cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
A Reverberation-Based Black Hole Mass for MCG-06-30-15
Creators: name: Bentz, Misty C.
name: Cackett, Edward M.
name: Crenshaw, D. Michael
name: Horne, Keith
name: Street, Rachel
name: Ou-Yang, Benjamin
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: We present the results of a reverberation campaign targeting MGC-06-30-15. Spectrophotometric monitoring and broad-band photometric monitoring over the course of 4 months in the spring of 2012 allowed a determination of a time delay in the broad H$β$ emission line of $τ=5.3\pm1.8$ days in the rest frame of the AGN. Combined with the width of the variable portion of the emission line, we determine a black hole mass of $M_{\rm BH} = (1.6 \pm 0.4) \times 10^6$ M$_{\odot}$. Both the H$β$ time delay and the black hole mass are in good agreement with expectations from the $R_{\rm BLR}$-$L$ and $M_{\rm BH}-σ_{\star}$ relationships for other reverberation-mapped AGNs. The H$β$ time delay is also in good agreement with the relationship between H$β$ and broad-band near-IR delays, in which the effective BLR size is $\sim 4-5$ times smaller than the inner edge of the dust torus. Additionally, the reverberation-based mass is in good agreement with estimates from the X-ray power spectral density break scaling relationship, and with constraints based on stellar kinematics derived from integral field spectroscopy of the inner $\sim 0.5$ kpc of the galaxy.
description: 13 pages, 9 figures, 4 tables, accepted for publication in ApJ
Modeling the gravitational potential of a cosmological dark matter halo with stellar streams
Creators: name: Sanderson, Robyn E.
name: Hartke, Johanna
name: Helmi, Amina
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences

description: Stellar streams result from the tidal disruption of satellites and star clusters as they orbit a host galaxy, and can be very sensitive probes of the gravitational potential of the host system. We select and study narrow stellar streams formed in a Milky-Way-like dark matter halo of the Aquarius suite of cosmological simulations, to determine if these streams can be used to constrain the present day characteristic parameters of the halo's gravitational potential. We find that orbits integrated in static spherical and triaxial NFW potentials both reproduce the locations and kinematics of the various streams reasonably well. To quantify this further, we determine the best-fit potential parameters by maximizing the amount of clustering of the stream stars in the space of their actions. We show that using our set of Aquarius streams, we recover a mass profile that is consistent with the spherically-averaged dark matter profile of the host halo, although we ignored both triaxiality and time evolution in the fit. This gives us confidence that such methods can be applied to the many streams that will be discovered by the Gaia mission to determine the gravitational potential of our Galaxy.
description: ApJ subm
ProofBuddy: A Proof Assistant for Learning and Monitoring
Creators: name: Karsten, Nadine
name: Jacobsen, Frederik Krogsdal
name: Eiken, Kim Jana
name: Nestmann, Uwe
name: Villadsen, Jørgen
Publisher: name: arXiv
Year: 2023
Subjects: subject: Logic in Computer Science (cs.LO)
subject: Computers and Society (cs.CY)
subject: FOS: Computer and information sciences
subject: K.3.2; D.1.1; F.3.1; D.2.4; D.2.6; G.4; H.5.2

description: Proof competence, i.e. the ability to write and check (mathematical) proofs, is an important skill in Computer Science, but for many students it represents a difficult challenge. The main issues are the correct use of formal language and the ascertainment of whether proofs, especially the students' own, are complete and correct. Many authors have suggested using proof assistants to assist in teaching proof competence, but the efficacy of the approach is unclear. To improve the state of affairs, we introduce ProofBuddy: a web-based tool using the Isabelle proof assistant which enables researchers to conduct studies of the efficacy of approaches to using proof assistants in education by collecting fine-grained data about the way students interact with proof assistants. We have performed a preliminary usability study of ProofBuddy at the Technical University of Denmark.
description: In Proceedings TFPIE 2023, arXiv:2308.06110
An Energy-Efficient Compressive Sensing Framework Incorporating Online Dictionary Learning for Long-term Wireless Health Monitoring
Creators: name: Xu, Kai
name: Li, Yixing
name: Ren, Fengbo
Publisher: name: arXiv
Year: 2016
Subjects: subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: Wireless body area network (WBAN) is emerging in the mobile healthcare area to replace the traditional wire-connected monitoring devices. As wireless data transmission dominates power cost of sensor nodes, it is beneficial to reduce the data size without much information loss. Compressive sensing (CS) is a perfect candidate to achieve this goal compared to existing compression techniques. In this paper, we proposed a general framework that utilize CS and online dictionary learning (ODL) together. The learned dictionary carries individual characteristics of the original signal, under which the signal has an even sparser representation compared to pre-determined dictionaries. As a consequence, the compression ratio is effectively improved by 2-4x comparing to prior works. Besides, the proposed framework offloads pre-processing from sensor nodes to the server node prior to dictionary learning, providing further reduction in hardware costs. As it is data driven, the proposed framework has the potential to be used with a wide range of physiological signals.
