Abdullatif Hakami

Although biodiesel seems to be a promising alternative fuel for compression ignition (CI) engines, its use can cause deposit formation on the catalytic converter and impact engine durability. The effects of 30 ppm multi-walled carbon nanotube (MWCNT) dispersed Pongamia biodiesel blends (B10, B20 and B30) on combustion characteristics, engine performance and catalytic converter deposits on 500 h engine operation are investigated. In-cylinder pressure, heat release rate, ignition delay and combustion duration were used to assess combustion characteristics, and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the catalyst deposits. The fuel with the best overall performance was B20-MWCNT, with the highest fuel efficiency of 34.62% and the lowest fuel consumption of 0.25 kg/kW-h. The lowest ignition delay time (5.7°CA) and combustion duration (30.8°CA) were also achieved with B20-MWCNT. The B20-MWCNT exhibited the highest peak cylinder pressure (69.62 bar) and heat release rate (83.94 J/°CA) which demonstrated better combustion when considering the addition of MWCNT. SEM/EDS analysis showed that the fouling was less with fine and compact deposits with SEM compared to neat biodiesel. These results showed that B20-MWCNT has the best performance in terms of combustion and durability of the catalytic converter, which can be used as an efficient and sustainable fuel in CI engine.

The doubly fed induction generator (DFIG) dominates the wind energy market, yet its direct stator-to-grid connection makes it vulnerable to grid faults, creating a tension between hardware self-protection and grid-code fault ride-through (FRT) compliance. This paper presents the modelling and FRT analysis of a 9 MW DFIG wind farm combining a 20 MVA Static Synchronous Compensator (STATCOM) with a ten-tier algorithmic protection scheme. A detailed phasor-domain MATLAB/Simulink R2024b model is complemented by physics-based reduced-order models integrated in Python, separating calibration targets, calibration-dependent derived quantities and quantities independent of the DC-link calibration. The aerodynamic model reproduces the power coefficient maximum of 0.48 at a tip–speed ratio of 8.1. The energy-balance model uses two parameters identified per scenario from the detailed DC-link trajectory; its peak-voltage agreement within 0.4% is therefore a calibrated consistency check, while the derived arming times, slopes, chopper sizing and latency budget remain conditional on that calibration. A first-order Thevenin analysis shows that the STATCOM supports a weak 25 kV point of common coupling of order 53 MVA short-circuit level, not the 2500 MVA source. The approximate 0.50-to-0.78 p.u. recovery requires about 29.7 M_var and 1.90 p.u. of STATCOM rated current for 150 ms, conditional on an assumed short-time envelope and adequate converter-voltage headroom; it is not attributable to continuous rated operation. FRT support for the selected recoverable dip is separated from converter survival during a zero-impedance fault, for which a 1700 V chopper pickup with a 1 ms gate delay, not the 10 ms isolation command, is the clamping mechanism. The assessment is explicitly conditional and requires electromagnetic-transient and hardware-in-the-loop confirmation.

A novel Gd³⁺-activated tellurite glass with the composition 65TeO₂–15MgO–9SrO–5ZnO–5Ta₂O₅–1Gd₂O₃ (TeMgSrTa³⁺) was developed through the conventional melt-quenching route to investigate its combined optical, luminescent, electron paramagnetic resonance, thermoluminescence, and radiation shielding characteristics within a single glass matrix. The novelty of this work lies in the incorporation of Ta₂O₅ and Gd³⁺ into the TeO₂–MgO–SrO–ZnO glass network, enabling the simultaneous realization of ultraviolet photoluminescence, favorable dosimetric response, and efficient photon and neutron attenuation, which has not been comprehensively reported for this glass composition. X-ray diffraction confirmed the formation of a completely amorphous structure, while FTIR analysis identified TeO₄ and TeO₃ structural units responsible for network modification. UV–Visible spectroscopy revealed excellent optical transparency, and the characteristic absorption bands observed at 209, 247, and 347 nm were assigned to the 4f–5d transitions of Gd³⁺ ions. Under ultraviolet excitation, the glass exhibited a strong emission centered at 313 nm, originating from the ⁶P₇/₂→⁸S₇/₂ transition of Gd³⁺, with chromaticity coordinates of x = 0.1487 and y = 0.0468, demonstrating its suitability for ultraviolet photonic applications. Comprehensive gamma-ray shielding analysis showed close agreement between experimental and theoretical attenuation parameters, including the mass attenuation coefficient, linear attenuation coefficient, half-value layer, tenth-value layer, and mean free path across a broad photon energy range. The measured fast neutron effective removal cross-section further confirmed the material’s capability for neutron shielding. Thermoluminescence investigations produced well-defined glow peaks with favorable kinetic parameters, indicating promising dosimetric performance. Electron paramagnetic resonance analysis verified the valence state and local coordination environment of Gd³⁺ ions, providing insight into the ligand field surrounding the activator. The synergistic combination of structural stability, ultraviolet luminescence, radiation attenuation efficiency, and dosimetric response demonstrates that the proposed TeMgSrTa³⁺ glass is a promising multifunctional material for advanced photonic devices, radiation protection systems, and radiation sensing technologies.

