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121.
Mass and Metallurgical Balance Forecast for a Zinc Processing Plant Using Artificial Neural Networks
Niquini Fernanda Gontijo Fernandes Costa João Felipe Coimbra Leite 《Natural Resources Research》2020,29(6):3569-3580
Natural Resources Research - The forecasting of ore concentrate and tailings mass and metallurgical recovery at a processing plant is not a simple task. It starts with data collection, which is... 相似文献
122.
The morphologic changes in estuaries and coastal lagoons are very complex and constitute a challenging task in coastal research.
The bathymetric changes result from the combined action of tides, waves, rivers discharge and wind stress in the area of interest.
Additionally, an accurate knowledge of the sediment transport is essential to achieve a good morphological characterization.
This work establishes the influence of the wave climate on the morphodynamics of the Ria de Aveiro lagoon inlet by analysing the numerical results of the morphodynamic modelling system MORSYS2D. The numerical simulations
considered a realistic coupled forcing of tidal currents and waves. The computed sediment fluxes and bathymetric changes are
analysed and compared with the erosion and accretion trends obtained from the numerical simulations forced only by tidal currents,
in order to establish the wave climate influence. The final bathymetry and the corresponding changes are compared with bathymetric
data collected through surveys. It is concluded that: (a) the morphodynamics of the study area is dominated by the wave regime
in the lagoon inlet and nearshore areas, while in the inner areas is tidally dominated; and (b) the inclusion of the wave
regime forcing constitutes an improvement in order to accurately reproduce the local morphodynamics. 相似文献
123.
124.
Jo De Waele 《Environmental Geology》2009,58(2):239-255
Evaluating the human disturbance on karst areas is a difficult task because of the complexity of these peculiar and unique
environments. The human impact on karstic geo-ecosystems is increasingly important and there is an increasing need for multidisciplinary
tools to assess the environmental changes in karst areas. Many disciplines, such as biology, geomorphology, hydrology and
social-economical sciences are to be considered to sufficiently evaluate the impact on these intrinsically vulnerable areas.
This article gives an overview of the evolution of environmental impact on karst areas of the island Sardinia (Italy). For
this particular case, the most important impacts in the past 50 years are derived from the following activities, in decreasing
importance: (1) mining and quarrying; (2) deforestation, agriculture and grazing; (3) building (widespread urbanisation, isolated
homes, etc.) and related infrastructures (roads, sewer systems, aqueducts, waste dumps, etc.); (4) tourism; (5) military activities.
To evaluate the present environmental state of these areas the Disturbance Index for Karst environments [Van Beynen and Townsend
(Environ Manage 36:101–116)] is applied in a slightly modified version. Instead of considering the indicators of environmental
disturbances used in the original method, this slightly modified index evaluates the disturbances causing the deterioration
of the environmental attributes. In the Sardinian case study, 27 disturbances have been evaluated, giving rise to the definition
of a Disturbance Index ranging between 0 (Pristine) and 1 (highly disturbed). This Disturbance Index simplifies the original
KDI method, appears to adequately measure disturbance on Mediterranean karst areas and could be applied with success to other
similar regions. 相似文献
125.
Climate change is expected to increase temperatures and lower rainfall in Mediterranean regions; however, there is a great degree of uncertainty as to the amount of change. This limits the prediction capacity of models to quantify impacts on water resources, vegetation productivity and erosion. This work circumvents this problem by analysing the sensitivity of these variables to varying degrees of temperature change (increased by up to 6·4 °C), rainfall (reduced by up to 40%) and atmospheric CO2 concentrations (increased by up to 100%). The SWAT watershed model was applied to 18 large watersheds in two contrasting regions of Portugal, one humid and one semi‐arid; incremental changes to climate variables were simulated using a stochastic weather generator. The main results indicate that water runoff, particularly subsurface runoff, is highly sensitive to these climate change trends (down by 80%). The biomass growth of most species showed a declining trend (wheat down by 40%), due to the negative impacts of increasing temperatures, dampened by higher CO2 concentrations. Mediterranean species, however, showed a positive response to milder degrees of climate change. Changes to erosion depended on the interactions between the decline in surface runoff (driving erosion rates downward) and biomass growth (driving erosion rates upward). For the milder rainfall changes, soil erosion showed a significant increasing trend in wheat fields (up to 150% in the humid watersheds), well above the recovery capacity of the soil. Overall, the results indicate a shift of the humid watersheds to acquire semi‐arid characteristics, such as more irregular river flows and increasingly marginal conditions for agricultural production. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
126.
