Miracle-dz/UniFAR-FTUs huggingface dataset:
The effects of taxation on income inequality in sub-Saharan Africa

We use instrumental-variable two-stage least squares and instrumental-variable quantile regression estimates. We find that taxation widens income inequality. We also show that the increasing effects of taxation on income inequality are higher in the most unequal countries than in the least unequal countries. Furthermore, we highlight an inverse U-shaped relationship between indirect taxes and income inequality. Governments in sub-Saharan Africa should increase indirect taxes to at least 28.36 per cent of gross domestic product in order to reap the dividends in terms of reducing inequality.
Asymptotic Boundary Forms for Tight Gabor Frames and Lattice Localization Domains

We consider Gabor localization operators defined by two parameters, the generating function of a tight Gabor frame , indexed by a lattice , and a domain whose boundary consists of line segments connecting certain points of . We provide an explicit formula for the boundary form , the normalized limit of the projection functional , where are the eigenvalues of the localization operators applied to dilated domains , R is an integer and is the area of the fundamental domain. The boundary form expresses quantitatively the asymptotic interactions between the generating function and the oriented boundary from the point of view of the projection functional, which measures to what degree a given trace class operator fails to be an orthogonal projection. Keeping the area of the localization domain bounded above corresponds to controlling the relative dimensionality of the localization problem.
Underwater Polarization Imaging Recovery Based on Polarimetric Residual Dense Network

Application of deep-learning to polarization imaging technology for image restoration has led to many technological breakthroughs, especially in underwater image recovery and recognition. In this work, a four-input deep learning model with the Polarimetric Residual Dense Network is proposed for underwater image recovery. The diverse polarization component images are trained and tested in different processes in the network for the recognition and dehazing by considering the physical model of polarization dehazing imaging. Our study reveals that the proposed method can efficiently recover the hazed images, and provide good performance for improving the quality of image restoration even in a high-turbidity complex underwater environment.
Limitations of the background field method applied to Rayleigh-B\'enard convection

We consider Rayleigh-B\'enard convection as modeled by the Boussinesq equations, in case of infinite Prandtl number. There is a broad interest in bounds of the upwards heat flux, as given by the Nusselt number ${\rm Nu}$, in terms of the forcing via the imposed temperature difference, as given by the Rayleigh number in the turbulent regime ${\rm Ra}\gg 1$. In several works, the background field method applied to the temperature field has been used to provide upper bounds on ${\rm Nu}$ in terms of ${\rm Ra}$. In these applications, the background field method comes in form of a variational problem where one optimizes a stratified temperature profile subject to a certain stability condition; the method is believed to capture marginal stability of the boundary layer. The best available upper bound via this method is ${\rm Nu}$ $\lesssim {\rm Ra}^\frac{1}{3}(\ln {\rm Ra})^\frac{1}{15}$; it proceeds via the construction of a stable temperature background profile that increases logarithmically in the bulk. In this paper, we show that the background temperature field method cannot provide a tighter upper bound in terms of the power of the logarithm. However, by another method one does obtain the tighter upper bound ${\rm Nu}\lesssim {\rm Ra}^\frac{1}{3}(\ln\ln {\rm Ra})^\frac{1}{3}$, so that the result of this paper implies that the background temperature field method is unphysical in the sense that it cannot provide the optimal bound.
Evaluation of the relationships and uncertainties of airborne and ground-based sea ice surface temperature measurements against remotely sensed temperature records

ABSTRACT Sea ice surface temperature (IST) is an important indicator of environmental changes in the Arctic Ocean. In this study, the relative performance of four mainstream IST records, i.e. airborne IST, infrared radiometer measured IST (IR IST), longwave radiation derived IST (LWR IST), and snow and ice mass balance array buoy derived IST (Buoy IST), were evaluated against the MODIS IST product. Bias, standard deviation (STD), and root mean square error (RMSE) were used to evaluate the data quality. Results revealed that airborne IST had the best accuracy, which was 0.21 K colder than MODIS IST, with STD of 1.46 K and RMSE of 1.47 K. Ground-based ISTs were biased with each other but all warmer than the MODIS IST. The IR IST had the best overall accuracy (bias = 0.55 K; STD = 1.52 K; RMSE = 1.61 K), while the LWR IST was the noisiest measurement with the largest outlier data percent. Besides, co-located IR and LWR ISTs were more consistent than any type of evaluated IST against MODIS IST (correlation coefficient = 0.99). Airborne and IR ISTs are thus the premier choice for monitoring the rapidly changing Arctic sea ice, together with satellite observations.
On null‐controllability of the heat equation on infinite strips and control cost estimate

