This special issue contains a selective collection of carefully

refereed papers based on talks presented during the 15th Baikal

International School-Seminar on Optimization Methods and

Their Applications held during June 23-29, 2011 and dedicated

to the memory of Valerian P. Bulatov (1935-2010), who made a

number of important contributions to the different fields of optimization

and who played a leading role in organization of Baikal

conferences.

These papers deal with both theoretical and practical aspects of

optimization.