Radius R0 Research Articles

Bursting Sand Balloons

Using linear elasticity theory, we describe the mechanical response of dry non-cohesive granular masses of Ottawa sand contained by spherical rubber balloons subject to sudden bursting in the earliest instants of the event. Due to the compression imposed by the balloon, the rupture produces a fast radial expansion of the sand front that depends on the initial radius R0, the initial pressure p originated by the balloon, and the effective modulus of compression Ke. The hydrostatic compression approximation allows for the theoretical study of this problem. We found a linear decompression wave that travels into the sand and that induces a radial expansion of the granular front in the opposite direction with similar behavior to the wave but with a slightly lower speed.

Realization of a circularly transformed Airyprime beam with powerful autofocusing ability.

The reported autofocusing ability of a ring Airyprime beam array reaches up to 8632.40, while the strongest autofocusing ability of a circular Airyprime beam (CAPB) is only 1822.49. How can the autofocusing ability of a single beam reach the autofocusing ability of a beam array? To achieve this goal, a circularly transformed Airyprime beam (CTAPB) is introduced by following two steps. First, a circular equation transformation on the two transverse coordinates in the electric field expression of a propagating Airyprime beam is performed. Then, the electric field expression of a propagating Airyprime beam is integrated over the angle. The intensity profile of a CTAPB on the initial plane changes significantly with varying the primary ring radius r0. With increasing r0, therefore, the autofocusing ability of a CTAPB undergoes a process of first increasing and then decreasing, while the focal length always increases. A CTAPB exhibits more powerful autofocusing ability than a CAPB. The maximum autofocusing ability of a CTAPB can reach up to 8634.76, which is 4.74 times that of a CAPB, while the corresponding focal length is 95.11% of a CAPB. A CTAPB on the initial plane can be approximately characterized by a ring Airyprime beam array with sufficient number of Airyprime beams. Due to the better symmetry, a CTAPB has a slightly stronger autofocusing ability than a ring Airyprime beam array and almost the same focal length as a ring Airyprime beam array. The CTAPB is also experimentally generated, and the experimental results indicate that the CTAPB has powerful autofocusing ability. As a replacement of a CAPB and a ring Airyprime beam array, this introduced CTAPB can be applied to the scenes which involve abruptly autofocusing effect.

Sidey V.I. ON THE IONIC RADIUS OF THE CYANIDE ION

Sidey V.I. ON THE IONIC RADIUS OF THE CYANIDE ION

Conical refraction with flat-topped vortex hollow beam through biaxial crystals

This paper presents a new theoretical method to determine conical refraction (CR) with a light beam by examining the flat-topped vortex hollow beam in a biaxial crystal. The analytical formula for the considered CR is derived in a closed form. Some graphical representations are plotted to show how the source beam parameters N and M, the control parameter ρ0 of CR between the cylinder radius R0 and the waist radius ω, and the propagation distance z, affect the transverse intensity pattern behind the biaxial crystal. Results show that the circularly polarized flat-topped vortex hollow beams entering the crystal will transform the classical double-ring pattern into a multi-ring one consisting of bright rings. The evolution properties of CR with vortex beams upon propagation is also discussed and compared with the reference beam. Through numerical simulations, we established a good agreement between the integrated expressions method and our analytical formula. The present study generalizes the cases of the circularly polarized Gaussian and the flat-topped Gaussian transformed by the CR in a biaxial crystal.

