Notch effects in tensile behavior of AM60 magnesium alloys

The deformation and failure behavior of an AM60 magnesium alloy was investigated using tensile test on circumferentially notched specimens with different notch radii. The strain and stress triaxiality corresponding to the failure point were evaluated using both analytical and finite element analyses. Combining with systematical observations of the fracture surfaces, it is concluded that deformation and failure of AM60 magnesium alloy are notch (constraint) sensitive. The failure mechanisms change from ductile tearing to quasi cleavage with the increase of constraint

Free vibration analysis of laminated composite plates based on FSDT using one-dimensional IRBFN method

This paper presents a new effective radial basis function (RBF) collocation technique for the free vibration analysis of laminated composite plates using the first order shear deformation theory (FSDT). The plates, which can be rectangular or non-rectangular, are simply discretised by means of Cartesian grids. Instead of using conventional differentiated RBF networks, one-dimensional integrated RBF networks (1D-IRBFN) are employed on grid lines to approximate the field variables. A number of examples concerning various thickness-to-span ratios, material properties and boundary conditions are considered. Results obtained are compared with the exact solutions and numerical results by other techniques in the literature to investigate the performance of the proposed method

The role of topography and lateral velocity heterogeneities on near-source scattering and ground-motion variability

The scattering of seismic waves travelling in the Earth is not only caused by random velocity heterogeneity but also by surface topography. Both factors are known to strongly affect ground-motion complexity even at relatively short distance from the source. In this study, we simulate ground motion with a 3-D finite-difference wave propagation solver in the 0-5Hz frequency band using three topography models representative of the Swiss alpine region and realistic heterogeneous media characterized by the Von Karman correlation functions. Subsequently, we analyse and quantify the characteristics of the scattered wavefield in the near-source region. Our study shows that both topography and velocity heterogeneity scattering may excite large coda waves of comparable relative amplitude, especially at around 1Hz, although large variability in space may occur. Using the single scattering model, we estimate average QC values in the range 20-30 at 1Hz, 36-54 at 1.5Hz and 62-109 at 3Hz for constant background velocity models with no intrinsic attenuation. In principle, envelopes of topography-scattered seismic waves can be qualitatively predicted by theoretical back-scattering models, while forward- or hybrid-scattering models better reproduce the effects of random velocity heterogeneity on the wavefield. This is because continuous multiple scattering caused by small-scale velocity perturbations leads to more gentle coda decay and envelope broadening, while topography abruptly scatters the wavefield once it impinges the free surface. The large impedance contrast also results in more efficient mode mixing. However, the introduction of realistic low-velocity layers near the free surface increases the complexity of ground motion dramatically and indicates that the role of topography in elastic waves scattering can be relevant especially in proximity of the source. Long-period surface waves can form most of the late coda, especially when intrinsic attenuation is taken into account. Our simulations indicate that both topography and velocity heterogeneity scattering may result in large ground-motion variability, characterized by standard deviation values in the range 0.2-0.5 also at short distance from the source. We conclude that both topography and velocity heterogeneity should be considered to correctly assess the ground-motion variability in earthquake scenario studies even at intermediate frequenc

Broad-band near-field ground motion simulations in 3-dimensional scattering media

The heterogeneous nature of Earth's crust is manifested in the scattering of propagating seismic waves. In recent years, different techniques have been developed to include such phenomenon in broad-band ground-motion calculations, either considering scattering as a semi-stochastic or purely stochastic process. In this study, we simulate broad-band (0-10Hz) ground motions with a 3-D finite-difference wave propagation solver using several 3-D media characterized by von Karman correlation functions with different correlation lengths and standard deviation values. Our goal is to investigate scattering characteristics and its influence on the seismic wavefield at short and intermediate distances from the source in terms of ground motion parameters. We also examine scattering phenomena, related to the loss of radiation pattern and the directivity breakdown. We first simulate broad-band ground motions for a point-source characterized by a classic ω2 spectrum model. Fault finiteness is then introduced by means of a Haskell-type source model presenting both subshear and super-shear rupture speed. Results indicate that scattering plays an important role in ground motion even at short distances from the source, where source effects are thought to be dominating. In particular, peak ground motion parameters can be affected even at relatively low frequencies, implying that earthquake ground-motion simulations should include scattering also for peak ground velocity (PGV) calculations. At the same time, we find a gradual loss of the source signature in the 2-5Hz frequency range, together with a distortion of the Mach cones in case of super-shear rupture. For more complex source models and truly heterogeneous Earth, these effects may occur even at lower frequencies. Our simulations suggests that von Karman correlation functions with correlation length between several hundred metres and few kilometres, Hurst exponent around 0.3 and standard deviation in the 5-10percent range reproduce the available observation

