Commutation modelling and sparks reduction based on coupled circuit method

The commutating machines have a notable effect on the exchanges in brush–commutator contact area, which is particularly obvious when determining the intensity of sparks located on the brush. With time, higher current density at the descending edge promote sparks excitation, which itself increases intensity of the electrical erosion, brush temperature and thus also the wear. So in order to make an analytical study of commutation phenomenon, the coupled circuit method was developed. Therefore, a generalized mathematical model of the commutation, for brush–commutator, is established and can be extended for any other types of commutation on the basis of electromagnetic field (e.g. transformers and phase shift transformer. This model provides a greater efficiency to explain the impact of the electromagnetic fluxes surrounding brush area (or switch), specially for the current transition of the commutation process. Successful commutation is defined as operation in normal service, with no serious damages to the commutator, brushes or switches due to sparking that might require abnormal maintenance. It is recognized that some visible sparking are not evidence of unsuccessful commutation. The recommendation to improve the commutation (to achieve longer brush life) is the implementation of the proposal (slotted brush), which provides a linear and a sweet transition of currents in the coils of commutation. Copyright © 2012 John Wiley & Sons, Ltd.     

Heterocyclic azo dyes. III. Azo Dyes Containing the Benzo-1,2,3-thiadiazole Nucleus

The synthesis, some dyeing and fastness properties of several new dispersed and acid dyes derived from 5-amino-benzo-1,2,3-thiadiazole are described. Comparison between the dyeing properties of some synthesised dyes and other similar dyes is also given.     

Isolation,Chemical Modification and Rheological Characterization of Leucaena Gum. Part I: Carboxymethylation

Leucaena gum was isolated from leucaena seeds and subjected to chemical modification via carboxymethylation under a variety of conditions. Variables studied include concentration of the etherifying agents and the preparation medium. It was found that the extent of carboxymethylation expressed as DS increases by increasing the concentration of the etherifying agents. Higher DS values were obtained in non-aqueous medium. The carboxymethylated leucaena derivatives are cold water soluble and can be precipitated by ethanol. Their pastes are characterized by non-Newtonian pseudoplastic behaviour regardless of the method of preparation or DS of the products. The apparent viscosity at various rates was thouroughly investigated. The effect of storing of these pastes on the rheological properties was also studied.     

Heterocyclic azo dyes. II. Azo Dyes Containing the Benzotriazole and/or benzimidazole nucleus

The synthesis, some dyeing, and fastness properties of several new dispersed and acid dyes derived from the amino-benzotriazoles 1 & 3 and the aminobenzimidazoles 2a , 2b & 4 are described. The suitability of the amino derivatives 1 , 2a , 2b , 3 & 4 as bases for azoic dyeing has also been studied. Several interesting observations between the properties of some synthesised dyes and the corresponding benzene or naphthalene analogues are cited.     

Wireless charging for cardiac pacemakers based on class-D power amplifier and a series–parallel spider-web coil

Biomedical implants (BMIs) and biomedical sensors (BMSs) help to improve quality of life, detect diseases, provide monitoring of vital signs, and take over the role of malfunctioning organs. These implants and sensors require continuous battery power to work effectively, but the batteries used are restricted by their limited capacity and lifetime. This research reported here involved the design and implementation of a wireless charging system based on a series–parallel spider-web coil (WPT-SP-SWC), specifically for cardiac pacemakers. The experimental design investigated several important parameters, including air gap, applied source voltage, coil size, and operating frequency. Performance metrics were evaluated in terms of output DC voltage, delivered output power, and power transfer efficiency. The target voltage was 5 V, which is adequate to charge a BMI such as a pacemaker, and three source voltages (5, 15, and 25 V) were tested. The design was examined at six operating frequencies, ranging from 1.78 MHz to 6.78 MHz. The most favorable results were achieved at 1.78 MHz. Power transfer efficiencies at a 10 mm air gap were 95.75% and 92.08% for applied voltages of 5 V and 15 V, respectively. The effectiveness of the proposed system was also validated by comparing the findings with previous articles.     

Photovoltaic Models Parameters Estimation Based on Weighted Mean of Vectors

Renewable energy sources are gaining popularity, particularly photovoltaic energy as a clean energy source. This is evident in the advancement of scientific research aimed at improving solar cell performance. Due to the non-linear nature of the photovoltaic cell, modeling solar cells and extracting their parameters is one of the most important challenges in this discipline. As a result, the use of optimization algorithms to solve this problem is expanding and evolving at a rapid rate. In this paper, a weIghted meaN oF vectOrs algorithm (INFO) that calculates the weighted mean for a set of vectors in the search space has been applied to estimate the parameters of solar cells in an efficient and precise way. In each generation, the INFO utilizes three operations to update the vectors’ locations: updating rules, vector merging, and local search. The INFO is applied to estimate the parameters of static models such as single and double diodes, as well as dynamic models such as integral and fractional models. The outcomes of all applications are examined and compared to several recent algorithms. As well as the results are evaluated through statistical analysis. The results analyzed supported the proposed algorithm’s efficiency, accuracy, and durability when compared to recent optimization algorithms.