Catálogo de publicaciones - revistas

<jats:p>The floor field model has been widely used in evacuation simulation research based on cellular automata model. However, conventional methods of setting floor field will lead to highly insufficient utilization of the exit area when people gather on one side of the exit. In this study, an extended cellular automata model with modified floor field is proposed to solve this problem. Additionally, a congestion judgment mechanism is integrated in our model, whereby people can synthetically judge the degree of congestion and distance in front of them to determine whether they need to change another exit to evacuate or not. We contrasted the simulation results of the conventional floor field model, the extended model proposed in this paper, and Pathfinder software in a same scenario. It is demonstrated that this extended model can ameliorate the problem of insufficient utilization of the exit area and the trajectory of pedestrian movement and the crowd shape of pedestrians in front of exit in this new model are more realistic than those of the other two models. The findings have implications for modeling pedestrian evacuation.</jats:p>

<jats:p>Current public-opinion propagation research usually focused on closed network topologies without considering the fluctuation of the number of network users or the impact of social factors on propagation. Thus, it remains difficult to accurately describe the public-opinion propagation rules of social networks. In order to study the rules of public opinion spread on dynamic social networks, by analyzing the activity of social-network users and the regulatory role of relevant departments in the spread of public opinion, concepts of additional user and offline rates are introduced, and the direct immune-susceptible, contacted, infected, and refractory (DI-SCIR) public-opinion propagation model based on real-time online users is established. The interventional force of relevant departments, credibility of real information, and time of intervention are considered, and a public-opinion propagation control strategy based on direct immunity is proposed. The equilibrium point and the basic reproduction number of the model are theoretically analyzed to obtain boundary conditions for public-opinion propagation. Simulation results show that the new model can accurately reflect the propagation rules of public opinion. When the basic reproduction number is less than 1, public opinion will eventually disappear in the network. Social factors can significantly influence the time and scope of public opinion spread on social networks. By controlling social factors, relevant departments can analyze the rules of public opinion spread on social networks to suppress the propagate of negative public opinion and provide a powerful tool to ensure security and stability of society.</jats:p>

<jats:p>Soliton molecules are firstly obtained by velocity resonance for the Gerdjikov–Ivanov equation, and <jats:italic>n</jats:italic>-order smooth positon solutions for the Gerdjikov–Ivanov equation are generated by means of the general determinant expression of <jats:italic>n</jats:italic>-soliton solution. The dynamics of the smooth positons of the Gerdjikov–Ivanov equation are discussed using the decomposition of the modulus square, the trajectories and time-dependent “phase shifts” of positons after the collision can be described approximately. Additionally, some novel hybrid solutions consisting solitons and positons are presented and their rather complicated dynamics are revealed.</jats:p>

<jats:p>In this study, we explore the far-zero behaviors of a scattered partially polarized spatially and spectrally partially coherent electromagnetic pulsed beam irradiating on a deterministic medium. The analytical formula for the cross-spectral density matrix elements of this beam in the spherical coordinate system is derived. Within the framework of the first-order Born approximation, the effects of the scattering angle <jats:italic>θ</jats:italic>, the source parameters (<jats:italic>i.e.</jats:italic>, the pulse duration <jats:italic>T</jats:italic> <jats:sub>0</jats:sub> and the temporal coherence length <jats:italic>T<jats:sub>cxx</jats:sub> </jats:italic>), and the scatterer parameter (<jats:italic>i.e.</jats:italic>, the effective width of the medium <jats:italic>σ<jats:sub>R</jats:sub> </jats:italic>) on the spectral density, the spectral shift, the spectral degree of polarization, and the degree of spectral coherence of the scattered source in the far-zero field are studied numerically and comparatively. Our work improves the scattering theory of stochastic electromagnetic beams and it may be useful for the applications involving the interaction between incident light waves and scattering media.</jats:p>

<jats:p>The generation and propagation characteristics of bright spatial bound-soliton pairs (BSPs) are investigated under the diffusion effect in photovoltaic photorefractive crystals by numerical simulation. The results show that two coherent solitons, one as the signal light and the other as the control light, can form a BSP when the peak intensity of the control light is appropriately selected. Moreover, under the diffusion effect, the BSP experiences a self-bending process during propagating and the center of the BSP moves on a parabolic trajectory. Furthermore, the lateral shift of the BSP at the output face of the crystal can be manipulated by adjusting the peak intensity of the control light. The research results provide a method for the design of all-optical switching and routing based on the manipulation of the lateral position of BSPs.</jats:p>

