cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Higher metal abundances do not solve the solar problem
Creators: name: Buldgen, G.
name: Eggenberger, P.
name: Noels, A.
name: Scuflaire, R.
name: Amarsi, A. M.
name: Grevesse, N.
name: Salmon, S.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Context. The Sun acts as a cornerstone of stellar physics. Thanks to spectroscopic, helioseismic and neutrino flux observations, we can use the Sun as a laboratory of fundamental physics in extreme conditions. The conclusions we draw are then used to inform and calibrate evolutionary models of all other stars in the Universe. However, solar models are in tension with helioseismic constraints. The debate on the ``solar problem'' has hitherto led to numerous publications discussing potential issues with solar models and abundances. Aims. Using the recently suggested high-metallicity abundances for the Sun, we investigate whether standard solar models, as well as models with macroscopic transport reproducing the solar surface lithium abundances and analyze their properties in terms of helioseismic and neutrino flux observations. Methods. We compute solar evolutionary models and combine spectroscopic and helioseismic constraints as well as neutrino fluxes to investigate the impact of macroscopic transport on these measurements. Results. When high-metallicity solar models are calibrated to reproduce the measured solar lithium depletion, tensions arise with respect to helioseismology and neutrino fluxes. This is yet another demonstration that the solar problem is also linked to the physical prescriptions of solar evolutionary models and not to chemical composition alone. Conclusions. A revision of the physical ingredients of solar models is needed in order to improve our understanding of stellar structure and evolution. The solar problem is not limited to the photospheric abundances if the depletion of light elements is considered. In addition, tighter constraints on the solar beryllium abundance will play a key role in the improvement of solar models.
description: Accepted for publication in Astronomy and Astrophysics
Normalization by Evaluation in the Delay Monad: A Case Study for Coinduction via Copatterns and Sized Types
Creators: name: Abel, Andreas
name: Chapman, James
Publisher: name: arXiv
Year: 2014
Subjects: subject: Logic in Computer Science (cs.LO)
subject: Programming Languages (cs.PL)
subject: FOS: Computer and information sciences
subject: D.3.3; F.3.2; F.3.3; F.4.1

description: In this paper, we present an Agda formalization of a normalizer for simply-typed lambda terms. The normalizer consists of two coinductively defined functions in the delay monad: One is a standard evaluator of lambda terms to closures, the other a type-directed reifier from values to eta-long beta-normal forms. Their composition, normalization-by-evaluation, is shown to be a total function a posteriori, using a standard logical-relations argument. The successful formalization serves as a proof-of-concept for coinductive programming and reasoning using sized types and copatterns, a new and presently experimental feature of Agda.
description: In Proceedings MSFP 2014, arXiv:1406.1534
Study of Simulation Method of Time Evolution of Atomic and Molecular Systems by Quantum Electrodynamics
Creators: name: Ichikawa, Kazuhide
name: Fukuda, Masahiro
name: Tachibana, Akitomo
Publisher: name: arXiv
Year: 2014
Subjects: subject: Atomic Physics (physics.atom-ph)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We discuss a method to follow step-by-step time evolution of atomic and molecular systems based on QED (Quantum Electrodynamics). Our strategy includes expanding the electron field operator by localized wavepackets to define creation and annihilation operators and following the time evolution using the equations of motion of the field operator in the Heisenberg picture. We first derive a time evolution equation for the excitation operator, the product of two creation or annihilation operators, which is necessary for constructing operators of physical quantities such as the electronic charge density operator. We then describe our approximation methods to obtain time differential equations of the electronic density matrix, which is defined as the expectation value of the excitation operator. By solving the equations numerically, we show "electron-positron oscillations", the fluctuations originated from virtual electron-positron pair creations and annihilations, appear in the charge density of a hydrogen atom and molecule. We also show that the period of the electron-positron oscillations becomes shorter by including the self-energy process, in which the electron emits a photon and then absorbs it again, and it can be interpreted as the increase in the electron mass due to the self-energy.
description: 32 pages; 3 figures
Muon-electron scattering at NNLO
Creators: name: Broggio, A.
name: Engel, T.
name: Ferroglia, A.
name: Mandal, M. K.
name: Mastrolia, P.
name: Rocco, M.
name: Ronca, J.
name: Signer, A.
name: Bobadilla, W. J. Torres
name: Ulrich, Y.
name: Zoller, M.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: We present the first calculation of the complete set of NNLO QED corrections for muon-electron scattering. This includes leptonic, non-perturbative hadronic, and photonic contributions. All fermionic corrections as well as the photonic subset that only corrects the electron or the muon line are included with full mass dependence. The genuine four-point two-loop topologies are computed as an expansion in the small electron mass, taking into account both, logarithmically enhanced as well as constant mass effects using massification. A fast and stable implementation of the numerically delicate real-virtual contribution is achieved by combining OpenLoops with next-to-soft stabilisation. All matrix elements are implemented in the McMule framework, which allows for the fully-differential calculation of any infrared-safe observable. This calculation is to be viewed in the context of the MUonE experiment requiring a background prediction at the level of 10 ppm. Our results thus represent a major milestone towards this ambitious precision goal.
description: 31 pages, 6 figures, 3 tables
Josephson current via spin and orbital states of a tunable double quantum dot
Creators: name: Debbarma, Rousan
name: Aspegren, Markus
name: Boström, Florinda Viñas
name: Lehmann, Sebastian
name: Dick, Kimberly
name: Thelander, Claes
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Supercurrent transport is experimentally studied in a Josephson junction hosting a double quantum dot (DQD) with tunable symmetries. The QDs are parallel-coupled to two superconducting contacts and can be tuned between strong inter-dot hybridization and a ring geometry where hybridization is suppressed. In both cases, we observe supercurrents when the two interacting orbitals are either empty or filled with spins, or a combination. However, when each QD hosts an unpaired spin, the supercurrent depends on the spin ground state. It is strongly suppressed for the ring geometry with a spin-triplet ground state at zero external magnetic field. By increasing the QD hybridization, we find that a supercurrent appears when the ground state changes to spin-singlet. In general, supercurrents are suppressed in cases of spin doublet ground state, but an exception occurs at orbital degeneracy when the system hosts one additional spin, as opposed to three, pointing to a broken particle-hole symmetry.
Pixel is All You Need: Adversarial Trajectory-Ensemble Active Learning for Salient Object Detection
Creators: name: Wu, Zhenyu
name: Wang, Lin
name: Wang, Wei
name: Xia, Qing
name: Chen, Chenglizhao
name: Hao, Aimin
name: Li, Shuo
Publisher: name: arXiv
Year: 2022
Subjects: subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Although weakly-supervised techniques can reduce the labeling effort, it is unclear whether a saliency model trained with weakly-supervised data (e.g., point annotation) can achieve the equivalent performance of its fully-supervised version. This paper attempts to answer this unexplored question by proving a hypothesis: there is a point-labeled dataset where saliency models trained on it can achieve equivalent performance when trained on the densely annotated dataset. To prove this conjecture, we proposed a novel yet effective adversarial trajectory-ensemble active learning (ATAL). Our contributions are three-fold: 1) Our proposed adversarial attack triggering uncertainty can conquer the overconfidence of existing active learning methods and accurately locate these uncertain pixels. {2)} Our proposed trajectory-ensemble uncertainty estimation method maintains the advantages of the ensemble networks while significantly reducing the computational cost. {3)} Our proposed relationship-aware diversity sampling algorithm can conquer oversampling while boosting performance. Experimental results show that our ATAL can find such a point-labeled dataset, where a saliency model trained on it obtained $97\%$ -- $99\%$ performance of its fully-supervised version with only ten annotated points per image.
description: 9 pages, 8 figures
Introduction: Localized Structures in Dissipative Media: From Optics to Plant Ecology
Creators: name: Tlidi, M.
name: Staliunas, K.
name: Panajotov, K.
name: Vladimirov, A. G.
name: Clerc, M. G.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Pattern Formation and Solitons (nlin.PS)
subject: FOS: Physical sciences

