Miracle-dz/UniFAR-FTUs huggingface dataset:
Electronic and transport properties of nanotubes

This article reviews the electronic and transport properties of carbon nanotubes. The focus is mainly theoretical, but when appropriate the relation with experimental results is mentioned. While simple band-folding arguments will be invoked to rationalize how the metallic or semiconducting character of nanotubes is inferred from their topological structure, more sophisticated tight-binding and ab initio treatments will be introduced to discuss more subtle physical effects, such as those induced by curvature, tube-tube interactions, or topological defects. The same approach will be followed for transport properties. The fundamental aspects of conduction regimes and transport length scales will be presented using simple models of disorder, with the derivation of a few analytic results concerning specific situations of shortand long-range static perturbations. Further, the latest developments in semiempirical or ab initio simulations aimed at exploring the effect of realistic static scatterers chemical impurities, adsorbed molecules, etc. or inelastic electron-phonon interactions will be emphasized. Finally, specific issues, going beyond the noninteracting electron model, will be addressed, including excitonic effects in optical experiments, the Coulomb-blockade regime, and the Luttinger liquid, charge density waves, or superconducting transition.
Fabrication of thin-film InGaN light-emitting diode membranes by laser lift-off

Indium–gallium nitride (InGaN) multiple-quantum-well (MQW) light-emitting diode (LED) membranes, prefabricated on sapphire growth substrates, were created using pulsed-excimer laser processing. The thin-film InGaN MQW LED structures, grown on sapphire substrates, were first bonded onto a Si support substrate with an ethyl cyanoacrylate-based adhesive. A single 600 mJ/cm2, 38 ns KrF (248 nm) excimer laser pulse was directed through the transparent sapphire, followed by a low-temperature heat treatment to remove the substrate. Free-standing InGaN LED membranes were then fabricated by immersing the InGaN LED/adhesive/Si structure in acetone to release the device from the supporting Si substrate. The current–voltage characteristics and room-temperature emission spectrum of the LEDs before and after laser lift-off were unchanged.
Formation and Persistence of Summertime Arctic Stratus Clouds.

Abstract We have developed a numerical model which can explain the principle observed properties of the summertime stratus clouds occurring over the Arctic Basin. Warm, moist air from the surrounding land masses is modified as it passes over the melting pack ice. Motions are calculated on the basis of a fixed pressure field, but all other relevant fields (temperature, mixing, solar and terrestrial radiation, water in the liquid and vapor phase) are calculated on the basis of an internally consistent thermodynamic model which is considered to be complete in all essential physical processes. The ubiquitous occurrence of stratus clouds is explained in terms of the relative unimportance of cloud dissipative processes over the Arctic Ocean. The commonly observed layering results from the trapping of solar radiation inside a cloud which is opaque to thermal radiation. The absence of similar layering in mid-latitude stratus is probably due to the diurnal variation of solar radiation, which is largely absent in t.
A double substrate “sandwich” structure for fiber surface enhanced Raman scattering detection

A double substrate “sandwiching” structure has been designed and tested for molecular detection using surface enhanced Raman scattering (SERS). With silver (Ag) nanoparticles as SERS substrates and rhodamine 6G (R6G) as a test molecule, the results show that the “sandwich” configuration exhibits significantly higher SERS enhancement compared to just one of the substrates or a simple sum of the signals from the two separate substrates. The improved SERS sensitivity is attributed to a stronger electromagnetic field enhancement by the double substrate sandwich structure.
A finite element approach for modelling hip joint contact

In this contribution a finite element model for the three dimensional investigation of hip joint contact is described. A shell‐like interface element with variable thickness is developed for modelling fluid flow in the synovial gap. For this purpose the Taylor‐Hood element is extended in order to take a spatial thickness distribution and local thickness changes into account. The interaction between the synovial fluid and the cartilage layers is solved by a staggered iteration using an artificial compressibility method. Cartilage is modelled using the theory of porous media and three dimensional geometries are reconstructed from medical imaging data. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge carrier dynamics in alpha particle tracks

An alpha particle event in a semiconductor device is modeled as the instantaneous generation of holes and electrons. The resulting axisymmetric potential of charge carriers is shown to be represented by a similarity solution of the drift-diffusion equations. The ordinary differential equations (ODEs) that arise are integrated numerically, after two quadratures. The results help to clarify the field funneling mechanism in dynamic random access memory (DRAM) storage devices.
Surface registration technique for close-range mapping applications

