2.3.2 Variable members of the women's army auxiliary corps, constants and flows of information (connections).
One is hardly inasmuch as it is possible to only create an entire model with levels and flows.
Powersim Study has some instruments added to you that they help to capture the phenomena of the real world in a model.
To realize a sure level of detail or to help in the formulation of equations for the percentages of flow, is some
time necessary in order to model one variable like helping like shown in figure 2.7.
Figure 2.7
A variable member of the women's army auxiliary corps is used in order to arrange or to reformulate information; she does not have a shape standard; it is a algebrico calculation
of some combinations of levels, flows or other auxiliary ones.
Even if the variable members of the women's army auxiliary corps can seem of the accumulations, they various do not have no memory from the levels.
The auxiliary ones are used in order to model information, not the physical flow of assets, therefore they change without delays,
instantaneously. They can constitute contributions to the flows but never directly to the levels, because the flows are only
the variable ones that can change their levels associate to you.
Variable of flow and the auxiliary ones are defined exactly to the same way; the difference is that first
they are connected to the flow valve and with that they control the flow directly.
The constants are, various from the variable ordinaries members of the women's army auxiliary corps, constants in the period of time of the simulation.
A rumble represents to them, like shown in figure 2.8.
Figure 2.8
One constant is defined from a value begins them, and maintains to this value in all the simulation, less than the customer not changes
manually the value.
As an example in a simulation of a year a society can have an essentially fixed force-job that it can be represented
from one constant. If the simulation were expanded to twenty years, the force-job could be dealt like a level and
be induced, therefore, to vary in the time.
There is therefore need to define the temporal borders of the model. Without a clear definition of the model to define
it is not possible to fix the correct borders.
Some time is not clear if an element of the system must be dealt like one constant or like a level.
It would have to think next to the period of time of the problematic behavior and if it is or he is not reasonable to expect that that element
changes in that period. In this way it is placed to us in a better position in order to decide which elements would have to be
constant and which would have to vary during the simulation.
The connections of information are made between constants, auxiliary and levels. These connections have the aspect of
thin connectors, like shown in figure 2.9.
Figure 2.9-I information connections connect various variable
The connections show as the elements characterize them of the system are puttinges together. They close the feedback cycles.
Already it has been looked at like the flows change the levels filling up them or exausting them. The information connections can transfer
of new the value of the level to the flow, indicating one dependency of the flow on the level, therefore like the dependency of the level
on the flow.
To every variable it goes then associated an equation that allows the calculating to determine the value of the variable ones and their
variation in the time.
It is obvious that if a model is wanted to be obtained much faithful to the truth, to establish the just equations it will be a job not less
onerous that to construct the structure of the model; often it will be even impossible to use true and own equations, and it will be rerun
to systems of tables that bring back “the true” values.
However, for having an idea of principle of the behavior of the usual model they are sufficient truly elementary equations:
therefore it is already succeeded to obtain many rivelatorie information on the behavior of principle of the system, and on the type of
strategies that can be adopted.