Miracle-dz/UniFAR-FTUs huggingface dataset:
On the Nonparametric Estimation of Covariance Functions

We describe kernel methods for estimating the covariance function of a stationary stochastic process, and show how to ensure that the estimator has the positive semidefiniteness property. From a practical viewpoint, our method is significant because it does not demand a parametric model for covariance. From a technical angle, our results exhibit a striking departure from those in more familiar cases of kernel estimation. For example, in the context of covariance estimation, kernel estimators can have the same convergence rates as maximum likelihood estimators, and can have exceptionally fast convergence rates when employed to estimate variance
Tellurite glasses for ultrabroadband fiber Raman amplifiers

Tellurite glasses optimized for higher Raman gain and broad bandwidth have been realized. These glasses were found to have improved thermal stabilities, which make them suitable for fiber devices applications. While maintaining the Raman gains at higher values, the Raman bandwidths could be broadened by proper addition of alkaline earth oxides and heavy metal oxides in to the tellurite glasses. The relative Raman gain and Raman cross sections of the present glasses are better than the tellurite-based glasses reported earlier. Thus, higher Raman gain and much broader Raman amplifications could be possible by using this tellurite glass system as a gain medium compared with the conventional tellurite-based fiber Raman amplifiers.
Image segmentation using watersheds and normalized cuts

The normalized cut algorithm is a graph partitioning algorithm that has previously been used successfully for image segmentation. It is originally applied to pixels by considering each pixel in the image as a node in the graph. In this paper we investigate the feasibility of applying the normalized cut algorithm to micro segments by considering each micro segment as a node in the graph. This will severely reduce the computational demand of the normalized cut algorithm, due to the reduction of the number of nodes in the graph. The foundation of the translation to micro segments will be the region adjacency graph. A floating point based rainfalling watershed algorithm will create the initial micro segmentation. We will first explain the rainfalling watershed algorithm. Then we will review the original normalized cut algorithm for image segmentation and describe the changes that are needed when we apply the normalized cut algorithm to micro segments. We investigate the noise robustness of the complete segmentation algorithm on an artificial image and show the results we obtained on photographic images. We also illustrate the computational demand reduction by comparing the running times.
Variable structure model reference adaptive control using only input and output measurements

Abstract A variable structure model reference adaptive controller (VS-MRAC) using only the input and output measurements of the plant is proposed. Stability and transient properties are analysed and discussed. Remarkable transient behaviour is revealed, in particular, model following can be perfectly achieved in a finite time. The effect of plant input disturbance is investigated and the performance of the VS controller is also shown to be qualitatively superior to that obtained with (conventional) integral adaptation algorithms. A link between the VS-MRAC and the conventional MRAC is suggested. Simulations are presented to highlight the theoretical results.
Rigid Body Orientation Analysis Model Based on Stereo Vision

In order to satisfy the orientation measuring requirements of rigid-body such as work piece, cutting tool in industry, the paper presents a binocular vision detection technique based on spatial position information of markers to extract rigid-body pose information and analyzes the pose accuracy of rigid-body using the principal component analysis (PCA) when spatial position error of markers exist. The simulation experiment demonstrates the maximum angle error of orientation is about 0.59 degree when the position error of markers satisfy the Gaussian distribution with the mean is zero and the standard deviation is 0~3mm. The experimental results verify this method can robustly solve the orientation of rigid body using the position information of markers with position errors, and it provides a theoretical and experimental basis for orientation measurement of rigid body.
Neutron and X-ray Scattering Studies of Relaxors

The extensive and wide-ranging neutron and x-ray scattering studies of relaxors carried out by Gen Shirane and his collaborators are reviewed. Among the many results they have reported in some 50 scientific papers published since 1999, there are three especially notable accomplishments; namely, the discovery of a monoclinic phase near the morphotropic phase boundary, the clarification of the existence and roles of transverse optic soft-mode phonons, and detailed studies of polar nanoregions particularly by diffuse scattering techniques. We will focus mostly on the above topics, and discuss the impact of these on the research and understanding of relaxors.
Optical monitoring of the quasar 4C 38.41

The results of a photometric monitoring of the quasar 4C 38.41, performed at the optical R and B bands in 2002 February-March, are presented. With a 60/90 cm Schmidt telescope at the Xinglong station of the National Astronomical Observatories of China, we observed the source exhibiting amplitude variations of up to 0.78 mag in both bands during the whole campaign. Intraday and even intranight variations are detected as well. A typical variability time-scale of about 36 d is derived from our 2-month observations at the optical bands, which is identical to that found at a radio wavelength of 92 cm, suggesting a common origin for the variations in 4C 38.41 from optical to radio bands.
When will Voyager 1 and 2 cross the termination shock?

