Graphene quantum dots (GQDs), as an emerging class of nascent carbon-based materials, demonstrate remarkable promise in fluorescence sensing applications. Those potentials stem from several factors, including their favorable photoluminescence (PL) characteristics, feasibility of surface functionalization, excellent biocompatibility, and low cytotoxicity. This review concentrates on the fundamental optical properties of GQDs, with specific reference to the manipulation of intrinsic characteristics both by heteroatom doping and surface/edge functionalization. These modifications permit the alteration of optical properties, thereby rendering GQDs more versatile for an array of applications. Subsequently, we then delve into the recent applications of GQDs in fluorescence sensing, encompassing both turn-off and turn-on mechanisms. Finally, it presents a systematic assessment of the current state of research on GQDs, along with discussions on challenges and prospects for expanding and improving their applications.
In order to improve the operation control performance of high-speed maglev trains, an improved finite-time rotor magnetic Field-Oriented Control method was proposed in this paper. Aiming at the stator current control problem of long-stator linear synchronous motors under parametric perturbation, this paper investigates the double-feeding mode, combines the predefined-time stability theory and designs an improved sliding mode controller to optimise the dynamic characteristics of the inner-loop system. In the outer-loop cruise control, the predefined-time sliding mode control is combined with a finite-time disturbance observer, which effectively solves the problems of inaccurate modelling and parameter ingestion. It was verified through simulation and analysis that the control strategy has significant advantages in improving the dynamic tracking performance and anti-interference ability, with the stator current stabilisation time within 0.1 s, the absolute value of the fluctuation error within 20 A, the outer-loop response time within 0.5 s, the maximum speed error within 0.0005 m/s and the maximum displacement error within 0.0005 m. The control strategy has the advantages of improving the dynamic tracking performance and anti-interference ability.
Materials of engineering and construction. Mechanics of materials, Production of electric energy or power. Powerplants. Central stations
Elmostafa Achbab, Rachid Lambarki, Hassan Rhinane
et al.
This research pioneers the integration of geographic information systems (GIS) and 3D modeling within a virtual reality (VR) framework to assess the viability and planning of a 20 MW hybrid wind-solar-photovoltaic (PV) system connected to the local grid. The study focuses on Dakhla, Morocco, a region with vast untapped renewable energy potential. By leveraging GIS, we are innovatively analyzing geographical and environmental factors that influence optimal site selection and system design. The incorporation of VR technologies offers an unprecedented level of realism and immersion, allowing stakeholders to virtually experience the project's impact and design in a dynamic, interactive environment. This novel methodology includes extensive data collection, advanced modeling, and simulations, ensuring that the hybrid system is precisely tailored to the unique climatic and environmental conditions of Dakhla. Our analysis reveals that the region possesses a photovoltaic solar potential of approximately 2400 kWh/m2 per year, with an average annual wind power density of about 434 W/m2 at an 80-meter hub height. Productivity simulations indicate that the 20 MW hybrid system could generate approximately 60 GWh of energy per year and 1369 GWh over its 25-year lifespan. To validate these findings, we employed the System Advisor Model (SAM) software and the Global Solar Photovoltaic Atlas platform. This comprehensive and interdisciplinary approach not only provides a robust assessment of the system's feasibility but also offers valuable insights into its potential socio-economic and environmental impact.
Production of electric energy or power. Powerplants. Central stations
Luis Jesús Fernández, Efraim Centeno, Sonja Wogrin
Energy systems increasingly rely on the synergistic operations of the electricity and hydrogen markets pursuing decarbonization. In this context, it is necessary to develop tools capable of representing the interactions between these two markets to understand the role of hydrogen as an energy vector. This paper introduces a bi-level optimization model that captures the interactions between the electricity and hydrogen markets, positioning hydrogen generators as strategic electricity price makers in the power market. The model can be efficiently solved and applied to real-world scenarios by reformulating it as a Mixed Integer Linear Program. The case studies analyze spot market behaviors when hydrogen generators are modeled as price makers in the electricity market. First, single-period simulations reveal the effects of price-making, and next, a year-long simulation assesses broader implications. The findings demonstrate that conventional modeling assumptions, such as the price-taker hydrogen generators in the electricity market and constant production cost hypothesis, lead to non-optimal hydrogen generation strategies that raise electricity prices while reducing the profit of hydrogen generators and the hydrogen market social welfare. These results highlight the need for models that accurately reflect the interdependencies between these two energy markets.
