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The coupling between soil moisture (SM) and evapotranspiration (ET) governs key dynamics of Earth's climate and biosphere productivity. Yet, prevailing statistical models fall short of capturing the physics of water–energy exchange across diverse hydroclimates. In this study, we introduce an optimal transport framework based on the hypothesis that hydroclimates regulate SM–ET coupling near a quasi‐optimum state. This state is characterized by least action principle, defined by dynamic convolution between the water potential gradient (Δω${\\Delta }\\omega $ ) driving land‐to‐atmosphere moisture flux and the time weighted mass flux (referred as the SM‐ET coupling metric, λSM−ET${\\lambda }_{SM-ET}$ ). Global validation of this framework using decadal (2010–2019) SM and ET remote sensing data reveals widespread convergence toward the least action state across hydroclimatic zones, supporting the notion of emergent climatic regulation in SM–ET coupling. As a corollary to the proposed hypothesis, we estimate two emergent properties of the SM–ET coupling: active root zone depth supporting ET, and the characteristic transit timescales over which SM is lost to atmosphere. Our root depth estimates show strong correspondence with in situ measurements (correlation >0.86) across biomes, underscoring the framework's physical realism. Notably, dynamic transit times are also validated against isotope measurements and findings suggest that SM perturbations often cycle back into the atmosphere within 3–7 days, calling into question traditional metrics of bulk residence time, that often overestimates the actual turnover. Overall, this framework provides a physically grounded way to study water–energy interactions across diverse environments.

Based on the actual operation scenario of metro, this paper proposes an uneven parameter stray current distribution model. The model combines the calculation method of multi-section traction power supply of metro and establishes an uneven parameter stray current distribution model in different calculation domains with the metro operation position and the traction substation position as the boundary points. The improved dynamic boundary conditions were used to calculate the model. Compared with the experimental data, the average maximum deviation between the two was 0.677. Meanwhile, the dynamic space–time distribution characteristics of stray current and the change law of rail-to-ground voltage were obtained through simulation analysis. In addition, the calculation model for ground potential gradient distribution under stray current interference was established by discretizing stray currents within each calculation domain, and the characteristics of ground potential gradient distribution were simulated and analyzed. The results showed that the distribution period of stray current was approximately equal to the headway, and the waveform change lagged behind the rail-to-ground voltage. The fluctuation degree of ground potential gradient was obviously affected by the length of power supply interval and train operation conditions.

ZnO varistor ceramics with a high potential gradient, as well as a high nonlinear coefficient, were reported and analyzed in this paper. With the use of nano-sized ZnO powders, the average grain size was reduced to about 2.6 μm, which successfully raised the potential gradient to 1172 V/mm. Moreover, the nonlinear coefficient increased to 48, and the leakage current was decreased to 8.4 μA/cm2 by doping a moderate amount of MnO (0.9 mol%). This was proven to be caused by the high Schottky barrier height formed at the grain boundary, where the Mn element segregated and, consequently, led to the increased density of interface states. Therefore, this could be considered as a potential method to simultaneously enhance the potential gradient and the nonlinear coefficient of ZnO varistor ceramics.

This paper presents an analysis of recorded variations (anomalies) in the potential gradient of electrical field in the atmosphere caused by the propagation of eruption plumes discharged by eruptions of Shiveluch and Bezymianny volcanoes in Kamchatka. The anomalies were recorded at various distances from eruption centers and under different conditions of atmospheric stratification. These conditions have enabled us to show that the eruption plumes of Shiveluch and Bezymianny possessed a 3D electrostatic structure that is consistent with a known phenomenological model derived on the basis of surveys conducted on various volcanoes worldwide. According to this model, the top of an eruption plume contains a positive volumetric electrostatic charge, while the respective charges are negative in the middle, and positive in the lower part of the plume.

Neutral zinc‐air batteries (ZABs) are promising candidates for the next‐generation power devices with considerably elongated lifetime comparing to conventional alkaline ZABs. However, neutral cathodic oxygen reduction reaction (ORR) is seriously limited by the mass transfer efficiency of hydroxyl due to insufficient interfacial chemical potential‐gradient between catalytic layer and electrolyte. Herein, we highlight that electrochemical oxidation‐induced surface microenvironment optimization could realize optimal chemical potential‐gradient around catalytic sites and bring outstanding neutral ORR activity. The electrodeposited sub‐nano Pt decorated surface‐microenvironment‐optimized Co2N samples (denoted as Pt‐SMO‐Co2N NWs) possessed 92 and 338 mV higher half‐wave potential than commercial Pt/C and pristine Co2N in 0.2 M PBS. As for neutral ZABs, Pt‐SMO‐Co2N NWs cathode delivers a power density of 67.9 mW*cm−2 and displays negligible decay after nearly 80 h stability test at 20 mA*cm−2. In‐depth characterization proposes that remarkable performance improvement originates from optimized microenvironment, which increases the surface chemical potential gradient and facilitates proton coupled electron transfer during ORR. We anticipated that such synergetic optimization of microenvironment and intrinsic activity of active sites is an effective strategy which may be extended to the catalytic reactions beyond ORR. Key points We demonstrated surface microenvironment optimization via in‐situ electrochemical oxidation as an effective way to design highly active ORR catalysts. Surface microenvironment optimization realized significantly enhanced ORR and Zn‐air battery performance in neutral media. Based on ideal material platform, the key role of activating H2O and facilitating proton transfer process in ORR catalysis was revealed. Microenvironment optimization via in‐situ electrochemical oxidation realizing significantly enhanced neutral ORR performance and revealing the key role of activating H2O and facilitating proton transfer process in ORR catalysis.

