Miracle-dz/UniFAR-FTUs huggingface dataset:
Forecast verification: Its Complexity and Dimensionality

Abstract Two fundamental characteristics of forecast verification problems—complexity and dimensionality—are described. To develop quantitative definitions of these characteristics, a general framework for the problem of absolute verification (AV) is extended to the problem of comparative verification (CV). Absolute verification focuses on the performance of individual forecasting systems (or forecasters), and it is based on the bivariate distribution of forecasts and observations and its two possible factorizations into conditional and marginal distributions. Comparative verification compares the performance of two or more forecasting systems, which may produce forecasts under 1) identical conditions or 2) different conditions. The first type of CV is matched comparative verification, and it is based on a 3-yariable distribution with possible factorizations. The second and more complicated type of CV is unmatched comparative verification, and it is based on a 4-variable distribution with 24 possible fact.
Nonlinear Mesoscopic Elasticity: Evidence for a New Class of Materials

A squash ball almost doesn't bounce; a Superball bounces first left then right, seeming to have a mind of its own. Remarkable and complex elastic behavior isn't confined to sports equipment and toys. Indeed, it can be found in some surprising places. When the elastic behavior of a rock is probed, for instance, it shows extreme nonlinearity hysteresis and discrete memory (the Flint‐stones could have had a computer that used a sandstone for random‐access memory). Rocks are an example of a class of unusual elastic materials that includes sand. soil, cement, concrete, ceramics and, it turns out, damaged materials, Many members of this class are the blue‐collar materials of daily life: They are in the bridges we cross on the way to work, the roofs over our heads and the ground beneath our cities—such as the Los Angeles basin (home to many earthquakes). The elastic behavior of these materials is of more than academic interest.
Perturbation model for photon migration imaging in the low scattering regime

I discuss a non-diffusion linear model relating changes in the optical properties of tissues to the changes in the observed signals. It expresses measurements in terms of the moments of statistical distributions characterizing light scattering. The inverse form of the model can be used for quantitative imaging in situations when the diffusion approximation is invalid, such as imaging of low-scattering tissues and small animal imaging.
Wave-breaking-free pulses in nonlinear-optical fibers

A qualitative as well as quantitative investigation is made of the conditions for avoiding wave breaking during pulse propagation in optical fibers. In particular, it is shown that pulses having a parabolic intensity variation are approximate wave-breaking-free solutions of the nonlinear Schrodinger equation in the high-intensity limit. A simple expression for the compression factor of a fiber-grating compressor based on parabolic pulses is also derived.
Bayesian analysis of the two-sample problem under the Lehmann alternatives

Papers that have been written on the use of the rank order statistic for the two-sample problem under the Lehmann alternatives have focused on the use of rank tests to determine whether there is a difference in the two populations. In particular, the test proposed by Savage (1956) is the rank test that is usually suggested to be used in this situation. In this paper a Bayesian analysis of the problem based on the rank order statistic is presented. Suppose that a random sample of m observations is obtained from distribution 1 and an independent random sample of n observations is obtained from distribution 2, and N = m+n. The rank order statistic will be denoted by z = (z1, .,ZN), where zi is 0 if the ith smallest observation is from distribution 1 and zi is 1 otherwise (i -1, ., N). Let F(x) and G(x) be the distribution functions of distributions 1 and 2, respectively, both assumed to be continuous. If G(x) is the Lehmann alternative 1{1 F(x)}k(k > 0), which holds, for example, if the population distributions are both exponential or both Weibull, then the rank order probability is
Two algorithms for compressing noise like signals

