Miracle-dz/UniFAR-FTUs huggingface dataset:
Synthesis of plane vector wave envelopes in two-dimensional random elastic media based on the Markov approximation and comparison with finite-difference simulations

SUMMARY High-frequency seismograms mainly consist of incoherently scattered waves. Their envelopes are a stable measure exhibiting characteristic features like peak amplitude decay and envelope broadening with increasing travel distance which can be used to infer stochastic parameters of the inhomogeneous Earth medium. As a simple model we study the propagation of plane P and S waves through a 2-D random elastic medium. If the wavelength is less than the correlation distance and the medium inhomogeneity is weak conversion scattering can be neglected, and a stochastic parabolic wave equation is derived. Solving the master equation for the two-frequency mutual coherence function and taking the Fourier transform, we obtain the temporal change of the mean squared amplitude at a fixed distance. The distribution of energy between longitudinal and transverse components can then be calculated by using the angular spectrum representation. For the case of a Gaussian autocorrelation function the solution is completely analytical. The theoretical envelopes are compared with the results of 2-D elastic finite-difference (FD) simulations. For a stable estimate of mean-squared envelopes the squared FD traces from different receiver positions and several realizations of the random medium have been averaged. The theoretical curves well explain the delay of the peak arrival from the onset and the broadening of the envelope with increasing propagation distance. Also the transverse component amplitude for P-wave incidence and the longitudinal component amplitude for S-wave incidence are precisely explained by the theory. The time integral of the mean-squared transverse component for P-wave incidence and of the mean-squared longitudinal component for S-wave incidence linearly increases with travel distance. The linear coefficient is a measure of the ratio of mean-squared fractional fluctuation to correlation distance.
Separately balanced realization and model reduction of 2-D separable-denominator transfer functions from input - output data

A method which uses 2-D pulse response data is developed for the determination of a separately balanced state-space model of a quarter-plane, causal, recursive, separable-denominator (CRSD) transfer function. This algorithm involves the Cholesky decomposition of two matrices constructed directly from the given data and the determination of the eigenvalues and eigenvectors of two real symmetric matrices which are determined directly from the given data and the matrices determined from the Cholesky decomposition.
Stationarity of a Family of GARCH Processes

A natural generalization of the first-order GARCH processes family introduced in 1999 to allow for higher-order past errors and conditional variances on the current conditional variance equation is proposed. This new family of GARCH processes includes many well-known GARCH processes. A sufficient and necessary condition for the existence of stationary solution of the family of GARCH processes is given. In particular, we proved the stationarity of the so-called family of IGARCH processes. Copyright The Author(s). Journal compilation Royal Economic Society 2009
L-probe fed thick-substrate patch antenna mounted on a finite ground plane

In this paper, the input impedance and radiation properties of the L-probe fed thick-substrate patch antennas with finite ground plane are studied using the finite-difference time-domain method. For validation, the theoretical predictions are compared with measurement. Good agreement is obtained. Initially, the effects of ground plane size are investigated. For the case of foam substrate, the input impedance almost remains constant for different ground plane sizes as the foam substrate does not support any surface wave. The dependence of the gain on the ground plane size is found to be periodic as the radiation patterns strongly depend on the ground plane size. The ground plane is then modified to reduce the backward radiation, or to shape the radiation beam. The investigations are extended to cases of the antennas surrounded fully or partially by metallic sidewalls, including sidewalls on both of the E- and H-plane edges, sidewalls only on the E-plane edges, and sidewalls only on the H-plane edges, respectively. New results are obtained to improve the radiation properties of the antenna. Finally, the sidewalls are angled to shape the beamwidth to a larger extent.
Short‐Time “Cepstrum” Pitch Detection

A short‐time cepstrum analyzer for vocal‐pitch detection has been simulated on an IBM‐7094 digital computer. (The cepstrum of a signal is defined as the square of the Fourier transform of the logarithm of the amplitude spectrum of the signal.) Since temporal periodicities in a speech signal cause periodic ripples in the amplitude spectrum, Fourier transformation of the spectrum gives the “frequency” of the ripple, which is inversely proportional to the fundamental frequency of the speech. Taking the logarithm of the amplitude spectrum makes the effects of the vocal tract (spectrum envelope) and the vocal source (spectrum fine structure) additive, thereby separating the low “frequencies” of the spectrum envelope from the usually higher frequencies of the spectrum fine structure. Cepstrum pitch detection is insensitive to phase distortion, amplitude distortion, additive noise, and the absence of the fundamental speech frequency. A general description of the technique and some recent results and examples are.
Widely tunable electroabsorption-modulated sampled-grating DBR laser transmitter

