Miracle-dz/UniFAR-FTUs huggingface dataset:
Spectral damping in Barkhausen noise

The spectral amplitude damping of Barkhausen noise is determined theoretically and experimentally as a function of distance inside the sample itself. Power spectra for noise amplitude and its time derivative are measured in some steel specimens over a wide frequency range. Some examples of the influence of the sample microstructure on the power spectra are also examined. The results, including spectral damping, suggest that the nature of Barkhausen noise changes continuously from nonrandom to random either with the thickness of the sample (0.1-5 mm) or with increasing magnetizing frequency (10-2-102Hz). This phenomenon as a whole is explained in terms of the clustering of elementary magnetization transitions.
FIRST UNAMBIGUOUS DETECTION OF THE RETURN OF PULSATIONS IN THE ACCRETING WHITE DWARF SDSS J074531.92+453829.6 AFTER AN OUTBURST

The primary white dwarf of the cataclysmic variable SDSS J074531.92+453829.6 was discovered to exhibit non-radial pulsations in 2006 January. This accreting white dwarf underwent its first recorded dwarf nova outburst in 2006 October, during which its brightness increased by more than 5 mag. A Hubble Space Telescope (HST) ultraviolet spectrum, obtained one year after the outburst, revealed a white dwarf temperature of 16,500 K, hotter than all other known accreting white dwarf pulsators. This implies that the accreting primary white dwarf of SDSS J074531.92+453829.6 was heated to temperatures beyond the instability strip during the outburst. Optical observations acquired a year after the outburst did not reveal any evidence of pulsations, suggesting that the white dwarf had not cooled to quiescence by then. We recently acquired optical high-speed time-series photometry on this cataclysmic variable SDSS J074531.92+453829.6 more than three years after its outburst to find that pulsations have now returned to the primary white dwarf. Moreover, the observed pulsation periods agree with pre-outburst periods within the uncertainties of a few seconds. This discovery is significant because it indicates that the outburst did not affect the interior stellar structure, which governs the observed pulsation frequencies. It also suggests that the surface of the white dwarf has now cooled to quiescence. Using this discovery in addition to the prior HST temperature measurement of 16,500 K, we have been able to constrain the matter accreted during the 2006 outburst. This is the first time an accreting white dwarf was unambiguously observed to resume pulsating after an outburst.
Momentum-space diffusion due to resonant wave–wave scattering of electromagnetic and electrostatic waves in a relativistic magnetized plasma

The momentum-space diffusion equation and the kinetic wave equation for resonant wave–wave scattering of electromagnetic and electrostatic waves in a relativistic magnetized plasma are derived from the relativistic Vlasov–Maxwell equations by perturbation theory. The p-dependent diffusion coefficient and the nonlinear wave—wave coupling coefficient are given in terms of third-order tensors which are amenable to analysis. The transport equations describing energy and momentum transfer between waves and particles are obtained by momentum-space integration of the momentum-space diffusion equation, and are expressed in terms of the nonlinear wave—wave coupling coefficient in the kinetic wave equation. The conservation laws for the total energy and momentum densities of waves and particles are verified from the kinetic wave equation and the transport equations. These equations are very useful for the theoretical analysis of transport phenomena or the acceleration and generation of high-energy or relativistic particles caused by quasi-linear and resonant wave—wave scattering processes.
Propagation Phenomena in a Bistable Reaction-Diffusion System

Consideration is given to a system of reaction-diffusion equations which have qualitative significance for several applications including nerve conduction and distributed chemical-biochemical systems. These equations are of the FitzHugh–Nagumo type and contain three parameters. For certain ranges of the parameters the system exhibits two stable singular points. A singular perturbation construction is given to illustrate that there may exist both pulse type and transition type traveling waves. A complete, rigorous, description of which of these waves exist for a given set of parameters and how the velocities of the waves vary with the parameters is given for the case when the system has a piecewise linear nonlinearity. Numerical results of solutions to these equations are also presented. These calculations illustrate how waves are generated from initial data, how they interact during collisions, and how they are influenced by local disturbances and boundary conditions. In one example, a righltward moving “.
Daily and Seasonal Variations of Shallow Seismic Velocities in Southern California From Joint Analysis of H/V Ratios and Autocorrelations of Seismic Waveforms

