Miracle-dz/UniFAR-FTUs huggingface dataset:
CONVERGENCE OF ADAPTIVE LEARNING AND EXPECTATIONAL STABILITY: THE CASE OF MULTIPLE RATIONAL-EXPECTATIONS EQUILIBRIA

This paper analyzes the relationship between the expectational stability of rational expectations solutions and the possible convergence of adaptive learning processes. Both concepts are used as selection criteria in the case of multiple rational expectations solutions. Results obtained using recursive least squares lead to the conjecture that there exists a general one-to-one correspondence between these two selection criteria. On the basis of a simple linear model and a stochastic gradient algorithm as an alternative learning procedure, it is demonstrated that such a conjecture would be incorrect: There are cases in which stochastic gradient learning converges to rational expectations solutions that are not expectationally stable.
Improvement of the EMD method and applications in defect diagnosis of ball bearings

Based on the analysis of the empirical mode decomposition (EMD) method in this paper, an improved arithmetic for local mean is presented in detail. In the new arithmetic, the local mean is obtained by connecting all window means of the signals between two successive extrema with the cubic spline interpolation. The new arithmetic is more time saving than that used in the conventional empirical mode decomposition method. The improvement of the new arithmetic is validated by decomposing simulating signals. Moreover, the improved empirical mode decomposition method is successfully applied in decomposing vibration signals of ball bearings and provides a new method to diagnose defects of ball bearings. In contrast to the traditional envelope analysis, the empirical mode decomposition method could decompose the signal into different frequency bands adaptively, and the central frequency and bandwidth of band-pass filter, which was used to extract the resonance vibration, should no longer be decided. The results show that the EMD method is powerful for defect diagnosis of ball bearings.
AGN jet-driven stochastic cold accretion in cluster cores

Several arguments suggest that stochastic condensation of cold gas and its accretion on to the central supermassive black hole (SMBH) is essential for active galactic nuclei (AGNs) feedback to work in the most massive galaxies that lie at the centres of galaxy clusters. Our 3-D hydrodynamic AGN jet-ICM (intracluster medium) simulations, looking at the detailed angular momentum distribution of cold gas and its time variability for the first time, show that the angular momentum of the cold gas crossing less than or similar to 1 kpc is essentially isotropic. With almost equal mass in clockwise and counterclockwise orientations, we expect a cancellation of the angular momentum on roughly the dynamical time. This means that a compact accretion flow with a short viscous time ought to form, through which enough accretion power can be channeled into jet mechanical energy sufficiently quickly to prevent a cooling flow. The inherent stochasticity, expected in feedback cycles driven by cold gas condensation, gives rise to a large variation in the cold gas mass at the centres of galaxy clusters, for similar cluster and SMBH masses, in agreement with the observations. Such correlations are expected to be much tighter for the smoother hot/Bondi accretion. The weak correlation between cavity power and Bondi power obtained from our simulations also matches observations.
Second- and third-order moment budgets in a turbulent patch resulting from internal gravity wave breaking

To study second- and third-order statistical moments in a quasi-steady turbulent region observed in stratified flows over obstacles after the wave breaking, the direct simulation method developed for variable density fields is used. The data of runs at Re = 4000, Fh = 0.6 (based on obstacle height and inflow velocity) are used to obtain time dependence and spatial distributions of Reynolds stress tensor components, turbulent kinetic energy, scalar variance, triple correlations, and terms of budgets of their transport equations. The analysis shows that the global balance for both scalar variance and turbulent kinetic energy is between mean-shear production, advection and dissipation, whereas locally buoyant production and turbulent transport due to third-order moments are significant. For normal Reynolds stresses, the pressure-strain term is important too, providing the redistribution of stress components. The studies allow us not only to explore the turbulent patch by means of statistical moments, but also to examine closure assumptions for separate items and evaluate geophysically interesting quantities produced from the averaged data.
Gauge theories from toric geometry and brane tilings

