Parametric correlations versus fidelity decay: the symmetry breaking case

We derive fidelity decay and parametric energy correlations for random matrix ensembles where time--reversal invariance of the original Hamiltonian is broken by the perturbation. Like in the case of a symmetry conserving perturbation a simple relation between both quantities can be established.Comment: 8 pages, 8 figure

The efficacy of halofantrine in the treatment of acute malaria in nonimmune travelers

A multicenter prospective trial was performed to investigate the efficacy and the tolerability of halofantrine in nonimmune patients with malaria imported from areas with drug-resistant falciparum parasites (mainly Africa). Forty-five of the 74 subjects were treated with a one-day regimen (3 x 500 mg) of halofantrine, and the other 29 received the same regimen with an additional treatment on day 7. In the second group, a 100% efficacy rate was demonstrated, but in the group receiving the one-day regimen, four recrudescences were observed in patients with falciparum malaria. Only five mild adverse reactions were seen, which disappeared spontaneously after the end of the treatment. We conclude that halofantrine is highly effective in curing malaria in nonimmune subjects. The treatment scheme for such persons should include an additional treatment on day 7 for nonimmune individuals. This drug was well tolerated in our patients, indicating that halofantrine will be useful in the treatment of multidrug-resistant malaria in nonimmune persons

Two-dimensional Dirac fermions in a topological insulator: transport in the quantum limit

Pulsed magnetic fields of up to 55T are used to investigate the transport properties of the topological insulator Bi_2Se_3 in the extreme quantum limit. For samples with a bulk carrier density of n = 2.9\times10^16cm^-3, the lowest Landau level of the bulk 3D Fermi surface is reached by a field of 4T. For fields well beyond this limit, Shubnikov-de Haas oscillations arising from quantization of the 2D surface state are observed, with the \nu =1 Landau level attained by a field of 35T. These measurements reveal the presence of additional oscillations which occur at fields corresponding to simple rational fractions of the integer Landau indices.Comment: 5 pages, 4 figure

Identification of Sparse Damage in Steel-Frame Buildings Using Dense Seismic Array Measurements

There is an unprecedented increase in the number of real-time measurements produced by permanent, dense accelerometer arrays in buildings, an example being the Community Seismic Network. In the present work, damage identification techniques are developed by coupling such datasets with linear and nonlinear finite-element models of buildings. Damage in steel-frame buildings is manifested in localized areas as cracks in beam-column connections or as an average stiffness reduction. High-fidelity linear or nonlinear finite-element models are developed to allow for realistic behavior, including modeling nonlinearities associated with the opening and closing of cracks. L1 regularization techniques and sparse Bayesian learning tools are further developed fully in the time domain to reduce ill-conditioning and account for the sparsity of damage. The effectiveness of the proposed methods in identifying the location and severity of damage is demonstrated using simulated acceleration data from a three-story steel frame building, and a 15-story building in downtown Los Angeles that is fully instrumented

Identification of Sparse Damage in Steel-Frame Buildings Using Dense Seismic Array Measurements

There is an unprecedented increase in the number of real-time measurements produced by permanent, dense accelerometer arrays in buildings, an example being the Community Seismic Network. In the present work, damage identification techniques are developed by coupling such datasets with linear and nonlinear finite-element models of buildings. Damage in steel-frame buildings is manifested in localized areas as cracks in beam-column connections or as an average stiffness reduction. High-fidelity linear or nonlinear finite-element models are developed to allow for realistic behavior, including modeling nonlinearities associated with the opening and closing of cracks. L1 regularization techniques and sparse Bayesian learning tools are further developed fully in the time domain to reduce ill-conditioning and account for the sparsity of damage. The effectiveness of the proposed methods in identifying the location and severity of damage is demonstrated using simulated acceleration data from a three-story steel frame building, and a 15-story building in downtown Los Angeles that is fully instrumented

Detecting failure events in buildings: a numerical and experimental analysis

A numerical method is used to investigate an approach for detecting the brittle fracture of welds associated with beam -column connections in instrumented buildings in real time through the use of time-reversed Green’s functions and wave propagation reciprocity. The approach makes use of a prerecorded catalog of Green’s functions for an instrumented building to detect failure events in the building during a later seismic event by screening continuous data for the presence of waveform similarities to one of the prerecorded events. This study addresses whether a set of Green’s functions in response to an impulsive force load can be used to approximate the response of the structure to a localized failure event such as a brittle weld fracture. Specifically, we investigate whether prerecorded Green’s functions can be used to determine the absolute time and location of a localized failure event in a building. We also seek to differentiate between sources such as a weld fracture that are structurally damaging and sources such as falling or colliding furniture and other non-structural elements that do not contribute to structural failure. This is explored numerically by comparing the dynamic response of a finite-element cantilevered beam model structure to a variety of loading mechanisms. A finite-element method is employed to determine the behavior of the resulting elastic waves and to obtain a general understanding of the structural response

Propagating waves in the steel, moment-frame factor building recorded during earthquakes

Wave-propagation effects can be useful in determining the system identification of buildings such as the densely instrumented University of California, Los Angeles, Factor building. Waveform data from the 72-channel array in the 17-story moment-resisting steel frame Factor building are used in comparison with finiteelement calculations for predictive behavior. The high dynamic range of the 24-bit digitizers allows both strong motions and ambient vibrations to be recorded with reasonable signal-to-noise ratios. A three-dimensional model of the Factor building has been developed based on structural drawings. Observed displacements for 20 small and moderate, local and regional earthquakes were used to compute the impulse response functions of the building by deconvolving the subbasement records as representative input motions at its base. The impulse response functions were then stacked to bring out wave-propagation effects more clearly. The stacked data are used as input into theoretical dynamic analysis simulations of the building’s response

A Method to Detect Structural Damage Using High-Frequency Seismograms

A numerical study is performed to gain insight into applying a novel method to detect high-frequency dynamic failure in buildings. The method relies on prerecorded catalog of Green's functions for instrumented buildings. Structural failure during a seismic event is detected by screening continuous data for the presence of waveform similarities to each of the cataloged building responses. In the first part of this numerical study, an impulse-like force is applied to a beam column connection in a linear elastic steel frame. A time-reversed reciprocal method is used to demonstrate that the resulting simulated displacements can be used to determine the absolute time and location of the applied force. In the second part of the study, a steel frame's response to two loading cases, an impulse-like force and an opening crack tensile stress, is computed on a temporal scale of microseconds. Results indicate that the velocity waveform generated by a tensile crack can be approximated by the velocity waveform generated by an impulse-like force load applied at the proper location. These results support the idea of using a nondestructive impulse-like force (e.g. hammer blow) to characterize the building response to high-frequency dynamic failure (e.g. weld fracture)

Interpretation of Millikan Library's Vibrating Modes Using A Magneto Coil To Measure Phase Shifts

A new set of natural frequencies for the 9-story reinforced concrete Millikan Library building on the Caltech campus is computed using the observed phase shift between the driving force of a shaker installed on the building’s roof and structural response at resonance. The phase of the shaker’s output force was recorded by a magneto coil and magnet attached to the shaker’s rotating mechanism, and the phase of the structural response was obtained from acceleration time series recorded by an accelerometer on the roof. These new results refute previous studies’ identification of the 3rd EW and 2nd torsional modes which used spectral analysis of forced and free vibrations, but did not consider the phase shift. In addition, the newly identified 3rd EW mode shape is independent of the other EW mode shapes, unlike previous findings. This new interpretation is compatible with results from subspace system identification based on two sets of earthquake records