This paper focuses on the long wavelength limit for the Euler-Poisson system arising in plasma including three species in three dimensional case. The goal here is to deduce rigorously the modified Korteweg-de Vries-ZK (mKdV-ZK) equation, under the Gardner-Morikawa transform epsilon 1/2(x1-Vt) -> x1, epsilon 1/2x2 -> x2, epsilon 1/2x3 -> x3, epsilon 3/2t -> t, as epsilon -> 0. By employing delicate energy method, we give uniform in epsilon estimate for the error between the mKdV-ZK equation and the Euler-Poisson system.
The Western Pacific Coasts (WPC) are the outlets of many large Asian rivers. In recent years, the interplay of climate changes and human activities has persistently altered the suspended sediment concentrations (SSC) in the WPC, triggering substantial shifts in coastal ecosystems. However, the scarcity of coastal observation stations hampered comprehensive investigations at large scales. This study employed three representative SSC retrieval models and utilized Landsat images acquired from 1990 to 2020 to estimate the SSC in the WPC with a focused endeavor to dissect the intricate spatial and temporal variability of SSC in the region. The findings revealed the following insights: (1) The outcomes derived from the three distinct SSC models consistently manifested a discernible decreasing pattern in SSC changes over the past three decades across all six major estuaries (Liao River Estuary, Yellow River Estuary, Yangtze River Estuary, Hangzhou Bay, Pearl River Estuary, and Mekong River Estuary). (2) The seasonal attributes of the six major estuaries differed, primarily due to distinct dominant influencing factors like precipitation, upstream sediment load, wind, and tides. (3) Collectively, SSC tends to be relatively higher in the Yangtze River Estuary, Hangzhou Bay, and Yellow River Estuary, while the Pearl River and Mekong River Estuaries exhibit relatively lower levels. Notably, the SSC exhibited distinct spatial traits along the coastlines of different estuaries. (4) SSC in the non-estuarine regions along the WPC, a similar significant declining trend in SSC is observed as in the estuaries, albeit the rate of decline generally appeared to be less pronounced. Furthermore, regions with faster rates of SSC reduction are typically concentrated near major estuaries in the northern part of the Coasts. The decline in estuarine SSC plays an important role in the overall decrease in SSC across the WPC. These study outcomes held substantial significance for advancing the stability and sustainable evolution of the WPC.
人口作为社会经济的重要指标,对城市韧性及可持续发展研究具有重要意义.国内外研究团队利用多源地理遥感数据已然研制了不同的全球人口空间化的数据产品.然而,受限于真实人口统计调查数据的长周期性和人口分布空间的复杂性,现有产品对于模拟国家级人口空间分布的实际准确度并未得到充分验证.本研究利用不同年份的人口普查数据与对应年份的现有4种人口空间数据集(GPW、Landscan、Worldpop、Cnpop)进行验证及评价.结果显示,4种不同人口产品对于模拟我国2010年和2015年区县级人口的总体精度均达到75％以上.其中,Worldpop和Cnpop数据产品对于模拟我国2010年的人口空间分布更精确,而World-pop 和Landscan产品对于模拟我国2015年的人口空间分布效果更优.同时,研究还发现,Worldpop数据产品对于模拟我国高密度人口地区,特别是城乡过渡带总体精度较高,即更加适宜于城市区域的相关研究.本研究为学界合理选择和使用不同人口空间化产品,以提高研究成果的精确度和针对性提供了重要参考.
登革热是由登革病毒经蚊媒传播引发的一种急性传染病,目前一种新型的生物控制策略是向野外释放感染Wolbachia的蚊子,这种蚊子能够有效抑制登革热病毒在人群之间的传播.基于经典的Beverton-Holt模型,文章假设在完全CI的条件下,建立一个具有世代重叠的扩展的Beverton-Holt模型,研究在4种不同的释放策略下该模型的动力学行为.通过应用差分方程稳定性与分支理论,证明该模型平衡点的存在性条件、稳定性性态和吸引域,成功找到了Wolbachia在野生蚊子种群中成功传播的释放阈值r*,并且当r=r*时,模型存在一个鞍结点分支,最后利用数值模拟证明所得出的结论.
近年来,智能合约已广泛应用于去中心化金融、供应链管理等领域.然而,智能合约漏洞给这些领域造成了严重的损失,由于智能合约部署在区块链上以后无法修改,开发人员写好智能合约后必须检测其安全性.现有的基于深度学习的检测方法大多使用字节码和源码,然而,基于字节码的检测方法无法定位到漏洞可能出现的位置且直接检测向量化源码准确率低.为了提高漏洞检测的准确率,增加检测结果的可解释性,文章提出了基于源码语义结构分析的智能合约漏洞检测方法.首先,将智能合约源代码转化为抽象语法树,研究源代码和抽象语法树的语法关系;其次,通过对以太坊中合约的抽象语法树属性特征和漏洞特性进行分析,发现5种漏洞相关属性特征,并围绕这些节点特征将抽象语法树进行切片,得到与漏洞特性相关的子树切片;最后,提取子树切片的结构特征和属性特征,并将其表示为图结构.使用具有更好图表示能力的图同构网络模型检测子树切片的图结构并利用33 812个以太坊上的智能合约进行实验,实验结果表明,文章所提出的方法有效性显著高于其他方法,Macro-F1超过90％,未检查返回值和重入这两种漏洞的F1-score分别达到97％和 92％.
