Search Results (13,891)

A 1319 nm, single-frequency, two-stage partially end-pumped slab (Innoslab) amplifier with high output power and excellent beam quality was reported. A 3 W, quasi-continuous wave pulsed, single-frequency all-fiber seed laser was amplified to a maximum average power of 154.0 W with a magnification of ~51.3 and overall optical-to-optical efficiency up to 12.0%. The output pulse width was 132.6 μs at a repetition rate of 500 Hz. The beam quality factors of M² were 1.4 and 1.3 in the horizontal and vertical directions, respectively. The power stability at the maximum output power was 0.43% (RMS) in 10 min. Higher output power and optical-to-optical efficiency could be achieved through optimizing mode matching between the pump beam and the seed laser beam. Full article

Electro-optic frequency combs (EOFCs), generated through the microwave-driven modulation of continuous-wave lasers, have emerged as a highly reconfigurable and system-compatible class of optical frequency combs with growing importance in microwave photonics, coherent communications, spectroscopy, and precision metrology. In contrast to mode-locked lasers and Kerr microresonator combs, EOFCs offer electrically programmable repetition rates, deterministic phase coherence, and intrinsic compatibility with radiofrequency electronic systems, making them particularly attractive for integrated and application-oriented implementations. As EOFCs evolve toward broader bandwidths, lower power consumption, and full on-chip integration, their achievable performance is increasingly constrained by the interplay between electro-optic physical mechanisms, modulator architectures, and material platform properties. This review establishes a unified analytical framework that systematically connects EOFC generation mechanisms, device configurations, key performance metrics, and platform-level limitations. We first summarize the fundamental electro-optic effects underpinning EOFC generation and analytically examine representative modulator architectures, including phase modulators, Mach–Zehnder modulators, and microresonator-based schemes, to clarify their respective comb-generation characteristics. Key performance determinants, such as modulation depth, bandwidth, electro-optic efficiency, and optical loss, are then discussed to elucidate their coupled influence on comb-line count, spectral flatness, output power, and phase noise. Subsequently, the performance of EOFCs implemented on major integrated platforms, including Silicon on Insulator (SOI), Indium Phosphide on Insulator (InPOI), Lithium Niobate on Insulator (LNOI), and Lithium Tantalate on Insulator (LTOI), is comparatively reviewed to highlight the material-dependent advantages and constraints. Finally, emerging directions based on heterogeneous integration and ferroelectric materials with ultrahigh electro-optic coefficients are discussed as promising pathways to overcome the current performance bottlenecks. This review provides clear physical insights and engineering guidance for the future development of high-performance, integrated EOFC systems. Full article

To enhance the accuracy and robustness of short-term photovoltaic (PV) power forecasting, this paper proposes a novel forecasting method that integrates data aggregation, adaptive frequency decomposition (AFD), modified improved beluga whale optimization (MIBWO), and a CNN-GRU-SE hybrid model. First, the Pearson correlation coefficient and the entropy weight method are combined to screen meteorological features that are strongly correlated with PV power output. Considering the geographical distance, a spatial data aggregation strategy is proposed to exploit the spatial correlation among neighboring PV stations and suppress the output volatility of individual stations. Then, the AFD is adopted to adaptively decompose the PV power series into trend and seasonal components, and the MIBWO algorithm is utilized to optimize the cutoff frequency of AFD and key hyperparameters of the CNN-GRU-SE forecasting model simultaneously. Finally, the SHAP method is employed for model interpretability analysis to quantify the contribution of each feature to the prediction results. Simulation results verified the power forecasting accuracy and robustness of the proposed method. Compared with CNN-GRU and BWO-CNN-GRU-SE, the proposed method reduces MAE by 96.23% and 95.03%, respectively. The method maintains stable performance with sunny and cloudy conditions. Full article

Maritime transport is under increasing pressure to cut greenhouse gas and pollutant emissions to meet global decarbonization goals and tighter environmental standards. Ship electric propulsion systems offer a promising solution for short-range maritime operations, particularly for small vessels and coastal activities. Full-electric vessels can significantly reduce operational emissions; however, a key challenge is the extensive charging time for onboard energy storage, which can affect operational continuity and logistical efficiency. This study examines mission planning and energy management for a hybrid multi-source electric mail boat operating in the Aeolian archipelago. It evaluates the viability and performance of a daily inter-island route powered by a high-temperature methanol fuel cell, batteries, and photovoltaic panels. A routing and simulation framework was developed to model the boat’s itinerary among seven islands, accounting for realistic navigation speeds, scheduled stops, solar energy availability, and battery state-of-charge constraints. The study analyzes distance, travel time, energy consumption, solar power generation, and fuel–electric usage with high temporal resolution, enabling detailed analysis of power flows during sailing and docking. Several operational strategies were assessed, including periods of increased speed supported by battery assistance and fuel–electric cell output, combined with coordinated energy management to keep battery levels above a lower acceptable threshold while completing the route in a single day. The methodology provides a practical tool for planning low-emission island networks and supports the integration of innovative energy systems into small electric workboats operating in specific maritime regions. Full article