Sensitivity of broad-band ground-motion simulations to earthquake source and Earth structure variations: an application to the Messina Straits (Italy)

In this paper, we investigate ground-motion variability due to different faulting approximations and crustal-model parametrizations in the Messina Straits area (Southern Italy). Considering three 1-D velocity models proposed for this region and a total of 72 different source realizations, we compute broad-band (0-10 Hz) synthetics for Mw 7.0 events using a fault plane geometry recently proposed. We explore source complexity in terms of classic kinematic (constant rise-time and rupture speed) and pseudo-dynamic models (variable rise-time and rupture speed). Heterogeneous slip distributions are generated using a Von Karman autocorrelation function. Rise-time variability is related to slip, whereas rupture speed variations are connected to static stress drop. Boxcar, triangle and modified Yoffe are the adopted source time functions. We find that ground-motion variability associated to differences in crustal models is constant and becomes important at intermediate and long periods. On the other hand, source-induced ground-motion variability is negligible at long periods and strong at intermediate-short periods. Using our source-modelling approach and the three different 1-D structural models, we investigate shaking levels for the 1908 Mw 7.1 Messina earthquake adopting a recently proposed model for fault geometry and final slip. Our simulations suggest that peak levels in Messina and Reggio Calabria must have reached 0.6-0.7 g during this earthquak

Solution of two-center time-dependent Dirac equation in spherical coordinates: Application of the multipole expansion of the electron-nuclei interaction

A non-perturbative approach to the solution of the time-dependent, two-center Dirac equation is presented with a special emphasis on the proper treatment of the potential of the nuclei. In order to account for the full multipole expansion of this potential, we express eigenfunctions of the two-center Hamiltonian in terms of well-known solutions of the "monopole" problem that employs solely the spherically-symmetric part of the interaction. When combined with the coupled-channel method, such a wavefunction-expansion technique allows for an accurate description of the electron dynamics in the field of moving ions for a wide range of internuclear distances. To illustrate the applicability of the proposed approach, the probabilities of the K- as well as L- shell ionization of hydrogen-like ions in the course of nuclear alpha-decay and slow ion-ion collisions have been calculated

Acceptance rate and reasons for rejection of manuscripts submitted to Veterinary Radiology & Ultrasound during 2012

Session: P2P ComputingP2P live media streaming systems have proliferated and become indispensable vehicles for Internet based entertainment applications. However, it is also well known that scalability of such systems is limited by the lack of proper incentive mechanisms. Specifically, it is notoriously hard to efficiently allocate upload bandwidth at each peer so as to maximize overall system performance. In this paper, we propose a new auction based mechanism for optimizing the allocation of upload bandwidth at each peer. One of the distinctive features in our approach is that peers use real 'goods' (i.e., their own bandwidth resources) for payments, instead of relying on some fictitious currency. Essentially, peers use a barter mechanism in the payment step in the auction. Simulation results indicate that our proposed auction approach consistently outperforms existing practical approaches (e.g., titfor-tat) in terms of average incoming stream rate, average playback delay, and control packets ratio. © 2011 IEEE.published_or_final_versionThe IEEE 17th International Conference on Parallel and Distributed Systems (ICPADS 2011), Tainan, Taiwan, 7-9 December 2011. In Proceedings of the 17th ICPADS, 2011, p. 573-58

My Hawaii You\u27re Calling Me

In the ev\u27ning when the stars are peeping thru,Skies of cloudless beauty that are ever blue,Sighing hearts their tales of love are telling,Same old tales I often told too. Bands are playing softly down at waikiki,Hula dancers swaying in their glee,There the moon is shinning and my heart is pining,Yes, I hear you calling me. REFRAINMy Hawaii, I\u27m coming back again,Your palmy shady lanes,Your songs and sweet refrains,Ever calling, Saying to me Come back to me beside the sea,My Hawaii, My Hawaii, you\u27re calling me. Dimpled maiden sang a fond farewell to me,When I left old Honolula by the sea;I still hear her dear sweet voice calling,That voice so full of melody. I shall count the hours till I\u27m back again,Strolling with my Honolula Lou,Ukuleles strumming, Hula maidens humming,Yes, I\u27m coming back to you