Miracle-dz/UniFAR-FTUs huggingface dataset:
First observation of an extremely large‐dipole infrared transition within the conduction band of a GaAs quantum well

A new type of optical transition in GaAs quantum wells has been observed. The dipole occurs between two envelope states of the conduction‐band electron wave function, and is called a quantum well envelope state transition (QWEST). The QWEST is observed by infrared absorption for two structures with 65‐A‐thick‐ and 82‐A‐thick wells. The transitions exhibit resonant energies of 152 and 121 meV respectively, full width at half‐maximum linewidths as narrow as 10 meV at room temperature, and an oscillator strength of 12.2. The material is anticipated to have subpicosecond relaxation times and be ideal for low‐power optical digital logic.
Non‐planar 3D crack growth by the extended finite element and level sets—Part II: Level set update

We present a level set method for treating the growth of non‐planar three‐dimensional cracks.The crack is defined by two almost‐orthogonal level sets (signed distance functions). One of them describes the crack as a two‐dimensional surface in a three‐dimensional space, and the second is used to describe the one‐dimensional crack front, which is the intersection of the two level sets. A Hamilton–Jacobi equation is used to update the level sets. A velocity extension is developed that preserves the old crack surface and can accurately generate the growing surface. The technique is coupled with the extended finite element method which approximates the displacement field with a discontinuous partition of unity. This displacement field is constructed directly in terms of the level sets, so the discretization by finite elements requires no explicit representation of the crack surface. Numerical experiments show the robustness of the method, both in accuracy and in treating cracks with significant changes in topology. Copyright © 2002 John Wiley & Sons, Ltd.
Emotion recognition from facial EMG signals using higher order statistics and principal component analysis

Higher order statistics (HOS) is an efficient feature extraction method used in diverse applications such as bio signal processing, seismic data processing, image processing, sonar, and radar. In this work, we have investigated the application of HOS to derive a set of features from facial electromyography (fEMG) signals for classifying six emotional states (happy, sad, afraid, surprised, disgusted, and neutral). fEMG signals were collected from different types of subjects in a controlled environment using audio-visual (film clips/ video clips) stimuli. Acquired fEMG signals were preprocessed using moving average filter and a set of statistical features were extracted from fEMG signals. Extracted features were mapped into corresponding emotions using k-nearest neighbor classifier. Principal component analysis was utilized to analyze the efficacy of HOS features over conventional statistical features on retaining the emotional information retrieval from fEMG signals. The results of this work indicate an improved mean emotion recognition rate of 69.5% from this proposed methodology to recognize six emotional states.
Surface hydrogenation of silicon nanocrystallites during pulsed laser ablation of silicon target in hydrogen background gas

The surface hydrogenated silicon nanocrystallites can be prepared by pulsed laser ablation of a silicon target in hydrogen background gas. Formation processes of the surface Si–H bonds were found by correlation between the surface structure of the deposited nanocrystal film and the time- and space-resolved spectra of plume emission during the deposition. A precursor of the hydrogenation is SiH species created in blast-wave stage by collision between ejected Si species and background hydrogen gas. Results of plume diagnostics indicate that the spatial or temporal separation between Si and SiH species is not an origin of the formation of the surface hydrogenated Si nanocrystallite. It is concluded that the correlation between the thermal stability of the Si–H bond and the temperature variation of the formed nanoparticle during the deposition is important for the formation of the chemical bonding on the surface.
MEASUREMENTS OF DETECTION THRESHOLDS PRESENTING NORMAL AND TANGENTIAL VIBRATIONS ON HUMAN HAIRY SKIN

The purpose of present study was to measure vibrotactile thresholds presenting normal and tangential vibrations to hairy skin and to investigate the mechanoreceptive mechanisms that determine the threshold curve shapes. The normal and tangential thresholds were measured for five subjects at the volar forearm. The normal threshold curve showed a U-shape with the lowest threshold at 100 Hz. The tangential threshold curve decreased linearly from 4 to 50 Hz, increased to 75 Hz, and decreased again above 75 Hz. Based on the results of present and previous studies, it was supposed that the shape of the normal threshold curve was determined by the RA (the hair-follicle receptors) and that the shape of the tangential threshold curve was determined by the SA II and FA II.
Helicon solitons in a layered semiconductor plasma via Zakharov equations

