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Naidu D.H.R.,Sri Sathya Sai Institute of Higher Learning | Srinivasan S.,Digital Signal
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2012

Single-microphone speech enhancement algorithms that employ trained codebooks of parametric representations of speech spectra have been shown to be successful in the suppression of non-stationary noise, e.g., in mobile phones. In this paper, we introduce the concept of a context-dependent codebook, and look at two aspects of context: dependency on the particular speaker using the mobile device, and on the acoustic condition during usage (e.g., hands-free mode in a reverberant room). Such context-dependent codebooks may be trained on-line. A new scheme is proposed to appropriately combine the estimates resulting from the context-dependent and context-independent codebooks under a Bayesian framework. Experimental results establish that the proposed approach performs better than the context-independent codebook in the case of a context match and better than the context-dependent codebook in the case of a context mismatch. © 2012 IEEE.

Anand B.,Sri Sathya Sai Institute of Higher Learning | Podila R.,Clemson University | Lingam K.,Clemson University | Krishnan S.R.,Sri Sathya Sai Institute of Higher Learning | And 4 more authors.
Nano Letters | Year: 2013

Nanostructured carbons are posited to offer an alternative to silicon and lead to further miniaturization of photonic and electronic devices. Here, we report the experimental realization of the first all-carbon solid-state optical diode that is based on axially asymmetric nonlinear absorption in a thin saturable absorber (graphene) and a thin reverse saturable absorber (C 60) arranged in tandem. This all-optical diode action is polarization independent and has no phase-matching constraints. The nonreciprocity factor of the device can be tuned by varying the number of graphene layers and the concentration or thickness of the C60 coating. This ultracompact graphene/C60 based optical diode is versatile with an inherently large bandwidth, chemical and thermal stability, and is poised for cost-effective large-scale integration with existing fabrication technologies. © 2013 American Chemical Society.

Anand B.,Sri Sathya Sai Institute of Higher Learning | Kaniyoor A.,Indian Institute of Technology Madras | Sai S.S.S.,Sri Sathya Sai Institute of Higher Learning | Philip R.,Raman Research Institute | Ramaprabhu S.,Indian Institute of Technology Madras
Journal of Materials Chemistry C | Year: 2013

We present the mechanism and performance of optical limiting (OL) in hydrogen exfoliated graphene (HEG), functionalized HEG (f-HEG) and its metal hybrids. At the wavelengths used, the mechanism of nonlinear absorption (NLA) involves two-photon absorption and excited state absorption in the nanosecond excitation regime, and saturable absorption in combination with two-photon absorption in the femtosecond (ultrafast) excitation regime. The role of defects in the OL performance of HEG and f-HEG is investigated with the help of their Raman spectra. OL efficiency of f-HEG is found to improve with Pt and Pd nanoparticle decoration due to an enhanced NLA, which arises mainly from interband transitions between the d band and the s-p conduction band in the metal NPs, and charge transfer between f-HEG and metal NPs. Thermally induced light scattering is negligible in these water dispersed systems. This journal is © 2013 The Royal Society of Chemistry.

Sai Siddhardha R.S.,Sri Sathya Sai Institute of Higher Learning | Lakshminarayanan V.,Raman Research Institute | Ramamurthy S.S.,Sri Sathya Sai Institute of Higher Learning
Journal of Power Sources | Year: 2015

Hydrogen has been proposed as the green fuel of the future in the wake of depleting fossil fuels. Recently, carbon paste electrodes (CPE) modified with nanomaterials as electrocatalysts have drawn wide attention for hydrogen evolution reaction (HER) in acid medium. The CPEs are advantageous owing to their chemical stability and ease of fabrication. Their applications for HER without any modification, however, are hampered on account of large hydrogen overpotential associated with carbon surface. In the present study, CPE has been modified with novel gold composites as electro-catalysts for HER in acid medium. The nanocomposites have shown ∼100 fold increased current density than unmodified CPE at -0.3 V. Most strikingly for the first time, this study has quantitatively brought out the difference in catalysis between surfactant capped and pristine gold nanoparticles in terms of their application as spot-free catalysts towards hydrogen gas production by electrochemical route. © 2015 Elsevier B.V. All rights reserved.

Suresh P.,Sri Sathya Sai Institute of Higher Learning | Thayaparan T.,Sri Sathya Sai Institute of Higher Learning | Obulesu T.,McMaster University | Venkataramaniah K.,Sri Sathya Sai Institute of Higher Learning
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

In this paper, we report the efficiency of the Fourier-Bessel transform (FBT) and time-frequency (TF)-based method in conjunction with the fractional Fourier transform (FrFT), for extracting micro-Doppler (m-D) radar signatures from the rotating targets. This approach comprises mainly of two processes, with the first being the decomposition of the radar return, in order to extract m-D features, and the second being the TF analysis to estimate motion parameters of the target. In order to extract m-D features from the radar signal returns, the time domain radar signal is decomposed into stationary and nonstationary components using the FBT in conjunction with the FrFT. The components are then reconstructed by applying the inverse Fourier-Bessel transform (IFBT). After the extraction of the m-D features from the target's original radar return, TF analysis is used to estimate the target's motion parameters. This proposed method is also an effective tool for detecting maneuvering air targets in strong sea clutter and is also applied to both simulated data and real-world experimental data. © 2013 IEEE.

