Miracle-dz/UniFAR-FTUs huggingface dataset:
Adventures in stochastic processes

Stochastic processes are necessary ingredients for building models of a wide variety of phenomena exhibiting time varying randomness. This text offers easy access to this fundamental topic for many students of applied sciences at many levels. It includes examples, exercises, applications, and computational procedures. It is uniquely useful for beginners and non-beginners in the field. No knowledge of measure theory is presumed.
Time-dependent, non-monotonic mixing in stratified turbulent shear flows: implications for oceanographic estimates of buoyancy flux

Abstract We employ direct numerical simulation to investigate the efficiency of diapycnal mixing by shear-induced turbulence in stably stratified free shear layers for flows with bulk Richardson numbers in the range $0. 12\leq R{i}_{0} \leq 0. 2$ and Reynolds number $Re= 6000$ . We show that mixing efficiency depends non-monotonically upon $R{i}_{0} $ , peaking in the range 0.14–0.16, which coincides closely with the range in which both the buoyancy flux and the dissipation rate are maximum. By detailed analyses of the energetics of flow evolution and the underlying dynamics, we show that the existence of high mixing efficiency in the range $0. 14\lt R{i}_{0} \lt 0. 16$ is due to the emergence of a large number of small-scale instabilities which do not exist at lower Richardson numbers and are stabilized at high Richardson numbers. As discussed in Mashayek & Peltier (J. Fluid Mech., vol. 725, 2013, pp. 216–261), the existence of such a well-populated ‘zoo’ of secondary instabilities at intermediate Richardson numbers and the subsequent high mixing efficiency is realized only if the Reynolds number is higher than a critical value which is generally higher than that achievable in laboratory settings, as well as that which was achieved in the majority of previous numerical studies of shear-induced stratified turbulence. We furthermore show that the primary assumptions upon which the widely employed Osborn (J. Phys. Oceanogr. vol. 10, 1980, pp. 83–89) formula is based, as well as its counterparts and derivatives, which relate buoyancy flux to dissipation rate through a (constant) flux coefficient ( $\Gamma $ ), fail at higher Richardson numbers provided that the Reynolds number is sufficiently high. Specifically, we show that the assumptions of fully developed, stationary, and isotropic turbulence all break down at high Richardson numbers. We show that the breakdown of these assumptions occurs most prominently at Richardson numbers above that corresponding to the maximum mixing efficiency, a fact that highlights the importance of the non-monotonicity of the dependence of mixing efficiency upon Richardson number, which we establish to be characteristic of stratified shear-induced turbulence. At high $R{i}_{0} $ , the lifecycle of the turbulence is composed of a rapidly growing phase followed by a phase of rapid decay. Throughout the lifecycle, there is considerable exchange of energy between the small-scale turbulence and larger coherent structures which survive the various stages of flow evolution. Since shear instability is one of the most prominent mechanisms for turbulent dissipation of energy at scales below hundreds of metres and at various depths of the ocean, our results have important implications for the inference of turbulent diffusivities on the basis of microstructure measurements in the oceanic environment.
A weighted distance measure based on the fine structure of feature space: application to speaker recognition

A weighted cepstral distance measure is proposed and tested in a speaker recognition system using a speaker-based vector quantization (VQ) approach. Based on the fine structure of the feature vector space, a statistically optimized distance measure is defined with weights equal to the partition-normalized inverse variance of cepstral coefficients. The weights can be adjusted individually for each partition and each component of the feature vector across all codebooks (speakers). Experiments on a 50-speaker database show that the suggested weighted cepstral distance measure works substantially better than the Euclidean cepstral distance or the inverse variance weighted cepstral distance. An accuracy of about 90% is achieved using a 16-level codebook in speaker verification. <<ETX>>
Estimates of AGN black hole mass and minimum variability timescale

Black hole mass is one of the fundamental physical parameters of active galactic nuclei (AGNs), for which many methods of estimation have been proposed. One set of methods assumes that the broad-line region (BLR) is gravitationally bound by the central black hole potential, so the black hole mass can be estimated from the orbital radius and the Doppler velocity. Another set of methods assumes the observed variability timescale is determined by the orbital timescale near the innermost stable orbit around the Schwarzschild black hole or the Kerr black hole, or by the characteristic timescale of the accretion disk. We collect a sample of 21 AGNs, for which the minimum variability timescales have been obtained and their black hole masses (M,) have been well estimated from the stellar velocity dispersion or the BLR size-luminosity relation. Using the minimum variability timescales we estimated the black hole masses for 21 objects by the three different methods, the results are denoted by M-s, M-k and M-d, respectively. We compared each of them with M-sigma individually and found that: (1) using the minimum variability timescale with the Kerr black hole theory leads to small differences between M-sigma and M-k, none exceeding one order of magnitude, and the mean difference between them is about 0.53 dex; (2) using the minimum variability timescale with the Schwarzschild black hole theory leads to somewhat larger difference between M-sigma and M-s, larger than one order of magnitude for 6 of the 21 sources, and the mean difference is 0.74 dex; (3) using the minimum variability timescale with the accretion disk theory leads to much larger differences between M-sigma and M-d, for 13 of the 21 sources the differences are larger than two orders of magnitude; and the mean difference is as high as about 2.01 dex.
An automated approach for clinical intravascular ultrasonic palpation

