Miracle-dz/UniFAR-FTUs huggingface dataset:
A model of bubble dynamics in a Hele–Shaw cell

A model of the interaction of small, well‐separated bubbles of one fluid propagating through another ‘‘resident’’ fluid in a Hele–Shaw cell is introduced and studied. In the model each bubble acts on the others by setting up a velocity field of the dipole type. A system of ordinary differential equations is developed for the bubble positions. The system is solved completely for the two‐bubble problem. The three‐bubble problem is addressed by numerical simulations. A set of self‐similar motions are also found analytically. The dynamics of rows of bubbles is investigated analytically and via numerical simulations. Although clearly an extreme idealization, the model appears to shed considerable light on what to expect in laboratory experiments.
The introduction of modern physics: overcoming a deformed vision of science

In this paper, we try to show initially that modern physics is usually introduced in high school curricula without reference to the difficulties of classical physics, simply juxtaposing the two paradigms or even mixing them up. As a result, serious misconceptions arise. We then present another way of introducing modern physics, based on a constructivist view of science learning, and give some results obtained with the new materials.
Finite‐time tracking control of a nonholonomic mobile robot

In this paper, the finite‐time tracking problem is investigated for a nonholonomic wheeled mobile robot in a fifth‐order dynamic model. We consider the whole tracking error system as a cascaded system. Two continuous global finite‐time stabilizing controllers are designed for a second‐order subsystem and a third‐order subsystem respectively. Then finite‐time stability results for cascaded systems are employed to prove that the closed‐loop system satisfies the finite‐time stability. Thus the closed‐loop system can track the reference trajectory in finite‐time when the desired velocities satisfy some conditions. In particular, we discuss the control gains selection for the third‐order finite‐time controller and give sufficient conditions by using Lyapunov and backstepping techniques. Simulation results demonstrate the effectiveness of our method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
On the Question of Computation of the Dyadic Green's Function at the Source Region in Waveguides and Cavities (Short Papers)

The derivation of the dyadic Green's function for rectangular waveguides and cavities is approached systematically by using the theory of distributions. It is shown that, in order to obtain a complete solution for the field distribution in the entire structure, one must add an additional term to the classical expansion which is valid only outside the source region.
Multifractal fluctuations in earthquake-related geoelectrical signals

Multifractal fluctuations in the time dynamics of geoelectrical data, recorded in a seismic area of southern Italy, have been analysed. We find that the multifractality of the signal depends mostly on the different long-range properties for small and large fluctuations. Furthermore, we quantitatively characterized the multifractality of the geoelectrical time series, on the basis of the characteristic parameters derived from the multifractal spectrum (maximum α0, asymmetry B and width W) (Shimizu Y, Thurner S and Ehrenberger K 2002 Fractals 10 103). We then analysed the time evolution of the multifractal parameters and we found that the multifractal degree of the signal, revealed by the variation of the width of the multifractal spectrum, is enhanced in association with the occurrence of the largest seismic event. This study aims to suggest another approach to investigate the complex dynamics of geoelectrical signals.
The influence of stoichiometry on the structural stability and on the optical emission of erbium silicate thin films

We report the effects of thermal annealing performed in N2 or O2 ambient at 1200°C on the structural and optical properties of Er silicate films having different compositions (Er2SiO5, Er2Si2O7, and their mixture). We demonstrate that the chemical composition of the stoichiometric films is preserved after the thermal treatments. All different crystalline structures formed after the thermal annealing are identified. Thermal treatments in O2 lead to a strong enhancement of the photoluminescence intensity, owing to the efficient reduction of defect density. In particular the highest optical efficiency is associated to Er ions in the α phase of Er2Si2O7.
PREDICTION OF ROTOR HIGH-SPEED IMPULSIVE NOISE WITH A COMBINED CFD–KIRCHOFF METHOD

Abstract A combined Computational Fluid Dynamics (CFD)–Kirchoff method is presented for predicting high-speed impulsive noise generated by a rotor in hover. Two types of Kirchoff integral formulas are used: one of them is a classical linear Kirchoff formulation and the other a non-linear Kirchoff formulation. An Euler finite-difference solver is executed first, from which a flow field is obtained to be used as an input to the Kirchoff formulation to predict the acoustic far-field. The calculations are performed at Mach numbers of 0·90 and 0·95 to investigate the effectiveness of the linear and non-linear Kirchoff formulas for delocalized flow. During these calculations, the retarded time equation is also carefully examined, in particular, for the cases where a control surface is located outside the sonic cylinder, for which multiple roots are obtained. Predicted results of acoustic far-field with the linear Kirchoff formulation agree well with the experimental data when the control surface is at a particular location ( R cs / R =1·46), but the correlation weakens as it moves away from this specific location of the control surface due to the delocalized non-linear aerodynamic flow field. Calculations based on the non-linear Kirchoff equation using the sonic cylinders as the control surfaces show reasonable agreements with the experimental data in the negative amplitudes for both tip Mach numbers of 0·90 and 0·95, except for some computational integration problems over a shock. It can be concluded that a non-linear formulation is necessary if the control surface is close to the blade and the flow is delocalized.
Identification of the variable X-ray sources GX 339-4 and MXB 1659-29 by the scanning modulation collimator on HEAO 1

