Vicky Papadopoulou

Vicky Papadopoulou
European University Cyprus · Department of Computer Science and Engineering

PhD

About

65
Publications
7,297
Reads
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430
Citations
Citations since 2016
15 Research Items
147 Citations
2016201720182019202020212022051015202530
2016201720182019202020212022051015202530
2016201720182019202020212022051015202530
2016201720182019202020212022051015202530
Additional affiliations
October 2008 - present
European University Cyprus
Position
  • Professor (Assistant)
January 2005 - September 2008
University of Cyprus
Position
  • PostDoc Position
September 1998 - September 2005
University of Patras
Position
  • Research Assistant

Publications

Publications (65)
Preprint
We present a new diagnostic diagram for local ultraluminous infrared galaxies (ULIRGs) and quasars, analysing particularly the Spitzer Space Telescope's Infrared Spectrograph (IRS) spectra of 102 local ULIRGs and 37 Palomar Green quasars. Our diagram is based on a special non-linear mapping of these data, employing the Kernel Principal Component An...
Article
Full-text available
In this article, we present a unified framework for the analysis and characterization of a complex system and demonstrate its application in two diverse fields: neuroscience and astrophysics. The framework brings together techniques from graph theory, applied mathematics, and dimensionality reduction through principal component analysis (PCA), sepa...
Article
We present a new diagnostic diagram for local ultraluminous infrared galaxies (ULIRGs) and quasars, analysing particularly the Spitzer Space Telescope’s Infrared Spectrograph (IRS) spectra of 102 local ULIRGs and 37 Palomar Green quasars. Our diagram is based on a special non-linear mapping of these data, employing the Kernel Principal Component An...
Article
Full-text available
In this paper we explore the use of spatial clustering algorithms as a new computational approach for modeling the cosmic web. We demonstrate that such algorithms are efficient in terms of computing time needed. We explore three distinct spatial methods which we suitably adjust for (i) detecting the topology of the cosmic web and (ii) categorizing...
Preprint
In this paper we explore the use of spatial clustering algorithms as a new computational approach for modeling the cosmic web. We demonstrate that such algorithms are efficient in terms of computing time needed. We explore three distinct spatial methods which we suitably adjust for (i) detecting the topology of the cosmic web and (ii) categorizing...
Preprint
We present the ultraviolet to submillimetre spectral energy distributions (SEDs) of the HERschel Ultra Luminous Infrared Galaxy Survey (HERUS) sample of 42 local ultraluminous infrared galaxies (ULIRGs) and fit them with a Markov chain Monte Carlo (MCMC) code using the CYprus models for Galaxies and their NUclear Spectra (CYGNUS) radiative transfer...
Article
We present the ultraviolet to submillimetre spectral energy distributions (SEDs) of the HERschel Ultra Luminous Infrared Galaxy Survey (HERUS) sample of 42 local Ultraluminous Infrared Galaxies (ULIRGs) and fit them with a Markov Chain Monte Carlo (MCMC) code using the CYprus models for Galaxies and their NUclear Spectra (CYGNUS) radiative transfer...
Article
Full-text available
We consider a game on a graph G=⟨V,E⟩\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$G=\langle V, E\rangle $$\end{document} with two confronting classes of randomized p...
Preprint
In this work we report the discovery of the hyperluminous galaxy HELP_J100156.75+022344.7 at the photometric redshift of z ~ 4.3. The galaxy was discovered in the Cosmological Evolution Survey (COSMOS) field, one of the fields studied by the Herschel Extragalactic Legacy Project (HELP). We present the spectral energy distribution (SED) of the galax...
Article
In this work we report the discovery of the hyperluminous galaxy HELP_J100156.75 + 022344.7 at a photometric redshift of $z$ ≈ 4.3. The galaxy was discovered in the Cosmological Evolution Survey (COSMOS) field, one of the fields studied by the Herschel Extragalactic Legacy Project (HELP). We present the spectral energy distribution (SED) of the gal...
Preprint
Full-text available
We propose an end-to-end approach for solving inverse problems for a class of complex astronomical signals, namely Spectral Energy Distributions (SEDs). Our goal is to reconstruct such signals from scarce and/or unreliable measurements. We achieve that by leveraging a learned structural prior in the form of a Deep Generative Network. Similar method...
Article
Probabilistic flooding is commonly considered in vehicular ad-hoc networks (VANETs) to alleviate the celebrated broadcast storm problem. Heuristics and simulations have so far proved to be an efficient way with which to design probabilistic information dissemination solutions with demonstrated effectiveness. Supplementing with mathematical analysis...
Article
Full-text available
