Time-focused clustering of trajectories of moving objects

Spatio-temporal, geo-referenced datasets are growing rapidly, and will be more in the near future, due to both technological and social/commercial reasons. From the data mining viewpoint, spatio-temporal trajectory data introduce new dimensions and, correspondingly, novel issues in performing the analysis tasks. In this paper, we consider the clustering problem applied to the trajectory data domain. In particular, we propose an adaptation of a density-based clustering algorithm to trajectory data based on a simple notion of distance between trajectories. Then, a set of experiments on synthesized data is performed in order to test the algorithm and to compare it with other standard clustering approaches. Finally, a new approach to the trajectory clustering problem, called temporal focussing, is sketched, having the aim of exploiting the intrinsic semantics of the temporal dimension to improve the quality of trajectory clustering. The authors are members of the Pisa KDD Laboratory, a joint research initiative of ISTI-CNR and the University of Pisa: .     

一种基于BX树的移动对象混合索引方法

为实现移动对象当前及未来位置索引,提出了一种自适应SABX树（Self-Adapt BX-tree）,考虑到移动对象在现实世界中分布密度不同的特点,利用时间划分和空间填充曲线技术计算移动对象位置信息,并引进了一个以秩的范围为标识的Hash辅助索引表,文中给出了SABX树的插入、删除、更新方法以及范围查询算法。实验表明,该索引结构的动态更新性能和查询效率优于BX树和传统的TPR树。     

一种自适应的运动目标阴影消除新算法

精确地消除活动阴影对运动目标的影响是智能视频监控的核心任务之一,对此提出了一种基于局部纹理分析的自适应阴影消除新算法。进行了基于高斯混合模型的背景重建,并根据阴影的光学特性进行了阴影区域的预检测,得到疑似阴影区域;提出了一种新的自适应动态纹理分析方法并在此基础上实现了活动阴影的检测与消除。实验结果验证了算法的有效性和实用性。     

移动对象子轨迹段分割与聚类算法

将运动轨迹作为整体聚类会丢失相似子轨迹段,而相似子轨迹段在实际应用中用处很大,如天气预报、交通控制等。提出一种新方法T-CLUS进行轨迹聚类,先将长轨迹分割成许多较短的直子段,再产生子段的增广聚类顺序,最后根据可达性图识别子轨迹聚类结构,得到子轨迹运动模式。实验结果表明T-CLUS方法在从轨迹数据库中发现相似子轨迹上是可伸缩的和正确的。     

3D reconstruction of free-formed line-like objects using NURBS representation

3D reconstruction of arbitrary free-formed objects is an important and challenging problem in computer vision. In this paper, we first discuss the importance of primitive selection in 3D reconstruction. Subsequently, a theorem, which reveals the perspective invariance of NURBS, is shown, making it a good choice as primitive in 3D reconstruction. Consequently, based on this theorem a new paradigm of free-formed line-like object reconstruction using NURBS as primitives is proposed. Furthermore, an approach for determining weights for 3D NURBS is presented, and the width effect of curved line-like objects is analyzed. Finally, experiments with line-like objects and machine part demonstrate the feasibility of our approach and prove the superiority of our approach over the point- or segment-based approaches as well as the B-spline-based reconstruction approach in terms of robustness and accuracy.     

基于单高斯背景模型运动目标检测方法的改进

针对背景减除法应用于运动目标检测中的背景模型更新和阴影消除问题,提出了一种改进的单高斯背景模型估计算法和快速的阴影消除方法。实验结果表明,算法在有效去除阴影的同时能够较好地提取运动目标,为后续的人体识别、行为分析等工作奠定了良好的基础。     

移动对象轨迹更新体系

在移动对象数据库中存在着移动对象位置的频繁更新,因而,如何管理移动对象轨迹（位置）的更新将成为移动对象数据库要解决的问题。对移动对象轨迹更新策略中存在的问题,提出了一个统一的移动对象轨迹更新体系。首先定义了移动对象的轨迹,从移动对象轨迹建模的角度,将移动对象轨迹的更新策略归纳为基于点与矢量的移动对象轨迹更新策略,给出了移动对象轨迹的更新原理及算法,并进行了两种更新策略的模拟实验比较。     

