cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Unimodular graphs and Eisenstein sums
Creators: name: Nica, Bogdan
Publisher: name: arXiv
Year: 2015
Subjects: subject: Combinatorics (math.CO)
subject: Rings and Algebras (math.RA)
subject: FOS: Mathematics
subject: 05C50, 05C25, 11T24

description: Motivated in part by combinatorial applications to certain sum-product phenomena, we introduce unimodular graphs over finite fields and, more generally, over finite valuation rings. We compute the spectrum of the unimodular graphs, by using Eisenstein sums associated to unramified extensions of such rings. We derive an estimate for the number of solutions to the restricted dot product equation $a\cdot b=r$ over a finite valuation ring. Furthermore, our spectral analysis leads to the exact value of the isoperimetric constant for half of the unimodular graphs. We also compute the spectrum of Platonic graphs over finite valuation rings, and products of such rings - e.g., $\mathbb{Z}/(N)$. In particular, we deduce an improved lower bound for the isoperimetric constant of the Platonic graph over $\mathbb{Z}/(N)$.
description: V2: minor revisions. To appear in the Journal of Algebraic Combinatorics
F-Theory Compactifications with Multiple U(1)-Factors: Constructing Elliptic Fibrations with Rational Sections
Creators: name: Cvetič, Mirjam
name: Klevers, Denis
name: Piragua, Hernan
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Algebraic Geometry (math.AG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: We study F-theory compactifications with U(1)xU(1) gauge symmetry on elliptically fibered Calabi-Yau manifolds with a rank two Mordell-Weil group. We find that the natural presentation of an elliptic curve E with two rational points and a zero point is the generic Calabi-Yau onefold in dP_2. We determine the birational map to its Tate and Weierstrass form and the coordinates of the two rational points in Weierstrass form. We discuss its resolved elliptic fibrations over a general base B and classify them in the case of B=P^2. A thorough analysis of the generic codimension two singularities of these elliptic Calabi-Yau manifolds is presented. This determines the general U(1)xU(1)-charges of matter in corresponding F-theory compactifications. The matter multiplicities for the fibration over P^2 are determined explicitly and shown to be consistent with anomaly cancellation. Explicit toric examples are constructed, both with U(1)xU(1) and SU(5)xU(1)xU(1) gauge symmetry. As a by-product, we prove the birational equivalence of the two elliptic fibrations with elliptic fibers in the two blow-ups Bl_(1,0,0)P^2(1,2,3) and Bl_(0,1,0)P^2(1,1,2) employing birational maps and extremal transitions.
description: 68 pages, 5 figures, 3 tables; v2: minor changes, 1 figure added; v3: typos corrected, references added
The influence of the meteorological forcing data on the reconstructions of historical storms in the Black Sea
Creators: name: Galabov, Vasko
name: Kortcheva, Anna
Publisher: name: arXiv
Year: 2013
Subjects: subject: Atmospheric and Oceanic Physics (physics.ao-ph)
subject: FOS: Physical sciences

description: The present article is a study of the applicability of different sources of meteorological forcing for the coastal wave and storm surge models, which provide the operational marine forecasts for the coastal early warning systems (EWS) and are used for reconstructions of historical storms. The reconstruction of historical storms is one of the approaches to the natural coastal hazard vulnerability assessment. We evaluate the importance of the input meteorological information for the mentioned types of coastal models. For two well documented historical storms, that caused significant damages along the Bulgarian coast we simulate the significant wave heights and sea level change, using SWAN wave model and a storm surge model. The wind and mean sea level pressure fields, which are used in the present study, are extracted from the ERA Interim reanalysis of the European Center for Medium range Forecasts (ECMWF) and from the output of the high resolution limited area numerical weather prediction model ALADIN. The overall conclusion is that for the successful historical storms reconstructions ERA Interim and ERA40 reanalysis are valuable source of meteorological forcing, but due to their limitations in terms of spatial and temporal resolution, it is recommended to produce a higher spatial and temporal resolution meteorological fields, using dynamical downscaling of the reanalyzed data.
description: submitted to SGEM2013 conference
title: Isola di Favignana: Οινοποιείο και Σχολή Αμπελουργίας - Οινοποιίας
Creators: name: Νταουντακη Ελλη
name: Σταυρουλακη Ναυσικα
Publisher: name: Technical University of Crete
Year: 2019

description: Η Favignana, ή Αιγούσα κατά τον Όμηρο, ανήκει στο σύμπλεγμα των Αιγάδων Νήσων και βρίσκεται δυτικά της Σικελίας. Πρόκειται για ένα μικρό, κατά βάση άγονο και σε μεγάλο βαθμό επίπεδο νησί, με εξαίρεση μια σειρά λόφων που το χωρίζει στα δύο. Η Favignana πέρασε από τα χέρια πολλών κατακτητών και έμεινε γνωστή ως τόπος φυλακής και εξορίας. Σήμερα υπάρχει επιθυμία να επαναπροσδιοριστεί ως πολιτιστικό κέντρο.

Μέχρι και τη δεκαετία του 1970, η αλιεία τόνου υπήρξε η κύρια ενασχόληση των κατοίκων, ωστόσο σήμερα η οικονομία στηρίζεται σχεδόν αποκλειστικά στον τουρισμό, ενώ ο πρωτογενής και δευτερογενής τομέας έχουν παραμεληθεί. Διατηρούνται ελάχιστες  καλλιέργειες σιταριού, κάποιοι ελαιώνες και αμπελώνες, χωρίς όμως να υπάρχουν εγκαταστάσεις μεταποίησης.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη και τον σχεδιασμό ενός οινολογικού κέντρου, το οποίο περιλαμβάνει οινοποιείο και σχολή αμπελουργίας-οινοποιίας.   Στόχος είναι να βρεθούν διέξοδοι απασχόλησης εκτός του τουρισμού και η ανάπτυξη μιας υγιούς τοπικής οικονομίας, εντεταγμένη στο ευρύτερο πολιτισμικό πλαίσιο.

