Polyraptor: embracing path and data redundancy in data centres for efficient data transport

In this paper, we introduce Polyraptor, a novel data transport protocol that uses RaptorQ (RQ) codes and is tailored for one-to-many and many-to-one data transfer patterns, which are extremely common in modern data centres. Polyraptor builds on previous work on fountain coding-based transport and provides excellent performance, by exploiting native support for multicasting in data centres and data resilience provided by data replication

Ποδόσφαιρο και εργατικά στρώματα στην Αγγλία του 19ου αιώνα

Κατά το δεύτερο μισό του 19ου αιώνα, το ποδόσφαιρο αναδείχθηκε ως το εθνικό άθλημα της Αγγλίας και οι εργατικές τάξεις διαδραμάτισαν καίριο ρόλο σε αυτήν τη διαδικασία. Γι’ αυτόν τον λόγο, στην εργασία μου επέλεξα να παρουσιάσω τη σχέση μεταξύ ποδοσφαίρου και εργατών. Πιο συγκεκριμένα, σκοπεύω να αναδείξω το «πώς» και «γιατί» δημιουργήθηκε αυτή η σχέση. Στο πρώτο κεφάλαιο, σκιαγραφείται η Βιομηχανική Επανάσταση, ως το ιστορικό πλαίσιο. Ύστερα, παρουσιάζεται η ταξική διάρθρωση της αγγλικής κοινωνίας και κατ’ επέκταση η ανάδυση της εργατικής τάξης, του πρωταγωνιστικού ιστορικού υποκειμένου. Έπειτα, εξετάζεται η δημιουργία κατάλληλων συνθηκών για την ενασχόληση των εργατών με το ποδόσφαιρο εκείνη την περίοδο. Τέλος, πραγματοποιείται μια αναδρομή της ιστορίας του ποδοσφαίρου, ώστε να ανιχνευθούν οι απαρχές του αθλήματος και να φανεί ποιον ρόλο κατείχε στην κοινωνία της Βικτωριανής Αγγλίας. Το δεύτερο κεφάλαιο επικεντρώνεται στην απτή σχέση μεταξύ εργατών και ποδοσφαίρου. Το κεφάλαιο στηρίζεται σε βιβλιογραφία με στοιχεία περί συλλόγων (π.χ. τρόπος ίδρυσης), περί παικτών (π.χ. μισθολογικά στοιχεία) και περί του δικτύου που είχε σχηματιστεί γύρω από το ποδόσφαιρο (π.χ. στοιχηματισμός). Στα επόμενα κεφάλαια διερευνώνται οι λόγοι για τους οποίους οι εργάτες επέλεξαν το ποδόσφαιρο ως το άθλημα που θα εξέφραζε την τάξη τους. Πιο συγκεκριμένα, στο τρίτο κεφάλαιο αποτυπώνεται η κοινωνικοπολιτική εξέλιξη της αγγλικής κοινωνίας του 19ου αιώνα. Το ποδόσφαιρο εξετάζεται αφενός ως μέσο κοινωνικού ελέγχου από τις ανώτερες ταξικές βαθμίδες προς τις κατώτερες και αφετέρου ως ένα μέσο αυτόνομης εργατικής δράσης. Ειδικότερα, παρουσιάζεται η εμπλοκή των εργατών με το ποδόσφαιρο με σκοπό τη βελτίωση της οικονομικής και ενδεχομένως και της κοινωνικής τους θέσης. Στο τέταρτο κεφάλαιο διερευνάται η ψυχολογία του μέσου εργάτη. Η σκληρή καθημερινότητά του αντιπαρατίθεται στο ποδόσφαιρο, το οποίο αντιμετωπίζεται ως πεδίο ψυχολογικής ανάτασης. Παράλληλα, το άθλημα συμβάλλει και στη συγκρότηση ορισμένων συλλογικοτήτων. Επομένως, η ανθρώπινη ανάγκη για κοινωνικότητα μέσω ομαδικών δραστηριοτήτων θα είναι το δεύτερο ζήτημα του κεφαλαίου. Το τελευταίο κεφάλαιο πραγματεύεται την έμφυλη διάσταση της σύνδεσης εργατών και ποδοσφαίρου. Αναλυτικότερα, το πρώτο μέρος του ερμηνεύει την επιθυμία των εργατών να ασχοληθούν με το ποδόσφαιρο, συσχετίζοντάς τη με την επιβεβαίωση του ανδρισμού τους. Το δεύτερο μέρος φέρνει και το γυναικείο φύλο στο προσκήνιο μέσω δύο επιμέρους ζητημάτων: το ποδόσφαιρο ως μια διέξοδος των ανδρών από τη γυναικεία παρουσία και επιρροή, και την ενασχόληση γυναικών με το άθλημα. Στον επίλογο συνοψίζονται τα συμπεράσματα των επιμέρους κεφαλαίων, αναδεικνύοντας τους κοινωνικοπολιτικούς, ψυχολογικούς και έμφυλους λόγους που ώθησαν που ώθησαν τους εργάτες να παίξουν, να παρακολουθήσουν, και να ζήσουν το ποδόσφαιρο εν γένει.During the second half of the 19th century, football emerged as the national sport of England. The working classes played a significant part in this process. As a result, I have chosen to showcase in my thesis the relation between football and the workers. More specifically, I aim to discover “how” and “why” this relation occurred. In the first chapter, the Industrial Revolution is set as the historical background. Afterwards, the stratification of the English society is presented, with emphasis on the working classes. Then, the circumstances under which the workers “meddled” with football are researched. In the end, the origins of football are traced and its role on the Victorian England is shown. The second chapter focuses on the direct relation between football and the workers. In greater detail, the chapter relies on bibliography based on evidence about clubs (e.g. about their establishment), about players (e.g. about their salaries), and about the network that had surrounded football (e.g. gambling). The workers chose football as the sport that would define their class. The reasons behind this decision are looked into the next chapters. Namely, the sociopolitical evolution of 19th century England is presented in the third chapter. Football can be seen as a means of social control directed from the upper social strata towards the lower ones. On the other hand, it can be viewed as a part of an autonomous working-class initiative. In the fourth chapter, the focus is set on the psychology of the average working-man. Football, as a way of emotional uplift, is juxtaposed with the harsh industrial daily life of his. Simultaneously, football can help in creating some collectivities (e.g. fan clubs). Therefore, the human need for sociability through team-related activities is the second subject of the chapter. Last but not least, the relation of football and the workers is influenced by gender. The final chapter delves into this matter, as it allows us to understand that men saw football as a means to confirm their masculinity and avoid their female partners, too. Women, though, are also in the spotlight, as football played a part in the process of their emancipation in the 19th-20th century. In the epilogue, the conclusions from each chapter are rounded up, in an effort to manifest the reasons that made workers play, watch, and, in general, live for football

