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  • Articles  (38)
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Journal
  • 1
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of natural products 48 (1985), S. 669-669 
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 52 (1984), S. 41-50 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The stability of a uniform cantilever column supported by a Maxwell type viscoelastic foundation and subjected to a constant tangential force is investigated. Stability conditions are obtained for the entire range of system parameters through an application of Routh-Hurwitz criteria. Unlike the case of conservative loading, the Maxwell foundation is shown to produce a stabilizing effect on this nonconservative problem. Furthermore, an optimum combination of foundation parameters exist to yield the maximum flutter load. An approximate analysis is also presented through an application of the Galerkin's method. It is shown that a two-term approximation may not be adequate to yield meaning-ful results in a certain range of system parameters.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Zeitschrift für angewandte Mathematik und Physik 27 (1976), S. 607-612 
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Zusammenfassung Die asymptotischen Stabilitätsresultate von Prichard für die Benard-und Taylor-Probleme, die mit Hilfe der Liapunov-Movchan-Theorie erhalten worden sind, werden durch Ungleichungen und Methoden der Variationsrechnung optimiert. Die Aequivalenz zwischen diesem Resultat und dem Ergebnis der Energiemethode wird nachgewiesen. Mögliche Anwendungen werden diskutiert, die sich auf die Symmetrie der Operatoren beziehen.
    Notes: Abstract The asymptotic stability result obtained by Pritchard for the Benard and Taylor problems employing the Liapunov-Movchan theory is optimized by using inequalities and variational techniques. The equivalence between this result and the one obtained by the energy theory is demonstrated. Future applications as related to the symmetry of the operators are discussed.
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  • 5
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archive of applied mechanics 62 (1992), S. 347-360 
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Übersicht Es wird ein neues Berechnungsverfahren für die Stabilitätsanalyse schlanker Stäbe mit veränderlichem Querschnitt unter allgemeinen Belastungen vorgestellt. Dabei werden die abhängigen Variablen und die variablen Koeffizienten der Bestimmungsgleichung in eine endliche Reihe von Tschebyscheff-Polynomen entwickelt. Die wesentliche Eigenschaft dieses Verfahrens ist die Reduzierung des ursprünglichen Randwertproblems einer Differentialgleichung auf ein algebraisches Eigenwertproblem. Angewandt wird die vorgeschlagene Methode auf die Euler-Knickung und das Flatterverhalten eines Kragträgers unter tangentialer Folgelast als konstanter Streckenlast. Die numerischen Ergebnisse nach diesem Verfahren erweisen sich als sehr genau im Vergleich zu Ergebnissen anderer Methoden, die in der Literatur zu finden sind. Es wird gezeigt, daß bei dieser Methode auch symbolische Lösungsverfahren angewandt werden können. Der Vorzug dieser neuen Methode gegenüber den Standard-Lösungsverfahren wie Finite-Differenzen- und Galerkin-Verfahren wird diskutiert.
    Notes: Summary A new computational technique for the stability analysis of slender rods with variable cross-sections under general loading conditions is presented. In this approach, the dependent variable and the variable coefficients appearing in the governing equations are expanded in a finite series of Chebyshev polynomials. The main feature of this technique is that the original boundary value problem associated with the differential equation is reduced to an algebraic eigenvalue problem. The proposed technique is applied to study the static buckling of Euler column and the flutter behavior of a cantilever column subjected to uniformly distributed tangential loading. The numerical results from the suggested technique are found to be extremely accurate when compared to other techniques available in literature. It is shown that this approach can also be employed in a symbolic form. The merits of the present method in comparison to the standard solution procedures like finite difference and Galerkin methods are discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 23 (2000), S. 35-55 
    ISSN: 1573-269X
    Keywords: normal forms ; time-periodic systems ; Liapunov–Floquet transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The structure of time-dependent resonances arising in themethod of time-dependent normal forms (TDNF) for one andtwo-degrees-of-freedom nonlinear systems with time-periodic coefficientsis investigated. For this purpose, the Liapunov–Floquet (L–F)transformation is employed to transform the periodic variationalequations into an equivalent form in which the linear system matrix istime-invariant. Both quadratic and cubic nonlinearities are investigatedand the associated normal forms are presented. Also, higher-orderresonances for the single-degree-of-freedom case are discussed. It isdemonstrated that resonances occur when the values of the Floquet multipliers result in MT-periodic (M = 1, 2,...) solutions. The discussion is limited to the Hamiltonian case (which encompasses allpossible resonances for one-degree-of-freedom). Furthermore, it is alsoshown how a recent symbolic algorithm for computing stability andbifurcation boundaries for time-periodic systems may also be employed tocompute the time-dependent resonance sets of zero measure in theparameter space. Unlike classical asymptotic techniques, this method isfree from any small parameter restriction on the time-periodic term inthe computation of the resonance sets. Two illustrative examples (oneand two-degrees-of-freedom) are included.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 16 (1998), S. 203-221 
    ISSN: 1573-269X
