cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
A spectral differential approach to characterizing low-mass companions to late-type stars
Creators: name: Kostogryz, N. M.
name: Kuerster, M.
name: Yakobchuk, T. M.
name: Lyubchik, Y.
name: Kuznetsov, M. K.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: In this paper, we develop a spectral differential technique with which the dynamical mass of low-mass companions can be found. This method aims at discovering close companions to late-type stars by removing the stellar spectrum through a subtraction of spectra obtained at different orbital phases and discovering the companion spectrum in the difference spectrum in which the companion lines appear twice (positive and negative signal). The resulting radial velocity difference of these two signals provides the true mass of the companion, if the orbital solution for the radial velocities of the primary is known. We select the CO line region in the K-band for our study, because it provides a favourable star-to-companion brightness ratio for our test case GJ1046, an M2V dwarf with a low-mass companion that most likely is a brown dwarf. Furthermore, these lines remain largely unblended in the difference spectrum so that the radial velocity amplitude of the companion can be measured directly. Only if the companion rotates rapidly and has a small radial velocity due to a high mass, does blending occur for all lines so that our approach fails. We also consider activity of the host star, and show that the companion difference flux can be expected to have larger amplitude than the residual signal from the active star so that stellar activity does not inhibit the determination of the companion mass. In addition to determining the companion mass, we restore the single companion spectrum from the difference spectrum using singular value decomposition.
description: 14 pages, 10 figures, accepted to Astronomische Nachrichten March 2013
Perspective Aware Road Obstacle Detection
Creators: name: Lis, Krzysztof
name: Honari, Sina
name: Fua, Pascal
name: Salzmann, Mathieu
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences
subject: I.4.6; I.4.8; I.5.4

description: While road obstacle detection techniques have become increasingly effective, they typically ignore the fact that, in practice, the apparent size of the obstacles decreases as their distance to the vehicle increases. In this paper, we account for this by computing a scale map encoding the apparent size of a hypothetical object at every image location. We then leverage this perspective map to (i) generate training data by injecting onto the road synthetic objects whose size corresponds to the perspective foreshortening; and (ii) incorporate perspective information in the decoding part of the detection network to guide the obstacle detector. Our results on standard benchmarks show that, together, these two strategies significantly boost the obstacle detection performance, allowing our approach to consistently outperform state-of-the-art methods in terms of instance-level obstacle detection.
Quick Tips for Online Instruction: The Basics
Creators: name: Baez, Johanna C.
name: Marquart, Matthea S.
name: Garay, Kristin
name: Chung, Rebecca Yae-Eun
Publisher: name: Columbia University
Year: 2020
Subjects: Web-based instruction
Distance education

description: Columbia University School of Social Work's award-winning Online Campus prepares educators with quick tips for online teaching. These are the basics to quickly move your teaching online.
Revisiting collisional dust growth in Class 0/I protostellar disks: Sweep-up can convert a few $10 M_\oplus$ of dust into kg pebbles in 0.1 Myr
Creators: name: Xu, Wenrui
name: Armitage, Philip J.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: Recent observations suggest that the first stages of planet formation likely take place in the Class 0/I phase of Young Stellar Object evolution, when the star and the disk are still embedded in an infalling envelope. In this study we perform grain coagulation calculations to investigate the very first stage of planet formation, the collisional growth of dust grains, in Class 0/I disks. We find that the slow increase in grain mass by high-velocity collision with much smaller grains ("sweep-up") allows $\sim 50 M_\oplus$ of grains to grow well beyond the fragmentation barrier into $\sim$kg pebbles by the end of Class 0/I (0.1 Myr). We analyze the linear growth and saturation of sweep-up to understand our results quantitatively, and test whether the sweep-up outcome is sensitive to disk parameters and details of the grain coagulation model. The sweep-up pebble population could be important for planet formation, because they are less well-coupled to the gas (compared to the main population below the fragmentation barrier) and therefore more favorable to known mechanisms of dust clump formation (which initiate planetesimal formation). It also contains enough mass to form all planet cores, based on observational estimates of the planet mass budget. Our findings motivate future studies of grain growth and planetesimal formation in Class 0/I disks, including the subsequent evolution of this sweep-up population.
description: 16 pages, 10 figures. Accepted for publication in ApJ
Bulk--Boundary Correspondence for Chiral Symmetric Quantum Walks
Creators: name: Asbóth, János. K.
name: Obuse, Hideaki
Publisher: name: arXiv
Year: 2013
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Discrete-time quantum walks (DTQW) have topological phases that are richer than those of time-independent lattice Hamiltonians. Even the basic symmetries, on which the standard classification of topological insulators hinges, have not yet been properly defined for quantum walks. We introduce the key tool of timeframes, i.e., we describe a DTQW by the ensemble of time-shifted unitary timestep operators belonging to the walk. This gives us a way to consistently define chiral symmetry (CS) for DTQW's. We show that CS can be ensured by using an "inversion symmetric" pulse sequence. For one-dimensional DTQW's with CS, we identify the bulk ZxZ topological invariant that controls the number of topologically protected 0 and pi energy edge states at the interfaces between different domains, and give simple formulas for these invariants. We illustrate this bulk--boundary correspondence for DTQW's on the example of the "4-step quantum walk", where tuning CS and particle-hole symmetry realizes edge states in various symmetry classes.
title: Καθορισμός βέλτιστων ορίων εκμετάλλευσης πολυστρωματικών λιγνιτικών κοιτασμάτων
Creators: name: Δεληγιωργης Βασιλειος
Publisher: name: Technical University of Crete
Year: 2017

