Including Radiation Losses Research Articles

Geodesics and gravitational waves in chaotic extreme-mass-ratio inspirals: the curious case of Zipoy-Voorhees black-hole mimickers

Due to the growing capacity of gravitational-wave astronomy and black-hole imaging, we will soon be able to emphatically decide if astrophysical dark objects lurking in galactic centers are black holes. Sgr A*, one of the most prolific astronomical radio sources in our galaxy, is the focal point for tests of general relativity. Current mass and spin constraints predict that the central object of the Milky Way is supermassive and slowly rotating, thus can be conservatively modeled as a Schwarzschild black hole. Nevertheless, the well-established presence of accretion disks and astrophysical environments around supermassive compact objects can significantly deform their geometry and complicate their observational scientific yield. Here, we study extreme-mass-ratio binaries comprised of a minuscule secondary object inspiraling onto a supermassive Zipoy-Voorhees compact object; the simplest exact solution of general relativity that describes a static, spheroidal deformation of Schwarzschild spacetime. We examine geodesics of prolate and oblate deformations for generic orbits and reevaluate the non-integrability of Zipoy-Voorhees spacetime through the existence of resonant islands in the orbital phase space. By including radiation loss with post-Newtonian techniques, we evolve stellar-mass secondary objects around a supermassive Zipoy-Voorhees primary and find clear imprints of non-integrability in these systems. The peculiar structure of the primary, allows for, not only typical single crossings of transient resonant islands, that are well-known for non-Kerr objects, but also inspirals that transverse through several islands, in a brief period of time, that lead to multiple glitches in the gravitational-wave frequency evolution of the binary. The detectability of glitches with future spaceborne detectors can, therefore, narrow down the parameter space of exotic solutions that, otherwise, can cast identical shadows with black holes.

Development of a Loss Method for Energy and Exergy Audit of Condensing Hot Water Boilers

Abstract Condensing boilers are used in commercial and residential buildings extensively. In this article, a loss method is proposed to estimate the energy and exergy efficiencies of condensing hot water boilers. The presented method is based on the development of the method presented in ASME PTC 4.1. Energy loss terms consist of exhaust flue gas, carbon monoxide formation, radiation, and condensate outflow sensible heat. Exergy loss terms also include radiation losses, physical exergy of the exhaust flue gas, chemical exergy of the exhaust flue gas, increase in the chemical exergy of the flue gas due to carbon monoxide formation, condensate outflow exergy, boiler exergy destruction, and economizer exergy destruction. Energy and exergy efficiencies are calculated by estimation of these loss terms. To depict the method’s capability and compare results with the direct method, an experimental setup was designed and constructed. Results of energy and exergy audition of the boiler by applying the loss method are compared with the direct method. The results show that, although the condensing economizer improves energy efficiency, it does not improve the exergy efficiency significantly. The energy and exergy efficiencies were 98.65% and 5.14%, respectively.

Mathematical Modelling of the Thermal State of a Ladle During Arc Heating of the Melt

The paper analyzes energy losses in the ladle furnace. In particular, the authors focus on electrical losses, namely total energy losses of the electric arc, conditionally including radiation losses of a part of the arc uncovered by slag. Managing these flows creates conditions for increasing the efficiency of heating. The calculations given in the paper showed that electrical losses decreased, during prolonged heating (about 8-12 minutes) with a sufficient amount of slag. This mode provides a reduction in heat loss by 4-5 %. By selecting options of changes in a sequence of stages and their duration, the proposed mathematical model makes it possible to apply a new technology to process molten steel in the ladle furnace characterized by lower power consumption.

The combustion of iso-octane droplets with initial diameters from 0.5 to 5 mm: Effects on burning rate and flame extinction

