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21.
John?Augustine Ioannis?CaragiannisEmail author Angelo?Fanelli Christos?Kalaitzis 《Algorithmica》2015,72(1):44-82
The efficient design of networks has been an important engineering task that involves challenging combinatorial optimization problems. Typically, a network designer has to select among several alternatives which links to establish so that the resulting network satisfies a given set of connectivity requirements and the cost of establishing the network links is as low as possible. The Minimum Spanning Tree problem, which is well-understood, is a nice example.In this paper, we consider the natural scenario in which the connectivity requirements are posed by selfish users who have agreed to share the cost of the network to be established according to a well-defined rule. The design proposed by the network designer should now be consistent not only with the connectivity requirements but also with the selfishness of the users. Essentially, the users are players in a so-called network design game and the network designer has to propose a design that is an equilibrium for this game. As it is usually the case when selfishness comes into play, such equilibria may be suboptimal. In this paper, we consider the following question: can the network designer enforce particular designs as equilibria or guarantee that efficient designs are consistent with users’ selfishness by appropriately subsidizing some of the network links? In an attempt to understand this question, we formulate corresponding optimization problems and present positive and negative results. 相似文献
22.
23.
A novel method based on fusion of texture and shape information is proposed for facial expression and Facial Action Unit (FAU) recognition from video sequences. Regarding facial expression recognition, a subspace method based on Discriminant Non-negative Matrix Factorization (DNMF) is applied to the images, thus extracting the texture information. In order to extract the shape information, the system firstly extracts the deformed Candide facial grid that corresponds to the facial expression depicted in the video sequence. A Support Vector Machine (SVM) system designed on an Euclidean space, defined over a novel metric between grids, is used for the classification of the shape information. Regarding FAU recognition, the texture extraction method (DNMF) is applied on the differences images of the video sequence, calculated taking under consideration the neutral and the expressive frame. An SVM system is used for FAU classification from the shape information. This time, the shape information consists of the grid node coordinate displacements between the neutral and the expressed facial expression frame. The fusion of texture and shape information is performed using various approaches, among which are SVMs and Median Radial Basis Functions (MRBFs), in order to detect the facial expression and the set of present FAUs. The accuracy achieved using the Cohn–Kanade database is 92.3% when recognizing the seven basic facial expressions (anger, disgust, fear, happiness, sadness, surprise and neutral), and 92.1% when recognizing the 17 FAUs that are responsible for facial expression development. 相似文献
24.
The non-linear behavior of multi-suspended roof systems for seismic loads is studied. The study is based on a formulation that can be easily employed for a preliminary design of multi-suspended roofs subjected to seismic loads. Specifically, applying Lagrange’s equations, the corresponding set of equations of motion for discrete models of multiple suspension roofs is obtained and numerical integration of the equations of motion is performed via the Runge–Kutta scheme. For representative realistic combinations of geometric, stiffness and damping parameters, a non-linear analysis is employed to study the behavior of suspended roofs for near-source and far-field seismic motions. The analysis demonstrates that: (i) code-specified design loads could dramatically underestimate the response of suspended roofs subjected to near-source ground motions and (ii) flexible roofing systems are greatly affected by near-source ground motions, a behavior that is not observed for stiff systems. 相似文献
25.
Smart card technology has evolved over the last few years following notable improvements in the underlying hardware and software platforms. Advanced smart card microprocessors, along with robust smart card operating systems and platforms, contribute towards a broader acceptance of the technology. These improvements have eliminated some of the traditional smart card security concerns. However, researchers and hackers are constantly looking for new issues and vulnerabilities. In this article we provide a brief overview of the main smart card attack categories and their corresponding countermeasures. We also provide examples of well-documented attacks on systems that use smart card technology (e.g. satellite TV, EMV, proximity identification) in an attempt to highlight the importance of the security of the overall system rather than just the smart card. 相似文献
26.