Describes a clinical prototype elasticity imaging system, which we have developed for measuring the elastic properties of vascular tissues. The system was based on a commercially available ultrasound scanner, which was equipped with a 20 MHz array catheter. Sequences of radio frequency (RF) echo frames were captured from the scanner at full frame rate, and transferred directly to PC memory using a fast data acquisition system. Palpograms were created by applying a one-dimensional tracking method in combination with global motion compensation, and multi-frame averaging to several pairs of RF echo frames that were obtained near end-diastole. The results of experiments conducted on patients demonstrate that this system is capable of producing robust palpograms under physiological conditions. Additionally, good correlation was observed between low strain values and regions of calcification as identified from the intravascular ultrasound images.
Dispersion and stability analyses of the linearized two‐dimensional shallow water equations in boundary‐fitted co‐ordinates

In the present investigation, a Fourier analysis is used to study the phase and group speeds of a linearized, two‐dimensional shallow water equations, in a non‐orthogonal boundary‐fitted co‐ordinate system. The phase and group speeds for the spatially discretized equations, using the second‐order scheme in an Arakawa C grid, are calculated for grids with varying degrees of non‐orthogonality and compared with those obtained from the continuous case. The spatially discrete system is seen to be slightly dispersive, with the degree of dispersivity increasing with an decrease in the grid non‐orthogonality angle or decrease in grid resolution and this is in agreement with the conclusions reached by Sankaranarayanan and Spaulding (J. Comput. Phys., 2003; 184: 299–320). The stability condition for the non‐orthogonal case is satisfied even when the grid non‐orthogonality angle, is as low as 30° for the Crank Nicolson and three‐time level schemes. A two‐dimensional wave deformation analysis, based on complex propagation factor developed by Leendertse (Report RM‐5294‐PR, The Rand Corp., Santa Monica, CA, 1967), is used to estimate the amplitude and phase errors of the two‐time level Crank–Nicolson scheme. There is no dissipation in the amplitude of the solution. However, the phase error is found to increase, as the grid angle decreases for a constant Courant number, and increases as Courant number increases. Copyright © 2003 John Wiley & Sons, Ltd.
Systems with Small Dissipation

Electromagnetic and mechanical oscillators are crucial in such diverse fields as electrical engineering, microwave technology, optical technology, and experimental physics. For example, such oscillators are the key elements in instruments for detecting extremely weak mechanical forces and electromagnetic signals are essential to highly stable standards of time and frequency. The central problem in developing such instruments is to construct oscillators that are as perfectly simple harmonic as possible; the largest obstacle is the oscillator's dissipation and the fluctuating forces associated with it. This book, first published in Russian in 1981 and updated with new data for this English edition, is a treatise on the sources of dissipation and other defects in mechanical and electromagnetic oscillators and on practical techniques for minimizing such defects. Written by a team of researchers from Moscow State University who are leading experts in the field, the book is a virtual encyclopedia of theoretical formulas, experimental techniques, and practical lore derived from twenty-five years of experience. Intended for the experimenter who wishes to construct near-perfect instrumentation, the book provides information on everything from the role of phonon-phonon scattering as a fundamental source of dissipation to the effectiveness of a thin film of pork fat in reducing the friction between a support wire and a mechanically oscillating sapphire crystal. The researchers that V. B. Braginsky has led since the mid-1960s are best known in the West for their contributions to the technology of gravitational-wave detection, their experimental search for quarks, their test of the equivalency principle, and their invention of new experimental techniques for high-precision measurement, including "quantum nondemolition movements. " Here, for the first time, they provide a thorough overview of the practical knowledge and experimental methods that have earned them a worldwide reputation for ingenuity, talent, and successful technique.
Lamb's problem at its simplest

This article revisits the classical problem of horizontal and vertical point loads suddenly applied onto the surface of a homogeneous, elastic half-space, and provides a complete set of exact, explicit formulae which are cast in the most compact format and with the simplest possible structure. The formulae given are valid for the full range of Poisson's ratios from 0 to 0.5, and they treat real and complex poles alike, as a result of which a single set of formulae suffices and also exact formulae for dipoles can be given.
Exploiting Sequent Structure in Membership Algorithms for the Lambek Calculus

