3D functional hetero-nanostructures of vertically anchored metal oxide nanowire arrays on porous graphene substrates

Sridhar, V.,Chun, H.H.,Park, H. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.79 No.-

Mesoporous three dimensional hierarchical structure of copper oxide nanowires vertically anchored on graphene substrate was synthesized by a facile and green 'alkali mediated synthesis' under microwave irradiation. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller surface area tests showed highly crystalline nanowires vertically anchored on porous graphene to give a unique mesoporous, hierarchical nanostructures. When applied as anode in lithium ion batteries, our materials exhibit capacity of 770mAhg<SUP>-1</SUP> even after 100 cycles with a Columbic efficiency in excess of 97%, reflecting the ability of the hierarchical network to accommodate the extreme volume changes of metal anodes that occur during the lithiation/delithiation reactions. The utility of our newly developed to synthesize anisotropic titania nano-wires or zinc oxide nano-flowers on graphene substrate is also reported.

Hollow SnO2@carbon core-shell spheres stabilized on reduced graphene oxide for high-performance sodium-ion batteries

Sridhar, V.,Park, H. Royal Society of Chemistry 2017 New journal of chemistry Vol.41 No.2

<P>Sodium ion batteries are rapidly emerging as attractive and costeffective devices in applications such as smart grids and large-scale energy storage. However, the large size of the sodium ion and its tendency to form NaC186 during electrochemical intercalation with carbon anodes necessitate the design of architectures which can accommodate the spatial requirements without sacrificing essential functional properties like good conductivity and high surface area. In this manuscript, we report the synthesis of three-dimensional, mesoporous, nano SnO2 cores encapsulated in carbon shells anchored on reduced graphene oxide (SnO2@ C-rGO) by a simple microwave induced catalytic transformation of diazoniumfunctionalized graphene oxide. The electrochemical results reveal that our SnO2@ C-rGO anodes have excellent electrochemical performance including high-capacity (493.12 mA h g(-1)), good capacity retention and large coulombic efficiency (96.2% after 150 cycles).</P>

Tunnel Recognition for Vision Based Driver Assistance System

Sridhar S,Jitesh K. Singh,Roh Seung Hyun 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11

Detecting changes in the environment while driving is critical in any vision based driving assistance system. These environmental changes have to be handled separately to enhance ADAS (advanced driver assistance system) performance. In particular, this paper focuses on detecting tunnel using a simple and computationally efficient approach. Conventional tunnel detection approaches use tunnel entry and exit information for its recognition. These approaches fail for different tunnel cases and during night condition. In this paper, we propose tunnel recognition algorithm using the pattern of lights available inside the tunnel. The first order line fitting algorithm is used to track the tunnel lights, which almost follow straight lines. The magnitude of error in line fitting decides whether the image has a tunnel or not. It has been observed that the intensity inside the tunnel is less compared to outside environment during day condition. Using this criterion, brightness parameter is calculated to avoid unnecessary processing of normal day image. The proposed algorithm has been tested on both day and night images captured from grayscale monocular camera mounted on the ego vehicle.

Asymmetric Formal Synthesis of (+)‐Lactacystin

Sridhar, Chirumarry,Vijaykumar, Bodduri V. D.,Radhika, Laghuvarapu,Shin, Dong‐,Soo,Chandrasekhar, Srivari WILEY‐VCH Verlag 2014 EUROPEAN JOURNAL OF ORGANIC CHEMISTRY Vol.2014 No.30

<P><B>Abstract</B></P><P>A formal synthesis of (+)‐lactacystin was achieved from commercially available isobutyraldehyde and ethyl acrylate. A Baylis–Hillman reaction, an intermolecular nucleophilic displacement under Mitsunobu conditions, a Sharpless asymmetric epoxidation, a palladium(0)‐catalyzed <I>syn</I>‐selective ring opening of an epoxide by treatment with an azide, a one‐pot azide reductive lactamization, and a ruthenium‐catayzed oxidation were employed as the key steps.</P>

Microwave synthesis of three dimensional graphene-based shell-plate hybrid nanostructures

Sridhar, V.,Lee, I.,Yoon, H.S.,Chun, H.H.,Park, H. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.61 No.-

Though free standing graphene has excellent physical, chemical and electrical properties, its tendency to restack is a major hurdle in realizing its full potential especially in applications such as lithium ion batteries and super capacitors. In this manuscript, we report synthesis of graphene-based three dimensional (3D) shell-plate nanostructures composed of 'nano-cup arrays' anchored on few-layered graphene (FLG) substrates. The synthesis was carried out by a simple process using eco-friendly ionic liquids and microwave irradiation as the energy source. Morphological studies by scanning electron microscopy and transmission electron microscopy showed vertically anchored graphene nano-cups on graphene substrate. Super capacitor electrodes fabricated with FLG/gCup nano-hybrids and its electrochemical properties are studied by cyclic voltammetry (CV) and galvanostatic charge/discharge (DC) methods. FLG/gCup electrodes showed good electrochemical performance, with a maximum specific capacitance of 421Fg<SUP>-1</SUP> at the charge/discharge current density of 100mAg<SUP>-1</SUP> in 1M KOH electrolyte, which is four times higher than pristine graphene sheets. The utility of our developed technique in synthesis of graphene nano-cup arrays on arbitrary surfaces (glass substrate) is also reported.

