Miracle-dz/UniFAR-FTUs huggingface dataset:
Dynamics accompanying polarization switching in vertical-cavity surface-emitting lasers

Experiments on quantum well and recently quantum dot VCSELs have shown that the increase of injection current may lead to a transition from a linearly polarized light emission at threshold to a region of nonlinear dynamics (self-pulsing) accompanying polarization switching between either two orthogonal linearly polarized states or non-orthogonal elliptically polarized states. The dynamics occurs on a nanosecond time-scale and relates either to the birefringence induced frequency splitting or to the relaxation oscillation frequency. In this contribution, we bring new light into the bifurcation mechanisms explaining the occurrence of deterministic self-pulsing accompanying polarization switching. We demonstrate theoretically that depending on the laser parameters, different polarization switching scenarios may be observed with self-pulsing dynamics at a dominant time-scale related to either linear cavity birefringence or relaxation oscillation, and with additional period doubling or quasiperiodicity. Our work therefore not only reconciles previous experiments with different conclusions on dynamical states, but also provides an improved understanding of the bifurcations underlying the commonly used spin flip model for VCSEL - hence motivating new in depth experiments of polarization dynamics at nanosecond time scale.
Weak solutions of hyperbolic-parabolic Volterra equations

The existence of a global weak solution, satisfying certain a priori L? -bounds, of the equation ut(t, x) = ft k(t s)(a(ux))x(s, x) ds + f(t, x) is established. The kernel k is locally integrable and log-convex, and a' has only one local minimum which is positive. INTRODUCTION The purpose of this paper is to establish the existence of a global weak solution of the equation (1) t Ut(t, X) = k k(t s) (a (ux)) x(s, x) ds + f(t, x) , t > O, x E (0, 1), u(O, x) = uo(x), x E {O, 1], u(t, O) = u(t, 1) = O, t > O (where the subscripts denote differentiation with respect to the corresponding variables), and to show that this weak solution satisfies certain a priori L? bounds. Equation (1) is of interest because it appears in mathematical models of viscoelasticity (see [18 and 31]), but also because it is of a form somewhere between a parabolic and a hyperbolic equation. This is due to the fact that when k -1 we get the nonlinear wave equation utt(t, x) = (a(UX))X(t, X) + ft(t, X), and if, on the other hand, k is replaced by the delta functional, then we get the nonlinear diffusion equation Ut(t, X) = (a(Ux))X(t, x) + f(t, x). The nonlinear wave equation (that corresponds to the completely elastic case in mechanics) has a weak solution with both ux and ut bounded and initially smooth solutions develop singularities (in the derivatives) in finite time. The Received by the editors September 22, 1992. 1991 Mathematics Subject Classification. Primary 45K05; Secondary 45D05, 45N05, 35K99, 35L99, 73F99.
Climatology of Thunderstorms for North Dakota, 2002-06

Abstract Radar and surface thunderstorm data in North Dakota were investigated to obtain the climatology of thunderstorms in the state. A life cycle analysis for the individual storm cells between 2002 and 2006 was carried out, and it was found that June and July were the peak months, late afternoon to early morning was the peak time for thunderstorms, the average lifetime of storm cells was 23.6 min, the average gust wind speed was 16.5 m s−1, the average track length was 21.8 km, and the average movement speed was 16.4 m s−1. The average movement of storm cells varied with months, and the storms moved toward the north, the northeast, and the east. It was also demonstrated that there were 19–35 thunderstorm days each year in North Dakota and that, of these, 9–14 thunderstorm days each year were associated with high speed winds. Severe thunderstorms composed 1.7% of all the thunderstorms in 2002–06. The most intense thunderstorm in North Dakota between 2002 and 2006 was associated with a 5-yr-high wind sp.
Inverse scattering for an impedance cylinder buried in a dielectric cylinder

