International Journal of Modern Physics B

Cross-sectional deformation of multiwalled carbon nanotubes under isotropic radial pressure is investigated in a realm of continuum elastic approximation. The nanotube we assumed is subjected to the embedment into an elastic medium and stiffener insertion into the core cavity. Combination of the two reinforcement manipulations is found to cause kaleidoscopic mode changes in the radial corrugation, in which the cylindrical walls exhibit wavy patterns along the circumferential direction. Physical consequences of the diverse corrugation patters are also discussed.

Oscillators under nonlocal couplings are systematically studied. We propose functions of inverse power as mathematical realization for nonlocal couplings among oscillators in a system. Power β in a function is taken as an important parameter in our study. Since its value determines a measure of "localization" while oscillators are nonlocally coupled it is then called the "nonlocal parameter". Together with the "phase lag parameter" α, which is vital for the existence of chimera states, we are able to demonstrate a valuable phase portrait in the β-α space. System dynamics is discussed in this phase diagram analogous to phase transitions in thermodynamics.

Using the generalized Fermi–Dirac distribution function arising from Tsallis statistical mechanics, we revisit the Sommerfeld model for metallic elements. The chemical potential, the total energy and the heat capacity are calculated. It is shown that the linearity between the heat capacity and the temperature is q-dependent, where q stands for the entropic index. In the limit q→1, the results of the usual model are recovered. Comparisons are made with experimental data and with the values of the usual model. The Pauli magnetic susceptibility is found not affected by the electron nonextensivity. Our results suggest that we can rely on the generalized nonextensive Sommerfeld model to expect achievement of reasonable agreement between theory and experiment. They may aid to constrain the values of the nonextensive parameter q for metallic elements and to determine more clearly the reality of nonextensive effects.

The degree of polymerization (DP) has been regarded as an important symbol of mechanical strength, reflecting the aging condition of transformer insulation paper. In this article, a new concept called fracture degree is proposed on the basis of DP. First, nine cellulose I_β crystal models with different fracture degrees were built. Then relevant mechanical parameters and hydrogen bond numbers were calculated by molecular dynamics (MD) simulation. Results showed that during the aging process of insulation paper with fracture of cellulose chain, the elastic constant C₃₃ produces appreciable impact on the Young's modulus (E). With the decrease of DP and increase of fracture degree, the Young's modulus step decreases. To the 50% and 100% fracture degree models respectively, the relationship between their different degrees of polymerization and Young's modulus is subjected to similar exponential distributions. With the increase of the fracture degree, the average hydrogen bond number drops, and the change rules apply to the Young's modulus. Since hydrogen bond is the main factor of mechanical strength, it can be inferred that the fracture degree influences mechanical strength seriously.

We study DNA dynamics relying on the plane-base rotator model for DNA. It is shown that this dynamics can be represented by kink and antikink solitons. We demonstrate that two velocities are relevant and these are the velocities of both a double and a single stranded DNA. A key question is which one is bigger as this is related to a value of the ratio of two parameters describing the hydrogen and the covalent interactions in DNA. If the velocity of double stranded DNA is larger than one of the single stranded chain then the two ferromagnetic strands are coupled antiferromagnetically. Otherwise, the two DNA strands are coupled ferromagnetically. We discuss possible experiments based on micromanipulation techniques that should be carried out to determine these velocities and the solitonic width.

Spectral properties related to the low-energy d–d excitations in nearly cubic vanadium perovskites are examined for the expected L-edge resonant inelastic X-ray scattering (RIXS) measurements. Multiplet structure of V³⁺ ion in the basic electron configuration is calculated with the help of ab initio quantum-chemical method applied to VO₆ cluster embedded in a crystalline environment. In the intermediate states of the RIXS process the induced 2p-core hole is taken into account by including strong 2p–3d electron interactions. A symmetry-group approach is applied to generate the basis set of many-electron wavefunctions of the intermediate core-hole states accessible in RIXS processes. Although a comprehensive description of the core-hole multiplets still remains a formidable task and requires using specially designed numerical codes, for particular resonant states the analysis is simplified and the calculation of RIXS amplitude can be carried out analytically to the end.

This paper offers two different attacks on a freshly proposed image encryption based on chaotic logistic map. The cryptosystem under study first uses a secret key of 80-bit and employed two chaotic logistic maps. We derived the initial conditions of the logistic maps from using the secret key by providing different weights to all its bits. Additionally, in this paper eight different types of procedures are used to encrypt the pixels of an image in the proposed encryption process of which one of them will be used for a certain pixel which is determined by the product of the logistic map. The secret key is revised after encrypting each block which consisted of 16 pixels of the image. The encrypting process have weakness, worst of which is that every byte of plaintext is independent when substituted, so the cipher text of the byte will not change even the other bytes have changed. As a result of weakness, a chosen plaintext attack and a chosen cipher text attack can be completed without any knowledge of the key value to recuperate the ciphered image.

Aiming at the drawbacks of the chaotic masking scheme, this paper optimizes this conventional scheme by using improved state observer method and system-alternating method, proposes a new secure communication scheme which can improve these drawbacks of chaotic method: (1) Restriction that the power of useful signal must be smaller than that of chaotic signal. (2) Low security. In addition, the model of this whole communication system is constructed under the system simulation environment of Simulink.