Establishing a baseline of ongoing secular velocity variations at the subsurface can improve the accuracy of detecting and interpreting short‐term velocity changes, and advance the understanding of observed seismic motions and the behavior of subsurface materials. Toward these goals, we develop and apply a deconvolved autocorrelation (DA) method to estimate regional daily and seasonal changes of seismic velocities in southern California. The DA method combines advantages of traditional autocorrelation and Horizontal‐to‐Vertical Spectral Ratio, and is used to analyze over 10 years of data recorded by 50 stations. The results indicate widespread daily and seasonal changes of up to 10% and 4%, respectively, in the top tens of meters of the crust. The thickness of the surface layer, distance from the coast, and topographic variations are important factors controlling the amplitudes of the resolved velocity variations. The results suggest that changes of soil moisture and thermoelastic strain are likely dominant factors affecting the daily and seasonal variations, respectively. The developed DA method can improve the accuracy and robustness of estimated changes of subsurface materials at other locations.
Active Redundancy Allocation in Coherent Systems

We introduce in this paper a new measure of component importance, called redundancy importance, in coherent systems. It is a measure of importance for the situation in which an active redundancy is to be made in a coherent system. This measure of component importance is compared with both the (Birnbaum) reliability importance and the structural importance of a component in a coherent system. Various models of component redundancy are studied, with particular reference to k/out / of / n systems, parallel-series systems, and series-parallel systems.
Groundbased investigation of asteroid 9969 Braille, target of the spacecraft mission Deep Space 1

Asteroid 9969 Braille (1992 KD) was encountered on July 29, 1999 by the Deep Space 1 mission, the first of NASA's New Millennium Program, launched on October 24 1998. The data obtained by the space mission seem to indicate a composition of the object similar to that of Vesta. To complete the information obtained in the infrared region by the Deep Space 1 mission we have performed a visible spectroscopic and photometric investigation of the asteroid respectively with the 1.5 m telescope and the NTT of ESO, La Silla. The spectrum was obtained in the spectral range 4500-8200 A and, for the photometry, BVRI filters were used. In this paper we report the results of the analysis of the data obtained indicating that, on the basis of our visible data, the composition of the asteroid may range from V-type to Q-type, but we observe also a strong similarity to the H-type ordinary chondrites.
Sound propagation in an urban environment. II: Preliminary FDTD model

A 2‐dimensional finite difference time domain (FDTD) method was used to simulate a data set recorded by a microphone array in an urban terrain. The FDTD model uses a coupled system of first‐order differential equations for excess pressure and particle velocity. The perfectly matched layer method was used to truncate the model domain. This technique is much more efficient in diminishing unwanted reflections from the domain boundaries than any other absorptive boundary technique. The numerical integration was carried out with a staggered grid system. This algorithm has been validated with comparison with analytical solutions for cases with uniform physical parameters and simple geometries. For the predicted sound levels, although they are in general agreement with the measured values at 13 sensor locations, there is a significant discrepancy occurred at one particular sensor location (microphone location 9) behind one building (Building A). The observed sound level is about an order of magnitude greater tha.
Comments on "Radiation and scattering from thin wires in chiral media"

Comments that the above paper (see Jaggard, Liu, Grot and Pelet, IEEE Trans. Antennas Propagat., vol.40, p.1273-1282, Nov. 1992) lacks the generality of the paper published by Monzon (see Antennas Propagat., vol.38, p.227-235, Feb. 1990). The latter paper contains an analysis for thin wires, including an explicit integral equation and method for numerical solution (summing impedance matrices), which renders the problem of trivial numerical implementation. Further, the analysis applies to full biisotropic regions, and is therefore more general than chiral since chiral is just a special case of biisotropic. It appears that Jaggard et. al. use the integral equation of Monzon and follow the numerical scheme therein literally. >
Fault detection and isolation for on‐board sensors of a general aviation aircraft

