Feature-Preserving Offset Mesh Generation from Topology-Adapted Octrees

We introduce a reliable method to generate offset meshes from input triangle meshes or triangle soups. Our method proceeds in two steps. The first step performs a Dual Contouring method on the offset surface, operating on an adaptive octree that is refined in areas where the offset topology is complex. Our approach substantially reduces memory consumption and runtime compared to isosurfacing methods operating on uniform grids. The second step improves the output Dual Contouring mesh with an offset-aware remeshing algorithm to reduce the normal deviation between the mesh facets and the exact offset. This remeshing process reconstructs concave sharp features and approximates smooth shapes in convex areas up to a user-defined precision. We show the effectiveness and versatility of our method by applying it to a wide range of input meshes. We also benchmark our method on the Thingi10k dataset: watertight and topologically 2-manifold offset meshes are obtained for 100% of the cases.     

Synthesis,structure and stability of fac-[FeII(CO)3X3]1− (X = Br,I)

fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are synthesized and their structures have been determined. They are the first crystallographically characterized iron tricarbonyl trihalide complexes. fac-[Fe^II(CO)₃X₃]^1? (X = Br, I) are fairly thermally stable and therefore lead themselves as excellent starting materials for the preparation of various iron carbonyl complexes since both the halide and carbonyl ligands are substitutionally labile.     

Holographie conoscopique. Reconstructions numériques

Conoscopic holography is a new method for forming holograms in coherent light which may be a solution to the design of a simple holographic system compatible with microcomputers and numerical processing. We present the basic principles of conoscopic holography and experimental setup of conoscopic cameras. The paper focuses on the possibilities of numerical processing of conoscopic holograms and, more specially, we describe algorithms for numerical reconstructions.     

Shell Effects in the Relaxation Energy of 2s-Core Ionization of Atoms from B through Xe

In this paper we investigate the variation, along the periodic table, of 2s-core ionization energies, using both relativistic and non-relativistic calculations. We show that electron relaxation energies display variations typical of the shell-filling process, while their relativistic contributions show specifically distorted shell features. Just as for the 1s-core ionization energies, investigated earlier, the sensitivity of these differential properties to the shell-filling process may be used as a probe of the accuracy of calculations of core ionization energies. Discrepancies with experimental results are critically analyzed.     

Connexionnisme,calcul, reconnaissance des formes et intelligence artificielle

This paper provides an introduction to the field of neural nets and associated learning procedures. Artificial intelligence and pattern recognition are taken in it as synonyms. Massively parallel, neural-like, networks are receiving increasing attention as a mechanism for expressing information processing models. The attempt to achieve human-like performances in the field of speech and image recognition justify this broadening of interest. Neural networks process information in new ways. The use of their properties appears to have promise for the development of solutions to problems that have intractable or unknown algorithms or are too computationally intense.     

Least-mean-squares phase unwrapping by use of an incomplete set of residue branch cuts

A new technique for the least-mean-squares (LMS) phase-unwrapping method is developed that incorporates the concept of branch cuts between phase singularities (residues), which are usually associated with the path-following gradient integration technique. These branch cuts are introduced by decomposition of the least-mean-squares unwrapped phase into two separate components. The first results from the transverse part of the wrapped phase gradient, which is induced by residues of the original phase, and the second component is due to a potential component, independent of the residues. This decomposition allows the reconstruction of phase patterns with a high level of accuracy and consistency with the initial (wrapped) phase, even when only partial knowledge of the placement of branch cuts between residues is available. We show how the residue-induced phase, ignored by conventional LMS phase estimators, is reconstructed for a given boundary-value problem. The method is illustrated with interferometric quality-control measurements of optical fiber-connector terminations and also with synthetic aperture radar interferometry. These experiments demonstrate the high accuracy of the method in practical situations in which only a limited number of branch cuts are available.     

Numerical analysis of a high-resolution fast tunable filter based on an intracavity Bragg grating

A fast tunable filtering technique is proposed associating a diffraction grating with an intracavity Bragg grating. The bandwidth and the tuning range of this filter can be easily adapted by changing the diffraction grating's orientation, or its period, and its response is uniform over the whole tuning range. A numerical simulation of the filter response to a Gaussian beam has been developed, and it fits the experimental results allowing a calculation of the performances that could be obtained with more specific elements. For example, using a commercial acousto-optic deflector would allow a separation of 500 frequencies. It would then be possible to have a tuning range of 100 nm with a bandwidth of 0.2 nm for optical telecommunications.     

Propagation analysis of forward degenerate four-wave mixing

We discuss the propagation problem associated with the forward four-wave degenerate mixing induced by the third-order non-linear susceptibilitychi_{(-omega; omega, omega, -omega)}^{(3)} = chi_{1}^{(3)} + ichi_{2}^{(3)}. Exact analytical solutions are presented of two-photon resonances, evidencing the influence of the Kerr effect on the efficiency of the process. Around a two-photon resonance, we solve the problem of the nearly parallel propagation of two beams undergoing auto and induced two-photon absorption (TPA). The resonant interaction is studied in detail and analytical solutions are provided with operational accuracy for current experimental conditions. We show by the way that in the two-beam two-photon experiments, when the phase matching condition is fulfilled, although TPA is governed bychi_{2}^{(3)}, the real part ofchi^{(3)}must be considered in a substantial way. All the above solutions are put in a form simple enough that the numerical computations can be performed on a programmable calculator.