Stelios Thomopoulos

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• PhD
• Managing Director at National Centre of Scientific Research "Demokritos"

SAFETY4RAILS is the acronym for the European Union Horizon 2020 co-funded innovation project entitled: "Data-based analysis for safety and security protection for detection, prevention, mitigation and response in trans-modal metro and railway networks" which started in October 2020. Its focus is to support the increase of security and resilience ag...

SYNTHESIS is a platform of platforms (PoP) for the management, curation, and creation of digital cultural experiences related to cultural heritage material (artifacts), and their visualization through mobile applications and virtual and augmented reality (VR/AR) technologies. The digital cultural experiences may relate to specific cultural heritage...

The increasing number of passengers and travellers along with the EU’s objective of integrated border management calls for a paradigm shift in the way security is managed in border crossing points in air, land and sea. Current horizontal controls imposed on the vast majority of law-abiding citizens are not sustainable in the long term. Border Guard...

The objective of this paper is to illustrate the common social need for preservation of Cultural Heritage (CH), through innovative and interactive processes of curation of exhibits and events in places of cultural interest or remotely [1]. Through the project “Narration” we are demonstrating ways for specialized and non-specialized users to create...

ESTIA is a research and innovation project that aspires to develop a comprehensive platform allowing the forecast, detection and management of incidents that are related with the risk of structural fires within Cultural Heritage (CH) settlements and sites. ESTIA aims to (a) enhance the management and preservation of CH, (b) limit the risks of fire...

The richness of Greek mythology, combined with the need to preserve and spread the intangible and tangible cultural heritage, constitute the incentives towards the exploration of new ways to narrate these fascinating “stories” and to display their artistic depictions. COSMOS offers the opportunity to record Greek mythology, both in its written and...

Risk-based security is a concept introduced in order to provide security checks without inconveniencing travelers that are being checked with unqualified scrutiny checks while maintaining the same level of security with current check point practices without compromising security standards. Furthermore, risk-based security, as a means of improving t...

Real-time behaviour analysis is of paramount importance to ensure the safety of passengers in border-crossing areas. It allows to recognize the security threats on time. Moreover, it can accelerate the security check since the security personnel only consider severe checks for passengers with suspicious behaviour. In this work, we consider the foll...

SYNTHESIS is a platform of platforms (PoP) for the management, curation, and creation of digital cultural experiences related to cultural heritage material (artifacts), and their visualization through mobile applications and virtual and augmented reality (VR/AR) technologies. The digital cultural experiences may relate to specific cultural heritage...

Maritime Surveillance command and control (C2) systems play a crucial role in ensuring the marine traffic safety and maritime border security. Through efficient integration of various sources (UAV, aircrafts, GIS data) and legacy systems (e.g. AIS, Radar, VMS) a more complete situational awareness picture of the activities at sea can be accomplishe...

To capture the dynamics of context-aware decision making for network functions in Mobile Ad Hoc Networks (MANETs), the paper introduces the concept of Decision-Related Event Occurrence Times (DREOTs). By considering a generic scenario, the paper develops a broadly applicable analysis methodology, which produces upper and lower bounds for the tail p...

Today, an increasing number of Internet of Things (IoT) healthcare devices, crucial to a person's wellbeing and life, connects to the internet and consequently is exposed to a variety of threats. These devices possess low computational resources, and as a result they cannot use security tools such as antivirus or firewalls. Consequently, they becom...

While we observe an ongoing interest in approaching cultural heritage analysis through digital design disciplines, protection policies aiming to preserve antiquities at times inhibit such methodologies and their efforts to convey the complexity of archaeological research in accessible ways. Τhe protocols of preserving antiquities often allow limite...

Detection of anomalous trajectories is an important problem with potential applications to various domains, such as video surveillance, risk assessment, vessel monitoring and high-energy physics. Modeling the distribution of trajectories with statistical approaches has been a challenging task due to the fact that such time series are usually non st...

Social Engineering holds one of the most critical threats to public and private organizations. In this paper we focus on phishing threats by measuring the positive impact that awareness methods may provide to them in a long-term period to companies and public bodies. The assessment criterion uses two phishing attacks in a period of 18 weeks. The ph...

The current chapter introduces a procedure that aims at determining regions that are on fire, based on Twitter posts, as soon as possible. The proposed scheme utilizes a deep learning approach for analyzing the text of Twitter posts announcing fire bursts. Deep learning is becoming very popular within different text applications involving text gene...

