Miracle-dz/UniFAR-FTUs huggingface dataset:
Mathematical models for class-D amplifiers

We here analyse a number of class-D amplifier topologies. Class-D amplifiers operate by converting an audio input signal into a high-frequency square wave output, whose lower-frequency components can accurately reproduce the input. Their high power efficiency and potential for low distortion makes them suitable for use in a wide variety of electronic devices. By calculating the outputs from a classical class-D design implementing different sampling schemes we demonstrate that a more recent method, called the Fourier transform/Poisson resummation method, has many advantages over the double Fourier series method, which is the traditional technique employed for this analysis. We thereby show that when natural sampling is used the input signal is reproduced exactly in the low-frequency part of the output, with no distortion. Although this is a known result, our calculations present the method and notation that we later develop. The classical class-D design is prone to noise, and therefore negative feedback is often included in the circuit. Subsequently we incorporate the Fourier transform/Poisson resummation method into a formalised and succinct analysis of a first-order negative feedback amplifier. Using perturbation expansions we derive the audio-frequency part of the output, demonstrating that negative feedback introduces undesirable distortion. Here we reveal the next order terms in the output compared with previous work, giving further insight into the nonlinear distortion. We then further extend the analysis to examine two more complex negative feedback topologies, namely a second-order and a derivative negative feedback design. Modelling each of these amplifiers presents an increased challenge due to the differences in their respective circuit designs, and in addition, for the derivative negative feedback amplifier we must consider scaling regimes based on the relative magnitudes of the frequencies involved. For both designs we establish novel expressions for the output, including the most significant distortion terms.
Switching of tunnel magnetoresistance by domain wall motion in (Ga,Mn)As-based magnetic tunnel junctions

Switching of tunnel magnetoresistance in magnetic tunnel junctions (MTJs) has been achieved by magnetic domain wall motion in one of the electrodes. The fabricated devices have two (Ga,Mn)As-based MTJs with a common bottom (Ga,Mn)As electrode, in which the domain wall motion takes place both by magnetic field and by current. This configuration allows not only the observation of switching but also time-resolved detection of the position of the domain wall by the tunnel magnetoresistance.
Resonant frequencies of cylindrical Helmholtz resonators

A simple analysis predicts the Helmholtz and higher modes of cylindrical resonators. Formulas for the quarter‐wave tube, the closed tube, and the classic Helmholtz resonator are special cases. It is found that the classic Helmholtz formula begins to lose accuracy for resonator lengths L≳λ/16. A corrected Helmholtz equation is given as an approximation to the exact result. The analysis requires values of inside and outside orifice end corrections. Rayleigh’s model of a piston in an infinite wall and Ingard’s calculations for a piston radiating into a tube give satisfactory results when the theory is compared to experiments. Resonator experiments were performed with k0L in the range π/8 to 3π/8 and orifice to cavity diameter ratios from 0.1 to 0.8. Subject Classification: 20.40.
Early Spectrum and Bolometric Corrections for SN 1987A

Un modele analytique de determination du spectre du continuum, de la magnitude bolometrique absolue et des corrections bolometriques est developpe pour les 2 premiers jours de SN 1987A. Ce modele inclut les equations du transfert radiatif et les relations entre l'epaisseur optique, la densite et la temperature
Optimization of Pt-based spin-Hall-effect spintronic devices

We study experimentally the routes to improve the characteristics of the spin-Hall-effect devices based on permalloy/Pt bilayers by optimization of the Pt layer thickness and by the addition of an antiferromagnetic spin-sinking layer. We experimentally determine the spin-diffusion length in Pt and show that Pt thickness can be reduced down to 2 nm without degradation of the device characteristics caused by the spin accumulation effects, which provides possibilities for significant reduction of the required driving currents. We also show that the addition of a spin-sinking layer results in a non-monotonic dependence of device efficiency on the Pt thickness.
Interaction Between the Solar Wind and the Interstellar Medium

The heliospheric and interstellar parameters of importance in the interaction between the solar wind and the ISM are discussed. The observationally inferred values of these parameters, including the uncertainties, are addressed, and the basic physical processes that are likely to be important in the interaction are examined theoretically. The theory is combined with observational information in an effort to develop the currently most likely picture of the heliosphere as it is shaped by the local ISM.
A Procedure for Controlling General Test Overlap in Computerized Adaptive Testing

To date, exposure control procedures that are designed to control test overlap in computerized adaptive tests (CATs) are based on the assumption of item sharing between pairs of examinees. However, in practice, examinees may obtain test information from more than one previous test taker. This larger scope of information sharing needs to be considered in conducting test overlap control. The purpose of this study is to propose a test overlap control method such that the proportion of overlapping items encountered by an examinee with a group of previous examinees (described as general test overlap rate) can be controlled. Results indicated that item exposure rate and general test overlap rate could be simultaneously controlled by implementing the procedure. In addition, these two indices were controlled on the fly without any iterative simulations conducted prior to operational CATs. Thus, the proposed procedure would be an efficient method for controlling both the item exposure and general test overlap in CATs.
The Pressure Distribution in the Auditory Canal in a Progressive Sound Field

