Miracle-dz/UniFAR-FTUs huggingface dataset:
Ion beam neutralization and properties of plasmas from low power ring cusp ion thrusters

The design and operation modes of a small, low power ion plasma thruster and the properties of the emitted plasma plumes are discussed. The ion beam is extracted from a primary plasma produced by a stationary low pressure electric discharge where the ion production rate is essentially determined by the discharge current. The experiments evidence that the electron neutralization current controls the space charge levels of the outgoing ion current and also influences the spatial properties of emitted plasmas. The electron plasma density increases with the discharge and the electron neutralization currents, while decreases as the plasma plume expands. However, the corresponding electron temperatures decrease when the electron neutralization currents increments. The collisional origin of this electron cooling effect is excluded because of the large collisional mean free paths involved. Then, these electron energy losses during the neutralization of the ion beam would be caused by more subtle physical mechanis.
Superficial changes on the Inconel 600 superalloy by picosecond Nd:YAG laser operating at 1064, 532, and 266 nm: Comparative study

AbstractA comparative study of superficial changes on the superalloy Inconel 600, induced by a picosecond Nd:YAG laseroperating at 1064, 532, and 266 nm, is presented. All of the laser wavelengths, as well as the used fluences of 2.5(1064 nm), 4.3 (532 nm), and 0.6 J/cm 2 (266 nm) were found to be adequate for inducing surface variations. Quitedifferent surface features were produced depending on the laser wavelength used. The measured surface damagethresholds were 0.25, 0.13 and 0.10 J/cm 2 for 1064, 532, and 266 nm, respectively. Drastic differences, in function ofthe wavelength used, were recorded for the crater depths, as well the appearance of hydrodynamic effects and periodicsurface structures. Differences in crater depths were explained via an easier propagation of the first harmonic laserradiation (1064 nm) through the ejected material and plasma compared to a radiation at 532 and 266 nm. Finally,changes in the surface oxygen content caused by ultrashort laser pulses were considered.Keywords: Laser ablation; Periodic surface structures; superalloy Inconel; Surface morphology
Microstructural, Electrical Properties and Temperature Stability of Resonant Frequency in Pb(Ni1/2W1/2)O3–Pb(Mn1/3Nb2/3)O3–Pb(Zr, Ti)O3 Ceramics for High-Power Piezoelectric Transformer

Piezoelectric properties of Pb1-aSra(Ni1/2W1/2)0.02(Mn1/3Nb2/3)b(Zrx, Tiy)1-0.02-bO3) ceramics, to which 0.5 wt% PbO, 0.3 wt% Fe2O3 and 0.25 wt% CeO2 were added, were investigated at different compositions of a=0–0.06, b=0.05–0.09, x=0.49–0.51, and y=0.49–0.51. In the ceramics with a constant composition of a=0 and b=0.07, mechanical quality factor, coercive field and Curie temperature increased with the decrease in Zr/Ti ratio due to the increase in tetragonality. With the increase of PMN mol% at a=0, x=0.51, and y=0.49 composition, grain size decreased and coercive field increased. At the composition of b=0.07, x=0.51, and y=0.49, the dielectric constant and mechanical quality factor increased while the Curie temperature and coercive field decreased with the amount of Sr. Taking into consideration the dielectric constant of 1,680, the mechanical quality factor of 1,814, and the temperature stability of the resonant frequency TCfr of 88, it was concluded that the ceramics with the composition of a=0.06, b=0.07, x=0.51, and y=0.49 were best for the high-power piezoelectric transformer application.
Topological dynamics and ergodic theory

Abstract It is shown that when viewed properly some concepts in topological dynamics and ergodic theory are not merely analogous but equivalent. Also the Mackey-Halmos-von Neumann theorem on ergodic processes with discrete spectrum is generalized and an account of the Mackey-Zimmer theory of minimal cocycles is given in a more general setting.
A Laser Projection Device for Locating Points on the Plane Object

Digital image processing technology can extract the main feature of an image. In order to achieve the interaction between virtual points and plane objects, we propose the equipment for indicating points on the plane object using laser projection. We designed the equipment with a bracket, stepper motor, two-dimensional turntable, PC control unit, and a laser pointer. Next, we analyzed the mathematical model of the equipment and developed an algorithm for solving the motor rotation angle. Finally, we verified our design with an image. Here, we develop a system that can control a laser projection to a specified location by adjusting coordinates of virtual points on a computer.
Empirical Likelihood for Efficient Semiparametric Average Treatment Effects

This article considers empirical likelihood in the context of efficient semiparametric estimators of average treatment effects. It shows that the empirical likelihood ratio converges to a nonstandard distribution, and proposes a corrected test statistic that is asymptotically chi-squared. A small Monte Carlo experiment suggests that the corrected empirical likelihood ratio statistic has competitive finite sample properties. The results of the article are applied to estimate the environmental effect of the World Trade Organisation.
An approach to direct selection of best subset ar model

