Symmetric Fluctuations Research Articles

Susceptible-Infectious-Susceptible Epidemic Model with Symmetrical Fluctuations: Equilibrium States and Stability Analyses for Finite Systems.

Accurate prediction of epidemic evolution faces challenges such as understanding disease dynamics and inadequate epidemiological data. A recent approach faced these issues by modeling susceptible-infectious-susceptible (SIS) dynamics based on the first two statistical moments. Here, we improve this approach by including finite-size populations and analyzing the stability of the resulting model. Results underscore the influence of uncertainties and population size in the natural history of the epidemic.

Thermal evolution of spin excitations in honeycomb Ising antiferromagnetic FePSe3

We use elastic and inelastic neutron scattering (INS) to study the antiferromagnetic (AF) phase transitions and spin excitations in the two-dimensional (2D) zig-zag antiferromagnet FePSe3. By determining the magnetic order parameter across the AF phase transition, we conclude that the AF phase transition in FePSe3 is first-order in nature. In addition, our INS measurements reveal that the spin waves in the AF ordered state have a large easy-axis magnetic anisotropy gap, consistent with an Ising Hamiltonian, and possible biquadratic magnetic exchange interactions. On warming across TN, we find that dispersive spin excitations associated with three-fold rotational symmetric AF fluctuations change into FM spin fluctuations above TN. These results suggest that the first-order AF phase transition in FePSe3 may arise from the competition between C3 symmetric AF and C1 symmetric FM spin fluctuations around TN, in place of a conventional second-order AF phase transition.

Numerical Study of Rayleigh Wave Interaction with Rolling Contact Fatigue Type of Defects

ABSTRACT Rolling Contact Fatigue or Damage (RCF/RCD) presents significant maintenance challenges to railroads across the globe. Quantifying RCF/RCD crack depths and density in rails is important for all railroads to manage their grinding programs effectively and efficiently and being able to conduct ultrasonic testing (UT) of rails for reliable detection of internal fatigue damage. This work focuses on the modeling of Rayleigh waves UT approach to detect and characterize RCF type of defects which can form as: vertical, oblique or branched shaped surface breaking defects in the rail head. Specifically, the transmission coefficient (Tc) of Rayleigh waves was studied using finite element analysis (FEA). The effect of crack tip geometry on Tc values is discussed. The results suggest that for oblique, and branch cracks, characterization based purely on the Tc can be challenging due to symmetric sinusoidal fluctuations in the Tc. A real crack using a micrograph image was also modeled to validate the Tc results for oblique and branched cracks. This points to the need for additional parameters to be identified for efficient and reliable characterization of RCF/RCD type of defects in rails.

Bounding Variance and Skewness of Fluctuations in Nonlinear Dynamical Systems with Stochastic Thermodynamics*

Fluctuations arising in nonlinear dissipative systems (diode, transistors, chemical reaction, etc.) subject to an external drive (voltage, chemical potential, etc.) are well known to elude any simple characterisation such as the fluctuation-dissipation theorem (also called Johnson-Nyquist law, or Einstein's law in specific contexts). Using results from stochastic thermodynamics, we show that the variance of these fluctuations exceeds the variance predicted by a suitably extended version of Johnson-Nyquist's formula, by an amount that is controlled by the skewness (third moment) of the fluctuations. As a consequence, symmetric fluctuations necessarily obey the extended Johnson-Nyquist formula. This shows the physical inconsistency of Gaussian approximation for the noise arising in some nonlinear models, such as MOS transistors or chemical reactions. More generally, this suggests the need for a stochastic nonlinear systems theory that is compatible with the teachings of thermodynamics.