We consider an infinite strip ΩL=(0,2πL)d−1×R , d≥2 , L>0 , and study the control problem of the heat equation on ΩL with Dirichlet or Neumann boundary conditions, and control set ω⊂ΩL . We provide a sufficient and necessary condition for null‐controllability in any positive time T>0 , which is a geometric condition on the control set ω. This is referred to as “thickness with respect to ΩL ” and implies that the set ω cannot be concentrated in a particular region of ΩL . We compare the thickness condition with a previously known necessity condition for null‐controllability and give a control cost estimate which only shows dependence on the geometric parameters of ω and the time T.
Subgraph Contrast for Self-Supervised Graph Representation Learning

As shown in the Fig. 1, BFS based sampling method samples subgraph by spreading outward from the center node. Specifically, considering the various size of different neighbors, we first set a target k(k > 1) for the subgraph sampler S. Then, for a specific node i, the subgraph sampler S first samples nodes in the first-order neighborhood. If the target is not reached, it moves to the next-order neighborhood for subsequent sampling until the target is reached. When the sampling goal is achieved, we can obtain the nodes of subgraph around node i. The index of chosen nodes and the nodes embeddings can be denoted as: idx = S(A, k) (1) Next, derive the connection relationship of the subgraph nodes from the adjacency matrix A. Ai = Aidx,idx (2)
Development and Characterization of Biocomposite Films Based on Polysaccharides Derived from Okra Plant Waste for Food Packaging Application

Polysaccharide-based composite films were developed using mucilage polysaccharides (OLP) and carboxymethyl cellulose (CMC) extracted from okra leafstalk wastes. The rheological properties of biocomposite OLP/CMC film-forming solutions were characterized using the Power-law model, and fabricated films were characterized for their potential food packaging applications. OLP/CMC solutions exhibited pseudo-plastic fluid characteristics and differences in rheological behavior (n, 0.478–0.743), and flow consistency (K, 1.731–9.154) with increasing content of OLP (5 to 30 % w/w of CMC) were associated with variations in the physical, mechanical, and barrier properties of films. Surface hydrophobicity (24%) increased and oxygen (39%) and water vapor (32%) permeability reduced in OLP/CMC films containing up to 10% OLP. Moreover, a higher content of OLP enhanced the antioxidant activity and thermal stability of OLP/CMC films. Subsequently, OLP/CMC was applied as a coating to preserve cherry tomatoes for 14 days at 30 °C. Quality deterioration characterized by high weight loss (22%), firmness loss (74.62%), and discoloration (∆E, 21.26) occurred in uncoated tomatoes and were within unusable/unmarketable limits based on their visual quality score. In contrast, OLP/CMC effectively minimized quality losses, and coated tomatoes exceeded the limit of marketability after 14 days of storage. This study successfully applied value-added polysaccharides derived from okra plant residues for edible food packaging.
Accurate solution method for the Maxey–Riley equation, and the effects of Basset history

