文章以我国跨部门政府数据共享为例,研究组织领地性如何阻碍跨组织数据共享。研究采用结构化文献综述方法,通过系统的文献检索、文献筛选和专题分析,为实证研究奠定理论基础。从中国知网、万方、维普、Web of Science数据库共检索到1,68...文章以我国跨部门政府数据共享为例,研究组织领地性如何阻碍跨组织数据共享。研究采用结构化文献综述方法,通过系统的文献检索、文献筛选和专题分析,为实证研究奠定理论基础。从中国知网、万方、维普、Web of Science数据库共检索到1,680篇论文,筛选后纳入60篇文章进行主题分析。文献分析表明,条块的政府结构和数据心理所有权促使政府部门表现出领地标记和领地防卫的集体行为,这极大地阻碍了跨部门政府数据的共享进程。文章从领地行为理论出发为研究跨部门政府数据共享提供了一个全新视角,以期丰富相关理论研究。展开更多
目的:采用Meta分析方法评价iRoot BP Plus与MTA分别用于年轻恒牙直接盖髓的疗效。方法:计算机检索VIP、WanFang Data 和 CNKI、PubMed、Cochrane Library数据库收录的iRoot BP Plus和MTA用于年轻恒牙直接盖髓的疗效随机对照试验(RCTs),...目的:采用Meta分析方法评价iRoot BP Plus与MTA分别用于年轻恒牙直接盖髓的疗效。方法:计算机检索VIP、WanFang Data 和 CNKI、PubMed、Cochrane Library数据库收录的iRoot BP Plus和MTA用于年轻恒牙直接盖髓的疗效随机对照试验(RCTs),检索时限从建库至2020年4月12日。在资料收集和提取后,采用Review Manager 5.3软件进行Meta分析。结果:共纳入8个RCTs,包括426例患者。iRoot BP Plus与MTA的成功率[RR=1.04,95%CI(0.98,1.11),P>0.00 001]和钙化桥形成率[RR=1.01,95%CI(0.91,1.12),P>0.00 001]无统计学差异;操作时间[RR=-2.24,95%CI(-2.35,-2.13),P<0.00 001]和变色率[RR=0.11,95%CI(0.04,0.29),P<0.00 001]比较,差异有统计学意义。结论:当前证据表明,相比于MTA,iRoot BP Plus用于年轻恒牙直接盖髓术操作时间更短、变色率更低,成功率、钙化桥形成率差异不显著,但有更高的趋势,取得了更好的临床治疗效果。受纳入研究数量和质量限制,上述结论有待更多、更高质量RCTs予以验证。展开更多
The packing densification of binary spherical mixtures under 3D mechanical vibration was studied experimentally. The influences of vibration frequency （ω）, volume fraction of large spheres （XL）, sphere size ratio...The packing densification of binary spherical mixtures under 3D mechanical vibration was studied experimentally. The influences of vibration frequency （ω）, volume fraction of large spheres （XL）, sphere size ratio （r, diameter ratio of small to large spheres）, and container size （D） on the random binary packing density （p） were systematically analyzed. For any given set of conditions, there exist optimal ω and XL to realize the densest random binary packing; too large or small ω and XL is not helpful for densification. The influences of both r and D on p are monotonic; either reducing r or increasing D leads to a high value of p. With all other parameters held constant, the densest random packing occurs when XL is dominant, which is in good agreement with the Furnas relation. Moreover, the highest random binary packing density obtained in our work agrees well with corresponding numerical and analytical results in the literature.展开更多
Systematic physical experiments examining the packing densification of mono-sized cylindrical parti- cles subject to 3D mechanical vibration were carried out. The influence of vibration conditions such as vibration ti...Systematic physical experiments examining the packing densification of mono-sized cylindrical parti- cles subject to 3D mechanical vibration were carried out. The influence of vibration conditions such as vibration time, frequency, amplitude, vibration strength, container size, and the aspect ratio and spheric- ity of the particle on the packing density were analyzed and discussed. For each initial packing density with a certain aspect ratio, operating parameters were optimized to achieve much denser packing. The results indicate that the packing density initially increases with vibration time and then remains con- stant. The effects of vibration frequency and amplitude on the packing densification have similar trends, i.e. the packing density first increases with the vibration frequency or amplitude to a high value and then decreases; too large or small frequency or amplitude does not enhance densification. Increasing the container size can reduce container wall effects and help achieve a high packing density. Varying the particle aspect ratio and sphericity can lead to different dense random packing structures. Overall, based on results of the examined systems, the highest random packing density obtained in an infinite sized container can reach 0.73, which agrees well with corresponding numerical and analytical results in the literature.展开更多
Packing densification of monosized regular icosahedral particles under three-dimensional mechanical vibration has been simulated by the discrete element method (DEM).The effects of the vibration conditions and contain...Packing densification of monosized regular icosahedral particles under three-dimensional mechanical vibration has been simulated by the discrete element method (DEM).The effects of the vibration conditions and container size on packing densification were systematically investigated.In addition to the macroscale properties (packing density and porosity),the microscale properties,such as the coordination number (CN),radial distribution function (RDF),particle contact type,particle orientation distribution,and stresses/forces,in random loose packing (RLP) and random close packing (RCP) were also characterized and analyzed.The results show that transformation of icosahedral particle packing from RLP to RCP can be realized by properly controlling the vibration conditions.The maximum random packing density without the wall effect reaches 0.7078.Microscale property analysis shows that the average CN increases after vibration.The RDF curves contain two clear peaks for RLP and three for RCP.From RLP to RCP,the probability of face to face contact between two particles increases,while the probabilities of edge to edge,edge to face,and face to vertex contact decrease.The orientation correlation functions indicate the randomness of the vibrated packing structure.In addition,more uniform force and stress distributions are observed within the dense packing structure.展开更多
