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In this paper, a reliable and effective local discontinuous Galerkin (LDG) scheme for numerically solving the classical Rosenau–Hyman equation with non-periodic boundary conditions has been proposed. This study employs the third-order nonlinearly stable total variation diminishing Runge–Kutta method and the LDG method, respectively, to discretize the temporal and spatial derivatives. Finally, numerical simulations are performed on various test problems and compared with the exact results as well as results produced by a few other numerical methods, to analyze the reliability and efficiency of the proposed method. The results generated, which validate the expected order of accuracy, are presented through multiple tables. In addition, several graphical representations of the problem are presented to depict the behavior of the solution. [ABSTRACT FROM AUTHOR]

Tantalum nitrides (TaN) have attracted much attention as a new material of energy exchangers in insensitive detonators, we mainly investigate its ignition law in this paper. Firstly, the paper utilizes numerical simulation to predict the influence of the substrate material, bridge zone thickness, bridge zone length and width on the ignition action. Then its reliability was verified by experiments, which provided technical support for the design of passivated pyrotechnics. [ABSTRACT FROM AUTHOR]

The trigonometric quintic B-spline scheme is used in this research paper to research Zakharov's (ZK) nonlinear dimensional equation's numerical solution. The ZK model's solutions explain the relationship between the high-frequency Langmuir and the low-frequency ion-acoustic waves with many applications in optical fiber, coastal engineering, and fluid mechanics of electromagnetic waves, plasma physics, and signal processing. Three recent computational schemes (the expanded exp (ϕ) -expansion method, generalized Kudryashov method, and modified Khater method) have recently been used to investigate this model's moving wave solution. Many innovative solutions have been established in this paper to determine the original and boundary conditions that allow numerous numerical schemes to be implemented. Here, the trigonometric quintic B-spline method is used to analyze the precision of the collected analytical solutions. To illustrate the precision of the numerical and computational solutions, distinct drawings are depicted. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the dynamics of the vortices in the homogeneous two-dimensional Bose–Einstein condensate by considering the condensate density variation. It is shown that the condensate density variation plays an important role when two vortices are close together. By the time-dependent Lagrangian functional method and the numerical simulation, we study how the interaction strength of the vortices varies with the distance between two vortices with the same or different topological charges, and generalize the results for the vortex pairs to the multi-vortex case. The numerical simulations demonstrate the validity of our theory. [ABSTRACT FROM AUTHOR]

In this paper, two important pseudo-parabolic type equations are studied for extracting soliton solutions via the generalized projective riccati equations method. These equations are Oskolkov equation and Oskolkov–Benjamin–Bona–Mahony–Burgers equation. The proposed method extracts dark soliton and singular soliton. Furthermore, the Painlevé test (P-test) has also been employed on pseudo-parabolic type equations for investigating integrability. The proposed equations are proved to be integrable by P-test. The numerical simulations have also been carried out by 3D and 2D graphs of some of the obtained solutions. [ABSTRACT FROM AUTHOR]

In this paper, the synchronization of discrete-time complex dynamical network with dynamic links is investigated. From the angle of large-scale system, if the links and nodes are time-varying, the complex dynamical network may be regarded to be composed of nodes subsystem (NS) and links subsystem (LS). The weighted value of links between nodes can be regarded as the state variables of LS, the above two subsystems are mutually coupled. The two subsystems are modeled mathematically by the state difference equations, especially, the dynamics of LS is modeled as Riccati matrix difference equation without control input. Different from the previous researches, this work concerns simultaneously the dynamics of LS and NS, by which the synchronization of NS is investigated. Associated with the given dynamic reference target for LS, the nodes controller is synthesized to ensure the state synchronization of NS to be achieved with the assistance of the LS. Finally, the numerical simulation is given to illustrate the effectiveness of the proposed theoretical results in this paper. [ABSTRACT FROM AUTHOR]

Hysteresis effect, which has a significant impact on transient characteristics of a pump-turbine, attracts more and more researchers' attention and shows great potential. Influences of hysteresis on dynamic characteristics of a pump-turbine are investigated during the transient process in this paper. Transient trajectories of pump-turbines actually do not match their static operation trajectories, especially in the condition of turbine braking. In order to establish a transient model of a pump-turbine in different moving directions of dynamic trajectories, time delays among the relative parameters are introduced in this paper. Furthermore, effects of hysteresis on the dynamic characteristics of the pump-turbine are analyzed in detail by using numerical simulation. Based on the established transient model, influences of unit head on the dynamic characteristics of the pump-turbine are studied during the bidirectional transient process. The simulation results show the transient characteristic of the pump-turbine can be improved with the enhancement of hysteresis effect. While it gradually loses stability with the increase of hysteresis. The conclusions provide us a new approach for regulating the transient performance and stability of pump-turbines by using hysteresis effect during transient process. [ABSTRACT FROM AUTHOR]

