Electrical Engineering

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Shiv Nadar University

In this paper we introduce the concept of Adaptive Orthogonal Frequency Division Multiplexing (AOFDM) for two-way relay systems. In order to implement AOFDM at the nodes, the Channel State Information (CSI) is required. Usually CSI is estimated and hence the effect of estimation error should be considered while implementing AOFDM. In the case of two-way relay, channel estimation at the nodes usually result in the overall channel between the source and relay. But for implementing AOFDM, we require the individual channel between node and relay. We propose a simple method to obtain the individual channel assuming that the estimate of combined channel is available. The loading algorithm used is the Levin-Campello loading algorithm. But the general frame work provided by us can be used to implement other loading algorithms for two-way relay systems. © 2013 IEEE.

World University root node

(SoE) School of Engineering

2013 Annual International Conference on Emerging Research Areas, AICERA 2013 and 2013 International Conference on Microelectronics, Communications and Renewable Energy, ICMiCR 2013 - Proceedings

AOFDM based two-way relay systems

Frequency modulated thermography is becoming a popular thermal non-destructive testing (TNDT) technique which like other active thermographic techniques, requires an external heating stimulus, preferably on a blackened surface. It is however, not immune to non-ideal situation like non-uniform heating and surface emissivity variation. The phase image helps to reduce the effect of surface emissivity variation to some extent, but is inadequate in case of large variations. Further, structural noise can significantly interfere with the process of defect detection, as in the case of carbon fibre composite materials. This paper proposes two image reconstruction algorithms for off-line reduction of structural noise. The first utilizes the periodic nature of structural noise if present, and removes it using 2-dimensional Fourier transformation and a spatial band-stop filter. The other uses time serial reconstruction algorithm to remove such noise. The latter was originally proposed by the authors to remove artifacts from surface emissivity variation on metallic samples. The performances of both algorithms are successfully demonstrated on a carbon fibre test piece, having 2mm, 4mm, and 6mm diameter back drilled holes at various depths ranging from 0.25mm to 2mm in steps of 0.25mm. © 2013 SPIE.

Proceedings of SPIE - The International Society for Optical Engineering

Structural noise reduction in frequency modulated thermal wave imaging of carbon fibre composite materials

In this work, 2,3,5,6-tetrafluoro-7,7′,8,8′- tetracyano quinodimethane (F4-TCNQ) diffusion has been studied using secondary ion mass spectroscopy (SIMS). SIMS depth profiling has been performed in dual beam mode, in which, a low energy oxygen beam has been used for etching and a high energy Bi1+ ion beam has been used for analysis. F4-TCNQ has been identified by the distinguishable presence of fluorine in organic layers. For this study, organic light emitting diodes (OLEDs) were fabricated with F4-TCNQ as a hole injection layer with 1, 2.5 and 5.5 nm thicknesses. The diffusion length and depth were measured to be 13, 19, 19.1 nm and 27, 28, 29 nm for 1, 2.5, 5.5 nm thicknesses of F 4-TCNQ, respectively. The diffusion of F4-TCNQ into the hole transport layer leads to the ionization of F4-TCNQ molecules and p-type doping of the hole transport material. The effect of the electric field on the diffusion was also studied by performing the depth profiling on electric field applied OLEDs and it was observed that the application of the electric field has increased both the diffusion length and depth of F4-TCNQ. This effect was found to be more pronounced for the OLED with 1 nm thickness of F4-TCNQ in comparison to the OLEDs with 2.5 and 5.5 nm thicknesses of F4-TCNQ. The field affected diffusion length and depth were found to be 14.5, 19.5, 19.6 and 35, 28.6, 29.6 nm for OLEDs with 1, 2.5, 5.5 nm thicknesses of F4-TCNQ hole injection layer. The decrease in the field effect has been ascribed as being due to the increase in the cluster density and size. Further, the effect of F4-TCNQ diffusion on OLEDs has been studied by capturing the optical images at different instances of time. OLEDs with 1 nm F4-TCNQ layer were found to be the most unstable. This effect has been ascribed as being due to diffusion of F4-TCNQ into the emissive layer which leads to the dissociation of excitons formed inside the emissive layer. © 2013 The Royal Society of Chemistry.

RSC Advances

Study of 2,3,5,6-tetrafluoro-7,7′,8,8′- tetracyano quinodimethane diffusion in organic light emitting diodes using secondary ion mass spectroscopy

We report the synthesis, mesomorphic behavior, and mobility values of a series of highly ordered N-substituted triindole-based columnar liquid crystals. Shortening the length of N-alkylic substituents from N-dodecyl to N-methyl chains results in a drastic approach of the disks within the columns and in an impressive increase in charge carrier mobility. An study of aggregation in solution provide insights into the intermolecular forces responsible of the reduction of the intrastack distance as the size of the N-alkyl chains is decreased and offer evidence of stabilization of the columns by the contribution of cooperative CH-π interactions. The materials presented here exhibit mobility values, even in totally misaligned columnar phases, that may compete with those of the best polycrystalline organic semiconductors, without the need of costly vacuum evaporation processes. © 2012 American Chemical Society.

