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The rock—paper—scissors (RPS) game is a nice model to study the biodiversity in an ecosystem. However, in the previous studies only the nearest-neighbor interaction among the species was considered. In this paper, taking the long-range migration into account, the effects of the interplay between nearest-neighbor-interaction and long-range-interaction given by Levy flight with distance distribution lh (−3 ≤ h < −1) in the spatial RPS game are investigated. Taking the probability, exchange rate, and power-law exponent of Levy flight as parameters, the coexistence conditions of three species are given. The critical curves for stable coexistence of three species in the parameter space are presented. It is also found that Levy flight has interesting effects on the final spatiotemporal pattern of the system. The results reveal that the long-range-interaction given by Levy flight exhibits pronounced effects on biodiversity of the ecosystem. [ABSTRACT FROM AUTHOR]

The effect of interaction between liquid crystal (LC) and photoalignment material on the speed of optical rewriting process is investigated. The theoretical analysis shows that a smaller frank elastic constant K22 of liquid crystal corresponds to a larger twist angle, which gives rise to a larger rewriting speed. Six different LC cells with the same boundary conditions (one substrate is covered with rubbed polyimide (PI) and the other with photo sensitive rewritable sulfuric dye 1(SD1)) are tested experimentally under the same illumination intensity (450 nm, 80 mW/cm2). The results demonstrate that with a suitable liquid crystal, the LC optical rewriting speed for e-paper application can be obviously improved. For two well known LC materials E7 (K22 is larger) and 5CB (K22 is smaller), they require 11 s and 6 s corresponding to change alignment direction for generating image information. [ABSTRACT FROM AUTHOR]

The composite systems can be non-uniquely decomposed into parts (subsystems). Not all decompositions (structures) of a composite system are equally physically relevant. In this paper we answer on theoretical ground why it may be so. We consider a pair of mutually un-coupled modes in the phase space representation that are subjected to the independent quantum amplitude damping channels. By investigating asymptotic dynamics of the degrees of freedom, we find that the environment is responsible for the structures non-equivalence. Only one structure is distinguished by both locality of the environmental influence on its subsystems and a classical-like description. [ABSTRACT FROM AUTHOR]

Ferroelectric HfO2 has attracted much attention owing to its superior ferroelectricity at an ultra-thin thickness and good compatibility with Si-based complementary metal–oxide–semiconductor (CMOS) technology. However, the crystallization of polar orthorhombic phase (o-phase) HfO2 is less competitive, which greatly limits the ferroelectricity of the as-obtained ferroelectric HfO2 thin films. Fortunately, the crystallization of o-phase HfO2 can be thermodynamically modulated via interfacial stress engineering. In this paper, the growth of improved ferroelectric Al doped HfO2 (HfO2:Al) thin films on (111)-oriented Si substrate has been reported. Structural analysis has suggested that nonpolar monoclinic HfO2:Al grown on (111)-oriented Si substrate suffered from a strong compressive strain, which promoted the crystallization of (111)-oriented o-phase HfO2 in the as-grown HfO2:Al thin films. In addition, the in-plane lattice of (111)-oriented Si substrate matches well with that of (111)-oriented o-phase HfO2, which further thermally stabilizes the o-phase HfO2. Accordingly, an improved ferroelectricity with a remnant polarization (2 P r) of 26.7 μC/cm2 has been obtained. The results shown in this work provide a simple way toward the preparation of improved ferroelectric HfO2 thin films. [ABSTRACT FROM AUTHOR]

Compared to conventional devices, metasurfaces offer the advantages of being lightweight, with planarization and tuning flexibility. This provides a new way to integrate and miniaturize optical systems. In this paper, a metasurface capable of generating multiple bottle beams was designed. Based on the Pancharatnamâ€"Berry (Pâ€"B) phase principle, the metasurface lens can accurately control the wavefront by adjusting the aspect ratio of the titanium dioxide nanopillars and the rotation angle. When irradiated by left-handed circularly polarized light with a wavelength of 632.8 nm, the optical system can produce multiple micron bottle beams. Taking two bottle beams as examples, the longitudinal full widths at half-maximum of the optical tweezers can reach 0.85 ÎĽm and 1.12 ÎĽm, respectively, and the transverse full widths at half-maximum can reach 0.46 ÎĽm and 0.6 ÎĽm. Also, the number of generated bottle beams can be varied by controlling the size of the annular obstacle. By changing the x -component of the unit rotation angle, the metasurface can also change the shape of the bottle beam â€" the beam cross-section can be changed from circular to elliptical. This paper also analyzes the trapping of ytterbium atoms by the multi bottle beam acting as optical tweezers. It is found that the multi bottle beam can cool and trap multiple ytterbium atoms. [ABSTRACT FROM AUTHOR]

