Prediction of rock fragmentation due to blasting using artificial neural network

Prediction of rock fragmentation is essential for optimizing blasting operation. Fragmentation depends on many parameters such as rock mass properties, blast geometry and explosive properties. In this paper, artificial neural network (ANN) method is implemented to develop a model to predict rock fragmentation due to blasting in an iron ore mine. In the developing of the proposed model eight parameters such as hole diameter, burden, powder factor, blastability index, etc., were incorporated. Training of the model was performed by back-propagation algorithm using 220 datasets. A four-layer ANN was found to be optimum with architecture 10-9-7-1. Sensitivity analysis revealed that the most effective parameters on rock fragmentation are blastability index (G), charge per delay (J), burden (C), SMR (F) and powder factor (E).     

Routine design with information content and fuzzy quality function deployment

Design can be classified into four basic categories: creative design, innovative design, redesign, and routine design. This paper describes a method for performing routine design by utilizing information content and fuzzy quality function deployment. An attempt has been made to associate with each critical characteristic of a product a value representing the information content, which is a measure of probability that a system can produce the parts as specified by the designer, using a specific manufacturing technology for making the parts. Once the information content of each design alternative is computed, the system will select an alternative with the minimum amount of information content. The proposed method provides us with a means for solving the critical design evaluation and validation problem.     

A Method for Calculation of Final Film Thickness in Free Coating of Viscoelastic Fluids onto a Vertical Surface

A method for the calculation of the final film thickness in free coating of a viscoelastic fluid onto a vertical surface withdrawn from its vessel is developed. The method is based on the definition of an objective function, the minimization of which guarantees that the kinematic as well as the dynamic conditions at the lower boundary of the dynamic meniscus region are simultaneously satisfied. A systematic approach is provided in order to localize the optimum value of the final film thickness within the optimization interval. It was observed that there was a clear relationship between the estimated final film thickness and the value of a parameter A. The closeness of this parameter to zero corresponds to the dynamic constraint being fulfilled at the lower boundary of the dynamic meniscus region. This relationship is used as an objective means of determining the direction to update the interval of optimization to obtain the final thickness of the film. The results of the proposed method are compared to the previous works on the free coating of viscoelastic fluids, which are based on a trial‐and‐error method. The performance of the previously applied rheological models to the formulation of the free coating process, mainly the modified Oldroyd models, is also compared by introducing the present method.     

Effect of Rock Wool Waste on Compressive Behavior of Pumice Lightweight Aggregate Concrete After Elevated Temperature Exposure

In the present study, the mechanical properties and the residual stress–strain behavior of lightweight concrete (LWC) containing pumice coarse aggregate and rock wool waste (consisting of mineral fibers) were explored prior to and following thermal loading. Key variables included the volume percentage of rock wool waste (0%, 2.5%, 5%, 7.5%, and 10%) and exposure temperature (20°C, 200°C, 400°C, and 600°C). Here, parameters playing a role in the compressive performance of LWC containing rock wool waste were examined. These parameters included the elastic modulus, compressive strength, strain at peak stress, ultimate strain, toughness index, stress–strain relationship, and failure mode. Then, several empirical relationships were proposed to predict different mechanical characteristics in terms of temperature and volume percentage of rock wool. Furthermore, the compressive strength, elastic modulus, and strain at peak stress values were compared to the prediction results of the ACI 216, EN 1994-1-2, ASCE, and CEB-FIP 1990 codes. The results demonstrated that the mechanical properties of the LWC specimens were degraded with temperature. The highest degradation in the temperature range under study occurred at 600°C, with around 50% and 80% drop in the compressive strength and elastic modulus, respectively. Furthermore, after exposure to 600°C, an increase of 2 to 2.8 folds occurred in the strain at peak stress and an increase of 2.6 to 3.4 folds occurred in the ultimate strain of the specimens relative to those at the ambient temperature. In the end, two stress–strain models were presented to capture the compressive performance of LWC including rock wool waste after elevated temperature exposure based on the empirical equations obtained for the mechanical characteristics. These models showed a relatively good correlation with the experimental data.

     

Equilibrium and kinetic adsorption study of a cationic dye by a natural adsorbent--silkworm pupa

In this work the use of silkworm pupa, which is the waste of silk spinning industries has been investigated as an adsorbent for the removal of C.I. Basic Blue 41. The amino acid nature of the pupa provided a reasonable capability for dye removal. Equilibrium adsorption isotherms and kinetics were investigated. The adsorption equilibrium data were analyzed by using various adsorption isotherm models and the results have shown that adsorption behavior of the dye could be described reasonably well by either Langmuir or Freundlich models. The characteristic parameters for each isotherm have been determined. The monolayer adsorption capacity was determined to be 555 mg/g. Kinetic studies indicated that the adsorption follows pseudo-second-order kinetics with a rate constant of 0.0434 and 0.0572 g/min mg for initial dye concentration of 200 mg/l at 20 and 40 degrees C, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process. The rate constant for intra-particle diffusion was estimated to be 1.985 mg/g min(0.5).     

