Nonzero Flux Research Articles

Search for GeV gamma-ray emission from SPT-CL J2012-5649 with six years of DAMPE data

We search for gamma-ray emission from the galaxy cluster SPT-CL J2012-5649 in the energy range from 3 GeV to 1 TeV using the DArk Matter Particle Explorer (DAMPE) telescope. For our analysis, we use three different templates: point source, radial disk, and radial Gaussian. We do not detect a signal with significance >3σ for any of these templates at any location within R200 of the cluster center. We obtain 95% C.L. upper limit on the energy flux ranging between ∼10−6 and 10−4MeVcm−2s−1 depending on the energy range. These upper limits are consistent with a previously reported non-zero flux detected by Fermi-LAT at 6σ significance. This work represents the first proof of principle search for gamma-ray emission from a single galaxy cluster using DAMPE data.

Search for MeV gamma-ray emission from TeV bright red dwarfs with COMPTEL

The SHALON atmospheric Cherenkov telescope has detected very high energy gamma-ray emission at TeV energies from eight red dwarfs, namely, V388 Cas, V547 Cas, V780 Tau, V962 Tau, V1589 Cyg, GJ 1078, GJ 3684 and GL 851.1. Consequently, these red dwarfs have been suggested as sources of ultra-high energy cosmic rays. In this work, we search for soft gamma-ray emission from these TeV bright red dwarfs between 0.75–30 MeV using archival data from the COMPTEL gamma-ray imaging telescope, as a follow-up to a similar search for GeV gamma-ray emission using the Fermi-LAT telescope. Although, prima-facie, we detect non-zero photon flux from three red dwarfs with high significance, these signals can attributed to contamination from nearby sources such as Crab and Cygnus, which are within the angular resolution of COMPTEL, and have been previously detected as very bright point sources at MeV energies. Therefore, we could not detect any statistically significant signal (> 3σ) from any of these eight red dwarfs from 0.75–30 MeV. We then report the 95% confidence level upper limits on the differential photon flux (at 30 MeV), integral photon flux and integral energy flux for all of the eight red dwarfs. The integral energy flux limits range between 10-11 - 10-10-ergs/cm2/s.

A study of gamma-ray emission from OJ 287 using Fermi-LAT from 2015-2023

We search for gamma-ray emission from OJ287 in the energy range from 0.1-300 GeV during 2015-2023, in coincidence with an extensive observing campaign to monitor the optical flux variability and polarization, as discussed in arXiv:2311.02372. We present results for eight segments in the aforementioned period, with each segment corresponding to an observing season. We report non-zero gamma-ray flux (with >10σ significance) for all the eight segments. The photon and energy flux observed during this period is and , respectively, while the SED can be fitted with a power law with a slope of 2.12±0.02. The observed luminosity is between 1045−1046 ergs/sec.

The use of nonlinear guided-wave features for detection and assessment of intermetallic compounds within dissimilar joints – an experimental investigation

Abstract Welding dissimilar materials is widely employed in industrial construction and manufacturing to enhance cost-effectiveness and performance, often utilizing non-fusion methods like solid-state and high-energy beam welding. However, a significant challenge is the formation of intermetallic compounds (IMCs) at the joint interface, which can weaken the bond and increase brittleness, leading to hidden internal cracks. Nonlinear ultrasound detection methods are employed as advanced, non-destructive testing techniques for early damage inspection in various materials. This research investigates the assessment of the thickness of the intermetallic layer within dissimilar joints using non-linear ultrasound-wave features. Numerical and experimental investigations were performed using four friction stir welding (FSW) lap joints, between AA5052-H32 aluminum and ASTM 516-70 steel, with various intermetallic thicknesses. The methodology involved examining the generation of second-order harmonic frequency by exciting Lamb waves (LW) at specific frequencies. To determine the necessary LWs' excitation frequency, synchronism, and non-zero power flux conditions were employed. The collected signals were measured and analyzed in the time and frequency domains to understand the behavior of the non-linear parameter β′ with the thickness of the intermetallic layer. The results show that β′ changes in a linear manner with the thickness of the intermetallic compound layer (several micrometers in thickness). This provides strong evidence that nonlinear LW features are sensitive to microstructural variations in the FSW joints, which enables them to effectively evaluate their strength.

