On the force constants of graphene

It has been shown that the inclusion of an additional short-range potential in the repulsion energy of neighboring atoms allows one to satisfactorily describe the frequency of the phonon doublet at the Γ point for atomic vibrations in the plane of the graphene sheet and to calculate the corresponding Grüneisen coefficient. The results obtained are compared with those derived by other authors.     

Nonlinear Boundary Stabilization of Nonuniform Timoshenko Beam

In this paper, the stabilization problem of nonuniform Timoshenko beam by some nonlinear boundary feedback controls is considered. By virtue of nonlinear semigroup theory, energy-perturbed approach and exponential multiplier method, it is shown that the vibration of the beam under the proposed control actiondecays exponentially or in negative power of time t as t→∞.     

Calculation of triaxial superdeformation in <Superscript>174</Superscript>Hf

A two-dimensional Total Routhian Surface (TRS) calculation with the fixed hexadecapole deformation ε4 = 0.03 was carried out for several configurations of 174Hf. Results indicate that the shell corrections have an important contribution to the formation of triaxial superdeformation in 174Hf and some possible configuration assignments are made to the 4 TSD bands experimentally found in 174Hf.     

Quantum secret sharing between multiparty and multiparty with four states

A protocol of quantum secret sharing between multiparty and multiparty with four states was presented. It was shown that this protocol can nullify the Trojan horse attack with a multi-photon signal, the fake-signal attack with Einstein-Podolsky-Rosen pairs, the attack with single photons, and the attack with invisible photons. In addition, the upper bounds of the average success probabilities were given for dishonest agent eavesdropping encryption using the fake-signal attack with any two-particle entangled states. Supported by the National Natural Science Foundation of China (Grant No. 10671054), the Key Project of Science and Technology Research of Education Ministry of China (Grant No. 207011) and the Natural Science Foundation of Hebei Province, China (Grant Nos. A2005000140 and 07M006)     

EPR parameters and defect structures of the off-center Ti ion on the Sr site in neutron-irradiated SrTiO3 crystal

The EPR parameters (g factors and hyperfine structure constants A) for the tetragonal Ti³⁺ center in cubic phase and the rhombic Ti³⁺ center in tetragonal phase in the neutron-irradiated SrTiO₃ crystals are calculated from the third-order perturbation formulas of EPR parameters for d¹ ions. These low-symmetry Ti³⁺ centers in both phases of SrTiO₃ are due to the Ti³⁺ ion at “off center” on the Sr²⁺ site. From the calculation, the defect models (including the direction and magnitude of the Ti³⁺ off-center displacement) of the two Ti³⁺ centers in SrTiO₃ are estimated and the EPR parameters of both Ti³⁺ centers are reasonably explained on the basis of the defect models. The results are discussed.     

Influence of thin AlAs layer insertion on intersubband optical transitions in GaAs/AlGaAs quantum- well structures

In this work, we demonstrate the thin AlAs layer insertion into GaAs/AlGaAs quantum well (QW) structures and its influence in energy transition in the frequency range of mid-infrared. To realize the more accurate calculation, the graded interface model of QW structures is integrated into our self-consistent solving of Schrodinger and Poisson equations to obtain the energy level and envelope wave functions of QW. We find the thin AlAs layer inserted at various positions in the well can obviously tune intersubband optical transitions. The corresponding tuning range can be 50 meV. We find that the thicker AlAs layer (2 monolayers) can provide wider tuning range and larger oscillator strength between subbands 1 and 3, compared with the thinner one (1 monolayer). Our results suggest that thin semiconductor layer may be an idea optimization design for the quantum well terahertz lasers which are based on optical pumping with mid-infrared lasers.     

Practical stability in terms of two measures for discrete hybrid systems

In this paper, using the variational Lyapunov method, we obtain practical stability criteria in terms of two measures for discrete hybrid systems.     

A cubically convergent Newton-type method under weak conditions

Under weak conditions, we present an iteration formula to improve Newton's method for solving nonlinear equations. The method is free from second derivatives, permitting f^′(x)=0 in some points and per iteration it requires two evaluations of the given function and one evaluation of its derivative. Analysis of convergence demonstrates that the new method is cubically convergent. Some numerical examples illustrate that the algorithm is more efficient and performs better than classical Newton's method.     

Exponential convergence of an epidemic model with time-varying delays

In this paper the convergence behavior of an epidemic model with time-varying delays are considered. Some sufficient conditions are established to ensure that all solutions of the epidemic model with permitted initial conditions converge exponentially to zero, which are new and complement previously known results.