Miracle-dz/UniFAR-FTUs huggingface dataset:
A Complete Characterization of ARMA Solutions to Linear Rational Expectations Models

Linear rational expectations models with expectations of future endogenous variables have multiple equilibria. For a scalar model with k forward expectational lags and l backward lags, this paper characterizes the complete set of ARMA solutions. It is shown that the maximum degree solutions are ARMA (k + l, k), that the solutions of maximum degree are obtained directly from the characteristic polynomial but have arbitrary MA parameters, and that all lower degree ARMA solutions are obtained by deleting common factors in the AR and MA lag polynomials. The results are applied to several macroeconomic examples.
A Jacobian‐free‐based IIM for incompressible flows involving moving interfaces with Dirichlet boundary conditions

In this paper, a finite difference marker‐and‐cell (MAC) scheme is presented for the steady Stokes equations with moving interfaces and Dirichlet boundary condition. The moving interfaces are represented by Lagrangian control points and their position is updated implicitly using a Jacobian‐free approach within each time step. The forces at the moving interfaces are calculated from the position of the interfaces and interpolated using cubic splines and then applied to the fluid through the related jump conditions. The proposed Jacobian‐free Newton–generalized minimum residual (GMRES) method avoids the need to form and store the matrix explicitly in the computation of the inverse of the Jacobian and betters numerical stability. The Stokes equations are discretized on a MAC grid via a second‐order finite difference scheme with the incorporation of jump contributions and the resulting saddle point system is solved by the conjugate gradient Uzawa‐type method. Numerical results demonstrate very well the accuracy and effectiveness of the proposed method. The present algorithm has been applied to solve incompressible Navier–Stokes flows with moving interfaces. Copyright © 2010 John Wiley & Sons, Ltd.
A unified view on skewed distributions arising from selections

Parametric families of multivariate nonnormal distributions have received considerable attention in the past few decades. The authors propose a new definition of a selection distribution that encompasses many existing families of multivariate skewed distributions. Their work is motivated by examples that involve various forms of selection mechanisms and lead to skewed distributions. They give the main properties of selection distributions and show how various families of multivariate skewed distributions, such as the skew‐normal and skew‐elliptical distributions, arise as special cases. The authors further introduce several methods of constructing selection distributions based on linear and nonlinear selection mechanisms.
Long-Term Nitrate Measurements in the Ocean Using the in situ Ultraviolet Spectrophotometer: Sensor Integration into the APEX Profiling Float

AbstractReagent-free optical nitrate sensors [in situ ultraviolet spectrophotometer (ISUS)] can be used to detect nitrate throughout most of the ocean. Although the sensor is a relatively high-power device when operated continuously (7.5 W typical), the instrument can be operated in a low-power mode, where individual nitrate measurements require only a few seconds of instrument time and the system consumes only 45 J of energy per nitrate measurement. Operation in this mode has enabled the integration of ISUS sensors with Teledyne Webb Research's Autonomous Profiling Explorer (APEX) profiling floats with a capability to operate to 2000 m. The energy consumed with each nitrate measurement is low enough to allow 60 nitrate observations on each vertical profile to 1000 m. Vertical resolution varies from 5 m near the surface to 50 m near 1000 m, and every 100 m below that. Primary lithium batteries allow more than 300 vertical profiles from a depth of 1000 m to be made, which corresponds to an endurance near f.
Long time behaviour of an integrable Heisenberg spin chain

We consider an integrable modification of the standard Heisenberg spin chain which is known to be a discretization of the continuous Heisenberg magnet model and indeed equivalent to a discretization of the nonlinear Schrödinger equation. In particular we investigate the long time behaviour of the system; we are mostly interested in the ‘non-soliton’ part, thus completing the discussion in Papanicolaou (1987) of the solitonic solutions. Our method makes use of the related inverse scattering problem and its formulation as a Riemann-Hilbert factorization problem. We show that the problem can be reduced to the analogous one for the Toda lattice and provide explicit asymptotic formulae.
A numerical approach for the determination of the tissue equivalent liquid used during SAR assessments

