Modern Physics Letters B

The concept of deterministic dynamical chaos has a long history and is well established by now. Nevertheless, its field theoretic essence and its stochastic generalization have been revealed only very recently. Within the newly found supersymmetric theory of stochastics (STS), all stochastic differential equations (SDEs) possess topological or de Rahm supersymmetry and stochastic chaos is the phenomenon of its spontaneous breakdown. Even though the STS is free of approximations and thus is technically solid, it is still missing a firm interpretational basis in order to be physically sound. Here, we make a few important steps toward the construction of the interpretational foundation for the STS. In particular, we discuss that one way to understand why the ground states of chaotic SDEs are conditional (not total) probability distributions, is that some of the variables have infinite memory of initial conditions and thus are not “thermalized”, i.e., cannot be described by the initial-conditions-independent probability distributions. As a result, the definitive assumption of physical statistics that the ground state is a steady-state total probability distribution is not valid for chaotic SDEs.

Special aspects of few cycle pulses propagation in semi-holographic Fermi liquid with impurities are considered in this paper. Green’s function poles which are in charge of excitation states dispersion law of the liquid under consideration were given according to the ADS/CFT correspondence. The impact of both Fermi liquid parameters and its impurities on the few cycle pulse shape was defined.

In this work, CdSe quantum dots (QDs) were synthesized using a microwave activated reaction between NaHSe and CdSO₄ in the presence of thioglycolic acid (TGA) as capping molecule and then using a one-pot method, ZnS shell was grown subsequently around CdSe cores by a room temperature reaction based on the photo-sensitivity of Na₂S₂O₃ dissociation. Synthesized QDs were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), UV-visible (UV-Vis) and photoluminescence (PL) spectroscopy. All these analyses confirmed the formation of CdSe QDs and successful growth of ZnS shell around CdSe cores.

We have demonstrated an effective way to suppress the viewing angle dependence of the emission intensity of top-emitting organic light-emitting devices (TOLEDs) by fabricating devices on curved surfaces. From this approach, curved light emission surface has been obtained and TOLEDs with curved surface exhibit a relatively dispersed light emission pattern. As a result, the variation of emission intensity with viewing angles can be relieved. In addition, we can almost observe the same luminance and efficiency in OLEDs with and without curved surface light emission.

A multi-band perfect metamaterial absorber (MA) based on a cylindrical waveguide with polarization independency is numerically presented and investigated in detail. The proposed absorber has a very simple configuration, and it operates at flexible frequency ranges within the microwave frequency regime by simply tuning the dimensions of the structure. The maximum absorption values are obtained as 99.9%, 97.5%, 85.8%, 68.2% and 40.2% at the frequencies of 1.34 GHz, 2.15 GHz, 3.2 GHz, 4.31 GHz and 5.41 GHz, respectively. The numerical studies verify that the proposed model can provide multi-band perfect absorptions at wide polarization and incident angles due to its rotational symmetry feature. We have also realized sensor and parametric study applications in order to show additional features of the suggested model. The suggested MA enables myriad potential applications in medical technologies, sensors and in defense industry etc.

A more general two-dimensional wave motion equation with consideration of attenuation and nonlinearity is proposed to describe propagating nonlinear Rayleigh waves of finite amplitude. Based on the quasilinear theory, the numerical solutions for the sound beams of fundamental and second harmonic waves are constructed with Green’s function method. Compared with solutions from the parabolic approximate equation, results from the general equation have more accuracy in both the near distance of the propagation direction and the far distance of the transverse direction, as quasiplane waves are used and non-paraxial Green’s functions are obtained. It is more effective to obtain the nonlinear Rayleigh sound beam distributions accurately with the proposed general equation and solutions. Brief consideration is given to the measurement of nonlinear parameter using nonlinear Rayleigh waves.

In this paper, we have theoretically investigated the effect of built-in-polarization field on various phonon scattering mechanisms in Al${}_x$Ga${}_{1-x}$N/GaN heterostructure. The built-in-polarization field enhances the elastic constant, phonon velocity and Debye frequency of Al${}_x$Ga${}_{1-x}$N alloy. As a result, various phonon scattering mechanisms are modified. Important phonon scattering mechanisms such as normal scattering, Umklapp scattering, point defect scattering, dislocation scattering and phonon–electron scattering processes have been considered. The combined relaxation time due to above scattering mechanisms has also been computed as a function of phonon frequency for various Al contents at room temperature. Our result shows that built-in-polarization field suppresses scattering rates leading to enhanced combined relaxation time. Increased relaxation time implies longer phonon mean free path and enhanced optical and thermal transport properties. The result can be used to determine the effect of built-in-polarization field on optical and thermal properties of Al${}_x$Ga${}_{1-x}$N/GaN heterostructure and will be useful, particularly, for improvement of thermoelectric performance of Al${}_x$Ga${}_{1-x}$N/GaN heterostructure through polarization engineering.

