A particle swarm optimisation for the no-wait flow shop problem with due date constraints.

Peer ReviewedThis paper considers the no-wait flow shop scheduling problem with due date constraints. In the no-wait flow shop problem, waiting time is not allowed between successive operations of jobs. Moreover, a due date is associated with the completion of each job. The considered objective function is makespan. This problem is proved to be strongly NP-Hard. In this paper, a particle swarm optimisation (PSO) is developed to deal with the problem. Moreover, the effect of some dispatching rules for generating initial solutions are studied. A Taguchi-based design of experience approach has been followed to determine the effect of the different values of the parameters on the performance of the algorithm. To evaluate the performance of the proposed PSO, a large number of benchmark problems are selected from the literature and solved with different due date and penalty settings. Computational results confirm that the proposed PSO is efficient and competitive; the developed framework is able to improve many of the best-known solutions of the test problems available in the literature

Studying the effect of server side constraints on the makespan of the no-wait flow shop problem with sequence dependent setup times.

Peer ReviewedThis paper deals with the problem of scheduling the no-wait flow-shop system with sequence-dependent set-up times and server side-constraints. No-wait constraints state that there should be no waiting time between consecutive operations of jobs. In addition, sequence-dependent set-up times are considered for each operation. This means that the set-up time of an operation on its respective machine is dependent on the previous operation on the same machine. Moreover, the problem consists of server side-constraints i.e. not all machines have a dedicated server to prepare them for an operation. In other words, several machines share a common server. The considered performance measure is makespan. This problem is proved to be strongly NP-Hard. To deal with the problem, two genetic algorithms are developed. In order to evaluate the performance of the developed frameworks, a large number of benchmark problems are selected and solved with different server limitation scenarios. Computational results confirm that both of the proposed algorithms are efficient and competitive. The developed algorithms are able to improve many of the best-known solutions of the test problems from the literature. Moreover, the effect of the server side-constraints on the makespan of the test problems is explained using the computational results

Studying the impact of merged and divided storage policies on the profitability of a remanufacturing system with deteriorating revenues

Peer ReviewedMerging capacity for a remanufacturing system is studied in this paper. In the system under study, there are two streams for returns and each stream has its dedicated processing line. However, the storage space is merged between the streams. Two strategies are investigated and compared in this paper. The first strategy is to divide the storage space between the two streams in the way that each type of return has its predetermined space in the storage area (divided capacity). In the second strategy, storage space is not split between the two streams and each unit of return, independent of its type, is admitted if there is vacant space (merged capacity). In both strategies, the value of remanufactured products decreases over time by a known factor called the decay rate. Mathematical models to maximize the total profit in each strategy is presented and also verified by a simulation model. From a practical point of view, selecting the correct strategy is an important decision for the remanufacturers because choosing the wrong policy leads to lost profits. Numerical experiments reveal that neither of the scenarios is always preferred to the other one and the choice of the optimal strategy depends on the parameters' values and product types. For instance, increasing the remanufacturing cost of the superior product, or increasing the sale price of the inferior product make the merged storage strategy more desirable. On the contrary, increasing the remanufacturing cost of the inferior product, or increasing the sale price of the superior product make the divided storage policy more appealing

On the exact solution of the no-wait flow shop problem with due date constraints

Peer ReviewedThis paper deals with the no-wait flow shop scheduling problem with due date constraints. In the no-wait flow shop problem, waiting time is not allowed between successive operations of jobs. Moreover, the jobs should be completed before their respective due dates; due date constraints are dealt with as hard constraints. The considered performance criterion is makespan. The problem is strongly NP-hard. This paper develops a number of distinct mathematical models for the problem based on different decision variables. Namely, a mixed integer programming model, two quadratic mixed integer programming models, and two constraint programming models are developed. Moreover, a novel graph representation is developed for the problem. This new modeling technique facilitates the investigation of some of the important characteristics of the problem; this results in a number of propositions to rule out a large number of infeasible solutions from the set of all possible permutations. Afterward, the new graph representation and the resulting propositions are incorporated into a new exact algorithm to solve the problem to optimality. To investigate the performance of the mathematical models and to compare them with the developed exact algorithm, a number of test problems are solved and the results are reported. Computational results demonstrate that the developed algorithm is significantly faster than the mathematical models

Increasing Supply Chain Resiliency Through Equilibrium Pricing and Stipulating Transportation Quota Regulation

