361 research outputs found
Prediction of spatially distributed seismic demands in specific structures: Ground motion and structural response
The efficacy of various ground motion intensity measures (IMâs) in the prediction of
spatially distributed seismic demands (Engineering Demand Parameters, EDPâs) within a
structure is investigated. This has direct implications to building-specific seismic loss
estimation, where the seismic demand on different components is dependent on the location of
the component in the structure. Several common intensity measures are investigated in terms
of their ability to predict the spatially distributed demands in a 10-storey office building,
which is measured in terms of maximum interstorey drift ratios and maximum floor
accelerations. It is found that the ability of an IM to efficiently predict a specific EDP
depends on the similarity between the frequency range of the ground motion which controls
the IM and that of the EDP. An IMâs predictability has a direct effect on the median response
demands for ground motions scaled to a specified probability of exceedance from a ground
motion hazard curve. All of the IMâs investigated were found to be insufficient with respect
to at least one of magnitude, source-to-site distance, or epsilon when predicting all peak
interstorey drifts and peak floor accelerations in a 10-storey RC frame structure. Careful
ground motion selection and/or seismic demand modification is therefore required to predict
such spatially distributed demands without significant bias
Prediction of spatially distributed seismic demands in specific structures: Structural response to loss estimation
A companion paper has investigated the effects of intensity measure (IM) selection in
the prediction of spatially distributed response in a multi-degree-of-freedom structure. This
paper extends from structural response prediction to performance assessment metrics such as:
probability of structural collapse; probability of exceeding a specified level of demand or
direct repair cost; and the distribution of direct repair loss for a given level of ground motion.
In addition, a method is proposed to account for the effect of varying seismological properties
of ground motions on seismic demand that does not require different ground motion records to
be used for each intensity level. Results illustrate that the conventional IM, spectral
displacement at the first mode, Sde(T1), produces higher risk estimates than alternative
velocity-based IMâs, namely spectrum intensity, SI, and peak ground velocity, PGV, because
of its high uncertainty in ground motion prediction and poor efficiency in predicting peak
acceleration demands
Probabilistic seismic indoor injury estimation
Most injury models in existence either estimate injuries at a regional level
and/or focus only on fatalities. In regions with good engineering practice, the likelihood
of building collapse is rare and hence fatality risk is also correspondingly low. Research
has shown that in such situations non-fatal injuries are likely to result in larger economic
loss than fatalities due to their higher incidence, despite non-fatalities having lower
consequence. A new building-specific method of indoor injury estimation is proposed in
this paper. Injuries are considered due to: (i) occupants being struck by toppling contents;
and (ii) occupants losing balance and falling. This model considers the spatial distribution
of occupants in the building, time-occupancy relationships, and the severity of injury to
occupants. A simple room layout is used to demonstrate the application of the model
Improved seismic hazard model with application to probabilistic seismic demand analysis
An improved seismic hazard model for use in performance-based earthquake engineering is presented. The model is an improved approximation from the so-called 'power law' model, which is linear in log-log space. The mathematics of the model and uncertainty incorporation is briefly discussed. Various means of fitting the approximation to hazard data derived from probabilistic seismic hazard analysis are discussed, including the limitations of the model. Based on these 'exact' hazard data for major centres in New Zealand, the parameters for the proposed model are calibrated. To illustrate the significance of the proposed model, a performance-based assessment is conducted on a typical bridge, via probabilistic seismic demand analysis. The new hazard model is compared to the current power law relationship to illustrate its effects on the risk assessment. The propagation of epistemic uncertainty in the seismic hazard is also considered. To allow further use of the model in conceptual calculations, a semi-analytical method is proposed to calculate the demand hazard in closed form. For the case study shown, the resulting semi-analytical closed form solution is shown to be significantly more accurate than the analytical closed-form solution using the power law hazard model, capturing the 'exact' numerical integration solution to within 7% accuracy over the entire range of exceedance rat
Transport spin polarization of Ni_xFe_{1-x}: electronic kinematics and band structure
We present measurements of the transport spin polarization of Ni_xFe_{1-x}
(0<x<1) using the recently-developed Point Contact Andreev Reflection
technique, and compare them with our first principles calculations of the spin
polarization for this system. Surpisingly, the measured spin polarization is
