The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Laszlo Techy - One of the best experts on this subject based on the ideXlab platform.
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CDC-ECE - Optimal navigation in a planar time-varying point-symmetric flow-field
IEEE Conference on Decision and Control and European Control Conference, 2011Co-Authors: Laszlo TechyAbstract:This paper is concerned with time-optimal navigation for flight vehicles in a planar, time-varying point-symmetric flow-field — such as inside vortices or regions of eddy-driven upwelling/downwelling—where the objective is to find the fastest trajectory between initial and final points. The primary contribution of the paper is the observation that for time-optimality the rate of the steering angle has to be equal to one-half of the instantaneous vertical vorticity. Consequently, if the vorticity is zero, then the steering angle has to be constant. The result can be applied to find the time-optimal trajectories in practical control problems, by reducing the infinite-dimensional continuous problem to numerical optimization involving at most two Unknown Scalar parameters.
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Optimal navigation in planar time-varying flow: Zermelo’s problem revisited
Intelligent Service Robotics, 2011Co-Authors: Laszlo TechyAbstract:This paper is concerned with time-optimal navigation for flight vehicles in a planar, time-varying flow-field, where the objective is to find the fastest trajectory between initial and final points. The primary contribution of the paper is the observation that in a point-symmetric flow, such as inside vortices or regions of eddie-driven upwelling/downwelling, the rate of the steering angle has to be equal to one-half of the instantaneous vertical vorticity. Consequently, if the vorticity is zero, then the steering angle is constant. The result can be applied to find the time-optimal trajectories in practical control problems, by reducing the infinite-dimensional continuous problem to numerical optimization involving at most two Unknown Scalar parameters.
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Optimal navigation in planar time-varying flow: Zermelo's problem revisited
Intelligent Service Robotics, 2011Co-Authors: Laszlo TechyAbstract:This paper is concerned with time-optimal navigation for flight vehicles in a planar, time-varying flow-field, where the objective is to find the fastest trajectory between initial and final points. The primary contribution of the paper is the observation that in a point-symmetric flow, such as inside vortices or regions of eddie-driven upwelling/downwelling, the rate of the steering angle has to be equal to one-half of the instantaneous vertical vorticity. Consequently, if the vorticity is zero, then the steering angle is constant. The result can be applied to find the time-optimal trajectories in practical control problems, by reducing the infinite-dimensional continuous problem to numerical optimization involving at most two Unknown Scalar parameters.
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CDC/ECC - Optimal navigation in a planar time-varying point-symmetric flow-field
IEEE Conference on Decision and Control and European Control Conference, 2011Co-Authors: Laszlo TechyAbstract:This paper is concerned with time-optimal navigation for flight vehicles in a planar, time-varying point-symmetric flow-field — such as inside vortices or regions of eddy-driven upwelling/downwelling—where the objective is to find the fastest trajectory between initial and final points. The primary contribution of the paper is the observation that for time-optimality the rate of the steering angle has to be equal to one-half of the instantaneous vertical vorticity. Consequently, if the vorticity is zero, then the steering angle has to be constant. The result can be applied to find the time-optimal trajectories in practical control problems, by reducing the infinite-dimensional continuous problem to numerical optimization involving at most two Unknown Scalar parameters.
Avelino Vicente - One of the best experts on this subject based on the ideXlab platform.
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Remarks on the Standard Model predictions for R (D) and R (D
Physical Review D, 2017Co-Authors: G. Lopez-castro, S. L. Tostado, Avelino VicenteAbstract:Semileptonic $b \to c$ transitions, and in particular the ratios $R(D^{(*)}) = \frac{\Gamma(B \rightarrow D^{(*)} \tau \nu )}{\Gamma(B \rightarrow D^{(*)} \ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly Unknown Scalar form factor. In constrast, the Standard Model prediction for $R(D^*)$ is found to be more robust, since possible pollutions from $B^*$ contributions turn out to be negligibly small, which indicates that $R(D^*)$ is a promising observable for searches of new physics.
