Frontiers in Science and Engineering is a monthly online, international, peer-reviewed journal, dedicated to publish empirical, academic, theoretical and review research articles that contribute to the practice in science, engineering, and related topics. All articles published are rigorously and fast reviewed meeting the Journal Quality standards.
A Review of Ship Energy Loss, Emission Characteristics and IMO Compliance Energy-Saving Technologies
Global maritime decarbonization driven by IMO regulations has become the core constraint for modern shipping operations. This study adopts bibliometric analysis (2015–2025) and PRISMA-based systematic review (2018–2025) to comprehensively investigate ship energy loss mechanisms, emission distribution characteristics and mainstream energy efficiency improvement technologies. This paper fully analyzes power system partial-load loss, thermal heat dissipation and actual energy waste data of merchant ships. The mandatory regulatory system including EEDI, EEXI, CII and SEEMP is systematically interpreted. Typical energy-saving technologies covering hull optimization, power system retrofitting, waste heat recovery and operational management are summarized. A quantitative comparison of technical performance, cost and emission reduction potential is presented. On this basis, staged low-carbon paths for different ship types are proposed. The research results can provide practical references for shipping enterprises to achieve CII compliance and ship energy-saving transformation.
Maritime decarbonization; ship energy loss; ship emission; IMO regulations; CII compliance; energy-saving technology.
Copyright (c) 2026 Frontiers in Science and Engineering https://creativecommons.org/licenses/by-nc/4.0
Fatigue Performance Evolution Law and Reliability Assessment Methodology of Wing Structures under Coupled Complex Loads and Environmental Conditions
The aging trend of the global civil aviation fleet has become increasingly significant, with a large number of in-service aircraft operating beyond their initial design service goals. Current deterministic damage tolerance analysis methods struggle to quantify the combined effects of multi-source uncertainties, including load randomness, environmental corrosion, and material dispersion, on structural safety. This study focuses on the fatigue performance evolution law and reliability assessment methodology of wing structures under coupled complex loads and environmental conditions. Through corrosion-fatigue coupling interrupted tests, damage constitutive modeling, time-dependent reliability algorithm development, and system reliability optimization design, this research aims to reveal the cross-scale cumulative mechanism of fatigue damage, develop efficient time-dependent reliability calculation methods for small failure probabilities, and construct a system reliability optimization theoretical framework considering failure path correlation. The findings will provide theoretical support for anti-fatigue lightweight collaborative design of next-generation civil aircraft, offer scientific evidence for aging aircraft life extension certification, and promote the transformation of aviation maintenance from scheduled inspection to condition-based maintenance.
Aging Aircraft; Corrosion-Fatigue Coupling; Time-Dependent Reliability; System Reliability Optimization; Bayesian Updating.
Research Progress of Bio-electro-Fenton System and Its Application in Wastewater Treatment
The bio-electro-Fenton (BEF) system integrates bioelectrochemistry with Fenton advanced oxidation technology. It can achieve self-sustained electricity generation via anaerobic microbial metabolism and construct an efficient advanced oxidation system relying on in-situ hydrogen peroxide production at the cathode. This system effectively addresses the limitation of conventional biological methods that struggle to treat refractory and highly toxic organic wastewater, thus holding promising application prospects in water pollution remediation. This paper systematically reviews the core reaction mechanisms of BEF systems, elaborates the microbial electrogenic oxidation mechanism at the bioanode as well as the oxygen reduction and Fenton catalytic oxidation mechanisms at the cathode, and summarizes recent research advances in modification and optimization of anode and cathode electrode materials. Emphasis is placed on analyzing the effects of carbon-based modification, nanocomposites and biochar-based electrode materials in boosting electron transfer efficiency and enhancing electricity generation performance and hydrogen peroxide production efficiency. Meanwhile, this paper compares and evaluates the merits and demerits of homogeneous iron-based catalysis and supported heterogeneous catalytic systems. It points out that traditional homogeneous catalysis suffers from narrow applicable pH range, high reagent consumption and high risk of secondary pollution. In contrast, supported heterogeneous catalysts have become a research hotspot for BEF catalytic materials owing to their advantages including stable active sites, low metal leaching, recyclability and strong adaptability under neutral conditions. At present, BEF technology still faces challenges such as easy electrode passivation, weak anti-interference capacity in complex water matrices, high material fabrication cost, and ambiguous interfacial mechanisms underlying multi-mechanism coupling. Future research should further develop long-term stable, low-cost functional electrodes and composite catalytic materials, deeply uncover the synergistic mechanisms among microbial metabolism, electron transfer and Fenton catalysis, and promote the transformation of bio-electro-Fenton technology from fundamental laboratory research to large-scale engineering applications for practical wastewater treatment.
Bio-electro-Fenton, wastewater treatment, in your paperelectrode materials.
A Review of Production Line Balancing and Optimization for Manufacturing Enterprises in the Context of Industry 4.0
As global manufacturing moves toward intelligent, digital transformation, the concept of Industry 4.0 has created an enormous demand for highly flexible and responsive production systems. To meet this demand, manufacturing enterprises of all kinds are actively adopting advanced technologies such as the Internet of Things, digital twins, and artificial intelligence to optimize production processes and reduce resource waste. This paper provides a comprehensive and systematic review of the current state of research on production line balancing and its optimization strategies in the context of Industry 4.0, in order to fill the conceptual gap left by the unclear relationship between traditional line balancing theory and the dynamic requirements of modern intelligent manufacturing. The findings show that academic attention has gradually shifted from traditional mathematical programming and static heuristic algorithms toward dynamic planning theories driven by real-time data, human-machine collaboration, and cyber-physical systems. The intelligent manufacturing technologies that enterprises adopt at the strategic and tactical levels profoundly shape line balance and efficiency through distinct elements and mechanisms. This review helps managers and production engineers identify best practices in the field and thus provides effective guidance for building smart factories and making operational decisions.