The burning characteristics of iso-octane droplets in the standard atmosphere are reported over a large range of initial droplet diameters (0.5mm<Do< 5mm) for near one-dimensional droplet flames as promoted by low gravity. A ground-based drop tower and a space-based platform (International Space Station) were used to provide an environment to examine the influence of Do that encompasses regimes where radiation does not have an effect on burning to where it does. For Do< 2.7mm, the droplets burned to completion without extinction. Larger droplets evidenced extinction due to radiative emissions from the flames to the ambience that produced a two stage burning process. The burning rate (K) was nearly constant in the first stage and then gradually decreased. Concurrently, radiation emissions dropped by two orders of magnitude and ‘flickering’ flames were noted during the transition. After extinction, burning entered a regime where K gradually decreased with time and approached values commensurate with evaporation in a heated environment (i.e., no combustion). Energy balances based on scale analyses related K and flame temperature (Tf) to Do: a balance at the flame including radiation losses led to the scaling K ∼ Do−n in reasonable agreement with the data for Do> 2mm; an energy balance at the droplet surface showed that Tf quickly dropped from ∼1600K to ∼700K after flame extinction, followed by a gradual reduction of Tf to near ambient temperature. The trends in the data are also discussed for potentially revealing a possible low temperature combustion regime.

Analytical Model for the Rectangular Power-Ground Structure Including Radiation Loss

An accurate analytical model to predict via coupling within rectangular power-return plane structures is developed. Loss mechanisms, including radiation loss, dielectric loss, and conductor loss, are considered in this model. The radiation loss is incorporated into a complex propagating wavenumber as an artificial loss mechanism. The quality factors associated with three loss mechanisms are calculated and compared. The effects of radiation loss on input impedances and reflection coefficients are investigated for both high-dielectric-loss and low-dielectric-loss printed circuit boards. Measurements are performed to validate the effectiveness of this model.

Wind-aided flame spread under oblique forced flow

The wind-aided flame spread process along a solid fuel rod under oblique forced flow is analyzed in absence of gravity or when the forced flow dominates the gravity-induced flow. The transverse velocity is large enough to ensure that mixing of the fuel vapors and air occurs in a thin boundary layer surrounding the fuel rod and we can use the boundary layer approximation to describe the gas-phase chemical reaction and downwind flame spread process. A global, second-order, Arrhenius expression is employed to describe the gas-phase reaction, while the solid surface gasification reaction is modeled in terms of a constant pyrolysis temperature. The solid is heated by the hot gases convected from the flame by the axial component of the velocity in the direction of the flame spread. The solid will be considered thermally thick, assuming the thickness of the heated layer in the solid to be small compared with the rod radius. The analysis determines the flame spread velocity and the flow structure in the flame front region. The analysis also shows that flame spread is not possible at large flow velocities due to finite rate effects, while at low velocities the gas-phase reaction is diffusion-controlled. By including radiation losses from the surface a flame spread limit, at low velocities, is also found in the present analysis.

A variational coupled-mode theory including radiation loss for grating-assisted couplers

We calculate higher order effects such as frequency shifts and radiation loss in grating waveguides and grating couplers. The approach follows a vector variational principle which incorporates the Floquet components correct to first order. It is unnecessary to bring radiation modes into the formalism. This yields a simple coupled-mode formulation which includes attenuation due to radiation loss, and is correct to third order in the index contrast of the grating. Numerous examples are given which show excellent agreement with rigorous numerical simulations.

MHD modelling of density limit disruptions in tokamaks

The magnetohydrodynamic (MHD) activity during density limit disruptions in tokamaks is modelled numerically by three-dimensional resistive reduced MHD simulations with a simple transport model including radiation losses. The simulations reproduce experimentally observed phenomena such as the destabilization of MHD modes near the plasma edge during the early profile contraction phase, followed by growth of the m = 2/n = 1 mode to large amplitude, a sequence of minor disruptions and the major disruption. A new theoretical model is given for the major disruption, which takes place in two phases: (1) an internal relaxation flattens the temperature in the central part of the discharge and (2) the current profile broadens. The internal instability of the first phase has a mainly m = 1/n = 1 convection pattern, but, because of non-linear coupling to the large m = 2/n = 1 mode, the magnetic perturbation has a strong m = 3/n = 2 component. During the internal relaxation, the large amplitude 2/1, 1/1 and 3/2 perturbations break up the magnetic surfaces isolating the q ≈ 1 region from the stochastic region around q = 2, and the magnetic field becomes stochastic in the entire q ≤ 2 region. In the second phase of the major disruption, MHD turbulence first develops on the stochasticized fields, resulting in current filamentation, initially in the central region where q ≤ 2. This leads to a broadening of the central current profile and a strong instability of the 2/1 mode. The disruption ends with rapid growth of the m > 2/n = 1 modes. The result is stochastic magnetic fields across the entire plasma and a large scale broadening of the current profile.