基金sponsored by the National Key Research and Development Program of China(No.2018YFB0704400)Key Research Project of Zhejiang Laboratory,China(No.2021PE0AC02)+1 种基金Key Program of Science and Technology of Yunnan Province,China(Nos.202002AB080001-2,202102AB080019-3)Key Project of Shanghai Zhangjiang National Independent Innovation Demonstration Zone,China(No.ZJ2021-ZD-006)。
文摘文章以我国跨部门政府数据共享为例,研究组织领地性如何阻碍跨组织数据共享。研究采用结构化文献综述方法,通过系统的文献检索、文献筛选和专题分析,为实证研究奠定理论基础。从中国知网、万方、维普、Web of Science数据库共检索到1,680篇论文,筛选后纳入60篇文章进行主题分析。文献分析表明,条块的政府结构和数据心理所有权促使政府部门表现出领地标记和领地防卫的集体行为,这极大地阻碍了跨部门政府数据的共享进程。文章从领地行为理论出发为研究跨部门政府数据共享提供了一个全新视角,以期丰富相关理论研究。
文摘目的:采用Meta分析方法评价iRoot BP Plus与MTA分别用于年轻恒牙直接盖髓的疗效。方法:计算机检索VIP、WanFang Data 和 CNKI、PubMed、Cochrane Library数据库收录的iRoot BP Plus和MTA用于年轻恒牙直接盖髓的疗效随机对照试验(RCTs),检索时限从建库至2020年4月12日。在资料收集和提取后,采用Review Manager 5.3软件进行Meta分析。结果:共纳入8个RCTs,包括426例患者。iRoot BP Plus与MTA的成功率[RR=1.04,95%CI(0.98,1.11),P>0.00 001]和钙化桥形成率[RR=1.01,95%CI(0.91,1.12),P>0.00 001]无统计学差异;操作时间[RR=-2.24,95%CI(-2.35,-2.13),P<0.00 001]和变色率[RR=0.11,95%CI(0.04,0.29),P<0.00 001]比较,差异有统计学意义。结论:当前证据表明,相比于MTA,iRoot BP Plus用于年轻恒牙直接盖髓术操作时间更短、变色率更低,成功率、钙化桥形成率差异不显著,但有更高的趋势,取得了更好的临床治疗效果。受纳入研究数量和质量限制,上述结论有待更多、更高质量RCTs予以验证。
文摘The packing densification of binary spherical mixtures under 3D mechanical vibration was studied experimentally. The influences of vibration frequency （ω）, volume fraction of large spheres （XL）, sphere size ratio （r, diameter ratio of small to large spheres）, and container size （D） on the random binary packing density （p） were systematically analyzed. For any given set of conditions, there exist optimal ω and XL to realize the densest random binary packing; too large or small ω and XL is not helpful for densification. The influences of both r and D on p are monotonic; either reducing r or increasing D leads to a high value of p. With all other parameters held constant, the densest random packing occurs when XL is dominant, which is in good agreement with the Furnas relation. Moreover, the highest random binary packing density obtained in our work agrees well with corresponding numerical and analytical results in the literature.
基金We are grateful to the financial support of National Natural Science Foundation of China （No. 51374070） and Fundamental Research Funds for the Central Universities of China （N120202001, N130102001）.
文摘Systematic physical experiments examining the packing densification of mono-sized cylindrical parti- cles subject to 3D mechanical vibration were carried out. The influence of vibration conditions such as vibration time, frequency, amplitude, vibration strength, container size, and the aspect ratio and spheric- ity of the particle on the packing density were analyzed and discussed. For each initial packing density with a certain aspect ratio, operating parameters were optimized to achieve much denser packing. The results indicate that the packing density initially increases with vibration time and then remains con- stant. The effects of vibration frequency and amplitude on the packing densification have similar trends, i.e. the packing density first increases with the vibration frequency or amplitude to a high value and then decreases; too large or small frequency or amplitude does not enhance densification. Increasing the container size can reduce container wall effects and help achieve a high packing density. Varying the particle aspect ratio and sphericity can lead to different dense random packing structures. Overall, based on results of the examined systems, the highest random packing density obtained in an infinite sized container can reach 0.73, which agrees well with corresponding numerical and analytical results in the literature.
基金the National Natural Science Foundation of China(51374070)Fundamental Research Funds for the Central Universities of China(N162505001)for financial support.
文摘Packing densification of monosized regular icosahedral particles under three-dimensional mechanical vibration has been simulated by the discrete element method (DEM).The effects of the vibration conditions and container size on packing densification were systematically investigated.In addition to the macroscale properties (packing density and porosity),the microscale properties,such as the coordination number (CN),radial distribution function (RDF),particle contact type,particle orientation distribution,and stresses/forces,in random loose packing (RLP) and random close packing (RCP) were also characterized and analyzed.The results show that transformation of icosahedral particle packing from RLP to RCP can be realized by properly controlling the vibration conditions.The maximum random packing density without the wall effect reaches 0.7078.Microscale property analysis shows that the average CN increases after vibration.The RDF curves contain two clear peaks for RLP and three for RCP.From RLP to RCP,the probability of face to face contact between two particles increases,while the probabilities of edge to edge,edge to face,and face to vertex contact decrease.The orientation correlation functions indicate the randomness of the vibrated packing structure.In addition,more uniform force and stress distributions are observed within the dense packing structure.
