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The Kondo hole is an isolated nonmagnetic impurity in a heavy-fermion lattice. Experimentally, the Kondo hole can be realized by La or Th atoms replacing a Ce ion in a stoichiometric Ce compound or by Th impurities in a U–heavy-fermion system. Adding impurities to a Kondo lattice gradually destroys the coherence of the heavy-fermion ground state. Perturbations of the coherent state are conveniently studied in the f-electron density of states. We consider a dispersionless orbitally nondegenerate f band locally hybridized with one nearest-neighbor hopping tight-binding conduction band on a simple cubic lattice. A hybridization gap opens in the symmetric case, and the Kondo hole introduces a bound state in the gap. We study the effects of the scattering on the local density of f states in the neighborhood of the nonmagnetic impurity. The effects of the correlations within the f band are introduced via a self-energy, evaluated to second-order perturbation in U, using the d=∞ treatment of Schweitzer and Czycholl [Solid State Commun. 74, 735 (1990)].

In prestack depth migration using explicit extrapolators, the attenuation and dispersion of the seismic wave has been neglected so far. We present a method for accommodating absorption and dispersion effects in depth migration schemes. Extrapolation operators that compensate for absorption and dispersion are designed using an optimization algorithm. The design criterion is that the wavenumber response of the operator should equal the true extrapolator. Both phase velocity and absorption macro models are used in the wavefield extrapolation. In a model with medium to high absorption, the images obtained are superior to those obtained using extrapolators without compensation for absorption.

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A new method for estimating the pressure wavefield generated by a marine air‐gun array is presented. It is assumed that data is acquired at a ministreamer located below the source array. Effective source signatures for each air gun are estimated by an inversion algorithm. The forward modeling scheme used in the inversion algorithm is based upon a physical modeling of the air bubble generated by each air gun. This means that typical inversion parameters are: gun depths, empirical damping coefficients, and reflection coefficient of the sea surface. Variations in streamer depth are also taken into account by the inversion scheme. The algorithm has been successfully tested on examples with unknown streamer positions, gun parameters, reflection coefficient of sea surface, and ministreamer data contaminated with white noise.