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The high-frequency pulse flow, equivalent to the natural frequency of rocks, is generated by a self-excited oscillating cavity to achieve resonance rock-breaking. The flow field and oscillating mechanism of the self-excited oscillating cavity were simulated using the large eddy simulation method of Computational Fluid Dynamics (CFD). A field-scale testing apparatus was developed to investigate the impulse characteristics and verify the simulation results. The results show that the fluid at the outlet at the tool is deflected due to the pulse oscillation of the fluid. The size and shape of low-pressure vortices constantly change, leading to periodic changes in fluid impedance within the oscillating cavity. The impulse frequency reaches its highest point when the length–diameter ratio is 0.67. As the length–diameter ratio increases, the tool pressure loss also increases. Regarding the cavity thickness, the impulse frequency of the oscillating cavity initially decreases, then increases, and finally decreases again. Moreover, both the impulse frequency and pressure loss increase with an increase in displacement. The numerical simulation findings align with the experimental results, thus confirming the validity of the theoretical model. This research provides theoretical guidance for the practical application of resonance rock-breaking technology. [ABSTRACT FROM AUTHOR]

The development of agriculture faces uncertainties due to global climate variability and the scarcity of agricultural resources. Enhancing agricultural development resilience is essential for improving agriculture's adaptability to the external environment and ensuring food security. It is imperative to prevent and control agricultural pollution as it worsens. Thus, enhancing the resilience of agricultural development requires balancing food security and ecological security. The present study constructs an evaluation system for agricultural development resilience in China with three levels: resistance, resilience, and reengineering ability. The agricultural development resilience of China's main grain-producing areas is evaluated using the entropy method, and regional differences are analyzed using kernel density estimation and the Theil index. The obstacle model was used to identify and analyze the obstacles that affect agricultural development's resilience to propose countermeasures. The results showed that (1) agricultural development resilience in China's main grain-producing areas has steadily increased from 0.317 to 0.427. The resilience of agrarian development in Heilongjiang, Shandong, and Henan provinces ranges from 0.473 to 0.575, which is far higher than the mean development level; (2) Regional differences in the main grain-producing areas are narrowing from 0.077 to 0.023; (3) The main grain-producing areas share common obstacle factors, emphasizing the critical role of technological innovation, investment, and machine-cultivated land resources in enhancing agricultural resilience against external risks. Paying attention to the amount of fertilizer usage is crucial to achieving ecological security goals. [ABSTRACT FROM AUTHOR]