Browsing by Subject "Recursive functions"

Now showing 1 - 10 of 10

Open Access
Adaptive filtering approaches for non-Gaussian stable processes
(IEEE, 1995-05) Arıkan, Orhan; Belge, Murat; Çetin, A. Enis; Erzin, Engin
A large class of physical phenomenon observed in practice exhibit non-Gaussian behavior. In this paper, α-stable distributions, which have heavier tails than Gaussian distribution, are considered to model non-Gaussian signals. Adaptive signal processing in the presence of such kind of noise is a requirement of many practical problems. Since, direct application of commonly used adaptation techniques fail in these applications, new approaches for adaptive filtering for α-stable random processes are introduced.
Open Access
Adaptive filtering for non-gaussian stable processes
(IEEE, 1994) Arıkan, Orhan; Çetin, A. Enis; Erzin, E.
A large class of physical phenomenon observed in practice exhibit non-Gaussian behavior. In this letter, a-stable distributions, which have heavier tails than Gaussian distribution, are considered to model non-Gaussian signals. Adaptive signal processing in the presence of such a noise is a requirement of many practical problems. Since direct application of commonly used adaptation techniques fail in these applications, new algorithms for adaptive filtering for α-stable random processes are introduced.
Open Access
AutopaR: An Automatic Parallelization Tool for Recursive Calls
(IEEE, 2014-09) Kalender, Mert Emin; Mergenci, Cem; Öztürk, Özcan
Manycore systems are becoming more and more powerful with the integration of hundreds of cores on a single chip. However, writing parallel programs on these manycore systems has become a problem since the amount of available parallel tools and applications are limited. Although exploiting parallelism in software is possible, it requires different design decisions, significant programmer effort and is error prone. Different libraries and tools try to make the transition to parallelism easier, however there is no concrete system to make it transparent to software developer. To this end, our proposed tool is a step forward to improve the current state. Our approach, Autopar, specifically aims at achieving automatic parallelization of recursive applications using static program analysis. It first decides on the recursive functions of a given program. Then, it performs analysis and collects information about these recursive functions. Our analysis module automatically collects program information without requiring any modification in the program design or developer involvement. Finally, it achieves automatic parallelization by introducing necessary OpenMP pragmas in appropriate places in the application. © 2014 IEEE.
Open Access
Composite regions of feasibility for certain classes of distance constrained network location problems
(INFORMS, 1996) Tansel, B. Ç.; Yeşilkökçen, G. N.
Distance constrained network location involves locating m new facilities on a transport network G so as to satisfy upper bounds on distances between pairs of new facilities and pairs of new and existing facilities. The problem is script N sign℘-complete in general, but polynomially solvable for certain classes. While it is possible to give a consistency characterization for these classes, it does not seem possible to give a global description of the feasible set. However, substantial geometrical insights can be obtained on the feasible set by studying its projections onto the network. The j-th projection defines the j-th composite region which is the set of all points in G at which new facility j can be feasibly placed without violating consistency. We give efficient methods to construct these regions for solvable classes without having to know the feasible set and discuss implications on consistency characterization, what if analysis, and recursive solution constructions.
Open Access
Cumulant-based parametric multichannel FIR system identification methods
(Elsevier, 1994) Özgen, M. T.; Alshebeili, S. A.; Çetin, A. Enis; Venetsanopoulos, A. N.
In this paper, “least squares” and recursive methods for simultaneous identification of four nonminimum phase linear, time-invariant FIR systems are presented. The methods utilize the second- and fourth-order cumulants of outputs of the four FIR systems of which the common input is an independent, identically distributed (i.i.d.) non-Gaussian process. The new methods can be extended to the general problem of simultaneous identification of three or more FIR systems by choosing the order of the utilized cumulants to be equal to the number of systems. To illustrate the effectiveness of our methods, two simulation examples are included.
Open Access
Image sequence analysis for emerging interactive multimedia services-the European COST 211 framework
(Institute of Electrical and Electronics Engineers, 1998-11) Alatan, A. A.; Onural, L.; Wollborn, M.; Mech, R.; Tuncel, E.; Sikora, T.
