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Sample records for supercritical hopf bifurcation

  1. Supercritical as well as subcritical Hopf bifurcation in nonlinear flutter systems

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Hopf bifurcations of an airfoil flutter system with a cubic nonlinearity are investigated,with the flow speed as the bifurcation parameter.The center manifold theory and complex normal form method are used to obtain the bifurcation equation.Interestingly,for a certain linear pitching stiffness the Hopf bifurcation is both supercritical and subcritical.It is found,mathematically,this is caused by the fact that one coefficient in the bifurcation equation does not contain the first power of the bifurcation parameter.The solutions of the bifurcation equation are validated by the equivalent linearization method and incremental harmonic balance method.

  2. Pushing amplitude equations far from threshold: application to the supercritical Hopf bifurcation in the cylinder wake

    Science.gov (United States)

    Gallaire, Francois; Boujo, Edouard; Mantic-Lugo, Vladislav; Arratia, Cristobal; Thiria, Benjamin; Meliga, Philippe

    2016-12-01

    The purpose of this review article is to push amplitude equations as far as possible from threshold. We focus on the Stuart-Landau amplitude equation describing the supercritical Hopf bifurcation of the flow in the wake of a cylinder for critical Reynolds number {{Re}}{{c}} ≈ 46. After having reviewed Stuart's weakly nonlinear multiple-scale expansion method, we first demonstrate the crucial importance of the choice of the critical parameter. For the wake behind a cylinder considered in this paper, choosing {ɛ }2={{Re}}{{c}}-1-{{Re}}-1 instead of ɛ {\\prime }2=\\tfrac{{Re}-{{Re}}{{c}}}{{{Re}}{{c}}2} considerably improves the prediction of the Landau equation. Although Sipp and Lebedev (2007 J. Fluid Mech 593 333-58) correctly identified the adequate bifurcation parameter ɛ, they have plotted their results adding an additional linearization, which amounts to using ɛ \\prime as approximation to ɛ. We then illustrate the risks of calculating ‘running’ Landau constants by projection formulas at arbitrary values of the control parameter. For the cylinder wake case, this scheme breaks down and diverges close to {Re} ≈ 100. We propose an interpretation based on the progressive loss of the non-resonant compatibility condition, which is the cornerstone of Stuart's multiple-scale expansion method. We then briefly review a self-consistent model recently introduced in the literature and demonstrate a link between its properties and the above-mentioned failure.

  3. Continuum Hamiltonian Hopf Bifurcation II

    CERN Document Server

    Hagstrom, G I

    2013-01-01

    Building on the development of [MOR13], bifurcation of unstable modes that emerge from continuous spectra in a class of infinite-dimensional noncanonical Hamiltonian systems is investigated. Of main interest is a bifurcation termed the continuum Hamiltonian Hopf (CHH) bifurcation, which is an infinite-dimensional analog of the usual Hamiltonian Hopf (HH) bifurcation. Necessary notions pertaining to spectra, structural stability, signature of the continuous spectra, and normal forms are described. The theory developed is applicable to a wide class of 2+1 noncanonical Hamiltonian matter models, but the specific example of the Vlasov-Poisson system linearized about homogeneous (spatially independent) equilibria is treated in detail. For this example, structural (in)stability is established in an appropriate functional analytic setting, and two kinds of bifurcations are considered, one at infinite and one at finite wavenumber. After defining and describing the notion of dynamical accessibility, Kre\\u{i}n-like the...

  4. Controlling hopf bifurcations: Discrete-time systems

    Directory of Open Access Journals (Sweden)

    Guanrong Chen

    2000-01-01

    Full Text Available Bifurcation control has attracted increasing attention in recent years. A simple and unified state-feedback methodology is developed in this paper for Hopf bifurcation control for discrete-time systems. The control task can be either shifting an existing Hopf bifurcation or creating a new Hopf bifurcation. Some computer simulations are included to illustrate the methodology and to verify the theoretical results.

  5. Subcritical Hopf bifurcations in low-density jets

    Science.gov (United States)

    Zhu, Yuanhang; Gupta, Vikrant; Li, Larry K. B.

    2016-11-01

    Low-density jets are known to bifurcate from a steady state (a fixed point) to self-excited oscillations (a periodic limit cycle) when the Reynolds number increases above a critical value corresponding to the Hopf point, ReH . In the literature, this Hopf bifurcation is often considered to be supercritical because the self-excited oscillations appear only when Re > ReH . However, we find that under some conditions, there exists a hysteretic bistable region at ReSN ReSN denotes a saddle-node bifurcation point. This shows that the Hopf bifurcation can also be subcritical, which has three main implications. First, low-density jets could be triggered into self-excited oscillations even when Re < ReH . Second, in the modeling of low-density jets, the subcritical or supercritical nature of the Hopf bifurcation should be taken into account because the former is caused by cubic nonlinearity whereas the latter is caused by square nonlinearity. Third, the response of the system to external forcing and noise depends on its proximity to the bistable region. Therefore, when investigating the forced response of low-density jets, it is important to consider whether the Hopf bifurcation is subcritical or supercritical.

  6. NUMERICAL HOPF BIFURCATION OF DELAY-DIFFERENTIAL EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper we consider the numerical solution of some delay differential equations undergoing a Hopf bifurcation. We prove that if the delay differential equations have a Hopf bifurcation point atλ=λ*, then the numerical solution of the equation also has a Hopf bifurcation point atλh =λ* + O(h).

  7. Hopf Bifurcation in a Nonlinear Wave System

    Institute of Scientific and Technical Information of China (English)

    HE Kai-Fen

    2004-01-01

    @@ Bifurcation behaviour of a nonlinear wave system is studied by utilizing the data in solving the nonlinear wave equation. By shifting to the steady wave frame and taking into account the Doppler effect, the nonlinear wave can be transformed into a set of coupled oscillators with its (stable or unstable) steady wave as the fixed point.It is found that in the chosen parameter regime, both mode amplitudes and phases of the wave can bifurcate to limit cycles attributed to the Hopf instability. It is emphasized that the investigation is carried out in a pure nonlinear wave framework, and the method can be used for the further exploring routes to turbulence.

  8. Diffusion-driven instability and Hopf bifurcation in Brusselator system

    Institute of Scientific and Technical Information of China (English)

    LI Bo; WANG Ming-xin

    2008-01-01

    The Hopf bifurcation for the Brusselator ordinary-differential-equation (ODE)model and the corresponding partial-differential-equation(PDE)model are investigated by using the Hopf bifurcation theorem.The stability of the Hopf bifurcation periodic solution is di8cu88ed by applying the normal form theory and the center manifold theorem.When parameters satisfy some conditions,the spatial homogenous equilibrium solution and the spatial homogenous periodic solution become unstable.Our results show that if parameters are properly chosen,Hopf bifurcation does not occur for the ODE system,but occurs for the PDE system.

  9. A model for the nonautonomous Hopf bifurcation

    Science.gov (United States)

    Anagnostopoulou, V.; Jäger, T.; Keller, G.

    2015-07-01

    Inspired by an example of Grebogi et al (1984 Physica D 13 261-8), we study a class of model systems which exhibit the full two-step scenario for the nonautonomous Hopf bifurcation, as proposed by Arnold (1998 Random Dynamical Systems (Berlin: Springer)). The specific structure of these models allows a rigorous and thorough analysis of the bifurcation pattern. In particular, we show the existence of an invariant ‘generalised torus’ splitting off a previously stable central manifold after the second bifurcation point. The scenario is described in two different settings. First, we consider deterministically forced models, which can be treated as continuous skew product systems on a compact product space. Secondly, we treat randomly forced systems, which lead to skew products over a measure-preserving base transformation. In the random case, a semiuniform ergodic theorem for random dynamical systems is required, to make up for the lack of compactness.

  10. Hopf Bifurcations of a Chemostat System with Bi-parameters

    Institute of Scientific and Technical Information of China (English)

    李晓月; 千美华; 杨建平; 黄启昌

    2004-01-01

    We study a chemostat system with two parameters, S0-initial density and D-flow-speed of the solution. At first, a generalization of the traditional Hopf bifurcation theorem is given. Then, an existence theorem for the Hopf bifurcation of the chemostat system is presented.

  11. Hopf bifurcation for tumor-immune competition systems with delay

    Directory of Open Access Journals (Sweden)

    Ping Bi

    2014-01-01

    Full Text Available In this article, a immune response system with delay is considered, which consists of two-dimensional nonlinear differential equations. The main purpose of this paper is to explore the Hopf bifurcation of a immune response system with delay. The general formula of the direction, the estimation formula of period and stability of bifurcated periodic solution are also given. Especially, the conditions of the global existence of periodic solutions bifurcating from Hopf bifurcations are given. Numerical simulations are carried out to illustrate the the theoretical analysis and the obtained results.

  12. Oscillatory Activities in Regulatory Biological Networks and Hopf Bifurcation

    Institute of Scientific and Technical Information of China (English)

    YAN Shi-Wei; WANG Qi; XIE Bai-Song; ZHANG Feng-Shou

    2007-01-01

    Exploiting the nonlinear dynamics in the negative feedback loop, we propose a statistical signal-response model to describe the different oscillatory behaviour in a biological network motif. By choosing the delay as a bifurcation parameter, we discuss the existence of Hopf bifurcation and the stability of the periodic solutions of model equations with the centre manifold theorem and the normal form theory. It is shown that a periodic solution is born in a Hopf bifurcation beyond a critical time delay, and thus the bifurcation phenomenon may be important to elucidate the mechanism of oscillatory activities in regulatory biological networks.

  13. Calculation of Coefficients of Simplest Normal Forms of Hopf and Generalized Hopf Bifurcations

    Institute of Scientific and Technical Information of China (English)

    TIAN Ruilan; ZHANG Qichang; HE Xuejun

    2007-01-01

    The coefficients of the simplest normal forms of both high-dimensional generalized Hopf and high-dimensional Hopf bifurcation systems were discussed using the adjoint operator method. A particular nonlinear scaling and an inner product were introduced in the space of homogeneous poiynomials. Theorems were established for the explicit expression of the simplest normal forms in terms of the coefficients of both the conventional normal forms of Hopf and generalized Hopf bifurcation systems. A symbolic manipulation was designed to perform the calculation of the coefficients of the simplest normal forms using Mathematica. The original ordinary differential equation was required in the input and the simplest normal form could be obtained as the output. Finally, the simplest normal forms of 6-dimensional generalized Hopf singularity of type 2 and 5-dimensional Hopf bifurcation system were discussed by executing the program. The output showed that the 5th- and 9th-order terms remained in 6-dimensional generalized Hopf singularity of type 2 and the 3rd- and 5th-order terms remained in 5-dimensional Hopf bifurcation system.

  14. Views on the Hopf bifurcation with respect to voltage instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Roa-Sepulveda, C.A. [Universidad de Concepcion, Concepcion (Chile). Dept. de Ingenieria Electrica; Knight, U.G. [Imperial Coll. of Science and Technology, London (United Kingdom). Dept. of Electrical and Electronic Engineering

    1994-12-31

    This paper presents a sensitivity study of the Hopf bifurcation phenomenon which can in theory appear in power systems, with reference to the dynamics of the process and the impact of demand characteristics. Conclusions are drawn regarding power levels at which these bifurcations could appear and concern the concept of the imaginary axis as a `hard` limit eigenvalue analyses. (author) 20 refs., 31 figs.

  15. Delay Induced Hopf Bifurcation of Small-World Networks

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, the stability and the Hopf bifurcation of small-world networks with time delay are studied. By analyzing the change of delay, we obtain several sufficient conditions on stable and unstable properties. When the delay passes a critical value, a Hopf bifurcation may appear. Furthermore, the direction and the stability of bifurcating periodic solutions are investigated by the normal form theory and the center manifold reduction. At last, by numerical simulations, we further illustrate the effectiveness of theorems in this paper.

  16. Adaptive Control of Electromagnetic Suspension System by HOPF Bifurcation

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    Aming Hao

    2013-01-01

    Full Text Available EMS-type maglev system is essentially nonlinear and unstable. It is complicated to design a stable controller for maglev system which is under large-scale disturbance and parameter variance. Theory analysis expresses that this phenomenon corresponds to a HOPF bifurcation in mathematical model. An adaptive control law which adjusts the PID control parameters is given in this paper according to HOPF bifurcation theory. Through identification of the levitated mass, the controller adjusts the feedback coefficient to make the system far from the HOPF bifurcation point and maintain the stability of the maglev system. Simulation result indicates that adjusting proportion gain parameter using this method can extend the state stability range of maglev system and avoid the self-excited vibration efficiently.

  17. On noise induced Poincaré-Andronov-Hopf bifurcation.

    Science.gov (United States)

    Samanta, Himadri S; Bhattacharjee, Jayanta K; Bhattacharyay, Arijit; Chakraborty, Sagar

    2014-12-01

    It has been numerically seen that noise introduces stable well-defined oscillatory state in a system with unstable limit cycles resulting from subcritical Poincaré-Andronov-Hopf (or simply Hopf) bifurcation. This phenomenon is analogous to the well known stochastic resonance in the sense that it effectively converts noise into useful energy. Herein, we clearly explain how noise induced imperfection in the bifurcation is a generic reason for such a phenomenon to occur and provide explicit analytical calculations in order to explain the typical square-root dependence of the oscillations' amplitude on the noise level below a certain threshold value. Also, we argue that the noise can bring forth oscillations in average sense even in the absence of a limit cycle. Thus, we bring forward the inherent general mechanism of the noise induced Hopf bifurcation naturally realisable across disciplines.

  18. On noise induced Poincaré–Andronov–Hopf bifurcation

    Energy Technology Data Exchange (ETDEWEB)

    Samanta, Himadri S., E-mail: hss@umd.edu [Biophysics Program, Institute For Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Bhattacharjee, Jayanta K., E-mail: director@hri.res.in [Harish-Chandra Research Institute, Allahabad (India); Bhattacharyay, Arijit, E-mail: a.bhattacharyay@iiserpune.ac.in [Indian Institute of Science Education and Research, Pune (India); Chakraborty, Sagar, E-mail: sagarc@iitk.ac.in [Department of Physics, Indian Institute of Technology Kanpur, Uttar Pradesh 208016 (India); Mechanics and Applied Mathematics Group, Indian Institute of Technology Kanpur, Uttar Pradesh 208016 (India)

    2014-12-01

    It has been numerically seen that noise introduces stable well-defined oscillatory state in a system with unstable limit cycles resulting from subcritical Poincaré–Andronov–Hopf (or simply Hopf) bifurcation. This phenomenon is analogous to the well known stochastic resonance in the sense that it effectively converts noise into useful energy. Herein, we clearly explain how noise induced imperfection in the bifurcation is a generic reason for such a phenomenon to occur and provide explicit analytical calculations in order to explain the typical square-root dependence of the oscillations' amplitude on the noise level below a certain threshold value. Also, we argue that the noise can bring forth oscillations in average sense even in the absence of a limit cycle. Thus, we bring forward the inherent general mechanism of the noise induced Hopf bifurcation naturally realisable across disciplines.

  19. DINÁMICA DE LA BIFURCACIÓN DE HOPF EN UNA CLASE DE MODELOS DE COMPETENCIA QUE EXHIBEN LA BIFURCACIÓN ZIP Hopf Bifurcation Dynamic in a Class of Competence Model Exhibiting Zip Bifurcation

    Directory of Open Access Journals (Sweden)

    Carlos Mario Escobar Callejas

    2011-12-01

    Full Text Available En el presente artículo de investigación se caracteriza el tipo de bifurcación de Hopf que se presenta en el fenómeno de la bifurcación de zip para un sistema tridimensional no lineal de ecuaciones diferenciales que satisface las condiciones planteadas por Butler y Farkas, las cuales modelan la competición de dos especies predadoras por una presa singular que se regenera. Se demuestra que en todas las variedades bidimensionales invariantes del sistema considerado se desarrolla una bifurcación de Hopf supercrítica lo cual es una extensión de algunos resultados sobre el tipo de bifurcación de Hopf que se forma en el fenómeno de la bifurcación de zip en sistema con respuesta funcional del predador del tipo Holling II, [1].This research article characterizes the type of Hopf bifurcation occurring in the Zip bifurcation phenomenon for a non-linear 3D system of differential equations which meets the conditions stated by Butler and Farkas to model competition of two predators struggling for a prey. It is shown that a supercritical Hopf bifurcation is developed in all invariant two-dimensional varieties of the system considered, which is an extension of some results about the kind of Hopf bifurcation which is formed in the Zip bifurcation phenomenon in a system with functional response of the Holling-type predator.

  20. An Approach to Robust Control of the Hopf Bifurcation

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    Giacomo Innocenti

    2011-01-01

    Full Text Available The paper illustrates a novel approach to modify the Hopf bifurcation nature via a nonlinear state feedback control, which leaves the equilibrium properties unchanged. This result is achieved by recurring to linear and nonlinear transformations, which lead the system to locally assume the ordinary differential equation representation. Third-order models are considered, since they can be seen as proper representatives of a larger class of systems. The explicit relationship between the control input and the Hopf bifurcation nature is obtained via a frequency approach, that does not need the computation of the center manifold.

  1. STOCHASTIC HOPF BIFURCATION IN QUASI-INTEGRABLE-HAMILTONIAN SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    GAN Chunbiao

    2004-01-01

    A new procedure is developed to study the stochastic Hopf bifurcation in quasiintegrable-Hamiltonian systems under the Gaussian white noise excitation. Firstly, the singular boundaries of the first-class and their asymptotic stable conditions in probability are given for the averaged Ito differential equations about all the sub-system's energy levels with respect to the stochastic averaging method. Secondly, the stochastic Hopf bifurcation for the coupled sub-systems are discussed by defining a suitable bounded torus region in the space of the energy levels and employing the theory of the torus region when the singular boundaries turn into the unstable ones. Lastly, a quasi-integrableHamiltonian system with two degrees of freedom is studied in detail to illustrate the above procedure.Moreover, simulations by the Monte-Carlo method are performed for the illustrative example to verify the proposed procedure. It is shown that the attenuation motions and the stochastic Hopf bifurcation of two oscillators and the stochastic Hopf bifurcation of a single oscillator may occur in the system for some system's parameters. Therefore, one can see that the numerical results are consistent with the theoretical predictions.

  2. Hopf and Generalized Hopf Bifurcations in a Recurrent Autoimmune Disease Model

    Science.gov (United States)

    Zhang, Wenjing; Yu, Pei

    This paper is concerned with bifurcation and stability in an autoimmune model, which was established to study an important phenomenon — blips arising from such models. This model has two equilibrium solutions, disease-free equilibrium and disease equilibrium. The positivity of the solutions of the model and the global stability of the disease-free equilibrium have been proved. In this paper, we particularly focus on Hopf bifurcation which occurs from the disease equilibrium. We present a detailed study on the use of center manifold theory and normal form theory, and derive the normal form associated with Hopf bifurcation, from which the approximate amplitude of the bifurcating limit cycles and their stability conditions are obtained. Particular attention is also paid to the bifurcation of multiple limit cycles arising from generalized Hopf bifurcation, which may yield bistable phenomenon involving equilibrium and oscillating motion. This result may explain some complex dynamical behavior in real biological systems. Numerical simulations are compared with the analytical predictions to show a very good agreement.

  3. An explicit example of Hopf bifurcation in fluid mechanics

    Science.gov (United States)

    Kloeden, P.; Wells, R.

    1983-01-01

    It is observed that a complete and explicit example of Hopf bifurcation appears not to be known in fluid mechanics. Such an example is presented for the rotating Benard problem with free boundary conditions on the upper and lower faces, and horizontally periodic solutions. Normal modes are found for the linearization, and the Veronis computation of the wave numbers is modified to take into account the imposed horizontal periodicity. An invariant subspace of the phase space is found in which the hypotheses of the Joseph-Sattinger theorem are verified, thus demonstrating the Hopf bifurcation. The criticality calculations are carried through to demonstrate rigorously, that the bifurcation is subcritical for certain cases, and to demonstrate numerically that it is subcritical for all the cases in the paper.

  4. Stability and Hopf bifurcation in a symmetric Lotka-Volterra predator-prey system with delays

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    Jing Xia

    2013-01-01

    Full Text Available This article concerns a symmetrical Lotka-Volterra predator-prey system with delays. By analyzing the associated characteristic equation of the original system at the positive equilibrium and choosing the delay as the bifurcation parameter, the local stability and Hopf bifurcation of the system are investigated. Using the normal form theory, we also establish the direction and stability of the Hopf bifurcation. Numerical simulations suggest an existence of Hopf bifurcation near a critical value of time delay.

  5. Model Reduction of Nonlinear Aeroelastic Systems Experiencing Hopf Bifurcation

    KAUST Repository

    Abdelkefi, Abdessattar

    2013-06-18

    In this paper, we employ the normal form to derive a reduced - order model that reproduces nonlinear dynamical behavior of aeroelastic systems that undergo Hopf bifurcation. As an example, we consider a rigid two - dimensional airfoil that is supported by nonlinear springs in the pitch and plunge directions and subjected to nonlinear aerodynamic loads. We apply the center manifold theorem on the governing equations to derive its normal form that constitutes a simplified representation of the aeroelastic sys tem near flutter onset (manifestation of Hopf bifurcation). Then, we use the normal form to identify a self - excited oscillator governed by a time - delay ordinary differential equation that approximates the dynamical behavior while reducing the dimension of the original system. Results obtained from this oscillator show a great capability to predict properly limit cycle oscillations that take place beyond and above flutter as compared with the original aeroelastic system.

  6. Stability and Hopf Bifurcation of a Predator-Prey Model with Distributed Delays and Competition Term

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    Lv-Zhou Zheng

    2014-01-01

    Full Text Available A class of predator-prey system with distributed delays and competition term is considered. By considering the time delay as bifurcation parameter, we analyze the stability and the Hopf bifurcation of the predator-prey system. According to the theorem of Hopf bifurcation, some sufficient conditions are obtained for the local stability of the positive equilibrium point.

  7. Hopf Bifurcation of a Differential-Algebraic Bioeconomic Model with Time Delay

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    Xiaojian Zhou

    2012-01-01

    Full Text Available We investigate the dynamics of a differential-algebraic bioeconomic model with two time delays. Regarding time delay as a bifurcation parameter, we show that a sequence of Hopf bifurcations occur at the positive equilibrium as the delay increases. Using the theories of normal form and center manifold, we also give the explicit algorithm for determining the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions. Numerical tests are provided to verify our theoretical analysis.

  8. Limit cycles and Hopf bifurcations in a Kolmogorov type system

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    Simona Muratori

    1989-04-01

    Full Text Available The paper is devoted to the study of a class of Kolmogorov type systems which can be used to represent the dynamic behaviour of prey and predators. The model is an extension of the classical prey-predator model since it allows intra-specific competition for the predator's species. The analysis shows that the system can only have Kolmogorov's two modes of behaviour: a globally stable equilibrium or a globally stable limit cycle. Moreover, the transition from one of these two modes to the other is a non-catastrophic Hopf bifurcation which can be specified analytically.

  9. Stability and Hopf Bifurcation Analysis of a Gene Expression Model with Diffusion and Time Delay

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    Yahong Peng

    2014-01-01

    Full Text Available We consider a model for gene expression with one or two time delays and diffusion. The local stability and delay-induced Hopf bifurcation are investigated. We also derive the formulas determining the direction and the stability of Hopf bifurcations by calculating the normal form on the center manifold.

  10. Hopf bifurcations in a predator-prey system with multiple delays

    Energy Technology Data Exchange (ETDEWEB)

    Hu Guangping [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China); School of Mathematics and Physics, Nanjing University of Information and Technology, Nanjing 210044 (China); Li Wantong [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China)], E-mail: wtli@lzu.edu.cn; Yan Xiangping [Department of Applied Mathematics, Lanzhou Jiaotong University, Lanzhou 730070 (China)

    2009-10-30

    This paper is concerned with a two species Lotka-Volterra predator-prey system with three discrete delays. By regarding the gestation period of two species as the bifurcation parameter, the stability of positive equilibrium and Hopf bifurcations of nonconstant periodic solutions are investigated. Furthermore, the direction of Hopf bifurcations and the stability of bifurcated periodic solutions are determined by applying the normal form theory and the center manifold reduction for functional differential equations (FDEs). In addition, the global existence of bifurcated periodic solutions are also established by employing the topological global Hopf bifurcation theorem, which shows that the local Hopf bifurcations imply the global ones after the second critical value of parameter. Finally, to verify our theoretical predictions, some numerical simulations are also included.

  11. WAMS-based monitoring and control of Hopf bifurcations in multi-machine power systems

    Institute of Scientific and Technical Information of China (English)

    Shao-bu WANG; Quan-yuan JIANG; Yi-jia CAO

    2008-01-01

    A method is proposed to monitor and control Hopf bifurcations in multi-machine power systems using the information from wide area measurement systems (WAMSs). The power method (PM) is adopted to compute the pair of conjugate eigenvalues with the algebraically largest real part and the corresponding eigenvectors of the Jacobian matrix of a power system. The distance between the current equilibrium point and the Hopf bifurcation set can be monitored dynamically by computing the pair of conjugate eigenvalues. When the current equilibrium point is close to the Hopf bifurcation set, the approximate normal vector to the Hopf bifurcation set is computed and used as a direction to regulate control parameters to avoid a Hopf bifurcation in the power system described by differential algebraic equations (DAEs). The validity of the proposed method is demonstrated by regulating the reactive power loads in a 14-bus power system.

  12. Stability and Hopf bifurcation analysis on Goodwin model with three delays

    Energy Technology Data Exchange (ETDEWEB)

    Cao Jianzhi [College of Mathematics and System Sciences, Xinjiang University, Urumqi 830046 (China); Jiang Haijun, E-mail: jianghai@xju.edu.cn [College of Mathematics and System Sciences, Xinjiang University, Urumqi 830046 (China)

    2011-08-15

    Highlights: > Stability and Hopf bifurcation on a delayed Goodwin model are studied. > The sum of the delays is chosen as the bifurcation parameter. > Hopf bifurcation would occur when the delay exceeds a critical value. > A numerical simulation is provided. - Abstract: In this paper, a class of Goodwin models with three delays is dealt. The dynamic properties including stability and Hopf bifurcations are studied. Firstly, we prove analytically that the addressed system possesses a unique positive equilibrium point. Moreover, using the Cardano's formula for the third degree algebra equation, the distribution of characteristic roots is proposed. And then, the sum of the delays is chosen as the bifurcation parameter and it is demonstrated that the Hopf bifurcation would occur when the delay exceeds a critical value. Finally, a numerical simulation for justifying the theoretical results is also provided.

  13. Global view of Hopf bifurcations of a van der Pol oscillator with delayed state feedback

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents both analytical and numerical studies on the global view of Hopf bifurcations of a van der Pol oscillator with delayed state feedback.Based on a detailed analysis of the stability switches of the trivial equilibrium of the system,the stability charts are given in a parameter space consisting of the time delay and the feedback gains.The center manifold reduc-tion and the normal form method are used to study Hopf bifurcations with respect to the time delay.To gain an insight into the persistence of a Hopf bifurcation as the time delay varies farther away from its critical value,the method of multiple scales is used to obtain the global view of Hopf bifurcations with respect to the time delay.Both the analytical results of Hopf bifurca-tions and global view of those bifurcations are validated via a collocation scheme implemented on DDE-Biftool.The most important discovery in this paper is the well-structured global view of Hopf bifurcations for the system of concern,showing the generality of the persistence of Hopf bifurcations.

  14. Stability and Hopf Bifurcation of Delayed Predator-Prey System Incorporating Harvesting

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    Fengying Wei

    2014-01-01

    Full Text Available A kind of delayed predator-prey system with harvesting is considered in this paper. The influence of harvesting and delay is investigated. Our results show that Hopf bifurcations occur as the delay τ passes through critical values. By using of normal form theory and center manifold theorem, the direction of Hopf bifurcation and the stability of the bifurcating periodic solutions are obtained. Finally, numerical simulations are given to support our theoretical predictions.

  15. LOCAL AND GLOBAL HOPF BIFURCATIONS IN A DELAYED HUMAN RESPIRATORY SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper considers a delayed human respiratory model. Firstly, the stability of the equilibrium of the model is investigated and the occurrence of a sequence of Hopf bifurcations of the model is proved. Secondly, the explicit algorithms which determine the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions are derived by applying the normal form method and the center manifold theory. Finally, the existence of the global periodic solutions is showed under some ass...

  16. Stability and Hopf Bifurcation in a Delayed SEIRS Worm Model in Computer Network

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    Zizhen Zhang

    2013-01-01

    Full Text Available A delayed SEIRS epidemic model with vertical transmission in computer network is considered. Sufficient conditions for local stability of the positive equilibrium and existence of local Hopf bifurcation are obtained by analyzing distribution of the roots of the associated characteristic equation. Furthermore, the direction of the local Hopf bifurcation and the stability of the bifurcating periodic solutions are determined by using the normal form theory and center manifold theorem. Finally, a numerical example is presented to verify the theoretical analysis.

  17. Hopf Bifurcation Control of Subsynchronous Resonance Utilizing UPFC

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    Μ. Μ. Alomari

    2017-06-01

    Full Text Available The use of a unified power flow controller (UPFC to control the bifurcations of a subsynchronous resonance (SSR in a multi-machine power system is introduced in this study. UPFC is one of the flexible AC transmission systems (FACTS where a voltage source converter (VSC is used based on gate-turn-off (GTO thyristor valve technology. Furthermore, UPFC can be used as a stabilizer by means of a power system stabilizer (PSS. The considered system is a modified version of the second system of the IEEE second benchmark model of subsynchronous resonance where the UPFC is added to its transmission line. The dynamic effects of the machine components on SSR are considered. Time domain simulations based on the complete nonlinear dynamical mathematical model are used for numerical simulations. The results in case of including UPFC are compared to the case where the transmission line is conventionally compensated (without UPFC where two Hopf bifurcations are predicted with unstable operating point at wide range of compensation levels. For UPFC systems, it is worth to mention that the operating point of the system never loses stability at all realistic compensation degrees and therefore all power system bifurcations have been eliminated.

  18. Hopf Bifurcation of a Positive Feedback Delay Differential Equation

    Institute of Scientific and Technical Information of China (English)

    陈玉明; 黄立宏

    2003-01-01

    Under some minor technical hypotheses, for each T larger than a certain Ts > 0, Krisztin, Walther and Wu showed the existence of a periodic orbit for the positive feedback delay differential equation x(t) =-Tμx(t) +Tf(x(t - 1)), where T and μ are positive constants and f : R→ R satisfies f(0) = 0 and f′ > 0 。Combining this with a unique result of Krisztin and Walther, we know that this periodic orbit is the one branched out from 0 through Hopf bifurcation. Using the normal form theory for delay differential equations, we show the same result underthe condition that f ∈ C3(R,R) is such that f″(0) = 0 and f″′(0) < 0, which is weaker than those of Krisztin and Walther。

  19. Hopf bifurcation for simple food chain model with delay

    Directory of Open Access Journals (Sweden)

    Mario Cavani

    2009-06-01

    Full Text Available In this article we consider a chemostat-like model for a simple food chain where there is a well stirred nutrient substance that serves as food for a prey population of microorganisms, which in turn, is the food for a predator population of microorganisms. The nutrient-uptake of each microorganism is of Holling type I (or Lotka-Volterra form. We show the existence of a global attractor for solutions of this system. Also we show that the positive globally asymptotically stable equilibrium point of the system undergoes a Hopf bifurcation when the dynamics of the microorganisms at the bottom of the chain depends on the history of the prey population by means of a distributed delay that takes an average of the microorganism in the middle of the chain.

  20. Clustering in Globally Coupled Oscillators Near a Hopf Bifurcation: Theory and Experiments

    CERN Document Server

    Kori, Hiroshi; Jain, Swati; Kiss, István Z; Hudson, John

    2014-01-01

    A theoretical analysis is presented to show the general occurrence of phase clusters in weakly, globally coupled oscillators close to a Hopf bifurcation. Through a reductive perturbation method, we derive the amplitude equation with a higher order correction term valid near a Hopf bifurcation point. This amplitude equation allows us to calculate analytically the phase coupling function from given limit-cycle oscillator models. Moreover, using the phase coupling function, the stability of phase clusters can be analyzed. We demonstrate our theory with the Brusselator model. Experiments are carried out to confirm the presence of phase clusters close to Hopf bifurcations with electrochemical oscillators.

  1. Hopf Bifurcation Analysis of a Predator-Prey Biological Economic System with Nonselective Harvesting

    OpenAIRE

    Biwen Li; Zhenwei Li; Boshan Chen; Gan Wang

    2015-01-01

    A modified predator-prey biological economic system with nonselective harvesting is investigated. An important mathematical feature of the system is that the economic profit on the predator-prey system is investigated from an economic perspective. By using the local parameterization method and Hopf bifurcation theorem, we analyze the Hopf bifurcation of the proposed system. In addition, the modified model enriches the database for the predator-prey biological economic system. Finally, numeric...

  2. Hopf bifurcation analysis in a dual model of Internet congestion control algorithm with communication delay

    CERN Document Server

    Ding, Dawei; Luo, Xiaoshu; Liu, Yuliang

    2007-01-01

    This paper focuses on the delay induced Hopf bifurcation in a dual model of Internet congestion control algorithms which can be modeled as a time-delay system described by a one-order delay differential equation (DDE). By choosing communication delay as the bifurcation parameter, we demonstrate that the system loses its stability and a Hopf bifurcation occurs when communication delay passes through a critical value. Moreover, the bifurcating periodic solution of system is calculated by means of perturbation methods. Discussion of stability of the periodic solutions involves the computation of Floquet exponents by considering the corresponding Poincare -Lindstedt series expansion. Finally, numerical simulations for verify the theoretical analysis are provided.

  3. Anti-Control of Hopf Bifurcation in the Chaotic Liu System with Symbolic Computation

    Institute of Scientific and Technical Information of China (English)

    LV Zhuo-Sheng; DUAN Li-Xia

    2009-01-01

    The anti-control of bifurcation refers to the task of creating a certain bifurcation with particular desired properties and location by appropriate controls. We consider, via feedback control and symbolic computation, the problem of anti-control of Hopf bifurcation in the chaotic Liu system. We propose an anti-control scheme and show that compared with the uncontrolled system, the anti-controlled Liu system can exhibit Hopf bifurcation in a much larger parameter region. The anti-control strategy used keeps the equilibrium structure of the Liu system and can be applied to generate Hopf bifurcation at the desired location with preferred stability. We illustrate the efficiency of the anti-control approach under different operating conditions.

  4. Undamped Oscillations Generated by Hopf Bifurcations in Fractional-Order Recurrent Neural Networks With Caputo Derivative.

    Science.gov (United States)

    Xiao, Min; Zheng, Wei Xing; Jiang, Guoping; Cao, Jinde

    2015-12-01

    In this paper, a fractional-order recurrent neural network is proposed and several topics related to the dynamics of such a network are investigated, such as the stability, Hopf bifurcations, and undamped oscillations. The stability domain of the trivial steady state is completely characterized with respect to network parameters and orders of the commensurate-order neural network. Based on the stability analysis, the critical values of the fractional order are identified, where Hopf bifurcations occur and a family of oscillations bifurcate from the trivial steady state. Then, the parametric range of undamped oscillations is also estimated and the frequency and amplitude of oscillations are determined analytically and numerically for such commensurate-order networks. Meanwhile, it is shown that the incommensurate-order neural network can also exhibit a Hopf bifurcation as the network parameter passes through a critical value which can be determined exactly. The frequency and amplitude of bifurcated oscillations are determined.

  5. HOPF BIFURCATION AND CHAOS OF FINANCIAL SYSTEM ON CONDITION OF SPECIFIC COMBINATION OF PARAMETERS

    Institute of Scientific and Technical Information of China (English)

    Junhai MA; Yaqiang CUI; Lixia LIU

    2008-01-01

    This paper studies the global bifurcation and Hopf bifurcation of one kind of complicated financial system with different parameter combinations. Conditions on which bifurcation happens, and the critical system structure when the system transforms from one kind of topological structure to another are studied as well. The criterion for identifying Hopf bifurcation under different parameter combinations is also given. The chaotic character of this system under quasi-periodic force is finally studied. The bifurcation structure graphs are given when two parameters of the combination are fixed while the other parameter varies. The presence and stability of 2 and 3 dimensional torus bifurcation are studied. All of the Lyapunov exponents of the system with different bifurcation parameters and routes leading the system to chaos with different parameter combinations are studied. It is of important theoretical and practical meaning to probe the intrinsic mechanism of such continuous complicated financial system and to find the macro control policies for such kind of system.

  6. Hopf bifurcation in a predator-prey system with discrete and distributed delays

    Energy Technology Data Exchange (ETDEWEB)

    Yang Yu [Department of Mathematics, Shanghai Jiao Tong University, Shanghai 200240 (China)], E-mail: yuy1981@126.com; Ye Jin [School of Computer Science and Technology, Donghua University, Shanghai 200051 (China)], E-mail: miniyejin@yahoo.com.cn

    2009-10-15

    In this paper, a predator-prey system with discrete and distributed delays is considered. By regarding the delay as the bifurcation parameter and analyzing the associated characteristic equation of the original system at the positive equilibrium, it is found that Hopf bifurcations occur when the delay passes through a certain critical value. Finally, numerical simulations are given to support our theoretical results.

  7. Stability and Hopf bifurcations in a competitive Lotka-Volterra system with two delays

    Energy Technology Data Exchange (ETDEWEB)

    Song Yongli E-mail: songyl@sjtu.edu.cn; Han Maoan; Peng Yahong

    2004-12-01

    We consider a Lotka-Volterra competition system with two delays. We first investigate the stability of the positive equilibrium and the existence of Hopf bifurcations, and then using the normal form theory and center manifold argument, derive the explicit formulas which determine the stability, direction and other properties of bifurcating periodic solutions.

  8. Stability and Hopf bifurcation in a diffusive predator-prey system incorporating a prey refuge.

    Science.gov (United States)

    Chang, Xiaoyuan; Wei, Junjie

    2013-08-01

    A diffusive predator-prey model with Holling type II functional response and the no-flux boundary condition incorporating a constant prey refuge is considered. Globally asymptotically stability of the positive equilibrium is obtained. Regarding the constant number of prey refuge m as a bifurcation parameter, by analyzing the distribution of the eigenvalues, the existence of Hopf bifurcation is given. Employing the center manifold theory and normal form method, an algorithm for determining the properties of the Hopf bifurcation is derived. Some numerical simulations for illustrating the analysis results are carried out.

  9. Hopf Bifurcation and Stability Analysis for a Predator-prey Model with Time-delay

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong-bing

    2015-01-01

    In this paper, a predator-prey model of three species is investigated, the necessary and sucient of the stable equilibrium point for this model is studied. Further, by introduc-ing a delay as a bifurcation parameter, it is found that Hopf bifurcation occurs when τ cross some critical values. And, the stability and direction of hopf bifurcation are determined by applying the normal form theory and center manifold theory. numerical simulation results are given to support the theoretical predictions. At last, the periodic solution of this system is computed.

  10. Hopf Bifurcations of a Stochastic Fractional-Order Van der Pol System

    Directory of Open Access Journals (Sweden)

    Xiaojun Liu

    2014-01-01

    Full Text Available The Hopf bifurcation of a fractional-order Van der Pol (VDP for short system with a random parameter is investigated. Firstly, the Chebyshev polynomial approximation is applied to study the stochastic fractional-order system. Based on the method, the stochastic system is reduced to the equivalent deterministic one, and then the responses of the stochastic system can be obtained by numerical methods. Then, according to the existence conditions of Hopf bifurcation, the critical parameter value of the bifurcation is obtained by theoretical analysis. Then, numerical simulations are carried out to verify the theoretical results.

  11. Delayed Feedback Control of Bao Chaotic System Based on Hopf Bifurcation Analysis

    Directory of Open Access Journals (Sweden)

    Farhad Khellat

    2014-11-01

    Full Text Available This paper is concerned with bifurcation and chaos control in a new chaotic system recently introduced by Bao et al [9]. First a condition that the system has a Hopf bifurcation is derived. Then by applying delayed feedback controller, the chaotic system is forced to have a stable periodic orbit extracting from chaotic attractor. This is done by making Hopf bifurcation value of the open loop and the closed loop systems identical. Also by suitable tuning of the controller parameters, unstable equilibrium points become stable. Numerical simulations verify the results.

  12. Delayed feedback control of time-delayed chaotic systems: Analytical approach at Hopf bifurcation

    Energy Technology Data Exchange (ETDEWEB)

    Vasegh, Nastaran [Faculty of Electrical Engineering, K.N. Toosi University of Technology, PO Box 16315-1355, Tehran (Iran, Islamic Republic of)], E-mail: vasegh@eetd.kntu.ac.ir; Sedigh, Ali Khaki [Faculty of Electrical Engineering, K.N. Toosi University of Technology, PO Box 16315-1355, Tehran (Iran, Islamic Republic of)

    2008-07-28

    This Letter is concerned with bifurcation and chaos control in scalar delayed differential equations with delay parameter {tau}. By linear stability analysis, the conditions under which a sequence of Hopf bifurcation occurs at the equilibrium points are obtained. The delayed feedback controller is used to stabilize unstable periodic orbits. To find the controller delay, it is chosen such that the Hopf bifurcation remains unchanged. Also, the controller feedback gain is determined such that the corresponding unstable periodic orbit becomes stable. Numerical simulations are used to verify the analytical results.

  13. Hopf bifurcation in a environmental defensive expenditures model with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Russu, Paolo [D.E.I.R., University of Sassari, Via Torre Tonda, 34, 07100 Sassari (Italy)], E-mail: russu@uniss.it

    2009-12-15

    In this paper a three-dimensional environmental defensive expenditures model with delay is considered. The model is based on the interactions among visitors V, quality of ecosystem goods E, and capital K, intended as accommodation and entertainment facilities, in Protected Areas (PAs). The tourism user fees (TUFs) are used partly as a defensive expenditure and partly to increase the capital stock. The stability and existence of Hopf bifurcation are investigated. It is that stability switches and Hopf bifurcation occurs when the delay t passes through a sequence of critical values, {tau}{sub 0}. It has been that the introduction of a delay is a destabilizing process, in the sense that increasing the delay could cause the bio-economics to fluctuate. Formulas about the stability of bifurcating periodic solution and the direction of Hopf bifurcation are exhibited by applying the normal form theory and the center manifold theorem. Numerical simulations are given to illustrate the results.

  14. Global Hopf Bifurcation on Two-Delays Leslie-Gower Predator-Prey System with a Prey Refuge

    Directory of Open Access Journals (Sweden)

    Qingsong Liu

    2014-01-01

    Full Text Available A modified Leslie-Gower predator-prey system with two delays is investigated. By choosing τ1 and τ2 as bifurcation parameters, we show that the Hopf bifurcations occur when time delay crosses some critical values. Moreover, we derive the equation describing the flow on the center manifold; then we give the formula for determining the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions. Numerical simulations are carried out to illustrate the theoretical results and chaotic behaviors are observed. Finally, using a global Hopf bifurcation theorem for functional differential equations, we show the global existence of the periodic solutions.

  15. Global hopf bifurcation on two-delays leslie-gower predator-prey system with a prey refuge.

    Science.gov (United States)

    Liu, Qingsong; Lin, Yiping; Cao, Jingnan

    2014-01-01

    A modified Leslie-Gower predator-prey system with two delays is investigated. By choosing τ 1 and τ 2 as bifurcation parameters, we show that the Hopf bifurcations occur when time delay crosses some critical values. Moreover, we derive the equation describing the flow on the center manifold; then we give the formula for determining the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions. Numerical simulations are carried out to illustrate the theoretical results and chaotic behaviors are observed. Finally, using a global Hopf bifurcation theorem for functional differential equations, we show the global existence of the periodic solutions.

  16. Hybrid Control of Delay Induced Hopf Bifurcation of Dynamical Small-World Network

    Institute of Scientific and Technical Information of China (English)

    DING Dawei; ZHANG Xiaoyun; WANG Nian; LIANG Dong

    2017-01-01

    In this paper,we focus on the Hopf bifurcation control of a small-world network model with time-delay.With emphasis on the relationship between the Hopf bifurcation and the time-delay,we investigate the effect of time-delay by choosing it as the bifurcation parameter.By using tools from control and bifurcation theory,it is proved that there exists a critical value of time-delay for the stability of the model.When the time-delay passes through the critical value,the model loses its stability and a Hopf bifurcation occurs.To enhance the stability of the model,we propose an improved hybrid control strategy in which state feedback and parameter perturbation are used.Through linear stability analysis,we show that by adjusting the control parameter properly,the onset of Hopf bifurcation of the controlled model can be delayed or eliminated without changing the equilibrium point of the model.Finally,numerical simulations are given to verify the theoretical analysis.

  17. Stability and Hopf Bifurcation Analysis of an Epidemic Model by Using the Method of Multiple Scales

    Directory of Open Access Journals (Sweden)

    Wanyong Wang

    2016-01-01

    Full Text Available A delayed epidemic model with nonlinear incidence rate which depends on the ratio of the numbers of susceptible and infectious individuals is considered. By analyzing the corresponding characteristic equations, the effects of time delay on the stability of the equilibria are studied. By choosing time delay as bifurcation parameter, the critical value of time delay at which a Hopf bifurcation occurs is obtained. In order to derive the normal form of the Hopf bifurcation, an extended method of multiple scales is developed and used. Then, the amplitude of bifurcating periodic solution and the conditions which determine the stability of the bifurcating periodic solution are obtained. The validity of analytical results is shown by their consistency with numerical simulations.

  18. Hopf Bifurcation Analysis for a Stochastic Discrete-Time Hyperchaotic System

    Directory of Open Access Journals (Sweden)

    Jie Ran

    2015-01-01

    Full Text Available The dynamics of a discrete-time hyperchaotic system and the amplitude control of Hopf bifurcation for a stochastic discrete-time hyperchaotic system are investigated in this paper. Numerical simulations are presented to exhibit the complex dynamical behaviors in the discrete-time hyperchaotic system. Furthermore, the stochastic discrete-time hyperchaotic system with random parameters is transformed into its equivalent deterministic system with the orthogonal polynomial theory of discrete random function. In addition, the dynamical features of the discrete-time hyperchaotic system with random disturbances are obtained through its equivalent deterministic system. By using the Hopf bifurcation conditions of the deterministic discrete-time system, the specific conditions for the existence of Hopf bifurcation in the equivalent deterministic system are derived. And the amplitude control with random intensity is discussed in detail. Finally, the feasibility of the control method is demonstrated by numerical simulations.

  19. Study on Chaos Created by Hopf Bifurcation of One Kind of Financial System and Its Application

    Institute of Scientific and Technical Information of China (English)

    JunhaiMa; BiaoRen; YanGao

    2004-01-01

    From a mathematical model of one kind complicated financial system, corresponding local topological structures of such kind system on condition of certain parametercombination, unstable equilibrium point of the system, conditions on which Hopf bifurcation is created and stability of the limit circle corresponding to the Hopf bifurcation as well as condition on which the limit circle is stable have been studied. From relationship between each parameter and the Hopf bifurcation all the way to route which leads to chaos etc have been studied. Following the above, conditions on which complicated behaviors created locally in such kind system has been analyzed. By applying fractal dimension, Lyapunov index, the intrinsic complexity of the system on such condition has been studied, and result of the numerical simulation proves the theory of this paper correct.

  20. Hopf bifurcation and chaos in a third-order phase-locked loop

    Science.gov (United States)

    Piqueira, José Roberto C.

    2017-01-01

    Phase-locked loops (PLLs) are devices able to recover time signals in several engineering applications. The literature regarding their dynamical behavior is vast, specifically considering that the process of synchronization between the input signal, coming from a remote source, and the PLL local oscillation is robust. For high-frequency applications it is usual to increase the PLL order by increasing the order of the internal filter, for guarantying good transient responses; however local parameter variations imply structural instability, thus provoking a Hopf bifurcation and a route to chaos for the phase error. Here, one usual architecture for a third-order PLL is studied and a range of permitted parameters is derived, providing a rule of thumb for designers. Out of this range, a Hopf bifurcation appears and, by increasing parameters, the periodic solution originated by the Hopf bifurcation degenerates into a chaotic attractor, therefore, preventing synchronization.

  1. Stability and Hopf Bifurcation Analysis on a Nonlinear Business Cycle Model

    Directory of Open Access Journals (Sweden)

    Liming Zhao

    2016-01-01

    Full Text Available This study begins with the establishment of a three-dimension business cycle model based on the condition of a fixed exchange rate. Using the established model, the reported study proceeds to describe and discuss the existence of the equilibrium and stability of the economic system near the equilibrium point as a function of the speed of market regulation and the degree of capital liquidity and a stable region is defined. In addition, the condition of Hopf bifurcation is discussed and the stability of a periodic solution, which is generated by the Hopf bifurcation and the direction of the Hopf bifurcation, is provided. Finally, a numerical simulation is provided to confirm the theoretical results. This study plays an important role in theoretical understanding of business cycle models and it is crucial for decision makers in formulating macroeconomic policies as detailed in the conclusions of this report.

  2. 近哈密顿系统的Hopf分岔%HOPF BIFURCATION OF A PERTURBEDHAMILTONIAN SYSTEM

    Institute of Scientific and Technical Information of China (English)

    郑吉兵; 谢建华; 孟光

    2001-01-01

    Hopf bifurcation conditions are studied for a perturbed Hamiltoniansystem in this paper by theoretical and numerical method. Saddle nodebifurcation of such system have been well studied by now, but its Hopfbifurcation and torus motion are not very clear. This paper obtains aseries of concise Hopf bifurcation conditions via sub-Melnikov methodand some mathematical skills, these conditions were mentioned in someearly researches but they are very complicated and unpractical. Usingthe simplified formula deduced in this paper, we can find the Hopfbifurcation curves easily in the parameter space. Associated with the theoretical analysis, numerical simulations about a kind ofDuffing equation are carried out. Numerical simulations show that ourtheory is correct because we get many odd number invariant circles andeven number ones resulting from Hopf bifurcation separately(we call themodd number order or even number order Hopf bifurcation respectively)according to the parameters obtained by our theory analysis, and theseinvariant circles clearly correspond to the KAM tori for the odd or evennumber order resonance in KAM theory. When the odd and even numberorder Hopf bifurcation conditions are satisfied at the same time, manyinteresting KAM tori corresponding multi-resonance can be obtained,which may be connected with further torus bifurcation of the system. Sothis paper's method may be very useful to study how Hopf bifurcationconnects with the KAM tori structure, further work will be done.%简化了Wiggins提出的关于近哈密顿系统的Hopf分岔条件,并结合硬弹簧Duffing系统,研究了该类系统的Hopf分岔行为,并用数值积分的方法验证了结果的正确性.

