Miracle-dz/UniFAR-FTUs huggingface dataset:
Compact and polarization controlled 1.55μm vertical-cavity surface-emitting laser using single-layer photonic crystal mirror

Vertical-cavity surface-emitting lasers (VCSELs) consist of a gain medium in which feedback is generally accomplished by two distributed Bragg reflectors (DBRs), for which sufficient reflectivity has to be achieved in order to obtain laser emission. As a consequence, DBRs generally consist of very thick layer stacks. In this letter, the authors report the realization of a VCSEL, of which the top mirror consists of a single-layer one-dimensional photonic crystal mirror (PCM). This PCM enables significantly improved device compactness and total polarization control, while providing a directive and single lateral mode emission.
Pattern prediction by linear analysis of turbulent flow with drag reduction by wall oscillation

Abstract A turbulent flow past a transverse-oscillating wall is considered. The oscillation parameters correspond to the regime where drag reduction is observed. Streak spacing and streak angle obtained from the generalized optimal perturbation approach are compared with results from direct numerical simulations. Other flow features of the generalized optimal perturbation are compared with conditionally-averaged data extracted from numerical simulations. The generalized optimal perturbation at a given instant in time is found to consist of an infinitely long structure at a certain angle to the main flow direction. This angle varies slowly with time for half a period, and then suddenly jumps to a different value, changing both sign and magnitude. The angle variation is shown to be slow, because there is a short time interval in the oscillation period when a small perturbation of a certain angle grows strongly and then remains dominant for almost the entire half-period. The transient growth mechanism of the generalized optimal perturbation is found to be a combination of the Orr mechanism due to the cross-flow shear, acting at the initial stage, followed by the lift-up mechanism of the velocity component directed along the structure by the wall-normal motion also oriented in the same direction.
Ward identity for nonequilibrium Fermi systems

A nonequilibrium Ward identity (NE WI) connecting the scalar transport vertex correction with one-particle self-energy is derived using the global $\mathrm{U}(1)$ symmetry of the fermion nonequilibrium Green's functions (NGF). The nonperturbative derivation does not depend on the details of the many-body system. A renormalized multiplicative composition rule for the NGF, reflecting time coherence, is obtained and related to the NE WI. Applications involve (i) testing the consistency of approximations shown in the example of a self-consistent Born approximation for disorder scattering, and (ii) in the general quantum transport theory, the formalism permits one to assess routes to generalized master equations, in particular those based on the generalized Kadanoff-Baym ansatz.
Observability Analysis for TDOA Passive Localization System

Observability in passive location and tracking system is an important problem. This paper investigates the observability of multi-station time difference measurements system. For a 2D plane N orders movement target, three algorithms, linear system theory, nonlinear system theory and algebraic equations are used to demonstrate the observability of multi-station time difference of arrivals (TDOA) passive location and tracking system. The minimum of observation station and observation number are obtained when the targets are observability.
Retrieval of Cloud Parameters from Satellite Sounder Data: A Simulation Study

Abstract Estimates of cloud-top pressure and effective fractional cloud cover may be retrieved from satellite infrared sounder data. This paper presents the results of a simulation study which provides some insights into the relative performance of different retrieval methods and of different combinations of spectral channels. The “minimum residual method,” a variant of a technique described previously by other authors, is presented. It is applied here to groups of HIRS-2 channels and some aspects of its performance for different combinations of channels are examined using simulated data. It is also compared with the “radiance rationing method. ” Calculations suggest that the minimum residual method is comparable in performance to the radiance rationing method for high cloud but better for midlevel cloud. The relationship (and relative performance) of these methods to that used operationally to assign pressures to cloud tracers in Meteosat data is also discussed. The methods presented are for retrieving cl.
A 3-manifold with a non-subgroup-separable fundamental group

