Evaluation of effect of blast design parameters on flyrock using artificial neural networks

Flyrock, the propelled rock fragments beyond a specific limit, can be considered as one of the most crucial and hazardous events in the open pit blasting operations. Involvement of various effective parameters has made the problem so complicated, and the available empirical methods are not proficient to predict the flyrock. To achieve more accurate results, employment of new approaches, such as artificial neural network (ANN) can be very helpful. In this paper, an attempt has been made to apply the ANN method to predict the flyrock in the blasting operations of Sungun copper mine, Iran. Number of ANN models was tried using various permutation and combinations, and it was observed that a model trained with back-propagation algorithm having 9-5-2-1 architecture is the best optimum. Flyrock were also computed from various available empirical models suggested by Lundborg. Statistical modeling has also been done to compare the prediction capability of ANN over other methods. Comparison of the results showed absolute superiority of the ANN modeling over the empirical as well as statistical models. Sensitivity analysis was also performed to identify the most influential inputs on the output results. It was observed that powder factor, hole diameter, stemming and charge per delay are the most effective parameters on the flyrock.     

Pancreatic Islets Accumulate Cadmium in a Rodent Model of Cadmium-Induced Hyperglycemia

Cadmium (Cd) is an anthropogenic as well as a naturally occurring toxicant associated with prediabetes and T2DM in humans and experimental models of Cd exposure. However, relatively few studies have examined the mechanism(s) of Cd-induced hyperglycemia. The purpose of this study was to examine the role of pancreatic islets in Cd-induced hyperglycemia. Male Sprague–Dawley rats were given daily subcutaneous doses of Cd at 0.6 mg/kg over 12 weeks. There was a resulting time-dependent increase in fasting blood glucose and altered insulin release in vitro. Islets isolated from control (saline-treated) and Cd-treated animals were incubated in low (0.5 mg/mL) or high (3 mg/mL) glucose conditions. Islets from 12 week Cd-treated animals had significantly less glucose-stimulated insulin release compared to islets from saline-treated control animals. The actual Cd content of isolated islets was 5 fold higher than the whole pancreas (endocrine + exocrine) and roughly 70% of that present in the renal cortex. Interestingly, islets isolated from Cd-treated animals and incubated in high glucose conditions contained significantly less Cd and zinc than those incubated in low glucose. These results show that within whole pancreatic tissue, Cd selectively accumulates in pancreatic islets and causes altered islet function that likely contributes to dysglycemia.     

Iron catalyst supported on carbon nanotubes for Fischer-Tropsch synthesis: Effects of Mo promotion

Our studies on the application of carbon nanotubes (CNTs) as support have shown that iron catalysts supported on CNTs are active and selective catalysts for Fischer-Tropsch synthesis (FTS). However, these catalysts experienced deactivation as a result of active site agglomerations. In order to control the agglomeration of active site, which is an important step in developing a novel catalyst supported on carbon-based supports, the effects of Mo promotion on deactivation behavior of iron catalysts supported on CNTs were studied. In this work the properties and catalytic performance of unpromoted iron catalysts were compared with a promoted catalyst with different Mo contents (0.5, 1, 5, and 12 wt%). Based on TEM and XRD analyses, promotion of the catalysts with Mo resulted in production of smaller metal particles compared to the unpromoted iron catalyst. According to XRD analysis, Mo species were deposited in their amorphous structure. TPR analyses showed that addition of Mo increased reduction temperature significantly. Based on TEM and XRD analyses, the particle size of the iron oxides in the unpromoted catalyst increased from 16 to 25 nm under FT operating conditions, while the particle size of the iron oxide in the Mo promoted catalysts (∼12-14 nm) did not change noticeably under the same operating conditions. Activity, selectivity and stability of the unpromoted and Mo promoted catalysts showed that addition of 0.5-1 wt% Mo resulted in a more stable catalyst. Higher contents of Mo (5 and 12 wt%) decreased the activity of the catalysts due to catalytic site coverage and lower extent of reduction. Mo promotion (0.5-12 wt%) increased the selectivity of the catalysts toward lighter hydrocarbons. The promotion of the iron catalyst with 0.5 wt% of Mo stabilized the activity of the catalyst with minimal increase (2%) in methane selectivity.     

