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推动Bokaro热轧机超过设计能力

钢铁 2003年第1期38卷 34-37页

作者： v.k.srivastava k.Aistleitner 等 Bokaro钢铁有限公司奥钢联工程技术公司

通过在Bokaro公司的热轧机上应用优化的先进工艺模型和工艺控制系统,以非常低的投资成本使其性能超出了原设计指标,最小轧制厚度由1.5 mm降到1.2 mm,而最大轧制厚度则由16 mm提高到20 mm.

关键词：热轧机优化工艺模型工艺控制系统板材轧机

Compositionally Graded Microstructure for Ag-Fe Nanoparticles

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Nano-Micro Letters 2012年第3期4卷 172-175页

作者： Chandan srivastava k.v.L.Sushma Department of Materials Engineering Indian Institute of Science

Ag-Fe nanoparticles with a highly Ag rich average composition were synthesized by the sonochemical ***-iron system exhibits a wide miscibility gap in the bulk ***,a graded compositional profile along the nanoparticle radius was *** at and near the surface of the nanoparticle contained both Ag and Fe *** composition got relatively deficient Fe towards the center of the particle with particle core made up of pure *** of Ag and Fe is confirmed by the absence of diffraction signal corresponding to pure Fe phase and presence of a paramagnetic phase in nanoparticles containing a diamagnetic(Ag)and ferromagnetic(Fe)elements.

关键词： Nanoparticles Electron Microscopy Ag-Fe Miscibility gap Solid solution Microstructure

Effect of hydrogen plasma treatment on the growth and microstructures of multiwalled carbon nanotubes

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Nano-Micro Letters 2010年第1期2卷 42-48页

作者： S.k.srivastava v.D.vankar v.kumar Department of Physics Indian Institute of Technology Delhi National Physical Laboratory Dr.K.S.Krishnan Marg

The effect of hydrogen plasma treatment of iron oxide films on the growth and microstructure of carbon nanotubes(CNTs)by microwave plasma enhanced chemical vapor deposition process has been *** plasma was characterized in-situ using optical emission *** of the films was examined by scanning electron *** analysis was carried out by high resolution transmission electron microscopy(HRTEM)equipped with energy dispersive X-ray spectroscopy(EDS)and micro-diffraction *** is found that oxide films without H_2 plasma pretreatment or treated for lesser time resulted in CNT films with high percentage of carbonaceous particles and with embedded particles/nanorods distributed discontinuously in the cavity of the *** embedded particles were found to be of iron carbide(Fe-C)as confirmed by HRTEM,EDS and micro-diffraction *** observations suggested that the iron oxide particles had poor catalytic action for CNT growth and in-situ reduction of oxide clusters to Fe by hydrogen plasma plays a key role in discontinuous filling of the nanotubes by the catalytic particles.

关键词： Carbon nanotubes Chemical vapor deposition Iron carbide MPECvD

Photoconductivity and surface chemical analysis of ZnO thin films deposited by solution-processing techniques for nano and microstructure fabrication

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Journal of Semiconductors 2013年第3期34卷 12-16页

作者： v.k.Dwivedi P.srivastava G.vijaya Prakash Nanophotonics Laboratory Department of PhysicsIndian Institute of Technology DelhiHauz khasNew Delhi-110 016India Nanostech Laboratory Department of PhysicsIndian Institute of Technology DelhiHauz khasNew Delhi-110 016India Nanophotonics Laboratory Department of PhysicsIndian Institute of Technology DelhiHauz khasNew Delhi-110016India

The fabrication of zinc oxide(ZnO) from inexpensive solution-processing techniques,namely,electrochemical deposition and electrospinning were explored on various conducting and mesoporous semiconducting *** conditions were derived for template- and self-assisted nano/micro structures and composites. ZnO thin films were annealed at a fixed temperature under ambient conditions and characterised using physical and optical *** photocurrent response in the Uv region shows a fast rise and double decay behaviour with a fast component followed by a slow oscillatory *** results were correlated with surface chemical analysis from X-ray photoelectron *** characterisation details reveal the importance of fabrication parameter optimisation for useful low-cost optoelectronic applications.

关键词： zinc oxide electrochemical deposition surface analysis X-ray photoelectron spectroscopy photocurrent response optoelectronic applications

Pd-gate MOS sensor for detection of methanol and propanol

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Journal of Natural Gas Chemistry 2011年第2期20卷 123-127页

作者： Preeti Pandey J. k. srivastava v. N. Mishra R. Dwivedi Center for Research in Microelectronics Department of Electronics Engineering Institute of Technology Banaras Hindu University

The present paper focused on the detection of methanol and propanol using Pd-gate metal-oxide-semiconductor （MOS） sensor. Surface mor- phology and composition of the gate film were studied by scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The response of the sensor for propanol and methanol was measured as shift in capacitance-voltage （C-v） and conductance-voltage （G-v） curves of the MOS structure. The sensitivity of the sensor towards methanol was found to be greater than that towards propanol. It was 58.2% for methanol and 32% for propanol （at 0.6 v, 1 MHz） in terms of capacitance measurements, while in terms of conductance results the sensitivity was found to be 57.2% for methanol and 38.9% for propanol at 1 kHz. The discontinuities or cracks present in the microstructure of the gate material are believed to be mainly responsible for the high sensitivity of the sensor, going with the decomposition of gas molecules and subsequent hydrogen permeation through Pd.

