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The hemispheric asymmetry of solar activity during the last century and the solar dynamo

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Chinese Journal of Astronomy and Astrophysics 2009年第1期9卷 115-126页

作者： Ashish Goel Arnab rai Choudhuri Department of Physics Indian Institute of Technology Department of Physics Indian Institute of Science

We believe the Babcock-Leighton process of poloidal field generation to be the main source of irregularity in the solar cycle. The random nature of this process may make the poloidal field in one hemisphere stronger than that in the other hemisphere at the end of a cycle. We expect this to induce an asymmetry in the next sunspot cycle. We look for evidence of this in the observational data and then model it theoretically with our dynamo code. Since actual polar field measurements exist only from the 1970s, we use the polar faculae number data recorded by Sheeley （1991, 2008） as a proxy of the polar field and estimate the hemispheric asymmetry of the polar field in different solar minima during the major part of the twentieth century. This asymmetry is found to have a reasonable correlation with the asymmetry of the next cycle. We then run our dynamo code by feeding information about this asymmetry at the successive minima and compare the results with observational data. We find that the theoretically computed asymmetries of different cycles compare favorably with the observational data, with the correlation coefficient being 0.73. Due to the coupling between the two hemispheres, any hemispheric asymmetry tends to get attenuated with time. The hemispheric asymmetry of a cycle either from observational data or from theoretical calculations statistically tends to be less than the asymmetry in the polar field （as inferred from the faculae data） in the preceding minimum. This reduction factor turns out to be 0.43 and 0.51 respectively in observational data and theoretical simulations.

关键词： Sun activity -- Sun magnetic fields -- sunspots

Analyzing hydro abrasive erosion in Kaplan turbine:A case study from India

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Journal of Hydrodynamics 2016年第5期28卷 863-872页

作者： Anant Kr.rai Arun KUMAR Alternate Hydro Energy Centre IIT Roorkee

Sediment flow through hydro turbine causes erosion of hydraulic components resulting in drop of turbine efficiency, parti- cularly in hydropower plants of the Himalayan region. The measurement of erosion and monitoring of sediment flow in turbine are major concerns in erosion study. Attempts have been made to study erosion mainly in Pelton and Francis turbines. In this study, a simple and effective method has been presented to measure erosion in a Kaplan turbine of a run-of-river scheme Chilla hydropower plant in foothills of Himalaya. Recent techniques were used to measure sediment parameters like concentration, size, shape and mineral content. A standard erosion model is applied to estimate the erosion in Kaplan turbine blade, runner chamber and draft tube cone. A calibration factor has been proposed to apply the erosion model for site specific conditions. It has been found that the outer trailing edges of the turbine blade and upper rtmner chamber are most erosion prone zones. Sediment analysis revealed that effective operation can reduce erosion in turbine components. The estimated erosion values from model are found to be consistent with measu- red values. Finally, suggestions for design improvements and effective operation of erosion affected hydropower plants are given.

关键词： turbine sediment erosion measurement IEC 62364 hydropower

A Thorough Investigation on Image Forgery Detection

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Computer Modeling in Engineering & Sciences 2023年第3期134卷 1489-1528页

作者： Anjani Kumar rai Subodh Srivastava Department of Electronics&Communication Engineering NITPatnaIndia

Image forging is the alteration of a digital image to conceal some of the necessary or helpful *** cannot be easy to distinguish themodified region fromthe original image in *** demand for authenticity and the integrity of the image drive the detection of a fabricated *** have been cases of ownership infringements or fraudulent actions by counterfeiting multimedia files,including re-sampling or *** work presents a high-level view of the forensics of digital images and their possible detection *** work presents a thorough analysis of digital image forgery detection techniques with their steps and *** methods have identified forgery and its type and compared it with state of the *** work will help us to find the best forgery detection technique based on the different *** also shows the current issues in other methods,which can help researchers find future scope for further research in this field.