We examine a 3-manifold Γ whose fundamental group is known to be non-subgroup-separable (non-LERF). We show that this manifold Γ is a graph manifold and that the subgroup known to be non-separable is not geometric. On the other hand, there are incompressible surfaces immersed in the manifold which do not lift to embeddings in any finite-degree covering space. We then prove that these bad incompressible surfaces must have non-empty boundary.
Nonlocal continuum theories of beams for the analysis of carbon nanotubes

The equations of motion of the Euler–Bernoulli and Timoshenko beam theories are reformulated using the nonlocal differential constitutive relations of Eringen [International Journal of Engineering Science 10, 1–16 (1972)]. The equations of motion are then used to evaluate the static bending, vibration, and buckling responses of beams with various boundary conditions. Numerical results are presented using the nonlocal theories to bring out the effect of the nonlocal behavior on deflections, buckling loads, and natural frequencies of carbon nanotubes.
Ab initio computation of the mean inner Coulomb potential of amorphous carbon structures

The mean inner Coulomb potential (MIP) of amorphous carbon structures was computed for slabs with mass densities between ρ=2.0g∕cm3 and ρ=3.5g∕cm3 by the full potential linearized augmented plane-wave (FLAPW) method. The amorphous carbon structures consisting of 64 carbon atoms were generated by a classical metropolis Monte Carlo procedure using the Tersoff potential for carbon. The MIP shows a linear dependence on the mass density. Values of the MIP of the amorphous carbon structures are compared with experimental values and with computed values for the MIP of graphite and diamond.
Optical identification of XMM sources in the Canada–France–Hawaii Telescope Legacy Survey

We present optical spectroscopic identifications of X-ray sources in ∼3 deg 2 of the XMM-Large Scale Structure survey (XMM―LSS), also covered by the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), obtained with the AAOmega instrument at the Anglo-Australian Telescope. In a flux-limited sample of 829 point-like sources in the optical band with g ' ≤ 22 ma g and the 0 . 5 - 2 keV flux (f 0.5―2 keV ) > 1 x 10 ―15 erg cm ―2 s ―1 , we observed 693 objects and obtained reliable spectroscopic identification for 487 sources, approximately 59 per cent of the overall sample. We therefore increase the number of identifications in this field by a factor close to 5. Galactic stellar sources represent about 15 per cent of the total (74/487). About 54 per cent (265/487) are broad-line active galactic nuclei (AGN) spanning redshifts between 0.15 and 3.87 with a median value of 1.68. The optical-to-X-ray spectral index (α ox ) of the broad-line AGN is 1.47 ± 0.03, typical of optically selected type I quasars, and is found to correlate with the rest-frame X-ray and optical monochromatic luminosities at 2 keV and 2500 A, respectively. Consistent with previous studies, we find α ox not to be correlated with z. In addition, 32 and 116 X-ray sources are, respectively, absorption- and emission-line galaxies at z < 0.76. From a line ratio diagnostic diagram, it is found that in about 50 per cent of these emission-line galaxies, the emission lines are powered significantly by the AGN. 30 of the XMM sources are detected at one or more radio frequencies. In addition, 24 sources have ambiguous identification: in eight cases, two XMM sources have a single optical source within 6 arcsec of each of them, whereas two and 14 XMM sources have, respectively, three and two possible optical sources within 6 arcsec of each of them. Spectra of multiple possible counterparts were obtained in such ambiguous cases.
Predicting chaos through an harmonic balance technique: an application to the time-delayed Chua's circuit

The time-delayed Chua's circuit (TDCC) can be considered as a paradigm for studying chaos in circuits described by difference-differential equations. The dynamics of such circuits cannot be investigated by means of the standard time-domain techniques developed for finite dimensional systems. We show that through a spectral approach the occurrence of periodic limit cycles and of chaotic attractors can be easily predicted, without performing any simulations.
An inequality in the theory of arithmetic on algebraic varieties