Force-dependent Fluxes of Adiabatic Classical and Quantum Rocking Ratchets

We consider the adiabatic mode of Brownian particle motion in a periodic potential under the action of symmetric dichotomous fluctuations of an external force F with zero mean value (rocking ratchet), in which the fluctuation frequency is much less than the inverse relaxation time of the particle in each of the states of the dichotomous process. Expressions are given for force-dependent fluxes of an adiabatic classical rocking ratchet. In the absence of thermal fluctuations, within the semiclassical approximation, analytical expressions are obtained for the rocking-ratchet tunneling flux in a sawtooth periodic potential of arbitrary asymmetry and in the potential of two sinusoids. It is shown that the tunneling flux has a linear asymptotics in modulus of small F due to (i) the absence of reverse tunneling fluxes with respect to the direction F and (ii) the root dependence of the integrand of the Gamow formula on the potential energy. The main parameters of the model are the energy barrier V0 and the period L of the potentials, as well as the rocking force F and the asymmetry parameter ξ = l / L of the sawtooth potential with the width of one of its teeth equal to l. It is shown that the direction of quantum ratchet motion is opposite to the motion direction of the corresponding classical ratchet in a limited range of values of the rocking force |F| L / V0 < αc , where the parameter αc changes from the value α1 = (√5 − 1) / 2 ≈ 0.618 for the extremely asymmetric sawtooth potential (ξ = 1) to the value α2 = 2 / 3 ≈ 0.667 for the symmetric potential (ξ= 1 / 2). In the range of values α2 < αc < α2, the sign of the tunneling flux changes with the change in the asymmetry parameter ξ. Numerical calculations for the potential of two sinusoids corresponding to the effective value ξ ≈ 0.655 of the asymmetry lead to similar results with αc ≈ 0.81.

Thermodynamics of a quantum corrected Schwarzschild black hole in AdS spacetime

The thermodynamics for a quantum corrected Schwarzschild black hole with AdS background is investigated. First, the black hole metric is introduced and given when the spherical symmetric quantum fluctuations of spacetime are considered for Schwarzschild AdS black hole. Then, based on AdS background, we get the free energy for the quantum corrected black hole by AdS gravity renormalization and saddle-point approximation. By the spherical symmetric quantum fluctuation in AdS spacetime is considered, there are three main results found. Firstly, due to quantum fluctuation, there is a divergence term in the Euclidean action, which contributes to the energy of spacetime. Secondly, the entropy of the modified black hole is still proportional to the horizon area. But when the contribution of quantum fluctuations is deducted, the relationship between entropy and area is not so. It shows that, the area entropy theorem for the black hole is the both effect of quantum fluctuations and black hole. Thirdly, quantum fluctuation doesn't affect the temperature of Hawking-Page transition, but the radius of the black hole of Hawking-Page transition will be corrected.

Search Frictions, Labor Supply, and the Asymmetric Business Cycle

AbstractWe develop a business cycle model that generates asymmetry between peaks and troughs of the unemployment rate and symmetric fluctuations of the participation rate as in the U.S. data. We calibrate the model and find that search frictions are solely responsible for the peak–trough asymmetry. Participation decisions do not generate asymmetry but contribute to the fluctuations in search frictions by changing the size and composition of the pool of job seekers, which in turn affects the tightness ratio and thereby slack in the labor market. The participation rate would be counterfactually asymmetric absent labor supply responses to shocks.

Search Frictions, Labor Supply, and the Asymmetric Business Cycle

We develop a business cycle model with search frictions in the labor market and a labor supply decision along the extensive margin that yields cyclical asymmetry between peaks and troughs of the unemployment rate and symmetric fluctuations of the labor force participation rate as in the U.S. data. We calibrate the model and find that cyclical changes in the extent of search frictions are solely responsible for the peak-trough asymmetry. Participation decisions do not generate asymmetry but contribute to the fluctuations in search frictions by changing the size and composition of the pool of job seekers, which in turn affects the tightness ratio and thereby slack in the labor market. The participation rate would be counterfactually asymmetric absent labor supply responses to shocks.