description: 2016 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)
Frequency-adaptive control of a three-phase single-stage grid-connected photovoltaic system under grid voltage sags
Creators: name: Rey-Boué, Alexis B.
name: Guerrero-Rodríguez, N. F.
name: Stöckl, Johannes
name: Strasser, Thomas I.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Systems and Control (eess.SY)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: The low-voltage ride-through service is carried out in this paper according to the voltage profile described by the IEC 61400-21 European normative when short-duration voltage sags happen, and some instantaneous reactive power is delivered to the grid in accordance with the Spanish grid code; the mandatory limitation of the amplitude of the three-phase inverter currents to its nominal value is carried out with a novel control strategy, in which a certain amount of instantaneous constant active power can also be delivered to the grid when small or moderate voltage sags happen. A Multiple second order generalized integrator frequency-locked loop synchronization algorithm is employed in order to estimate the system frequency without harmonic distortions, as well as to output the positive- and the negative- sequence of the α\b{eta} quantities of the three-phase grid voltages when balanced and unbalanced voltage sags happen in a frequency-adaptive scheme. The current control is carried out in the stationary reference frame, which guarantees the cancellation of the harmonic distortions in the utility grid currents using a Harmonic compensation structure, and the implementation of a constant active power control in order to protect the DC link capacitor from thermal stresses avoiding the appearance of large harmonic distortions at twice the fundamental frequency in the DC link voltage. A case study of a three-phase single-stage grid-connected PV system with a maximum apparent power about 500 kVA is tested with several simulations using MATLAB/SIMULINK firstly, and secondly, with some experiments using the Controller hardware-in-the-loop (CHIL) simulation technique for several types of voltage sags in order to do the final validation of the control algorithms.
Regulation Theory
Creators: name: Bouvet, F.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: This paper reviews the design of regulation loops for power converters. Power converter control being a vast domain, it does not aim to be exhaustive. The objective is to give a rapid overview of the main synthesis methods in both continuous- and discrete-time domains.
description: 23 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 2014
Dissecting a SN impostor's circumstellar medium: MUSEing about the SHAPE of eta Car's outer ejecta
Creators: name: Mehner, A.
name: Steffen, W.
name: Groh, J. H.
name: Vogt, F. P. A.
name: Baade, D.
name: Boffin, H. M. J.
name: Davidson, K.
name: de Wit, W. J.
name: Humphreys, R. M.
name: Martayan, C.
name: Oudmaijer, R. D.
name: Rivinius, T.
name: Selman, F.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Aims. The structural inhomogeneities and kinematics of massive star nebulae are tracers of their mass-loss history. We conduct a three-dimensional morpho-kinematic analysis of the ejecta of eta Car outside its famous Homunculus nebula. Methods. We carried out the first large-scale integral field unit observations of eta Car in the optical, covering a field of view of 1'x1' centered on the star. Observations with the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT) reveal the detailed three-dimensional structure of eta Car's outer ejecta. Morpho-kinematic modeling of these ejecta is conducted with the code SHAPE. Results. The largest coherent structure in eta Car's outer ejecta can be described as a bent cylinder with roughly the same symmetry axis as the Homunculus nebula. This large outer shell is interacting with the surrounding medium, creating soft X-ray emission. We establish the shape and extent of the ghost shell in front of the southern Homunculus lobe and confirm that the NN condensation can best be modeled as a bowshock in the orbital/equatorial plane. Conclusions. The SHAPE modeling of the MUSE observations indicates that the kinematics of the outer ejecta measured with MUSE can be described by a spatially coherent structure, and this structure also correlates with the extended soft X-ray emission associated with the outer debris field. The ghost shell just outside the southern Homunculus lobe hints at a sequence of eruptions within the time frame of the Great Eruption from 1837-1858 or possibly a later shock/reverse shock velocity separation. Our 3D morpho-kinematic modeling and the MUSE observations constitute an invaluable dataset to be confronted with future radiation-hydrodynamics simulations. Such a comparison may shed light on the yet elusive physical mechanism responsible for eta Car-like eruptions.
description: 14 pages, 8 figures, accepted in A&A
Disco: A Functional Programming Language for Discrete Mathematics
Creators: name: Yorgey, Brent A.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Programming Languages (cs.PL)
subject: Discrete Mathematics (cs.DM)
subject: FOS: Computer and information sciences
subject: D.1.1; G.2.0; K.3.0

description: Disco is a pure, strict, statically typed functional programming language designed to be used in the setting of a discrete mathematics course. The goals of the language are to introduce students to functional programming concepts early, and to enhance their learning of mathematics by providing a computational platform for them to play with. It features mathematically-inspired notation, property-based testing, equirecursive algebraic types, subtyping, built-in list, bag, and finite set types, a REPL, and student-focused documentation. Disco is implemented in Haskell, with source code available on GitHub [https://github.com/disco-lang/disco], and interactive web-based REPL available through replit [https://replit.com/@BrentYorgey/Disco#README.md].
