Search Results (124)

A collaborative inter-laboratory study was conducted to characterise the performance of the novel 250 W External Discharge Plasma Thruster (XPT) with a channel-less Hall effect-type thruster designed to address lifetime limitations and lower-power efficiency challenges in conventional Hall effect thrusters. This study aimed to validate performance measurements across different facilities and thrust stands, investigating potential facility effects on thrust characterisation. Performance testing was conducted both at the University of Surrey using a torsional thrust balance and at the University of Southampton with a double inverted pendulum thrust stand, providing independent verification of the thrust and efficiency metrics. The comparison highlighted the importance of cross-facility testing with differing background pressures, calibration methods, and thrust balance types. These differences provide valuable insights, ensuring more robust and reliable low-power thruster characterisation. The XPT thruster demonstrated consistent performance across both the University of Surrey and University of Southampton facilities, with thrust levels ranging from 1.60 mN to 11.8 mN, specific impulses from 327 s to 1067 s, and anode efficiencies up to 11%. Higher anode voltages and mass fluxes at Southampton enabled extended operational envelopes, revealing performance plateaus at elevated powers, particularly for flow rates above 8 sccm. Cross-facility testing highlighted facility-dependent influences, with Southampton achieving a higher thrust and specific impulse at lower flow rates (5–6 sccm) due to increased anode currents, while discrepancies between test sites of up to 25% were observed at higher flow rates (8–10 sccm) and powers above 200 W. Characterisation identified an optimal operating range at 200 W of anode power with a mass flux below 8 sccm. This work underscores the importance of inter-laboratory validation in electric propulsion testing and provides insights into the best practices for assessing next-generation Hall effect-type thrusters. Full article

Precision air conditioning (PAC) systems are prone to various types of failures, leading to inefficiencies, increased energy consumption, and possible reductions in equipment performance. This study proposes an automatic real-time fault detection and diagnosis system. It classifies events as either faulty or normal by analyzing key status signals such as pressure, temperature, current, and voltage. This research is based on data-driven models and machine learning, where a specific strategy is proposed for five types of system failures. The work was carried out on a Rittal PAC, model SK3328.500 (cooling unit), installing capacitive pressure sensors, Hall effect current sensors, electromagnetic induction voltage sensors, infrared temperature sensors, and thermocouple-type sensors. For the implementation of the system, a dataset of PAC status signals was obtained, initially consisting of 31,057 samples after a preprocessing step using the Random Under-Sampler (RUS) module. A database with 20,000 samples was obtained, which includes normal and failed operating events generated in the PAC. The selection of the models is based on accuracy criteria, evaluated by testing in both offline (database) and real-time conditions. The Support Vector Machine (SVM) model achieved 93%, Decision Tree (DT) 93%, Gradient Boosting (GB) 91%, K-Nearest Neighbors (KNN) 83%, and Naive Bayes (NB) 77%, while the Random Forest (RF) model stood out, having an accuracy of 96% in deferred tests and 95.28% in real-time. Finally, a validation test was performed with the best-selected model in real time, simulating a real environment for the PAC system, achieving an accuracy rate of 93.49%. Full article

This study presents a detailed investigation of the torque-speed characteristics of a WEG single-phase squirrel-cage induction motor (SPSCIM) of (1/2 hp), 110/220 V at 60 Hz. The primary objective was to derive the motor’s equivalent circuit and validate its performance curves through finite element analysis (FEA), simulation using MATLAB^®/Simulink^®, and experimental testing. Finite element simulations were conducted using the software FEMM (Finite Element Method Magnetics) to model the magnetic flux distribution within the motor’s stator and rotor. These simulations, based on the motor’s dimensions and nameplate data, provided essential insights into the electromagnetic behavior, including flux density and saturation effects, which are crucial for accurate torque-speed curve predictions. For experimental validation, tests were performed under open-circuit and locked-rotor conditions through a universal machine as a load emulator. The torque-speed characteristics were determined using the Suhr method and the classical approach, with the resulting curves compared to experimental measurements. Voltage and current were measured using AC PZEM-004T and DC PZEM-017 meters, while rotor speed was monitored with a Hall effect sensor (A3144). The results revealed strong agreement between the FEM simulations, Surh method, and experimental data, demonstrating the reliability and accuracy of the combined simulation and analytical methods for modeling the motor’s performance. The estimations using classical and Suhr methods, Simulink simulations, and FEMM yielded low error percentages, mostly below 2%. However, in the FEMM simulation, rotor resistance showed a higher error of around 20% due to unavailable data on the exact number of windings turns, a modifiable parameter that can be corrected through further adjustments in the simulation. The torque-speed curves obtained at different voltage levels showed an excellent correlation, confirming the effectiveness of the proposed approach in characterizing the motor’s operational behavior. Full article

