Description Of Field Research Articles

Bayesian inference of signatures of hyperons inside neutron stars

The possible signatures of the presence of hyperons inside neutron stars are discussed within a Bayesian inference framework applied to a set of models based on a density-dependent relativistic mean-field description of hadronic matter. Nuclear matter properties, hypernuclei properties, and observational information are used to constrain the models. General properties of neutron stars such as the maximum mass, radius, tidal deformability, proton fraction, hyperon fraction, and speed of sound are discussed. It is shown that the two solar mass constraint imposes that neutron stars described by equations of state that include hyperons have on average a larger radius, $\gtrsim 0.5$km, and a larger tidal deformability, $\gtrsim 150$, than the stars determined from a nucleonic equation of state, while the speed of sound at the center of the star is more than 25\% smaller. If a 1.4 M$_\odot$ star with a radius $\lesssim 12.5$ km is measured it is quite improbable that a massive star described by the same model contains hyperons. A similar conclusion is drawn if a two solar mass star with a radius $\lesssim 11.5$ km or a neutron star with a mass above 2.2 M$_\odot$ is observed: the possible hyperon content of these stars is ruled out or very reduced. The hyperon presence inside neutron stars is compatible with the present NICER mass-radius observations of the pulsars PSR J0030+0451 and PSR J0740+6620 and the gravitational wave detection GW170817. {It is shown that if the polytropic index $\gamma=\partial\ln p/\partial\ln\epsilon$ takes values of the order of 1.75 at not too large densities, it may indicate the onset of some kind of exotic matter, but not necessarily of deconfined quark matter.

Electrodynamics from the viewpoint of modern continuum theory—A review

AbstractThis paper wants to draw attention to several issues in electrodynamic field theory and to make way for a rational continuum approach to the subject. The starting point are the balances for magnetic flux and electric charge, both in a very general formulation for volumes and for open surfaces, all of which can deform and be immaterial or material. The spatial point‐of‐view for the description of fields is favored and its advantages in comparison to the concept of material particles is explained. A straightforward answer to the question of how to choose units for the electromagnetic fields most suitably is also presented. The transformation properties of the electromagnetic fields are addressed by rewriting the balances in space–time notation. Special attention is paid to the connection between the two sets of electromagnetic fields through the so‐called Maxwell–Lorentz–æther relations. The paper ends with an outlook into constitutive theory of matter under the influence of electromagnetic fields and a discussion on curious developments in context with Maxwell's equations.

Superstatistical Wind Fields from Pointwise Atmospheric Turbulence Measurements

Accurate models of turbulent wind fields have become increasingly important in the atmospheric sciences, e.g., for the determination of spatiotemporal correlations in wind parks, the estimation of individual loads on turbine rotor and blades, or the modeling of particle-turbulence interaction in atmospheric clouds or pollutant distributions in urban settings. Because of the difficult task of resolving the fields across a broad range of scales, one oftentimes has to invoke stochastic wind field models that fulfill specific, empirically observed, properties. Whereas commonly used Gaussian random field models solely control second-order statistics (i.e., velocity correlation tensors or kinetic energy spectra), we explicitly show that our extended model emulates the effects of higher-order statistics as well. Most importantly, the empirically observed phenomenon of small-scale intermittency, which can be regarded as one of the key features of atmospheric turbulent flows, is reproduced with a very high level of accuracy and at considerably low computational cost. Our method is based on a multipoint statistical description of turbulent velocity fields that consists of a superposition of multivariate Gaussian statistics with fluctuating covariances. We propose a new and efficient sampling algorithm for this Gaussian scale mixture and demonstrate how such “superstatistical” wind fields can be constrained on a certain number of real-world measurement data points from a meteorological mast array.Received 12 April 2022Revised 26 July 2022Accepted 22 August 2022DOI:https://doi.org/10.1103/PRXEnergy.1.023006Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAtmospheric scienceBoundary layersShear flowsStochastic processesStructure & turbulence of boundary layersSustainabilityTurbulenceWind energyEnergy Science & TechnologyNonlinear DynamicsFluid DynamicsStatistical Physics

Lamprophyre sites of Wajrakarur Kimberlite Field, Southern India: Potential candidates for developing as geoparks