Our Solar System moves through a warm (∼6,500 K), partly ionized local interstellar cloud (LIC) with a relative speed of ∼26 km/s. The solar wind interacts with the LIC to form a cavity around the Sun called the heliosphere. The solar wind meets the interstellar charged component at the heliopause, where solar wind pressure balances the pressure of the LIC. Before reaching the heliopause, the supersonic solar wind is decelerated at an extended shock wave, the heliospheric termination shock (TS). The two Voyager spacecraft are cruising away from the Sun and approaching the termination shock. Here we present predictions of when the Voyagers will encounter the termination shock by calculating the position of the TS using a numerical multi‐component model of the heliospheric interface and improved measurements of interstellar H atoms. Interstellar atoms penetrate into the heliosphere where they are ionized and detected as pickup ions by the SWICS instrument on Ulysses. We conclude that the most probable crossing of the termination shock by Voyager 1 will occur between 2007 and 2012.
Quasimonoenergetic GeV electron bunch generation by the wake-field of the chirped laser pulse

One-dimensional nonlinear analysis of wake-field generation and electron bunch acceleration by a chirped laser pulse were investigated numerically. It was found that the optimum linear chirp parameter leads to the wake-field amplitude increase by one order of magnitude and accordingly the acceleration gradient. In our external injection scheme, electrons were accelerated using the initial energy of 100 KeV (γin=1.2). When the pulse passes through the electron bunch most part of the electrons trapped in the first cycle of the laser wake-field and accelerate to about 1 GeV in 1.8 mm. We concluded that the expensive electron preacceleration mechanism could be omitted in a laser-aided electron acceleration scheme.
A Millimeter-Wave E-Plane Band-pass Filter using Multilayer Low Temperature Co-Fired Ceramic (LTCC) Technology

This paper presents a substrate integrated waveguide (SIW)-based millimeter-wave E-plane band-pass filter (BPF) with multilayer Low Temperature Co-fired Ceramic (LTCC) technology. The vertical metal walls of SIW and metal fins of the evanescent waveguides are realized by closely spacing metallic via-holes. A three-order Chebyshev E-plane BPF is developed and verified by full-wave simulation. The proposed filter is fabricated using LTCC technology, and a tapered line is designed as the transition between the SIW and microstrip line. Good agreement between simulated and measured results is observed.
Initialization, distances and local minima in audio applications of the non‐negative matrix factorization

The use of the non‐negative matrix factorization (NMF) as a decomposition technique has dramatically grown in various signal processing applications over the last years. Its computation, based on the iterative minimization of a cost function, relies on several choices, among which the distance involved in the cost function itself but also the initialization of the algorithm. These choices are all the more crucial as the usual algorithms, iterative, only ensure convergence to a local minimum. In this work, we compare three typical distances in the NMF problem (namely Euclidian, Kullback‐Leibler divergence and Itakura‐Saito distance) and their combination with different initializations, in an audio context: decomposition of the time‐frequency representation for the transcription of polyphonic music. Both the existence of global and local minima, and the efficiency of transcription are examined. Moreover, NMF update rules can be formulated in a unified framework for the three aforementioned cost functions. T.
Reflection at Free Surface in Micropolar Thermoelastic Solid with two Temperatures

The present investigation is concerned with the effect of two temperatures on reflection coefficients in a micropolar thermoelastic solid half space. With two relaxation times, reflection of plane waves impinging obliquely at a plane interface of the micropolar generalized thermoelastic solid half space with two temperatures is investigated. The incident wave is assumed to be striking at the plane surface after propagating through the micropolar generalized thermoelastic solid with two temperatures. Amplitude ratios of the various reflected waves are obtained in closed form and it is found that these are functions of angle of incidence, frequency and are affected by the elastic properties of the media. The effect of two temperatures is shown on these amplitude ratios for a specific model.
Theoretical model of Saturn's kilometric radiation spectrum

A theoretical model is developed here in order to determine an envelope for the average spectrum of the Saturnian kilometric radiation (SKR). The microscopic generation mechanism is supposed to be the so-called synchrotron (or cyclotron) maser instability. As in recent works on the terrestrial kilometric radiation, the effect of the magnetic field inhomogeneity on the generation process must be taken into account. Then, assuming that the emission is nonlinearly saturated by trapping, the calculation allows the authors to put an upper limit on the SKR spectral intensity very simply: the maximum level of the wave electric field within the source region is indeed linked to a few macroscopic plasma parameters, which can be derived from the observations (the structure of the magnetospheric magnetic field, the cold plasma density, and the characteristic energy of the hot emitting electrons). They have used a dipolar magnetic field model, while the plasma distribution results from the superposition of two components, an ionospheric population and a plasma disc, whose scale heights have been roughly determined from Voyager measurements. The energetic electrons responsible for the emission are supposed to precipitate along the high-latitude magnetic field lines where SKR emission is known to take place. The widthmore » of the source region can be self-consistently estimated from the model. A very good agreement is obtained between the theoretical spectrum and the observational radio data. The calculated spectral intensities exceed the most intense observed intensities by up to 1 order of magnitude, suggesting that the SKR emission is only marginally saturated by nonlinear processes. « less
Determination of local transport coefficients by heat flux analysis and comparisons with theoretical models