An inverse scattering problem is considered for arbitrarily shaped cylindrical objects that have inhomogeneous impedance boundaries and are buried in arbitrarily shaped cylindrical dielectrics. Given the shapes of the impedance object and the dielectric, the inverse problem consists of reconstructing the inhomogeneous boundary impedance from a measured far field pattern for an incident time-harmonic plane wave. Extending the approach suggested by Akduman and Kress [Direct and inverse scattering problems for inhomogeneous impedance cylinders of arbitrary shape. Radio Sci. 38 (2003), pp. 1055–1064] for an impedance cylinder in an homogeneous background medium, both the direct and the inverse scattering problem are solved via boundary integral equations. For the inverse problem, representing the scattered field as a potential leads to severely ill-posed linear integral equations of the first kind for the densities. For their stable numerical solution Tikhonov regularization is employed. Knowing the scattered field, the boundary impedance function can be obtained from the boundary condition either by direct evaluation or by a least squares approach. We provide a mathematical foundation of the inverse method and illustrate its feasibility by numerical examples.
Effects of Global and Local Contexts on Harmonic Expectancy

Several psycholinguistic studies have investigated the influence of local and global semantic contexts on word processing. The first aim of the present study was to examine local and global level contributions to harmonic priming. The second was to test a spreading-activation account of harmonic context effects (Bharucha, 1987). The expectations for the last chord (the target) of eight-chord sequences were varied by simultaneously manipulating the harmonic relationship of the target to the first six chords (global context) and to the seventh chord (local context). Human performances demonstrated that harmonic expectancies are derived from both the global and local levels of musical structure. Bharucha9s connectionist model provides a possible account of local and global context effects. In isochronous chord sequences, harmonic priming seems to result from activation spreading via a schematic knowledge of tonal hierarchies.
Subsonic Round and Plane Macro/Micro‐jets in a Transverse Acoustic Field

Results of experimental studies on the mechanism of plane evolution and round macro‐and micro‐jet flows at low Reynolds numbers in a transverse acoustic field are discussed. New data on the jet development mechanism are obtained through hot‐wire measurements. Smoke visualization of the jet flow with the use of stroboscopic laser illumination of the jet at frequencies of the acoustic influence on the latter. A lot of the new phenomena in development of the macro and micro‐jets in a cross acoustic field are found out.
Hyperbolic travelling fronts

Since the work of R. A. Fisher [2] and Kolmogorov, Petrovskij and Piskunov [7] (see [6] for further references) the problem of travelling fronts in reaction–diffusion equations has been extensively studied. For the equation with F(0) = F(1) = 0 a travelling front is a solution where the function of one variable φ is decreasing and satisfies φ(−∞) = 1, φ(+∞) = 0. The function φ describes the shape of the front and the constant c is the speed of propagation. There are two main types of the problem. In the all-positive case, where the function F satisfies there is a half-line [c0, ∞), c0>0, of speeds. For each c∈[c0, ∞) there is, up to translation, a unique travelling front. Fronts for different c can be distinguished by the rate of decay towards +∞. In the threshold case, where F has the property, for some λ∈(0, 1), there is a unique speed c0 with a travelling front, which is unique up to translation. In this case the sign of c0 is determined by the sign of the integral
Computational Analysis and Validation for Lateral Jet Controlled Missiles

Comparison of three-dimensional, viscous, turbulent Navier–Stokes simulation for generic missile bodies with wind-tunnel tests have been performed with and without lateral jet thrusters for  ow Mach number range of 2–5 and angles of attack of 0–20 deg. Computationalresults show good overall engineering predictive capability for the surface pressure, normal force coef cient, and jet interaction effects. Further analysisof the computationalresults shows that the favorable upstream pressure zone (lambda zone) created by the lateral jet, unfavorable pressure loss behind the jet caused by its blockage effect, and the jet wraparound effect are the three principal competing physical mechanisms that inhibit or enhance the jet ampli cation factor. Canted jet studies to enhance the  rst of these effects show substantial increase in favorable pressure; however, it does not recover axial component of the thrust vector. Qualitative computations for multijets and hot/binary gas thruster jets have been presented to demonstrate the overall computational capability for missile design applications.
Distributed strain measurement in perfluorinated polymer optical fibres using optical frequency domain reflectometry