description: Localised structures in dissipative appears in various fields of natural science such as biology, chemistry, plant ecology, optics and laser physics. The proposed theme issue is to gather specialists from various fields of non-linear science toward a cross-fertilisation among active areas of research. This is a cross-disciplinary area of research dominated by the nonlinear optics due to potential applications for all-optical control of light, optical storage, and information processing. This theme issue contains contributions from 18 active groups involved in localized structures field and have all made significant contributions in recent years.
description: 14 pages, 0 figure, submitted to Phi. Trasaction Royal Society
title: Connections. Collaborative imaginaries of territories in change across Europe. An itinerant book
Creators: name: Moralli, Melissa
name: Szytniewski, Bianca
Publisher: name: University of Bologna
Year: 2023

description: Hillside and mountain villages, green fields and endless plains with scattered settlements, post-industrial medium-sized towns constitute Europe as much as the big cities we all know. These places have long been considered peripheral in opposition to the large urban centres and have often been associated with a certain passivity, stagnation and resistance to change. Yet, within their interstices, inlets and plains, a closer look into these places shows that they also move, live and transform. And, they are also continuously enriched with new voices and new stories. This exhibition intends to start precisely from these stories to tell the everyday life of Europe's shrinking areas, where the narratives of old and new inhabitants, but also of returnees, come together. In this way, the stories of those who leave, those who arrive and those who return intertwine in a new rhythm of life that over time transforms and is transformed by the space in which these new communities settle. Through an itinerant research, travelling photography workshops were carried out in Italy, Poland, Spain, the Netherlands and Germany in spring and summer 2022, following the traces of these changes outside the spaces of urbanity. We have listened to the voices of those who live in the so-called peripheries of Europe, starting from a simple question: what makes the place where you live welcoming and how would you capture this in an image? The exhibition shows the stories, the photographs and the emotional maps created directly by those who live the everyday life in these communities - The result is the co-construction of a different, new imaginary, anchored in the time and space of lesser-known Europe. The images that follow are full of hopes for the future, desire for change, complex encounters, collective utopias. We invite you to immerse yourself in this itinerant exploration, to get to know through their eyes the life in a lesser-known but fascinating Europe, the Europe of outskirts.
Resilience of topological superconductivity under particle current
Creators: name: Maiellaro, Alfonso
name: Romeo, Francesco
name: Illuminati, Fabrizio
name: Citro, Roberta
Publisher: name: arXiv
Year: 2022
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: We investigate the robustness of topological superconductors under the perturbing influence of a finite charge current. To this aim, we introduce a modified Kitaev Hamiltonian parametrically dependent on the quasiparticle momentum induced by the current. Using different quantifiers of the topological phase, such as the Majorana polarization and the edge state quantum conditional mutual information, we prove the existence of a finite critical value of the quasiparticle momentum below which edge modes and topological superconductivity survive. We also discuss how a finite current breaks time reversal symmetry and changes the topological class in the Altland-Zirnbauer classification scheme compared to the case of isolated systems. Our findings provide a nontrivial example of the interplay between topology and the nonequilibrium physics of open quantum systems, a relation of crucial importance in the quest to a viable topological quantum electronics.
description: 8 pages, 3 figures, regular paper
Polymonadic Programming
Creators: name: Hicks, Michael
name: Bierman, Gavin
name: Guts, Nataliya
name: Leijen, Daan
name: Swamy, Nikhil
Publisher: name: arXiv
Year: 2014
Subjects: subject: Programming Languages (cs.PL)
subject: FOS: Computer and information sciences
subject: D.3.1