This paper will examine the open problem of whether or not a se- quent is derivable in the Lambek Calculus (L) in polynomial-time. This will be done through an investigation of Lambek Calculus Graphs (LC-Graphs), which were introduced by Penn(7) to represent the well-formedness constraints of a se- quent's derivation in L. Presented here is a simplified version of LC-Graphs and their integrity criteria. We also show that storing a small amount of structural information about a sequent during parsing can reduce the number of integrity criteria for LC-Graphs from four to two. To this e! ect, a polynomial-time mem- bership algorithm is presented that recognizes all derivable sequents and falsely recognizes an identifiable class of underivable sequents.
A hybrid Pareto-based local search algorithm for multi-objective flexible job shop scheduling problems

This paper presents a hybrid Pareto-based local search (PLS) algorithm for solving the multi-objective flexible job shop scheduling problem. Three minimisation objectives are considered simultaneously, i.e. the maximum completion time (makespan), the total workload of all machines, and the workload of the critical machine. In this study, several well-designed neighbouring approaches are proposed, which consider the problem characteristics and thus can hold fast convergence ability while keep the population with a certain level of quality and diversity. Moreover, a variable neighbourhood search (VNS) based self-adaptive strategy is embedded in the hybrid algorithm to utilise the neighbouring approaches efficiently. Then, an external Pareto archive is developed to record the non-dominated solutions found so far. In addition, a speed-up method is devised to update the Pareto archive set. Experimental results on several well-known benchmarks show the efficiency of the proposed hybrid algorithm. It is concluded that the PLS algorithm is superior to the very recent algorithms, in term of both search quality and computational efficiency.
Super-resolution frequency estimation of the sinusoidal signals with unknown lowpass envelopes

The problem of estimating the frequency of the sinusoidal signals with low pass envelopes in the presence additive white Gaussian noise is addressed. A super-resolution frequency estimator based on the eigenanalysis and quadratic programming is proposed. The frequency estimation is achieved from the single experiment data without a priori knowledge of the lowpass envelop, which is omnipresent in many applications. The performance studies, which include the theory analysis, the numerical simulations of the mean square errors (MSEs) of the frequency estimates compared with the Cramer-Rao bound (CRB), the comparisons between the proposed method and the other representative methods, are presented.
Intermingled basins for the triangle map

Abstract A family of quadratic maps of the plane has been found numerically for certain parameter values to have three attractors, in a triangular pattern, with ‘intermingled’ basins. This means that for every open set S, if the basin of attraction of one of the attractors intersects S in a set of positive Lebesgue measure, then so do the other two basins. In this paper we mathematically verify this observation for a particular parameter, and prove that our results hold for a set of parameters with positive Lebesgue measure.
Sensitivity of resolved mountain drag to model resolution for MAP case‐studies

Seven mountain wave case‐studies from the Mesoscale Alpine Programme (MAP) have been used to investigate the behaviour of the resolved Alpine pressure drag with model horizontal resolution. Three independent modelling systems show that the magnitude of the resolved surface pressure drag increases monotonically as the horizontal model resolution is increased from 125 km down to a few kilometres. A substantial proportion of the drag will still need to be parametrized in the next generation of mesoscale models, with horizontal resolutions of 3 or 4 km. This is particularly true for the most important drag cases, when the jet stream directly above the mountains produces larger wind speeds near mountain crest level, resulting in much larger total Alpine drags. Copyright © 2006 Royal Meteorological Society
Solving Higher Dimensional Initial Boundary Value Problems by Variational Iteration Decomposition Method

In this paper, we apply a relatively new technique which is called the variational iteration decomposition method (VIDM) by combining the traditional variational iteration and the decomposition methods for solving higher dimensional initial boundary value problems. The proposed method is an elegant combination of variational iteration and the decomposition methods. The analytical results of the problems have been obtained in terms of convergent series with easily computable components. The method is quite efficient and is practically well suited for use in these problems. Several examples are given to verify the accuracy and efficiency of the proposed technique.
PROVISOS FOR CLASSIC LINEAR OSCILLATOR DESIGN METHODS. NEW LINEAR OSCILLATOR DESIGN BASED ON THE NDF/RRT

In this paper, the classic oscillator design methods are reviewed, and their strengths and weaknesses are shown. Provisos for avoiding the misuse of classic methods are also proposed. If the required provisos are satisfled, the solutions provided by the classic methods (oscillator start-up linear approximation) will be correct. The provisos veriflcation needs to use the NDF (Network Determinant Function). The use of the NDF or the most suitable RRT (Return Relation Transponse), which is directly related to the NDF, as a tool to analyze oscillators leads to a new oscillator design method. The RRT is the \true" loop-gain of oscillators. The use of the new method is demonstrated with examples. Finally, a comparison of NDF/RRT results with the HB (Harmonic Balance) simulation and practical implementation measurements prove the universal use of the new methods.
SENSOR VALIDATION IN DAMAGE LOCATING VECTOR METHOD FOR STRUCTURAL HEALTH MONITORING