Rheology of magnetorheological shear thickening polishing fluids with micro diamond abrasive particles

Magnetorheological shear thickening polishing (MRSTP) has the dual effect of shear thickening and magnetization enhancement, thereby enhancing polishing efficiency. MRSTP fluids (MRSTPFs) were prepared using polyethylene glycol (PEG), silicon dioxide (SiO2), carbonyl iron particles (CIPs), and diamond micro-abrasive particles. MRSTPFs containing diamond particles of various sizes were prepared for rheological tests. A rheological hypothesis was proposed regarding the development of CIPs chains and the ability to aggregate PEG and SiO2. Rheological tests results indicated that each sample exhibited shear thickening and magnetization enhancement effects under the magnetic field and shear rate. The shear thickening effect decreased with increasing magnetic flux density, while the overall viscosity and shear stress increased. As the magnetic flux density increased from 0 mT to 112 mT, the thickening ratio of MRSTPFs containing 3 μm diamond particles decreased from 18.94 to 1.37, but the peak viscosity increased from 5.208 Pa·s to 3639 Pa·s. The thickening ratios of MRSTPFs with different abrasive sizes showed a slight variation from 0.11 to 1.76 at the same magnetic flux density of 22 mT, 45 mT, 68 mT, 90 mT, and 112 mT, respectively. It demonstrated that the diamond particle size did not have a significant effect on the rheological properties of MRSTPFs. The correctness of the hypothesis was confirmed. The storage modulus of MRSTPFs exceeded the loss modulus at non-zero magnetic flux density, indicating that the MRSTPFs had become semi-solid. The microscopic mechanism showed that the rheological characteristics were determined by the evolution of the chain structure of CIPs and the binding ability of PEG to SiO2. This study provided valuable insights into exploring mechanisms of MRSTPFs and demonstrating the potential application of MRSTP.

Damage assessment in L-shaped bends by nonlinear feature guided waves

L-shaped bends are crucial lightweight structural components in aerospace manufacturing, renowned for their high specific strength and stiffness. However, the geometric configuration of these bends makes them susceptible to stress concentration in the bending zone. Effective technique for damage assessment of the bending region of L-shaped bends is highly demanded. This paper proposes a nondestructive testing method using nonlinear ultrasonic feature guided waves (FGWs) for early damage assessment of L-shaped bends. Semi-analytical finite element (SAFE) method and perfectly matched layer (PML) technique are employed to analyze FGW propagation in L-shaped bends. Three-dimensional finite element models are utilized to investigate the FGWs propagation in the bending region of L-shaped bends in a numerical perspective. Cumulative second harmonic generation (SHG) of FGWs is successfully observed by selecting suitable mode pairs based on synchronism and non-zero power flux conditions, which provides a promising alternative for early damage assessment in L-shaped bends. Experimental findings are consistent with the numerical ones. Subsequently, thermal damage and plastic deformation with varying gradients were introduced into the bending region of L-shaped bends. The use of SHG of selected FGW mode has effectively assessed the damage with an improved sensitivity, compared to conventional linear acoustic one. This investigation substantiates the potential of nonlinear FGWs in detecting early damage in L-shaped bends, offering promise for future industrial testing applications.