The variation of the sound pressure along the auditory canal was determined experimentally on a number of subjects, male and female, placed in a progressive sound field. This was accomplished by insertion of a small flexible probe microphone at various positions along the length of the auditory canal. The subjects were placed in the sound field of a loudspeaker in a room free from acoustic wall reflections. The measurements were carried out over the significant range of audio‐frequencies at various orientations in azimuth of the subjects with respect to the sound source. The free‐field sound pressure was also determined at the subjects' location. The sound pressure at the eardrum is greater than the free‐field pressure. The average ratio of these two quantities is a function of frequency and reaches values of about 20 db in the vicinity of 3000 c.p.s. The human ear is thus an effective acoustic “amplifier. ” This amplification is a combination effect of diffraction around the head and pinna and resonance i.
Low-chirp and external optical feedback resistant characteristics in /spl lambda//8 phase-shifted distributed-feedback laser diodes under direct modulation

Clarifies that phase shift value in directly modulated distributed feedback laser diodes (DFB-LDs) affects their chirp characteristics and resistance to external optical feedback because of the feedback effect of mirror loss (FEML). Comparing /spl lambda//8, /spl lambda//4, and 3//spl lambda/8 phase-shifted DFB-LDs, theoretically and experimentally, showed that the negative FEML in /spl lambda//8 phase-shifted DFB-LDs improves their transmission performance and makes them more resistant to external optical feedback. It was demonstrated with 2.5-Gb/s directly modulated 1.55-/spl mu/m /spl lambda//8 phase-shifted DFB-LDs that a very low-power penalty for 100-km transmissions (less than 1 dB for BER=10/sup -10/) can be obtained within a wide extinction ratio from 8.5 to 14.5 dB. Excellent resistance to optical feedback was also demonstrated using /spl lambda//8 phase-shifted DFB-LDs: isolator-free 80-km transmission was successful under -14-dB external optical feedback. In addition, the relation of transmission characteristics to coupling coefficient /spl kappa/L and detuning between oscillation wavelength and gain maximum was also discussed here for designing low chirp /spl lambda//8 phase-shifted DFB-LDs.
A nonlinear scale-space filter by physical computation

Using the maximum entropy principle and statistical mechanics, the author derives and demonstrates a nonlinear scale-space filter. For each datum in a signal, a neighborhood of weighted data is used for scale-space clustering. The cluster center becomes the filter output. The filter is governed by a single scale parameter which dictates the spatial extent of nearby data used for clustering. This, together with the local characteristic of the signal, determine the scale parameter in the output space, which dictates the influences of these data on the output. This filter is thus completely unsupervised and data-driven. It provides a mechanism for a) removing noise; b) preserving edges and c) improved smoothing of nonimpulsive noise. <<ETX>>
Eclipse mapping of late-type close binary stars

The presence of abnormally bright or dark regions on the inner face of either component of an eclipsing binary produces observable distortion of the eclipse profile in a broad-band light curve. The changes in the light level as the eclipsing component scans across the inner face of its companion can be used to reconstruct the surface brightness distribution in the eclipsed region. The purpose of this paper is to describe a code that uses the maximum entropy method (MEM) for eclipse mapping. Light curves synthesized with the code are found to give close agreement with results obtained using Hill's LIGHT2 light-curve synthesis code. Reconstruc­ tions using simulated data sets derived from known starting images are used to assess the performance of the code and the sensitivity of the reconstructed images to small systematic errors in the eclipse geometry.
Shintani Descent for Special Linear Groups

Abstract In this paper, the Shintani descent of irreducible characters of finite special linear groups is discussed. We parametrize irreducible characters of SL n ( F q ) by making use of (modified) generalized Gelfand–Graev characters. Shintani descent of irreducible characters of SL n ( F q m ) is determined by investigating the Shintani descent of generalized Gelfand–Graev characters. Our results hold for arbitrary p and q .
Comparative Study on Ion‐Dynamics for Broadening of Lyman Lines in Dense Hydrogen Plasmas

Broadening of spectral lines by a plasma surrounding can be used for plasma diagnostics. Full hydrogen Lyman line profiles are calculated with a quantum‐statistical approach. The effects of plasma electrons and ions on the emitter states are considered separately. The influence of electrons is considered in a dynamically screened Born approximation (collision approximation). For the ions, we apply the quasi‐static approximation and two different approaches to account for ion‐dynamics, namely, the model microfield method (MMM) and the frequency fluctuation model (FFM). We compare resulting widths of Lyman lines in the temperature range T = 104 to 107 K and the free electron density range ne = 1023 to 1026 m–3. For Lα, the error made by neglecting ion‐dynamics increases with increasing temperature and decreasing density, and is at least –15%. Due to the double peaked structure of Lβ the situation is less systematic. However, a large region exists, where ion‐dynamics does not affect the line shape of Lβ. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stabilized updated Lagrangian corrected SPH for explicit dynamic problems