Exploiting functional connectivity inference for efficient root cause analysis

A crucial step in remedying faults within network infrastructure is to determine their root cause. However, the large-scale, complex and dynamic nature of modern architecture makes root cause analysis challenging. Statistical approaches for causal inference are promising, however, their deployment has been historically limited due to their high time complexity. In this paper we propose a general framework for leveraging the concept of functional connectivity to reduce the computational overhead of causal inference algorithms. We demonstrate on synthetic data that our approach can achieve substantial speedups when combined with state-of-the-art causal discovery algorithms, with only a small cost in terms of loss of causal information in some cases

Functional topology inference from network events

In this paper we present a novel approach for inferring functional connectivity within a large-scale network from time series of emitted node events. We do so under the following constraints: (a) non-stationarity of the underlying connectivity, (b) sparsity of the time-series of events, and (c) absence of an explicit model describing how events propagate through the network. We develop an inference method whose output is an undirected weighted network, where the weight of an edge between two nodes denotes the probability of these nodes being functionally connected. Two nodes are assumed to be functionally connected if they show significantly more coincident or short-lagged events than randomly picked pairs of nodes with similar levels of activity. We develop a model of time-varying connectivity whose parameters are determined by maximising the model’s predictive power from one time window to the next. We assess the accuracy, efficiency and scalability of our method on a real dataset of network events spanning multiple months

Internal network monitoring with DNN and network tomography for in-vehicle networks

With the advancements in Internet-of-Things (IoTs), particularly in Internet-of-Vehicles (IoVs), the vehicle becomes more vulnerable to more attack types caused by connecting the vehicle to the outside world. Moreover, the shift towards automotive Ethernet exposes the vehicle to IP-based attacks similar to attacks on computer networks. Most of such attacks tamper with the internal network components in order to gain control or disable some (or all) of the vehicle’s functions. To this end, in this work, we study two in-vehicle network monitoring approaches based on network tomography. The first approach relies purely on deep neural network (DNN) and we call it DNN-based tomography approach, while the second was proposed in a previous work and it uses algebraic network tomography with deep neural network, we call this one DNN-based algebraic approach. We evaluated the inference performance of both approaches using simulations and found that the DNNbased algebraic tomography approach outperforms DNN-based tomography approach with less inference error of about 4.5µs

Why are thoracic operations postponed?

