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Unsteady natural convection Couette flow of heat generating/absorbing fluid between vertical parallel plates filled with porous material

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Applied mathematics and mechanics(English Edition) 2012年第3期33卷 303-314页

作者： B.k.jha m.k.mUSA Department of mathematics Ahmadu Bello UniversityZaria 234Nigeria mathematics Unit School of Basic and Remedial StudiesAhmadu Bello UniversityFuntua 6007Nigeria

The extended Brinkman Darcy model for momentum equations and an energy equation is used to calculate the unsteady natural convection Couette flow of a viscous incompressible heat generating/absorbing fluid in a vertical channel （formed by two infinite vertical and parallel plates） filled with the fluid-saturated porous medium. The flow is triggered by the asymmetric heating and the accelerated motion of one of the bounding plates. The governing equations are simplified by the reasonable dimensionless parameters and solved analytically by the Laplace transform techniques to obtain the closed form solutions of the velocity and temperature profiles. Then, the skin friction and the rate of heat transfer are consequently derived. It is noticed that, at different sections within the vertical channel, the fluid flow and the temperature profiles increase with time, which are both higher near the moving plate. In particular, increasing the gap between the plates increases the velocity and the temperature of the fluid, however, reduces the skin friction and the rate of heat transfer.

关键词： heat generating/absorbing fluid natural convection flow porous material acceleration motion

master curve generation and modeling of ac conductivity for mn_(0.7+x)Zn_(0.3)Si_(x)Fe_(2-2x)O_(4) spinel ferrite system

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Journal of Advanced Dielectrics 2017年第3期7卷 54-63页

作者： N.H.Vasoya Prafulla k.jha k.G.Saija J.A.Bhalodia k.B.modi Department of Physics Faculty of ScienceM.S.University of Baroda Vadodara 390002India Smt.R.P.Bhalodia mahila College Upleta 360490India Department of Physics Saurashtra UniversityRajkot 360005India

The compositional dependence of ac conductivity(δac),real(δ′)and imaginary(δ′′)parts of complex electric conductivity(δ*)was investigated as a function of temperature(T)and frequency(f) for mn_(0.7+x)Zn_(0.3)Si_(x)Fe_(2-2x)O_(4),x=0.0,0.1,0.2 and 0.3 spinel ferrite *** compositional dependence of lattice constant values suggested that the most of the substituted Si4+-ions reside at grain boundaries and only a few Si-ions are inside *** variation ofδ_(ac)(x,f,T)is explained on the basis of segregation and diffusion of Si4+ions at grain boundaries and grains,respectively,and the electrode *** variation of ac conductivity at fixed frequency suggested two different mechanisms which could be responsible for conduction in the *** is found that δ*is not the preferred presentation for dielectric data and the scaling process of real part of conductivity by normalized frequency and the scaled frequency were found *** fitting results of ac conductivity data with path percolation approximation were found suitable in low-frequency regime while in high-frequency regime,effective medium approximation(EmA)was found successful.

关键词： Ferrites ac conductivity scaling modeling.

Unsteady generalized Couette flow in composite microchannel

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Applied mathematics and mechanics(English Edition) 2011年第1期32卷 23-32页

作者： m.L.kAURANGINI B.k.jha Department of mathematical Sciences Kano University of Science and Technology Department of mathematics Ahmadu Bello University

A numerical study is reported on the fully developed unsteady laminar fluid flow in microchannel parallel-plates partially filled with a uniform porous medium and partially filled with a clear fluid. The flow is induced by the movement of one of the plates and the pressure gradient. The Brinkman-extended Darcy model is utilized to model the flow in the porous region, while the Stokes equation is used in the clear fluid region. A theoretical analysis is also presented for the fully developed steady flow to find closed- form expressions for the interracial velocity and the velocity and skin frictions at the bounding plates. Numerical computations shows excellent agreement between the closedform solutions for fully developed steady flow and the numerical solution to unsteady flow at large values of time.

关键词： unsteady flow composite microchannel

Achieving higher strength in Cu–Ag–Zr alloy by warm/hot rolling

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Rare metals 2017年第4期36卷 263-267页

作者： S. Chenna krishna Abhay k. jha Bhanu Pant koshy m. George materials and mechanical Entity Vikram Sarabhai Space Centre Trivandrum 695022 India

High-strength Cu-3Ag-0.5Zr alloy plates were produced by multi-pass rolling in the temperature range of 500-800 ℃. An increase in strength was observed by rolling in the aforementioned range without significant loss in ductility. All the rolled samples show higher strength than solution-treated and aged samples. The maximum strength was observed for plates rolled at 500 ℃ with a yield strength and ultimate tensile strength of 311 and 385 mPa, respectively, and retaining a ductility of 23 %. Transmission electron microscopy （TEm） studies showed uniform distribution of fine silver precipitates and high dislocation density in the rolled samples. Nevertheless, the size of precipitates and dislocation density varied with the rolling temperature. The superior strength achieved in the rolled samples is attributed to grain refinement, dislocation strengthening, and precipitation hardening. This method can be employed to produce high-strength plates of pre- cipitation hardenable copper alloys.