This paper addresses the problem of the detection and isolation of the input and output sensor faults on a general aviation aircraft, which is characterized by a non‐linear model, in the presence of wind gusts, atmospheric turbulence and measurement errors. In particular, this work proposes a polynomial approach for the design of residual generators in order to realize complete diagnosis schemes when additive faults are present. In fact, the use of an input–output description for the linearized model of the aircraft allows to compute in a straightforward way the residual generators. This approach leads to dynamic filters that can achieve both good disturbance signal decoupling and robustness properties with respect to both linearization error and measurement noise. Mathematical descriptions of the aircraft measurement sensors are also taken into account. The results obtained in the simulation of the faulty behaviour of a PIPER PA30 aircraft and a comparison with other FDI approaches (both linear and non‐linear) are finally reported. Copyright © 2006 John Wiley & Sons, Ltd.
Net structure and control logic synthesis of controlled Petri nets

Control logic synthesis of discrete-event systems is considered in the setting of controlled Petri nets. The problem is to find a control policy that restricts the behavior of a controlled Petri net so that a collection of forbidden state conditions is satisfied. S-decreases are introduced as a tool for the control synthesis. The S-decreases are weight vectors defined on the places of a net such that the weighted sum of tokens in the net never increases with any transition firing. On the basis of S-decreases, the authors propose an efficient method for the synthesis of the maximally permissive state feedback control polity for a class of controlled Petri nets whose uncontrolled subnets are forward and backward conflict-free nets. This method upgrades all integer linear programming-based methods for which one only requires to solve the much simpler linear programming problems to determine maximally permissive controls.
Kinetic structure and wave properties associated with sharp dipolarization front observed by Cluster

Multiple dipolarization fronts (DFs) were observed by Cluster spacecraft in the magnetotail during a substorm. These DFs were kinetic structures, embedded in the bursty plasma flow, and moved earthward (mainly) and dawnward. Intense electric field, parallel and perpendicular currents were detected in the DF layer. These front layers were energy dissipation region (load region) where the energy of electromagnetic fields were transferred to the plasma thermal and kinetic energy. This dissipation was dominated by electrons. There were enhancements of plasma waves around the DF region: wavelet results show that wave activities around the ion cyclotron frequency in the front layer were generated by Alfven ion cyclotron instability; whistler waves were also detected before, during and after the DFs, which are triggered by electron temperature anisotropy and coincident with enhancement of energetic electron fluxes. The observation of these waves could be important for the understanding of evolution of DF and electron energization during the substorm. We discuss the generation mechanism of the DFs and suggest that these DFs were generated in the process of transient reconnection, and then traveled toward the Earth.
Cascade Inequalities for Forced-Dissipated Geostrophic Turbulence

Abstract Analysis of spectral kinetic energy fluxes in satellite altimetry data has demonstrated that an inverse cascade of kinetic energy is ubiquitous in the ocean. In geostrophic turbulence models, a fully developed inverse cascade results in barotropic eddies with large horizontal scales. However, midocean eddies contain substantial energy in the baroclinic mode and in compact horizontal scales (scales comparable to the deformation radius Ld). This paper examines the possibility that relatively strong bottom friction prevents the oceanic cascade from becoming fully developed. The importance of the vertical structure of friction is demonstrated by contrasting numerical simulations of two-layer quasigeostrophic turbulence forced by a baroclinically unstable mean flow and damped by bottom Ekman friction with turbulence damped by vertically symmetric Ekman friction (equal decay rates in the two layers). “Cascade inequalities” derived from the energy and enstrophy equations are used to interpret the numeri.
The role of merged interaction regions and drafts in the heliospheric modulation of cosmic rays beyond 20 AU - A computer simulation

