949 resultados para oscillator strengths


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Energy levels and radiative rates (. A-values) for transitions in Cr-like Cu VI and Zn VII are reported. These data are determined in the quasi-relativistic approach (QR), by employing a very large configuration interaction (CI) expansion which is highly important for these ions. No radiative rates are available in the literature to compare with our results, but our calculated energies are in close agreement with those compiled by NIST and other available theoretical data, for a majority of the levels. The A-values (and resultant lifetimes) are listed for all significantly contributing E1, E2 and M1 radiative transitions among the energetically lowest 322 levels of each ion.

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We report calculations of energy levels and radiative rates (A-values) for transitions in Cr-like Co IV and Ni V. The quasi-relativistic Hartree-Fock (QRHF) code is adopted for calculating the data although grasp (general-purpose relativistic atomic structure package) and flexible atomic code (fac) have also been employed for comparison purposes. No radiative rates are available in the literature to compare with our results, but our calculated energies are in close agreement with those compiled by NIST for a majority of the levels. However, there are discrepancies for a few levels of up to 3%. The A-values are listed for all significantly contributing E1, E2 and M1 transitions, and the corresponding lifetimes reported, although unfortunately no previous theoretical or experimental results exist to compare with our data.

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Calculations of energy levels, radiative rates and lifetimes are reported for eight ions of tungsten, i.e. S-like (W LIX) to F-like (W LXVI). A large number of levels have been considered for each ion and extensive configuration interaction has been included among a range of configurations. For the calculations, the general-purpose relativistic atomic structure package (. grasp) has been adopted, and radiative rates (as well as oscillator strengths and line strengths) are listed for all E1, E2, M1, and M2 transitions of the ions. Comparisons have been made with earlier available experimental and theoretical energies, although these are limited to only a few levels for most ions. Therefore for additional accuracy assessments, particularly for energy levels, analogous calculations have been performed with the flexible atomic code (. fac).

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Energies and lifetimes are reported for the eight Br-like ions with 43≤Z≤50, namely Tc IX, Ru X, Rh XI, Pd XII, Ag XIII, Cd XIV, In XV, and Sn XVI. Results are listed for the lowest 375 levels, which mostly belong to the 4s24p5, 4s24p44ℓ, 4s4p6,4s24p45ℓ, 4s24p34d2, 4s4p54ℓ, and 4s4p55ℓ configurations. Extensive configuration interaction among 39 configurations (generating 3990 levels) has been considered and the general-purpose relativistic atomic structure package (grasp) has been adopted for the calculations. Radiative rates are listed for all E1, E2, M1, and M2 transitions involving the lowest 375 levels. Previous experimental and theoretical energies are available for only a few levels of three, namely Ru X, Rh XI and Pd XII. Differences with the measured energies are up to 4% but the present results are an improvement (by up to 0.3 Ryd) in comparison to other recently reported theoretical data. Similarly for radiative rates and lifetimes, prior results are limited to those involving only 31 levels of the 4s24p5, 4s24p44d, and 4s4p6 configurations for the last four ions. Moreover, there are generally no discrepancies with our results, although the larger calculations reported here differ by up to two orders of magnitude for a few transitions.

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Calculations of energy levels, radiative rates and lifetimes are reported for 17 F-like ions with 37≤Z≤53. For brevity, results are only presented among the lowest 113 levels of the 2s22p5, 2s2p6, 2s22p43ℓ, 2s2p53ℓ, and 2p63ℓ configurations, although the calculations have been performed for up to 501 levels in each ion. The general-purpose relativistic atomic structure package (grasp) has been adopted for the calculations, and radiative rates (along with oscillator strengths and line strengths) are listed for all E1, E2, M1, and M2 transitions of the ions. Comparisons are made with earlier available experimental and theoretical energies, although these are limited to only a few levels for most ions. Therefore for additional accuracy assessments, particularly for energy levels, analogous calculations have been performed with the Flexible Atomic Code (fac), for up to 72 259 levels. Limited previous results are available for radiative rates for comparison purposes, and no large discrepancy is observed for any transition and/or ion.