Calculation of Soft X-Ray Output from Neon Plasma of Z-Pinch Devices using a Magnetohydrodynamic Model, Including Radiation Loss

Calculation of Soft X-Ray Output from Neon Plasma of Z-Pinch Devices using a Magnetohydrodynamic Model, Including Radiation Loss

Characteristics of an electrical discharge with full ionization of seed

The characteristics of an electrical discharge in potassium seeded argon were investigated experimentally. Experiments were carried out using a cylindrical glass tube filled with low pressure potassium seeded argon. A current was applied from a.d.c. power supply. Discharge characteristics, such as electrical conductivity, electron temperature, diameter and radial distribution of the line spectrum were measured for various discharge currents. The measured electrical conductivity has shown good agreement with calculated results obtained on the basis of the two-temperature model, including radiation loss. The measured electron temperatures also agreed with the results of calculations for high current densities. It is found that the discharge fills the entire cross section of the tube when the seed is fully ionized, and at the same time, the discharge becomes quite uniform, except near the tube wall, even for high current densities.

Characterization of microstrip discontinuities on multilayer dielectric substrates including radiation losses

A two-dimensional space-domain method-of-moments treatment of open microstrip discontinuities on multi-dielectric-layer substrates is presented. The full-wave analysis accounts for electromagnetic coupling, radiation, and all substrate effects. The technique is utilized to characterize commonly used discontinuities on one and two dielectric layers, and numerical results for step, corner, and T-junction discontinuities are included. On the microstrip conductors, both current components are expanded by rooftop basis functions. Once the current distribution is evaluated, transmission line theory is used to determine the network parameters. Numerical results from this technique demonstrate excellent agreement with measurement and the spectral-domain technique in the case of single dielectric layers. >

X-ray generation in a cavity heated by 1.3- or 0.44- microm laser light. III. Comparison of the experimental results with theoretical predictions for x-ray confinement.

Radiation confinement in laser-heated gold cavities is analyzed on the basis of self-similar solutions of the hydrodynamic equations. The analysis is extended to include radiation losses through holes in the cavity. The possibility that a conversion layer on the inner wall of the cavity contributes to the measured radiation is also taken into account. The comparison with experiments performed at laser wavelengths of 0.44 and 1.3 \ensuremath{\mu}m with the Asterix iodine laser shows reasonable agreement with the theoretical predictions. The major difficulty in the comparison is the lack of detailed information about the conversion of laser light into x rays, especially in the 1.3-\ensuremath{\mu}m experiments.

Propagating-beam model for a single-mode-fibre fused coupler

A scalar two-dimensional analysis of a single-mode-fibre fused coupler is presented. Two theoretical models (one analytical and one numerical) are implemented and compared. The first model is based on the mode coupling in the central cross-section of the coupler, the second model employs the propagating-beam algorithm (PBA). Contrary to the analytical model, the PBA is suited to the analysis of the transition from guidance by the core to guidance by the cladding taking place in the tapers, including radiation loss. The influence of the external refractive index on the power transfer is investigated. The results obtained are in qualitative agreement with the experiments presented by Hill et al.

Effect of radiation losses on scaling laws in laser-produced plasmas

The effect of radiation losses in determining scaling laws of electron temperature on laser flux Φ is discussed for moderate Z plasmas created by lasers in the flux range 1011–1013 W/cm.2 Temperature scaling slower and faster than Φ4/9, observed by various authors, is explained by including radiation losses in a self-regulatory model. Results of experiments on carbon plasma produced by 1-GW, 5-nsec Nd: glass laser show temperature scaling Φ0.25 and Φ0.75 , and are in good agreement with the predicted behavior.

Method of Analysis of Planar Networks Including Radiation Loss

A general approach to the analysis of microwave planar structures, specifically intended to account for radiation loss is presented. By expanding the internal electromagnetic (EM) field in terms of resonant modes, also the external field is obtained in the form of a series, each term of which corresponds to the field radiated by a resonant mode excited in the structure. Neglecting the effect of the thin dielectric substrate on the power radiated and the coupling between the modes, occurring at the lateral surface of the structure, a simplified formulation is obtained which is shown to be in very good agreement with experiments, performed in the frequency range 2-12.4 GHz, which could not be explained on the basis of a Iossless model.