No abstract

No abstract

No abstract

This paper presents a realistic ray casting model on a curved surface. Guided by the model, we derive an analytical solution for spherical surfaces and propose a mathematical model by solving one problem in two spaces. By using the solution, we introduce a novel framework for spherical height field rendering. We have successfully implemented a spherical height field rendering framework on the graphics processing unit and obtained real-time rendering rates with screen error below 1 pixel. Copyright

Estimating the cardinality of data streams over a sliding window is an important problem in many applications, such as network traffic monitoring, web access log analysis and database. The problem becomes more difficult in largescale data streams when time and space complexity is taken into account. In this paper, we present a novel randomized data structure to address the problem. The significant contributions are as follows. (1) A space-efficient counter vector sketch (CVS) are proposed, which extends the well-known bitmap sketch to sliding window settings. (2) Based on the CVS, a random update mechanism is introduced, whereby a small fixed number of entries are randomly chosen from CVS in a step and then updated. This means that the update procedure just costs constant time. (3) Furthermore, estimating cardinality by CVS just needs one-pass scan of the data. (4) Finally, a theoretical analysis is given to show the accuracy of CVS-based estimators. Our comprehensive experiments confirm that the CVS-based schema attains high accuracy, and that its time efficiency in comparison with the timestemp vector (TSV) and the auxiliary indexing method.

No abstract

This paper presents a method for incremental updating on consumer electronic devices, called differential compression based on Dijkstra algorithm (DDIFF). It describes the similarities between the old and new versions as a directed weighted graph. In the graph, the shortest path between the start and end vertices corresponds to the minimal delta. As a result, the delta-encoding problem is reduced to the single-source shortest path problem. Experiments show that the proposed method is feasible, and average data transmission saving is as high as 69.3%. In comparison with the existing methods, DDIFF constructs the minimal patch, and the patch costs less time to apply 1 .

Summary The past few years have witnessed the prosperity in the mobile Internet. The increased traffic with diverse QoS requirements calls for a more capable and flexible infrastructure. The satellite systems with global coverage capability can be used as the backbone network to interconnect autonomous systems worldwide. In this context, routing data in the satellite networks is of great importance considering the integration of the satellite networks with the terrestrial Internet protocol networks. This paper provides a systematic routing design in the geostationary orbit/low earth orbit (LEO) hybrid satellite networks. We first give the description of the architecture of the geostationary orbit/LEO satellite networks based on which the user mobility management mechanism is proposed. The core idea of the user mobility management mechanism lies in the division of the earth surface, which results in the separation of the user and the satellite segment along with the separation of the user identifier and locator. We then give an analysis of the division of the earth surface. Based on the separation of the user and the satellite segment, the hop‐constrained adaptive routing mechanism with load balancing capability is proposed. The simulations on an Iridium‐like LEO satellite network further document and confirm the positive characteristics of the proposed routing mechanism. Copyright © 2016 John Wiley & Sons, Ltd.