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Total tardiness minimization in permutation flow shops: a simple approach based on a variable greedy algorithm

This paper addresses the problem of scheduling jobs in a permutation flowshop with the objective of minimizing the total tardiness of jobs. To tackle this problem, it is suggested that a procedure based on a greedy algorithm is employed that successively iterates over an increasing number of candidate solutions. The computational experiments carried out show this algorithm outperforms the best existing one for the problem under consideration. In addition, out some tests are carried out to analyse the efficiency of the adopted design.     

Input control and dispatching rules in a dynamic CONWIP flow-shop

The purpose of this paper is to study the input control and dispatching rules that might be used in a flow shop controlled by a constant work-in-process system (CONWIP) within a make-to-stock environment. The CONWIP system was originally conceived for a single card-count control and a FCFS dispatching rule, although in this paper it is shown that its performance can be increased by using other input controls as well as different dispatching rules.     

A multi-objective iterated greedy search for flowshop scheduling with makespan and flowtime criteria

In this paper, we tackle the problem of total flowtime and makespan minimisation in a permutation flowshop. For this, we introduce a multi-criteria iterated greedy search algorithm. This algorithm iterates over a multicriteria constructive heuristic approach to yield a set of Pareto-efficient solutions (a posteriori approach). The proposed algorithm is compared against the best-so-far heuristic for the problem under consideration. The comparison shows the proposal to be very efficient for a wide number of multicriteria performance measures. Aside, an extensive computational experience is carried out in order to analyse the different parameters of the algorithm. The analysis shows the algorithm to be robust for most of the considered performance measures.     

Miniature dielectric-loaded personal telephone antennas with lowuser exposure

Cellphone handsets of low specific energy absorption rate can be realised by making the near fields have low intensity close to the antenna. The authors describe an antenna which projects a magnetic field minimum and a radiated far field minimum towards the head     

Miniaturised dielectrically-loaded quadrifilar antenna for globalpositioning system (GPS)

A new approach to designing a handset antenna for satellite applications is reported. It is based on precise control of the phasing between two bifilar helices, giving accurate resonant frequency position and radiation pattern volute. Results show an antenna with a gain of -2 dBi, 19 dB discrimination between the right and left hand circular polarisations and an axial ratio less than 1 dB. The front-to-back ratio is 24 dB. A return loss of 14.6 dB is also measured     

A note on scheduling jobs with missing operations in permutation flow shops

Flowshop scheduling problems are usually handled as permutation flowshops because of computational complexity although the technical framework in realworld problems often allows that jobs pass each other. Having a missing operation of a job on a machine, this job passing becomes a natural way to process jobs unless the underlying system is not an inflexible flow-line. However, when scheduling, missing operations are usually handled as zero processing time operations not allowing for any job passing. It is shown that even permitting job passing for missing operations while keeping the permutation constraint improves total completion time only under rather specific circumstances. We propose 'partial permutation flowshop sequencing' to overcome these specific formal requirements with respect to the real-world problem setting.