Trend analysis of groundwater using non-parametric methods (case study: Ardabil plain)

In the present study, the trends in groundwater level and fifteen hydro-geochemical elements at 32 piezometric stations located in the Ardabil plain of the northwest of Iran were analyzed using the non-parametric Mann–Kendall method after removing the effect of significant lag-1 serial correlation from the respective time series by pre-whitening. The magnitudes of trends were computed using the Sen’s estimator method. The homogeneity of trend was tested using the method proposed by van Belle and Hughes as well. Results showed that significant (α < 0.1) negative trends in groundwater level were witnessed for all but five stations of the Ardabil plains during the last 22 years from 1988 to 2009. The groundwater levels over Ardabil plain have declined at the rate of about 18 cm/year, with the strongest decline (1.93 m/year) witnessed at Khalife-loo-sheikh station. The results of homogeneity of trends showed that trends were homogeneous for months but not for stations. Strong positive trends were detected in the groundwater quality concentration across the whole plain. Decline in groundwater level and increase in geochemical elements in the groundwater were attributed to the human activities in the Ardabil plain located in the northwest of Iran.     

Application of Leeb Hardness Test in Prediction of Dynamic Elastic Constants of Sedimentary and Igneous Rocks

Geotechnical and Geological Engineering - The Leeb hardness test is a non-destructive and portable technique that can be used both in the laboratory and in-field applications. The main purpose of...     

Non-linear damping of visco-resistive Alfvén waves in solar spicules

Interaction of Alfvén waves with plasma inhomogeneities generates phase mixing which can lead to dissipate Alfvén waves and to heat the solar plasma. Here we study the dissipation of Alfvén waves by phase mixing due to viscosity and resistivity variations with height. We also consider nonlinear magnetohydrodynamic (MHD) equations in our theoretical model. Non-linear terms of MHD equations include perturbed velocity, magnetic field, and density. To investigate the damping of Alfvén waves in a stratified atmosphere of solar spicules, we solve the non-linear MHD equations in the x–z plane. Our simulations show that the damping is enhanced due to viscosity and resistivity gradients. Moreover, energy variations is influenced due to nonlinear terms in MHD equations.     

Conceptual study of X-braced frames with different steel grades using cyclic half-scale tests

In this paper,an experimental and analytical study of two half-scale steel X-braced frames with equal nominal shear strength under cyclic loading is described.In these tests,all members except the braces are similar.The braces are made of various steel grades to monitor the effects of seismic excitation.Internal stiffeners are employed to limit the local buckling and increase the fracture life of the steel bracing.A heavy central core is introduced at the intersection of the braces to decrease their effective length.Recent seismic specifications are considered in the design of the X-braced frame members to verify their efficiency.The failure modes of the X-braced frames are also illustrated.It is observed that the energy dissipation capacity,ultimate load capacity and ductility of the system increase considerably by using lower grade steel and proposed detailing.Analytical modeling of the specimens using nonlinear finite element software supports the experimental findings.     

Evaluation of total load sediment transport formulas using ANN

The calculated results from various sediment transport formulas often differ from each other and from measured data. Some parameters in the sediment transport formulas are more effective than others to estimate total sediment load. In this study, an Artificial Neural Network （ANN） model is trained using four dominant parameters of sediment transport formulas. ANN models are able to reveal hidden laws of natural phenomena such as sediment transport process. The results of ANN and some total bed material load sediment transport formulas have been compared to indicate the importance of variables which can be used in developing sediment transport formulas. To train ANN, average flow velocity, water surface slopes, average flow depth, and median particle diameter are used as dominant parameters to estimate total bed material load. Two hundreds and fifty samples are used to train the ANN model. Twenty-four sets of field data not used in the training nor calibration of ANN are used to compare or verify the accuracy of ANN and some well-known total bed material load formulas. The test results show that the ANN model developed in this study using minimum number of dominant factors is a reliable and uncomplicated method to predict total sediment transport rate or total bed material load transport rate. Results show that the accuracy of formulas in descending order are those by Yang （1973）, Laursen （1958）, Engelund and Hansen （1972）, Ackers and White （1973）, and Toffaleti （1969）. These results are similar to those made by ASCE （1982） based on laboratory and field data not used in this paper. Study results also show that the formulas based on physical laws of sediment transport, like those formulas that were developed based on power concept, are more accurate than other formulas for estimating total bed material sediment load in rivers.     

Biosorption of Pb, Cd, Cu and Zn from the wastewater by treated Azolla filiculoides with H2O2/MgCl2

The adsorption of heavy metals onto treated Azolla filiculoides by H₂O₂/MgCl₂, as a cosmopolitan free-floating waterfern, was investigated from aqueous solutions in the batch biosorption experiments. The maximum uptake capacities of the collected Azolla from rice field at the optimal conditions for Pb, Cd, Cu and Zn ions were approximately 228, 86, 62 and 48 mg/g (dry Azolla), respectively. On the other hand, the maximum uptake capacities of the collected Azolla from the Anzali International Wetland in the north part of Iran at the same conditions for these heavy metals were about 124, 58, 33 and 34 mg/g (dry Azolla), respectively. Such decrease of uptakes is due to the pollution of Anzali International Wetland, which reduces the capacity uptake of metals. The recovery of biosorbed heavy metals from the rice field Azolla was carried out by HCl and NaCl desorbents that the recovery of 64–86% and 51–72% was occurred, respectively.     

Toxic effect of Pb, Cd, Ni and Zn on Azolla filiculoides in the International Anzali Wetland

The limitation of plant growth in the polluted mediums can be used as a factor to determine of plant tolerance and the toxic effect of these mediums. In this work, the effect of Pb²⁺, Cd²⁺, Ni²⁺and Znsu2+ (individually) on Azolla filiculoides growth in the aqueous solution and using this method to water post treatment were studied. During 15 days the biomass the fresh Azolla with initial mass of 20 g was grown on the nutrient solution containing these metal ions, each in a concentration 4 mg/l. The presence of these ions, caused about 25%, 42%, 31% and 17% inhibition of biomass growth, respectively, in comparison to Azolla control weight which had not heavy metals. The water salinity of 1, 2 and 4 g. NaCl/l decreased the removal of these heavy metals about 4–7%, 20–24% and 40–55%, respectively. The addition of total dissolved solids (TDS) from 50 to 300 ppm. (as CaCO₃) into the samples of containing heavy metals increased Azolla growth, but decreased the control Azolla growth.     

Transverse oscillations in solar spicules induced by propagating Alfvénic pulses

The excitation of Alfvénic waves in solar spicules by localized Alfvénic pulses is investigated. A set of incompressible MHD equations in the two-dimensional x–z plane with steady flows and sheared magnetic fields is solved. Stratification due to gravity and transition region between chromosphere and corona is taken into account. An initially localized Alfvénic pulse launched below the transition region can penetrate from transition region into the corona. We show that the period of the transversal oscillations is in agreement with those observed in spicules. Moreover, it is found that the excited Alfvénic waves spread during propagation along the spicule length, and suffer efficient damping of the oscillations amplitude. The damping time of the transverse oscillations increased with decreasing k _b values.