Miracle-dz/UniFAR-FTUs huggingface dataset:
Complexity-reduced digital nonlinear compensation for coherent optical system

The high complexity of conventional intra-channel nonlinearity compensation algorithms, such as back-propagation, is considered as the major obstacle for the implementation. To reduce the complexity, perturbation analysis is applied because it considers multi-span transmission as one stage. In those perturbation based algorithms, such as perturbation back-propagation (PBP) and perturbation pre-distortion, the number of required compensation stage is much less than that of conventional back-propagation. To reduce the complexity further, the multi-tap finite impulse response filter (FIR) in PBP is replaced with one-tap infinite impulse response (IIR) filter. The number of required compensation stage of IIR PBP is only 15% of conventional back-propagation, whereas the complexity of each stage is almost same. In perturbation pre-distortion, the proposed perturbation combination reduces the number of terms from 19732 to 41, whereas no performance degradation is observed.
Combining M- and L-edge resonant inelastic x-ray scattering for studies of 3d transition metal compounds

S. G. Chiuzbăian,1,* T. Schmitt,2 M. Matsubara,3 A. Kotani,4,5 G. Ghiringhelli,6 C. Dallera,7 A. Tagliaferri,8 L. Braicovich,8 V. Scagnoli,9 N. B. Brookes,9 U. Staub,2 and L. Patthey2 1Laboratoire de Chimie Physique–Matière et Rayonnement, UPMC Université Paris 06, CNRS UMR 7614, 75005 Paris, France 2Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland 3Laboratoire des Colloïdes, Verres et Nanomatèriaux (UMR 5587), Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France 4RIKEN/Spring8, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan 5Photon Factory, IMSS, High Energy Accelerator Research Organization, 1-1 Oho Tsukuba, Ibaragi 305-0801, Japan 6Dipartimento di Fisica, CNR/INFM Coherentia and SOFT, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy 7Dipartimento di Fisica, CNR/INFM ULTRAS, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy 8Dipartimento di Fisica, CNR/INFM SOFT, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy 9European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France Received 15 July 2008; revised manuscript received 16 October 2008; published 2 December 2008
INTERNATIONAL CENTRE FOR THEORETICAL PHYSICS AND

The Freund-Rubin mechanism is based on the equation R ik = ^ 8 ik ' where l> °)> which, via Myers 1 Theorem, implies "spontaneous compactification. The difficulties connected with the cosmological constant in this approach can be resolved if torsion is introduced and \ set equal to zero, but then compactification "by hand" is necessary, since the equation R - 0 can be satisfied both on compact and on non-compact manifolds. In this paper we discuss the global geometry of Ricci-flat manifolds with torsion, and suggest ways of restoring the "spontaneity" of the compactification.
Global dynamics of planetary systems with the MEGNO criterion

In this paper we apply a new technique alternative to the numerically computed Lyapunov Characteristic Number (LCN) for studying the dynamical behaviour of planetary systems in the framework of the gravitational N-body problem. The method invented by P. Cincotta and C. Sim o is called the Mean Exponential Growth of Nearby Orbits (MEGNO). It provides an ecient way for investigation of the ne structure of the phase space and its regular and chaotic components in any conservative Hamiltonian system. In this work we use it to study the dynamical behaviour of the multidimensional planetary systems. We investigate the recently discovered And planetary system, which consists of a star of 1:3 M and three Jupiter-size planets. The two outermost planets have eccentric orbits. This system appears to be one of the best candidates for dynamical studies. The mutual gravitational interaction between the two outermost planets is strong. Moreover the system can survive on a stellar evolutionary time scale as it is claimed by some authors (e.g., Rivera & Lissauer 2000b). As the main methodological result of this work, we conrm important properties of the MEGNO criterion such as its fast convergence, and short motion times (of the order of 10 4 times the longest orbital period) required to distinguish between regular and chaotic behaviors. Using the MEGNO technique we found that the presence of the innermost planet may cause the whole system to become chaotic with the Lyapunov time scale of the order of 10 3 {10 4 yr only. Chaos does not induce in this case visible irregular changes of the orbital elements, and therefore its presence can be overlooked by studying variations of the elements. We conrm explicitly the strong and sensitive dependence of the dynamical behaviour on the companion masses.
Structural conditions of systems of simple sequential processes with resources nets without weakly dependent siphons

