cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Propulsive performance of oscillating plates with time-periodic flexibility
Creators: name: Yudin, David
name: Floryan, Daniel
name: Van Buren, Tyler
Publisher: name: arXiv
Year: 2022
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: FOS: Physical sciences

description: We use small-amplitude inviscid theory to study the swimming performance of a flexible flapping plate with time-varying flexibility. The stiffness of the plate oscillates at twice the frequency of the kinematics in order to maintain a symmetric motion. Plates with constant and time-periodic stiffness are compared over a range of mean plate stiffness, oscillating stiffness amplitude, and oscillating stiffness phase for isolated heaving, isolated pitching, and combined leading edge kinematics. We find that there is a profound impact of oscillating stiffness on the thrust, with a lesser impact on propulsive efficiency. Thrust improvements of up to 35% relative to a constant-stiffness plate are observed. For large enough frequencies and amplitudes of the stiffness oscillation, instabilities emerge. The unstable regions may confer enhanced propulsive performance; this hypothesis must be verified via experiments or nonlinear simulations.
description: 31 pages, 11 figures
Neural networks: solving the chemistry of the interstellar medium
Creators: name: Branca, Lorenzo
name: Pallottini, Andrea
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Machine Learning (cs.LG)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Non-equilibrium chemistry is a key process in the study of the InterStellar Medium (ISM), in particular the formation of molecular clouds and thus stars. However, computationally it is among the most difficult tasks to include in astrophysical simulations, because of the typically high (>40) number of reactions, the short evolutionary timescales (about $10^4$ times less than the ISM dynamical time) and the characteristic non-linearity and stiffness of the associated Ordinary Differential Equations system (ODEs). In this proof of concept work, we show that Physics Informed Neural Networks (PINN) are a viable alternative to traditional ODE time integrators for stiff thermo-chemical systems, i.e. up to molecular hydrogen formation (9 species and 46 reactions). Testing different chemical networks in a wide range of densities ($-2< \log n/{\rm cm}^{-3}< 3$) and temperatures ($1 < \log T/{\rm K}< 5$), we find that a basic architecture can give a comfortable convergence only for simplified chemical systems: to properly capture the sudden chemical and thermal variations a Deep Galerkin Method is needed. Once trained ($\sim 10^3$ GPUhr), the PINN well reproduces the strong non-linear nature of the solutions (errors $\lesssim 10\%$) and can give speed-ups up to a factor of $\sim 200$ with respect to traditional ODE solvers. Further, the latter have completion times that vary by about $\sim 30\%$ for different initial $n$ and $T$, while the PINN method gives negligible variations. Both the speed-up and the potential improvement in load balancing imply that PINN-powered simulations are a very palatable way to solve complex chemical calculation in astrophysical and cosmological problems.
description: 16 pages, 12 figures, accepted for publication on MNRAS
Real-space construction of crystalline topological superconductors and insulators in 2D interacting fermionic systems
Creators: name: Zhang, Jian-Hao
name: Yang, Shuo
name: Qi, Yang
name: Gu, Zheng-Cheng
Publisher: name: arXiv
Year: 2020
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: The construction and classification of crystalline symmetry protected topological (SPT) phases in interacting bosonic and fermionic systems have been intensively studied in the past few years. Crystalline SPT phases are not only of conceptual importance, but also provide great opportunities towards experimental realization since space group symmetries naturally exist for any realistic material. In this paper, we systematically classify the crystalline topological superconductors (TSC) and topological insulators (TI) in 2D interacting fermionic systems by using an explicit real-space construction. In particular, we discover an intriguing fermionic crystalline topological superconductor that can only be realized in interacting fermionic systems (i.e., not in free-fermion or bosonic SPT systems). Moreover, we also verify the recently conjectured crystalline equivalence principle for generic 2D interacting fermionic systems.
description: 39+37 pages, 10+13 figures, 3+1 tables, all comments and suggestions are very welcome
title: Development of a simple correlation utilizing field data and the standing-katz gas Z-factor method for predicting the oil formation volume factor at undersaturated conditions
Creators: name: Τυρακης Νικολαος
Publisher: name: Technical University of Crete
Year: 2016

