Miracle-dz/UniFAR-FTUs huggingface dataset:
Divergent integrals of post-Newtonian gravity: Nonanalytic terms in the near-zone expansion of a gravitationally radiating system found by matching

We study the divergent integrals that occur in all post-Newtonian (PN) treatments of radiation reaction in slow-motion, gravitationally bound systems in general relativity. The PN methods implicitly assume that the near-zone metric has a valid asymptotic expansion in powers of the small velocity parameter epsilon. We first show explicitly (for the gauge to be used here) that a PN-approximation method leads to a divergent integral at 4-PN order. This divergence arises from the second iteration. Matching arguments are then used to calculate a near-zone term of O(log epsilon) larger than 4-PN order. On the basis of this calculation and several previous model problems, we argue that the PN divergences signify the breakdown of the PN power-series assumption, rather than a breakdown of the near and wave zones. Our results suggest that the PN calculations in fact give correct answers at least up to the orders at which divergences appear. The nonanalytic term of O(log epsilon) beyond 4-PN order arises in the near zone via matching to the wave-zone expansion when we include terms of O(epsilon/sup 3/) beyond linearized order. (This order corresponds to the second PN iteration.) We also solve the wave-zone equations at O(epsilon/sup 6/) beyond linearized order andmore » analyze the inner expansion of the solutions. Matching gives rise to a nonanalytic term in the wave zone at O(epsilon/sup 11/log/sup epsilon/), i.e., at O(e/sup 6/log/sup epsilon/) beyond linearized order. A straining technique is used in the wave-zone expansion to give a sufficiently accurate approximation to the null surfaces near past and future null infinity. The lowest-order strained solution at first appears to contribute a large, anomalous, time-odd piece to the reaction potential. However, after analyzing the contribution of higher-order wave-zone terms, we obtain agreement with the Burke reaction potential. Our results thus strongly support the usual quadrupole formula. « less
Experimental observation of the propagation-dependent beam profile distortion and Goos–Hänchen shift under the surface plasmon resonance condition

We accurately measure the profiles of a reflected divergent beam under a very common surface plasmon resonance configuration in both the near- and far-field regions. Through analysis of the normalized beam shapes, significant propagation-dependent distortion is experimentally revealed. The results are in very good agreement with the theoretical estimations, considering the nonlinear phase distribution within the angular range covered by the focused beam. The corresponding minimal positions of the angular reflectance spectrum measured at different locations could shift as much as a few tens of millidegrees. The propagation-dependent Goos–Hanchen shifts are also accurately obtained, and they significantly deviate from the estimates based on the traditional linear phase response but match very well with the simulation results from our model. This verifies our previous theoretical predictions of the propagation-dependent beam distortion, and it could have further implications for various sensing and device applications.
Microelectromechanical Systems–Based Feedback Control of Turbulence for Skin Friction Reduction

This article focuses on the feedback control of turbulence for skin friction reduction and reviews the state of the art of control algorithms and distributed microsensors and microactuators. From a viewpoint of possible practical applications, we discuss only the control schemes based on the wall-surface sensing of shear stress and pressure fluctuations with their assessment in direct numerical simulation. The rapid development of microelectromechanical systems (MEMS) flow sensors/actuators is sketched, and a prototype feedback control system assembled for a turbulent channel flow is introduced. Finally, several major remaining issues in control algorithms and massive fabrication of microdevices are discussed.
A Study of Backscattering From Multiscale Rough Surface

Most of the rough surfaces are generally multiscale in nature as observed by radar even at narrow-band. In this paper, we apply the modulation concept to study the characteristics of backscattering from such a multiscale surface, using the IEM scattering model. The modulated surface is special kind of multiscale surface in that a random surface is superimposed upon a periodic type surface. The modulation is rationed from the fact the measured correlation function usually exhibits zero-crossing which equally states the fact that the maxima of surface spectra is shifted toward the higher wavenumber. The amount of the frequency shift depends on the modulation wavenumber. It changes the spectral decay rates behind the peak valued. The normal incidence angle can be significantly shifted as well. It is also found the maximum modulation wavenumber is related by the inverse of base-band correlation length. In all cases studied, it was found that the modulation effects significantly changes the backscattering beha.
Audibility of Periodic Pulses and a Model for the Threshold

