Miracle-dz/UniFAR-FTUs huggingface dataset:
Analysis of 3D head rotations for eye tracking calibration in large computer monitors

In order to operate in the center of the vision field, the computer user maintains a frontal pose with respect to the screen. In this ideal situation, the computer user can visually explore the screen, moving only the eyes. The user activity changes when the computer screen is large, and it is necessary to change the pose and gaze orientation in order to explore the entire screen. The availability of high-end and high-size computer monitors (621mm width, 341mm height, or bigger), improves the possibilities of computer visualization but requires constant head pose changes to be performed by the computer user. In this study, we evaluate the 3D head rotation activity for the process of calibration on eye tracking. We compare the activity data for a fixed zigzag calibration pattern with respect to a random calibration pattern. The results show that the rotation data provide important information about the user screen exploration
Adaptive Fuzzy Superpixels for Polarimetric SAR Images Classification

—The increasing applications of Polarimetric SAR (PolSAR) image classification demand for effective superpixels algorithms. Fuzzy superpixels algorithms reduce the misclassification rate by dividing pixels into superpixels, which are groups of pixels of homogenous appearance, and undetermined pixels. However, two key issues remain to be addressed in designing a fuzzy superpixel algorithm for PolSAR image classification. Firstly, the polarimetric scattering information, which is unique in PolSAR images, is not effectively used. Such information can be utilized to generate superpixels more suitable for PolSAR images. Secondly, the ratio of undetermined pixels is fixed for each image in the existing techniques, ignoring the fact that the difficulty of classifying different objects varies in an image. To address these two issues, we propose a polarimetric scattering information based adaptive fuzzy superpixels (AFS) algorithm for PolSAR images classification. In AFS, the correlation between pixels’ polarimetric scattering information, for the first time, is considered to generate superpixels. This correlation is further used to dynamically and adaptively update the ratio of undetermined pixels. AFS is evaluated extensively against different evaluation metrics and compared with the state-of-the-art superpixels algorithms on three PolSAR images. The experimental results demonstrate the superiority of AFS on PolSAR image classification problems.
Gravitational lensing limits on the cosmological constant in a flat universe

Inflationary cosmological theories predict, and some more general aesthetic criteria suggest, that the large-scale spatial curvature of the universe k should be accurately zero (i.e., flat), a condition which is satisfied when the universe's present mean density and the value of the cosmological constant Lambda have certain pairs of values. Available data on the frequency of multiple image-lensing of high-redshift quasars by galaxies suggest that the cosmological constant cannot make a dominant contribution to producing a flat universe. In particular, if the mean density of the universe is as small as the baryon density inferred from standard cosmic nucleosynthesis calculations or as determined from typical dynamical studies of galaxies and galaxy clusters, then a value of Lambda large enough to produce a k = 0 universe would result in a substantially higher frequency of multiple-image lensing of quasars than has been observed so far. Shortcomings of the available lens data and uncertainties concerning galaxy properties allow some possibility of escaping this conclusion, but systematic searches for a gravitational lenses and continuing investigations of galaxy mass distributions should soon provide decisive information. It is also noted that nonzero-curvature cosmological models can account for the observed frequency of galaxy-quasar lens systems andmore » for a variety of other constraints. 61 refs.« less
Regression-Based Methods for Finding Coupled Patterns

There are a variety of multivariate statistical methods for analyzing the relations between two datasets. Two commonly used methods are canonical correlation analysis (CCA) and maximum covariance analysis (MCA), which find the projections of the data onto coupled patterns with maximum correlation and covariance, respectively. These projections are often used in linear prediction models. Redundancy analysis and principal predictor analysis construct projections that maximize the explained variance and the sum of squared correlations of regression models. This paper shows that the above pattern methods are equivalent to different diagonalizations of the regression between the two datasets. The different diagonalizations are computed using the singular value decomposition of the regression matrix developed using data that are suitably transformed for each method. This common framework for the pattern methods permits easy comparison of their properties. Principal component regression is shown to be a special case of CCA-based regression. A commonly used linear prediction model constructed from MCA patterns does not give a least squares estimate since correlations among MCA predictors are neglected. A variation, denoted least squares estimate (LSE)-MCA, is suggested that uses the same patterns but minimizes squared error. Since the different pattern methods correspond to diagonalizations of the same regression matrix, they all produce the same regression model when a complete set of patterns is used. Different prediction models are obtained when an incomplete set of patterns is used, with each method optimizing different properties of the regression. Some key points are illustrated in two idealized examples, and the methods are applied to statistical downscaling of rainfall over the northeast of Brazil.
A Comment on “On Density-dependent and Temperature-dependent Ground-State and Continuum Effects in the Equation of State for Stellar Interiors”

