Rheological characteristics of coal–water slurry using microwave pretreatment – A statistical approach

B.K. Sahoo,B.C. Meikap,S. De,M. Carsky 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.1

The present study addresses the treatment of microwave energy for rheological characteristics of coal–water slurries (CWS) performed in an online Bohlin viscometer. Detailed experimental investigations were carried out for high ash Indian coal (Jamadoba washery, 38% ash). Experiments were conducted at high power level (900 W) for all the test samples in microwave oven. The exposure times were fixed at 30, 60, 90 and 120 s. Before and after treatment, the test samples were ground and sieved into different fractions for chemical and physical analysis. Central composite design (CCD) was applied to study the influence of particle diameter, solid concentration, microwave (MW) exposure time and shear rate on apparent viscosity for rheology characteristics of coal–water slurry. A quadratic model was developed for apparent viscosity using Design-Expert software. The model was used to calculate the optimum operating conditions for minimization of apparent viscosity. The apparent viscosity (22.83 mPa s)produced at these operating conditions showed an excellent agreement with the amounts predicted by the models.

Carbon nanoflake growth from carbon nanotubes by hot filament chemical vapor deposition

Sahoo, S.C.,Mohapatra, D.R.,Lee, H.J.,Jejurikar, S.M.,Kim, I.,Lee, S.C.,Park, J.K.,Baik, Y.J.,Lee, W.S. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.67 No.-

We report the growth of carbon nanoflakes (CNFs) on Si substrate by the hot filament chemical vapor deposition without the substrate bias or the catalyst. CNFs were grown using the single wall carbon nanotubes and the multiwall carbon nanotubes as the nucleation center, in the Ar-rich CH<SUB>4</SUB>-H<SUB>2</SUB>-Ar precursor gas mixture with 1% CH<SUB>4</SUB>, at the chamber pressure and the substrate temperature of 7.5Torr and 840<SUP>o</SUP>C, respectively. In the H<SUB>2</SUB>-rich condition, CNF synthesis failed due to severe etch-removal of carbon nanotubes (CNTs) while it was successful at the optimized Ar-rich condition. Other forms of carbon such as nano-diamond or mesoporous carbon failed to serve as the nucleation centers for the CNF growth. We proposed a mechanism of the CNF synthesis from the CNTs, which involved the initial unzipping of CNTs by atomic hydrogen and subsequent nucleation and growth of CNFs from the unzipped portion of the graphene layers.

DESIGN AND DEVELOPMENT OF A HEADING ANGLE CONTROLLER FOR AN UNMANNED GROUND VEHICLE

S. SAHOO,S. C. SUBRAMANIAN,N. MAHALE,S. SRIVASTAVA 한국자동차공학회 2015 International journal of automotive technology Vol.16 No.1

This paper describes the design and implementation of a controller to track the desired heading angle for an unmanned ground vehicle (UGV) considering the limits on rotation of steering wheel and steering motor rate. The well-known “bicycle model” approximation, that considers the vehicle slip angle and ground-wheel interaction, has been used. In this work, combined closed loop control for steering motor and heading angle of the vehicle has been considered for better accuracy. The challenge in designing this control system is to include the actuator dynamics as the response time to steer the front wheel is in the same order as that of the heading angle dynamics of the vehicle. Experiments have been conducted, analysis of data collected is presented and the resulting mathematical representation is explained in detail. Results from both simulation and experimental implementation are also compared. It has been found that the vehicle controller can be tuned effectively to achieve the desired heading angle changes up to twenty degrees within three seconds when the vehicle is moving at a speed of 1.4 m/sec.

Porous Ternary High Performance Supercapacitor Electrode Based on Reduced Graphene Oxide, NiMn₂O₄, and Polyaniline

Sahoo, S.,Zhang, S.,Shim, J.J. Pergamon Press 2016 ELECTROCHIMICA ACTA Vol.216 No.-

This paper reports a novel porous ternary nanohybrid based on NiMn<SUB>2</SUB>O<SUB>4</SUB>, reduced graphene oxide, and polyaniline (GNMOP) as a superior supercapacitor electrode material. GNMOP was fabricated using a hydrothermal-assisted thermal annealing method, followed by the conductive wrapping of polyaniline through in-situ polymerization. The structure and morphology of the ternary nanohybrid were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). FTIR, XRD, and XPS confirmed the formation of ternary nanohybrid. SEM and Brunauer-Emmett-Teller (BET) measurement revealed the porous nature of GNMOP, whereas HRTEM analysis demonstrated the wrapping of conducting polyaniline (PANI) on binary composite. Such PANI wrapping enhanced the electrochemical performance of the binary nanocomposite. A specific capacitance of 757Fg<SUP>-1</SUP> was achieved for GNMOP at a current density of 1Ag<SUP>-1</SUP>, which is much higher than that of the binary nanocomposite and mixed transition metal oxide. In addition, GNMOP exhibited a maximum energy density of 70Whkg<SUP>-1</SUP> and high capacitance retention of ~93% after 2000 cycles. These outstanding electrochemical performances of GNMOP can be attributed to the proper wrapping of conducting polymer and the synergistic impact of distinct components.

