Miracle-dz/UniFAR-FTUs huggingface dataset:
Continued Investigation of Arc Flash in Single Phase Systems

IEEE 1584 - 2018 documents the standard method for calculating arc flash incident energy. This value is then used to establish one of several safety boundaries around exposed, energized electrical conductors and to select protective equipment. While 1584 covers three-phase configurations in detail, it currently excludes single-phase calculations. Prevalence of single-phase AC power distribution inspired curiosity about possible hazards of fire and injury arising from arc flash in such systems. This paper extends work previously published and covers the conclusion of doctoral research into single-phase arc flash in one laboratory configuration. Further experimental work supported the hypothesis that incident energy would be low (less than 1 cal/cm2) for single-phase events below some threshold voltage and for available fault currents up to 22,000 amperes. This threshold voltage appears to be near 434VAC. Repeated test groups at greater than 434V sustained the conclusion that such configurations develop dangerous levels of heat and blast pressure even when the source is single-phase.
Human intracortical responses to varying electrical stimulation conditions are separable in low-dimensional subspaces

Electrical stimulation is a powerful tool for targeted neurorehabilitation, and recent work in adaptive stimulation where stimulation can be adjusted in real-time has shown promise in improving stimulation outcomes and reducing stimulation-induced side effects. Mapping the relationship between electrical stimulation input and neural activity response can help reveal their interactions and can give us tools to iterate and improve on our stimulation protocols. Here, we introduce methods for identifying low-dimensional subspaces of human intracortical responses to electrical stimulation in invasive electroencephalography. In epilepsy patients (n=4) undergoing clinical monitoring, we applied a stimulation protocol of varying amplitude and frequency in 5-second intervals to capture a range of responses to different stimulation conditions. We characterized these responses using time-frequency spectral power, applied baseline subtraction and outlier removal procedures, and performed principal component analysis across frequencies. We identified that intracortical responses to different stimulation conditions can be represented in a 3-dimensional subspace, accounting for more than 95% of the variance. Using support vector machine classification, we demonstrated separability of intracortical responses in different stimulation conditions across subjects, where this separability was contingent on applying baseline subtraction and outlier removal. Our results represent a first step towards building a predictive model of neural response from stimulation input, an important prerequisite for adaptive closed-loop stimulation for targeted neurorehabilitation.
High-power single-mode multijunction VCSEL

We demonstrate a single mode 940nm VCSEL with a five-junction bipolar cascade active region. The device achieves 11 mW output power and 44 dB sidemode suppression ratio under continuous wave, room temperature operation. Peak power conversion and slope efficiency are 51% and 5.4 W/ A, respectively.
A Novel Scheme for Switching Between a Self-excited Induction Generator and a Series Connected Self-excited Synchronous Generator

This paper proposes a novel switching scheme to operate an autonomous three-phase wound-rotor induction machine (IM) as two self-excited AC generators. The first generator is a self-excited induction generator (SEIG) with short-circuited Y-connected rotor terminals. The second generator is a series connected self-excited synchronous generator (SCSESG) with Y-connected rotor windings in series with its stator windings in different phase sequence. The three-phase IM model is derived to analyze the performance operated as an SEIG or an SCSESG. To validate the proposed IM model switching between an SEIG and an SCSESG under various loading conditions, the simulated steady-state and transient results are compared with the experimental results obtained from a laboratory 1.1-kW wound-rotor IM. It can be concluded from the simulated and experimental results that the proposed model is adequate to simulate the performance of the IM operated as an SEIG or an SCSESG.
Correlation between core ion energization, suprathermal electron bursts, and broadband ELF plasma waves

