29763170
Fractal image compression: a randomized approach
The fractal image compression is inherently time intensive and thus there is a growing need to increase its speedup. This paper presents a fast encoding scheme where the domain blocks are searched randomly for every range block. An analysis of the basic fractal image compression method has been carried out and on the basis of the analysis a method for image characterization has been proposed. Then a detailed theoretical analysis of this randomized fractal compression scheme has been presented and the results are validated with the experimental ones. The random approach has been found to be quite efficient giving considerable increase in speed-up compared to several other approaches.
1136530
A graph-theoretic approach for studying the convergence of fractal encoding algorithm
In this paper, we present a graph-theoretic interpretation of convergence of fractal encoding based on partial iterated function system (PIFS). First we have considered a special circumstance, where no spatial contraction has been allowed in the encoding process. The concept leads to the development of a linear time fast decoding algorithm from the compressed image. This concept is extended for the general scheme of fractal compression allowing spatial contraction (on averaging) from larger domains to smaller ranges. A linear time fast decoding algorithm is also proposed in this situation, which produces a decoded image very close to the result obtained by an ordinary iterative decompression algorithm.
30827173
Implementation of MPI over HTTP
Message Passing Interface[2] is the de facto standard for multicomputer and cluster message passing;. In this paper we explore a new paradigm of high performance distributed computing by implementing a message passing interface over HTTP[1]. This provides a platform independent implementation of MPI and also develops a base for web based computation to achieve global parallel processing. The conventional approach to message passing is through the use of Parallel Virtual Machine(PVM) or MPI software packages that optimize the communication and the synchronization functions for the message passing paradigm needed in high performance distributed computing environments. However the recent trend in Internet communication has been to use the HTTP for inter-linking information and files across the World Wide Web. The HTTP [1], over the years has matured to be a very efficient tool for communication and is fit enough to warrant consideration as a vehicle for inter-processor communication. The perfor ance of our implementation was compared with the standard MPI implementation over a cluster of workstations connected by a Shared Ethernet network and the results are very encouraging.
26381722
Cooperating Mobile Agents and Stabilization
In the execution of distributed algorithms on a network of processes, the actions of the individual processes are scheduled by their local schedulers or demons. The schedulers communicate with their immediate neighbors using shared registers or message passing. This paper examines an alternative approach to the design of distributed algorithms, where mobile agents are allowed to traverse a network, extract state information, and make appropriate modification of the local states to steer the system towards a global goal. The primary emphasis of this paper is system stabilization. Both single-agent and multi-agent protocols are examined, and the advantages and disadvantages of agent-based stabilization are discussed.
1421735
Scalable Self-Stabilization
This paper presents a methodology for a synchronous non-reactive distributed system on a tree topology to stabilize from a k-faulty configuration in a time independent of the size n of the system. In the proposed methodology, processes first measure and compare the sizes of the faulty regions, and then use this information to schedule actions in such a way that the size of the faulty regions progressively shrink, until they completely disappear. We demonstrate that when k processes fail, the stabilization time is O(k2). Apart from its applicability to a wide class of problems, the proposed method achieves scalability with a low space complexity of O(�.(�.k+log2n)) per process, where � is the maximum degree of a node.
25755124
An Algorithm for Computing a Convex and Simple Path of Bounded Curvature in a Simple Polygon

AbstractAbstract. In this paper we study the collision-free path planning problem for a point robot, whose path is of bounded curvature(i.e., constrained to have curvature at most 1), moving in the plane inside an n -sided simple polygon P . Given two points sand tinside Pand two directions of travel, one at sand one at t , the problem is to compute a convex and simple path of bounded curvature inside Pfrom sto tconsisting of straight-line segments and circular arcs such that (i) the radius of each circular arc is at least 1, (ii) each segment on the path is the tangent between the two consecutive circular arcs on the path, (iii) the given initial direction at sis tangent to the path at sand (iv) the given final direction at tis tangent to the path at t . We propose an O(n4)time algorithm for this problem. Using the notion of complete visibility, Pis pruned to another polygon P'such that any convex and simple path from sto tinside Palso remains inside P' . Then our algorithm constructs the locus of center of a circle of unit radius translating along the boundary of P'and, using this locus, the algorithm constructs a convex and simple path of bounded curvature. Our algorithm is based on the relationship between the Euclidean shortest path, link paths and paths of bounded curvature, and uses several properties derived here on convex and simple paths of bounded curvature. We also show that the path computed by our algorithm can be transformed in O(n)time to a minimalconvex and simple path of bounded curvature. Using this transformation and two necessary conditions proposed here for the shortest convex and simple path of bounded curvature, a minimalbounded curvature path is located in O(n4)time whose length, except in special situations involving arcs of length greater than π , is at most twice the length of a shortest convex and simple path of bounded curvature.

14429447
iSimBioSys: a discrete event simulation platform for 'in silico' study of biological systems
With the availability of huge databases cataloguing the various molecular "parts" of complex biological systems, researchers from multiple disciplines have focused on developing modeling and simulation tools for studying the variability of cellular behavior at a system level - encompassing the dynamics arising from many species of interacting molecules. In this work, we present a system engineering approach to model biological processes. In this approach, a biological process is modeled as a collection of interacting functions driven in time by a set of discrete events. We focus on the discrete event simulation platform, called "iSimBioSys", which we have developed for studying the dynamics of cellular processes in silico. As a test-bed for studying our approach we model the two component PhoPQ system, responsible for the expression of several virulence genes in Salmonella Typhimurium. We analyzed the effect of extra cellular magnesium on the behavioral dynamics of this pathway using our framework and compared the results with an experimental system. We also analyze the performance of iSimBioSys, based on the model biological system, in terms of system usage and response.