Precise celestial positions have been obtained with the HEAO 1 scanning modulation collimators for the highly variable X-ray source GX 339--4 (4U 1658--48) and the X-ray burst source MXB 1659--29. Both sources are identified with faint (17-18 mag) blue objects with He II lambda4686 and lambdalambda4640--50 emission.
Bayesian Updating of Structural Models and Reliability using Markov Chain Monte Carlo Simulation

In a full Bayesian probabilistic framework for "robust" system identification, structural response predictions and performance reliability are updated using structural test data D by considering the predictions of a whole set of possible structural models that are weighted by their updated probability. This involves integrating h(θ)p(θ|D) over the whole parameter space, where θ is a parameter vector defining each model within the set of possible models of the structure, h(θ) is a model prediction of a response quantity of interest, and p(θ|D) is the updated probability density for θ, which provides a measure of how plausible each model is given the data D. The evaluation of this integral is difficult because the dimension of the parameter space is usually too large for direct numerical integration and p(θ|D) is concentrated in a small region in the parameter space and only known up to a scaling constant. An adaptive Markov chain Monte Carlo simulation approach is proposed to evaluate the desired integral that is based on the Metropolis-Hastings algorithm and a concept similar to simulated annealing. By carrying out a series of Markov chain simulations with limiting stationary distributions equal to a sequence of intermediate probability densities that converge on p(θ|D), the region of concentration of p(θ|D) is gradually portrayed. The Markov chain samples are used to estimate the desired integral by statistical averaging. The method is illustrated using simulated dynamic test data to update the robust response variance and reliability of a moment-resisting frame for two cases: one where the model is only locally identifiable based on the data and the other where it is unidentifiable.
Large‐eddy simulation of urban boundary‐layer flows by generating turbulent inflows from mesoscale meteorological simulations

We propose an approach to generate turbulent flows by using mesoscale meteorological simulations in order to conduct building‐resolving large‐eddy simulations (LESs) of boundary‐layer flows over urban areas under realistic meteorological conditions. The urban surface geometry was explicitly represented in the LES model. This approach was applied for a strong wind event in Tokyo owing to the landfall of a major typhoon whose intensity and track were well reproduced in the meteorological simulation. The observed ranges of wind fluctuations and gust factors and significant decelerations of wind speeds within the urban canopy layer were successfully represented in the LES. Copyright © 2012 Royal Meteorological Society
An Effective Method for Combining Kernels with Class Separability

We propose a simple but effective method to determine the kernel weights for convex combination of multiple kernels. The key property of the proposed method is that it adopts a class separability criterion as the evaluation function to measure the goodness of the individual kernel. Based on the principle of class separability, we assign a weight to each kernel that is proportional to the quality of the kernel. Experimental results on Image Segmentation data set show the proposed method can improve accuracy in comparison with that using a single kernel or uniformly-combined kernel.
HMM-based noisy-speech pitch contour estimation

A robust pitch contour estimation algorithm that makes use of hidden Markov models (HMMs) is proposed for speech signals corrupted by various kinds of noise at low SNR. The HMM contains three states. For the output p.d. f. , multivariate continuous Gaussian distributions are chosen, having pitch and its derivatives as the random variables. Pitch estimation via two steps is suggested so that information among inter- and intra-analysis frames can be fully used. Conventional algorithms are thus modified to provide a group of weighted pitch candidates. For all possible candidate sequences with given a priori probabilities, the HMM-based algorithm calculates the output probabilities and selects the best contour from the candidates in the maximum-likelihood (ML) sense. To solve the problems of excessively using memory space and missing wanted candidates, beam search, pruning and candidate prediction are used. Advantages of HMM estimation over the conventional smoothing and dynamic programming (DP) are also discussed. The preliminary simulations showed its robustness. <<ETX>>
Vector Map Data Compression with Wavelets

This paper was first presented at a Symposium on ‘Advanced Moving-Map Displays’ held on the 3rd and 4th of August 1999 by the US Naval Research Laboratory Detachment at the NASA Stennis Space Centre, Mississippi, and is reproduced in modified form with the kind permission of the NRL Commanding Officer, Captain Douglas H. Rau USN. Wavelets and wavelet transforms can be used for vector-map data compression. The choice of wavelet, the level of decomposition, the method of thresholding, the height of the threshold, relative CPU times and file sizes, and reconstructed map appearance were investigated using the Wavelet Toolbox of MATLAB. Quantitative error measures were obtained. For two test vector-map data sets consisting of longitude and latitude points, compressions of 35 to 50 percent (1·5[ratio ]1 to 2[ratio ]1) were obtained with root-mean-square errors less than 0·003 to 0·01° longitude/latitude for wavelet packet decompositions using selected wavelets.
Interpolation using the fast Fourier transform

