Miracle-dz/UniFAR-FTUs huggingface dataset:
Fast dynamos, cosmic rays, and the galactic magnetic field

It is suggested here that the dynamo believed to be responsible for the magnetic field of the Galaxy is a fast dynamo due to the dynamical reconnection of the azimuthal field of the Galaxy as the field is deformed by the instability of the gaseous disk and the rapid inflation of magnetic lobes by the cosmic-ray gas to form the Galactic halo. The reconnection of adjacent lobes carries out both the alpha effect and field dissipation essential for the existence of the Galactic alpha-omega dynamo. The azimuthal field is generated primarily in the gaseous disk, while the alpha effect is carried out in the halo.
Precision Measurement of Absolute Specular Reflectance with Minimized Systematic Errors

Instruments for making precision measurements of the specular reflectance at essentially normal incidence in the near ultraviolet, visible, and infrared regions of the spectrum are described. The square of the absolute reflectance is measured, with a resultant increase in measuring precision, and the major sources of systematic error in making reflectance measurements have been reduced or eliminated. The difficulty in making precision reflectance measurements in the infrared, where integrating spheres cannot be used, has been overcome by a unique compensating feature in the infrared reflectometer which prevents the image on the detector from changing size or position because of a slight tilt of the sample. The measurements made with these instruments on high reflectance samples are believed to be good to ±0.001.
A note on unbounded solutions of a class of second order rational difference equations

We investigate the unbounded solutions of the second order difference equation where all parameters and C and initial conditions are nonnegative and such that for all n. We give a characterization of unbounded solutions for this equation showing that whenever an unbounded solution exists the subsequence of even indexed (resp. odd) terms tends to and the subsequence of odd indexed (resp. even) terms tends to a nonnegative number. We also show that two sets in the plane of initial conditions corresponding to the two cases are separated by the global stable manifold of the unique positive equilibrium. Our result answers two open problems posed by Kulenović and Ladas (2001, Dynamics of Second Order Rational Difference Equations with Open Problems and Conjectures, Boca Raton/London: Chapman and Hall/CRC).
Progressive transmission of images using wavelets: evaluation using the Renyi generalized entropy

This paper explores the quality of successive steps in a wavelet based progressive image transmission, using the Renyi generalized dimension D/sub q/. The Renyi generalized dimension is used to measure the multifractal complexity within an image giving us a tool for evaluating image quality other than the traditional PSNR. We apply this to a wavelet based progressive image transmission scheme through denoising, zerotree coding, and adaptive arithmetic coding to see how D/sub q/ changes as the image is reconstructed.
Statistical properties of tail plasma sheet electrons above 40 keV

[1] We use data from four tail seasons (2001–2004) of the Cluster spacecraft to study statistical features of energetic electrons (40–400 keV) in the magnetotail plasma sheet in combination with plasma parameters and indices of geomagnetic activity. We find that the horizontal magnetic field magnitude best orders the energetic electron observations. Using this method we observe a statistical flux gradient toward the neutral sheet. The fluxes also increase with an increase in the vertical magnetic field component (dipolarization). The intensity of supra-thermal electrons is observed to increase strongly as function of plasma temperature. Although the energetic electron fluxes also appear to increase strongly with geomagnetic activity this is found to be mainly due to the increase in plasma temperature with increasing Kp. Investigation of neutral sheet fluxes and phase space densities at fixed first adiabatic invariant (μ) indicates that adiabatic heating can explain observed flux increases during field dipolarization. The spectral slope in the supra-thermal range is observed to be independent of geomagnetic activity (Kp), while there is a significant local time dependence, with harder spectra observed at dawn compared to the dusk side.
Electron injection by relativistic protons in active galactic nuclei

It is shown that protons with Lorentz factors larger than about 1,000,000 are cooled very rapidly by collisions with soft photons in the environment of an AGN. If the energy distribution of accelerated protons is sufficiently flat, then most of the energy contained in relativistic protons will be transformed to pairs, and then to radiation. Under these conditions, proton cooling due to p-gamma interactions is much more important than energy losses due to inelastic proton-proton collisions. 25 references.
The critical state: a trapped wave model of vortex breakdown

A model of vortex breakdown is presented and its predictions compared with the experiments of Sarpkaya (1971). The model is cntred about a theory of long, weakly nonlinear waves propagating on critical flows in tubes of variable cross-section. Although the weakly nonlinear theory must be extended beyond its domain of formal validity, many of the experimentally observed features of vortex breakdown are reproduced by the model. The description of the time evolution of the flow field that is presented requires numerical calculations that are not simple, but some important conclusions may be determined by easy computations. In particular, the axial position of a breakdown may be found from a very simple equation (10).
A Comparison of Two Area Measures for Detecting Differential Item Functioning

