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result(s) for
"Papadakis, Nikos"
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A Comprehensive Analysis of Wind Turbine Blade Damage
by
Katsaprakakis, Dimitris Al
,
Papadakis, Nikos
,
Ntintakis, Ioannis
in
Alternative energy sources
,
anti-icing methods
,
de-icing
2021
The scope of this article is to review the potential causes that can lead to wind turbine blade failures, assess their significance to a turbine’s performance and secure operation and summarize the techniques proposed to prevent these failures and eliminate their consequences. Damage to wind turbine blades can be induced by lightning, fatigue loads, accumulation of icing on the blade surfaces and the exposure of blades to airborne particulates, causing so-called leading edge erosion. The above effects can lead to damage ranging from minor outer surface erosion to total destruction of the blade. All potential causes of damage to wind turbine blades strongly depend on the surrounding environment and climate conditions. Consequently, the selection of an installation site with favourable conditions is the most effective measure to minimize the possibility of blade damage. Otherwise, several techniques and methods have already been applied or are being developed to prevent blade damage, aiming to reduce damage risk if not able to eliminate it. The combined application of damage prevention strategies with a SCADA system is the optimal approach to adequate treatment.
Journal Article
The YouGovern Secure Blockchain-Based Self-Sovereign Identity (SSI) Management and Access Control
by
Hatzivasilis, George
,
Papadakis, Nikos
,
Papatheodorou, Nikos
in
Access control
,
binance smart chain
,
Blockchain
2025
Self-sovereign identity (SSI) is an emerging model for digital identity management that empowers individuals to control their credentials without reliance on centralized authorities. This work presents YouGovern, a blockchain-based SSI system deployed on Binance Smart Chain (BSC) and compliant with W3C Decentralized Identifier (DID) standards. The architecture includes smart contracts for access control, decentralized storage using the Inter Planetary File System (IPFS), and long-term persistence via Web3.Storage. YouGovern enables users to register, share, and revoke identities while preserving privacy and auditability. The system supports role-based permissions, verifiable claims, and cryptographic key rotation. Performance was evaluated using Ganache and Hardhat under controlled stress tests, measuring transaction latency, throughput, and gas efficiency. Results indicate an average DID registration latency of 0.94 s and a peak throughput of 12.5 transactions per second. Compared to existing SSI systems like Sovrin and uPort, YouGovern offers improved revocation handling, lower operational costs, and seamless integration with decentralized storage. The system is designed for portability and real-world deployment in academic, municipal, or governmental settings.
Journal Article
Enhancing Discoverability: A Metadata Framework for Empirical Research in Theses
by
Vassiliou, Giannis
,
Nipurakis, Thomas
,
Tsamis, George
in
Data collection
,
data documentation initiative
,
Dissertations & theses
2025
Despite the significant volume of empirical research found in student-authored academic theses—particularly in the social sciences—these works are often poorly documented and difficult to discover within institutional repositories. A key reason for this is the lack of appropriate metadata frameworks that balance descriptive richness with usability. General standards such as Dublin Core are too simplistic to capture critical research details, while more robust models like the Data Documentation Initiative (DDI) are too complex for non-specialist users and not designed for use with student theses. This paper presents the design and validation of a lightweight, web-based metadata framework specifically tailored to document empirical research in academic theses. We are the first to adapt existing hybrid Dublin Core–DDI approaches specifically for thesis documentation, with a novel focus on cross-methodological research and non-expert usability. The model was developed through a structured analysis of actual student theses and refined to support intuitive, structured metadata entry without requiring technical expertise. The resulting system enhances the discoverability, classification, and reuse of empirical theses within institutional repositories, offering a scalable solution to elevate the visibility of the gray literature in higher education.
