cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Witnessing the fragmentation of a filament into prestellar cores in Orion B/NGC 2024
Creators: name: Shimajiri, Y.
name: André, Ph.
name: Peretto, N.
name: Arzoumanian, D.
name: Ntormousi, E.
name: Könyves, V.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Recent Herschel observations of nearby clouds have shown that filamentary structures are ubiquitous and that most prestellar cores form in filaments. Probing the density ($n$) and velocity ($V$) structure of filaments is crucial for the understanding of the star formation process. To characterize both the $n$ and the $V$ field of a fragmenting filament, we mapped NGC2024. 13CO, C18O, and H13CO+ trace the filament seen in the $N_{H_2}$ data. The radial profile from the $N_{H_2}$ data shows $D_{HP}$~0.081 pc, which is similar to the Herschel findings. The $D_{HP}$ from 13CO and C18O are broader, while the $D_{HP}$ from H13CO+ is narrower, than $D_{HP}$ from Herschel. These results suggest that 13CO and C18O trace only the outer part of the filament and H13CO+ only the inner part. The H13CO+ $V_{centroid}$ map reveals $V$ gradients along both filament axis, as well as $V$ oscillations with a period $λ$~0.2 pc along the major axis. Comparison between the $V$ and the $n$ distribution shows a tentative $λ$/4 shift in H13CO+ or C18O. This $λ$/4 shift is not simultaneously observed for all cores in any single tracer but is tentatively seen in either H13CO+ or C18O. We produced a toy model taking into account a transverse $V$ gradient, a longitudinal $V$ gradient, and a longitudinal oscillation mode caused by fragmentation. Examination of synthetic data shows that the oscillation component produces an oscillation pattern in the velocity structure function (VSF) of the model. The H13CO+ VSF shows an oscillation pattern, suggesting that our observations are partly tracing core-forming motions and fragmentation. We also found that the mean $M_{core}$ corresponds to the effective $M_{BE}$ in the filament. This is consistent with a scenario in which higher-mass cores form in higher line-mass filaments.
description: accepted in A&A
Will there be again a transition from acceleration to deceleration in course of the dark energy evolution of the universe?
Creators: name: Pan, Supriya
name: Chakraborty, Subenoy
Publisher: name: arXiv
Year: 2013
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In this work we consider the evolution of the interactive dark fluids in the background of homogeneous and isotropic FRW model of the universe. The dark fluids consist of a warm dark matter and a dark energy and both are described as perfect fluid with barotropic equation of state. The dark species interact non-gravitationally through an additional term in the energy conservation equations. An autonomous system is formed in the energy density spaces and fixed points are analyzed. A general expression for the deceleration parameter has been obtained and it is possible to have more than one zero of the deceleration parameter. Finally, vanishing of the deceleration parameter has been examined with some examples.
description: 15 pages, 3 figures, 1 table
The DUNE-DPG library for solving PDEs with Discontinuous Petrov-Galerkin finite elements
Creators: name: Gruber, Felix
name: Klewinghaus, Angela
name: Mula, Olga
Publisher: name: Archive of Numerical Software
Year: 2017
Subjects: discontinuous Petrov-Galerkin; partial differential equations; inf-sup stability; transport equation; finite elements; DUNE

description: In the numerical solution of partial differential equations (PDEs), a central question is the one of building variational formulations that are inf-sup stable not only at the infinite-dimensional level, but also at the finite-dimensional one. These properties are important since they represent the rigorous foundations for a posteriori error control and the development of adaptive strategies. The essential difficulty lies in finding systematic procedures to build variational formulations for which these desirable stability properties are (i) provable at the theoretical level while (ii) the approach remains implementable in practice and (iii) its computational complexity does not explode with the problem size. In this framework, the so-called Discontinuous Petrov–Galerkin (DPG) concept seems a promising approach to enlarge the scope of problems beyond second order elliptic PDEs for which this is possible. In the context of DPG, the result for the elliptic case was proven by Gopalakrishnan and Qiu [2014] and requires a p-enriched test space. Recently, the same type of result has been proven by Broersen et al. [2015] for certain classes of linear transport problems using an appropriate hp-enrichment to build the finite dimensional test space. In the light of this new result, we present Dune-DPG, a C++ library which allows to implement the test spaces introduced in Broersen et al. [2015]. The library is built upon the multi-purpose finite element package Dune (see Blatt et al. [2016]). In this paper, we present the current version 0.2 of Dune-DPG which has so far been tested only for elliptic and transport problems. An example of use via a simple transport equation is described. We conclude outlining future work and applications to more complex problems. Dune-DPG is licensed under the GPL 2 with runtime exception and a source code tarball is available together with this paper.
description: Archive of Numerical Software, Vol 5, No 1 (2017)
Bubbles and outflows: the novel JWST/NIRSpec view of the z=1.59 obscured quasar XID2028
Creators: name: Cresci, Giovanni
name: Tozzi, Giulia
name: Perna, Michele
name: Brusa, Marcella
name: Marconcini, Cosimo
name: Marconi, Alessandro
name: Carniani, Stefano
name: Brienza, Marisa
name: Giroletti, Marcello
name: Belfiore, Francesco
name: Ginolfi, Michele
name: Mannucci, Filippo
name: Ulivi, Lorenzo
name: Scholtz, Jan
name: Venturi, Giacomo
name: Arribas, Santiago
name: Übler, Hanna
name: D'Eugenio, Francesco
name: Mingozzi, Matilde
name: Balmaverde, Barbara
name: Capetti, Alessandro
name: Parlanti, Eleonora
name: Zana, Tommaso
Publisher: name: arXiv
Year: 2023
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, although direct observational evidence is still scarce and debated. Here we present Early Release Science JWST NIRSpec IFU observations of the z=1.59 prototypical obscured Active Galactic Nucleus (AGN) XID2028: This target represents a unique test case for studying quasar feedback at the peak epoch of AGN-galaxy co-evolution because extensive multi-wavelength coverage is available and a massive and extended outflow is detected in the ionised and molecular components. With the unprecedented sensitivity and spatial resolution of the JWST, the NIRSpec dataset reveals a wealth of structures in the ionised gas kinematics and morphology that were previously hidden in the seeing-limited ground-based data. In particular, we find evidence of an interaction between the interstellar medium of the galaxy and the quasar-driven outflow and radio jet that produces an expanding bubble from which the fast and extended wind detected in previous observations emerges. The new observations confirm the complex interplay between the AGN jet, wind and the interstellar medium of the host galaxy, highlighting the role of low-luminosity radio jets in AGN feedback. They also clearly show the new window that NIRSpec opens for detailed studies of feedback at high redshift.
description: 12 pages, 11 figures, accepted for publication in A&A
Germanische Begräbnisstätten am Niederrhein. Mit besonderer Berücksichtigung der Keramik
Creators: name: Rademacher, Carl
Publisher: name: Bonner Jahrbücher
Year: 2017

