A General Linear Wave Theory for Water Waves Propagating over Uneven Porous Bottoms

Starting from the widespread phenomena of porous bottoms in the near shore region, considering fully the diversity of bottom topography and wave number variation, and including the effect of evanescent modes, a general linear wave theory for water waves propagating over uneven porous bottoms in the near shore region is established by use of Green‘s scond identity. This theory can be reduced to a number of the most typical mild-slope equations curreutly in use and provide a reliable research basis for follow-up development of nonlinear water wave theory involving porous bottoms.     

Recognition of Gas Hydrate Using AVO-Attribute Crossplots Based on the Porous Medium Theory

Gas hydrate is gradually considered as a potential energy resource. The presence of gas hydrate is commonly inferred from the appearance of “bottom simulating reflector”(BSR) on seismic section. Understanding the properties of hydrate-bearing sediments and studying the AVO characteristics of BSR are of great significance. Although more and more domestic and international studies have been conducted on the subjects mentioned above, they are still in the primary stage and need a long way to go to be appled in practice, especially in the field of gas hydrate. Aiming at the identification of gas hydrate, we studied the characteristics of the AVO attributes based on the Biot‘s theory when the sediments were bearing gas hydrate or free gas. The AVO attribute crossplots obtained from seismic sections with the forward simulation by means of staggered-grid finite-difference were compared with that of theoretic models. The coincidence shows that utilization of AVO attribute crossplots is an effective way to recognize gas hydrate and free gas.     

Porous Properties of Nano-fibriform Silica from Natural Chrysotile

With the TEM and physical gas adsorption techniques, porous properties of nano-ribriform silica （MLD： 92.73%） from natural chrysotile are studied in this paper. The results indicate that porous nano-fibriform silica results from brucite octahedral sheets of nature chrysotile dissolved completely and Si-O tetrahedral sheets collapsed by acid leaching. Its length is at a micron or nanometer scale. There are two types of pores： pores among neighboring fibers and pores in nanoriber. These pores （less than 6.5 nm in diameter, mostly 2.1 nm and 3.8 nm） all belong to mesopores. The pores in fibers consist of those among SiO2 particles, those among aggregates, remnant nanotubes and capillary tubes. Nanoribriform silica proves better than the traditional silica as a carrier of catalyzer and a filler for reinforce rubber and plastics.