Το κέντρο τοποθετείται σε κομβικό σημείο, ανάμεσα στον αστικό ιστό και τη βραχώδη κορυφή του νησιού, όπου δεσπόζει το φρούριο Santa Caterina. Παράλληλα με τις κτηριακές δομές οργανώνεται ένας αμπελώνας 50 στρεμμάτων, στον οποίο θα καλλιεργούνται οι τοπικές ποικιλίες.

Συγκεκριμένα, προτείνεται η δημιουργία:

    • μιας «ανοιχτής» σχολής, η οποία δύναται να φιλοξενεί εκπαιδευτικά προγράμματα εκμάθησης και επιμόρφωσης, συνέδρια και εκδηλώσεις που αφορούν στον οίνο και
    • οινοποιητικών εγκαταστάσεων, επισκέψιμων για το κοινό και διαχειριζόμενων από το προσωπικό και τους μαθητευόμενους της σχολής. Οι εγκαταστάσεις θα είναι ικανές σε μέγεθος να αναλάβουν και τον όγκο παραγωγής του ήδη υπάρχοντος οργανωμένου αμπελώνα της περιοχής.

Η επέμβαση θα αποτελέσει το κέντρο μιας πολιτισμικής διαδρομής με αφετηρία το λιμάνι του νησιού, έως το ιστορικό φρούριο. Θα είναι συνδετήριος κρίκος πόλης–αγρού και χώρος-πυκνωτής διαφόρων δραστηριοτήτων, που θα λειτουργεί όλο το χρόνο και θα απευθύνεται τόσο στους κατοίκους όσο και τους επισκέπτες του νησιού.
Transverse Top Quark Polarization and the ttbar Forward-Backward Asymmetry
Creators: name: Baumgart, Matthew
name: Tweedie, Brock
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: The forward-backward asymmetry in top pair production at the Tevatron has long been in tension with the Standard Model prediction. One of the only viable new physics scenarios capable of explaining this anomaly is an s-channel axigluon-like resonance, with the quantum numbers of the gluon but with significant axial couplings to quarks. While such a resonance can lead to a clear bump or excess in the ttbar or dijet mass spectra, it may also simply be too broad to cleanly observe. Here, we point out that broad ttbar resonances generally lead to net top and antitop polarizations transverse to the production plane. This polarization is consistent with all discrete spacetime symmetries, and, analogous to the forward-backward asymmetry itself, is absent in QCD at leading order. Within the parameter space consistent with the asymmetry measurements, the induced polarization can be sizable, and might be observable at the Tevatron or the LHC.
description: 28 pages, 6 figures. v2: expanded discussion of constraints
The Dynamics of Sex Ratio Evolution: From the Gene Perspective to Multilevel Selection
Creators: name: Argasinski, Krzysztof
Publisher: name: arXiv
Year: 2013
Subjects: subject: Populations and Evolution (q-bio.PE)
subject: Classical Analysis and ODEs (math.CA)
subject: Adaptation and Self-Organizing Systems (nlin.AO)
subject: FOS: Biological sciences
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: The new dynamical game theoretic model of sex ratio evolution emphasizes the role of males as passive carriers of sex ratio genes. This shows inconsistency between population genetic models of sex ratio evolution and classical strategic models. In this work a novel technique of change of coordinates will be applied to the new model. This will reveal new aspects of the modelled phenomenon which cannot be shown or proven in the original formulation. The underlying goal is to describe the dynamics of selection of particular genes in the entire population, instead of in the same sex subpopulation, as in the previous paper and earlier population genetics approaches. This allows for analytical derivation of the unbiased strategic model from the model with rigorous non-simplified genetics. In effect, an alternative system of replicator equations is derived. It contains two subsystems: the first describes changes in gene frequencies (this is an alternative unbiased formalization of the Fisher-Dusing argument), whereas the second describes changes in the sex ratios in subpopulations of carriers of genes for each strategy. An intriguing analytical result of this work is that fitness of a gene depends on the current sex ratio in the subpopulation of its carriers, not on the encoded individual strategy. Thus, the argument of the gene fitness function is not constant but is determined by the trajectory of the sex ratio among carriers of that gene. This aspect of the modelled phenomenon cannot be revealed by the static analysis. Dynamics of the sex ratio among gene carriers is driven by a dynamic "tug of war" between female carriers expressing the encoded strategic trait value and random partners of male carriers expressing the average population strategy (a primary sex ratio). This mechanism can be called "double level selection". Therefore, gene interest perspective leads to multi-level selection.
description: 3 figures
Counting Permutations Modulo Pattern-Replacement Equivalences for Three-Letter Patterns
Creators: name: Kuszmaul, William
Publisher: name: arXiv
Year: 2013
Subjects: subject: Combinatorics (math.CO)
subject: FOS: Mathematics

description: We study a family of equivalence relations on $S_n$, the group of permutations on $n$ letters, created in a manner similar to that of the Knuth relation and the forgotten relation. For our purposes, two permutations are in the same equivalence class if one can be reached from the other through a series of pattern-replacements using patterns whose order permutations are in the same part of a predetermined partition of $S_c$. When the partition is of $S_3$ and has one nontrivial part and that part is of size greater than two, we provide formulas for the number of classes created in each previously unsolved case. When the partition is of $S_3$ and has two nontrivial parts, each of size two (as do the Knuth and forgotten relations), we enumerate the classes for $13$ of the $14$ unresolved cases. In two of these cases, enumerations arise which are the same as those yielded by the Knuth and forgotten relations. The reasons for this phenomenon are still largely a mystery.
Virulence of Hindutva
Creators: name: Ahmed Asif, Manan
Publisher: name: Columbia University
Year: 2020
Subjects: Hindutva
Muslims
COVID-19 (Disease)--Social aspects
Islamophobia
History

description: An essay on the process of Islamophobic response to COVID-19 in India. I draw upon a longer history of minoritizations, such as in Europe and in US to draw parallels to how Hindutva structures Muslim presences in 2020 India
On operator norms for hyperbolic groups
Creators: name: Nica, Bogdan
Publisher: name: arXiv
Year: 2015
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics
subject: 20F67, 22D10, 22D20