Wave Generation by Flare-accelerated Ions and Implications for 3He Acceleration

The waves generated by high-energy proton and alpha particles streaming from solar flares into regions of colder plasma are explored using particle-in-cell simulations. Initial distribution functions for the protons and alphas consist of two populations: an energetic, streaming population represented by an anisotropic (T ∥ > T ⊥), one-sided kappa function and a cold, Maxwellian background population. The anisotropies and nonzero heat fluxes of these distributions destabilize oblique waves with a range of frequencies below the proton cyclotron frequency. These waves scatter particles out of the tails of the initial distributions along constant-energy surfaces in the wave frame. Overlap of the nonlinear resonance widths allows particles to scatter into near-isotropic distributions by the end of the simulations. The dynamics of 3He are explored using test particles. Their temperatures can increase by a factor of nearly 20. Propagation of such waves into regions above and below the flare site can lead to heating and transport of 3He into the flare acceleration region. The amount of heated 3He that will be driven into the flare site is proportional to the wave energy. Using values from our simulations, we show that the abundance of 3He driven into the acceleration region should approach that of 4He in the corona. Therefore, waves driven by energetic ions produced in flares are a strong candidate to drive the enhancements of 3He observed in impulsive flares.

Setting Up a Large-Eddy Simulation to Focus on the Atmospheric Surface Layer

Large-eddy simulations (LES) above forests and cities typically constrain the simulation domain to the first 10–20% of the Atmospheric Boundary Layer (ABL), aiming to represent the finer details of the roughness elements and sublayer. These simulations are also commonly driven by a constant pressure gradient term in the streamwise direction and zero stress at the top, resulting in an unrealistic fast decay of the total stress profile. In this study, we investigate five LES setups, including pressure and/or top-shear driven flows with and without the Coriolis force, with the aim of identifying which option best represents turbulence profiles in the atmospheric surface layer (ASL). We show that flows driven solely by pressure not only result in a fast-decaying stress profile, but also in lower velocity variances and higher velocity skewnesses. Top-shear driven flows, on the other hand, better replicate ASL statistics. Overall, we recommend, and provide setup guidance for, simulation designs that include both a large scale pressure forcing and a non-zero stress and scalar flux at the top of the domain, and that also represent the Coriolis force. Such setups retain all the forces used in typical full ABL cases and result in the best match of the profiles of various statistical moments.

Capturing non-equilibrium effects in cylindrical Couette flow problem using the Extended Onsager-13 moment equations

In the present work, cylindrical Couette flow is analyzed using the recently derived third-order accurate 13-moment transport equations by transforming them into cylindrical coordinates. Assuming the Mach number and normalized temperature difference between the cylinders to be relatively small, closed-form expressions for all relevant quantities, velocity, pressure, temperature, heat flux, and stresses, are obtained from the semi-linearized form of the equations. These closed-form expressions from the present study have been validated against the corresponding linearized Grad 13 moment (G13) equation solutions. It is further demonstrated that contrary to the G13 equations, the pressure in the cylinder annulus is not constant, while the temperature depends upon the magnitude of viscous heating apart from non-isothermal boundary conditions. The coupling among velocity, temperature, heat flux, and stress and its effect on the variation of various physical quantities across the annulus has been discussed. The obtained analytical solution shows that the equations correctly capture most known non-equilibrium effects, such as the presence of a Knudsen layer, non-Newtonian stresses, and non-Fourier heat flux for Knudsen numbers falling well into the transition regime through a quantitative agreement with direct simulation Monte Carlo data, G13, and regularized 13-moment equations. The presence of non-zero radial and tangential heat fluxes, even when both the cylinders are at the same temperature, has been observed. The analysis helps us to demonstrate the ability of the recently derived equations in accurately solving complex rarefied flow problems. Moreover, understanding of higher-order rarefaction effects should greatly improve with the availability of closed-form analytical expressions of all physical quantities obtained here.