The Propagation Characteristics of Circular Airy Beams with Propagational Fractional-Order Optical Vortices

We investigate the propagation properties of circular Airy beams (CABs) with propagational fractional-order optical vortices (OVs). The superposition of the phase singularity and polarization singularity from a vortex vector beam (VVB) plays a significant role in creating a propagational fractional vortex beam. Propagational fractional vortex beams can be considered as a superposition of left and right circularly polarized vortex beams with different integer topological charges (TCs). We study the propagation characteristics of two kinds of propagational fractional vortex CABs, and the results show that both of the two kinds of beams can stably propagate in free space, and they exhibit an “abruptly auto-focusing” property and “self-healing” property during the propagation. The intensity distribution of the first kind of propagational fractional vortex CAB has an odd number of petals (2m + 1), while the second kind of beam has a crescent-shaped intensity distribution. The influence of turbulence on the beam propagation through atmosphere under different turbulence strengths is also numerically studied in this paper. A fractional vortex CAB with an initial radius r0 = 10 mm can retain its shape after propagating 20 m when the atmospheric refractive-index structure constant CN2=0.2×10−12m−2/3. Our results are expected to broaden the application of CABs.

Effect of the Curvature Radius on Single-Droplet Dynamic Characteristics within a Concave-Wall Jet

The centrifugal force field in a hydrocyclone was affected by the concave-wall curvature radius R0, and the mechanism underlying droplet deformation was closely related to the mass transfer efficiency. Numerical simulation and experimental data were collected to reveal the deformation characteristics and mechanism of a single droplet crossing concave-wall jet. Normalized interfacial energy γ and stretching performance were provided to investigate the droplet deformation process. The results showed that the droplet was stretched along the streamwise direction and shrank along the spanwise direction in the concave-wall jet. The droplet interfacial energy and deformation were the largest when the droplet crossed the jet boundary at t = 0.20 s. The maximum γ value increased with the increase in R0 by 57.3% to 71.4%, and the distance between the droplet and concave wall increased with R0. The Q-criterion was exported to show the increase in the vortex strength with the decrease in R0 at the jet boundary. The pressure distribution inside the droplet showed that the pressure decreased as R0 increased, while the pressure difference increased along the streamwise and wall-normal directions. This study suggested that the droplet breakup was more difficult for a smaller R0, which was beneficial for liquid–liquid heterogeneous separation.

Shear Waves in an Elastic Plate with a Hole Resting on a Rough Base

The article is devoted to the analytical and numerical study of the pattern of propagation and attenuation, due to Coulomb friction, of shear waves in an infinite elastic thin plate with a circular orifice of radius r0 lying on a rough base. Considering the friction forces and their influence on the sample of wave propagation in extended rods or thin plates is important for calculating the stress–strain state in them and the size of the area of motion. An exact analytical solution of a nonlinear boundary value problem for tangential stresses and velocities is obtained in quadratures by the Laplace transform, with respect to time. It turned out that the complete exhaustion of the wave front of a strong rupture occurs at a finite distance r* from the center of the orifice, and an elementary formula is given for this distance (the case of tangential shock stresses suddenly applied to the orifice boundary is considered). For various ratios of the magnitude of the limiting friction force to the amplitude of the applied load, the stopping (trailing) wave fronts are calculated. After passing them, a state of static equilibrium between the elastic and friction forces with a nonlinear distribution of residual stresses is established in the region r0≤r≤r*. For the first time, a precise analytical solution was obtained for the boundary value problem of the propagation of elastic shear waves in an infinite isotropic space with a cylindrical cavity, when a tangential shock load is set on its surface.

Bifurcation and dynamics of periodic solutions to the Rayleigh–Plesset equation: Theory and numerical simulation

In this paper, we study the oscillation of a gas-filled spherical bubble immersed in an infinite domain of incompressible liquid under the influence of a time-periodic acoustic field. The oscillation is described by the Rayleigh–Plesset equation, which is derived from the Navier–Stokes equation under the assumptions of spherical symmetry. Taking the initial radius R0, or the initial instantaneous partial pressure Pg0, of the gas-filled bubble as a parameter, we present a saddle–node bifurcation of periodic solutions to the Rayleigh–Plesset equation in the parameter space, provided the mean value of applied pressure is greater than the vapor pressure. Further, we show that the Rayleigh–Plesset equation has two classes of periodic solutions, as R0 (resp. Pg0) tends to +∞, the first class of solutions uniformly diverges to +∞ at the rate of R05 (resp. Pg05/2), while the second class converges to 0 at the rate of R0−5 (resp. Pg0−5/2). As for the case where the density of the liquid ρ is chosen as a parameter, we observe an interesting nonlinear phenomenon that, for some ρ, the Rayleigh–Plesset equation may possess four positive T-periodic solutions: two of them are stable, while the rest of them are unstable. This is quite different from the phenomenon that occurs when R0 (or Pg0) is chosen as a parameter.

