Miracle-dz/UniFAR-FTUs huggingface dataset:
Implementation of liquid crystal-based polarimeters: trade-off between speed and performance

This work considers the implementation of polarimeters with liquid crystal (LC) cells as polarizing elements. Most works generally try to implement architectures with one or two pure retarding modulators such as nematic devices. In this case, rather thick LC devices able to provide a 2π retardation are generally used. Unfortunately, LC device switching speed is known to evolve as the inverse square of their thickness, which leads to practical implementations limited to a few tens of Hertz in the visible region. The alternative consisting in using much faster devices made of ferroelectric liquid crystals is not that obvious since these devices often operate in bistable mode. We show that using thinner, therefore faster nematic devices is possible with a minimal penalty in terms of performance. Therefore, several solutions can be considered. Performance evaluation will be performed through studying the system matrix condition number.
Nonlinear fluorescence through intermolecular energy transfer and resolution increase in fluorescence microscopy

We investigate a novel concept to efficiently generate multiphoton induced fluorescence from organic molecules. The concept is based on frustrating the energy transfer between a fluorescent donor and one or more acceptors in conjugated molecules. The nonlinearity is not based on higher order molecular susceptibilities but entirely on their linear properties. Therefore, in contrast to nonresonant multiphoton absorption, this method does not require high local intensities. Likewise, the production of visible fluorescence does not require an infrared excitation wavelength. Hence, when applied to scanning microscopy this property is predicted to increase spatial resolution. Instead of the ∼10 GW/cm2 required in non‐resonant multiphoton excitation, focal intensities ∼10 MW/cm2 are expected to produce an equally strong nonlinear signal. The predicted resolution is up to 30% greater than that of an ideal confocal microscope operating at the same fluorescence wavelength. The resolution improvement over non‐resonant two‐photon absorption microscopes is about two‐fold in all directions.
Using fundamental solutions in inverse scattering

We provide a brief description of recent results in inverse scattering theory having as a common mathematical framework the exploitation of the behaviour of the fundamental solution to the Helmholtz equation, in particular the fact that for the source point on the boundary ∂D of the scattering object such a solution is not in the Sobolev space H1/2(∂D). Included in our discussion are uniqueness theorems, decomposition methods (including the point-source method), the method of singular sources, the linear sampling method and the factorization method.
BOUNDARY CONDITIONS FOR FINITE ELEMENT SIMULATIONS OF CONVECTIVE FLOWS WITH ARTIFICIAL BOUNDARIES

SUMMARY We examine the use of natural boundary conditions and conditions of the Sommerfeld type for finite element simulations of convective transport in viscous incompressible flows. We show that natural boundary conditions are superior in the sense that they always provide a correct boundary condition, as opposed to the Sommerfeld-type conditions, which can lead to a singular formulation and a great loss of accuracy. For the Navier-Stokes equations, the natural boundary conditions must be combined with a simple method to eliminate perturbations on the pressure at the open boundary, which is the source of most errors.
A superconductor–insulator–normal metal bolometer with microwave readout suitable for large-format arrays

We demonstrate high bandwidth and low-noise readout of a superconductor–insulator–normal metal–insulator–superconductor hot-electron bolometer element. We measure a noise equivalent temperature of better than 0. 6μK∕Hz1∕2 and infer an electrical noise equivalent power of 7×10−17W∕Hz1∕2 for a normal-metal volume of 4. 5μm3 at an operating temperature of 270mK. Using a pulsed bias technique we measure a thermal time constant of 1. 2μs at 270mK. The microwave readout method we employ is compatible with large-format arrays of 103–105pixels required by future far-infrared space and ground-based observatories.
Trapping in GaN-based metal-insulator-semiconductor transistors: Role of high drain bias and hot electrons