In this paper, the discrete-time complex dynamical networks with dynamic weighted value of connection relationships are regarded to be composed of the node and link subsystems, and the state variables of the two subsystems are mutually coupled. Different from most of the existing researches on synchronization or stabilization of nodes, the emphasis of this paper is on the links instead of nodes. This paper mainly focuses on the generation mechanism of structural balance in the link subsystem, the nodes only play an auxiliary role. Associated with the dynamic coupling term in the link subsystem, the suitable controller is proposed for node subsystem such that the structural balance of link subsystem without control input be achieved indirectly. Finally, a numerical simulation is given to show the effectiveness of the method in this paper. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional (3D) randomly packed bed model is established to research the filtration combustion process. 3D numerical simulation of premixed combustion in the randomly packed bed is carried out, and the temperature distributions and flame propagation characteristics are predicted and discussed. Simulation results show that the change rules of the temperature field and the flame surface in the random model are consistent with the classical theory, and the stochastic packed model is more promising for numerical simulation of filtration combustion in comparison with the traditional regular structures. [ABSTRACT FROM AUTHOR]

This paper proposes a new density gradient continuous traffic flow model, and analyzes the linear stability of the model, as well as the bifurcation type of the model. Numerical simulation of the new model verifies the usability of the model. From the perspective of system stability, the bifurcation analysis method is used to analyze the nonlinear traffic phenomena on the expressway. The equilibrium solution of the model is discussed. On this basis, Hopf bifurcation, saddle bifurcation and Bogdanov–Takens bifurcation are obtained, and the existence conditions and fractional types of Hopf bifurcation and saddle bifurcation are obtained. The traffic flow characteristics of Hopf bifurcation and saddle node bifurcation are analyzed. [ABSTRACT FROM AUTHOR]

Classical statistical thermodynamics was developed in the second half of the 19th century. The implied fact is that since then all processes and effects that fall into the domain of classical statistical thermodynamics have been discovered and explained. However, analyzing the outputs from our numerical model of an ideal gas, we noticed that the atoms separate during the expansion of the gas into empty space. This separation occurs as a consequence of the distribution of molecules by velocities. Namely, faster molecules will move further away from their initial position than slower ones. The objective of this paper is to describe the existence of this process and to present some basic physical consequences of this effect. [ABSTRACT FROM AUTHOR]

The primary goal of this paper is to seek solutions to the coupled nonlinear partial differential equations (CNPDEs) by the use of q-homotopy analysis transform method (q-HATM). The CNPDEs considered are the coupled nonlinear Schrödinger–Korteweg–de Vries (CNLS-KdV) and the coupled nonlinear Maccari (CNLM) systems. As a basis for explaining the interactive wave propagation of electromagnetic waves in plasma physics, Langmuir waves and dust-acoustic waves, the CNLS-KdV model has emerged as a model for defining various types of wave phenomena in mathematical physics, and so forth. The CNLM model is a nonlinear system that explains the dynamics of isolated waves, restricted in a small part of space, in several fields like nonlinear optics, hydrodynamic and plasma physics. We construct the solutions (bright soliton) of these models through q-HATM and present the numerical simulation in form of plots and tables. The solutions obtained by the suggested approach are provided in a refined converging series. The outcomes confirm that the proposed solutions procedure is highly methodological, accurate and easy to study CNPDEs. [ABSTRACT FROM AUTHOR]

A new type of nonlinear sub-grid scale (SGS) model is adopted based on the helicity analysis and is verified by predicting the internal flow in a rotating channel. A stress term that contains helicity constraint is introduced into the original SGS model to construct a nonlinear sub-grid model. This additional term representing the helicity constraint effect in the momentum equations is shown to give predictions that are in better agreement with the experimental data. In this paper, the Detached-Eddy Simulation (DES) and the nonlinear SGS model are used to further study the turbulence statistics of the rotating channel flow. Combining with the Reynolds stress transport equations and the turbulent kinetic energy transport equation, the change of turbulence statistics near the wall of the rotating channel is analyzed. The newly added term changes the turbulent viscosity near the wall, which changes the velocity gradient near the wall and further affects other turbulence statistics near the wall. [ABSTRACT FROM AUTHOR]