Industry 4.0; Production Line Balancing; Intelligent Manufacturing; Optimization Algorithms; Digital Twin; Strategy and Tactics.
Research Progress and Prospects of the Geographical Detector
Geographical detectors have become a widely used statistical tool in soil science for identifying dominant factors and interactions driving spatial differentiation of soil properties. This paper systematically reviews the basic principles, core functions (factor detection, interaction detection, risk area detection, and ecological detection), and application progress of the geographical detector in soil heavy metal pollution identification, soil erosion risk assessment, and digital soil mapping. By analyzing existing case studies, we summarize current limitations including sensitivity to discretization of continuous variables, scale dependence, lack of causal inference, insufficient characterization of interaction mechanisms, static single-time-snapshot analysis, and absence of systematic uncertainty evaluation. To address these challenges, future directions are proposed: (1) developing adaptive discretization methods (e.g., MIC, genetic algorithms) and continuous geographical detectors; (2) conducting multi-scale modeling across watershed, county, and national levels; (3) coupling with causal inference frameworks (SEM, Bayesian networks, causal forests); (4) integrating machine learning (random forest, XGBoost, SHAP) and nonlinear models (GAM) to quantify interaction forms; (5) constructing spatiotemporal geographical detectors using multi-temporal remote sensing data; (6) establishing a standardized uncertainty assessment framework based on NUSAP and Monte Carlo simulation; and (7) fusing multi-source big data (Sentinel-2, GEDI, MODIS) with deep learning. These advancements will significantly enhance the scientific value of geographical detectors in soil pollution source tracing, erosion risk early warning, and ecological restoration decision-making, with important implications for soil protection in key regions such as the black soil region of Northeast China and the karst region of South China.
Geographical Detector, Soil science, Spatial heterogeneity.
Research Progress and Engineering Application Prospects of Hybrid Fiber Reinforced Steel Slag Powder Ultra-High Performance Concrete: A Review
Ultra-high performance concrete (UHPC) has attracted extensive attention in the field of advanced cement-based materials due to its superior mechanical properties, excellent durability, and potential for lightweight and high-performance structural applications. However, the widespread application of UHPC is still restricted by its high cement consumption, high production cost, and associated environmental impacts. The development of sustainable UHPC through the incorporation of industrial solid wastes has therefore become an important research direction. Steel slag powder, as a major by-product of the steel industry, possesses potential hydraulic activity and micro-filling effects, making it a promising supplementary cementitious material for partially replacing Portland cement in UHPC systems. Despite its excellent compressive strength, the highly dense matrix of UHPC results in inherent brittleness and limited deformation capacity. Fiber reinforcement has been widely adopted to overcome this limitation, and different types of fibers exhibit distinct strengthening mechanisms. Steel fibers mainly contribute to macro-crack bridging and post-cracking load-bearing capacity, while polymer fibers and basalt fibers provide effective control of micro-crack initiation and propagation. Hybrid fiber systems combining multiple fibers can achieve multi-scale crack control and improve the comprehensive mechanical performance of UHPC. This paper reviews recent advances in steel slag powder-based UHPC and hybrid fiber reinforced UHPC systems. The characteristics and utilization potential of steel slag powder are first discussed, followed by an analysis of hydration behavior, microstructure evolution, and its influence on UHPC properties. The reinforcement mechanisms of steel fibers, polypropylene fibers, polyvinyl alcohol fibers, and basalt fibers are summarized. Furthermore, the synergistic effects of hybrid fibers on mechanical properties, toughness, durability, and high-temperature resistance are systematically reviewed. Finally, the engineering application prospects, existing challenges, and future research directions of hybrid fiber reinforced steel slag powder UHPC are discussed. This review provides theoretical guidance for the development of sustainable, high-performance, and multifunctional cement-based materials.
Ultra-high performance concrete, steel slag powder, hybrid fiber, steel fiber, polypropylene fiber, PVA fiber, basalt fiber, toughness, sustainable concrete.
An Exploration of the Strengths and Limitations of Utilitarianism in Engineering Practice
Utilitarianism centers on the greatest happiness and adheres to the principles of consequentialism, utilitarian calculus and impartiality. Its pursuit of efficiency and benefits, compatibility with quantitative analytical tools, and ethical justification for collective decision-making enable its in-depth alignment with engineering practice, making it a vital ethical framework for engineering decision-making. In engineering practice, utilitarianism sets a value orientation centered on public interests, optimizes resource allocation, and facilitates technological innovation and progress. The comprehensive flood control, power generation and shipping benefits of the Three Gorges Project serve as a typical example. Nevertheless, utilitarianism bears prominent limitations. It tends to overlook individual rights and the interests of minority groups and triggers imbalances between short-term and long-term interests. Furthermore, uncertainties in the prediction of engineering consequences escalate the risks of its application, and the Fukushima nuclear power plant accident has revealed the hazards arising from the one-sided pursuit of utility. Therefore, diverse ethical theories such as deontology and virtue ethics should be introduced. It is essential to strengthen responsibility ethics and full-life-cycle risk management, and improve mechanisms for public participation and democratic decision-making, so as to promote engineering practice to realize the coordinated development of economic benefits, social equity and environmental sustainability.