  3. Hopf Bifurcation in a Delayed Predator-prey System with Modified Leslie-Gower and Holling-type Ⅲ Schemes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zi-Zhen; YANG Hui-Zhong

    2013-01-01

    In this paper,we consider a predator-prey system with modified Leslie-Gower and Holling type III schemes.By regarding the time delay as the bifurcation parameter,the local asymptotic stability of the positive equilibrium is investigated.And we find that Hopf bifurcations can occur as the time delay crosses some critical values.In particular,special attention is paid to the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions.In addition,the global existence of periodic solutions bifurcating from the Hopf bifurcation are considered by applying a global Hopf bifurcation result.Finally,numerical simulations are carried out to illustrate the main theoretical results.

  4. Hopf Bifurcation of a Delayed Epidemic Model with Information Variable and Limited Medical Resources

    Directory of Open Access Journals (Sweden)

    Caijuan Yan

    2014-01-01

    Full Text Available We consider SIR epidemic model in which population growth is subject to logistic growth in absence of disease. We get the condition for Hopf bifurcation of a delayed epidemic model with information variable and limited medical resources. By analyzing the corresponding characteristic equations, the local stability of an endemic equilibrium and a disease-free equilibrium is discussed. If the basic reproduction ratio ℛ01, we obtain sufficient conditions under which the endemic equilibrium E* of system is locally asymptotically stable. And we also have discussed the stability and direction of Hopf bifurcations. Numerical simulations are carried out to explain the mathematical conclusions.

  5. Significance of the resting angles of hair-cell bundles for Hopf bifurcation criticality

    Science.gov (United States)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2016-08-01

    We investigate the significance of the inclined angle of a hair bundle at equilibrium. We find that, while the angle gives a geometrical conversion factor between the bundle deflection and the ion channel displacement, it also controls the dynamics of the bundle. We show that a Hopf bifurcation, which enhances sensitivity, can be driven by the geometrical factor. However, existing experimental data indicate that mammalian auditory hair-cell bundles are located far away from the Hopf bifurcation point, suggesting that the high sensitivity of mammalian hearing might come from other mechanisms.

  6. Theoretical and Experimental Study of Hopf Bifurcation and Limit Cycles of Railway Vehicle Hunting

    Institute of Scientific and Technical Information of China (English)

    Zeng Jing; Zhang Weihua; Shen Zhiyun

    1996-01-01

    The nonlinear hunting stability of railway vehicles is studied theoretically and experimentally in this paper. The Hopf bifurcation point is determined through calculating the eigenvalues of the system linearization equations incorporating with the golden cut method. The bifurcated limit cycles are computed by use of the shooting method to solve the boundary value problem of the system differential equations. Experimental validation to the numerical results is carricd out by utilizing the full scale roller test rig.

  7. On the Computation of Degenerate Hopf Bifurcations for n-Dimensional Multiparameter Vector Fields

    Directory of Open Access Journals (Sweden)

    Michail P. Markakis

    2016-01-01

    Full Text Available The restriction of an n-dimensional nonlinear parametric system on the center manifold is treated via a new proper symbolic form and analytical expressions of the involved quantities are obtained as functions of the parameters by lengthy algebraic manipulations combined with computer assisted calculations. Normal forms regarding degenerate Hopf bifurcations up to codimension 3, as well as the corresponding Lyapunov coefficients and bifurcation portraits, can be easily computed for any system under consideration.

  8. Hopf bifurcation of a ratio-dependent predator-prey system with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Celik, Canan [TOBB Economics and Technology University, Faculty of Arts and Sciences, Department of Mathematics, Soeguetoezue 06560, Ankara (Turkey)], E-mail: canan.celik@etu.tr

    2009-11-15

    In this paper, we consider a ratio dependent predator-prey system with time delay where the dynamics is logistic with the carrying capacity proportional to prey population. By considering the time delay as bifurcation parameter, we analyze the stability and the Hopf bifurcation of the system based on the normal form approach and the center manifold theory. Finally, we illustrate our theoretical results by numerical simulations.

  9. Stability and Hopf bifurcation in a delayed competitive web sites model

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Min [Department of Mathematics, Southeast University, Nanjing 210096 (China): Department of Mathematics, Nanjing Xiaozhuang College, Nanjing 210017 (China); Cao Jinde [Department of Mathematics, Southeast University, Nanjing 210096 (China)]. E-mail: jdcao@seu.edu.cn

    2006-04-24

    The delayed differential equations modeling competitive web sites, based on the Lotka-Volterra competition equations, are considered. Firstly, the linear stability is investigated. It is found that there is a stability switch for time delay, and Hopf bifurcation occurs when time delay crosses through a critical value. Then the direction and stability of the bifurcated periodic solutions are determined, using the normal form theory and the center manifold reduction. Finally, some numerical simulations are carried out to illustrate the results found.

  10. HOPF BIFURCATION AND UNIQUENESS OF LIMIT CYCLE FOR A CLASS OF QUARTIC SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper studies a class of quartic system which is more general and realistic than the quartic accompanying system.x' = -y + ex + lx2 + mxy + ny2, y' = x(1 - Ay)(1 + Cy2), (*)where C > 0. Sufficient conditions are obtained for the uniqueness of limit cycle of system (*)and some more in-depth conclusion such as Hopf bifurcation.

  11. Stability and Hopf Bifurcation for Two Advertising Systems, Coupled with Delay

    Science.gov (United States)

    Sterpu, Mihaela; Rocşoreanu, Carmen

    2007-09-01

    Two advertising systems were linearly coupled via the first variable, with time delay. The stability and the Hopf bifurcation corresponding to the symmetric equilibrium point (the origin) in the 4D system are analyzed. Different types of oscillations corresponding to the limit cycles are compared.

  12. Mixed-Mode Oscillations Due to a Singular Hopf Bifurcation in a Forest Pest Model

    DEFF Research Database (Denmark)

    Brøns, Morten; Desroches, Mathieu; Krupa, Martin

    2015-01-01

    In a forest pest model, young trees are distinguished from old trees. The pest feeds on old trees. The pest grows on a fast scale, the young trees on an intermediate scale, and the old trees on a slow scale. A combination of a singular Hopf bifurcation and a “weak return” mechanism, characterized...

  13. Degenerate Hopf bifurcation in a self-exciting Faraday disc dynamo

    Indian Academy of Sciences (India)

    WEIQUAN PAN; LIJIE LI

    2017-06-01

    In order to further understand a self-exciting Faraday disc dynamo (Hide $\\it{et al}$, in $\\it{Proc. R. Soc}.$ A $\\bf{452}$, 1369 1996), showing chaotic attractors with very complicated topological structures, we present codimension one and two (degenerate) Hopf bifurcations and prove the existence of periodic solutions. In addition, numerical simulations are given for confirming the theoretical results.

  14. Hopf bifurcation in a partial dependent predator-prey system with delay

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Huitao [Department of Applied Mathematics, Kunming University of Science and Technology, Kunming, Yunnan 650093 (China); Department of Mathematics and Information Science, Zhoukou Normal University, Zhoukou, Henan 466001 (China)], E-mail: taohuiz@sohu.com; Lin Yiping [Department of Applied Mathematics, Kunming University of Science and Technology, Kunming, Yunnan 650093 (China)], E-mail: linyiping689@sohu.com

    2009-10-30

    In this paper, a partial dependent predator-prey model with time delay is studied by using the theory of functional differential equation and Hassard's method, the condition on which positive equilibrium exists and Hopf bifurcation occurs are given. Finally, numerical simulations are performed to support the analytical results, and the chaotic behaviors are observed.

  15. Hopf Bifurcation and Chaos in a Single Inertial Neuron Model with Time Delay

    OpenAIRE

    Li, Chunguang; Chen, Guanrong; Liao, Xiaofeng; Yu, Juebang

    2004-01-01

    A delayed differential equation modelling a single neuron with inertial term is considered in this paper. Hopf bifurcation is studied by using the normal form theory of retarded functional differential equations. When adopting a nonmonotonic activation function, chaotic behavior is observed. Phase plots, waveform plots, and power spectra are presented to confirm the chaoticity.

  16. Hopf and steady state bifurcation analysis in a ratio-dependent predator-prey model

    Science.gov (United States)

    Zhang, Lai; Liu, Jia; Banerjee, Malay

    2017-03-01

    In this paper, we perform spatiotemporal bifurcation analysis in a ratio-dependent predator-prey model and derive explicit conditions for the existence of non-constant steady states that emerge through steady state bifurcation from related constant steady states. These explicit conditions are numerically verified in details and further compared to those conditions ensuring Turing instability. We find that (1) Turing domain is identical to the parametric domain where there exists only steady state bifurcation, which implies that Turing patterns are stable non-constant steady states, but the opposite is not necessarily true; (2) In non-Turing domain, steady state bifurcation and Hopf bifurcation act in concert to determine the emergent spatial patterns, that is, non-constant steady state emerges through steady state bifurcation but it may be unstable if the destabilising effect of Hopf bifurcation counteracts the stabilising effect of diffusion, leading to non-stationary spatial patterns; (3) Coupling diffusion into an ODE model can significantly enrich population dynamics by inducing alternative non-constant steady states (four different states are observed, two stable and two unstable), in particular when diffusion interacts with different types of bifurcation; (4) Diffusion can promote species coexistence by saving species which otherwise goes to extinction in the absence of diffusion.

  17. Generalized Hopf Bifurcation for Non-smooth Planar Dynamical Systems: the Corner Case

    Institute of Scientific and Technical Information of China (English)

    邹永魁; TassiloKǖpper; 黄明游

    2001-01-01

    Piece-wise smooth systems are an important class of ordinary differential equations whosedynamics are known to exhibit complex bifurcation scenarios and chaos. Broadly speaking,piece-wise smooth systems can undergo all the bifurcation that smooth ones can. Moreinterestingly, there is a whole class of bifurcation that are unique to piece-wise smoothsystems, such as the bifurcation caused by the geometric shape of the region in which thevector field is analyzed. For example (see Figure 1), the region is divided into two partsI and Ⅱ by a discontinuity boundary which contains a corner at O. When an orbit crossthe corner, border-collision bifurcation may occur (cf. [1]). The present paper deals withthe mechanics of the generalized Hopf bifurcation when the stationary point locates at thecorner.

  18. Hopf bifurcations in a three-species food chain system with multiple delays

    Directory of Open Access Journals (Sweden)

    Xie Xiaoliang

    2017-04-01

    Full Text Available This paper is concerned with a three-species Lotka-Volterra food chain system with multiple delays. By linearizing the system at the positive equilibrium and analyzing the associated characteristic equation, the stability of the positive equilibrium and existence of Hopf bifurcations are investigated. Furthermore, the direction of bifurcations and the stability of bifurcating periodic solutions are determined by the normal form theory and the center manifold theorem for functional differential equations. Finally, some numerical simulations are carried out for illustrating the theoretical results.

  19. Stability and Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback

    Science.gov (United States)

    Liu, Shuang; Zhao, Shuang-Shuang; Wang, Zhao-Long; Li, Hai-Bin

    2015-01-01

    The stability and the Hopf bifurcation of a nonlinear electromechanical coupling system with time delay feedback are studied. By considering the energy in the air-gap field of the AC motor, the dynamical equation of the electromechanical coupling transmission system is deduced and a time delay feedback is introduced to control the dynamic behaviors of the system. The characteristic roots and the stable regions of time delay are determined by the direct method, and the relationship between the feedback gain and the length summation of stable regions is analyzed. Choosing the time delay as a bifurcation parameter, we find that the Hopf bifurcation occurs when the time delay passes through a critical value. A formula for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions is given by using the normal form method and the center manifold theorem. Numerical simulations are also performed, which confirm the analytical results. Project supported by the National Natural Science Foundation of China (Grant No. 61104040), the Natural Science Foundation of Hebei Province, China (Grant No. E2012203090), and the University Innovation Team of Hebei Province Leading Talent Cultivation Project, China (Grant No. LJRC013).

  20. Stabilizing fixed points of time-delay systems close to the Hopf bifurcation using a dynamic delayed feedback control method

    Energy Technology Data Exchange (ETDEWEB)

    Rezaie, B; Motlagh, M R Jahed; Analoui, M [Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Khorsandi, S [Amirkabir University of Technology, Hafez St., Tehran (Iran, Islamic Republic of)], E-mail: brezaie@iust.ac.ir

    2009-10-02

    This paper deals with the problem of Hopf bifurcation control for a class of nonlinear time-delay systems. A dynamic delayed feedback control method is utilized for stabilizing unstable fixed points near Hopf bifurcation. Using a linear stability analysis, we show that under certain conditions of the control parameters, and without changing the operating point of the system, the onset of Hopf bifurcation is delayed. Meanwhile, by applying the center manifold theorem and the normal form theory, we obtain formulas for determining the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions of the closed loop system. Numerical simulations are given to justify the validity of the analytical results for the system controlled by the proposed method.

  1. Hopf bifurcation in a diffusive Lotka-Volterra type system with nonlocal delay effect

    Science.gov (United States)

    Guo, Shangjiang; Yan, Shuling

    2016-01-01

    The dynamics of a diffusive Lotka-Volterra type model for two species with nonlocal delay effect and Dirichlet boundary conditions is investigated in this paper. The existence and multiplicity of spatially nonhomogeneous steady-state solutions are obtained by means of Lyapunov-Schmidt reduction. The stability of spatially nonhomogeneous steady-state solutions and the existence of Hopf bifurcation with the changes of the time delay are obtained by analyzing the distribution of eigenvalues of the infinitesimal generator associated with the linearized system. By the normal form theory and the center manifold reduction, the stability and bifurcation direction of Hopf bifurcating periodic orbits are derived. Finally, our theoretical results are illustrated by a model with homogeneous kernels and one-dimensional spatial domain.

  2. Hopf bifurcation analysis for a dissipative system with asymmetric interaction: Analytical explanation of a specific property of highway traffic

    Science.gov (United States)

    Nomura, Yasuyuki; Saito, Satoshi; Ishiwata, Ryosuke; Sugiyama, Yuki

    2016-01-01

    A dissipative system with asymmetric interaction, the optimal velocity model, shows a Hopf bifurcation concerned with the transition from a homogeneous motion to the formation of a moving cluster, such as the emergence of a traffic jam. We investigate the properties of Hopf bifurcation depending on the particle density, using the dynamical system for the traveling cluster solution of the continuum system derived from the original discrete system of particles. The Hopf bifurcation is revealed as a subcritical one, and the property explains well the specific phenomena in highway traffic: the metastability of jamming transition and the hysteresis effect in the relation of car density and flow rate.

  3. Hopf bifurcation of an (n + 1) -neuron bidirectional associative memory neural network model with delays.

    Science.gov (United States)

    Xiao, Min; Zheng, Wei Xing; Cao, Jinde

    2013-01-01

    Recent studies on Hopf bifurcations of neural networks with delays are confined to simplified neural network models consisting of only two, three, four, five, or six neurons. It is well known that neural networks are complex and large-scale nonlinear dynamical systems, so the dynamics of the delayed neural networks are very rich and complicated. Although discussing the dynamics of networks with a few neurons may help us to understand large-scale networks, there are inevitably some complicated problems that may be overlooked if simplified networks are carried over to large-scale networks. In this paper, a general delayed bidirectional associative memory neural network model with n + 1 neurons is considered. By analyzing the associated characteristic equation, the local stability of the trivial steady state is examined, and then the existence of the Hopf bifurcation at the trivial steady state is established. By applying the normal form theory and the center manifold reduction, explicit formulae are derived to determine the direction and stability of the bifurcating periodic solution. Furthermore, the paper highlights situations where the Hopf bifurcations are particularly critical, in the sense that the amplitude and the period of oscillations are very sensitive to errors due to tolerances in the implementation of neuron interconnections. It is shown that the sensitivity is crucially dependent on the delay and also significantly influenced by the feature of the number of neurons. Numerical simulations are carried out to illustrate the main results.

  4. HOPF BIFURCATION AND ANALYSIS OF EQUILIBRIUM FOR A THIRD-ORDER DIFFERENTIAL EQUATION IN A MODEL OF COMPETITION

    Institute of Scientific and Technical Information of China (English)

    LORNA S. ALMOCERA; 井竹君; POLLY W. SY

    2001-01-01

    In this paper, a mathematical model of competition between plasmid-bearing and plasmidfree organisms in a chemostat with an inhibitor is investigated. The model is in the form of a system of nonlinear differential equations. By using qualitative methods, the conditions for the existence and local stability of the equilibria are obtained. The existence and stability of periodic solutions of the Hopf type are studied. Numerical simulations about the Hopf bifurcation value and Hopf limit cycle are also given.

  5. Equation-free detection and continuation of a Hopf bifurcation point in a particle model of pedestrian flow

    DEFF Research Database (Denmark)

    Corradi, Olivier; Hjorth, Poul G.; Starke, Jens

    2012-01-01

    an onset of oscillations of the net pedestrian flux through the doorway, described by a Hopf bifurcation. An equation-free continuation of the Hopf point in the two parameters, door width and ratio of the pedestrian velocities of the two crowds, is performed. © 2012 Society for Industrial and Applied...

  6. Delayed Hopf bifurcation in time-delayed slow-fast systems

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents an investigation on the phenomenon of delayed bifurcation in time-delayed slow-fast differential systems.Here the two delayed’s have different meanings.The delayed bifurcation means that the bifurcation does not happen immediately at the bifurcation point as the bifurcation parameter passes through some bifurcation point,but at some other point which is above the bifurcation point by an obvious distance.In a time-delayed system,the evolution of the system depends not only on the present state but also on past states.In this paper,the time-delayed slow-fast system is firstly simplified to a slow-fast system without time delay by means of the center manifold reduction,and then the so-called entry-exit function is defined to characterize the delayed bifurcation on the basis of Neishtadt’s theory.It shows that delayed Hopf bifurcation exists in time-delayed slow-fast systems,and the theoretical prediction on the exit-point is in good agreement with the numerical calculation,as illustrated in the two illustrative examples.

  7. HOPF BIFURCATION OF A NONLINEAR RESTRAINED CURVED PIPE CONVEYING FLUID BY DIFFERENTIAL QUADRATURE METHOD

    Institute of Scientific and Technical Information of China (English)

    WangLin; NiQiao; HuangYuying

    2003-01-01

    This paper proposes a new method for investigating the Hopf bifurcation of a curved pipe conveying fluid with nonlinear spring support. The nonlinear equation of motion is derived by forces equilibrium on microelement of the system under consideration. The spatial coordinate of the system is discretized by the differential quadrature method and then the dynamic equation is solved by the Newton-Raphson method. The numerical solutions show that the inner fluid velocity of the Hopf bifurcation point of the curved pipe varies with different values of the parameter,nonlinear spring stiffness. Based on this, the cycle and divergent motions are both found to exist at specific fluid flow velocities with a given value of the nonlinear spring stiffness. The results are useful for further study of the nonlinear dynamic mechanism of the curved fluid conveying pipe.

  8. Microcavity with saturable nonlinearity under simultaneous resonant and nonresonant pumping: multistability, Hopf bifurcations and chaotic behaviour.

    Science.gov (United States)

    Iorsh, Ivan; Alodjants, Alexander; Shelykh, Ivan A

    2016-05-30

    We studied optical response of microcavity non-equilibrium exciton-polariton Bose-Einstein condensate with saturable nonlinearity under simultaneous resonant and non-resonant pumping. We demonstrated the emergence of multistabile behavior due to the saturation of the excitonic absorption. Stable periodic Rabi-type oscillations of the excitonic and photonic condensate components in the regime of the stationary pump and their transition to the chaotic dynamics through the cascade of Hopf bifurcations by tuning of the electrical pump are revealed.

  9. Microcavity with saturable nonlinearity under simultaneous resonant and nonresonant pumping: multistability, Hopf bifurcations and chaotic behaviour

    CERN Document Server

    Iorsh, Ivan; Shelykh, Ivan

    2016-01-01

    We studied optical response of microcavity non-equilibrium exciton-polariton Bose-Einstein condensate with saturable nonlinearity under simultaneous resonant and non-resonant pumping. We demonstrated the emergence of multistabile behavior due to the satutration of the excitonic absorbtion. Stable periodic Rabi- type oscillations of the excitonic and photonic condensate components in the regime of the stationary pump and their transition to the chaotic dynamics through the cascade of Hopf bifurcations by tuning of the electrical pump are revealed.

  10. Hopf Bifurcation and Eigenvalue Sensitivity Analysis of Doubly Fed Induction Generator Wind Turbine System

    DEFF Research Database (Denmark)

    Yang, Lihui; Xu, Zhao; Østergaard, Jacob;

    2009-01-01

    This paper first presents the Hopf bifurcation analysis for a vector-controlled doubly fed induction generator (DFIG) which is widely used in wind power conversion systems. Using three-phase back-to-back pulse-width-modulated (PWM) converters, DFIG can keep stator frequency constant under variable...... rotor speed and provide independent control of active and reactive power output. The oscillatory instability of the DFIG has been observed by simulation study. The detailed mathematical model of the DFIG closed-loop system is derived and used to analyze the observed bifurcation phenomena. The loci...

  11. Hopf bifurcation and eigenvalue sensitivity analysis of doubly fed induction generator wind turbine system

    DEFF Research Database (Denmark)

    Yang, Li Hui; Xu, Zhao; Østergaard, Jacob;

    2010-01-01

    This paper first presents the Hopf bifurcation analysis for a vector-controlled doubly fed induction generator (DFIG) which is widely used in wind power conversion systems. Using three-phase back-to-back pulse-width-modulated (PWM) converters, DFIG can keep stator frequency constant under variable...... rotor speed and provide independent control of active and reactive power output. The oscillatory instability of the DFIG has been observed by simulation study. The detailed mathematical model of the DFIG closed-loop system is derived and used to analyze the observed bifurcation phenomena. The loci...

  12. Hopf Bifurcation Analysis and Chaos Control of a Chaotic System without ilnikov Orbits

    Directory of Open Access Journals (Sweden)

    Na Li

    2015-01-01

    Full Text Available This paper mainly investigates the dynamical behaviors of a chaotic system without ilnikov orbits by the normal form theory. Both the stability of the equilibria and the existence of local Hopf bifurcation are proved in view of analyzing the associated characteristic equation. Meanwhile, the direction and the period of bifurcating periodic solutions are determined. Regarding the delay as a parameter, we discuss the effect of time delay on the dynamics of chaotic system with delayed feedback control. Finally, numerical simulations indicate that chaotic oscillation is converted into a steady state when the delay passes through a certain critical value.

  13. Fold-Hopf bifurcation in a simplified four-neuron BAM (bidirectional associative memory) neural network with two delays

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The bidirectional associative memory (BAM) neural network with four neurons and two delays is considered in the present paper.A linear stability analysis for the trivial equilibrium is firstly employed to provide a possible critical point at which a zero and a pair of pure imaginary eigenvalues occur in the corresponding characteristic equation.A fold-Hopf bifurcation is proved to happen at this critical point by the nonlinear analysis.The coupling strength and the delay are considered as bifurcation parameters to investigate the dynamical behaviors derived from the fold-Hopf bifurcation.Various dynamical behaviours are qualitatively classified in the neighbourhood of the fold-Hopf bifurcation point by using the center manifold reduction (CMR) together with the normal form.The bifurcating periodic solutions are expressed analytically in an approximate form.The validity of the results is shown by their consistency with the numerical simulation.

  14. Hopf and homoclinic bifurcations for near-Hamiltonian systems

    Science.gov (United States)

    Tian, Yun; Han, Maoan

    2017-02-01

    We study homoclinic bifurcation of limit cycles in perturbed planar Hamiltonian systems. Suppose that a homoclinic loop is defined by H =hs. Our main result is that a new method is established for computing the coefficients of the expansion of Melnikov functions at h =hs. Then by using those coefficients, more limit cycles would be found around homoclinic loops. An example is also provided to illustrate our method.

  15. A Fractional-Order Phase-Locked Loop with Time-Delay and Its Hopf Bifurcation

    Science.gov (United States)

    Yu, Ya-Juan; Wang, Zai-Hua

    2013-11-01

    A fractional-order phase-locked loop (PLL) with a time-delay is firstly proposed on the basis of the fact that a capacitor has memory. The existence of Hopf bifurcation of the fractional-order PLL with a time-delay is investigated by studying the root location of the characteristic equation, and the bifurcated periodic solution and its stability are studied simply by using “pseudo-oscillator analysis". The results are checked by numerical simulation. It is found that the fractional-order PLL with a time-delay reduces the locking time, and it minimizes the amplitude of the bifurcated periodic solution when the order is properly chosen.

  16. HOPF BIFURCATION OF AN OSCILLATOR WITH QUADRATIC AND CUBIC NONLINEARITIES AND WITH DELAYED VELOCITY FEEDBACK

    Institute of Scientific and Technical Information of China (English)

    WANG Huailei; WANG Zaihua; HU Haiyan

    2004-01-01

    This paper studies the local dynamics of an SDOF system with quadratic and cubic stiffness terms, and with linear delayed velocity feedback. The analysis indicates that for a sufficiently large velocity feedback gain, the equilibrium of the system may undergo a number of stability switches with an increase of time delay, and then becomes unstable forever. At each critical value of time delay for which the system changes its stability, a generic Hopf bifurcation occurs and a periodic motion emerges in a one-sided neighbourhood of the critical time delay. The method of Fredholm alternative is applied to determine the bifurcating periodic motions and their stability. It stresses on the effect of the system parameters on the stable regions and the amplitudes of the bifurcating periodic solutions.

  17. Analysis of the Stability and Hopf Bifurcation of Currency Supply Delay in an Opened Kaldorian Business Cycle Model

    Directory of Open Access Journals (Sweden)

    Liming Zhao

    2016-01-01

    Full Text Available First of all, we establish a three-dimension open Kaldorian business cycle model under the condition of the fixed exchange rate. Secondly, with regard to the model, we discuss the existence of equilibrium point and the stability of the system near it with a time delay in currency supply as the bifurcating parameters of the system. Thirdly, we discuss the existence of Hopf bifurcation and investigate the stability of periodic solution generated by the Hopf bifurcation; then the direction of the Hopf bifurcation is given. Finally, a numerical simulation is given to confirm the theoretical results. This paper plays an important role in theoretical researching on the model of business cycle, and it is crucial for decision-maker to formulate the macroeconomic policies with the conclusions of this paper.

  18. Pitchfork and Hopf bifurcation thresholds in stochastic equations with delayed feedback.

    Science.gov (United States)

    Gaudreault, Mathieu; Lépine, Françoise; Viñals, Jorge

    2009-12-01

    The bifurcation diagram of a model stochastic differential equation with delayed feedback is presented. We are motivated by recent research on stochastic effects in models of transcriptional gene regulation. We start from the normal form for a pitchfork bifurcation, and add multiplicative or parametric noise and linear delayed feedback. The latter is sufficient to originate a Hopf bifurcation in that region of parameters in which there is a sufficiently strong negative feedback. We find a sharp bifurcation in parameter space, and define the threshold as the point in which the stationary distribution function p(x) changes from a delta function at the trivial state x=0 to p(x) approximately x(alpha) at small x (with alpha=-1 exactly at threshold). We find that the bifurcation threshold is shifted by fluctuations relative to the deterministic limit by an amount that scales linearly with the noise intensity. Analytic calculations of the bifurcation threshold are also presented in the limit of small delay tau-->0 that compare quite favorably with the numerical solutions even for moderate values of tau .

  19. Periodically perturbed Hopf bifurcation of a kind of nonlinear systems%一类非线性系统的周期扰动Hopf 分支

    Institute of Scientific and Technical Information of China (English)

    殷红燕

    2014-01-01

    The influence of small periodic perturbations on a kind of nonlinear systems exhibiting Hopf bi-furcation is studied. In particular, we discuss the existence of bifurcating periodic solutions in the case that the excitation frequency and the critical natural frequency of Hopf bifurcation is resonance and subharmonic resonance. In this work, the ideas related method of averaging. It is shown that in some parameter regions the systems exhibit harmonic solution bifurcation and subharmonic solution bifurcation. Furthermore, the stability of subharmonic solutions is discussed.%研究了小周期扰动对一类存在Hopf 分支的非线性系统的影响。特别是应用平均法讨论了扰动频率与Hopf分支固有频率在共振及二阶次调和共振的情形周期解分支的存在性。表明了在某些参数区域内,系统存在调和解分支和次调和解分支,并进一步讨论了二阶次调和分支周期解的稳定性。

  20. Hopf bifurcation in epidemic models with a time delay in vaccination.

    Science.gov (United States)

    Khan, Q J; Greenhalgh, D

    1999-06-01

    Two SIR models for the spread of infectious diseases which were originally suggested by Greenhalgh & Das (1995, Theor. Popul. Biol. 47, 129-179; 1995, Mathematical Population Dynamics: Analysis of Heterogeneity, pp. 79-101, Winnipeg: Wuerz Publishing) are considered but with a time delay in the vaccination term. This reflects the fact that real vaccines do not immediately confer permanent immunity. The population is divided into susceptible, infectious, and immune classes. The contact rate is constant in model I but it depends on the population size in model II. The death rate depends on the population size in both models. There is an additional mortality due to the disease, and susceptibles are vaccinated and may become permanently immune after a lapse of some time. Using the time delay as a bifurcation parameter, necessary and sufficient conditions for Hopf bifurcation to occur are derived. Numerical results indicate that that for diseases in human populations Hopf bifurcation is unlikely to occur at realistic parameter values if the death rate is a concave function of the population size.

  1. Stability and Hopf bifurcation in a ratio-dependent predator-prey system with stage structure

    Energy Technology Data Exchange (ETDEWEB)

    Xu Rui [Institute of Applied Mathematics, Shijiazhuang Mechanical Engineering College, No. 97 Heping West Road, Shijiazhuang 050003, Hebei Province (China); Department of Applied Mathematics, School of Science, Xi' an Jiaotong University, Xi' an 710049 (China)], E-mail: rxu88@yahoo.com.cn; Ma Zhien [Department of Applied Mathematics, School of Science, Xi' an Jiaotong University, Xi' an 710049 (China)

    2008-11-15

    A ratio-dependent predator-prey model with stage structure for the predator and time delay due to the gestation of the predator is investigated. By analyzing the characteristic equations, the local stability of a positive equilibrium and a boundary equilibrium is discussed, respectively. Further, it is proved that the system undergoes a Hopf bifurcation at the positive equilibrium when {tau} = {tau}{sub 0}. By using an iteration technique, sufficient conditions are derived for the global attractivity of the positive equilibrium. By comparison arguments, sufficient conditions are obtained for the global stability of the boundary equilibrium. Numerical simulations are carried out to illustrate the main results.

  2. The Goodwin model revisited: Hopf bifurcation, limit-cycle, and periodic entrainment

    Science.gov (United States)

    Woller, Aurore; Gonze, Didier; Erneux, Thomas

    2014-08-01

    The three-variable Goodwin oscillator is a minimal model demonstrating the emergence of oscillations in simple biochemical feedback systems. As a prototypical oscillator, this model was extensively studied from a theoretical point of view and applied to various biological systems, including circadian clocks. Here, we reexamine this model, derive analytically the amplitude equation near the Hopf bifurcation and investigate the effect of a periodic modulation of the oscillator. In particular, we compare the entrainment performance when the free oscillator displays either self-sustained or damped oscillations. We discuss the results in the context of circadian oscillators.

  3. THE UNIQUENESS OF BIFURCATION TO SEPARATRIX LOOPS IN SUPERCRITICAL CASES

    Institute of Scientific and Technical Information of China (English)

    SUNJIANHUA

    1994-01-01

    In paper[4] the existence of bifurcation to separatrix loops in supercritical cases on the plane is studied.This note is a continuation of [4].The author proves the uniqueness of limit cycles in a neighb-orhood of the separatrix loop,and the results strengthen the relevant conclusions in[1-6].

  4. Stability of small-amplitude periodic solutions near Hopf bifurcations in time-delayed fully-connected PLL networks

    Science.gov (United States)

    Ferruzzo Correa, Diego P.; Bueno, Átila M.; Castilho Piqueira, José R.

    2017-04-01

    In this paper we investigate stability conditions for small-amplitude periodic solutions emerging near symmetry-preserving Hopf bifurcations in a time-delayed fully-connected N-node PLL network. The study of this type of systems which includes the time delay between connections has attracted much attention among researchers mainly because the delayed coupling between nodes emerges almost naturally in mathematical modeling in many areas of science such as neurobiology, population dynamics, physiology and engineering. In a previous work it has been shown that symmetry breaking and symmetry preserving Hopf bifurcations can emerge in the parameter space. We analyze the stability along branches of periodic solutions near fully-synchronized Hopf bifurcations in the fixed-point space, based on the reduction of the infinite-dimensional space onto a two-dimensional center manifold in normal form. Numerical results are also presented in order to confirm our analytical results.

  5. Global Hopf bifurcation analysis of an susceptible-infective-removed epidemic model incorporating media coverage with time delay.

    Science.gov (United States)

    Zhao, Huitao; Zhao, Miaochan

    2017-12-01

    An susceptible-infective-removed epidemic model incorporating media coverage with time delay is proposed. The stability of the disease-free equilibrium and endemic equilibrium is studied. And then, the conditions which guarantee the existence of local Hopf bifurcation are given. Furthermore, we show that the local Hopf bifurcation implies the global Hopf bifurcation after the second critical value of delay. The obtained results show that the time delay in media coverage can not affect the stability of the disease-free equilibrium when the basic reproduction number is less than unity. However, the time delay affects the stability of the endemic equilibrium and produces limit cycle oscillations while the basic reproduction number is greater than unity. Finally, some examples for numerical simulations are included to support the theoretical prediction.

  6. Time Delay Effects on Coupled Limit Cycle Oscillators at Hopf Bifurcation

    CERN Document Server

    Reddy, D V R; Johnston, G L

    1998-01-01

    We present a detailed study of the effect of time delay on the collective dynamics of coupled limit cycle oscillators at Hopf bifurcation. For a simple model consisting of just two oscillators with a time delayed coupling, the bifurcation diagram obtained by numerical and analytical solutions shows significant changes in the stability boundaries of the amplitude death, phase locked and incoherent regions. A novel result is the occurrence of amplitude death even in the absence of a frequency mismatch between the two oscillators. Similar results are obtained for an array of N oscillators with a delayed mean field coupling and the regions of such amplitude death in the parameter space of the coupling strength and time delay are quantified. Some general analytic results for the N tending to infinity (thermodynamic) limit are also obtained and the implications of the time delay effects for physical applications are discussed.

  7. Stability and Hopf bifurcation of a delayed ratio-dependent predator-prey system

    Institute of Scientific and Technical Information of China (English)

    Wan-Yong Wang; Li-Jun Pei

    2011-01-01

    Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-prey model is studied in this paper with gestation time delays of predators and preys taken into consideration. The stability of the positive equilibrium is investigated by the Nyquist criteria,and the existence of the local Hopf bifurcation is analyzed by employing the theory of Hopf bifurcation. By means of the center manifold and the normal form theories, explicit formulae are derived to determine the stability, direction and other properties of bifurcating periodic solutions. The above theoretical results are validated by numerical simulations with the help of dynamical software WinPP. The results show that if both the gestation delays are small enough, their sizes will keep stable in the long run, but if the gestation delays of predators are big enough, their sizes will periodically fluctuate in the long term. In order to reveal the effects of time delays on the ratio-dependent predator-prey model, a ratiodependent predator-prey model without time delays is considered. By Hurwitz criteria, the local stability of positive equilibrium of this model is investigated. The conditions under which the positive equilibrium is locally asymptotically stable are obtained. By comparing the results with those of the model with time delays, it shows that the dynamical behaviors of ratio-dependent predator-prey model with time delays are more complicated. Under the same conditions, namely, with the same parameters, the stability of positive equilibrium of ratio-dependent predator-prey model would change due to the introduction of gestation time delays for predators and preys. Moreover

  8. Anticontrol of Hopf Bifurcation and Control of Chaos for a Finance System through Washout Filters with Time Delay

    Science.gov (United States)

    Lu, Mengxia; Zuo, Junmei

    2014-01-01

    A controlled model for a financial system through washout-filter-aided dynamical feedback control laws is developed, the problem of anticontrol of Hopf bifurcation from the steady state is studied, and the existence, stability, and direction of bifurcated periodic solutions are discussed in detail. The obtained results show that the delay on price index has great influences on the financial system, which can be applied to suppress or avoid the chaos phenomenon appearing in the financial system. PMID:24977239

  9. Routes to chaos in the Hopf-saddle-node bifurcation for fixed points of 3D-diffeomorphisms

    NARCIS (Netherlands)

    Vitolo, Renato; Broer, Henk; Simo, Carles

    Dynamical phenomena are studied near a Hopf-saddle-node bifurcation of fixed points of 3D-diffeomorphisms. The interest lies in the neighbourhood of weak resonances of the complex conjugate eigenvalues. The 1 : 5 case is chosen here because it has the lowest order among the weak resonances, and

  10. Stability and Bifurcation in a State-Dependent Delayed Predator-Prey System

    Science.gov (United States)

    Hou, Aiyu; Guo, Shangjiang

    In this paper, we consider a class of predator-prey equations with state-dependent delayed feedback. Firstly, we investigate the local stability of the positive equilibrium and the existence of the Hopf bifurcation. Then we use perturbation methods to determine the sub/supercriticality of Hopf bifurcation and hence the stability of Hopf bifurcating periodic solutions. Finally, numerical simulations supporting our theoretical results are also provided.

  11. Flow Around a Slender Circular Cylinder: A Case Study on Distributed Hopf Bifurcation

    Directory of Open Access Journals (Sweden)

    J. A. P. Aranha

    2009-01-01

    Full Text Available This paper presents a short overview of the flow around a slender circular cylinder, the purpose being to place it within the frame of the distributed Hopf bifurcation problems described by the Ginzburg-Landau equation (GLE. In particular, the chaotic behavior superposed to a well tuned harmonic oscillation observed in the range Re > 270, with Re being the Reynolds number, is related to the defect-chaos regime of the GLE. Apparently new results, related to a Kolmogorov like length scale and the rms of the response amplitude, are derived in this defect-chaos regime and further related to the experimental rms of the lift coefficient measured in the range Re > 270.

  12. Hopf bifurcation and uncontrolled stochastic traffic-induced chaos in an RED-AQM congestion control system

    Science.gov (United States)

    Wang, Jun-Song; Yuan, Rui-Xi; Gao, Zhi-Wei; Wang, De-Jin

    2011-09-01

    We study the Hopf bifurcation and the chaos phenomena in a random early detection-based active queue management (RED-AQM) congestion control system with a communication delay. We prove that there is a critical value of the communication delay for the stability of the RED-AQM control system. Furthermore, we show that the system will lose its stability and Hopf bifurcations will occur when the delay exceeds the critical value. When the delay is close to its critical value, we demonstrate that typical chaos patterns may be induced by the uncontrolled stochastic traffic in the RED-AQM control system even if the system is still stable, which reveals a new route to the chaos besides the bifurcation in the network congestion control system. Numerical simulations are given to illustrate the theoretical results.

  13. Hopf bifurcation and uncontrolled stochastic traffic-induced chaos in an RED-AQM congestion control system

    Institute of Scientific and Technical Information of China (English)

    Wang Jun-Song; Yuan Rui-Xi; Gao Zhi-Wei; Wang De-Jin

    2011-01-01

    We study the Hopf bifurcation and the chaos phenomena in a random early detection-based active queue management (RED-AQM) congestion control system with a communication delay. We prove that there is a critical value of the communication delay for the stability of the RED-AQM control system. Furthermore,we show that the system will lose its stability and Hopf bifurcations will occur when the delay exceeds the critical value. When the delay is close to its critical value,we demonstrate that typical chaos patterns may be induced by the uncontrolled stochastic traffic in the RED-AQM control system even if the system is still stable,which reveals a new route to the chaos besides the bifurcation in the network congestion control system. Numerical simulations are given to illustrate the theoretical results.

  14. Hopf Bifurcation and Global Periodic Solutions in a Predator-Prey System with Michaelis-Menten Type Functional Response and Two Delays

    OpenAIRE

    Yunxian Dai; Yiping Lin; Huitao Zhao

    2014-01-01

    We consider a predator-prey system with Michaelis-Menten type functional response and two delays. We focus on the case with two unequal and non-zero delays present in the model, study the local stability of the equilibria and the existence of Hopf bifurcation, and then obtain explicit formulas to determine the properties of Hopf bifurcation by using the normal form method and center manifold theorem. Special attention is paid to the global continuation of local Hopf bifurcation when the delay...

  15. Complexity and Hopf Bifurcation Analysis on a Kind of Fractional-Order IS-LM Macroeconomic System

    Science.gov (United States)

    Ma, Junhai; Ren, Wenbo

    On the basis of our previous research, we deepen and complete a kind of macroeconomics IS-LM model with fractional-order calculus theory, which is a good reflection on the memory characteristics of economic variables, we also focus on the influence of the variables on the real system, and improve the analysis capabilities of the traditional economic models to suit the actual macroeconomic environment. The conditions of Hopf bifurcation in fractional-order system models are briefly demonstrated, and the fractional order when Hopf bifurcation occurs is calculated, showing the inherent complex dynamic characteristics of the system. With numerical simulation, bifurcation, strange attractor, limit cycle, waveform and other complex dynamic characteristics are given; and the order condition is obtained with respect to time. We find that the system order has an important influence on the running state of the system. The system has a periodic motion when the order meets the conditions of Hopf bifurcation; the fractional-order system gradually stabilizes with the change of the order and parameters while the corresponding integer-order system diverges. This study has certain significance to policy-making about macroeconomic regulation and control.

  16. Hopf Bifurcation Characteristics of Dual-Front Axle Self-Excited Shimmy System for Heavy Truck considering Dry Friction

    Directory of Open Access Journals (Sweden)

    Daogao Wei

    2015-01-01

    Full Text Available Multiaxle steering is widely used in commercial vehicles. However, the mechanism of the self-excited shimmy produced by the multiaxle steering system is not clear until now. This study takes a dual-front axle heavy truck as sample vehicle and considers the influences of mid-shift transmission and dry friction to develop a 9 DOF dynamics model based on Lagrange’s equation. Based on the Hopf bifurcation theorem and center manifold theory, the study shows that dual-front axle shimmy is a self-excited vibration produced from Hopf bifurcation. The numerical method is adopted to determine how the size of dry friction torque influences the Hopf bifurcation characteristics of the system and to analyze the speed range of limit cycles and numerical characteristics of the shimmy system. The consistency of results of the qualitative and numerical methods shows that qualitative methods can predict the bifurcation characteristics of shimmy systems. The influences of the main system parameters on the shimmy system are also discussed. Improving the steering transition rod stiffness and dry friction torque and selecting a smaller pneumatic trail and caster angle can reduce the self-excited shimmy, reduce tire wear, and improve the driving stability of vehicles.

  17. Complexity dynamics and Hopf bifurcation analysis based on the first Lyapunov coefficient about 3D IS-LM macroeconomics system

    Science.gov (United States)

    Ma, Junhai; Ren, Wenbo; Zhan, Xueli

    2017-04-01

    Based on the study of scholars at home and abroad, this paper improves the three-dimensional IS-LM model in macroeconomics, analyzes the equilibrium point of the system and stability conditions, focuses on the parameters and complex dynamic characteristics when Hopf bifurcation occurs in the three-dimensional IS-LM macroeconomics system. In order to analyze the stability of limit cycles when Hopf bifurcation occurs, this paper further introduces the first Lyapunov coefficient to judge the limit cycles, i.e. from a practical view of the business cycle. Numerical simulation results show that within the range of most of the parameters, the limit cycle of 3D IS-LM macroeconomics is stable, that is, the business cycle is stable; with the increase of the parameters, limit cycles becomes unstable, and the value range of the parameters in this situation is small. The research results of this paper have good guide significance for the analysis of macroeconomics system.

  18. Stability and Hopf Bifurcation in a Modified Holling-Tanner Predator-Prey System with Multiple Delays

    Directory of Open Access Journals (Sweden)

    Zizhen Zhang

    2012-01-01

    Full Text Available A modified Holling-Tanner predator-prey system with multiple delays is investigated. By analyzing the associated characteristic equation, the local stability and the existence of periodic solutions via Hopf bifurcation with respect to both delays are established. Direction and stability of the periodic solutions are obtained by using normal form and center manifold theory. Finally, numerical simulations are carried out to substantiate the analytical results.

  19. Stability and Hopf Bifurcation in a Delayed HIV Infection Model with General Incidence Rate and Immune Impairment

    Science.gov (United States)

    Li, Fuxiang; Jiang, Zhichao

    2015-01-01

    We investigate the dynamical behavior of a delayed HIV infection model with general incidence rate and immune impairment. We derive two threshold parameters, the basic reproduction number R 0 and the immune response reproduction number R 1. By using Lyapunov functional and LaSalle invariance principle, we prove the global stability of the infection-free equilibrium and the infected equilibrium without immunity. Furthermore, the existence of Hopf bifurcations at the infected equilibrium with CTL response is also studied. By theoretical analysis and numerical simulations, the effect of the immune impairment rate on the stability of the infected equilibrium with CTL response has been studied. PMID:26413141

  20. Global Stability and Hopf Bifurcation of a Predator-Prey Model with Time Delay and Stage Structure

    Directory of Open Access Journals (Sweden)

    Lingshu Wang

    2014-01-01

    Full Text Available A delayed predator-prey system with Holling type II functional response and stage structure for both the predator and the prey is investigated. By analyzing the corresponding characteristic equations, the local stability of each of the feasible equilibria of the system is addressed and the existence of a Hopf bifurcation at the coexistence equilibrium is established. By means of persistence theory on infinite dimensional systems, it is proved that the system is permanent. By using Lyapunov functions and the LaSalle invariant principle, the global stability of each of the feasible equilibria of the model is discussed. Numerical simulations are carried out to illustrate the main theoretical results.

  1. Stability and Hopf Bifurcation in a Delayed HIV Infection Model with General Incidence Rate and Immune Impairment

    Directory of Open Access Journals (Sweden)

    Fuxiang Li

    2015-01-01

    Full Text Available We investigate the dynamical behavior of a delayed HIV infection model with general incidence rate and immune impairment. We derive two threshold parameters, the basic reproduction number R0 and the immune response reproduction number R1. By using Lyapunov functional and LaSalle invariance principle, we prove the global stability of the infection-free equilibrium and the infected equilibrium without immunity. Furthermore, the existence of Hopf bifurcations at the infected equilibrium with CTL response is also studied. By theoretical analysis and numerical simulations, the effect of the immune impairment rate on the stability of the infected equilibrium with CTL response has been studied.

  2. Stability and Hopf Bifurcation in a Delayed HIV Infection Model with General Incidence Rate and Immune Impairment.

    Science.gov (United States)

    Li, Fuxiang; Ma, Wanbiao; Jiang, Zhichao; Li, Dan

    2015-01-01

    We investigate the dynamical behavior of a delayed HIV infection model with general incidence rate and immune impairment. We derive two threshold parameters, the basic reproduction number R 0 and the immune response reproduction number R 1. By using Lyapunov functional and LaSalle invariance principle, we prove the global stability of the infection-free equilibrium and the infected equilibrium without immunity. Furthermore, the existence of Hopf bifurcations at the infected equilibrium with CTL response is also studied. By theoretical analysis and numerical simulations, the effect of the immune impairment rate on the stability of the infected equilibrium with CTL response has been studied.

  3. A modified averaging scheme with application to the secondary Hopf bifurcation of a delayed van der Pol oscillator

    Institute of Scientific and Technical Information of China (English)

    Z. H. Wang; H. Y. Hu

    2008-01-01

    In this paper, a modified averaging scheme is presented for a class of time-delayed vibration systems with slow variables. The new scheme is a combination of the averaging techniques proposed by Hale and by Lehman and Weibel, respectively. The averaged equation obtained from the modified scheme is simple enough but it retains the required information for the local nonlinear dynamics around an equilibrium. As an application of the present method, the delay value for which a secondary Hopf bifurcation occurs is successfully located for a delayed van der Pol oscillator.

  4. Non-smooth Hopf-type bifurcations arising from impact-friction contact events in rotating machinery.

    Science.gov (United States)

    Mora, Karin; Budd, Chris; Glendinning, Paul; Keogh, Patrick

    2014-11-01

    We analyse the novel dynamics arising in a nonlinear rotor dynamic system by investigating the discontinuity-induced bifurcations corresponding to collisions with the rotor housing (touchdown bearing surface interactions). The simplified Föppl/Jeffcott rotor with clearance and mass unbalance is modelled by a two degree of freedom impact-friction oscillator, as appropriate for a rigid rotor levitated by magnetic bearings. Two types of motion observed in experiments are of interest in this paper: no contact and repeated instantaneous contact. We study how these are affected by damping and stiffness present in the system using analytical and numerical piecewise-smooth dynamical systems methods. By studying the impact map, we show that these types of motion arise at a novel non-smooth Hopf-type bifurcation from a boundary equilibrium bifurcation point for certain parameter values. A local analysis of this bifurcation point allows us a complete understanding of this behaviour in a general setting. The analysis identifies criteria for the existence of such smooth and non-smooth bifurcations, which is an essential step towards achieving reliable and robust controllers that can take compensating action.

  5. Infinite period and Hopf bifurcations for the pH-regulated oscillations in a semibatch reactor (H(2)O(2)-Cu(2+)-S(2)O(2-) (3)-NaOH system).

    Science.gov (United States)

    Strizhak, Peter E.; Pojman, John A.