The area between two item response functions is often used as a measure of differential item functioning under item response theory. This area can be measured over either an open interval (i.e., exact) or closed interval. Formulas are presented for com puting the closed-interval signed and unsigned areas. Exact and closed-interval measures were estimated on data from a test with embedded items intentionally constructed to favor one group over another. No real differences in detection of these items were found between exact and closed-interval methods.
First-principles calculation of the electronic structure and EELS spectra at the graphene/Ni(111) interface

A spin-polarized ﬁrst-principles calculation of the atomic and electronic structure of the graphene/Nis111dinterface is presented. Different structural models have been considered, which differ in the positions of thecarbon atoms with respect to the nickel topmost layer. The most probable structure, which has the lowestenergy, has been determined. The distance between the ﬂoating carbon layer and the nickel surface is foundsmaller than the distance between graphene sheets in bulk graphite, in accordance with experimental measure-ments. The electronic structure of the graphene layer is strongly modiﬁed by interaction with the substrate andthe magnetic moment of the surface nickel atoms is lowered in the presence of the graphene layer. Severalinterface states have been identiﬁed in different parts of the interface two-dimensional Brillouin zone. Theirinﬂuence on the electron energy loss spectra has been evaluated.DOI: 10.1103/PhysRevB.71. 075402 PACS numberssd: 68.43. Fg, 73.20. At, 75.70. Ak, 79.20. UvI. INTRODUCTION
College Environments and Student Academic Achievement

In this study, selected aspects of the college environment were related to student academic achievement at 27 small liberal arts colleges. Academic achievement was measured by senior students' scores on the Area Tests of the Graduate Record Examination; the Scholastic Aptitude Test (Verbal and Mathematics) scores of these same students prior to college entrance were used as a control measure for differences in initial aptitude. The colleges' social and academic environment were assessed through students' perceptions and included five scales describing the extent of faculty-student interaction, student activism, curriculum flexibility, academic challenge, and the colleges' cultural facilities. All but the Activism scale were related to student over or underachievement on one or more of the three Area Tests (Humanities, Natural Science, Social Science). In particular, students at colleges with high scores on the Faculty-Student Interaction scale more often overachieved on two of the criteria tests, while students at colleges with low scores on this scale underachieved on all three of the tests. The results suggest that certain student-described college environmental features are related to academic achievement, although replication with another group of colleges would be desirable.
Small Sample Properties of LIML and Jackknife IV Estimators: Experiments with Weak Instruments

Using Monte Carlo simulations we study the small sample performance of the traditional TSLS, the LIML and four new jackknife IV estimators when the instruments are weak. We find that the new estimators and LIML have a smaller bias but a larger variance than the TSLS. In terms of root mean square error, neither LIML nor the new estimators perform uniformly better than the TSLS. The main conclusion from the simulations and an empirical application on labour supply functions is that in a situation with many weak instruments, there still does not exist an easy way to obtain reliable estimates in small samples. Better instruments and/or larger samples is the only way to increase precision in the estimates. Since the properties of the estimators are specific to each data-generating process and sample size it would be wise in empirical work to complement the estimates with a Monte Carlo study of the estimators' properties for the relevant sample size and data-generating process believed to be applicable. Copyright © 1999 John Wiley & Sons, Ltd.
Differential Cratering of Synchronously Rotating Satellites by Ecliptic Comets

Abstract We use Monte Carlo methods to simulate impacts of ecliptic comets on the synchronously rotating satellites of giant planets. We reconfirm the long-standing prediction that the cratering rate should be much higher on the leading hemispheres than on the trailing hemisphere; indeed we find that previously published analytical formulations modestly underestimate the degree of apex–antapex asymmetry to be expected. We then compare our results to new mapping of impact craters on Ganymede, Callisto, and Triton. Ganymede reveals a pronounced apex–antapex asymmetry that is nonetheless much less than predicted. All of Triton's confirmed impact craters are clustered toward the apex of motion, far exceeding the predicted asymmetry. No asymmetry is observed on Callisto. In each case at least one of our basic assumptions must be wrong. Likely candidates include the following: (i) the surfaces of all but the most sparsely cratered satellites are saturated or nearly saturated with impact craters; (ii) these satellites have rotated nonsynchronously over geological time; (iii) most of the craters are made not by heliocentric (Sun-orbiting) comets and asteroids but rather by planetocentric (planet-orbiting) debris of indeterminate origin; or (iv) pathological endogenic resurfacing has created illusions of structure. Callisto's surface is readily classified as nearly saturated. Ganymede's bright terrains, although less heavily cratered than those of Callisto, can also be explained by crater densities approaching saturation on a world where endogenic processes were active. The leading alternative is nonsynchronous rotation, an explanation supported by the distribution of catenae (crater chains produced by impact of tidally disrupted comets). Triton's craters can be explained by planetocentric debris or by capricious resurfacing, but both hypotheses are inherently improbable.
Polarization rotation, switching, and electric-field-temperature phase diagrams of ferroelectric BaTiO 3 : a molecular dynamics study