We report on a widely tunable transmitter based on a sampled-grating distributed Bragg reflector (SG-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA) and an electroabsorption (EA) modulator. Modulated time-averaged powers in excess of 5 dBm, RF extinction ratios >10 dB, and error-free transmission at 2.5 Gb/s for 350 km of standard single-mode fiber have been demonstrated across a 40-nm tuning range. In CW mode of operation, the module meets all long-haul system requirements for externally modulated laser sources: stability, power (>10 mW), RIN ( 100 yr for output wavelength stability and power across all channels.
DYNAMIC MODELLING AND VIBRATION ANALYSIS OF A FLEXIBLE CABLE-STAYED BEAM STRUCTURE

In this paper, the non-linear vibration of a cable-stayed beam with time-varying length and tension in the cable is investigated. A set of non-linear, time-varying differential equations describing this coupling system is derived by Hamilton's principle and the finite element method. According to the results of numerical simulation, the tension of the cable is related to the cable length, which in turn is a function of the longitudinal and transverse displacements of the cable. Furthermore, it is shown that the tension and length of the cable can be considerably different by using linear and non-linear models.
GLMM approach to study the spatial and temporal evolution of spikes in the small intestine

Mixed models can be applied in a wide range of settings. Probably, they are most commonly used to handle grouping in the data. In addition, mixed models can be used for smoothing purposes as well. When dealing with non-normal data, the use of smoothing methods within the generalized linear mixed models (GLMM) framework is less familiar. We explore the use of GLMM for smoothing purposes in both spatial and longitudinal dimensions. The methodology is illustrated by analysis of spike potentials in the small intestine of different cats. Spatio-temporal models that use two-dimensional smoothing splines across the spatial dimension and random effects to account for the correlations during successive slow-waves are developed. A major advantage of the mixed-model approach is that it can handle smoothing together with grouping (or other types of correlations) in a unified model. In this way, areas with high spike incidence compared with other areas can be detected. Also, the temporal and spatial characteristics of spikes during successive slow-waves can be identified.
A statistical and geometrical edge detector for SAR images

A constant-false-alarm-rate (CFAR) edge detector based on the ratio between pixel values is described. The probability distribution of the image obtained by applying the edge detector is derived. Hence, the decision threshold can be theoretically determined for a given probability of false alarm as a function of the number of looks of the image under study and the size of the processing neighborhood. For a better and finer detection, the edge detector operates along the four usual directions over windows of increasing sizes. A test performed, for a given direction, on a radar image of an agricultural scene shows good agreement with the theoretical study. The operator is compared with the CFAR edge detectors suitable for radar images. >
Power transfer efficiency between focused circular antennas with Gaussian illumination in Fresnel region

The power transfer efficiency between two circular aperture antennas in the Fresnel region is obtained analytically and explicitly. They are focused at each other and illuminated as a simple Gaussian taper. Two apertures also have generally different sizes and unequal illuminations. It is shown that the Gaussian distribution is close to the optimum, which is derived from the theory of the confocal optical resonators. The effect of the deviation of the illumination from the optimum upon the efficiency is numerically evaluated. The result shows that the reduction of the efficiency for a constant deviation increases as the Fresnel number decreases. The dissimilarity of both aperture illuminations also reduces the efficiency. The qualitative trend is such that the larger the dissimilarity, the smaller the efficiency. When the order of dissimilarity is small or the taper of the aperture is large, the efficiency can be approximately predicted by assuming equal illumination with the geometrical mean of the two illuminations. A simplified approximate efficiency which can be applied to the greatly tapered illumination is also derived.
Nonlinear shear and heat transfer in hypersonic rarefied flows past flat plates

This paper is a theoretical modeling study of the nonlinear transport of momentum and energy in a hypersonic rarefied flow past a sharp leading-edge flat plate at zero angle of attack. A characteristic parameter Vrx is introduced to describe the non-Newtonian shear and non-Fourier heat transfer features in the near-continuum flow regime via approximate analyses on the corresponding terms from the Burnett equation. Modified formulas based on Vrx are proposed to quantitatively predict the skin friction and heat flux along the plate, and the Reynolds analogy is proved to still be valid in the near-continuum flow regime. The physical meaning of Vrx and the flow mechanism are discussed. The direct simulation Monte Carlo method is also employed to validate the analytical results and to show the existence of a general analogy between the skin friction and heat flux in the whole flow regime from the continuum through the transition to the free molecular flow limit.
Rough sets used in the measurement of similarity of mixed mode data

Similarity is important in knowledge discovery. Cluster analysis, classification, and granulation each involve some notion or definition of similarity. The measurement of similarity is selected based on the domain and distribution of the data. Even within a specific domain, some similarity metrics may be considered more useful than others. There is an amount of uncertainty in quantitatively measuring the similarity between records of mixed data. The uncertainty develops from the lack of scale that both nominal and ordinal data have. Rough set theory is one tool developed for handling uncertainty. Rough sets can be used in dissimilarity analysis of qualitative data. It would seem that rough sets could be applied in measuring similarity between records containing both quantitative and qualitative data for the purpose of clustering the records.
Thin Film Equations With van der Waals Force

