Anita Ahmad

Improving Vector Evaluated Particle Swarm Optimisation by Incorporating Nondominated Solutions

The Vector Evaluated Particle Swarm Optimisation algorithm is widely used to solve multiobjective optimisation problems. This algorithm optimises one objective using a swarm of particles where their movements are guided by the best solution found by another swarm. However, the best solution of a swarm is only updated when a newly generated solution has better fitness than the best solution at the objective function optimised by that swarm, yielding poor solutions for the multiobjective optimisation problems. Thus, an improved Vector Evaluated Particle Swarm Optimisation algorithm is introduced by incorporating the nondominated solutions as the guidance for a swarm rather than using the best solution from another swarm. In this paper, the performance of improved Vector Evaluated Particle Swarm Optimisation algorithm is investigated using performance measures such as the number of nondominated solutions found, the generational distance, the spread, and the hypervolume. The results suggest that the improved Vector Evaluated Particle Swarm Optimisation algorithm has impressive performance compared with the conventional Vector Evaluated Particle Swarm Optimisation algorithm.

Improving Vector Evaluated Particle Swarm Optimisation Using Multiple Nondominated Leaders

The vector evaluated particle swarm optimisation (VEPSO) algorithm was previously improved by incorporating nondominated solutions for solving multiobjective optimisation problems. However, the obtained solutions did not converge close to the Pareto front and also did not distribute evenly over the Pareto front. Therefore, in this study, the concept of multiple nondominated leaders is incorporated to further improve the VEPSO algorithm. Hence, multiple nondominated solutions that are best at a respective objective function are used to guide particles in finding optimal solutions. The improved VEPSO is measured by the number of nondominated solutions found, generational distance, spread, and hypervolume. The results from the conducted experiments show that the proposed VEPSO significantly improved the existing VEPSO algorithms.

Isoprenaline and atropine effect on atrial arrhythmias study

Atrial Fibrillation (AF) is the most common disorder of the heart rhythms. There are about 2.3 million people in United States and 4.5 million people in the European Union with AF [Go et.al, 2001]. It is also one of the factors that may contribute to mortality and morbidity. Researchers who apply spectral techniques show that certain areas of the atria can have higher activation frequencies than other areas. Frequency analysis is used to measure changes in Dominant Frequency (DF). We access the electrical propagation inside the atria by spectrogram plotting and examining the effect of isoprenaline and atropine on frequency changes.Copyright

Characterization of heat flow in silicon nanowire arrays for efficient thermoelectric power harvesting

ABSTRACT We report the performance of Silicon Nanowire Arrays (SiNWA) with two different lengths (30 μm and 50 μm) for both p- and n-type Si(100) as a material applied for thermoelectric power harvesting, followed by comparing the recorded performance to that bulk Si. Heat flow from top to the bottom Cu sheet had noticeably decreased in SiNWA samples, resulting in a higher temperature difference, ΔT and Seebeck voltage, Voc than in bulk Si. The results suggested that both p- and n-type SiNWA samples (50 μm) have achieved 100 and 80% increase in ΔT, respectively, relative to the bulk Si.

A Particle Swarm Optimization Based Predictive Controller for Delay Compensation in Networked Control Systems

This paper addresses transmission delays problem in network control systems. Network-induced delay is an inherent constraint in NCS implementation that could lead to system degradation and destabilization. A particle swarm optimization (PSO) tuning algorithm was adopted to optimally tune the parameters of Generalized Predictive Controller (GPC) to solve networked-induced delay problem. Furthermore, a modified PSO-GPC was designed by replacing the standard GPC objective function with an Integral Time Squared Error (ITSE) performance index in the GPC controller design. A particle swarm optimization based PI controller in the Smith predictor structure is designed to compare the performances of the original PSO-GPC and the modified PSO-GPC. The results show that the modified PSO-GPC performed better than the PSO-GPC in terms of transient response and enhanced NCS performance in the occurrence of network delays.

Modelling electrophysiological data in persistent atrial fibrillation studies using the evolution of 3-dimensional dominant frequency mapping

The dominant frequency (DF) of atrial electrogram was claimed by researchers as to be correlated to the electrical activation of the atrial fibrillation (AF). By assessing the DF of AF data of 5 patients with persistent AF, this paper presented some AF signal analysis done to study the performance of the raw data, which is the data without QRS-T subtraction, data with QRS-T subtraction and rectification. The resultant data were mapped in 3-dimensional shapes of respective patients left atrium (LA), showing the DF activity changes during 21 s data recorded. The maps are useful for further analysis to justify which of the mentioned signal processing step is more reliable and also to study the relation between particular sites on the LA with the source (sites) of activation of AF.

QRS subtraction effect on frequency changes of persistent atrial fibrillation data due to isoprenaline and atropine infusion

Atrial fibrillation (AF) has been one of the frequent discussed cardiac arrhythmias topic nowadays. One of the previous researches by Ahmad, A. has overall proven the ability of isoprenaline drug to increase the heart rate, thus increasing the dominant frequency (DF) after infusion as well as the ability of the atropine drug to reduce the heart rate, thus decreasing the DF of AF patients after infusion. However, the effect of QRS subtraction on the persistent AF data was not analyzed. Hence, this paper is intended to investigate the effect of QRS subtraction on the DF changes of the persistent AF data due to isoprenaline and atropine infusion. The same patient data were used for the research, but with two labels chosen and an additional step of QRS subtraction performed before applying Fast Fourier Transform (FFT) method for DF analysis. The results show that the use of QRS subtraction step could help increase the percentage of positive respond of DF under isoprenaline and atropine drugs influence.

An Improved VEPSO Algorithm for Multi-objective Optimisation Problems

Multi-objective optimisation problem is the problem which contains more than one objective that needs to be solved simultaneously. The vector evaluated particle swarm optimisation algorithm is widely used for such purpose, where this algorithm optimised one objective using one swarm of particles by the guidance from the best solution found by another swarm. However, this best solution is only updated when a solution is better with respect to the optimised objective and results in poor performance. Therefore, the vector evaluated particle swarm optimisation algorithm is improved by incorporating the non-dominated solutions for guiding the particle movement during optimisation. The performance of the improved algorithm is analysed with several performance measures and simulated on various test functions. The results suggest that the improved algorithm outperformed the performance of the original algorithm.