关键词： Warm/hot rolling Higher strength Copperalloy Strengthening

Impacts of climate change on hydrology,water quality and crop productivity in the Ohio-Tennessee River Basin

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International Journal of Agricultural and Biological Engineering 2015年第3期8卷 36-53页

作者： Yiannis Panagopoulos Philip W.Gassman Raymond W.Arritt Daryl E.Herzmann Todd D.Campbell Adriana Valcu manoj k.jha Catherine L.kling Raghavan Srinivasan michael White Jeffrey G.Arnold Center for Agricultural and Rural Development(CARD) Iowa State UniversityAmesIA 50011-1070USA Department of Agronomy 2104 Agronomy HallIowa State UniversityAmes IA 50011-1010USA Department of Civil Architectural and Environmental Engineering456 McNair HallNorth Carolina A&T State UniversityGreensboroNC 27411USA Departments of Ecosystem Sciences and management and Biological and Agricultural Engineering 1500 Research ParkwaySuite B223220 TAMUTexas A&M UniversityCollege StationTX 77843-2120USA Grassland Soil and Water Research Laboratory U.S.Department of Agriculture-Agricultural Research Service808 East Blackland RoadTempleTX 76502USA

Nonpoint source pollution from agriculture is the main source of nitrogen and phosphorus in the stream systems of the Corn Belt region in the midwestern *** eastern part of this region is comprised of the Ohio-Tennessee River Basin(OTRB),which is considered a key contributing area for water pollution and the Northern Gulf of mexico hypoxic zone.A point of crucial importance in this basin is therefore how intensive corn-based cropping systems for food and fuel production can be sustainable and coexist with a healthy water environment,not only under existing climate but also under climate change conditions in the *** address this issue,a OTRB integrated modeling system has been built with a greatly refined 12-digit subbasin structure based on the Soil and Water Assessment Tool(SWAT)water quality model,which is capable of estimating landscape and in-stream water and pollutant yields in response to a wide array of alternative cropping and/or management strategies and climatic *** effects of three agricultural management scenarios on crop production and pollutant loads exported from the crop land of the OTRB to streams and rivers were evaluated:(1)expansion of continuous corn across the entire basin,(2)adoption of no-till on all corn and soybean fields in the region,(3)implementation of a winter cover crop within the baseline *** effects of each management scenario were evaluated both for current climate and projected mid-century(2046-2065)climates from seven global circulation models(GCms).In both present and future climates each management scenario resulted in reduced erosion and nutrient loadings to surface water bodies compared to the baseline agricultural management,with cover crops causing the highest water pollution *** and soybean yields in the region were negligibly influenced from the agricultural management *** the other hand,both water quality and crop yield numbers under climate change deviated considerably f

关键词： agricultural management scenarios corn-based systems global circulation models hydrology water quality crop yields SWAT Ohio-Tennessee River Basin

Plasma production and preliminary results From the ADITYA Upgrade tokamak

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Plasma Science and Technology 2018年第7期20卷 7-14页

作者： R L TANNA J GHOSH Harshita RAJ Rohit kUmAR Suman AICH Vaibhav RANJAN k A JADEJA k m PATEL S B BHATT k SATHYANARAYANA P k CHATTOPADHYAY m N mAkWANA k S SHAH C N GUPTA V k PANCHAL Praveenlal EDAPPALA Bharat ARAmBHADIYA minsha SHAH Vismay RAULJI m B CHOWDHURI S BANERJEE R mANCHANDA D RAJU P k ATREY Umesh NAGORA J RAVAL Y S JOISA k TAHILIANI S k.jha S k.jha m V GOPALkRISHANA Institute for Plasma Research BhatGandhinagar 382 428India HBNI Training School complexAnushakti NagarMumbai 400085India

The Ohmically heated circular limiter tokamak ADITYA （R0 = 75 cm, a = 25 cm） has been upgraded to a tokamak named the ADITYA Upgrade （ADITYA-U） with an open divertor configuration with divertor plates. The main goal of ADITYA-U is to carry out dedicated experiments relevant for bigger fusion machines including ITER, such as the generation and control of runaway electrons, disruption prediction, and mitigation studies, along with an improvement in confinement with shaped plasma. The ADITYA tokamak was dismantled and the assembly of ADITYA-U was completed in march 2016. Integration of subsystems like data acquisition and remote operation along with plasma production and preliminary plasma characterization of ADITYA-U plasmas are presented in this paper.

