Earth observation : An integral part of a smart and sustainable city

Over the course of the 21st century, a century in which the urbanization process of the previous one is ever on the rise, the novel smart city concept has rapidly evolved and now encompasses the broader aspect of sustainability. Concurrently, there has been a sea change in the domain of Earth observation (EO) where scientific and technological breakthroughs are accompanied by a paradigm shift in the provision of open and free data. While the urban and EO communities share the end goal of achieving sustainability, cities still lack an understanding of the value EO can bring in this direction, an next a consolidated framework for tapping the full potential of EO and integrating it in their operational modus operandi. The “SMart URBan Solutions for air quality, disasters and city growth” H2020 project (SMURBS/ERA-PLANET) sits at this scientific and policy crossroad, and, by creating bottom-up EO-driven solutions against an array of environmental urban pressures, and by expanding the network of engaged and exemplary smart cities that push the state-of-the-art in EO uptake, brings the international ongoing discussion of EO for sustainable cities closer to home and contributes in this discussion. This paper advocates for EO as an integral part of a smart and sustainable city and aspires to lead by example. To this end, it documents the project's impacts, ranging from the grander policy fields to an evolving portfolio of smart urban solutions and everyday city operations, as well as the cornerstones for successful EO integration. Drawing a parallel with the utilization of EO in supporting several aspects of the 2030 Agenda for Sustainable Development, it aspires to be a point of reference for upcoming endeavors of city stakeholders and the EO community alike, to tread together, beyond traditional monitoring or urban planning, and to lay the foundations for urban sustainability.Peer reviewe

Real-time DNA microarray analysis

We present a quantification method for affinity-based DNA microarrays which is based on the real-time measurements of hybridization kinetics. This method, i.e. real-time DNA microarrays, enhances the detection dynamic range of conventional systems by being impervious to probe saturation in the capturing spots, washing artifacts, microarray spot-to-spot variations, and other signal amplitude-affecting non-idealities. We demonstrate in both theory and practice that the time-constant of target capturing in microarrays, similar to all affinity-based biosensors, is inversely proportional to the concentration of the target analyte, which we subsequently use as the fundamental parameter to estimate the concentration of the analytes. Furthermore, to empirically validate the capabilities of this method in practical applications, we present a FRET-based assay which enables the real-time detection in gene expression DNA microarrays

GOTRIPLE:a user-centric process to develop a discovery platform

Social sciences and humanities (SSH) research is divided across a wide array of disciplines, sub-disciplines and languages. While this specialization makes it possible to investigate the extensive variety of SSH topics, it also leads to a fragmentation that prevents SSH research from reaching its full potential. The TRIPLE project brings answers to these issues by developing an innovative discovery platform for SSH data, researchers’ projects and profiles. Having started in October 2019, the project has already three main achievements that are presented in this paper: (1) the definition of main features of the GOTRIPLE platform; (2) its interoperability; (3) its multilingual, multicultural and interdisciplinary vocation. These results have been achieved thanks to different methodologies such as a co-design process, market analysis and benchmarking, monitoring and co-building. These preliminary results highlight the need for respecting diversity of practices and communities through coordination and harmonization

Addendum: Dumouchel, S., et al. GOTRIPLE: A User-Centric Process to Develop a Discovery Platform. Information 2020, 11, 563

The authors would like to add the following reference to the “Reference” section of their paper [...

A study on torsional vibration attenuation in automotive drivetrains using absorbers with smooth and non-smooth nonlinearities

The automotive industry is predominantly driven by legislations on stringent emissions. This has led to the introduction of downsized engines, incorporating turbocharging to maintain output power. As downsized engines have higher combustion pressures, the resulting torsional oscillations (engine order vibrations) are of broadband nature with an increasing severity, which affect noise and vibration response of the drive train system. Palliative devices, such as clutch pre-dampers and dual mass flywheel have been used to mitigate the effect of transmitted engine torsional oscillations. Nevertheless, the effectiveness of these palliative measures is confined to a narrow band of response frequencies. The nonlinear targeted energy transfer is a promising approach to study vibration mitigation within a broader range of frequencies, using nonlinear vibration absorbers (or nonlinear energy sinks – NESs). These devices would either redistribute vibration energy within the modal space of the primary structure, thus dissipating the vibrational energy more efficiently through structural damping, or passively absorb and locally dissipate a part of this energy (in a nearly irreversible manner) from the primary structure. The absence of a linear resonance frequency of an NES, enables its broadband operation (in contrast to the narrowband operation of current linear tuned mass dampers). Parametric studies are reported to determine the effectiveness of various smooth or non-smooth nonlinear stiffness characteristics of such absorbers. A reduced drivetrain model, incorporating single and multiple absorber attachments is used and comparison of the predictions to numerical integrations proves its efficacy

On the effect of multiple parallel nonlinear absorbers in palliation of torsional response of automotive drivetrain

