Search Results (6,557)

In this work, a sol–gel spin coating method was applied to obtain ZnO and ZnO:Ga thin films on a glass and ITO-coated glass substrate. Their structural, optical, and electrical properties were investigated with respect to their dependence on the different substrates, the number of layers (two and four), and the annealing temperature (300 and 400 °C). X-ray diffraction (XRD) patterns showed a hexagonal structure corresponding to the wurtzite phase for ZnO and ZnO:Ga films. ZnO films, deposited on a glass substrate, reveal greater crystallite sizes compared with ZnO films obtained from an ITO substrate. A Ga dopant worsened film crystallization. X-Ray photoelectron spectroscopy (XPS) proves the presence of Ga in a ZnO structure. ZnO films show lower transparency and haze values up to 44.12 (glass substrate) and 33.73 (ITO substrate) at a wavelength of 550 nm. The significant enhancement of ZnO film transparency is observed with Ga doping (with average transmittance in the visible spectral range above 85%, independent of the substrate used). Sheet resistance values are lower for ZnO:Ga films, and the figure of merit values are better compared with those of undoped ZnO films. Work function is studied for ZnO and ZnO:Ga films, deposited on Si, ITO, and glass substrates. Full article

Very low Earth orbit (VLEO) satellites are confronted with the challenge of orbital decay caused by thin atmospheres, and the volume and power limitations of micro satellites further restrict the application of traditional electric propulsion systems. In response to the above requirements, this study proposes an innovative scheme of radio frequency plasma micro-thrusters based on magnetic nozzle acceleration technology. By optimizing the magnetic nozzle configuration through the system, the plasma confinement efficiency was significantly enhanced. Combined with the mixed working medium (5 sccm Xe + 10 sccm air), the thrust reached 1.7 mN at a power of 130 W. Experiments show that the configuration of the magnetic nozzle directly affects the plasma beam morphology and ionization efficiency, and a multi-magnet layout can form a stable trumpet-shaped plume. The air in the mixed working medium has a linear relationship with the thrust gain (60 μN/sccm), but xenon gas is required as a “seed” to maintain the discharge stability. The optimized magnetic nozzle enables the thruster to achieve both high thrust density (13.1 μN/W) and working medium adaptability at a power level of hundreds of watts. This research provides a low-cost and miniaturized propulsion solution for very low Earth orbit satellites. Its magnetic nozzle-hybrid propellant collaborative mechanism holds significant engineering significance for the development of air-aspirating electric propulsion technology. Full article

Background: The growing demand for fresh food leads to extensive use of cold chain logistics (CCL) that significantly contributes to greenhouse gas (GHG) emissions due to its dependence on energy-intensive transport refrigeration units (TRUs). Understanding the need to balance food preservation with environmental sustainability, this paper explores practical strategies for reducing GHG emissions in CCL, focusing on fresh food products. Methods: The quantitative and qualitative analyses are applied to analyse data from Transport for London and Transport Scotland. Emission data were assessed to evaluate the impact of alternative TRU technologies and route optimisation practices. Results: The findings reveal that electric and cryogenic TRUs, along with improved route planning and operational practices, can significantly reduce the emissions of carbon dioxide, nitrogen oxides and particulate matter. These results highlight the potential strategy for industry-led emission reductions without compromising food quality. Conclusions: This paper recommends the coordination of government policy and industry to support technological adaptation and infrastructure upgrades and to research into real-time monitoring and renewable energy integration in CCL systems. Full article

To address the challenges of power generation rights trading and profit distribution in the integrated energy system of multi-park combined cooling, heating, and power (CCHP) with new energy grid integration, we constructed a hierarchical game model involving multi-energy system aggregators. By having aggregators price electricity, heat, cold, and carbon costs, the model establishes a hierarchical game framework with the linkage of the four prices (electricity, heat, cold, and carbon), achieving inter-park peer-to-peer (P2P) multi-energy dynamic price matching for the first time. It aims to coordinate distribution network dispatching, renewable energy, energy storage, gas turbine units, demand response, cooling–heating–power coupling, and inter-park P2P multi-energy interaction. With the goal of optimizing the profits of integrated energy aggregators, a hierarchical game mechanism is established, which integrates power generation rights trading models and incentive-based demand response. The upper layer of this mechanism is the profit function of integrated energy aggregators, while the lower layer is the cost function of park microgrid alliances. A hierarchical game mechanism with Two-Level Optimization, integrating the Adaptive Disturbance Quantum Particle Swarm Optimization (ADQPSO) algorithm and the branch and bound method (ADQPSO-Driven Branch and Bound Two-Level Optimization), is used to determine dynamic prices, thereby realizing dynamic matching of energy supply and demand and cross-park collaborative optimal allocation. Under the hierarchical game mechanism, the convergence speed of the ADQPSO-driven branch and bound method is 40% faster than that of traditional methods, and the optimization profit accuracy is improved by 1.59%. Moreover, compared with a single mechanism, the hierarchical game mechanism (Scenario 4) increases profits by 17.17%. This study provides technical support for the efficient operation of new energy grid integration and the achievement of “dual-carbon” goals. Full article

