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Boundedness
Selected AbstractsIntelligent control using multiple neural networksINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2003Lingji Chen Abstract In this paper a framework for intelligent control is established to adaptively control a class of non-linear discrete-time dynamical systems while assuring boundedness of signals. A linear robust adaptive controller and multiple non-linear neural network based adaptive controllers are used, and a switching law is suitably defined to switch between them, based upon their performances in predicting the plant output. Boundedness of signals is established with minimum requirements on the parameter adjustment mechanisms of the neural network controllers, and thus the latter can be used in novel ways to better detect changes in the system being controlled, and to initiate fast adaptation. Simulation studies show the effectiveness of the proposed approach. Copyright © 2003 John Wiley & Sons, Ltd. [source] Boundedness in Lurie system with stiffening nonlinearitiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 6 2008Abdallah Ben Abdallah Abstract In this paper, we deal with the problem of boundedness of solutions in single-input single-output Lurie system. We prove the boundedness of solutions from the stability of zero dynamics under a restriction on the nonlinearity. The linear block is supposed to be of relative degree one or two, stabilizable by high-gain output feedback and not necessary minimum phase. The nonlinearity is required to have the stiffening property. Copyright © 2007 John Wiley & Sons, Ltd. [source] An integral formulation procedure for the solutions to Helmholtz's equation in spherically symmetric mediaMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2010Giacomo Caviglia Abstract Starting from Helmholtz's equation in inhomogeneous media, the associated radial second-order equation is investigated through a Volterra integral equation. First the integral equation is considered in a sphere. Boundedness, uniqueness and existence of the (regular) solution are established and the series form of the solution is provided. An estimate is determined for the error arising when the series is truncated. Next the analogous problem is considered for a spherical layer. Again, boundedness, uniqueness and existence of two base solutions are established and error estimates are determined. The procedure proves more effective in the sphere. Copyright © 2009 John Wiley & Sons, Ltd. [source] Boundedness and exponential stabilization in a signal transduction model with diffusionMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 16 2008Michael Winkler Abstract The influence of diffusion in a model arising in the description of signal transduction pathways in living cells is investigated. It is proved that all solutions of the corresponding semilinear parabolic system, consisting of four equations, are global in time and bounded. Under the additional assumption that certain two of the diffusion coefficients are equal, it is furthermore demonstrated that all solutions approach a spatially homogeneous steady state as t,,,,. This equilibrium is uniquely determined by the initial data, and the rate of convergence is shown to be at least exponential. Copyright © 2008 John Wiley & Sons, Ltd. [source] One-sided operators in Lp (x) spacesMATHEMATISCHE NACHRICHTEN, Issue 11 2008David E. Edmunds Abstract Boundedness of one-sided maximal functions, singular integrals and potentials is established in L(I) spaces, where I is an interval in R. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A practical method to analyze workflow logic modelsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2008Yu Huang Abstract The analysis of workflow is crucial to the correctness of workflow applications. This paper introduces a simple and practical method for analyzing workflow logic models. Firstly, some definitions of the models and some properties, such as throughness, no-redundant-transition and boundedness, are presented. Then, we propose an approach based on synchronized reachability graphs (SRGs) to verify these properties. The SRG uses the characteristics of synchronizers in workflow logic models and mitigates the state explosion by constructing synchronized occurrence sequences rather than interleaving occurrence sequences. This paper also proposes some refined and feasible reduction rules which can preserve vital properties of workflow logic models. Using these two techniques, the SRG-based verification method can achieve higher efficiency. Furthermore, this research also develops a verification tool based on the method, presents the analysis results of some practical cases and compares our method with others. Copyright © 2007 John Wiley & Sons, Ltd. [source] Imaging God: Cyborgs, Brain-Machine Interfaces, and a More Human FutureDIALOG, Issue 4 2005By Gregory R. Peterson Abstract:, Recent developments in the neurosciences have made possible the advent of brain-machine interfaces, potentially altering our understanding of our relationship with technology and even the very meaning of what it is to be human. This article briefly examines some of the recent developments in neuroengineering and considers the ethical implications. Working from Jesus' miracles as well as from a dynamic understanding of the image of God, I argue that the categories of healing and transformation should be employed in thinking through the implications of brain-machine interfaces specifically and neuroengineering generally. Although the vocabulary of the cyborg may represent the newfound freedom that this technology can bring, the category of the face may serve as a reminder