We present the latest advances in distributed strain measurement in perfluorinated polymer optical fibres (POFs) using backscatter techniques. Compared to previously introduced poly(methyl methacrylate) POFs, the measurement length can be extended to more than 500 m at improved spatial resolution of a few centimetres. It is shown that strain in a perfluorinated POF can be measured up to 100%. In parallel to these investigations, the incoherent optical frequency domain reflectometry (OFDR) technique is introduced to detect strained fibre sections and to measure distributed length change along the fibre with sub-millimetre resolution by applying a cross-correlation algorithm to the backscatter signal. The overall superior performance of the OFDR technique compared to the optical time domain reflectometry in terms of accuracy, dynamic range, spatial resolution and measurement speed is presented. The proposed sensor system is a promising technique for use in structural health monitoring applications where the precise detection of high strain is required.
Variability of the Supersaturation in Cumulus Clouds.

Abstract The quasi-steady supersaturation in cumulus clouds from the Cooperative Convective Precipitation Experiment of 1981 are calculated from measurements of vertical wind, cloud droplet size, temperature and pressure. Mean values and spectral characteristics of the supersaturation are presented. The supersaturation values in 147 cloud regions averaged near 0%, with standard deviations in the (10-m average) supersaturation values that ranged from 0.1% in unmixed regions to about 0.4% in regions about 80% diluted by entrainment. The Eulerian variance spectra for vertical wind, integral radius and supersaturation were determined, and a technique is described for estimating the Lagrangian spectra. The Lagrangian characteristic times for supersaturation were estimated to be about 50 s for mixed regions but substantially larger for some regions with strong updrafts. It is argued that the observed variability in supersaturation is comparable to that needed to account for typical dispersions in droplet size s.
Local Bifurcation of Critical Periods in Vector Fields With Homogeneous Nonlinearities of the Third Degree

Abstract In this paper we study the local bifurcation of critical periods of periodic orbits in the neighborhood of a nondegenerate centre of a vector field with a homogeneous nonlinearity of the third degree. We show that at most three local critical periods bifurcate from a weak linear centre of finite order or from the linear isochrone and at most two local critical periods from the nonlinear isochrone. Moreover, in both cases, there are perturbations with the maximum number of critical periods.
Hot accretion disks with electron-positron pairs

The hot thermal accretion disks of the 1970s are studied and consideration is given to the effects of electron-positron pairs, which were originally neglected. It is found that disks cooled by internally produced photons have a critical accretion rate above which equilibrium is not possible in a radial annulus centered around r = 10 GM/c-squared, where M is the mass of the central object. This confirms and extends previous work by Kusunose and Takahara. Above the critical rate, pairs are created more rapidly than they can be destroyed. Below the critical rate, there are two solutions to the disk structure, one with a high pair density and one with a low pair density. Depending on the strength of the viscosity, the critical accretion rate corresponds to a critical luminosity of about 3-10 percent of the Eddington limit. 32 refs.
The constancy of the ratio of the molecular hydrogen lines at 3.8 μm in Orion

The 1-0 O(7) and 0-0 S(13) lines of H2, at 3.807 and 3.846 microns, have been mapped over the region of the Orion molecular outflow. The intensity ratio of these lines is found to be independent of position in the outflow. From this it is inferred that the structure of the shocks and their cooling flows in Orion may be more akin to hydrodynamic shocks than the low-temperature C-shocks that are currently favored.
Symmetrization of low-energy electron diffraction patterns

Using the layer-by-layer approach to low-energy electron diffraction (LEED) the authors explain how to symmetrize the beam scattering matrix for layers. The coincidence structure formed by the layers may be dense or open and may possess any of the 17 two-dimensional space group symmetries. The beams of the electron field become diffracted by the layers in a manner determined by von Laue's diffraction conditions. These conditions turn out to arrange the beams in mutually independent bundles. After establishing the transformation properties of bundles of beams under the point group part of the two-dimensional space group the authors derive a scheme for finding symmetrized combinations of interacting beams. The formalism is applied to the layer-KKR method for LEED calculation. In particular the symmetrization of the beam patterns created by three overlayer structures on surfaces of face-centred cubic crystals are described: the primitive 2*2 structure and the ( square root 2* square root 2)45 degrees structure on the (100) surface together with the ( square root 3* square root 3)30 degrees structure on the (111) surface.
Pseudojump operators. I. The r.e. case

