Miracle-dz/UniFAR-FTUs huggingface dataset:
v -DSMV: a fast simulation method for rarefield flow

A new approximate simulation method for rarefied flows, ν-DSMC, is described and tested by comparison with results from Bird's direct simulation Monte–Carlo (DSMC) method, and with a previously proposed ‘relaxation time’ simulation method (RTSM) which solves the BGK equation. Both ν-DSMC and RTSM execute about twice (or more) as fast as DSMC. In ν-DSMC all collision pairs (amongst near neighbours) are equally likely so the collision loops are suitable for parallel execution. In order to reproduce any desired viscosity law μ=μ(T) the collision rate must be altered by making the total collision cross-section a function of the local kinetic temperature. The approximate methods have been compared to DSMC in three test cases: (1) simple relaxation calculations, (2) high speed Couette flow, and (3) the plane normal shock problem. Both approximate methods produce the same relaxation rate as DSMC, but only the new method produces a nonequilibrium distribution function similar to that for DSMC. For the Couette flow, ν-DSMC produces profiles of flow velocity, density, and temperature which agree with DSMC results to within 3–5%, while the BGK solution produces temperatures which are up to 18% greater. Similar results were found for the normal shock wave. ν-DSMC predicts the location and size of the peak Tx temperature more accurately than does RTSM. The deviation of the temperature profiles from the DSMC results are 2–3 times greater for RTSM than for ν-DSMC. The conclusion from all test cases is clear: the incorrect Prandtl number predicted by the BGK equation detracts from the usefulness of the BGK equation as a model for rarefied flow; the new approximate simulation method is just as fast as solving the BGK equation and gives results which are in much better agreement with DSMC.
Patterns of Current Helicity for Solar Cycle 22

Using a 1988-1997 data set of original photospheric vector magnetograms from the Solar Magnetic Field Telescope (SMFT) of the Huairou Solar Observing Station of Beijing Astronomical Observatory, we computed the local current helicity Bz∙(𝛁×B)z for 422 active regions. We found that any given active region contained mixed signs of current helicity, but in most cases current helicity with a particular sign was dominant over a whole region area. In our data set, 84% of the active regions in the northern hemisphere have negative helicity, and 81% in the southern hemisphere have positive helicity. It is estimated that the noise and error in our calculation are at the 2 σ level. In addition, we have studied the evolution of the large-scale surface current helicity during the cycle 22, which is a running mean of absolute current helicity of the active regions observed over a Carrington rotation period. By comparing with monthly mean sunspot number, we found that the average current helicity has a good correlation with solar activity.
Improvement of graphene–metal contact resistance by introducing edge contacts at graphene under metal

We report an alternative approach to lower contact resistance and extend charge transfer length by forming graphene antidot arrays under metal electrode to introduce edge contact of graphene. The edge contact resistivity of ∼2.2 × 10−9 Ω·cm2 is experimentally estimated, based on the experiment and one-dimensional equivalent circuit model, and the result agrees well with the previous theoretical report. The proposed contact module structure can open alternative ways to overcome the poor contact performance and the current crowding effect at the metal-graphene contact.
Modelling the periodical variations in multiband polarization and photometry for discs of binary Be stars

The tidal interaction of a Be star with a binary companion forms two spiral arms that cause orbital modulation of the Be disc structure. The aim of this work is to identify observables in which this modulation is apparent. The structure of a Be disc in a coplanar circular binary system is computed with a smoothed-particle hydrodynamics code, and a radiation transfer code calculates the spectral energy distribution. Line depolarisation was confirmed, with polarisation profiles nearly reverse to emission-line profiles. The continuum flux maximizes for pole-on discs, but photometric variability maximizes for edge-on discs. The linear polarisation exhibits one or two maxima per orbital cycle. While polarisation variability in visible passbands is important only at low inclinations, infrared bands may demonstrate high orbital variability even at large inclinations. More evident is the modulation in the polarisation angle (PA) for low inclinations. The latter can be used to track azimuthal asymmetries for pole-on discs, where the spectroscopic variability in the violet-to-red (V/R) emission-component ratio disappears. PA reversals coincide with phases where V/R=1, tracking lines of sight directed towards regions where the approaching and receding arms overlap. Continuum flux and polarisation are mostly in phase for neighbouring wavelength regions. It is suggested that studies of non-symmetric discs distorted by tidal forces from a secondary star may be used to study disc variabilities of other origins.
Tex2Shape: Detailed Full Human Body Geometry From a Single Image