In the present work we investigate the propagation of helicon envelope solitons in a layered semiconductor plasma. The nonlinear evolution equations governing the propagation of these envelope solitons is the set of Zakharov equations (which are a more generalized form of the nonlinear Schrodinger equation). The set of equations which have a known envelope soliton solution are derived and the relationship between various parameters entering the system is established. In order to investigate the propagation of helicon envelope solitons in a layered medium we use the standard Kronig - Penney model along with its relevant boundary conditions. These boundary conditions are used for the envelope soliton solution thereby connecting the envelope soliton fields across the layers. This in turn leads to a nonlinear dispersion relation which relates the nonlinear analogue of the Bloch wave number with different parameters. We have numerically investigated the dependence of the nonlinear Bloch wave number on the propagation frequency and have established a propagation band and gap structure for the helicon envelope soliton in a layered semiconductor plasma.
An Exponential-Family Multidimensional Scaling Mixture Methodology

A multidimensional scaling methodology (STUNMIX) for the analysis of subjects' preference/choice of stimuli that sets out to integrate the previous work in this area into a single framework, as well as to provide a variety of new options and models, is presented. Locations of the stimuli and the ideal points of derived segments of subjects on latent dimensions are estimated simultaneously. The methodology is formulated in the framework of the exponential family of distributions, whereby a wide range of different data types can be analyzed. Possible reparameterizations of stimulus coordinates by stimulus characteristics, as well as of probabilities of segment membership by subject background variables, are permitted. The models are estimated in a maximum likelihood framework. The performance of the models is demonstrated on synthetic data, and robustness is investigated. An empirical application is provided, concerning intentions to buy portable telephones.
A comparative study on low‐order, amplitude‐equation and perturbation approaches in thermal convection

A comparison among three weakly nonlinear approaches for thermo‐gravitational instability in a Newtonian fluid layer heated from below is presented. First, the dynamical systems describing the time evolution of the problem from different weakly nonlinear approaches, namely, the Lorenz model, the amplitude equations and the perturbation expansion approaches are obtained. Next, the steady states and their stability, as well as the transient behaviour are obtained from each dynamical system. The similarity and difference among the three models are emphasized. The role of each of the nondimensional groups, the Rayleigh number and the Prandtl number is compared for the three models. The different approaches lead to similar behaviours when the Rayleigh number is just above its critical value and Prandtl number is high. However, only the dynamical system obtained from the amplitude equations is able to reflect the role of the Prandtl number. On the other hand, the amplitude equations and perturbation expansion techniques are not suitable for predicting the uniform oscillatory behaviour observed frequently in Rayleigh–Bénard convection. The novelty of the current work lies in studying the critical differences in the findings of the three popular approaches to investigate weakly nonlinear thermal convection for the first time. Copyright © 2011 John Wiley & Sons, Ltd.
An iterative ensemble Kalman smoother

The iterative ensemble Kalman filter (IEnKF) was recently proposed in order to improve the performance of ensemble Kalman filtering with strongly nonlinear geophysical models. The IEnKF can be used as a lag‐one smoother and extended to a fixed‐lag smoother: the iterative ensemble Kalman smoother (IEnKS). The IEnKS is an ensemble variational method. It does not require the use of the tangent linear of the evolution and observation models, nor the adjoint of these models: the required sensitivities (gradient and Hessian) are obtained from the ensemble. Looking for optimal performance, out of the many possible extensions we consider a quasi‐static algorithm. The IEnKS is explored for the Lorenz '95 model and for a two‐dimensional turbulence model. As the logical extension of the IEnKF, the IEnKS significantly outperforms standard Kalman filters and smoothers in strongly nonlinear regimes. In mildly nonlinear regimes (typically synoptic‐scale meteorology), its filtering performance is marginally but clearly better than the standard ensemble Kalman filter and it keeps improving as the length of the temporal data assimilation window is increased. For long windows, its smoothing performance outranks the standard smoothers very significantly, a result that is believed to stem from the variational but flow‐dependent nature of the algorithm. For very long windows, the use of a multiple data assimilation variant of the scheme, where observations are assimilated several times, is advocated. This paves the way for finer reanalysis, freed from the static prior assumption of 4D‐Var but also partially freed from the Gaussian assumptions that usually impede standard ensemble Kalman filtering and smoothing.
THE FORMATION OF PRIMORDIAL STARS

