1667264
Path extendability of claw-free graphs
Let G be a connected, locally connected, claw-free graph of order n and x,y be two vertices of G. In this paper, we prove that if for any 2-cut S of G, S@?{x,y}=@A, then each (x,y)-path of length less than n-1 in G is extendable, that is, for any path P joining x and y of length h(
4362564
More powerful closure operations on graphs
Abstract Bondy and Chvatal have observed the following result: G =( V , E ) is a simple graph of order n . If uv ∉ E and d ( u )+ d ( v )⩾ n , then G is Hamiltonian iff G + uv is Hamiltonian. Thus, we can obtain a graph C n ( G ), named the n -closure of G , from G by successively joining pairs of non-adjacent vertices whose degree sum is at least n . Therefore, G is Hamiltonian if C n ( G ) is Hamiltonian. Moreover, Bondy and Chvatal [2] generalized this idea to several properties on G . In the paper, we present some more powerful closure operations that extend the idea of Bondy and Chvatal.
20128924
Long path connectivity of regular graphs
Abstract Any pair of vertices in a 4-connected non-bipartite k -regular graph are joined by a Hamilton path or a path of length at least 3 k −6.
1145290
Hamilton cycles in regular 3-connected graphs
Abstract We show in this paper that for k ⩾63, every 3-connected, k -regular simple graph on at most 22 7 k vertices is hamiltonian.
28041688
Real-Time GPU-Based Simulation of Dynamic Terrain
Although a great deal of research effort has been devoted to the realistic and efficient rendering of terrain data, the existing research mainly focuses on displaying static terrain. The realistic simulation of dynamic terrain, including vehicle-terrain interactions, is absent in most 3D graphical applications. In this paper, we present a new GPU-based algorithm for dynamic terrain simulation. A key component of this algorithm is a Dynamically-Displaced Height Map (DDHM) which is generated and manipulated on the GPU. In addition, our method achieves real-time performance by using new features of the latest graphics hardware and shader technology. We demonstrate our algorithm by simulating a ground vehicle traveling on soft terrain. Our algorithm is particularly useful for ground based visual simulation applications as well as 3D games.
6725306
Design and Implementation of a Workflow Rendering Engine
Business visualization is an effective tool for business decision making and problem solving. Despite its obvious benefits, 3D visualization is far less common in practice than it should be due to the lack of software support. To address this problem, we have developed a workflow rendering engine that facilitates the 3D visualization of business process information for organizational process analysis and efficiency studies. The workflow information is represented in XML format to be compatible with the new Web graphics standard X3D. The rendering engine is implemented using C++ and OpenGL in order to take full advantage of modern 3D graphics hardware. The object-oriented design makes this engine highly extensible.
2274256
Overlay Networks with Linear Capacity Constraints
Overlay networks are virtual networks residing over the IP network; consequently, overlay links may share hidden lower level bottlenecks. Previous work has assumed an independent overlay model: a graph with independent link capacities. We introduce a model of overlays that incorporates correlated link capacities and linear capacity constraints (LCC) to formulate hidden shared bottlenecks; we refer to these as LCC-overlays. We define metrics to qualitatively measure overlay quality in terms of its accuracy (in representing the true network topology) and efficiency (that is, performance). Through analysis and simulations, we show that LCC-overlay is perfectly accurate and, hence, enjoys much higher efficiency than the inaccurate independent overlay. We discover that even a highly restricted LCC class-node-based LCC-yields near-optimal accuracy and significantly higher efficiency. We study two network flow problems in the context of LCC-graphs: widest path and maximum flow. We prove that Widest Path with LCC is NP-complete. We formulate Maximum Flow with LCC as a linear program and propose an efficient distributed algorithm to solve it. Based on the LCC model, we further study the problem of optimizing delay while still maintaining optimal or near-optimal bandwidth. We also outline a distributed algorithm to efficiently construct an overlay with node-based LCC.
15428033
On Optimal Physical Carrier Sensing: Theoretical Analysis and Protocol Design
Traditional Physical Carrier Sensing (PCS), which aims at eliminating hidden terminals in wireless networks, causes too many exposed terminals and deteriorates the throughput per user seriously. Some existing work has proven that an aggressive PCS can improve the throughput by balancing the tradeoff between hidden terminals and exposed terminals. However, little work has been conducted to optimize the PCS according to the network conditions. In this paper, we develop an analytical model to study the behaviors of a user in the aggressive PCS scenario, with which the optimal PCS threshold can be derived. Then, to avoid the complicated computation, we present a heuristic algorithm, in which the parameters required for PCS tuning are estimated by the carrier sensing mechanism employed in IEEE 802.11. Simulation results show that the proposed heuristic algorithm can make the PCS threshold approach to the theoretical optimal one. Moreover, the proposed heuristic algorithm can obtain significant throughput gain compared to the traditional PCS threshold setting solutions.
38631034
A Receiver-Centric Transport Protocol for Mobile Hosts with Heterogeneous Wireless Interfaces
Numerous transport protocols have been proposed in related work for use by mobile hosts over wireless environments. A common theme among the design of such protocols is that they specifically address the distinct characteristics of the last-hop wireless link, such as random wireless errors, round-trip time variations, blackouts, handoffs, etc. In this paper, we argue that due to the defining role played by the wireless link on a connection’s performance, locating the intelligence of a transport protocol at the mobile host that is adjacent to the wireless link can result in distinct performance advantages. To this end, we present a receiver-centric transport protocol called RCP (Reception Control Protocol) that is a TCP clone in its general behavior, but allows for better congestion control, loss recovery, and power management mechanisms compared to sender-centric approaches. More importantly, in the context of recent trends where mobile hosts are increasingly being equipped with multiple interfaces providing access to heterogeneous wireless networks, we show that a receiver-centric protocol such as RCP can enable a powerful and comprehensive transport layer solution for such multi-homed hosts. Specifically, we describe how RCP can be used to provide: (i) a scalable solution to support interface specific congestion control for a single active connection; (ii) seamless server migration capability during handoffs; and (iii) effective bandwidth aggregation when receiving data through multiple interfaces, either from one server, or from multiple replicated servers. We use both packet level simulations, and real Internet experiments to evaluate the proposed protocol.