Miracle-dz/UniFAR-FTUs huggingface dataset:
Plasma transport across magnetic field lines in low-temperature plasma sources

Plasma transport across magnetic field lines plays a key role not only in hot fusion plasmas but also in low-temperature plasma sources operating at low pressure, which often rely on external magnetic fields for their operation. Transport in these sources involves different physics than that in fusion plasmas: the ions are not (completely) magnetized, the plasma is sensitive to wall effects because the magnetic field lines intercept the chamber walls, and the neutral gas density is often much larger than the plasma density. This paper gives an overview of the main principles of magnetized low-temperature plasma transport as they are currently understood, including recent insights on the role of magnetic drift. Three important forms of magnetized low-temperature plasma transport are discussed: magnetized plasma diffusion, transport in E × B fields and magnetic drift. These phenomena are illustrated with recent numerical modeling results on a dipolar microwave source, an End-Hall ion source, and simplified version of the ITER negative ion source. For the latter source it is shown that obstructed magnetic drift can lead to plasma asymmetry and increased cross-field transport.
Velocity dispersions in galaxy clusters

We analyze the velocity dispersions of 79 galaxy clusters having at least 30 galaxies with available redshifts. We show that different estimates of velocity dispersion give similar results on cluster samples of at least ∼20 galaxies each. However, only robust estimates of velocity dispersion seem to be efficient on cluster samples with ∼10 galaxies each. A significant correlation is found to exist between the velocity dispersion and the cluster richness. We provide the distribution function of cluster velocity dispersions, normalized to the complete sample by Abell, Corwin, & Olowin (1989). Available theoretical models are compared with this distribution function
Impact of photonic crystals on LED light extraction efficiency: approaches and limits to vertical structure designs

The enhancement of the extraction efficiency in light emitting diodes (LEDs) through the use of photonic crystals (PhCs) requires a structure design that optimizes the interaction of the guided modes with the PhCs. The main optimization parameters are related to the vertical structure of the LED, such as the thickness of layers, depth of the PhCs, position of the quantum wells as well as the PhC period and fill factor. We review the impact of the vertical design of different approaches of PhC LEDs through a theoretical and experimental standpoint, assessing quantitatively the competing mechanisms that act over each guided mode. Three approaches are described to overcome the main limitation of LEDs with surface PhCs, i.e. the insufficient interaction of low order guided modes with the PhCs. The introduction of an AlGaN confining layer in such structure is shown to be effective in extracting a fraction of the optical energy of low order modes; however, this approach is limited by the growth of the lattice mismatched AlGaN layer on GaN. The second approach, based on thin-film LEDs with PhCs, is limited by the presence of an absorbing reflective metal layer close to the guided modes that plays a major role in the competition between PhC extraction and metal dissipation. Finally, we demonstrate both experimentally and theoretically the superior extraction of the guided light in embedded PhC LEDs due to the higher interaction between all optical modes and the PhCs, which resulted in a close to unity extraction efficiency for this device. The use of high-resolution angle-resolved measurements to experimentally determine the PhC extraction parameters was an essential tool for corroborating the theoretical models and quantifying the competing absorption and extraction mechanisms in LEDs.
The effect of pressure gradient on the collapse of cavitation bubbles in normal and reduced gravity

Keywords: cavitation ; bubble ; collapse ; pressure gradient ; microjet ; shock wave ; luminescence ; energy partition ; bubble gas content These Ecole polytechnique federale de Lausanne EPFL, n° 5674 (2013)Programme doctoral MecaniqueFaculte des sciences et techniques de l'ingenieurInstitut de genie mecaniqueLaboratoire de machines hydrauliquesJury: M. Parlange (president), O. Minster, D. Obreschkow, J.R. Thome Public defense: 2013-3-1 Reference doi:10.5075/epfl-thesis-5674Print copy in library catalog Record created on 2013-02-25, modified on 2017-05-10
Operation of the sapphire Cerenkov laser