description: The Oil Formation Volume Factor, Bo, is used in almost all the Reservoir and Production Engineering calculations for converting subsurface fluid volumes to surface ones.  The knowledge of its value is a prerequisite for evaluating reliably initial hydrocarbon volumes in place, predicting hydrocarbon recovery and future reservoir performance and identifying the drive mechanism.
The values of the Oil Formation Volume Factor are measured during the PVT study and they become usually available several months after the well has been tested. In the meanwhile, crucial reservoir engineering decisions have to be made by the Operator, including the estimation of the reserves and the future production plans for which values of Bo are provided by widely used correlations which only require data that are measured in the field during the Well Test (solution GOR, API, Sg, Tres). Given that these correlations are equations fitted against experimental data of oils from certain origin and composition, their accuracy is doubtful.
The present master thesis deals with the development of a simple correlation, called liquid Z-factor based method, using fundamental relationships, for the determination of the Bo at undersaturated conditions. The correlation expresses the Bo as a function of data that are measured in the field during the Well Test and the reservoir density at reservoir pressure. The DAK representation of the Standing-Katz Z-factor chart was used for the computation of the crude oil density, and an Excel spreadsheet was developed to incorporate all the above calculations.
A literature review was conducted to qualify 5 correlations currently used by the oil industry. These correlations were also included in the Excel spreadsheet.
The field data of reservoir oils from all over the world was used for testing the performance of the developed correlation against the performance of the other well-known correlations.
The results are very encouraging, since, the proposed method proved not only comparable but even more accurate and applicable in a wider range of Bo than the other presented correlations.
Partition functions on squashed seven-spheres and holography
Creators: name: Zhang, Xuao
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: Our paper presents two main results. First, we study the renormalized free energies of Euclidean Einstein gravity in asymptotically AdS$_8$ and various field theories on a squashed seven sphere. In the gravity theory, we demonstrate the absence of the Hawking-Page transition, while in the field theory, we focus on the O($N$) vector model and the massless free fermion model. The conformal symmetry governs the universal behaviors of the free energies for small and large squashings, which we confirm numerically and analytically. Second, we evaluate the second-order derivative of CFT free energy with respect to the squashing parameter, finding universal results that hold for generic conformal field theories. We examine two different squashings, one with an SU(2) bundle, which is the primary focus of our paper, and another with a U(1) bundle, where our results align with the conjectured formula from the gravity side in the literature.
description: 46 pages
Impact of the nonthermal electron radiation effects on the horizon scale image structure of Sagittarius A*
Creators: name: Zhao, Shan-Shan
name: Huang, Lei
name: Lu, Rusen
name: Shen, Zhiqiang
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The Event Horizon Telescope (EHT), with $\sim$20 $μ$as high angular resolution, recently resolved the millimeter image of the suppermassive black hole in the Galaxy, Sagittarius A*. This opens a new window to study the plasma on horizon scales. The accreting disk probably contains a small fraction of nonthermal electrons and their emissions should contribute to the observed image. We study if such contributions are sufficient to cause structural differences detectable by current and future observational capabilities. We introduce nonthermal electrons in a semi-analytical accretion disk, which considers viscosity-leading heating processes, and adopt a continued hybrid electron energy distribution of thermal distribution and power-law tail. We generate the black hole images and extract the structural features as crescent parameters. We find the existence of nonthermal electron radiation makes the crescent much brighter, slightly larger, moderately thicker, and much more symmetric. When the nonthermal connecting Lorentz factor $γ_c=65$, which is equivalent to the nonthermal electrons accounting for $\sim1.5$% of the totals, nonthermal effects cause $\sim2$% size difference at 230 GHz. Comparing with the structural changes caused by other physical factors, including inclination between the system and the observer, black hole spin, and interstellar medium scattering effects, we find that although nonthermal electron radiation takes the most unimportant role at 230 GHz, it becomes more significant at 345 GHz.
Avenues for Analytic exploration in Axisymmetric Spacetimes. Foundations and the Triad Formalism
Creators: name: Brink, Jeandrew
name: Zimmerman, Aaron
name: Hinderer, Tanja
Publisher: name: arXiv
Year: 2013
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: Axially symmetric spacetimes are the only models for isolated systems with continuous symmetries that also include dynamics. For such systems, we review the reduction of the vacuum Einstein field equations to their most concise form by dimensionally reducing to the three-dimensional space of orbits of the Killing vector, followed by a conformal rescaling. The resulting field equations can be written as a problem in three-dimensional gravity with a complex scalar field as source. This scalar field, the Ernst potential is constructed from the norm and twist of the spacelike Killing field. In the case where the axial Killing vector is twist-free, we discuss the properties of the axis and simplify the field equations using a triad formalism. We study two physically motivated triad choices that further reduce the complexity of the equations and exhibit their hierarchical structure. The first choice is adapted to a harmonic coordinate that asymptotes to a cylindrical radius and leads to a simplification of the three-dimensional Ricci tensor and the boundary conditions on the axis. We illustrate its properties by explicitly solving the field equations in the case of static axisymmetric spacetimes. The other choice of triad is based on geodesic null coordinates adapted to null infinity as in the Bondi formalism. We then explore the solution space of the twist-free axisymmetric vacuum field equations, identifying the known (unphysical) solutions together with the assumptions made in each case. This singles out the necessary conditions for obtaining physical solutions to the equations.
description: 40 pages, 3 figures, reflects published version
Thinking About Emerging Adults and Violent Crime
Creators: name: Bersani, Bianca E.
name: Laub, John H.
name: Western, Bruce P.
Publisher: name: Columbia University
Year: 2019
Subjects: subject: Criminal justice, Administration of
subject: Violent crimes
subject: Violent offenders
subject: Young adults--Legal status, laws, etc.
subject: Youth--Legal status, laws, etc.
subject: Sociology
subject: FOS: Sociology