description: In Proceedings TFPIE 2023, arXiv:2308.06110
Rethinking the Actual Security Strategy of Vietnam, a Middle Power’s Status in the International Order
Creators: name: Celine, Clement
Publisher: name: University of Chicago
Year: 2022
Subjects: subject: Middle power
subject: security
subject: soft-balancing
subject: agenda-setting policy
subject: Vietnam
subject: COVID-19

description: Middle powers do matter within the international order. They are therefore capable of implementing their own agenda and security policy. However, to what extent does their policy have an impact on great powers' agenda? Especially when middle powers are navigating triangular relations with two other great powers, how can they display a security strategy that allows them to be a proactive actor in the world order? The conventional wisdom is that middle powers hedge vis-à-vis great powers, which means they are neither balancing nor bandwagoning, but this strategy encompasses different definitions according to each scholar. Moreover, hedging possesses limits when it comes to different forms of power display and how to ascertain it and its evolution in the long run. Thereby I argue that middle powers can practice soft-balancing with accommodations of their own capabilities and to a certain extent, display a setting-agenda policy vis-à-vis great power. And they can achieve this policy by taking advantage of major outbreaks such as the COVID-19 pandemic. Thus, middle powers can make full use of their economic growth, national identity, role in institutions and coalitions, and practice new and innovative forms of diplomacy which redefine their status. To demonstrate my argument, I am examining the case of Vietnam, a Southeast Asian country that since the COVID-19 pandemic, has been capable of progressing towards a globalist approach to its security strategy and role in the international order.
Coulomb interactions induced perfect spin filtering effect in a quadruple quantum-dot cell
Creators: name: Kagan, M. Yu.
name: Val'kov, V. V.
name: Aksenov, S. V.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Strongly Correlated Electrons (cond-mat.str-el)
subject: FOS: Physical sciences

description: A quadruple quantum-dot (QQD) cell is proposed as a spin filter. The transport properties of the QQD cell were studied in linear response regime on the basis of the equations of motion for retarded Green's functions. The developed approach allowed us to take into account the influence of both intra- and interdot Coulomb interactions on carriers' spin polarization. It was shown that the presence of the insulating bands in the conductance due to the Coulomb correlations results in the emergence of spin-polarized windows (SPWs) in magnetic field leading to the high spin polarization. We demonstrated the SPWs can be effectively manipulated by gate fields and considering the hopping between central dots in both isotropic and anisotropic regimes.
description: 4 pages, 7 figures
Mesoscale pattern formation of self-propelled rods with velocity reversal
Creators: name: Großmann, Robert
name: Peruani, Fernando
name: Bär, Markus
Publisher: name: arXiv
Year: 2016
Subjects: subject: Statistical Mechanics (cond-mat.stat-mech)
subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: We study self-propelled particles with velocity reversal interacting by uniaxial (nematic) alignment within a coarse-grained hydrodynamic theory. Combining analytical and numerical continuation techniques, we show that the physics of this active system is essentially controlled by the reversal frequency. In particular, we find that elongated, high-density, ordered patterns, called bands, emerge via subcritical bifurcations from spatially homogeneous states. Our analysis reveals further that the interaction of bands is weakly attractive and, consequently, bands fuse upon collision in analogy with nonequilibrium nucleation processes. Moreover, we demonstrate that a renormalized positive line tension can be assigned to stable bands below a critical reversal rate, beyond which they are transversally unstable. In addition, we discuss the kinetic roughening of bands as well as their nonlinear dynamics close to the threshold of transversal instability. Altogether, the reduction of the multi-particle system onto the dynamics of bands provides a framework to understand the impact of the reversal frequency on the emerging nonequilibrium patterns in self-propelled particle systems. In this regard, our results constitute a proof-of-principle in favor of the hypothesis in microbiology that reversal of gliding rod-shaped bacteria regulates the occurrence of various self-organized pattens observed during life-cycle phases.
description: 7 pages, 5 figures; submitted to Phys. Rev. E
The Evolution and Internal Structure of Jupiter and Saturn with Compositional Gradients
Creators: name: Vazan, A.
name: Helled, R.
name: Podolak, M.
