FFT computation with linear processor arrays using a data-driven control scheme

We consider the practical design of linear controllers to meet a given set ofH ₂ specifications. TheQ-parametrization reduces the problem to a quadratic minimization subject to multiple quadratic constraints, which we solve using semi-definite programming (SDP) methods. Each SDP iteration requires calculating a primal and dual search direction and minimizing the cost function along the plane defined by these search directions. The primal direction requires solving a least squares problem whose normal equation matrix is composed of a block-Toeplitz portion plus other structured matrices. We make use of Kronecker products and FFT's to greatly reduce the calculation. The dual search direction and plane search are accelerated by low-rank representations of the SDP structured matrices. As an example, we design controllers which explore the optimal tradeoff between in-band residual and out-of-band enhancement of acoustic radiation from a (mathematically modeled) submerged spherical shell, while simultaneously constraining two sensitivity measures. For this example we show that significant reduction in out-of-band enhancement is possible with only minor in-band penalties.     

Design and Dynamic Analysis of an Adjustable Inertia Absorber for Semiactive Structural Vibration Attenuation

A new class of adaptive tuned vibration absorber, a variable effective inertia absorber, is presented to impart optimum vibration absorption. The tuning scheme has two facets: spectral analysis of the excitation and a concurrent in situ tuning of the absorber. The spectral analysis reveals the frequency content of the excitation. The online tuning uses the frequency content of the excitation to reposition a moving mass and change the damping coefficient of a variable rate damper for optimal (broadband) or tonal vibration suppression. The nonlinear differential equations of motion are linearized and then utilized to develop the online tonal and the broadband tuning of the variable effective inertia absorber. A case study is presented to demonstrate the novelty of the concept. The results show that the retuned absorber delivers considerable vibration suppression improvement over the detuned one.     

Optimal Placement of Spare Modules in a Cascaded Chain

A class of redundant cascaded chains with i.i.d. modules is considered in which recovery from a failure takes place by replacing the faulty module by a spare module. The complexity of the reconfiguration process depends upon the location of spare modules in the cascade. This paper deals with the question of optimally placing the spare modules in order to minimize the s-expected recovery time (down time) of the system. Exact analysis is carried out for cascades with one and two spare modules and an approximate analysis is given for three or more spares. Even though exact analysis does not seem to be practical in the general case, the symmetry of spare module positions in the special cases discussed here and linearity of the system suggest that one might expect the optimal positions to be symmetric in general. Because of this symmetry, one can reduce the number of variables to be considered in the general case, however, some inaccuracies might be introduced.     

Combination of neural network and wavelet transform for islanding detection of distributed generation in a small-scale network

In this paper, an optimum and intelligent method is proposed for islanding detection using wavelet transform. The suggested relay is based on neural network (NN) in which different heuristic algorithms are used for training the NN. In the proposed method, the appropriate signals for detection procedure as well as mother wavelet are selected optimally, based on the mean square error (MSE) concept. Lately, the desired relay is trained by the optimally selected signals using four different algorithms and the optimum condition of the fault detector is identified. Simulation results approved that non detection zone (NDZ) has a significant reduction utilising the proposed intelligent technique. The contributions of the proposed method include presenting an appropriate signal selection method based on MSE, selecting optimum number of relay input signals using the proposed technique, fast training of intelligent relay by using least information, solving threshold selection problem and reduction of NDZ approximately to zero.     

Low-power optical switching with Kerr nonlinear material in two-dimensional photonic crystal nanocavity

We investigate numerically optical bistability in direct-coupled cavity–waveguide photonic crystal system using the finite-difference time-domain method. The quality factor of the cavity is optimized by engineering the geometrical parameters. Numerical results indicate that the threshold power of optical bistability can be reduced greatly due to the increased quality factor.     

High-speed and low-power scalable Hamming weight comparator based on a non-weighted switched-capacitor array

Many practical applications require a comparison of the Hamming weights of two N-bit binary vectors. This comparison can be performed in a fully digital manner or by a mix of analog and digital techniques. In this paper, we propose a design in the latter category that exhibits advantages in speed and power dissipation compared with the best previous designs. The proposed design comprises of two switched-capacitor arrays associated with two comparators placed in parallel, collectively providing a complete comparison outcome of “>”, “<”, or “=”. The switched-capacitor array circuit is composed of uniform capacitances, thus associating identical charges with all bits, independent of their positions in the input bit-vectors. Once charge accumulation has occurred based on the asserted inputs, the two comparators release the final decision concurrently. The structure is shown to support wide input vectors on the order of 64 bits, while requiring a small silicon area for capacitor array structures, CMOS switches, and latched comparators to compute and store the comparison outcome. HSPICE simulation shows a total power consumption of 1.136 mW, evaluated at the operating frequency of 1 GHz (based on input-to-decision delay) for 16 bit input vectors under 0.15 μm TSMC technology.     

Decentralized adaptive terminal sliding mode control design for nonlinear connected system in the presence of external disturbance

In this article, a decentralized adaptive integral terminal sliding mode control is presented for a class of nonlinear connected systems. It is assumed that the system is also confronted by unknown disturbances, while the interconnections between subsystems are assumed unknown. An integral terminal sliding surface for each subsystem is locally considered to guarantee the stability of the closed-loop system, and to increase the convergence speed during a tracking task. The unknown interconnections between subsystems are estimated using adaptive rules. An appropriate Lyapunov candidate is chosen to perform global stability analysis. In this regard, design parameters are chosen such that the closed-loop stability is ensured. Performance of the proposed method for a mechanical connected system, including two chaotic subsystems, is shown through simulations.     

Simulation-based optimization of ecological leasing: a step toward extended producer responsibility (EPR)

In recent years, due to severe environmental legislations and extended producer responsibility, leasing has been recommended as a strategy for increasing resources productivity and minimizing waste generation during consumption and product end-of-life (EOL) phase. Hence, it is essential to develop a model that can help leasing company for achieving sustainable production management. In this paper, a model is developed which optimizes the environmental and economical impact of product during leasing and its EOL phase from customers and leasing company point of view. To solve the problem, simulation-based optimization approach is investigated and the integrated mathematical and simulation model is developed for incorporating uncertainty during leasing period. Finally a case study with data from industry is used to validate the approach and potential applications of the developed model are illustrated.