In the current environmental and political scenario, hybrid vehicles play crucial roles in the transition to sustainable mobility. The role of internal combustion engines (ICEs) is also of utmost importance to comply with the even more stringent emissions regulations. To that end, also considering the need for increased power density in ICEs, turbocharging allows for improved performance and reduced emissions. Within this context, the present paper introduces the novelties of a patented turbo compound layout with supercharging capabilities, i.e., the Turbo Generator Electric Multistage Supercharger (TGEMS) system. The analysis also allowed for providing evidence of a “backpressure supercompensation effect” associated with rising exhaust backpressure in the ICE. TGEMS introduces a novel compressor group decoupled from the turbine. The analyses were carried out on a 2.0 L turbocharged gasoline direct injection engine. The “supercompensation” phenomenon was isolated using a stepwise procedure in which TGEMS was initially applied to the baseline engine to be exploited on a modified configuration featuring a downscaled turbine. The results were analyzed from the perspectives of specific fuel consumption reduction and total power output as well as operating flexibility increase. The results indicate that, in a context like TGEMS, the assumption that rising exhaust backpressure is always penalizing is no longer valid. Under higher backpressure conditions, TGEMS alone achieved −4.92% in specific fuel consumption at 5000 rpm, with +8.75% in maximum power output. Moreover, with the configuration with a downscaled turbine and the possibility to control the engine operating line, specific fuel consumption reductions of −7.93% at 5000 rpm and −6.83% at 3000 rpm were achieved. The maximum power output increment was +11.04%. These outcomes could open up to new downsizing perspectives and a new generation of “super-backpressured engines”. Full article

Conventional optimization algorithms face challenges such as lengthy computation times, premature termination at non-convergent points, and the generation of local optima when addressing multi-objective optimization. A multi-objective optimization method based on the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) is proposed for optimizing Doherty power amplifier circuits. The pre-layout simulation results show that, compared to traditional design methods, the optimized Doherty power amplifier circuit achieves a 6.4% increase in saturation efficiency, a 3.3% increase in 6 dB roll-off efficiency, and a 1 dB increase in saturation output power at 2.63 GHz. This approach enables multi-objective optimization design for more complex PA circuits and enhances the overall circuit performance. Full article

As a green energy technology, triboelectric nanogenerators (TENGs) convert mechanical energy into electricity and have gained significant attention in response to growing global environmental concerns. However, the widespread use of petroleum-based polymers as triboelectric materials in high-performance TENGs raises concerns over plastic pollution. In this work, we report a high-performance biodegradable TENG utilizing chitosan/laser-induced graphene (LIG) composite films as triboelectric layers. Modified chitosan substrates were first converted into LIGs via a convenient one-step CO₂ laser engraving, subsequently incorporated into chitosan matrices to form homogeneous composite films. A TENG device was designed by pairing the LIG/chitosan composite film with the fluorinated ethylene propylene (FEP) film, and copper electrodes. The introduction of LIG effectively strengthens charge storage and dielectric properties of the chitosan matrix, thereby significantly boosting the triboelectric output performance. Experimental results demonstrate that the as-assembled TENG with an LIG concentration of 1 wt.% achieves a peak open-circuit voltage of 196 V and short-circuit current of 2.1 μA, with a maximum power density of 295 mW/m². It can drive LED lights and small low-power electronic devices. Furthermore, the designed TENG device exhibits good biodegradability, flexibility, and stability, serving as a self-powered sensor for monitoring human joint movements. This work provides a simple and scalable strategy for integrating laser-induced graphene with biomass-based polymers, offering new insights into the design of high-performance, biobased triboelectric materials. Full article

