Reflection tomography in the migrated domain can help reconstruct heterogeneous, anisotropic velocity fields needed for accurate depth imaging of complex geologic structures. The presence of anisotropy, however, increases the uncertainty in velocity analysis and typically requires a priori constraints on the model parameters. Here, we develop a 2D P-wave tomographic algorithm for heterogeneous ...

This report gives an exposition of the Process-Grammar, published originally in the journal Artificial Intelligence in 1988, together with a description of some of the subsequent applications of the grammar in meteorology, biology, computer-aided design, chemical engineering, and geology. The Process-Grammar is a means of recovering the process-history of a smooth shape from its curvature extre...

This report gives an exposition of the Process-Grammar, published originally in the journal Artificial Intelligence in 1988, together with a description of some of the subsequent applications of the grammar in meteorology, biology, computer-aided design, chemical engineering, and geology. The Process-Grammar is a means of recovering the process-history of a smooth shape from its curvature extre...

A glass with the mol% composition 17 Y2O3·33 Al2O3·40 SiO2·2 AlF3·3 Na2O·2 CeF3·3 B2O3 is heat treated at 1000 °C for 6-24 h. This results in the surface nucleation and growth of YAG. Nucleation and growth of star-shaped alumina and later of monoclinic β-Y2Si2O7 and orthorhombic δ-Y2Si2O7 are additionally observed in the bulk. Phase identification and localization are performed by electron back...

In the title polymer, {[Cu(SO(4))(C(12)H(9)N(3)O)(2)(H(2)O)(2)]·4H(2)O}(n), both the metal center and the sulfate anion are located on a twofold axis. The Cu(II) ion is coordinated by two pyridyl N atoms from two symmetry-related organic ligands, two O atoms from two symmetry-related water mol-ecules, and two O atoms from two symmetry-related sulfate anions, resulting in a distorted octa-hedral...

We calculate the quantum tunneling rate of a ferromagnetic particle of ∼ 100Å diameter in a magnetic field of arbitrary angle. We consider the magnetocrystalline anisotropy with the biaxial symmetry and that with the tetragonal symmetry. Using the spin-coherent-state path integral, we obtain approximate analytic formulas of the tunneling rates in the small ǫ(= 1−H/Hc)-limit for the magnetic fie...

We perform a complete classification of two-band k·p theories at band crossing points in 3D semimetals with n-fold rotation symmetry and broken time-reversal symmetry. Using this classification, we show the existence of new 3D topological semimetals characterized by C(4,6)-protected double-Weyl nodes with quadratic in-plane (along k(x,y)) dispersion or C(6)-protected triple-Weyl nodes with cubi...

In the title compound, C(8)H(7)N(4)O(4) (+)·Cl(-), the cation possesses twofold symmetry, with the twofold axis bis-ecting the 2-methyl-5,6-dinitro-benzimidazolium cation. The methyl H atoms are disordered about this twofold axis and were assigned equal half-occupancies. The chloride anion also lies on a twofold axis. In the crystal, N-H⋯Cl and C-H⋯O hydrogen bonds link the ions to form a three...

In the title compound C(21)H(21)P, the P atom is situated on a crystallographic threefold rotatory-inversion axis, resulting in threefold rotation symmetry of the title compound. The dihedral angles between the symmetry-related benzene rings are 87.40 (18)°.

In the crystal structure of the title compound, C(4)H(12)N(+)·BH(4) (-), the tetra-methyl-ammonium cations are situated on special positions with site symmetry [Formula: see text]m2. The borohydride anions are situated on special positions with 4mm site symmetry and show rotational disorder around the fourfold axis.