cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
State Estimation in Lithium-ion Batteries Using Pulse Perturbation and Feedforward Neural Networks
Creators: name: Li, Alan Gen
Publisher: name: Columbia University
Year: 2020
Subjects: Electrical engineering
Lithium ion batteries
Battery management systems
Neural networks (Computer science)--Industrial applications
Pulse techniques (Electronics)

description: Predicting battery stored charge, available capacity, and peak power quickly and accurately is important for understanding pack performance and stability. It is proposed that a feedforward neural network (FNN) can estimate this information using cell voltage response to an injected current. Voltage response varies with the internal chemistry, represented by charge, capacity, and impedance. These characteristics are quantified here using state of charge (SoC), state of energy (SoE), and state of power (SoP). Cell response data is collected for various states at constant temperature, resulting in 234 unique voltage responses for training and evaluating the FNN. Training is performed using 3 distinct variations on the data: (1) the full voltage response, (2) individual portions of the response, such as charging or relaxation periods, and (3) fractions of the charge and discharge periods ranging from one-half to a single open-circuit voltage measurement. Using the full response, the average mean absolute error (MAE) is 0.0057 for SoE estimation. The average MAE is below 0.0080 for SoC and SoP estimation. The results for pulse portions show that Charge-rest or Discharge-rest responses perform almost as well as the full pulse. This may inform future pulse design for further optimization. The results for pulse fractions show that error increases as the amount of input data decreases, which validates the hypothesis that pulse perturbation yields high performance in FNN. The technique can be expanded to other temperatures, with potential for estimation of other states, and even degradation mechanisms. Estimation requires 3 minutes of voltage and current data, with no charging history needed and low computational complexity. The proposed method is thus suitable for development of advanced battery management systems in electric vehicles.
Entanglement measure using Wigner function: case of generalized vortex state formed by multiphoton subtraction
Creators: name: Banerji, Anindya
name: Singh, Ravindra P.
name: Bandyopadhyay, Abir
Publisher: name: arXiv
Year: 2013
Subjects: subject: Quantum Physics (quant-ph)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The negativity of the Wigner function is discussed as a measure of the non classicality and the quantum interference pattern obtained therein as a possible measure of the entanglement between the two modes of the vortex states. This measure of entanglement is compared with the results obtained from concurrence.
description: 7 pages, revtex4, 19 figures. Final version
Exact and many-body perturbation solutions of the Hubbard model applied to linear chains
Creators: name: Honet, Antoine
name: Henrard, Luc
name: Meunier, Vincent
Publisher: name: arXiv
Year: 2021
Subjects: subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: This study examines how the GW approximation, one of the techniques covered by Green's functions and on many-body approximations (GFMBA), fares compared to the treatment of the Hubbard model solved using an exact diagonalization (ED) approach. We show that, for small linear chains, the GW approximation corrects the usual mean-field (MF) approach by reducing the total energy as well as the magnetization from the MF approximation. The energy gap shows also a better agreement with ED, especially in even-number of atoms systems where no plateau is observed below the predicted phase transition as in MF approximation. In terms of density of states, the GW approximation induces quasi-particles and side satellites peaks via a splitting process of MF peaks. At the same time, GW slightly changes the localization (e.g., edges or center) of the states. We also extend to GW approximation the Löwdin's symmetry dilemma and show that GW predicts a paramagnetic-antiferromagnetic phase transition at a higher Hubbard parameter than MF.
Alfred Schäfer, Tempel und Kult in Sarmizegetusa. Eine Untersuchung zur Formierung religiöser Gemeinschaften in der Metropolis Dakiens
Creators: name: Eingartner, Johannes
Publisher: name: Bonner Jahrbücher
Year: 2017

description: Rezension zu: Alfred Schäfer, Tempel und Kult in Sarmizegetusa. Eine Untersuchung zur Formierung religiöser Gemeinschaften in der Metropolis Dakiens. Verlag Scriptorium, Marsberg-Padberg 2007. VI und 405 Seiten mit 49 Abbildungen, 96 Tafeln
description: Bonner Jahrbücher, Bd. 209.2009(2011): Bonner Jahrbücher
Constraints on single-field inflation with WMAP, SPT and ACT data -- A last-minute stand before Planck
Creators: name: Cheng, Cheng
name: Huang, Qing-Guo
name: Ma, Yin-Zhe
Publisher: name: arXiv
Year: 2013
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We constrain models of single field inflation with the pre-\textit{Planck} CMB data. The data used here is the 9-year Wilkinson Microwave Anisotropy Probe (\textit{WMAP}) data, South Pole Telescope (SPT) data and Atacama Cosmology Telescope (ACT) data. By adding in running of spectral index parameter, we find that the $χ^2$ is improved by a factor of $Δχ^2=8.44$, which strongly indicates the preference of this parameter from current data. In addition, we find that the running of spectral index $α_s$ does not change very much even if we switch to different pivot scales, which suggests that the power law expansion of power spectrum is accurate enough till the 1st order term. Furthermore, we find that the joint constraints on $r-n_{s}$ give very tight constraints on single-field inflation models, and the models with power law potential $ϕ^{p}$ can only survive if $0.9 \lesssim p \lesssim 2.1$, so a large class of inflation models have already been ruled out before \textit{Planck} data. Finally, we use the $f_{NL}$ data to constrain the non-trivial sound speed $c_s$. We find that the current constraint is dominated by the power spectrum constraints which have some inconsistency with the constraints from $f_{NL}$. This poses important questions of consistency between power spectrum and bispectrum of \textit{WMAP} data.
description: 13 pages, 9 figures, 2 tables; version accepted for publication in JCAP
Reexamination of Early Lunar Chronology With GRAIL Data: Terranes, Basins, and Impact Fluxes
Creators: name: Evans, Alexander J.
name: Andrews-Hanna, Jeffrey C.
name: Head, James W.
name: Soderblom, Jason M.
name: Solomon, Sean C.
name: Zuber, Maria T.
Publisher: name: Columbia University
Year: 2018
Subjects: subject: Moon
subject: Lunar geology
subject: Geochemistry
subject: FOS: Earth and related environmental sciences
subject: Impact craters