description: We estimate the operator norm of radial non-negative functions on hyperbolic groups. As a consequence, we show that several forms of Haagerup's inequality are optimal.
description: 4 pages
Strong field lensing by Damour-Solodukhin wormhole
Creators: name: Nandi, K. K.
name: Izmailov, R. N.
name: Zhdanov, E. R.
name: Bhattacharya, Amrita
Publisher: name: arXiv
Year: 2018
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We investigate the strong field lensing observables for the Damour-Solodukhin wormhole and examine how small the values of the deviation parameter $λ$ need be for reproducing the observables for the Schwarzschild black hole. While the extremely tiny values of $λ$ indicated by the matter accretion or Hawking evaporation are not disputed, it turns out that $λ$ could actually assume values considerably higher than those tiny values and still reproduce black hole lensing signatures. The lensing observations thus provide a surprising counterexample to the intuitive expectation that all experiments ought to lead to the mimicking of black holes for the same range of values of $λ$.
description: 6 pages
Lensing observables: Massless dyonic vis-à-vis Ellis wormhole
Creators: name: Lukmanova, R. F.
name: Tuleganova, G. Y.
name: Izmailov, R. N.
name: Nandi, K. K.
Publisher: name: arXiv
Year: 2018
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Stable massless wormholes are theoretically interesting in their own right as well as for astrophysical applications, especially as galactic halo objects. Therefore, the study of gravitational lensing observables for such objects is of importance, and we do here by applying the parametric post-Newtonian method of Keeton and Petters to massless dyonic charged wormholes of the Einstein-Maxwell-Dilaton field theory and to the massless Ellis wormhole of the Einstein minimally coupled scalar field theory. The paper exemplifies how the lensing signatures of two different solutions belonging to two different theories could be qualitatively similar from the observational point of view. Quantitative differences appear depending on the parameter values. Surprisingly, there appears an unexpected divergence in the correction to differential time delay, which seems to call for a review of its original derivation.
description: 16 pages, 7 figures
title: Αναγνώριση κινούμενων αντικειμένων σε βίντεο και υλοποίηση σε (Digital Signal Processor) εξειδικευμένο επεξεργαστή
Creators: name: Γεωργάκης Μιχάλης
Publisher: name: Technical University of Crete
Year: 2009

description: Μη διαθέσιμο
title: Ανάπτυξη οδηγού λειτουργικού συστήματος ανοιχτού λογισμικού (Linux) και VHDL κώδικα για σειριακή επικοινωνία υψηλής ταχύτητας (PCle) ηλεκτρονικού υπολογιστή με την αναδιατασσόμενη συσκευή Virtex-5 Xilinx
Creators: name: Καρτσωνάκης Ιωάννης
Publisher: name: Technical University of Crete
Year: 2009

description: Μη διαθέσιμο
title: A haptic glove prototype for tactile feedback in 3D interactive applications
title: Ένα πρωτότυπο γάντι για την προσομοίωση της αίσθησης αφής σε τρισδιάστατες διαδραστικές εφαρμογές (A haptic glove)
Creators: name: Μπουσιο Μιχαλ
Publisher: name: Technical University of Crete
Year: 2017

description: Although Haptic technologies have been in existence for the last couple of decades, the recent rise of virtual reality applications has intensified the demand for consumer-grade haptics as well as sophisticated methods of haptic implementation. Besides wearable technology, haptics can already be encountered in a number of everyday consumer electronics. From mobile devices, to video game controllers the simulation of touch is used to bridge the gap between reality and the virtual world.

Motivated to develop a cheap and portable system which offers the haptic sensation, this thesis offers an approach to haptic feedback provision by developing a prototype system, able to supply vibrotactile feedback through a glove. The wearable glove was designed as a CAD model using a 3D modeling application and brought to life through the process of 3D printing. As all haptic systems the implemented system comprised of a software suit determining the forces that result when a user’s virtual identity interacts with an object and a device through which those forces can be applied to the user. The haptic forces were supplied to the user with the help of electric motors and the control of these motors was achieved using the Arduino microcontroller. The haptic glove is able to offer 10 different points of haptic simulation on the user’s hand, two points on each finger. A haptic point exists on the tip of each finger and a second on the bottom part. Each point is enabled independently when a collision with a virtual object occurs. In addition, the glove is able to provide different vibration strengths by decreasing or increasing the voltage supplied on the motors. A 3D interactive game was also developed with the purpose of showcasing the glove’s features and capabilities. The system utilizes the Leap Motion controller for hand and finger tracking and the Unity software framework for collision detection and graphics rendering.
title: Κατανεμημένος προσδιορισμός θέσης με ραδιόφωνα ελεγχόμενα από λογισμικό πολύ χαμηλού κόστους
title: Distributed localization with 5-Euro SDRS (Software Defined Radios)
Creators: name: Τζαγκαρακης Ελευθεριος
Publisher: name: Technical University of Crete
Year: 2017