Close-range mapping applications such as cultural heritage restoration, virtual reality modeling for the entertainment industry, and anatomical feature recognition for medical activities require 3D data that is usually acquired by high resolution close-range laser scanners. Since these datasets are typically captured from different viewpoints and/or at different times, accurate registration is a crucial procedure for 3D modeling of mapped objects. Several registration techniques are available that work directly with the raw laser points or with extracted features from the point cloud. Some examples include the commonly known Iterative Closest Point (ICP) algorithm and a recently proposed technique based on matching spin-images. This research focuses on developing a surface matching algorithm that is based on the Modified Iterated Hough Transform (MIHT) and ICP to register 3D data. The proposed algorithm works directly with the raw 3D laser points and does not assume point-to-point correspondence between two laser scans. The algorithm can simultaneously establish correspondence between two surfaces and estimates the transformation parameters relating them. Experiment with two partially overlapping laser scans of a small object is performed with the proposed algorithm and shows successful registration. A high quality of fit between the two scans is achieved and improvement is found when compared to the results obtained using the spin-image technique. The results demonstrate the feasibility of the proposed algorithm for registering 3D laser scanning data in close-range mapping applications to help with the generation of complete 3D models.
Natural Distance Based Curve Reconstruction

In this paper, we consider a curve reconstruction problem from unorganized point clouds with noise. In general, the result of curve reconstruction depends on how to select and order the representative points to resemble the shape of the clouds. We exploit a natural distance based on a property of one dimensional Brownian motion to order sample points, which reflect an orientation of the ordering of sample points, so that our algorithm is able to reconstruct not only simple curves but also non-simple curves. Moreover, for unorganized point clouds, this method can efficiently extract the skeletons of the clouds by cutting out the outliers.
Oscillating flows over periodic ripples

Oscillating flows over periodic ripples are of practical as well as scientific interest because of their relevance to beach processes. When either the ripples are sufficiently steep or the amplitude of ambient oscillations large, streamlines of a viscous flow are no longer parallel to the ripple surface. Circulation cells are formed which can help redistribute suspended sediments. Here we study theoretically these cells for a low-viscosity fluid such as pure water over rigid ripples. In particular we have calculated cells whose dimensions are as large as the ripple wavelength and therefore represent viscous effects far above the usual Stokes boundary layer. An idea of Stuart which was originated for stationary mean circulations around a cylinder is extended here. For large ambient amplitude, large oscillating vortices drifting with the ambient flow are found by seeking the stationary cells in a moving coordinate system.
Head‐related transfer functions via the fast multipole accelerated boundary element method

Computation of head‐related transfer functions (HRTF) via geometrical meshes and numerical methods has been suggested by a number of authors. An issue facing this approach is the large computational time needed for high frequencies, where the discretization must include hundreds of thousands of elements. Conventional computational methods are unable to achieve such computations without excessive time or memory. We use a newly developed fast multipole accelerated boundary element method (FMM/BEM) that scales linearly both in time and memory. The method is applied to the mesh of the widely used KEMAR manikin and its HRTF computed up to 20 kHz. The results are compared with available experimental measurements.
Robust identification/fingerprinting of audio signals using spectral flatness features

Recently, the problem of content‐based identification material has received increased attention as an important technique for managing the ever‐increasing amount of multimedia assets available to users today. This talk discusses the problem of robust identification of audio signals by comparing them to a known reference (‘‘fingerprint’’) in the feature domain. Desirable properties of the underlying features include robustness with respect to common signal distortions and compactness of representation. A family of suitable features with favorable properties is described and evaluated for their recognition performance. Some applications of signal identification are discussed, including MPEG‐7 Audio.
Dark Baryons and Disk-to-Halo Mass Coupling in M33

The universal coupling relation between the baryonic matter of spiral galaxy disks and the inner part of the corresponding dark halos requires the existence of a secondary dark component in faint late-type spirals. In the present paper, this empirical relation is used to predict the amount of this secondary component within 1.5-2 optical radii of the nearby spiral M33. At such radii there is no clear need of any additional disk dark mass, but the low value of the derived stellar mass-to-light ratio suggests masses of the order 0.5-1M for this component, if any. At four optical radii, the coupling relation between detected disk baryons and dark halo cannot describe the observed rotation curve. The luminous mass (stars and gas) in M33 appears to have a higher collapse factor with respect to the halo than in galaxies where the coupling relation has been successfully tested, in bright galaxies in particular. An alternative solution is to invoke a disk dark baryonic component. The density distribution of such a component is not proportional to that of the neutral hydrogen at large radii and must have a larger scale length. A distribution obtained by scaling radially the H I distribution is a possible solution. The nature of this component cannot be easily inferred from its distribution. If it is made of cold molecular H2, the observational constraint is the detection of a column density of N ~ 6 × 1021 cm-2.
Detection of THz radiation with semiconductor superlattices at polar-optic phonon frequencies