Compression is a technique that is used to encode data so that the data needs less storage/memory space. Compression of random data is vital in case where data where we need preserve data that has low redundancy and whose power spectrum is close to noise. In case of noisy signals that are used in various data hiding schemes the data has low redundancy and low energy spectrum. Therefore, upon compressing with lossy compression algorithms the low energy spectrum might get lost. Since the LSB plane data has low redundancy, lossless compression algorithms like Run length, Huffman coding, Arithmetic coding are in effective in providing a good compression ratio. These problems motivated in developing a new class of compression algorithms for compressing noisy signals. In this paper, we introduce a two new compression technique that compresses the random data like noise with reference to know pseudo noise sequence generated using a key. In addition, we developed a representation model for digital media using the pseudo noise signals. For simulation, we have made comparison between our methods and existing compression techniques like Run length that shows the Run length cannot compress when data is random but the proposed algorithms can compress. Furthermore, the proposed algorithms can be extended to all kinds of random data used in various applications.
B-Spline Curve Fitting Based on Adaptive Particle Swarm Optimization Algorithm

For fitting of ordered plane data by B-spline curve with the least squares, the genetic algorithm is generally used, accompanying the optimization on both the data parameter values and the knots to result in good robust, but easy to fall into local optimum, and without improved fitting precision by increasing the control points of the curve. So what we have done are: combining the particle swarm optimization algorithm into the B-spline curve fitting, taking full advantage of the distribution characteristic for the data, associating the data parameters with the knots, coding simultaneously the ordered data parameter and the number of the control points of the B-spline curve, proposing a new fitness function, dynamically adjusting the number of the control points for the B-spline curve. Experiments show the proposed particle swarm optimization method is able to adaptively reach the optimum curve much faster with much better accuracy accompanied less control points and less evolution times than the genetic algorithm.
The friction of lubricated metals

An analysis has been made of the kinetic friction between metals sliding under conditions of boundary lubrication. With mineral oils and many other lubricants an intermittent clutching and breaking away of the surfaces still occurs through the oil film. The friction, the surface temperature and the area of contact all show violent fluctuations and the behaviour may be essentially the same as with unlubricated metals. Certain substances, however, are able to prevent this “ stick-slip” motion and allow continuous sliding to take place. With short-chain fatty acids, for example, the motion is “ stick-slip”, but when the chain reaches a certain length continuous sliding occurs. Alcohols and saturated hydrocarbons of the same, or longer, chain length do not cause continuous sliding. Even with the best lubricant the film breaks down to some extent during sliding and some wear of the surfaces takes place. The metal is torn to a depth which is large compared with the dimensions of a molecule. The frictional force between lubricated metals must therefore be greatly influenced by the bulk properties of the metals concerned. The frictional behaviour of metallic surfaces covered with successive monolayers of lubricant has also been investigated. A single layer can cause a large reduction in the friction but the film is soon worn away. With multilayers the rate at which the film wears off is markedly dependent on its molecular thickness and methods are described for measuring the rate of wear of lubricant films. A single film of long-chain fatty acid molecules is more effective than a single film of the flat leaf-shaped cholesterol molecule. It is clear that a primary film is not sufficient, but that for effective boundary lubrication it is necessary to have present a layer of lubricant several molecules thick. The experiments show that boundary lubrication cannot be regarded as a purely surface phenomenon. On the basis of these experiments a theory has been put forward to explain boundary lubrication. In general it appears that even with lubricated surfaces the local pressures in the region of contact are very high, so that the lubricant film between the surfaces is partly broken down. If the sliding speeds are appreciable this breakdown is aided by the local high temperatures. Metallic junctions, the size of which is large compared with the dimensions of a molecule, are formed between the surfaces. There will, of course, be some resistance due to the interaction of the surface films themselves, but under many conditions of sliding the resistance to motion is due mainly to the force necessary to break the junctions. The frictional behaviour of boundary lubricated surfaces is therefore largely governed by the extent to which the lubricant film breaks down during sliding.
A numerical method for the calculation of incompressible, steady, separated flows around aerofoils

