Correlation Radius Research Articles

Dentex maroccanus Valenciennes, 1830 Otolith Morphology, Age, and Growth in the Aegean Sea (E. Mediterranean).

Otoliths are important structures for balance and hearing of fish and constitute a useful tool in fisheries science. This study provides, for the first time in the Mediterranean, information on the otolith morphometrics of Dentex maroccanus, collected from the South Aegean Sea, and enriches the existing information on its age and growth by sex. The otolith shape variables examined showed a more circular to square otolith shape, related to the body size. Significant differences between sexes were detected for the otolith Area, Diameter, Perimeter, and Radius. Exponential regressions were used to examine the relationship of the otolith variables with total body length, from which five showed a strong correlation (Diameter, Width, Radius, Area, and Perimeter). The eviscerated weight-length relationship exhibited an isometric growth for both sexes, whereas when total weight was applied, a positive allometric growth was found for females. Sagittal otolith readings revealed four age groups for females and five for males. A Bhattacharya method was used for age validation. Von Bertalanffy growth parameters were as follows: L∞ = 23.08, k = 0.27, t0 = -1.93 for females and L∞ = 24.07, k = 0.24, t0 = -2.26 for males. This research offers valuable biological information for Dentex maroccanus useful in fisheries science.

Paramagnetic susceptibility and spin correlation function of ferromagnetic metals in the critical region

We study paramagnetic characteristics of ferromagnetic metals near the Curie temperature TC using the dynamic spin fluctuation theory. In contrast with most first-principles calculations, our results for the uniform paramagnetic susceptibility show a clear deviation from the Curie–Weiss law. We demonstrate that the susceptibility and correlation radius have the power-law behavior at temperatures up to 1.1–1.15TC, which gives an estimate for the region of critical temperatures in metals. Our theoretical critical exponents for Fe, Co, and Ni are in reasonable agreement with the low-field susceptibility measurements and neutron scattering experiments.

Controlling sodium chloride concentration modulates the supramolecular structure and sol features of wheat starch-acetylated starch binary matrix

The sol performance of wheat starch (WS) matrix incorporating acetylated starch (AS) is crucial for the processing and quality features of wheat products. From a supramolecular structure view, how regulating salt (sodium chloride) concentration modulates the sol features, e.g., pasting, zero-shear viscosity (ZSV) and thixotropy of WS-AS binary matrix was explored. Compared to the salt-free counterpart, the saline matrices exhibited a delayed pasting profile and a decreased viscoelasticity. Thereinto, the sol at 0.02 M NaCl exhibited the smallest ZSV (23,710 Pa·s) and the greatest in-shear recovery ratio (33.7 %). Such variations could be attributed to the weakened coil-helix, nematic-smectic and isotropy-anisotropy transitions from a side-chain liquid-crystalline perspective. Meanwhile, the correlation length (ξ) and radius of gyration (Rg) obtained from small angle X-ray scattering analysis were increased by 5.2 and 9.6 Å respectively, which disclosed a restrained entanglement and an enhanced chain mobility. These results would provide a reference for the design of fluid/semisolid products with optimized qualities.

Study on the magnetic shielding properties of nanocrystalline strips under bending stress

The study of the magnetic properties of nanocrystalline materials under stress is of great significance for the construction of small and lightweight magnetic shielding rooms. Therefore, this paper investigates the effect of stress on the magnetic properties of nanocrystalline materials under the action of external bending stress. By comparing the test results of the soft magnetic measuring device with and without bending stress, it is found that the magnetic permeability (μ i) decreases by about 51.41% when the introduced bending stress σ is increased by about 5.96 × 107 pa, whereas the KuFe−Si (induced magnetic anisotropy constant) and Hk (field of magnetic anisotropy) increase by 5.30 × 102 J m–3 and 1.08 × 102 A m−1, respectively. The Jiles-Atherton (J-A) model considering the bending stress and radius of change correlation is established, and the typical parameters of the J-A model are fitted using the Gazelle Optimization Algorithm (GOA), and the RMSE (root mean square error) of all of them are less than 0.056 T. The magnetic domain density increased with the increase of bending stress, which verified the correlation between the J-A model parameters and the bending stress. Our results reveal that the nanocrystalline macroscopic and micromechanical magnetic properties can be effectively combined with the J-A model, which will provide a theoretical basis for the simulation study of the nanocrystalline magnetic shielding device in the actual stress situation.

