Miracle-dz/UniFAR-FTUs huggingface dataset:
Level sets of additive Lévy processes

We provide a probabilistic interpretation of a class of natural capacities on Euclidean space in terms of the level sets of a suitably chosen multiparameter additive Levy process X. We also present several probabilistic applications of the aforementioned potential-theoretic connections. They include areas such as intersections of Levy processes and level sets, as well as Hausdorff dimension computations.
Mechanical behavior of axially magnetized permanent-magnet gears

We studied permanent-magnet (PM) gears with axially magnetized permanent magnets and a plane air gap in terms of mechanical behavior. We determined the torque and forces exerted between the two rotors of these devices, using a seminumerical method based on the calculation of the forces between the magnets of the rotors. The study deals with the general behavior of such devices and presents some very interesting configurations for their mechanical stability.
Power generating device using compound magnetic wire

A new method of generating power using compound magnetic wires is proposed. The coercive force of twisted Vicalloy (40Fe–50Co–10 V) wire is about 20 Oe in the outer shell near the surface and 60 Oe in the inner core. By applying an external magnetic field to the wire, a pulse voltage, owing to a large Barkhausen jump, is induced in a search coil wound around the wire. The voltage of 4 V for 1.2 ms was obtained with a bundle of 150 compound magnetic wires and a 2000 turn search coil.
Horizon entanglement entropy and universality of the graviton coupling

We argue that the entropy of a black hole is due to the entanglement of matter fields and gravitons across the horizon. While the entanglement entropy of the vacuum is divergent because of UV correlations, we show that low-energy perturbations of the vacuum result in a finite change in the entanglement entropy. The change is proportional to the energy flux through the horizon, and equals the change in area of the event horizon divided by 4 times Newton's constant - independently from the number and type of matter fields. The phenomenon is local in nature and applies both to black hole horizons and to cosmological horizons, thus providing a microscopic derivation of the Bekenstein-Hawking area law. The physical mechanism presented relies on the universal coupling of gravitons to the energy-momentum tensor, i.e. on the equivalence principle.
A Measurement of the Neutral B Meson Lifetime using Partially Reconstructed B0 -> D*-pi+ Decays

The neutral B meson lifetime has been measured with the data collected by the BABAR detector at the PEP-II storage ring during the year 2000 for a total integrated luminosity of 20.3 fb{sup -1}. The B{sup 0} {yields} D*{sup -} {pi}{sup +} decays have been selected with a partial reconstruction method in which only the fast pion from the B{sup 0} decay and the slow pion from D*{sup -} {yields} {bar D}{sup 0}{pi}{sup -} are reconstructed. The B{sup 0} lifetime has been measured to be 1.510 {+-} 0.040 {+-} 0.038 ps with a sample of 6971 {+-} 241 reconstructed signal events.
A physical-model study of the statistics of seismic waveform fluctuations in random heterogeneous media

SUMMARY Using laboratory-scale physical models, we studied seismic waveform fluctuation in 3-D heterogeneous media, and evaluated the effects of short-wavelength random heterogeneity on seismic waves. We made two series of experiments: (1) waves are excited by the same source signal and propagate through three kinds of granitic rocks with different scales of heterogeneity, and (2) waves are excited by different frequencies but propagating through the same rock. A compression-mode piezoelectric transducer was attached to one side of the block, and the waveforms were measured at a 10 mm radius circular array with a 2 ° spacing, located on the other side. 180 waveforms are obtained at equal source–receiver distances with an equal wave radiation from the source. The source signals are one- or two-cycle sine-wave pulse with 0.5 MHz for different heterogeneities, and 0.25, 0.5, 1 and 2 MHz for the same heterogeneity. Waveforms were recorded by using a system equipped with a laser Doppler vibrometer as a sensor of elastic waves. The rock heterogeneities were investigated as the 1-D velocity fluctuations obtained from the 2-D microstructure images of the rock. By applying the exponential autocorrelation function, heterogeneities in the three rocks are characterized by similar fluctuation intensities (7.9–9.3 per cent) but different scale lengths ranging from 0.22 to 0.92 mm. We calculated the spatial correlation of waveforms, the correlation between an averaged waveform and observed waveforms, the energy partition with respect to lapse time, and the statistical distributions of the waveform parameters: correlation coefficients, traveltimes of P wave, and the log values of the P-phase energy. Correlation of waveforms, energy partition and statistical parameters of waveforms are investigated as a function of the normalize scale parameter ka: the product of wave number and the characteristic scale length of heterogeneity. We found that waveform parameters change the trends at ka∼0.2–0.3. When ka exceeds 0.2–0.3, scattered waves become strong and waveforms become more complicated. This may indicate a transition from an equivalent homogeneous medium to a scattering medium for seismic waves propagating through random heterogeneous medium.
An expansion of Wigner distribution and its applications