关键词： Forgery detection digital forgery image forgery localization image segmentation image forensics multimedia security

Toxicological effects of TiO_(2) nanoparticles on plant growth promoting soil bacteria

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Emerging Contaminants 2020年第1期6卷 87-92页

作者： Sangeeta Chavan vishwas Sarangdhar Vigneshwaran Nadanathangam Caius Research Laboratory St.Xavier’s CollegeMumbaiIndia Nanotechnology Research Group Central Institute for Research on Cotton TechnologyMumbaiIndia

Emerging contaminants like metal nanoparticles get introduced into soil through different *** effects of these contaminants on plant growth-promoting bacteria(PGPB),which influence plant productivity,can be detrimental to soil *** dioxide is one of the most produced nanomaterials in the world and therefore potentially the most released nanoform in *** objective of this study was to evaluate the toxic effects of titanium dioxide nanoparticles(TiO2 NPs)on plant growth-promoting *** types of PGPB,viz.,nitrogen fixers,phosphate solubilizers and biofilm formers were exposed to TiO2 *** results suggest that direct contact of the bacteria with these NPs is inhibitory as compared to when these bacteria are growing in laboratory nutrient media in the presence of *** inhibitory effect did not follow a linear dose response but instead showed a pronounced step *** with their varying characteristics may not afford the same protection to bacteria as laboratory nutrient media and thus TiO2 NPs may cause some sensitive PGPB to disappear from *** resultant shift in bacterial community composition may affect ecosystem functioning.

关键词： Titanium dioxide nanoparticles PGPB Nitrogen fixers Phosphate solubilizers Biofilm formers Step response

Er^(3+)/Yb^(3+)/Li^+/Zn^(2+):Gd_2(MoO_4)_3 upconverting nanophosphors in optical thermometry

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Journal of Rare Earths 2019年第3期37卷 242-247页

作者： Anita Kumari Lakshmi Mukhopadhyay Vineet Kumar rai Laser and Spectroscopy Laboratory Department of Applied Physics Indian Institute of Technology (Indian School of Mines)

Er^(3+)-Yb^(3+)-Li^+:Gd_2(MoO_4)_3 and Er^(3+)-Yb^(3+)-Zn^(2+):Gd_2(MoO_4)_3 nanophosphors, synthesized by chemical co-precipitation technique were characterized through XRD,FESEM,dynamic light scattering(DLS),diffuse reflectance, photoluminescence, photometric and decay time analysis. The enhancement of about～28, ～149 and ～351 times in the green upconversion emission band is observed for the optimized Er^(3+)-Yb^(3+),Er^(3+)-Yb^(3+)-Li^+ and Er^(3+)-Yb^(3+)-Zn^(2+):Gd_2(MoO_4)_3 nanophosphors in comparison to the singly Er^(3+) doped nanophosphors. The electric dipole-dipole interaction is found to be responsible for the concentration quenching. The temperature dependent behaviour of the two green thermally coupled levels of the Er^(3+) ions based on the fluorescence intensity ratio technique was studied. The maximum sensor sensitivity ～38.7 × 10^(-3) K^(-1) at 473 K for optimized Er^(3+)-Yb^(3+)-Zn^(2+) codoped Gd_2(MoO_4)_3 nanophosphors is reported with maximum population redistribution ability～88% among the ~2H_(11/2) and ~4S_(3/2) levels.

关键词： Upconversion Phosphors Dynamic light scattering Non-lanthanide ions Optical thermometry Rare earths

Dielectric behavior of CaCu_(3)Ti_(4)O_(12) electro-ceramic doped with La,Mn and Ni synthesized by modified citrate-gel route

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Journal of Advanced Ceramics 2013年第2期2卷 119-127页

作者： Laxman SINGH U.S.rai Alok Kumar rai K.D.MANDAL Department of Chemistry Centre of Advanced StudyFaculty of ScienceBanaras Hindu UniversityVaranasi 221005U.P.India Department of Materials Science and Engineering Chonnam National University300 Yongbong-dongBukguGwangju 500-757Republic of Korea Department of Applied Chemistry Indian Institute of TechnologyBanaras Hindu UniversityVaranasi 221005U.P.India

The effect of La^(3+),Mn^(2+)and Ni^(2+)doped calcium copper titanate,CaCu_(3)Ti_(4)O_(12)(CCTO),at higher concentrations(CR1 and CR2 with 5 mol%and 10 mol%,respectively),has been examined by semi-wet route at relatively lower *** semi-wet route employs citrate-nitrate gel chemical method using TiO_(2) solid powders.X-ray diffraction(XRD)analysis confirms the formation of single phase in the doped samples sintered at 900℃for 8 *** electron micrographs(SEM)show that the average grain size for CR2 is larger than that of CR1 *** energy dispersive X-ray spectroscopy(EDX)is used to study the percentage compositions of different ions present in both *** constant(εr)and dielectric loss(tanδ)values of CR1 are comparatively higher than those of CR2 ceramic at all measured frequencies and *** nature of temperature-dependent relaxation behavior of the ceramics is also studied by impedance,modulus spectroscopic analysis and confirms Maxwell-Wagner relaxation.