description: Monads are a popular tool for the working functional programmer to structure effectful computations. This paper presents polymonads, a generalization of monads. Polymonads give the familiar monadic bind the more general type forall a,b. L a -> (a -> M b) -> N b, to compose computations with three different kinds of effects, rather than just one. Polymonads subsume monads and parameterized monads, and can express other constructions, including precise type-and-effect systems and information flow tracking; more generally, polymonads correspond to Tate's productoid semantic model. We show how to equip a core language (called lambda-PM) with syntactic support for programming with polymonads. Type inference and elaboration in lambda-PM allows programmers to write polymonadic code directly in an ML-like syntax--our algorithms compute principal types and produce elaborated programs wherein the binds appear explicitly. Furthermore, we prove that the elaboration is coherent: no matter which (type-correct) binds are chosen, the elaborated program's semantics will be the same. Pleasingly, the inferred types are easy to read: the polymonad laws justify (sometimes dramatic) simplifications, but with no effect on a type's generality.
description: In Proceedings MSFP 2014, arXiv:1406.1534
"Infanzia infera". Il mondo poetico-pittorico di Toti Scialoja
Creators: name: Ottieri, Alessandra
Publisher: name: Universita degli studi di Salerno
Year: 2014
Subjects: subject: L-FIL-LET/11 LETTERATURA ITALIANA CONTEMPORANEA
subject: Astrattismo
subject: Nonsense
subject: Poesia

description: 2011 - 2012
description: L’immagine che a tutt’oggi si ha di Toti Scialoja è quella di un pittore professionista, tra i più quotati esponenti dell’espressionismo astratto italiano, animato da «una grande voglia di poesia», come recita il titolo di un importante scritto auto-esegetico degli anni Ottanta. Si tratta di un’immagine semplicistica e pregiudiziale che fa torto al poeta e limita la piena comprensione del pittore, la cui attività artistica è strettamente correlata con quella poetica. Se confrontiamo le date, e crediamo a quanto ci ha raccontato nel corso degli anni lo stesso Scialoja, la passione per la letteratura addirittura precede quella per la pittura («Ho cominciato a scrivere poesia verso i dieci anni. Erano strofette comico-grottesche, per lo più concentrate sugli animali. Sono stato pascoliano, crepuscolare, a diciott’anni ero innamorato di Ungaretti, a venti fui ipnotizzato da Mallarmé»). Tuttavia il giudizio sbrigativo e crudele di un amico “competente” (al quale il giovane Toti sottopone le sue prime prove poetiche) lo induce a cambiare rotta e a “virare” verso la pittura che dopo i vent’anni diviene l’interesse predominante. Scialoja, quindi, abbandona temporaneamente la poesia, ma continua a scrivere, pubblicando numerose recensioni e cronache d’arte su «Mercurio» (dopo la Liberazione) e più tardi su «Immagine» di Cesare Brandi. Il ritorno alla poesia si compie solo nel 1961, quando Scialoja, ormai artista affermato, si trasferisce a Parigi dove risiede fino al 1964. A partire da quegli anni il percorso poetico di Scialoja procede parallelamente a quello pittorico, caratterizzato quest’ultimo da una costante ricerca di nuovi stimoli e linguaggi, da continue “crisi” e “rinascite” che scandiscono un itinerario sofferto, articolato in almeno quattro fasi principali. .. [a cura dell'Autore]
Lehre als Zugang zum Fach - Plädoyer für eine didaktische Wissenschaftssozialisation
Creators: name: Eugster, Balthasar
name: Tremp, Peter
Publisher: name: Zenodo
Year: 2018
Subjects: subject: gnd:4015428-2
subject: gnd:4025226-7
subject: gnd:4126887-8
subject: gnd:4117622-4

description: Lehren und Lernen an Hochschulen unterscheiden sich von Lehren und Lernen in den vorangehenden Stufen des Bildungssystems. Dieses Grundpostulat der Hochschuldidaktik wird in diesem Beitrag insbesondere mit dem Verweis auf die Wissenschaftsorientierung der Hochschulen und die enge Verknüpfung von Lehren, Lernen und Forschen begründet. Aus dieser Verknüpfung wird hier – ergänzend zum forschenden Lernen – ein lehrendes Lernen vorgeschlagen. Denn das reflektierte Lehren, so die Begründung, eröffnet den Zugang zu einem der Wesenskerne eines jeden Faches: Lehre und Vermittlung sind konstituierende Elemente einer wissenschaftlichen Disziplin, die im Gang durch die Studienstufen im Zuge der wissenschaftlichen Sozialisation erworben werden müssen, so wie dies für die disziplinspezifischen Forschungsmethoden gilt.
description: +repphzhbib2018F
On the use of the index N2 to derive the metallicity in metal-poor galaxie
Creators: name: Morales-Luis, A. B.
name: Perez-Montero, E.
name: Almeida, J. Sanchez
name: Tunon, C. Munoz
Publisher: name: arXiv
Year: 2014
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: The N2 index ([N II]6584/Ha) is used to determine emission line galaxy metallicities at all redshifts, including high redshift, where galaxies tend to be metal-poor. The initial aim of the work was to improve the calibrations used to infer oxygen abundance from N2 employing updated low-metallicity galaxy databases. We compare N2 and the metallicity determined using the direct method for the set of extremely metal-poor galaxies compiled by Morales-Luis et al. (2011). To our surprise, the oxygen abundance presents a tendency to be constant with N2, with a very large scatter. Consequently, we find that the existing N2 calibrators overstimate the oxygen abundance for most low metallicity galaxies, and then they can be used only to set upper limits to the true metallicity in low-metallicity galaxies. An explicit expression for this limit is given. In addition, we try to explain the observed scatter using photoionization models. It is mostly due to the different evolutionary state of the HII regions producing the emission lines, but it also arises due to differences of N/O among the galaxies.
description: Accepted for publication in ApJ. 7 pages, 5 figures
Koka: Programming with Row Polymorphic Effect Types
Creators: name: Leijen, Daan
Publisher: name: arXiv
Year: 2014
Subjects: subject: Programming Languages (cs.PL)
subject: FOS: Computer and information sciences

