Miracle-dz/UniFAR-FTUs huggingface dataset:
Structure of Atomically Smoothed LiNbO3 (0001) Surface

LiNbO3 (LN) is a substrate material used extensively for various optical or piezoelectric devices. We investigated an atomic-scale smoothing process of a LN single-crystal (0001) surface. Atomic force microscopy (AFM) observation revealed a surface morphology flattened from threefold symmetry to a step-terrace structure. The marked change of the surface was found to be dominated by a balance of surface diffusion and crystal growth within a period of 1–5 hours. An atomically flat surface with a straight and single-step height of 0.22 nm was obtained for a conventional LN substrate on the market. Next, we evaluated the surface composition and structure of the atomically flat LN (0001) surface by coaxial-impact collision ion scattering spectroscopy (CAICISS). We found that the atomically smoothed surface was terminated by a Nb atomic layer in which the Nb atoms were not shifted from the bulk position.
Controlled creation of a carbon nanotube diode by a scanned gate

We use scanning gate microscopy to precisely locate the gating response in field-effect transistors (FETs) made from semiconducting single-wall carbon nanotubes. A dramatic increase in transport current occurs when the device is electrostatically doped with holes near the positively biased electrode. We ascribe this behavior to the turn-on of a reverse biased Schottky barrier at the interface between the p-doped nanotube and the electrode. By positioning the gate near one of the contacts, we convert the nanotube FET into a rectifying nanotube diode. These experiments both clarify a longstanding debate over the gating mechanism for nanotube FETs and indicate a strategy for diode fabrication based on controlled placement of acceptor impurities near a contact.
The effects of nonuniform magnetic field strength on density flux and test particle transport in drift wave turbulence

The extended Hasegawa–Wakatani equations generate fully nonlinear self-consistent solutions for coupled density n and vorticity ∇2ϕ, where ϕ is electrostatic potential, in a plasma with background density inhomogeneity κ=−∂ ln n0/∂x and magnetic field strength inhomogeneity C=−∂ ln B/∂x. Finite C introduces interchange effects and ∇B drifts into the framework of drift turbulence through compressibility of the E×B and diamagnetic drifts. This paper addresses the direct computation of the radial E×B density flux Γn=−n∂ϕ/∂y, tracer particle transport, the statistical properties of the turbulent fluctuations that drive Γn and tracer motion, and analytical underpinnings. Systematic trends emerge in the dependence on C of the skewness of the distribution of pointwise Γn and in the relative phase of density-velocity and density-potential pairings. It is shown how these effects, together with conservation of potential vorticity Π=∇2ϕ−n+(κ−C)x, account for much of the transport phenomenology. Simple analytical arg.
A Comparison Study on Wavelet Sparsification for Solving Acoustic Scattering Problems over a Wide Frequency Range

Solution of the integral equation of acoustic scattering problem results in an operator/matrix equation. The resulting matrices are complex and highly dense. The complexity of solving such equations exaggerates as the frequency of scattered acoustic wave increases. Wavelets can be used in sparsifying the problem matrix and accordingly reduce the solution complexity. In this work, two approaches to the sparsification process are used. The first one utilizes the properties of the discrete-wavelet transform (DWT) of a matrix while the other applies the expansion of an unknown function in terms of orthogonal wavelet bases within the method of moment. The matrix resulting from either technique is then thresholded to obtain a highly sparse matrix. The complexities of different forms of such sparsification operators are compared for the solution of the acoustic scattering from a hard sphere over a wide frequency range. A wavelet-based preconditioning is also employed to improve the accuracy of the sparsfied system of equations. The results show that the wavelet bases expansion gives a solution with lower complexity for low problem size. The use of DWT achieves higher accuracy than the wavelet-bases method with larger complexity. DWT preconditioners reduce the error resulting from the sparsification process on a slight increase in the computational load. Tests on larger problem sizes show that the iterative solution enhances the complexity.
An intensity-based, coarse-to-fine approach to reliably measure binocular disparity