The time-dependent, axially symmetric transport equation of cosmic rays in the heliosphere was solved numerically using the Voyager 2 magnetic field measurements to simulate merged interaction regions (MIRs) and rarefaction regions (RRs) for the period 1985-1989. Concurrently, the wavy neutral sheet was used as a time-dependent, drift parameter. The two approaches were first modeled separately and then in combination in this exploratory study. The drift approach proved to be the more successful for 1985 to early 1988 because it could reproduce the intensity levels, the factor modulation, and latitudinal gradients for 1 GeV protons at 23 AU without difficulties
Interpolating Spline Methods for Density Estimation I. Equi-Spaced Knots

Abstract : Statistical properties of the histospline density estimate of Boneva-Kendall-Stefanov-Schoenberg are found. This density estimate is the derivative of a cubic spline of interpolation to the sample cumulative distribution at equally spaced points. The spacing of these points is chosen in an optimal manner. The boundary values of the spline are estimated from the data. It is shown that the mean square convergence rate of this density estimate at a point achieves the best obtainable rate. (Author)
Viscous forces on a circular cylinder in orbital flow at low Keulegan—Carpenter numbers

The flow structures giving rise to the force on a circular cylinder in uniform, circular, orbital flows have been investigated for keulegan—Carpenter numbers (K) less than 2 and a Stokes parameter (β) of 483 using the random-vortex method. Comparisons with analysis using the method of inner and outer expansions are made and good agreement is found for K = 0.1. For higher K-values, the viscous force (the difference between the total force and the potential-flow force) acts mainly in opposition to the potential-flow force causing a substantial reduction in total force, in keeping with experimental measurements. Significant separation does not occur at K ≤ 1.5 and vorticity organizes itself asymmetrically about the line through the cylinder centre parallel to the incident velocity vector. Vorticity of one sense of rotation remains close to the half-surface lagging the velocity vector, while an area of vorticity of the opposite sense wraps itself around the cylinder. The net circulation in the flow (the circulation within a path encircling the cylinder at a large radius) is zero. Vortex shedding occurs at K > 1.5. Viscous forces due to non-uniform, orbital flows around a horizontal cylinder beneath waves were similar although vortex shedding tended to occur at lower K-values.
Lattice dynamics of magnesium oxide

Measurements of the inelastic neutron scattering by longitudinal optic phonons in MgO are reported. These results and those previously obtained for other branches are used in an investigation of various lattice dynamical models, including shell and breathing shell models. It is shown that the agreement with the measured data is improved by the inclusion of breathing effects.
A review of the fate of inhaled α-quartz in the lungs of rats

Abstract The distribution of dust particles within the lungs and their excretion are highly associated with their pulmonary toxicity. Literature was reviewed to discern pulmonary translocation pathways for inhaled α-quartz compared to those for inhaled TiO2. Accordingly, it was hypothesized α-quartz particles in the alveoli were phagocytized by alveolar macrophages but silica-containing macrophages remained in the alveoli for longer time in contrast to the rapid elimination from the alveoli seen for TiO2-containing macrophages. In addition, it was presumed that free silica particles are translocated in the interstitium, possibly through the cytoplasm of Type I epithelial cells, as observed with TiO2. Free silica particles are presumed to be phagocytized by interstitial macrophages soon after the particles penetrate the interstitium; these dust cells are then translocated to the ciliated airway regions in the lumen through bronchus-associated lymphoid tissue (BALT). The pulmonary retention half-time of dust particles in rats exposed to α-quartz is several times longer than that of rats exposed to TiO2, as long as the lung dust burden is ≈ 3 mg. The reduced pulmonary particle clearance ability in rats exposed to α-quartz aerosol is presumably attributed to the long-term retention of dust cells both in the alveoli and in the interstitium; this retention may be caused by the reduced chemotactic abilities of α-quartz-containing dust cells. However, the accumulation of α-quartz-containing dust cells in the lungs is not associated with the occurrence of pulmonary inflammation.
Zooming into the Future: Implementing Theory into Practice for Educational Crisis Times