We present a simple yet effective method to infer detailed full human body shape from only a single photograph. Our model can infer full-body shape including face, hair, and clothing including wrinkles at interactive frame-rates. Results feature details even on parts that are occluded in the input image. Our main idea is to turn shape regression into an aligned image-to-image translation problem. The input to our method is a partial texture map of the visible region obtained from off-the-shelf methods. From a partial texture, we estimate detailed normal and vector displacement maps, which can be applied to a low-resolution smooth body model to add detail and clothing. Despite being trained purely with synthetic data, our model generalizes well to real-world photographs. Numerous results demonstrate the versatility and robustness of our method.
Nuclear outflow from the edge-on galaxy NGC 3628

New evidence is presented for collimated outflow from a starburst nucleus in the edge-on galaxy NGC 3628. A plume of X-ray emission along the minor axis of this galaxy is suggested by the distribution of counts in the softer energy channels of the Einstein Observatory IPC. Plumes of H-alpha emission are visible in a CCD image of the southern minor axis region, at a position angle consistent with that of the X-ray plume, while extended, possibly filamentary, H-alpha emission is visible in the north. Optical spectroscopy along the northern minor axis clearly detects line emission, with line ratios of H-alpha, N II, and S II changing from those characteristic of normal H II regions near the nucleus, to a low-ionization state, consistent with shock heating, farther out. All this evidence, and the IR and radio continuum properties of this galaxy, make NGC 3628 another member of the growing class of galaxies with starburst nuclear activity and outflowing winds, to which NGC 253 and M82 already belong. 27 refs.
Perturbation Method for a Nonlinear Wave Modulation. II

A perturbation method given in a previous paper of this series is applied to two physical examples, the electron plasma wave and a nonlinear Klein‐Gordon equation. In these systems, and probably in most physical systems, an assumed condition for a mode of l = 0 is not valid. Consequently, the direct application of the method is impossible. In the present paper, we shall illustrate by these examples how this difficulty can be overcome to allow us to use the method. As a result we shall find that, in either case, the original equation can be reduced to the nonlinear Schrodinger equation.
Microwave Interferometer Measurements in Shocked Air

Microwave transmission measurements of the electrical properties of shock‐ionized air in the range 8≤Ms≤12 and initial pressures of 1, 2, 5, 10, and 20 Torr are presented. The test arm of the microwave transmission bridge is X band waveguide, which passes through the shock tube and has an affixed nozzle to section out a portion of the shocked gas. This gas is constrained to a rectangular cross section and passes through the waveguide where it interacts with the microwave signal. An 0.5‐in. and a 1.5‐in. nozzle are used, and it is shown that nozzle length has a negligible effect on both the ionization rate and the level. The data are presented in terms of dielectric constant, electron density, collision frequency, conductivity, attenuation, and reflection coefficient. The data are compared with results obtained from other experimental methods and discrepancies are noted. Values of Ne and ν are calculated initially from the Lorentz relation with ν independent of velocity; these data are then recalculated by.
Inference by Eye: Pictures of Confidence Intervals and Thinking About Levels of Confidence

A picture of a 95% confidence interval (CI) implicitly contains pictures of CIs of all other levels of confidence, and information about the p‐value for testing a null hypothesis. This article discusses pictures, taken from interactive software, that suggest several ways to think about the level of confidence of a CI, p‐values, and what conclusions can be drawn from inspecting a CI.
Integral properties of the swash zone and averaging. Part 3. Longshore shoreline boundary conditions for wave-averaged nearshore circulation models