description: We propose a programming model where effects are treated in a disciplined way, and where the potential side-effects of a function are apparent in its type signature. The type and effect of expressions can also be inferred automatically, and we describe a polymorphic type inference system based on Hindley-Milner style inference. A novel feature is that we support polymorphic effects through row-polymorphism using duplicate labels. Moreover, we show that our effects are not just syntactic labels but have a deep semantic connection to the program. For example, if an expression can be typed without an exn effect, then it will never throw an unhandled exception. Similar to Haskell's `runST` we show how we can safely encapsulate stateful operations. Through the state effect, we can also safely combine state with let-polymorphism without needing either imperative type variables or a syntactic value restriction. Finally, our system is implemented fully in a new language called Koka and has been used successfully on various small to medium-sized sample programs ranging from a Markdown processor to a tier-splitted chat application. You can try out Koka live at www.rise4fun.com/koka/tutorial.
description: In Proceedings MSFP 2014, arXiv:1406.1534
Supercritical CO2 impregnation of PLA/PCL films with natural substances for bacterial growth control in food packaging
Creators: name: Milovanovic, Stoja
name: Hollermann, Gesa
name: Errenst, Cornelia
name: Pajnik, Jelena
name: Frerich, Sulamith
name: Kroll, Stephen
name: Rezwan, Kurosch
name: Ivanovic, Jasna
Publisher: name: Elsevier {BV}
Year: 2018
Subjects: subject: Antibacterial food packaging
subject: Poly(lactic acid)
subject: Poly(ε-caprolactone)
subject: Supercritical CO(2) impregnation
subject: Thyme extract
subject: Thymol
subject: 620