This paper describes an extensive analysis of the role of off-state and semi-on state bias in inducing the trapping in GaN-based power High Electron Mobility Transistors. The study is based on combined pulsed characterization and on-resistance transient measurements. We demonstrate that—by changing the quiescent bias point from the off-state to the semi-on state—it is possible to separately analyze two relevant trapping mechanisms: (i) the trapping of electrons in the gate-drain access region, activated by the exposure to high drain bias in the off-state; (ii) the trapping of hot-electrons within the AlGaN barrier or the gate insulator, which occurs when the devices are operated in the semi-on state. The dependence of these two mechanisms on the bias conditions and on temperature, and the properties (activation energy and cross section) of the related traps are described in the text.
First-principles investigation of phase stability in Li x CoO 2

In this work, the phase diagram of Li xCoO2 is calculated from first principles for x ranging from 0 to 1. Our calculations indicate that there is a tendency for Li ordering at x5 1 2 in agreement with experiment @J. N. Reimers and J. R. Dahn, J. Electrochem. Soc. 139, 2091~1992! #. At low Li concentration, we find that a staged compound is stable in which the Li ions selectively segregate to every other Li plane leaving the remaining Li planes vacant. We do not find the two-phase region observed at high Li concentration and speculate that this two-phase region is caused by the metal-insulator transition that occurs at concentrations slightly below x 51. @S0163-1829 ~98! 06529-1#
Dynamical friction. I. General considerations: the coefficient of dynamical friction

In this paper it is shown that a star must experience dynamical friction, i.e., it must suffer from a systematic tendency to be decelerated in the direction of its motion. 'This dynamical friction which stars experience is one of the direct consequences of the fluctuating force acting on a star due to the varying complexion of the near neighbors. From considerations of a very general nature it is concluded that the coefficient of dynamical friction, η, must be of the order of the reciprocal of the time of relaxation of the system. Further, an independent discussion based on the two-body approximation for stellar encounters leads to the following explicit formula for the coefficient of dynamical friction: η = 4πml (ml + m2)G2/v3 loge [D0|u|2/G(m1+m2)]∫ 0 v N(v1) dv1, where ml and m2 denote the masses of the field star and the star under consideration, respectively; G, the constant of gravitation; Do, the average distance between the stars; |u|2, the mean square velocity of the stars; N(v1) dv1, the number of field stars with velocities between v1 and v1 + dv1; and, finally, v, the velocity of the star under consideration. It is shown that the foregoing formula for η is in agreement with the conclusions reached on the basis of the general considerations. Finally, some remarks are made concerning the further development of these ideas on the basis of a proper statistical theory.
Application of Orthogonal Decomposition Approaches to Long-Term Monitoring of Infrastructure Systems

The long-range monitoring of civil infrastructure systems monitored with dense sensor arrays that are capable of generating voluminous amounts of data from continuous online monitoring requires the implementation of a proper data processing and archiving scheme to maximize the benefits of structural health monitoring operations. This paper focuses on the areas of data management, data quality control, and feature extraction of meaningful parameters to describe the response of large-scale infrastructure systems to ambient excitation in the context of structural health monitoring (SHM). Recordings from the monitoring system installed on the Vincent Thomas Bridge (VTB) in San Pedro, California form the database of the proposed data-management and archiving methodology. The data processing methodology for the VTB is based on the calculation of the sensor array acceleration covariance matrices for every hour of available data and the subsequent orthogonal decomposition of the covariance matrices. The dominant proper orthogonal modes of the bridge are determined, and their statistical variations over an extended observation period covering several months of continuous data are quantified and analyzed. The empirical probability density functions for the mean daily bridge accelerations are computed and used to compare the statistical variations in different periods of operation of the bridge (working days, weekends, holidays). It is shown that the computed statistical distributions of the bridge response can provide a quantitative baseline through which to facilitate the early detection of any anomalies indicative of a possible structural deterioration resulting from fatigue (service loads) or extreme loading events, i.e., earthquakes, artificial hazards, or other natural hazards.
Continuous acquisition and storage of uncompressed image data based on a personal computer equipped with a CCD camera and an external hard disk drive

