A novel geometric approach for 3-D geological modelling

This paper presents a graphics system called the prism network and its boundary (PNB) aimed at representing the stratified solids that are formed in the subsurface terrain. It allows full 3D modelling of these types of spaces formed by superimposed layers bounded by stratification surfaces. A set of boreholes in the ground is used to generate a network of prisms that models the solid space and serves as the basis for creating two secondary networks, one of triangles and another of quadrilaterals, which define the model boundaries. This graphics system has been implemented in C++, using the standard OpenGL graphics API. The paper first defines and implements a model in the PNB data structure, the process by means of which it is generated is then described, and, finally, a range of applications to specific cases is presented and graphically illustrated.     

Spectroscopy and Lasing of Yb-Doped ${hbox {NaY}}{({hbox {WO}}_{4})}_{2}$: Tunable and Femtosecond Mode-Locked Laser Operation

Tetragonal (space group f4 macr) single crystals of NaY(WO₄)₂ doped with Yb to a density of 4.52 times 10²⁰ cm^-3 have been employed as laser active materials for the 1-mum spectral range, operating at room temperature. Using Ti:sapphire laser pumping, slope efficiencies as high as 74.6% were achieved without special cooling for the pi-polarization. The Yb-laser was continuously tunable from 1003.7 to 1073.0 nm with a birefringent filter. Pulses as short as 53 fs were obtained at 1035 nm by SESAM passive mode-locking with intracavity dispersion compensation and additional extracavity pulse compression using analogous prism pairs. Experimental data on the spectroscopic properties of Yb³⁺ in the 5-300 K temperature range and the room temperature optical properties of this novel Yb-host is also presented.     

Diode-pumped femtosecond Yb:NaY(WO/sub 4/)/sub 2/

Pulses as short as 97 fs for an average power of 70 mW were obtained directly from a SESAM modelocked diode pumped laser based on the tetragonal NaY(WO₄)₂, a locally disordered double tungstate, doped with Yb. An extracavity prism pair helped to reduce the pulse duration to 90 fs with a corresponding time-bandwidth product of 0.321.