43377675
Approximating the Medial Axis from the Voronoi Diagram with a Convergence Guarantee
We show that the medial axis of a surface S ? R3 can be approximated as a subcomplex of the Voronoi diagram of a point sample of S. The subcomplex converges to the true medial axis as the sampling density approaches infinity. Moreover, the subcomplex can be computed in a scale and density independent manner. Experimental results as detailed in a companion paper corroborate our theoretical claims.
7021110
Approximating the Medial Axis from the Voronoi Diagram with a Convergence
Guarantee
Abstract
The medial axis of a surface in 3D is the closure of all points that
have two or more closest points on the surface. 
It is an essential geometric structure in a number of applications involving 
3D geometric shapes. Since exact computation of the medial axis
is difficult in general, efforts continue to improve their approximations.
Voronoi diagrams turn out to be useful for this
approximation. Although it is known that Voronoi vertices for a sample
of points from a curve in 2D 
approximate its medial axis, a similar result does not hold
in 3D. Recently, it has been discovered that only a subset
of Voronoi vertices converge to the medial axis
as sample density approaches infinity. However, most applications
need a nondiscrete approximation as opposed to a discrete one. To date
no known algorithm can compute this approximation straight
from the Voronoi diagram with a guarantee of convergence. We present
such an algorithm and its convergence analysis in this 
paper. One salient feature of the algorithm is that it is
scale and density independent.
Experimental results corroborate our theoretical claims.


551942
Shape Dimension and Approximation from Samples 


Abstract. There are many scientific and engineering applications where an automatic detection of shape dimension from sample data is necessary. Topological dimensions of shapes constitute an important global feature of them. We present a Voronoi-based dimension detection algorithm that assigns a dimension to a sample point which is the topological dimension of the manifold it belongs to. Based on this dimension detection, we also present an algorithm to approximate shapes of arbitrary dimension from their samples. Our empirical results with data sets in three dimensions support our theory.

9772845
Performance Measurements for Privacy Preserving Data Mining
This paper establishes the foundation for the performance measurements of privacy preserving data mining techniques. The performance is measured in terms of the accuracy of data mining results and the privacy protection of sensitive data. On the accuracy side, we address the problem of previous measures and propose a new measure, named “effective sample size”, to solve this problem. We show that our new measure can be bounded without any knowledge of the data being mined, and discuss when the bound can be met. On the privacy protection side, we identify a tacit assumption made by previous measures and show that the assumption is unrealistic in many situations. To solve the problem, we introduce a game theoretic framework for the measurement of privacy.
5322268
Fault-tolerant real-time communication in FDDI-based networks
FDDI-Based Reconfigurable Networks have an architecture that is suitable for delivering messages that have hard real-time constraints as well as certain fault-tolerance requirements. This architecture uses multiple FDDI networks to connect hosts and provides for automatic reconfiguration to maintain high network bandwidth in spite of faults. An important open problem is how resources in such networks should be managed in order to guarantee that the fault-tolerant real-time requirements of messages are met. This paper presents an efficient and practical solution to this problem. Our solution consists of off-line and on-line components. On-line management deals with run-time manipulation of messages and network resources. A message grouping approach simplifies on-line management. Off-line management deals with message grouping, bandwidth allocation and schedulability verification. Three approaches are investigated: spatial redundancy, temporal redundancy and an integrated approach. It is shown that the integrated approach has the best performance. Our solution is compatible with the FDDI and SAFENET standards.
16063472
On the confidential auditing of distributed computing systems
We propose a confidential logging and auditing service for distributed information systems. We propose a cluster-based TTP (trusted third party) architecture for the event log auditing services, so that no single TTP node can have the full knowledge of the logs, and thus no single node can misuse the log information without being detected. On the basis of a relaxed form of secure distributed computing paradigms, one can implement confidential auditing service so that the auditor can retrieve certain aggregated system information, e.g. the number of transactions, the total volume, the event traces, etc., without having to access the full log data. Similar to the peer relationship of routers to provide global network routing services, the mutually supported, mutually monitored cluster TTP architecture allows independent systems to collaborate in network-wide auditing without compromising their private information.
9589474
DotSlash: A Self-Configuring and Scalable Rescue System for Handling Web Hotspots Effectively
DotSlash allows different web sites to form a mutual-aid community, and use spare capacity in the community to relieve web hotspots experienced by any individual site. As a rescue system, DotSlash intervenes when a web site becomes heavily loaded, and is phased out once the workload returns to normal. It aims to complement the existing web server infrastructure to handle short-term load spikes effectively. DotSlash is self-configuring, scalable, cost-effective, easy to use, and transparent to clients. It targets small web sites, although large web sites can also benefit from it. We have implemented a prototype of DotSlash on top of Apache. Experiments show that using DotSlash a web server can increase the request rate it supported and the data rate it delivered to clients by an order of magnitude, even if only HTTP redirect is used. Parts of this work may be applicable to other services such as Grid computational services.
2999153
Distributed policy processing in virtual private operation environment for large scale networks
VPOE (virtual private operation environment) is an infrastructure to provide customized services for applications in large-scale heterogeneous networks. In this infrastructure, the programmable network devices - called "middleware boxes" can be deployed at some functional locations in the network and provide services effectively corresponding to the service requirements. The basic functionality of middleware box is to execute customized policies. With the number of applications increasing and new services becoming popular, the policy matching and processing have been becoming a bottleneck for the middleware box performance. We focus on designing a scalable policy processing architecture, aiming to deal with this issue. Particularly, our technologies include: (1) a distributed policy processing architecture for the middleware box; (2) two policy partitioning algorithms to achieve conflict-free policies for the distributed policy processing architecture and guarantee the correctness of the policy execution. We conduct extensive performance evaluations on different architectures and algorithms. The evaluation results show that the distributed architecture can achieve over 70 percent increase of performance/price ratio with proper assignment of the policy distribution degree. The experimental results also demonstrate that to make the policy both partition capable and conflict free, more new policies have to be generated, which can be effectively reduced by using the policy compression schemes.