S U M M A R Y We consider the problem of using scattered waves to recover an image of the medium in which the waves propagate. We address the case of scalar waves when the sources and receivers are sparse and irregularly spaced. Our approach is based on the single-scattering (Born) approximation and the generalized Radon transform. The key to handling sparse sources and receivers is the develop...

Hysteresis in a piezoelectric actuator must be compensated for, and this compensation constitutes the main challenge high-precision motion control of piezo-actuated stages. This paper presents an output-feedback sliding-mode (SMC) scheme to suppress unknown nonlinearity; scheme, hysteresis behavior is considered external disturbance, complex models are thus not required. The functions absence t...

We consider situations where, in a continuous-time dynamical system, a nonchaotic attractor coexists with a nonattracting chaotic saddle, as in a periodic window. Under the influence of noise, chaos can arise. We investigate the fundamental dynamical mechanism responsible for the transition and obtain a general scaling law for the largest Lyapunov exponent. A striking finding is that the topolo...

A stochastic model predictive control framework over unreliable Bernoulli communication channels, in the presence of unbounded process noise and under bounded inputs, is presented for tracking a reference signal. The data losses channel are compensated by carefully designed transmission protocol, those sensor dropout compensator. class saturated, disturbance feedback policies proposed noisy com...

The three-dimensional shapes of tectonic plates that sink into the Earth’s mantle (slabs) are the starting point for a range of geoscience studies, from determining the forces driving the motion of tectonic plates, to potential seismic and tsunami hazards, to the sources of magmas beneath active volcanos. For many of these applications finite element methods are used to model the deformation or...

In order to fill gaps in Russian early-warning systems, sensors can be deployed cooperatively near the silos of intercontinental ballistic missiles (ICBMs) that would sense a launch and would transmit continuously the information that no launch has occurred. The extremely loud launch noise propagates to kilometers and can be detected passively in all weather conditions by the induced ground mot...

[1] Sliding glaciers and brittle ice failure generate seismic body and surface wave energy characteristic to the source mechanism. Here we analyze continuous seismic recordings from an array of nine short-period passive seismometers located on Bench Glacier, Alaska (USA) (61.033 N, 145.687 W). We focus on the arrival-time and amplitude information of the dominant Rayleigh wave phase. Over a 46-...

Seismic data are subject to different kinds of unwanted perturbations. These random or organised noises, which can be acquisition or processing related for instance, may disturb geophysical interpretations and thwart attempts at automated processing methods. Since the relative features (e.g. amplitude, spectrum) of the signals of interest and the noises may vary locally, signal and noise separa...

Subsurface models, obtained by structural interpretation of seismic images, underpin all decisions in hydrocarbon exploration and production. The main interest in this field is directed towards the interpretation of horizons and faults: Horizons are strong reflection events which indicate boundaries between rock layering while faults are discrete fractures along which appreciable displacement h...

Most evaluations of the effects of human activities on wild animals have focused on estimating changes in abundance and distribution of threatened species; however, ecosystem disturbances also affect aspects of animal behavior such as short-term movement, activity budgets, and reproduction. It may take a long time for changes in behavior to manifest as changes in abundance or distribution. Ther...