description: Flooding of the lunar surface by ancient mare basalts has rendered uncertain the ages of lunar geochemical terranes and several impact basins. Here we combine craters having recognizable surface expressions with craters identified only by their gravitational signatures in Gravity Recovery and Interior Laboratory data to reassess the chronological sequence of lunar impact basins and the ages of major lunar geochemical terranes. Our results indicate that although volcanically flooded regions are deficient in craters with diameters greater than 20 km by more than 50% relative to unflooded regions, craters with diameters greater than 90 km can be readily recognized either by topography or by gravity anomaly. On the basis of the areal density of craters with diameters greater than 90 km we conclude that (1) the Serenitatis basin could be as young as the Imbrium basin; (2) the areal density of craters within the Procellarum KREEP Terrane is significantly lower than that for the South Pole‐Aitken basin and the Feldspathic Highlands Terrane; (3) if the youngest age of final crystallization of the lunar magma ocean is adopted as a lower bound on the age of the Procellarum KREEP Terrane, a minimum age of approximately 4.3 Ga is inferred for ~40% of lunar impact basins, including South Pole‐Aitken; and (4) the flux of impactors capable of forming craters with diameters of at least 90 km decreased substantially through the Nectarian and Imbrian periods.
Display Location and Customer Service in Retail Produce Departments
Creators: name: Anderson, Dale L.
name: Shaffer, Paul F.
name: Anderson, Dale L.
name: Shaffer, Paul F.
Publisher: name: Unknown
Year: 1961
Subjects: subject: Labor and Human Capital
subject: Marketing
subject: FOS: Economics and business
subject: Research and Development/Tech Change/Emerging Technologies

description: Excerpts from the report: The layout of the produce display areas in retail food stores and the procedures for weighing and price-marking produce may have significant effects on operating costs and sales volume. The retail produce department constitutes from 8 to 12 percent of the dollar sales of retail supermarkets and operates with a gross profit of approximately 25 percent. The objectives of the study on which this report is based were: (1) To measure the effectiveness of different layouts of the produce display area and to develop improvements; (2) to evaluate different types and locations of customer service stations and to develop improved methods for them; and (3) to evaluate produce weighing as performed at different types of checkout counters.
title: Exploring the potential benefits of inflation overshooting
Creators: name: Amano, Robert
name: Gosselin, Marc-André
name: See, Kurt
Publisher: name: Bank of Canada
Year: 2021

description: After a period with the interest rate at the effective lower bound, temporarily overshooting inflation may offer important economic benefits. This may be especially true for vulnerable segments of the population, such as workers with low attachment to the labour force and the long-term unemployed.

description: Après une période où le taux directeur est à sa valeur plancher, le dépassement temporaire de la cible d’inflation peut procurer d’importants avantages économiques. Cela peut être particulièrement vrai pour les segments vulnérables de la population, tels que les travailleurs qui ont de faibles liens avec le marché du travail et les chômeurs de longue durée.
Fermionization of two-component few-fermion systems in a one-dimensional harmonic trap
Creators: name: Lindgren, E. J.
name: Rotureau, J.
name: Forssén, C.
name: Volosniev, A. G.
name: Zinner, N. T.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Quantum Gases (cond-mat.quant-gas)
subject: Nuclear Theory (nucl-th)
subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The nature of strongly interacting Fermi gases and magnetism is one of the most important and studied topics in condensed-matter physics. Still, there are many open questions. A central issue is under what circumstances strong short-range repulsive interactions are enough to drive magnetic correlations. Recent progress in the field of cold atomic gases allows to address this question in very clean systems where both particle numbers, interactions and dimensionality can be tuned. Here we study fermionic few-body systems in a one dimensional harmonic trap using a new rapidly converging effective-interaction technique, plus a novel analytical approach. This allows us to calculate the properties of a single spin-down atom interacting with a number of spin-up particles, a case of much recent experimental interest. Our findings indicate that, in the strongly interacting limit, spin-up and spin-down particles want to separate in the trap, which we interpret as a microscopic precursor of one-dimensional ferromagnetism in imbalanced systems. Our predictions are directly addressable in current experiments on ultracold atomic few-body systems.
description: 12 pages, 6 figures, published version including two appendices on our new numerical and analytical approach
title: Συρραπτικός περίπατος, ανάγνωση της αστικής διαστραμάτωση του Γαλεριακού συγκροτήματος
Creators: name: Περδοφορίδου Άννα
Publisher: name: Technical University of Crete
Year: 2011

