Miracle-dz/UniFAR-FTUs huggingface dataset:
Exponential Integrators and their application to solving Richards ’ Equation

The ability to predict the movement of water in unsaturated porous media is vital to applications of groundwater flow and is commonly achieved with Richards’ equation. Obtaining a numerical solution to the governing partial differential equation is difficult, not only due to the nonlinearities present in the equation, but also the sharp fronts that feature in the solutions. Typically, spatially discrete solutions are advanced implicitly in time, using backward differentiation approximations to the time derivative. These implementations, however, often encounter mass-balance and convergence problems, motivating the need for improved time integration techniques. We investigated the use of exponential integrators applied to Richards’ equation in a two-dimensional setting. These schemes are purely explicit and based on the classical Euler and higher-order Rosenbrock integrators. Both formulae require the computation of the matrix function φ(A) = A−1(eA−I) where A is large and sparse and we presented two techniques for approximating φ(A)v for a vector v as required in each integration scheme. The first method is based on best rational approximations to φ and relies on the efficient solution of a number of shifted linear systems of the form (A − ζI)x = v for a complex scalar ζ. We proposed and compared some GMRES-like strategies to deal with these types of equations. The second method is concerned with projecting the large matrix A onto a small Krylov subspace so that the only evaluation of φ is performed on a matrix of much smaller dimension. It was found that using GMRES strategies embedded in best rational approximants yielded methods that were competitive with the established Krylov techniques for computing φ(A)v. Our numerical investigations concluded that exponential Euler outperformed the higher-order exponential Rosenbrock scheme for the chosen two-dimensional Richards’ equation problem. In addition, it was shown that both of these exponential schemes convincingly outperformed the established backward Euler method for the test problem.
Analyst Behaviour: The Geography of Social Interaction

An analyst who works in Germany is more likely to publish a high (low) price target regarding a DAX30 stock if other Germany based analysts are also optimistic (pessimistic) about the same stock. This finding is not biased by the fact that DAX30 companies are headquartered in Germany. In times of bull markets, price targets of analysts who regularly exchange their opinion are higher correlated compared to other analysts. This effect vanishes in a bearish market environment. This suggests that communication among analysts indeed plays an important role. However, analysts’ incentives induce them not to deviate too much from the overall average during an economic downturn.
Stochastic integration of functions with values in a Banach space

Let H be a separable real Hilbert space and let E be a real Banach space. In this paper we construct a stochastic integral for certain operator-valued functions Φ : (0, T ) → L (H,E) with respect to a cylindrical Wiener process {WH(t)}t∈[0,T ]. The construction of the integral is given by a series expansion in terms of the stochastic integrals for certain E-valued functions. As a substitute for the Itô isometry we show that the square expectation of the integral equals the radonifying norm of an operator which is canonically associated with the integrand. We obtain characterizations for the class of stochastically integrable functions and prove various convergence theorems. The results are applied to the study of linear evolution equations with additive cylindrical noise in general Banach spaces. An example is presented of a linear evolution equation driven by a one-dimensional Brownian motion which has no weak solution. In this paper we construct a theory of stochastic integration of operator-valued functions with respect to a cylindrical Wiener process. The range space of the operators is allowed to be an arbitrary real Banach space E. A stochastic integral of this type can be used for solving the linear stochastic Cauchy problem (0.1) dU(t) = AU(t) dt+B dWH(t), t ∈ [0, T ], U(0) = u0. Here, A is the infinitesimal generator of a strongly continuous semigroup {S(t)}t>0 of bounded linear operators on E, the operator B is a bounded linear operator from a separable real Hilbert space H into E, and {WH(t)}t∈[0,T ] is a cylindrical H-Wiener process. Formally, equation (0.1) is solved by the stochastic convolution process (0.2) U(t) = S(t)u0 + ∫ t 0 S(t− s)B dWH (s). It is well known that the integral on the right hand side can be interpreted as an Itô stochastic integral if E is a Hilbert space. A comprehensive theory of abstract stochastic differential equations in Hilbert spaces is presented in the monograph by Da Prato and Zabczyk [5]. More generally the integral can be defined for spaces E with martingale type 2. This has been worked out by Brzeźniak [2]. Examples of martingale type 2 spaces are Hilbert spaces and the Lebesgue spaces L(μ) with p ∈ [2,∞). In both settings, the integral is defined for step functions first, and for general functions the integral is obtained by a limiting argument. Such a limiting argument depends on 2000 Mathematics Subject Classification. Primary: 60H05; Secondary: 28C20, 35R15, 47D06, 60H15.
Is Racial Discrimination an Equal Opportunity Health Risk ? Racial Discrimination , Social Class and Health Status Among Black and White Adults