Geodesic structure of the quantum-corrected Schwarzschild black hole surrounded by quintessence

By considering the back-reaction of the spacetime through the spherically symmetric quantum fluctuations of the background metric, Kazakov and Solodukhin removed the singularity of the Schwarzschild black hole. This regular Schwarzschild black hole has a spherical central region with a radius of the order of the Planck length. On the other hand, due to the positively accelerating expansion of the Universe, it seems that there exists a universal repulsive force known as dark energy. In the framework of quantum field theories, the quintessence field is a candidate model for investigating and modeling dark energy. Accordingly, by taking into account the quintessential matter field in the background of the Schwarzschild black hole, Kiselev gained the metric of this black hole surrounded by quintessence. By combining these two above ideas, in this study, we consider the quantum-corrected Schwarzschild black hole surrounded by quintessence to investigate null and time-like geodesics structure. Generally, this study points out that black holes are quantum-gravitational objects. We will show that the accelerated expansion of the Universe, instead of dark energy, happens because of the presence of quantum effects in this setup. Also, due to the presence of the central Planck-size sphere, the regular black hole has been possessed a shifting over radial coordinate in its inner structure.

A quantum corrected R–N–AdS black hole and it’s thermodynamics of phase transition

To investigate the quantum gravity effects on the black hole thermodynamics, we studied the phase transition in a quantum corrected R–N–AdS black holes. First, based on the work of Kazakov and Solodukhin, the spherically symmetric quantum fluctuation is applied to R–N–AdS black hole, and the metric is given. Next, we investigate the basic thermodynamic quantity and Smarr formula, and then propose that the quantum correction parameter a should also be treated as a variable to ensure the establishment of the new Smarr formula. Finally, the P–V diagram and phase transition for the quantum corrected R–N–AdS black hole are studied. Compared with the existing research on R–N–AdS black hole, some effects by quantum fluctuation are analyzed and presented. First, the quantum correction will weaken the charge effect of the black hole. Second, the P–V curve of the quantum corrected black hole is no longer analogous to that of Van Der Waals (VDW) gas exactly. Third, the black hole has two more phase states than R–N–AdS black hole. One is a remnant phase state, the other is an unstable phase state. And both are derived from the quantum corrections of the black hole.

Dynamic interaction between fluctuations with different origins in a linear magnetized plasma

This paper presents the experimental identification of the dynamic interaction between three fluctuations excited by different thermodynamical forces in a linear plasma. The observed fluctuations are characterized as an axial symmetric mode, a drift wave, and an azimuthally symmetric potential fluctuation from the spatiotemporal structures measured with Langmuir probe arrays. The intermittent burst of the axial symmetric mode is observed by the instantaneous wave number spectrum. The energy transfer analysis revealed that the axially symmetric mode gains energy from the other mode during the burst while the drift wave loses energy. The intermittent burst synchronizes with the azimuthal symmetric potential fluctuation.

Isotope effect on zonal flow and its configuration dependence in low-density electron-cyclotron-resonance heated plasmas in Heliotron J

The hydrogen/deuterium (H/D) isotope effect on a zonal flow and its configuration dependence are experimentally studied in a helical device, Heliotron J. The isotope dependence of a toroidally symmetric potential fluctuation in the frequency range of <∼4 kHz, a zonal flow, is observed in low-density electron cyclotron resonance heated plasmas in Heliotron J. In the standard configuration, the zonal flow interacting with turbulence is enhanced as the D gas fraction increases. The zonal flow is more dominated against turbulent fluctuation in D plasmas, which should have a favourable impact on turbulence transport. Interestingly, however, the opposite dependence of the zonal flow activity on the isotope ratio is also observed in the different magnetic configurations. The configuration dependence observed in this experiment could be one of the factors to explain the difference in the isotope effect of confinement improvement between tokamaks and helical devices. Impurities and radial electric field, which can also be influenced by isotope mass through the difference in neoclassical transport and plasma-wall interaction, have insignificant influences on the zonal flow behaviour in this experiment.