Supply chain disruption can occur for a variety of reasons, including natural disasters or market dynamics for which resilient strategies should be designed. If the disruption is profound and with dire consequences for the economy, it calls for the regulator's intervention to minimize the impact for the betterment of the society. This paper considers a shipping company with limited capacity which will ship a group of products with heterogeneous transportation and production costs and prices, and investigates the minimum quota regulation on transportation amounts stipulated by the government. An interesting example can happen in North American rail transportation market, where the rail capacity is used for a variety of products and commodities such as oil and grains. Similarly, in Europe supply chain of grains produced in Ukraine is disrupted by the Ukraine war and the blockade of sea transportation routes, which puts pressure on rail transportation capacity of Ukraine and its neighboring countries to the west that needs to be shared for shipping a variety of products including grains, military, and humanitarian supplies. Such situations require a proper execution of government intervention for effective management of the limited transportation capacity to avoid the rippling effects throughout the economy. We propose mathematical models and solutions for the market players and the government in a Canadian case study. Subsequently, the conditions that justify government intervention are identified, and an algorithm to obtain the optimum minimum quotas is presented

Evaluation of Exposure to BTEX in Hookah Smokers and Carcinogenic and Non- Carcinogenic Risk Assessment

To investigate the demographic characteristics, concentration of Benzene, Toluene, Ethyl benzene and Xylenes (BTEX) in output smoke and health risk assessment in hookah smokers in hookah cafés, Iran. We checked hookah cafés in the different parts of Hamadan city and analyzed location and social station of each cafés in 2016. Finally, 20 cafés selected and five samples on each cafés (total of 100 samples). BTEX compounds were sampled in output smoke from mouth smokers using charcoal and analyzed by GC- MS according to NIOSH1501 method. The quantitative risk assessment of exposure to BTEX as recommended by the United State Environmental Protection Agency method was used. The smokers' demographic characteristics collected using a self-designed questionnaire. The average concentrations of benzene, toluene, ethyl benzene, o, m-Xylene and p- Xylene were 6.45, 7.02, 10.07, 7.21 and 8.36 mg/m3, respectively. The mean cancer risk for benzene was estimated as 529 × 10-5 and mean non-carcinogenic risks for toluene, ethyl benzene and o, m-Xylene and p–Xylene (TEXs) were 17.57, 5.03, 24.03 and 27.88, respectively. Hookah smoking is prevalent among youths and smokers are exposed to benzene level higher than the threshold limit value recommended by ACGIH. Cancer risk for benzene and non-carcinogenic risk for TEXs were much higher than recommended limits. Thus, in order to prevent diseases stemming from hookah smoking, urgent and increased notification about its adverse health effects and intensified regulatory laws are needed to decrease hookah smoking in hookah cafés

Investigation on the trophic status of Ekbatan reservoir: a drinking water supply reservoir in Iran

BACKGROUND: Eutrophication is one of the detrimental environmental problems in water reservoirs dye to the irregular introducing nutrients (phosphorus and nitrogen). This study aimed to explore the eutrophication state of Ekbatan Reservoir, Hamadan, western Iran. METHODS: Monthly sampling was conducted during April 2010 to March 2011. Seven sampling stations were selected in the various locations of the reservoir and the samples were collected in the depth of 50 cm. The grab sampling of water for nitrogen, phosphorous and chlorophyll-a was carried out at all localities by Hatch sampler. The trophic state of the dam was determined by Carlson's Trophic State Index (TSI) and Chapra's classification. RESULTS: The highest concentrations of phosphorus and chlorophyll-a were measured in August and the lowest concentration for both of the parameters was determined in February. The TSI index according phosphorus concentration showed that the reservoir was in eutrophic status during May to November and was in mesotrophic status over November to May. CONCLUSIONS: It seems that the eutrophication process in the lake was resulted from the rural wastewaters and agricultural fertilizers. Therefore, using long term management methods including prevent of uncontrolled discharge of agricultural wastewaters is recommended in order to reduce the eutrophication in the reservoir. Decrease of phosphorus concentration in the dam by 50 can convert the eutrophic state to mesotrophic state

The survey of Ultrasound – Electrocoagulation process in removal of Ciprofloxacin from aqueous through central composite design