The fast Fourier transform (FFT) algorithm has had widespread influence in many areas of computation since its "rediscovery" by Cooley and Tukey [1]. An efficient and accurate method for interpolation of functions based on the FFT is presented. As an application, the generation of the characteristic polynomial in the "generalized eigenvalue problem" [2] is considered.
Photon-echo technique for reducing the decoherence of a quantum bit

Abstract A useful method for reducing the decoherence of a quantum bit (qubit) is proposed, which is based on the photon-echo phenomenon in coherent optical transient. The decoherence of the qubit is caused by the dephasing coupling with a bosonic thermal reservoir. In the method, successive coherent π pulses are applied with very short pulse widths to reduce the decoherence. It is found that the decoherence of the qubit disappears at a certain time which can be controlled by appropriately choosing the pulse separation time and the number π pulses.
Fractional differential algorithms for rock fracture images

Abstract It is a new research topic that fractional differential theory is used into image processing. This paper presents a new type of algorithms to improve the fractional differential Tiansi operator, which can significantly enhance the edge detection result. The studied algorithms are based on the enhancement ability of fractional differential to image details, and they can be used to analyse the properties of fractional differential. The general procedure of the algorithms is as follows: firstly, Tiansi template is divided into eight sub-templates with different directions around the detecting pixel, and then the eight weight sum values for the eight sub-templates are obtained. Furthermore, those eight weights are classified into different groups. In this way, the three improved algorithms with different enhancing ranges are obtained. Finally, the experiments of edge detection show that the improved algorithms can obtain edge information more effectively and can show much more detailed information than traditional edge detection operators especially for the images of fine edges such as complicated rock fracture images.
A kind of on-off control method based on EEG dimension complexity detection

Some studies show that Environment Control System (ECS) improves severe disabled people life, one of which is based on analyzing alpha wave following eye closure. This paper proposes a method for detecting the difference of dimension complexity between eye opening and eye closure. By modifying Grassberger and Procaccia algorithm for calculating correlation dimension, this improved method can process overlapped data segment effectively. The value, calculated by this method, is called EEG dimension complexity, which indicates the variability of brain function. Experiments show that EEG dimension complexity is suitable and precise to distinguish two states between eye opening and closure. New method decreases computational cost, and its application shows that this method can be used to control light switch on and off.
Parallel implementation of a non‐hydrostatic model for free surface flows with semi‐Lagrangian advection treatment

The parallel implementation of an unstructured‐grid, three‐dimensional, semi‐implicit finite difference and finite volume model for the free surface Navier–Stokes equations (UnTRIM) is presented and discussed. The new developments are aimed to make the code available for high‐performance computing in order to address larger, complex problems in environmental free surface flows. The parallelization is based on the mesh partitioning method and message passing and has been achieved without negatively affecting any of the advantageous properties of the serial code, such as its robustness, accuracy and efficiency. The key issue is a new, autonomous parallel streamline backtracking algorithm, which allows using semi‐Lagrangian methods in decomposed meshes without compromising the scalability of the code. The implementation has been carefully verified not only with simple, abstract test cases illustrating the application domain of the code but also with advanced, high‐resolution models presently applied for research and engineering projects. The scheme performance and accuracy aspects are researched and discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Measurement of out-of-plane displacement with a digital real-time holography

A digital real-time holographic measurement system is designed based on the principles of double-exposed digital holography in this paper. In order to adapt this system to the variation of specimen size, a concave lens is placed in the classic 4f system, and then the object light path of this system, which transverse magnification can be adjusted by regulating the positions of lens, is equivalent to the 4f system. The object spectrum arriving at charge-coupled device camera (CCD) can be obtained by the Fourier transformation, and the complex amplitude of object wave can be obtained by the Fourier inversion. The phase variation corresponding to the initial object wave when the specimen is deformed can be gained by computer, and furthermore, phase variation corresponding to any of the two different displacement status can also be obtained. That is to say, with the help of this system, we can get much more information than that obtained by classic holography. The system has been used to measure the out-of-plane displacement of PMM specimen containing cracks. The holograms quality obtained by this system is close to that obtained by classic holography. The holograms obtained by digital real-time holography are also compared well with those obtained by classic holography. The digital real-time holography described in this paper can also be adapted for the variation of projection size of the specimen, therefore this system can be used to measure the specimens those projection size are larger than that of area-array of CCD.
Deformation and Fracture of Bone

