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Phase-only synthesis (POS) techniques represent an important tool for reflectarray design. Indeed, although based on approximate scattering models, for planar antennas, they are numerically effective thanks to the use of fast Fourier transform (FFT) routines. Conformal reflectarrays are becoming of interest as they reduce the frequency dependence of the feed/elements path length. Although synthesis...
We investigate the problem of calculating optimal mechanical ventilator settings using computer simulation coupled with the global optimization algorithm. Four ventilator settings (tidal volume, ventilation rate, IE and PEEP) are optimised simultaneously to ensure adequate arterial oxygenation and acid-base balance while minimising the risk of ventilator-associated lung injuries arising from barotrauma...
Premature convergence is a well known problem that occurs with Genetic Algorithm (GA). Inspired by ecological competitive which can decrease survival and reproduction as the similar individuals approaches the carrying capacity, a novel Competitive Genetic Algorithm (CGA) is proposed to avoid the premature convergence of GA. Using the mechanism of competitive, the number of individuals who have the...
A printed UWB Vivaldi antenna is presented in this paper. Its geometry is based on a novel spline shape and optimised by an efficient global optimisation algorithm. A U-shaped slot is introduced into the geometry to notch out the 5.1 GHz to 5.8 GHz WLAN band. This can be used to mitigate interference between WLAN and UWB systems.
During the planning of Wireless Local Area Network (WLAN) systems, it is important to determine the optimal number of access points (APs) in order to maximise their coverage with minimum cost. It is also essential to take proactive steps to secure their position in order to enhance the physical security of the network. In this paper we describe a mathematical model that finds the minimum number of...
The wireless link is still the bottleneck in 802.11 WLAN systems, especially in a public WLAN deployment with high-demand users. The most common way of improving the system performance is by accurate site planning, but this still does not cope with dynamic demand from users, such as in hotspots at an airport where travellers with WLAN laptops tend to gather at different gates at different times. In...
Direct radiating arrays ('DRA') have been proven to be an interesting solution for reconfigurable multibeam transmit antennas, as spreading naturally the RF power to be radiated over the whole aperture, and avoiding cold redundancies thanks to graceful degradation. DRA are in general designed following two main constraints : (1) Antenna diameter is determined by directivity and isolation specifications...
The application of global optimisation algorithms for modelling of enzyme kinetics and parameters of the central metabolism is analyzed. The model is a set of 10 highly complex stiff ordinary differential equations with 132 adaptive parameters. The efficacies of Nedler-Mead, simulated annealing, and differential evolution for minimization of variance between simulations of a model of the central metabolism...
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