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Wyszukujesz frazę "estimates" wg kryterium: Temat


Wyświetlanie 1-10 z 10
Tytuł:
Inverse/observability estimates for Schroedinger equations with variable coefficients
Autorzy:
Triggiani, R.
Yao, P.
Powiązania:
https://bibliotekanauki.pl/articles/206775.pdf
Data publikacji:
1999
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
równanie Schroedingera
Carleman estimates
exact controllability
inverse/observability estimates
Riemannian manifold
Schroedinger equation
Opis:
We consider a general Schroedinger equation defined on an open bounded domain [Omega is a subset of R^n] with variable coefficients in both the elliptic principal part and in the first-order terms as well. At first, no boundary conditions (B.C.) are imposed. Our main result (Theorem 3.5) is a reconstruction, or inverse, estimate for solutions w: under checkable conditions on the coefficients of the principal part, the H[sup l](Omega)-energy at time t = T, or at time t = 0, is dominated by the L[sub2](Sigma)-norms of the boundary traces [...] and w[sub t] modulo an interior lower-order term. Once homogeneous B.C. are imposed, our results yield - under a uniqueness theorem, needed to absorb the lower order term - continuous observability estimates for both the Dirichlet and Neumann case, with an arbitrarily short observability time ; hence, by duality, exact controllability results. Moreover, no artificial geometrical conditions are imposed on the controlled part of the boundary in the Neuman case. In contrast to existing literature, the first step of our method employs a Riemann geometry approach to reduce the original variable coefficient principal part problem in [Omega is a subset of R^n] to a problem on an appropriate Riemannian manifold (determined by the coefficients of the principal part), where the principal part is the Laplacian. In our second step, we employ explicit Carleman estimates at the differential level to take care of the va.riable first-order (energy level) terms. In our third step, we employ micro-local analysis yielding a sharp trace estimate to remove artificial geometrical conditions on the controlled part of the boundary in the Neumann case.
Źródło:
Control and Cybernetics; 1999, 28, 3; 627-664
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New estimate for the curvature of an order-convex set and related questions
Autorzy:
Ramazanov, Ali B.
Powiązania:
https://bibliotekanauki.pl/articles/2050043.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
gradient
estimates
curvature
convexity
algorithm
Opis:
It is well known that in discrete optimization problems, gradient (local) algorithms do not always guarantee an optimal solution. Therefore, the problem arises of finding the accuracy of the gradient algorithm. This is a fairly well-known problem and numerous publications have been devoted to it. In establishing accuracy, various approaches are used. One of these approaches is to obtain guaranteed estimates of the accuracy of the gradient algorithm in terms of the curvature of the admissible domain. With this approach, it is required to find the curvatures of the admissible region. Since finding the exact value of curvature is a difficult problem to solve, curvature estimates in terms of more or less simply calculated parameters of the problem are relevant. A new improved bound for the curvature of an order-convex set is found and is presented in this paper in terms of the steepness and parameters of strict convexity of the function.
Źródło:
Control and Cybernetics; 2020, 49, 2; 233-240
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Global existence for strong solutions of viscous Burgers equation. (1) The bounded case
Autorzy:
Unterberger, J.
Powiązania:
https://bibliotekanauki.pl/articles/206077.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
viscous Burgers equation
conservation laws
maximum principle
Schauder estimates
Opis:
We prove that the viscous Burgers equation (∂t−∆)u(t, x)+( u •∇)u(t, x) = g(t, x), (t, x) ∈ R+ × Rd (d ≥ 1) has a globally defined smooth solution in all dimensions provided the initial condition and the forcing term g are smooth and bounded together with their derivatives. Such solutions may have infinite energy. The proofdoes not rely on energy estimates, but on a combinationof the maximumprinciple and quantitative Schauder estimates. We obtain precise bounds on the sup norm of the solution and its derivatives, making it plain that there is no exponential increase in time. In particular, these bounds are time-independent if g is zero. To get a classical solution, it suffices to assume that the initial condition and the forcing term have bounded derivatives up to order two.
Źródło:
Control and Cybernetics; 2017, 46, 2; 109-136
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A note on variational discretization of elliptic Neumann boundary control
Autorzy:
Hinze, M.
Matthes, U.
Powiązania:
https://bibliotekanauki.pl/articles/969695.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
elliptic optimal control problem
error estimates
Neumann boundary control
variational discretization
Opis:
We consider variational discretization of Neumann-type elliptic optimal control problems with constraints on the control. In this approach the cost functional is approximated by a sequence of functionals, which are obtained by discretizing the state equation with the help of linear finite elements. The control variable is not discretized. Error bounds for control and state are obtained both in two and three space dimensions. Finally, we discuss some implementation issues of a generalized Newton method applied to the numerical solution of the problem class under consideration.
Źródło:
Control and Cybernetics; 2009, 38, 3; 577-591
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Regularization error estimates and discrepancy principle for optimal control problems with inequality constraints
Autorzy:
Wachsmuth, D.
Wachsmuth, G.