description: [nicht vorhanden / not available]
description: Bonner Jahrbücher, Bd. 105 (1900): Bonner Jahrbücher : Jahrbücher des Vereins von Altertumsfreunden im Rheinlande
title: The sense of architexture
Creators: name: Παλαιογιαννη Παντελιτσα
Publisher: name: Technical University of Crete
Year: 2015

description: Ο τίτλος της διπλωματικής πρόκειται για ένα λογοπαίγνιο με την αρχιτεκτονική και την υφή. Σε πρώτο στάδιο, πρόκειται για μια έρευνα, για τα στοιχεία εκείνα του χώρου που τον καθιστούν ασφαλή, λειτουργικό και εμπειρικά ενδιαφέρον για άτομα με μειωμένη ή ολική απώλεια όρασης και σε δεύτερο επίπεδο για την σχεδιαστική εφαρμογή των στοιχείων της έρευνας σε ένα σχολείο συνεκπαίδευσης με τυφλά και μη παιδιά.
Variational Principles on Geometric Rough Paths and the Lévy Area Correction
Creators: name: Diamantakis, Theo
name: Holm, Darryl D.
name: Pavliotis, Grigorios A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Chaotic Dynamics (nlin.CD)
subject: Dynamical Systems (math.DS)
subject: Probability (math.PR)
subject: Classical Physics (physics.class-ph)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: In this paper, we describe two effects of the Lévy area correction on the invariant measure of stochastic rigid body dynamics on geometric rough paths. From the viewpoint of dynamics, the Lévy area correction introduces an additional deterministic torque into the rigid body motion equation on geometric rough paths. When the dynamics is driven by coloured noise, and for rigid body dynamics with double-bracket dissipation, theoretical and numerical results show that this additional deterministic torque shifts the centre of the probability distribution function by shifting the Hamiltonian function in the exponent of the Gibbsian invariant measure.
description: 39 pages, 9 figures, 3rd version, comments welcome
Discovering strongly lensed quasar candidates with catalogue-based methods from DESI Legacy Surveys
Creators: name: He, Zizhao
name: Li, Nan
name: Cao, Xiaoyue
name: Li, Rui
name: Zou, Hu
name: Dye, Simon
Publisher: name: arXiv
Year: 2023
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: The Hubble tension, revealed by a $\sim 5σ$ discrepancy between measurements of the Hubble-Lemaitre constant from early- and local-Universe observations, is one of the most significant problems in modern cosmology. In order to better understand the origin of this mismatch, independent techniques to measure $H_0$, such as strong lensing time delays, are required. Notably, the sample size of such systems is key to minimising statistical uncertainties and cosmic variance, which can be improved by exploring the datasets of large-scale sky surveys like DESI (Dark Energy Spectroscopic Instrument). We identify possible strong lensing time-delay systems within DESI by selecting candidate multiply imaged lensed quasars from a catalogue of 24,440,816 candidate QSOs contained in the 9th data release of the DESI Legacy Imaging Surveys (DESI-LS). Using a friend-of-friends-like algorithm on spatial co-ordinates, our method generates an initial list of compact quasar groups. This list is subsequently filtered using a measure of the similarity of colours of a group's members and the likelihood that they are quasars. A visual inspection finally selects candidate strong lensing systems based on the spatial configuration of the group members. We identify 620 new candidate multiply imaged lensed quasars (101 Grade-A, 214 Grade-B, 305 Grade-C). This number excludes 53 known spectroscopically confirmed systems and existing candidate systems identified in other similar catalogues. When available, these new candidates will be further checked by combining the spectroscopic and photometric data from DESI. The catalogues and images of the candidates in this work are available online (https://github.com/EigenHermit/lensed_qso_cand_catalogue_He-22/).
description: Accepted by A&A. 14 pages, 11 figures. Comments are welcome
The generalized discrimination score for ensemble forecasts
Creators: name: Weigel, Andreas
name: Mason, Simon J.
Publisher: name: Columbia University
Year: 2011
Subjects: Long-range weather forecasting
Climatic changes--Forecasting
Statistical weather forecasting--Methodology