关键词： MOS structure gas sensor palladium cracks sensitivity

Structural and micro structural studies of PbO-doped SnO_2 sensor for detection of methanol, propanol and acetone

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Journal of Natural Gas Chemistry 2011年第2期20卷 179-183页

作者： J. k. srivastava Preeti Pandey v. N. Mishra R. Dwivedi Center for Research in Microelectronics Department of Electronics Engineering Institute of Technology Banaras Hindu University

In the present work the structural information of PbO-doped SnO2 thick film sensor has been investigated with X-ray diffractometer （XRD） and scanning electron microscope （SEM）. Initially, SnO2 powder was derived using sol-gel process and was subsequently doped with PbO and ground up to nanosized particles. A suitable gas sensor structure was fabricated on 1′′×1′′ alumina substrate using thick film technology. The necessary paste for screen printing was also developed. SEM results showed sol-gel derived powder gets more agglomerated in the thick film form. The sensitivity of the sensor has been investigated at different temperatures （150 ？C？350 ？C） upon exposure to methanol, propanol and acetone, yielding a maximum at 250 ？C for acetone with 1 wt% PbO-doping while at 350 ？C for propanol with 3 wt% PbO-doping of the sensor. The reduction of particle size to nanometers （validated through XRD） leads to a dramatic improvement in sensitivity of sensors for the chosen organic vapors. The results also correlate well with the microstructural properties of the material and the dopant.

关键词： gas sensor nanosized SnO2 Sol-gel thick film

Models and form factors for stand volume estimation in natural forest ecosystems: a case study of katarniaghat Wildlife Sanctuary (kGWS), Bahraich District, India

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Journal of Forestry Research 2013年第2期24卷 217-226页

作者： v. A. J Adekunle k. N. Nair A. k. srivastava N. k. Singh Federal University of Technology Dept of Forestry & Wood Technology National Botanical Research Institute (Council for Scientific & Industrial Research) Plant Diversity Systematics & Herbarium Division Rana Pratap Marg Department of Forests Sidhauli Forest Division

In view of the difficulties in stand volume estimation in natural forests, we derived real form factors and models for volume estimation in these types of forest ecosystems, using katarniaghat Wildlife Sanctuary as a case study. Tree growth data were obtained for all trees （dbh 〉10 cm） in 4 plots （25 × 25 m） randomly located in each of three strata selected in the forest. The form factor calculated for the stand was 0.42 and a range of 0.42 0.57 was estimated for selected species （density 〉10）. The parameters of model variables were consistent with general growth trends of trees and each was statistically significant. There was no significant difference （p〉0.05） between the observed and predicted volumes for all models and there was very high correlation between observed and predicted volumes. The output of the performance statistics and the logical signs of the regression coefficients of the models demonstrated that they are useful for volume estimation with minimal error. Plotting the biases with respect to considerable regressor variables showed no meaningful and evident trend of bias values along with the independent variables. This showed that the models did not violate regression assumptions and there were no heteroscedacity or multiculnarity problems. We recommend use of the form factors and models in this ecosystem and in similar ones for stand and tree volume estimation.

关键词： natural forest tree volume Estimation biodiversity tree height forest inventory

Application of IITM-RANS3D to free-fall water entry of prismatic and non-prismatic finite wedges

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Journal of Hydrodynamics 2023年第3期35卷 417-430页

作者： Shaswat Saincher kshitij srivastava R.vijayakumar v.Sriram Center for Maritime Experiments to Maritime Experience(ME2ME) Indian Institute of Technology MadrasChennaiIndia Department of Ocean Engineering Indian Institute of Technology MadrasChennaiIndia

High-speed watercraft and ships undergo coupled motions which make the front portion of the hull exit and violently re-enter *** induces short-term slamming loads that may compromise the structural integrity of the *** slamming of the bow can be modeled as straight wedges of different deadrise angles(DRAs)falling into water from different *** advent of computational fluid dynamics has allowed the problem of wedge-slamming to be simulated using the full Navier-Stokes equations thus complementing the pioneering studies based on ***,most researchers are opting to use commercial software to simulate the wedge-impact problem as it allows access to overset meshing algorithms which are robust in modeling the wedge as a moving *** boundary methods(EBMs)offer some advantages over overset meshing in that the mesh only needs to be generated once and Cartesian mesh-based solvers can be ***,the application of EBMs to wedge-impact has been limited in the literature and merits further *** this context,we investigate the applicability of the fast-fictitious-domain(FFD)based embedded boundary treatment to simulate the violent water-entry of *** extend our in-house Navier-Stokes model IITM-RANS3D to handle floating bodies through integration of a rigid-body dynamics solver and an algorithm to embed three-dimensional stereolithography(STL)geometries as solids over a Cartesian *** proposed algorithm is extensively benchmarked against variable DRA wedge-slamming experiments reported in the literature as well as constant DRA wedge-slamming experiments performed *** good agreement is reported in terms of the time-history of hydrodynamic impact pressures measured at various locations on the hull as well as the wedge motion responses thus demonstrating the suitability of FFD for simulating the coupled hydrodynamics of slamming for simplified hull geometries.

关键词： Wedge water entry slamming fast-fictitious-domain IITM-RANS3D experiments

THEORY OF INTERPOLATION ON INFINITE INTERvAL—Ⅰ(UNIFORM CONvERGENCE OF STABLE INTERPOLATION PROCESSES)

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Acta Mathematica Scientia 1986年第4期6卷 373-378页

作者： k.B.srivastava Department of Mathematics Indian Institute of Technology kanpur-208016 India

§1. Preliminaries and Results Let us begin by defining a triangular matrix L whose n-th row consists of n distinct points xvn, v=1, n; n=1, 2, … such that 01n2n<…nn<∞. （1.1） Denote by H_n.（f, x, L）≡H_n（f, L... 详细信息

关键词： THEORY OF INTERPOLATION ON INFINITE INTERvAL UNIFORM CONvERGENCE OF STABLE INTERPOLATION PROCESSES