description: Μη διαθέσιμο
Logarithmic Conformal Field Theory: Beyond an Introduction
Creators: name: Creutzig, Thomas
name: Ridout, David
Publisher: name: arXiv
Year: 2013
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: This article aims to review a selection of central topics and examples in logarithmic conformal field theory. It begins with a pure Virasoro example, critical percolation, then continues with a detailed exposition of symplectic fermions, the fractional level WZW model on SL(2;R) at level -1/2 and the WZW model on the Lie supergroup GL(1|1). It concludes with a general discussion of the so-called staggered modules that give these theories their logarithmic structure, before outlining a proposed strategy to understand more general logarithmic conformal field theories. Throughout, the emphasis is on continuum methods and their generalisation from the familiar rational case. In particular, the modular properties of the characters of the spectrum play a central role and Verlinde formulae are evaluated with the results compared to the known fusion rules. Moreover, bulk modular invariants are constructed, the structures of the corresponding bulk state spaces are elucidated, and a formalism for computing correlation functions is discussed.
description: Invited review by J Phys A for a special issue on LCFT; v2 updated references; v3 fixed a few minor typos
title: Νέα Εθνική Βιβλιοθήκη στην Αθήνα
Creators: name: Δασκαλάκης Γεώργιος
name: Μπουργανού Αλεξάνδρα
Publisher: name: Technical University of Crete
Year: 2011

description: Μη διαθέσιμο
Symmetry protected entanglement in random mixed states
Creators: name: Hejazi, Kasra
name: Shapourian, Hassan
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: Symmetry is an important property of quantum mechanical systems which may dramatically influence their behavior in and out of equilibrium. In this paper, we study the effect of symmetry on tripartite entanglement properties of typical states in symmetric sectors of Hilbert space. In particular, we consider Abelian symmetries and derive an explicit expression for the logarithmic entanglement negativity of systems with $\mathbb{Z}_N$ and $U(1)$ symmetry groups. To this end, we develop a diagrammatic method to incorporate partial transpose within the random matrix theory of symmetric states and formulate a perturbation theory in the inverse of the Hilbert space dimension. We further present entanglement phase diagrams as the subsystem sizes are varied and show that there are qualitative differences between systems with and without symmetries. We also design a quantum circuit to simulate our setup.
title: Ανάπτυξη συστήματος MPPT για φωτοβολταϊκούς μετατροπείς DC/DC ανύψωσης τάσης
title: Development of an MPPT system for photovoltaic DC/DC step-up converters
Creators: name: Γεωργιαδης Βασιλειος
Publisher: name: Technical University of Crete
Year: 2018

description: Αντικείμενο αυτής της διπλωματικής εργασίας ήταν η ανάπτυξη ενός ηλεκτρονικού συστήματος διαχείρισης ενέργειας με στόχο τη μεγιστοποίηση της παραγωγής ενέργειας από ένα φωτοβολταϊκό σύστημα. Το σύστημα διαχείρισης ενέργειας αποτελείται από έναν ηλεκτρονικό μετατροπέα DC/DC ανύψωσης τάσης, έναν μικροελεγκτή και τους απαραίτητους αισθητήρες. Σκοπός του συστήματος αυτού είναι, μέσω κατάλληλου ελέγχου του ηλεκτρονικού μετατροπέα ισχύος, η φωτοβολταϊκή συστοιχία να λειτουργεί στο σημείο μέγιστης παραγωγής ισχύος και, ταυτόχρονα, να μεγιστοποιείται σε πραγματικό χρόνο ο βαθμός απόδοσης του μετατροπέα DC/DC. Επιπλέον, το σύστημα που υλοποιήθηκε αντιμετωπίζει το πρόβλημα της μερικής σκίασης και μπορεί να λειτουργεί αποτελεσματικά τόσο σε ομοιόμορφη όσο και σε ανομοιόμορφη πρόσπτωση ηλιακής ακτινοβολίας στην φωτοβολταϊκή συστοιχία. Για τον κατάλληλο έλεγχο του μετατροπέα DC/DC υλοποιήθηκαν 4 εναλλακτικοί αλγόριθμοι και αξιολογήθηκε πειραματικά η απόδοσης τους σε πραγματικές συνθήκες λειτουργίας ενός φωτοβολταϊκού συστήματος. Οι αλγόριθμοι αυτοί ελέγχουν τη λειτουργία του μετατροπέα DC/DC και έχουν ως στόχο τη μεγιστοποίηση της παραγόμενης ισχύος τόσο στην είσοδο όσο και στην έξοδο του μετατροπέα DC/DC. Τα πειραματικά αποτελέσματα έδειξαν ότι το σύστημα της εργασίας αυτής αυξάνει σημαντικά την ισχύ που μεταφέρεται από τη φωτοβολταϊκή συστοιχία στην έξοδο του μετατροπέα DC/DC.
title: A recommendation system for personalized reviews in Apache Spark
title: Ένα σύστημα παροχής συστάσεων για εξατομικευμένες κριτικές στο Apache Spark
Creators: name: Μαριολου Νεκταρια
Publisher: name: Technical University of Crete
Year: 2018