Best subset AR models involve computationally intensive exhaustive search techniques. The aim of this paper is to avoid such computationally intensive exhaustive search procedures for obtaining best subset AR models. A methodology was proposed (Sarkar and Kanjilal, 1995) using singular value decomposition (SVD) and orthonormal with column pivoting factorisation (QRcp) for extracting a reduced subset from an exhaustive candidate set of regressors. Here the spurious regressor variables from this set are identified and eliminated by a test of significance based on the asymptotic normality of the maximum likelihood estimates (m.l.e) of themodel parameters and a model selection information criterion. This method obtains subset AR models directly and efficiently. Fitting procedure is demonstrated with a simulated series and some important real life time series. Some subset models have been found to generate better forecasts than their respective full models.
On some hyperbolic equations with operator coefficients

1. We consider first the class of singular Cauchy problems for u e C(E) on [0, T]. (1.1) u+(2m+l) coth t u? +m(m+l)u=Au (1.2) u(0) u0 u(0) 0 where u0 e E is given and A is the generator of a locally equicontinuous group T(t)= exp At in a complete locally convex Hausdorff space E (cf. [9]). When A is replaced by the Laplace-Beltrami operator /in function spaces E over M=SL(2, R)/S0(2) and m>0 is an integer, these equations arise in a canonical way from certain Lie group theoretic considerations and are parallel to the corresponding Euler-PoissonDarboux (EPD) equations (cf. [2], [4], [10]); in fact there are many parallel theories for canonical classes of singular Cauchy problems but we will only deal here with (1.1)-(1.2) (cf. [5], [10] for other situations). Now there are two canonical recursion relations arising from the group theory when A is replaced by z/which we write in the form (1.3) u+2m coth t u=2m csch t usinh t [A_m(m+l)]u+ (1.4) u 2(m+ 1) and (1.3) leads directly to a generalized Sonine formula (sh=sinh and ch=cosh)
Event generators for address event representation transmitters

Address Event Representation (AER) is an emergent neuromorphic interchip communication protocol that allows for real-time virtual massive connectivity between huge number neurons located on different chips. By exploiting high speed digital communication circuits (with nano-seconds timings), synaptic neural connections can be time multiplexed, while neural activity signals (with mili-seconds timings) are sampled at low frequencies. Also, neurons generate 'events' according to their activity levels. More active neurons generate more events per unit time, and access the interchip communication channel more frequently, while neurons with low activity consume less communication bandwidth. In a typical AER transmitter chip, there is an array of neurons that generate events. They send events to a peripheral circuitry (let's call it "AER Generator") that transforms those events to neurons coordinates (addresses) which are put sequentially on an interchip high speed digital bus. This bus includes a parallel multi-bit address word plus a Rqst (request) and Ack (acknowledge) handshaking signals for asynchronous data exchange. There have been two main approaches published in the literature for implementing such "AER Generator" circuits. They differ on the way of handling event collisions coming from the array of neurons. One approach is based on detecting and discarding collisions, while the other incorporates arbitration for sequencing colliding events . The first approach is supposed to be simpler and faster, while the second is able to handle much higher event traffic. In this article we will concentrate on the second arbiter-based approach. Boahen has been publishing several techniques for implementing and improving the arbiter based approach. Originally, he proposed an arbitration squeme by rows, followed by a column arbitration. In this scheme, while one neuron was selected by the arbiters to transmit his event out of the chip, the rest of neurons in the array were freezed to transmit any further events during this time window. This limited the maximum transmission speed. In order to improve this speed, Boahen proposed an improved 'burst mode' scheme. In this scheme after the row arbitration, a complete row of events is pipelined out of the array and arbitered out of the chip at higher speed. During this single row event arbitration, the array is free to generate new events and communicate to the row arbiter, in a pipelined mode. This scheme significantly improves maximum event transmission speed, specially for high traffic situations were speed is more critical. We have analyzed and studied this approach and have detected some shortcomings in the circuits reported by Boahen, which may render some false situations under some statistical conditions. The present paper proposes some improvements to overcome such situations. The improved "AER Generator" has been implemented in an AER transmitter system
Robust control charts