Air pollution and the emission of toxic gases represent a critical global concern, posing significant threats to human health and environmental stability. Resistive gas sensors are widely employed to detect toxic gases, owing to their cost-effectiveness, high stability, sensitivity, and swift dynamics. Among various sensing materials, comparatively less attention has been paid to CeO₂ despite its good catalytic activity and high stability. In this review paper, we are focusing on CeO₂ gas sensors in pristine, doped, decorated, and composite forms. Using numerous examples, we have shown the great potential of CeO₂ for gas sensing. The main features of CeO₂ as a gas sensor include excellent environmental stability, the abundance of oxygen vacancies, high mechanical strength, cost-effectiveness, and good catalytic activity. However, low electrical conductivity is the main shortage of CeO₂ as a gas sensor. With a high emphasis on the sensing mechanism, we believe that this review paper is highly useful for researchers working in this field. Full article

Crosswell electromagnetic imaging serves as a pivotal method for analyzing the distribution of residual oil in oil and gas reservoirs, as well as for optimizing drilling strategies. Current challenges in crosswell electromagnetic (EM) modeling encompass large-scale discretization, with limited research addressing the effects of magnetic sources in anisotropic media or the influence of borehole air. This study introduces a novel iterative Fourier domain integral algorithm for three-dimensional (3D) magnetic-source magnetic simulation in an anisotropic medium. The proposed method employs the Fourier domain method and quasi-complete Fourier techniques to realize adaptive sampling and efficient 3D modeling. The accuracy and efficiency of the method are validated through models. Parametric analyses quantify the impact of several factors, including source depth, frequency, borehole air effects, and conductivity anisotropy on magnetic field components. For the dynamic monitoring of oil and gas reservoirs, the relationship among the magnetic field, frequency, and water saturation is discussed. Furthermore, comparative response differences between electric and magnetic sources are examined, thereby providing theoretical foundations for real-time EM imaging in anisotropic hydrocarbon reservoirs. Full article

DC arcs are widely used in many fields such as shipbuilding, machinery manufacturing, and aerospace due to their advantages of high energy density, simple structure, and low price. However, there are few studies on the sensitivity of the arc pressure and temperature fields to current and protective gas flow rate. In order to solve this problem, this paper establishes a numerical model for the coupling of DC arc electric–thermal–flow multi-physical fields. Based on this model, the variation rules of the arc temperature, pressure, and potential field with current or protective gas flow rate are studied, respectively, when the current is 100–600 A or the gas flow rate is 18–48 L/min. The results show that the current is the most important factor in the sensitivity of the arc temperature and potential field to the current and protective gas flow rate. With the increase in current, the Joule heat power increases significantly, and the arc central temperature shows a nonlinear increase to 27,000 K. With increasing current, the peak of the pressure field gradually shifts to the region below the top of the wire arc, and the highest pressure increases by 14 times. When the current is small, the increase in argon flow rate can inhibit the spreading of the temperature field by forced convection; when the current is large, the arc contraction with an increasing argon flow rate leads to an anomalous increase in the arc-central temperature. In addition, the energy accumulation mechanism in the strong-current–high-flow-rate coupling region is also revealed, a coupled mathematical model of arc contraction and turbulent loss under the Lorentz force is constructed, and the thermodynamic properties of the arc under the coupling of multi-physical fields are elucidated. Full article

