A TWO-STAGE GREEDY HEURISTIC FOR A FLOWSHOP SCHEDULING PROBLEM UNDER TIME-OF-USE ELECTRICITY TARIFFS

This paper studies a two-machine flowshop scheduling problem under time-dependent electricity tariffs, in which electricity prices may vary from time to time throughout the day. The main issue is to assign a set of jobs to available time slots with different electricity prices to minimise the total resource cost required for processing the jobs. The main contribution of this work is two-fold. First, a new continuous-time mixed-integer linear programming (MILP) model is proposed for the problem. Second, a two-stage greedy heuristic is developed. A computational experiment on randomly generated instances demonstrates that the greedy algorithm can improve the objective function by almost 40 percent. The algorithm can be applied by production managers to scheduling jobs in a flowshop under time-of-use (TOU) electricity tariffs to save electricity costs

Evaluation of nutritional composition and antioxidant activity of Borage (Echium amoenum) and Valerian (Valerian officinalis)

The nutritional composition and antioxidant activity (in aqueose and solvent extracts) of two medicinal plants of Iranian origin Borage (Echium amoenum) and Valerian (Valerian officinalis) used as tea were determined. Samples were analyzed for antioxidant components viz. polyphenols, vitamin C, β carotene, flavonoids, anthocyanins and tannins. Antioxidant assays such as free radical scavenging activity, reducing power and total antioxidant activity were carried out for ethanol, methanol, acetone, 80% methanol and 80% ethanolic extracts. In borage highest and least activity was observed in water and acetone extract respectively in all assays. In Valerian, 80% methanolic extract showed highest activity in reducing power and free radical scavenging activity assay. Total polyphenols in borage and valerian were 1,220 and 500 mg in ethanolic extracts and 25 and 130 mg in acetonic extracts respectively. Total carotenoids and vitamin C contents were 31.6 and 133.69 mg and 51.2 and 44.87 mg for borage and valerian respectively. Highest amount of tannins were extracted in 80% methanolic extract. It can be concluded that borage and valerian exhibited antioxidant activity in all extracts. The antioxidant activity could be attributed to their polyphenol and tannin and flavonoids contents. In all assays borage showed higher activity than valerian

Single-machine batch scheduling minimizing weighted flow times and delivery costs with job release times

This paper addresses scheduling a set of weighted jobs on a single machine in presence of release date for delivery in batches to customers or to other machines for further processing. The problem is a natural extension of minimizing the sum of weighted flow times by considering the possibility of delivering jobs in batches and introducing batch delivery costs. The classical problem is NP-hard and then the extended version of the problem is NP-hard. The objective function is that of minimizing the sum of weighted flow times and delivery costs. The extended problem arises in a real supply chain network by cooperation between two layers of chain. Structural properties of the problem are investigated and used to devise a branch-and-bound solution scheme. Computational experiments show the efficiency of suggested algorithm for solving instances up to 40 jobs