Background and aims: Presence of antibiotics as emerging pollutants have aroused increasing concerns. The modelling of electrocoagulation process with ultrasound in the removal of Ciprofloxacin in aqueous solutions was aimed in the present study.Materials and Methods: In this study a reactor with 1000 mL volume was used. Copper and iron electrodes were exploited as cathode and anode electrodes. Electrodes were connected to a direct electrical current supply as monopolar. The optimization of pH, current density, initial concentration of CIP and reactiontime were conducted by CCD and finally suitable model was presented. In optimized conditions, the amount of electrode corrosion, COD and TOC removal, changes in the UV-Vis adsorption and FT-IR spectrum was measured. All procedures in study were conducted ethically.Results: Optimum conditions were found to occur at pH, current density, and reaction time of 7. 4, 1.5 In this situation the predicted and.A and 30 min, respectively in 15 mg CIP /L as an initial concentration actual efficiencies were 88.21 and 86.37 %, respectively. Also, a moderate COD and TOC removal, about64 and 51 percent was achieved, respectively. Result of FT-IR analysis showed considerable changes in functional groups during removal process. Synergist effect of US in electrocoagulation process was estimated to be only 14 percent.Conclusion: The results indicate that the proposed process have a good efficiency in CIP removal. It is possible to decrease the concentrations of similar pollutants before their discharge to the environment by the use of this method.Keywords: Ultrasound – Electrocoagulation process, modelling, Ciprofloxacin, Central composite design, aqueou

Evaluation of Exposure to BTEX in Hookah Smokers and Carcinogenic and Non- Carcinogenic Risk Assessment

To investigate the demographic characteristics, concentration of Benzene, Toluene, Ethyl benzene and Xylenes (BTEX) in output smoke and health risk assessment in hookah smokers in hookah cafés, Iran. We checked hookah cafés in the different parts of Hamadan city and analyzed location and social station of each cafés in 2016. Finally, 20 cafés selected and five samples on each cafés (total of 100 samples). BTEX compounds were sampled in output smoke from mouth smokers using charcoal and analyzed by GC- MS according to NIOSH1501 method. The quantitative risk assessment of exposure to BTEX as recommended by the United State Environmental Protection Agency method was used. The smokers' demographic characteristics collected using a self-designed questionnaire. The average concentrations of benzene, toluene, ethyl benzene, o, m-Xylene and p- Xylene were 6.45, 7.02, 10.07, 7.21 and 8.36 mg/m3, respectively. The mean cancer risk for benzene was estimated as 529 × 10-5 and mean non-carcinogenic risks for toluene, ethyl benzene and o, m-Xylene and p–Xylene (TEXs) were 17.57, 5.03, 24.03 and 27.88, respectively. Hookah smoking is prevalent among youths and smokers are exposed to benzene level higher than the threshold limit value recommended by ACGIH. Cancer risk for benzene and non-carcinogenic risk for TEXs were much higher than recommended limits. Thus, in order to prevent diseases stemming from hookah smoking, urgent and increased notification about its adverse health effects and intensified regulatory laws are needed to decrease hookah smoking in hookah cafés

Adsorptive Removal of Methylene Blue in Aqueous Solutions Through Raw and Modified Cantaloupe Peel Wastes: Kinetic and Isotherm Study

Since large amounts of agricultural wastes are produced in Iran and these wastes have lignocellulosic nature, the current study was performed to survey the adsorption performance of methylene blue dye from aqueous solutions by means of raw and modified cantaloupe peel. The adsorbents used were characterized using techniques like scanning electron microscope (SEM), as well as Fourier transform infrared spectroscopy (FTIR). In this study, the effects of a few key variables including pH, reaction time, dye concentration, adsorbent dosage and temperature on the adsorption performance were investigated. Optimum values were attained at 0.04 and 0.08 g doses of modified and raw cantaloupe peel, pH of 7 after mixing for 120 and 90 minutes for raw and modified cantaloupe peel, respectively. The equilibrium information was fitted to the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich equations and the respective data for all models were tested. An increase in adsorbent dose and temperature caused the efficiency to rise. The mechanism and rate of adsorption were ascertained by analyzing the experimental data at various contact times according to traditional kinetic equations: pseudo-first-order and second order, Elovich, and intra-particle diffusion. The findings illustrated that the data accorded closely with the pseudo-second-order model. Moreover, it was found that these wastes can be applied to remove environmental pollutants, particularly methylene blue dye