Miracle-dz/UniFAR-FTUs huggingface dataset:
Acceleration Across California: Shorter Pathways in Developmental English and Math

Change • May/June 2012 D evelopmental courses in English, math, and reading have an important purpose in higher education, especially in the open-access world of community colleges. These classes—also referred to as “remedial”—are intended to give less-prepared students a chance to catch up and meet the challenges of college-level coursework. And yet, despite these noble intentions, remedial course sequences have become the place where college dreams go to die. Nationwide studies have shown that the more semesters of remediation a student is required to take, the less likely that student is to ever complete a college-level math or English course, never mind reach a longer-term goal such as earning a degree or transferring to a four-year college or university. In a multi-state study of 57 community colleges, the Community College Research Center found that among students who are placed three or more levels below college math, fewer than 10 percent ever go on to complete a college-level math course. Put differently, community colleges weed out more than 90 percent of these students before they get through the first gate. This bleak reality has motivated a growing number of California community colleges to re-think their approach to remediation. Joseph Gerda is now the vice-president of instruction at College of the Canyons, but in spring 2011 he was a mathematics instructor who was looking for a solution to what he calls the “tremendous blood loss” in remedial math. He and a group of colleagues attended a workshop organized by the California Community Colleges’ Success Network (3CSN), where they heard Myra Snell talk about a new developmental course she’d developed at Los Medanos College. Instead of accepting the traditional curriculum as a given, Snell set out to design an alternative, accelerated pathway for students who would go on to take statistics as their college-level math requirement. The solution: Path2Stats, a
X-ray irradiation of interstellar grains in active galaxies : evaporation and infrared spectra

A fundamental physical study of grains heated transiently by X-rays is presented. The X-ray photoionization cross sections used to determine the rate of energy deposition into the grains are given. A grain model is constructed and the radiative and evaporative responses of grains into X-ray absorption are described. The basic theory of stochastic grain heating is outlined, and analytical expressions for the temperature distributions of flickering grains are provided. The resulting IR spectra due to X-ray illumination are given, and the relevance of the present work to the IR continua of active galaxies is discussed. The present model provides two observational predictions: the infrared spectra of grains, even if they are superheated, should show a cutoff between 1 and 3 microns; and X-ray-illuminated environments should exhibit no PAH emissions.
An elementary proof and an extension of Thas' theorem on k-arcs

Let q be the finite field of q elements. Denote by Sr q the projective space of dimension r over q. In Sr,q, where r ≥ 2, a k-arc is defined (see [4]) as a set of k points such that no j + 2 lie in a Sj,q, for j = 1,2,…, r−1. (For a k-arc with k > r, this last condition holds for all j when it holds for j = r−1.) A rational curve Cn of order n in Sr,q, is the set
Effect of plasma on modal dispersion characteristics of elliptical Bragg waveguide

In this paper, the dispersion characteristics of a plasma filled elliptical Bragg waveguide is investigated. The modal characteristic equations of the proposed Bragg waveguide for both ω > ωp and ω < ωp are derived. The effects of plasma frequency, numbers of cladding layers and the eccentricity of elliptical Bragg waveguide on the dispersion characteristics are studied. The analysis shows that the introduction of plasma in the proposed waveguide allows to control the propagation of modes.
Potential flow about two-dimensional hydrofoils

This paper describes a very general method for determining the steady two-dimensional potential flow about one or more bodies of arbitrary shape operating at arbitrary Froude number near a free surface. The boundary condition of zero velocity (solid wall) or prescribed velocity (suction or blowing) normal to the body surface is satisfied exactly, and the boundary condition of constant pressure on the free surface is satisfied using the classic small-wave approximation. Calculations made by the present method are compared with analytic results, other theoretical calculations and experimental data. Examples for which no comparison exists are also presented to illustrate the capability of the method.
Translation, rotation and scale stabilisation of image sequences

Translation, rotation and scale stabilisation of image sequences is presented with phase correlation based estimation of motion parameters. Phase correlation and log-polar magnitude spectra representation is utilised to obtain translation, rotation and scale parameters. Stabilised frame positions are obtained through Kalman filtering of absolute parameters, and image frames are processed accordingly so as to result in a sequence that displays smooth global movements only.
Band structures of two-dimensional magnonic crystals with different shapes and arrangements of scatterers

The spin-wave band structures of two-dimensional magnonic crystals with different shapes and arrangements of scatterers are investigated numerically. It is shown that the magnonic band gap of spin waves in magnonic crystals can be optimized by changing the shape or the arrangement of scatterers in background materials. The largest absolute gap can be achieved when the scatterer has the same symmetry as that of the coordination polygon of lattice point, such as the case of square rods in square lattices. For a given shape of scatterer, the gap width is the largest when the lattice has the largest coordination number if the scatterer does not reduce the symmetry.
Flow movement and sediment transport in compound channels

