# Vicky PapadopoulouEuropean University Cyprus · Department of Computer Science and Engineering

Vicky Papadopoulou

PhD

## About

65

Publications

7,297

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430

Citations

Citations since 2016

Introduction

Additional affiliations

October 2008 - present

January 2005 - September 2008

September 1998 - September 2005

## Publications

Publications (65)

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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 networks size, economic and performance reasons, it is capable to provide safety, i.e. clean nodes f...

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...

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...

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...

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...

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...

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...

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...

We employ here the Probabilistic Method, a way of reasoning which shows existence of combinatorial structures and properties to prove refute conjectures.

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...

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...

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...

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...

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...

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...

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...

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...

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)

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?

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..