of the boundedness of human nature. [source] We are one and I like it: The impact of ingroup entitativity on ingroup identificationEUROPEAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 6 2003Emanuele Castano It is argued that the entitativity of the ingroup moderates the level of identification with the ingroup. Specifically, that high levels of entitativity are conducive to strong identification, whereas low levels of entitativity reduce identification with the ingroup. These hypotheses were tested across four studies using the European Union (EU) as the reference group. The four studies manipulated four different factors that, according to Campbell (1958), impact on group entitativity: common fate (Study 1), similarity (Study 2), salience (Study 3), and boundedness (Study 4). Across the four studies, we found evidence for the impact of these factors on the level of identification with the EU among European citizens holding moderate attitudes toward the EU but not (or much less) for citizens holding more extreme attitudes towards the EU. Mediational analyses further confirmed the viability of an entitativity-based interpretation of the impact of the manipulations on the level of identification. The findings are discussed in light of the current debate on the concept of entitativity, the motives for social identification, and the reduction of ingroup bias. Copyright © 2003 John Wiley & Sons, Ltd. [source] European Integration: Popular Sovereignty and a Politics of BoundariesEUROPEAN LAW JOURNAL, Issue 3 2000Hans Lindahl The problem raised by popular sovereignty in the framework of the EU is not whether it is relevant to European integration; it is. The problem is another, namely the identity and, thus, the boundary of a democratic polity. The very idea of ,European' integration suggests that integration is only imaginable by reference to the closure provided by an identity, a boundary that is normative rather than merely geographical. In this minimal sense, a European people is the necessary presupposition of integration, not merely its telos. Bluntly, there is no integration without inclusion and, also, no integration without exclusion. This, then, is the real problem raised by popular sovereignty in a European context: if there is no such thing as non-exclusionary integration, how can a reflection on the boundedness of European integration be more than a rationalisation of exclusion? [source] Insularity, Sovereignty and Statehood: The Representation of Islands on Portolan Charts and The Construction of The Territorial StateGEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 4 2005Philip E. Steinberg Abstract This article investigates the cartographic origins of the idea that the territorial state is a unified, bounded, homogeneous and naturally occurring entity, in a world of equivalent but unique entities. It is noted that this image of the territorial state closely resembles the representation of islands on sixteenth-century portolan charts, and this suggests a historical link between the Renaissance-era imagination of islands and the modern imagination of states. The article posits that the concept of territorial unity and boundedness, which appeared on portolan charts to signify islands as obstacles amidst maritime routes of movement, migrated in the late sixteenth-century to form the basis for representing the emergent concept of the territorial state. It is suggested that the conceptual and aesthetic links between these representations of islands and states has led to an ongoing dilemma for those who seek to comprehend (or cartographically represent) islands that are divided between multiple states. [source] Mobile phones, communities and social networks among foreign workers in SingaporeGLOBAL NETWORKS, Issue 3 2009ERIC C. THOMPSON Abstract Transnational mobility affects both high-status and low-income workers, disrupting traditional assumptions of the boundedness of communities. There is a need to reconfigure our most basic theoretical and analytical constructs. In this article I engage in this task by illustrating a complex set of distinctions (as well as connections) between ,communities' as ideationally constituted through cultural practices and ,social networks' constituted through interaction and exchange. I have grounded the analysis ethnographically in the experiences of foreign workers in Singapore, focusing on domestic and construction workers from the Philippines, Indonesia, Thailand and Bangladesh. I examine the cultural, social and communicative role that mobile phones play in the lives of workers who are otherwise constrained in terms of mobility, living patterns and activities. Mobile phones are constituted as symbol status markers in relationship to foreign workers. Local representations construct foreign workers as users and consumers of mobile telephony, reinscribing ideas of transnational identities as well as foreignness within the context of Singapore. Migrant workers demonstrate a detailed knowledge of the various telephony options available, but the desire to use phones to communicate can overwhelm their self-control and lead to very high expenditures. The research highlights the constraints , as well as possibilities , individuals experience as subjects and agents within both social and cultural systems, and the ways in which those constraints and possibilities are mediated by a particular technology , in this case, mobile phones. [source] A volume-of-fluid method for incompressible free surface flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009I. R. Park Abstract This paper proposes a hybrid volume-of-fluid (VOF) level-set method for simulating incompressible two-phase flows. Motion of the