The inequality which is proved here was established under different conditions in a paper entitled ‘Periodic points on an algebraic variety', which is to appear in the Annals of Mathematics. It is hoped that the new formulation will be more useful for applications. The present investigations use the rather sophisticated techniques of the ‘Theory of distributions’ which was developed by Weil (1). As the content of this theory may be unfamiliar to the reader, Weil's results are described at some length, though of course, his proofs are not given. The one result which we need and which is not given explicitly by Weil, is proved in detail.
Femtosecond Kerr-lens mode-locked Cr:LiSGaF laser

We demonstrate a femtosecond Kerr-lens mode-locked Cr:LiSGaF laser that based on a compact cavity geometry. For the first time to our knowledge, with a combination of 488-, 476- and 458-nm lines from Argon-ion laser as a pump source, 58-fs pulses centered at 845 nm were generated. The average output power is 30 mW, and the time-band product is 0.331, assuming a sech2 pulse shape. Neither Acousto-modulator nor physical aperture or slit were used in this cavity to start and sustain the Kerr-lens mode-locking operation.
Ultrafast characteristics of InGaP-InGaAlP laser amplifiers

We characterize a visible, 670 nm, diode laser amplifier with respect to parameters of interest in short pulse generation and amplification. With a single pulse in the amplifier, we measure the differential gain and saturation energy of the amplifier, and changes in the optical spectrum of a pulse traveling through the amplifier. We also measure the ultrafast gain dynamics using a pump and probe technique. We find the ultrafast gain recovery time due to carrier heating is 400 fs/spl plusmn/30 fs. Our results differ quantitatively from those reported for InGaAsP and AlGaAs amplifiers.
On the ultimate lower limit of attenuation in glass optical waveguides

The fabrication of an extremely‐low‐loss glass optical waveguide, having as little as 4 dB/km total attenuation, has allowed interpretation of the absorption spectrum to a much greater degree than previously possible. It is shown that, beyond about 700 nm, intrinsic ultraviolet absorption will have no effect. Between 700 and 1100 nm, all absorption can be accounted for on the basis of OH to within ±0.7 dB/km. Marked reduction of the water content will leave the scattering as the major loss mechanism, thereby permitting total attenuations of about 2 dB/km.
Absolute measurement of absorption coefficient by combining photoacoustics and acousto-optics

Quantitative measurements of the chromophores concentration in vivo present a challenge in photoacoustic imaging. The obtained signal depends on the absorbed optical density which is the product of absorption coefficient and local fluence. As a result of wavelength-dependent optical attenuation and scattering, the local fluence in biological media varies with depth and the optical wavelength. This fluence heterogeneity needs to be compensating in the order to recover the absolute absorption coefficient. In this paper we describe a new approach to recover the absolute optical absorption coefficient from measured PA signals based in combination between photoacoustic and acousto-optic signals. The present method is based on two principles, a given photon trajectory through a scattering medium can be travelled in two directions with equal probability and photons which traverse a certain volume can be labeled in that volume with the use of focused ultrasound. We give proof of the principle using Monte Carlo simulation and we demonstrate the experimental feasibility of the technique in tissue-mimicking phantom by correcting a fluence heterogeneity caused by the optical diffusion.
Development of an integrated modelling framework for retailers of perishable products: a dynamic programming approach

In today’s extremely competitive global market scenario, retailers of perishable products are facing the challenges of maintaining inventory and deciding on the optimal order quantity so as to fulfil customer demands as well as to minimise cost. This paper proposes an integrated model that allows easy and quick exploration and selection of the best ordering policy from among various available alternatives regarding perishable products at the retailer end. Using this approach, retailers can take decisions at any instant regarding placing of orders on the basis of available inventory and allocation of products with respect to shelf life to customers. The modelling algorithm is based on dynamic programming approach, and is developed using the programming platform of MATLAB software. An example, case problem is used to demonstrate the applicability of the proposed integrated approach.
Dialectal differences in diphthong perception.