The present work deals with the numerical calculation of the incompressible turbulent flow around aerofoils. An orthogonal curvilinear grid of ‘C’ type is used for the solution of the time averaged equations and Reynolds stresses are modelled according to the κ-e turbulence model. PISO and SIMPLE algorithms are used to solve the strongly coupled system of the derived finite volume equations and convergence is improved by applying the method of variable local underrelaxation factors. Comparisons between the calculated and measured pressure distributions are presented for NACA 0012 and NACA 4412 wing sections. The formation of separation bubbles according to calculations is also shown.
Gravitational waves from isolated sources

Using general relativity we study gravitational waves from isolated, axially-symmetric sources. We start with a metric due to Bondi, and use the double-series approximation method. In the linear approximation we obtain a general solution for the 2s axially-symmetric multipole field. Passing to the non-linear approximations, we demonstrate that the source loses mass on account of the quadrupole-quadrupole interaction, and that it recoils because of the quadrupole-octupole interaction. The mass and momentum changes of the source agree with the results obtained by means of the pseudo tensor of energy and momentum. We explain why we believe that these waves have tails, and discuss this in relation to a paper by Bondi, Van der Burg & Metzner.
Beyond covariance realism: a new metric for uncertainty realism

In the space surveillance tracking domain, it is often necessary to assess not only the covariance consistency or covariance realism of an object's state estimate, but also the realism (proper characterization) of its full estimated probability density function. In other words, there is a need for “uncertainty realism. " We propose a new metric (applicable to any tracking domain) that generalizes the covariance realism metric based on the Mahalanobis distance to one that tests uncertainty realism. We then review various goodness-of-fit and distribution matching tests that exploit the uncertainty realism metric and describe how these tests can be applied to assess uncertainty realism in off-line simulations with multiple Monte-Carlo trials or on-line with real data when truth is available.
Microwave transmission measurements through wire array photonic crystals

We have measured the microwave transmission between 12 and 18 GHz through wire arrays formed into two dimensional square lattices. One array made of copper wire 0.14 mm in radius consisted of five rows by 21 columns having a lattice constant of 5.2 mm. This array exhibited a pass band above 15 GHz, in good agreement with the calculated plasma frequency found from an expression for the permittivity derived in the long wavelength limit. A second array was made with Nichrome wire of radius 18 μm and lattice constant 1.1 mm. This array was filled with dielectric loaded with powdered magnetite. A sample of this metamaterial 5.8 mm thick and with no externally applied magnetic field exhibited a pass band above 17 GHz. Implications for creating metamaterials with a negative index of refraction from wire arrays embedded in a magnetic host are discussed.
Adaptive VOF with curvature‐based refinement

Adaptive refinement is implemented in the context of the volume‐of‐fluid (VOF) methodology in order to study the efficacy of resolving interfaces adaptively based on the local value of curvature. The usual uniform mesh VOF implementation is modified slightly to ensure accurate advection of fluxes between cells at different resolutions. Normals and curvatures are calculated accurately via height functions. Results of a series of tests indicate that in most instances the use of adaptive refinement (when compared to uniform refinement with a similar number of cells) leads to more accurate VOF advection. The results also clearly show that curvature‐based adaptive refinement leads to a distribution of errors along an interface that is nearly independent of curvature. Copyright © 2007 John Wiley & Sons, Ltd.
Optimal Properties of Exponentially Weighted Forecasts

Abstract The exponentially weighted average can be interpreted as the expected value of a time series made up of two kinds of random components: one lasting a single time period (transitory) and the other lasting through all subsequent periods (permanent). Such a time series may, therefore, be regarded as a random walk with “noise” superimposed. It is also shown that, for this series, the best forecast for the time period immediately ahead is the best forecast for any future time period, because both give estimates of the permanent component. The estimate of the permanent component is imperfect, and so the estimate of a regression coefficient is inconsistent in a relation involving the permanent (e.g. consumption as a function of permanent income). Its bias is small, however.
Supersonic turbulence as an agent of structure formation in space

