Mechanism of the Large Surface Deformation Caused by Rayleigh-Taylor Instability at Large Atwood Number

Studying the dynamical behaviors of the liquid spike formed by Rayleigh-Taylor instability is important to understand the mechanisms of liquid atomization process. In this paper, based on the information on the velocity and pressure fields obtained by the coupled-level-set and volume-of- fluid (CLSVOF) method, we describe how a freed spike can be formed from a liquid layer under falling at a large Atwood number. At the initial stage when the surface deformation is small, the amplitude of the surface deformation increases exponentially. Nonlinear effect becomes dominant when the amplitude of the surface deformation is comparable with the surface wavelength (~0.1λ). The maximum pressure point, which results from the impinging flow at the spike base, is essential to generate a liquid spike. The spike region above the maximum pressure point is dynamically free from the bulk liquid layer below that point. As the descending of the maximum pressure point, the liquid elements enter the freed region and elongate the liquid spike to a finger-like shape.

Rising grain prices in response to phased climatic change during 1736–1850 in the North China Plain

Grain price volatility during historical periods is regarded as an important indicator of the impact of climate change on economic system, as well as a key link to adjust food security and social stability. The present study used the wheat prices in Baoding Prefecture, China, during 1736–1850 to explore connections between climatic transition and grain price anomalies in the North China Plain. The main findings were as follows:(1) The grain price change showed an apparent correspondence with climatic transition. The period 1781–1820 was a transition phase, with more extremes and decreased precipitations when the climate shifted from a warm phase to a cold one. Corresponding with the climatic transition, the grain price during 1781–1820 was characterized by that the mean of the original grain price series was significantly higher(lower) than the previous(later)phase, and the variance and anomaly amplitude of the detrended grain price series was the highest during 1736–1850.(2) The correspondence between grain price extremes and drought events occurred in phases. Five grain price extremes occurred following drought events during 1781–1810, while extreme droughts were the direct cause of the grain price spike during 1811–1820.(3) Social stability affected by climate change also played an important role in the grain price spike between 1811 and 1820. Paralleling the pathway of "precipitation-grain production-grain price", climate change could have an impact on grain price via the pathway of "precipitation-grain production-grain price-famine-uprising-grain price", as shown during the Tianli Uprising in 1813. These findings could contribute to an improved understanding of the interaction between climate change and human society during the historical period.

Value Evaluation Method for Pumped Storage in the New Power System

When integrating the generation of large-scale renewable energy,such as wind and solar energy,the supply and demand sides of the new power system will exhibit high uncertainty.Pumped storage power stations can improve flexible resource supply regulation in the power system,which is the key support and important guarantee for building low-carbon,safe,and efficient new power systems.Limited by the current operation mode and electricity price mechanism,the pumped storage power station cost cannot be effectively recovered,and the value cannot be reasonably compensated,resulting in difficult return on investment,single investment subjects,and notable industry development difficulties.According to the operational requirements of the new power system,combined with the various functions of pumped storage power stations,the value of pumped storage power stations in the new power system was analyzed.Based on the equivalent value substitution principle and system operation simulation,a pumped storage value evaluation method for the new power system was proposed.The new power system operation was simulated considering the dispatching model of wind and photovoltaic power abandonment penalties.Under the same dispatching objectives,the output of various power sources and power generation operating costs with and without pumped storage power stations in the system were compared.From economic,safety,social,and environmental benefit perspectives,a quantitative model of the pumped storage power station value was established,covering seven dimensions:asset investment savings,power generation operating cost reduction,flexible adjustment capability improvement,system resilience enhancement,power outage loss reduction,renewable energy consumption,and emission reduction promotion.Based on the new power system operation and planning data for southern China,the value of typical pumped storage power stations was analyzed,and the results showed that with new power system’s construction and development,the value of pumped storage power stations is increasing,and the value structure is closely related to power grid characteristics.This value evaluation method could provide references for pumped storage investment decisions,subsidy policies,and price mechanisms to fully utilize the role of pumped storage power stations and promote high-quality development of new power systems.

Survival outcomes of conversion surgery for metastatic pancreatic ductal adenocarcinoma after neoadjuvant therapy

Objective:To evaluate the survival outcomes of patients who underwent conversion surgery for metastatic pancreatic ductal adenocarcinoma(mPDAC)after neoadjuvant therapy(NAT)and to identify potential candidates that may benefit from this treat-ment strategy.Background:The role and eligibility population of conversion surgery for mPDAC remains controversial in the era of NAT.Methods:A consecutive cohort of patients diagnosed with mPDAC and treated with NAT followed by conversion surgery be-tween 2019 and 2021 were confirmed from a prospective database maintained by the Department of Pancreatic Hepatobiliary Surgery of Changhai Hospital.In accordance with residual metastases and technical resectability after NAT,patients were classi-fied as the complete pathological response of metastases(ypM0)resection group,residual metastases(ypM1)resection group,and exploration group.Median overall survival(mOS)was calculated using the Kaplan-Meier method,uni-and multivariable cox regression was performed to identify clinicopathological predictors of OS.Results:A total of 244 patients with mPDAC were identified from the prospective database,with 19(7.8%)patients who un-derwent ypM0 resection,22(9.0%)underwent ypM1 resection,and 23(9.4%)underwent explorative laparotomy.The mOS was 32.6 months for ypM0 resected patients,15.1 months for ypM1 resected patients,and 13.4 months for those who underwent explorative laparotomy(P<.001).Univariable and multivariable Cox regression analyses confirmed that ypM0 resection,normal-ization of preoperative CA19-9 levels,and continued adjuvant therapy were independent prognostic factors of conversion surgery for mPDAC after NAT.Subgroup analyses revealed that oligometastases and continued adjuvant therapy were associated with improved prognosis in the ypM1 resection group.Conclusion:In patients with mPDAC who underwent NAT followed by conversion surgery,the complete pathological response of metastases,normalization of preoperative CA19-9 levels,and continued adjuvant therapy were independent risk factors for prognosis.Patients with residual oligometastases after treatment were expected to prolong survival through resection.These patients may benefit from conversion surgery and should be potential candidates for this treatment strategy.