Misunderstandings have occurred regarding the conclusions of the paper "On Density-dependent and Temperature-dependent Ground-State and Continuum Effects in the Equation of State for Stellar Interiors" by S. Arndt, W. Däppen, & A. Nayfonov (1998, ApJ, 498, 349). On occasion, its results have been interpreted as if it showed basic flaws in the general theory of dynamical screening. The aim of this comment is to emphasize the context in which the conclusions of the paper must be understood in order to avoid misinterpretations.
On variable structure output feedback controllers

In a recent work by Zak-Hui (1993), a sliding-mode controller for MIMO systems using static output feedback was proposed. Very nice geometric conditions for how to design sliding surfaces were given. However, there are two restrictive assumptions in it. One is that the uncertainties in the system must be bounded by a known function of outputs which excludes some possible uncertainties in the A matrix if the system is described by the triple (A, B, C). The other one requires a matrix equality to be held which may also be very difficult to satisfy in many systems. In this paper, we propose a modification of the sliding mode controller for a class of single-input/single-output (SISO) systems which can eliminate the above-mentioned limitations and, under certain conditions, guarantee global closed-loop stability. Hence the range of applicability of Zak-Hui's method can be greatly broadened.
A computational code for two-dimensional unsteady magnetohydrodynamics by the method of characteristics

A computational code for solving two-dimensional, time-dependent MHD equations by the method of characteristics is presented. Its capabilities are demonstrated by solving two very different problems for which analytical solutions exist: linearized, standing MHD wave motions in a magnetized cylindrical plasma, and nonlinear self-similar expansion of a magnetized plasma ball. The nonlinear development of standing MHD wave solutions in a cylindrical plasma is also studied. The method can be naturally embedded in the computational architecture of massively parallel processors. 23 references.
Doping effects of C, Si and Ge in wurtzite [0001] GaN, AlN, and InN nanowires

We have performed an ab initio investigation, within the spin-polarized density functional theory, of the energetic stability and electronic properties of substitutional Si, Ge, and C impurities in [0001] GaN, AlN, and InN nanowires (NWs). Our total energy results show that C impurities in the cation site (CGa, CAl, and CIn) present lower formation energies at the surface of the NWs as compared to their counterparts in the core of the NW or the bulk system. In these position donor likely properties are obtained for GaN and InN NWs, whereas for the AlN NW deep levels are observed inside the bandgap. In contrast, CN must be distributed uniformly along the NW diameter and gives rise to a deep electronic level inside the NW bandgap. Si in GaN and InN and Ge in InN are most stable at the cation site in the core of the NWs, and lead the systems to show a n-type semiconductor properties. For the AlN NW we obtain that Si and Ge are most likely in a N site at the surface of the NW and introduce deep levels inside .
The Heaviside-Feynman expression for the fields of an accelerated dipole

The fields due to an accelerated dipole are calculated using straightforward electromagnetic theory. It is shown that the potentials and fields may be written so that the static field, its first correction and the radiation field are separated. The expression for the fields and potentials is therefore analogous to the expression for the field of a point charge discovered by Heaviside and Feynman.
Unsteady lift for the Wagner problem in the presence of additional leading/trailing edge vortices

This study amends the inviscid Wagner lift model for starting flow at relatively large angles of attack to account for the influence of additional leading edge and trailing edge vortices. Two methods are provided for starting flow of a flat plate. The first method is a modified Wagner function, which assumes a planar trajectory of the trailing edge vortex sheet accounting for a temporal offset from the original Wagner function given release of leading edge vortices and a concentrated starting point vortex at the initiation of motion. The second method idealizes the trailing edge sheet as a series of discrete vortices released sequentially. The models presented are shown to be in good agreement with high-fidelity simulations. Through the present theory, a vortex force line map is generated, which clearly indicates lift enhancing and reducing directions and, when coupled with streamlines, allows one to qualitatively interpret the effect of the sign and position of vortices on the lift and to identify the origins of lift oscillations and peaks. It is concluded that leading edge vortices close to the leading edge elevate the Wagner lift curve while a strong leading edge vortex convected to the trailing edge is detrimental to lift production by inducing a strong trailing edge vortex moving in the lift reducing direction. The vortex force line map can be employed to understand the effect of the different vortices in other situations and may be used to improve vortex control to enhance or reduce the lift.
Formation of the slow solar wind in a coronal streamer