In real-world systems, one random failure or targeted attack may lead to the cascading destruction within a system, and even create the systemic collapse among multiple correlated ones. With the help of network science, modeling the cascade failure on complex networks has become a challenging topic. In this paper, we put forward an improved cascading model on two interdependent networks to further explore the impact of the specific detachment logic on the system collapse, where the distinct condition to leave the system for a pair of nodes exists on the two-layered networks. Meanwhile, once the detachment logic is satisfied, two different criteria are adopted to determine whether this pair of nodes will leave the interdependent networks. Through extensive numerical simulations, we analyze the effects of detachment logic, network topology, departure criteria and nodal coupling relationship between layers in detail. It is found that in our detachment logic, both criteria will render the whole system to exhibit the phenomenon of pseudo-steady state and sudden collapse. In particular, two critical thresholds to characterize the evolution of system crashing emerge, which is different from previous findings under other detachment logic conditions on two-layered networks. Current results are conducive to further understanding the crashing behaviors of interdependent networks and designing the more robust networked systems in practice. [ABSTRACT FROM AUTHOR]

This paper recommends a method to reduce harmonic distortion of MEMS accelerometer. The fifth-order MEMS accelerometer interface circuit designed in this work used the Cascade-of-Integrators, Feedforward modulation structure. This paper analyzes and calculates the main sources of HD, the unstable problem brought by the vacuum encapsulation sensitive structure. The use of front-phase compensation and the increase in loop forward gain helps ensure the system’s stability as well as reduce the system harmonic distortion. Simulink is used to get the simulation results. After harmonic optimization, the third harmonic reached −141.83 dB, the Signal-to-Noise-and-Distortion-Ratio rose to 118.1 dB, the noise density is under 200 ng/Hz 1 / 2 , the effective number of bits rose up to 19.33 bits. [ABSTRACT FROM AUTHOR]

Chen–Lee–Liu (CLL) lattice equation is an integrable discretization of the CLL equation which can be used to model the evolution of the self-steepening optical pulses without self-phase modulation. In this paper, the discrete N-fold Darboux transformation (DT) is used to derive the discrete kink multi-soliton solutions in terms of determinant for CLL lattice equation. Soliton fission and fusion interaction structures of such solutions are shown graphically. The details of their evolution are investigated by using numerical simulations, showing that a small noise with amplitude less than or equal to 0.01 produces a strong oscillation and instability of these kink soliton solutions. The discrete generalized perturbation (n,N−n)-fold DT is constructed to express some rational solutions in terms of the determinants of CLL lattice equation by modifying the discrete N-fold DT. Infinitely many conservation laws for CLL lattice equation are constructed based on its Lax representation. Results in this paper might be helpful for understanding the propagation of optical pulses. [ABSTRACT FROM AUTHOR]

This paper introduces a new four-dimensional chaotic system with a unique unstable equilibrium and multiple coexisting attractors. The dynamic evolution analysis shows that the system concurrently generates two symmetric chaotic attractors for fixed parameter values. Based on this system, an effective method is established to construct an infinite number of coexisting chaotic attractors. It shows that the introduction of some non-linear functions with multiple zeros can increase the equilibria and inspire the generation of coexisting attractor of the system. Numerical simulations verify the availability of the method. [ABSTRACT FROM AUTHOR]

With both analytical and numerical methods, local dynamic behaviors including stability and Hopf bifurcation of a new four-dimensional hyper-chaotic system are studied in this paper. All the equilibrium points and their stability conditions are obtained with the Routh–Hurwitz criterion. It is shown that there may exist one, two, or three equilibrium points for different system parameters. Via Hopf bifurcation theory, parameter conditions leading to Hopf bifurcation is presented. With the aid of center manifold and the first Lyapunov coefficient, it is also presented that the Hopf bifurcation is supercritical for some certain parameters. Finally, numerical simulations are given to confirm the analytical results and demonstrate the chaotic attractors of this system. It is also shown that the system may evolve chaotic motions through periodic bifurcations or intermittence chaos while the system parameters vary. [ABSTRACT FROM AUTHOR]