Study of the N126 dust bubble in the infrared wavelength range

In recent years, the researchof bubbles,partially circular structures in the interstellar medium, consisting of dust and gas, has received the considerable attention. The analysis of the structure and evolution of bubbles provides insight into the conditions under which stars and planets form inthe interstellar medium. Dust bubbles are inextricably linked with star formation regions and are powerful tools for studying the interaction of young stellar objects with their environment at various stages of evolution.The main goal of this articleisto study the region of the N126 dust bubble, search for and identify young stellar objects. Identification of young stellar objects by their fluxes at infrared wavelengths is relatively recent, and identification criteria are still at the stage of improvement. Therefore, in this article, the criteria for identifying young stellar objects were used according to the works of Koenig X.P. (2012), Koenig X.P. & Leisawitz D.V. (2014) and Fischer W.J. (2016), which are based on analysis of WISE observational datain the near-and mid-infrared bands W1 (3.4 μm), W2 (4.6 μm), W3 (12 μm), and W4 (22 μm). The datafrom the 2MASS and AllWISE catalogswith reliable non-zero fluxes of infrared radiation sourceswere used in that work. For the researched dust bubble, young stellar objects of class 0 (protostars) and class I were not detected. 4 objects of class II, 1 object of the class of transition disks and 48 objects of class III were identified. Energy distributions in the spectra for class II objectswere constructed, which also confirmed their evolutionary status. For all identified YSOs, color diagrams were constructed showing the locations of the found objects with their corresponding areas of evolution. Maps of the distribution of YSOs in space are analyzed, which indicate possible signs of an initiated star formation process in the N126 dust bubble.

Gyrokinetic turbulence modeling of a high performance scenario in JT-60SA

Local gyrokinetic simulations are used to model turbulent transport for the first time in a representative high-performance plasma discharge projected for the new JT-60SA tokamak. The discharge features a double-null separatrix, 41 MW of combined neutral beam heating and electron cyclotron heating, and a high predicted ratio of the normalized plasma kinetic to magnetic pressure β. When considering input parameters computed from reduced transport models, gyrokinetic simulations predict a turbulent heat flux well below the injected 41 MW. Increasing the background gradients, on the other hand, can trigger a non-zonal transition (NZT), causing heat fluxes to no longer saturate. Furthermore, when considering fast ions in the simulations, a high-frequency mode is destabilized that substantially impacts the turbulence. The NZT is avoided by reducing the electron pressure by 10% below its nominal value, and the fast-ion resonance is removed by reducing the fast-ion temperature. The thus-obtained simulation features broadband frequency spectra and density and temperature fluctuation levels δn/n≈1% –2%, δT/T≈1% –6% that should be measurable with fluctuation diagnostics planned for JT-60SA. The temperature profile is fixed by the critical main-ion temperature gradient as a consequence of the high stiffness; heat fluxes increase by a factor of ten when increasing the main ion temperature gradient by 17%. Despite large gradients, it is demonstrated that, due to the large β, retaining compressional magnetic field fluctuations and in particular, the contribution of the pressure gradient in the ∇B drifts, is crucial to achieving non-zero heat fluxes.

Von Neumann algebra description of inflationary cosmology

We study the von Neumann algebra description of the inflationary quasi-de Sitter (dS) space. Unlike perfect dS space, quasi-dS space allows the nonzero energy flux across the horizon, which can be identified with the expectation value of the static time translation generator. Moreover, as a dS isometry associated with the static time translation is spontaneously broken, the fluctuation in time is accumulated, which induces the fluctuation in the energy flux. When the inflationary period is given by (ϵHH)-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\epsilon _H H)^{-1}$$\\end{document} where ϵH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon _H$$\\end{document} is the slow-roll parameter measuring the increasing rate of the Hubble radius, both the energy flux and its fluctuation diverge in the G→0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$G \\rightarrow 0$$\\end{document} limit. Taking the fluctuation in the energy flux and that in the observer’s energy into account, we argue that the inflationary quasi-dS space is described by Type II∞\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_\\infty $$\\end{document} algebra. As the entropy is not bounded from above, this is different from Type II1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_1$$\\end{document} description of perfect dS space in which the entropy is maximized by the maximal entanglement. We also show that our result is consistent with the observation that the von Neumann entropy for the density matrix reflecting the fluctuations above is interpreted as the generalized entropy.

