34686455
Drawing planar graphs with circular arcs
In this paper we address the problem of drawing planar graphs with circular arcs while maintaining good angular resolution and small drawing area. We present a lower bound on the area of drawings in which edges are drawn using exactly one circular arc. We also give an algorithm for drawing n-vertex planar graphs such that the edges are sequences of two continuous circular arcs. The algorithm runs in O(n) time and embeds the graph on the O(n) × O(n) grid, while maintaining Θ(1/d(v)) angular resolution, where d(v) is the degree of vertex v. Since in this case we use circular arcs of infinite radius, this is also the first algorithm that simultaneously achieves good angular resolution, small area, and at most one bend per edge using straight-line segments. Finally, we show how to create drawings in which edges are smooth C1-continuous curves, represented by a sequence of at most three circular arcs.
1870789
Replication and retrieval strategies of multidimensional data on parallel disks
Aside from enhancing data availability during disk failures, replication of data is also used to speed up I/O performance of read-intensive applications. There are two issues that need to be addressed: (a) data placement (Which disks should store the copies of each data block?) and (b) scheduling (Given a query Q, and a placement scheme P of the data, from which disk should each block in Q be retrieved so that retrieval time is minimized?) In this paper, we consider range queries and assume that the dataset is a multidimensional grid and r copies of each unit block of the grid must be stored among M disks. To accurately measure performance of a scheduling algorithm, we consider a metric that takes into account the scheduling overhead as well as the time it takes to retrieve the data blocks from the disks. We describe several combinations of data placement schemes and scheduling algorithms and analyze their performance for range queries with respect to the above metric. We then present simulation results for the most interesting case r=2, showing that the strategies do perform better than the previously known method, especially for large queries.
29287906
Further complexity reduction of parallel FIR filters
Based on recently published low complexity parallel FIR filter structures, this paper proposes a new scheme to further reduce their hardware complexity. A FIR filter is firstly transformed into linear convolution, which is then implemented by the iterated short convolution algorithm. This linear convolution structure for FIR filter is used as a processing core to implement the subfilters of previously proposed parallel FIR filter structures. A large amount of hardware can be saved by the new scheme. For example, for a 576-tap FIR filter, when the parallelism level changes from 12 to 72, the new scheme can save 1755 to 3375 multiplications at the cost of 21 to 4658 additions and 1516 to 4749 delay elements, respectively.