Abstract Disparity estimation is an ill-conditioned problem: at certain locations, the disparity vectors cannot be estimated solely using local intensity patterns. According to the strategy they use to solve this problem, the algorithms to estimate disparity vectors can be divided into two classes: the feature-based and intensity-based algorithms. In this paper, a new strategy is proposed. First, the disparity vectors are estimated, and then the unreliable and unfeasible vectors are eliminated. The method bears some resemblance with methods of both classes. In principle, the new approach is intensity-based, but it will be proved that because of the elimination process it determines the features on a binocular basis: the binocular raw primal sketch is constructed. A computational technique is developed for this new strategy. This technique is based on the simplex algorithm and its associated sensitivity analysis. Methods to reduce the required storage space and computation time are discussed. Numerical results are given for a random dot stereogram and an artificially generated stereo pair. Qualitative results are given for natural stereo pairs.
Shape Optimization of Inclined Elliptic Dimples in a Cooling Channel

Nomenclature A = area of heat transfer, mm Dh = hydraulic diameter of the channel, mm da = average diameter of the ellipse, d1 d2 =2, mm d1 = major diameter of the ellipse, mm d2 = minor diameter of the ellipse, mm F = objective function Ff = objective function related to the pressure drop FNu = objective function related to the heat transfer f = friction factor of the channel H = height of the channel, mm Hd = dimple depth, mm k = fluid thermal conductivity,W=m K Nu = Nusselt number Nua = area-averaged Nusselt number P = streamwise distance between the dimples, mm Pr = Prandtl number q = wall heat flux, 600 W=m Re = Reynolds number, UbDh=v S = spanwise distance between the dimples, mm Tb = bulk temperature, K Tw = wall temperature, K Ub = average velocity at the inlet, m=s x, y, z = orthogonal coordinate system = angle of major diameter to the streamwise directions, p = pressure drop, Pa v = kinematic viscosity, m=s = fluid density, kg=m
A novel approach to finite-aperture tapered unstable resonator lasers

A novel concept of a Finite Aperture Tapered Unstable Resonator Laser (FATURL), based on two distributed Bragg reflectors (DBRs) at the rear and front facets with different lateral widths, is presented. The passive resonator analysis using Fresnel-Kirchhoff diffraction theory shows that with the grating widths the losses of the different lateral resonator modes change differently. This leads to resonator geometries, characterized by nearly integral Fresnel-numbers with higher modal discrimination of the fundamental lateral mode. In spatial-temporal simulations of the active device the influence of carrier-photon interaction on that effect is studied showing that the inhomogeneous index change by spatial hole-burning in the carrier density may become dominant over the geometric modal discrimination. Both, the influence of the grating widths on the suppression of higher order modes as well as the influence of spatial hole-burning is found in the experimental characterization of a first generation of fabricated devices.
Baxter-Chacon topology and optimality for multivariate multiple stopping problems

Abstract This paper is concerned with optimal stopping problems for discrete time stochastic processes with the multiple stopping rules, which are also called multivariate stopping problems or cooperative stopping problems. The compactness of the set of all randomized multiple stopping rules in the Baxter-Chacon topology is proved. Then it is applied to prove the existence theorems of optimal multivariate multiple stopping problems for Banach-valued stochastic processes.
Spatially varying temperature trends in a Central California Estuary

We consider monthly temperature data collected over a period of 16 years at 24 stations in the estuarine wetlands of the Elkhorn Slough watershed, located in the Monterey Bay area in Central California, USA. Our goal is to develop a statistical model in order to separate the seasonal cycle, short-term fluctuations, and long-term trends, while accounting for the spatial variability of these features. In the model, each station has a specific, time-invariant mixture of two seasonal patterns, to encompass the spatial variability of oceanic influence. Likewise, trends are modeled as local mixtures of two patterns, to include the spatial variability of long-term temperature change. Finally, all stations share a common baseline, whose temporal variability is linearly dependent on a variable that summarizes several atmospheric measurements. We use a Bayesian approach with a purposely developed Markov chain Monte Carlo method to explore the posterior distribution of the parameters. We find that the seasonal cycles have changed in time, that neighboring stations can have substantially different behaviors, and that most stations show significant warming trends.
Third-Order, Minimal-Parameter Solution of the Orthogonal Matrix Differential Equation

