Miracle-dz/UniFAR-FTUs huggingface dataset:
A novel multi-level model for quasi-brittle cracking analysis with complex microstructure

The paper presents a novel multi-level model for quasi-brittle cracking analysis. Based on the partition of unity and information transmission technology, it provides a new non-re-meshing way to describe the cracking phenomenon in structures constructed from materials with complex microstructures. In the global model the concept of the material particle is defined and the basic unknowns are the boundary displacements of these particles, which is different from the concept of the traditional displacement field. A series of enrichment functions with continuous steps is proposed, describing the boundary displacement affected by crack bands and allowing the intersections of crack bands with particle boundaries a priori unknown. Simultaneously, additional equations are introduced to determine element status and make the degrees of freedom of the global model remain at a stable level. Compared with previous research by our group, where the local description is equal to the global description on the boundary of a material particle, the introduced enrichment functions enable more accurate capture of the characteristics of the crack band. The model avoids the complex and dynamic model adjustments due to the activation and exit of representative volume elements (RVEs) and the accuracy of the description of the crack pattern can be ensured. The RVEs are activated at first, but then many of them exit the computation due to the unloading which reduces many of the degrees of freedom. Two examples of concrete specimens are analyzed, and the concrete fracture experiment and the digital image correlation (DIC) test are conducted. Compared with the reference solutions and the experimental data, even though the microstructure of concrete is very complex, the cracking process and crack pattern can be obtained accurately.
The horizontal and vertical structure of east Asian winter monsoon pressure surges

East Asian cold‐air outbreaks, accompanied by increasing surface pressure (‘pressure surges’), are shown to be an important aspect of the subseasonal variability of the winter monsoon system. In this study the statistical linear relationship between pressure surges, tropical convection, and tropospheric circulation is assessed using a ten‐year data set (1985/86‐1994/95) of the European Centre for Medium‐Range Weather Forecasts gridded operational analyses. From spectral analysis the pressure, wind, and temperature fluctuations indicative of strong pressure surges are found to have statistically‐significant spectral peaks at submonthly periods (6 to 30 days). Linear regression analysis is used to detail the time evolution of the dominant horizontal and vertical structure of east Asian pressure surges. Surges are shown to relate significantly to circulation anomalies in both the meridional and zonal components of the lower‐tropospheric wind. Relationships between east Asian pressure surges in the submonthly band and tropical circulation anomalies are found over the Bay of Bengal, the eastern Indian Ocean, Indonesia, and the western Pacific regions. Submonthly surges over the South China Sea are related to strong surges and convective activity south of Indonesia, over the South China Sea, the eastern Indian Ocean, and the Philippine regions. Surge‐enhanced convective activity is found to precede an enhancement of the local east Asian Hadley cell. Submonthly surges over the Philippine Sea are related to periods of westerly‐wind anomalies and convective activity in the western Pacific. Upper‐level wave activity over western Asia precedes submonthly surges. the wave activity amplifies in the region of the Pacific jet stream, and can be traced dispersing equatoward through the region of upper‐level westerlies over the eastern tropical Pacific.
Advection-diffusion modelling using the modified QUICK scheme

In recent years the QUICK finite difference scheme has been increasingly used in solving the advection-diffusion equation, particularly for water quality modelling studies relating to coastal and estuarine flows. This scheme has the benefits of mass conservation, reasonably high accuracy and computational efficiency in comparison with many other higher-order-accurate schemes reported in the recent literature. A von Neumann stability analysis showed that the explicit QUICK scheme has a severe stability constraint which depends upon the diffusion coefficient. It can be proved that this scheme is numerically unstable for the case of pure advection. Various modified forms of the implicit QUICK scheme have been formulated and their numerical stability properties have been studied and analysed. The modified QUICK schemes considered have been tested for transient simulations for the cases of pure advection and of advection and diffusion in an idealized one-dimensional basin using three different initial boundary conditions: (a) a sharp front concentration gradient, (b) a Gaussian concentration distribution and (c) a plug source. Details of the comparisons between these modified schemes and with other typical second-order-accurate difference schemes are given, together with comparisons with the analytical solutions for each case. A two-dimensional version of the semi-time-centred QUICK scheme (ADI-QUICK), has also been applied to a two-dimensional test case using the standard ADI technique and has been shown to be attractive in comparison with other comparable second-order schemes.
Imaging spheres with general incident wavefronts using a dipole decomposition

