Web 2.0的出现使信息构建(IA)的内容发生了深刻变化,IA已进入"信息构建2.0"(IA2.0)阶段。在IA2.0阶段,IA作为一门学科、一种角色和一类社团的协调统一体而存在,它强调真正"以用户为中心"和"丰富的用户体验&qu...Web 2.0的出现使信息构建(IA)的内容发生了深刻变化,IA已进入"信息构建2.0"(IA2.0)阶段。在IA2.0阶段,IA作为一门学科、一种角色和一类社团的协调统一体而存在,它强调真正"以用户为中心"和"丰富的用户体验"的核心理念,以满足新环境下的用户需求。Web2.0网站的IA,是IA2.0的典型应用,也是IA2.0阶段研究的主要内容,本文将其称为网站IA2.0。文中设计了一个网站IA2.0模型,并进行了简单的实例分析。展开更多
细颗粒物浓度是评估空气质量的重要指标之一,精确预测PM2.5浓度仍是国内外研究的挑战,也是政府和学术界关注的重点。文章以2014年1月1日至2024年9月30日的乌鲁木齐市PM2.5日平均浓度为研究对象,对其线性回归模型应用两阶段自适应Lasso...细颗粒物浓度是评估空气质量的重要指标之一,精确预测PM2.5浓度仍是国内外研究的挑战,也是政府和学术界关注的重点。文章以2014年1月1日至2024年9月30日的乌鲁木齐市PM2.5日平均浓度为研究对象,对其线性回归模型应用两阶段自适应Lasso多变点检测与估计方法检测并估计回归系数的多变点,建立了更精准的分段线性回归模型来刻画乌鲁木齐市PM2.5日平均浓度。The concentration of fine particulate matter (PM2.5) is one of the key indicators for assessing air quality. Accurate prediction of PM2.5 concentration remains a challenge in both domestic and international research and is a major focus of attention for governments and scholars. This study takes the daily average PM2.5 concentrations in Urumqi City from January 1, 2014 to September 30, 2024 as the research object. A two-stage adaptive Lasso multiple change-point detection and estimation method is applied to detect and estimate multiple change points in the regression coefficients of the linear regression City daily average PM2.5 concentrations in Urumqi City.展开更多
Bridged bicyclic cores have been recognized as valuable bioisosteres of benzene ring,which are of great value in medicinal chemistry.However,the development of fluorinated bicyclic skeletons,which encompass two privil...Bridged bicyclic cores have been recognized as valuable bioisosteres of benzene ring,which are of great value in medicinal chemistry.However,the development of fluorinated bicyclic skeletons,which encompass two privileged elements widely acknowledged for fine tuning the working effect of target molecules,are far less common.Herein,we present a general and practical synthesis of gem-difluorobicyclo[2.1.1]hexanes(diF-BCHs)from readily available difluorinated hexa-1,5-dienes through energy transfer photocatalysis.By taking advantage of an efficient Cope rearrangement,the preparation of both constitutional isomers of diF-BCHs is readily achieved under identical conditions.The operational simplicity,mild conditions and wide scope further highlight the potential application of this protocol.Moreover,computational studies indicated a positive effect of fluorine atoms in lowering either the triplet or FMO energies of the hexa-1,5-diene substrates,thus promoting the present photoinduced[2+2]cycloaddition.展开更多
文摘细颗粒物浓度是评估空气质量的重要指标之一,精确预测PM2.5浓度仍是国内外研究的挑战,也是政府和学术界关注的重点。文章以2014年1月1日至2024年9月30日的乌鲁木齐市PM2.5日平均浓度为研究对象,对其线性回归模型应用两阶段自适应Lasso多变点检测与估计方法检测并估计回归系数的多变点,建立了更精准的分段线性回归模型来刻画乌鲁木齐市PM2.5日平均浓度。The concentration of fine particulate matter (PM2.5) is one of the key indicators for assessing air quality. Accurate prediction of PM2.5 concentration remains a challenge in both domestic and international research and is a major focus of attention for governments and scholars. This study takes the daily average PM2.5 concentrations in Urumqi City from January 1, 2014 to September 30, 2024 as the research object. A two-stage adaptive Lasso multiple change-point detection and estimation method is applied to detect and estimate multiple change points in the regression coefficients of the linear regression City daily average PM2.5 concentrations in Urumqi City.
基金the National Natural Science Foundation of China(No.22271151)the Distinguished Youth Foundation of Jiangsu Province.
文摘Bridged bicyclic cores have been recognized as valuable bioisosteres of benzene ring,which are of great value in medicinal chemistry.However,the development of fluorinated bicyclic skeletons,which encompass two privileged elements widely acknowledged for fine tuning the working effect of target molecules,are far less common.Herein,we present a general and practical synthesis of gem-difluorobicyclo[2.1.1]hexanes(diF-BCHs)from readily available difluorinated hexa-1,5-dienes through energy transfer photocatalysis.By taking advantage of an efficient Cope rearrangement,the preparation of both constitutional isomers of diF-BCHs is readily achieved under identical conditions.The operational simplicity,mild conditions and wide scope further highlight the potential application of this protocol.Moreover,computational studies indicated a positive effect of fluorine atoms in lowering either the triplet or FMO energies of the hexa-1,5-diene substrates,thus promoting the present photoinduced[2+2]cycloaddition.