This study systematically investigates the electrical characteristics of the vertical NPN bipolar junction transistor (VNPN BJT) in the strong magnetic field environment, focusing on analyzing the effects of magnetic field direction and intensity on key parameters such as terminal current and current gain (β). The simulation results show that the magnetic field induces changes in the carrier distribution, thereby affecting the current transport path. Through the in-depth analysis of electron motion trajectories, potential distribution, and Hall voltage, this paper reveals the physical mechanisms behind the device’s characteristic changes under the magnetic field and discovers that the inherent asymmetry of the BJT structure induces significant magnetic anisotropy effects. On this basis, a design for interference-resistant structures in strong magnetic field environments is proposed, effectively suppressing the adverse effects of magnetic-field-sensitive directions on BJT performance and significantly improving the device’s stability in complex magnetic field environments. Full article

This paper presents a Maxwell–Wien bridge for use in the calibration of standard inductances with values between 100 µH and 10 H and frequencies from 20 Hz to 20 kHz. The inductances are measured by comparison with a variable standard capacitor, in parallel association with a variable standard resistor, on the bridge modified by a Wagner balance. The variable standards are calibrated after the bridge balance. The other resistors in the bridge are standard resistors, pre-calibrated in AC using an automatic Wheatstone bridge and in DC after the bridge has been balanced using a comparison bridge with standard resistors traceable to the quantum Hall effect standards. PXI modules are used to supply the bridge with two voltages controllable in amplitude and phase. Design details and the uncertainty budget are discussed. For an inductance of 100 mH characterized by an internal resistance of 83 Ω, the expanded uncertainties are less than 6 µH on the inductance and 20 mΩ on the internal resistance. For inductances from 100 µH to 10 H, the relative uncertainties are less than 0.02% of the inductance and 0.2% of the internal resistance from 20 Hz to 20 kHz. Full article

High-voltage direct-current (HVdc) transmission lines are gaining more attention as an integral part of modern power system networks. Monitoring the dc current is important for metering and the development of dynamic line rating control schemes. However, this has been a challenging task, and there is a need for wireless sensing methods with high accuracy and a dynamic range. Conventional methods require direct contact with the high-voltage conductors and utilize bulky and complex equipment. In this paper, an ultra-high-frequency (UHF) radio frequency identification (RFID)-based sensor is introduced for the monitoring of the dc current of an HVdc transmission line. The sensor is composed of a passive RFID tag with a custom-designed antenna, integrated with a Hall effect magnetic field device and an RF power harvesting unit. The dc current is measured by monitoring the dc magnetic field around the conductor using the Hall effect device. The internal memory of the RFID tag is encoded with the magnetic field data. The entire RFID sensor can be wirelessly powered and interrogated using a conventional RFID reader. The advantage of this approach is that the sensor does not require batteries and does not need additional maintenance during its lifetime. This is an important feature in a high-voltage environment where any maintenance requires either an outage or special equipment. In this paper, the detailed design of the RFID sensor is presented, including the antenna design and measurements for both the RFID tag and the RF harvesting section, the microcontroller interfacing design and testing, the magnetic field sensor calibration, and the RF power harvesting section. The UHF RFID-based magnetic field sensor was fabricated and tested using a laboratory experimental setup. In the experiment, a 40 mm-diameter-aluminum conductor, typically used in 500 kV HVdc transmission lines carrying a dc current of up to 1200 A, was used to conduct dc current tests for the fabricated sensor. The sensor was placed near the conductor such that the Hall effect device was close to the surface of the conductor, and readings were acquired by the RFID reader. The sensitivity of the entire RFID sensor was 30 mV/mT, with linear behavior over a magnetic flux density range from 0 mT to $4.5$ mT. Full article

Two-dimensional (2D) Xenes, including graphene where X represents C, Si, Ge, and Te, represent a groundbreaking class of materials renowned for their extraordinary electrical transport properties, robust photoresponse, and Quantum Spin Hall effects. With the growing interest in 2D materials, research on germanene-based systems remains relatively underexplored despite their potential for tailored optoelectronic functionalities. Herein, we demonstrate a facile and rapid chemical synthesis of tellurium-doped germanene hydride (Te-GeH) nanostructures (NSs), achieving precise atomic-scale control. The 2D Te-GeH NSs exhibit a broadband optical absorption spanning ultraviolet (UV) to visible light (VIS), which is a critical feature for multifunctional photodetection. Leveraging this property, we engineer photoelectrochemical (PEC) photodetectors via a simple drop-casting technique. The devices deliver excellent performance, including a high responsivity of 708.5 µA/W, ultrafast response speeds (92 ms rise, 526 ms decay), and a wide operational bandwidth. Remarkably, the detectors operate efficiently at zero-bias voltage, outperforming most existing 2D-material-based PEC systems, and function as self-powered broadband photodetectors. This work not only advances the understanding of germanene derivatives but also unlocks their potential for next-generation optoelectronics, such as energy-efficient sensors and adaptive optical networks. Full article