This paper focuses on the efficiency improvement of a centrifugal fan used in a vacuum cleaner. In order to check the performance of the centrifugal fan system, computational fluid dynamics (CFD) analysis is used. The numerical simulation with CFD tool is carried out with RNG k − 𝜀 two-equation turbulence model based on Reynolds-averaged Navier–Stokes equations. To perform the coupling between rotating impeller and stationary area, the multiple reference frame (MRF) model is used. The numerical results of the fan are validated against with experimental results and are found to be highly reliable. The design and optimization of diffuser and impeller of a centrifugal fan are realized by using numerical investigations. For reducing the kinetic energy loss inside the fan, a guide baffle is added to optimize diffuser. The optimization results show that overall efficiency of the fan is improved by 5.27% and considering the lower efficiency of impeller caused by blockage at the blade inlet, etc., the design of impeller with long-short blades is proposed. Several cases of affecting factors under different operating conditions are simulated. Relative length (denoted as σ) and circumferential position of short blades are chosen as design variables. It is found that the efficiency of a fan with a relative length of 0.7 can be increased by 9.34%, and the best circumferential position of short blades is between two adjacent long blades. [ABSTRACT FROM AUTHOR]

In this paper, the steady state characteristics and stochastic resonance (SR) in two-dimensional FitzHugh–Nagumo (FHN) neuron system driven by Lévy noise are studied. The system is simulated by Janicki–Weron algorithm and fourth-order Runge–Kutta method, and the steady state characteristics of the system are analyzed by stationary probability density (SPD) functions. Then, the SR is determined by the classical measure of signal-to-noise ratio (SNR). Through numerical simulation, it is found that the Lévy noise can induce the transition of the system. In addition, the effects of different parameters on the SR are analyzed by SNR. [ABSTRACT FROM AUTHOR]

In this paper, we consider the Von Kármán swirling-flow problem, which is described by an ordinary equations system. The explicit asymptotic solutions are given by applying the homotopy renormalization method. Furthermore, the numerical simulations verify that our asymptotic solutions have high precision and the absolute errors are less than 0.03, which means that the results obtained are truly valid and can be used practically. [ABSTRACT FROM AUTHOR]

In this paper, a new two-lane lattice hydrodynamic model is presented by accounting for the "backward looking" effect and the relative flow information. Linear analysis is applied to deduce the linear stability condition. With this method, we can demonstrate that "backward looking" and relative flow information have great positive significance in improving traffic flow stability. Nonlinear analysis is performed to derive the mKdV equation, which can represent transmission characteristic of density waves. The results achieved by the numerical simulation are consistent with theoretical analytical results. Numerical results indicate that both "backward looking" effect and relative flow information are helpful to heighten the traffic flow stability efficiently in two-lane traffic model. [ABSTRACT FROM AUTHOR]

In recent paper, Nowak et al. report a charged wire interferometer for atoms, and employ analytical method to explain the interference patterns [ Phys. Rev. Lett. 81 (1998) 5792]. In this paper, a numerical calculation with semi-classical method is carried out and the experimental patterns are rebuilt very well. The interference patterns are interpreted by path integral. We also calculate the fringe period for different voltages and the agreement with experiment is more rigorous than the analytical expression. Besides, the fringe visibility of the interference patterns at different applied voltages and degrees is also discussed. [ABSTRACT FROM AUTHOR]

As an essential dynamic evolving mechanism, triangle behavior can be observed ubiquitously in the real world. Combining transfer mechanism with weighted dynamic, in this paper, we propose a new community model and deduce the strength distribution. Consistent with the theoretical results, numerical simulations show decent right-skewed scale-free characters of strength distribution. Moreover, we calculate some important coefficients to analyze the correlations of nodes and demonstrate the disassortative property of this model. Finally, the process of epidemic spreading with different weighted transmission rate is introduced on the weighted community network, and the results indicate that the triangle behavior has a significant influence on the dynamic of the epidemic spreading. Composed with the models proposed already, our model is supposed to be closer to the realistic network and imitate the real system more accurately and exactly. [ABSTRACT FROM AUTHOR]

With the increase of vehicles, traffic congestion has become a prominent problem. Environmental pollution, energy waste and even traffic accidents are easily caused by congestion. Nowadays, with the help of V2V and V2I communications, real-time interaction of vehicle information can be achieved. Vehicles can easily get information about other vehicles. In reality, a driver looks at the following car (i.e. upstream traffic condition) as well as the preceding car while driving. However, the effect of upstream condition is rarely analyzed. In the paper, a term describing the upstream traffic condition is added in Nagatani's model. The effect of the upstream traffic condition to linear stability is obtained by applying the perturbation method. Nonlinear stability equations, such as the mKdV equation, are also derived. Theoretical results of linear stability and nonlinear stability are shown intuitively through numerical simulations. It can be found that traffic is more stable when the upstream traffic condition is considered. [ABSTRACT FROM AUTHOR]

