A taboo search approach for deadlock-free scheduling of automated manufacturing systems

This paper addresses the scheduling problem of a class of automated manufacturing systems. A new manufacturing system model is proposed. In this model, a set of jobs is to be processed and each job requires a sequence of operations. Each operation may need more than one resource. Upon the completion of an operation, resources needed in the next operation of the same job cannot be released and the remaining resources cannot be released until the start of the next operation. The scheduling problem consists in sequencing the operations on the resources in order to avoid deadlocks and to minimize the makespan. The classical disjunctive graph representation is extended to model the scheduling problem. A taboo search algorithm is then proposed using an original neighborhood structure defined by two basic moves: the permutation of disjunctive arcs of critical paths and a deadlock recovery move if the former fails. Numerical results presented in the paper show the efficiency of the proposed algorithm.     

A genetic local search algorithm for minimizing total weighted tardiness in the job-shop scheduling problem

This paper considers the job-shop problem with release dates and due dates, with the objective of minimizing the total weighted tardiness. A genetic algorithm is combined with an iterated local search that uses a longest path approach on a disjunctive graph model. A design of experiments approach is employed to calibrate the parameters and operators of the algorithm. Previous studies on genetic algorithms for the job-shop problem point out that these algorithms are highly depended on the way the chromosomes are decoded. In this paper, we show that the efficiency of genetic algorithms does no longer depend on the schedule builder when an iterated local search is used. Computational experiments carried out on instances of the literature show the efficiency of the proposed algorithm.     

Experimental and Monte Carlo evaluation of the neutron flux of an assembly with two AmBe sources

This work aimed to determine the irradiator thermal (under-cadmium) and fast (over-cadmium) neutron fluxes, of the Nuclear Experimental Laboratory of the Nuclear Engineering Center (CNEN-IPEN, S?o Paulo, Brazil), and the possibility of this irradiator use for Neutron Activation Analysis (NAA), by the absolute method. To establish the facility specifications, the neutron flux values along the irradiator axis were determined experimentally and calculated by Monte Carlo method. The irradiator presents the advantage of supplying a stable neutron flux for a long period, eliminating the need to use standard material (comparative method), so that the process becomes agile, practical and economical.     

In situ thin film differential thermal analysis of amorphous V2O5 thin films

In situ differential thermal analysis (DTA) experiments were performed on highly quenched amorphous V₂O₅ thin films directly evaporated onto a thin film differential thermocouple microprobe. Irreversible low temperature relaxations were thus evidenced, a result impossible to obtain with a classical DTA apparatus using microcrucibles such as Setaram or Mettler TA 2000 devices.     

Performance analysis of Otsu thresholding for sign language segmentation

Multimedia Tools and Applications - Sign language recognition system generally consists of three main processes, which are segmentation, modelling, and classification. Image segmentation plays a...     

Plastic flow and ductile rupture of a 2198 Al–Cu–Li aluminum alloy

Plasticity and fracture mechanisms of a 2198 Al–Cu–Li thin sheet alloy having a thickness equal to 6 mm are investigated. Two heat treatments are studied: T351 and T851. Mechanical tests are carried out on flat specimens including smooth tensile samples and U-notched specimens. Test data are used to identify the parameters of constitutive equations describing plastic anisotropy. The microscopic fracture surfaces of the different specimens are observed using scanning electron microscopy. Smooth and notched samples exhibit a slant fracture surface. Two microscopic fracture mechanisms are identified: fibrous fracture involving grain boundary decohesion and dimple fracture. Observed fracture modes depend on specimen geometry (notches increase stress triaxiality and favor dimple fracture) but also on loading direction. Loading along the rolling direction leads to predominant fibrous fracture. Reducing sheet thickness to 2 mm also favors fibrous fracture. Finally a localization indicator based on Rice’s analysis of bifurcation is used to analyse finite element simulations and predict observed fracture plane orientations.     

The strength of particulate polymer composite: A new insight on crystallinity and structural morphology

We have demonstrated the significant impact of high density polyethylene (HDPE) crystallinity and structural morphology on the tensile strength of 60/40 NR/HDPE polymer blend composites. Introducing nanoscale Boron Carbide (B4C-type compounds) fillers noticeably changed the crystallinity and morphology of HDPE, leading to the formation of fine spherulites. Conversely, microscale fillers mainly impacted the crystallinity while preserving a coarse architecture. Although both composites experienced a reduction in crystallinity, the nanocomposites outperformed microcomposites and even the pristine polymer blend in terms of strength, implying the effect of a fine structure. The nanocomposite with a filler loading of 2 wt% exhibited the highest strength. This investigation provides novel insights into the interplay between crystallinity, HDPE structure, and the size of fillers, which heavily influence the strength of polymer blend composites.     

A novel aqueous micellar two-phase system composed of surfactant and mannitol for purification of polygalacturonase enzyme from Durio zibethinus Murray and recycling phase components

A novel aqueous micellar two-phase system composed of surfactant and mannitol was employed for the first time to purify polygalacturonase from Durio zibethinus Murray. The influences of different parameters such as type of surfactants, composition of surfactant/mannitol, pH and crude load on polygalacturonase partitioning were investigated. The results indicated that the polygalacturonase was recovered in 25% Tween 80 and 22% mannitol, at 68.2% of Tie line length, crude load of 30% at pH 5.0. The enzyme was successfully recovered with a high purification factor of 16.1 and yield of 97.3% while phase components were also recovered and recycled above 95%.