Impact of active and passive control of nanoparticles in ternary nanofluids across a rotating sphere

The anticipation around future technologies has sparked a keen interest in the study of fluid flows, which include the intricate interplay of several aspects. The design of rotating machinery, cooling of rotating machinery parts, and fiber coating, among other applications, have all given practical importance to the issue of fluid flow from rotating surfaces. This study examines the behavior of a ternary nanofluid over a rotating sphere. Combining Tiwari and Das’s model with Buongiorno’s model is considered for the flow model. When combined with the condition of non-zero normal flux, the zero normal flux of nanoparticles at the surface aims to push the particles away from the surface. Boundary layer equations are used to formulate the physical flow problem, and after that, by using the appropriate variables, these equations are transformed into dimensionless forms. Additionally, mathematical computation software helps in obtaining a numerical solution. Utilizing graphs, it has been determined how different physical flow parameters affect the profiles of velocity, temperature, and concentration. Further, the wall’s heat and mass transfer rates and the skin friction coefficient are graphically assessed and discussed. The outcomes show that increasing acceleration and rotational parameters increases primary velocity and surface drag force while decreasing secondary velocity, temperature, and concentration profiles. The concentration is reduced by Brownian and Schmidt's numbers while increasing for thermophoresis constraint. In both active and passive management of nanoparticles, the mass distribution rate improves for thermophoresis and Brownian parameters. Solid volume fraction improves the thermal distribution while declines the concentration.

Steady-state solutions for a reaction–diffusion equation with Robin boundary conditions: Application to the control of dengue vectors

AbstractIn this paper, we investigate an initial-boundary value problem of a reaction–diffusion equation in a bounded domain with a Robin boundary condition and introduce some particular parameters to consider the non-zero flux on the boundary. This problem arises in the study of mosquito populations under the intervention of the population replacement method, where the boundary condition takes into account the inflow and outflow of individuals through the boundary. Using phase plane analysis, the present paper studies the existence and properties of non-constant steady-state solutions depending on several parameters. Then, we prove some sufficient conditions for their stability. We show that the long-time efficiency of this control method depends strongly on the size of the treated zone and the migration rate. To illustrate these theoretical results, we provide some numerical simulations in the framework of mosquito population control.

Microscopic derivation of Ginzburg–Landau theory and the BCS critical temperature shift in general external fields

We consider the Bardeen–Cooper–Schrieffer (BCS) free energy functional with weak and macroscopic external electric and magnetic fields and derive the Ginzburg–Landau functional. We also provide an asymptotic formula for the BCS critical temperature as a function of the external fields. This extends our previous results in Deuchert et al. (Microscopic derivation of Ginzburg-Landau theory and the BCS critical temperature shift in a weak homogeneous magnetic field, PMP 4(1), 1–89 (2023)) for the constant magnetic field to general magnetic fields with a nonzero magnetic flux through the unit cell.

Non-self-adjoint model statement of boundary problem of acoustics. Part 1

Based on the mathematical definition of a non-self-adjoint operator and the physical meaning of a specific boundary value problem, a non-self-adjoint model statement of boundary value problems in acoustics is formulated. As an example, boundary value problems for the reflection of a plane wave and a spherical wave at the interface between two liquid media are considered. A new definition of the reflection coefficient of a spherical wave is introduced. In the region of subcritical angles of incidence, the new definition takes into account the appearance in the total sound field of converging recoil waves corresponding to the eigenfunctions of the adjoint operator. In the region of supercritical angles of incidence, the participation of the eigenfunctions of two conjugate operators in the total sound field forms a nonzero power flux through the interface and its transformation into the vortex component of the intensity vector at the total internal reflection horizon. The definition of the total internal reflection horizon is given. Experimental data are presented that confirm the new definition of the reflection coefficient and the physical correctness of the non-self-adjoint model statement.

Early Dark Energy in Type IIB String Theory

Early Dark Energy (EDE) is a promising model to resolve the Hubble Tension, that, informed by Cosmic Microwave Background data, features a generalization of the potential energy usually associated with axion-like particles. We develop realizations of EDE in type IIB string theory with the EDE field identified as either a C4 or C2 axion and with full closed string moduli stabilization within the framework of either KKLT or the Large Volume Scenario. We explain how to achieve a natural hierarchy between the EDE energy scale and that of the other fields within a controlled effective field theory. We argue that the data-driven EDE energy scale and decay constant can be achieved without any tuning of the microscopic parameters for EDE fields that violate the weak gravity conjecture, while for states that respect the conjecture it is necessary to introduce a fine-tuning. This singles out as the most promising EDE candidates, amongst several working models, the C2 axions in LVS with 3 non-perturbative corrections to the superpotential generated by gaugino condensation on D7-branes with non-zero world-volume fluxes.