Thresholds of audibility are determined by the Bekesy technique for four periodic trains of rectangular pulses. The pulses of a given train are uniform in amplitude and duration, and the trains differ in their periodic patterns of pulse polarity. The parameters considered are pulse rate, pulse duration, and polarity pattern. The stimuli are presented binaurally in quiet over headphones. Data for four subjects are reported. The results show the threshold amplitudes to be little dependent upon polarity pattern. For pulse rates less than about 100 pps the thresholds are also little dependent upon pulse rate. They approach constant values determined by pulse duration. Above 100 pps the thresholds diminish with increasing pulse rate. The experimental technique also provides an estimate of the intensity limen at threshold. An analytical specification of the stimulus is derived which provides an objective correlate of the threshold percept. An electrical circuit model of the threshold is developed which takes ac.
Dynamic Analysis and Optimization of a Three-phase Control Mode of a Mobile System with an Internal Mass

The dynamical system consisting of a rigid body and an internal mass is investigated in this paper. The rigid body can move along a rough horizontal plane with a piece-wise linear resistance law due to the special periodic internal motions. A three-phase control is constructed and the motion of the body relative to the environment is controlled by varying the relative acceleration of the internal mass. The relationships between the control parameters for the realization of a directed velocity-periodic motion of the rigid body are established through both theoretical and numerical methods. Optimal and practical parameters of the internal motion, at which the maximal mean velocity of the body is reached, are determined.
Relativistic effects in many electron hyperfine structure I. Theory

A theory is developed which simplifies the calculation and interpretation of relativistic hyperfine structure effects in many electron atoms. This is achieved through the introduction of the concept of an LS coupled relativistic state. By means of a series of effective Hamiltonians acting between these states the relativistic problem is turned into a non-relativistic one which can be solved more easily. Some qualitative applications are discussed; quantitative applications are treated in the two papers following.
Inverse control of room acoustics using multiple loudspeakers and/Or microphones

A novel theorem is proposed for realizing exact inverse-control of a linear finite-impulse-response (FIR) system. It is named the multiple-input/output inverse theorem (MINT). It is impossible to realize exact inverse-control of a nonminimum-phase system with previously reported methods. However, even in such a case, inverse-control can be realized by using the MINT. According to this theorem, the exact inverse is constructed from multiple FIR filters (transversal filters) by setting extra signal-transmission channels to the linear system. The coefficients of these FIR filters can be computed by the well-known rules of matrix algebra. The MINT can be applied to room acoustics by using multiple loudspeakers or microphones. An experiment is made for realizing inverse-control in a sound-field. It is ascertained that The MINT is grately superior to previous methods which use only one signal-transmission channel.
Resolution Enhancement by Wavefield Extrapolation

cause the resultant wavefield is band-limited, the oversampled wavefield within the receiving aperture can be extrapolated over to an extended region. Then the resolution of the images can be considerably imh(x) = - exp (i2nr/~) cos + proved due to the extension of the aperture after extrapolation. (jAr)1'2 - 1z exp (j2nr/X)
Coupling modes between two flapping filaments

