University of Piraeus

About: University of Piraeus is a education organization based out in Piraeus, Attiki, Greece. It is known for research contribution in the topics: Context (language use) & Computer science. The organization has 1731 authors who have published 6209 publications receiving 106699 citations.

Comparing the Trust and Security Models of Mobile Agents

Abstract: Mobile agent systems employ a number of security features to address the various threats. Despite this common need for security, there doesn't seem to exist a generic trust and security model that covers all the levels of their operation and that could be used as a standard. This paper intends to present the advances of modern trust and security models by presenting and comparing the security architecture of four major mobile agent platforms. The conclusions drawn are then used to point out deficiencies of current technology and highlight issues that need to be addressed by future research.

Easily Testable Cellular Carry Lookahead Adders

Abstract: Cellular Carry Lookahead (CLA) adders are systematically implemented in arithmetic units due to their regular, well-balanced structure. In terms of testability and with respect to the classical Cell Fault Model (CFM), cellular CLA adders have poor testability by construction. Design-for-testability (DFT) modifications for cellular CLA adders have been proposed in the literature providing complete CFM testability making the adders either level-testable or C-testable. These designs impose significant area and performance overheads. In this paper, we propose DFT modifications for cellular CLA adders to achieve complete CFM testability with special emphasis on the minimum impact in terms of area and performance. Complete CFM testability is achieved without adding any extra inputs to the adder, with very small area and performance overheads, thus providing a practical solution. The proposed DFT scheme requires only 1 extra output and it is not necessary to put the circuit in a special test mode, while the earlier schemes require the addition of 2 extra inputs to set the circuit in test mode. A rigorous proof of the linear-testability of the adder is given and a sufficient linear-sized test set is provided that guarantees 100% CFM fault coverage. Surprisingly, the size of the proposed linear-sized test set is, in most practical cases, comparable or even smaller than a logarithmic-sized test set proposed in the literature.

A Methodological Study for Optimizing Material Selection in Sustainable Product Design

Abstract: A computational intelligence-based identification of the properties of maximally sustainable materials for a given application, as derived from key properties of existing candidate materials, is put forward. The correlation surface between material properties (input) and environmental impact (EI) values (output) of the candidate materials is initially created using general regression (GR) artificial neural networks (ANNs). Genetic algorithms (GAs) are subsequently employed for swiftly identifying the minimum point of the correlation surface, thus exposing the properties of the maximally sustainable material. The ANN is compared to and found to be more accurate than classic polynomial regression (PR) interpolation/prediction, with sensitivity and multicriteria analyses further confirming the stability of the proposed methodology under variations in the properties of the materials as well as the relative importance values assigned to the input properties. A nominal demonstration concerning material selection for manufacturing maximally sustainable liquid containers is presented, showing that by appropriately picking the pertinent input properties and the desired material selection criteria, the proposed methodology can be applied to a wide range of material selection tasks.

Complex Event Recognition Languages: Tutorial

Abstract: Complex event recognition (CER) refers to the detection of events in Big Data streams. The paper presents a summary of the most prominent models and algorithms for CER, and discusses the main conceptual links and the differences between them.

T-Warehouse: Visual OLAP analysis on trajectory data

Abstract: Technological advances in sensing technologies and wireless telecommunication devices enable novel research fields related to the management of trajectory data. As it usually happens in the data management world, the challenge after storing the data is the implementation of appropriate analytics for extracting useful knowledge. However, traditional data warehousing systems and techniques were not designed for analyzing trajectory data. Thus, in this work, we demonstrate a framework that transforms the traditional data cube model into a trajectory warehouse. As a proof-of-concept, we implemented T-WAREHOUSE, a system that incorporates all the required steps for Visual Trajectory Data Warehousing, from trajectory reconstruction and ETL processing to Visual OLAP analysis on mobility data.