The aim of the present work, final of a three-part series, is to analyse in detail flow motions within the swash zone and define suitable shoreline boundary conditions for the longshore flow for wave-averaged circulation models. The analyses of Parts 1 and 2 are extended to cover horizontally two-dimensional flows. An analytical solution for the longshore motion representing the drift velocity of the whole swash zone water mass is found. This is seen to be approximated well by the ratio between the time integral of the longshore momentum flux crossing the swash lower boundary and the swash zone net water volume. Further, a complete set of shoreline boundary conditions, taking into account wave–wave interactions, is obtained on the basis of fully numerical solutions of the nonlinear shallow-water equations. The main focus of the work is to clarify the structure of the shoreline boundary conditions for the longshore flow, but attention has also been paid to their derivation and assessment from the numerical solutions. The latter have been obtained on the basis of a fairly broad range of input wave conditions which, though biased towards those typical of reflective beaches, are believed to cover conditions also typical of moderate dissipative beaches. Two main terms are found to contribute to the longshore drift velocity: (i) a term, proportional to the shallow-water velocity, accounting for short-wave interactions, frictional swash zone forces and continuous forcing due to non-breaking wave nonlinearities and (ii) a drift-type term representing the momentum transfer due to wave breaking.
Expansive dynamics on zero-dimensional groups

Abstract If X is a compact, zero-dimensional group and T is an expansive, transitive automorphism then (X, T) is shown to be topologically conjugate to a full shift on finitely many symbols. The problem of classifying such automorphisms up to simultaneous algebraic isomorphism and topological conjugacy is discussed but not solved. It is proved that for any entropy there are only finitely many such equivalence classes. When the entropy is log p for a prime p, there is only one equivalence class. All are then equivalent to
Application of the Boundary Element Method to Predicting Acoustic Performance of Expansion Chamber Mufflers With Mean Flow

Abstract A boundary element method (BEM) is applied to predicting the acoustic performance of expansion chamber mufflers with mean flow. The formulation of the boundary element method is derived for three-dimensional and axisymmetric expansion chambers incorporating only the convective effect of mean flow, by means of which the four-pole parameters including high order mode effects can be easily obtained at any frequency; therefore the acoustic performance such as transmission loss can be predicted. A substructure boundary element method is presented for long or complex shape mufflers. Predicted values of transmission loss of expansion chambers without and with mean flow are compared with those reported in the literature and they agree very well.
The Inversion of an Integral Equation Involving a General Class of Polynomials

Abstract The object of the present paper is to derive the solution of a certain convolution integral equation of Fredholm type whose kernel involves a generalization of numerous polynomial systems including, for example, the classical Hermite, Laguerre, and Bessel polynomials, and the Konhauser biorthogonal polynomials. Some interesting applications of the main inversion theorem are also mentioned. One of these applications is shown to lead to the correct solutions of certain integral equations which were considered recently.
DYNAMIC ANALYSIS OF ELASTOPLASTIC SHAKEDOWN OF STRUCTURES

This paper deals with the dynamics of a single-degree-of-freedom elastoplastic oscillator. The model adopted herein is useful for understanding the dynamic behavior of civil engineering structures, such as steel structures, especially when plastic inelasticity is of concern. Using appropriate internal variables, the dynamic hysteretic system can be written as a singular autonomous system. The free vibration of such a nonlinear system reduces to periodic motion. The harmonic forced oscillator can exhibit periodic or quasi-periodic behaviors. A bifurcation diagram is numerically computed, which indicates that periodic elastoplastic limit cycles exist for some ranges of structural parameters. The bifurcation boundary separates the shakedown from other alternating plasticity phenomena.
On nonparametric multivariate binary discrimination