关键词： oxide materials chemical synthesis dielectric properties grain boundaries X-ray diffraction(XRD)

Natural compounds as potential inhibitors of SARS-CoV-2 main protease: An insilico study

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Asian Pacific Journal of Tropical Biomedicine 2021年第4期11卷 155-163页

作者： Amaresh Mishra Yamini Pathak Anuj Kumar Surabhi Kirti Mishra vishwas Tripathi School of Biotechnology Gautam Buddha UniversityGreater Noida-201310India Bioinformatics Laboratory Uttarakhand Council for BiotechnologyBiotech BhawanPantnagarU.S.NagarUttarakhand-263145India Advanced Centre for Computational and Applied Biotechnology Uttarakhand Council for BiotechnologyDehradun-248007India School of Biotechnology Jawaharlal Nehru UniversityNew DelhiIndia

Objective:To explore natural compounds as potential inhibitors against main protease(Mpro)of ***:In the current study,systematic molecular docking analysis was conducted using AutoDock 4.2 to determine the binding affinities and interactions between natural compounds and *** natural compounds were further validated using a combination of molecular dynamic(MD)simulations and molecular mechanic Poisson-Boltzmann surface area(MM/PBSA)free energy c alculation ***:Out of twenty natural compounds,four natural metabolites namely,amentoflavone,guggulsterone,puerarin,and piperine were found to have strong interaction with Mpro of SARS-CoV-2 based on docking *** MD simulations,all four natural compounds bound to Mpro at 50 ns and MM/G/P/BSA free energy calculations showed that all four shortlisted ligands had stable and favorable energies with strong binding to Mpro ***:Guggulsterone is a potential inhibitor of COVID-19 main protease *** in vitro and pre-clinical studies are needed.

关键词： SARS-CoV-2 COVID-19 Amentoflavone Guggulsterone Puerarin Piperine

Spectroscopy of the ?_(ccb) baryon in the hypercentral constituent quark model

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Chinese Physics C 2018年第5期42卷 25-29页

作者： Zalak Shah Ajay Kumar rai Department of Applied Physics Sardar Vallabhbhai National Institute of Technology

We extract the mass spectrum of the triply heavy baryon ?ccbusing the hypercentral constituent quark model. The first order correction is also added to the potential term of the Hamiltonian. The radial and orbital exc... 详细信息

关键词： baryons potential model Regge trajectories

Optimized Controller Gains Using Grey Wolf Algorithm for Grid Tied Solar Power Generation with Improved Dynamics and Power Quality

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Chinese Journal of Electrical Engineering 2022年第2期8卷 75-85页

作者： Veramalla Rajagopal Danthurthi Sharath Gundeboina vishwas Jampana Bangarraju Sabha Raj Arya Challa Venkatesh Department of Electrical and Electronics Engineering Kakatiya Institute of Technology and Science WarangalTelangana 506015India Department of Electrical and Electronics Engineering B V Raju Institute of TechnologyTelangana 502313India Department of Electrical Engineering Sardar Vallabhbhai National Institute of Technology SuratGujarat 395007India

This study proposes a control algorithm based on synchronous reference frame theory with unit templates instead of a phase locked loop for grid-connected photovoltaic(PV)solar system,comprising solar PV panels,DC-DC converter,controller for maximum power point tracking,resistance capacitance ripple filter,insulated-gate bipolar transistor based controller,interfacing inductor,linear and nonlinear *** dynamic performance of the grid connected solar system depends on the effect operation of the control algorithm,comprising two proportional-integral *** controllers estimate the reference solar-grid currents,which in turn generate pulses for the three-leg voltage source *** grey wolf optimization algorithm is used to optimize the controller gains of the proportional-integral controllers,resulting in excellent performance compared to that of existing optimization *** compensation for neutral current is provided by a star-delta transformer(non-isolated),and the proposed solar PV grid system provides zero voltage regulation and eliminates harmonics,in addition to load *** power extraction from the solar panel is achieved using the incremental conductance algorithm for the DC-DC converter supplying solar power to the DC bus capacitor,which in turn supplies this power to the grid with improved dynamics and *** solar system along with the control algorithm and controller is modeled using Simulink in Matlab 2019.

关键词： Control algorithm solar power generation DC-DC converter star-delta transformer maximum power point tracking power quality grey wolf optimization algorithm