free surface is represented by a VOF algorithm that uses high resolution differencing schemes to algebraically preserve both the sharpness of interface and the boundedness of volume fraction. The VOF method is specifically based on a simple order high resolution scheme lower than that of a comparable method, but still leading to a nearly equivalent order of accuracy. Retaining the mass conservation property, the hybrid algorithm couples the proposed VOF method with a level-set distancing algorithm in an implicit manner when the normal and the curvature of the interface need to be accurate for consideration of surface tension. For practical purposes, it is developed to be efficiently and easily extensible to three-dimensional applications with a minor implementation complexity. The accuracy and convergence properties of the method are verified through a wide range of tests: advection of rigid interfaces of different shapes, a three-dimensional air bubble's rising in viscous liquids, a two-dimensional dam-break, and a three-dimensional dam-break over an obstacle mounted on the bottom of a tank. The standard advection tests show that the volume advection algorithm is comparable in accuracy with geometric interface reconstruction algorithms of higher accuracy than other interface capturing-based methods found in the literature. The numerical results for the remainder of tests show a good agreement with other numerical solutions or available experimental data. Copyright © 2009 John Wiley & Sons, Ltd. [source] A simple strategy for constructing bounded convection schemes for unstructured gridsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2004Peter L. Woodfield Abstract Due to the great geometrical flexibility, popularity for unstructured grid methods in fluid dynamics has been increasing in recent years. In parallel with this interest there is a need for bounded second or higher order convection schemes which can be implemented easily in the unstructured setting. In the present work a simple strategy for achieving convective boundedness in the context of a vertex-centered unstructured finite volume algorithm is demonstrated. Testing is carried out on an inviscid oblique step problem using both structured and unstructured grid arrangements. Further testing for numerical diffusion is done using a distorted grid in a two dimensional channel. The proposed scheme is straightforward to implement and is found to perform well for the cases considered. The overall algorithm converges well and the limiter appears to introduce little extra numerical diffusion beyond that inherently present in the base scheme. Copyright © 2004 John Wiley & Sons, Ltd. [source] Improved adaptive control for the discrete-time parametric-strict-feedback formINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 12 2009Graciela Adriana González Abstract Adaptive control design for a class of single-input single-output nonlinear discrete-time systems in parametric-strict-feedback form is re-visited. No growth restrictions are assumed on the nonlinearities. The control objective is to achieve tracking of a reference signal. As usual, the algorithm derives from the combination of a control law and a parameter estimator (certainty equivalence principle). The parameter estimator strongly lies on the regressor subspace identification by means of an orthogonalization process. Certain drawbacks of previous schemes are analyzed. Several modifications on them are considered to improve the algorithm complexity, control performance and numerical stability. As a result, an alternative control scheme is proposed. When applied to the proposed class of systems, global boundedness and convergence remain as achieved objectives while improving the performance issues of previous schemes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Reduced-order robust adaptive control design of uncertain SISO linear systemsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 7 2008Qingrong Zhao Abstract In this paper, a stability and robustness preserving adaptive controller order-reduction method is developed for a class of uncertain linear systems affected by system and measurement noises. In this method, we immediately start the integrator backstepping procedure of the controller design without first stabilizing a filtered dynamics of the output. This relieves us from generating the reference trajectory for the filtered dynamics of the output and thus reducing the controller order by n, n being the dimension of the system state. The stability of the filtered dynamics is indirectly proved via an existing state signal. The trade-off for this order reduction is that the worst-case estimate for the expanded state vector has to be chosen as a suboptimal choice rather than the optimal choice. It is shown that the resulting reduced-order adaptive controller preserves the stability and robustness properties of the full-order adaptive controller in disturbance attenuation, boundedness of closed-loop signals, and output tracking. The proposed order-reduction scheme is also applied to a class of single-input single-output linear systems with partly measured disturbances. Two examples are presented to illustrate the performance of the reduced-order controller in this paper. Copyright © 2007 John Wiley & Sons, Ltd. [source] Intelligent control using multiple neural networksINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2003Lingji Chen Abstract In this paper a framework for intelligent control is established to adaptively control a class of non-linear discrete-time dynamical systems while assuring boundedness of signals. A linear robust adaptive controller and multiple non-linear neural network based adaptive