description: Σκοπός της εργασίας είναι να καθοριστούν τα βέλτιστα τελικά όρια εκσκαφής του ορυχείου ενός
λιγνιτικού πολυστρωματικού κοιτάσματος με οικονομικά κριτήρια. Τα κοιτάσματα αυτού του τύπου παρου-
σιάζουν δυσκολία στην προσομοίωσή τους λόγω της περίπλοκης γεωλογικής δομής τους (δυσκολία στην
κατασκευή του ψηφιακού τους ομοιώματος) αλλά και των σύνθετων μεθόδων που απαιτούνται για την
εκμετάλλευσης τους (ειδικές τεχνικές εκτίμησης των εκμεταλλεύσιμων στρωμάτων). Αρχικά αναλύονται οι
παράγοντες και ο τρόπος που επιδρούν στον καθορισμό των ορίων του κοιτάσματος και στην συνέχεια πε-
ριγράφεται ο τρόπος με τον οποίο υλοποιούνται τα ψηφιακά ομοιώματα αλλά και οι δυσκολίες-ιδιαιτερό-
τητες που υπάρχουν στα πολυστρωματικά κοιτάσματα. Προτείνεται μία νέα μεθοδολογία κατασκευής ψη-
φιακών ομοιωμάτων η οποία έχει ως βασικά μέρη της την χρήση της αξίας ως ιδιότητας και την διαφορική
διαμέριση του χώρου. Το ομοίωμα αυτό χρησιμοποιείται σε μεθόδους βελτιστοποίησης όπως ο αλγόριθμος
Lerchs-Grossman για τον καθορισμό των ορίων της εκσκαφής και της οικονομικής αξίας της εκμετάλλευσης.
Η ορθότητα της αναπτυχθείσας μεθοδολογίας επαληθεύτηκε με την εφαρμογή της σε ένα υποθετικό κοίτα-
σμα απλής γεωμετρίας με προκαθορισμένα γεωμετρικά και ποιοτικά χαρακτηριστικά, του οποίου τα βέλτι-
στα τελικά όρια εκσκαφής είναι γνωστά. Στη συνέχεια εφαρμόστηκε σε πολυστρωματικό λιγνιτικό κοίτασμα
από την περιοχή της Δυτικής Μακεδονίας και εκτιμήθηκε η τελική μορφή του ορυχείου καθώς και η καθαρή
παρούσα αξία της εκμετάλλευσης. Με βάση αυτή, εφόσον υπάρξουν οι κατάλληλες συνθήκες, είναι δυνα-
τόν να αυξηθούν σημαντικά τα μεταλλευτικά αποθέματα και η προστιθέμενη αξία της εκμετάλλευσης. Τέλος
συμπεραίνεται ότι οι συνθήκες ανταγωνισμού της κοινής Ευρωπαϊκής αγοράς μειώνουν την αποδοτικότητα
του πόρου αυτού (λιγνίτη) και συνολικά την ανταγωνιστικότητα του συνόλου της εγχώριας αγοράς ηλεκτρι-
κής ενέργειας.
Paradoxical constitutive law between donor O-H bond length and its stretching frequency in water dimer
Creators: name: Liu, Rui
name: Yang, Xinrui
name: Yu, Famin
name: Wang, Zhigang
Publisher: name: arXiv
Year: 2022
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Atomic and Molecular Clusters (physics.atm-clus)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Physical sciences

description: The constitutive laws of hydrogen bonds (H-bonds) are central to understanding microphysical processes not precisely observed, especially in terms of structural properties. Previous experiences in water H-bonding revealed that as the intermolecular O...O distance shortens, the O-H stretching frequency redshifts; thus, an elongated O-H bond length can be empirically inferred, which is described as the constitutive law under the cooperative effect. Here, using the high-precision CCSD(T) method, we report a violation of the conventional constitutive law in water dimer. That is, when the variation in the O...O distance changes from stretching by 0.06 to contracting by -0.15 angstrom compared to the equilibrium position, the donor O-H bond length decreases from 0.9724 to 0.9717 angstrom, and the O-H stretching frequency redshifts from 3715 to 3708 cm-1. Our work highlights that the O-H bond length decreases simultaneously with its stretching frequency, which is clearly inconsistent with the previously recognized constitutive law.
description: 10 pages, 2 figures
title: Σύγκριση δύο εναλλακτικών μεθόδων διάνοιξης συνδετήριας στοάς Ολυμπιάδας-Μαδέμ Λάκου
Creators: name: Θεοδωρακοπουλος Ιωαννης-Παναγιωτης
name: Λεκιδης Γεωργιος
Publisher: name: Technical University of Crete
Year: 2017

