Effect of different size of joint enlargement on seismic behavior of gravity load designed RC beam‐column connections

Effect of different size of planer joint enlargement as a noninvasive and practical strategy for seismic retrofit of gravity load designed external reinforced concrete beam‐column connections was experimentally investigated. The joint region was enlarged using steel angles that are mounted using prestressed cross‐ties. Reverse cyclic load tests on five half‐scale control and retrofitted external RC beam‐column connections were conducted. Three different size of planer joint enlargement being 180, 140, and 90 mm were considered for retrofitted specimens. The performance of the retrofitted specimens is compared with that of the control gravity load designed beam‐column connections, in terms of load–displacement hysteresis curve, energy dissipation and ductility capacities, and global strength and stiffness degradation behavior. The experimental results showed that increasing the size of planer joint enlargement significantly enhances the seismic capacity of the retrofitted connections, in terms of strength, stiffness, energy dissipation, and ductility capacity and also planer joint enlargement can relocate beam plastic hinges to outside the joint panel.     

No-wait two stage hybrid flow shop scheduling with genetic and adaptive imperialist competitive algorithms

This article studies a no-wait two-stage flexible flow shop scheduling problem with setup times aiming to minimize the total completion time. The problem is solved using an adaptive imperialist competitive algorithm (AICA) and genetic algorithm (GA). To test the performance of the proposed AICA and GA, the algorithms are compared with ant colony optimisation, known as an effective algorithm in the literature. The performance of the algorithms are evaluated by solving both small and large-scale problems. Their performance is evaluated in terms of relative percentage deviation. Finally the results of the study are discussed and conclusions and potential areas for further study are highlighted.     

An intelligent hybrid meta-heuristic for solving a case of no-wait two-stage flexible flow shop scheduling problem with unrelated parallel machines

This paper addresses the problem of no-wait two-stage flexible flow shop scheduling problem (NWTSFFSSP) considering unrelated parallel machines, sequence-dependent setup times, probable reworks and different ready times to actualize the problem. The performance measure used in this study is minimizing maximum completion time (makespan). Because of the complexity of addressed problem, we propose a novel intelligent hybrid algorithm [called hybrid algorithm (HA)] based on imperialist competitive algorithm (ICA) which are combined with simulated annealing (SA), variable neighborhood search (VNS) and genetic algorithm (GA) for solving the mentioned problem. The hybridization is carried out to overcome some existing drawbacks of each of these three algorithms and also for increasing the capability of ICA. To achieve reliable results, Taguchi approach is used to define robust parameters' values for our proposed algorithm. A simulation model is developed to study the performance of our proposed algorithm against ICA, SA, VNS, GA and ant colony optimization (ACO). The results of the study reveal the relative superiority of HA studied. In addition, potential areas for further researches are highlighted.     

The effect of pH,solid content,water chemistry and ore mineralogy on the galvanic interactions between chalcopyrite and pyrite and steel balls

The role of pH, solid content, water chemistry and ore mineralogy on the galvanic interactions between chalcopyrite and pyrite and low alloy steel balls were investigated in the grinding of Sarcheshmeh porphyry copper sulfide ore. All these factors strongly affect the galvanic current between the minerals and the steel during the grinding process. The galvanic current density decreased as the solution pH and percent solids increased. In addition, changing the water in the ball mill from tap to distilled water reduced the galvanic current between the minerals and the balls. Potentiodynamic polarization curves showed that pyrite and chalcopyrite demonstrated typical active-passive-transpassive anodic behavior in the grinding of copper ore. However, the nature of their transitions from the active to the passive state differed. This behavior was not seen in the grinding of pure minerals. In addition, an EDTA extraction technique was employed to quantify the amount of oxidized iron in the mill discharge. The amount of extractable iron was influenced by the same experimental factors and in the same way as the galvanic current.     

Workshop scheduling using practical (inaccurate) data Part 3: A framework to integrate job releasing,routing and scheduling functions to create a robust predictive schedule

A comprehensive simulation study conducted by the authors investigated the robustness of a predictive scheduling system in a dynamic and stochastic environment. The results revealed that to improve the robustness of a scheduling system, besides using a robust scheduling method with a frequent rescheduling policy, the shop load should be well controlled and kept balanced. Integrating the planning and the scheduling functions has been shown to achieve this objective. This paper discusses the effects of the planning i.e. job releasing and routing and the scheduling functions in creating a robust schedule and a framework to integrate the above functions is proposed. This system consists of a planning module that is concerned with job releasing and routing decisions and a scheduling module that provides the detailed scheduling. A mathematical model using the integer programming technique is use to demonstrate a solution for the planning module. In addition, a heuristic algorithm is used to solve the scheduling problem. It is shown that, in terms of shop load balance level and job delivery time, the proposed system performs better than a benchmark loading strategy on the basis of minimum processing cost.     

Effect of Flotation Reagents on the Activity of L. Ferrooxidans

Froth flotation is the most preferred processing technique for the enrichment of low-grade sulfides. Bioleaching is an eco-friendly method for metallurgical extraction from flotation products. Flotation reagents (collectors, frothers, etc.) have various impacts on bioleaching and bacterial activities. In this investigation, the effect of a number of sulfide flotation collectors [potassium amyl-xanthate, potassium isobutyl-xanthate, sodium ethyl-xanthate, potassium isopropyl-xanthate, and Dithiophosphate (Aero3477)], and frothers (pine oil and methyl isobutyl carbinol) with different dosages is studied on Leptospirillum ferrooxidans activities. The results of various measurements indicated that these flotation chemicals can have positive or negative influences on the bacterial activities, based on their chemical compositions and/or concentrations. These results can extensively be used for the selection of flotation reagents when bioleaching is chosen as the metallurgical extraction method after flotation enrichment.     

Modeling the effects of ore properties on water recovery in the thickening process

A better understanding of solid-liquid separation would assist in improving the thickening performance and perhaps water recovery as well. The present work aimed to develop an empirical model to study the effects of ore properties on the thickening process based on pilot tests using a column. A hydro-cyclone was used to prepare the required samples for the experiments. The model significantly predicted the experimental underflow solid content using a regression equation at a given solid flux and bed level for different samples, indicating that ore properties are the effective parameters in the thickening process. This work confirned that the water recovery would be increased about 5% by separating the feed into two parts, overflow and underflow, and introducing two different thickeners into them separately. This is duo to the fact that thickeners are limited by permeability and compressibility in operating conditions.     

Removal of copper from molybdenite concentrate by mesophilic and extreme thermophilic microorganisms

Mixed mesophilic and extreme thermophilic bioleaching were evaluated to remove copper from the molybdenite concentrate. Bioleaching tests were carried out in shake flasks and in a 50-L bioreactor. The shake flask tests were performed with different inoculum size, solids density, pH, and temperature in order to identify optimum conditions. The highest amount of copper elimination, 75% was obtained with extreme thermophilic microorganisms (at 12% inoculation, 10% solids, 65 °C and a pH of 1.5). The highest copper elimination by mesophilic microorganisms was 55% (at 12% inoculation, 5% solids, 30 °C at pH 2). The optimum conditions in shake flask tests were applied to 7 days batch tests in a 50-L bioreactor. Extreme thermophilic experiment gave the best copper elimination of 60% (at 12% inoculation, 10% solids, 65 °C and pH 1.5). Mesophilic test removed 50% of the copper (at 12% inoculation, 10% solids, 35 °C at pH 2).