The present paper describes a finite difference time domain-based numerical approach to determine the dielectric properties of the tissue equivalent liquid employed in homogeneous phantoms when testing the specific absorption rate (SAR) compliance of mobile phones. A first numerical simulation performed with a realistic anatomical head model provides the reference averaged SAR value. Several similar simulations are then carried out using a homogeneous head model by varying the dielectric parameters of the tissue equivalent liquid. The desired dielectric parameters of the liquid are derived by matching the maximum averaged SAR with the reference value.
Efficient Sieve Maximum Likelihood Estimation of Time-Transformation Models

Time transformation models assume the survival time to be linearly related to covariates through an unknown monotonic transformation function and an error term with known distribution. In this article, the sieve method of maximum likelihood is used to estimate the unknown monotonic transformation of survival time. More specifically, a suitable class of Bernstein polynomials is used to estimate the transformation function while preserving monotonicity and smoothness. The proposed estimation method is less parametrically intensive than current time transformation methods. Furthermore, the method produces a smooth estimate of the time transformation, and hence the survival function. We discuss the selection of the number of parameters for the polynomial asymptotically, and for moderate sample sizes. The asymptotic properties of the estimators are shown, including the asymptotic normality and efficiency of the regression coefficient. Simulation studies illustrate that our estimator has good empirical properties in practical sample sizes. The method is demonstrated on two data sets and compared to previous similar works.
Evaluation of a Numerical Weather Forecast Model Using Boundary Layer Cloud-Top Temperature Retrieved from AVHRR

Abstract This study concerns the evaluation of the boundary layer (BL) subgrid parameterization of a numerical weather forecast model on the synoptic scale. The method presented aims at separating the two possible origins of model defficiencies in representing a cloud-topped boundary layer: (i) large-scale data assimilation issues, and (ii) BL parameterization. The method combines two sources of data: model analyzed fields from the SEMAPHORE field experiment, and the Advanced Very High Resolution Radiometer (AVHRR) dataset from the NOAA-11 and -12 Satellite. The application focuses on an anticyclonic period during field experiment (10–17 November 1993), for which a special version of ARPEGE—The Meteo-France Numerical Weather Prediction model—is used to analyze the data from the field experiment. In the proposed method, the boundary layer is globally characterized by its height which is converted to an inversion layer temperature in the model. Low-level cloud-top temperatures of optically thick clouds are .
On the hydrodynamic equations for flow of liquid helium II with mutual friction

The flow of liquid helium II at subcritical velocities can be described by hydrodynamic equations which assume the possibility of independent motions of the two fluid components, but difficulties arise in supercritical flows with forces of mutual friction between the component fluids. The extensive evidence that mutual friction is caused by scattering of the thermal excitations in the velocity fields of the quantized vortex lines suggests that the equations should include mutual forces which are large near the vortex-lines and negligible elsewhere. In their original theory, Hall & Vinen (1956) did assume this, and here the implications of the assumption are examined in detail. Serious difficulties are found in reconciling localization of the mutual friction with fully developed flow in channels, and it is suggested that, although the mutual friction arises from scattering near the vortex lines, the force on the superfluid is distributed uniformly over distances comparable with the distance between adjacent vortex lines.
Ultraviolet variability of the helium-peculiar star a Centauri