description: Σκοπός αυτής της διπλωματικής εργασίας ήταν ο κατανεμημένος προσδιορισμός θέσης με ραδιόφωνα ελεγχόμενα από λογισμικό, πολύ χαμηλού κόστους. Ως δέκτες, χρησιμοποιήθηκαν τα εμπορικά ραδιόφωνα RTL, σε συνδυασμό με το GNU Radio για τις ανάγκες της δειγματοληψίας. Στην συνέχεια, μελετήθηκε το μαθηματικό μοντέλο των λαμβανόμενων σημάτων των δύο δεκτών και με βάση αυτό, δημιουργήθηκε ο αλγόριθμος για την εξαγωγή της γωνίας άφιξης των σημάτων (angle of arrival). Η ψηφιακή επεξεργασία των σημάτων και υλοποίηση του αλγορίθμου, περιλαμβάνει τη διόρθωση της μετατόπισης της συχνότητας του φέροντος, χρησιμοποιώντας την τεχνική του περιοδογράμματος. Η εύρεση της χρονικής διαφοράς μεταξύ των εκκινήσεων της δειγματοληψίας των δύο δεκτών (λόγω της έλλειψης συγχρονισμού μεταξύ τους), γίνεται με τη συσχέτιση του λαμβανόμενου σήματος καθώς έχει συγκεκριμένη δομή. Σε επόμενο βήμα, γίνεται εκτίμηση της γωνίας και της εναπομένουσας μετατόπισης στη συχνότητα του φέροντος, μέσω της γραμμικοποίησης που γίνεται με τη μεθοδολογία των ελαχίστων τετραγώνων. Η γραμμικοποίηση λειτουργεί και ως ένα είδος αποθορυβοποίησης, δεδομένης της ευαισθησίας των RTL. Στον αλγόριθμο υπολογίζονται όλες οι απαιτούμενες παράμετροι για την εκτίμηση της γωνίας, εκτός από την χρονική στιγμή που εκκινεί το πρώτο RTL να λαμβάνει. Τα πειραματικά αποτελέσματα συμφωνούν με την θεωρία.
Two applications of strong hyperbolicity
Creators: name: Nica, Bogdan
Publisher: name: arXiv
Year: 2019
Subjects: subject: Group Theory (math.GR)
subject: Operator Algebras (math.OA)
subject: FOS: Mathematics

description: We present two analytic applications of the fact that a hyperbolic group can be endowed with a strongly hyperbolic metric. The first application concerns the crossed-product C*-algebra defined by the action of a hyperbolic group on its boundary. We construct a natural time flow, involving the Busemann cocycle on the boundary. This flow has a natural KMS state, coming from the Hausdorff measure on the boundary, which is furthermore unique when the group is torsion-free. The second application is a short new proof of the fact that a hyperbolic group admits a proper isometric action on an $\ell^p$-space, for large enough $p$.
description: 8 pages; final version (February 2017), to appear in Kyoto Journal of Mathematics
Solving the PCAC puzzle for nucleon axial and pseudoscalar form factors
Creators: name: Bali, G. S.
name: Collins, S.
name: Gruber, M.
name: Schäfer, A.
name: Wein, P.
name: Wurm, T.
Publisher: name: Universität Regensburg
Year: 2019
Subjects: subject: 530 Physik

description: It has been observed in multiple lattice determinations of isovector axial and pseudoscalar nucleon form factors, that, despite the fact that the partial conservation of the axialvector current is fulfilled on the level of correlation functions, the corresponding relation for form factors (sometimes called the generalized Goldberger–Treiman relation in the literature) is broken rather badly. In this work we trace this difference back to excited state contributions and propose a new projection method that resolves this problem. We demonstrate the efficacy of this method by computing the axial and pseudoscalar form factors as well as related quantities on ensembles with two flavors of improved Wilson fermions using pion masses down to 150 MeV. To this end, we perform the z -expansion with analytically enforced asymptotic behaviour and extrapolate to the physical point.
Second moment of the pion distribution amplitude with the momentum smearing technique
Creators: name: Bali, G. S.
name: Braun, V. M.
name: Göckeler, M.
name: Gruber, M.
name: Hutzler, F.
name: Korcyl, P.
name: Lang, B.
name: Schäfer, A.
Publisher: name: Universität Regensburg
Year: 2017
Subjects: subject: LATTICE QCD; MASS; Lattice QCD; Pion wave function
subject: 530 Physik

description: Using the second moment of the pion distribution amplitude as an example, we investigate whether lattice calculations of matrix elements of local operators involving covariant derivatives may benefit from the recently proposed momentum smearing technique for hadronic interpolators. Comparing the momentum smearing technique to the traditional Wuppertal smearing we find-at equal computational cost-a considerable reduction of the statistical errors. The present investigation was carried out using N-f = 2+ 1 dynamical non-perturbatively order a improved Wilson fermions on lattices of different volumes and pion masses down to 220 MeV. (c) 2017 The Author(s). Published by Elsevier B.V.
description: SCOAP3
Emanuel C. Hofacker, Rückführung illegal verbrachter italienischer Kulturgüter nach dem Ende des 2. Weltkrieges
Creators: name: Froehlich, Annette
Publisher: name: Kunstrechtsspiegel
Year: 2017

description: Rezension zu: Emanuel C. Hofacker, Rückführung illegal verbrachter italienischer Kulturgüter nach dem Ende des 2. Weltkrieges, Schriften zum Kulturgüterschutz, De Gruyter Recht, Berlin 2004, S. 222, € 84.
description: Kunstrechtsspiegel, Nr. 4 (2008): Kunstrechtsspiegel
A relative bound for independence
Creators: name: Nica, Bogdan
Publisher: name: arXiv
Year: 2019
Subjects: subject: Combinatorics (math.CO)
subject: FOS: Mathematics

description: We prove an upper bound for the independence number of a graph in terms of the largest Laplacian eigenvalue, and of a certain induced subgraph. Our bound is a refinement of a well-known Hoffman-type bound.
description: 10 pages; preprint, comments are welcome
title: Ανάπτυξη ενός αποτελεσματικού συστήματος εξατομικευμένων συστάσεων με χρήση Markov Chain Monte Carlo
title: Markov Chain Monte Carlo for effective personalized recommendations
Creators: name: Παπιλαρης Μιχαηλ-Αγγελος
Publisher: name: Technical University of Crete
Year: 2017