Aitchison & Aitken (1976) introduced a novel and ingenious nonparametric method for estimating probabilities in a multidimensional binary space. The technique is designed for use in multivariate binary discrimination. Their estimator depends crucially on an unknown smoothing parameter A, and Aitchison & Aitken proposed a maximum likelihood method for determining A from the sample. Unfortunately this leads to an adaptive estimator which can behave very erratically when there are a number of empty or near empty cells present. We demonstrate this both theoretically and by example. To overcome these difficulties we introduce another method of estimating A which is designed to minimize a global function of the mean squared error.
Enhanced effect of polarization on electron transport properties in AlGaN/GaN double-heterostructure field-effect transistors

In order to understand the effect of polarization on the electron transport properties in AlGaN/GaN heterostructures, the dependence of the two-dimensional electron gas mobility on the density has been examined both in the GaN single- and 200-A GaN double-heterostructure field-effect transistors, by means of the Hall effect measurement under the gate-voltage application at 4.2 K. In the single heterostructure, a maximum mobility of 5700 cm2/V s has been obtained at 9.0×1012 cm−2; whereas in the double heterostructure, a higher maximum mobility of 8100 cm2/V s has been obtained at a lower electron density of 6.8×1012 cm−2. The results have been analyzed in terms of potential profiles and electron distributions in both structures where both piezoelectric and spontaneous polarization effects are taken into account. The analysis has shown that the observed mobility enhancement is mainly due to the enhanced polarization-induced electron confinement in the double heterostructure and, additionally, to the improv.
Computer simulation of inner magnetospheric dynamics for the magnetic storm of July 29, 1977

We present preliminary results of applying the Rice convection model to the early main phase of the magnetic storm of July 29, 1977. The computer model self-consistently computes electric fields and currents, as well as plasma distributions and velocities, in the inner-magnetosphere/ionosphere system. In the equatorial plane, the region modeled includes geocentric distances less than about the magnetopause standoff distance. Particle loss, parallel electric fields, and neutral winds are neglected. On the basis of solar wind parameters and the AL index as input, the model predicts the injection of plasma-sheet plasma to form a substantial storm time ring current. The total strength of the model-predicted ring current agrees accurately with the observed Dst index. Comparison of the model results with electric fields and Birkeland currents measured by S3-3 shows qualitative agreement but interesting quantitative discrepancies. During this event, region 1 currents, which in standard convection theory would connect to the outer magnetosphere, are observed as low as 60/sup 0/ invariant latitude at dawn and dusk. We examine the possibility that the magnetic field might be so highly inflated that 60/sup 0/ field lines extend to the outer magnetosphere. In the model, distortion of the inner edge of the plasma sheetmore » by the magnetospheric compression associated with the sudden commencement temporarily disturbs the normal Birkeland-current pattern. The normal tendency for the plasma sheet's inner edge to shield low L alues from the convection electric field is also temporarily disrupted. Normal Birkeland currents and shielding reassert themselves after about an hour. Time-integrated Joule heating in the model ionosphere over the first 5.5 hours of the storm main phase is about half the increase in model ring-current energy. « less
The 'emergent scaling' phenomenon and the dielectric properties of random resistor-capacitor networks

An efficient algorithm, based on the Frank–Lobb reduction scheme, for calculating the equivalent dielectric properties of very large random resistor–capacitor (R–C) networks has been developed. It has been used to investigate the network size and composition dependence of dielectric properties and their statistical variability. The dielectric properties of 256 samples of random networks containing: 512, 2048, 8192 and 32 768 components distributed randomly in the ratios 60% R–40% C, 50% R–50% C and 40% R–60% C have been computed. It has been found that these properties exhibit the anomalous power law dependences on frequency known as the 'universal dielectric response' (UDR). Attention is drawn to the contrast between frequency ranges across which percolation determines dielectric response, where considerable variability is found amongst the samples, and those across which power laws define response where very little variability is found between samples. It is concluded that the power law UDRs are emergent properties of large random R–C networks.
THREE-DIMENSIONAL PRESENTATIONS FOR THE GROUPS OF ORDER AT MOST 30