Traffic congestion has attracted considerable attention in modern society. Many researchers have proposed tremendous traffic flow models. These models can be divided into microscopic model, mesoscopic model and macroscopic model. With the progress of technology, it is possible to get the information of the preceding vehicles, i.e. the downstream traffic condition. Drivers can adjust their driving behaviors according to the downstream condition. This mechanism has been considered in microscopic model, and it is found that this mechanism can not only stabilize the traffic, but also bring about some new phenomena, such as synchronized traffic pattern. In the macroscopic model, what will the traffic flow be after considering the mechanism? In this paper, a term describing the downstream traffic condition is added in Nagatani's single-lane lattice model. Through theoretical study and numerical simulation, it can be found that traffic is more stable when the downstream traffic condition is considered. Besides, the modified model can reproduce the soliton wave, kink wave properly. Moreover, the amplitude and frequency of density wave with different influence forms of the front lattices on the current lattice are almost the same as found to reflect the different influence forms do not have significant effect on the stability. [ABSTRACT FROM AUTHOR]

Azimuthal electromagnetic wave logging-while-drilling (LWD) technology can detect weak electromagnetic wave signal and realize real-time resistivity imaging. It has great values to reduce drilling cost and increase drilling rate. In this paper, self-adaptive hp finite element method (FEM) has been used to study the azimuthal resistivity LWD responses in different conditions. Numerical simulation results show that amplitude attenuation and phase shift of directional electromagnetic wave signals are closely related to induced magnetic field and azimuthal angle. The peak value and polarity of geological guidance signals can be used to distinguish reservoir interface and achieve real-time geosteering drilling. Numerical simulation results also show the accuracy of the self-adaptive hp FEM and provide physical interpretation of peak value and polarity of the geological guidance signals. [ABSTRACT FROM AUTHOR]

In this paper, the mean first-passage time (MFPT) in simplified FitzHugh–Nagumo (FHN) neural model driven by correlated multiplicative non-Gaussian noise and additive Gaussian white noise is studied. Firstly, using the path integral approach and the unified colored-noise approximation (UCNA), the analytical expression of the stationary probability distribution (SPD) is derived, and the validity of the approximation method employed in the derivation is checked by performing numerical simulation. Secondly, the expression of the MFPT of the system is obtained by applying the definition and the steepest-descent method. Finally, the effects of the multiplicative noise intensity D, the additive noise intensity Q, the noise correlation time τ , the cross-correlation strength λ and the non-Gaussian noise deviation parameter q on the MFPT are discussed. [ABSTRACT FROM AUTHOR]

In this paper, a new semi-discrete coupled system which was firstly proposed by Bronsard and Pelinovsky is under investigation. Based on its known Lax pair, the infinitely-many conservation laws and discrete N-fold DT for this system are constructed. As applications, bell-shaped multi-soliton and breather solutions in terms of determinants for this system are firstly derived by means of the discrete N-fold DT. Propagation and elastic interaction structures of such soliton solutions are shown graphically: (1) Propagation characteristics of one-, two-, three- and four-soliton solutions are discussed from vanishing background. (2) Propagation characteristics of one- and two-breather solutions are analyzed from the plane wave background. The details of the dynamical evolutions for such soliton and breather solutions are studied via numerical simulations. Numerical results show the accuracy of our numerical scheme and the stable evolutions of these solitons with or without a noise in a relatively short period of time, while the evolutions exhibit obviously larger oscillations and strong instability with the increase in time. These results may be useful for understanding the propagation of orthogonally polarized optical waves in an isotropic medium and circularly polarized few-cycle pulses in Kerr media described by the coupled NLS and coupled complex mKdV equations, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear analysis of a viscous continuum traffic flow model is studied. The stability condition of the viscous continuum model is given by using the linear analysis method. The Korteweg–de Vries (KdV) equation is derived to describe the traffic jams. The effect of the viscous term is investigated by numerical simulations. The results show that the existence of the viscous term induces oscillation of traffic flow and the amplitude of the oscillation increases with increasing the coefficient of the viscous term. It is also found that the local clusters are compressed by increasing the coefficient of the viscous term. [ABSTRACT FROM AUTHOR]

In this paper, we study lump-kink solutions of a (2+1)-dimensional bidirectional Sawada–Kotera equation and discuss their dynamics. A Hirota bilinear form of a (2+1)-dimensional bidirectional Sawada–Kotera equation is deduced via a dependent logarithmic transformation. Based on this Hirota bilinear equation, we obtain eight classes of lump-kink solutions which combine stripe soliton and lump soliton by using symbolic computations. Our simulation results with the appropriate choice of the arbitrary parameters that show the motion of lump soliton and the process of interaction between lump soliton and a stripe soliton. [ABSTRACT FROM AUTHOR]