An experimental investigation of personality types impact on pair effectiveness in pair programming 总被引:1,自引:1,他引:0
Panagiotis Sfetsos Ioannis Stamelos Lefteris Angelis Ignatios Deligiannis 《Empirical Software Engineering》2009,14(2):187-226
In this paper, pair programming is empirically investigated from the perspective of developer personalities and temperaments
and how they affect pair effectiveness. A controlled experiment was conducted to investigate the impact of developer personalities
and temperaments on communication, pair performance and pair viability-collaboration. The experiment involved 70 undergraduate
students and the objective was to compare pairs of heterogeneous developer personalities and temperaments with pairs of homogeneous
personalities and temperaments, in terms of pair effectiveness. Pair effectiveness is expressed in terms of pair performance, measured by communication, velocity, design correctness and passed acceptance tests, and pair collaboration-viability measured by developers’ satisfaction, knowledge acquisition and participation. The results have shown that there is important
difference between the two groups, indicating better communication, pair performance and pair collaboration-viability for
the pairs with heterogeneous personalities and temperaments. In order to provide an objective assessment of the differences
between the two groups of pairs, a number of statistical tests and stepwise Discriminant Analysis were used.
Panagiotis Sfetsos is an Assistant Professor at the Department of Informatics at the Alexander Technological Educational Institute of Thessaloniki, Greece. He received his B.Sc. in Computer Science and Statistics from the University of Uppsala, Sweden (1981), and the Ph.D. degree in Computer Science from the Aristotle University of Thessaloniki (2007). His Ph.D. Thesis was on “Experimentation in Object Oriented Technology and Agile Methods”. His research interests include empirical software evaluation, measurement, testing, quality, agile methods and especially extreme programming. Ioannis G. Stamelos is an Associate Professor of Computer Science at the Aristotle University of Thessaloniki, Dept. of Informatics. He received a degree in Electrical Engineering from the Polytechnic School of Thessaloniki (1983) and the Ph. D. degree in Computer Science from the Aristotle University of Thessaloniki (1988). He teaches object-oriented programming, software engineering, software project management and enterprise information systems at the graduate and postgraduate level. His research interests include empirical software evaluation and management, software education and open source software engineering. He is author of 90 scientific papers and member of the IEEE Computer Society. Lefteris Angelis received his B.Sc. and Ph.D. degree in Mathematics from Aristotle University of Thessaloniki (A.U.Th.). He works currently as an Assistant Professor at the Department of Informatics of A.U.Th. His research interests involve statistical methods with applications in software engineering and information systems, computational methods in mathematics and statistics, planning of experiments and simulation techniques. Ignatios Deligiannis is an Associate Professor at Alexander Technological Education Institute of Thessaloniki, Greece. His main interests are Object-Oriented software methods, and in particular design assessment and measurement. He received his B.Sc. in Computer Science from Lund University, Sweden, in 1979, and then worked for several years in software development at Siemens Telecommunications industry. He was member of ESERG (Empirical Software Engineering Research Group at Bournemouth University, UK). Currently, he is a research partner of Software Engineering Group::Plase laboratory, Aristotle University of Thessaloniki, Greece. 相似文献
Ignatios DeligiannisEmail: |
Panagiotis Sfetsos is an Assistant Professor at the Department of Informatics at the Alexander Technological Educational Institute of Thessaloniki, Greece. He received his B.Sc. in Computer Science and Statistics from the University of Uppsala, Sweden (1981), and the Ph.D. degree in Computer Science from the Aristotle University of Thessaloniki (2007). His Ph.D. Thesis was on “Experimentation in Object Oriented Technology and Agile Methods”. His research interests include empirical software evaluation, measurement, testing, quality, agile methods and especially extreme programming. Ioannis G. Stamelos is an Associate Professor of Computer Science at the Aristotle University of Thessaloniki, Dept. of Informatics. He received a degree in Electrical Engineering from the Polytechnic School of Thessaloniki (1983) and the Ph. D. degree in Computer Science from the Aristotle University of Thessaloniki (1988). He teaches object-oriented programming, software engineering, software project management and enterprise information systems at the graduate and postgraduate level. His research interests include empirical software evaluation and management, software education and open source software engineering. He is author of 90 scientific papers and member of the IEEE Computer Society. Lefteris Angelis received his B.Sc. and Ph.D. degree in Mathematics from Aristotle University of Thessaloniki (A.U.Th.). He works currently as an Assistant Professor at the Department of Informatics of A.U.Th. His research interests involve statistical methods with applications in software engineering and information systems, computational methods in mathematics and statistics, planning of experiments and simulation techniques. Ignatios Deligiannis is an Associate Professor at Alexander Technological Education Institute of Thessaloniki, Greece. His main interests are Object-Oriented software methods, and in particular design assessment and measurement. He received his B.Sc. in Computer Science from Lund University, Sweden, in 1979, and then worked for several years in software development at Siemens Telecommunications industry. He was member of ESERG (Empirical Software Engineering Research Group at Bournemouth University, UK). Currently, he is a research partner of Software Engineering Group::Plase laboratory, Aristotle University of Thessaloniki, Greece. 相似文献
27.
