Patterns and bifurcations in low-Prandtl number Rayleigh-Benard convection

We present a detailed bifurcation structure and associated flow patterns for low-Prandtl number ($P=0.0002, 0.002, 0.005, 0.02$) Rayleigh-B\'{e}nard convection near its onset. We use both direct numerical simulations and a 30-mode low-dimensional model for this study. We observe that low-Prandtl number (low-P) convection exhibits similar patterns and chaos as zero-P convection \cite{pal:2009}, namely squares, asymmetric squares, oscillating asymmetric squares, relaxation oscillations, and chaos. At the onset of convection, low-P convective flows have stationary 2D rolls and associated stationary and oscillatory asymmetric squares in contrast to zero-P convection where chaos appears at the onset itself. The range of Rayleigh number for which stationary 2D rolls exist decreases rapidly with decreasing Prandtl number. Our results are in qualitative agreement with results reported earlier

INTERVENTION of Bluetooth with WLAN and WIMAX

Bluetooth technology unplugs the digital peripherals and comes as cable replacement technology. IEEE 802.11 and Bluetooth are two operating in the unlicensed 2.4 GHz frequency. WiMAX is operating both licensed and unlicensed frequencies (2-11GHz). The devices equipped with IEEE 802.11 and Bluetooth are mobiles, laptops, watches and many more and in future with WiMAX. Result is the number of co-located devices may cause interference issues in the 2.4 GHz radio frequency spectrum. Bluetooth supports both voice (SCO) and data (ACL) packets. In ACL, there is retransmission of packet if it is lost while transmitting but in SCO there is no retransmission of packet. So, retransmission is big issue in Bluetooth. In this thesis, these interference issues are investigated and implement a new Bluetooth voice packet named synchronous connection-oriented with Repeated Transmission (SCORT) with WLAN interference and WiMAX interference to study the improvement in performance by using MATLAB Simulink. SCORT technique also helps in reducing co-existing interference by using HV3 type of packet in voice signal. By this technique BER does not effect at all and very minimal delay comes due to retransmission

Role of Bulk flow in Turbulent Convection

In this paper we present scaling of large-scale quantities like Pecl\'{e}t and Nusselt numbers, and the dissipation rates of kinetic energy and entropy. Our arguments are based on the scaling of bulk quantities and earlier experimental and simulation results. We also present the inertial-range properties of spectra and fluxes of kinetic energy and entropy.Comment: 15 pages, to Appear in the proceedings of "Senfest, International Conference on Complex Processes in Plasmas and Nonlinear Dynamical Systems

Online monitoring of voltage stability margin using PMU measurements

With the growing smart grid concept it becomes important to monitor health of the power system at regular intervals for its secure and reliable operation. Phasor Measurement Units (PMUs) may play a vital role in this regard. This paper presents voltage stability monitoring in real time framework using synchrophasor measurements obtained by PMUs. Proposed approach estimates real power loading margin as well as reactive power loading margin of most critical bus using PMU data. As system operating conditions keep on changing, loading margin as well as critical bus information is updated at regular intervals using fresh PMU measurements. Simulations have been carried out using Power System Analysis Toolbox (PSAT) software. Accuracy of proposed Wide Area Monitoring System (WAMS) based estimation of voltage stability margin has been tested by comparing results with loading margin obtained by continuation power flow method (an offline approach for accurate estimation of voltage stability margin) under same set of operating conditions. Case studies performed on IEEE 14-bus system, New England 39-bus system and a practical 246-bus Indian power system validate effectiveness of proposed approach of online monitoring of loading margin

Outcome of vascularised muscle pedicle bone graft for scaphoid non-union

Background: The objective of the study was to assess the outcome of vascularised muscle pedicle bone graft for scaphoid non-union.Methods: 14 men and 6 women aged 18-45 (mean 25) years with non-union of scaphoid involving proximal pole (n=4), waist (n=14), distal pole (n=2) were randomized to undergo vascularised muscle pedicle bone graft with Herbert screw fixation. The mean duration of non-union was 10 months (range 4-14 months).Results: The mean follow up duration was 24 months. 17 of 20 achieved union. 12 of 20 achieved correction of both scapholunate and radiolunate angle. 5 of 20 did not achieve full correction of sacpholunate and radiolunate angle. 3 of 20 did not achieve union. 2 of these 3 were associated with proximal pole absorption. There was no hardware failure or any iatrogenic fracture during pedicle dissection. Conclusions: The use of vascularised bone graft has proved to be an effective method for treating scaphoid non-union, especially non-union with an avascular proximal pole and those that have failed to heal after previous procedure