1. Stock and Flow Diagram Roesfiansjah Rasjidin PS Teknik Industri FT - UEU

2. Stock-and-flow diagram is built using a particular diagramming notation:  Stocks  Flows  Valves and  Clouds. Diagramming Notation

3.  Stocks or levels are represented by rectangles or boxes  Stock or level variables describe accumulations in the system. Stocks

4.  Flows or rates are represented by pipes  There are two types of flows which are inflows and outflows  Inflows are represented by a pipe (arrow) pointing into (adding to) the stock  Outflows are represented by pipes pointing out of (substracting from) the stock. Flows

5.  Flow controls are represented by valves  Clouds represent the sources and sinks for the flows  A source represents the stock from which a flow originating outside the boundary of the model arises  Sinks represent the stocks into which flows leaving the model boundary drain  Sources and sinks are assumed to have infinite capacity and can never constrain the flows they support Valves and Clouds

6. The general structure of stock-and-flow diagram

7.  Stocks accumulate or integrate their flows  where inflow(s) represents the value of the inflow at any time s between the initial time t 0 and the current time t  It represents the concept that the stock accumulates its inflows less its outflows, beginning with an initial value of Stocks (t0) (Sterman, 2000) Mathematical representation of stocks and flows

8. Discussion