    1996-09-01

    Dynamic behavior of the pH-regulated oscillations has been studied for the hydrogen peroxide oxidation of thiosulfate ions in the presence of trace amounts of copper(II) ions in a semibatch reactor. A solution of 0.08 M Na(2)S(2)O(3) and 0.112 M NaOH was flowed at 0.160 mL/min into 300 mL of solution containing the H(2)O(2) and Cu(2+) in a vessel. There exists a critical value of the H(2)O(2) or Cu(2+) concentrations below which the system does not oscillate. The oscillations appear due to an infinite period bifurcation at low initial concentrations of the H(2)O(2). The initial concentration of Cu(2+) may be considered as a bifurcation parameter in this case. Increase of the initial hydrogen peroxide concentration causes the pH-regulated oscillations through a nondegenerate supercritical Hopf bifurcation. The classification of bifurcations is based on the analysis of the behavior of oscillation amplitude and period at different initial concentrations of the H(2)O(2) and Cu(2+). Our results show a possibility to distinguish different scenarios for the appearance of transient oscillations in semibatch experiments. (c) 1996 American Institute of Physics.

  6. Infinite period and Hopf bifurcations for the pH-regulated oscillations in a semibatch reactor (H2O2-Cu2 + -S2O2 - 3-NaOH system)

    Science.gov (United States)

    Strizhak, Peter E.; Pojman, John A.

    1996-09-01

    Dynamic behavior of the pH-regulated oscillations has been studied for the hydrogen peroxide oxidation of thiosulfate ions in the presence of trace amounts of copper(II) ions in a semibatch reactor. A solution of 0.08 M Na2S2O3 and 0.112 M NaOH was flowed at 0.160 mL/min into 300 mL of solution containing the H2O2 and Cu2+ in a vessel. There exists a critical value of the H2O2 or Cu2+ concentrations below which the system does not oscillate. The oscillations appear due to an infinite period bifurcation at low initial concentrations of the H2O2. The initial concentration of Cu2+ may be considered as a bifurcation parameter in this case. Increase of the initial hydrogen peroxide concentration causes the pH-regulated oscillations through a nondegenerate supercritical Hopf bifurcation. The classification of bifurcations is based on the analysis of the behavior of oscillation amplitude and period at different initial concentrations of the H2O2 and Cu2+. Our results show a possibility to distinguish different scenarios for the appearance of transient oscillations in semibatch experiments.

  7. BIFURCATION ANALYSIS OF EQUILIBRIUM POINT IN TWO NODE POWER SYSTEM

    Directory of Open Access Journals (Sweden)

    Halima Aloui

    2014-01-01

    Full Text Available This study presents a study of bifurcation in a dynamic power system model. It becomes one of the major precautions for electricity suppliers and these systems must maintain a steady state in the neighborhood of the operating points. We study in this study the dynamic stability of two node power systems theory and the stability of limit cycles emerging from a subcritical or supercritical Hopf bifurcation by computing the first Lyapunov coefficient. The MATCONT package of MATLAB was used for this study and detailed numerical simulations presented to illustrate the types of dynamic behavior. Results have proved the analyses for the model exhibit dynamical bifurcations, including Hopf bifurcations, Limit point bifurcations, Zero Hopf bifurcations and Bagdanov-taknes bifurcations.

  8. 非光滑系统的广义Hopf分支%Generalized Hopf Bifurcation for Non-smooth Planar Dynamical Systems: the Corner Case

    Institute of Scientific and Technical Information of China (English)

    邹永魁; Tassilo Küpper

    2001-01-01

    @@ Piece-wise smooth systems are an important class of ordinary differential equations whose dynamics are known to exhibit complex bifurcation scenarios and chaos. Broadly speaking,piece-wise smooth systems can undergo all the bifurcation that smooth ones can. More interestingly, there is a whole class of bifurcation that are unique to piece-wise smooth systems, such as the bifurcation caused by the geometric shape of the region in which the vector field is analyzed. For example (see Figure 1), the region is divided into two parts Ⅰ and Ⅱ by a discontinuity boundary which contains a corner at O. When an orbit cross the corner, border-collision bifurcation may occur (cf. [1]). The present paper deals with the mechanics of the generalized Hopf bifurcation when the stationary point locates at the corner.

  9. Hopf bifurcation in a dynamic IS-LM model with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Neamtu, Mihaela [Department of Economic Informatics, Mathematics and Statistics, Faculty of Economics, West University of Timisoara, str. Pestalozzi, nr. 16A, 300115 Timisoara (Romania)]. E-mail: mihaela.neamtu@fse.uvt.ro; Opris, Dumitru [Department of Applied Mathematics, Faculty of Mathematics, West University of Timisoara, Bd. V. Parvan, nr. 4, 300223 Timisoara (Romania)]. E-mail: opris@math.uvt.ro; Chilarescu, Constantin [Department of Economic Informatics, Mathematics and Statistics, Faculty of Economics, West University of Timisoara, str. Pestalozzi, nr. 16A, 300115 Timisoara (Romania)]. E-mail: cchilarescu@rectorat.uvt.ro

    2007-10-15

    The paper investigates the impact of delayed tax revenues on the fiscal policy out-comes. Choosing the delay as a bifurcation parameter we study the direction and the stability of the bifurcating periodic solutions. We show when the system is stable with respect to the delay. Some numerical examples are given to confirm the theoretical results.

  10. Hopf bifurcation control for a class of delay differential systems with discrete-time delayed feedback controller

    Science.gov (United States)

    Su, Huan; Mao, Xuerong; Li, Wenxue

    2016-11-01

    This paper is concerned with the asymptotical stabilization for a class of unstable delay differential equations. Continuous-time delayed feedback controller (C-TDFC) and discrete-time delayed feedback controller (D-TDFC) are presented and studied, respectively. To our best knowledge, applying Hopf bifurcation theory to delay differential equations with D-TDFC is original and meaningful. The difficulty brought by the introduction of sampling period has been overcome. An effective control range which ensures the asymptotical stability of equilibrium for the system with C-TDFC is obtained. Sequently, another effective control range for the system with D-TDFC is gotten, which approximates the one of C-TDFCS provided that the sampling period is sufficiently small. Meanwhile, efforts are paid to estimate a bound on sampling period. Finally, the theoretical results are applied to a physiological system to illustrate the effectiveness of the two control ranges.

  11. ANALYSIS VOLTAGE STABILITY USING HOPF BIFURCATION THEORY%电压稳定中的Hopf分歧分析

    Institute of Scientific and Technical Information of China (English)

    王洪哲; 邓集祥

    2000-01-01

    本文采用Hopf分歧理论结合相关因子法研究探讨电压稳定性问题,Hopf分歧理论比较全面地考虑系统的非线性性态,能够比传统的分析方法更深刻地探讨电力系统在临界点附近的稳定问题,并且能够在一定程度上将功角稳定问题和电压稳定问题联系起来提供统一的数学分析基础。%The combination of the bifurcation theory and relevant factortheory is proposed to search and discuss the voltage stability in this paper. Hopf bifurcation theory can more comprehensively reveal the nonlinear character of the system ,so it can more deeply search and discuss the stability nearby the critical point than the traditional analyzing method. To the extent,it can connect the P-δ stability with the voltage stability and provide the general mathematics analysis foundation.

  12. Stability and Hopf Bifurcation of a Delayed Density-Dependent Predator-Prey System with Beddington-DeAngelis Functional Response

    Science.gov (United States)

    Li, Haiyin; Meng, Gang; She, Zhikun

    In this paper, we investigate the stability and Hopf bifurcation of a delayed density-dependent predator-prey system with Beddington-DeAngelis functional response, where not only the prey density dependence but also the predator density dependence are considered such that the studied predator-prey system conforms to the realistically biological environment. We start with the geometric criterion introduced by Beretta and Kuang [2002] and then investigate the stability of the positive equilibrium and the stability switches of the system with respect to the delay parameter τ. Especially, we generalize the geometric criterion in [Beretta & Kuang, 2002] by introducing the condition (i‧) which can be assured by the condition (H2‧), and adopting the technique of lifting to define the function S˜n(τ) for alternatively determining stability switches at the zeroes of S˜n(τ)s. Afterwards, by the Poincaré normal form for Hopf bifurcation in [Kuznetsov, 1998] and the bifurcation formulae in [Hassard et al., 1981], we qualitatively analyze the properties for the occurring Hopf bifurcations of the system (3). Finally, an example with numerical simulations is given to illustrate the obtained results.

  13. BIFURCATIONS OF AIRFOIL IN INCOMPRESSIBLE FLOW

    Institute of Scientific and Technical Information of China (English)

    LiuFei; YangYiren

    2005-01-01

    Bifurcations of an airfoil with nonlinear pitching stiffness in incompressible flow are investigated. The pitching spring is regarded as a spring with cubic stiffness. The motion equations of the airfoil are written as the four dimensional one order differential equations. Taking air speed and the linear part of pitching stiffness as the parameters, the analytic solutions of the critical boundaries of pitchfork bifurcations and Hopf bifurcations are obtained in 2 dimensional parameter plane. The stabilities of the equilibrium points and the limit cycles in different regions of 2 dimensional parameter plane are analyzed. By means of harmonic balance method, the approximate critical boundaries of 2-multiple semi-stable limit cycle bifurcations are obtained, and the bifurcation points of supercritical or subcritical Hopf bifurcation are found. Some numerical simulation results are given.

  14. LOCAL AND GLOBAL HOPF BIFURCATIONS FOR A PREDATOR-PREY SYSTEM WITH TWO DELAYS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, the Leslie predator-prey system with two delays is studied. The stability of the positive equilibrium is discussed by analyzing the associated characteristic transcendental equation. The direction and stability of the bifurcating periodic solutions are determined by applying the center manifold theorem and normal form theory. The conditions to guarantee the global existence of periodic solutions are given.

  15. THE LIMIT CYCLES AND HOPF BIFURCATION OF A CLASS OF SIMPLIFIED HOLLING TYPE-IV PREDATOR-PREY SYSTEM WITH LINEAR STATE FEEDBACK

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper, a class of simplified Type-IV predator-prey system with linear state feedback is investigated. We prove the boundedness of the positive solutions to this system, and analyze the quality of the equilibria and the existence of limit cycles of the system surrounding the positive equilibra. By Hopf bifurcation theory, the result of having two limit cycles to the system is obtained.

  16. Discretization analysis of bifurcation based nonlinear amplifiers

    Science.gov (United States)

    Feldkord, Sven; Reit, Marco; Mathis, Wolfgang

    2017-09-01

    Recently, for modeling biological amplification processes, nonlinear amplifiers based on the supercritical Andronov-Hopf bifurcation have been widely analyzed analytically. For technical realizations, digital systems have become the most relevant systems in signal processing applications. The underlying continuous-time systems are transferred to the discrete-time domain using numerical integration methods. Within this contribution, effects on the qualitative behavior of the Andronov-Hopf bifurcation based systems concerning numerical integration methods are analyzed. It is shown exemplarily that explicit Runge-Kutta methods transform the truncated normalform equation of the Andronov-Hopf bifurcation into the normalform equation of the Neimark-Sacker bifurcation. Dependent on the order of the integration method, higher order terms are added during this transformation.A rescaled normalform equation of the Neimark-Sacker bifurcation is introduced that allows a parametric design of a discrete-time system which corresponds to the rescaled Andronov-Hopf system. This system approximates the characteristics of the rescaled Hopf-type amplifier for a large range of parameters. The natural frequency and the peak amplitude are preserved for every set of parameters. The Neimark-Sacker bifurcation based systems avoid large computational effort that would be caused by applying higher order integration methods to the continuous-time normalform equations.

  17. A bifurcation analysis of boiling water reactor on large domain of parametric spaces

    Science.gov (United States)

    Pandey, Vikas; Singh, Suneet

    2016-09-01

    The boiling water reactors (BWRs) are inherently nonlinear physical system, as any other physical system. The reactivity feedback, which is caused by both moderator density and temperature, allows several effects reflecting the nonlinear behavior of the system. Stability analyses of BWR is done with a simplified, reduced order model, which couples point reactor kinetics with thermal hydraulics of the reactor core. The linear stability analysis of the BWR for steady states shows that at a critical value of bifurcation parameter (i.e. feedback gain), Hopf bifurcation occurs. These stable and unstable domains of parametric spaces cannot be predicted by linear stability analysis because the stability of system does not include only stability of the steady states. The stability of other dynamics of the system such as limit cycles must be included in study of stability. The nonlinear stability analysis (i.e. bifurcation analysis) becomes an indispensable component of stability analysis in this scenario. Hopf bifurcation, which occur with one free parameter, is studied here and it formulates birth of limit cycles. The excitation of these limit cycles makes the system bistable in the case of subcritical bifurcation whereas stable limit cycles continues in an unstable region for supercritical bifurcation. The distinction between subcritical and supercritical Hopf is done by two parameter analysis (i.e. codimension-2 bifurcation). In this scenario, Generalized Hopf bifurcation (GH) takes place, which separates sub and supercritical Hopf bifurcation. The various types of bifurcation such as limit point bifurcation of limit cycle (LPC), period doubling bifurcation of limit cycles (PD) and Neimark-Sacker bifurcation of limit cycles (NS) have been identified with the Floquet multipliers. The LPC manifests itself as the region of bistability whereas chaotic region exist because of cascading of PD. This region of bistability and chaotic solutions are drawn on the various

  18. DROP TAIL AND RED QUEUE MANAGEMENT WITH SMALL BUFFERS:STABILITY AND HOPF BIFURCATION

    Directory of Open Access Journals (Sweden)

    Ganesh Patil

    2011-06-01

    Full Text Available There are many factors that are important in the design of queue management schemes for routers in the Internet: for example, queuing delay, link utilization, packet loss, energy consumption and the impact of router buffer size. By considering a fluid model for the congestion avoidance phase of Additive Increase Multiplicative Decrease (AIMD TCP, in a small buffer regime, we argue that stability should also be a desirable feature for network performance. The queue management schemes we study are Drop Tail and Random Early Detection (RED. For Drop Tail, the analytical arguments are based on local stability and bifurcation theory. As the buffer size acts as a bifurcation parameter, variations in it can readily lead to the emergence of limit cycles. We then present NS2 simulations to study the effect of changing buffer size on queue dynamics, utilization, window size and packet loss for three different flow scenarios. The simulations corroborate the analysis which highlights that performance is coupled with the notion of stability. Our work suggests that, in a small buffer regime, a simple Drop Tail queue management serves to enhance stability and appears preferable to the much studied RED scheme.

  19. Steady-state, self-oscillating and chaotic behavior of a PID controlled nonlinear servomechanism by using Bogdanov-Takens and Andronov-Poincaré-Hopf bifurcations

    Science.gov (United States)

    Pérez-Molina, Manuel; Pérez-Polo, Manuel F.

    2014-10-01

    This paper analyzes a controlled servomechanism with feedback and a cubic nonlinearity by means of the Bogdanov-Takens and Andronov-Poincaré-Hopf bifurcations, from which steady-state, self-oscillating and chaotic behaviors will be investigated using the center manifold theorem. The system controller is formed by a Proportional plus Integral plus Derivative action (PID) that allows to stabilize and drive to a prescribed set point a body connected to the shaft of a DC motor. The Bogdanov-Takens bifurcation is analyzed through the second Lyapunov stability method and the harmonic-balance method, whereas the first Lyapunov value is used for the Andronov-Poincaré-Hopf bifurcation. On the basis of the results deduced from the bifurcation analysis, we show a procedure to select the parameters of the PID controller so that an arbitrary steady-state position of the servomechanism can be reached even in presence of noise. We also show how chaotic behavior can be obtained by applying a harmonical external torque to the device in self-oscillating regime. The advantage of achieving chaotic behavior is that it can be used so that the system reaches a set point inside a strange attractor with a small control effort. The analytical calculations have been verified through detailed numerical simulations.

  20. Hopf Bifurcation of Traveling Wave of Delayed Nicholson's Blowflies Equation%时滞Nicholson's Blowflies方程中行波解的Hopf分支

    Institute of Scientific and Technical Information of China (English)

    杨高翔; 赵临龙

    2011-01-01

    主要利用时滞微分方程中Hopf分支理论探讨时滞Nicholson's Blowflies方程中行波解随时滞量τ大小变化的分支行为.结果发现时滞量经过某一数值τ0=1/cω0arcsin-cω0/p时,原系统会产生分支现象,最终导致形成周期性行波解.%Mainly employing Hopf bifurcation theory of delayed differential equation to study the bifurcation behavior of the traveling wave solution of the delayed Nicholson's Blowflies equation as the delayed term (T)changes. The results showed that when the delayed term(T)pass through(T)0= (1/cω0) arcsin (-cω0/p), the original system will take place bifurcation phenomenon and eventually lead to become the periodic traveling wave solution.

  1. 一个正反馈时滞微分方程的Hopf分支%Hopf Bifurcation of a Positive Feedback Delay Differential Equation

    Institute of Scientific and Technical Information of China (English)

    陈玉明; 黄立宏

    2003-01-01

    Under some minor technical hypotheses, for each τ larger than a certain τs > 0, Krisztin, Walther and Wu showed the existence of a periodic orbit for the positive feedback delay differential equation x(t) = -τμx(t) + τf(x(t - 1)), where τ and μ are positive constants and f: R → R satisfies f(0) = 0 and f′> 0.Combining this with a unique result of Krisztin and Walther, we know that this periodic orbit is the one branched out from 0 through Hopf bifurcation. Using the normal form theory for delay differential equations, we show the same result under the condition that f ∈ C3(R, R) is such that f"(0) = 0 and f′"(0) < 0, which is weaker than those of Krisztin and Walther.

  2. Clusters of decelerations of heart rate appear to be a Hopf bifurcation, and provide early warning of illness in premature infants

    Science.gov (United States)

    Flower, Abigail; Moorman, Randall; Lake, Douglas; Delos, John

    2009-03-01

    The pacemaking system of the heart is complex; a healthy heart constantly integrates and responds to extracardiac signals, resulting in highly complex heart rate patterns with a great deal of variability. In the laboratory and in some pathological or age-related states, however, dynamics can show reduced complexity that is more readily described and modeled. Reduced heart rate complexity has both clinical and dynamical significance -- it may provide warning of impending illness or clues about the dynamics of the heart's pacemaking system. Here we describe uniquely simple and interesting heart rate dynamics observed in premature human infants - reversible transitions to large-amplitude periodic oscillations. We propose a mathematical interpretation based on Hopf bifurcation theory. (Supported by NIGMS, by the National Heart, Lung, and Blood Institute, and by NSF, with computing support provided by William and Mary.)

  3. Pattern formation, long-term transients, and the Turing-Hopf bifurcation in a space- and time-discrete predator-prey system.

    Science.gov (United States)

    Rodrigues, Luiz Alberto Díaz; Mistro, Diomar Cristina; Petrovskii, Sergei

    2011-08-01

    Understanding of population dynamics in a fragmented habitat is an issue of considerable importance. A natural modelling framework for these systems is spatially discrete. In this paper, we consider a predator-prey system that is discrete both in space and time, and is described by a Coupled Map Lattice (CML). The prey growth is assumed to be affected by a weak Allee effect and the predator dynamics includes intra-specific competition. We first reveal the bifurcation structure of the corresponding non-spatial system. We then obtain the conditions of diffusive instability on the lattice. In order to reveal the properties of the emerging patterns, we perform extensive numerical simulations. We pay a special attention to the system properties in a vicinity of the Turing-Hopf bifurcation, which is widely regarded as a mechanism of pattern formation and spatiotemporal chaos in space-continuous systems. Counter-intuitively, we obtain that the spatial patterns arising in the CML are more typically stationary, even when the local dynamics is oscillatory. We also obtain that, for some parameter values, the system's dynamics is dominated by long-term transients, so that the asymptotical stationary pattern arises as a sudden transition between two different patterns. Finally, we argue that our findings may have important ecological implications.

  4. Bifurcation and Limit Cycle of a Ratio-dependent Predator-prey System with Refuge on Prey

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-wei; LIU Xia

    2013-01-01

    Influences of prey refuge on the dynamics of a predator-prey model with ratiodependent functional response are investigated.The local and global stability of positive equilibrium of the system are considered.Theoretical analysis indicates that constant refuge leads to the system undergo supercritical Hopf bifurcation twice with the birth rate of prey species changing continuously.

  5. 一类具时滞和非线性传染率的SIS传染病模型的Hopf分支%Hopf Bifurcation of a SIS Epidemic Model with Time Delay and Nonlinear incidence

    Institute of Scientific and Technical Information of China (English)

    童姗姗; 窦霁虹; 王佳颖

    2011-01-01

    研究了一类具恢复期时滞且发生率为非线性的SIS传染病模型,讨论了该系统地方病平衡点的稳定性。利用Hopf分支理论,以时间τ为参数给出了系统在地方病平衡点处产生Hopf分支的充分条件。%A class of an SIS epidemic mathematic model with constant recruitment,time delay and nonlinear incidence is studied,and its stability of endemic equilibrium is discussed.By applying the theorem of Hopf bifurcation,the sufficient conditions of the endemic equilibrium occurring Hopf bifurcation with delay as parameter is given.

  6. The stability and Hopf bifurcation for a kind of predator system with time delay%一类时滞捕食系统的稳定性与Hopf分支

    Institute of Scientific and Technical Information of China (English)

    王建芳; 陈斯养

    2012-01-01

    The stability and Hopf bifurcation for a kind of predator system with time delay is discussed. Appying Hurwitz discriminant method and eigenvalue theory, the sufficient condition of equilibrium being local asymptotic stability and the condition of Hopf bifurcation existence are obtained. By using Matlab software package, the fitting graph of solution curve is given. The feasibility of theorem conditions is also shown by an example.%讨论了一类时滞捕食系统的稳定性与Hopf分支问题.应用Hurwitz判别法及特征值理论得到平衡点局部渐近稳定的充分条件和Hopf分支存在的条件;利用Matlab给出了解曲线的拟合图,并举例验证了定理条件和结论的一致性.

  7. Stability Switches and Hopf Bifurcation in a Coupled FitzHugh-Nagumo Neural System with Multiple Delays

    Directory of Open Access Journals (Sweden)

    Shengwei Yao

    2014-01-01

    Full Text Available A FitzHugh-Nagumo (FHN neural system with multiple delays has been proposed. The number of equilibrium point is analyzed. It implies that the neural system exhibits a unique equilibrium and three ones for the different values of coupling weight by employing the saddle-node bifurcation of nontrivial equilibrium point and transcritical bifurcation of trivial one. Further, the stability of equilibrium point is studied by analyzing the corresponding characteristic equation. Some stability criteria involving the multiple delays and coupling weight are obtained. The results show that the neural system exhibits the delay-independence and delay-dependence stability. Increasing delay induces the stability switching between resting state and periodic activity in some parameter regions of coupling weight. Finally, numerical simulations are taken to support the theoretical results.

  8. Identification of Bifurcations from Observations of Noisy Biological Oscillators.

    Science.gov (United States)

    Salvi, Joshua D; Ó Maoiléidigh, Dáibhid; Hudspeth, A J

    2016-08-23

    Hair bundles are biological oscillators that actively transduce mechanical stimuli into electrical signals in the auditory, vestibular, and lateral-line systems of vertebrates. A bundle's function can be explained in part by its operation near a particular type of bifurcation, a qualitative change in behavior. By operating near different varieties of bifurcation, the bundle responds best to disparate classes of stimuli. We show how to determine the identity of and proximity to distinct bifurcations despite the presence of substantial environmental noise. Using an improved mechanical-load clamp to coerce a hair bundle to traverse different bifurcations, we find that a bundle operates within at least two functional regimes. When coupled to a high-stiffness load, a bundle functions near a supercritical Hopf bifurcation, in which case it responds best to sinusoidal stimuli such as those detected by an auditory organ. When the load stiffness is low, a bundle instead resides close to a subcritical Hopf bifurcation and achieves a graded frequency response-a continuous change in the rate, but not the amplitude, of spiking in response to changes in the offset force-a behavior that is useful in a vestibular organ. The mechanical load in vivo might therefore control a hair bundle's responsiveness for effective operation in a particular receptor organ. Our results provide direct experimental evidence for the existence of distinct bifurcations associated with a noisy biological oscillator, and demonstrate a general strategy for bifurcation analysis based on observations of any noisy system.

  9. Study on Global Existence of Hopf Bifurcation in a Cohen-Grossberg Neural Networks with Time Delays%具有时滞的Cohen-Grossberg神经网络的Hopf分支全局存在性研究

    Institute of Scientific and Technical Information of China (English)

    刘启明; 杜艳可

    2013-01-01

    利用泛函微分方程的度理论,研究一类具有时滞的Cohen-Grossberg神经网络的全局分支的存在性,研究结果为该类神经网络的应用设计提供理论基础.%Based on the degree theory of functional differential equations,global existence of Hopf bifurcation in a class of delayed Cohen-Grossberg neural networks is investigated. The results are theoretical foundation for practical design of the neural networks.

  10. 恒电流刺激下神经元Chay模型的Hopf分岔分析%The Hopf Bifurcation Analysis of the Neuronal Chay Model under Constant Current Stimulation

    Institute of Scientific and Technical Information of China (English)

    李洪明; 张素丽

    2013-01-01

    The Hopf bifurcation of the neuronal Chay model under constant current stimulation is analyzed. Firstly, with the help of software Matlab, the equilibrium point of the Chay model under the considered parameters was found and the stability of equilibrium point was established according to its Jacobian matrix. Secondly, the stability theory was used to study the neuronal Chay model under constant current stimulation. The results show that the the Hopf bifurcation of the Chay model occurs as the considered parameter Ⅰ varies. Finally, the software Mat-lab was employed to support the above theoretical analysis and present numeric simulations.%研究了恒电流刺激下神经元Chay模型的Hopf分岔.首先,利用Matlab软件计算出系统在给定参数下的平衡点,据其Jacobian矩阵得到平衡点的稳定性.其次,根据稳定性理论,研究了恒电流刺激下神经元Chay模型,结果表明随着控制参数I的变化,系统将发生Hopf分岔.最后利用Matlab给出了支持理论分析的数值模拟.

  11. Bifurcation analysis of hydro-turbine regulating system with saturation nonlinearity for hydropower station with upstream and downstream surge chambers

    Science.gov (United States)

    Chen, J. P.; Yang, J. D.; Guo, W. C.

    2016-11-01

    A nonlinear mathematical model of hydraulic turbine regulating system is applied to describe hydropower stations with upstream and downstream surge chambers. This model features saturation nonlinearity including pipeline system and turbine regulating system used in stability analysis. First, the existence conditions and direction of Hopf bifurcation are obtained. Second, based on the algebraic criteria for the occurrence of Hopf bifurcation, the stability domain is drawn in a coordinate system, where the proportional gain Kp is the abscissa and the integral gain Ki is the ordinate. Third, the nonlinear dynamic behaviour of a regulating system with different state parameters are analyzed, and the variations of the system stability around the two sides of the bifurcation point are numerically calculated. Based on this work we conclude that the Hopf bifurcation of system is supercritical. The bifurcation parameters that are far from the bifurcation point would be advantageous to the rapid system regulation needed to sustain equilibrium. Furthermore, it is established that using a PID controller is more conducive to stability than a PI controller. The unit stability regulation gets worse by taking into account the saturation nonlinearity.

  12. Finite-size effects lead to supercritical bifurcations in turbulent rotating Rayleigh-B\\'enard convection

    CERN Document Server

    Weiss, Stephan; Zhong, Jin-Qiang; Clercx, Herman J H; Lohse, Detlef; Ahlers, Guenter; 10.1103/PhysRevLett.105.224501

    2011-01-01

    In turbulent thermal convection in cylindrical samples of aspect ratio \\Gamma = D/L (D is the diameter and L the height) the Nusselt number Nu is enhanced when the sample is rotated about its vertical axis, because of the formation of Ekman vortices that extract additional fluid out of thermal boundary layers at the top and bottom. We show from experiments and direct numerical simulations that the enhancement occurs only above a bifurcation point at a critical inverse Rossby number $1/\\Ro_c$, with $1/\\Ro_c \\propto 1/\\Gamma$. We present a Ginzburg-Landau like model that explains the existence of a bifurcation at finite $1/\\Ro_c$ as a finite-size effect. The model yields the proportionality between $1/\\Ro_c$ and $1/\\Gamma$ and is consistent with several other measured or computed system properties.

  13. Synchronization and bifurcation structures in coupled periodically forced non-identical Duffing oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Vincent, U E [Department of Physics, Olabisi Onabanjo University, PMB 2002, Ago-Iwoye (Nigeria); Kenfack, A [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany)], E-mail: kenfack@pks.mpg.de

    2008-04-15

    We study the bifurcation structure and the synchronization of a double-well Duffing oscillator coupled to a single-well one and subjected to periodic forces. Using the amplitudes and the frequencies of these driving forces as control parameters, we show that our model presents phenomena which were not observed in a similar system but with identical potentials. In the regime of relatively weak coupling, bubbles of bifurcations and chains of symmetry-breaking are identified. For much stronger couplings, Hopf bifurcations born from orbits of higher periodicity, as well as subcritical and supercritical Neimark bifurcations emerge. Varying the coupling strength, we also find a threshold for which the system remains quasiperiodic. Moreover, tori-breakdown route to a strange non-chaotic attractor is another highlight of features found in this model. In two parameter diagrams, regions of chaos and quasiperiodicity are clearly identified. Finally, threshold parameters for which synchronization occurs have been found.

  14. Stability and Bifurcation in Magnetic Flux Feedback Maglev Control System

    Directory of Open Access Journals (Sweden)

    Wen-Qing Zhang

    2013-01-01

    Full Text Available Nonlinear properties of magnetic flux feedback control system have been investigated mainly in this paper. We analyzed the influence of magnetic flux feedback control system on control property by time delay and interfering signal of acceleration. First of all, we have established maglev nonlinear model based on magnetic flux feedback and then discussed hopf bifurcation’s condition caused by the acceleration’s time delay. The critical value of delayed time is obtained. It is proved that the period solution exists in maglev control system and the stable condition has been got. We obtained the characteristic values by employing center manifold reduction theory and normal form method, which represent separately the direction of hopf bifurcation, the stability of the period solution, and the period of the period motion. Subsequently, we discussed the influence maglev system on stability of by acceleration’s interfering signal and obtained the stable domain of interfering signal. Some experiments have been done on CMS04 maglev vehicle of National University of Defense Technology (NUDT in Tangshan city. The results of experiments demonstrate that viewpoints of this paper are correct and scientific. When time lag reaches the critical value, maglev system will produce a supercritical hopf bifurcation which may cause unstable period motion.

  15. Codimension-Two Bifurcation Analysis in Hindmarsh-Rose Model with Two Parameters

    Institute of Scientific and Technical Information of China (English)

    DUAN Li-Xia; LU Qi-Shao

    2005-01-01

    @@ Bifurcation phenomena in a Hindmarsh-Rose neuron model are investigated. Special attention is paid to the bifurcation structures off two parameters, where codimension-two generalized-Hopf bifurcation and fold-Hopf bifurcation occur. The classification offiring patterns as well as the transition mechanism in different regions on the parameter plane are obtained.

  16. 一类具有时滞的病菌-免疫力模型的Hopf分歧%The Hopf Bifurcation of a Bacteria-immunity Model with Time Delay

    Institute of Scientific and Technical Information of China (English)

    项晶菁; 权豫西

    2012-01-01

    考虑病菌的一种信息交流机制,建立一类病菌与免疫系统竞争的时滞传染病模型.分析正平衡点的存在性、渐近稳定性、Hopf分歧的存在性及方向.运用计算机数值模拟验证所得理论结果,为传染病的控制和预防提供了理论基础和数值依据.%In view of an exchanging information mechanism of bacteria,a delayed epidemic model with the competition between bacteria and the immune system is formulated. In the sequel, the existence and stability of the positive equilibrium are investigated, respectively. Then,the existence and direction of Hopf bifurcation are discussed. At last,numerical simulations are curried out to verify the theory results,and which provide theory and numerical basis to control and prevent the epidemic disease.

  17. Bifurcation analysis of the simplified models of boiling water reactor and identification of global stability boundary

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Vikas; Singh, Suneet, E-mail: suneet.singh@iitb.ac.in

    2017-04-15

    Highlights: • Non-linear stability analysis of nuclear reactor is carried out. • Global and local stability boundaries are drawn in the parameter space. • Globally stable, bi-stable, and unstable regions have been demarcated. • The identification of the regions is verified by numerical simulations. - Abstract: Nonlinear stability study of the neutron coupled thermal hydraulics instability has been carried out by several researchers for boiling water reactors (BWRs). The focus of these studies has been to identify subcritical and supercritical Hopf bifurcations. Supercritical Hopf bifurcation are soft or safe due to the fact that stable limit cycles arise in linearly unstable region; linear and global stability boundaries are same for this bifurcation. It is well known that the subcritical bifurcations can be considered as hard or dangerous due to the fact that unstable limit cycles (nonlinear phenomena) exist in the (linearly) stable region. The linear stability leads to a stable equilibrium in such regions, only for infinitesimally small perturbations. However, finite perturbations lead to instability due to the presence of unstable limit cycles. Therefore, it is evident that the linear stability analysis is not sufficient to understand the exact stability characteristics of BWRs. However, the effect of these bifurcations on the stability boundaries has been rarely discussed. In the present work, the identification of global stability boundary is demonstrated using simplified models. Here, five different models with different thermal hydraulics feedback have been investigated. In comparison to the earlier works, current models also include the impact of adding the rate of change in temperature on void reactivity as well as effect of void reactivity on rate of change of temperature. Using the bifurcation analysis of these models the globally stable region in the parameter space has been identified. The globally stable region has only stable solutions and

  18. Stability and Hopf bifurcation of an HIV model with time delay%一类具有时滞的HIV感染模型的稳定性分析

    Institute of Scientific and Technical Information of China (English)

    车培红

    2011-01-01

    The HIV infection in vivo model with time delay is studied, which incorporates the duration for the infected T* cells to release the virus as the delay parameter.The global stability of the boundary equilibria is obtained by using the Routh-Hurwitz criteria,constructing Lyapunov function and the nonnegative invariance analysis of the system.And the existence of the threshold τ0 is proved, the inner equilibria is local asymptotic stable as τ < τ0; the inner equilibria is unstable as τ = τ0, it appears a Hopf bifurcation in the system as τ > τ0.At last the numerical simulation is given with the Matlab software, and the rationality of the theoretical analysis is verified.%研究了一类具有时滞的HⅣ体内感染模型,引入了以受感染T*细胞释放出病毒的持续时间为时滞参数.通过Routh-Hurwitz准则和构造Lyapunov函数及对系统非负不变性分析,得出边界平衡点具有全局稳定性.并证明了存在临界值τ0,当τ<τ0时,内部平衡点是局部渐近稳定的;当τ>τ0时,内部平衡点是不稳定的;当τ=τ0时,系统具有Hopf分支.最后利用Madab软件进行数值模拟并验证了分析的合理性.

  19. On pointed Hopf superalgebras

    CERN Document Server

    Andruskiewitsch, Nicolás; Yamane, Hiroyuki

    2010-01-01

    We discuss the relationship between Hopf superalgebras and Hopf algebras. We list the braided vector spaces of diagonal type with generalized root system of super type and give the defining relations of the corresponding Nichols algebras.

  20. Bifurcation Phenomena in a Lotka-Volterra Model with Cross-Diffusion and Delay Effect

    Science.gov (United States)

    Yan, Shuling; Guo, Shangjiang

    2017-06-01

    This paper focuses on a Lotka-Volterra model with delay and cross-diffusion. By using Lyapunov-Schmidt reduction, we investigate the existence, multiplicity, stability and Hopf bifurcation of spatially nonhomogeneous steady-state solutions. Furthermore, we obtain some criteria to determine the bifurcation direction and stability of Hopf bifurcating periodic orbits by using Lyapunov-Schmidt reduction.

  1. DYNAMIC BIFURCATION OF NONLINEAR EVOLUTION EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    MA TIAN; WANG SHOUHONG

    2005-01-01

    The authors introduce a notion of dynamic bifurcation for nonlinear evolution equations, which can be called attractor bifurcation. It is proved that as the control parameter crosses certain critical value, the system bifurcates from a trivial steady state solution to an attractor with dimension between m and m + 1, where m + 1 is the number of eigenvalues crossing the imaginary axis. The attractor bifurcation theory presented in this article generalizes the existing steady state bifurcations and the Hopf bifurcations. It provides a unified point of view on dynamic bifurcation and can be applied to many problems in physics and mechanics.

  2. Hopf points of codimension two in a delay differential equation modeling leukemia

    CERN Document Server

    Ion, Anca Veronica

    2012-01-01

    This paper continues the work contained in two previous papers, devoted to the study of the dynamical system generated by a delay differential equation that models leukemia. Here our aim is to identify degenerate Hopf bifurcation points. By using an approximation of the center manifold, we compute the first Lyapunov coefficient for Hopf bifurcation points. We find by direct computation, in some zones of the parameter space (of biological significance), points where the first Lyapunov coefficient equals zero. For these we compute the second Lyapunov coefficient, that determines the type of the degenerate Hopf bifurcation.

  3. Bifurcation Analysis of a Lotka-Volterra Mutualistic System with Multiple Delays

    Directory of Open Access Journals (Sweden)

    Xin-You Meng

    2014-01-01

    Full Text Available A class of Lotka-Volterra mutualistic system with time delays of benefit and feedback delays is introduced. By analyzing the associated characteristic equation, the local stability of the positive equilibrium and existence of Hopf bifurcation are obtained under all possible combinations of two or three delays selecting from multiple delays. Not only explicit formulas to determine the properties of the Hopf bifurcation are shown by using the normal form method and center manifold theorem, but also the global continuation of Hopf bifurcation is investigated by applying a global Hopf bifurcation result due to Wu (1998. Numerical simulations are given to support the theoretical results.

  4. Bifurcation analysis in single-species population model with delay

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A single-species population model is investigated in this paper.Firstly,we study the existence of Hopf bifurcation at the positive equilibrium.Furthermore,an explicit algorithm for determining the direction of the Hopf bifurcation and stability of the bifurcation periodic solutions are derived by using the normal form and the center manifold theory.At last,numerical simulations to support the analytical conclusions are carried out.

  5. Ecological public goods games: cooperation and bifurcation.

    Science.gov (United States)

    Hauert, Christoph; Wakano, Joe Yuichiro; Doebeli, Michael

    2008-03-01

    The Public Goods Game is one of the most popular models for studying the origin and maintenance of cooperation. In its simplest form, this evolutionary game has two regimes: defection goes to fixation if the multiplication factor r is smaller than the interaction group size N, whereas cooperation goes to fixation if the multiplication factor r is larger than the interaction group size N. Hauert et al. [Hauert, C., Holmes, M., Doebeli, M., 2006a. Evolutionary games and population dynamics: Maintenance of cooperation in public goods games. Proc. R. Soc. Lond. B 273, 2565-2570] have introduced the Ecological Public Goods Game by viewing the payoffs from the evolutionary game as birth rates in a population dynamic model. This results in a feedback between ecological and evolutionary dynamics: if defectors are prevalent, birth rates are low and population densities decline, which leads to smaller interaction groups for the Public Goods game, and hence to dominance of cooperators, with a concomitant increase in birth rates and population densities. This feedback can lead to stable co-existence between cooperators and defectors. Here we provide a detailed analysis of the dynamics of the Ecological Public Goods Game, showing that the model exhibits various types of bifurcations, including supercritical Hopf bifurcations, which result in stable limit cycles, and hence in oscillatory co-existence of cooperators and defectors. These results show that including population dynamics in evolutionary games can have important consequences for the evolutionary dynamics of cooperation.

  6. LOCAL STABILITY AND BIFURCATION IN A THREE—UNIT DELAYED NEURAL NETWORK

    Institute of Scientific and Technical Information of China (English)

    LINYiping; LIJibin; 等

    2003-01-01

    A system of three-unit networks with coupled cells is investigated.The general formula for bifurcation direction of Hopf bifurcation is calculated and the estimate formula of period of the periodic solution is given.

  7. BIFURCATION OF PERIODIC SOLUTION IN A THREE-UNIT NEURAL NETWORK WITH DELAY

    Institute of Scientific and Technical Information of China (English)

    林怡平; ROLAND LEMMERT; PETER VOLKMANN

    2001-01-01

    A system of three-unit networks with no self-connection is investigated, the general formula for bifurcation direction of Hopf bifurcation is calculated, and the estimation formula of the period for periodic solution is given.

  8. Stability and Bifurcation Analysis of Man-machine System with Time Delay

    Institute of Scientific and Technical Information of China (English)

    YANG Ji-hua; LIU Mei

    2012-01-01

    A mathematical model of man-machine system is considered.Based on the reference [4],the direction and stability of the Hopf bifurcation are determined using the normal form method and the center manifold theory.Furthermore,the existence of Hopf-zero bifurcation is discussed.In the end,some numerical simulations are carried out to illustrate the results found.

  9. Bounded global Hopf branches for stage-structured differential equations with unimodal feedback

    Science.gov (United States)

    Shu, Hongying; Wang, Lin; Wu, Jianhong

    2017-03-01

    We consider a class of stage-structured differential equations with unimodal feedback. By using the time delay as a bifurcation parameter, we show that the number of local Hopf bifurcation values is finite. Furthermore, we analytically prove that these local Hopf bifurcation values are neatly paired, and each pair is jointed by a bounded global Hopf branch. We use the well-known Mackey-Glass equation with a stage structure as an illustrative example to demonstrate that bounded global Hopf branches can induce interesting and rich dynamics. As the delay increases over a finite interval, the stage-structured Mackey-Glass equation exhibits certain symmetric dynamic patterns: the solutions evolve from a stable equilibrium to sustained stable periodic oscillations, to chaotic-like aperiodic oscillations and back to sustained stable periodic oscillations, to a stable equilibrium.

  10. Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

    Directory of Open Access Journals (Sweden)

    Xin Qi

    2015-02-01

    Full Text Available Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To predict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynamics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurcation and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders series of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

  11. Generalized braided Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    LU Zhong-jian; FANG Xiao-li

    2009-01-01

    The concept of (f, σ)-pair (B, H)is introduced, where B and H are Hopf algebras. A braided tensor category which is a tensor subcategory of the category HM of left H-comodules through an (f, σ)-pair is constructed. In particularly, a Yang-Baxter equation is got. A Hopf algebra is constructed as well in the Yetter-Drinfel'd category HHYD by twisting the multiplication of B.

  12. Characteristics of Period-Adding Bursting Bifurcation Without Chaos in the Chay Neuron Model

    Institute of Scientific and Technical Information of China (English)

    YANG Zhuo-Qin; LU Qi-Shao

    2004-01-01

    @@ A period-adding bursting sequence without bursting-chaos in the Chay neuron model is studied by bifurcation analysis. The genesis of each periodic bursting is separately evoked by the corresponding periodic spiking patterns through two period-doubling bifurcations, except for the period-1 bursting occurring via Hopf bifurcation. Hence,it is concluded that this period-adding bursting bifurcation without chaos has a compound bifurcation structure closely related to period-doubling bifurcations of periodic spiking in essence.

  13. Codimension two bifurcation of a vibro-bounce system

    Institute of Scientific and Technical Information of China (English)

    Guanwei Luo; Yandong Chu; Yanlong Zhang; Jianhua Xie

    2005-01-01

    A three-degree-of-freedom vibro-bounce system is considered. The disturbed map of period one single-impact motion is derived analytically. A center manifold theorem dimensional one, and the normal form map associated with Hopf-flip bifurcation is obtained. Dynamical behavior of the system, near the point of codimension two bifurcation, is investigated by using qualitative analysis and numerical simulation. It is found that near the point of Hopf-flip bifurcation there exists not only Hopf bifurcation of period one singleimpact motion, but also Hopf bifurcation of period two double-impact motion. The results from simulation show that there exists an interesting torus doubling bifurcation near the codimension two bifurcation. The torus doubling bifurcation makes the quasi-periodic attractor associated with period one single-impact motion transform to the other quasi-periodic attractor represented by two attracting closed circles. The torus bifurcation is qualitatively different from the typical torus doubling bifurcation occurring in the vibro-impact systems. Different routes from period one single-impact motion to chaos are observed by numerical simulation.

  14. Bifurcation Analysis of a Discrete Logistic System with Feedback Control

    Institute of Scientific and Technical Information of China (English)

    WU Dai-yong

    2015-01-01

    The paper studies the dynamical behaviors of a discrete Logistic system with feedback control. The system undergoes Flip bifurcation and Hopf bifurcation by using the center manifold theorem and the bifurcation theory. Numerical simulations not only illustrate our results, but also exhibit the complex dynamical behaviors of the system, such as the period-doubling bifurcation in periods 2, 4, 8 and 16, and quasi-periodic orbits and chaotic sets.

  15. Neural Excitability and Singular Bifurcations.

    Science.gov (United States)

    De Maesschalck, Peter; Wechselberger, Martin

    2015-12-01

    We discuss the notion of excitability in 2D slow/fast neural models from a geometric singular perturbation theory point of view. We focus on the inherent singular nature of slow/fast neural models and define excitability via singular bifurcations. In particular, we show that type I excitability is associated with a novel singular Bogdanov-Takens/SNIC bifurcation while type II excitability is associated with a singular Andronov-Hopf bifurcation. In both cases, canards play an important role in the understanding of the unfolding of these singular bifurcation structures. We also explain the transition between the two excitability types and highlight all bifurcations involved, thus providing a complete analysis of excitability based on geometric singular perturbation theory.

  16. Experiments on bifurcation of periodic states into tori for a periodically forced chemical oscillator

    Science.gov (United States)

    Vance, William; Ross, John

    1988-05-01

    We study experimentally continuous transitions from quasiperiodic to periodic states for a time-periodically forced chemical oscillator. The chemical reaction is the hydration of 2,3-epoxy-1-propanol, and is carried out in a continuous stirred tank reactor (CSTR). Periodic oscillatory states are observed to arise in the autonomous system through supercritical Hopf bifurcations as either the total flow rate or the cooling coil temperature is changed. Under conditions of oscillation for the autonomous system, small-amplitude periodic variation of the total flow rate generates an attracting two-torus from the stable limit cycle. From the experiments we determine the structure of the toroidal flow, stroboscopic phase portraits, and circle maps as a function of the forcing amplitude and period. A continuous transition from the quasiperiodic to a periodic state, in which the two-torus contracts to a closed curve (Neimark-Sacker torus bifurcation), is observed as the forcing amplitude is increased at a constant forcing period, or as the forcing period is changed at a constant moderate forcing amplitude. Qualitative theoretical predictions compare well with the experimental observations. This paper presents the first experimental observation of a Neimark-Sacker torus bifurcation in a forced chemical oscillator system, and relates the bifurcation diagram of the unforced system to that of the forced system.

  17. Automorphism groups of pointed Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    YANG Shilin

    2007-01-01

    The group of Hopf algebra automorphisms for a finite-dimensional semisimple cosemisimple Hopf algebra over a field k was considered by Radford and Waterhouse. In this paper, the groups of Hopf algebra automorphisms for two classes of pointed Hopf algebras are determined. Note that the Hopf algebras we consider are not semisimple Hopf algebras.

  18. Fundamentals of Hopf algebras

    CERN Document Server

    Underwood, Robert G

    2015-01-01

    This text aims to provide graduate students with a self-contained introduction to topics that are at the forefront of modern algebra, namely, coalgebras, bialgebras, and Hopf algebras.  The last chapter (Chapter 4) discusses several applications of Hopf algebras, some of which are further developed in the author’s 2011 publication, An Introduction to Hopf Algebras.  The book may be used as the main text or as a supplementary text for a graduate algebra course.  Prerequisites for this text include standard material on groups, rings, modules, algebraic extension fields, finite fields, and linearly recursive sequences. The book consists of four chapters. Chapter 1 introduces algebras and coalgebras over a field K; Chapter 2 treats bialgebras; Chapter 3 discusses Hopf algebras and Chapter 4 consists of three applications of Hopf algebras. Each chapter begins with a short overview and ends with a collection of exercises which are designed to review and reinforce the material. Exercises range from straightforw...

  19. Global bifurcations of a rotating pendulum with irrational nonlinearity

    Science.gov (United States)

    Han, Ning; Cao, Qingjie

    2016-07-01

    In this paper, the authors consider a rotating pendulum under nonlinear perturbation which allows us to study various kinds of bifurcations and limit cycles. This system exhibits smooth or discontinuous dynamics depending on the value of a mechanical parameter. It is shown that the perturbed smooth system undergoes a pitchfork bifurcation, a homo-heteroclinic orbits transition, a single Hopf bifurcation, a double Hopf bifurcation, a pair of homoclinic bifurcations, a Hopf-homoclinic bifurcation and two saddle-node bifurcation of periodic orbits. The number, position and stability of all the oscillating and rotational limit cycles are given as the parameters vary. We find five limit cycles in the smooth case due to two saddle-node bifurcation of periodic orbits existing. Unlike the smooth case, the perturbed discontinuous system has a homoclinic-like bifurcation and without any saddle-node bifurcation of periodic orbits. Additionally, some results obtained herein bear significant similarities to the codimension-two bifurcation of duffing oscillator and SD oscillator, which may be helpful to explore the codimension bifurcation of the cylindrical pendulum system with irrational nonlinearity.

  20. Local Bifurcations Analysis of a State-Dependent Delay Differential Equation

    Directory of Open Access Journals (Sweden)

    V. O. Golubenets

    2015-01-01

    Full Text Available In this paper, a first-order equation with state-dependent delay and with a nonlinear right-hand side is considered. Conditions of existence and uniqueness of the solution of initial value problem aresupposed to be executed. The task is to study the behavior of solutions of the considered equation in a small neighborhood of its zero equilibrium. Local dynamics depends on real parameters which are coefficients of equation right-hand side decomposition in a Taylor series. The parameter which is a coefficient at the linear part of this decomposition has two critical values which determine a stability domain of zero equilibrium. We introduce a small positive parameter and use the asymtotic method of normal forms in order to investigate local dynamics modifications of the equation near each two critical values. We show that the stability exchange bifurcation occurs in the considered equation near the first of these critical values, and the supercritical Andronov – Hopf bifurcation occurs near the second of them (if the sufficient condition is executed. Asymptotic decompositions according to correspondent small parameters are obtained for each stable solution. Next, a logistic equation with state-dependent delay is considered as an example. The bifurcation parameter of this equation has one critical value. A simple sufficient condition of Andronov – Hopf bifurcation occurence in the considered equation near a critical value is obtained as a result of applying the method of normal forms.

