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Satellite remote sensing of the island mass effect on the Sub-Antarctic Kerguelen Plateau, Southern Ocean

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Frontiers of Earth Science 2016年第3期10卷 479-486页

作者： Babula jena ESSO-National Centre for Antarctic and Ocean Research Ministry of Earth Sciences (MoES) Headland Sada Goa 403804 India

The presence of the Kerguelen Plateau and surrounding bathymetric features has a strong influence on the persistently eastward flowing Antarctic Circumpolar Current （ACC）, resulting in enhancement of surface chlorophyll-a （Chl-α） in the downstream section of the plateau along the polar front （PF）. The phenomenon is reported in this paper as the island mass effect （IME）. Analysis of climatological Chl-a datasets from Aqua- Moderate Resolution Imaging Spectroradiometer （Aqua- MODIS） and Sea-viewing Wide Field-of-view Sensor （SeaWiFS） shows distinct bloomy plumes （Chl-α 〉 0.5 mg/m3） during austral spring-summer spreading as far as -1800 km offshore up to 98°E along the downstream of the north Kerguelen Plateau （NKP）. Similar IME phenomena is apparent over the south Kerguelen Plateau （SKP） with the phytoplankton bloom extending up to 96.7°E, along the southern boundary of ACC. The IME phenomena are pronounced only during austral spring-summer period with the availability of light and sedimentary source of iron from shallow plateau to sea surface that fertilizes the mixed layer. The NKP bloom peaks with a maximum areal extent of 1.315 million km2 during December, and the SKP bloom peaks during January with a time lag of one month. The blooms exist for at least 4 months of a year and are significant both as the base of regional food web and for regulating the biogeochemical cycle in the Southern Ocean. Even though the surface water above the Kerguelen Plateau is rich in Chl-a, an exception of an oligotrophic condition dominated between NKP and SKP due to apparent intrusion of iron limited low phytoplankton regime waters from the Enderby basin through the north- eastward Fawn Trough Current.

关键词： island mass effect Antarctic CircumpolarCurrent Aqua-MODIS SeaWiFS

ANN modeling for diffusivity of mushroom and vegetables using a fluidized bed dryer

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Particuology 2013年第5期11卷 607-613页

作者： Subasini jena Abanti Sahoo Chemical Engineering Department National Institute of TechnologyRourkela 769008OrissaIndia

Drying characteristics in terms of diffusivity were studied for mushrooms and different vegetables in a fluidized bed dryer. Drying characteristics with falling rate regime were computed for all the sampi^z. Effective diffusivity of each sample was calculated. Mass transfer coefficients were determined. Mass transfer kinetics for drying of different samples was also found out. Correlations for the diffusivity of samples were developed by relating the experimentally observed data with the different system parame- ters on the basis of regression analysis. The developed correlations for effective moisture diffusivity of the samples are validated by artificial neural network （ANN） modeling. Finally calculated values of diffusivity obtained through both the methods are compared with the experimentally measured values which show a very good approximation thereby indicating the wide applicability of the developed correlations for industrial uses.

关键词： Activation energyEffective diffusivityDrying rateMass transfer kineticsRegression analysisArtificial neural network

A numerical study of violent sloshing problems with modified MPS method

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Journal of Hydrodynamics 2017年第4期29卷 659-667页

作者： Debadatta jena Kishore Chandra Biswal Department of Civil Engineering National Institute of Technology

A numerical study on violent liquid sloshing phenomenon in a partially filled rectangular container is carried out by using moving particle semi-implicit（MPS） method. The present study deals with the implementation of five modifications all together over the original MPS method. The modifications include improved source terms for pressure Poisson equation, special approximation technique for the representation of gradient differential operator, collective action of mixed free surface particle identification boundary conditions, effecting Neumann boundary condition on solving the PPE and fixing judiciously the parting distance among particles to prevent collision. The suitability of the kernel function used in the original MPS method along with these five modifications is investigated for violent sloshing problems. The present model ensures a good agreement between numerical results with the existing experimental observations. The model is successfully applied to a partially filled tank undergoing horizontal sinusoidal excitation to compute the sloshing wave amplitudes and pressure on tank walls. The assessment of dynamic behaviour manifested in terms of base shear, overturning moment and impact pressure load exerted on tank ceiling induced by violent sloshing motion using MPS method is not reported in the open literature and has been efficiently carried out in the present study.