Sensitivity to noise, presence of undesirable interfering cross-terms and generally redundant encoding of information, are major factors that limit the scope of applications of the Wigner distribution(WD). An outer product expansion is proposed, based on the singular value decomposition, for data compression of the WD. It is then used, with synthetic and experimental data, to suppress aforementioned effects and enhance the estimate of the WD.
An Iterative Simulation Approach for Solving Stochastic Control Problems in Finance

We develop a numerical method that combines functional approximations and dynamic programming to solve high-dimensional discrete-time stochastic control problems under general constraints. The method employs quasi-random grids and radial basis functions to handle high-dimensional state spaces; Lagrange multipliers to incorporate constraints and obtain first order optimality conditions; and a new algorithm that iteratively approximates conditional expectations of the value function with second order polynomials and shrinking approximation regions --- the test region iterative contraction algorithm (TRIC). We provide asymptotic results for the convergence and the speed of convergence of the TRIC algorithm, and apply the method to two Finance applications: a) dynamic portfolio choice with labor income and financial constraints, a continuous control problem; b) dynamic portfolio choice with capital gain taxation, a high-dimensional singular control problem.
Radiation from concentric‐circle grating, surface‐emitting planar waveguides: The volume current method

This letter describes the volume current boundary perturbation method and uses this method to find the field radiated by a set of concentric rings located at the film‐cover interface of a three‐layer, planar optical waveguide. Waveguides with annular and full (extending from the origin) sets of circular gratings, and with both traveling and standing guided waves, are analyzed. The resulting analytical expression for the radiation field and far‐field intensity patterns are compared with results of the field‐expansion boundary perturbation method.
An approach to the plasma magnetic contour identification in presence of eddy currents

The research in the thermonuclear fusion area has entered the design phase of ITER, the first experimental Tokamak reactor. In the ITER device, the plasma shape and position are controlled by an active system on the basis of a real-time estimate of the plasma magnetic boundary. This identification process must be prompt and accurate enough to satisfy the tight control requirements. In this paper, a brief discussion about the reconstruction of the plasma boundary by means of the "equivalent currents" (EC) method, in presence of conducting structures, will be presented. Some hints about a possible way to include the differential equations describing the vessel eddy currents will be illustrated.
Resonant tunneling in quantum cascade lasers

Experimental evidence that in quantum cascade lasers electron injection into the active region is controlled by resonant tunneling between two-dimensional subbands is discussed. A quantitative analysis is carried out using an equation for the current density based on a tight-binding approximation. Electron injection into the active region is optimized when the current density is limited by the lifetime of the excited state of the laser transition. In this regime, quasi-equilibrium is reached between the population of the injector ground state and that of the excited state of the laser transition characterized by a common quasi-Fermi level. The design of the injector depends on the selected laser active region; in particular, the choice of physical parameters, such as doping concentration and injection barrier thicknesses, is in general different for vertical or diagonal transition lasers. The paper concludes with an investigation of the transport properties at threshold and its dependence on stimulated emission; a relationship between the differential resistance above threshold and the value of the slope efficiency is deduced.
The lower-hybrid-drift instability as a source of anomalous resistivity for magnetic field line reconnection

It is shown that the lower-hybrid-drift instability can be unstable over a large region of the magnetotail where collisionless reconnection is expected to occur. For typical quiescent tail parameters the instability threshold is much lower than the ion acoustic instability. Preliminary considerations indicae that it can produce anomalous resistivity substantially larger than classical, reconnection rates of the order 10/sup -1/ V/sub A/, electromagnetic noise is the frequency range . omega. /sub L H/<. omega.very-much-less-than.cap omega. /sub e/ and field aligned relativistic electron fluxes.
Quantitative x-ray microtomography with a conventional source

In 1981, Elliott and Dover designed an X-ray microtomography scanner as a means of measuring the local mineral concentration in teeth. Although slow, this first generation system gave accurate measurements of the X-ray linear attenuation coefficient (LAC) due to its use of energy dispersive photon counting apparatus. Attaining such accuracy with integrating detectors in third generation scanners is difficult, but has been the goal of our ongoing development. The current "MuCat 2" system uses a 6cm square CCD chip with a parallel fibre-optic faceplate coupled to a CsI scintillator. Time delay integration readout (with sliding camera) is used to eliminate ring artefacts and enable high dynamic range X-ray projections to be acquired. The beam is collimated with a moving aperture (tracking the camera) to reduce X-ray scatter. Beam hardening is reduced by the use of filtering and corrected using data from an aluminium step wedge to optimise a model of polychromatic X-ray generation, attenuation and detection. Adjustments can be made to the model to allow for known specimen composition. Projections are corrected for distortion and repeatable wobble in the rotation stage. Where high absolute accuracy of the LAC is required, a pure aluminium wire is included in the scan and used to "fine-tune" the grey level after reconstruction.
A Novel Image Retrieval System Based on Histogram Factorization and Contextual Similarity Learning