description: Τα συστήματα παροχής εξατομικευμένων συστάσεων παίζουν ολοένα και αυξανόμενα καθοριστικό ρόλο στη διαδικασία λήψης αποφάσεων του πελάτη. Οι διάφορες ιστοσελίδες ηλεκρονικού εμπορίου διαφέρουν ως προς τους στόχους,τις λειτουργίες και τα χαρακτηριστικά τους αλλά ο πρωταρχικός στόχος τους είναι να εντοπίσουν αποτελεσματικά την απόφαση του χρήστη. Η πιο συχνή προσέγγιση είναι η επιλογή των κριτικών με το μεγαλύτερο ποσοστό χρησιμότητας που έχει προκύψει από τους ψήφους των χρηστών που τις έχουν ήδη διαβάσει. Έτσι, καταλήγουν με μια επιλογή η οποία πηγάζει από ένα περιορισμένο εύρος κριτιρίων. Σε αυτή την εργασία, επικεντρωνόμαστε στην ανάκτηση ενός υποσυνόλου κριτικών, χρησιμοποιώντας εξατομικευμένα κριτήρια. Προκειμένου να καθορίσουμε το ποιο σύνολο κριτικών μπορεί να αντιστοιχεί σε μεμονωμένους χρήστες, επικεντρωνόμαστε στη σημασία των πτυχών του κάθε προιόντος για τον κάθε χρήστη. Το σύστημα μας είναι χτισμένο στο Apache Spark, επιτρέποντας την επεξεργασία των κριτικών, το αξιολογούμε με δεδομένα από το Amazon και τα δεδομένα ευρετηριάζονται στην κατανεμημένη μηχανή αναζήτησης, Elasticsearch.
description: Personalized recommendation systems play an increasingly growing role in customer's decision making process. The various e-commerce sites differ in their objectives, functions and characteristics but their common primary goal is to identify efficiently user decision. The most frequent approach is the selection of the reviews with the highest percentage of helpfulness' votes by users who have read the reviews. Thus, they end up with a selection derived from a limited scope of criteria. In this work, we focus on retrieving a subset of reviews, using personalized criteria. In order to determine which set of reviews may correspond to individual users' preferences, we focus on the importance of product aspects for each user. Our system is built on Apache Spark enabling the processing of reviews, we evaluate it with a dataset from Amazon and the results are indexed in the distributed search engine, Elasticsearch
Imaging Mercury's polar deposits during MESSENGER's low‐altitude campaign
Creators: name: Chabot, Nancy L.
name: Ernst, Carolyn M.
name: Paige, David A.
name: Nair, Hari
name: Denevi, Brett W.
name: Blewett, David T.
name: Murchie, Scott L.
name: Deutsch, Ariel N.
name: Head, James W.
name: Solomon, Sean C.
Publisher: name: Columbia University
Year: 2016
Subjects: Planetary science
Planets--Observations

description: Images obtained during the low‐altitude campaign in the final year of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission provide the highest‐spatial‐resolution views of Mercury's polar deposits. Images for distinct areas of permanent shadow within 35 north polar craters were successfully captured during the campaign. All of these regions of permanent shadow were found to have low‐reflectance surfaces with well‐defined boundaries. Additionally, brightness variations across the deposits correlate with variations in the biannual maximum surface temperature across the permanently shadowed regions, supporting the conclusion that multiple volatile organic compounds are contained in Mercury's polar deposits, in addition to water ice. A recent large impact event or ongoing bombardment by micrometeoroids could deliver water as well as many volatile organic compounds to Mercury. Either scenario is consistent with the distinctive reflectance properties and well‐defined boundaries of Mercury's polar deposits and the presence of volatiles in all available cold traps.
Magnetic moments of the hidden-charm strange pentaquark states
Creators: name: Gao, Feng
name: Li, Hao-Song
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: This paper calculates the magnetic moments of the hidden-charm strange pentaquark states with a quantum number of $J^P={\frac{1}{2}}^{\pm}$, ${\frac{3}{2}}^{\pm}$, ${\frac{5}{2}}^{\pm}$, and ${\frac{7}{2}}^{+}$ in the molecular, diquark-diquark-antiquark, and diquark-triquark models, respectively. Numerical results demonstrate that the magnetic moments change for a different spin-orbit coupling with the same model and when involving different models with the same angular momentum.
title: ΑΜRules for fraud detection with Spark Streaming
title: ΑΜRules για ανίχνευση απάτης με Spark Streaming
Creators: name: Φραγκιαδουλακης Εμμανουηλ
Publisher: name: Technical University of Crete
Year: 2018

description: In this day and age, an important part of our daily interaction with our electronic devices is on-line payments, which results in a great amount of transactions. In order to handle these transactions, to determine if they're fraudulent, we need an efficient, distributed and streamable machine learning algorithm, that can process big amount of incoming data and react to it instantly. Thus, we implemented the distributed Adaptive Model Rules on Spark Streaming, an extension of the Spark Core API which enables the development of scalable, fault-tolerant streaming applications. Adaptive Model Rules is an one-pass algorithm for training its model from streaming data and is robust to outliers and irrelevant features. The experimental results concluded, that there is a noticeable speedup from Vertical Adaptive Model Rules to Hybrid Adaptive Model Rules at the cost of reduced accuracy.
description: Στις μέρες μας, ένα σημαντικό κομμάτι της καθημερινότητας μας όσον αφορά τις ηλεκτρονικές μας συσκευές είναι οι online πληρωμές, το οποίο έχει ως αποτέλεσμα πληθώρα συναλλαγών. Με σκοπό να διαχειριστούμε αυτές τις συναλλαγές, για να καθορίσουμε αν είναι απάτη, χρειαζόμαστε έναν αποτελεσματικό, κατανεμημένο και streamable αλγόριθμο μηχανικής μάθησης, όπου να μπορεί να διαχειριστεί μεγάλη μέγεθος εισερχόμενων δεδομένων και να αντιδρά σε αυτά άμεσα. Έτσι, υλοποιήσαμε τον κατανεμημένο Adaptive Model Rules στο Spark Streaming, μία επέκταση του Spark Core API, που επιτρέπει την υλοποίηση scalable, με ανθεκτικότητα σε σφάλματα εφαρμογών streaming. O Αdaptive Model Rules είναι ένας αλγόριθμος ενός περάσματος για την εκπαίδευση του μοντέλου του από ροές δεδομένων και είναι ανθεκτικός σε απότομες αλλαγές και άσχετες ιδιότητες. Τα πειραματικά αποτελέσματα κατέληξαν στο ότι υπάρχει σημαντική αλλαγή στο χρόνο από τον κάθετο Adaptive Model Rules στο υβριδικό Αdaptive Model Rules, το οποίο έχει ως κόστος την μείωση της ακρίβειας.
title: Smart spectral imaging for material identification
title: Έξυπνη φασματική απεικόνιση για αναγνώριση υλικών
Creators: name: Βασταρουχα Στεργιανη
Publisher: name: Technical University of Crete
Year: 2018