Utilitarianism; Engineering Ethics; Engineering Decision-Making; Social Responsibility; Risk Management.
Automated Caption-Guided Image Retrieval: A Multi-Positive Contrastive Learning Paradigm
[Objective] This study aims to improve textual similarity measurement for image retrieval while mitigating the anisotropy of sentence embeddings. [Methods] We propose an image-caption semantic encoder trained with a multi-positive contrastive loss. The conventional contrastive objective is extended to accommodate multiple positive samples, and image captioning is used to generate training data automatically. On this basis, we construct a caption-based image-to-image retrieval framework. [Results] Experiments show that the proposed model outperforms baseline methods on semantic textual similarity (STS) benchmarks and improves the agreement between retrieval results and human semantic judgments. [Limitations] Short captions cannot fully represent the complex semantics, ambiguity, and fine-grained details of an image. [Conclusion] The proposed Multi-Positive Example Contrastive Learning (MPC) model provides more discriminative sentence embeddings and improves semantic similarity measurement in image retrieval.
Image-to-Image Retrieval; Semantic Representation; Multi-Positive Contrastive Loss; Contrastive Learning.
Research Progress and Outlook on Rebar Anchoring Technology
As a core form of post-installed anchoring technology, rebar planting has been widely applied in engineering fields such as the reinforcement of existing structures, the connection of new and existing structures, and the construction of new structural joints, thanks to its advantages of construction flexibility, reliable anchoring, and strong adaptability.In recent years, with the expansion of engineering applications and the emergence of new structural materials, the scope of research on rebar anchoring technology has gradually extended from traditional concrete substrates to new materials such as engineered bamboo, ultra-high-performance concrete, and 3D-printed concrete. The research focus has deepened from the basic performance of individual rebars to the mechanical properties of structural members, the seismic performance of structural systems, and long-term service performance.Based on the findings of relevant domestic theses from 2021 to 2025, this paper focuses on two major areas—the anchoring performance of rebar in concrete substrates and the anchoring performance of rebar in bamboo and wood structures—systematically reviews research progress in areas such as interfacial bonding mechanisms, performance evolution under complex environmental conditions, stress characteristics of special construction details, and the mechanical properties of components and structural systems. It summarizes the current characteristics and shortcomings of the research and outlines future research directions, with the aim of providing a reference for further research and engineering applications of rebar anchoring technology.
Rebar anchoring,bond performance, interfacial shear strength, service environment, bamboo and wood structures, research progress.
Comparative Analysis of Ear Electroencephalography (Ear-EEG) and Scalp Electroencephalography (Scalp-EEG) in Wearable Brain-computer Interfaces
This paper compares and analyzes ear-based electroencephalography (Ear-EEG) and scalp-based electroencephalography (Scalp-EEG) in wearable brain-computer interfaces (BCIs) to examine how signal fidelity, robustness, and usability are balanced. The study evaluates signal quality (event-related potentials ERP, signal-to-noise ratio SNR), resistance to motion artifacts, comfort, wearability, and practical applicability. The results indicate that, despite moderate signal attenuation (amplitude loss of 21% to 44% compared to optimized Scalp-EEG) and limited spatial coverage (1–6 channels), Ear-EEG still achieves clinically relevant sensitivity for key auditory ERP components (Hedges' *g* = 0.25–0.77) and alpha-band oscillations. Ear-EEG has inherent resistance to ocular artifacts but is highly sensitive to interference from jaw/head movements. In terms of usability metrics, Ear-EEG significantly outperforms Scalp-EEG: the dry electrode design supports over 40 hours of continuous wear with minimal discomfort (only approximately 15% of users reported noticeable foreign body sensation), can be self-installed within 5 minutes, and has approximately 45% higher social acceptability. However, Scalp-EEG still holds advantages in whole-brain coverage, high-fidelity tasks (such as N400 semantic decoding), and motion robustness during walking (no artifacts at 3.0 km/h). Additionally, this paper demonstrates the feasibility of Ear-EEG for mobile, long-term monitoring applications (such as sleep tracking and epilepsy detection), while also clarifying the unique application scenarios where Scalp-EEG remains irreplaceable.
Ear-EEG; Scalp-EEG; Brain–Computer Interface (BCI); Neural signal monitoring; Wearable neurotechnology.