Stock prices and economic activity nexus in OECD countries: new evidence from an asymmetric panel Granger causality test in the frequency domain

This study investigates the stock price–economic activity nexus in 12 member countries of the Organization for Economic Cooperation and Development (OECD) by employing monthly data over the period 1981:1–2018:3. For this purpose, the study uses Granger causality in the frequency domain in the panel setting by decomposing the symmetric and asymmetric fluctuations. This methodology determines whether the predictive power of interested variables is concentrated on quickly, moderately, or slowly fluctuating components. Our findings show that the stock prices have predictive power for future long-term economic activity in the panel setting. However, economic activity has more reliable information for stock prices for negative components. Additionally, empirical findings for asymmetric shocks are not fully consistent with those of symmetric ones. Besides, the country-specific results provide different causal linkages across members and frequencies. These findings may provide valuable information for policymakers to design proper and effective policies in OECD countries regarding the stock market and economic activity nexus.

Magnetic Manipulation and Assembly of Nonmagnetic Colloidal Rods in a Ferrofluid.

We investigated experimentally and theoretically the interactions and assembly of rodlike colloids in a ferrofluid confined at solid/liquid interface by the gravity under external magnetic fields. We first derived analytical expressions for the interaction energy of a single rod with the external magnetic field and the interaction between two rods using classical electromagnetism. The theory well captured the experimentally observed alignment of a single rod along the field direction under an in-plane field and switching between the horizontal and the vertical configurations in an out-of-plane field due to the competition between the magnetic energy and the gravitational energy. The theory can also predict the symmetric position fluctuations of a free rod on a fixed one at 90° and the gradual bias toward the end of the fixed rod as the angle was reduced to 0°, favoring the tip-toe arrangement. Finally, we showed that this anisotropic interaction led to the formation of chain-like structures, whose growth kinetics followed a simple scaling behavior with time. This work provides a theoretical framework for understanding the behaviors of rodlike colloids in ferrofluids and highlights the importance of shape anisotropy in manipulating colloids and their self-assembly.

Determining the content of macronutrients in berry sauces using a method of IR-spectroscopy

This paper has substantiated the possibility of using an IR spectroscopy method to study patterns in the chemical composition of wild and cultivated raw materials with the addition of algae as iodine-containing supplements. It has been found that the IR spectra of sauces based on the mashed blueberry and sea buckthorn or cranberry with or without algae demonstrate a set of absorption bands attributed to the respective types of oscillations. The valence fluctuations in the hydroxyl groups in the molecules of organic acids, carbohydrates, flavonoids are observed at 3,365 cm -1 to 3,400 cm -1 ν(ОН). The bands of valence and deformation fluctuations of the ‒CH double bond of polyunsaturated fatty acids manifest themselves in the range of 3,005 cm -1 and722 cm -1 . The bands of 2,925 cm -1 , 2,855 cm -1 belong to the asymmetric and symmetric valence oscillations of the n(С–Н) carbon skeleton in -CH 2 -. The presence of the carboxylic, amino-, and fatty acids is indicated by the following absorption bands: 1,746 cm -1 ‒ ν (C=O) valence fluctuations in the protonated carboxyl group ‒COOH; 1,545 cm –1 ‒ ν as (C=O; 1,415 cm –1 ‒ ν s (C=O) ‒ the asymmetric and symmetric valence fluctuations of the СОО - groups; and 1,240 cm –1 ‒ the valence fluctuations of ν(C‒O). The presence of flavonoids is confirmed by the presence of bands at 1,380 cm -1 and 1,050 cm -1 ‒ the deformation δ(O‒H) and symmetrical fluctuations of O‒H groups. The fluctuations of pyranose cycles of pectins are manifested in the range of 1,163 cm – 1 . It is noted that the composition of berry raw materials and sauces include polyunsaturated fatty acids, anthocyanins, flavonoids, organic acids, and pectin substances. An analysis of the IR spectra of berry sauce samples with the addition of algae has shown that the use of these additives in sauce technologies ensures a significant increase in the content of the physiological and functional ingredients and improves the hydrophobic properties of the raw materials