description: Hyperspectral Imaging is a powerful analytical tool that enables the acquisition of a series of images in narrow spectral bands. This technique makes it possible to extract both spatial and spectral information about the scene under investigation. Therefore, it is widely used for nondestructive and non-invasive analysis in a variety of fields, ranging from food quality assessment to biomedical applications. Material Identification is the key to all these applications, which is achieved by using a library of spectral signatures of materials of interest and Spectral Similarity Measurements. Finding the right Spectral Similarity Measure is an important step and many studies have been conducted for their evaluation in terms of accuracy. However, in these studies the evaluation is made using members of the libraries (labeled data) and time performance is never assessed. This study proposes a series of steps that should be followed in Spectral Similarity Measures evaluation, including both labeled and unlabeled data for comparison. More specifically, reflectance measurements of various materials were gathered from online public spectral libraries to construct a database of spectral signatures. Furthermore, a series of Spectral Similarity algorithms were implemented and tested for their speed and accuracy. The accuracy of the algorithms has been assessed on the basis of their ability to produce a right match when an unknown spectrum is compared against the reference spectra of the database. The Spectral Similarity algorithms tested in this study are: a) SAM, b) ED, c) SID, d) SCA, e) SGA, f) SID-SAM, g) SID-SCA, h) AWN, i) SSS, j) NS3, k) SSD and l) SPM. Finally, hyperspectral measurements of skin lesions have been used as a test case for the final evaluation of the implemented comparison methods. The combination of a spectral database of references with the right Spectral Similarity algorithms can provide a valuable tool for material identification, with applications in a variety of scientific and industrial fields.
title: Σχεδίαση φωτοβολταϊκών συστημάτων ενσωματωμένων σε κτίρια
title: Design of building-integrated photovoltaic systems
Creators: name: Γιαννοπουλος Ασημακης
Publisher: name: Technical University of Crete
Year: 2018

description: Σημαντική εφαρμογή της φωτοβολταϊκής τεχνολογίας αποτελεί η ενσωμάτωση φωτοβολταϊκών συστημάτων σε κτίρια (Building-integrated photovoltaics – BIPVs), καθώς συμβάλλει στη δημιουργία κτιρίων “σχεδόν μηδενικής κατανάλωσης ενέργειας” (Nearly zero‑energy buildings - NZEBs). Σε αυτά τα συστήματα, η αξιοποίηση της διαθέσιμης ηλιακής ενέργειας μπορεί να πραγματοποιηθεί με τοποθέτηση φωτοβολταϊκών πλαισίων τόσο σε στέγες, όσο και σε άλλες διαθέσιμες επιφάνειες των κτιρίων όπως προσόψεις, παράθυρα κλπ.

Σκοπός αυτής της διπλωματικής εργασίας ήταν η ανάπτυξη λογισμικού για τον βέλτιστο σχεδιασμό αυτόνομων φωτοβολταϊκών συστημάτων που ενσωματώνονται σε κτίρια. Ο αλγόριθμος που αναπτύχθηκε, υπολογίζει τον βέλτιστο αριθμό και τη βέλτιστη διάταξη των επιμέρους δομικών στοιχείων του φωτοβολταϊκού συστήματος (φωτοβολταϊκά πλαίσια, συσσωρευτές κλπ.) έτσι ώστε να πραγματοποιείται η βέλτιστη αξιοποίηση όλων των διαθέσιμων επιφανειών του κτιρίου. Ταυτόχρονα, εξασφαλίζεται η πλήρης κάλυψη των αναγκών του κτιρίου σε ηλεκτρική ενέργεια και με το ελάχιστο δυνατό οικονομικό κόστος κατά τη διάρκεια του χρόνου ζωής του φωτοβολταϊκού συστήματος.
Compensating the electron beam energy spread by the natural transverse gradient of laser undulator in all-optical x-ray light sources
Creators: name: Zhang, Tong
name: Feng, Chao
name: Deng, Haixiao
name: Wang, Dong
name: Dai, Zhimin
name: Zhao, Zhentang
Publisher: name: arXiv
Year: 2013
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: FOS: Physical sciences