Copyright (c) 2025 Frontiers in Science and Engineering https://creativecommons.org/licenses/by-nc/4.0
Finite Element Analysis of Bond Behavior between Steel Plate, Prestressed CFRP, and Concrete
To investigate the interfacial bond behavior between steel plate-prestressed carbon fiber reinforced polymer (CFRP) sheets and concrete, a numerical model of the steel plate-prestressed CFRP sheet-concrete specimen was established via ABAQUS, and cohesive elements were adopted to simulate the nonlinear bond-slip characteristics of the interface. This study analyzed the influences of different prestress levels of CFRP sheets, bond lengths and CFRP sheet widths on the interfacial bond behavior between prestressed CFRP sheets and concrete in the single shear test model, as well as the bond-slip performance under the composite reinforcement of steel plates. The simulation results indicate that: compared with specimens without steel plates, the peak load of specimens with steel plates increases by approximately 16.8%, and the interfacial bond strength increases by 22.1%. Moreover, the post-peak load drops more gently, and the residual bearing capacity is higher. The prestress level has a significant effect on the interfacial bond behavior: when the prestress level increases from 10% to 20%, the interfacial peak stress and strength utilization rate increase significantly; when the prestress level reaches 30%, the peak stress decreases due to the accumulation of initial micro-damage. The effective bond length increases with the increase of prestress level. When the prestress level is excessively high and the bond length is insufficient, premature debonding occurs under interfacial loading. Under the condition that other parameters remain unchanged, when the bond length increases from 100 mm to 140 mm, the peak load increases by 16.3%, while the increase in bearing capacity is relatively marginal when the bond length is 180 mm, indicating that the effective bond length of CFRP sheets with 20% prestress is approximately 140 mm. When the width of CFRP sheet is 10 mm, tensile fracture occurs due to excessively small cross-sectional area; when the width is 20 mm or above, the failure mode transfers to interfacial debonding. Compared with bond length, increasing the width of CFRP sheet has a relatively limited effect on improving bearing capacity: when the width of CFRP sheet increases from 30 mm to 40 mm, the peak load of the specimen only increases by 5%. Based on the comprehensive analysis of various parameters, the optimal parameter combination is determined as 20% prestress level, 30 mm CFRP sheet width and 140 mm bond length. The numerical model proposed in this paper is verified by comparison with experimental results, and the research findings can provide a theoretical basis for the design and application of steel plate-CFRP composite reinforced concrete structures.
Finite element analysis; Prestressed CFRP fabric; Bonding performance; Single shear specimen; Composite reinforcement.
Investigation of Turbulent Flow Behavior in Complex Geometries Using Computational Fluid Dynamics
This paper examines the behavior of a complex geometry (a 90-degree pipe bend) by undertaking a detailed analysis of the turbulent flow via computational fluid dynamics. k-ω Shear Stress Transport Navier-Stokes simulations with Reynolds number between 10,000 and 50,000 were done with Reynolds-Averaged Navier-Stokes simulations. Systematic mesh refinement was strictly used to achieve grid independence with a value of less than 3% as the Grid Convergence Index. The k-ω SST model showed better predictive power than conventional k-ε models with a mean absolute percentage error of 3.2% in prediction of pressure drop with correlation coefficient R² = 0.998 against experimental results. Findings indicate notable amplification of turbulent kinetic energy (180% gain) in the bend region that is consistent with Re 0.5 scaling law and flow recovery is 5-7 pipe diameters long. Asymmetric velocity distributions and high wall shear stress on inner bend surfaces were observed and the formation of dean vortices and patterns of secondary flows was achieved successfully. The intensity contours of turbulence were found to be highly spatially heterogeneous with maximum values of 18% close to walls. The study sets up the best computational practice in predicting turbulent flow through complex geometries, which gives quantitative advice to the design of industrial piping systems in form of equipment location requirements, the consideration of vibration related to the flow, and erosion-corrosion control policies.
Turbulent flow, Computational fluid dynamics, k-ω SST turbulence model, Complex geometries.
Treatment of Shipboard Oily Wastewater Using Modified-Anode Microbial Fuel Cells
With the rapid development of the shipping industry, pollution caused by shipboard oily wastewater has become an increasingly serious threat to marine ecosystems. Conventional physical, chemical, and biological treatment methods have limitations such as high energy consumption, unstable treatment performance, and potential secondary pollution when treating highly emulsified oily wastewater. To improve the electricity-generation and oily-wastewater-treatment performance of microbial fuel cells (MFCs), three anodes, namely CF, CeO₂/CF, and CeO₂-β-CD/CF, were prepared using carbon felt as the substrate and applied in dual-chamber MFCs. The effects of different anode materials on electricity generation and oil degradation were comparatively investigated. The water contact angles of CF, CeO₂/CF, and CeO₂-β-CD/CF were 101.632°, 86.845°, and 66.877°, respectively, indicating that the combined modification with CeO₂ and β-CD significantly improved the surface wettability of carbon felt. SEM observations showed that the modification increased the surface roughness of the carbon fibers without noticeably damaging their original three-dimensional fibrous structure. The maximum output voltages of the MFCs equipped with the three anodes were 0.5313 V, 0.6300 V, and 0.6785 V, respectively, and the maximum voltage of the CeO₂-β-CD/CF-based MFC was 27.71% higher than that of the CF-based MFC. After 7 days of continuous operation, the corresponding oil degradation rates were 58.23%, 71.48%, and 77.16%, respectively. These results demonstrate that the CeO₂-β-CD composite modification provides favorable conditions for microbial attachment, biofilm formation, and sufficient contact between the electrode and anolyte by improving the surface wettability and morphology of carbon felt, thereby enhancing both electricity generation and oil-pollutant degradation. This study provides a promising technical approach for the efficient treatment of shipboard oily wastewater.
Microbial fuel cell; Shipboard oily wastewater; Carbon felt; Cerium oxide; β-Cyclodextrin.
Implementation of A Liquefaction Subroutine in ABAQUS Based on The Modified Hardin-drnevich Soil Backbone Curve Model
Liquefaction caused by earthquakes can affect the stability of underground structures. Numerical simulation of liquefaction is therefore necessary. By combining the modified Hardin-Drnevich soil constitutive model with Byrne's modified Martin pore pressure increment model, this paper develops an ABAQUS subroutine incorporating the modified Hardin-Drnevich soil constitutive model and the Byrne pore pressure increment model based on the implicit interface of ABAQUS. Numerical models in ABAQUS and FLAC3D are established respectively based on the undrained dynamic triaxial test results of Nanjing saturated fine sand, and the effective analytical capability of the proposed subroutine is preliminarily verified. Through comparing a total of 6 groups of numerical calculation results under different working conditions, this study verifies the influences of pore pressure growth trend, initial effective pore pressure and dynamic shear ratio on the liquefaction process. It is proved that the calculation results of the proposed subroutine in dynamic triaxial tests are superior to those of FLAC3D. The causes of numerical calculation errors are discussed, and the feasibility of developing the liquefaction numerical simulation subroutine for ABAQUS is verified.