Automated decision making emerges as the enabler for risk-based and smarter security. However, ethics, privacy, and the General Data Protection Regulation (GDPR) provide a very challenging setting along with monitoring fairness and bias detection when applying artificial intelligence (AI) security solutions.

MARINE-EO is a Research and Development project using a Pre-Commercial Procurement (PCP) mechanism with the scope to develop innovative beyond the state-of-the-art downstream applications which meet the demand of maritime authorities and stakeholders, leveraging on the existing services and other products from the Copernicus portfolio. More specifi...

MARINE-EO is a Research and Development project using a Pre-Commercial Procurement (PCP) mechanism with the scope to develop innovative beyond the state-of-the-art downstream applications which meet the demand of maritime authorities and stakeholders, leveraging on the existing services and other products from the Copernicus portfolio. More specifi...

Maritime “Awareness” is currently a top priority for Europe. “Awareness” sought either in regards of maritime security, border control against irregular immigration and safety of navigation while at the same time “awareness” sought in regards of the marine environment and climate change. “Awareness” is sought both for sea-basins of traditional inte...

The aim of this paper is to present the sensor monitoring and decision level fusion scheme for early fire detection which has been developed in the context of the AF3 Advanced Forest Fire Fighting European FP7 research project, adopted specifically in the OCULUS-Fire control & command system and tested during a firefighting field test in Greece wit...

A Digital Immersive Cultural Environment (DICE) consists of a VR/AR (virtual & augmented reality) platform, a CMS (Content Management System) and a GIS (Geographic Information System) for geo-referencing both space and content and for providing immersive navigation in the VR/AR space. Such a platform offers 3D reconstruction of space, geo-coding of...

wayGoo is a fully functional application whose main functionalities include content geolocation, event scheduling, and indoor navigation. However, significant information about events do not reach users’ attention, either because of the size of this information or because some information comes from real – time data sources. The purpose of this wor...

Structural fires continue to pose a great threat towards human life and property. Due to the complexity and non-deterministic characteristics of a building fire disaster, it is not a straightforward task to assess the effectiveness of fire protection measures embedded in the building design, planned evacuation strategies and potential modes of resp...

wayGoo² is a platform for Geolocating and Managing indoor and outdoor spaces and content with multidimensional indoor and outdoor Navigation and Guidance. Its main components are a Geographic Information System, a back-end server, front-end applications and a web-based Content Management System (CMS). It constitutes a fully integrated 2D/3D space a...

Location-based and navigation services are really needed to help visitors and audience of big events, complex buildings, shopping malls, airports and large companies. However, the lack of GPS and proper mapping indoors usually renders location-based applications and services useless or simply not applicable in such environments. SYNAISTHISI introdu...

Initially designed in the context of the TASS (Total Airport Security System) FP-7 project, the Crowd Simulation platform developed by the Integrated Systems Lab of the Institute of Informatics and Telecommunications at N.C.S.R. Demokritos, has evolved into a complete domain-independent agent-based behavior simulator with an emphasis on crowd behav...

The scope of the present study is to research the dynamics that determine the commission of crimes in the US society. Our study is part of a model we are developing to understand urban crime dynamics and to enhance citizens’ “perception of security” in large urban environments. The main targets of our research are to highlight dependence of crime r...

AF3 (Advanced Forest Fire Fighting2) is a European FP7 research project that intends to improve the efficiency of current fire-fighting operations and the protection of human lives, the environment and property by developing innovative technologies to ensure the integration between existing and new systems. To reach this objective, the AF3 project...

Complementing the ACI/IATA efforts, the FLYSEC European H2020 Research and Innovation project (http://www.fly-sec.eu/) aims to develop and demonstrate an innovative, integrated and end-to-end airport security process for passengers, enabling a guided and streamlined procedure from the landside to airside and into the boarding gates, and offering fo...

Locally aware routing protocols base their next-hop selection on information about their immediate neighborhood, gathered by means of a beaconing mechanism. In general, beacons may be proactively broadcasted from nodes to their neighbors (‘receiver-initiated’ beaconing) or may be solicited by the node carrying the routed message (‘on-demand’ beacon...

Oculus Sea is a complete solution regarding maritime surveillance and communications at Local as well as Central Command and Control level. It includes a robust and independent track fusion service whose main functions include: 1) Interaction with the User to suggest the fusion of two or more tracks, confirm Track ID and Vessel Metadata creation fo...