A model for fast electron-driven high-density plasma is proposed to describe the effect of injected fast electrons on the temperature and inner pressure of the plasma in the fast heating process of the double-cone ignition (DCI) scheme. Due to the collision of the two low-density plasmas, the density and volume of the high-density plasma vary. Therefore, the ignition temperature and energy requirement of the high-density plasma vary at different moments, and the required energy for hot electrons to heat the plasma also changes. In practical experiments, the energy input of hot electrons needs to be considered. To reduce the energy input of hot electrons, the optimal moment and the shortest time for injecting hot electrons with minimum energy are analyzed. In this paper, it is proposed to inject hot electrons for a short time to heat the high-density plasma to a relatively high temperature. Then, the alpha particles with the high heating rate and P d V work heat the plasma to the ignition temperature, further reducing the energy required to inject hot electrons. The study of the injection time of fast electrons can reduce the energy requirement of fast electrons for the high-density plasma and increase the probability of successful ignition of the high-density plasma. [ABSTRACT FROM AUTHOR]

Remote sensing images carry crucial ground information, often involving the spatial distribution and spatiotemporal changes of surface elements. To safeguard this sensitive data, image encryption technology is essential. In this paper, a novel Fibonacci sine exponential map is designed, the hyperchaotic performance of which is particularly suitable for image encryption algorithms. An encryption algorithm tailored for handling the multi-band attributes of remote sensing images is proposed. The algorithm combines a three-dimensional synchronized scrambled diffusion operation with chaos to efficiently encrypt multiple images. Moreover, the keys are processed using an elliptic curve cryptosystem, eliminating the need for an additional channel to transmit the keys, thus enhancing security. Experimental results and algorithm analysis demonstrate that the algorithm offers strong security and high efficiency, making it suitable for remote sensing image encryption tasks. [ABSTRACT FROM AUTHOR]

Seizures are caused by increased neuronal firing activity resulting from reduced inhibitory effect and enhancement of inhibitory modulation to suppress this activity is used as a therapeutic tool. However, recent experiments have shown a counterintuitive phenomenon that inhibitory modulation does not suppress but elicit post-inhibitory rebound (PIR) spike along with seizure to challenge the therapeutic tool. The nonlinear mechanism to avoid the PIR spike can present theoretical guidance to seizure treatment. This paper focuses on identifying credible bifurcations that underlie PIR spike by modulating multiple parameters in multiple theoretical models. The study identifies a codimension-2 bifurcation called saddle--node homoclinic orbit (SNHOB), which is an intersection between saddle node bifurcation on invariant cycle (SNIC) and other two bifurcations. PIR spike cannot be evoked for the SNIC far from the SNHOB but induced for the SNIC close to the SNHOB, which extends the bifurcation condition for PIR spike from the well-known Hopf to SNIC. Especially, in a thalamic neuron model, increases of conductance of T-type Ca2+ (T Ca) channel induce SNIC bifurcation approaching to the SNHOB to elicit PIR spikes, closely matching experimental results of the absence seizure or Parkinson diseases. Such results imply that, when inhibition is employed to relieve absence seizure and Parkinson diseases related to PIR spike, modulating SNIC to get far from the SNHOB to avoid PIR spike is the principle. The study also addresses the complex roles of T Ca current and comprehensive relationships between PIR spike and nonlinear conceptions such as bifurcation types and shapes of threshold curve. [ABSTRACT FROM AUTHOR]

This work builds an isobaric steady-state fluid analytical-physical model of the plasma conduction region in a conical target. The hydrodynamic instability in the double-cone ignition scheme[] for inertial confinement fusion (ICF) proposed by Zhang is studied with the built model. With this idealized model, the relevant parameters, such as density, temperature, and length of the plasma in the conduction region of the conical target under long-pulse conditions are given. The solution of the proposed analytical model dovetails with the trend of the numerical simulation. The model and results in this paper are beneficial for discussing how to attenuate Rayleighâ€"Taylor instability in ICF processes with conical and spherical targets. [ABSTRACT FROM AUTHOR]

Shear-thinning fluids have been widely used in microfluidic systems, but their internal flow mechanism is still unclear. Therefore, in this paper, molecular dynamics simulations are used to study the laminar flow of shear-thinning fluid in a microchannel. We validated the feasibility of our simulation method by evaluating the mean square displacement and Reynolds number of the solution layers. The results show that the change rule of the fluid system's velocity profile and interaction energy can reflect the shear-thinning characteristics of the fluids. The velocity profile resembles a top-hat shape, intensifying as the fluid's power law index decreases. The interaction energy between the wall and the fluid decreases gradually with increasing velocity, and a high concentration of non-Newtonian fluid reaches a plateau sooner. Moreover, the velocity profile of the fluid is related to the molecule number density distribution and their values are inversely proportional. By analyzing the radial distribution function, we found that the hydrogen bonds between solute and water molecules weaken with the increase in velocity. This observation offers an explanation for the shear-thinning phenomenon of the non-Newtonian flow from a micro perspective. [ABSTRACT FROM AUTHOR]