Mathematical properties of optimal fluxes in cellular reaction networks at balanced growth.

The physiology of biological cells evolved under physical and chemical constraints, such as mass conservation across the network of biochemical reactions, nonlinear reaction kinetics, and limits on cell density. For unicellular organisms, the fitness that governs this evolution is mainly determined by the balanced cellular growth rate. We previously introduced growth balance analysis (GBA) as a general framework to model and analyze such nonlinear systems, revealing important analytical properties of optimal balanced growth states. It has been shown that at optimality, only a minimal subset of reactions can have nonzero flux. However, no general principles have been established to determine if a specific reaction is active at optimality. Here, we extend the GBA framework to study the optimality of each biochemical reaction, and we identify the mathematical conditions determining whether a reaction is active or not at optimal growth in a given environment. We reformulate the mathematical problem in terms of a minimal number of dimensionless variables and use the Karush-Kuhn-Tucker (KKT) conditions to identify fundamental principles of optimal resource allocation in GBA models of any size and complexity. Our approach helps to identify from first principles the economic values of biochemical reactions, expressed as marginal changes in cellular growth rate; these economic values can be related to the costs and benefits of proteome allocation into the reactions' catalysts. Our formulation also generalizes the concepts of Metabolic Control Analysis to models of growing cells. We show how the extended GBA framework unifies and extends previous approaches of cellular modeling and analysis, putting forward a program to analyze cellular growth through the stationarity conditions of a Lagrangian function. GBA thereby provides a general theoretical toolbox for the study of fundamental mathematical properties of balanced cellular growth.

Neoclassical transport in strong gradient regions of large aspect ratio tokamaks

We present a new neoclassical transport model for large aspect ratio tokamaks where the gradient scale lengths are of the size of the ion poloidal gyroradius. Previous work on neoclassical transport across transport barriers assumed large density and potential gradients but a small temperature gradient, or neglected the gradient of the mean parallel flow. Using large aspect ratio and low collisionality expansions, we relax these restrictive assumptions. We define a new set of variables based on conserved quantities, which simplifies the drift kinetic equation whilst keeping strong gradients, and derive equations describing the transport of particles, parallel momentum and energy by ions in the banana regime. The poloidally varying parts of density and electric potential are included. Studying contributions from both passing and trapped particles, we show that the resulting transport is dominated by trapped particles. We find that a non-zero neoclassical particle flux requires parallel momentum input which could be provided through interaction with turbulence or impurities. We derive upper and lower bounds for the energy flux across a transport barrier in both temperature and density and present example profiles and fluxes.

Modeling and simulation of zero-group velocity combined harmonic generated by guided waves mixing

In this paper, modelling and numerical perspective of zero-group velocity (ZGV) combined harmonic generated by guided waves mixing are investigated. The conditions for the generation of the ZGV combined harmonic are analyzed by S0-S0 and SH0-SH0 guided waves mixing in an isotropic plate, respectively. The generation of ZGV combined harmonics at sum frequency caused by counter-directional guided waves mixing is observed. It is confirmed that the ZGV combined harmonic with a considerable magnitude can be generated by this counter-directional guided waves mixing when both the internal resonant condition and non-zero power flux are satisfied. The application of generated ZGV combined harmonics for localized material degradation assessment is numerically examined in the given plate. The obtained results indicate that the generated ZGV combined harmonic induced by the counter-directional guided waves mixing can be used to assess the localized material degradation with improved signal-to-noise ratio. This study provides an insight into the physical process of the ZGV combined harmonic generation, and meanwhile offer a promising means for localized material degradation assessment by ZGV combined harmonics generated by guided waves mixing.