Algorithms for scheduling jobs on two serial duplicate stations

In automated assembly or production lines, some stations are duplicated due to their long cycle times. Material handling considerations may require these stations to be arranged in series rather than in parallel. Each job needs to be processed on any one of the duplicate stations. This study deals with scheduling of n available jobs on two serial duplicate stations in an automated production line. The performance measures considered are mean flowtime, makespan, and station idle time. After the problem is formulated, two algorithms are developed to determine the optimal schedules with respect to the performance measures.     

No-wait and separate setup three-machine flowshop with total completion time criterion

This paper considers the three-machine no-wait flowshop problem with the objective of minimizing total completion time where setup times are considered as separate from processing times and sequence independent. We present optimal solutions for certain cases, and a dominance relation for the general case. We also develop and evaluate five heuristic algorithms for small and large number of jobs. Computational experience for up to 100 jobs shows that the proposed heuristics are quite effective and their performance do not depend on the number of jobs. The computational experience has been conducted for the uniform processing time distributions of U (1, 10) and U (1, 100). The best heuristic gives an overall average error of 0.47% for U (1, 10) and it gives an overall average error of 1.23% for U (1, 100).     

Increasing the profitability and competitiveness in a production environment with random and bounded setup times

The link between makespan and the profitability and competitiveness of a firm is addressed first. We then study the problem of minimising makespan in a two-machine flowshop with setup times. Jobs have random setup times that are bounded within certain intervals. The distributions of job setup times are not known. We propose a polynomial time algorithm that generalises Yoshida and Hitomi's algorithm. The algorithm uses a weighted average of lower and upper bounds for setup times. Different combinations of weights result in nine different versions of the algorithm. The computational results indicate that one of the versions, with equal weights given to the lower and upper bounds of setup times, performs much better than the others. Next, the performance of this best version is compared with that of the optimal solution, which is obtained by Yoshida and Hitomi's algorithm applied to the problem after setup times have been realised. Computational analysis shows that the overall average absolute error of the best algorithm is 0.03%, and this decreases in size as the number of jobs increases. The analysis also shows that the proposed best version yields robust results regardless of setup-time distributions and the range of setup times.     

Heuristics for the two-machine flowshop scheduling problem to minimise makespan with bounded processing times

The two-machine flowshop scheduling problem of minimising makespan is addressed where jobs have random processing times that are bounded within certain intervals. The probability distributions of job processing times within intervals are not known. The only known information about job processing times is the lower and upper bounds. The decision concerning the solution to the problem, i.e. finding a sequence, has to be made based on these bounds. Different heuristics using the bounds are proposed, and the proposed heuristics are compared based on randomly generated data. Computational analysis has shown that three of the proposed heuristics perform well with an overall average error of less than one percent. Moreover, for symmetric distributions, it is also shown that one of the heuristics, which applies Johnson's algorithm to the average of the lower and upper bounds, performs best with an overall average percentage error of 0.71. The obtained results are also shown to be consistent with recent results reported in the literature.     

Stochastic proportionate flowshop scheduling with setups

This paper addresses the problem of scheduling n jobs on a proportionate two-machine flowshop where the machines are subject to random breakdowns and setup times are considered separate from processing times. The considered performance measure is makespan. Sequences that minimize makespan with probability 1 are obtained when the first or the second machine is subject to random breakdowns without making any assumptions about downtime distributions or counting processes. It is assumed that the processing and setup times on one machine dominate the corresponding times on the other machine. In the case that processing and setup times on the first and second machines are proportionate, it is shown that the longest processing time (LPT) rule gives an optimal solution when only the first machine is subject to breakdowns, while the shortest processing time (SPT) rule yields an optimal solution when only the second machine suffers breakdowns.     

A branch-and-bound algorithm for the three-machine flowshop scheduling problem with bicriteria of makespan andtotal flowtime

This paper addresses the three‐machine flowshop scheduling problem with a bicriteria of minimizing a weighted sum of makespan and total flowtime. Three lower bounds, an upper bound, and several dominance relations are developed. The upper bound is developed using a two‐phase hybrid heuristic method. A branch‐and‐bound algorithm, incorporating the developed bounds and dominance relations, is presented. An extensive computational analysis on randomly generated problems is conducted. The analysis indicates that the proposed bounds, dominance relations, and branch‐and‐bound algorithm are efficient.     