移动对象XML数据库的存储与索引

如何对移动对象的XML数据记录进行快速的查找,关键在于合理地存储模型与索引结构。为了减少时空条件索引时的文件I/O操作,提出一个移动对象XML数据存储模型（时空XML存储模型）,基于这个模型给出了通过一定时空条件对XML数据记录进行聚集的ATS（Append Track node to Spatial node）算法。针对3DR树的缺点与时态条件在移动对象索引中的重要性,提出了HSTR（Hashing-Spatio-Temporal-Rtree）与HC3DR（Hashing-Changing-3DRtree）两种复合索引结构,能够有效地支持涉及时空条件的查询。实验结果表明,时空XML存储模型与两种索引提高了查询效率。     

Efficient tracking of moving objects using a relational database

Tracking uncooperative moving objects by means of radar is a complex task due to clutter and association problems in multi-target scenarios. An approach to solve this problem is probabilistic multiple hypothesis tracking (PMHT). This method combines classical track filtering with a likelihood ratio test for the estimation of the plot-to-track association. The basics of PMHT and similar algorithms have gained much attention recently. However, the efficient implementation of real world applications of this technique still represents a challenging task. Since a common requirement in this context is the reliable storage of track data in a database, an implementation of the tracker's calculation inside a database management system (DBMS) using SQL views is desirable. A naive implementation of PMHT using a commercial DBMS, however, usually leads to performance problems because of the high frequency of measurement updates. In this paper, we propose possible optimizations for solving these performance problems. Their usage leads to a dramatic run-time improvement in our sample case and makes the implementation of PMHT in a database context feasible.     

移动对象反向最近邻查询处理技术研究进展

随着移动通信技术的快速发展和个人移动通信终端功能的不断完善,移动计算技术有了更加广阔的应用背景,尤其是移动对象的反向最近邻查询处理技术得到了研究人员的广泛关注。对近几年提出的移动对象反向最近邻查询方法进行了研究,根据其查询处理过程,将反向最近邻查询方法分为基于预处理的方法和基于空间修剪的方法;总结了近年来提出的有效解决方法和研究进展,最后介绍了移动对象反向最近邻查询处理技术的最新发展趋势。     

移动对象预测聚集范围查询方法

为了更好地实现预测范围聚集查询,提出了aTPRA-tree。TPR-tree随着时间的推移,性能不断恶化。aTPRA-tree是基于TPR-tree,它考虑了移动对象的方向角度进行构造,减小了结点面积和结点重叠面积,并且在索引结点中增加了聚集信息。实验结果表明,在更新和预测范围聚集查询性能方面,aTPRA-tree性能优于TPR-tree。     

基于对极几何约束的动态背景下运动目标检测

针对动态背景下运动目标的检测问题,提出了一种基于对极几何约束的检测方法。该方法利用了视频序列中相继帧对应的背景角点满足对极几何约束条件这一原理,先提取前一帧的Harris角点,然后利用金字塔分层的Lucas-Kanade光流法获得在下一帧的对应点;利用随机采样一致性算法估计出基础矩阵,来识别背景角点和前景角点;对得到的前景角点进行聚类,每一类对应于一个运动目标区域。实验结果表明,该方法检测准确度高、检测速度快,满足实时处理的需求。     

利用FPGA实现视频移动目标的有效检测

利用FPGA实现了一个视频移动目标检测系统,算法的基础是背景差分法。为了准确检测和定位移动目标,利用了灰度漂移算法和多颜色空间信息融合算法。灰度漂移算法是课题组最近在研究高斯混合模型的过程中提出的一种消除背景差分法检测的移动目标存在过多噪声杂点的算法,可以非常有效地消除由于微震动、空气扰动等原因导致的像素灰度在邻近区域发生漂移的现象;多颜色空间信息融合就是利用多个颜色空间中的一些互补分量共同确定移动目标。利用FPGA实现了上述两种算法,在移动目标的实时检测和跟踪中取得了很好的效果,对于丰富和增强监控系统功能有重要意义。     

Optimal rotation alignment of 3D objects using a GPU-based similarity function

In this paper, we address the challenging task of finding the best alignment between two 3D objects by solving a global optimization problem in the space of rotations SO(3). The objective function to be optimized is a newly developed rotation-variant similarity measure, which is obtained directly from the object's geometry and is entirely implemented on the GPU. By exploiting the modern GPU's parallel architecture, we can process considerably greater amounts of data than a CPU implementation can do in the same amount of time. This allows us to create a similarity measure which combines speed and accuracy. The actual problem of rotation alignment is then solved by finding the global maximum of this similarity function in the space of rotations. A special rotation representation allows for an efficient local optimization on the manifold SO(3). Furthermore, unwanted local maxima can be avoided by a heuristic global optimization procedure which exploits rotational symmetry. Due to this common sense heuristics, the global search can be gradually reduced to a lower-dimensional problem up to a 1D line search to handle objects with high rotational symmetry. We show that our method is superior to existing normalization techniques such as PCA and provides a high degree of precision despite remarkably short runtimes.     