Image retrieval has been a top topic in the field of both computer vision and machine learning for a long time. Content based image retrieval, which tries to retrieve images from a database visually similar to a query image, has attracted much attention. Two most important issues of image retrieval are the representation and ranking of the images. Recently, bag-of-words based method has shown its power as a representation method. Moreover, nonnegative matrix factorization is also a popular way to represent the data samples. In addition, contextual similarity learning has also been studied and proven to be an effective method for the ranking problem. However, these technologies have never been used together. In this paper, we developed an effective image retrieval system by representing each image using the bag-of-words method as histograms, and then apply the nonnegative matrix factorization to factorize the histograms, and finally learn the ranking score using the contextual similarity learning method. The proposed novel system is evaluated on a large scale image database and the effectiveness is shown.
Maximum acyclic and fragmented sets in regular graphs

We show that a typical d‐regular graph G of order n does not contain an induced forest with around ${2 {\rm In} d \over d}$ vertices, when n ≫ d ≫ 1, this bound being best possible because of a result of Frieze and Łuczak [6]. We then deduce an affirmative answer to an open question of Edwards and Farr (see [4]) about fragmentability, which concerns large subgraphs with components of bounded size. An alternative, direct answer to the question is also given. © 2007 Wiley Periodicals, Inc. J Graph Theory 57: 149–156, 2008
The Development and Validation of a Group Test of Logical Thinking

The paper describes the development of the Test of Logical Thinking (TOLT) to measure five modes of formal reasoning: controlling variables, proportional reasoning, combinatorial reasoning, probabilistic reasoning, and correlational reasoning. Each of the 10 items requires participants to select a correct response and justification from a number of alternatives. Analysis of data from 682 students from grades 6 through college indicated high test reliability (coefficient α = .85) and provided confirmation that the test measured one major underlying dimension termed formal thought. Evidence of criterion-related validity was obtained from a study in which 88 students from grades 10 through college were assessed on the TOLT and on five interview tasks. A correlation of . 80 (p < .0001) suggested a strong relationship between the two measures of formal reasoning.
On the use of compensatory strategies in simultaneous interpretation

Weller (1990) believes that Krashen's concept of "comprehensible input" can play a key role in the simultaneous interpretation process even though this concept is most frequently cited in relation to second and foreign language learning. The "comprehensible input" concept is referred to here as the spoken or written pieces of information that are understood and interpreted by the hearer. Such information comes in the form of words, sentences, utterances, or even paragraphs.Based on Weller's recommendation, Krashen's concept is used as a framework for this study to analyze compensatory strategies employed by a small group of Jordanian interpreters who worked for an American television network during the Gulf War.This paper first examines the type of input that causes problems for interpreters.Second, it examines the strategies these interpreters use to compensate for difficult or incomprehensible input. The findings of the study detected five types of compensatory strategies that were employed by four interpreters. These strategies were grouped into two general types: achievement and reduction. These are discussed with recommendations at the end in the hope of providing more insight into how human beings process language under conditions of stress.
Numerical solution of an inverse 2D Cauchy problem connected with the Helmholtz equation

In this paper, the Cauchy problem for the Helmholtz equation is investigated. By Green's formulation, the problem can be transformed into a moment problem. Then we propose a numerical algorithm for obtaining an approximate solution to the Neumann data on the unspecified boundary. Error estimate and convergence analysis have also been given. Finally, we present numerical results for several examples and show the effectiveness of the proposed method.
Hysteresis losses in a thin high-temperature superconductor strip exposed to ac transport currents and magnetic fields

In many prospective power applications based on high-temperature superconductors, the hysteresis losses will be an important parameter. To obtain an optimized device, models of the hysteresis losses valid at applicationlike conditions are needed. In this article the superconductor is modeled as a thin strip with negligible thickness, a geometry which probably is especially suitable for the new wires of the coated-conductor type. The strip is assumed to carry a transport current in phase with an externally applied magnetic field perpendicular to the strip. Calculations of the hysteresis losses, based on the critical state theory, are performed resulting in exact analytical equations.
Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 2—Detailed Measurements