Although scattering for spheres with plane wave illumination was solved precisely by Mie in 1909, often it is of interest to image spheres with non-planar illumination. An extension of Mie theory which incorporates non-planar illumination requires knowledge of the coefficients for a spherical harmonic expansion of the incident wavefront about the center of the sphere. These coefficients have been determined for a few special cases, such as Gaussian beams, which have a relatively simple model. Using a vectorized Huygen's principle, a general vector wavefront can be represented as a superposition of dipole sources. We have computed the spherical wave function expansion coefficients of an arbitrarily placed dipole and hence the scattering from a sphere illuminated by a general wavefront can be computed. As a special case, Mie's solution of plane wave scattering was recovered. POtential applications include scattering with partially coherent illumination. Experimental results from the scattering from polystyrene spheres using Koehler illumination show agreement with numerical tests.
Dynamical evolution of the 2003 southern hemisphere stratospheric winter using Envisat trace‐gas observations

Data from the MIPAS instrument on Envisat, supplemented by meteorological analyses from ECMWF and the Met Office, are used to study the meteorological and trace‐gas evolution of the stratosphere in the southern hemisphere during winter and spring 2003. A pole‐centred approach is used to interpret the data in the physically meaningful context of the evolving stratospheric polar vortex. The following salient dynamical and transport features are documented and analysed: the merger of anticyclones in the stratosphere; the development of an intense, quasi‐stationary anticyclone in spring; the associated top‐down breakdown of the polar vortex; the systematic descent of air into the polar vortex; and the formation of a three‐dimensional structure of a tracer filament on a planetary scale. The paper confirms and extends existing paradigms of the southern hemisphere vortex evolution. The quality of the MIPAS observations is seen to be generally good, though the water vapour retrievals are unrealistic above 10 hPa in the high‐latitude winter. Copyright © 2006 Royal Meteorological Society
Highly linear and efficient phase modulators based on GaInAsP-InP three-step quantum wells

Highly linear and efficient phase modulators based on three-step quantum wells are reported. The spatial separation of electron and hole wave functions in the three-step quantum well leads to enhancement of the linear electro-optic component. In parallel, the quadratic electro-optic component is suppressed using a method based on tailored doping profile. Measured modulation efficiency is 48°∕mm V, and the ratio of linear to quadratic components of the phase modulation is 640 at λ=1560nm. The efficiency is similar to the best reported values for semiconductor modulators at this wavelength, while the linearity is more than one order of magnitude higher.
A High-Resolution Study of Gas and Dust around Young Intermediate-Mass Stars: Evidence for Circumstellar Disks in Herbig Ae Systems

As part of a long-term program of observations to search for and characterize disks of gas and dust around intermediate-mass counterparts to solar-mass T Tauri stars, we have probed the environments of seven pre-main-sequence stars of spectral type Ae using millimeter-wave continuum and molecular line aperture synthesis imaging. In each case we identify a compact region of thermal continuum emission centered on the star. Upper limits to radii are in the range 200-300 AU for five members of our sample, and 680 AU for the distant source HD 245185. We identify an elongated continuum source around HD 163296, with a semimajor axis of 110 AU. Adopting relatively high values for dust grain opacities, we obtain minimum masses of circumstellar dust and gas in the range 0.005-0.034 M☉ for the seven sources, assuming that the observed continuum emission is optically thin. We detect molecular line emission from gas regions centered on four of the stars. Two of these regions are spatially resolved and are found to be elongated, with semimajor axes of 310 and 450 AU for HD 163296 and AB Aur, respectively. Ordered velocity gradients along the major axes of both of these structures point strongly to the presence of orbiting material in disklike configurations, and we argue that the nebular environments of our entire sample include substantial disk components.
Output feedback control for stochastic nonholonomic systems with growth rate restriction

