Determination of optimum cutoff grade with considering dilution

In open pit mining, cutoff grade is one of the most important factors in production planning, which is simply defined as a grade that discriminates between ore and waste. It is also a sensitive parameter can have a major impact on the net present value and cash flow of the projects. On the other hand, dilution is one of the most important and sensitive parameters in the mining projects, which is closely related to the cutoff grade. Choosing the optimum cutoff grade is of considerable importance, since it has a significant impact on the mining operations. One of the most popular algorithms for determination of the optimum cutoff grade is the Lane’s algorithm. But in the Lane’s algorithm, mining dilution and its cost is not considered during the cutoff grade optimization. In this paper, effects of dilution on the cutoff grade are studied using Lane’s theory. Dilution and its cost is inserted directly into cutoff grade optimization process. The cutoff grades obtained using suggested method will be more realistic rather than ones by using the original form of the Lane’s formulation. Results of the study showed that with an increase of dilution, average grade decreases and consequently the cutoff grade increases. As a result of dilution, the quantity Q _m increases and the quantities Q _c and Q _r decrease. Therefore, the annual profit and NPV of project is very significantly reduced.     

Partitioning of metals in sediments of the Haraz River (Southern Caspian Sea basin)

The Haraz River flows northwards through the Iranian Alborz mountains in the central region of Mazandaran province and empties into the Caspian Sea. This area has been a rich source of minerals from times immemorial. About 45 mines (coal, limestone, sand and gravel, etc.) have been operational for the last eight decades. Towards the estuary, the river receives a discharge of industrial, agricultural and urban wastes. Eight sediment samples from the Haraz River and its main tributaries were collected and analyzed for base metals as well as Sr and Fe. The chemical partitioning of metals (Cu, Zn, As, Cd, Pb, Fe, Ni, Cr, Co and Sr) in each sample was determined in four fractions (acid-soluble, reducible, oxidizable and residual). The total content of each metal was also determined. The results showed relatively higher concentrations of Cd, As, Sr and Pb in comparison to that of shale. However, based on the chemical partitioning of metals, it is found that Pb, Co, Cd and Sr are the most mobile metals. In spite of the high As concentrations in sediments, it is not likely that this element is a major hazard for the aquatic environment, since it is found mainly in the residual fraction. Cadmium is the metal that showed the highest percentages in the acid-soluble fraction (the most labile) and the lowest in the residual fraction. However, Fe, Cr and Ni are present in the greatest percentages in the residual fraction, which implies that these metals are strongly linked to the sediments.     

Bayesian estimation of b-value in Gutenberg–Richter relationship: a sample size reduction approach

Natural Hazards - One of the most widely used relationships for prediction of b-value is the Aki–Utsu relationship, which is based on the maximum likelihood estimating. This method has some...     

Central Composite Design Optimization of Biological Dye Removal in the Presence of Macroalgae Chara sp.

Response surface methodology (RSM) was employed to investigate the effects of different operational parameters on the biological decolorization of a dye solution containing malachite green (MG) in the presence of macroalgae Chara sp. The investigated variables were the initial pH, initial dye concentration, algae amount, and reaction time. Central composite design (CCD) was used for the optimization of biological decolorization process. Predicted values were found to be in good agreement with experimental values (R² = 0.982 and Adj‐R² = 0.966), which indicated suitability of the employed model and the success of RSM. The results of optimization predicted by the model showed that maximum decolorization efficiency was achieved at the optimum condition of the initial pH 6.8, initial dye concentration 9.7 mg/L, algae amount 3.9 g, and reaction time 75 min. UV–VIS spectra and FT‐IR analysis showed degradation of MG.     

Effects of climate change on wind energy production in Iran

Arabian Journal of Geosciences - This study explores the effect of future climate change on wind energy conversion in Iran, based on data from existing wind farms. In an effort to estimate and...     

Experimental evaluation of the performance of earth levees deteriorated by wildlife activities

In this study, an earth levee model is constructed to investigate the impact of animal burrows on the integrity and performance of earthen structures. A series of centrifuge experiments are conducted on homogenous scaled-down 1H:1V levee models built from the natural Kasama soil. Both intact and deteriorated models were subject to a 35g acceleration level. Invasive animal intrusions were introduced in the form of horizontal array of idealized cylindrical burrows at the mid-height of the levee. The water level was gradually increased during the centrifuge flight, and the response of the levee was monitored throughout the test. Pore pressures were recorded using pressure transducers placed at preselected locations within the model. Surface displacements were measured using laser LVDTs and supplemented with three digital cameras for tracking the overall deformation pattern of the levee model. A summary of the test procedure and selected results is presented herewith. The observed deformation mechanism due to the presence of animal burrows is also described. As compared with the intact levee, the presence of burrows is found to alter the pattern of the water flow through the deteriorated levee structure—leading to a notable increase in the exit hydraulic gradient, internal erosion, and subsequently slope failure.