description: Η σήραγγα προσπέλασης και μεταφοράς του μεταλλείου Ολυμπιάδας έχει σχεδιασθεί να έχει μήκος περίπου 8,3 km. Επί του παρόντος είναι υπό κατασκευή με τη συμβατική υβριδική διαδικασία διάνοιξης σηράγγων με την τεχνική διάτρησης-ανατίναξης. Μέχρι τώρα, περισσότερο από δύο έτη μετά την έναρξη της κατασκευής της, έχει γίνει εκσκαφή μόνο 1.600 m της σήραγγας. Η εξαιρετικά αργή πρόοδος (συνολικός μέσος όρος 2,1 m/d) οφείλεται μερικώς στις εργασίες εμποτισμού του ρηγματωμένου πετρώματος με ρευστά κονιάματα (τσιμεντενέσεις), οι οποίες εκτελέσθηκαν προκειμένου να μειωθούν οι αυξημένες εισροές  υδάτων αλλά και στο σχεδιασμό της μεθόδου κατασκευής καθεαυτής. Ως εναλλακτική μέθοδος εξετάσθηκε στην παρούσα εργασία η τεχνική συνεχούς όρυξης σηράγγων με προσβολή όλου του μετώπου με μηχανή TBM. Σκοπός μας ήταν (α) η συλλογή γεωτεχνικών και άλλων δεδομένων την περίοδο Σεπτ-Δεκ 2016, (β) η παρουσίαση της τεχνικής μελέτης διάνοιξης σηράγγων με TBM και η περαιτέρω ανάλυση της όσον αφορά τον καταλληλότερο τύπο TBM συναρτήσει της μεθόδου έμφραξης των περιοχών αυξημένης εισροής υδάτων. Τέλος, δεν θα ήταν ολοκληρωμένη η συγκριτική αυτή ανάλυση χωρίς την θεώρηση και του σχεδιασμού της τεχνικής διάτρησης-ανατίναξης, με σκοπό στο τέλος να συγκριθούν οι δύο μέθοδοι ως προς την ταχύτητα όρυξης της συνδετήριας σήραγγας και το κόστος. Η προκαταρκτική αυτή συγκριτική αυτή ανάλυση με 3 διαφορετικά σενάρια ποιότητας βραχομάζας και καθυστερήσεων στην εγκατάσταση και λειτουργία του TBM, έδειξε ότι η συμβατική μέθοδος διάτρησης-ανατίναξης είναι πιο συμφέρουσα από τη μέθοδο TBM.
Locally normal subgroups of totally disconnected groups. Part I: General theory
Creators: name: Caprace, Pierre-Emmanuel
name: Reid, Colin D.
name: Willis, George A.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics
subject: 22D05, 20E15, 20E18

description: Let G be a totally disconnected, locally compact group. A closed subgroup of G is locally normal if its normaliser is open in G. We begin an investigation of the structure of the family of closed locally normal subgroups of G. Modulo commensurability, this family forms a modular lattice, called the structure lattice of G. We show that G admits a canonical maximal quotient H for which the quasi-centre and the abelian locally normal subgroups are trivial. In this situation the structure lattice of H has a canonical subset called the centraliser lattice, forming a Boolean algebra whose elements correspond to centralisers of locally normal subgroups. If H is second-countable and acts faithfully on its centraliser lattice, we show that the topology of H is determined by its algebraic structure (and thus invariant by every abstract group automomorphism), and also that the action on the Stone space of the centraliser lattice is universal for a class of actions on profinite spaces. Most of the material is developed in the more general framework of Hecke pairs.
description: 71 pages; revised version
title: Λειτουργική ασφάλεια αντλιοστασίων και εξοικονόμηση ενέργειας
Creators: name: Κονταρακης Κωνσταντινος
Publisher: name: Technical University of Crete
Year: 2017

description: Η λειτουργία των αντλιοστασίων ύδρευσης, άρδευσης και λυμάτων,  είναι  στενά  συνδεδεμένη με την εργασιακή ασφάλεια, καθώς πρόκειται ουσιαστικά για χώρους βιομηχανικής  χρήσης, τους οποίους οι εργαζόμενοι επισκέπτονται συχνά,  τόσο κατά  τη λειτουργία  τους, όσο και κατά την εμφάνιση βλαβών, με στόχο την αποκατάσταση τους.
Tα αντλιοστάσια χρησιμοποιούν για τη λειτουργία τους ηλεκτρική ενέργεια για τα φορτία ισχύος και κίνησης των ηλεκτρικών κινητήρων, του φωτισμού και του λοιπού εξοπλισμού των χώρων. Επίσης, για τα συμπληρωματικά δίκτυα ασθενών ρευμάτων, τα οποία συντελούν στην ορθή λειτουργία των συγκεκριμένων εγκαταστάσεων.
Στα πλαίσια αυτά, έγινε εκτενής βιβλιογραφική έρευνα για την εξοικονόμηση ενέργειας στα αντλιοστάσια  και για τη λειτουργική τους ασφάλεια, με αποτέλεσμα τα δύο αυτά μείζονα θέματα να εξεταστούν ταυτόχρονα. Κατ’ αυτήν την έννοια, η εργασία επικεντρώνεται κυρίως στα ήδη λειτουργούντα αντλιοστάσια. Υπάρχει πρόβλεψη  ο σχεδιασμός και οι προτάσεις που παρουσιάζονται να εφαρμοστούν σε νέα σχεδιαζόμενα, ή στα τελούντα υπό σχεδιασμό αντλιοστάσια.  Τέλος, υπάρχει πλήθος παραγόντων που επηρεάζουν την εξοικονόμηση ενέργειας στα αντλιοστάσια και οι οποίοι αναλύονται στη διατριβή.
Στο 1ο κεφάλαιο της εργασίας, παρουσιάζονται ορισμοί και έννοιες σχετικά με τη λειτουργική ασφάλεια των αντλιοστασίων και την εξοικονόμηση της ενέργειας και  γίνεται ανασκόπηση της σχετικής βιβλιογραφίας. Γίνεται σύντομη κριτική θεώρηση των αποτελεσμάτων - συμπερασμάτων  που έχουν προκύψει και παρουσίαση-σύγκριση της  βασική ιδέας της προτεινόμενης από την εργασία αυτή μεθοδολογίας με τις έως τώρα υπάρχουσες. Στη συνέχεια αναπτύσσεται το θεωρητικό τμήμα της εργασίας, όπου παρουσιάζεται η φιλοσοφία της εξοικονόμησης ενέργειας στα αντλιοστάσια, γίνεται ανάλυση του θεωρητικού μέρους που αφορά στο πεδίο της λειτουργικής ασφάλειας επιλέγονται, αναλύονται και προτείνονται, οι συνηθέστεροι  μέθοδοι εκτίμησης των αστοχιών και κατά επέκταση των κινδύνων για της αντίστοιχους χώρους. Επιπλέον, παρουσιάζονται περιπτώσεις λειτουργίας σε πραγματικά λειτουργούντα αντλιοστάσια και αποσαφηνίζονται λεπτομέρειες που σχετίζονται με τις παραμέτρους που οφείλουμε να λαμβάνουμε υπόψη, σε σχέση με το βέλτιστο σχεδιασμό και τη λειτουργία του αντλιοστασίου.
Στο 2ο κεφάλαιο, παρουσιάζεται η εφαρμογή του θεωρητικού μέρους της λειτουργικής ασφάλειας, σε ένα τυπικό  παράδειγμα αντλιοστασίου, προκειμένου  να εξαχθούν ουσιαστικά  και συγκεκριμένα  πραγματικά αποτελέσματα. Κατά την ανάλυση του συγκεκριμένου κεφαλαίου μέσω της εκτενούς βιβλιογραφικής έρευνας έγινε μια αρχική εκτίμηση για το αντλιοστάσιο του Βλητέ, με στόχο να προταθούν μέτρα για τη βελτίωση της ενεργειακής εξοικονόμησης και της λειτουργικής ασφάλειας.
Η ανάλυση ολοκληρώνεται  στο 3ο κεφάλαιο με την  παρουσίαση  των προτάσεων και  των συμπερασμάτων  της διατριβής. Τέλος η εργασία ολοκληρώνεται με  την  παράθεση της σχετικής  βιβλιογραφίας.
DiPPS: Differentially Private Propensity Scores for Bias Correction
Creators: name: Chen, Liangwei
name: Hartmann, Valentin
name: West, Robert
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cryptography and Security (cs.CR)
subject: FOS: Computer and information sciences

