Miracle-dz/UniFAR-FTUs huggingface dataset:
The circular Bedrosian identity for translation‐invariant operators: existence and characterization

The analytic signal method via the circular Hilbert transform H~ is a critical tool in the time–frequency analysis of signals of finite duration. The circular Bedrosian identity H~(fg)=fH~g is of major theoretical and practical value in the method. The identity holds whenever the Fourier coefficients of f,g∈L2([−π,π]) are respectively supported on A = [−n,m] and B=Z∖[−m,n] for some non‐negative integers 0≤n,m≤+∞. In this note, we investigate the existence of such an identity for a general‐bounded linear translation‐invariant operator on L2([−π,π]d) and for general support sets A,B⊆Zd . We give an insightful geometric characterization of the support sets for the existence. In addition, we find all the support sets for the partial Hilbert transforms. Copyright © 2015 John Wiley & Sons, Ltd.
A phase field model of capillarity

The phenomenological derivation of a phase field model of capillarity that accounts for the structure of an interfacial layer formed by two immiscible incompressible liquids is addressed. A rheological expression for the reversible component of capillary stresses is obtained in terms of the free energy of a binary fluid, which depends on the absolute temperature, composition, and gradient of composition. This model can be applied to those flows that involve change of topology of a capillary interface, such as coalescence and breakup of drops. As an illustration, an equilibrium of a binary fluid with either a flat or spherical interfacial layer is analyzed, and a thermocapillary flow in an infinite gap is considered.
SCUBA observations of the sources detected in the MAMBO 1200-μm survey

We have observed 23 sources from the Max-Planck Millimetre Bolometer (MAMBO) array 1200-μm survey with SCUBA at 850 μm, detecting 19 of the sources. The sources generally have low values for the ratio of 850- to 1200-μm flux. Two possible explanations for the low values are either that the sources are at very high redshifts or that the global properties of the dust in the MAMBO sources are different from the global properties of dust in low-redshift galaxies. If the former explanation is correct, we estimate that 15 of the MAMBO sources lie at z > 3.
Current-driven chaotic magnetization dynamics in microwave assisted switching of spin-valve elements

The switching process of a uniformly magnetized spin-valve is considered. The system is subject to external dc applied fields and injected radio-frequency (RF) spin-polarized currents. The possibility of using the RF power to obtain a reduced coercivity of the particle is related to the onset of chaotic magnetization dynamics for moderately low values of the RF current amplitude. Perturbation technique for the estimation of the reduced coercive field is developed and applied to the microwave assisted switching of the particle. Numerical simulations confirm the predictions of the theory.
A new 60 millisecond X-ray pulsar and its massive early-type companion

Einstein Observatory IPC and HRI observations of a serendipitous, variable, X-ray source in the galactic plane in Carina are presented. Timing analysis shows the source to have a periodicity P ~ 60 msec. The optical identification with the 12.7 mag Wack 2134 star, suggested by the positional coincidence, is confirmed by spectroscopic observations done at ESO La Silla. The star appears to be probably of 05 type. The X-ray and optical data suggest the discovery of a new binary system where a hot massive star loses mass to a spinning neutron star, which would then be the fastest X-ray binary pulsar to date.
Lecture Notes on Elementary Topology and Geometry.

1 Some point set topology. - 1.1 Naive set theory. - 1.2 Topological spaces. - 1.3 Connected and compact spaces. - 1.4 Continuous functions. - 1.5 Product spaces. - 1.6 The Tychonoff theorem. - 2 More point set topology. - 2.1 Separation axioms. - 2.2 Separation by continuous functions. - 2.3 More separability. - 2.4 Complete metric spaces. - 2.5 Applications. - 3 Fundamental group and covering spaces. - 3.1 Homotopy. - 3.2 Fundamental group. - 3.3 Covering spaces. - 4 Simplicial complexes. - 4.1 Geometry of simplicial complexes. - 4.2 Barycentric subdivisions. - 4.3 Simplicial approximation theorem. - 4.4 Fundamental group of a simplicial complex. - 5 Manifolds. - 5.1 Differentiable manifolds. - 5.2 Differential forms. - 5.3 Miscellaneous facts. - 6 Homology theory and the De Rham theory. - 6.1 Simplicial homology. - 6.2 De Rham's theorem. - 7 Intrinsic Riemannian geometry of surfaces. - 7.1 Parallel translation and connections. - 7.2 Structural equations and curvature. - 7.3 Interpretation of curvature. - 7.4 Geodesic coordinate systems. - 7.5 Isometries and spaces of constant curvature. - 8 Imbedded manifolds in R3.
Magnetic Forces in an Isopedic Disk

