Unformatted text preview: Of course, one can simply move the objects in the environment to the system itself, thus making it a closed system. However, this may make the system more complex. Thus, we see that the boundary of a system is flexible. When to keep an object in the system or in environment depends on the intuition of the modeller. It is a subjective decision. One rule could be to keep only the essential objects in the system and others can go to environment. It is to simplify the RWM. The objects in the system and those in environment interact through the variables common to both. 5. Parameters and Variables of the system: The attributes or characteristics of the objects are described in terms of variables and parameters. Parameters are those attributes which are intrinsic to the objects. The variables are those characteristics which describe interactions between objects. 6. Relations: Once we have a system, we should try to define the relationship (interactions) between the objects. Some examples: 1. Weight lifting Problem: One can consider various objects, e.g. weight lifters, weight to be lifted, location of competition, climate etc. However, it is the first two which are important and others hardly influence the outcome (i.e. the weight lifted). Thus one can consider it to be closed system with objects as weight lifters and weight to be lifted. In this case the parameters are (i) body weight of the lifter, (ii) weights to be lifted; and the variable is ‘weight lifted’ by the lifters. 2. Supermarket Problem of Checkout counters: Here the system consists of (i) customers, (ii) items for sale, and (iii) counters. Anything else? If not, then system is a closed system. However, if there is a supermarket in the neighbourhood, then it may influence the customers by providing better service. In that case we can consider the system to be open with an environment (other supermarket). The variables of interest is the queue length and the items purchased by a customer, what else? Parameters – price of various items, number...
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This document was uploaded on 01/25/2014.
- Winter '14