description: Biodegradable polymers with antibacterial properties are highly desirable materials for active food packaging applications. Thymol, a dietary monoterpene phenol with a strong antibacterial activity is abundant in plants belonging to the genus Thymus. This study presents two approaches for supercritical CO2 impregnation of poly(lactic acid)(PLA)/poly(ε-caprolactone)(PCL) blended films to induce antibacterial properties of the material: (i) a batch impregnation process for loading pure thymol, and (ii) an integrated supercritical extraction-impregnation process for isolation of thyme extract and its incorporation into the films, operated in both batch or semi-continuous modes with supercritical solution circulation. The PCL content in films, impregnation time and CO2 flow regime were varied to maximize loading of the films with thymol or thyme extract with preserving films' structure and thermal stability. Representative film samples impregnated with thymol and thyme extract were tested against Gram (-) (Escherichia coli) and Gram(+) (Bacillus subtilis) model strains, by measuring their metabolic activity and re-cultivation after exposure to the films. The film containing thymol (35.8 wt%) showed a strong antibacterial activity leading to a total reduction of bacterial cell viability. Proposed processes enable fast, controlled and organic solvent-free fabrication of the PLA/PCL films containing natural antibacterial substances at moderately low temperature, with a compact structure and a good thermal stability, for potential use as active food packaging materials.
Beating the Heat! Automated Characterization of Piezoelectric Tubes for Starbugs
Creators: name: Piersiak, Rafal
name: Goodwin, Michael
name: Gilbert, James
name: Muller, Rolf
Publisher: name: arXiv
Year: 2014
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: The Australian Astronomical Observatory has extensively prototyped a new robotic positioner to allow simultaneous positioning of optical fibers at the focal plane called 'Starbugs'. The Starbug devices each consist of two concentric piezoelectric tubes that 'walk' the optical fiber over the focal plane to accuracy of several microns. Ongoing research has led to the development of several Starbug prototypes, but lack of performance data has hampered further progress in the design of the Starbug positioners and the support equipment required to power and control them. Furthermore, Starbugs have been selected for the TAIPAN instrument, a prototype for MANIFEST on the GMT. A need now arises to measure and characterize 100's of piezoelectric tubes before full scale production of Starbugs for TAIPAN. The manual measurements of these piezoelectric tubes are a time consuming process taking several hours. Therefore, a versatile automated system is needed to measure and characterize these tubes in the laboratory before production of Starbugs. We have solved this problem with the design of an automated LabVIEW application that significantly reduces test times to several minutes. We present the various design aspects of the automation system and provide analyses of example piezoelectric tubes for Starbugs.
description: 17 Pages, 20 figures, 3 tables, 10 references, SPIE Astronomical Telescopes + Instrumentation 2014, 9147-357
New insights into the helium star formation channel of AM CVn systems with explanations of Gaia14aae and ZTFJ1637+49
Creators: name: Sarkar, Arnab
name: Ge, Hongwei
name: Tout, Christopher A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We model helium-rich stars with solar metallicity ($X=0.7,\:Z=0.02$) progenitors that evolve to form AM Canum Venaticorum systems through a helium-star formation channel, with the aim to explain the observed properties of Gaia14aae and ZTFJ1637+49. We show that semi-degenerate, H-exhausted ($X\leq 10^{-5}$), He-rich ($Y\approx0.98$) donors can be formed after a common envelope evolution (CEE) phase if either additional sources of energy are used to eject the common envelope, or a different formalism of CEE is implemented. We follow the evolution of such binary systems after the CEE phase using the Cambridge stellar evolution code, when they consist of a He-star and a white dwarf accretor, and report that the mass, radius, and mass-transfer rate of the donor, the orbital period of the system, and the lack of hydrogen in the spectrum of Gaia14aae and ZTFJ1637+49 match well with our modelled trajectories wherein, after the CEE phase Roche lobe overflow is governed not only by the angular momentum loss (AML) owing to gravitational wave radiation ($\mathrm{AML_{GR}}$) but also an additional AML owing to $α-Ω$ dynamos in the donor. This additional AML is modelled with our double-dynamo (DD) model of magnetic braking in the donor star. We explain that this additional AML is just a consequence of extending the DD model from canonical cataclysmic variable donors to evolved donors. We show that none of our modelled trajectories match with Gaia14aae or ZTFJ1637+49 if the systems are modelled only with $\mathrm{AML_{GR}}$.
description: 11 pages, 11 figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society
NLTE analysis of the methylidyne radical (CH) molecular lines in metal-poor stellar atmospheres
Creators: name: Popa, S. A.
name: Hoppe, R.
name: Bergemann, M.
name: Hansen, C. J.
name: Plez, B.
name: Beers, T. C.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: An analysis of the CH molecule in non-local thermodynamic equilibrium (NLTE) is performed for the physical conditions of cool stellar atmospheres typical of red giants (log g = 2.0, Teff = 4500 K) and the Sun. The aim of the present work is to explore whether the G-band of the CH molecule, which is commonly used in abundance diagnostics of Carbon-Enhanced Metal-Poor (CEMP) stars, is sensitive to NLTE effects. LTE and NLTE theoretical spectra are computed with the MULTI code. We use one-dimensional (1D) LTE hydrostatic MARCS model atmospheres with parameters representing eleven red giant stars with metallicities ranging from [Fe/H] = -4.0 to [Fe/H] = 0.0 and carbon-to-iron ratios [C/Fe] = 0.0, +0.7, +1.5, and +3.0. The CH molecule model is represented by 1981 energy levels, 18377 radiative bound-bound transitions, and 932 photo-dissociation reactions. The rates due to transitions caused by collisions with free electrons and hydrogen atoms are computed using classical recipes. Our calculations suggest that NLTE effects in the statistical equilibrium of the CH molecule are significant and cannot be neglected for precision spectroscopic analysis of C abundances. The NLTE effects in the G-band increase with decreasing metallicity. We show that the C abundances are always under-estimated if LTE is assumed. The NLTE corrections to C abundance inferred from the CH feature range from +0.04 dex for the Sun to +0.21 dex for a red giant with metallicity [Fe/H] = -4.0. Departures from the LTE assumption in the CH molecule are non-negligible and NLTE effects have to be taken into account in the diagnostic spectroscopy based on the CH lines. We show here that the NLTE effects in the optical CH lines are non-negligible for the Sun and red giant stars, but further calculations are warranted to investigate the effects in other regimes of stellar parameters.
description: Accepted for publication in Astronomy & Astrophysics
title: Between theory & practice in Plato’s “the Republic” & “Laws”
title: Between theory and practice in Plato’s “the Republic” and “Laws"
titleType: AlternativeTitle
Creators: name: Dragon, Drake Sterling
Publisher: name: The University of Texas at Austin
Year: 2019
Subjects: Plato
Republic
Laws
Socrates

description: One of the most comical implications of Socrates’ (in)famous suggestion that "philosopher-kings" be made to rule the city alone is how far the illustrated model of the "philosopher kings" in the “the Republic” diverges from and falls short of being a genuine or complete philosophers on the model of Socrates himself. Why would Socrates propose the “Third Wave” if it is untenable, even in theory, and what does this suggest about the possibilities for radical political revolution in a democratic system? The activity of philosophy, as practiced by Socrates, is extremely problematic from the city’s perspective, and must be radically transformed if it is to be coetaneous with political life. In “Laws”, Plato presents use with a political philosopher who appears to actually succeed in this endeavour. The Athenian Stranger, as a character-type representative of the genuine philosopher, is noticeably different from Socrates. He is able to present himself, not merely as a theoretician or conceptual idealist, but a man with keen insight into the practical world of political institutions and legal practice. What changes would “philosophy” or the “philosopher” have to undergo in order to be made civic-minded or, atleast, legally permissible? Would these be antithetical to the core of Socratic political philosophy, properly understood? This essay seeks to shed light on the prior questions through an analysis of key differences in the character and rhetorical approach or “action” of Socrates and the Athenian Stranger in either dialogue.
Autonomous Upper Stage Guidance with Robust Splash-Down Constraint
Creators: name: Benedikter, Boris
name: Zavoli, Alessandro
name: Colasurdo, Guido
name: Pizzurro, Simone
name: Cavallini, Enrico
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics

