Showing papers by "SRM University published in 2006"

Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system

Abstract: This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.

Security in Ad Hoc Networks: an Extension of Dynamic Source Routing In Mobile Ad Hoc Networks

Abstract: The lack of any centralized infrastructure in mobile ad hoc networks raises many security issues. Thus communication in mobile ad hoc networks functions properly only if the participating nodes cooperate in routing and forwarding. However, some of the nodes may be selfish, for example, by not forwarding the packets to the destination, thereby saving the battery power. Some others may act malicious by launching security attacks like denial of service. In this paper, some of the security attacks are addressed and few related works done on security are analyzed. A new approach based on the extent of friendship between the nodes is proposed over the DSR protocol which makes the nodes to co-operate in an ad hoc environment.

Growth and characterization of borono phenylalanine

Abstract: Borono phenylalanine abbreviated as BPA is a biologically important compound which is obtained from L-Phenylalanine (C9H11NO2) in which a boron atom is bonded. BPA is an amino acid analogue, helpful in the treatment of glioblastoma multiforme, a highly malignant form of brain tumor is crystallized in silica gel under pH 6.0 by single diffusion method in a period of 30 minutes. The grown crystals were characterized by x-ray powder diffraction, Fourier Transform infrared spectroscopy and visible ultraviolet spectroscopy. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A necessary condition for local asymptotic stability of nonlinear systems with exogenous disturbance

Abstract: Local asymptotic stability of nonlinear systems with real-parametric uncertainty or disturbance is one of the important problems in control systems literature. In this paper, we investigate this problem for nonlinear systems with time-varying disturbance. We assume that the disturbance vector is generated by an exosystem, which is neutrally stable. Thus, the disturbances that we consider include both constant and periodic signals. For this class of nonlinear systems with time-varying disturbance, we derive a necessary condition for local asymptotic stability of equilibria. As corollaries of our general result, we deduce the necessary condition obtained by Byrnes and Sundarapandian [1] for nonlinear systems with constant real parametric uncertainty, and the necessary condition obtained by Brockett [2] for nonlinear autonomous systems. We illustrate our result with several examples.

Ontology-driven Model for Knowledge-Based Software Engineering.

Abstract: Software engineering performance can improve if knowledge generated during software development is captured and structured formally for reuse. The developers need a knowledge framework to produce and consume knowledge within software engineering environment. Ontologies have matured to provide knowledge representation and retrieval with semantic completeness and sound reasoning. The explicit knowledge of software process and application domains in the context of software projects can be semantically expressed using ontological concepts and relations. Tacit knowledge from experience can be accumulated as instances of the respective concepts. This paper proposes a model for ontology-driven software engineering environment where explicit and tacit knowledge are accumulated using ontologies represented by OWL (Web Ontology Language). The preliminary results of a pilot implementation of this model have confirmed that structuring of application domain and process knowledge facilitates a better environment for domain modeling, process improvement and instant access to knowledge resources.

Influence of stator and rotor profiles on torque ripple minimization in SRM

Abstract: A major problem of switched reluctance machine is torque ripple, which causes undesirable acoustic noise and vibration This paper presents the results of two dimensional finite element analysis carried out on a 8/6 switched reluctance machine for studying the influence of various rotor and stator profiles on torque ripple in switched reluctance machine

Performance analysis of cross layer AODV for heterogeneously powered ad-hoc networks

Abstract: Heterogeneously powered ad-hoc networks are characterized by asymmetry links. The low power nodes are able to receive from high power nodes but not vice versa. This poses challenges to routing discovery processes of routing protocols, those dependent on symmetry links. In this paper, we propose a cross layer design that effectively improves route discovery and hence the overall performance of heterogeneously powered ad-hoc networks. Our approach identifies and rejects the unidirectional links and seamlessly supports the usage of bi-directional links at the routing layer. This approach is based on calculating the path loss experienced by RREQ packet and judging the ability of the receiving node in delivering the RREP packet to the sending node of the link. That is, it integrates the routing decision of network layer, with signal strength of physical layer. Simulations are performed to study the performance of cross layer AODV (CLAODV) protocol using GloMoSim, the global mobile simulator. This cross layer protocol reduces delay in route discovery and improves packet delivery ratio around 25-35% in the heterogeneously powered ad-hoc network. It also reduces routing overhead around 75-85% and thereby reduces MAC collisions around 70-80%. In summary our design offers a simple, but efficient cross layer routing protocol to support routing in heterogeneously powered ad-hoc networks.

A necessary condition for local asymptotic stability of discrete-time nonlinear systems with exogenous disturbance

Abstract: Local asymptotic stability of nonlinear systems with real-parametric uncertainty or disturbance is one of the important problems in the control systems literature. In this paper, we investigate the problem of asymptotic stability for discrete-time nonlinear systems with time-varying disturbance. We assume that the disturbance vector is generated by an exosystem, which is neutrally stable. Thus, the disturbances that we consider include both constant and periodic signals. For this class of nonlinear systems with time-varying disturbance, we derive a necessary condition for local asymptotic stability of equilibria. As corollaries of our general result, we deduce the necessary condition obtained by Sundarapandian [1] for discrete-time nonlinear systems with constant real parametric uncertainty, and the necessary condition obtained by Lin and Byrnes [2] for discrete-time nonlinear autonomous systems. We illustrate our result with several examples.