description: In response to fears of an unrelenting crime wave, dramatic changes to sentencing policy, particularly for violent offenders, occurred in the 1980s and 1990s. Today, more than half of state prisoners are serving time for a violent offense. Increases in the severity of criminal justice sanctions (e.g., decision to prosecute, reclassification of charges, use of incarceration, and lengthening prison sentences) for those convicted of violent offenses has fueled mass incarceration. Despite major reductions of crime, including violence, over the past two decades, an intense focus on violent offenders as distinct and different endures. This brief summarizes research on violent criminal behavior over the life course. We focus special attention on emerging adults because they have the highest rates of both violent offending and violent victimization. First, drawing on a large body of longitudinal research on crime, we present the known ‘facts’ about violence. Note that this research literature uses criminal justice records of those officially sanctioned as well as self-reports of offending and victimization. Second, we discuss the experiences and consequences of living with violence. Third, we conclude with policy recommendations for responding to violent crime.
Approximating inverse cumulative distribution functions to produce approximate random variables
Creators: name: Sheridan-Methven, Oliver
name: Giles, Michael
Publisher: name: arXiv
Year: 2020
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics
subject: 65C10, 41A10, 65D15, 65C05, 62E17, 65Y20, 60H35, 65C30

description: For random variables produced through the inverse transform method, approximate random variables are introduced, which are produced by approximations to a distribution's inverse cumulative distribution function. These approximations are designed to be computationally inexpensive, and much cheaper than exact library functions, and thus highly suitable for use in Monte Carlo simulations. Two approximations are presented for the Gaussian distribution: a piecewise constant on equally spaced intervals, and a piecewise linear using geometrically decaying intervals. The error of the approximations are bounded and the convergence demonstrated, and the computational savings measured for C and C++ implementations. Implementations tailored for Intel and Arm hardwares are inspected, alongside hardware agnostic implementations built using OpenMP. The savings are incorporated into a nested multilevel Monte Carlo framework with the Euler-Maruyama scheme to exploit the speed ups without losing accuracy, offering speed ups by a factor of 5--7. These ideas are empirically extended to the Milstein scheme, and the Cox-Ingersoll-Ross process' non central chi-squared distribution, which offer speed ups by a factor of 250 or more.
description: 20 pages, 4 figures
Unravelling the role of Sm 4f electrons in the magnetism of SmFeO$_3$
Creators: name: Amoroso, Danila
name: Dupe, Bertrand
name: Verstraete, Matthieu J.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Magnetic rare-earth orthoferrites $R$FeO$_3$ host a variety of functional properties from multiferroicity and strong magnetostriction, to spin-reorientation transitions and ultrafast light-driven manipulation of magnetism, which can be exploited in spintronics and next-generation devices. Among these systems, SmFeO$_3$ is attracting a particular interest for its rich phase diagram and the high temperature Fe-spin magnetic transitions, which combines with a very low temperature and as yet unclear Sm-spin ordering. Various experiments suggest that the interaction between the Sm and Fe magnetic moments (further supported by the magnetic anisotropy), is at the origin of the complex cascade of transitions, but a conclusive and clear picture has not yet been reached. In this work, by means of comprehensive first-principles calculations, we unravel the role of the magnetic Sm ions in the Fe-spin reorientation transition and in the detected anomalies in the lattice vibrational spectrum, which are a signature of a relevant spin-phonon coupling. By including both Sm-$f$ electrons and non-collinear magnetism, we find frustrated and anisotropic Sm interactions, and a large magnetocrystalline anisotropy mediated by the SOC of the Sm-$4f$ electrons, which drive the complex magnetic properties and phase diagram of SmFeO$_3$.
Galaxy And Mass Assembly (GAMA): The Dependence of Star Formation on Surface Brightness in Low Redshift Galaxies
Creators: name: Phillipps, S.
name: Bellstedt, S.
name: Bremer, M. N.
name: De Propris, R.
name: James, P. A.
name: Casura, S.
name: Liske, J.
name: Holwerda, B. W.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The star formation rate in galaxies is well known to correlate with stellar mass (the `star-forming main sequence'). Here we extend this further to explore any additional dependence on galaxy surface brightness, a proxy for stellar mass surface density. We use a large sample of low redshift ($z \leq 0.08$) galaxies from the GAMA survey which have both SED derived star formation rates and photometric bulge-disc decompositions, the latter providing measures of disc surface brightness and disc masses. Using two samples, one of galaxies fitted by a single component with Sérsic index below 2 and one of the discs from two-component fits, we find that once the overall mass dependence of star formation rate is accounted for, there is no evidence in either sample for a further dependence on stellar surface density.
description: Accepted for publication in MNRAS
The Future of Youth Justice: A Community Based Alternative to the Youth Prison Model
Creators: name: McCarthy, Patrick
name: Schiraldi, Vincent N.
name: Shark, Miriam
Publisher: name: Columbia University
Year: 2016
Subjects: Criminal justice, Administration of
Youth--Legal status, laws, etc.
Prisons
Community-based corrections