almost composition-independent. The results clearly demonstrate that the sign
of the transport spin polarization does not coincide with that of the
difference of the densities of states at the Fermi level. Calculations indicate
that the independence of the spin polarization of the composition is due to
compensation of density of states and Fermi velocity in the s- and d- bands
Higher-order mutual coherence of optical and matter waves
We use an operational approach to discuss ways to measure the higher-order
cross-correlations between optical and matter-wave fields. We pay particular
attention to the fact that atomic fields actually consist of composite
particles that can easily be separated into their basic constituents by a
detection process such as photoionization. In the case of bosonic fields, that
we specifically consider here, this leads to the appearance in the detection
signal of exchange contributions due to both the composite bosonic field and
its individual fermionic constituents. We also show how time-gated counting
schemes allow to isolate specific contributions to the signal, in particular
involving different orderings of the Schr\"odinger and Maxwell fields.Comment: 11 pages, 2 figure
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Microcraters in aluminum foils exposed by Stardust
We will present preliminary results on the nature and size frequency distribution of microcraters that formed in aluminum foils during the flyby of comet Wild 2 by the Stardust spacecraft
Quantum Vacuum Experiments Using High Intensity Lasers
The quantum vacuum constitutes a fascinating medium of study, in particular
since near-future laser facilities will be able to probe the nonlinear nature
of this vacuum. There has been a large number of proposed tests of the
low-energy, high intensity regime of quantum electrodynamics (QED) where the
nonlinear aspects of the electromagnetic vacuum comes into play, and we will
here give a short description of some of these. Such studies can shed light,
not only on the validity of QED, but also on certain aspects of nonperturbative
effects, and thus also give insights for quantum field theories in general.Comment: 9 pages, 8 figur
Allergic Eosinophil-rich Inflammation Develops in Lungs and Airways of B Cellâdeficient Mice
Immunoglobulins (Ig), particularly IgE, are believed to be crucially involved in the pathogenesis of asthma and, equally, in allergic models of the disease. To validate this paradigm we examined homozygous mutant C57BL/6 mice, which are B cell deficient, lacking all Ig. Mice were immunized intraperitoneally with 10 ÎŒg ovalbumin (OVA) plus alum, followed by daily (day 14â20) 30 min exposures to OVA aerosol (OVA/OVA group). Three control groups were run: OVA intraperitoneally plus saline (SAL) aerosol (OVA/SAL group); saline intraperitoneally plus saline aerosol; saline intraperitoneally plus OVA aerosol (n = 6â7). Lung and large airway tissues obtained 24 h after the last OVA or SAL exposure were examined by light microscopy and transmission electron microscopy (TEM). The Ig-deficient mice receiving OVA/ OVA treatment had swollen and discolored lungs and exhibited marked eosinophilia both in large airway subepithelial tissue (49.2 ± 12.0 cells/mm basement membrane [BM] versus OVA/ SAL control 1.2 ± 0.3 cells/mm BM; P <0.001), and perivascularly and peribronchially in the lung (49.3 ± 9.0 cells/unit area versus OVA/SAL control 2.6 ± 0.6 cells/unit area; P <0.001). The eosinophilia extended to the regional lymph nodes. TEM confirmed the subepithelial and perivascular localization of eosinophils. Mucus cells in large airway epithelium increased from 1.5 ± 0.8 (OVA/SAL mice) to 39.5 ± 5.7 cells/mm BM in OVA/OVA treated mice (P <0.001). OVA/SAL mice never differed from the other control groups. Corresponding experiments in wild-type mice (n = 6â7 in each group) showed qualitatively similar but less pronounced eosinophil and mucus cell changes. Macrophages and CD4+ T cells increased in lungs of all OVA/OVA-treated mice. Mast cell number did not differ but degranulation was detected only in OVA/OVA-treated wild-type mice. Immunization to OVA followed by OVA challenges thus cause eosinophil-rich inflammation in airways and lungs of mice without involvement of B cells and Ig
A Phenomenological Analysis of Gluon Mass Effects in Inclusive Radiative Decays of the and $\Upsilon
The shapes of the inclusive photon spectra in the processes \Jp \to \gamma
X and \Up \to \gamma X have been analysed using all available experimental
data.
Relativistic, higher order QCD and gluon mass corrections were taken into
account in the fitted functions. Only on including the gluon mass corrections,
were consistent and acceptable fits obtained. Values of
GeV and GeV were found for the
effective gluon masses (corresponding to Born level diagrams) for the \Jp and
\Up respectively. The width ratios \Gamma(V \to {\rm hadrons})/\Gamma(V \to
\gamma+ {\rm hadrons}) V=\Jp, \Up were used to determine and . Values consistent with the current world
average were obtained only when gluon mass correction factors,
calculated using the fitted values of the effective gluon mass, were applied. A
gluon mass GeV, as suggested with these results, is consistent with
previous analytical theoretical calculations and independent phenomenological
estimates, as well as with a recent, more accurate, lattice calculation of the
gluon propagator in the infra-red region.Comment: 50 pages, 11 figures, 15 table
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