Numerical simulation; Byrne incremental model; Modified Hardin-Drnevich; Liquefaction.
Progress in Ship Pollution Prevention and Control Technologies: Regulatory Drivers, Technical Pathways and Intelligent Governance
Shipping underpins global trade, yet ship operations remain an important source of environmental pressure through oil pollution, exhaust emissions, ballast-water-mediated biological invasions, sewage, garbage discharge, antifouling-system releases, and biofouling-related ecological risks. Under the progressively strengthened framework of MARPOL, the Ballast Water Management Convention, the Anti-Fouling Systems Convention, and the IMO energy-efficiency and carbon-intensity requirements, ship pollution control is moving from isolated end-of-pipe treatment toward an integrated regime that combines source reduction, process control, terminal treatment, and digital compliance governance. This review examines the major categories of ship-generated pollution and the corresponding control demands, with emphasis on oil-pollution prevention, exhaust aftertreatment, alternative and low-carbon fuels, shore power, ballast water treatment, sewage and garbage management, antifouling coatings, and biofouling control. It further evaluates the emerging role of digital monitoring, data-driven risk assessment, and port-ship-shore coordination in improving regulatory compliance and environmental performance. The literature indicates that low-sulfur fuels, exhaust gas cleaning systems, selective catalytic reduction, ballast water management systems, and shore-side electricity have reached different degrees of technical maturity. However, their environmental benefits remain conditional on fuel life cycles, port infrastructure, equipment cost, operational maintenance, washwater management, data reliability, and enforcement capacity. Future research should therefore move beyond single-pollutant control toward life-cycle assessment, multi-pollutant co-optimization, verifiable digital monitoring, and integrated governance across vessels, ports, energy suppliers, and regulatory authorities.
Ship pollution; pollution prevention; MARPOL; exhaust emissions; ballast water treatment; shore power; alternative fuels; intelligent governance.
Preparation and Properties of Pine Powder-Bacillus pasteurii Microspheres
Aiming at the problems of low survival rate and weak mineralization activity of microorganisms in the high- alkali and high- shear environment of concrete, pine powder and nanomaterials were used as composite carriers to prepare Bacillus pasteurii microspheres by embedding method. The optimal culture conditions of microorganisms were determined by single factor experiments, the mix ratio of microspheres was optimized by orthogonal design, and systematic characterization was carried out from physical properties, mechanical strength, microscopic morphology and phase composition. The results show that the growth and urease activity of Bacillus pasteurii are optimal when the culture temperature is 30℃, initial pH=7, inoculation amount is 2%, and culture time is 24h; the optimal mass ratio of pine powder, nanomaterials and bacterial solution is 1:1:3, at this time, the average particle size of microspheres is 2.1±0.3mm, the embedding rate is 91.6%, the 24h bacterial burst release rate is less than 8.5%, and the mass loss rate after shaking for 24h is only 2.35%; SEM and XRD confirm that the microspheres form a porous composite structure, where microorganisms colonize well and can induce the formation of calcite-type calcium carbonate. The microspheres can effectively protect the bacteria and meet the application requirements of concrete self-healing.
Pine Powder; Bacillus pasteurii; Microspheres; Embedding Method; Mineralization Performance; Concrete Self-healing.
Fuel Cell Power Systems for Maritime Applications: Hybrid Architectures, Energy Management and Deployment Challenges
The decarbonization of maritime transport is accelerating the transition from conventional diesel-based propulsion to low- and zero-emission power systems. Fuel cells are increasingly regarded as a promising option for ferries, inland vessels, harbor craft, research vessels and other mission-defined ships because they convert chemical energy into electricity with high efficiency, low acoustic signatures and zero local carbon emissions when operated on hydrogen. Nevertheless, their deployment at sea remains constrained by slow transient response, stack degradation, hydrogen storage volume, safety requirements, cost and the availability of bunkering infrastructure. For these reasons, most practical fuel-cell ship concepts adopt hybrid configurations in which fuel cells are coupled with batteries, supercapacitors or diesel generators. This review summarizes recent progress in maritime fuel-cell power systems from four interrelated perspectives: fuel-cell technologies and shipboard architectures; hybridization and energy management; hydrogen storage, vessel integration and safety; and life-cycle emissions and commercialization barriers. Particular attention is paid to fuel-cell/battery systems, multi-stack power allocation, health-aware control and real-time energy management strategies. The review argues that future research should move beyond feasibility demonstrations and fuel-saving-oriented control toward integrated design frameworks that combine state-aware fuel-cell operation, degradation mitigation, mission-based sizing, safety-by-design and well-to-wake environmental assessment. Such an approach is essential for translating fuel-cell vessels from pilot projects into reliable and economically viable components of maritime decarbonization.
Fuel cell ships; hydrogen; hybrid propulsion; energy management; PEMFC; battery storage; shipboard microgrid; maritime decarbonization.