The problem of minimal-parameter solution of the orthogonal matrix differential equation is addressed. This well-knownequationarisesnaturallyinthree-dimensionalattitudedeterminationproblems (inaircraftandsatellite navigation systems ), as well as in the square-root solution of the matrix Riccati differential equation. A direct solution of this equation involves n 2 integrations for the elements of the nth-order solution matrix. However, since an orthogonal matrix is determined by only n(n i 1)/2 independent (albeit nonunique ) parameters, a much more efe cient solution may, conceivably, be obtained by a parametrization of the problem in terms of such parameters. A new, third-order minimal parametrization, which is motivated by the Peano ‐Baker solution of linear matrix differential equations, isintroduced. Theparametersand theircorresponding differential equation arevery simple and natural. The proposed method is used to provide a new derivation of a closed-form third-order quaternion propagationalgorithm, which iscommonly usedin strapdown inertialnavigation systemsutilizing rate-integrating gyros. A numerical example is used to demonstrate the viability and high efe ciency of the new algorithm.
Two-color control of laser induced electron diffraction

We present an analysis using intense, few-cycle two-color laser pulses to image the structure of small molecules with nearly 1 fs temporal and sub-Å spatial resolution. We perform analytical calculations using S-matrix techniques to obtain laser-induced electron diffraction images of a diatomic molecule. The two-color field allows us to control recollision through the combination of two-color gating and polarization gating. By tuning the parameters of the two-color field we reduce the recollision to a single event, obtaining cleaner image and significantly improving time-resolution. In this paper we examine a 5 fs FWHM pulse with the second color ω2 = 1. 5ω1.
Propagation of radio waves in a model nonuniform terrestrial waveguide

The paper deals with propagation of radio waves in multimode waveguides of arbitrary height. In this work the boundaries are assumed to be perfectly reflecting. For the case when the height of the multimode waveguide increases monotonically in the direction of propagation, the required solution is obtained by a generalised quasioptical approach which assumes that the waveguide consists of an infinity of infinitesimal radial waveguides cascaded together. To extend the solution for both directions of propagation, the reciprocity theorem has been employed, thereby accounting for reflections. The results have been applied to the study of v.l. f. radio propagation when the effective height of reflection at the ionosphere varies along the path of propagation. Laboratory measurements obtained from a two-dimensional microwave model are compared with the theoretical solution to substantiate the analysis.
The Bohm criterion for the dusty plasma sheath

The Bohm criterion for the dusty plasma sheath is investigated with a fluid model. It is shown that the presence of dust particles near the interface between the bulk plasma and the sheath should have effects upon the ion Mach number. The dust particles charging and density variation are taken into account, and therefore the self-consistent relation between the dust surface potential and ion Mach number at the sheath edge is derived. The numerical results reveal that both the ion critical Mach number and the dust critical Mach number with variation of density ratio of dust-to-electron begin to decline after a maximum.
Effect of inversion asymmetry on the conduction subbands in G a A s − G a 1 − x Al x As heterostructures

Spin splitting of conduction subbands in ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\ensuremath{-}\mathrm{G}\mathrm{a}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}\mathrm{As}$ heterostructures due to both bulk and structure inversion asymmetry is considered theoretically using a five-level $\mathbf{k}\mathbf{\ensuremath{\cdot}}\mathbf{p}$ model. A formula for the splitting related to the structure inversion asymmetry is derived and it is explicitly demonstrated that this splitting is not proportional to the average electric field in the system. The theory is shown to describe well existing Raman data on anisotropic spin splitting in ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\ensuremath{-}\mathrm{G}\mathrm{a}}_{1\ensuremath{-}\mathrm{x}}{\mathrm{Al}}_{\mathrm{x}}\mathrm{As}$ heterostructures for various directions of the Fermi wave vector. It is shown that the splitting is dominated by the bulk inversion asymmetry at low two-dimensional electron densities and by the structure inversion asymmetry at high densities. Various simplifications of the presented complete theory are discussed.
C-QWIP material design and growth