Planar Hall magnetoresistance (PHMR) sensors are widely utilized due to their high sensitivity, simple structure, and cost-effectiveness. However, their performance is influenced by both the driving mode and the thickness of the ferromagnetic layer, yet the combined effects of these factors remain insufficiently explored. This study systematically investigates the impact of Ni₈₀Fe₂₀ thickness (5–35 nm) on PHMR sensor performance under constant current (CC) and constant voltage (CV) modes, with a focus on optimizing the peak-to-peak voltage (V_p-p). In CC mode, electron surface scattering at 5–10 nm increases resistance, leading to a sharp rise in V_p-p, followed by a decline as the thickness increases. In contrast, CV mode minimizes resistance-related effects, with sensor signals predominantly governed by magnetization-dependent resistivity. Experimentally, the optimal V_p-p was observed at 25 nm in CV mode. However, for thicknesses beyond this point, the reduction in sensor resistance suggests that voltage distribution across both the sensor and external load resistance significantly influences performance. These findings provide practical insights into optimizing PHMR sensors by elucidating the interplay between driving modes and material properties. The results contribute to the advancement of high-performance PHMR sensors with enhanced signal stability and sensitivity for industrial and scientific applications. Full article

This study used a direct dispersion and filtration technique to produce hybrid buckypaper (BP) composites of copper oxide nanoparticles (NPs) and entangled multiwalled carbon nanotubes (CNTs). The photocurrent generation of the BP sheets under two different (direct and gradient) illumination conditions was investigated by varying copper oxide loadings (10–50 wt%). The structure and morphology of the composites examined through X-ray diffraction and scanning electron microscopy (SEM) confirmed the presence of monoclinic cupric oxide nanoparticles in the CNT network. The difference in electrical resistivity between bulk-filled and surface-filled CuO-BP composites was assessed using the four-probe Hall measurement. The studies disclosed that the surface-loaded CuO on the CNT network demonstrated a superior ON and OFF response under the gradient illumination conditions with peak values of 17.69 μA and 350.04 μV for photocurrent and photovoltage, respectively. The significant photocurrent observed at zero applied voltage revealed the existence of a photovoltaic effect in the BP composites. An intense photoresponse was detected in the surface-filled sample CuO-BP composite in both illumination conditions. Additionally, at an illumination level of 150 W/m², wavelength-dependent photovoltaic effects on pure BP were observed using red, green, and blue filters. Full article

This study investigates the fabrication and characterization of flexible PN diode devices using phosphorus- and boron-doped carbon nanotube (CNT) paper, also known as Buckypaper (BP). The BP substrate is fabricated from multi-walled carbon nanotubes (MWCNTs) and doped with phosphorus and boron to form N-type and P-type semiconductors, respectively. Various experimental techniques, including Raman spectroscopy, Hall effect measurements, and scanning electron microscopy (SEM), are employed to analyze the properties of the doped BP. The results reveal that the current-voltage (I-V) and capacitance-voltage (C-V) characteristics preliminarily exhibit the basic electrical properties of a diode after doping with P-type and N-type carriers. Subsequently, optimized vertical stacking combined with parallel electrode configurations for the BP diode devices demonstrates that vertical series stacking gradually enhances the thermoelectric voltage, while horizontal parallel connections approximately scale up the thermoelectric and photovoltaic voltages proportionally. The findings underscore the critical role of creating heterogeneously doped CNT-paper PN junction electric fields in improving the performance of carbon-based semiconductor devices. Furthermore, we demonstrate that these directionally oriented energy devices, when stacked, can form modular systems with enhanced efficiency. This work highlights the potential of flexible carbon material-based devices for advanced thermoelectric and photovoltaic applications. Full article

In response to the difficulties and poor timeliness in detecting feeding metallic foreign objects during high-yield continuous crushing operations in coal mines, this paper proposes a new method for detecting metallic foreign objects, combining pulsed eddy current testing with the Truncated Region Eigenfunction Expansion (TREE) method. This method is suitable for the harsh working conditions in coal mine crushing stations, which include high dust, strong vibration, strong electromagnetic interference, and low temperatures in winter. A model of the eddy current field of feeding metallic foreign objects in the truncated region is established using a coaxial excitation and receiving coil with a Hall sensor. The full-cycle time-domain analytical solution for the induced voltage and magnetic induction intensity of the reflective field under practical square wave signals is obtained. Simulation and experimental results show that the effective time range, peak value, and time to peak of the received voltage and magnetic induction signals can be used to classify and identify the size, thickness, conductivity, and magnetic permeability of feeding metallic foreign objects. Experimental results meet the actual needs for removing feeding metallic foreign objects in coal mine sites. This provides core technical support for the establishment of a predictive fault diagnosis system for crushing equipment. Full article