We consider the magnetic forces in electrically conducting thin disks threaded by magnetic fields originating in the external (interstellar) medium. We focus on disks that have dimensionless ratios λ of the mass to flux that are spatially constant, a condition that we term isopedic. For arbitrary distributions of the surface density Σ (which can be nonaxisymmetric and time dependent), we show that the magnetic tension exerts a force in the plane of the disk equal to -1/λ2 times the self-gravitational force. In addition, if the disk maintains magnetostatic equilibrium in the vertical direction, the magnetic pressure, integrated over the z-height of the disk, may be approximated as (1 + η2)/(λ2 + η2) times the gas pressure integrated over z, where η ≡ f‖/2πGΣ and f‖ is the component of the local gravitational field parallel to the plane of the disk. We apply these results to the problem of the stability of magnetized isothermal disks to gravitational fragmentation into subcondensations of a size comparable to the vertical scale height of the disk. Contrary to common belief, such dynamical fragmentation probably does not occur. In particular, the case of the magnetized singular isothermal disk undergoes not dynamical fragmentation into many subcondensations, but inside-out collapse into a single compact object, a self similar problem that is studied in a companion paper (Li & Shu 1997).
On Jacobi methods for singular value decompositions

An improvement of the Jacobi singular value decomposition algorithm is proposed. The matrix is first reduced to a triangular form. It is shown that the row-cyclic strategy preserves the triangularity. Further improvements lie in the convergence properties. It is shown that the method converges globally and a proof of the quadratic convergence is indicated as well. The numerical experiments confirm these theoretical predictions. Our method is about 2-3 times slower than the standard QR method but it almost reaches the latter if the matrix is diagonally dominant or of low rank.
Phase I Monitoring of Polynomial Profiles

In some statistical process control applications, quality of a process or product is characterized by a relationship between two or more variables which is referred to as profile. In many practical situations, a profile can be modeled as a polynomial regression. In this article, three methods are developed for monitoring polynomial profiles in Phase I. Their performance is evaluated using power criterion. Furthermore, a method based on likelihood ratio test is developed to identify the location of shifts. Numerical simulation is used to evaluate the performance of the developed method.
High-entropy fireballs and jets in gamma-ray burst sources

Two mechanisms are presented whereby compact coalescing binaries can produce relatively «clean» fireballs via neutrino-antineutrino annihilation. Pre-ejected mass due to tidal heating will collimate the fireball into jets. The resulting anisotropic gamma-ray emission can be efficient and intense enough to provide an acceptable model for gamma-ray bursts, if these originate at cosmological distances
Extensions of the multiarmed bandit problem: The discounted case

There are N independent machines. Machine i is described by a sequence {X^{i}(s), F^{i}(s)} where X^{i}(s) is the immediate reward and F^{i}(s) is the information available before i is operated for the sth lime. At each time one operates exacfiy one machine; idle machines remain frozen. The problem is to schedule the operation of the machines so as to maximize the expected total discounted sequence of rewards. An elementary proof shows that to each machine is associated an index, and the optimal policy operates the machine with the largest current index. When the machines are completely observed Markov chains, this coincides with the well-known Gittins index rule, and new algorithms are given for calculating the index. A reformulation of the bandit problem yields the tax problem, which includes, as a special case, Klimov's waiting time problem. Using the concept of superprocess, an index rule is derived for the case where new machines arrive randomly. Finally, continuous time versions of these problems are considered for both preemptive and nonpreemptive disciplines.
Characterization of multiterawatt laser-solid interactions for proton acceleration

A comprehensive characterization of experimental parameters in a study of proton acceleration by short-pulse laser–solid interactions at intensities up to 1019 W cm−2 is reported. Laser pulse and prepulse conditions were measured, with a contrast ratio of the order of 10−6 obtained. The focused laser intensity was experimentally calibrated using a time-of-flight spectrometer to resolve the stages of ionization of a target gas. By comparing the measured ion yields with predictions of an atomic tunneling ionization model a factor of 1.5 uncertainty in the focused intensity was determined. Drive mechanisms for mounting solid targets with thickness in the range of 0.2 to 125 μm have been developed for use with high-repetition rate lasers. A retro-focus imaging system has also been implemented to position the target relative to the laser focus. The techniques have been applied to study proton acceleration as a function of various laser and target parameters. Measurements of the energy distribution of protons a.
Torsion pendulum facility for ground testing of gravitational sensors for LISA