description: Whether the benefits and costs of youth prisons are weighed on a scale of public dollars, community safety, or young people’s futures, they are damaging the very people they are supposed to help and have been for generations. It is difficult to find an area of U.S. policy where the benefits and costs are more out of balance, where the evidence of failure is clearer, or where we know with more clarity what we should be doing differently. This ill-conceived and outmoded approach is a failure, with high costs and recidivism rates and institutional conditions that are often appalling. Our approach to youth in trouble with the law requires a watershed change to one that is more effective, more informed by evidence of what works, more likely to protect public safety, more developmentally appropriate, more humane, and more community based. Every youth prison in the country should be closed and replaced with a network of community-based programs and small facilities near the youth’s communities. Closing these failed institutions requires a clear-headed, common-sense, bipartisan policy approach, and a commitment to replace these facilities with effective alternatives that are already available.
Generalized non-unitary Haagerup-Izumi modular data from 3D S-fold SCFTs
Creators: name: Gang, Dongmin
name: Kim, Dongyeob
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: By applying the recently proposed (3D rank-0 $\mathcal{N}$=4 SCFT)/(non-unitary TQFTs) correspondence to S-fold SCFTs, we construct an exotic class of non-unitary TQFTs labelled by an integer $k\geq 3$. The SCFTs are obtained by gauging diagonal $SU(2)$ subgroup of $T[SU(2)]$ theory with Chern-Simons level $k$. We give the explicit expression for modular data, $S$ and $T$ matrices, of the TQFTs. When $k=4m^2+4m+3$ with an integer $m\geq 1$, the modular data (modulo a decoupled semion) is identical to a non-unitary Haagerup-Izumi modular data. Thus, we give a physical realization of the exotic non-unitary modular data as well as its generalization using an exotic class of SCFTs.
description: 10 pages, v2: minor changes, typos corrected, v3: typos corrected and discussions clarified, v4: typos corrected
Ultrafast Frustration-Breaking and Magnetophononic Driving of Singlet Excitations in a Quantum Magnet
Creators: name: Giorgianni, Flavio
name: Wehinger, Björn
name: Allenspach, Stephan
name: Colonna, Nicola
name: Vicario, Carlo
name: Puphal, Pascal
name: Pomjakushina, Ekaterina
name: Normand, Bruce
name: Rüegg, Christian
Publisher: name: arXiv
Year: 2021
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Ideal magnetic frustration forms the basis for the emergence of exotic quantum spin states that are entirely nonmagnetic. Such singlet spin states are the defining feature of the Shastry-Sutherland model, and of its faithful materials realization in the quantum antiferromagnet SrCu$_2$(BO$_3$)$_2$. To address these states on ultrafast timescales, despite their lack of any microscopic order parameter, we introduce a nonlinear magnetophononic mechanism to alter the quantum spin dynamics by driving multiple optical phonon modes coherently and simultaneously. We apply intense terahertz pulses to create a nonequilibrium modulation of the magnetic interactions that breaks the ideal frustration of SrCu$_2$(BO$_3$)$_2$, such that previously forbidden physics can be driven in a coherent manner. Specifically, this driving populates a purely magnetic excitation, the singlet branch of the two-triplon bound state, by resonance with the difference frequency of two pumped phonons. Our results demonstrate how light-driven phonons can be used for the ultrafast and selective manipulation of interactions in condensed matter, even at frequencies far from those of the pump spectrum, offering valuable additional capabilities for the dynamical control of quantum many-body phenomena.
description: 21 pages, 13 figures
Constraining constant and tomographic coupled dark energy with low-redshift and high-redshift probes
Creators: name: Goh, Lisa W. K.
name: Gómez-Valent, Adrià
name: Pettorino, Valeria
name: Kilbinger, Martin
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We consider coupled dark energy (CDE) cosmologies, where dark matter particles feel a force stronger than gravity, due to the fifth force mediated by a scalar field which plays the role of dark energy. We perform for the first time a tomographic analysis of coupled dark energy, where the coupling strength is parametrized and constrained in different redshift bins. This allows us to verify which data can better constrain the strength of the coupling and how large the coupling can be at different epochs. First, we employ cosmic microwave background data from Planck, the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT), showing the impact of different choices that can be done in combining these datasets. Then, we use a range of low redshift probes to test CDE cosmologies, both for a constant and for a tomographic coupling. In particular, we use for the first time data from weak lensing (the KiDS-1000 survey), galaxy clustering (BOSS survey), and their combination, including 3x2pt galaxy-galaxy lensing cross-correlation data. We do not find evidence for nonzero coupling, either for a constant or tomographic case. A nonzero coupling is however still in agreement with current data. For CMB and background datasets, a tomographic coupling allows for $β$ values up to one order of magnitude larger than in previous works, in particular at $z<1$. The use of 3x2pt analysis then becomes important to constrain $β$ at low redshifts, even when coupling is allowed to vary: for 3x2pt we find, at $0.5 < z < 1$, $β=0.0180_{-0.011}^{+0.007}$, comparable to what CMB and background datasets would give for a constant coupling. This makes upcoming galaxy surveys potentially powerful probes to test CDE models at low redshifts. (abridged)
description: 25 pages, 17 figures. Accepted for publication in Physical Review D
title: Πετρογραφικά χαρακτηριστικά ψαμμιτών του νεογενούς - Περιοχή Τεφελίου, Μεσσαρά, Κρήτη

