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1.

001-es BibID:BIBFORM048051
Első szerző:Do, Tien Van
Cím:An efficient method to solve a two-server heterogeneous retrial queue with threshold policy / T. V. Do, R. Chakka, J. Sztrik, T. Bérczes, D. Efrosinin
Dátum:2013
Megjegyzések:In this paper we introduce a new method to examine a Markovian queueing systemwith two-server heterogeneous retrial queue with threshold policy and constant retrial rate.The system operates under a threshold policy:we used the faster server whenever it is idle anda customer tries to occupy it.The slower server can be activated only when the numberof waiting customers exceeds a threshold level.The model of the system can describe as a quasi-birth-and-death (QBD) process with threshold dependent block-tridiagonal infinitesimal matrix.The computation of the rate matrix R (the minimal non-negative solution to the matrix equation)can be expressed in a closed formula.The main performance measures were calculated.
ISBN:978-606-93094-8-3
Tárgyszavak:Műszaki tudományok Informatikai tudományok előadáskivonat
Controllable queueing system
retrial queue
Megjelenés:Pre-Proceedings of 9th International Conference on Applied Mathematics : 25-28 September, 2013 Baia Mare, Romania. - p. 71-73. -
További szerzők:Chakka, R. Sztrik János (1953-) (informatikus, matematikus) Bérczes Tamás (1975-) (informatikus) Efrosinin, Dmitry
Pályázati támogatás:TÁMOP-4.2.2.C-11/1/KONV-2012-0001
TÁMOP
Hálózatok modellezése és analízise
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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2.

001-es BibID:BIBFORM114847
035-os BibID:(cikkazonosító)4002 (Scopus)85176386721
Első szerző:Efrosinin, Dmitry
Cím:Robustness of the c[mu]-Rule for an Unreliable Single-Server Two-Class Queueing System with Constant Retrial Rates / Dmitry Efrosinin, Natalia Stepanova, Janos Sztrik
Dátum:2023
ISSN:2227-7390
Megjegyzések:We study the robustness of the c[mu]-rule for the optimal allocation of a resource consisting of one unreliable server to parallel queues with two different classes of customers. The customers in queues can be served with respect to a FIFO retrial discipline, when the customers at the heads of queues repeatedly try to occupy the server at a random time. It is proved that for scheduling problems in the system without arrivals, the c[mu]-rule minimizes the total average cost. For the system with arrivals, it is difficult directly to prove the optimality of the same policy with explicit relations. We derived for an infinite-buffer model a static control policy that also prescribes the service for certain values of system parameters exclusively for the class-i customers if both of the queues are not empty, with the aim to minimize the average cost per unit of time. It is also shown that in a finite buffer case, the c[mu]-rule fails.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
queueing system
c[mu]-rule
scheduling problem
static policy
average cost
Megjelenés:Mathematics. - 11 : 18 (2023), p. 1-14. -
További szerzők:Stepanova, Natalia Sztrik János (1953-) (informatikus, matematikus)
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3.

001-es BibID:BIBFORM099836
Első szerző:Efrosinin, Dmitry
Cím:Full Version for Algorithmic Analysis of Finite-Source Multi-Server Heterogeneous Queues / D. Efrosinin, N. Stepanova, J. Sztrik
Dátum:2021
ISBN:9785914502581
Tárgyszavak:Természettudományok Matematika- és számítástudományok előadáskivonat
könyvrészlet
Megjelenés:Distributed Computer and Communication Networks: Control, Computation, Communications / Vishnevskiy Vladimir M. - p. 424-453. -
További szerzők:Stepanova, Natalia Sztrik János (1953-) (informatikus, matematikus)
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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4.

001-es BibID:BIBFORM097475
035-os BibID:(cikkazonosító)2624 (WoS)000716353200001 (Scopus)85117468799
Első szerző:Efrosinin, Dmitry
Cím:Algorithmic Analysis of Finite-Source Multi-Server Heterogeneous Queueing Systems / Dmitry Efrosinin, Natalia Stepanova, Janos Sztrik
Dátum:2021
ISSN:2227-7390
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Mathematics. - 9 : 20 (2021), p. 1-24. -
További szerzők:Stepanova, Natalia Sztrik János (1953-) (informatikus, matematikus)
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5.