Observations of the lowest energy or core ions provide a particularly sensitive measure of the early stages of auroral ion energization. Freja satellite observations of 0-20 eV core ions in the topside auroral ionosphere and cusp/cleft show signs of heating within both regions of VLF hiss and broadband ELF plasma waves. However, heating to several eV or more is associated predominantly with the ELF waves. A correlation analysis of wave and core ion data formed from orbital segments shows that, on average, correlations are highest for wave frequencies below several hundred Hz, and less at VLF hiss frequencies. A similar analysis shows a higher correlation between electron precipitation and ion heating for electron energies below several hundred eV (i.e., the energies associated with suprathermal electron bursts) and a lower correlation above the 1 keV energies associated with auroral inverted-V's. Signs of core ion heating begin to appear when wave power at the O + gyrofrequency exceeds about 10- (mV m -1 ) 2 /Hz, and when the integrated field-aligned electron flux exceeds a few times 10 7 cm -2 s -1 sr -1 , This electron energy flux threshold is at least an order of magnitude lower than previously inferred from earlier studies comparing suprathermal electron fluxes and energetic ions. Almost all observed heating events occur during enhanced or active geomagnetic conditions; i.e., K p > 4. While the most intense core ion heating is correlated with broadband ELF waves, we also present one example of weak ion heating of a few eV in a region of VLF auroral hiss.
Modelling and control of a canting keel-based ship roll stabilization system for crane operations

This paper considers the use of a novel canting keel system for the roll stabilization of ships subjected to unbalanced loading occurring, for example, in crane operations at zero surge velocities. A simplified 1 degree-of-freedom mathematical model of a monohull marine vessel based on the lumped parameter approach is considered along with the canting keel system. Then, in order to compensate for unknown plant dynamics as well as time-varying load disturbances, a simple sliding-mode controller is proposed. Simulation results are finally given to illustrate the potential of the approach.
Curved spacetimes with local κ -Poincaré dispersion relation

We use our previously developed identification of dispersion relations with Hamilton functions on phase space to locally implement the $\ensuremath{\kappa}$-Poincar\'e dispersion relation in the momentum spaces at each point of a generic curved spacetime. We use this general construction to build the most general Hamiltonian compatible with spherical symmetry and the Plank-scale-deformed one such that in the local frame it reproduces the $\ensuremath{\kappa}$-Poincar\'e dispersion relation. Specializing to Planck-scale-deformed Schwarzschild geometry, we find that the photon sphere around a black hole becomes a thick shell since photons of different energy will orbit the black hole on circular orbits at different altitudes. We also compute the redshift of a photon between different observers at rest, finding that there is a Planck-scale correction to the usual redshift only if the observers detecting the photon have different masses.
K-mouflage imprints on cosmological observables and data constraints

We investigate cosmological constraints on K-mouflage models of modified gravity. We consider two scenarios: one where the background evolution is free to deviate from ΛCDM (K-mouflage) and another one which reproduces a ΛCDM expansion (K-mimic), implementing both of them into the EFTCAMB code. We discuss the main observational signatures of these models and we compare their cosmological predictions to different datasets, including CMB, CMB lensing, SNIa and different galaxy catalogues. We argue about the possibility of relieving the H0 and weak lensing tensions within these models, finding that K-mouflage scenarios effectively ease the tension on the Hubble Constant. Our final 95% C.L. bounds on the ϵ2,0 parameter that measures the overall departure from ΛCDM (corresponding to ϵ2,0 = 0) are −0.04⩽ ϵ2,0 ⩽ 0 for K-mouflage and 0 ⩽ ϵ2,0 ⩽ 0.002 for K-mimic. These translate into an upper bound for the coupling strength: β <0.22 for K-mouflage and β < 0.026 for K-mimic. In the former case the main constraining power comes from changes in the background expansion history, while in the latter case the model is strongly constrained by measurements of the amplitude of matter perturbations. The sensitivity of these cosmological constraints closely matches that of solar system probes. We show that these constraints could be significantly tightened with future ideal probes like CORE.
Modelling of proton acceleration in application to a ground level enhancement

