Browsing by Subject "Data Processing"

Now showing 1 - 3 of 3

Open Access
Representing objects as rays, or how to pile up an octree?
(Elsevier, 1989) Akman, V.; Franklin, Wm. R.
Quadtrees, octrees, and in general k-trees have established themselves as useful hierarchical data structures in computer graphics, image processing, and solid modeling. A fundamental operation in a system based on k-trees is the construction of a k-tree. Here, we review a new way of doing this operation. Basically, we have invented a method to store an object as a set of rays and an algorithm for converting such a set into a k-tree. (For example, in 3D a ray is a thin parallelepiped.) The algorithm is conceptually simple, works for any k, and piles up, using an approach we call stacking, a k-tree from the rays very fast. It produces a minimal k-tree and does not lead to intermediate storage swell. For large-scale realistic objects, which consist of many thousands of rays, the algorithm debunks the "expensive octree creation" myth. © 1989.
Open Access
A study of two transaction-processing architectures for distributed real-time data base systems
(Elsevier, 1995) Ulusoy, Özgür
A real-time data base system (RTDBS) is designed to provide timely response to the transactions of data-intensive applications. Processing a transaction in a distributed RTDBS environment presents the design choice of how to provide access to remote data referenced by the transaction. Satisfaction of the timing constraints of transactions should be the primary factor to be considered in scheduling accesses to remote data. In this article, we describe and analyze two different alternative approaches to this fundamental design decision. With the first alternative, transaction operations are executed at the sites where required data pages reside. The other alternative is based on transmitting data pages wherever they are needed. Although the latter approach is characterized by large message volumes carrying data pages, it is shown in our experiments to perform better than the other approach under most of the work loads and system configurations tested. The performance metric used in the evaluations is the fraction of transactions that satisfy their timing constraints. © 1995.
Open Access
Time-varying lifting structures for single-tree complexwavelet transform
(IEEE, 2012) Keskin, Furkan; Çetin, A. Enis
In this paper, we describe a single-tree complex wavelet transform method using time-varying lifting structures. In the dualtree complex wavelet transform (DT-CWT), two different filterbanks are executed in parallel to analyze a given input signal, which increases the amount of data after analysis. DT-CWT leads to a redundancy factor of 2 d for d-dimensional signals. In the proposed single-tree complex wavelet transform (ST-CWT) structure, filters of the lifting filterbank switch back and forth between the two analysis filters of the DT-CWT. This approach does not increase the amount of output data as it is a critically sampled transform and it has the desirable properties of DT-CWT such as shift-invariance and directional selectivity. The proposed filterbank is capable of constructing a complex wavelet-like transform. Examples are presented. © 2012 IEEE.