Evaluation of cortical bone strength using a quantitative ultrasound measurement device in dogs.

This study was performed to evaluate cortical bone strength in dogs using a quantitative ultrasound measurement device. In this study, 16 clinically healthy dogs with no lameness underwent measurement of the ultrasound propagation velocity of cortical bone (namely, speed of sound [SOS]) at the radius and tibia. Additionally, computed tomography examination with a calibration phantom was performed in 10 dogs. We calculated the bone mineral density (BMD) and Young's modulus from the computed tomography data using bone strength evaluation software. SOS, BMD, and Young's modulus were statistically compared between the radius and tibia. In addition, we examined the correlation between SOS and BMD and between SOS and Young's modulus. We also examined the correlation between SOS and age in the 13 dogs whose age was known. BMD and Young's modulus were not significantly different between the radius and tibia, but SOS was significantly different (P<0.05). Moreover, SOS and BMD showed a positive correlation in both radius and tibia. Similarly, SOS and Young's modulus showed a positive correlation. In addition, SOS and age showed a strong positive correlation (radius: r=0.77, P<0.05, tibia: r=0.83, P<0.05). Our finding that SOS of the radius and tibia cortical bone was correlated with BMD and Young's modulus indicates that quantitative ultrasound can be useful for evaluating cortical bone strength in dogs.

Kriticheskie yavleniya v dinamicheskoy teorii spinovykh fluktuatsiy

Paramagnetic susceptibility and spin-density correlation function near the Curie temperature TC are studied using the dynamic spin fluctuation theory. The calculated critical indices of the susceptibility and correlation radius for Fe, Co, and Ni are found in reasonable agreement with bulk susceptibility measurements and neutron scattering experiments. It is shown that the critical power-law behavior holds at temperatures up to 1.10–1.15TC, which gives an estimate of the critical temperature region in ferromagnetic metals.

Fourth-order moments analysis for partially coherent electromagnetic beams in random media

A theory for the characterization of the fourth-order moment of electromagnetic wave beams is presented in the case when the source is partially coherent. A Gaussian–Schell model is used for the partially coherent random source. The white-noise paraxial regime is considered, which holds when the wavelength is much smaller than the correlation radius of the source, the beam radius of the source, and the correlation length of the medium, which are themselves much smaller than the propagation distance. The complex wave amplitude field can then be described by the Itô-Schrödinger equation. This equation gives closed evolution equations for the wave field moments at all orders and here the fourth-order moment equations are considered. The general fourth-order moment equations are solved explicitly in the scintillation regime (when the correlation radius of the source is of the same order as the correlation radius of the medium, but the beam radius is much larger) and the result gives a characterization of the intensity covariance function. The form of the intensity covariance function derives from the solution of the transport equation for the Wigner distribution associated with the second-order wave moment. The fourth-order moment results for polarized waves are used in an application for imaging of partially coherent sources.

Modulation instability of incoherent beams revisited.

We examine the spatial modulation instability (MI) of a partially incoherent laser beam. We show that the P < (a/rc)2P0 criterion of beam stability, with a laser peak power P, beam radius a, correlation radius rc, and critical power of self-focusing P0, is applicable only to a limited class of MIs, viz., MIs that can be described as instabilities of a pertinent transverse correlation function found as a solution to the evolution equation, where the expectation of the four-field-product nonlinear source term is factorized as a product of the field intensity and a two-point transverse correlation function. When extended to a more general class of MIs, field evolution analysis of partially coherent beams suggests that MIs can be attenuated, but never completely suppressed. We show that spatial incoherence can lower the MI-buildup rate, thus helping avoid MI-induced beam breakup in physical settings where the MI-buildup length lMI can be kept longer than the length of the nonlinear medium L. Because the lMI > L condition sets a limitation on the field intensity rather than the laser peak power, MI-induced beam breakup can be avoided, even at laser peak powers well above the critical power of self-focusing P0.