Production of electric energy or power. Powerplants. Central stations
This article investigates the fragmentation of rock during the indentation process with a conical pick. The study explores the impact of indentation dip angle, indentation spacing, and confining pressure on rock fragmentation through simulation using the discrete element method. Rock models of coal and red sandstone are created and calibrated for the simulation. The findings indicate that the indentation force increases exponentially with the increase of indentation dip angle for both coal and red sandstone. The specific energy increases first and then decreases with the increase of indentation dip angle. The maximum specific energy is found in the condition of indentation dip angle of 25° for red sandstone, while it is 20° for coal. The indentation force increases logarithmically with the increase of indentation spacing tending to be an unrelieved indentation condition. The optimal indentation spacing with the lowest specific energy is determined to be 50 mm for breaking coal and 34 mm for breaking red sandstone. Additionally, the indentation force increases exponentially for coal while it increases linearly for red sandstone with the increase of the confining pressure. For both coal and red sandstone, specific energy increases with the increase of the confining pressure.
Production of electric energy or power. Powerplants. Central stations, Renewable energy sources
Tiago Afonso Salgueiro, Rita Carvalho Veloso, João Ventura
et al.
The global environmental crisis necessitates reliable, sustainable, and safe energy storage solutions. The current systems are nearing their capacity limits due to the reliance on conventional liquid electrolytes, which are fraught with stability and safety concerns, prompting the exploration of solid-state electrolytes, which enable the integration of metal electrodes. Solid-state sodium-ion batteries emerge as an appealing option by leveraging the abundance, low cost, and sustainability of sodium. However, low ionic conductivity and high interfacial resistance currently prevent their widespread adoption. This study explores polyvinyl-based polymers as wetting agents for the NASICON-type NZSP (Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub>) solid electrolyte, resulting in a combined system with enhanced ionic conductivity suitable for Na-ion solid-state full cells. Electrochemical impedance spectroscopy (EIS) performed on symmetric cells employing NZSP paired with different wetting agent compositions demonstrates a significant reduction in interfacial resistance with the use of poly(vinyl acetate)—(PVAc-) based polymers, achieving an impressive ionic conductivity of 1.31 mS cm<sup>−1</sup> at room temperature, 63.8% higher than the pristine material, notably reaching 7.36 mS cm<sup>−1</sup> at 90 °C. These results offer valuable insights into the potential of PVAc-based polymers for advancing high-performance solid-state sodium-ion batteries by reducing their total internal resistance.
Production of electric energy or power. Powerplants. Central stations, Industrial electrochemistry
A. M. Gribkov, N. D. Chichirova, K. M. Mirsalikhov
In a number of cases, for example, when choosing the design of the exit part of a chimney, when taking into account the characteristics of the underlying surface and meteorological characteristics of the area, or as a means of verifying variant calculations in the ANSYS environment, a study of the trajectory of the smoke plume in natural conditions is required. One of the simplest, most convenient and cheapest ways to determine a trajectory is to photograph it and then decipher it. So, for example, a vertical chimney, if the direction of the camera is raised above the horizon, and the chimney is not located in the center of the photo, it looks inclined in the photo. This means that at the top of the image and at the bottom there are different horizontal linear scales of the image. The angle at which the camera was installed can also be calculated from the photograph. In addition, the same vertical height interval occupies a smaller length in the upper part of the pipe and a larger one in the lower part. This means that in the upper part of the image and in the lower part there are different vertical linear scales of the image. It is also necessary to take into account the fact that objects of the same size have different sizes in the picture. The further away an object is located, the less space it takes up in the photo. Thus, in order to calculate the trajectory of a smoke plume from a photograph, we need to know the orientation of the main optical axis during the photograph and the distance to the photograph plane, which we choose perpendicular to the main optical axis and passing through the object, from which we can determine the initial average linear scales, and the direction smoke plume spread.TARGET. Development of a new, simpler method for recalculating the trajectory of a smoke plume from a chimney using available Google maps to calculate the original scales in a photograph.METHODOLOGY Allows you to trace the entire sequence of actions from determining the coordinates of the shooting point to recalculating the coordinates of the selected points of the torch boundaries in the photograph relative to the emission source onto an orthogonal plane.RESULTS. A new method for calculating the trajectory of a smoke plume from a single photograph has been developed, the accuracy of which was tested using known sizes in the original objects, and which turned out to be higher than that previously used for these purposes.
