Environmental Engineering Reference
In-Depth Information
health). An indicator has to be measurable more easily than the target that it
indicates. To be usable as an indicator, it needs to have a defined relationship to
the ecological condition that is indicated.
Ecosystem Resilience The ability of an ecological system to resist external
disturbances and to maintain its primary state with state variables, driving variables,
and parameters. To trigger a
!
phase-shift
the disturbance has to be stronger in
higher resilient systems.
Eigenvalue
It is a number
l
satisfying the equation Av =
l
v, the non-zero
vector v being the eigenvector of the
square matrix
A. In general, a matrix
acts on a vector by changing both its magnitude and its direction. A matrix acts on
an eigenvector by multiplying its magnitude by a factor, which is positive if its
direction is unchanged and negative if its direction is reversed. This factor is the
eigenvalue associated with that eigenvector. They both give important information
about the matrix, and can be used e.g. in matrix factorization.
!
Eigenvector
See
eigenvalue
.
Emergent Properties On the basis of interactions between lower-level compo-
nents, new qualities can appear on higher hierarchical integration levels which
represent more than the sum of the constituting elements.
Exergy A thermodynamical concept, that indicates the sum of the energy in a
system that can realize work, when the system is brought into a thermodynamic
equilibrium.
Feedback Process
cause-effect chain
,in
which the output signal loops back and influences the input conditions.
It describes the mechanism in a
!
Fractal A geometric term to describe objects which show self-similarity on
different levels of magnification. Any part of the object thus has the same type of
basic pattern/structure as the whole. The geometry of many natural phenomena like
coastlines, snowflakes, clouds, dispersal pathways, can be described using fractal
geometry. Plotting the measured quantities versus scale on a log-log graph gives a
straight line with the slope indicating the fractal dimension.
Functional Groups Collection of organisms that respond to environmental stimuli
in a similar way or have similar properties with respect to the investigated questions.
Gaussian Distribution A very common continuous probability distribution,
based on the central limit theorem stating that a collection of independent random
variables with n
!1
, is normally distributed around a single mean value (normal
distribution).