The field of Homeland Security focuses on the air, land, and sea borders surveillance in order to prevent illegal activities while facilitating lawful travel and trade. The achievement of this goal requires collaboration of complex decentralized systems and services, and transfer of huge amount of information between the remote surveillance areas a...

OCULUS Sea™ is a C2 platform for Integrated Maritime Surveillance. The platform consists of “loosely coupled” National/ Regional and Local C2 Centers which are “centrally governed”. “Loosely coupled” as C2 Centers are located separately, share their Situational Pictures via a Message Oriented Middleware but preserve their administrational and opera...

Obtaining location information can be of paramount importance in the context of pervasive and context-aware computing applications. Many systems have been proposed to date, e.g. GPS that has been proven to offer satisfying results in outdoor areas. The increased effect of large and small scale fading in indoor environments, however, makes localizat...

Obtaining location information can be of paramount importance in the context of pervasive and context-aware computing applications. Many systems have been proposed to date, e.g. GPS that has been proven to offer satisfying results in outdoor areas. The increased effect of large and small scale fading in indoor environments, however, makes localizat...

Genetic algorithms belong to a stochastic class of evolutionary techniques, whose robustness and global search of the solutions space have made them extremely popular among researchers. They have been successfully applied to electromagnetic optimization, including antenna design as well as smart antennas design. In this paper, extensive reference t...

Crowd behaviour models are divided into agent-based, flow-based and particle-based in terms of whether the behaviour emerges from simulating all people (agents) individually (Koh and Zhou, 2011; Braun et al., 2005; Luo et al., 2008; Pan et al., 2007; Shendarkar et al., 2006; Narain et al., 2009), is programmatically defined a priori using fluid dyn...

The study in this paper belongs to a more general research of discovering facial sub-clusters in different ethnicity face databases. These new sub-clusters along with other metadata (such as race, sex, etc.) lead to a vector for each face in the database where each vector component represents the likelihood of participation of a given face to each...

Market analysis studies of recent years have shown a steady and significant increase in the usage of RFID technology. Key factors for this growth were the decreased costs of passive RFIDs and their improved performance compared to the other identification technologies. Besides the benefits of RFID technologies into the supply chains, warehousing, t...

Location awareness is a core capability in many context-aware computing platforms. Multiple existing systems either provide inadequate accuracy or require extensive calibration or preexisting measurements in order to be functional. This work presents an extensive study of indoor tracking based on the chirp spread spectrum (CSS) specification and an...

Different degrees and types of visual impairment have become a common condition among the elderly, as aging inevitably affects the health and lifestyle of individuals. Partial or complete lack of sight is often accompanied by other ailments and conditions which further hinder the individual's activities. In this work, a novel Ambient Assisted Livin...

One of the greatest problems that First Responders (FRs) of various services (fire brigade, police, etc.) have to overcome during emergency situation incidents inside critical and highly dangerous infrastructures is the lack of information about the actual position of the First Responders, the environmental conditions FRs operate under, and the sur...

The majority of currently available wireless devices’ localization systems are based on received signal strength (RSS) measurements. The input to the localization technique is configured by the average of a number of N instantaneous RSS samples; thereupon, during simulation of such techniques, it is necessary to generate N RSS samples and calculate...

In this paper we explore the interplay of node density, mobility and cooperation in routing decisions for mobile networks. Specifically, routing is based on a novel metric that jointly accounts for all three aforementioned attributes and helps identify the most promising venue available for getting the message closer/faster to the destination, even...

Broadband communication networks have begun to spread rapidly over fixed networks, with wireless networks following at close distance. The excess capacity allows the offering of broadband services at competitive rates. Location-based services (LBS) over wireless broadband networks are becoming mainstream in an emerging ambient intelligence society....

A low-cost and profile switched-beam array, suitable for fixed and portable DVB-T applications in the V UHF band, is proposed in this paper. The array comprises eight wire elements lying on the horizontal plane and a set of four switching beam patterns is provided. Sufficient front gain and impedance matching is achieved with the aid of a genetic a...

Wireless sensor networks (WSNs) have attracted a great deal of research interest during the last few years, with potential applications making them ideal for the development of the envisioned world of ubiquitous and pervasive computing. Energy and computational efficiency constraints are the main key issues when dealing with this type of network. T...

Wireless Sensor Networks (WSNs) have attracted a great deal of research interest during the last few years. Potential applications make them ideal for the development of the envisioned world of ubiquitous and pervasive computing. Localization is a key aspect of such networks, since the knowledge of a sensor's location is critical in order to proces...