This paper focuses on coexistence and self- coexistence challenges between secondary heterogeneous wireless networks/users sharing TV Whitespace spectrum. The coexistence problems arise from having several primary and secondary networks of different technologies cohabiting the same licensed spectrum simultaneously. The self- coexistence problems ar...
Chapter
Full-text available
The high popularity of Wi-Fi technology for wireless access has led to a common problem of densely deployed access points (APs) in residential or commercial buildings, competing to use the same or overlapping frequency channels and causing degradation to the user experience due to excessive interference. This degradation is partly caused by the res...
Conference Paper
Abstract—The high popularity of Wi-Fi technology for wireless access has led to a common problem of densely deployed access points (APs) in residential or commercial buildings, competing to use the same or overlapping frequency channels and causing a degradation to the user experience due to excessive interference. This degradation is partly caused...
Conference Paper
The high popularity of Wi-Fi technology for wireless access has led to a common problem of densely deployed access points (APs) in residential or commercial buildings, competing to use the same or overlapping frequency channels and causing a degradation to the user experience due to excessive interference. This degradation is partly caused by the r...
Conference Paper
Full-text available
Information hovering is relevant in vehicular ad hoc networks in cases where critical information needs to be made available to all vehicles in a bounded geographical area, called the hovering area, for a specific amount of time. In cases of low traffic density within the hovering area, a number of vehicles may not receive the critical information...
Conference Paper
Human error is one of the principal influencing factors that lead to road accidents, and is attributed to increased mental workload induced by distractions such as advertisements and in-vehicle music. Workload, however, is characterized by intrinsic properties and hence difficult to be observed and quantified. Phenotype behaviours, such as lateral...
Conference Paper
Full-text available
Urban residential areas are becoming increasingly dense with more and more wireless home networks being deployed in close proximity. Considering that in such a dense urban residential area, each unit has its own wireless access point (AP), deployed without any coordination with other such units, then a need arises for reducing interference and incr...
Article
Full-text available
Software project change is a common problem in project management. Changes in requirements, activities or peoples roles however are usually not free from conflicts, which in some cases if not dealt adequately could bring the whole project to a standstill. Herein, we present a method that examines the impact of change to project duration. The method...
Conference Paper
Full-text available
Risks are unavoidable in systems engineering projects due to emerging changes during the lifetime of projects. Changes in activities and peoples' roles are usually not free from conflicts, which in some cases if not dealt adequately, increase the project failure risks and could bring the whole project to a standstill. Herein, we present a method th...
Chapter
Full-text available
Security requirements validation is traditionally performed through security-specific testing. Ideally, validation should be performed on all possible network conditions expressed by test scenarios. However, examining all possible scenarios [AD93, AS02] to validate security requirement early in the design phase of a prospective network, constitutes...
Article
Next Generation Communication Networks employ the idea of convergence, where heterogeneous access technologies may coexist, and a user may be served by anyone of the participating access networks, motivating the emergence of a Network Selection mechanism. The triggering and execution of the Network Selection mechanism becomes a challenging task due...
Conference Paper
Full-text available
Central to smart home security is the need for adequate surrounding awareness. Security systems have been designed for remote exploration and control, however, these still lack the simplicity needed by elderly and disabled. The majority of elderly people find the control of such systems laborious. This highlights the need for usable designs that ta...
Conference Paper
Nowadays, more than ever, security is considered to be critical issue for all electronic transactions. This is the reason why security services like those described in IPSec are mandatory to IPV6 which will be adopted as the new IP standard the next years. Moreover the need for security services in every data packet that is transmitted via IPv6, il...
Conference Paper
Full-text available
Non-functional requirements (NFR) such as network security recently gained widespread attention in distributed information systems. Despite their importance however, there is no systematic approach to validate these requirements given the complexity and uncertainty characterizing modern networks. Traditionally, network security requirements specifi...
