Automatic FLAC3D Mesh Generation Based on Advancing-Frontal Method

For the disadvantage in modeling at complex areas, advancing-frontal triangulation method was firstly applied in building numerical model of FLAC3D software. Suitable date structure and algorithm based on Fish program language was mainly studied. The position criterion of adjacent edges to current edge is brought in to improve the efficiency of algorithm; equilateral triangle or isosceles triangle mesh is generated to improve elements’ quality; element size is controlled by simple mathematics means so smooth graded triangular mesh is constructed. Through the research, the first independent FLAC3D pre-process is developed successfully, without relying on other modeling software. Application example shows the feasibility of the method.

Hydrogen and Oxygen Chemisorptions and Titrations by Platinum on Zirconia Catalysts Reduced between 673 and 1273 K

Some 10 wt % Pt supported on zirconia catalysts were investigated by hydrogen and oxygen chemisorptions and titrations by means of automated catharometric equipment (frontal method). Microcalorimetry was further used to determine the heats of oxygen chemisorption. The temperature of reduction by hydrogen, TR, was varied between 673 and 1273 K. At 673 K, the H and O coverages of Pt were about the same as for Pt supported on SiO2 (Euro Pt catalyst). The increase in TR from 673 to 873 K was accompanied by a strong decrease of the hydrogen to oxygen chemisorption ratio. It is proposed that this is due to Pt1– xZr x alloy formation, with small values of x (≤0·05). When TR was above 873 K, x determined by X-ray diffraction analysis increased up to 0·25. The hydrogen chemisorption is confined to Pt s, while the oxygen chemisorption takes place on Pt s and Zr sO x. The surface composition may be derived and is found twice as rich in Zr as the mean composition of the alloy particles.