The output feedback stabilization problem is investigated in this paper for nonholonomic systems with stochastic disturbances. The objective is to design global asymptotical stabilization output feedback controllers in probability for systems by using discontinuous control. A switching control strategy based on the output measurement of the first subsystem is employed to achieve almost global asymptotical stabilization in probability. The input‐state scaling technique is introduced for discontinuous feedback and a high gain observer is introduced for states estimate. Thereby, the integrator backstepping technique is applied to the design of the controllers. The output feedback global asymptotical stabilization in probability is realized. An example is given to show the effectiveness of the proposed scheme.
On the photoionization of the intergalactic medium by quasars at high redshift

We discuss the reionization of the intergalactic medium (IGM) by quasars at high redshift. We compute the integrated UV background from observed QSOs, taking into account the hydrogen opacity associated with intervening Lyα clouds and Lyman limit systems. We note that the published data appear to indicate a significant underdensity of absorption systems in the Lyα forest with column densities N HI >10 15 cm −2 . This deficit, if real, would result in a reduction of the opacity of the universe at high redshift by a factor of 1.5-3 relative to previous estimates
Local anisotropy in incompressible magnetohydrodynamic turbulence

It is a well known fact that in the presence of a dc applied magnetic field, magnetohydrodynamic (MHD) turbulence develops spectral anisotropy from isotropic initial conditions. Typically, the reduced spectrum is steeper in the direction of the magnetic field than it is in any transverse direction. One might expect that a dc field is not essential, and it is the local mean field that is responsible. To address this issue, three-dimensional MHD pseudo-spectral incompressible relaxation simulations are performed, and structure functions computed according to whether the separation is parallel to, or transverse to, the local mean magnetic field. Correlation lengths are longer in the locally averaged magnetic field direction than in any perpendicular direction, even when the global mean magnetic field is zero. Local anisotropy is observed to be stronger in regions of strong magnetic field. A general definition of anisotropy angles and a methodology to study local anisotropy are proposed.
Stellar Contents of the Galactic Giant H II Region NGC 3603

We present CCD UBVRI and Ha photometry for the starburst cluster associated with the galactic giant HII region NGC 3603. The mean reddening of the cluster members comes out to be (E(B — V)) = 1.48±0.21 (s.d.). The surface distribution of the reddening shows a radial variation with a minimum near to the cluster center and two local maxima at radii ~ 30" and ~ 70". Our photometric data indicate an anomalous reddening law for the dust inside the cluster region, and the ratio of the total to the selective extinction, R, is found to be ~ 4.3. A comparison of the observational and intrinsic colour-magnitude digrams (CMDs) yields a mean distance modulus of (m — M)o = 14.0, which corresponds to a distance of 6.3 ±0.6 kpc. This distance is smaller than those obtained in earlier works (e.g., 7.2 kpc, Melnick et al. 1989, AAA 49.132.013) but is in good agreement with the kinematic distance (6.1 ± 0.6 kpc) recently reported by De Pree et al. (1999, AAA 71.132.041). The cluster shows a large age spread, containing stars as old as up to several Myr. However, the mean age of the cluster is found to be < 1 Myr. We estimate a minimum star formation efficiency of ~ 25% and a gas removal time of r ~ 4.6 Myr.
On the Mach reflection of a solitary wave: revisited