A nonparametric fusion method for extracting accurate distance measurements from low-quality sensors is proposed. The method applies to sensors with error functions that are monotonically increasing with respect to (w.r.t.) the actual value to be measured (arguments are presented on why a monotonically increasing error function is something to be e...

Radio frequency identification (RFID) systems based on passive tags are used successfully in a wide range of object identification applications. However, the increasing needs to meet new demands on applications of localization and tracking create a new field for evolution of the RFID technology. This paper presents the design, implementation, and e...

This paper proposes a routing protocol that jointly exploits location and motion information in a dynamically adjusted way, towards self-adaptability in different combinations of mobility and node density conditions. The protocol employs a metric of the rate at which a packet approaches its destination over a multihop path, as an effect of both the...

A new range-free solution based on simple RSSI measurements is presented herein. The proposed method includes a two-stage algorithm and is able to incorporate fingerprints of specific locations, when available, in order to enhance localization accuracy. The proposed algorithm requires a strategic placement of nodes in each room while being easily s...

Indoor localization is considered to be a key aspect of future context-aware, ubiquitous and pervasive systems, while Wireless Sensor Networks (WSNs) are expected to constitute the critical infrastructure in order to sense and interact with the environment surrounding them. In the context of developing ambient-assisted living and aftermath crisis m...

Location information is critical for the development of value-added location-based services, such as fraud protection, location-aware network access, person/asset tracking etc. Herein, a method for the enhancement of localization systems in terms of achieved accuracy is proposed, which can be applied to new as well as existing systems regardless th...

A compact Switched Parasitic Array (SPA) suitable for 2.4 GHz ISM applications is presented in this paper, which is designed using a proposed method based on self and mutual impedance measurements and optimized by a custom-designed Genetic Algorithm (GA). The proposed technique is applicable for Electronically Steerable Passive Array Radiator (ESPA...

Location information is a cornerstone for the development of the so-called location-based services. A method for the enhancement of a localization system in terms of achieved accuracy is proposed herein, which can be applied to new as well as existing systems regardless of the underlying localization technique. The method is based on modelling the...

A method for the design of electronically steerable passive array radiator (ESPAR) antennas is proposed herein, based on impedance-matrix measurements and a genetic algorithm. The proposed technique is best suited for cases where commercial elements are used as building blocks for ESPAR development, since in such cases the conventional numerically...

A fusion-based localization technique for location-based services in indoor environments is introduced herein, based on ultrasound time-of-arrival measurements from multiple off-the-shelf range estimating sensors which are used in a market-available localization system. In-situ field measurements results indicated that the respective off-the-shelf...

Localization of elderly people is considered to be a key task in ambient assisted living platforms. The problem of timely and valid emergency medical services notifications may be addressed in the context of a location-aware, event-triggered system provided an accurate, robust and reliable underlying localization system exists. Furthermore, first r...

Small-scale fading strongly affects the performance of a radio link; therefore radio channel simulation tools and models are broadly being used in order to evaluate the impact of fading. Furthermore, channel simulation tools and models are considered to be of utmost importance for efficient design and development of new products and services for Ne...

In this paper we present the results of the Taxi on Demand (ToD) system Test Trial which was conducted on 25-29 June, 2007. The ToD system, featuring a location-based and traffic-sensitive methodology, incorporates automated taxi booking, dispatching and monitoring functionalities. The ToD solution effectively addresses current taxi sector needs, a...

Switched-beam arrays (SBAs) are considered to be attractive alternatives to fully adaptive arrays (mainly due to deployment and maintenance cost) and can be used in order to increase system capacity and spectral efficiency. In this paper, dual-band operation and array failure correction of switched beam dipole arrays are considered. Dual-band opera...

In this paper we present a novel taxi on demand (ToD) management system that implements a location based and traffic-sensing approach and incorporates automated taxi booking, dispatching, and monitoring application. ToD solution effectively addresses current taxi sector needs, and could be potentially expanded to emerging car-pooling/sharing models...

Switched-beam antenna arrays (SBAs) are widely used in communications systems in order to increase system capacity and spectral efficiency. If an element fails during operation, a significant degradation of the array's performance is observed, even after redistribution of the array's excitation coefficients. Furthermore, redistribution of the excit...

Switched-beam arrays (SBAs) are considered as an attractive alternative to fully adaptive arrays, mostly due to easy installation and inexpensive maintenance. In this paper, a new technique is proposed in order to design dual-band switched-beam dipole arrays. The scope of the proposed technique is to design arrays with balanced radiation characteri...