Cluster-Based Opportunistic Spectrum Allocation in CRWMN’s Using Co-operative Mechanism

With the innovation of Cognitive Radio Wireless Mesh Network’s, Opportunistic Spectrum Allocation can possibly moderate spectrum lack, by letting Secondary User’s a chance to sense and use unused bits of opportunistic licensed spectrum without any unfavourable effect on the Primary User’s. In Cognitive Radio Wireless Mesh Network’s, the Medium-Access-Control protocols characterizes the utilization of spectrum proficiently by allocating the channels among the users. Majority of proposed Medium-Access-Control protocols are utilizing Common-Control-Channel for dealing with the assets of Secondary-Users. The major downsides of these Medium-Access-Control protocols are broadcasting of Control-channel when substantial number of Secondary-User exists. In contrast with these Medium-Access-Control protocols, we develop an algorithm Time-Slotted-Allocation-Medium-Access-Control (TSA-MAC) protocol which is based on Clustered Time-Division-Medium-Access approach, which permits Secondary-User’s to allocate opportunistic spectrum with the help of co-operative decisions by exchange control information. In this approach, we are dividing the channels as different slots on which Secondary-User’s can transfer control and data packets. The TSA-MAC protocol will enhance the throughput for the Secondary-User’s over the communication channel. And also this method will facilitate to decide and allocate free channels for Secondary-User’s without interfering with Primary User’s.     

Strain paint: noncontact strain measurement using single-walled carbon nanotube composite coatings

Composite coatings have been developed that reveal strains in underlying structural elements through noncontact optical measurement. Dilute individualized single-walled carbon nanotubes are embedded in a polymeric host and applied to form a thin coating. Strain in the substrate is transmitted through the polymer to the nanotubes, causing systematic and predictable spectral shifts of the nanotube near-infrared fluorescence peaks. This new method allows quick and precise strain measurements at any position and along any direction of the substrate.     

Trust region‐based optimization of PKI neural models for RF/microwave devices

This article proposes a new trust region‐based optimization technique for Radio Frequency (RF)/microwave devices. The proposed approach is apt for modeling scenarios, where standard ANN multilayer perceptron (MLP) and Prior Knowledge Input (PKI) models fail to deliver a satisfactory model. This approach feeds output of standard ANN model as knowledge input to PKI model. The ANN model and the PKI model form a symbiotic pair to yield accurate results. In this paper, the dogleg routine is exploited in the process of optimization to obtain valid trust region steps. The proposed method is compared with sensitivity technique via several RF/microwave components. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Flexible Piezoelectric ZnO–Paper Nanocomposite Strain Sensor

The fabrication of a mechanically flexible, piezoelectric nanocomposite material for strain sensing applications is reported. Nanocomposite material consisting of zinc oxide (ZnO) nanostructures embedded in a stable matrix of paper (cellulose fibers) is prepared by a solvothermal method. The applicability of this material as a strain sensor is demonstrated by studying its real‐time current response under both static and dynamic mechanical loading. The material presented highlights a novel approach to introduce flexibility into strain sensors by embedding crystalline piezoelectric material in a flexible cellulose‐based secondary matrix.     

Effects of simultaneous switching noise on the tapered bufferdesign

Complementary metal-oxide-semiconductor (CMOS) output buffers, comprised of a series of tapered inverters, are used to drive large off-chip capacitances. The ratio of the size of transistors between two consecutive stages is the buffer taper factor. With higher frequency of operation and simultaneous switching of the output drivers, the parasitic inductance present at the pin-pad-package interface results in significant switching noise on the power lines. A comprehensive analysis and estimate of simultaneous switching noise (SSN) including the velocity saturation effects seen in the submicron transistors during the switching of output drivers is presented. The effect of SSN on the overall buffer propagation delay and transition time is discussed. The presence of SSN results in an increase in the optimum taper factor between inverter stages for a given capacitive load. Beyond a critical value, the output transition time of a tapered buffer increases with reducing taper factor due to SSN. SSN can be reduced by skewing the switching of output buffers, SPICE simulation results show that skewing buffer switching with additional inverter stages reduces SSN and increases buffer propagation delay     

The strain sensing and thermal–mechanical behavior of flexible multi-walled carbon nanotube/polystyrene composite films

The strain sensing and thermal–mechanical behaviors of well dispersed multi-walled carbon nanotube/polystyrene (MWCNT/PS) composite films with different wt.% of carbon nanotubes were analyzed. The thermal–mechanical properties are studied using a dynamical mechanical analyzer and the results give their storage modulus (E′) and loss modulus (E″) as a function of temperature. We found an increase in E′ of up to 122% at 80 °C for a 6 wt.% MWCNT/PS composite compared to PS. The glass transition temperature increased significantly with an increase in MWCNTs concentration. The strain sensing behavior of the films is measured by applying an axial load over film which is attached to a brass specimen. The composite films exhibit excellent strain sensing behavior for different MWCNT contents. The result shows that an electromechanical response of the composite films varies linearly with applied strain even at high strains.     

Variable-taper CMOS buffers

A variable-taper (VT) approach to buffer design in which the taper from one inverter stage to the next is a function of the position of the inverter within the buffer chain is proposed. Though the minimum delay obtained by using a VT buffer is about 15% more than the minimum delay obtained from conventional fixed-taper (FT) buffers, a small modification to the initial stages of the VT buffer reduces this difference to less than 2%. For similar delays, a VT buffer usually takes less area and consumes less power than an FT buffer