Calculation Of Effective Cross Sections Research Articles

A Simple Method for the Design of Aluminium Structures

Deflections at the serviceability limit state are often decisive in the design of aluminium structures due to the low elastic modulus. Where design is based on deflections, it may not be necessary to calculate the resistance exactly and simple conservative methods are sufficient. The proposed method may be used to generate a quick, approximate and safe solution, perhaps for the purpose of initial member sizing, with the opportunity to refine the calculation for final design. Another reason for the simple method is enhancing ease of use of Eurocode 9.The principal of the proposed method is to eliminate calculation of effective cross-sections by reducing the elastic resistance with the reduction factor for the most slender part of the cross-section or the factor for HAZ softening whichever is less. This means that you don’t need to define the cross-section class. The disadvantage is that you don’t utilize the plastic reserve for class 1 and 2 cross-sections, nor the redistribution of stresses in the post-buckling range of class 4 cross-sections or sections with HAZ. The procedure is similar to the method with permissible stresses familiar to most engineers.

Molecular Dynamics Simulation for the Dynamics and Kinetics of Folding Peptides in the Gas Phase.

The conformations of flexible molecular species, such as oligomers and oligopeptides, and their interconversion in the gas phase have been probed by ion mobility spectrometry measurements. The ion motion is interpreted through the calculation of effective cross sections in the case of stable conformations of the macromolecules. However, when the molecular structures transform to each other as the ions collide with gas atoms during their flight through the drift tube, the introduction of an average cross section is required. To provide a direct way for the reproduction of the ion motion, we employ a nonequilibrium molecular dynamics simulation method and consider a molecular model that consists of two connected stiff cylindrical bodies interacting through an intramolecular model potential. With this procedure we have calculated the ion mobility as a function of temperature for a prototype peptide that converts between a helical and an extended globular form. The results are in good agreement with ion mobility spectrometry data confirming that an angular vibration coordinate can be used for the interpretation of the shifting of the drift-time distributions at high temperatures. The approach produces mean kinetic energies as well as various combined distributions of the ion degrees of freedom. It is easily applied to flexible macromolecular ions and can be extended to include additional degrees of freedom.

Improvement of Neutronics Calculation Methods for Fast Reactors

To accurately estimate neutronics properties of fast reactors, particularly Japan Sodium-cooled Fast Reactor of 1,500 MW electric, calculational methods are being improved in Japan. This paper describes the planning and the ongoing development of the neutronics calculation methods in the field of 1) assembly calculations including the calculations of effective cross sections, 2) core calculations and 3) uncertainty evaluation and uncertainty reduction.

Photon production through multi-step processes important in nuclear resonance fluorescence experiments

We present calculations describing the production of photons through multi-step processes occurring when a beam of gamma-rays interacts with a macroscopic material. These processes involve the creation of energetic electrons through Compton scattering, photo-absorption and pair production, the subsequent scattering of these electrons, and the creation of energetic photons occurring as these electrons are slowed through Bremsstrahlung emission. Unlike single Compton collisions, during which an energetic photon that is scattered through a large angle loses most of its energy, these multi-step processes result in a sizable flux of energetic photons traveling at large angles relative to an incident photon beam. These multi-step processes are also a key background in experiments that measure nuclear resonance fluorescence by shining photons on a thin foil and observing the spectrum of back-scattered photons. Effective cross sections describing the production of back-scattered photons are presented in a tabular form that allows simple estimates of backgrounds expected in a variety of experiments. Incident photons with energies between 0.5MeV and 8MeV are considered. These calculations of effective cross sections may be useful for those designing NRF experiments or systems that detect specific isotopes in well-shielded environments through observation of resonance fluorescence.

A comparison between classical trajectory and infinite-order sudden calculations of transport and relaxation cross sections for N2-Ne mixtures

Classical trajectory calculations of effective cross sections have been carried out for the N2-Ne system using the recent HFD3(N2-Ne) potential surface of McCourt et al. Forty-five such cross sections governing a wide variety of transport and relaxation phenomena in binary gaseous mixtures have been calculated at a number of temperatures ranging from 77K to 1100K. Wherever possible, we have made comparisons with much cheaper infinite-order sudden approximation (IOSA) calculations in order to assess their reliability. For cross sections relating to diffusion and viscosity, IOSA errors are less than 5·4 per cent, but, for cross sections which vanish for isotropic interactions, the IOSA is much less reliable, with possible errors of up to a factor of two. At the same time, we have compared our classical trajectory results for this surface with available experimental results. We find that the HFD3(N2-Ne) surface is too anisotropic, by as much as 20 per cent.

Close-coupling calculations of transport and relaxation cross sections for H2 in Ar

Close-coupling calculations of effective cross sections for transport and relaxation processes in Ar+H2 mixtures are performed, using both the recent TT3(6,8) potential of Le Roy and Hutson and the older BC3(6,8) potential of Carley and Le Roy. The cross sections calculated are those involved in sound absorption, thermal diffusion, shear viscosity, pressure broadening and shifting of rotational Raman lines, depolarized Rayleigh light scattering, nuclear magnetic relaxation, and the Senftleben–Beenakker effects. Comparisons with experimental results are made wherever possible.

Covariant calculation of effective cross sections in quantum electrodynamics. II

Covariant calculation of effective cross sections in quantum electrodynamics. II

Covariant calculation of effective cross sections in quantum electrodynamics. I

Equations are derived for expressing the exchange terms of an S-matrix element in terms of nonexchange terms. There is a discussion of a method for transforming from the matrix element to the effective cross section in which the cross section can be obtained in explicitly covariant form.

Calculation of Effective Cross Section in Doppler Resonance Region of Large Fast Reactor

Calculation of Effective Cross Section in Doppler Resonance Region of Large Fast Reactor

Calculation of Effective Cross Section in Doppler Resonance Region of Large Fast Reactor

Calculation of Effective Cross Section in Doppler Resonance Region of Large Fast Reactor