description: All-optical ideas provide a potential to dramatically cut off the size and cost of x-ray light sources to the university-laboratory scale, with the combination of the laser-plasma accelerator and the laser undulator. However, the large longitudinal energy spread of the electron beam from laser-plasma accelerator may hinder the way to high brightness of these all-optical light sources. In this paper, the beam energy spread effect is proposed to be significantly compensated by the natural transverse gradient of a laser undulator when properly transverse-dispersing the electron beam. Theoretical analysis and numerical simulations on conventional laser-Compton scattering sources and high-gain all-optical x-ray free-electron lasers with the electron beams from laser-plasma accelerators are presented.
description: 9 pages, 4 figures
Converting the sub-Jovian desert of exoplanets to a savanna with TESS, PLATO and Ariel
Creators: name: Kálmán, Szilárd
name: Szabó, Gyula M.
name: Borsato, Luca
name: Bódi, Attila
name: Pál, András
name: Szabó, Róbert
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: There is a lack of exoplanets with sizes similar to Neptune orbiting their host stars with periods $\lesssim 3$ days -- hence the name ``sub-Jovian/Neptune desert''. Recently, several exoplanets have been confirmed to reside in the desert transforming it into a ``savanna'' with several ``giraffe'' planets (such as LTT 9779 b and TOI-674 b). The most prominent scenarios put forward for the explanation of the formation of the desert are related to the stellar irradiation destroying the primary atmosphere of certain specific exoplanets. We aim to present three targets (LTT 9779 b, TOI-674 b and WASP-156 b) which, when observed at wide wavelength ranges in infrared (IR), could prove the presence of these processes, and therefore improve the theories of planetary formation/evolution. We simulate and analyse realistic light curves of the selected exoplanets with PLATO/NCAM and the three narrow-band filters of Ariel (VISPhot, FGS1 and FGS2) based on TESS observations of these targets. We improved the precision of the transit parameters of the three considered planets from the TESS data. We find that the combination of the three narrow-band filters of Ariel can yield inner precision of $\lesssim 1.1\%$ for the planetary radii. Data from the three telescopes together will span decades, allowing the monitoring of changes in the planetary atmosphere through radius measurements. The three selected ``giraffe'' planets can be golden targets for Ariel, whereby the loss of planetary mass due to stellar irradiation could be studied with high precision, multi-wavelength (spectro-)photometry.
description: Accepted for publication in MNRAS; 16 pages, 17 figures
An upper mantle seismic discontinuity beneath the Galápagos Archipelago and its implications for studies of the lithosphere‐asthenosphere boundary
Creators: name: Byrnes, Joseph S.
name: Hooft, Emilie E. E.
name: Toomey, Douglas R.
name: Villagómez, Darwin R.
name: Geist, Dennis J.
name: Solomon, Sean C.
Publisher: name: Columbia University
Year: 2015
Subjects: subject: Seismology
subject: Geophysics
subject: FOS: Earth and related environmental sciences
subject: Mantle plumes

description: An upper mantle seismic discontinuity (the Gutenberg or G discontinuity), at which shear wave velocity decreases with depth, has been mapped from S‐to‐p conversions in radial receiver functions recorded across the Galápagos Archipelago. The mean depth of the discontinuity is 91 ± 8 km beneath the southeastern archipelago and 72 ± 5 km beneath surrounding regions. The discontinuity appears deeper beneath the portion of the Nazca plate that we infer passed over the Galápagos mantle plume than elsewhere in the region. We equate the depth of the G discontinuity to the maximum depth extent of anhydrous melting, which forms an overlying layer of dehydrated and depleted mantle. We attribute areas of shallow discontinuity depth to the formation of the dehydrated layer near the Galápagos Spreading Center and areas of greater discontinuity depth to its modification over a mantle plume with an excess temperature of 115 ± 30°C. The G discontinuity lies within a high‐seismic‐velocity anomaly that we conclude forms by partial dehydration and a gradual but steady increase in seismic velocity with decreasing depth after upwelling mantle first encounters the solidus for volatile‐bearing mantle material. At the depth of the solidus for anhydrous mantle material, removal of remaining water creates a sharp decrease in velocity with depth; this discontinuity may also mark a site of melt accumulation. Results from seismic imaging, the compositions of Galápagos lavas, and rare‐earth‐element concentrations across the archipelago require that mantle upwelling and partial melting occur over a broad region within the dehydrated and depleted layer. We conclude that the G discontinuity beneath the archipelago does not mark the boundary between rigid lithosphere and convecting asthenosphere.
Bayesian Model Selection for LISA Pathfinder
Creators: name: Karnesis, Nikolaos
name: Nofrarias, Miquel
name: Sopuerta, Carlos F.
name: Gibert, Ferran
name: Armano, Michele
name: Audley, Heather
name: Congedo, Giuseppe
name: Diepholz, Ingo
name: Ferraioli, Luigi
name: Hewitson, Martin
name: Hueller, Mauro
name: Korsakova, Natalia
name: Plagnol, Eric
name: Vitale, and Stefano
Publisher: name: arXiv
Year: 2013
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Physical sciences

description: The main goal of the LISA Pathfinder (LPF) mission is to fully characterize the acceleration noise models and to test key technologies for future space-based gravitational-wave observatories similar to the eLISA concept. The data analysis team has developed complex three-dimensional models of the LISA Technology Package (LTP) experiment on-board LPF. These models are used for simulations, but more importantly, they will be used for parameter estimation purposes during flight operations. One of the tasks of the data analysis team is to identify the physical effects that contribute significantly to the properties of the instrument noise. A way of approaching this problem is to recover the essential parameters of a LTP model fitting the data. Thus, we want to define the simplest model that efficiently explains the observations. To do so, adopting a Bayesian framework, one has to estimate the so-called Bayes Factor between two competing models. In our analysis, we use three main different methods to estimate it: The Reversible Jump Markov Chain Monte Carlo method, the Schwarz criterion, and the Laplace approximation. They are applied to simulated LPF experiments where the most probable LTP model that explains the observations is recovered. The same type of analysis presented in this paper is expected to be followed during flight operations. Moreover, the correlation of the output of the aforementioned methods with the design of the experiment is explored.
Equation of state and neutron star properties constrained by nuclear physics and observation
Creators: name: Hebeler, K.
name: Lattimer, J. M.
name: Pethick, C. J.
name: Schwenk, A.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Experiment (nucl-ex)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: Microscopic calculations of neutron matter based on nuclear interactions derived from chiral effective field theory, combined with the recent observation of a 1.97 +- 0.04 M_sun neutron star, constrain the equation of state of neutron-rich matter at sub- and supranuclear densities. We discuss in detail the allowed equations of state and the impact of our results on the structure of neutron stars, the crust-core transition density, and the nuclear symmetry energy. In particular, we show that the predicted range for neutron star radii is robust. For use in astrophysical simulations, we provide detailed numerical tables for a representative set of equations of state consistent with these constraints.
description: 35 pages, 12 figures, NORDITA preprint 2013-22
Alignment dependent enhancement of the photo-electron cutoff for multi-photon ionization of molecules
Creators: name: Smeenk, C T L
name: Arissian, L
name: Sokolov, A V
name: Spanner, M
name: Lee, K F
name: Staudte, A
name: Villeneuve, D M
name: Corkum, P B
Publisher: name: arXiv
Year: 2013
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Atomic Physics (physics.atom-ph)
subject: FOS: Physical sciences