name: Kovetz, A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences

description: The internal structure of gas giant planets may be more complex than the commonly assumed core-envelope structure with an adiabatic temperature profile. Different primordial internal structures as well as various physical processes can lead to non-homogenous compositional distributions. A non-homogenous internal structure has a significant impact on the thermal evolution and final structure of the planets. In this paper, we present alternative structure and evolution models for Jupiter and Saturn allowing for non-adiabatic primordial structures and the mixing of heavy elements by convection as these planets evolve. We present the evolution of the planets accounting for various initial composition gradients, and in the case of Saturn, include the formation of a helium-rich region as a result of helium rain. We investigate the stability of regions with composition gradients against convection, and find that the helium shell in Saturn remains stable and does not mix with the rest of the envelope. In other cases, convection mixes the planetary interior despite the existence of compositional gradients, leading to the enrichment of the envelope with heavy elements. We show that non-adiabatic structures (and cooling histories) for both Jupiter and Saturn are feasible. The interior temperatures in that case are much higher that for standard adiabatic models. We conclude that the internal structure is directly linked to the formation and evolution history of the planet. These alternative internal structures of Jupiter and Saturn should be considered when interpreting the upcoming Juno and Cassini data.
description: accepted for publication in ApJ
Low-tubal-rank Tensor Completion using Alternating Minimization
Creators: name: Liu, Xiao-Yang
name: Aeron, Shuchin
name: Aggarwal, Vaneet
name: Wang, Xiaodong
Publisher: name: arXiv
Year: 2016
Subjects: subject: Machine Learning (cs.LG)
subject: Information Theory (cs.IT)
subject: FOS: Computer and information sciences

description: The low-tubal-rank tensor model has been recently proposed for real-world multidimensional data. In this paper, we study the low-tubal-rank tensor completion problem, i.e., to recover a third-order tensor by observing a subset of its elements selected uniformly at random. We propose a fast iterative algorithm, called {\em Tubal-Alt-Min}, that is inspired by a similar approach for low-rank matrix completion. The unknown low-tubal-rank tensor is represented as the product of two much smaller tensors with the low-tubal-rank property being automatically incorporated, and Tubal-Alt-Min alternates between estimating those two tensors using tensor least squares minimization. First, we note that tensor least squares minimization is different from its matrix counterpart and nontrivial as the circular convolution operator of the low-tubal-rank tensor model is intertwined with the sub-sampling operator. Second, the theoretical performance guarantee is challenging since Tubal-Alt-Min is iterative and nonconvex in nature. We prove that 1) Tubal-Alt-Min guarantees exponential convergence to the global optima, and 2) for an $n \times n \times k$ tensor with tubal-rank $r \ll n$, the required sampling complexity is $O(nr^2k \log^3 n)$ and the computational complexity is $O(n^2rk^2 \log^2 n)$. Third, on both synthetic data and real-world video data, evaluation results show that compared with tensor-nuclear norm minimization (TNN-ADMM), Tubal-Alt-Min improves the recovery error dramatically (by orders of magnitude). It is estimated that Tubal-Alt-Min converges at an exponential rate $10^{-0.4423 \text{Iter}}$ where $\text{Iter}$ denotes the number of iterations, which is much faster than TNN-ADMM's $10^{-0.0332 \text{Iter}}$, and the running time can be accelerated by more than $5$ times for a $200 \times 200 \times 20$ tensor.
Thermal Effects on Decays of a Metastable Brane Configuration
Creators: name: Nakai, Yuichiro
name: Ookouchi, Yutaka
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We study thermal effects on a decay process of a false vacuum in type IIA string theory. At finite temperature, the potential of the theory is corrected and also thermally excited modes enhance the decay rate. The false vacuum can accommodate a string-like object. This cosmic string makes the bubble creation rate much larger and causes an inhomogeneous vacuum decay. We investigate thermal corrections to the DBI action for the bubble/string bound state and discuss a thermally assisted tunneling process. We show that thermally excited states enhance the tunneling rate of the decay process, which makes the life-time of the false vacuum much shorter.
description: 15 pages, 8 figures
A review of the degradation mechanisms of NCM cathodes and corresponding mitigation strategies
Creators: name: Britala, Liga
name: Marinaro, Mario
name: Kucinskis, Gints
Publisher: name: arXiv
Year: 2023
Subjects: subject: Applied Physics (physics.app-ph)
subject: FOS: Physical sciences

description: Li-ion batteries (LIBs) are the most widely used form of energy storage in mobile electronic devices and electric vehicles. Li-ion battery cathodes with the composition LiNixMnyCozO2 (NCMs) currently display some of the most promising electrochemical characteristics for high performance LIBs. NCM compositions with high nickel content (x > 0.8) exhibit the largest specific capacity while undergoing fast degradation and presenting safety issues. As the main degradation mechanisms of NCM materials and the mitigation of their degradation, are still subjects of many ongoing studies, this work summarizes the current knowledge on the subject. Here, the existing literature is reviewed to present the structural and electrochemical degradation of NCM with varying Ni stoichiometries (NCM111, NCM622, NCM811, and beyond). Routes for hindering the degradation of NCM are discussed as a function of Ni content in NCM and include doping, application of protective coatings, and engineering of the microstructure. A comprehensive understanding of the main degradation pathways of NCM is key to applying the most appropriate mitigation strategies and keep advancing towards higher energy NCM materials with longer cycle-life.