  1. Coloured Hopf algebras

    CERN Document Server

    Quesne, C

    1997-01-01

    Quite recently, a ``coloured'' extension of the Yang-Baxter equation has appeared in the literature and various solutions of it have been proposed. In the present contribution, we introduce a generalization of Hopf algebras, to be referred to as coloured Hopf algebras, wherein the comultiplication, counit, and antipode maps are labelled by some colour parameters. The latter may take values in any finite, countably infinite, or uncountably infinite set. A straightforward extension of the quasitriangularity property involves a coloured universal ${\\cal R}$-matrix, satisfying the coloured Yang-Baxter equation. We show how coloured Hopf algebras can be constructed from standard ones by using an algebra isomorphism group, called colour group. Finally, we present two examples of coloured quantum universal enveloping algebras.

  2. Classically Isospinning Hopf Solitons

    CERN Document Server

    Battye, Richard A

    2013-01-01

    We perform full 3-dimensional numerical relaxations of isospinning Hopf solitons with Hopf charge up to 8 in the Skyrme-Faddeev model with mass terms included. We explicitly allow the soliton solution to deform and to break the symmetries of the static configuration. It turns out that the model with its rich spectrum of soliton solutions, often of similiar energy, allows for transmutations, formation of new solution types and the rearrangement of the spectrum of minimal-energy solitons in a given topological sector when isospin is added. We observe that the shape of isospinning Hopf solitons can differ qualitatively from that of the static solution. In particular the solution type of the lowest energy soliton can change. Our numerical results are of relevance for the quantization of the classical soliton solutions.

  3. Local bifurcation analysis of a four-dimensional hyperchaotic system

    Institute of Scientific and Technical Information of China (English)

    Wu Wen-Juan; Chen Zeng-Qiang; Yuan Zhu-Zhi

    2008-01-01

    Local bifurcation phenomena in a four-dimensional continuous hyperchaotic system, which has rich and complex dynamical behaviours, are analysed. The local bifurcations of the system are investigated by utilizing the bifurcation theory and the centre manifold theorem, and thus the conditions of the existence of pitchfork bifurcation and Hopf bifurcation are derived in detail. Numerical simulations are presented to verify the theoretical analysis, and they show some interesting dynamics, including stable periodic orbits emerging from the new fixed points generated by pitchfork bifurcation, coexistence of a stable limit cycle and a chaotic attractor, as well as chaos within quite a wide parameter region.

  4. About Landau–Hopf scenario in a system of coupled self-oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsov, Alexander P.; Kuznetsov, Sergey P.; Sataev, Igor R.; Turukina, Ludmila V., E-mail: lvtur@rambler.ru

    2013-12-17

    The conditions are discussed for which an ensemble of interacting oscillators may demonstrate the Landau–Hopf scenario of successive birth of multi-frequency quasi-periodic motions. A model is proposed that is a network of five globally coupled oscillators characterized by controlled degree of activation of individual oscillators. Illustrations are given for successive birth of tori of increasing dimension via quasi-periodic Hopf bifurcations.

  5. Effects of Hard Limits on Bifurcation, Chaos and Stability

    Institute of Scientific and Technical Information of China (English)

    Rui-qi Wang; Ji-cai Huang

    2004-01-01

    An SMIB model in the power systems,especially that concering the effects of hard limits on bifurcations, chaos and stability is studied.Parameter conditions for bifurcations and chaos in the absence of hard limits are compared with those in the presence of hard limits.It has been proved that hard limits can affect system stability.We find that (1)hard limits can change unstable equilibrium into stable one;(2)hard limits can change stability of limit cycles induced by Hopf bifurcation;(3)persistence of hard limits can stabilize divergent trajectory to a stable equilibrium or limit cycle;(4)Hopf bifurcation occurs before SN bifurcation,so the system collapse can be controlled before Hopf bifurcation occurs.We also find that suitable limiting values of hard limits can enlarge the feasibility region.These results are based on theoretical analysis and numerical simulations, such as condition for SNB and Hopf bifurcation,bifurcation diagram,trajectories,Lyapunov exponent,Floquet multipliers,dimension of attractor and so on.

  6. Bifurcation analysis and control of periodic solutions changing into invariant tori in Langford system

    Institute of Scientific and Technical Information of China (English)

    Liu Su-Hua; Tang Jia-Shi; Qin Jin-Qi; Yin Xiao-Bo

    2008-01-01

    Bifurcation characteristics of the Langford system in a general form are systematically analysed,and nonlinear controls of periodic solutions changing into invariant tori in this system are achieved.Analytical relationship between control gain and bifurcation parameter is obtained.Bifurcation diagrams are drawn,showing the results of control for secondary Hopf bifurcation and sequences of bifurcations route to chaos.Numerical simulations of quasi-periodic tori validate analytic predictions.

  7. BIFURCATION IN A TWO-DIMENSIONAL NEURAL NETWORK MODEL WITH DELAY

    Institute of Scientific and Technical Information of China (English)

    WEI Jun-jie; ZHANG Chun-rui; LI Xiu-ling

    2005-01-01

    A kind of 2-dimensional neural network model with delay is considered. By analyzing the distribution of the roots of the characteristic equation associated with the model, a bifurcation diagram was drawn in an appropriate parameter plane. It is found that a line is a pitchfork bifurcation curve. Further more, the stability of each fixed point and existence of Hopf bifurcation were obtained. Finally, the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions were determined by using the normal form method and centre manifold theory.

  8. Quasi-periodic Bifurcations of Invariant Circles in Low-dimensional Dissipative Dynamical Systems

    NARCIS (Netherlands)

    Vitolo, Renato; Broer, Henk; Simo, Carles

    2011-01-01

    This paper first summarizes the theory of quasi-periodic bifurcations for dissipative dynamical systems. Then it presents algorithms for the computation and continuation of invariant circles and of their bifurcations. Finally several applications are given for quasiperiodic bifurcations of Hopf, sad

  9. STABILITY AND BIFURCATION OF A HUMAN RESPIRATORY SYSTEM MODEL WITH TIME DELAY

    Institute of Scientific and Technical Information of China (English)

    沈启宏; 魏俊杰

    2004-01-01

    The stability and bifurcation of the trivial solution in the two-dimensional differential equation of a model describing human respiratory system with time delay were investigated. Formulas about the stability of bifurcating periodic solution and the direction of Hopf bifurcation were exhibited by applying the normal form theory and the center manifold theorem. Furthermore, numerical simulation was carried out.

  10. Contribution à l'Etude de la Bifurcation de Hopf dans le Cadre des Equations Différentielles à Retard, Application à un Problème en Dynamique de Population.

    OpenAIRE

    Yafia, Radouane

    2005-01-01

    Our first goal in this work is to give a proof of exchange of stability from the trivialbranch to the bifurcated one. This proof is based on the two following steps:i) reduction of the equation to a two-dimensional system via the variation of constantformula end the center manifold theorem.ii) Estimation of the distance between solutions of the original equation and the bifurcatedperiodic solutions.We obtain an estimate of the stability region.The second goal is to study the dynamics of Haema...

  11. Localization on Hopf surfaces

    CERN Document Server

    Assel, Benjamin; Martelli, Dario

    2014-01-01

    We discuss localization of the path integral for supersymmetric gauge theories with an R-symmetry on Hermitian four-manifolds. After presenting the localization locus equations for the general case, we focus on backgrounds with S^1 x S^3 topology, admitting two supercharges of opposite R-charge. These are Hopf surfaces, with two complex structure moduli p,q. We compute the localized partition function on such Hopf surfaces, allowing for a very large class of Hermitian metrics, and prove that this is proportional to the supersymmetric index with fugacities p,q. Using zeta function regularisation, we determine the exact proportionality factor, finding that it depends only on p,q, and on the anomaly coefficients a, c of the field theory. This may be interpreted as a supersymmetric Casimir energy, and provides the leading order contribution to the partition function in a large N expansion.

  12. Hopf algebras in noncommutative geometry

    CERN Document Server

    Varilly, J C

    2001-01-01

    We give an introductory survey to the use of Hopf algebras in several problems of noncommutative geometry. The main example, the Hopf algebra of rooted trees, is a graded, connected Hopf algebra arising from a universal construction. We show its relation to the algebra of transverse differential operators introduced by Connes and Moscovici in order to compute a local index formula in cyclic cohomology, and to the several Hopf algebras defined by Connes and Kreimer to simplify the combinatorics of perturbative renormalization. We explain how characteristic classes for a Hopf module algebra can be obtained from the cyclic cohomology of the Hopf algebra which acts on it. Finally, we discuss the theory of noncommutative spherical manifolds and show how they arise as homogeneous spaces of certain compact quantum groups.

  13. COCLEFT EXTENSIONS OF HOPF ALGEBRAS

    Institute of Scientific and Technical Information of China (English)

    祝家贵

    2006-01-01

    Let B and H be finitely generated projective Hopf algebras over a commutative ring R,with B cocommutative and H commutative. In this paper we investigate cocleft extensions of Hopf algebras, and prove that the isomorphism classes of cocleft Hopf algebras extensions of B by H are determined uniquely by the group C(B, H) = ZC(B, H)/d(B, H) .

  14. Singularly perturbed bifurcation subsystem and its application in power systems

    Institute of Scientific and Technical Information of China (English)

    An Yichun; Zhang Qingling; Zhu Yukun; Zhang Yan

    2008-01-01

    The singularly perturbed bifurcation subsystem is described,and the test conditions of subsystem persistence are deduced.By use of fast and slow reduced subsystem model,the result does not require performing nonlinear transformation.Moreover,it is shown and proved that the persistence of the periodic orbits for Hopf bifurcation in the reduced model through center manifold.Van der Pol oscillator circuit is given to illustrate the persistence of bifurcation subsystems with the full dynamic system.

  15. Effect of nonlinear void reactivity on bifurcation characteristics of a lumped-parameter model of a BWR: A study relevant to RBMK

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Dinkar, E-mail: dinkar@iitk.ac.in [Nuclear Engineering and Technology Program, Indian Institute of Technology Kanpur, Kanpur 208 016 (India); Kalra, Manjeet Singh, E-mail: drmanjeet.singh@dituniversity.edu.in [DIT University, Dehradun 248 009 (India); Wahi, Pankaj, E-mail: wahi@iitk.ac.in [Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016 (India)

    2017-04-15

    Highlights: • A simplified model with nonlinear void reactivity feedback is studied. • Method of multiple scales for nonlinear analysis and oscillation characteristics. • Second order void reactivity dominates in determining system dynamics. • Opposing signs of linear and quadratic void reactivity enhances global safety. - Abstract: In the present work, the effect of nonlinear void reactivity on the dynamics of a simplified lumped-parameter model for a boiling water reactor (BWR) is investigated. A mathematical model of five differential equations comprising of neutronics and thermal-hydraulics encompassing the nonlinearities associated with both the reactivity feedbacks and the heat transfer process has been used. To this end, we have considered parameters relevant to RBMK for which the void reactivity is known to be nonlinear. A nonlinear analysis of the model exploiting the method of multiple time scales (MMTS) predicts the occurrence of the two types of Hopf bifurcation, namely subcritical and supercritical, leading to the evolution of limit cycles for a range of parameters. Numerical simulations have been performed to verify the analytical results obtained by MMTS. The study shows that the nonlinear reactivity has a significant influence on the system dynamics. A parametric study with varying nominal reactor power and operating conditions in coolant channel has also been performed which shows the effect of change in concerned parameter on the boundary between regions of sub- and super-critical Hopf bifurcations in the space constituted by the two coefficients of reactivities viz. the void and the Doppler coefficient of reactivities. In particular, we find that introduction of a negative quadratic term in the void reactivity feedback significantly increases the supercritical region and dominates in determining the system dynamics.

  16. Bifurcations and Chaos in a Discrete Predator-prey System with Holling Type-Ⅳ Functional Response

    Institute of Scientific and Technical Information of China (English)

    Ji-cai Huang

    2005-01-01

    A discrete predator-prey system with Holling type-Ⅳ functional response obtained by the Euler method is first investigated. The conditions of existence for fold bifurcation, flip bifurcation and Hopf bifurcation are derived by using the center manifold theorem and bifurcation theory. Furthermore, we give the condition for the occurrence of codimension-two bifurcation called the Bogdanov-Takens bifurcation for fixed points and present approximate expressions for saddle-node, Hopf and homoclinic bifurcation sets near the Bogdanov-Takens bifurcation point. We also show, the existence of degenerated fixed point with codimension three at least. The numerical simulations, including bifurcation diagrams, phase portraits, and computation of maximum Lyapunov exponents, not only show the consistence with the theoretical analysis but also exhibit the rich and complex dynamical behaviors such as the attracting invariant circle, period-doubling bifurcation from period-2,3,4 orbits,interior crisis, intermittency mechanic, and sudden disappearance of chaotic dynamic.

  17. Cyclic cohomology of Hopf algebras

    NARCIS (Netherlands)

    Crainic, M.

    2001-01-01

    We give a construction of ConnesMoscovicis cyclic cohomology for any Hopf algebra equipped with a character Furthermore we introduce a noncommutative Weil complex which connects the work of Gelfand and Smirnov with cyclic cohomology We show how the Weil complex arises naturally when looking at Hopf

  18. Subcritical versus supercritical transition to turbulence in curved pipes

    CERN Document Server

    Kühnen, J; Schwegel, M; Kuhlmann, H; Hof, B

    2015-01-01

    Transition to turbulence in straight pipes occurs in spite of the linear stability of the laminar Hagen--Poiseuille flow if the amplitude of flow perturbations as well as the Reynolds number exceed a minimum threshold (subcritical transition). As the pipe curvature increases centrifugal effects become important, modifying the basic flow as well as the most unstable linear modes. If the curvature (tube-to-coiling diameter $d/D$) is sufficiently large a Hopf bifurcation (supercritical instability) is encountered before turbulence can be excited (subcritical instability). We trace the instability thresholds in the $Re-d/D$ parameter space in the range $0.01\\leq\\ d/D \\leq0.1$ by means of laser-Doppler velocimetry and determine the point where the subcritical and supercritical instabilities meet. Two different experimental setups were used: a closed system where the pipe forms an axisymmetric torus and an open system employing a helical pipe. Implications for the measurement of friction factors in curved pipes are...

  19. Stability and bifurcation behaviour of electrostatic torsional NEMS varactor influenced by dispersion forces

    Energy Technology Data Exchange (ETDEWEB)

    Lin Wenhui [College of Science, China Agricultural University, Beijing 100083 (China); Zhao Yapu [State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China)

    2007-03-21

    The influences of Casimir and van der Waals forces on the nano-electromechanical systems (NEMS) electrostatic torsional varactor are studied. A one degree of freedom, the torsional angle, is adopted, and the bifurcation behaviour of the NEMS torsional varactor is investigated. There are two bifurcation points, one of which is a Hopf bifurcation point and the other is an unstable saddle point. The phase portraits are also drawn, in which periodic orbits are around the Hopf bifurcation point, but the periodic orbit will break into a homoclinic orbit when meeting the unstable saddle point.

  20. Stability and bifurcation behaviour of electrostatic torsional NEMS varactor influenced by dispersion forces

    Science.gov (United States)

    Lin, Wen-Hui; Zhao, Ya-Pu

    2007-03-01

    The influences of Casimir and van der Waals forces on the nano-electromechanical systems (NEMS) electrostatic torsional varactor are studied. A one degree of freedom, the torsional angle, is adopted, and the bifurcation behaviour of the NEMS torsional varactor is investigated. There are two bifurcation points, one of which is a Hopf bifurcation point and the other is an unstable saddle point. The phase portraits are also drawn, in which periodic orbits are around the Hopf bifurcation point, but the periodic orbit will break into a homoclinic orbit when meeting the unstable saddle point.

  1. Regularizations of two-fold bifurcations in planar piecewise smooth systems using blowup

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Hogan, S. J.

    2015-01-01

    rigorously how singular canards can persist and how the bifurcation of pseudo-equilibria is related to bifurcations of equilibria in the regularized system. We also show that PWS limit cycles are connected to Hopf bifurcations of the regularization. In addition, we show how regularization can create another...... type of limit cycle that does not appear to be present in the original PWS system. For both types of limit cycle, we show that the criticality of the Hopf bifurcation that gives rise to periodic orbits is strongly dependent on the precise form of the regularization. Finally, we analyse the limit cycles...

  2. Measuring the universal synchronization properties of coupled oscillators across the Hopf instability

    CERN Document Server

    Romanelli, Marco; Brunel, Marc; Vallet, Marc

    2013-01-01

    Phase-locking of coupled oscillators is destroyed usually by two instabilities: the saddle-node, as in the Adler model, and the Hopf bifurcation. Here we provide a quantitative measure of the degree of synchronization across the Hopf bifurcation, and demonstrate experimentally and numerically that, surprisingly, synchronization not only persists well outside the phase-locking range, but is also completely insensitive to the onset of the instability. Furthermore, by studying numerically a generic, minimal model, we conclude that such a behavior is universal. Given the ubiquitous appearance of the Hopf mechanism, we expect these results to be relevant for a wide range of systems, such as opto-mechanical, micro-mechanical, or delay-coupled oscillators and networks.

  3. The Hopf-van der Pol system: Failure of a homotopy method

    NARCIS (Netherlands)

    Meijer, H.G.E.; Kalmár-Nagy, T.

    2012-01-01

    The purpose of this article to provide an explicit example where continuation based on the homotopy method fails. The example is a one-parameter homotopy for periodic orbits between two well-known nonlinear systems, the normal form of the Hopf bifurcation and the van der Pol system. Our analysis sho

  4. Border Collision Bifurcations in Two Dimensional Piecewise Smooth Maps

    CERN Document Server

    Banerjee, S; Banerjee, Soumitro; Grebogi, Celso

    1999-01-01

    Recent investigations on the bifurcations in switching circuits have shown that many atypical bifurcations can occur in piecewise smooth maps which can not be classified among the generic cases like saddle-node, pitchfork or Hopf bifurcations occurring in smooth maps. In this paper we first present experimental results to establish the theoretical problem: the development of a theory and classification of the new type of bifurcations resulting from border collision. We then present a systematic analysis of such bifurcations by deriving a normal form --- the piecewise linear approximation in the neighborhood of the border. We show that there can be eleven qualitatively different types of border collision bifurcations depending on the parameters of the normal form, and these are classified under six cases. We present a partitioning of the parameter space of the normal form showing the regions where different types of bifurcations occur. This theoretical framework will help in explaining bifurcations in all syst...

  5. Integrals for braided Hopf algebras

    CERN Document Server

    Bespalov, Yu N; Lyubashenko, V V; Turaev, V G; Bespalov, Yuri; Kerler, Thomas; Lyubashenko, Volodymyr; Turaev, Vladimir

    1997-01-01

    Let H be a Hopf algebra in a rigid braided monoidal category with split idempotents. We prove the existence of integrals on (in) H characterized by the universal property, employing results about Hopf modules, and show that their common target (source) object Int H is invertible. The fully braided version of Radford's formula for the fourth power of the antipode is obtained. Connections of integration with cross-product and transmutation are studied. The results apply to topological Hopf algebras, e.g. a torus with a hole, which do not have additive structure.

  6. Nonlinear instability and dynamic bifurcation of a planeinterface during solidification

    Institute of Scientific and Technical Information of China (English)

    吴金平; 侯安新; 黄定华; 鲍征宇; 高志农; 屈松生

    2001-01-01

    By taking average over the curvature, the temperature and its gradient, the solute con-centration and its gradient at the flange of planar interface perturbed by sinusoidal ripple during solidifi-cation, the nonlinear dynamic equations of the sinusoidal perturbation wave have been set up. Analysisof the nonlinear instability and the behaviors of dynamic bifurcation of the solutions of these equationsshows that (i) the way of dynamic bifurcation of the flat-to-cellular interface transition vades with differ-ent thermal gradients. The quasi-subcritical-lag bifurcation occurs in the small interface thermal gradientscope, the supercritical-lag bifurcation in the medium thermal gradient scope and the supercritical bifur-cation in the large thermal gradient scope. (ii) The transition of cellular-to-flat interface is realizedthrough supercritical inverse bifurcation in the rapid solidification area.

  7. Renormalization automated by Hopf algebra

    CERN Document Server

    Broadhurst, D J

    1999-01-01

    It was recently shown that the renormalization of quantum field theory is organized by the Hopf algebra of decorated rooted trees, whose coproduct identifies the divergences requiring subtraction and whose antipode achieves this. We automate this process in a few lines of recursive symbolic code, which deliver a finite renormalized expression for any Feynman diagram. We thus verify a representation of the operator product expansion, which generalizes Chen's lemma for iterated integrals. The subset of diagrams whose forest structure entails a unique primitive subdivergence provides a representation of the Hopf algebra ${\\cal H}_R$ of undecorated rooted trees. Our undecorated Hopf algebra program is designed to process the 24,213,878 BPHZ contributions to the renormalization of 7,813 diagrams, with up to 12 loops. We consider 10 models, each in 9 renormalization schemes. The two simplest models reveal a notable feature of the subalgebra of Connes and Moscovici, corresponding to the commutative part of the Hopf ...

  8. Bifurcations of a singular prey-predator economic model with time delay and stage structure

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xue [Institute of Systems Science, Northeastern University, Shenyang, Liaoning 110004 (China); Key Laboratory of Integrated Automation of Process Industry (Northeastern Univ.), Ministry of Education, Shenyang, Liaoning 110004 (China)], E-mail: zhangxueer@gmail.com; Zhang Qingling [Institute of Systems Science, Northeastern University, Shenyang, Liaoning 110004 (China); Key Laboratory of Integrated Automation of Process Industry (Northeastern Univ.), Ministry of Education, Shenyang, Liaoning 110004 (China)], E-mail: qlzhang@mail.neu.edu.cn; Liu Chao [Institute of Systems Science, Northeastern University, Shenyang, Liaoning 110004 (China); Key Laboratory of Integrated Automation of Process Industry (Northeastern Univ.), Ministry of Education, Shenyang, Liaoning 110004 (China); Xiang Zhongyi [Department of Mathematics, Hubei University for Nationalities, Enshi, Hubei 445000 (China)

    2009-11-15

    This paper studies a singular prey-predator economic model with time delay and stage structure. Compared with other researches on dynamics of prey-predator population, this model is described by differential-algebraic equations due to economic factor. For zero economic profit, this model exhibits three bifurcational phenomena: transcritical bifurcation, Hopf bifurcation and singular induced bifurcation. For positive economic profit, the model undergoes a saddle-node bifurcation at critical value of positive economic profit, and the increase of delay destabilizes the positive equilibrium point of the system and bifurcates into small amplitude periodic solution. Finally, by using Matlab software, numerical simulations illustrate the effectiveness of the results.

  9. On period doubling bifurcations of cycles and the harmonic balance method

    Energy Technology Data Exchange (ETDEWEB)

    Itovich, Griselda R. [Departamento de Matematica, FAEA, Universidad Nacional del Comahue, Neuquen Q8300BCX (Argentina)] e-mail: gitovich@arnet.com.ar; Moiola, Jorge L. [Departamento de Ingenieria Electrica y de Computadoras Universidad Nacional del Sur, Bahia Blanca B8000CPB (Argentina)] e-mail: jmoiola@criba.edu.ar

    2006-02-01

    This works attempts to give quasi-analytical expressions for subharmonic solutions appearing in the vicinity of a Hopf bifurcation. Starting with well-known tools as the graphical Hopf method for recovering the periodic branch emerging from classical Hopf bifurcation, precise frequency and amplitude estimations of the limit cycle can be obtained. These results allow to attain approximations for period doubling orbits by means of harmonic balance techniques, whose accuracy is established by comparison of Floquet multipliers with continuation software packages. Setting up a few coefficients, the proposed methodology yields to approximate solutions that result from a second period doubling bifurcation of cycles and to extend the validity limits of the graphical Hopf method.

  10. Bifurcation Analysis for a Delayed Predator-Prey System with Stage Structure

    Directory of Open Access Journals (Sweden)

    Jiang Zhichao

    2010-01-01

    Full Text Available Abstract A delayed predator-prey system with stage structure is investigated. The existence and stability of equilibria are obtained. An explicit algorithm for determining the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions is derived by using the normal form and the center manifold theory. Finally, a numerical example supporting the theoretical analysis is given.

  11. Electron Bifurcation

    Energy Technology Data Exchange (ETDEWEB)

    Peters, John W.; Miller, Anne-Frances; Jones, Anne K.; King, Paul W.; Adams, Michael W. W.

    2016-04-01

    Electron bifurcation is the recently recognized third mechanism of biological energy conservation. It simultaneously couples exergonic and endergonic oxidation-reduction reactions to circumvent thermodynamic barriers and minimize free energy loss. Little is known about the details of how electron bifurcating enzymes function, but specifics are beginning to emerge for several bifurcating enzymes. To date, those characterized contain a collection of redox cofactors including flavins and iron-sulfur clusters. Here we discuss the current understanding of bifurcating enzymes and the mechanistic features required to reversibly partition multiple electrons from a single redox site into exergonic and endergonic electron transfer paths.

  12. Bifurcation Analysis and Chaos Control in a Modified Finance System with Delayed Feedback

    Science.gov (United States)

    Yang, Jihua; Zhang, Erli; Liu, Mei

    2016-06-01

    We investigate the effect of delayed feedback on the finance system, which describes the time variation of the interest rate, for establishing the fiscal policy. By local stability analysis, we theoretically prove the existences of Hopf bifurcation and Hopf-zero bifurcation. By using the normal form method and center manifold theory, we determine the stability and direction of a bifurcating periodic solution. Finally, we give some numerical solutions, which indicate that when the delay passes through certain critical values, chaotic oscillation is converted into a stable equilibrium or periodic orbit.

  13. Stability and Bifurcation in a Delayed Reaction-Diffusion Equation with Dirichlet Boundary Condition

    Science.gov (United States)

    Guo, Shangjiang; Ma, Li

    2016-04-01

    In this paper, we study the dynamics of a diffusive equation with time delay subject to Dirichlet boundary condition in a bounded domain. The existence of spatially nonhomogeneous steady-state solution is investigated by applying Lyapunov-Schmidt reduction. The existence of Hopf bifurcation at the spatially nonhomogeneous steady-state solution is derived by analyzing the distribution of the eigenvalues. The direction of Hopf bifurcation and stability of the bifurcating periodic solution are also investigated by means of normal form theory and center manifold reduction. Moreover, we illustrate our general results by applications to the Nicholson's blowflies models with one- dimensional spatial domain.

  14. Bifurcation Analysis in an n-Dimensional Diffusive Competitive Lotka-Volterra System with Time Delay

    Science.gov (United States)

    Chang, Xiaoyuan; Wei, Junjie

    2015-06-01

    In this paper, we investigate the stability and Hopf bifurcation of an n-dimensional competitive Lotka-Volterra diffusion system with time delay and homogeneous Dirichlet boundary condition. We first show that there exists a positive nonconstant steady state solution satisfying the given asymptotic expressions and establish the stability of the positive nonconstant steady state solution. Regarding the time delay as a bifurcation parameter, we explore the system that undergoes a Hopf bifurcation near the positive nonconstant steady state solution and derive a calculation method for determining the direction of the Hopf bifurcation. Finally, we cite the stability of a three-dimensional competitive Lotka-Volterra diffusion system with time delay to illustrate our conclusions.

  15. Inductions and coinductions for Hopf extensions

    Institute of Scientific and Technical Information of China (English)

    Freddy Van Oystaeyen; 许永华; 张印火

    1996-01-01

    The induction and coinduction functors for the two types of Hopf extensions (Hopf Galois extensions and dual to Hopf Galois extension) and the symmetry between them are studied; by using the theory of separable functors further links between these two classes are provided.

  16. Twisting theory for weak Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    CHEN Ju-zhen; ZHANG Yan; WANG Shuan-hong

    2008-01-01

    The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the (braided) monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl (2000).

  17. Coxeter groups and Hopf algebras

    CERN Document Server

    Aguiar, Marcelo

    2011-01-01

    An important idea in the work of G.-C. Rota is that certain combinatorial objects give rise to Hopf algebras that reflect the manner in which these objects compose and decompose. Recent work has seen the emergence of several interesting Hopf algebras of this kind, which connect diverse subjects such as combinatorics, algebra, geometry, and theoretical physics. This monograph presents a novel geometric approach using Coxeter complexes and the projection maps of Tits for constructing and studying many of these objects as well as new ones. The first three chapters introduce the necessary backgrou

  18. Generalization of Hopf Functional Equation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This paper generalizes the Hopf functional equation in order to apply it to a wider class of not necessarily incompressible fluid flows. We start by defining characteristic functionals of the velocity field, the density field and the temperature field of a compressible field. Using the continuity equation, the Navier-Stokes equations and the equation of energy we derive a functional equation governing the motion of an ideal gas flow and a van der Waals gas flow, and then give some general methods of deriving a functional equation governing the motion of any compressible fluid flow. These functional equations can be considered as the generalization of the Hopf functional equation.

  19. Bifurcation of Vortex Density Current in Trapped Bose Condensates

    Institute of Scientific and Technical Information of China (English)

    XU Tao; ZHANG ShengLi

    2002-01-01

    Vortex density current in the Gross-Pitaevskii theory is studied. It is shown that the inner structure of the topological vortices can be classified by Brouwer degrees and Hopf indices of φ-mapping. The dynamical equations of vortex density current have been given. The bifurcation behavior at the critical points of the current is discussed in detail.

  20. Hopf Bifurcation in a Cobweb Model with Discrete Time Delays

    Directory of Open Access Journals (Sweden)

    Luca Gori

    2014-01-01

    Full Text Available We develop a cobweb model with discrete time delays that characterise the length of production cycle. We assume a market comprised of homogeneous producers that operate as adapters by taking the (expected profit-maximising quantity as a target to adjust production and consumers with a marginal willingness to pay captured by an isoelastic demand. The dynamics of the economy is characterised by a one-dimensional delay differential equation. In this context, we show that (1 if the elasticity of market demand is sufficiently high, the steady-state equilibrium is locally asymptotically stable and (2 if the elasticity of market demand is sufficiently low, quasiperiodic oscillations emerge when the time lag (that represents the length of production cycle is high enough.

  1. On the Bifurcations of a Hamiltonian Having Three Homoclinic Loops under Z3 Invariant Quintic Perturbations

    Institute of Scientific and Technical Information of China (English)

    Yu Hai WU; Mao An HAN

    2007-01-01

    A cubic system having three homoclinic loops perturbed by Z3 invariant quintic polynomials is considered.By applying the qualitative method of di erential equations and the numeric computing method,the Hopf bifurcation,homoclinic loop bifurcation and heteroclinic loop bifurcation of the above perturbed system are studied.It is found that the above system has at least 12 limit cycles and the distributions of limit cycles are also given.

  2. Stability and Bifurcation of Two Kinds of Three-Dimensional Fractional Lotka-Volterra Systems

    Directory of Open Access Journals (Sweden)

    Jinglei Tian

    2014-01-01

    Full Text Available Two kinds of three-dimensional fractional Lotka-Volterra systems are discussed. For one system, the asymptotic stability of the equilibria is analyzed by providing some sufficient conditions. And bifurcation property is investigated by choosing the fractional order as the bifurcation parameter for the other system. In particular, the critical value of the fractional order is identified at which the Hopf bifurcation may occur. Furthermore, the numerical results are presented to verify the theoretical analysis.

  3. Global Bifurcation of a Novel Computer Virus Propagation Model

    Directory of Open Access Journals (Sweden)

    Jianguo Ren

    2014-01-01

    Full Text Available In a recent paper by J. Ren et al. (2012, a novel computer virus propagation model under the effect of the antivirus ability in a real network is established. The analysis there only partially uncovers the dynamics behaviors of virus spread over the network in the case where around bifurcation is local. In the present paper, by mathematical analysis, it is further shown that, under appropriate parameter values, the model may undergo a global B-T bifurcation, and the curves of saddle-node bifurcation, Hopf bifurcation, and homoclinic bifurcation are obtained to illustrate the qualitative behaviors of virus propagation. On this basis, a collection of policies is recommended to prohibit the virus prevalence. To our knowledge, this is the first time the global bifurcation has been explored for the computer virus propagation. Theoretical results and corresponding suggestions may help us suppress or eliminate virus propagation in the network.

  4. The Persistence of a Slow Manifold with Bifurcation

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Palmer, P.; Robert, M.

    2012-01-01

    his paper considers the persistence of a slow manifold with bifurcation in a slow-fast two degree of freedom Hamiltonian system. In particular, we consider a system with a supercritical pitchfork bifurcation in the fast space which is unfolded by the slow coordinate. The model system is motivated...

  5. Hopf cyclic cohomology and transverse characteristic classes

    CERN Document Server

    Moscovici, Henri

    2010-01-01

    By refining the cyclic cohomological apparatus for computing the Hopf cyclic cohomology of the Hopf algebras associated to infinite primitive Cartan-Lie pseudogroup, we explicitly identify, as a Hopf cyclic complex, the image of the canonical homomorphism from the Gelfand-Fuks complex to the Bott complex for equivariant cohomology. Distinct from the original realization due to A. Connes and the first named author of the cyclic cohomology of such Hopf algebras as differentiable cyclic cohomology, this construction provides a convenient front-end model for their Hopf cyclic cohomology. Relying on it, we produce characteristic homomorphisms from newly developed models for Hopf cyclic characteristic classes to the cyclic cohomology of the convolution algebras of \\'etale holonomy groupoids, which in particular work in the relative case with no compactness restriction. As an illustration, we apply the latter feature to transfer the universal Hopf cyclic Chern classes found by us in a previous paper, and produce in ...

  6. Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Xin Qi; Shi Zhongke

    2015-01-01

    Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To pre-dict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynam-ics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurca-tion and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders ser-ies of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

  7. STABILITY AND BIFURCATION ANALYSIS OF A PREDATOR-PREY MODEL WITH CROWLEY-MARTIN TYPE FUNCTIONAL RESPONSE AND TIME DELAY

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    In this paper,a class of predator-prey model with Crowley-Martin type functional response and time delay is considered.By choosing the delay as a bifurcation parameter,it is shown that Hopf bifurcation occurs as the delay passes through a certain critical value.Some numerical simulations for verifying the main results are also provided.

  8. Bifurcation analysis on a generalized recurrent neural network with two interconnected three-neuron components

    Energy Technology Data Exchange (ETDEWEB)

    Hajihosseini, Amirhossein, E-mail: hajihosseini@khayam.ut.ac.ir [School of Mathematics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5746 (Iran, Islamic Republic of); Center of Excellence in Biomathematics, School of Mathematics, Statistics and Computer Science, University of Tehran, Tehran 14176-14411 (Iran, Islamic Republic of); Maleki, Farzaneh, E-mail: farzanmaleki83@khayam.ut.ac.ir [School of Mathematics, Statistics and Computer Science, College of Science, University of Tehran, Tehran 14176-14411 (Iran, Islamic Republic of); School of Mathematics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5746 (Iran, Islamic Republic of); Center of Excellence in Biomathematics, School of Mathematics, Statistics and Computer Science, University of Tehran, Tehran 14176-14411 (Iran, Islamic Republic of); Rokni Lamooki, Gholam Reza, E-mail: rokni@khayam.ut.ac.ir [School of Mathematics, Statistics and Computer Science, College of Science, University of Tehran, Tehran 14176-14411 (Iran, Islamic Republic of); School of Mathematics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5746 (Iran, Islamic Republic of); Center of Excellence in Biomathematics, School of Mathematics, Statistics and Computer Science, University of Tehran, Tehran 14176-14411 (Iran, Islamic Republic of)

    2011-11-15

    Highlights: > We construct a recurrent neural network by generalizing a specific n-neuron network. > Several codimension 1 and 2 bifurcations take place in the newly constructed network. > The newly constructed network has higher capabilities to learn periodic signals. > The normal form theorem is applied to investigate dynamics of the network. > A series of bifurcation diagrams is given to support theoretical results. - Abstract: A class of recurrent neural networks is constructed by generalizing a specific class of n-neuron networks. It is shown that the newly constructed network experiences generic pitchfork and Hopf codimension one bifurcations. It is also proved that the emergence of generic Bogdanov-Takens, pitchfork-Hopf and Hopf-Hopf codimension two, and the degenerate Bogdanov-Takens bifurcation points in the parameter space is possible due to the intersections of codimension one bifurcation curves. The occurrence of bifurcations of higher codimensions significantly increases the capability of the newly constructed recurrent neural network to learn broader families of periodic signals.

  9. The Noncommutative Inhomogeneous Hopf Algebra

    CERN Document Server

    Lagraa, M

    1997-01-01

    From the bicovariant first order differential calculus over inhomogeneous Hopf algebra B we construct the set of right-invariant Maurer Cartan one-forms considered as a right-invariant basis of a bicovariant B-bimodule over which we develope the Woronowicz'general theory differential calculus on quantum groups. In this context, we derive the inhomogeneous commutation rules and investigate the properties of their different terms.

  10. The Noncommutative Inhomogeneous Hopf Algebra

    OpenAIRE

    1997-01-01

    From the bicovariant first order differential calculus on inhomogeneous Hopf algebra ${\\cal B}$ we construct the set of right-invariant Maurer-Cartan one-forms considered as a right-invariant basis of a bicovariant ${\\cal B}$-bimodule over which we develop the Woronowicz's general theory of differential calculus on quantum groups. In this formalism, we introduce suitable functionals on ${\\cal B}$ which control the inhomogeneous commutation rules. In particular we find that the homogeneous par...

  11. Backward bifurcations, turning points and rich dynamics in simple disease models.

    Science.gov (United States)

    Zhang, Wenjing; Wahl, Lindi M; Yu, Pei

    2016-10-01

    In this paper, dynamical systems theory and bifurcation theory are applied to investigate the rich dynamical behaviours observed in three simple disease models. The 2- and 3-dimensional models we investigate have arisen in previous investigations of epidemiology, in-host disease, and autoimmunity. These closely related models display interesting dynamical behaviors including bistability, recurrence, and regular oscillations, each of which has possible clinical or public health implications. In this contribution we elucidate the key role of backward bifurcations in the parameter regimes leading to the behaviors of interest. We demonstrate that backward bifurcations with varied positions of turning points facilitate the appearance of Hopf bifurcations, and the varied dynamical behaviors are then determined by the properties of the Hopf bifurcation(s), including their location and direction. A Maple program developed earlier is implemented to determine the stability of limit cycles bifurcating from the Hopf bifurcation. Numerical simulations are presented to illustrate phenomena of interest such as bistability, recurrence and oscillation. We also discuss the physical motivations for the models and the clinical implications of the resulting dynamics.

  12. Stability and bifurcation analysis for the Kaldor-Kalecki model with a discrete delay and a distributed delay

    Science.gov (United States)

    Yu, Jinchen; Peng, Mingshu

    2016-10-01

    In this paper, a Kaldor-Kalecki model of business cycle with both discrete and distributed delays is considered. With the corresponding characteristic equation analyzed, the local stability of the positive equilibrium is investigated. It is found that there exist Hopf bifurcations when the discrete time delay passes a sequence of critical values. By applying the method of multiple scales, the explicit formulae which determine the direction of Hopf bifurcation and the stability of bifurcating periodic solutions are derived. Finally, numerical simulations are carried out to illustrate our main results.

  13. Dynamical Systems with a Codimension-One Invariant Manifold: The Unfoldings and Its Bifurcations

    Science.gov (United States)

    Saputra, Kie Van Ivanky

    2015-06-01

    We investigate a dynamical system having a special structure namely a codimension-one invariant manifold that is preserved under the variation of parameters. We derive conditions such that bifurcations of codimension-one and of codimension-two occur in the system. The normal forms of these bifurcations are derived explicitly. Both local and global bifurcations are analyzed and yield the transcritical bifurcation as the codimension-one bifurcation while the saddle-node-transcritical interaction and the Hopf-transcritical interactions as the codimension-two bifurcations. The unfolding of this degeneracy is also analyzed and reveal global bifurcations such as homoclinic and heteroclinic bifurcations. We apply our results to a modified Lotka-Volterra model and to an infection model in HIV diseases.

  14. Semi-Hopf Algebra and Supersymmetry

    OpenAIRE

    Gunara, Bobby Eka

    1999-01-01

    We define a semi-Hopf algebra which is more general than a Hopf algebra. Then we construct the supersymmetry algebra via the adjoint action on this semi-Hopf algebra. As a result we have a supersymmetry theory with quantum gauge group, i.e., quantised enveloping algebra of a simple Lie algebra. For the example, we construct the Lagrangian N=1 and N=2 supersymmetry.

  15. Bifurcations and Stability Boundary of a Power System

    Institute of Scientific and Technical Information of China (English)

    Ying-hui Gao

    2004-01-01

    A single-axis ux decay model including an excitation control model proposed in [12,14,16] is studied. As the bifurcation parameter P m (input power to the generator) varies, the system exhibits dynamics emerging from static and dynamic bifurcations which link with system collapse. We show that the equilibrium point of the system undergoes three bifurcations: one saddle-node bifurcation and two Hopf bifurcations. The state variables dominating system collapse are different for different critical points, and the excitative control may play an important role in delaying system from collapsing. Simulations are presented to illustrate the dynamical behavior associated with the power system stability and collapse. Moreover, by computing the local quadratic approximation of the 5-dimensional stable manifold at an order 5 saddle point, an analytical expression for the approximate stability boundary is worked out.

  16. Multiparametric bifurcations of an epidemiological model with strong Allee effect.

    Science.gov (United States)

    Cai, Linlin; Chen, Guoting; Xiao, Dongmei

    2013-08-01

    In this paper we completely study bifurcations of an epidemic model with five parameters introduced by Hilker et al. (Am Nat 173:72-88, 2009), which describes the joint interplay of a strong Allee effect and infectious diseases in a single population. Existence of multiple positive equilibria and all kinds of bifurcation are examined as well as related dynamical behavior. It is shown that the model undergoes a series of bifurcations such as saddle-node bifurcation, pitchfork bifurcation, Bogdanov-Takens bifurcation, degenerate Hopf bifurcation of codimension two and degenerate elliptic type Bogdanov-Takens bifurcation of codimension three. Respective bifurcation surfaces in five-dimensional parameter spaces and related dynamical behavior are obtained. These theoretical conclusions confirm their numerical simulations and conjectures by Hilker et al., and reveal some new bifurcation phenomena which are not observed in Hilker et al. (Am Nat 173:72-88, 2009). The rich and complicated dynamics exhibit that the model is very sensitive to parameter perturbations, which has important implications for disease control of endangered species.

  17. Dynamic Bifurcations

    CERN Document Server

    1991-01-01

    Dynamical Bifurcation Theory is concerned with the phenomena that occur in one parameter families of dynamical systems (usually ordinary differential equations), when the parameter is a slowly varying function of time. During the last decade these phenomena were observed and studied by many mathematicians, both pure and applied, from eastern and western countries, using classical and nonstandard analysis. It is the purpose of this book to give an account of these developments. The first paper, by C. Lobry, is an introduction: the reader will find here an explanation of the problems and some easy examples; this paper also explains the role of each of the other paper within the volume and their relationship to one another. CONTENTS: C. Lobry: Dynamic Bifurcations.- T. Erneux, E.L. Reiss, L.J. Holden, M. Georgiou: Slow Passage through Bifurcation and Limit Points. Asymptotic Theory and Applications.- M. Canalis-Durand: Formal Expansion of van der Pol Equation Canard Solutions are Gevrey.- V. Gautheron, E. Isambe...

  18. Bifurcations of emerging patterns in the presence of additive noise.

    Science.gov (United States)

    Agez, Gonzague; Clerc, Marcel G; Louvergneaux, Eric; Rojas, René G

    2013-04-01

    A universal description of the effects of additive noise on super- and subcritical spatial bifurcations in one-dimensional systems is theoretically, numerically, and experimentally studied. The probability density of the critical spatial mode amplitude is derived. From this generalized Rayleigh distribution we predict the shape of noisy bifurcations by means of the most probable value of the critical mode amplitude. Comparisons with numerical simulations are in quite good agreement for cubic or quintic amplitude equations accounting for stochastic supercritical bifurcation and for cubic-quintic amplitude equation accounting for stochastic subcritical bifurcation. Experimental results obtained in a one-dimensional Kerr-like slice subjected to optical feedback confirm the analytical expression prediction for the supercritical bifurcation shape.

  19. Stability and bifurcation in a voltage controlled negative-output KY Boost converter

    Science.gov (United States)

    Wang, Fa-Qiang; Ma, Xi-Kui

    2011-03-01

    The stability and bifurcation in a voltage controlled negative-output KY Boost converter is studied in this Letter. A glimpse at the stability and bifurcation from the power electronics simulator (PSIM) software are given. And then, its mathematical model and corresponding discrete model are derived. The stability and bifurcation of the converter are determined with the help of the loci of eigenvalues of the Jacobian matrix. It is found that the Hopf bifurcation is easy to come in this converter when the value of its energy-transferring capacitor increases. Finally, the analytical results are confirmed by the circuit experiment.

  20. Stability, bifurcation and a new chaos in the logistic differential equation with delay

    Science.gov (United States)

    Jiang, Minghui; Shen, Yi; Jian, Jigui; Liao, Xiaoxin

    2006-02-01

    This Letter is concerned with bifurcation and chaos in the logistic delay differential equation with a parameter r. The linear stability of the logistic equation is investigated by analyzing the associated characteristic transcendental equation. Based on the normal form approach and the center manifold theory, the formula for determining the direction of Hopf bifurcation and the stability of bifurcation periodic solution in the first bifurcation values is obtained. By theoretical analysis and numerical simulation, we found a new chaos in the logistic delay differential equation.

  1. Bifurcation analysis of the transition of dune shapes under a unidirectional wind.

    Science.gov (United States)

    Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku

    2012-04-13

    A bifurcation analysis of dune shape transition is made. By use of a reduced model of dune morphodynamics, the Dune Skeleton model, we elucidate the transition mechanism between different shapes of dunes under unidirectional wind. It was found that the decrease in the total amount of sand in the system and/or the lateral sand flow shifts the stable state from a straight transverse dune to a wavy transverse dune through a pitchfork bifurcation. A further decrease causes wavy transverse dunes to shift into barchans through a Hopf bifurcation. These bifurcation structures reveal the transition mechanism of dune shapes under unidirectional wind.

  2. Twisted derivations of Hopf algebras

    CERN Document Server

    Davydov, Alexei

    2012-01-01

    In the paper we introduce the notion of twisted derivation of a bialgebra. Twisted derivations appear as infinitesimal symmetries of the category of representations. More precisely they are infinitesimal versions of twisted automorphisms of bialgebras. Twisted derivations naturally form a Lie algebra (the tangent algebra of the group of twisted automorphisms). Moreover this Lie algebra fits into a crossed module (tangent to the crossed module of twisted automorphisms). Here we calculate this crossed module for universal enveloping algebras and for the Sweedler's Hopf algebra.

  3. Locally homogeneous structures on Hopf surfaces

    CERN Document Server

    McKay, Benjamin

    2009-01-01

    We study holomorphic locally homogeneous geometric structures modelled on line bundles over the projective line. We classify these structures on primary Hopf surfaces. We write out the developing map and holonomy morphism of each of these structures explicitly on each primary Hopf surface.

  4. Connes-Moscovici-Kreimer Hopf Algebras

    OpenAIRE

    Kastler, Daniel

    2001-01-01

    These notes hopefully provide an aid to the comprehension of the Connes-Moscovici and Connes-Kreimer works, by isolating common mathematical features of the Connes-Moscovici, rooted trees, and Feynman-graph Hopf algebras (as a new special branch of the theory of Hopf algebras expected to become important). We discuss in particular the dual Milnor-Moore situation.

  5. Hopf Algebroids and Their Cyclic Theory

    NARCIS (Netherlands)

    Kowalzig, N.

    2009-01-01

    The main objective of this thesis is to clarify concepts of generalised symmetries in noncommutative geometry (i.e., the noncommutative analogue of groupoids and Lie algebroids) and their associated (co)homologies. These ideas are incorporated by the notion of Hopf algebroids and Hopf-cyclic (co)hom

  6. Semisimplicity of u-Quasi-Hopf Algebra

    Institute of Scientific and Technical Information of China (English)

    WANG Xiu-rong

    2008-01-01

    The notions of u-quasi-Hopf algebras and the quantum dimensioa dimu M of a representation M by u are introduced. It is shown that a u-quasi-Hopf algebra H is semisimple if and only if there is a fmite-dimeasional projective H-module P such that dimu P is invertible.

  7. Reconstruction of weak quasi-Hopf algebras

    CERN Document Server

    Häring, Reto Andreas

    1995-01-01

    All rational semisimple braided tensor categories are representation categories of weak quasi Hopf algebras. To proof this result we construct for any given category of this kind a weak quasi tensor functor to the category of finite dimensional vector spaces. This allows to reconstruct a weak quasi Hopf algebra with the given category as its representation category.

  8. Hopf Algebroids and Their Cyclic Theory

    NARCIS (Netherlands)

    Kowalzig, N.|info:eu-repo/dai/nl/304349755

    2009-01-01

    The main objective of this thesis is to clarify concepts of generalised symmetries in noncommutative geometry (i.e., the noncommutative analogue of groupoids and Lie algebroids) and their associated (co)homologies. These ideas are incorporated by the notion of Hopf algebroids and Hopf-cyclic

  9. Connes-Moscovici-Kreimer Hopf Algebras

    OpenAIRE

    Kastler, Daniel

    2001-01-01

    These notes hopefully provide an aid to the comprehension of the Connes-Moscovici and Connes-Kreimer works, by isolating common mathematical features of the Connes-Moscovici, rooted trees, and Feynman-graph Hopf algebras (as a new special branch of the theory of Hopf algebras expected to become important). We discuss in particular the dual Milnor-Moore situation.