Torsional vibrations transmitted from the engine to the drivetrain system induce a plethora of noise, vibration and harshness (NVH) concerns, such a transmission gear rattle and clutch in-cycle vibration, to name but a few. The main elements of these oscillations are variations in the inertial imbalance and the constituents of combustion power torque, collectively referred to as engine order vibration. To attenuate the effect of these transmitted vibrations and their oscillatory effects in the drive train system, a host of palliative measures are employed in practice, such as clutch pre-dampers, slipping discs, dual mass flywheel and others, all of which operate effectively over a narrow band of frequencies and have various unintended repercussions. These include increased powertrain inertia, installation package space and cost. This paper presents a numerical study of the use of multiple Nonlinear Energy Sinks (NES) as a means of attenuating the torsional oscillations for an extended frequency range and under transient vehicle manoeuvres. Frequency–Energy Plots (FEP) are used to obtain the nonlinear absorber parameters for multiple NES coupled in parallel to the clutch disc of a typical drivetrain configuration. The results obtained show significant reduction in the oscillations of the transmission input shaft, effective over a broad range of response frequencies. It is also noted that the targeted reduction of the acceleration amplitude of the input shaft requires significantly lower NES inertia, compared with the existing palliative measures

Επεξεργασία XML επερωτήσεων: Αρχιτεκτονική και αλγόριθμοι για βελτιστοποίηση και εκτέλεση

This thesis proposes a design for XPath processing on relational back-ends and a design for a generic and modular framework for cost-based execution of XPath queries. Based on these designs two complete systems have been developed, the PPFx system and the GeCOEX system, respectively. PPFx is an XML database system based on identifying, processing and combining Primitive Path Fragments (PPFs) on XPath expressions that runs on top of a relational back-end. A set of novel techniques is presented that significantly limit the number of SQL joins required, take advantage of the strengths of modern SQL query processors and exploit XML schema information to achieve big performance gains with low implementation complexity. The PPF-based XPath-to-SQL translation algorithm leads to SQL queries that involve only the absolutely necessary relations, with the minimum number of structural joins and the maximum exploitation of root-to-node path ids for the holistic evaluation of multi-step PPFs based on optimized regular expression filtering method. Moreover, the thesis presents a very efficient technique for backwards navigation that substitutes expensive backward structural joins with simple and cheap string manipulation, yielding performance improvement of up to 35% for reversible descendant-ancestor structural joins and of orders of magnitude for general descendant-ancestor structural joins. Furthermore, the thesis describes an optimization technique for accelerating, under specific and well-defined conditions, queries that have forward predicates, yielding - when applicable - performance improvements that range from 61% up to 99.6%. An extensive experimental study confirms the performance benefits of all these novel techniques and shows that PPFx running on top of a commercial RDBMS is competitive with respect to query performance with other native and relational-based state-of-the-art XPath processing systems, commercial as well as research prototypes. The thesis also presents in detail a Generic and Extensible Cost-based Optimization and Execution system for XPath, named GeCOEX. The cost-based optimizer of GeCOEX always picks the cheapest estimated plan, among a very large number of possible plans, for a wide range of XPath queries and different datasets in a very small fraction of the time required for efficient execution. The optimizer is based on XPAlgebra, a novel navigation based logical algebra and on a comprehensive set of rewritings. Experimental evaluation of the effectiveness of the overall GeCOEX system have shown that the execution time of the chosen plan is within 12% of the optimal execution time in all but one of the queries in the tested workloads. The GeCOEX system contains a framework for XPath execution that includes physical operator implementations along with cost models, as well as the necessary infrastructure for their easy deployment. The framework can be effectively used with a variety of different storage engines. The thesis describes two novel families of algorithms, namely Lookup and Sort-Merge-based, for all the major XPath “operations”, including forward and backward navigation, and demonstrate experimentally their performance advantages compared to existing techniques. The algorithms are implemented as physical operators for the XPAlgebra algebra which, along with physical operator implementations corresponding to existing XPath processing techniques, are all plugged in the GeCOEX system. Experimental results provide strong evidence of the performance benefits of the execution framework in general and the Lookup and Sort-Merge-based physical operator in particular. Cost models for all proposed physical operators have been defined whose accuracy have been evaluated experimentally.Τα τελευταία χρόνια η XML υιοθετήθηκε σε μία σειρά εφαρμογών ηλεκτρονικού επιχειρείν, ως μοντέλο ανταλλαγής μηνυμάτων μεταξύ εφαρμογών και υπηρεσιών ιστού, ως μοντέλο δεδομένων για εφαρμογές ολοκλήρωσης δεδομένων αλλά και ως μοντέλο αποθήκευσης και επεξεργασίας δεδομένων εφαρμογών. Το θέμα της διδακτορικής διατριβής είναι η επεξεργασία επερωτήσεων σε ημιδομημένα δεδομένα, και συγκεκριμένα σε XML έγγραφα, και χωρίζεται σε δύο ενότητες. Η πρώτη ενότητα αφορά στην επεξεργασία επερωτήσεων σε XML δεδομένα, επερωτήσεις των οποίων η αποδοτικότητα είναι υψίστης σημασίας για συστήματα ολοκλήρωσης πληροφορίας που βασίζονται σε XML. Η δεύτερη ενότητα αφορά στην ανάπτυξη ενός ολοκληρωμένου βελτιστοποιητή βάσει εκτίμησης κόστους για XPath επερωτήσεις, ο οποίος βασίζεται σε μία λογική άλγεβρα για XPath επερωτήσεις και στον σχεδιασμό και υλοποίηση αποδοτικών φυσικών τελεστών για τους λογικές τελεστές που περιλαμβάνει η συγκεκριμένη άλγεβρα. Ειδικότερα, όσον αφορά την πρώτη ενότητα της διδακτορικής διατριβής, μελετήθηκε η σχετική υπάρχουσα βιβλιογραφία και αναπτύχθηκε μία μέθοδος επεξεργασίας επερωτήσεων σε ημιδομημένα δεδομένα, και συγκεκριμένα σε XML, η οποία χρησιμοποιεί την λειτουργικότητα των Σχεσιακών Συστημάτων Διαχείρισης Βάσεων Δεδομένων (ΣΣΔΒΔ). Η συγκεκριμένη ερευνητική δουλειά χωρίζεται σε δύο φάσης: στην πρώτη φάση αναπτύχθηκαν οι βασικές μέθοδοι και αλγόριθμοι για την επεξεργασία αυτού του είδους των επερωτήσεων ενώ στην δεύτερη οι μέθοδοι αυτοί βελτιώθηκαν και επεκτάθηκαν σημαντικά, τόσο σε σχέση με την αποδοτικότητά τους όσο σε σχέση με την λειτουργικότητα τους. Η δεύτερη ενότητα της διδακτορικής διατριβής επικεντρώθηκε στην δημιουργία ενός βελτιστοποιητή XPath επερωτήσεων που βασίζεται σε εκτίμηση κόστους. Συγκεκριμένα δημιουργήθηκε ένα πλαίσιο βελτιστοποίησης βασιζόμενης σε εκτίμηση κόστους και εκτέλεσης XPath επερωτήσεων και εκτιμήθηκε πειραματικά η αποδοτικότητα και η αποτελεσματικότητα του συστήματος. Το πλαίσιο βασίζεται σε μία λογική XPath άλγεβρα με πρωτότυπα χαρακτηριστικά και τελεστές καθώς και σε ένα σύνολο κανόνων μετασχηματισμού που μαζί επιτρέπουν να εκφραστούν αλγεβρικά πολλές υπάρχοντες αλλά και πρωτότυπες στρατηγικές επεξεργασίας XPath επερωτήσεων. Ένα σημαντικό συστατικό στοιχείο του πλαισίου είναι ένας ιδιαίτερα αποδοτικός αλγόριθμος επιλογής φυσικού πλάνου για XPath επερωτήσεις. Ο βελτιστοποιητής είναι ανεξάρτητος του φυσικού μοντέλου δεδομένων και του συστήματος αποθήκευσης αλλά και των διαθέσιμων υλοποιήσεων φυσικών τελεστών. Βασίζεται σε ένα σύνολο καλά ορισμένων API. Αναπτύχθηκαν διάφορες υλοποιήσεις των συγκεκριμένων API, που περιλαμβάνουν βασικές μεθόδους πρόσβασης δεδομένων, οι οποίες αντιστοιχούν σε διαφορετικά συστήματα αποθήκευσης XML δεδομένων. Παράλληλε υλοποιήθηκε ένα μεγάλο σύνολο από φυσικούς τελεστές, εκτιμητές στατιστικών και μοντέλα κόστους