We have investigated a magnetohydrodynamic mechanism that accounts for several fundamental properties of the slow solar wind, in particular its variability, latitudinal extent, and bulk acceleration. In view of the well-established association between the streamer belt and the slow wind, our model begins with a simplified representation of a streamer beyond the underlying coronal helmet: a neutral sheet embedded in a plane fluid wake. This wake-neutral sheet configuration is characterized by two parameters that vary with distance from the Sun: the ratio of the cross-stream velocity scale to the neutral sheet width, and the ratio of the typical Alfven velocity to the typical flow speed far from the neutral sheet. Depending on the values of these parameters, our linear theory predicts that three kinds of instability can develop when this system is perturbed: a tearing instability and two ideal fluid instabilities with different cross-stream symmetries (varicose and sinuous). In the innermost, magnetically dominated region beyond the helmet cusp, we find that the streamer is resistively and ideally unstable, evolving from tearing-type reconnection in the linear regime to a nonlinear varicose fluid instability. Traveling magnetic islands are formed which are similar to features recently revealed by the large-angle spectroscopic coronagraph on the joint European Space Agency/NASA Solar and Heliospheric Observatory (SOHO) [Brueckner et al., 1995]. During this process, the center of the wake is accelerated and broadened slightly. Past the Alfven point, where the kinetic energy exceeds the magnetic energy, the tearing mode is suppressed, but an ideal sinuous fluid mode can develop, producing additional acceleration up to typical slow wind speeds and substantial broadening of the wake. Farther from the Sun, the system becomes highly turbulent as a result of the development of ideal secondary instabilities, thus halting the acceleration and producing strong filamentation throughout the core of the wake. We discuss the implications of this model for the origin and evolution of the slow solar wind, and compare the predicted properties with current observations from SOHO.
An overview of a multiobjective heuristic search algorithm for AND/OR graphs

We develop and analyze a heuristic search algorithm that determines the nondominated set of solution graphs for a multiobjective AND/OR graph. This algorithm, MOAO*, is a multiobjective generalization of AO*. MOAO* uses sets of vector-valued heuristic estimates to give guidance to the search. We show that MOAO* satisfies termination, completeness, and admissibility conditions, generalizing results associated with AO*. Further, we prove that if the heuristic sets satisfy a monotonicity condition, then MOAO* possesses an efficiency property reminiscent of a well-known result associated with A*. <<ETX>>
Circuit size optimization with multiple sources of variation and position dependant correlation

The growing impact of process variation on circuit performance requires statistical design approaches in which circuits are designed and optimized subject to an estimated variation. Previous work [1] has shown that by including extra margins in each of the gate delays and optimizing the gate sizes, the circuit delay variation can be reduced by half. Our work goes further by deploying extended models that include delay variations due to Vth and Leff, as well as position dependant variation. Two types of models have been proposed to account for various variations: 1) a model that explicitly adds spatial correlation terms to the design objective; 2) a model that implicitly includes such effect through the use of a modified version of Pelgrom's model. These design models are used to size a 32-bit Ladner-Fischer adder and the circuit delay distributions are obtained from Monte Carlo simulations. The analysis shows that both types of models have a noticeable performance improvements over the model presented in [1]. In addition, the second model appears to be a more adequate method for modeling various variation components and has a better performance over the first model; the drawback is a more complicated object function.
System identification based on wavelet packets decomposition

This paper is concerned with a new system identification approach based on the wavelet packets (WP) decomposition. The impulse response in the WP transform domain is estimated by using the least squares (LS) method by use of the transformed input/output data. Then the estimate of the original impulse response can be reconstructed from the estimate in the transform domain by using the property of the inverse WP transform. The mean square error (MSE) is evaluated and investigated, then it is clarified that the MSE can be minimized by an optimal choice of the resolution level and the packets. Therefore, it will be very effective in ill-conditioned system identification using a band-limited input signal.
Design of complex large-scale photonic integrated circuits (PICs) based on ring-resonator structures

The exponentially growing number of components in complex large-scale Photonic Integrated Circuits (PICs) requires the necessity of photonic design tools with system-level abstraction, which are efficient for designs enclosing hundreds of elements. Ring-resonators and derived structures represent one example for large-scale photonics integration. Their characteristics can be parameterized in the frequency-domain and described by scattering matrix (S-matrix) parameters. The S-matrix method allows time efficient numerical simulations, decreasing the simulation time by several orders of magnitude compared to time-domain approaches yielding a better modeling accuracy as the number of PIC elements increases. We present the modeling of optical waveguides within a sophisticated design environment using application examples that contain ring-resonators as fundamental structure. In the models, the two orthogonally polarized guided modes are characterized by their specific index and loss parameters. Systematic variation of circuit parameters, such as coupling factor or refractive index, allows a comfortable design, analysis and optimization of many types of complex integrated photonic structures.
Low-crosstalk fabrication-insensitive echelle grating multiplexers and passives for the silicon photonics toolbox