description: This article refers to the study of Mason and Weigel, where the generalized discrimination score D has been introduced. This score quantifies whether a set of observed outcomes can be correctly discriminated by the corresponding forecasts (i.e., it is a measure of the skill attribute of discrimination). Because of its generic definition, D can be adapted to essentially all relevant verification contexts, ranging from simple yes–no forecasts of binary outcomes to probabilistic forecasts of continuous variables. For most of these cases, Mason and Weigel have derived expressions for D, many of which have turned out to be equivalent to scores that are already known under different names. However, no guidance was provided on how to calculate D for ensemble forecasts. This gap is aggravated by the fact that there are currently very few measures of forecast quality that could be directly applied to ensemble forecasts without requiring that probabilities be derived from the ensemble members prior to verification. This study seeks to close this gap. A definition is proposed of how ensemble forecasts can be ranked; the ranks of the ensemble forecasts can then be used as a basis for attempting to discriminate between corresponding observations. Given this definition, formulations of D are derived that are directly applicable to ensemble forecasts.
Superconductivity in functionalized niobium-carbide MXenes
Creators: name: Sevik, Cem
name: Bekaert, Jonas
name: Milosevic, Milorad V.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We show the effect of Cl and S functionalization on the superconducting properties of layered (bulk) and monolayer niobium carbide (Nb$_2$C) MXene crystals, based on first-principles calculations combined with Eliashberg theory. For the bulk layered Nb$_2$CCl$_2$, the calculated superconducting transition temperature ($T_c$) is in very good agreement with the recently measured value of 6 K. We show that $T_c$ is enhanced to 10 K for monolayer Nb$_2$CCl$_2$, due to an increase in the density of states at the Fermi level, and the corresponding electron-phonon coupling. We further demonstrate a feasible gate-induced enhancement of $T_c$ up to 40 K for both bulk-layered and monolayer Nb$_2$CCl$_2$ crystals. For the S-functionalized cases our calculations reveal the importance of phonon softening in understanding their superconducting properties. Finally, we predict that Nb$_3$C$_2$S$_2$ in bulk-layered and monolayer form is potentially superconducting, with a $T_c$ around 30 K. Considering that Nb$_2$C is not superconducting in pristine form, our findings promote functionalization as a pathway towards robust superconductivity in MXenes.
Elastic demand dynamic network user equilibrium: Formulation, existence and computation
Creators: name: Han, Ke
name: Friesz, Terry L.
name: Szeto, W. Y.
name: Liu, Hongcheng
Publisher: name: arXiv
Year: 2013
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics
subject: 90B06, 90B10, 90B20, 90C90

description: This paper is concerned with dynamic user equilibrium with elastic travel demand (E-DUE) when the trip demand matrix is determined endogenously. We present an infinite-dimensional variational inequality (VI) formulation that is equivalent to the conditions defining a continuous-time E-DUE problem. An existence result for this VI is established by applying a fixed-point existence theorem (Browder, 1968) in an extended Hilbert space. We present three algorithms based on the aforementioned VI and its re-expression as a differential variational inequality (DVI): a projection method, a self-adaptive projection method, and a proximal point method. Rigorous convergence results are provided for these methods, which rely on increasingly relaxed notions of generalized monotonicity, namely mixed strongly-weakly monotonicity for the projection method; pseudomonotonicity for the self-adaptive projection method, and quasimonotonicity for the proximal point method. These three algorithms are tested and their solution quality, convergence, and computational efficiency compared. Our convergence results, which transcend the transportation applications studied here, apply to a broad family of infinite-dimensional VIs and DVIs, and are the weakest reported to date.
description: 32 pages, 6 figures, 2 tables
Local Optimization Often is Ill-conditioned in Genetic Programming for Symbolic Regression
Creators: name: Kronberger, Gabriel
Publisher: name: arXiv
Year: 2022
Subjects: subject: Neural and Evolutionary Computing (cs.NE)
subject: FOS: Computer and information sciences

description: Gradient-based local optimization has been shown to improve results of genetic programming (GP) for symbolic regression. Several state-of-the-art GP implementations use iterative nonlinear least squares (NLS) algorithms such as the Levenberg-Marquardt algorithm for local optimization. The effectiveness of NLS algorithms depends on appropriate scaling and conditioning of the optimization problem. This has so far been ignored in symbolic regression and GP literature. In this study we use a singular value decomposition of NLS Jacobian matrices to determine the numeric rank and the condition number. We perform experiments with a GP implementation and six different benchmark datasets. Our results show that rank-deficient and ill-conditioned Jacobian matrices occur frequently and for all datasets. The issue is less extreme when restricting GP tree size and when using many non-linear functions in the function set.
description: Submitted to International Symposium on Symbolic and Numeric Algorithms for Scientific Computing 2022 https://synasc.ro/
Stability of switched linear differential systems
Creators: name: Mayo-Maldonado, J. C.
name: Rapisarda, P.
name: Rocha, P.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics

description: We study the stability of switched systems where the dynamic modes are described by systems of higher-order linear differential equations not necessarily sharing the same state space. Concatenability of trajectories at the switching instants is specified by gluing conditions, i.e. algebraic conditions on the trajectories and their derivatives at the switching instant. We provide sufficient conditions for stability based on LMIs for systems with general gluing conditions. We also analyse the role of positive-realness in providing sufficient polynomial-algebraic conditions for stability of two-modes switched systems with special gluing conditions.
title: Χαρακτηρισμός μητρικών πετρωμάτων πετρελαίου με θερμικές μεθόδους ανάλυσης
title: Petroleum source rocks characterization using thermal methods of analysis
Creators: name: Γιανναρη Φανη
Publisher: name: Technical University of Crete
Year: 2017