  10. Supercritical water

    CERN Document Server

    Marcus, Yizhak

    2012-01-01

    Discover the many new and emerging applications of supercritical water as a green solvent Drawing from thousands of original research articles, this book reviews and summarizes what is currently known about the properties and uses of supercritical water. In particular, it focuses on new and emerging applications of supercritical water as a green solvent, including the catalytic conversion of biomass into fuels and the oxidation of hazardous materials. Supercritical Water begins with an introduction that defines supercritical fluids in general. It then defines supercritical wa

  11. Self-Dual Weak Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    Munir AHMED; Fang LI

    2008-01-01

    In this paper, we define the notion of self-dual graded weak Hopf algebra and self-dual semilattice graded weak Hopf algebra. We give characterization of finite-dimensional such algebras when they are in structually simple forms in the sense of E. L. Green and E. N. Morcos. We also give the definition of self-dual weak Hopf quiver and apply these types of quivers to classify the finite-dimensional self-dual semilattice graded weak Hopf algebras. Finally, we prove partially the conjecture given by N. Andruskiewitsch and H.-J. Schneider in the case of finite-dimensional pointed semilattice graded weak Hopf algebra H when grH is self-dual.

  12. Stability and Bifurcation Analysis of a Modified Epidemic Model for Computer Viruses

    Directory of Open Access Journals (Sweden)

    Chuandong Li

    2014-01-01

    Full Text Available We extend the three-dimensional SIR model to four-dimensional case and then analyze its dynamical behavior including stability and bifurcation. It is shown that the new model makes a significant improvement to the epidemic model for computer viruses, which is more reasonable than the most existing SIR models. Furthermore, we investigate the stability of the possible equilibrium point and the existence of the Hopf bifurcation with respect to the delay. By analyzing the associated characteristic equation, it is found that Hopf bifurcation occurs when the delay passes through a sequence of critical values. An analytical condition for determining the direction, stability, and other properties of bifurcating periodic solutions is obtained by using the normal form theory and center manifold argument. The obtained results may provide a theoretical foundation to understand the spread of computer viruses and then to minimize virus risks.

  13. Bifurcation in the Lengyel–Epstein system for the coupled reactors with diffusion

    Directory of Open Access Journals (Sweden)

    Shaban Aly

    2016-01-01

    Full Text Available The main goal of this paper is to continue the investigations of the important system of Fengqi et al. (2008. The occurrence of Turing and Hopf bifurcations in small homogeneous arrays of two coupled reactors via diffusion-linked mass transfer which described by a system of ordinary differential equations is considered. I study the conditions of the existence as well as stability properties of the equilibrium solutions and derive the precise conditions on the parameters to show that the Hopf bifurcation occurs. Analytically I show that a diffusion driven instability occurs at a certain critical value, when the system undergoes a Turing bifurcation, patterns emerge. The spatially homogeneous equilibrium loses its stability and two new spatially non-constant stable equilibria emerge which are asymptotically stable. Numerically, at a certain critical value of diffusion the periodic solution gets destabilized and two new spatially nonconstant periodic solutions arise by Turing bifurcation.

  14. Bifurcation and Turing patterns of reaction-diffusion activator-inhibitor model

    Science.gov (United States)

    Wu, Ranchao; Zhou, Yue; Shao, Yan; Chen, Liping

    2017-09-01

    Gierer-Meinhardt system is one of prototypical pattern formation models. Turing instability could induce various patterns in this system. Hopf bifurcation analysis and its direction are performed on such diffusive model in this paper, by employing normal form and center manifold reduction. The effects of diffusion on the stability of equilibrium point and the bifurcated limit cycle from Hopf bifurcation are investigated. It is found that under some conditions, diffusion-driven instability, i.e, Turing instability, about the equilibrium point and the bifurcated limit cycle will happen, which are stable without diffusion. Those diffusion-driven instabilities will lead to the occurrence of spatially nonhomogeneous solutions. As a result, some patterns, like stripe and spike solutions, will form. The explicit criteria about the stability and instability of the equilibrium point and the limit cycle in the system are derived, which could be readily applied. Further, numerical simulations are presented to illustrate theoretical analysis.

  15. The dynamo bifurcation in rotating spherical shells

    CERN Document Server

    Morin, Vincent; 10.1142/S021797920906378X

    2010-01-01

    We investigate the nature of the dynamo bifurcation in a configuration applicable to the Earth's liquid outer core, i.e. in a rotating spherical shell with thermally driven motions. We show that the nature of the bifurcation, which can be either supercritical or subcritical or even take the form of isola (or detached lobes) strongly depends on the parameters. This dependence is described in a range of parameters numerically accessible (which unfortunately remains remote from geophysical application), and we show how the magnetic Prandtl number and the Ekman number control these transitions.

  16. Global bifurcation investigation of an optimal velocity traffic model with driver reaction time

    Science.gov (United States)

    Orosz, Gábor; Wilson, R. Eddie; Krauskopf, Bernd

    2004-08-01

    We investigate an optimal velocity model which includes the reflex time of drivers. After an analytical study of the stability and local bifurcations of the steady-state solution, we apply numerical continuation techniques to investigate the global behavior of the system. Specifically, we find branches of oscillating solutions connecting Hopf bifurcation points, which may be super- or subcritical, depending on parameters. This analysis reveals several regions of multistability.

  17. Bifurcation analysis on a delayed SIS epidemic model with stage structure

    Directory of Open Access Journals (Sweden)

    Kejun Zhuang

    2007-05-01

    Full Text Available In this paper, a delayed SIS (Susceptible Infectious Susceptible model with stage structure is investigated. We study the Hopf bifurcations and stability of the model. Applying the normal form theory and the center manifold argument, we derive the explicit formulas determining the properties of the bifurcating periodic solutions. The conditions to guarantee the global existence of periodic solutions are established. Also some numerical simulations for supporting the theoretical are given.

  18. Bifurcation analysis of a forest-grassland ecosystem

    Science.gov (United States)

    Russo, Lucia; Spiliotis, Konstantinos G.

    2016-06-01

    The nonlinear analysis of a forest-grassland ecosystem is performed as the main system parameters are changed. The model consists of a couple of nonlinear ordinary differential equations which include dynamically the human perceptions of forest/grassland value. The system displays multiple steady states corresponding to different forest densities as well as periodic regimes characterized by oscillations in time. We performed the bifurcation analysis of the system as the parameter relative to the human opinions influence is changed. We found that the main mechanisms which regulate the transitions occurring between different states or the appearance of new steady and dynamic regimes are transcritical, saddle/node and Hopf bifurcations.

  19. Defining universality classes for three different local bifurcations

    Science.gov (United States)

    Leonel, Edson D.

    2016-10-01

    The convergence to the fixed point at a bifurcation and near it is characterized via scaling formalism for three different types of local bifurcations of fixed points in differential equations, namely: (i) saddle-node; (ii) transcritical; and (iii) supercritical pitchfork. At the bifurcation, the convergence is described by a homogeneous function with three critical exponents α, β and z. A scaling law is derived hence relating the three exponents. Near the bifurcation the evolution towards the fixed point is given by an exponential function whose relaxation time is marked by a power law of the distance of the bifurcation point with an exponent δ. The four exponents α, β, z and δ can be used to defined classes of universality for the local bifurcations of fixed points in differential equations.

  20. Calabi-Yau pointed Hopf algebras of finite Cartan type

    CERN Document Server

    Yu, Xiaolan

    2011-01-01

    We study the Calabi-Yau property of pointed Hopf algebra $U(\\mc{D},\\lmd)$ of finite Cartan type. It turns out that this class of pointed Hopf algebras constructed by N. Andruskiewitsch and H.-J. Schneider contains many Calabi-Yau Hopf algebras. To give concrete examples of new Calabi-Yau Hopf algebras, we classify the Calabi-Yau pointed Hopf algebras $U(\\mc{D},\\lmd)$ of dimension less than 5.

  1. Analyses of Bifurcations and Stability in a Predator-prey System with Holling Type-IV Functional Response

    Institute of Scientific and Technical Information of China (English)

    Ji-cai Huang; Dong-mei Xiao

    2004-01-01

    In this paper the dynamical behaviors of a predator-prey system with Holling Type-IV functional response are investigated in detail by using the analyses of qualitative method,bifurcation theory,and numerical simulation.The qualitative analyses and numerical simulation for the model indicate that it has a unique stable limit cycle.The bifurcation analyses of the system exhibit static and dynamical bifurcations including saddlenode bifurcation,Hopf bifurcation,homoclinic bifurcation and bifurcation of cusp-type with codimension two(ie,the Bogdanov-Takens bifurcation),and we show the existence of codimension three degenerated equilibrium and the existence of homoclinic orbit by using numerical simulation.

  2. κ-Poincaré–Hopf algebra and Hopf algebroid structure of phase space from twist

    Energy Technology Data Exchange (ETDEWEB)

    Jurić, Tajron, E-mail: Tajron.Juric@irb.hr [Rudjer Bošković Institute, Bijenička c.54, HR-10002 Zagreb (Croatia); Meljanac, Stjepan, E-mail: meljanac@irb.hr [Rudjer Bošković Institute, Bijenička c.54, HR-10002 Zagreb (Croatia); Štrajn, Rina, E-mail: r.strajn@jacobs-university.de [Jacobs University Bremen, 28759 Bremen (Germany)

    2013-11-15

    We unify κ-Poincaré algebra and κ-Minkowski spacetime by embedding them into quantum phase space. The quantum phase space has Hopf algebroid structure to which we apply the twist in order to get κ-deformed Hopf algebroid structure and κ-deformed Heisenberg algebra. We explicitly construct κ-Poincaré–Hopf algebra and κ-Minkowski spacetime from twist. It is outlined how this construction can be extended to κ-deformed super-algebra including exterior derivative and forms. Our results are relevant for constructing physical theories on noncommutative spacetime by twisting Hopf algebroid phase space structure.

  3. NONHOMOGENEOUS HOPF EQUATIONS IN HIGHER DIMENSIONS

    Institute of Scientific and Technical Information of China (English)

    JIU QUANSEN

    1999-01-01

    The existence and uniqueness of the localclassical solution of nonhomogenuous Hopf equationsin higher dimensions are proved in this paper. Thissolution is obtained by vanishing the viscosity termof Burger's equations in higher dimensions.

  4. Ambiguities in input-output behavior of driven nonlinear systems close to bifurcation

    Directory of Open Access Journals (Sweden)

    Reit Marco

    2016-06-01

    Full Text Available Since the so-called Hopf-type amplifier has become an established element in the modeling of the mammalian hearing organ, it also gets attention in the design of nonlinear amplifiers for technical applications. Due to its pure sinusoidal response to a sinusoidal input signal, the amplifier based on the normal form of the Andronov-Hopf bifurcation is a peculiar exception of nonlinear amplifiers. This feature allows an exact mathematical formulation of the input-output characteristic and thus deeper insights of the nonlinear behavior. Aside from the Hopf-type amplifier we investigate an extension of the Hopf system with focus on ambiguities, especially the separation of solution sets, and double hysteresis behavior in the input-output characteristic. Our results are validated by a DSP implementation.

  5. A Hopf algebra deformation approach to renormalization

    CERN Document Server

    Ionescu, L M; Ionescu, Lucian M.; Marsalli, Michael

    2003-01-01

    We investigate the relation between Connes-Kreimer Hopf algebra approach to renomalization and deformation quantization. Both approaches rely on factorization, the correspondence being established at the level of Wiener-Hopf algebras, and double Lie algebras/Lie bialgebras, via r-matrices. It is suggested that the QFTs obtained via deformation quantization and renormalization correspond to each other in the sense of Kontsevich/Cattaneo-Felder.

  6. String Quantization and the Shuffle Hopf Algebra

    CERN Document Server

    Bahns, Dorothea

    2011-01-01

    The Poisson algebra $\\mathfrak h$ of invariants of the Nambu-Goto string, which was first introduced by K. Pohlmeyer in 1982, is described using the Shuffle Hopf algebra. In particular, an underlying auxiliary Lie algebra is reformulated in terms of the image of the first Eulerian idempotent of the Shuffle Hopf algebra. This facilitates the comparison of different approaches to the quantization of $\\mathfrak h$.

  7. Study on a General Hopf Hierarchy

    Science.gov (United States)

    Cui, Min-Jie; Lou, Sen-Yue

    2016-04-01

    By using a general symmetry theory related to invariant functions, strong symmetry operators and hereditary operators, we find a general integrable hopf heirarchy with infinitely many general symmetries and Lax pairs. For the first order Hopf equation, there exist infinitely many symmetries which can be expressed by means of an arbitrary function in arbitrary dimensions. The general solution of the first order Hopf equation is obtained via hodograph transformation. For the second order Hopf equation, the Hopf-diffusion equation, there are five sets of infinitely many symmetries. Especially, there exist a set of primary branch symmetry with which contains an arbitrary solution of the usual linear diffusion equation. Some special implicit exact group invariant solutions of the Hopf-diffusion equation are also given. Supported by the National Natural Science Foundation of China Grant under Nos. 11435005, 11175092, and 11205092, Shanghai Knowledge Service Platform for Trustworthy Internet of Things under Grant No. ZF1213 and K.C. Wong Magna Fund in Ningbo University

  8. Bifurcation in a thin liquid film flowing over a locally heated surface

    CERN Document Server

    Katkar, Harshwardhan H

    2014-01-01

    We investigate the non-linear dynamics of a two-dimensional film flowing down a finite heater, for a non-volatile and a volatile liquid. An oscillatory instability is predicted beyond a critical value of Marangoni number using linear stability theory. Continuation along the Marangoni number using non-linear evolution equation is used to trace bifurcation diagram associated with the oscillatory instability. Hysteresis, a characteristic attribute of a sub-critical Hopf bifurcation, is observed in a critical parametric region. The bifurcation is universally observed for both, a non-volatile film and a volatile film.

  9. Local Bifurcations and Optimal Theory in a Delayed Predator-Prey Model with Threshold Prey Harvesting

    Science.gov (United States)

    Tankam, Israel; Tchinda Mouofo, Plaire; Mendy, Abdoulaye; Lam, Mountaga; Tewa, Jean Jules; Bowong, Samuel

    2015-06-01

    We investigate the effects of time delay and piecewise-linear threshold policy harvesting for a delayed predator-prey model. It is the first time that Holling response function of type III and the present threshold policy harvesting are associated with time delay. The trajectories of our delayed system are bounded; the stability of each equilibrium is analyzed with and without delay; there are local bifurcations as saddle-node bifurcation and Hopf bifurcation; optimal harvesting is also investigated. Numerical simulations are provided in order to illustrate each result.

  10. Snaking bifurcations in a self-excited oscillator chain with cyclic symmetry

    Science.gov (United States)

    Papangelo, A.; Grolet, A.; Salles, L.; Hoffmann, N.; Ciavarella, M.

    2017-03-01

    Snaking bifurcations in a chain of mechanical oscillators are studied. The individual oscillators are weakly nonlinear and subject to self-excitation and subcritical Hopf-bifurcations with some parameter ranges yielding bistability. When the oscillators are coupled to their neighbours, snaking bifurcations result, corresponding to localised vibration states. The snaking patterns do seem to be more complex than in previously studied continuous systems, comprising a plethora of isolated branches and also a large number of similar but not identical states, originating from the weak coupling of the phases of the individual oscillators.

  11. Forcing an entire bifurcation diagram: Case studies in chemical oscillators

    Science.gov (United States)

    Kevrekidis, I. G.; Aris, R.; Schmidt, L. D.

    1986-12-01

    We study the finite amplitude periodic forcing of chemical oscillators. In particular, we examine systems that, when autonomous, (i.e. for zero forcing amplitude) exhibit a single stable oscillation. Using one of the system parameters as a forcing variable by varying it periodically, we show through extensive numerical work how the bifurcation diagram of the autonomous system with respect to this parameter affects the qualitative response of the full forced system. As the forcing variable oscillates around its midpoint, its instantaneous values may cross points (such as Hopf bifurcation poiints) of the autonomous bifurcation diagram so that the characterization of the system as a simple forced oscillator is no longer valid. Such a neighboring Hopf bifurcation of the unforced system is found to set the scene for the interaction of resonance horns and the loss of tori in the full forced system as the amplitude of the forcing grows. Our test case presented here is the Continuous Stirred Tank Reactor (CSTR) with periodically forced coolant temperature.

  12. Nonlinear aeroelastic analysis of airfoils: bifurcation and chaos

    Science.gov (United States)

    Lee, B. H. K.; Price, S. J.; Wong, Y. S.

    1999-04-01

    Different types of structural and aerodynamic nonlinearities commonly encountered in aeronautical engineering are discussed. The equations of motion of a two-dimensional airfoil oscillating in pitch and plunge are derived for a structural nonlinearity using subsonic aerodynamics theory. Three classical nonlinearities, namely, cubic, freeplay and hysteresis are investigated in some detail. The governing equations are reduced to a set of ordinary differential equations suitable for numerical simulations and analytical investigation of the system stability. The onset of Hopf-bifurcation, and amplitudes and frequencies of limit cycle oscillations are investigated, with examples given for a cubic hardening spring. For various geometries of the freeplay, bifurcations and chaos are discussed via the phase plane, Poincaré maps, and Lyapunov spectrum. The route to chaos is investigated from bifurcation diagrams, and for the freeplay nonlinearity it is shown that frequency doubling is the most commonly observed route. Examples of aerodynamic nonlinearities arising from transonic flow and dynamic stall are discussed, and special attention is paid to numerical simulation results for dynamic stall using a time-synthesized method for the unsteady aerodynamics. The assumption of uniform flow is usually not met in practice since perturbations in velocities are encountered in flight. Longitudinal atmospheric turbulence is introduced to show its effect on both the flutter boundary and the onset of Hopf-bifurcation for a cubic restoring force.

  13. Stability and Bifurcation Analysis for a Predator-Prey Model with Discrete and Distributed Delay

    Directory of Open Access Journals (Sweden)

    Ruiqing Shi

    2013-01-01

    Full Text Available We propose a two-dimensional predatory-prey model with discrete and distributed delay. By the use of a new variable, the original two-dimensional system transforms into an equivalent three-dimensional system. Firstly, we study the existence and local stability of equilibria of the new system. And, by choosing the time delay τ as a bifurcation parameter, we show that Hopf bifurcation can occur as the time delay τ passes through some critical values. Secondly, by the use of normal form theory and central manifold argument, we establish the direction and stability of Hopf bifurcation. At last, an example with numerical simulations is provided to verify the theoretical results. In addition, some simple discussion is also presented.

  14. SAYD modules over Lie-Hopf algebras

    CERN Document Server

    Rangipour, B

    2011-01-01

    In this paper a general van Est type isomorphism is established. The isomorphism is between the Lie algebra cohomology of a bicrossed sum Lie algebra and the Hopf cyclic cohomology of its Hopf algebra. We first prove a one to one correspondence between stable-anti-Yetter-Drinfeld (SAYD) modules over the total Lie algebra and SAYD modules over the associated Hopf algebra. In contrast to the non-general case done in our previous work, here the van Est isomorphism is found at the first level of a natural spectral sequence, rather than at the level of complexes. It is proved that the Connes-Moscovici Hopf algebras do not admit any finite dimensional SAYD modules except the unique one-dimensional one found by Connes- Moscovici in 1998. This is done by extending our techniques to work with the infinite dimensional Lie algebra of formal vector fields. At the end, the one to one correspondence is applied to construct a highly nontrivial four dimensional SAYD module over the Schwarzian Hopf algebra. We then illustrate...

  15. SAYD Modules over Lie-Hopf Algebras

    Science.gov (United States)

    Rangipour, Bahram; Sütlü, Serkan

    2012-11-01

    In this paper a general van Est type isomorphism is proved. The isomorphism is between the Lie algebra cohomology of a bicrossed sum Lie algebra and the Hopf cyclic cohomology of its Hopf algebra. We first prove a one to one correspondence between stable-anti-Yetter-Drinfeld (SAYD) modules over the total Lie algebra and those modules over the associated Hopf algebra. In contrast to the non-general case done in our previous work, here the van Est isomorphism is proved at the first level of a natural spectral sequence, rather than at the level of complexes. It is proved that the Connes-Moscovici Hopf algebras do not admit any finite dimensional SAYD modules except the unique one-dimensional one found by Connes-Moscovici in 1998. This is done by extending our techniques to work with the infinite dimensional Lie algebra of formal vector fields. At the end, the one to one correspondence is applied to construct a highly nontrivial four dimensional SAYD module over the Schwarzian Hopf algebra. We then illustrate the whole theory on this example. Finally explicit representative cocycles of the cohomology classes for this example are calculated.

  16. Hopf C~* -algebras related to the Latin square

    Institute of Scientific and Technical Information of China (English)

    郭懋正; 蒋立宁; 钱敏

    2000-01-01

    A sufficient condition is given for the multiparametric Hopf algebras to be Hopf * -algebras. Then a special subclass of the * -algebra related to a Latin square is given. After being completed, its generators are all of norm one.

  17. Hopf C*-algebras related to the Latin square

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A sufficient condition is given for the multiparametric Hopf algebras to be Hopf*-algebras. Then a special subclass of the *-algebra related to a Latin square is given. After being completed, its generators are all of norm one.

  18. Generalized Cole–Hopf transformations for generalized Burgers equations

    Indian Academy of Sciences (India)

    B Mayil Vaganan; E Emily Priya

    2015-11-01

    A detailed review of the invention of Cole–Hopf transformations for the Burgers equation and all the subsequent works which include generalizations of the Burgers equation and the corresponding developments in Cole–Hopf transformations are documented.

  19. Bifurcation Control of an Electrostatically-Actuated MEMS Actuator with Time-Delay Feedback

    Directory of Open Access Journals (Sweden)

    Lei Li

    2016-10-01

    Full Text Available The parametric excitation system consisting of a flexible beam and shuttle mass widely exists in microelectromechanical systems (MEMS, which can exhibit rich nonlinear dynamic behaviors. This article aims to theoretically investigate the nonlinear jumping phenomena and bifurcation conditions of a class of electrostatically-driven MEMS actuators with a time-delay feedback controller. Considering the comb structure consisting of a flexible beam and shuttle mass, the partial differential governing equation is obtained with both the linear and cubic nonlinear parametric excitation. Then, the method of multiple scales is introduced to obtain a slow flow that is analyzed for stability and bifurcation. Results show that time-delay feedback can improve resonance frequency and stability of the system. What is more, through a detailed mathematical analysis, the discriminant of Hopf bifurcation is theoretically derived, and appropriate time-delay feedback force can make the branch from the Hopf bifurcation point stable under any driving voltage value. Meanwhile, through global bifurcation analysis and saddle node bifurcation analysis, theoretical expressions about the system parameter space and maximum amplitude of monostable vibration are deduced. It is found that the disappearance of the global bifurcation point means the emergence of monostable vibration. Finally, detailed numerical results confirm the analytical prediction.

  20. A Maschke Type Theorem for Weak Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    J. N. ALONSO (A)LVAREZ; J. M. FERN(A)NDEZ VILABOA; R. GONZ(A)LEZ RODR(I)GUEZ; A. B. RODR(I)GUEZ RAPOSO

    2008-01-01

    In this paper, we give a necessary and sufficient condition for a comodule algebra over a weak Hopf algebra to have a total integral, thus extending the classical theory developed by Doi in the Hopf algebra setting. Also, from these results, we deduce a version of Maschke's Theorem for (H, S)-Hopf modules associated with a weak Hopf algebra H and a right H-comodule algebra B.

  1. Products in Hopf-Cyclic Cohomology

    CERN Document Server

    Kaygun, Atabey

    2007-01-01

    We construct several pairings in Hopf-cyclic cohomology of (co)module (co)algebras with arbitrary coefficients. The key ideas instrumental in constructing these pairings are the derived functor interpretation of Hopf-cyclic and equivariant cyclic (co)homology, and the Yoneda interpretation of Ext-groups. As a special case of one of these pairings, we recover the Connes-Moscovici characteristic map in Hopf-cyclic cohomology. We also prove that this particular pairing, along with few others, would stay the same if we replace the derived category of (co)cyclic modules with the homotopy category of (special) towers of $X$-complexes, or the derived category of mixed complexes.

  2. Quasi-periodic bifurcations and “amplitude death” in low-dimensional ensemble of van der Pol oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Emelianova, Yu.P., E-mail: yuliaem@gmail.com [Department of Electronics and Instrumentation, Saratov State Technical University, Polytechnicheskaya 77, Saratov 410054 (Russian Federation); Kuznetsov, A.P., E-mail: apkuz@rambler.ru [Kotel' nikov' s Institute of Radio-Engineering and Electronics of RAS, Saratov Branch, Zelyenaya 38, Saratov 410019 (Russian Federation); Turukina, L.V., E-mail: lvtur@rambler.ru [Kotel' nikov' s Institute of Radio-Engineering and Electronics of RAS, Saratov Branch, Zelyenaya 38, Saratov 410019 (Russian Federation); Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam (Germany)

    2014-01-10

    The dynamics of the four dissipatively coupled van der Pol oscillators is considered. Lyapunov chart is presented in the parameter plane. Its arrangement is discussed. We discuss the bifurcations of tori in the system at large frequency detuning of the oscillators. Here are quasi-periodic saddle-node, Hopf and Neimark–Sacker bifurcations. The effect of increase of the threshold for the “amplitude death” regime and the possibilities of complete and partial broadband synchronization are revealed.

  3. Degeneration, Rigidity and Irreducible Components of Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    Abdenacer Makhlouf

    2005-01-01

    The aim of this work is to discuss the concepts of degeneration, deformation and rigidity of Hopf algebras and to apply them to the geometric study of the varieties of Hopf algebras. The main result is the description of the n-dimensional rigid Hopf algebras and the irreducible components for n < 14 and n = p2 with p a prime number.

  4. Stability and dynamics of a controlled van der Pol-Duffing oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Ji, J.C. [School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia)] e-mail: jcji@mecheng.adelaide.edu.au; Hansen, C.H. [School of Mechanical Engineering, University of Adelaide, SA 5005 (Australia)] e-mail: chansen@mecheng.adelaide.edu.au

    2006-04-01

    The trivial equilibrium of a van der Pol-Duffing oscillator under a linear-plus-nonlinear feedback control may change its stability either via a single or via a double Hopf bifurcation if the time delay involved in the feedback reaches certain values. It is found that the trivial equilibrium may lose its stability via a subcritical or supercritical Hopf bifurcation and regain its stability via a reverse subcritical or supercritical Hopf bifurcation as the time delay increases. A stable limit cycle appears after a supercritical Hopf bifurcation occurs and disappears through a reverse supercritical Hopf bifurcation. The interaction of the weakly periodic excitation and the stable bifurcating solution is investigated for the forced system under primary resonance conditions. It is shown that the forced periodic response may lose its stability via a Neimark-Sacker bifurcation. Analytical results are validated by a comparison with those of direct numerical integration.

  5. Induced Modules of Semisimple Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    Jun Hu; Yinhuo Zhang

    2007-01-01

    Let K be a field. Let H be a finite-dimensional K-Hopf algebra and D(H) be the Drinfel'd double of H. In this paper, we study Radford's induced module Hβ, whereβ is a group-like element in H*. Using the commuting pair established in [7], we obtain an analogue of the class equation for H*β when H is semisimple and cosemisimple. In case H is a finite group algebra or a factorizable semisimple cosemisimple Hopf algebra, we give an explicit decomposition of each Hβ into a direct sum of simple D(H)-modules.

  6. Categorification and Quasi-Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    常文静; 王志玺; 吴可; 杨紫峰

    2011-01-01

    We categorify the notion of coalgebras by imposing a co-associative law up to some isomorphisms on the co-multiplication map and requiring that these isomorphisms satisfy certairl law of their own, which is called the copentagon identity. We also set up a 2-category of 2-coalgebras. The purpose of this study is from the idea of reconsidering the quasi-Hopf algebras by the categorification process, so that we can study the theory of quasi-Hopf algebras and their representations in some new framework of higher category theory in natural ways.

  7. A diagrammatic approach to Hopf monads

    CERN Document Server

    Willerton, Simon

    2008-01-01

    Given a Hopf algebra in a symmetric monoidal category with duals, the category of modules inherits the structure of a monoidal category with duals. If the notion of algebra is replaced with that of monad on a monoidal category with duals then Bruguieres and Virelizier showed when the category of modules inherits this structure of being monoidal with duals, and this gave rise to what they called a Hopf monad. In this paper it is shown that there are good diagrammatic descriptions of dinatural transformations which allows the three-dimensional, object-free nature of their constructions to become apparent.

  8. Topological Aspect and Bifurcation of Disclination Lines in Two—Dimensional Liquid Crystals

    Institute of Scientific and Technical Information of China (English)

    YANGGuo-Hong; ZHANGHui; 等

    2002-01-01

    Using φ-mapping method and topological current theory,the topological structure and bifurcation of disclination lines in two-dimensional liquid crystals are studied.By introducing the strength density and the topological current of many disclination lines,the total disclination strength is topologically quantized by the Hopf indices and Brouwer degrees at the singularities of the director field when the Jacobian determinant of director field does not vanish.When the Jacobian determinant vanishes,the origin,annihilation and bifurcation processes of disclination lines are studied in the neighborhoods of the limit points and bifurcation points,respectively.The branch solutions at the limit point and the different directions of all branch curves at the bifurcation point are calculated with the conservation law of the topological quantum numbers.It is pointed out that a disclination line with a higher strength is unstable and it will evolve to the lower strength state through the bifurcation process.

  9. Topological Aspect and Bifurcation of Disclination Lines in Two-Dimensional Liquid Crystals

    Institute of Scientific and Technical Information of China (English)

    YANG Guo-Hong; ZHANG Hui; DUAN Yi-Shi

    2002-01-01

    Using φ-mapping method and topological current theory, the topological structure and bifurcation ofdisclination lines in two-dimensional liquid crystals are studied. By introducing the strength density and the topologicalcurrent of many disclination lines, the total disclination strength is topologically quantized by the Hopf indices andBrouwer degrees at the singularities of the director field when the Jacobian determinant of director field does not vanish.When the Jacobian determinant vanishes, the origin, annihilation and bifurcation processes of disclination lines arestudied in the neighborhoods of the limit points and bifurcation points, respectively. The branch solutions at the limitpoint and the different directions of all branch curves at the bifurcation point are calculated with the conservation lawof the topological quantum numbers. It is pointed out that a disclination line with a higher strength is unstable and itwill evolve to the lower strength state through the bifurcation process.

  10. Lie Algebra of Noncommutative Inhomogeneous Hopf Algebra

    CERN Document Server

    Lagraa, M

    1997-01-01

    We construct the vector space dual to the space of right-invariant differential forms construct from a first order differential calculus on inhomogeneous quantum group. We show that this vector space is equipped with a structure of a Hopf algebra which closes on a noncommutative Lie algebra satisfying a Jacobi identity.

  11. Partial results on extending the Hopf Lemma

    CERN Document Server

    Li, YanYan

    2009-01-01

    In [1], Theorem 3, the authors proved, in one dimension, a generalization of the Hopf Lemma, and the question arose if it could be extended to higher dimensions. In this paper we present two conjectures as possible extensions, and give a very partial answer. We write this paper to call attention to the problem.

  12. The cyclic theory of Hopf algebroids

    NARCIS (Netherlands)

    Kowalzig, N.; Posthuma, H.

    2011-01-01

    We give a systematic description of the cyclic cohomology theory of Hopf alge\\-broids in terms of its associated category of modules. Then we introduce a dual cyclic homology theory by applying cyclic duality to the underlying cocyclic object. We derive general structure theorems for these theories

  13. A Coquasi-Hopf Algebra H

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@In this note ,we always assume that H is a finite-dimensional commutative Hopf algebra[1] with antipode S and ФE H H H,a normalized 3-cocycle,i. e. ,Ф is convolution invertible and satisfies the following conditions:

  14. Renormalization, Hopf algebras and Mellin transforms

    CERN Document Server

    Panzer, Erik

    2014-01-01

    This article aims to give a short introduction into Hopf-algebraic aspects of renormalization, enjoying growing attention for more than a decade by now. As most available literature is concerned with the minimal subtraction scheme, we like to point out properties of the kinematic subtraction scheme which is also widely used in physics (under the names of MOM or BPHZ). In particular we relate renormalized Feynman rules $\\phi_R$ in this scheme to the universal property of the Hopf algebra $H_R$ of rooted trees, exhibiting a refined renormalization group equation which is equivalent to $\\phi_R: H_R \\rightarrow K[x]$ being a morphism of Hopf algebras to the polynomials in one indeterminate. Upon introduction of analytic regularization this results in efficient combinatorial recursions to calculate $\\phi_R$ in terms of the Mellin transform. We find that different Feynman rules are related by a distinguished class of Hopf algebra automorphisms of $H_R$ that arise naturally from Hochschild cohomology. Also we recall...

  15. Sprinkler Bifurcations and Stability

    Science.gov (United States)

    Sorensen, Jody; Rykken, Elyn

    2010-01-01

    After discussing common bifurcations of a one-parameter family of single variable functions, we introduce sprinkler bifurcations, in which any number of new fixed points emanate from a single point. Based on observations of these and other bifurcations, we then prove a number of general results about the stabilities of fixed points near a…

  16. Bifurcations and complex dynamics of an SIR model with the impact of the number of hospital beds

    Science.gov (United States)

    Shan, Chunhua; Zhu, Huaiping

    2014-09-01

    In this paper we establish an SIR model with a standard incidence rate and a nonlinear recovery rate, formulated to consider the impact of available resource of the public health system especially the number of hospital beds. For the three dimensional model with total population regulated by both demographics and diseases incidence, we prove that the model can undergo backward bifurcation, saddle-node bifurcation, Hopf bifurcation and cusp type of Bogdanov-Takens bifurcation of codimension 3. We present the bifurcation diagram near the cusp type of Bogdanov-Takens bifurcation point of codimension 3 and give epidemiological interpretation of the complex dynamical behaviors of endemic due to the variation of the number of hospital beds. This study suggests that maintaining enough number of hospital beds is crucial for the control of the infectious diseases.

  17. Dynamic bifurcation and strange nonchaos in a two-frequency parametrically driven nonlinear oscillator

    Science.gov (United States)

    Premraj, D.; Suresh, K.; Palanivel, J.; Thamilmaran, K.

    2017-09-01

    A periodically forced series LCR circuit with Chua's diode as a nonlinear element exhibits slow passage through Hopf bifurcation. This slow passage leads to a delay in the Hopf bifurcation. The delay in this bifurcation is a unique quantity and it can be predicted using various numerical analysis. We find that when an additional periodic force is added to the system, the delay in bifurcation becomes chaotic which leads to an unpredictability in bifurcation delay. Further, we study the bifurcation of the periodic delay to chaotic delay in the slow passage effect through strange nonchaotic delay. We also report the occurrence of strange nonchaotic dynamics while varying the parameter of the additional force included in the system. We observe that the system exhibits a hitherto unknown dynamical transition to a strange nonchaotic attractor. With the help of Lyapunov exponent, we explain the new transition to strange nonchaotic attractor and its mechanism is studied by making use of rational approximation theory. The birth of SNA has also been confirmed numerically, using Poincaré maps, phase sensitivity exponent, the distribution of finite-time Lyapunov exponents and singular continuous spectrum analysis.

  18. Analytical determination of the bifurcation thresholds in stochastic differential equations with delayed feedback.

    Science.gov (United States)

    Gaudreault, Mathieu; Drolet, François; Viñals, Jorge

    2010-11-01

    Analytical expressions for pitchfork and Hopf bifurcation thresholds are given for a nonlinear stochastic differential delay equation with feedback. Our results assume that the delay time τ is small compared to other characteristic time scales, not a significant limitation close to the bifurcation line. A pitchfork bifurcation line is found, the location of which depends on the conditional average , where x(t) is the dynamical variable. This conditional probability incorporates the combined effect of fluctuation correlations and delayed feedback. We also find a Hopf bifurcation line which is obtained by a multiple scale expansion around the oscillatory solution near threshold. We solve the Fokker-Planck equation associated with the slowly varying amplitudes and use it to determine the threshold location. In both cases, the predicted bifurcation lines are in excellent agreement with a direct numerical integration of the governing equations. Contrary to the known case involving no delayed feedback, we show that the stochastic bifurcation lines are shifted relative to the deterministic limit and hence that the interaction between fluctuation correlations and delay affect the stability of the solutions of the model equation studied.

  19. Dynamics and bifurcations of a coupled column-pendulum oscillator

    Science.gov (United States)

    Mustafa, G.; Ertas, A.

    1995-05-01

    This study deals with the dynamics of a large flexible column with a tip mass-pendulum arrangement. The system is a conceptualization of a vibration-absorbing device for flexible structures with tip appendages. The bifurcation diagrams of the averaged system indicate that the system loses stability via two distinct routes; one leading to a saddle-node bifurcation, and the other to the Hopf bifurcation, indicating the existence of an invariant torus. Under the change of forcing amplitude, these bifurcations coalesce. This phenomenon has important global ramifications, in the sense that the periodic modulations associated with the Hopf bifurcation tend to have an infinite period, a strong indicator of existence of homoclinic orbits. The system also possesses isolated solutions (the so-called "isolas") that form isolated loops bounded away from zero. As the forcing amplitude is varied, the isolas appear, disappear or coalesce with the regular solution branches. The response curves indicate that the column amplitude shows saturation and the pendulum acts as a vibration absorber. However, there is also a frequency range over which a reverse flow of energy occurs, where the pendulum shows reduced amplitude at the cost of large amplitudes of the column. The experimental dynamics shows that the periodic motion gives rise to a quasi-periodic response, confirming the existence of tori. Within the quasi-periodic region, there are windows containing intricate webs of mode-locked periodic responses. An increase in the force amplitude causes the tori to break up, a phenomenon similar to the onset of turbulence in hydrodynamics.

  20. About Bifurcational Parametric Simplification

    CERN Document Server

    Gol'dshtein, V; Yablonsky, G

    2015-01-01

    A concept of "critical" simplification was proposed by Yablonsky and Lazman in 1996 for the oxidation of carbon monoxide over a platinum catalyst using a Langmuir-Hinshelwood mechanism. The main observation was a simplification of the mechanism at ignition and extinction points. The critical simplification is an example of a much more general phenomenon that we call \\emph{a bifurcational parametric simplification}. Ignition and extinction points are points of equilibrium multiplicity bifurcations, i.e., they are points of a corresponding bifurcation set for parameters. Any bifurcation produces a dependence between system parameters. This is a mathematical explanation and/or justification of the "parametric simplification". It leads us to a conjecture that "maximal bifurcational parametric simplification" corresponds to the "maximal bifurcation complexity." This conjecture can have practical applications for experimental study, because at points of "maximal bifurcation complexity" the number of independent sys...

  1. Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Shi Zhongke; Fan Li

    2013-01-01

    To investigate the longitudinal motion stability of aircraft maneuvers conveniently,a new stability analysis approach is presented in this paper.Based on describing longitudinal aerodynamics at high angle-of-attack (α < 50°) motion by polynomials,a union structure of two-order differential equation is suggested.By means of nonlinear theory and method,analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight.Applying the theories of bifurcations,many kinds of bifurcations,such as equilibrium,Hopf,homoclinic (heteroclinic) orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived.The bifurcation curves divide the parameter plane into several regions; moreover,the complete bifurcation diagrams and phase portraits in different regions are obtained.Finally,our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium.The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack.

  2. Equilibrium points and bifurcation control of a chaotic system

    Institute of Scientific and Technical Information of China (English)

    Liang Cui-Xiang; Tang Jia-Shi

    2008-01-01

    Based on the Routh-Hurwitz criterion,this paper investigates the stability of a new chaotic system.State feedback controllers are designed to control the chaotic system to the unsteady equilibrium points and limit cycle.Theoretical analyses give the range of value of control parameters to stabilize the unsteady equilibrium points of the chaotic system and its critical parameter for generating Hopf bifurcation.Certain nP periodic orbits can be stabilized by parameter adjustment.Numerical simulations indicate that the method can effectively guide the system trajectories to unsteady equilibrium points and periodic orbits.

  3. Ideal Relaxation of the Hopf Fibration

    CERN Document Server

    Smiet, Christopber Berg; Bouwmeester, Dirk

    2016-01-01

    We study the topology conserving relaxation of a magnetic field based on the Hopf fibration in which magnetic field lines are closed circles that are all linked with one another. In order to find a stable plasma configuration in which the pressure gradient balances the Lorentz forces, and the magnetic field preserves its Hopf topology we take the following steps. First, we take the magnetic Hopf fibration at constant pressure as initial condition. Second, we let the system evolve under a non-resistive evolution in order to preserve the magnetic field topology while balancing pressure gradients can build up. Third, we add viscosity to damp any oscillatory fluid motion. In this way we find an equilibrium plasma configuration, characterized by a lowered pressure in a toroidal region, with field lines lying on surfaces of constant pressure, and as such the field is in a Grad-Shafranov equilibrium. Such a field configuration is of interest to astrophysical plasma and earth-based fusion plasma.

  4. Hopf monoids from class functions on unitriangular matrices

    CERN Document Server

    Aguiar, Marcelo; Thiem, Nathaniel

    2012-01-01

    We build, from the collection of all groups of unitriangular matrices, Hopf monoids in Joyal's category of species. Such structure is carried by the collection of class function spaces on those groups, and also by the collection of superclass function spaces, in the sense of Diaconis and Isaacs. Superclasses of unitriangular matrices admit a simple description from which we deduce a combinatorial model for the Hopf monoid of superclass functions, in terms of the Hadamard product of the Hopf monoids of linear orders and of set partitions. This implies a recent result relating the Hopf algebra of superclass functions on unitriangular matrices to symmetric functions in noncommuting variables. We determine the algebraic structure of the Hopf monoid: it is a free monoid in species, with the canonical Hopf structure. As an application, we derive certain estimates on the number of conjugacy classes of unitriangular matrices.

  5. Bifurcation threshold of the delayed van der Pol oscillator under stochastic modulation.

    Science.gov (United States)

    Gaudreault, Mathieu; Drolet, François; Viñals, Jorge

    2012-05-01

    We obtain the location of the Hopf bifurcation threshold for a modified van der Pol oscillator, parametrically driven by a stochastic source and including delayed feedback in both position and velocity. We introduce a multiple scale expansion near threshold, and we solve the resulting Fokker-Planck equation associated with the evolution at the slowest time scale. The analytical results are compared with a direct numerical integration of the model equation. Delay modifies the Hopf frequency at threshold and leads to a stochastic bifurcation that is shifted relative to the deterministic limit by an amount that depends on the delay time, the amplitude of the feedback terms, and the intensity of the noise. Interestingly, stochasticity generally increases the region of stability of the limit cycle.

  6. Cellular instability in rapid directional solidification - Bifurcation theory

    Science.gov (United States)

    Braun, R. J.; Davis, S. H.

    1992-01-01

    Merchant and Davis performed a linear stability analysis on a model for the directional solidification of a dilute binary alloy valid for all speeds. The analysis revealed that nonequilibrium segregation effects modify the Mullins and Sekerka cellular mode, whereas attachment kinetics has no effect on these cells. In this paper, the nonlinear stability of the steady cellular mode is analyzed. A Landau equation is obtained that determines the amplitude of the cells. The Landau coefficient here depends on both nonequilibrium segregation effects and attachment kinetics. This equation gives the ranges of parameters for subcritical bifurcation (jump transition) or supercritical bifurcation (smooth transition) to cells.

  7. Cup products in Hopf cyclic cohomology via cyclic modules I

    CERN Document Server

    Rangipour, Bahram

    2007-01-01

    This is the first one in a series of two papers on the continuation of our study in cup products in Hopf cyclic cohomology. In this note we construct cyclic cocycles of algebras out of Hopf cyclic cocycles of algebras and coalgebras. In the next paper we consider producing Hopf cyclic cocycle from "equivariant" Hopf cyclic cocycles. Our approach in both situations is based on (co)cyclic modules and bi(co)cyclic modules together with Eilenberg-Zilber theorem which is different from the old definition of cup products defined via traces and cotraces on DG algebras and coalgebras.

  8. On the Structure of Graded λ-Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    Jian Hua SUN; Pu ZHANG

    2009-01-01

    Let G be an abelian group, B the G-graded λ-Hopf algebra with λ being a bicharacter on G. By introducing some new twisted algebras (coalgebras), we investigate the basic properties of the graded antipode and the structure for B. We also prove that a G-graded λ-Hopf algebra can be embedded in a usual Hopf algebra. As an application, it is given that if G is a finite abelian group then the graded antipode of a finite dimensional G-graded λ-Hopf algebra is invertible.

  9. The Influence of Machine Saturation on Bifurcation and Chaos in Multimachine Power Systems

    Science.gov (United States)

    Alomari, Majdi M.; Zhu, Jian Gue

    A bifurcation theory is applied to the multimachine power system to investigate the effect of iron saturation on the complex dynamics of the system. The second system of the IEEE second benchmark model of Subsynchronous Resonance (SSR) is considered. The system studied can be mathematically modeled as a set of first order nonlinear ordinary differential equations with (µ = Xc/XL) as a bifurcation parameter. Hence, bifurcation theory can be applied to nonlinear dynamical systems, which can be written as dx/dt = F(x;µ). The results show that the influence of machine saturation expands the unstable region when the system loses stability at the Hopf bifurcation point at a less value of compensation.

  10. BIFURCATIONS OF A CANTILEVERED PIPE CONVEYING STEADY FLUID WITH A TERMINAL NOZZLE

    Institute of Scientific and Technical Information of China (English)

    Xu Jian; Huang Yuying

    2000-01-01

    This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to investigate the stability of the periodic motions. A Runge-Kutta scheme is used to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.

  11. A Computational Method for Robust Bifurcation Analysis and Its Application to Biomolecular Systems

    Science.gov (United States)

    Inoue, Masaki; Ikuta, Hikaru; Adachi, Shuichi; Imura, Jun-Ichi; Aihara, Kazuyuki

    2015-06-01

    We consider a general uncertain nonlinear dynamical system defined in a certain model set, and reformulate a problem of robustness bifurcation analysis (RBA), which has been originally formulated in our previous work. As such, we develop an efficient computational method for the RBA, which can be used for quantitative evaluation of bifurcation robustness in uncertain dynamical systems. Specifically, we first linearize the uncertain system properly and then apply a feedback transformation technique to reduce the RBA problem to a linear robustness analysis one, which can be solved using μ-analysis, a common analysis technique in robust control theory. Finally, we provide robustness analysis of a gene regulatory network model where oscillatory behavior appears according to Hopf bifurcation. We give quantitative evaluation of the bifurcation robustness using the RBA method proposed here.

  12. Bifurcations of Limit Cycles in A Perturbed Quintic Hamiltonian System with Six Double Homoclinic Loops

    Institute of Scientific and Technical Information of China (English)

    Yong-xi Gao; Yu-hai Wu; Li-xin Tian

    2008-01-01

    This paper concerns with the number and distributions of limit cycles of a quintic subject to a seven-degree perturbation. With the aid of numeric integral computation provided by Mathematica 4.1, at least 45 limit cycles are found in the above system by applying the method of double homoclinic loops bifurcation,Hopf bifurcation and qualitative analysis. The four configurations of 45 limit cycles of the system are also shown.The results obtained are useful to the study of the weakened 16th Hilbert Problem.

  13. Bifurcation and chaos in a ratio-dependent predator-prey system with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Gan Qintao [Institute of Applied Mathematics, Shijiazhuang Mechanical Engineering College, Shijiazhuang 050003 (China)], E-mail: ganqintao@sina.com; Xu Rui [Institute of Applied Mathematics, Shijiazhuang Mechanical Engineering College, Shijiazhuang 050003 (China); Department of Applied Mathematics, Xi' an Jiaotong University, Xi' an 710049 (China); Yang Pinghua [Institute of Applied Mathematics, Shijiazhuang Mechanical Engineering College, Shijiazhuang 050003 (China)

    2009-02-28

    In this paper, a ratio-dependent predator-prey model with time delay is investigated. We first consider the local stability of a positive equilibrium and the existence of Hopf bifurcations. By using the normal form theory and center manifold reduction, we derive explicit formulae which determine the stability, direction and other properties of bifurcating periodic solutions. Finally, we consider the effect of impulses on the dynamics of the above time-delayed population model. Numerical simulations show that the system with constant periodic impulsive perturbations admits rich complex dynamic, such as periodic doubling cascade and chaos.

  14. Pitchfork bifurcation and vibrational resonance in a fractional-order Duffing oscillator

    Indian Academy of Sciences (India)

    J H Yang; M A F Sanjuán; W Xiang; H Zhu

    2013-12-01

    The pitchfork bifurcation and vibrational resonance are studied in a fractional-order Duffing oscillator with delayed feedback and excited by two harmonic signals. Using an approximation method, the bifurcation behaviours and resonance patterns are predicted. Supercritical and subcritical pitchfork bifurcations can be induced by the fractional-order damping, the exciting highfrequency signal and the delayed time. The fractional-order damping mainly determines the pattern of the vibrational resonance. There is a bifurcation point of the fractional order which, in the case of double-well potential, transforms vibrational resonance pattern from a single resonance to a double resonance, while in the case of single-well potential, transforms vibrational resonance from no resonance to a single resonance. The delayed time influences the location of the vibrational resonance and the bifurcation point of the fractional order. Pitchfork bifurcation is the necessary condition for the double resonance. The theoretical predictions are in good agreement with the numerical simulations.

  15. Unfolding the Riddling Bifurcation

    DEFF Research Database (Denmark)

    Maistrenko, Yu.; Popovych, O.; Mosekilde, Erik

    1999-01-01

    We present analytical conditions for the riddling bifurcation in a system of two symmetrically coupled, identical, smooth one-dimensional maps to be soft or hard and describe a generic scenario for the transformations of the basin of attraction following a soft riddling bifurcation.......We present analytical conditions for the riddling bifurcation in a system of two symmetrically coupled, identical, smooth one-dimensional maps to be soft or hard and describe a generic scenario for the transformations of the basin of attraction following a soft riddling bifurcation....

  16. Torus Bifurcation Under Discretization

    Institute of Scientific and Technical Information of China (English)

    邹永魁; 黄明游

    2002-01-01

    Parameterized dynamical systems with a simple zero eigenvalue and a couple of purely imaginary eigenvalues are considered. It is proved that this type of eigen-structure leads to torns bifurcation under certain nondegenerate conditions. We show that the discrete systems, obtained by discretizing the ODEs using symmetric, eigen-structure preserving schemes, inherit the similar torus bifurcation properties. Fredholm theory in Banach spaces is applied to obtain the global torns bifurcation. Our results complement those on the study of discretization effects of global bifurcation.