For the purpose of deadlock control, siphons in a Petri net (PN) can be divided into elementary and dependent ones; the latter can further be distinguished by strongly and weakly dependent siphons (WDS). The computation of the elementary siphons in a PN is essential but expensive since a complete siphon enumeration is needed. The results reported in the literature show that the control of WDS is quite conservative. Li et al. present two open problems. First, for what kinds of PN, we can definitely find a set of elementary siphons such that no WDS can be derived? Secondly, could we develop an algorithm to find a set of elementary siphons that can minimise the number of WDS in a net? The aim here is to answer the first problem for an systems of simple sequential processes with resources (S3PR) by investigating its structural conditions under which there are no WDS in it. The authors address such an issue by using an incremental approach for the synthesis of subnets (to compute an strict minimal siphon) of a strongly connected resource component. At each step, the authors add a PP-handle Hi with at least one interior resource place. The structural condition for the absence of WDS is derived and show that the maximal class of S3PR is a 2c+-system.
H∞ Fuzzy Tracking Control Design for Nonlinear Active Fault Tolerant Control Systems

This paper studies the problem of H ∞ fuzzy tracking control design for nonlinear active fault tolerant control systems based on the Takagi and Sugeno fuzzy model. Two random processes with Markovian transition characteristics are introduced to model the system component fault process and the fault detection and isolation decision process used to reconfigure the control law, respectively. The random behavior of the FDI process is conditioned on the fault process state. The parallel distributed compensation scheme is employed for the control design. As a result, a closed-loop fuzzy system with two Markovian jump parameters is obtained. Based on a stochastic Lyapunov function, a sufficient condition for stochastic stability of the closed-loop fuzzy system with a guaranteed H ∞ model reference tracking performance is first derived. A linear matrix inequality approach to the control design is then developed to reduce the effect of the external disturbance and reference input on tracking error as small as possible. Finally, a simulation example is presented to illustrate the effectiveness of the proposed design method.
Mixing in coaxial jets

The stirring and mixing properties of one-phase coaxial jets, with large outer (annular) to inner velocity ratio ru = u2/u1 are investigated. Mixing is contemplated according to its geometrical, statistical and spectral facets with particular attention paid to determining the relevant timescales of the evolution of, for example, the interface area generation between the streams, the emergence of its scale-dependent (fractal) properties and of the mixture composition after the mixing transition. The two key quantities are the vorticity thickness of the outer, fast stream velocity profile which determines the primary shear instability wavelength and the initial size of the lamellar structures peeled-off from the slow jet, and the elongation rate γ = (u2 − u1)/e constructed with the velocity difference between the streams and the gap thickness e of the annular jet. The kinetics of evolution of the interface corrugations, and the rate at which the mixture evolves from the initial segregation towards uniformity is prescribed by γ−1. The mixing time ts, that is the time needed to bring the initial scalar lamellae down to a transverse size where molecular diffusion becomes effective, and the corresponding dissipation scale s(ts) are formula here where Re and Sc denote the gap Reynolds number and the Schmidt number, respectively. The persistence of the large-scale straining motion is also apparent from the spectra of the scalar fluctuations which exhibit a k−1 shape on the inertial range of scales.
The rheology of multiwalled carbon nanotube and carbon black suspensions

This paper is concerned with a direct experimental and modeling comparison of the rheology of carbon black (CB) and multiwalled carbon nanotube (CNT) suspensions within a Newtonian epoxy matrix. Experimental observations of the effect of shear on CB and CNT microstructure are reported for a range of CB and CNT suspension concentrations. Steady shear, time dependent shear behavior, and oscillatory linear viscoelasticity (LVE) of the suspensions are reported and remarkably strong similarities were observed between the CB and CNT suspension rheology, for example, 4 wt. % CB and 0.4 wt. % CNT suspensions. Optical observations showed that both the CB and CNT microstructures were shear rate sensitive and a structure-dependent hybrid Maxwell-Voigt phenomenological model with a yield stress was developed that gave a reasonable fit to the rheological data. The structure model parameters for both systems were found to be of a similar order of magnitude, although the onset of rheology development for the two systems.
Dynamics of gas bubbles in time-variant temperature fields

