Miracle-dz/UniFAR-FTUs huggingface dataset:
Oblique Mixed Shocks in Extragalactic Jets

Analytical calculations of the spectra obtained from the first-order Fermi acceleration mechanism with oblique shocks are presented. They are a generalization of the quasi-parallel configuration, where the streaming instability modifies the acceleration process, and of the quasi-perpendicular configuration, where the magnetic pressure is significant. It is shown that the influence of the streaming instability on the compression ratio of the fluid is always negligible, and it changes the spectral index only through the modification of the effective compression ratio of the scattering centers. The observational constraints on the cutoff frequency imply that the magnetic turbulence in extragalactic jets must be weak and most probably of Kraichnan type. The application of these calculations to the jet of 3C 273 shows that the theory of diffusive acceleration in oblique shocks works quite well with a nonrelativistic flow velocity and yields narrow ranges for the different parameters. 28 refs.
Temporary Threshold Shift in Hearing from Exposure to Different Noise Spectra at Equal dBA Level

The intent of this study was to determine whether sound‐level measurements in dBA could adequately depict harmfulness to hearing from exposures to noises differing widely in spectra. Each of 11 male listeners, aged 20–26 yr, were exposed on two separate occasions to three noises whose spectral slopes were −6, 0, and +6 dB per octave band. All such noises were presented for 30 min via an earphone at 100 dBA. Analyses of variance of the post‐exposure threshold data (corrected to 2 mm, TTS2) found insignificant differences due to the spectral variations for both test and retest conditions as averaged across audiometric frequencies 250–8000 Hz. Interactive effects between spectra and test frequencies were significant, the −6 and 0 dB spectral conditions causing relatively more TTS2 at frequencies below 3000 Hz, and the +6 dB spectrum more TTS2 at frequencies above 3000 Hz. Implication of results for noise‐hazard rating schemes using dBA measures are noted.
Flexible inverted polymer solar cells with an indium-free tri-layer cathode

Indium tin oxide (ITO)-free inverted polymer solar cells (PSCs) have been fabricated without the need of an additional electron transport layer. The indium-free transparent electrode consists of a tri-layer stack ZnO (30 nm)/Ag (14 nm)/ZnO (30 nm) deposited on glass and plastic substrates via ion-beam sputtering. The tri-layer electrodes exhibit similar physical properties to its ITO counterpart, specifically yielding high transmittance and low resistivity (76.5% T at 550 nm, Rsq of 8 Ω/◻) on plastic substrates. The novel tri-layer electrode allows for the fabrication of inverted PSCs without the additional ZnO interfacial layer commonly deposited between ITO and the photoactive layer. This allows for the preparation of thinner plastic solar cells using less material than conventional architectures. Initial studies involving the newly realized architecture (tri-layer electrode/P3HT:PCBM/PEDOT:PSS/Ag) have shown great promise for the transition from ITO to other viable electrodes in organic electronics.
The Stabilised Retinal Image

A beam of light reflected from a mirror attached to a contact lens, worn by the subject, produces a test object whose image does not move across the retina in response to eye-movements. This is called the stabilised retinal image. In this paper, conditions for accurate stabilisation are discussed. It is shown that a small defect of stabilisation is important and that normal vision may be restored by introducing small movements which simulate some of the normal movements of a retinal image. Experiments on the stabilised image with light interrupted at different frequencies are described and it is shown that normal vision is obtained near the flicker fusion frequency. Un rayon lumineux, reflechi par un miroir fixe sur un verre de contact porte par le sujet, forme l'image d'un test objet dont l'image est immobile sur la retine quels que soient les mouvements du globe oculaire; cette image est dite « stabilisee ». Le present article traite des conditions requises pour une stabilisation tres precise. Il sera m.
Numerical study of turbulent secondary flows in curved ducts