Context. The source of high-energy protons (above ~500 MeV) responsible for ground level enhancements (GLEs) remains an open question in solar physics. One of the candidates is a shock wave driven by a coronal mass ejection, which is thought to accelerate particles via diffusive-shock acceleration. Aims. We perform physics-based simulations of proton acceleration using information on the shock and ambient plasma parameters derived from the observation of a real GLE event. We analyse the simulation results to find out which of the parameters are significant in controlling the acceleration efficiency and to get a better understanding of the conditions under which the shock can produce relativistic protons. Methods. We use the results of the recently developed technique to determine the shock and ambient plasma parameters, applied to the 17 May 2012 GLE event, and carry out proton acceleration simulations with the Coronal Shock Acceleration (CSA) model. Results. We performed proton acceleration simulations for nine individual magnetic field lines characterised by various plasma conditions. Analysis of the simulation results shows that the acceleration efficiency of the shock, i.e. its ability to accelerate particles to high energies, tends to be higher for those shock portions that are characterised by higher values of the scattering-centre compression ratio rc and/or the fast-mode Mach number MFM. At the same time, the acceleration efficiency can be strengthened by enhanced plasma density in the corresponding flux tube. The simulations show that protons can be accelerated to GLE energies in the shock portions characterised by the highest values of rc. Analysis of the delays between the flare onset and the production times of protons of 1 GV rigidity for different field lines in our simulations, and a subsequent comparison of those with the observed values indicate a possibility that quasi-perpendicular portions of the shock play the main role in producing relativistic protons.
Lift generation with optimal elastic pitching for a flapping plate

Abstract The lift-generating capabilities of a translating and passively pitching rectangular plate are assessed experimentally. The plate pitch dynamics are generated by a rotational spring, and a genetic algorithm isolates a set of spring parameters maximizing the average lift. Our experiments identified a range of parameters that produce kinematic trajectories associated with optimal lift production. The stroke length and the dynamic response of the spring at the driving frequency are revealed to play crucial roles in the generation of such trajectories. Measurements taken with digital particle image velocimetry are used to analyse the results.
Does Classroom Diversity Improve Academic Outcomes? ∗

This paper estimates the causal eﬀect of racial diversity in the classroom on academic outcomes. I exploit a quasi-experimental setting where ﬁrst-year students in a year-long mandatory humanities writing course at a U.S. liberal-arts college are assigned to discussion conference groups with varying levels of diversity in terms of classmate racial composition. This within-classroom diversity is eﬀectively random conditional on students’ scheduling availability, given the institutional features determining conference assignment, and the fact that students do not know (ex-ante) and cannot manipulate the racial composition of peers in their enrolled conference. I ﬁnd that a higher degree of racial diversity in the conference causes a statistically signiﬁcant increase in the humanities course grade and the grade point average (GPA) at graduation. However, diversity has no statistically signiﬁcant eﬀect on GPA at the end of the ﬁrst year. These results contribute to the debate over aﬃrmative action in higher education, and oﬀer modest justiﬁcation for race-based admissions policies.
Accuracy of finite-difference and finite-element modeling of the scalar and elastic wave equations

Numerical solutions of the scalar and elastic wave equations have greatly aided geophysicists in both forward modeling and migration of seismic wave fields in complicated geologic media, and they promise to be invaluable in solving the full inverse problem. This paper quantitatively compares finite‐difference and finite‐element solutions of the scalar and elastic hyperbolic wave equations for the most popular implicit and explicit time‐domain and frequency‐domain techniques. In addition to versatility and ease of implementation, it is imperative that one choose the most cost effective solution technique for a fixed degree of accuracy. To be of value, a solution technique must be able to minimize (1) numerical attenuation or amplification, (2) polarization errors, (3) numerical anisotropy, (4) errors in phase and group velocities, (5) extraneous numerical (parasitic) modes, (6) numerical diffraction and scattering, and (7) errors and transmission coefficients. This paper shows that in homogeneous media the.
FRB 121102 Bursts Show Complex Time–Frequency Structure