We report here on a torsion pendulum facility for ground-based testing of the Laser Interferometer Space Antenna (LISA) gravitational sensors. We aim to measure weak forces exerted by a capacitive position sensor on a lightweight version of the LISA test mass, suspended from a thin torsion fibre. This facility will permit measurement of the residual, springlike coupling between the test mass and the sensor and characterization of other stray forces relevant to LISA drag-free control. The expected force sensitivity of the proposed torsion pendulum is limited by the intrinsic thermal noise at ≈3 × 10−13 N Hz−1/2 at 1 mHz. We briefly describe the design and implementation of the apparatus, its expected performance and preliminary experimental data.
Modelling soccer matches using bivariate discrete distributions with general dependence structure

In this paper copulas are used to generate bivariate discrete distributions. These distributions are fitted to soccer data from the English Premier League. An interesting aspect of these data is that the primary variable of interest, the discrete pair shots‐for and shots‐against, exhibits negative dependence; thus, in particular, we apply bivariate Poisson‐related distributions that allow such dependence. The paper focuses on Archimedian copulas, for which the dependence structure is fully determined by a one‐dimensional projection that is invariant under marginal transformations. Diagnostic plots for copula fit based on this projection are adapted to deal with discrete variables. Covariates relating to within‐match contributions such as numbers of passes and tackles are introduced to explain variability in shot outcomes. The results of this analysis would appear to support the notion that playing the ‘beautiful game’ is an effective strategy—more passes and crosses contribute to more effective play and more shots on the goal.
Triplets of quasars as lighthouses of rich galaxy clusters

In this Letter, we investigate the very large-scale environments of cluster-scale triplets of type 1 Seyfert galaxies, lower luminosity counterparts of quasars, detected at z < 0.2 in the fourth Data Release of the Sloan Digital Sky Survey. The search for cluster scale triplets (object-object separations <2.0 h−1 Mpc and <2000 km s−1) in a combined sample of Seyferts and quasars resulted in only 7 triplets, 3 of which are at z < 0.2. We investigated their environments and found a strong association of z < 0.2 triplets with the richest central parts of superclusters. In two out of three cases, the members of the triplets have been found on the periphery of an extremelly rich galaxy cluster (Abell class 2 and 3). The third triplet also appears associated with a very rich cluster of galaxies but on a somewhat larger scale. Nevertheless, on a small scale, it is still associated with a cluster but of lesser richness. These results suggest that triplets of type 1 Seyfert galaxies at low redshifts are excellent tracers of very rich clusters. Following these results we conclude that triplets of quasars, bright counterparts of type 1 Seyfert galaxies, may be the most successful means of finding distant, very rich, galaxy clusters.
A method for intermediate strain rate compression testing and study of compressive failure mechanism of Mg-Al-Zn alloy

Obtaining meaningful information from the test results is a challenge in the split-Hopkinson pressure bar (SHPB) test method if the specimen does not fail during the test. Although SHPB method is now widely used for high strain rate testing, this limitation has made it difficult to use it for characterization of materials in the intermediate strain rate range (typically 10−1000 s−1). In the present work, a method is developed to characterize materials in the intermediate strain rate range using SHPB setup. In this method, the specimen is repeatedly tested under compression at a given strain rate until failure is achieved. The stress–strain graphs obtained from each test cycle are used to plot the master stress–strain graph for that strain rate. This method is used to study the strain rate dependence of compressive response of a Mg-Al-Zn alloy in the intermediate strain rate range. A remarkable difference is observed in the failure mechanism of the alloy under quasi-static and intermediate strain rate comp.
Relationships between articulatory and acoustic measurements from an x‐ray microbeam study of variability in the production of the vowels /i/ and /a/

We have reported previously that midsagittal distributions of points on the dorsal tongue surface for multiple repetitions of the vowels /i/ and /a/ show more variation along a direction parallel to the vocal tract midline than perpendicular to the midline. This finding was interpreted as support for a hypothesis based on articulatory‐to‐acoustic modeling: the programming of movements towards the vowel targets is sensitive to non‐linear relationships between articulatory displacements and formants [J. S. Perkell and W. L. Nelson in Speech Motor Control, edited by S. Grillner, A. Persson, B. Lindblom, and J. Lubker (Pergamon, New York, 1982)]. Statistics on formant values for one subject have been calculated, and pairwise regressions of displacement and formant data have been run. An articulatory synthesizer [P. Rubin, T. Baer, and P. Mermelstein, J. Acoust. Soc. Am. 70, 321–328 (1981)] has been manipulated through displacements similar to the subject's articulatory variation. The range of formant variatio.
New models of solar faculae