Creators: name: Γιοφκος Μιχαηλ
Publisher: name: Technical University of Crete
Year: 2016

description: Οι ψαμμίτες είναι ιζηματογενή πετρώματα με σχετικά μεγάλο πορώδες και διαπερατότητα και ως εκ τούτου αποτελούν αντικείμενο μελέτης πολλών γεωεπιστημονικών ειδικοτήτων. Στην κατηγορία όμως των ψαμμιτών εμπίπτουν επίσης πετρώματα που εκτός από το ψαμμιτικό κλάσμα περιέχουν και ποσοστά ιλυολιθικού αλλά και αργιλικού κλάσματος. Μέσω της διαγένεσης τα βασικά πετροφυσικά χαρακτηριστικά αυτών των πετρωμάτων επηρεάζονται καθοριστικά. Τα αποθετικά περιβάλοντα των ψαμμιτών μπορεί να είναι διαφορετικά από νηριτικά μέχρι και αβυσσικά μέσω τουρβιδιτικών ρευμάτων. Ψαμμίτες δομούν ένα σημαντικό τμήμα των Νεογενών σχηματισμών στην κεντρική Κρήτη.
 Σε μια εκτεταμένη περιοχή στην κεντρική Κρήτη, εντός των νεογενών σχηματισμών της λεκάνης της Μεσσαράς, έχουν παρατηρηθεί σε υδρογεωτρήσεις διαφυγές μεθανίου διαγενετικής προέλευσης. Γεωτρητικά δεδομένα υπέδειξαν ότι το μεθάνιο βρίσκεται πέραν των ιλυολίθων εντός ψαμμιτικών στρωμάτων που φιλοξενούν νερό υψηλής αλατότητας. Ψαμμίτες έχουν δημιουργηθεί στην ευρύτερη αποθετική λεκάνη της Μεσσαράς διαχρονικά από το Μέσο Μειόκαινο έως το Πλειόκαινο σε διαφορετικά αποθετικά περιβάλλοντα. Ως επακόλουθο τα κύρια πετροφυσικά τους χαρακτηριστικά το πορώδες και η διαπερατότητα εξαρτώνται άμεσα από τις αρχικές αυτές ιζηματολογικές συνθήκες και τις συνεπακόλουθες διεργασίες της διαγένεσης.
Στόχος της εργασίας αυτής είναι η μέτρηση του πορώδους και της διαπερατότητας, για πρώτη φορά σε ψαμμίτες του Νεογενούς από διαφορετικά αποθετικά περιβάλλοντα σε 45 δείγματα που πάρθηκαν από τέσσερεις γεωλογικές τομές αντιπροσωπευτικές των τριών κύριων σχηματισμών του Μέσου-Ανώτερου Μειοκαίνου στην ευρύτερη λεκάνη της Μεσσαράς: του Βιάννου, Σκοινιά και Αμπελούζου. Κατά μήκος αυτών των τομών  παρατηρούνται ψαμμιτικοί πάγκοι σε εναλλαγές με κροκαλοπαγή και μάργες.   Αν και οι διαφορές στο πορώδες  των σχηματισμών αυτών είναι εμφανείς, δεν συμβαίνει το ίδιο με την διαπερατότητα, συνέπεια του σχετικά υψηλού ποσοστού αργιλικού και ιλυολιθικού κλάσματος εντός των ψαμμιτών, που διαγενετικά την καθόρισε.
Embodied Mental Rotation – Does It Affect Postural Stability?
Creators: name: Hofmann, Philipp
name: Jost, Leonardo
name: Jansen, Petra
Publisher: name: Taylor & Francis
Year: 2022
Subjects: subject: Neuroscience
subject: Physiology
subject: FOS: Biological sciences
subject: Sociology
subject: FOS: Sociology
subject: 69999 Biological Sciences not elsewhere classified
subject: 111714 Mental Health
subject: FOS: Health sciences

description: The effect of different human body part stimuli in mental rotation tasks (MRTs) on postural stability was investigated in two dual-task experiments. There were significant differences within egocentric MRTs (Experiment 1, N = 46): Hand and foot stimuli tended to cause more body sway than whole-body figures and showed increased body sway for higher rotation angles in the MRTs. In object-based MRTs (Experiment 2, N = 109) different stimuli did not evoke different levels of body sway, but higher rotation angles led to higher body sway. Both experiments showed a stabilizing effect of MRTs compared to the control condition. Exploratorily analyses identified reaction time in MRTs as a significant predictor of body sway. The results suggest a heterogeneous impact of mental rotation on postural stability.
Sustainability in Engineering Education: A Paradigm Shift with Transfer‐of‐Learning and Authentic Assessment
Creators: name: Tan, Cheng Hock Alfred
name: Della, Christian
name: Lim, Li Hong Idris
name: Ong, Chee Ming
name: Wang, Pengcheng
name: Molina-Cristobal, Arturo
name: Shavrina, E.
Publisher: name: Singapore Institute of Technology
Year: 2024