Detailed heat/mass transfer distributions are presented inside a two-pass rotating ribbed coolant channel for two profiled-rib configurations. Several profiled-rib configurations have been studied (Acharya et al., 2000), and it was found that the best performance was achieved by saw-tooth ribs, and a pyramid-valley rib combination. The profiled ribs were placed directly opposite to each other on the leading and trailing surfaces. Smooth side walls were used in all the experiments. Heat transfer measurements were compared with straight ribs of equal blockage ratio. The measurements were made in a two-pass rotating facility using the naphthalene sublimation mass transfer technique, which provides highly resolved surface distributions. The results presented are for a Reynolds number of 30,000, two rotation numbers (0 and 0.3), and include average heat/mass transfer over the entire inter-rib module as well as detailed heat/mass transfer contours for two profiled-rib cases. Significant enhancement of up to 25 percent in heat/mass transfer was obtained with the pyramid-valley and saw-tooth shaped ribs under rotating conditions.
A NOTE ON THE LATTICE BOLTZMANN VERSUS FINITE-DIFFERENCE METHODS FOR THE NUMERICAL SOLUTION OF THE FISHER'S EQUATION

We assess the Lattice Boltzmann (LB) method versus centered finite-difference schemes for the solution of the advection–diffusion–reaction (ADR) Fisher's equation. It is found that the LB method performs significantly better than centered finite-difference schemes, a property we attribute to the near absence of dispersion errors.
Relative-error-based non-linear inversion: application to seismic traveltime tomography

SUMMARY The aim of geophysical inversion is to infer information about the subsurface model parameters subject to certain constraints and plausibility considerations. It is achieved through a systematic adjustment of model parameters along a solution path to the minimum of an objective function. The objective function is related to both the observations (data) and the a priori information about the subsurface model parameters (model). When different statistics are assumed for the data and the a priori information about the model, different objective functions are constructed and different solution models become inevitable. Traditionally, data residuals are used directly in constructing the objective function. If the residuals are statistically proportional to the data magnitudes, a least-squares (LS) method often leads to a solution model biased towards (i.e. which emphasizes) observations of large magnitude, whereas a least absolute deviation (LAD) method can reduce this datamagnitude-dependent effect. An alternative is to formulate the objective function in terms of relative differences. It completely eliminates the possible solution bias due to the intrinsic magnitude-dependent discrepancies in the objective function. The solution path is altered in such a way that.data residuals are reduced in a more uniform manner. The idea is illustrated through a seismic traveltime tomographic inversion. Traveltime residuals are often correlated with ray-path lengths. Greater residuals of long ray paths dominate the objective function in the traditional tomographic formulation. The solution path is thus strongly affected by those long ray paths, and short ray paths play a reduced role in the inversion. The final solution is biased toward longer ray paths. The new alternative formulation eliminates this bias by exploiting the relative-error measure to give equal weights to data of the same quality regardless of their ray-path lengths.
EVIDENCE FOR GENTLY SLOPING PLASMA DENSITY PROFILES IN THE DEEP CORONA: TYPE III OBSERVATIONS

Type III radio bursts are produced near the local electron plasma frequency fp and near its harmonic 2fp by fast electrons ejected from the solar active regions and moving through the corona and solar wind. The coronal bursts have dynamic spectra with frequency rapidly falling with time, the typical duration being about 1–3 s. In the present paper, 37 well-defined coronal type III radio bursts (25–450 MHz) are analyzed. The results obtained substantiate an earlier statement that the dependence of the central frequency of the emission on time can be fitted to a power-law model, f(t) ∝ (t − t0)−α, where α can be as low as 1. In the case of negligible plasma acceleration and conical flow, it means that the electron number density within about 1 solar radius above the photosphere will decrease as r−2, like in the solar wind. For the data set chosen, the index α varies in the range from 0.2 to 7 or bigger, with mean and median values of 1.2 and 0.5, respectively. A surprisingly large fraction of events, 84%, have α ⩽ 1.2. These results provide strong evidence that in the type III source regions the electron number density scales as n(r) ∝ (r − r0)−β, with minimum, mean, and median β = 2α of 0.4, 2.4, and 1.0, respectively. Hence, the typical density profiles are more gently sloping than those given by existing empirical coronal models. Several events are found with a wind-like dependence of burst frequency on time. Smaller power-law indices could result from the effects of non-conical geometry of the plasma flow tubes, deceleration of coronal plasma, and/or the curvature of the magnetic field lines. The last effect is shown to be too weak to explain such low power-law indices. A strong tendency is found for bursts from the same group to have similar power-law indices, thereby favoring the hypothesis that they are usually produced by the same source region.
On Monte Carlo methods for estimating ratios of normalizing constants

Recently, estimating ratios of normalizing constants has played an important role in Bayesian computations. Applications of estimating ratios of normalizing constants arise in many aspects of Bayesian statistical inference. In this article, we present an overview and discuss the current Monte Carlo methods for estimating ratios of normalizing constants. Then we propose a new ratio importance sampling method and establish its theoretical framework. We find that the ratio importance sampling method can be better than the current methods, for example, the bridge sampling method (Meng and Wong) and the path sampling method (Gelman and Meng), in the sense of minimizing asymptotic relative mean-square errors of estimators. An example is given for illustrative purposes. Finally, we present two special applications and the general implementation issues for estimating ratios of normalizing constants.