Grid-connected photovoltaic (PV) systems paired with battery storage are becoming a core element of low-carbon distribution networks. This paper develops a complete closed-form formulation together with an independent, simulation-based verification of a single-phase grid-connected PV-battery microgrid sized for high-irradiance residential conditions in Saudi Arabia, using measured solar-resource and tariff data for Riyadh. A 6.25 kW monocrystalline array feeds a 400 V DC link through a perturb-and-observe boost stage; a bidirectional converter couples a 13.5 kWh LiFePO₄ battery; and an IEEE 1547 smart inverter interfaces a 230 V grid through an LCL filter. Governing equations for every subsystem are derived and evaluated numerically, and a Python re-implementation of the phasor power-flow model verifies the analysis over a 24 h cycle run to periodic steady state, reproducing the reference design values with a mean absolute error of 0.5%. Using measured monthly solar-resource and temperature data for Riyadh, a full twelve-month analysis gives an annual self-sufficiency of 51.8% and a PV self-consumption of 72.9% for the optimised energy-management scheme. A dedicated time-domain switching simulation with FFT analysis shows that the LCL filter limits grid-current total harmonic distortion to 0.8%, far below the L-filter value of 6.2% and below the 5% current-distortion reference of IEEE 519 (full compliance additionally requires the PCC short-circuit ratio). Twelve-month, battery-size and load-sensitivity studies confirm robustness, and a techno-economic assessment based on the Saudi Electricity Company residential tariff quantifies levelized cost, payback and battery degradation, showing that economic viability hinges on tariff reform.

Electric Vehicle drive systems must provide fast torque response, low or minimal torque ripple, robustness to both parameter variations and external disturbances. Permanent Magnet Synchronous Motors (PMSMs) are commonly found in electric vehicle propulsion applications due to their high power density, high efficiency, and excellent dynamic performance. However, performance degradation in torque control of PMSMs under time-varying conditions arises from the nonlinear characteristics of motors and their high sensitivity to changes in system parameters. This paper presents a torque-control method with high dynamic bandwidth that combines three techniques: (1) Nonlinear Sliding Mode Torque Control; (2) Predictive Current Control; and (3) Disturbance Estimation. The sliding mode controller provides improved robustness against uncertainties about the system. In addition, the predictive current control provides improved accuracy in current tracking and significantly reduces the time required to achieve a steady state. A disturbance observer is used to compensate for load disturbances and model errors in the motor model. The integrated control architecture is simulated and modeled in MATLAB/Simulink for a typical EV driving environment. The simulation framework produced faster and more accurate torque tracking than conventional PI-type vector controllers, as well as reduced torque ripple and improved disturbance rejection under similar operating conditions. The results demonstrate that the proposed method is a viable candidate for high-performance EV propulsion systems while acknowledging practical limitations such as chattering, tuning complexity, sampling time sensitivity, and the need for further experimental validation.