Powiązania:
https://bibliotekanauki.pl/articles/206129.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
source condition
discrepancy principle
nonsmooth optimization
convex constraints
sparsity
regularization error estimates
Opis:
In this article we study the regularization of optimization problems by Tikhonov regularization. The optimization problems are subject to pointwise inequality constraints in L²(Ω). We derive a-priori regularization error estimates if the regularization parameter as well as the noise level tend to zero. We rely on an assumption that is a combination of a source condition and of a structural assumption on the active sets. Moreover, we introduce a strategy to choose the regularization parameter in dependence of the noise level. We prove convergence of this parameter choice rule with optimal order.
Źródło:
Control and Cybernetics; 2011, 40, 4; 1125-1158
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Error analysis of discrete approximations to bang-bang optimal control problems: the linear case
Autorzy:
Veliov, V. M.
Powiązania:
https://bibliotekanauki.pl/articles/970563.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
liniowy system sterowania
aproksymacja dyskretna
szacowanie błędów
linear control systems
discrete approximations
error estimates
Opis:
The paper presents an error estimate for Runge-Kutta direct discretizations of terminal optimal control problems for linear systems. The optimal control for such problems is typically discontinuous, and Lipschitz stability of the solution with respect to perturbations does not necessarily hold. The estimate (in terms of the optimal controls) is of first order if certain recently obtained sufficient conditions for structural stability hold, and of fractional order, otherwise. The main tool in the proof is the established relation between the local convexity index of the reachable set and the multiplicity of zeros of appropriate switching functions associated with the problem.
Źródło:
Control and Cybernetics; 2005, 34, 3; 967-982
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimality system POD and a-posteriori error analysis for linear-quadratic problems
Autorzy:
Volkwein, S.
Powiązania:
https://bibliotekanauki.pl/articles/206100.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
optimal control
model reduction
proper orthogonal decomposition
a-posteriori error estimates
optimality system POD
Opis:
In this paper an abstract linear-quadratic optimal control problem governed by an evolution equation is considered. To solve this problem numerically a reduced-order approach based on proper orthogonal decomposition (POD) is applied. The error between the POD suboptimal control and the optimal control of the original problem is controlled by an a-posteriori error analysis. However, if the POD basis has bad approximation properties, a huge number of POD basis function is required to solve the reduced-order problem with the desired accuracy. To overcome this problem, optimality system POD (OS-POD) is utilized, where the POD basis is chosen with respect to the optimization criteria.
Źródło:
Control and Cybernetics; 2011, 40, 4; 1109-1124
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Rotundity, smoothness and duality
Autorzy:
Penot, J.-P.
Powiązania:
https://bibliotekanauki.pl/articles/970589.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
sprzężoność
wypukłość
sprzężenie
dwoistość
estymacja
wypukłość uogólniona
gładkość
conjugacy
convexity
coupling
duality
estimates
generalized convexity
rotundity
smoothness
subdifferential
Opis:
The duality between smoothness and rotundity of functions is studied in a nonlinear abstract framework. Here smoothness is enlarged to subdifferentiability properties and rotundity is formulated by means of approximation properties.
Źródło:
Control and Cybernetics; 2003, 32, 4; 711-733
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Existence and uniqueness of solutions to wave equations with nonlinear degenerate damping and source terms
Autorzy:
Barbu, V.
Lasiecka, I.
Rammaha, A.
Powiązania:
https://bibliotekanauki.pl/articles/970548.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
równanie falowe
rozwiązania słabe
wave equations
damping and source terms
weak solutions
subdifferential
blow-up of solutions
energy estimates
Opis:
In this article we focus on the global well-posedness of the differential equation u [...] in Omega x(O, T), where j' denotes the derivative of a C1 convex and real valued function j. The interaction between degenerate damping and a source term constitutes the main challenge of the problem. Problems with non-degenerate damping (k = 0) have been studied in the literature (Georgiev and Todorova, 1994; Levine and Serrin, 1997; Vitillaro, 2003). Thus the degeneracy of monotonicity is the main novelty of this work. Depending on the level of interaction between the source and the damping we characterize the domain of the parameters p, m, k, n (see below) for which one obt ains existence, regularity or finite time blow up of solutions. More specifically, when p [is less than or equal to] m + k global existence of generalized solutions in H1 x L2 is proved. For p > m + k, solutions blow up in a finite time. Higher energy solutions are studied as well. For H2 x H1 initial data we obtain both local and global solutions with the same regularity. Higher energy solutions are also proved to be unique.
Źródło:
Control and Cybernetics; 2005, 34, 3; 665-687
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Error estimates for the finite-element approximation of a semilinear elliptic control problem
Autorzy:
Casas, E.
Troeltzsch, F.
Powiązania:
https://bibliotekanauki.pl/articles/206743.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
aproksymacja numeryczna
metoda elementu skończonego
równanie eliptyczne półliniowe
sterowanie rozproszone
distributed control
error estimates
finite element method
numerical approximation
semilinear elliptic equation
Opis:
We consider the finite-element approximation of a distributed optimal control problem governed by a semilinear elliptic partial differential equation, where pointwise constraints on the control are given. We prove the existence of local approximate solutions converging to a given local reference solution. Moreover, we derive error estimates for local solutions in the maximum norm.
Źródło:
Control and Cybernetics; 2002, 31, 3; 695-712
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-10 z 10

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