When a process is first submitted to statistical quality control, a standard procedure is to collect 20–40 subgroups of about five units each and then to construct control charts, such as charts and R charts, with limits determined by the data. These control charts are then used to detect problems in control such as outhers or excess variability in subgroup means that may have a special cause. In this article, the robustness of these charting procedures is investigated. If the number of false alarms when the process is in control is held constant, the most sensitive procedures for detecting the out-of-control state are those that plot a subgroup statistic that is sensitive to outliers (e.g., mean or range) but determine the control limits in a resistant fashion. Ordinary charting procedures, such as the standard and R charts, perform less well, and the worst performance is turned in by procedures in which the subgroup statistics are themselves resistant (e.g., median charts). To illustrate the point that .
Analysis of Bending Deformation in Triangle Heating of Steel Plates with Induction Heating Process Using Laminated Plate Theory

Abstract The steel-forming process in shipyards is considered an important stage with respect to productivity and precision of curved plates. The induction heating process has been of interest to steel formation because the power and its distribution are easier to control and reproduce. Besides, induction heating equipment can be easily integrated with a robotic system for automation. The heating process usually utilizes line heating or triangle heating methods to form hull plates. Even though a number of studies on the line heating method have been performed, there have been few studies on the triangle heating method. In this study, using a simplified elasto-plastic model and laminated plate theory, an analytic means of predicting the bending deformation in triangle heating of steel plates is derived. For the purpose of this, the induction heating process is modeled in advance, with numerical heat flux and heat flow analyses to determine the plastic region. The plastic region is considered as an inclusion that has eigenstrains in the laminated plate. The analytic solution is applied to predict deformations to verify its exactness. The results of the analytic solution are quite good compared with those of the triangle heating experiment, revealing the effectiveness of the analytic solution.
Metallicity gradients in early-type galaxies

Long-slit spectra in the range 4500-6500 A have been obtained for a sample of 42 galaxies. Rotation velocities and velocity dispersions, together with radial line strength gradients of Mg 2 , Mg 1 , Hβ, Na D, TiO 1 , TiO 2 and Fe 5270 , have been measured to, on average, half an effective radius. To a high level of significance, Mg 2 gradients positively correlate with those of Mg 2 and Na D, but no correlation is observed with the other indices. In addition, correlations of Mg 2 gradients with various physical parameters are studied. For galaxies smaller than about 10 11 M ○. , the Mg 2 gradient increases with increasing mass, but more massive objects show no correlation. In low-mass galaxies, the correlation of Mg 2 gradients with mass suggests dissipative collapse as the mechanism acting during the initial star formation episode
Lateralization Threshold as a Function of Stimulus Duration

Measurement on experienced listeners of interaural time difference (ITD) thresholds for wide‐band random noise indicates that the threshold varies systematically with duration of stimulation. In order to determine the point at which increase duration no longer decreases ITD threshold, stimulus (noise burst) duration was varied between 0.01 and 1.94 sec. A given ITD was maintained throughout any particular burst, starting time included. All stimuli were presented at a level of 65 db SPL to each phone. The “duration” versus “ITD threshold” function reaches asymptote at approximately 0.7 sec, indicating that the binaural system which effects the comparison necessary for a lateralization judgment may integrate information over that period for the kind of stimulus used.
A method for the measurement of reflectances of spherical surfaces

A simple procedure for the measurement of normal reflectances of curved (spherical) surfaces using a conventional double-beam spectrophotometer is developed. It requires the attachment of a suitable sample holder to the spectrophotometer and using a surface having the same radius of curvature as the sample as a reflectance reference. The procedure is especially useful for measurement of single-face reflectance of lenses, at either the convex or the concave side.
The statistics of microlensing light curves — II. Temporal analysis

Microlensing at cosmological distances can induce violent fluctuations in the observed light curves of macro lensed quasars. In a previous publication the amplification probability distributions for a large sample of microlensing light curves were presented. This paper extends these earlier results and presents a temporal analysis for this light-curve sample. The temporal properties are explored using the first-order structure function. The results of this study show that (1) the asymptotic global curvature of the structure function depends on the macrolensing parameters (J' * and y and not on the detail of the mass distribution, (2) the characteristic timescale for variability due to microlensing is oc.J , where is the average mass of the micro lensing objects, and again does not depend on the detailed shape of the mass distribution, and (3) the structure function time-scale does not vary with shear angle as a purely geometric transformation, but does possess an underlying symmetry solely dependent on the macro lensing parameters. A comparison of simulations of the quadruple lens, 2237 + 0305, with the currently available temporal light curves suggests that the average mass distribution of the lensing objects in 2237 + 0305 is within the range 0.1 < 10 Mo'
Robust optical alignment systems using geometric invariants