The spectrophotometric variability of the classical magnetic chemically peculiar star a Cen in the ultraviolet spectral region from 1150 to 3100 A is investigated. This study is based on archival International Ultraviolet Explorer data obtained at various phases of the rotational cycle. The light variations in wavelengths shorter than λ1616 A are mainly in antiphase to the light variations in the longer-wavelength region. The brightness of the star in the spectral region λλ1616–1640 A is constant over the period of rotation, which means that a so-called ‘null wavelength region’ exists over these wavelengths. There is also a second ‘null wavelength region’ in the spectrum of a Cen. According to our investigation, the semi-amplitude of the light variations is practically zero over the period of rotation in the spectral region λλ1244–1343 A. The exception is the light variation in the depressions at λλ1265 and 1300 A, which are formed by resonance lines of silicon. However, the fluxes are constant at the cores of some features and in small depressions. An explanation for the light variations of a Cen is flux redistribution through bound–free and bound–bound silicon transitions combined with an inhomogeneous surface distribution of silicon on the stellar surface. The influence of other elements on the flux redistribution is discussed.
Light Diffraction by Ultrasonic Surface Waves of Arbitrary Standing‐Wave Ratio

The diffraction of monochromatic light by reflection off a single‐frequency ultrasonic surface wave of arbitrary standing‐wave ratio is analyzed theoretically, with the assumption that the light and sound beams share a direction of symmetry. The diffraction integral is solved for the case in which the surface illumination has a uniform intensity cross section, and also for a Gaussian intensity cross section. The dependences of the diffracted light intensities in the limiting case of small sound‐beam intensity are examined in detail for varying standing‐wave ratios.
Crystalline structure and symmetry dependence of acoustic nonlinearity parameters

A quantitative measure of elastic wave nonlinearity in crystals is provided by the acoustic nonlinearity parameters. The nonlinearity parameters are defined for arbitrary propagation modes for solids of arbitrary crystalline symmetry and are determined along the pure mode propagation directions for 33 crystals of cubic symmetry from data reported in the literature. The magnitudes of the nonlinearity parameters are found to exhibit a strong dependence on the crystalline structure and symmetries associated with the modal direction in the solid. Calculations based on the Born–Mayer potential for crystals having a dominant repulsive contribution to the elastic constants from the interatomic pair potential suggest that the origin of the structure dependence is associated with the shape rather than the strength of the potential. Considerations based on variations in crystal symmetry during loading along pure mode propagation directions of face‐centered‐cubic solids provide a qualitative explanation for the depe.
Optical identifications in the Marano field XMM-Newton survey

The “Marano field”, a deep optical quasar survey field, has been observed by the XMM Newton EPIC camera with 16 overlapping pointings totalling at ∼ 120 ksec integration time. Source detection in the merged observations resulted in more than 600 X-ray sources. Here we present the status of optical follow up observations which were undertaken to identify and classify the newly found X-ray sources.
Beamforming using the synthetic sine wave for ultrasonic imaging system

Synthetic sine wave employs pulsed plane wave as, transmit beam using a full aperture array with linear time delay curve. The received echoes in different. transmit directions at different transmit times are superposed at imaging points with proper time delay compensation using synthetic focusing schemes. This scheme, which uses full aperture on transmit, overcomes the low SNR problem in conventional synthetic focusing, and also features high lateral resolution by using two way dynamic focusing at all imaging depths. We have applied the scheme to obtain phantom and in-vivo images using a linear array of 5 MHz and 128 elements. In phantom test, experimental images show high resolution over a more extended imaging depth than conventional fixed point transmit and receive dynamic focusing schemes. In-vivo images show that the resolution could not overcome conventional focusing systems because of motion blurring and/or aberration of tissue, but that the frame rate can be increased by a factor of more than 5 compared to conventional focusing schemes, with competitive resolution at all imaging depths.
Improved thermoelectric figure of merit in n-type CoSb3 based nanocomposites

Nanocomposites offer a promising approach to incorporate nanostructured constituents to bulk thermoelectric materials. n-type CoSb3 nanocomposites were prepared by hot pressing the mixture of nanoscale and microsized CoSb3 powders synthesized by solvothermal method and melting, respectively. Microstructure analysis shows that the bulk materials are composed of nano- and micrograins. The nanocomposite structures are effective in reducing thermal conductivity more than electrical conductivity, hence in improving the thermoelectric performance. A dimensionless figure of merit of 0.71 is obtained for the nanocomposite with 40wt% nanopowder inclusions, about 54% increase of that without nanopowder inclusions.
A comparison of synthetic seismograms of core phases generated by the full wave theory and by the reflectivity method

