A new phototransistor based on the mechanically exfoliated single-layer MoS(2) nanosheet is fabricated, and its light-induced electric properties are investigated in detail. Photocurrent generated from the phototransistor is solely determined by the illuminated optical power at a constant drain or gate voltage. The switching behavior of photocurrent generation and annihilation can be completely finished within ca. 50 ms, and it shows good stability. Especially, the single-layer MoS(2) phototransistor exhibits a better photoresponsivity as compared with the graphene-based device. The unique characteristics of incident-light control, prompt photoswitching, and good photoresponsivity from the MoS(2) phototransistor pave an avenue to develop the single-layer semiconducting materials for multifunctional optoelectronic device applications in the future.
Abstract Thermally conductive polymer composites offer new possibilities for replacing metal parts in several applications, including power electronics, electric motors and generators, heat exchangers, etc., thanks to the polymer advantages such as light weight, corrosion resistance and ease of processing. Current interest to improve the thermal conductivity of polymers is focused on the selective addition of nanofillers with high thermal conductivity. Unusually high thermal conductivity makes carbon nanotube (CNT) the best promising candidate material for thermally conductive composites. However, the thermal conductivities of polymer/CNT nanocomposites are relatively low compared with expectations from the intrinsic thermal conductivity of CNTs. The challenge primarily comes from the large interfacial thermal resistance between the CNT and the surrounding polymer matrix, which hinders the transfer of phonon dominating heat conduction in polymer and CNT. This article reviews the status of worldwide research in the thermal conductivity of CNTs and their polymer nanocomposites. The dependence of thermal conductivity of nanotubes on the atomic structure, the tube size, the morphology, the defect and the purification is reviewed. The roles of particle/polymer and particle/particle interfaces on the thermal conductivity of polymer/CNT nanocomposites are discussed in detail, as well as the relationship between the thermal conductivity and the micro- and nano-structure of the composites.
M.A. Kovalenko, S.S. Tsyvinskyi, I.Y. Kovalenko
et al.
Мета роботи. Визначення залежностей питомої потужності та питомого об’єму від розрахункової потужності та конструктивних розмірів для формування критеріїв оцінки ефективності ваго-габаритних показників високошвидкісного синхронного двигуна із постійними магнітами та зовнішнім ротором.
Методи дослідження. Класичні методи електромагнітного розрахунку основних розмірів синхронних двигунів із магнітоелектричним збудженням.
Отримані результати. За результатами розрахунків ваго-габаритних показників високошвидкісних синхронних двигунів із постійними магнітами, виконаного класичним методом, визначено вагу та об’єм активних матеріалів: магнітного осердя, постійних магнітів та міді обмотки статора. Для розрахунку прийнято діапазон потужності від 250 Вт до 15 кВт при 10000 об/хв, що відповідає найбільш часто використовуваними двигунами по потужності в різних галузях техніки та застосуваннях. Встановлено нелінійний характер зміни питомих показників синхронних двигунів із постійними магнітами. Визначено, що максимальна питома потужність (близько 80 кВт/кг) досягається в діапазоні 7–9 кВт, після чого цей показник знижується через теплові обмеження та зростання маси конструктивних елементів. Оптимальний діапазон потужності за критерієм питомого об’єму, при циліндричній конструкції прототипу із зовнішнім ротором, становить 1,5–4,5 кВт. Результати досліджень показують, що зі зростанням потужності змінюється баланс мас: відносна частка міді в обмотці статора збільшується, тоді як частка магнітного осердя зменшується. Це зумовлено необхідністю мінімізації електричних втрат для підтримки високого ККД та обмеженнями щодо тепловідведення.
Наукова новизна. Систематизовано залежності питомих характеристик високошвидкісних показників синхронних двигунів із постійними магнітами із зовнішнім ротором від їх геометричних параметрів та рівня використання активних матеріалів, що дозволило ідентифікувати зони найвищої ефективності конструкції при незмінній швидкості обертання.
Практична цінність. Запропонований підхід надає інженерні критерії для обґрунтованого вибору топології та основних розмірів високошвидкісних двигунів на ранніх етапах проєктування, забезпечуючи досягнення найкращих масо-габаритних характеристик.
Andrzej Gębura, Andrzej Szelmanowski, Ilona Jacyna-Gołda
et al.