The Maxey–Riley equation has been extensively used by the fluid dynamics community to study the dynamics of small inertial particles in fluid flow. However, most often, the Basset history force in this equation is neglected. Analytical solutions have almost never been attempted because of the difficulty in handling an integro-differential equation of this type. Including the Basset force in numerical solutions of particulate flows involves storage requirements which rapidly increase in time. Thus the significance of the Basset history force in the dynamics has not been understood. In this paper, we show that the Maxey–Riley equation in its entirety can be exactly mapped as a forced, time-dependent Robin boundary condition of the one-dimensional diffusion equation, and solved using the unified transform method. We obtain the exact solution for a general homogeneous time-dependent flow field, and apply it to a range of physically relevant situations. In a particle coming to a halt in a quiescent environment, the Basset history force speeds up the decay as a stretched exponential at short time while slowing it down to a power-law relaxation, ${\sim}t^{-3/2}$ , at long time. A particle settling under gravity is shown to relax even more slowly to its terminal velocity ( ${\sim}t^{-1/2}$ ), whereas this relaxation would be expected to take place exponentially fast if the history term were to be neglected. An important mechanism for the growth of raindrops is by the gravitational settling of larger drops through an environment of smaller droplets, and repeatedly colliding and coalescing with them. Using our solution we estimate that the rate of growth rate of a raindrop can be grossly overestimated when history effects are not accounted for. We solve exactly for particle motion in a plane Couette flow and show that the location (and final velocity) to which a particle relaxes is different from that due to Stokes drag alone. For a general flow, our approach makes possible a numerical scheme for arbitrary but smooth flows without increasing memory demands and with spectral accuracy. We use our numerical scheme to solve an example spatially varying flow of inertial particles in the vicinity of a point vortex. We show that the critical radius for caustics formation shrinks slightly due to history effects. Our scheme opens up a method for future studies to include the Basset history term in their calculations to spectral accuracy, without astronomical storage costs. Moreover, our results indicate that the Basset history can affect dynamics significantly.
Wormholes with nonexotic matter in Born-Infeld gravity

We show that, in contrast to general relativity, in Eddington-inspired Born-Infeld gravity (EiBI), a violation of the null convergence condition does not necessarily lead to a violation of the null energy condition, by establishing a relationship between them. This serves as a motivation for finding wormhole solutions which can be supported by nonexotic matter in this gravity theory. We then obtain exact solutions of the field equations in EiBI gravity coupled to arbitrary nonlinear electrodynamics and anisotropic fluids. Depending on the signs and values of different parameters, the general solutions can represent both black holes and wormholes. In this work, we analyze the wormhole solutions. These wormholes are supported by nonexotic matter, i.e., matter satisfying all the energy conditions. As special cases of our general solutions, we work out several specific examples by considering Maxwell, power-law, Born-Infeld electrodynamics models and a particular form of an anisotropic fluid.
Role of environment and gas temperature in the formation of multiple protostellar systems: molecular tracers

Context. Simulations suggest that gas heating due to radiative feedback is a key factor in whether or not multiple protostellar systems will form. Chemistry is a good tracer of the physical structure of a protostellar system, since it depends on the temperature structure. Aims. We aim to study the relationship between envelope gas temperature and protostellar multiplicity. Methods. Single dish observations of various molecules that trace the cold, warm, and UV-irradiated gas were used to probe the temperature structure of multiple and single protostellar systems on 7000 AU scales. Results. Single, close binary, and wide multiples present similar current envelope gas temperatures, as estimated from H2CO and DCO+ line ratios. The temperature of the outflow cavity, traced by c-C3H2, on the other hand, shows a relation with bolometric luminosity and an anticorrelation with envelope mass. Although the envelope gas temperatures are similar for all objects surveyed, wide multiples tend to exhibit a more massive reservoir of cold gas compared to close binary and single protostars. Conclusions. Although the sample of protostellar systems is small, the results suggest that gas temperature may not have a strong impact on fragmentation. We propose that mass, and density, may instead be key factors in fragmentation.
Diffusion approximation for efficiency-driven queues: A space-time scaling approach

Motivated by call center practice, we propose a tractable model for $\mbox{GI}/\mbox{GI}/n+\mbox{GI}$ queues in the efficiency-driven (ED) regime. We use a one-dimensional diffusion process to approximate the virtual waiting time process that is scaled in both space and time, with the number of servers and the mean patience time as the respective scaling factors. Using this diffusion model, we obtain the steady-state distributions of virtual waiting time and queue length, which in turn yield simple formulas for performance measures such as the service level and the effective abandonment fraction. These formulas are generally accurate when the mean patience time is several times longer than the mean service time and the patience time distribution does not change rapidly around the mean virtual waiting time. For practical purposes, these formulas outperform existing results that rely on the exponential service time assumption. To justify the diffusion model, we formulate an asymptotic framework by considering a sequence of queues, in which both the number of servers and the mean patience time go to infinity. We prove that the space-time scaled virtual waiting time process converges in distribution to the one-dimensional diffusion process. A fundamental result for proving the diffusion limit is a functional central limit theorem (FCLT) for the superposition of renewal processes. We prove that the superposition of many independent, identically distributed stationary renewal processes, after being centered and scaled in space and time, converges in distribution to a Brownian motion. As a useful technical tool, this theorem characterizes the service completion process in heavy traffic, allowing us to greatly simplify the many-server analysis when service times follow a general distribution.
Note on neutron star equation of state in the light of GW170817

