Infrastructure Performance Assessment of Subway Networks

Subway networks are the most crucial transit systems of large cities. According to reports, ridership is growing and will continue to do so in the following decade. The 2013 America’s Infrastructure Report Card evaluated transit infrastructure with a grade of D which is translated in poor condition. Large amount of capital investment is required, for instance, the “Société de Transport de Montréal” has assigned around $500 Million for renovation works of its infrastructure. Despite that, transit authorities so far have been relying on empirical management approaches based on engineering judgment and decision makers’ preference. Few models are currently found in which, they either focus on stations solely or examine structural performance only. Taking into account the deterioration severity and the amount of passengers, the duty of proper subway asset management becomes a critical public safety issue. New models are required since they will ensure passenger safety, assist in repair planning and optimize budget allocation. This research is aiming at developing a model for subway network performance assessment including structural, electrical and mechanical infrastructure. To achieve this objective, a typical breakdown is introduced including network, lines, stations, tunnels and components. The methodology passes through two main phases. First, a condition assessment model for components is developed based on identified defects. Subsequently, the condition index of stations and tunnels is calculated, followed by the rating of subway lines and the entire network. The Analytic Hierarchy and Network Processes, along with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and systems reliability are utilized in the computation procedure. Second, a condition prediction model is developed using Weibull theory, which constructs deterioration curves for all the network levels. In addition, the above two phases are incorporated in a user-friendly computerized application. Data for the relative importance weights are collected through on-line surveys sent to subway experts. It is concluded that components related to passenger safety and client services, such as emergency lightning and escalators, are the most important of the subway network. The developed methodology is also applied to a sub-network of Athens Metro system. The results show that stations are recording condition indexes of more than 7/10 and the network has satisfactory performance. Repair actions need to be planned for 2020. This research provides a new subway network asset management tool that considers all aspects of infrastructure, measures the condition based on actual defects and offers future condition prediction. The outcomes of this research are relevant to transit authorities, asset managers, engineers and researchers

A new proposal for trust management in wireless sensor networks based on validation

[EN] Due to their many advantages, WSNs are getting more and more important in the field of monitoring and control systems. Despite their many advantages WSNs have some disadvantages that need to be solved. Trust-based networking can be applied to WSNs in order to get better their performance. In this paper, we proposed a new model for trust management between sensor nodes in a WSN based on false alarms they produced. The existence of validators in the WSN supports the node to determine if the alarm is a false positive. A communication model is proposed and its messages are described. Furthermore, we have performed several tests to validate the benefits of our proposal, measuring the energy consumed by the network and each individual node in the network in five scenarios. They showed us that not trusting all of the nodes in a WSN, can have better results in the total energy consumption of the network. However, having a high number of malicious nodes causes an increment of energy consumption in the rest of the nodesRego Mañez, A.; Gkountis, C.; García-García, L.; Lloret, J. (2017). A new proposal for trust management in wireless sensor networks based on validation. International Journal of Trust Management in Computing and Communications. 4(1):1-16. doi:10.1504/IJTMCC.2017.089588S1164

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Lawrence Durrell et la Grèce

NANTERRE-BU PARIS10 (920502102) / SudocPARIS12-Bib. électronique (940280011) / SudocSudocFranceF

Ασφάλεια σε ευφυή-προγραμματιζόμενα-δίκτυα

Τα Ευφυή-Προγραμματιζόμενα-Δίκτυα (ΕΠΔ) είναι μια ανερχόμενη τεχνολογία δικτύων για το σχεδιασμό και τη διαχείριση των δικτύων των υπολογιστών. Ο στόχος των ΕΠΔ είναι να προσφέρει καλύτερο και πιο αποτελεσματικό έλεγχο του δικτύου. Αυτό το επιτυγχάνει με την απόζευξη των επιπέδων ελέγχου και δεδομένων, εισάγοντας την οντότητα ενός κεντρικού ελεγκτή. Πάρα το γεγονός ότι ο ελεγκτής παρέχει τεράστια πλεονεκτήματα, είναι επίσης μοναδικό σημείο αποτυχίας αν καταρρεύσει ύστερα από Destributed Denial of Service (DDoS) επιθέσεις. Ο κύριος σκοπός αυτής της εργασίας είναι να μελετήσει και να επισημάνει τις ευπάθειες των ΕΠΔ συστημάτων και να προτείνει μια λύση που να είναι αποτελεσματική εναντίον DDoS επιθέσεων στον ελεγκτή χωρίς να επιβαρύνει σημαντικά τους πόρους του ελεγκτή. Επιπλέον, αυτή η εργασία δείχνει πως οι DDoS επιθέσεις μπορούν να εξαντλήσουν τους πόρους του ελεγκτή και των μεταγωγέων, και δίνει μια λύση για την ανίχνευση και τον μετριασμό τέτοιων επιθέσεων με βάση την επεξεργασία των στατιστικών που κρατάει ο μεταγωγέας. Μέσω πειραμάτων δοκιμής και σύγκρισης με προγενέστερα σχήματα προστασίας κατά DDoS επιθέσεις, αποδείξαμε ότι η λύση μας παρουσιάζει καλύτερα αποτελέσματα όταν πρόκειται για ΕΠΔ συστήματα

