Recursive algorithms for estimating states of nonlinear physical systems are presented. Orthogonality properties are rediscovered and the associated polynomials are used to linearize state and observation models of the underlying random processes. This requires some key hypotheses regarding the structure of these processes, which may then take account of a wide range of applications. The latter include streamflow forecasting, flood estimation, environmental protection, earthquake engineering, and mine planning. The proposed estimation algorithm may be compared favorably to Taylor series-type filters, nonlinear filters which approximate the probability density by Edgeworth or Gram-Charlier series, as well as to conventional statistical linearization-type estimators. Moreover, the method has several advantages over nonrecursive estimators like disjunctive kriging. To link theory with practice, some numerical results for a simulated system are presented, in which responses from the proposed and extended Kalman algorithms are compared. 相似文献
Optical absorption spectra are presented for taramellite, traskite and neptunite, all of which have both Fe2+ and Ti4+ as major elements. The spectra of each of these minerals are dominated by a single, intense absorption band in the 415 to 460 nm region with 7000 to 9000 cm?1 halfwidth. These transitions, assigned to Fe2+-Ti4+ intervalence charge transfer, showed little difference in intensity at 80 and 300 K and have molar absorptivities which range from ~100 to ~1300 M?1 cm?1. The Fe2+-Ti4+ absorptions in these standards generally compare well to other mineral spectra in which Fe2+ — Ti4+ intervalence absorption has previously been proposed with the exception of the most cited example, blue corundum. 相似文献
The electron-gas theory of crystals is extended to include the effects of many-body forces that arise from both electrostatic and overlap interactions. These effects are incorporated through a self-consistent spherical relaxation of the ionic charge distributions such that the crystal binding energy is minimized. This variational model is used to compute the elastic constants and equations of state of MgO and CaO, and we compare its results to those derived from earlier electron-gas models. In the variational model, the anion charge distributions are markedly more sensitive to the local crystal environment than they are in the PIB or other electron-gas models. We find that for these oxides the variational model gives the best overall agreement with experiment for lattice constants, equations of state, dissociation energies, and elastic moduli. 相似文献
A well-defined pahoehoe lava type that is very common medially and distally in Hawaii is characterized by a high concentration and fairly uniform distribution of spherical or near-spherical vesicles. Measurements of vesicle sizes and concentrations have been made on ten of these spongy pahoehoe lava flow-units. The vesicles increase in size toward the middle, accompanied by a moderate increase in lava porosity. The close approach to bilateral symmetry on either side of the horizontal median plane and the common occurrence of a median gas blister shows that no significant upward movement of vesicles occurred, suggesting that the lava possessed a yield strength and was more or less static. Olivine phenocrysts when present are, however, concentrated in the lower half of the same flow units, showing that the lava previously lacked a significant yield strength. The vesicles are regarded as early, inherited from the vent, but the size characteristics of the vesicle population are a late-formed feature. Vesicles grew in static lava mostly by coalescence, and it is postulated that coalescence was promoted by the presence of abundant diktytaxitic voids which punctured the walls of contiguous vesicles. Zones in which the vesicle concentration is lower and the vesicles are larger and strongly deformed interrupt the symmetry of some spongy pahoehoe units, and gas blisters higher than the median plane occur in many examples. These zones are interpreted to result from late-stage shearing, and point to a mechanism by which vesicles may be eliminated from a lava. 相似文献
After reaction with a pH < 4, the surface of labradorite is extensively enriched in Si and H, and depleted in Al, Ca and Na relative to an unreacted crystal. However, the amount of hydrogen measured in the reacted surface is less than that predicted on the basis of exchange of hydrogen (or hydronium) ions for cations in the feldspar. By analogy with studies of silicate glass, this low concentration of hydrogen suggests that some silanol groups in the reacted surface repolymerize subsequent to ion-exchange and depolymerization reactions. The net result is a relatively porous, Si-rich leached layer which is amorphous to electron diffraction, and which allows rapid diffusion of unreactive solutes.
Both the surface area of the reacted feldspar and the porosity increase with acid hydrolysis. Modeling of nitrogen sorption onto the surface suggests that the pores have a nominal radius of 20–80 Å or less. This distribution of pore sizes resembles other acid-reacted silicate materials, such as glass, chrysotile and kaolinite. Although the mineral surface clearly becomes more porous during acid hydrolysis, the increase in powder area also does not coincide with an increase in the flux of dissolved Si from the powder. We thus attribute most of this increase in area to spallation of the silica-rich surface from the feldspar upon drying. 相似文献
This literature survey covers data on the distribution, genetics and biology ofArtemia from the People's Republic of China (P. R. China) and the use of the brine shrimp in aquaculture and salt production. The vastness of the territory, the unfamiliar geography and the diversity of the habitats, have often lead to ambiguities and contradictions, leaving a gap in our knowledge about the Chinese populations ofArtemia. However, information aboutArtemia from P. R. China has recently become available and this is an attempt to summarize it.International interdisciplinary study onArtemia populations coordinated by the Laboratory of Aquaculture &Artemia Reference Center, University of Ghent, Belgium. 相似文献