Ioannis Pogkas Vassil Kriakov Zhongqiang Chen Alex Delis 《Peer-to-Peer Networking and Applications》2009,2(1):37-59
To address the two most critical issues in P2P file-sharing systems: efficient information discovery and authentic data acquisition, we propose a Gnutella-like file-sharing protocol termed Adaptive Gnutella Protocol (AGP) that not only improves the querying efficiency in a P2P network but also enhances the quality of search results at the same time. The reputation scheme in the proposed AGP evaluates the credibility of peers based on their contributions to P2P services and subsequently clusters nodes together according to their reputation and shared content, essentially transforming
the P2P overlay network into a topology with collaborative and reputed nodes as its core. By detecting malicious peers as well as
free-riders and eventually pushing them to the edge of the overlay network, our AGP propagates search queries mainly within the core of the topology, accelerating the information discovery process. Furthermore,
the clustering of nodes based on authentic and similar content in our AGP also improves the quality of search results. We have implemented the AGP with the PeerSim simulation engine and conducted thorough experiments on diverse network topologies and various mixtures of honest/dishonest
nodes to demonstrate improvements in topology transformation, query efficiency, and search quality by our AGP.
Ioannis Pogkas received his BS in Computer Science in 2007 and is currently pursuing postgraduate studies at the Department of Informatics and Telecommunications of the Univesrity of Athens. His research interests focus on search, reputation andtopology adaptation mechanisms in peer-to-peer networks. He is also interested in embedded and operating systems. Vassil Kriakov received his B.S. and M.S. from Polytechnic University in 2001 and is now completing his doctoral studies at the Polytechnic Institute of New York University (NYU-Poly). His PhD research has been partially sponsored by a US Department of Education GAANN Graduate Fellowship. His research interests include distributed spatio-temporal data indexing, correlations in high-frequency data streams, and data management in grid and peer-to-peer networks. Zhongqiang Chen is a senior software engineer at Yahoo! He holds a PhD in Computer Science and MS degrees in both Computer Science and Electrical Engineering all from Polytechnic University in Brooklyn, NY. He is a Computer Engineering MS and BS graduate of Tsinghua University, Beijing, P.R. China. He is interested in network security, information retrieval, and distributed computing and is the recipient of the 2004 Wilkes Award for outstanding paper contribution in The Computer Journal. Alex Delis is a Professor of Computer Science at the University of Athens. He holds a PhD and an MS from the University of Maryland College Park as well as a Diploma in Computer Engineering from the University of Patras. His research interests are in distributed computing systems, networked information systems, databases and information security. He is a member of IEEE Computer Society, the ACM and the Technical Chamber of Greece. 相似文献
Alex DelisEmail: |
Ioannis Pogkas received his BS in Computer Science in 2007 and is currently pursuing postgraduate studies at the Department of Informatics and Telecommunications of the Univesrity of Athens. His research interests focus on search, reputation andtopology adaptation mechanisms in peer-to-peer networks. He is also interested in embedded and operating systems. Vassil Kriakov received his B.S. and M.S. from Polytechnic University in 2001 and is now completing his doctoral studies at the Polytechnic Institute of New York University (NYU-Poly). His PhD research has been partially sponsored by a US Department of Education GAANN Graduate Fellowship. His research interests include distributed spatio-temporal data indexing, correlations in high-frequency data streams, and data management in grid and peer-to-peer networks. Zhongqiang Chen is a senior software engineer at Yahoo! He holds a PhD in Computer Science and MS degrees in