Under investigation in this paper are the three-coupled nonlinear Schrödinger (CNLS) equations, which govern the dynamics of solitonic excitations along three-spine α -helical protein with inhomogeneous effect. The vector periodic solitons (VPSs) of three-CNLS equations have been obtained by a transformation that transforms the corresponding equations to the integrable mixed three-CNLS equations. The VPSs getting from two-bright-one-dark solitons are different to the ones from two-dark-one-bright solitons. The latter propagates on periodic wave background and the interspine interaction coefficient adjusts the oscillation period. Moreover, the different-type VPSs are reported through manipulating external inhomogeneity potential. And it shows that VPSs can transform into bright–bright–bright solitons in the special conditions. Dynamic behaviors of those solitons are discussed through graphic simulation. [ABSTRACT FROM AUTHOR]

In this paper, based on the Back Propagation (BP) neural network algorithm, we introduce the idea of the Simulated Annealing (SA), and then propose a new neural network algorithm: Time Simulated Annealing-Back Propagation (TSA-BP) algorithm. The proposed algorithm can improve the convergence rate and numerical stability. By using this proposed algorithm, the learning rates and initial weights in the BP neural network could be easily adjusted. We show that the TSA-BP algorithm could reduce the errors caused by human-made factors. Several numerical experiments have been tested by using different disease data. Furthermore, we compared the TSA-BP algorithm to the other existing, well-known algorithms. Numerical results show higher accuracy and efficiency of the TSA-BP algorithm. [ABSTRACT FROM AUTHOR]

This paper constructs a new 4D chaotic system from the Sprott B system. The system is dissipative, chaotic with two saddle foci. The bifurcation diagrams verify that the system exists multiple attractors with different initial values, including two strange attractors, two periodic attractors. Furthermore, we apply the passive control to control the system. A controller is designed for driving the system to the origin. The simulations show our theoretical results visually. [ABSTRACT FROM AUTHOR]

In this paper, we systematically research periodic orbits of the Kuramoto–Sivashinsky equation (KSe). In order to overcome the difficulties in the establishment of one-dimensional symbolic dynamics in the nonlinear system, two basic periodic orbits can be used as basic building blocks to initialize cycle searching, and we use the variational method to numerically determine all the periodic orbits under parameter ν = 0.02991. The symbolic dynamics based on trajectory topology are very successful for classifying all short periodic orbits in the KSe. The current research can be conveniently adapted to the identification and classification of periodic orbits in other chaotic systems. [ABSTRACT FROM AUTHOR]

Grid adaptation is an important strategy to improve the accuracy of output functions (e.g. drag, lift, etc.) in computational fluid dynamics (CFD) analysis and design applications. This paper presents a modified robust grid adaptation and error correction method for reducing simulation errors in integral outputs. The procedure is based on discrete adjoint optimization theory in which the estimated global error of output functions can be directly related to the local residual error. According to this relationship, local residual error contribution can be used as an indicator in a grid adaptation strategy designed to generate refined grids for accurately estimating the output functions. This grid adaptation and error correction method is applied to subsonic and supersonic simulations around three-dimensional configurations. Numerical results demonstrate that the sensitive grids to output functions are detected and refined after grid adaptation, and the accuracy of output functions is obviously improved after error correction. The proposed grid adaptation and error correction method is shown to compare very favorably in terms of output accuracy and computational efficiency relative to the traditional featured-based grid adaptation. [ABSTRACT FROM AUTHOR]

As part of the nodule-harvesting process, sediment tailings are released underwater. Due to the long period of clouding in the water during the settling process, this presents a significant environmental and ecological concern. One possible solution is to release a mixture of sediment tailings and seawater, with the aim of reducing the settling duration as well as the amount of spreading. In this paper, we present some results of numerical simulations using the smoothed particle hydrodynamics (SPH) method to model the release of a fixed volume of pre-mixed sediment-water mixture into a larger body of quiescent water. Both the sediment-water mixture and the 'clean' water are modeled as two different fluids, with concentration-dependent bulk properties of the sediment-water mixture adjusted according to the initial solids concentration. This numerical model was validated in a previous study, which indicated significant differences in the dispersion and settling process between dilute and dense mixtures, and that a dense mixture may be preferable. For this study, we investigate a wider range of volumetric concentration with the aim of determining the optimum volumetric concentration, as well as its overall effectiveness compared to the original process (100% sediment). [ABSTRACT FROM AUTHOR]

