Gröbner Bases and Multidimensional FIR Multirate Systems

The polyphase representation with respect to sampling lattices in multidimensional (M-D) multirate signal processing allows us to identify perfect reconstruction (PR) filter banks with unimodular Laurent polynomial matrices, and various problems in the design and analysis of invertible MD multirate systems can be algebraically formulated with the aid of this representation. While the resulting algebraic problems can be solved in one dimension (1-D) by the Euclidean Division Algorithm, we show that Gröbner bases offers an effective solution to them in the M-D case.     

A group theoretic approach to multidimensional filter banks: theoryand applications

In this paper, we provide a new method for analyzing multidimensional filter banks. This method enables us to solve various open problems in multidimensional filter bank characterization and design. The essential element in this new approach is the redefinition of polyphase components. It will be shown that a rich set of mathematical tools, in particular algebraic group theory, will become available for use in the analysis of filter banks. We demonstrate the elegance and power of the tool set by employing it for the characterization of multidimensional filter banks and applying it to two open problems. The first problem is concerned with the development of a general method to design multichannel (⩾2), multidimensional filter banks using transformations, while the second problem is concerned with the derivation of general restrictions on group delays in linear phase filter banks. The treatment of these problems is only an illustration of the power of the tool set of algebraic group theory, employed for the first time in the context of multidimensional filter banks     

Transient Rolling Contact Phenomena

Two cylinders of identical purely elastic materials are pressed together with parallel axes under the action of a normal force so that a contact strip forms. The cylinders are then shifted with respect to each other, which, under the influence of dry friction, gives rise to Cattaneo's (2) traction distribution with two slip areas. Subsequently they are rolled under the influence of a constant couple, reaching eventually Carter's (3) steady state with one slip area.

The question arises how the former traction distribution passes into the latter as a function of time. It is answered in the framework of a more general rolling contact problem.

The problem is solved numerically under the assumption of vanishing inertial effects, and results are presented. In the problem mentioned above it is found that Carter's (3) distribution is virtually attained when one to two contact widths have been traversed.     

A Review of Audio Fingerprinting

An audio fingerprint is a compact content-based signature that summarizes an audio recording. Audio Fingerprinting technologies have attracted attention since they allow the identification of audio independently of its format and without the need of meta-data or watermark embedding. Other uses of fingerprinting include: integrity verification, watermark support and content-based audio retrieval. The different approaches to fingerprinting have been described with different rationales and terminology: Pattern matching, Multimedia (Music) Information Retrieval or Cryptography (Robust Hashing). In this paper, we review different techniques describing its functional blocks as parts of a common, unified framework. Pedro Cano received a B.Sc and M. Sc. Degree in Electrical Engineering from the Universitat Politècnica de Catalunya in 1999. In 1997, he joined the Music Technology Group of the Universitat Pompeu Fabra where he is currently pursuing his Ph.D. on Content-based Audio Identification. He has been assistant professor in the Department of Technologies of the Universitat Pompeu Fabra since 1999. His research interests and recent work include: signal processing for music applications, within a real-time voice morphing system for karaoke applications, pattern matching and information retrieval, specifically content-based audio identification. Eloi Batlle received his M.S. degree in electronic engineering in 1995 from the Politechnical University of Catalunya in Barcelona, Spain. He then joined the Signal Processing Group at the same university where he was working on robust speech recognition. He received a PhD on this subject in 1999. While he was a PhD student he also worked as a researcher at the Telecom Italia Lab during 1997. In 2000 he joined the Audiovisual Institute (a part of the Pompeu Fabra University). Currently he is a member of the Music Technology Group of the same Institute where he leads several reseach projects on music identification and similarity. In 2000 he also joined the Department of Technologies of the Pompeu Fabra University and he teaches several subjects to undergraduate and graduate students. From 2001 he is the Deputy Director of this Department. His research interests include information theory, music similary, statistical signal processing and pattern recognition. Ton Kalker was born in The Netherlands in 1956. He received his M.S. degree in mathematics in 1979 from the University of Leiden, The Netherlands. From 1979 until 1983, while he was a Ph.D. candidate, he worked as a Research Assistant at the University of Leiden. From 1983 until December 1985 he worked as a lecturer at the Computer Science Department of the Technical University of Delft. In January 1986 he received his Ph.D. degree in Mathematics. In December 1985 he joined the Philips Research Laboratories Eindhoven. Until January 1990 he worked in the field of Computer Aided Design. He specialized in (semi) automatic tools for system verification. Currently he is a member of the Processing and Architectures for Content MANagement group (PACMAN) of Philips Research, where he is working on security of multimedia content, with an emphasis on watermarking and fingerprinting for video and audio. In November 1999 he became a part-time professor in the Signal Processing Systems group of Jan Bergmans in the area of ‘signal processing methods for data protection’. He is a Fellow of the IEEE for his contributions to practical applications of watermarking, in particular watermarking for DVD-Video copy protection. His other research interests include wavelets, multirate signal processing, motion estimation, psycho physics, digital video compression and medical image processing. Jaap Haitsma was born in 1974 in Easterein, the Netherlands. He received his B.Sc. in Electronic Engineering from the Noordelijke Hogeschool Leeuwarden in 1997. He did his thesis in 1997 at the Philips Research Laboratories in Redhill, England, on the topic of: “Colour Management for Liquid Crystal Displays”. Currently he is with the Philips Research Laboratories, Eindhoven, the Netherlands, where he has been doing research into digital watermarking and fingerprinting of audio and video since late 1997. From 1999 to 2002 he was also a part-time student at the Technical University of Eindhoven, where he obtained his M.Sc. in Electronic Engineering. His areas of interest include digital signal processing, database search algorithms and software engineering.     