This study attempts to determine if speech perception varies across dialects as production does. Synthetic stimuli based on one talker from Binghamton, NY (northern US) and one from Birmingham, AL (southern US) were presented to subjects from both regions. The stimuli were 18 vowel continua in CVC context. These 10‐point continua had initial tokens containing nonhigh vowels, such as hot /hat/, with formant values and durations manipulated to result in final tokens containing diphthongs, such as hot /hɪt/. Other continua contained endpoints such as sad /saed/ and side /saɪd/, or bought /bt/ and bout/baut/. The production of diphthongs differs between these dialects, varying from the Canadian raising of the North to the monophthongization of the South. The question to be resolved in this study is whether perception of diphthongs differs between the dialects. It was found in a direct boundary estimation task that southern subjects perceived southern tokens as diphthongs earlier in the continua than northern s.
Magnetic properties of single‐crystal {110} iron films grown on GaAs by molecular beam epitaxy (invited)

Single‐crystal {110} Fe films, grown for the first time by molecular beam epitaxy on GaAs, have been studied by a variety of techniques in order to determine the dependence of the magnetic properties upon film thickness L and quality, and an overview of these results is presented. The dependence of the ferromagnetic resonance (FMR) field upon its orientation in the (110) plane was measured at 16.4 GHz and shows that the magnetically easy axis is [110] for L<50 A and [001] for L≳150 A. A theory of FMR which incorporates magnetocrystalline surface anisotropy is outlined. It successfully interprets the thickness dependence of the FMR data in the ultrathin (L≲50 A) regime and shows them to be surface dominated. FMR data at 9.2 GHz, which contain both aligned and nonaligned resonance branches, are presented as a function L. In addition, the dependence of the branches on frequency f for 8 GHz
A New Assault on the 92 Centimeter Line of D i

Results are reported from a search for the 92-cm line of D I in the ISM toward the Galactic anticenter, performed using the 25.9-m UC Berkeley telescope at Hat Creek during 1984-1986 and the 42.7-m NRAO telescope at Green Bank during 1984. The spectrum for single-channel-equivalent integration time 1.7 Msec is presented and shown to be consistent with detection of the line at 2-3 mK, corresponding to primordial and solar-vicinity D/H ratios of about 0.00005 and less than about 0.00002-0.00003, respectively. The possibility that the present detection is only apparent (considering the spectrum rms noise level of 1.6 mK) is examined, and the implications of a nondetection at this level for theoretical models are discussed. 15 references.
Semi-Parametric Estimation in the Nonlinear Structural Errors-in-Variables Model

In the nonlinear structural errors-in-variables model, we propose a consistent estimator of the unknown parameter using a modified least squares criterion. We give an upper bound of its rate of convergence which is strongly related to the regularity of the regression function and is generally slower than the parametric rate of convergence n -1/2 , Nevertheless, the rate is of order n -1/2 for some particular analytic regression functions. For instance, when the regression function is either a polynomial function or an exponential function, we prove that our estimator achieves the parametric rate of convergence.
The Large Magellanic Cloud Bar West field

Infrared photometry is presented for an unbiased sample of M giants in the Bar West field of the LMC. The m(bol), J-K color-magnitude diagram is dominated by AGB stars with properties similar to those of giants in intermediate-age clusters in the LMC. About 20 percent of the AGB population has properties similar to those of young clusters. The brightest stars are all of M type; a mean (Fe/H) = -0.5 + or - 0.3, nearly a factor of 10 lower than the mean (Fe/H) in Baade's window, is estimated for them. The presence of two sequences of AGB stars can be interpreted as evidence for at least two major episodes of star formation in the Bar West field. The young population appears to have a measurably higher metallicity than the older population. 39 refs.
Bayesian Inference With Incomplete Multinomial Data: A Problem in Pathogen Diversity