The effect of time-variant temperature on the dynamics of a single gas bubble in a liquid is investigated. With changes in temperature, several physical parameters controlling bubble behaviour change including surface tension, diffusivity, vapour pressure and gas solubility. A single-bubble model is formulated and a numerical simulation implemented to model the radius–time profile of a bubble, across a range of initial bubble sizes and rates of heating, taking into account the aforementioned parameter temperature dependences. The model is validated experimentally in a xanthan gum gel phantom, tracking the evolution of the bubbles using digital photography and an image analysis sizing algorithm. It is shown that the natural tendency for a bubble to dissolve can be reversed by an increase in temperature, but only above a certain radius-dependent threshold rate of heating.
A model for Saharan dust transport

Abstract In this paper the source strength and the deposition rate of the dust emerging from the Sahara are assessed. For this purpose a multichannel sunphotometer has been developed and a turbidity network covering 11 stations has been set up in the Sahara, in the Sahel region and the surrounding southern area for a duration of about two years. A correlation analysis connecting observed aerosol turbidity parameters and mineral dust mass concentration has been performed during a four-week field campaign in Agadez (Niger). An appropriate box model including the aerosol turbidity parameters, actual wind field data of the source regions, the general circulation pattern over Africa and dry and wet deposition reveals a total mass production of about 630 × 106 and 710 × 106 t yr−1 for all suspended particulate matter, 80 × 106 and 90 × 106 t yr−1 for aerosol particles smaller than 5 μm radius for the years 1981 and 1982 respectively. About 60% of the mass moves southward to the Gulf of Guinea, 28% westward to t.
Dust Quasiatom in a Magnetoplasma

We present a quasiatomic structure of electrostatic oscillations of the plasma density inside the Debye sphere around a dust grain in a magnetoplasma. We discuss the role of an external magnetic field on the Debye-Hückel screening potential, the screening radius, and the eigenstate equation for high-frequency oscillations in the presence of a nonuniform potential that is created by a nonuniform potential distribution around a charged dust grain in plasmas.
Sensor design for cancer tissue diagnostics

In this paper, the design of a metamaterial-based sensor, operating in the mid-infrared frequency range, is proposed. The sensor consists of a planar array of complementary circular inclusions. The resonant frequencies of the sensor are designed to coincide with the proteins and lipids spectral characteristics, in order to detect the presence of cancer tissues, by absorption measurements. This sensor can be also used for the recognition of different benign tumours in a highly accurate and sensitive way. A new analytical circuit model has been developed, useful to describe its resonant behavior. The sensing device is, then, optimized to obtain high selectivity performances and has been tested through proper full-wave simulations. The structure can be used as a biological sensor with possible applications in medical diagnostics.
Pre-flight performance of a micro-satellite TSUBAME for X-ray polarimetry of gamma-ray bursts

To measure the polarization of gamma-ray bursts in X-ray energy band, we have developed a 50 kg micro-satellite named "SUBAME". The satellite has a compact and high-sensitive hard X-ray polarimeter employing newly-developed shock resistant multi-anode photomultipliers and Si avalanche photodiodes. Thanks to the ultra low-noise detectors and signal processors, the polarimeter can cover a wide energy range of 30􀀀200 keV even at 25°C with a high modulation factor of 62 %. TSUBAME is in the phase of final functional tests waiting for shipping to Baikonur and will be launched into a sun-synchronous orbit at an altitude of 700 km in late 2014. In this paper, the pre-ight performance of the gamma-ray detector system and the satellite bus system are presented.
Surface brightness and evolution of galaxies