First operation of a sapphire‐based Cerenkov free electron laser is reported. It is a tunable source of coherent millimeter and submillimeter radiation. The phase velocity of light in sapphire is about one‐tenth of that in free space so that Cerenkov radiation is obtained at modest electron beam energies. In addition to its role as a Cerenkov coupler, the sapphire forms a high Q resonator obviating external mirrors. The spontaneous Cerenkov emission is well‐confined by this resonator and can build to watts of power. Measured tuning and threshold currents are presented and compared with the predictions of free electron laser theory.
Optical angiography from optical coherence tomograhy using a computational phase-shift

We present a novel method to obtain optical angiographies (OAG) on a standard optical coherence tomography (OCT) system. The moving reference arm is simulated by introducing a phase-shift at the post-processing stage. The method can be applied bi-directionally from a single scan, one or more velocity-thresholds can be adjusted during post-processing. First in-vivo results are shown.
C1 1358 + 6245 at Z = 0.32 - an X-ray selected, distant, rich cluster of galaxies

BVRI CCD photometric observations of an extremely rich, X-ray selected cluster of galaxies, Cl 1358+6245, are presented. Spectroscopy of the optically dominant cluster galaxy indicate a redshift of z = 0.32 for the cluster. The photometric catalog contains 322 galaxies measured in at least two colors detected in the CCD field. The cluster luminosity function and color-magnitude diagrams are included. Cl 1358+6245 is extremely rich, contains a compact, concentrated core of galaxies, exhibits the Butcher-Oemler effect with a blue galaxy fraction 0.10 < f b < 0.18, and is X-ray luminous
Synchronous adaptive filters with delayed coefficient adaption

The authors present exact descriptions of the behaviour of a class of adaptive filters with delayed coefficient adaption. This coefficient update delay is demonstrated to occur as a natural consequence of introducing compensation for nonminimum phase systems under the control of a least mean square based adaptive filter, as in the adaptive control of acoustic noise. A linear, time-invariant equivalent transfer function model of the adaptive system is developed, which can be used to study steady-state performance and the stability limits imposed by the coefficient update delay. <<ETX>>
Ionospheric scintillation near the anomaly crest in relation to the variability of ambient ionization

Ionospheric scintillation near the anomaly crest is a matter of great concern for the design of transionospheric communication and navigation links and forecasting of the same is an important aspect of ensuing space weather scenario. Under present investigation, amplitude scintillation data at VHF/UHF, total electron content (TEC) data from Calcutta (geographic: longitude 88.38°E, latitude 22.58°N, dip: 32°N), situated virtually below the northern crest of equatorial ionization anomaly, are analyzed to study any correspondence between occurrences of postsunset equatorial scintillations and daytime ambient ionization characteristics. The study reveals distinctive features of diurnal TEC profiles on scintillation and non‐scintillation days. The differences are reflected in daytime TEC parameters like diurnal peak values of TEC, its occurrence time, 3‐dB width of diurnal TEC profile, daytime integrated TEC and average TEC level around the local sunset. The analysis reveals that local time of diurnal TEC maximum in conjunction with daytime integrated TEC values may potentially be selected to develop forecasting capability of postsunset scintillation for the equinoctial months of high solar activity years under quiet geomagnetic condition. The results are discussed in terms of sustenance probability of high ambient ionization in the postsunset period.
On numerical solution of hyperbolic heat conduction

The finite element solution of the hyperbolic heat conduction equations is addressed. The governing system of equations is solved for the temperature and heat fluxes as independent variables. A standard Galerkin method is used for the spatial discretization and a Crank–Nicolson method is adopted for marching in the time domain. It is shown that the proposed method can easily evaluate the entropy production within the domain and assess the thermodynamic equilibrium of the system. The performance of the proposed algorithm is verified by solving a 1D test case. A 2D test case is also studied and some interesting features of the hyperbolic heat conduction are demonstrated. Copyright © 1999 John Wiley & Sons, Ltd.
Hopf bifurcation for equivariant conservative and time-reversible systems