In this paper, an aircraft model was tested in the wind tunnel with different degrees of yaw-roll coupling at different angles of attack. The dynamic increments of yawing and rolling moments are compared to study the coupling effects on damping characteristics. The characteristic time constants are calculated to study the changes of flow field structure related to coupling ratios. The damping characteristics and time lag effects of aerodynamic loads calculated by dynamic derivative method are also compared with experimental results to estimate the applicability of linear superposition principle at large angles of attack. [ABSTRACT FROM AUTHOR]

In this paper, a fluid-structural-thermal integrated method is presented based on finite volume method. A unified integral equations system is developed as the control equations for physical process of aero-heating and structural heat transfer. The whole physical field is discretized by using an up-wind finite volume method. To demonstrate its capability, the numerical simulation of Mach 6.47 flow over stainless steel cylinder shows a good agreement with measured values, and this method dynamically simulates the objective physical processes. Thus, the integrated algorithm proves to be efficient and reliable. [ABSTRACT FROM AUTHOR]

In this paper, a numerical study of the interaction between transverse cold jets on slender body in front of or between X-shape rudders with rudders in the oncoming free stream is presented. Firstly, the flow field at different jet conditions is simulated and analyzed. Then, the total force and moment amplification factors of the corresponding slender body with jet at different locations are analyzed and compared with those results of non-jet flow. Numerical results show that interactions take a great effect to the configuration of the flow field around rudders and the pressure distribution on slender surface. Moreover, the force and moment amplification changes regularly along with the location of jet nozzle. [ABSTRACT FROM AUTHOR]

The aerodynamic performance of laminar flow nacelle is highly sensitive to uncertain working conditions, especially the surface roughness. An efficient robust aerodynamic optimization method on the basis of non-deterministic computational fluid dynamic (CFD) simulation and Efficient Global Optimization (EGO)algorithm was employed. A non-intrusive polynomial chaos method is used in conjunction with an existing well-verified CFD module to quantify the uncertainty propagation in the flow field. This paper investigates the roughness modeling behavior with the -Ret shear stress transport model including modeling flow transition and surface roughness effects. The roughness effects are modeled to simulate sand grain roughness. A Class-Shape Transformation-based parametrical description of the nacelle contour as part of an automatic design evaluation process is presented. A Design-of-Experiments (DoE) was performed and surrogate model by Kriging method was built. The new design nacelle process demonstrates that significant improvements of both mean and variance of the efficiency are achieved and the proposed method can be applied to laminar flow nacelle design successfully. [ABSTRACT FROM AUTHOR]

In this paper, a CMOS active down-conversion mixer is presented for wideband applications. Specifically, a LO generation chain is suggested to convert AC LO signal to shaped trapezoid burst, which reduces the sinusoidal LO power level requirement by the mixer. The current-reuse technique by stacked nMOS/ pMOS architecture is used to save the power consumption of the circuit. Moreover, this complementary configuration is also employed to compensate second-order nonlinearity of the circuit. Implemented in a 0.18-m CMOS process, post-simulations show that, driven by only −10 dBm sinusoidal LO signal, the proposed inductorless mixer provides a maximal conversion gain of 15.7 dB and a noise figure (NF) of 9.1-12 dB across RF input frequency range 0.5-1.6 GHz. The IIP3 and IP1dB of 3.5 dBm and −4.8 dBm are obtained, respectively. The mixer core only consumes 3.6 mW from a 1.8-V supply. [ABSTRACT FROM AUTHOR]

In recent years, neutral-type differential-difference equations have been applied extensively in the field of engineering, and their dynamical behaviors are more complex than that of the delay differential-difference equations. In this paper, the equations used to describe a neutral-type neural network system of differential difference equation with two delays are studied (i.e. neutral-type differential equations). Firstly, by selecting τ1, τ2 respectively as a parameter, we provide an analysis about the local stability of the zero equilibrium point of the equations, and sufficient conditions of asymptotic stability for the system are derived. Secondly, by using the theory of normal form and applying the theorem of center manifold introduced by Hassard et al., the Hopf bifurcation is found and some formulas for deciding the stability of periodic solutions and the direction of Hopf bifurcation are given. Moreover, by applying the theorem of global Hopf bifurcation, the existence of global periodic solution of the system is studied. Finally, an example is given, and some computer numerical simulations are taken to demonstrate and certify the correctness of the presented results. [ABSTRACT FROM AUTHOR]