In this communication, we report about the design, fabrication, and testing of echelle grating (de-)multiplexers for the 100GBASE-LR4 norm and other passive architectures such as vertical fiber-couplers and slow-wave waveguides in the O-band (1.31-μm) for Silicon-based photonic integrated circuits (Si-PICs). In detail, two-point stigmatic 20th-order echelle gratings (TPSGs) on the 300-nm-thick SOI platform designed for 4x800-GHz-spaced wavelength division multiplexing featuring extremely low crosstalk (< -30 dB), precise channel spacing and optimized average insertion losses (~ 3 dB) are presented. Distributed Bragg reflectors (DBRs) are used to improve the grating facets reflectivity, while multi-mode interferometers (MMIs) are used in optimized perfectly-chirped echelle gratings (PCGs) for pass-band flattening. Moreover, 200-mm CMOS pilot lines processing tools including VISTEC variable-shape e-beam lithography are employed for the fabrication. In addition, wafer-level statistics of the multiplexers clearly shows the echelle grating to be inherently fabrication-insensitive to processing drifts, resulting in a minimized dispersion of the multiplexer performances over the wafer. In particular, the echelle grating spectral response remains stable over the wafer in terms of crosstalk, channel spacing and bandwidth, with the wavelength dispersion of the filter comb being limited to just 0.8 nm, thus highlighting the intrinsic robustness of design, fab pathways as well as the reliability of modeling tools. As well as that, apodized one-dimensional vertical fiber couplers, optimized multi-mode interferometers (MMIs) and extremely low-losses slow-light waveguides are demonstrated and discussed. The adiabatic apodization of such 1-D gratings is capable to provide band-edge group indices ng as high as 30 with propagation losses equivalent to the indexlike propagation regime.
An inverse problem for higher order differential operators on star-type graphs

We study an inverse spectral problem for arbitrary order ordinary differential equations on compact star-type graphs. As the main spectral characteristics we introduce and study the so-called Weyl-type matrices which are a generalization of the Weyl function (m-function) for the classical Sturm–Liouville operator. We provide a procedure for constructing the solution of the inverse problem and prove its uniqueness.
The Critical Mass for Protoplanets Revisited: Massive Envelopes through Convection

Abstract According to the nucleated instability hypothesis giant planets form by accreting planetesimals onto a core. As the core's gravity increases, gas from the solar nebula is attracted and the protogiant planet approaches a "critical" mass. Previous investigations found the values of the critical core and envelope masses to be insensitive to the outer boundary conditions. This is a consequence of the radiative stratification of their outer envelopes. This article shows that (a) some of the outer envelopes of published critical mass protoplanets are close to convective instability; (b) they become convectively unstable for properties of proposed solar nebula models. (c) The critical core and envelope masses for protoplanets with convective outer envelopes depend on the outer boundary conditions. (d) Critical mass protogiant planets with solar composition envelopes and "interstellar" dust opacities may have masses up to 60 earth masses (12 in the core). (e) Along a sequence with increasing solar nebula density the critical mass models become increasingly convective and justify (f) an analytical model for fully convective protogiant planets which explicitly shows the dependence of the critical mass on the outer boundary conditions. I propose two classes of protogiant planets: (1) a class with radiative outer envelopes and a constant M core / M tot ratio at the critical mass and (2) a class with convective outer envelopes having a wide range (5-48 earth masses for the parameter range explored in this article) of critical envelope masses. The main difference of this new class to the fully convective models of F. Perri and A. G. W. Cameron (1974, Icarus 22, 416-425) lies in the opacity gap, where the stratification always remains radiative.
The solar flare myth

Many years of research have demonstrated that large, nonrecurrent geomagnetic storms, shock wave disturbances in the solar wind, and energetic particle events in interplanetary space often occur in close association with large solar flares. This result has led to a paradigm of cause and effect - that large solar flares are the fundamental cause of these events in the near-Earth space environment. This paradigm, which the author calls, {open_quotes}the solar flare myth,{close_quotes} dominates the popular perception of the relationship between solar activity and interplanetary and geomagnetic events and has provided much of the pragmatic rationale for the study of the solar flare phenomenon. Yet there is good evidence that this paradigm is wrong and that flares do not generally play a central role in producing major transient disturbances in the near-Earth space environment. In this paper the author outlines a different paradigm of cause and effect that removes solar flares from their central position in the chain of events leading from the Sun to near-Earth space. Instead, this central role is given to events known as coronal mass ejections. 85 refs., 16 figs., 3 tabs.