For each group G of order up to 30 we compute a small 3-dimensional CW-space X with 1X D G and 2X D 0, and we quantify the ‘efficiency’ of X. Furthermore, we give a theoretical result for treating the case when G is a semi-direct product of two groups for which 3-presentations are known. We also describe the ZG-module structure on the second homotopy group 2X 2 of the 2-skeleton of X. This module structure can in principle be used to determine the cohomology groups H 2 . G; A/ and H 3 . G; A/ with coefficients in a ZG-module A. Our computations, which involve the Todd‐Coxeter procedure for coset enumeration and the LLL algorithm for finding bases of integer lattices, are rather naive in that the LLL algorithm is applied to matrices of dimension a multiple of jGj. Thus, in their present form, our techniques can be used only on small groups (say of order up to several hundred). They can in principle be used to construct (crossed) ZG-resolutions of Z, but again, only for small G. The paper is accompanied by two attachment files. The first of these is a summary of our computations in HTML format. The second contains various GAP programs used in the computations.
Determination of semiconductor energy gaps using the microwave cavity perturbation method

A simple fitting procedure is described which helps to overcome the difficulties often encountered in extracting the complex dielectric constant epsilon using the cavity perturbation method for samples of irregular shape. The aim of this method is to determine the temperature dependence of the imaginary part of epsilon of a semiconductor with sufficient accuracy to give reliable values for its energy gap. The automatised experimental set-up used to verify the proposed method is presented and examples of application to germanium, silicon and to some new materials are given.
An Algorithm That is Globally Convergent with Probability One for a Class of Nonlinear Two-Point Boundary Value Problems

It is shown that the Chow–Yorke algorithm (a homotopy-type method) may be applied to a class of nonlinear two-point boundary value problems by solving the nonlinear system of equations defined by shooting. The resultant method is globally convergent with probability one, in the sense that it may fail for starting points in a set of Lebesgue measure zero. Some numerical results are given.
Set standard deviation, repeatability and offset of absolute gravimeter A10-008

The set standard deviation, repeatability and offset of absolute gravimeter A10-008 were assessed at the Walferdange Underground Laboratory for Geodynamics (WULG) in Luxembourg. Analysis of the data indicates that the instrument performed within the specifications of the manufacturer. For A10-008, the average set standard deviation was (1.6 ± 0.6) µGal (1Gal ≡ 1 cm s−2), the average repeatability was (2.9 ± 1.5) µGal, and the average offset compared to absolute gravimeter FG5-216 was (3.2 ± 3.5) µGal.
Optical solitons and quantum solitons

We return to the notion of optical solitons as these were first introduced—namely as exact soliton and multi-soliton solutions of the semi-classical self-induced transparency (SIT) equations. The SIT equations, even in their most general inhomogeneously broadened forms, are infinite dimensional, completely integrable Hamiltonian systems, and thus display much mathematical structure, yet their exact soliton solutions display well the nonlinear (self-induced) transparency features of the physical phenomenon. The mathematical feature of complete integrability is handed down from the SIT equations to the nonlinear Schrodinger equations and from this point of view the nonlinear Schrodinger (NLS) equations equations are studied first of all at classical level and then at quantum level. The 'quantum soliton' of the quantum attractive NLS model is defined and its properties investigated in detail, particularly in a comparison with the particular properties ascribed to the 'quantum soliton' as described in a recently published article (Abraham 1999 Phys. World (February) 21) with this title; as suggested in that article, the quantum NLS soliton is seen as a qubit for quantum information purposes. The covariant form of the quantum attractive NLS model is the quantum sine-Gordon model and this is briefly studied in the context of quantum information also; new results for large area Josephson junctions are reported in this context. The quantum soliton of the one dimensional attractive NLS model has apparently been observed in 2002 in a Bose condensed metal vapour (7Li, (Khaykovich et al 2002 Science 296 1290)) and a detailed calculation suggests that the condensate undergoes a 'collapse' from three to one space dimensions thus forming an exact soliton solution of the one dimensional quantum attractive NLS model.