Using GA–ANN algorithm to optimize soft magnetic properties of nanocrystalline mechanically alloyed Fe–Si powders

In this investigation a theoretical model based on artificial neural network (ANN) and genetic algorithm (GA) has been developed to optimize the magnetic softness in nanocrystalline Fe–Si powders prepared by mechanical alloying (MA). The ANN model was used to correlate the milling time, chemical composition, milling speed, and ball to powders ratio (BPR) to coercivity and crystallite size of nanocrystalline Fe–Si powders. The GA–ANN combined algorithm was incorporated to find the optimal conditions for achieving the minimum coercivity. By comparing the predicted values with the experimental data it is demonstrated that the combined GA–ANN algorithm is a useful, efficient and strong method to find the optimal milling conditions and chemical composition for producing nanocrystalline Fe–Si powders with minimum coercivity.     

Prediction of flow and heat transfer through a microtube filled with bidisperse porous medium under local thermal nonequilibrium condition

In this paper, the thermal and hydrodynamic solutions of a microtube filled with bidisperse porous medium (BDPM) under the local thermal nonequilibrium (LTNE) condition are presented. Considering the LTNE condition, the energy equations have been numerically solved. The rarefaction effects are considered for Knudsen numbers ranging from 0 to 0.1; therefore, first‐order boundary condition is applied on the wall. The temperature distribution of each phase is examined with respect to the involved parameters in the BDPM system. For the first time, the Nusselt number ratio (NRDP) is introduced to study the influence of Darcy number on the Nusselt number more precisely. Also, the effect of different thermophysical parameters on the Nusselt number is studied. The advantage of BDPM system over monodisperse porous medium (MDPM) structure is examined through the heat transfer performance parameter. The findings exhibit a good agreement with the literature. Also, the LTNE condition produces more realistic results in comparison to local thermal equilibrium assumption. On the whole, although implementing the BDPM enhances the heat transfer rate compared with the MDPM, it does not improve the thermal hydrodynamic performance significantly.     

PVA nanofibers containing ofloxacin/α-cyclodextrin inclusion complexes: improve ofloxacin water solubility

Abstract

Ofloxacin (OFL) is an antibiotic with a wide range of bacterial infections but its low water solubility and photo stability restricts its applications, so improve its solubility and stability is a challenge. Inclusion complex formation between α-cyclodextrin (α-CD) and OFL was prepared under various circumstances to obtained desirable water solubility. The effect of polyethylene glycol physiologically compatible solubilizing agent and mixing condition were investigated in the formation of an inclusion complex between α-CD/OFL. FTIR, H-NMR, DSC and XRD results indicated the formation of an inclusion complex between α-CD/OFL. Phase solubility test for obtaining α-CD/OFL complexes indicated a rise in aqueous solubility of OFL and formation of inclusion complexes and obviating OFL aqueous solubility limitation. SEM and EDX results indicated OFL/CD/PVA nanofibers without beading defect. Antibacterial activities of OFL/CD nanoparticles were investigated by them inhabitation of bacteria growth. Obtained nanofibers showed significant antibacterial effect against Escherichia Coli and Staphylococcus aureus.     

An insight into mode II fracture toughness testing using SCB specimen

The effect of friction forces between the test specimen and its bottom supports on the mode II fracture toughness values obtained using the semicircular bend (SCB) specimen is investigated. First, a number of experiments were conducted on SCB specimen in order to determine the mode II fracture toughness of polymethyl methacrylate (PMMA) according to the conventional approaches available in the literature. Three different types of supports that have been frequently employed by researchers in recent years were used to evaluate the effect of support type on the fracture loads. It was found that the friction forces between the supports and the SCB specimen have a significant effect on the value of mode II fracture toughness measured using the SCB samples. Then, the specimen was simulated using finite element method for more detailed investigation on the near crack tip stress field evolution when friction forces increase between the supports and the SCB specimen. The finite element results confirmed that the type of support affects not only the stress intensity factors K_I and K_II but also the T‐stress. The experimental and numerical results showed that the use of the crack tip parameters available in literature for frictionless contact between the supports and the SCB specimen can result in significant errors when the mode II experiments are performed by using the fixed or roller‐in‐grove types of supports.     

Effect of comonomer on the viscoelastic behavior of co-poly (acrylonitrile) solutions

Three copolymers of acrylonitrile-methacrylic acid [P(AN-co-MAA)], acrylonitrile-ammonium salt of methacrylic acid [P(AN-co-AMA)], acrylonitrile-methacrylamide-itaconic acid [P(AN-MAM-IA)] and PAN homopolymer were synthesized by aqueous dispersion polymerization technique. The polymerization conditions were adjusted in such a way to produce polymers with similar composition and molecular weight. The influence of comonomer nature on the viscoelastic behavior and spinnability of copolymer/dimethylsulfoxide (DMSO) solutions were investigated. It was found that incorporation of these comonomers into PAN chains led to intense decrease in zero-shear viscosity to lower value as well as appearance of distinct plateau in comparison with PAN homopolymer. However, comparing the results of complex viscosity and shear viscosity of each PAN polymer showed different shear-thinning behavior, typical deviation from Cox-Merz rule at high deformation rates. Amongst these copolymer solutions, P(AN-co-AMA) exhibited the longest relaxation time (λ) at low and medium frequencies. The lower values of frequency dependence of G′ (n′) and cross over frequency (ω_c) of storage modulus (G′) and loss modulus (G″) indicated that P(AN-co-AMA) was more elastic than other PAN copolymer solutions. The log-log plots of tan δ versus ω demonstrated that the comonomer nature affects the sol-gel transition behavior and elastic character of copolymer solutions. On average, based upon the slope of logG? versus logG? data, the incorporation of comonomers inside PAN chains led to ~50 % increase in the homogeneity of solutions compared to PAN homopolymer.