The problem of star formation from gas of primordial composition is discussed. The thermal evolution and fragmentation of primordial clouds, and the early evolution of the resulting stars, have been followed in calculations done with Palla (Arcetri) and Salpeter (Cornell). Although the clouds lacked the coolants provided by metals in present-day molecular clouds, they could have fragmented to low- and intermediate-mass stars if they contracted to sufficiently high density. Primordial protostars collapse faster and have larger hydrostatic covers than their Population I counterparts. The shock radiation emanating from these cores is optically visible, with an effective temperature of about 5000 K. The pre-main-sequence contraction phase resembles that in present-day stars, despite very different initial conditions.
Pairs of Bloch electrons and magnetic translation groups

A product of irreducible representations of magnetic translation group is considered. It leads to irreducible representations which were previously rejected as nonphysical. A very simple example indicates a possible application of these representations. In particular, they are important in descriptions of pairs of electrons in a magnetic field and a periodic potential. The periodicity of some properties with respect to the charge of a particle is briefly discussed.
Whispering gallery microcavity lasers

Whispering gallery mode (WGM) optical microresonators have attracted intense interests in the past decades. The combination of high quality factors (Q) and small mode volumes of modes in WGM resonators significantly enhances the light‐matter interactions, making them excellent cavities for achieving low threshold and narrow linewidth lasers. In this Review, the progress in WGM microcavity lasers is summarized, and the laser performance considering resonator geometries and materials as well as lasing mechanisms is discussed. Label‐free detection using WGM resonators has emerged as highly sensitive detection schemes. However, the resolution is mainly limited by the cavity Q factor which determines the mode linewidth. Microcavity lasers, due to their narrow laser spectral width, could greatly improve the detection resolution. Some recent developments in sensing using microcavity lasers are discussed.
Quantum Amplitudes in Black-Hole Evaporation II. Spin-0 Amplitude

This work on spin-0 amplitudes in black-hole evaporation is based on the underlying results and methods outlined in our first paper, "I. Complex Approach". The main result here, and the model calculation for work on all higher spins, as described in several further papers, is the computation of the quantum amplitude (rather than merely the probability) for a given slightly anisotropic configuration of a scalar field $\phi$ on a space-like hypersurface $\Sigma_F$ at a very late time $T$. For simplicity, one may take the initial data for gravity and the massless scalar field at an initial surface $\Sigma_I$ to be spherically symmetric. This applies to perturbations of spherically-symmetric collapse to a black hole, starting from a diffuse, nearly-stationary configuration, where the bosonic part of the Lagrangian consists of Einstein gravity and the massless scalar field. As in Paper I, Feynman's $+i\epsilon$ approach is taken; this involves a rotation into the complex: $T\to {\mid}T{\mid} \exp (-i\theta)$, with $0 0$; although for $\theta =0$ (Lorentzian time-separation), the classical boundary-value problem is badly posed. Once the amplitude is found for $\theta>0$, one can take the limit $\theta\to 0_+$ to find the Lorentzian amplitude. The paper also includes a discussion of adiabatic solutions of the scalar wave equation, needed for the spin-0 calculation.
Minimalist-design, high-functionality, micro-ring resonator-based optical filter with narrow linewidth and low group delay using Looped Back Over- and Under-coupled Resonator (LOBOUR)