An image acquisition and storage system without data compression was constructed by combining a personal computer, an external hard disk drive and a charge-coupled device camera (1024 × 768 pixels, monochrome 8 bit/pixel) operating at 30 frame s−1. Test runs indicated the system performance: the storage time, size and speed of 37 min, 55 GB and 25 MB s−1 respectively. The design of the system program was shown and discussed on the basis of the test run results. The constructed system can be applied to various scientific and engineering applications including digital microscopy. The technical information shown in this study is helpful to researchers and engineers in constructing their own system by themselves.
A Comparison of Several Formulas on Lightly Damped, Oscillatory Problems

We examine members of three different formula families in an attempt to find a set of formulas that could be the basis of a code suitable for lightly damped, oscillatory problems. We first obtain estimates for the number of arithmetic operations per integration step required by a member of each family and then use these estimates to help us compare the performance of several trial codes, which are based on certain members from each family.
Tailoring unstructured meshes for use with a 3D time domain co‐volume algorithm for computational electromagnetics

The Yee algorithm is a highly efficient time domain co‐volume method for computational electromagnetics using a pair of staggered orthogonal cartesian meshes. An equivalent unstructured mesh process is readily implemented on a primal Delaunay tetrahedral mesh and its orthogonal Voronoï dual. The difficulty, for practical applications, is ensuring that both the Delaunay and the Voronoï meshes possess the necessary properties to enable an accurate and efficient solution to be obtained by this approach. This is a mesh generation problem and it is addressed here by using a combination of a point distribution provided by an ideal tetrahedral mesh, a constrained centroidal Voronoï tessellation method and a mesh quality optimization procedure. For the selected application area of electromagnetic wave scattering problems, the computational efficiency is enhanced by using a hybrid primal mesh, consisting of tetrahedral elements in the vicinity of the scatterer and hexahedral elements elsewhere. Three examples are included to demonstrate the viability of the proposed approach and to indicate the numerical performance that can be achieved. Copyright © 2010 John Wiley & Sons, Ltd.
The effect of categorizing returned products in remanufacturing

An increasing number of companies have been implementing comprehensive recycling and remanufacturing programs. These endeavors typically involve the operation of joint manufacturing and remanufacturing systems. One of the major challenges in managing such hybrid systems is the stochastic nature of product returns. In particular, there is significant variability in the condition of the returns. This paper presents an approach for assessing the impact of quality-based categorization of returned products. Through extensive numerical studies on a continuous-time Markov chain model, we show that incorporation of returned product quality in the remanufacturing and disposal decisions can lead to significant cost savings. We find that these savings are amplified as the return quality decreases, and as the return rate increases. We also show that prioritizing higher quality returns in remanufacturing is, in general, a better strategy.
Perception of English vowels and use of visual cues by learners of English and English native speakers.

English vowels may be difficult to discriminate for many learners of English (L2 learners). Research in L2 speech perception has shown that the use of visual cues improves speech perception, at least for visually-salient contrasts. This study investigated the use of visual cues in the perception of English vowels by L2 Advanced learners (Spanish native speakers) and English native speakers (ENS). 37 L2 learners and 20 ENS were given a vowel test that presented real CVC words in audio (A), audiovisual (AV) and video-alone (V) mode. The A and AV conditions were presented in noise (-10 dB SNR) to ENS and in quiet to L2 learners. For ENS, identification rates were significantly higher in AV than in A condition, suggesting there were visual cues to vowel identity. For L2 learners, A scores were significantly lower than for ENS, and AV scores did not differ significantly from results in A mode. This suggests low sensitivity to visual cues to vowel identification, though L2 learners achieved better than chance s.
Quantum Electrodynamical Effects in Kerr-Newmann Geometries