description: Η έρευνα του πετρελαίου αποσκοπεί στην αναζήτηση νέων κοιτασμάτων. Πέρα από τις γεωλογικές και γεωφυσικές μελέτες και τις ερευνητικές γεωτρήσεις, για την εκμετάλλευση κοιτασμάτων είναι απαραίτητη η γεωχημική έρευνα. Η γεωχημική έρευνα παρέχει πληροφορίες σχετικά με την ωριμότητα, την πιθανότητα εύρεσης μητρικών πετρωμάτων και διαφοροποιεί τις περιοχές εξερεύνησης πετρελαίου με βάση την πιθανότητα παραγωγής πετρελαίου ή αερίου, κάτι που είναι οικονομικά επιθυμητό. Η ανάλυση και ο χαρακτηρισμός της χημικής σύστασης των δειγμάτων δεν είναι ποτέ πλήρης λόγω της πολυπλοκότητας της σύστασης τους γι΄ αυτό η επιλογή των μεθόδων που θα χρησιμοποιηθούν εξαρτάται αποκλειστικά από τον στόχο κάθε μελέτης.
Στην εργασία αυτή ασχοληθήκαμε με την συγκριτική αποτίμηση των αποτελεσμάτων θερμικών μεθόδων ανάλυσης μητρικών πετρωμάτων πετρελαίου. Οι θερμικές μέθοδοι ανάλυσης είναι μια ομάδα τεχνικών που μετρούν κάποια φυσική ή χημική ιδιότητα μιας ουσίας ή των προιόντων αντίδρασης της ως συνάρτηση της θερμοκρασίας όταν αυτή μεταβάλλεται κατά ένα προγραμματισμένο τρόπο. Πιο συγκεκριμένα με την μέθοδο της πυρόλυσης, μιμούμαστε στο εργαστήριο την διαδικασία δημιουργίας των υδρογονανθράκων που πραγματοποιείται στην φύση. Η ανάλυση Rock-Eval, η θερμοβαρυτομετρική ανάλυση και η στοιχειακή ανάλυση είναι κάποιες βασικές θερμικές μέθοδοι ανάλυσης.
Ζητούμενο ήταν να προσδιορισθεί αν οι διαφορετικές αναλυτικές τεχνικές δίνουν δεδομένα τα οποία οδηγούν σε ίδια συμπληρωματικά ή αντιφατικά αποτελέσματα όσον αφορά το χαρακτηρισμό των δειγμάτων με όρους γεωχημείας πετρελαίου. Ο άνθρακας πέρα από το οργανικό υπάρχει και στο ανόργανο κλάσμα των δειγμάτων ως συστατικό των ανθρακικών ορυκτών. Συνεπώς, πραγματοποιήθηκε και ορυκτολογική ανάλυση των δειγμάτων για την καλύτερη αξιολόγηση των αποτελεσμάτων. Διαλέχθηκαν 11 δείγματα πλούσια και φτωχά σε οργανικό υλικό και έπειτα από την επεξεργασία τους με διάφορες εργαστηριακές μεθόδους δημιουργήθηκαν συμπληρωματικά δείγματα, με αποτέλεσμα την ανάλυση συνολικά 33 δειγμάτων.
Τα αποτελέσματα των θερμικών μεθόδων ανάλυσης παρουσίαζουν κάποια διαφορά στις τιμές μεταξύ των διαφορετικών συστημάτων ανάλυσης, όμως με όλους τους δείκτες καταλήγουν στον ίδιο γεωχημικό χαρακτηρισμό των δειγμάτων. Παράλληλα, αποδείχθηκε πως η χρήση της ορυκτολογικής ανάλυσης  XRD βοηθάει στην κατανόηση αποτελεσμάτων άλλων εργαστηριακών αναλύσεων παρέχοντας λεπτομερή περιγραφή των δειγμάτων. Τέλος, παρατηρήθηκε πως μέσω της θερμοβαρυτομετρικής ανάλυσης μπορεί να υπολογισθεί ποιοτικά το περιεχόμενο οργανικό υλικό των δειγμάτων. Δεν είναι αξιόπιστος ο ποσοτικός προσδιορισμός του οργανικού υλικού μέσω αυτής της μεθόδου διότι δεν γνωρίζουμε τις μεταβολές των ανόργανων συστατικών των δειγμάτων. Επιπλέον, μέσω τις μεθόδου αυτής, μπορούν να εντοπιστούν δείγματα ανόμοια ορυκτολογικά μεταξύ τους.
title: Ανάπτυξη και εφαρμογή αναλυτικών τεχνικών χαρακτηρισμού του κλάσματος των ρητινών (NSO) του πετρελαίου
Creators: name: Μητσιοπουλου Ολγα
Publisher: name: Technical University of Crete
Year: 2017

