Objective: In this study we consider a two-state retrial queueing system with feedback having two identical parallel servers. Transient state probabilities for exact number of arrivals and departures from the will be obtained when both, one or none servers is busy. Numerical graphical solutions also obtained. Methods: The difference-differential equations governing are solved recursively, Lapla...

Abstract We consider the assignment of servers to two phases service in a two-stage tandem queueing system when customers can abandon from each stage service. New jobs arrive at both stations. Jobs arriving station 1 may go through and 2 only one phase Stage-dependent holding lump-sum abandonment costs are incurred. Continuous-time Markov decision process formulations developed that minimize di...

We consider two servers (server i, i-1, 2) in tandem for which the order of servers can be changed. Server 1 has a general service time distribution and server 2 has either its 'shifted' or 'truncated' distribution. This permits that the service times at the two servers are overlapping. An unlimited queue is allowed in front of the first server. For the systems having zero buffer capacity betwe...

We consider 2-server algorithms with time complexity O(1) per each request. We show that the previously known algorithm BALANCE2 has competitiveness constant not better than 6, and present another algorithm whose competitiveness constant is 4.

A group of agents are waiting for their job to be processed in a facility. We assume that each agent needs the same amount of processing time and incurs waiting costs. The facility has two parallel servers, being able to serve two agents at a time. We are interested in finding the order to serve agents and the (positive or negative) monetary compensations they should receive. We introduce two r...

The High-Energy Lightcurve Generator (HILIGT) is a new web-based1 tool which allows the user to generate long-term lightcurves of X-ray sources. It provides historical data and calculates upper limits from image in real-time. HILIGT utilizes twelve satellites, both modern missions such as XMM-Newton Swift, earlier facilities ROSAT, EXOSAT, Einstein or Ariel V. Together, this enables query 50 ye...