We present a minimalist design but high functionality micro-ring resonator based optical filter with narrow linewidth and low group delay using a novel design we called LOBOUR for LOoped-Back Over- and Under- Coupled Resonator (LOBOUR). The characteristics of both narrow linewidth and low group delay (low chromatic dispersion) generally do not come together especially when using a single ring resonator. The Cascaded Over- and Under-Coupled Resonator (COUR) design was able to achieve this goal but introduced many practical fabrication issues. Here, we present an alternative design to COUR which uses only one ring resonator and without fabrication and manufacturing issues. It can achieve 50 dB extinction ratio and tens of ps performance. We also present important parameter selection mapping for LOBOUR.
06 11 05 0 v 1 5 N ov 2 00 6 3 D and 4 D noncommutative electromagnetic duality and the role of the slowly varying fields limit

We study classical noncommutative (NC) electromagnetic du ality in both 3D and 4D space-times through the Seiberg-Witten (SW) map to all orders in θ . We evaluate the role of space-time dimensions, of the gauge coupling constant g2 inversion, of the slowly varying fields (SVF) limit and of the ruleθ duality −→ θ̃ = g2 ⋆θ (where⋆ is the Hodge duality operator), which was originally found in the 4D space-time. Among our results, a new scalar pi cture for NC electromagnetism to second order inθ is established, a formula which simplifies considerably the application of the SW map in 3D is presented and we show that the SVF limit has a crucial role in this duality starting from the third order inθ for any dimension: outside this limit the symmetry between θ andθ̃ is lost.
Queues with Censored Demand and Autoregressive Net Input

We develop methods for simulating a queue with an autoregressive net-input process and for recovering characteristics of such a net-input process from samples of queue lengths. We apply these methods to the problem of estimating the censored (unsatisfied) demand for the queue's content and show how to model a queue for which the censoring of demand is graduated in a neighborhood of the queue's zero lower bound. As an example, we estimate the monthly unsatisfied demand for U.S. nonfarm jobs based on samples of job openings through a period including the last two recessions.
Nanometer-scale scanning sensors fabricated using stencil lithography

We describe a flexible technique for fabricating 10-nm-scale devices for use as high-resolution scanning sensors and functional probes. Metallic structures are deposited directly onto atomic force microscope tips by evaporation through nanoscale holes fabricated in a stencil mask. We report on the lithographic capabilities of the technique and discuss progress in one initial application, to make high-spatial-resolution magnetic force sensors.
Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

A newly designed microwave electron cyclotron resonance (ECR) plasma etching reactor has been developed for 450 mm wafer processing. The etching rates of polycrystalline silicon (poly-Si) and SiO2 across the wafer were evaluated as a function of ECR position. Two-dimensional (radial and vertical) distributions of the ion flux in the reactor were also investigated using a movable single probe system. A ring-shaped region of high-density plasma along the ECR plane was observed. This reveals the mechanism that the etching-rate distribution could be controlled by the ECR position. As a result, a polycrystalline silicon etching rate uniformity of 1.5% across a wafer was successfully obtained. Furthermore, the uniformity control of critical dimensions (CDs) based on wafer temperature was also investigated, and CD uniformity below 3 nm across the wafer was obtained in the optimum temperature distribution.
Modified Pad\'e Approach to the S-Wave Charmonium Spectroscopy in QCD

We calculate the $S$-wave charmonium spectroscopy using the Hamiltonian with the non-relativistic QCD (NRQCD) potential. The logarithmic factor $\ln \mu r$, appearing in the next-to-leading order QCD loop corrections to the potential, is expanded about $r=1/\mu$, where $\mu$ corresponds to the typical charmonium scale. The resulting potential characterized by the Coulombic and linear components is consistent with the form of the Cornell potential. We obtain $\chi^2$ fitting results for the masses of the $S$-wave charmonium states, $\eta_c(1^1S_0)$, $J/\psi(1^3S_1)$, $\eta_c(2^1S_0)$, and $\psi(2^3S_1)$ in remarkable accordance with data. Our results successfully account for the hyperfine splitting for the 1S state as well as for the 2S state. We further use the three best fit parameters: the charm quark mass $m_c$, coupling constant $\alpha_s$ and the corresponding scale $\mu$ to predict the $S$-wave mass spectrum with $n\leq 6$. The hints for results are discussed.
Floating gate based ultra-high-sensitivity two-terminal AlGaN/GaN HEMT hydrogen sensor