description: Στη χημική ανάλυση του πετρελαίου έχει επικρατήσει τα δείγματα να διαχωρίζονται σε κλάσματα αρωματικών, κορεσμένων, ασφαλτενίων και ρητινών. Τα κλάσματα των κορεσμένων και αρωματικών είναι εκείνα που συνήθως αναλύονται περαιτέρω λόγω της απλούστερης σύστασής τους. Το κλάσμα των ρητινών αποτελείται από πολικά μόρια, τα οποία συχνά περιέχουν ετεροάτομα όπως άζωτο, οξυγόνο και θείο. Επιπλέον, οι ρητίνες έχουν μεγαλύτερη  αναλογία H/C από τα ασφαλτένια, είναι δομικά παρόμοιες με τα ασφαλτένια, αλλά έχουν μικρότερο μοριακό βάρος. Το κλάσμα των ρητινών κατέχει σημαντικό ρόλο τόσο όσο αφορά την σταθερότητα του πετρελαίου όσο και την δημιουργία γαλακτωμάτων νερού στο πετρέλαιο, λόγω προβλημάτων που αντιμετωπίζονται κατά την παραγωγή και την επεξεργασία του πετρελαίου.
Στην παρούσα διπλωματική εργασία μελετώνται δείγματα ρητινών, τα οποία έχουν διαχωριστεί με διαφορετικές μεθόδους και προέρχονται από διαφορετικά πετρελαϊκά δείγματα. Για την μελέτη των δειγμάτων χρησιμοποιήθηκε η μέθοδος υπέρυθρης φασματοσκοπίας με μετασχηματισμό Φουριέ (FTIR). Η υπέρυθρη φασματοσκοπία παρέχει πληροφορίες για την χημική σύσταση των οργανικών υλικών καθώς και για την δομή των χαρακτηριστικών ομάδων που απαντώνται στα δείγματα που αναλύονται. Οι δύο τεχνικές που αναπτύχθηκαν στα πλαίσια της διπλωματικής εργασίας για τον σκοπό αυτό είναι η τεχνική Εσωτερικής Ανάκλασης (ATR) και η τεχνική ανάλυσης δισκίων βρωμιούχου καλίου (KBr Pellets). Από τις αναλύσεις, έγινε εντοπισμός των χαρακτηριστικών ομάδων στα δείγματα ρητινών καθώς και σύγκριση των εμβαδών για κάθε περιοχή απορρόφησης στα φάσματα των  δειγμάτων μεταξύ τους. Η σύγκριση πραγματοποιήθηκε μέσω δεικτών και εμβαδών που προέκυψαν από το λογισμικό Spectrum, για όλο το φάσμα, και από έναν αλγόριθμο αποσυνέλιξης (Deconvolution), για τις περιοχές του φάσματος που απαντώνται οι ομάδες των αρωματικών, των μεθυλίων και των μεθυλενίων. Τα αναλυτικά αποτελέσματα έδειξαν ότι η τεχνική της φασματοσκοπίας FTIR μπορεί – υπό προϋποθέσεις - να εντοπίσει διαφορές ανάμεσα σε ίδιας φύσης δείγματα πετρελαίου, συμβάλλοντας με τον τρόπο αυτό στην συνολική κατανόηση της σύστασης των σύνθετων πετρελαϊκών μιγμάτων.
Reconstruction of three-dimensional turbulent flow structures using surface measurements for free-surface flows based on a convolutional neural network
Creators: name: Xuan, Anqing
name: Shen, Lian
Publisher: name: arXiv
Year: 2023
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: A model based on a convolutional neural network (CNN) is designed to reconstruct the three-dimensional turbulent flows beneath a free surface using surface measurements, including the surface elevation and surface velocity. Trained on datasets obtained from the direct numerical simulation (DNS) of turbulent open-channel flows with a deformable free surface, the proposed model can accurately reconstruct the near-surface flow field and capture the characteristic large-scale flow structures away from the surface. The reconstruction performance of the model, measured by metrics such as the normalised mean squared reconstruction errors and scale-specific errors, is considerably better than that of the traditional linear stochastic estimation (LSE) method. We further analyse the saliency maps of the CNN model and the kernels of the LSE model and obtain insights into how the two models utilise surface features to reconstruct subsurface flows. The importance of different surface variables is analysed based on the saliency map of the CNN, which reveals knowledge about the surface-subsurface relations. The CNN is also shown to have a good generalization capability with respect to the Froude number if a model trained for a flow with a high Froude number is applied to predict flows with lower Froude numbers. The results presented in this work indicate that the CNN is effective regarding the detection of subsurface flow structures and by interpreting the surface-subsurface relations underlying the reconstruction model, the CNN can be a promising tool for assisting with the physical understanding of free-surface turbulence.
Eigenvalues of a one-dimensional Dirac operator pencil
Creators: name: Elton, Daniel M.
name: Levitin, Michael
name: Polterovich, Iosif
Publisher: name: arXiv
Year: 2013
Subjects: subject: Spectral Theory (math.SP)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 34L40, 35P20

description: We study the spectrum of a one-dimensional Dirac operator pencil, with a coupling constant in front of the potential considered as the spectral parameter. Motivated by recent investigations of graphene waveguides, we focus on the values of the coupling constant for which the kernel of the Dirac operator contains a square integrable function. In physics literature such a function is called a confined zero mode. Several results on the asymptotic distribution of coupling constants giving rise to zero modes are obtained. In particular, we show that this distribution depends in a subtle way on the sign variation and the presence of gaps in the potential. Surprisingly, it also depends on the arithmetic properties of certain quantities determined by the potential. We further observe that variable sign potentials may produce complex eigenvalues of the operator pencil. Some examples and numerical calculations illustrating these phenomena are presented.
description: 50 pages, 8 figures; substantially revised version, several results added, bibliography extended
The 1997-98 summer rainfall season in southern Africa. Part I: Observations
Creators: name: Lyon, Bradfield
name: Mason, Simon J.
Publisher: name: Columbia University
Year: 2007
Subjects: Rain and rainfall--Observations
Teleconnections (Climatology)
Atmospheric circulation

description: Following the onset of the strong El Niño of 1997–98 historical rainfall teleconnection patterns and dynamical model predictions both suggested an enhanced likelihood of drought for southern Africa, but widespread dry conditions failed to materialize. Results from a diagnostic study of NCEP–NCAR reanalysis data are reported here demonstrating how the large- and regional-scale atmospheric circulations during the 1997–98 El Niño differed from previous events. Emphasis is placed on the January–March 1998 season and comparisons with the strong 1982–83 El Niño, although composites of eight events occurring between 1950 and 2000 are also considered. In a companion paper, simulation runs from three atmospheric general circulation models (AGCMs), and forecasts from three fully coupled models are employed to investigate the extent to which the anomalous atmospheric circulation patterns during the 1997–98 El Niño may have been anticipated. Observational results indicate that the 1997–98 El Niño displayed significant differences from both the 1982–83 episode and the composite event. An unusually strong Angola low, exceptionally high sea surface temperatures (SSTs) in the western Indian and eastern tropical South Atlantic Oceans, and an enhanced northerly moisture flux from the continental interior and the western tropical Indian Ocean all appear to have contributed to more seasonal rainfall in 1997–98 over much of the southern Africa subcontinent than in past El Niño events.
Badly approximable points on manifolds
Creators: name: Beresnevich, Victor
Publisher: name: arXiv
Year: 2013
Subjects: subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: 11J13, 11J83