    Keywords: Time-periodic systems ; nonlinear ; time-invariant forms ; critical systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this study dynamically equivalent time-invariant forms are obtained for linear and non-linear systems with periodically varying coefficients via Lyapunov–Floquet (L–F) transformation. These forms are equivalent in the sense that the local stability and bifurcation characteristics are identical for both systems in the entire parameter space. It is well known that the L–F transformation converts a linear periodic first order system into a time-invariant one. In the first part of this study a set of linear second order periodic equations is converted into an equivalent set of time-independent second order equations through a sequence of linear transformations. Then the transformations are applied to a time-periodic quadratic Hamiltonian to obtain its equivalent time-invariant form. In the second part, time-invariant forms of nonlinear equations are studied. The application of L–F transformation to a quasi-linear periodic equation converts the linear part to a time-invariant form and leaves the non-linear part with time-periodic coefficients. Dynamically equivalent time-invariant forms are obtained via time-periodic center manifold reduction and time-dependent normal form theory. Such forms are constructed for general hyperbolic systems and for some simple critical cases, including that of one zero eigenvalue and a purely imaginary pair. As a physical example of these techniques, a single and a double inverted pendulum subjected to periodic parametric excitation are considered. The results thus obtained are verified by numerical simulation.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 17 (1998), S. 1-21 
    ISSN: 1573-269X
    Keywords: Symbolic computation ; stability ; bifurcation ; nonlinear ; time-periodic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A new technique is presented for symbolic computation of local stability boundaries and bifurcation surfaces for nonlinear multidimensional time-periodic dynamical systems as an explicit function of the system parameters. This is made possible by the recent development of a symbolic computational algorithm for approximating the parameter-dependent fundamental solution matrix of linear time-periodic systems. By evaluating this matrix at the end of the principal period, the parameter-dependent Floquet Transition Matrix (FTM), or the linear part of the Poincaré map, is obtained. The subsequent use of well-known criteria for the local stability and bifurcation conditions of equilibria and periodic solutions enables one to obtain the equations for the bifurcation surfaces in the parameter space as polynomials of the system parameters. Further, the method may be used in conjunction with a series expansion to obtain perturbation-like expressions for the bifurcation boundaries. Because this method is not based on expansion in terms of a small parameter, it can be successfully applied to periodic systems whose internal excitation is strong. Also, the proposed method appears to be more efficient in terms of cpu time than the truncated point mapping method. Two illustrative example problems, viz., a parametrically excited simple pendulum and a double inverted pendulum subjected to a periodic follower force, are included.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Nonlinear dynamics 8 (1995), S. 21-43 
    ISSN: 1573-269X
    Keywords: Nonlinear dynamic systems ; parametric excitation ; bifurcation ; time-periodic systems ; critical cases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this study a new procedure for analysis of nonlinear dynamical systems with periodically varying parameters under critical conditions is presented through an application of the Liapunov-Floquet (L-F) transformation. The L-F transformation is obtained by computing the state transition matrix associated with the linear part of the problem. The elements of the state transition matrix are expressed in terms of Chebyshev polynomials in timet which is suitable for algebraic manipulations. Application of Floquet theory and the eigen-analysis of the state transition matrix at the end of one principal period provides the L-F transformation matrix in terms of the Chebyshev polynomials. Since this is a periodic matrix, the L-F transformation matrix has a Fourier representation. It is well known that such a transformation converts a linear periodic system into a linear time-invariant one. When applied to quasi-linear equations with periodic coefficients, a dynamically similar system is obtained whose linear part is time-invariant and the nonlinear part consists of coefficients which are periodic. Due to this property of the L-F transformation, a periodic orbit in original coordinates will have a fixed point representation in the transformed coordinates. In this study, the bifurcation analysis of the transformed equations, obtained after the application of the L-F transformation, is conducted by employingtime-dependent center manifold reduction andtime-dependent normal form theory. The above procedures are analogous to existing methods that are employed in the study of bifurcations of autonomous systems. For the two physical examples considered, the three generic codimension one bifurcations namely, Hopf, flip and fold bifurcations are analyzed. In the first example, the primary bifurcations of a parametrically excited single degree of freedom pendulum is studied. As a second example, a double inverted pendulum subjected to a periodic loading which undergoes Hopf or flip bifurcation is analyzed. The methodology is semi-analytic in nature and provides quantitative measure of stability when compared to point mappings method. Furthermore, the technique is applicable also to those systems where the periodic term of the linear part does not contain a small parameter which is certainly not the case with perturbation or averaging methods. The conclusions of the study are substantiated by numerical simulations. It is believed that analysis of this nature has been reported for the first time for this class of systems.
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