Transform Domain Techniques Research Articles

Image and edge detail detection algorithm for object-based coding

This paper presents a novel approach to extract image and edge details that are useful for segmentation of video objects in object-based coding. The proposed approach provides a transform domain technique and uses perceptual properties and edge contrast information in the transform coefficients along with the human visual system weighting to extract image and edge details that are perceptually most significant.

Narrow-band interference excision in spread-spectrum systems using self-orthogonalizing transform-domain adaptive filters

Among many transform-domain interference excision techniques, transform-domain adaptive filtering has many advantages. It is based on a true optimization of some particular performance parameters such as the bit-error rate (BER). Moreover, it is insensitive to jammer frequency. However, transform-domain adaptive filtering also has the drawback of being incapable of tracking a rapidly changing interference because most adaptive algorithms require time to converge to the optimal solution. In this paper, a self-orthogonalizing transform-domain least mean square (SO-TRLMS) algorithm is used to speed up the convergence. Compared to a traditional transform-domain least mean square (TRLMS) algorithm, the SO-TRLMS algorithm can significantly improve the convergence rate of the LMS algorithm, thus making the transform-domain adaptive filtering technique more suitable for real-time processing. In order to show how the system performance is affected by various factors such as interference power and the transform used, this paper presents an analytical result for the BER performance that is applicable for arbitrary orthogonal linear transforms. Simulation results are also presented to demonstrate the validity of the analysis.

A critical evaluation of image and video indexing techniques in the compressed domain

Image and video indexing techniques are crucial in multimedia applications. A number of indexing techniques that operate in the pixel domain have been reported in the literature. The advent of compression standards has led to the proliferation of indexing techniques in the compressed domain. In this paper, we present a critical review of the compressed domain indexing techniques proposed in the literature. These include transform domain techniques using Fourier transform, cosine transform, Karhunen–Loeve transform, Subbands and wavelets, and spatial domain techniques using vector quantization and fractals. In addition, temporal indexing techniques using motion vectors are also discussed.

A domain transformation technique in oxygen diffusion problems with moving oxidation fronts on unbounded domains

In this paper we study numerical computations of oxygen diffusion problems with a moving oxidation front on unbounded domains of planar, cylindrical and spherical geometrical shapes. A new domain transformation technique of space variables and time variable is introduced in the application of the variable grid method for numerical computation of these problems. Some upper bound estimates of oxidation fronts are obtained. A numerical algorithm is proposed and discussed. © 1998 John Wiley & Sons, Ltd.

Numerical computation of metal oxidation problems on bounded domains

This paper is a study of metal oxidation problems with moving oxidation fronts, modeled by Fickian oxygen diffusion through the oxide scale and metal. A numerical algorithm is developed and implemented based on a variable grid finite difference scheme. A domain transformation technique is introduced for the space and time variables, resulting in a transformed problem defined over a fixed domain but with non-linear diffusion equations. The numerical algorithm is implemented for nominal values of the material constants corresponding to titanium alloys at elevated temperatures. Three different benchmark problems with planar, cylindrical and spherical oxidation fronts are analyzed in this work. Also, the influence of the geometry of bounded domains on moving oxidation fronts is discussed.

An improvement to the harmonic-balance technique for analyzing nonlinear circuits

In this paper, an improved method, which is based on the harmonic-balance technique, for speeding up the convergence iteration procedure is presented. As an example, it is applied to the nonlinear analysis of microwave mixer, in which a simple time domain to frequency domain transformation technique for the mixer diode is firstly introduced. The use of this technique saves computing time dramatically. And the analyzed results are in good agreement with the results published. The improved method can also be extende to the CAA of nonlinear circuits with multi-devices.

On Nonlinear Binary Sequential Circuits and Their Inverses

This paper discusses single-input, single-output binary sequential circuits composed of adders, multipliers and delay units. The principal results are: 1) Finite feedforward circuits are characterized by a response function (rf) which permits the determination of the output for an arbitrary input. 2) Corresponding to every rf is a transfer function (tf) which is obtained by a multidimensional Z-transform of the rf. This tf permits the determination of the response of a feedforward circuit by transform domain techniques. 3) Every tf may be synthesized as a physical circuit. 4) A canonic form is defined for every tf. With this canonic form is identified an implementation which contains a minimum number of delay units and adders. 5) Nonfeedforward circuits are called well defined if they meet certain physically meaningful restrictions. 6) Well-defined circuits may be classified as those which have inverses (class I) and those which do not. Membership in class I is shown to be a property of circuits which established one-one maps of inputs onto outputs. Circuits which do not belong to class I have neither left nor right inverses. 7) An intimate connection between inverses and feedback circuits is established. It is shown that any well-defined feedback circuit and a related circuit in I are mutually inverse. 8) It is shown that the necessary and sufficient condition for a feedback circuit to be well defined is that the circuit in the feedback loop contains delay.