Robust regulation in the presence of norm-bounded uncertainty

We consider robust regulation (against steps and sinusoids) in the presence of unstructured uncertainty. The unstructured uncertainty is norm bounded by a constant that is given a priori. This problem is equivalent to a certain multiobjective problem where one objective is robust regulation and the other is the standard objective of H_∞ suboptimal control. It is shown that a solution to this problem exists if and only if the standard H_∞ problem admits a solution and certain matrix inequalities are satisfied. These solvability conditions are readily computable. Controller synthesis is also addressed     

Feedback stabilization of semiconductor laser arrays with complexcoupling coefficients

In this paper, we show that a coupled diode-injection laser stripe array system with complex coupling coefficients can be stabilized around the lowest order supermode using a feedback-control law and verify the system performance by numerical simulations. The symmetry of the array can be exploited to obtain a feedback-control law of a particularly simple form     

Time series determination of transfer functions in random fatigue

Time series determination of the transfer function which relates the input random excitation and the output response in random fatigue experiment is established. This process involves determination of univariate time series of input and output, transfer function and noise models, and the transfer functionnoise model.     

An efficient hybrid security mechanism based on chaos and improved BPCS

Commonly used security mechanisms such as cryptography and steganography suffer from weaknesses when used in a standalone manner. Extra efforts in the form of additional permutations/diffusions etc. result in higher ciphering/deciphering time complexity. Thus, there is a requirement for a security mechanism(s) which can provide adequate security without putting a considerable burden on ciphering/deciphering time complexity. This paper is an effort in this direction. The paper proposes a hybrid mechanism that employs chaotic based encryption scheme to encrypt data and an improved Bit-Plane Complexity Segmentation Steganography algorithm to embed the data. The proposed mechanism uses two new complexity measures to differentiate between noisy regions and simple ones appropriately. The scheme was implemented in MATLAB, and the simulation results show that the proposed mechanism has high embedding capacity, high security with a moderate decrease in PSNR value and is computationally fast.     

A Performance Enhancement and High Speed Spectrum Sliced Free Space Optical System

Wireless Personal Communications - A cost effective Kerr nonlinearity based spectrum sliced (SS) WDM free space optical communication system is demonstrated under different weather instabilities....     

A procedure for creep and shrinkage analysis of frames with low beam stiffness

Adjacent vertical members in tall buildings undergo differential time‐dependent deformations due to creep and shrinkage. These deformations result in differential deflections at floor levels and redistribution of forces. An available practical procedure in the literature to estimate these deformations, taking into account the sequential nature of the loading, utilizes the rate of creep method (RCM) to evaluate the stress transfer between concrete and steel. This procedure is designated as Procedure(RCM) and is prone to errors since the creep recovery of concrete is neglected in RCM. A more accurate procedure designated as Procedure(AEMM) using the age‐adjusted effective modulus method (AEMM) as a stress transfer method, and taking into account the sequential nature of the loading, is proposed. The proposed procedure is more accurate than Procedure(RCM) since creep recovery of concrete is considered in AEMM. Numerical studies are carried out in this paper to compare the results from these two procedures. Copyright © 2007 John Wiley & Sons, Ltd.     

Control of Creep and Shrinkage Effects in Steel Concrete Composite Bridges with Precast Decks

Creep and shrinkage in concrete deck of steel-concrete composite bridges can result in significant redistribution and consequent increase in bending moments at continuity supports and also increase in deflections. Studies are presented for the control of creep and shrinkage effects in steel-concrete composite bridges with precast concrete decks. A hybrid procedure recently developed by the authors has been used for carrying out the studies. The procedure accounts for creep, shrinkage and progressive cracking in concrete decks. Single span, three span and five span bridges have been analyzed for different thicknesses of concrete decks and grades of concrete. Both the shored and unshored constructions have been considered. It is shown that, for both constructions, the increase in bending moments and midspan deflections can be controlled to a significant degree, without putting constraints on design parameters, by simply delaying the time of mobilization of composite action between the precast concrete deck panels and the steel section. It is also observed that though the percentage change in bending moments due to creep and shrinkage is similar for shored and unshored constructions, the percentage change in midspan deflection is significantly higher for shored construction.     

Determination of surface area/monolayer capacity or limiting micropore volume of carbons from binary and ternary mixtures

It is shown that one can predict the adsorption of binary and ternary mixtures in any percentage ratio from the adsorption of individual component gases by means of John's isotherm equation. The surface area of mesoporous materials or the limiting micropore volume of microporous materials from binary and ternary mixture adsorption isotherms is given. The relation given by Lewis et al. may be used to prove the validity of the above method and determine the contribution of each component of the mixture.