description: In surveys, it is typically up to the individuals to decide if they want to participate or not, which leads to participation bias: the individuals willing to share their data might not be representative of the entire population. Similarly, there are cases where one does not have direct access to any data of the target population and has to resort to publicly available proxy data sampled from a different distribution. In this paper, we present Differentially Private Propensity Scores for Bias Correction (DiPPS), a method for approximating the true data distribution of interest in both of the above settings. We assume that the data analyst has access to a dataset $\tilde{D}$ that was sampled from the distribution of interest in a biased way. As individuals may be more willing to share their data when given a privacy guarantee, we further assume that the analyst is allowed locally differentially private access to a set of samples $D$ from the true, unbiased distribution. Each data point from the private, unbiased dataset $D$ is mapped to a probability distribution over clusters (learned from the biased dataset $\tilde{D}$), from which a single cluster is sampled via the exponential mechanism and shared with the data analyst. This way, the analyst gathers a distribution over clusters, which they use to compute propensity scores for the points in the biased $\tilde{D}$, which are in turn used to reweight the points in $\tilde{D}$ to approximate the true data distribution. It is now possible to compute any function on the resulting reweighted dataset without further access to the private $D$. In experiments on datasets from various domains, we show that DiPPS successfully brings the distribution of the available dataset closer to the distribution of interest in terms of Wasserstein distance. We further show that this results in improved estimates for different statistics.
description: 11 pages, 2 figures. Current version: conference version
Sensitivity‐based singular value decomposition parametrization and optimal regularization in finite element model updating
Creators: name: Bartilson, Daniel Thomas
name: Jang, Jinwoo
name: Smyth, Andrew W.
Publisher: name: Columbia University
Year: 2020
Subjects: Structural analysis (Engineering)
Structural analysis (Engineering)--Mathematical models
Finite element method--Mathematical models
Singular value decomposition

description: Model updating is used to reduce error between measured structural responses and corresponding finite element (FE) model outputs, which allows accurate prediction of structural behavior in future analyses. In this work, reduced‐order parametrizations of an underlying FE model are developed from singular value decomposition (SVD) of the sensitivity matrix, thereby improving efficiency and posedness in model updating. A deterministic error minimization scheme is combined with asymptotic Bayesian inference to provide optimal regularization with estimates for model evidence and parameter efficiency. Natural frequencies and mode shapes are targeted for updating in a small‐scale example with simulated data and a full‐scale example with real data. In both cases, SVD‐based parametrization is shown to have good or better results than subset selection with very strong results on the full‐scale model, as assessed by Bayes factor.
Second harmonic and cascaded third harmonic generation in generalized quasi-periodic poled lithium niobate waveguides
Creators: name: Zhang, Li
name: Wu, Xiao
name: Hao, Zhenzhong
name: Ma, Rui
name: Gao, Feng
name: Bo, Fang
name: Zhang, Guoquan
name: Xu, Jingjun
Publisher: name: arXiv
Year: 2023
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Lithium niobate (LN) thin film has recently emerged as an important platform for nonlinear optical investigations for its large $χ^{(2)}$ nonlinear coefficients and ability of light localization. In this paper, we report the first fabrication of LN on insulator (LNOI) ridge waveguides with generalized quasi-periodic poled superlattices using the electric field polarization technique and microfabrication techniques. Benefiting from the abundant reciprocal vectors, we observed efficient second-harmonic and cascaded third-harmonic signals in the same device, with the normalized conversion efficiency 1735% W$^{-1}$cm$^{-2}$ and 0.41% W$^{-2}$cm$^{-4}$, respectively. This work opens a new direction of nonlinear integrated photonics based on LN thin film.
description: 4 pages, 4 figures
Chern-Simons terms in Lifshitz like quantum electrodynamics
Creators: name: Alves, Van Sérgio
name: Charneski, B.
name: Gomes, M.
name: Nascimento, Leonardo
name: Peña, Francisco
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In this work the generation of generalized Chern-Simons terms in three dimensional quantum electrodynamics with high spatial derivatives is studied. We analyze the self-energy corrections to the gauge field propagator by considering an expansion of the amplitude up to third order in the external momenta. The divergences of the corrections are determined and explicit forms for the Chern-Simons terms with high derivatives are obtained. Some unusual aspects of the calculation are stressed and the existence of a smooth isotropic limit is proved. The transversality of the anisotropic gauge propagator is also discussed.
description: Shortened version published in Phys. Rev. D
title: Αξιολόγηση γεωλογικών σχηματισμών με αργιλικές προσμίξεις. Εφαρμογή σε διαγραφίες από τις γεωτρήσεις ΡΑ-4, ΡΒ-18 και ΡΒ-20 του κοιτάσματος πρίνος
Creators: name: Σπανακης Ιωαννης
Publisher: name: Technical University of Crete
Year: 2017

