Modern Physics Letters B

In this paper, a modified microscopic traffic flow model accounting for the optimal velocity has been proposed. Different with previous models, drivers’ response ability and the maximum of accelerations are considered in the term of the optimal velocity. The effect of parameters in the term of the optimal velocity on bifurcations in the rotary traffic is studied here. Besides, the evolvement of bifurcations in the system is calculated by performing numerical simulation experiments. Moreover, the linear stability analysis of the proposed model is presented.

The structural, electronic, vibrational, mechanical and thermodynamic properties of Rh₅B₄ have been investigated within the framework of the density functional theory (DFT) and the direct method using first-principles calculations. The calculated lattice parameters are in good agreement with the available experimental data. The electronic structure suggests that Rh₅B₄ should exhibit the metallic behavior and hybridizations exist between Rh-d and B-s, B-p orbitals, which illuminates that the bonding between them has certain covalent character. Mechanical properties including elastic constants, bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio $\upsilon$ are calculated. Phonon dispersions and phonon density of states (DOS) are obtained, respectively. Our results indicate that Rh₅B₄ is dynamically and mechanically stable with better ductility (B/G = 3.28) at ambient pressure. In addition, the phonon frequencies at the center ($\mathrm{\Gamma }$ point) of the first Brillouin zone are predicted and Raman-active and infrared-active modes are also assigned. Finally, the phonon contribution to the Helmholtz free energy F, the phonon contribution to the internal energy E, the constant volume specific heat Cv and vibrational entropy S are studied over the range 0 $\sim$ 1000 K.

As ammonium dihydrogen phosphate (ADP) is a popular nonlinear optical crystal, to engineer its linear and nonlinear optical properties, the chalcogenide compound cobalt sulphide (CoS) was doped and the crystals were grown by the slow solvent evaporation method. To increase the solubility of CoS in water, its nanoparticles were synthesized by wet chemical technique using ethylene diamine as the capping agent followed by microwave irradiation. The nanoparticle sample exhibited finite solubility in water and was used to dope in ADP crystals. The powder XRD patterns showed the single phase nature of the doped crystals. The FTIR spectra confirmed the presence of various functional groups and EDAX gave the estimation of Co and S elements. The EPR spectroscopy also confirmed the presence of cobalt in the doped samples. TGA indicated slightly less thermal stability of the doped crystals compared to the pure ADP. The dielectric study was carried out at room temperature in the frequency range from 100Hz to 1MHz. Also, various linear optical parameters were evaluated for pure and doped crystals using UV–Vis spectroscopy. The second harmonic generation (SHG) efficiency of Nd:YAG laser was evaluated by the Kurtz and Parry method for the doped samples, it was found to be slightly lesser than that of the pure ADP crystals.

The mechanical properties and deformation mechanisms of Au nanowire during the tensile processes at different strain rates are revealed by the molecular dynamics method. It is found that the Au nanowire displays three distinct types of mechanical behaviors when tensioning at low, medium and high strain rates, respectively. At the low strain rate, the stress–strain curve displays a periodic zigzag increase–decrease feature, and the plastic deformation is resulted from the slide of dislocation. The dislocations nucleate, propagate, and finally annihilate in every decreasing stages of stress, and the nanowire always can recover to FCC-ordered structure. At the medium strain rate, the stress–strain curve gently decreases during the plastic process, and the deformation is contributed from sliding and twinning. The dislocations formed in the yield stage do not fully propagate and further escape from the nanowire. At the high strain rate, the stress-strain curve wave-like oscillates during the plastic process, and the deformation is resulted from amorphization. The FCC atoms quickly transform into disordered amorphous structure in the yield stage. The relative magnitude between the loading velocity of strain and the propagation velocity of phonons determines the different deformation mechanisms. The mechanical behavior of Au nanowire is similar to Ni, Cu and Pt nanowires, but their deformation mechanisms are not completely identical with each other.

Mo₂Ga₂C, which is a new member of MAX phases family discovered recently, has been regarded as the first compound of M₂A₂X family considering that no members of M₂A₂X phases have been found. Our work conducted first-principles calculations of new nanolaminate Mo₂Ga₂C followed by comparison with Mo-containing M₂AX phases (Mo₂GaC). Our results have shown that electric conductivity and ductile properties are greatly increased by adding Ga-layer, while theoretical hardness is retained. The Mo₂Ga₂C is found to possess more metallicity.