We use molecular dynamics simulations to understand the mechanisms of polarization switching in ferroelectric ${\text{BaTiO}}_{3}$ achieved with external electric field. For tetragonal and orthorhombic ferroelectric phases, we determine the switching paths and show that polarization rotation through intermediate monoclinic phases (a) facilitates switching at low fields and (b) is responsible for a sharp anisotropy in polarization switching. We develop an understanding of this through the determination of detailed electric-field\char21{}temperature phase diagrams that are fundamental to technological applications based on electromechanical and switching response of ferroelectrics.
Fine Control over the Projective Characters of the Centre of a Group

In this article we will study the restriction of the irreducible projective characters of a finite group to a central subgroup. We will also consider under what conditions on the restriction of such irreducible projective characters to an abelian normal subgroup that we can deduce that the subgroup is central. Finally, we will investigate the relationship between the inertia subgroup and the absolute centralizer of a central subgroup relative to a fixed 2-cocycle of the group.
Multi-peak standing waves for nonlinear Schrödinger equations with a general nonlinearity

We consider singularly perturbed elliptic equations $\varepsilon^2\Delta u - V(x) u + f(u)=0, x\in R^N, N \ge 3. $ For small $\varepsilon > 0,$ we glue together localized bound state solutions concentrating at isolated components of positive local minimum of $V$ under conditions on $f$ we believe to be almost optimal.
A Fixed Point Approach to Solve the Average Cost Optimality Equation for Semi-Markov Decision Processes with Feller Transition Probabilities

Semi-Markov control processes with Feller (also known as weakly continuous) transition probabilities and unbounded cost functions are considered. We give sufficient conditions for the existence of a lower semicontinuous and continuous solutions to the average cost optimality equation. The proof is based on a fixed point argument.
On the global optimality of generalized trust region subproblems

Quadratically constrained quadratic programming is an important class of optimization problems. We consider the case with one quadratic constraint. Since both the objective function and its constraint can be neither convex nor concave, it is also known as the ‘generalized trust region subproblem. ’ The theory and algorithms for this problem have been well studied under the Slater condition. In this article, we analyse the duality property between the primal problem and its Lagrangian dual problem, and discuss the attainability of the optimal primal solution without the Slater condition. The relations between the Lagrangian dual and semidefinite programming dual is also given.
Connection between Weather Types and Air Pollution Levels: A 19-Year Study in Nine EMEP Stations in Spain

This study focuses on the analysis of the distribution, both spatial and temporal, of the PM10 (particulate matter with a diameter of 10 µm or less) concentrations recorded in nine EMEP (European Monitoring and Evaluation Programme) background stations distributed throughout mainland Spain between 2001 and 2019. A study of hierarchical clusters was used to classify the stations into three main groups with similarities in yearly concentrations: GC (coastal location), GNC (north–central location), and GSE (southeastern location). The highest PM10 concentrations were registered in summer. Annual evolution showed statistically significant decreasing trends in PM10 concentration in all the stations covering a range from −0.21 to −0.50 µg m−3/year for Barcarrota and Víznar, respectively. Through the Lamb classification, the weather types were defined during the study period, and those associated with high levels of pollution were identified. Finally, the values exceeding the limits established by the legislation were analyzed for every station assessed in the study.
Using Rapid-Cycle Change to Improve COVID-19 Vaccination Strategy in Primary Care

During the COVID-19 pandemic, misinformation and distrust exacerbated disparities in vaccination rates by race and ethnicity throughout the United States. Primary care, public health systems, and community health centers have shifted their vaccination outreach strategies toward these disparate, unvaccinated populations. To support primary care, we developed the SAVE Sprint model for implementing rapid-cycle change to improve vaccination rates by overcoming community outreach barriers and workforce limitations. Participants were recruited for the 10-week SAVE Sprint program through partnerships with the National Association of Community Health Centers (NACHC) and the Resilient American Communities (RAC) Initiative. The majority of the participants were from community health centers. Data were evaluated during the program through progress reports and surveys, and interviews conducted three months post-intervention were recorded, coded, and analyzed. The SAVE Sprint model of rapid-cycle change exceeded participants’ expectations and led to improvements in patient education and vaccination among their vulnerable populations. Participants reported building new skills and identifying strategies for targeting specific populations during a public health emergency. However, participants reported that planning for rapid-pace change and trust-building with community partners prior to a health care crisis is preferable and would make navigating an emergency easier.
A Search for Periodicities in the X-Ray Emission from Cataclysmic Variables