A Review of Multi-objective Green Flexible Job Shop Scheduling Based on Intelligent Optimization Algorithms
The flexible job shop scheduling problem (FJSP) is a representative and complex optimization problem in production scheduling because it simultaneously involves operation sequencing and machine assignment. With the rapid development of green manufacturing and intelligent manufacturing, research on FJSP has gradually shifted from traditional efficiency-oriented objectives, such as makespan and machine utilization, toward multi-objective green optimization that considers energy consumption, carbon emissions, energy cost, processing cost, and resource balance. From the perspective of industrial engineering and management, this paper reviews recent studies on multi-objective green flexible job shop scheduling. First, it clarifies the basic characteristics and research evolution of FJSP. Second, it summarizes the main research progress from three aspects: green objective modeling, realistic constraint scenarios, and intelligent optimization algorithms. Third, it evaluates the applicability of genetic algorithms, NSGA-II, memetic algorithms, hybrid metaheuristics, and deep reinforcement learning. Finally, it identifies current limitations in green indicator systems, model realism, algorithm interpretability, and engineering implementation, and proposes future research directions. The review indicates that multi-objective green FJSP has moved beyond the stage of simply comparing algorithmic performance and is increasingly becoming a comprehensive optimization problem for complex manufacturing systems. Future research should strengthen systematic modeling of green objectives, dynamic scenario representation, and integration with real enterprise production systems.
Flexible job shop; Green scheduling; Multi-objective optimization; Intelligent optimization algorithm; Literature review.
Numerical Analysis of Mechanical Properties of White Sandstone Granite Composite Rock Mass with Prefabricated Cracks
The development and propagation of fractures within rocks have a significant impact on their mechanical behavior and engineering stability. This study focuses on composite rock masses composed of sandstone and granite and uses the PFC2D numerical simulation platform based on the discrete element method to systematically investigate the mechanical responses, damage evolution, and failure patterns of composite rock masses containing pre-existing fractures under uniaxial compression. By constructing models of pre-existing fractures with different inclinations 0°, 15°, 30°, 45°, 60°, 75° and lengths 10 mm, 15 mm, 20 mm, 25 mm, the influence of fracture geometric parameters on peak strength, peak strain, elastic modulus, and crack propagation paths of the rock masses was analyzed. The results indicate that when the fracture inclination is 30°, both the peak strength and peak strain of the rock mass are lowest, showing the most significant degradation effect; when the inclination is 75°, the mechanical performance of the rock mass is optimal. The influence of fracture length is regulated by the inclination: at 30°, the elastic modulus decreases with increasing fracture length, while at 60°, the effect is not significant. The crack initiation location and final failure mode exhibit regular evolution with changing inclination, with 45° being the optimal angle for shear-through failure.
Mixed rock mass; Prefabricated cracks; Mechanical properties; Damage evolution; destruction mode.
Current Development and Practical Thinking of NiFe-based Electrocatalysts for Alkaline Oxygen Evolution Reaction
The oxygen evolution reaction (OER) is the kinetically-limiting half-reaction in alkaline water electrolysis, and is fundamental to the viability of industrial-scale green hydrogen production. NiFe based electrocatalysts represent the most studied class of non-precious metal OER catalysts considering their superior intrinsic activity, earth-abundance and structural variety. In this work, the current progress of NiFe-based electrocatalysts for alkaline OER is summarised from three aspects including mechanistic knowledge, material engineering strategies and stability concerns. The adsorbate evolution mechanism (AEM) and lattice oxygen mechanism (LOM) are critically explored for NiFe layered double hydroxides (NiFe-LDH) and their in-situ regenerated NiFeOOH phases. Systematic reviews on engineering approaches such as heteroatom doping, defect engineering, heterostructure fabrication and substrate integration are offered. The primary obstacles for commercialisation are identified to be stability issues associated with iron segregation, structural degradation and catalyst delamination and potential new mitigation measures are proposed including oxyanion stabilisation and self-healing designs. The review concludes with practical ideas on bridging laboratory performance criteria and industry needs in electrolysis.
NiFe-based electrocatalysts; oxygen evolution reaction; alkaline water electrolysis; NiFe-LDH; surface reconstruction; stability; green hydrogen.
Study on the Differences in Mechanical Properties and Energy Evolution of Sandstone under Different Loading and Unloading Modes
To study the mechanical properties and energy evolution of sandstone under cyclic loading, experiments were conducted on intact prefabricated sandstone specimens using different loading and unloading methods, and the macroscopic failure characteristics of the rock samples were observed and analyzed. The mechanical properties and energy evolution of the rock samples were analyzed based on the stress-strain curves. The results indicate that the hysteresis loop areas differ under the two loading and unloading methods. The method with increasing upper limits mainly shows that the higher the stress peak, the stronger the material's energy dissipation capacity, and the more energy is consumed by plastic deformation and damage. In the method of increasing the upper limit and decreasing the lower limit, the hysteresis loop area gradually increases, indicating that an elevated stress level enhances the material's energy dissipation capacity, and damage induces internal friction or microcrack propagation. In both loading methods, energy evolution and damage failure characteristics are dominated by the stress application pattern: the stress concentration effect in the upper-limit-increasing method accelerates the compaction of the elastic framework and energy dissipation due to damage, resulting in a greater increase in total input energy, elastic energy, and dissipated energy, and the energy conversion efficiency is also higher due to more favorable elastic energy storage. In the upper-limit-increasing and lower-limit-decreasing method, simultaneously adjusting the stress upper and lower limits weakens stress concentration, resulting in smoother energy growth and increased damage energy consumption due to stress fluctuations. The growth rate of dissipated energy density shows a 'burst-decline-leveling-off' trend, corresponding to three damage stages, revealing the non-uniform evolution of damage. The upper-limit-increasing method results in tensile failure dominated by a single vertical main crack, with damage occurring as a directional superposition effect, while the upper-limit-increasing and lower-limit-decreasing method results in dispersed failure driven by a multi-directional crack network, with damage extending at multiple scales.
