Radiation Heat Transfer in Thermal Argon Plasma with Iron Vapors

The objective of this paper consists of approximate calculations of thermal radiation heat transfer in ar-gon arc plasma with admixtures of iron vapors. As a mathematical tool, the P1-approximation has been used. To simplify the calculations, the frequency dependence of absorption coefficients has been handled by means of Planck and Rosseland averaging methods. Calculations has been performed for isothermal cylindrical plasma of various radii (0.01 to 10 cm) in temperature range 1 000 – 30 000 K

Objective Function for Numerical Mean Absorption Bands Optimization

Mean absorption coefficients (MACs) offer great potential for fast numerical calculation of radiation heat transfer. They are based on replacing complex absorption coefficient spectrum by a handful of frequency bands with a single, temperature dependent value assigned to each band. Accuracy of radiation transfer calculation thus depends on the accurate interpretation of the mean value inside each frequency band as well as on the proper band distribution. Yet finding optimal band distribution is not an easy task often requiring numerical optimization process. This contribution focuses on the parameters of such optimization process, namely selection of an objective function and its effect on the optimal band distribution. It demonstrates, that improper objective functions can produce physically unreasonable artifacts in the calculation of radiation heat transfer. Optimal formulation of the objective function is proposed in this contribution

Approximate Determination of Radiation Properties in the Arc Plasmas With Admixtures of Copper Vapours

The aim of this paper is to evaluate radiation properties of air arc plasmas with various admixtures of copper vapours. The first order of the method of spherical harmonics (P1-approximation) has been used as the way to solve the equation of radiation transfer. Calculations of the absorption coefficients for a thermal plasma have been performed as a function of the temperature and the frequency. The frequency variable in the equation of transfer was handled by means of multigroup method. Methods for prediction of the average absorption coefficients were described and compared in detail. The net emission coefficients have been determined for comparison

Radiation Transfer in Arc Plasmas

In this paper, attention has been given to the absorption properties of the arc plasma at the different pressure conditions. Calculations of the absorption coefficients for a thermal plasma have been performed as a function of the temperature and the frequency. Methods for prediction of the average absorption coefficients were described and compared in detail

Optimization of 3-band Mean Absorption Coefficients

In this paper we present a process for mean absorption coefficient optimal band selection applied to the 3-band model of radiation in an air electrical arc. For fixed temperature, the divergence of radiation flux in an infinite cylindrical plasma column is calculated using spectrally resolved absorption coefficient and serves as a reference value. Optimization process is used to properly select the bands of 3-band mean absorption approximation using both unmodified and limited Planck mean absorption coefficient. The ac-curacy of aforementioned two approximation methods is evaluated

Modelling of Radiative Transfer in Air Arc Plasma

The objective of this work is to compare the accuracy of several approximate models of radiative properties for the prediction of radiative transfer in air arc plasma at the temperatures in the range of 300 - 25 000 K and the pressure of 0.1 MPa. Calculated absorption coefficients are used to generate the parameters of different models. The radiative transfer inside the cylindrically symmetrical air plasma with prescribed temperature profile was studied. The equation of radiative transfer was solved using the P1 and SP3 approximations, calculated radiative source term in the energy equation (net emission) was compared with results obtained by spectral integration

Consistency tests of AMPCALCULATOR and chiral amplitudes in SU(3) Chiral Perturbation Theory: A tutorial based approach

Ampcalculator is a Mathematica based program that was made publicly available some time ago by Unterdorfer and Ecker. It enables the user to compute several processes at one-loop (upto $O(p^4)$) in SU(3) chiral perturbation theory. They include computing matrix elements and form factors for strong and non-leptonic weak processes with at most six external states. It was used to compute some novel processes and was tested against well-known results by the original authors. Here we present the results of several thorough checks of the package. Exhaustive checks performed by the original authors are not publicly available, and hence the present effort. Some new results are obtained from the software especially in the kaon odd-intrinsic parity non-leptonic decay sector involving the coupling $G_{27}$. Another illustrative set of amplitudes at tree level we provide is in the context of $\tau$-decays with several mesons including quark mass effects, of use to the BELLE experiment. All eight meson-meson scattering amplitudes have been checked. Kaon-Compton amplitude has been checked and a minor error in published results has been pointed out. This exercise is a tutorial based one, wherein several input and output notebooks are also being made available as ancillary files on the arXiv. Some of the additional notebooks we provide contain explicit expressions that we have used for comparison with established results. The purpose is to encourage users to apply the software to suit their specific needs. An automatic amplitude generator of this type can provide error-free outputs that could be used as inputs for further simplification, and used in varied scenarios such as applications of chiral perturbation theory at finite temperature, density and volume. This can also be used by students as a learning aid in low-energy hadron dynamics.Comment: 25 pages, plain latex, corresponds to version to appear in EPJA, additional ancillary files adde

Discrete breathers in nonlinear lattices: Experimental detection in a Josephson array

We present an experimental study of discrete breathers in an underdamped Josephson-junction array. Breathers exist under a range of dc current biases and temperatures, and are detected by measuring dc voltages. We find the maximum allowable bias current for the breather is proportional to the array depinning current while the minimum current seems to be related to a junction retrapping mechanism. We have observed that this latter instability leads to the formation of multi-site breather states in the array. We have also studied the domain of existence of the breather at different values of the array parameters by varying the temperature.Comment: 5 pages, 5 figures, submitted to Physical Revie