Determining location of voltage fluctuation source in radial power grid

The effects of voltage fluctuation are a common reason for complaints about low power quality. Voltage fluctuations in power grids are usually caused by changes in states of loads. In order to counteract this problem, it is required to determine the location of the source of voltage fluctuations as well as their parameters. The paper presents examples of locating disturbance loads which cause symmetric and asymmetric voltage fluctuation in LV radial power grid. In the process, the results of voltage fluctuation indices’ measurements have been used. The results of location process have been used to describe the propagation of voltage fluctuation in an example power grid. In addition, the current variation which causes the observed voltage fluctuation has also been determined.

The Self-Consistent Field Method and the Macroscopic Universe Consisting of a Fluid and Black Holes

The article discusses and substantiates a self-consistent approach to the macroscopic description of systems with gravitational interaction. Corrections to the equation of state of the fluid are found, based on the macroscopic Einstein equations which were obtained by averaging over microscopic spherically symmetric metric fluctuations created by primordial black holes in a fluid medium. It is shown that these corrections are effectively equivalent to addition to the system of a fluid with the equation of state p = −ε. In addition, it is shown that, in this case, the mass of black holes can grow at a modern stage of evolution to very large values.

Simulation of the Transient Characteristics of Water Pipeline Leakage with Different Bending Angles

Rapid global development has resulted in the widespread use of water pipelines in industrial and agricultural production and life. During water transportation and deployment, water pipes with different angles need to be positioned according to different geographical and topographical problems. Flowmaster simulation software was used to simulate the leakage process of pipelines with different angles. The transient characteristics of fluids in the pipeline were studied in detail. The influences of parameters, such as the bending coefficient R/D (R is the turning radius of pipe, D is the inner diameter of pipe), leakage position, and leakage aperture on the transient flow law of pipelines with and without leakage, were analyzed. The results show that the periodic decay of the upstream flow and pressure curve at the valve with and without leakage has an insignificant relationship with the bending coefficient R/D; however, the amplitude of the sudden position change is positively correlated with the magnitude of R/D. The leakage aperture is positively correlated with the leakage flow and negatively correlated with the pressure value at the leak location node. The farther the leak position is from the valve, the greater the amplitude of the valve end pressure and the upstream flow curve, and symmetric fluctuations occur.

Theory of microscopic electrodeposition under a uniform parallel magnetic field - 1. Nonequilibrium fluctuations of magnetohydrodynamic (MHD) flow

Nonequilibrium fluctuations of concentration, velocity and so on are formulated for electrode reactions including electrodeposition under a uniform magnetic field parallel to electrode surface. In electrodeposition, nonequilibrium fluctuations occur on the both sides of the electrode surface and solution; on the electrode-surface side, three-dimensional (3D) and two-dimensional (2D) nucleation proceed under the control of symmetrical and asymmetrical nonequilibrium fluctuations, respectively. On the solution side, a characteristic laminar flow called magnetohydrodynamic (MHD) flow with microscopic convection flows called micro-MHD flows are induced, so that the fluctuations on the solution side are described as Fourier components of complex 2D plane waves traveling with the MHD flow. The fluctuations on the electrode-surface side are interfered with the micro-MHD flows, yielding characteristic 3D and 2D nuclei. In Part 1 of the present paper, the amplitudes of the micro-MHD flows and concentration fluctuation on the solution side are first established independent of the fluctuations on the electrode-surface side.

The asymmetric cyclical behavior of the U.S. labor market

The employment rate in the United States fluctuates asymmetrically over the business cycle: it contracts deeply and sharply during recessions, but it recovers slowly and gradually during expansions. By contrast, aggregate output exhibits nearly symmetric fluctuations about trend. I explain these facts using an equilibrium business cycle model with search frictions in the labor market and worker heterogeneity in productivity, featuring endogenous job destruction and fluctuations in labor composition. The model predicts that the response of the employment rate to shocks greatly varies over the business cycle; notably, it raises in recessions and declines in expansions.