The pressure driven, fully-developed turbulent flow of an incompressible viscous fluid in curved ducts of square-section is studied numerically by making use of a finite volume method. A nonlinear Kappa - Iota model is used to represent the turbulence. The results for both straight and curved ducts are presented. For the case of fully-developed turbulent flow in straight and curved ducts, the secondary flow is characterized by an eight-vortex structure for which the computed flowfield is shown to be in good agreement with available experimental data. The introduction of moderate curvature is shown to cause a substantial increase in the strength of the secondary flow and to change the secondary flow pattern to either a double-vortex or a four-vortex configuration.
Balanced Dual-Band BPF using only Equal-Electric-Length SIRs for Common-Mode Suppression

This paper presents a new balanced dual-band bandpass filter (BPF) designed for 2.4/5.2 GHz wireless local area networks (WLANs). Because adopted in the BPF are only bi-section equal-electric-length stepped-impedance resonators (SIRs), whose dimensions can be determined using analytic formulas, the BPF can be easily and efficiently designed. The inner SIRs are designed to resonate only at the odd-mode resonant frequencies of the input and output SIRs but not at the even-mode ones. This leads to well-behaved differential-mode (DM) transmission and excellent common-mode (CM) suppression for the BPF. Simulated and measured results are found to agree quite well to each other. The measured minimum DM insertion losses in the two passbands are 2.1 and 2.54 dB, whereas the measured CM rejections are higher than 33 dB in the frequency range from 1 to 7 GHz.
Asynchronous Distributed Optimization over Lossy Peer-to-Peer Networks via ADMM: Stability and Exponential Convergence

In this work we focus on the problem of minimizing the sum of convex cost functions in a distributed fashion over a peer-to-peer network. In particular we are interested in the case in which communications between nodes are lossy and the agents are not synchronized among themselves. We address this problem by proposing a modified version of the relaxed ADMM (R-ADMM), which corresponds to the generalized Douglas-Rachford operator applied to the dual of our problem. By exploiting results from operator theory we are then able to prove the almost sure convergence of the proposed algorithm under i.i. d. random packet losses and asynchronous operation of the agents. By further assuming the cost functions to be strongly convex, we are able to prove that the algorithm converges exponentially fast in mean square in a neighborhood of the optimal solution. Moreover, we provide an upper bound to the convergence rate. Finally, we present numerical simulations of the proposed algorithm over random geometric graphs in the aforementioned lossy and asynchronous scenario.
Instabilities in the Time-Dependent Neutrino Disk in Gamma-Ray Bursts

We investigate the properties and evolution of accretion tori formed after the coalescence of two compact objects. At these extreme densities and temperatures, the accreting torus is cooled mainly by neutrino emission produced primarily by electron and positron capture on nucleons (β-reactions). We solve for the disk structure and its time evolution by introducing a detailed treatment of the equation of state which includes photodisintegration of helium, the condition of β-equilibrium, and neutrino opacities. We self-consistently calculate the chemical equilibrium in the gas consisting of helium, free protons, neutrons, and electron-positron pairs and compute the chemical potentials of the species, as well as the electron fraction throughout the disk. We find that, for sufficiently large accretion rates (Ṁ ≳ 10 M☉ s-1), the inner regions of the disk become opaque and develop a viscous and thermal instability. The identification of this instability might be relevant for GRB observations.
Eclipse Mapping of the Accretion Disk Wind in the Cataclysmic Variable UX Ursae Majoris

We present the results of an effort to model recent HST eclipse observations of the C IV 1550 Å resonance line in the high-inclination nova-like cataclysmic variable UX UMa. Assuming this line to be predominantly wind-formed, we are able to roughly reproduce the shapes and strengths of the observed line profiles (both away from and during eclipse) within the framework of a simple kinematic model in which the outflow is described as a rotating, biconical accretion disk wind. Our preferred model also matches most of the detailed behavior of different parts of the C IV line profile (blue wing, line center, and red wing) as a function of orbital phase. The most important result of our modeling is that it strongly suggests the presence of a high column (NH ~ 1023 cm-2), relatively dense (ne ≃ 4 × 1012 cm-3), and only slowly outflowing (vpoloidal ≪ vescape) transition region between the disk photosphere and the fast-moving wind. We also find that the outflow from UX UMa is probably only moderately collimated (the outer opening angle of our preferred model is θmax ≃ 65°). Finally, the rotational disturbance seen in the data is fitted reasonably well by our model, in which the rotational component of motion in the wind is fixed by conserving the specific angular momentum of the outflowing material. The implications of these results for dynamical models of disk-driven winds are discussed.
Duality in finite element exterior calculus

