Proceedings of the ninth annual ACM symposium on Parallel algorithms and architectures - SPAA '97, 1997
In this paper general simulations of algorithms designed for fully operational BSP machines onBSP... more In this paper general simulations of algorithms designed for fully operational BSP machines onBSP machines with faulty or unavailable processors, are developed. The fail-stop model is consideredfor the fault occurrences, that is, if a processor fails or becomes unavailable, it remains so until theend of the computation. The faults are random, in the sense that a processor may fail independentlywith
... Weighted Cut Problem through Derandomization* Grammati Pantziou I Paul Spirakis 1,2 Christos ... more ... Weighted Cut Problem through Derandomization* Grammati Pantziou I Paul Spirakis 1,2 Christos Zaroliagis I ... [Alon, Babai, Itai, 86] provide an excellent account of this approach and credit the original ideas to [Joffe, 74] and [Lancaster, 65], also [Bernstein, 45]. ...
We provide here efficient sequential and parallel solutions to the following problem: given a pla... more We provide here efficient sequential and parallel solutions to the following problem: given a planar digraph G (with real edge weights but no negative cycles) for preprocessing, answer on-line queries requesting the shortest distance (or path) between any two vertices in G. Our algorithms for preprocessing need O(n log n + q 2) space and O(n log n + q
Page 1. Optimal Parallel Algorithms for Grammati E. Pantziou t Paul G. Spirakis 1,2 Sparse Graphs... more Page 1. Optimal Parallel Algorithms for Grammati E. Pantziou t Paul G. Spirakis 1,2 Sparse Graphs* Christos D. Zaroliagis 1 (1) Computer Technology Institute, PO Box 1122, 26110 Patras, Greece Computer Sc and Eng Dept, University of Patras, Greece ...
Proceedings of the 4th International Conference on PErvasive Technologies Related to Assistive Environments - PETRA '11, 2011
ABSTRACT Advances in sensor networks and mobile technologies enable the provision of improved med... more ABSTRACT Advances in sensor networks and mobile technologies enable the provision of improved medical services through monitoring of patients; however by recording continuously location data there is an increased privacy risk. Recording user related data requires the creation of appropriate privacy preserving policies, which often depend on the good intention of the data collector. Since it is often feasible for a malicious or negligent data provider to expose these data to an unauthorized user, one solution is to protect the patient's privacy by making difficult a linkage between specific measurements with patient's identity. In this paper we present a privacy preserving architecture which builds upon the concept of k-anonymity. While patient vital parameters can be constantly recorded with the use of sensor networks and critical events produce alerts that are notifying the medical personnel, we prevent an outsider to link the signals received with the identity of the user carrying the sensor. The collected data cannot be further used for identification of diseases or other important questions.
The use of mobile agents for data fusion in wireless sensor networks has been recently proposed i... more The use of mobile agents for data fusion in wireless sensor networks has been recently proposed in the literature to answer the scalability problem of client/server model. In this article, we consider the problem of calculating a near-optimal route for a mobile agent that incrementally fuses the data as it visits the nodes in a distributed sensor network. The order
In this paper we present efficient, scalable and portable parallel algorithms written in the Coar... more In this paper we present efficient, scalable and portable parallel algorithms written in the Coarse-Grained Multi- computer (CGM) and the Bulk SynchronousParallel (BSP) models for the off-line clustering, the on-line retrieval and the update phases of the text retrieval problem based on the vector space model and using clustering to organize and handle a dynamic document collection. To the best
Proceedings of the 1st ACM international conference on PErvasive Technologies Related to Assistive Environments - PETRA '08, 2008
Abstract Wireless Sensor Networks (WSNs) has been identified as a promising technology for suppor... more Abstract Wireless Sensor Networks (WSNs) has been identified as a promising technology for supporting assistive environments. This article introduces PROTECT, a system that employs autonomous software objects referred to as Mobile Agents (MAs) able of locating and informing visually impaired persons for potential risks. PROTECT utilizes a 3-tier architecture where the first tier comprises a Base Station (BS), the second tier mobile sinks (carried by blinds on their sticks) and the third tier stationary sensor nodes. This WSN is ...
Proceedings of the ninth annual ACM symposium on Parallel algorithms and architectures - SPAA '97, 1997
In this paper general simulations of algorithms designed for fully operational BSP machines onBSP... more In this paper general simulations of algorithms designed for fully operational BSP machines onBSP machines with faulty or unavailable processors, are developed. The fail-stop model is consideredfor the fault occurrences, that is, if a processor fails or becomes unavailable, it remains so until theend of the computation. The faults are random, in the sense that a processor may fail independentlywith
... Weighted Cut Problem through Derandomization* Grammati Pantziou I Paul Spirakis 1,2 Christos ... more ... Weighted Cut Problem through Derandomization* Grammati Pantziou I Paul Spirakis 1,2 Christos Zaroliagis I ... [Alon, Babai, Itai, 86] provide an excellent account of this approach and credit the original ideas to [Joffe, 74] and [Lancaster, 65], also [Bernstein, 45]. ...