Supersonic turbulence is a main agent for structure formation in space, from stellar winds to wind‐blown bubbles, supernovae remnants, ‐ray bursts, and star‐formation in molecular clouds. Dissipation is mostly due to shocks. Under isothermal conditions, the density follows a log‐normal distribution whose variance grows with Mach number. The exact scaling is under debate. We focus on problems with not strictly periodic boundary conditions and present 2D and 3D numerical simulation of supersonic turbulence in plan‐parallel slabs. From dimensional analysis we derive scaling laws for the mean quantities under isothermal conditions. Simulations including spatially extended radiative cooling layers reveal a complex interplay between turbulence and RM‐ and RT‐unstable interfaces. Turbulent Mach numbers here are significantly reduced compared to the isothermal case and are of order 1. However, unstable interfaces between the different thermal component of the gas are equally able to produce structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of forming mechanisms for Sedna-type objects through an observational simulator

The aim of this work is to investigate the primordial orbital formation of objects in the inner border of the Oort Cloud, of which Sedna is supposedly a member. Among the several scenarios that discuss the formation of these orbits, two specific ones are compared for their ability to describe the dynamical formation of objects in the inner Oort Cloud: the planetary mass solar companion scenario that aims at explaining Sedna’s orbit through the perturbation of a distant solar system planet, and the stellar dense cluster scenario based on the perturbation of a primordial star cluster to which the Sun supposedly belonged. We constructed the orbital distribution of ice objects from the above scenarios and statisticaly compared both using an observational simulator that evaluates objects, sizes using a cumulative power law distribution with slope λ. We investigated the dependence on λ of the average number of observations realized by the simulator until one member of the inner Oort Cloud is observed. The results obtained by both scenarios show that both reproduce the orbits of Sedna-like objects well for specific values of the parameters. A statistical analysis considering a particular observational survey is also performed, and we find that the probability of obtaining a Sedna-type object from a population of 14 or less scattered objects as obtained in that survey is quite low (mostly below 15%) for both models, implying that the observation of the first inner Oort Cloud member occurred much earlier than would normally be expected for a first member detection of that population. We also conclude that it is necessary to observe new objects belonging to the inner Oort Cloud to precisely characterize which scenario is better for describing the origin of these objects. Possibly the best orbital element to analyze for a distinction between models is the inclination.
Convective Cells in Altocumulus Observed with a High-Resolution Radar

AbstractVery-high-resolution Doppler radar observations are used together with aircraft measurements to document the dynamic and thermodynamic structure of a dissipating altocumulus cloud system associated with a deep virga layer. The cloud layer circulation is shown to consist of shallow vertical velocity couplets near cloud top and a series of subkilometer-scale Rayleigh–Benard-like cells that extend vertically through the depth of the cloud layer. The subcloud layer was observed to contain a number of narrow virga fall streaks that developed below the more dominant Rayleigh–Benard updraft circulations in the cloud layer. These features were discovered to be associated with kilometer-scale horizontally orientated rotor circulations that formed along the lateral flanks of the streaks collocated downdraft circulation. The Doppler analysis further reveals that a layer mean descent was present throughout both the cloud and subcloud layers. This characteristic of the circulation is analyzed with regard to th.
Explicit determination of nontrivial torsion structures of elliptic curves over quadratic number fields

We determine equations of the modular curves X1(N) for N = 11, 13, 14, 15, 16, 17 and 18. Except for N = 17, these are the only existing elliptic or hyperelliptic X1(N). Applying these X1(N), we calculate tables of elliptic curves E over quadratic fields K with torsion groups of one of the following isomorphism types: Etor(K) -Z/mZ, m = 11, 13, 14,15, 16 and 18.
Observations of supra-glacial lakes in west Greenland using winter wide swath Synthetic Aperture Radar

