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109 results on '"Karbowski, Andrzej"'

1. Remarks to the paper 'Control system for reducing energy consumption in backbone computer network' from 'Concurrency and Computation: Practice and Experience' journal

Author

Karbowski, Andrzej

Subjects
Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Networking and Internet Architecture
Abstract

This paper indicates two errors in the formulation of the main optimization model in the article "Control system for reducing energy consumption in backbone computer network" by Niewiadomska-Szynkiewicz et al. and shows how to fix them., Comment: 5 pages. arXiv admin note: substantial text overlap with arXiv:1610.02551

Published
2016

2. Correction to the article 'Dynamic power management in energy-aware computer networks and data intensive computing systems' published in 'Future Generation Computer Systems' journal

Author

Karbowski, Andrzej

Subjects
Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Networking and Internet Architecture, Computer Science - Systems and Control
Abstract

This paper indicates two errors in the formulation of the main optimization model in the article "Dynamic power management in energy-aware computer networks and data intensive computing systems" by Niewiadomska-Szynkiewicz et al. [FGCS, vol.37 (2014), pp.284-296] and shows how to fix them., Comment: 7 pages

Published
2016

4. Real–Time Hierarchical Predictive Risk Assessment at the National Level: Mutually Agreed Predicted Service Disruption Profiles

Author

Malinowski Krzysztof and Karbowski Andrzej

Subjects
risk assessment, cyber security, hierarchical approach, service disruption profiles, coordination, Mathematics, QA1-939, Electronic computers. Computer science, QA75.5-76.95
Abstract

We present a real-time hierarchical approach to an on-line risk assessment at the national level taking into account both local risk analyses performed by key service operators and relevant interdependencies between those services. For this purpose we define mutually agreed predicted service disruption profiles and then propose a coordination mechanism to align those profiles. A simple, four-entity example is provided to illustrate the coordination.

Published
2020
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5. Amdahl's and Gustafson-Barsis laws revisited

Author

Karbowski, Andrzej

Subjects
Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Computer Science and Game Theory, Computer Science - Performance
Abstract

The paper presents a simple derivation of the Gustafson-Barsis law from the Amdahl's law. In the computer literature these two laws describing the speedup limits of parallel applications are derived separately. It is shown, that treating the time of the execution of the sequential part of the application as a constant, in few lines the Gustafson-Barsis law can be obtained from the Amdahl's law and that the popular claim, that Gustafson-Barsis law overthrows Amdahl's law is a mistake.

Published
2008

6. Errors in Low and Lapsley's article 'Optimization Flow Control, I: Basic Algorithm and Convergence'

Author

Karbowski, Andrzej

Subjects
Computer Science - Networking and Internet Architecture, Computer Science - Distributed, Parallel, and Cluster Computing, C.2.3, G.1.6
Abstract

In the note two errors in Low and Lapsley's article "Optimization Flow Control, I: Basic Algorithm and Convergence", "IEEE/ACM Transactions on Networking", 7(6), pp. 861-874, 1999, are shown. Because of these errors the proofs of both theorems presented in the article are incomplete and some assessments are wrong., Comment: The mathematical errors in one of the most cited network publication are presented

Published
2002

7. Correction to Low and Lapsley's article 'Optimization Flow Control, I: Basic Algorithm and Convergence'

Author

Karbowski, Andrzej

Subjects
Computer Science - Networking and Internet Architecture, Computer Science - Distributed, Parallel, and Cluster Computing, C.2.3, G.1.6
Abstract

In the note an error in Low and Lapsley's article ("Optimization Flow Control, I: Basic Algorithm and Convergence", IEEE/ACM Transactions on Networking, 7(6), pp. 861-874, 1999) is pointed out. Because of this error the proof of the Theorem 2 presented in the article is incomplete and some assessments are wrong. In the second part of the note the author proposes a correction to this proof., Comment: The corrections to errors in one of the most important articles on network management are presented

Published
2002

11. Parampl: A Simple Approach for Parallel Execution of AMPL Programs

Author

Olszak, Artur, Karbowski, Andrzej, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Kobsa, Alfred, Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Wyrzykowski, Roman, editor, Dongarra, Jack, editor, Karczewski, Konrad, editor, and Waśniewski, Jerzy, editor

Published
2014
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12. Simultaneous routing and flow rate optimization in energy–aware computer networks

Author

Jaskóła Przemysław, Arabas Piotr, and Karbowski Andrzej

Subjects
minlp, miqp, network optimization, green networking, fairness, multi-criteria, Mathematics, QA1-939, Electronic computers. Computer science, QA75.5-76.95
Abstract

The issue of energy-aware traffic engineering has become prominent in telecommunications industry in the last years. This paper presents a two-criteria network optimization problem, in which routing and bandwidth allocation are determined jointly, so as to minimize the amount of energy consumed by a telecommunication infrastructure and to satisfy given demands represented by a traffic matrix. A scalarization of the criteria is proposed and the choice of model parameters is discussed in detail. The model of power dissipation as a function of carried traffic in a typical software router is introduced. Then the problem is expressed in a form suitable for the mixed integer quadratic programming (MIQP) solver. The paper is concluded with a set of small, illustrative computational examples. Computed solutions are implemented in a testbed to validate the accuracy of energy consumption models and the correctness of the proposed traffic engineering algorithm.

Published
2016
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49. Combined positron-annihilation and structural studies of hydrothermally grown zirconia

Author

Mariazzi, Sebastiano, Fidelus, Janusz D., Werner-Malento, Ewa, Brusa, Roberto S., Karwasz, Grzegorz P., Zhou, Wuzong, and Karbowski, Andrzej

Abstract

Nanoporous zirconia is used in gas sensors and as a membrane in high-temperature fuel cells. In the present work, positron annihilation spectroscopy and transmission electron microscopy (TEM) were performed on pure zirconia-sintered nanopowders, to determine the porosity. The ortho-positronium annihilation parameter R of zirconia samples, treated at 800°C and 700°C and annealed in oxygen–nitrogen atmosphere with different O2 contents, were obtained. The photoluminescence, positron annihilation spectroscopy, and TEM studies show presence of defects in all samples. Furthermore, the positron annihilation studies indicate a presence of large free volumes (of the order of few atomic units, at least), open towards the nanocrystals surface what was confirmed by TEM observations which detected a few types of defects such as voids within ˜2–4 interplane distances, stacking faults, terraces and point defects.Nanoporous zirconia is used in gas sensors and as a membrane in high-temperature fuel cells. In the present work, positron annihilation spectroscopy and transmission electron microscopy (TEM) were performed on pure zirconia-sintered nanopowders, to determine the porosity. The ortho-positronium annihilation parameter R of zirconia samples, treated at 800°C and 700°C and annealed in oxygen–nitrogen atmosphere with different O2 contents, were obtained. The photoluminescence, positron annihilation spectroscopy, and TEM studies show presence of defects in all samples. Furthermore, the positron annihilation studies indicate a presence of large free volumes (of the order of few atomic units, at least), open towards the nanocrystals surface what was confirmed by TEM observations which detected a few types of defects such as voids within ˜2–4 interplane distances, stacking faults, terraces and point defects.

Published
2016
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