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Remarks on the Standard Model predictions for $R(D)$ and $R(D^*)$
Physical Review D, 2017Co-Authors: Choong Sun Kim, G. Lopez-castro, S. L. Tostado, Avelino VicenteAbstract:Semileptonic $b \to c$ transitions, and in particular the ratios $R(D^{(*)}) = \frac{\Gamma(B \rightarrow D^{(*)} \tau \nu )}{\Gamma(B \rightarrow D^{(*)} \ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly Unknown Scalar form factor. In constrast, the Standard Model prediction for $R(D^*)$ is found to be more robust, since possible pollutions from $B^*$ contributions turn out to be negligibly small, which indicates that $R(D^*)$ is a promising observable for searches of new physics.
G. Lopez-castro - One of the best experts on this subject based on the ideXlab platform.
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Remarks on the Standard Model predictions for R (D) and R (D
Physical Review D, 2017Co-Authors: G. Lopez-castro, S. L. Tostado, Avelino VicenteAbstract:Semileptonic $b \to c$ transitions, and in particular the ratios $R(D^{(*)}) = \frac{\Gamma(B \rightarrow D^{(*)} \tau \nu )}{\Gamma(B \rightarrow D^{(*)} \ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly Unknown Scalar form factor. In constrast, the Standard Model prediction for $R(D^*)$ is found to be more robust, since possible pollutions from $B^*$ contributions turn out to be negligibly small, which indicates that $R(D^*)$ is a promising observable for searches of new physics.
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Remarks on the Standard Model predictions for $R(D)$ and $R(D^*)$
Physical Review D, 2017Co-Authors: Choong Sun Kim, G. Lopez-castro, S. L. Tostado, Avelino VicenteAbstract:Semileptonic $b \to c$ transitions, and in particular the ratios $R(D^{(*)}) = \frac{\Gamma(B \rightarrow D^{(*)} \tau \nu )}{\Gamma(B \rightarrow D^{(*)} \ell \nu )}$, can be used to test the universality of the weak interactions. In light of the recent discrepancies between the experimental measurements of these observables by BaBar, Belle and LHCb and the Standard Model predicted values, we study the robustness of the latter. Our analysis reveals that $R(D)$ might be enhanced by lepton mass effects associated to the mostly Unknown Scalar form factor. In constrast, the Standard Model prediction for $R(D^*)$ is found to be more robust, since possible pollutions from $B^*$ contributions turn out to be negligibly small, which indicates that $R(D^*)$ is a promising observable for searches of new physics.
Ali Zemouche - One of the best experts on this subject based on the ideXlab platform.
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Observer design for a class of Lipschitz time-delay systems
International Journal of Modelling Identification and Control, 2008Co-Authors: Ali Zemouche, Mohamed Boutayeb, G.i. BaraAbstract:This paper deals with observers design of non-linear time-delay systems.We investigate in particular, a useful technique based on the use of the Differential Mean Value Theorem (DMVT) and the Lyapunov-Krasovskii functionals to give a very suitable sufficient synthesis condition to assure exponential convergence. The obtained condition is formulated in terms of matrix inequality which becomes linear whenever an Unknown Scalar is chosen a priori. On the other hand, we introduce a simple and relevant transformation to show how to extend the obtained results to a particular class of continuous but non-differentiable systems. To show performances of the proposed approach and the large class of systems that may be concerned, numerical examples are provided.
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ACC - Observer Design for a Class of Nonlinear Time-Delay Systems
2007 American Control Conference, 2007Co-Authors: Ali Zemouche, Mohamed Boutayeb, G. Iulia BaraAbstract:In this paper, we investigate a new method for the observer design problem for a class of nonlinear time-delay systems. The main contribution lies in the use of a new structure for the proposed observer. This new structure has as objective to obtain an approach applicable on a large class of nonlinear time-delay systems and to reduce the conservatism of the synthesis condition ensuring the exponential convergence of the estimation error towards zero. The stability analysis is performed using a Lyapunov-Krasovskii functional that leads to the solvability of a matrix inequality, which becomes linear (LMI) whenever an Unknown Scalar variable is chosen a priori. A numerical example is presented in order to show the efficiency of our method.