Journal Article
Event Prediction Using Spatial–Temporal Data for a Predictive Traffic Accident Approach Through Categorical Logic
by
Koutsaki, Eleftheria
,
Vardakis, George
,
Papadakis, Nikos
in
Alcohol
,
Algorithms
,
Artificial intelligence
2025
An event is an occurrence that takes place at a specific time and location that can be either weather-related (snowfall), social (crime), natural (earthquake), political (political unrest), or medical (pandemic) in nature. These events do not belong to the “normal” or “usual” spectrum and result in a change in a given situation; thus, their prediction would be very beneficial, both in terms of timely response to them and for their prevention, for example, the prevention of traffic accidents. However, this is currently challenging for researchers, who are called upon to manage and analyze a huge volume of data in order to design applications for predicting events using artificial intelligence and high computing power. Although significant progress has been made in this area, the heterogeneity in the input data that a forecasting application needs to process—in terms of their nature (spatial, temporal, and semantic)—and the corresponding complex dependencies between them constitute the greatest challenge for researchers. For this reason, the initial forecasting applications process data for specific situations, in terms of number and characteristics, while, at the same time, having the possibility to respond to different situations, e.g., an application that predicts a pandemic can also predict a central phenomenon, simply by using different data types. In this work, we present the forecasting applications that have been designed to date. We also present a model for predicting traffic accidents using categorical logic, creating a Knowledge Base using the Resolution algorithm as a proof of concept. We study and analyze all possible scenarios that arise under different conditions. Finally, we implement the traffic accident prediction model using the Prolog language with the corresponding Queries in JPL.
Journal Article
The “April” Dictatorship’s Policy in Universities and Students’ Activism and Resistance against the Dictatorship, in Greece
2024
This paper analyzes the main components, ideological features and practices that constitute the (overall) educational and specifically, the higher education policy of the “April” Dictatorship in Greece (1967–1974).The analysis of the relevant research material shows that this policy was characterized by:• the intention to redefine the relations of the Universities with the (“occupied”) State,• the coordinated effort to insert specific ideological authoritarian interpretations in the discourses and policies for higher education and consequently, in the reform efforts of the Dictatorship,• the institutionalization of a new economy of power based on control technologies which favored the formation of (ideologically over-determined) discipline and extended state intervention into every aspect of the Higher Education Institutions,• the construction of a surveillance, punishment, control and discipline framework, strictly demarcated and authoritarian.Simultaneously, the above-mentioned policy aimed a) at the extensive criminalization of behavior, as well as of the “non-nationalistic” and ideologically “un-orthodox” thinking in universities and in other Educational Institutions, b) at the reduction of any degree of teaching staff and students autonomy, and c) at the promotion of some alleged- ostensible, seemingly “liberal”, measures and proposals. The ultimate objective was both these specific measures and the overall (authoritarian) higher education policy to become feasible (legitimizing-permissible strategy) and subsequently implemented.In addition, students’ (persistent, influential and multi-level) resistance (at the level of both discourse and political action) to the higher education “reforms” attempted by the April Dictatorship, as well as against the Dictatorship per se and subsequently against the state and constitutional infringement, will be also analytically examined and contextualized.
Journal Article
ShinyAnonymizer Enhanced Version and Beyond: A Further Exploration of Privacy-Preserving Solutions in Health Data Management
by
Papadakis, Nikos
,
Tampouratzis, Manolis
,
Vardalachakis, Marios
in
Accountability
,
data anonymization
,
Data encryption
2024
Healthcare institutions generate massive amounts of valuable patient data in the digital age. Finding the right balance between patient privacy and the demand for data-driven medical enhancements is essential. Since data privacy has become increasingly important, robust technologies must be developed to safeguard private data and allow meaningful exploration. This issue was addressed by ShinyAnonymizer, which was first created to anonymize health data. It achieves this by rendering anonymization methods easily available to users. The enhanced version of ShinyAnonymizer, with an essential improvement in performance, is presented in this study. We explain the merging of data analysis, visualization, and privacy-focused statistics paradigms with data anonymization, hashing, and encryption, offering researchers and data analysts an extensive collection of tools for trustworthy data management.
Journal Article
An IoT-Based Participatory Antitheft System for Public Safety Enhancement in Smart Cities
by
Stavrakas, Ilias
,
Christakis, Ioannis
,
Koukoulas, Nikos
in
antitheft systems
,
Bluetooth Low Energy
,
public safety
2021
The risk of theft of goods is certainly an important source of negative influence in human psychology. This article focuses on the development of a scheme that, despite its low cost, acts as a smart antitheft system that achieves small property detection. Specifically, an Internet of Things (IoT)-based participatory platform was developed in order to allow asset-tracking tasks to be crowd-sourced to a community. Stolen objects are traced by using a prototype Bluetooth Low Energy (BLE)-based system, which sends signals, thus becoming a beacon. Once such an item (e.g., a bicycle) is stolen, the owner informs the authorities, which, in turn, broadcast an alert signal to activate the BLE sensor. To trace the asset with the antitheft tag, participants use their GPS-enabled smart phones to scan BLE tags through a specific smartphone client application and report the location of the asset to an operation center so that owners can locate their assets. A stolen item tracking simulator was created to support and optimize the aforementioned tracking process and to produce the best possible outcome, evaluating the impact of different parameters and strategies regarding the selection of how many and which users to activate when searching for a stolen item within a given area.