The reliability of a structural health-monitoring system is very dependent on the quality of signals that are acquired and fed into the damage detection algorithm. Developed herein is an algorithm for sensor validation in the context of the damage locating vector (DLV) method for detecting damage in structures. Given the signals from ns sensors, ns combinatorial sets of signals from (ns - 1) sensors are formed. For each set, the change in the flexibility matrix relative to that of the reference or undamaged structure is computed and singular value decomposition is performed to estimate the number of nonzero singular values (NZV). The set that produces the smallest NZV is associated with healthy sensors whereas sensors that do not belong to that combination are suspected to be faulty. The performance of the proposed algorithm is illustrated using both simulated and experimental data obtained from a 3D modular truss structure monitored by sensors, some of which are faulty.
Ising models and multiresolution quad-trees

We study percolation and Ising models defined on generalizations of quad-trees used in multiresolution image analysis. These can be viewed as trees for which each mother vertex has 2 d daughter vertices, and for which daughter vertices are linked together in d-dimensional Euclidean configurations. Retention probabilities and interaction strengths differ according to whether the relevant bond is between mother and daughter or between neighbours. Bounds are established which locate phase transitions and show the existence of a coexistence phase for the percolation model. Results are extended to the corresponding Ising model using the Fortuin-Kasteleyn random-cluster representation.
Observations of Wall Cloud Formation in Supercell Thunderstorms during VORTEX2

AbstractThis study presents an integrated analysis of dual-Doppler, cloud photogrammetry, surface mobile mesonet, and sounding data to examine wall cloud formation in two supercells observed during the Verification of the Origins of Rotation in Tornadoes Experiment II (VORTEX2). One of the wall clouds contained significant rotation and spawned an (enhanced Fujita) EF2 tornado, while the other was clearly displaced horizontally from the mesocyclone and exhibited little rotation at the time of data collection. Backward parcel trajectories show that the majority of the air entering the wall cloud base originates in the forward-flank region. A small fraction of the parcels enter the wall cloud base from the inflow. Some rear-flank downdraft parcels descend into the strongly rotating wall cloud. For both wall clouds, much of the observed wall cloud lowering is attributed to evaporatively cooled parcels in the forward-flank region being ingested into the low-level updraft. Additional wall cloud-base lowering is.
Integral methods for analysis and design of low-frequency conductive shields

This paper presents and compares two different approaches to the analysis and design of nonferrous shields for extremely low-frequency magnetic fields. The first method is based on a circuital approach where the shield is modeled by a set of conductors coupled with each other by a matrix of self and mutual inductances. The second technique is based on an algebraic formulation of electromagnetic fields and adapted by means of integral equations to the analysis of thin conductive sheets. The paper shows the accuracy of the two methods for calculating induced current density inside the shield and for evaluating magnetic flux density in the shielded region.
Differential atomic magnetometry based on a diverging laser beam

The authors demonstrate a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over single-channel operation. They also suggest ways in which the current sensitivity of 28pT∕√Hz may be improved further without sacrificing size or simplicity.
Single-differential and integral cross sections for electron-impact ionization for the damage of carbon clusters irradiated with x-ray free-electron lasers

Single-differential and integral cross sections for electron-impact ionization of the C atom and its ions were calculated with the binary-encounter-dipole model [Y. -K. Kim and M. E. Rudd, Phys. Rev. A 50, 3954 (1994)] to study the distribution of free-electron energies in carbon clusters after being irradiated with an x-ray free-electron laser (XFEL). The averaged energies of the secondary electrons for the C atom, and ${\mathrm{C}}^{1+}$, ${\mathrm{C}}^{2+}$, and ${\mathrm{C}}^{3+}$ ions were about $20$, $70$, $160$, and $200$ eV, respectively, when incident electron energy was about $20$ keV, while those energies were in the order of tens of electronvolts when the incident electron energy was about $250$ eV. The damage to carbon clusters irradiated with the XFEL was also investigated with time-dependent rate equations, considering photoionization, Compton scattering, Auger decay, and electron-impact ionization of the C atom and its ions. The results show that the electron-impact ionization becomes a more important process as the x-ray flux decreases, while the effect of Auger decay gradually appears as the x-ray flux increases. The energy dependence of the incident x ray was also investigated to evaluate the resolution of the diffraction pattern. These results indicate that we should make the XFEL pulse a few fs and about $16$ keV to suppress damage and obtain desired resolution of the diffraction pattern.