铜仁学院

Despite rapid expansion of farmland transfer in rural China, the quality of contractual governance often fails to keep pace, raising the question of whether spatial consolidation arrangements can promote more complete contract terms. This study examines how coordinated land transfer promotes the standardization of farmland rental contracts within China’s three-rights separation framework. Drawing on primary household survey data from 1101 farming households across four counties in Guizhou Province, this study documents a robust positive relationship between the degree of spatial contiguity in transfer arrangements and the level of contract standardization. Mediation analysis applying the KHB decomposition method reveals that this effect is transmitted primarily through two operational channels: economies of scale and technology adaptation through mechanization adoption. Heterogeneity analysis further reveals that the standardization effect concentrates among operators with greater financial capacity, in regions with stronger market connectivity and irrigation infrastructure, and in villages where collective governance is comparatively weak.

Abstract Biochar applied in ecological restoration shows a significant dose-dependent effect. Therefore, determining an appropriate rate for specific environments is essential in practical applications. To this end, we integrated soil profiles and biogeochemical and microbiome datasets from six major ecosystems (agricultural, grassland, forest, coastal wetlands, desert, and polar tundra), constructed a global biochar remediation threshold map, and investigated the driving mechanisms of threshold formation. Simultaneously, differentiated application frequency strategies tailored to each ecosystem are proposed. The results showed that the appropriate thresholds for different ecosystems were 5–30 t ha−1 (agricultural), 5–40 t ha−1 (grassland), 5–40 t ha−1 (forest), 10–50 t ha−1 (coastal wetlands), 10–40 t ha−1 (desert), and 20–60 t ha−1 (polar tundra). Within the threshold range, in combination with customized application frequency, biochar enhances ecological functions by increasing soil water-holding capacity (by approximately 10–14.3%), reducing greenhouse gas emissions (by approximately 16.4–31.5%), lowering soil heavy metal content, and increasing soil organic matter. Exceeding the threshold can cause sharp fluctuations in soil pH, increases in bioavailable polycyclic aromatic hydrocarbons, and decreases in microbial diversity, thereby inhibiting remediation. Inadequate application frequency also weakens the ecological restoration efficacy of biochar. The thresholds are environmentally dependent. The threshold window can be expanded or narrowed by the joint regulation of preparation parameters, soil characteristics, climate, and human management. Based on this, we propose a framework of “threshold identification–mechanism analysis–targeted intervention” and customized application paths for ecosystems (e.g., on-farm biochar + fertilizer single/strip application, low-dose staged application in grassland, forest low-dose dispersal single intervention, combination of wetland surface and spot combined with seasonal application, desert inter-root precision single application, and zoned management of medium and low doses in polar regions). The framework provides a quantitative and mechanistic basis for formulating standards for the production and application of biochar and for promoting precise remediation. Graphical Abstract

A series of 2-(2-hydroxyphenyl)benzothiazole derivatives with different hydroxyl substituent positions were synthesized, and their solubility in 1 M HCl solution was preliminarily evaluated; moreover, the corrosion inhibition performance of two derivatives with good solubility (DH4 and DH5) on mild steel was studied in detail. A multi-methodological approach was employed, including ultraviolet-visible (UV-vis) spectroscopy, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), weight loss measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), density functional theory (DFT), and molecular dynamics (MD) simulations. Among the four derivatives examined, DH5 showed the highest solubility, whereas DH4 exhibited the most effective inhibition performance. In contrast, DH3 and DH6 demonstrated both poor solubility and inferior corrosion inhibition. Adsorption isotherm modeling based on electrochemical data indicated that the protective behavior of DH4 and DH5 followed the El-Awady model. Quantum chemical calculations suggested that the position of the hydroxyl group influences the intramolecular hydrogen bonding strength, which may regulate solubility in acidic media. Molecular dynamics simulations further corroborated the distinction in corrosion inhibition efficacy between DH4 and DH5. This work underscores the critical role of hydroxyl substituent positioning in determining the solubility and corrosion inhibition performance of benzothiazole derivatives in hydrochloric acid solution.

Background: Corrosion inhibitors play a crucial role in protecting metals during acid pickling processes. Developing environmentally friendly and efficient inhibitors with high inhibition performance and thermal stability remains of significant interest. Methods: In this study, Daucus carota var. sativa Hoffm extract was prepared using a water extraction method and investigated as a green corrosion inhibitor for a copper-nickel alloy in H2SO4 solution. The inhibition mechanism was systematically studied using electrochemical measurements, adsorption isotherm analysis, surface morphology characterization (SEM and AFM), XPS analysis, quantum chemical calculations, and molecular dynamics simulations. Significant findings: Electrochemical tests revealed that the extract achieved a maximum corrosion inhibition efficiency exceeding 97% at a concentration of 800 mg/L, and the inhibition efficiency remained above 95% with increasing temperature, demonstrating excellent thermal stability. Surface morphology analyses confirmed that the adsorption of the extract significantly reduced corrosion damage on the alloy surface. Adsorption isotherm analysis showed that the extract followed a Langmuir monolayer adsorption model, involving both physical and chemical adsorption processes. XPS results confirmed the formation of N-Cu bonds, indicating stable chemical adsorption between the active components of the extract and the copper surface. Furthermore, quantum chemical calculations and molecular dynamics simulations demonstrated that the main active constituents of the extract exhibit strong corrosion inhibition potential, consistent with the experimental observations. The combined experimental and theoretical results confirm that Daucus carota var. sativa Hoffm extract is an efficient and thermally stable green corrosion inhibitor for copper-nickel alloys in acidic media.

An adaptive moving grid method is developed to solve the time-fractional integrodifferential governing equations of viscoelastic nanofluid. The momentum equation is derived based on a dual-parameter fractional Maxwell constitutive relation, and the energy equation employs a generalized Cattaneo heat conduction relation. To improve solution accuracy, a monitor function based on the equidistribution principle is constructed, and an adaptive mesh redistribution strategy is developed in the spatial domain. The temporal fractional-order operators are approximated by the L1 algorithm and the weighted-shifted Grunwald difference method. Numerical experiments demonstrate that the adaptive grid achieves 77.6-88.4% higher accuracy compared to uniform grids at the same grid scale, along with enhanced stability in convergence. Parametric analysis indicates that increasing the fractional-order derivative in the energy equation results in a thickening of both the velocity and thermal boundary layers. Furthermore, the dual-fractional Maxwell model exhibits a thicker velocity boundary layer than its classical single-parameter counterpart. The proposed method offers an efficient and robust approach for simulating complex viscoelastic nanofluid systems with memory effects and multi-field coupling.