both Computer Science and Electrical Engineering all from Polytechnic University in Brooklyn, NY. He is a Computer Engineering MS and BS graduate of Tsinghua University, Beijing, P.R. China. He is interested in network security, information retrieval, and distributed computing and is the recipient of the 2004 Wilkes Award for outstanding paper contribution in The Computer Journal. Alex Delis is a Professor of Computer Science at the University of Athens. He holds a PhD and an MS from the University of Maryland College Park as well as a Diploma in Computer Engineering from the University of Patras. His research interests are in distributed computing systems, networked information systems, databases and information security. He is a member of IEEE Computer Society, the ACM and the Technical Chamber of Greece. 相似文献
28.
Ioannis K. Konstantopoulos Panos J. Antsaklis 《Journal of Intelligent and Robotic Systems》1995,12(3):197-228
Designing controllers with diagnostic capabilities is important as in a feedback control system, detection and isolation of failures is generally affected by the particular control law used. Therefore, a common approach to control and failure diagnosis problems has significant merit. Controllers capable of performing failure diagnosis have additional diagnostic outputs to detect and isolate sensor and actuator faults. A linear such controller is usually called a four-parameter controller. Neural networks have proved to be a very powerful tool in the control systems area, where they have been used in the modelling and control of dynamical systems. In this paper, a neural network model of a controller with diagnostic capabilities (CDC) is presented for the first time. This nonlinear neural controller is trained to operate as a traditional controller, while at the same time it provides reproduction of the failure occurring either at the actuator or the sensor. The cases of actuator and sensor failure are studied independently. The validity of the results is verified by extensive simulations.A version of this paper under the title The Four-Parameter Controller. A Neural Network Implementation was presented at the IEEE Mediterranean Symposium on New Directions in Control Theory and Applications, Chania, Crete, Greece, June 21–23, 1993. 相似文献
29.
Segkouli Sofia Giakoumis Dimitrios Votis Konstantinos Triantafyllidis Andreas Paliokas Ioannis Tzovaras Dimitrios 《Universal Access in the Information Society》2023,22(1):37-49
Universal Access in the Information Society - Pervasive technologies such as Artificial Intelligence, Virtual Reality and the Internet of Things, despite their great potential for improved... 相似文献
30.
Operator context scanning to support high segmentation rates for real time license plate recognition
Ioannis Giannoukos Author Vitae Christos-Nikolaos Anagnostopoulos Author VitaeAuthor Vitae Eleftherios Kayafas Author Vitae 《Pattern recognition》2010,43(11):3866-3878
Introducing high definition videos and images in object recognition has provided new possibilities in the field of intelligent image processing and pattern recognition. However, due to the large amount of information that needs to be processed, the computational costs are high, making the HD systems slow. To this end, a novel algorithm applied to sliding window analysis, namely Operator Context Scanning (OCS), is proposed and tested on the license plate detection module of a License Plate Recognition (LPR) system. In the LPR system, the OCS algorithm is applied on the Sliding Concentric Windows pixel operator and has been found to improve the LPR system’s performance in terms of speed by rapidly scanning input images focusing only on regions of interest, while at the same time it does not reduce the system effectiveness. Additionally, a novel characteristic is presented, namely, the context of the image based on a sliding windows operator. This characteristic helps to quickly categorize the environmental conditions upon which the input image was taken. The algorithm is tested on a data set that includes images of various resolutions, acquired under a variety of environmental conditions. 相似文献