Narrow Results

We study the adaptive behavior of a computational ecosystem in the presence of time-periodic resource utilities as seen, for example in the day-night load variations of computer use and in the price fluctuations of seasonal products. We do so within the context of the Huberman-Hogg model of such systems. The dynamics is studied for the cases of competitive and cooperative payoff functions with time-modulated resource utilities, and the system’s adaptability is measured by tracking its performance in response to a time-varying environment,

A detail study on the in-degree distribution (ID) of cellular automata is obtained by exact enumeration. The results indicate large deviation from multi-scaling and classification according to various IDs are discussed. We further augment the transfer matrix such that the distributions for more complicated rules are obtained. Dependence of ID on the lattice size have also been found for some rules including R50 and R77.

Dynamic characteristics and sensitivity analysis of a tubular pump unit during starting process are proposed in this paper. A dynamic model of the pump unit, suitable for describing its transient characteristics during starting process, is established by using rigid body dynamics, fluid dynamics and hydraulic theory. The extended Fourier amplitude sensitivity test (EFAST) analysis method is used to investigate the influence of unit parameters on system outputs. Simulation of the pump unit is carried out for the starting process to verify the sensitivity analysis and explore the dynamic characteristics of the pump unit. The dynamic responses of the system parameter (rotating speed, flow and head) are revealed by the start-up simulation. Research results provide theoretical guidance for the rational design and safe operation of tubular pump stations.

In this paper, a numerical procedure is presented for the dynamic analysis of elastic cables subjected to turbulent wind excitation in quasi-steady conditions. The proposed methodology, which takes geometrical and aerodynamic non-linearities into account, is based on artificial simulation of turbulence, on finite-element modeling of the cables and on a step-by-step implicit procedure for the integration of the dynamic equilibrium equations. As a first application, the dynamic behaviour of a cable in 1 : 2 internal resonance conditions is studied, focusing on some aspects of the influence of wind turbulence on galloping oscillations.

This study proposes an approach to set up a continuum full bridge model with spatially inclined cables based on the Hamilton principle. The dynamic governing functions, considering the geometric non-linearities of cables and deck, represent simultaneously the vertical motion of deck and vertical–horizontal motion of cable. With the comparison of the modal properties obtained from the model to those from the accurate model, results show that the proposed model is capable of accurately simulating the modal properties. The primary resonance responses and corresponding frequency-response curves are obtained through the multiple-scale-method. A finite element (FE) model is established, and the corresponding non-linear dynamic analysis in time domain is conducted. Comparing the results from two models, it can be checked that the proposed model is reliable. According to the results of the proposed model, it is found that the second-order shape functions (SOSFs) play a significant role in the system response. Once the non-linear vibration of the bridge becomes significant only considering the excited mode with using the classical Galerkin decomposition cannot correctly predict the structure response. The SOSFs can be classified into stationary and vibrating components. The vibrating component can deviate the time-series of response from the harmonic wave, and the stationary component directly determines the mean value of the time-series.

This work is a theoretical study of fronts propagating into an uniaxial ferromagnetic medium with velocity v, when the magnetization, M, is driven by a DC applied magnetic field, H₀, from the demagnetized to the magnetized state. It is assumed that the dynamics of M is govern by the Landau–Lifshitz–Gilbert equation (LLGE). We also consider an effective field that includes in-plane uniaxial, H_U, and shape anisotropy fields, H_D. We show that, in the particular case of uniformly translating profiles, this equation reduces to a damped-forced Duffing's equation, with a family of solutions that describe periodic oscillating (PO), damped oscillating (DO) or exponential front profiles (EF). Of particular interest is the existence of a critical speed, v₀, below which there are no stable states for the magnetization. When the velocity of the profile exactly equals v_osc, the only stable states are the PO profiles. Above v_osc, there is an asymptotic speed, v*, that separates the DO profiles from EF profiles. This velocity (v*) is connected with the existence of a non-linear marginal stability point for front propagation. Both v₀ and v* depend on the applied field and on the anisotropy constants of the material. A stability diagram for front propagation and magnetization curves are also calculated.

Modal discretization is commonly applied for dynamic analysis of non-linear continuum system. Considering the possible coupling effect between modes is necessary to obtain accurate results. In this case, the system may become increasingly complex, as the number of adopted modes can be a lot. Such complexity will lead to the difficulty of solution finding. This paper proposes a generic technique to simplify the governing functions by making non-linear stiffness matrix symmetric. The symmetric non-linear stiffness matrix is constructed by utilizing the mode shape vectors. The proposed procedure can theoretically guarantee non-linear stiffness matrix symmetric. The incremental harmonic balance (IHB) method is served as the main tool for finding solutions of systems. Dynamic analysis of axially moving beam and generalized suspension bridge are presented in this study for illustration. Results proved that the neighboring modes are critical during the resonance of target mode, which suggests the necessity of including sufficient modes for non-linear dynamic analysis. By applying the proposed technique, it is found that calculating time of IHB method can greatly shortened, especially for the case included modes becomes large. Results show that the time consumption with using the proposed method can be half of that not using it, when more than 5 modes are considered in the calculation.

The advent of multiple electrode recording, dense arrays and mathematical techniques such as non-linear dynamics has invigorated brain electrical recording techniques. Taking advantage of the excellent temporal resolution of the EEG, this summary review details several innovations, concentrating on (1) the rapid changes in electrical activity and a consequent stable complex pattern; and (2) the utilization of engineering techniques that have been applied across scales ranging upward from quantum physics. The implications for brain localization and for communication science are developed.

In single-step two-stage algorithms for the approximate solution of the equations of dynamic equilibrium, the displacement and velocity of nodes at the end of a time step are expressed in terms of the values at the beginning of the time step using an amplification matrix. In this paper, a new form of the exact amplification matrix for SDOF problems is presented and some interesting properties are noted. A new family of algorithms using any order of polynomial approximation and incorporating these properties is then discussed. The algorithms are unconditionally stable, and incorporate algorithmic damping. The algorithms are then successfully used in the analysis of Bathe's pendulum.

Galaxies are argued to manifest complexity, thereby contradicting models of smooth parametric galactic phase space densities. An estimation of chaos in models of our galaxy is forwarded to suggest strength and possible causes of non-linearities in phase space. A Bayesian nonparametric methodology that is designed to acknowledge uncertainties in measured data, when applied to an observed external galaxy, indicates a non-linear galactic phase space density that could result from a bistable system potential. The effect of such a phase space structure on the inverse modelling of phase space data is discussed.

Mountain highways are restricted by the comprehensive effect of road alignment, longitudinal slope and complex road conditions, which results in a larger accident rate. This article firstly studies the road alignment of mountain highways and attributes of random interference factors, and analyzes the laws of traffic flows in mountain highways. Then by incorporating the impacts of environment factors of mountain highways into the traditional car following model, it puts forward a nonlinear car-following model on the basis of nonlinear dynamics principles. The results conducted on VISSIM proved the correctness and practicability of the newly-established model. This study has provided theoretical support for traffic safety in mountain highways.