This article presents field description of lamprophyres of the Wajrakarur Kimberlite Field (WKF) emphasising their geoscientific potential to develop and popularize them as geoparks. Also presented are other places of geological importance and heritage sites to visit, such as kimberlite pipe locations, syenite body at Danduvaripalli, ancient Hindu shrines and Batrepalli waterfall etc. to develop as a geotourism corridor. The WKF is largest of all kimberlite fields in the Indian shield and is bestowed with all types of rare mantle derived lamprophyre clan rocks (LCRs) such as lamprophyres, lamproites and kimberlites. The LCRs represent geological anomalies and act as the focal points of diamond exploration. They have been significant in mantle petrological research. The geopark evaluation reveals that the lamprophyre sites deserve to be considered for geopark development. A geotoruism strategy through SWOT evaluation of eligibility criteria of lamprophyres shows that they have geoscientific potential to be developed as geoparks in conjunction with other geological and cultural sites in the proximity. As the outcrops are small, developing them as geoparks and their maintenance is not tough, however, it requires investment, maintenance and wide publicity. If developed as geoparks, these will attract geology researchers and enthusiasts and stands as an example for other similar sites in the country to inculcate awareness of geotourism. Proactive and aggressive involvement of national geological organisations and institutes is inevitable to achieve the goal of unraveling new geoparks of this sort.

ASM and finite beam description of the excited leaky Lamb wave fields in a fluid-immersed plate

An angular spectrum method (ASM) full-wave description of stress and energy density in a fluid-immersed plate for the optimization of leaky Lamb wave applications is presented. It models the case when leaky Lamb waves are generated by an external finite transmitter in the immersion fluid, and can calculate the associated stress, energy density, and other field variables within the plate. The normal component of the stress tensor and the energy density are compared against calculations in COMSOL with good agreement, but with some differences due to the two methods. The spatial field of the stress is analyzed using the angular spectrum (plane wave) representation of the stress, which is also used as a reference to exemplify the discrepancies between a pure plane wave approach in leaky Lamb wave applications and the spatial fields that accounts for diffraction and dispersion effects. Comments on the insight that the spatial fields within the plate may provide towards NDT/SHM applications are also given, along with a discussion on why the derivation and implementation of the ASM model is valuable when compared against a benchmarked, ready-to-use software such as COMSOL.

Digital Leadership: A Bibliometric Analysis

Digital disruption has changed organizations in an unprecedented way. The thriving field of digital leadership is expanding fast and few retrospective studies on this evolution have been made so far. This study presents a bibliometric and network analysis combining both Scopus and Web of Science databases to provide fresh insights into the evolution of the digital leadership research field. This study is based on a review of 79 publications from 57 journals, published between 2000 and 2020. The newness of the topic and the range of journals in which it is published confirms that digital leadership has gained interest from several different areas. Bibliometric analysis provides a description of the research field identifying the leading publishing journals, affiliation statistics, and most influential authors and expressive publications in the research field. Network analyses identify keyword evolution over time, co-citation relationships, and research clusters. Content analysis is used to identify key topics in the field with attention paid to interrelations among them. A brief description of each paper in the dataset and its methodological approach is provided. The results suggest that the topic will continue to attract more research, as it has not yet entered its maturity stage. This paper contributes to the literature by analyzing the relationship between digital leadership and e-leadership. This study also identifies the most leading digital leadership capabilities for a fast-changing world. Limitations and future avenues are also discussed.

Experimental study of flow visualisation using fluorescent dye

Flow visualisation is an important and effective tool in the study of fluid dynamics as it is able to provide a quick visible presentation and qualitative and quantitative description of the entire real-time flow field of an unsteady flow. Some flow visualisation techniques have been used in a wide range of industries. Flow visualisation using a fluorescent dye is an effective technique to qualitatively investigate flow patterns for various configurations which usually involve low flow velocities and small lab scale geometries. In the present study, a Kármán vortex street flow at the Reynolds number of about 2520 was chosen to be visualised to investigate the performance of various dye types (fluorescein dye, rhodamine B dye, and blue food dye), dye tracer concentrations, and injection nozzle sizes, and post-processing techniques were used to extract quantitative pixel intensity data from the obtained flow pattern images. The analysis showed that the image intensity of the dye in the flow is dependent on the concentration and injection nozzle size. Visualisation results for 60 different arrangements were presented and analysed to ultimately conclude the superiority of fluorescein dye at a concentration of 1250 mg/L, for the flow visualisation considered. Additionally, it was found that the injection nozzles with the diameters of 0.51 mm and 0.9 mm allowed for a precise and natural release of dye into the inlet flow where the flow pattern was clearly presented downstream of the geometry. These outcomes provide some new and additional experimental evidences and data for the improvement of flow visualisation techniques.

