Cryo-electron microscopy makes use of transmission electron microscopy to image vitrified biological samples and reconstruct their three-dimensional structures from two-dimensional projections via computational approa...Cryo-electron microscopy makes use of transmission electron microscopy to image vitrified biological samples and reconstruct their three-dimensional structures from two-dimensional projections via computational approaches. After over40 years of development, this technique is now reaching its zenith and reforming the research paradigm of modern structural biology. It has been gradually taking over X-ray crystallography as the mainstream method. In this review, we briefly introduce the history of cryo-EM, recent technical development and its potential power to reveal dynamic structures. The technical barriers and possible approaches to tackle the upcoming challenges are discussed.展开更多
With the development of computer graphics,the three-dimensional(3D)visualization brings new technological revolution to the traditional cartography.Therefore,the topographic 3D-map emerges to adapt to this technologic...With the development of computer graphics,the three-dimensional(3D)visualization brings new technological revolution to the traditional cartography.Therefore,the topographic 3D-map emerges to adapt to this technological revolution,and the applications of topographic 3D-map are spread rapidly to other relevant fields due to its incomparable advantage.The researches on digital map and the construction of map database offer strong technical support and abundant data source for this new technology,so the research and development of topographic 3D-map will receive greater concern.The basic data of the topographic 3D-map are rooted mainly in digital map and its basic model is derived from digital elevation model(DEM)and 3D-models of other DEM-based geographic features.In view of the potential enormous data and the complexity of geographic features,the dynamic representation of geographic information becomes the focus of the research of topographic 3D-map and also the prerequisite condition of 3D query and analysis.In addition to the equipment of hardware that are restraining,to a certain extent,the 3D representation,the data organization structure of geographic information will be the core problem of research on 3D-map.Level of detail(LOD),space partitioning,dynamic object loading(DOL)and object culling are core technologies of the dynamic 3D representation.The object-selection,attribute-query and model-editing are important functions and interaction tools for users with 3D-maps provided by topographic 3D-map system,all of which are based on the data structure of the 3D-model.This paper discusses the basic theories,concepts and cardinal principles of topographic 3D-map,expounds the basic way to organize the scene hierarchy of topographic 3D-map based on the node mechanism and studies the dynamic representation technologies of topographic 3D-map based on LOD,space partitioning,DOL and object culling.Moreover,such interactive operation functions are explored,in this paper,as spatial query,scene editing and management of topographic 3D-map.Finally,this paper describes briefly the applications of topographic 3D-map in its related fields.展开更多
在众多现实场景中数据以流的形式持续产生,由于流数据具有动态变化的特点,在生成过程中可能产生新的类别,也被称为概念演化.概念演化是流数据挖掘模型预测性能衰退甚至预测失效的主要原因.因此,能及时发现类空间变化并提醒模型做出适应...在众多现实场景中数据以流的形式持续产生,由于流数据具有动态变化的特点,在生成过程中可能产生新的类别,也被称为概念演化.概念演化是流数据挖掘模型预测性能衰退甚至预测失效的主要原因.因此,能及时发现类空间变化并提醒模型做出适应性调节的概念演化检测方法受到广泛关注.然而,目前多数概念演化检测方法基于特征空间静态不变的假设构建算法.在现实场景中,特征空间同样具有动态性,属于开放的空间.具体来说,随时间推移可能出现部分特征消失和新特征产生的现象,从而破坏上述假设并导致已有算法失效.针对这一问题,本文提出一种面向开放特征空间的概念演化检测方法(Concept evolution Detection method for Open Feature space,CD_OF).该方法通过构建微簇集成模型对新进实例分类,对于开放特征空间中的旧特征消失问题,通过利用转移矩阵将旧特征中包含的信息转换到共享特征中;对于新出现的特征,拓展共享特征空间并重构集成模型.在此基础上,根据样本的共享邻域信息定义样本间相似度以检测概念演化,并建立动态衰减模型,以解决开放特征空间下的类消失和类循环问题.实验结果表明,本文所提出的方法能够对开放特征空间中特征的变化作出及时响应,增强概念演化检测的能力,在特征空间变化的真实流数据中与现有方法相比,错误率降低了1.7%~11.4%.展开更多
文摘Cryo-electron microscopy makes use of transmission electron microscopy to image vitrified biological samples and reconstruct their three-dimensional structures from two-dimensional projections via computational approaches. After over40 years of development, this technique is now reaching its zenith and reforming the research paradigm of modern structural biology. It has been gradually taking over X-ray crystallography as the mainstream method. In this review, we briefly introduce the history of cryo-EM, recent technical development and its potential power to reveal dynamic structures. The technical barriers and possible approaches to tackle the upcoming challenges are discussed.
