Search Results (1,079)

The decarbonization of maritime transport demands propulsion and onboard energy systems that simultaneously achieve ultra-low emissions, high power density, and robust operational reliability. Nuclear propulsion, particularly when coupled with small modular reactors (SMRs), offers a compelling pathway due to its near-zero operational emissions and exceptional energy density; however, the efficient utilization of high-grade nuclear thermal energy under shipboard constraints remains a critical challenge. To address this issue, this study presents a comprehensive thermodynamic and exergy-based assessment of a novel cascaded waste heat recovery (WHR) architecture designed for a 100 MW class nuclear-powered vessel, integrating a supercritical carbon dioxide (sCO₂) cycle with downstream steam Rankine (SRC) and Kalina cycles. Detailed process modeling is performed using Aspen HYSYS to quantify energy and exergy performance at the component and system levels. The proposed cascade exploits the complementary thermodynamic characteristics of each cycle, enabling staged recovery of high-, medium-, and low-grade heat from the nuclear secondary loop. Results indicate that while the sCO₂ cycle dominates gross power generation due to its high power density and favorable high-temperature performance, its net efficiency is constrained by substantial compression work and associated auxiliary losses. In contrast, the SRC and Kalina cycles exhibit significantly higher energy efficiencies, demonstrating superior suitability for medium- and low-temperature waste heat utilization. Through thermodynamic synergy, the integrated sCO₂–SRC–Kalina configuration achieves an overall energy efficiency of 20.73%, representing a substantial improvement over a standalone sCO₂-based WHR system. Exergy destruction analysis reveals that system irreversibilities are primarily concentrated in heat exchangers, particularly the primary heat exchanger interfacing the nuclear heat source with the sCO₂ loop, whereas turbomachinery contributions are comparatively minor. These findings highlight heat exchanger design optimization and improved temperature matching as the most effective pathways for further performance enhancement. Overall, this study demonstrates that multi-cycle cascade integration provides a viable and high-efficiency solution for nuclear marine energy recovery, with strong implications for advanced hydrogen energy systems and other high-performance power generation applications requiring compactness, scalability, and thermodynamic robustness. Full article

This paper presents a fast electrothermal coupled analysis method that combines a temperature-dependent loss model with an analytical multilayer thermal model for multiple heat sources to predict the junction temperatures of silicon carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) cooled by a heat-pipe heat sink. Mori–Tanaka homogenization is used to represent the heat-pipe heat sink as an equivalent anisotropic medium, and the temperature field is obtained using a Fourier-series analytical solution. Thermal coupling among four SiC MOSFETs is captured by an influence-coefficient matrix to update junction temperatures via a simple matrix–vector product during electrothermal iterations. The proposed method is validated through PSpice and ANSYS Icepak simulations. The maximum junction-temperature error is 2.17 °C, and the total computation time is reduced from 8134 to 75 s, corresponding to an ~108× speedup. These results confirm that the proposed method is an accurate and computationally efficient junction-temperature prediction tool for the iterative thermal design of high-power-density converters. Full article

Mass and volume penalties associated with fuel cell integration have hindered the manufacturing and integration of hybrid power systems into civil aircraft. To address this issue, a novel scheme, a turbofan engine integrated with solid oxide fuel cells, is proposed in this paper, which has the advantage of high thermal efficiency and propulsion efficiency, where the electricity produced by the solid oxide fuel cell (SOFC) is used to drive the ducted fan. Then, a multidimensional model that accounts for mass, volume, and thermodynamic performance is established. The equivalence ratio and split ratio have a significantly stronger influence on the volume and mass ratios than the current density. These two parameters directly determine the power ratio between the fuel cell and the gas turbine. An increase in the power ratio leads to a simultaneous rise in both the volume and mass ratios; however, the overall efficiency cannot be continuously improved, with its maximum value being approximately 63% without mass and volume constraints. During the multi-objective optimization process, the weight and volume of the hybrid engine have a linear relationship with the overall efficiency when the efficiency is lower than 50%. However, both mass and volume exhibit exponential increasing trends as the overall efficiency is over 50%. This is caused by the nonlinear change in the fuel cell reaction area; as polarization loss decreases, the thermal efficiency of the hybrid system improves. The maximum overall efficiency is taken as the optimization objective, with the constraints that the mass fraction of the fuel cell does not exceed 0.4 of the total engine mass and that the volume fraction of the fuel cell stack is less than 0.2 of the gas turbine engine volume. Compared with the CFM56 3C1, the thermal efficiency for the novel hybrid engine is increased by 21%, and its propulsion efficiency is increased by 42%. Full article