Reflection of an obliquely incident solitary wave at a vertical wall is studied experimentally in the laboratory wave tank. Precision measurements of water-surface variations are achieved with the aid of laser-induced fluorescent (LIF) technique and detailed features of the Mach reflection are captured. During the development stage of the reflection process, the stem wave is not in the form of a Korteweg–de Vries (KdV) soliton but a forced wave, trailing by a continuously broadening depression. Evolution of stem-wave amplification is in good agreement with the Kadomtsev–Petviashvili (KP) theory. The asymptotic characteristics and behaviours are also in agreement with the theory of Miles (J. Fluid Mech., vol. 79, 1977b, p. 171) except those in the neighbourhood of the transition between the Mach reflection and the regular reflection. The predicted maximum fourfold amplification of the stem wave is not realized in the laboratory environment. On the other hand, the laboratory observations are in excellent agreement with the previous numerical results of the higher-order model of Tanaka (J. Fluid Mech., vol. 248, 1993, p. 637). The present laboratory study is the first to sensibly analyse validation of the theory; note that substantial discrepancies exist from previous (both numerical and laboratory) experimental studies. Agreement between experiments and theory can be partially attributed to the large-distance measurements that the precision laboratory apparatus is capable of. More important, to compare the laboratory results with theory, the corrected interaction parameter is derived from proper interpretation of the theory in consideration of the finite incident wave angle. Our laboratory data indicate that the maximum stem wave can reach higher than the maximum solitary wave height. The wave breaking near the wall results in the substantial increase in wave height and slope away from the wall.
Multilayer 500 Gbyte Optical Disk

To confirm the feasibility of realizing subterabyte or terabyte optical memories, we evaluated a multilayer read-only disk having 20 information layers. We propose a new disk structure, which is an alternative structure to reduce interlayer crosstalk, optimized by computer simulations. We fabricated multilayer read-only optical disks using a conventional manufacturing process for Blu-ray disk (BD) dual-layer media. Moreover, we improved the reproduction system to compensate for the large spherical aberration. From the experimental results, we obtained sufficiently low jitter values reproduced from a 20-layer disk. We confirmed the feasibility of the multilayer read-only disk with a capacity of 500 Gbytes.
Numerical Analysis of Two-Dimensional Nonsteady Detonations

In the present work, a system of two-dimension al nonsteady hydrodynamic and chemical kinetic equations was numerically integrated for an exothermic system. An assumed two-step reaction model simulates an oxyhydrogen mixture. The calculation starts from a plane Chapman-Jouguet detonation as an initial condition. Two-dimensional disturbances are generated by artificially placing nonuniformities ahead of the detonation front. Regardless of the difference in the given initial disturbances, a fixed number of triple shock waves were produced for a fixed combination of mixture model and geometry when the transition period was over. This shows that for a given detonation tube geometry, any exothermic system has its own characteristic multidimensional structure. The obtained number of triple shock waves contained in the detonation front was in agreement with existing experimental observations under the same condition.
Plasma rotation in a quasi-symmetric stellarator

The equilibrium plasma rotation in a general toroidal magnetic field is nearly always subsonic and is determined by the requirement that the collisional particle transport should be ambipolar in lowest order in the small-ion-gyroradius expansion. Only in quasi-symmetric fields, where collisional particle transport is intrinsically ambipolar, can the plasma rotate freely and then only in the quasi-symmetry direction. Sonic rotation velocities are allowed in this case. In this paper the effect of rotation in a quasi-axisymmetric field is investigated, and it is found that the symmetry is broken when the rotation speed exceeds the diamagnetic speed appreciably, leading to reappearance of the non-intrinsically ambipolar 1/ν-transport regime. Fortunately, this transport scales with the fourth power of the rotation Mach number and is expected to be modest in most plasmas of interest.
Invasion Percolation on the Cayley Tree: Exact Solution of a Modified Percolation Model