Implementing an effective energy management system (EMS) is essential for optimizing electric vehicle (EV) charging stations (EVCSs), especially when combined with battery energy storage systems (BESSs). This study analyzes a real-world EVCS scenario and compares several EMS approaches, aiming to reduce operating costs while accounting for BESS degradation. Initially, significant savings were achieved by optimizing the EV charging schedule using genetic algorithms (GAs), even without storage. Next, different BESS-based EMSs, including rule-based and fuzzy logic systems, were optimized via GAs. Finally, in a dynamic scenario with variable electricity prices and demand, the adaptive GA-optimized fuzzy logic EMS was found to achieve the best performance, reducing annual operating costs by 15.6% compared to the baseline strategy derived from real fleet data. Full article

This review explores the pressing need for decarbonization strategies in the off-grid Indigenous communities of Northern Quebec, particularly focusing on Nunavik, where reliance on diesel and fossil fuels for heating and electricity has led to disproportionately excessive greenhouse gas emissions. These emissions underscore the urgent need for sustainable energy alternatives. This study investigates the potential for improving building energy efficiency through advanced thermal insulation, airtight construction, and the elimination of thermal bridges. These measures have been tested in practice; for instance, a prototype house in Quaqtaq achieved over a 54% reduction in energy consumption compared to the standard model. Beyond efficiency improvements, this review assesses the feasibility of renewable energy sources such as wood pellets, solar photovoltaics, wind power, geothermal energy, and run-of-river hydropower in reducing fossil fuel dependence in these communities. For instance, the Innavik hydroelectric project in Inukjuak reduced diesel use by 80% and is expected to cut 700,000 t of CO₂ over 40 years. Solar energy, despite seasonal limitations, can complement other systems, particularly during sunnier months, while wind energy projects such as the Raglan Mine turbines save 4.4 million liters of diesel annually and prevent nearly 12,000 t of CO₂ emissions. Geothermal and run-of-river hydropower systems are identified as long-term and effective solutions. This review emphasizes the role of Indigenous knowledge in guiding the energy transition and ensuring that solutions are culturally appropriate for community needs. By identifying both technological and socio-economic barriers, this review offers a foundation for future research and policy development aimed at enabling a sustainable and equitable energy transition in off-grid Northern Quebec communities. Full article

Currently, the market for cars based on alternative fuels is developing very dynamically, which is caused by the growing needs in the field of environmental protection and the desire to reduce dependence on fossil fuels. Many countries have introduced various forms of support for people who decide to buy an electric or a hybrid car. The European Union has also introduced increasingly restrictive CO₂ emission standards, which accelerates the transition to alternative drives. The main research question in the paper was how the market for alternative energy sources in transport is developing in individual countries of the community, what the infrastructure looks like, and whether there is a large diversity in this field in the countries under study. The taxonomic methods (the TOPSIS method and the cluster analysis) have been applied for the research. The data were taken from Eurostat and the European Alternative Fuels Observatory statistical data. The analysis allowed an identification of key regularities that characterize the process of transformation of road transport in the European Union. Firstly, there is a clear division in countries with a high level of electrification (clusters I, IV, and VI) and countries that prefer gas drives (cluster V) or that are at an early stage of transformation (clusters II and III). Secondly, a strong relationship between the development of charging infrastructure, especially ultra-fast stations, and the level of adoption of electric vehicles was confirmed. Full article

Gas sensors based on graphene have gained considerable attention because of graphene’s remarkable properties, such as its extensive surface area, impressive electrical conductivity, and exceptional mechanical strength. This review critically analyzes recent developments in functionalization strategies designed to enhance the sensitivity, selectivity, and stability of graphene-based sensors. It discusses various chemical, physical, and hybrid functionalization methods, illustrating how surface alterations affect graphene’s interaction with target gas molecules. The paper also investigates the fundamental sensing mechanisms, including charge transfer, carrier mobility modulation, and Schottky barrier modification, to provide a thorough understanding of sensor response characteristics. Additionally, it highlights emerging applications in environmental monitoring, healthcare diagnostics, and industrial safety, demonstrating the transformative potential of these sensors in real-world settings. Finally, the review addresses challenges concerning reproducibility, long-term stability, and large-scale production, while also offering future insights on utilizing innovative nanomaterials and artificial intelligence to advance the next generation of graphene-based gas sensing technologies. Full article