We provide a general set of rules for extracting the data defining a quiver gauge theory from a given toric Calabi-Yau singularity. Our method combines information from the geometry and topology of Sasaki-Einstein manifolds, AdS/CFT, dimers, and brane tilings. We explain how the field content, quantum numbers, and superpotential of a superconformal gauge theory on D3-branes probing a toric Calabi-Yau singularity can be deduced. The infinite family of toric singularities with known horizon Sasaki-Einstein manifolds La,b,c is used to illustrate these ideas. We construct the corresponding quiver gauge theories, which may be fully specified by giving a tiling of the plane by hexagons with certain gluing rules. As checks of this construction, we perform a-maximisation as well as Z-minimisation to compute the exact R-charges of an arbitrary such quiver. We also examine a number of examples in detail, including the infinite subfamily La,b,a, whose smallest member is the Suspended Pinch Point.
Density-functional study of the structure and stability of ZnO surfaces

An extensive theoretical investigation of the nonpolar (1010) and (1120) surfaces as well as the polar zinc-terminated (0001)-Zn and oxygen-terminated (0001)-O surfaces of ZnO is presented. Particular attention is given to the convergence properties of various parameters such as basis set, k-point mesh, slab thickness, or relaxation constraints within local-density and generalized-gradient approximation pseudopotential calculations using both plane-wave and mixed-basis sets. The pros and cons of different approaches to deal with the stability problem of the polar surfaces are discussed. Reliable results for the structural relaxations and the energetics of these surfaces are presented and compared to previous theoretical and experimental data, which are also concisely reviewed and commented.
Correcting for fibre assignment incompleteness in the DESI Bright Galaxy Survey

The Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey (BGS) will be a survey of bright, low-redshift galaxies, which is planned to cover an area of ∼14000 square degrees in three passes. Each pass will cover the survey area with ∼2000 pointings, each of area ∼8 square degrees. The BGS is currently proposed to consist of a bright high priority sample to an r-band magnitude limit r ∼ 19.5, with a fainter low priority sample to r ∼ 20. The geometry of the DESI fibre positioners in the focal plane of the telescope affects the completeness of the survey and has a non-trivial impact on clustering measurements. Using a BGS mock catalogue, we show that completeness due to fibre assignment primarily depends on the surface density of galaxies. Completeness is high (>95 per cent) in low-density regions, but very low (<10 per cent) in the centre of massive clusters. We apply the pair inverse probability (PIP) weighting correction to clustering measurements from a BGS mock which has been through the fibre assignment algorithm. This method is only unbiased if it is possible to observe every galaxy pair. To facilitate this, we randomly promote a small fraction of the fainter sample to be high priority, and dither the set of tile positions by a small angle. We show that inverse pair weighting combined with angular upweighting provides an unbiased correction to galaxy clustering measurements for the complete three pass survey, and also after one pass, which is highly incomplete.
Seismic diagnostics of solar-like oscillating stars

High precision and long-lasting Kepler data enabled us to estimate stellar properties with asteroseismology as an accurate tool. We performed asteroseismic analysis on six solar-like stars observed by the Kepler mission: KIC 6064910, KIC 6766513, KIC 7107778, KIC 10079226, KIC 10147635 and KIC 12069127. The extraction of seismic information includes two parts. First, we obtained two global asteroseismic parameters, mean large separation Δν and frequency of maximum power νmax , with autocorrelation function and collapsed autocorrelation function. Second, we extracted individual oscillation modes νnl with low-l degree using a least-squares fit. Stellar grid models were built with Yale Rotating Stellar Evolution Code (YREC) to analyze stellar properties. They covered the range of M=0.8∼1.8M⊙ with a step of 0.02 M⊙ and [Fe/H]=−0.3∼0.4 dex with a step of 0.1 dex. We used a Bayesian approach to estimate stellar fundamental parameters of the six stars, under the constraints of asteroseismic parameters ( Δν , νmax ) and non-asteroseismic parameters ( Teff , [Fe/H] ). We discover that the six targets include five sub-giant stars with 1.2∼1.5M⊙ and one main-sequence star with 1.08M⊙ , and with ages in the range of 3∼5Gyr .
Structure of collective modes in transitional and deformed nuclei