description: Personalized recommender systems aim to help users access and retrieve relevant information or items from large collections, by automatically finding and suggesting products or services of potential interest. User preferences are difficult to infer, and doing so often requires a tedious elicitation process relying on evidence of others’ behavior. To overcome such limitations, we propose a Bayesian approach for finding personalized top recommendations, by capturing user preferences using a utility function which the system learns via a passive preference elicitation sampling-based framework. In brief, instead of asking the user to specify this function explicitly, which is unrealistic, we explicitly model the uncertainty over the utility function and learn it through feedback, in the form of clicks, provided by the user. The utility function is a linear combination of (weighted) features, and beliefs are maintained using a Markov Chain Monte Carlo algorithm. Additionally, we handle situations where not enough data about the user is available, by exploiting the information from clusters of (feature) weight vectors created by observing other users’ behavior. Finally, in order to evaluate our system’s performance, we applied it in the online hotel booking recommendations domain using a real-world dataset.
description: Τα εξατομικευμένα συστήματα συστάσεων, αποσκοπούν να βοηθήσουν τους χρήστες να ανακτήσουν πληροφορίες από μεγάλες συλλογές, εντοπίζοντας και προτείνοντας προϊόντα ή υπηρεσίες δυνητικού ενδιαφέροντος. Συχνά η διαδικασία εξαγωγής προτιμήσεων των χρηστών είναι περίπλοκη και βασίζεται σε στοιχεία για την συμπεριφορά άλλων χρηστών. Για να ξεπεραστούν αυτοί οι περιορισμοί, προτείνουμε μια Μπαεσιανή προσέγγιση για την εξαγωγή εξατομικευμένων προτάσεων, καταγράφοντας παθητικά τις προτιμήσεις των χρηστών, χρησιμοποιώντας μια συνάρτηση χρησιμότητας (utility function) την οποία το σύστημα μαθαίνει. Πιο συγκεκριμένα, αντί να ζητάμε από το χρήστη να καθορίσει την συνάρτηση χρησιμότητας, το οποίο είναι μη ρεαλιστικό, μαθαίνουμε τη συνάρτηση χρησιμότητας παρατηρώντας έμμεσα τον χρήστη και τις επιλογές του (clicks), και συντηρώντας σχετικές (πιθανοτικές) πεποιθήσεις. Η συνάρτηση χρησιμότητας αποτελείται από έναν γραμμικό συνδυασμό (σταθμισμένων) χαρακτηριστικών και οι πεποιθήσεις ενημερώνονται χρησιμοποιώντας έναν αλγόριθμο Markov Chain Monte Carlo. Επιπρόσθετα, σε περιπτώσεις όπου δεν έχουμε συλλέξει αρκετά δεδομένα σχετικά με τον χρήστη, σχηματίσαμε ομάδες (clusters) που δημιουργήσαμε από τα δεδομένα που έχουμε συλλέξει από άλλους χρήστες. Τέλος, προκειμένου να αξιολογήσουμε την απόδοση του συστήματός μας, το εφαρμόσαμε στον τομέα των συστάσεων για ηλεκτρονικές κρατήσεις ξενοδοχείων χρησιμοποιώντας πραγματικά σύνολα δεδομένων (datasets).
On bounded elementary generation for $SL_n$ over polynomial rings
Creators: name: Nica, Bogdan
Publisher: name: arXiv
Year: 2019
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics

description: Let $F[X]$ be the polynomial ring over a finite field $F$. It is shown that, for $n\geq 3$, the special linear group $SL_n(F[X])$ is boundedly generated by the elementary matrices.
description: 6 pages; final version (January 2017)
title: High throughput “on-the-fly” stream data processing on hybrid FPGA-based
platform
title: Υψηλής απόδοσης επεξεργασία ροών δεδομένων με χρήση υβριδικής πλατφόρμας βασισμένη σε αναδιατασσόμενη λογική
Creators: name: Ρουσοπουλος Χρηστος
Publisher: name: Technical University of Crete
Year: 2017

description: With the dawn of social networks and the growth of the Internet of Things market, huge volumes of data are generated every second in various fields, such as banking, agriculture, finance, health care, bioinformatics etc. This data congestion drives the need for systems that offer real-time fast processing of this high-volume and velocity data, while looking for low-cost and power efficient solutions. The stream join is a fundamental and computationally expensive operation for relating information from different data streams, usually applied over a specific time-based window due to the unbounded size of the data streams. This thesis presents an innovative high performance FPGA-based system for accelerating stream join processing.
The implemented system achieves at least one order of magnitude better processing throughput in comparison to other state-of-the-art software-based solutions and totally outperforms all lately proposed hardware-based solutions. Finally, the proposed hardware- based architecture is fully configurable and can be used as generic template for mapping stream processing algorithms on reconfigurable logic, taking into consideration real-world challenges and restrictions.
Inversion of walkaway VSP data in the presence of lateral velocity heterogeneity
Creators: name: Grechka, Vladimir
name: Tsvankin, Ilya
name: Contreras, Pedro
Publisher: name: arXiv
Year: 2019
Subjects: subject: Geophysics (physics.geo-ph)
subject: FOS: Physical sciences