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Luminescent excitation spectra were measured for the F and M centers in KCl; in particular, for the F band, M band, and the M2 transition. In all 3 cases, the spectra were nearly double-Gaussian in shape, and the efficiency for luminescence was nearly independent of the wavelength of the exciting light. A comparison of the absorption spectrum with the excitation spectrum of the F-band region of crystals with M centers present and oriented provided further evidence for the existence of the M2 transition of van Doorn and Haven and of Okamoto, and against the energy transfer theory of Lambe and Compton. The efficiency for luminescence of the M center upon M-band excitation was equal to the efficiency for F centers in pulse-annealed crystals of low F-center concentrations. The ratio of the efficiencies of the Ml to M2 transitions was 1.2 ± .25. The oscillator strengths of 3 of the M-center transitions in KCl relative to the oscillator strength for the F center were found to be in better agreement with the results reported by Okamoto, than with the results reported by Delbecq. The polarization of luminescence of M centers in KCl was measured at right angles to the exciting light, and was found to agree with the predictions of the van Doorn-Haven model of the M center. In NaF crystals having no absorption bands to the red side of the M band, the absorption and excitation spectra of the M band were accurately double-Gaussian over a wide range of wavelengths; the efficiency of luminescence of the M center was independent of the wavelength of the exciting light in that range; and the polarization of luminescence upon M-band excitation agreed well with the calculations based on the van DoornHaven model of the M center, In crystals in which the F band was bleached sufficiently to make it smaller in absorption height than the M band, several new color centers appeared on the red side of the M band, in contrast to the results reported by Blum; in these crystals, the polarization of luminescence of the M center upon M-band excitation disagreed strongly with theory, even though the absorptions for the new color centers were small compared to the M-band absorption.

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The Shifman-Vainshtein-Zakharov method of determining the eigenvalues and coupling strengths, from the operator product expansion, for the current correlation functions is studied in the nonrelativistic context, using the semiclassical expansion. The relationship between the low-lying eigenvalues, and the leading corrections to the imaginary-time Green function is elucidated by comparing systems which have almost identical spectra. In the case of an anharmonic oscillator it is found that with the procedure stated in the paper, that inclusion of more terms to the asymptotic expansion does not show any simple trend towards convergence to the exact values. Generalization to higher partial waves is given. In particular for the P-level of the oscillator, the procedure gives poorer results than for the S-level, although the ratio of the two comes out much better.

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In this paper, the classic oscillator design methods are reviewed, and their strengths and weaknesses are shown. Provisos for avoiding the misuse of classic methods are also proposed. If the required provisos are satisfied, the solutions provided by the classic methods (oscillator start-up linear approximation) will be correct. The provisos verification needs to use the NDF (Network Determinant Function). The use of the NDF or the most suitable RRT (Return Relation Transponse), which is directly related to the NDF, as a tool to analyze oscillators leads to a new oscillator design method. The RRT is the "true" loop-gain of oscillators. The use of the new method is demonstrated with examples. Finally, a comparison of NDF/RRT results with the HB (Harmonic Balance) simulation and practical implementation measurements prove the universal use of the new methods.

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We investigate known security flaws in the context of security ceremonies to gain an understanding of the ceremony analysis process. The term security ceremonies is used to describe a system of protocols and humans which interact for a specific purpose. Security ceremonies and ceremony analysis is an area of research in its infancy, and we explore the basic principles involved to better understand the issues involved.We analyse three ceremonies, HTTPS, EMV and Opera Mini, and use the information gained from the experience to establish a list of typical flaws in ceremonies. Finally, we use that list to analyse a protocol proven secure for human use. This leads to a realisation of the strengths and weaknesses of ceremony analysis.