description: Οι μέθοδοι γεωφυσικής διασκόπησης παίζουν σημαντικό ρόλο στην μελέτη της δομής των επιφανειακών στρωμάτων του φλοιού της Γης. Σκοπός τους είναι ο εντοπισμός κατάλληλων γεωλογικών συνθηκών που ευνοούν τον σχηματισμό κοιτασμάτων πετρελαίου και φυσικού αερίου. Στις μεθόδους αυτές συγκαταλέγονται και οι γεωφυσικές διαγραφίες. Στη παρούσα διπλωματική εργασία επεξεργάστηκαν και αξιολογήθηκαν δεδομένα γεωφυσικών διαγραφιών από την περιοχή του Πρίνου-Καβάλας και ειδικότερα από τις γεωτρήσεις PA-4 ,PB-18 και PB-20, που παραχωρήθηκαν από την εταιρεία Energean Oil&Gas.
Αναλυτικότερα, πραγματοποιήθηκε κατάλληλη επεξεργασία με σκοπό αρχικά την εύρεση του βάθους των ταμιευτήρων σε κάθε μία από τις γεωτρήσεις σύμφωνα με το γεωλογικό μοντέλο. Στην συνέχεια πραγματοποιήθηκε εκτίμηση του πορώδους (φ), της ειδικής ηλεκτρικής αντίστασης (Rt), του βαθμού κορεσμού σε νερό (Sw) και του δείκτη παραγωγικότητας που υπολογίζεται από το λόγο Sw/Sxo. Κατασκευάστηκαν διαγράμματα πορώδους και βαθμού κορεσμού σε νερό συναρτήσει του βάθους. Παρατηρείται ότι το πορώδες είναι κατά κανόνα μεγαλύτερο στο ταμιευτήρα Α1 και στις τρεις γεωτρήσεις σε σχέση με τους υπόλοιπους ταμιευτήρες.
Ο βαθμός κορεσμού σε νερό και ο βαθμός κορεσμού σε διήθημα της λάσπης, παρουσιάζουν τις μικρότερες τιμές στην PB-20. Ο λόγος Sw/Sxo ο οποίος αποτελεί δείκτη της παραγωγικότητας παρουσιάζει τιμές κάτω από τη μονάδα μόνο στη γεώτρηση ΡΒ-18 και κυμαίνεται μεταξύ 0,73-0,85.
title: The effect of the reservoir fluid phase behavior treatment on the reservoir simulation predictions output
Creators: name: Τριμη Πολυανθη-Μαρια
Publisher: name: Technical University of Crete
Year: 2017