Defect-engineered mesoporous ternary nanoarchitecture of zinc-cobalt-oxide/nitrogen-doped graphene as anode material in lithium ion batteries

Sahoo, S.,Bae, S.H.,Lee, Y.S.,Lee, J.M.,Ahn, J.M.,Kim, C.G.,Oh, I.K. Pergamon Press ; Elsevier Science Ltd 2015 Carbon Vol.94 No.-

We report a defect-engineered self-assembly route to a mesoporous ternary ZnCo<SUB>2</SUB>O<SUB>4</SUB>/nitrogen-doped graphene nanoarchitecture as an anode material for lithium ion batteries through a hydrothermal and thermal annealing process. A hetero-nanostructure showed flower-like ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanosheets which were well dispersed and firmly decorated on nitrogen-doped reduced graphene oxide, as atomic-scale defects such as nitrogen-doped sites and oxygen-functional groups in chemically modified graphene oxide can be more reactive nucleation sites to anchor metallic nanoparticles strongly. Strong synergy between N-doped graphene and ZnCo<SUB>2</SUB>O<SUB>4</SUB> is observed as a high-performance anode electrode material for much higher capacity levels and more durable electrochemical stability in lithium ion batteries. The mesoporous nanoarchitecture electrode shows enhanced reversible performance in cyclic anode tests, maintaining a specific energy capacity of 998mAhg<SUP>-1</SUP> after 30cycles at current density of 100mAg<SUP>-1</SUP>.

Stat6 and c-Jun Mediate Th2 Cell-Specific IL-24 Gene Expression

Sahoo, A.,Lee, C.-G.,Jash, A.,Son, J.-S.,Kim, G.,Kwon, H.-K.,So, J.-S.,Im, S.-H. American Association of Immunologists 2011 JOURNAL OF IMMUNOLOGY Vol.186 No.7

Derivation of Instantaneous Current References for Three Phase PV Inverter Connected to Grid with Active and Reactive Power flow Control

S. Dasgupta,S. N. Mohan,S. K. Sahoo,S. K. Panda 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In this paper, inverter reference current generation for a three phase grid connected PV inverter under generalized grid voltage conditions is proposed. The proposed method facilitates high bandwidth grid active and reactive power flow control along with minimum DC link ripples with grid current THD control facility by finding suitable current reference directly in the a-b-c frame. The proposed method is much faster than the conventional methods because of the absence of phase lock loop (PLL) and Park’s transformation requirements. The proposed method is also independent of grid voltage fundamental frequency and capable of rejecting the grid voltage harmonics. These advantages make it more suitable for micro-grid applications. The proposed method is validated with rigorous experiments and test results presented depict the efficacy of the proposed system.

Temperature and Frequency Dependent Multiferroic Features of Gadolinium Doped BiFeO3 -PbTiO3 Electronic System

S. K. Pradhan,S. N. Das,S. Bhuyan,Seshadev Sahoo,R. N. P. Choudhary 한국전기전자재료학회 2020 Transactions on Electrical and Electronic Material Vol.21 No.2

Multiferroic gadolinium (Gd) doped BiFeO 3 (BFO) and PbTiO 3 (PT) samples [(Pb 1−x Bi 0.5x Gd 0.5x )(Fe x Ti 1−x )O 3 ] with x = 0.1, 0.3, 0.5 and 0.7 are formulated by adopting the solid state reaction process. The impact of gadolinium substitution in the crystal structure, morphological behavior and electrical properties has been studied. By altering the Gd concentration in the solid solution a change in the structure is observed that is from tetragonal to rhombohedral. The size of the grain in the compounds reduces as a result of enrich in gadolinium content of the furnished sample. The subsidence of lead minimizes the toxic behavior of the material with significant improvements in dielectric response of gadolinium modifi ed BiFeO3 – PbTiO 3synthesized system. From the impedance study, the material presents negative temperature coefficient of resistance characteristics and the impedance is due to the presence of grain and grain boundary eff ect inside the materials. It is realized that the remnant polarization decreases and frequency dependent ac conductivity increases with the concentration of gadolinium in the electronic system. From conductivity study, the equipped electronic materials show non-exponential type of conductivity relaxation.

Parametric Resonance Characteristics of Laminated Composite Curved Shell Panels in a Hygrothermal Environment

S.K Sahu,M.K.Rath,P.K Datta,R. Sahoo 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.3

The present study deals with the parametric resonance behaviour of laminated composite curved shell panels in a hygrothermal environment using Bolotin’s approach. A simple laminated model is developed using first order shear deformation theory (FSDT) for the vibration and dynamic stability analysis of laminated composite shells subjected to hygrothermal conditions. A computer program based on the finite element method (FEM) in a MATLAB environment is developed to perform all necessary computations. Quantitative results are presented to show the effects of curvature, ply-orientations, degree of orthotropy and geometry of laminates on the parametric instability of composite curved shell panels for different temperature and moisture concentrations. The excitation frequencies of laminated composite panels decrease with the increase of temperature and moisture due to reduction of stiffness for all laminates.

A Lyapunov function based current controller to control active and reactive power flow in a three phase grid connected PV inverter under generalized grid voltage conditions

S. Dasgupta,S. N. Mohan,S. K. Sahoo,S. K. Panda 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In this paper, a novel control system is proposed to control the active and reactive grid power flow in a three phase grid connected PV inverter. The control system not only controls the grid power but also reduces the grid current THD in the presence of typical non-linear loads in parallel with grid at the point of common coupling (PCC). The proposed control system also takes care of not only the grid voltage unbalance but also the unbalance in the connecting line side inductors. The stability of the proposed control system is ensured by the direct method of Lyapunov. The proposed control system is not only simple to implement in the digital form but also provides superior performance over the conventional multiple PI or resonant control methods. A new grid connected inverter modeling technique is also proposed to take care of unbalances in the inverter system. Experimental results are provided to show the efficacy of the proposed control system.