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property that the discrete solutions u satisfy
h
u − u ≤ Cinf
u − v .
Q Here, u ∈ V denotes the solution of the continu-
h V
h V
v h ∈V h
ous variational problem. In a strict sense, the
constant C> 0 must not depend on the choice of
V . In a loose sense, it may depend on the family
h
QCD See chromodynamics, quantum.
of finite elements, but not on the triangulation,
on which V is built. In a very loose sense, if fam-
h
quantum yield, ) ) ) The number of defined
ilies of triangulations are involved, one demands
events which occur per photon absorbed by the
that the constant C be independent of the mesh
system. The integral quantum yield is:
width, but it may depend on shape regularity.
) = (number of events)/(number of photons
absorbed)
quasi-uniform A family {; } , H an
For a photochemical reaction: h h∈H
index set, of triangulations of a domain ; ⊂ R n
) =(amountofreactantconsumedorproduct
is called quasi-uniform, if there exists a C> 0
formed)/(amount of photons absorbed)
such that
d[x]/dt (
) = max{diam(K), K ∈ ; }
h
n sup ,h ∈ H ≤ C.
min{diam(K), K ∈ ; }
h
where d[x]/dt is the rate of change of a mea-
surable quantity, and n the amount of photons Sloppily speaking, the cells of all meshes of
(mol or its equivalent einstein) absorbed per unit a quasi-uniform family have about the same
time. ) can be used for photophysical processes diameter. This permits us to provide asymptotic
or photochemical reactions. a priori estimates for interpolation and approxi-
mation errors of finite element spaces in terms of
quasi-optimal Describing a V -conforming the mesh widths.
finite element scheme used to discretize a vari-
ational problem posed over the space V with the quotient space See equivalence relation.

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