Chemistry of Materials

High hole mobility in triindole-based columnar phases: Removing the bottleneck of homogeneous macroscopic orientation

Wireless sensor networks (WSN) MAC protocol has been the active research area since last few years because of application specific nature of these networks. This paper studies popular contention based SMAC protocol in multihop scenario and analyzes its suitability in mission critical WSN applications. Along with the residual energy, the throughput and packet delivery ratio are considered as the important parameters for mission critical applications. Improvements are suggested in the SMAC protocol with the simulation results in NS-2. © 2013 IEEE.

Proceedings of the 2013 3rd IEEE International Advance Computing Conference, IACC 2013

Analysis of SMAC protocol for missioon critical applications in wireless sensor networks

Lock-in (LI) thermography is a popular thermal-nondestructive-testing technique which, like other active thermographic techniques, requires an external heating stimulus, preferably on a blackened surface. It is not, however, immune to nonideal situations like nonuniform heating and surface emissivity variation. The phase image, to some extent, helps to reduce the effect of these artifacts but is inadequate if the variations are large. For example, a poorly blackened metallic sample with reflecting patches on its surface is very difficult to actively thermograph because of direct reflection from the surface. This paper proposes an image reconstruction algorithm for offline removal of such artifacts. In addition, the proposed algorithm enables LI thermography tests in the transient regime and removes temperature gradients due to nonuniform heating. The algorithm was tested with a mild-steel sample having 20-mm-diameter back-drilled holes at various depths ranging from 0.2 to 7.7 mm, stimulated at 20-, 40-, 50-, 60-, and 80-mHz excitation frequencies. The effect of the total number of heating cycles is also presented. © 2011 IEEE.

IEEE Transactions on Instrumentation and Measurement

Image enhancement in transient lock-in thermography through time series reconstruction and spatial slope correction

Pulsed thermography (PT), being simple and fast, remains one of the most popular thermographic NDE techniques, though it has intrinsic limitations. An alternative method is suggested and named frequency modulated thermal wave imaging (FMTWI), where the heating waveform phase relations are adjusted over a bandwidth (B) in such a way, that a chirp (frequency modulated) signal of duration T, with much reduced peak power is produced. FMTWI, while retaining all characteristics of lock-in thermography, has the added advantage of overcoming the blind frequency problem. It can be processed by matched filtering (pulse compression) to improve sensitivity. © 2012 American Institute of Physics.

AIP Conference Proceedings

Frequency modulated thermal wave imaging

A new type of intrinsic photoconductor was used as a donor in bulk heterojunction solar cells, in blends with PCBM. The donor is a square planar cyclopalladated coordination complex, with a Nile red moiety and a Schiff base as ligands, coordinated by a Pd(II) metal center. The photoconducting properties of the complex were characterized. Photovoltaic devices exhibit low performance, but the analysis of the wavelength dependence of the efficiency reveals a much higher photocurrent upon absorption of the complex, when compared to the photocurrent obtained via absorption by PCBM. This effect is tied to the higher tendency of the intrinsic photoconductor towards exciton dissociation at the heterojunction. © 2012 Copyright Taylor and Francis Group, LLC.

Molecular Crystals and Liquid Crystals

Enhancement of exciton dissociation efficiency in bulk heterojunction solar cells by using an intrinsic photoconductor component

Various OSIC MIMO detectors are considered suboptimal in terms of performance and complexity, however suffers from error propagation. QR-LRL is considered to be most effective to mitigate error performance as it detects the least reliable layer(LRL) symbol first. It achieves hard ML performance, but suffers from empty vector set(EVS) problem for soft output generation. Some of the previous work mitigates this problem effectively and achieves soft ML performance at the cost of complexity. QR-LRL based IDD(Iterative Detection and Decoding) is an alternative solution, which exchanges the extrinsic information between detector and decoder. Based on feed back knowledge from decoder, decision is made to update candidate vector set for soft output generation. Simulation results shows that significant performance improvement is achieved while keeping the receiver design simple. © 2012 IEEE.

International Conference on ICT Convergence

Efficiently using extrinsic gain for candidate vectors selection in QR-LRL based IDD MIMO receiver

<p>A plasma cathode electron (PCE) gun has capabilities for generating high-current, broad, and focused beams for plasma-assisted microwave sources. A pseudospark-based hollow cathode PCE gun has been designed and developed for microwave generation which is operated in argon atmosphere. An analysis of the electron beam profile inside the drift space at different operating conditions has been carried out. This has been performed at several axial and radial locations inside the drift space which shows coherent phases of beam profiles in radial direction. The focusing and defocusing points in axial direction are also obtained. The beam current at different axial location for different applied voltages has been estimated. The obtained beam current is in close agreement with the beam current estimated by the particle-in-cell simulation code for the same geometry.</p>