The results of a search for periodicities in the X-ray emission from cataclysmic variables observed with the Einstein Observatory's IPC are presented. The search was conducted in the energy band 0.16-3.5 keV and covered the frequency range 0.01-2.5 Hz. It is found that the majority of systems show no coherent periodicities in their X-ray emission, which is consistent with a model in which the X-rays are produced in a disk/white dwarf boundary layer. The X-ray emission from AE Aqr is found to be modulated with a period of 33.08 s, which agrees with the period found in its optical light, and in GK Per, evidence of higher harmonics of the 351 s oscillations detected by EXOSAT are found.
Numerical simulation of unconfined flow past a triangular cylinder

Numerical simulations of two‐dimensional laminar flow past a triangular cylinder placed in free‐stream at low Reynolds number (10⩽Re⩽250) are performed. A finite volume method, second‐order accurate in space and time, employing non‐staggered arrangement of the variables with momentum interpolation for the pressure–velocity coupling is developed. Global mode analysis predicts Recr=39.9 which confirms the results of earlier studies. Vortex shedding phenomena is found to be similar to the square cylinder with no second bifurcation in the range of Re studied. A discussion on the time‐averaged drag coefficient, rms of lift coefficient and Strouhal number is presented. Particle tracking and the instantaneous streaklines provide an excellent means of visualizing the von Kármán vortex street. Copyright © 2006 John Wiley & Sons, Ltd.
The use of Spitzer's identity in the investigation of the busy period and other quantities in the queue GI/G/1

As an illustration of the use of his identity [10], Spitzer [11] obtained the Pollaczek-Khintchine formula for the waiting time distribution of the queue M/G/1. The present paper develops this approach, using a generalised form of Spitzer's identity applied to a three-demensional random walk. This yields a number of results for the general queue GI/G/1, including Smith' solution for the stationary waiting time, which is established under less restrictive conditions that hitherto (§ 5). A soultion is obtained for the busy period distribution in GI/G/1 (§ 7) which can be evaluated when either of the distributions concerned has a rational characteristic function. This solution contains some recent results of Conolly on the quene GI/En/1, as well as well-known results for M/G/1.
Revenue Metering of Unbalanced Prosumers in Energy Communities

The presence of power generating plants owned by prosumers may lead to unbalanced bidirectional energy flows at the points of connection to the relevant distribution systems. This will impact future energy communities, where appropriate metering within the community is a crucial issue for billing purposes. This paper shows that the current metrics for active energy measurement and the registration of three-phase revenue meters may fail to fairly charge unbalanced prosumers for their use of the distribution system as an inherent phase-to-phase balancer. On the other hand, it is proven here that adopting metrics based on positive sequence power/energy measurement would lead to more fair billing within the community. A comparative study was performed using a simplified but realistic model of a distribution system feeding two prosumers (i.e., an archetype of an energy community). First, representative case studies were considered. Then, a more realistic simulation of a single day of operation was conducted. The main contribution of the paper is a detailed and systematic comparison of the methods used for measuring and sorting energy into registers in revenue meters to support the ongoing discussions about fair metering within future energy communities.
Invasive Apple Snails in Wetlands of Selangor, Malaysia: Species, Distribution, and Ecological Associations

Apple snails in the genus Pomacea are among the worst invasive species in Southeast Asia. Our objectives were to survey a selection of different wetlands in Selangor for Pomacea, verify which species of Pomacea occurred in that location, and assess basic environmental parameters associated with their presence and relative abundance. Aquatic parameters including pH and concentrations of selected electrolytes were measured at 25 wetland sites distributed among eight localities in Selangor. DNA from snails collected at each locality was extracted and the mitochondrial cytochrome c oxidase subunit I (COI) was sequenced. We detected two of the most successful invaders of this genus: P. canaliculata was found in five localities and P. maculata in two. Both pH and calcium ion concentrations were negatively associated with Pomacea presence. Pomacea were absent in brackish wetlands with high pH and calcium concentrations reflecting possible physiological intolerance or that dispersal into these habitats has yet to occur. P. maculata is reported to tolerate pH as low as 4.5-6; thus most freshwater wetlands in Selangor and most of Malaysia can potentially be invaded. Pomacea canaliculata and P. maculata have demonstrated remarkable capacity for depleting aquatic macrophytes and may cause rapid changes in aquatic plant communities with potential impacts to wetland state and function. Public awareness and environmentally safe recommendations to mitigate the reproduction and spread of this invasive snail is needed for protecting the biodiversity and health of natural wetlands.