Traditional coarse pointing, acquisition, and tracking (CPAT) systems are pre-calibrated to have the center pixel of the camera aligned to the laser pointing vector and the center pixel is manually moved to the target of interest to complete the alignment process. Such a system has previously demonstrated its capability in aligning with distant targets and the pointing accuracy is on the order of sensor resolution. However, aligning with targets at medium range where the distance between angular sensor and transceiver is not negligible is its Achilles Heel. This limitation can be resolved by imposing constraints, such as the trifocal tensor (TT), which is deduced from the geometrical dependence between cameras and transceivers. Two autonomous CPAT systems are introduced for FSO transceiver alignment in mid- and long-range scenarios. This work focuses on experimental results that validate the pointing performance for targets at different distances, backed up by the theoretical derivations. A mid-range CPAT system, applying a trifocal tensor as its geometric invariant, includes two perspective cameras as sensors to perceive target distances. The long-range CPAT system, applying linear mapping as the invariant, requires only one camera to determine the pointing angle. Calibration procedures for both systems are robust to measurement noise and the resulting system can autonomously point to a target of interest with a high accuracy, which is also on the order of sensor resolution. The results of this work are not only beneficial to the design of CPAT systems for FSO transceiver alignment, but also in new applications such as surveillance and navigation.
Delay-Dependent Non-Fragile Robust H∞ Control for Switched Systems with Multiple Time Delays

The non-fragile robust H∞ control problem is investigated for the uncertain switched discrete time systems with multiple state and input time delays. As the system and controller parameters are polytopically uncertain, the delay-dependent sufficient conditions for the existence of the non-fragile robust H∞ controller via state feedback are presented for the systems based on the multiple Lyapunov functions and state dependent switching rules. By using the cone complementarity linearization algorithm, the nonlinear matrix inequalities relevant to the controller design can be transformed into the nonlinear programming problems constrained by the linear matrices. The simulation results show the effectiveness of the controller design method.
Hopf‐pitchfork bifurcation in a two‐neuron system with discrete and distributed delays

Both discrete and distributed delays are considered in a two‐neuron system. We analyze the influence of interaction coefficient and time delay on the Hopf‐pitchfork bifurcation. First, we obtain the codimension‐2 unfolding with original parameters for Hopf‐pitchfork bifurcation by using the center manifold reduction and the normal form method. Next, through analyzing the unfolding structure, we give complete bifurcation diagrams and phase portraits, in which multistability and other dynamical behaviors of the original system are found, such as a stable periodic orbit, the coexistence of two stable nontrivial equilibria, and the coexistence of a stable periodic orbit and two stable equilibria. In addition, the obtained theoretical results are verified by numerical simulations. Finally, we perform the comparisons of the obtained results of Hopf‐pitchfork bifurcation with other Hopf‐fold bifurcation results in some biological neural systems and give the obtained mathematical results corresponding to the physical states of neurons. Copyright © 2015 JohnWiley & Sons, Ltd.
goGPS: open source software for enhancing the accuracy of low-cost receivers by single-frequency relative kinematic positioning

goGPS is a free and open source satellite positioning software package aiming to provide a collaborative platform for research and teaching purposes. It was first published in 2009 and since then several related projects are on-going. Its objective is the investigation of strategies for enhancing the accuracy of low-cost single-frequency GPS receivers, mainly by relative positioning with respect to a base station and by a tailored extended Kalman filter working directly on code and phase observations. In this paper, the positioning algorithms implemented in goGPS are presented, emphasizing the modularity of the software design; two specific strategies to support the navigation with low-cost receivers are also proposed and discussed, namely an empirical observation weighting function calibrated on the receiver signal-to-noise ratio and the inclusion of height information from a digital terrain model as an additional observation in the Kalman filter. The former is crucial when working with high-sensitivity receivers, while the latter can significantly improve the positioning in the vertical direction. The overall goGPS positioning accuracy is assessed by comparison with a dual-frequency receiver and with the positioning computed by a standard low-cost receiver. The benefits of the calibrated weighting function and the digital terrain model are investigated by an experiment in a dense urban environment. It comes out that the use of goGPS and low-cost receivers leads to results comparable with those obtained by higher level receivers; goGPS has good performances also in a dense urban environment, where its additional features play an important role.
Ultraviolet interstellar absorption toward HD 5980 in the Small Magellanic Cloud

Individual high-dispersion International Ultraviolet Explorer (IUE) spectra of extragalactic stars are noisy because of the long exposure times required and the inherent limitations of the IUE detectors. A program has, therefore, been undertaken to obtain multiple ultraviolet spectra of the brightest Magellanic Cloud stars in order to produce composite spectra with higher signal-to-noise ratios than in individual spectra. The present investigation is concerned with results for HD 5980. The target star, HD 5980, is one of the brightest extragalactic far-ultraviolet sources in the sky. HD 5980 is located in the northeast quadrant of NGC 346, the largest H II region and OB star cluster in the SMC. The analysis of the interstellar line spectrum of HD 5980 provides a number of conclusions about the complex absorption characteristics of the interstellar gas toward the SMC.