On-line estimation of nonlinear physical systems

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.     

Fe2+-Ti4+ charge transfer in stoichiometric Fe2+,Ti4+-minerals

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.     

Variational stabilization of the ionic charge densities in the electron-gas theory of crystals: Applications to MgO and CaO

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.     

International study onArtemia. L. Review of the literature onArtemia from salt lakes in the People's Republic of China

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.     

Silver and copper accumulation in two estuarine bivalves,the eastern oyster (Crassostrea virginica) and the hooked mussel (Ischadium recurvum) in the Patuxent River estuary,Maryland

In order to assess the source of trace elements and to compare uptake between different bivalve species, oysters and mussels were transplanted to five sites in the upper Patuxent River estuary during 1988. Transplant sites were located above and below the discharge of Chalk Point Steam Electric Station (CPSES)—a historic point source for copper. Organisms were sampled approximately monthly for 1 yr and analyzed for copper and silver. During spring and summer, concentrations of silver and copper increased in oysters at the upstream stations. There was very little change in silver and copper concentrations in the mussels with either time or among stations. Copper concentrations accumulated by oysters approached those found during previous periods when CPSES used Cu?Ni alloy condenser tubes (1966–1987), suggesting that corrosion from the Cu?Ni condenser tubes was only a minor contributor to the copper burdens of oysters in the river nearby. The lack of accumulation by mussels at the same sites suggests that part of the reason for the accumulation by oysters may be a taxonomically specific physiological effect caused by the salinity regime in the upper Patuxent.