description: This paper is motivated by two problems in the theory of Diophantine approximation, namely, Davenport's problem regarding badly approximable points on submanifolds of a Euclidean space and Schmidt's problem regarding the intersections of the sets of weighted badly approximable points. The problems have been recently settled in dimension two but remain open in higher dimensions. In this paper we develop new techniques that allow us to tackle them in full generality. The techniques rest on lattice points counting and a powerful quantitative result of Bernik, Kleinbock and Margulis. The main theorem of this paper implies that any finite intersection of the sets of weighted badly approximable points on any analytic nondegenerate submanifold of $R^n$ has full dimension. One of the consequences of this result is the existence of transcendental real numbers badly approximable by algebraic numbers of any degree.
Utz Böhner, Die Schicht E3 der Sesselfelsgrotte und die Funde aus dem Abri I am Schulerloch. Späte Micoquien-Inventare und ihre Stellung zum Moustérien
Creators: name: Bolus, Michael
Publisher: name: Bonner Jahrbücher
Year: 2017

description: Rezension zu: Utz Böhner, Die Schicht E3 der Sesselfelsgrotte und die Funde aus dem Abri I am Schulerloch. Späte Micoquien-Inventare und ihre Stellung zum Moustérien. Sesselfelsgrotte, Band IV. Verlag Franz Steiner, Stuttgart 2008. 307 Seiten mit 133 Abbildungen und 31 Tabellen, 1 Farbtafel und 51 Schwarzweißtafeln; dazu 4 Faltbeilagen sowie 1 CD-Beilage mit Katalog und 139 Abbildungen
description: Bonner Jahrbücher, Bd. 209.2009(2011): Bonner Jahrbücher
20 ps Time Resolution with a Fully-Efficient Monolithic Silicon Pixel Detector without Internal Gain Layer
Creators: name: Zambito, S.
name: Milanesio, M.
name: Moretti, T.
name: Paolozzi, L.
name: Munker, M.
name: Cardella, R.
name: Kugathasan, T.
name: Martinelli, F.
name: Picardi, A.
name: Elviretti, M.
name: Rücker, H.
name: Trusch, A.
name: Cadoux, F.
name: Cardarelli, R.
name: Débieux, S.
name: Favre, Y.
name: Fenoglio, C. A.
name: Ferrere, D.
name: Gonzalez-Sevilla, S.
name: Iodice, L.
name: Kotitsa, R.
name: Magliocca, C.
name: Nessi, M.
name: Pizarro-Medina, A.
name: Iglesias, J. Sabater
name: Saidi, J.
name: Pinto, M. Vicente Barreto
name: Iacobucci, G.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: A second monolithic silicon pixel prototype was produced for the MONOLITH project. The ASIC contains a matrix of hexagonal pixels with 100 μm pitch, readout by a low-noise and very fast SiGe HBT frontend electronics. Wafers with 50 μm thick epilayer of 350 Ωcm resistivity were used to produce a fully depleted sensor. Laboratory and testbeam measurements of the analog channels present in the pixel matrix show that the sensor has a 130 V wide bias-voltage operation plateau at which the efficiency is 99.8%. Although this prototype does not include an internal gain layer, the design optimised for timing of the sensor and the front-end electronics provides a time resolutions of 20 ps.
description: 11 pages, 11 figures
Jennifer Morscheiser-Niebergall, Die Anfänge Triers im Kontext augusteischer Urbanisierungspolitik nördlich der Alpen
Creators: name: Grünewald, Martin
Publisher: name: Bonner Jahrbücher
Year: 2017