Summary. Because the computation of synthetic seismograms has become an invaluable tool for the study of the Earth, it is of major interest to know whether two different methods, the reflectivity method and the full wave theory, generate identical record sections when applied to the same body wave problem. The full wave theory employs approximations by assuming decoupling of P and SV potentials in arbitrarily thick radially inhomogeneous layers and by representing radial eigenfunctions by the first term in a uniformly asymptotic series. The reflectivity method employs approximations by transforming depth-dependent variables of a spherically symmetric Earth to those of a plane-layered medium and by replacing this medium by a stack of homogenous layers. We have compared record sections generated by the two methods using the same Earth model, source parameters, distance ranges and body waves. Specifically, we examined core phases, which should provide a stringent comparison because they contain a wide range of frequencydependent phenomena including diffraction and the effects that arise from a cusp and a caustic. It is found that the synthetic record sections of the two techniques are identical when displacements are low-pass filtered. This is the case for many practical purposes, for displacement generally must be convolved with an instrument response and a source function of several seconds
Stability Condition for Single-Relaxation Time Isothermal Lattice Boltzmann Formulation

In this present research, the Lattice Boltzmann method has been used to determine the stability condition of the single relaxation time. The range of Reynolds number is 100,400 and 1000. Meanwhile, the range of mesh size is varying between 31 to 251. The results show that the increase in both mesh size and Reynolds number give an effect on deviation percentages. The deviation percentages for all mesh and Reynolds number also presented.
EM wave excitation and propagation in a generally anisotropic homogeneous medium: a coordinate-free approach

A simple coordinate-free approach for the derivation of spectral Green's functions is presented referring to a generally anisotropic homogeneous medium with spatial dispersion. On this basis, an elegant method to determine the plane-wave modes and the associated modes by properly specifying the excitation is proposed. These results are applicable, e.g., to bianisotropic and diffusive media, as well as the mean field problems in random media. For anisotropic magnetodielectric media, asympotic expressions for the radiation field of finite sources are obtained highlighting the excitation of an associated mode along an optic axis. The absorbing boundary conditions on a spherical surface and their approximate version for an arbitrary convex surface are developed.
ABM-V: An Adaptive Backoff Mechanism for Mitigating Broadcast Storm in VANETs

In vehicular ad hoc networks (VANETs), the broadcast storm problem may disable road safety applications and cause congestion or traffic accidents. Existing schemes propose broadcast storm mitigation by reducing the number of relay vehicles. Concurrently, in improving reachability, these schemes stipulate that vehicles expected to transmit packets to more next-hop neighbors have higher relay priority. However, the potential redundancy caused by duplicate reception by neighbors is ignored, which exacerbates the contention and collisions in transmission. This paper proposes an adaptive backoff mechanism for mitigating broadcast storm in VANETs (ABM-V). Specifically, the receiver estimates the expected benefit and redundancy by combining the distribution of neighbors. Then, the receiver adaptively adjusts the backoff time by utilizing Dempster-Shafer evidence theory. Finally, the receiver with the shortest backoff time becomes the relay and rebroadcasts the packet to its neighbors. Simulation results illustrate that ABM-V significantly reduces the rebroadcast ratio and redundancy ratio compared with the existing typical schemes while maintaining stable reachability.
A Novel Multi-Modal Teleoperation of a Humanoid Assistive Robot with Real-Time Motion Mimic