description: The multiphoton ionization rate of molecules depends on the alignment of the molecular axis with respect to the ionizing laser polarization. By studying molecular frame photo-electron angular distributions from N$_2$, O$_2$ and benzene, we illustrate how the angle-dependent ionization rate affects the photo-electron cutoff energy. We find alignment can enhance the high energy cutoff of the photo-electron spectrum when probing along a nodal plane or when ionization is otherwise suppressed. This is supported by calculations using a tunneling model with a single ion state.
description: 4 pages, 4 figures
First Glimpse into the Kaon Gluon Parton Distribution Using Lattice QCD
Creators: name: Salas-Chavira, Alejandro
name: Fan, Zhouyou
name: Lin, Huey-Wen
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: In this work, we present the first results on the gluon parton distribution of the kaon from lattice quantum chromodynamics. We carry out the lattice calculation at pion mass around 310~MeV and two lattice spacings, 0.15 and 0.12~fm, using $2+1+1$-flavor HISQ ensembles generated by MILC Collaboration. The kaon correlators are calculated using clover fermions and momentum-smearing sources with maximum boost momentum around 2~GeV and high statistics (up to 324,000 measurements). We study the dependence of the resulting reduced Ioffe-time pseudo-distributions at multiple boost momenta and lattice spacings. We then extract the kaon gluon distribution function in the $\overline{\text{MS}}$ scheme at $μ= 2$~GeV, neglecting the mixing between the gluon and singlet-quark sectors. Our results at the smaller lattice spacing are consistent with phenomenological determinations.
description: 8 pages, 5 figures. arXiv admin note: text overlap with arXiv:2104.06372
The moment of core collapse in star clusters with a mass function
Creators: name: Fujii, M. S.
name: Zwart, S. Portegies
Publisher: name: arXiv
Year: 2013
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Star clusters with multi-mass components dynamically evolve faster than those modeled with equal-mass components. Using a series of direct $N$-body simulations, we investigate the dynamical evolution of star clusters with mass functions, especially their core collapse time. Multi-mass clusters tend to behave like systems with a smaller number of particles, which we call the effective number of particles ($N_{eff}$) and for which $N_{eff} = M/m_{max}$ (here $M$ and $m_{max}$ are the total cluster mass and the mass of the most massive star in the cluster, respectively). We find that the time of core collapse is inversely proportional to the mass of the most massive star in the cluster and analytically confirm that this is because the core collapse of clusters with a mass function proceeds on the dynamical friction timescale of the most massive stars. As the mass of the most massive star increases, however, the core-collapse time, which is observed as a core bounce of the cluster core from the evolution of the core density or core radius, becomes ambiguous. We find that in that case the total binding energy of the hard binaries gives a good diagnosis for determining the moment of core collapses. Based on the results of our simulations, we argue that the core bounce becomes ambiguous when the mass of the most massive star exceeds 0.1\% of the total mass of the cluster.
description: 13 pages, 11 figures, accepted for MNRAS
title: Reed-Solomon burst error decoding
title: Αποκωδικοποίηση Reed-Solomon για ριπές σφαλμάτων
Creators: name: Γρυπιωτης Ιωαννης
Publisher: name: Technical University of Crete
Year: 2018

description: Οι κώδικες Reed-Solomon (RS) είναι από τους παλαιότερους κώδικες ανίχνευσης και διόρθωσης σφαλμάτων. Ωστόσο, χρησιμοποιούνται έως και σήμερα, σε πληθώρα εφαρμογών οι οποίες περιλαμβάνουν, αλλά δεν περιορίζονται σε, τηλεπικοινωνίες και μέσα αποθήκευσης. Σε αυτή τη διπλωματική εργασία, μελετούμε την δομή τους, την κωδικοποίησή τους και την αποκωδικοποίησή τους. Επιπροσθέτως, κατασκευάζουμε έναν καινοτόμο αλγόριθμο διόρθωσης ριπών σφαλμάτων σε κώδικες Reed-Solomon. Ως προαπαιτούμενα, αρχικά παρουσιάζουμε εν συντομία τα σώματα Galois, καθώς επίσης τους κώδικες Bose-Chaudhuri-Hocquenghem (BCH), οι οποίοι σχετίζονται άμεσα με τους κώδικες RS.
description: Reed-Solomon (RS) codes are some of the oldest error detection and correction codes. However, they are widely used today in various applications, including communications and storage systems. In this work, we study their structure and their conventional encoding and decoding. Furthermore, we implement a novel burst error correction algorithm for RS codes. As a prerequisite for this work, we first present a short introduction to Galois Fields and the Bose-Chaudhuri-Hocquenghem (BCH) codes, a family of codes which are closely related to RS codes.
Analysis of MESSENGER high‐resolution images of Mercury's hollows and implications for hollow formation
Creators: name: Blewett, David T.
name: Stadermann, Amanda C.
name: Susorney, Hannah C.
name: Ernst, Carolyn M.
name: Xiao, Zhiyong
name: Chabot, Nancy L.
name: Denevi, Brett W.
name: Murchie, Scott L.
name: Kinczyk, Mallory J.
name: Gillis-Davis, Jeffrey J.
name: Solomon, Sean C.
Publisher: name: Columbia University
Year: 2016
Subjects: Planetary science
Planets--Geology
Planets--Surfaces
Planets--Observations