Article
Full-text available
Network security requirements have recently gained widespread attention in the requirements engineering community. Despite this, it is not yet clear how to systematically validate these requirements given the complexity and uncertainty characterizing modern networks. Traditionally, network security requirements specification has been the results of...
Article
In a distributed system with {\it attacks} and {\it defenses,} both {\it attackers} and {\it defenders} are self-interested entities. We assume a {\it reward-sharing} scheme among {\it interdependent} defenders; each defender wishes to (locally) maximize her own total {\it fair share} to the attackers extinguished due to her involvement (and possib...
Conference Paper
The work described here draws on the emergent need to internationalise the curriculum in higher education. The paper in particular focuses on the internationalisation of the Management Information Systems (MIS) module and the identification of learning differences among the two dominant cultural groups in higher education in the UK: Asian and Europ...
Book
This book constitutes the refereed proceedings of the Second International Symposium on Algorithmic Game Theory, SAGT 2009, held in Paphos, Cyprus, in October 2009. The 29 revised full papes presented together with 3 invited lectures were carefully reviewed and selected from 55 submissions. The papers are intended to cover all important areas such...
Conference Paper
Full-text available
In a Voronoi game, there is a finite number of players who each chooses a point in some metric space. A player's utility is the total measure of all points that are closer to him than to any other player, where points equidistant to several players are split up evenly among the closest players. In a recent paper, Dürr and Thang (2007) considered di...
Article
Full-text available
Consider an information network with threats called attackers; each attacker uses a probability distribution to choose a node of the network to damage. Opponent to the attackers is a protector entity called defender; the defender scans and cleans from attacks some part of the network (in particular, a link), which it chooses independently using its...
Conference Paper
Full-text available
In a distributed system with attacks and defenses, an economic investment in defense mechanisms aims at increasing the degree of system protection against the attacks. We study such investments in the selfish setting, where both attackers and defenders are self-interested entities. In particular, we assume a reward-sharing scheme among interdepende...
Chapter
Methods from game theory and mechanism design have been proven to be a powerful mathematical tool in order to understand, control, and efficiently design dynamic, complex networks, such as the Internet. Game theory provides a good starting point for computer scientists to understand selfish rational behavior of complex networks with many agents. Su...
Conference Paper
Full-text available
Consider a network vulnerable to security attacks and equipped with defense mechanisms. How much is the loss in the provided security guarantees due to the selfish nature of attacks and defenses? The Price of Defense was recently introduced in [7] as a worst-case measure, over all associated Nash equilibria, of this loss. In the particular strategi...
Article
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. A Radiocoloring (RC) of a graph is an assignment function such that , when are ne...
Conference Paper
Full-text available
We consider a strategic game with two classes of confronting randomized players on a graph G(V, E): v attackers, each choosing vertices and wishing to minimize the probability of being caught, and a defender, who chooses edges and gains the expected number of attackers it catches. The Price of Defense is the worst-case ratio, over all Nash equilibr...
Conference Paper
Full-text available
We consider a security problem on a distributed network. We assume a network whose nodes are vulnerable to infection by threats (e.g. viruses), the attackers. A system security software, the defender, is available in the system. However, due to the network’s size, economic and performance reasons, it is capable to provide safety, i.e. clean nodes f...
Article
Abstract Consider a distributed information network with harmful procedures called attackers (e.g., viruses); each attacker uses aprobability distribution to choose a node of the network to damage. Opponent to the attackers is the system protector scanning and cleaning from attackers some,part of the network (e.g., an edge or a simple path), which...
Conference Paper
Full-text available
Consider an information network with harmful procedures called attackers (e.g., viruses); each attacker uses a probability distribution to choose a node of the network to damage. Opponent to the attackers is the system protector scanning and cleaning from attackers some part of the network (e.g., an edge or a path), which it chooses independently u...
