International Journal of Modern Physics B

Nonlinear Markov processes are known to arise from diffusion approximations of nonlinear master equations and generalized Boltzmann equations and have been studied in their own merit in the context of nonlinear Fokker–Planck equations. Nonlinear Markov processes can account for collective phenomena, collective oscillations, and collective chaotic behavior. Despite the importance of nonlinear Markov processes for the physics of stochastic processes, relatively little is known about the Chapman–Kolmogorov equation of nonlinear Markov processes. The manuscript derives the exact solution of the Chapman–Kolmogorov equation for a recently proposed deterministic Markov model. Numerical solutions of the Chapman–Kolmogorov equation are used to demonstrate the nonlinear semi-group property of conditional probabilities of nonlinear Markov processes.

Ground state properties of zinc-blende structures ZnS and ZnSe are investigated from first principles using plane wave basis, projector augmented wave method and local orbital-dependent potential, as well as a basis set of Gaussian-type functions with hybrid functionals for the approximation of exchange-correlation energy. The results of DFT calculations with the LDA, LDA+U, GGA, GGA+U, BLYP, B3P86, P3PW, BH-HP, KMLYP and B3LYP approximations are compared. It is shown that the hybrid functional B3LYP provides an accurate quantitative description of the structural, electronic and vibrational properties of ZnS and ZnSe in comparison with experimental data.

A family of integrable lattice equations with four potentials is constructed from a new discrete three-by-three matrix spectral problem. The Hamiltonian structures of the integrable lattice equations in the family are derived by applying the discrete trace identity. Finally, infinitely many common commuting conserved functionals of the resulting integrable lattice equations are given.

A carbon nanotube field effect transistor (CNTFET) has been studied based on the Schrödinger–Poisson formalism. To improve the saturation range in the output characteristics, new structures for CNTFETs are proposed. These structures are simulated and compared with the conventional structure. Simulations show that these structures have a wider output saturation range. With this, larger drain-source voltage (Vds) can be used, which results in higher output power. In the digital circuits, higher Vds increases noise immunity.

Impedance measurements were made on technological important ferroelectric ceramics, namely PZT and La_0.75 Bi_3.25Ti₃O₁₂ (BLT), in the frequency range of 100 Hz to 1 MHz, from room temperature to 500°C. Combined impedance and modulus spectroscopic analysis along with the detailed conductivity (ac and dc) data was used to understand the heterogeneity of the ceramics and the results were corroborated with temperature coefficient of dc-conductivity (figure of merit) data for the further understanding. AC-conductivity plots against frequency at different temperatures for PZT and BLT suggest the response of obeying Jonscher's and modified Jonscher's law, respectively.

Mn₂O₃/Mn₅O₈ and MnO/Mn nanoparticles were prepared by annealing manganese nanoparticles in air and hydrogen, respectively. The antiferromagnetic Mn₂O₃/Mn₅O₈ and MnO/Mn nanoparticles exhibit anomalous magnetic properties, such as large moments, and large coercivity of up to 169 kA/m and 105 kA/m, respectively. This ferromagnetic-like behavior is attributed to the finite size effect of antiferromagnetic nanoparticles and the presence of ferrimagnetic Mn₃O₄ phases.

The dependencies of the melting point and the lattice parameter of supported metal nanoclusters as functions of clusters height are theoretically investigated in the framework of the uniform approach. The vacancy mechanism describing the melting point and the lattice parameter shifts in nanoclusters with decrease in their sizes is proposed. It is shown that under the high vacuum conditions (p < 10^-7torr) the essential role in clusters melting point and lattice parameter shifts is played by van der Waals forces of cluster–substrate interaction. The proposed model satisfactorily accounts for the experimental data.

In this paper, we correlate the internal stress and the characteristics of a vibrational mode in wet foam. Using microscope images, we estimate the average size of the bubbles in wet foam, at specific time intervals, over a duration of 24 h. Raman spectra are also recorded at the same time intervals, over the same time frame. We show that the internal stress, originated from the microscopic structural change of foam with aging, can be related to the observed Raman shift of the low-frequency methylene rocking mode of the constituent surfactant molecules in foam. In this paper, we also show the capability of the Raman spectroscopy to reveal the crystallinity in foamy materials, when studied for a longer period of time.

Structure, Curie temperature, and magnetostriction have been systemically investigated for Tb_0.27Dy_0.73 Fe_1.9+xTi_0.05 compounds using X-ray diffraction, vibrating sample magnetometer, and standard strain gauge technique. The samples show pure MgCu₂-type Laves phase when x≥0.2, and a small amount of second phases appear when x>0.2. The lattice parameters and the Curie temperatures change modestly with increasing Fe content. The magnetostriction of Tb_0.27Dy_0.73Fe_1.9+xTi_0.05 compounds shows strong dependence on Fe content.

Starting from a Painlevé–Bäcklund transformation, an exact variable separation solution with four arbitrary functions for the (2+1)-dimensional generalized Sasa–Satsuma (GSS) system are derived. Based on the derived exact solutions in the paper, some complex wave excitations in the (2+1)-dimensional GSS system and revealed, which describe solitons moving on a periodic wave background. Some interesting evolutional properties for these solitary waves propagating on the periodic wave background are also briefly discussed.