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ComputerAided_Design_Engineering_amp_Manufactur.pdf

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therefore:<br />

Now merge the lists and eliminate the repeated pointers thus:<br />

The pointers are eliminated from left to right because they are listed with the pointers in the deepest<br />

level occupying the leftmost position in the list. Therefore, to solve this simple ex<strong>amp</strong>le requires evaluating<br />

the expressions in the order 1-3-4-2.<br />

Because not all systems may be solved using this technique, it is necessary to check that the system<br />

satisfies the necessary conditions. If one of the following two conditions is not satisfied then the iterative<br />

solution will be invoked. The first condition that is checked is the presence of slings, which are detected<br />

when an expression defining a variable contains the same variable as part of its definition. The second<br />

condition requires an acyclic system. In the next section, Newton-Raphson will be introduced when<br />

either of these two conditions is not satisfied.<br />

Iterative Solution<br />

There are various methods of finding roots or solutions for nonlinear equations, of which Newton’s<br />

method is one of the most commonly used because it has better convergence properties than direct<br />

iteration methods. The Newton-Raphson technique is a generalization to Newton’s method, and it is<br />

used to determine the zeros of a set of simultaneous nonlinear equations.<br />

The general formulation for nonlinear systems can be stated in the following form. Given n-functions<br />

fi in terms on n-unknowns xi: The basis for the Newton-Raphson method is a Taylor’s expansion of the n equations about some<br />

point ( x0, y0) :<br />

If the higher order terms are dropped, the problem becomes one of finding the roots of the linear system:<br />

© 2001 by CRC Press LLC<br />

root a : ( 1,3,1,4)<br />

root b : ( 1,3,2)<br />

list : ( 1,3,1,4,1,3,2)<br />

final : ( 1,3,4,2).<br />

f1( x1, x2,..., xn) � 0<br />

f2( x1, x2,..., xn) � 0<br />

�<br />

�<br />

�<br />

fn( x1, x2,..., xn) � 0<br />

f1( x1 � x,…x n � x)<br />

� f1( x1,…, xn) � x1f …<br />

x � � xn fn � Higher order terms.<br />

.<br />

.<br />

fn( x1 � x,…x n � x)<br />

� fn( x1,…, xn) � x1f …<br />

x � � xnf n � Higher order terms.<br />

f 11 f 12 . . f 1n<br />

f21 f22 . . f1n .<br />

.<br />

.<br />

fn1 fn2 fnn X 1<br />

X 2<br />

.<br />

.<br />

X n<br />

�<br />

�f1<br />

�f2 .<br />

.<br />

�fn

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