A combined potential flow–BEM model to study the tower shadow effect in wind turbines

This paper aims to improve the understanding of the wind turbine tower shadow effect by developing a model that combines potential flow and blade-element momentum theory. The change in the flow field due to the presence of the tower is discussed in detail, together with the resulting variations in the aerodynamic forces acting on the rotating blades, as well as the effect on the output power and the blade root bending moment. The tower shadow effect is not only due to the change in wind speed but also to the change in angle of attack. A one-dimensional description of the flow field is therefore bound to be inadequate. The impact of the tower diameter and blade-tower clearance on the rotor power and blade root bending moment can be expressed as a quadratic function of a non-dimensional parameter. Apart from a mild Reynolds-number effect, the results presented are independent of turbine size.

A convenient method to validate the gas flow of a CFD-CT simulation applied on a packed bed used in gas biofiltration through residence time distributions

In this work, the validation of a Computational Fluid Dynamics (CFD) model coupled with a 3D computational tomography (CT) bed description of the gas flow field inside a packed column used for gas biofiltration was conducted using a low-cost metal oxide sensor. The validation was carried out in terms of gas residence time distribution (RTD), which was constructed from the sensor measurements using a mathematical model to filter the transient signal behavior. The coupled CFD-CT model was used to obtain the steady-state velocity field inside the packed bed by numerically solving the incompressible Navier-Stokes equations. Later, the tracer injection was simulated over the obtained velocity field by solving a transport equation for a passive scalar. Finally, the experimental and simulated RTD were compared to validate the model. The comparison between the experiments and the CFD simulations showed good agreement between both shapes of the RTD distribution with a relative difference of 4.167% for the mean RTD, denoting the potential of the proposed methodology to validate the CFD model and predict the moments of the RTD. This methodology can become a very useful tool for the validation of CFD simulations with the final purpose of studying the processes at the microscale undergoing inside packed bed biofiltration reactors.

Ramsey envelope modulation in NV diamond magnetometry

Nitrogen-vacancy (NV) spin ensembles in diamond provide an advanced magnetic sensing platform, with applications in both the physical and life sciences. The development of isotopically engineered $^{15}$NV diamond offers advantages over naturally occurring $^{14}$NV for magnetometry, due to its simpler hyperfine structure. However, for sensing modalities requiring a bias magnetic field not aligned with the sensing NV axis, the absence of a quadrupole moment in the $^{15}$N nuclear spin leads to pronounced envelope modulation effects in time-dependent measurements of $^{15}$NV spin evolution. While such behavior in spin echo experiments are well studied, analogous effects in Ramsey measurements and the implications for magnetometry remain under-explored. Here, we derive the modulated $^{15}$NV Ramsey response to a misaligned bias field, using a simple vector description of the effective magnetic field on the nuclear spin. The predicted modulation properties are then compared to experimental results, revealing significant magnetic sensitivity loss if unaddressed. We demonstrate that double-quantum coherences of the NV $S=1$ electronic spin states dramatically suppress these envelope modulations, while additionally proving resilient to other parasitic effects such as strain heterogeneity and temperature shifts.

Few-mode field quantization for multiple emitters.

The control of the interaction between quantum emitters using nanophotonic structures holds great promise for quantum technology applications, while its theoretical description for complex nanostructures is a highly demanding task as the electromagnetic (EM) modes form a high-dimensional continuum. We here introduce an approach that permits a quantized description of the full EM field through a small number of discrete modes. This extends the previous work in ref. (I. Medina, F. J. García-Vidal, A. I. Fernández-Domínguez, and J. Feist, “Few-mode field quantization of arbitrary electromagnetic spectral densities,” Phys. Rev. Lett., vol. 126, p. 093601, 2021) to the case of an arbitrary number of emitters, without any restrictions on the emitter level structure or dipole operators. The low computational demand of this method makes it suitable for studying dynamics for a wide range of parameters. We illustrate the power of our approach for a system of three emitters placed within a hybrid metallodielectric photonic structure and show that excitation transfer is highly sensitive to the properties of the hybrid photonic–plasmonic modes.