The porthole die extrusion process of profiled cross-section hollow aluminum alloy is influenced by numerous factors, which brings inconvenience to the process design. In this paper, 7075 aluminum alloy is taken as an example, the fitting model of the ultimate load is analyzed by variance and regression analysis using response surface method (RSM). The influences of extrusion speed, friction factor and initial temperature on the change of extruded ultimate load are investigated systematically, and the important influence factors (initial temperature $>$ friction factor $>$ extrusion speed) to the load are determined eventually. By comparison, the error between the ultimate load model obtained after fitting and the calculated value is only 2.4%, further verifying the reliability of this model. The optimal objective is to minimize the ultimate load, then the optimum technological parameters are obtained by optimizing the process, where the initial temperature, the extrusion speed and the friction factor are 430${}^{\circ }$C, 2.28mm/s and 0.31, respectively. The results provide a theoretical basis for the scientific design of the porthole die extrusion process of profiled cross-section hollow aluminum alloy.

The curvature and interface shear stress of GaN-sapphire system are studied by establishing the mechanical equations based on two main assumptions: (a) the thickness of GaN film can be compared to the thickness of sapphire substrate, and (b) the thickness of GaN film is non-uniform. Our results show that the curvature of GaN-sapphire system is a variable within the whole circular system. The interface shear stress changes direction around at the middle of radius for the circular system, and the curvature have an important effect on the interface shear stress due to the consideration of non-uniform thickness for GaN film.

In this paper, a new Hamiltonian lattice hierarchy is analytically investigated, which can be reduced to some classic integrable lattice hierarchies, such as Ablowitz–Ladik hierarchy, Volterra hierarchy and multi-Hamiltonian lattice hierarchy, etc. By choosing the auxiliary problem $V_n^{(m)}$, we present a Darboux transformation (DT) to the new discrete matrix spectral problem. As its applications, a series of analytical solutions are generated in a recursive manner. Finally, the graphical analysis of these analytical solutions are presented, respectively. The DT of other lattice hierarchies can be also constructed in this method.

The structural properties of Mo₂Ga₂C are simulated by first-principles under pressure. At 40 GPa, the axial compressibilities of $c$- and $a$-axes are 0.9763 and 0.9264, respectively, which are the known largest and smallest values in the $M_{n+1}A{X}_n(n=1)$ compounds. A phase transition at 48 GPa is observed with an abrupt increase of $c$-axis and a rapid decrease of $a$-axis. The elastic properties and phonon imaginary frequencies confirmed the structural transition at 48 GPa, which probably should be the lowest-pressure transition in the $M_{n+1}A{X}_n$ ($n=1,2,3$, etc.) phases. The anti-expansion of Mo–Mo bond length is responsible for the $c$-axis ultra-incompressibility as well as the structural transition at 48 GPa.

Within the framework of the fermion-spin theory, the charge transport in the doped Mott insulators on a honeycomb lattice is studied by taking into account the pseudogap effect. It is shown that the conductivity spectrum in the low-doped regime is separated by the pseudogap into a low-energy non-Drude peak followed by a broad mid-infrared band. However, the decrease of the pseudogap with the increase of doping leads to a shift of the position of the mid-infrared band towards the low-energy non-Drude peak, and then the low-energy Drude behavior recovers in the high-doped regime. The combined results of both the doped honeycomb-lattice and square-lattice Mott insulators indicate that the two-component conductivity induced by the pseudogap is a universal feature in the doped Mott insulators.

A hybrid structure composed of a local resonance mass and an external oscillator is proposed in this paper for restraining the elastic longitudinal wave propagation. Theoretical model has been established to investigate the dispersion relation and band gaps of the structure. The results show that the hybrid structure can produce multi-band gaps wider than the multi-resonator acoustic metamaterials. It is much easier for the hybrid structure to yield wide and low band gaps by adjusting the mass and stiffness of the external oscillator. Small series spring constant ratio results in low-frequency band gaps, in which the external oscillator acts as a resonator and replaces the original local resonator to hold the band gaps in low frequency range. Compared with the one-dimensional phononic crystal (PC) lattice, a new band gap emerges in lower frequency range in the hybrid structure because of the added local resonance, which will be a significant assistance in low-frequency vibration and noise reduction. Further, harmonic response analysis using finite element method (FEM) has been performed, and results show that elastic longitudinal waves are efficiently forbidden within the band gaps.

Industry clusters have outperformed in economic development in most developing countries. The contributions of industrial clusters have been recognized as promotion of regional business and the alleviation of economic and social costs. It is no doubt globalization is rendering clusters in accelerating the competitiveness of economic activities. In accordance, many ideas and concepts involve in illustrating evolution tendency, stimulating the clusters development, meanwhile, avoiding industrial clusters recession. The term chaos theory is introduced to explain inherent relationship of features within industry clusters. A preferred life cycle approach is proposed for industrial cluster recessive theory analysis. Lyapunov exponents and Wolf model are presented for chaotic identification and examination. A case study of Tianjin, China has verified the model effectiveness. The investigations indicate that the approaches outperform in explaining chaos properties in industrial clusters, which demonstrates industrial clusters evolution, solves empirical issues and generates corresponding strategies.