description: This paper explores a holistic approach to learning sustainability in engineering education. Students are exposed to authentic learning and assessments through e-computer simulations, which benefits the transfer-of-learning within the curriculum and even from school to work. Computer simulation is a readily accessible approach for learners to achieve sustainability by assessing the environmental footprint of their design and optimizing them for efficiency and performance. Simulation software, such as Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD), are essential tools for students to bridge the gap between theoretical knowledge and practical applications. By immersing learners in realistic workplace problems through simulation exercises, we create a direct connection between classroom learning and real-world challenges. One approach is by performing parametric studies via simulation, thereby reducing waste by limiting physical prototyping and testing. One challenge here is to change the mindset of learners in accepting that simulation has a direct relation in supporting the United Nation’s sustainable development goals. When addressed carefully, this will promote a cycle of responsible consumption and production. Here, we share insights from our experience in implementing this approach within a mechanical engineering program. Open-ended survey data captured from following student cohort will shed light on how students conceptualize the purposeful integration of sustainable practices within their curriculum. We also showcase examples of simulation-based learning activities, discuss strategies for facilitating the transfer of sustainability principles to real-world situations, and highlight the effectiveness of authentic assessment in evaluating students' readiness to address sustainability challenges.
MeV Dark Matter with MeV Dark Photons in Abelian Kinetic Mixing Theories
Creators: name: Compagnin, Federico
name: Profumo, Stefano
name: Fornengo, Nicolao
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We consider the cosmology and phenomenology of a dark photon portal to a simple dark sector consisting of a single, light, fermionic dark matter particle species with mass in the MeV range. We entertain three possible kinetic mixing structures of a new Abelian gauge group U(1)$_{\text{dark}}$ with the visible sector through U(1)$_{\text{e.m.}}$, U(1)$_{\text{Y}}$ and T[SU(2)$_{\text{L}}$]. We assume the dark photon to be massive and around the MeV scale, thus close to the mass scale of the dark matter candidate. We compute the dark matter relic density via freeze-out and freeze-in, entertaining the additional possibilities of (i) a late inflationary period that could dilute the dark matter yield of heavy candidates, and (ii) additional production modes, for models with under-abundant thermal production. We explore the parameter space compatible with a variety of experimental and astrophysical bounds, and discuss prospects for discovery with new CMB probes and MeV gamma-ray telescopes.
Robustness of Topological Order in Semiconductor-Superconductor Nanowires in the Coulomb Blockade Regime
Creators: name: Zocher, Björn
name: Horsdal, Mats
name: Rosenow, Bernd
Publisher: name: arXiv
Year: 2013
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: Semiconductor-superconductor hybrid systems are promising candidates for the realization Majorana fermions and topological order, i.e. topologically protected degeneracies, in solid state devices. We show that the topological order is mirrored in the excitation spectra and can be observed in nonlinear Coulomb blockade transport through a ring-shaped nanowire. Especially, the excitation spectrum is almost independent of magnetic flux in the topologically trivial phase but acquires a characteristic $h/e$ magnetic flux periodicity in the nontrivial phase. The transition between the trivial and nontrivial phase is reflected in the closing and reopening of an excitation gap. We show that the signatures of topological order are robust against details of the geometry, electrostatic disorder, and the existence of additional subbands and only rely on the topology of the nanowire and the existence of a superconducting gap. Finally, we show that the coherence length in the nontrivial phase is much longer than in the trivial phase. This opens the possibility to coat the nanowire with superconducting nanograins and thereby significantly reduce the current due to cotunneling of Cooper pairs and to enhance the Coulomb charging energy without destroying the superconducting gap.
description: 20 pages, 7 figures
MVRackLay: Monocular Multi-View Layout Estimation for Warehouse Racks and Shelves
Creators: name: Pathre, Pranjali
name: Sahu, Anurag
name: Rao, Ashwin
name: Prabhu, Avinash
name: Nigam, Meher Shashwat
name: Karandikar, Tanvi
name: Pandya, Harit
name: Krishna, K. Madhava
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences

description: In this paper, we propose and showcase, for the first time, monocular multi-view layout estimation for warehouse racks and shelves. Unlike typical layout estimation methods, MVRackLay estimates multi-layered layouts, wherein each layer corresponds to the layout of a shelf within a rack. Given a sequence of images of a warehouse scene, a dual-headed Convolutional-LSTM architecture outputs segmented racks, the front and the top view layout of each shelf within a rack. With minimal effort, such an output is transformed into a 3D rendering of all racks, shelves and objects on the shelves, giving an accurate 3D depiction of the entire warehouse scene in terms of racks, shelves and the number of objects on each shelf. MVRackLay generalizes to a diverse set of warehouse scenes with varying number of objects on each shelf, number of shelves and in the presence of other such racks in the background. Further, MVRackLay shows superior performance vis-a-vis its single view counterpart, RackLay, in layout accuracy, quantized in terms of the mean IoU and mAP metrics. We also showcase a multi-view stitching of the 3D layouts resulting in a representation of the warehouse scene with respect to a global reference frame akin to a rendering of the scene from a SLAM pipeline. To the best of our knowledge, this is the first such work to portray a 3D rendering of a warehouse scene in terms of its semantic components - Racks, Shelves and Objects - all from a single monocular camera.
title: Επεξεργασία συνθετικών δεδομένων σεισμικής ανάκλασης για τη Δυτική Μεσσαρά
Creators: name: Χατζημιχαηλιδου Ραφαηλια
Publisher: name: Technical University of Crete
Year: 2016