description: This paper presents a novel algorithm, based on model predictive control (MPC), for the optimal guidance of a launch vehicle upper stage. The proposed strategy not only maximizes the performance of the vehicle and its robustness to external disturbances, but also robustly enforces the splash-down constraint. Indeed, uncertainty on the engine performance, and in particular on the burn time, could lead to a large footprint of possible impact points, which may pose a concern if the reentry points are close to inhabited regions. Thus, the proposed guidance strategy incorporates a neutral axis maneuver (NAM) that minimizes the sensitivity of the impact point to uncertain engine performance. Unlike traditional methods to design a NAM, which are particularly burdensome and require long validation and verification tasks, the presented MPC algorithm autonomously determines the neutral axis direction by repeatedly solving an optimal control problem (OCP) with two return phases, a nominal and a perturbed one, constrained to the same splash-down point. The OCP is transcribed as a sequence of convex problems that quickly converges to the optimal solution, thus allowing for high MPC update frequencies. Numerical results assess the robustness and performance of the proposed algorithm via extensive Monte Carlo campaigns.
description: arXiv admin note: text overlap with arXiv:2210.14610
title: Τροφοδοσία αιθανόλης ή φυσικού αερίου σε σύστημα παραγωγής ισχύος με χρήση κυψελών καυσίμου SOFC : εξεργειακή ανάλυση και βελτιστοποίηση
titleType: AlternativeTitle
Creators: name: Ανδρεάδης, Γεώργιος
Publisher: name: University of Thessaly
Year: 2008
Subjects: subject: ΚΕΛΙΑ ΚΑΥΣΙΜΩΝ
subject: ΚΕΛΙΑ ΚΑΥΣΙΜΩΝ ΣΤΕΡΕΩΝ ΟΞΕΙΔΙΩΝ

description: Στην παρούσα μεταπτυχιακή εργασία πραγματοποιείται η εξεργειακή ανάλυση και βελτιστοποίηση ενός συστήματος παραγωγής ισχύος με χρήση κυψελών καυσίμου στερεού οξειδίου (SOFC) και τροφοδοσία δύο καυσίμων, της αιθανόλης και του φυσικού αερίου. Συγκεκριμένα, στο Κεφάλαιο 1 γίνεται σύντομη εισαγωγή σε περιβαλλοντικά θέματα, στην οικονομία του υδρογόνου και την ανάγκη χρήσης νέων εναλλακτικών συστημάτων μετατροπής ενέργειας, φιλικότερων προς το περιβάλλον, όπως των κυψελών καυσίμου. Στο Κεφάλαιο 2 πραγματοποιείται η ταξινόμηση των κυψελών καυσίμου ανάλογα με το είδος του ηλεκτρολύτη τους και τα χαρακτηριστικά λειτουργίας τους, ενώ παρατίθενται τα πλεονεκτήματα και τα μειονεκτήματα τους. Επιπλέον, γίνεται σύντομη αναφορά στην παρούσα ανάπτυξη και τις εφαρμογές τους. Η εξεργειακή ανάλυση και βελτιστοποίηση του συστήματος επιτυγχάνεται βάσει των δύο νόμων της θερμοδυναμικής. Έτσι, στο Κεφάλαιο 3, παρουσιάζεται λεπτομερώς, το θεωρητικό υπόβαθρο που είναι απαραίτητο για την επιτέλεση της παρούσας εργασίας. Αναλυτικότερα, παρατίθενται οι δύο νόμοι και οι ορισμοί τους, καταγράφονται τα ισοζύγια εντροπίας και εξέργειας καθώς και οι σχέσεις υπολογισμού της απόδοσης λειτουργίας διάφορων υπομονάδων που απαρτίζουν το σύστημα παραγωγής ισχύος. Τέλος, πραγματοποιείται λεπτομερής προσέγγιση της θερμοδυναμικής των κυψελών καυσίμου. Στο Κεφάλαιο 4, περιγράφεται η εξεργειακή ανάλυση και βελτιστοποίηση του συστήματος παραγωγής ισχύος με χρήση κυψελών καυσίμου SOFC με τροφοδοσία αιθανόλης ή φυσικού αερίου. Αρχικά περιγράφεται το σύστημα και η τοπολογία του. Στη συνέχεια, παρουσιάζεται λεπτομερώς η διαδικασία που πρέπει να ακολουθηθεί για την ελαχιστοποίηση των ενεργειακών απωλειών του. Οι κυριότερες παράμετροι με βάση τις οποίες πραγματοποιείται η ανάλυση του είναι το εύρος της αναμόρφωσης του καυσίμου, ο συντελεστής αναμόρφωσης του καυσίμου και ο παράγοντας χρήσης του υδρογόνου. Ακολουθεί παρουσίαση των αποτελεσμάτων και σχολιασμός τους, ενώ τέλος, εξετάζονται διάφορες αλλαγές στην τοπολογία του συστήματος με σκοπό την περαιτέρω βελτιστοποίησή του.
Recursive estimation of Systemic Vascular Resistance using measurements from a left ventricular assist device
Creators: name: Pawar, Suraj Rajendra
Publisher: name: The University of Texas at Austin
Year: 2019
Subjects: Estimation
Kalman Filter
Extended Kalman Filter
Bond graphs
Cardiovascular system
Modeling
Impedance analysis
Estimability
LVAD
Left ventricular assist device