  17. BIFURCATION OF A SHAFT WITH HYSTERETIC-TYPE INTERNAL FRICTION FORCE OF MATERIAL

    Institute of Scientific and Technical Information of China (English)

    丁千; 陈予恕

    2003-01-01

    The bifurcation of a shaft with hysteretic internal friction of material was analysed. Firstly, the differential motion equation in complex form was deduced using Hamilton principle. Then averaged equations in primary resonances were obtained using the averaging method. The stability of steady-state responses was also determined. Lastly, the bifurcations of both normal motion (synchronous whirl) and self-excited motion (nonsynchronous whirl) were investigated using the method of singularity. The study shows that by a rather large disturbance, the stability of the shaft can be lost through Hopf bifurcation in case the stability condition is not satisfied. The averaged self-excited response appears as a type of unsymmetrical bifurcation with high orders of co-dimension. The second Hopf bifurcation, which corresponds to double amplitude-modulated response, can occur as the speed of the shaft increases. Balancing the shaft carefully to decrease its unbalance level and increasing the external damping are two effective methods to avoid the appearance of the self-sustained whirl induced by the hysteretic internal friction of material.

  18. Bifurcation analysis of delay-induced patterns in a ring of Hodgkin-Huxley neurons.

    Science.gov (United States)

    Kantner, Markus; Yanchuk, Serhiy

    2013-09-28

    Rings of delay-coupled neurons possess a striking capability to produce various stable spiking patterns. In order to reveal the mechanisms of their appearance, we present a bifurcation analysis of the Hodgkin-Huxley (HH) system with delayed feedback as well as a closed loop of HH neurons. We consider mainly the effects of external currents and communication delays. It is shown that typically periodic patterns of different spatial form (wavenumber) appear via Hopf bifurcations as the external current or time delay changes. The Hopf bifurcations are shown to occur in relatively narrow regions of the external current values, which are independent of the delays. Additional patterns, which have the same wavenumbers as the existing ones, appear via saddle-node bifurcations of limit cycles. The obtained bifurcation diagrams are evidence for the important role of communication delays for the emergence of multiple coexistent spiking patterns. The effects of a short-cut, which destroys the rotational symmetry of the ring, are also briefly discussed.

  19. Bifurcation analysis of nephron pressure and flow regulation

    DEFF Research Database (Denmark)

    Barfred, Mikael; Mosekilde, Erik; Holstein-Rathlou, N.-H.

    1996-01-01

    One- and two-dimensional continuation techniques are applied to study the bifurcation structure of a model of renal flow and pressure control. Integrating the main physiological mechanisms by which the individual nephron regulates the incoming blood flow, the model describes the interaction between...... the tubuloglomerular feedback and the response of the afferent arteriole. It is shown how a Hopf bifurcation leads the system to perform self-sustained oscillations if the feedback gain becomes sufficiently strong, and how a further increase of this parameter produces a folded structure of overlapping period......-doubling cascades. Similar phenomena arise in response to increasing blood pressure. The numerical analyses are supported by existing experimental results on anesthetized rats. ©1996 American Institute of Physics....

  20. Isochronous bifurcations in second-order delay differential equations

    Directory of Open Access Journals (Sweden)

    Andrea Bel

    2014-07-01

    Full Text Available In this article we consider a special type of second-order delay differential equations. More precisely, we take an equation of a conservative mechanical system in one dimension with an added term that is a function of the difference between the value of the position at time $t$ minus the position at the delayed time $t-\\tau$. For this system, we show that, under certain conditions of non-degeneration and of convergence of the periodic solutions obtained by the Homotopy Analysis Method, bifurcation branches appearing in a neighbourhood of Hopf bifurcation due to the delay are isochronous; i.e., all the emerging cycles have the same frequency.

  1. Morphological Transitions of Sliding Drops -- Dynamics and Bifurcations

    CERN Document Server

    Engelnkemper, Sebastian; Gurevich, Svetlana V; Thiele, Uwe

    2016-01-01

    We study fully three-dimensional droplets that slide down an incline employing a thin-film equation that accounts for capillarity, wettability and a lateral driving force in small-gradient (or long-wave) approximation. In particular, we focus on qualitative changes in the morphology and behavior of stationary sliding drops. We employ the inclination angle of the substrate as control parameter and use continuation techniques to analyze for several fixed droplet sizes the bifurcation diagram of stationary droplets, their linear stability and relevant eigenmodes. The obtained predictions on existence ranges and instabilities are tested via direct numerical simulations that are also used to investigate a branch of time-periodic behavior (corresponding to pearling-coalescence cycles) which emerges at a global instability, the related hysteresis in behavior and a period-doubling cascade. The non-trivial oscillatory behavior close to a Hopf bifurcation of drops with a finite-length tail is also studied. Finally, it ...

  2. Symmetric bifurcation analysis of synchronous states of time-delayed coupled Phase-Locked Loop oscillators

    Science.gov (United States)

    Ferruzzo Correa, Diego Paolo; Wulff, Claudia; Piqueira, José Roberto Castilho

    2015-05-01

    In recent years there has been an increasing interest in studying time-delayed coupled networks of oscillators since these occur in many real life applications. In many cases symmetry patterns can emerge in these networks, as a consequence a part of the system might repeat itself, and properties of this subsystem are representative of the dynamics on the whole phase space. In this paper an analysis of the second order N-node time-delay fully connected network is presented which is based on previous work: synchronous states in time-delay coupled periodic oscillators: a stability criterion. Correa and Piqueira (2013), for a 2-node network. This study is carried out using symmetry groups. We show the existence of multiple eigenvalues forced by symmetry, as well as the existence of Hopf bifurcations. Three different models are used to analyze the network dynamics, namely, the full-phase, the phase, and the phase-difference model. We determine a finite set of frequencies ω , that might correspond to Hopf bifurcations in each case for critical values of the delay. The Sn map is used to actually find Hopf bifurcations along with numerical calculations using the Lambert W function. Numerical simulations are used in order to confirm the analytical results. Although we restrict attention to second order nodes, the results could be extended to higher order networks provided the time-delay in the connections between nodes remains equal.

  3. Stability and Bifurcation for a Simply Supported Functionally Graded Material Plate with One-to-One Internal Resonance

    Directory of Open Access Journals (Sweden)

    Dongmei Zhang

    2014-01-01

    Full Text Available Stability and bifurcation behaviors for a model of simply supported functionally graded materials rectangular plate subjected to the transversal and in-plane excitations are studied by means of combination of analytical and numerical methods. The resonant case considered here is 1 : 1 internal resonances and primary parametric resonance. Two types of degenerated equilibrium points are studied in detail, which are characterized by a double zero and two negative eigenvalues, and a double zero and a pair of pure imaginary eigenvalues. For each case, the stability regions of the initial equilibrium solution and the critical bifurcation curves are obtained in terms of the system parameters which may lead to Hopf bifurcation and 2D torus. With both analytical and numerical methods, bifurcation behaviors on damping parameters and detuning parameters are studied, respectively. A time integration scheme is used to find the numerical solutions for these bifurcation cases, and numerical results agree with the analytic predictions.

  4. On Discreteness of the Hopf Equation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The principle aim of this essay is to illustrate how different phenomena is captured by different discretizations of the Hopf equation and general hyperbolic conservation laws. This includes dispersive schemes, shock capturing schemes as well as schemes for computing multi-valued solutions of the underlying equation. We introduce some model equations which describe the behavior of the discrete equation more accurate than the original equation. These model equations can either be conveniently discretized for producing novel numerical schemes or further analyzed to enrich the theory of nonlinear partial differential equations.

  5. From Hopf fibrations to exotic causal replacements

    CERN Document Server

    Bezares, Miguel; Palomera, Gonzalo; Pons, Daniel J; Reyes, Enrique G

    2016-01-01

    Topological solitons are relevant in several areas of physics [1]. Recently, these configurations have been investigated in contexts as diverse as hydrodynamics [2], Bose-Einstein condensates [3], ferromagnetism [4], knotted light [5] and non-abelian gauge theories [6]. In this paper we address the issue of wave propagation about a static Hopf soliton in the context of the Nicole model. Working within the geometrical optics limit we show that several nontrivial lensing effects emerge due to nonlinear interactions as long as the theory remains hyperbolic. We conclude that similar effects are very likely to occur in effective field theories characterized by a topological invariant such as the Skyrme model of pions.

  6. The Leibniz-Hopf algebra and Lyndon words

    NARCIS (Netherlands)

    Hazewinkel, M.

    1996-01-01

    Let ${cal Z$ denote the free associative algebra ${ol Z langle Z_1 , Z_2 , ldots rangle$ over the integers. This algebra carries a Hopf algebra structure for which the comultiplication is $Z_n mapsto Sigma_{i+j=n Z_i otimes Z_j$. This the noncommutative Leibniz-Hopf algebra. It carries a natural gra

  7. L-R smash products for multiplier Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    ZHAO Li-hui; LU Di-ming; FANG Xiao-li

    2008-01-01

    The theory of L-R smash product is extended to multiplier Hopf algebras and a sufficient condition for L-R smash product to be regular multiplier Hopf algebras is given. In particular the result of the paper implies Delvaux's main theorem in the case of smash products.

  8. The Leibniz-Hopf algebra and Lyndon words

    NARCIS (Netherlands)

    M. Hazewinkel (Michiel)

    1996-01-01

    textabstractLet ${cal Z$ denote the free associative algebra ${ol Z langle Z_1 , Z_2 , ldots rangle$ over the integers. This algebra carries a Hopf algebra structure for which the comultiplication is $Z_n mapsto Sigma_{i+j=n Z_i otimes Z_j$. This the noncommutative Leibniz-Hopf algebra. It carries a

  9. Deformed Covariant Quantum Phase Spaces as Hopf Algebroids

    CERN Document Server

    Lukierski, Jerzy

    2015-01-01

    We consider the general D=4 (10+10)-dimensional kappa-deformed quantum phase space as given by Heisenberg double \\mathcal{H} of D=4 kappa-deformed Poincare-Hopf algebra H. The standard (4+4) -dimensional kappa - deformed covariant quantum phase space spanned by kappa - deformed Minkowski coordinates and commuting momenta generators ({x}_{\\mu },{p}_{\\mu }) is obtained as the subalgebra of \\mathcal{H}. We study further the property that Heisenberg double defines particular quantum spaces with Hopf algebroid structure. We calculate by using purely algebraic methods the explicite Hopf algebroid structure of standard kappa - deformed quantum covariant phase space in Majid-Ruegg bicrossproduct basis. The coproducts for Hopf algebroids are not unique, determined modulo the coproduct gauge freedom. Finally we consider the interpretation of the algebraic description of quantum phase spaces as Hopf bialgebroids.

  10. Adaptive Control of Fast-Scale Bifurcation in Peak Current Controlled Buck-Boost Inverter via One-Cycle Compensation

    Science.gov (United States)

    Zhang, Hao; Dong, Shuai; Guan, Weimin; Yi, Chuanzhi; He, Bo

    In this paper, one-cycle compensation (OCC) method is proposed to realize adaptive control of fast-scale bifurcation in the peak current controlled buck-boost inverter because the proposed control method can adjust the slope of the integrator’s output voltage automatically through extracting a sinusoidal signal from the absolute value of the reference voltage. In order to reveal their underlying mechanisms of fast-scale bifurcations, a modified averaged model which can capture the sample-and-hold effect is derived in detail to describe the fast-scale dynamics of the buck-boost inverter. Based on the proposed model, a theoretical analysis is performed to identify both the fast-scale period-doubling bifurcation and the fast-scale Hopf one by judging in what way the poles loci move. It has been shown that the OCC method can be used not only to discover the unknown dynamical behaviors (i.e. fast-scale Hopf bifurcation), but also to enlarge the stable region in peak current controlled buck-boost inverter. In addition, the critical bifurcation angles and the parameter behavior boundary are given to verify the effectiveness of the adaptive bifurcation control method. Finally, PSpice circuit experiments are performed to verify the above theoretical and numerical results.

  11. Bifurcations and transitions to chaos in an inverted pendulum

    Science.gov (United States)

    Kim, Sang-Yoon; Hu, Bambi

    1998-09-01

    We consider a parametrically forced pendulum with a vertically oscillating suspension point. It is well known that, as the amplitude of the vertical oscillation is increased, its inverted state (corresponding to the vertically-up configuration) undergoes a cascade of ``resurrections,'' i.e., it becomes stabilized after its instability, destabilize again, and so forth ad infinitum. We make a detailed numerical investigation of the bifurcations associated with such resurrections of the inverted pendulum by varying the amplitude and frequency of the vertical oscillation. It is found that the inverted state stabilizes via alternating ``reverse'' subcritical pitchfork and period-doubling bifurcations, while it destabilizes via alternating ``normal'' supercritical period-doubling and pitchfork bifrucations. An infinite sequence of period-doubling bifurcations, leading to chaos, follows each destabilization of the inverted state. The critical behaviors in the period-doubling cascades are also discussed.

  12. Rota-Baxter Algebras on Quasi Hopf Module Algebras%拟Hopf-模上的Rota-Baxter代数

    Institute of Scientific and Technical Information of China (English)

    程腾; 王顶国; 程诚

    2014-01-01

    Let H be a Hopf algebra,the main aim of this paper is to extend the theorem of Hopf(co) quasigroup.Let H be a Hopf quasigroup and (M,φ)be an right quasi H-Hopf module algebra,then (M, P )is a Rata-Baxter algebra of weight-1 .%把 Run-qiang Jian文中的H 为 Hopf代数的情况推广到H 为 Hopf(余)拟群,其主要结论:设H是 Hopf拟群,(M,φ)是一右拟H-Hopf模代数,则(M,P)是权为-1的 Rota-Baxter代数。

  13. Stochastic bifurcation characteristics of SMA intravascular stent subjected to radial and axial excitations.

    Science.gov (United States)

    Zhu, Zhiwen; Zhang, Wendi; Xu, Jia

    2014-01-01

    A kind of shape memory alloy (SMA) hysteretic nonlinear model is developed, and the stochastic bifurcation characteristics of SMA intravascular stents subjected to radial and axial excitations are studied in this paper. A new nonlinear differential item is introduced to interpret the hysteretic phenomena of SMA strain-stress curves, and the dynamic model of SMA intravascular stent subjected to radial and axial stochastic excitations is established. The conditions of the system's stochastic stability are determined, and the probability density function of the system response is obtained. Finally, the stochastic Hopf bifurcation characteristics of the system are analyzed. Theoretical analysis and numerical simulation show that the system stability varies with bifurcation parameters, and stochastic Hopf bifurcation occurs in the process; there are two limit cycles in the stationary probability density of the system response in some cases, which means that there are two vibration amplitudes whose probability are both very high; jumping phenomena between the two vibration amplitudes appears with the change of conditions, which may cause stent fracture or loss. The results of this paper are helpful for application of SMA intravascular stent in biomedical engineering fields.

  14. Bifurcation analysis of a delay reaction-diffusion malware propagation model with feedback control

    Science.gov (United States)

    Zhu, Linhe; Zhao, Hongyong; Wang, Xiaoming

    2015-05-01

    With the rapid development of network information technology, information networks security has become a very critical issue in our work and daily life. This paper attempts to develop a delay reaction-diffusion model with a state feedback controller to describe the process of malware propagation in mobile wireless sensor networks (MWSNs). By analyzing the stability and Hopf bifurcation, we show that the state feedback method can successfully be used to control unstable steady states or periodic oscillations. Moreover, formulas for determining the properties of the bifurcating periodic oscillations are derived by applying the normal form method and center manifold theorem. Finally, we conduct extensive simulations on large-scale MWSNs to evaluate the proposed model. Numerical evidences show that the linear term of the controller is enough to delay the onset of the Hopf bifurcation and the properties of the bifurcation can be regulated to achieve some desirable behaviors by choosing the appropriate higher terms of the controller. Furthermore, we obtain that the spatial-temporal dynamic characteristics of malware propagation are closely related to the rate constant for nodes leaving the infective class for recovered class and the mobile behavior of nodes.

  15. Relative Lyapunov Center Bifurcations

    DEFF Research Database (Denmark)

    Wulff, Claudia; Schilder, Frank

    2014-01-01

    Relative equilibria (REs) and relative periodic orbits (RPOs) are ubiquitous in symmetric Hamiltonian systems and occur, for example, in celestial mechanics, molecular dynamics, and rigid body motion. REs are equilibria, and RPOs are periodic orbits of the symmetry reduced system. Relative Lyapunov...... center bifurcations are bifurcations of RPOs from REs corresponding to Lyapunov center bifurcations of the symmetry reduced dynamics. In this paper we first prove a relative Lyapunov center theorem by combining recent results on the persistence of RPOs in Hamiltonian systems with a symmetric Lyapunov...... center theorem of Montaldi, Roberts, and Stewart. We then develop numerical methods for the detection of relative Lyapunov center bifurcations along branches of RPOs and for their computation. We apply our methods to Lagrangian REs of the N-body problem....

  16. Construct Weak Hopf Algebras by Using Borcherds Matrix

    Institute of Scientific and Technical Information of China (English)

    Zhi Xiang WU

    2009-01-01

    We define a new kind quantized enveloping algebra of a generalized Kac-Moody algebra y by adding a new generator J satisfying Jm = J for some integer m. We denote this algebra by wU τ q (y. This algebra is a weak Hopf algebra if and only if m = 2,3. In general, it is a bialgebra, and contains a Hopf subalgebra. This Hopf subalgebra is isomorphic to the usual quantum envelope algebra U q(y) of a generalized Kac-Moody algebra y.

  17. Three Hopf algebras and their common simplicial and categorical background

    CERN Document Server

    Gálvez-Carrillo, Imma; Tonks, Andrew

    2016-01-01

    We consider three a priori totally different setups for Hopf algebras from number theory, mathematical physics and algebraic topology. These are the Hopf algebras of Goncharov for multiple zeta values, that of Connes--Kreimer for renormalization, and a Hopf algebra constructed by Baues to study double loop spaces. We show that these examples can be successively unified by considering simplicial objects, cooperads with multiplication and Feynman categories at the ultimate level. These considerations open the door to new constructions and reinterpretation of known constructions in a large common framework.

  18. Comment on "Generalized q-oscillators and their Hopf structures"

    CERN Document Server

    Quesne, C

    1995-01-01

    In a recent paper (1994 {\\sl J.\\ Phys.\\ A: Math.\\ Gen.\\ }{\\bf 27} 5907), Oh and Singh determined a Hopf structure for a generalized q-oscillator algebra. We prove that under some general assumptions, the latter is, apart from some algebras isomorphic to su_q(2), su_q(1,1), or their undeformed counterparts, the only generalized deformed oscillator algebra that supports a Hopf structure. We show in addition that the latter can be equipped with a universal \\cR-matrix, thereby making it into a quasitriangular Hopf algebra.

  19. Wigner oscillators, twisted Hopf algebras and second quantization

    Energy Technology Data Exchange (ETDEWEB)

    Castro, P.G.; Toppan, F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mails: pgcastro@cbpf.br; toppan@cbpf.br; Chakraborty, B. [S. N. Bose National Center for Basic Sciences, Kolkata (India)]. E-mail: biswajit@bose.res.in

    2008-07-01

    By correctly identifying the role of central extension in the centrally extended Heisenberg algebra h, we show that it is indeed possible to construct a Hopf algebraic structure on the corresponding enveloping algebra U(h) and eventually deform it through Drinfeld twist. This Hopf algebraic structure and its deformed version U{sup F}(h) is shown to be induced from a more 'fundamental' Hopf algebra obtained from the Schroedinger field/oscillator algebra and its deformed version, provided that the fields/oscillators are regarded as odd-elements of a given superalgebra. We also discuss the possible implications in the context of quantum statistics. (author)

  20. Revisiting the redistancing problem using the Hopf-Lax formula

    Science.gov (United States)

    Lee, Byungjoon; Darbon, Jérôme; Osher, Stanley; Kang, Myungjoo

    2017-02-01

    This article presents a fast new numerical method for redistancing objective functions based on the Hopf-Lax formula [1]. The algorithm suggested here is a special case of the previous work in [2] and an extension that applies the Hopf-Lax formula for computing the signed distance to the front. We propose the split Bregman approach to solve the minimization problem as a solution of the eikonal equation obtained from Hopf-Lax formula. Our redistancing procedure is expected to be generalized and widely applied to many fields such as computational fluid dynamics, the minimal surface problem, and elsewhere.

  1. Wilsonian renormalization, differential equations and Hopf algebras

    CERN Document Server

    Thomas, Krajewski

    2008-01-01

    In this paper, we present an algebraic formalism inspired by Butcher's B-series in numerical analysis and the Connes-Kreimer approach to perturbative renormalization. We first define power series of non linear operators and propose several applications, among which the perturbative solution of a fixed point equation using the non linear geometric series. Then, following Polchinski, we show how perturbative renormalization works for a non linear perturbation of a linear differential equation that governs the flow of effective actions. Finally, we define a general Hopf algebra of Feynman diagrams adapted to iterations of background field effective action computations. As a simple combinatorial illustration, we show how these techniques can be used to recover the universality of the Tutte polynomial and its relation to the $q$-state Potts model. As a more sophisticated example, we use ordered diagrams with decorations and external structures to solve the Polchinski's exact renormalization group equation. Finally...

  2. STUDY FOR THE BIFURCATION TOPOLOGICAL STRUCTURE AND THE GLOBAL COMPLICATED CHARACTER OF A KIND OF NONLINEAR FINANCE SYSTEM(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    马军海; 陈予恕

    2001-01-01

    Based on the work discussed on the former study, this article first starts from the mathematical model of a kind of complicated financial system, and analyses all possible things that the model shows in the operation of our country' s macro-financial system: balance, stable periodic, fractal, Hopf-bifurcation, the relationship between parameters and Hopf-bifurcation,and chaotic motion etc. By the changes of parameters of all economic meanings, the conditions on which the complicated behaviors occur in such a financial system, and the influence of the adjustment of the macro-economic policies and adjustment of some parameter on the whole financial system behavior have been analyzed. This study will deepen people' s understanding of the lever function of all kinds of financial policies.

  3. STUDY FOR THE BIFURCATION TOPOLOGICAL STRUCTURE AND THE GLOBAL COMPLICATED CHARACTER OF A KIND OF NONLINEAR FINANCE SYSTEM(Ⅰ)

    Institute of Scientific and Technical Information of China (English)

    马军海; 陈予恕

    2001-01-01

    Based on the mathematical model of a kind of complicated financial system, all possible things that the model shows in the operation of our country's macro-financial system were analyzed, such as balance, stable periodic, fractal,Hopf-bifurcation, the relationship between parameters and Hopf-bifurcations, and chaotic motion etc. By the changes of parameters of all economic meanings, the conditions on which the complicated behaviors occur in such a financial system, and the influence of the adjustment of the macro-economic policies and adjustment of some parameter on the whole financial system behavior were analyzed. This study will deepen people ' s understanding of the lever function of all kinds of financial policies.

  4. Nonlinear dynamics approach of modeling the bifurcation for aircraft wing flutter in transonic speed

    DEFF Research Database (Denmark)

    Matsushita, Hiroshi; Miyata, T.; Christiansen, Lasse Engbo

    2002-01-01

    The procedure of obtaining the two-degrees-of-freedom, finite dimensional. nonlinear mathematical model. which models the nonlinear features of aircraft flutter in transonic speed is reported. The model enables to explain every feature of the transonic flutter data of the wind tunnel tests...... conducted at National Aerospace Laboratory in Japan for a high aspect ratio wing. It explains the nonlinear features of the transonic flutter such as the subcritical Hopf bifurcation of a limit cycle oscillation (LCO), a saddle-node bifurcation, and an unstable limit cycle as well as a normal (linear......) flutter condition with its linear pan. At a final procedure of improve a quantitative matching with the test data. the continuation method for analyzing the bifurcation is extensively used....

  5. Bifurcations in time-delay fully-connected networks with symmetry

    Directory of Open Access Journals (Sweden)

    Ferruzzo Correa Diego Paolo

    2014-01-01

    Full Text Available In this work a brief method for finding steady-state and Hopf bifurcations in a (R + 1-th order N-node time-delay fully-connected network with symmetry is explored. A self-sustained Phase-Locked Loop is used as node. The irreducible representations found due to the network symmetry are used to find regions of time-delay independent stability/instability in the parameter space. Symmetry-preserving and symmetry-breaking bifurcations can be computed numerically using the Sn map proposed in [1]. The analytic results show the existence of symmetry-breaking bifurcations with multiplicity N − 1. A second-order N-node network is used as application example. This work is a generalization of some results presented in [2].

  6. Turing Bifurcation and Pattern Formation of Stochastic Reaction-Diffusion System

    Directory of Open Access Journals (Sweden)

    Qianiqian Zheng

    2017-01-01

    Full Text Available Noise is ubiquitous in a system and can induce some spontaneous pattern formations on a spatially homogeneous domain. In comparison to the Reaction-Diffusion System (RDS, Stochastic Reaction-Diffusion System (SRDS is more complex and it is very difficult to deal with the noise function. In this paper, we have presented a method to solve it and obtained the conditions of how the Turing bifurcation and Hopf bifurcation arise through linear stability analysis of local equilibrium. In addition, we have developed the amplitude equation with a pair of wave vector by using Taylor series expansion, multiscaling, and further expansion in powers of small parameter. Our analysis facilitates finding regions of bifurcations and understanding the pattern formation mechanism of SRDS. Finally, the simulation shows that the analytical results agree with numerical simulation.

  7. Bifurcation and Resonance of a Mathematical Model for Non-Linear Motion of a Flooded Ship in Waves

    Science.gov (United States)

    Murashige, S.; Aihara, K.; Komuro, M.

    1999-02-01

    A flooded ship can exhibit undesirable non-linear roll motion even in waves of moderate amplitude. In order to understand the mechanism of this non-linear phenomenon, the non-linearly coupled dynamics of a ship and flood water are considered using a mathematical model for the simplified motion of a flooded ship in regular beam waves. This paper describes bifurcation and resonance of this coupled system. A bifurcation diagram shows that large-amplitude subharmonic motion exists in a wide range of parameters, and that the Hopf bifurcation is observed due to the dynamic effects of flood water. Resonance frequencies can be determined by linearization of this model. Comparison between the resonant points and the bifurcation curves suggests that non-linear resonance of this model can bring about large-amplitude subharmonic motion, even if it is in the non-resonate state of the linearized system.

  8. Bifurcation Analysis and Control of a Differential-Algebraic Predator-Prey Model with Allee Effect and Time Delay

    Directory of Open Access Journals (Sweden)

    Xue Zhang

    2014-01-01

    Full Text Available This paper studies systematically a differential-algebraic prey-predator model with time delay and Allee effect. It shows that transcritical bifurcation appears when a variation of predator handling time is taken into account. This model also exhibits singular induced bifurcation as the economic revenue increases through zero, which causes impulsive phenomenon. It can be noted that the impulsive phenomenon can be much weaker by strengthening Allee effect in numerical simulation. On the other hand, at a critical value of time delay, the model undergoes a Hopf bifurcation; that is, the increase of time delay destabilizes the model and bifurcates into small amplitude periodic solution. Moreover, a state delayed feedback control method, which can be implemented by adjusting the harvesting effort for biological populations, is proposed to drive the differential-algebraic system to a steady state. Finally, by using Matlab software, numerical simulations illustrate the effectiveness of the results.

  9. On Clifford representation of Hopf algebras and Fierz identities

    CERN Document Server

    Rodríguez-Romo, S

    1996-01-01

    We present a short review of the action and coaction of Hopf algebras on Clifford algebras as an introduction to physically meaningful examples. Some q-deformed Clifford algebras are studied from this context and conclusions are derived.

  10. A duality theorem of crossed coproduct for Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    王栓宏

    1995-01-01

    A duality theorem for Hopf crossed coproduct is proved. This theorem plays a role similar to that appearing in the work of Koppinen (which generalized the corresponding results of group grraded ring).

  11. A Super Version of the Connes-Moscovici Hopf Algebra

    CERN Document Server

    Khalkhali, Masoud

    2010-01-01

    We define a super version of the Connes-Moscovici Hopf algebra, $\\mathcal{H}_1$. For that, we consider the supergroup $G^s=Diff^+(\\mathbb{R}^{1,1})$ of orientation preserving diffeomorphisms of the superline $\\mathbb{R}^{1,1}$ and define two (super) subgroups $G^s_1$ and $G^s_2$ of $G^s$ where $G^s_1$ is the supergroup of affine transformations. The super Hopf algebra $\\mathcal{H} ^s_1$ is defined as a certain bicrossproduct super Hopf algebra of the super Hopf algebras attached to $G^s_1$ and $G^s_2$. We also give an explicit description of $\\mathcal{H} ^s_1$ in terms of generators and relations.

  12. Combinatorial Hopf Algebras in (Noncommutative) Quantum Field Theory

    CERN Document Server

    Tanasa, Adrian

    2010-01-01

    We briefly review the r\\^ole played by algebraic structures like combinatorial Hopf algebras in the renormalizability of (noncommutative) quantum field theory. After sketching the commutative case, we analyze the noncommutative Grosse-Wulkenhaar model.

  13. Qualitative properties and hopf bifurcation in haematopoietic disease model with chemotherapy

    Directory of Open Access Journals (Sweden)

    Yafia R.

    2014-01-01

    Full Text Available In this paper, we consider a model describing the dynamics of Hematopoietic Stem Cells (HSC disease with chemotherapy. The model is given by a system of three ordinary differential equations with discrete delay. Its dynamics are studied in term of local stability of the possible steady states for the case without drug intervention term. We prove the existence of periodic oscillations for each case when the delay passes trough a critical values. In the end, we illustrate our results by some numerical simulations.

  14. Hopf Bifurcation and Delay-Induced Turing Instability in a Diffusive lac Operon Model

    Science.gov (United States)

    Cao, Xin; Song, Yongli; Zhang, Tonghua

    In this paper, we investigate the dynamics of a lac operon model with delayed feedback and diffusion effect. If the system is without delay or the delay is small, the positive equilibrium is stable so that there are no spatial patterns formed; while the time delay is large enough the equilibrium becomes unstable so that rich spatiotemporal dynamics may occur. We have found that time delay can not only incur temporal oscillations but also induce imbalance in space. With different initial values, the system may have different spatial patterns, for instance, spirals with one head, four heads, nine heads, and even microspirals.

  15. Bifurcations in Spatiotemporal Systems.

    Science.gov (United States)

    Vastano, John Andrew

    The bifurcations leading from simple to complex spatial and temporal behavior in extended systems are just beginning to be characterized. Numerical studies of several one-dimensional reaction-diffusion systems have been conducted to discover the possible bifurcations and to test new diagnostic tools for spatiotemporal systems. Steady state pattern formation was studied in an open reactor with a simple autocatalytic model chemistry. When the diffusion coefficients of all the chemical species are equal, patterns can only form by bifurcations from an already unstable homogeneous state. When the diffusion coefficients are different, patterns can arise via a bifurcation off of the stable homogeneous state. These "Turing bifurcations" yield patterns that have an intrinsic wavelength determined by the interplay of chemical reaction and diffusion. A description of all bifurcations from the steady state for the model system was obtained by using a steady state continuation technique to follow stable and unstable branches of bifurcating solutions. The bifurcations leading to time-dependent patterns in reaction-diffusion systems were studied in a system that models a current experiment by W. Y. Tam and H. L. Swinney. The model chemistry used displays only steady state and limit cycle behavior in a well-mixed system, but when diffusive effects were included, a regime was found in which the system undergoes a transition to chaos as a chemical parameter is tuned. The bifurcation sequence was shown to be that of a single, periodically forced, nonlinear oscillator. The physical mechanisms that cause this behavior were discovered. The model results were shown to be in good agreement with experimental results, indicating that the same physical processes occur in the experiment. In some extended systems the physical mechanisms that create globally observed chaotic behavior are localized. A novel method for characterizing these systems was suggested: an information

  16. Quantum walks, deformed relativity and Hopf algebra symmetries.

    Science.gov (United States)

    Bisio, Alessandro; D'Ariano, Giacomo Mauro; Perinotti, Paolo

    2016-05-28

    We show how the Weyl quantum walk derived from principles in D'Ariano & Perinotti (D'Ariano & Perinotti 2014Phys. Rev. A90, 062106. (doi:10.1103/PhysRevA.90.062106)), enjoying a nonlinear Lorentz symmetry of dynamics, allows one to introduce Hopf algebras for position and momentum of the emerging particle. We focus on two special models of Hopf algebras-the usual Poincaré and theκ-Poincaré algebras.

  17. Supercharacters, symmetric functions in noncommuting variables, and related Hopf algebras

    CERN Document Server

    Aguiar, Marcelo; Benedetti, Carolina; Bergeron, Nantel; Chen, Zhi; Diaconis, Persi; Hendrickson, Anders; Hsiao, Samuel; Isaacs, I Martin; Jedwab, Andrea; Johnson, Kenneth; Karaali, Gizem; Lauve, Aaron; Le, Tung; Lewis, Stephen; Li, Huilan; Magaard, Kay; Marberg, Eric; Novelli, Jean-Christophe; Pang, Amy; Saliola, Franco; Tevlin, Lenny; Thibon, Jean-Yves; Thiem, Nathaniel; Venkateswaran, Vidya; Vinroot, C Ryan; Yan, Ning; Zabrocki, Mike

    2010-01-01

    We identify two seemingly disparate structures: supercharacters, a useful way of doing Fourier analysis on the group of unipotent uppertriangular matrices with coefficients in a finite field, and the ring of symmetric functions in noncommuting variables. Each is a Hopf algebra and the two are isomorphic as such. This allows developments in each to be transferred. The identification suggests a rich class of examples for the emerging field of combinatorial Hopf algebras.

  18. Noncommutative string theory, the R-matrix, and Hopf algebras

    Science.gov (United States)

    Watts, P.

    2000-02-01

    Motivated by the form of the noncommutative /*-product in a system of open strings and Dp-branes with constant nonzero Neveu-Schwarz 2-form, we define a deformed multiplication operation on a quasitriangular Hopf algebra in terms of its R-matrix, and comment on some of its properties. We show that the noncommutative string theory /*-product is a particular example of this multiplication, and comment on other possible Hopf algebraic properties which may underlie the theory.

  19. Emergence of the bifurcation structure of a Langmuir–Blodgett transfer model

    KAUST Repository

    Köpf, Michael H

    2014-10-07

    © 2014 IOP Publishing Ltd & London Mathematical Society. We explore the bifurcation structure of a modified Cahn-Hilliard equation that describes a system that may undergo a first-order phase transition and is kept permanently out of equilibrium by a lateral driving. This forms a simple model, e.g., for the deposition of stripe patterns of different phases of surfactant molecules through Langmuir-Blodgett transfer. Employing continuation techniques the bifurcation structure is numerically investigated using the non-dimensional transfer velocity as the main control parameter. It is found that the snaking structure of steady front states is intertwined with a large number of branches of time-periodic solutions that emerge from Hopf or period-doubling bifurcations and end in global bifurcations (sniper and homoclinic). Overall the bifurcation diagram has a harp-like appearance. This is complemented by a two-parameter study in non-dimensional transfer velocity and domain size (as a measure of the distance to the phase transition threshold) that elucidates through which local and global codimension 2 bifurcations the entire harp-like structure emerges.

  20. Hopf (bi-)modules and crossed modules in braided monoidal categories

    CERN Document Server

    Bespalov, Yu N; Bespalov, Yuri; Drabant, Bernhard

    1995-01-01

    Hopf (bi-)modules and crossed modules over a bialgebra B in a braided monoidal category C are considered. The (braided) monoidal equivalence of both categories is proved provided B is a Hopf algebra (with invertible antipode). Bialgebra projections and Hopf bimodule bialgebras over a Hopf algebra in C are found to be isomorphic categories. As a consequence a generalization of the Radford-Majid criterion for a braided Hopf algebra to be a cross product is obtained. The results of this paper turn out to be fundamental for the construction of (bicovariant) differential calculi on braided Hopf algebras.

  1. Renormalization Hopf algebras and combinatorial groups

    CERN Document Server

    Frabetti, Alessandra

    2008-01-01

    These are the notes of five lectures given at the Summer School {\\em Geometric and Topological Methods for Quantum Field Theory}, held in Villa de Leyva (Colombia), July 2--20, 2007. The lectures are meant for graduate or almost graduate students in physics or mathematics. They include references, many examples and some exercices. The content is the following. The first lecture is a short introduction to algebraic and proalgebraic groups, based on some examples of groups of matrices and groups of formal series, and their Hopf algebras of coordinate functions. The second lecture presents a very condensed review of classical and quantum field theory, from the Lagrangian formalism to the Euler-Lagrange equation and the Dyson-Schwinger equation for Green's functions. It poses the main problem of solving some non-linear differential equations for interacting fields. In the third lecture we explain the perturbative solution of the previous equations, expanded on Feynman graphs, in the simplest case of the scalar $\\...

  2. Ideal relaxation of the Hopf fibration

    Science.gov (United States)

    Smiet, Christopher Berg; Candelaresi, Simon; Bouwmeester, Dirk

    2017-07-01

    Ideal magnetohydrodynamics relaxation is the topology-conserving reconfiguration of a magnetic field into a lower energy state where the net force is zero. This is achieved by modeling the plasma as perfectly conducting viscous fluid. It is an important tool for investigating plasma equilibria and is often used to study the magnetic configurations in fusion devices and astrophysical plasmas. We study the equilibrium reached by a localized magnetic field through the topology conserving relaxation of a magnetic field based on the Hopf fibration in which magnetic field lines are closed circles that are all linked with one another. Magnetic fields with this topology have recently been shown to occur in non-ideal numerical simulations. Our results show that any localized field can only attain equilibrium if there is a finite external pressure, and that for such a field a Taylor state is unattainable. We find an equilibrium plasma configuration that is characterized by a lowered pressure in a toroidal region, with field lines lying on surfaces of constant pressure. Therefore, the field is in a Grad-Shafranov equilibrium. Localized helical magnetic fields are found when plasma is ejected from astrophysical bodies and subsequently relaxes against the background plasma, as well as on earth in plasmoids generated by, e.g., a Marshall gun. This work shows under which conditions an equilibrium can be reached and identifies a toroidal depression as the characteristic feature of such a configuration.

  3. Evidence for a Border-Collision Bifurcation in Paced Cardiac Tissue

    Science.gov (United States)

    Berger, Carolyn

    2005-11-01

    Bifurcations in the electrical response of cardiac tissue can destabilize spatial-temporal waves of electrical activity in the heart, leading to tachycardia or even fibrillation. Therefore, it is important to characterize the types of bifurcations occurring in cardiac tissue. Our goal is to classify the bifurcation that occurs in cardiac cells when a change in pacing rate induces a transition from 1:1 to 2:2 phase-locked behavior. Current mathematical models predict that the bifurcation mediating the transition is a supercritical pitchfork type. For such a bifurcation, small random noise is predicted to be amplified by greater amounts as the bifurcation is approached (Weisenfeld). However, our experimental observations of paced bullfrog myocardium driven by small beat-to-beat alternations in the pacing rate (rather than driven by noise) displays de-amplification as the bifurcation is approached. To explain this surprising result, we hypothesize that the transition to 2:2 behavior is mediated by border-collision bifurcation, which is predicted to show little noise amplification. Wiesenfeld, K. Phys. Rev. A 32, 1744 (1985).

  4. Bifurcation of hyperbolic planforms

    CERN Document Server

    Chossat, Pascal; Faugeras, Olivier

    2010-01-01

    Motivated by a model for the perception of textures by the visual cortex in primates, we analyse the bifurcation of periodic patterns for nonlinear equations describing the state of a system defined on the space of structure tensors, when these equations are further invariant with respect to the isometries of this space. We show that the problem reduces to a bifurcation problem in the hyperbolic plane D (Poincar\\'e disc). We make use of the concept of periodic lattice in D to further reduce the problem to one on a compact Riemann surface D/T, where T is a cocompact, torsion-free Fuchsian group. The knowledge of the symmetry group of this surface allows to carry out the machinery of equivariant bifurcation theory. Solutions which generically bifurcate are called "H-planforms", by analogy with the "planforms" introduced for pattern formation in Euclidean space. This concept is applied to the case of an octagonal periodic pattern, where we are able to classify all possible H-planforms satisfying the hypotheses o...

  5. Do Dogs Know Bifurcations?

    Science.gov (United States)

    Minton, Roland; Pennings, Timothy J.

    2007-01-01

    When a dog (in this case, Tim Pennings' dog Elvis) is in the water and a ball is thrown downshore, it must choose to swim directly to the ball or first swim to shore. The mathematical analysis of this problem leads to the computation of bifurcation points at which the optimal strategy changes.

  6. Maschke-type theorem and Morita context over weak Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    ZHANG Liangyun

    2006-01-01

    This paper gives a Maschke-type theorem over semisimple weak Hopf algebras,extends the well-known Maschke-type theorem given by Cohen and Fishman and constructs a Morita context over weak Hopf algebras.

  7. C*-Structure of Quantum Double for Finite Hopf C*-Algebra

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Let H be a finite Hopf C*-algebra and H' be its dual Hopf algebra. Drinfeld's quantum double D(H) of H is a Hopf *-algebra. There is a faithful positive linear functional θ on D(H). Through the associated Gelfand-Naimark-Segal (GNS) representation, D(H) has a faithful *-representation so that it becomes a Hopf C*-algebra. The canonical embedding map of H into D(H) is isometric.

  8. On the Central Charge of a Factorizable Hopf Algebra

    CERN Document Server

    Sommerhaeuser, Yorck

    2009-01-01

    For a semisimple factorizable Hopf algebra over a field of characteristic zero, we show that the value that an integral takes on the inverse Drinfel'd element differs from the value that it takes on the Drinfel'd element itself at most by a fourth root of unity. This can be reformulated by saying that the central charge of the Hopf algebra is an integer. If the dimension of the Hopf algebra is odd, we show that these two values differ at most by a sign, which can be reformulated by saying that the central charge is even. We give a precise condition on the dimension that determines whether the plus sign or the minus sign occurs. To formulate our results, we use the language of modular data.

  9. A New Route to the Interpretation of Hopf Invariant

    Institute of Scientific and Technical Information of China (English)

    REN Ji-Rong; LI Ran; DUAN Yi-Shi

    2008-01-01

    We discuss an object from algebraic topology,Hopf invariant,and reinterpret it in terms of the φ-mapping topological current theory.The main purpose of this paper is to present a new theoretical framework,which can directly give the relationship between Hopf invariant and the linking numbers of the higher dimensional submanifolds of Euclidean space R2n-1.For the sake of this purpose we introduce a topological tensor current,which can naturally deduce the (n- 1)-dimensional topological defect in R2n-1 space.If these (n- 1)-dimensional topological defects are closed oriented submanifolds of R2n-1,they are just the (n - 1)-dimensional knots.The linking number of these knots is well defined.Using the inner structure of the topological tensor current,the relationship between Hopf invariant and the linking numbers of the higher-dimensional knots can be constructed.

  10. Symptoms of chaos in observed oscillations near a bifurcation with noise

    Science.gov (United States)

    Harding, Robert H.; Ross, John

    1988-10-01

    We examine an experimental transition from periodic to aperiodic and back to periodic dynamics in the combustion of acetaldehyde(ACH) in a continuous stirred tank reactor (CSTR) with power spectra, autocorrelation functions, phase portraits, Poincaŕe sections, the Wolf-Swift-Swinney-Vastano (WSSV) method for determining the largest Lyapounov exponent, and the Grassberger-Procaccia (GP) method for determining correlation dimension. Each technique gives some indications of a transition to chaos, but there are discrepancies in that the largest Lyapounov exponent is positive but does not converge and the GP method results in a correlation dimension between one and two for two aperiodic data sets. We explore in instructive detail possible explanations for false indications of chaos by comparing our results with calculations on the Rössler chaotic attractor and the van der Pol periodic attractor modified to examine the effects of uneven point distribution and three types of experimental noise. An uneven distribution of points results in a decreased range of length scales for convergence and a larger required embedding dimension for the GP method, but does not explain our experimental results. Observation noise (a Gaussian noise added to each term in the time series but not entering in the equations of motion) and constraint shift (the motion relaxes to an attractor but a constraint changes monotonically during the course of measurement) added to a periodic attractor both result in a low length scale cutoff below which the attractor dimension does not converge with embedding dimension, and above which it converges to 1. Constraint variation noise (a Gaussian noise is added to each term in the time series and enters into the equations of motion as a stochastic perturbation) does yield correlation dimensions between 1 and 2. The experimental transition shows many similarities to a Hopf bifurcation found in another experiment on the same system and to a theoretical Hopf

  11. Stability and Bifurcation of Autonomous Vehicles in the Presence of Positional Information Time Lags

    Science.gov (United States)

    1993-09-23

    PSI) A(4,2)- DCOS(PSI) A(4,3)-0.ODO A(4,4)-0.ODO 63 0S CALL DSTABL (DEOSWI, WI ,FREQ) ALPHL-DEOS OMEGL -FREQ C DALPHA- (ALPHR-ALPHL) / (XDR-XDL) DONEGA...OMEGR- OMEGL 1/ (XDR-XDL)4 C Evaluation of Hopf Bifurcation Coefficients C ~COEFl-3 . *Rll+R13+R22+3.0*R24 COEF2-3 .0*R21+R23-R12-3.0*R14 AMU2 --COEF1

  12. Local Bifurcations in DC-DC Converters

    OpenAIRE

    2012-01-01

    Three local bifurcations in DC-DC converters are reviewed. They are period-doubling bifurcation, saddle-node bifurcation, and Neimark bifurcation. A general sampled-data model is employed to study the types of loss of stability of the nominal (periodic) solution and their connection with local bifurcations. More accurate prediction of instability and bifurcation than using the averaging approach is obtained. Examples of bifurcations associated with instabilities in DC-DC converters are given.

  13. Eventual Regularity of the Two-Dimensional Boussinesq Equations with Supercritical Dissipation

    Science.gov (United States)

    Jiu, Quansen; Wu, Jiahong; Yang, Wanrong

    2015-02-01

    This paper studies solutions of the two-dimensional incompressible Boussinesq equations with fractional dissipation. The spatial domain is a periodic box. The Boussinesq equations concerned here govern the coupled evolution of the fluid velocity and the temperature and have applications in fluid mechanics and geophysics. When the dissipation is in the supercritical regime (the sum of the fractional powers of the Laplacians in the velocity and the temperature equations is less than 1), the classical solutions of the Boussinesq equations are not known to be global in time. Leray-Hopf type weak solutions do exist. This paper proves that such weak solutions become eventually regular (smooth after some time ) when the fractional Laplacian powers are in a suitable supercritical range. This eventual regularity is established by exploiting the regularity of a combined quantity of the vorticity and the temperature as well as the eventual regularity of a generalized supercritical surface quasi-geostrophic equation.

  14. Bifurcation of Scramjet Unstart

    Science.gov (United States)

    Jang, Ik; Nichols, Joseph; Duraisamy, Karthik; Moin, Parviz

    2011-11-01

    We investigate the bifurcation structure of catastrophic unstart in scramjets. The bifurcation of quasi-one-dimensional Rayleigh flow is first analyzed, followed by a numerical investigation of a more realistic model scramjet isolator (Wagner et al., AIAA paper, 2010). We show that the quasi-one-dimensional model recovers a similar hysteresis behavior as that observed in steady Reynolds-Averaged Navier-Stokes simulations of the model scramjet isolator close to the onset of unstart. In the hysteresis zone, steady but unstable solutions are obtained by means of pseudo-arclength continuation. Automatic differentiation permits the use of fully discrete Jacobians that result in an accurate representation of functional dependencies and linearized dynamics. Furthermore, we use an Arnoldi method to extract the least stable direct and adjoint eigenfunctions spanning the system dynamics close to unstart and obtain the system response to both harmonic and stochastic forcing. This information, along with the final bifurcation structure, allows us to evaluate the effectiveness of different metrics as indicators of the onset of unstart. Supported by the PSAAP program of DOE

  15. Cuntz Semigroups of Compact-Type Hopf C*-Algebras

    Directory of Open Access Journals (Sweden)

    Dan Kučerovský

    2017-01-01

    Full Text Available The classical Cuntz semigroup has an important role in the study of C*-algebras, being one of the main invariants used to classify recalcitrant C*-algebras up to isomorphism. We consider C*-algebras that have Hopf algebra structure, and find additional structure in their Cuntz semigroups. We show that in many cases, isomorphisms of Cuntz semigroups that respect this additional structure can be lifted to Hopf algebra (biisomorphisms, up to a possible flip of the co-product. This shows that the Cuntz semigroup provides an interesting invariant of C*-algebraic quantum groups.

  16. Hopf-algebra description of noncommutative-spacetime symmetries

    OpenAIRE

    2003-01-01

    I give a brief summary of the results reported in hep-th 0306013 in collaboration with G. Amelino-Camelia and F. D'Andrea. I focus on the analysis of the symmetries of $\\kappa$-Minkowski noncommutative space-time, described in terms of a Weyl map. The commutative space-time notion of Lie-algebra symmetries must be replaced by the one of Hopf-algebra symmetries. However, in the Hopf algebra sense, it is possible to construct an action in $\\kappa$-Minkowski which is invariant under a 10-generat...

  17. Hopf-Algebra Description of Noncommutative-Spacetime Symmetries

    Science.gov (United States)

    Agostini, Alessandra

    2003-11-01

    A brief summary is given of the results reported in [hep-th/0306013], in collaboration with G. Amelino-Camelia and F. D'Andrea. It is focused on the analysis of the symmetries of -Minkowski noncommutative spacetime, described in terms of a Weyl map. The commutative-spacetime notion of Lie-algebra symmetries must be replaced by the one of Hopf-algebra symmetries. However, in the Hopf-algebra sense, it is possible to construct an action in -Minkowski, which is invariant under a 10-generators Poincaré-like symmetry algebra.

  18. The decay of Hopf solitons in the Skyrme model

    CERN Document Server

    Foster, David

    2016-01-01

    It is understood that the Skyrme model has a topologically interesting baryonic excitation which can model nuclei. So far no stable knotted solutions, of the Skyrme model, have been found. Here we investigate the dynamics of Hopf solitons decaying to the vacuum solution in the Skyrme model. In doing this we develop a matrix-free numerical method to identify the minimum eigenvalue of the Hessian of the corresponding energy functional. We also show that as the Hopf solitons decay, they emit a cloud of isospinning radiation.