description: Accepted manuscript, 94 pages, 12 figures, 1 table
High Precision Current Measurement for Power Converters
Creators: name: Bastos, M. Cerqueira
Publisher: name: arXiv
Year: 2016
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: The accurate measurement of power converter currents is essential to controlling and delivering stable and repeatable currents to magnets in particle accelerators. This paper reviews the most commonly used devices for the measurement of power converter currents and discusses test and calibration methods.
description: 10 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 2014
Portmanteau Tests for ARMA Models with Infinite Variance
Creators: name: Lin, Jen-Wen
name: McLeod, A. Ian
Publisher: name: arXiv
Year: 2016
Subjects: subject: Statistics Theory (math.ST)
subject: FOS: Mathematics
subject: 62M10, 91B84

description: Autoregressive and moving-average (ARMA) models with stable Paretian errors is one of the most studied models for time series with infinite variance. Estimation methods for these models have been studied by many researchers but the problem of diagnostic checking fitted models has not been addressed. In this paper, we develop portmanteau tests for checking randomness of a time series with infinite variance and as a diagnostic tool for checking model adequacy of fitted ARMA models. It is assumed that least-squares or an asymptotically equivalent estimation method, such as Gaussian maximum likelihood in the case of AR models, is used. And it is assumed that the distribution of the innovations is IID stable Paretian. It is seen via simulation that the proposed portmanteau tests do not converge well to the corresponding limiting distributions for practical series length so a Monte-Carlo test is suggested. Simulation experiments show that the proposed test procedure works effectively. Two illustrative applications to actual data are provided to demonstrate that an incorrect conclusion may result if the usual portmanteau test based on the finite variance assumption is used.
description: 36 pages, 3 figures, 5 tables
A HSS Matrix-Inspired Butterfly-Based Direct Solver for Analyzing Scattering from Two-dimensional Objects
Creators: name: Liu, Yang
name: Guo, Han
name: Michielssen, Eric
Publisher: name: arXiv
Year: 2016
Subjects: subject: Numerical Analysis (math.NA)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: A butterfly-based fast direct integral equation solver for analyzing high-frequency scattering from two-dimensional objects is presented. The solver leverages a randomized butterfly scheme to compress blocks corresponding to near- and far-field interactions in the discretized forward and inverse electric field integral operators. The observed memory requirements and computational cost of the proposed solver scale as O(Nlog^2N) and O(N^1.5 logN), respectively. The solver is applied to the analysis of scattering from electrically large objects spanning over ten thousand of wavelengths and modeled in terms of five million unknowns.
Synthesis of sexual selection: registration for a systematic map and bibliometric analysis of meta-analyses
Creators: name: Lagisz, Malgorzata
name: Nakagawa, Shinichi
name: Culina, Antica
name: Pollo, Pietro
name: Yang, Yefeng
Publisher: name: Open Science Framework
Year: 2023
Subjects: subject: Life Sciences
subject: Ecology and Evolutionary Biology

description: Registration for a systematic map of existing meta-analyses on topics related to sexual selection, with critical appraisal and bibliometric analysis.
Near-field measurement of modal interference in optical nanofibers for sub-Angstrom radius sensitivity
Creators: name: Fatemi, Fredrik K.
name: Hoffman, Jonathan E.
name: Solano, Pablo
name: Fenton, Eliot F.
name: Beadie, Guy
name: Rolston, Steven L.
name: Orozco, Luis A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Optical nanofibers (ONF) of subwavelength dimensions confine light in modes with a strong evanescent field that can trap, probe, and manipulate nearby quantum systems. To measure the evanescent field and propagating modes, and to optimize ONF performance, a surface probe is desirable during fabrication. We demonstrate a nondestructive measurement of light propagation in ONFs by sampling the local evanescent field with a microfiber. This approach reveals the behavior of all propagating modes, and because the modal beat lengths in cylindrical waveguides depend strongly on radius, simultaneously provides exquisite sensitivity to the ONF radius. We show that our measured spatial frequencies provide a map of the average ONF radius (over a 600 micrometer window) along the 10 mm ONF waist with 40 picometer resolution and high signal-to-noise ratio. The measurements agree with scanning electron microscopy (SEM) to within SEM instrument resolution. This fast method is immune to polarization, intrinsic birefringence, mechanical vibrations, scattered light, and provides a set of constraints to protect from systematic errors in the measurements
Nanoparticle ordering in sandwiched polymer brushes
Creators: name: Curk, Tine
name: Martinez-Veracoechea, Francisco J.
name: Frenkel, Daan
name: Dobnikar, Jure
Publisher: name: arXiv
Year: 2016
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: The organization of nano-particles inside grafted polymer layers is governed by the interplay of polymer-induced entropic interactions and the action of externally applied fields. Earlier work had shown that strong external forces can drive the formation of colloidal structures in polymer brushes. Here we show that external fields are not essential to obtain such colloidal patterns: we report Monte Carlo and Molecular dynamics simulations that demonstrate that ordered structures can be achieved by compressing a `sandwich' of two grafted polymer layers, or by squeezing a coated nanotube, with nano-particles in between. We show that the pattern formation can be efficiently controlled by the applied pressure, while the characteristic length--scale, i.e. the typical width of the patterns, is sensitive to the length of the polymers. Based on the results of the simulations, we derive an approximate equation of state for nano-sandwiches.