Synopsis We study the bifurcation of small periodic solutions at a non-semi-simple 1:1-resonance in equivariant conservative or equivariant time-reversible systems. By using an equivariant Liapunov-Schmidt method and restricting to solutions with an appropriate isotropy, we reduce the problem to a scalar bifurcation equation. The analysis of this equation shows a bifurcation behaviour similar to that found for the Hamiltonian Hopf bifurcation.
Effect of Particle Residence Time on Particle Dispersion in a Plane Mixing Layer

A particle dispersion has been experimentally investigated in a two-dimensional mixing layer with a large relative velocity between particle and gas-phase in order to clarify the effect of particle residence time on particle dispersion. Spherical glass particles 42, 72, and 135 {mu}m in diameter were loaded directly into the origin of the shear layer. Particle number density and the velocities of both particle and gas phase were measured by a laser Doppler velocimeter with modified signal processing for two-phase flow. The results confirmed that the characteristic time scale of the coherent eddy apparently became equivalent to a shorter characteristic time scale due to a less residence time. The particle dispersion coefficients were well correlated to the extended Stokes number defined as the ratio of the particle relaxation time to the substantial eddy characteristic time scale which was evaluated by taking account of the particle residence time.
Near-infrared electroluminescence in polymer composites based on organic nanocrystals

IR electroluminescence was revealed in single-layer light-emitting diodes based on a type of electroactive polymer nanocomposites-electron-hole conducting aromatic polyimide and organic nanocrystalline particles of cyanine molecules, known as J-aggregates. These materials exhibit a very narrow emission band with a maximum at 815 nm. Dramatic increase of charge-carrier mobility was observed for these layers containing the J-aggregate nanocrystalline phase.
A vibroacoustic application of modeling and control of linear parameter-varying systems

This paper applies recent advances in both modeling and control of Linear Parameter-Varying (LPV) systems to a vibroacoustic setup whose dynamics is highly sensitive to variations in the temperature. Based on experimental data, an LPV model is derived for this system using the State-space Model Interpolation of Local Estimates (SMILE) technique. This modeling technique interpolates linear time-invariant models estimated at distinct operating conditions of the system (in this case, different temperatures). Using the obtained LPV model, gain-scheduled and robust multiobjective H2/H∞ state feedback controllers are designed such that can consider a priori known bounds on the rate of parameter variation. Numerical simulations using the closed-loop systems are performed to validate the controllers and to show the advantages and versatility of the proposed techniques.
Dispersion in a curved tube during oscillatory flow

The effect of curvature on longitudinal dispersion in an axially uniform toroidal tube during oscillatory flow is investigated. The regimes of dispersion and the rate of longitudinal transport are estimated by order-of-magnitude arguments. Experiments are reported for the range, 0.66 < Dn2/α4 < 2.4, 5.4 < α < 26, Sc = 0.68, where Dn is the Dean number, α is the Womersley number and Sc is the Schmidt number. For β2 = α2Sc > 30, curvature causes a sharp increase in the effective diffusivity, relative to that for a straight tube, by a factor of about 6 at Dn2/α4 ≈ 2. The results from two numerical simulation methods are also presented. One, a Monte Carlo simulation (0.01 < Dn < 10, 0.01 < α < 0.32, Sc = 104), predicts the spread of a bolus in quasi-steady flow. The other, a spectral-element method (1 < Dn < 1000, 1 < α < 100, Sc = 0.68), is used to find the dispersion in unsteady oscillatory flow subjected to a constant longitudinal concentration gradient. Two mechanisms are identified by which axial transport is modified by curvature. First, the enhanced lateral transport due to secondary flow decreases axial transport by a factor of up to 5 for low β2 and increases axial transport by an even greater amount for high β2. Second, axial transport is enhanced owing to a form of resonance when the secondary flow circulation time is equal to the cycle period.
Multivariable control by ‘individual channel design’

