@article{MTMT:2606206, title = {Computational Aspects for Steady State Analysis of QBD Processes}, url = {https://m2.mtmt.hu/api/publication/2606206}, author = {Tran Tuan, Hung and Do, Van Tien}, journal-iso = {PERIOD POLYTECH ELECTR ENG}, journal = {PERIODICA POLYTECHNICA-ELECTRICAL ENGINEERING}, volume = {44}, unique-id = {2606206}, issn = {0324-6000}, year = {2000}, eissn = {1587-3781}, pages = {179-200} } @article{MTMT:2606205, title = {Generalised Invariant Subspace based Method for Steady State Analysis of QBD-M Processes}, url = {https://m2.mtmt.hu/api/publication/2606205}, author = {Tran Tuan, Hung and Do, Van Tien}, journal-iso = {PERIOD POLYTECH ELECTR ENG}, journal = {PERIODICA POLYTECHNICA-ELECTRICAL ENGINEERING}, volume = {44}, unique-id = {2606205}, issn = {0324-6000}, year = {2000}, eissn = {1587-3781}, pages = {159-178} } @article{MTMT:2629256, title = {Numerical analysis of large Markov reward models}, url = {https://m2.mtmt.hu/api/publication/2629256}, author = {Telek, Miklós and Racz, S}, doi = {10.1016/S0166-5316(99)00032-2}, journal-iso = {PERFORM EVALUATION}, journal = {PERFORMANCE EVALUATION}, volume = {36-37}, unique-id = {2629256}, issn = {0166-5316}, abstract = {A first analysis of Markov Reward Models (MRM) resulted in a double transform expression, whose numerical solution is based on the inverse transformations both in time and reward variable domain. Better numerical methods were proposed based on the time domain properties of these models, such as the set of partial differential equations describing the process evolution in time. This paper introduces an effective numerical method for the analysis of MRMs based on the transform domain description of the system, which allows the evaluation of models with large state space (similar to 10(6) states). The proposed method provides the moments of reward measures on the same computational cost and memory requirement as the transient analysis of the underlying Continuous Time Markov Chain and benefits from the advantages of the randomization method, which avoids numerical instabilities and provides global error bound in advance of the computation. implementation notes and numerical examples demonstrate the numerical properties of the proposed method are also provided. (C) 1999 Elsevier Science B.V. All rights reserved.}, year = {1999}, eissn = {1872-745X}, pages = {95-114}, orcid-numbers = {Telek, Miklós/0000-0001-9600-6084} } @inproceedings{MTMT:2629710, title = {On the analysis of software rejuvenation policies}, url = {https://m2.mtmt.hu/api/publication/2629710}, author = {Garg, S and Puliafito, A and Telek, Miklós and Trivedi, KS}, booktitle = {COMPASS '97: Are we making progress towards computer assurance?}, unique-id = {2629710}, abstract = {Software rejuvenation is a technique for software fault tolerance which involves occasionally stopping the executing software, ''cleaning'' the ''internal state'' and restarting. This cleanup is done at desirable times during execution on a preventive basis so that unplanned failures, which result in higher costs compared to planned stopping, are avoided. Since during rejuvenation, the software is typically unavailable or in a degraded mode of operation, the operation involves a cost. In this paper, we present an analytical model of a software system which serves transactions. Due to ''aging'', not only the service rate of the software decreases with time but the software itself experiences occasional crash/hang failures. We propose and compare two rejuvenation policies. The policies are evaluated for the resulting steady state availability as well the probability that a transaction is denied service. We also numerically illustrate the use of our model to compute the optimal rejuvenation interval which minimizes (maximizes) the loss probability (steady state availability).}, year = {1997}, pages = {88-96}, orcid-numbers = {Telek, Miklós/0000-0001-9600-6084} }