Direct-to-cell (D2C) non-terrestrial networks (NTNs) based on 5G technology are emerging as a key complement to terrestrial cellular networks, extending connectivity to underserved and remote areas while enabling integration with existing mobile ecosystems. As these systems begin operating in frequency bands already used by terrestrial International Mobile Telecommunications (IMT) networks, coexistence becomes critical. This paper presents a victim-centric methodology for evaluating D2C interference into terrestrial 5G networks in the 694/698 MHz-2.7 GHz regulatory study range. Seven downlink carrier cases and four uplink carrier cases between 734 and 2620 MHz are evaluated. For a prescribed external interference-to-noise ratio, the external contribution is referenced to receiver thermal noise, while terrestrial intra-network interference remains part of the baseline and interfered signal-to-interference-plus-noise ratio (SINR). The resulting throughput loss is translated into candidate power-flux-density (PFD) and equivalent-power-flux-density (EPFD) protection levels. A reference non-geostationary-satellite-orbit (NGSO) system is used only to motivate the assumed receiver-exposure fractions; the numerical network results are therefore conditional on those exposure assumptions. The same external interference level produces approximately three times greater network throughput loss at base stations than at user equipment, so direction-specific protection levels are required. For downlink protection, the tested 3 dB noise-rise case gives candidate PFD levels from −109.23 to −98.17 dB(W/(m²·MHz)); for opposite-direction cross-border uplink protection, I/N = −6 dB gives candidate EPFD levels from −138.23 to −130.18 dB(W/(m²·MHz)) for non-AAS base stations. The approximately 11 dB offset for AAS cases results from the maximum-gain normalization used in EPFD and should not be interpreted as evidence of greater satellite exposure. These values are tested candidate levels rather than estimates of an exact 5% crossing point. Full article

Multi-module DC–DC converters are well suited to shipboard DC power systems with stringent requirements for high power density, operational safety, and continuous power supply. By distributing the system voltage, current, and power among multiple submodules (SMs), the modular architecture reduces device stresses and facilitates capacity expansion, maintenance, and redundant operation. Among the available modular configurations, the input-series output-parallel (ISOP) structure is particularly suitable for interfacing high-voltage DC buses with low-voltage, high-current loads. However, conventional voltage- or current-sharing strategies generally neglect efficiency differences among SMs. Under equal power sharing, low-efficiency SMs generate greater losses and experience higher thermal stress, resulting in thermal imbalance and accelerated aging. To address this issue, an efficiency-consensus-based power-distribution strategy is proposed for ISOP LLC-DAB hybrid converters. A distributed efficiency observer based on multi-agent consensus theory dynamically regulates the power references according to the relative efficiencies of the SMs, allowing high-efficiency modules to process more power while reducing the loading of low-efficiency modules. Experimental results obtained from a three-module prototype include comparative efficiency measurements and temperature-distribution tests. The results demonstrate that the proposed strategy improves the efficiency consistency among the three SMs, redistributes power according to their relative efficiency states, and reduces the temperature difference among the modules, thereby mitigating localized loss concentration and thermal imbalance. The proposed method provides a feasible solution for improving the electrothermal operating conditions of modular DC–DC converters. The achieved reduction in thermal imbalance may contribute to enhanced long-term reliability by alleviating uneven electrothermal stress. Full article

Biomass-derived carbons hold substantial promise for sustainable electrochemical energy storage due to their low cost, wide availability, and intrinsic heteroatom- and mineral-rich nature. However, the fundamental influence of carbonization temperature on the structural evolution of non-activated biomass-derived carbons remains insufficiently understood. In this work, corn straw-derived carbon (CS) is produced without any chemical additives to isolate the intrinsic effects of carbonization temperature on its physicochemical properties. Systematic temperature variation from 600 to 1000 °C reveals pronounced changes in micro-morphology, pore development, defect density, and the ordering of the carbon matrix, all strongly governed by the inherent mineral content of corn straw. Electrochemical evaluation in alkaline electrolyte demonstrates that CS-800 delivers the highest specific capacitance of 53.8 F g⁻¹ at 1 A g⁻¹ in a three-electrode configuration and maintains favorable rate capability in a symmetric supercapacitor device. The symmetric coin-cell supercapacitor device assembled with CS-800 as the electrodes achieved an energy density of 3.64/5.8 Wh kg⁻¹ and a power density of 5200/750 W kg⁻¹, along with remarkable cycling stability over 30,000 cycles with negligible capacitance loss. Overall, this study provides mechanistic insight into temperature-driven structural evolution in non-activated biomass-derived carbons, offering a fundamental understanding that may guide the rational design and future development of sustainable carbon electrodes for electrochemical energy-storage applications. Full article