Following the classical approach of Sauter, of Heisenberg and Euler and of Schwinger, the process of vacuum polarization in the field of a ''bare'' Kerr-- Newman geometry is studied. The value of the critical strength of the electromagnetic fields is given together with an analysis of the feedback of the discharge on the geometry. The relevance of this analysis for current astrophysical observations is mentioned.
Some Item Analysis and Test Theory for a System of Computer-Assisted Test Construction for Individualized Instruction

Under given conditions, conventional testing and computer-generated repeatable testing (CGRT) are equally effective for estimating examinee ability; CGRT is more effective than conventional testing for estimating the mean ability level of a group; and CGRT is less effective for estimating ability differences among individuals. These conclusions are drawn from domain-referenced test theory as distinguished from norm-referenced test theory.
Spectral decomposition of NAD(P)H fluorescence components recorded by multi-wavelength fluorescence lifetime spectroscopy in living cardiac cells

We report a novel analytical approach to identify individual components of a cell’s endogenous fluorescence, recorded by spectrally-resolved time-correlated single photon counting (TCSPC). Time-resolved area-normalized emission spectroscopy (TRANES) and principal component analysis (PCA) were applied to estimate the number of spectral components after metabolic modulation of cardiac cells following excitation with a 375 nm picosecond laser. Linear unmixing of TCSPC data spectrally decomposed individual components in living cells, while using characteristics of endogenously fluorescing molecules in solvents as a reference spectral database. Our data demonstrate the presence of three individual components, corresponding to the nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) in organic and inorganic solvents and to the residual flavoprotein fluorescence. The presented analytical approach offers a new alternative for the spectral separation of multi-wavelength fluorescence lifetime spectroscopy data to the conventional analysis, and opens a new possibility for the use of pattern recognition for fast resolution of components in 2D fluorescence lifetime microscopy images.
On frequency estimation

SUMMARY t This paper discusses a least-squares procedure and the use of the periodogram for isolating a discrete harmonic of a time series. It is shown that the usual asymptotics on estimation of frequency, amplitude and phase of such a harmonic have to be used with great caution from a moderate sample perspective. Computational issues are discussed and some illustrations are provided. Bolt & Brillinger (1979) make use of these asymptotic results. We consider a time series model of the form X, = a cos {wt + (f>) + e,, where e, is a stationary noise sequence, and one is interested in estimating the amplitude, frequency and phase of the harmonic component. The asymptotic theory of the least-squares estimates of these parameters has a long history. Whittle (1951,1953) obtained some of the earliest results. More recent results are by Hasan (1982), Hannan (1973) and Walker (1971), who formalize and extend Whittle's results. In these works it is shown that the asymptotic variance of the frequency estimate is of order n~3 and that the asymptotic variances of the other two components are of the more usual order n~\ These results extend when there are several harmonic components. The rate for the estimate of w seems almost unbelievably good, and our work was motivated by a desire to see how reliable the asymptotic theory is. In brief, we find that the product of the amplitude and the sample size, n, must be quite large in order for the asymptotic theory to be meaningful. If this product is not large, the frequency estimate is much more variable than indicated by the asymptotic theory and the amplitude estimate is severely biased. In applications in which the amplitude is small, giving rise to a small peak in the periodogram, these results suggest that naive application of the asymptotic theory to gauge resolution can be quite misleading. Section 2 of this paper is devoted to a review and examination of the asymptotic theory. We are also concerned with computational issues arising from the least-squares problem. This problem is nonlinear in the parameters, so that some sort of iterative search must be employed. Typically, search methods start from an initial guess and then proceed by a sequence of modified Newton-Raphson steps. For this nonlinear least-squares problem, it turns out that there are many local minima with a separation in frequency about n~l which makes the stationary point to which the iterative scheme converges extremely sensitive to the starting values, and this problem gets worse as the sample size increases. Furthermore, it follows from the results of § 2 that the estimate of the amplitude is very biased unless the frequency is resolved with order o(n~') so that failure to converge to the global minimum may give a very poor estimate of amplitude. The problem becomes
On the extensions of continuous functions from dense subspaces