On the adequacy of the Peterson-Bogert model and on the effects of viscosity in cochlear dynamics

Summary Based on a simplified model of the cochlea a one-dimensional approach (the Peterson-Bogert model) is compared with a three-dimensional one. The results appear to be in agreement provided the impedance of the partition is large. This is true for low frequencies except in the region of maximum membrane amplitude. For low frequencies, moreover, the fluid can be considered as incompressible. The influence of the viscosity is investigated by localizing the entire viscous force in a boundary layer. This layer is shown to occur in the fluid. Besides it is concluded that the rotation is approximately largest where the membrane has its maximum amplitude. This can be an explanation for the appearance of eddies at that point.     

Contrast echocardiography for pulmonary blood volume quantification

Pulmonary blood volume quantification is important both for diagnosis and for monitoring of the circulatory system. It requires employment of transpulmonary indicator dilution techniques, which are very invasive due to the need for double catheterization. This paper presents a new minimally invasive technique for blood volume quantification. An ultrasound contrast agent bolus is injected peripherally and detected by an ultrasound transducer in the central circulation. Several echocardiographic views permit simultaneous detection of contrast in different cardiac cavities and central vessels, and acoustic backscatter measurements produce multiple indicator dilution curves (IDCs). Contrast mean-transit-time differences are derived from the IDC analysis and multiplied times cardiac output for the assessment of blood volumes between different detection sites. For pulmonary blood volume estimates, the right ventricle and the left atrium IDCs are measured. The mean transit time of the IDC is estimated by specific modelling. The Local Density Random Walk and the First Passage Time models were tested for IDC interpolation and interpretation. The system was validated in vitro for a wide range of flows. The results show very accurate volume measurements. The volume estimate determination coefficient is greater than 0.999 for both model fits. A preliminary study in patients shows promising results.     

Simulation of the development of a railway wheel profile through wear

In this paper a method of calculation is presented for determination of the evolution by wear of railway wheels. The results are compared with the development of the profile of the wheels in the Amsterdam Metro, and satisfactory agreement is achieved. For ordinary railway lines the agreement is worse, since we did not take into account wear due to flanging.     

The computation of three-dimensional rolling contact with dry friction

In this paper the computer code Duvorol, dealing with the computation of three-dimensional rolling contact with dry friction, is described. It is based on the variational principle of Duvaut and Lions for dry friction, which leads to an incremental theory. The relevant properties of Duvorol are:

• 1 Generality. All half-space steady-state rolling contact problems with Hertzian normal contact can be treated.
• 2 Reliability. The total tangential force is always found with reasonable accuracy by a standard discretization.
• 3 Speed. On an IBM 370/158 the calculation of a case then takes only several seconds.