Production of electric energy or power. Powerplants. Central stations
AbstractThis review paper examines the types of electric vehicle charging station (EVCS), its charging methods, connector guns, modes of charging, and testing and certification standards, and the current status of Indian standards with respect to international standards. The paper also discusses key challenges in the standardization of EVCS worldwide and provides recommendations. It is recommended to use the combined charging system (CCS) charging methodology which will cater to the electric vehicle (EV) market in the country as well as abroad and help promote faster adoption of EVs. With many advantages with CCS charging methodology such as single connector, both AC and DC charging, high power capacity, promoted by a large number of EV manufacturers across the globe, etc., it is recommended to use CCS charging methodology. CHArge de MOve (CHAdeMO) is the only charging methodology having a vehicle to grid (V2G) functionality that can be made compatible with local grid codes which can support the grid during peak load demand using the combination of bidirectional EVCS and EV batteries acting as energy storage equipment. Finally, a comparative analysis is provided between the Indian standards and international standards from Europe, China, Japan, Germany, North America, and International Organization for Standardization (ISO).
Trailing-edge noise (TE noise) is an aeroacoustic sound radiated from an isolated airfoil in the specific ranges of low-speed flow. We used a pulsed laser as an actuator to reduce the TE noise without modifying the airfoil’s surface. The wind tunnel test was conducted to verify the capability of an Nd:YAG laser as the actuator. The laser beam was focused into the air just outside the velocity boundary layer on the lower side of an NACA0012 airfoil. The experimental result shows that the TE noise is suppressed for a certain period after beam irradiations. We then analyzed the physical mechanism of the noise reduction with the laser actuation by the implicit large eddy simulation (ILES), a high-fidelity numerical method for computational fluid dynamics (CFD). The numerical investigations indicate that the pulsed energy deposition changes the unstable velocity amplification mode of the boundary layer, the source of an acoustic feedback loop radiating the TE noise, to another mode that does not generate the TE noise. The sound wave attenuation is observed once the induced velocity fluctuations and consequently generated vortices sweep out the flow structure of the unstable mode. We also examined the effect of the laser irradiation zone’s shape by numerical simulations. The results show that the larger irradiation zone, which introduces the disturbances over a wider range in the span direction, is more effective in reducing the TE noise than the shorter focusing length with the same energies.
Materials of engineering and construction. Mechanics of materials, Production of electric energy or power. Powerplants. Central stations
Stoica Dorel, Mohammed Gmal Osman, Cristian-Valentin Strejoiu
et al.
This paper presents a comparative analysis of different battery charging strategies for off-grid solar PV systems. The strategies evaluated include constant voltage charging, constant current charging, PWM charging, and hybrid charging. The performance of each strategy is evaluated based on factors such as battery capacity, cycle life, DOD, and charging efficiency, as well as the impact of environmental conditions such as temperature and sunlight. The results show that each charging strategy has its advantages and limitations, and the optimal approach will depend on the specific requirements and limitations of the off-grid solar PV system. This study provides valuable insights into the performance and effectiveness of different battery charging strategies, which can be used to inform the design and operation of off-grid solar PV systems. This paper concludes that the choice of charging strategy depends on the specific requirements and limitations of the off-grid solar PV system and that a careful analysis of the factors that affect performance is necessary to identify the most appropriate approach. The main needs for off-grid solar photovoltaic systems include efficient energy storage, reliable battery charging strategies, environmental adaptability, cost-effectiveness, and user-friendly operation, while the primary limitations affecting these systems encompass intermittent energy supply, battery degradation, environmental variability, initial investment costs, fluctuations in energy demand, and maintenance challenges, emphasizing the importance of careful strategy selection and system design to address these factors. It also provides valuable insights for designing and optimizing off-grid solar PV systems, which can help to improve the efficiency, reliability, and cost-effectiveness of these systems.
