International Journal of Modern Physics B

In this paper, the time-dependent variable-coefficient KdV equation with a forcing term is considered. Based on the Hirota bilinear method, the bilinear form of this equation is obtained, and the multi-soliton solutions are studied. Then the periodic wave solutions are obtained by using Riemann theta function, and it is also shown that classical soliton solutions can be reduced from the periodic wave solutions.

Our aim is to contribute to comprehension of the phenomena of precipitation in the Al–Zn–Mg alloys. For this, we have made a comparative study of the transformations of phases using the differential scanning calorimetric and the dilatometry. This last technique is relatively new in the case of Al–Zn–Mg alloys. It consists of two opposite effects (contraction and expansion) observed on the dilatometric curves. These effects translate two opposite metallurgical phenomena which are generally the precipitation and the dissolution.

The glass transition temperature (Tg) in the amorphous region of an insulation paper is one of the most important characteristics for thermal stability. Molecular dynamic simulations have been performed on three micro-structural models, namely, amorphous pure cellulose, amorphous cellulose with water and amorphous cellulose with oil, to study the microscopic mechanism of the glass transition process for oil-immersed transformer insulation paper. Using the method of specific volume versus temperature curve, the Tg of amorphous pure cellulose, cellulose with water, and cellulose with oil was determined as 448, 418 and 440 K, respectively. The current study may provide some information for thermal aging. The simulation results show that during the glass transition process, both the chain motion and mechanical properties of cellulose changes significantly. Relative to the oil molecules, water molecules immersed in the amorphous region of insulation paper can disrupt hydrogen bonds between cellulose chains. This phenomenon results in a significant reduction in the glass transition temperature and affects the thermal stability of the insulation paper.

The effects of long-range interactions between peptides on the protein–DNA dynamics in the long-wave limit are studied. The investigation, done at the physiological temperature, is based on a coupled spin system of DNA molecule which includes the helicoidal geometry of DNA molecule and the Kac–Baker long-range interaction between the peptides of the protein molecule. By using the Holstein–Primakoff bosonic representation of the spin operators, we show that the original discrete equations for the protein–DNA interaction dynamics can be reduced to the nonlinear Schrödinger (NLS) equation of which the dispersive and the nonlinear coefficients depend among other things on the protein long-range interaction parameter and on the helicoidal coupling coefficient. Furthermore, we find that the amplitude and the width of the resulting breather solution, in the form of the bubble moving along the DNA molecule, are strongly influenced by the long-range and helicoidal interactions. This result shows a relevant length scale for real protein–DNA interaction.

The hydration effects of water on the high-pressure elastic properties of three Mg₂SiO₄ polymorphs have been investigated using first-principles simulation density functional theory. The effect of water incorporation was simulated by considering Mg₂SiO₄ crystals with water contents of 0, 1.65 and 3.3 wt%. With increasing water content, the calculated bulk/shear modulus and sound velocities decrease and their pressure derivatives tend to increase. Thus the hydration effect becomes less obvious at higher pressure. The bulk velocity contrasts from olivine to wadsleyite and from wadsleyite to ringwoodite are found to decrease after water incorporation. Our theoretical results indicate that water content and partition around the phase boundaries have profound impact on the structural and seismic properties of the mantle.

A quantum phase analysis of inhomogeneous arrays of superconducting quantum dots (SQD) is presented. Existence of Josephson decoupling (JD) phase is observed at the half-filling. It occurs due to fluctuations of Josephson couplings over the sites. This JD phase is the phase incoherent gapped state of the system. In JD phase superconductivity disappears even in the absence of Coulomb blockade phase. It is also observed that the inhomogeneity of on-site Coulomb charging energy produces the relevant coupling term that yields Coulomb blockade gapped phase. The presence of nearest-neighbor and next-nearest-neighbor Coulomb interaction yields the same physics for inhomogeneous and homogeneous SQD.

We propose that the degree of freedom of measurement by quantum mechanical observers originates in the Goldstone mode of the spontaneously broken time reparametrization symmetry. Based on the classification of quantum states by their nonunitary temporal behavior as seen in the measurement processes, we describe the concepts of the quantum mechanical observers via the time reparametrization symmetry.

Molecular dynamics simulations have been performed to study the primary damage formation in α-Fe by collision cascades in the recoil energy range 0.5–20 keV. Two near-neighbor analysis methods including the near-neighbor defect density (NPDD) analysis and cluster analysis were introduced to characterize the spatial aggregation of point defects and the morphologies of clusters, respectively. It is found that the NPDD of self-interstitial atom (SIA) and the number of Frenkel pairs show a similar variation trend, while the NPDD of vacancy exhibits a peak at shorter time than that of SIA. Furthermore, we find that the clusters of point defects exist mostly in the form of chainlike structure in the course and the end of cascades, but the proportion of chainlike clusters decreases with increasing the number of point defects included in one cluster. Therefore, the present methods are found to be effective to characterize the aggregation and the near-neighbor structure of point defects by displacement cascades at any time.