The collective structure of atomic nuclei intermediate between spherical and quadrupole deformed structure presents challenges to theoretical understanding. However, models have recently been proposed in terms of potentials which are soft with respect to the quadrupole deformation variable beta. To test these models, information is needed on low-spin states of transitional nuclei. The present work involves measurement of electromagnetic decay properties of low-spin states for nuclei in the A=100 (gamma-soft) and N=90 (axially symmetric) transition regions. Population in beta-decay and thermal neutron capture are used, and measurements are carried out using gamma-ray coincidence spectroscopy, fast electronic scintillation timing, and gamma-ray induced Doppler broadening techniques, in experiments at Yale, TRIUMF ISAC, and the ILL. To facilitate interpretation of these nuclei, a new approach is developed that simplifies the application of the geometric collective model by use of scaling properties. Solutions are also obtained for the E(5) Hamiltonian for finite well depth.
The fluid running in the subnanochannel with functional surface

We have researched the motion of gas in the subnanochannel with functional surface which wettability has a gradient for the fluid by using molecular dynamics simulation. The results show that the gas is driven to flow under a single heat source and without any other work or energy applied to the system. The driving source is owed to the potential gradient of the functional face which keeps the fluid running in the subnanochannel. The width of the channel and the pressure of the reservoir has a significant influence on the flow velocity, which, respectively, has an optimal value for the maximum velocity. The flow velocity grows with the increasing temperature.
Decoherence of Bose-Einstein condensates in traps at finite temperature

The phase diffusion of the order parameter of trapped Bose-Einstein condensates at temperature ${k}_{B}T\ensuremath{\gg}\ensuremath{\Elzxh}\overline{\ensuremath{\omega}}$ is determined, which gives the fundamental limit of the linewidth $\ensuremath{\Delta}\ensuremath{\nu}$ of an atom laser. In addition a prediction of the number fluctuations in the condensate and their correlation time ${\ensuremath{\tau}}_{c}$ is made and a general relation for $\ensuremath{\Delta}\ensuremath{\nu}{\ensuremath{\tau}}_{c}$ is derived from the fluctuation-dissipation relation.
Gaussian quantum fluctuations in the superfluid–Mott-insulator phase transition

Recent advances in cooling techniques make now possible the experimental study of quantum phase transitions, which are transitions near absolute zero temperature accessed by varying a control parameter. A paradigmatic example is the superfluid-Mott transition of interacting bosons on a periodic lattice. From the relativistic Ginzburg-Landau action of this superfluid-Mott transition we derive the elementary excitations of the bosonic system, which contain in the superfluid phase a gapped Higgs mode and a gappless Goldstone mode. We show that this energy spectrum is in good agreement with the available experimental data and we use it to extract, with the help of dimensional regularization, meaningful analytical formulas for the beyond-mean-field equation of state in two and three spatial dimensions. We find that, while the mean-field equation of state always gives a second-order quantum phase transition, the inclusion of Gaussian quantum fluctuations can induce a first-order quantum phase transition. This prediction is a strong benchmark for next future experiments on quantum phase transitions.
A pilot survey of the binarity of Massive Young Stellar Objects withK-band adaptive optics

We present the first search for binary companions of Massive Young Stellar Objects (MYSOs) using AO-assisted $K$ band observations, with NaCo at the VLT. We have surveyed 32 MYSOs from the RMS catalogue, probing the widest companions, with a physical separation range of 400 - 46,000 au, within the predictions of models and observations for multiplicity of MYSOs. Statistical methods are employed to discern whether these companions are physical rather than visual binaries. We find 18 physical companions around 10 target objects, amounting to a multiplicity fraction of 31$\pm$8\% and a companion fraction of 53$\pm$9\%. For similar separation and mass ratio ranges, MYSOs seem to have more companions than T Tauri or O stars, respectively. This suggests that multiplicity increases with mass and decreases with evolutionary stage. We compute very rough estimates for the mass ratios from the $K$ band magnitudes, and these appear to be generally larger than 0.5. This is inconsistent with randomly sampling the IMF, as predicted by the binary capture formation theory. Finally, we find that MYSOs with binaries do not show any different characteristics to the average MYSO in terms of luminosity, distance, outflow or disc presence.
A new robust filtering for a GPS/SINS loosely coupled integration system