Low-tar,highly burnable gas production from the gasification of pelletized palm empty fruit bunch

Gasification is an attractive method to convert lignocellulosic biomass into a combustible gas mixture for electricity and power generation. To control the tar concentration in the produced gas to be within the allowable limit of downstream applications, it is important for a gasification system to be integrated with a tar removal process. In this study, an integrated gasification system consisting of a downdraft gasifier and a secondary catalytic tar-cracking reactor was designed and tested for the gasification of pelletized oil palm empty fruit bunch. To further purify the producer gas, the system was also integrated with a cyclone, a water scrubber, and a carbon-bed filter. Biomass was fed at a rate of 5 kg/h, while the air equivalence ratio (ER) and the gasification temperature were set at 0.1 and 800°C, respectively. In total, 5 kg of the specially developed low-cost Fe/activated carbons (AC) catalyst was used in the hot gas catalytic tar-cracking reactor. Results indicate that our integrated gasification system was able to produce a clean burnable gas with a lower heating value (LHV) of 9.05 MJ/Nm³, carbon conversion efficiency (CCE) of 79.4%, cold gas efficiency (CGE) of 89.9%, and H₂ and CH₄ concentrations of 29.5% and 10.3%, respectively. The final outlet gas was found to only contain 32.5 mg/Nm³ of tar, thus making it suitable for internal combustion engine (ICE) application.     

A molecular model for carbon black primary particles with internal nanoporosity

A molecular model of primary particles of porous carbon black has been developed. Using the hexagonal graphite sheets as building units, we simulated formation of carbon particles consisting of a core–shell structure. Several structural properties of carbon were examined. Graphite layers arrange in a concentric fashion in the shell region near the external surface of carbon. This trend gradually diminishes toward the center of carbon particles, resulting in an amorphous characteristic in the core region. In line with XRD experiments, our simulations show that about half of the graphite sheets in the carbon shell form microcrystalline domains typically consisting of 2–5 layers with a broad interlayer spacing of 0.34–0.4 nm. Starting from nonporous carbon particles with a high density of 2 g/cm³, a ‘digging’ approach was further developed to particularly model the internal nanoporosity of mesoporous carbon materials that are often obtained by the silica templating technique. The validity of the modeling technique to generate pores inside carbon particles is discussed in view of reproducing targeted PSDs.     

Oscillatory structure–property correlation in azelate polyols and thermoplastic polyurethanes

Azelate polyols of 2000 g mol^?1 have been successfully prepared via esterification of renewable azelaic acid with linear diols containing different number of CH₂ repeating units. Structure–property correlation of the azelate polyols had been evaluated in thermoplastic polyurethanes (TPUs). TPUs based on azelate polyols of longer chained linear diols with >4 CH₂ repeat units retained higher degrees of crystallinity associated with the polyol soft segment. The ratio of hydrogen bonded urethane in the hard segment to free urethane phase mixed with the soft segment in the TPUs showed a complex oscillating dependence with increased number of CH₂ repeating unit in the linear diols of azelate polyols. Correspondingly, static and dynamic properties of TPUs also showed the oscillatory dependence, whereby dynamic properties maximized with odd number of CH₂ repeating unit and material strength maximized with even number of CH₂ repeating unit. The results therefore can be used as guide to select appropriate azelate polyols to target specific TPU performance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46258.     

Thermal effects in dynamic storage of hydrogen by adsorption

Thermal effects in dynamic hydrogen storage by adsorption at room temperature and high pressure are studied theoretically and experimentally. The system of adsorbate–adsorbent used was hydrogen in granular activated carbon. The theoretical analysis was based on heat- and mass-transfer modeling in a packed-bed adsorber, with particular emphasis on the thermal effects occurring during charge and discharge steps. The influence of gas flow rate and storage pressure (up to 15 MPa) on the total amount stored or delivered was investigated. Operating conditions were compatible with practical application for onboard vehicle storage. The experimental study was carried out in cylindrical 2-L reservoirs filled with granular activated carbon in which the bed temperature was measured at various positions. The temperature changes during both charge and discharge agreed well with the model predictions.