Using genetic algorithms for the single allocation hub location problem

Hub location problem is an NP-hard problem that frequently arises in the design of transportation and distribution systems, postal delivery networks, and airline passenger flow. This work focuses on the Single Allocation Hub Location Problem (SAHLP). Genetic Algorithms (GAs) for the capacitated and uncapacitated variants of the SAHLP based on new chromosome representations and crossover operators are explored. The GAs is tested on two well-known sets of real-world problems with up to 200 nodes. The obtained results are very promising. For most of the test problems the GA obtains improved or best-known solutions and the computational time remains low. The proposed GAs can easily be extended to other variants of location problems arising in network design planning in transportation systems.

Commemorative stamps, British, American and Canadian, 1974-1977, 1982-1984, 1996.

The Guernsey post office stamps consist of 2 exhibition series souvenir sheets commemorating Major-General Sir Issac Brock, 1769-1812. The stamp was issued in 1996 to celebrate Guernsey’s attendance at Canada’s international stamp exhibition CAPEX 96. The stamps issued by the United States postal service consist of 1 sheet of stamps commemorating the 50th anniversary of the Peace Bridge, 1927-1977. The stamps issued by Canada Post include 5 commemorative day-of-issue envelopes with stamps featuring William Hamilton Merritt and the Welland Canal. This stamp was issued in 1974 to celebrate the 150th anniversary of the canal. There is also a set of 4 inscription corner blocks of stamps. These items are contained in an envelope addressed to Mr. J.N. Jackson, St. Catharines, ON. There is also a separate sheet of the same stamp. Also issued by Canada Post are 2 full sheets of stamps, one commemorating the 50th anniversary of the Peace Bridge (1927-1977), and one commemorating 25 years of the St. Lawrence Seaway (1959-1984). Lastly, there are 2 full sheets of stamps commemorating the 100th anniversary of the Royal Henley Regatta, issued in 1982.