Flexibility and efficiency of coding, content extraction, and content-based search are key research topics in the field of interactive multimedia. Ongoing ISO MPEG-4 and MPEG-7 activities are targeting standardization to facilitate such services. European COST Telecommunications activities provide a framework for research collaboration. COST 211 bis and COST 211 tcr activities have been instrumental in the definition and development of the ITU-T H.261 and H.263 standards for video-conferencing over ISDN and videophony over regular phone lines, respectively. The group has also contributed significantly to the ISO MPEG-4 activities. At present a significant effort of the COST 211 tcr group activities is dedicated toward image and video sequence analysis and segmentation - an important technological aspect for the success of emerging object-based MPEG-4 and MPEG-7 multimedia applications. The current work of COST 211 is centered around the test model, called the Analysis Model (AM). The essential feature of the AM is its ability to fuse information from different sources to achieve a high-quality object segmentation. The current information sources are the intermediate results from frame-based (still) color segmentation, motion vector based segmentation, and change-detection-based segmentation. Motion vectors, which form the basis for the motion vector based intermediate segmentation, are estimated from consecutive frames. A recursive shortest spanning tree (RSST) algorithm is used to obtain intermediate color and motion vector based segmentation results. A rule-based region processor fuses the intermediate results; a postprocessor further refines the final segmentation output. The results of the current AM are satisfactory; it is expected that there will be further improvements of the AM within the COST 211 project.
Open Access
Multi-level direct K-way hypergraph partitioning with multiple constraints and fixed vertices
(Academic Press, 2008-05) Aykanat, Cevdet; Cambazoglu, B. B.; Uçar, B.
K-way hypergraph partitioning has an ever-growing use in parallelization of scientific computing applications. We claim that hypergraph partitioning with multiple constraints and fixed vertices should be implemented using direct K-way refinement, instead of the widely adopted recursive bisection paradigm. Our arguments are based on the fact that recursive-bisection-based partitioning algorithms perform considerably worse when used in the multiple constraint and fixed vertex formulations. We discuss possible reasons for this performance degradation. We describe a careful implementation of a multi-level direct K-way hypergraph partitioning algorithm, which performs better than a well-known recursive-bisection-based partitioning algorithm in hypergraph partitioning with multiple constraints and fixed vertices. We also experimentally show that the proposed algorithm is effective in standard hypergraph partitioning. © 2007 Elsevier Inc. All rights reserved.
Open Access
Optimal timing of project control points
(Elsevier, 2000) Raz, T.; Erel, E.
The project control cycle consists of measuring the status of the project, comparing to the plan, analysis of the deviations, and implementing any appropriate corrective actions. We present an analytical framework for determining the optimal timing of project control points throughout the life cycle of the project. Our approach is based on maximizing the amount of information generated by the control points, which depends on the intensity of the activities carried out since the last control point and on the time elapsed since their execution. The optimization problem is solved with a dynamic programming approach. We report the results of numerical experimentation with the model involving different types of activity intensity profiles and several levels of information loss. For each combination, we compared the optimal amount of information to the amount of information obtained with two simpler policies: control at equal time intervals, and control at equal activity contents intervals. We also investigated the effect of adding more control points on the amount of information generated.
Open Access
Spectra of self-similar Laplacians on the Sierpinski gasket with twists
(World Scientific Publishing Co. Pte. Ltd., 2008) Blasiak, A.; Strichartz, R. S.; Ugurcan, B. E.
We study the spectra of a two-parameter family of self-similar Laplacians on the Sierpinski gasket (SG) with twists. By this we mean that instead of the usual IFS that yields SG as its invariant set, we compose each mapping with a reflection to obtain a new IFS that still has SG as its invariant set, but changes the definition of self-similarity. Using recent results of Cucuringu and Strichartz, we are able to approximate the spectra of these Laplacians by two different methods. To each Laplacian we associate a self-similar embedding of SG into the plane, and we present experimental evidence that the method of outer approximation, recently introduced by Berry, Goff and Strichartz, when applied to this embedding, yields the spectrum of the Laplacian (up to a constant multiple). © 2008 World Scientific Publishing Company.
Open Access
A wavelet based recursive reconstruction algorithm for linear measurements
(IEEE, 1996) Arıkan, Orhan
A recursive algorithm is proposed to obtain an efficient regularized least squares solution to large linear system of equations which arises in many physical measurement models. The algorithm recursively updates the solution in an increasingly larger dimensional subspace whose basis vectors are chosen as a subset of a complete wavelet basis. Robust criterions on how to chose the basis vectors at each iteration, and when to stop the iterations are given.