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Exact weighted time fields: two-field form

Emanating from the two-field form and using the Greens' formula for the equation (1.3) in a consistent manner yields

  equation7621

First, the weighted time fields tex2html_wrap_inline28221 are chosen to satisfy the following first-order ordinary differential equation associated with the adjoint operator of the original semi-discretized two-field form:

  equation7636

and the initial condition

  equation7642

We first obtain the closed form solution for the above first-order ordinary differential equation, namely, equations (3.95-3.96) to yield the weighted time fields, tex2html_wrap_inline33670 as

  equation7651

where the matrix tex2html_wrap_inline33672 and a matrix tex2html_wrap_inline33674 are defined in series form as

displaymath33676

and

displaymath33678

Substituting the fundamental solution equation (3.97), into equation (1.22), we have the closed form solution of the equation (3.91) as

  equation7672

A key idea towards the generic theoretical design and development of a new generation of a generalized family of time discretized operators pertaining to Type 2 classification is that the matrix tex2html_wrap_inline33178 is first decomposed into a symmetric and unsymmetric part as

  equation7684

where

  eqnarray7694

  eqnarray7710

tex2html_wrap_inline27621 and tex2html_wrap_inline27693 are typical control parameters introduced for convenience in the theoretical design and are subsequently discussed for each special case in the sections to follow.

It should be noted that this kind of `sum decomposition' must satisfy a condition that modal superposition can be applied for the linear dynamic system to permit applicability of the Lax equivalence theorem.

Thus, the weighted time fields, tex2html_wrap_inline33670 which still preserve the original theoretical matrix form may be expressed as

  equation7730

After some algebra we have the closed form explicit representation as

  equation7740

In its present form, the time discretized operator, namely equation (3.103) pertains to Type 1 classification and is still the exact representation of the dynamic equations (3.91-3.92) or is termed as an exact integral operator [EIO]. Any approximation to the load yields an approximate integral operator [AIO] in time. As is readily seen, the Type 1 classification is the result emanating from a generalized time weighted philosophy of the semi-discretized dynamic equations of motion and is an outcome based on the selection of tex2html_wrap_inline28299 which does not impose any conditions whatsoever upon the dependent field variable(s).


next up previous contents
Next: Case of and : Up: Time Discretized Operators: Type Previous: Generic design and theoretical

Xiangmin Zhou
Wed Sep 6 20:47:30 CDT 2000

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