PROOF. SUFFICIENCY. We suppose some f: X-> Y has no extension to all of aX. Now Y, being realcompact, is embeddable as a closed copy in Rm for some cardinal m (R denotes the reals; see [3, p. 160]) and we look on Y as being this subset of Rm. Consider the space (Rm) * = (RU g } )m where RU { oo } is the one-point compactification of R. Then (Rm) * is compact. Then f: X>(Rm) * also and this function does admit an extension f*: aX--+(Rm) *. To show this we use Taimanov's result quoted above: Let F1 and F2 be disjoint closed subsets of (Rm)* and set Fl' = F1nRm and F2' = F2nRm. Then F1, F2 are disjoint in Rm and by hypothesis, claXf-'[FY' ] n claxf'[F2'] =,0. But f[F. ] =J[F! '], i = 1, 2 since f maps into Rm. Thus there exists a continuous extension f*: oaX--(Rm) *. But then for some poEEaX-X, f*(po) has oo for at least one coordinate. Consider now the sets Fn =(R-(-n, n))m, closed in the product Rm. Then nnFn=0 but Po l nn claXf-1 [Fn].
A classroom exercise to determine the Earth–Moon distance

A simple indoor exercise to obtain the value of the Earth–Moon distance, in terms of the Earth’s radius, is described. The student measures on a photograph the ratio of the diameter of the Moon to the diameter of the shadow of the Earth during a lunar eclipse. A simple but adequate reduction of the measurement is given.
A Partial Histogram Maintenance Mode

Although histogram has been introduced into the optimizer of the relational database to assist cardinality estimates for more than thirty years, the issue of histogram maintenance is not addressed well. The application of the query feedback information provides a new way of thinking for the histogram maintenance. But it is not mature until now and inefficiency is the main problem. The query feedback-based histogram maintenance approach adopts the entire update mode and the whole histogram will be updated in each maintenance process. This mode brings huge computation for the maintenance process and becomes the most important reason for its inefficiency. Therefore, we propose the partial update mode in this paper to replace the entire update mode and try to improve the maintenance efficiency by limiting the updating range and decreasing the computation in each maintenance process.
On modifications of the Zakharov equation for surface gravity waves

The Zakharov integral equation for surface gravity waves is modified to include higher-order (quintet) interactions, for water of constant (finite or infinite) depth. This new equation is used to study some aspects of class I (4-wave) and class II (5-wave) instabilities of a Stokes wave.
Geometrical MHD wave coupling

Refraction and/or magnetic field curvature can lead to ‘geometrical mode coupling’ between the MHD modes. The effect is linear, but it is a finite-wavelength effect. It is studied here for a simple configuration which is amenable to analysis and which illustrates the basic features of the coupling. In the solar wind the geometrical coupling may be operative only in the solar corona or in the interaction regions of high-speed streams. In the latter case the geometrical coupling may provide an explanation for the non-Alfvenic fluctuations but only for long-period waves (greater than several hours) in small interaction regions (<0.1 AU).
Simulations of a rainfall process in Southeastern China with WRF and MM5

In an attempt to understand the relative strengths of two state-of-art mesoscale models: WRF (Weather Research and Forecasting Model) and Penn State/NCAR MM5, a nested domain was constructed to simulate a precipitation process induced by land-sea wind shear in Southeastern China with the two models. The results indicate that both WRF and MM5 capture the local circulation and the heavy rainfall area well, but precipitation amounts are overestimated relative to observations. The WRF model is better than the MM5 in precipitation strength, but worse in the location of maximum rainfall. In comparison with the observations, the simulation by both MM5 and WRF is larger than observation, but the simulation of WRF is closer to observation than MM5. Except that the distribution tendency of simulated wind field by MM5 is better than by WRF, the distribution trend of 2-m temperature and precipitation simulated by WRF is closer to observation than by MM5, but there exists phase difference between simulation by WRF and observation, for precipitation with lagged phase, and for temperature with phase ahead