







n 

 I 



n + 

 _ 1 



1/2 





— ^- 













/i 







- 





*€) 





-•> V 



Ax 











1 





' 



'_ 





+ 1/2 



. 



J 













' 



Ay 









I 



' 















Figure 7. Cell notation 



For the a. (x)-sweep (taken along a grid cell column parallel to the 

 a.. -axis) , 



1 „r+l „r-l) U . , M r. V - ,..r. 



2AT\ U " U + ^^ W ^~^h W 



x ' X 1 1 y22 



2y Aa, a i 

 x 1 L 



-lA****- 1 )* 



orb 



> r u r+1 



6 fs r ) + _JL_ * I s* 



p Aa. a. \ xx / 2y Aa_ 2a„\ xy 



Pd 

 -11 1 



6 (V 1 ) 



'x \i \i Aa Aa, a_a.. 

 y x 2 1 2 1 



6 (U r ) + - -6 — 6„_ (U r ) 



(Vz) 



1 1 



2 a 2 a 2 



6« le 16 IV / = 



„ ,. .2 a y 2a„ 

 2y (Aa„) 2 y 2 



y 2 



2y y Aa.AcL 2a„ \ x/ a 

 xv 2 1 2 \ / 



(37) 



at (n,m + 1/2) 



26 