description: 18 pages, 4 figures
On the paradoxical evolution of the number of photons in a new model of interpolating Hamiltonians
Creators: name: Valverde, C.
name: Baseia, B.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We introduce a new Hamiltonian model which interpolates between the Jaynes-Cummings model and other types of such Hamiltonians. It works with two interpolating parameters, rather than one as traditional. Taking advantage of this greater degree of freedom, we can perform continuous interpolation between the various types of these Hamiltonians. As applications we discuss a paradox raised in literature and compare the time evolution of photon statistics obtained in the various interpolating models. The role played by the average excitation in these comparisons is also highlighted.
description: 6 pages, 4 figures
Implications of supermassive neutron stars for the form of the equation of state of hybrid stars
Creators: name: Sun, Hongyi
name: Wen, Dehua
Publisher: name: arXiv
Year: 2023
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: The observations of PSR J0952-0607 and the second object in GW190814 event indicate the possible existence of supermassive neutron stars. In this work, by using the Constant-Sound-Speed (CSS) parametrization to describe the equation of state (EOS) of quark matter, the constraints on the EOS parameters from supermassive hybrid stars are investigated through the Maxwell and Gibbs constructions. It is shown that to support a supermassive hybrid star, a lower transition energy density, a smaller energy density discontinuity and a higher sound speed of quark matter are favored. For the constructed hybrid star EOS model, the maximum mass of the corresponding hybrid stars will not meet the lower mass limit of the second object in GW190814 if the energy density discontinuity takes a value higher than $180~{\rm MeV~fm^{-3}}$. Moreover, it is confirmed that the supermassive neutron star observation can also rule out the existence of twin stars as a supermassive hybrid star requires a relatively small energy density discontinuity. Finally, we give a rough estimate of the lower limit of the dimensionless tidal deformability of neutron stars which ranges from 2 to 3.
description: 12 pages, 5 figures
Linear stability analysis of magnetized jets: the rotating case
Creators: name: Bodo, G.
name: Mamatsashvili, G.
name: Rossi, P.
name: Mignone, A.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We perform a linear stability analysis of magnetized rotating cylindrical jet flows in the approximation of zero thermal pressure. We focus our analysis on the effect of rotation on the current driven mode and on the unstable modes introduced by rotation. We find that rotation has a stabilizing effect on the current driven mode only for rotation velocities of the order of the Alfvén velocity. Rotation introduces also a new unstable centrifugal buoyancy mode and the "cold" magnetorotational instability. The first mode is analogous to the Parker instability with the centrifugal force playing the role of effective gravity. The magnetorotational instability can be present, but only in a very limited region of the parameter space and is never dominant. The current driven mode is characterized by large wavelenghts and is dominant at small values of the rotational velocity, while the buoyancy mode becomes dominant as rotation is increased and is characterized by small wavelenghts.
description: 25 pages, 19 figures, accepted in MNRAS
Testing relativistic reflection and resolving outflows in PG 1211+143 with XMM-Newton and NuSTAR
Creators: name: Lobban, Andrew
name: Pounds, Ken
name: Vaughan, Simon
name: Reeves, James
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We analyze the broad-band X-ray spectrum (0.3-50 keV) of the luminous Seyfert 1 / quasar PG 1211+143 - the archetypal source for high-velocity X-ray outflows - using near-simultaneous XMM-Newton and NuSTAR observations. We compare pure relativistic reflection models with a model including the strong imprint of photoionized emission and absorption from a high-velocity wind (Pounds16a,16b), finding a spectral fit that extrapolates well over the higher photon energies covered by NuSTAR. Inclusion of the high S/N XMM-Newton spectrum provides much tighter constraints on the model parameters, with a much harder photon index / lower reflection fraction compared to that from the NuSTAR data alone. We show that pure relativistic reflection models are not able to account for the spectral complexity of PG 1211+143 and that wind absorption models are strongly required to match the data in both the soft X-ray and Fe K spectral regions. In confirming the significance of previously reported ionized absorption features, the new analysis provides a further demonstration of the power of combining the high throughput and resolution of long-look XMM-Newton observations with the unprecedented spectral coverage of NuSTAR.