FRB 121102 is the only known repeating fast radio burst source. Here we analyze a wide-frequency-range (1–8 GHz) sample of high signal-to-noise, coherently dedispersed bursts detected using the Arecibo and Green Bank telescopes. These bursts reveal complex time–frequency structures that include subbursts with finite bandwidths. The frequency-dependent burst structure complicates the determination of a dispersion measure (DM); we argue that it is appropriate to use a DM metric that maximizes frequency-averaged pulse structure, as opposed to peak signal-to-noise, and find DM = 560.57 ± 0.07 pc cm−3 at MJD 57,644. After correcting for dispersive delay, we find that the subbursts have characteristic frequencies that typically drift lower at later times in the total burst envelope. In the 1.1–1.7 GHz band, the ∼0.5–1 ms subbursts have typical bandwidths ranging from 100 to 400 MHz, and a characteristic drift rate of ∼200 MHz ms−1 toward lower frequencies. At higher radio frequencies, the subburst bandwidths and drift rate are larger, on average. While these features could be intrinsic to the burst emission mechanism, they could also be imparted by propagation effects in the medium local to the source. Comparison of the burst DMs with previous values in the literature suggests an increase of ΔDM ∼ 1–3 pc cm−3 in 4 yr; though, this could be a stochastic variation as opposed to a secular trend. This implies changes in the local medium or an additional source of frequency-dependent delay. Overall, the results are consistent with previously proposed scenarios in which FRB 121102 is embedded in a dense nebula.
GRB 111005A at z = 0.0133 and the Prospect of Establishing Long–Short GRB/GW Association

GRB 111005A, a long-duration gamma-ray burst (GRB) that occurred within a metal-rich environment that lacks massive stars with , is not coincident with supernova emission down to a stringent limit and thus should be classified as a “long–short” GRB (lsGRB; also known as an SN-less long GRB or hybrid GRB), like GRB 060505 and GRB 060614. In this work, we show that in the neutron star merger model the non-detection of the optical/infrared emission of GRB 111005A requires sub-relativistic neutron-rich ejecta with a mass of , which is (significantly) less massive than that of GRB 130603B, GRB 060614, GRB 050709, and GRB 170817A. The lsGRBs are found to have a high rate density and the neutron star merger origin model can be unambiguously tested by the joint observations of the second-generation gravitational-wave (GW) detectors and the full-sky gamma-ray monitors such as Fermi-GBM and the proposed GECAM. If no lsGRB/GW association is observed in the 2020s, alternative scenarios have to be systematically investigated. With the detailed environmental information achievable for the nearby events, a novel kind of merger or explosion origin may be identified.
Mesoscale and convective-scale downdrafts as distinct components of squall-line structure

Abstract This paper describes the two different kinds of downdraft air frequently observed to the rear of some squall lines at low levels. The primary data source is measurements taken during aircraft penetrations of certain low-latitude squall lines; they are supplemented by satellite data, radar data, surface meteorological data, and soundings ahead of and behind the squall lines. A shallow layer of cool, near-saturated air occupies the lowest few hundred meters and is separated by a marked stable layer from a deep layer of highly unsaturated air. The lowest layer is hypothesized to be the product of convective-scale saturated downdrafts, and the drier air is shown to be the result of mesoscale unsaturated downdrafts as described by Zipser (1969). Over a warm ocean, there is a large latent and sensible heat flux from the surface into the lowest layer, which rapidly becomes a new mixed layer and incorporates the drier air from above by entrainment. Mesoscale sinking in the post-squall region is shown to .
Detection prospects for high energy neutrino sources from the anisotropic matter distribution in the local Universe

Constraints on the number and luminosity of the sources of the cosmic neutrinos detected by IceCube have been set by targeted searches for point sources. We set complementary constraints by using the 2MASS Redshift Survey (2MRS) catalogue, which maps the matter distribution of the local Universe. Assuming that the distribution of the neutrino sources follows that of matter, we look for correlations between ``warm'' spots on the IceCube skymap and the 2MRS matter distribution. Through Monte Carlo simulations of the expected number of neutrino multiplets and careful modelling of the detector performance (including that of IceCube-Gen2), we demonstrate that sources with local density exceeding 10−6 Mpc−3 and neutrino luminosity Lν ≲ 1042 erg s−1 (1041 erg s−1) will be efficiently revealed by our method using IceCube (IceCube-Gen2). At low luminosities such as will be probed by IceCube-Gen2, the sensitivity of this analysis is superior to requiring statistically significant direct observation of a point source.
Superconductivity in the Hubbard model: a hidden-order diagnostics from the Luther-Emery phase on ladders