Numerical computations through the finite element method (FEM) are used to determine the impact of doping on carrier concentration and recombination between charges in time for organic semiconductor diodes having low mobility. The Hall effect is used to determine the effects of doping on the performance and reliability of organic semiconductor devices by accurately modeling these processes. In this work, the number density of charge carriers and Hall voltages are computed for n-type doped semiconductors with two different recombination processes, such as non-Langevin and Langevin-type. The findings reveal that in the Langevin system with ${\beta }^{\prime }=1$, the number density of charge carriers is almost five and four times lower compared with the non-Langevin system with ${\beta }^{\prime }=0.01$ for increasing dopant concentrations of $N_{p_d}$ = 1 and 3, respectively. The Langevin system also had lower Hall voltages than the steady-state and non-Langevin systems for different magnetic fields with dopants, and the non-Langevin system had nearly identical Hall voltages as the steady-state case. The outcome of the current work provides insights into charge transportation mechanisms in low-mobility doped organic semiconductors with Hall effect measurements to improve device efficiency. Full article

ZnO thin films were deposited using RF sputtering by varying the argon:oxygen gas flow rates and substrate temperatures. Structural, optical and electrical characterization of ZnO thin films were systematically carried out using X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible spectroscopy, X-Ray photoelectron spectroscopy (XPS) and Hall measurements. Film deposited at room temperature and annealed at 300 °C exhibited low O₂ incorporation with localized defects and a high percentage of Zn interstitials. A large crystalline size and fewer grain boundaries resulted in a high Hall mobility of 46.09 cm²/V-s Deposition at higher substrate temperatures resulted in improvement in O₂ incorporation through the annihilation of localized defects and decrease in oxygen vacancies and Zn interstitials. Urbach tails within the bandgap were identified using the absorption spectrum and compared with the % defects from XPS. Bottom-gate thin-film transistors were subsequently fabricated on a SiO₂/p-Si substrate using the combination of RF sputtering, wet etching and photolithography. Variation in the substrate temperature showed performance enhancement in terms of the leakage current, threshold voltage, sub-threshold swing and I_ON/I_OFF ratio. Thin-film transistor (TFT) devices deposited at 300 °C resulted in an O₂-rich surface through chemisorption, which led to a reduction in the leakage current of up to 10⁻¹² A and a 10-fold reduction in the sub-threshold swing (SS) from 30 V to 2.8 V. Further TFT optimization was carried out by reducing the ZnO thickness to 50 nm, which resulted in a field-effect mobility of 1.1 cm²/V-s and I_ON/I_OFF ratio of 10⁵. Full article

In this article, we report a novel pressure sensing method based on the Hall effect and a hard magnet magnetorheological elastomer (hmMRE). The elastic property of the MRE under pressure was used to generate spatial variation in the magnetic flux density around the MRE, and the variation was detected by the Hall effect device underneath. As the first development in this kind of pressure sensing mechanism, we conducted research for the following three purposes: (1) to verify the Hall effect on the output signal, (2) to understand the sensor output variations under different modes of operation, and (3) to utilize the mechanism as a pressure sensor. We characterized the sensor with its operation parameters, such as signal polarity switching depending on wiring directions, signal amplitude, and offset shift depending on the input voltage. Based on the analyses, we concluded that the Hall voltage represents the pressure applied on the hmMRE, and the new pressure sensing mechanism was devised successfully. Full article

The results from a wide-ranging parametric investigation into the behavior of the collisionless partially magnetized plasma discharge of three propellants—xenon, krypton, and argon—are reported in this two-part article. These studies are performed using high-fidelity reduced-order particle-in-cell (PIC) simulations in a 2D configuration that represents an axial–azimuthal cross-section of a Hall thruster. In this part I paper, we discuss the effects of discharge voltage and current density (mass flow rate). Our parametric studies assess the spectra of the resolved instabilities under various plasma conditions. We evaluate the ability of the relevant theories from the literature to explain the variations in the instabilities’ characteristics across the studied plasma parameter space and for various propellants. Moreover, we investigate the changes in the electrons’ cross-magnetic-field transport, as well as the significance of the contribution of different momentum terms to this phenomenon across the analyzed cases. In terms of salient observations, the ion acoustic instability (IAI)-related modes are found to be dominant across the simulation cases, with the ion transit time instability also seen to develop at low current density values. Across the explored parameter space, the instabilities have the main contributions to the electrons’ transport within the plume region. The peak of the electric momentum force term, representing the effect of the instabilities, overall shifts toward the plume as either the current density or the discharge voltage increases. The numerical findings are compared against relevant experimental observations reported in the literature. Full article