Racial differences in health have only begun to account for the influence of discriminatory treatment. Prior studies show that perceiving treatment as racist has a deleterious effect on health for racial minorities, possibly representing the missing link in racial health disparities. Using data from the 2004 wave of the Behavioral Risk Factor Surveillance System, we assess whether perceived racial discrimination explain Black-White racial disparities in self-rated health. We find that measures discrimination in combination of social class variables explain disparities, however, does this reflect the influence of discrimination has for Blacks? Surprisingly, analyses reveal that the effect of discrimination appears to be more detrimental to the health of Whites than to Blacks. Our analyses reveal this arises due to complicated relationship between race, social class and racial discrimination where Whites report more discrimination at the lower end of the socioeconomic spectrum while Blacks report more discrimination at the higher end. *Authors listed alphabetically, contribution is equal.
Attenuating the Forward Guidance Puzzle: Implications for Optimal Monetary Policy

We examine the implications of less powerful forward guidance for optimal policy using a sticky-price model with an effective lower bound (ELB) on nominal interest rates as well as a discounted Euler equation and Phillips curve. When the private-sector agents discount future economic conditions more in making their decisions today, an announced cut in future interest rates becomes less effective in stimulating current economic activity. While the implication of such discounting for optimal policy depends on its degree, we find that, under a wide range of plausible degrees of discounting, it is optimal for the central bank to compensate for the reduced effect of a future rate cut by keeping the policy rate at the ELB for longer.
DISCOVERY OF EIGHT z ∼ 6 QUASARS FROM Pan-STARRS1

High-redshift quasars are currently the only probes of the growth of supermassive black holes and potential tracers of structure evolution at early cosmic time. Here we present our candidate selection criteria from the Panoramic Survey Telescope & Rapid Response System 1 and follow-up strategy to discover quasars in the redshift range 5.7 ≲ z ≲ 6.2. With this strategy we discovered eight new 5.7 ⩽ z ⩽ 6.0 quasars, increasing the number of known quasars at z > 5.7 by more than 10%. We additionally recovered 18 previously known quasars. The eight quasars presented here span a large range of luminosities (−27.3 ⩽ M1450 ⩽ −25.4; 19.6 ⩽ zP1 ⩽ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show a weak or no Lyα emission line (25% with rest-frame equivalent width of the Lyα +N v line lower than 15 Å). We find a larger fraction of weak-line emission quasars than in lower redshift studies. This may imply that the weak-line quasar population at the highest redshifts could be more abundant than previously thought. However, larger samples of quasars are needed to increase the statistical significance of this finding.
Data assimilation of Sea-ice motion vectors: Sensitivity to the parameterization of Sea-ice Strength

Abstract Data assimilation techniques are one method by which to improve the quality of model Simulations of Sea ice. The availability of daily gridded fields of Sea-ice motion makes this field one that can be readily assimilated. These fields are generally of higher resolution than forcing values Such as atmospheric wind which are used to drive the model, and on any given day may depict ice circulation that is dramatically different than what the model Solution represents. Typically, a blending method Such as optimal interpolation (OI) is used and corrections are applied to the initial modeled velocity field Such that the new Solution corresponds better with actual observations. However, care must be taken in Such a technique, as the corrections are not applied directly to the model physics, and the underlying physical assumptions in the ice dynamics may be violated. Previous Studies have Shown that improvements in the ice-motion Solution come at the cost of the quality of other modeled fields. The Strength parameterization in Sea-ice models controls the ice velocity in the model, and is obtained in part by comparison with observed motions. Here we investigate the Sensitivity of the Sea-ice model to variations in the Strength parameterization, and determine the effect of using data assimilation to impose observed velocities. We find that the alternation of the frictional loss parameter has limited effect on model performance. Rather, it is the assimilated data that overwhelm and degrade the Solution, bringing into question whether underlying physical assumptions in the model may be compromised.
Characterization of 15 overlooked Ruprecht clusters with ages within 400 Myr and 3 Gyr

We derive fundamental, structural, and photometric parameters of 15 overlooked Ruprecht (hereafter Ru) star clusters by means of 2MASS photometry and field-star decontamination. Ru1, 10, 23, 26, 27, 34, 35, 37, 41, 54, 60, 63, 66, and 152 are located in the third Galactic quadrant, while Ru174 is in the first. With the constraints imposed by the field-decontaminated colour-magnitude diagrams (CMDs) and stellar radial density profiles (RDPs), we derive ages in the range 400Myr — 1Gyr, except for the older Ru37, with � 3Gyr. Distances from the Sun are within 1.5 . d⊙(kpc) . 8.0. The RDPs are well-defined and can be described by a King-like profile for most of the radial range, except for Ru23, 27, 41, 63, and 174, which present a conspicuous stellar density excess in the central region. The clusters dwell between (or close to) the Perseus and Sagittarius-Carina arms. We derive evidence in favour of cluster size increasing with distance to the Galactic plane (ZGP), which is consistent with a low frequency of tidal stress associated with high-|ZGP| regions. The clusters are rather faint even in the near-infrared, with apparent integrated J magnitudes within 6.4 . mJ . 9.8, while their absolute magnitudes are 6.6 . MJ . 2.6. Extrapolation of the relation between MV and MJ, derived for globular clusters, suggests that they are low-luminosity optical clusters, with 5 . MV . 1.
Nutrient cycling in the water column of a subtropical seagrass meadow

