Specifying the Inputs to a Material Delay

Within the Material Delay properties dialog, two sets of Display Units must be specified for a Material Delay (the Outflow Units and the Quantity Units), one for each of the element’s outputs. The Outflow Units determine the dimensions of the Material Delay’s primary output.

Note: GoldSim encourages (but does not require) you to specify Outflow Units for a Material Delay whose dimensions are consistent with a flow of materials. In particular, it expects the units to have dimensions of mass/time, volume/time, energy/time, currency/time, or 1/time. When you first specify the Outflow Units, GoldSim will warn you if your units do not have one of these dimensions. GoldSim will not, however, prevent you from using other units.

The primary output (the Outflow) can only be specified as a value, but can be specified as a scalar, a vector or a matrix. You can specify whether the Material Delay is a scalar, vector or matrix by pressing the Type… button. By default, the output of a new Material Delay element is a scalar, dimensionless value. You can also use Material Delay elements to operate on and create vectors and matrices.

The Quantity Units determine the Display Units for the secondary output of the element, the Amount_in_Transit. The dimensions of this output must be the same as those of the Outflow multiplied by Time. For example, if the Outflow Units have dimensions of Mass/Time, the Quantity Units must have dimensions of Mass.

A Material Delay can have multiple Inflows. You add an Inflow to the element by pressing the Add Material Inflow button (the green +). A browser tree showing all of the elements in the model will be displayed.

Note that this tree is organized by containment in the same manner as the main browser. To insert a link from this dialog, you select a specific output object (or an element having a primary output), and then press OK. If you press Cancel, GoldSim will insert a new blank item. In either case, the dialog will close and the item will be added to the list of Inflows in the properties dialog for the element:

The Inflows must have the same attributes (order and dimensions) as the primary output (the Outflow). Although you can edit any of the input fields after the Inflow is added, the Inflows must all be single links to another element (i.e., you cannot enter an expression here). In addition, the Inflows must be non-negative.

The Initial Outflow to the Material Delay must have the same attributes (order and dimension) as the Outflow.

Note: The Initial Outflow must be a number or a link from a static variable (e.g., a constant Data element or a Stochastic).

Note: The Delay Time for a Material Delay must be greater than or equal to the timestep. That is, GoldSim cannot delay a signal for a smaller time period than a timestep. If you enter a Delay Time which is less than a timestep, GoldSim internally treats the Delay Time as being equal to a timestep. Delay Times that are less than zero will result in a fatal error.

The Dispersion drop-list provides three choices: “None” (the default), “Erlang n”, and “Std. Deviation”.

If one of the latter two is selected, you must enter a value that quantifies the degree of dispersion to the right of this field. If “Erlang n” is selected, you must enter a dimensionless value greater than or equal to 1. If “Std. Deviation” is selected, you must enter a value with dimensions of time. The value must be greater than or equal to zero and less than or equal to the Delay Time.

If the Material Delay is specified as being an array (i.e., a vector or a matrix), you can specify whether the Delay Time and Dispersion are defined as scalars (with the same value being applied to all items of the array), or as arrays (with different values applied to each item of the array). This is done via the Use scalar delay time and dispersion checkbox. If this box is checked (the default), the Delay Time and Dispersion must be entered as scalars. If the box is cleared (which is only possible if the element is specified as an array), the Delay Time and Dispersion must be entered as arrays.