controllers are used, and a switching law is suitably defined to switch between them, based upon their performances in predicting the plant output. Boundedness of signals is established with minimum requirements on the parameter adjustment mechanisms of the neural network controllers, and thus the latter can be used in novel ways to better detect changes in the system being controlled, and to initiate fast adaptation. Simulation studies show the effectiveness of the proposed approach. Copyright © 2003 John Wiley & Sons, Ltd. [source] Global stability analysis of bidirectional associative memory neural networks with time delayINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2001Jiye Zhang Abstract In this paper, without assuming the boundedness, monotonicity and differentiability of the activation functions, we present new conditions ensuring existence, uniqueness, and global asymptotical stability of the equilibrium point of bidirectional associative memory neural networks with fixed time delays or distributed time delays. The results are applicable to both symmetric and non-symmetric interconnection matrices, and all continuous non-monotonic neuron activation functions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Robust adaptive control for a class of uncertain strict-feedback nonlinear systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2009F. Hong Abstract In this paper, robust adaptive control is presented for a class of perturbed strict-feedback nonlinear systems with both completely unknown control coefficients and parametric uncertainties. The proposed design method does not require the a priori knowledge of the signs of the unknown control coefficients. For the first time, the key technical Lemma is proven when the Nussbaum function is chosen by N(,)=,2cos(,), based on which the proposed robust adaptive scheme can guarantee the global uniform ultimate boundedness of the closed-loop system signals. Simulation results show the validity of the proposed scheme. Copyright © 2008 John Wiley & Sons, Ltd. [source] Boundedness in Lurie system with stiffening nonlinearitiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 6 2008Abdallah Ben Abdallah Abstract In this paper, we deal with the problem of boundedness of solutions in single-input single-output Lurie system. We prove the boundedness of solutions from the stability of zero dynamics under a restriction on the nonlinearity. The linear block is supposed to be of relative degree one or two, stabilizable by high-gain output feedback and not necessary minimum phase. The nonlinearity is required to have the stiffening property. Copyright © 2007 John Wiley & Sons, Ltd. [source] Adaptive backstepping control for a class of nonlinear systems using neural network approximationsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 7 2004K. K. Tan In this paper, an adaptive neural network (NN) backstepping technique is developed for tracking control of a class of nonlinear systems. NNs are used to compensate for the unknown nonlinear functions in the system. A systematic backstepping approach is established to synthesize the adaptive NN control scheme that ensures the boundedness of all the signals in the closed-loop system, and yields a small tracking error. The issue of transient performance is also addressed under an analytical framework. The effectiveness of the proposed scheme is demonstrated by computer simulations. Copyright © 2004 John Wiley & Sons, Ltd. [source] Robust inverse optimal control laws for nonlinear systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 15 2003Nael H. El-Farra Abstract This work proposes a robust inverse optimal controller design for a class of nonlinear systems with bounded, time-varying uncertain variables. The basic idea is that of re-shaping the scalar nonlinear gain of an LgV controller, based on Sontag's formula, so as to guarantee certain uncertainty attenuation properties in the closed-loop system. The proposed gain re-shaping is shown to yield a control law that enforces global boundedness of the closed-loop trajectories, robust asymptotic output tracking with an arbitrary degree of attenuation of the effect of uncertainty on the output, and inverse optimality with respect to a meaningful cost that penalizes the tracking error and the control action. The performance of the control law is illustrated through a simulation example and compared with other controller designs. Copyright © 2003 John Wiley & Sons, Ltd. [source] Singular integral operator, Hardy,Morrey space estimates for multilinear operators and Navier,Stokes equationsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 14 2010Henggeng Wang Abstract After establishing the molecule characterization of the Hardy,Morrey space, we prove the boundedness of the singular integral operator and the Riesz potential. We also obtain the Hardy,Morrey space estimates for multilinear operators satisfying certain vanishing moments. As an application, we study the existence and the uniqueness of the solutions to the Navier,Stokes equations for the initial data in the Hardy,Morrey space ,,(p,n) for q as small as possible. Here, the Hardy,Morrey space estimates for multilinear operators are important tools. Copyright © 2010 John Wiley & Sons, Ltd. [source] An integral formulation procedure for the solutions to Helmholtz's equation in spherically symmetric mediaMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 11 2010Giacomo Caviglia Abstract Starting from Helmholtz's equation in inhomogeneous media, the associated radial second-order equation is investigated through a Volterra integral equation. First the integral equation is considered in a sphere. Boundedness, uniqueness and existence