The abrupt transition from face‐to‐face classes to online learning during March 2020 occurred as a result of the Covid‐19 pandemic. Teachers were forced to shift to online teaching with no prior training, while students had to adapt to a new learning format. The physical distance between students and teachers led to changes in interactions. The current study examines the instructional approaches used for online teaching and learning during the Covid‐19 crisis. The research focuses on using the Covid‐19 pandemic as a case study to explore crisis events and their impact on education system. The study uses a qualitative approach, with three junior and high schools participating. Thirteen teachers were interviewed, and 27 students participated in three focus groups, one from each school. The study's theoretical framework is based on the Transactional Distance Theory (TDT) and the Connectivism Learning Theory (CLT). The main finding focuses on teachers' use of autonomy to vary their teaching approaches, while students felt they did not know how to cope with the autonomy given to them and even felt neglected by their teachers. Therefore, in order to strengthen learners' autonomy, teachers need to design and monitor the scaffoldings by both structure (curriculum) and dialog (teacher‐student and student–student).
Simulation of flow across a row of transversely oscillating square cylinders

A numerical study of flow across a row of transversely oscillating square cylinders (of diameter d) has been undertaken using the lattice Boltzmann method, for a better understanding of fluid–structure interaction problems. The effects of cylinder oscillation frequency ratio (fe/fo, where fe is the cylinder oscillation frequency and fo is the corresponding vortex shedding frequency for stationary row of cylinders), amplitude ratio (A/d), non-dimensional spacing between the cylinders (s/d) and Reynolds number (Re) on ensuing flow regimes and flow parameters have been studied to understand the flow physics. Six different flow regimes observed in this study are the quasi-periodic non-lock-on-I, synchronous lock-on, quasi-periodic lock-on, quasi-periodic non-lock-on-II, synchronous non-lock-on and chaotic non-lock-on. It is observed that the range of the lock-on regime depends upon the relative dominance of incoming flow and cylinder motion. Although the lock-on regime in the case of Re = 80, s/d = 4 and A/d = 0.2 is substantially larger as compared to that for a single oscillating cylinder, the range of the lock-on regime shrinks with a reduction in the cylinder spacing, increase in the Reynolds number or decrease in the oscillation amplitude. It is also observed that the wake interaction behind the cylinders weakens with an increase in fe/fo, Re, A/d or s/d, leading to the formation of independent wakes and synchronous nature of the flow. For fe/fo ≥ 1.2, independent and intact oscillating wakes are noted and an additional frequency (wake oscillation frequency) is obtained in the time series of the lift coefficient. Although it was expected that the complexity in the wake interaction would increase with cylinder oscillation or amplitude ratio, an opposite effect (that is, formation of independent wakes) is noted from the results.
Pressure Fluctuations Beneath Turbulent Spots and Instability Wave Packets in a Hypersonic Boundary Layer

The development of turbulent spots in a hypersonic boundary layer was studied on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Under quiet flow conditions, the nozzle wall boundary layer remains laminar and grows very thick over the long nozzle length. This allows the development of large turbulent spots that can be readily measured with pressure transducers. Measurements of naturally occurring wave packets and developing turbulent spots were made. The peak frequencies of these natural wave packets were in agreement with second-mode computations. For a controlled study, the breakdown of disturbances created by spark and glow perturbations were studied at similar freestream conditions. The spark perturbations were the most effective at creating large wave packets that broke down into turbulent spots. The flow disturbances created by the controlled perturbations were analyzed to obtain amplitude criteria for nonlinearity and breakdown as well as the convection velocities of the turbulent spots. Disturbances first grew into linear instability waves and then quickly became nonlinear. Throughout the nonlinear growth of the wave packets, large harmonics are visible in the power spectra. As breakdown begins, the peak amplitudes of the instability waves and harmonics decrease into the rising broad-band frequencies. Instability waves are stillmore » visible on either side of the growing turbulent spots during this breakdown process. « less