Term

Definition

x_j

number of backup units for component j (decision variable)

n

number of possible backup units for any component

m

number of components in system

i

backup unit index

j

component index

r_ij

reliability of i parallel units for component j

c_ij

cost of i parallel units for component j

pher_ij

pheromone associated with i parallel units for component j

imp_ij

number of times i parallel units for component j has been in the best solution

prob_ij

probability of selecting i parallel units for component j

r_s

system reliability

c_s

system cost

maxR

highest obtained value of system reliability

A

pheromone amplifier

D

discount factor

B

budget