The energy confinement properties of different regimes of JET plasmas are investigated. The results of local transport analysis in both L- and H-mode regimes are discussed and the properties of H-mode plasmas produced by neutral beam injection and/or ion cyclotron resonance heating are compared. Two aspects of transport analysis are addressed. Firstly, the relative importance of the electron and ion heat conductivities and a comparison with the effective particle diffusivity since this determines the nature of the turbulence responsible for the degradation in confinement. The second issue is whether theoretical models adequately describe the radial dependence of the measured heat flux. Several theoretical models are considered: the ion temperature gradient driven turbulence model, the Rebut-Lallia critical temperature gradient model, the dissipative and collisionless trapped electron drift wave mode, the Carreras-Diamond resistive ballooning model and the neoclassical pressure gradient driven turbulence model.
Temporal Summation and Backward Masking

Appropriate transformations based on the theory of temporal summation were used to determine backward masking as a function of the time interval between the onset of a 1000‐cps tone and the onset of 40‐, 60‐, and 80‐dB narrow‐band noise bursts that partially masked the tone. It was shown that under these experimental conditions backward masking consists of at least three phases: (1) a short phase immediately preceding the onset of the masking sound in which threshold is determined by the level of the masker; (2) a long phase in which threshold is independent of the level of the masker; and (3) a transition phase that lies between the short and long phases. The short phase and the transition phase each last about 25 msec, while the long phase extends from 50 to about 200 msec ahead of the masking sound. It was also shown that the theory of temporal summation is sufficient to predict threshold differences during the long phase of backward masking, and probably during the short phase also. During the transition phase, however, the threshold for tones does not vary as a function of their duration.
Newcomb: a scientific interferometry mission at low cost

Newcomb is a design concept for an astrometric optical interferometer with nominal single-measurement accuracy of 100 microseconds of arc ((mu) as). In a 30-month mission life, it will make scientifically interesting measurements of O-star, RR Lyrae, and Cepheid distances, probe the dark matter in our Galaxy via parallax measurements of K giants in the disk, establish a reference grid with internal consistency better than 50 (mu) as, and lay groundwork for the larger optical interferometers that are expected to produce a profusion of scientific results during the next century. With an extended mission life, Newcomb could do a useful search for other planetary systems.
Uncertainty of total solar irradiance: an assessment of the last twenty years of space radiometry

A complete set of total solar irradiance measurements from space is available dating from November 1978, yielding a time series of more than twenty years. From measurements made by different space radiometers (HF on NIMBUS-7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on SOHO) a composite record of solar total irradiance can be compiled. The corrections needed for each radiometer, mainly to compensate for degradation, are based on a detailed study of the behaviour of the VIRGO (Variability of Solar Irradiance and Gravity Oscillations) radiometers. Moreover, several errors arising from operational changes or interruptions, which influence the overall uncertainty more than corrections for degradation, have to be corrected. A composite of the corrected time series is constructed in order to estimate the long-term stability, which is much better than the estimated 1 part in 105 per annum deduced as an upper limit from VIRGO radiometry. The absolute accuracy of the data, however, is more difficult to estimate.
Coding Choices for Textual Analysis: A Comparison of Content Analysis and Map Analysis

Content and map analysis, procedures for coding and understanding texts, are described and contrasted. Where content analysis focuses on the extraction of concepts from texts, map analysis focuses on the extraction of both concepts and the relationships among them. Map analysis thus subsumes content analysis. Coding choices that must be made prior to employing content-analytic procedures are enumerated, as are additional coding choices necessary for employing map-analytic procedures. The discussion focuses on general issues that transcend specific software procedures for coding texts from either a content-analytic or map-analytic perspective.
New Approach for the Evolution and Expansion of Space Debris Scenario

The evolution of the space debris scenario consisting of a very large number of fragments is described using the propagation of the characteristics of equivalent fragments without propagating each and every individual debris fragment. This is similar to characterizing a fluid in terms of the average density, pressure, and temperature without considering the velocities of individual molecules in a fluid element. The space debris fragments are assigned to a three-dimensional bin of semimajor axis, eccentricity, and ballistic coefficient. A suitably defined representative semimajor axis, eccentricity, and an equivalent ballistic coefficient (a, e, B) are defined for the equivalent fragments in each of the bins.Aconstant gain Kalman filtering technique based on 1) propagating the above characteristics, and 2) updating them as and when further measurements become available, has been proposed. Further the assimilation of the information from other breakups with the passage of time is also possible. The robustness of the constant Kalman gain approach instead of using the Kalman filter statistics helps to handle better the unmodeled or unmodelable errors due to the finite bin size and the environmental perturbations. This methodology is also suggested to handle massive atmospheric data assimilation problems.
Radial distribution of space-charge force in compensated positive-ion beams (invited)