Recently, large format and high quantum efficiency corrugated quantum well infrared photodetector (C-QWIP) FPAs have been demonstrated. Since the detector light coupling scheme does not alter the intrinsic absorption spectrum of the material, the QWIPs can now be designed with different bandwidths and lineshapes to suit various applications. Meanwhile, the internal optical field distribution of the C-QWIPs is different from that of a grating coupled detector, the material structure thus should be designed and optimized differently with respect to quantum efficiency, conversion efficiency and operating temperature. In this paper, we will provide a framework for the material design. Specifically, we will present a theoretical detector performance model and discuss two specific examples, namely with 9.2 and 10.2 μm cutoff wavelengths. We found that for both λc, the photocurrent to dark current ratio is maximized at an electron doping density ND of 0.28 × 1018 cm-3. The dark current limited detectivity meanwhile reaches a maximum at a higher ND of 0.45 × 1018 cm-3. But the lowest noise equivalent noise temperature difference is actually obtained at an even higher ND of 1.0 × 1018 cm-3 due to the larger quantum efficiency, if there are no limitations on the readout charge capacity. These predictions are compared with the data of a 1024 × 1024 C-QWIP FPA hybridized to a fan-out circuit, and the results are consistent.
Experimental and numerical investigation into buckling instability of carbon nanotube probes under nanoindentation

This study employs a series of experimental nanoindentation tests and molecular dynamics simulations to investigate buckling instabilities of carbon nanotube probes. It is found that the buckling mechanism varies as a function of probe lengths and initial inclination angles. The experimental results show that longer nanotubes buckle in local-buckling mode, whereas shorter nanotubes undergo global buckling. This study also suggests that the inclination angle also plays a key role in determining buckling behaviors of nanotube probes.
Numerical studies of edge localized instabilities in tokamaks

A new computational tool, edge localized instabilities in tokamaks equilibria (ELITE), has been developed to help our understanding of short wavelength instabilities close to the edge of tokamak plasmas. Such instabilities may be responsible for the edge localized modes observed in high confinement H-mode regimes, which are a serious concern for next step tokamaks because of the high transient power loads which they can impose on divertor target plates. ELITE uses physical insight gained from analytic studies of peeling and ballooning modes to provide an efficient way of calculating the edge ideal magnetohydrodynamic stability properties of tokamaks. This paper describes the theoretical formalism which forms the basis for the code.
A real‐time dual‐microphone signal‐processing system for hearing aids

A real‐time dual‐microphone‐based signal‐processing system has been developed that suppresses off‐axis interference from multiple sound sources. The system employs optimal filtering methods to attenuate the amplitude of all signals other than that from a desired receive direction. The algorithm was implemented on a Texas Instruments TMS320C62 fixed‐point digital signal‐processor evaluation board installed in a PC. Input/output was accomplished via a 16‐bit codec controlled by optimized assembly language routines. To simplify algorithm coding, the main algorithm was written in C and executes using approximately 55 processor time, allowing for future additions to enhance performance. It has a delay of 15 ms. The system can significantly improve the intelligibility of speech in noisy environments, as evidenced in off‐line tests by a marked intelligibility weighted SNR gain [Link and Buckley, J. Acoust. Soc. Am. 91, 1662 (1992)]. Initial real‐time testing with actual binaural signals supports the conclusion t.
Summary of observations of the infrared camera (IRC) onboard AKARI