Two-parameter elastic-plastic fracture criterion and corrected fracture toughness

The basic aspects of the J-A concept of elastic-plastic two-parameter fracture mechanics, based on a three-term asymptotic description of the stress field at the crack tip are presented. It is noted that the field of elastic-plastic stresses at the crack tip is controlled by two parameters of fracture mechanics, namely, J-integral and parameter A. Parameter A is a measure of the deviation of the stress field from the HRR-stress field and can be considered a parameter of elastic-plastic constraint at the crack tip both under conditions of small- and large-scale yielding. The results of studying the influence of the exponent of the strain hardening of the material, crack aspect ratio and the thickness of standard specimens with a crack on the elastic-plastic stress intensity factor and parameter A are presented. A two-parameter elastic-plastic J-A fracture criterion based on the relationship between J-integral and strain(stress) on the surface of the crack-notch and the principle of linear summation of damage is formulated. To reflect the crack-tip constraint, the parameter A is introduced into the criterion equation as a function of applied failure stresses. The elastic-plastic fracture toughness as a function of the crack-tip constraint in the fracture criterion is interpreted as the corrected elastic-plastic fracture toughness of a specimen with the corresponding constraint parameters A. The results of studying the normalized corrected fracture toughness as a function of failure stresses, crack aspect ratio and strain hardening exponent of the material are presented.

Automated optimization of multilevel models of collective behaviour: application to mixed society of animals and robots

Animal societies exhibit complex dynamics that require multi-level descriptions. They are difficult to model, as they encompass information at different levels of description, such as individual physiology, individual behaviour, group behaviour and features of the environment. The collective behaviour of a group of animals can be modelled as a dynamical system. Typically, models of behaviour are either macroscopic (differential equations of population dynamics) or microscopic (such as Markov chains, explicitly specifying the spatio-temporal state of each individual). These two kind of models offer distinct and complementary descriptions of the observed behaviour. Macroscopic models offer mean field description of the collective dynamics, where collective choices are considered as the stable steady states of a nonlinear system governed by control parameters leading to bifurcation diagrams. Microscopic models can be used to perform computer simulations or as building blocks for robot controllers, at the individual level, of the observed spatial behaviour of animals. Here, we present a methodology to translate a macroscopic model into different microscopic models. We automatically calibrate the microscopic models so that the resulting simulated collective dynamics fit the solutions of the reference macroscopic model for a set of parameter values corresponding to a bifurcation diagram leading to multiple steady states. We apply evolutionary algorithms to simultaneously optimize the parameters of the models at different levels of description. This methodology is applied, in simulation, to an experimentally validated shelter-selection problem solved by gregarious insects and robots. Our framework can be used for multi-level modelling of collective behaviour in animals and robots.

Stochastic epidemic model on a simplicial complex

Complex networks with pairwise connections have been vastly used for the modeling of interactions within systems. Although these type of models are capable of capturing rich structures and different phases within a great variety of situations, their lack of explicit higher order interactions might result, in some contexts, limited. In this work a stochastic epidemic model on a simplicial complex is defined, generalizing the known Markovian SIR epidemic process on networks. The stochastic microscopic process is studied by direct simulations and a homogeneous mean field description is developed. The simple dissipative SIR infection dynamics permits a thorough characterization of the epidemic for arbitrarily high order interactions.

Nonclassicality of axionlike dark matter through gravitational self-interactions

Axion-like particles (ALPs) are promising dark matter candidates. They are typically described by a classical field, motivated by large phase space occupation numbers. Here we show that such a description is accompanied by a quantum effect: squeezing due to gravitational self-interactions. For a typical QCD axion today, the onset of squeezing is reached on $\mathrm{\mu s}$-scales and grows over millennia. Thus within the usual models based on the classical Schr\"odinger-Poisson equation, a type of Gross-Pitaevskii equation, any viable ALP is nonclassical. We also show that squeezing may be relevant on the scales of other self-gravitating systems such as galactic haloes, or solitonic cores. Conversely, our results highlight the incompleteness and limitations of the classical single field description of ALPs.

Quantization of interacting Galilean field theories

We present the quantum field description of Galilean electrodynamics minimally coupled to massless Galilean fermion in (3 + 1)-dimensions. At classical level, the Lagrangian is obtained as a null reduction of a relativistic theory in one higher dimension. We use functional techniques to develop the quantum field description of the theory. Quantum corrections to the propagators and vertex are obtained upto first order and the theory is found to be renormalizable to this order. The beta function of the theory is found to grow linearly; the theory is not asymptotically free.