The variable speed limit (VSL) is a kind of active traffic management method. Most of the strategies are used in the expressway traffic flow control in order to ensure traffic safety. However, the urban expressway system is the main artery, carrying most traffic pressure. It has similar traffic characteristics with the expressways between cities. In this paper, the improved link transmission model (LTM) combined with VSL strategies is proposed, based on the urban expressway network. The model can simulate the movement of the vehicles and the shock wave, and well balance the relationship between the amount of calculation and accuracy. Furthermore, the optimal VSL strategy can be proposed based on the simulation method. It can provide management strategies for managers. Finally, a simple example is given to illustrate the model and method. The selected indexes are the average density, the average speed and the average flow on the traffic network in the simulation. The simulation results show that the proposed model and method are feasible. The VSL strategy can effectively alleviate traffic congestion in some cases, and greatly promote the efficiency of the transportation system. [ABSTRACT FROM AUTHOR]

Because of the difference in vehicle type or driving skill, the driving strategy is not exactly the same. The driving speeds of the different vehicles may be different for the same headway. Since the optimal velocity function is just determined by the safety distance besides the maximum velocity and headway, an extended car-following model accounting for random safety distance with different probabilities is proposed in this paper. The linear stable condition for this extended traffic model is obtained by using linear stability theory. Numerical simulations are carried out to explore the complex phenomenon resulting from multiple safety distance in the optimal velocity function. The cases of multiple types of safety distances selected with different probabilities are presented. Numerical results show that the traffic flow with multiple safety distances with different probabilities will be more unstable than that with single type of safety distance, and will result in more stop-and-go phenomena. [ABSTRACT FROM AUTHOR]

Polarization is a property of transverse waves that specify the geometrical orientation of the oscillations, and it is of significant importance to control the polarization of waves at the information storage and processing. In this paper, we propose a new type of polarization conversion metasurface based on the -shaped structure in reflection mode. An ultrawideband cross-polarization conversion is obtained. The simulated results show that this metasurface can rotate the polarized direction of the linearly polarized electromagnetic wave by 90 and the polarization conversion efficiency reaches up to 90% in the ultrawideband from 6.9 GHz to 22.2 GHz. The relative bandwidth is 105%. In addition, the experimental results of polarization conversion efficiency are in good agreement with the simulations. With the advantages of high conversion efficiency, ultrawide operating band and the simple geometric structure, the application of this polarization conversion metasurface structure can be extended to the frequency range of terahertz or even the visible light. [ABSTRACT FROM AUTHOR]

Considering the effect of headway changes with memory, an improved continuum model of traffic flow is proposed in this paper. By means of linear stability theory, the new model's linear stability with the effect of headway changes with memory is obtained. Through nonlinear analysis, the KdV-Burgers equation is derived to describe the propagating behavior of traffic density wave near the neutral stability line. Numerical simulation is carried out to study the improved traffic flow model, which explores how the headway changes with memory affected each car's velocity, density and energy consumption. Numerical results show that when considering the effects of headway changes with memory, the traffic jams can be suppressed efficiently. Furthermore, research results demonstrate that the effect of headway changes with memory can avoid the disadvantage of historical information, which will improve the stability of traffic flow and minimize car energy consumption. [ABSTRACT FROM AUTHOR]

Based on the two velocity difference model (TVDM), an extended car-following model is developed to investigate the effect of driver's memory and jerk on traffic flow in this paper. By using linear stability analysis, the stability conditions are derived. And through nonlinear analysis, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are obtained, respectively. The mKdV equation is constructed to describe the traffic behavior near the critical point. The evolution of traffic congestion and the corresponding energy consumption are discussed. Numerical simulations show that the improved model is found not only to enhance the stability of traffic flow, but also to depress the energy consumption, which are consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

We investigate through numerical simulation the anomalous reflection (AR) of acoustic waves with perfect phononic crystals (PCs). Broadband AR is observed in a wide angle for the oblique incidence. The AR is due to the unsymmetrical specific acoustic impedance (SAI) profile along the surface, which is caused by the high frequency incidence. The findings in this paper complement the theories for the AR of acoustic waves with PCs, and may find applications in acoustic engineerings. [ABSTRACT FROM AUTHOR]

This paper investigates the finite-time synchronization of complex networks (CNs) with non-identical nodes and impulsive disturbances. By utilizing stability theories, new 1-norm-based analytical techniques and suitable comparison, systems, several sufficient conditions are obtained to realize the synchronization goal in finite time. State feedback controllers with and without the sign function are designed. Results show that the controllers with sign function can reduce the conservativeness of control gains and the controllers without sign function can overcome the chattering phenomenon. Numerical simulations are offered to verify the effectiveness of the theoretical analysis. [ABSTRACT FROM AUTHOR]