4 research outputs found
Rail-freight crew scheduling with a genetic algorithm
peer reviewedThis article presents a novel genetic algorithm designed for the solution
of the Crew Scheduling Problem (CSP) in the rail-freight industry. CSP is the task
of assigning drivers to a sequence of train trips while ensuring that no driver’s
schedule exceeds the permitted working hours, that each driver starts and finishes
their day’s work at the same location, and that no train routes are left without a
driver. Real-life CSPs are extremely complex due to the large number of trips,
opportunities to use other means of transportation, and numerous government
regulations and trade union agreements. CSP is usually modelled as a set-covering
problem and solved with linear programming methods. However, the sheer
volume of data makes the application of conventional techniques computationally
expensive, while existing genetic algorithms often struggle to handle the large
number of constraints. A genetic algorithm is presented that overcomes these
challenges by using an indirect chromosome representation and decoding
procedure. Experiments using real schedules on the UK national rail network
show that the algorithm provides an effective solution within a faster timeframe
than alternative approaches
Fuzzy-logic controlled genetic algorithm for the rail-freight crew-scheduling problem
AbstractThis article presents a fuzzy-logic controlled genetic algorithm designed for the solution of the crew-scheduling problem in the rail-freight industry. This problem refers to the assignment of train drivers to a number of train trips in accordance with complex industrial and governmental regulations. In practice, it is a challenging task due to the massive quantity of train trips, large geographical span and significant number of restrictions. While genetic algorithms are capable of handling large data sets, they are prone to stalled evolution and premature convergence on a local optimum, thereby obstructing further search. In order to tackle these problems, the proposed genetic algorithm contains an embedded fuzzy-logic controller that adjusts the mutation and crossover probabilities in accordance with the genetic algorithm’s performance. The computational results demonstrate a 10% reduction in the cost of the schedule generated by this hybrid technique when compared with a genetic algorithm with fixed crossover and mutation rates
Strain induced abnormal grain growth in nickel base superalloys
Under certain circumstances abnormal grain growth occurs in Nickel base superalloys during thermomechanical forming. Second phase particles are involved in the phenomenon, since they obviously do not hinder the motion of some boundaries, but the key parameter is here the stored energy difference between adjacent grains. It induces an additional driving force for grain boundary migration that may be large enough to overcome the Zener pinning pressure. In addition, the abnormal grains have a high density of twins, which is likely due to the increased growth rate. © (2013) Trans Tech Publications, Switzerland