It is well known that before the redshift-magnitude diagram of galaxies could be used for determination of the cosmological parameters one must know the evolution of the galaxies. We propose use of apparent surface brightness: which depends only on the redshift and is independent of the cosmological model and the inhomogeneities in the universe: for observational determination of the evolution of galaxies. The needed observations are isophotal angular diameters and apparent magnitudes within this or any other reasonable angular diameter. The application of the results for determination of q/sub 0/ is discussed briefly. (AIP)
Spin-torque-driven ballistic precessional switching with 50 ps impulses

We demonstrate reliable spin-torque-driven ballistic precessional switching using 50 ps current impulses in a spin-valve device that includes both in-plane and out-of-plane spin polarizers. Different threshold currents as the function of switching direction and current polarity enable the final orientation of the magnetic free layer to be steered, in accord with a macrospin analysis, by the sign of the pulse, eliminating the need for read-before-write toggle operation. The pulse amplitude windows for this deterministic operation are wider and more symmetric as a function of current polarity for shorter impulses, while inhomogeneous fringe fields from the polarizers lead to asymmetries as a function of current direction.
Binary interactions of solitary pulses in falling liquid films

We examine binary interaction of two-dimensional solitary pulses in falling liquid films. We make use of a two-field system of equations for the local flow rate and interface position that includes (second-order) viscous dispersion effects. By applying a coherent-structure theory, we obtain a dynamical system for the separation length between the pulses. The system is re-formulated in terms of a potential function which not only allows us to predict bound-state formation but also to interpret physically this formation. Numerical results of the fully non-linear second-order model are in very good agreement with the theoretically predicted distances. In addition, we numerically show that there are different types of dynamics associated with each bound state, including an overdamped, underdamped and undamped oscillating state depending on both the initial separation length and the Reynolds number.
Analysis of spatial high-order finite difference methods for Maxwell's equations in dispersive media

We study the stability properties of, and the phase error present in, several higher-order (in space) staggered finite difference schemes for Maxwell’s equations coupled with a Debye or Lorentz polarization model. We present a novel expansion of the symbol of finite difference approximations, of arbitrary (even) order, of the first-order spatial derivative operator. This alternative representation allows the derivation of a concise formula for the numerical dispersion relation for all (even-) order schemes applied to each model, including the limiting (infinite-order) case. We further derive a closed-form analytical stability condition for these schemes as a function of the order of the method. Using representative numerical values for the physical parameters, we validate the stability criterion while quantifying numerical dissipation. Lastly, we demonstrate the effect that the spatial discretization order, and the corresponding stability constraint, has on the dispersion error.
Signature of links

Let L be an oriented tame link in the three sphere S3. We study the Murasugi signature, a(L), and the nullity, r(L). It is shown that a(L) is a locally flat topological concordance invariant and that r(L) is a topological concordance invariant (no local flatness assumption here). Known results about the signature are re-proved (in some cases generalized) using branched coverings. 0. Introduction. Let L be an (oriented) tame link of multiplicity ,u in the three-sphere S3. That is, L consists of,u oriented circles K1, . , Kg disjointly imbedded in S3. Various authors have investigated a numerical invariant, the signature of L (notation: u(L)). The signature was first defined for knots (, = 1) by H. Trotter [21]. J. Milnor found another definition for this knot signature (see [1 2]) in terms of the cohomology ring structure of the infinite cyclic cover of the knot complement. In [2], D. Erle showed that the definitions of Milnor and Trotter are equivalent. In [15], K. Murasugi formulated a definition of signature for arbitrary links. In this paper we investigate the Murasugi signature in the context of branched covering spaces. To be specific, let D4 denote the four dimensional ball with 3D4 = S3, and let L C S3 be a link and F C D4 a properly imbedded, orientable, locally flat surface with 3F = L C S3. Let M denote the double branched cover of D4 along F. Then we show that u(L) is the signature of the four manifold M (see Lemma 1.1 and Theorem 3.1). Our proof of Theorem 3.1 contains the technicalities necessary to show this in the topological category. Using this viewpoint we are able to prove that u(L) is a topological concordance invariant (Theorem 3.8). We also rederive many of Murasugi's results, generalizing some of them (see Theorems 3.9-3.16). The paper is organized as follows: ? 1 contains the classical definitions of the signature and nullity of a link. It also deals with necessary background concerning branched coverings. Received by the editors November 4, 1974 and, in revised form, December 4, 1974 and April 11, 1975. AMS (MOS) subject classifications (1970). Primary SSA25.
Electronic structure of chromia aerogels from soft x-ray absorption spectroscopy

