A novel simplified mathematical model for antennas used in medical imaging applications

In this paper a new technique is proposed to model the current across a monopole antenna and thereby the radiation fields of the antenna can be calculated. Generally, the Method of Moments (MOM) technique is used for this purpose whereby the integral equations are discretised to find the fields of an antenna. The proposed model requires only the knowledge of three parameters (Initial Current I0, Damping coefficient a and the radial parameter ?) and hence considerably reduces the computational time and space as its results do not depend on the number of functions involved. The new technique is also developed to take account of the conductivity property of the surrounding medium. Hence this technique can be used in field prediction for antennas employed in medical imaging applications. Initial results obtained from the new technique show good correlation in comparison with the MOM technique

Determination of annual periodicity in annuli formation in Atlantic bluefin tuna otoliths.

Controversies remain regarding the periodicity, or seasonality, of otolith growth band formation which directly influences a correct age determination of Atlantic bluefin tuna using otoliths. Thereby, the aim of this work was to apply marginal increment analysis (MIA) and marginal edge analysis (EA) to determine the timing of band deposition. The index of completion (MIA) was also analyzed using General Additive Models. Results indicated that the opaque band begin to form in July and would finish forming in November. From the end of the year and the beginning of the following year there is minimal marginal edge growth and this is when the translucent band begins to form and reaches its maximum development in June. MIA and EA has evidenced that the annulus has been formed in November in the Atlantic Bluefin tuna otolith. This would mean to delay the date of the current July 1st adjustment criterion to November 30

An improved optimization technique for estimation of solar photovoltaic parameters

The nonlinear current vs voltage (I-V) characteristics of solar PV make its modelling difficult. Optimization techniques are the best tool for identifying the parameters of nonlinear models. Even though, there are different optimization techniques used for parameter estimation of solar PV, still the best optimized results are not achieved to date. In this paper, Wind Driven Optimization (WDO) technique is proposed as the new method for identifying the parameters of solar PV. The accuracy and convergence time of the proposed method is compared with results of Pattern Search (PS), Genetic Algorithm (GA), and Simulated Annealing (SA) for single diode and double diode models of solar PV. Furthermore, for performance validation, the parameters obtained through WDO are compared with hybrid Bee Pollinator Flower Pollination Algorithm (BPFPA), Flower Pollination Algorithm (FPA), Generalized Oppositional Teaching Learning Based Optimization (GOTLBO), Artificial Bee Swarm Optimization (ABSO), and Harmony Search (HS). The obtained results clearly reveal that WDO algorithm can provide accurate optimized values with less number of iterations at different environmental conditions. Therefore, the WDO can be recommended as the best optimization algorithm for parameter estimation of solar PV

Wind Driven Optimization Technique for Estimation of Solar Photovoltaic Parameters

In order to increase the efficiency of the solar photovoltaic (PV) system, accurate electrical modeling of the system under different environmental conditions is necessary. The double diode electrical model of solar PV is known to be more accurate than its single diode model counterpart since it takes into account the effect of recombination. However, because of its nonlinear characteristics, the parameters of the double diode model have to be identified using ptimization algorithms. In this paper, the Wind Driven Optimization (WDO) algorithm is proposed as a potential new method for identifying the parameters of a twelveparameter double diode model (12p-DDM) of the solar PV. The accuracy and flexibility of the proposed method are verified using three different sets of data: (i) experimental data at the controlled environmental condition, (ii) data sheet values of different solar PV modules and (iii) real-time experimental data at the uncontrolled environmental condition. Additionally, the performance of the WDO is compared to other well-known existing optimization techniques. The obtained results show that the WDO algorithm can provide optimized values with reduced Mean Absolute Error in Power (MAEP) and reduced Root Mean Square Error (RMSE) for different types of solar PV modules at different environmental conditions. We show that the WDO can be confidently recommended as a reliable optimization algorithm for parameter estimation of solar PV model

Optical Fibre Sensors for Monitoring Phase Transitions in Phase Changing Materials

A platinum coated singlemode-multimode (SM) structure is investigated in this paper as an optical fibre sensor (OFS) to monitor the phase transition of a phase change material (PCM). Paraffin wax has been used as an example to demonstrate the sensor\u27s performance and operation. Most materials have the same temperature but different thermal energy levels during the phase change process, therefore, sole dependency on temperature measurement may lead to an incorrect estimation of the stored energy in PCM. The output spectrum of the reflected light from the OFS is very sensitive to the bend introduced by the PCM where both liquid and solid states exist during the phase transition. The measurement of strain experienced by the OFS during the phase change of the PCM is utilized for identifying the phase transition of paraffin wax between the solid and liquid states. The experimental results presented in this paper show that the OFS with a shorter multimode fibre section has better performance for monitoring the phase transition of paraffin wax with a measured phase transition temperature range of 41.5 °C–57.7 °C for the SM based OFS with a 5 mm long multimode fibre section

Report of the ICCAT GBYP international workshop on Atlantic bluefin tuna growth

In the last Atlantic bluefin tuna assessment, an age-length database coming from direct ageing was presented for the first time. It was observed that otolith age estimates for fish younger than 8 years old had a smaller size at age compared to spine (first dorsal fin radius) age estimates. This difference, although small, was enough to misallocate the year class. This misallocation was solved when introducing a vector of bias corrected aged otoliths based on paired otolithspine samples. We have identified two possible causes for over-estimating age in the otolith agelength data: the current age adjustment criterion (to convert the bands counting into ages) and a reading bias in age estimations from some laboratories. Otolith preparation and reading protocols have been reviewed. The edge type and marginal increment analysis showed that the formation of opaque zones would seem likely to occur primarily between December through to June, contrary to what was thought until now, for which a new criterion for age adjustment has been proposed

An observer for a class of disturbance driven nonlinear systems

An observer design for a class of nonlinear systems driven by disturbances or uncertainties is presented. The design is based on a high gain strategy, and the gain of the proposed observer is explicitly given. © 1998 Elsevier Science Ltd. All rights reserved

High-order sliding mode control of a DC motor drive via a switched controlled multi-cellular converter

In this article, we present a high-order sliding mode controller of a DC motor drive connected to a multi-cellular converter. More specifically, we design a second-order (super-twisting) control algorithm for the speed regulation of a DC motor. For this, a switching control for the multi-cellular converter is derived in order to supply the correct reference value for the speed regulation. A practical implementation of the controller is realised using a laboratory set-up. The performance and the validity of the controller are shown experimentally

A state observer for nonlinear systems

A new state observer design methodology for a class of nonlinear systems is proposed. The nonlinear observer design methodology is, in fact, an extension of linear observer design techniques using transformations related to linear observability matrices