The nonlinear response of GaAs/AlAs superlattices to THz radiation has been analyzed over a wide frequency range (0.1 THz–15 THz), including the range of polar-optic phonon frequencies. Assuming that free electrons in a superlattice subjected to both a static and a THz field perform frequency-modulated damped Bloch oscillations, we have calculated a superlattice current responsivity, i.e., the ratio of the direct current change to the power of the incident radiation. The responsivity of superlattices has been measured in several recent experiments. An equivalent circuit taking into account the resonant properties associated with polar-optic phonons was used in a self-consistent treatment of the problem. It is shown that the responsivity is suppressed at frequencies of infrared-active, transverse polar-optic phonons due to dynamic screening of the THz field by the lattice. In contrast, the responsivity strongly increases at longitudinal polar-optic phonon frequencies due to a large enhancement of the THz f.
Extraordinary Hall effect in (111) and (100)-orientated Co/Pt superlattices

We have fabricated a series of (111)- and (100)-orientated Co/Pt superlattices of high quality. (111)-orientated superlattices acquire a perpendicular magnetic anisotropy for samples with thin Co layers whereas for the (100)-orientated superlattices the easy magnetization direction remains in plane. Analysis of the extraordinary Hall effect (EHE) verifies the applicability of simple scaling laws between the resistivity and the EHE coefficient for these layered materials. In addition, we have found a marked dependence of the skew coefficient on Co layer thickness. The contribution to EHE from quantum side-jump remains relatively constant.
Stiffness matrix method with improved efficiency for elastic wave propagation in layered anisotropic media

This paper presents the recursive algorithm of stiffness matrix method with improved efficiency for computing the total and surface stiffness matrices for a general multilayered anisotropic media. Based on the eigensolutions commonly available for analysis of such media, the recursive algorithm deals with eigen-submatrices directly and bypasses all intermediate layer stiffness submatrices. The improved algorithm obviates the need to compute certain inverse of the original scheme and makes the stiffness matrix recursion more robust. In situation where transfer matrix is numerically stable and easily accessible, an improved recursive algorithm is also given directly in terms of transfer submatrices without involving their explicit inverse.
Integration and calibration of a plasticity model for granular materials

A new macroscopic constitutive model for non‐cohesive granular materials, with the focus on coarse‐sized materials (railway ballast), is presented. The model is based on the concepts of rate‐independent isotropic plasticity. The Backward Euler rule is used for integrating the pertinent evolution equations. The resulting incremental relations are solved in the strain space that is extended with the internal (hardening) variables. The model is calibrated using data from Conventional Triaxial Compression (CTC) tests, carried out at the University of Colorado at Boulder. A function evaluation method is used for the optimization, whereby a ‘multi‐vector’ strategy for choosing the appropriate start vector is proposed. Copyright © 2002 John Wiley & Sons, Ltd.
AN APPLICATION OF DIFFERENTIAL TRANSFORMATION TO STABILITY ANALYSIS OF HEAVY COLUMNS

This paper uses a recently developed technique, known as the differential transformation, to determine the critical buckling load of axially compressed heavy columns of various support conditions. In solving the problem, it is shown that the differential transformation technique converts the governing differential equation into an algebraic recursive equation, which must be solved together with the differential transformation of the boundary conditions. Although a fairly large number of terms are required for convergence of the solution, the differential transformation method is nonetheless efficient and fairly easy to implement. The method is also shown to be very accurate when compared with a known analytical solution. The stability of heavy columns is further examined using approximate formulae currently available in the literature. In this case, the differential transformation method offers a reference for assessing the accuracy of the approximate buckling formulae.
Polynomial approximations in cross‐sectional models

The time-series distributed lag techniques of econometrics can be usefully applied to cross-sectional, spatial and cross-section time-series situations. The application is perfectly natural in cross-section, time-series models when regression coefficients evolve systematically as the cross-section grouping variable changes. The evolution of such coefficients lends itself to polynomial approximation or more general smoothing restrictions. These ideas are not new, Gersovitz and McKinnon (1978) and Trivedi and Lee (1981) providing two of the earliest applications of cross-equation smoothing techniques. However, their applications were in the context of coefficient variation due to seasonal changes and this may account for the non-diffusion of these techniques. The approach here is illustrated in the context of age-specific household formation equations based on census data, using Almon polynomials when the regression coefficients vary systematically by age group. A second application is provided, using spatial data, explaining the incidence of crime, by region; using polynomial and geometric smoothing to model distance declining regional effects.
On the Meaning of Within-Factor Correlated Measurement Errors

The meaning of correlated measurement errors is discussed within a hierarchical framework of error terms provided by true score, first-order factor, and second-order factor models: random error, indicator specific error, and group specific error, respectively. Group specific error can be represented either as extraneous first-order factors or as unwanted components of first-order factors that define a second-order factor. The uncritical use of correlated measurement errors without theoretical justification is shown to lead merely to more acceptable fit while obfuscating a more meaningful theoretical structure.
Tunable pulsed vacuum ultraviolet light source for surface science and materials spectroscopy based on high order harmonic generation