There are many studies in literature on chiral metamaterials (MTMs) to obtain large chiralities with dynamic optical activities. With this regard, this new generation planar chiral MTM study focuses on a small, non-dispersive (constant/flat) chirality admittance over an indicated frequency band which has not been investigated so far in literature. This new generation planar chiral MTM provides a small and a constant/fixed chirality which is mostly ignored by the scientists. This study numerically and experimentally investigates and examines these new generation MTMs based on circular split ring resonators (SRRs) with an increased capacitance in details. Obtained results show that the suggested structure can provide a small and constant/flat chirality admittance over a certain frequency band and hence it can be used to design myriad novel electromagnetic (EM) devices such as transmission and antireflection filters, polarization rotators for any desired frequency regions.

In this paper, we have comparatively studied the “electron spin resonance” (ESR) of SiO₂ nanoparticles before and after neutron irradiation. From the comparative analysis of samples at the full sweep (sweep 5000 G at center field of 3300 G) in the same system, amount of defects were found to increase. At the field line around 3350 G, we found the free electron $g$ species $(g=2.002)$ and determined that this situation is more sustainable than the other observed cases (the cases existing in values 2.5–3 and 3–5 of $g$-factor). Moreover, expanded section near $g=2.002$ repeated with a sweep of 100 G and at two power due to microwave saturation effects has been studied.

In vivo chromosomal behavior is dictated by the organization of genomic DNA at length scales ranging from nanometers to microns. At these disparate scales, the DNA conformation is influenced by a range of proteins that package, twist and disentangle the DNA double helix, leading to a complex hierarchical structure that remains undetermined. Thus, there is a critical need for methods of structural characterization of DNA that can accommodate complex environmental conditions over biologically relevant length scales. Based on multiscale molecular simulations, we report on the possibility of measuring supercoiling in complex environments using angular correlations of scattered X-rays resulting from X-ray free electron laser (xFEL) experiments. We recently demonstrated the observation of structural detail for solutions of randomly oriented metallic nanoparticles [D. Mendez et al., Philos. Trans. R. Soc. B 360 (2014) 20130315]. Here, we argue, based on simulations, that correlated X-ray scattering (CXS) has the potential for measuring the distribution of DNA folds in complex environments, on the scale of a few persistence lengths.

The structural and elastic properties of neutral and ionized dichlorocarbene (CCl₂) functionalized single-walled carbon nanotubes (SWCNTs) were studied using density functional theory (DFT). The Young’s modulus of ionized pristine SWCNTs is found to decrease in comparison to that of neutral models. The interesting effect of increase in Young’s modulus values of ionized functionalized SWCNTs is observed. We ascribe this feature to the concurrent processes of the bond elongation on ionization and the local deformation on cycloaddition. The strong dependence of the elasticity modulus on the number of addends is also observed. However, the CCl₂-attached SWCNTs in their neutral and ionized forms remain strong enough to be suitable for the reinforcement of composites. In contrast to the elastic properties, the binding energies do not change significantly, irrespective of CCl₂ coverage.

In this paper, we have calculated the structural, electronic, magnetic and optical properties of Sr₂NiO₃ and Sr₂CoO₃ using density functional theory (DFT) within generalized gradient approximation (GGA). The crystal structure of both materials is well described with Immm (No. 71) symmetry which are isostructural with Sr₂CuO₃ and both are quasi-one-dimensional (1D) rectangular lattice G-type antiferromagnets, in consistent with the experimental data.

Due to a distortion, Sr₂CoO₃ lifts the near-degeneracy $d_{xz}$ and $d_{yz}$ states of the local Co electronic configuration, which demonstrates a strong coupling between the structural lattice and the electronic configuration. The calculated band structure shows a band gap of 1.376 eV for Sr₂NiO₃ and a band gap of 1.735 eV for Sr₂CoO₃. Ni and Co ions are in the high-spin $S=1$ and $S=3/2$ configurations with the magnetic moments of 1.585 ${\mu }_B$ and 2.587 ${\mu }_B$, respectively. Based on the Heisenberg Hamiltonian model, we conclude that the superexchange intrachain TM–O–TM superexchange interaction is predominant and interaction between the 1D chains is weak. According to the calculated dielectric function, absorption spectrum and electron energy loss spectrum, the optical responses suggest that Sr₂NiO₃ shows the unique anisotropic structure and interaction of the application in optoelectronics.

The paper was presented to study the microstructure and magnetic properties of Mo/[NdFeB/Mo] × 10/Mo multilayered films prepared by magnetron sputtering on Si(100) substrate. The SEM observation of microstructure showed that the specimen had fine multilayer structure and the NdFeB layers were successfully separated by Mo layers on the cross-section. The interface between the NdFeB and Mo layer disappeared after annealing. X-ray diffraction patterns of the annealed films revealed that there are a large amount of Nd₂Fe${}_{14}$B phases. The thickness of Mo layer had obvious effects on magnetic properties of the samples. When it reached 21 nm, the number and the intensity of NdFeB phase increase, and the remanent magnetization ratio Mr/Ms suddenly rise. The influences of annealing on surface morphology and microstructure of NdFeB thin films were also studied.