Abstract A new approach—individual channel design (ICD)—to an enduring problem— multivariable feedback control—is presented. The approach is applications-oriented: it starts from the engineering premise that feedback control design is interactive; it involves an interplay between customer specification, uncertain plant characteristics, and the multivariable feedback design process itself. It is shown that individual signal transmission channels arise naturally from customer specification on selected plant outputs with no loss of structural (loop interaction) information. By invoking customer performance specification on different channels, highly successful single-input single-output classical (Nyquist-Bode) design is made possible. ICD is not a design method per se per se; rather it is a global structural framework wherein the possibilities and limitations for local-loop-shaping design (e.g. Bode or Nichols) of a particular plant are made apparent from the outset. Also, the conditions are established whe.
A Period Study and Spot Model for the Eclipsing Binary TU Bootis

We present the photometric properties of the eclipsing binary TU Boo from detailed studies of the period and light variations, based on our new BVR observations and historical data collected from the literature. A total of 349 times of minimum light over 80 yr, including our four timings, were used for the period study. An analysis of the resulting O–C diagram reveals that the orbital period of TU Boo has varied in a quasi‐sinusoidal way superposed on a long‐term period decrease. The secular variation presumably indicates that mass is thermally transferred from the more massive primary star to its companion at a rate of about 7.24 × 10−8 M⊙ yr−1. The period and semiamplitude of the cyclical variation are 54.5 yr and 0.0177 days, respectively, which could be produced by either a light‐time effect or a magnetic activity cycle. Our light curves are asymmetrical, with max I about 0.02–0.03 mag brighter than max II. Among possible spot models, the light variations were best‐fit by using a two‐spot model with both a cool spot and a hot spot on the secondary star. These may be formed by a combination of effects from a magnetic dynamo and mass transfer. We suggest that TU Boo is probably a triple system, consisting of a massive primary star with a spectral type of G3, a secondary component of spectral type G5–6, and a low‐mass M‐type tertiary companion with a minimum mass of about M3 = 0.34 M⊙.
Formation and evolution of luminous supersoft X-ray sources

Luminous supersoft X-ray sources, with characteristic luminosities of approximately 10(exp 38) ergs/s and temperatures, kT, of approximately 35 eV, have been established as a new and distinct class of X-ray source through recent Roentgen Satellite (ROSAT) observations. Several possible physical models have been proposed for these sources. One promising scenario (van den Heuvel et al. 1992) involves mass transfer, which is unstable on a thermal timescale, from a main-sequence or subgiant donor star onto the surface of a white dwarf. For a narrow range of accretion rates, steady nuclear burning of the accreted matter can take place. This process can provide the high luminosities and the correct range of temperatures observed in the supersoft sources. However, given the limited range of mass transfer rates that are consistent with this phenomenon, it is far from obvious that a sufficient population of such systems exists in galaxies such as our own, M31, and the Magellanic Clouds, in order to account for the large number of supersoft sources which can be inferred from present observations. This work addresses the population question in detail, through a Monte Carlo simulation of the formation and evolution of such systems, which starts with zero-age primordial binaries. In order to evolve into close binary systems which contain a white dwarf component and a companion transferring mass at a rate within the requisite narrow range, a binary system must undergo a specific progression of evolutionary steps. We find that a sufficient subset of our initial binaries evolve to become systems with the requisite properties, so that they can account for the population of supersoft sources that is inferred from observations. In particular, we find that there should be more than 1000 systems in the Galaxy today with properties that very closely match those of the observed supersoft sources. From our models, we find expected luminosities, white dwarf effective temperatures, and orbital periods in the ranges of 10(exp 37) - 10(exp 38) ergs/s, (1-5) x 10(exp 5) K, and 8 hr-1.4 days, respectively. The masses of the white dwarf and donor star are expected to lie in the range of 0.7-1.05 solar mass and 1.3-2.7 solar mass. Finally, we discuss the role that supersoft X-ray sources may play as the progenitors of Type Ia supernovae, and estimate the rate of production via this channel.
Robust Control for a Class of Uncertain Switched Fuzzy Systems with Saturating Actuators