Multi-objective optimization of concrete pumping S-pipe based on DEM and NSGA-II algorithm

In the process of fresh concrete pumping, the S-pipe plays a crucial role in the pumping system. The impact and scratching of concrete aggregate on the wall of S-pipe will cause the wear of the wall and lessen its service life. The structural design of the pumping S-pipe typically relies on experience, and the cost for experiments is too expensive. In addition, the influence mechanism of structural parameters on S-pipe wear is still unclear. In view of this, to reduce the wear of S-pipe and investigate the influence of structural parameters on the wear of S-pipe, the structural parameters of S-pipe (curvature radius r1 and r2, horizontal dimension l3, and inclination angle θ) were optimised through discrete element numerical simulation combined with the non-dominated sorting genetic algorithm-II (NSGA-II) in this paper. Firstly, the wear coefficient was determined by friction and wear test. The discrete element method (DEM) model of pumping suction unit was simplified, and the S-pipe was parameterised. Secondly, sample points and their exact values of the optimization objectives were obtained by Latin hypercube sampling (LHS) plan and DEM simulations, respectively. From these, a Kriging surrogate model was constructed. Taking the average wear rate and the maximum wear of the S-pipe as the optimization objectives, a multi-objective optimization design was performed based on the NSGA-II and the Kriging models. After optimization, a series of Pareto optimal S-pipe models were obtained. Comparing the optimised model with the original model, the average wear rate and maximum wear amount of the S-pipe were reduced by 9% and 26%, respectively.

Radon exhalation behavior and determination of diffusion migration parameters in spherical porous emanation media

There is a significant impact of the radon diffusion coefficient and the free radon production rate on the exhalation of radon from porous materials that can be regarded as spheres, hexahedrons, or cylinders. To understand this effect, the radon exhalation rules of spherical porous media with different radii were studied according to the radon diffusion migration theory. A specialized method for simultaneous determination of the radon diffusion coefficient and the free radon production rate of the spherical porous media was proposed, and applied to determine the above two parameters for two hemispherical test blocks with different radii. The results show that:(1) For spherical porous media with a certain radon diffusion length (Ld), as the radius (r0) of the sphere increases, the radon exhalation rate first increases, and tends to stabilize at r0≥6Ld; The free radon release share gradually decreases from approximately 1, and drops to a steady state at r0≥18Ld. (2) Compared with conventional methods, the relative error of the free radon production rate determined by the proposed method is within 3.9%, which verifies the reliability of the new method.

Jellyfish galaxies with the IllustrisTNG simulations – citizen-science results towards large distances, low-mass hosts, and high redshifts

ABSTRACT We present the ‘Cosmological Jellyfish’ project – a citizen-science classification program to identify jellyfish (JF) galaxies within the IllustrisTNG cosmological simulations. JF are satellite galaxies that exhibit long trailing gas features – ‘tails’ – extending from their stellar body. Their distinctive morphology arises due to ram-pressure stripping (RPS) as they move through the background gaseous medium. Using the TNG50 and TNG100 simulations, we construct a sample of $\sim 80\, 000$ satellite galaxies spanning an unprecedented range of stellar masses, $10^{8.3}{-}10^{12.3}\, \mathrm{M_\odot }$, and host masses, $M_\mathrm{200,c}=10^{10.4}{-}10^{14.6}\, \mathrm{M_\odot }$ back to z = 2. Based on this sample, $\sim 90\, 000$ galaxy images were presented to volunteers in the citizen-science Zooniverse platform, who were asked to determine whether the galaxy image resembles a JF. Based on volunteer votes, each galaxy received a score determining if it is a JF or not. This paper describes the project, the inspected satellite sample, the methodology, and the classification process that resulted in a data set of 5307 visually identified JF galaxies. We find that JF is common in nearly all group- and cluster-sized systems, with the JF fraction increasing with host mass and decreasing with satellite stellar mass. We highlight JF galaxies in three relatively unexplored regimes: low-mass hosts of $M_\mathrm{200,c}\sim 10^{11.5}{-}10^{13}\, \mathrm{M_\odot }$, radial positions within hosts exceeding the virial radius R200, c, and at high redshift up to z = 2. The full data set of our JF scores is publicly available and can be used to select and study JF galaxies in the IllustrisTNG simulations.

