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CHAPTER II Powersim Study

2.1 Approach to the dynamics analysis of the systems (System dynamics approach)

Many models of simulation contain variable that they change continuously. In other models the changes of the variable ones happen gradually in a period of extensive time; however they can be dealt like continuous.
An example could wholesale be the amount of the inventory of a store, in a productive system of distribution, the course of many years. In the moment in which the question of the customer it is fulfilled the inventory is emptied and that induces to a new order towards the factory in order to re-establish the supply in warehouse.
With the time, particularly if the orders are small and frequent, as it happens in the just-in-Time system, the level of inventory can be represented from a continuous function.
Variable the continuous ones are often variable calls of state. A continuous model of simulation defines the equations for relazionare between they the variable ones of state so that the dynamic behaviors of the system can be study to you in the course of the time.
A methodology in order to simulate the continuous systems is a activity-scanning approach in which the time it is subdivided in small you leave.
Le equazioni che definiscono il modello sono usate by determinare come le variabili di stato cambiano durante un periodo di tempo.
A specific methodology of continuous simulation is called system dynamics (SD) that is dynamics analysis of systems (ADS).
System dynamics is a methodology of simulation based on it uses of the computer developed near Massachusetts Institute of Technology (MIT) in the years fifty like one instrument for the managers in order to analyze complex problems.
Nowadays its main public is constituted still from the managers even if its I use has extended also in academy, where university professors and students use in order to model it systems of every conceivable discipline, from the history and literature to Biology, physics and economy.
The word “dynamics” implies continuous changes and is that that the dynamic systems make - they change continuously with the time. Their position, or be, is not the same today like it was yesterday and tomorrow it will change still.
De la “eventi no a solas del gli de di vedere del possibilitŕ del la del silicio ha simulación de la dinámica del sistema” de Usando, tempo del mA anche modelli di comportamento col.
The simulation is is time behind to turns out to you historical but it watches ahead also in in order foretelling the possible ones turns out to you future.
SD extension as the structure of a system is the cause of its successes or failures. This structure is represented from a series of relations causal connected between they.
The simulations of the dynamic systems not only serve to communicate what you would happen, but also because.
This because the simulations are planned in order to correspond to what it is, or it could happen, in the real world.
System dynamics focuses on the structure and the behavior of the systems that are composed from interactions between variable.
A system dynamics model usually it takes the shape of an infuence diagram that extension the relations and interactions between a set of variable.
System dynamics is, therefore, an approach experiences them to the systems analysis.
A way in order to understand complex systems modifying them or changing them in some way. It is also an approach for valicare or estimating the consequences of a implementation analytics of a model or recommendations for a report of a study case.
Important to evidence that this approach door to see the organization in terms of flows and not of functions. SD is the ideal instrument in order to support the decisional process in the planning and programming activity, in how much:

Important to predefine the level of analysis of detail to which it is wanted to be arrived or the distance that is wanted to be taken in order better to comprise is real the problematic ones is the context. From the methodological point of view SD it is, moreover, the much taken care of in guiding customer in the modellizzazione process and of definition of the several ones it is made:
  1. location of the key factor of the problem;
  2. location of relative the variable ones;
  3. classification and characterized levels of importance of the variable ones;
  4. formalizzazione of the problem, definition of the variable relations between important;
  5. design of the model (qualitative phase, that is cartacea schematizzazione);
  6. realization of the computerized model (quantitative phase, that is simulation model);
  7. simulation and test of the model.
The customer comes also supported along all the decisional process:
  1. location of the solutions (alternatives);
  2. definition of the systems of measurement of turns out to you and of the impacts in terms it is quantitati to you that qualitati to you (where possible);
  3. evidenziazione of the qualitative factors you;
  4. appraisal and comparazione of the various ones turn out to you;
  5. appraisal of the effects of the various considered hypotheses;
  6. chosen of that optimal one;
  7. final decision.
The risk that can be run is in getting lost in the realization of mega-models, constructed in order to manage all variable possible and the imaginable ones; the force of these types of system is in their ability to synthetize macro-models and to develop the important sub-models of detail to the decisional process in action
This result can be caught up is implementing the model of departure synthesis, is developing other models and integrating them from each other.
The process previews translate (to transform) the formal model in model computerized before in order to verify of the behaviors, then in order to verify the decisional political in existence, projecting them and simulating some it is turns out to you is the impacts acclimatizes them deriving from the eventual performance of the decision to take.
Every enterprise has of objects to you, more or less it formalizes to you, and it is task of the organization to monitorare the trend managerial in order to guarantee the attainment of objects to you same.
After all it can be asserted that SD incorporates characteristics that render it especially useful for sure problems:
  • SD can model to the effect of the feedback information (feedback information) on the future direction of the model. As an example if the time of the cycle of a production process becomes excessive, the management would take part typically in order to bring changes to the same process, while simulating several times the process would evidence simply that the time of the cycle was continuing to grow. System dynamics maneggia tutto ciň facilmente.
  • In order to facilitate the use of the feedback of information SD it accurately separates to the accumulated information on the state of the system and the information fed from that state in order to control the evolution of the future states.
These two characteristics key qualify a model of system dynamics addressing in appropriate way situations that evolvono with the time.



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