description: Multi-azimuth walkaway vertical seismic profiling (VSP) is an established technique for the estimation of in situ slowness surfaces and inferring anisotropy parameters. Normally, this the technique requires the assumption of lateral homogeneity, which makes the horizontal slowness components at depths of downhole receivers equal to those measured at the surface. Any violations of this assumption, such as lateral heterogeneity or a nonzero dip of intermediate interfaces, lead to distortions in reconstructed slowness surfaces and, consequently, to errors in estimated anisotropic parameters. Here, we relax the assumption of lateral homogeneity and discuss how to correct VSP data for weak, lateral heterogeneity (LH). We describe a procedure of downward continuation of recorded travel times that accounts for the presence of both vertical inhomogeneity and weak lateral heterogeneity, which produces correct slowness surfaces at depths of downhole receivers. Once the slowness surfaces are found and the desired type of anisotropic model to be inverted is selected, the corresponding anisotropic parameters, providing the best fit to the estimated slowness can be obtained. We invert the slowness surfaces of $P$-waves for parameters of the simplest anisotropic model describing dipping fractures -- transversely isotropic medium with a tilted symmetry axis. Five parameters of this model -- the $P$-wave velocity $V_0$ in the direction of the symmetry axis, Thomsen's anisotropic coefficients $ε$ and $δ$, the tilt $ν$, and the azimuth $β$ of the symmetry axis can be estimated in a stable manner when maximum source offset is greater than half of the receiver depth.
description: 23 PAGES, 9 FIGURES. Energy Geoscience, 2023, 100255, ISSN 2666-7592
Modified gravity black hole lensing observables in weak and strong field of gravity
Creators: name: Izmailov, R. N.
name: Karimov, R. Kh.
name: Zhdanov, E. R.
name: Nandi, K. K.
Publisher: name: arXiv
Year: 2019
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We extend a recent work on weak field first order light deflection in the MOdified Gravity (MOG) by comprehensively analyzing the actual observables in gravitational lensing both in the weak and strong field regime. The static spherically symmetric black hole (BH) obtained by Moffat is what we call here the Schwarzschild-MOG (abbreviated as SMOG) containing repulsive Yukawa-like force characterized by the MOG parameter $α>0$ diminishing gravitational attraction. We point out a remarkable feature of SMOG, viz., it resembles a regular \textit{brane-world} BH in the range $-1<α<0$ giving rise to a negative "tidal charge" $Q$ ($=\frac{1}{4}\frac{α}{1+α}$) interpreted as an imprint from the $5D$ bulk with an imaginary source charge $q$ in the brane. The Yukawa-like force of MOG is attractive in the brane-world range enhancing gravitational attraction. For $-\infty <α<-1$, the SMOG represents a naked singularity. Specifically, we shall investigate the effect of $α$ or Yukawa-type forces on the weak (up to third PPN order) and strong field lensing observables. For illustration, we consider the supermassive BH SgrA* with $α=0.055$ for the weak field to quantify the deviation of observables from GR but in general we leave $α$ unrestricted both in sign and magnitude so that future accurate lensing measurements, which are quite challenging, may constrain $α$.
description: 11 pages, 11 figures
True SYK or (con)sequences
Creators: name: Khveshchenko, D. V.
Publisher: name: arXiv
Year: 2019
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Some generalizations of the Sachdev-Ye-Kitaev (SYK) model and different patterns of their reparametrization symmetry breaking are discussed. The analysis of such (pseudo)holographic systems relates their generalized one-dimensional Schwarzian dynamics to (quasi) two-dimensional Liouvillian quantum mechanics. As compared to the original SYK case, the latter might be dissipative or have discrete states in its spectrum, either of which properties alters thermodynamics and correlations while preserving the underlying $SL(2,R)$ symmetry.
description: Latex, no figures
Counseling and Support for Decent Work, Equity and Inclusion: Passwords for the Present and the Future
Creators: name: Nota, Laura
Publisher: name: Network for Innovation in Guidance and Counselling in Europe (NICE)
Year: 2017

description: Announcement: International Conference at the University of Padova from October 5-7, 2017
description: NICE Newsletter, No 1 (2017)
Asymptotically minimax empirical Bayes estimation of a sparse normal mean vector
Creators: name: Martin, Ryan
name: Walker, Stephen G.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics

description: For the important classical problem of inference on a sparse high-dimensional normal mean vector, we propose a novel empirical Bayes model that admits a posterior distribution with desirable properties under mild conditions. In particular, our empirical Bayes posterior distribution concentrates on balls, centered at the true mean vector, with squared radius proportional to the minimax rate, and its posterior mean is an asymptotically minimax estimator. We also show that, asymptotically, the support of our empirical Bayes posterior has roughly the same effective dimension as the true sparse mean vector. Simulation from our empirical Bayes posterior is straightforward, and our numerical results demonstrate the quality of our method compared to others having similar large-sample properties.
description: 18 pages, 3 figures, 3 tables
Can massless wormholes mimic a Schwarzschild black hole in the strong field lensing?
Creators: name: Izmailov, Ramil N.
name: Zhdanov, Eduard R.
name: Bhattacharya, Amrita
name: Potapov, Alexander A.
name: Nandi, Kamal K.
Publisher: name: arXiv
Year: 2019
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Recent trend of research indicates that not only massive but also massless (asymptotic Newtonian mass zero) wormholes can reproduce post-merger initial ring-down gravitational waves characteristic of black hole horizon. In the massless case, it is the non-zero charge of other fields, equivalent to what we call here the "Wheelerian mass", that is responsible for mimicking ring-down quasi-normal modes. In this paper, we enquire whether the same Wheelerian mass can reproduce black hole observables also in an altogether different experiment, viz., the strong field lensing. We examine two classes of massless wormholes, one in the Einstein-Maxwell-Dilaton (EMD) theory and the other in the Einstein-Minimally-coupled-Scalar field (EMS) theory. The observables such as the radius of the shadow, image separation and magnification of the corresponding Wheelerian masses are compared with those of a black hole (idealized SgrA* chosen for illustration) assuming that the three types of lenses share the same minimum impact parameter and distance from the observer. It turns out that, while the massless EMS\ wormholes can closely mimic the black hole in terms of strong field lensing observables, the EMD wormholes show considerable differences due to the presence of dilatonic charge. The conclusion is that masslessless alone is enough to closely mimic Schwarzschild black hole strong lensing observables in the EMS theory but not in the other, where extra parameters also influence those observables. The motion of timelike particles is briefly discussed for completeness.
description: 13 pages, 2 figures
Kloosterman sums over finite Frobenius rings
Creators: name: Nica, Bogdan
Publisher: name: arXiv
Year: 2019
Subjects: subject: Number Theory (math.NT)
subject: Rings and Algebras (math.RA)
subject: FOS: Mathematics
subject: Primary: 11L05, 11T24. Secondary: 16L60, 16D50