<jats:p>C<jats:sub>70</jats:sub> nanotubes with a fcc lattice structure are polymerized through being irradiated by lasers with a wavelength of 514.5 nm at various power values. Raman spectra and photoluminescence (PL) spectra are employed to characterize the polymeric phases of the laser treated samples, showing that the disordered C<jats:sub>70</jats:sub> oligomers are formed in the C<jats:sub>70</jats:sub> nanotubes irradiated by such strong green lasers. Comparative studies further indicate that intermolecular bonds are formed between C<jats:sub>70</jats:sub> molecules on the surface of nanotubes, which are similar to those formed under high pressure and high temperature (HPHT) conditions. And the content of intermolecular bonds increases obviously with the laser power increasing.</jats:p>

<jats:p>To obtain the adjustable photonic crystals (PCs), we numerically investigate one-dimensional (1D) PCs with alternating VO<jats:sub>2</jats:sub> and SiO<jats:sub>2</jats:sub> layers through transfer matrix method. The dispersion relation agrees well with the transmittance obtained by the finite element calculation. Tunable band gaps are achieved with the thermal stimuli of VO<jats:sub>2</jats:sub>, which has two crystal structures. The monoclinic crystal structure VO<jats:sub>2</jats:sub> (R) at low temperature exhibits insulating property, and the high temperature square rutile structure VO<jats:sub>2</jats:sub> (M) presents metal state. Concretely, the bandwidth is getting narrower and red shift occurs with the higher temperature in VO<jats:sub>2</jats:sub> (R)/SiO<jats:sub>2</jats:sub> PCs structure. Based on the phase change characteristics of VO<jats:sub>2</jats:sub>, we can flexibly adjust the original structure as VO<jats:sub>2</jats:sub> (R)/VO<jats:sub>2</jats:sub> (M)/SiO<jats:sub>2</jats:sub>. By increasing the phase ratio of VO<jats:sub>2</jats:sub> (R) to VO<jats:sub>2</jats:sub> (M), the band gap width gradually becomes wider and blue shift occurs. The discrete layers of gradient composites on the dispersion of 1D PCs are also investigated, which enhances the feasibility in practical operation. Thus, our proposed thermal modulation PCs structure paves a new way to realize thermal tunable optical filters and sensors.</jats:p>

<jats:p>The optical components of the visible light band are widely used in daily life and industrial development. However due to the serious loss of light and the high cost, the application is limited. The broadband gap metasurface will change this situation due to its low absorption and high efficiency. Herein, we simulate a size-adjustable metasurface of the Al doped ZnO (AZO) nanorod arrays based on finite difference time domain method (FDTD) which can realize the conversion of amplitude polarization and phase in the full visible band. The corresponding theoretical polarization conversion efficiency can reach as high as 91.48% (450 nm), 95.27% (530 nm), and 91.01% (65 nm). The modulation of focusing wavelength can be realized by directly adjusting the height of the AZO nanorod. The designed half-wave plate and metalens can be applied in the imaging power modulation halfwave conversion and enriching the spectroscopy.</jats:p>

<jats:p>The optimization of high power terahertz monolithic integrated circuit (TMIC) is systemically studied based on the physical model of the Schottky barrier varactor (SBV) with interface defects and tunneling effect. An ultra-thin dielectric layer is added to describe the extra tunneling effect and the damping of thermionic emission current induced by the interface defects. Power consumption of the dielectric layer results in the decrease of capacitance modulation ration (<jats:italic>C</jats:italic> <jats:sub>max</jats:sub>/<jats:italic>C</jats:italic> <jats:sub>min</jats:sub>), and thus leads to poor nonlinear <jats:italic>C</jats:italic>–<jats:italic>V</jats:italic> characteristics. The proposed Schottky metal-brim (SMB) terminal structure could improve the capacitance modulation ration by reducing the influence of the interface charge and eliminating the fringing capacitance effect. Finally, a 215 GHz tripler TMIC is fabricated based on the SMB terminal structure. The output power is above 5 mW at 210–218 GHz and the maximum could exceed 10 mW at 216 GHz, which could be widely used in terahertz imaging, radiometers, and so on. This paper also provides theoretical support for the SMB structure to optimize the TMIC performance.</jats:p>

<jats:p>Acoustic vortex (AV) beam is triggering the significant research interest in information and communication sciences due to its infinite and mutual orthogonal orbital angular momentums (OAMs). Therefore, measuring the topological charges of an AV beams become a task with great significance. In this work, we present a Fraunhofer diffraction (FD) pattern of an AV beam that can be used to quantitatively detect the OAMs of AV beams. We both theoretically and numerically investigate the FD patterns of AV beams passing through a multipoint interferometer (MPI). It is demonstrated that the topological charges of the AV beams can be determined from the interference intensity patterns. The proposed method may pave the way to the practical applications of AV beams.</jats:p>