The electronic structure of ultralow density nanoporous chromia monoliths (aerogels) is studied by soft x-ray absorption near-edge structure (XANES) spectroscopy. These aerogels are prepared by the epoxide sol-gel method. High-resolution O K edge and Cr L2,3 edge XANES spectra of aerogels (before and after thermal annealing at 550°C) are compared with spectra of microcrystalline α‐Cr2O3 and orthorhombic CrO3 powders, α‐Cr2O3 (0001) and (11¯02) single crystals, and an unrelaxed amorphous phase of full-density Cr2O3. Spectra are interpreted based on the results of crystal-field multiplet calculations (for Cr L2,3 edge) and ab initio spin-polarized density functional theory calculations with and without a Hubbard-type on-site Coulomb repulsion (for O K edge). Results show that the electronic structure of as-prepared aerogels, with a large fraction of undercoordinated surface atoms, is significantly different from that of bulk α‐Cr2O3, CrO3, or amorphous Cr2O3. Thermal treatment transforms the as-prepared amo.
PODEn4DVar-based radar data assimilation scheme: formulation and preliminary results from real-data experiments with advanced research WRF (ARW)

The Proper Orthogonal Decomposition (POD)-based ensemble four-dimensional variational (4DVar) assimilation method (referred to as PODEn4DVar) is a hybrid assimilation method that exploits the strengths of both the ensemble Kalman filter (EnKF) and the 4DVar assimilation method. Its feasibility and validity have been demonstrated using ideal models through observing system simulation experiments (OSSEs). In this study, we further utilise this approach to build a PODEn4DVar-based radar data assimilation scheme (PRAS). In a PRAS, radar observations including radial velocity and reflectivity, after some necessary data preprocessing, are assimilated directly to improve model initialisation. A group of single-observation-based OSSEs are first designed to generally evaluate the validity of PRAS. Subsequently, a group of comparison experiments are also carried out between PRAS and an LETKF-based radar assimilation scheme (LRAS), which shows that PRAS is able to produce results better than (at least as good as) LRAS. Thirdly, to evaluate the potential impact for PRAS in the operational context, a group of cycling assimilation experiments of radar data are performed, which demonstrates that PRAS can gradually improve the accuracy of analysis field by cycling assimilation. Finally, a heavy convective-rainfall case study was selected to investigate the performance of PRAS in assimilating real radar observations and the impacts of assimilating radar observations on numerical forecasts, with the Weather Research and Forecasting (WRF) model as our forecasting model. The results show that significant improvements in predicting heavy rainfall can be achieved due to the improved initial conditions for the convective system's dynamics and microphysics after assimilating the radar observations with PRAS. In summary, the results show that the PODEn4DVar is a promising method for atmospheric data assimilation.
Two Modified for Chaos Negative Impedance Converter Op Amp Oscillators with Symmetrical and Antisymmetrical Nonlinearities

Two sinusoidal oscillator circuits, that employ an operational amplifier (op amp) as a current negative impedance converter (CNIC), are modified for chaos using a nonlinear resistor of anti-symmetrical current-voltage characteristics formed by a junction field effect transistor (JFET) operating in the triode region. The internal op amp dominant pole is found to contribute significantly to the chaotic nature of one circuit while the other circuit develops different chaotic attractors when cubic and fifth power odd symmetrical nonlinearities are used. Mathematical models of the two generators are presented. Experimental laboratory results, circuit simulations and numerical simulations of the mathematical models well agree and are included.