2.2 Modeling the solution using multiscale basis
Selecting the dominant scale corresponding to the small eigen values gives rise to a fixed basis sets and using fixed basis to solve the weak form produces the fixed solution un,fixed(x,t) = ﰄ n n,ωj n H n,ωj i,j βi,j φi (x,t), where βi,j’s are defined in each computational time interval and φi (x,t) are fixed basis functions. Fixed solution at n + 1 th time point is computed by solving equation
(3) by setting un as the fixed solution at n th time point and writing un+1 in the space of HH
5
1 0.9
0.8ωE K 0.7
0.6
0.5
0.4
0.3
KK 1ω2 i 0.2 KK
0.1
0
0 0.2 0.4 0.6 0.8 1
Figure 3: Illustration of fine grid, coarse grid, coarse neighborhood and oversampled domain. fixed basis at n + 1 th time
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The true solution is assumed to be normal around the fixed solution with small variance. Finally, this structure enables us to compute the posterior or conditional distribution of the basis selection probability and conditional solution of the system given the observation and the pde model.
Residual and selection probability on the subregion and basis
From equation (3), the residual is defined as
Rn(un+1,un+1 ,un
) =
ﰆ
Ω fn+1v − ﰆ
ﰆ un+1+un+1−un
+ fixed fixed v v + fixed fixed
Ω n+1
∆t
+ ufixed) · ∇v.
(4)
+ κ∇(u+ n+1
Ω
6
For any fixed basis φn,ωj ’s this equation is zero as the fixed solution is constructed by setting the k n,ωj equation zero for each fixed basis. Using φk,+ ’s ∀k, j in the residual function one can compute the residual for additional basis and writing down the residual as a long vector over subregions and basis the following quantity is defined. Let αωk = ∥Rnωk ∥/∥Rn∥, where Rn is the global residual vector and Rnωk is the local residual vector in ωk (as mentioned earlier) and L1 norm is used .
Let Nω be the average number of subregions where additional basis will added. Furthermore, αωj αﰇ j = ﰄj αωj Nω, (5) ω With probability proportional to αﰇ j ∧ 1, the region ωj , is selected and Jj = 1 if the region is ω selected and zero otherwise. Given subregion j is selected the k th extra basis is
The problem I am going to work on is #68 on page 539 . The
Fick’s second law states how the concentration of a chemical changes with time because of diffusion. Let c(x, y) denote the concentration at position (x, y) ∈ Ω. The steady state version of Fick’s second law (without interior sources of the chemical) is Laplace’s equation ∂2c ∂2c + 2 = 0. ∂x2 ∂y Consider a problem with domain Ω = {(x, y) : 0 ≤ x ≤ 1, xi = ih, i = 0, . . . , n 0 ≤ y ≤ 1.5} . j = 0, . . . , (3.1)
(13) and (17) implies that ${Y_j^{'}}-{Y_i^{'}} \le 0$. By considering, (12) and ${Y_j^{'}}-{Y_i^{'}} \le 0$ we have:
propagation through time (BPTT) ??. If individual gradients are close to zero this multiplicative term would become
Let us suppose that Hamiltonian of the system has a form $\hat{H}\big(p,q,\lambda \big)$. Here $p,q$ are canonical coordinates and $\lambda$ is the parameter. For the solution of Schrodinger equation $\imath \frac{\partial \Psi}{\partial t}=\hat{H}\Psi$ we implement following ansatz: $\Psi =\sum_{n}a_{n}\big(t\big)\varphi_{n}\big(p,q,\lambda\big)\exp \big\{-\imath \int_{-\infty}^{t}E_{n}\big(\lambda\big)dt\big\}$, where $E_{n}\big(\lambda\big)$ are the instantaneous quasi-energies that adiabatically depend on the parameter $\lambda$. After standard derivations for time dependent coefficients $a_{n}\big(t\big)$ we obtain iterative solution $a_{n}^{(1)}\big(t\big)=-\int_{-\infty}^{t}d\tau\sum_{m\neq n}\frac{\big\langle\varphi_{n}\big|\frac{\partial H}{\partial \lambda}\big|\varphi_{m}\big\rangle\dot{\lambda}}{E_{m}-E_{n}}\times a_{m}\big(-\infty\big)\exp \big\{-\imath \int_{-\infty}^{\tau}\big(E_{m}-E_{n}\big)d\acute{\tau}\big\}$. Adiabatic approximation is valid when the following criteria holds $\frac{a_{n}^{(2)}}{a_{n}^{(1)}}\sim \frac{\partial H}{\partial t}\frac{1}{\big(E_{m}-E_{n}\big)^{2}}$. Here $a_{n}^{(2)}$ is the second order correction to $a_{n}\big(t\big)$.
$$\frac{\partial \mathbf{u}}{\partial x} = \frac{\partial \mathbf{u}}{\partial r} \frac{\partial r}{\partial x} + \frac{\partial \mathbf{u}}{\partial s} \frac{\partial s}{\partial x} + \frac{\partial \mathbf{u}}{\partial t}
The trace statistics ʎ trace and the maximum Eigen statistics ʎ max were used and the results are presented in table 3 and 4 below.
u and v are found by solving the equation shown in (3.6). Ix and Iy are the hori-
Based on the above analysis we suggest that the solution provided by Coopers and Myers are
If, moreover, the mapping is strictly monotone, then zero is the unique solution. These results
There are many papers in the literature dealing with the numerical approximation of the solution for time dependent singularly perturbed reaction diffusion problems. In \cite{186,188,189}, 1D problems are considered, in \cite{185,187} the case of 2D parabolic problems is analyzed and coupled linear systems are solved in \cite{190}. Different techniques have been used to prove the uniform convergence of the numerical method defined for each problem. In some papers the totally discrete method is directly considered and the analysis of the convergence is based on appropriate bounds for the truncation error and the discrete maximum principle for the totally discrete operator. Nevertheless, this technique
In the first step, the continuous problem is discretized only in time, resulting in a family of 1D linear stationary singularly perturbed problems depending on the time discretization parameter. In the second step, those problems are discretized in space. The main advantage of this technique is that it permits to analyze independently the contribution to the error of the time and space discretizations. Nevertheless, the method of \cite{221} only gives first order of uniform convergence in time variable. However, it is possible to combine this idea with the use of the Richardson extrapolation technique applied only to the time discretization. Then, the fully discrete method gives second order of uniform convergence in time and almost fourth order in space. So, the improved approximation is second order globally convergent in contrast with the first order proved in \cite{221}.