The electrification of transportation pushes traction inverters, on-board chargers, and aircraft propulsion systems toward higher power density, increasingly enabled by wide-bandgap devices, thereby concentrating ever-larger heat fluxes on power semiconductor dies as package-level cooling nears its sustainable limit. Junction temperature is the resulting bottleneck: it caps the usable rating and, through the thermal cycling that fatigues module interconnects, governs reliability and service life. Managing junction temperature therefore requires a coupled chain of processes spanning the device loss that generates the heat, the models that predict it, the parameters which these models require as input, the cooling that removes it, and the control that bounds its excursion. This review traces heat transfer along this chain, organizing each link by method class and comparing representative methods against the limitation that marks its open problem. The methods within each link are relatively mature, whereas the couplings between links and their validation against realistic missions are not. The cross-cutting gaps, among them sparse drive-cycle validation, weak coupling between electro-thermal and aging models, and the absent co-design of cooling and control, are consolidated into a forward research agenda. Full article

Multi-phase permanent magnet synchronous generators (PMSGs) are increasingly adopted in renewable energy systems and isolated microgrids due to their improved fault tolerance, reduced per-phase current stress, and enhanced power density compared to conventional three-phase machines. This article presents a systematic performance comparison between 15-phase and 9-phase PMSGs under four distinct operating conditions: healthy mode, single-phase open-circuit fault (Phase 1), and two fault-tolerant control (FTC) strategies. The first FTC technique involves opening a second phase with approximately 90-degree phase displacement from the faulty phase to attenuate power oscillations and reduce current amplitude imbalances. The second technique involves isolating a complete three-phase set containing the faulty phase without adapting the machine model. Both machines are modeled using the vector space decomposition (VSD) approach under field-oriented control (FOC), and simulations are performed in MATLAB/Simulink. Performance metrics include power efficiency, power losses, power ripple factor, electromagnetic power ripple, stator RMS current evolution, and stator current balance. Results demonstrate that the 15-phase PMSG consistently exhibits lower power ripple (6.5% vs. 15.54% under open-circuit fault), higher efficiency (89.02% vs. 87.44%), and reduced power losses across all fault scenarios. The first fault-tolerant strategy improves performance in both machines but is more effective in the 15-phase configuration. To validate the findings beyond offline simulation, hardware-in-the-loop (HIL) experiments are conducted on an OPAL-RT real-time platform, where the complete system—the PMSG and converter models together with the FOC and fault-tolerant control algorithms—is implemented within its FPGA framework. The HIL results for electromagnetic power and d–q axis stator currents show close agreement with the MATLAB/Simulink results across all operating conditions, confirming the FPGA implementability of the proposed control strategies under real-time constraints. These findings provide actionable insights for the design and control of high-phase-count generators in grid-connected and isolated power systems. Full article

This paper presents the design and multi-objective optimization of a six-limb magnetically integrated hybrid distribution transformer (HDT). The increasing demand for efficient and compact transformer solutions in modern distribution networks motivates the development of improved design methodologies. In this work, a detailed design procedure is established, including core geometry definition, winding configuration, and magnetic circuit considerations. A multi-objective optimization framework is formulated to minimize total transformer mass and power losses while satisfying operational constraints such as magnetic flux density and current density limits in the windings. Key design parameters, including core dimensions and winding configurations, are systematically varied to identify an optimal trade-off between material usage and performance. The optimization results show a noticeable reduction in total mass with a slight improvement in total losses, while all design constraints are maintained within acceptable limits. A laboratory-scale prototype was constructed to demonstrate the proposed magnetic configuration, and experimental validation was performed under steady-state, open-loop operating conditions to verify the voltage injection principle through the integrated control and extension windings. The presented approach offers a structured pathway for the design and optimization of HDT and can serve as a basis for further studies involving advanced control and operational strategies. Full article