Journal Article
A Multi-Constrained Knapsack Approach for Educational Resource Allocation: Genetic Algorithm with Category- Specific Optimization
by
Kondylakis, Haridimos
,
Vassiliou, Giannis
,
Tsamis, George
in
Algorithms
,
Budgets
,
Comparative analysis
2025
Educational institutions face complex challenges when allocating limited teaching resources to specialized seminars, where budget, capacity, and balanced disciplinary representation must all be satisfied simultaneously. We address this for the first time in the educational domain by formulating the teacher seminar selection problem as a multi-dimensional knapsack variant with category-specific benefit multipliers. To solve it, we design a constraint-aware genetic algorithm that incorporates smart initialization, category-sensitive operators, adaptive penalties, and targeted repair mechanisms. In experiments on a realistic dataset representing multiple academic categories, our method achieved an 11.5% improvement in solution quality compared to the best constraint-aware greedy baseline while maintaining perfect constraint satisfaction (100% feasibility) vs. 0–30% for baseline methods. Statistical tests confirmed significant and practically meaningful advantages. For comprehensive benchmarking, we also implemented binary particle swarm optimization (PSO) and Tabu Search (TS) solvers with standard parameterizations. While PSO consistently produced feasible solutions with high budget utilization, its optimization quality was substantially lower than that of the GA. Notably, Tabu Search achieved the highest performance, with a mean fitness of 1557.3 compared to GA’s 1533.2, demonstrating that memory-based local search can be highly competitive for this problem structure. These findings show that metaheuristic approaches, particularly those integrating constraint-awareness into evolutionary or memory-based search, provide effective, scalable decision-support frameworks for complex, multi-constraint educational resource allocation.
Journal Article
Cost-Effective Design, Content Management System Implementation and Artificial Intelligence Support of Greek Government AADE, myDATA Web Service for Generic Government Infrastructure, a Complete Analysis
by
Mylona, Anastasia
,
Evangelos, Georgios
,
Vassiliou, Giannis
in
AADE
,
Artificial intelligence
,
Citizen participation
2025
One significant digital initiative that is changing Greece’s tax environment is the myDATA platform. The platform, which is a component of the wider digital governance agenda, provides significant added value to enterprises and the tax administration, despite the challenges of adaption. Despite the positive response, we find that the development of the platform could have been carried out quickly and at a significantly lower cost and could have been able to cope much faster with the rapid and necessary changes that the platform will have to comply with. For these reasons, development in WordPress would be considered essential as this CMS platform guarantees a fast and developer-friendly environment. In this publication, as a contribution, we provide all the necessary information to develop a myDATA-like platform in a fast, economical and functional way using the WordPress CMS. Our contribution also contains the analysis of the minimum necessary amount of services of the myDATA platform in order to perform its basic functionalities, the description of the according database relational model, which must be implemented in order to provide the same functionality with the myDATA platform, and the analysis of available methods to quickly create the necessary forms and services. In addition, we study how to develop Artificial Intelligence mechanisms with a success rate reaching up to 90% for automatic tax violation detection algorithms.
Journal Article
Constructing Semantic Summaries Using Embeddings
by
Kondylakis, Haridimos
,
Trouli, Georgia Eirini
,
Papadakis, Nikos
in
Algorithms
,
Approximation
,
graph summaries
2024
The increase in the size and complexity of large knowledge graphs now available online has resulted in the emergence of many approaches focusing on enabling the quick exploration of the content of those data sources. Structural non-quotient semantic summaries have been proposed in this direction that involve first selecting the most important nodes and then linking them, trying to extract the most useful subgraph out of the original graph. However, the current state of the art systems use costly centrality measures for identifying the most important nodes, whereas even costlier procedures have been devised for linking the selected nodes. In this paper, we address both those deficiencies by first exploiting embeddings for node selection, and then by meticulously selecting approximate algorithms for node linking. Experiments performed over two real-world big KGs demonstrate that the summaries constructed using our method enjoy better quality. Specifically, the coverage scores obtained were 0.8, 0.81, and 0.81 for DBpedia v3.9 and 0.94 for Wikidata dump 2018, across 20%, 25%, and 30% summary sizes, respectively. Additionally, our method can compute orders of magnitude faster than the state of the art.
Journal Article