The cycling of nutrients was studied over a 16 mo period to determine how processes occurring between the water column and benthos influenced nutrient dynamics in a Thalassia testudinum dominated seagrass meadow. Nutrient concentrations were low and ranged from below detection to 0.59 μM ammonium (NH 4 + ), 0.04 to 0.29 μM nitrate plus nitrite (NO 3 - + NO 2 - ), and below detection to 0.22 μM soluble reactive phosphate (SRP). Water column and benthic fluxes of NO 3 - + NO 2 - and SRP were usually below detection. The benthic fluxes of NH 4 + ranged from an uptake of -228 μmol N m -2 d -1 to a release of 363 μmol N m -2 d -1 . Positive fluxes (i.e. directed out of the sediment) occurred primarily in light incubations and from seagrass-dominated sediments. Water column fluxes of NH 4 + ranged from a net uptake of -145 μmol N m -2 d -1 to a net regeneration of 643 μmol N m -2 d -1 . The net regeneration of NH 4 + in the water column usually exceeded the release of NH 4 + from the benthos. There was a significant correlation between the regeneration of NH 4 + in the water column and the light-mediated release of dissolved organic matter (DOM) from the benthos, indicating that benthic-derived DOM supported the regeneration of NH 4 + in the water column. Bacterioplankton growth efficiencies were significantly and positively correlated to the regeneration of NH 4 + in the water column, possibly resulting from changes in the composition of DOM released from the benthos. The C:N ratios of the organic matter remineralized in the water column were variable and ranged from 14 to 81, with lowest values occurring in late summer and highest values in spring. The results of this study indicated that temporal variations in the source and composition of DOM significantly influenced the cycling of nutrients in the water column of this seagrass meadow.
Children’s excessive daydreaming in Maladaptive daydreaming: causes and symptoms

Fantasizing is inscribed in children natural development and should not be a cause for concern until it becomes a mechanism of mood regulation. In the Maladaptive daydreaming, the child concentrates its feelings, fears and desires in fantasies. It is fully aware, but it feels compelled to return to fantasy, which is often accompanied by somatic symptoms. Kontradaptacyjne fantazjowanie (in English, Maladaptive daydreaming) is a disturbing absorption of the mind that affects interpersonal interactions, disrupting the child functioning. The article presents literature referring to the problem of excessive fantasizing. The aim of the work is to communicate and approximate, in Polish language, the phenomenon of maladaptive daydreaming. And presenting the role of fantasy in child development. The paper attempts to clarify this phenomenon according to DSM-V, and clinical cases with the proposed treatment. Fantasies and dreams are an indispensable attribute of a man. Everyone dreams, but not everyone becomes addicted to fantasy and does not use them as an escape mechanism. Already in 1908, Sigmund Freud noted fantasizing as an attempt to solve problems and internal conflicts. At the end of the 1980s, Csikzentmihalyi studied patients who daydreaming for more than half of the day. He noted that 4% of the population has a predisposition to fantasize for longer than just a few minutes. Patients suffering from maladaptive daydreaming in preliminary diagnoses are often diagnosed with schizophrenia or psychosis. This is a misdiagnosis the basic criterion that differentiates them from the maladaptive daydreaming is the fact of consciousness [7,1]. During daydreaming, patient is fully aware that he fantasizes, knows who he is and what he does. Previous work [1, 2, 3, 4, 8, 10, 10] indicates the beginning of a maladaptive daydreaming in childhood. It is supposed to be a mechanism educated by children
Robust Misspecification Tests for the Heckman's Two-Step Estimator

This article constructs and evaluates Lagrange multiplier (LM) and Neyman's C(α) tests based on bivariate Edgeworth series expansions for the consistency of the Heckman's two-step estimator in sample selection models, that is, for marginal normality and linearity of the conditional expectation of the error terms. The proposed tests are robust to local misspecification in nuisance distributional parameters. Monte Carlo results show that testing marginal normality and linearity of the conditional expectations separately have a better size performance than testing bivariate normality. Moreover, the robust variants of the tests have better empirical size than nonrobust tests, which determines that these tests can be successfully applied to detect specific departures from the null model of bivariate normality. Finally, the tests are applied to women's labor supply data.
The Effect of Area Ratio Change via Increased Hole Length for Shaped Film Cooling Holes with Constant Expansion Angles