Call an operator J on the power set of co a pseudo jump operator if J(A) is uniformly recursively enumerable in A and A is recursive in J(A) for all subsets A of c. Thus the (Turing) jump operator is a pseudo jump operator, and any existence proof in the theory of r.e. degrees yields, when relativized, one or more pseudo jump operators. Extending well-known results about the jump, we show that for any pseudo jump operator J, every degree > 0' has a representative in the range of J, and that there is a nonrecursive r.e. set A with J(A) of degree 0'. The latter result yields a finite injury proof in two steps that there is an incomplete high r.e. degree, and by iteration analogous results for other levels of the H", Ln hierarchy of r.e. degrees. We also establish a result on pairs of pseudo jump operators. This is combined with Lachlan's result on the impossibility of combining splitting and density for r.e. degrees to yield a new proof of Harrington's result that 0' does not split over all lower r.e. degrees. 1. We prove some generalizations of theorems about the Turing jump operator (denoted A H A') to theorems about operators of the form A * A ED WA, for an arbitrary fixed Godel number e. (Here A ED B is the recursive join of A and B and WA is the eth set r.e. in A in a fixed standard enumeration.) For instance, Friedberg (see (25, Theorem 4.1)) showed that there is a nonrecursive r.e. set A with A' TK (where K is a complete r.e. set). We prove by a finite injury priority argument similar to Friedberg's that for every e there is a nonrecursive r.e. set A with A ED WA-T K. Now Friedberg's argument relative to an arbitrary oracle B yields a fixed Godel
One-way mode transmission in one-dimensional phononic crystal plates

We investigate theoretically the band structures of one-dimensional phononic crystal (PC) plates with both antisymmetric and symmetric structures, and show how unidirectional transmission behavior can be obtained for either antisymmetric waves (A modes) or symmetric waves (S modes) by exploiting mode conversion and selection in the linear plate systems. The theoretical approach is illustrated for one PC plate example where unidirectional transmission behavior is obtained in certain frequency bands. Employing harmonic frequency analysis, we numerically demonstrate the one-way mode transmission for the PC plate with finite superlattice by calculating the steady-state displacement fields under A modes source (or S modes source) in forward and backward direction, respectively. The results show that the incident waves from A modes source (or S modes source) are transformed into S modes waves (or A modes waves) after passing through the superlattice in the forward direction and the Lamb wave rejections in the backward direction are striking with a power extinction ratio of more than 1000. The present structure can be easily extended to two-dimensional PC plate and efficiently encourage practical studies of experimental realization which is believed to have much significance for one-way Lamb wave mode transmission.
Graphitization at diamond dislocation cores

We examine possible mechanisms for graphitization at dislocation cores in diamond, both as an explanation for brown coloration in natural brown diamond and as a model for annealing in amorphous carbon materials. We find a metastable structure for the 90° partial dislocation core where bonds are broken in both single- and double-period structures leading to a row of paired sp2 C atoms. We examine the effect of hydrogen and other impurities on this core structure both through direct interaction and potential charging effects. We also investigate a mechanism for progressive aromatization through the migration and aggregation of 30° partial dislocations.
On the Fourier space decomposition of free shear flow measurements and mode degeneration in the pairing process

A two‐dimensional shear layer perturbed by low level perturbation is studied experimentally. The driving signal is composed of two sine waves of fundamental and subharmonic modes of the most unstable natural frequency, with an adjustable phase angle. The flow is examined in a Fourier space and a phase measuring technique is employed to capture the disturbance field, including the subharmonic and its three higher harmonics. The flow field composed of the mean motion and the above‐mentioned modes is reassembled. By this quantitative method the crucial connection between the evolution of superposed instability waves, based on hydrodynamic stability theory, and the experimentally observed large‐scale orderly structures is made feasible. By considering the fundamental frequency field superimposed on the mean flow, two different Fourier mode structures, having two different phase speeds, are observed in the pairing region. This mode degeneration process is also observed in the fields of other higher harmonics o.
A SMOOTHING-TYPE ALGORITHM FOR ABSOLUTE VALUE EQUATIONS