The evolution of aircraft power systems has been driven by increasing electrical demands and advancements in aviation technology. Background: This study provides a comprehensive review and experimental validation of on-board electrical network development, analyzing power management strategies in both conventional and modern aircraft, including the Mi-24 helicopter, F-22 multirole aircraft, and Boeing 787 passenger airplane. Methods: The research categorizes aircraft electrical systems into three historical phases: pre-1960s with 28.5 V DC networks, up to 2000 with three-phase AC networks (3 × 115 V/200 V, 400 Hz), and post-2000 with 270 V DC networks derived from AC generators via transformer–rectifier units. Beyond theoretical analysis, this work introduces experimental findings on hybrid-electric aircraft power solutions, particularly evaluating the performance of the Modular Power System for Aircraft (MPSZE). The More Electric Aircraft (MEA) concept is analyzed as a key innovation, with a focus on energy efficiency, frequency stability, and ground power applications. The study investigates the integration of alternative energy sources, including photovoltaic-assisted power supplies and fuel-cell-based auxiliary systems, assessing their feasibility for aircraft system checks, engine startups, field navigation, communications, and radar operations. Results: Experimental results demonstrate that hybrid energy storage systems, incorporating lithium-ion batteries, fuel cells, and photovoltaic modules, can enhance MEA efficiency and operational resilience under real-world conditions. Conclusions: The findings underscore the importance of MEA technology in the future of sustainable aviation power solutions, highlighting both global and Polish research contributions, particularly from the Air Force Institute of Technology (ITWL).
Federico Barrero, Mario Bermúdez, Manuel R. Arahal
et al.
Modern electric machines are attracting the greatest interest from the research community due to their current increasing number of applications, including electric vehicles and wind power generators. Their use requires the development of complex regulators, where predictive controllers appear as interesting and viable alternatives in recent research works. Although these controllers have an easy formulation and high flexibility to incorporate different control objectives in multidimensional systems, they have limitations that require attention and limit their application: a high computational cost and current harmonic content. This work presents a novel controller that focuses on these limitations, where the additional degree of freedom introduced in the predictive controller through the lead-pursuit guidance law concept is combined with the use of virtual voltage vectors to reduce the harmonic content in a controlled drive. The effectiveness of the proposed controller is explored using a five-phase drive and several figures of merit, such as the root mean square error in current tracking, the total harmonic distortion in the stator currents, and the number of switching commutations per cycle. Different predictive controllers are compared with the proposal in terms of speed regulation, stator current control, and steady-state performance, where the results obtained are analyzed to show the interest, improvements, and limitations of the proposal.
Sokratis Mamarikas, Stylianos Doulgeris, Nikolaos Aletras
et al.
This paper focuses on energy consumption modeling approaches for traffic and examines how they deviate when applied to evaluate Battery Electric Buses (BEBs), in a try to identify an approach that combines simplicity with accuracy. To do so, the paper exploits three of them: a micro, a meso and a macro one. The microscopic approach relies on a detailed power-based vehicle model that uses second-by-second vehicle speed profiles as traffic activity input, and it serves here as a reference tool. The approach of average speed was employed to represent the macroscopic one that uses a single traffic activity input. For the mesoscopic case, a new function had to be developed that would require traffic inputs on a level-of-detail in between the macroscopic and microscopic scale. A statistical analysis on several standardized driving cycles was conducted to select such inputs, leading to a relationship that associates consumption with two stop-related variables (number and duration). The mesoscopic and macroscopic models could then be evaluated, by comparing their consumption estimations with the detailed microscopic calculations over the same cases (real-world urban traffic of Athens & Hong-Kong, and traffic measures). While the macroscopic results revealed well-known limitations in accuracy of the average speed approach, as it deviated from the microscopic model by 10 % for urban traffic and 20 % for measures, the mesoscopic one closely matched the microscopic model (max 5 % error). Thus, for BEBs, a mesoscopic approach with only two activity inputs (stop-related variables) can satisfy requirements from energy modeling for valid estimations and simplicity in use. With these characteristics, the approach presents exploitation potential in multiple applications of urban transportation systems.
Abstract This paper proposes a new low‐noise sensorless control strategy for the permanent magnet synchronous motor (PMSM) drives to tackle audible noise caused by high‐frequency injection method. The traditional noise reduction methods face limitation in improving estimated accuracy of rotor position due to the signal delay with fixed frequency signal. To overcome this issue, a low‐noise sensorless control strategy is developed, which consists of two parts. First, with the injection of the proposed variable‐frequency voltage signal, significant noise reduction can be achieved due to its characteristics of multi‐frequency switching and multi‐modal amplitude tuning. Secondly, a delayed effects‐aware demodulated signal is designed to reduce the impact of system delay, which can further improve the estimation accuracy of rotor position. As a result, the proposed low‐noise sensorless control scheme can suppress audible noise and further improve position estimation accuracy. Also, the steady‐state and dynamic performances of the motor drive system can be enhanced. Finally, comparative experiments under steady‐state and dynamic conditions demonstrate the superiority of the proposed method in PMSM.