The microscopic yield stress (the stress to produce a plastic strain of 2×10−6 in./in.) and the variation of plastic strain with applied stress have been established for bone. A feature of the deformation is the large anelastic contraction which occurs after unloading plastically strained specimens. The fracture characteristics of bone, as determined in impact loading and tensile experiments, are a function of specimen orientation and are also notch sensitive. A study of the temperature dependence of fracture in the range from −190° to 900°C shows that specimens oriented parallel to the length of the bone exhibit a pronounced maximum in strength at 0°C.
Generation of magnetic field and electrostatic shock wave driven by counterstreaming pair plasmas

By using a two-dimensional (2D) relativistic fully electromagnetic particle-in-cell code, the interaction process of counterstreaming pair (electron–positron) plasmas is investigated. The counterstreaming plasmas become unstable against the collisionless electromagnetic counterstreaming instability, similar to the Weibel instability. In the linear phase, magnetic and electric fields with the scale of skin depth size are generated through the electromagnetic counterstreaming instability. The behavior of plasma in the nonlinear phase is also made clear. The small-scale magnetic fields coalesce with each other, merging through the inverse cascade process which occurs characteristically in 2D dynamics, and change into larger unit. The large-scale magnetic fields propagate more slowly than the initial plasma flow as a low-frequency wave. Behind the magnetic fields, plasmas are isotropically heated by the mixing of counterstreaming plasmas. On the other hand, the electric fields propagate the same as the initia.
Nanopatterning of optical surfaces during low-energy ion beam sputtering

Abstract. Ion beam figuring (IBF) provides a highly deterministic method for high-precision optical surface fabrication, whereas ion-induced microscopic morphology evolution would occur on surfaces. Consequently, the fabrication specification for surface smoothness must be seriously considered during the IBF process. In this work, low-energy ion nanopatterning of our frequently used optical material surfaces is investigated to discuss the manufacturability of an ultrasmooth surface. The research results indicate that ion beam sputtering (IBS) can directly smooth some amorphous or amorphizable material surfaces, such as fused silica, Si, and ULE® under appropriate processing conditions. However, for IBS of a Zerodur® surface, preferential sputtering together with curvature-dependent sputtering overcome ion-induced smoothing mechanisms, leading to the granular nanopatterns’ formation and the coarsening of the surface. Furthermore, the material property difference at microscopic scales and the continuous impurity incorporation would affect the ion beam smoothing of optical surfaces. Overall, IBS can be used as a promising technique for ultrasmooth surface fabrication, which strongly depends on processing conditions and material characters.
Simulation and analysis of gain-transparent SOA used as optical phase-modulator in DPSK applications

Gain-transparent semiconductor optical amplifier (GT-SOA) can be used as optical phase-modulators in Mach-zehnder interferometer configuration for 2R or 3R regeneration, wavelength conversion of differential phase modulated signals and all-optical format conversion from on-off keying (OOK) to binary phase shift keying (BPSK). Numerical simulation of the phase modulation effect of GT-SOA is performed using a wideband dynamic model and the performance is evaluated using the differential-phase-Q factor. Performance improvement by holding light injection is analyzed and non-return-to-zero (NRZ) and return-to-zero (RZ) modulation formats of the OOK signal are considered.
Analysis of interval‐censored data from clustered multistate processes: application to joint damage in psoriatic arthritis

Summary. A conditionally Markov multiplicative intensity model is described for the analysis of clustered progressive multistate processes under intermittent observation. The model is motivated by a long‐term prospective study of patients with psoriatic arthritis with the aim of characterizing progression of joint damage via an irreversible four‐state model. The model accommodates heterogeneity in transition rates between different individuals and correlation in transition rates within patients. To do this we introduce subject‐specific multivariate random effects in which each component acts multiplicatively on a specific transition intensity. Through the association between the components of the random effect, correlations in transition intensities are accommodated. A Monte Carlo EM algorithm is developed for estimation, which features closed form expressions for estimators at each M‐step.
Superionicity Study from Electronic State Calculation of Metal Halide Cluster

The electronic states of silver halides and sodium halides are calculated by the DV-Xα cluster method to get more microscopic evidence for the p – d hybridization in noble metal halides. The calculations are carried out for the (A 13 B 14 ) - (A=Ag + and Na + , B = halogen ion) clusters. It is found that both components of anti-bonding and bonding exist in the diagram of overlap population (DOP) for AgX (X=halogen) and these two components are made up of the 4 d band of Ag + and the p band of halogen ion, which form the p – d hybridization. On the other hand, the DOP of alkali halides is occupied by almost only bonding component. It is inferred that the origin of AgI type superionic conductor is in the weakness of p – d hybridization. The hypothetical rock-salt AgI is also discussed to investigate the unstableness of rock-salt AgI.