Understanding of attachment efficiency and induction time between bubbles and pyrite particles in flotation

The fundamental flotation models are useful for understanding flotation mechanisms. However, these models cannot be used for design and optimization of flotation circuits because it is very difficult to determine induction times experimentally during flotation despite using advanced high-speed cameras. Thus, there is a need to develop the model that can be used for practical applications, which is the main objective in this work. The developed models were successful in predicted P_a (attachment efficiency) and t_i (induction time) at various chemical conditions. The values of P_a (attachment efficiency) were strongly affected by particle size, collector concentration and pulp pH while the values of t_i (induction time) were affected by particle size and collector concentration and the values of k (flotation rate constant) were affected by collector concentration only. It means that P_a is much more sensitive than t_i and k to detect the changes in the flotation experimental conditions. The slopes of t_i vs P_a functions were larger at different particle sizes than those at different collector concentrations, demonstrating that the effect of particle size was more dominant than the effect of collector concentration on P_a. This paper demonstrated that understanding of P_a is essential for better analysing flotation mechanisms.     

Influence of slip length on filtration performance of fine particles

Fine particle filtration has been known to become progressively inefficient as the filter cake builds up owing to restricted movement of liquid through the small cavities formed in the cake. In different chemical industries, this restricts higher throughput rates and also results in higher transportation costs due to increase in moisture content. This paper discusses the influence of using a surfactant, DAH (dodecylamine hydrochloride), in enhancing the filtration rate of a finely ground particles and the reduction of moisture content in the cake. The observed enhanced filtration rate has been attributed to a reduction in the resistance to liquid flow due to the increase in hydrophobicity at the particle surface. The resulting enhanced filtration rate has been modelled by superimposing a slip velocity at the boundary of the capillaries formed in the cake. The model evaluates the cake and medium resistances by incorporating a slip length into the filtration equation which varies with the concentration of hydrophobic reagent and the effective size of capillaries. The increase in filtration rate is more pronounced for finer particle slurries. Also, it has been observed that the moisture content of the filter cakes formed was reduced.     

In-depth study of mechanical properties of poly(lactic acid)/thermoplastic polyurethane/hydroxyapatite blend nanocomposites

Journal of Materials Science - The present study evaluates the effect of adding different contents of hydroxyapatite (HA) nanoparticles on the mechanical properties of poly(lactic...     

Probabilistic Event Based Rainfall-Runoff Modeling Using Copula Functions

Multivariate probability analysis of hydrological elements using copula functions can significantly improve the modeling of complex phenomena by considering several dependent variables simultaneously. The main objectives of this study were to: (i) develop a stand-alone and event-based rainfall-runoff (RR) model using the common bivariate copula functions (i.e. the BCRR model); (ii) improve the structure of the developed copula-based RR model by using a trivariate version of fully-nested Archimedean copulas (i.e. the FCRR model); and (iii) compare the performance of the developed copula-based RR models in an Iranian watershed. Results showed that both of the developed models had acceptable performance. However, the FCRR model outperformed the BCRR model and provided more reliable estimations, especially for lower joint probabilities. For example, when joint probabilities were increased from 0.5 to 0.8 for the peak discharge (q_p) variable, the reliability criteria value increased from 0.0039 to 0.8000 in the FCRR model, but only from 0.0010 to 0.6400 in the BCRR model. This is likely because the FCRR considers more than one rainfall predictor, while the BCRR considers only one.

     

Application of ZnO and TiO<Subscript>2</Subscript> nanoparticles coated onto montmorillonite in the presence of H<Subscript>2</Subscript>O<Subscript>2</Subscript> for efficient removal of cephalexin from aqueous solutions

This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO₂ (TiO₂/GLM) in the presence of H₂O₂. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔG ^o and ΔH ^o revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO₂/GLM, respectively. Temkin constant (B _T ) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.     

New Approaches to Routing in Mobile Ad hoc Networks

Worldwide Interoperability for Microwave Access (Wimax) is power station through which mobile network, commonly known as A Mobile Ad-hoc Network (MANET) is used by the people. A MANET can be described as an infrastructure-less and self-configure network with autonomous nodes. Participated nodes in MANETs move through the network constantly causing frequent topology changes. Designing suitable routing protocols to handle the dynamic topology changes in MANETs can enhance the performance of the network. In this regard, this paper proposes four algorithms for the routing problem in MANETs. First, we propose a new method called Classical Logic-based Routing Algorithm for the routing problem in MANETs. Second is a routing algorithm named Fuzzy Logic-based Routing Algorithm (FLRA). Third, a Reinforcement Learning-based Routing Algorithm is proposed to construct optimal paths in MANETs. Finally, a fuzzy logic-based method is accompanied with reinforcement learning to mitigate existing problems in FLRA. This algorithm is called Reinforcement Learning and Fuzzy Logic-based (RLFLRA) Routing Algorithm. Our proposed approaches can be deployed in dynamic environments and take four important fuzzy variables such as available bandwidth, residual energy, mobility speed, and hop-count into consideration. Simulation results depict that learning process has a great impact on network performance and RLFLRA outperforms other proposed algorithms in terms of throughput, route discovery time, packet delivery ratio, network access delay, and hop-count.

     

Comparative Study of Tocopherol Contents and Fatty Acids Composition in Twenty Almond Cultivars of Afghanistan

Afghanistan is the fourth largest producer of almonds in the world producing 78 native and 6 imported cultivars. However, till date, there have been no comprehensive data on nutrient profiles of the native cultivars. Thus, in the present investigation, tocopherol contents and fatty acid composition from the kernels of 20 selected native almond cultivars of Afghanistan were analyzed. The ranges of variability for the studied nutrients were similar to those already reported for almonds grown in other countries, such as 47.8–66.1% of total lipids (fresh weight basis), 62.54–81.57% of oleic acid in the total lipids, and 139.1–355.0 μg/g α-tocopherol in kernels. With respect to cultivars, significantly (p < 0.05) high content of total lipids were recorded in ‘Belabai’ and ‘Sattarbai’ (Afghan grade), oleic acid in ‘Khairodini’ and of α-tocopherol in ‘Khairodini-161 Samangan’ and ‘Belabai’ cultivars. Kernels from these cultivars can be used for nutrient dense food formulations. Daily consumption of 50 g almonds is sufficient to meet the RDA of α-tocopherol (15 mg/day), considering the average 300 μg/g of α-tocopherol in Afghan almonds. Also, these nutrient rich cultivars can be used in almond breeding programs globally, to focus on improving kernel oil composition and nutrient contents.     

A case study on the soil–pile–structure interaction of a long span arched structure

Different concepts for modelling of soil-foundation in complete dynamic interaction analysis for a 110-m height 70-m span arched structure on 180 piles were investigated in this paper. The modelling approaches consisted of a sophisticated procedure to account for soil compliance and foundation flexibility by defining frequency-dependent springs and dashpots; namely, flexible-impedance base model. The results of this model were compared with those of the conventional modelling procedures; namely, fixed base model and flexible base model by defining frequency-independent springs. In the flexible-impedance base model, the substructure approach was employed through finite element modelling. To account for the kinematic interaction, the numerical model of the soil, foundation and piles were developed using a verified finite element model in ABAQUS. The free field time history and design spectrum were modified to obtain the foundation input motion. The impedance of pile groups with different length was obtained by the finite element model to assess the inertial interaction. The comparison of the results of the employed models showed that rocking and torsional responses were greatly affected by soil–structure interaction, indicating redistribution of seismic demands. It was also proven that the internal demands of the conventional model considering frequency-independent Winkler springs might be higher than those of the model including pile–soil–structure interaction effects.