Production of electric energy or power. Powerplants. Central stations, Industrial electrochemistry
The accessible and convenient hydrogen supply is the foundation of successful materialization for hydrogen-powered vehicles (HVs). This paper proposes a novel optimal scheduling model for gaseous-liquid hydrogen generation and storage plants powered by renewable energy to enhance the economic feasibility of investment. The gaseous-liquid hydrogen generation and storage plant can be regarded as an energy hub to supply concurrent service to both the transportation sector and ancillary market. In the proposed model, the power to multi-state hydrogen (P2MH) process is analyzed in detail to model the branched hydrogen flow constraints and the corresponding energy conversion relationship during hydrogen generation, processing, and storage. To model the coupling and interaction of diverse modules in the system, the multi-energy coupling matrix is developed, which can exhibit the mapping of power from the input to the output. Based on this, a multi-product optimal scheduling (MPOS) algorithm considering complementarity of different hydrogen products is further formulated to optimize dispatch factors of the energy hub system to maximize the profit within limited resources. The demand response signals are incorporated in the algorithm to further enhance the operation revenue and the scenario-based method is deployed to consider the uncertainty. The proposed methodology has been fully tested and the results demonstrate that the proposed MPOS can lead to a higher rate of return for the gaseous-liquid hydrogen generation and storage plant.
Production of electric energy or power. Powerplants. Central stations, Renewable energy sources
Taking the upper sub-member of Sha 4 in Well Fanye 1 and Well Niuye 1 in Dongying Sag, Jiyang Depression, Bohai Bay Basin as a typical example, this paper adopts the method of combining macro and micro laminar characterization and complementing each other. The characteristics of laminar development are studied by means of fine description of rock thin sections by cores and electron microscopic observation Reconstruction of the Bohai Bay Basin in sand four period of ancient sedimentary environment, it is concluded that the sand on the four period of development of four complete filling sedimentary cycle. Using Milankovitch cycles method, reveals the ancient climate control mechanism of lithofacies, formed by organic laminae under hot and humid climate and a small amount of calcite laminated lithofacies, in hot and humid climate, the lithofacies is mainly composed of organic lamina and a small amount of calcite lamina, while in cold and dry climate, the lithofacies is mainly composed of calcite lamina, and the lithofacies is mainly composed of organic lamina, silty lamina and gypsum lamina. Micro-laminar research is an important scientific issue in unconventional oil and gas eology. It can provide basic data for unconventional oil and gas exploration, such as the types, distribution and extension of laminar, especially the determination of sampling targets. Different laboratory samples can be analyzed according to the laminar types.
Production of electric energy or power. Powerplants. Central stations, Renewable energy sources
Abstract Smart windows refer to those which can dynamically modulate the transmitted light by changing their colors. Dual‐band electrochromic materials (ECMs) refer to materials that can change their colors and regulate light transmission in both visible (VIS) and infrared (IR) regions under different voltages. The dual‐band ECMs‐based building windows can thus regulate the indoor temperature to reduce the energy consumption for heating and air‐conditioning systems. Therefore, the wide application of ECMs in building windows will contribute a lot to establishing an energy‐saving society. During the past decades, enormous efforts have been made to improve the performance of dual‐band ECMs. This review presents a summary of the recent progress of dual‐band ECMs, focusing on their modulation mechanism, material design, and performance optimization. Finally, the challenges and outlook of dual‐band ECMs are also discussed.
Renewable energy sources, Production of electric energy or power. Powerplants. Central stations
This letter develops a fast analytical method for uncertainty quantification of electromechanical oscillation frequency due to varying generator dampings. By employing the techniques of matrix determinant reduction, two types of uncertainty analysis are investigated to quantify the impact of the generator damping on electromechanical oscillation frequency, i.e., interval analysis and probabilistic analysis. The proposed analytical frequency estimation formula is verified against conventional methods on two transmission system models. Then, Monte Carlo experiments and interval analysis are respectively conducted to verify the established lower/upper bound formulae and probability distribution formulae. Results demonstrate the accuracy and speed of the proposed method.
Production of electric energy or power. Powerplants. Central stations, Renewable energy sources