description: Η παρούσα διπλωματική εργασία πραγματεύεται την επεξεργασία συνθετικών δεδομένων σεισμικής ανάκλασης για τη δυτική Μεσσαρά (Νομός Ηρακλείου) για την λεπτομερή απεικόνιση του αλπικού υποβάθρου.
Στη λεκάνη της Μεσσαράς σεισμικά δεδομένα τα οποία συλλέχθηκαν από την Δημόσια Επιχείρηση Πετρελαίου (ΔΕΠ) την δεκαετία του 1980 δεν παρέχουν επαρκή στοιχεία για την χαρτογράφηση του αλπικού υποβάθρου λόγω του αραιού δικτύου σεισμικών γραμμών.
Για το σχεδιασμό της σεισμικής διασκόπησης πραγματοποιήθηκε προσομοίωση της διάδοσης των σεισμικών κυμάτων και τρισδιάστατη απεικόνιση των σεισμικών τομών. Πιο αναλυτικά, επιλέχθηκαν 5 θέσεις σεισμικών γραμμών μελέτης. Στη συνέχεια, με βάση τα διαθέσιμα γεωφυσικά και γεωτρητικά στοιχεία δημιουργήθηκαν τα μοντέλα σεισμικής ταχύτητας. Ακολούθησε η επεξεργασία των συνθετικών δεδομένων με την εφαρμογή της σεισμικής χωροθέτησης και της αποσυνέλιξης πρόβλεψης και παρουσιάστηκαν τα αποτελέσματα της εφαρμογής τους. Στη συνέχεια έγινε προσπάθεια ερμηνείας των αποτελεσμάτων από την οποία προέκυψε η ανάγκη για πιο ρεαλιστική προσομοίωση λαμβάνοντας υπόψιν και τα ρήγματα.
Density of fiberwise orbits in minimal iterated function systems on the circle
Creators: name: Barrientos, Pablo G.
name: Fakhari, Abbas
name: Sarizadeh, Ali
Publisher: name: arXiv
Year: 2013
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics

description: We study the minimality of almost every orbital branch of minimal iterated function systems (IFSs). We prove that this kind of minimality holds for forward and backward minimal IFSs generated by orientation-preserving homeomorphisms of the circle. We provide new examples of iterated functions systems where this behavior persists under perturbation of the generators.
Features that Predict the Acceptability of Java and JavaScript Answers on Stack Overflow
Creators: name: Omondiagbe, Osayande P.
name: Licorish, Sherlock A.
name: MacDonell, Stephen G.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Software Engineering (cs.SE)
subject: FOS: Computer and information sciences

description: Context: Stack Overflow is a popular community question and answer portal used by practitioners to solve problems during software development. Developers can focus their attention on answers that have been accepted or where members have recorded high votes in judging good answers when searching for help. However, the latter mechanism (votes) can be unreliable, and there is currently no way to differentiate between an answer that is likely to be accepted and those that will not be accepted by looking at the answer's characteristics. Objective: In potentially providing a mechanism to identify acceptable answers, this study examines the features that distinguish an accepted answer from an unaccepted answer. Methods: We studied the Stack Overflow dataset by analyzing questions and answers for the two most popular tags (Java and JavaScript). Our dataset comprised 249,588 posts drawn from 2014-2016. We use random forest and neural network models to predict accepted answers, and study the features with the highest predictive power in those two models. Results: Our findings reveal that the length of code in answers, reputation of users, similarity of the text between questions and answers, and the time lag between questions and answers have the highest predictive power for differentiating accepted and unaccepted answers. Conclusion: Tools may leverage these findings in supporting developers and reducing the effort they must dedicate to searching for suitable answers on Stack Overflow.
description: Conference, 11 pages, 3 figures, 2 tables
Quantum circuits with classical versus quantum control of causal order
Creators: name: Wechs, Julian
name: Dourdent, Hippolyte
name: Abbott, Alastair A.
name: Branciard, Cyril
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: Quantum supermaps are transformations that map quantum operations to quantum operations. It is known that quantum supermaps which respect a definite, predefined causal order between their input operations correspond to fixed-order quantum circuits. A systematic understanding of the physical interpretation of more general types of quantum supermaps--in particular, those incompatible with a definite causal structure--is however lacking. Here we identify two new types of circuits that naturally generalise the fixed-order case and that likewise correspond to distinct classes of quantum supermaps, which we fully characterise. We first introduce "quantum circuits with classical control of causal order", in which the order of operations is still well-defined, but not necessarily fixed in advance: it can in particular be established dynamically, in a classically-controlled manner, as the circuit is being used. We then consider "quantum circuits with quantum control of causal order", in which the order of operations is controlled coherently. The supermaps described by these classes of circuits are physically realisable, and the latter encompasses all known examples of physically realisable processes with indefinite causal order, including the celebrated "quantum switch". Interestingly, it also contains new examples arising from the combination of dynamical and coherent control of causal order, and we detail explicitly one such process. Nevertheless, we show that quantum circuits with quantum control of causal order can only generate "causal" correlations, compatible with a well-defined causal order. We furthermore extend our considerations to probabilistic circuits that produce also classical outcomes, and we demonstrate by an example how our characterisations allow us to identify new advantages for quantum information processing tasks that could be demonstrated in practice.
description: 34+17 pages, 13 figures. V3: corrected the statement of Proposition 7, specifying that the process matrix $W$ itself has to be positive semidefinite
Multiscale methods for solving wave equations on spatial networks
Creators: name: Görtz, Morgan
name: Ljung, Per
name: Målqvist, Axel
Publisher: name: arXiv
Year: 2022
Subjects: subject: Numerical Analysis (math.NA)
subject: FOS: Mathematics