We are interested in the steady states of thin films in a cylindrical container with van der Waals forces which lead to a singular elliptic equation in a bounded domain with Neumann boundary conditions. Using the prescribed volume of the thin film as a variable parameter we investigated the structure of radial solutions and their associated energies using rigorous asymptotic analysis and numerical computation. Motivated by the existence of rupture solutions for thin film equations, we considered elliptic equations with more general non linearity and obtained sufficient condition for the existence of weak rupture solutions for a class of generalized elliptic equations. Finally such results can be generalized to a class of quasi-linear elliptic partial differential equations.
Thermal conductivity modeling of copper and tungsten damascene structures

Thermal conductivity of copper and tungsten nanowires, copper damascene structures are modeled theoretically on the basis of Boltzmann transport equation. The size-dependent thermal conductivities of the nanowires are obtained by taking into account interface scattering, grain boundary scattering, and interface roughness effect. Expressions for the thermal conductivity of thin films including the above mechanisms are extended to the case of rectangular cross-sectional nanowires. The fractal model is also used to predict the contribution of interface roughness to the thermal conductivity of nanowires. It is shown that the interface roughness is important for the nanowires with lateral dimensions down to the sub-30 nm region. Calculated thermal conductivities are in good agreement with the experimental data for copper and tungsten nanowires. Furthermore, it is found that the titanium nitride barrier layer obviously leads to further thermal conductivity reduction in the copper damascene structures.
A systematic search for galactic supernova remnants.

The positions of all known radio supernova remnants have been searched for optical emission nebulosity. New optical supernova remnants identified during this program are G130.7 + 3.1= 3C 58, G206.9 + 2.3= PKS 0646 + 06, G296.1--0.7, G326.3--1.8= MSH 15--56, and G327.6 + 14.5= PKS 1459--41= Lupus SN 1006. New observations suggest that G74.8 + 0.6, G78.1 + 1.8, G284.2--1.8, and G339.2--0.4 are unlikely to be supernova remnants.Of 124 probable galactic SNRs listed in Table 1 all but one (G343.2--5.6) are known to be radio sources. A total of 29 SNRs have now been observed optically. In the anticenter direction (90/sup 0/
Interoperability of SeaSondes and Wellen Radars in Mapping Radial Surface Currents

AbstractA dual-station high-frequency (HF) Wellen Radar (WERA) transmitting at 16 MHz has observed near-real-time surface currents over an approximate range of 100 km across the Florida Straits since July 2004. During a 10-day period in April 2005 (15–25 April), a pair of 12.6-MHz SeaSondes (SS) were deployed south of the WERAs sites by NOAA's Center for Operational Oceanographic Products and Services (CO-OPS). The resulting SS grid overlapped the southern portion of the WERA domain. During the same period of time, a bottom-mounted acoustic Doppler current profiler (ADCP) acquired subsurface current measurements within these HF radar grids starting at 14 m below the surface in water of 86-m depth. The interoperability of beam-forming (WERA) and direction-finding (SS) HF radar technologies was examined. Comparisons of radial and vector currents for an 8-day concurrent time series suggested good agreement in current direction over both domains, where the surface currents' magnitudes were a maximum of 1.2 m .
Three-dimensional viscous flows with large secondary velocity

A new system of approximating equations is derived for three-dimensional steady viscous compressible flows in which a primary flow direction is present, but in which both transverse velocity components can be large. If the transverse velocity vector which corrects a given potential flow is first decomposed into ‘potential’ and ‘rotational’ vector components, then a re-examination of three-dimensional boundary-layer theory shows that both components (vϕ, wϕ) of the potential-velocity vector may be assumed small, whereas both components (vψ, wψ) of the rotational-velocity vector and hence of the composite secondary flow (v, w) can remain of order unity. An assumption of small scalar potential then leads to a system of governing equations whose characteristic polynomial has a non-elliptic form for arbitrary Mach number, without introducing any direct approximation of either streamwise or transverse pressure gradient terms. These non-elliptic equations can be solved very economically as a well-posed initial/boundary-value problem. Computed results for laminar subsonic flow in a curved square duct confirm the small scalar-potential approximation for both large (R/d = 100) and small (R/d = 2) radius of curvature. Other computations for R/d = 2.3 are in good agreement with the measurements of Taylor, Whitelaw & Yianneskis (1980).
Stable walking of 3D compass-like biped robot with underactuated ankles using discrete transverse linearization