Cycle loading and unloading; mechanical properties; energy evolution; failure characteristics.
Model Predictive Control for the Activated Sludge Process
To address the issues of large fluctuations in influent load, high aeration energy consumption caused by conservative traditional on-off control strategies, unstable dissolved oxygen (DO) concentration, and poor sensor reliability in the activated sludge wastewater treatment process, a Model Predictive Control (MPC) method integrating data quality monitoring and a feedforward disturbance mechanism is proposed. A multi-input multi-output prediction framework based on an incremental Auto-Regressive eXogenous (ARX) model is constructed. The influent disturbance observer (BOD) load is introduced into the model as a feedforward variable. An MPC method based on a feedforward disturbance mechanism is designed to solve the hysteresis problem of feedback control. For the discrete characteristics of the actuators, PWM modulation is used to realize continuous control. Long-term actual engineering verification was carried out in a wastewater treatment plant in Jiaozuo, Henan. The results show that compared with the traditional PLC on-off control, this system reduces the average aeration energy consumption by more than 25%. The treatment efficiency is increased by 25%. The energy consumption per unit BOD removal stably reaches 0.8 kWh/kg BOD, which is an excellent industry level. The annual CO₂ emission is reduced by about 260 tons. The effluent quality compliance rate is not affected. This system can effectively suppress the invalid overshoot of DO concentration. It solves the control problems caused by multi-variable strong coupling and sensor failures. On the premise of ensuring absolute safety of effluent quality, significant energy saving, economic and environmental benefits are realized.
Water Pollution; Wastewater Treatment; Model Predictive Control; Disturbance Observer.
Preparation and Properties of CdS/SnO2 Composite Photocatalyst
In this paper, CdS/SnO2 heterojunction photocatalysts with different CdS composite ratios were prepared via a hydrothermal method. Their phase structure, microstructure, specific surface area, surface chemical state, optical properties, and photocatalytic performance were systematically investigated. XRD results indicate that CdS and SnO2 coexist in the form of a physical heterointerface without lattice doping or distortion. TEM/HRTEM and EDS analyses show that SnO2 nanoparticles are uniformly dispersed on the surface of the CdS plate-like structure, forming a closely contacted heterointerface that facilitates efficient separation of photogenerated charge carriers. BET tests reveal that the composite possesses a mesoporous structure with a specific surface area of 23.82 m2/g. XPS analysis confirms the existence of a built-in electric field at the heterojunction interface, consistent with type II band alignment characteristics. UV-Vis absorption spectra demonstrate that the introduction of CdS extends the photoresponse range into the visible light region, with the 0.6-CdS/SnO2 (Cd:Sn = 3:5) sample exhibiting the strongest light absorption capability. PL and TRPL further demonstrate that this sample has the highest photogenerated carrier separation efficiency. Photocatalytic degradation experiments of Rhodamine B (RhB) show that 0.6-CdS/SnO2 achieves a degradation rate of 93.43% within 70 min, with a reaction rate constant of 3.75×10-2 min-1, approximately 4.88 times that of commercial P25 catalyst. Cyclic test results indicate that the composite material possesses good photocatalytic stability and reusability.
CdS, SnO2, composite photocatalyst, heterojunction.
Review of Granite-Related Gold Mineralization in the Altai Region: Deposit Classification and Exploration Prediction
The Altai region of Xinjiang represents one of the most significant gold metallogenic belts in China. In recent years, an increasing number of gold deposits have been identified as intimately associated with intermediate-acidic intrusive rocks, particularly granites. The Altai region extensively exposes multi-episodic, multi-source granitic plutons exhibiting distinct spatiotemporal distribution characteristics, which are closely related to gold mineralization. Based on a systematic review of previous research findings, combined with the orogeny, magmatism, and tectonism of the Altai orogenic belt, this paper classifies four representative gold deposits that exhibit close spatiotemporal relationships with granites in the Altai region. The primary characteristics of orogenic-type, low-temperature epithermal-type, and subvolcanic-structural alteration rock-type gold deposits are summarized, aiming to provide theoretical references and practical guidance for exploration prediction of granite-related gold mineralization in Xinjiang.
Altai orogenic belt, granite, gold mineralization.
ETAS Spatio-temporal Model and Seismic Activity Analysis
Conventional Coulomb transfer only considers the triggering effect of moderate and strong earthquakes, ignoring that every earthquake has the ability of self-triggering. Statistical model, epidemic aftershock sequence model (ETAS), represents the normal seismic activity in a region. The quietness and activity of seismic activity can be detected by the systematic deviation between seismic activity and prediction rate, which can be regarded as the trigger effect of previous events and has a strong correlation with the coseismic trigger of Coulomb fracture stress change caused by strong earthquake transfer. The simulation results of Wenchuan-Lushan-Jiuzhaigou earthquake sequence show that the earthquake is not instantaneous, but triggered by the accumulation of seismic activity caused by the weak value of Coulomb change, which is consistent with the fracture theory of concave-convex body.
Empirical statistical model; Seismic activity simulation; Earthquake calm; Coseismic stress triggering.