With recent advances in genetic analysis, it has become feasible to classify a pathogen into genetically distinct variants even though they apparently cause an infected subject similar symptoms. The availability of such data opens up the interesting problem of studying the spatiotemporal variation in the diversity of variants of a pathogen. Data on pathogen variants often suffer the problems of (i) low cell counts, (ii) incomplete classification due to laboratory problems (e.g., contamination), and (iii) unseen variants. Shannon’s entropy may be used as a measure of variant diversity. A Bayesian approach can be used to deal with the problems of low cell counts and unseen variants. Bayesian analysis of incomplete multinomial data may be carried out by Markov chain Monte Carlo techniques. However, for pathogen-variant data, there often is only one source of missingness—namely, some subjects are known to be infected by some unidentified pathogen variant. We point out that for incomplete data with disjoint sources of missingness, Bayesian analysis can be done more efficiently using an iid sampling scheme from the posterior distribution. We illustrate the method by analyzing a data set on the prevalence of bartonella infection among individual colonies of prairie dogs at the study site in Colorado between 2003 and 2006. We compare the result from the proposed Monte Carlo method with the results from other methods, including a model that entertains within-variant spatial correlation but no between-variant spatial correlation. This article has supplementary material online.
Investigation of the graphene based planar plasmonic filters

We investigate numerically the edge modes supported by graphene ribbons and the planar band-stop filter consisting of a graphene ribbon lateral coupled a graphene ring resonator by using the finite-difference time-domain method. Simulation results reveal that the edge modes can enhance the electromagnetic coupling between objects indeed and this structure realizes perfect, tunable filtering effect. Successively, the channel-drop filter is constructed. Especially, the proposed structures can be designed and the size of the ring is changed by creating non-uniform conductivity patterns on monolayer graphene. Our studies will benefit the fabrication of the planar, ultra-compact devices in the mid-infrared region.
ASCA observations of non‐thermal emissions from groups of galaxies

ASCA detected hard X-ray emission associated with several groups of galaxies. Analysis of HCG62 data, whose data quality is the best of all, indicates that hard X-ray emission is extended over groups. The luminosity of hard emission is typically 1041–42 erg/s. The possible emission mechanism is non-thermal bremsstrahlung by sub-relativistic particles or inverse compton scattering of CMB photons by relativistic electrons. Whichever it is, leading results will be interesting for studies of particle acceleration in the clusters of galaxies.
The hypergiant masers: episodic mass loss, convection and magnetic fields

Abstract The cool hypergiants are the most luminous known stars in the upper HR Diagram in the apparent temperature range represented by spectral types A to M. Most of the stars in this regime are unstable as evidenced by their high mass loss rates, variability, and in some cases large IR excesses and circumstellar ejecta. We have obtained high resolution multi-wavelength images with HST/WFPC2 of several of the most known evolved cool stars including several well known stellar masers. VX Sgr and S Per were marginally resolved, while NML Cyg has a peculiar asymmetric envelope that has been shaped by its environment. The powerful maser sources IRC+10420 and VY CMa have extensive and complex circumstellar ejecta due to high mass loss episodes apparently driven by large-scale convective activity.
Stability of Liquid Interfaces in Porous Media

An analysis is presented for the stability of liquid interfaces moving with uniform velocities in homogeneous isotropic porous media. The effects of viscosity, surface tension, and body forces are taken into account. The first part of this investigation concerns the linear stability of a finite depth liquid layer bounded by two semi‐infinite liquids. It is found that the critical conditions separating stable from unstable disturbances are independent of the depth of the liquid layer. For a sufficiently large flow velocity, the system is stable if, across each interface, the viscosity decreases in the direction of flow, and it is unstable if viscosity increases in the direction of flow across at least one interface. The second part treats the nonlinear frontal stability of two semi‐infinite liquids. The results show that the nonlinearity is destabilizing owing to the decrease of the surface tension force. Deviations from Darcy's law are found to be stabilizing when the flow is from the denser to the lighte.