Smooth particle hydrodynamics with a total Lagrangian formulation are, in general, more robust than finite elements for large distortion problems. Nevertheless, updating the reference configuration may still be necessary in some problems involving extremely large distortions. However, as discussed here, a standard updated formulation suffers the presence of zero‐energy modes that are activated and may completely spoil the solution. It is important to note that, unlike an Eulerian formulation, the updated Lagrangian does not present tension instability but only zero‐energy modes. Here a stabilization technique is incorporated to the updated formulation to obtain an improved method without any mechanisms and which is capable to solve problems with extremely large distortions. Copyright © 2006 John Wiley & Sons, Ltd.
Randomised Features in Discriminative Machine Learning

Discriminative models are a class of learning methods where the focus is on learning class memberships, as opposed to Generative models, where the interest is in full class densities. While several approaches to discriminative modelling exist, we concentrate on the Maximum Entropy Framework, based on a theoretical argument developed by Jaynes [1957]. Maximum Entropy methods are featurebased: in order to infer an empirical distribution from the data they encode relevant statistics using features. In general, the quality of the model grows with the number and scope of features: unfortunately, the computational and memory resources needed to manipulate them also grow accordingly, often to an unmanageable extent. We investigate the possibility of representing features using randomised techniques. Exploring one class of important one-sided error randomised data structures derived from the Bloom Filter, our study concentrates on the logarithmicfrequency Bloom Filter [Talbot and Osborne, 2007a,b] and the Bloom Map [Talbot and Talbot, 2008]. Both are introduced and tested in a discriminative learning context for the first time in this thesis. We provide details of a Randomised Maximum Entropy Framework, where we examine integration possibilities and propose an integration scenario. Following from this, we define a NLP-related case-study and use it as a test-bed to design a variety of experiments involving our new model. A number of interesting findings lead us to argue that the Randomised Maximum Entropy and the old model deliver comparable performances, with remarkable space savings introduced by our model. We conclude by suggesting directions for further refinement through which we believe a Randomised Maximum Entropy model might improve upon the state of the art.
Absence of weak electron localization in (Co/Pt)n‐multilayer‐nanowires with perpendicular anisotropy

We report on low temperature resistance and magnetoresistance (MR) measurements for various (Co/Pt)n‐multilayer‐nanowires with perpendicular magnetic anisotropy and different widths, designed as model systems for the experimental observation of weak electron localization effects in ferromagnetic systems as proposed by Dugaev et al. [Phys. Rev. B 64, 144423 (2001)]. The low temperature MR is found to originate from both the anisotropic MR and domain wall scattering. The temperature dependence of the resistance shows a logarithmic resistance increase with decreasing temperature, as it is typical for quantum corrections in two dimensional systems. Upon application of a perpendicular magnetic field, however, the slope of the logarithmic resistance increase does not change in magnitude, which proofs that weak localization effects are not present, at least within the accuracy of our measurements. Instead, the observed quantum corrections of the resistance are well explained by enhanced electron‐electron interaction effects in two dimensions. The results are discussed with regard to recent experimental as well as theoretical works.
Circuit Controlled Current Instabilities in ``S‐Shaped'' Negative Differential Conductivity Elements

We compare the results of our theoretical analysis of an ``S‐shaped'' negative differential conductivity (NDC) element in a circuit containing a capacitor in parallel with the NDC element in series with an inductor, with the results of our experiments on PNPN and Ovonic diodes. All the major features of the experimental results are accounted for by the theory. These include, for the PNPN diode, switching to stable points in the DNC region and the appearance of damped chirps in response to a voltage ramp; for the Ovonic diode, voltage tunable relaxation oscillations. The theory provides a framework within which one can categorize and characterize the various modes of behavior observed in all S‐shaped NDC elements.
On the high-energy gamma-ray signature of cosmic-ray sources

Monte Carlo simulations of the gamma-ray emission from hypothetical cosmic-ray sources are performed. Sources which might correspond to acceleration by supernova shocks in 'average' interstellar conditions and deep within giant molecular clouds are considered. The consequences of dropping the common assumption that the cosmic-ray spectrum at the sources is the same as that observed at earth are examined. Spectral effects which can be related to the depth of the material shroud and the population of accelerated particles are explored using these simulations and are described. The results are compared with the COS B catalog of gamma-ray sources, and the implications for the underlying particle populations and source mechanisms are discussed. 44 references.
Nucleation and growth of supported clusters at defect sites: Pd/MgO(001)