From the very first multimessenger event of GW170817, clean robust constraints can be obtained for the tidal deformabilities of the two stars involved in the merger, which provides us unique opportunity to study the equation of states (EOSs) of dense stellar matter. In this contribution, we employ a model from the quark level, describing consistently a nucleon and many-body nucleonic system from a quark potential. We check that our sets of EOSs are consistent with available experimental and observational constraints at both sub-nuclear saturation densities and higher densities. The agreements with ab-initio calculations are also good. Especially, we tune the density dependence of the symmetry energy (characterized by its slope at nuclear saturation $L$) and study its influence on the tidal deformability. The so-called $QMF18$ EOS is named after the case of $L=40~\rm MeV$, and it gives $M_{\rm TOV} =2.08~M_\odot$ and $R= 11.77~\rm km$, $\Lambda=331$ for a $1.4\,M_\odot$ star. The tidal signals are demonstrated to be insensitive to the uncertain crust-core matching, despite the good correlation between the symmetry energy slope and the radius of the star.
Spin and charge dynamics of the one-dimensional extended hubbard model

We investigate the dynamical spin and charge structure factors and the one-particle spectral function of the one-dimensional extended Hubbard model at half band-filling using the dynamical density-matrix renormalization group method. The influence of the model parameters on these frequency- and momentum-resolved dynamical correlation functions is discussed in detail for the Mott-insulating regime. We find quantitative agreement between our numerical results and experiments for the optical conductivity, resonant inelastic X-ray scattering, neutron scattering, and angle-resolved photoemission spectroscopy in the quasi-one-dimensional Mott insulator SrCuO$_2$.
On the rational Tur\'an exponents conjecture

The extremal number $\mathrm{ex}(n,F)$ of a graph $F$ is the maximum number of edges in an $n$-vertex graph not containing $F$ as a subgraph. A real number $r \in [1,2]$ is realisable if there exists a graph $F$ with $\mathrm{ex}(n , F) = \Theta(n^r)$. Several decades ago, Erd\H{o}s and Simonovits conjectured that every rational number in $[1,2]$ is realisable. Despite decades of effort, the only known realisable numbers are $0,1, \frac{7}{5}, 2$, and the numbers of the form $1+\frac{1}{m}$, $2-\frac{1}{m}$, $2-\frac{2}{m}$ for integers $m \geq 1$. In particular, it is not even known whether the set of all realisable numbers contains a single limit point other than two numbers $1$ and $2$. In this paper, we make progress on the conjecture of Erd\H{o}s and Simonovits. First, we show that $2 - \frac{a}{b}$ is realisable for any integers $a,b \geq 1$ with $b>a$ and $b \equiv \pm 1 ~({\rm mod}\:a)$. This includes all previously known ones, and gives infinitely many limit points $2-\frac{1}{m}$ in the set of all realisable numbers as a consequence. Secondly, we propose a conjecture on subdivisions of bipartite graphs. Apart from being interesting on its own, we show that, somewhat surprisingly, this subdivision conjecture in fact implies that every rational number between 1 and 2 is realisable.
Deep ALMA search for CO gas in the HD 95086 debris disc

Deutsche Forschungsgemeinschaft [Kr 2164/15-1, Lo 1715/2-1]; Smithsonian Institution; STFC via the Institute of Astronomy, Cambridge Consolidated Grant; National Science Foundation (NSF) [AST-1412647]; NSF Astronomy and Astrophysics Postdoctoral Fellowship [AST-1701406]
Variational integrators for anelastic and pseudo-incompressible flows

