A new species of Aleurolobus Quaintance et Baker (Homoptera, Aleyrodidae) from Southern Europe.

Aleurolobus teucrii n. sp. is described from southern Italy and the Maltese Islands (Central Mediterranean). The species seems to be monophagous on Teucrium fruticans L. A key to the European species of this genus (A. niloticus Priesner et Hosny, A. olivinus (Silvestri), A. wunni (Ryberg) and A. teucrii n. sp.) is provided.peer-reviewe

Response of beams resting on viscoelastically damped foundation to moving oscillators

The response of beams resting on viscoelastically damped foundation under moving SDoF oscillators is scrutinized through a novel state-space formulation, in which a number of internal variables is introduced with the aim of representing the frequency-dependent behaviour of the viscoelastic foundation. A suitable single-step scheme is provided for the numerical integration of the equations of motion, and the Dimensional Analysis is applied in order to define the dimensionless combinations of the design parameters that rule the responses of beam and moving oscillator. The effects of boundary conditions, span length and number of modes of the beam, along with those of the mechanical properties of oscillator and foundation, are investigated in a new dimensionless form, and some interesting trends are highlighted. The inaccuracy associated with the use of effective values of stiffness and damping for the viscoelastic foundation, as usual in the present state-of-practice, is also quantified

An earthquake response spectrum method for linear light secondary substructures

YesEarthquake response spectrum is the most popular tool in the seismic analysis and design of structures. In the case of combined primary-secondary (P-S) systems, the response of the supporting P substructure is generally evaluated without considering the S substructure, which in turn is only required to bear displacements and/or forces imposed by the P substructure (¿cascade¿ approach). In doing so, however, dynamic interaction between the P and S components is neglected, and the seismic-induced response of the S substructure may be heavily underestimated or overestimated. In this paper, a novel CQC (Complete Quadratic Combination) rule is proposed for the seismic response of linear light S substructures attached to linear P substructures. The proposed technique overcomes the drawbacks of the cascade approach by including the effects of dynamic interaction and different damping in the substructures directly in the cross-correlation coefficients. The computational effort is reduced by using the eigenproperties of the decoupled substructures and only one earthquake response spectrum for a reference value of the damping ratio

Peak response of non-linear oscillators under stationary white noise

The use of the Advanced Censored Closure (ACC) technique, recently proposed by the authors for predicting the peak response of linear structures vibrating under random processes, is extended to the case of non-linear oscillators driven by stationary white noise. The proposed approach requires the knowledge of mean upcrossing rate and spectral bandwidth of the response process, which in this paper are estimated through the Stochastic Averaging method. Numerical applications to oscillators with non-linear stiffness and damping are included, and the results are compared with those given by Monte Carlo Simulation and by other approximate formulations available in the literature

A numerical method for the time‐domain dynamic analysis of buildings equipped with viscoelastic dampers

A novel numerical scheme for the time-domain dynamic analysis of buildings incorporating energy dissipation devices of viscoelastic type is presented. Two alternative state-space representations are considered for the frequency-dependent behaviour of the viscoelastic dampers, namely generalized Maxwell's (GM) model and Laguerre's polynomial approximation (LPA) technique. The computational burden is dramatically reduced by using a convenient modal transformation of coordinates, where the equilibrium modulus of the viscoelastic devices is included in the evaluation of modal shapes and undamped modal frequencies. Both GM model and LPA technique lead to closed-form expressions for the parameters characterizing the modal relaxation functions of the building, which in turn are exploited in deriving the exact integration operators for the modal oscillators. Importantly, all the matrices required in the proposed cascade scheme are directly computable from the exact transition matrices of traditional state variables (displacements and velocities) and additional internal variables (for either GM model or LPA technique). A simple application to a Single-DoF oscillator demonstrates the unconditional stability of the numerical method; the numerical efficiency is proved with the dynamic analysis of a discretized structural system with a large number of degrees of freedom; the accuracy is confirmed by the seismic response analysis of a realistic 10-storey building equipped with viscoelastic dampers. Copyright © 2010 John Wiley & Sons, Ltd

Radiative transition rates and collision strengths for Si II

Aims. This work reports radiative transition rates and electron impact excitation collision strengths for levels of the 3s23p, 3s3p2, 3s24s, and 3s23d configurations of Siii. Methods. The radiative data were computed using the Thomas-Fermi-Dirac-Amaldi central potential, but with the modifications introduced by Bautista (2008) that account for the effects of electron-electron interactions. We also introduce new schemes for the optimization of the variational parameters of the potential. Additional calculations were carried out with the Relativistic Hartree-Fock and the multiconfiguration Dirac-Fock methods. Collision strengths in LS-coupling were calculated in the close coupling approximation with the R-matrix method. Then, fine structure collision strengths were obtained by means of the intermediate-coupling frame transformation (ICFT) method which accounts for spin-orbit coupling effects. Results. We present extensive comparisons between the results of different approximations and with the most recent calculations and experiment available in the literature. From these comparisons we derive a recommended set of gf- values and radiative transition rates with their corresponding estimated uncertainties. We also study the effects of different approximations in the representation of the target ion on the electron-impact collision strengths. Our most accurate set of collision strengths were integrated over a Maxwellian distribution of electron energies and the resulting effective collision strengths are given for a wide range of temperatures. Our results present significant differences from recent calculations with the B-spline non-orthogonal R-matrix method. We discuss the sources of the differences.Comment: 6 figures, 5 tables within text, 2 electronic table