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4.3.1.3 Time Dependent Variables
Since AMI supports
PDEs which might be time dependent every model has implicitly defined time
dependent variables even if they are not used. Each quantity defined in
the solution vector of an analytical model has got three different timesteps
that represent the current state and the state of the last two time iterations.
Furthermore, AMI predefines the
variable t that holds the current calculated time (t_{0})
and again the time of the two last calculated timesteps (t_{t
 1},t_{t  2}). The syntax used to distinguish between
different times within the model description language looks like:
t = t.t0 # timestep t
t.t1 # timestep t1
t.t2 # timestep t2
<Q> = <Q.t0> # value of the quantity Q at time t
<Q.t1> # value of the quantity Q at time t1
<Q.t2> # value of the quantity Q at time t2
With this mechanisms it is possible to handle discretized
derivatives of time:

first order discretization

second order discretization
Next:4.3.1.4
Model DefinitionUp:4.3.1
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Operators and Functions
Mustafa Radi
19981211