Due to the fact that a memristor with memory properties is an ideal electronic component for implementation of the artificial neural synaptic function, a brand-new tristable locally active memristor model is first proposed in this paper. Here, a novel four-dimensional fractional-order memristive cellular neural network (FO-MCNN) model with hidden attractors is constructed to enhance the engineering feasibility of the original CNN model and its performance. Then, its hardware circuit implementation and complicated dynamic properties are investigated on multi-simulation platforms. Subsequently, it is used toward secure communication application scenarios. Taking it as the pseudo-random number generator (PRNG), a new privacy image security scheme is designed based on the adaptive sampling rate compressive sensing (ASR-CS) model. Eventually, the simulation analysis and comparative experiments manifest that the proposed data encryption scheme possesses strong immunity against various security attack models and satisfactory compression performance. [ABSTRACT FROM AUTHOR]

This paper explores a double quantum images representation (DNEQR) model that allows for simultaneous storage of two digital images in a quantum superposition state. Additionally, a new type of two-dimensional hyperchaotic system based on sine and logistic maps is investigated, offering a wider parameter space and better chaotic behavior compared to the sine and logistic maps. Based on the DNEQR model and the hyperchaotic system, a double quantum images encryption algorithm is proposed. Firstly, two classical plaintext images are transformed into quantum states using the DNEQR model. Then, the proposed hyperchaotic system is employed to iteratively generate pseudo-random sequences. These chaotic sequences are utilized to perform pixel value and position operations on the quantum image, resulting in changes to both pixel values and positions. Finally, the ciphertext image can be obtained by qubit-level diffusion using two XOR operations between the position-permutated image and the pseudo-random sequences. The corresponding quantum circuits are also given. Experimental results demonstrate that the proposed scheme ensures the security of the images during transmission, improves the encryption efficiency, and enhances anti-interference and anti-attack capabilities. [ABSTRACT FROM AUTHOR]

Quantum dialogue (QD) enables two communication parties to directly exchange secret messages simultaneously. In conventional QD protocols, photons need to transmit in the quantum channel for two rounds. In this paper, we propose a one-step QD protocol based on the hyperentanglement. With the help of the non-local hyperentanglement-assisted Bell state measurement (BSM), the photons only need to transmit in the quantum channel once. We prove that our one-step QD protocol is secure in theory and numerically simulate its secret message capacity under practical experimental condition. Compared with previous QD protocols, the one-step QD protocol can effectively simplify the experiment operations and reduce the message loss caused by the photon transmission loss. Meanwhile, the non-local hyperentanglement-assisted BSM has a success probability of 100% and is feasible with linear optical elements. Moreover, combined with the hyperentanglement heralded amplification and purification, our protocol is possible to realize long-distance one-step QD. [ABSTRACT FROM AUTHOR]

In this review we will focus on recent progress in the field of two-dimensional (2D) and three-dimensional (3D) display technologies. We present the current display materials and their applications, including organic light-emitting diodes (OLEDs), flexible OLEDs quantum dot light emitting diodes (QLEDs), active-matrix organic light emitting diodes (AMOLEDs), electronic paper (E-paper), curved displays, stereoscopic 3D displays, volumetric 3D displays, light field 3D displays, and holographic 3D displays. Conventional 2D display devices, such as liquid crystal devices (LCDs) often result in ambiguity in high-dimensional data images because of lacking true depth information. This review thus provides a detailed description of 3D display technologies. [ABSTRACT FROM AUTHOR]

To address the restriction of fiber-optic surface plasmon resonance (SPR) sensors in the field of multi-sample detection, a novel dual-channel fiber-optic SPR sensor based on the cascade of coaxial dual-waveguide D-type structure and microsphere structure is proposed in this paper. The fiber sidepolishing technique converts the coaxial dual-waveguide fiber into a D-type one, and the evanescent wave in the ring core leaks, generating a D-type sensing region; the fiber optic fused ball push technology converts the coaxial dual waveguides into microspheres, and the stimulated cladding mode evanescent wave leaks, producing the microsphere sensing region. By injecting light into the coaxial dual-waveguide middle core alone, the sensor can realize single-stage sensing in the microsphere sensing area; it can also realize dual-channel sensing in the D-type sensing area and microsphere sensing area by injecting light into the ring core. The refractive index measurement ranges for the two channels are 1.333–1.365 and 1.375–1.405, respectively, with detection sensitivities of 981.56 nm/RIU and 4138 nm/RIU. The sensor combines wavelength division multiplexing and space division multiplexing technologies, presenting a novel research concept for multi-channel fiber SPR sensors. [ABSTRACT FROM AUTHOR]