The anelastic and pseudo-incompressible equations are two well-known soundproof approximations of compressible flows useful for both theoretical and numerical analysis in meteorology, atmospheric science, and ocean studies. In this paper, we derive and test structure-preserving numerical schemes for these two systems. The derivations are based on a discrete version of the Euler-Poincare variational method. This approach relies on a finite dimensional approximation of the (Lie) group of diffeomorphisms that preserve weighted-volume forms. These weights describe the background stratification of the fluid and correspond to the weighed velocity fields for anelastic and pseudo-incompressible approximations. In particular, we identify to these discrete Lie group configurations the associated Lie algebras such that elements of the latter correspond to weighted velocity fields that satisfy the divergence-free conditions for both systems. Defining discrete Lagrangians in terms of these Lie algebras, the discrete equations follow by means of variational principles. Descending from variational principles, the schemes exhibit further a discrete version of Kelvin circulation theorem, are applicable to irregular meshes, and show excellent long term energy behavior. We illustrate the properties of the schemes by performing preliminary test cases.
Borcea–Voisin mirror symmetry for Landau–Ginzburg models

FJRW theory is a formulation of physical Landau-Ginzburg models with a rich algebraic structure, rooted in enumerative geometry. As a consequence of a major physical conjecture, called the Landau-Ginzburg/Calabi-Yau correspondence, several birational morphisms of Calabi-Yau orbifolds should correspond to isomorphisms in FJRW theory. In this paper it is shown that not only does this claim prove to be the case, but is a special case of a wider FJRW isomorphism theorem, which in turn allows for a proof of mirror symmetry for a new class of cases in the Landau-Ginzburg setting. We also obtain several interesting geometric applications regarding the Chen-Ruan cohomology of certain Calabi-Yau orbifolds.
On $\ast $-Semi Homogeneous Domains

Let $\ast $ be a finite character star operation defined on an integral domain $D. $ Call a nonzero $\ast $-ideal $I$ of finite type a $\ast $ -homogeneous ($\ast $-homog) ideal, if $I\subsetneq D$ and $(J+K)^{\ast }\neq D$ for every pair $D\supsetneq J,K\supseteq I$ of proper $\ast $ -ideals of finite type$. $ Call an integral domain $D$ a $\ast $-Semi Homogeneous Domain ($\ast $-SHD) if every proper principal ideal $xD$ of $D$ is expressible as a $\ast $-product of finitely many $\ast $-homog ideals. We show that a $\ast $-SHD contains a family $\mathcal{F}$ of prime ideals such that (a) $D=\cap_{P\in \mathcal{F}}D_{P},$ a locally finite intersection and (b) no two members of $\mathcal{F}$ contain a common non zero prime ideal. The $\ast $-SHDs include h-local domains, independent rings of Krull type, Krull domains, UFDs etc. We show also that we can modify the definition of the $\ast $-homog ideals to get a theory of each special case of a $\ast $-SH domain.
Concentration Phenomena for Fractional Elliptic Equations Involving Exponential Critical Growth

Abstract In this paper, we deal with the singular perturbed fractional elliptic problem ε⁢(-Δ)1/2⁢u+V⁢(z)⁢u=f⁢(u)$\varepsilon(-\Delta)^{1/2}{u}+V(z)u=f(u)$ in ℝ$\mathbb{R}$, where (-Δ)1/2⁢u${(-\Delta)^{1/2}u}$ is the square root of the Laplacian and f⁢(s)${f(s)}$ has exponential critical growth. Under suitable conditions on f⁢(s)${f(s)}$, we construct a localized bound state solution concentrating at an isolated component of the positive local minimum points of the potential of V as ε goes to 0.
Invariance principles for operator-scaling Gaussian random fields

Recently, Hammond and Sheffield introduced a model of correlated random walks that scale to fractional Brownian motions with long-range dependence. In this paper, we consider a natural generalization of this model to dimension $d\geq 2$. We define a $\mathbb Z^d$-indexed random field with dependence relations governed by an underlying random graph with vertices $\mathbb Z^d$, and we study the scaling limits of the partial sums of the random field over rectangular sets. An interesting phenomenon appears: depending on how fast the rectangular sets increase along different directions, different random fields arise in the limit. In particular, there is a critical regime where the limit random field is operator-scaling and inherits the full dependence structure of the discrete model, whereas in other regimes the limit random fields have at least one direction that has either invariant or independent increments, no longer reflecting the dependence structure in the discrete model. The limit random fields form a general class of operator-scaling Gaussian random fields. Their increments and path properties are investigated.