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Regression analysis of squeezing-induced hybrid nanofluid flow in Darcy-Forchheimer porous medium

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Applied mathematics and mechanics(English Edition) 2025年第1期46卷 193-208页

作者： k.mUHAmmAD m.SARFRAZ Department of Humanities and Sciences School of Electrical Engineering and Computer Science National University of Sciences and Technology Department of mathematics Quaid-i-Azam University

This article presents a mathematical model addressing a scenario involving a hybrid nanofluid flow between two infinite parallel plates. One plate remains stationary, while the other moves downward at a squeezing velocity. The space between these plates contains a Darcy-Forchheimer porous medium. A mixture of water-based fluid with gold(Au) and silicon dioxide(Si O2) nanoparticles is formulated. In contrast to the conventional Fourier's heat flux equation, this study employs the Cattaneo-Christov heat flux equation. A uniform magnetic field is applied perpendicular to the flow direction, invoking magnetohydrodynamic(mHD) effects. Further, the model accounts for Joule heating, which is the heat generated when an electric current passes through the fluid. The problem is solved via NDSolve in mATHEmATICA. Numerical and statistical analyses are conducted to provide insights into the behavior of the nanomaterials between the parallel plates with respect to the flow, energy transport, and skin *** findings of this study have potential applications in enhancing cooling systems and optimizing thermal management strategies. It is observed that the squeezing motion generates additional pressure gradients within the fluid, which enhances the flow rate but reduces the frictional drag. Consequently, the fluid is pushed more vigorously between the plates, increasing the flow velocity. As the fluid experiences higher flow rates due to the increased squeezing effect, it spends less time in the region between the plates. The thermal relaxation, however, abruptly changes the temperature, leading to a decrease in the temperature fluctuations.

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LRS Bianchi Type-II Cosmological model with a Decaying Lambda Term

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Chinese Physics Letters 2012年第1期29卷 35-37页

作者： R.k.tiwari D.tiwari Pratibha Shukla Department of mathematics Govt.Model Science College RewaM.P.486001India

We consider a locally rotationally symmetric(LRS)Bianchi type-Ⅱspacetime with a perfect fluid and a variable cosmological constant∧.To solve the Einstein field equations we consider the cosmological term∧to be proportional to R^(-m) with R being the scale factor and m a constant[***.D 58(1998)043506].In this model we obtain∧~H^(2),∧~(R)/R and Larnbda~t^(-2),in agreement with the main dynamical laws for the decay of∧.The physical significance of the cosmological model is also discussed.

关键词： Bianchi Cosmo perfect

Anisotropic Bianchi Type-Ⅰmodel with a Varying A Term

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Chinese Physics Letters 2012年第3期29卷 41-43页

作者： R.k.tiwari Divya Singh Department of mathematics Govt.Model Science College RewaM.P.486001India

Einstein field equations with variable gravitational and cosmological constants are considered in the presence of a perfect fluid for a Bianchi type-I universe by assuming that the cosmological term is proportional to the Hubble parameter..The variation law for vacuum density was recently proposed by Schützhold on the basis of quantum field estimation in a curved expanding *** cosmological term tends asymptotically to a genuine cosmological constant and the model tends to a de Sitter *** obtain that the present universe is accelerating with a large fraction of cosmological density in the form of a cosmological term.

关键词： universe parameter gravitational

Tree species composition and diversity in montane forests of Garhwal Himalaya in relation to environmental and soil properties

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Journal of mountain Science 2020年第12期17卷 3097-3111页

作者： Dinesh Singh RAWAT P.tiwari Sudipta kumar DAS J.k.tiwari Department of Botany&microbiology HNB Garhwal UniversitySrinagar(Garhwal)-246174UttarakhandIndia Central National Herbarium Botanical Survey of IndiaHowrah-711103West BengalIndia

The montane forests of Garhwal Himalaya were investigated for tree species composition and diversity in relation to environmental and edaphic variables.A stratified random sampling approach was adopted to collect the field data from each forest.A total of 39 tree species belonging to 31 genera and 23 families were recorded from the sampling area(6 forest stands ×10 plots in each).Lauraceae with 5 species was the largest family while Quercus(4 species) emerged as the largest ***-area curve(asymptote) predicted more species than the observed number of *** analysis has shown that the two Abies pindrow dominant forest stands had the highest similarity in tree species *** tree stem density ranged from 540-1170 ha-1,basal area 23.01-55.94 m^2 ha-1,ShannonWiener diversity index 1.69-2.49,evenness index0.42-0.74,beta diversity 0.40-0.82 and similarity index 0.17-0.54 in the six studied ***-way indicator species analysis(TWINSPAN) identified four distinct tree communities in the study area with Daphniphyllum himalayense,Abies pindrow,Quercus oblongata,and Pinus roxburghii as indicator species of corresponding *** correspondence analysis(CCA) ascertained the TWINSPAN results and revealed the relation of tree species with environmental and edaphic *** phytosociological attributes of tree species varied from one forest stand to another;however,the tree species richness,density,and diversity peaked at intermediate elevation on the north *** reveal that tree composition and diversity in the montane forests of Garhwal Himalaya are influenced by both environmental(elevation and slope aspect)and soil variables(texture,water holding capacity,moisture content,available N,exchangeable P,and pH).This study will help in understanding the forest distribution across the western Himalaya,guiding the conservationists and policymakers in carrying out conservation-related management activities,designing the long-