The flapping coupling between two filaments is studied theoretically and experimentally in this paper. A temporal linear instability analysis is carried out based on a simplified hydrodynamic model. The dispersion relationship between the eigen-frequency ω and wavenumber k is expressed by a quartic equation. Two special cases of flapping coupling, i.e. two identical filaments having the same length and two filaments having different lengths, are studied in detail. In the case of two identical filaments, the theoretical analysis predicts four coupling modes, i.e. the stretched-straight mode, the antisymmetrical in-phase mode, the symmetrical out-of-phase mode and the indefinite mode. The theory also predicts the existence of an eigenfrequency jump during transition between the in-phase and out-of-phase modes, which has been observed in previous experiments and numerical simulations. In the case of two filaments having different lengths, four modes similar to those in the former case are identified theoretically. The distribution of coupling modes for both the cases is shown in two planes. One is a dimensionless plane of S vs. U, where S is the density ratio of solid filament to fluid and U2 is the ratio of fluid kinetic energy to solid elastic potential energy. The other is a dimensional plane of the half-distance (h) between two filaments vs. the filament length (L). Relevant experiments are carried out in a soap-film tunnel and the stable and unstable modes are observed. Theory and experiment are compared in detail. It should be noted that the model used in our analysis is a very simplified one that can provide intuitional analytical results of the coupling modes as well as their qualitative distributions. The factors neglected in our model, such as vortex shedding, viscous and nonlinear effects, do not allow the model to predict results precisely consistent with the experiments. Moreover, the Strouhal numbers of the flapping filaments are found to be generally around a fixed value in the experiments for both cases, implying that the filaments try to maintain a lower potential energy state.
Quantum cosmology at finite temperature in superstring theory

We study cosmology induced by an ideal superstring gas at finite temperature. The thermal/quantum effects of the string gas generate a nontrivial effective potential at one-loop level. At certain points in the moduli space where generically massive states become massless, the effective potential develops local minima. The latter serve as moduli attractors, which induce time-dependent scalar masses decreasing in cosmological time. As a result, the coherent scalar oscillations dilute before nucleosynthesis, and the cosmological moduli problem is avoided. In particular, we study moduli stabilization in the cases of cosmology induced by i) a maximally supersymmetric heterotic string gas; ii) a gas of type II string compactified on Calabi-Yau three-folds. In case i), the local minima of the potential arise at enhanced gauge symmetry points, which can stabilize all moduli but the dilaton. In case ii), local minima of the effective potential are reached at the loci where 2-spheres or 3-spheres in the Calabi-Yau space shrink to zero size, giving rise to either conifold transitions or non Abelian gauge symmetries. Extra massless states are induced by D-brane wrapping the shrinking spheres, and the stabilized moduli are those controlling the volume of those spheres. In addition, in the two cases we also study respectively the type I dual theory which is maximally supersymmetric and the heterotic dual theory compactified on K3xT2. We show that dual moduli can be stabilized by novel non-perturbative effects implied by duality maps.
Classifying segmented hyperspectral data from a heterogeneous urban environment using support vector machines

Classifying remotely sensed images from urban environments is challenging. Urban land cover classes are spectrally heterogeneous and materials from different classes have similar spectral properties. Image segmentation has become a common preprocessing step that helped to overcome such problems. However, little attention has been paid to impacts of segmentation on the data's spectral information content. Here, urban hyperspectral data is spectrally classified using support vector machines (SVM). By training a SVM on pixel information and applying it to the image before segmentation and after segmentation at different levels, the classification framework is maintained and the influence of the spectral generalization during image segmentation hence directly investigated. In addition, a straightforward multi-level approach was performed, which combines information from different levels into one final map. A stratified accuracy assessment by urban structure types is applied. The classification of the unsegmented data achieves an overall accuracy of 88.7%. Accuracy of the segment-based classification is lower and decreases with increasing segment size. Highest accuracies for the different urban structure types are achieved at varying segmentation levels. The accuracy of the multi-level approach is similar to that of unsegmented data but comprises the positive effects of more homogeneous segment-based classifications at different levels in one map.
Non-linear weak shock diffraction