This paper investigates the robust control problem for a class of uncertain switched fuzzy systems with saturating actuators. The asymptotical stability for fuzzy subsystems subject to actuator saturation is not assumed. Based on the multiple Lyapunov functions method, we design a switching law and a state feedback control law such that the closed‐loop system is asymptotically stable. Additionally, the estimation of the domain of attraction is presented by solving an optimization problem. Finally, simulation results verify the feasibility and effectiveness of the proposed method.
Multi-task oriented design of an asymmetric 3T1R type 4-DOF parallel mechanism

In performing tasks requiring less than 6 degrees-of-freedom (DOF), lower mobility robots having a parallel structure are effective. This work investigates an asymmetric type 4 degrees-of-freedom parallel mechanism having Schönflies motions. This mechanism would be useful for multi-purpose tasks because it incorporates a transmission linkage with appropriate output modules. The mobility analysis, kinematic modelling, and singularity analysis for the mechanism are performed. Optimal design parameters with respect to both the workspace size and kinematic isotropy are identified by employing composite global design index. In addition, to cope with the singularity problem, a new design involving redundant actuation is suggested. And dynamic simulations are conducted to reaffirm its high potential in real manufacturing applications.
EXACT, SINGLE EQUATION, CLOSED-FORM SOLUTION OF VIBRATING SYSTEMS WITH PIECEWISE LINEAR SPRINGS

Abstract A method is proposed to obtain in a single equation the exact, closed-form displacement response of both free undamped vibrations and the steady state of forced damped vibrations of systems with piecewise linear springs, with continuous or discontinuous force–deflection relations. Since the displacement equations are exact the velocity and acceleration responses are obtained by differentiation. The solutions are complete, they apply for any value of time from zero to infinity. The method is designed to be handled in a computer either in conjunction with a Symbolic Mathematics package, like Mathematica or Maple, or without it. However, for certain relatively simple problems the phase-plane solution may be obtained even in a hand-held calculator. Two examples are presented.
How long does it take for a gas to fill a porous container

Let us consider the problem u,(x, t) = Aum(x, t) for (x, t) E D x [0, +x), u(x, 0) = uo(x) for x E D, and (Oum/On)(x, t) = h(x, t) for (x, t) E AD x [0, +oo) . Here we assume D c RN, m > 1, uo > 0,and h > 0. It is well known that solutions to this problem have the property of finite speed propagation of the perturbations. By this we mean that if z is an interior point of D and exterior to the support of uo, then there exists a time T(z) > O so that u(z, t) = 0 for t 0 for t > T(z) . In this note we give, in an elementary way, an upper bound for T(z) for the case of bounded convex domains and in the case of a half space.
Discussion: integrating SPC and APC

We would like to thank Box and Kramer for a thought-provoking commentary on a very timely topic. We found their tone much more open-minded than the typical “Shewhart bashing” currently in vogue. We believe that the authors have accomplished their objective of removing misunderstanding in this area, particularly for explaining that the fundamental issue is not choosing statistical process control (SPC) or automatic process control (APC), but how to integrate them effectively. We would like to note that in 1944, Deming suggested that “good engineering control of the process” must be part of any qualitycontrol program (Deming 1944, p. 177). Our interest in this topic is primarily from an applications point of view; hence we will focus on the practical issues versus the theoretical.
Nonlinearities in Financial Engineering

There are several kinds of nonlinearities in financial engineering. They range from the modeling of market mechanisms to numerical schemes and to bifurcation phenomena. This paper discusses some related issues. The bifurcation problem is a model of volatility clustering due to Lux (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new technique to estimate the regularity of refinable functions

We study the regularity of refinable functions by analyzing the spectral properties of special operators associated to the refinement equation; in particular, we use the Fredholm determinant theory to derive numerical estimates for the spectral radius of these operators in certain spaces. This new technique is particularly useful for estimating the regularity in the cases where the refinement equation has an infinite number of nonzero coefficients and in the multidimensional cases.