Conference Paper
Full-text available
Consider a network vulnerable to viral infection. The system security software can guarantee safety only to a limited part of the network. We model this practical network scenario as a non-cooperative multi-player game on a graph, with two kinds of players, a set of attackers and a protector player, representing the viruses and the system security...
Article
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters, by exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. A Radiocoloring (RC) of a graph G(V,E) is an assignment function Φ:V→ℕ such t...
Conference Paper
In this work we experimentally study the min order Radiocoloring problem (RCP) on Chordal, Split and Permutation graphs, which are three basic families of perfect graphs. This problem asks to find an assignment using the minimum number of colors to the vertices of a given graph G, so that each pair of vertices which are at distance at most two apar...
Article
Full-text available
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters, by exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. A Radiocoloring (RC) of a graph G(V, E) is an assignment function Φ : V → N s...
Article
Full-text available
Introduction, Our Results and Related Work Hierarchical specifications are more concise in describing objects than ordinary graph representations. A well known hierarchical specification model, considered in this work, is that of Lengauer, introduced in [13, 14], referred to as L-specifications. In this work we study RCP on L-specified hierarchical...
Article
We employ here the Probabilistic Method, a way of reasoning which shows existence of combinatorial structures and properties to prove refute conjectures.
Conference Paper
Full-text available
Hierarchical specifications of graphs have been widely used in many important applications, such as VLSI design, parallel programming and software engineering. A well known hierarchical specification model, considered in this work, is that of Lengauer [9, 10] referred to as L-specifications. In this paper we discuss a restriction on the L-specifica...
Conference Paper
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. The Radiocoloring (RC) of a graph G(V,E) is an assignment function Φ: V → IN such...
Article
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. The Radiocoloring (RC) of a graph G(V; E) is an assignment function : V ! IN such...
Article
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters, exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modeled by variations of graph coloring. In this work we first survey the variations of the FAP and then we study two (similar but sti...
Article
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters, exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modeled by variations of graph coloring. In this work we first survey the variations of the FAP and then we study one interesting vari...
Article
Introduction Nowadays, one of the most highly growing elds in Computer Science is Mobile Computing. Although, mobile computers seem to be a natural need for people's daily work, the remarkable achievements of Computers Technology turn this ideal work environment to reality. It's expected that in the near future millions of people will use lightweig...
Conference Paper
The Frequency Assignment Problem (FAP) in radio networks is the problem of assigning frequencies to transmitters exploiting frequency reuse while keeping signal interference to acceptable levels. The FAP is usually modelled by variations of the graph coloring problem. The Radiocoloring (RC) of a graph G(V; E) is an assignment function : V ! IN such...
Article
Full-text available
We survey a research line recently initiated by Mavronicolas et al. (14, 15, 16), concerning a strategic game on a graph G(V,E) with two confronting classes of randomized players: � attackers who choose vertices and wish to minimize the probability of being caught by the defender, who chooses edges and gains the expected number of attackers it catc...
Article
Full-text available
Copyright (c) All rights reserved The following report describes a game theoretic approach for the network selection decision in heterogeneous converged next generation communication networks. The game theoretic formula-tion follows an evaluation using Matlab which reinforces the claim of this game theoretic model, i.e. that it presents a satisfyin...

Questions

Questions (2)
Question
Hi, I have a question on imperfect graphs; Is the condition of existence of cycles of size greater then 4 necessary for a graph to be imperfect (i.e. chi(G)> omega(G)? can somebody help?
Question
Did you try to investiagte the problem through Game theory? Game theory had applied sucessfullu for solving multiobjctive optimization problems viewed throught the utility functions of the various players of the corresponding game modleing the problem..

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