Abstract Perturbation expansions are sought for the flow variables associated with the diffraction of a plane weak shock wave around convex-angled corners in a polytropic, inviscid, thermally-nonconducting gas. Lighthill's method of strained co-ordinates [4] produces a uniformly valid expansion for most of the diffracted front, while the remainder of this front is treated by a modification of the shock-ray theory of Whitham [6]. The solutions from these approaches are patched just inside the ‘shadow’ region yielding a plausible description of the entire diffracted shock front.
GRADIENT-CORRECTED CORRELATION WITH NEARLY EXACT KOHN-SHAM EXCHANGE : CALCULATIONS FOR SI AND GE

We have constructed a pseudopotential that reduces the errors inherent in ordinary pseudopotentials when used together with nonlocal exchange potentials. Using the very accurate approximation of Krieger, Li, and Iafrate to the exact Kohn-Sham exchange potential together with correlation in the local-density approximation (LDA) both with and without the generalized gradient correction of Perdew and Wang, we calculated the electronic and physical properties of Si and Ge. The gradient corrections result in a large reduction of the indirect energy gaps, worsening agreement with experiment. They also reduce the total energy of both of the atoms and both of the crystals, resulting in increases of the Si and Ge cohesive energies which improve their agreement with experiment. In addition we have studied the effect of adding gradient corrections when the valence electrons see a Hartree-Fock potential from the core electrons and LDA exchange and correlation among themselves.
Modeling and Experimental Evaluation of a Circular Magnetic-Fluid Deformable Mirror

This article presents an analytical model for the dynamic surface shape of a magnetic fluid deformable mirror (MFDM) in cylindrical coordinates. Such a mirror is proposed as a high-performance alternative to existing costly and fragile wavefront correctors in ophthalmic adaptive optics systems. Results of an experimental investigation aimed at validating the developed analytical model are also presented. A novel approach to linearize and amplify the response of the MFDM surface to the applied magnetic field is introduced and experimentally validated. The developed model will make it possible to design effective surface shape control algorithms for the mirror.
Cost of Living Indexes and Exact Index Numbers

The paper reviews and extends the theory of exact and superlative index numbers. Exact index numbers are empirical index number formula that are equal to an underlying theoretical index, provided that the consumer has preferences that can be represented by certain functional forms. These exact indexes can be used to measure changes in a consumerâs cost of living or welfare. Two cases are considered: the case of homothetic preferences and the case of nonhomothetic preferences. In the homothetic case, exact index numbers are obtained for square root quadratic preferences, quadratic mean of order r preferences and normalized quadratic preferences. In the nonhomothetic case, exact indexes are obtained for various translog preferences.
Recovery of inclusion separations in strongly heterogeneous composites from effective property measurements

An effective property of a composite material consisting of inclusions within a host matrix depends on the geometry and connectedness of the inclusions. This dependence may be quite strong if the constituents have highly contrasting properties. Here, we consider the inverse problem of using effective property data to obtain information on the geometry of the microstructure. While previous work has been devoted to recovering the volume fractions of the constituents, our focus is on their connectedness—a key feature in critical behaviour and phase transitions. We solve exactly a reduced inverse spectral problem by bounding the volume fraction of the constituents, an inclusion separation parameter and the spectral gap of a self-adjoint operator that depends on the geometry of the composite. We present a new algorithm based on the Möbius transformation structure of the forward bounds whose output is a set of algebraic curves in parameter space bounding regions of admissible parameter values. These results advance the development of techniques for characterizing the microstructure of composite materials. As an example, we obtain inverse bounds on the volume fraction and separation of the brine inclusions in sea ice from measurements of its effective complex permittivity.
A possible detection of diffuse extended X-ray emission in the environment of the globular cluster NGC 6779

ABSTRA C T We report the possible detection of diffuse X-ray emission in the environment of NGC 6779, and find the emission to be well aligned with the proper motion of the cluster. The position of the emission suggests we are observing heated ISM in the wake of the cluster that could be the result of an interaction between the intracluster medium and the halo gas surrounding
Frequency-dependent transformation matrices for untransposed transmission lines using Newton-Raphson method