description: Two different methods are used for solving the phase behavior problem during reservoir simulation applied
to hydrocarbon reservoirs; the black oil Tables and the compositional approaches. The black oil Tables
simulators use Tables of volumetric factors (solution gas-oil ratio, oil formation volume factor, gas
formation volume factor, oil content) versus pressure and by performing interpolation at each pressure
step the produced volumes are calculated. On the other hand, the compositional simulators, perform the
phase behavior calculations by using an equation of state so as to calculate the equilibrium phases and
their properties at different operating conditions.
The main advantages of the black-oil Tables simulators are that they require low calculation (CPU) time low
computer memory. On the other hand, compositional simulators are more accurate and can perform better
with volatile oils and gas condensates. Nevertheless, operators still use black-oil simulators to simulate
volatile oils and gas condensates, valuing thus more the speed of calculations as the expense of accuracy. The
question is how much information is lost with respect to the compositional approach and how much off the
black oil tables approach reservoir simulation predictions can be.
For this thesis, the commercial software IMEX and GEM of Computer Modeling Group has been used.
These models are presented in detail and the different options that they offer are discussed. The objective of
this work was to discuss to present the available models of the black oil tables and compositional simulators
as well as their difference in predictions and to assess their differences in predicting the reservoir production
performance. A simple reservoir containing volatile oil was modeled and its depletion was simulated using
both simulators and their results were compared.
The two simulators exhibited a small divergence between their predictions for the initial volumes in place
and the simulation runs. However, the compositional simulator is thought to be more accurate than the black
oil simulator in its predictions as it is a compositional simulator. Moreover, it was found that the black oil
simulator calculated almost the same amount of initial volumes in place, whereas it over-predicted the oil
recovery and the oil cumulative production.
AF Lep b: the lowest mass planet detected coupling astrometric and direct imaging data
Creators: name: Mesa, D.
name: Gratton, R.
name: Kervella, P.
name: Bonavita, M.
name: Desidera, S.
name: D'Orazi, V.
name: Marino, S.
name: Zurlo, A.
name: Rigliaco, E.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Aims. Using the direct imaging technique we searched for low mass companions around the star AF Lep that presents a significant proper motion anomaly (PMa) signal obtained from the comparison of Hipparcos and Gaia eDR3 catalogs. Methods. We observed AF Lep in two epochs with VLT/SPHERE using its subsystems IFS and IRDIS in the near-infrared (NIR) covering wavelengths ranging from the Y to the K spectral bands (between 0.95 and 2.3 μm). The data were then reduced using the high-contrast imaging techniques angular differential imaging (ADI) and spectral differential imaging (SDI) to be able to retrieve the signal from low mass companions of the star. Results. A faint companion was retrieved at a separation of ~0.335" from the star and with a position angle of ~70.5 deg in the first epoch and with a similar position in the second epoch. This corresponds to a projected separation of ~9 au. The extracted photometry allowed us to estimate for the companion a mass between 2 and 5 MJup. This mass is in good agreement with what is expected for the dynamic mass of the companion deduced using astrometric measures (5.2-5.5 MJup). This is the first companion with a mass well below the deuterium burning limit discovered coupling direct imaging with PMa measures. Orbit fitting done using the orvara tool allowed to further confirm the companion mass and to define its main orbital parameters.
description: 10 pages, 8 Figures, accepted for publication on A&A
Wireless Information and Power Transfer: Energy Efficiency Optimization in OFDMA Systems
Creators: name: Ng, Derrick Wing Kwan
name: Lo, Ernest S.
name: Schober, Robert
Publisher: name: arXiv
Year: 2013
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: This paper considers orthogonal frequency division multiple access systems with simultaneous wireless information and power transfer. We study the resource allocation algorithm design for maximization of the energy efficiency of data transmission. In particular, we focus on power splitting hybrid receivers which are able to split the received signals into two power streams for concurrent information decoding and energy harvesting. Two scenarios are investigated considering different power splitting abilities of the receivers. In the first scenario, we assume receivers which can split the received power into a continuous set of power streams with arbitrary power splitting ratios. In the second scenario, we examine receivers which can split the received power only into a discrete set of power streams with fixed power splitting ratios. In both scenarios, we formulate the corresponding algorithm design as a non-convex optimization problem which takes into account the circuit power consumption, the minimum data rate requirements of delay constrained services, the minimum required system data rate, and the minimum amount of power that has to be delivered to the receivers. Subsequently, by exploiting fractional programming and dual decomposition, suboptimal iterative resource allocation algorithms are proposed to solve the non-convex problems. Simulation results illustrate that the proposed iterative resource allocation algorithms approach the optimal solution within a small number of iterations and unveil the trade-off between energy efficiency, system capacity, and wireless power transfer.
description: 7 figures and 2 table, accepted for publication in the IEEE Transactions on Wireless Communications
Exploring the mass and redshift dependence of the cluster pressure profile with stacks on thermal SZ maps
Creators: name: Tramonte, Denis
name: Ma, Yin-Zhe
name: Yan, Ziang
name: Maturi, Matteo
name: Castignani, Gianluca
name: Sereno, Mauro
name: Bardelli, Sandro
name: Giocoli, Carlo
name: Marulli, Federico
name: Moscardini, Lauro
name: Puddu, Emanuella
name: Radovich, Mario
name: Van Waerbeke, Ludovic
name: Wright, Angus H.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We provide novel constraints on the parameters defining the universal pressure profile (UPP) within clusters of galaxies, and explore their dependence on the cluster mass and redshift, from measurements of Sunyaev-Zel'dovich Compton-$y$ profiles. We employ both the $\textit{Planck}$ 2015 MILCA and the ACT-DR4 $y$ maps over the common $\sim 2,100\,\text{deg}^2$ footprint. We combine existing cluster catalogs based on KiDS, SDSS and DESI observations, for a total of 23,820 clusters spanning the mass range $10^{14.0}\,\text{M}_{\odot}
description: 39 pages, 22 figures. Accepted for publication in ApjS
title: Σύνθεση και ιδιότητες γεωπολυμερών από σκωρίες ηλεκτρικής καμίνου παραγωγής σιδηρονικελίου
Creators: name: Ζαχαράκη Δήμητρα
Publisher: name: Technical University of Crete
Year: 2004

description: Μη διαθέσιμο
Implications of Different Solar Photospheric Flux-Transport Models for Global Coronal and Heliospheric Modeling
Creators: name: Barnes, Graham
name: DeRosa, Marc L.
name: Jones, Shaela I.
name: Arge, Charles N.
name: Henney, Carl J.
name: Cheung, Mark C. M.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Space Physics (physics.space-ph)
subject: FOS: Physical sciences

