Dear scheduling researcher, We are delighted to announce the talk given by Rubing Chen (Zhengzhou University). The title is "Single-machine hierarchical scheduling with release dates and preemption to minimize the total completion time and a regular criterion". The seminar will take place on Zoom on Wednesday, May 7 at 13:00 UTC. Join Zoom Meeting https://cesnet.zoom.us/j/95815007611?pwd=uA3Wt322MOaLW9M9F8M7UErCNPiZaw.1 Meeting ID: 958 1500 7611 Passcode: 629296 You can follow the seminar online or offline on our Youtube channel as well: https://www.youtube.com/channel/UCUoCNnaAfw5NAntItILFn4A The abstract follows. In this talk, we consider the single-machine hierarchical scheduling problems with release dates and preemption, where the primary criterion is the total completion time and the secondary criterion is an arbitrarily regular scheduling criterion, which is of either the sum-form or the max-form. We aim to find a feasible preemptive schedule that minimizes the secondary criterion, subject to the condition that the primary criterion is minimized. We show that the variants of the problems under study are polynomially solvable. To address these problems, we establish some hereditary properties for the feasible schedules and instances, and present a complete description of the feasible schedules through some elaborately constructed job-permutations. The next talk in our series will be: Zhi-Long Chen (Univ of Maryland) | May 21 | Online Integrated Production and Distribution Scheduling For more details, please visit https://schedulingseminar.com/ With kind regards Zdenek Hanzalek, Michael Pinedo and Guohua Wan -- Zdenek Hanzalek Industrial Informatics Department, Czech Institute of Informatics, Robotics and Cybernetics, Czech Technical University in Prague, Jugoslavskych partyzanu 1580/3, 160 00 Prague 6, Czech Republic https://rtime.ciirc.cvut.cz/~hanzalek/