关键词： ADITYA-U tokamak Phase I plasma operation toroidal limiter enhanced parameters

Influence of in-flight particle state diagnostics on properties of plasma sprayed YSZ-CeO_(2) nanocomposite coatings

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International Journal of Smart and Nano materials 2014年第3期5卷 207-216页

作者： S.mantry B.B.jha A.mandal D.k.mishra B.k.mishra m.Chakraborty CSIR-Institute of minerals&materials Technology Bhubaneswar 751013OdishaIndia School of minerals Metallurgical and Materials EngineeringIndian Institute of Technology BhubaneswarBhubaneswar 751007OdishaIndia Department of Physics Institute of Technical Education and ResearchSiksha‘O’Anusandhan UniversityKhandagiri SquareBhubaneswar 751030OdishaIndia Department of Physics College of ScienceEngineering and TechnologyUniversity of South AfricaJohannesburgSouth Africa

This article describes the influence of controlling in-flight hot particle characteristics on properties of plasma sprayed nanostructured yttria stabilized zirconia(YSZ)*** article depicts dependence of adhesion strength of as-sprayed nanostructured YSZ coatings on particle temperature,velocity and size of the splat prior to impact on the metallic *** temperature measurement is based on two-color pyrometry and particle velocities are measured from the length of the particle traces during known exposure *** microstructure and adhesion strength of as-sprayed nano-YSZ coatings were *** emission scanning electron microscopy results revealed that morphology of coating exhibits bimodal microstructure consisting of nano-zones reinforced in the matrix of fully melted *** coating adhesion strength is noticed to be greatly affected by the melting state of *** adhesion strength of 42.39 mPa has been experimentally found out by selecting optimum levels of particle temperature and *** enhanced bond strength of nano-YSZ coating may be attributed to higher interfacial toughness due to cracks being interrupted by adherent nano-zones.

关键词： CeYSZ nano-zones spray diagnostics adhesion plasma spraying

Two-dimensional finite element model to study calcium distribution in astrocytes in presence of excess buffer

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International Journal of Biomathematics 2014年第3期7卷 137-147页

作者： Brajesh kumar jha Neeru Adlakha m. N. mehta Department of mathematics and Computer Science School of Technology Pandit Deendayal Petroleum University Raisen Gandhinagar Gujarat 382007 India Department of mathematicsm. A. National Institute of Technology Bhopal India Department of Applied mathematicsS. V. National Institute of Technology Surat India

In this paper a finite element model is developed to study cytosolic calcium concen- tration distribution in astrocytes for a two-dimensional steady-state case in presence of excess buffer. The mathematical model of calcium diffusion in astrocytes leads to a boundary value problem involving elliptical partial differential equation. The model con- sists of reaction-diffusion phenomena, association and dissociation rates and buffer. A point source of calcium is incorporated in the model. Appropriate boundary conditions have been framed. Finite element method is employed to solve the problem. A mATLAB program has been developed for the entire problem and simulated to compute the numer- ical results. The numerical results have been used to plot calcium concentration profiles in astrocytes. The effect of ECTA, BAPTA and aCa influx on calcium concentration distribution in astrocytes is studied with the help of numerical results.

关键词： Ca2+ profile buffer finite element method.

Palaeogeographic reconstruction of a fluvio-marine transitional system in Narmada rift basin, India——Implications on Late Cretaceous global sea-level rise

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Journal of Palaeogeography 2021年第1期10卷 76-97页

作者： Biplab Bhattacharya Suparna jha Prantik mondal Department of Earth Sciences Indian Institute of TechnologyRoorkee 247667India Geological Survey of India Jabalpur 482003India

Rising sea-levels in tectonically active epicontinental basins often lead to varied depositional settings and palaeogeography, mostly influenced by the net accommodation resulting from mutual interference of the extent and nature of landward encroachment by the sea and the net sedimentation. The Cenomanian Nimar Sandstone Formation, Bagh Group, Narmada rift basin, uniquely portrays the effect of sea-level rise within an intra-cratonic setting and attributes to the corresponding palaeogeographic changes in west-central India. An integrated sedimentological–sequence-stratigraphic study of the broadly fining-upward Nimar Sandstone Formation(thickness~ 20–30 m) depicts the actual nature of changeover from a fluvial to a marine-dominated transitional depositional setting. Detailed sedimentological study reveals total seventeen facies, grouped in five facies associations, viz., the channel-fill facies association(FA-1), the overbank facies association(FA-2), the fluvial-dominated fluvio-tidal facies association(FA-3), the tide-dominated fluvio-tidal facies association(FA-4), and the shoreface facies association(FA-5). Overall facies architecture indicates a west-to-eastward marine encroachment, resulting in stacking of three distinct palaeo-depositional conditions:(i) an initial fluvial system with channel and overbank, changing into a tideinfluenced fluvial bay-head delta in the inner estuary, followed by(ii) marine encroachment leading to a tidedominated central estuary with inter-to sub-tidal settings, and finally,(iii) with further intense marine encroachments, a wave-reworked open shore condition in the outer estuary zone. The overall fining-up succession with a systematic change from fluvial to marine-dominated depositional systems points to a landward shift of the shoreline, signifying a major transgressive event correlated to the Cenomanian global sea-level rise. Characteristic stratal stacking patterns point to four coarsening-and fining-up hemicycles, embedded w

关键词： Late Cretaceous Fluvial-estuary transition Nimar Sandstone Formation Bagh Group Narmada rift basin Transgressive–regressive cycles Global sea-level