Analysis and application of spatio-temporal correlation characteristics of measured ocean ambient noise

Gain in sonar signal processing is closely linked to the spatio-temporal coherence characteristics of the ocean ambient noise field. The gain relies on the spatio-temporal coherence coefficient of the signal and noise, with the aim of maximizing the former and minimizing the latter. Currently, there has been ample research on the spatial characteristics of the noise field, while studies on the temporal coherence characteristics of single-point noise fields are limited. In this paper, a temporal and spatial coherence model of wind-induced noise is established based on the normal mode theory, and the impact of bandwidth and spectral structure on the time coherence coefficient of wind-induced noise is analyzed.To measure the environmental noise in 103 m of shallow water in the South China Sea, a 64-element vertical array was utilized. The results demonstrate that the measured vertical spatial correlation coefficient aligns closely with the theoretical findings when wind-induced noise is predominant. The measured temporal correlation coefficient of narrowband noise exhibits a cosine function with gradual attenuation of the envelope, and the correlation radius remains independent of frequency. As the bandwidth increases, the measured broadband noise temporal correlation radius gradually decreases. Wind speed has minimal influence on the temporal and spatial correlation coefficients of wind-induced noise. In the presence of interferences such as ships and pulses, the measured temporal and spatial correlation coefficients of wind-induced noise exhibit larger values in certain intervals.Lastly, leveraging the characteristic that the temporal coherence radius of noise is significantly smaller than that of the line spectrum signal, a single-hydrophone cross-spectrum method is proposed to process the line spectrum signal. This approach effectively enhances the signal-to-noise ratio of the line spectrum.

Study of the Bose-Einstein correlations of same-sign pions in proton-lead collisions

Correlations of same-sign charged pions are analysed using proton-lead collision data collected by the LHCb experiment at a nucleon-nucleon centre-of-mass energy of 5.02 TeV, corresponding to an integrated luminosity of 1.06 nb−1. Bose-Einstein correlations are observed in the form of an enhancement of pair production for same-sign charged pions with a small four-momentum difference. The dependence of the correlation radius and the intercept parameter on the reconstructed charged-particle multiplicity is investigated. The measured correlation radii scale linearly with the cube root of the reconstructed charged-particle multiplicity, being compatible with predictions of hydrodynamic models on the collision system evolution.

Simulation of the Three-Component Potts Model on a Hexagonal Lattice by the Monte Carlo Method

Computer simulation of the three-component Potts model on a hexagonal lattice was carried out using the Monte Carlo method. Systems with linear dimensions L × L = N, L = 10–320 in units of interatomic distances are considered. Based on the theory of finite-size scaling, the static critical exponents of heat capacity α, susceptibility γ, magnetization β, and correlation radius ν are calculated. The data we obtained confirm that in the considered Potts model on a hexagonal lattice, a second-order phase transition is observed with critical exponents corresponding to the universality class of the three-component Potts model.

The plasmon–polariton scattering by random-impedance surface defects: The interplay between localization and outflow

We study the scattering of TM-polarized surface plasmon-polariton (SPP) by the finite section of flat metal–vacuum interface with a random impedance. We analyze the solution to the integral equation that connect the scattered field and the incident plasmon–polariton, and is valid for any strength of the scattering and dissipative characteristics of the conducting half-space. We show that the norm of the intermode scattering operator as a measure of scattering strength is not only determined by the parameters of the random impedance (the variance, correlation radius, the length of the heterogeneous section of the interface), but also crucially depends on the metal conductivity. For a small norm of the integral operator, the incident surface plasmon polariton radiates effectively into vacuum, resulting in excitation of quasi-isotropic Norton-type waves above the conducting surface. The intensity of the leaking field is expressed in terms of the pair correlation function of the impedance, whose dependence on wave numbers of incident and scattered waves demonstrates the possibility to observe a phenomenon similar to Wood’s anomalies of wave scattering by periodic gratings. Under strong scattering regime, the radiation into the upper half-space is highly suppressed and the SPP wave is mainly backscattered from the heterogeneous surface segment. For the lossless conducting half-space, the surface plasmon–polariton becomes unstable for arbitrarily small fluctuations of the conductor polarizability. The mirroring should also take place at small norm of the scattering operator, yet in this case it is related to Anderson’s localization of the SPP within the disordered section.