Bridge Inspection, Maintenance, and Management Practices in Canada

ABSTRACT The crumbling state of bridge Infrastructure in the developed countries, such as the United States and Canada, has been recently making news headline stories, and drawing both public and official attention to the matter's criticality. Given the limited budget at hand, the state/provincial and federal transportation agencies are facing a steep challenge to upkeep their bridge inventories at safe conditions and/or acceptable service levels. This has created auxiliary needs for more efficient allocation of bridge maintenance funds, which urged transportation agencies to sponsor the development of Bridge Management Systems (BMS) since the early 1990's. Since then, the practice has gone through ample evolution, and had to benefit from incidents and accumulated experience. In an effort to form an understanding and update the knowledge about the contemporary state of the practice, this paper presents a survey of the current trends in bridge inspection, maintenance and management across Canada. Although most of the findings show similarities in the applied data collection and information management methods, differences were recorded in data interpretation, and intervention/ maintenance strategies. The paper provides insights of the latest trends in bridge management and preservation, which is ultimately believed to form a basis for educated future bridge management decisions. ABSTRACT The crumbling state of bridge Infrastructure in the developed countries, such as the United States and Canada, has been recently making news headline stories, and drawing both public and official attention to the matter's criticality. Given the limited budget at hand, the state/provincial and federal transportation agencies are facing a steep challenge to upkeep their bridge inventories at safe conditions and/or acceptable service levels. This has created auxiliary needs for more efficient allocation of bridge maintenance funds, which urged transportation agencies to sponsor the development of Bridge Management Systems (BMS) since the early 1990's. Since then, the practice has gone through ample evolution, and had to benefit from incidents and accumulated experience. In an effort to form an understanding and update the knowledge about the contemporary state of the practice, this paper presents a survey of the current trends in bridge inspection, maintenance and management across Canada. Although most of the findings show similarities in the applied data collection and information management methods, differences were recorded in data interpretation, and intervention/ maintenance strategies. The paper provides insights of the latest trends in bridge management and preservation, which is ultimately believed to form a basis for educated future bridge management decisions

Assessment of Demand Side Flexibility in European Electricity Markets: A Country Level Review

Power systems in many countries have recently undergone a significant transition towards renewable and carbon-free generation sources. Those sources pose new challenges to the grid operation due to their intermittency and uncertainty. Consequently, advanced policy strategies and technologies offering new flexibility solutions on the inelastic demand side are required to maintain the reliability of power systems. Given the diversity of situations, legislation and needs across European countries and the varying nature of distribution system operators, this article reviews the deployment of demand side flexibility at national level to identify best practices and main barriers. The analysis concerns European countries of different progress in solutions that leverage flexibility towards offering electricity grid services. The scope is to explore the operation principles of European electricity markets, to assess the participation of emerging flexible resources, and to propose new approaches that facilitate the integration of flexible assets in the distribution grid. The countries reviewed are the United Kingdom, Belgium, Italy and Greece. These countries were selected owing to their diversity in terms of generation mix and market design. Barriers for market access of flexibility resources are also identified in order to form relevant country-specific recommendations

Multi-Criteria Decision Making Models for Water Pipelines

The deterioration of water pipelines leads to impaired water quality, increased breakage rate, and reduced hydraulic capacity. The planning of maintenance programs for water pipelines is essential to minimize health and safety concerns and ensure an adequate supply of water in a safe, cost-effective, reliable, and sustainable manner. It is essential to assess the performance of water pipelines to assist municipalities in planning inspection and rehabilitation programs for their pipelines. Several models have been developed to assess the condition or performance of water pipelines based on several affecting factors. However, none of them considered the interdependency relationships between the factors. Moreover, some models did not account for the factors' weights uncertainty. This paper presents the development of performance assessment models for water pipelines. The models consider three groups of factors affecting water pipeline performance, namely, physical, environmental, and operational. The models were developed using data collected from questionnaire surveys distributed among water pipeline experts in Qatar. The factors' weights were calculated using four different methods, namely, analytic hierarchy process (AHP), fuzzy AHP (FAHP), analytic network process (ANP), and fuzzy ANP (FANP). The results showed that the FANP is the most accurate method since it incorporates the interdependency and uncertainty into the decision making process.Qatar National Research Fund (QNRF) for this research project under Award No. QNRF-NPRP 4-529-2-193.Scopu