001-es BibID:BIBFORM088719
035-os BibID:(cikkazonosító)1803 (WoS)000587008800001 (Scopus)85093092194
Első szerző:Efrosinin, Dmitry
Cím:Approximations in Performance Analysis of a Controllable Queueing System with Heterogeneous Servers / Dmitry Efrosinin, Natalia Stepanova, Janos Sztrik, Andreas Plank
Dátum:2020
ISSN:2227-7390
Megjegyzések:The paper studies a controllable multi-server heterogeneous queueing system where servers operate at different service rates without preemption, i.e., the service times are uninterrupted. The optimal control policy allocates the customers between the servers in such a way that the mean number of customers in the system reaches its minimal value. The Markov decision model and the policy-iteration algorithm are used to calculate the optimal allocation policy and corresponding mean performance characteristics. The optimal policy, when neglecting the weak influence of slow servers, is of threshold type defined as a sequence of threshold levels which specifies the queue lengths for the usage of any slower server. To avoid time-consuming calculations for systems with a large number of servers, we focus here on a heuristic evaluation of the optimal thresholds and compare this solution with the real values. We develop also the simple lower and upper bound methods based on approximation by an equivalent heterogeneous queueing system with a preemption to measure the mean number of customers in the system operating under the optimal policy. Finally, the simulation technique is used to provide sensitivity analysis of the heuristic solution to changes in the form of inter-arrival and service time distributions.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Mathematics. - 8 : 10 (2020), p. 1-18. -
További szerzők:Stepanova, Natalia Sztrik János (1953-) (informatikus, matematikus) Plank, Andreas
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6.

001-es BibID:BIBFORM076551
Első szerző:Efrosinin, Dmitry
Cím:Reliability Analysis of an Aging Unit with a Controllable Repair Facility Activation / Dmitry Efrosinin, Janos Sztrik, Mais Farkhadov, Natalia Stepanova
Dátum:2018
ISSN:2194-1009
Megjegyzések:The chapter utilizes the continuous-time Markov chain for modeling the processes of the gradual aging with maintenance on a finite discrete set of an intermediate failure states. The transitions occur according to the birth-and-death process, and the unit fails completely after visiting the last available state. The unit of a multiple and single use is studied. The switching of the repair facility is performed by a hysteresis control policy with two threshold levels for switching on/off the repair server. We provide the expressions for the stationary and non-stationary performance and reliability characteristics, solution of optimization problems, and sensitivity analysis of the reliability function.
ISBN:978-3-319-76034-6 978-3-319-76035-3
Tárgyszavak:Műszaki tudományok Informatikai tudományok tanulmány, értekezés
Megjelenés:Statistics and Simulation / ed. Jürgen Pilz, Dieter Rasch, Viatcheslav B. Melas, Karl Moder. - p. 403-417. -
További szerzők:Sztrik János (1953-) (informatikus, matematikus) Farkhadov, Mais Stepanova, Natalia
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7.

001-es BibID:BIBFORM075189
035-os BibID:(WoS)000442060500013 (Scopus)85049473459
Első szerző:Efrosinin, Dmitry
Cím:An algorithmic approach to analysing the reliability of a controllable unreliable queue with two heterogeneous servers / Dmitry Efrosinin, Janos Sztrik
Dátum:2018
ISSN:0377-2217
Megjegyzések:We consider a Markovian queueing system with two unreliable heterogeneous servers and one common queue. The servers serve customers without preemption and fail only if they are busy. Customers are allocated to one or the other server via a threshold control policy which prescribes using the faster server whenever it is free and the slower server only when the number of waiting customers exceeds a specified threshold level that depends on the state of the faster server. This paper focuses on the reliability analysis of a system with unreliable heterogeneous servers. First, we obtain the stationary state distribution using a matrix-geometric solution method. Second, we analyse the lifetimes of the servers and of the system. We provide algorithms for calculating the stationary reliability characteristics, reliability functions in terms of the Laplace transform and the mean times to the first failure. A new reliability measure is introduced in the form of the discrete distribution function of the number of failures during a specified life time that is derived from a probability generating function. The effects of various parameters on these reliability characteristics are analysed numerically.
Tárgyszavak:Műszaki tudományok Informatikai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:European Journal Of Operational Research. - 271 : 3 (2018), p. 934-952. -
További szerzők:Sztrik János (1953-) (informatikus, matematikus)
Pályázati támogatás:RUDN University Program 5-100
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8.