The system of absolute value equations $Ax+B|x|=b$, denoted by AVEs, is proved to be NP-hard, where $A, B$ are arbitrary given $n\times n$ real matrices and $b$ is arbitrary given $n$-dimensional vector. In this paper, we reformulate AVEs as a family of parameterized smooth equations and propose a smoothing-type algorithm to solve AVEs. Under the assumption that the minimal singular value of the matrix $A$ is strictly greater than the maximal singular value of the matrix $B$, we prove that the algorithm is well-defined. In particular, we show that the algorithm is globally convergent and the convergence rate is quadratic without any additional assumption. The preliminary numerical results are reported, which show the effectiveness of the algorithm.
Extended emission-line gas in NGC 1275 and the central galaxy in A1795: evidence for a distributed rather than a central source of ionization

Les donnees spectrometriques de la galaxie elliptique geante NGC 1275 presentees ici sont clairement en desaccord avec les modeles de photoionisation par une source centrale. Plusieurs causes possibles d'ionisation etendue sont considerees et etudiees. Les donnees spectrales de NGC 1275 sont comparees a celles de la galaxie centrale de l'amas a 1795
Synthesis of active fault-tolerant control based on Markovian jump system models

In this paper active fault-tolerant control (FTC) is designed in a stochastic framework. The fault-tolerant control system (FTCS) is formulated as a set of linear systems governed by two continuous-time finite-state Markov chains, which are used to characterise the system failure modes and the fault detection and isolation (FDI) scheme. This framework is widely accepted for stability analysis of FTCS; however, the design of a controller only accessing the FDI mode is still a challenging problem. We solve this synthesis problem by using convex optimisation techniques. First, a sufficient condition for the mean exponential stability is given in terms of a linear matrix inequality (LMI). The results are then extended to uncertain systems design for stability and in system performance using a stochastic integral quadratic constraint. Due to the complexity of the problem, the controller is obtained using the iterative LMI technique.
BBXRT and Ginga observations of the Seyfert 1 galaxy Markarian 335

We present new X-ray observations of Mrk 335 in the 0.4-10 keV band using BBXRT and in the 2-20 keV band with Ginga. The BBXRT data show a break to a softer spectrum below about 1 keV. The Ginga data show evidence for variability in absorption, uncorrelated with flux changes of the continuum source. The inconsistency between the opacity observed at the iron K edge and at softer X-ray energies implies that the absorber has an ionization state about FeXV. We suggest that the nuclear emission can be explained by a self-consistent pair cascade model as developed by Zdziarski et al. (1990) and Zdziarski and Coppi (1991), where the compactness parameter inferred from the spectral fits to both data sets is in good agreement with the value calculated from the ratio of observed X-ray luminosity and variability time scale.
Conditions for accretion-induced collapse of white dwarfs

Recent discovery of an unexpectedly large number of low-mass binary pulsars (LMBPs) in globular clusters has instigated active discussions on the evolutionary origin of binary pulsars. Prompted by the possibility that at least some of LMBPs originate from accretion-induced collapse (AIC) of white dwarfs, a reexamination is conducted as to whether or not AIC occurs for the new models of O + Ne + Mg white dwarfs and solid C + O white dwarfs that can ignite explosive nuclear burning at significantly lower central densities than in the previous models. Even with low critical densities, AIC is still much more likely than explosion for both types of white dwarfs. Possible regions for AIC are presented in a diagram of mass accretion rate vs initial mass of the white dwarfs. 42 refs.
Modified clifford analysis

The following generalization of the Cauchy-Riemann system is being considered . This system, denoted by (H), is closely related to the hyperbolic metric on R n+1 +. Embedding R n+1 + into the Clifford algebra Cn, the powers xk(k∈N) yield solutions of (H). Also, compositions of solution with Mobius transformations in R n+1 + lead to solutions of (H). General rules associating new solutions to given ones are finally being investigated.