The operation range of two-stroke engines can be significantly narrowed with increasing adoption of electrified powertrains, enabling more targeted port design optimization. A one-dimensional (1D) engine system model and a three-dimensional (3D) computational fluid dynamics model were established in this study for a Curtis loopscavenged two-stroke engine and validated using experimental data. A coupled 1D-3D simulation method was developed to investigate the influence of exhaust port opening timing (EPO) and scavenging port opening timing (SPO) on the gas exchange process and engine performance. Temporal evolution and spatial distribution of the in-cylinder gas flow were jointly analyzed to reveal the mechanisms that govern the scavenging behavior. The results show that EPO timing has a dominant effect on the scavenging process, flow pattern, and exhaust gas purity, while SPO primarily affects the in-cylinder flow path and residual gas distribution. Variations in port timing affect effective compression ratio, pumping loss, and trapped volumetric efficiency, leading to changes in power and fuel consumption. Under the baseline port timing combination, the brake power is 25.6 kW, while the BSFC is 520 [g/(kW center dot h)]. The optimized port timing combination of EPO = 80 degrees CA and SPO = 117 degrees CA enhances engine power by 10.4%, whereas EPO = 80 degrees CA and SPO = 127 degrees CA reduces fuel consumption by 19.6%. The findings demonstrate that the coupled 1D-3D approach provides a novel tool for cross-dimensional analysis and offers valuable insights into the design and optimization of two-stroke engine scavenging systems.
The development of stable Fe-based catalysts for CO2 hydrogenation to long-chain hydrocarbons faces a critical trade-off between selectivity and durability. Here, we demonstrate that ultra-high potassium loading (up to 30 wt %) on FeCu/gamma-Al2O3 catalysts modifying this limitation through electronic modification and mixed-phase stabilization. The optimized 25 wt% K catalyst achieves notable C5+ hydrocarbon selectivity of 52.6% while maintaining stable performance over 100 h. High-loading potassium promotion transforms the catalyst through: (1) electronic donation accelerating Fe5C2 formation, (2) enhanced surface basicity suppressing hydrogenation, and (3) stabilization of mixed Fe3O4/Fe5C2 phases resistant to deactivation. Although increased K induces carbon deposition, the deposited carbon is predominantly amorphous and carbide-type and is not associated with measurable activity loss within the test window. The gamma-Al2O3 support effectively disperses excess potassium, preserving catalyst porosity at ultra-high loadings. Long-term testing confirms sustained activity over 100 h with 15.6% C5+ yield and suppressed methane formation (12% selectivity), providing a design strategy for industrial CO2-to-fuel applications.
Ferroresonance is a typical abnormal operating condition in distribution networks. The overvoltages it produces can damage potential transformers (PTs) and, in extreme cases, cause switchgear explosions and electrical fires. The wide spectrum and strong nonlinearity of ferroresonance signals render conventional time-frequency methods inadequate. This paper proposes a Markov-graph co-design framework that tightly couples a theoretically grounded encoding stage with a structure-aware classifier. First, the first-order Markov approximation for quantised ferroresonance sequences is assessed using conditional mutual information and a conditional-independence test, with partial autocorrelation and Ljung-Box residual diagnostics used as supporting evidence. The combined results provide an empirical basis for Markov Transition Field (MTF) encoding without imposing an ordinal interpretation on the categorical states. Second, MTF converts one-dimensional voltage signals into weighted directed graphs whose edge weights encode state-transition probabilities. Third, a GNN-Dual-ViT architecture with progressive multimodal fusion exploits the resulting graph topology. The framework is evaluated against seven representative baselines reimplemented on a common ATP-EMTP dataset under identical protocols with multiple random seeds, and is further stress-tested under low SNR and load fluctuation. A cross-voltage study distinguishes same-mechanism transfer to a 35 kV PT system from adaptation to a physically different 110 kV CCVT regime. The results indicate that transfer is feasible with lightweight domain adaptation and limited labelled target data, while regime-specific calibration remains necessary for deployment. A branchwise qualitative analysis, a failure-case taxonomy, and a maximum-mean-discrepancy audit of the sim-to-field domain gap characterise both the mechanism and the boundary of applicability of the proposed framework.
Gallium (Ga)-based biomaterials have emerged as versatile therapeutic platforms owing to the iron-mimicking properties and broad biological activities of gallium. Coordination engineering regulates Ga speciation, stability, transport, and therapeutic activation; however, optimizing individual physicochemical properties does not necessarily improve biological performance. Excessive coordination stability may restrict ligand exchange and therapeutic activation, whereas insufficient stability may cause premature dissociation, nonspecific exposure, and reduced target delivery.In this Review, we propose Biological Accessibility as a multidimensional, time-dependent property describing the spatiotemporal availability of biologically active gallium species to relevant biological environments, cells, and molecular or tissue targets throughout the therapeutic lifecycle. We first examine ligand chemistry, coordination thermodynamics, ligand-exchange kinetics, gallium speciation under physiological conditions, and disease-responsive coordination evolution. We then review representative coordination-engineered gallium platforms and their applications in antibacterial therapy, immunomodulation, cancer treatment, bone regeneration, bioimaging, and theranostics, highlighting coordination-regulated transport, localization, cellular accessibility, activation, retention, and clearance. Building on these advances, we develop a dynamic framework linking continuous coordination evolution with Biological Accessibility across systemic, pathological, and intracellular environments. We further discuss Therapeutic and Off-target Accessibility, disease-specific accessibility windows, mechanistic attribution of biological functions, quantitative evaluation, in vivo coordination evolution, predictive modeling, artificial intelligence-assisted design, biosafety, and clinical translation. This framework provides a conceptual basis for accessibility-guided design of next-generation gallium biomaterials and broader coordination-engineered therapeutic systems.
The fretting fatigue damage issue of nickel-based single crystal (NBSC) fir-tree tenon joints is the core bottleneck restricting the reliability and service durability of aero-engine turbine blades. In this paper, systematic research on the fretting fatigue damage mechanism of NBSC fir-tree tenons is carried out through high-temperature fretting fatigue tests under various loads, combined with crack observation systems and crystal plasticity finite element (CPFE) simulations. The results indicate that plastic deformation of the fir-tree tenon joint intensifies with increasing load, accompanied by aggravated fretting damage in the contact area. Consequently, the crack initiation life of each tooth is shortened and the crack propagation rate is accelerated. Under all loading conditions, cracks preferentially initiate at the first tooth of the tenon, then successively emerge and continuously propagate at the second and third teeth until structural failure occurs. All cracks nucleate at peeling or microcracks induced by fretting wear at the lower edge of the contact zone, which is consistent with the stress concentration locations obtained from CPFE results. In the early stage, cracks formed on all tenons propagate along the {111} slip planes. In contrast, the crack propagation path of the second tooth exhibits obvious load-dependent evolution characteristics. As the applied peak load declines, crack propagation morphology sequentially shifts from straight to zigzag and finally to smooth. This transition arises from the combined synergistic effects of varying crack propagation driving force and microstructural evolution.