Melt water gathered in supra-glacial lakes on the Greenland ice sheet contributes to reduced basal friction by the input of water from the surface to the bed during the melt season. Supra-glacial lakes change on both annual and inter-annual timescales. The high temporal resolution and moderate spatial resolution Moderate Resolution Imaging Spectroradiometer (MODIS) can be used to capture annual changes on the highly transient/fast-draining lakes. However, MODIS imagery lacks the ability to penetrate clouds. Using ENVISAT Synthetic Aperture Radar (SAR) winter images, we show that SAR images can be used to identify seasonal/inter-annual changes in the lake area. Furthermore, winter SAR images identify lakes obscured to optical data by ice and snow cover. However, the SAR imagery systematically failed to discriminate narrow lakes and lakes in corrugated topography. Thus, SAR images can be used as a complement to existing visible–near-infrared data but do not offer a viable replacement.
Time-averaged flow over a hydrofoil at high Reynolds number

At high Reynolds number, the flow of an incompressible viscous fluid over a lifting surface is a rich blend of fluid dynamic phenomena. Here, boundary layers formed at the leading edge develop over both the suction and pressure sides of the lifting surface, transition to turbulence, separate near the foil's trailing edge, combine in the near wake, and eventually form a turbulent far-field wake. The individual elements of this process have been the subject of much prior work. However, controlled experimental investigations of these flow phenomena and their interaction on a lifting surface at Reynolds numbers typical of heavy-lift aircraft wings or full-size ship propellers (chord-based Reynolds numbers, $Re_C {\sim} 10^7{-}10^8$) are largely unavilable. This paper presents results from an experimental effort to identify and measure the dominant features of the flow over a two-dimensional hydrofoil at nominal $Re_C$ values from near one million to more than 50 million. The experiments were conducted in the US Navy's William B. Morgan Large Cavitation Channel with a solid-bronze hydrofoil (2.1 m chord, 3.0 m span, 17 cm maximum thickness) at flow speeds from 0.25 to 18.3 m s$^{-1}$. The foil section, a modified NACA 16 with a pressure side that is nearly flat and a suction side that terminates in a blunt trailing-edge bevel, approximates the cross-section of a generic naval propeller blade. Time-averaged flow-field measurements drawn from laser-Doppler velocimetry, particle-imaging velocimetry, and static pressure taps were made for two trailing-edge bevel angles (44$ ^\circ$ and 56$ ^\circ$). These velocity and pressure measurements were concentrated in the trailing-edge and near-wake regions, but also include flow conditions upstream and far downstream of the foil, as well as static pressure distributions on the foil surface and test section walls. Observed Reynolds-number variations in the time-averaged flow over the foil are traced to changes in suction-side boundary-layer transition and separation. Observed Reynolds-number variations in the time-averaged near wake suggest significant changes occur in the dynamic flow in the range of $Re_C$ investigated.
SODIUM-OXYGEN ABUNDANCE ANTICORRELATIONS AND DEEP MIXING SCENARIOS FOR GLOBULAR CLUSTER GIANTS

We explore and extend the suggstion that 23Na might be produced in the interior of an evolving low-mass globular cluster giant and mixed to the surface (Kudryashov & Tutukov 1988, Denisenkov & Denisenkova 1990). The reaction rates alone show that sodium will be produced by proton captures on 22Ne in the region of a globulr cluster giant in which oxygen is being depleted. A more detailed calculation shows that significant amounts of the much more abundant 20Ne can be transformed into 23Na on somewhat longer timescales. Atmospheric oxygen depletions that are the result of very deep mixing are bound to be accompanied by sodium enhancements due to 22Ne(p,gamma)23Na reactions; they are quite likely to be accopanied by larger sodium enhancements that begin with proton captures on 20Ne. One cannot argue that a Na-O anticorrelation is strong evidence for a primordial account of the observed variations in O and Na. We find that 27Al can also be produced by very deep mixing and that the aluminum enhancements that would result are likely to be smaller than the sodium enhancements. Finally, we suggest a number of ways in which the consequences of this sort of very deep mixing might be distinguished from primordial variations in oxygen, sodium and aluminum.