In this research, we consider a two-machine permutation flowshop with ready times and limited waiting times of jobs in a semiconductor fab. In the flowshop, each job has its corresponding ready time (arrival time) at machine 1 (for the first operation) and limited waiting time between the completion time of the first operation on machine 1 and the starting time of the second operation on machin...

This paper deals with a common due date parallel machines scheduling problem in which each job has a different tardiness penalty. The objective is to minimize the total weighted tardiness. The scheduling problem of minimizing the total weighted tardiness with a common due date on a single machine is known to be ordinary NP-hard. This is also the case for problem Pm|di = d| ∑ wiTi. A new dynamic...

Simple bioaccumulation models predict a monotonic increase in concentration with time until an equilibrium concentration is reached. However, unconsidered dynamics including deterministic oscillations occur if realistic time lags are incorporated. Stability criteria are provided for difference and differential forms of the simplest model. These criteria provide the means of identifying systems ...

In this paper we introduce a new scheduling model with learning effects in which the actual processing time of a job is a function of the total normal processing times of the jobs already processed and of the job’s scheduled position. We show that the single-machine problems to minimize makespan and total completion time are polynomially solvable. In addition, we show that the problems to minim...

In this paper we study the resource-constrained project scheduling problem with weighted earliness-tardiness penalty costs. Project activities are assumed to have a known deterministic due date, a unit earliness as well as a unit tardiness penalty cost and constant renewable resource requirements. The objective is to schedule the activities in order to minimize the total weighted earliness-tard...

This study considers outsourcing decisions in a flexible flow shop scheduling problem, in which each job can be processed by either an in-house production line or outsourced. The selected objective function aims to minimize the weighted sum of tardiness costs, in-house production costs, and outsourcing costs with respect to the jobs due date. The purpose of the problem is to select the jobs tha...

time-dependent vehicle routing problem is one of the most applicable but least-studied variants of routing and scheduling problems. in this paper, a novel mathematical formulation of time-dependent vehicle routing problems with heterogeneous fleet, hard time widows and multiple depots, is proposed. to deal with the traffic congestions, we also considered that the vehicles are not forced to come...

An MILP model for the optimal scheduling of a lube oil and paraffin production plant is presented. The plant is composed of processing units that operate in continuous and discontinuous modes, and some are also duplicated. The raw materials for the process are stored in dedicated tanks, and the plant presents finite intermediate storage. The mathematical formulation was developed under a contin...

In data warehouses measures are analyzed along different dimensions. Although the structures of these dimensions change over time, data warehouse tools currently in use are not able to deal with these modifications in a sophisticated way. In this paper we present a bitemporal extension of the COMET metamodel. This extension enables us to represent not only the valid time of structural modificat...