description: We present and analyze a multiscale method for wave propagation problems, posed on spatial networks. By introducing a coarse scale, using a finite element space interpolated onto the network, we construct a discrete multiscale space using the localized orthogonal decomposition (LOD) methodology. The spatial discretization is then combined with an energy conserving temporal scheme to form the proposed method. Under the assumption of well-prepared initial data, we derive an a priori error bound of optimal order with respect to the space and time discretization. In the analysis, we combine the theory derived for stationary elliptic problems on spatial networks with classical finite element results for hyperbolic problems. Finally, we present numerical experiments that confirm our theoretical findings.
Positive feedback, quenching and sequential super star cluster (SSC) formation in NGC 4945
Creators: name: Bellocchi, Enrica
name: Martín-Pintado, Jesús
name: Rico-Villas, Fernando
name: Martín, Sergio
name: Jiménez-Sierra, Izaskun
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We have used ALMA imaging (resolutions 0.1\arcsec-0.4\arcsec) of ground and vibrationally excited lines of HCN and HC$_3$N toward the nucleus of NGC 4945 to trace the protostellar phase in Super Star Clusters (proto-SSC). Out of the 14 identified SSCs, we find that 8 are in the proto-SSC phase showing vibrational HCN emission with 5 of them also showing vibrational HC$_3$N emission. We estimate proto-SSC ages of 5-9.7$\times$10$^4$ yr. The more evolved ones, with only HCN emission, are close to reach the Zero Age Main Sequence (ZAMS; ages $\gtrsim$10$^5$ yr). The excitation of the parental cloud seems to be related to the SSC evolutionary stage, with high ($\sim$65 K) and low ($\sim$25 K) rotational temperatures for the youngest proto and ZAMS SSCs, respectively. Heating by the HII regions in the SSC ZAMS phase seems to be rather local. The youngest proto-SSCs are located at the edges of the molecular outflow, indicating SSC formation by positive feedback in the shocked regions. The proto-SSCs in NGC 4945 seem to be more evolved than in the starburst galaxy NGC 253. We propose that sequential SSC formation can explain the spatial distribution and different ages of the SSCs in both galaxies.
description: 5 pages, 4 figures, 3 tables. Accepted for publication in MNRAS Letters
Dissolved organic matter stimulates N₂ fixation and nifH gene expression in Trichodesmium
Creators: name: Benavides, Mar
name: Duhamel, Solange
name: Van Wambeke, France
name: Shoemaker, Katyanne M.
name: Moisander, Pia H.
name: Salamon, Ellen
name: Riemann, Lasse
name: Bonnet, Sophie
Publisher: name: Columbia University
Year: 2020
Subjects: Biogeochemistry
Marine microbiology
Marine plankton
Trichodesmium
Nitrogen--Fixation

description: Mixotrophy, the combination of heterotrophic and autotrophic nutrition modes, is emerging as the rule rather than the exception in marine photosynthetic plankton. Trichodesmium, a prominent diazotroph ubiquitous in the (sub)tropical oceans, is generally considered to obtain energy via autotrophy. While the ability of Trichodesmium to use dissolved organic phosphorus when deprived of inorganic phosphorus sources is well known, the extent to which this important cyanobacterium may benefit from other dissolved organic matter (DOM) sources is unknown. Here we provide evidence of carbon-, nitrogen- and phosphorus-rich DOM molecules enhancing N₂ fixation rates and nifH gene expression in natural Trichodesmium colonies collected at two stations in the western tropical South Pacific. Sampling at a third station located in the oligotrophic South Pacific Gyre revealed no Trichodesmium but showed presence of UCYN-B, although no nifH expression was detected. Our results suggest that Trichodesmium may behave mixotrophically in response to certain environmental conditions, providing them with metabolic plasticity and adding up to the view that mixotrophy is widespread among marine microbes.
Electric charge catalysis by magnetic fields and a nontrivial holonomy
Creators: name: Bruckmann, F.
name: Buividovich, P. V.
name: Sulejmanpasic, T.
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We describe a generic mechanism by which a system of Dirac fermions in thermal equilibrium acquires electric charge in an external magnetic field. To this end the fermions should have an additional quantum number, isospin or color, and should be subject to a second magnetic field, which distinguishes the isospin/color, as well as to a corresponding isospin chemical potential. The role of the latter can be also played by a nontrivial holonomy (Polyakov loop) along the Euclidean time direction. The charge is accumulated since the degeneracies of occupied lowest Landau levels for particles of positive isospin and anti-particles of negative isospin are different. We discuss two physical systems, where this phenomenon can be realized. One is monolayer graphene, where the isospin is associated with two valleys in the Brillouin zone and the strain-induced pseudo-magnetic field acts differently on charge carriers in different valleys. Another is hot QCD, for which the relevant non-Abelian field configurations with both nonzero chromo-magnetic field and a nontrivial Polyakov loop can be realized as calorons - topological solutions of Yang-Mills equations at finite temperature. The induced electric charge on the caloron field configuration is studied numerically. We argue that due to the fluctuations of holonomy external magnetic field should tend to suppress charge fluctuations in the quark-gluon plasma and estimate the importance of this effect for off-central heavy-ion collisions.
description: 16 pages RevTeX, 11 figures, v3: published version