An improved stability result for linear time-delay system using a new Lyapunov–Krasovskii functional and extended reciprocally convex inequality

This paper is concerned with the stability analysis of a linear system with interval time-varying delay using an augmented Lyapunov–Krasovskii (LK) functional approach. A delay-dependent stability criterion is developed in LMI framework to estimate the maximum allowable bound of the time-delay within which the system remains asymptotically stable in the sense of Lyapunov. Conservatism in the proposed delay-dependent stability analysis is reduced by introducing a new LK functional along with the Wirtinger's inequality and extended reciprocally convex matrix inequality. Finally, two numerical examples and the load frequency control problem have been solved to validate the superiority of the proposed stability criterion compared to existing literature.     

Static and decentralized-adaptive load balancing in a starconfigured distributed computing system

The problem of minimizing the average job response time (sojourn time) in a star configured distributed computing system (DCS) with N peripheral processors and one central processor is studied. Each peripheral processor (satellite) receives a stream of Poisson arrivals. A job arriving at a satellite S_i will be processed with a probability (1-P_i) by itself and routed to the central site for remote processing with probability P_i. The service time distribution at each processor is arbitrary with means 1/μ_i and second moments E[Y_i²], i=0,…,N. We first develop an algorithm to compute the optimal routing probabilities when the arrival and the service parameters are known a priori. We then develop an adaptive estimator to be used by each satellite to compute its optimal routing probability, when the parameters (everywhere) are unknown a priori, a copy of the algorithm runs on each peripheral processor and uses the sojourn time measurements that the peripheral processor can gather on its own from those jobs that are sent to the central processor and returned to the originating site after service     

Controlled Drug Delivery of Ph Dependent Soluble Drug-Pindolol

Pindolol, a pH dependent soluble beta adrenoceptor blocker has been formulated into a controlled drug delivery system. Drug pellets were prepared by extrusion spheronization technique. These were coated with different retardant polymers, namely ethylcellulose and Eudragit RS 100. The effect of different variables such as coating level and pH of dissolution medium have been studied. Drug release from pellets were found to be influenced by the pH of the dissolution medium. A flux release of the drug in the acidic buffer was observed from pellets coated with these polymers. To avoid this flux, a top coat using different pH sensitive polymers, namely Hydroxypropylmethyl cellulose phthalate (HPMCP 55) and Eudragit S 100 was successfully attempted and the drug release from the pellets was modified.     

Implementation of curvilinear geometry into p-version HT plate elements

The formulation of the recently presented hybrid-Trefftz (HT) p-version elements¹ has thus far been restricted to straight-sided polygonal elements. The present paper removes this limitation. Two alternative formulations are studied. In the first one any curvilinear geometry is represented accurately but the rigid body modes are recovered only in the limit as the p-refinement level is increased. In contrast, the second formulation represents the rigid modes exactly while the actual curvilinear geometry is approached with increasing accuracy as the p-refinement level is increased. The practical efficiency of the two alternative approaches is studied and assessed on pertinent examples of thin plates in bending.     

A doubly curved quadrilateral finite element for the analysis of laminated anisotropic thin shells of revolution

The details of development of the stiffness matrix for a doubly curved quadrilateral element suited for static and dynamic analysis of laminated anisotropic thin shells of revolution are reported. Expressing the assumed displacement state over the middle surface of the shell as products of one-dimensional first order Hermite polynomials, it is possible to ensure that the displacement state for the assembled set of such elements, is geometrically admissible. Monotonic convergence of total potential energy is therefore possible as the modelling is successively refined. Systematic evaluation of performance of the element is conducted, considering various examples for which analytical or other solutions are available.     

Experimental study on interfacial heat-transfer coefficients at the casting/die interface in squeeze casting under transient condition

ABSTRACT

By using two-dimensional transient state inverse problems method, the interfacial heat-transfer coefficient (IHTC) was evaluated, based on experimentally measured temperature distributions of solidification of an Al alloy under various pressures (40, 50 and 60?MPa). The value of IHTC obtained from the mould and the casting varies with time subsequent to pouring the molten metal into a mould cavity. The impact of different applied pressure with different positions of mould insulation on IHTC was experimentally measured and calculated for the analysis. The calculated heat-transfer coefficients were used for solidification simulation in the compress casting process.