Evaluation and driving factors analysis of agricultural green development level in Beijing from 1978 to 2022

Agricultural green development (AGD) plays an important role in achieving a sustainable society. This paper evaluates the AGD level of Beijing from 1978 to 2022 by means of a comprehensive evaluation method, coupling coordination degree (CCD), and grey relational degree model (GRA) with the purpose of exploring relevant stages and characteristics, as well as analyzing the characteristics of different stages and the coupling relationship of various factors and quantitatively calculating the driving factors for AGD change. The results showed that: 1) the AGD level of Beijing generally improved from 1978 to 2022, mainly involving four stages of steady rising, fluctuating, oscillating decreasing, and rapid upgrading; 2) the CCD of the development subsystems of AGD, agricultural resource utilization, agricultural environment conditions, agricultural industry development, and farmers’ living standard, all rose and the coordination type of each subsystem gradually went through a verge imbalance stage, reluctantly coordinated stage, and primary coordinated stage to an intermediate coordinated stage, and then reached a well-coordinated stage in 2019; 3) the AGD level of Beijing is influenced by economic development, the industrial structure, urbanization, technological progress, and agricultural structure. Finally, some policy suggestions to promote AGD in Beijing are put forward. This paper is of great significance to promoting the green and sustainable development of agriculture in Beijing and provides technical support and policy guidance for AGD in other regions

Material Removal Mechanism and Force Model of Nanofluid Minimum Quantity Lubrication Grinding

Numerous researchers have developed theoretical and experimental approaches to force prediction in surface grinding under dry conditions. Nevertheless, the combined effect of material removal and plastic stacking on grinding force model has not been investigated. In addition, predominant lubricating conditions, such as flood, minimum quantity lubrication (MQL), and nanofluid minimum quantity lubrication (NMQL), have not been considered in existing force models. In this study, material removal mechanism under different lubricating conditions was researched. An improved theoretical force model that considers material removal and plastic stacking mechanisms was presented. Grain states, including cutting and ploughing, are determined by cutting efficiency (β). The influence of lubricating conditions was also considered in the proposed force model. Simulation was performed to obtain the cutting depth (a g) of each “dynamic active grain.” Parameter β was introduced to represent the plastic stacking rate and determine the force algorithms of each grain. The aggregate force was derived through the synthesis of each single-grain force. Finally, pilot experiments were conducted to test the theoretical model. Findings show that the model’s predictions were consistent with the experimental results, with average errors of 4.19% and 4.31% for the normal and tangential force components, respectively

Existence of positive solutions for nonlinear four-point Caputo fractional differential equation with p-Laplacian

Abstract In this article, the existence of positive solutions is considered for nonlinear four-point Caputo fractional differential equation with p-Laplacian operator. We use the monotone iterative technique to acquire the existence of positive solutions for the boundary value problem and get iterative schemes for approximating the solutions. An example is also presented to illustrate the effectiveness of the main results

Water-Scarcity Footprint Associated with Crop Expansion in Northeast China: A Case Study Based on AquaCrop Modeling

In recent decades, China’s crop production experienced a spatial shift, and this shift may significantly influence the national water resources due to the geographical mismatch between water resources and cropland. By applying the widely applied AquaCrop model, this study quantified the impact of grain crop (rice and maize) expansion in northeastern China on the country’s water resources. We found that the production of rice and maize increased by 60% and 43%, respectively, in the northeast, whereas the water scarcity-footprint (WSF) increased by 200% and 125%. Using sensitivity analysis, we found that the increase in the WSF was mainly caused by the increase in regional water scarcity, as reflected by a water scarcity index, and by the increase in production. To alleviate regional water scarcity, crop expansion into regions that experience high water stress should be constrained. A detailed reassessment of this situation is urgently needed

Evaluation of the Potential for Territorial Ecological Restoration: A Case Study of Zhaoping County, China

Territorial ecological restoration (TER) is a critical step for promoting the development of an ecological civilization, as well as a significant strategic task relating to national ecological security and the well-being of a population. However, calculating the ecological restoration potential (ERP) is a key challenge in TER. Using Zhaoping County as an example, this study calculated the ecological restoration natural potential (ERNP), including the vegetation coverage potential, water conservation potential, windbreak and sand fixation potential, and biodiversity potential, and proposed an ERP calculation method based on the correction of ERNP with an ecological security pattern (ESP) and social support (SS). The findings revealed several key points. First, using the similarity habitat method to calculate ERNP highlighted significant disparities in the vegetation coverage, water conservation, windbreak and sand fixation, and biodiversity across Zhaoping County. These variations were contrary to regional ecological service functions. Second, overall, the ESP levels in Zhaoping County were high, accounting for about 60.42% of its total area being classified as high or relatively high level, with the towns exhibiting strong SS abilities primarily located in the northern region. Third, the ERP results which are between 0 and 1 indicated that areas with higher potential were mainly found in the west and northeast of Zhaoping, while lower potential areas were concentrated in the northwest and south; of them, the ERP index value in most regions is between 0.2 and 0.3, accounting for about 43.97% of the area. Finally, suggestions for the TER project layout and measures to enhance the ERP were proposed based on these ERP calculations. This study offers new insights into ERP strategies while providing guidance for identifying critical areas requiring restoration

Strain Control of the Tunable Physical Nature of a Newly Designed Quaternary Spintronic Heusler Compound ScFeRhP

Recently, an increasing number of rare-earth-based equiatomic quaternary compounds have been reported as promising novel spintronic materials. The rare-earth-based equiatomic quaternary compounds can be magnetic semiconductors (MSs), spin-gapless semiconductors (SGSs), and half-metals (HMs). Using first-principle calculations, we investigated the crystal structure, density of states, band structure, and magnetic properties of a new rare-earth-based equiatomic quaternary Heusler (EQH) compound, ScFeRhP. The results demonstrated that ScFeRhP is a HM at its equilibrium lattice constant, with a total magnetic moment per unit cell of 1 μB. Furthermore, upon introduction of a uniform strain, the physical state of this compound changes with the following transitions: non-magnetic-semiconductor-(NMS) → MS → SGS → HM → metal. We believe that these results will inspire further studies on other rare-earth-based EQH compounds for spintronic applications

Palladium (III) Fluoride Bulk and PdF3/Ga2O3/PdF3 Magnetic Tunnel Junction: Multiple Spin-Gapless Semiconducting, Perfect Spin Filtering, and High Tunnel Magnetoresistance

Spin-gapless semiconductors (SGSs) with Dirac-like band crossings may exhibit massless fermions and dissipationless transport properties. In this study, by applying the density functional theory, novel multiple linear-type spin-gapless semiconducting band structures were found in a synthesized R 3 − c -type bulk PdF3 compound, which has potential applications in ultra-fast and ultra-low power spintronic devices. The effects of spin-orbit coupling and on-site Coulomb interaction were determined for the bulk material in this study. To explore the potential applications in spintronic devices, we also performed first-principles combined with the non-equilibrium Green’s function for the PdF3/Ga2O3/PdF3 magnetic tunnel junction (MTJ). The results suggested that this MTJ exhibits perfect spin filtering and high tunnel magnetoresistance (~5.04 × 107)