The near-infrared (NIR) emission and the excellent excitonic properties of carbon nanotubes (CNTs) are the basis for their potential use as nanoscale light sources in photonics, biomedical applications, and quantum communication. However, these are impeded by exciton quenching, environmental instability, and, in terms of chirality control, but only limited control. In this review, we summarize in depth the recent progress in interfacial engineering strategies to address these challenges, such as chemical defect functionalization, protective encapsulation, nanoscale heterostructure integration with two-dimensional (2D) and photonic materials, and chirality-selective self-assembly. It also reviews the photoluminescence (PL) and electroluminescence (EL) processes of CNT emitters, with a particular focus on the effect of interface interaction on exciton dynamics, emission efficiency, and device performance. Applications in silicon photonics, single photon sources for quantum optics, flexible optoelectronics, and NIR bio-imaging are critically discussed and key challenges, including dark exciton bottlenecks, interfacial degradation, scalable fabrication, and deterministic control of chirality, are discussed. The current review includes an overview of interfacial engineering, optical emission mechanisms, heterostructure design, and new surface engineering optimization strategies based on AI, unlike previous reviews that have concentrated on either CNT emitters or single interface modification strategies. It also pinpoints existing research gaps and outlines future directions for the development of high efficiency, stable and scalable CNT-based photonic and optoelectronic devices.

Thermochromic materials (TCMs) reversibly change their color or near‐infrared response with temperature, and a growing literature treats them as passive self‐regulating components in energy‐efficient buildings, wearable diagnostics, cold‐chain monitoring, and adaptive optical systems. Most existing reviews, however, are descriptive surveys that catalog mechanisms and processing routes without testing them against one another or against the realities of deployment. The present review takes a deliberately critical and comparative stance. Rather than an inventory of eight unconnected switching effects, the underlying physics is grouped into three families, namely, electronic and structural transitions in solids, molecular reconfiguration in discrete species, and supramolecular ordering in mesophases, and a common set of performance descriptors lets dissimilar materials be compared on an equal footing. The platforms are then assessed against those descriptors, with emphasis on the doping trade‐offs that govern the transition temperature of vanadium dioxide, the toxicity and regulation that render mercury‐based ionic conductors effectively unusable, and the photodegradation and cycling fatigue that constrain organic leuco‐dye and spiro systems. Synthesis, microencapsulation, and coating are treated as a single manufacturing chain and judged on scalability, reproducibility, cost, and technology readiness, since these factors, not laboratory optical contrast, ultimately decide whether a technology reaches the market. Durability is analyzed through combined ultraviolet, thermal, oxidative, and hydrolytic stress, and through the reproducibility gap left by nonstandard accelerated‐aging protocols. Deployment is framed within intelligent engineering systems, where TCMs act as passive actuators alongside sensor networks, building‐management systems, and digital‐twin models. The argument is supported by eight original schemes and eight comparative tables. We conclude that the principal barriers to adoption are no longer the questions of scientific novelty but of durability, cost at scale, standardization, and system‐level integration, and we map the research directions most likely to close these gaps.

This research addresses the acoustic feedback and stability performance of Active Noise Control (ANC) systems. The Filtered Cross Least Mean Square (FxLMS) algorithm is one of ANC’s most successful adaptive algorithms for reducing undesired noise. The ANC filters have their convergence speeds reduced by significant acoustic feedback, making them unstable in the worst-case scenario. It is possible to eliminate acoustic feedback using a fixed feedback neutralization filter that can be acquired offline. However, the feedback path could change over time, so we might have to make modifications often while the ANC system is online. This paper proposes two enhancements to the FxLMS algorithm to address the ANC’s performance difficulties. To address acoustic feedback problems, the first alteration improves the ANC duct’s feedback path modeling by incorporating the online Feedback Naturalization (FN) concept with an Active function normalized LMS algorithm (AF-NLMS). The second modification, the vector-decimation-based method, is proposed in this paper as a way to improve stability, convergence speed, and robustness. It is achieved by decimating the filter weight vector into small vectors and then updating each vector using the harmonic mean error of the VSS FxLMS. To ensure the enhanced effectiveness of the proposed solution, the AF-FxLMS, online-AFFNFxLMS, and HM-AFFNFxLMS algorithms are used to update the filter weights as a demonstration. The proposed method has superior noise reduction effectiveness compared to other algorithms, which indiscriminately attenuate the control filter across all frequencies. The validation of the proposed approach was achieved via simulations and experimental tests in a PVC duct ANC system, showing that robust stability can be achieved while keeping relatively good performance.