Model-based control of a simulated moving bed chromatographic process for the separation of fructose and glucose

Chromatographic separations are an expanding technology for the separation of high value products, particularly in the area of pharmaceutics, food, and fine chemicals. The simulated moving bed (SMB) process as a continuous chromatographic separation process is an interesting alternative to conventional batch chromatography, and gained more and more impact recently. The SMB process is realized by connecting several single chromatographic columns in series. A countercurrent movement of the bed is approximated by a cyclic switching of the inlet and outlet ports in the direction of the fluid stream. Because of its complex dynamics, the optimal operation and automatic control of SMB processes is a challenging task. This paper presents the design of a model-based optimization and control scheme for SMB chromatographic separation processes and its application to the separation of fructose and glucose. We propose a two-layer control architecture where the optimal operating trajectory is calculated off-line by dynamic optimization based on a rigorous process model. The parameters of the model are adapted based on online measurements. The low-level control task is to keep the process on the optimal trajectory despite disturbances and plant/model mismatch. Here identification models based on simulation data of the rigorous process model along the optimal trajectory are combined with a suitable local controller. The efficiency of the trajectory control algorithm is shown in a simulation study for the separation of fructose and glucose on an 8-column SMB plant.     

An efficient data processing framework for mining the massive trajectory of moving objects

Recently, there has been increasing development of positioning technology, which enables us to collect large scale trajectory data for moving objects. Efficient processing and analysis of massive trajectory data has thus become an emerging and challenging task for both researchers and practitioners. Therefore, in this paper, we propose an efficient data processing framework for mining massive trajectory data. This framework includes three modules: (1) a data distribution module, (2) a data transformation module, and (3) a high performance I/O module. Specifically, we first design a two-step consistent hashing algorithm, which takes into account load balancing, data locality, and scalability, for a data distribution module. In the data transformation module, we present a parallel strategy of a linear referencing algorithm with reduced subtask coupling, easy-implemented parallelization, and low communication cost. Moreover, we propose a compression-aware I/O module to improve the processing efficiency. Finally, we conduct a comprehensive performance evaluation on a synthetic dataset (1.114 TB) and a real world taxi GPS dataset (578 GB). The experimental results demonstrate the advantages of our proposed framework.     

集合几何体的三维动态建模研究

虚拟现实通常通过强化计算能力或优化模型提升效果,本文通过库房内部堆垛的三维建模实践,提出一种跟踪瞬间状态,结合瞬时状态参数和纹理构成规律,快速动态计算建立集合几何体模型的处理方案。该方案计算量小,生成模型优化,高效提升数量大、变化快场景的虚拟实现效果。     

Multi-scale 2D tracking of articulated objects using hierarchical spring systems

This paper presents a flexible framework to build a target-specific, part-based representation for arbitrary articulated or rigid objects. The aim is to successfully track the target object in 2D, through multiple scales and occlusions. This is realized by employing a hierarchical, iterative optimization process on the proposed representation of structure and appearance. Therefore, each rigid part of an object is described by a hierarchical spring system represented by an attributed graph pyramid. Hierarchical spring systems encode the spatial relationships of the features (attributes of the graph pyramid) describing the parts and enforce them by spring-like behavior during tracking. Articulation points connecting the parts of the object allow to transfer position information from reliable to ambiguous parts. Tracking is done in an iterative process by combining the hypotheses of simple trackers with the hypotheses extracted from the hierarchical spring systems.     

具有强鲁棒性的三维对象多视变分分割方法

针对校准摄像机采集系列图像的三维分割重构问题,提出了一种新的面向概率描述的变分方法。首先,计算系列图像的极大似然曲面,可重构与分割保持一致的三维曲面;接着,融合联合概率,可重构目标对象及图像背景的平均强度及标准差;最后,采用水平集框架,可实现对曲面能量方程的数值模拟。该方法适用于复杂拓扑结构重构及噪声数据处理。实验结果表明,该方法实用性好,鲁棒性强,对任意三维对象的分割重构效果较形状雕刻方法及体视分割方法理想。