Hall thruster is an electric propulsion device for attitude control and position maintenance of satellites. The discharge process of Hall thruster will produce divergent plume. The plume will cause erosion, static electricity, and other interference to the main components, such as solar sailboard, satellite body, and thruster. Therefore, reducing the divergence of the plume is an important content in the research of thruster plume. The additional electrode to the plume area is a way to reduce the divergence angle of the plume, but there are few related studies. This paper uses the particle-in-cell (PIC) simulation method to simulate the effect of the additional electrode on the discharge of the Hall thruster, and further explains the effect mechanism of the additional electrode on parameters such as the electric field and plume divergence angle. The simulation results show that the existence of the additional electrode can enhance the potential near the additional position. The increase of the potential can effectively suppress the radial diffusion of ions, and effectively reduce the plume divergence angle. The simulation results show that when the additional electrode is 30 V, the half plume divergence angle can be reduced by 18.21%. However, the existence of additional electric electrode can also enhance the ion bombardment on the magnetic pole. The additional electrode is relatively outside, the plume divergence angle is relatively small, and it can avoid excessive ion bombardment on the magnetic pole. The research work of this paper can provide a reference for the beam design of Hall thruster. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have attracted wide attention from academia and industry because of their advantages such as high emitting efficiency, narrow half-peak width, and continuously adjustable emitting wavelength. QDs light emitting diodes (QLEDs) are expected to become the next generation commercial display technology. This paper reviews the progress of QLED from physical mechanism, materials, to device engineering. The strategies to improve QLED performance from the perspectives of quantum dot materials and device structures are summarized. [ABSTRACT FROM AUTHOR]

The transient radial shearing interferometry technique based on fast Fourier transform (FFT) provides a means for the measurement of the wavefront phase of transient light field. However, which factors affect the spatial bandwidth of the wavefront phase measurement of this technology and how to achieve high-precision measurement of the broad-band transient wavefront phase are problems that need to be studied further. To this end, a theoretical model of phase-retrieved bandwidth of radial shearing interferometry is established in this paper. The influence of the spatial carrier frequency and the calculation window on phase-retrieved bandwidth is analyzed, and the optimal carrier frequency and calculation window are obtained. On this basis, a broad-band transient radial shearing interference phase-retrieval method based on chirp Z transform (CZT) is proposed, and the corresponding algorithm is given. Through theoretical simulation, a known phase is used to generate the interferogram and it is retrieved by the traditional method and the proposed method respectively. The residual wavefront RMS of the traditional method is 0.146λ, and it is 0.037λ for the proposed method, which manifests an improvement of accuracy by an order of magnitude. At the same time, different levels of signal-to-noise ratios (SNRs) from 50 dB to 10 dB of the interferogram are simulated, and the RMS of the residual wavefront is from 0.040λ to 0.066λ. In terms of experiments, an experimental verification device based on a phase-only spatial light modulator is built, and the known phase on the modulator is retrieved from the actual interferogram. The RMS of the residual wavefront retrieved through FFT is 0.112λ, and it decreases to 0.035λ through CZT. The experimental results verify the effectiveness of the method proposed in this paper. Furthermore, the method can be used in other types of spatial carrier frequency interference, such as lateral shearing interference, rotational shearing interference, flipping shearing interference, and four-wave shearing interference. [ABSTRACT FROM AUTHOR]

All-inorganic, hole-transporting-layer-free CsPbIBr2 perovskite solar cells have great potential for development, but their device performance needs to be further improved. Recently, metal nanostructures have been successfully applied in the field of solar cells to improve their performance. Nano Ag-enhanced power conversion efficiency (PCE) in one CsPbIBr2 perovskite solar cell utilizing localized surface plasmons of Ag nanoparticles (NPs) on the surface has been researched experimentally and by simulation in this paper. The localized surface plasmon resonance of Ag NPs has a near-field enhancement effect, which is expected to improve the light absorption of CsPbIBr2 perovskite photovoltaic devices. In addition, Ag NPs have a forward-scattering effect on the incident light, which can also improve the performance of CsPbIBr2-based perovskite photovoltaic devices. By directly assembling Ag NPs (with a size of about 150 nm) on the surface of fluorine-doped tin oxide it is found when the particle surface coverage is 10%, the CsPbIBr2 perovskite photovoltaic device achieves a best PCE of 2.7%, which is 9.76% higher than that of the control group. Without changing any existing structure in the ready-made solar cell, this facile and efficient method has huge applications. To the best of our knowledge, this paper is the first report on nano Ag-enhanced photoelectric conversion efficiency in this kind of CsPbIBr2 perovskite solar cell. [ABSTRACT FROM AUTHOR]

The Berry–Tabor (BT) conjecture is a famous statistical inference in quantum chaos, which not only establishes the spectral fluctuations of quantum systems whose classical counterparts are integrable but can also be used to describe other wave phenomena. In this paper, the BT conjecture has been extended to Lévy plates. As predicted by the BT conjecture, level clustering is present in the spectra of Lévy plates. The consequence of level clustering is studied by introducing the distribution of nearest neighbor frequency level spacing ratios P (r ∼) , which is calculated through the analytical solution obtained by the Hamiltonian approach. Our work investigates the impact of varying foundation parameters, rotary inertia, and boundary conditions on the frequency spectra, and we find that P (r ∼) conforms to a Poisson distribution in all cases. The reason for the occurrence of the Poisson distribution in the Lévy plates is the independence between modal frequencies, which can be understood through mode functions. [ABSTRACT FROM AUTHOR]