文摘With the development of computer graphics,the three-dimensional(3D)visualization brings new technological revolution to the traditional cartography.Therefore,the topographic 3D-map emerges to adapt to this technological revolution,and the applications of topographic 3D-map are spread rapidly to other relevant fields due to its incomparable advantage.The researches on digital map and the construction of map database offer strong technical support and abundant data source for this new technology,so the research and development of topographic 3D-map will receive greater concern.The basic data of the topographic 3D-map are rooted mainly in digital map and its basic model is derived from digital elevation model(DEM)and 3D-models of other DEM-based geographic features.In view of the potential enormous data and the complexity of geographic features,the dynamic representation of geographic information becomes the focus of the research of topographic 3D-map and also the prerequisite condition of 3D query and analysis.In addition to the equipment of hardware that are restraining,to a certain extent,the 3D representation,the data organization structure of geographic information will be the core problem of research on 3D-map.Level of detail(LOD),space partitioning,dynamic object loading(DOL)and object culling are core technologies of the dynamic 3D representation.The object-selection,attribute-query and model-editing are important functions and interaction tools for users with 3D-maps provided by topographic 3D-map system,all of which are based on the data structure of the 3D-model.This paper discusses the basic theories,concepts and cardinal principles of topographic 3D-map,expounds the basic way to organize the scene hierarchy of topographic 3D-map based on the node mechanism and studies the dynamic representation technologies of topographic 3D-map based on LOD,space partitioning,DOL and object culling.Moreover,such interactive operation functions are explored,in this paper,as spatial query,scene editing and management of topographic 3D-map.Finally,this paper describes briefly the applications of topographic 3D-map in its related fields.
文摘在众多现实场景中数据以流的形式持续产生,由于流数据具有动态变化的特点,在生成过程中可能产生新的类别,也被称为概念演化.概念演化是流数据挖掘模型预测性能衰退甚至预测失效的主要原因.因此,能及时发现类空间变化并提醒模型做出适应性调节的概念演化检测方法受到广泛关注.然而,目前多数概念演化检测方法基于特征空间静态不变的假设构建算法.在现实场景中,特征空间同样具有动态性,属于开放的空间.具体来说,随时间推移可能出现部分特征消失和新特征产生的现象,从而破坏上述假设并导致已有算法失效.针对这一问题,本文提出一种面向开放特征空间的概念演化检测方法(Concept evolution Detection method for Open Feature space,CD_OF).该方法通过构建微簇集成模型对新进实例分类,对于开放特征空间中的旧特征消失问题,通过利用转移矩阵将旧特征中包含的信息转换到共享特征中;对于新出现的特征,拓展共享特征空间并重构集成模型.在此基础上,根据样本的共享邻域信息定义样本间相似度以检测概念演化,并建立动态衰减模型,以解决开放特征空间下的类消失和类循环问题.实验结果表明,本文所提出的方法能够对开放特征空间中特征的变化作出及时响应,增强概念演化检测的能力,在特征空间变化的真实流数据中与现有方法相比,错误率降低了1.7%~11.4%.
