arXiv subjects

A. Mahmood

Publications and source records attributed to A. Mahmood.

23 records · Page 2Linked to original sources

arXiv2012

Monitoring and Controlling Power using Zigbee Communications

Smart grid is a modified form of electrical grid where generation, transmission, distribution and customers are not only connected electrically but also through strong communication network with each other as well as with market, operation and service provider. For achieving good communication link among them, it is very necessary to find suitable protocol. In this paper, we discuss different hardware techniques for power monitoring, power management and remote power controlling at home and transmission side and also discuss the suitability of Zigbee for required communication link. Zigbee has major role in monitoring and direct load controlling for efficient power utilization. It covers enough area needed for communication and it works on low data rate of 20Kbps to 250Kbps with minimum power consumption. This paper describes the user friendly control home appliances, power on/off through the internet, PDA using Graphical User Interface (GUI) and through GSM cellular mobile phone.

cs.NI↗

arXiv2012

Energy Efficient MAC Protocols

This paper presents a survey of energy efficiency of Medium Access Control (MAC) protocols for Wireless Body Area Sensor Networks (WBASNs). We highlight the features of MAC protocols along with their advantages and limitations in context of WBASNs. Comparison of Low Power Listening (LPL), Scheduled Contention and Time Division Multiple Access (TDMA) is also elaborated. MAC protocols with respect to different approaches and techniques which are used for energy minimization, traffic control mechanisms for collision avoidance are discussed.We also present a survey of path loss models for In-body, On-body and Off-body communications in WBASNs and analytically discuss that path loss is maximum in In-body communication because of low energy levels to take care of tissues and organs located inside the body. Survey of Power model for WBANs of CSMA/CA and beacon mode is also presented.

cs.NI↗

arXiv2012

Quasiparticle scattering off phase boundaries in epitaxial graphene

We investigate the electronic structure of terraces of single layer graphene (SLG) by scanning tunneling microscopy (STM) on samples grown by thermal decomposition of 6H-SiC(0001) crystals in ultra-high vacuum. We focus on the perturbations of the local density of states (LDOS) in the vicinity of edges of SLG terraces. Armchair edges are found to favour intervalley quasiparticle scattering, leading to the (\surd3\times\surd3)R30° LDOS superstructure already reported for graphite edges and more recently for SLG on SiC(0001). Using Fourier transform of LDOS images, we demonstrate that the intrinsic doping of SLG is responsible for a LDOS pattern at the Fermi energy which is more complex than for neutral graphene or graphite, since it combines local (\surd3\times\surd3)R30° superstructure and long range beating modulation. Although these features were already reported by Yang et al. Nanoletters 10, 943 (2010), we propose here an alternative interpretation based on simple arguments classically used to describe standing wave patterns in standard two-dimensional systems. Finally, we discuss the absence of intervalley scattering off other typical boundaries: zig-zag edges and SLG/bilayer graphene junctions.

cond-mat.mes-hall↗

arXiv2009

On the energetic balance for the flow of an Oldroyd-B fluid induced by a constantly accelerating plate

Exact and approximate expressions are established for dissipation, the power of the shear stress at the wall and the boundary layer thickness corresponding to the motion of an Oldroyd-B fluid induced by a constantly accelerating plate. The similar expressions for Maxwell, Newtonian and second grade fluids, performing the same motion, are obtained as limiting cases of our general results. The specific features of the four models are emphasized by means of the asymptotic approximations.

math-ph↗

arXiv2007

Few layer graphene on SiC, pyrolitic graphite and graphene: a Raman scattering study

The results of micro-Raman scattering measurements performed on three different ``graphitic'' materials: micro-structured disks of highly oriented pyrolytic graphite, graphene multi-layers thermally decomposed from carbon terminated surface of 4H-SiC and an exfoliated graphene monolayer are presented. Despite its multi-layer character, most parts of the surface of the graphitized SiC substrates shows a single-component, Lorentzian shape, double resonance Raman feature in striking similarity to the case of a single graphene monolayer. Our observation suggests a very weak electronic coupling between graphitic layers on the SiC surface, which therefore can be considered to be graphene multi-layers with a simple (Dirac-like) band structure.

cond-mat.mes-hall↗