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Nonlinear observers for Lipschitz discrete-time systems. Application to synchronization and input recovery
2007 European Control Conference (ECC), 2007Co-Authors: Ali Zemouche, Mohamed Boutayeb, G. Iulia BaraAbstract:In this note, a new observer design method for a class of nonlinear Lipschitz discrete-time systems is proposed. The developed method presents significant improvements with respect to the results of [1] and [2]. This is due, firstly, to the use of another structure of the observer introduced recently in [3] and, secondly, to the use of a detailed form of the system by specifying the distribution matrix of the nonlinearities in the system and the dependence matrix of the nonlinearities on the state of the system. The stability analysis is performed using a particular Lyapunov function that leads to the solvability of matrix inequalities which become linear (LMIs) whenever Unknown Scalar variables are chosen a priori. An illustrative example is given in order to show the efficiency of our method with respect to [1] and [2]. This new design approach is then generalized to systems with Unknown inputs. In this paper, we have considered the problem of synchronization and input recovery. This generalization is tested successfully by a numerical application.
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On observers design for nonlinear time-delay systems
2006 American Control Conference, 2006Co-Authors: Ali Zemouche, Mohamed Boutayeb, G.i. BaraAbstract:In this note, we investigate a new approach for observer synthesis of nonlinear time delay systems. This approach is based on the differential mean value theorem (DMVT). Using the Lyapunov-Krasovskii functionals and the DMVT, we give new sufficient synthesis conditions for the observer design problem. These conditions are formulated as matrix inequalities which become linear whenever an Unknown Scalar variable is chosen a priori
Romuald A Janik - One of the best experts on this subject based on the ideXlab platform.
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The AdS 5 ×S 5 superstring worldsheet S matrix and crossing symmetry
Physical Review D, 2006Co-Authors: Romuald A JanikAbstract:An S matrix satisfying the Yang-Baxter equation with symmetries relevant to the AdS{sub 5}xS{sup 5} superstring recently has been determined up to an Unknown Scalar factor. Such Scalar factors are typically fixed using crossing relations; however, due to the lack of conventional relativistic invariance, in this case its determination remained an open problem. In this paper we propose an algebraic way to implement crossing relations for the AdS{sub 5}xS{sup 5} superstring worldsheet S matrix. We base our construction on a Hopf-algebraic formulation of crossing in terms of the antipode and introduce generalized rapidities living on the universal cover of the parameter space which is constructed through an auxillary, coupling-constant dependent, elliptic curve. We determine the crossing transformation and write functional equations for the Scalar factor of the S matrix in the generalized rapidity plane.
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the ads 5 s 5 superstring worldsheet s matrix and crossing symmetry
Physical Review D, 2006Co-Authors: Romuald A JanikAbstract:An S matrix satisfying the Yang-Baxter equation with symmetries relevant to the AdS{sub 5}xS{sup 5} superstring recently has been determined up to an Unknown Scalar factor. Such Scalar factors are typically fixed using crossing relations; however, due to the lack of conventional relativistic invariance, in this case its determination remained an open problem. In this paper we propose an algebraic way to implement crossing relations for the AdS{sub 5}xS{sup 5} superstring worldsheet S matrix. We base our construction on a Hopf-algebraic formulation of crossing in terms of the antipode and introduce generalized rapidities living on the universal cover of the parameter space which is constructed through an auxillary, coupling-constant dependent, elliptic curve. We determine the crossing transformation and write functional equations for the Scalar factor of the S matrix in the generalized rapidity plane.