In order to generalize finite element methods to differential forms, Arnold, Falk, and Winther constructed two families of spaces of polynomial differential forms on a simplex $T$, the $\mathcal P_r\Lambda^k(T)$ spaces and the $\mathcal P_r^-\Lambda^k(T)$ spaces, where $k$ is the degree of the form and $r$ is the degree of its coefficients. The geometric decomposition for these finite element spaces hinges on a duality relationship between the $\mathcal P$ and $\mathcal P^-$ spaces proved by Arnold, Falk, and Winther. In this article, we give a natural alternate construction of the $\mathcal P_r\Lambda^k(T)$ and $\mathcal P_r^-\Lambda^k(T)$ spaces, leading to a new basis-free proof of this duality relationship using a modified Hodge star operator.
ELECTRIC DIPOLE MOMENT OF THE NEUTRON IN THE TWO-FLAVOR SKYRME MODEL

We calculate the semiclassical electric dipole moment Dn of the neutron in the two-flavor Skyrme model and compare with other calculations. In terms of the QCD θ-angle we find (including sign) Dn=1.4×10-16θe0cm, where e0 is the electric charge of the proton.
Spectral Diagnostics of Chromospheres—A Signature of Emergent Magnetic Flux

The chromospheres of the Sun and solar-like stars respond to the underlying magnetic activity. The spectral lines of singly ionized calcium (e.g., Ca II K at 3933 Å) exhibit single or double reversals and serve as diagnostic tools for the magnetic activity. We present observations showing that the Ca II K spectral line may exhibit reversals in addition to the well-known K1, K2, and K3 components, when observed with high angular and spectral resolution. These Ca II K spectral line anomalies occur when small-scale, subarcsecond magnetic fields emerge through the chromosphere. The anomalous profiles originate at locations that are cospatial with Hα brightening at footpoints of dark active region fibrils, or active region filaments. The photospheric magnetic field is bipolar (small opposite polarity magnetic nodules) or has neutral lines at cospatial locations where the spectral lines are anomalous. Small-scale reconnective processes can cause these anomalous profiles. From a simultaneous time series of magnetic field data, we find that the emerging magnetic flux is associated with these profiles. The additional reversals primarily occur redward of the familiar K3 absorption trough, implying chromospheric downflow velocities that lead to the formation of shocks. The magnitude of the Doppler shift is of the order 40-50 km s-1. We present evidence to suggest that a combination of subresolution elements, each of which has regular profiles with large relative Doppler shifts could explain the formation of some of these profiles. A heuristic model that combines buoyant magnetic fields, convective collapse, gas evacuation, shock formation, heating, and a multicomponent model atmosphere can reproduce these profiles.
Frequency regulation optimization for wind storage based on frequency regulation reliability and state of charge in isolated island off‐grid

To further improve the frequency regulation stability of wind farm, and optimize the state of charge (SOC) basepoint, charge and discharge rate and recovery capacity of energy storage. In an isolated, off‐grid state, a two‐layer optimization method is proposed, taking into account the frequency regulation reliability and SOC adaptive adjustment of the wind storage. In the upper layer, the model predictive control theory is adopted to optimize the energy‐storage frequency regulation output power with the goal of minimizing the wind storage frequency regulation power deviation. While solving the problem of low‐frequency regulation reliability of wind farm, the SOC recovery basepoint and frequency regulation power of energy storage are optimized. At the SOC optimization layer, based on the upper SOC recovery basis point, we propose a dynamic recovery method for energy‐storage SOC that considers both the SOC recovery demand and grid‐bearing capacity, to determine the energy‐storage recovery power. By determining the frequency regulation or recovery power, we propose a calculation method to optimize the energy‐storage charge and discharge coefficients as per the SOC for avoiding excessive charging and discharging. The simulation results show that, under continuous disturbance, the root‐mean‐square deviations of the proposed method is 80.13% and 62.63% lower than those of the fixed K and SOC methods, respectively. Furthermore, the proposed method exhibits the best SOC maintenance effect.
On certain equations of arbitrary length over torsion-free groups.