Aiming at insufficient rated torque and excessive magnet thermal loss of vehicle high-power-density BLDC motors, a multi-objective optimization framework integrating a surrogate model and NSGA-II is proposed. An eight-pole 48-slot finite-element model is built to analyze initial electromagnetic defects. Taguchi experiments conduct parameter sensitivity screening to reduce simulation cost. Two surrogate models (RSM, BP neural network) are quantitatively compared via R² and MSE; the BP network achieves R² = 0.995 for magnet loss with overall error below 5%. Combined with NSGA-II, Pareto-optimal structural parameters are obtained. Simulation results show that optimized motor rated torque rises by 9.01% and peak magnet loss drops by 16.5%, while torque ripple and cogging torque meet engineering standards. This method features high efficiency and precision, providing references for automotive BLDC optimal design. Full article

In this work, a novel all-optical 4-to-2 encoder employing nonlinear resonant cavities in a two-dimensional photonic crystal is proposed and numerically investigated. The encoder consists of a lattice of chalcogenide rods incorporating nonlinear Kerr-effect cavities, enabling selective wavelength coupling through intensity-controlled resonance. By assigning three distinct optical input power levels, the proposed architecture successfully realizes all encoding states without requiring additional control signals or complex resonator configurations. Numerical results demonstrate correct encoding functionality with normalized logic-1 output powers ranging from 0.89 to 1.71 and logic-0 levels below 0.013, yielding a high contrast ratio of 18.35 dB. The encoder exhibits ultrafast temporal performance with a maximum rise time of only 108 fs, corresponding to a data transmission capability of 4.63 Tbit/s, while maintaining a low insertion loss of 3.73 dB. Furthermore, the proposed structure occupies an ultra-compact footprint of only 95 μm², outperforming previously reported photonic crystal encoders in terms of integration density and speed. With regard to its compactness, high switching speed, excellent signal discrimination, and compatibility with current nanofabrication technologies, the proposed encoder represents a promising building block for future photonic integrated circuits, optical computing systems, and high-capacity optical communication networks. Full article

We evaluate WRF 90 m wind speeds over Hami, China, using hourly observations from 12 towers during June 2016–May 2017. The study combines a tower-point seasonal hindcast, a four-model comparison at six WRF anchors, a bidirectional cross-farm evaluation, and monthly residual interpolation with 2016–2018 wind-power-density (WPD) scenarios. The March–May 2017 hindcast uses causal feature construction and training-period-only fitting on 26,367 matched tower-hour samples. Its two-stage ExtraTrees correction reduces central error relative to its power-law baseline but detects none of the 128 observed hours at or above 25 m⁻¹, revealing substantial loss of the high-wind tail. In a separate leave-one-WRF-anchor-out comparison, ET, DLinear, TCN, and CVAE use identical 48 h power-law wind histories at the six anchors; their unweighted anchor mean RMSE values span 3.521–3.540 m⁻¹ and all strongly underdetect 25 m⁻¹ h. In the cross-farm evaluation, shared-anchor observations were excluded from fitting: all models predict zero of 223 YW exceedance hours when trained with BLK observations, while the reverse direction gives low and variable POD values. For the monthly product, all towers at a held WRF coordinate were excluded from IDW donors. Across six anchors and 72 anchor-month comparisons, the unweighted mean RMSE decreases from 1.04 to 0.77 m⁻¹. The published power-2, fixed-density central WPD remains 726.7 W m⁻²; across 162 sensitivity cases varying IDW power, residual, cubic factor, density, and penalty weight, fixed-density and ISA means span 457.3–1102.5 and 411.0–988.5 W m⁻², respectively. Only 8.36% of product cells lie inside the six-anchor convex hull. Together, these analyses distinguish tower-point prediction, monthly interpolation, and regional WPD comparison. The maps support regional comparison and identify locations for follow-up measurement within the one-year tower record and six-anchor network. Full article