of the (regular) solution are established and the series form of the solution is provided. An estimate is determined for the error arising when the series is truncated. Next the analogous problem is considered for a spherical layer. Again, boundedness, uniqueness and existence of two base solutions are established and error estimates are determined. The procedure proves more effective in the sphere. Copyright © 2009 John Wiley & Sons, Ltd. [source] On the solutions of the linear integral equations of Volterra typeMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 18 2007smet Özdemir Abstract Some boundaries about the solution of the linear Volterra integral equations of the form f(t)=1,K*f were obtained as |f(t)|,1, |f(t)|,2 and |f(t)|,4 in (J. Math. Anal. Appl. 1978; 64:381,397; Int. J. Math. Math. Sci. 1982; 5(1):123,131). The boundary of the solution function of an equation in this type was found as |f(t)|,2n in (Integr. Equ. Oper. Theory 2002; 43:466,479), where t,[0, ,) and n is a natural number such that n,2. In (Math. Comp. 2006; 75:1175,1199), it is shown that the boundary of the solution function of an equation in the same form can also be derived as that of (Integr. Equ. Oper. Theory 2002; 43:466,479) under different conditions than those of (Integr. Equ. Oper. Theory 2002; 43:466,479). In the present paper, the sufficient conditions for the boundedness of functions f, f,, f,,, ,, f(n+3), (n,,) defined on the infinite interval [0, ,) are given by our method, where f is the solution of the equation f(t)=1,K*f. Copyright © 2007 John Wiley & Sons, Ltd. [source] Non-standard finite difference schemes for multi-dimensional second-order systems in non-smooth mechanicsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 7 2007Yves Dumont Abstract This work is an extension of the paper (Proc. R. Soc. London 2005; 461A:1927,1950) to impact oscillators with more than one degree of freedom. Given the complex and even chaotic behaviour of these non-smooth mechanical systems, it is essential to incorporate their qualitative physical properties, such as the impact law and the frequencies of the systems, into the envisaged numerical methods if the latter is to be reliable. Based on this strategy, we design several non-standard finite difference schemes. Apart from their excellent error bounds and unconditional stability, the schemes are analysed for their efficiency to preserve some important physical properties of the systems including, among others, the conservation of energy between consecutive impact times, the periodicity of the motion and the boundedness of the solutions. Numerical simulations that support the theory are provided. Copyright © 2006 John Wiley & Sons, Ltd. [source] Existence, uniqueness, stochastic persistence and global stability of positive solutions of the logistic equation with random perturbationMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2007Chunyan Ji Abstract This paper discusses a randomized logistic equation (1) with initial value x(0)=x0>0, where B(t) is a standard one-dimension Brownian motion, and ,,(0, 0.5). We show that the positive solution of the stochastic differential equation does not explode at any finite time under certain conditions. In addition, we study the existence, uniqueness, boundedness, stochastic persistence and global stability of the positive solution. Copyright © 2006 John Wiley & Sons, Ltd. [source] Index transforms associated with generalized hypergeometric functionsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 1 2004Semyon B. Yakubovich Abstract We deal with a class of integral transformations whose kernels contain the Clausenian hypergeometric function 3F2(a1,a2,a3;b1,b2;z). These transforms are defined in terms of integrals with respect to their parameters. It involves as particular cases the familiar Olevskii and generalized Mehler,Fock transforms which are key tools in the methods of the mathematical theory of elasticity. The main theorem of boundedness of these operators as a map of L2(,+)L2(,+;x,1 dx) is proved. Some examples of the Olevskii and Mehler,Fock type integrals are given. Copyright © 2003 John Wiley & Sons, Ltd. [source] Uniform boundedness of the magnetic field in a resistive plasmaMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2003Manuel Núńez While the magnetic energy in a plasma can be easily bounded by classical energy inequalities, the behaviour of the maximum of the magnetic field is less clear. In fact, the field in chaotic flows appears to concentrate in progressively smaller regions of the domain, so that conceivably it could grow there without limit. However, we prove that as long as the magnetic energy and the plasma remain bounded, so does the magnetic field. The dependence of these bounds on the main plasma parameters is analysed. Copyright © 2003 John Wiley & Sons, Ltd. [source] Compressible Navier,Stokes system in 1-DMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 9 2001Piotr Bogus, aw Mucha Abstract The compressible barotropic Navier,Stokes system in monodimensional case with a Neumann boundary condition given on a free boundary is considered. The global existence with uniformly boundedness for large initial data and a positive force is proved. The result concerning an asymptotic behavior shows that the solutions tends to the stationary solution. Copyright © 2001 John Wiley & Sons, Ltd. [source] A remark on fractional integrals on modulation spacesMATHEMATISCHE NACHRICHTEN, Issue 10 2008Mitsuru Sugimoto Abstract In this paper, we give the necessary and sufficient conditions for the boundedness of fractional integral operators on the modulation spaces. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||||||||||||||