The liquid-liquid structure change in eutectic Ga-Sn alloy

• The liquid-liquid structure transition did occur around the liquidus temperature. • Another liquid-liquid structure transition did occur in the range from 1073-1273 K. • Below and above the liquidus temperature, the liquid exhibits differences in viscosity, coordination numbers, correlation radius of cluster. The effect of temperature on dynamic viscosity and atomistic structure in liquid eutectic Ga-Sn alloy have been investigated by using a torsional oscillating viscometer, an X-ray diffractometer and the ab initio molecular dynamics simulation. The results indicated that the liquid-liquid structure transitions did occur around the liquidus temperature and in the range from 1073-1273 K. Below and above these temperatures the liquid exhibits differences in viscosity, coordination numbers, correlation radius of cluster, which are reflected from structural changes of structural disorder and local atomic packing. This work will trigger a further study on the liquid-to-liquid crossover in the liquid-solid transition.

Structural characteristics of radiation‐amorphized ZrSiO4:U,Th according to Raman spectroscopy of Boson peak

AbstractThe structure of the amorphous fraction and the tensile‐compressive stresses in amorphous‐crystalline radiation‐damaged zircon ZrSiO:U,Th depending on radiation dose and temperature (8–350 K) are investigated according to Raman spectroscopy of Boson peak for the first time. The Boson peak at 60–70 cm−1 associated with localized phonon states in the amorphous fraction ( ) is recorded at low temperatures ( K) for samples with and over the entire temperature range 8–350 K for . The wider localized states distribution in the latter case is considered as a sign of the amorphous phase structure evolution with an increase in radiation dose. The estimates of an atomic correlation radius based on the Ioffe–Regel criterion are similar to those in glasses, nm. The monotonic increase in value during heating of zircon with is governed by thermal expansion of the percolating amorphous fraction. The nonmonotonic variations of the value in zircon with is determined by the stresses in the amorphous fraction due to the mismatch in thermal expansion coefficient (CTE) and elastic moduli of the amorphous and crystalline phases depending on temperature; a change in the sign of the crystalline fraction CTE at 30 K is assumed. The Boson peak disappearance at 100 K in zircon with during heating conforms to with the violation of the phonon localization as a consequence of amorphous fraction contraction and partial ordering. The data obtained are important for predicting the thermal and mechanical properties of heterogeneous radiation‐damaged materials and nanocomposites.

Spheroidal expansion and freeze-out geometry of heavy-ion collisions in the few-GeV energy regime

A spheroidal model of the expansion of hadronic matter produced in heavy-ion collisions in the few-GeV energy regime is proposed. It constitutes an extension of the spherically symmetric Siemens-Rasmussen blast-wave model used in our previous works. The spheroidal form of the expansion, combined with a single-freeze-out scenario, allows for a significantly improved description of both the transverse-mass and the rapidity distributions of the produced particles. With the model parameters determined by the hadronic abundances and spectra, we make further predictions of the pion Hanbury-Brown--Twiss correlation radii that turn out to be in a qualitative agreement with the measured ones. The overall successful description of the data supports the concept of spheroidal symmetry of the produced hadronic systems in this energy range.

Estimation of the average particle flux in a stochastically homogeneous medium by Monte Carlo method

Abstract The paper is focused on the study of the superexponential growth of the average number of particles in a stochastically homogeneous propagating medium. A mosaic Voronoi field (‘mosaic’) is considered as a random density model. The notion of ‘effective’ correlation radius is introduced to compare the results with previously obtained estimates of superexponential parameters for a spherically symmetric layered mosaic. It is shown that transition from the layered random density model to a chaotic one preserving the correlation scale and one-dimensional distribution weakens the ‘superexponential’ property of the particle flux.