Damage evaluation of RC beams strengthened with hybrid fibers

Sridhar, Radhika,Prasad, Ravi Techno-Press 2019 Advances in concrete construction Vol.8 No.1

This paper describes an experimental investigation on hybrid fiber reinforced concrete (HYFRC) beams. And the main aim of this present paper is to examine the dynamic characteristics and damage evaluation of undamaged and damaged HYFRC beams under free-free constraints. In this experimental work, totally four RC beams were cast and analyzed in order to evaluate the dynamic behavior as well as static load behavior of HYFRCs. Hybrid fiber reinforced concrete beams have been cast by incorporating two different fibers such as steel and polypropylene (PP). Damage of HYFRC beams was obtained by cracking of concrete for one of the beams in each set under four-point bending tests with different percentage variation of damage levels as 50%, 70% and 90% of maximum ultimate load. And the main dynamic characteristics such as damping, fundamental natural frequencies, mode shapes and frequency response function at each and every damage level has been assessed by means of non-destructive technique (NDT) with hammer excitation. The fundamental natural frequency and damping values obtained through dynamic tests for HYFRC beams were compared with control (reference) RC beam at each level of damage which has been acquired through static tests. The static experimental test results emphasize that the HYFRC beam has attained higher ultimate load as compared with control reinforced concrete beam.

Class D audio amplifier with hybrid control

Sridhar Joshi,Parthasarathi Sensarma 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

R-modeled speaker fed by sliding mode(SM) controlled half bridged audio amplifier(HBA) show significant phase difference between reference voltage and speaker current. The causes of phase difference possibly are inaccurate speaker model and phase lead/lag introduced by the output filter. To investigate phase difference, the transfer function of HBA and approximated first order model of the speaker were considered. With the aim of eliminating the phase difference between reference voltage and speaker current, a hybrid approach comprising SM controlled amplifier with linear control technique is proposed in this paper. The prototype sliding mode controlled amplifier of 20 W, 20 Hz to 20 kHz with 4/8 Ω speaker load is developed. Frequency response and experimental results with the prototype are experimentally obtained which show excellent command following of the speaker current with minimal phase lag.

Microwave synthesis of nitrogen-doped carbon nanotubes anchored on graphene substrates

Sridhar, Vadahanambi,Lee, Inwon,Chun, Ho-Hwan,Park, Hyun Elsevier 2015 Carbon Vol.87 No.-

<P><B>Abstract</B></P> <P>We report a fast and facile microwave technique to synthesize nitrogen-doped carbon nanotubes anchored on graphene substrates from azobis(cyclohexanecarbonitrile), a commodity chemical, commonly used as a radical initiator in polymerization reactions as the nanotube precursor. Micrometer-long, nitrogen-doped carbon nanotubes vertically anchored on graphene was obtained to produce mesoporous, hierarchical nanostructures. X-ray photoelectron spectroscopy reveals that nitrogen moieties exist as pyridinic and graphitic nitrogen. When applied as anodes in lithium-ion batteries, our materials exhibit a high capacity of 1342mAhg<SUP>−1</SUP> even after prolonged cycling reflecting the ability of the three-dimensional network to accommodate the extreme volume changes occurring during the lithiation/delithiation reactions.</P>

Sediment geochemistry with population of recent benthic ostracoda in Palk Bay, southeast coast of India

Sridhar G.D. Sithu,Baskar Kuppusamy,Maniyarasan Subramaniyan,Hussain M. Sheik 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.2

Seasonal observation on trace elements of shallow inner shelf sediments and their correlation with the population of recent benthic ostracoda off Rameswaram, Ramanathapuram District, Tamil Nadu, Southeast coast of India is the aim of this study. The sediments were analysed for trace elements Al, Fe, Mn, Zn, Cu, Pb, Cd, Ni, Co and Cr and being correlated with the population of benthic ostracoda for four different seasons. Cu has a positive correlation, and Fe, Mn, Zn, Pb, Cd, Ni, Co and Cr have negative correlation with the total population of ostracoda. Al has no considerable correlation with the total population of ostracoda. In the middle segment plenty of corals were found in the study area and their effect being discussed.

Manganese nitride stabilized on reduced graphene oxide substrate for high performance sodium ion batteries, super-capacitors and EMI shielding

Sridhar, Vadahanambi,Park, Hyun Elsevier 2019 JOURNAL OF ALLOYS AND COMPOUNDS Vol.808 No.-

<P><B>Abstract</B></P> <P>Though the utility of manganese compounds such as oxides, sulphides has been well researched in energy storage applications such as super-capacitors and lithium-ion batteries, the utility of manganese nitrides hasn't been reported yet, especially as anode in sodium-ion batteries. In this manuscript we report synthesis of manganese nitride decorated reduced graphene oxide (MnN@rGO) prepared by simple microwave nitridation technique and its utility as anode material in sodium-ion batteries, electrodes in super-capacitors and in EMI shielding applications. In energy storage applications such as sodium ion batteries, MnN@rGO electrodes exhibited sodium storage capacity of 716 mAhg<SUP>−1</SUP> whereas when used as electrodes in super-capacitors, a high capacitance value of 639.2 Fg<SUP>-1</SUP> at scan rates of 10 mVs<SUP>−1</SUP> in 1 M Na<SUB>2</SUB>SO<SUB>4</SUB> aqueous electrolyte was achieved. The EMI shielding effectiveness measured in the X-band region of 2–18 GHz was about 30–32 dB which is 300% more than reduced graphene oxide.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report microwave synthesis of manganese nitride nano-particles dispersed on reduced graphene oxide substrate (MnN@rGO). </LI> <LI> The applicability of MnN@rGO in sodium-ion batteries, super-capacitors and EMI shielding applications is reported. </LI> <LI> The versatility of our newly developed technique to synthesize MnN nanoparticles on carbon fibers is also demonstrated. </LI> </UL> </P>