Influence mechanism of the three-zone synergistic efficiency-enhancing pattern on the 3D flow field and thermal resistance characteristics for wet cooling towers

For a super-large natural draft wet cooling tower (S-NDWCT) equipped in a 1000 MW unit, a 3D numerical model of the three-zone synergistic efficiency-enhancing pattern (TSEP) was established and validated. This study focused on the influence mechanism of the three-zone parameters on the 3D flow field and thermal resistance characteristics, including the installation height h, installation angle θ, total coverage area S, length L and number n of the split-flow plate, water distribution partition radius R1, the proportion of inner zone water amount P, and fillings partition radius R2. The results showed that the TSEP reconfigures and comprehensively optimizes the airflow field, and presents the more uniform air-water ratio and water temperature fields. The volumetric heat transfer coefficient hv increases and then reduces as h, θ, S, n, R1, P and R2 increase, and increases continuously with increasing L in the range studied. Additionally, the ventilation G increases and then reduces with the increase of h, θ, R1 and P, increases with rising S, n and R2, and reduces with L increases. Finally, the relatively optimized values of the three-zone parameters are obtained. In this case, compared with a conventional tower, the hv and G increase by 11.3% and 10.6%, respectively.

Numerical study on aerodynamic performance improvement of the straight-bladed vertical axis wind turbine by using wind concentrators

The present study proposes a new concept of Straight-bladed Vertical Axis Wind Turbines (SB-VAWTs) with convex-shaped wind concentrator. The wind concentrator is installed up and down the rotor, which is designed to capture more airflow and improve the flow characteristics inside the rotor. The profile of the wind concentrator is generated based on the B-spline, the quadratic rotational orthogonal combination design method is used to study the effects of bottom radius R1, top radius R2, inlet angle α1, and outlet angle α2 of the concentrator, and the distance ΔL between the concentrator and the rotor on the aerodynamic performance of the SB-VAWT by numerical simulation. It is found that the installation of the wind concentrator improves the flow characteristics inside the rotor and enhances the aerodynamic performance of the SB-VAWT, particularly at lower wind speeds. Under the condition of this study, the average torque coefficient and maximum power coefficient of the SB-VAWT with the wind concentrator are enhanced by up to 24.7 % and 52.7 %. This study can provide a reference for using a wind concentrator to improve the aerodynamic characteristics of SB-VAWTs and demonstrate the potential of using this kind of SB-VAWT for wind energy utilization systems.

Development of the heavy ion RFQ for CAFE2

A radio frequency quadrupole (RFQ) accelerator which accelerates particles with a mass-to-charge ratio up to 3 to over 1.33 MeV/u was developed. This RFQ was designed based on the existing 162.5 MHz solid-state power sources of the Chinese Accelerator Driven System (C-ADS) injector II. The frequency is relatively high to a heavy ion RFQ which means a weak transverse focusing strength and brings challenges to the beam loss and quality control. The average radius r0 of the RFQ was appropriately chosen to make a compromise between the transverse focusing strength and the maximum surface field. The beam dynamics parameters were carefully optimized to improve the quality of the RFQ output beam so that the beam could be well transported in the following superconducting structure. Beam dynamics simulations and an error study have been performed to evaluate the RFQ and a method which is more suitable for the analyses of small acceptance RFQs has been adopted. And the results of the beam commissioning have been proved to agree well with the simulations.