The space-charge compensated state of drifting dc beams of He+ ions of 10 keV ion energy and 0.14 and 1.5 mA current was determined with an electron beam probe, a rf resonance probe, the analysis of residual gas ion energies, and emittance measurement. The results are compatible with a basic model describing a two-dimensional multiplicity of possible self-consistent radial density distributions of beam ions, residual gas ions, and compensating electrons. The effects of electron drainage and beam current oscillations on space-charge compensation are pointed out.
On the number of real roots of a random algebraic equation

Abstract Let Nn(ω) be the number of real roots of the random algebraic equation Σnv = 0 avξv (ω)xv = 0, where the ξv(ω)'s are independent, identically distributed random variables belonging to the domain of attraction of the normal law with mean zero and P{ξv(ω) ≠ 0} > 0; also the av 's are nonzero real numbers such that (kn/tn) = 0(log n) where kn = max0≤v≤n |av| and tn = min0≤v≤n |av|. It is shown that for any sequence of positive constants (εn, n ≥ 0) satisfying εn → 0 and ε2nlog n → ∞ there is a positive constant μ so that for all n0 sufficiently large.
Iris image selection and localization based on analysis of specular reflection

We present a method for selecting good quality iris images from a sequence based on the position and quality of the specular reflection relative to the pupil. Using a simple low complexity yet robust technique, fast image selection is achieved along with immediate iris localization. Initial screening is achieved by accepting images with appropriate specular reflection intensity, width, height and area. Finer selection is then based on graylevel changes between light-pupil and pupil-iris regions. The method has been evaluated on numerous problem images and all were correctly rejected. Connected-component algorithms are used to find exact pupil boundaries and iris edges are modeled by ellipses based on left-right segmented boundaries. On a test set of 400 classes consisting of over 60000 images, no false acceptances are noted.
Biaxial strain effect on the electronic and magnetic phase transitions in double perovskite La2FeMnO6: A first-principles study

The influence of biaxial strain on both the electronic and magnetic properties in double perovskite La2FeMnO6 is investigated by using density-functional calculations. The results show that La2FeMnO6 exhibits ferromagnetic semiconductor at ambient condition and turns into ferromagnetic half-metal under the whole tensile strain applied in this work, while the compound transfers into ferromagnetic metal under the compressive strain within −8% and into ferrimagnetic semiconductor with the compressive strain beyond −9%. For both ferromagnetic half-metallic and metallic La2FeMnO6, they exhibit very slight change in the electronic states and magnetic moments of the ions, comparing with those of the compound at ambient condition. The electronic configurations of Fe and Mn originating from the high-spin state Fe3+ and intermediate-spin state Mn3+ in ferromagnetic La2FeMnO6 emerge in the low-spin state and high-spin state in ferrimagnetic La2FeMnO6, respectively, when the compressive strain is beyond −9%.
Coupling and option price comparisons in a jump-diffusion model

In this paper, we examine the dependence of option prices in a general jump-diffusion model on the choice of martingale pricing measure. Since the model is incomplete, there are many equivalent martingale measures. Each of these measures corresponds to a choice for the market price of diffusion risk and the market price of jump risk. Our main result is to show that for convex payoffs, the option price is increasing in the jump-risk parameter. We apply this result to deduce general inequalities, comparing the prices of contingent claims under various martingale measures, which have been proposed in the literature as candidate pricing measures. Our proofs are based on couplings of stochastic processes. If there is only one possible jump size then we are able to utilize a second coupling to extend our results to include stochastic jump intensities.
Decoherence recuperating fast environmental dynamics

We examine the exact internal decoherence dynamics of a qubit in an isolated Josephson charge-qubit quantum computer in the presence of one- and two-body static internal imperfections. By help of open system dynamics quantifiers, i.e. purity, fidelity, covariance and Loschmidt echo, we distinguish between non-unitary and unitary components of internal decoherence dynamics and show that the non-unitary component consists of two processes: system-environment entanglement and incoherence. Our results indicate that the incoherence process is the major source of internal decoherence rather than system-environment entanglement. We find that strong one-body intra–environmental interactions, which generate fast environmental dynamics, result in a rapid suppression of decoherence induced by both system–environment entanglement and incoherence processes. We explain the mechanisms of suppression of decoherence for these two processes and discuss our results.