description: Accepted for publication in ApJ; 9 pages, 6 figures, 2 tables
title: Optimisation of Renewable Energy Microgrid Systems for Developing Countries
Creators: name: Abah, Josephine Ukpojo
Publisher: name: University of Central Lancashire
Year: 2021

description: This research proposes a strategy for reducing the running costs of hybrid microgrids which include both renewable and conventional power generation. The developed system uses metaheuristic methods for microgrid optimisation enabling the planning, maintenance, and effective cost management of the system. The target application for the research is a typical Nigerian remote rural community, not connected to any form of centralised power supply with the dwellers of the community practising peasant farming. The location for application of the proposed microgrid is first examined to determine renewable resources available, current power supply source, their behaviour and electricity consumption patterns, future plans for consumption, and willingness to purchase electricity if provided. In the absence of smart metering, energy use data are gathered through questionnaires and the bottom-up approach adopted for hourly time-step load demand profiles development. Using both end-use and econometric indices, a ten year load forecast is done with the fifth year forecast employed in design analysis. These forecast based on real world questionnaire will provide good resource in real world application. The Hybrid Microgrid (HMG) system is designed using HOMER to cope with variability from both weather and unexpected changes in the load, and has photovoltaic panels, wind turbines, battery storage systems, and a diesel generator in its configuration. The research compares the effectiveness of three optimization strategies, the Genetic Algorithms (GA), Particle Swarm Optimisation (PSO), and Simulated Annealing (SA) by tuning algorithm parameters to improve the speed and quality of solutions. This is the first time its being used for developing country microgrids. The HMG optimisation objective is to minimise its operating costs by reducing the generator running hours. The optimisation is constrained by the requirement to meet the variable load demand at all times. The results showed PSO had the lowest diesel generator run hours, a 65.2% reduction in the diesel running hours is, achieved compared to HOMER simulations of the HMG. The adaptability of the system means that the operator can choose the optimisation strategy based on the required output.
Phase separation of a supersaturated nanocrystalline Cu Co alloy and its influence on thermal stability
Creators: name: Bachmaier, Andrea
name: Pfaff, Marina
name: Stolpe, Moritz
name: Aboulfadl, Hisham
name: Motz, Christian
Publisher: name: arXiv
Year: 2016
Subjects: subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: The thermal decomposition behavior, the microstructural evolution and its influence on the mechanical properties of a supersaturated Cu Co solid solution with ~100 nm average grain size prepared by severe plastic deformation is investigated under non-isothermal and isothermal annealing conditions. Pure fine grained Cu and Co exhibit substantial grain growth upon annealing, whereas the Cu Co alloy is thermally stable at the same annealing temperatures. The annealed microstructures are studied by independent characterization methods, including scanning electron microscopy, electron energy loss spectroscopy and atom probe tomography. The phase separation process in the Cu Co alloy proceeds by the same mechanism, but on different length scales: a fine scaled spinodal type decomposition is observed in the grain interior, simultaneously Co and Cu regions with a larger scale are formed near the grain boundary regions. Subsequent grain growth at higher annealing temperatures results in a microstructure consisting of the pure equilibrium phases. Such mechanisms can be used to tailor nano structures to optimize certain properties.
Fake Conformal Symmetry in Unimodular Gravity
Creators: name: Oda, Ichiro
Publisher: name: arXiv
Year: 2016
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We study Weyl symmetry (local conformal symmetry) in unimodular gravity. It is shown that the Noether currents for both Weyl symmetry and global scale symmetry, identically vanish as in the conformally invariant scalar-tensor gravity. We clearly explain why in the class of conformally invariant gravitational theories, the Noether currents vanish by starting with the conformally invariant scalar-tensor gravity. Moreover, we comment on both classical and quantum-mechanical equivalences among Einstein's general relativity, the conformally invariant scalar-tensor gravity and the Weyl-transverse (WTDiff) gravity. Finally, we discuss the Weyl current in the conformally invariant scalar action and see that it is also vanishing.
description: 13 pages
Structure of iso-density sets in supersonic isothermal turbulence
Creators: name: Thiesset, Fabien
name: Federrath, Christoph
Publisher: name: arXiv
Year: 2023
Subjects: subject: Fluid Dynamics (physics.flu-dyn)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Context: The gas density structure of the cold molecular phase of the interstellar medium is the main controller of star formation. Aims: A theoretical framework is proposed to describe the structural content of the density field in isothermal supersonic turbulence. Methods: It makes use of correlation and structure functions of the phase indicator field defined for different iso-density values. The relations between these two-point statistics and the geometrical features of iso-density sets such as the volume fraction, the surface density, the curvature, and fractal characteristics are provided. An exact scale-by-scale budget equation is further derived revealing the role of the turbulent cascade and dilation on the structural evolution of the density field. Although applicable to many flow situations, this tool is here first invoked for characterising supersonic isothermal turbulence, using data from the currently best-resolved numerical simulation. Results: We show that iso-density sets are surface fractals rather than mass fractals, with dimensions that markedly differ between dilute, neutral, and dense regions. The surface-size relation is established for different iso-density values. We further find that the turbulent cascade of iso-density sets is directed from large towards smaller scales, in agreement with the classical picture that turbulence acts to concentrate more surface into smaller volumes. Intriguingly, there is no range of scales that complies with a constant transfer rate in the cascade, challenging our fundamental understanding of interstellar turbulence. Finally, we recast the virial theorem in a new formulation drawing an explicit relation between the aforementioned geometrical measures and the dynamics of iso-density sets.
