Talagrand's correlation inequality [25] provides quantitative lower bounds on the covariance of two increasing Boolean functions in terms of their coordinate influences, but, in general, a logarithmic loss is necessary. Motivated by a question of Kalai, Keller and Mossel [14, Problem 6.1], we identify a natural log-free regime. We prove that if two increasing Boolean functions on {0,1}n are either both submodular or both supermodular, thenE[fg]−E[f]E[g]≥14⋅∑i=1nInfi[f]Infi[g], where the constant 1/4 is optimal. We also prove a real-valued extension: for two functions with the same second-difference sign, the covariance is bounded below by the sum of products of their Level-1 Fourier coefficients. As a consequence, we verify the Friedgut–Kahn–Kalai–Keller spectral conjecture [11, Conjecture 5.8] in this structured setting. The proofs combine a heat-semigroup representation based on second-order discrete derivatives with an independent induction argument for the Boolean case.
In liquid-fuel detonation systems, such as rotating detonation engines (RDEs), the propagation of detonation waves often occurs in an inhomogeneous two-phase environment where fuel droplets and air coexist. High-resolution numerical simulations are performed to investigate the one-dimensional propagation dynamics of liquid-fuel detonation across air layers in n-heptane droplet-air mixtures. A coupled Euler-Lagrange framework is employed, in which the gaseous phase is solved using the reactive Navier-Stokes equations with a skeletal mechanism, while droplet dynamics, evaporation, and phase interactions are tracked in a Lagrangian manner. The influences of air-layer length, fuel-section length, and droplet diameter on detonation structure are systematically examined. Four distinct propagation modes are identified as the detonation wave traverses the air layer: high-intensity shock-detonation, low-intensity shock-detonation, low-intensity shock-deflagration, and low-intensity shock-delayed deflagration. The transitions between these regimes are primarily associated with the strength of the detonation wave across the air layer, the induction time and detonation initiation time of the n-heptane droplets/air mixture. A theoretical model is developed to predict the regime transitions, demonstrating that the propagation behavior is primarily controlled by the phase-velocity differential that determines the droplet evaporation rate. This study provides fundamental insights into the dynamics of liquid-fuel detonation propagation in non-uniform media and offers a framework for modelling detonation-phase interactions in multiphase reactive flows.
With the rapid advancement of lithium-ion batteries, the risks of fire and explosion triggered by thermal-runaway-induced off-gassing have become increasingly prominent, particularly under overcharge conditions. Compared with conventional fire-extinguishing methods, immersion suppression offers potential in cooling, thermal propagation inhibition, and gas control, but its mechanism remains unclear. Therefore, this study examined thermal runaway evolution in 52 Ah LiFePO4 batteries under heating, overcharge, and immersion-overcharge conditions, explored the immersion suppression mechanism, and to evaluate the suppression performance differences among five immersion media (deionized water, FW-1800, water–ethylene glycol mixture, dimethyl silicone oil, and KOSTCHILL). Results show overcharge yields the highest gas (2.0591 mol) and heating the highest temperature (457 °C). Water immersion reduces gas to 1.6087 mol, peak temperature to 98 °C, and extends the thermal runaway window by 83.3 %. In terms of gas generation, immersion effectively suppresses high-temperature-dependent gases like H2 (1.185 → 0.832 mol) and CO (0.085 → 0.075 mol). Different immersion media show distinct suppression behaviors. Water-based systems perform better in temperature and gas suppression, suitable for single cells; FW-1800 performs best (Tmax = 88 °C, Vtotal = 1.1904 mol). Oil-based systems offer superior insulation (0 μS/cm), suitable for high-voltage modules; KOSTCHILL performs best (Tmax = 160.6 °C, Vtotal = 1.657 mol). This study provides theoretical and data support for developing immersion thermal safety technologies and optimizing immersion media for energy storage systems.
Aiming at the problem that grid-connected photovoltaic (PV) system has strict requirements for fault diagnosis accuracy and response time, an online intelligent diagnosis method for grid-connected PV system faults based on MAFDT is proposed. This study enhances PV fault diagnosis by combining CBDF-based multi-agile features with a DT in the MAFDT framework and deploying DSP-based online diagnosis to reduce response time and improve reliability. Firstly, the output data of the PV system is subjected to multi-agile features extraction; Secondly, the information Gain (IG) is used to select features to improve the interpretability of the model; Then, the proposed method was validated using data from the MPPT mode within the GPVS-faults and other dataset, and comparing the accuracy and calculation time of the MAFDT and other supervised learning models; Finally, the MAFDT model is deployed on the DSP for online fault diagnosis of grid-connected PV system. The results maintain 100% accuracy while cutting monitoring and diagnosis times to 0.0201 ms and 0.0364 ms, delivering 66-fold and 22-fold speed gains and high accuracy on the other dataset, which is especially suitable for online diagnosis of grid-connected PV system faults, and can ensure the reliability and safety of online operation of the system.
Boron (B), as a commonly used combustible agent in energetic materials, offers advantages such as high calorific value and combustion products that are free of corrosive or greenhouse gases. However, the oxide layer on the surface of boron powder leads to difficulties in ignition and low combustion efficiency. In this paper, the wet ball milling method with hot acetonitrile as the control agent was used to remove part of the oxide layer on the surface of boron powder, and the pretreated boron powder with high reactivity was obtained. The effect of oxide layer on the combustion performance of amorphous boron particles was analyzed by laser ignition and combustion experiment and thermogravimetric analysis. The experimental results indicate that the ignition delay time of the pretreated boron powder is significantly shortened, and the duration of intense light emission in the combustion process is relatively long. Based on the molecular dynamics calculation method of ReaxFF reactive force field, the ignition and combustion (3500 K) reactions of boron particles with different oxide thickness were studied. The high temperature combustion mechanism of boron particles and the influence of oxide layer on ignition and combustion process were analyzed. The computational results indicate that with the increase of the thickness of the oxide layer, the ignition delay time increases continuously, and the final energy release efficiency of the system decreases. However, when the oxide layer reaches a certain thickness, the change of the ignition delay time tends to stabilize. For the combustion reaction process of boron particles, the combustion dynamics model of amorphous boron particles was established, and the multi-stage reaction characteristics of boron particle combustion were revealed: initial reaction stage (similar to 1900 K), ignition combustion stage (1900 similar to 3500 K) and continuous combustion stage (3500 K). In this paper, the mechanism of ignition and combustion reaction of boron particles is explored by combining experiments and calculation methods, which provides a theoretical basis for the development of application technology of boron metal fuel in energetic materials.