Non-radiative carrier loss originating from material defects together with slow charge migration act as two major limiting factors heavily suppressing the power output performance of organic bulk-heterojunction (BHJ) photovoltaic devices (OSCs). Herein, two-dimensional (2D) CdSe nanoplatelets (NPLs) are introduced into conventional P3HT:PCBM and high-efficiency PBDB-T:PCBM photoactive films as multi-purpose doping additives, aiming to finely tune film microstructures, refine interfacial energy level matching, accelerate carrier migration, and eliminate native trap sites inside the active layer. Statistical measurement data verify that 3 mg CdSe NPLs as the ideal doping dosage can realize concurrent performance upgrades for the two distinct OSC architectures investigated here. As for devices built on P3HT:PCBM blend films, the component modified with optimized CdSe NPL additives delivers boosted charge mobility rising from 0.87 × 10⁻⁵ cm²/V·s up to 2.58 × 10⁻⁵ cm²/V·s. Meanwhile, trap site concentration drops markedly from 7.41 × 10¹⁵ cm⁻³ to 4.33 × 10¹⁵ cm⁻³, which lifts the device power conversion efficiency (PCE) from 2.77% to 3.15%. Even more noticeable improvements are observed in PBDB-T:PCBM photovoltaic units; the refined doping recipe raises carrier mobility from 5.42 × 10⁻⁴ cm²/V·s to 8.69 × 10⁻⁴ cm²/V·s and cuts trap density down from 7.13 × 10¹⁶ cm⁻³ to 3.15 × 10¹⁶ cm⁻³, thus bringing about a substantial PCE boost ranging from 6.52% to 9.14%. The present study confirms the bifunctional advantages possessed by 2D CdSe NPLs, which can adjust BHJ microphase separation and electronic characteristics simultaneously. This research offers a simple and broadly applicable route to fabricate organic photovoltaic cells with superior efficiency. Full article

Soft magnetic materials determine the efficiency, size, thermal burden, and reliability of transformers, inductors, electrical machines, electromagnetic interference (EMI) components, and magnetic sensors. This review differs from property-by-property surveys by using a condition-aware, application-driven framework: magnetic performance is compared only together with frequency, peak magnetic flux density, temperature, waveform, direct current (DC) bias, geometry, and processing route. After a concise treatment of coercivity, permeability, saturation polarization, magnetostriction, and loss mechanisms, the major material families are quantitatively compared in terms of magnetic performance, processing, cost, and industrial maturity. The review then maps these families onto grid transformers, high-speed electrical machines, wide-bandgap power converters, integrated magnetics, wireless power transfer, aerospace electrical systems, and radiofrequency components. Particular attention is given to the trade-offs among saturation polarization, permeability, core loss, mechanical strength, thermal stability, manufacturability, and sustainability. Recent advances in strong and ductile soft magnets, wide-temperature ferrites, vortex and easy-plane composites, mixed-powder soft magnetic composites, nanocrystalline flake-ribbon cores, and additive manufacturing are assessed by technology maturity. A prioritized roadmap identifies near-term needs for standardized condition-specific data and manufacturing control, medium-term opportunities in magnetic–thermal co-design and digital twins, and longer-term prospects for adaptive, self-healing, and GHz magnetic architectures. The resulting framework is intended to support both material development and defensible industrial material selection. Full article

The growth of cloud services and immersive applications based on extended reality (XR), including Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR), imposes increasingly demanding requirements on access networks. The large-scale integration of IoT devices in smart buildings further increases the need for high throughput, low latency and jitter, and reliable connectivity. Traditional Fiber-to-the-Home (FTTH) networks with a single access point (AP) become quite limiting when there are high performance requirements, with many users with indoor mobility and high device density. Fiber-to-the-Room (FTTR) is an extension of FTTH, which brings fiber optics to each room of the house through a Main FTTR Unit (MFU) and several Sub FTTR Units (SFU) along with the APs, with centralized device management. Green FTTR networks are characterized by their energy efficiency through centralized control of signal power and Dynamic Bandwidth Allocation (DBA) management. The fgONT architecture allows for deterministic network slicing, enabling the allocation of specific resources isolated from the rest of the network traffic, allowing for predictable bandwidth and QoS. This work presents a framework that allows for a comparative analysis of FTTR and FTTH networks in different scenarios in order to ensure a compromise between transmission quality, network energy efficiency, and the user’s perceived experience. The results obtained show that, in high device density scenarios, FTTR reduces the average packet loss from 52.69% to less than 0.08%, decreases the average latency from 151 ms to less than 2 ms, and maintains the overall QoE above 0.974, compared to 0.27 in FTTH with a single AP. Full article