This paper presents the analytical performances of an AlGaN/GaN High Electron Mobility Transistor (HEMT) based sensor for the detection of H2 gas. The model calculates the changes in drain-to-source current and sensitivity of the device due to adsorbed atomic density of gas at the gate terminal. Simulated results indicate that AlGaN/GaN HEMT based floating gate sensors are highly suitable for the extreme environment detection of various gases with concentration as low as ~ ppb level.
Formation and Collapse of Gels of Sterically Stabilised Colloidal Particles

Colloidal silica spheres (diameter 88 nm) with a thick steric stabilization layer of polystyrene (PS; Mw = 26 600 g mol-1) were prepared. In cyclohexane, a marginal solvent for PS, particle aggregation and gelation were observed on lowering the temperature. Near the gelation temperature and at particle concentrations of a few per cent by weight, the gels were sufficiently weak to slowly compact under gravity. On quenching to slightly lower temperatures, the gels still settled, but the top of the sediment did not become flat, as is usually the case. This seems to be related to an unusual mechanism for gel compaction, which starts by forming a more dense structure at the top of the sample. It is proposed that this is related to the entangled polymer chains on neighbouring particles resisting substantial rearrangement of the local structure. The transient gelation phenomenon, observed previously for mixtures of colloid and non-adsorbing polymer, has so far not been observed for our system.
Asymptotic efficiency of logistic regression relative to linear discriminant analysis

SUMMARY We calculate the asymptotic efficiency of logistic regression relative to linear discriminant analysis for testing hypotheses about the parameters when the explanatory variables are normally distributed. The Pitman asymptotic efficiency for hypothesis tests in this context is the same as the asymptotic relative efficiency calculated using misclassification rates and is independent, of the number of explanatory variables and the number of parameters to be tested.
Efficient implementation of robust adaptive beamforming based on worst-case performance optimisation

Traditional adaptive beamforming methods undergo serious performance degradation when a mismatch between the presumed and the actual array responses to the desired source occurs. Such a mismatch can be caused by desired look direction errors, distortion of antenna shape, scattering due to multipath, signal fading as well as other errors. This mismatch entails robust design of the adaptive beamforming methods. Here, the robust minimum variance distortionless response (MVDR) beamforming based on worst-case (WC) performance optimisation is efficiently implemented using a novel ad hoc adaptive technique. A new efficient implementation of the robust MVDR beamformer with a single WC constraint is developed. Additionally, the WC optimisation formulation is generalised to include multiple WC constraints which engender a robust linearly constrained minimum variance (LCMV) beamformer with multiple-beam WC (MBWC) constraints. Moreover, the developed LCMV beamformer with MBWC constraints is converted to a system of nonlinear equations and is efficiently solved using a Newton-like method. The first proposed implementation requires low computational complexity compared with the existing techniques. Furthermore, the weight vectors of the two developed adaptive beamformers are iteratively updated using iterative gradient minimisation algorithms which eliminate the estimation of the sample matrix inversion. Several scenarios including angle-of-incidence mismatch and multipath scattering with small and large angular spreads are simulated to study the robustness of the developed algorithms.
AlGaN/GaN heterostructure prepared on a Si (110) substrate via pulsed sputtering

GaN films were grown on Si (110) substrates using a low-temperature growth technique based on pulsed sputtering. Reduction of the growth temperature suppressed the strain in the GaN films, leading to an increase in the critical thickness for crack formation. In addition, an AlGaN/GaN heterostructure with a flat heterointerface was prepared using this technique. Furthermore, the existence of a two dimensional electron gas at the heterointerface with a mobility of 1360 cm2/Vs and a sheet carrier density of 1.3 × 1013 cm−2 was confirmed. Finally, the use of the AlGaN/GaN heterostructure in a high electron mobility transistor was demonstrated. These results indicate that low-temperature growth via pulsed sputtering is quite promising for the fabrication of GaN-based electronic devices.