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21.
Here we study a nonlinear hyperbolic integrodifferential system which was proposed by H.G. Rotstein et al. to
describe certain peculiar phase
transition phenomena. This system governs the evolution of the (relative) temperature and the order parameter (or phase-field)
. We first consider an initial and boundary value problem associated with the system and we frame it in a history space setting.
This is done by introducing two additional variables accounting for the histories of and . Then we show that the reformulated problem
generates a dissipative dynamical system in a suitable infinite-dimensional phase space. Finally, we prove the existence of a universal attractor. 相似文献
22.
Visual servoing has become a popular paradigm for the control of complex robotic systems: this sensor based approach exploits
the image informations provided by one ore more cameras in a feedback control loop to drive the system to the desired configuration.
Here authors will refers to a monocular system where the camera is mounted on the end effector of a 6-DOF manipulator. Among
different Visual Servoing approaches Image Based Visual Servoing (IBVS) has been the most investigated in the literature because
of its nice properties of robustness with respect to both robot modeling and camera calibration errors: in IBVS the control
loop is in fact directly closed in the image; moreover IBVS doesn’t require the knowledge of the target/scene model (model-free
approach). Despite its advantages IBVS may be affected by singularity and local minima problems of the control law: these
drawbacks arise especially when the initial and the goal camera images respectively corresponding to the actual and desired
system configurations are very different (i.e for large system displacements). To overcome these problems an image path planning
can be exploited to ensure system convergence. In this paper author presents an off-line image path planning that can be used
to execute system positioning task also in presence of large camera displacements: planning trajectories has been developed
such as to make the robot end effector move on a 3D helix, connecting the initial and the desired arm configuration, by generating
feasible robot twist-screws and keeping the target in the image field of view. During control execution also 3D target informations
are retrieved through an adaptive estimation law. Both simulations and experimental results show the feasibility of the proposed
approach. 相似文献
23.
24.
Pasquale Laise Duccio Fanelli Annarosa Arcangeli 《Communications in Nonlinear Science & Numerical Simulation》2012,17(4):1795-1804
Apoptosis is a biological process crucial for the development and maintenance of healthy living organism. A deregulated apoptosis underlies many diseases, including cancer. Under hypoxic conditions, p53 starts to accumulate and competes with HIF-1 for their common binding target p300. This can lead to the repression of HIF-1, and trigger the apoptotic derive. In addition apoptosis is accompanied by an enhancement of potassium (K+) fluxes, which in turn create a low-potassium intracellular micro-environment, which cooperates to the activation of caspases, the final actors of the apoptotic cascade. Based on this scenario, we elaborate a dynamical model aimed at resolving the complex dynamical interplay between the aforementioned processes. In the ideal continuum limit, the model reduces to a system of coupled differential equations, whose dynamics is analytically inspected. 相似文献
25.
Turillazzi S Bruschini C Lambardi D Francese S Spadolini I Mastrobuoni G 《Journal of mass spectrometry : JMS》2007,42(2):199-205
The average spectral profiles and the exact mass weight (MW) of biomolecules present in the medium fraction (from 900 to 3000 Da) of the venom of five social wasps (three European and one North American Polistes and the European hornet Vespa crabro) were determined by matrix assisted laser desorption ionization time of flight (MALDI-TOF) MS. Data were obtained analyzing the venom of single specimens (N = 46) and elaborated with the ClinProTools 2.0 (CPT) software to search for differences among the five species examined. Interesting differences in the spectral profiles were found, allowing the discrimination of venoms belonging to the different species, and their possible use as a quality control method in venom immunotherapy (VIT) for allergic patients. 相似文献
26.
We here discuss the emergence of quasistationary states (QSS), a universal feature of systems with long-range interactions. With reference to the Hamiltonian mean-field model, numerical simulations are performed based on both the original N-body setting and the continuum Vlasov model which is supposed to hold in the thermodynamic limit. A detailed comparison unambiguously demonstrates that the Vlasov-wave system provides the correct framework to address the study of QSS. Further, analytical calculations based on Lynden-Bell's theory of violent relaxation are shown to result in accurate predictions. Finally, in specific regions of parameters space, Vlasov numerical solutions are shown to be affected by small scale fluctuations, a finding that points to the need for novel schemes able to account for particle correlations. 相似文献
27.
Monica Conti Stefania Gatti Vittorino Pata 《Central European Journal of Mathematics》2007,5(4):720-732
This note is concerned with the linear Volterra equation of hyperbolic type
on the whole space ℝ
N
. New results concerning the decay of the associated energy as time goes to infinity were established.
相似文献
28.
Guaspari (J Symb Logic 48:777–789, 1983) conjectured that a modal formula is it essentially Σ1 (i.e., it is Σ1 under any arithmetical interpretation), if and only if it is provably equivalent to a disjunction of formulas of the form ${\square{B}}$ . This conjecture was proved first by A. Visser. Then, in (de Jongh and Pianigiani, Logic at Work: In Memory of Helena Rasiowa, Springer-Physica Verlag, Heidelberg-New York, pp. 246–255, 1999), the authors characterized essentially Σ1 formulas of languages including witness comparisons using the interpretability logic ILM. In this note we give a similar characterization for formulas with a binary operator interpreted as interpretability in a finitely axiomatizable extension of IΔ 0 + Supexp and we address a similar problem for IΔ 0 + Exp. 相似文献
29.
We investigate the finite size corrections to the equilibrium magnetization of an Ising model on a random graph with N nodes and Nγ edges, with 1<γ≤2. By conveniently rescaling the coupling constant, the free energy is made extensive. As expected, the system displays a phase transition of the mean-field type for all the considered values of γ at the transition temperature of the fully connected Curie-Weiss model. Finite size corrections are investigated for different values of the parameter γ, using two different approaches: a replica based finite N expansion, and a cavity method. Numerical simulations are compared with theoretical predictions. The cavity based analysis is shown to agree better with numerics. 相似文献
30.
Vittorino Pata 《Central European Journal of Mathematics》2009,7(3):487-492
A classical result on the existence of global attractors for gradient systems is extended to the case of a semigroup S(t) lacking strong continuity, but satisfying the weaker property of being a closed map for every fixed t ≥ 0.
相似文献