<p>Abstract</p> <p>Aim</p> <p>To investigate and present the reasons that cause the postponement of thoracic surgical operations.</p> <p>Methods</p> <p>We retrospectively included in the study all patients submitted to elective thoracic surgery in our department during the 4-year period 2007-2010 and noted all cases of postponement after official inclusion in the operating schedule.</p> <p>Results</p> <p>81 out of a total of 542 patients (14.9%) scheduled for elective thoracic operation had their procedure postponed. The reasons were mainly organisatory (in 42 cases, 51.85%), which in order of significance were: shortage in matching erythrocyte units, shortage in anaesthetic/nursing staff and unavailability in operating rooms. The rest of the cases (39, 48.1%) were postponed due to medical reasons, which in descending order of significance were: respiratory infections and exacerbations of COPD, cardiological problems, misregulation of antiplatelet/antithrombotic drugs and infections from other systems (gastrointestinal, urinary, etc.). Elderly male patients planned for major/oncologic surgery were most possible to have their operation postponed for medical reasons.</p> <p>Discussion-Conclusions</p> <p>Thoracic operations are postponed owed to organisatory as well as medical reasons, the latter mainly affecting elderly, morbid patients awaiting for major/oncologic surgery.</p

Experimental investigation of the thermosiphonic phenomenon in domestic solar water heaters

The deeper understanding of the ‘thermosiphonic phenomenon’ and the identification of the key parameters affecting it, is the main aim of a research project currently in process in Cyprus. In this work a review of the existing standards and scientific knowledge concerning domestic solar water heaters is presented. The first preliminary results of the experimental investigation of the ‘thermosiphonic phenomenon’ in domestic solar water heaters are also presented. For this purpose a special test rig was set up and equipped with all sensors necessary to measure all parameters that are most likely to affect the ‘thermosiphonic phenomenon’. All tests were conducted according to ISO 9459- 2:1995(E). At first, the solar collector was tested according to EN12975-2:2006 in order to determine the thermal performance characteristics at a flow and operation conditions specified by the standard. Consequently, the efficiency of the collector operating thermosiphonically was calculated based on quasi-dynamic approach. Finally, a series of correlations were attempted using the data acquired when the collector is operating themosiphonically which are the following: (i) the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ) with the solar global radiation, (ii) the water mass flow with the solar global radiation, (iii) the water mass flow with the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ). The results of the data analysis showed that these parameters are very well correlated between them since the coefficient of determination (R2) is over 0.91 in all cases

Investigation of the parameters affecting the thermosiphonic phenomenon in solar water heaters

Cyprus is currently the leading country in the world with respect to the application of solar water heaters for domestic applications, with more than 93% of the houses equipped with such a system. The great majority of these solar water heaters are of the thermosiphonic type. Thermosiphonic is a natural phenomenon where the flow of the solar heated water from the collector to the storage tank occurs from a small flow created due to the difference in density between hot and cold water. The main advantage of such systems is that they do not require a pump for circulating the water and circulation exists as long as there is sunshine. This reduces the maintenance requirements and the system is foolproof. In spite of the fact that extensive analyses of the performance of solar water heaters has been carried out by numerous researchers, almost all of them concerned forced circulation systems which use a circulating pump. Currently, the knowledge on the parameters affecting the ‘thermosiphonic phenomenon’ is rather poor while on an international level (ISO and CEN committees) there isn’t any standard to test thermosiphon solar collectors. The deeper understanding of the ‘thermosiphonic phenomenon’ and the identification of the key parameters affecting it, is the main aim of a research project currently in process in Cyprus. In this work the first preliminary results of the experimental procedure are presented. More specifically, a special test rig was set up and equipped with all sensors necessary to measure all parameters that are most likely to affect the ‘thermosiphonic phenomenon’. All tests were conducted according to ISO 9459- 2:1995(E). The system was able to operate in various weather and operating conditions and could accommodate the change of inclination of the collector. Initially, the solar collector was tested according to EN12975-2:2006 in order to determine the thermal performance at a flow and operation conditions specified by the standard. Subsequently, the efficiency of the collector operating thermosiphonically was calculated based on quasi-dynamic approach. Finally, a series of correlations were attempted using the data acquired when the collector is operating themosiphonically which are the following: (i) the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ) with the solar global radiation, (ii) the water mass flow with the solar global radiation, (iii) the water mass flow with the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ). The results of the data analysis showed that these parameters are very well correlated between them since the coefficient of determination (R2) is over 0.91 in all cases