3479727
p-Percent Coverage Schedule in Wireless Sensor Networks
We investigate the p-percent coverage problem in this paper and propose two algorithms to prolong network lifetime based on the fact that for some applications full coverage is not necessary and different subareas of the monitored area may have different coverage requirements. The first algorithm, CPCA, is a centralized algorithm which selects the least number of nodes to monitor p-percent of the monitored area. The second algorithm, DPCP, is a distributed algorithm which can determine a set of nodes in a distributed manner to cover p-percent of the monitored area. Both of the algorithms guarantee network connectivity. The simulation results show that our algorithms can remarkably prolong network lifetime, have less than 5% unrequired coverage for large networks and employ nodes fairly for most cases.
37286032
A Random Key Management Scheme for Wireless Sensor Networks
The establishment of shared keys between communicating neighbor nodes in wireless sensor networks is a challenge due to resource-constrained sensor networks. Several key pre-distribution schemes have been proposed in literatures to establish pairwise keys between sensor nodes. However, many of them are either too complicated to fit for wireless sensor networks or insecure for some common aggressions. In this paper, we propose a random key management scheme based on random key pre-distribution for wireless sensor networks. To achieve better performance and security, the proposed scheme employs two different phases to establish enhanced pairwise keys between neighboring nodes. Compared with other existing random key pre-distribution schemes, our scheme has better resilience against node capture and also performs better in terms of network connectivity and scalability with appropriate memory, computation and communication overheads.
122609601
Attractor dimension estimates for two-dimensional shear flows
Abstract We study the large time behavior of boundary and pressure-gradient driven incompressible fluid flows in elongated two-dimensional channels with emphasis on estimates for their degrees of freedom, i.e., the dimension of the attractor for the solutions of the Navier-Stokes equations. For boundary driven shear flows and flux driven channel flows we present upper bounds for the degrees of freedom of the form cα Re 3 2 where c is a universal constant, α denotes the aspect ratio of the channel (length/width), and Re is the Reynolds number based on the channel width and the imposed “outer” velocity scale. For fixed pressure gradient driven channel flows we obtain an upper bound of form c'α Re2, where c' is another universal positive constant and the Reynolds number is based on a velocity defined by the infimum, over all possible trajectories, of the time averaged mass flux per unit channel width. We discuss these results in terms of physical arguments based on small length scales in turbulent flows.
12453473
A feature-based topological optimization for structure design
The feature-based modeling technology in computer aided design (CAD) has been widely studied, which greatly facilitates the manufacture of the design. We have incorporated the standard idea into topology optimization, and developed a feature-based structure topology optimization method. The method applies a real valued function to implicitly represent complex material interfaces of a design structure, and employs constructive solid geometry (CSG) to describe the design structure based on a set of simple geometric primitives during the topological optimization process. Meanwhile, the topological derivative analysis is adopted to determine where a simple geometric primitive is inserted in the current structure, and the morphing technology is used to determine which is chosen among the given geometric primitives by combining with the sensitivity analysis. In addition, Boolean operations on the geometric primitives are implemented by R-function method, which guarantees the regularity of the structure representation function, and which meets the need of the structure boundary smoothness for finite element analysis in the fixed Euler meshes. Finally, in order to further simplify the design structure, the shape matching technique is applied to merge the given geometric primitives so that each connected perforation is only constructed by one based geometric primitive.
2311114
A Novel Privacy and Copyright Protection Enforced Peer-to-Peer Network
Peer-to-peer (P2P) networks are widely used to share copyrighted contents and software illegally around the world. Development and applications of P2P technologies have faced strong legal and legislative challenges. A P2P network has to have built-in copyright protection to enable P2P technologies to advance on its own without court's and legislature's interference. In this paper, we propose a novel and practical P2P network with a strong privacy protection and reliable tracking mechanism to track the original uploader of any material in the P2P network. When a pirated material is found, its uploader is tracked down, and can be punished by revoking the access to the network, removing his or her uploaded materials, etc. The whole protection system is completely transparent to end users. The proposed scheme would effectively deter users from uploading illegally any copyrighted materials to and dramatically reduce copyrighted materials shared through our P2P network.
1202188
Load-Balancing Performance of Consistent Hashing: Asymptotic Analysis of Random Node Join
Balancing of structured peer-to-peer graphs, including their zone sizes, has recently become an important topic of distributed hash table (DHT) research. To bring analytical understanding into the various peer-join mechanisms based on consistent hashing, we study how zone-balancing decisions made during the initial sampling of the peer space affect the resulting zone sizes and derive several asymptotic bounds for the maximum and minimum zone sizes that hold with high probability. Several of our results contradict those of prior work and shed new light on the theoretical performance limitations of consistent hashing. We use simulations to verify our models and compare the performance of the various methods using the example of recently proposed de Bruijn DHTs.
8744802
On static and dynamic partitioning behavior of large-scale networks
In this paper, we analyze the problem of network disconnection in the context of large-scale P2P networks and understand how both static and dynamic patterns of node failure affect the resilience of such graphs. We start by applying classical results from random graph theory to show that a large variety of deterministic and random P2P graphs almost surely (i.e., with probability 1-o(1)) remain connected under random failure if and only if they have no isolated nodes. This simple, yet powerful, result subsequently allows us to derive in closed-form the probability that a P2P network develops isolated nodes, and therefore partitions, under both types of node failure. We finish the paper by demonstrating that our models match simulations very well and that dynamic P2P systems are extremely resilient under node churn as long as the neighbor replacement delay is much smaller than the average user lifetime