Search

Introduction of ray tracing can effectively solve problems of multi-path propagation, non-line-of-sight (NLOS) noise and hearability faced by localization algorithms in complex circumstances. However, the environment models are often too ideal and thus may affect the actual application of ray tracing; meanwhile, measurement errors of localization parameters can severely undermine the tracing results of signals' propagation paths. To address these problems, a reverse ray tracing algorithm is proposed based on cluster analysis. First, a two-dimensional propagation environment model is built, with the building surface assumed as the quasi-mirror to simulate the actual propagation environment of rays; second, the position orientating path and the area orientating path are defined based on features of the propagation path of multi-path localization signals. The algorithm proposed uses the branch tracing and search algorithm to calculate feasible paths according to the estimated TOA and AOA values of multi-path localization signals, and then employs cluster analysis to recognize position orientating paths and trace their propagations, based on which the sub-section weighting method is used to trace the maximum recognizable path among area orientating paths. Finally, simulation results demonstrate the rationality and effectiveness of the algorithm.

This paper presents a method which discretizes long and narrow belt-shaped structure into sequence of cross-sections and creates cross-section models automatically based on the real construction data. Then completion and schedule model of construction are obtained by connecting cross-section schedule models. This Method reduces data volumes effectively and improves automation degree and scalability of modeling constructions. The experiment has shown that this system is full-featured, the modeling and visualization of construction processes can meet the requirement of real-time.

The traditional volumetric visual hull generating methods were not applicable to real-time objects due to frame by frame calculations. A fast new algorithm based on inter frame coherence was represented for fast reconstructing an object's visual hull from its silhouettes in this paper. Utilizing frame to frame coherence of inter frame visual hulls and motion estimation, the numbers of voxels that need to be calculated were adjusted dynamically without having to calculate all the voxels. The solution improved the time efficiency by decreasing the computation cost. The results of the experiments show that this generation algorithm is superior to some classical visual hull methods, as far as its reconstruction function for time complexity is concerned.

A majority of urban pretimed traffic signal control systems deploy multiple signal time-intervals to account for traffic demand changes during a day. There have been some mature studies on the algorithms of time-intervals split of TOD. However, these algorithms neglected the variation of traffic flow among days of week. In this research, a Nonparametric Test is applied to reflect the variation of traffic flow among days of week and classify the days of week into different categories, and then each day is divided into several timeintervals by adopting an ordered sample cluster algorithm according to the former categories. This method could eliminate the impact of traffic flow uncertainty on the timeintervals split and will provide more accurate time-intervals split for the urban pretimed traffic signal control systems.

We present an improved ROAM algorithm for keeping region when rendering terrain. Concerning the region broken problem of ROAM algorithm in rendering terrain, a method of keeping region in rendering terrain with enhancing the triangle splitting condition is proposed. The concept of optimum triangulation for region is used to set the splitting vertex and its parent active. The rending algorithm sets status of the active vertex according to the view direction and the distance between viewpoint and region, and produces the terrain region s level of detail. The results of experiments show that our algorithm with LOD has a satisfactory performance in keeping region during rending terrain.