Research on Green Transport Mode of Chinese Bulk Cargo Based on Fourth-Party Logistics

Table 1

Parameters, sets, and decision variables.

Symbol	Description
	The distance from the shipper j to the freight n (km)
	The distance from the consignee i to the freight n (km)
qijkn	The unit transportation capacity of the vehicle k from the shipper j to the consignee i through the freight enterprise n
cijkn	The cost of per vehicle per unit distance (yuan/km)
I	The set including suppliers indexed by i, I = {0, 1, 2, ..., i}
J	The set including shippers indexed by j, J = {0, 1, 2, ..., j}
P	The set including supply and demand points from shipper j to consignee i
K	The set including freight vehicles indexed by k
N	The set including freight enterprises indexed by n, N = {0, 1, 2, ..., n}
Gn	Maximum load of the freight enterprise n
Cn	The cost of loading and unloading cargo of the freight enterprise n per unit time
Si	The set including cargo quantity obtained by the consignee i
Dj	The set including cargo quantity issued by the shipper j
Wn	The freight handling capacity of the freight enterprise n
α1, α2	The carbon tax rate of bulk cargo transport network with/without fourth-party logistics
β1, β2	The carbon emission factors per unit distance per product in road/rail transport
d^p	The number of emergency supplies between the point pair p in the period, p ∈ P
V = I ∪ J ∪ N
H	The opening cost of the fourth-party logistics service
CI	The information transaction cost of the traditional bulk cargo transport network
E	Carbon emissions from bulk cargo transport networks
Qn	Maximum load of carbon emission capacity of all vehicles in the freight enterprise n
xijkn∈{0, 1}	If the vehicle k is transported from the shipper j to the consignee i via the freight enterprise n, then xijkn = 1; otherwise, xijkn = 0
yn∈{0, 1}	If the fourth-party logistics service is opened, then yn = 1; otherwise, yn = 0
	If the shipper j to the consignee i is transported by the vehicle k and serves the point pair p via freight enterprise n, then apijkn = 1; otherwise, apijkn = 0
	If the freight enterprise n is served the supply and demand point p, then  = 1; otherwise,  = 0.
X^+ = {xijkn|∀i ∈ V, ∀j ∈ V, ∀n ∈ V, ∀k ∈ K}
X^- = {apijkn|∀i ∈ V, ∀j ∈ V, ∀n ∈ V, ∀k ∈ K, ∀p ∈ P}
Y = {yn|∀n ∈ N}