When a laser is transmitted in fog, and the water droplets will scatter and absorb the laser, which affects the intensity of the laser transmission and the accuracy of radar detection. Therefore, it is of great significance to study the laser transmission in the fog. At present, the main method of calculating the scattering and attenuation characteristics of fog is based on the radiation transmission theory, which is realized by a large number of numerical calculations or physical simulation methods, which takes time and cannot meet the requirements for obtaining the fast and accurate results. Therefore, in this paper established are a new laser forward attenuation model and backward attenuation model in low visibility fog. It is found that in low visibility environments, the results calculated by the Monte Carlo method are more accurate than those from most of the existing forward attenuation models. For the cases of 0.86-μm, 1.06-μm, 1.315-μm, 10.6-μm typical lasers incident on different fogs with different visibilities, a backscatter model is established, the error between the fitting result and the calculation result is analyzed, the backward attenuation fitting parameters of the new model are tested, and a more accurate fitting result is obtained. [ABSTRACT FROM AUTHOR]

In traditional viewpoint, excitatory modulation always promotes neural firing activities. On contrary, the negative responses of complex bursting behaviors to excitatory self-feedback mediated by autapse with time delay are acquired in the present paper. Two representative bursting patterns which are identified respectively to be "Fold/Big Homoclinic" bursting and "Circle/Fold cycle" bursting with bifurcations are studied. For both burstings, excitatory modulation can induce less spikes per burst for suitable time delay and strength of the self-feedback/autapse, because the modulation can change the initial or termination phases of the burst. For the former bursting composed of quiescent state and burst, the mean firing frequency exhibits increase, due to that the quiescent state becomes much shorter than the burst. However, for the latter bursting pattern with more complex behavior which is depolarization block lying between burst and quiescent state, the firing frequency manifests decrease in a wide range of time delay and strength, because the duration of both depolarization block and quiescent state becomes long. Therefore, the decrease degree of spike number per burst is larger than that of the bursting period, which is the cause for the decrease of firing frequency. Such reduced bursting activity is explained with the relations between the bifurcation points of the fast subsystem and the bursting trajectory. The present paper provides novel examples of paradoxical phenomenon that the excitatory effect induces negative responses, which presents possible novel modulation measures and potential functions of excitatory self-feedback/autapse to reduce bursting activities. [ABSTRACT FROM AUTHOR]

The spatiotemporal evolutions of a one-dimensional collisionless decaying plasma bounded by two electrodes with an externally applied electrostatic field are studied by theoretical analyses and particle-in-cell (PIC) simulations with the ion extraction process in a laser-induced plasma as the major research background. Based on the theoretical analyses, the transport process of the charged particles including electrons and ions can be divided into three stages: electron oscillation and ion matrix sheath extraction stage, sheath expansion and ion rarefaction wave propagation stage and the plasma collapse stage, and the corresponding criterion for each stage is also presented. Consequently, a complete analytical model is established for describing the ion extraction flux at each stage during the decaying of the laser-induced plasmas under an electrostatic field, which is also validated by the PIC modeling results. Based on this analytical model, influences of the key physical parameters, including the initial electron temperature and number density, plasma width and the externally applied electric voltage, on the ratio of the extracted ions are predicted. The calculated results show that a higher applied electric potential, smaller initial plasma number density and plasma width lead to a higher ratio of the extracted ions during the first stage; while in this stage, the initial electron temperature shows little effect on it. Meanwhile, more ions will be extracted before the plasma collapse once a higher electric potential is applied. The theoretical model presented in this paper is helpful not only for a deep understanding to the charged particle transport mechanisms for a bounded decaying plasma under an applied electrostatic field, but also for an optimization of the ion extraction process in practical applications. [ABSTRACT FROM AUTHOR]

Nonlinear elastic metamaterial, a topic which has attracted extensive attention in recent years, can enable broadband vibration reduction under relatively large amplitude. The combination of damping and strong nonlinearity in metamaterials may entail extraordinary effects and offer the capability for low-frequency and broadband vibration reduction. However, there exists a clear lack of proper design methods as well as the deficiency in understanding properties arising from this concept. To tackle this problem, this paper numerically demonstrates that the nonlinear elastic metamaterials, consisting of sandwich damping layers and collision resonators, can generate very robust hyper-damping effect, conducive to efficient and broadband vibration suppression. The collision-enhanced hyper damping is persistently presented in a large parameter space, ranging from small to large amplitudes, and for small and large damping coefficients. The achieved robust effects greatly enlarge the application scope of nonlinear metamaterials. We report the design concept, properties and mechanisms of the hyper-damping and its effect on vibration transmission. This paper reveals new properties offered by nonlinear elastic metamaterials, and offers a robust method for achieving efficient low-frequency and broadband vibration suppression. [ABSTRACT FROM AUTHOR]