  19. Neimark-Sacker bifurcations and evidence of chaos in a discrete dynamical model of walkers

    Science.gov (United States)

    Rahman, Aminur; Blackmore, Denis

    2016-10-01

    Bouncing droplets on a vibrating fluid bath can exhibit wave-particle behavior, such as being propelled by interacting with its own wave field. These droplets seem to walk across the bath, and thus are dubbed walkers. Experiments have shown that walkers can exhibit exotic dynamical behavior indicative of chaos. While the integro-differential models developed for these systems agree well with the experiments, they are difficult to analyze mathematically. In recent years, simpler discrete dynamical models have been derived and studied numerically. The numerical simulations of these models show evidence of exotic dynamics such as period doubling bifurcations, Neimark--Sacker (N--S) bifurcations, and even chaos. For example, in [Gilet, PRE 2014], based on simulations Gilet conjectured the existence of a supercritical N-S bifurcation as the damping factor in his one-dimensional path model. We prove Gilet's conjecture and more; in fact, both supercritical and subcritical (N-S) bifurcations are produced by separately varying the damping factor and wave-particle coupling for all eigenmode shapes. Then we compare our theoretical results with some previous and new numerical simulations, and find complete qualitative agreement. Furthermore, evidence of chaos is shown by numerically studying a global bifurcation.

  20. Bifurcations of a two-dimensional discrete time plant-herbivore system

    Science.gov (United States)

    Khan, Abdul Qadeer; Ma, Jiying; Xiao, Dongmei

    2016-10-01

    In this paper, bifurcations of a two dimensional discrete time plant-herbivore system formulated by Allen et al. (1993) have been studied. It is proved that the system undergoes a transcritical bifurcation in a small neighborhood of a boundary equilibrium and a Neimark-Sacker bifurcation in a small neighborhood of the unique positive equilibrium. An invariant closed curve bifurcates from the unique positive equilibrium by Neimark-Sacker bifurcation, which corresponds to the periodic or quasi-periodic oscillations between plant and herbivore populations. For a special form of the system, which appears in Kulenović and Ladas (2002), it is shown that the system can undergo a supercritical Neimark-Sacker bifurcation in a small neighborhood of the unique positive equilibrium and a stable invariant closed curve appears. This bifurcation analysis provides a theoretical support on the earlier numerical observations in Allen et al. (1993) and gives a supportive evidence of the conjecture in Kulenović and Ladas (2002). Some numerical simulations are also presented to illustrate our theocratical results.

  1. Bifurcations of nontwisted heteroclinic loop

    Institute of Scientific and Technical Information of China (English)

    田清平; 朱德明

    2000-01-01

    Bifurcations of nontwisted and fine heteroclinic loops are studied for higher dimensional systems. The existence and its associated existing regions are given for the 1-hom orbit and the 1-per orbit, respectively, and bifurcation surfaces of the two-fold periodic orbit are also obtained. At last, these bifurcation results are applied to the fine heteroclinic loop for the planar system, which leads to some new and interesting results.

  2. Supercritical fluid extraction

    Science.gov (United States)

    Wai, Chien M.; Laintz, Kenneth

    1994-01-01

    A method of extracting metalloid and metal species from a solid or liquid material by exposing the material to a supercritical fluid solvent containing a chelating agent. The chelating agent forms chelates that are soluble in the supercritical fluid to allow removal of the species from the material. In preferred embodiments, the extraction solvent is supercritical carbon dioxide and the chelating agent is a fluorinated or lipophilic crown ether or fluorinated dithiocarbamate. The method provides an environmentally benign process for removing contaminants from industrial waste without using acids or biologically harmful solvents. The chelate and supercritical fluid can be regenerated, and the contaminant species recovered, to provide an economic, efficient process.

  3. Bifurcation and nonlinear analysis of a time-delayed thermoacoustic system

    Science.gov (United States)

    Yang, Xiaochuan; Turan, Ali; Lei, Shenghui

    2017-03-01

    In this paper, of primary concern is a time-delayed thermoacoustic system, viz. a horizontal Rijke tube. A continuation approach is employed to capture the nonlinear behaviour inherent to the system. Unlike the conventional approach by the Galerkin method, a dynamic system is naturally built up by discretizing the acoustic momentum and energy equations incorporating appropriate boundary conditions using a finite difference method. In addition, the interaction of Rijke tube velocity with oscillatory heat release is modeled using a modified form of King's law. A comparison of the numerical results with experimental data and the calculations reported reveals that the current approach can yield very good predictions. Moreover, subcritical Hopf bifurcations and fold bifurcations are captured with the evolution of dimensionless heat release coefficient, generic damping coefficient and time delay. Linear stability boundary, nonlinear stability boundary, bistable region and limit cycles are thus determined to gain an understanding of the intrinsic nonlinear behaviours.

  4. Stochastic bifurcations caused by multiplicative noise in systems with hard excitement of auto-oscillations.

    Science.gov (United States)

    Bashkirtseva, Irina; Ryazanova, Tatyana; Ryashko, Lev

    2015-10-01

    We study a stochastic dynamics of systems with hard excitement of auto-oscillations possessing a bistability mode with coexistence of the stable equilibrium and limit cycle. A principal difference in the results of the impact of additive and parametric random disturbances is shown. For the stochastic van der Pol oscillator with increasing parametric noise, qualitative transformations of the probability density function form "crater"-"peak+crater"-"peak" are demonstrated by numerical simulation. An analytical investigation of such P bifurcations is carried out for the stochastic Hopf-like model with hard excitement of self-oscillations. A detailed parametric description of the response of this model on the additive and multiplicative noise and corresponding stochastic bifurcations are presented and discussed.

  5. Bifurcations in a nonlinear model of the baroreceptor-cardiac reflex

    Science.gov (United States)

    Seidel, H.; Herzel, H.

    1998-04-01

    We investigate the dynamic properties of a nonlinear model of the human cardio-baroreceptor control loop. As a new feature we use a phase effectiveness curve to describe the experimentally well-known phase dependency of the cardiac pacemaker's sensitivity to neural activity. We show that an increase of sympathetic time delays leads via a Hopf bifurcation to sustained heart rate oscillations. For increasing baroreflex sensitivity or for repetitive vagal stimulation we observe period-doubling, toroidal oscillations, chaos, and entrainment between the rhythms of the heart and the control loop. The bifurcations depend crucially on the involvement of the cardiac pacemaker's phase dependency. We compare the model output with experimental data from electrically stimulated anesthetized dogs and discuss possible implications for cardiac arrhythmias.

  6. Bifurcation analysis in the diffusive Lotka-Volterra system: An application to market economy

    Energy Technology Data Exchange (ETDEWEB)

    Wijeratne, A.W. [Department of Mathematics, Harbin Institute of Technology, Harbin 150001 (China); Department of Agri-Business Management, Sabaragamuwa University of Sri Lanka, Belihuloya 70140 (Sri Lanka); Yi Fengqi [Department of Mathematics, Harbin Institute of Technology, Harbin 150001 (China); Wei Junjie [Department of Mathematics, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: weijj@hit.edu.cn

    2009-04-30

    A diffusive Lotka-Volterra system is formulated in this paper that represents the dynamics of market share at duopoly. A case in Sri Lankan mobile telecom market was considered that conceptualized the model in interest. Detailed Hopf bifurcation, transcritical and pitchfork bifurcation analysis were performed. The distribution of roots of the characteristic equation suggests that a stable coexistence equilibrium can be achieved by increasing the innovation while minimizing competition by each competitor while regulating existing policies and introducing new ones for product differentiation and value addition. The avenue is open for future research that may use real time information in order to formulate mathematically sound tools for decision making in competitive business environments.

  7. Uncertainty analysis near bifurcation of an aeroelastic system

    Science.gov (United States)

    Ghommem, M.; Hajj, M. R.; Nayfeh, A. H.

    2010-08-01

    Variations in structural and aerodynamic nonlinearities on the dynamic behavior of an aeroelastic system are investigated. The aeroelastic system consists of a rigid airfoil that is supported by nonlinear springs in the pitch and plunge directions and subjected to nonlinear aerodynamic loads. We follow two approaches to determine the effects of variations in the linear and nonlinear plunge and pitch stiffness coefficients of this aeroelastic system on its stability near the bifurcation. The first approach is based on implementation of intrusive polynomial chaos expansion (PCE) on the governing equations, yielding a set of nonlinear coupled ordinary differential equations that are numerically solved. The results show that this approach is capable of determining sensitivity of the flutter speed to variations in the linear pitch stiffness coefficient. On the other hand, it fails to predict changes in the type of the instability associated with randomness in the cubic stiffness coefficient. In the second approach, the normal form is used to investigate the flutter (Hopf bifurcation) boundary that occurs as the freestream velocity is increased and to analytically predict the amplitude and frequency of the ensuing LCO. The results show that this mathematical approach provides detailed aspects of the effects of the different system nonlinearities on its dynamic behavior. Furthermore, this approach could be effectively used to perform sensitivity analysis of the system's response to variations in its parameters.

  8. Invariants of 3-Manifolds derived from finite dimensional hopf algebras

    CERN Document Server

    Kauffman, L H; Louis H Kauffman; David E Radford

    1994-01-01

    Abstract: This paper studies invariants of 3-manifolds derived from certain fin ite dimensional Hopf algebras. The invariants are based on right integrals for these algebras. It is shown that the resulting class of invariants is distinct from the class of Witten-Reshetikhin-Turaev invariants.

  9. Euler potentials for the MHD Kamchatnov-Hopf soliton solution

    NARCIS (Netherlands)

    Semenov, VS; Korovinski, DB; Biernat, HK

    2002-01-01

    In the MHD description of plasma phenomena the concept of magnetic helicity turns out to be very useful. We present here an example of introducing Euler potentials into a topological MHD soliton which has non-trivial helicity. The MHD soliton solution (Kamchatnov, 1982) is based on the Hopf invarian

  10. The Planar Algebra of a Semisimple and Cosemisimple Hopf Algebra

    Indian Academy of Sciences (India)

    Vijay Kodiyalam; V S Sunder

    2006-11-01

    To a semisimple and cosemisimple Hopf algebra over an algebraically closed field, we associate a planar algebra defined by generators and relations and show that it is a connected, irreducible, spherical, non-degenerate planar algebra with non-zero modulus and of depth two. This association is shown to yield a bijection between (the isomorphism classes, on both sides, of) such objects.

  11. Combinatorial Hopf algebras in quantum field theory I

    CERN Document Server

    Figueroa, H; Figueroa, Hector; Gracia-Bondia, Jose M.

    2004-01-01

    This manuscript collects and expands for the most part a series of lectures on the interface between combinatorial Hopf algebra theory (CHAT) and renormalization theory, delivered by the second-named author in the framework of the joint mathematical physics seminar of the Universites d'Artois and Lille 1, from late January till mid-February 2003. The plan is as follows: Section 1 is the introduction, and Section 2 contains an elementary invitation to the subject. Sections 3-7 are devoted to the basics of Hopf algebra theory and examples, in ascending level of complexity. Section 8 contains a first, direct approach to the Faa di Bruno Hopf algebra. Section 9 gives applications of that to quantum field theory and Lagrange reversion. Section 10 rederives the Connes-Moscovici algebras. In Section 11 we turn to Hopf algebras of Feynman graphs. Then in Section 12 we give an extremely simple derivation of (the properly combinatorial part of) Zimmermann's method, in its original diagrammatic form. In Section 13 gener...

  12. Cup products in Hopf cyclic cohomology with coefficients in contramodules

    CERN Document Server

    Rangipour, Bahram

    2010-01-01

    We use stable anti Yetter-Drinfeld contramodules to improve the cup products in Hopf cyclic cohomology. The improvement fixes the lack of functoriality of the cup products previously defined and show that the cup products are sensitive to the coefficients.

  13. Implications of the Hopf algebra properties of noncommutative differential calculi

    OpenAIRE

    1996-01-01

    We define a noncommutative algebra of four basic objects within a differential calculus on quantum groups: functions, 1-forms, Lie derivatives and inner derivations, as the cross-product algebra associated with Woronowicz's (differential) algebra of functions and forms. This definition properly takes into account the Hopf algebra structure of the Woronowicz calculus. It also provides a direct proof of the Cartan identity.

  14. Implications of the Hopf algebra properties of noncommutative differential calculi

    OpenAIRE

    Vladimirov, A.A.

    1996-01-01

    We define a noncommutative algebra of four basic objects within a differential calculus on quantum groups: functions, 1-forms, Lie derivatives and inner derivations, as the cross-product algebra associated with Woronowicz's (differential) algebra of functions and forms. This definition properly takes into account the Hopf algebra structure of the Woronowicz calculus. It also provides a direct proof of the Cartan identity.

  15. New Hopf Structures on Binary Trees (Extended Abstract)

    CERN Document Server

    Forcey, Stefan; Sottile, Frank

    2009-01-01

    The multiplihedra {M_n} form a family of polytopes originating in the study of higher categories and homotopy theory. While the multiplihedra may be unfamiliar to the algebraic combinatorics community, it is nestled between two families of polytopes that certainly are not: the permutahedra {S_n} and associahedra {Y_n}. The maps between these families reveal several new Hopf structures on tree-like objects nestled between the Malvenuto-Reutenauer (MR) Hopf algebra of permutations and the Loday-Ronco (LR) Hopf algebra of planar binary trees. We begin their study here, constructing a module over MR and a Hopf module over LR from the multiplihedra. Rich structural information about this module is uncovered via a change of basis--using M\\"obius inversion in posets built on the 1-skeleta of the {M_n}. Our analysis uses the notion of an interval retract, which should have independent interest in poset combinatorics. It also reveals new families of polytopes, and even a new factorization of a known projection from th...

  16. A selection-quotient process for packed word Hopf algebra

    CERN Document Server

    Duchamp, G H E; Tanasa, A

    2013-01-01

    In this paper, we define a Hopf algebra structure on the vector space spanned by packed words using a selection-quotient coproduct. We show that this algebra is free on its irreducible packed words. Finally, we give some brief explanations on the Maple codes we have used.

  17. Skew Littlewood-Richardson rules from Hopf algebras

    CERN Document Server

    Lam, Thomas; Sottile, Frank

    2009-01-01

    We use Hopf algebras to prove a version of the Littlewood-Richardson formula for skew Schur functions, which implies a conjecture of Assaf and McNamara. We also establish a similar skew Littlewood-Richardson formula for Schur P- and Q-functions.

  18. Combinatorial Hopf Algebras in Quantum Field Theory I

    Science.gov (United States)

    Figueroa, Héctor; Gracia-Bondía, José M.

    This paper stands at the interface between combinatorial Hopf algebra theory and renormalization theory. Its plan is as follows: Sec. 1.1 is the introduction, and contains an elementary invitation to the subject as well. The rest of Sec. 1 is devoted to the basics of Hopf algebra theory and examples in ascending level of complexity. Section 2 turns around the all-important Faà di Bruno Hopf algebra. Section 2.1 contains a first, direct approach to it. Section 2.2 gives applications of the Faà di Bruno algebra to quantum field theory and Lagrange reversion. Section 2.3 rederives the related Connes-Moscovici algebras. In Sec. 3, we turn to the Connes-Kreimer Hopf algebras of Feynman graphs and, more generally, to incidence bialgebras. In Sec. 3.1, we describe the first. Then in Sec. 3.2, we give a simple derivation of (the properly combinatorial part of) Zimmermann's cancellation-free method, in its original diagrammatic form. In Sec. 3.3, general incidence algebras are introduced, and the Faà di Bruno bialgebras are described as incidence bialgebras. In Sec. 3.4, deeper lore on Rota's incidence algebras allows us to reinterpret Connes-Kreimer algebras in terms of distributive lattices. Next, the general algebraic-combinatorial proof of the cancellation-free formula for antipodes is ascertained. The structure results for commutative Hopf algebras are found in Sec. 4. An outlook section very briefly reviews the coalgebraic aspects of quantization and the Rota-Baxter map in renormalization.

  19. 一类Hodgkin-Huxley模型的分支研究%Bifurcation Analysis of a Hodgkin-Huxley-Type Model

    Institute of Scientific and Technical Information of China (English)

    李敏; 刘宣亮; 刘深泉

    2013-01-01

    This paper consider the Hodgkin-Huxley model in muscels, by using the bifurcation theory of differential equations and mumerical simulation, we discuss the one-parameter and two-parameter bifurcations of the model. The Bogdanov-Takens bifurcation are also discussed. We obtain the saddle-node bifurcation curve, the Hopf bifurcation curve and the Homoclinic bifurcation curve near the Bogdanov-Takens point.%考虑一类描述肌细胞膜电位变化的Hodgkin-Huxley模型的分支问题.利用常微分方程的分支理论,结合数值模拟结果,对模型的单参数分支与双参数分支进行了讨论.分析了Bogdanov-Takens分支,得到了相应的鞍结点分支曲线, Hopf分支曲线与同宿分支曲线.

  20. Blowout bifurcation of chaotic saddles

    Directory of Open Access Journals (Sweden)

    Tomasz Kapitaniak

    1999-01-01

    Full Text Available Chaotic saddles are nonattracting dynamical invariant sets that can lead to a variety of physical phenomena. We describe the blowout bifurcation of chaotic saddles located in the symmetric invariant manifold of coupled systems and discuss dynamical phenomena associated with this bifurcation.

  1. Impedance matching at arterial bifurcations.

    Science.gov (United States)

    Brown, N

    1993-01-01

    Reflections of pulse waves will occur in arterial bifurcations unless the impedance is matched continuously through changing geometric and elastic properties. A theoretical model is presented which minimizes pulse wave reflection through bifurcations. The model accounts for the observed linear changes in area within the bifurcation, generalizes the theory to asymmetrical bifurcations, characterizes changes in elastic properties from parent to daughter arteries, and assesses the effect of branch angle on the mechanical properties of daughter vessels. In contradistinction to previous models, reflections cannot be minimized without changes in elastic properties through bifurcations. The theoretical model predicts that in bifurcations with area ratios (beta) less than 1.0 Young's moduli of daughter vessels may be less than that in the parent vessel if the Womersley parameter alpha in the parent vessel is less than 5. Larger area ratios in bifurcations are accompanied by greater increases in Young's moduli of branches. For an idealized symmetric aortic bifurcation (alpha = 10) with branching angles theta = 30 degrees (opening angle 60 degrees) Young's modulus of common iliac arteries relative to that of the distal abdominal aorta has an increase of 1.05, 1.68 and 2.25 for area ratio of 0.8, 1.0 and 1.15, respectively. These predictions are consistent with the observed increases in Young's moduli of peripheral vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

  2. Hypercrater Bifurcations, Attractor Coexistence, and Unfolding in a 5D Model of Economic Dynamics

    Directory of Open Access Journals (Sweden)

    Toichiro Asada

    2011-01-01

    Full Text Available Complex dynamical features are explored in a discrete interregional macrodynamic model proposed by Asada et al., using numerical methods. The model is five-dimensional with four parameters. The results demonstrate patterns of dynamical behaviour, such as bifurcation processes and coexistence of attractors, generated by high-dimensional discrete systems. In three cases of two-dimensional parameter subspaces the stability of equilibrium region is determined and its boundaries, the flip and Neimark-Hopf bifurcation curves, are identified by means of necessary coefficient criteria. In the first case closed invariant curves (CICs are found to occur through 5D-crater-type bifurcations, and for certain ranges of parameter values a stable equilibrium coexists with an unstable CIC associated with the subcritical bifurcation, as well as with an outer stable CIC. A remarkable feature of the second case is the coexistence of two attracting CICs outside the stability region. In both these cases the related hysteresis effects are illustrated by numerical simulations. In the third case a remarkable feature is the apparent unfolding of an attracting CIC before it evolves to a chaotic attractor. Examples of CICs and chaotic attractors are given in subspaces of phase space.

  3. Speciation and bifurcations.

    Science.gov (United States)

    Volkenstein, M V; Livshits, M A

    1989-01-01

    The interrelations of physics and biology are discussed. It is shown that Darwin can be considered as one of the founders of the important field of contemporary physics called physics of dissipative structures or synergetics. The theories of gradual and punctual evolution are presented. The contradiction between these theories can be solved on the basis of molecular theory of evolution and on the basis of the phenomenological physical treatment. The general physical properties of living systems, considered as open systems being far from equilibrium, are listed and simple non-linear mathematical models describing gradual and punctual speciation are suggested. The usual pictures which present these two kinds of speciation can possess physico-mathematical sense. Punctuated speciation means bifurcation, a kind of non-equilibrium phase transition.

  4. Bifurcations sights, sounds, and mathematics

    CERN Document Server

    Matsumoto, Takashi; Kokubu, Hiroshi; Tokunaga, Ryuji

    1993-01-01

    Bifurcation originally meant "splitting into two parts. " Namely, a system under­ goes a bifurcation when there is a qualitative change in the behavior of the sys­ tem. Bifurcation in the context of dynamical systems, where the time evolution of systems are involved, has been the subject of research for many scientists and engineers for the past hundred years simply because bifurcations are interesting. A very good way of understanding bifurcations would be to see them first and study theories second. Another way would be to first comprehend the basic concepts and theories and then see what they look like. In any event, it is best to both observe experiments and understand the theories of bifurcations. This book attempts to provide a general audience with both avenues toward understanding bifurcations. Specifically, (1) A variety of concrete experimental results obtained from electronic circuits are given in Chapter 1. All the circuits are very simple, which is crucial in any experiment. The circuits, howev...

  5. Extension of a quantized enveloping algebra by a Hopf algebra

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Suppose that H is a Hopf algebra,and g is a generalized Kac-Moody algebra with Cartan matrix A =(aij)I×I,where I is an index set and is equal to either {1,2,...,n} or the natural number set N.Let f,g be two mappings from I to G(H),the set of group-like elements of H,such that the multiplication of elements in the set {f(i),g(i)|i ∈I} is commutative.Then we define a Hopf algebra Hgf Uq(g),where Uq(g) is the quantized enveloping algebra of g.

  6. Higher genus mapping class group invariants from factorizable Hopf algebras

    CERN Document Server

    Fuchs, Jurgen; Stigner, Carl

    2012-01-01

    Lyubashenko's construction associates representations of mapping class groups Map_{g,n} of Riemann surfaces of any genus g with any number n of holes to a factorizable ribbon category. We consider this construction as applied to the category of bimodules over a finite-dimensional factorizable ribbon Hopf algebra H. For any such Hopf algebra we find an invariant of Map_{g,n} for every g and n. More generally, we obtain such invariants for any pair (H,omega), where omega is a ribbon automorphism of H. Our results are motivated by the quest to understand correlation functions of bulk fields in two-dimensional conformal field theories with chiral algebras that are not necessarily semisimple, so-called logarithmic conformal field theories.

  7. Electrochemistry in supercritical fluids

    Science.gov (United States)

    Branch, Jack A.; Bartlett, Philip N.

    2015-01-01

    A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide–acetonitrile and supercritical HFCs. PMID:26574527

  8. Electrochemistry in supercritical fluids.

    Science.gov (United States)

    Branch, Jack A; Bartlett, Philip N

    2015-12-28

    A wide range of supercritical fluids (SCFs) have been studied as solvents for electrochemistry with carbon dioxide and hydrofluorocarbons (HFCs) being the most extensively studied. Recent advances have shown that it is possible to get well-resolved voltammetry in SCFs by suitable choice of the conditions and the electrolyte. In this review, we discuss the voltammetry obtained in these systems, studies of the double-layer capacitance, work on the electrodeposition of metals into high aspect ratio nanopores and the use of metallocenes as redox probes and standards in both supercritical carbon dioxide-acetonitrile and supercritical HFCs.

  9. HOPF ALGEBRAIC APPROACH TO THE n LINEARLY RECURSIVE SEQUENCES

    Institute of Scientific and Technical Information of China (English)

    LIANGGUI

    1994-01-01

    It is proved that a linearly recursive sequence of n indicea over field F(n≥1) is autorntatically a product of n lioearly recurplve sequencea of 1-lndex over F by the theory of Hopf algebras.By the way,the correspondence between the set of linearly recursive sequenoes of 1-index and F[X]0 is generalised to the case of n-index.

  10. Holomorphic Vector Bundle on Hopf Manifolds with Abelian Fundamental Groups

    Institute of Scientific and Technical Information of China (English)

    Xiang Yu ZHOU; Wei Ming LIU

    2004-01-01

    Let X be a Hopf manifolds with an Abelian fundamental group. E is a holomorphic vector bundle of rank r with trivial pull-back to W = Cn - {0}. We prove the existence of a non-vanishing section of L(×) E for some line bundle on X and study the vector bundles filtration structure of E. These generalize the results of D. Mall about structure theorem of such a vector bundle E.

  11. Weak Hopf Algebras Corresponding to Borcherds-Cartan Matrices

    Institute of Scientific and Technical Information of China (English)

    Li Xia YE; Zhi Xiang WU; Xue Feng MEI

    2007-01-01

    Let y be a generalized Kac-Moody algebra with an integral Borcherds-Cartan matrix. Inthis paper, we define a d-type weak quantum generalized Kac-Moody algebra wUdq(y), which is a weakHopf algebra. We also study the highest weight module over the weak quantum algebra wUdq(y) andWeak A-forms of wUdq(y).

  12. Second Hopf map and supersymmetric mechanics with Yang monopole

    Energy Technology Data Exchange (ETDEWEB)

    Gonzales, M.; Toppan, F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Kuznetsova, Z. [Universidade Federal do ABC, Santo Andre, SP (Brazil); Nersessian, F. [Artsakh State University, Stepanakert (Armenia); Yeghikyan, V. [Yerevan State University (Armenia)

    2009-07-01

    We propose to use the second Hopf map for the reduction (via SU(2) group action) of the eight-dimensional supersymmetric mechanics to five-dimensional supersymmetric systems specified by the presence of an SU(2) Yang monopole. For our purpose we develop the relevant Lagrangian reduction procedure. The reduced system is characterized by its invariance under the N = 5 or N = 4 supersymmetry generators (with or without an additional conserved BRST charge operator) which commute with the su(2) generators. (author)

  13. Quantum Clifford-Hopf Algebras for Even Dimensions

    CERN Document Server

    López, E

    1994-01-01

    In this paper we study the quantum Clifford-Hopf algebras $\\widehat{CH_q(D)}$ for even dimensions $D$ and obtain their intertwiner $R-$matrices, which are elliptic solutions to the Yang- Baxter equation. In the trigonometric limit of these new algebras we find the possibility to connect with extended supersymmetry. We also analyze the corresponding spin chain hamiltonian, which leads to Suzuki's generalized $XY$ model.

  14. Kitaev Lattice Models as a Hopf Algebra Gauge Theory

    Science.gov (United States)

    Meusburger, Catherine

    2017-07-01

    We prove that Kitaev's lattice model for a finite-dimensional semisimple Hopf algebra H is equivalent to the combinatorial quantisation of Chern-Simons theory for the Drinfeld double D( H). This shows that Kitaev models are a special case of the older and more general combinatorial models. This equivalence is an analogue of the relation between Turaev-Viro and Reshetikhin-Turaev TQFTs and relates them to the quantisation of moduli spaces of flat connections. We show that the topological invariants of the two models, the algebra of operators acting on the protected space of the Kitaev model and the quantum moduli algebra from the combinatorial quantisation formalism, are isomorphic. This is established in a gauge theoretical picture, in which both models appear as Hopf algebra valued lattice gauge theories. We first prove that the triangle operators of a Kitaev model form a module algebra over a Hopf algebra of gauge transformations and that this module algebra is isomorphic to the lattice algebra in the combinatorial formalism. Both algebras can be viewed as the algebra of functions on gauge fields in a Hopf algebra gauge theory. The isomorphism between them induces an algebra isomorphism between their subalgebras of invariants, which are interpreted as gauge invariant functions or observables. It also relates the curvatures in the two models, which are given as holonomies around the faces of the lattice. This yields an isomorphism between the subalgebras obtained by projecting out curvatures, which can be viewed as the algebras of functions on flat gauge fields and are the topological invariants of the two models.

  15. Hopf-Algebra Description of Noncommutative-Space Symmetries

    Science.gov (United States)

    Agostini, Alessandra; Amelino-Camelia, Giovanni; D'Andrea, Francesco

    In the study of certain noncommutative versions of Minkowski space-time a lot remains to be understood for a satisfactory characterization of their symmetries. Adopting as our case study the κ-Minkowski noncommutative space-time, on which a large literature is already available, we propose a line of analysis of noncommutative-space-time symmetries that relies on the introduction of a Weyl map (connecting a given function in the noncommutative Minkowski with a corresponding function in commutative Minkowski). We provide new elements in favor of the expectation that the commutative-space-time notion of Lie-algebra symmetries must be replaced, in the noncommutative-space-time context, by the one of Hopf-algebra symmetries. While previous studies appeared to establish a rather large ambiguity in the description of the Hopf-algebra symmetries of κ-Minkowski, the approach here adopted reduces the ambiguity to the description of the translation generators, and our results, independently of this ambiguity, are sufficient to clarify that some recent studies which argued for an operational indistinguishability between theories with and without a length-scale relativistic invariant, implicitly assumed that the underlying space-time would be classical. Moreover, while usually one describes theories in κ-Minkowski directly at the level of equations of motion, we explore the nature of Hopf-algebra symmetry transformations on an action.

  16. Hopfing and Puffing Warped Anti-de Sitter Space

    CERN Document Server

    Anninos, Dionysios

    2009-01-01

    Three dimensional spacelike warped anti-de Sitter space is studied in the context of Einstein theories of gravity and string theory, where there is no gravitational Chern-Simons term in the action. We propose that it is holographically dual to a two-dimensional conformal field theory with equal left and right moving central charges. Various checks of the central charges are offered, based on the Bekenstein-Hawking entropy of the stretched warped black holes and warped self-dual solutions. The proposed central charges are applied to compute the Bekenstein-Hawking entropy of the Hopf T-dual of six-dimensional dyonic black strings which have a near horizon consisting of three dimensional warped anti-de Sitter space times a three-sphere. We find that the Hopf T-duality is a map between thermal states with equal entropy of the CFTs dual to the dyonic black string and the Hopf T-dualized black string.

  17. Yetter-Drinfel’d Hopf algebras over groups of prime order

    CERN Document Server

    Sommerhäuser, Yorck

    2002-01-01

    Being the first monograph devoted to this subject, the book addresses the classification problem for semisimple Hopf algebras, a field that has attracted considerable attention in the last years. The special approach to this problem taken here is via semidirect product decompositions into Yetter-Drinfel'd Hopf algebras and group rings of cyclic groups of prime order. One of the main features of the book is a complete treatment of the structure theory for such Yetter-Drinfel'd Hopf algebras.

  18. Generalizing the Connes Moscovici Hopf algebra to contain all rooted trees

    CERN Document Server

    Agarwala, Susama

    2013-01-01

    This paper defines a generalization of the Connes-Moscovici Hopf algebra, $\\h(1)$ that contains the entire Hopf algebra of rooted trees. A relationship between the former, a much studied object in non-commutative geometry, and the later, a much studied object in perturbative Quantum Field Theory, has been established by Connes and Kreimer. The results of this paper open the door to study the cohomology of the Hopf algebra of rooted trees.

  19. Generalizing the Connes Moscovici Hopf algebra to contain all rooted trees

    Science.gov (United States)

    Agarwala, Susama; Delaney, Colleen

    2015-04-01

    This paper defines a generalization of the Connes-Moscovici Hopf algebra, H ( 1 ) , that contains the entire Hopf algebra of rooted trees. A relationship between the former, a much studied object in non-commutative geometry, and the latter, a much studied object in perturbative quantum field theory, has been established by Connes and Kreimer. The results of this paper open the door to study the cohomology of the Hopf algebra of rooted trees.

  20. Generalizing the Connes Moscovici Hopf algebra to contain all rooted trees

    Energy Technology Data Exchange (ETDEWEB)

    Agarwala, Susama [Mathematical Institute, Radcliff Observatory Quarter, Oxford University, Woodstock Road, Oxford (United Kingdom); Delaney, Colleen [University of California Santa Barbara, South Hall, Room 6607, Santa Barbara, California 93106 (United States)

    2015-04-15

    This paper defines a generalization of the Connes-Moscovici Hopf algebra, H(1), that contains the entire Hopf algebra of rooted trees. A relationship between the former, a much studied object in non-commutative geometry, and the latter, a much studied object in perturbative quantum field theory, has been established by Connes and Kreimer. The results of this paper open the door to study the cohomology of the Hopf algebra of rooted trees.

  1. Bifurcation Adds Flavor to Basketball

    CERN Document Server

    Min, Byeong June

    2016-01-01

    We report an emergence of bifurcation in basketball, a single-particle system governed by Newtonian mechanics. When shooting the basketball, the obvious control parameters are the launch speed and the launch angle. We propose to use the three-dimensional velocity phase-space volume associated with the given launch parameters to quantify the difficulty of the shooting. The optimal launch angle that maximizes the associated phase-space volume undergoes a bifurcation as the launch speed is increased, if the shooter is farther than a critical distance away from the hoop. Thus, the bifurcation makes it very important to control the launch speed accurately. If the air resistance is removed, the bifurcation disappears and the phase-space volume distribution becomes dispersionless and shrinks in magnitude.

  2. Supercritical Airfoil Coordinates

    Data.gov (United States)

    National Aeronautics and Space Administration — Rectangular Supercritical Wing (Ricketts) - design and measured locations are provided in an Excel file RSW_airfoil_coordinates_ricketts.xls . One sheet is with Non...

  3. Topological defect with nonzero Hopf invariant in Yang–Mills–Higgs model

    Directory of Open Access Journals (Sweden)

    Yan He

    2014-12-01

    Full Text Available We propose a topological defect or instanton solution with nonzero Hopf invariant to the 3+1D non-Abelian gauge theory coupled with scalar fields. This solution, which we call Hopf defect, represents a spacetime event that makes a 2π rotation of vacuum manifold of the monopole. Although the action of this Hopf defect is logarithmically divergent, it may still give relevant contributions in a finite-sized system. Since the Chern–Simons term for the unbroken U(1 gauge field may appear in the low energy effective theory, the Hopf defect may possibly generate a phase factor change for the monopoles.

  4. Bifurcation and chaos in a discrete-time predator-prey system of Holling and Leslie type

    Science.gov (United States)

    Hu, Dongpo; Cao, Hongjun

    2015-05-01

    A discrete-time predator-prey system of Holling and Leslie type with a constant-yield prey harvesting obtained by the forward Euler scheme is studied in detail. The conditions of existence for flip bifurcation and Hopf bifurcation are derived by using the center manifold theorem and bifurcation theory. Numerical simulations including bifurcation diagrams, maximum Lyapunov exponents, phase portraits display new and rich nonlinear dynamical behaviors. More specifically, when the integral step size is chosen as a bifurcation parameter, this paper presents the finding of period- 1, 2, 11, 17, 19, 22 orbits, attracting invariant cycles, and chaotic attractors of the discrete-time predator-prey system of Holling and Leslie type with a constant-yield prey harvesting. These results demonstrate that the integral step size plays a vital role to the local and global stability of the discrete-time predator-prey system with the Holling and Leslie type after the original continuous-time predator-prey system is discretized.

  5. The structure of renormalization Hopf algebras for gauge theories I: Representing Feynman graphs on BV-algebras

    OpenAIRE

    Suijlekom, W.D. van

    2008-01-01

    We study the structure of renormalization Hopf algebras of gauge theories. We identify certain Hopf subalgebras in them, whose character groups are semidirect products of invertible formal power series with formal diffeomorphisms. This can be understood physically as wave function renormalization and renormalization of the coupling constants, respectively. After taking into account the Slavnov-Taylor identities for the couplings as generators of a Hopf ideal, we find Hopf subalgebras in the c...

  6. Quasi Hopf algebras, group cohomology and orbifold models

    Energy Technology Data Exchange (ETDEWEB)

    Dijkgraaf, R. (Princeton Univ., NJ (USA). Joseph Henry Labs.); Pasquier, V. (CEA Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France). Inst. de Recherche Fondamentale (IRF)); Roche, P. (Ecole Polytechnique, 91 - Palaiseau (France). Centre de Physique Theorique)

    1991-01-01

    We construct non trivial quasi Hopf algebras associated to any finite group G and any element of H{sup 3}(G,U)(1). We analyze in details the set of representations of these algebras and show that we recover the main interesting datas attached to particular orbifolds of Rational Conformal Field Theory or equivalently to the topological field theories studied by R. Dijkgraaf and E. Witten. This leads us to the construction of the R-matrix structure in non abelian RCFT orbifold models. (orig.).

  7. Noncommutative geometry in string and twisted Hopf algebra of diffeomorphism

    Science.gov (United States)

    Watamura, Satoshi

    2011-09-01

    We discuss the Hopf algebra structure in string theory and present the twist quantization as a unified formulation of the world sheet quantization of the string and the symmetry of the target spacetime. Applying it to the case with a nonzero B-field background, we explain a method to decompose the twist into two successive twists. There are two different possibilities of decomposition: The first is a natural decomposition from the viewpoint of the twist quantization, leading to a new type of twisted Poincaré symmetry. The second decomposition reveals the relation of our formulation to the twisted Poincaré symmetry on the Moyal type noncommutative space.

  8. Lie algebra type noncommutative phase spaces are Hopf algebroids

    Science.gov (United States)

    Meljanac, Stjepan; Škoda, Zoran; Stojić, Martina

    2016-11-01

    For a noncommutative configuration space whose coordinate algebra is the universal enveloping algebra of a finite-dimensional Lie algebra, it is known how to introduce an extension playing the role of the corresponding noncommutative phase space, namely by adding the commuting deformed derivatives in a consistent and nontrivial way; therefore, obtaining certain deformed Heisenberg algebra. This algebra has been studied in physical contexts, mainly in the case of the kappa-Minkowski space-time. Here, we equip the entire phase space algebra with a coproduct, so that it becomes an instance of a completed variant of a Hopf algebroid over a noncommutative base, where the base is the enveloping algebra.

  9. Lie algebra type noncommutative phase spaces are Hopf algebroids

    CERN Document Server

    Meljanac, Stjepan

    2014-01-01

    For a noncommutative configuration space whose coordinate algebra is the universal enveloping algebra of a finite dimensional Lie algebra, it is known how to introduce an extension playing the role of the corresponding noncommutative phase space, namely by adding the commuting deformed derivatives in a consistent and nontrivial way, therefore obtaining certain deformed Heisenberg algebra. This algebra has been studied in physical contexts, mainly in the case of the kappa-Minkowski space-time. Here we equip the entire phase space algebra with a coproduct, so that it becomes an instance of a completed variant of a Hopf algebroid over a noncommutative base, where the base is the enveloping algebra.

  10. International Workshop "Groups, Rings, Lie and Hopf Algebras"

    CERN Document Server

    2003-01-01

    The volume is almost entirely composed of the research and expository papers by the participants of the International Workshop "Groups, Rings, Lie and Hopf Algebras", which was held at the Memorial University of Newfoundland, St. John's, NF, Canada. All four areas from the title of the workshop are covered. In addition, some chapters touch upon the topics, which belong to two or more areas at the same time. Audience: The readership targeted includes researchers, graduate and senior undergraduate students in mathematics and its applications.

  11. Differential Hopf algebra structures on the universal enveloping algebra ofa Lie algebra

    NARCIS (Netherlands)

    Hijligenberg, N.W. van den; Martini, R.

    1995-01-01

    We discuss a method to construct a De Rham complex (differential algebra) of Poincar'e-Birkhoff-Witt-type on the universal enveloping algebra of a Lie algebra $g$. We determine the cases in which this gives rise to a differential Hopf algebra that naturally extends the Hopf algebra structure of $U(g

  12. A word Hopf algebra based on the selection/quotient principle

    CERN Document Server

    Duchamp, G H E; Tanasa, A

    2013-01-01

    In this paper, we define a Hopf algebra structure on the vector space spanned by packed words using a selection/quotient coproduct. We show that this algebra is free on its irreducible packed words. We also construct the Hilbert series of this Hopf algebra and we investigate its primitive elements.

  13. Cyclic cohomology of Hopf algebras, and a non-commutative Chern-Weil theory

    NARCIS (Netherlands)

    Crainic, M.

    2001-01-01

    We give a construction of ConnesMoscovicis cyclic cohomology for any Hopf algebra equipped with a character Furthermore we introduce a noncommutative Weil complex which connects the work of Gelfand and Smirnov with cyclic cohomology We show how the Weil complex arises naturally when looking at Hopf

  14. Differential Hopf algebra structures on the universal enveloping algebra ofa Lie algebra

    NARCIS (Netherlands)

    N.W. van den Hijligenberg; R. Martini

    1995-01-01

    textabstractWe discuss a method to construct a De Rham complex (differential algebra) of Poincar'e-Birkhoff-Witt-type on the universal enveloping algebra of a Lie algebra $g$. We determine the cases in which this gives rise to a differential Hopf algebra that naturally extends the Hopf algebra

  15. Differential Hopf algebra structures on the Universal Enveloping Algebra of a Lie Algebra

    NARCIS (Netherlands)

    van den Hijligenberg, N.W.; van den Hijligenberg, N.; Martini, Ruud

    1995-01-01

    We discuss a method to construct a De Rham complex (differential algebra) of Poincaré–Birkhoff–Witt type on the universal enveloping algebra of a Lie algebra g. We determine the cases in which this gives rise to a differential Hopf algebra that naturally extends the Hopf algebrastructure of U(g).

  16. Differential Hopf algebra structures on the universal enveloping algebra of a Lie algebra

    NARCIS (Netherlands)

    van den Hijligenberg, N.W.; van den Hijligenberg, N.W.; Martini, Ruud

    1995-01-01

    We discuss a method to construct a De Rham complex (differential algebra) of Poincar'e-Birkhoff-Witt-type on the universal enveloping algebra of a Lie algebra $g$. We determine the cases in which this gives rise to a differential Hopf algebra that naturally extends the Hopf algebra structure of

  17. Effects of time delays on bifurcation and chaos in a non-autonomous system with multiple time delays

    Energy Technology Data Exchange (ETDEWEB)

    Sun Zhongkui [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)]. E-mail: sunzk205@mail.nwpu.edu.cn; Xu Wei [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)]. E-mail: weixu@nwpu.edu.cn; Yang Xiaoli [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); College of Mathematics and Information Science, Shaanxi Normal University, Xi' an 710062 (China); Fang Tong [Department of Applied Mechanics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2007-01-15

    Time delays are often sources of complex behavior in dynamic systems. Yet its complexity needs to be further explored, particularly when multiple time delays are present. As a purpose to gain insight into such complexity under multiple time delays, we investigate the mechanism for the action of multiple time delays on a particular non-autonomous system in this paper. The original mathematical model under consideration is a Duffing oscillator with harmonic excitation. A delayed system is obtained by adding delayed feedbacks to the original system. Two time delays are involved in such system, one of which in the displacement feedback and the other in the velocity feedback. The time delays are taken as adjustable parameters to study their effects on the dynamics of the system. Firstly, the stability of the trivial equilibrium of the linearized system is discussed and the condition under which the equilibrium loses its stability is obtained. This leads to a critical stability boundary where Hopf bifurcation or double Hopf bifurcation may occur. Then, the chaotic behavior of such system is investigated in detail. Particular emphasis is laid on the effect of delay difference between two time delays on the chaotic properties. A Melnikov's analysis is employed to obtain the necessary condition for onset of chaos resulting from homoclinic bifurcation. And numerical analyses via the bifurcation diagram and the top Lyapunov exponent are carried out to show the actual time delay effect. Both the results obtained by the two analyses show that the delay difference between two time delays plays a very important role in inducing or suppressing chaos, so that it can be taken as a simple but efficient 'switch' to control the motion of a system: either from order to chaos or from chaos to order.

  18. Nonlinear dynamics and bifurcation characteristics of shape memory alloy thin films subjected to in-plane stochastic excitation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhi-Wen [Department of Mechanics, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China); Tianjin Key Laboratory of Nonlinear Dynamics and Chaos Control 92 Weijin Road, Nankai District, Tianjin 300072 (China); Zhang, Qing-Xin [Department of Mechanics, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China); Xu, Jia, E-mail: xujia_ld@163.com [Department of Mechanics, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China)

    2014-11-03

    A kind of shape memory alloy (SMA) hysteretic nonlinear model was developed, and the nonlinear dynamics and bifurcation characteristics of the SMA thin film subjected to in-plane stochastic excitation were investigated. Van der Pol difference item was introduced to describe the hysteretic phenomena of the SMA strain–stress curves, and the nonlinear dynamic model of the SMA thin film subjected to in-plane stochastic excitation was developed. The conditions of global stochastic stability of the system were determined in singular boundary theory, and the probability density function of the system response was obtained. Finally, the conditions of stochastic Hopf bifurcation were analyzed. The results of theoretical analysis and numerical simulation indicate that self-excited vibration is induced by the hysteretic nonlinear characteristics of SMA, and stochastic Hopf bifurcation appears when the bifurcation parameter was changed; there are two limit cycles in the stationary probability density of the dynamic response of the system in some cases, which means that there are two vibration amplitudes whose probabilities are both very high, and jumping phenomena between the two vibration amplitudes appear with the change in conditions. The results obtained in this current paper are helpful for the application of the SMA thin film in stochastic vibration fields. - Highlights: • Hysteretic nonlinear model of shape memory alloy was developed. • Van der Pol item was introduced to interpret hysteretic strain–stress curves. • Nonlinear dynamic characteristics of the shape memory alloy film were analyzed. • Jumping phenomena were observed in the change of the parameters.

  19. Dynamical analysis for a model of asset prices with two delays

    Science.gov (United States)

    Wang, Luxuan; Niu, Ben; Wei, Junjie

    2016-04-01

    This paper provides a new perspective to understand the mechanism on the market stability or oscillation by investigating a two-dimensional asset price model with two delays. Stability conditions and the existence of Hopf bifurcation are obtained by investigating the characteristic equation. Then an explicit algorithm for determining the criticality of Hopf bifurcation and stability of the bifurcating solutions is derived, using the center manifold reduction method. The global continuation of bifurcating periodic solutions is detected using a global Hopf bifurcation theorem. It is found that delay may induce supercritical Hopf bifurcations, hence bring oscillation into the asset price model. Moreover, when time delay gets larger, the period of oscillation also increases. Finally, some numerical illustrations with Matlab and DDE-Biftool are carried out to support the theoretical analysis.

  20. Drug delivery goes supercritical

    Directory of Open Access Journals (Sweden)

    Patrick J. Ginty

    2005-08-01

    Full Text Available In the field of drug delivery, the ability to control the size, morphology, and release of drug particles is fundamental to good targeting, but is often hampered by harsh processing conditions or inadequate methods; likewise for the processing of polymeric controlled-release systems. However, the use of supercritical fluids such as supercritical CO2 (scCO2 has provided a ‘clean’ and effective alternative to traditional methods of drug and polymer processing. In particular, scCO2 has a number of unique properties that make it possible to process both bioactive molecules and amorphous polymers without using toxic organic solvents or elevated temperatures. Here, we review the positive impact that supercritical fluids have had on the micronization, encapsulation, and impregnation of molecules of interest to both the pharmaceutical and biotechnology industries.

  1. Invariant manifolds and global bifurcations.

    Science.gov (United States)

    Guckenheimer, John; Krauskopf, Bernd; Osinga, Hinke M; Sandstede, Björn

    2015-09-01

    Invariant manifolds are key objects in describing how trajectories partition the phase spaces of a dynamical system. Examples include stable, unstable, and center manifolds of equilibria and periodic orbits, quasiperiodic invariant tori, and slow manifolds of systems with multiple timescales. Changes in these objects and their intersections with variation of system parameters give rise to global bifurcations. Bifurcation manifolds in the parameter spaces of multi-parameter families of dynamical systems also play a prominent role in dynamical systems theory. Much progress has been made in developing theory and computational methods for invariant manifolds during the past 25 years. This article highlights some of these achievements and remaining open problems.

  2. H-可分的Hopf Galois扩张与Azumaya代数%H-separable Hopf Galois Extensions and Azumaya Algebra

    Institute of Scientific and Technical Information of China (English)

    祝家贵

    2001-01-01

    Let H be a finite dimensional semisimple Hopf algebra over a field and A an H-module algebra. In this paper, we characterize any H-separable Galois extension of an Azumaya algebra. Assuming that A/AH is an H-separable extension,we prove that A/AH is H*-Galois and AH is Azumaya if and only if A#H is an Azumaya Z-algebra, where Z is the center of A#H(not necessarily C(A)H).

  3. Materials processing using supercritical fluids

    Directory of Open Access Journals (Sweden)

    Orlović Aleksandar M.

    2005-01-01

    Full Text Available One of the most interesting areas of supercritical fluids applications is the processing of novel materials. These new materials are designed to meet specific requirements and to make possible new applications in Pharmaceuticals design, heterogeneous catalysis, micro- and nano-particles with unique structures, special insulating materials, super capacitors and other special technical materials. Two distinct possibilities to apply supercritical fluids in processing of materials: synthesis of materials in supercritical fluid environment and/or further processing of already obtained materials with the help of supercritical fluids. By adjusting synthesis parameters the properties of supercritical fluids can be significantly altered which further results in the materials with different structures. Unique materials can be also obtained by conducting synthesis in quite specific environments like reversed micelles. This paper is mainly devoted to processing of previously synthesized materials which are further processed using supercritical fluids. Several new methods have been developed to produce micro- and nano-particles with the use of supercritical fluids. The following methods: rapid expansion of supercritical solutions (RESS supercritical anti-solvent (SAS, materials synthesis under supercritical conditions and encapsulation and coating using supercritical fluids were recently developed.

  4. Supercritical Synthesis of Biodiesel

    Directory of Open Access Journals (Sweden)

    Michel Vaultier

    2012-07-01

    Full Text Available The synthesis of biodiesel fuel from lipids (vegetable oils and animal fats has gained in importance as a possible source of renewable non-fossil energy in an attempt to reduce our dependence on petroleum-based fuels. The catalytic processes commonly used for the production of biodiesel fuel present a series of limitations and drawbacks, among them the high energy consumption required for complex purification operations and undesirable side reactions. Supercritical fluid (SCF technologies offer an interesting alternative to conventional processes for preparing biodiesel. This review highlights the advances, advantages, drawbacks and new tendencies involved in the use of supercritical fluids (SCFs for biodiesel synthesis.

