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881.
Anna Worobiec E. Anna Stefaniak Sanja Potgieter-Vermaak Zbigniew Sawlowicz Zoya Spolnik René Van Grieken 《Applied Geochemistry》2007
The effectiveness of electrostatic separation of zircon and TiO2 phases during the processing of heavy mineral concentrates derived from heavy mineral sands depends upon the chemical, physical and mineralogical characteristics of the concentrates. Here the authors’ demonstrate the use of combined micro-Raman spectrometry (MRS), scanning electron microscopy (SEM) and computer controlled scanning electron microscopy coupled with an energy-dispersive X-ray detector (CC-SEM/EDX), followed by hierarchical cluster analysis (HCA) to determining these characteristics on samples from the non-magnetic fraction of the Richards Bay (South Africa) heavy mineral concentrate. All samples were found to be predominately comprised a heterogeneous population of grains of zircon and rutile and other TiO2 polymorphs with diverse physicochemical properties. Combined MRS and CC-SEM/EDX enabled the identification of textural characteristics which impacted on the efficiency of electrostatic separation of zircon and rutile concentrate streams. 相似文献
882.
The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform
layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain
was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes
of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures.
Determination of velocity is the recursive process which means that the wavefield on depth level z
n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z
n
. The velocity ν [x, z
n
− z
n−1] can be thus treated as interval velocity in Δz
n
= z
n
− z
n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media. 相似文献
883.
In biological wastewater treatment, bacteria tend to aggregate by forming flocs, biofilms and even granules. A large part of the floc structure in activated sludge is composed of extracellular polymers. The extracellular polymeric substances (EPS) are mainly responsible for the structural and functional integrity of biofilms/flocs and they are considered to be important for the physico‐chemical properties of activated sludge. This review considers the composition of EPS and proportion between the constituents. Moreover it includes the relationship between the EPS constituents and sludge properties such as sludge retention time, hydrophobicity and surface charge. 相似文献
884.
The paper presents a method for correction of amplitude of prestack migration using the reflectivity function. The solution
of wave equations for heterogeneous media expressed in the form of Neumann series for converted waves was used to find the
reflectivity function. The performance of the proposed method was verified using synthetic models of wavefields. The synthetic
models of wavefields were also used to compare amplitude correction levels required by the presented method and the standard
amplitude correction methods, i.e., the methods using the spherical divergence and extention factor. 相似文献
885.
The Main Endeavour Field, northern Juan de Fuca Ridge, experienced intense seismic activity in June 1999. Hydrothermal vent fluids were collected from sulfide structures in September 1999 and July 2000 and analyzed for the abundance of H2, H2S, CH4, CO2, NH3, Mg and Cl to document temporal and spatial changes following the earthquakes. Dissolved concentrations of CO2, H2, and H2S increased dramatically in the September 1999 samples relative to pre-earthquake abundances, and subsequently decreased during the following year. In contrast, dissolved NH3 and CH4 concentrations in 1999 and 2000 were similar to or less than pre-earthquake values. Aqueous Cl abundances showed large decreases immediately following the earthquakes followed by increases to near pre-earthquake values. The abundances of volatile species at the Main Endeavour Field were characterized by strong inverse correlations with chlorinity. Phase separation can account for 20-50% enrichments of CO2, CH4, and NH3 in low-chlorinity fluids, while temperature- and pressure-dependent fluid-mineral equilibria at near-critical conditions are responsible for order of magnitude greater enrichments in dissolved H2S and H2. The systematic variation of dissolved gas concentrations with chlorinity likely reflects mixing of a low-chlorinity volatile-enriched vapor generated by supercritical phase separation with a cooler gas-poor hydrothermal fluid of seawater chlorinity. Decreased abundances of sediment-derived NH3 and CH4 in 1999 indicate an earthquake-induced change in subsurface hydrology. Elevated CO2 abundances in vent fluids collected in September 1999 provide evidence that supports a magmatic origin for the earthquakes. Temperature-salinity relationships are consistent with intrusion of a shallow dike and suggest that the earthquakes were associated with movement of magma beneath the ridge crest. These data demonstrate the large and rapid response of chemical fluxes at mid-ocean ridges to magmatic activity and associated changes in subsurface temperature and pressure. 相似文献
886.
887.