A new semiempirical model of photospheric faculae is presented in tabular form. In an earlier paper (Chapman) a preliminary version of this model was used to construct line profiles that were compared with observations. The magnetic field is estimated from horizontal pressure equilibrium without tension forces. The geometry of the flux tube is determined from this estimated magnetic field and an assumed flux of 4.4 x 10/sup 17/ gauss cm/sup 2/. The model is discussed in relation to recent observations.
Effect of horizontal divergence on the geostrophic turbulence on a beta-plane: Suppression of the Rhines effect

An investigation is made on the effect of strong stratification, or horizontal divergence, on almost freely decaying geostrophic turbulence on a β-plane. In a model ocean, the surface layer is assumed to be active above the quiet deep layer, so that barotropification is prohibited a priori to purify the effect of horizontal divergence. Spectral evolution is accelerated numerically by an adjustment to keep kinetic energy constant against the retarding effect of horizontal divergence. First, numerical experiment is carried out for small or moderate horizontal divergence as control runs for comparison; UF/β<O(1), where U is the characteristic velocity of turbulence and F the squared inverse of the radius of deformation. As has been reported repeatedly, the β-effect induces a highly anisotropic field characterized by a band of zonal currents. It is confirmed also that kinetic energy has a one-dimensional spectrum approximately proportional to k−5 at high wave numbers k. Then, horizontal divergence is enlarged.
A new method of synthesis of reactance networks

In the insertion-loss design method for filters, compensating networks and other frequency-selective 4-terminal devices, the final step is the synthesis of a network of coils and capacitors which possesses a set of characteristic functions of frequency, in the form of one of several alternative kinds of matrix, previously deduced from the desired overall frequency behaviour. The present paper is chiefly concerned with this step.Practical experience has shown that the most satisfactory way of synthesizing a complicated network is to use a chain of sub-networks connected in cascade. For such a synthesis the most convenient matrix is the so-called “chain matrix,” since the chain matrix of a chain of networks is simply the product of the individual chain matrices. Conversely, a specified chain matrix can be synthesized by factorizing it into sub-matrices, each of sufficiently small degree to allow of direct synthesis, and then connecting all the corresponding networks in cascade.In previous methods of factorizing a given chain matrix it has always been necessary to split off small network sections one at a time. In the present method sections of arbitrary size can be split off in each stage. The importance of this is that the larger the size of section to be directly synthesized, the greater is the likelihood of being able to avoid coupled coils in the design.The method depends on a new theorem of a novel and far-reaching character concerning reactance and impedance functions. In proving and discussing this, reference has to be made to certain properties of such functions which are of great importance in themselves but have not hitherto been presented in a connected manner. Accordingly, a systematic treatment of these is first given, including a number of results believed to be new.A possible extension of the method, potentially of considerable value, to general dissipative networks is indicated.
Photo-Dember terahertz emitter excited with an Er:fiber laser

A terahertz emitter based on the lateral photo-Dember effect is shown to efficiently generateterahertz radiation with a peak frequency of 0.7 THz and an electric field amplitude up to 5 V/cm when excited by 90 fs pulses centered at 1.55 μ m . A thin layer of In 0.53 Ga 0.47 As grown on InP provides the substrate material in which unidirectional lateral photo-Dember currents are excited. Since photo-Dember terahertz emitters do not require an external bias, they do not suffer from high dark currents limiting the application of biased InGaAs photoconductive terahertz emitters.
A three‐dimensional high Mach number asymmetric magnetopause model from global MHD simulation

The numerical results from a physics‐based global magnetohydrodynamic (MHD) model are used to examine the effect of the interplanetary magnetic field (IMF), solar wind dynamic pressure, and dipole tilt angle on the size and shape of the magnetopause. The subsolar magnetopause is identified using the plasma velocity and density, the cusps are identified using the thermal pressure, and the whole shape of the magnetopause is determined with the three‐dimensional streamlines traced through the simulation domain. The magnetopause surface obtained from the simulations is fitted with a three‐dimensional surface function controlled by ten configuration parameters, which provide a description of the subsolar magnetopause, the cusp geometry, the flaring angle, the azimuthal asymmetry, the north‐south asymmetry, and the twisting angle of the magnetopause. Effects of the IMF, solar wind dynamic pressure, and dipole tilt angle on the configuration parameters are analyzed and fitted by relatively simple functions. It is found that the solar wind dynamic pressure mainly affects the magnetopause size; the IMF mainly controls the magnetopause flaring angle, azimuthal asymmetry, and twisting angle; and the dipole tilt angle mainly affects the magnetopause north‐south asymmetry and the cusp geometry. The model is validated by comparing with available empirical models and observational results, and it is demonstrated that the new model can describe the magnetopause for typical solar wind conditions.