Increasing frequency and intensity of extreme weather events motivates the assessment of power system resilience. The random nature of power system failures during these events mandates probabilistic resilience assessment, but state-of-the-art methods are computationally inefficient. In this paper, an enhanced PCE method to quantify power system resilience based on the extended AC Cascading Failure Model (AC-CFM) model is proposed. To address repeatability issues arising from PCE computation with different sample sets, we propose a novel experiment design method. Numerical studies on the IEEE 39-bus system illustrate the improved repeatability and convergence of the method. The enhanced PCE method is then used to efficiently assess the system's resilience and propose adaptation measures.
Marcelo D. Silva, Mila Naghibian, Magnus Jansson
et al.
ABSTRACT Rare earth elements (REEs) are central to the current solutions used for traction applications. However, REEs have fragile supply chains, which exposes them to supply interruptions and price spikes. Research has been focusing on REE‐free solutions, either exploring REE‐free topologies, such as induction and electromagnetised machines, or investigating the use of alternative hard magnetic materials, such as ferrite permanent magnets (PMs). This paper presents a novel methodology for designing and optimising spoke type permanent magnets synchronous machines (spoke machines) with ferrite PMs. The novelty of the methodology is the unique strategy used to integrate mechanical and demagnetisation constraints. Using this methodology, a novel rotor is optimised using FEM simulations to directly substitute a previous REE‐based motor. The optimised design represents a unique rotor, mainly due to its large magnet size, which enables a demagnetisation‐safe high‐torque motor. A prototype is built and tested to verify the FEM results experimentally. The experimental results show a prototype magnetically resilient to permanent demagnetisation and with higher efficiencies at field weakening when compared with an equivalent REE machine.
ABSTRACT This study investigates the modelling and predictive control methods for electromechanical actuators (EMAs) used in the retraction and extension system of all‐electric nose landing gears. By integrating predictive control theory, the proposed approach aims to enhance control performance and system reliability. A discrete‐time EMA model is developed to establish the relationship between predicted current and actuator dynamics. A cost function minimisation algorithm is constructed using switching states, predicted current and measured current values to determine the optimal switching sequence, thereby generating the voltage vectors required for motor operation. To address potential faults such as unbalanced loads, magnetic interference or environmental factors, this study employs a fault diagnosis method based on feedback current, predicted current and adaptive thresholds. Upon detecting actuator failure, a secondary control loop enables emergency gear release. This dual‐loop strategy ensures routine and emergency functionality, delivering over 2000 N of thrust at operating speeds ranging from 5 mm/s to 8 mm/s. A prototype EMA system was developed, and experimental results confirm its feasibility, accuracy and robustness, providing a reliable solution for all‐electric landing gear applications.
Artem Krasilov, Irina Lebedeva, Ruslan Yusupov
et al.
Many emerging applications, such as factory automation, electric power distribution, and intelligent transportation systems, require multicast Ultra-Reliable Low-Latency Communications (mURLLC). Since 3GPP Release 17, 5G systems natively support multicast functionality, including multicast Hybrid Automatic Repeat Request and various feedback schemes. Although these features can be promising for mURLLC, the specifications and existing studies fall short in offering guidance on their efficient usage. This paper presents the first comprehensive system-level evaluation of mURLLC, leveraging insights from 3GPP specifications. It points out (i) how mURLLC differs from traditional multicast broadband wireless communications, and (ii) which approaches to provide mURLLC require changing the paradigm compared with the existing solutions. Finally, the paper provides recommendations on how to satisfy strict mURLLC requirements efficiently, i.e., with low channel resource consumption, which increases the capacity of 5G systems for mURLLC. Simulation results show that proper configuration of multicast mechanisms and the corresponding algorithms for mURLLC traffic can reduce resource consumption up to three times compared to the baseline solutions proposed for broadband multicast traffic, which significantly increases the system capacity.
The reactive Power Take Off (PTO) force is the key to maximizing mechanical power absorption and electric power generation of Wave Energy Converters (WECs) from ocean waves with variable frequency, but its study is limited due to its difficulty in physical realization. This paper presents a simple yet effective $LC$-tuned WEC that generates a tunable reactive PTO force from tunable inductor $L$ and capacitor $C$ in the WEC. A complete closed loop system model of the WEC is derived first, then three quantitative rules are obtained from analyzing the model. These rules are used to tune the $LC$ network, and hence the reactive PTO force that drives the WEC, to resonate with the input wave force and generate maximal electric power over a range of wave frequencies. Mathematical analysis of the WEC and tuning rules reveals the analytical and quantitative descriptions of the WEC's mechanical power absorption, active and reactive electric power generation and power factor, optimal electric resistance load, and the generator and $LC$ capacity requirements. Simulation results show the effectiveness and advantages of the proposed WEC and verify the analysis results.