description: Cardiovascular disease is the leading cause of deaths worldwide, and one of the ways to treat patients with congestive heart failure is to perform a heart transplant. As the demand for this procedure rises, the disproportionate availability of suitable donors needs to be countered with ways to care and sustain patients who are waiting for a transplant. In this regard, the use of left ventricular assist devices (LVAD) has increased. The research conducted in this Thesis is primarily concerned with the TORVAD [superscript TM] (Windmill Cardiovascular Systems In., Austin , TX), a rotary blood pump type LVAD. The load faced by the left ventricle during ejection of blood is termed as Systemic Vascular Resistance (SVR), and is an important parameter that can indicate cardiovascular health. Abnormalities in SVR have been found to be a good indicator of hypertension, heart failure, shock and sepsis. A consistently low SVR can even be a predictor of mortality. The goal of this Thesis is to investigate ways of recursively estimating SVR in a patient, by using measurements that the TORVAD [superscript TM] provides. The Extended Kalman Filter is used to develop an estimation algorithm based on a reduced order model of the cardiovascular system. The estimation accuracy of the algorithm is tested by generating data through simulations of a computational model of the cardiovascular system, and by collecting measurements from the TORVAD [superscript TM] while it operates in a mock circulation loop. The algorithm is found to estimate SVR satisfactorily using the available measurements, and is robust to different initial conditions.
Metric- and frame-like higher-spin gauge theories in three dimensions
Creators: name: Fredenhagen, Stefan
name: Kessel, Pan
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study the relation between the frame-like and metric-like formulation of higher-spin gauge theories in three space-time dimensions. We concentrate on the theory that is described by an SL(3) x SL(3) Chern-Simons theory in the frame-like formulation. The metric-like theory is obtained by eliminating the generalised spin connection by its equation of motion, and by expressing everything in terms of the metric and a spin-3 Fronsdal field. We give an exact map between fields and gauge parameters in both formulations. To work out the gauge transformations explicitly in terms of metric-like variables, we have to make a perturbative expansion in the spin-3 field. We describe an algorithm how to do this systematically, and we work out the gauge transformations to cubic order in the spin-3 field. We use these results to determine the gauge algebra to this order, and explain why the commutator of two spin-3 transformations only closes on-shell.
description: 26 pages, no figures
Transit assisted emergency evacuation of high density clusters in urban areas : a case study on container terminals
Creators: name: Μαστρογιαννίδου, Χριστίνα
Publisher: name: University of Thessaly
Year: 2009
Subjects: subject: ΚΥΚΛΟΦΟΡΙΑΚΗ ΤΕΧΝΙΚΗ
subject: ΑΣΤΙΚΕΣ ΜΕΤΑΦΟΡΕΣ -- ΑΝΑΠΤΥΣΣΟΜΕΝΕΣ ΧΩΡΕΣ

description: Ο σχεδιασμός της εκκένωσης σε περιπτώσεις εκτάκτων αναγκών είναι ένα κρίσιμο στοιχείο που μπορεί να σώσει ζωές. Σε πολλές περιπτώσεις επικίνδυνων γεγονότων έκτακτης ανάγκης, η καλύτερη επιλογή είναι η μετεγκατάσταση των απειλούμενων πληθυσμών σε ασφαλέστερες περιοχές χρησιμοποιώντας τα μέσα μαζικής μεταφοράς. Η αποτελεσματική αντιμετώπιση των φυσικών και ανθρωπογενών καταστροφών απαιτεί γρήγορη και καλά οργανωμένη προσπάθεια, η οποία εξαρτάται σε μεγάλο βαθμό όχι μόνο από τον ενεργό, προληπτικό σχεδίασμά αντιμετώπισης αλλά και από τη δυνατότητα ορθών αποφάσεων οι οποίες πρέπει να ληφθούν κατά τη διάρκεια των γεγονότων. Οι υπάρχουσες προσεγγίσεις για την αντιμετώπιση θεμάτων εκκένωσης βασίζονται κατά κύριο λόγο στον ενεργό, προληπτικό σχεδίασμά. Ωστόσο, η κίνηση που παρατηρείται σε κάποιο οδικό δίκτυο, παρουσιάζει περισσότερες προκλήσεις, λόγω της δυναμικής δομής και των χαρακτηριστικών του δικτύου, καθιστώντας τον προληπτικό σχεδίασμά λιγότερο αποτελεσματικό για την προστασία των εκκενωθέντων. Σε αυτή τη μεταπτυχιακή εργασία παρουσιάζουμε την εκκένωση περιοχών μεγάλης πληθυσμιακής κάλυψης με τη βοήθεια των μέσων μαζικής μεταφοράς με τη χρήση ενός μοντέλου δυναμικού δικτύου. Ο απώτερος στόχος είναι να παρουσιάσουμε ολοκληρωμένες λύσεις που συνδυάζουν τα πιο εξελιγμένα πακέτα προσομοίωσης της κυκλοφορίας με μοντέλα βελτιστοποίησης εκκένωσης περιοχών μεγάλης πληθυσμιακής κάλυψης, για να αποδείξουμε τη χρησιμότητα των μέσων μαζικής μεταφοράς στην εκκένωση πληθυσμών υπό διάφορες συνθήκες. Αρχικά, παρουσιάζουμε μία μικρή εισαγωγή στο πρόβλημα προς επίλυση καθώς και τους λόγους που μας οδήγησαν στη μελέτη και επίλυση του συγκεκριμένου προβλήματος. Στη συνέχεια παρουσιάζουμε τη βιβλιογραφική ανασκόπηση, τα δυναμικά χαρακτηριστικά που συνοδεύουν τις διαδικασίες εκκένωσης καθώς και τα πακέτα προσομοίωσης που υπάρχουν διαθέσιμα. Στο τρίτο κεφάλαιο, παρουσιάζεται αναλυτικά το πρόβλημα προς επίλυση και αναπτύσσεται η μέθοδος, η οποία βασίζεται στη θεωρία του ακέραιου προγραμματισμού. Η υλοποίηση και η επίλυση του προβλήματος γίνονται με τη βοήθεια της γλώσσας μαθηματικού προγραμματισμού AMPL. Επίσης, παρουσιάζεται η πιλοτική εφαρμογή σε εμπορικούς λιμένες. Στο τέταρτο κεφάλαιο παρουσιάζονται τα αποτελέσματα και τα συμπεράσματα που προκύπτουν από τη χρήση της μεθόδου. Τα αποτελέσματα δείχνουν ότι η μέθοδος λειτουργεί σωστά και αποτελεσματικά, παρέχει τη βέλτιστη λύση και επομένως είναι δυνατή η μελλοντική εφαρμογή της από τους υπευθύνους διαχείρισης καταστάσεων έκτακτης ανάγκης, έτσι ώστε να καθίσταται γρηγορότερη η εκκένωση πληθυσμών σε περιπτώσεις καταστροφών. Τέλος, στο πέμπτο κεφάλαιο παρουσιάζονται τα συνολικά συμπεράσματα της παρούσης δουλειάς καθώς και κάποιες κατευθύνσεις για μελλοντική έρευνα.
Development of a Cooperative Localization System using a UWB Network and BLE Technology
Creators: name: Brunacci, Valerio
name: De Angelis, Alessio
name: Costante, Gabriele
Publisher: name: arXiv
Year: 2022
Subjects: subject: Robotics (cs.RO)
subject: Systems and Control (eess.SY)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: This paper presents the development of a system able to estimate the 2D relative position of nodes in a wireless network, based on distance measurements between the nodes. The system uses ultra wide band ranging technology and the Bluetooth Low Energy protocol to acquire data. Furthermore, a nonlinear least squares problem is formulated and solved numerically for estimating the relative positions of the nodes. The localization performance of the system is validated by experimental tests, demonstrating the capability of measuring the relative position of a network comprised of 4 nodes with an accuracy of the order of 3 cm and an update rate of 10 Hz. This shows the feasibility of applying the proposed system for multi-robot cooperative localization and formation control scenarios.
description: 6 pages, 12 figures, 2022 IEEE International Symposium on Measurements & Networking (M&N)
Categorical Semantics for Functional Reactive Programming with Temporal Recursion and Corecursion
Creators: name: Jeltsch, Wolfgang
Publisher: name: arXiv
Year: 2014
Subjects: subject: Programming Languages (cs.PL)
subject: Logic in Computer Science (cs.LO)
subject: FOS: Computer and information sciences
subject: F.3.2; D.1.1; F.4.1