description: The concept of surface-flux transport (SFT) is commonly used in evolving models of the large-scale solar surface magnetic field. These photospheric models are used to determine the large-scale structure of the overlying coronal magnetic field, as well as to make predictions about the fields and flows that structure the solar wind. We compare predictions from two SFT models for the solar wind, open magnetic field footpoints, and the presence of coronal magnetic null points throughout various phases of a solar activity cycle, focusing on the months of April in even-numbered years between 2012 and 2020, inclusive. We find that there is a solar cycle dependence to each of the metrics considered, but there is not a single phase of the cycle in which all the metrics indicate good agreement between the models. The metrics also reveal large, transient differences between the models when a new active region is rotating into the assimilation window. The evolution of the surface flux is governed by a combination of large scale flows and comparatively small scale motions associated with convection. Because the latter flows evolve rapidly, there are intervals during which their impact on the surface flux can only be characterized in a statistical sense, thus their impact is modeled by introducing a random evolution that reproduces the typical surface flux evolution. We find that the differences between the predicted properties are dominated by differences in the model assumptions and implementation, rather than selection of a particular realization of the random evolution.
description: Accepted for publication in The Astrophysical Journal
Statistical analysis of the figure of merit of a two-level thermoelectric system: a random matrix approach
Creators: name: Abbout, Adel
name: Ouerdane, Henni
name: Goupil, Christophe
Publisher: name: arXiv
Year: 2013
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Using the tools of random matrix theory we develop a statistical analysis of the transport properties of thermoelectric low-dimensional systems made of two electron reservoirs set at different temperatures and chemical potentials, and connected through a low-density-of-states two-level quantum dot that acts as a conducting chaotic cavity. Our exact treatment of the chaotic behavior in such devices lies on the scattering matrix formalism and yields analytical expressions for the joint probability distribution functions of the Seebeck coefficient and the transmission profile, as well as the marginal distributions, at arbitrary Fermi energy. The scattering matrices belong to circular ensembles which we sample to numerically compute the transmission function, the Seebeck coefficient, and their relationship. The exact transport coefficients probability distributions are found to be highly non-Gaussian for small numbers of conduction modes, and the analytical and numerical results are in excellent agreement. The system performance is also studied, and we find that the optimum performance is obtained for half-transparent quantum dots; further, this optimum may be enhanced for systems with few conduction modes.
A Statistical Analysis of Galactic Radio Supernova Remnants
Creators: name: Ranasinghe, S.
name: Leahy, D.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present an revised table of 390 Galactic radio supernova remnants (SNRs) and their basic parameters. Statistical analyses are performed on SNR diameters, ages, spectral indices, Galactic heights and spherical symmetries. Furthermore, the accuracy of distances estimated using the $Σ$-D relation is examined. The arithmetic mean of the Galactic SNR diameters is $30.5$ pc with standard error $1.7$ pc and standard deviation $25.4$ pc. The geometric mean and geometric standard deviation factor of Galactic SNR diameters is $21.9$ pc and $2.4$, respectively. We estimate ages of 97 SNRs and find that the supernova (SN) birth rate to be lower than, but within $2σ$ of currently accepted values for SN birth rate. The mean spectral index of shell-type SNRs is $-0.51 \pm 0.01$ and no correlations are found between spectral indices and the SNR parameters of molecular cloud (MC) association, SN type, diameter, Galactic height and surface brightness. The Galactic height distribution of SNRs is best described by an exponential distribution with a scale height of $48 \pm 4$ pc. The spherical symmetry measured by the ovality of radio SNRs is not correlated to any other SNR parameters considered here or to explosion type.
description: 12 pages, 9 figures
Sticky Intuitions and the Future of Sexual Orientation Discrimination
Creators: name: Goldberg, Suzanne B.
Publisher: name: Columbia University
Year: 2010
Subjects: subject: Law
subject: FOS: Law
subject: Gay rights
subject: Homophobia
subject: Discrimination--Law and legislation

description: As once-accepted empirical justifications for discriminating against lesbians and gay men have fallen away, the major stumbling block to equality lies in a set of intuitions, impulses, and so-called common sense views regarding sexual orientation and gender. This Article takes up these impulses and views, which I characterize as “sticky intuitions,” to consider both their sustained influence and the prospects for their destabilization. In this effort, I first offer a framework for locating the intuitions’ work within contemporary doctrine, culture, and politics. I then advance an extended typology of the intuitions themselves, drawing from case law, scholarly literature, and public discourse. Although the individual intuitions will not surprise those familiar with the field, their amalgamation into a typology sheds light on their synergies as well as the complex nature of their influence. After describing these entangled intuitions, I offer several provisional observations regarding intuitions’ influence on lawmaking generally. I then raise what is likely to be a critical question going forward: In an era in which courts and legislatures continue to sustain sexual orientation discrimination, despite empirical data negating any legitimate basis for the embraced distinctions, how much candor ought there be in challenges to judicial and public squeamishness about homosexuality and gender roles? Cognitive theorists offer helpful insights, although operationalizing what we know about altering intuitions may be particularly difficult in the litigation context. Still, there are a number of options that warrant continued consideration by both theorists and strategists in the field.
Inhomogeneous transport in model hydrated polymer electrolyte supported ultra-thin films
Creators: name: Borges, D. Damasceno
name: Franco, A. A.
name: Malek, K.
name: Gebel, G.
name: Mossa, S.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: Structure of polymer electrolytes membranes, e.g., Nafion, inside fuel cell catalyst layers has significant impact on the electrochemical activity and transport phenomena that determine cell performance. In those regions, Nafion can be found as an ultra-thin film, coating the catalyst and the catalyst support surfaces. The impact of the hydrophilic/hydrophobic character of these surfaces on the structural formation of the films and, in turn, on transport properties, has not been sufficiently explored yet. Here, we report about classical Molecular Dynamics simulations of hydrated Nafion thin-films in contact with unstructured supports, characterized by their global wetting properties only. We have investigated structure and transport in different regions of the film and found evidences of strongly heterogeneous behavior. We speculate about the implications of our work on experimental and technological activity.
Stability of a Random Multiple Access Channel with "Success-Failure" Feedback
Creators: name: Foss, Sergey
name: Hajek, Bruce
name: Turlikov, Andrey
Publisher: name: arXiv
Year: 2013
Subjects: subject: Probability (math.PR)
subject: FOS: Mathematics

description: We consider a model of a decentralized multiple access system with a non-standard binary feedback where the empty and collision situations cannot be distinguished. We show that, like in the case of a ternary feedback, for any input rate λ< 1/e, there exists a "doubly randomized" adaptive transmission protocol which stabilizes the behavior of the system. We discuss also a number of related problems and formulate some hypotheses.
description: 11 pages, ! figure
title: Συγκριτική μελέτη χρηματοδοτικής μίσθωσης και μεσοπρόθεσμου δανεισμού για την προμήθεια-αντικατάσταση μηχανολογικού εξοπλισμού σε μεταλλευτικές επιχειρήσεις
Creators: name: Κωνσταντινίδης Κωνσταντίνος
Publisher: name: Technical University of Crete
Year: 1994