description: Rezension zu: Jennifer Morscheiser-Niebergall, Die Anfänge Triers im Kontext augusteischer Urbanisierungspolitik nördlich der Alpen. Philippika. Marburger altertumskundliche Abhandlungen, Band 30. Verlag Harrassowitz, Wiesbaden 2009. 258 Seiten mit 30 Abbildungen, 47 Tafeln
description: Bonner Jahrbücher, Bd. 209.2009(2011): Bonner Jahrbücher
NMR Relaxation by Redfield's equation in a spin system $I=7/2$
Creators: name: Consuelo-Leal, A.
name: Araujo-Ferreira, A. G.
name: Lucas-Oliveira, E.
name: Bonagamba, T. J.
name: Auccaise, R.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Redfield's master equation is solved analytically for a nuclear system with spin $I=7/2$. The solutions of each density matrix element are computed using the irreducible tensor operator basis. The $^{133}$Cs nuclei of the caesium-pentadecafluorooctanoate molecule in a lyotropic liquid crystal sample at the nematic phase and at room temperature was used as an experimental setup. Experimental longitudinal and transverse magnetization dynamics of the $^{133}$Cs nuclei signal were monitored and by numerical procedures the theoretical approach generates valuable mathematical expressions with the highest accuracy. The methodology introduced could be extended without major difficulties to other nuclei species.
Topological effective field theories for Dirac fermions from index theorem
Creators: name: Palumbo, Giandomenico
name: Catenacci, Roberto
name: Marzuoli, Annalisa
Publisher: name: arXiv
Year: 2013
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Dirac fermions have a central role in high energy physics but it is well known that they emerge also as quasiparticles in several condensed matter systems supporting topological order. We present a general method for deriving the topological effective actions of (3+1) massless Dirac fermions living on general backgrounds and coupled with vector and axial-vector gauge fields. The first step of our strategy is standard (in the Hermitian case) and consists in connecting the determinants of Dirac operators with the corresponding analytical indices through the zeta-function regularization. Then, we introduce a suitable splitting of the heat kernel that naturally selects the purely topological part of the determinant (i.e. the topological effective action). This topological effective action is expressed in terms of gauge fields using the Atiyah-Singer index theorem which computes the analytical index in topological terms. The main new result of this paper is to provide a consistent extension of this method to the non Hermitian case where a well-defined determinant does not exist. Quantum systems supporting relativistic fermions can thus be topologically classified on the basis of their response to the presence of (external or emergent) gauge fields through the corresponding topological effective field theories.
description: 7 pages, published version
Synchrotron radiation by slowly rotating fermions
Creators: name: Buzzegoli, Matteo
name: Kroth, Jonathan D.
name: Tuchin, Kirill
name: Vijayakumar, Nandagopal
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study the synchrotron radiation emitted by a charged fermion, rotating as a part of a larger system, in a constant magnetic field $B$ parallel to the axis of rotation. The rotation is classical and independent of the magnetic field. The angular velocity of rotation $Ω$ is assumed to be much smaller than the inverse magnetic length $\sqrt{qB}$ which allows us to ignore the boundary effects at $r=1/Ω$. We refer to such rotation as slow, even though in absolute value it may be an extremely rapid rotation. Using the exact solution of the Dirac equation we derived the intensity of electromagnetic radiation, its spectrum and chirality. We demonstrate by explicit numerical calculation that the effect of rotation on the radiation intensity increases with the particle energy. Depending on the relative orientation of the vectors $\bfΩ$ and $\bf B$ and the sign of the electric charge, the rotation can either strongly enhance or strongly suppress the radiation.
description: 5 pages, 3 figures. V2: minor text improvements, Figs 1,2 updated, new Fig 3. V3: reference line in Fig.2 corrected; v4: the sign of qB in figure captions and elsewhere corrected
Klaus Scherberich, Koinè symmachía. Untersuchungen zum Hellenenbund Antigonos’ III. Doson und Philipps V. (224–197 v. Chr.)
Creators: name: Kleu, Michael
Publisher: name: Bonner Jahrbücher
Year: 2017

description: Rezension zu: Klaus Scherberich, Koinè symmachía. Untersuchungen zum Hellenenbund Antigonos’ III. Doson und Philipps V. (224–197 v. Chr.). Historia Einzelschriften, Band 184. Verlag Franz Steiner, Stuttgart 2009. 254 Seiten
description: Bonner Jahrbücher, Bd. 209.2009(2011): Bonner Jahrbücher
title: Υδρογεωλογική μελέτη των καρστικών πηγών των περιοχών Κεφαλόβρυσσα και Κόκκινη Ρίζα στους ποταμούς Αμαρίου Ρεθύμνης
Creators: name: Βαβαδάκης Διονύσιος
Publisher: name: Technical University of Crete
Year: 1994

description: Μη διαθέσιμο
A Machine Learning approach for correcting radial velocities using physical observables
Creators: name: Perger, M.
name: Anglada-Escudé, G.
name: Baroch, D.
name: Lafarga, M.
name: Ribas, I.
name: Morales, J. C.
name: Herrero, E.
name: Amado, P. J.
name: Barnes, J. R.
name: Caballero, J. A.
name: Jeffers, S. V.
name: Quirrenbach, A.
name: Reiners, A.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Machine Learning (cs.LG)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Precision radial velocity (RV) measurements continue to be a key tool to detect and characterise extrasolar planets. While instrumental precision keeps improving, stellar activity remains a barrier to obtain reliable measurements below 1-2 m/s accuracy. Using simulations and real data, we investigate the capabilities of a Deep Neural Network approach to produce activity free Doppler measurements of stars. As case studies we use observations of two known stars (Eps Eridani and AUMicroscopii), both with clear signals of activity induced RV variability. Synthetic data using the starsim code are generated for the observables (inputs) and the resulting RV signal (labels), and used to train a Deep Neural Network algorithm. We identify an architecture consisting of convolutional and fully connected layers that is adequate to the task. The indices investigated are mean line-profile parameters (width, bisector, contrast) and multi-band photometry. We demonstrate that the RV-independent approach can drastically reduce spurious Doppler variability from known physical effects such as spots, rotation and convective blueshift. We identify the combinations of activity indices with most predictive power. When applied to real observations, we observe a good match of the correction with the observed variability, but we also find that the noise reduction is not as good as in the simulations, probably due to the lack of detail in the simulated physics. We demonstrate that a model-driven machine learning approach is sufficient to clean Doppler signals from activity induced variability for well known physical effects. There are dozens of known activity related observables whose inversion power remains unexplored indicating that the use of additional indicators, more complete models, and more observations with optimised sampling strategies can lead to significant improvements in our detrending capabilities.
Accessing and using climate data and information in fragile, data-poor states
Creators: name: Mason, Simon J.
name: Kruckiewicz, Andrew
name: Ceccato, Pietro
name: Crawford, Alec
Publisher: name: Columbia University
Year: 2015
Subjects: Climatic changes
Climatic changes--Data processing
Climatic changes--Decision making
Climatic changes--Risk assessment
Meteorology
Peace-building