Let $G$ be a non-trivial torsion free group and $t$ be an unknown. In this paper we consider three equations (over $G$) of arbitrary length and show that they have a solution (over $G$) provided two relations among their coefficients hold. Such equations appear for all lengths greater than or equal to eight and the results presented in this article can substantially simplify their solution.
Critical line of the Ising model on 2-dimensional CDT and its dual

In this paper we study the annealed coupling of an Ising model with 2-dimensional causal dynamical triangulation model. After a short review of previous results, we prove the existence of the so-called critical line and derive its analytical properties and asymptotics. In addition, relations between the model and its dual are investigated.
Algebraic sets of types A, B, and C coincide

It is proved that the definition of an algebraic set of type ${\sf A}$ (a notion related to the multidimensional Hamburger moment problem) does not depend on the choice of a polynomial describing the algebraic set in question and that an algebraic set of type ${\sf B}$ is always of type ${\sf A}$. This answers in the affirmative two questions posed in 1992 by the second author. It is also shown that an algebraic set is of type ${\sf A}$ if and only if it is of type ${\sf C}$ (a notion linked to orthogonality of polynomials of several variables). This, in turn, enables us to answer three questions posed in 2005 by Cicho\'n, Stochel, and Szafraniec.
Patterns of vowel‐to‐vowel coarticulation in Greek and English

Many previous studies have indicated that coarticulatory behavior differs systematically across languages. One specific hypothesis, made by Manuel and Krakow (1984), is that languages with larger vowel inventories show reduced vowel‐to‐vowel coarticulation because their crowded vowel spaces impose more stringent requirements for maintaining phonological distinctiveness. The present study is designed (a) to test this prediction in Greek versus English, which have small and large vowel inventories, respectively; and (b) to investigate which parameters of the vowel system are most responsible for shaping language‐specific coarticulatory constraints. Adult monolingual speakers of each language were recorded, producing VCV utterances embedded in phonologically similar carrier phrases. Vowels included all five vowels of Greek, /i,e,a,o,u/, and their closest counterparts in American English, and the medial consonant varied between labial and alveolar places of articulation. To provide an independent measure of production variability for each vowel, speakers also produced the vowels in real words of the form /pVt/ or /bVt/, embedded in the same carrier phrases. Preliminary data are presented for two speakers of each language, and discussed in terms of vowel type, distribution within the vowel space, and the size of vowel areas within F1−F2 space.
High-performance AlGaN∕GaN lateral field-effect rectifiers compatible with high electron mobility transistors

A high electron mobility transistor (HEMT)-compatible power lateral field-effect rectifier (L-FER) with low turn-on voltage is demonstrated using the same fabrication process as that for normally off AlGaN∕GaN HEMT, providing a low-cost solution for GaN power integrated circuits. The power rectifier features a Schottky-gate-controlled two-dimensional electron gas channel between the cathode and anode. By tying up the Schottky gate and anode together, the forward turn-on voltage of the rectifier is determined by the threshold voltage of the channel instead of the Schottky barrier. The L-FER with a drift length of 10μm features a forward turn-on voltage of 0.63V at a current density of 100A∕cm2. This device also exhibits a reverse breakdown voltage (BV) of 390V at a current level of 1mA∕mm and a specific on resistance (RON,sp) of 1. 4mΩcm2, yielding a figure of merit (BV2∕RON,sp) of 108MW∕cm2. The excellent device performance, coupled with the lateral device structure and process compatibility with AlGaN∕GaN.
Note On Elliptic Primitive Points

Let $E$ be an elliptic curve of rank $\text{rk}(E) \geq 1$, and let $P \in E(\mathbb{Q})$ be a point of infinite order. The number of elliptic primes $p \leq x$ for which $\langle P\rangle=E(\mathbb{F}_p)$ is expected to be $\pi(x,E,P)=\delta(E,P)x/\log x+o(x/\log x)$, where $\delta(E,P)\geq 0$ is a constant. This note proves the lower bound $\pi(x,E,P) \gg x/\log x$.
Simulation and experimental study of Taylor cone and jet evolution process parameters in electrohydrodynamics