关键词： Diversity Tree species montane forests Soil properties Western Himalaya

Effect of orientation on the drag of a cone settling in a Bingham plastic fluid

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Particuology 2019年第2期17卷 157-170页

作者： Pragya mishra A.k. tiwari R.P. Chhabra Department of Chemical Engineering. Indian Institute of Technology Kanpur 208016 India m2NeT Laboratory Wilfrid Laurier University 75 University Avenue West Waterloo ON N2L 3C5 Canada

Effects of the orientation and apex angle on the settling velocity of conical particles in Bingham plas-tic fluids are numerically investigated over a Reynolds number range of 1 ≤Re ≤100, Bingham number range of 0 ≤ Bn ≤ 100, and cone angle range of 20 ≤α≤ 150°. Governing equations (of continuity and momentum) are solved numerically using the finite element method to obtain velocity and pressure fields that are postprocessed to obtain values of the drag ***, the effect of cone ori-entation on the flow field is visualized and explored in terms of streamline contours and the morphology of yielded/uny ielded regions. Finally, the obtai ned values of drag are correlated via a simple predictive expression in terms of the modified Reynolds number. The effect of the cone angle on drag is found to be moderate because the drag force acting on the lateral surface is a small fraction of the overall drag.

关键词： Bingham number Reynolds number Yielded/unyielded regions Drag

Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

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Defence Technology（防务技术） 2023年第10期28卷 56-73页

作者： Nikhil khaire Gaurav tiwari Vivek Patel m.A.Iqbal Department of mechanical Engineering Indian Institute of Technology DelhiNew Delhi110016India Department of mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur440026India School of mechanical Engineering Dr.Vishwanath Karad MIT World Peace UniversityPune411038India Department of Civil Engineering Indian Institute of Technology RoorkeeRoorkee247667India

In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb *** high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of ***,the explicit solver was run in Abaqus to create the finite element *** numerically obtained test results were compared with the experimental to check the accuracy of the *** numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in ***,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was *** result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact *** panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset ***,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy ***,inscribe circle diameter had a negative influence on the ballistic ***,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation *** energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.

关键词： Honeycomb sandwich structure Offset impact Energy dissipation characteristic Deformation and failure mode Geometry effect

Radio spectral index from NVSS and TGSS

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Research in Astronomy and Astrophysics 2019年第7期19卷 59-66页

作者： Prabhakar tiwari National Astronomical Observatories Chinese Academy of Sciences

I extract the radio spectral index,α,from 541 195 common sources observed in the 150 mHz TIFR GmRT Sky Survey(TGSS) and the 1.4 GHz NRAO VLA Sky Survey(NVSS).This large common source catalog covers about 80% of the *** flux density limits in these surveys are such that the observed galaxies are presumably hosts of active galactic nuclei(AGNs).I confirm the steepening of αwith increasing flux density for this large sample and provide a parametric fit between α and flux ***,I divide the data into low flux(LF) and high flux(HF) density samples with roughly equal numbers of *** LF sample contains all galaxies below 100 m Jy TGSS and 20 m Jy NVSS flux density and the HF sample is all galaxies above 100 m Jy TGSS and 20 m Jy NVSS.I observe an increase in α with source size(TGSS measured),saturating for large sizes to 0.89 ± 0.22 and 0.76 ± 0.21 for the LF and HF sources,respectively.I discuss the observed results and possible physical mechanisms to explain observedα dependence with source size for LF and HF samples.

关键词： galaxies:high-redshift galaxies:active galactic nuclei

Bianchi type-I cosmological models with perfect fluid in general relativity

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Research in Astronomy and Astrophysics 2010年第4期10卷 291-300页

作者： Rishi kumar tiwari Department of mathematics Govt.Model Science College

Einstein＇s field equations with variable gravitational and cosmological constants are considered in the presence of perfect fluid for the Bianchi type-I universe by assuming that the cosmological term is proportional to R-m （R is a scale factor and m is a constant）.A variety of solutions are *** physical significance of the respective cosmological models are also discussed.

关键词： cosmological parameters - cosmology: theory - relativity

Contribution of NTFPs to cash income of the War khasi community of southern meghalaya,North-East India

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Forestry Studies in China 2012年第1期14卷 47-54页

作者： H.TYNSONG B.k.tiwari m.DkHAR ministry of Environment and Forest Goverment of IndiaRegional OfficeShillong-793022India Department of Environmental Studies North-Eastern Hill UniversityShillong-793022India Union Christian Collage Umiam KhwanShillong-793122India

Ever since their emergence on this planet, human beings have depended on forest resources for their requirements, ranging from food, fuel to shelter. Sustainable extraction of forest resources has been promoted by conservationists and development agencies as a feasible strategy for forest dwellers, which does not diminish the resource base. Yet surveys of actual resource use suggest that for poorer resource-dependent communities without access to markets, non-timber forest products （NTFPs） can only act as a safety- net and a supplementary income source. In southern meghalaya of India, NTFPs and medicinal and aromatic plants （mAPs） have become an important source of cash and subsistence income for poor people living in or near forests. People in this region have tradi- tionally been collecting different forest products from private forests as well as community conserved forests, The study reveals that NTFPs contribute significantly towards the annual cash income of the local population. The contribution of NTFPs to their income was highest in the case of poor families （9.89%）, followed by middle income families （3.34%） and the least for the higher income families （1.34%）. Our household survey revealed that 100% of the population is directly or indirectly dependent on NTFPs. House- hold response indicates diversity in both the types and uses of products collected.

关键词： forest products cash income management livelihood