Nonstationary Stochastic Simulation of Strong Ground-Motion Time Histories : Application to the Japanese Database

For earthquake-resistant design, engineering seismologists employ time-history analysis for nonlinear simulations. The nonstationary stochastic method previously developed by Pousse et al. (2006) has been updated. This method has the advantage of being both simple, fast and taking into account the basic concepts of seismology (Brune's source, realistic time envelope function, nonstationarity and ground-motion variability). Time-domain simulations are derived from the signal spectrogram and depend on few ground-motion parameters: Arias intensity, significant relative duration and central frequency. These indicators are obtained from empirical attenuation equations that relate them to the magnitude of the event, the source-receiver distance, and the site conditions. We improve the nonstationary stochastic method by using new functional forms (new surface rock dataset, analysis of both intra-event and inter-event residuals, consideration of the scaling relations and VS30), by assessing the central frequency with S-transform and by better considering the stress drop variability.Comment: 10 pages; 15th World Conference on Earthquake Engineering, Lisbon : Portugal (2012

A set of Eurocode 8-compatible synthetic time-series as input to dynamic analysis

International audienceNon-linear dynamic analysis of existing or planned structures often requires the use of accelerograms that match a target design spectrum. Here, our main concern is to generate a set of motions with a good level of fit to the Eurocode 8 (EC8) design spectra for France. Synthetic time series are generated by means of a non-stationary stochastic method. To calibrate the distributions of various strong-motion parameters, we first select a reference set of accelerograms for a type B site category from the PEER Ground-Motion Database, which are then adjusted to the target spectrum through wavelet addition. Finally, we analyse non-linear seismic responses of a soil column including pore pressure effects and ductile structures using these records, revealing considerable variability despite the similarities in terms of spectral acceleration

Self-sustained spin-polarized current oscillations in multiquantum well structures

Nonlinear transport through diluted magnetic semiconductor nanostructures is investigated. We have considered a II–VI multiquantum well nanostructure whose wells are selectively doped with Mn. The response to a dc voltage bias may be either a stationary or an oscillatory current. We have studied the transition from stationary to time-dependent current as a function of the doping density and the number of quantum wells. Analysis and numerical solution of a nonlinear spin transport model shows that the current in a structure without magnetic impurities is stationary, whereas current oscillations may appear if at least one well contains magnetic impurities. For long structures having two wells with magnetic impurities, a detailed analysis of nucleation of charge dipole domains shows that self-sustained current oscillations are caused by repeated triggering of dipole domains at the magnetic wells and motion towards the collector. Depending on the location of the magnetic wells and the voltage, dipole domains may be triggered at both wells or at only one. In the latter case, the well closer to the collector may inhibit domain motion between the first and the second well inside the structure. Our study could allow design of oscillatory spin-polarized current injectors

STRONG SEISMIC MOTIONS ESTIMATED FROM A ONE DIRECTION-THREE COMPONENTS ("1D-3C") APPROACH, APPLICATION TO THE CITY OF ROME, ITALY

International audienceStrong seismic motions in soils generally lead to both a stiffness reduction and an increase of the energy dissipation in the surficial layers. In order to study such phenomena, several nonlinear constitutive models were proposed and were generally implemented for 1D soil columns. However, one of the main difficulties of complex rheologies is the large number of parameters needed to describe the model. In this sense, the multi-surface cyclic plasticity approach, developed by Iwan in 1967 but linked to Prandtl or Preisach theoretical work, is an interesting choice: the only data needed is the modulus reduction curve. Past studies have generally implemented such models for one-directional shear wave propagation in a "1D" soil column considering one motion component only ("1C"). Conversely, this work aims at studying strong motion amplification by considering seismic wave propagation in a "1D" soil column accounting for the influence of the 3D loading path on the nonlinear behavior of each soil layer. In the "1D-3C" approach, the three components (3C) of the outcrop motion are simultaneously propagated into a horizontally layered soil for which a three-dimensional constitutive relation is used (Finite Element Method). The alluvial site considered in this study corresponds to the Tiber River Valley, close to the historical centre of Rome (Italy). The computations are performed considering the waveforms referred as the 14th October 1997 Umbria-Marche earthquake, recorded on outcropping bedrock. Time histories and stress-strain hysteretic loops are computed all along the soil column. The octahedral stress, the strain-depth profiles and the transfer functions in acceleration (surface/outcrop spectral ratios) are estimated for the 1D-1C and the 1D-3C approaches, evidencing the influence of the three-dimensional loading path

Predominant-Period Site Classification for Response Spectra Prediction Equations in Italy