001-es BibID:BIBFORM070809
Első szerző:Efrosinin, Dmitry
Cím:Reliability analysis of a two-server heterogeneous unreliable queueing system with a threshold control policy / Dmitry Efrosinin, Janos Sztrik, Mais Farkhadov, Natalia Stepanova
Dátum:2017
ISSN:1865-0929
Megjegyzések:Heterogeneous servers which can differ in service speed and reliability are getting more popular in modeling of modern communication systems. For a two-server queueing system with unreliable servers the allocation of customers between the servers is performed via a threshold control policy which prescribes to use the fastest server whenever it is free and the slower one only if the number of waiting customers exceeds some threshold level depending on the state of faster server. The main task of the paper consists in reliability analysis of the proposed system including evaluation of the stationary availability and reliability function. The effects of different parameters on introduced reliability characteristics are analyzed numerically.
ISBN:978-3-319-68068-2 978-3-319-68069-9
Tárgyszavak:Műszaki tudományok Informatikai tudományok tanulmány, értekezés
Megjelenés:Information technologies and mathematical modelling : Queueing theory and applications / Eds. Alexander Dudin, Anatoly Nazarov, Alexander Kirpichnikov. - p. 13-27. -
További szerzők:Sztrik János (1953-) (informatikus, matematikus) Farkhadov, Mais Stepanova, Natalia
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9.

001-es BibID:BIBFORM068363
Első szerző:Efrosinin, Dmitry
Cím:Reliability analysis of a controllable queueing system with two heterogeneous servers subject to failures / D. Efrosinin, J. Sztrik, M. Farkhadov
Dátum:2016
Megjegyzések:To make modern communication systems superior in performance and reliability to the previous generation systemsthey can be supplied with heterogeneous communication links. Such links can differ in availability, link datathroughputs, power consumption and reliability characteristics. To model the dynamic behaviour of the links withdifferent properties a queueing system with non-reliable heterogeneous servers can be used. While the first steps inthe performance analysis of controllable heterogeneous queueing systems have already been developed for completelyreliable servers, a missing link to an applicability of these models is reliability analysis of such queues withservers subject to failures. In this paper we use a matrix transform based method to evaluate reliability measuressuch as reliability function and mean time to the first failure for each server separately and for the total servicefacility under the fixed threshold allocation control policy. The reliability functions are obtained in terms of theLaplace transform and numerical inversion algorithm is used to get the time dependent functions. Additionally anew discrete reliability metric which can be treated as a discrete counterpart to the distribution of the time to failureis introduced. This function specifies the distribution of the number of repairs of the server until a complete failureof the service facility occurs. Some numerical examples illustrate the efficiency of the proposed algorithms.
Tárgyszavak:Műszaki tudományok Informatikai tudományok előadáskivonat
Megjelenés:European Conference On Queueing Theory 2016. Toulouse July 18 - 20, 2016. - p. 44.
További szerzők:Sztrik János (1953-) (informatikus, matematikus) Farkhadov, Mais
Internet cím:Intézményi repozitóriumban (DEA) tárolt változat
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10.

001-es BibID:BIBFORM065278
Első szerző:Efrosinin, Dmitry
Cím:Optimal control of a two-server heterogeneous queueing system with breakdowns and constant retrials / Dmitry Efrosinin, János Sztrik
Dátum:2016
ISSN:1865-0929
Megjegyzések:Heterogeneous servers which can differ in service speed and reliability are becoming more popular in the modelling of modern communication systems. For a two-server queueing system with one non-reliable server and constant retrial discipline we formulate an optimal allocation problem for minimizing a long-run average cost per unit of time. Using a Markov decision process formulation we prove a number of monotone properties for the increments of the dynamic-programming value function. Such properties imply the optimality of a two-level threshold control policy. This policy prescribes the usage of a less productive server if the number of customers in the queue becomes higher than a predefined level which depends on the state of a non-reliable more powerful server. We provide also a heuristic solution for the optimal threshold levels in explicit form as a function of system parameters.
ISBN:978-3-319-44614-1 (print) 978-3-319-44615-8 (online)
Tárgyszavak:Műszaki tudományok Informatikai tudományok könyvfejezet
optimal allocation
Markov decision process
monotonicity properties
threshold policy
heterogeneous servers
long-run average cost
Megjelenés:Information technologies and mathematical modelling - queueing theory and applications : 15th International Scientific Conference, ITMM 2016, named after A.F. Terpugov, Katun, Russia, September 12-16, 2016. Proceedings / Eds. Alexander Dudin, Alexander Gortsev, Anatoly Nazarov, Rafael Yakupov. - p. 57-72. -
További szerzők:Sztrik János (1953-) (informatikus, matematikus)
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11.