Thermal stability and effects of thermal fluctuations on the static and spherically symmetric hairy black hole by gravitational decoupling

In this paper, we explore the thermodynamic aspects of the hairy black hole solution developed by gravitational decoupling in the spherical symmetry, considering its energy emission, Gibbs free energy, and thermal fluctuations. Our analysis involves the calculation of various quantities, including the Hawking temperature, geometric mass, and heat capacity to discuss the thermodynamic stability at local and global scales. To determine the temperature of the black hole, we utilize the first law of thermodynamics. Additionally, we evaluate the energy emission rate and establish its proportionality to the decoupling parameter α. By calculating the Gibbs free energy, we investigate the phase transition behavior through the swallowing tails of the hairy black holes. Furthermore, we derive the corrected entropy to examine the impact of thermal fluctuations on small and large black holes. We also calculated horizon radius r0, inner stable circular orbit rISCO , photon sphere radius rph, and shadows radius Rsh. Remarkably, the length scale parameters α (decoupling parameter) and β exhibit substantial influences on the thermodynamic properties of under consideration hairy black holes.

SOLAR-TYPE ECLIPSING BINARY KIC 4832197: PHYSICAL PROPERTIES AND INTRINSIC VARIABILITY OF THE COMPONENTS

Comprehensive analysis of optical spectroscopy and space photometry of the solar type eclipsing binary system KIC 4832197 is presented. The system is composed of F7V + F9V components with masses of M1 = 1.16 ± 0.12 M☉, M2 = 1.07 ± 0.10 M☉ and radii of R1 = 1.26 ± 0.04 R☉, R2 = 1.03 ± 0.03 R☉. The position of the components on the Log Teff – Log L/L☉ plane suggests an age of 2.8 ± 0.8 Gyr for the system. Inspection of out-of-eclipse brightness in time reveals a wave-like variability pattern, whose amplitude and shape quickly change on order of days. Frequency analysis of this variability results in two significant peaks in the amplitude spectrum, which are interpreted as rotational modulation of spots on the components. Assuming both spots are on the same component, a lower limit for the differential rotation coeffcient is computed as k = 0.12, which is weaker compared to the solar value of k☉ = 0.189.

A Closer Look at the Evolution of Supercooled Cloud Droplet Temperature and Lifetime in Different Environmental Conditions with Implications for Ice Nucleation in the Evaporating Regions of Clouds

Abstract This study investigates the evolution of temperature and lifetime of evaporating, supercooled cloud droplets considering initial droplet radius (r0) and temperature (), and environmental relative humidity (RH), temperature (T∞), and pressure (P). The time (tss) required by droplets to reach a lower steady-state temperature (Tss) after sudden introduction into a new subsaturated environment, the magnitude of ΔT = T∞ − Tss, and droplet survival time (tst) at Tss are calculated. The temperature difference (ΔT) is found to increase with T∞, and decrease with RH and P. ΔT was typically 1–5 K lower than T∞, with highest values (∼10.3 K) for very low RH, low P, and T∞ closer to 0°C. Results show that tss is <0.5 s over the range of initial droplet and environmental conditions considered. Larger droplets (r0 = 30–50 μm) can survive at Tss for about 5 s to over 10 min, depending on the subsaturation of the environment. For higher RH and larger droplets, droplet lifetimes can increase by more than 100 s compared to those with droplet cooling ignored. Tss of the evaporating droplets can be approximated by the environmental thermodynamic wet-bulb temperature. Radiation was found to play a minor role in influencing droplet temperatures, except for larger droplets in environments close to saturation. The implications for ice nucleation in cloud-top generating cells and near cloud edges are discussed. Using Tss instead of T∞ in widely used parameterization schemes could lead to enhanced number concentrations of activated ice-nucleating particles (INPs), by a typical factor of 2–30, with the greatest increases (≥100) coincident with low RH, low P, and T∞ closer to 0°C. Significance Statement Cloud droplet temperature plays an important role in fundamental cloud processes like droplet growth and decay, activation of ice-nucleating particles, and determination of radiative parameters like refractive indices of water droplets. Near cloud boundaries such as cloud tops, dry air mixes with cloudy air exposing droplets to environments with low relative humidities. This study examines how the temperature of a cloud droplet that is supercooled (i.e., has an initial temperature < 0°C) evolves in these subsaturated environments. Results show that when supercooled cloud droplets evaporate near cloud boundaries, their temperatures can be several degrees Celsius lower than the surrounding drier environment. The implications of this additional cooling of droplets near cloud edges on ice particle formation are discussed.