Libório Matheus Pereira de Abreu João Francisco Ekel Petr Iakovlevitch Machado Alexei Manso Correa 《Journal of Geographical Systems》2023,25(2):185-211
Journal of Geographical Systems - The weighting of sub-indicators is widely debated in the composite indicator literature. However, these weighting schemes’ effects on the composite... 相似文献
127.
128.
Slim Khedhiri Khadija Semhi Joëlle Duplay Fadila Darragi 《Environmental Earth Sciences》2011,62(5):1013-1025
A sequential extraction procedure applied to surface sediments from El Kelbia Lagoon determined the partitioning of Ba, Co,
Cr, Cu, Ni, Sr, V and Zn among evaporites, carbonates, Fe–Mn oxides, organic matter and silicates. To validate the procedure,
the sequential extraction results (SER) were compared to principal components analysis (PCA) using major and trace element
concentrations and mineralogical quantitative data of surface sediments. SER showed that a part of Sr was highly mobile; Cu,
Sr, and Zn and a part of Co and Ni were mobile depending on pH conditions; Cr and V were strongly bound to silicate phases;
Co and Ni were partitioned between carbonates, oxides and silicates, and a great part of Ba and Sr were bound to organic matter
or sulfides. An agreement was found with PCA in terms of partitioning among minerals for most trace elements. Moreover, the
absence of correlation between Ca concentrations and the abundances of calcite, gypsum or dolomite could be explained by an
important fraction of Ca bound to organic matter. Also, unexpected negative correlations between abundances of smectite and
illite could be explained by a transformation of illite into smectite. Thus, SER and PCA were mostly convergent, which enabled:
(1) validation of the extraction procedure used, and (2) refinement of interpretations of the origin and relations between
minerals. 相似文献
129.
Ricardo Conceição Hugo Gonçalves Silva Alec Bennett Rui Salgado Daniele Bortoli Maria João Costa Manuel Collares Pereira 《Boundary-Layer Meteorology》2018,166(1):69-81
The spectral response of atmospheric electric potential gradient gives important information about phenomena affecting this gradient at characteristic time scales ranging from years (e.g., solar modulation) to fractions of a second (e.g., turbulence). While long-term time scales have been exhaustively explored, short-term scales have received less attention. At such frequencies, space-charge transport inside the planetary boundary layer becomes a sizeable contribution to the potential gradient variability. For the first time, co-located (Évora, Portugal) measurements of boundary-layer backscatter profiles and the 100-Hz potential gradient are reported. Five campaign days are analyzed, providing evidence for a relation between high-frequency response of the potential gradient and strong dry convection. 相似文献
130.
Stability is a key issue in any mining or tunnelling activity. Joint frequency constitutes an important input into stability
analyses. Three techniques are used herein to quantify the local and spatial joint frequency uncertainty, or possible joint
frequencies given joint frequency data, at unsampled locations. Rock quality designation is estimated from the predicted joint
frequencies. The first method is based on kriging with subsequent Poisson sampling. The second method transforms the data
to near-Gaussian variables and uses the turning band method to generate a range of possible joint frequencies. The third method
assumes that the data are Poisson distributed and models the log-intensity of these data with a spatially smooth Gaussian
prior distribution. Intensities are obtained and Poisson variables are generated to examine the expected joint frequency and
associated variability. The joint frequency data is from an iron ore in the northern part of Norway. The methods are tested
at unsampled locations and validated at sampled locations. All three methods perform quite well when predicting sampled points.
The probability that the joint frequency exceeds 5 joints per metre is also estimated to illustrate a more realistic utilisation.
The obtained probability map highlights zones in the ore where stability problems have occurred. It is therefore concluded
that the methods work and that more emphasis should have been placed on these kinds of analyses when the mine was planned.
By using simulation instead of estimation, it is possible to obtain a clear picture of possible joint frequency values or
ranges, i.e. the uncertainty. 相似文献