This paper presents an analysis of the feasibility and sustainability of using local photovoltaic systems, ON-GRID central photovoltaic systems, and HYBRID systems for street lighting. By generating electricity from renewable sources (photovoltaic panels), solar energy contributes to environmental protection by avoiding the use of fossil fuels and nuclear fission energy, while also aligning with the European Union’s Energy Strategy commitments for the medium term (until 2030) and long term (toward 2050). The implementation of local/central photovoltaic systems for street lighting largely depends on the existing power supply infrastructure, the solar potential of the site, and a clear understanding of potential electricity and cost savings. This study compares local and central photovoltaic systems for street lighting to analyze their technical performance and economic feasibility. The main sustainable objective that this work aims to achieve is Sustainable Development Goal 7. The optimal solution for photovoltaic systems in street lighting was determined through this analysis. The estimated cost for implementing an ON-GRID photovoltaic power plant with a capacity of 153.90 kWp is approximately EUR 773,977.22, with a discounted Payback Time of about 9.33 years. The implementation of this solution results in an annual reduction in greenhouse gas emissions by approximately 58.52 tons of CO₂. Full article

Gas coolers are critical elements of turbogenerator cooling systems, which ensure the reliability and stability of the thermal mode of high-power electric machines. The aim of this research is to improve the accuracy of thermal calculations of gas coolers by combining analytical methods with numerical CFD-modeling (Computation Fluid Dynamics). The cooler’s total cooling capacity is approximately 3.8 MW, distributed across three identical sections.An analytical calculation of heat transfer for a hydrogen-water gas cooler with finned tubes was performed, using classical dependencies to determine the heat transfer coefficients and pressure losses. The results were verified using three-dimensional CFD-modeling of the hydrogen flow through the cooler using the standard k-ε (k-epsilon) turbulence model. The discrepancy between the results of analytical and numerical calculations is less than 10%. The temperature of the cooled hydrogen at the outlet meets the design requirements (+40 °C); however, areas of uneven temperature distribution were identified that require further design optimization. The study introduces, for the first time, a combined approach using analytical calculations and CFD by thoroughly evaluating the heat exchange between the cooling tube fins and hydrogen. This scientific solution enabled the simulation of hydrogen flow within the multi-stage cooler system. The proposed method has proven to be reliable and can be applied both at the design stage and for the analysis of upgraded cooling systems of turbogenerators. Full article

Hexagonal Boron Nitride (h-BN) is an exceptional dielectric material with significant potential for high-performance electronic and optoelectronic devices. While previous studies have explored its role in GaN-based MIS (metal/insulator/semiconductor) structures, the influence of few-layer h-BN on AlGaN MIS devices—particularly with varying Al compositions—remains unexplored. In this work, we systematically investigate the Fowler–Nordheim tunneling effect in few-layer h-BN integrated into AlGaN MIS architectures, focusing on the critical roles h-BN layer count, AlGaN alloy composition, and interfacial properties in determining device performance. Through combined simulations and experiments, we accurately determine key physical parameters, such as the layer-dependent effective mass and band alignment, and analyze their role in optimizing MIS device characteristics. Our findings reveal that the 2D h-BN insulating layer not only enhances breakdown voltage and reduces leakage current but also mitigates interfacial defects and Shockley–Read–Hall recombination, enabling high-performance AlGaN MIS devices under elevated voltage and power conditions. This study provides fundamental insights into h-BN-based AlGaN MIS structures and advances their applications in next-generation high-power and high-frequency electronics. Full article

Tribological performance is critical for the longevity and efficiency of machined components in industries such as aerospace, automotive, and biomedical. This study investigates whether electrical discharge machining recast layers can serve as a cost-effective and time-efficient alternative to conventional tungsten inert gas cladding coatings for enhancing surface properties. The samples were prepared using electrical discharge machining and tungsten inert gas cladding. For electrical discharge machining, various combinations of electrical and non-electrical parameters were applied using Taguchi’s L18 orthogonal array. Similarly, tungsten inert gas cladding coatings were prepared using a suitable combination of current, voltage, powder size, and speed. The samples were characterized using, scanning electron microscopy, optical microscopy, microhardness testing, tribological testing, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and profilometry. The electrical discharge machining recast layers exhibited superior tribological performance compared to tungsten inert gas cladding coatings. This improvement is attributed to the formation of carbides, such as TiC and Ti₆C_3.75. The coefficient of friction and specific wear rate were reduced by 11.11% and 1.57%, respectively, while microhardness increased by 10.93%. Abrasive wear was identified as the predominant wear mechanism. This study systematically compares electrical discharge machining recast layers with tungsten inert gas cladding coatings. The findings suggest that optimized electrical discharge machining recast layers can serve as effective coatings, offering cost and time savings. Full article