description: We study Kloosterman sums in a generalized ring-theoretic context, that of finite commutative Frobenius rings. We prove a number of identities for twisted Kloosterman sums, loosely clustered around moment computations.
description: 27 pages
Constraining Monodromy Inflation
Creators: name: Peiris, Hiranya
name: Easther, Richard
name: Flauger, Raphael
Publisher: name: arXiv
Year: 2013
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We use cosmic microwave background (CMB) data from the 9-year WMAP release to derive constraints on monodromy inflation, which is characterized by a linear inflaton potential with a periodic modulation. We identify two possible periodic modulations that significantly improve the fit, but it is unclear whether this improvement is associated with a "signal" or with the scatter in the measured angular power spectrum. The unmodulated potential is mildly favored by standard model selection criteria. A modulated inflationary potential can generate substantial primordial non-Gaussianity, of a specific and characteristic form. For the best-fit parameters to the WMAP angular power spectrum, the corresponding non-Gaussianity might be detectable in upcoming CMB data, allowing nontrivial consistency checks on the predictions of a modulated inflationary potential.
description: Version 3 -- minor editorial corrections. Version 2 -- significant revision from v1 (Overall amplitude of the potential added as a free parameter; still see two localized peaks in modulation frequency, but the best fit has significantly improved, to -2 \Delta log(L) ~ -20 with respect to reference model)
title: A full system simulator for disaggregated computing platforms and cloud data centers
title: Ένας προσομοιωτής πλήρους συστήματος για κατανεμημένες υπολογιστικές πλατφόρμες και βάσεις δεδομένων στο νέφος
Creators: name: Κυριακιδης Κωνσταντινος
Publisher: name: Technical University of Crete
Year: 2017

description: Όλα τα σύγχρονα συστήματα βάσεων δεδομένων, χαμηλής ή υψηλής κατανάλωσης, κατασκευάζονται με βάση μια κοινή αρχή: Τήν κεντρική πλατφόρμα(mainboard) και τα υπολογιστικά κομμάτια της (hardware components) ώς ένα μονολιθικό σχέδιο, γύρο από το οποίο αναπτύσσεται οποιαδήποτε προσθήκη hardware ή software. Η αναλογικότητα των πόρων παραμένει στατική καθ’ όλη τη διάρκεια της ζωής της βάσης, κάτι που επιφέρει μια πληθώρα περιορισμών σε θέματα διαχείρισης των πόρων, κατανάλωσης ενέργειας και πανάκριβες διεργασίες αναβάθμισης.
	Ώς αποτέλεσμα, προτείνεται μια καινοτόμα αρχιτεκτονική που έχει σκοπό να επαναστατικοποιήσει την αγορά χαμηλής ενέργειας, καθώς σπάει τα αυστηρά όρια των βάσεων δεδομένων εισάγοντας ιδέες κατανεμημένων συστημάτων. Βέβαια, μια τέτοια καινοτόμα προσέγγιση απαιτεί πολύ καλό σχεδιασμό και προεργασία για να υλοποιηθεί άρτια.
	Η διπλωματική αυτή εργασία, έχει ως στόχο να εισάγει την ιδέα ενός προσομοιωτή πλήρους συστήματος για την μοντελοποίηση αυτόυ του νέου μοντέλου, με απότερο σκοπό την αποτίμηση της λειτουργίας ενός τέτοιου συστήματος. Επίσης, αποτελεί μια εισαγωγή στις εικονικές πλατφόρμες προσομοίωσης (virtual platforms), που αποτελούν τον πιό γρήγορο και αξιόπιστο τρόπο αξιολόγησης ενός νέου τύπου hardware πρίν δημιουργηθεί πρωτότυπη πλατφόρμα για δοκιμές.
A Perturbed Sums of Squares Theorem for Polynomial Optimization and its Applications
Creators: name: Muramatsu, Masakazu
name: Waki, Hayato
name: Tuncel, Levent
Publisher: name: arXiv
Year: 2013
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics

description: We consider a property of positive polynomials on a compact set with a small perturbation. When applied to a Polynomial Optimization Problem (POP), the property implies that the optimal value of the corresponding SemiDefinite Programming (SDP) relaxation with sufficiently large relaxation order is bounded from below by $(f^\ast - ε)$ and from above by $f^\ast + ε(n+1)$, where $f^\ast$ is the optimal value of the POP. We propose new SDP relaxations for POP based on modifications of existing sums-of-squares representation theorems. An advantage of our SDP relaxations is that in many cases they are of considerably smaller dimension than those originally proposed by Lasserre. We present some applications and the results of our computational experiments.
Blind Identification of SIMO Wiener Systems based on Kernel Canonical Correlation Analysis
Creators: name: Van Vaerenbergh, Steven
name: Via, Javier
name: Santamaria, Ignacio
Publisher: name: arXiv
Year: 2013
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: We consider the problem of blind identification and equalization of single-input multiple-output (SIMO) nonlinear channels. Specifically, the nonlinear model consists of multiple single-channel Wiener systems that are excited by a common input signal. The proposed approach is based on a well-known blind identification technique for linear SIMO systems. By transforming the output signals into a reproducing kernel Hilbert space (RKHS), a linear identification problem is obtained, which we propose to solve through an iterative procedure that alternates between canonical correlation analysis (CCA) to estimate the linear parts, and kernel canonical correlation (KCCA) to estimate the memoryless nonlinearities. The proposed algorithm is able to operate on systems with as few as two output channels, on relatively small data sets and on colored signals. Simulations are included to demonstrate the effectiveness of the proposed technique.
title: Αστική επέμβαση στην πόλη του Περάματος. Συγκερασμός κλιμάκων
Creators: name: Ντιμερης Βασιλειος-Μαριος
Publisher: name: Technical University of Crete
Year: 2018