Nucleation and growth of Pd on cleaved MgO(001) surfaces were studied by variable-temperature atomic force microscopy in the temperature range 200-800 K. Constant island densities (similar to 3x10(12)cm(-2)) were observed over a wide temperature range, indicating nucleation kinetics governed by point defects with a high trapping energy. These results are compared to a rate equation model that describes the principal atomistic nucleation and growth processes, including nucleation at attractive point defects. Energies for defect trapping, adsorption, surface diffusion, and pair binding are deduced, and compared with recent nb initio calculations.
On Classes of Unique-Sink Orientations Arising from Pivoting in Linear Complementarity

The P-matrix linear complementarity problem (P-LCP) has been conjectured to be solvable in polynomial time. In this thesis we look at simple principal pivoting algorithms, identified by a pivot rule, as solving methods. We employ the combinatorial unique-sink orientation (USO) abstraction for the study of their behavior. The problem addressed is to estimate the chances whether there is a polynomial time pivot rule for the P-LCP. Therefore we determine bounds on sizes of USO classes arising from pivoting in P-LCPs. There are at most 2 ) P-USOs of order n and for a lower bound, two explicit construction schemes give 2 ) LP-realizable USOs. These are shown to be solvable in at most n + 1 pivot steps by Lemke’s pivoting algorithm. In addition, we show that the classes of LP-realizable USOs and hidden K-USOs are the same. Furthermore, we define the strongly Holt-Klee USO condition, which is satisfied by every P-USO, and show that there are at least 2 /poly(n) such USOs of order n. By comparing the upper bound for the P-USO class and the lower bound for the strongly Holt-Klee USO class, we conclude that P-USOs contain much more combinatorial structure. The goal of future research is to extract this additional structure in order to prove polynomial runtime of an existing pivot rule or to devise superior rules for simple principal pivoting algorithms. Altogether, the conjecture that there is a polynomial-time pivot rule for the P-LCP is supported.
Assessing influence on predictions from generalized linear models

Influence diagnostics for predictions from a normal linear model examine the effect of deleting a single case on either the point prediction or the predictive density function. Instead of deleting cases, we apply the local influence method of Cook (1986) to assess the effect of small perturbations of continuous data on a specified point prediction from a generalized linear model. Based on local perturbations of the vector of responses, case weights, explanatory variables, or the components of one case, the diagnostics can detect different kinds of influence. Some of the diagnostics are illustrated with an example and compared to standard diagnostic methods.
Solid phase based DNA solution of the coloring problem

Abstract DNA computing has the potential to tackle computationally difficult problems that have real-world implications. The parallel search capabilities of DNA make it a valuable tool for approaching intractable computational problems, for which conventional computers have limited potentials. Up to now, many accomplishments have been achieved to improve its performance and increase its reliability. In this paper, the coloring problem has been solved by means of molecular biology techniques. The coloring problem is a well-known NP-complete problem. This work represents further evidence for the ability of DNA computing to solve NP-complete problems.
Illumination with solid state lighting technology

High-power light-emitting diodes (LEDs) have begun to differentiate themselves from their more common cousins the indicator LED. Today these LEDs are designed to generate 10-100 lm per LED with efficiencies that surpass incandescent and halogen bulbs. After a summary of the motivation for the development of the high-power LED and a look at the future markets, we describe the current state of high-power LED technology and the challenges that lay ahead for development of a true "solid state lamp. " We demonstrate record performance and reliability for high-power colored and white LEDs and show results from the worlds first 100-plus lumen white LED lamp, the solid state equivalent of Thomas Edison's 20-W incandescent lightbulb approximately one century later.
A Direct Existence Proof for the Vortex Equations Over a Compact Riemann Surface

We give a direct proof of an existence theorem for the vortex equations over a compact Riemann surface, exploiting the interpretation of these equations in terms of moment maps. 1. The vortex equations In this paper we shall describe a direct existence proof for the vortex equations over a compact Riemann surface. These equations are a straightforward generalization of the vortex equations on U which were introduced in 1950 by Ginzburg and Landau [10] in the theory of superconductivity. From a geometric point of view, they correspond to the absolute minima of the Yang-Mills-Higgs functional. This is defined for a unitary connection A on a hermitian line bundle over R and a smooth section 0 of that bundle as
A study of the stability radius for descriptor systems

This paper studies the structural stability of linear time invariant descriptor systems of the form: Ex/spl dot/=Ax where E and A are subject to real or complex perturbations, and various definitions related to structural regularity, structurally impulsive and exponential stability are presented. A variety of perturbation patterns is introduced and studied, and formulas to calculate the regularity radius, impulsive stability radius and exponential stability radius are given.