Exit choice is one of the most important pedestrian behaviors during evacuation. Distance to the exit is a generally recognized factor influencing expected moving time to the exit. Visual range determines how much information a pedestrian can perceive, thus the number of pedestrians within the visual field can be used to estimate waiting time at the exit. Besides, the choice firmness that reflects the degree to which a pedestrian would persist in his/her previous choice of exit is proposed. By integrating game theory into a cellular automata simulation framework, the pedestrian exit choice mechanism is investigated and explicitly modeled in this paper. A systematic analysis of the key factors influencing pedestrian evacuation is conducted, including visual radius and choice firmness of a pedestrian, initial crowd distribution of the room, exit layout as well as exit width. It is found that low choice firmness level can lead to unnatural pedestrian behavior such as wandering, which is adverse to evacuation. The longer the pedestrian's visual radius, the earlier the pedestrian can determine his/her final selection of the exit. Compared with the scenario where the pedestrians are randomly distributed, pedestrians clustered together in a corner of the room lead to high crowd density and imbalanced use of exits. Furthermore, the exit layout and exit width also have a certain influence on pedestrian evacuation process. The results of this paper may be of benefit to the formulation of behavioral rules in other pedestrian simulation models. [ABSTRACT FROM AUTHOR]

The size reduction of atomic clocks is a long-standing research issue. Many atomic clocks such as passive hydrogen masers (PHMs) and compact rubidium masers (CRMs) use iris-loaded resonance cavities (IRCs) as their microwave cavities because they can dramatically reduce the radical sizes of the atomic clocks. In this paper, the electromagnetic characteristic of the IRC is investigated by a theoretical model based on electromagnetic field theory. The formulas to calculate the resonance frequency, quality factor, and magnetic energy filling factor are presented. The relationship between the IRC structure and its electromagnetic characteristic is clarified. The theoretical calculation results accord well with the electromagnetic software simulations and experimental results. The results in this paper should be helpful in understanding the physical mechanism of the IRC and designing the atomic clocks. [ABSTRACT FROM AUTHOR]

For digital image transmission security and information copyright, a new holographic image self-embedding watermarking encryption scheme is proposed. Firstly, the plaintext is converted to the RGB three-color channel, the corresponding phase hologram is obtained by holographic technology and the watermark is self-embedded in the frequency domain. Secondly, by applying the Hilbert transform principle and genetic center law, a complete set of image encryption algorithms is constructed to realize the encryption of image information. Finally, simulation results and security analysis indicate that the scheme can effectively encrypt and decrypt image information and realize the copyright protection of information. The introduced scheme can provide some support for relevant theoretical research, and has practical significance. [ABSTRACT FROM AUTHOR]

This paper is a further work of the authors' paper published previously (Liao T H and Gao Q 2005 Chin. Phys. Lett. 22 2316). The amplitudes of fractional Fourier transform of Cantor sets are analysed from the viewpoint of multifractal by wavelet transform maxima method (WTMM). An integral operation is carried out before the application of WTMM, such that the function obtained can be considered as the perturbed devil staircase. Also, wavelets with large number of vanishing moments are used, which makes the complete singularity spectrum more accessible. The validity of multifractal formalism is guaranteed by restricting parameter q to a proper range, so that the phenomenon of multifractal phase transition can be explained reasonably. Particularly, the method of determining the range of parameter q in the above paper is developed to be more operational and rigorous. [ABSTRACT FROM AUTHOR]

We investigate the general condition for an operator to be unitary. This condition is introduced according to the definition of the position operator in curved space. In a particular case, we discuss the concept of translation operator in curved space followed by its relation with an anti-Hermitian generator. Also we introduce a universal formula for adjoint of an arbitrary linear operator. Our procedure in this paper is totally different from others, as we explore a general approach based only on the algebra of the operators. Our approach is only discussed for the translation operators in one-dimensional space and not for general operators. [ABSTRACT FROM AUTHOR]

This paper analyzes the characteristics of emotion state and group behavior in the evacuation process. During the emergency evacuation, emotion state and group behavior are interacting with each other, and indivisible. The emotion spread model with the effect of group behavior, and the leader–follower model with the effect of emotion state are proposed. On this basis, exit choice strategies with the effect of emotion state and group behavior are proposed. Fusing emotion spread model, leader–follower model, and exit choice strategies into a cellular automata (CA)-based pedestrian simulation model, we simulate the evacuation process in a multi-exit case. Simulation results indicate that panic emotion and group behavior are two negative influence factors for pedestrian evacuation. Compared with panic emotion or group behavior only, pedestrian evacuation efficiency with the effects of both is lower. [ABSTRACT FROM AUTHOR]

Solving nonlinear partial differential equations have attracted intensive attention in the past few decades. In this paper, the Darboux transformation method is used to derive several positon and hybrid solutions for the (2+1)-dimensional complex modified Korteweg–de Vries equations. Based on the zero seed solution, the positon solution and the hybrid solutions of positon and soliton are constructed. The composition of positons is studied, showing that multi-positons of (2+1)-dimensional equations are decomposed into multi-solitons as well as the (1+1)-dimensions. Moreover, the interactions between positon and soliton are analyzed. In addition, the hybrid solutions of b-positon and breather are obtained using the plane wave seed solution, and their evolutions with time are discussed. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the resistance law of a rod vertically penetrating different kinds of multilayer granular rafts with a constant velocity so as to reveal the mechanical properties of the multilayer granular rafts. The resistance was quasi-static under the chosen velocity. Experiments were conducted with different granular thicknesses, rod diameters and combinations of particles and liquids. The study shows that the resistance–displacement relation of the rod has three smooth stages. In the first stage, the resistance rapidly increased. In the second stage, the resistance curve maintained an almost constant slope. In the third stage, the resistance smoothly changed with its slope continuously increasing. Based on the corresponding physical models for each stage, the study reveals the exponential dependence of the load-bearing capacity of the multilayer granular raft on its thickness, and clarifies the capillary effects on the resistance law. The study extends the knowledge of the granular raft from monolayer to multilayer structure. [ABSTRACT FROM AUTHOR]