  5. Rota-Baxter algebras and the Hopf algebra of renormalization

    Energy Technology Data Exchange (ETDEWEB)

    Ebrahimi-Fard, K.

    2006-06-15

    Recently, the theory of renormalization in perturbative quantum field theory underwent some exciting new developments. Kreimer discovered an organization of Feynman graphs into combinatorial Hopf algebras. The process of renormalization is captured by a factorization theorem for regularized Hopf algebra characters. Hereby the notion of Rota-Baxter algebras enters the scene. In this work we develop in detail several mathematical aspects of Rota-Baxter algebras as they appear also in other sectors closely related to perturbative renormalization, to wit, for instance multiple-zeta-values and matrix differential equations. The Rota-Baxter picture enables us to present the algebraic underpinning for the Connes-Kreimer Birkhoff decomposition in a concise way. This is achieved by establishing a general factorization theorem for filtered algebras. Which in turn follows from a new recursion formula based on the Baker-Campbell-Hausdorff formula. This allows us to generalize a classical result due to Spitzer to non-commutative Rota-Baxter algebras. The Baker-Campbell-Hausdorff based recursion turns out to be a generalization of Magnus' expansion in numerical analysis to generalized integration operators. We will exemplify these general results by establishing a simple representation of the combinatorics of renormalization in terms of triangular matrices. We thereby recover in the presence of a Rota-Baxter operator the matrix representation of the Birkhoff decomposition of Connes and Kreimer. (orig.)

  6. Hopf-algebra description of noncommutative-spacetime symmetries

    CERN Document Server

    Agostini, A; D'Andrea, F; Andrea, Francesco D'

    2003-01-01

    In the study of certain noncommutative versions of Minkowski spacetime there is still a large ambiguity concerning the characterization of their symmetries. Adopting as our case study the kappaMinkowski noncommutative space-time, on which a large literature is already available, we propose a line of analysis of noncommutative-spacetime symmetries that relies on the introduction of a Weyl map (connecting a given function in the noncommutative Minkowski with a corresponding function in commutative Minkowski) and of a compatible notion of integration in the noncommutative spacetime. We confirm (and we establish more robustly) previous suggestions that the commutative-spacetime notion of Lie-algebra symmetries must be replaced, in the noncommutative-spacetime context, by the one of Hopf-algebra symmetries. We prove that in kappaMinkowski it is possible to construct an action which is invariant under a Poincare-like Hopf algebra of symmetries with 10 generators, in which the noncommutativity length scale has the r...

  7. Hopf Algebra Structure of a Model Quantum Field Theory

    CERN Document Server

    Solomon, A I; Blasiak, P; Horzela, A; Penson, K A

    2006-01-01

    Recent elegant work on the structure of Perturbative Quantum Field Theory (PQFT) has revealed an astonishing interplay between analysis(Riemann Zeta functions), topology (Knot theory), combinatorial graph theory (Feynman Diagrams) and algebra (Hopf structure). The difficulty inherent in the complexities of a fully-fledged field theory such as PQFT means that the essential beauty of the relationships between these areas can be somewhat obscured. Our intention is to display some, although not all, of these structures in the context of a simple zero-dimensional field theory; i.e. a quantum theory of non-commuting operators which do not depend on spacetime. The combinatorial properties of these boson creation and annihilation operators, which is our chosen example, may be described by graphs, analogous to the Feynman diagrams of PQFT, which we show possess a Hopf algebra structure. Our approach is based on the partition function for a boson gas. In a subsequent note in these Proceedings we sketch the relationship...

  8. On Hopf algebroid structure of kappa-deformed Heisenberg algebra

    CERN Document Server

    Lukierski, Jerzy; Woronowicz, Mariusz

    2016-01-01

    The $(4+4)$-dimensional $\\kappa$-deformed quantum phase space as well as its $(10+10)$-dimensional covariant extension by the Lorentz sector can be described as Heisenberg doubles: the $(10+10)$-dimensional quantum phase space is the double of $D=4$ $\\kappa$-deformed Poincar\\'e Hopf algebra $\\mathbb{H}$ and the standard $(4+4)$-dimensional space is its subalgebra generated by $\\kappa$-Minkowski coordinates $\\hat{x}_\\mu$ and corresponding commuting momenta $\\hat{p}_\\mu$. Every Heisenberg double appears as the total algebra of a Hopf algebroid over a base algebra which is in our case the coordinate sector. We exhibit the details of this structure, namely the corresponding right bialgebroid and the antipode map. We rely on algebraic methods of calculation in Majid-Ruegg bicrossproduct basis. The target map is derived from a formula by J-H. Lu. The coproduct takes values in the bimodule tensor product over a base, what is expressed as the presence of coproduct gauge freedom.

  9. Stability and Bifurcation Analysis of a Delayed Leslie-Gower Predator-Prey System with Nonmonotonic Functional Response

    Directory of Open Access Journals (Sweden)

    Jiao Jiang

    2013-01-01

    Full Text Available A delayed Leslie-Gower predator-prey model with nonmonotonic functional response is studied. The existence and local stability of the positive equilibrium of the system with or without delay are completely determined in the parameter plane. Using the method of upper and lower solutions and monotone iterative scheme, a sufficient condition independent of delay for the global stability of the positive equilibrium is obtained. Hopf bifurcations induced by the ratio of the intrinsic growth rates of the predator and prey and by delay, respectively, are found. Employing the normal form theory, the direction and stability of Hopf bifurcations can be explicitly determined by the parameters of the system. Some numerical simulations are given to support and extend our theoretical results. Two limit cycles enclosing an equilibrium, one limit cycle enclosing three equilibria and different types of heteroclinic orbits such as connecting two equilibria and connecting a limit cycle and an equilibrium are also found by using analytic and numerical methods.

  10. Thermodynamic geometry and critical aspects of bifurcations.

    Science.gov (United States)

    Mihara, A

    2016-07-01

    This work presents an exploratory study of the critical aspects of some well-known bifurcations in the context of thermodynamic geometry. For each bifurcation its normal form is regarded as a geodesic equation of some model analogous to a thermodynamic system. From this hypothesis it is possible to calculate the corresponding metric and curvature and analyze the critical behavior of the bifurcation.

  11. Solution and transcritical bifurcation of Burgers equation

    Institute of Scientific and Technical Information of China (English)

    Tang Jia-Shi; Zhao Ming-Hua; Han Feng; Zhang Liang

    2011-01-01

    Burgers equation is reduced into a first-order ordinary differential equation by using travelling wave transformation and it has typical bifurcation characteristics. We can obtain many exact solutions of the Burgers equation, discuss its transcritical bifurcation and control dynamical behaviours by extending the stable region. The transcritical bifurcation exists in the (2 + 1)-dimensional Burgers equation.

  12. Bifurcations of optimal vector fields

    NARCIS (Netherlands)

    Kiseleva, T.; Wagener, F.

    2015-01-01

    We study the structure of the solution set of a class of infinite-horizon dynamic programming problems with one-dimensional state spaces, as well as their bifurcations, as problem parameters are varied. The solutions are represented as the integral curves of a multivalued optimal vector field on sta

  13. Bifurcation of Codimension 3 in a Predator-Prey System of Leslie Type with Simplified Holling Type IV Functional Response

    Science.gov (United States)

    Huang, Jicai; Xia, Xiaojing; Zhang, Xinan; Ruan, Shigui

    It was shown in [Li & Xiao, 2007] that in a predator-prey model of Leslie type with simplified Holling type IV functional response some complex bifurcations can occur simultaneously for some values of parameters, such as codimension 1 subcritical Hopf bifurcation and codimension 2 Bogdanov-Takens bifurcation. In this paper, we show that for the same model there exists a unique degenerate positive equilibrium which is a degenerate Bogdanov-Takens singularity (focus case) of codimension 3 for other values of parameters. We prove that the model exhibits degenerate focus type Bogdanov-Takens bifurcation of codimension 3 around the unique degenerate positive equilibrium. Numerical simulations, including the coexistence of three hyperbolic positive equilibria, two limit cycles, bistability states (one stable equilibrium and one stable limit cycle, or two stable equilibria), tristability states (two stable equilibria and one stable limit cycle), a stable limit cycle enclosing a homoclinic loop, a homoclinic loop enclosing an unstable limit cycle, or a stable limit cycle enclosing three unstable hyperbolic positive equilibria for various parameter values, confirm the theoretical results.

  14. NEW BIFURCATION PATTERNS IN ELEMENTARY BIFURCATION PROBLEMS WITH SINGLE-SIDE CONSTRAINT

    Institute of Scientific and Technical Information of China (English)

    吴志强; 陈予恕

    2001-01-01

    Bifurcations with constraints are open problems appeared in research on periodic bifurcations of nonlinear dynamical systems, but the present singularity theory doesn't contain any analytical methods and results about it. As the complement to singularity theory and the first step to study on constrained bifurcations, here are given the transition sets and persistent perturbed bifurcation diagrams of 10 elementary bifurcation of codimension no more than three.

  15. Stochastic bifurcation and fractal and chaos control of a giant magnetostrictive film-shape memory alloy composite cantilever plate subjected to in-plane harmonic and stochastic excitation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhiwen, E-mail: zhuzhiwentju@163.com [Department of Mechanics, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Nonlinear Dynamics and Chaos Control, Tianjin 300072 (China); Zhang, Qingxin, E-mail: zqxfirst@163.com; Xu, Jia, E-mail: xujia-ld@163.com [Department of Mechanics, Tianjin University, Tianjin 300072 (China)

    2014-05-07

    Stochastic bifurcation and fractal and chaos control of a giant magnetostrictive film–shape memory alloy (GMF–SMA) composite cantilever plate subjected to in-plane harmonic and stochastic excitation were studied. Van der Pol items were improved to interpret the hysteretic phenomena of both GMF and SMA, and the nonlinear dynamic model of a GMF–SMA composite cantilever plate subjected to in-plane harmonic and stochastic excitation was developed. The probability density function of the dynamic response of the system was obtained, and the conditions of stochastic Hopf bifurcation were analyzed. The conditions of noise-induced chaotic response were obtained in the stochastic Melnikov integral method, and the fractal boundary of the safe basin of the system was provided. Finally, the chaos control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that stochastic Hopf bifurcation and chaos appear in the parameter variation process. The boundary of the safe basin of the system has fractal characteristics, and its area decreases when the noise intensifies. The system reliability was improved through stochastic optimal control, and the safe basin area of the system increased.

  16. Stochastic bifurcation and fractal and chaos control of a giant magnetostrictive film-shape memory alloy composite cantilever plate subjected to in-plane harmonic and stochastic excitation

    Science.gov (United States)

    Zhu, Zhiwen; Zhang, Qingxin; Xu, Jia

    2014-05-01

    Stochastic bifurcation and fractal and chaos control of a giant magnetostrictive film-shape memory alloy (GMF-SMA) composite cantilever plate subjected to in-plane harmonic and stochastic excitation were studied. Van der Pol items were improved to interpret the hysteretic phenomena of both GMF and SMA, and the nonlinear dynamic model of a GMF-SMA composite cantilever plate subjected to in-plane harmonic and stochastic excitation was developed. The probability density function of the dynamic response of the system was obtained, and the conditions of stochastic Hopf bifurcation were analyzed. The conditions of noise-induced chaotic response were obtained in the stochastic Melnikov integral method, and the fractal boundary of the safe basin of the system was provided. Finally, the chaos control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that stochastic Hopf bifurcation and chaos appear in the parameter variation process. The boundary of the safe basin of the system has fractal characteristics, and its area decreases when the noise intensifies. The system reliability was improved through stochastic optimal control, and the safe basin area of the system increased.

  17. HHM模型的多参数Hopf分岔分析%Multi-parameters Hopf-bifurcation of the HHM

    Institute of Scientific and Technical Information of China (English)

    王江; 耿建明; 费向阳

    2005-01-01

    现代科学证明,不少疾病都与生物细胞膜离子通道病变有关,表现为生物模型中相关参数的异常变化,这类疾病可归类为离子通道疾病.以肌肉中的Hodgkin-Huxley模型为研究对象,选取漏电导数和钠离子通道反电势作为分岔参数,分析其Hopf分岔并探讨分岔对HH模型的影响.采用高维方程的代数判据进行Hodgkin-Huxley模型多参数动态分岔分析,简化了分析过程.并用研究结果解释相应的生理过程,试图从生物系统动态过程异变的角度探讨生理疾病的成因.

  18. Bifurcation in Disease Dynamics with Latent Period of Infection and Media Awareness

    Science.gov (United States)

    Singh, Harkaran; Dhar, Joydip; Bhatti, Harbax Singh

    2016-06-01

    In the present study, an SIS epidemic model with a latent period of infection and media awareness as control strategy is proposed. The asymptotic stability of the model is studied for both disease-free equilibrium and endemic equilibrium states with respect to the basic reproduction number R0. It is observed that the coefficient of media awareness m does not affect R0, but significantly affects the level of endemic equilibrium. Further, the specific conditions for the existence of Hopf bifurcation have been obtained for the endemic equilibrium state. We also performed the sensitivity analysis of the basic reproduction number and state variables at endemic steady state with respect to the model parameter and identified the respective sensitive parameters. Numerical simulations have been presented in support of our analytic findings.

  19. Bifurcation Analysis and Dynamic Behaviour of an Inverted Pendulum with Bounded Control

    Science.gov (United States)

    Nikolov, Svetoslav; Nedev, Valentin

    2016-03-01

    This paper presents an investigation on the behaviour of con- ventional inverted pendulum with an inertia disk in its free extreme. The system is actuated by means of torques applied to the disk by a DC mo- tor, mounted on the pendulum's arm. Thus, the system is underactuated since the pendulum can rotate freely around its pivot point. The dynam- ical model is given with three ordinary nonlinear differential equations. Using Poincare-Andronov-Hopf's theory, we find a new analytical formula for the first Lyapunov's value at the boundary of stability. It enables one to study in detail the bifurcation behaviour of the above dynamic system. We check the validity of our analytical results on the first Lyapunov's value by numerical simulations. Hence, we find some new results.

  20. Asset Price Dynamics in a Chartist-Fundamentalist Model with Time Delays: A Bifurcation Analysis

    Directory of Open Access Journals (Sweden)

    Loretti I. Dobrescu

    2016-01-01

    Full Text Available This paper studies the dynamic behavior of asset prices using a chartist-fundamentalist model with two speculative markets. To this effect, we employ a differential system with delays à la Dibeh (2007 to describe the price dynamics and we assume that the two markets are coupled via diffusive coupling terms. We study two different time delay cases, namely, when both markets experience the same time delay and when the time delay is different across markets. First, we theoretically determine that the equilibrium exists and investigate its stability. Second, we establish the general conditions for the existence of local Hopf bifurcations and analyze their direction and stability. The common conclusion from both the delay scenarios we consider is that coupled speculative markets with heterogeneous agents in each, but with different price dynamics, can be synchronized through diffusive coupling. Finally, we provide some numerical illustrations to confirm our theoretical findings.

  1. ROBUST CONTROL OF PERIODIC BIFURCATION SOLUTIONS

    Institute of Scientific and Technical Information of China (English)

    梁建术; 陈予恕; 梁以德

    2004-01-01

    The topological bifurcation diagrams and the coefficients of bifurcation equation were obtained by C-L method.According to obtained bifurcation diagrams and combining control theory,the method of robust control of periodic bifurcation was presented,which differs from generic methods of bifurcation control.It can make the existing motion pattern into the goal motion pattern.Because the method does not make strict requirement about parametric values of the controller,it is convenient to design and make it.Numerical simulations verify validity of the method.

  2. Numerical bifurcation of Hamiltonian relative periodic orbits

    DEFF Research Database (Denmark)

    Wulff, Claudia; Schilder, Frank

    2009-01-01

    that the family of choreographies rotating around the $e^2$-axis bifurcates to the family of rotating choreographies that connects to the Lagrange relative equilibrium. Moreover, we compute several relative period-doubling bifurcations and a turning point of the family of planar rotating choreographies, which...... to symmetry-breaking/symmetry-increasing pitchfork bifurcations or to period-doubling/period-halving bifurcations. We apply our methods to the family of rotating choreographies which bifurcate from the famous figure eight solution of the three-body problem as angular momentum is varied. We find...

  3. Insight into Phenomena of Symmetry Breaking Bifurcation

    Institute of Scientific and Technical Information of China (English)

    FANG Tong; ZHANG Ying

    2008-01-01

    @@ We show that symmetry-breaking (SB) bifurcation is just a transition of different forms of symmetry, while still preserving system's symmetry. SB bifurcation always associates with a periodic saddle-node bifurcation, identifiable by a zero maximum of the top Lyapunov exponent of the system. In addition, we show a significant phase portrait of a newly born periodic saddle and its stable and unstable invariant manifolds, together with their neighbouring flow pattern of Poincaré mapping points just after the periodic saddle-node bifurcation, thus gaining an insight into the mechanism of SB bifurcation.

  4. Escape statistics for parameter sweeps through bifurcations.

    Science.gov (United States)

    Miller, Nicholas J; Shaw, Steven W

    2012-04-01

    We consider the dynamics of systems undergoing parameter sweeps through bifurcation points in the presence of noise. Of interest here are local codimension-one bifurcations that result in large excursions away from an operating point that is transitioning from stable to unstable during the sweep, since information about these "escape events" can be used for system identification, sensing, and other applications. The analysis is based on stochastic normal forms for the dynamic saddle-node and subcritical pitchfork bifurcations with a time-varying bifurcation parameter and additive noise. The results include formulation and numerical solution for the distribution of escape events in the general case and analytical approximations for delayed bifurcations for which escape occurs well beyond the corresponding quasistatic bifurcation points. These bifurcations result in amplitude jumps encountered during parameter sweeps and are particularly relevant to nano- and microelectromechanical systems, for which noise can play a significant role.

  5. Bifurcations analysis of turbulent energy cascade

    Energy Technology Data Exchange (ETDEWEB)

    Divitiis, Nicola de, E-mail: n.dedivitiis@gmail.com

    2015-03-15

    This note studies the mechanism of turbulent energy cascade through an opportune bifurcations analysis of the Navier–Stokes equations, and furnishes explanations on the more significant characteristics of the turbulence. A statistical bifurcations property of the Navier–Stokes equations in fully developed turbulence is proposed, and a spatial representation of the bifurcations is presented, which is based on a proper definition of the fixed points of the velocity field. The analysis first shows that the local deformation can be much more rapid than the fluid state variables, then explains the mechanism of energy cascade through the aforementioned property of the bifurcations, and gives reasonable argumentation of the fact that the bifurcations cascade can be expressed in terms of length scales. Furthermore, the study analyzes the characteristic length scales at the transition through global properties of the bifurcations, and estimates the order of magnitude of the critical Taylor-scale Reynolds number and the number of bifurcations at the onset of turbulence.

  6. Combinatorial Hopf algebraic description of the multiscale renormalization in quantum field theory

    CERN Document Server

    Krajewski, Thomas; Tanasa, Adrian

    2012-01-01

    We define in this paper several Hopf algebras describing the combinatorics of the so-called multi-scale renormalization in quantum field theory. After a brief recall of the main mathematical features of multi-scale renormalization, we define assigned graphs, that are graphs with appropriate decorations for the multi-scale framework. We then define Hopf algebras on these assigned graphs and on the Gallavotti-Nicol\\`o trees, particular class of trees encoding the supplementary informations of the assigned graphs. Several morphisms between these combinatorial Hopf algebras and the Connes-Kreimer algebra are given. Finally, scale dependent couplings are analyzed via this combinatorial algebraic setting.

  7. Differential and Twistor Geometry of the Quantum Hopf Fibration

    CERN Document Server

    Brain, Simon

    2011-01-01

    We study a quantum version of the SU(2) Hopf fibration $S^7 \\to S^4$ and its associated twistor geometry. Our quantum sphere $S^7_q$ arises as the unit sphere inside a q-deformed quaternion space $\\mathbb{H}^2_q$. The resulting four-sphere $S^4_q$ is a quantum analogue of the quaternionic projective space $\\mathbb{HP}^1$. The quantum fibration is endowed with compatible non-universal differential calculi. By investigating the quantum symmetries of the fibration, we obtain the geometry of the corresponding twistor space $\\mathbb{CP}^3_q$ and use it to study a system of anti-self-duality equations on $S^4_q$, for which we find an `instanton' solution coming from the natural projection defining the tautological bundle over $S^4_q$.

  8. Quasi-Hopf twistors for elliptic quantum groups

    CERN Document Server

    Jimbo, M; Odake, S; Shiraishi, J

    1997-01-01

    The Yang-Baxter equation admits two classes of elliptic solutions, the vertex type and the face type. On the basis of these solutions, two types of elliptic quantum groups have been introduced (Foda et al., Felder). Fronsdal made a penetrating observation that both of them are quasi-Hopf algebras, obtained by twisting the standard quantum affine algebra U_q(g). In this paper we present an explicit formula for the twistors in the form of an infinite product of the universal R matrix of U_q(g). We also prove the shifted cocycle condition for the twistors, thereby completing Fronsdal's findings. This construction entails that, for generic values of the deformation parameters, representation theory for U_q(g) carries over to the elliptic algebras, including such objects as evaluation modules, highest weight modules and vertex operators. In particular, we confirm the conjectures of Foda et al. concerning the elliptic algebra A_{q,p}(^sl_2).

  9. Structural Transition in Supercritical Fluids

    Directory of Open Access Journals (Sweden)

    Boris I. Sedunov

    2011-01-01

    Full Text Available The extension of the saturation curve ( on the PT diagram in the supercritical region for a number of monocomponent supercritical fluids by peak values for different thermophysical properties, such as heat capacities and and compressibility has been studied. These peaks signal about some sort of fluid structural transition in the supercritical region. Different methods give similar but progressively diverging curves st( for this transition. The zone of temperatures and pressures near these curves can be named as the zone of the fluid structural transition. The outstanding properties of supercritical fluids in this zone help to understand the physical sense of the fluid structural transition.

  10. Z3等变近Hamiltonian系统的极限环分支%Limit Cycles Bifurcated from a Z3- equivariant Near-Hamiltonian System

    Institute of Scientific and Technical Information of China (English)

    杨素敏

    2012-01-01

    The number of limit cycles of a Z3-equivariant cubic Hamiltonian system under Z3-equivariant quartic perturbations was studied using the methods of Hopf bifurcation theory. The results show that the perturbed system can have 6 small limit cycles.%在Z3等变四次扰动下,利用Hopf分支理论的方法,证明Z3等变Hamiltonian系统可以扰动出6个小振幅极限环.

  11. Bifurcations of Fibonacci generating functions

    Energy Technology Data Exchange (ETDEWEB)

    Ozer, Mehmet [Istanbul Kultur University, E5 Karayolu Uzeri Sirinevler, 34191 Istanbul (Turkey) and Semiconductor Physics Institute, LT-01108 and Vilnius Gediminas Technical University, Sauletekio 11, LT-10223 (Lithuania)]. E-mail: m.ozer@iku.edu.tr; Cenys, Antanas [Semiconductor Physics Institute, LT-01108 and Vilnius Gediminas Technical University, Sauletekio 11, LT-10223 (Lithuania); Polatoglu, Yasar [Istanbul Kultur University, E5 Karayolu Uzeri Sirinevler, 34191 Istanbul (Turkey); Hacibekiroglu, Guersel [Istanbul Kultur University, E5 Karayolu Uzeri Sirinevler, 34191 Istanbul (Turkey); Akat, Ercument [Yeditepe University, 26 Agustos Campus Kayisdagi Street, Kayisdagi 81120, Istanbul (Turkey); Valaristos, A. [Aristotle University of Thessaloniki, GR-54124, Thessaloniki (Greece); Anagnostopoulos, A.N. [Aristotle University of Thessaloniki, GR-54124, Thessaloniki (Greece)

    2007-08-15

    In this work the dynamic behaviour of the one-dimensional family of maps F{sub p,q}(x) = 1/(1 - px - qx {sup 2}) is examined, for specific values of the control parameters p and q. Lyapunov exponents and bifurcation diagrams are numerically calculated. Consequently, a transition from periodic to chaotic regions is observed at values of p and q, where the related maps correspond to Fibonacci generating functions associated with the golden-, the silver- and the bronze mean.

  12. Carnot群上的Hopf-Lax型公式%The Hopf-Lax Type Formula in Carnot Group

    Institute of Scientific and Technical Information of China (English)

    贾化冰; 徐伟

    2008-01-01

    文中研究了Hamilton-Jacobi方程ut+H(u,Du)=0,(p,t)∈G×(0,+∞),这里G是Carnot群,Du表示u的水平梯度.当函数H(γ,x)对变量,γ∈R是单调增的,而关于变量x∈Rm是凸的、径向且一阶齐次时,建立了该方程在有界连续初值u(p,0)=g(p)下有界粘性解的存在唯-性,其解由Hopf-Lax公式给出u(p,t)=min q∈G{h(p-1-p/t)vg(q)}其中函数h是由函数H(γ,X)关于变量X∈Rm的拟凸对偶提升到G上的,且关于Carnot-Caxathéodory距离是径向的.

  13. Bifurcations analysis of oscillating hypercycles.

    Science.gov (United States)

    Guillamon, Antoni; Fontich, Ernest; Sardanyés, Josep

    2015-12-21

    We investigate the dynamics and transitions to extinction of hypercycles governed by periodic orbits. For a large enough number of hypercycle species (n>4) the existence of a stable periodic orbit has been previously described, showing an apparent coincidence of the vanishing of the periodic orbit with the value of the replication quality factor Q where two unstable (non-zero) equilibrium points collide (named QSS). It has also been reported that, for values below QSS, the system goes to extinction. In this paper, we use a suitable Poincaré map associated to the hypercycle system to analyze the dynamics in the bistability regime, where both oscillatory dynamics and extinction are possible. The stable periodic orbit is identified, together with an unstable periodic orbit. In particular, we are able to unveil the vanishing mechanism of the oscillatory dynamics: a saddle-node bifurcation of periodic orbits as the replication quality factor, Q, undergoes a critical fidelity threshold, QPO. The identified bifurcation involves the asymptotic extinction of all hypercycle members, since the attractor placed at the origin becomes globally stable for values Qbifurcation, these extinction dynamics display a periodic remnant that provides the system with an oscillating delayed transition. Surprisingly, we found that the value of QPO is slightly higher than QSS, thus identifying a gap in the parameter space where the oscillatory dynamics has vanished while the unstable equilibrium points are still present. We also identified a degenerate bifurcation of the unstable periodic orbits for Q=1.

  14. Hopf algebras of rooted forests, cocyles, and free Rota-Baxter algebras

    Science.gov (United States)

    Zhang, Tianjie; Gao, Xing; Guo, Li

    2016-10-01

    The Hopf algebra and the Rota-Baxter algebra are the two algebraic structures underlying the algebraic approach of Connes and Kreimer to renormalization of perturbative quantum field theory. In particular, the Hopf algebra of rooted trees serves as the "baby model" of Feynman graphs in their approach and can be characterized by certain universal properties involving a Hochschild 1-cocycle. Decorated rooted trees have also been applied to study Feynman graphs. We will continue the study of universal properties of various spaces of decorated rooted trees with such a 1-cocycle, leading to the concept of a cocycle Hopf algebra. We further apply the universal properties to equip a free Rota-Baxter algebra with the structure of a cocycle Hopf algebra.

  15. KEGEL'S THEOREM OVER WEAK HOPF GROUP COALGEBRAS%弱Hopf群余代数Kegel定理

    Institute of Scientific and Technical Information of China (English)

    周璇; 杨涛

    2013-01-01

    In this article,we consider the left weak π-H-comodule algebra for a cotriangular weak Hopf π-coalgebra H.By constructing the derived π-σ-Lie algebra for a left weak π-H-comodule algebra,we obtain the Kegel's theorem over weak Hopf π-coalgebras,which generalizes the results in paper [4].%本文研究了余三角弱Hopfπ-余代数H的左弱π-H-余模代数.通过构造左弱π-H-余模代数的导出π-σ-李代数,得到了弱Hopf π-余代数Kegel定理,推广了文献[4]的结果.

  16. Supercritical solvent coal extraction

    Science.gov (United States)

    Compton, L. E. (Inventor)

    1984-01-01

    Yields of soluble organic extract are increased up to about 50% by the supercritical extraction of particulate coal at a temperature below the polymerization temperature for coal extract fragments (450 C.) and a pressure from 500 psig to 5,000 psig by the conjoint use of a solvent mixture containing a low volatility, high critical temperature coal dissolution catalyst such as phenanthrene and a high volatility, low critical temperature solvent such as toluene.

  17. Differential Hopf algebra structures on the universal enveloping algebra of a lie algebra

    OpenAIRE

    Hijligenberg, van den, N.W.; Martini, R.

    1995-01-01

    We discuss a method to construct a De Rham complex (differential algebra) of Poincar'e-Birkhoff-Witt-type on the universal enveloping algebra of a Lie algebra $g$. We determine the cases in which this gives rise to a differential Hopf algebra that naturally extends the Hopf algebra structure of $U(g)$. The construction of such differential structures is interpreted in terms of colour Lie superalgebras.

  18. 一类具有周期扰动的向日葵方程的次调和分支%Subharmonic Bifurcation of a Sunflower Equation with Periodic Perturbations

    Institute of Scientific and Technical Information of China (English)

    殷红燕

    2012-01-01

    研究了一类具有周期扰动的向日葵方程,讨论了在系统的扰动频率与Hopf分支固有频率为二阶次调和共振的情形下,次调和分支解的存在性,并且讨论了其稳定性.%In this paper, a Sunflower equation with periodic perturbations is studied. In particular, the existence of subharmonic bifurcation solution is discussed under the condition that excitation frequency and the critical natural frequency of Hopf bifurcation are two-order subharmonic resonance. Furthermore, the stability of subharmonie bifurcation solution is also discussed.

  19. Bifurcations in the response of a flexible rotor in squeeze-film dampers with retainer springs

    Energy Technology Data Exchange (ETDEWEB)

    Inayat-Hussain, Jawaid I. [School of Engineering, Monash University Malaysia, No. 2, Jalan Kolej, Bandar Sunway, 46150 Petaling Jaya, Selangor Darul Ehsan (Malaysia)], E-mail: jawaid.inayat-hussain@eng.monash.edu.my

    2009-01-30

    Squeeze-film dampers are commonly used in conjunction with rolling-element or hydrodynamic bearings in rotating machinery. Although these dampers serve to provide additional damping to the rotor-bearing system, there have however been some cases of rotors mounted in these dampers exhibiting non-linear behaviour. In this paper a numerical study is undertaken to determine the effects of design parameters, i.e., gravity parameter, W, mass ratio, {alpha}, and stiffness ratio, K, on the bifurcations in the response of a flexible rotor mounted in squeeze-film dampers with retainer springs. The numerical simulations were undertaken for a range of speed parameter, {omega}, between 0.1 and 5.0. Numerical results showed that increasing K causes the onset speed of bifurcation to increase, whilst an increase of {alpha} reduces the onset speed of bifurcation. For a specific combination of K and {alpha} values, the onset speed of bifurcation appeared to be independent of W. The instability of the rotor response at this onset speed was due to a saddle-node bifurcation for all the parameter values investigated in this work with the exception of the combination of {alpha} = 0.1 and K = 0.5, where a secondary Hopf bifurcation was observed. The speed range of non-synchronous response was seen to decrease with the increase of {alpha}; in fact non-synchronous rotor response was totally absent for {alpha}=0.4. With the exception of the case {alpha} = 0.1, the speed range of non-synchronous response was also seen to decrease with the increase of K. Multiple responses of the rotor were observed at certain values of {omega} for various combinations of parameters W, {alpha} and K, where, depending on the values of the initial conditions the rotor response could be either synchronous or quasi-periodic. The numerical results presented in this work were obtained for an unbalance parameter, U, value of 0.1, which is considered as the upper end of the normal unbalance range of most practical

  20. Einstein's Field Equations as a Fold Bifurcation

    CERN Document Server

    Kohli, Ikjyot Singh

    2016-01-01

    It is shown that Einstein's field equations for \\emph{all} perfect-fluid $k=0$ FLRW cosmologies have the same form as the topological normal form of a fold bifurcation. In particular, we assume that the cosmological constant is a bifurcation parameter, and as such, fold bifurcation behaviour is shown to occur in a neighbourhood of Minkowski spacetime in the phase space. We show that as this cosmological constant parameter is varied, an expanding and contracting de Sitter universe \\emph{emerge} via this bifurcation.

  1. Thermodynamic behaviour of supercritical matter.

    Science.gov (United States)

    Bolmatov, Dima; Brazhkin, V V; Trachenko, K

    2013-01-01

    Since their discovery in 1822, supercritical fluids have been of enduring interest and have started to be deployed in many important applications. Theoretical understanding of the supercritical state is lacking and is seen to limit further industrial deployment. Here we study thermodynamic properties of the supercritical state and discover that specific heat shows a crossover between two different regimes, an unexpected result in view of currently perceived homogeneity of supercritical state in terms of physical properties. We subsequently formulate a theory of system thermodynamics above the crossover, and find good agreement between calculated and experimental specific heat with no free-fitting parameters. In this theory, energy and heat capacity are governed by the minimal length of the longitudinal mode in the system only, and do not explicitly depend on system-specific structure and interactions. We derive a power law and analyse supercritical scaling exponents in the system above the Frenkel line.

  2. Bifurcation analysis of oscillating network model of pattern recognition in the rabbit olfactory bulb

    Science.gov (United States)

    Baird, Bill

    1986-08-01

    A neural network model describing pattern recognition in the rabbit olfactory bulb is analysed to explain the changes in neural activity observed experimentally during classical Pavlovian conditioning. EEG activity recorded from an 8×8 arry of 64 electrodes directly on the surface on the bulb shows distinct spatial patterns of oscillation that correspond to the animal's recognition of different conditioned odors and change with conditioning to new odors. The model may be considered a variant of Hopfield's model of continuous analog neural dynamics. Excitatory and inhibitory cell types in the bulb and the anatomical architecture of their connection requires a nonsymmetric coupling matrix. As the mean input level rises during each breath of the animal, the system bifurcates from homogenous equilibrium to a spatially patterned oscillation. The theory of multiple Hopf bifurcations is employed to find coupled equations for the amplitudes of these unstable oscillatory modes independent of frequency. This allows a view of stored periodic attractors as fixed points of a gradient vector field and thereby recovers the more familiar dynamical systems picture of associative memory.

  3. Bifurcation characteristics and safe basin of MSMA microgripper subjected to stochastic excitation

    Directory of Open Access Journals (Sweden)

    Z. W. Zhu

    2015-02-01

    Full Text Available A kind of magnetic shape memory alloy (MSMA microgripper is proposed in this paper, and its nonlinear dynamic characteristics are studied when the stochastic perturbation is considered. Nonlinear differential items are introduced to explain the hysteretic phenomena of MSMA, and the constructive relationships among strain, stress, and magnetic field intensity are obtained by the partial least-square regression method. The nonlinear dynamic model of a MSMA microgripper subjected to in-plane stochastic excitation is developed. The stationary probability density function of the system’s response is obtained, the transition sets of the system are determined, and the conditions of stochastic bifurcation are obtained. The homoclinic and heteroclinic orbits of the system are given, and the boundary of the system’s safe basin is obtained by stochastic Melnikov integral method. The numerical and experimental results show that the system’s motion depends on its parameters, and stochastic Hopf bifurcation appears in the variation of the parameters; the area of the safe basin decreases with the increase of the stochastic excitation, and the boundary of the safe basin becomes fractal. The results of this paper are helpful for the application of MSMA microgripper in engineering fields.

  4. Bifurcation characteristics and safe basin of MSMA microgripper subjected to stochastic excitation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Z. W., E-mail: zhuzhiwen@tju.edu.cn; Li, X. M., E-mail: lixinmiaotju@163.com [Department of Mechanics, Tianjin University, Tianjin 300072 (China); Xu, J., E-mail: xujia-ld@163.com [Department of Mechanics, Tianjin University, Tianjin 300072 (China); Tianjin Key Laboratory of Nonlinear Dynamics and Chaos Control, Tianjin 300072 (China)

    2015-02-15

    A kind of magnetic shape memory alloy (MSMA) microgripper is proposed in this paper, and its nonlinear dynamic characteristics are studied when the stochastic perturbation is considered. Nonlinear differential items are introduced to explain the hysteretic phenomena of MSMA, and the constructive relationships among strain, stress, and magnetic field intensity are obtained by the partial least-square regression method. The nonlinear dynamic model of a MSMA microgripper subjected to in-plane stochastic excitation is developed. The stationary probability density function of the system’s response is obtained, the transition sets of the system are determined, and the conditions of stochastic bifurcation are obtained. The homoclinic and heteroclinic orbits of the system are given, and the boundary of the system’s safe basin is obtained by stochastic Melnikov integral method. The numerical and experimental results show that the system’s motion depends on its parameters, and stochastic Hopf bifurcation appears in the variation of the parameters; the area of the safe basin decreases with the increase of the stochastic excitation, and the boundary of the safe basin becomes fractal. The results of this paper are helpful for the application of MSMA microgripper in engineering fields.

  5. Integrable Hopf twists, marginal deformations and generalised geometry

    CERN Document Server

    Dlamini, Hector

    2016-01-01

    We study the symmetries of an N=1 superconformal marginal deformation of the N=4 SYM theory which depends on a real parameter w. It is a special case of the two-complex-parameter Leigh-Strassler family of superconformal deformations of N=4 SYM, which is one-loop planar-integrable. On the gauge theory side of the AdS/CFT correspondence, we construct the Hopf twist leading to the deformed global symmetry of the theory and use it to define a star product between its three scalar superfields. Turning to the gravity side of the correspondence, we adapt the above star product to deform the pure spinors of six-dimensional flat space in its generalised geometry description. This leads us to a new N=2 NS-NS solution of IIB supergravity. Starting from this precursor solution, adding D3-branes and taking the near-horizon limit leads us to an exact AdS_5x(S^5)_w solution which we conjecture to be the gravity dual of the w-deformed gauge theory. Unlike the dual to the beta-deformed Leigh-Strassler theory, the internal par...

  6. Lie Symmetry Analysis of the Hopf Functional-Differential Equation

    Directory of Open Access Journals (Sweden)

    Daniel D. Janocha

    2015-08-01

    Full Text Available In this paper, we extend the classical Lie symmetry analysis from partial differential equations to integro-differential equations with functional derivatives. We continue the work of Oberlack and Wacławczyk (2006, Arch. Mech. 58, 597, (2013, J. Math. Phys. 54, 072901, where the extended Lie symmetry analysis is performed in the Fourier space. Here, we introduce a method to perform the extended Lie symmetry analysis in the physical space where we have to deal with the transformation of the integration variable in the appearing integral terms. The method is based on the transformation of the product y(xdx appearing in the integral terms and applied to the functional formulation of the viscous Burgers equation. The extended Lie symmetry analysis furnishes all known symmetries of the viscous Burgers equation and is able to provide new symmetries associated with the Hopf formulation of the viscous Burgers equation. Hence, it can be employed as an important tool for applications in continuum mechanics.

  7. 具有时滞的非线性纵向飞行模型稳定性和分支分析%Stability and bifurcation analysis of nonlinear model for longitudinal motion with time delay

    Institute of Scientific and Technical Information of China (English)

    范丽; 史忠科

    2013-01-01

      研究一类具有时滞的非线性飞行模型的稳定性和分支问题。首先考虑数据测量的时间延迟,给出了含时滞的大迎角纵向多项式飞行模型;然后应用泛函微分方程Hopf分支理论和中心流形等非线性方法给出了该模型稳定性和分支的解析分析,得到了由时滞引起的Hopf分支存在条件、分支点计算公式以及分支周期解的稳定性判别准则;最后利用所得结论进行了飞行实例分析,分析结果表明,数据测量延时可能会引起飞行稳定性的改变,而且延时超过一定临界值时将产生Hopf分支,出现纵向周期振荡,其结论具有实际参考意义。%  The stability and bifurcations of a nonlinear flight system with time delay are investigated. Firstly, considering the time delay in measurement of angle of attack, a polynomial differential system with time delay for aircraft longitudinal motion is suggested. Then by applying Hopf bifurcation and center manifold theories of functional differential equations, the stability and bifurcations of the time-delayed system are studied analytically, and existence conditions for Hopf bifurcations as well as formulas for calculating bifurcation points and stability of the bifurcation limit cycle are derived. Finally, the theoretical conclusions are applied to analyze a practical example of high angle-of-attack flight. The results show that the delay in the measurement of angle of attack can cause instability, moreover, the Hopf bifurcation occurs and the periodic oscillation of longitudinal direction arises when the measurement delay exceeds the critical value. The conclusion has the reference significance in practice.

  8. Bifurcations of optimal vector fields: an overview

    NARCIS (Netherlands)

    Kiseleva, T.; Wagener, F.; Rodellar, J.; Reithmeier, E.

    2009-01-01

    We develop a bifurcation theory for the solution structure of infinite horizon optimal control problems with one state variable. It turns out that qualitative changes of this structure are connected to local and global bifurcations in the state-costate system. We apply the theory to investigate an

  9. Perturbed bifurcations in the BCS gap equation

    DEFF Research Database (Denmark)

    Spathis, P. N.; Sørensen, Mads Peter; Lazarides, Nickos

    1992-01-01

    . The transitions from d- or s- to mixed s- and d-wave solutions result from pitchfork bifurcations. In the case of slightly different pairing strength in the x and y directions, perturbed pitchfork bifurcations emerge, leading to a dramatic change in the physical properties of the superconducting state....

  10. BIFURCATION IN PRESCRIBED MEAN CURVATURE PROBLEM

    Institute of Scientific and Technical Information of China (English)

    马力

    2002-01-01

    This paper discusses the existence problem in the study of some partial differential equations. The author gets some bifurcation on the prescribed mean curvature problem on the unit ball, the scalar curvature problem on the n-sphere, and some field equations. The author gives some natural conditions such that the standard bifurcation or Thom-Mather theory can be used.

  11. Local and Global Bifurcations With Nonhyperbolic Equilibria

    Institute of Scientific and Technical Information of China (English)

    孙建华; 罗定军

    1994-01-01

    The normal forms of coupling functions governing local and global bifurcations are studied for a generic (d+1) -parameter family of three-dimensional systems with a heteroclinic orbit connecting a hyperbolic saddle and a nonhyperbolic equilibrium occurring in the saddle-node,transcritical and pitchfork bifurcations,respectively.Singularity theory and a version of Melnikov function are used in this paper.

  12. Corrosion in supercritical fluids

    Energy Technology Data Exchange (ETDEWEB)

    Propp, W.A.; Carleson, T.E.; Wai, Chen M.; Taylor, P.R.; Daehling, K.W.; Huang, Shaoping; Abdel-Latif, M.

    1996-05-01

    Integrated studies were carried out in the areas of corrosion, thermodynamic modeling, and electrochemistry under pressure and temperature conditions appropriate for potential applications of supercritical fluid (SCF) extractive metallurgy. Carbon dioxide and water were the primary fluids studied. Modifiers were used in some tests; these consisted of 1 wt% water and 10 wt% methanol for carbon dioxide and of sulfuric acid, sodium sulfate, ammonium sulfate, and ammonium nitrate at concentrations ranging from 0.00517 to 0.010 M for the aqueous fluids. The materials studied were Types 304 and 316 (UNS S30400 and S31600) stainless steel, iron, and AISI-SAE 1080 (UNS G10800) carbon steel. The thermodynamic modeling consisted of development of a personal computer-based program for generating Pourbaix diagrams at supercritical conditions in aqueous systems. As part of the model, a general method for extrapolating entropies and related thermodynamic properties from ambient to SCF conditions was developed. The experimental work was used as a tool to evaluate the predictions of the model for these systems. The model predicted a general loss of passivation in iron-based alloys at SCF conditions that was consistent with experimentally measured corrosion rates and open circuit potentials. For carbon-dioxide-based SCFs, measured corrosion rates were low, indicating that carbon steel would be suitable for use with unmodified carbon dioxide, while Type 304 stainless steel would be suitable for use with water or methanol as modifiers.

  13. Voltage stability, bifurcation parameters and continuation methods

    Energy Technology Data Exchange (ETDEWEB)

    Alvarado, F.L. [Wisconsin Univ., Madison, WI (United States)

    1994-12-31

    This paper considers the importance of the choice of bifurcation parameter in the determination of the voltage stability limit and the maximum power load ability of a system. When the bifurcation parameter is power demand, the two limits are equivalent. However, when other types of load models and bifurcation parameters are considered, the two concepts differ. The continuation method is considered as a method for determination of voltage stability margins. Three variants of the continuation method are described: the continuation parameter is the bifurcation parameter the continuation parameter is initially the bifurcation parameter, but is free to change, and the continuation parameter is a new `arc length` parameter. Implementations of voltage stability software using continuation methods are described. (author) 23 refs., 9 figs.

  14. Twisted and Nontwisted Bifurcations Induced by Diffusion

    CERN Document Server

    Lin, X B

    1996-01-01

    We discuss a diffusively perturbed predator-prey system. Freedman and Wolkowicz showed that the corresponding ODE can have a periodic solution that bifurcates from a homoclinic loop. When the diffusion coefficients are large, this solution represents a stable, spatially homogeneous time-periodic solution of the PDE. We show that when the diffusion coefficients become small, the spatially homogeneous periodic solution becomes unstable and bifurcates into spatially nonhomogeneous periodic solutions. The nature of the bifurcation is determined by the twistedness of an equilibrium/homoclinic bifurcation that occurs as the diffusion coefficients decrease. In the nontwisted case two spatially nonhomogeneous simple periodic solutions of equal period are generated, while in the twisted case a unique spatially nonhomogeneous double periodic solution is generated through period-doubling. Key Words: Reaction-diffusion equations; predator-prey systems; homoclinic bifurcations; periodic solutions.

  15. Crisis bifurcations in plane Poiseuille flow.

    Science.gov (United States)

    Zammert, Stefan; Eckhardt, Bruno

    2015-04-01

    Many shear flows follow a route to turbulence that has striking similarities to bifurcation scenarios in low-dimensional dynamical systems. Among the bifurcations that appear, crisis bifurcations are important because they cause global transitions between open and closed attractors, or indicate drastic increases in the range of the state space that is covered by the dynamics. We here study exterior and interior crisis bifurcations in direct numerical simulations of transitional plane Poiseuille flow in a mirror-symmetric subspace. We trace the state space dynamics from the appearance of the first three-dimensional exact coherent structures to the transition from an attractor to a chaotic saddle in an exterior crisis. For intermediate Reynolds numbers, the attractor undergoes several interior crises, in which new states appear and intermittent behavior can be observed. The bifurcations contribute to increasing the complexity of the dynamics and to a more dense coverage of state space.

  16. INFLUENCE OF ELECTRICAL AND STRUCTURAL PARAMETERS ON THE PERFORMANCE OF THE SPACERS IN HOPFED

    Institute of Scientific and Technical Information of China (English)

    Zhong Xuefei; Wilbert van der Poel; Daniel den Engelsen; Yin Hanchun

    2006-01-01

    The HOPping Field Emission Display (HOPFED) is a new architecture for field emission displays.The main difference between a conventional Field Emission Display (FED) device and a HOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance of a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension,the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer's layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.

  17. 具有leakage时滞与传输时滞的神经网络的分支%Bifurcation of a Two-Neuron Network with Time Delay in the Leakage Terms

    Institute of Scientific and Technical Information of China (English)

    李哲; 徐瑞

    2014-01-01

    The Hopf bifurcation of a two-neuron network with two time delays in the leakage terms and activation functions is investigated.By choosing the leakage delay and discrete delay as the bifurcation parameter respectively,we prove that the system is locally asymptotically stable in a range of the time delay and Hopf bifurcation occurs as the time delay crosses a critical value.Fi-nally,two examples are given to illustrate the theoretical results.%研究一类具有 leakage时滞与传输时滞的两神经元神经网络的分支,分别以 leakage时滞和传输时滞为分支参数,通过对模型对应的特征方程进行分析,得到出现 Hopf分支的临界性条件,并通过数值例子验证该理论结果。

  18. ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION

    Science.gov (United States)

    This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. This information is provided to assist remedial project managers, contractors...

  19. Hero's journey in bifurcation diagram

    Science.gov (United States)

    Monteiro, L. H. A.; Mustaro, P. N.

    2012-06-01

    The hero's journey is a narrative structure identified by several authors in comparative studies on folklore and mythology. This storytelling template presents the stages of inner metamorphosis undergone by the protagonist after being called to an adventure. In a simplified version, this journey is divided into three acts separated by two crucial moments. Here we propose a discrete-time dynamical system for representing the protagonist's evolution. The suffering along the journey is taken as the control parameter of this system. The bifurcation diagram exhibits stationary, periodic and chaotic behaviors. In this diagram, there are transition from fixed point to chaos and transition from limit cycle to fixed point. We found that the values of the control parameter corresponding to these two transitions are in quantitative agreement with the two critical moments of the three-act hero's journey identified in 10 movies appearing in the list of the 200 worldwide highest-grossing films.

  20. Nonassociative geometry in quasi-Hopf representation categories I: Bimodules and their internal homomorphisms

    CERN Document Server

    Barnes, Gwendolyn E; Szabo, Richard J

    2014-01-01

    We systematically study noncommutative and nonassociative algebras A and their bimodules as algebras and bimodules internal to the representation category of a quasitriangular quasi-Hopf algebra. We enlarge the morphisms of the monoidal category of A-bimodules by internal homomorphisms, and describe explicitly their evaluation and composition morphisms. For braided commutative algebras A the full subcategory of symmetric A-bimodule objects is a braided closed monoidal category, from which we obtain an internal tensor product operation on internal homomorphisms. We describe how these structures deform under cochain twisting of the quasi-Hopf algebra, and apply the formalism to the example of deformation quantization of equivariant vector bundles over a smooth manifold. Our constructions set up the basic ingredients for the systematic development of differential geometry internal to the quasi-Hopf representation category, which will be tackled in the sequels to this paper, together with applications to models o...