraction peaks of K0.36CoO2 can be indexed by an orthorhombic cell similar to Na0.5CoO2, and K0.36CoO2.0.8H2O is isostructural with its sodium analog, monolayer hydrate NaxCoO2.yH2O. While the samples KxCoO2 and K0.36CoO2yH2O (y

The well-known superconducting oxide LiTi2O4 has a structural phase transition from spinel to ramsdellite around 900 degrees C. We have successfully obtained the superconducting spinel phase and the non-superconducting ramsdellite phase of LiTi2O4 using a hybrid microwave method. The samples are characterized by x-ray powder diffraction, scanning electron microscopy, and measurements of resistivity and magnetic susceptibility. The results show that the low-temperature spinel phase is a superconductor with Tc = 13 K, while the high-temperature ramsdellite phase is a semiconductor. By comparison between the crystal structures of the spinel and the ramsdellite phases, it is suggested that the geometrical frustration plays an important role in the superconductivity of the spinel LiTi2O4.

Two statistical properties, the nearest neighbor energy level spacing distribution P(s) and the spectral rigidity Delta(3)(L), are reported for energy level of a quantum well in a tilted magnetic field. Time-reversal (T) symmetry is broken in the system. The system is invariant under the anti-unitary combination of symmetric operations which include T, leading to what is called false T-violation. With the increasing magnetic field, P(s) and Delta(3)(L) change from Brody type-like distribution to the Gaussian orthogonal ensemble (GOE) distribution. This result is a dear manifestation of quantum chaos in the system and is in agreement with the prediction of which the false T-violation suffices to give the energy spectra the properties of the GOE, instead of the Gaussian unitary ensemble (GUE). The result indicates that the system translates from mixed-type state to quantum chaotic state. However, the spectral rigidity Delta(3) (L) turns into GUE with the magnetic field increasing. The different demonstration of P(s) and the Delta(3)(L) is due to the counting of only finite semi-classical orbits.

Relativistic momentum and energy equations of electrons in an intense laser field are derived with Hamilton-Jacobi equation. For initial electrons in non-equilibrium or Maxwellian equilibrium distributions in preplasmas, suprathermal electron energy distributions are obtained analytically and numerically. The calculation results agree well with the experiments.

The eigenvalues and eigenfunctions of the stadium-shaped quantum dot subjected to a constant magnetic field in the perpendicular direction are computed by a simple and efficient method. With the magnetic field increasing, the nearest-neighour-energy-level-spacing distribution of the stadium-shaped quantum dot is found to transform gradually from the Wigner distribution to the Poisson distribution. The transition of the nearest-neighour-energy-level-spacing distribution indicates that system changes from quantum chaotic to regular. The variation of the spatial charge distribution indicates that the system varies from bulk Landau state to the edge state that mainly affects the transport properties of the stadium-shaped quantum dot. The change of the two dimensional charge distribution near the anticrossing point is also discussed.

The aim of the present work is to generalize the method introduced by Guemez et al. [Phys. Rev. E52 (1995) R2145] Using feedback scheme, two systems can be synchronized by signals or variables which come from the driving system. Furthermore, it is possible for the systems to be synchronized by different driving signals which come from the third of fourth system. So the unmasking procedure becomes more difficult. Numerical simulations are given.

We perform a comparison study on characteristic regimes in shocked porous materials whose mechanical properties cover a wide range. Via the Minkowski functional analysis, it is found that different materials may show the same fractional size of characteristic regimes in the shock-loading procedure, even if one uses the same threshold value to define those regimes. Characteristic regimes in the material with larger initial yield are more dispersed. For a fixed shock strength, there exists a material strength with which the shock wave reaction contributes the maximum plastic work. With the decreasing of shock strength, this material strength becomes smaller. These observations may present helpful indications for new material designs.

We undertake a numerical simulation of shock experiments on tin reported in the literature, by using a multiphase equation of state (MEOS) and a multiphase Steinberg Guinan (MSG) constitutive model for tin in the β, γ and liquid phases. In the MSG model, the Bauschinger effect is considered to better describe the unloading behavior. The phase diagram and Hugoniot of tin are calculated by MEOS, and they agree well with the experimental data. Combined with the MEOS and MSG models, hydrodynamic computer simulations are successful in reproducing the measured velocity profile of the shock wave experiment. Moreover, by analyzing the mass fraction contour as well as stress and temperature profiles of each phase for tin, we further discuss the complex behavior of tin under shock-wave loading.