There are many studies on the flow movement in compound channels, yet few are concerned with sediment transport. An experimental study on the flow movement and sediment transport in compound channels is presented. The experimental results indicate that the distribution of longitudinal velocity with depth in the main channel and the floodplains has a logarithmic component. The longitudinal velocity with flow depth in the interactive region does not obey a logarithmic distribution, but involves a wake function. In the boundary region, the longitudinal velocity obeys a parabolic distribution. In addition, based on the suspended sediment diffusion equation and the flow interaction between main channel and floodplains, expressions are derived to predict the lateral eddy viscosity and the sediment diffusion coefficients. Finally, an analytical solution for the lateral distribution of the depth-averaged velocity and sediment concentration in a compound channel is obtained. The results from the analytical solution agree well with experimentation.
An experimental investigation on the interaction of hydraulic jumps formed by two normal impinging circular liquid jets

The flow field due to two normal impinging liquid jets is different from the flow field associated with a single normal impinging liquid jet, and even from the flow field around two normal impinging compressible fluid jets. Depending on the spacing between the two jets and their relative strengths, different kinds of hydraulic jump interactions are possible, resulting in a variety of flow patterns. The present study experimentally elucidates the jump--jump interactions formed in such cases, for different values of inter-jet spacings and for different strengths of the individual jets. Analogous flow fields associated with the interactions between a single impinging jet and a fence are also studied to allow convenient experimental flow vizualizations.
The Observatory

explores the interpretation and policy use of performance indicators. Policy-makers use HSPA to make sense of indicators and comparisons and assess what performance measurement means in terms of their policy choices. The HSPA framework developed by the Observatory with WHO (Regional Office for Europe and Headquarters), with inputs from the European Commission and many leading agencies and institutions
Angular Momentum Evolution of Young Stars and Disks

The effects of angular momentum play an important role in star formation. However, when a young star emerges on the Hertzsprung-Russell diagram it is generally rotating slowly. This article reviews the observations regarding the angular momentum of molecular cloud cores, of proto stars, and of the disks, binary orbits, and spin of young stars. Various physical processes for transfer of angular momentum during the star formation process are discussed, including magnetic braking during the molecular cloud stage; fragmentation during the protostar collapse; viscosity, magnetic torques, and gravitational torques in disks; and magnetically driven mass loss in a star-disk system. Important problems for future study are highlighted.
The ensemble‐transform scheme adapted for the generation of stochastic forecast perturbations

A method for generating stochastic perturbations is derived from the ensemble‐transform analysis‐error sampling scheme. The method produces stochastic perturbations that not only have multivariate spatial correlation, balance, and prescribed mean and variance statistics, but also conditioning for growth. The perturbations can serve as modification for numerical weather prediction (NWP) ensemble forecasts either during integration or post‐processing. A practical demonstration of the method is given, in which operational global NWP ensemble forecasts are modified with the stochastic perturbations as a post‐processing exercise. The results suggest that the method can produce stochastic perturbations whose spatially‐integrated statistics match target mean and variance statistics reasonably well, if a moderate number of archived NWP forecast perturbations are provided as input. They also suggest that the stochastic perturbations' correlation, balance, and conditioning for growth are functional, in the sense that the perturbations are not predisposed to marked decay at the outset of integration by an NWP model. Copyright © 2007 Royal Meteorological Society
Cracking particles: a simplified meshfree method for arbitrary evolving cracks

A new approach for modelling discrete cracks in meshfree methods is described. In this method, the crack can be arbitrarily oriented, but its growth is represented discretely by activation of crack surfaces at individual particles, so no representation of the crack's topology is needed. The crack is modelled by a local enrichment of the test and trial functions with a sign function (a variant of the Heaviside step function), so that the discontinuities are along the direction of the crack. The discontinuity consists of cylindrical planes centred at the particles in three dimensions, lines centred at the particles in two dimensions. The model is applied to several 2D problems and compared to experimental data. Copyright © 2004 John Wiley & Sons, Ltd.
Simulation of climate change over europe using a nested regional‐climate model. I: Assessment of control climate, including sensitivity to location of lateral boundaries

