D • CONDUCTION OF HEAT 



y = o 



Fig. D,17b. 



h(x) 

 Fig. D,17c. 



case when /i is a rapidly varying function of x, and this is indeed the 

 case in practice. 



On the other hand, a reasonable approximate solution can be obtained 

 on the basis of the following simplified, yet representative, model: The 

 actual /i-distribution is approximated by a rectangular symmetric dis- 

 tribution as shown in Fig. D,17c, while the slab is assumed to extend to 

 ± =0 . It is shown in [30] that this ideahzation is a reasonable one. Finally, 



( 286 > 