The frequency-dependent aspects of transmission line transformation matrices along with their asymptotic behaviours at high and low frequencies are thoroughly investigated in this paper. The Newton-Raphson (NR) method for evaluating the transformation matrices as smooth functions of frequency is introduced. A different technique which utilizes a conventional diagonalization algorithm and a correlation technique for tracking the order of the eigenvectors and eigenvalues is used to confirm the validity of the NR method. Transformation matrices for typical line configurations are evaluated and discussed. The paper concludes that the NR method is more efficient and appropriate for use in the time domain frequency-dependent line models in the Electromagnetic Transient Program (EMTP).
Characterization and analysis of graded index optical waveguides for the realization of low-power, high-density, and high-speed optical link

This paper describes an advanced optical link model composed of multimode waveguide that is used to aid the development of low-power, high-density, and high-speed multi-channel interconnects. The model consists of a VCSEL, a pair of multi-channel rectangular step-index (SI) or graded-index (GI) type optical waveguides, a graded-index multimode fiber (GI MMF), and a photo detector. Here we assume that each waveguide is integrated on a printed circuit board (PCB), and these two PCBs are connected by the GI MMF ribbon (board-to-board interconnection). Then, we focus on the connection of these link components. For optical links with low-power consumption, the link penalty should be minimized. In this paper, the benefits of GI waveguides over SI waveguides are investigated, particularly about the coupling losses. We start the analysis using the fundamental ray optics. The rays emit from a VSCEL with Gaussian angular intensity distribution. Both between the laser source and the waveguide (Tx side), and between the waveguide and the photodiode (Rx side), a 50 μm gap is assumed, which is filled with a uniform medium with similar refractive index to the core center for the purpose of reducing the Fresnel reflection loss. Furthermore, the two waveguides are connected by a GI MMF, which guides the light from the Tx side to the Rx side. The characteristics such as near field pattern (NFP) and connection loss are addressed. The calculated results show the GI waveguides confine the lightwave intensity near the core center more tightly than the SI waveguide, which result in lower coupling loss (0.46 dB for GI waveguide vs. 1.35 dB for the SI counterpart) between the 35 μm core size waveguides and the 35 μm diameter photo diode (PD). This calculation helps us to characterize the high performance optical link with a more reliable model.
Linear image reconstruction for a diffuse optical mammography system in a noncompressed geometry using scattering fluid

Diffuse optical tomography (DOT) is a potential new imaging modality to detect or monitor breast lesions. Recently, Philips developed a new DOT system capable of transmission and fluorescence imaging, where the investigated breast is hanging freely into the measurement cup containing scattering fluid. We present a fast and robust image reconstruction algorithm that is used for the transmission measurements. The algorithm is based on the Rytov approximation. We show that this algorithm can be used over a wide range of tissue optical properties if the reconstruction is adapted to each patient. We use estimates of the breast shape and average tissue optical properties to initialize the reconstruction, which improves the image quality significantly. We demonstrate the capability of the measurement system and reconstruction to image breast lesions by clinical examples.
Approximation of solutions of singular second-order boundary value problems

The boundary value problems \[ ({\text{P}}_1 )\begin{array}{*{20}c} {y'' + \frac{{n - 1}}{x}y' + f(x,y) = 0,} \\ {y'(0) = y(1) = 0,} \\ \end{array} \] and \[ \begin{gathered} y'' + f(x,y) = 0, \hfill \\ ({\text{P}}_2 )\quad \alpha y(0) - \beta y'(0) = 0, \hfill \\ \gamma y(1) + \delta y'(1) = 0 \hfill \\ \end{gathered} \] with the function $f(x,y)$ satisfying conditions that allow for singularities to be present are studied with the view of obtaining general existence, uniqueness, and approximation of positive solutions. Furthermore, the behavior of solutions near $x = 1$ is described for the special case $f(x,y) = a(x)y^{ - p} $.