Bernie Nickel and David Wilkinson Schhimberger-Doll Research, Ridgefield, Connecticut 06877 (Received 4 April 1983) A modified form of percolation theory is solved exactly on a Cayley tree of arbitrary coordination number. In this model, cluster growth proceeds "dynamically" by invasion along a path of least resistance. Although there are clear parallels to ordinary "static" percolation at the percolation threshold, there are also significant differences. In parti cular, the scaling function which describes the shape of large clusters is different in the two models.
Two-dimensional model and algorithm analysis for a class of iterative learning control systems

The iterative learning control system (ILCS) has attracted considerable research interest in recent years. However the theoretical results on some fundamental properties of the ILCS have not yet been established. One of the common drawbacks shared by current approaches is lack of a suitable mathematical model which can clearly describe both the dynamics of the control system itself and the behaviour of the learning process as well. In this paper, a class of iterative learning control systems is analysed from the point of view of two-dimensional (2-D) system theory. The 2-D model for a class of ILCS is established in the form of‘Roessor's model’, based on which a general type of learning controller is proposed. Analysis of the 2-D error equation shows that the 2-D asymptotic stability of the 2-D model guarantees the learning convergence of an ILCS. Design criteria for a learning controller is also suggested. The learning gain matrices are obtained from a recursive 2-D identifier using the input and output .
Likelihood ratio tests with boundary constraints using data-dependent degrees of freedom

When the null hypothesis constrains parameters to the boundary of the parameter space, the asymptotic null distribution of the likelihood ratio statistic is often a mixture of chi-squared distributions, giving rise to the so-called chi-bar test, where weights can depend on the true unknown parameter and be difficult to calculate. We consider the test that conditions on the observed number of null hypothesis parameters in the interior of the parameter space. This approach uses simple chi-squared thresholds, yields conservative asymptotic Type I error, and is guaranteed to give power improvements over the naive approach of simply ignoring boundary constraints. Simulations validate the theoretical results, illustrate application settings, and find power comparable with but usually less than that of the chi-bar test. Copyright 2013, Oxford University Press.
Experimental study on the evaluation of stage acoustics by musicians using a 6-channel sound simulation system

In order to investigate the effect of a hall response on music players, subjective tests on professional players were performed in an electrically simulated sound field. For the experimental system, a 6-channel sound simulation technique has been contrived in which 6-channnel directional impulse responses measured in real halls are used to synthesize the test sound field in an anechoic room. In the subjective experiment, the subjects (players) performed several types of notes and responded to the questionnaires. From the result of the experiment, the relationship between the subjective judgments and acoustical properties of the sound field was examined.
Jordan derivations revisited

Let d be a Jordan derivation from a ring $\cal{A}$ into an $\cal{A}$-bimodule $\cal{M}$. Our main result shows that the restriction of d to the ideal of $\cal{A}$ generated by certain higher commutators of $\cal{A}$ is a derivation. This general statement is used for proving that under various additional conditions d must be a derivation on $\cal{A}$. Furthermore, several examples of proper Jordan derivations are given, $C^{\ast}$-algebras admitting proper additive jordan derivations are characterized, and the connections with the related problems on jordan homomorphisms and jordan $\cal{A}$-module homomorphisms are discussed.
Localization in the Vibration of an Axially Loaded Two-span Weakened Column

This paper is devoted to the dynamic analysis of two connected beam columns with a variation of the bending connection and minor perturbations of the length of each span. The point of reduced bending stiffness represented by a rotational spring may result from a crack. This rotational spring can also be associated with a semi-rigid connection in the field of steel or composite structures, for instance. The dynamics of this axially loaded two-span weakened column appears to exhibit strong localization for small values of stiffness of the rotational spring. The vibration mode shapes indicate a strong confinement of the vibration level to a fraction of the column. A quantitative criterion of localization is established and is correlated to well-known phenomena such as curve veering effect or close eigenvalues. Such a result is quite encouraging as localization is strongly associated with the flexibility values of the rotational spring. When considering the open crack analogy, localization only appears for severely damaged columns. It can then be understood as an indicator of the damage level of the global structure.