Short-range antiferromagnetic correlations are known to open a spin gap in the repulsive Hubbard model on ladders with \boldsymbol{M}𝐌 legs, when \boldsymbol{M}𝐌 is even. We show that the spin gap originates from the formation of correlated pairs of electrons with opposite spin, captured by the hidden ordering of a spin-parity operator. Since both spin gap and parity vanish in the two-dimensional limit, we introduce the fractional generalization of spin parity and prove that it remains finite in the thermodynamic limit. Our results are based upon variational wave functions and Monte Carlo calculations: performing a finite size-scaling analysis with growing \boldsymbol{M}𝐌, we show that the doping region where the parity is finite coincides with the range in which superconductivity is observed in two spatial dimensions. Our observations support the idea that superconductivity emerges out of spin gapped phases on ladders, driven by a spin-pairing mechanism, in which the ordering is conveniently captured by the finiteness of the fractional spin-parity operator.
Computation of ion production rate and short, mid and long term ionization effect by cosmic rays during Bastille day event

The galactic cosmic rays are the main source of ionization in the Earth stratosphere and troposphere. The induced by primary cosmic ray particles ionization is important in various processes related to atmospheric physics and chemistry, specifically the minor constituents. The ion production in the atmosphere is enhanced compared to the average following major solar energetic particles events, specifically over the polar caps. During the solar cycle 23 we observed several strong ground level enhancements, one of the strongest among them been the Bastille day event on 14 July 2000. In the work presented here we apply a full Monte Carlo 3-D model in order to compute the cosmic ray induced ionization. The model is based on atmospheric shower simulation with the PLANETOCOSMICS code and the ion production rate is considered as a superposition of cosmic rays with galactic and solar origin. The ion production rate is computed as a function of the altitude above the sea level and the short, mid and long term ionization effect relative to the average due to galactic cosmic rays is computed.
Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids

We present metallicities, [Fe/H], and elemental abundance ratios, [X/Fe], for a sample of 24 Cepheids in the outer Galactic disk based on high-resolution echelle spectra. The sample members have galactocentric distances covering 12 kpc ≤ RGC ≤ 17.2 kpc, making them the most distant Galactic Cepheids upon which detailed abundance analyses have been performed. We find subsolar ratios of [Fe/H] and overabundances of [α/Fe], [La/Fe], and [Eu/Fe] in the program stars. All abundance ratios exhibit a dispersion that exceeds the measurement uncertainties. As seen in our previous studies of old open clusters and field giants, enhanced ratios of [α/Fe] and [Eu/Fe] reveal that recent star formation has taken place in the outer disk with Type II supernovae preferentially contributing ejecta to the interstellar medium and with Type Ia supernovae playing only a minor role. The enhancements for La suggest that asymptotic giant branch stars have contributed to the chemical evolution of the outer Galactic disk. Some of the young Cepheids are more metal-poor than the older open clusters and field stars at comparable galactocentric distances. This demonstrates that the outer disk is not the end result of the isolated evolution of an ensemble of gas and stars. We showed previously that the older open clusters and field stars reached a basement metallicity at about 10-11 kpc. The younger Cepheids reach the same metallicity but at larger galactocentric distances, roughly 14 kpc. This suggests that the Galactic disk has been growing with time, as predicted from numerical simulations. The outer disk Cepheids appear to exhibit a bimodal distribution for [Fe/H] and [α/Fe]. Most of the Cepheids continue the trends with galactocentric distance exhibited by S. M. Andrievsky's larger Cepheid sample, and we refer to these stars as the "Galactic Cepheids. " A minority of the Cepheids show considerably lower [Fe/H] and higher [α/Fe], and we refer to these stars as the "Merger Cepheids. " One signature of a merger event would be composition differences between the Galactic and Merger Cepheids. The Cepheids satisfy this requirement, and we speculate that the distinct compositions suggest that the Merger Cepheids may have formed under the influence of significant merger or accretion events. The short lifetimes of the Cepheids reveal that the merger event may be ongoing, with the Monoceros Ring and Canis Major galaxy being possible merger candidates.