Publications

Temperature, current density and magnetic field distributions in YBCO bulk superconductor during a pulsed-field magnetization (PFM) process are calculated using the finite difference method. Simulations are based on the heat diffusion equation with account of the heat produced by flux motion, and Maxwell's equations. A power law with temperature and magnetic field dependent parameters is used to characterize the electromagnetic behavior of the superconducting material. We analyze how the stored magnetic energy depends on the temperature and field dependences of the power law.

Cement production is a major contributor to global CO2 emissions, necessitating the development of sustainable alternatives such as fiber-reinforced concrete incorporating supplementary cementing materials (SCMs) and agricultural waste. This approach keeps the environment safe by reducing the consumption of conventional raw materials for concrete production. Incorporating the SCMs in concrete can potentially improve the mechanical and durability properties. This research evaluated the behavior of concrete mixtures using different proportions of natural wheat straw fiber, bentonite, and silica fume (SF). The fresh property was investigated by using a workability test, and mechanical properties were investigated by using compressive strength and split tensile strength. Bulk density, water absorption, and sorptivity tests were also performed to investigate the durability of concrete. Scanning electron microscopy (SEM) was conducted to evaluate the microstructure and morphology of the developed concrete mixtures. The results revealed that the slump value decreased with incorporating SCMs and fibers (83-42 mm). The compressive strength ranged from 11 MPa to 23 MPa, increasing with the increased Bentonite and SF dosages. Splitting tensile strength ranged from 2.2 MPa to 2.7 MPa, showing an increase with increased dosages of SCMs and fibers. The addition of WSFR compromised the compressive strengths of the developed mixtures, however, the ductility of the mixtures was improved with the incorporation of the WSFR. The SEM confirmed the CSH gel formation in the mixtures containing bentonite and SF. This gel formation improved the mechanical properties of the concrete, reduced water absorption, and increased its resistance to acid. The resulting concrete mixtures can address the carbon emissions associated with cement production and provide a sustainable construction material.

In this paper, a superconducting motor has been designed and realized. An axial topology based on the magnetic field concentration method has been used. The inductor is made of one solenoid to create a homogenous flux density, and YBaCuO plates are used to modulate the flux density in the air gap of the motor. The three-phase axial armature is made of copper. The armature is rotating and the inductor stationary. Sliding contacts are used to supply the armature. Magnetic calculations are carried out using the Monte Carlo Method. The influence of several parameters has been investigated. A theoretical study of an extrapolated superconducting inductor has been made for low-temperature superconducting and high-temperature superconducting solenoids.

Abstract The shear strength of reinforced concrete members with or without shear reinforcement is influenced by the shear span to effective depth and longitudinal tensile reinforcement ratios. In high-strength concrete, if the paste has a higher strength than the aggregates, then propagation of cracks is possible through the aggregates rather than around the aggregates, and the concrete may fail with a brittle failure, which is against most of the guideline’s philosophies. This paper investigates experimentally the influence of the shear-span to effective depth ratio and the longitudinal tensile reinforcement ratios on the behavior of the shear strength of HSC beams having no shear reinforcement. A total of fifteen reinforced high-strength concrete beams with different longitudinal reinforcement ratios were fabricated and then tested under a two-point bending test with shear-span to effective depth ratios varying from 1 to 3. Experimental results were compared based on design codes and state-of-the-art models. The influence of shear-span to effective depth ratio and longitudinal tensile reinforcement ratio is unaccounted for in most design guidelines and prediction models; therefore, the predicted values are either underestimated (up to 50%) or overestimated, except for the Zsutty Model, which has accurately predicted the shear strength values for all shear-span to effective depth and longitudinal tensile reinforcement ratios. As in the future, high-strength concrete will be more likely used in RC construction, this study directs the understanding of model assumptions for shear prediction before its use.

This paper deals with fault diagnosis of induction machines based on the discrete wavelet transform. By using the wavelet decomposition, the information on the health of a system can be extracted from a signal over a wide range of frequencies. This analysis is performed in both time and frequency domains. The Daubechies wavelet is selected for the analysis of the stator current. Wavelet components appear to be useful for detecting different electrical faults. In this paper, we will study the problem of broken rotor bars, end-ring segment, and loss of stator phase during operation.

This paper presents a new space vector pulsewidth modulation (SVPWM) technique for the control of six-phase voltage source inverter (VSI)-fed dual stator induction machines (DSIM).A DSIM is an induction machine which has two sets of three-phase stator windings spatially shifted by 30 electrical degrees and fed by two three-phase VSIs.Despite their advantage of power segmentation, these machines are characterized by large zero sequence harmonic currents, and in particular those of order 6k ± 1, which are due to the mutual cancellation between the two stator windings.The proposed SVPWM scheme, while easy to implement digitally, reduces significantly these extra stator harmonic currents.Experimental results, collected from a 15 kW prototype machine controlled by a digital signal processor are presented and discussed.