Transport of Temperature and Humidity Variance and Covariance in the Marine Surface Layer 总被引:3,自引:3,他引:0
In this paper we address the budget of potential temperature T and moisture mixing ratio q variances as well as the q-T covariance budget. We focus on the vertical transport and study the quantities contained in these terms. Estimates of transport terms are rare and to the best of our knowledge they have never been shown together in the literature. For this purpose an extensive set of humidity and temperature turbulence data from two heights in a marine environment has been analysed. We discuss and compare our results with results from earlier studies for a range of stability from near-neutral to unstable. Similarity and differences between T and q behaviour in the surface layer over water are presented. 相似文献
888.
地磁场总强度空间线性相关在预报武定,丽江强震中的应用及机理 总被引:1,自引:0,他引:1
介绍了地磁场空间线性相关的计算方法。详细阐述了利用此方法在预报武定地震 (1 995年 1 0月 2 4日 ,MS6.5)及丽江地震 (1 996年 2月 3日 MS7.0 )中的应用。笔者对此方法进行了理论推导 ,结果表明相关参量与台站经纬度的选择有关 ,而地磁场的空间线性相关的规律与台站的经纬度选择无关。该结果对台组的选择起到了指导作用 相似文献
889.
Francesca Barnaba Ferdinando De Tomasi Gian Paolo Gobbi Maria Rita Perrone Anna Tafuro 《Atmospheric Research》2004,70(3-4):229-259
Functional relationships linking at λ0=351 nm aerosol extinction αλ0aer and backscatter coefficient βλ0aer of maritime and desert type aerosols are determined to allow for inversion of the single-wavelength lidar signals. Such relationships are derived as mean behavior of 20,000 extinction versus backscatter computations, performed for aerosol size distributions and compositions whose describing parameters are randomly chosen within the naturally observed variability. For desert-type aerosols, the effect of the particle non-sphericity is considered and it is shown that the extinction to backscatter ratio of non-spherical dust particles can be up to 60% larger than the values obtained for spherical particles. Aerosol extinction and backscatter coefficient profiles obtained inverting the single-wavelength lidar signal with the modeled relationships are then compared to the same profiles measured by a combined elastic-Raman lidar operating at 351 nm. Analytical back trajectories and satellite images are used to characterize advection patterns during lidar measurements and to properly choose the modeled functional relationship. A good accordance between the two techniques is found for advection patterns over the lidar site typical of maritime and dust conditions. Maximum differences between the model-based αλ0aer and βλ0aer vertical profiles and the corresponding ones measured by the combined elastic-Raman lidar technique are of 30% and 40% in maritime and desert dust conditions, respectively. The comparison of elastic-Raman lidar measurements and model-based results also reveals that particle non-sphericity must be taken into account when mineral dust-type aerosols are directly advected over the measurement site. 相似文献
890.
Zoosporic aquatic fungi growing on dead specimens of 29 freshwater crustacean species 总被引:1,自引:0,他引:1
The authors investigated aquatic fungi growing on the carapaces of 29 species of dead crustaceans (13 species of Copepoda, 13 species of Cladocera and 3 species of Ostracoda) in the water from six limnological and trophical different water bodies (two springs, one river, one lake and two ponds). All of these waterbodies are strongly loaded. 146 species of aquatic fungi were found on the carapaces: 40 Chytridiomycetes, 1 Hyphochytriomycete and 105 Oomycetes. The most common fungus species were Karlingia chitinophila, Myzocytium microsporum, Myzocytium zoophthorum, Pythium acanthicum, Pythium butleri and Pythium myriotylum. Most zoosporic fungus species were observed on the specimens of Daphnia pulex (50 fungus species), Daphnia magna (48) and Cyclocypris laevis (44), fewest on Cyclops fuscus and Cyclops vicinus (each 10).The most fungi were growing in the water from River Supraśl (86), the fewest in the water from Pond Fosa (53). Cluster analysis of the investigated parameters carried out in water bodies during the experiment on zoosporic fungus species has revealed that in the water from springs and Pond Fosa the number of fungus species is closely associated with the concentration of sulphates, in water from River Supraśl and Lake Komosa with calcium and in the water from Pond Dojlidy with chlorides. Out of these 146 species, 21 are known as parasites or necrotrophs of fish. Some dead specimens of crustacean species are a new substrate for some fungus species. 相似文献