description: This report provides peacebuilding practitioners with guidance for accessing and using climate data and information in fragile contexts. It describes some of the challenges to generating, accessing and understanding climate information in contexts of state fragility. It introduces the types of climate information relevant to national and international peacebuilding practitioners operating in fragile contexts and provides a review of relevant and accessible climate data. The report addresses how climate information can be effectively used in a peacebuilding context, and highlights some of the immediate priorities and sequencing needs for fragile states attempting to rebuild their national capacities to generate climate information.
title: Μελέτη του εντατικού πεδίου γύρω από κυλινδρική εκσκαφή σε πέτρωμα με τη βοήθεια της μεθόδου των συνοριακών στοιχείων
Creators: name: Ταμπάκης Βασίλειος
Publisher: name: Technical University of Crete
Year: 1994

description: Μη διαθέσιμο
A sluggish random walk with subdiffusive spread
Creators: name: Zodage, Aniket
name: Allen, Rosalind J.
name: Evans, Martin R.
name: Majumdar, Satya N.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We study a one-dimensional sluggish random walk with space-dependent transition probabilities between nearest-neighbour lattice sites. Motivated by trap models of slow dynamics, we consider a model in which the trap depth increases logarithmically with distance from the origin. This leads to a random walk which has symmetric transition probabilities that decrease with distance $|k|$ from the origin as $1/|k|$ for large $|k|$. We show that the typical position after time $t$ scales as $t^{1/3}$ with a nontrivial scaling function for the position distribution which has a trough (a cusp singularity) at the origin. Therefore an effective central bias away from the origin emerges even though the transition probabilities are symmetric. We also compute the survival probability of the walker in the presence of a sink at the origin and show that it decays as $t^{-1/3}$ at late times. Furthermore we compute the distribution of the maximum position, $M(t)$, to the right of the origin up to time $t$, and show that it has a nontrivial scaling function. Finally we provide a generalisation of this model where the transition probabilities decay as $1/|k|^α$ with $α>0$.
description: 17 pages, revised version accepted for J. Stat. Mech
title: Αξιολόγηση αργίλων της περιοχής Κολυμβαρίου με σκοπό τη χρήση τουςστην κεραμική βιομηχανία
Creators: name: Βασιλάτος Κωνσταντίνος
Publisher: name: Technical University of Crete
Year: 1993

description: Μη διαθέσιμο
Reduced Gröbner Bases and Macaulay-Buchberger Basis Theorem over Noetherian Rings
Creators: name: Francis, Maria
name: Dukkipati, Ambedkar
Publisher: name: arXiv
Year: 2013
Subjects: subject: Symbolic Computation (cs.SC)
subject: Commutative Algebra (math.AC)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: In this paper, we extend the characterization of $\mathbb{Z}[x]/\ < f \ >$, where $f \in \mathbb{Z}[x]$ to be a free $\mathbb{Z}$-module to multivariate polynomial rings over any commutative Noetherian ring, $A$. The characterization allows us to extend the Gröbner basis method of computing a $\Bbbk$-vector space basis of residue class polynomial rings over a field $\Bbbk$ (Macaulay-Buchberger Basis Theorem) to rings, i.e. $A[x_1,\ldots,x_n]/\mathfrak{a}$, where $\mathfrak{a} \subseteq A[x_1,\ldots,x_n]$ is an ideal. We give some insights into the characterization for two special cases, when $A = \mathbb{Z}$ and $A = \Bbbk[θ_1,\ldots,θ_m]$. As an application of this characterization, we show that the concept of border bases can be extended to rings when the corresponding residue class ring is a finitely generated, free $A$-module.
title: Παραμετρική ανάλυση της ευστάθειας εδαφικών πρανων με τη συνήθη μέθοδο των λωρίδων
Creators: name: Πατηνιώτη Ελισάβετ
Publisher: name: Technical University of Crete
Year: 1994

description: Μη διαθέσιμο
Revealing Topology in Metals using Experimental Protocols Inspired by $K$-Theory
Creators: name: Cheng, Wenting
name: Cerjan, Alexander
name: Chen, Ssu-Ying
name: Prodan, Emil
name: Loring, Terry A.
name: Prodan, Camelia
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: Topological metals are special conducting materials with gapless band structures and nontrivial edge-localized resonances, whose discovery has proved elusive because the traditional topological classification methods do not apply in this context. Inspired by recent theoretical developments that leveraged techniques from the field of $C^*$-algebras to identify topological metals \cite{cerjan_local_2021}, here, we directly observe topological phenomena in gapless acoustic crystals and provide a general experimental technique to demonstrate their topology. Specifically, we not only observe robust boundary-localized states in a topological acoustic metal, but also re-interpret a composite operator, mathematically derived from the K-theory of the problem, as a new Hamiltonian, whose physical implementation allows us to directly observe a topological spectral flow and measure the topological invariants. Our observations and experimental protocols may offer insights for discovering topological behavior across a wide array of artificial and natural materials that lack bulk band gaps.
Sven Kalmring, Der Hafen von Haithabu
Creators: name: Edberg, Rune
Publisher: name: Bonner Jahrbücher
Year: 2017

description: Rezension zu: Sven Kalmring, Der Hafen von Haithabu. Die Ausgrabungen in Haithabu. Volume XIV. Publisher Wachholz, Neumünster 2010. 668 pages, with numerous photos, drawings, tables, plans, and maps
description: Bonner Jahrbücher, Bd. 209.2009(2011): Bonner Jahrbücher
title: Μοντελοποίηση συστήματος αφαλάτωσης θαλασσινού νερού με χρήση ηλιακού συλλέκτη
Creators: name: Μανουράς Γεώργιος
Publisher: name: Technical University of Crete
Year: 2010

description: Μη διαθέσιμο