description: 15 pages, 14 figures
Analogue to Digital and Digital to Analogue Converters (ADCs and DACs): A Review Update
Creators: name: Pickering, J.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Accelerator Physics (physics.acc-ph)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: This is a review paper updated from that presented for CAS 2004. Essentially, since then, commercial components have continued to extend their performance boundaries but the basic building blocks and the techniques for choosing the best device and implementing it in a design have not changed. Analogue to digital and digital to analogue converters are crucial components in the continued drive to replace analogue circuitry with more controllable and less costly digital processing. This paper discusses the technologies available to perform in the likely measurement and control applications that arise within accelerators. It covers much of the terminology and 'specmanship' together with an application-oriented analysis of the realisable performance of the various types. Finally, some hints and warnings on system integration problems are given.
description: 15 pages, contribution to the 2014 CAS - CERN Accelerator School: Power Converters, Baden, Switzerland, 7-14 May 2014
A phononic crystal coupled to a transmission line via an artificial atom
Creators: name: Bolgar, Aleksey N.
name: Kirichenko, Daniil D.
name: Shaikhaidarov, Rais. S.
name: Sanduleanu, Shtefan V.
name: Semenov, Alexander V.
name: Dmitriev, Aleksey Yu.
name: Astafiev, Oleg V.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: We study a phononic crystal interacting with an artificial atom { a superconducting quantum system { in the quantum regime. The phononic crystal is made of a long lattice of narrow metallic stripes on a quatz surface. The artificial atom in turn interacts with a transmission line therefore two degrees of freedom of different nature, acoustic and electromagnetic, are coupled with a single quantum object. A scattering spectrum of propagating electromagnetic waves on the artificial atom visualizes acoustic modes of the phononic crystal. We simulate the system and found quasinormal modes of our phononic crystal and their properties. The calculations are consistent with the experimentally found modes, which are fitted to the dispersion branches of the phononic crystal near the first Brillouin zone edge. Our geometry allows to realize effects of quantum acoustics on a simple and compact phononic crystal.
A MAD Model for Gamma-Ray Burst Variability
Creators: name: Lloyd-Ronning, Nicole
name: Dolence, Joshua C.
name: Fryer, Christopher L.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We present a model for the temporal variability of long gamma-ray bursts during the prompt phase (the highly variable first 100 seconds or so), in the context of a magnetically arrested disk (MAD) around a black hole. In this state, sufficient magnetic flux is held on to the black hole such that it stalls the accretion near the inner region of the disk. The system transitions in and out of the MAD state, which we relate to the variable luminosity of the GRB during the prompt phase, with a characteristic timescale defined by the free fall time in the region over which the accretion is arrested. We present simple analytic estimates of the relevant energetics and timescales, and compare them to gamma-ray burst observations. In particular, we show how this model can reproduce the characteristic one second time scale that emerges from various analyses of the prompt emission light curve. We also discuss how our model can accommodate the potentially physically important correlation between a burst quiescent time and the duration of its subsequent pulse (Ramirez-Ruiz & Merloni 2001).
Minimizing Polarization in Noisy Leader-Follower Opinion Dynamics
Creators: name: Xu, Wanyue
name: Zhang, Zhongzhi
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computers and Society (cs.CY)
subject: FOS: Computer and information sciences

description: The operation of creating edges has been widely applied to optimize relevant quantities of opinion dynamics. In this paper, we consider a problem of polarization optimization for the leader-follower opinion dynamics in a noisy social network with $n$ nodes and $m$ edges, where a group $Q$ of $q$ nodes are leaders, and the remaining $n-q$ nodes are followers. We adopt the popular leader-follower DeGroot model, where the opinion of every leader is identical and remains unchanged, while the opinion of every follower is subject to white noise. The polarization is defined as the steady-state variance of the deviation of each node's opinion from leaders' opinion, which equals one half of the effective resistance $\mathcal{R}_Q$ between the node group $Q$ and all other nodes. Concretely, we propose and study the problem of minimizing $\mathcal{R}_Q$ by adding $k$ new edges with each incident to a node in $Q$. We show that the objective function is monotone and supermodular. We then propose a simple greedy algorithm with an approximation factor $1-1/e$ that approximately solves the problem in $O((n-q)^3)$ time. To speed up the computation, we also provide a fast algorithm to compute $(1-1/e-\eps)$-approximate effective resistance $\mathcal{R}_Q$, the running time of which is $\Otil (mk\eps^{-2})$ for any $\eps>0$, where the $\Otil (\cdot)$ notation suppresses the ${\rm poly} (\log n)$ factors. Extensive experiment results show that our second algorithm is both effective and efficient.
description: This paper has been accepted in CIKM'23 conference