Uncovering the community structure in complex network is a hot research point in recent years. How to identify the community structure accurately in complex network is still an open question under research. There are lots of methods based on topological information, which have some good performances at the expense of longer runtimes. In this paper, we propose a new fuzzy algorithm which follows the line of fuzzy c-means algorithm. A steepest descent framework with projection by optimizing the quality function is presented under the generalized framework. The results of experiments on both real-world networks and synthetic networks show that the proposed method achieves the highest efficiency and is easy for detecting fuzzy community structure in large-scale complex networks.

In this study, ZnO nanobelts were successfully fabricated by flash synthesis without any expensive catalyst at a relatively low temperature (600${}^{\circ }$C). The whole process took just $\sim$30 min. Introducing a solution tank containing a mixture of polyvinyl alcohol (PVA) and Zn(AC)₂, was an auxiliary process to elevate the quality of the products. The morphology of the ZnO nanobelts was systematically investigated by means of field emission scanning electron microscopy (FRSEM) and high-resolution transmission electron microscopy (HRTEM). The products had an average width of 200nm and a length of more than 10$\mu \mathrm{\text{m}}$. X-ray diffraction analysis indicated that the ZnO nanobelts had a typical wurtzite structure. Finally, the growth mechanism of the unique morphology of the ZnO nanobelts is discussed. An assembly-line production method is also proposed based on the results.

In this paper, extremely low frequency band gaps of beam-like inertial amplification metamaterials are investigated based on local resonance theory. Inertial amplification mechanism is proposed to obtain extremely low frequency band gaps by altering geometry parameters of the beam-like structures rather than modulating material properties, which allow first lower band gap (BG) to be attained easily compared to traditional local resonance structures. Band structures, frequency response functions (FRFs) plots and vibration modes of the beam-like structures are calculated and analyzed by employing finite element method. Numerical results show that first BG of the structure ranges from 23 Hz to 21 Hz. FRFs are in accordance with the dispersion relationship. It is found that interaction between inertial amplification and traveling wave modes in the proposed structure are responsible for formation of the first BG. This type of beam-like inertial amplification metamaterials has many potential applications in the field of low frequency vibration and noise reduction.

The robustness of complex networks against cascading failures has been of great interest, while most of the researchers have considered undirected networks. However, to be more realistic, a part of links of many real systems should be described as unidirectional. In this paper, by applying three link direction-determining (DD) strategies, the tolerance of cascading failures is investigated in various networks with both unidirectional and bidirectional links. By extending the utilization of a classical global betweenness method, we propose a new cascading model, taking into account the weights of nodes and the directions of links. Then, the effects of unidirectional links on the network robustness against cascaded attacks are examined under the global load-based distribution mechanism. The simulation results show that the link-directed methods could not always lead to the decrease of the network robustness as indicated in the previous studies. For small-world networks, these methods certainly make the network weaker. However, for scale-free networks, the network robustness can be significantly improved by the link-directed method, especially for the method with non-random DD strategies. These results are independent of the weight parameter of the nodes. Due to the strongly improved robustness and easy realization with low cost on networks, the method for enforcing proper links to the unidirectional ones may be useful for leading to insights into the control of cascading failures in real-world networks, like communication and transportation networks.

By considering the pseudogap effect, the doping and energy dependences of thermal conductivity in cuprate superconductors are studied. Our results show that the thermal conductivity as a function of energy exhibits a characteristic peak from underdoping to overdoping due to the presence of the pseudogap in pseudogap phase of cuprate superconductors. The thermal conductivity is strongly doping dependent. On the one hand, with increasing doping concentration, the weight of thermal conductivity increases quickly, especially the residual thermal conductivity which is in qualitative agreement with the experimental data. On the other hand, the characteristic energy corresponding to the position of the characteristic peak decreases monotonically upon increasing doping concentration, and it scales with the doping dependence of pseudogap. In particular, we have studied the doping dependence of the ratio of quasiparticle velocities normal and tangential to the Fermi surface at the nodes $v_F/v_2$. It is shown that $v_F/v_2$ increases with the increase of doping concentration. Moreover, we explain that both the residual thermal conductivity and $v_F/v_2$ increase rapidly upon the increase in doping concentration in heavily overdoped cuprate superconductors.