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In FMBIEM, we follow the techniques proposed by Song et
al.[76] to truncate the infinite series taking P terms, where



(3.132) 
k is the wave number and R is the diameter of a sphere which
circumscribes a cell. One has
,
where D is the edge
length of a cell. This means that we must change P as the level
changes. Also, P increases as the size of a cell or the wave number
becomes large. This property leads to a lot of computational cost when
one deals with high frequency problems or largescale problems. In order to
overcome this problem some techniques are proposed by several authors
(e.g. Rokhlin et al.[71] or Greengard et al.[34]).
However, we do not use these techniques in this thesis since we are
interested in low frequency problems.
Figure 3.39:
kR vs P

Kenichi Yoshida
20010728