The Promotion Strategy Analysis for Green Degree of Railway Engineering Based on a System Dynamic Flow Diagram

Table 3

Parameter list of GRE system.

Type	Character	Name	Symbol
Level variable (L)	A variable that determines the behavior of the system over time. The value of the current moment is equal to the value of the past moment plus the change in time over time	Ecological damage degree	L1
		Environmental pollution degree	L2
		Land occupation degree	L3
		Resource consumption degree	L4
Rate variable (R)	A variable that directly changes a level variable, reflecting the speed at which the state variable is input or output	Environment damage rate	R11
		Ecological restoration rate	R12
		Pollution emission rate	R21
		Pollution treatment rate	R22
		Land occupancy rate	R31
		Release occupancy rate	R32
		Resource consumption rate	R41
Auxiliary variable (A)	Variables that affect the system but do not directly control the level variable have independent values at each time	Green schemes	A1
		Control values from green schemes	A11∼A14
		Green knowledge innovation	A21
		Green culture creative	A22
		Deviations form level variable	A31∼A34
		Engineering garbage	A4
		Garbage recycling	A41
		Wastage	A42
External variable (E)	It varies over time but not by any other variable in the system	Eco-environmental carrying capacity	E1
		Green resource conditions	E2
		Green knowledge reserve	E3
		Green talent reserve	E4