This research shows the development of a teleoperation system with an assistive robot (NAO) through a Kinect V2 sensor, a set of Meta Quest virtual reality glasses, and Nintendo Switch controllers (Joycons), with the use of the Robot Operating System (ROS) framework to implement the communication between devices. In this paper, two interchangeable operating models are proposed. An exclusive controller is used to control the robot’s movement to perform assignments that require long-distance travel. Another teleoperation protocol uses the skeleton joints information readings by the Kinect sensor, the orientation of the Meta Quest, and the button press and thumbstick movements of the Joycons to control the arm joints and head of the assistive robot, and its movement in a limited area. They give image feedback to the operator in the VR glasses in a first-person perspective and retrieve the user’s voice to be spoken by the assistive robot. Results are promising and can be used for educational and therapeutic purposes.
On magnetohydrodynamic solitons in jets

Nonlinear solitary wave propagation in a compressible magnetic beam model of an extragalactic radio jet is examined and shown to lead to solitons of the Benjamin-Ono type. A number of similarities between such magnetic beam models of jets and models of solar photospheric flux tubes are pointed out and exploited. A single soliton has the appearance of a symmetric bulge on the jet which propagates faster than the jet's flow. 35 references.
Development and Test Results of a Dual Compensation Chamber Loop Heat Pipe

A dual compensation chamber loop heat pipe is developed to solve the problem of the relative orientation limit between the evaporator and the compensation chambers. The construction of the evaporator and the compensation chambers is presented. The concurrent design method of the working fluid charge mass and the compensation chamber volumes, that can realize the objectives where, within a certain temperature range, the dual compensation chamber loop heat pipe cannot only start up and operate normally at any orientation, but can also avoid the most difficult startup situation, is introduced. The operation and the thermal control characteristics of the dual compensation chamber loop heat pipe are investigated. Test results indicate that in some heat load regions, the operating temperatures vary with the relative orientation between the evaporator and the compensation chambers. This is explained by the thermal equilibrium of the compensation chamber and the usage efficiency of the return liquid subcooling. The test results and discussion of the dual compensation chamber loop heat pipe suggest that part of the return liquid subcooling that cools the liquid to be locally subcooled must be considered in the mathematical modeling of the loop heat pipe.
Incrementally Contrastive Learning of Homologous and Interclass Features for the Fault Diagnosis of Rolling Element Bearings

Bearing condition is a non-negligible part of mechanical equipment health monitoring. Most of the existing bearing fault diagnosis methods are based on the premise that all data classes are known and lack the capability of incremental diagnosis of fault modes. However, in engineering practice, the initial monitoring data only provide normal condition, and the subsequent data of different classes of faults are collected gradually. To address this practical problem, we propose incremental contrastive learning (CL) of homologous and interclass features for bearing to achieve incremental diagnosis of bearing fault modes from single to multiple classes. Important homologous and interclass features of bearings are first extracted by CL. The obtained features are then employed to establish a distance threshold for the anomaly diagnosis of subsequent samples. Upon appearing anomalies incrementally up to a certain amount, novel classes are upgraded and fed back to the model. In this way, new class data are treated as incremental learning resources. The proposed method was evaluated using both benchmark bearing and gearbox bearing experiments. Results show supreme diagnostic performance compared to peer state-of-the-art approaches. The present method is intrinsic in extracting homologous and interclass features for practical bearing fault diagnostics.
Improving the Pyroelectric Coefficient of Ceramic/Polymer Composite by Doping the Polymer Matrix

To obtain an optimum coupling of the pyroelectric activity of ferroelectric inclusions to the electrodes of a 0–3 composite film, the dielectric constants of matrix material and inclusions would have to be comparable. While there is no way to substantially raise the real part of the dielectric constant of the polymer matrix, the imaginary part can be increased by an appropriate doping. The results from theoretical modelling predict a significant increase of the pyroelectric coefficient and especially the pyroelectric signal power. Experimental investigations on composites of lead titanate particles in polyurethane doped with potassium bromide show the improvement and give hints to further optimization of its pyroelectric performance.