关键词： Sloshing particle method impact pressure base shear overturning moment

Backstepping sliding mode control of a variable speed wind turbine for power optimization

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Journal of Modern Power Systems and Clean Energy 2015年第3期3卷 402-410页

作者： Saravanakumar RAJENDRAN Debashisha jena National Institute of Technology Karnataka SurathkalIndia

To optimize the energy capture from the wind,wind turbine(WT)should operate at variable *** on the wind speed,the operating regions of the WT are divided into two parts:below and above the rated wind *** main aim at below rated wind speed is to maximize the energy capture from the wind with reduced oscillation on the drive *** above rated wind speed,the aim is to maintain the rated power by using pitch *** paper presents the control of WT at below rated wind speed by using backstepping sliding mode control(BSMC).In BSMC,generator torque is considered as the control input that depends on the optimal rotor ***,this optimal rotor speed is derived from effective wind *** this paper,effective wind speed is estimated from aerodynamic torque and rotor speed by using the modified Newton Rapshon(MNR)***,a conventional sliding mode controller(SMC)is applied to the WT,but the performance of the controller was found to be less robust with respect to ***,WT external disturbance is not *** overcome the above drawback,BSMC is proposed and both the controllers are tested with mathematical model and finally validated with the fatigue,aerodynamics,structures,and turbulence(FAST)WT simulator in the presence of *** the results,it is concluded that the proposed BSMC is more robust than conventional SMC in the presence of disturbances.

关键词： Nonlinear control Single mass model Modified Newton Raphson(MNR) Backstepping sliding mode control(BSMC)

Variable speed wind turbine for maximum power capture using adaptive fuzzy integral sliding mode control

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Journal of Modern Power Systems and Clean Energy 2014年第2期2卷 114-125页

作者： Saravanakumar RAJENDRAN Debashisha jena National Institute of Technology Karnataka SurathkalIndia

This paper presents a nonlinear control approach to variable speed wind turbine(VSWT)with a wind speed *** dynamics of the wind turbine(WT)is derived from single mass *** this work,a modified Newton Raphson estimator has been considered for exact estimation of effective wind *** main objective of this work is to extract maximum energy from the wind at below rated wind speed while reducing drive train *** order to achieve the above objectives,VSWT should operate close to the optimal power *** generator torque is considered as the control input to achieve maximum energy *** the literature,it is clear that existing linear and nonlinear control techniques suffer from poor tracking of WT dynamics,increased power loss and complex control *** addition,they are not robust with respect to input *** order to overcome the above drawbacks,adaptive fuzzy integral sliding mode control(AFISMC)is proposed for VSWT *** proposed controller is tested with different types of disturbances and compared with other nonlinear controllers such as sliding mode control and integral sliding mode *** result shows the better performance of AFISMC and its robustness to input *** this paper,the discontinuity in integral sliding mode controller is smoothed by using hyperbolic tangent function,and the sliding gain is adapted using a fuzzy technique which makes the controller more robust.

关键词： Variable speed wind turbine Integral sliding mode controller(ISMC) Sliding mode control(SMC) Adaptive fuzzy integral sliding mode control(AFISMC)

Transition metal-based single-atom catalysts(TM-SACs);rising materials for electrochemical CO_(2) reduction

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Journal of Energy Chemistry 2022年第7期31卷 444-471,I0012页

作者： Bishnupad Mohanty Suddhasatwa Basu Bikash Kumar jena Materials Chemistry Department CSIR-Institute of Minerals and Materials TechnologyBhubaneswar 751013India Academy of Scientific&Innovative Research(AcSIR) Ghaziabad 201002India

The continuous increase of global atmospheric CO_(2) concentrations brutally damages our environment. A series of methods have been developed to convert CO_(2) to valuable fuels and value-added chemicals to maintain the equilibrium of carbon cycles. The electrochemical CO_(2) reduction reaction(CO_(2)RR) is one of the promising methods to produce fuels and chemicals, and it could offer sustainable paths to decrease carbon intensity and support renewable energy. Thus, significant research efforts and highly efficient catalysts are essential for converting CO_(2) into other valuable chemicals and fuels. Transition metal-based single atoms catalysts(TM-SACs) have recently received much attention and offer outstanding electrochemical applications with high activity and selectivity opportunities. By taking advantage of both heterogeneous and homogeneous catalysts, TM-SACs are the new rising star for electrochemical conversion of CO_(2) to the value-added product with high selectivity. In recent years, enormous research effort has been made to synthesize different TM-SACs with different M–Nxsites and study the electrochemical conversion of CO_(2) to CO. This review has discussed the development and characterization of different TMSACs with various catalytic sites, fundamental understanding of the electrochemical process in CO_(2) RR,intrinsic catalytic activity, and molecular strategics of SACs responsible for CO_(2)RR. Furthermore, we extensively review previous studies on 1 st-row transition metals TM-SACs(Ni, Co, Fe, Cu, Zn, Sn) and dual-atom catalysts(DACs) utilized for electrochemical CO_(2) conversions and highlight the opportunities and challenges.

