Errata
Equation 8.24 on page 178 is incorrect. The correct equation is
UE = CV2/2
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The two-dimensional triangular finite element program fem_ed_1.m as presented
is corrupted. The nine lines that create the matrix a shown on page
297 should be replaced with the following (nine) lines:
a(n1,n1) = a(n1,n1) + Area*(b(1,tri)^2 + c(1,tri)^2);
a(n1,n2) = a(n1,n2) + Area*(b(1,tri)*b(2,tri) + c(1,tri)*c(2,tri));
a(n1,n3) = a(n1,n3) + Area*(b(1,tri)*b(3,tri) + c(1,tri)*c(3,tri));
a(n2,n2) = a(n2,n2) + Area*(b(2,tri)^2 + c(2,tri)^2);
a(n2,n1) = a(n2,n1) + Area*(b(2,tri)*b(1,tri) + c(2,tri)*c(1,tri));
a(n2,n3) = a(n2,n3) + Area*(b(2,tri)*b(3,tri) + c(2,tri)*c(3,tri));
a(n3,n3) = a(n3,n3) + Area*(b(3,tri)^2 + c(3,tri)^2);
a(n3,n1) = a(n3,n1) + Area*(b(3,tri)*b(1,tri) + c(3,tri)*c(1,tri));
a(n3,n2) = a(n3,n2) + Area*(b(3,tri)*b(2,tri) + c(3,tri)*c(2,tri));
The discussion leading to the generation of these terms, Section 13.3, is correct and the example, equation (13.13), is also correct.
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The program listing for fd5.m has an error in the 4th line of code. The line
[Imin, Imax, Jmin, Jmax, hi, hj, bc_nodes] = prob9_1(ns);
should read
[Imin, Imax, Jmin, Jmax, hi, hj, bc_nodes] = get_ijk(Imin,Imax,Jmin, Imax,Jmax,0);
This and other programs in chapter 9 require the function get_ijk(...).m. This file may be found in the folder of programs for chapter 8 on the John Wiley website.