Vassalos: “Improving the Efficiency of XPath Execution on Relational Systems”. EDBT

Abstract: This work describes a method for processing XPath on a relational back-end that significantly limits the number of SQL joins required, takes advantage of the strengths of modern SQL query processors, exploits XML schema information and has low implementation complexity. The method is based on the splitting of XPath expressions into Primary Path Fragments (PPFs) and their subsequent combination using an efficient structural join method, and is applicable to all XPath axes. A detailed description of the method is followed by an experimental study that shows our technique yields significant efficiency improvements over other XPath processing techniques and systems.

XPath on Steroids: Exploiting Relational Engines for XPath Performance †

A lot of research has been conducted by the database community on methods and techniques for efficient XPath processing, with great success. Despite the progress made, significant opportunities for optimization of XPath still exist. One key to further improvements is to utilize more effectively existing facilities of relational RDBSes for the processing of XPath queries. After taking a comprehensive look at such facilities, we present techniques for XPath processing that work by identifying the best relational join algorithms, indices and file organization strategies for XPath queries. Our techniques both reduce the latency of the resulting SQL translations and guarantee their pipelined execution. We also propose a new technique for XML reconstruction from relations-mapped XML that "splits the difference " between schema-aware and schema-oblivious XML-to-relational mapping for a significant performance improvement. An extensive experimental study confirms the performance benefits of our optimization techniques and shows that a system implementing these techniques on top of a commercial RDBMS is competitive with respect to query performance with other native and relationalbased state-of-the-art XPath processing systems, commercial as well as research prototypes