With the continuous decline in the cost of renewable energy such as wind power and photovoltaic power generation, the economic competitiveness in the power supply structure is increasing, and traditional thermal power units are gradually being replaced, resulting in a profound adjustment of the power supply structure. However, the unclear alternative between units may lead to system redundancy configuration or power supply shortage. At the same time, the volatility of the new energy output and the flexible allocation of resources and other factors work together, resulting in the cost of the power system showing complex evolution characteristics. Therefore, it is of great significance to study the evolution of system cost in the process of thermal power substitution. This paper first analyzes the internal mechanism of the cost change of the new power system. Second, the cost accounting model of the power system is constructed to reveal the relationship between ‘thermal power substitution mode-system cost’ in the process of thermal power installed capacity substitution. Finally, the Garver-6 system is taken as an example to carry out simulation analysis, solve the optimal thermal power substitution mode under different renewable energy penetration rates, and explore the evolution law of system cost. The results of the example show that with the increase of renewable energy penetration, the total cost of the system first decreases and then increases, and the optimal substitution method is ‘unit thermal power to replace more renewable energy’. Full article

Accurate thermal analysis of steel solidification and heat transfer in the continuous casting mold is essential for understanding and controlling solidification, shell thickness uniformity, interfacial gap phenomena, and defects such as cracks and breakouts. This study investigates heat transfer in a funnel mold slab caster using the in-house thermal model, Con1D. A new methodology is introduced to predict the slag layer roughness, and its effect on interface resistance. To account for the multidimensional thermal behavior near water channels and thermocouples, finite-element models are developed in Abaqus to calibrate Con1D to match three-dimensional calculations of mold heat transfer. After calibration to match plant measurements for one set of casting conditions, Con1D predictions are validated with plant measurements at different casting speeds and mold plate thicknesses. Key outputs analyzed include the heat flux profile, mold and shell temperatures, shell thickness, shell shrinkage, and interfacial parameters such as slag layer thickness. Increasing casting speed causes higher heat flux, higher shell surface and mold temperatures, and decreased shell and slag layer thicknesses. Decreasing mold plate thickness increases heat flux slightly due to reduced thermal resistance of both the mold and interfacial gap. The modeling approach presented here is a powerful methodology to gain quantitative fundamental understanding of mold heat transfer in continuous casting, especially including phenomena in the interfacial gap. Full article

Multi-output, single-switch, hard-switched Pulse-Width Modulated (PWM) converters suffer from high switching losses, which strictly limit their power density. To significantly reduce these losses, this work proposes a novel family of non-isolated multi-output DC-DC converters based on a quasi-resonant, single-switch cell operating in the megahertz (MHz) range. Sixteen configurations are derived to enhance power density and minimize component stress. A comprehensive analysis derives the fundamental analytical expressions for operation, switching conditions, and power flow. These expressions form the basis of a design tool that facilitates parametric component selection and optimization. The developed tool calculates voltage and current stresses, alongside power losses, using RMS current analysis and user-defined parameters such as ESR and semiconductor non-idealities. Finally, experimental results from prototypes operating at approximately 1 MHz in both full-wave and half-wave modes, with step-up and step-down capabilities, confirm the accuracy of the analytical design tool and the simulation model. Full article

Understanding how carbon emission responsibilities evolve within interconnected electricity systems is essential for effective environmental governance and sustainable energy transitions. This study develops a carbon-extended multi-dynamic interregional input-output shift-share framework to examine how structural dynamics reshape carbon emission responsibilities in China’s power sector. Using provincial multi-regional input-output data for 31 provinces in 2012, 2015, and 2017, the framework integrates production-based and consumption-based accounting into a unified multi-level analytical structure. The results reveal four key findings. First, production-based emissions are primarily concentrated in central and western power-generation provinces, whereas consumption-based emissions cluster in eastern and central demand centers, reflecting a persistent spatial mismatch between electricity production and consumption. Second, under production-based accounting, the power sector shifts from having a lower emission growth rate than the provincial average to exceeding it, while consumption-based emissions consistently grow more slowly than the provincial average. Third, the national level increasingly dominates emission growth transmission in both accounting perspectives, with stronger influence on the production side and greater provincial heterogeneity on the consumption side. Fourth, structural upgrading becomes increasingly concentrated at the provincial level under both perspectives. These findings highlight the importance of multi-level structural dynamics in shaping carbon responsibility allocation and provide policy-relevant insights for coordinated decarbonization, sustainable electricity transition, and cross-regional carbon governance. This study contributes to the understanding of sustainable development pathways in carbon-intensive energy systems and offers practical implications for achieving low-carbon and sustainable power sector transformation. Full article