description: Η παρούσα διπλωματική εργασία είναι ένας αστικός σχεδιασμός σε μια μικρή πόλη, αυτήν του Περάματος, που αποτελεί συνέχεια του Πειραιά και του Κερατσινίου, χωρίς όμως η συνέχεια αυτή να φαίνεται στη δόμηση, τα δίκτυα, την επικοινωνία ή την αστική φόρμα και τις υποδομές. Μεγαλό βάρος δίνεται στην ανάπτυξη των υποδομών του λιμένα Πειραιώς και στη σύνδεση της ακτογραμμής από το επιβατικό λιμάνι έως το εμπορικό και κατ’ επέκταση έως το λιμάνι της Σαλαμίνας. Λαμβάνονται υπ’ όψιν νέες δομές που προκύπτουν από τη διαχείριση του εμπορικού λιμανιού από την Cosco καθώς και το πλάνο ανάπτυξης της Αττικής έως το 2021 (ΡΣΑ). Κεντροβαρές στοιχείο του σχεδιασμού είναι η πλατεία Περάματος και ένα κτήριο πολλαπλών χρήσεων που τοποθετείται σε αυτήν ώστε να καλύψει ελλείψεις της πόλης, καθώς και η διαχείριση του παραλιακού μετώπου, όπου λαμβάνει έναν περισσότερο δημόσιο χαρακτήρα.
Παίρνοντας παράδειγμα από μεγάλα λιμάνια που ιστορικά πλέον έχουν αποδείξει τη σταθερότητα και την αξία τους, όπως το λιμάνι του Rotterdam στην Ολλανδία ή το λιμάνι της Sines στην Πορτογαλία και χρησιμοποιώντας για εργαλεία ενεργειακούς χάρτες διδασκόμενος από το Δοξιάδη και μοτίβα σχεδίασης (patterns) του C. Alexander αναθεωρώ την πόλη του Περάματος αναδιαπραγ-ματευόμενος τα κενά και τα πλήρη. Γνωρίζοντας ότι η πόλη φτιάχνεται περισσότερο από τους κατοίκους παρά από τους σχεδιαστές τα κενά είναι πολλά. Είναι όμως χωρικά κενά και όχι απουσία σκέψης ή πρόνοιας, είναι κενά που θα πληρωθούν σε βάθος χρόνου και από μελετητές πολύ πιο εξειδικευμένους από έναν φοιτητή αρχιτεκτονικής. Παρουσιάζεται ένα μονάχα στάδιο μελέτης που δεν είναι καν το πρώτο, καθώς το πρώτο μέλημα πρέπει να είναι η ανάπτυξη επικοινωνίας της πόλης του Περάματος με τα μεγάλα κέντρα του Πειραιά και της Αθήνας. Στο στάδιο μελέτης τα καρνάγια έχουν επανατοποθετηθεί σε νέα περιοχή, η πόλη εκτονώνεται όχι με τη μορφή αστικής διάχυσης αλλά στην προσπάθεια συνεχούς δόμησης μέχρι το Κερατσίνι, η νέα πλωτή προβλήτα εγκαθιδρύεται στο στενό Περάματος-Ψυττάλειας, η Σαλαμίνα ενωποιείται και αποτελεί την «επέκταση» του λιμανιού και η πόλη αρχίζει κάνει τα πρώτα της βήματα για αλλαγή χρήσεων γης και χώρων για τους πολίτες. Η λύση που διαφαίνεται στην παρούσα διπλωματική είναι η ενωποίηση της μεγάλης κλίμακας του λιμανιού του Πειραιά με τη μικρή κλίμακα της πόλης του Περάματος. Η συνεχής εξάρτηση της ξηράς με τη θάλασσα δεν μπορεί παρά να δημιουργήσει αυτό που ο N. Salingaros καλεί ομοιόσταση του οργανισμού της πόλης. Σημαντικό της μελέτης δεν είναι ο χώρος που αποτυπώνεται αλλά μάλλον ο χώρος που καλείται να διαμορφωθεί καθώς η εξέλιξη θα συνεχίσει το έργο της.
Der Marberg bei Pommern an der Mosel und seine Kultstätte
Creators: name: Klein, Joseph
Publisher: name: Bonner Jahrbücher
Year: 2017

description: [nicht vorhanden / not available]
description: Bonner Jahrbücher, Bd. 101 (1897): Bonner Jahrbücher : Jahrbücher des Vereins von Altertumsfreunden im Rheinlande
Revisiting some physics issues related to the new mass limit for magnetized white dwarfs
Creators: name: Das, Upasana
name: Mukhopadhyay, Banibrata
Publisher: name: arXiv
Year: 2013
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: We clarify important physics issues related to the recently established new mass limit for magnetized white dwarfs which is significantly super-Chandrasekhar. The issues include, justification of high magnetic field and the corresponding formation of stable white dwarfs, contribution of the magnetic field to the total density and pressure, flux freezing, variation of magnetic field and related currents therein. We also attempt to address the observational connection of such highly magnetized white dwarfs.
description: 14 pages including 2 figures; based on the comments/questions from friends, colleagues and critics, triggered by our proposal of significantly super-Chandrasekhar white dwarfs; version to appear in MPLA
Greedy Feature Selection for Subspace Clustering
Creators: name: Dyer, Eva L.
name: Sankaranarayanan, Aswin C.
name: Baraniuk, Richard G.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Machine Learning (cs.LG)
subject: Numerical Analysis (math.NA)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: Unions of subspaces provide a powerful generalization to linear subspace models for collections of high-dimensional data. To learn a union of subspaces from a collection of data, sets of signals in the collection that belong to the same subspace must be identified in order to obtain accurate estimates of the subspace structures present in the data. Recently, sparse recovery methods have been shown to provide a provable and robust strategy for exact feature selection (EFS)--recovering subsets of points from the ensemble that live in the same subspace. In parallel with recent studies of EFS with L1-minimization, in this paper, we develop sufficient conditions for EFS with a greedy method for sparse signal recovery known as orthogonal matching pursuit (OMP). Following our analysis, we provide an empirical study of feature selection strategies for signals living on unions of subspaces and characterize the gap between sparse recovery methods and nearest neighbor (NN)-based approaches. In particular, we demonstrate that sparse recovery methods provide significant advantages over NN methods and the gap between the two approaches is particularly pronounced when the sampling of subspaces in the dataset is sparse. Our results suggest that OMP may be employed to reliably recover exact feature sets in a number of regimes where NN approaches fail to reveal the subspace membership of points in the ensemble.
description: 32 pages, 7 figures, 1 table