Present-day climate simulations for Europe are presented, based on a 50 km regional-climate model (RCM) driven by output from a global general-circulation model (GCM) using a one-way nesting approach. Both models are components of the Meteorological Office Unified Forecast/Climate Model and use the same subgrid-scale physics. the relationship between the RCM circulation and that of the driving GCM was assessed in seasonal RCM integrations using domains of different sizes. In the larger domains, both the mean flow and the day-to-day variability in the RCM diverge from that of the GCM on the synoptic scale, rendering the RCM solution physically inconsistent with the GCM solution external to the RCM domain. At the grid-point scale the RCM freely generates its own features, even in the smaller domains—only at points adjacent to the boundary buffer zone is there evidence of significant distortion by the lateral boundary forcing from the GCM. Using one of the smaller domains, a 10-year RCM simulation was carried out, driven by a coupled atmosphere/mixed-layer-ocean version of the GCM. Over the region of interest the general circulation and daily synoptic variability is realistically simulated by the GCM and, therefore, also by the RCM (see above). Stronger vertical motions in the RCM lead to a general increase in dynamical precipitation relative to the GCM, and thus a drier and warmer troposphere and reduced convective cloud and precipitation. Layer-cloud cover is also reduced in the RCM, due to a time-step dependence in the treatment of the dissipation of ice cloud. Significant changes occur in the surface heat balance. the spatial patterns of surface air temperature and precipitation over Europe are well simulated by both the GCM and the RCM on scales resolved by the former. At finer scales the RCM contains a strong signal which is related to orographic height. Validation against a detailed observed climatology for Great Britain demonstrates that this signal contains considerable skill.
A Possible Mechanism for the Eye Rotation of Typhoon Herb

An elliptical eye that rotated cyclonically with a period of approximately 144 minutes in Typhoon Herb 1996 was documented. The elliptical region had a semimajor axis of 30 km and a semiminor axis of 20 km. Two complete periods of approximately 144 min were observed in the Doppler radar data. The rotation of the elliptical eye in the context of barotropic dynamics at three levels were explored: linear waves on a Rankin vortex, a nonlinear Kirchhoff vortex, and with a nonlinear spectral model. The linear wave theory involves the existence of both the high (potential) vorticity gradient near the eye edge and the cyclonic mean tangential flow in the typhoon. The propagation of (potential) vorticity waves in the cyclonic mean flow makes the elliptical eye rotate cyclonically. The rotation period is longer than the period of a parcel trajectory moving in the cyclonic mean flow around the circumference, because the vorticity wave propagates upwind. The nonlinear theory stems from the rotation of Kirchhoff’s vortex. Estimates of the eye rotation period from both linear and nonlinear theories agree with observations of the eye rotation period when the observed maximum wind from Herb is used. Nonlinear numerical computations suggest the importance of the interaction of neutral vorticity waves, which determine the shape and the rotation period of the eye. The calculations also support the rotation of the eye in approximately 144 min in the presence of axisymmetrization, vorticity redistribution, wave breaking, and vortex merging processes.
Statistical analysis of sets of congeneric tests

Various models for sets of congeneric tests are considered, including models appropriate for the analysis of multitrait-multimethod data. All models are illustrated with real data. The special cases when two or more tests within a set are tau-equivalent or parallel are also considered. All data analyses are done within the framework of a general model by Jöreskog [1970].
Laser-driven generation of high-quality ultra-relativistic positron beams

An ultra-relativistic electron beam propagating through a high-Z solid triggers an electromagnetic cascade, whereby a large number of high-energy photons and electron–positron pairs are produced mainly via the bremsstrahlung and Bethe–Heitler processes, respectively. These mechanisms are routinely used to generate positron beams in conventional accelerators such as the electron–positron collider (LEP). Here we show that the application of similar physical mechanisms to a laser-driven electron source allows for the generation of high-quality positron beams in a much more compact and cheaper configuration. We anticipate that the application of these results to the next generation of lasers might open the pathway for the realization of an all-optical high-energy electron–positron collider.
Four-Year Overview of Winter Colony Losses in Greece: Citizen Science Evidence That Transitioning to Organic Beekeeping Practices Reduces Colony Losses