We provide here efficient sequential and parallel solutions to the following problem: given a pla... more We provide here efficient sequential and parallel solutions to the following problem: given a planar digraph G (with real edge weights but no negative cycles) for preprocessing, answer on-line queries requesting the shortest distance (or path) between any two vertices in G. Our algorithms for preprocessing need O(n log n + q 2) space and O(n log n + q
Page 1. Optimal Parallel Algorithms for Grammati E. Pantziou t Paul G. Spirakis 1,2 Sparse Graphs... more Page 1. Optimal Parallel Algorithms for Grammati E. Pantziou t Paul G. Spirakis 1,2 Sparse Graphs* Christos D. Zaroliagis 1 (1) Computer Technology Institute, PO Box 1122, 26110 Patras, Greece Computer Sc and Eng Dept, University of Patras, Greece ...
Proceedings of the 4th International Conference on PErvasive Technologies Related to Assistive Environments - PETRA '11, 2011
ABSTRACT Advances in sensor networks and mobile technologies enable the provision of improved med... more ABSTRACT Advances in sensor networks and mobile technologies enable the provision of improved medical services through monitoring of patients; however by recording continuously location data there is an increased privacy risk. Recording user related data requires the creation of appropriate privacy preserving policies, which often depend on the good intention of the data collector. Since it is often feasible for a malicious or negligent data provider to expose these data to an unauthorized user, one solution is to protect the patient's privacy by making difficult a linkage between specific measurements with patient's identity. In this paper we present a privacy preserving architecture which builds upon the concept of k-anonymity. While patient vital parameters can be constantly recorded with the use of sensor networks and critical events produce alerts that are notifying the medical personnel, we prevent an outsider to link the signals received with the identity of the user carrying the sensor. The collected data cannot be further used for identification of diseases or other important questions.
The use of mobile agents for data fusion in wireless sensor networks has been recently proposed i... more The use of mobile agents for data fusion in wireless sensor networks has been recently proposed in the literature to answer the scalability problem of client/server model. In this article, we consider the problem of calculating a near-optimal route for a mobile agent that incrementally fuses the data as it visits the nodes in a distributed sensor network. The order
In this paper we present efficient, scalable and portable parallel algorithms written in the Coar... more In this paper we present efficient, scalable and portable parallel algorithms written in the Coarse-Grained Multi- computer (CGM) and the Bulk SynchronousParallel (BSP) models for the off-line clustering, the on-line retrieval and the update phases of the text retrieval problem based on the vector space model and using clustering to organize and handle a dynamic document collection. To the best
Proceedings of the 1st ACM international conference on PErvasive Technologies Related to Assistive Environments - PETRA '08, 2008
Abstract Wireless Sensor Networks (WSNs) has been identified as a promising technology for suppor... more Abstract Wireless Sensor Networks (WSNs) has been identified as a promising technology for supporting assistive environments. This article introduces PROTECT, a system that employs autonomous software objects referred to as Mobile Agents (MAs) able of locating and informing visually impaired persons for potential risks. PROTECT utilizes a 3-tier architecture where the first tier comprises a Base Station (BS), the second tier mobile sinks (carried by blinds on their sticks) and the third tier stationary sensor nodes. This WSN is ...
19th IEEE Symposium on Computers and Communications (ISCC 2014), Jun 24, 2014
A critical issue dealt with in Wireless Sensor and Actor Networks (WSANs) is the real time respon... more A critical issue dealt with in Wireless Sensor and Actor Networks (WSANs) is the real time response of actors to events occurring in the network area. The fast notification of actors from Sensor Nodes (SNs) about the events as well as the effective coordination of actors for prompt event handling is most important in these networks. In this paper, we introduce a distributed protocol for effective event handling in a WSAN. Existing approaches mainly favoring actors near the current event for handling it, may lead to highly ineffective solutions for certain worst-case scenarios. Through a randomized approach, our solution also selects distant actors for handling events, and guarantees fast average responsiveness to events and a balanced energy distribution among actors. In addition, it features efficient distributed algorithms for sensor to actor and actor to actor coordination which are of independent interest.
6th International Conference on Ubiquitous and Future Networks (ICUFN 2014), Jul 9, 2014
Mobile agents (MAs) have been proposed as a distributed middleware approach suitable for autonomi... more Mobile agents (MAs) have been proposed as a distributed middleware approach suitable for autonomic data aggregation operations in Wireless Sensor Networks (WSN). Determining optimal itineraries for MAs traveling through WSN nodes is a non-trivial problem. Thus, several heuristics have been proposed to perform efficient itinerary planning for MAs. However, the evaluation of these heuristics is typically performed on the ground of different parameter spaces and assumptions about the underlying network and the capabilities of nodes. Herein, we implement, simulate and compare the most prominent itinerary planning algorithms upon a common parameter space, making realistic network-level assumptions.
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Papers by Grammati Pantziou