To address the issue of traditional bistable vibration energy harvesters (BVEHs) being prone to becoming trapped in a single potential well—which results in a narrowed energy harvesting bandwidth and reduced efficiency—this paper proposes a method that utilizes the nonlinear electromagnetic force generated during the induction process to modulate the kinematic behavior of the oscillator. The characteristics and influencing factors of the nonlinear force produced during electromagnetic induction are analyzed. A dual-cantilever beam structure is designed, with an iron-core coil and a magnet placed at the respective free ends. A mathematical model of a piezoelectric–electromagnetic coupled bimodal broadband vibration energy harvester is established and numerically simulated. Furthermore, a vertical vibration experimental platform is constructed to conduct frequency sweep tests. The experimental results demonstrate that the proposed piezoelectric–electromagnetic coupled bimodal broadband vibration energy harvester effectively improves energy harvesting efficiency. Within the frequency range of 5–20 Hz, the system exhibits two vibration modes, with resonant frequencies of approximately 7.7 Hz and 15.7 Hz. For a single-layer PVDF piezoelectric film, the maximum output power at the first and second resonance points is 8.9 μW and 9.7 μW, respectively. The electromagnetic module achieves maximum output powers of 0.39 W and 0.71 W. Moreover, within the frequency ranges of 6.3–9.8 Hz and 14–17.7 Hz (a total bandwidth of 7.2 Hz), the device maintains a stable power output. The effective bandwidth is broadened by approximately 80%, demonstrating excellent broadband performance. Full article

This research focuses on the design and simulation of a V-band single-chip transmit-and-receive front-end integrating an LNA, PA and switching functions for ISL terminals. Two technologies are compared: a 60 nm GaN/Si HEMT from MESC and a 100 nm GaAs HEMT from UMS. In Tx mode, the proposed design targets a saturated output power of at least 20 dBm and a power-added efficiency of no less than 5%. In Rx mode, the goal is 4 dB noise figure. In both cases, the small signal gain must exceed 20 dB across the 59–71 GHz band. Full article

To address the issue of insufficient output voltage of the self-powered unit of intelligent bearings under low-amplitude working conditions, a piezoelectric–friction composite energy harvester driven by rotating magnetic force is proposed based on the multi-physical field coupling and synergy of magnetoelectric, piezoelectric and triboelectric effects, which effectively enhances the voltage output in low-amplitude vibration environments. The intelligent bearing adopts an extended structure, consisting of an outer ring sleeve, an inner ring extension ring, magnetic poles and a composite energy harvester. The outer ring sleeve is nested on the outer ring of the bearing and fixes the composite energy harvester, while the inner ring extension ring is fixed on the inner ring of the bearing and installs the magnetic poles. The composite energy harvester adopts a magnetic double-mass block single-crystal piezoelectric simply supported beam structure and integrates a contact-separation type triboelectric nanogenerator in the vibration direction, achieving the collaborative power supply of the piezoelectric and triboelectric units. A mechanical-electrical coupling dynamic model of the composite energy harvester is developed. Using COMSOL software, the effects of various structural dimensions and magnetic pole configurations on the output voltage are analyzed. Experimental validation confirms the model’s effectiveness. The results demonstrate that the energy harvester operates effectively under varying bearing rotational speeds. The rotational speed of the magnetic poles has little influence on the output voltage amplitude but primarily affects its frequency. Under the condition that the rotational speed is within 600 r/min, the piezoelectric module stably outputs a peak voltage of approximately 16.6 V, and the triboelectric unit stably outputs a peak voltage of approximately 4.4 V, which can effectively meet the self-driving requirements of intelligent bearings. Full article

With the increasing power fluctuations and growing pressure on grid stability resulting from the high penetration of renewable energy, the demand for exploring various energy storage technologies with large-scale, long-duration, and low-cost features has become increasingly urgent. This paper proposes a novel single-track gravity energy storage generation system. This system utilizes non-standardized masses (such as natural rocks) operating stably on an inclined track, and combines coordinated feedforward–feedback electromagnetic torque control, multi-station loading scheduling, and synchronous loading/unloading strategies to effectively smooth the power fluctuations of renewable energy sources such as wind power. The core innovations of this system lie in: (1) utilizing non-standardized mass units to achieve gravity energy storage, thereby expanding the application scenarios and design flexibility of solid gravity energy storage systems; and (2) introducing intelligent scheduling strategies and multi-station loading coordination to effectively smooth the power output fluctuations caused by load randomness, rendering the system insensitive to load variations. Simulation results verify that, for power smoothing in a 10 MW-level wind farm, the system can accurately track the target power and maintain a stable output over a long duration. The power fluctuations are controlled to under 0.2%, even when the total load varies by 10% and the instantaneous load fluctuates by 5%. This system demonstrates the theoretical feasibility and scalability of utilizing natural rock resources in mountainous terrains for long-duration energy storage, providing a novel solution for long-duration power smoothing in renewable energy systems. Full article