Harmonic oscillators realized using current amplifiers and grounded capacitors

New configurations of harmonic oscillators, realized using current amplifier blocks and only grounded capacitors, are introduced in this article. The proposed configurations are based on a grounded inductor simulator scheme and on a loop constructed from first‐order sections, respectively. Comparison with the already published topologies shows that the new configurations have attractive characteristics concerning their implementation in integrated form. Copyright © 2006 John Wiley & Sons, Ltd.     

Design of Sinh‐Domain filters using complementary operators

A new systematic method for designing Sinh‐Domain filters is introduced in this paper. This is achieved by employing an appropriate set of complementary operators, in order to transpose the conventional functional block diagram representation of each linear operation to the corresponding one into the Sinh‐Domain. The proposed method offers the benefits of facilitating the design procedure of high‐order Sinh‐Domain filters and of the absence of any restriction concerning the type and/or the order of the realized filter function. As an example, a third‐order Sinh‐Domain leapfrog filter is designed by employing the proposed set of operators. Two possible realizations are given and their performance has been evaluated and compared through simulation results. Copyright © 2011 John Wiley & Sons, Ltd.     

0.5‐V fractional‐order companding filters

Novel configurations of fractional‐order filter topologies, realized through the employment of the concept of companding filtering, are introduced in this paper. As a first step, the design procedure is presented in a systematic algorithmic way, while in the next step, the basic building blocks of sinh‐domain and log‐domain integrators are presented. Because of the employment of metal–oxide–semiconductor (MOS) transistors operated in the subthreshold region, the derived filter structures offer the capability for operation in an ultra‐low‐voltage environment. In addition, because of the offered resistorless realizations, the proposed topologies are reconfigurable, in the sense that the order of the filter could be chosen through appropriate bias current sources. The performance of the derived fractional‐order filters has been evaluated through simulation and comparison results using the Analog Design Environment of the Cadence software and MOS transistor parameters provided by the Taiwan Semiconductor Manufacturing Company (TSMC) 180‐nm complementary MOS (CMOS) process. Copyright © 2014 John Wiley & Sons, Ltd.     

Monte Carlo circuits for the abelian permutation group intersection problem

Summary We show that the problem of computing a basis for an abelian transitive permutation group is in N C ^k and also we show that the problem of computing a basis for an abelian permutation group and the problem of computing the intersection of two abelian groups acting on n points, can be solved in depth (log n)^k on a Monte Carlo Boolean circuit of polynomial size. Moreover the latter two problems are shown to be in N C ^k in the restricted case of bounded number of generators.     

Fuzzy systems design: direct and indirect approaches

A systematic classification of the data-driven approaches for design of fuzzy systems is given in the paper. The possible ways to solve this modelling and identification problem are classified on the basis of the optimisation techniques used for this purpose. One algorithm for each of the two basic categories of design methods is presented and its advantages and disadvantages are discussed. Both types of algorithms are self-learning and do not require interaction during the process of fuzzy model design. They perform adaptation of both the fuzzy model structure (rule-base) and the parameters. The indirect approach exploits the dual nature of Takagi-Sugeno (TS) models and is based on recently introduced recursive clustering combined with Kalman filtering-based procedure for recursive estimation of the parameter of the local sub-models. Both algorithms result in finding compact and transparent fuzzy models. The direct approach solves the optimisation problem directly, while the indirect one decomposes the original problem into on-line clustering and recursive estimation problems and finds a sub-optimal solution in real-time. The later one is computationally very efficient and has a range of potential applications in real-time process control, moving images recognition, autonomous systems design etc. It is extended in this paper for the case of multi-input–multi-output (MIMO systems). Both approaches have been tested with real data from an engineering process.     

Design of Concrete Flexural Members Strengthened in Shear with FRP

The present study describes a simple design model for the calculation of the fiber-reinforced polymer (FRP) contribution to the shear capacity of strengthened RC elements according to the design formats of the Eurocode, American Concrete Institute, and Japan Concrete Institute. The key element in the model is the calculation of an effective FRP strain, which is calculated when the element reaches its shear capacity due to concrete diagonal tension. Diagonal tension failure may be combined with FRP debonding or tensile fracture, and the latter also may occur at a stage beyond the ultimate shear capacity. An upper limit (maximum) to the FRP effective strain also is defined and aimed at controlling crack opening. The effective strain, obtained through calibration with >75 experimental data, is shown to decrease with the FRP axial rigidity divided by the concrete shear strength. It also is demonstrated that the contribution of FRP to shear capacity is typically controlled by either the maximum effective strain or by debonding and, for a given concrete strength, it increases linearly with the FRP axial rigidity until the latter reaches a limiting value beyond which debonding controls and the gain in shear capacity is relatively small. However, proper anchoring (e.g., full wrapping) suppresses the debonding mechanism and results in considerable increases in shear capacity with the FRP axial rigidity. Finally it is demonstrated that, when compared with others, the proposed model gives better agreement with most of the test results available.     

Efficient bufferless packet switching on trees and leveled networks

In bufferless networks the packets cannot be buffered while they are in transit; thus, once injected, the packets have to move constantly. Bufferless networks are interesting because they model optical networks. The objective of this work is to demonstrate that efficient bufferless packet switching is achievable in particular, interesting network topologies.     

Optimal controller tuning for nonlinear processes

The present work proposes a systematic methodology for the optimal selection of controller parameters in the sense of minimizing a performance index, which is a quadratic function of the tracking error and the control effort. The performance index is calculated explicitly as an algebraic function of the controller parameters by solving Zubov's partial differential equation (PDE). Standard optimization techniques are then employed for the calculation of the optimal values of the controller parameters. The solution of Zubov's PDE is also used to estimate the closed-loop stability region for the chosen values of the controller parameters. The proposed approach is finally illustrated in a chemical reactor control problem.     

Shape Connectivity: Multiscale Analysis and Application to Generalized Granulometries

This paper develops a multiscale connectivity theory for shapes based on the axiomatic definition of new generalized connectivity measures, which are obtained using morphology-based nonlinear scale-space operators. The concept of connectivity-tree for hierarchical image representation is introduced and used to define generalized connected morphological operators. This theoretical framework is then applied to establish a class of generalized granulometries, implemented at a particular problem concerning soilsection image analysis and evaluation of morphological properties such as size distributions. Comparative results demonstrate the power and versatility of the proposed methodology with respect to the application of typical connected operators (such as reconstruction openings). This multiscale connectivity analysis framework aims at a more reliable evaluation of shape/size information within complex images, with particular applications to generalized granulometries, connected operators, and segmentation.