Terahertz wave is between microwave and infrared bands in the electromagnetic spectrum with the frequency range from 0.1 THz to 10 THz. Controlling and processing of the polarization state in terahertz wave are the focus due to its great influence on the characteristics. In this paper, a transmissive metasurface terahertz polarization converter is designed in 3D structure with an upper surface of ruler-like rectangular, an intermediate dielectric layer and a lower surface of metal grid wires. Numerical simulations of the converter show that the polarization conversion ratio (PCR) is above 99.9% at 0.288 THz–1.6 THz, the polarization rotation angle (PRA) is close to 90° at 0.06 THz–1.4 THz, and the ellipticity angle (EA) is close to 0° at 0.531 THz–1.49 THz. The origin of the efficient polarization conversion is explained by analyzing the electric field intensity, magnetic field intensity, surface current, electric field energy density, and magnetic field energy density distributions of the converter at 1.19 THz and 0.87 THz, which are consistent with the energy transmittance and transmittance coefficient. In addition, the effects of different thickness and material of intermediate layer, thickness of upper surface material, polarized wave incidence angle, and metasurface materials on the performance of the polarization converter are discussed, and how they affect the conversion performance of the polarization converter are also explained. Our results provide a strong theoretical basis and technical support to develop high performance transmission-type terahertz polarization converters, and play an important role to promote the development of terahertz science and technology. [ABSTRACT FROM AUTHOR]

The key parameters of vertical AlN Schottky barrier diodes (SBDs) with variable drift layer thickness (DLT) and drift layer concentration (DLC) are investigated. The specific on-resistance (Ron,sp) decreased to 0.5 mΩ ⋅ cm2 and the breakdown voltage (VBR) decreased from 3.4 kV to 1.1 kV by changing the DLC from 1015 cm−3 to 3 × 1016 cm−3. The VBR increases from 1.5 kV to 3.4 kV and the Ron,sp also increases to 12.64 mΩ ⋅ cm2 by increasing DLT from 4-μm to 11-μm. The VBR enhancement results from the increase of depletion region extension. The Baliga's figure of merit (BFOM) of 3.8 GW/cm2 was obtained in the structure of 11-μm DLT and 1016 cm−3 DLC without FP. When DLT or DLC is variable, the consideration of the value of BFOM is essential. In this paper, we also present the vertical AlN SBD with a field plate (FP), which decreases the crowding of electric field in electrode edge. All the key parameters were optimized by simulating based on Silvaco-ATLAS. [ABSTRACT FROM AUTHOR]

Cyclo[18]carbon has received considerable attention thanks to its novel geometric configuration and special electronic structure. Superalkalis have low ionization energy. Doping a superalkali in cyclo[18]carbon is an effective method to improve the optical properties of the system because considerable electron transfer occurs. In this paper, the geometry, bonding properties, electronic structure, absorption spectrum, and nonlinear optical (NLO) properties of superalkaline M 3O (M = Li, Na)-doped cyclo[18]carbon were studied by using density functional theory. M 3O and the C18 rings are not coplanar. The C18 ring still exhibits alternating long and short bonds. The charge transfer between M 3O and C18 forms stable [ M 3O]+[C18]− ionic complexes. C18 M 3O (M = Li, Na) shows striking optical nonlinearity, i.e., their first- and second-order hyperpolarizability (β vec and γ ||) increase considerably at λ = 1907 nm and 1460 nm. [ABSTRACT FROM AUTHOR]

Diffusion in narrow curved channels with dead-ends as in extracellular space in the biological tissues, e.g., brain, tumors, muscles, etc. is a geometrically induced complex diffusion and is relevant to different kinds of biological, physical, and chemical systems. In this paper, we study the effects of geometry and confinement on the diffusion process in an elliptical comb-like structure and analyze its statistical properties. The ellipse domain whose boundary has the polar equation ρ (θ) = b 1 − e 2 cos 2 θ with 0 < e < 1, θ ∈ [0,2 π ], and b as a constant, can be obtained through stretched radius r such that Υ = r ρ (θ) with r ∈ [0,1]. We suppose that, for fixed radius r = R, an elliptical motion takes place and is interspersed with a radial motion inward and outward of the ellipse. The probability distribution function (PDF) in the structure and the marginal PDF and mean square displacement (MSD) along the backbone are obtained numerically. The results show that a transient sub-diffusion behavior dominates the process for a time followed by a saturating state. The sub-diffusion regime and saturation threshold are affected by the length of the elliptical channel lateral branch and its curvature. [ABSTRACT FROM AUTHOR]

