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[en] Highlights: • The PaSR-based soot model proposed by the authors’ group has been further improved. • The present model is physically more sound. • The improved model has been implemented into the in-house version of the FireFOAM code. • New formulas have been proposed to compute characteristic time for soot formation and oxidation. • The predictions have achieved improved agreement with the experimental measurements. - Abstract: The extension of the laminar smoke point based approach to turbulent combustion using the partially stirred reactor (PaSR) concept proposed by Chen et al. (2014) has been further improved to overcome the limitation in the formulations of Chen et al. (2014) which assumed infinitely fast soot oxidation chemistry and constant soot formation characteristic time. In the PaSR approach, each computational cell is split into two zones: the reacting zone and the non-reacting zone. Soot formation and oxidation are assumed to take place at finite rates in the reacting zone and computed from the corresponding laminar rates and the mass fractions for soot formation and oxidation, which are evaluated in each computational cell from the characteristic time scales for turbulent mixing, soot formation and oxidation. Since soot would be produced in not only the fine structures but also surrounding fluids in the Eddy-Dissipation-Concept (EDC) model, the average field parameters between the fine structure and surrounding fluid are employed instead of those Favre-averaged values in Chen et al.’s soot formation model. The newly extended model has been implemented in FireFOAM, a large eddy simulation (LES) based solver for fire simulation based on the open source CFD code OpenFOAM®. Numerical simulations of a 30 cm diameter heptane and toluene pool fires tested by Klassen and Gore (1992) were performed for validation. The predicted soot volume fraction and temperature have achieved improved agreement with the experimental measurements in comparison with that of Chen et al. (2014), demonstrating the potential of the improved PaSR-based soot model for fire applications.
[en] The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different electronic structure methods for core excitations. We report high resolution experimental measurements performed at the SOLEIL synchrotron facility. These are compared with theoretical spectra calculated using coupled cluster theory and algebraic diagrammatic construction theory. The coupled cluster singles and doubles with perturbative triples model known as CC3 is shown to accurately reproduce the experimental excitation energies as well as the spacing of the vibrational transitions. In conclusion, the computational results are also shown to be systematically improved within the coupled cluster hierarchy, with the coupled cluster singles, doubles, triples, and quadruples method faithfully reproducing the experimental vibrational structure.
[en] The X-ray absorption coefficient of niobium in the energy range 18.5-19.7 keV around the k-edge is measured using scanning EXAFS synchrotron radiation source. The discrepancies between the measured absorption coefficients and alternative theoretical predictions are discussed. (author)
[en] Extended X-ray absorption fine structure data at the K-edge for three cobalt compounds viz., cobalt sulphate (I), cobalt nitrate (II) and cobalt chloride (III) have been analyzed for the estimation of phase parameters alpha1, beta1 and delta1. On the basis of our studies it may be concluded that backscattering phase shift and the total phase shift varies with the change in ligands. The total phase shift values for the presently studied compounds exhibit a linear variation with wave vector k. Average bond distances have been obtained for the samples studied using Levy's and Lytle, Stern, Sayers (LSS) method. The present method of determination of phase parameters using the graphical technique is simple and comparable to the other theoretical methods. (author)
[en] In this paper total mass attenuation coefficient (MAC) for compounds Lanthanum oxide and Lanthanum sulphate, at different X-ray energies were measured. The results compared with theoretical values, agreement found to be good when the incident photon energy is far below and away from the L edge, disagreement is observed near L absorption edges. The mass attenuation co-efficient for a compound is computed using the mixture rule, is given by μ/ρ = Σ ωi (μ/ρ)i. Where ωi is the proportion by weight if the ith element present in the compound and (μ/ρ)i is the mass attenuation coefficient of the ith constituent element of the compound. For a chemical compound ωi can be written as, ωi = ai Ai / Σ(aj Aj). Ai is the atomic weight of the ith element and aj is the number of formula units
[en] Energy levels, line strengths, oscillator strengths, radiative decay rates and fine structure collision strengths are presented for six-times ionized krypton (Kr VII). The atomic data are calculated with the AUTOSTRUCTURE code, where relativistic corrections are introduced according to the Breit-Pauli distorted wave approach. We present calculations of atomic data for 40 fine-structure levels generated from nine configurations ((1s22s22p63s23p63d10)4s2, 4lnl, n = 4, 5; l = 0, 1; and l′ ≤ 3) of the Zn-like Kr ion. Fine structure collision strengths for transitions from the ground and the first four excited levels are presented at six electron energies: 8, 15, 30, 45, 60, and 80 Ryd. Our atomic structure data are compared with the available experimental and theoretical results. (author)
[en] Application of a linear combination of the Lorentzian function and its square has led to better description of Mössbauer spectra obtained using a resonance detector, compared with description using a simple Lorentzian. Mathematical fitting and description of the spectra were done for solid solutions based on beryllium with 0.09–0.80 wt.% iron. The fine structure parameters for the solid solutions match literature data. We discuss some features of using the method for fast processing of experimental spectra.
[en] An optical quantum thermometer with a submicron spatial resolution that is based on the physical phenomenon of optical response in the system of spin centers in silicon carbide under conditions of cross-relaxation between the optically active centers in quadruplet spin state and triplet centers, where there is anomalously strong dependence of the splitting of the fine structure on temperature, has been proposed.
[en] The XIV International conference «Moessbauer spectroscopy and applications» was held from September 28 to October 1, 2016, in Kazan. The conference is another in the cycle of traditional All-Russian (All-Union) international scientific conferences devoted to the study of ultrathin interactions in condensed media using the Moessbauer spectroscopy method. An opportunity has been provided for Russian scientists and their foreign colleagues to discuss the latest achievements in the field of gamma-radiation interaction with matter. The subject of discussion was the fundamental and applied results obtained in condensed matter physics using Moessbauer and synchrotron radiation. The works carried out by NMR and NQR in solid state physics and chemistry were considered
[ru]XIV Международная конференция «Мессбауэровская спектроскопия и ее применения» состоялась с 28 сентября по 1 октября 2016 года в г. Казань. Конференция является очередной в цикле традиционных Всероссийских (Всесоюзных) международных научных конференций, посвященных исследованиям сверхтонких взаимодействий в конденсированных средах методом мессбауэровской спектроскопии. Предоставлена возможность российским ученым и их зарубежным коллегам обсудить последние достижения в области взаимодействия гамма-излучения с веществом. Предметом обсуждения явились фундаментальные и прикладные результаты, полученные в физике конденсированного состояния с использованием мессбауэровского и синхротронного излучения. Рассматривались работы, выполненные методами ЯМР и ЯКР в физике и химии твердого тела
[en] Quantum electrodynamics is the theory that describes the interaction of particles with electromagnetic fields. As soon as 1940 the study of the energy levels of the hydrogen atom and of the anomaly of the electron's gyromagnetic ratio were at the origin of quantum electrodynamics. Today measurements performed on simple atomic systems allow the testing of this theory predictions at a very high level of accuracy: about 3*10-10 for the electron magnetic moment anomaly, and about 7*10-10 for the fine structure constant. The experimental setting for the measurement of the 1S-3S, 205 nm transition of the hydrogen atom is detailed, this measurement has allowed a new determination of the value of the proton radius: 0.877 fm. This new value disagrees with the value previously deduced from the muonic hydrogen (0.84087 fm). Another experimental setting is presented, it allows the measurement of the ℎ/electron mass ratio through the measurement of the recoil velocity of the rubidium atom when this atom absorbs a photon. In both experiments measurement are turned into measurements of optical frequencies. (A.C.)