AKARI, the Japanese satellite mission dedicated to infrared astronomy was launched in 2006 February and exhausted its liquid helium in 2007 August. During the cold mission phase, the Infrared Camera (IRC) onboard carried out an all-sky survey at 9 and 18µm with better spatial resolution and higher sensitivity than IRAS. Both bands also have slightly shorter wavelength coverage than IRAS 12 and 25μm bands and thus provide different information on the infrared sky. All-sky image data of the IRC are now in the final processing and will be released to the public within a year. After the exhaustion of the cryogen, the telescope and focal plane instruments of AKARI had still been kept at sufficiently low temperatures owing to the onboard cryocooler. Near-infrared (NIR) imaging and spectroscopic observations with the IRC had continued until 2011 May, when the spacecraft had a serious problem in the power supply system that forced us to terminate the observation. The IRC carried out nearly 20000 pointing observations in total despite of its near-earth orbit. About a half of them were performed after the exhaustion of the cryogen in the spectroscopic modes, which provided high-sensitivity NIR spectra from 2 to 5µm without disturbance of the terrestrial atmosphere. During the warm mission phase, the temperature of the instrument gradually increased and changed the array operation conditions. We present a summary of AKARI/IRC observations, including the all-sky mid-infrared diffuse data as well as the data taken in the warm mission phase.
Iterative reduced-state decoding for coded partial-response channels

The conventional iterative decoding based on the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm rises exponentially in terms of channel memory length. In this paper, we propose a low-complexity soft-input/soft-output (SISO) channel detector based on tentative hard estimates fed back from the outer decoder in the previous iteration. The computational complexity of the proposed detector is polynomial in terms of the channel memory length. To demonstrate the performance/complexity tradeoff of the proposed detector, we present simulation results for 9-tap, 11-tap, and 12-tap channels. We show that the proposed detector significantly reduces the computational complexity with only slight performance degradation compared to the full-complexity BCJR algorithm.
Ultrahigh power compression for X-ray amplification: multiphoton cluster excitation combined with nonlinear channelled propagation

The ability to apply power densities controllably at or above vigorous thermonuclear levels (>1019 W cm-3) in materials is the basic issue for achieving efficient amplification of X-rays. Recent experimental and theoretical findings concerning (i) the multiphoton production of X-rays from clusters and (ii) high-intensity modes of channelled propagation in plasmas indicate an entirely new method for producing the conditions necessary for strong amplification in the multi-kV range. These two new nonlinear phenomena are being united to produce and control the imperative power compression; the multiphoton mechanism serves to establish the condition locally while the confined propagation provides the required spatial organization. The present work, which experimentally demonstrates the first combined expression of these two complex nonlinear processes through direct X-ray imaging of Xe(M) emission ( approximately 1 keV) in stable self-trapped channels, ( alpha ) reveals the exceptional compatibility of their mutual scaling for realizing the necessary power density, ( beta ) provides confirming evidence for the action of a superstrong coherent multi-electron intense-field interaction in the X-ray generation from the Xe clusters, and ( gamma ) furnishes new detailed information on the dynamics of the radial intensity distributions associated with the channelled propagation. The resulting knowledge of the scaling relations underlying these phenomena enables the optimum conditions for amplification to be specified up to a quantum energy of approximately 5 keV. The harmonious use of these new nonlinear processes is expected to lead to an advanced generation of extraordinarily bright X-ray sources in the multi-kV region having a peak brightness of approximately 1031-1033 gamma s-1 (mrad)-2 (mm)-2 (0.1% BW)-1, a level sufficient for biological holographic imaging capable of providing a high resolution visualization of the molecular anatomy of cells, tissues and organisms in the natural state.
Adaptive Optics Observations of the Binary Star HD 43587

We present adaptive optics observations of HD 43587, one of the primary targets of the COROT (Convection, Rotation, and Planetary Transits) asteroseismology and planet-finding space mission and a star that was previously detected as a spectroscopic binary by Vogt and coworkers. We resolve a close companion, which is responsible for the radial velocity variations of the primary. Our observations over a 3 year interval measure the orbital displacement of the companion. Combining these measurements with the radial velocity data of Vogt and coworkers, we solve for the three-dimensional orbit of the system and derive individual masses for HD 43587 and its companion. This is particularly interesting in the perspective of the upcoming COROT mission. These observations were part of a preparatory program for COROT, in which we observed all COROT potential primary targets and some of its secondary targets with adaptive optics. The majority of these stars have potential companions in a 30″ field. Most of these are probably background objects, but some are found within a few arcseconds of the COROT targets and are likely to be true physical companions.