Optimal selection of module instances for modular products in reconfigurable manufacturing systems

A method for optimizing the variety of a modular products, manufactured in a Reconfigurable Manufacturing System, is proposed. The optimization is achieved through appropriately selecting the subsets of module instances from given sets. The problem is formulated as an integer nonlinear programming problem to find a trade-off between the quality loss due to modularity and the cost of reconfiguration for given sets of customer requirements. The proposed formulation is general in the sense that products can have any number of modules. The formulation is an extension to the available formulation that was developed for products with only two modules. Moreover, the current work addresses the effect of different order priorities, customer importance, and demands. The proposed method has been applied to a modular assembly problem and found to be efficient in determining optimum subsets of module instances.     

Processing–Property Relations in Grain-Oriented Lead Metaniobate Ceramics Fabricated by Layered Manufacturing

Highly grain-oriented lead metaniobate (PbNb₂O₆; PN) ceramics were prepared by a layered manufacturing (LM) process. This process has enabled us to obtain a net-shaped piezoelectric ceramic component with grain orientation of f ∼89%, and improvement in electromechanical properties. The LM feedstock (filament) includes equiaxed (matrix; 90 vol%) and anisometric PN templates (10 vol%), both dispersed uniformly in a thermoplastic binder. The needle-like PN templates were synthesized by molten salt synthesis technique, while the equiaxed PN powder was prepared by conventional ceramic processing methods. The processing conditions were studied and optimized to obtain orthorhombic phase fine powder and anisometric templates.
Samples were obtained through layer-by-layer deposition of the filament through a small diameter (500 μm) nozzle. After binder removal, the PN samples were sintered in a temperature range of 1150°–1300°C for 1 h. SEM observation revealed strong grain orientation perpendicular to the deposition direction. Relative permittivity at the Curie point ( T _c: 560°C) was 18 100 and 14 600 for the LM and random polycrystalline samples, respectively. Improved properties in piezoelectric figure of merit by 71%, d ₃₃ by 23%, and g ₃₃ by 31% were observed in the grain-oriented samples. Remnant polarization also showed about 80% improvement, increasing from 4.5 to 8.1 μC/cm² for the grain-oriented LM samples.     

TEM study of the surface morphology of extracted ZrO2-Al2O3 fibres

The surface morphology and microstructure of a series of melt extracted ZrO₂-Al₂O₃ based fibres (ZA, ZAT and ZAS) have been imaged at the nanometre scale by transmission electron microscopy (TEM) using an advanced Pt/C replica technique. Growth characteristics of ZrO₂, Al₂O₃ and other crystalline phases formed upon heating up to 1550 °C are illustrated and described. Several grain morphologies including spherical and polygonal grains, as well as grains with rounded plate-like growth were observed indicating different active growth mechanisms. ZrO₂ particles on the surface of the fibres were almost spherical with some facetting and rounding of corners. These grains were very fine (< 50 nm) in the ZA and ZAS fibres while they were several microns in size in the ZAT fibres. Al₂O₃ grains were generally much larger (up to several microns) and exhibited two distinct growth morphologies of layered and rhombohedral type. Different grain morphologies of the ZA and ZAS fibres have been correlated to the phases identified by X-ray diffraction.     

Spectroscopic Investigated Interaction between Silver Nanocomposites Based of Poly-N-Vinylpyrrolidone and Doxorubicin for Drug Delivering

It is investigated to synthesis of Ag nanoparticles by presence the synthetic polymer poly-N-vinylpyrrolidone. It was determined with X-ray analyses that the size ofnanoparticles changed between 18-42 nm. Then, the authors studied sorption process of doxorubicine by silver nanocomposites and investigated chemical interaction between antibiotic and poly-N-vinyplyrrolidone with UV-VIS （ultraviolet visible） and FT-IR （Fourier transform infrared） spectroscopy. It is shown that formation of the nanoparticles doxorubicin complex mainly occurs in the 190-208 nm wavelengths on polymers 〉C=O functional groups. Also, the four main absorbing peaks of doxorubicin--234, 253, 288 and 495 nm undergo chemists shift （A2 = 12-15 nm）. When increases to pH = 7-8, the size of Ag-doxorubicin particles decreases. It is determined that the 410 nm absorption peak of Ag nanoparticles undergo 409-418 nm interval and the 3,500, 1,600, 1,645 and 1,190 sm^-1 absorption lines of PVPr （polymer poly-N-vinylpyrrolidone） slightly altered.