Images Segmentation Based on Cutting the Graph into Communities

This article considers the problem of image segmentation based on its representation as an undirected weighted graph. Image segmentation is equivalent to partitioning a graph into communities. The image segment corresponds to each community. The growing area algorithm search communities on the graph. The average edge weight in the community is a measure of the separation quality. The correlation radius determines the number of next nearest neighbors connected by edges. Edge weight is a function of the difference between color and geometric coordinates of pixels. The exponential law calculates the weights of an edge in a graph. The computer experiment determines the parameters of the algorithm.

On the efficiency of using correlative randomized algorithms for solving problems of gamma radiation transfer in stochastic medium

Abstract To solve problems of radiation balance, optical sounding, and tomography, it may be necessary to take into account multiple scattering of radiation in a stochastically inhomogeneous medium. In real radiation models, for this purpose, the numerical-statistical ‘majorant cross-section method’ (MCM, delta-Woodcock tracking) is used based on the alignment of the optical density field by adding an artificial ‘delta scattering’ event. However, the computation cost of the corresponding unbiased estimate of the averaged problem solution infinitely increases as the correlation scale (correlation radius L) of standard mosaic models for a random medium density decreases. Previously, we constructed the MCM randomization providing asymptotically (for L → 0) unbiased estimates of the required functionals, in which the value of the physical attenuation coefficient is randomly chosen at the end of the particle free path l under condition l &gt; L. Otherwise the value of the physical attenuation coefficient is the same as at the starting point of the particle (CR algorithm). In a more accurate functional correlative randomized algorithm (FCR algorithm), the coefficient remains the same with a probability determined by the correlation function. These correlative randomized algorithms were implemented for a mixture of homogeneous substance (water) and a Poisson ensemble of ‘empty’ balls. In the present paper, we construct correlative randomized algorithms for problems related to transfer through a ‘thick’ layer containing a water and a Poisson ensemble of ‘empty’ layers. A detailed comparative analysis of the results obtained by exact direct simulation (MCM) and approximate algorithms (CR, FCR) for the problems of gamma radiation transfer through a ‘thick’ water layer containing a Poisson ensemble of ‘empty’ layers or balls is presented.

Heralded single-photon source based on an ensemble of Raman-active molecules

Light with high mutual correlations at different frequencies can be used to create heralded single-photon sources, which may serve as the basic elements of existing quantum cryptography and quantum teleportation schemes. One of the important examples in natural systems of light with high mutual correlations is the light produced by spontaneous Raman scattering on an ensemble of molecules. In this paper, we investigate the possibility of using Raman light to create a heralded single-photon source. We show that when using Stokes scattered light for postselection of anti-Stokes scattered light, the latter may possess single-photon properties. We analyze the influence of various negative factors on the characteristics of such a heralded single-photon source, which include a time delay between Stokes and anti-Stokes photons, the finiteness of the correlation radius of an external source, and background radiation. We show that the low value of the second-order autocorrelation function of the single-photon source is preserved even when the flow of uncorrelated photons exceeds the flow of correlated photons in scattered Raman light by an order of magnitude.

Particle Multiplicity Fluctuations and Spatiotemporal Properties of Particle-Emitting Source of Strongly Interacting Matter for NICA and RHIC Energies

The results of the model analysis of hadron femtoscopic correlations and factorial moments of particle multiplicity in heavy ion collisions for the energy range of the Beam Energy Scan (BES) program at RHIC and future NICA collider are presented. For this purpose, the simulation of Au+Au collisions at center-of-mass energies 7.7 and 11.5 GeV per nucleon pair using the UrQMD, vHLLE+UrQMD (with the crossover and first-order equation of states), and HYDJET++ event generators was performed. The sensitivity of pion and kaon correlation radii and the dependence of the factorial moments on heavy ion beam energy to quark–hadron phase transition details was studied. In addition, the possible influence of some relevant detector effects on the corresponding experimental observables is discussed.