In melt electrospinning, accurate control of jet evolution and Taylor cone process parameters helps to control the final fiber properties. High-speed photography was employed to observe the jet's formation process and the Taylor cone's morphology. A multi-physics model of nonisothermal heat transfer was used to predict the fluid flow direction and velocity change. In addition, we investigated the relationships between the process parameters of the Taylor cone and the diameter of melt electrospun fiber. The results show an excellent linear relationship between the process parameters (cone angle, curvature, and Taylor cone height) and fiber diameter. According to the simulation results, the axial fluid flow keeps the maximum and accelerates continuously until the collector captures it. In addition, with the increase of voltage, the fiber strength is lower, and the crystallinity is improved. This work analyzes diameter and process parameters and offers a fresh perspective on electrostatic-fluid interaction and a method to forecast fiber diameter.
Geometric Homology

The purpose of this paper is to introduce a version of singular homology based on smooth mappings of manifolds with corners. Although variants of such a theory exists in the literature (see [3], [1], [16]), we felt that certain points were not adequately addressed. In particular, our goal is to construct a chain level theory based on smooth mappings of manifolds with corners. In addition, we will avoid using the fact that smooth manifolds with can be triangulated. As we shall see, transversality and intersections play a major role in setting up this theory. From a pedagogical viewpoint, having intersection theory arguments available from the start facilitates simple and intuitive computations.
Euler tours and unicycles in the rotor-router model

A recurrent state of the rotor-routing process on a finite sink-free graph can be represented by a unicycle that is a connected spanning subgraph containing a unique directed cycle. We distinguish between short cycles of length 2 called ‘dimers’ and longer ones called ‘contours’. Then the rotor-router walk performing an Euler tour on the graph generates a sequence of dimers and contours which exhibits both random and regular properties. Imposing initial conditions randomly chosen from the uniform distribution we calculate expected numbers of dimers and contours and correlation between them at two successive moments of time in the sequence. On the other hand, we prove that the excess of the number of contours over dimers is an invariant depending on planarity of the subgraph but not on initial conditions. In addition, we analyze the mean-square displacement of the rotor-router walker in the recurrent state.
Image Segmentation Research Based on Particle Swarm Optimization

As one of the difficulties and hot of computer vision and image processing, Image segmentation is highly valued by the research workers. Yet there is no image segmentation algorithm which is generic, and it is difficult to obtain an optimal feature representation method. In this paper, particle swarm optimization has proposed to segment the image. PSO algorithm can improve the efficiency and quality of the picture some extent through the experimental results. The algorithm has some versatility, as long as the corresponding parameters are adjusted, it can also handle the other images. The results show that PSO algorithm is very stable, and the fusion result is more satisfactory.
Thermal and Structural Characterization of a Titanium Carbide/Carbon Composite for Nuclear Applications

In the framework of ISOL (isotope separation on-line) facilities, porous carbides are among the most employed target materials for the production of radioactive ion beams for research. As foreseen by the ISOL technique, a production target is impinged by an energetic particle beam, inducing nuclear reactions from such an interaction. The resulting radionuclides are subsequently released, thanks to the high target working temperature (1600–2000 °C); ionized; and extracted into a beam. Since the target microstructure and porosity play a fundamental role in the radionuclide release efficiency, custom-made target materials are often specifically produced, resulting in unknown thermal and structural properties. Considering that such targets might undergo intense thermal stresses during operation, a thermal and structural characterization is necessary to avoid target failure under irradiation. In the presented work, a custom-made porous titanium carbide that was specifically designed for application as an ISOL target was produced and characterized. The thermal characterization was focused on the evaluation of the material emissivity and thermal conductivity in the 600–1400 °C temperature range. For the estimation of a reference material tensile stress limit, the virtual thermoelastic parameter approach was adopted. In particular, for the aforementioned temperature range, an emissivity between 0.7 and 0.8 was measured, whereas a thermal conductivity between 8 and 10 W/mK was estimated.