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Stakeholders.
The actors involved in the design process in the case study include the
designer, optimizer and modeler. The roles were manned by research teams involved
in the project.
The designer had the main responsibility of the project. He carried out the require-
ment elicitation with the end-customer, proposed a conceptual design and initiated the
problem formulation for the optimization. He then had a key role in data acquisition
for the model building. After getting the optimization results, he made the decisions
according to the end-users preferences.
The optimizer participated in the problem formulation by having an opinion what
kind of problems can be solved with optimization. After the problem formulation, the
optimizer then asks the modeler to build necessary models for optimization and then
chose the right optimization method. Finally, a suitable method for presenting the
results was chosen.
The modeler was responsible for creating a model simple enough to be calculated.
The modeler was also responsible to make sure that the simplifications do not affect
to the problem to be solved.
Business Process.
The project could be divided into four main tasks: problem formu-
lation, model building, problem solving (optimization) and result interpretation.
Problem Formulation.
At the starting point of the case study a part of the conceptual
design was already performed, e.g. the number of storage towers and material flows
between them was defined. The designer and optimizer then discussed the possibilities
for a manageable optimization problem. They designed that the optimization activity
concerns only about operation design and the dimensioning part of the structure design.
Also the amount of optimized parameters was reduced in negotiations between the
designer and the optimizer. During the optimization activity a mathematical model of
the problem was created and used for finding an optimal design under the specified
requirements. The design problem was formulated as follow:
4
HV
(
)
i
,max)
i
=
1
{
}
2
Eq nq
(
( )
−
)
ψ
Filler
0,
Filler
{
}
2
Eqnq
(()
−
)
min
(2)
ψ
bw
0,
bw
d
{
}
2
Eq
(
( ))
n
ψ
strength
{
}
2
Eun
((
+−
1)
un
())
ψ
{}
−
ET
ψ
v
where
,
is the investment cost of the 4 selected tower volumes,
is the time
till one of the towers goes empty or flows over, and
E
Ψ
{} denotes the expectation
value of the system performance as
Ψ
is the stochastic process with applied dosage
policy.[31]
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