Katuri J.,Sri Sathya Sai Institute of Higher Learning | Katuri J.,Intelligent Group
Angewandte Chemie - International Edition | Year: 2015

Chemically powered micro- and nanomotors are small devices that are self-propelled by catalytic reactions in fluids. Taking inspiration from biomotors, scientists are aiming to find the best architecture for self-propulsion, understand the mechanisms of motion, and develop accurate control over the motion. Remotely guided nanomotors can transport cargo to desired targets, drill into biomaterials, sense their environment, mix or pump fluids, and clean polluted water. This Review summarizes the major advances in the growing field of catalytic nanomotors, which started ten years ago. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Venkatesh S.,Sri Sathya Sai Institute of Higher Learning | Badiya P.K.,Sri Sathya Sai Institute of Higher Learning | Ramamurthy S.S.,Sri Sathya Sai Institute of Higher Learning
Chemical Communications | Year: 2015

We have engineered the use of 2D, 1D and 0D carbon allotropes as spacers to achieve in excess of 1000-fold fluorescence enhancements in a Surface plasmon-coupled emission (SPCE) platform. We also have demonstrated the femtomolar sensitivity of silver decorated carbon dots (AgCD) in the detection of a radiating dipole. © The Royal Society of Chemistry 2015.

Sood P.C.,Sri Sathya Sai Institute of Higher Learning | Gowrishankar R.,Sri Sathya Sai Institute of Higher Learning | Dora A.K.,Sri Sathya Sai Institute of Higher Learning
Physical Review C - Nuclear Physics | Year: 2014

Whereas the 7.2 min Np240, first identified over 60 years ago, has been assigned conflicting configuration by various investigators, the 62 min Np240 is assigned aconfiguration, deduced in each case by primarily focusing on just a single connected pair of levels in either Np240 () 240Pu or 240U () Np240 decay. We evaluate the level energies of physically admissible 2qp configurations in 93240Np147 employing a three-step procedure, with experimental inputs at each step, and using a well tested two-particle rotor model with inclusion of residual n-p interaction and other contributions. This exercise clearly establishes that the 62 min Np240 and the 7.2 min Np240 isomers constitute a Gallagher-Moszkowski (GM) doublet corresponding to the two-quasiparticle (2qp) configuration 5+{p5/2+[642]±n5/2+[622]}0+ with JÏ€K=1+0 for the higher-lying 7.2 min isomer. This assignment is conclusively confirmed in a level-by-level analysis of data on 23 transitions in these decays. Structures of a few other Np240 levels populated in 240U decay are also discussed. © 2014 American Physical Society.

Sood P.C.,Sri Sathya Sai Institute of Higher Learning | Gowrishankar R.,Sri Sathya Sai Institute of Higher Learning
Physical Review C - Nuclear Physics | Year: 2014

Though the neutron-rich odd-odd nucleus Ta73186113 was first produced in 1955, even after 60 years its ground state (g.s.) and both of its two other isomers remain undefined. We use the well-tested two-quasiparticle rotor model, which explicitly includes residual neutron-proton n-p interaction and other contributing factors, to evaluate the bandhead energies of the physically admissible low-lying two-particle structures in Ta186 with inputs from experimentally observed structures in neighboring isotopes and isotones to characterize these levels. Our analysis assigns Kπ = 5-{p:7/2[404] - n:3/2[512]} configuration to the 10.5 min Ta186(g.s.) and the antiparallel-spin Kπ=2- of the same configuration to the 1.54 min isomer with Ex = 90(10) keV. We further assign Kπ=8-{p:7/2[404] - n:9/2[505]} configuration to the recently identified 3.0 min isomer with Ex=336 (20) keV. These assignments are shown to be consistent with all the available experimental data. Further, they are seen to fit nicely as another instance of highly hindered ΔI=3 isomeric transitions, and also of low-lying long-lived isomer triplets, frequently observed in numerous odd-odd Z=61(2)75 nuclides. © 2014 American Physical Society.

Venkatesh S.,Sri Sathya Sai Institute of Higher Learning | Ghajesh S.,Sri Sathya Sai Institute of Higher Learning | Ramamurthy S.S.,Sri Sathya Sai Institute of Higher Learning
Plasmonics | Year: 2015

In this work, we report green advancements in surface plasmon-coupled emission (SPCE) spacer layer engineering with the shortest preparation time to realize ≥35-fold enhancements in the fluorescence emission intensity. A simple linker free spin coat of polyvinyl alcohol (PVA) dispersed nanoparticles on a SPCE substrate was employed as a spacer layer to achieve tunable enhancements in plasmon-coupled fluorescence emission intensities. Based on the current findings, the enhancements achieved in the SPCE can be tuned simply by varying the nanomaterial and its size. In the technique developed by us, nanomaterials having any capping agent, shape, and origin can be used as a spacer material as the nanomaterials are coated on the silver thin film in the form of a PVA-embedded hybrid spacer without the use of any linker or bond forming chemicals. We also demonstrate the use of biogenic nanoparticles as SPCE spacer layers for enabling tuning of SPCE enhancements. © 2014, Springer Science+Business Media New York.

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