In order to improve the mechanical system performances such as wear resistance and vibration damping behavior, it was focused on the micro-topography of the surface machined by electro-chemical mechanical finishing (ECMF) in this paper. The ECMF was applied in this investigation as a result of it providing more controllable process parameters including the electric potential gradient (EPG), current density, mechanical force, and passive film. The simulation based on the finite element method was applied to analyze the influence of the EPG and the current density on the surface micro-topography under the different magnitudes of mechanical pressure and thicknesses of the passive film. It was shown that the mechanical pressure and the mass percent of the electrolyte which had been controlled are profitable and necessary to gain the feature of arc-like micro-topography on the surface and the growth in material removal rate. The unusual micro-topography of the surface with Ra0.2024μm was finished by using ECMF within 2 min on the condition of 20% NaNO 3 electrolyte and 0.2 MPa of mechanical pressure. The investigation on dynamic pressure effect was carried out to confirm the influence of the unusual micro-topography on the thickness in the oil film. The result indicated that compared with the surface machined by fine grinding (FG), the surface finished by ECMF can make an increase in the average film thickness of 3% and a reduction in the square deviation of 46.5%. A discussion was set up to determine the cause of the difference in the results of the experiment. It was shown that the reason for the difference is the distinction in the micro-topography of the surface obtained by ECMF and FG. The micro-topography of the surface finished by ECMF is more favorable to establish a stranger and stable dynamic pressure effect as the result of its fractal dimension, scale coefficient, kurtosis and skewness. The discussion indicated that the finish method impacts the surface topography, and the machining accuracy affects the cross-scale effect of the surface dynamic pressure effect.

Water availability is a major constraint for crop production in semiarid environments. The impact of tillage practices on water potential gradient, water transfer resistance, yield, and water use e ciency (WUEg) of spring wheat was determined on the western Loess Plateau. Six tillage practices implemented in 2001 and their e ects were determined in 2016 and 2017 including conventional tillage with no straw (T), no-till with straw cover (NTS), no-till with no straw (NT), conventional tillage with straw incorporated (TS), conventional tillage with plastic mulch (TP), and no-till with plastic mulch (NTP). No-till with straw cover, TP, and NTP significantly improved soil water potential at the seedling stage by 42, 47, and 57%, respectively; root water potential at the seedling stage by 34, 35, and 51%, respectively; leaf water potential at the seedling stage by 37, 48, and 42%, respectively; tillering stage by 21, 24, and 30%, respectively; jointing stage by 28, 32, and 36%, respectively; and flowering stage by 10, 26, and 16%, respectively, compared to T. These treatments also significantly reduced the soil–leaf water potential gradient at the 0–10 cm soil depth at the seedling stage by 35, 48, and 35%, respectively, and at the 30–50 cm soil depth at flowering by 62, 46, and 65%, respectively, compared to T. Thus, NTS, TP, and NTP reduced soil–leaf water transfer resistance and enhanced transpiration. Compared to T, the NTS, TP, and NTP practices increased biomass yield by 18, 36, and 40%; grain yield by 28, 22, and 24%; and WUEg by 24, 26, and 24%, respectively. These results demonstrate that no-till with straw mulch and plastic mulching with either no-till or conventional tillage decrease the soil–leaf water potential gradient and soil–leaf water transfer resistance and enhance sustainable intensification of wheat production in semi-arid areas.

The spectral response of atmospheric electric potential gradient gives important information about phenomena affecting this gradient at characteristic time scales ranging from years (e.g., solar modulation) to fractions of a second (e.g., turbulence). While long-term time scales have been exhaustively explored, short-term scales have received less attention. At such frequencies, space-charge transport inside the planetary boundary layer becomes a sizeable contribution to the potential gradient variability. For the first time, co-located (Évora, Portugal) measurements of boundary-layer backscatter profiles and the 100-Hz potential gradient are reported. Five campaign days are analyzed, providing evidence for a relation between high-frequency response of the potential gradient and strong dry convection.

The oxygen permeability of polycrystalline α-alumina wafers, which served as model alumina scales formed on heat-resistant alloys, was evaluated at a temperature of 1873 K. Mass transfer along grain boundaries (GBs) in an alumina wafer exposed to a large oxygen potential gradient (dμO), where both oxygen and aluminum mutually diffuse along GBs, was analyzed using 18O2 and SIMS. 18O was concentrated at GB ridges on the high oxygen partial pressure (PO2(hi)) surface and along the GBs near the PO2(hi) surface. 18O adsorbed on the surface diffused almost immediately to surface GBs, resulting in the formation of new alumina by reaction with aluminum diffusing outward along the GBs. Oxygen GB diffusion coefficients in the vicinity of the PO2(hi) surface were determined from the 18O depth profile along each GB for the 18O map of the cross section of the exposed alumina wafer. The oxygen GB diffusion coefficients were comparable to the values calculated from the oxygen permeability constants assuming an electronic conductivity and were obviously lower than those of oxygen GB self-diffusion without an oxygen potential gradient.

The potential gradient method is proposed for system scalability of pulsed power networks. The pulsed power network is already proposed for the seamless integration of distributed generations. In this network, each power transmission is decomposed into a series of electric pulses located at specified power slots in consecutive time frames synchronized over the network. Since every power transmission path is pre-reserved in this network, distributed generations can transmit their power to individual consumers without conflictions among other paths. In the network operation with a potential gradient method, each power source selects its target consumer that has the maximum potential gradient among others. This gradient equals the division of power demand of the consumer by the distance to its location. Since each of the target consumer selection is shared by power routers within the power transmission path, the processing load of each system component is kept reasonable regardless of the network volume. In addition, a large-scale power grid is autonomously divided into soft clusters, according to the current system status. Owing to these properties, the potential gradient method brings the system scalability on pulsed power networks. Simulation results are described that confirm the performance of soft clustering.