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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     

Enhancing Properties in Microwave Ceramics Using a Designer Sintering Aid

It has recently been shown that 0.2CaTiO₃–0.8(Li_0.5Nd_0.5)TiO₃ (CTLNT) with the addition of 4 wt% Bi₄B₂O₉ (BBO) as a liquid‐phase sintering aid gives rise to exceptional microwave (MW) dielectric properties, (relative permittivity, ε_r = 125, quality factor, Qf₀ and temperature coefficient of the resonant frequency, τ_f = 4 ppm/°C) at reduced sintering temperatures (1200°C). In this study, X‐ray diffraction and scanning and transmission electron microscopy have been used to elucidate the mechanism by which MW dielectric properties are optimized. It is demonstrated that highly polarizable Bi³⁺ ions enter the perovskite lattice thereby increasing ε_r. The concomitant ex‐solution of TiO₂ as BBO concentration increases implies that ionic compensation occurs through the formation of in the perovskite lattice and infers that Bi³⁺ substitutes on the A‐site for lower valence ionic species according to the equation: . The residual boron rich material acts as a sintering aid with strongly ?ve τ_f that compensates for the +ve τ_f of the perovskite matrix. This mechanism points to a new way of utilizing designer sintering aids in the development of microwave ceramics.