Abstract We propose a site classification scheme based on the predominant period of the site, as determined from the average horizontal-to-vertical (H/V) spectral ratios of ground motion. Our scheme extends Zhao et al. (2006) classifications by adding two classes, the most important of which is defined by flat H/V ratios with amplitudes less than 2. The proposed classification is investigated by using 5%-damped response spectra from Italian earthquake records. We select a dataset of 602 three-component analog and digital recordings from 120 earthquakes recorded at 214 seismic stations within an hypocentral distance of 200 km. Selected events are in the moment-magnitude range 4.0 ≤ Mw ≤ 6.8 and focal depths from a few kilometers to 46 km. We computed H/V ratios for these data and used these to classify each site into one of six classes. We then investigate the impact of this classification scheme on empirical ground-motion prediction equations by comparing its performance with that of the conventional rock/soil classification. Although the adopted approach results in a only a small reduction of overall standard deviation, the use of H/V spectral ratios in site classification does capture the signature of sites with flat frequency-response, well as deep and shallow soil profiles, characterized 2 C:\di_alessandro\site_classification_italy\final_version_of_paper\bssa-d-11-00084_di_alessandro_etal_final_revisions.doc by long-and short-period resonance, respectively; in addition, the classification scheme is relatively quick and inexpensive, which is an advantage over schemes based on measurements of shear-wave velocity

In-vivo, non-invasive detection of hyperglycemic states in animal models using mm-wave spectroscopy

Chronic or sustained hyperglycemia associated to diabetes mellitus leads to many medical complications, thus, it is necessary to track the evolution of patients for providing the adequate management of the disease that is required for the restoration of the carbohydrate metabolism to a normal state. In this paper, a novel monitoring approach based on mm-wave spectroscopy is comprehensively described and experimentally validated using living animal models as target. The measurement method has proved the possibility of non-invasive, in-vivo, detection of hyperglycemia associated conditions in different mouse models, making possible to clearly differentiate between several hyperglycemic states

PRENOLIN project. Results of the validation phase at sendai site

One of the objectives of the PRENOLIN project is the assessment of uncertainties associated with non-linear simulation of 1D site effects. An international benchmark is underway to test several numerical codes, including various non-linear soil constitutive models, to compute the non-linear seismic site response. The preliminary verification phase (i.e. comparison between numerical codes on simple, idealistic cases) is now followed by the validation phase, which compares predictions of such numerical estimations with actual strong motion data recorded from well-known sites. The benchmark presently involves 21 teams and 21 different non-linear computations. Extensive site characterization was performed at three sites of the Japanese KiK-net and PARI networks. This paper focuses on SENDAI site. The first results indicate that a careful analysis of the data for the lab measurement is required. The linear site response is overestimated while the non-linear effects are underestimated in the first iteration. According to these observations, a first set of recommendations for defining the non-linear soil parameters from lab measurements is proposed. PRENOLIN is part of two larger projects: SINAPS@, funded by the ANR (French National Research Agency) and SIGMA, funded by a consortium of nuclear operators (EDF, CEA, AREVA, ENL)

Differential requirements for Gli2 and Gli3 in the regional specification of the mouse hypothalamus.

Secreted protein Sonic hedgehog (Shh) ventralizes the neural tube by modulating the crucial balance between activating and repressing functions (GliA, GliR) of transcription factors Gli2 and Gli3. This balance—the Shh-Gli code—is species- and context-dependent and has been elucidated for the mouse spinal cord. The hypothalamus, a forebrain region regulating vital functions like homeostasis and hormone secretion, shows dynamic and intricate Shh expression as well as complex regional differentiation. Here we asked if particular combinations of Gli2 and Gli3 and of GliA and GliR functions contribute to the variety of hypothalamic regions, i.e. we wanted to clarify the hypothalamic version of the Shh-Gli code. Based on mouse mutant analysis, we show that: 1) hypothalamic regional heterogeneity is based in part on differentially stringent requirements for Gli2 or Gli3; 2) another source of diversity are differential requirements for Shh of neural vs non-neural origin; 3) Gli2 is indispensable for the specification of a medial progenitor domain generating several essential hypothalamic nuclei plus the pituitary and median eminence; 4) the suppression of Gli3R by neural and non-neural Shh is essential for hypothalamic specification. Finally, we have mapped our results on a recent model which considers the hypothalamus as a transverse region with alar and basal portions. Our data confirm the model and are explained by it

Combinations of single-top-quark production cross-section measurements and vertical bar f(LV)V(tb)vertical bar determinations at root s=7 and 8 TeV with the ATLAS and CMS experiments

This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb(-1) at = 7 TeV and 12.2 to 20.3 fb(-1) at = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 +/- 5.7 pb and 87.7 +/- 5.8 pb at = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 +/- 4.1 pb and 23.1 +/- 3.6 pb at = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 +/- 1.4 pb at = 8 TeV. The square of the magnitude of the CKM matrix element V-tb multiplied by a form factor f(LV) is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |V-td|, |V-ts| << |V-tb|. All the |f(LV)V(tb)|(2) determinations, extracted from individual ratios at = 7 and 8 TeV, are combined, resulting in |f(LV)V(tb)| = 1.02 +/- 0.04 (meas.) +/- 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions.Peer reviewe