A Review on the Research of Marine Electric Propulsion Systems
Marine electric propulsion system is a core technology at the intersection of shipping low-carbonization, ship intellectualization and comprehensive electrification. Compared with traditional mechanical propulsion, electric propulsion is not a simple replacement of diesel engines with electric motors. Instead, it takes generator sets, energy storage devices, fuel cells, shore power interfaces, ship power grids, power electronic converters, propulsion motors, propellers/podded thrusters and energy management systems as the core, forming a ship integrated energy system with multi-energy sources, multi-loads and multiple constraints. Its main advantages include flexible layout, improved efficiency under low load, enhanced redundancy and maneuverability, and easy access to new energy sources such as batteries and fuel cells. Meanwhile, it still faces challenges including low battery energy density, thermal runaway risks, poor reliability of power electronic devices, electromagnetic compatibility issues, insufficient port energy supply infrastructure and difficulties in full-life-cycle carbon emission accounting. This paper reviews the research background, significance, system architecture, key equipment, energy management strategies, typical applications, safety specifications, technical bottlenecks and development trends of marine electric propulsion systems, and conducts comparative analysis on various circuit topologies and application scenarios based on published literature. The review indicates that in the coming period, pure electric and battery hybrid propulsion will be preferentially applied to coastal short-distance vessels, inland waterway ships, harbor tugs, ferries and engineering working ships. In contrast, ocean-going merchant ships will mostly adopt a progressive electrification route combining low/zero-carbon fuel main engines, shaft power generation, energy storage peak shaving, shore power connection and digital energy management.
Marine electric propulsion; Integrated power system; Hybrid power ship; Battery energy storage; Fuel cell; energy management; Low-carbon shipping.
Quantitative Assessment of Soybean Seedling Uniformity Based on Multi-Feature Fusion
Accurate assessment of soybean seedling uniformity is essential for evaluating sowing quality and guiding early-stage field management, yet conventional manual inspection remains subjective and inefficient. This study presents a quantitative uniformity assessment framework based on multi-feature fusion using high-resolution RGB images. Per-plant masks and spatial positions are obtained through instance segmentation of soybean seedling images. Five categories of plot-level uniformity features are then extracted—emergence rate, plant spacing, inter-row angle, canopy coverage, and evenness index—along with their means, standard deviations, and coefficients of variation. An XGBoost classifier is trained to map these features to three uniformity grades, achieving an overall accuracy of 86.7% without cross-level misclassification. Feature importance analysis reveals that the standard deviation of plant spacing, emergence rate, and mean plant spacing emerge as the most influential predictors, providing explicit guidance for diagnosing the causes of poor uniformity. The proposed framework offers an interpretable and quantitative solution for automated seedling uniformity evaluation in soybean breeding programs.
Soybean seedling uniformity; multi-feature fusion; XGBoost; feature importance; RGB imagery; precision agriculture.
The Application of Nuclear Magnetic Resonance Technology in Study of Concrete Materials
As one of the most widely used structural materials in modern society, the optimization and improvement of concrete performance has always been a hot topic in material science research. As a non-destructive analysis method, nuclear magnetic resonance ( NMR ) technology has shown unique advantages in the study of concrete materials because it can provide material microstructure and dynamic information. This paper reviews the application of nuclear magnetic resonance technology in the hydration process, pore structure analysis and durability evaluation of concrete materials, and discusses the application progress of nuclear magnetic resonance technology in the quantitative analysis of cement-based materials. By analyzing the advantages and limitations of different nuclear magnetic resonance techniques, it provides theoretical basis and technical support for further research and engineering application of concrete materials.
Concrete, nuclear magnetic resonance, solid-state nuclear magnetic resonance, pore structure.
A Review on Event-Triggered State Estimation for Time-Delay Neural Networks
In practical engineering applications, time delays are inherent in neural networks due to signal transmission lags, hardware response limits and network communication constraints, which may induce oscillation, chaos and even system instability. Meanwhile, limited measurable outputs and external noise make it impossible to obtain full neuron states directly, so state estimation has become an indispensable technique. However, traditional time-triggered transmission leads to massive redundant data and unnecessary communication consumption. Event-triggered mechanism (ETM) transmits data only when system states violate preset trigger conditions, which effectively reduces communication load while ensuring satisfactory estimation performance. This paper systematically reviews the research progress of event-triggered state estimation for time-delay neural networks. Firstly, basic concepts, system modeling and core problems are introduced. Then, key theoretical tools including Lyapunov-Krasovskii (L-K) functional, integral inequalities and stability analysis methods are summarized. Furthermore, typical event-triggered protocols, estimator design approaches and unified performance indices are elaborated. Finally, existing challenges and future research directions are discussed, aiming to provide a clear reference for researchers in related fields.
Time-delay neural networks; State estimation; Event-triggered mechanism; Lyapunov-Krasovskii functional; Linear matrix inequality; Dissipativity.
Research on Airborne Time and Frequency Synchronization Technologies for Aircraft
This paper systematically investigates airborne time and frequency synchronization technologies, overall system architectures and major technical challenges under complex and harsh aerospace environments. It analyzes feasible synchronization methods including satellite timing and two-way time comparison, presents two typical system architectures, elaborates on core critical technologies, discusses future development trends, and verifies the synchronization precision and operational reliability of relevant equipment, providing solid technical support for stable operation of avionic systems and efficient implementation of cooperative combat missions.
Airborne time and frequency synchronization, Avionic systems, High-precision time synchronization, Satellite-based time synchronization, IRIG-B code,Low phase-noise crystal oscillator, Rubidium atomic clock, Radar networking, Passive localization, Anti-vibration.