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.

Defect-Engineered Three-Dimensional Graphene–Nanotube–Palladium Nanostructures with Ultrahigh Capacitance

Sridhar, Vadahanambi,Kim, Hyun-Jun,Jung, Jung-Hwan,Lee, Changgu,Park, Sungjin,Oh, Il-Kwon American Chemical Society 2012 ACS NANO Vol.6 No.12

<P>The development of three-dimensional carbon-based nanostructures is the next step forward for boosting industrial applications of carbon nanomaterials such as graphenes and carbon nanotubes. Some defects, which have been considered as detrimental factors for maintaining exceptional materials properties of two-dimensional graphene, can be actively used to synthesize three-dimensional graphene-based carbon nanostructures. Here we describe a fast and heretofore unreported defect-engineered method to synthesize three-dimensional carbon nanohybrid structures with strong bonding between graphene nanoplatelets and carbon nanotubes using simple microwave irradiation and an ionic liquid. Our one-pot method utilizes defect-engineered sequential processes: microwave-based defect generation on graphene nanoplatelets, anchoring of palladium nanoparticles on these defects, and subsequent growth of carbon nanotubes by use of an ionic liquid. The unique three-dimensional nanostructures showed an ultrahigh redox capacitance due to high porosity, a high surface-to-volume ratio from the spacer role of vertically standing one-dimensional carbon nanotubes on graphene sheets, and capacitance-like redox response of the palladium nanoparticles. The proposed defect-engineered method could lead to novel routes to synthesizing three-dimensional graphene-based nanostructures with exceptionally high performance in energy storage systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-12/nn3046133/production/images/medium/nn-2012-046133_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn3046133'>ACS Electronic Supporting Info</A></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.

Microwave extraction of graphene from carbon fibers

Sridhar, V.,Jeon, Jin-Han,Oh, Il-Kwon Elsevier 2011 Carbon Vol.49 No.1

<P><B>Graphical abstract</B></P><P><ce:figure id='f0030'></ce:figure></P><P><B>Research highlights</B></P><P>► Graphene synthesis from turbostratic carbon fibers. ► Eco-friendly chemicals. ► Microwave radiation.</P> <P><B>Abstract</B></P><P>A microwave method for extracting graphene and few-graphene stacks from turbostratic carbon fibers is reported. Microwave radiation is used as an additional energy source in the unzipping of tubular carbon structures in conjunction with hydrogen peroxide, a mild oxidizing agent. This minimizes the problems associated with excessive oxidation and considerably shortens the overall processing time.</P>

Synthesis of Cyclic Type Semi-Fluorinated Disodium Alkanesulfonate

Sridhar Chirumarry,고요한,장기완,신동수 대한화학회 2016 대한화학회지 Vol.60 No.4

A new perfluorobutyl substituted cyclic type disodium alkanesulfonate is designed, synthesized and characterized as alternative substance to perfluorooctane sulfonic acid (PFOS, 1), a well-known surfactant. Cylic type sulfonate was accomplished from commercially available 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol in four steps. Bio-degradable perfluorobutyl moiety was introduced from fluorous diol, which is symmetrically substituted amphiphile via installation of an intermediate trifluoromethanesulfonyl ester and easily manipulated by double displacement of triflate using potassium malonate and further reduction followed by nucleophilic ring opening are key reactions to get target disodium alkanesulfonate. The efficiency and simplicity in the synthesis of this material offer a new strategy to design PFOS alternatives.

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.

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.

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.

Blister Packing of Copper Hydroxide and Titania Nanoparticles on Graphene and Its Recycling

Sridhar, Vadahanambi,Gangaraju, Deepa,Chun, Ho-Hwan,Park, Hyun American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.23

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.