Shaped film cooling holes are used as a cooling technology in gas turbines to reduce metal temperatures and improve durability, and they generally consist of a small metering section connected to a diffuser that expands in one or more directions. The area ratio of these holes is defined as the area at the exit of the diffuser, divided by the area at the metering section. A larger area ratio increases the diffusion of the coolant momentum, leading to lower average momentum of the coolant jet at the exit of the hole and generally better cooling performance. Cooling holes with larger area ratios are also more tolerant of high blowing ratio conditions, and the increased coolant diffusion typically better prevents jet liftoff from occurring. Higher area ratios have traditionally been accomplished by increasing the expansion angle of the diffuser while keeping the overall length of the hole constant. The present study maintains the diffuser expansion angles and instead increases the length of the diffuser, which results in longer holes. Various area ratios have been examined for two shaped holes: one with forward and lateral expansion angles of 7° (7-7-7 hole) and one with forward and lateral expansion angles of 12° (12-12-12 hole). Each hole shape was tested at numerous blowing ratios to capture trends across various flow rates. Adiabatic effectiveness measurements indicate that for the baseline 7-7-7 hole, a larger area ratio provides higher effectiveness, especially at higher blowing ratios. Measurements also indicate that for the 12-12-12 hole, a larger area ratio performs better at high blowing ratios but the hole experiences ingestion at low blowing ratios. Steady RANS simulations did not accurately predict the levels of adiabatic effectiveness, but did predict the trend of improving effectiveness with increasing area ratio for both hole shapes. Flowfield measurements with PIV were also performed at one downstream plane for a low and high area ratio case, and the results indicate an expected decrease in jet velocity due to a larger diffuser.Copyright © 2017 by ASME
Propagation of curved shock fronts using shock ray theory and comparison with other theories

Shock ray theory (SRT) has been found to be useful and computationally efficient in finding successive positions of a curved weak shock front. In this paper, we solve some piston problems and show that the shock ray theory with two compatibility conditions gives shock positions, which are very close to those obtained by solving the same problems by the numerical solution of Euler's equations (Euler solutions). Comparison of the results obtained by shock ray theory and geometrical shock dynamics (GSD) of Whitham (J. Fluid Mech. vol. 2, 1957, p. 146) with the Euler solution shows that the shock ray theory gives more accurate results for any piston motion. The aim of the work is not just this comparison, but also to investigate the role of the nonlinearity in accelerating the process of the evolution of a shock, produced by an explosion of a non-circular finite charge, into a circular shock front. We find that the nonlinear waves propagating on the shock front appreciably accelerate this process. We also discuss a situation, for shock Mach number very close to 1, when GSD and shock ray theory may fail to give any result.
Prospective teachers’ beliefs about problem-solving: Cypriot and English cultural constructions

In this paper we report on a small-scale comparative examination of prospective elementary teachers' beliefs about problem-solving in Cyprus and England. First year undergraduate students (13 from Cyprus and 14 from England) from a well-regarded university in each country were qualitatively interviewed at the commencement of their respective teacher education programmes. Data, which were analysed by means of a combination of theory- and data-driven coding, indicated that, in both countries, students entered university with beliefs about problems and problem-solving that were not only products of the cultures in which they were educated, but also frequently incommensurate with the problem-solving expectation of the curricular frameworks within which they would have to work as teachers. Also, the outcomes confirmed that, despite researchers’ assumptions of definitional convergence, the expressions ‘mathematical problem’ and ‘problem-solving’ continue to be used differently across cultures. Some implications for teacher education are discussed.
Imaging of High-Angle Annular Dark Field Scanning Transmission Electron Microscopy and Microscopy Studies of GaN-based Light Emitting Diodes and Laser Diodes

Atomic-resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) has been used to the structural and compositional analysis of materials. The first part of this paper is a review of our recent HAADF-STEM investigations, which comprise physics to understand its imaging, and illustration of artifacts in images and imaging process. Next, we present our investigations of the multiple InGaN/GaN quantum wells and the strained AlGaN/GaN superlattice cladding in InGaN-based light emitting diodes or laser diodes, which have been performed by HAADF-STEM, high-resolution field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The observation of ultra-high density InGaN quantum dots is also shown.
Type III and II universal spacetimes

We briefly summarize our recent results on universal spacetimes. We show that universal spacetimes are necessarily CSI, i.e. for these spacetimes, all curvature invariants constructed from the Riemann tensor and its derivatives are constant. Then, we focus on type III universal spacetimes and discuss a proof of universality for a class of type III Kundt spacetimes. We also mention explicit examples of type III and II universal spacetimes.