description: Functional reactive programming (FRP) makes it possible to express temporal aspects of computations in a declarative way. Recently we developed two kinds of categorical models of FRP: abstract process categories (APCs) and concrete process categories (CPCs). Furthermore we showed that APCs generalize CPCs. In this paper, we extend APCs with additional structure. This structure models recursion and corecursion operators that are related to time. We show that the resulting categorical models generalize those CPCs that impose an additional constraint on time scales. This constraint boils down to ruling out $ω$-supertasks, which are closely related to Zeno's paradox of Achilles and the tortoise.
description: In Proceedings MSFP 2014, arXiv:1406.1534
Numerical study of a stochastic weighted particle method for a model kinetic equation
Creators: name: Rjasanow, Sergej
name: Wagner, Wolfgang
Publisher: name: Weierstrass Institute
Year: 1996
Subjects: subject: nonlinear integral equations
subject: nonlinear kinetic equations
subject: stochastic weighted particle method
subject: Boltzmann equation
subject: 65C05
subject: 76P05
subject: 82C80

description: A stochastic weighted particle method is applied to a model nonlinear kinetic equation. A detailed study of various numerical approximations is presented. The main effect achieved by the new method is an artificial increase of the relative number of simulation particles with prescribed velocities.
On an information-type inequality for the Hellinger process
Creators: name: Gushchin, Alexander A.
Publisher: name: Weierstrass Institute
Year: 1996
Subjects: subject: semimartingale
subject: Hellinger process
subject: Cramér-Rao inequality
subject: linear regression
subject: 60G07
subject: 60G48

description: Let (Ω,퓕,픽) be a filtered space with two probability measures P and P' on (Ω,퓕). Let X be a d-dimensional locally square-integrable semimartingale relative to P and P' with the canonical decomposition X = X0 + M + A and X = X0 + M' + A' respectively. We give a lower bound for the Hellinger process h(1⁄2; P, P') of order 1/2 between P and P' in terms of A, A' and the quadratic characteristic of M and M'. This result implies simple sufficient conditions for the entire separation of measures in a linear regression model with martingale errors.
Comparing Simple Quasar Demographics Models
Creators: name: Veale, Melanie
name: White, Martin
name: Conroy, Charlie
Publisher: name: arXiv
Year: 2014
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: This paper explores several simple model variations for the connections among quasars, galaxies, and dark matter halos for redshifts 1 < z < 6. A key component of these models is that we enforce a self-consistent black hole (BH) history by tracking both BH mass and BH growth rate at all redshifts. We connect objects across redshift with a simple constant-number-density procedure, and choose a fiducial model with a relationship between BH and galaxy growth rates that is linear and evolves in a simple way with redshift. Within this fiducial model, we find the quasar luminosity function (QLF) by calculating an "intrinsic" luminosity based on either the BH mass or BH growth rate, and then choosing a model of quasar variability with either a lognormal or truncated power-law distribution of instantaneous luminosities. This gives four model variations, which we fit to the observed QLF at each redshift. With the best-fit models in hand, we undertake a detailed comparison of the four fiducial models, and explore changes to our fiducial model of the BH-galaxy relationship. Each model variation can successfully fit the observed QLF, the shape of which is generally set by the "intrinsic" luminosity at the faint end and by the scatter due to variability at the bright end. We focus on accounting for the reasons that physically different models can make such similar predictions, and on identifying what observational data or physical arguments are most essential in breaking the degeneracies among models.
description: 14 pages, 8 figures, 1 table