001-es BibID:BIBFORM061918
Első szerző:Efrosinin, Dmitry
Cím:Performance analysis and statistical modeling of the single-server non-reliable retrial queueing system with a threshold-based recovery / Dmitry Efrosinin, János Sztrik
Dátum:2015
Megjegyzések:In this paper we study a single-server Markovian retrial queueing system with non-reliable server and threshold-based recovery policy. The arrived customer finding a free server either gets service immediately or joins a retrial queue. The customer at the head of the retrial queue is allowed to retry for service. When the server is busy, it is subject to breakdowns. In a failed state the server can be repaired with respect to the threshold policy: the repair starts when the number of customers in the system reaches a fixed threshold level. Using a matrix-analytic approach we perform a stationary analysis of the system. The optimization problem with respect to the average cost criterion is studied. We derive expressions for the Laplace transforms of the waiting time. The problem of estimation and confidence interval construction for the fully observable system is studied as well.
ISBN:978-3-319-25860-7 (print) 978-3-319-25861-4 (online)
Tárgyszavak:Műszaki tudományok Informatikai tudományok könyvfejezet
quasi-birth-and-death process
retrial queues
performance analysis
confidence intervals
Megjelenés:Information Technologies and Mathematical Modelling - Queueing Theory and Applications : 14th International Scientific Conference, ITMM 2015, named after A. F. Terpugov, Anzhero-Sudzhensk, Russia, November 18-22, 2015, Proceedings / Alexander Dudin, Anatoly Nazarov, Rafael Yakupov. - p. 330-343. -
További szerzők:Sztrik János (1953-) (informatikus, matematikus)
Pályázati támogatás:Austro-Hungarian Cooperation Grant No. 90u6, OMAA 2014
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12.

001-es BibID:BIBFORM055918
Első szerző:Efrosinin, Dmitry
Cím:Optimal allocation problem in the machine repairman system with heterogeneous servers / Dmitry Efrosinin, Christopher Spannring, Janos Sztrik
Dátum:2014
ISSN:1865-0929
Megjegyzések:A controllable repairman model consists of L machines subject to failures and two repair servers working at different speeds. The problem of optimal allocation of failed machines between the servers is examined. The optimal control policy is calculated versus cost structures. As a result the optimal policy can be of threshold type, hysteretic type or have more complicated form. It is shown that the corresponding Markov process for hysteretic control policy belongs to the class of the Quasi-Birth-and-Death processes (QBD) with three diagonal block infinitesimal matrix. The stationary characteristics in this case are derived in matrix analytic form. Some numerical results are used to illustrate a number of features of the controlled model under study.
ISBN:978-3-319-13670-7 (softcover) 978-3-319-13671-4 (e-book)
Tárgyszavak:Műszaki tudományok Informatikai tudományok könyvfejezet
Machine repairman system
performance analysis
dynamic- programming
optimal allocation
threshold policy
hyster etic policy
Hálózatok modellezése és analízise
Megjelenés:Information Technologies and Mathematical Modelling : 13th International Scientific Conference, named after A.F. Terpugov, ITMM 2014, Anzhero-Sudzhensk, Russia, November 20-22, 2014. Proceedings / ed. Alexander Dudin, Anatoly Nazarov, Rafael Yakupov, Alexander Gortsev. - p. 113-122. -
További szerzők:Spannring, Christopher Sztrik János (1953-) (informatikus, matematikus)
Pályázati támogatás:TÁMOP-4.2.2.C-11/1/KONV-2012-0001
TÁMOP
Hálózatok modellezése és hatékonyságvizsgálatai
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