Magnetostatic (MSW) modes in a Dielectric@Ferromagnetic (Core@Shell) spherical structure

The solutions for magnetostatic spin waves (MSW) modes in a spherical structure were studied. A spherical core@shell structure, of soft ferromagnetic (FM) shell and a dielectric core material, was the geometry used for the calculation by solving the Walker equation. The dielectric is a sphere of radius r1 covered by an FM shell of inner radius r1 and outer radius r2. The transformation of the Walker equation in the FM shell was performed based on the solution proposed by Plumier. The resultant expression of solution presented here for the MSW modes are not reported in the literature. The solution involves integrals that are solved numerically and the result are the dispersion relations curves. These curves show deviations from the solution for an empty shell with no core (vacuum@FM) previously reported. The changes in the presented curves are mainly due to the displacement currents that arise in the dielectric core. The curves were calculated for silica and for alumina core, the most commonly used to grow spherical shells. This result here is important because hollow spherical structures are usually grown on dielectric support.

Multi-bubble scattering acoustic fields in viscoelastic tissues under dual-frequency ultrasound

Bubbles are widely used in the medical field due to their strong acoustic scattering properties, and the interaction between bubbles affects the scattering acoustic field caused by the bubble cluster. In this study, the dynamic equations of bubbles oscillating in viscoelastic tissues are solved numerically. The effect of bubble interaction on the scattered acoustic pressure under dual-frequency ultrasound is analyzed. In addition, the frequency spectra of the scattered acoustic waves due to the bubbles with and without considering the interaction are compared. The results show that the suppression or enlargement of the scattered sound pressure caused by the interaction between bubbles is related to the bubble radius and the incident frequency. Moreover, when the incident frequency is equal to the resonant frequency of the bubble with equilibrium radius R0, the effect of resonant bubbles is stronger than that of non-resonant bubbles. Meanwhile, for the multi-bubble system with a small bubble number density, the total response of the bubble cluster can be approximated as an algebraic sum of the dynamical behavior of individual bubbles.

The abruptly autofocusing characteristics of the circular Airyprime beam in a chiral medium

In this paper, the abruptly autofocusing characteristics of the circular Airyprime beam (CAPB) propagating in a chiral medium is investigated for the first time. The results show that the CAPB splits into the left-handed circularly polarized (LCP) and the right-handed circularly polarized (RCP) beams with different propagating trajectories in the chiral medium. The focal length Zf, the depth of focal length Zw and the peak intensity of two focal field spots in the chiral medium can be effectively manipulated by the combination of initial beam parameters of CAPB (the primary ring radius r0, the scaling factor w0 and the exponential decay factor a) and the chiral medium parameter h. In addition, the expression of Zf derived from CAB can be well applied to CAPB. The Zf and the Zw of LCP and RCP components of CAPB and CAB are the same, but the autofocusing ability of CAPB is about 7 times of that of CAB under the same condition in the chiral medium, almost the same as that in free space. Due to the abruptly autofocusing ability and the propagation properties in a chiral medium, the CAPB may have potential applications in many fields such as biomedical treatment and optical manipulation.