Simple Summary Today, the monitoring and analysis of honey bee losses in more than 36 countries is carried out, in particular, through citizen science and the annual participation of volunteer beekeepers in the “COLOSS” (honey bee research non-governmental association) questionnaire on winter colony losses. Greece’s first participation in the COLOSS survey since 2018 has offered valuable analyzed data, from almost all regions, in detail for the first time in this study. In line with EU recommendations, our four-year monitoring showed a recent transition in the local beekeeping sector towards more natural practices concomitant with a decrease in overwintering colony losses. Among the different factors that influenced the winter colony losses, our study showed that the avoidance of agricultural habitats for honey production, together with the gradual substitution of chemical acaricides by more natural substances, are two major factors that could have improved colony survival. The current analysis can provide beekeepers with the relevant means to compare with their own hives’ performance. It could also serve as a basis for future more in-depth analyses of Greek winter losses and highlight beekeeping trends for the development of a successful organic transition. Abstract The honey bee is one of the most important pollinators with a close relationship to humans. The questionnaire from the non-governmental association “COLOSS”, answered by beekeepers around the world, is a valuable tool for monitoring and analyzing factors involved in overwintering losses, as well as for understanding the evolution of the beekeeping sector over the years. Between 2018–2021, Greece’s participation in this survey involved collecting data from 752 beekeepers and 81,903 hives, from almost the whole country, with a stable balance between professional/non-professional participants and hives, providing a solid representation of the beekeeping practices and winter losses during this period. The results of this study identify a transition towards more natural beekeeping practices concomitant with a significant decrease in winter losses (average losses in 2018: 22.3% and 2019: 24%, dropped in 2020: 14.4% and 2021: 15.3%). Indeed, some factors, such as the increased use of natural landscapes for honey production (from 66.7% usage in 2018 to 76.3% in 2021) and the reduction in the exclusive use of synthetic acaricides (from 24.7% usage in 2018 to 6.7% in 2021) seem to have a significant impact on hive survival. Although these correlations remain to be confirmed experimentally, our study shows that Greek beekeepers follow recommendations and policies toward more sustainable practices. In the future, these trends could be further analyzed and integrated into training programs to strengthen the cooperation and information exchange between citizens and science.
Optimal Envisat advanced synthetic aperture radar image parameters for mapping and monitoring Sahelian floodplains

Floodplains in the Sahel region of Africa are of exceptional socio-economical and ecological importance. Due to their large extent and highly dynamic nature, monitoring these ecosystems can only be performed by means of remote sensing. The capability of the Envisat Advanced Synthetic Aperture Radar (ASAR) sensor to capture radar backscattering at various incident angles and with different polarization combinations, provides opportunities for improved wetland mapping and monitoring. However, little is known of the optimal image parameters, i.e. incident angle, polarization combination, and acquisition time. Backscatter σ° signatures of Land Use and Land Cover (LULC) classes in and around the Waza-Logone floodplain (Cameroon) were analyzed to determine these optimal image parameters. Based on Jeffries-Matusita (JM) distances between all LULC classes it was determined that best separation was obtained with images acquired in the middle of the flooding cycle at a steep incident angle. Furthermore, separability of cross-polarized images was higher than for co-polarized images. The combination of two and three ASAR Alternating Polarization images with highest separability were used as input for a LULC classification. Two methods were evaluated: Pixel-based Maximum Likelihood and object-based Nearest Neighbour (NN) classification. Best results were obtained with the object-based approach.
Self Learning Fuzzy Models Using Stochastic Approximat ion

In this paper a self learning algorithm for fuzzy re lational models is proposed. During the learning phase the degrees of possibility for the rules are adjusted such that the variance of the quadratic error is minimised. The algorithm employed is based on the stochastic approximation approach. Two numerical examples, using the gas furnace data from Box and Jenkins [3], and a nonlinear discrete time system equation prove the good performance of the self learning approach.
Sampling theorem for multidimensional, multiband signals

We approach the problem of sub-Nyquist sampling of multidimensional, multiband signals, with known spectral support that does not necessarily tile RN under translation. Undersampling is achieved by adapting the Papoulis' multichannel sampling scheme. Minimum (Landau) sampling density is obtained in some special conditions.
Desgin and comparative study of some sequential jump detection algorithms for digital signals

The purpose of this paper is to analyze the behavior of several jump detection algorithms when applied to the same real data (geophysical signals) and to compare these algorithms from different points of view: complexity, efficiency, robustness, and ability to characterize the detected jumps. Three types of algorithms are investigated: "filtered derivatives" detectors, cumulative sum (cusum) tests, and Willsky's generalized likelihood ratio (GLR) algorithm. A modified version of this last test is elaborated, and a new detector, mixing GLR and cusum tests, is presented.
Option pricing techniques under stochastic delay models

The Black-Scholes model and corresponding option pricing formula has led to a wide and extensive industry, used by financial institutions and investors to speculate on market trends or to control their level of risk from other investments. From the formation of the Chicago Board Options Exchange in 1973, the nature of options contracts available today has grown dramatically from the single-date contracts considered by Black and Scholes (1973) to a wider and more exotic range of derivatives. These include American options, which can be exercised at any time up to maturity, as well as options based on the weighted sums of assets, such as the Asian and basket options which we consider. Moreover, the underlying models considered have also grown in number and in this work we are primarily motivated by the increasing interest in past-dependent asset pricing models, shown in recent years by market practitioners and prominent authors. These models provide a natural framework that considers past history and behaviour, as well as present information, in the determination of the future evolution of an underlying process. In our studies, we explore option pricing techniques for arithmetic Asian and basket options under a Stochastic Delay Differential Equation (SDDE) approach. We obtain explicit closed-form expressions for a number of lower and upper bounds before giving a practical, numerical analysis of our result. In addition, we also consider the properties of the approximate numerical integration methods used and state the conditions for which numerical stability and convergence can be achieved.