Integrated global positioning system (GPS)/strap-down inertial navigation system (SINS) systems are widely used for positioning and attitude determination applications. Kalman filtering is the most common method to combine both sensors. A standard Kalman filter (SKF) relies on the correct definition of the measurement and process models and cannot handle measurements with outliers. The H∞ filter can achieve better robustness performance based on minimising the worst-case estimation error. Different to other adaptive KFs, the H∞ filter controls its robustness by a restriction parameter γ. The γ parameter is usually set and fixed by experience. In this paper, an adaptive strategy to gain a time-varying γ is proposed. The construction of the time-varying parameter is based on a two-segment function of an approximate ratio of the traces of the calculated predicted residual's covariance and the theoretical covariance. The test results indicate that the proposed filtering can achieve the expected robustness performance and efficiency more comprehensively when compared with other filtering methods.
Maxwell‐compensated design of asymmetric gradient waveforms for tensor‐valued diffusion encoding

Diffusion encoding with asymmetric gradient waveforms is appealing because the asymmetry provides superior efficiency. However, concomitant gradients may cause a residual gradient moment at the end of the waveform, which can cause significant signal error and image artifacts. The purpose of this study was to develop an asymmetric waveform designs for tensor‐valued diffusion encoding that is not sensitive to concomitant gradients.
Positioning optimization of a low cast portable star tracker up to 200 meters accuracy

Using a portable star tracking system, we are able to obtain the geographical position of the observer, longitude, latitude and North direction. In this work, a new optimization method has been applied to improve accuracy in calculation of the observer position better than 6 arcsec (200 meters). In this method, we used 80 to 100 stars in each taken picture from the sky to apply optimization method. To obtain the accuracy it has been recorded observations for frequent 50 nights. In each night it has been taken 100 images.
Semiclassical expansion of the Bethe scalar products in the XXZ spin chain

In this note we adress the problem of performing the semiclassical expansion of the scalar product of Bethe states in the case of the XXZ spin chain. Our approach closely follows the one developped in [1]: after expressing the scalar products in terms of a central quantity - the B functional, we reinterpret it as a grand partition function of a gas of particles with pairwise interaction potential. This work has been done as part of the author's master thesis under the supervision of Ivan Kostov and Didina Serban at Institut de Physique Th\'eorique (CEA Saclay) in September 2015 - February 2016, and present a consice summary of the results obtained at that time.
ASYMPTOTIC DISTRIBUTIONS FOR TWO ESTIMATORS OF THE SINGLE-INDEX MODEL

The single-index model is one of the most popular semiparametric models in applied quantitative sciences. Two new estimation methods have been proposed recently by Hristache, Juditski, and Spokoiny (2001, Annals of Statistics 29, 595–623) and Xia, Tong, Li, and Zhu (2002, Journal of the Royal Statistical Society, Series B 64, 363–410), respectively. However, their asymptotic distributions have not been investigated yet. In this paper, alternative versions for the methods are investigated. Asymptotic distributions of the estimators are derived. Efficiency comparisons between the estimation methods are made.The author is most grateful to Professor O. Linton and Professor W. Härdle for helpful discussions. Valuable comments from two anonymous reviewers have improved the presentation of the paper substantially. The research has been partially supported by NUS research grant R-155-000-048-112, National University of Singapore, Singapore, and the Alexander von Humboldt Foundation, Germany.
Oxygen-neon-rich merger during common envelope evolution