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Higher-order spectral (bispectral and trispectral) analyses of numerical solutions of the Duffing equation with a cubic stiffness are used to isolate the coupling between the triads and quartets, respectively, of nonlinearly interacting Fourier components of the system. The Duffing oscillator follows a period-doubling intermittency catastrophic route to chaos. For period-doubled limit cycles, higher-order spectra indicate that both quadratic and cubic nonlinear interactions are important to the dynamics. However, when the Duffing oscillator becomes chaotic, global behavior of the cubic nonlinearity becomes dominant and quadratic nonlinear interactions are weak, while cubic interactions remain strong. As the nonlinearity of the system is increased, the number of excited Fourier components increases, eventually leading to broad-band power spectra for chaos. The corresponding higher-order spectra indicate that although some individual nonlinear interactions weaken as nonlinearity increases, the number of nonlinearly interacting Fourier modes increases. Trispectra indicate that the cubic interactions gradually evolve from encompassing a few quartets of Fourier components for period-1 motion to encompassing many quartets for chaos. For chaos, all the components within the energetic part of the power spectrum are cubically (but not quadratically) coupled to each other.

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The rate of emotional and behavioral disturbance in children with intellectual disability (ID) is up to four times higher than that of their typically developing peers. It is important to identify these difficulties in children with ID as early as possible to prevent the chronic co-morbidity of ID and psychopathology. Children with ID have traditionally been assessed via proxy reporting, but appropriate and psychometrically rigorous instruments are needed so that children can report on their own emotions and behaviors. In this study, the factor structure of the self-report version of the Strengths and Difficulties Questionnaire (SDQ) was examined in a population of 128 children with ID (mean age = 12 years). Exploratory and Confirmatory Factor Analysis showed a three factor model (comprising Positive Relationships, Negative Behavior and Emotional Competence) to be a better measure than the original five factor SDQ model in this population.

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This paper presents the details of numerical studies on the shear behaviour and strength of lipped channel beams (LCBs) with stiffened web openings. Over the last couple of decades, cold-formed steel beams have been used extensively in residential, industrial and commercial buildings as primary load bearing structural components. Their shear strengths are considerably reduced when web openings are included for the purpose of locating building services. Our research has shown that shear strengths of LCBs were reduced by up to 70% due to the inclusion of web openings. Hence there is a need to improve the shear strengths of LCBs with web openings. A cost effective way to improve the detrimental effects of a large web opening is to attach appropriate stiffeners around the web openings in order to restore the original shear strength and stiffness of LCBs. Hence numerical studies were undertaken to investigate the shear strengths of LCBs with stiffened web openings. In this research, finite element models of LCBs with stiffened web openings in shear were developed to simulate the shear behaviour and strength of LCBs. Various stiffening methods using plate and LCB stud stiffeners attached to LCBs using screw-fastening were attempted. The developed models were then validated by comparing their results with experimental results and used in parametric studies. Both finite element analysis and experimental results showed that the stiffening arrangements recommended by past re-search for cold-formed steel channel beams are not adequate to restore the shear strengths of LCBs with web openings. Therefore new stiffener arrangements were proposed for LCBs with web openings based on experimental and finite element analysis results. This paper presents the details of finite element models and analyses used in this research and the results including the recommended stiffener arrangements.

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Steady state entanglement in ensembles of harmonic oscillators with a common squeezed reservoir is studied. Under certain conditions the ensemble features genuine multipartite entanglement in the steady state. Several analytic results regarding the bipartite and multipartite entanglement properties of the system are derived. We also discuss a possible experimental implementation which may exhibit steady state genuine multipartite entanglement.

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Aboriginal protocol usually links the right to tell a story with a declaration of involvement or connection to the story. I am Aboriginal . . . I am a woman, daughter, sister, aunty and wife. I am also a mother to three beautiful children aged 6, 4 and 2 years. To my children at this point in their lives, I am their provider, nurturer, teacher, cook, taxi driver, mediator, stylist, Elder, slave, and expert on all there is to know in the world. Being the centre of the universe to three impressionable young minds is a role that I cherish deeply, and I take the responsibilities of it very seriously. I love the job of parenting. As any parent would agree, it is the most challenging and difficult job of all, but the opportunity to bring a life into the world and shape and mould a little person into a big person brings rewards that no career can.