Incompressible energy spectrum from wave turbulence

Bose–Einstein condensates with their superfluidity property provide an interesting parallel to classical fluids. Due to the Kolmogorov spectrum of homogeneous turbulence the statistics of the incompressible velocity field is of great interest, but in superfluids obtaining quantities such as the statistics of the velocity field from the macroscopic wavefunction turns out be a complicated task; therefore, most of the work up to now has been numerical in nature. We made use of the Weak Wave Turbulence (WWT) theory, which provides the statistics of the macroscopic wavefunction, to obtain the statistics of the velocity field, which allowed us to produce a semi analytical procedure for extracting the incompressible energy spectrum in the WWT regime. This is done by introducing an auxiliary wavefunction that preserves the relevant statistical and hydrodynamical properties of the condensate but with a homogeneous density thus allowing for a simpler description of the velocity field.

JCOPE-FGO: an eddy-resolving quasi-global ocean reanalysis product

In the present research, we provide a brief description and assessment of the oceanic fields analyzed in the newly developed eddy-resolving quasi-global ocean reanalysis product, named the Japan Coastal Ocean Predictability Experiments-Forecasting Global Ocean (JCOPE-FGO). This product covers the quasi-global ocean with a horizontal resolution of 0.1° × 0.1°. Validations of analyzed temperature and salinity fields by JCOPE-FGO against in situ observations revealed that our product can capture various aspects of observed hydrographic structures in the world ocean, including frontal structures near the surface and thermohaline properties of water masses, as well as their spatiotemporal variability. Furthermore, we have assessed dynamical fields analyzed in JCOPE-FGO using satellite altimeters and surface drifters, and found that our product can represent the mean state and variability of the upper ocean circulation in many regions. A notable feature of JCOPE-FGO is the inclusion of an updated global river runoff, and impacts of river forcing have been assessed by an additional reanalysis experiment without river forcing. We found that the removal of continental river discharge leads to dramatic changes in the near-surface salinity and related fields around river mouths of large rivers, but large changes are mostly confined to narrow regions near the coast. As an example of the substantial impact of river runoff, we discuss the dispersion of low-salinity water from the Mississippi river to the Gulf of Mexico: a comparison between the analyzed salinity fields from both reanalysis products with those from satellite observations demonstrated that the inclusion of river runoff is essential for an accurate representation of its seasonal variability. Several key issues that warrant further improvements are discussed for future development.

Nonsingular Stress Distribution of Edge Dislocations near Zero-Traction Boundary.

Among many types of defects present in crystalline materials, dislocations are the most influential in determining the deformation process and various physical properties of the materials. However, the mathematical description of the elastic field generated around dislocations is challenging because of various theoretical difficulties, such as physically irrelevant singularities near the dislocation-core and nontrivial modulation in the spatial distribution near the material interface. As a theoretical solution to this problem, in the present study, we develop an explicit formulation for the nonsingular stress field generated by an edge dislocation near the zero-traction surface of an elastic medium. The obtained stress field is free from nonphysical divergence near the dislocation-core, as compared to classical solutions. Because of the nonsingular property, our results allow the accurate estimation of the effect of the zero-traction surface on the near-surface stress distribution, as well as its dependence on the orientation of the Burgers vector. Finally, the degree of surface-induced modulation in the stress field is evaluated using the concept of the -norm for function spaces and the comparison with the stress field in an infinitely large system without any surface.

Accurate Recognition of Motion Patterns Based on Artificial Visual Neural Network

In order to improve the accuracy of motion pattern recognition, this paper combines the artificial visual neural network to construct a motion pattern recognition system. Moreover, this paper discusses the psychological perception properties of human eyes to color stimuli and gives a description of the observation field of view where the color stimuli are located. At the same time, this paper analyzes the phenomenon of color adaptation and provides a method of color appearance matching through modeling to achieve color appearance matching under variable observation conditions. Based on the chromatic adaptation transformation, a chromatic appearance model is given, which can predict the corresponding color and also predict the chromatic appearance properties of color stimuli under given observation conditions. In addition, this paper constructs an intelligent motion pattern recognition system combined with artificial visual neural network. The experimental results show that the motion pattern recognition system based on artificial visual neural network can accurately identify the motion pattern category.