description: High‐resolution images from MESSENGER provide morphological information on the nature and origin of Mercury's hollows, small depressions that likely formed when a volatile constituent was lost from the surface. Because graphite may be a component of the low‐reflectance material that hosts hollows, we suggest that loss of carbon by ion sputtering or conversion to methane by proton irradiation could contribute to hollows formation. Measurements of widespread hollows in 565 images with pixel scales <20 m indicate that the average depth of hollows is 24 ± 16 m. We propose that hollows cease to increase in depth when a volatile‐depleted lag deposit becomes sufficiently thick to protect the underlying surface. The difficulty of developing a lag on steep topography may account for the common occurrence of hollows on crater central peaks and walls. Disruption of the lag, e.g., by secondary cratering, could restart growth of hollows in a location that had been dormant. Images at extremely high resolution (~3 m/pixel) show that the edges of hollows are straight, as expected if the margins formed by scarp retreat. These highest‐resolution images reveal no superposed impact craters, implying that hollows are very young. The width of hollows within rayed crater Balanchine suggests that the maximum time for lateral growth by 1 cm is ~10,000 yr. A process other than entrainment of dust by gases evolved in a steady‐state sublimation‐like process is likely required to explain the high‐reflectance haloes that surround many hollows.
title: Monetary Policy, Trends in Real Interest Rates and Depressed Demand
Creators: name: Beaudry, Paul
name: Meh, Cesaire
Publisher: name: Bank of Canada
Year: 2021

description: Over the last few decades, real interest rates have trended downward in many countries. The most common explanation is that this reflects depressed demand due to demographic, technological and other real factors such as income inequality. In this paper we explore the claim that these trends may have been amplified by certain features of monetary policy. We show that when long-run asset demands by households are C-shaped in relation to real interest rates, a feature we motivate through bequest motives, monetary policy has the potential to affect steady-state properties even if money is neutral in the long run. In particular, we show that if monetary policy reacts aggressively to inflation, this supports a steady state where inflation is close to the central bank’s target. However, the same aggressive policy simultaneously favours the emergence of, and the convergence to, a second stable and determinate steady state where both the real interest rate and inflation are lower and monetary policy is constrained by the effective lower bound. We discuss how fiscal policy can be used to escape this low-real-rate, low-inflation trap with the potential for a discontinuous response of long-run inflation.

description: Au cours des dernières décennies, les taux d’intérêt réels se sont inscrits en baisse dans de nombreux pays. L’explication la plus courante est que ces tendances reflètent la faiblesse de la demande, qui s’explique par des facteurs démographiques et technologiques et d’autres facteurs réels, tels que les inégalités de revenu. Dans la présente étude, nous examinons l’hypothèse selon laquelle ces tendances ont pu être amplifiées par certaines caractéristiques de la politique monétaire. Nous montrons que, quand la demande à long terme d’actifs par les ménages présente une relation en forme de C par rapport aux taux d’intérêt réels, ce que nous expliquons par la volonté des ménages de constituer un héritage, la politique monétaire est susceptible d’influer sur les propriétés de l’état stationnaire même si la monnaie est neutre à long terme. Plus précisément, notre étude révèle que, si la politique monétaire réagit vigoureusement à l’inflation, cela soutient un état stationnaire où l’inflation avoisine la cible de la banque centrale. Toutefois, la même politique vigoureuse favorise simultanément l’apparition, et la coexistence, d’un deuxième état stationnaire stable et déterminé où le taux d’intérêt réel et l’inflation sont tous deux moins élevés et où la politique monétaire est limitée par la valeur plancher. Nous expliquons également comment la politique budgétaire peut être utilisée pour s’échapper de cette trappe de bas taux d’intérêt réel et de basse inflation qui pourrait provoquer une réaction discontinue de l’inflation à long terme.
Spaces of Besov-Sobolev type and a problem on nonlinear approximation
Creators: name: Domínguez, Óscar
name: Seeger, Andreas
name: Street, Brian
name: Van Schaftingen, Jean
name: Yung, Po-Lam
Publisher: name: arXiv
Year: 2021
Subjects: subject: Functional Analysis (math.FA)
subject: Numerical Analysis (math.NA)
subject: Classical Analysis and ODEs (math.CA)
subject: FOS: Mathematics

description: We study fractional variants of the quasi-norms introduced by Brezis, Van Schaftingen, and Yung in the study of the Sobolev space $\dot W^{1,p}$. The resulting spaces are identified as a special class of real interpolation spaces of Sobolev-Slobodecki\uı spaces. We establish the equivalence between Fourier analytic definitions and definitions via difference operators acting on measurable functions. We prove various new results on embeddings and non-embeddings, and give applications to harmonic and caloric extensions. For suitable wavelet bases we obtain a characterization of the approximation spaces for best $n$-term approximation from a wavelet basis via smoothness conditions on the function; this extends a classical result by DeVore, Jawerth and Popov.
description: 45 pages