In this study, a walking manner of a spatial compass-like biped robot with underactuated ankles is presented. This biped robot has 3 degrees of freedom with only one actuator. The hip joint is equipped with a constraint mechanism to lock the angle when it retracts to a desired value. With the Poincare shooting method, a limit cycle of 3D walking gait on level ground is obtained. This limit cycle is unstable by checking the Jacobian of the Poincare map. We use this limit cycle as a reference trajectory and then introduce a method based on discrete transverse linearization to transform the reference trajectory tracking problem to a stabilization problem of a discrete periodic linear system. Thus, the classical discrete-time linear quadratic regulator is recalled to solve the stabilization problem. That is, a stable walking control law is obtained for the proposed 3D robot with a constraint mechanism.
Near-field dielectric optics near the thermodynamic limit

Practical aplanatic optics crafted from transpar- ent dielectrics can approach the thermodynamic limit for ra- diative transfer in near-field systems. Designs are presented for the particularly challenging realm of high numerical aper- ture NA at the source and/or target. These light couplers can alleviate difficulties in aligning system components and can achieve the fundamental compactness limit for optical devices that satisfy Fermat's principle. Examples and perfor- mance estimates based on ray-trace simulations are presented. © 2006 Society of Photo-Optical Instrumentation Engineers.
Panel Effects in the American National Election Studies

Parallel panel and fresh cross-section samples in recent National Election Study surveys provide valuable leverage for assessing the magnitude of biases in statistical analyses of survey data due to panel attrition and panel conditioning. My analyses employing a variety of typical regression models suggest that substantial panel biases are likely to be fairly rare in these data, even when panel and cross-section respondents have markedly different characteristics. However, two of the dependent variables considered here—campaign interest and turnout—do appear to be sufficiently sensitive to panel effects to warrant significant discounting or adjustment of panel data. I propose adjustments for panel effects in both cross-sectional and dynamic analyses, based upon variants of the “fractional pooling” (Bartels 1996) and “two-stage auxiliary instrumental variables” (Franklin 1990) methods.
Reducing asymmetric imaging errors through selective assembly and tolerance desensitization

Asymmetric imaging errors are frequently the main cause for tight tolerances and high demands on manufacture and assembly of optical systems. In order to simultaneously increase robustness and reduce manufacturing cost, desensitization strategies can be applied. Tolerance effects have been included into the optimization function (merit function) by some lens designers to find insensitive designs 1-5 and frequently compensators are employed to further improve the performance of assembled lenses. Compensators are limited to a small number of system parameters, but selective assembly of components can extend the number of parameters available for compensation. It can be employed to reduce tolerance effects of disturbed parameters by finding the best matches out of a set of components. The potential of using tolerance desensitization in conjunction with selective assembly to reduce asymmetric errors in imaging optical systems is investigated. A focus is given on strategies to find tolerance insensitive design forms under the presence of selective assembly compensators and the selection of suitable parameters for desensitization and measurement.
Self-similarity of Julia sets of the composition of polynomials

In the classical iteration theory we say that for a given polynomial $f$ a point $z_0\in\C$ belongs to the Julia set if the sequence of iterates $(f^n)$ is not normal in any neighbourhood of $z_0$. In this paper, we look at the set of non-normality of $(F_n)$, $F_n:=f_n\circ\cdots\circ f_1$, where $(f_n)$ is a given sequence of polynomials of degree at least two. If we can find a hyperbolic domain $M$ which is invariant under all $f_n$, $n\in\N$, $\infty\in M$ and $F_n\to\infty\ (n\to\infty)$ locally uniformly in $M$, then we ask whether these sets of non-normality, which we will also call Julia sets, have properties which we know from the classical case. We show that the Julia set is self-similar. Furthermore, the Julia set is perfect or finite. The finite case may actually occur. We will also give some sufficient conditions for the Julia set being perfect. In the last section we give some examples of sequences of polynomials (where no domain $M$ exists) which have a pathological behaviour in contrast to the classical case.
Identification of the plasma magnetic contour from external magnetic measurements by means of equivalent currents

One of the main research issues in the thermonuclear fusion area is the identification of plasma contour starting from external magnetic measurements. Possible approaches to this inverse problem make use of equivalent currents to represent the plasma internal current density, regularizing in this way the magnetic field reconstruction. Of course, the choice of the representation basis for such equivalent currents is critical. The paper aims at analyzing the effect of the number and position of base currents on the performance of the identification algorithm.
Integration of Optical Manipulation and Electrophysiological Tools to Modulate and Record Activity in Neural Networks

We present an optical system that combines IR (1064 nm) holographic optical tweezers with a sub-nanosecond-pulsed UV (355 nm) laser microdissector for the optical manipulation of single neurons and entire networks both on transparent and non-transparent substrates in vitro. The phase-modulated laser beam can illuminate the sample concurrently or independently from above or below assuring compatibility with different types of microelectrode array and patch-clamp electrophysiology. By combining electrophysiological and optical tools, neural activity in response to localized stimuli or injury can be studied and quantified at sub-cellular, cellular, and network level.