Due to its great potential applications in thermal management, heat control, and quantum information, phononics has gained increasing attentions since the first publication in Rev. Mod. Phys. 84 1045 (2012). Many theoretical and experimental progresses have been achieved in the past decade. In this paper, we first give a critical review of the progress in thermal diodes and transistors, especially in classical regime. Then, we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics. In the third part, we discuss the potential applications. Last but not least, we point out the outlook and challenges ahead. [ABSTRACT FROM AUTHOR]

Individuals' preventive measures, as an effective way to suppress epidemic transmission and to protect themselves from infection, have attracted much academic concern, especially during the COVID-19 pandemic. In this paper, a reinforcement learning-based model is proposed to explore individuals' effective preventive measures against epidemics. Through extensive simulations, we find that the cost of preventive measures influences the epidemic transmission process significantly. The infection scale increases as the cost of preventive measures grows, which means that the government needs to provide preventive measures with low cost to suppress the epidemic transmission. In addition, the effective preventive measures vary from individual to individual according to the social contacts. Individuals who contact with others frequently in daily life are highly recommended to take strict preventive measures to protect themselves from infection, while those who have little social contacts do not need to take any measures considering the inevitable cost. Our research contributes to exploring the effective measures for individuals, which can provide the government and individuals useful suggestions in response to epidemics. [ABSTRACT FROM AUTHOR]

In high intensity focused ultrasound (HIFU) treatment, it is crucial to accurately identify denatured and normal biological tissues. In this paper, a novel method based on compressed sensing (CS) and refined composite multi-scale fuzzy entropy (RCMFE) is proposed. First, CS is used to denoise the HIFU echo signals. Then the multi-scale fuzzy entropy (MFE) and RCMFE of the denoised HIFU echo signals are calculated. This study analyzed 90 cases of HIFU echo signals, including 45 cases in normal status and 45 cases in denatured status, and the results show that although both MFE and RCMFE can be used to identify denatured tissues, the intra-class distance of RCMFE on each scale factor is smaller than MFE, and the inter-class distance is larger than MFE. Compared with MFE, RCMFE can calculate the complexity of the signal more accurately and improve the stability, compactness, and separability. When RCMFE is selected as the characteristic parameter, the RCMFE difference between denatured and normal biological tissues is more evident than that of MFE, which helps doctors evaluate the treatment effect more accurately. When the scale factor is selected as 16, the best distinguishing effect can be obtained. [ABSTRACT FROM AUTHOR]

To improve the complexity of chaotic signals, in this paper we first put forward a new three-dimensional quadratic fractional-order multi-scroll hidden chaotic system, then we use the Adomian decomposition algorithm to solve the proposed fractional-order chaotic system and obtain the chaotic phase diagrams of different orders, as well as the Lyaponov exponent spectrum, bifurcation diagram, and SE complexity of the 0.99-order system. In the process of analyzing the system, we find that the system possesses the dynamic behaviors of hidden attractors and hidden bifurcations. Next, we also propose a method of using the Lyapunov exponents to describe the basins of attraction of the chaotic system in the matlab environment for the first time, and obtain the basins of attraction under different order conditions. Finally, we construct an analog circuit system of the fractional-order chaotic system by using an equivalent circuit module of the fractional-order integral operators, thus realizing the 0.9-order multi-scroll hidden chaotic attractors. [ABSTRACT FROM AUTHOR]

Quantum simulation has been developed extensively over the past decades, widely applied to different models to explore dynamics in the quantum regime. Rydberg atoms have strong dipole–dipole interactions and interact with each other over a long distance, which makes it straightforward to build many-body interacting quantum systems to simulate specific models. Additionally, neutral atoms are easily manipulated due to their weak interactions. These advantages make Rydberg many-body system an ideal platform to implement quantum simulations. This paper reviews several quantum simulations for different models based on Rydberg many-body systems, including quantum Ising models in one dimension and two dimensions mainly for quantum magnetism, XY model for excitation transport, SSH model for symmetry-protected topological phases, and critical self-organized behaviors in many-body systems. Besides, some challenges and promising directions of quantum simulations based on Rydberg many-body system are discussed in this paper. [ABSTRACT FROM AUTHOR]

In order to obtain a clear image of the retina of model eye, an adaptive optics system used to correct the wave-front error is introduced in this paper. The spatial light modulator that we use here is a liquid crystal on a silicon device instead of a conversional deformable mirror. A paper with carbon granule is used to simulate the retina of human eye. The pupil size of the model eye is adjustable (3-7 mm). A Shack-Hartman wave-front sensor is used to detect the wave-front aberration. With this construction, a value of peak-to-valley is achieved to be 0.086 l, where l is wavelength. The modulation transfer functions before and after corrections are compared. And the resolution of this system after correction (691p/m) is very close to the dirraction limit resolution. The carbon granule on the white paper which has a size of 4.7 mm is seen clearly. The size of the retina cell is between 4 and 10 mu;m. So this system has an ability to image the human eye's retina. [ABSTRACT FROM AUTHOR]