We conduct a population synthesis study of the common envelope evolution (CEE) of a white dwarf (WD) and an asymptotic giant branch (AGB) star and find that the potential number of type Ia supernovae (SNe Ia) from the core degenerate (CD) and from the double degenerate (DD) scenarios are of the same order of magnitude. For the CD scenario we consider cases where a carbon oxygen rich (CO) AGB core and a CO WD merge during the CEE and leave a WD remnant with a mass of >1.35Mo, and for the DD scenario we count surviving CO WD binary systems that merge within a time of 10 Gyr. When either the AGB core or the WD are oxygen neon rich (ONe) we assume that the outcome might be a peculiar SN Ia. We find that the number of potential peculiar SNe Ia in the channels we study, that do not include peculiar SNe Ia that involve helium WDs or helium donors, is non-negligible, but less than the number of normal SNe Ia. If a SN Ia or a peculiar SN Ia explosion takes place within about million year after CEE, whether in the CD scenario or in the DD scenario, a massive circumstellar matter is present at explosion time. Our results are compatible with the suggestion that Chandrasekhar-mass SNe Ia mostly come from the CD scenario, and sub-Chandrasekhar SNe Ia mostly come from the DD scenario.
Rigidity percolation control of the brittle-ductile transition in disordered networks

In ordinary solids, material disorder is known to increase the size of the process zone in which stress concentrates at the crack tip, causing a transition from localized to diffuse failure. Here, we report experiments on disordered 2D lattices, derived from frictional particle packings, in which the mean coordination number $\langle z \rangle$ of the underlying network provides a similar control. Our experiments show that tuning the connectivity of the network provides access to a range of behaviors from brittle to ductile failure. We elucidate the cooperative origins of this transition using a frictional pebble game algorithm on the original, intact lattices. We find that the transition corresponds to the isostatic value $\langle z \rangle = 3$ in the large-friction limit, with brittle failure occurring for structures vertically spanned by a rigid cluster, and ductile failure for floppy networks containing nonspanning rigid clusters. Furthermore, we find that individual failure events typically occur within the floppy regions separated by the rigid clusters.
The dusty tori of nearby qsos as constrained by high-resolution mid-ir observations

We present mid-infrared (MIR, 7.5-13.5 $\mu$m) imaging and spectroscopy observations obtained with the CanariCam (CC) instrument on the 10.4m Gran Telescopio CANARIAS for a sample of 20 nearby, MIR bright and X-ray luminous QSOs. We find that for the majority of QSOs the MIR emission is unresolved at angular scales nearly 0.3 arcsec, corresponding to physical scales $ 2$ per cent) and low geometrical covering factors ($f_{2}<0.6$), as expected for AGN with broad lines in their optical spectra.
The X-ray background and the AGN X-ray luminosity function

ROSAT deep and shallow surveys have provided an almost complete inventory of the constituents of the soft X-ray background which led to a population synthesis model for the whole X-ray background with interesting cosmological consequences. According to this model the X-ray background is the “echo” of mass accretion onto supermassive black holes, integrated over cosmic time. A new determination of the soft X-ray luminosity function of active galactic nuclei (AGN) is inconsistent with pure luminosity evolution. The comoving volume density of AGN at redshift 2–3 approaches that of local normal galaxies. This indicates that many larger galaxies contain black holes and it is likely that the bulk of the black holes was produced before most of the stars in the universe. However, only X-ray surveys in the harder energy bands, where the maximum of the energy density of the X-ray background resides, will provide the acid test of this picture.
Transient modeling of Lamb waves generated in viscoelastic materials by surface bonded piezoelectric transducers

In order to help optimize health monitoring systems based on Lamb wave propagation, a hybrid finite element–normal mode expansion modeling technique has been developed. This technique allows one to predict the Lamb waves generated in a structure as a function of the transducer parameters (size, location, material, etc.). The present paper shows how this hybrid modeling, initially valid for nonlossy materials and harmonic excitation, can be extended to lossy (viscoelastic) materials and transient excitation. For this purpose, simplifying assumptions have been proposed and validity conditions have been established and verified. Moreover, numerical results concerning Lamb wave generation have been successfully compared to experimental ones. As a result, the method has proved to be pertinent and practically unrestrictive.