description: Μη διαθέσιμο
Deterministic generation of multi-photon bundles in a quantum Rabi model
Creators: name: Liu, Cheng
name: Huang, Jin-Feng
name: Tian, Lin
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Multi-photon bundle states are crucial for a broad range of applications such as quantum metrology, quantum lithography, quantum communication, and quantum biology. Here we propose a scheme that generates multi-photon bundles via virtual excitations in a quantum Rabi model. Our approach utilizes a Ξ-type three-level atom, where the upper two levels are coupled to a cavity field to form a quantum Rabi model with ultrastrong coupling, and the transition between the lower two levels is driven by two sequences of Gaussian pulses. We show that the driving pulses induce deterministic emission of multiple photons from the eigenstates of the quantum Rabi model via the stimulated Raman adiabatic passage technique, and hence can create bundles of multiple photons on-demand in the cavity output field. We calculate the generalized second-order correlation functions of the output photons, which reveal that the emitted photons form antibunched multi-photon bundles.
description: 11 pages, 11 figures
Obergefell at the Intersection of Civil Rights and Social Movements
Creators: name: Goldberg, Suzanne B.
Publisher: name: Columbia University
Year: 2015
Subjects: subject: Same-sex marriage
subject: Civil rights movements
subject: Social movements
subject: Social change
subject: Law
subject: FOS: Law
subject: Constitutional law

description: A judicial decision striking down formalized discrimination marks a crucial moment for those it affects and, in some instances, for the surrounding society as well. The Supreme Court’s ruling in Obergefell v. Hodges was unquestionably one of those instances. In this Essay, I consider the distinct ways in which the civil rights and social movements for marriage equality helped give rise to a durable socio-political transformation, as reflected in the widespread acceptance of the Court’s decision. By drawing this civil rights/social movement distinction, I mean to separate efforts to achieve new rights from efforts to achieve greater acceptance or affirmation. In the case of marriage equality, I argue that the two movements—one focused primarily on law reform and the other on social change—had an unusually strong coalescence in their goals and desires. This coalescence enabled social changes to propel legal changes and vice versa.
title: Εκτίμηση του ταμιευτήρα Πρίνος βασισμένη σε δεδομένα εργαστηριακής ανάλυσης πυρήνων γεωτρήσεων και διαγραφιών
Creators: name: Τόμος Χρήστος
Publisher: name: Technical University of Crete
Year: 1992

description: Μη διαθέσιμο
Vortex states in nanoscale superconducting squares: the influence of quantum confinement
Creators: name: Zhang, L. -F.
name: Covaci, L.
name: Milošević, M. V.
name: Berdiyorov, G. R.
name: Peeters, F. M.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Bogoliubov-de Gennes theory is used to investigate the effect of the size of a superconducting square on the vortex states in the quantum confinement regime. When the superconducting coherence length is comparable to the Fermi wavelength, the shape resonances of the superconducting order parameter have strong influence on the vortex configuration. Several unconventional vortex states, including asymmetric ones, giant multi-vortex combinations, and states comprising giant antivortex, were found as ground states and their stability was found to be very sensitive on the value of $k_Fξ_0$, the size of the sample $W$, and the magnetic flux $Φ$. By increasing the temperature and/or enlarging the size of the sample, quantum confinement is suppressed and the conventional mesoscopic vortex states as predicted by the Ginzburg-Laudau (GL) theory are recovered. However, contrary to the GL results we found that the states containing symmetry-induced vortex-antivortex pairs are stable over the whole temperature range. It turns out that the inhomogeneous order parameter induced by quantum confinement favors vortex-antivortex molecules, as well as giant vortices with a rich structure in the vortex core - unattainable in the GL domain.
Spin-3/2 and spin-2 charged massive states in a constant electromagnetic background
Creators: name: Benakli, Karim
name: Daniel, Cassiano A.
name: Ke, Wenqi
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We develop in components the superspace action obtained in arXiv:2110.07623 describing the first massive level of the open charged superstring in a flat four-dimensional spacetime. In the absence of an electromagnetic background, we show how the Rarita-Schwinger and Fierz-Pauli Lagrangians are retrieved for spin-3/2 and 2, respectively. We then write different forms of the action in the presence of the electromagnetic background. The resulting equations of motion describe the propagation of fields of charged spin-3/2 and spin-1/2 on the one hand, and spin-2, 1 and 0 on the other.
description: 70 pages, summary of the main results was presented in arXiv:2211.13689 and arXiv:2211.13691
title: Μελέτη της ορυκτολογικής σύστασης και των φυσικοχημικών και τεχνικών χαρακτηριστικών σκυροδέματος και κονιάματος που χρησιμοποιήθηκαν σε επεμβάσεις συντήρησης οικίας του ανακτόρου της Κνωσού και του λιμενοβραχίονα Χανίων
Creators: name: Αμπαριώτη Μαρία
name: Ροτόντο Παυλίνα Ι.
Publisher: name: Technical University of Crete
Year: 1995

description: Μη διαθέσιμο
Lower bound of quantum uncertainty from extractable classical information
Creators: name: Pramanik, T.
name: Mal, S.
name: Majumdar, A. S.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The sum of entropic uncertainties for the measurement of two non-commuting observables is not always reduced by the amount of entanglement (quantum memory) between two parties, and in certain cases may be impacted by quantum correlations beyond entanglement (discord). An optimal lower bound of entropic uncertainty in the presence of any correlations may be determined by fine-graining. Here we express the uncertainty relation in a new form where the maximum possible reduction of uncertainty is shown to be given by the extractable classical information. We show that the lower bound of uncertainty matches with that using fine-graining for several examples of two-qubit pure and mixed entangled states, and also separable states with non-vanishing discord. Using our uncertainty relation we further show that even in the absence of any quantum correlations between the two parties, the sum of uncertainties may be reduced with the help of classical correlations.
description: 12 pages, 2 figures, accepted for publication in Quantum Information Processing