关键词： CO_(2)RR Single-atom catalyst SACs Dual-atom catalyst DACs Transition metals Support catalysts

An Improved Differential Evolution Trained Neural Network Scheme for Nonlinear System Identification

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International Journal of Automation and computing 2009年第2期6卷 137-144页

作者： Bidyadhar Subudhi Debashisha jena Center for Industrial Electronics & Robotics Department of Electrical Engineering National Institute of Technology

This paper presents an improved nonlinear system identification scheme using di？erential evolution （DE）, neural network （NN） and Levenberg Marquardt algorithm （LM）. With a view to achieve better convergence of NN weights optimization during the training, the DE and LM are used in a combined framework to train the NN. We present the convergence analysis of the DE and demonstrate the efficacy of the proposed improved system identification algorithm by exploiting the combined DE and LM training of the NN and suitably implementing it together with other system identification methods, namely NN and DE＋NN on a number of examples including a practical case study. The identification results obtained through a series of simulation studies of these methods on different nonlinear systems demonstrate that the proposed DE and LM trained NN approach to nonlinear system identification can yield better identification results in terms of time of convergence and less identification error.

关键词： Differential evolution neural network (NN) nonlinear system identification Levenberg Marquardt algorithm

Strain and carrier-induced coexistence of topologically insulating and superconducting phase in iodized Si（111） films

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Nano Research 2016年第6期9卷 1578-1589页

作者： Jian Zhou QianWang Qiang Sun Puru jena Physics Department Virginia Commonwealth University Richmond VA 23284 USA Center for Applied Physics and Technology College of Engineering Peking University Beijing 100871 China Department of Materials Science and Engineering College of Engineering Peking University Beijing 100871 China

The importance of silicon in modem electronic devices has led to considerable interest in exploring the unconventional electronic properties of Si-based materials for future applications in spintronics and quantum computing. Here, using density functional theory, we present the results of a systematic study of the effect of strain on Si（lll） thin films whose surfaces are functionalized with iodine. Films with an odd number of layers under biaxial strain are found to undergo a phase transition from a normal insulator to a topological insulator and ultimately to a metal. The spin-orbit coupling-induced topologically nontrivial band gap at the F point is found to be as large as 0.50 eV, which not only surpasses that of other Si-based topological materials, it is also large enough for practical realization of quantum spin Hall states at room temperature. No such nontrivial states are found in films for such a strain-induced transition with an even number of layers. Mechanisms are illustrated by a tight-binding model composed of s, px, and py orbitals. Equally important, we predict that iodized silicene, when stretched and hole-doped, would be a phonon-mediated super- conductor with a critical temperature of 9.2 K. This coexistence of a topological insulator and a superconducting phase in a single material is unusual; it has the potential for applications in electronic circuits and for the realization of Majorana fermions in quantum computations.

关键词： Si(lll) film topological insulator phonon-mediatedsuperconductor strain effects spin-orbit coupling

Dynamics of sea-ice biogeochemistry in the coastal Antarctica during transition from summer to winter

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Geoscience Frontiers 2017年第3期8卷 507-516页

作者： Suhas Shetye Babula jena Rahul Mohan National Institute of Oceanography Donapaula Goa 403004 India National Centre for Antarctic and Ocean Research Headland Sada Goa 403 804 India

The seasonality of carbon dioxide partial pressure （pC02）, air-sea CO2 fluxes and associated environ- mental parameters were investigated in the Antarctic coastal waters. The in-situ survey was carried out from the austral summer till the onset of winter （January 2012, February 2010 and March 2009） in the Enderby Basin. Rapid decrease in pCO2 was evident under the sea-ice cover in January, when both water column and sea-ice algal activity resulted in the removal of nutrients and dissolved inorganic carbon （DIC） and increase in pH. The major highlight of this study is the shift in the dominant biogeochemica/ factors from summer to early winter. Nutrient limitation （low Si/N）, sea-ice cover, low photosynthetically active radiation （PAR）, deep mixed layer and high upwelling velocity contributed towards higher pCO2 during March （early winter）. CO2 fluxes suggest that the Enderby Basin acts as a strong CO2 sink during January （-81 mmol m-2 d 1）, however it acts as a weak sink of CO2 with -2.4 and -1.7 mmol m 2 d-1 during February and March, respectively. The present work, concludes that sea ice plays a dual role towards climate change, by decreasing sea surface pCO2 in summer and enhancing in early winter. Our observations emphasize the need to address seasonal sea-ice driven CO2 flux dynamics in assessing Antarctic contributions to the global oceanic CO2 budget.

关键词： pCO2 fluxes Upwelling Antarctica Sea-ice