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D^2EA:Depict the Epidemic Picture of COVID-19 被引量:1
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作者 LIU Chenzhengyi ZHAO Jingwei +2 位作者 LIU Guohang GAO Yuannin GAO Xiaofeng 《Journal of Shanghai Jiaotong university(Science)》 EI 2020年第2期165-176,共12页
The outbreak of coronavirus disease 2019(COVID-19)has aroused a global alert.To release social panic and guide future schedules,this article proposes a novel mathematical model,the Delay Differential Epidemic Analyzer... The outbreak of coronavirus disease 2019(COVID-19)has aroused a global alert.To release social panic and guide future schedules,this article proposes a novel mathematical model,the Delay Differential Epidemic Analyzer(D2EA),to analyze the dynamics of epidemic and forecast its future trends.Based on the traditional Susceptible-Exposed-Infectious-Recovered(SEIR)model,the D2EA model innovatively introduces a set of quarantine states and applies both ordinary differential equations and delay differential equations to describe the transition between two states.Potential variations of practical factors are further considered to reveal the true epidemic picture.In the experiment part,we use the D^2EA model to simulate the epidemic in Hubei Province.Fitting to the collected real data as non-linear optimization,the D^2EA model forecasts that the accumulated confirmed infected cases in Hubei Province will reach the peak at the end of February and then steady down.We also evaluate the effectiveness of the quarantine measures and schedule the date to reopen Hubei Province. 展开更多
关键词 CORONAVIRUS disease 2019(COVID-19) EPIDEMIC model QUARANTINE states Susceptible-Exposed-Infectious-Recovered(SEIR) delay differential equation non-linear optimization
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Python实现简单的Web服务器 被引量:1
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作者 叶子平 高远 刘聪 《电脑编程技巧与维护》 2017年第1期76-76,87,共2页
研究利用Python实现简单的Web服务器功能,并加深对于HTTP等协议的理解。给出了该Web服务器的建立和改进的实现过程,研究HTTP协议和Web服务的基本原理,给出了Python实现Web服务请求、响应、错误处理及CGI协议,并给出了运行结果。
关键词 WEB系统 PYTHON语言 CGI协议
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CIRD-F:Spread and Influence of COVID-19 in China
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作者 ZHOU Lingyun WU Kaiwei +2 位作者 LIU Hanzhi GAO Yuanning GAO Xiaofeng 《Journal of Shanghai Jiaotong university(Science)》 EI 2020年第2期147-156,共10页
The outbreak of coronavirus disease 2019(COVID-19)has been spreading rapidly in China and the Chinese government took a series of policies to control the epidemic.Therefore,it will be helpful to predict the tendency o... The outbreak of coronavirus disease 2019(COVID-19)has been spreading rapidly in China and the Chinese government took a series of policies to control the epidemic.Therefore,it will be helpful to predict the tendency of the epidemic and analyze the influence of official policies.Existing models for prediction,such as cabin models and individual-based models,are either oversimplified or too meticulous,and the influence of the epidemic was studied much more than that of official policies.To predict the epidemic tendency,we consider four groups of people,and establish a propagation dynamics model.We also create a negative feedback to quantify the public vigilance to the epidemic.We evaluate the tendency of epidemic in Hubei and China except Hubei separately to predict the situation of the whole country.Experiments show that the epidemic will terminate around 17 March 2020 and the final number of cumulative infections will be about 78191(prediction interval,74872 to 82474).By changing the parameters of the model accordingly,we demonstrate the control effect of the policies of the government on the epidemic situation,which can reduce about 68%possible infections.At the same time,we use the capital asset pricing model with dummy variable to evaluate the effects of the epidemic and official policies on the revenue of multiple industries. 展开更多
关键词 CORONAVIRUS disease 2019(COVID-19) EPIDEMIC prediction MODEL negative feedback CAPITAL ASSET pricing MODEL DUMMY variable
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基于中间层的可扩展学习索引技术 被引量:14
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作者 高远 叶金标 +2 位作者 杨念祖 高晓沨 陈贵海 《软件学报》 EI CSCD 北大核心 2020年第3期620-633,共14页
在大数据与云计算时代,数据访问速度是衡量大规模存储系统性能的一个重要指标.因此,如何设计一种轻量、高效的数据索引结构,从而满足系统高吞吐率、低内存占用的需求,是当前数据库领域的研究热点之一.Kraska等人提出使用机器学习模型代... 在大数据与云计算时代,数据访问速度是衡量大规模存储系统性能的一个重要指标.因此,如何设计一种轻量、高效的数据索引结构,从而满足系统高吞吐率、低内存占用的需求,是当前数据库领域的研究热点之一.Kraska等人提出使用机器学习模型代替传统的B树索引,并在真实数据集上取得了不错的效果,但其提出的模型假设工作负载是静态的、只读的,对于索引更新问题没有提出很好的解决办法.提出了基于中间层的可扩展的学习索引模型Dabble,用来解决索引更新引发的模型重训练问题.首先,Dabble模型利用K-Means聚类算法将数据集划分为K个区域,并训练K个神经网络分别学习不同区域的数据分布.在模型训练阶段,创新性地把数据的访问热点信息融入到神经网络中,从而提高模型对热点数据的预测精度.在数据插入时,借鉴了LSM树延迟更新的思想,提高了数据写入速度.在索引更新阶段,提出一种基于中间层的机制将模型解耦,从而缓解由于数据插入带来的模型更新问题.分别在Lognormal数据集以及Weblogs数据集上进行实验验证,结果表明,与当前先进的方法相比,Dabble模型在查询以及索引更新方面都取得了非常好的效果. 展开更多
关键词 学习索引 聚类 神经网络 动态更新
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