We report here the development of a tunable vacuum ultraviolet light source, providing subpicosecond pulses over the wavelength range from 114 (∼11 eV) to 32 nm (∼39 eV), designed for surface science experiments. The source is based on high order harmonic generation. The experimental setup is described in detail and the harmonic yield as a function of the gas type (xenon or argon) is compared with theoretical descriptions. We address in particular the tunability of the source, desirable for surface science applications. Absolute characterization of the harmonic yield has also been performed and validated with time-resolved fluorescence measurements. The results are extremely promising, with intensities of ∼1010 photons/s, with regard to the use of this coherent source for surface science and spectroscopy.
Sparse optimization for nonconvex group penalized estimation

We consider a linear regression model where there are group structures in covariates. The group LASSO has been proposed for group variable selections. Many nonconvex penalties such as smoothly clipped absolute deviation and minimax concave penalty were extended to group variable selection problems. The group coordinate descent (GCD) algorithm is used popularly for fitting these models. However, the GCD algorithms are hard to be applied to nonconvex group penalties due to computational complexity unless the design matrix is orthogonal. In this paper, we propose an efficient optimization algorithm for nonconvex group penalties by combining the concave convex procedure and the group LASSO algorithm. We also extend the proposed algorithm for generalized linear models. We evaluate numerical efficiency of the proposed algorithm compared to existing GCD algorithms through simulated data and real data sets.
A Markov Model of Football: Using Stochastic Processes to Model a Football Drive

A team is backed into a 4th-and-26 from their own 25, down 3 points. What are the odds that drive ends in a field goal? In the 2003 playoffs, Donovan McNabb and the Eagles scoffed at such a probability as they converted and ultimately kicked a field goal to send the game into overtime. This study creates a mathematical model of a football drive that can calculate such probabilities, labeling down, distance, and yard line into states in an absorbing Markov chain. The Markov model provides a basic framework for evaluating play in football. With all the details of the model—absorption probabilities, expected time until absorption, expected points—we gain a much greater situational understanding for in-game analysis.
New Tests for Multivariate Ordered Alternatives

Abstract We consider testing the equality of vector means against a multivariate ordered alternative. An extension of the Abelson and Tukey test is first derived under the assumption that the covariance matrix is known. The asymptotic distribution is obtained when the covariance is estimated. We also extend Schaafsma and Smid's somewhere most powerful test to multivariate normal settings, under the assumption that the covariance matrix is known. An empirical power study shows that these tests perform better than their multi-sided χ2 test counterparts.
Concerning an integral arising in the study of laser‐drilling equations

The mathematical study of laser drilling is based on solving the heat equation at the moving boundary where the laser impinges on and vaporizes the material being drilled. In this context, one encounters integrals of the form and the closely related form Integrals of this kind can be found in books of tables [1‐3], but in the first two of these references the evaluation is given for an upper limit of infinity, and no reference to the means by which the integrals have been evaluated is given in any of the references. If more details are available at all in the literature, then the sources are obscure. Here we give a brief discussion of the derivation of these integrals in the laser‐drilling context, then exhibit the substitutions which allow evaluation of the integrals.
Performance of multilayer coatings in relationship to microstructure of metal layers. Characterization and optical properties of Mo/Si multilayers in extreme ultra-violet and x-ray ranges

Here we present a development of multilayer-based optics for the extreme ultra-violet (EUV) and x-ray range. The authors discuss results of the study of optical performance of Mo/Si coatings with regard to the microstructure of metal layers, which was analysed by x-ray diffraction (XRD) and by transmission electron microscopy (TEM). We have demonstrated an ability to control the microstructure of the multilayers via optimization of the deposition process, which is important for various EUV and x-ray applications of multilayer optics.
O-Minimality and Diophantine Geometry

Preface A. J. Wilkie and G. O. Jones 1. The Manin-Mumford conjecture, an elliptic curve, its torsion points and their Galois orbits P. Habegger 2. Rational points on definable sets A. J. Wilkie 3. Functional transcendence via o-minimality Jonathan Pila 4. Introduction to abelian varieties and the Ax-Lindemann-Weierstrass theorem Martin Orr 5. The Andre-Oort conjecture via o-minimality Christopher Daw 6. Lectures on elimination theory for semialgebraic and subanalytic sets A. J. Wilkie 7. Relative Manin-Mumford for abelian varieties D. Masser 8. Improving the bound in the Pila-Wilkie theorem for curves G. O. Jones 9. Ax-Schanuel and o-minimality Jacob Tsimerman.